Thermal Resistance

It directly affects how much current a trace can carry safely without overheating, influencing performance, reliability, and cost. This guide explains how copper thickness impacts current capacity, introduces key industry standards, and provides practical design guidance. Understanding Copper Thickness in PCBs The "Ounce" System Copper thickness is typically measured in ounces per square foot (oz/ft²), a weight-based system that converts to a physical thickness: • 0.5 oz ≈ 0.7 mil ≈ 0.018 mm • 1 oz ≈ 1.4 mil ≈ 0.035 mm • 2 oz ≈ 2.8 mil ≈ 0.070 mm Most standard boards use 1 oz copper, but higher-current applications often require 2 oz or more.

Experiments were conducted to investigate forced convective cooling performance of an air cooled parallel plate fin heat sink with and without circular pin fins between the plate fins. The original parallel plate heat sink was fabricated consist of 9 parallel plates of length 53 mm with cross-sectional area of 1.4 mm in width by 20 mm height for each plate. The second heat sink has the same geometry of original one but with some circular pins between the plate fins. Thermal and hydrodynamics performances of the heat sinks have been assessed from the results obtained for the pressure drop, thermal resistance and overall performance with the free stream air velocity ranging from 4.7 to 12.5 m/s. Results show that the free stream air velocity has a significant effect on the thermal and hydrodynamics performance of the system. With increasing free stream velocity, the heat transfer coefficient increases and consequently the thermal resistance decreases while pressure drop increases due to higher inertial of fluid at higher velocities. Furthermore, at the same free stream air velocity the thermal resistance for the heat sink with circular pin is about 37.7% lower than that of the original heat sink.

In this paper the influence of the surface properties on heterogeneous nucleation of calcium sulphate hemihydrate is investigated. While the roughness of the investigated stainless steel samples was kept constant, the surface properties were varied by direct ion implantation of fluorine, oxygen, hydrogen and neon. The completed fouling tests show that the induction periods of the fluorine and oxygen implanted surfaces were consistently longer than those for the untreated ones, with fluorine implantation producing the longest induction times. On the other hand, the hydrogen and especially the neon ion implanted samples showed significantly shorter induction times than the untreated surfaces. Unfortunately this trend could not be correlated with calculated surface energies measured by the sessile drop contact angle method. The heterogeneous nucleation was determined by plotting ln (induction period) vs. ln -2 (supersaturation ratio), where the supersaturation ratio was varied from 1.65 to 2. A linear relationship between the slope of the heterogeneous nucleation curves and the electro-negativity of the implanted ions was discovered. Furthermore, a clear change-over from mass transfer controlled to reaction controlled fouling can be identified during variation of the flow velocity between 0.125 and 0.200 m/s -i.e. Reynolds numbers between 5400 and 11442. Additionally, it can be clearly seen that the surface properties in the case of mass transfer controlled fouling have less influence than for reaction controlled crystal deposition.

In this paper the influence of the surface properties on heterogeneous nucleation of calcium sulphate hemihydrate is investigated. While the roughness of the investigated stainless steel samples was kept constant, the surface properties were varied by direct ion implantation of fluorine, oxygen, hydrogen and neon. The completed fouling tests show that the induction periods of the fluorine and oxygen implanted surfaces were consistently longer than those for the untreated ones, with fluorine implantation producing the longest induction times. On the other hand, the hydrogen and especially the neon ion implanted samples showed significantly shorter induction times than the untreated surfaces. Unfortunately this trend could not be correlated with calculated surface energies measured by the sessile drop contact angle method. The heterogeneous nucleation was determined by plotting ln (induction period) vs. ln -2 (supersaturation ratio), where the supersaturation ratio was varied from 1.65 to 2. A linear relationship between the slope of the heterogeneous nucleation curves and the electro-negativity of the implanted ions was discovered. Furthermore, a clear change-over from mass transfer controlled to reaction controlled fouling can be identified during variation of the flow velocity between 0.125 and 0.200 m/s -i.e. Reynolds numbers between 5400 and 11442. Additionally, it can be clearly seen that the surface properties in the case of mass transfer controlled fouling have less influence than for reaction controlled crystal deposition.

This paper presents a compact low-power bidirectional current mirror suitable for low-voltage applications. The key element is the use of a CMOS complementary input stage working in subthreshold regime; which allows setting a reduced bias current through the mirror. The circuit was simulated using LTSpice and presents class AB operation with a THD of 1% at 1MHz. The power consumption is close to 3μW as shown by simulations and experimental data from a fabricated prototype using 0.5μm CMOS technology.

A two dimensional lumped parameter model (LPM) which provides the steady state solution of temperatures within axisymmetric single-sided, slotted axial flux generators is presented in this paper. The two dimensional model refers to the heat modelling in the radial and axial directions. The heat flow in the circumferential direction is neglected. In this modelling method, the solid components and the internal air flow domain of the axial flux machine are split into a number of interacting control volumes. Subsequently, each of these control volumes is represented by thermal resistances and capacitances to form a two dimensional axisymmetric LPM thermal circuit. Both conductive and convective heat transfers are taken into consideration in the LPM thermal circuit by using annular conductive and convective thermal circuits respectively. In addition, the thermal circuit is formulated out of purely dimensional information and constant thermal coefficients. Thus, it can be easily adapted to a range of machine sizes. CFD thermal modelling and experimental testing are conducted to validate the temperatures predicted from the LPM thermal circuit. It is shown that the LPM thermal circuit is capable of predicting the surface temperature accurately and potentially replacing the CFD modelling in the axial flux machine rapid design process.

The primary factors that determine the net thermal performance of a window system are its overall heat transfer rate (U-value), its air leakage characteristics and its sun control capability. With managed window systems these basic properties may be drastically altered on an hourly basis as movable insulating and shading devices are deployed over the prime windows. A large building energy analysis computer program, DOE-2, has been modified to model the thermal performance of a variety of window management devices. The deployment of these devices is simulated based upon fixed hourly schedules or the value of critical climatic factors such as solar intensity. Automatic operation may be modeled or manual operation with varying degrees of human fallibility may be simulated. The model couples reductions in infiltration rate to the deployment of an insulating or shading device. Results of heating load calculations are presented for the cases of single-and double-glazed windows in a typical house with glass-tofloor area ratios of 15 to 40%, and for window management devices with varying thermal resistance, air leakage rates and different modes of operation. window syster.ls with building thermal characteristics, orientation, and climate as controlled variables. (1.

In this paper the experimental study of the behavior of screen wick and nanofluid to improve the performance of a circular heat pipe. Pure water and Al 2 O 3 -water based nanofluid are used as working fluids. An experimental setup is designed and constructed to study the heat pipe performance under different operating conditions. The effect of filling ratio, volume fraction of nano-particle in the base fluid, screen mesh as a wick and heat input rate on the thermal resistance is investigated. Total thermal resistance of the heat pipe for pure water and Al 2 O 3 -water based nanofluid is also predicted. An experimental correlation is obtained to predict the influence of Prandtl number and dimensionless heat transfer rate, K q on thermal resistance. Thermal resistance decreases with increasing Al 2 O 3 -water based nanofluid compared to that of pure water. The experimental data is compared to the available data from previous work. The range of operating parameter are filling ratio 40% to 100%, nanofluid concentration from 0.0% to 2.0%, and heat rate from 8 to 32 watt. The agreement is found to be fairly good.

We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species. Using a toy model, the physics underlying the violation of resistance summation rule is investigated. It is demonstrated that equivalent resistance of two scatterers having the same resistances can be close to the sum of the constituents or ∼70% of it depending on the relative positions of the antiresonances. The relative positions of the antiresonances determine the net change in transmission, therefore the equivalent resistance. Since the entire spectrum is involved in phonon spectrum changes in different parts of the spectrum become important. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be useful to tailor the thermal transport through low dimensional materials, especially for thermoelec-

We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species. Using a toy model, the physics underlying the violation of resistance summation rule is investigated. It is demonstrated that equivalent resistance of two scatterers having the same resistances can be close to the sum of the constituents or ∼70% of it depending on the relative positions of the antiresonances. The relative positions of the antiresonances determine the net change in transmission, therefore the equivalent resistance. Since the entire spectrum is involved in phonon spectrum changes in different parts of the spectrum become important. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be useful to tailor the thermal transport through low dimensional materials, especially for thermoelec-

We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates on the surface, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species, which is a consequence of the bosonic statistics. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species, also because of the bosonic nature of phonons. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be made useful to tailor the thermal transport through low dimensional materials, especially for thermoelectric and thermal management applications. The method enables to change thermal conductance within a ...

We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species. Using a toy model, the physics underlying the violation of resistance summation rule is investigated. It is demonstrated that equivalent resistance of two scatterers having the same resistances can be close to the sum of the constituents or ∼70% of it depending on the relative positions of the antiresonances. The relative positions of the antiresonances determine the net change in transmission, therefore the equivalent resistance. Since the entire spectrum is involved in phonon spectrum changes in different parts of the spectrum become important. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be useful to tailor the thermal transport through low dimensional materials, especially for thermoelec-

This paper addresses experimental and numerical analysis of the thermal resistance of M-Pore ® copper foam. The findings suggest a separation of the thermal resistance into two components: material resistance and contact resistance. Finite element analysis is used to calculate the thermal material resistance. Calculation models are based on micro-computed tomography data in order to account for the complex material geometry. The same samples are used for experimental analysis. A transient method is applied where a time-dependent temperature change is related to the thermal resistance. In addition to material resistance, experimental measurement values inevitably include thermal contact resistance. Although a thermally conducting paste is used in order to minimise this effect, a significant thermal contact resistance is found. As a result, the experimentally measured thermal resistance can no longer be considered as a material property but depends on the sample size and the particular shape of the contact surfaces. Furthermore, it is demonstrated that the traditional approach to experimentally obtain thermal contact resistance by changing the specimen size is impractical for cellular metals. Instead, the contact resistance is obtained by comparing experimental and numerical results.

This paper addresses experimental and numerical analysis of the thermal resistance of M-Pore ® copper foam. The findings suggest a separation of the thermal resistance into two components: material resistance and contact resistance. Finite element analysis is used to calculate the thermal material resistance. Calculation models are based on micro-computed tomography data in order to account for the complex material geometry. The same samples are used for experimental analysis. A transient method is applied where a time-dependent temperature change is related to the thermal resistance. In addition to material resistance, experimental measurement values inevitably include thermal contact resistance. Although a thermally conducting paste is used in order to minimise this effect, a significant thermal contact resistance is found. As a result, the experimentally measured thermal resistance can no longer be considered as a material property but depends on the sample size and the particular shape of the contact surfaces. Furthermore, it is demonstrated that the traditional approach to experimentally obtain thermal contact resistance by changing the specimen size is impractical for cellular metals. Instead, the contact resistance is obtained by comparing experimental and numerical results.

Transition metal diborides, phase equilibria, solid solutions, high entropy diborides Compositions in the AlB2-ScB2-YB2-ZrB2-HfB2-NbB2-TaB2 system were selected to determine the effect of electronic structure on phase equilibria and solid solubility. The Group IVB diborides have the highest stability considering a melting point criterion (eg., ZrB2 with 10 valence electrons per unit cell, or 10 e-/uc) and three systems were investigated to characterize phase equilibria at or near this optimum valence electron sum. The materials were synthesized by hot-pressing diboride powder mixtures at 1750°C followed by heat-treatments at 1900 and 2000°C. The compositions in the system xScB2-(1-x)TaB2 (varying from 9 to 11 e-/uc, respectively), with a metal atom radius difference of 7.4%, exhibited complete solid solubility that could be attributed to the change of the net valence electron sum toward the optimum 10 e-/uc value. The xScB2-(1-x)ZrB2 system (varying from 9 to 10 e-/uc, respectively) was found to be quasi-binary, but exhibited insignificant solid solubility despite the metal atom radius of Sc being smaller than Zr by only 1.2%. The lack of solubility is attributed to an electronic structure based incompatibility. The system x(ZrB2)-(1-x)(0.5ScB2 -0.5TaB2), with a valence electron sum of 10 e-/uc for all x, exhibited complete solid solubility. Very similar results were found for the YB2-ZrB2-TaB2 system, with the exception that significant solubility of ZrB2 in YB2 was observed. The unidirectional solubility is attributed to an electronic structure based stabilization of the YB2. The compatibilities observed for all compositions investigated indicate that ZrB2-ScB2-TaB2 and ZrB2-YB2-TaB2 are quasi-ternary systems. Additional 4, 5, and 6 component diboride systems with an average valence sum of 10 e-/fu were also investigated in the AlB2-ScB2-YB2-ZrB2-HfB2-NbB2-TaB2 system, and many formed solid solutions. The results confirm the significance of electronic structure for phase equilibria and solid solubilities for these diborides. The solid solutions also provide a basis for further investigations as high entropy boride systems

The High-Temperature Gas-cooled Reactor (HTGR) is a generation-IV advanced nuclear reactor, which has a special nuclear fuel design, and the tiny TRISO particle (~1 mm) is adopted. Each TRISO particle is coated with four layers, and silicon carbide (SiC) and pyrolytic carbon (PyC) are the two main components. The heat transfer process at the SiC/PyC interface is important to compute the temperature distribution inside the TRISO particle, but it is quite difficult to research this phenomenon based on experimental results. However, the Molecular dynamics (MD) method could be seen as a viable simulation scheme in micro-scale phenomena. The nonequilibrium molecular dynamics (NEMD) was employed to compute the temperature profile and interfacial resistance of SiC/PyC nanocomposites. In addition, seven atomic models embedded with noble metal fission products, including silver (Ag), palladium (Pd), and ruthenium (Ru), were built, with both aggregated nanoparticle state and atomically dispersed state being investigated. The phonon density of states was used to quantify differences in heat transfer performance. The results show that the Kapitza resistance of the SiC/PyC interface decreases gradually with increasing temperature due to the weakening of phonon scattering, but the FP atoms could reduce the heat transfer capability of SiC/PyC nanocomposites; the dispersed atoms have a more significant effect than the FP nanoparticle as an integral part. This study reveals the mechanism underlying the fission products' influence on the heat transfer characteristics of TRISO coating layers, providing a theoretical basis for enhancing the comprehension of their interaction.

Renovation usually increases the aesthetic and market value of buildings. Consequently, with the rapid growth of the city's population and skyrocketing demand for decent housing, the current trend of building conversion and renovation of existing and dilapidated property stock within city centres has become rampant. The rise in demand has pushed beyond the boundaries that every real estate investor wants to maximize profit, and it has resulted in the prevalence of uncontrolled building development, land use conversion, and non-compliance with building requirements, etc. Renovations that involve changes in building elements (especially the window system) that can influence energy saving and ventilation efficiency have thus become very common. However, the effects of building renovations on ventilation and energy efficiency have not been fully examined, particularly in Enugu (Nigeria), a rapidly growing colonial metropolis. This research employed a qualitative research approach to investigate the effects of building renovation on ventilation and energy saving in Achara layout, Enugu City, Nigeria. Four blocks of flat residential buildings were the derived sample size using a judgmental sampling technique. Physical measurements, an observation schedule, and oral interviews with site workers centred on window size, area, property, and fenestration type were used to collect empirical data involving the window system. The result reveals a very significant difference between the as-built and renovated window design systems of all studied variables. Its conclusion hinged on the fact that a renovated structure does not encourage effective natural ventilation and hence will consume more energy in cooling and lighting. It recommends the re-introduction of appropriate window systems and construction techniques for the tropical environment to reduce heat stress build-up within building units.

The analysis of scientific information sources showed that a global trend is developing in the world to develop methods for increasing the overall energy efficiency of buildings for various purposes using appropriate technologies aimed at reducing energy flows through their envelope. At the same time, a combination of an extensive passive approach to increasing the thermal insulation parameters of building envelopes through the use of individual materials with the use of active regulation of the thermal regime of the building envelope using renewable energy sources, etc. is gaining wide development. The purpose of this study was to determine the main thermal parameters of a conventional building envelope, which includes a coolant circulation circuit to maintain its corresponding thermal regime. This technology is designed to actively increase the effective thermal resistance of the building envelope during the operation of the thermal barrier system. The main technological advantages of this technical solution are analyzed, a method for calculating the main thermal parameters that can determine its energy efficiency of operation and the results of calculations using this method are presented. A simplified schematic diagram of a system using a thermal barrier, for which the initial low-potential source is the soil massif, is also proposed. Analysis of the obtained data showed the energy feasibility of using such technology in the cold season to reduce heat losses in premises and potentially increase the energy efficiency of the building as a whole.

An analytical DMOS model for circuit simulation based on a subcircuit approach is extended for a variable number of cells. The subcircuit itself consists of a minimal number of elements whose models are physically based and optimized for the special DMOS structure. The DC-description is continous (smooth transitions between the different operating regions of the device), the AC-description is charge based and the model also accounts for temperature effects. Over a wide range of cell numbers the same parameters can be used due to the scalability of the model.

SCOuT) lander thermal control system (TCS). They provide variable conductivity by utilizing the heat transfer limitations. This allows the heat pipes to act as thermal switches without additional constructive elements, thus leveraging the simple and compact design of conventional heat pipes. Two cylindrical methanol-copper heat pipes with shell length of 0.482 m and 0.438 m and external diameter of 0.006 m, having copper discrete metal fiber wick and copper shell were constructed and verified in the temperature range between -75 and +60 °C. The purpose is to apply this design into the MASCOT thermal control system and to investigate the heat pipes' regulative characteristics and heat transfer limitations. VCHPs show a change of thermal resistivity from 70 K/W at a heat sink temperature of -60 °C, to 0.8 K/W at a heat sink temperature of +60 °C; with an obtained maximal heat transfer rate of 5 W and 16 W, respectively. It is found that the switching effect of the heat pipes is governed by the sonic velocity limitation, the saturation vapor pressure of the working fluid and the maximal capillary pressure of the wick. The operation of the heat pipes as the part of the TCS has confirmed their variable thermal properties.

Heat pipe technology became an integral part of the thermal control systems of space missions to transfer heat and control the temperature. The selection, design and the integration of heat pipes in space hardware requires the knowledge about their thermal performance. One of the major characteristics is the longitudinal resistance. This paper presents the experimental results of the longitudinal heat transfer in constant and variable thermal resistance heat pipes (HP) with diameters between 0.006 to 0.012 m: "a") aluminium -ammonia HP with axial grooved capillary structure; "b") stainless steel -methanol HP with stainless steel discrete metal fibre capillary structure; "c") copper -methanol HP with copper discrete metal fibre capillary structure. The tests have been performed within a wide range of operation parameters: heat sink temperature from -75 up to +60 o C, the transferred heat power from 0.5 up to 100 W, the axial heat flux density up to 250 W/cm 2 . As characteristic parameter the longitudinal thermal resistance R HP =(T ev -T con )/Q HP is used, where Q HP is the transferred heat power and T ev and T con are the average temperatures of the heat input and output zones, respectively. For the HPs "a" the parameter R HP varies from 0.06 to 0.045 K/W. The change of T con has no essential impact on the HP thermal resistance. For the HP "b", R HP changes from 80 to 4 K/W. The physical basis of such behaviour is related to the formation of vapor and non-condensable gas boundary in the coldest part of the heat pipe and, as consequence, a heat transfer intensity variation. The HPs "c" have shown essential impact of T con on resistance, which varies from 70 to 0.4 K/W. The physical basis of such behaviour is connected a change of the vapor flow regime in the inner vapor space and with change of the inner heat transfer

The high power RF device performance decreases as operation temperature increases (e.g. fall of electron mobility impacting the cut-off frequencies and degradation of device reliability). Therefore the determination of device temperature is a key issue for device topology optimisation. This work presents the comparison between pulsed I-V at different temperature and DC measurements of AlGaN/GaN HEMTs grown on two different substrates: sapphire and silicon. This technique allows the determination of mean channel temperature and the device thermal resistance. The thermal resistance is a classical way to define the average channel temperature as a function of the dissipated power. In this work the thermal resistance ratio of the HEMT grown on sapphire compared to the one grown on silicon is found to be 1.7 instead of 3 as expected from straightforward thermal conductivity ratio. This lower difference is clearly attributed to the contribution of the GaN buffer layer.

This paper reports the influence of surfactant Triton X-100 on boron nitride nanotubes (BNNTs) nanofluid in non-optimized and optimized microchannel heat sink (MCHS) at 30⁰ C and 50⁰ C. The MCHS performance was evaluated in terms of thermal resistance and pressure drop, utilizing experimental thermophysical properties of distilled water, a mixture of distilled water and surfactant Triton X-100 as base fluid, and nanofluid BNNTs at weight concentration of 0.001% into MCHS models which further optimized with the Multiple Objective Particle Swarm Optimization (MOPSO) technique. It is found that the surfactant at 30⁰ C improves MCHS thermal capabilities without nanotubes by 0.8% even after optimizing MCHS according to the fluid properties. Conversely, surfactant Triton X-100 reduces pressure drop greatly with any change in thermal resistance at 50⁰ C and paired cooperatively with BNNTs nanofluid 0.001wt.% -mitigating pressure drop increment caused by the nanofluid resulting an overall performance improvement by 1.25% and 1.97% for thermal resistance and pressure drop respectively in MCHS systems and reduced to 1.3% and 3.2% after optimization. Optimized MCHS dimensions given by MOPSO could be manufactured and additionally gave wider solutions for large reduction of pressure drop up to 80% for economic MCHS with a drawback of higher thermal resistance.

Lightweight and compact microcoolers are needed for advanced, hand-held infrared systems. A temperature of 150 K is adequate for high sensitivity with some of the latest IR detectors, which simplifies the cooling requirements compared to 80 K detectors. The largest and heaviest component of most gas-cycle cryocoolers has been the compressor. This paper describes how the use of a 150 K, five-stage, cascade Joule-Thomson (JT) cycle significantly reduces the total refrigerant flow rate and total compressor swept volume compared with other types of cryocoolers for this temperature range. The use of vapor compression in each of the five stages results in very high specific refrigeration powers and low flow rates even with no recuperative heat exchangers and with pressure ratios of only about 4:1 Such low pressure ratios are needed for the use of chip-scale compressors. We discuss the thermodynamic design of a five-stage planar polyimide cold head for a range of refrigeration powers up to about 350 mW at 150 K. We compare the use of single-layer and double-layer construction over this range of refrigeration powers. In the double-layer construction, the high-pressure fluid streams are on the bottom and the low-pressure fluid streams are on top. Such construction allows for simple recuperative heat exchangers and leads to a compact planar geometry of about 20 mm by 30 mm for 350 mW refrigeration power at 150 K. The ideal fluid input power for the five-stage system at 150 K with no recuperative heat exchangers is 1.59 W per watt of net refrigeration power. For a heat exchanger ineffectiveness of 0.05 the specific power is 1.29 W/W for an efficiency of 89.2 % of Carnot with perfect compressors. The paper describes the geometry of the condensers, evaporators and Joule-Thomson impedances to achieve the high heat flux required for minimum size.

In this paper, a GaN-LED with sapphire structure and a thin-film LED without sapphire structure are characterized in the photo-electro-thermal (PET) modeling framework for comparison. Starting from the analysis and modeling of internal quantum efficiency as a function of current and temperature of blue LED, this work develops the thin-film LED device model and derives its optical power and the heat dissipation coefficient. The device parameters of the two LED devices with different structural designs are then compared. Practical optical power measurements are compared with theoretical predictions based on the two types of fabricated devices. It is shown that the thin-film LED device has much lower thermal resistance and optical power loss.

Microchannels are crucial for thermal management in microelectronic cooling, medical equipment, and space technology. Microchannel designing with optimal heat transfer and minimum pressure drop is still a challenging task even today. Conventional approaches like computational fluid dynamics (CFD) and experimentations consume enormous time and computational power. Here, in this paper, an optimization framework based on deep learning (DL) for the microchannel heat transfer performance is presented. We introduce a CNN-PINN-based hybrid model for the prediction of heat transfer coefficients and pressure drop in different microchannel geometries and flow rates. Our proposed model is compared to high-fidelity CFD simulations and experiments and found to be more accurate and efficient. As a demonstration example, electronics cooling is utilized and demonstrates that DL-optimized wavy-channel possesses a 22% decrease in thermal resistance compared to conventional straight channels. The platform is designed to provide an evidence-based pathway toward the creation of next-generation microchannel systems for future applications in renewable energy, electric cars, and advanced manufacturing.

A non-invasive sensor equipped with a programmable thermostat has been developed to assess in vivo the heat flow transmitted by conduction from human skin to the sensor thermostat. This device enables the assessment of the thermal properties of a 2 × 2 cm2 skin surface with a thermal penetration depth of 3–4 mm. In this work, we report the thermal magnitudes recorded with this sensor in 6 different areas (temple, hand, abdomen, thigh, wrist and heel) of 6 healthy subjects of different genders and ages, which were measured under resting conditions. Heat flow and equivalent thermal resistance are proportionally related to each other and are highly variable in magnitude and different for each zone. The heat capacity is also different for each zone. The heat flow values varied from 362 ± 17 mW at the temple to 36 ± 12 mW at the heel for the same subject, when the sensor thermostat was set at 26 °C. The equivalent thermal resistance ranged from 23 ± 2 K W−1 in the volar area of the wrist...

In vivo determination of the skin’s thermal properties is of growing interest. Several types of sensors are being designed and tested. In this field, we have developed a skin calorimeter for the determination of the heat flow, the heat capacity and the thermal resistance of the skin. The calorimeter calibration consists of the determination of the parameters of the model we have chosen to represent the behavior of the device. This model considers the heat capacity and the thermal resistance of the skin, which depend on the case (body zone, subject, physical state, etc.) and also have a strong time dependence. Therefore, this work includes a validation study with reference materials. Finally, it is concluded that the heat capacity determined is a function of the thermal penetration depth of the measurement characteristics. In the case of high thermal conductivity materials in which the thermal penetration is nearly total, the heat capacity obtained coincides with that of the referenc...

Cette étude, basée sur une modélisation hygrothermique rigoureuse, démontre que le béton de balle de riz (BBR) réduit significativement la consommation énergétique liée au refroidissement dans les bâtiments en climat tropical. Le BBR limite efficacement les surchauffes grâce à ses propriétés thermiques et hygroscopiques, bien qu'il ne favorise pas des températures minimales plus basses. L'analyse souligne également l'importance stratégique de son usage en toiture, où il optimise la réduction des gains solaires et les besoins en refroidissement. Enfin, l'augmentation de l'épaisseur de l'enveloppe et la présence d'une cavité améliorent encore la performance thermique du BBR. Ces résultats confirment le potentiel du BBR comme matériau biosourcé performant et durable pour les constructions tropicales, contribuant à des bâtiments plus confortables et économes en énergie.
3ème Conférence Internationale sur les Sciences Appliquées et l'Innovation (CISAI-2025)

NASA Glenn Research Center is presently developing and applying a range of sensor and electronic technologies that can enable future planetary missions. These include space qualified instruments and electronics, high temperature sensors for Venus missions, mobile sensor platforms, and Microsystems for detection of a range of chemical species and particulates. A discussion of each technology area and its level of maturity is given. It is concluded that there is a strong need for low power devices which can be mobile and provide substantial characterization of the planetary environment where and when needed. While a given mission will require tailoring of the technology for the application, basic tools which can enable new planetary missions are being developed.

Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Ce rap port est l'aboutissement d'une co o pé ra tion de re cherche entre le LPEE et l'Université de Lund au cours de la pé riode 1997 à 2002. Du rant cette pé riode, de nom breu ses per son nes nous ont ap por té leurs précieux conseils et leurs connais san ces et nous te nons ici à les re mer cier. Nous ci te rons, tout d'abord, les par ti ci pants aux ta bles ron des te nues au cours du pro jet et qui, à ces oc ca sions, nous ont fait part de leurs avis qui nous ont été d'une aide pré cieuse et ont lar ge ment con tri bué à la réa li sa tion de ce rap port, qu'il s'agisse des re pré sen tants des pouvoirs pu blics ou des cher cheurs et des consul tants. Le per son nel tech nique du LPEE qui a par ti ci pé ac ti ve ment à la réa lisa tion du pro jet, prin ci pa le ment en ce qui concerne leur en ga ge ment dans les re le vés cli ma ti ques à Fès. Nous te nons éga le ment à re mer cier les fa mil les des quar tiers Sef farine et Ada ris sa de Fès qui nous ont per mis d'installer les ins tru ments de me sure. Enfin, nous vou lons re mer cier la so cié té Te pro Bygg ma te rial AB pour leur concours et leurs conseils ap por tés lors des es sais de fa bri ca tion des pan neaux en laine de bois à par tir de ma tiè res pre miè res ma rocai nes. 6 Table des matières Ré su mé Sum mary Intro duc tion L'objectif du pro jet Réa li sa tion du pro jet Pré sen ta tion des cha pi tres Les par ti ci pants au pro jet Coo pé ra tion tech ni que fi nan cée par con trat LPEE HDM Asdi Cha pi tre 1 L'habitat au Ma roc La si tua tion du lo ge ment Le sec teur du lo ge ment La po li ti que du lo ge ment La lé gis la tion La typo lo gie de l'habitat Les mo des de cons truc tion Cha pi tre 2 Cli mat au Ma roc et con fort ther mi que Le cli mat au Ma roc Le cli mat à Fès Le cli mat à Ouar za za te Cli mat ur bain Les ca rac té ris ti ques du cli mat ur bain Con fort ther mi que Influen ce du cli mat sur le con fort ther mi que Dé fi ni tion des zo nes de con fort Le con fort ther mi que ur bain à Fès Cha pi tre 3 Urba nis me adap té au cli mat La vi lle de Fès Quar tier Sef fa ri ne -Mé di na L'espace ur bain -rues et pla ces Typo lo gie Les points de me su re Quar tier Ada ris sa -Nou ve lle Vi lle L'espace ur bain -rues et pla ces Typo lo gie Les points de me su re Con clu sion des quar tiers étu diés Me su res du cli mat ur bain a Fès Pro cé du re de me su res Equi pe ment de me su re L'emplacement de l'équipement de me su re Etu de com pa ra ti ve du cli mat ur bain des deux quar tiers Va ria tions cli ma ti ques au cours de l'année étu diée Com pa rai son en tre la pé rio de d'hiver et d'été Con fort ther mi que à l'extérieur Con clu sion Etu des et si mu la tions du cli mat ur bain Le modè le CTTC Cal cul de la lon gueur de l'ombre Con clu sion Con cep tion ur bai ne adap tée au cli mat Re com man da tions au ni veau Quar tier Re com man da tions au ni veau du can yon ur bain Re com man da tions au ni veau Bâti ment Con clu sion Cha pi tre 4 Vers une ré gle men ta tion ther mi que Com pa rai son des dif fé ren tes ré gle men ta tions in ter na tio na les Ré gle men ta tion fran çai se Ré gle men ta tion al gé rien ne Ré gle men ta tion li ba nai se Ré gle men ta tion amé ri cai ne Ré gle men ta tion sué doi se Ré gle men ta tion bri tan ni que Con clu sion Dé cou pa ge du Ma roc en zo nes cli ma ti ques Zo na ge cli ma ti que d'hiver Zo na ge cli ma ti que d'été Va li da tion du dé cou pa ge cli ma ti que Con clu sion Exi gen ces ther mi ques pour la ré gion de Fès Mét ho do lo gie d'approche Ré sul tats du pro ces sus d'optimisation Con clu sion Source : Banque Mon diale (2000)

Methanol-steam reforming can be utilized as a fuel processing system for hydrogen fuel cells. A study of the reacting flow in packed-bed and wall-coated catalytic reactors is presented. The wall-coated reformer has a smaller power requirement for delivering fuel than the packed catalytic bed reformer. Also, the coated catalytic layer has a smaller thermal resistance compared to the packed catalytic bed. This yields enhanced thermal field management for the wall-coated reformer that is essential for reformer performance. Understanding the transport in reformers is essential for improving both the efficiency of the reforming process and the quality of the processed fuel.

This work presents an experimental study of thermal conductivity, compressive strength, first crack strength and ductility indices of recycled PET fiber-reinforced concrete (RPETFRC). We examine PET filaments industrially extruded from recycled PET bottle flakes with different mechanical properties and profiles. On considering a volumetric fiber dosage at 1%, we observe marked improvements in thermal resistance, mechanical strengths and ductility of RPETFRC, as compared to plain concrete. A comparative study with earlier literature results indicates that RPETFRC is also highly competitive over polypropylenefiber-reinforced concrete in terms of compressive strength and fracture toughness.

The transport of thermal energy is typically modeled by the parabolic heat equation, which implies an infinite propagation speed-a physical inconsistency for high-frequency phenomena. This paper presents a comparative analysis of this classical diffusive model against the hyperbolic heatwave equation, derived from the Cattaneo-Vernotte model. Rather than presenting a novel derivation, this work provides a pedagogical and computational framework to explore the transition from diffusive to propagative heat transfer. We conduct a physical analysis via the dispersion relation, revealing how the system's response is frequency-dependent, behaving diffusively at low frequencies and as a damped wave at high frequencies. This synthesized approach clarifies the physical regimes where the hyperbolic model is not just relevant but essential for accurate prediction.

Lu, Toh-Ming (2025). My road to semiconductor research (second edition). In: "Evolutionary Progress in Science, Technology, Engineering, Arts and Mathematics", Wang, Lawrence K. and Tsao, Hung-ping  (Editors). Volume 7, Number 8A, 7(8A), August 8, 2025, 40 pages. Lenox Institute Press, Auburndale, Massachusetts, USA. Lenox.Institute@gmail.com; lut@rpi.edu.   
ABSTRACT: This electronic book is a memoir recalling how I entered semiconductor research and how I got involved in the US semiconductor research consortium called “Semiconductor Research Corporation (SRC)”. In the late 1990’s I became the director of “Center for Advanced Interconnect Science and Technology” funded by SRC. The Center involved 15 universities, 30 faculty, and 40 graduate students doing advanced interconnect research. SRC member companies include Intel, IBM, AMD, TI, UMC (Taiwan), and Chartered Semiconductor Manufacturing (Singapore). The Center produced over 100 PhD students who later played leadership roles in semiconductor industry. In 2004, Novellus Systems, a major semiconductor manufacturing equipment company, donated a Cu deposition system to Fudan University in anticipation of future business in China. The company organized a workshop in Shanghai, China.  I highlighted some of the activities. I also described some international students graduated from my group, in particular, the interesting and unusual educational and career paths of some Chinese graduate students, who eventually served semiconductor industry. Some future possibilities beyond the current Si technology are also briefly discussed. 
KEY WORDS: vacuum tubes, semiconductor transistors, integrated circuits, interconnect, Semiconductor Research Corporation, Novellus Systems, beyond Si technology, quantum physics, quantum computing. 
ACKNOWLEDGEMENT: I thank Professor Jian Shi for valuable discussions on future computing strategies.

An experimental setup to measure the thermal contact conductance across a silicon-copper (Si-Cu) interface is described, and the results obtained are presented. The resulting thermal contact resistance data are used in estimating the thermo-mechanical and optical performance of optical substrates cooled by interfaced copper cooling blocks. Several factors influence the heat transfer across solid interfaces. These include the material properties, interface pressure, flatness and roughness of the contacting surfaces, temperature, and interstitial matenal, if any. Results presented show the variation of thermal contact conductance as a function of applied interface pressure for a Cu-Si interface. Various interstitial materials investigated include iridium foil, silver foil and a liquid eutectic (Ga-In-Sn). As expected, thermal contact resistance decreases as interface pressure increases, except in the case of the eutectic, in which it was nearly constant. The softer the interstitial material, the lower the thermal contact resistance, Liquid metal provides the lowest thermal contact resistance across the Cu-Si interface, followed by the iridium foil, and then the silver foil.

Due to high heat flux generation inside microprocessors, water-cooled heat sinks have gained special attention. For the durability of the microprocessor, this generated flux should be effectively removed. The effective thermal management of high-processing devices is now becoming popular due to high heat flux generation. Heat removal plays a significant role in the longer operation and better performance of heat sinks. In this work, to tackle the heat generation issues, a slotted fin minichannel heat sink (SFMCHS) was investigated by modifying a conventional straight integral fin minichannel heat sink (SIFMCHS). SFMCHSs with fin spacings of 0.5 mm, 1 mm, and 1.5 mm were numerically studied. The numerical results were then compared with SIFMCHSs present in the literature. The base temperatures recorded for two slots per fin minichannel heat sink (SPFMCHS), with 0.5 mm, 1 mm, and 1.5 mm fin spacings, were 42.81 °C, 46.36 °C, and 48.86 °C, respectively, at 1 LPM. The reductions in base...

crystals of a new hybrid compound, (C5H6N2O)2[Co(H2O)6]3(SO4)4.2H2O, were synthesized in aqueous solution and characterized. This compound crystallizes in the triclinic system with the space group P-1, the unit cell :a=6.632(3) Å, b=11.769(5) Å, c=14.210(6) Å, α=67.86(4)°, β=81.32(4)°, γ=85.18(4)° and V=1015.14(8) Å 3 . Its crystal structure can be described as a packing of alternated inorganic and organic layers. The different components are connected by a threedimensional network of O-H…O and N-H…O hydrogen bonds.

A fin heat sink (FHS) is a thermal heat transfer device employed to dissipate heat from a high temperature heat source to a lower temperature surrounding. A typical FHS consists of a flat metal base with an array of cooling fins on top. A problem normally encountered in thermal management of electronic packages is thermal heat spreading resistance which occurs as heat flows by conduction from a high temperature heat source to a low temperature heat sink with different cross-sectional areas. As high powered semiconductor chips are made more compact and requiring greater heat dissipation, more effective cooling systems have to be devised. There are various methods employed to minimize this heat spreading resistance. These include increasing the thickness of the base of the FHS or height of the fins. Another method is to use more expensive highly conductive materials like aluminum, copper and diamond which would increase cost. A more economical alternative would be to combine a flat he...

The mechanical vapor compression heat pumps are modern systems, recently used as an alternative to the thermal fossil fuel stations. The incorrect determination of the vaporization ther-mal power needed for the ground–coupled heat pumps with vertical closed–loops leads to unfavorable effects for this systems: under–sizing the catching system used for the vaporization of the refri-gerant determines the reduction of heat pump nominal thermal power; over–sizing catching system leads to additional investments that puts under discussion the opportunity of using such systems. Therefore is very important to know the thermal conductivity of the soil and the thermal resistance of the vertical ground loop for esta-blish the right number of loops to be realized, depending on energy to be transfered to the heat pump. For this purpose is needed to be made a ground thermal response test, using a prove borehole. In this paper is presented a working methodology and is developed an ana-lytical model...

In this paper 1D crystal lattice is analyzed within harmonic approximation, with one atom per elementary cell and nearest neighbor interaction included. For this type of crystal lattice dispersion relations are well known. Thermodynamic functions (specific heat and phonon thermal conductivity) are calculated via phonon density of states given in exact form. Thermodynamic variables are calculated for a whole temperature range. In limiting cases of low and high temperatures these thermodynamic variables can be found in analytic forms. For thermal conductivity the results of Callaway model for exact phonon density of states are compared with the results of Callaway model for Debye approximation of phonon density of states.

In this paper, a pressure sensing device for analysing pressure comfort on elastic garments was designed and developed. The device was calibrated and tested on different compression garments for its reliability. This pressure comfort measurement device is used to measure the pressure between the human body and garments. The fabric resistance due to each and every body movement is noted to evaluate the effect of fabric compression on body muscles in order to assess the pressure comfort for sports persons. The new device proved that elastic garments certainly improve stamina and speed through its quick recovery and lower stress with higher elongation. There is a good correlation found between the pressure values given by the new sensing device and the Instron tester.

This paper presents an approach for the multiobjective optimization of the flat plate heat sink using Taguchi design of experiments-based Grey relational analysis. The responses studied were electromagnetic emitted radiation, thermal resistance, average heat transfer coefficient, pressure drop, and the mass of the flat plate heat sink. The heat sink is modeled using Ansoft High Frequency Structure Simulator (HFSS) software version 12 and the value of the emitted radiation is obtained by simulation. The same heat sink is modeled using Flotherm V7.2 software for finding the thermal resistance, pressure drop, and average heat transfer coefficient. Experimental investigation was performed to find the thermal resistance and emitted radiations from the heat sink and thus the simulation model was validated with the experimental results. The simulations were continued for the combinations generated by the L27 (6 factors, three levels) Taguchi's design of experiments using Minitab software. The factors considered for optimization are the length and width of the heat sink, fin height, base height, number of fins, and fin thickness. The multi-objective optimization problem is then converted into single-objective optimization problem using Grey relational analysis and the optimum design settings of the heat sink geometry were obtained. Also, ANOVA test was carried out for finding out the contribution and impact of each heat sink design factor towards the multiple responses of the heat sink.