Journal articles on the topic '1-D transient thermal network'
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NISHI, Koji, Tomoyuki HATAKEYAMA, and Masaru ISHIZUKA. "J012032 Transient Thermal Analysis for Electronic Equipment Utilizing One-Dimensional Thermal Network Modeling of Transient Thermal Resistance Behavior." Proceedings of Mechanical Engineering Congress, Japan 2013 (2013): _J012032–1—_J012032–5. http://dx.doi.org/10.1299/jsmemecj.2013._j012032-1.
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Gerstenmaier, Y. C., and G. Wachutka. "Rigorous model and network for transient thermal problems." Microelectronics Journal 33, no. 9 (September 2002): 719–25. http://dx.doi.org/10.1016/s0026-2692(02)00055-1.
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Ren, Guo Tao, Kai Lin Pan, Wei Tao Zhu, Jiao Pin Wang, and Jing Huang. "Study on Thermal Contact Resistance for Heat Transfer of High Power LED Packaging." Advanced Materials Research 199-200 (February 2011): 1477–81. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.1477.
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Thermal contact resistance is one of key technologies for heat transfer of high power light emitting diodes (LED) packaging. In this paper, based on the resistance network model of LED packaging, a 3-D finite element simulation model (FEM) is established and thermal transient testing experiments are also performed by Thermal Transient tester (T3Ster). Experiment date indicates thermal contact resistance for 48% of the total thermal resistance. The thermal interface material (TIM) layer of high power LED packaging is studied to analysis thermal contact resistance which impacts on thermal performance of LED packaging. The total thermal resistance and the thermal resistance of TIM layer are separately calculated from simulation and experiment. To the resistance of TIM layer, the result of experiment is only a 1% error compared to the result of FEM simulation. Therefore, The FEM simulation and experiment are mutually validated. In order to thoroughly study on thermal contact resistance, based on the principle of structure function, thermal resistance of three different types of TIM layer between metal core printed circuit board (MCPCB) and aluminum heat sink are measured and compared. Experiment results indicate that the quality of interface affects the thermal contact resistance to a great extent.
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Kefalas, Themistoklis D., and Antonios G. Kladas. "3-D FEM and Lumped-Parameter Network Transient Thermal Analysis of Induction and Permanent Magnet Motors for Aerospace Applications." Materials Science Forum 856 (May 2016): 245–50. http://dx.doi.org/10.4028/www.scientific.net/msf.856.245.
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Three dimensional (3–D), finite–element (FE) models and original lumped–parameter networks are developed for the transient thermal analysis of a permanent magnet motor (PMM) and an induction motor (IM) specifically designed and optimized for a demanding aerospace actuation application. A systematic comparison between the two different thermal modeling approaches is carried out using different loading conditions.
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Tianjian Lu and Jian-Ming Jin. "Transient Electrical-Thermal Analysis of 3-D Power Distribution Network With FETI-Enabled Parallel Computing." IEEE Transactions on Components, Packaging and Manufacturing Technology 4, no. 10 (October 2014): 1684–95. http://dx.doi.org/10.1109/tcpmt.2014.2345651.
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Nirmalan, Nirm V., Ronald S. Bunker, and Carl R. Hedlund. "The Measurement of Full-Surface Internal Heat Transfer Coefficients for Turbine Airfoils Using a Nondestructive Thermal Inertia Technique." Journal of Turbomachinery 125, no. 1 (January 1, 2003): 83–89. http://dx.doi.org/10.1115/1.1515798.
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A new method has been developed and demonstrated for the non-destructive, quantitative assessment of internal heat transfer coefficient distributions of cooled metallic turbine airfoils. The technique employs the acquisition of full-surface external surface temperature data in response to a thermal transient induced by internal heating/cooling, in conjunction with knowledge of the part wall thickness and geometry, material properties, and internal fluid temperatures. An imaging Infrared camera system is used to record the complete time history of the external surface temperature response during a transient initiated by the introduction of a convecting fluid through the cooling circuit of the part. The transient data obtained is combined with the cooling fluid network model to provide the boundary conditions for a finite element model representing the complete part geometry. A simple 1-D lumped thermal capacitance model for each local wall position is used to provide a first estimate of the internal surface heat transfer coefficient distribution. A 3-D inverse transient conduction model of the part is then executed with updated internal heat transfer coefficients until convergence is reached with the experimentally measured external wall temperatures as a function of time. This new technique makes possible the accurate quantification of full-surface internal heat transfer coefficient distributions for prototype and production metallic airfoils in a totally nondestructive and non-intrusive manner. The technique is equally applicable to other material types and other cooled/heated components.
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Bissuel, Valentin, Quentin Dupuis, Najib Laraqi, and Jean-Gabriel Bauzin. "Using statistical inverse methods for detecting defects in electronic components." Journal of Physics: Conference Series 2116, no. 1 (November 1, 2021): 012078. http://dx.doi.org/10.1088/1742-6596/2116/1/012078.
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Abstract The thermal modeling of electronic components is mandatory to optimize the cooling design versus reliability. Indeed most of failures are due to thermal phenomena [1]. Some of them are neglected or omitted by lack of data: ageing, manufacturing issues like voids in glue or solder joints, or material properties variability. Transient measurements of the junction-to-board temperature supply real thermal behavior of the component and PCB assembly to complete these missing data[2]. To complement and supplement the numerical model, inverse methods identification based on a statistical deconvolution approach, such as Bayesian one, is applied on these measurements to extract a Foster RC thermal network. The identification algorithm performances have been demonstrated on numerical as well as experimental dataset. Furthermore defects or voids can be detected using the extracted Foster RC networks.
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Chuttar, Aditya, and Debjyoti Banerjee. "Machine Learning (ML) Based Thermal Management for Cooling of Electronics Chips by Utilizing Thermal Energy Storage (TES) in Packaging That Leverages Phase Change Materials (PCM)." Electronics 10, no. 22 (November 13, 2021): 2785. http://dx.doi.org/10.3390/electronics10222785.
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Miniaturization of electronics devices is often limited by the concomitant high heat fluxes (cooling load) and maldistribution of temperature profiles (hot spots). Thermal energy storage (TES) platforms providing supplemental cooling can be a cost-effective solution, that often leverages phase change materials (PCM). Although salt hydrates provide higher storage capacities and power ratings (as compared to that of the organic PCMs), they suffer from reliability issues (e.g., supercooling). “Cold Finger Technique (CFT)” can obviate supercooling by maintaining a small mass fraction of the PCM in a solid state for enabling spontaneous nucleation. Optimization of CFT necessitates real-time forecasting of the transient values of the melt-fraction. In this study, the artificial neural network (ANN) is explored for real-time prediction of the time remaining to reach a target value of melt-fraction based on the prior history of the spatial distribution of the surface temperature transients. Two different approaches were explored for training the ANN model, using: (1) transient PCM-temperature data; or (2) transient surface-temperature data. When deployed in a heat sink that leverages PCM-based passive thermal management systems for cooling electronic chips and packages, this maverick approach (using the second method) affords cheaper costs, better sustainability, higher reliability, and resilience. The error in prediction varies during the melting process. During the final stages of the melting cycle, the errors in the predicted values are ~5% of the total time-scale of the PCM melting experiments.
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Mohamed, Abdalla, Ahmed Hemeida, Alireza Rasekh, Hendrik Vansompel, Antero Arkkio, and Peter Sergeant. "A 3D Dynamic Lumped Parameter Thermal Network of Air-Cooled YASA Axial Flux Permanent Magnet Synchronous Machine." Energies 11, no. 4 (March 28, 2018): 774. http://dx.doi.org/10.3390/en11040774.
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To find the temperature rise for high power density yokeless and segmented armature (YASA) axial flux permanent magnet synchronous (AFPMSM) machines quickly and accurately, a 3D lumped parameter thermal model is developed and validated experimentally and by finite element (FE) simulations on a 4 kW YASA machine. Additionally, to get insight in the thermal transient response of the machine, the model accounts for the thermal capacitance of different machine components. The model considers the stator, bearing, and windage losses, as well as eddy current losses in the magnets on the rotors. The new contribution of this work is that the thermal model takes cooling via air channels between the magnets on the rotor discs into account. The model is parametrized with respect to the permanent magnet (PM) angle ratio, the PM thickness ratio, the air gap length, and the rotor speed. The effect of the channels is incorporated via convection equations based on many computational fluid dynamics (CFD) computations. The model accuracy is validated at different values of parameters by FE simulations in both transient and steady state. The model takes less than 1 s to solve for the temperature distribution.
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Zhang, Xiuxiang, Kang He, Quan Yang, and Chengcai Xi. "Analysis on heat transfer and start-up performance of mercury heat pipe." E3S Web of Conferences 245 (2021): 03012. http://dx.doi.org/10.1051/e3sconf/202124503012.
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Mercury heat pipe has the advantages of good thermal stability and low saturated vapor pressure, which is the best choice for the transition from water heat pipe to liquid metal heat pipe. The effects of heating power and heat pipe structure on start-up time and steady-state heat transfer performance of mercury heat pipe were studied by using transient thermal network model. The results showed that: 1) Increasing the length of condenser is beneficial to reducing the start-up time and thermal resistance; 2) Increasing the heating power or wall thickness will reduce the thermal resistance, but increase the start-up time, and increasing the porosity of wick is just the opposite; 3) Increasing the thickness of wick can increase both the start-up time and the thermal resistance.
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Zhang, Shiling. "Lumped RC Thermal Network Method Applied to Transient Temperature Calculation of High Voltage Bushing and Its Insulation Life Assessment." Journal of Physics: Conference Series 1637 (September 2020): 012110. http://dx.doi.org/10.1088/1742-6596/1637/1/012110.
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Ohlsson, KE Anders, Ronny Östin, and Thomas Olofsson. "Step-transient method for measurement of the heat transfer coefficient at surfaces exposed to simulated building outdoor environments using the sol-air thermometer." Journal of Building Physics 42, no. 3 (April 17, 2018): 373–87. http://dx.doi.org/10.1177/1744259118764823.
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The environmental boundary conditions of the building exterior surface could be expressed in terms of the sol-air temperature To and the heat transfer coefficient ho. This has previously been derived by applying Thevenin’s theorem to the linear thermal network model of the convective and radiative environment. Here, the sol-air thermometer, previously used only for measurement of To, was applied for accurate measurement of ho. The step-transient method was used, where the temperature of the sol-air thermometer was initially raised to above To and then monitored during its transient return to thermal equilibrium. This method was validated by (1) comparison of ho results against values obtained with a steady-state method and (2) comparison of predicted heat flux against the electrical heater power, supplied for validation purpose. Accurate results were obtained, with 7.3% measurement uncertainty. The present sol-air thermometer time constant τ was around 1 h. Based on predictions from dynamic modelling, the τ could be reduced 10-fold, with only small effects on the accuracy from heat loss through the insulation layer.
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Nielsen, Thomas, Simon Jakobsen, and Mehdi Savaghebi. "Dynamic Rating of Three-Core XLPE Submarine Cables for Offshore Wind Farms." Applied Sciences 9, no. 4 (February 25, 2019): 800. http://dx.doi.org/10.3390/app9040800.
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This article aims to determine the most suitable cross-sectional area for a high voltage alternating current (HVAC) submarine cable in the design phase of new projects. A thermal ladder network method (LNM) was used to analyse the thermal behaviour in the centre of the conductor as the hottest spot of the cable. On the basis of the calculated cable parameters and a thermal cable analysis of transient conditions applied by a step function with a time duration greater than 1 h, this article proposes a method for a dynamic rating of submarine cables. The dynamic rating is accomplished through an iterative process. The method was tested with a MATLAB simulation and validated in comparison with a finite element method (FEM)-based approach.
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Letcher, Theodore W., and Justin R. Minder. "The Simulated Response of Diurnal Mountain Winds to Regionally Enhanced Warming Caused by the Snow Albedo Feedback." Journal of the Atmospheric Sciences 74, no. 1 (December 15, 2016): 49–67. http://dx.doi.org/10.1175/jas-d-16-0158.1.
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Abstract The snow albedo feedback (SAF) is an important climate feature of mountain regions with transient snow cover. In these regions, where patterns of snow cover are largely determined by the underlying terrain, the SAF is highly variable in space and time. Under climate warming, these variations may affect the development of diurnal mountain winds either by altering the thermal contrast between high and low elevations or by increasing boundary layer mixing. In this study, high-resolution regional climate modeling experiments are used to investigate and characterize how the SAF modulates changes in diurnal wind systems in the Rocky Mountains of Colorado and Utah during the spring when SAF strength is at a maximum. Two separate 7-yr pseudo–global warming climate change experiments with differing model configurations are examined. An evaluation of the control simulations against a mesoscale network of observations reveals that the models perform reasonably well at simulating diurnal mountain winds within this region. In the experiment with a strong SAF, there is a clear increase in the strength of daytime upslope flow under climate warming, which leads to increased convergence and cloudiness near the snow margin. Additionally, there is a decrease in the strength of nighttime downslope flows. In the simulation with a weaker SAF, the results are generally similar but less pronounced. In both experiments, an altered thermal contrast, rather than increased boundary layer mixing, appears to be the primary mechanism driving changes in diurnal mountain wind systems in this region.
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Charny, C. K., and R. L. Levin. "Bioheat Transfer in a Branching Countercurrent Network During Hyperthermia." Journal of Biomechanical Engineering 111, no. 4 (November 1, 1989): 263–70. http://dx.doi.org/10.1115/1.3168377.
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A bioheat transfer model which computes the spatial variations in the arteriole, venule, and muscle temperatures in a human extremity under both resting and hyperthermic conditions is presented. This model uses the two-parameter model first proposed by Baish et al. [2] to account for the heat exchange between tissue and the paired arterioles and venules that comprise the microcirculation. Thermoregulation of the muscle blood flow during hyperthermia is also incorporated into the model. Results show that even when the paired arteriole and venule are assumed to have equal radii, the mean temperature under both steady and transient conditions is not equal to the mean of the arteriole and venule blood temperatures. Tissue temperature profiles during hyperthermia computed with the three-equation model presented in this study are similar in shape and magnitude to those predicted by the traditional one-equation Pennes bioheat transfer model [1]. This is due primarily to the influence of thermoregulatory mechanism in the heated muscle. The unexpected agreement is significant given the inherent relative simplicity of the traditional Pennes model. An “experimental” thermal conductivity is presented to relate the theoretical results to experimental procedures that are widely used to estimate the enhancement of conductivity by perfusion.
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Nindos, A., C. E. Alissandrakis, S. Patsourakos, and T. S. Bastian. "Transient brightenings in the quiet Sun detected by ALMA at 3 mm." Astronomy & Astrophysics 638 (June 2020): A62. http://dx.doi.org/10.1051/0004-6361/202037810.
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Aims. We investigate transient brightenings, that is, weak, small-scale episodes of energy release, in the quiet solar chromosphere; these episodes can provide insights into the heating mechanism of the outer layers of the solar atmosphere. Methods. Using Atacama Large Millimeter/submillimeter Array (ALMA) observations, we performed the first systematic survey for quiet Sun transient brightenings at 3 mm. Our dataset included images of six 87″ × 87″ fields of view of the quiet Sun obtained with angular resolution of a few arcsec at a cadence of 2 s. The transient brightenings were detected as weak enhancements above the average intensity after we removed the effect of the p-mode oscillations. A similar analysis, over the same fields of view, was performed for simultaneous 304 and 1600 Å data obtained with the Atmospheric Imaging Assembly. Results. We detected 184 3 mm transient brightening events with brightness temperatures from 70 K to more than 500 K above backgrounds of ∼7200 − 7450 K. All events showed light curves with a gradual rise and fall, strongly suggesting a thermal origin. Their mean duration and maximum area were 51.1 s and 12.3 Mm2, respectively, with a weak preference of appearing at network boundaries rather than in cell interiors. Both parameters exhibited power-law behavior with indices of 2.35 and 2.71, respectively. Only a small fraction of ALMA events had either 304 or 1600 Å counterparts but the properties of these events were not significantly different from those of the general population except that they lacked their low-end energy values. The total thermal energies of the ALMA transient brightenings were between 1.5 × 1024 and 9.9 × 1025 erg and their frequency distribution versus energy was a power law with an index of 1.67 ± 0.05. We found that the power per unit area provided by the ALMA events could account for only 1% of the chromospheric radiative losses (10% of the coronal ones). Conclusions. We were able to detect, for the first time, a significant number of weak 3 mm quiet Sun transient brightenings. However, their energy budget falls short of meeting the requirements for the heating of the upper layers of the solar atmosphere and this conclusion does not change even if we use the least restrictive criteria possible for the detection of transient brightenings.
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Ge, Li, Huaqi Li, Xiaoyan Tian, Zeyu Ouyang, Xiaoya Kang, Da Li, Jianqiang Shan, and Xinbiao Jiang. "Improvement and Validation of the System Analysis Model and Code for Heat-Pipe-Cooled Microreactor." Energies 15, no. 7 (April 1, 2022): 2586. http://dx.doi.org/10.3390/en15072586.
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Heat-pipe-cooled microreactors (HPMR) use a passive high-temperature alkali metal heat pipe to directly transfer the heat of solid core to the hot end of the intermediate heat exchanger or thermoelectric conversion device, thus avoiding a single point failure. To analyze and evaluate the transient safety characteristics of an HPMR system under accident conditions, such as heat pipe failure in the core or a loss of system heat sink and other accidents, a previously developed model for transient analysis of a heat-pipe-cooled space nuclear reactor power system (HPSR) was improved and validated in this study. The models improved mainly comprise: (1) An entire 2-D solid-core heat transfer model is established to analyze the accident conditions of core heat pipe failure and system heat sink loss. In this model, radial and axial Fourier heat conduction equations are used to divide the core into r-θ direction control volumes. The physical parameters of the material in the control volume are calculated according to the volume-weighted average. (2) By coupling the heat transfer limit model and the two-dimensional thermal resistance network model, the transient model of a heat pipe for HPMR system analysis is improved. (3) Conversion system models are established to simulate the system characteristics of the advanced HPMR concept, such as thermoelectric conversion, Stirling conversion, and the open Brayton conversion analysis model. Based on the improved models, the HPMR system analysis program TAPIRSD was developed, which was verified by experimental data of the separated conversion components and the ground nuclear test device KRUSTY. The maximum deviation of the power output predicted by the energy conversion model is less than 8%. The accident conditions of the KRUSTY tests, such as load change, core heat pipe failure, and heat sink loss accident, were studied by using TAPIRSD. The results show that the simulation results of the TAPIRSD code agree well with the experimental data of the KRUSTY prototype reactor. The maximum error between the TAPIRSD code prediction and the measured value of the core temperature under accident conditions is less than 10 K, and the maximum deviation is less than 2%. The results show that the developed code can predict the transient response process of the HPMR system well. At the same time, the accuracy and reliability of the improved model are proved. The TAPIRSD is suitable for system transient analysis of different types of HPMRs and provides an optional tool for the system safety characteristics analysis of HPMR.
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Keeney, J. A., and B. R. Bass. "Fracture Analysis of the NESC-1 Spinning Cylinder Experiment." Journal of Pressure Vessel Technology 119, no. 1 (February 1, 1997): 52–56. http://dx.doi.org/10.1115/1.2842266.
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This paper presents finite-element analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The objective of the NESC-1 project is to focus on a complete process for assessing the structural integrity of aged reactor pressure vessels. A new cylinder specimen was reconstituted from segments of the previously tested SC-4 and SC-6 specimens because the relatively high fracture toughness of the original specimen might preclude achieving the test objectives. The wall thickness is greater for the reconstituted specimen when compared with the previous specimen geometry (175 versus 150 mm). Also, the initial and coolant temperatures for the proposed thermal shock may be reduced as much as 25°C to increase the probability of achieving cleavage initiation. Analyses were carried out to determine the combined effects of increasing the wall thickness and lowering the initial and coolant temperatures in the experiment. Estimates were made of the change in hoop strain on the clad inner surface directly above a subclad crack due to initiation and axial propagation of the crack. Three-dimensional finite-element models of the cladded cylinder were generated with 6:1 and 2:1 semi-elliptical 70-mm-deep subclad cracks. The cylinder specimen was subjected to thermal-shock and centrifugal loading conditions and analyzed with a thermo-elastic-plastic material model. The analytical results indicate that lowering the initial and coolant temperatures by 25°C will not significantly change the peak driving force, but will shift the stress-intensity factor (KI) versus temperature curves so that the crack will become critical at an earlier time in the transient. The peak KI value occurs at a lower temperature (after the crack becomes critical), which increases the probability of achieving cleavage initiation. Also, the calculated hoop strains for the two crack aspect ratios (simulation of 2:1 crack propagating axially) provide an estimated change in hoop strain in the range of 3 to 4 percent on the clad inner surface.
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Gaudio, Pasquale, Roberto Montanari, Ekaterina Pakhomova, Maria Richetta, and Alessandra Varone. "Surface Morphology of Refractory Metals Submitted to a Single Laser Pulse." Materials Science Forum 1016 (January 2021): 1526–31. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1526.
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The work investigates refractory metals (bulk W, W produced via plasma spraying, W-1% La2O3 and Mo) of interest as plasma facing materials in future nuclear fusion reactors. They have been irradiated by a single Nd:YAG laser pulse to simulate the effects of transient thermal loads of high energy occurring in a tokamak under operative conditions and then examined by SEM observations. In all the materials the laser pulse induces a crater in the central area of laser spot surrounded by a ridge due to movement of molten metal while in a more external area a network of cracks is observed. Diameter and depth of the crater, ablated volume and morphological features of the surrounding area exhibit differences depending on the specific metal, its physical and microstructural characteristics which affect vaporization, melting and heat propagation from the irradiated spot.
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Ali, Sajeda Abd, Ibtisam A. Hasan, and Ekbal Hussain. "A Comparison Between Half and Full Fins at Nanofluids in Transformers." IOP Conference Series: Earth and Environmental Science 961, no. 1 (January 1, 2022): 012088. http://dx.doi.org/10.1088/1755-1315/961/1/012088.
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Abstract Power transformers characterize the biggest section of capital investment within the distribution substations as well as transmission. Additionally, outages of those transformers have a substantial economic influence on the functioning of an electrical network due to the fact that the power transformers are one of the utmost overpriced constituents in an electricity structure. A suggested thermal model for a distribution transformer is investigated. The temperature distribution in the three-phase transformer (250 KVA 11/.416 KV core type, mineral oil) was obtained using “COMSOL PROGRAM” after a 3D simulation utilizing a transient analysis in light of the Finite Element Method (FEM). Meanwhile, the suggested model is being used to examine the impacts of different types of oil on HOST. To test the effect of nanoparticles on heat transfer process, the insulation oil was changed with Nanofluids and hybrid nanofluids; For present work, can be concluded when add nanofluids (Al2O3, CuO, SiC) for oil of transformer under different concentration ratio (0.3,0.5,0.8,1,1.2,1.4 % wt) and add hybrid nanofluids (oil+ Al2O3+CuO), (oil+ Al2O3+SiC), (oil+ SiC +CuO) at different concentration ratio (1,1.2,1.4 % wt). The concentration of nanofluids show a direct influence on the temperature reduction for the studied cases. Finally it can be said, the proposed model was succeeded in simulating the distribution transformer, which is in good agreement with the experimental tests adopted for this work, and it could be used as a design tool with assist of COMSOL Multiphysics Package. The present model successfully accomplished for expecting the temperature distribution at any locations in the transformer when compared with practical measurement.
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Ma, Xiaoqin, Chenxia Hao, Zhaokang Zhang, Huiting Jiang, Weixia Zhang, Jingjing Huang, Xiaofei Chen, and Wanhua Yang. "Shenjinhuoxue Mixture Attenuates Inflammation, Pain, and Cartilage Degeneration by Inhibiting TLR-4 and NF-κB Activation in Rats with Osteoarthritis: A Synergistic Combination of Multitarget Active Phytochemicals." Oxidative Medicine and Cellular Longevity 2021 (October 21, 2021): 1–21. http://dx.doi.org/10.1155/2021/4190098.
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Osteoarthritis (OA), a highly prevalent chronic joint disease, involves a complex network of inflammatory mediators that not only triggers pain and cartilage degeneration but also accelerates disease progression. Traditional Chinese medicinal shenjinhuoxue mixture (SHM) shows anti-inflammatory and analgesic effects against OA with remarkable clinical efficacy. This study explored the mechanism underlying anti-OA properties of SHM and evaluated its efficacy and safety via in vivo experiments. Through network pharmacology and published literature, we identified the key active phytochemicals in SHM, including β-sitosterol, oleanolic acid, licochalcone A, quercetin, isorhamnetin, kaempferol, morusin, lupeol, and pinocembrin; the pivotal targets of which are TLR-4 and NF-κB, eliciting anti-OA activity. These phytochemicals can enter the active pockets of TLR-4 and NF-κB with docking score ≤ − 3.86 kcal / mol , as shown in molecular docking models. By using surface plasmon resonance assay, licochalcone A and oleanolic acid were found to have good TLR-4-binding affinity. In OA rats, oral SHM at mid and high doses (8.72 g/kg and 26.2 g/kg) over 6 weeks significantly alleviated mechanical and thermal hyperalgesia ( P < 0.0001 ). Accordingly, the expression of inflammatory mediators (TLR-4, interleukin (IL-) 1 receptor-associated kinase 1 (IRAK1), NF-κB-p65, tumor necrosis factor (TNF-) α, IL-6, and IL-1β), receptor activator of the NF-κB ligand (RANKL), and transient receptor potential vanilloid 1 (TRPV1) in the synovial and cartilage tissue of OA rats was significantly decreased ( P < 0.05 ). Moreover, pathological observation illustrated amelioration of cartilage degeneration and joint injury. In chronic toxicity experiment of rats, SHM at 60 mg/kg demonstrated the safety. SHM had an anti-inflammatory effect through a synergistic combination of active phytochemicals to attenuate pain and cartilage degeneration by inhibiting TLR-4 and NF-κB activation. This study provided the experimental foundation for the development of SHM into a more effective dosage form or new drugs for OA treatment.
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Elzanati, Osama, Said Mouzeyar, and Jane Roche. "Dynamics of the Transcriptome Response to Heat in the Moss, Physcomitrella patens." International Journal of Molecular Sciences 21, no. 4 (February 22, 2020): 1512. http://dx.doi.org/10.3390/ijms21041512.
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Thermal stress negatively impacts crop yields, and as the overall temperature of the earth’s atmosphere is gradually increasing, the identification of the temperature transduction pathway of the heat signal is essential in developing new strategies in order to adapt plant breeding to warmer climates. Heat stress damages the molecular structures and physiological processes in plants in proportion to the level and duration of the stress, which leads to different types of responses. In general, plants respond more efficiently when they are first subjected to a moderate temperature increase before being subjected to a higher temperature stress. This adaptive response is called the acclimation period and has been investigated in several plant species. However, there is a lack of information on the dynamic of the Heat Shock Response (HSR) over a continuous period of temperature rise without an acclimation period. In this paper, we investigated the effects of mild (30 °C) and high (37 °C) continuous heat stress over a 24-h period. Through RNA-Seq analysis, we assessed the remodeling of the transcriptome in the moss Physcomitrella patens. Our results showed that the 30 °C treatment particularly affected the expression of a few genes at 1 and 24 h, suggesting a biphasic response. Up-regulated genes at 1 h encode mainly HSR proteins (protein folding and endoplasmic reticulum stress), indicating an early heat response; while the up-regulated genes at 24 h belong to the thiamine biosynthesis pathway. In contrast, the genes involved in photosynthesis and carbon partitioning were repressed by this treatment. Under a higher temperature stress (37 °C), the induction of the HSR occurred rapidly (1 h) and was then attenuated throughout the time points investigated. A network approach (Weighted Gene Correlation Network Analysis, WGCNA) was used to identify the groups of genes expressing similar profiles, highlighting a HsfA1E binding motif within the promoters of some unrelated genes which displayed rapid and transient heat-activation. Therefore, it could be suggested that these genes could be direct targets of activation by a HsfA1E transcription factors.
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Dershowitz, Bill, Paul LaPointe, Thorsten Eiben, and Lingli Wei. "Integration of Discrete Feature Network Methods With Conventional Simulator Approaches." SPE Reservoir Evaluation & Engineering 3, no. 02 (April 1, 2000): 165–70. http://dx.doi.org/10.2118/62498-pa.
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Summary The discrete feature network (DFN) approach offers many key advantages over conventional dual porosity (DP) approaches, particularly when issues of connectivity dominate recovery and reservoir stimulation in fractured and heterogeneous reservoirs. DP models have been developed for complex multiphase and thermal effects, and have been implemented for basin scale modeling. However, DP models address only the dual porosity nature of fractured reservoirs, generally simplifying connectivity and scale-dependent heterogeneity issues which are modeled efficiently and more accurately by the DFN approach. This paper describes the development of techniques to integrate DFN and DP approaches. These techniques allow the analyst to maintain many of the advantages of the DP simulator approach without losing the realism of complex fracture system geometry and connectivity, as captured by DFN models. The techniques described are currently used within a DOE funded research project for linking a DFN and a DP thermal simulation model for the Yates field, Texas. The paper describes some of the geological and engineering aspects of the Yates field and gives two examples of how DP parameters for the thermal simulation can be derived using DFN modeling techniques. Introduction Reservoir simulation can be significantly more challenging for fractured reservoirs than it is for conventional clastic reservoirs. The dual porosity (DP) approach for the simulation of fractured reservoirs adds a second interacting continuum to reflect storage and permeability characteristics but does not adequately address connectivity issues. These effects, which play a key role in fractured reservoirs, are generally better addressed by discrete feature network (DFN) models.1 Another advantage of DFN models is that they are generally implemented as stochastic models, in which multiple realizations provide a quantitative measure for uncertainty and variability. Despite the significant simplifications made regarding the geometry of the fracture network in equivalent porous medium DP models (Fig. 1) and the recent progress made in developing powerful DFN modeling software, DP models still offer advantages regarding the level of sophistication of available multiphase flow solvers. In many cases, DP models also offer advantages regarding model size and speed. As a result, there is a need to link DP and DFN models to be able to take maximum advantage of each approach. This paper presents a series of techniques, which can be used to develop DP models that more accurately reflect the anisotropy, heterogeneity, and most important, the scale-dependent connectivity structure of fractured reservoirs. These techniques will allow the DP approach to take advantage of some of the features of the DFN approach. The approach adopted is to derive grid cell and well parameters through DFN models. The first section of this paper discusses which fracture porosity parameters can be derived for DP models from DFN models and how they are derived. The second section describes different techniques that can be used to link DP and DFN models. At the end of the paper two examples are given based on data from the Yates field, Texas. DP Input Parameter from DFN Modeling Fracture System Porosity. The fracture system porosity fF can be directly calculated as the product of the fracture intensity expressed as fracture area per unit volume (P32) and the storage aperture of the fractures (e):… Because the fracture system porosity depends on the number of fractures per unit volume, the fracture size distribution and the fracture aperture distribution, a different porosity needs to be calculated for every portion of the continuum model where these parameters vary. Using a full field DFN model, the fracture system porosity can be calculated separately for each grid cell. The primary issue in definition of fracture porosity from fracture intensity P32 is the selection of an appropriate measure for storage aperture e. Possible measures include:aperture derived from transient hydraulic response,mechanical aperture,aperture derived from fracture permeability or transmissivity ("cubic law"),aperture derived from geophysical measurements (gamma density, matrix porosity), andcorrelations to fracture size and orientation. Directional Fracture System Permeability. The permeability of the fracture system depends on the fracture intensity, the connectivity of the fracture network, and the distribution of fracture transmissivities. Approaches for calculation of approximate measures of grid cell effective directional permeability include the tensor approach of Oda,2 and the use of DFN simulations with a range of orientations for a unit gradient. Oda's2 method begins by considering the orientation of fractures in a grid cell, expressed as a unit normal vector n. Integrating the fractures over all of the unit normals N, Oda obtained the mass moment of inertia of fracture normals distributed over a unit sphere: ….For a specific grid cell with known fracture areas Ak and transmissivities Tk obtained from the DFN model, an empirical fracture tensor can be calculated by adding the individual fractures weighted by their area and transmissivity:…. Oda's permeability tensor is derived from Fij by assuming that Fij expresses fracture flow as a vector along the fracture's unit normal. Assuming that fractures are impermeable in a direction parallel to their unit normal, Fij must be rotated into the planes of permeability ….
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Grosu, Vicentiu, Chris Lindgren, and Tamas Vejsz. "Thermal Management Solutions for enhanced Digital Flight Data Acquisition Unit in Avionics Applications." International Symposium on Microelectronics 2015, no. 1 (October 1, 2015): 000517–25. http://dx.doi.org/10.4071/isom-2015-wp64.
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According to the Federal Aviation Administration, the commercial airline industry should expect to see the number of passengers traveling per year to grow from its current level of 750 million to nearly 1 billion by 2030. To meet this demand, airlines are placing orders for thousands of new aircraft over the next decade and beyond. With this increase in airline traffic, newer aircraft systems will generate an ever increasing amount of data per flight, data that allows airlines to further enhance their flight operations, flight safety, and reliability. For commercial avionics, the migration of the data acquisition and reporting functions from the traditional interface environments to newer, faster, and more network-centric architectures is creating a new generation of “smart” aircraft. Teledyne Controls' enhanced Digital Flight Data Acquisition Unit is an integral part of a new generation of aircraft and combines the functions of Mandatory Data Acquisition and Recording with a sophisticated Aircraft Conditioning Monitoring System that the aircraft operator uses to monitor the performance and reliability of each aircraft in its fleet. Some of the critical goals in the development of the Digital Flight Data Acquisition Unit are reducing the size and weight over previous generations, while maximizing performance and reducing cost. All of these opposing requirements make the design and fabrication very challenging. One such challenge includes dissipating high power in a confined space, and this makes thermal management a critical component of the overall LRU (line-replaceable unit) design. In addition, to increase the reliability over the lifespan of the unit, passive cooling systems are often required in place of internal fans. This presents another set of challenges, such as optimizing the airflow provided by the aircraft in the electronics bay compartment. This paper will present some of the critical elements in thermal management such as heat sinks, components placement, thermal interface materials, thermal vias, thermal links, packaging approaches and cooling strategy. The design and optimization of the system are based on analytical solutions, conjugated heat transfer and experimental results. The LRU should safely operate under various environmental conditions: ground operation, flight operation, high operating temperature and loss of cooling air where each environmental condition has different parameters for coolant airflow rate, effect of the surroundings, and ambient and coolant air temperature. Draw-Through and Blow-Through cooling analysis were performed using CFD (Computational Fluid Dynamics). The thermal analysis problems solved are conjugated heat transfer for laminar flow with radiation in steady-state or transient regimes. Multiple approaches were identified to remove heat from the critical components through optimization of the components and subsystems. These same approaches can also be used to increase the system's performance and reliability.
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Hofmann, Joachim Werner, Bernd Sitzmann, John Dickinson, Dominique Kunz, and Ralph Eismann. "Use of machine-learning for monitoring solar thermal plants." Journal of Physics: Conference Series 2042, no. 1 (November 1, 2021): 012007. http://dx.doi.org/10.1088/1742-6596/2042/1/012007.
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Abstract A machine-learning algorithm (MLA) was developed to assess the operational state of solar thermal plants, based on the data of only one temperature sensor, and the irradiance and ambient temperature data from the nearest weather station. A detailed requirements analysis of the situation results in the classification of a multivariate time series problem. Neural networks used in the field of data science are ideally suited for problems of this type. Data from the operational monitoring system, which runs a rule-based algorithm, were used to train the neural network using the software framework TensorFlow. It was shown that the chosen MLA can detect malfunctions such as heat loss due to gravity-driven circulation during night. However, further development towards a practical tool requires not only far more data for training and validation. It became clear that corresponding pressure data are needed to classify temperature transients and to attribute these classes to certain malfunctions.
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Serrano, José Ramón, Andrés Tiseira, Luis Miguel García-Cuevas, and Tatiana Rodríguez Usaquén. "Adaptation of a 1-D tool to study transient thermal in turbocharger bearing housing." Applied Thermal Engineering 134 (April 2018): 564–75. http://dx.doi.org/10.1016/j.applthermaleng.2018.01.085.
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Hristov, Jordan, and Ganaoui El. "Thermal impedance estimations by semi-derivatives and semi-integrals: 1-D semi-infinite cases." Thermal Science 17, no. 2 (2013): 581–89. http://dx.doi.org/10.2298/tsci120522211h.
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Simple 1-D semi-infinite heat conduction problems enable to demonstrate the potential of the fractional calculus in determination of transient thermal impedances under various boundary conditions imposed at the interface (x=0). The approach is purely analytic and very effective because it uses only simple semi-derivatives (half-time) and semi-integrals and avoids development of entire domain solutions. 0x=
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Cheng, Tao, Wenjing Qin, Youyun Lian, Xiang Liu, Jun Tang, Guangxu Cai, Shijian Zhang, Xiaoyun Le, Changzhong Jiang, and Feng Ren. "High Transient-Thermal-Shock Resistant Nanochannel Tungsten Films." Nanomaterials 11, no. 10 (October 11, 2021): 2663. http://dx.doi.org/10.3390/nano11102663.
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Developing high-performance tungsten plasma-facing materials for fusion reactors is an urgent task. In this paper, novel nanochannel structural W films prepared by magnetron sputtering deposition were irradiated using a high-power pulsed electron beam or ion beam to study their edge-localized modes, such as transient thermal shock resistance. Under electron beam irradiation, a 1 μm thick nanochannel W film with 150 watt power showed a higher absorbed power density related cracking threshold (0.28–0.43 GW/m2) than the commercial bulk W (0.16–0.28 GW/m2) at room temperature. With ion beam irradiation with an energy density of 1 J/cm2 for different pulses, the bulk W displayed many large cracks with the increase of pulse number, while only micro-crack networks with a width of tens of nanometers were found in the nanochannel W film. For the mechanism of the high resistance of nanochannel W films to transient thermal shock, a residual stress analysis was made by Grazing-incidence X-ray diffraction (GIXRD), and the results showed that the irradiated nanochannel W films had a much lower stress than that of the irradiated bulk W, which indicates that the nanochannel structure can release more stress, due to its special nanochannel structure and ability for the annihilation of irradiation induced defects.
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Yee, Cheang Soon, K. N. Seetharamu, G. A. Quadir, and Z. A. Zainal. "Investigation of Steady State and Transient Thermal Management in Portable Telecommunication Product – Part 1." Journal of Microelectronics and Electronic Packaging 2, no. 1 (January 1, 2005): 40–54. http://dx.doi.org/10.4071/1551-4897-2.1.40.
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Steady state and transient thermal management in a portable telecommunication product was investigated. The steady state analysis portion will be discussed in details in Part 1. The investigation was conducted using finite element analysis (FEA) simulation on a cellular phone model. The three-dimensional simulation is based on a solid conduction cellular phone model cooled by natural convection and radiation. The FEA simulation method was verified with experimental results. In this paper, simulation study was carried out to examine various thermal solution options to improve on the heat transfer from the package to the surrounding. As conduction is the predominant heat transfer within the cellular phone, the thermal resistance can be reduced by creating a solid conduction path between the heat dissipating packages with the housing wall and improving the housing wall conduction material.
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Hristov, Jordan. "Thermal impedance at the interface of contacting bodies: 1-D examples solved by semi-derivatives." Thermal Science 16, no. 2 (2012): 623–27. http://dx.doi.org/10.2298/tsci111125017h.
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Simple 1-D semi-infinite heat conduction problems enable to demonstrate the potential of the fractional calculus in determination of transient thermal impedances of two bodies with different initial temperatures contacting at the interface ( x = 0 ) at t = 0 . The approach is purely analytic and uses only semi-derivatives (half-time) and semi-integrals in the Riemann-Liouville sense. The example solved clearly reveals that the fractional calculus is more effective in calculation the thermal resistances than the entire domain solutions.
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Peng Hong, Liem, Pinem Surian, Sembiring Tagor Malem, and Nam Tran Hoai. "Status on development and verification of reactivity initiated accident analysis code for PWR (NODAL3)." Nuclear Science and Technology 6, no. 1 (September 24, 2021): 1–13. http://dx.doi.org/10.53747/jnst.v6i1.139.
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A coupled neutronics thermal-hydraulics code NODAL3 has been developed based on the nodal few-group neutron diffusion theory in 3-dimensional Cartesian geometry for a typical pressurized water reactor (PWR) static and transient analyses, especially for reactivity initiated accidents (RIA).The spatial variables are treated by using a polynomial nodal method (PNM) while for the neutron dynamic solver the adiabatic and improved quasi-static methods are adopted. A simple single channel thermal-hydraulics module and its steam table is implemented into the code. Verification works on static and transient benchmarks are being conducted to assess the accuracy of the code. For the static benchmark verification, the IAEA-2D, IAEA-3D, BIBLIS and KOEBERG light water reactor (LWR) benchmark problems were selected, while for the transient benchmark verification, the OECD NEACRP 3-D LWR Core Transient Benchmark and NEA-NSC 3-D/1-D PWR Core Transient Benchmark (Uncontrolled Withdrawal of Control Rods at Zero Power). Excellent agreement of the NODAL3 results with the reference solutions and other validated nodal codes was confirmed
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Shrinivas, Ajay B., and Gary R. Hunt. "Transient ventilation dynamics induced by heat sources of unequal strength." Journal of Fluid Mechanics 738 (December 2, 2013): 34–64. http://dx.doi.org/10.1017/jfm.2013.579.
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AbstractWe examine theoretically the transient displacement flow and density stratification that develops within a ventilated box after two localized floor-level heat sources of unequal strengths are activated. The heat input is represented by two non-interacting turbulent axisymmetric plumes of constant buoyancy fluxes ${B}_{1} $ and ${B}_{2} \gt {B}_{1} $. The box connects to an unbounded quiescent external environment of uniform density via openings at the top and base. A theoretical model is developed to predict the time evolution of the dimensionless depths ${\lambda }_{j} $ and mean buoyancies ${\delta }_{j} $ of the ‘intermediate’ $(j= 1)$ and ‘top’ $(j= 2)$ layers leading to steady state. The flow behaviour is classified in terms of a stratification parameter , a dimensionless measure of the relative forcing strengths of the two buoyant layers that drive the flow. We find that $\mathrm{d} {\delta }_{1} / \mathrm{d} \tau \propto 1/ {\lambda }_{1} $ and $\mathrm{d} {\delta }_{2} / \mathrm{d} \tau \propto 1/ {\lambda }_{2} $, where $\tau $ is a dimensionless time. When $\hspace{0.167em} \hspace{0.167em} \ll \hspace{0.167em} \hspace{0.167em} $1, the intermediate layer is shallow (small ${\lambda }_{1} $), whereas the top layer is relatively deep (large ${\lambda }_{2} $) and, in this limit, ${\delta }_{1} $ and ${\delta }_{2} $ evolve on two characteristically different time scales. This produces a time lag and gives rise to a ‘thermal overshoot’, during which ${\delta }_{1} $ exceeds its steady value and attains a maximum during the transients; a flow feature we refer to, in the context of a ventilated room, as ‘localized overheating’. For a given source strength ratio $\psi = {B}_{1} / {B}_{2} $, we show that thermal overshoots are realized for dimensionless opening areas $A\lt {A}_{oh} $ and are strongly dependent on the time history of the flow. We establish the region of $\{ A, \psi \} $ space where rapid development of ${\delta }_{1} $ results in ${\delta }_{1} \gt {\delta }_{2} $, giving rise to a bulk overturning of the buoyant layers. Finally, some implications of these results, specifically to the ventilation of a room, are discussed.
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Kim, Jichul, Jae Choon Kim, Mina Choi, Eunseok Cho, Hyunggil Baek, HoGeon Song, and Sayoon Kang. "Simultaneous Characterization of Theta-JC and Theta-JB Using Through-Package 1-D Heat Flow." International Symposium on Microelectronics 2011, no. 1 (January 1, 2011): 000947–52. http://dx.doi.org/10.4071/isom-2011-tha2-paper5.
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A new technique is proposed for simultaneous, in-situ characterization of in-package thermal resistances (junction-to-case and junction-to-board) in a single test. A thin resistive heater is patterned on package top surface to establish one-dimensional heat conduction along the package vertical direction. Accompanying temperature rise at the heater is measured using a thermocouple and analyzed to estimate equivalent thermal R-C network model of the package. Due to the one-dimensionality of the probing thermal wave, the derived R-C network model represents physical package thermal structure, enabling simultaneous estimation of both thermal resistances (theta-JC and theta-JB). The proposed technique is validated by measuring theta-JC and JB of an overmolded flip-chip ball grid array package. The proposed method eliminates need for a separate test setup for the characterization of each thermal resistance, enhancing the accuracy and efficiency of the package thermal characterization. In addition, use of the external heater and sensing element, instead of on-chip heater and temperature sensor, enables in-situ thermal characterization of a real package mounted on the set board.
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Chang, F. C., T. Sofu, J. Hull, D. Weber, S. Malipeddi, and R. Dupree. "Thermal analysis of an off-road machine with a conjoint 3-D CFD and 1-D network simulation package." International Journal of Heavy Vehicle Systems 14, no. 1 (2007): 85. http://dx.doi.org/10.1504/ijhvs.2007.011798.
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Agarwal, S., N. Tosi, D. Breuer, S. Padovan, P. Kessel, and G. Montavon. "A machine-learning-based surrogate model of Mars’ thermal evolution." Geophysical Journal International 222, no. 3 (May 13, 2020): 1656–70. http://dx.doi.org/10.1093/gji/ggaa234.
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SUMMARY Constraining initial conditions and parameters of mantle convection for a planet often requires running several hundred computationally expensive simulations in order to find those matching certain ‘observables’, such as crustal thickness, duration of volcanism, or radial contraction. A lower fidelity alternative is to use 1-D evolution models based on scaling laws that parametrize convective heat transfer. However, this approach is often limited in the amount of physics that scaling laws can accurately represent (e.g. temperature and pressure-dependent rheologies or mineralogical phase transitions can only be marginally simulated). We leverage neural networks to build a surrogate model that can predict the entire evolution (0–4.5 Gyr) of the 1-D temperature profile of a Mars-like planet for a wide range of values of five different parameters: reference viscosity, activation energy and activation volume of diffusion creep, enrichment factor of heat-producing elements in the crust and initial temperature of the mantle. The neural network we evaluate and present here has been trained from a subset of ∼10 000 evolution simulations of Mars ran on a 2-D quarter-cylindrical grid, from which we extracted laterally averaged 1-D temperature profiles. The temperature profiles predicted by this trained network match those of an unseen batch of 2-D simulations with an average accuracy of $99.7\, {\rm per~cent}$.
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Zhao, Qing-Tai, Fengben Xi, Yi Han, Jin Hee Bae, and Detlev Gruetzmacher. "(Invited, Digital Presentation) Approach to Neuromorphic Computing with Ferroelectric Schottky Barrier FETs." ECS Meeting Abstracts MA2022-01, no. 29 (July 7, 2022): 1298. http://dx.doi.org/10.1149/ma2022-01291298mtgabs.
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Neuromorphic computing inspired by neural network systems of the human brain enables energy efficient computing as a solution of the von Neumann bottleneck. A neural network consists of thousands or even millions of neurons which communicate with each other through connected synapses. Synapses can memorize and process the information simultaneously. The plasticity of a synapse to strengthen or weaken its activity over time make it be capable of learning and computing. Thus, artificial synapses which can emulate functionalities and the plasticity of bio-synapses form the backbone of a neuromorphic computing system. Non-volatile memories with two-terminals, like resistive random-access memory (ReRAM), phase change memory (PCM), are attractive candidates for artificial synapses. However, signal processing and learning cannot be performed simultaneously in these two-terminal synapses. FeFET, similar to a MOSFET structure using CMOS compatible HfO2 based ferroelectrics as gate oxide forms three-terminal synapses offering high endurance, good performance and high energy efficiency. In contrast to two-terminal devices, three terminal FeFET based synapses can perform processing and learning at the same time. In order to maintain the ferroelectric properties of an HfO2 based ferroelectric film, high temperature annealing should be avoided after the ferroelectric layer deposition. In this paper, we present ferroelectric NiSi2 source/drain Schottky barrier (SB) MOSFET (FE-SBFET) structure (Fig.1a), which requires neither ion implantation nor thermal activation of source/drain contacts at high temperatures. FE-SBFETs were fabricated on SOI substrates with a boron-doped (1016 B/cm-3), 55 nm thick top Si layer and a 145 nm thick buried oxide (BOX) layer. Very thin (9 nm) single crystalline NiSi2 layers which offer superior properties of uniform and stable SB contacts on Si are used at source/drain regions. A gate stack consisting of 10 nm thick Hf0.5Zr0.5O2 (HZO) layer and a 40 nm thick TiN layer are deposited by ALD and sputtering, respectively. A rapid thermal annealing at 500 °C is performed to crystallize the HZO into a ferroelectric phase before the gate patterning. The fabricated device has a channel length of 10 µm and a gate width of 10 µm. The overlap between the top gate and NiSi2 is 6 µm along the channel and 10 µm wide on each side. The ferroelectric polarization modulates both the SB at the source/drain contacts as well as the potential in the channel, thus changing the carrier injection through the SB. The Id-Vg transfer characteristics of a p-type FE-SBFET shows a clockwise hysteresis which is caused by the ferroelectric polarization switch. The excitatory post-synaptic current (EPSC), one of the typical short-term synaptic plasticity features for biologic synapses, is characterized by measuring the transient drain currents for a voltage pulse on the gate of a FE-SBFET (Fig.1b). The amplitude of the pulse VAM changes from -0.2 to -1.2 V with a fixed pulse width tpw=1 μs. We found that the EPSC peak value increases linearly with VAM. It shows a very low energy/spike consumption of 2fJ/spike at VAM=-0.2 V, demonstrating a very high energy efficiency. From the EPSC measurements with repeated gate voltage pulses paired-pulse facilitation/depression (PPF/PPD) are characterized showing an exponential decay, similar to biological synapses. The long-term synaptic plasticity of FE-SBFET synapses is characterized by a series repeated identical or non-identical pulses. The later can improve the long-term potentiation/depression (LTP/LTD) symmetry and linearity. The measurements show a large Gmax/Gmin ratio, very high endurance and small cycle-to-cycle (CTC) variation (1.06%) due to the perfect contact of NiSi2 (Fig.1c). The biological neuron-like spike-timing-dependent plasticity (STDP) is characterized for the FE-SBFET synapse. The results show an asymmetric anti-Hebbian STDP, which is one of the biological STDP functionalities (Fig.1d). In conclusion, the fabricated FE-SBFET synapse exhibits multiple synaptic functions with high endurance and small variations. The ultra-low energy/spike consumption indicates a high potential for low power neuromorphic computing applications. Acknowledgement: This work was supported by the Federal Ministry of Education and Research (BMBF, Germany) in the project NEUROTEC (16ME0398K). Figure 1
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Eydam, Agnes, Gunnar Suchaneck, and Gerald Gerlach. "Evaluation of the Polarization State of Integrated Piezoelectric Sensors and Actuators Using the Thermal Wave Method." Key Engineering Materials 543 (March 2013): 503–6. http://dx.doi.org/10.4028/www.scientific.net/kem.543.503.
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In this work, we investigate the polarization state of a Low-Temperature-Cofired-Ceramics (LTCC)/PZT sensor-actuator and a Macro-Fiber Composite (MFC) actuator. An analytical solution for a 1-D thermal problem was derived for an embedded piezoelectric plate. Transient thermal analysis of the more complicated MFC actuator was performed using finite element modelling. At modulation frequencies below 10 Hz both modules are well described by a harmonically heated piezoelectric plate exhibiting heat losses to the environment.
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Nafar Sefiddashti, Mohammad, Brian Edwards, and Bamin Khomami. "Individual Molecular Dynamics of an Entangled Polyethylene Melt Undergoing Steady Shear Flow: Steady-State and Transient Dynamics." Polymers 11, no. 3 (March 12, 2019): 476. http://dx.doi.org/10.3390/polym11030476.
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The startup and steady shear flow properties of an entangled, monodisperse polyethylene liquid (C1000H2002) were investigated via virtual experimentation using nonequilibrium molecular dynamics. The simulations revealed a multifaceted dynamical response of the liquid to the imposed flow field in which entanglement loss leading to individual molecular rotation plays a dominant role in dictating the bulk rheological response at intermediate and high shear rates. Under steady shear conditions, four regimes of flow behavior were evident. In the linear viscoelastic regime ( γ ˙ < τ d − 1 ), orientation of the reptation tube network dictates the rheological response. Within the second regime ( τ d − 1 < γ ˙ < τ R − 1 ), the tube segments begin to stretch mildly and the molecular entanglement network begins to relax as flow strength increases; however, the dominant relaxation mechanism in this region remains the orientation of the tube segments. In the third regime ( τ R − 1 < γ ˙ < τ e − 1 ), molecular disentangling accelerates and tube stretching dominates the response. Additionally, the rotation of molecules become a significant source of the overall dynamic response. In the fourth regime ( γ ˙ > τ e − 1 ), the entanglement network deteriorates such that some molecules become almost completely unraveled, and molecular tumbling becomes the dominant relaxation mechanism. The comparison of transient shear viscosity, η + , with the dynamic responses of key variables of the tube model, including the tube segmental orientation, S , and tube stretch, λ , revealed that the stress overshoot and undershoot in steady shear flow of entangled liquids are essentially originated and dynamically controlled by the S x y component of the tube orientation tensor, rather than the tube stretch, over a wide range of flow strengths.
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Ataieyan, Atousa, Seyed Ayyoubzadeh, Abdolreza Nabavi, Salvador Gomez-Lopera, and Gennaro Sepede. "Simulation of mass transfer in a river with dead zones using network simulation method." Thermal Science 23, Suppl. 6 (2019): 1917–27. http://dx.doi.org/10.2298/tsci190430352a.
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In this study, network simulation method is applied to solve a 1-D solute transfer problem governed by transient storage model in a mountain stream including dead zones. In this computational method, for each node of the discretized domain, the terms of governing equation are substituted by the equivalent electrical devices which are connected to each other based on Kirchhoff?s current law. Finally, the total electric circuit is solved using an appropriate electrical code to obtain the unknown value at the nodes. Because no analytical solutions for this model have been presented so far, to verify network simulation method, the problem is solved by finite volume method, as well. According to the results, estimations made by network simulation method and finite volume method are in good agreement. Further, network simulation method is easier in implementation, especially in implementation of boundary conditions, and faster than finite volume method in computation. Therefore, in the case of 1-D mass transfer problems with a set of coupled equations, network simulation method is recommended to be used as an efficient alternative to numerical methods.
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Leng, XinYu, Chao Xiao, Lu Chen, Zheng Su, Kang Zheng, Xian Zhang, and XingYou Tian. "An efficient approach for constructing 3-D boron nitride networks with epoxy composites to form materials with enhanced thermal, dielectric, and mechanical properties." High Performance Polymers 31, no. 3 (February 25, 2019): 350–58. http://dx.doi.org/10.1177/0954008318772331.
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Thermally conductive epoxy composites of 3-D boron nitride (BN) networks were synthesized via a facile template method, wherein an epoxy was infiltrated into the network. The 3-D BN network skeletons, which use polystyrene (PS) microspheres as a framework support, were prepared by hot compression and ablation techniques. Field emission scanning electron microscope indicated that the content of BN filler and its dispersion greatly influences the integrity and density of the resultant network. With a BN loading of 40 vol%, the composites showed a maximum thermal conductivity of 1.98 W mK−1, which is 1000% times higher than the pristine epoxy material. In addition, the thermal stabilities, mechanical properties, and dielectric properties of the fabricated BN/epoxy composites were also largely improved. This facile method is an effective approach to designing and fabricating composites with high thermal conductivities.
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Zhang, Mengzhao, and Chunlin Guo. "VSG damping adaptive adjustment based on BP neural network." Journal of Physics: Conference Series 2121, no. 1 (November 1, 2021): 012036. http://dx.doi.org/10.1088/1742-6596/2121/1/012036.
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Abstract The moment of inertia and damping of virtual synchronous generator (VSG) can be adjusted flexibly, which also has a significant impact on the transient performance of VSG. Constant damping or moment of inertia can not reduce frequency overshoot and fast response performance, so it is necessary to introduce adaptive damping control. Based on universal approximation theorem, BP neural network can fit continuous nonlinear function well. At the same time, it has the advantages of simple algorithm, powerful learning ability and fast learning speed. Based on the characteristics of the control object, the BP neural network is improved and a new adaptive control strategy is designed. The strategy uses improved BP neural network to adjust VSG virtual damping D online. Python-MATLAB-Simulink was used for co-simulation, BP neural network algorithm was integrated into the control object to establish an adaptive simulation model, and the proposed control strategy was simulated and verified. Simulation results show that the adaptive control strategy can eliminate overshoot and respond quickly when the frequency and active power of virtual synchronous generator change.
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Beeson, Helen W., and Scott W. McCoy. "Geomorphic signatures of the transient fluvial response to tilting." Earth Surface Dynamics 8, no. 1 (February 19, 2020): 123–59. http://dx.doi.org/10.5194/esurf-8-123-2020.
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Abstract. Nonuniform rock uplift in the form of tilting has been documented in convergent margins, postorogenic landscapes, and extensional provinces. Despite the prevalence of tilting, the transient fluvial response to tilting has not been quantified such that tectonic histories involving tilt can be extracted from river network forms. We used numerical landscape evolution models to characterize the transient erosional response of a river network initially at equilibrium to rapid tilting. We focus on the case of punctuated rigid-block tilting, though we explore longer-duration tilting events and nonuniform uplift that deviates from perfect rigid-block tilting such as that observed when bending an elastic plate or with more pronounced internal deformation of a fault-bounded block. Using a model river network composed of linked 1-D river longitudinal profile evolution models, we show that the transient response to a punctuated rigid-block tilting event creates a suite of characteristic forms or geomorphic signatures in mainstem and tributary profiles that collectively are distinct from those generated by other perturbations, such as a step change in the uniform rock uplift rate or a major truncation of the headwater drainage area, that push a river network away from equilibrium. These signatures include (1) a knickpoint in the mainstem that separates a downstream profile with uniform steepness (i.e., channel gradient normalized for drainage area) from an upstream profile with nonuniform steepness, with the mainstem above the knickpoint more out of equilibrium than the tributaries following forward tilting toward the outlet, versus the mainstem less out of equilibrium than the tributaries following back tilting toward the headwaters; (2) a pattern of mainstem incision below paleo-topography markers that increases linearly up to the mainstem knickpoint or vice versa following back tilting; and (3) tributary knickzones with nonuniform steepness that mirrors that of the mainstem upstream of the slope-break knickpoint. Immediately after a punctuated tilting event, knickpoints form at the mainstem outlet and each mainstem–tributary junction. Time since the cessation of rapid tilting is recorded by the mainstem knickpoint location relative to base level and by the upstream end of tributary knickzones relative to the mainstem–tributary junction. Tilt magnitude is recorded in the spatial gradient of mainstem incision depth and, in the forward tilting case, also by the spatial gradient in tributary knickzone drop height. Heterogeneous lithology can modulate the transient response to tilting and, post tilt, knickpoints can form anywhere in a stream network where more erodible rock occurs upstream of less erodible rock. With a full 2-D model, we show that stream segments flowing in the tilt direction have elevated channel gradient early in the transient response. Tilting is also reflected in network topologic changes via stream capture oriented in the direction of tilt. As an example of how these geomorphic signatures can be used in concert with each other to estimate the timing and magnitude of a tilting event, we show a sample of rivers from two field sites: the Sierra Nevada, California, USA, and the Sierra San Pedro Mártir, Baja California, Mexico, two ranges thought to have been tilted westward toward river outlets in the late Cenozoic.
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Ernawati, Lusi, Ruri Agung Wahyuono, Abdul Halim, Roslan Noorain, Widiyastuti Widiyastuti, Rizna Triana Dewi, and Toshiharu Enomae. "Hierarchically 3-D Porous Structure of Silk Fibroin-Based Biocomposite Adsorbent for Water Pollutant Removal." Environments 8, no. 11 (November 16, 2021): 127. http://dx.doi.org/10.3390/environments8110127.
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This study explored the tunability of a 3-D porous network in a freeze-dried silk fibroin/soursop seed (SF:SS) polymer composite bioadsorbent. Morphological, physical, electronic, and thermal properties were assessed using scanning electron microscopy, the BET N2 adsorption-desorption test, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). A control mechanism of pore opening–closing by tuning the SS fraction in SF:SS composite was found. The porous formation is apparently due to the amount of phytic acid as a natural cross-linker in SS. The result reveals that a large pore radius is formed using only 20% wt of SS in the composite, i.e., SF:SS (4:1), and the fibrous network closes the pore when the SS fraction increases up to 50%, i.e., SF:SS (1:1). The SF:SS (4:1) with the best physical and thermal properties shows an average pore diameter of 39.19 nm, specific surface area of 19.47 m2·g−1, and thermal stability up to ~450 °C. The removal of the organic molecule and the heavy metal was assessed using crystal violet (CV) dye and the Cu2+ adsorption test, respectively. The adsorption isotherm of both CV and Cu2+ on SF:SS (4:1) follows the Freundlich model, and the adsorption kinetic of CV follows the pseudo-first-order model. The adsorption test indicates that physisorption dominates the adsorption of either CV or Cu2+ on the SF:SS composites.
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Jamali Arand, Saadat, Amir Akbari, and Mohammad Ardebili. "Investigation into the Thermal Behavior and Loadability Characteristic of a YASA-AFPM Generator via an Improved 3-D Coupled Electromagnetic-Thermal Approach." International Journal of Engineering and Technology Innovation 11, no. 2 (April 1, 2021): 88–102. http://dx.doi.org/10.46604/ijeti.2021.6221.
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The objective of this paper is to investigate the thermal behaviour and loadability characteristic of a yokeless and segmented armature axial-flux permanent-magnet (YASA-AFPM) generator, which uses an improved 3-D coupled electromagnetic-thermal approach. Firstly, a 1-kW YASA-AFPM generator is modelled and analysed by using the proposed approach; the transient and steady-state temperatures of different parts of the generator are determined. To improve the modelling accuracy, the information is exchanged between the thermal and electromagnetic models at each step of the co-simulation, considering both the accurate calculation of losses and the impacts of temperature rise on the temperature-dependent characteristics of the materials. Then, by using the proposed approach, the impact of the slot opening width and the turn number of stator segments on the generator loadability are investigated. After that, the experimental tests are performed. The results reveal the effectiveness and accuracy of the approach to predict the machine loadability and thermal behavior.
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Dutta, Goutam, Jin Jiang, Rohit Maitri, and Chao Zhang. "A Numerical Thermal-Hydraulic Model to Simulate the Fast Transients in a Supercritical Water Channel Subjected to Sharp Pressure Variations." Communications in Computational Physics 19, no. 5 (May 2016): 1529–41. http://dx.doi.org/10.4208/cicp.scpde14.42s.
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AbstractThe present work demonstrates the extension of a thermal-hydraulic model, THRUST, with an objective to simulate the fast transient flow dynamics in a supercritical water channel of circular cross section. THRUST is a 1-D model which solves the nonlinearly coupled mass, axial momentum and energy conservation equations in time domain based on a characteristics-dependent fully implicit finite difference scheme using an Eulerian approach. The model developed accounts for the compressibility of the supercritical flow by considering the finite value of acoustic speed in the solution algorithm and treats the boundary conditions naturally. A supercritical water channel of circular cross section, for which the experimental data is available at steady state operating conditions, is chosen for the transient simulations to start with. Two different case studies are undertaken with a purpose to assess the capability of the model to analyze the fast transient processes caused by the large reduction in system pressure. The first transient case study is where the initial exit pressure is reduced by 1MPaexponentially in a time span of 5s. In the second case study, the transient is initiated with a sudden step decrease in the exit pressure by the same amount. Results obtained for both the case studies show the desired performance from the model developed.
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Gungormus, Mustafa, and Guzin Neda Hasanoglu Erbasar. "Transient Heat Transfer in Dental Implants for Thermal Necrosis-Aided Implant Removal: A 3D Finite Element Analysis." Journal of Oral Implantology 45, no. 3 (June 1, 2019): 196–201. http://dx.doi.org/10.1563/aaid-joi-d-18-00210.
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Removal of osseointegrated but otherwise failed (mechanical failure, mispositioning, esthetics, etc) dental implants is a traumatic process resulting in loss of healthy bone and complicating the treatment process. The traumatic effects of implant removal can be reduced by weakening the implant-bone attachment. Thermal necrosis-aided implant removal has been proposed as a minimally invasive method toward this end. In this method, an electrocautery tip is contacted to the implant to increase the temperature to 47°C and generate a limited and controlled thermal necrosis at the bone-implant interface. So far, no controlled studies have been performed to investigate the optimal clinical parameters for this method. In this study, we aimed to investigate, using finite element analysis method, the optimal settings to achieve intentional thermal necrosis on 3 implant systems, at 5 W and 40 W device power and with different size tips. The temperature increase of the implants at 40 W power was very sudden (< 0.5 seconds) and as the bone reached 47°C, the implants were at unacceptable temperatures. At 5 W power, temperature increase of the implants happened at manageable durations (< 1 second). Moreover, the temperature increase was even slower with larger implants and larger tip sizes. Therefore, low power settings must be used for thermal necrosis-aided implant removal. Also, the size of the implant and the tip must be taken into consideration in deciding the duration of contact with the electrocautery tip and the implant.
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Yao, Rui, Jinshan Ju, and Zhengjun Yao. "Novel 3-D hierarchical multiconfiguration graphene/polyaniline-based aerogels with directed higher performances." Cellular Polymers 39, no. 1 (October 31, 2019): 42–53. http://dx.doi.org/10.1177/0262489319885031.
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Novel three-dimensional (3-D) hierarchical multiconfiguration graphene/polyaniline-based aerogels were synthesized via in situ polymerization and directed freeze-drying method. The composite aerogels enhanced excellent thermal and electrical performances, at the same time, their 3-D hierarchical multiconfiguration was robust and stable, which made them more beneficial to be applied to thermal or electrical fields. Graphene oxide/polyaniline (GO/AP) and reduced graphene oxide (RGO/AP) were prepared. The multiconfiguration structure can be apparently observed through scanning electron microscopy image of GO/AP aerogel: the aerogels were composed of skeleton structure with paralleled open holes; the skeleton structure was made up by hierarchical GO sheet with AP network; and the AP network consisted of AP skeleton and nanopores. GO/AP aerogels showed higher heat resistance than single AP aerogel. In addition, compared with GO/AP and AP aerogels, RGO/AP aerogel had the best electrical performances (vertical electrical conductivity: 1.23 S cm−1 and specific capacitance: 580 F g−1). What is more, attributed to the multiconfiguration structure, the composite aerogels exhibited excellent performances in holes extending direction.
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Wu, Yutian, Richard Seager, Tiffany A. Shaw, Mingfang Ting, and Naomi Naik. "Atmospheric Circulation Response to an Instantaneous Doubling of Carbon Dioxide. Part II: Atmospheric Transient Adjustment and Its Dynamics." Journal of Climate 26, no. 3 (February 1, 2013): 918–35. http://dx.doi.org/10.1175/jcli-d-12-00104.1.
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Abstract The dynamical mechanisms underlying the transient circulation adjustment in the extratropical atmosphere after the instantaneous doubling of carbon dioxide are investigated using the National Center for Atmospheric Research Community Atmosphere Model version 3 coupled to a Slab Ocean Model. It is shown that the transient process during the first few months of integration is important in setting up the extratropical circulation response in equilibrium such as the poleward shift of the tropospheric jet streams. Three phases are found during the transient thermal/dynamical adjustment in the Northern Hemisphere: 1) a radiatively driven easterly anomaly in the subpolar stratosphere, 2) an acceleration of the westerly anomaly in the subpolar stratosphere as a result of anomalous planetary-scale eddy momentum flux convergence, and 3) a “downward migration” of the westerly anomaly from the lower stratosphere to the troposphere, followed by the tropospheric jet shift. Several proposed mechanisms for inducing the poleward shift of the tropospheric jet streams are examined. No significant increase in eddy phase speed is found. The rise in tropopause height appears to lead the tropospheric jet shift but no close relation is observed. The length scale of transient eddies does increase but does not lead the tropospheric jet shift. Finally, the tropospheric jet shift can be captured by changes in the index of refraction and the resulting anomalous eddy propagation in the troposphere.
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Essajai, R., I. Tabtab, A. Mzerd, O. Mounkachi, N. Hassanain, and M. Qjani. "Molecular dynamics study of thermal properties of nanofluids composed of one-dimensional (1-D) network of interconnected gold nanoparticles." Results in Physics 15 (December 2019): 102576. http://dx.doi.org/10.1016/j.rinp.2019.102576.
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Tai, Pei, Chao Zhou, Yubo Zhou, and Sheqiang Cui. "Thermal conductivity of Toyoura sand at various moisture and stress conditions." E3S Web of Conferences 205 (2020): 04010. http://dx.doi.org/10.1051/e3sconf/202020504010.
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Thermal conductivity of soils is a crucial characteristic in various geotechnical applications, such as geothermal pumps, energy piles and buried pipelines. Previous researchers have done extensive works on the factors that may affect the soil thermal conductivity, including soil porosity, degree of saturation, mineralogy, testing temperatures, particle size and gradation. A modified oedometer frame that can incorporate the transient heat probe method is adopted to investigate the influence of stress state on thermal conductivity of Toyoura sand. Preliminary test under 1-D compression shows that the thermal conductivity of sand increases with the rise of vertical stress, and the variation exhibits hysteresis during a loading and unloading cycle. In addition, the effects of void ratio and water content were also studied and test results agreed well with previous values reported in the literature.