Passive Temperature Research Articles

Assembly and Packaging Technologies for High-Temperature and High-Power GaN Devices

This paper gives a detailed analysis on the assembly and packaging technologies for the state-of-the-art GaN-based high-electron-mobility transistors, which are suitable for high-temperature and high-power applications. Silver sintering and transient liquid phase bonding were selected as die-attachment techniques, and gold and palladium were investigated for electrical interconnection materials. Both the die-attachments were characterized for their high-temperature stability up to 450 °C. Systematic electrical characterizations were performed from on-wafer measurements to the final assembly. The thermal and thermomechanical influences of the assembly were assessed. For die-attachments and interconnections, passive temperature shock cycling and active power cycling were performed as an initial attempt to characterize the assembly reliability. Finally, a complete package along with the base plate was proposed, which can survive high temperatures up to 480 °C.

Passive temperature compensation in hydraulic dashpot used for the shut-off rod drive mechanism of a nuclear reactor

Passive temperature compensating hydraulic dashpot has been studied numerically as well as experimentally in this paper. Study is focused on reducing the clearances of the hydraulic dashpot at elevated temperature which intern compensates for the reduction in viscosity of damping oil and the dashpot gives uniform performance for wide range of temperature variation. Temperature compensation effects are mainly due to difference in the thermal expansion of materials. Different combinations of materials are used to reduce the dashpot clearances at elevated temperature. Finite element commercial code COMSOL Multiphysics 5.1 has been used for numerical analysis. Fluid-structure analysis has been carried-out to study the thermal expansion and pressure generated in the hydraulic dashpot. Multiphysics study with solid mechanics, laminar flow and moving mesh interfaces has been carried-out. Thermal expansion results of study-1 (solid mechanics) are further extended in to study-2 (laminar flow and moving mesh) and dashpot pressure is estimated. These results show that bimetallic strip improves the dashpot performance at 55°C but do not fully compensate beyond that and less severe impacts occurs. Specific combinations of design and materials have been presented in this paper for obtaining maximum temperature compensation. A novel passive temperature compensating hydraulic dashpot design has been presented, which is suggested for use over wide range of temperature change without much variation in the damping performance.

Early establishment of trees at the alpine treeline: idiosyncratic species responses to temperature-moisture interactions.

On a global scale, temperature is the main determinant of arctic and alpine treeline position. However on a local scale, treeline form and position vary considerably due to other climatic factors, tree species ecology and life-stage-dependent responses. For treelines to advance poleward or uphill, the first steps are germination and seedling establishment. These earliest life stages may be major bottlenecks for treeline tree populations and will depend differently on climatic conditions than adult trees. We investigated the effect of soil temperature and moisture on germination and early seedling survival in a field experiment in the French Alps near the local treeline (2100 m a.s.l.) using passive temperature manipulations and two watering regimes. Five European treeline tree species were studied: Larix decidua, Picea abies, Pinus cembra, Pinus uncinata and Sorbus aucuparia In addition, we monitored the germination response of three of these species to low temperatures under controlled conditions in growth chambers. The early establishment of these trees at the alpine treeline was limited either by temperature or by moisture, the sensitivity to one factor often depending on the intensity of the other. The results showed that the relative importance of the two factors and the direction of the effects are highly species-specific, while both factors tend to have consistent effects on both germination and early seedling survival within each species. We show that temperature and water availability are both important contributors to establishment patterns of treeline trees and hence to species-specific forms and positions of alpine treelines. The observed idiosyncratic species responses highlight the need for studies including several species and life-stages to create predictive power concerning future treeline dynamics.

Hot water immersion induces an acute cytokine response in cervical spinal cord injury

The dysfunctional sympathetic nervous system in individuals with cervical spinal cord injury (CSCI) impairs adrenergic responses and may, therefore, contribute to the blunted post-exercise cytokine response. The purpose of this study was to investigate an alternative way to exercise to induce an acute cytokine response by passive core temperature elevation in CSCI. Seven male participants with a motor complete CSCI and 8 male able-bodied controls were immersed for 60min in water set at a temperature 2°C above the individuals' resting oesophageal temperature. Blood was collected pre, post, and every hour up to 4h post-immersion. Hot water immersion resulted in an IL-6 plasma concentration mean increase of 133±144% in both groups (P=0.001). On a group level, IL-6 plasma concentrations were 68±38% higher in CSCI (P=0.06). In both groups, IL-8 increased by 14±11% (P=0.02) and IL-1ra by 18±17% (P=0.05). Catecholamine plasma concentrations were significantly reduced in CSCI (P<0.05) and did not increase following immersion. Passive elevation of core temperature acutely elevates IL-6, IL-8 and IL-1ra in CSCI despite a blunted adrenergic response, which is in contrast to earlier exercise interventions in CSCI. The present study lays the foundation for future studies to explore water immersion as an alternative to exercise to induce an acute cytokine response in CSCI.

Error Correction Method for Passive and Wireless Resonant SAW Temperature Sensor

The resonant surface acoustic wave (SAW) sensors have advantages in the harsh application environments. However, the burst noise in the same frequency range, signal shadowing and a range of weather conditions introduce strong interferences to the wireless measurement system. Inspired by the theory of low-rank matrix completion generalized from the compress sensing, an algorithm suitable for passive wireless SAW temperature sensor system, which requires none of system modeling, probability distribution assumption, and extra sensors to obtain the corrected current frequency, is used to correct errors in the resonant frequency measurement. The proposed method suitable for passive wireless SAW resonant sensor system is employed to correct the frequency estimation errors in the measuring process. The performance and its validity are verified by simulations and experiments.

MO‐AB‐BRA‐03: Calorimetry‐Based Absorbed Dose to Water Measurements Using Interferometry

Purpose:Interferometry‐based calorimetry is a novel technique to measure radiation‐induced temperature changes allowing the measurement of absorbed dose to water (ADW). There are no mechanical components in the field. This technique also has the possibility of obtaining 2D dose distributions. The goal of this investigation is to calorimetrically‐measure doses between 2.5 and 5 Gy over a single projection in a photon beam using interferometry and compare the results with doses calculated using the TG‐51 linac calibration.Methods:ADW was determined by measuring radiation‐induced phase shifts (PSs) of light passing through water irradiated with a 6 MV photon beam. A 9×9×9 cm3 glass phantom filled with water and placed in an arm of a Michelson interferometer was irradiated with 300, 400, 500 and 600 monitor units. The whole system was thermally insulated to achieve sufficient passive temperature control. The depth of measurement was 4.5 cm with a field size of 7×7 cm2. The intensity of the fringe pattern was monitored with a photodiode and used to calculate the time‐dependent PS curve. Data was acquired 60 s before and after the irradiation. The radiation‐induced PS was calculated by taking the difference in the pre‐ and post‐irradiation drifts extrapolated to the midpoint of the irradiation. Results were compared to computed doses.Results:Average comparison of calculated ADW values with interferometry‐measured values showed an agreement to within 9.5%. k=1 uncertainties were 4.3% for calculations and 14.7% for measurements. The dominant source of uncertainty for the measurements was a temperature drift of about 30 µK/s caused by heat conduction from the interferometer's surroundings.Conclusion:This work presented the first absolute ADW measurements using interferometry in the dose range of linac‐based radiotherapy. Future work to improve measurements’ reproducibility includes the implementation of active thermal control techniques.

Synthetic clay as an alternative backing material for passive temperature control of photovoltaic cells

This paper evaluates the operational advantages of using a backing material for photovoltaic modules different than the industry-standard Tedlar. Synthetic clay, composed mostly of gypsum, is investigated to be part of cells backing and has been found to provide passive cooling properties, successfully reducing the operating temperatures of tested cells from 28 °C to 10 °C. The XRD (X-Ray diffraction) and SEM (Scanning Electron Microscopy) microstructural examination, as well as porosity tests have revealed the random pore distribution of the clay and their volumetric stability at high operating temperatures, which is essential in enhancing evaporation. The characterization of IV performance of bare cells compared with ones backed by clay and aluminum revealed the structural and thermal advantages of using clay, while Nyquist plots revealed the independence of cell impedance from the mist of cooling water provided to clay medium, adding an extra 34.6% of power output when the former is compared to reference cells.

A Novel Capacitive Temperature Sensor for Real-Time Monitoring of Temperature in the Silicone Oil Fan Clutch

This paper presents a novel capacitive sensor for real-time monitoring of temperature in the silicone oil fan clutch. The structure of the temperature sensor is designed and fabricated by the Silicon-On-Glass (SOG) process based on the bonding technology. The silicone oil is designed as the temperature sensing materials in the capacitive sensor. The capacitance of the embedded sensor is changing with respect to temperature of the silicone oil fan clutch. Experimental results show that the sensor provides a sensitivity of 27.3fF/°C in the -30 to 40°C range, 58.2fF/°C in the 50 to 110°C rang. It is also demonstrated that the temperature sensitive capacitor can be integrated with a copper inductance antenna and tests as a passive wireless temperature sensor. The resonant frequency of the inductor-capacitor (LC) resonator changes with respect to the changing capacitance. Then temperature changes can be remotely determined towards a frequency spectrum study. Experimental results show that the LC type passive wireless sensor provides a sensitivity of 6.35kHz/°C in the -30 to 110°C range.

Passive and Semi-Passive Wireless Temperature and Humidity Sensors Based on EPC Generation-2 UHF Protocol

This paper proposes passive and semi-passive wireless temperature and humidity sensors based on electronic product code (EPC) global Class-1 Generation-2 UHF communication protocol. The wireless sensors consist of a sensor key chip and off-chip temperature and humidity sensors. The sensor key chip integrates RF/analog front-end circuit, digital baseband processor, nonvolatile memory, on-chip temperature sensor, and sensor interface. The sensor interface connects the off-chip sensors and the sensor key chip. The sensor key chip with the on-chip temperature sensor can operate without battery power (passive mode), and also can co-operate with the off-chip temperature and humidity sensors powered by battery (semi-passive mode). The RF/analog front-end circuit provides the dc power to the sensor key chip and communicates with the interrogator passively. Advanced low-power techniques are adopted to reduce the power consumption of the sensor key chip. The sensor key chip is fabricated in 0.18- $\mu $ m CMOS process. In passive mode, the maximum wireless sensitivity of on-chip sensor is −15.1/−11.2 dBm for reading and sensing operation, respectively, and the temperature sensing error is −1 °C/0.8 °C over operating range from −20 °C to 50 °C. It achieves a reading/sensing distance of over 9.5/6 m with 4-W effective isotropic radiated power (EIRP) by the commercial interrogator. In semi-passive mode, the temperature and humidity sensing distance of off-chip sensors is 2.7 m.

Comparison of Airborne Passive and Active L-Band System (PALS) Brightness Temperature Measurements to SMOS Observations During the SMAP Validation Experiment 2012 (SMAPVEX12)

In this letter, it is shown that spaceborne observations made by the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite agreed closely with the Passive Active L-band System (PALS) brightness temperature acquisitions during the Soil Moisture Active Passive (SMAP) Validation Experiment 2012. The difference between the SMOS and PALS measurements was less than 5 K and 6 K for vertical and horizontal polarizations, respectively, over the relatively homogeneous agricultural areas. These values are less than the SMOS subpixel variability determined from the PALS measurement. This result demonstrated that the measurements obtained in the experiment are scalable to spaceborne brightness temperature observations, are representative of the expected SMAP observations, and will be of value in the development of soil moisture algorithms for spaceborne missions.

A Monolithic CMOS-MEMS Oscillator Based on an Ultra-Low-Power Ovenized Micromechanical Resonator

A fully monolithic complimentary metal-oxide- semiconductor-microelectormechanical systems (CMOS-MEMS) oscillator comprised of an ovenized double-ended tuning fork resonator to enable ultra-low heater power operation of only 0.47 mW over entire temperature span (-40 °C to 85 °C) and a low noise sustaining circuit to achieve low phase noise has been demonstrated in a Taiwan Semiconductor Manufacturing Company (TSMC) 0.35-μm CMOS process. The combination of low thermal conductivity material and high thermal isolation design is the key to attaining ultra-low-power heater operation in a sub-mW level. Passive temperature compensation scheme is also conducted in the proposed CMOS-MEMS resonator by an oxide-metal composite structure, showing a low temperature coefficient of frequency (TC f ) of only +5.1 ppm/°C, which is suited for the use in ovenized oscillator systems. By implementing a constant-resistance temperature control scheme, the frequency drift of the resonator smaller than 120 ppm from -40 °C to 85 °C is demonstrated in this paper, indicating an equivalent TC f smaller than 1 ppm/°C, a record-low value against its CMOSMEMS counterparts. The CMOS-MEMS oscillator operating at 1.2 MHz demonstrates a phase noise of -112 dBc/Hz at 1-kHz offset and -120 dBc/Hz at 1-MHz offset while drawing less than 1.3 mW. The entire power consumption of the ovenized oscillator system is confirmed to be less than 1.8 mW (oscillator + micro-oven), verifying the great potential of low power oven-controlled MEMS oscillators realized in CMOS-MEMS technology.

Concept and Model of a Metamaterial-Based Passive Wireless Temperature Sensor for Harsh Environment Applications

Wireless passive temperature sensors are receiving increasing attention due to the ever-growing need of improving energy efficient and precise monitoring of temperature in high-temperature energy conversion systems, such as gas turbines and coal-based power plants. Unfortunately, the harsh environment, such as high temperature and corrosive atmosphere present in these systems, has significantly limited the reliability and increased the costs of current solutions. Therefore, this paper presents the concept and design of a low cost, passive, and wireless temperature sensor that can withstand high temperature and harsh environments. The temperature sensor was designed following the principle of metamaterials by utilizing closed ring resonators in a dielectric ceramic matrix. The proposed wireless, passive temperature sensor behaves like an $LC$ circuit, which has a temperature-dependent resonance frequency. Full-wave electromagnetic solver Ansys Ansoft HFSS was used to validate the model and evaluate the effect of different geometry and combination of split ring resonator structures on the sensitivity and electrical sizes of the proposed sensor. The results demonstrate the feasibility of the sensor and provide guidance for future fabrication and testing.

Wireless Passive Temperature Sensors Using Integrated Cylindrical Resonator/Antenna for Harsh-Environment Applications

Wireless passive temperature sensors for harsh-environment applications based on cylindrical microwave cavity resonators are presented herein. Slot antennas are integrated with sensors with zero additional volume. The resonant frequencies of the sensors are determined by the dielectric constants of the ceramic materials, which monotonically increase versus temperature. Silicoboron carbonitride (SiBCN) ceramic materials, which are very robust inside harsh environments featuring high temperatures and corrosive gases, are optimized in this paper to reduce dielectric losses and increase sensing ranges and accuracies. A robust interrogation antenna is developed to wirelessly measure the sensors up to 1300 °C. Two sensors based on Si 6 B 1 and Si 4 B 1 ceramics are measured up to 1050 °C and 1300 °C, respectively, with a sensitivity of ~0.78 MHz/°C at 1050 °C. This type of wireless, passive, and robust sensor can be used for many harsh-environment applications, such as gas turbines.

Errors associated with estimating vegetation water content from radar for use in passive microwave brightness temperature algorithms

The Soil Moisture Active Passive Validation Experiment 2012 was conducted as a pre-launch validation campaign for the Soil Moisture Active Passive mission over 6 weeks in June and July 2012. During this campaign, the Passive Active L-Band System (PALS) was flown at a low altitude, providing radar and radiometer measurements that were contained within a single agricultural field. The campaign domain consisted of 55 agricultural fields, where soil moisture was measured coincident to the PALS flight times and measurements of vegetation volumetric water content (VWC) and leaf area index (LAI) were measured weekly. The low-altitude flights allowed for the comparison between measured VWC and LAI for 11 fields to radar parameters derived from the radar backscatter. Only the correlation between the HV backscatter and the soybean VWC was considered strong (|r| > 0.7). All other correlations between the radar parameters and the VWC (or LAI) were moderate (0.3 < |r| < 0.7) or weak (|r|< 0.3). The established relationships between radar parameters and VWC were used in a forward radiation transfer model to estimate H-pol brightness temperature. It was found that the RMSE between the brightness temperatures estimated using the measured VWC was lowest when using the relationship between VWC and LAI (3.9 K for soybeans, 6.8 K for spring wheat, and 9.3 K when all crop data are combined). Despite a lower correlation, the RMSE associated with using the radar vegetation index relationship with VWC was less than when HV was used (7.9 K) for soybeans, which would result in an error in soil moisture estimation of just over 4%. The RMSEs for all other VWC and radar parameter relationships were greater than 10 K.

An Embedded Passive Resonant Sensor Using Frequency Diversity Technology for High-Temperature Wireless Measurement

This paper presents an embedded wireless passive temperature sensor for measurements in high-temperature applications, such as compressors and turbine engines. The performance of the sensor was improved by optimizing its performance parameters. A high-temperature-resistant material was used, and an embedded structure design was introduced to enable the sensor to operate in high-temperature environments. A series <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonant circuit containing a fixed inductance coil and variable capacitance that varies with temperature was embedded in an alumina ceramic substrate using high-temperature cofired ceramic technology. The temperature in the high-temperature environment was detected wirelessly via the frequency diversity of the sensor. Furthermore, the experimental results showed that the sensor can measure temperatures ranging from room temperature to 1000 °C, and the average sensitivity of the sensor is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 2$ </tex-math></inline-formula> KHz/°C.

Wireless Passive Temperature Sensor Realized on Multilayer HTCC Tapes for Harsh Environment

A wireless passive temperature sensor is designed on the basis of a resonant circuit, fabricated on multilayer high temperature cofired ceramic (HTCC) tapes, and measured with an antenna in the wireless coupling way. Alumina ceramic used as the substrate of the sensor is fabricated by lamination and sintering techniques, and the passive resonant circuit composed of a planar spiral inductor and a parallel plate capacitor is printed and formed on the substrate by screen-printing and postfiring processes. Since the permittivity of the ceramic becomes higher as temperature rises, the resonant frequency of the sensor decreases due to the increasing capacitance of the circuit. Measurements on the input impedance versus the resonant frequency of the sensor are achieved based on the principle, and discussions are made according to the exacted relative permittivity of the ceramic and quality factor (Q) of the sensor within the temperature range from 19°C (room temperature) to 900°C. The results show that the sensor demonstrates good high-temperature characteristics and wide temperature range. The average sensitivity of the sensor with good repeatability and reliability is up to 5.22 KHz/°C. It can be applied to detect high temperature in harsh environment.

Lunar regolith thickness estimation using dual frequency microwave brightness temperature and influence of vertical variation of FeO+TiO2

Desiccated lunar regolith emits substantial amount of radiation in microwave region, which can be used to decipher regolith thickness distribution. We have evolved a dual frequency microwave brightness index for the estimation of regolith thickness using simulated passive microwave brightness temperature (TB) expected from Chandrayaan-2 at L (1.25GHz)- and S (2.1GHz)-bands. We used a three-layer model to simulate TB by varying the dominant parameters like bulk density (ρ), dielectric permittivity and FeO+TiO2 (S) content. The inversion of regolith thickness is carried out using simulation of TB for both the frequencies under a variety of ρ and S contents. Subsequently, a first order empirical model for regolith thickness estimation is evolved using a new dual frequency index involving both the TB. Inverted regolith thickness has been shown to be in good agreement with in-situ measurements at Apollo regions, using single (L-band) and dual frequency index. Inverted thickness for the Apollo14 and Apollo17 locations differ from mare and highland region estimation, which is further analysed to elucidate the role of vertical variation of FeO+TiO2 content. With the FeO+TiO2 variation vertically by ±1–2wt%, the first order assessment of estimated regolith thickness is found to vary by ~0.5m and ~1m, respectively, by single- and dual-frequency approaches. Impact basin ejecta (Apollo14) and mare-highland transition region (Apollo17) are probable zones where vertical variation of FeO+TiO2 occurs along with lateral variations. This lateral- and vertical-mixing of FeO+TiO2 may influence the emitted TB from lunar regolith.

Wireless passive high-temperature sensor based on multifunctional reflective patch antenna up to 1050 degrees centigrade

A novel wireless passive temperature sensor based on a reflective patch is demonstrated up to 1050°C herein. This reflective patch acts as a patch resonator (temperature sensor) and an integrated antenna at the same time. The temperature sensing mechanism is the monotonic increase of the dielectric constant of alumina versus temperature, which reduces the resonant frequency of a patch resonator formed on such an alumina substrate. By properly designing the shape and dimensions of the patch, it can also act as a transmit/receive antenna for wireless passive sensing. Therefore, temperatures can be wirelessly sensed by measuring the resonant frequency of the temperature sensor using an interrogation antenna. This temperature sensor uses robust alumina and platinum materials for high-temperature applications. In addition, this wireless passive temperature sensor is simple in mechanical structure and low in profile, with the potential to be in conformal shape. A temperature sensor using this reflective patch was designed, fabricated and tested from 50 to 1050°C in ambient. The resonant frequency of the sensor decreases from 5.07 to 4.58GHz, which corresponds to a dielectric constant change from 9.7 to 11.4 for the alumina substrate. The temperature measurement sensitivity is found to be 0.58MHz/°C at 1050°C. Being wireless, passive, planar and low profile, the proposed high-temperature sensor can be used for various harsh-environment applications.

Passive control of microclimate in museum display cases: A lumped parameter model and experimental tests

Abstract Inappropriate values, large and fast variations of air humidity and temperature could enhance the risks of damages to works of art and to cultural materials hosted in museums. The use of showcases as a microclimate control tool is widely accepted and ever increasing. The microclimate control of the air inside display cases relies on passive means (air-tightness, thermal insulation and inertia, adsorption capacity) or on active means (equipment to heat, cool, humidify, dehumidify the air). This paper only deals with passive type display cases. The aim has been the development and the validation of a lumped parameters model, able to simulate the air temperature and humidity behaviors inside a showcase under different conditions of the museum indoor air. The simulation model allows explicit consideration of the impact (on internal temperature and humidity) of the display case design features, such as size, material properties, air-tightness, etc., and of some other possible passive temperature and/or humidity control systems (added thermal capacity and water vapor adsorption capacity). A re-configurable freestanding showcase has been experimentally tested in a climatic test chamber under different conditions of temperature and humidity. The simulated showcase internal conditions agree well with the experimental ones. Hence, the model may be regarded as a useful simulation tool for new showcase design optimization, operation and maintenance, as well as for assessment of existing ones.

Field survey of overheating problems in Estonian apartment buildings

In Nordic countries overheating problems have not constituted a recognized problem to date. However, modern buildings, typically with larger windows, have changed this situation. New regulations based on Energy Performance of Buildings Directive (EPBD) directive require that overheating problems are controlled and recommend the use of passive cooling measures. EPBD sets that temperature simulations or other verifications are to be used at the design stage. If necessary, passive measures may be supported with active cooling systems to meet the requirements for summer thermal comfort. During this study field measurements were conducted in more than 100 Estonian apartments by recording indoor temperatures from a 3-month period; an overheating assessment and the impact of ventilation, orientation and window size on recorded overheating were studied. Our results show that overheating occurs in the modern buildings where the average room temperature was continuously about 1K higher than in the old buildings. According to the criterion of weighted excess degree hours over+27°C used in Estonian regulation to prevent overheating, no overheating occurred in old apartment buildings, but the criterion was exceeded in 13.7% of the apartments in new apartment buildings. The results showed that, without adequate passive temperature damping measures used, modern buildings were regularly overheated.