bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and Mechanical Design of the Fastest Supercomputer of the World in Cognitive Systems: IBM POWER AC 922
Authors: Yuksel Anil , Mahaney Vic , Marroquin Chris , Tian Shurong , Hoffmeyer Mark , Schultz Mark , Takken Todd 
Published: December 2019

Abstract
High performance computing (HPC), artificial intelligence (AI) and cognitive systems have initiated a new era of computing. Efficient thermal management technologies of these systems have been vital due to the increasing power density in the electronic components. In 2018 IBM delivered the fastest supercomputer of the world through Summit with 200 petaflops computing performance with LINPACK benchmarks. The system is both air and water cooled, where water is employed to cool the high power dissipated electronic components which are the IBM POWER9 processors and NVIDIA GPUs. In this paper, we highlight the overview of the thermal and mechanical design strategies applied on these systems. In air cooled systems, we discuss the fan and heat sink designs, as well as the preheating effect on PCI section. Liquid cooled system has a unique coldplate design which cool the processors and the GPUs with water. We examine the water flow path design for the processor and the GPUs by providing the thermal performance of the coldplate. Also, an overview of the cooling assemblies such as TIMs and air baffles in the servers are discussed. Moreover, unit and rack manifolds are investigated; flow and pressure distribution at the node and rack level are provided.
Surface Temperature Effect on Convective Heat Transfer Coefficients for Jet Impingement Cooling of Electric Machines With Automatic Transmission Fluid
Authors: Kekelia Bidzina , Bennion Kevin , Feng Xuhui , Moreno Gilberto , Cousineau J. Emily , Narumanchi Sreekant , Tomerlin Jeff 
Published: December 2019

Abstract
In this study, the results of NREL’s continued work on experimental characterization of the thermal performance of free-surface jets of automatic transmission fluid impinged on a heated target surface are presented. The measured heat transfer coefficients are useful for understanding factors influencing performance of driveline fluid-based cooling systems for electric machines and help designers in developing high-performance, power-dense and reliable machines. Experiments were carried out for different fluid and target surface temperatures (50°C, 70°C, and 90°C for the fluid and 90°C, 100°C, 110°C, and 120°C for the target surface). Impinging jet velocities (0.5 m/s to 7.5 m/s) and the jet position on the target surface (center versus edge) were also varied. The impinging angle was kept at 90° relative to the target surface. It was found that higher target surface temperature increased heat transfer coefficients, namely, increasing surface temperature from 90°C to 120°C enhanced heat transfer coefficient values at higher impinged jet velocities (7.5 m/s) by up to 15%.
Piezoresistive Theory for 4H Silicon Carbide Stress Sensors on Four-Degree Off-Axis Wafers
Authors: Chen Jun , Jaeger R. C. , Suhling J. C. 
Published: December 2019

Abstract
Piezoresistive stress sensors have been shown to be a powerful tool for experimental evaluation of die stress distributions. Silicon Carbide (SiC) wide bandgap semiconductors are promising materials for development of high temperature power electronics. In the past, the analysis and design of stress sensors on silicon carbide have assumed that the wafer surface is aligned with the crystallographic axes. However, 4H silicon carbide wafers are produced with a four-degree off-axis cut to ensure high-quality homoepitaxial growth, so that the tilted wafer surface does not perfectly coincide with the fundamental crystallographic axis. Thus, the prior “on-axis” theory is an approximation, and errors in piezoresistive theory caused by such tilted wafer plane need to be discussed. These errors can affect both the results from calibration experiments as well as the stresses extracted during application of sensor rosettes.
This paper discusses the theory and extraction of piezoresistive coefficients for 4H-SiC silicon carbide materials in the presence of off-axis starting wafers. Coordinate transformations for the piezoresistive coefficients are reviewed, the required direction cosines between the new rotated axes and the ideal axes are discussed, and the 6 × 6 matrix of piezoresistive coefficients (π-matrix) for the on-axis and off-axis cases are calculated. Many of the elements of the ideal on-axis π-matrixes are zero. In contrast, the off-axis is completely filled with non-zero values indicating additional coupling, particularly among the shear coefficients. Examples of the overall impact of these new terms on calibration and stress measurement are discussed.
Thermal Assessment and In-Situ Monitoring of Insulated Gate Bipolar Transistors in Power Electronic Modules
Authors: Gutierrez Erick , Lin Kevin , DeVoto Douglas , McCluskey Patrick 
Published: December 2019

Abstract
Insulated gate bipolar transistor (IGBT) power modules are devices commonly used for high-power applications. Operation and environmental stresses can cause these power modules to progressively degrade over time, potentially leading to catastrophic failure of the device. This degradation process may cause some early performance symptoms related to the state of health of the power module, making it possible to detect reliability degradation of the IGBT module. Testing can be used to accelerate this process, permitting a rapid determination of whether specific declines in device reliability can be characterized. In this study, thermal cycling was conducted on multiple power modules simultaneously in order to assess the effect of thermal cycling on the degradation of the power module. In-situ monitoring of temperature was performed from inside each power module using high temperature thermocouples. Device imaging and characterization were performed along with temperature data analysis, to assess failure modes and mechanisms within the power modules. While the experiment aimed to assess the potential damage effects of thermal cycling on the die attach, results indicated that wire bond degradation was the life-limiting failure mechanism.
Parametric Study of Silicon-Based Embedded Microchannels With 3D Manifold Coolers (EMMC) for High Heat Flux (~1 kW/cm2) Power Electronics Cooling
Authors: Jung Ki Wook , Hazra Sougata , Kwon Heungdong , Piazza Alisha , Jih Edward , Asheghi Mehdi , Gupta Man Prakash , Degner Mike , Goodson Kenneth E. 
Published: December 2019

Abstract
Thermal management of power electronics continues to be one of the limiting factors in the peak power capability of the traction inverter system and overall efficiency of the e-drive. Successful design and implementation of Embedded Microchannels with a 3D-Manifold Cooler, or EMMC, could enable higher power density that allows increase in the inverter peak power output. In the present work, we have conducted a parametric study on geometric dimensions of the EMMCs to analyze thermofluidic performance by using computational fluid dynamics (CFD) simulations. The study was conducted for a 5 mm × 5 mm cold-plate foot print, heat flux 800 W/cm2, and single-phase water as working fluid at inlet temperature of 25 °C. We implemented strategies such as i) symmetric distribution of manifold inlet/outlet conduits, ii) reducing the thickness of cold-plate substrate, iii) increasing fluid-solid interfacial area in cold-plate microchannels that resulted in reduction in thermal resistance of the baseline EMMC design from 0.1 to 0.04 cm2-K/W with pressure drop from 8 to 37 kPa.
Packaging Environmental Sensors for an Internet-of-Things Solution for Urban-Microclimate Studies
Authors: Dey Shuv , Joshi Yogendra , Brown J. Michael 
Published: December 2019

Abstract
Cities are experiencing a number of negative effects caused by increasing urbanization. For decades, the effects of pollution have been recognized and studied and steps have been taken attempting to control this problem. Many urban environments are also experiencing the effect of the Urban Heat Island (UHI). UHIs are metropolitan areas that have measurably warmer average air temperatures during several periods during the year, than their surrounding rural areas. There is a great interest in studying UHI and pollution and its effects on the environment as well as urban residents. However, in order to study these phenomena, we need more information than we currently have. Thus, an IoT based low cost sensor network can be used to collect the data necessary to study UHI and pollution. There are several key challenges associated with an IoT based solution to environmental data monitoring. This study explores these challenges by looking at what effect the packaging has on the deployed environmental sensors, and how and where to deploy sensor modules. Sensor data collected over a few months’ timeframe are analyzed and presented.
Modeling of Light Emitting Device Populations in the Electrical, Thermal, and Optical Domain for Luminaire Design
Authors: Farkas Gabor , Vass-Varnai Andras , Gaal Lajos , Rencz Marta 
Published: December 2019

Abstract
A modeling methodology to speed up the design of luminaires composed of solid state light emitting devices has been elaborated in the Delphi4LED research project of the European Union. Starting with integrated and automated measurements of packaged LED devices in the electric, thermal and optical domain; the methodology provides SPICE like models, which besides the electrical properties also reflect the thermal and optical ones.
The electrical and optical model is based directly on semiconductor physics, for precise modeling of the low-current and high-current decay of efficiency. The compact model of the thermal domain is based on the methodology defined in the previous DELPHI project. Measured data on the population are converted in an optimization process to best fit the model parameter sets.
The paper presents the elaborated methodology and also outlines a new JEDEC standard encompassing multiple thermal test environments.
Advanced Packaging and Thermal Management of High-Power DC-DC Converters
Authors: Yuruker Sevket U. , Mandel Raphael K. , McCluskey Patrick , Ohadi Michael M. , Chakraborty Shiladri , Park Yongwan , Yun He , Khaligh Alireza , Boteler Lauren , Hinojosa Miguel 
Published: December 2019

Abstract
Thermal management of high-power electronics is often a major obstacle in achieving improved packaging density. Emergence of SiC devices allows higher voltage and temperature limits, but thermal management is still a bottleneck in achieving compact, reliable and high-performance systems. This study introduces the design of an advanced packaging configuration of a dual-active-bridge 10 kW DC-DC converter module with 97% efficiency and ∼1.5 × 104 kW/m3 power density based on preliminary modeling analysis. The proposed packaging scheme allows for significant volume reduction and considerably lighter weight at greater power levels than commercially available converter modules. We introduce an improved placement of high power/high frequency MOSFET switches on the board that enables double-sided cooling, where the dissipated heat is removed from both sides of the switches via manifold-microchannel cooler modules. The cooler modules are additively manufactured monolithic structures made out of a thermally and electrically conductive material, which in turn allows them to double function as electrical terminals for the switches. Their unique shape minimizes footprint utilization on the board while still providing significant area enhancement over the heat dissipating chips’ footprint. Moreover, thermal management of other components with significant heat flux, such as the transformer coils and magnetic core are also accomplished via dielectric liquid cooling with electrically insulating but thermally conductive 3D printed coolers. The overall circuit diagram, assembly configuration and flow routing within the system are demonstrated. The advantages of the proposed design over commercially available modules are discussed in detail.
Effect of Charge-Discharge Depth and Environment Use Conditions on Flexible Power Sources
Authors: Lall Pradeep , Soni Ved , Abrol Amrit , Leever Ben , Miller Scott 
Published: December 2019

Abstract
Recent surge in demand for wearable technology products such as activity tracking smartwatches, and for medical devices has necessitated development of flexible secondary lithium ion batteries which also possess high capacity, robustness and thin form factors. Oftentimes, these power sources are only charged up to a partial state of charge (SoC) before use (shallow charge). Their usage continues until the SoC reaches almost zero, after which they are recharged again. Nowadays, the ‘fast-charge ‘feature used to charge the battery at higher C-rates, is a necessity in consumer electronics rather than an amenity. Also, in everyday use, these batteries are exposed to higher-than-ambient temperatures due to perpetual human body contact and also to the high temperatures resulting from poor thermal management in compact devices. This study investigates the compounded influence of partial charge, high temperatures and high C-rates on the capacity degradation of a flexible Li-ion power source subjected to accelerated life testing. The battery current and terminal voltage were logged for multiple charge-discharge cycles and were used to compute the battery capacity and energy efficiency. Finally, a regression model based on several parameters was developed to estimate the battery capacity as a function of the cycle number.
Data Center Thermal Efficiency Improvement by Cooling Flow Vectoring Using Synthetic Jets
Authors: Jiménez Eduardo Sepúlveda , d’Alençon Jean Paul , Silva-Llanca Luis 
Published: December 2019

Abstract
Electronic cooling represents a major portion of a Data Centers energy consumption, thus efficient thermal management dramatically impacts energy savings. This work proposes reducing the energy consumption associated with server air-cooling by vectoring (tilting) the main upward tile flow using adjacent synthetic jets. The particular fluid dynamics generated by synthetic jets allows controlling the angle at which the tile flow emanates, directing the cooling air toward areas with higher cooling demand. Three-dimensional simulations were performed using k–ε standard turbulence model with the commercial software Ansys Fluent. In order to quantify and localize the inefficiencies of the system, we estimated the Exergy Destruction distribution in the cold aisle and servers. In previous studies, this technique proved successful in finding optimum operation conditions in Data Center cooling. As opposed to a base case without flow control, the adjacent synthetic jets directed the incoming fluid to areas with higher cooling demand, thus saving energy by avoiding over-provisioning air into servers operating under normal demand. The decrease in the overall Exergy Destruction demonstrated that vectoring improves the system’s global energy efficiency.
Oceanic slab-top melting during subduction: Implications for trace-element recycling and adakite petrogenesis
Authors: Hernández-Uribe David , Hernández-Montenegro Juan David , Cone Kim A. , Palin Richard M. 
Published: December 2019

Abstract
Arc volcanism and trace-element recycling are controlled by the devolatilization of oceanic crust during subduction. The type of fluid—either aqueous fluids or hydrous melts—released during subduction is controlled by the thermal structure of the subduction zone. Recent thermomechanical models and results from experimental petrology argue that slab melting occurs in almost all subduction zones, although this is not completely supported by the rock record. Here we show via phase equilibrium modeling that melting of either fresh or hydrothermally altered basalt rarely occurs during subduction, even at water-saturated conditions. Melting occurs only along the hottest slab-top geotherms, with aqueous fluids being released in the forearc region and anatexis restricted to subarc depths, leading to high-SiO2 adakitic magmatism. We posit that aqueous fluids and hydrous melts preferentially enhance chemical recycling in “hot” subduction zones. Our models show that subducted hydrothermally altered basalt is more fertile than pristine basaltic crust, enhancing fluid and melt production during subduction and leading to a greater degree of chemical recycling. In this contribution, we put forward a petrological model to explain (the lack of) melting during the subduction of oceanic crust and suggest that many large-scale models of mass transfer between Earth’s surface and interior may require revision.
Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes
Authors: DiBiase Roman A. , Lamb Michael P. 
Published: December 2019

AbstractLandscapes following wildfire commonly have significant increases in sediment yield and debris flows that pose major hazards and are difficult to predict. Ultimately, post-wildfire sediment yield is governed by processes that deliver sediment from hillslopes to channels, but it is commonly unclear the degree to which hillslope sediment delivery is driven by wet versus dry processes, which limits the ability to predict debris-flow occurrence and response to climate change. Here we use repeat airborne lidar topography to track sediment movement following the 2009 CE Station Fire in southern California, USA, and show that post-wildfire debris flows initiated in channels filled by dry sediment transport, rather than on hillsides during rainfall as typically assumed. We found widespread patterns of 1–3 m of dry sediment loading in headwater channels immediately following wildfire and before rainfall, followed by sediment excavation during subsequent storms. In catchments where post-wildfire dry sediment loading was absent, possibly due to differences in lithology, channel scour during storms did not occur. Our results support a fire-flood model in bedrock landscapes whereby debris-flow occurrence depends on dry sediment loading rather than hillslope-runoff erosion, shallow landslides, or burn severity, indicating that sediment supply can limit debris-flow occurrence in bedrock landscapes with more-frequent fires.
Abdominal visceral and subcutaneous adipose tissues in association with cardiometabolic risk in children and adolescents: the China Child and Adolescent Cardiovascular Health (CCACH) study
Authors: Yan Yinkun , Liu Junting , Zhao Xiaoyuan , Cheng Hong , Huang Guimin , Mi Jie 
Published: December 2019

ObjectiveTo investigate the association of abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with cardiometabolic risk factors in children and adolescents.Research design and methodsThis cross-sectional study consisted of 8460 children and adolescents aged 6–18 years from Chinese urban areas who underwent dual-energy X-ray absorptiometry scan and had metabolic risk factors measured.ResultsIn multivariate analysis adjusted for region, family income, age, puberty development, physical activity, and smoking, VAT and SAT were significantly associated with all metabolic risk factors for both sexes (all p<0.01). After additional adjustment for fat mass index, most of these associations remain significantly positive. In boys, SAT had greater ORs for all risk factors compared with VAT; in girls, however, SAT had greater odds for high triglycerides, smaller odds for high low-density lipid cholesterol, and similar odds for other risk factors compared with VAT. In addition, boys had greater magnitude of associations of SAT with high total cholesterol, high low-density lipid cholesterol, and low high-density lipid cholesterol compared with girls; no sex differences for VAT were observed.ConclusionsBoth abdominal VAT and SAT have adverse impacts on most of the cardiometabolic risk factors in youth. However, their relative contributions differ between sexes.
In vivo investigation of the tissue response to commercial Teflon insulin infusion sets in large swine for 14 days: the effect of angle of insertion on tissue histology and insulin spread within the subcutaneous tissue
Authors: Eisler Gabriella , Kastner Jasmin R , Torjman Marc C , Khalf Abdurizzagh , Diaz David , Dinesen Alek R , Loeum Channy , Thakur Mathew L , Strasma Paul , Joseph Jeffrey I 
Published: December 2019

ObjectiveThis study investigated the effects of the inflammatory tissue response (ITR) to an insulin infusion set (IIS) on insulin bolus spread over wear time, as well as the effect of cannula insertion angle on the ITR, bolus shape, and pump tubing pressure.Research design and methodsAngled or straight IISs were inserted every other day for 14 days into the subcutaneous tissue of 11 swine and insulin was delivered continuously. Prior to euthanasia, a 70 µL bolus of insulin/X-ray contrast agent was infused while recording a pressure profile (peak tubing pressure, pmax; area under the pressure curve, AUC), followed by the excision of the tissue-catheter specimen. Bolus surface area (SA) and volume (V) were assessed via micro-CT. Tissue was stained to analyze total area of inflammation (TAI) and inflammatory layer thickness (ILT) surrounding the cannula.ResultsA bolus delivered through an angled IIS had a larger mean SA than a bolus delivered through a straight cannula (314.0±84.2 mm2vs 229.0±99.7 mm2, p<0.001) and a larger volume (198.7±66.9 mm3vs 145.0±65.9 mm3, p=0.001). Both decreased significantly over wear time, independent of angle. There was a significant difference in TAI (angled, 9.1±4.0 mm2vs straight, 14.3±8.6 mm2, p<0.001) and ILT (angled, 0.7±0.4 vs straight, 1.2±0.7 mm, p<0.001). pmax(p=0.005) and AUC (p=0.014) were lower using angled IIS. As ILT increased, pmaxincreased, while SA and V decreased.ConclusionsThe progression of the ITR directly affected bolus shape and tubing pressure. Although straight insertion is clinically preferred, our data suggest that an angled IIS elicits lower grades of ITR and delivers a bolus with lower tubing pressure and greater SA and V. The subcutaneous environment plays a crucial role in IIS longevity, and the insertion angle needs to be considered in future IIS designs and clinical trials.