Thousand Oaks, CA, United States
Thousand Oaks, CA, United States

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Semenic T.,Teledyne Scientific and Imaging | You S.M.,University of Texas at Arlington
Heat Transfer Engineering | Year: 2013

To minimize flow boiling instabilities in two-phase heat sinks, two different types of microporous coatings were developed and applied on mini-and small-channel heat sinks and tested using degassed R245fa refrigerant. The first coating was epoxy based and was sprayed on heat sink channels, while the second coating was formed by sintering copper particles on heat sink channels. Minichannel heat sinks had overall dimensions 25.4mm 25.4mm 6.4mm and 12 rectangular channels with a hydraulic diameter 1.7mm and a channel aspect ratio of 2.7. Small-channel heat sinks had the same overall dimensions, but only three rectangular channels with hydraulic diameter 4.1mm and channel aspect ratio 0.6. The microporous coatings were found to minimize parallel channel instabilities for minichannel heat sinks and to reduce the amplitude of heat sink base temperature oscillations from 6C to slightly more than 1C. No increase in pressure drop or pumping power due to the microporous coating was measured. The minichannel heat sinks with porous coating had on average 1.5times higher heat transfer coefficient than uncoated heat sinks. Also, the small-channel heat sinks with the best porous coating had on average 2.5times higher heat transfer coefficient and the critical heat flux was 1.5 to 2times higher compared with the uncoated heat sinks. © 2013 Copyright Taylor and Francis Group, LLC.


Knez I.,Rice University | Knez I.,IBM | Du R.-R.,Rice University | Sullivan G.,Teledyne Scientific and Imaging
Physical Review Letters | Year: 2012

We present an experimental study of S-N-S junctions, with N being a quantum spin Hall insulator made of InAs/GaSb. A front gate is used to vary the Fermi level into the minigap, where helical edge modes exist. In this regime we observe a ∼2e2/h Andreev conductance peak, consistent with a perfect Andreev reflection on the helical edge modes predicted by theories. The peak diminishes under a small applied magnetic field due to the breaking of time-reversal symmetry. This work thus demonstrates the helical property of the edge modes in a quantum spin Hall insulator. © 2012 American Physical Society.


Knez I.,Rice University | Du R.-R.,Rice University | Sullivan G.,Teledyne Scientific and Imaging
Physical Review Letters | Year: 2011

We present an experimental study of low temperature electronic transport in the hybridization gap of inverted InAs/GaSb composite quantum wells. An electrostatic gate is used to push the Fermi level into the gap regime, where the conductance as a function of sample length and width is measured. Our analysis shows strong evidence for the existence of helical edge modes proposed by Liu et al. Edge modes persist in spite of sizable bulk conduction and show only a weak magnetic field dependence-a direct consequence of a gap opening away from the zone center. © 2011 American Physical Society.


Spanton E.M.,SLAC | Spanton E.M.,Stanford University | Nowack K.C.,SLAC | Nowack K.C.,Stanford University | And 5 more authors.
Physical Review Letters | Year: 2014

Quantum spin Hall devices with edges much longer than several microns do not display ballistic transport; that is, their measured conductances are much less than e2/h per edge. We imaged edge currents in InAs/GaSb quantum wells with long edges and determined an effective edge resistance. Surprisingly, although the effective edge resistance is much greater than h/e2, it is independent of temperature up to 30 K within experimental resolution. Known candidate scattering mechanisms do not explain our observation of an effective edge resistance that is large yet temperature independent. © 2014 American Physical Society.


Knez I.,IBM | Rettner C.T.,IBM | Yang S.-H.,IBM | Parkin S.S.P.,IBM | And 3 more authors.
Physical Review Letters | Year: 2014

We observe edge transport in the topologically insulating InAs/GaSb system in the disordered regime. Using asymmetric current paths we show that conduction occurs exclusively along the device edge, exhibiting a large Hall signal at zero magnetic fields, while for symmetric current paths, the conductance between the two mesoscopicly separated probes is quantized to 2e2/h. Both quantized and self-averaged transport show resilience to magnetic fields, and are temperature independent for temperatures between 20 mK and 1 K. © 2014 American Physical Society.


Cai Q.,Teledyne Scientific and Imaging | Chen C.-L.,Teledyne Scientific and Imaging
Journal of Heat Transfer | Year: 2010

With the increase in power consumption in compact electronic devices, passive heat transfer cooling technologies with high-heat-flux characteristics are highly desired in microelectronic industries. Carbon nanotube (CNT) clusters have high thermal conductivity, nanopore size, and large porosity and can be used as wick structure in a heat pipe heatspreader to provide high capillary force for high-heat-flux thermal management. This paper reports investigations of high-heat-flux cooling of the CNT biwick structure, associated with the development of a reliable thermometer and high performance heater. The thermometer/heater is a 100-nm-thick and 600 μm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2×2 mm 2 wick area. As a heater, it provides a direct heating effect without a thermal interface and is capable of high-temperature operation over 800°C. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation versus temperature after the annealing process is applied. The thermally oxidized layer on the silicon substrate is around 1-μm-thick and pinhole-free, which ensures the platinum thermometer/heater from the severe CNT growth environments without any electrical leakage. For high-heat-flux cooling, the CNT biwick structure is composed of 250 μm tall and 100 μm wide stripelike CNT clusters with 50 μm stripe-spacers. Using 1×1 cm 2 CNT biwick samples, experiments are completed in both open and saturated environments. Experimental results demonstrate 600 W/cm 2 heat transfer capacity and good thermal and mass transport characteristics in the nanolevel porous media. © 2010 by ASME.


Du L.,Rice University | Knez I.,Rice University | Knez I.,IBM | Sullivan G.,Teledyne Scientific and Imaging | Du R.-R.,Rice University
Physical Review Letters | Year: 2015

We have engineered electron-hole bilayers of inverted InAs/GaSb quantum wells, using dilute silicon impurity doping to suppress residual bulk conductance. We have observed robust helical edge states with wide conductance plateaus precisely quantized to 2e2/h in mesoscopic Hall samples. On the other hand, in larger samples the edge conductance is found to be inversely proportional to the edge length. These characteristics persist in a wide temperature range and show essentially no temperature dependence. The quantized plateaus persist to a 12 T applied in-plane field; the conductance increases from 2e2/h in strong perpendicular fields manifesting chiral edge transport. Our study presents a compelling case for exotic properties of a one-dimensional helical liquid on the edge of InAs/GaSb bilayers. © 2015 American Physical Society.


Daneshgar S.,University of California at Santa Barbara | Daneshgar S.,University of California at San Diego | Griffith Z.,Teledyne Scientific and Imaging | Seo M.,Sungkyunkwan University | Rodwell M.J.W.,University of California at Santa Barbara
IEEE Journal of Solid-State Circuits | Year: 2014

We report 50 GSamples/s track-hold amplifier (THA) and sample-hold amplifier (SHA) designed and fabricated in a 250 nm InP double heterojunction bipolar transistor (DHBT) technology. Because the base-emitter junction reverse breakdown voltage is low in the process technology employed, the circuits use a base-collector junction diode as the switching element in the signal path. Operating with - 5 V and - 2.5 V supplies, the THA achieves > +16 dBm input-referred third-order intercept (IIP3) at signal frequencies below 22 GHz, while the SHA achieves IIP3> +17 dBm for 2-22 GHz inputs. © 1966-2012 IEEE.


Knez I.,Rice University | Du R.R.,Rice University | Sullivan G.,Teledyne Scientific and Imaging
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We have studied experimentally the low-temperature conductivity of mesoscopic size InAs/GaSb quantum well Hall bar devices in the inverted regime. Using a pair of electrostatic gates we move the Fermi level into the electron-hole hybridization state, observing a mini gap and Van Hove singularity at its edge. Temperature dependence of the conductivity in the gap shows a residual conductivity, which can be consistently explained by the contributions from the free as well as the hybridized carriers in the presence of impurity scattering, as proposed by Naveh and Laikhtman, [Europhys. Lett. 55, 545 (2001)]. Experimental implications for the stability of proposed quantum spin Hall helical edge states will be discussed. © 2010 The American Physical Society.


News Article | April 29, 2015
Site: www.techtimes.com

The Defense Advanced Research Projects Agency (DARPA) of the Department of Defense is moving forward with its goal to develop a self-steering bullet that can change its direction in mid-air to hit a moving target. DARPA has released a new video demonstrating the accuracy of the Extreme Accuracy Tasked Ordnance (EXACTO) bullet, a 0.50-caliber round equipped with the ability to keep its target well within its sights and hit it right on the mark all the time. The bullet is being developed by Thousand Oaks, California-based Teledyne Scientific and Imaging in a project funded by DARPA. The video shows the EXACTO bullet used in a live-fire test where expert snipers trained in the use of the special bullet hit a moving target during all of the seven tries. It also shows a novice marksman accurately hitting a moving target using the EXACTO bullet. "True to DARPA's mission, EXACTO has demonstrated what was once thought impossible: the continuous guidance of a small-caliber bullet to target," says Jerome Dunn, DARPA program manager, in a statement. "This live-fire demonstration from a standard rifle showed that EXACTO is able to hit moving and evading targets with extreme accuracy at sniper ranges unachievable with traditional rounds." DARPA does not provide details of how the bullet keeps track of its target. However, it does say that the .50-caliber bullet, about the size of a Sharpie marker, is equipped with a guidance system that allows it to track it's target's location at all times and change its course if that target moves. DARPA also says that EXACTO takes into consideration changeable factors such as wind movement, weather, and the target's movement. One of DARPA's biggest challenges was fitting the entire guidance system into such a small package, making the feat of cramming it all into a .50-caliber bullet a milestone in itself. "Fitting EXACTO's guidance capabilities into a small .50-caliber size is a major breakthrough and opens the door to what could be possible in the future," Dunn says. Such an extremely accurate bullet is useful for soldiers in combat by providing increased sniper effectiveness, especially in conditions marked by high winds or dusty terrains. EXACTO also offers better safety for troops by allowing a greater shooter standoff range and less time engaging with targets.

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