Crime is on the rise. Between burglary, drug-related robberies, and kidnapping, it's wise to prepare in advance how you will protect your home and family. In the event of an attack or break-in, there are many ways to protect your family, but preparation is a must. Your family members, even those who are young, should have a plan.
Weaponry to Protect, Not to Kill
Though many families have guns hidden away for protection, guns are dangerous. Accidents can occur within the family or in the event of trying to defend the family; the burglar could take the gun from you and murder everyone in the family. Also, there's often an emotional breakdown if someone is killed, even in self-defense. It's a good idea to have weaponry that de-mobilizes the burglar, but doesn't kill them. Some forms of weaponry that many are using include stun guns and pepper spray.
How Stun Guns Work
Stun guns disrupt the attacker's body by generating a high-voltage electrical charge with low amperage. The stun gun's charge applies much pressure but little intensity. The charge can pass through thick clothing and skin. Its charge is not intense enough to do damage to the attacker's body unless it is applied for extended periods of time.
A stun gun can, however, confuse the attacker by sending mixed signals to his brain. He can become temporarily or partially paralyzed, confused and unbalanced. This can give you or a family member enough time to get away and contact the police.
It's important not attempt any heroic acts; only use the stun gun as protection for your life or the lives of your family members. Then, get away as quickly as possible.
Stun Gun Voltage
Stun guns can be chosen according to voltage. They might contain from 20,000 volts all the way up to about 1,000,000 volts! They usually operate on 9-volt batteries. The batteries supply the stun gun with electricity to an electrical circuit. Components within the circuit give the voltage a boost while reducing the amperage. The stun gun has electrodes, which are usually small metal pieces with a gap in between. The gap is where a conductor must be placed. The conductor, of course, may be the arm, shoulder or hand of your attacker! There are also liquid stun guns and taser guns.
The Citizen's Protector
For ordinary home protection, citizens often choose medium-voltage stun guns that are easy to operate and store. There are stun guns that are disguised as umbrellas, flashlights, or other objects to create the element of surprise. Military personnel, security officers, and police officials often use more complex stun guns.
Stun Guns: Where to Buy Them
You can buy stun guns at home security outlets or stores in your hometown or in a nearby larger city. Or if you're pressed for time, there are places on the Internet that offer these products at great prices. You can shop for all sorts of security products online such as Talon stun guns, pepper sprays, alarms, and so forth. You can also save money by buying discount stun guns or even wholesale stun guns from an online store.
Before making a purchase, check out the company to be sure it is a reputable business. Also, check with your state and city laws to be sure the type of stun gun you are buying is legal in your area.
Don't leave your family unprotected. Although they can't be used in every situation, stun guns can give added security in these uncertain days!
http://www.majon.com/articles/Electronics/stun_guns_559.html
Wednesday, June 20, 2007
For the Small Business: Affordable Consumer Electronics
It can be a hassle to shop for electronics and other business goods when you're a small business owner. You need products that are dependable, affordable, and easy to use. Computers, office equipment, mo bile phones, and many other business necessities are available both online and off-line, so you have many options to consider.
Tips for In-Store Buying
When shopping for electronics or computers at a local store, compare brand names, features and pricing carefully. Sometimes a low price means sacrificing the quality or features you really need. For instance, if you're planning to buy a computer desk, consider the design of the desk and all its features. Does it have drawers or shelves to make organization easy? Does it have a pullout keyboard or a desktop keyboard? Also, consider the size of the desk and the quality of its materials (steel, solid wood or particle board).
When buying a computer, consider brand name, size of the hard drive and memory, as well as any pre-installed software it may contain. Avoid buying computers that have "advertising" menu bars pre-installed on the Windows screen. These tend to hang up often and are not worth the hassle although they are usually lower in price. Look for reputable brand names such as Dell, Pentium, Acer, and Compaq. Dependable laptops are available from these companies: Dell, Averatec, Compaq, HP Pavillion, Acer, Gateway, and IBM.
Avoid rebate offers. Rebates are often more trouble than they're worth, and your name might get added to hundreds of mailing lists! Instead, shop around for a great value up front to get the PC or laptop that will meet your needs.
Refurbished Products
With refurbished electronics or computers, find a reputable company that has a good standing with the Better Business Bureau. Some companies will advertise refurbished items, but will not follow through with a guarantee. Before buying a refurbished item, check for a guarantee and do a little research on the company to find out if other customers were satisfied with the products and service. If buying refurbished computers online, use the search engines to find out as much information as you can about the company.
Buying Electronics and Computers Online
Shop around online for great bargains on brand name electronics and computers. If you're pressed for time, there are discount home electronics online superstores that carry almost everything you'll need for your small business. Some of the products you might find include cables, office equipment, TV and video accessories, scanners, GPS, power protection products, mobile phones, digital recorders, formatted diskettes, CDs, and more.
Online electronics stores for small business can offer you better prices because they have few overhead costs when operating on the Web. You can usually expect to save up to 20% on items.
You'll find shopping online to be a great time-saver because you can shop from your home or office without visiting busy stores.
Use these tips to find electronics, computers and other products for your small business at great prices without sacrificing quality.
http://www.majon.com/articles/Electronics/electronics_store_for_small_busines_571.html
Tips for In-Store Buying
When shopping for electronics or computers at a local store, compare brand names, features and pricing carefully. Sometimes a low price means sacrificing the quality or features you really need. For instance, if you're planning to buy a computer desk, consider the design of the desk and all its features. Does it have drawers or shelves to make organization easy? Does it have a pullout keyboard or a desktop keyboard? Also, consider the size of the desk and the quality of its materials (steel, solid wood or particle board).
When buying a computer, consider brand name, size of the hard drive and memory, as well as any pre-installed software it may contain. Avoid buying computers that have "advertising" menu bars pre-installed on the Windows screen. These tend to hang up often and are not worth the hassle although they are usually lower in price. Look for reputable brand names such as Dell, Pentium, Acer, and Compaq. Dependable laptops are available from these companies: Dell, Averatec, Compaq, HP Pavillion, Acer, Gateway, and IBM.
Avoid rebate offers. Rebates are often more trouble than they're worth, and your name might get added to hundreds of mailing lists! Instead, shop around for a great value up front to get the PC or laptop that will meet your needs.
Refurbished Products
With refurbished electronics or computers, find a reputable company that has a good standing with the Better Business Bureau. Some companies will advertise refurbished items, but will not follow through with a guarantee. Before buying a refurbished item, check for a guarantee and do a little research on the company to find out if other customers were satisfied with the products and service. If buying refurbished computers online, use the search engines to find out as much information as you can about the company.
Buying Electronics and Computers Online
Shop around online for great bargains on brand name electronics and computers. If you're pressed for time, there are discount home electronics online superstores that carry almost everything you'll need for your small business. Some of the products you might find include cables, office equipment, TV and video accessories, scanners, GPS, power protection products, mobile phones, digital recorders, formatted diskettes, CDs, and more.
Online electronics stores for small business can offer you better prices because they have few overhead costs when operating on the Web. You can usually expect to save up to 20% on items.
You'll find shopping online to be a great time-saver because you can shop from your home or office without visiting busy stores.
Use these tips to find electronics, computers and other products for your small business at great prices without sacrificing quality.
http://www.majon.com/articles/Electronics/electronics_store_for_small_busines_571.html
Novel Explanation Offered For Puzzling Electron 'Gas' Experiments
Science Daily — CHAMPAIGN, Ill. -- Recent experiments confirming the existence of a novel conducting phase in a two-dimensional electron "gas" sandwiched between semiconductors have posed a dilemma for scientists seeking to explain their observations. Now, physicists at the University of Illinois say superconductivity can account for what had seemed to be puzzling findings.
The experiments in question were performed on a silicon metal-oxide semiconductor field-effect transistor. "In such a device, electrons are confined to move at the interface between the metal oxide and the semiconductor," explained Philip Phillips, a U. of I. professor of physics who led a team that analyzed the experiments, which were carried out elsewhere. "Because the electrons move only at the interface, they are said to be confined to two dimensions."
The experimenters probed a range of electron densities never before examined at low temperature. In this regime, they observed that below a certain electron density, the electrons behaved as they do in an insulator. Above a certain density, however, a conducting state was observed.
"The presence of this conducting state is remarkable, because standard theory predicts that in two dimensions as you lower the temperature, the resistivity will continue to increase and the system will become an insulator," Phillips said. "Until now, no one had come up with an acceptable explanation for this conducting state that was appropriate for the description of these experiments."
Writing in the Sept. 17 issue of the journal Nature, Phillips, postdoctoral research associate Yi Wan, and graduate students Ivar Martin, Sergey Knysh and Denis Dalidovich claim that this odd conducting phase is due to a novel kind of superconductor.
To support their conclusion, the researchers cite several key observations. First, features of the conducting transition, such as current-voltage characteristics and the scaling of the resistivity, resemble those of known insulator-superconductor phase transitions. Second, magnetoresistance measurements offer clear evidence for a critical magnetic field above which the conducting phase is destroyed.
"There are not many states of matter that are consistent with a critical magnetic field," Phillips said. "A critical parallel magnetic field indicates that the electrons are paired up in spin singlet states. The only conducting state that is compatible with this observation is a superconducting one."
Because the conductivity was independent of temperature at a particular electron density, that density marks the transition between the conducting and insulating phases, Phillips said.
"In this density regime, the Coulomb interactions dominate. In the insulator, strong Coulomb interactions and disorder prevent the electrons from moving. But as the density is increased, these strong Coulomb interactions can lead to the formation of Cooper pairs, a prerequisite for superconductivity."
While additional measurements must be performed to confirm their findings, "at present, the insulator-superconductor scenario can explain the known experimental observations," Phillips said.
http://www.sciencedaily.com/releases/1998/10/981005074512.htm
The experiments in question were performed on a silicon metal-oxide semiconductor field-effect transistor. "In such a device, electrons are confined to move at the interface between the metal oxide and the semiconductor," explained Philip Phillips, a U. of I. professor of physics who led a team that analyzed the experiments, which were carried out elsewhere. "Because the electrons move only at the interface, they are said to be confined to two dimensions."
The experimenters probed a range of electron densities never before examined at low temperature. In this regime, they observed that below a certain electron density, the electrons behaved as they do in an insulator. Above a certain density, however, a conducting state was observed.
"The presence of this conducting state is remarkable, because standard theory predicts that in two dimensions as you lower the temperature, the resistivity will continue to increase and the system will become an insulator," Phillips said. "Until now, no one had come up with an acceptable explanation for this conducting state that was appropriate for the description of these experiments."
Writing in the Sept. 17 issue of the journal Nature, Phillips, postdoctoral research associate Yi Wan, and graduate students Ivar Martin, Sergey Knysh and Denis Dalidovich claim that this odd conducting phase is due to a novel kind of superconductor.
To support their conclusion, the researchers cite several key observations. First, features of the conducting transition, such as current-voltage characteristics and the scaling of the resistivity, resemble those of known insulator-superconductor phase transitions. Second, magnetoresistance measurements offer clear evidence for a critical magnetic field above which the conducting phase is destroyed.
"There are not many states of matter that are consistent with a critical magnetic field," Phillips said. "A critical parallel magnetic field indicates that the electrons are paired up in spin singlet states. The only conducting state that is compatible with this observation is a superconducting one."
Because the conductivity was independent of temperature at a particular electron density, that density marks the transition between the conducting and insulating phases, Phillips said.
"In this density regime, the Coulomb interactions dominate. In the insulator, strong Coulomb interactions and disorder prevent the electrons from moving. But as the density is increased, these strong Coulomb interactions can lead to the formation of Cooper pairs, a prerequisite for superconductivity."
While additional measurements must be performed to confirm their findings, "at present, the insulator-superconductor scenario can explain the known experimental observations," Phillips said.
http://www.sciencedaily.com/releases/1998/10/981005074512.htm
Plastic With Changeable Conductivity Developed By Chemical Engineer
Science Daily — Dr. Yueh-Lin (Lynn) Loo at The University of Texas at Austin has modified a plastic so its ability to carry an electrical current can be altered during manufacturing to meet the needs of future electronic devices.
Loo, an assistant professor of chemical engineering, studies the plastic called polyaniline because it could serve as flexible, inexpensive wiring in future products such as military camouflage that changes colors, foldable electronic displays and medical sensors.
By combining polyaniline with a chemical that gives it conductivity, Loo discovered she could increase the plastic’s conductivity one- to six-fold based on the version of the chemical added. The results involving the chemical polymer acid were published in the April 7 issue of the Journal of Materials Chemistry.
Chemically altered polyaniline has several advantages over the more commonly used metals, like gold and copper, in devices other than computers. For example, Loo’s previous research has demonstrated that “doped” polyaniline can be manufactured in solution at room temperatures and without vacuum chambers. Producing metal-based wires requires special manufacturing conditions in addition to the high cost of the metals.
Since Loo’s laboratory submitted their research to the Journal of Materials Chemistry, they have developed a version of polyaniline whose conductivity is 10 times higher than before. However, that level of electrical conductivity still doesn’t rival that of copper, which is used to produce high-speed interconnections.
That effort will be based on the greater understanding Loo has gained of the polyaniline/polymer acid described in the Journal of Materials Chemistry article. In the article, graduate student Joung Eun Yoo and other members of Loo’s laboratory began determining how higher-mass versions of polymer acid improve the plastic’s conductivity when the two materials are combined. So far, they have learned that the higher mass acids attach to the plastic in longer chains, and induce a less-ordered internal structure (crystallinity) within the plastic.
“Understanding how the structure of this polyaniline material changes when its conductivity changes will be crucial for selecting the right material for different consumer applications,” Loo said.
She noted that the ability of the plastic to change colors depending on whether it was conductive or not could be especially useful.
“Its general versatility could lead to a variety of new consumer products in upcoming years,” she said.
http://www.sciencedaily.com/releases/2007/04/070409115804.htm
Loo, an assistant professor of chemical engineering, studies the plastic called polyaniline because it could serve as flexible, inexpensive wiring in future products such as military camouflage that changes colors, foldable electronic displays and medical sensors.
By combining polyaniline with a chemical that gives it conductivity, Loo discovered she could increase the plastic’s conductivity one- to six-fold based on the version of the chemical added. The results involving the chemical polymer acid were published in the April 7 issue of the Journal of Materials Chemistry.
Chemically altered polyaniline has several advantages over the more commonly used metals, like gold and copper, in devices other than computers. For example, Loo’s previous research has demonstrated that “doped” polyaniline can be manufactured in solution at room temperatures and without vacuum chambers. Producing metal-based wires requires special manufacturing conditions in addition to the high cost of the metals.
Since Loo’s laboratory submitted their research to the Journal of Materials Chemistry, they have developed a version of polyaniline whose conductivity is 10 times higher than before. However, that level of electrical conductivity still doesn’t rival that of copper, which is used to produce high-speed interconnections.
That effort will be based on the greater understanding Loo has gained of the polyaniline/polymer acid described in the Journal of Materials Chemistry article. In the article, graduate student Joung Eun Yoo and other members of Loo’s laboratory began determining how higher-mass versions of polymer acid improve the plastic’s conductivity when the two materials are combined. So far, they have learned that the higher mass acids attach to the plastic in longer chains, and induce a less-ordered internal structure (crystallinity) within the plastic.
“Understanding how the structure of this polyaniline material changes when its conductivity changes will be crucial for selecting the right material for different consumer applications,” Loo said.
She noted that the ability of the plastic to change colors depending on whether it was conductive or not could be especially useful.
“Its general versatility could lead to a variety of new consumer products in upcoming years,” she said.
http://www.sciencedaily.com/releases/2007/04/070409115804.htm
New Technique Measures Chemical Composition Of Tiny Details
Science Daily — Chemistry researchers at Eindhoven University of Technology (TUE), funded by NWO's Chemical Sciences Council, recently discovered a way to determine the chemical composition of chips or coatings which are only a few nanometers across. This technique makes a major contribution to further miniaturisation in the field of micro-electronics and semiconductors, in which the smallest structural details are about 200 nanometers in size.
The method which the Eindhoven have developed is based on the radiation emitted by an object when it is irradiated by a beam of electrons. The measurable phenomenon occurs because the electrons in the beam collide with electrons in the atoms making up the object so that they enter an excited state. When the electrons return to the free state, with lower energy, X-rays are emitted. The wavelength of this radiation is characteristic of the chemical element, while the intensity of the radiation depends on the overall composition of the material.
The Dutch researchers combined a model for determining the chemical composition on the basis of the measured intensity with the use of a high resolution electron microscope. The beam of electrons which the microscope produces irradiates a minimum area of 10 by 10 nanometers. Using the X-rays emitted from this area, it is possible to determine precisely which chemical elements occur at that location and in what quantity.
Using this technique, research is now being carried out on a new type of electrical contact within chips constructed of a thin layer of cobalt deposited on a semiconductor. The cobalt forms an electrical connection for the semiconductor. When heat is applied, a chemical reaction takes place between the cobalt and the semiconductor, improving the mechanical strength and the electrical conductivity of the contact. The new chemical technique allowed the researchers to determine accurately where chemical changes had developed as a result of the heat-treatment.
In industry, micro-electronics or semiconductor components with a diameter of less than 1 micrometre are now commonplace. Further miniaturisation of the smallest structures within equipment, such as electrical connections and junctions within a chip, will only be possible if researchers are in a position to measure the chemical composition of the smallest details of the new materials.
http://www.sciencedaily.com/releases/2000/01/000127082008.htm
The method which the Eindhoven have developed is based on the radiation emitted by an object when it is irradiated by a beam of electrons. The measurable phenomenon occurs because the electrons in the beam collide with electrons in the atoms making up the object so that they enter an excited state. When the electrons return to the free state, with lower energy, X-rays are emitted. The wavelength of this radiation is characteristic of the chemical element, while the intensity of the radiation depends on the overall composition of the material.
The Dutch researchers combined a model for determining the chemical composition on the basis of the measured intensity with the use of a high resolution electron microscope. The beam of electrons which the microscope produces irradiates a minimum area of 10 by 10 nanometers. Using the X-rays emitted from this area, it is possible to determine precisely which chemical elements occur at that location and in what quantity.
Using this technique, research is now being carried out on a new type of electrical contact within chips constructed of a thin layer of cobalt deposited on a semiconductor. The cobalt forms an electrical connection for the semiconductor. When heat is applied, a chemical reaction takes place between the cobalt and the semiconductor, improving the mechanical strength and the electrical conductivity of the contact. The new chemical technique allowed the researchers to determine accurately where chemical changes had developed as a result of the heat-treatment.
In industry, micro-electronics or semiconductor components with a diameter of less than 1 micrometre are now commonplace. Further miniaturisation of the smallest structures within equipment, such as electrical connections and junctions within a chip, will only be possible if researchers are in a position to measure the chemical composition of the smallest details of the new materials.
http://www.sciencedaily.com/releases/2000/01/000127082008.htm
How "Micro" Can We Go?
Weizmann Institute scientists have provided one of the answers to this question. Making simple and elegant use of a chemical theory of liquids, they developed a way to predict the minimal possible size of bipolar transistors, one of the major types of transistors commonly used in microelectronics. They then managed to manufacture such a tiny structure using the experimental semiconductor copper indium diselenide. With an inner core of just 20 nanometers (billionths of a meter) and total width of 50 nanometers -- less than one-thousandth the width of a human hair -- the device is five times smaller than today's smallest standard transistors of this type.
This research, reported recently in Applied Physics Letters, was performed by doctoral student Shachar Richter, working with Prof. David Cahen of the Materials and Interfaces Department, Dr. Yishay Manassen, formerly of Weizmann's Chemical Physics Department and now a professor of physics at Ben-Gurion University of the Negev, and Dr. Sidney Cohen, head of Weizmann's Surface Analysis Unit.
In his research, Richter used atomic force microscopy -- a technique in which a phonograph-like stylus probes the surface of a material -- to manipulate atoms in a semiconductor. Normally, such microscopes can only shift atoms on the surface of a material, but Richter, building on earlier research by Prof. Cahen, managed to move these atoms around inside the semiconductor.
Richter achieved his results by applying a voltage to the semiconductor and passing a current through the material. Aided by the slight heating produced by the current, the voltage caused atoms called dopants, which determine the material's conductivity, to be propelled in a particular direction. Even though only 100 to 200 dopants were moved in this manner, this sufficed to produce a tiny transistor. It consisted of a hemispherical layer of relatively high conductivity containing the redistributed dopants, flanked on both sides by material with different conductivity.
Next, Richter used the same microscope stylus -- at low voltage -- to map the conductivity of this miniature structure. Richter's new mapping method, called scanning spreading resistance, reveals the precise path that would be taken by an electric current flowing through a transistor of this type. This new type of measurement, developed independently by Belgian researchers around the time of Richter's study, promises to become an important tool for evaluating miniature electronic devices.
These findings don't necessarily mean that microelectronic devices will eventually get as small as Richter's transistor. His device, however, can serve as a valuable research tool for studying the limits of miniaturization.
Funding for this research was provided by the Israel Science Foundation and the Minerva Foundation, Munich, Germany.
http://www.sciencedaily.com/releases/1998/12/981204074905.htm
Researchers Produce Insulation With Lowest Thermal Conductivity Ever
Science Daily — A new insulation material with the lowest thermal conductivity ever measured for a fully dense solid has been created at the University of Oregon and tested by researchers at three other U.S. institutions. While far from having immediate application, the principles involved, once understood, could lead to improved insulation for a wide variety of uses, the scientists say.
In a paper published online Dec. 14 on Science Express, in advance of regular publication in the journal Science, the scientists describe how they used a novel approach to synthesize various thicknesses of tungsten diselenide. This effort resulted in a random stacking of tungsten-diselenide planes (WSe2), possibly leading to a localization of lattice vibrations.
The resulting synthesized material, they report, resulted in thermal conductivity -- the rate at which heat flows through a material -- 30 times smaller than that for single-crystal WSe2 and a factor six smaller that the minimum level predicted by theoretical computations for the cross-plane thin films used in the experiments.
Surprisingly, creating a fully disordered structure by bombarding the films with ions to destroy the order in the two-dimensional planes actually increases thermal conductivity, said David C. Johnson, a professor of chemistry at the University of Oregon and member of the UO Materials Science Institute.
"The reason for the extraordinarily low thermal conductivity that we've now achieved is an unusual structure which is crystalline in two directions but has a subtle rotational disorder in the direction of low-heat conduction," Johnson said.
The material prepared in Johnson's lab "is the closest thing that anyone has found to making a dense solid into a perfect thermal insulator," said co-author and corresponding investigator David G. Cahill, a professor of materials science and engineering at the University of Illinois at Urbana-Champaign. "This material would not be practical for insulating a refrigerator, the wall of a house or parts inside a turbine engine, but the new physical properties displayed by this material might some day point the way toward methods of creating more effective practical insulations."
The approach is a new alternative to one described by Cahill and others in separate journals in the last two years in which researchers reduced minimum thermal conductivity by manipulating thin films of metals and oxides by adjusting interfaces of the materials by only a few nanometers.
"Thermal conductivity is an important property in both conserving energy and in converting between forms of energy," Johnson said. "Obtaining low thermal conductivity in a thermoelectric material, which converts temperature gradients into electrical energy, increases efficiency."
The properties of Johnson's material were measured in Cahill's Illinois laboratory. The structure was analyzed at the Argonne National Laboratory in Argonne, Ill. Computational simulations and molecular modeling of the layered crystals was carried out by researchers at Rensselaer Polytechnic Institute (RPI) in Troy, N.Y.
Co-authors Pawel Keblinski and Arun Bodapati, both at RRI, said that the observed ultra-low thermal conductivity is not limited to tungsten diselenide and likely could be applied to a wide variety of disordered layered crystals.
Other co-authors were Catalin Chiritescu, a student in Cahill's lab at the University of Illinois, Ngoc Nguyen, a doctoral student in Johnson's UO lab, and Paul Zschack of Argonne National Laboratory's Advanced Photon Source.
Johnson also is the founder of the Center for Advance Materials Characterization in Oregon (CAMCOR) and the co-director of research at the Oregon Nanoscience and Microtechnologies Institute. ONAMI is an Oregon Signature Research Center made up of collaborating researchers from the UO, Oregon State University, Portland State University and the Pacific Northwest National Laboratory who pursue fundamental and applied research projects with industry in the Northwest.
The Office of Naval Research and the U.S. Department of Energy provided funding for various components of the project.
http://www.sciencedaily.com/releases/2006/12/061215091011.htm
In a paper published online Dec. 14 on Science Express, in advance of regular publication in the journal Science, the scientists describe how they used a novel approach to synthesize various thicknesses of tungsten diselenide. This effort resulted in a random stacking of tungsten-diselenide planes (WSe2), possibly leading to a localization of lattice vibrations.
The resulting synthesized material, they report, resulted in thermal conductivity -- the rate at which heat flows through a material -- 30 times smaller than that for single-crystal WSe2 and a factor six smaller that the minimum level predicted by theoretical computations for the cross-plane thin films used in the experiments.
Surprisingly, creating a fully disordered structure by bombarding the films with ions to destroy the order in the two-dimensional planes actually increases thermal conductivity, said David C. Johnson, a professor of chemistry at the University of Oregon and member of the UO Materials Science Institute.
"The reason for the extraordinarily low thermal conductivity that we've now achieved is an unusual structure which is crystalline in two directions but has a subtle rotational disorder in the direction of low-heat conduction," Johnson said.
The material prepared in Johnson's lab "is the closest thing that anyone has found to making a dense solid into a perfect thermal insulator," said co-author and corresponding investigator David G. Cahill, a professor of materials science and engineering at the University of Illinois at Urbana-Champaign. "This material would not be practical for insulating a refrigerator, the wall of a house or parts inside a turbine engine, but the new physical properties displayed by this material might some day point the way toward methods of creating more effective practical insulations."
The approach is a new alternative to one described by Cahill and others in separate journals in the last two years in which researchers reduced minimum thermal conductivity by manipulating thin films of metals and oxides by adjusting interfaces of the materials by only a few nanometers.
"Thermal conductivity is an important property in both conserving energy and in converting between forms of energy," Johnson said. "Obtaining low thermal conductivity in a thermoelectric material, which converts temperature gradients into electrical energy, increases efficiency."
The properties of Johnson's material were measured in Cahill's Illinois laboratory. The structure was analyzed at the Argonne National Laboratory in Argonne, Ill. Computational simulations and molecular modeling of the layered crystals was carried out by researchers at Rensselaer Polytechnic Institute (RPI) in Troy, N.Y.
Co-authors Pawel Keblinski and Arun Bodapati, both at RRI, said that the observed ultra-low thermal conductivity is not limited to tungsten diselenide and likely could be applied to a wide variety of disordered layered crystals.
Other co-authors were Catalin Chiritescu, a student in Cahill's lab at the University of Illinois, Ngoc Nguyen, a doctoral student in Johnson's UO lab, and Paul Zschack of Argonne National Laboratory's Advanced Photon Source.
Johnson also is the founder of the Center for Advance Materials Characterization in Oregon (CAMCOR) and the co-director of research at the Oregon Nanoscience and Microtechnologies Institute. ONAMI is an Oregon Signature Research Center made up of collaborating researchers from the UO, Oregon State University, Portland State University and the Pacific Northwest National Laboratory who pursue fundamental and applied research projects with industry in the Northwest.
The Office of Naval Research and the U.S. Department of Energy provided funding for various components of the project.
http://www.sciencedaily.com/releases/2006/12/061215091011.htm
UB Engineer Discovers Carbon Composite Is A Semiconductor
Science Daily — SAN DIEGO, Calif. -- A University at Buffalo engineer has made the first observation of semiconducting behavior in a carbon composite material, a finding that could revolutionize the fields of "smart" structures and electronics.
The discovery lays the foundation for structural electronics, a new technology with the extraordinary potential to endow structural materials with electronic capabilities without computer chips or electrical leads.
The new technology could make possible aircraft components that are themselves huge energy-storage devices, solar cars whose body panels are capable of storing tremendous amounts of energy from sunlight and, eventually, even computers without chips.
"This is a whole new level of 'smartness' in materials," said Deborah Chung, Ph.D., professor of mechanical and aerospace engineering at UB and principal investigator. "We can use the structural material itself as the electronics." The research was presented here today (March 4, 1998) at the International Symposium on Smart Structures and Materials in San Diego.
Chung, who also is Niagara Mohawk Chair of Materials Research at UB, co-authored the paper with Shoukai Wang, a doctoral candidate in the UB Department of Mechanical and Aerospace Engineering.
Made from carbon fibers embedded in a polymer matrix, the new semiconducting material would be easier and less expensive to fabricate than traditional silicon-based electronics. Because it would spread electronic capabilities over a much larger surface area, heat dissipation -- now one of the biggest technological challenges facing electronic packaging -- would no longer be a problem.
Known for their durability and light weight, carbon composites are used primarily to manufacture aircraft parts and are being used increasingly in automotive components, bridges, machinery and sporting equipment.
Currently, optical or electronic sensors for detecting strain and deformation are embedded in carbon composites used to make aircraft parts, a process that itself can weaken significantly the structural component.
"In addition, these devices can only be embedded in certain locations, not throughout the whole component," said Chung.
"With this material, the whole piece is 'smart' and no electrical interconnection is needed," she said.
A structural electronic material also would have exceptional energy-storage potential, she added, allowing an aircraft component to act like a huge solar cell.
It also would make solar cars more feasible because energy could be stored throughout body panels constructed of carbon composites.
The discovery is unusual because it unites advances in two disciplines that typically don't "talk" to each other, Chung explained.
"In the semiconductor world, silicon dominates so completely that people tend not to think about other kinds of materials, especially structural materials," she said. "On the other hand, structural engineers would never think of their materials as semiconductors."
Chung, who is a materials engineer, made the discovery while examining the electrical behavior of carbon composites as a way to improve damage detection. She was focusing on how changes in temperature in composite structures could be sensed using the structural material itself.
She found that the electrical properties of the composite material changed with temperature.
"That variation in temperature is a signature of a semiconductor," she said. "But what's even more unusual about this particular material is that it is semiconducting in one direction and metallic in another," she said. "Usually, a semiconductor, like silicon, is semiconducting in all directions."
The research shows that the carbon-fiber composite, consisting of layers of carbon fibers, is semiconducting perpendicular to the plane of the junction where the fibers intersect and metallic along its horizontal plane.
The advantage of having both in one material, Chung explained, is that the metal characteristics provide a system of built-in electrical contacts and leads for the composite to which a meter can be connected.
In addition, she said, by using the fibers as a conductor and putting an insulator in between the fiber layers, a large capacitor is formed, so that energy can be stored throughout an aircraft or automotive component made of the composite.
Chung plans to focus on optoelectronic and electronic devices made from the composite.
A patent has been filed on the invention.
http://www.sciencedaily.com/releases/1998/03/980306043213.htm
The discovery lays the foundation for structural electronics, a new technology with the extraordinary potential to endow structural materials with electronic capabilities without computer chips or electrical leads.
The new technology could make possible aircraft components that are themselves huge energy-storage devices, solar cars whose body panels are capable of storing tremendous amounts of energy from sunlight and, eventually, even computers without chips.
"This is a whole new level of 'smartness' in materials," said Deborah Chung, Ph.D., professor of mechanical and aerospace engineering at UB and principal investigator. "We can use the structural material itself as the electronics." The research was presented here today (March 4, 1998) at the International Symposium on Smart Structures and Materials in San Diego.
Chung, who also is Niagara Mohawk Chair of Materials Research at UB, co-authored the paper with Shoukai Wang, a doctoral candidate in the UB Department of Mechanical and Aerospace Engineering.
Made from carbon fibers embedded in a polymer matrix, the new semiconducting material would be easier and less expensive to fabricate than traditional silicon-based electronics. Because it would spread electronic capabilities over a much larger surface area, heat dissipation -- now one of the biggest technological challenges facing electronic packaging -- would no longer be a problem.
Known for their durability and light weight, carbon composites are used primarily to manufacture aircraft parts and are being used increasingly in automotive components, bridges, machinery and sporting equipment.
Currently, optical or electronic sensors for detecting strain and deformation are embedded in carbon composites used to make aircraft parts, a process that itself can weaken significantly the structural component.
"In addition, these devices can only be embedded in certain locations, not throughout the whole component," said Chung.
"With this material, the whole piece is 'smart' and no electrical interconnection is needed," she said.
A structural electronic material also would have exceptional energy-storage potential, she added, allowing an aircraft component to act like a huge solar cell.
It also would make solar cars more feasible because energy could be stored throughout body panels constructed of carbon composites.
The discovery is unusual because it unites advances in two disciplines that typically don't "talk" to each other, Chung explained.
"In the semiconductor world, silicon dominates so completely that people tend not to think about other kinds of materials, especially structural materials," she said. "On the other hand, structural engineers would never think of their materials as semiconductors."
Chung, who is a materials engineer, made the discovery while examining the electrical behavior of carbon composites as a way to improve damage detection. She was focusing on how changes in temperature in composite structures could be sensed using the structural material itself.
She found that the electrical properties of the composite material changed with temperature.
"That variation in temperature is a signature of a semiconductor," she said. "But what's even more unusual about this particular material is that it is semiconducting in one direction and metallic in another," she said. "Usually, a semiconductor, like silicon, is semiconducting in all directions."
The research shows that the carbon-fiber composite, consisting of layers of carbon fibers, is semiconducting perpendicular to the plane of the junction where the fibers intersect and metallic along its horizontal plane.
The advantage of having both in one material, Chung explained, is that the metal characteristics provide a system of built-in electrical contacts and leads for the composite to which a meter can be connected.
In addition, she said, by using the fibers as a conductor and putting an insulator in between the fiber layers, a large capacitor is formed, so that energy can be stored throughout an aircraft or automotive component made of the composite.
Chung plans to focus on optoelectronic and electronic devices made from the composite.
A patent has been filed on the invention.
http://www.sciencedaily.com/releases/1998/03/980306043213.htm
Using Electromagnetic Induction To Trace Soil Nitrogen
Science Daily — Nitrogen, a chemical nutrient needed by many growing crops, can accidentally end up in surface or subsurface water. Now an Agricultural Research Service scientist is using electromagnetic induction (EI) to measure changes in the soil's electrical conductivity, a quality that can provide important clues to the amount of nutrients present in the soil.
Roger A. Eigenberg is an agricultural engineer at the ARS Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb. He has used EI to study several fields and create a map with light-shaded areas representing high electrical conductivity--or areas of high nitrate concentration--and dark areas that indicate low conductivity, or low nitrate concentration.
Eigenberg has compared fields with and without a winter cover crop and fields with added manure or compost. He discovered that EI could be used to monitor the effects of winter cover crops, because EI changes corresponded to soil nutrient changes as the cover crop took up nutrients in the fall and released them back to the soil in the spring.
Another Clay Center research location was a former manure compost site. In the past, scientists had to take numerous soil samples to determine where manure rows had been located. Using the commercially available EI equipment, Eigenberg was able to locate them in a fraction of the time. He tracked nutrient movement over a four-year period and found that using equipment such as the EI meter can determine nutrient buildup and movement to help prevent nitrate leaching into groundwater.
ARS is the U.S. Department of Agriculture's chief scientific research agency.
http://www.sciencedaily.com/releases/2004/10/041011075626.htm
Roger A. Eigenberg is an agricultural engineer at the ARS Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb. He has used EI to study several fields and create a map with light-shaded areas representing high electrical conductivity--or areas of high nitrate concentration--and dark areas that indicate low conductivity, or low nitrate concentration.
Eigenberg has compared fields with and without a winter cover crop and fields with added manure or compost. He discovered that EI could be used to monitor the effects of winter cover crops, because EI changes corresponded to soil nutrient changes as the cover crop took up nutrients in the fall and released them back to the soil in the spring.
Another Clay Center research location was a former manure compost site. In the past, scientists had to take numerous soil samples to determine where manure rows had been located. Using the commercially available EI equipment, Eigenberg was able to locate them in a fraction of the time. He tracked nutrient movement over a four-year period and found that using equipment such as the EI meter can determine nutrient buildup and movement to help prevent nitrate leaching into groundwater.
ARS is the U.S. Department of Agriculture's chief scientific research agency.
http://www.sciencedaily.com/releases/2004/10/041011075626.htm
Thermal Superconductivity In Carbon Nanotubes Not So 'Super' When Added To Certain Materials
Superb conductors of heat and infinitesimal in size, carbon nanotubes might be used to prevent overheating in next-generation computing devices or as fillers to enhance thermal conductivity of insulating materials, such as durable plastics or engine oil. But a research team at Rensselaer Polytechnic Institute has discovered that the nanotubes' role as thermal superconductors is greatly diminished when mixed with materials such as polymers that make up plastics.
"Carbon nanotubes are superior thermal conductors by themselves. But, that doesn't mean they will exhibit the same level of high conductivity when integrated into other materials," says Pawel Keblinski, assistant professor of materials science and engineering and head of Rensselaer's research team. His team's research is published in this month's issue of Nature Materials.
A global team of researchers was optimistic when a one-percent fraction of carbon nanotubes was added to epoxy and other organic materials, and the thermal conductivity of the newly created composites increased two- or threefold. But, using conventional engineering estimates, Keblinski noted that the composites' conductivity should have had 50-fold increases.
Why such disparity between the experiment and the expectations?
"Atoms forming stiff carbon nanotubes vibrate at much higher frequencies than the atoms in the surrounding material. This leads to high interfacial resistance for the heat flow between the tubes and the other elements," Keblinski says.
Energy exchange between two different elements is immediate and plentiful when frequencies in both are similar. Interfacial resistance happens when the frequencies are different, and the heat energy has a difficult time taking the leap from one element to the next.
To test the magnitude of the problem, Keblinski and his Rensselaer collaborators performed computer simulations on a model nanotube composite. Meanwhile, another research group headed by David Cahill at the University at Illinois at Urbana Champaign, heated real carbon nanotubes with a laser.
From the rate of cooling, in both the simulation and the physical experiment, the researchers derived the value of the interfacial resistance. In both instances, they found the resistance is so high that it limits the thermal conductivity of the nanotubes
One way to reduce the interfacial resistance in such nanocomposites is to induce a stronger bond between the nanotube and other materials to make it easier for heat to cross from one element to the next. However, extensive bonding may distort the original nanotube structure that allows the tubes to be a superconductor of heat in the first place.
Still, Keblinski is optimistic about the use of carbon nanotubes to improve insulating materials. "By adding a small fraction of carbon nanotubes to such materials, we can still increase the thermal as well as electrical conductivity. So, although we may have to lower our expectations, we have not given up hope quite yet that nanotubes will improve materials for a number of applications," Keblinski says.
http://www.sciencedaily.com/releases/2003/11/031112072719.htm
"Carbon nanotubes are superior thermal conductors by themselves. But, that doesn't mean they will exhibit the same level of high conductivity when integrated into other materials," says Pawel Keblinski, assistant professor of materials science and engineering and head of Rensselaer's research team. His team's research is published in this month's issue of Nature Materials.
A global team of researchers was optimistic when a one-percent fraction of carbon nanotubes was added to epoxy and other organic materials, and the thermal conductivity of the newly created composites increased two- or threefold. But, using conventional engineering estimates, Keblinski noted that the composites' conductivity should have had 50-fold increases.
Why such disparity between the experiment and the expectations?
"Atoms forming stiff carbon nanotubes vibrate at much higher frequencies than the atoms in the surrounding material. This leads to high interfacial resistance for the heat flow between the tubes and the other elements," Keblinski says.
Energy exchange between two different elements is immediate and plentiful when frequencies in both are similar. Interfacial resistance happens when the frequencies are different, and the heat energy has a difficult time taking the leap from one element to the next.
To test the magnitude of the problem, Keblinski and his Rensselaer collaborators performed computer simulations on a model nanotube composite. Meanwhile, another research group headed by David Cahill at the University at Illinois at Urbana Champaign, heated real carbon nanotubes with a laser.
From the rate of cooling, in both the simulation and the physical experiment, the researchers derived the value of the interfacial resistance. In both instances, they found the resistance is so high that it limits the thermal conductivity of the nanotubes
One way to reduce the interfacial resistance in such nanocomposites is to induce a stronger bond between the nanotube and other materials to make it easier for heat to cross from one element to the next. However, extensive bonding may distort the original nanotube structure that allows the tubes to be a superconductor of heat in the first place.
Still, Keblinski is optimistic about the use of carbon nanotubes to improve insulating materials. "By adding a small fraction of carbon nanotubes to such materials, we can still increase the thermal as well as electrical conductivity. So, although we may have to lower our expectations, we have not given up hope quite yet that nanotubes will improve materials for a number of applications," Keblinski says.
http://www.sciencedaily.com/releases/2003/11/031112072719.htm
Optical Electronic Devices Could Benefit From New Semiconductor Standard
2006 was indeed a banner year for portable related consumer electronics. Apple released a new generation of iPods, Microsoft debuted a direct competitor to the iPod in the Zune and every other major MP3 player manufacturer was showcasing unique products as well. Portable DVD players continued to be popular and kids electronics became more creative as alternatives to expensive electronics for your children. For some ideas on the best portable electronics in 2006, read on.
1. Apple iPod
The fifth generation of the Apple iPod proves once again why Apple is at the top of the MP3 player heap. It is available in a 30GB model for $249 and an 80GB model, which holds up to 20,000 songs or 100 hours of video, for $349. It offers gapless music playback and new search and scroll functions for more quickly finding music selections. It can also support playback of popular video games downloaded from the iTunes Store for a fee. Other features of the new iPod 5G (video) include up a longer battery life, body color choices of black or white, a 2.5-inch color and the ability to display photos.
A wide range of optical electronic devices, from laser disk players to traffic lights, may be improved in the future thanks to a small piece of semiconductor, about the size of a button, coated with aluminum, gallium, and arsenic (AlGaAs).
The 1-centimeter square coating, just 3 micrometers thick, is the first standard for the chemical composition of thin-film semiconductor alloys issued by the National Institute of Standards and Technology (NIST). Standard Reference Material (SRM) 2841 was requested by the compound semiconductor industry to help measure and control thin film composition as a basis for optimizing material and device properties. The SRM can be used to calibrate equipment for making or analyzing these materials. Buyers are expected to include companies that grow or characterize thin films or use them to make devices, as well as government and university laboratories.
AlGaAs is used as a barrier material to increase conductivity in high-speed circuits for wireless communication; semiconductor lasers for optical disk drives, bar code scanning, xerography, and laser surgery; and light-emitting diodes for remote controls, traffic lights, and medical instruments. The NIST standard is expected to increase the accuracy of chemical characterization of AlGaAs films by an order of magnitude over the current state of the art. Improved accuracy will reduce wasteful duplication of reference wafers, increase the free exchange of thin-film materials between vendors and their customers, and ultimately improve the accuracy of data on relationships between material composition and properties.
http://www.sciencedaily.com/releases/2006/10/061012184139.htm
1. Apple iPod
The fifth generation of the Apple iPod proves once again why Apple is at the top of the MP3 player heap. It is available in a 30GB model for $249 and an 80GB model, which holds up to 20,000 songs or 100 hours of video, for $349. It offers gapless music playback and new search and scroll functions for more quickly finding music selections. It can also support playback of popular video games downloaded from the iTunes Store for a fee. Other features of the new iPod 5G (video) include up a longer battery life, body color choices of black or white, a 2.5-inch color and the ability to display photos.
A wide range of optical electronic devices, from laser disk players to traffic lights, may be improved in the future thanks to a small piece of semiconductor, about the size of a button, coated with aluminum, gallium, and arsenic (AlGaAs).
The 1-centimeter square coating, just 3 micrometers thick, is the first standard for the chemical composition of thin-film semiconductor alloys issued by the National Institute of Standards and Technology (NIST). Standard Reference Material (SRM) 2841 was requested by the compound semiconductor industry to help measure and control thin film composition as a basis for optimizing material and device properties. The SRM can be used to calibrate equipment for making or analyzing these materials. Buyers are expected to include companies that grow or characterize thin films or use them to make devices, as well as government and university laboratories.
AlGaAs is used as a barrier material to increase conductivity in high-speed circuits for wireless communication; semiconductor lasers for optical disk drives, bar code scanning, xerography, and laser surgery; and light-emitting diodes for remote controls, traffic lights, and medical instruments. The NIST standard is expected to increase the accuracy of chemical characterization of AlGaAs films by an order of magnitude over the current state of the art. Improved accuracy will reduce wasteful duplication of reference wafers, increase the free exchange of thin-film materials between vendors and their customers, and ultimately improve the accuracy of data on relationships between material composition and properties.
http://www.sciencedaily.com/releases/2006/10/061012184139.htm
Compound insulates wires and cables
Comprised of base compound with catalyst masterbatch that promotes cross-linking, halogen-free Megolon[R] XLi710 insulates wires as small as 1 mm[sup.2] and complies with BS7211 specification for thermosetting cable insulation rated to 450/750 V. Activated by heat and water, compound is fire-retardant as well as chemical and abrasion resistant. It is suited for range of cables including copper data and telecommunication, optic fiber data, RF, and energy cables.
Windsor, Connecticut - September 19, 2005….Scapa Polymerics has introduced Megolon[R] XLi710 for wires and cables used in public facilities. Megolon Xli710 is a cross-linking, halogen free, fire retardant insulation grade compound used to insulate and sheath a wide range of cables including copper data and telecommunication, optical fiber data, radio frequency, energy and special fire survival cables.
On exposure to fire or high temperatures, Megolon compounds are difficult to ignite and generate only small amounts of pale smoke whereas PVC cables emit dense black smoke after only 3 minutes. This allows emergency exits to remain visible longer for safe evacuation. Megolon compounds are ideal for use in underground railways, airports, power stations, shopping centers and passenger ships.
Megolon XLi710 has been developed to comply with the BS7211 specification for thermosetting cable insulation rated to 450/750 volts. The material is comprised of a base compound with a catalyst masterbatch that promotes cross-linking. Designed using silane technology, Xli710 combines excellent electrical and fire retardant properties with outstanding extrusion to produce a proven stable compound with reliable consistency of performance. Activated by heat and water, Xli710 eliminates the need for cable manufacturers to invest in expensive e-beam equipment.
This cross-linkable grade possesses not only superior temperature performance and enhanced tensile strength, but also increased chemical and abrasion resistance. It can be used to insulate wires as small as 1mm[sup.2]http://www.electronics-automation.com/articles/
Industrial VFD Cables suit AC motor drive applications
Offered in 5 sizes from 1-4/0 AWG, Large AWG Symmetrical VFD cables feature 3 stranded XLPE TC circuit conductors, 2 spiral copper tape shields for flexibility and EMI/RFI noise protection, and 3 symmetrical bare copper ground wires. Signal Pair VFD Brake Cables, comprised of 16-8 AWG VFD cables, feature 3 stranded XLPE TC circuit conductors, full size insulated green/yellow ground wire, dual (foil/braid) shield for EMI/RFI noise reduction, and signal pair for brake.
RICHMOND, IN - Belden CDT Electronics Division, a world leader in the development of specialty cable products for the industrial, commercial, broadcast and residential markets, announces the expansion of its line of Variable Frequency Drive (VFD) cables for industrial AC motor drive applications. Line additions include five Large AWG Symmetrical VFD cables and five new Signal Brake Pair VFD cables. The new cables supplement Belden’s classic line of 16 to 2 AWG flexible VFD cables.
In industrial settings, VFD cables are used to carry power from AC drive systems to AC motors. In doing so, they are subjected to the high power levels of pulse-width modulated (PWM) signals, and also to extreme voltage. Voltage extremes can lead to a corona discharge between the cable’s conductors, damaging not only the cabling, but the motors, bearings, drives and related equipment. This can result in drive failure and costly production downtime. Conventional VFD cabling solutions, such as armored cable and lead wire conduit, are cumbersome and difficult to install and do not solve noise and corona discharge problems. Belden’s full line of VFD cables were designed and engineered to overcome these challenges.
The Belden series of VFD cables now includes:
- Large AWG VFD Cable with Symmetrical Design. The new 1 to 4/0 AWG cables feature three stranded XLPE TC circuit conductors and two spiral copper tape shields that improve flexibility and EMI/RFI noise protection. Three symmetrical bare copper ground wires provide a balance ground system to reduce AC motor shaft voltage, which reduces the likelihood of premature motor bearing or insulation failure. The large VFD cables are designed for use on larger, more powerful AC motor drives.
- Signal Pair VFD Brake Cables. Belden’s new 16 to 8 AWG VFD cables feature three stranded XLPE TC circuit conductors plus a full size insulated green/yellow ground wire, a dual (foil/braid) shield for effective EMI/RFI noise reduction, plus a signal pair for brake. The cables are round and smooth to allow proper sealing of glands and molding applications.
- Classic Series VFD Cables. Belden’s classic line of VFD cables, offered in 16 to 2 AWG, continues to be the highest performing solution in the market. Oversized XLPE insulation provides the lowest capacitance available in a VFD cable and highly effective dual (foil/braid) shielding offers effective EMI low frequency and RFI high frequency noise protection. The cables also include a full-sized insulated green/yellow ground wire, plus they are round and smooth to allow proper sealing of glands and molding applications.
All of Belden’s VFD 1000V UL flexible motor supply cables meet applicable industry standards and offer the robust construction required for superior electrical performance and reliability in the most demanding industrial environments. Thicker, industrial-grade XLPE insulation provides lower capacitance and more stable electrical performance and heavy-duty PVC jackets ensure oil and sunlight resistance. Belden VFD cables are tested and approved for use in Rockwell Automation AC drives and are also suitable for use with drives from other major manufacturers.
Tantalum Capacitors come in miniature T case size
Featuring max height of 1.2 mm, TLJ Series enriches audio in miniature applications such as PDAs, mobile phones, and digital camera modules by producing clear filtering, piezoless, deep bass performance. RoHS-compliant devices operate over -55 and +125[degrees]C range, providing capacitance versus voltage ratio of 220 [micro]F 4 V in miniature 1411 footprint. They also offer capacitance tolerance of [+ or -]20%.
TLJ Series capacitors enriches sound quality in miniature device applications…
Myrtle Beach, S.C. (February 8, 2007) - AVX Corporation, a leading manufacturer of advanced passive components, has extended its TLJ Series tantalum capacitor family to include a miniature T case size. Known for its high capacitance versus voltage ratio, the TLJ Series is designed to enrich audio performance in miniature applications such as PDAs, mobile phones, MP3 players and digital camera modules.
The TLJ increases the sound quality by producing a clear filtering, piezoless, deep bass performance for low frequency miniature devices.
“The TLJ Series tantalum capacitor is the first on the market to offer this capacitance value in a T case size,” said Dan Lane, AVX Tantalum Marketing Manager. “Until now, because of space constraints, designers were limited to coupling capacitors with a range up to 100[micro]F, resulting in limited performance in the low frequency spectrum.
Displaying a maximum height of 1.2mm, the TLJ tantalum capacitor offers a capacitance versus voltage ratio of 220[micro]F 4V in a miniature 1411 footprint. The capacitor also delivers a capacitance tolerance of [+ or -]20% and an operating temperature range between -55[degrees]C and +125[degrees]C. Complying with RoHS requirements, the TLJ Series provides 3x reflow, 260[degrees]C peak temperature lead-free assembly systems.
The TLJ Series is also available in standard EIA case sizes A, B, C D and the low profile W.
Typical pricing for the TLJ T case size tantalum capacitor starts at $0.65 in quantities of 10,000 pieces with a lead time of stock to 14 weeks.
Motor Driver offers crossover-current circuit protection
BSD-02 single-axis microstepping driver is suitable for driving bipolar and unipolar step motors from 50 mA to 2.5 A and up to 30 V. Amount of heat dissipated in switching IC is reduced by using 8 external discrete Schottky diodes. Driver can operate in Full-, Half-, Quarter- or Eighth-Step without requiring phase-sequence tables, high frequency control lines, or complex interfaces to program. It can be connected directly to microcontroller or PC and adjusted with on-board potentiometer.
What makes this driver different from others isour unique approach to transfer the heat from IC to a large heat sink.
Also, we were able to reduce the amount of heat dissipated in switching IC by
using eight (8) external discrete Schottky diodes (often not found on other drivers). This way we
ended up with the driver that barely needs any forced air cooling and it still costs less.
In most applications additional cooling fan will not be necessary (see user manual), what saves more money and simplifies design.
The BSD-02 module is a complete single-axis microstepping driver suitable for driving bipolar and unipolar step motors from 50mA to 2.5A and up to 30V. Requires only single power supply.
Driver can operate in one of the 4 stepping modes: Full-, Half-, Quarter- or Eighth- Step without requiring any phase-sequence tables, high frequency control lines or complex interfaces to program. Easy to use STEP/DIRECTION inputs require simple TTL signals. Can be connected directly to the microcontroller or PC
if common safety guidance are followed. Driver can be easily adjusted to virtually any motor up to 2.5A by adjusting on- board potentiometer. It may be used to drive bipolar as well as unipolar motors, 6- and 8-wire types. It will not drive 5-wire motors.
Features
o +/- 2.5A, 30V Output Rating
o Eight external Schottky diodes on board
o Crossover-Current Circuit Protection
o Under-Voltage Lockout Protection
o Thermal Shutdown Protection
o Automatic Current-Decay Mode
o Enable and Sleep Inputs
o Built-in Translator
o Translator Home State Output
o Reduced audible motor noise
o Increased step accuracy
o Low Quiescent Current (10mA MAX)
o Single power supply
o Small footprint 2.75″x2.75″
http://www.electronics-automation.com/articles/
Circuit Breakers feature arc flash protection
Offered in 3 frame sizes from 800-5,000 A, WL Circuit Breakers feature integrated racking handles, pull apart front-mounted terminal blocks, and modular accessories. Dynamic Arc-Flash Sentry detects worker approaching energized equipment and automatically lowers trip time of breaker, minimizing potential arc-flash energy. Extended Instantaneous Protection accommodates 100% of full withstand rating of frame while allowing breaker to be applied to max interrupting rating.
ATLANTA (August 4, 2005) - Siemens Energy & Automation has expanded its line of WL Circuit Breakers with the new WL UL 489 family of insulated case circuit breakers available in three frame sizes, 800-5000 Amps. The new WL Circuit Breakers are efficient and easy to use with features such as integrated racking handles, pull apart front-mounted terminal blocks and modular accessories. The breakers have two new and exclusive features that distinguish them from their competitors and offer a safer and more reliable circuit breaker: Dynamic Arc-Flash Sentry technology and Extended Instantaneous Protection.
Due to Siemens’ unique Dynamic Arc-Flash Sentry (DAS) technology, the WL UL 489 offers a pioneering approach to arc-flash protection, meeting the stringent safety requirements of NFPA 70E. The WL UL 489 breaker, when used with an appropriate safety-rated sensing device, detects a worker approaching the energized equipment. The DAS technology then automatically lowers the trip time of the breaker and thus reduces the potential arc-flash energy. DAS capability is available on Siemens’ Electronic Trip Units 755 and 776 and can be implemented on all frames in the WL 489 circuit breaker family as well as on the current WL ANSI family.
The second new and exclusive feature is Siemens` Extended Instantaneous Protection, which accommodates 100 percent of the full withstand rating of the frame while still allowing the breaker to be applied up to the maximum interrupting rating. The WL overcomes the limitations of typical power circuit breakers by providing full withstand capability and full coordination with a minus 0% short-time band tolerance up to 85kA on frame Size II and 100kA on frame Size III.
The introduction of a new smaller size, Frame Size 1, presents increased flexibility when space is a concern. Further flexibility is offered due to the front mounted plug-in accessories that are common to the entire WL line and the field-upgradeable trip units, which allow the user make last-minute adaptations as necessary.
Reliability of the WL circuit breaker is assured with the highly accurate internal Rogowski CTs that deliver precision protection and metering with accuracy to within 1 percent. In addition, the WL 489 circuit breaker can keep in touch with the user through MODBUS or PROFIBUS communications modules, informing the user of breaker, switch, meter, relay and motor control functions. A front-panel, ready-to-close visual indicator confirms several breaker conditions are met before closing the panel giving the user peace of mind.
1st Circuit: PROTECTION OF WITNESS ISN’T DUE PROCESS RIGHT
Police failure to protect a prosecution witness from violence falls short of a violation of due process rights, the 1st Circuit Court of Appeals held.
Due process protections come into play only when the government “has played a role in creating the danger or has enhanced the danger to an individual,” the court said.
Iris Rivera filed a federal suit on behalf of her 15-year-old daughter, Jennifer, a prosecution witness murdered to prevent her testimony about a homicide near her home.
The Rivera family claimed the state of Rhode Island, the city of Providence, and the Providence Police Department bore the responsibility for their failure to protect Jennifer from harm.
Several days before a trial was to begin, Jennifer was shot dead in front of her house to stop her from testifying that she saw Charles Pona, the defendant in the trial, fleeing from the scene of a murder in August 1999.
Jennifer’s mother filed a federal lawsuit alleging the police had violated Jennifer’s constitutional substantive due process right to life by failing, after promising to do so, to protect Jennifer from the danger posed by the murder suspect if she agreed to testify against him.
The civil rights lawsuit named Providence Police Chief Urbano Prignano for failing to train and properly supervise his officers; and the city for having a policy and practice of not protecting endangered witnesses who were given assurances of protection.
Providence police detectives confirmed they had been repeatedly informed of the death threats made against Jennifer and promised to protect her.
But the circuit panel said Jennifer did not have a constitutional right to protection as a witness and consequently could make no claim against the government or any officer.
The three-judge panel said there is a split among the circuits on whether the government can be held responsible for witness protection. At least three circuit courts-the 6th, 7th and 9th-”have recognized the existence of a constitutional violation when, on particular facts, the state fails to protect against private violence under this state created danger theory.”
The 5th Circuit “has flatly rejected the theory” and the 4th Circuit has discussed the theory without rendering an interpretation, the 1st Circuit panel said.
Subscribe to:
Posts (Atom)