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A four-tether silicon microthermocycler for point-of-care PCR analytical systems is proposed. Substituting the commonly employed platinum with titanium in the fabrication of thin film resistance temperature detectors and heaters enabled the realization of a smaller device without compromising temperature accuracy or increasing heater lead power losses. The device was extensively analyzed through analytical modeling and FEM numerical simulations using a 3-D thermo-mechanical simulation model in COMSOL. Numerical simulations revealed that the four-tether design provides a 460% improvement in mechanical strength and a 57% reduction in the thermal time constant compared with a similar three-tether design, with a trade-off of a 22% increase in heat losses. Detailed structural and thermal analyses of crucial design parameters guided the optimization of the final geometry, leading to the successful fabrication of prototypes. It was shown that the current of 60 mA was sufficient to heat the fabricated solid and hollow silicon structure to 132 °C and 134 °C in 10 s for an applied heater power of 510 mW and 525 mW, respectively. [ABSTRACT FROM AUTHOR]

A four-tether silicon microthermocycler for point-of-care PCR analytical systems is proposed. Substituting the commonly employed platinum with titanium in the fabrication of thin film resistance temperature detectors and heaters enabled the realization of a smaller device without compromising temperature accuracy or increasing heater lead power losses. The device was extensively analyzed through analytical modeling and FEM numerical simulations using a 3-D thermo-mechanical simulation model in COMSOL. Numerical simulations revealed that the four-tether design provides a 460% improvement in mechanical strength and a 57% reduction in the thermal time constant compared with a similar three-tether design, with a trade-off of a 22% increase in heat losses. Detailed structural and thermal analyses of crucial design parameters guided the optimization of the final geometry, leading to the successful fabrication of prototypes. It was shown that the current of 60 mA was sufficient to heat the fabricated solid and hollow silicon structure to 132 °C and 134 °C in 10 s for an applied heater power of 510 mW and 525 mW, respectively.

An alternative method was developed to determine the thermal time constant of a relatively cumbersome temperature sensor in still oil. A relationship between the take‐off gradient, initial temperature, thermal time constant, and final steady‐state temperature was deduced. An experiment was then performed using a Pt100 temperature sensor to test the veracity of the relationship. The Pt100 temperature sensor was subjected to five different step changes in temperature from an initial temperature of 60 °C. This resulted in five exponential curves with five different take‐off gradients. The linearization method was used to determine the thermal time constant as a control experiment. The new method was then applied to the same data set. It agrees very well with the linearization method within the limits of experimental error. [ABSTRACT FROM AUTHOR]

We report the first detailed study of the diurnal thermal structure of upper mesosphere/lower thermosphere (∼80 to 160 km) of Mars from stellar occultation observations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Due to stray light contamination, analyses of this data set to date have been confined to the nighttime events. This study makes use of a revised algorithm for removal of stray light from occultation spectra to retrieve the dayside events as well. The dayside is observed to be warmer than the nightside, with the maximum day/night difference of ∼30 K in the lower thermosphere, ∼20 K around the mesopause, with little diurnal variations at lower altitudes. This is consistent with the radiative time constant which is of the order of 1 Mars day in the 3×10−4 $3\times {10}^{-4}$ to 3×10−3 $3\times {10}^{-3}$ Pa region. The data also shows that the regions at pressure less than 2×10−3 $2\times {10}^{-3}$ Pa are under strong solar control with no prominent migrating tidal signatures. In contrast, on Earth, the radiative time constant near the mesopause is ∼10 Earth days and the temperature variations due to tides are quite large. The Mars Climate Database shows a diurnal trend opposite to the data in the mesosphere, with the dayside mesopause predicted to be cooler than the nightside by ∼10 K along with signatures of a vertically propagating tide. The IUVS data set provides an unprecedented constraint on the structure of the Martian mesosphere. Plain Language Summary: The dayside Mars Atmosphere and Volatile EvolutioN/Imaging Ultraviolet Spectrograph stellar occultation observations are often contaminated by stray light and are not processed by the current data reduction pipeline. We have developed an improved algorithm to retrieve these dayside events as well, therefore expanding the usable data set. There have been very few observations of Mars in 80–160 km altitude range, a region that is influenced by the wave perturbations from lower atmosphere and solar forcing from above, with no data set providing a complete local time coverage to study the day/night differences. Therefore, we have enabled the first detailed study of the diurnal thermal structure of Mars in this region by salvaging the dayside events. We find the dayside atmosphere to be always warmer than the nightside at these altitudes. Though it is expected but has not been established for the Martian mesosphere. In contrast, the Mars Climate Database shows an opposite diurnal trend at the mesopause, along with inconsistent tidal signatures with the data. The mesopause is controlled by the energy balance between radiative processes. These data‐model inconsistencies thus imply that our current understanding of the dynamics and structure of the Martian mesosphere is inadequate and this data set can provide important constraints on the models. Key Points: First detailed study of the diurnal thermal structure of Mars for 10−5−10−2 ${10}^{-5}-{10}^{-2}$ Pa pressure levels from 3003 stellar occultationsDayside is observed to be warmer than the nightside at these pressure levels with no detectable migrating tidal signaturesGCM predictions are inconsistent with the data and show dayside mesopause cooler than the nightside, with a vertically propagating tide [ABSTRACT FROM AUTHOR]

Graphene resonant sensors have shown strong competitiveness with respect to sensitivity and size. To advance the applications of graphene resonant sensors, the damage behaviors of graphene harmonic oscillators after thermal annealing and laser irradiation were investigated by morphology analysis and frequency domain vibration characteristics. The interface stress was proven to be the key factor that directly affected the yield of resonators. The resulting phenomenon could be improved by appropriately controlling the annealing temperature and size of resonators, thereby achieving membrane intactness of up to 96.4%. However, micro-cracks were found on the graphene sheets when continuous wave (CW) laser power was more than 4 mW. Moreover, the fluctuating light energy would also cause mechanical fatigue in addition to the photothermal effect, and the threshold damage power for the sinusoidally modulated laser was merely 2 mW. In this way, based on the amplitude-frequency surface morphology of the graphene resonator, the thermal time constant of the order of a few microseconds was confirmed to evaluate the damage of the graphene oscillator in situ and in real time, which could be further extended for those resonators using other 2D materials. [ABSTRACT FROM AUTHOR]

Blood‐contaminated fingermarks are significant evidence for forensic investigators in high‐profile cases providing a direct link between the suspect and the crime. Although these marks are often visible, blood enhancement techniques are operationally used to recover maximal ridge detail. The standard protein dye‐staining procedure includes a chemical blood‐fixing step, which requires an initial, prolonged drying period, for natural coagulation to occur. However, in special cases, when it is crucial to detect forensic traces quickly, there is a need to speed up the enhancement process. This study explored, both theoretically and empirically, the use of heat as an alternative method to the standard chemical fixing. Three consecutive experiments were conducted in which blood‐contaminated fingerprints were deposited on different types of surfaces (car parts, glass, and flooring tiles), and heated for different periods, prior to development by amido black solution. The results showed that heat was successful in fixing blood, while the required temperature and heating durations, were inversely proportional. This observation was in correlation with theoretical heat‐transfer data, calculated by the Lumped Heat Capacity model, also demonstrating the impact of the thermal time constant of each surface, on the conditions required for the full fixing of blood. The experimental findings led to a design of a portable, and tailor‐made heating device, examined for the use in crime scenes, allowing to shorten the necessary fixing process from hours to minutes. For future crime‐scene work, this novel approach may be utilized for a rapid blood‐fixing, especially in cases when the scene cannot be preserved. [ABSTRACT FROM AUTHOR]

Radiant system design standards and guidebooks classify radiant systems as a function of their structure and geometry. We assume that design approaches, testing methods, and control strategies of radiant systems can be more clearly described and classified based on thermal parameters. We calculated using computational fluid dynamics method the thermal time con-stants for 66 radiant system cases. We found pipe spacing, thickness and material properties of structural layer have a significant impact on time constant, while operative temperature, water temperature and water flow regime do not. We found time constants of radiant ceiling panels vary between 30-91 s; for embedded surface systems between 0.25-3.5 h; for thermally activated building systems with pipes embedded in the massive concrete slabs, between 2.4-7.7 h; and for capillary pipes embedded in a layer at the inner surface, between 0.1-0.6 h. A preliminary radiant system classification scheme based on thermal time constant is proposed.

The ignition process of a hypergolic hybrid rocket fuel presents a significant challenge due to its complex and interconnected nature. However, understanding its underlying physics is crucial for accurately estimating the delay time and ignition performance. In this study, we employed an approximate analytical method to directly address the transient conduction problem with nonlinear surface heat generation. By using the Arrhenius equation and considering dual heat flux directions in both the liquid and solid domains, we propose a model for determining the delay time of heterogeneous hypergolic ignition. Our solution is straightforward and computationally efficient. Notably, when subjected to identical initial conditions and property settings, our results exhibit similarity with the solutions derived from other models. Moreover, we advance our approach by developing a particle packing model through the utilization of a well-established algorithm. By simulating the particle arrangement within the pellet, the surface layer properties and the thermal time constant of certain fuel designs can be modeled. This simulation serves the purpose of incorporating the particle size effect of the fuel pellet into our ignition model. The results generated by our heterogeneous hypergolic ignition model, in conjunction with the particle packing model, demonstrated impressive agreement with the experimental data derived from droplet tests. This study utilized a novel solving method to address a transient conduction problem with non-linear heat generation on the surface during a heterogeneous hypergolic ignition process. The study successfully derived an analytical solution, providing a simpler method for calculating ignition delay times. A scenario involving different initial temperatures was also examined. Additionally, the research integrated particle packing model data and thermal time constants to assess the effect of particle size. The model results were in agreement with the experimental data, confirming its accuracy and offering a reliable method for estimating the heterogeneous hypergolic ignition delay time. [ABSTRACT FROM AUTHOR]

The decentralized feed-ins from distributed energy resources (DER) represent a significant change in the manner in which the power grid is used. If this leads to high loads on electrical equipment, its aging can be accelerated. This applies in particular with regard to the thermal aging of older generations of power cables, namely paper insulated lead covered (PILC) cables. This type of power cable can still be found frequently in medium voltage (MV) networks. If aging of these cables is significantly accelerated in the presence of DER, distribution system operators (DSO) could face unplanned premature cable failures and a high replacement demand and costs. Therefore, this paper investigates the thermal aging of PILC cables in a MV distribution network benchmark for different load scenarios, using standardized load profiles and representative expansion scenarios for wind power and photovoltaics plants in particularly affected network areas in Germany. A main objective of this paper is to present a methodology for estimating the thermal degradation of PILC cables. An approach is used to draw simplified conclusions from the loading of cables to their conductor or insulation temperature. For this purpose, mainly Joule losses are considered. In addition, thermal time constants are used for the heating and cooling processes. Based on the insulation temperature, thermal aging is determined using the Arrhenius law or the Montsinger rule. However, it is important to note that there is an urgent need for research on reference data in this area. For this reason, the results of the lifetime estimation presented in this paper should only be considered as an approximation if the selected reference data from the literature for the aging model are actually applicable. The lifetime assessment is performed for a highly utilized line segment of the network benchmark. Accordingly, extreme values are examined. Different operational control strategies of DSO to limit cable utilization are investigated. The results show that the expansion of DER can lead to a short but high cable utilization, although the average utilization does not increase or increases only slightly. This can lead to significantly lower cable lifetimes. The possible influence of these temporarily high loads is shown by comparing the resulting cable lifetime with previous situations without DER. It is also shown that DSO could already reduce excessive aging of PILC cables by preventing overloads in a few hours of a year. In addition to these specific results, general findings on the network load due to the influence of DER are obtained, which are of interest for congestion management.

Two-dimensional (2D) Ti 3 C 2 T x MXene materials show great potential in electrochemical and flexible sensors due to their high electrical conductivity, good chemical stability, and special delaminated structure. However, their thermal properties were rarely studied, which remarkably affect the stability and safety of various devices. Here, we fabricated a suspended MXene drum resonator photothermally driven by a sinusoidally modulated laser, measured the thermal time constant by demodulating the thermomechanical motion, and then calculated the thermal conductivity and thermal diffusivity of the MXene film. Experiments show the thermal conductivity of the film increases from 3.10 to 3.58 W/m·K while the thermal diffusivity from 1.06 × 10 -6 to 1.22 × 10 -6 m 2 /s when temperature increases from 300 to 360 K. We also confirm the film thermal conductivity is mainly contributed by phonon transport rather than electron transport. Furthermore, the relationship between the mechanical and thermal properties of the MXene films was disclosed. The thermal conductivity decreases when film strain increases, caused by enhanced phonon scattering and softening of high-frequency phonons. The measurements provide a noninvasive method to analyze the thermal characteristics of suspended MXene films, which can be further extended to the thermal properties of other 2D materials.

Thermal-based germination models are widely used to predict germination rate and germination timing of plants. However, comparison of model parameters between large numbers of species is rare. In this study, seeds of 27 species including 12 C4 and 15 C3 species were germinated at a range of constant temperatures from 5 °C to 40 °C. We used a modified thermal time model to calculate germination parameters at suboptimal temperatures. Generally, the optimal germination temperature was higher for C4 species than for C3 species. The thermal time constant for the 50% germination percentile was significantly higher for C3 than C4 species. The thermal time constant of perennials was significantly higher than that of annuals. However, differences in base temperatures were not significant between C3 and C4, or annuals and perennial species. The relationship between germination rate and seed mass depended on plant functional type and temperature, while the base temperature and thermal time constant of C3 and C4 species exhibited no significant relationship with seed mass. The results illustrate differences in germination characteristics between C3 and C4 species. Seed mass does not affect germination parameters, plant life cycle matters, however.

Abstract Mn 1.2 Co 1.5 Ni 0.3 O 4 ceramic chips with 90, 100, 110 and 120 µm thickness were developed using the tape casting method. The structure, electrical properties and thermal time constant have been investigated as a function of the thickness of the miniature NTC chip thermistors. The ρ 25 increased from 127 to 449.7 Ω cm and the thermal constant B 25/50 increased from 52.8 to 180.5 K as the thickness increased. This could be a result of the increased grain boundary resistance and Mn3+/Mn4+ ratio (0.7–1.02) from the increased thickness. The thermal time constants were 0.83, 0.89, 1.05 and 1.10 s for chip thermistors with thicknesses from 90 to 120 µm, respectively. This reveals that the thickness of chips could affect the thermal time constant, a result of significantly different dissipation constants and heat capacities in MCN thermistors. The proposed sensors demonstrated a superior temporal response. [ABSTRACT FROM AUTHOR]

Non-dispersive infrared- (NDIR-) gas sensors usually consist of a thermal infrared emitter, a tube and a pyroelectric detector with a filter that is transparent to the characteristic wavelength of the gas to be detected. Since pyroelectric sensors are only sensitive to alternating radiation, the radiation must be modulated. This is easiest to achieve by electrical modulation of the emitter. Under this cyclic excitation the thermodynamic properties of the IR source affect the emitted infrared radiation and, in consequence, the sensor signal. Optimal gas sensor operations (e.g. with regard to gas measurement resolution) require to know which factors influence the thermodynamic properties of thermal emitters. In the course of miniaturization and with regard to portable use, gas measuring devices must also become more compact and energy-efficient. Consequently, the radiation source must have low power consumption and high (radiation) efficiency. The heating and cooling curves measured during electrical (square-wave) modulation contain all information about the thermal losses of real emitters and, therefore, about their energy efficiency as well. In this paper, a thermodynamic model of an infrared emitter will be introduced, which also includes all thermal losses (radiation, heat conduction and convection in the filling gas). The comparison of the measured and calculated heating and cooling curves allows to quantify the thermal losses of the emitter and to draw conclusions about its energy efficiency. As a result, this paper reveals that the majority of the electrical energy supplied is dissipated into the filling gas by convection and heat conduction, which significantly reduces the energy efficiency of the radiation source. Vacuum measurements confirm this assumption and support the model. [ABSTRACT FROM AUTHOR]

Due to the high dissipated power densities present in GaN high-electron-mobility transistors (HEMTs) in high-power radio frequency applications, thermal analysis and thermal management of these devices are important in achieving their full potential. In this paper, we present a fundamental study of the transient thermal behavior of GaN HEMTs to aid in understanding the complex contributions of multidimensional thermal spreading, multiple epitaxial layers, multiple gate fingers, and thermal boundary resistance to the temperature rise. This complex behavior cannot be accurately described by one or two thermal time constants. Rather, a broad spectrum of time constants from ~1 ns up to several milliseconds are present in the device due to aggressive multidimensional thermal spreading from the narrow region of power dissipation next to each HEMT gate through the substrate, die attach, and package. In order to accurately model the temperature response, at least one time constant per decade over the timescale of interest is required. These findings are crucial in developing an intuitive understanding of the transient thermal behavior of GaN HEMTs and properly accounting for transient temperature rise in electrothermal modeling of high-power GaN-based amplifiers. [ABSTRACT FROM PUBLISHER]

This paper presents an experimental study of the thermal inertia of a pallet loaded with returnable plastic crates containing primary packages of smoked ham. Based on this, food quality variations within the pallet were also investigated. Thermal time constants from 83 sensor locations were identified by studying the temperature changes when the pallet was exposed to instant temperature drops (16 °C–2 °C) and temperature elevations (2 °C–16 °C). The thermal time constants were used in microbiological prediction models to calculate the maximum difference in shelf life between packages at the two most extreme spots in the pallet unit load, when temperature elevated from 4 °C to a higher temperature (ranging from 4.5 °C to 12 °C), during different periods of time (ranging from 0.5 h to 200 h). The results showed a maximum difference in shelf life of approximately 1.8 days. The identified thermal time constants were also used to calculate the maximum difference in shelf life between packages at the two most extreme spots of a pallet unit load, in a real chilled food supply chain lasting for about 2.5 days. This resulted in a maximum difference of 0.1 days. The results imply that the location of a product in a pallet has a relatively low influence on the product shelf life. This means that a temperature sensor used for calculating the predicted shelf life of a product, can be placed relatively far from the product itself (e.g. on the secondary package or even on the pallet) without jeopardizing the reliability of the resulting shelf-life prediction. However, the results also emphasize the importance of continuous temperature monitoring along the entire chilled food supply chains. [ABSTRACT FROM AUTHOR]

To reduce the influence of temperature distribution of pantograph-catenary system on the electrical contact characteristics, a temperature field simulation model was established with COMSOL Multiphysics software. The validity of the model was verified with lots of temperature experiments. And both thermal time constant and stable temperature rise of contact wire were simulated under flexible contact pressure conditions. The thermal time constant decreases gradually and the stable temperature rise firstly decreases then increases with the increase of sliding speed. The thermal time constant keeps constant and stable temperature rise changes slightly with the increase of contact current. When sliding speed and contact current keep constant, both the thermal time constant and stable temperature rise under flexible contact pressure conditions are smaller than that of under rigid contact pressure conditions. [ABSTRACT FROM AUTHOR]

To develop effective control optimization strategies for managing residential electricity consumption in a smart grid environment, predictive algorithms are needed that are simple to implement, minimize custom configuration, and provide sufficient accuracy to enable meaningful control decisions. This paper presents a self‐learning algorithm for predicting indoor temperature in a single-family residence using a first-order lumped capacitance (1R1C) model that can be used to evaluate the consequences of energy saving or load shifting strategies on thermal comfort. The algorithm is formulated in such a way that key design details such as window size/configuration, thermal insulation, and airtightness (all major factors that affect heat loss and solar heat gain) are combined into effective parameters that can be learned from observation. This approach eliminates the need for a custom configuration for each residence. The model was validated using experimental data from the National Institute of Standards and Technology (NIST) Net-Zero Energy Residential Test Facility. It was found that with a simple temperature decay test to determine a thermal time constant and a seven-day sliding window of training data to account for seasonal variations in other parameters, the algorithm can reliably predict indoor temperatures for a 24 h period using a solar irradiance forecast, an outdoor air temperature forecast, and heat pump output. The average root mean square temperature prediction error was found to be 2.2%. [ABSTRACT FROM AUTHOR]

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Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bolometer detector is one of thermal detectors. In this research the essential concepts and parameters are included which cover the main types of bolometer detectors. But the actual values of parameters used here in simulation are adopted from [7] for semiconductor bolometer. This detector operates for all optical wavelengths of different sources. From analysis and results obtained, it is shown that minimum and maximum values of specific Detectivity D* for cryogenic temperatures from 0.5 K to 10 K are 0.25~10 / and 5 ~ 10 / , respectively and the values between them when the incident radiation frequency is 100 Hz.. It is seen that for frequency greater than 1Hz, the specific Detectivity increases rapidly which means that the bolometer detector will respond for high frequencies in a manner more speed than that of low frequencies. It is found that as the value of Ąth is increased, the temperature change in detector sensor is decreased. That is decreasing Ąth enhance the performance of bolometer detector. It is found that the responsivity of this detector follow its output voltage which in turn follow the bolometer temperature change.

With the vigorous development of new nanodevices and nanomaterials, improvements in the quantitation and resolution of the measurement of nanoscale energy transport/conversion phenomena have become increasingly important. Although several new advanced methods for scanning thermal microscopy (SThM) have been developed to meet these needs, such methods require a drastic enhancement of SThM probe performance. In this study, by taking advantage of the characteristics of micromechanical structures where their mechanical stability is maintained even when the film that composes the structures becomes extremely thin, we develop a new design of SThM probe whose tip is made of ultra-thin SiO 2 film (~100 nm), fabricate the SThM probes, and demonstrate experimentally that the tip radius, thermal time constant, and thermal sensitivity of the probe are all improved. We expect the development of new high-performance SThM probes, along with the advanced measurement methods, to allow the measurement of temperature and thermal properties with higher spatial resolution and quantitative accuracy, ultimately making essential contributions to diverse areas of science and engineering related to the nanoscale energy transport/conversion phenomena. [ABSTRACT FROM AUTHOR]

A new technique for characterizing the thermal properties of heat-assisted magnetic recording media (HAMR) using pulsed near-field heating recording with a static tester is reported. It has the advantage over traditional recording techniques of enabling studies of the 1–100 ns transient thermal configurations rather than only thermal steady states. The technique is applied to HAMR media with different heatsink thicknesses. While each media has a different steady-state temperature profile, the heatsinking differences are eliminated or enhanced by tuning the pulse duration for each media. The technique is used to extract thermal properties of the media. [ABSTRACT FROM PUBLISHER]