nanotube sheets stealthier submarines

Two years ago, Chinese scientists coated one side of a flag with a thin sheet of nanotubes, then played a song using the flapping sheet-coated flag as a speaker. It was a demonstration of flexible speaker technology, in which nanotubes can be made to generate sound waves via a thermoacoustic effect – every time an electrical pulse is sent through the microscopic layer of nanotubes, it causes the air around them to heat up, which in turn creates a sound wave. Now, an American scientist has taken that technology underwater, where he claims it could allow submariners to detect other submarines, and to remain hidden themselves.

Research scientist Ali Aliev, of the University of Texas at Dallas, has determined that the low-frequency sound waves created by carbon nanotube sheets can be used by sonar systems to determine the location, depth, and speed of underwater objects. Aliev and his team also determined that the sheets could be tuned to transmit specific frequencies that would cancel out certain noises... noises such as those that a submarine makes while passing through the water, for instance.

One obstacle that Aliev had to overcome was the fact that the sheets do not do well in direct contact with water. The sheets can oxidize when in contact with water at high temperatures, the high surface tension and vibrational frequency of water causes the nanotubes to bundle into acoustically-poor ropes, and ocean water can cause the sheets to short circuit. On the plus side, however, the hydrophobic (water-repellent) nature of the sheets causes an air envelope to form around the nanotubes, which in turn acts as a kind of resonating chamber for the sound waves, boosting their strength.

Be that as it may, the sheets still needed to be protected from the water. In order to do so, Aliev encapsulated them in thin, flat gas-filled containers with acoustically-transparent windows. As with the air envelopes, the resonance that resulted from the sound waves being generated in such an enclosed space proved to be a benefit – the encapsulated sheets were actually ten times more effective at transmitting low-frequency sound underwater than non-encapsulated sheets.

The researchers also experimented with stacking the sheets several deep, but found that this negatively affected the desired thermoacoustics. The optimum arrangement turned out to be a layer of just two separated sheets, which received their electrical pulses alternately instead of simultaneously.

The research has just been published in the journal Nano Letters.

Semiconductors promises better LEDs

One of the biggest challenges in creating a better light-emitting diode (LED) is the search for a way to efficiently extract the light generated in the semiconductor device into the surrounding air, while avoiding the internal light reflection that is cause for a considerable waste of energy. A team of Japanese researchers have recently managed to achieve just that, in what is believed to be a huge step toward significantly more energy-efficient LEDs.

All of the materials currently used for the production of LEDs are characterized by a high refractive index. Air, by contrast, has a very low refractive index. According to the laws of optics, this means that when light is extracted from the one to the other, a vast portion of the light emitted by the semiconductor will be inevitably reflected back into the semiconductor, where it usually degenerates into heat.

The portion of light that is wasted is indeed very substantial. When a light-emitting semiconductor is deposited on a flat surface, it is only possible to extract a small percentage (~2 percent with gallium arsenide, ~4 percent with gallium nitride) of the total light generated. Researchers have therefore gone out of their way to avoid this waste of energy by trying to maximize the portion of the light that is released outward, leading to higher-efficiency devices.

Some of the strategies used so far to counter the unwanted reflection include embedding the device in a hemispheric package, so that the light rays strike its surface perpendicularly; the addition of an anti-reflective coating; designing the LED so that it will reabsorb and re-emit the reflected light (a process known as photon recycling); creating random roughness in the reflective surface with so-called moth-eye patterns; and even using nano-imprint lithography to create billions of tiny holes in the device to allow more photons out.

While all these techniques have led to some improvement, the one developed by the Japanese research team is by far the most promising yet, as it allows for an astounding 50 percent of the light to be extracted. They managed to do so by fabricating narrow ridges on the semiconductor surface, and then coating them with a layer of silicon dioxide (SiO2), whose refractive index is lower than that of the semiconductor.

The improved efficiency is due to the double coupling of so-called "evanescent waves" – a special kind of light existing only in the vicinity of the reflection interface – generated at two interfaces. Two evanescent waves are generated symmetrically on the two sidewalls of a ridge upon the total reflection of light. Coupling of these two evanescent waves occurs when they meet at the flat plane at the top of the ridge, and allows the evanescent waves to be efficiently transformed into light that propagate into the air.

The results were obtained on GaAs/AlGaAs-based materials, which emit light outside the visible spectrum. The team is now working on enhancing light-extraction efficiency in materials used in visible LEDs, such as AlGaInP-based and GaN-based materials, and to develop visible LEDs capable of high-efficiency light extraction.

The research was carried out by the National Institute of Advanced Industrial Science and TechnologyNanosystem Research Institute. The study was in part financed by the Japan Society for the Promotion of Science. (AIST) and its

Current Compensated Ring Core Power Chokes by TDK-EPC

TDK-EPC has released a new sample kit of EPCOS current-compensated ring core power chokes designed for a voltage of 250 V AC with current capabilities of between 0.4 and 6.0 A. The EMC components have inductance between 0.2 and 39 mH. The power chokes of the series B82721 are designed for suppression of common-mode interference in compact switch-mode power supplies as well as converters of all types.

The new series is capable of suppressing symmetrical interference, thanks to their stray inductance of about 1 percent of the rated inductance. The sample kit contains a selection of available types in horizontal with dimension of 17.9 x 17.3 x 12.6 mm3 (L x W x H) and vertical versions with dimension of 18.2 x 13.2 x 20.3 mm3 (LxWxH). The new series are in compliance with UL, VDE and RoHS.
 source  

New Power MOSFET Products by RENESAS

Renesas Electronics has released three new power MOSFET products, the RJK0210DPA, RJK0211DPA, and RJK0212DPA, designed for DC/DC converters that area used in such application as general point-of-load, base stations, computer servers as well as notebook PCs. The new power MOSFET are capable of controlling the voltage conversion circuits of the CPU and memory, like being used as a step-down circuit for converting the 12-volt voltage supplies by a battery to 1.05 V for use by CPU. The new products achieve approximately 40% lower figure of merit (FOM), on-state resistance times gate charge in comparison to the company’s existing products, resulting in reduction of power loss during the voltage conversion.

Furthermore, the new power MOSFET feature a voltage tolerance of 25 V and maximum current of 40 amps (A) RJK0210DPA, 30 A for the RJK0211DPA and 25 A for the RJK0212DPA device. The new MOSFET uses company’s WPAK package measuring 5.1 x 6.1 mm and 0.8 mm thick. The underside of the device has a die pad allowing heat to pass to the printed wiring board while the MOSFET is operating, allowing the power MOSFET to handle large current. Samples of all three MOSFET are currently available with mass production to commence in December of 2010, with a planned monthly production of 2,000,000 units by July 2011.

JESD204A CGV Fast track your design

Reduce board space, design time and costs while improving conversion performance

Next generation precision electronic instruments are using higher input and output sampling frequencies, while evolving air interfaces place increasing performance and low power demands on data converters. Synchronized serial digital data interfaces are the key for tomorrow's data acquisition applications - helping to simplify your design, reduce board space and improve conversion performance.

The JEDEC JESD204A high-speed serial interface option included in our data converter portfolio meets these important system design requirements. Furthermore, NXP assures interoperability with SERDES-based FPGAs from Altera, Lattice and Xilinx, when used with the JESD204A IP blocks sourced from these suppliers. So you can now fast track your designs for communications, instrumentation, medical and aerospace systems.
The optimal balance between linearity and power dissipation

Our conversion solutions deliver wide analog bandwidth and an optimal balance between linearity and power dissipation. This ensures the best possible signal fidelity in both receive and transmit paths between the antenna and the digital baseband processor in wireless infrastructure equipment.

To improve ease-of-use in light of increasing design complexity, NXP has worked with key base station OEMs and other partners to develop the JESD204A standard. The JESD204A interface has several technical merits, including the use of 8B / 10B coding which yields a DC balanced signal (allowing the data transmission line to be ac-coupled capacitively, inductively or optically), and in-band control characters to establish and maintain lane synchronization. JESD204A includes an optional data scrambling protocol which can reduce or eliminate spurs in the analog spectral domain caused by periodic digital data patterns.

Improve data acquisition while keeping RF and digital circuitry securely isolated

In our advanced DACs and ADCs, the serial digital signals on the JESD204A lanes are optionally scrambled and sample-synchronized irrespective of physical length. This enables new system architectures in which the RF circuits are securely isolated from the digital circuits while maintaining high data acquisition performance.

In addition to outstanding performance, aerospace applications require extended environmental operating robustness. NXP has proven capabilities in extended temperature ceramic package device characterization and qualification, and can offer radiation hardened (rad hard) qualification services to aerospace customers.

Keep your images free from noise and enhance cost competitiveness

Medical imaging applications are typically judged by image quality and the speed at which images are generated. Dynamic range and signal-to-noise ratio are the fundamental quality metrics in these systems. Ideal for demanding medical imaging, NXP's high-speed data converters combine high SFDR / SNR, support for high input frequencies and sampling rates, with high functional integration and low power dissipation.

Serial interface data converters reduce development cost and BOM cost without sacrificing analog performance. JESD204A-based converters enable higher converter density on a fixed-sized PCB, due to the smaller device package size and relaxed routing constraints enabled by this new industry standard. Thus higher capability next generation medical imaging equipment can be offered in current form factor enclosures.

Maximize dynamic range across all your operating temperatures

The exceptional dynamic performance, low power dissipation, optional input buffer and multi-lane JESD204A-compliant data interface is a unique and powerful combination of features for the diverse industrial and instrumentation equipment application segments.

NXP's new ADCs and DACs include an embedded and user-transparent self-calibration scheme that ensures a maximum 2 dB SFDR fluctuation across operating temperature (-40°C to +85°C). The DAC1408D also supports the optional JESD204A MDS feature, enabling data streams from several DACs to be sample synchronized and phase coherent. Among other benefits, this simplifies development of quadrature sampling test equipment.

New Raven controller PS3

The controller is probably the gamers’ most important tool. The controller that was first released for the original PlayStation back in December 1994 has remained largely unchanged in design through the release of the PS2 and the current PS3 to become a classic and instantly recognizable to gamers the world over. Despite its iconic status, some PS3 gamers prefer the feel of the the Xbox controller in their hands and, while there are plenty of third-party controllers floating around, there are few that cater to this market 

 Online Store Available Product

Raven Motion Sensing Wireless Controller for PS3 (Alternate Layout) US$34.99.

Maybe it’s my oversized paws or the fact that I purchased an Xbox before a PS2, but I have to admit I have always preferred the slightly larger controller available for Microsoft’s consoles – the S, not the bulky original Xbox controller. Although I own both a PS3 and an Xbox 360, that preference has often been a deciding factor in opting for a multi-platform title on the 360 over the PS3 version. Nyko’s Raven controller could help even the playing field by providing a distinctly Xbox-like controller for Sony’s console.

Like the Xbox controller, Nyko’s Raven sports a bit more bulk to wrap your mitts around than the PS3’s DualShock controller and swaps the positions of the directional pad and left analogue thumbstick around. The stumpy triggers of Sony’s DualShock controller have also posed problems for yours truly by providing a less than adequate surface area in particularly intense gaming moments, so the Raven’s angled triggers that are designed to keep fingers from slipping off also sound like a welcome addition. The Raven features the full array of buttons and a Soft Feel surface covering its entire body. It also comes with full multi-axis motion and rumble support.

The only downside is the use of USB dongle for wireless communication instead of Bluetooth like the DualShock, but with a range of 25 feet (7.6m) it’s only a minor annoyance. The built-in lithium-ion battery provides up to 25 hours of game time and can be recharged through any Mini USB cable or Nyko’s Charge Base 2.

Of course, gaming controllers are a personal preference and many are happy with their DualShock controllers just the way they are, thank you very much. In the future maybe Nyko will bring out a controller for the Xbox 360 fashioned after that iconic design to appeal to those gamers.

 Online Store Available Product

Raven Motion Sensing Wireless Controller for PS3 (Alternate Layout) US$34.99.

LED Contest

LED Contest is back! We're happy about this because we love LEDs and we know that many of you out there love them as well. So let's see what awesome ideas are out there with a contest!

The rules are super-simple. In fact, there's just one rule to be aware of: to enter the contest your Instructable must involve at least one LED. That's it. Your project can be very small or truly epic, it just needs to involve LEDs in some way.

For prizes we are once again teaming up with the cool folks at Phenoptix. First prize includes everything you need to build two kits: the floodlight and the MR16. To make it even better we're throwing in a custom laser-etched Leatherman Juice and our Instructables Prize Pack which includes a one-year Pro membership, t-shirt, and more! Runners-up will get the MR16 kit and the Instructables Prize Pack.

So what are you waiting for? Get out your LEDs and make something great!

• Multiples entries are accepted, but each entrant can only win one prize
• International entries are accepted

ECC802S Shunt Regulated Push-Pull Tube Preamplifier

If you are into audio electronic projects have a look at this ECC802S Shunt Regulated Push-Pull Tube Preamplifier. One thing about these tube amp builds is that the housing looks just as nice as the circuit construction.

 Thanks Gio.

“After the success with the various Odd Block amplifiers that used a SRPP (shunt-regulated PP) driver stage I started to do some research and modeling on a SRPP. The advantages of such a line stage are much the same as those when a SRPP is used as a driver. Good linearity, low distortion, low impedance output, good power supply noise rejection and modest gain.”

Microscope reveals water's murky secrets

Some burning questions have just got to be answered, no matter the substantial costs involved. One such question demanding attention is: can a laser pointer be used to examine the microscopic contents of a drop of water? Happily, the answer is yes, and without the aforementioned prohibitive expense. In this home experiment, a laser pointer was shone through a drop of water collected from the base of a potted plant and the magnified image projected on an opposing wall. Read on to see a video showing a bemused-looking cat watching the resulting light show.

The DIY experiment featured here was spawned after a mosquito's enlarged image could be seen in the distant view dot of a laser pointer's beam. Much forum discussion followed, which eventually led to a member placing a 250mW green laser pointer on top of a book and shining its light through a drop of water collected from the bowl of a six year-old spider plant, and then filming the resulting light show on the opposite wall. The drop of water was pushed out of a syringe to the point just before the surface tension gave way to falling water.

 The opposite wall hosted a light show reminiscent of a concert at San Francisco's Fillmore Auditorium in the late 1960s: 

The drop of water acts as a small spherical lens and as the light beam passes through, refraction causes a magnified image to appear on the wall beyond. The shadows of microbial life dotting around the wall can clearly be seen dancing, feeding and apparently battling it out in the spooky green pool of light. Similar setups using pond water liquid lenses have yielded monstrous images of such microscopic organisms as mosquito larvae, water fleas and paramecium.

Okay, so it's not exactly cutting-edge nano-science, but it does makes compelling viewing nonetheless.

fuel cells could be powered Mitochondria

In Back to the Future, the Mr. Fusion cold fusion device could produce electricity from food scraps. Well, cold fusion is still some ways off (depending on who you talk to), but powering electronics with food may not be. Shelley Minteer, a Professor of Chemistry at Saint Louis University in Missouri, announced this Wednesday the development of a biofuel cell that could be powered by sugars or fats like those found in soda pop or vegetable oil. The device incorporates mitochondria, which are found within the cells of our own bodies, where they serve to produce energy from ingested calories. Are you listening, Doc Brown?

 In their creation of the first-ever mitochondria biofuel cell, Minteer and her St. Louis team sandwiched a thin layer of mitochondria between two electrodes, one of which was gas-permeable. In a living organism, mitochondria use a chemical called pyruvate, formed from the digestion of sugar and fats, to produce another substance called adenosine triphosphate (ATP), which stores energy until the body needs it. They perform a similar function in the biofuel cell, which has successfully produced electricity using sugar and cooking oil byproducts as fuel.

"This is the first demonstration of a new class of biofuel cells," said Minteer. "When further developed, these devices have the potential for replacing disposable and rechargeable batteries in a wide variety of consumer electronics and other products. It is the first such device based on one of the microscopic parts of the billions upon billions of cells that make up the body."

Scientists have designed other types of biofuel cells in the recent past, including ones that produce electricity via enzymes and bacteria.