Abstract: Over the past several years, the steady reduction in SOFC operating temperatures to the intermediate range of 700~850oC [1] has made it feasible for lanthanum chromite to be supplanted by metals or alloys as the interconnect materials. Compared to doped lanthanum chromite, metals or alloys offer significantly lower raw material and fabrication costs. However, to be a durable and reliable, a metal or alloy has to satisfy several functional requirements specific to the interconnect under SOFC operating conditions. Specifically, the interconnect metal or alloy should possess the following properties: (i) Good surface stability (resistance to oxidation, hot corrosion, and carburization) in both cathodic (air) and anodic (fuel) atmospheres; (ii) Thermal expansion matching to the ceramic PEN (positive cathode-electrolyte-negative anode) and seal materials (as least for a rigid seal design); (iii) High electrical conductivity through both the bulk material and in-situ formed oxide scales; (iv) Bulk and interfacial thermal mechanical reliability and durability at the operating temperature; (v) Compatibility with other materials in contact with interconnects such as seals and electrical contact materials.

Abstract: Leakage power is emerging as a key design challenge in current and future CMOS designs. Since leakage is critically dependent on operating temperature and power supply, we present a full chip leakage estimation technique which accurately accounts for power supply and temperature variations. State of the art techniques are used to compute the thermal and power supply profile of the entire chip. Closed-form models are presented which relate leakage to temperature and VDD variations. These models coupled with the thermal and VDD profile are used to generate an accurate full chip leakage estimation technique considering environmental variations. The results of this approach are demonstrated on large-scale industrial designs.

Abstract: Method and system are disclosed for compensating for color variations due to thermal differences in LED based lighting systems The method and system involves characterizing the LEDs to determine what PWM (pulse-width modulation) is needed at various operating temperatures to achieve a desired resultant color The characterization data is then stored in the microprocessor either in the form of a correction factor or as actual data When an operating temperature that is different from a calibration temperature is detected, the characterization data is used to adjust the PWM of the LEDs to restores the LEDs to the desired resultant color

Abstract: A novel microelectronic gas sensor utilizing carbon nanotubes (CNTs) in a thin-layered Pd/CNTs/n+-Si structure for hydrogen detection has been achieved. The sensor is fabricated on an n-type silicon wafer, which is needed as an ohmic supporting substrate. Multiwalled CNTs were grown selectively on the substrate via catalytic activation with microwave plasma enhanced chemical vapor deposition. The I–V characteristics of the sensor exhibit Schottky diode behavior at room temperature with marked sensitivity or current changes in the presence of hydrogen. Increasing detection sensitivity in hydrogen sensing was observed with increasing operating temperature. The results demonstrate that CNTs configured as a gas sensor has high sensitivity to hydrogen over a wide temperature range. Behaviors of the sensor in the presence of hydrogen and at elevated temperature were discussed. The successful utilization of CNTs in gas sensors may open a new door for the development of novel nanostructure gas-sensing devices.

Abstract: A recuperated gas turbine engine system and associated method employing catalytic combustion, wherein the combustor inlet temperature can be controlled to remain above the minimum required catalyst operating temperature at a wide range of operating conditions from full-load to part-load and from hot-day to cold-day conditions. The fuel is passed through the compressor along with the air and a portion of the exhaust gases from the turbine. The recirculated exhaust gas flow rate is controlled to control combustor inlet temperature.

Abstract: A high-sensitivity In0.6Ga0.4As/GaAs quantum-dot infrared photodetector (QDIP) with detection wave band in 6.7–11.5 μm and operating temperature up to 260 K under normal incident illumination has been demonstrated. The peak detection wavelength shifts from 7.6 to 8.4 μm when the temperature rises from 40 to 260 K. The background limited performance (BLIP) detectivity (DBLIP*) measured at Vb=−2.0 V, T=77 K, and λp=7.6 μm was found to be 1.1×1010 cm Hz1/2/W, with a corresponding responsivity of 0.22 A/W. The high operating temperature is attributed to the very low dark current and long carrier lifetime in the quantum dots of this device. The results show that this QDIP can operate at high temperature without using the large band gap material such as AlGaAs or InGaP as blocking barrier to reduce the device dark current.

Abstract: The Solar Thermal Group at the Australian National University is continuing experimental investigations with solar-driven ammonia-based closed-loop thermochemical energy storage system. The system uses a cavity receiver containing 20 reactor tubes filled with iron based catalyst material, which collects the radiation from a 20m dish solar concentrator. Reliable operation over a range of conditions including cloud transients has been demonstrated. Parallel theoretical investigations have established that maximising the potential for electrical power production from ammonia synthesis reactors, can largely be achieved through appropriate choice of average operating temperature in standard reactors. The possibility of operating the ammonia based system using trough concentrators has also been investigated theoretically, and the preliminary results indicate encouraging energy storage efficiencies in the region of 53%.

Abstract: A system and method for controlling the heat of an ultrasonic transducer is disclosed. In the presently preferred embodiments, the system and method controls the temperature of the transducer by changing operating system parameters based on feedback from temperature sensing elements placed in the transducer. The chosen mutable system parameters may be preset by the construction of the ultrasonic system, under the control of the ultrasonic system user, or a combination of the two. In several exemplary embodiments, the one or more mutable system parameters are altered by an amount proportionate to the difference between the current temperature and a preferred operating temperature. In another exemplary embodiment, the system switches to a lower power imaging mode when the temperature feedback indicates a threshold temperature has been reached.

Abstract: With power density and hence cooling costs rising exponentially, processor packaging can no longer be designed for the worst case, and there is an urgent need for runtime processor-level techniques that can regulate operating temperature when the package’s capacity is exceeded. Evaluating such techniques, however, requires a thermal model that is practical for architectural studies. This paper expands upon the discussion and results that were presented in our conference paper [43]. It describes HotSpot, an accurate yet fast model based on an equivalent circuit of thermal resistances and capacitances that correspond to microarchitecture blocks and essential aspects of the thermal package. Validation was performed using finite-element simulation. The paper also introduces several effective methods for dynamic thermal management (DTM): “temperature-tracking” frequency scaling, localized toggling, and migrating computation to spare hardware units. Modeling temperature at the microarchitecture level also shows that power metrics are poor predictors of temperature, that sensor imprecision has a substantial impact on the performance of DTM, and that the inclusion of lateral resistances for thermal diffusion is important for accuracy.

Abstract: The performance test results of three NEXT ion engines are presented. These ion engines exhibited peak specific impulse and thrust efficiency ranges of 4060 4090 s and 0.68 0.69, respectively, at the full power point of the NEXT throttle table. The performance of the ion engines satisfied all project requirements. Beam flatness parameters were significantly improved over the NSTAR ion engine, which is expected to improve accelerator grid service life. The results of engine inlet pressure and temperature measurements are also presented. Maximum main plenum, cathode, and neutralizer pressures were 12,000 Pa, 3110 Pa, and 8540 Pa, respectively, at the full power point of the NEXT throttle table. Main plenum and cathode inlet pressures required about 6 hours to increase to steady-state, while the neutralizer required only about 0.5 hour. Steady-state engine operating temperature ranges throughout the power throttling range examined were 179 303 C for the discharge chamber magnet rings and 132 213 C for the ion optics mounting ring.

Abstract: Electron transport in a terahertz GaAs/AlGaAs quantum-cascade laser is calculated using a fully self-consistent intersubband scattering model. Subband populations, carrier transition rates, and current densities are calculated and all relevant intra- and interperiod electron–electron and electron–LO-phonon scattering mechanisms are included. Employing an energy balance equation that includes the influence of both electron–LO-phonon and electron–electron scattering, the method also enables evaluation of the average electron temperature of the nonequilibrium carrier distributions in the device. In particular, the influence of the lattice temperature on the degradation of population inversion and device performance is investigated. The threshold currents, electric-field-current-density characteristics, and temperature-dependent performance are in good qualitative and quantitative agreement with measurement in a recent experimental realization [Kohler et al., Nature (London) 417, 156 (2002)]. Calculations indicate that an important mechanism limiting its operating temperature is the increase of leakage current from the injector to low levels in the active region, and this feature should be improved in future designs.

Abstract: Effects of poly ethylene glycol (PEG) addition on the microstructure and CO sensing characteristics of SnO2 thin films prepared by sol–gel method were investigated. Microstructure of SnO2 thin film was drastically developed by the addition of PEG, indicating that the addition of PEG was effective to prevent the agglomeration of SnO2 particles. CO sensitivity of SnO2 thin films increased as PEG content increased, and drastically improved to 565 at operating temperature of 773 K. This result shows about 12 times larger than that of PEG-free SnO2 thin film (48). It is considered that the enhancement of the sensitivity was caused by high surface area of nano-sized SnO2 particles.

Abstract: WO 3 thin film microgas sensor was fabricated with micro-electromechanical system (MEMS) technology and NO 2 gas sensing characteristics were measured. The membrane embedded with Pt interdigitating electrodes and heater was prepared on silicon wafer, its size is 1.4 mm ×1.4 mm. The device is 3 mm ×3 mm in area. The power consumption to maintain the operating temperature of 300 °C is about 75 mW. WO 3 thin films were prepared by magnetron sputtering on the membrane. The deposition parameters and operating temperatures were optimized to obtain the best performance of the WO 3 film in the response to NO 2 gas. The WO 3 thin film deposited at 300 °C and then annealed in air at 600 °C for 4 h shows good sensing characteristics to NO 2 gas at the operating temperature of 250 °C. The film morphology, crystalline phase and chemical composition were characterized through SEM, XRD and XPS.

Abstract: Setting the clock frequency provided to a load circuit as function of the operating temperature and supply voltage of the load circuit, and setting the supply voltage as a function of the operating temperature of the load circuit. The load circuit can be safely operated above the frequency which would be the limit if the load circuit were operating at the maximum test temperature. At the given operating temperature, the supply voltage can be raised to permit even higher frequency operation, or lowered to reduce power.

Abstract: A main heater controller is adapted to control operation of the LCD heater. A temperature controlled override switch is adapted to disable the LCD heater, independent of the main heater controller, upon a temperature reaching a shut-off temperature above a normal operating temperature of the LCD. The temperature controlled switch has a current flow path made of a material whose conductivity is a function of temperature. A cavity in which the temperature controlled switch is located is also provided. The cavity is adapted to transfer heat in air emanating from the LCD heater to the temperature controlled switch.

Abstract: Systems and methods are provided that facilitate the formation of micro-mechanical structures and related systems on a laminated substrate. More particularly, a micro-mechanical device and a three-dimensional multiple frequency antenna are provided for in which the micro-mechanical device and antenna, as well as additional components, can be fabricated together concurrently on the same laminated substrate. The fabrication process includes a low temperature deposition process allowing for deposition of an insulator material at a temperature below the maximum operating temperature of the laminated substrate, as well as a planarization process allowing for the molding and planarizing of a polymer layer to be used as a form for a micro-mechanical device.

Abstract: A method and apparatus maintain the temperature of a automobile battery within a predetermined temperature range even though the ambient temperature is outside of the predetermined temperature range. The apparatus and the method utilize a thermoelectric device that provides lower temperatures on one surface and higher temperature on another surface thereof in response to the direction of an electrical current passing through the device. The thermoelectric device is thermally coupled by a fan, air ducts and a heat transfer structure between the automobile battery and the ambient atmosphere. An electrical circuit having a heat sensor is thermally coupled to the automobile battery and selectively controls the current through the thermoelectric device to maintain the temperature of the automobile battery within the predetermined temperature range.

Abstract: The metal oxide silicon carbide field effect transistor (MISiCFET) sensor has several possible car engine applications, such as an ammonia sensor in selective catalytic reduction (SCR) systems or as a lambda-sensitive device for enhancing catalytic converter efficiency. Both these applications involve closed loop control of the engine and thereby require fast sensors, that is why it is important to investigate the speed of response of the devices. The sensor consists of a SiC-based MOSFET device with a buried channel design and a catalytic gate metal, which makes it sensitive to a wide range of different gases. The selectivity and sensitivity of the sensor to a specific gas depends mainly on the choice of gate metal, its structure and the operating temperature. In this presentation, the speed of response of MISiCFET devices with many different gate metals at several operating temperatures are compared. The tests have been performed in the laboratory using the moving gas outlet (MGO) equipment. The equipment allows two gas outlets to move back and forth under the sensor, which makes it possible to change the atmosphere surrounding the sensor from synthetic air to the test gas quickly. The method is verified by changing the temperature of the device and frequency of the moving gas outlets. The test gas is either ammonia or hydrogen. The time constant of the sensors is shown to be very small; <100 ms when exposing a 25 nm porous Pt sensor to ammonia at 300 8C and <10 ms for a 10 nm TaSix 100 nm Pt device exposed to hydrogen. The temperature is found to have a large influence on the speed of response. The results show that the speed of response is well beyond the current requirements for use in both SCR and lambda control systems, respectively. # 2003 Elsevier Science B.V. All rights reserved.

Abstract: In one embodiment, the present invention recites a temperature control subsystem for use with an air conditioning system. The temperature control subsystem comprises a temperature sensor located in proximity to a heat-generating device disposed within a housing, where the temperature sensor generates data corresponding to the temperature of the heat-generating device. The temperature control subsystem further comprises an air-flow control feature coupled to the housing, whereby the air-flow control feature is configured to regulate the delivery of cooling air to the housing. Cooling air is provided by the air conditioning system. A local control subsystem is coupled to the air-flow control feature to control the air flow of cooling air to the housing so that the air flow is adjustable to correspond to the temperature data received from the temperature sensor.

Abstract: We have designed, fabricated, and tested microwave power limiter based on high-temperature superconductor thin-film technology. The power limiter takes the form of a 50 /spl Omega/ coplanar waveguide transmission line that is reversibly driven from the low-loss superconducting state to the high-loss normal state when the microwave currents within the device exceed a critical value. When operated at 70 K, the power limiter displays very low insertion loss in the nonlimiting state ( 40 GHz), with constant impedance over the entire microwave range. The maximum power transmitted by the device can be engineered by varying the transmission-line dimensions, and can be further tuned once the device has been fabricated by varying the operating temperature. In the over-power state the device continues to pass a portion of the incident signal, although with reduced linearity. Switching times for the power limiter are estimated to be on the order of microseconds or less, based on both pulsed rf measurements and on measurements using a periodic amplitude-modulated drive signal. We expect this device to be useful for protecting high-performance receiver circuits from over-power conditions without limiting the dynamic range or bandwidth of receiver systems.

Abstract: This communication presents a modulated mode of operation for MOSFET gas sensors. A low-power micromachined device allows pulsing the temperature of MOSFET gas sensors with a time constant less than 100ms. Modulating the temperature during the gas exposure modifies the kinetics of the gas reactions with the sensing film. The way the sensor response is modified by the temperature modulation depends on the sensor "history", on the nature of the surrounding gaseous atmosphere, and on the type of materials used as catalytic sensing film. Pulsing the temperature up just after the gas exposure can reduce the recovery time for specific applications, such as for hydrogen detection. Cycling the temperature can allow the discrimination between different gas mixtures. Discrimination was shown for gaseous mixtures of hydrogen and ammonia in air. The results obtained indicate that a "smart" combination of sample and temperature profile could be used to expand the information content in the sensor response. © 2003 Elsevier Science B.V. All rights reserved.

Abstract: Si0.8Ge0.2 thin film was sputtered on an alumina substrate by the RF-sputtering method. After annealing in flowing Ar atmosphere, platinum film, which acts as a catalyst of the combustible sample gas, was further sputtered on half the surface area of SiGe film. The hydrogen-sensing properties were investigated for the development of potential applications of the device structure as a hydrogen sensor that makes use of the thermoelectric (TE) effect. The measurement results indicate that a reliable output voltage signal was successfully realized when the element was exposed to an environment with a certain hydrogen concentration. The operating temperature for the device was around 100°C, and the response and recovery time corresponding to 90% voltage change were both shorter than 50 s on switching the atmosphere from synthetic air to 3% H2. The detectable concentration of the device ranged from 0.01% to 3%. Furthermore, a good selectivity to hydrogen was also exhibited.

Abstract: Apparatus and methods in accordance with the present invention provide self-contained, closed-loop microchannel/electrokinetic pump cooling systems that can be integrated into the microelectronic die and the integrated heat sink to provide microelectronic die cooling. Microchannel/electrokinetic pump cooling systems utilize active cooling technology to reduce thermal gradients and operating temperature of a microelectronic die. This system disclosed here will enhance heat dissipation and provide immediate cooling of localized hot spots within the microelectronic die. This will have the effect of reducing the microelectronic die temperature or spreading the heat internally within the microelectronic die depending on the layout of the microchannels.

Abstract: Quantum cascade lasers emitting at λ ∼ 5µm based on different ac- tive region designs are investigated. Using lattice-matched GaInAs/AlInAs on InP substrates the maximum peak optical power as well as the maximum pulsed-mode operating temperature is enhanced by incorporating AlAs blocking barriers together with strain-compensating InAs layers into the active regions. Further improvement is achieved by employing strain-compensated GaInAs/AlInAs quantum wells for which maximum pulsed-mode operating temperatures in excess of 350K are ob- served. High-reflectivity coated devices mounted substrate-side down show a maxi- mum continuous-wave operating temperature of 194 K. Also the normalized relative intensity noise is investigated. Finally, a comparison trace-gas sensing experiment employing one of the present quantum cascade lasers and a lead-chalcogenide laser is presented. Detecting the P(25) absorption line of CO, higher stability is obtained using a quantum cascade laser.