bluuebunny/crossref_metadata_2025 huggingface dataset:
High Efficiency Natural Gas Engine Combustion Using Controlled Auto-Ignition
Authors: Hampson Gregory J.
Published: December 2019

Increasingly restrictive limits on Oxides of Nitrogen - NOx levels and desire for low methane emissions from gas engines are driving the change from lean-burn to stoichiometric combustion strategies on heavy-duty on-highway natural gas engines in order to take advantage of inexpensive and effective three-way catalyst technology. The change to stoichiometric combustion has led to increased tendency for engine knock due to higher in-cylinder temperatures. To suppress engine knock, Exhaust Gas Recirculation (EGR) rates from 10 to 30% are used. While high EGR rates nominally improve Brake Thermal Efficiency (BTE) and reduce exhaust gas temperatures, they also slow down combustion. However, by deploying a controlled spark triggered homogeneous charge volumetric ignition, very short burn durations can be achieved without the destructive effects of engine knocking towards high efficiency gas engines.

In the interest of achieving 45% BTE in spark ignited an on-highway class 8 truck engines fueled on natural gas and to meet EURO 6 and future California emissions standards of 0.02 gm/kw-hr NOx, Controlled Auto-Ignition (CAI) is herein demonstrated on a 15 liter truck engine. CAI is enabled by (a) having a combustion device capable of exceptionally good combustion stability in the presence of high EGR rates (COV of IMEP < 0.75 %), (b) cylinder pressure based combustion feedback, and (c) fast closed loop combustion control (using a Woodward RT-CDC control system).

This system enables significant reduction in burn duration by controlling a two phase combustion event. The first phase is normal spark ignited propagating flame, which then triggers the second phase which is volumetric auto-ignition. The location and percentage of fuel that burns in the volumetric auto-ignition event is controlled relative to that which occurs via the conventional spark ignited flame propagation process by use of high speed combustion in the loop feedback control. Auto-ignition mass fraction burned (MFB) ratios of 25–50% have been achieved yielding higher heat release rates at the end of combustion than at the center of combustion with the result being a shortening of the combustion burn duration from a nominal 20–30 degrees to a near optimal 10–15 degrees even with EGR rates as high as 25%. A novel and patent pending burn duration control strategy is employed to stably maintain this knock-free combustion strategy even with compression ratio as high as 14:1. The benefits are significant increase in Brake Thermal Efficiency and substantial reduction in engine out methane emissions without sacrifice of transient responsiveness.
Assessing the Performance of Advanced Cooling Techniques on Thermal Management of Next-Generation Power Electronics
Authors: Acharya Palash V. , Bahadur Vaibhav , Hebner Robert , Ouroua Abdelhamid , Strank Shannon
Published: December 2019

Rapid miniaturization alongwith increasing heat loads in power electronics devices like insulated-gate bipolar transistors (IGBTs) have necessitated the need for advanced thermal management technologies in the packaging of these devices. This study quantifies the benefits of key advanced thermal management solutions for packaging of power electronics packages. Thermal resistance network modeling is used to estimate the maximum heat flux that can be dissipated by an IGBT package, while maintaining the junction temperature below 125 °C and 200 °C for silicon and silicon carbide (wide bandgap material) devices, respectively. While the model is completely analytical, it does address important complexities associated with heat flow in packages via the use of a sub-model to account for thermal spreading. The advanced cooling technologies evaluated in this study include the use of high thermal conductivity polymer heat sinks, double-sided heat sinking of packages, liquid cooling (single and two-phase), jet impingement and spray cooling. Additionally, combinations of these cooling technologies are evaluated as well. The heat dissipation achievable from these technologies is compared with that from an air cooled copper heat sink (baseline). The results of this study provide insights and a starting point for selecting thermal management technologies (or combinations) based on the heat dissipation requirements of power electronics packages.
Effect of Inclined Angle of Radiator on Natural Convective Heat Dissipation Performance
Authors: Ma Tengfei , Wang Wen
Published: December 2019

The effects of inclined angle on the heat transfer of radiators under natural convection are analyzed with experiment and numerical simulation, there are three radiators with straight fin, oblique fin and pin fin respectively (based on 150 × 150 × 45mm). The numerical simulation could agree with the experiment. The straight fin radiator could provide the best heat dissipation performance under experimental conditions and normal installation angle. The pin fin radiator has the largest heat transfer coefficient, around 7 W/m2·K. The influence of deflection angle is discussed on the heat dissipation capability of the radiator. The heat dissipation of the pin fin radiator is less sensitive to the gravity direction than the straight fin and oblique fin ones.
Automated Method Using Finite Element Analysis to Identify Plated Through Holes and Microvia Stacks at Failure Risk in Complex PCB Designs
Authors: Kalayeh Kourosh M. , Hernandez Natalie , Blattau Nathan , Hillman Craig
Published: December 2019

Since the introduction of plated through holes and microvias into the electronics industry, the reliability and manufacturability of these interconnects have been of great concern to the board designers, specifically in automotive and semiconductor industries. The failure of these structures is one of the main causes of an open circuit in printed circuit boards (PCBs). Typically, single and staggered microvias are not the cause of the failures, therefore, only stacked microvias and plated through holes (PTHs) are considered and analyzed in this study. This study includes broad parametric studies, using the finite element method (FEM), to investigate the effect of different geometrical parameters on the reliability and manufacturability of the stacked microvias and plated through holes. A fully automated methodology is developed to 1) analyze complex PCB designs with thousands of microvias and plated through holes, 2) identify and mark configurations susceptible to failure, and 3) build and run finite element simulations on the marked configurations. In doing so, the PCB drill files are first parsed, and the configurations are binned into three main categories; stacked, staggered and PTH configurations. Then using the related nearest-neighbor algorithms and based on the parametric study results, the configurations prone to failure are identified. Finally, finite element models are generated and simulated under thermal loading for the identified configurations. The simulations results are post processed for both reliability (fatigue life prediction under thermal cyclic loading over PCB service life) and manufacturability (overstress due to thermal shock during solder reflow). The modeling results and predictions correlate well to the experimental results available in the literature.
Double Side System in Package Development Challenge for Heterogeneous Integration
Authors: Kao Feng , Wang Yu-Po , Wang Davidlion , Tsai Jensen , Tsai Mike , Chiu Ryan , He Eric
Published: December 2019

With consumer functionality increasing, more and more active die and passive component integrated into one packaging. Next 5G product design trend is requiring small form factor and better thermal dissipation, original single side product is no larger on optimized solution with larger package size, expensive coreless substrate structure stacked via, in order to accommodate product electrical and characteristic requirement. Considering market driving force toward high performance and lower package cost, double side system in package (SiP) structure is able to realize and fulfill form factor and product characteristic requirement.

On this paper, double side SiP package platform will use dual side Surface Mount Technology (SMT) technology and double side molding structure to form outline and also shrink the overall package size. The calculation of package thermal performance can be enhance around 30% and package size can be shrunk around 40% area, compared to single side SiP which package area could be reduced from 64 mm2 to 36 mm2. With form factor change, product simulation is becoming important in order to mitigate assembly risk. The package characterization are including warpage and thermal simulation.

Table1: Basic information comparison for traditional SiP & double side SiP PKG

By utilizing advanced package technology and material, such as high speed SMT placement, molding technology, specific copper substrate design and interconnect material integrating into system in package module which provided a unique opportunity to address cost, performance, and time-to-market advantages. The SiP is also a good package platform to consolidate heterogeneous chips. It could be future package trend to accommodate market demand.

The SiP structure has proceed the typical reliability testing results as a verification method. Finally, this paper shows the suitable double side SiP structure which can be adopt in smart phone, IoT and wearable devices product application.
System Electrothermal Transient Analysis of a High Current (40A) Synchronous Step Down Converter
Authors: Murugan Rajen , Chen Jie , Harrison Todd , Kao C. T. , Ai Nathan
Published: December 2019

In this paper, we detailed the system electrothermal transient co-design modeling and silicon validation effort that led to the industry’s first highly efficient, highest power density (40A) synchronous step-down converter. The device was designed in an innovative multichip module (MCM) low-profile LQFN packaging technology. By integrating the control and drive circuitry with two discrete N-channel power MOSFETs, significant reduction in system on-resistance, RDS(ON), was achieved. The validity of the co-design electrothermal modeling methodology was assessed by comparing directly to silicon thermal measurements made on an evaluation module (EVM) which comprises the inductor, capacitor, and other essential components. Correlation between simulation and laboratory measurements on the integrated solution will be discussed.
Investigation Regarding Transient Compact Thermal Model for Microprocessor Packages
Authors: Nishi Koji
Published: December 2019

In recent years, not only static thermal design but also realtime thermal control become important for power efficiency on computing systems. Three-dimensional thermal simulation is widely used to design computing system, however, it takes too long time for intelligent power and thermal management validation because it requires transient thermal simulation with very short time step. To enable rapid simulation environment, compact thermal model which can be employed with both three-dimensional transient thermal simulation and transient thermal network is required. Therefore, this research aims to establish transient state compact thermal model for microprocessor package. This paper briefly introduces steady state compact thermal model for microprocessor, which is proposed as previous work, then, points out key point to extend the model to transient state model. Transient thermal spreading resistance is emulated and the effect is checked by comparing with three-dimensional simulation.
Vandal Glass Heat Distribution and the Effect of Glass Gap Adjustments in Outdoor Digital Display Components
Authors: Kim Jeho , Brown J. Michael , Joshi Yogendra , O’Connor Kevin , Diaz Marcos , Zhang Zhuomin , Yang Peiyan
Published: December 2019

The use of computational fluid dynamics/heat transfer (CFD/HT) software has become common in exploring the thermal and hydrodynamic behavior of many electronic products. Well-designed CFD/HT models are very valuable for driving the product design, but accurate models can be difficult to develop in some cases for a practical use. Manufacturing Resources International (MRI) uses CFD/HT modeling to predict the display limitations of outdoor digital displays under various hazardous environmental conditions. Both the surrounding ambient temperature and solar irradiance are the major contributors to temperature rise inside outdoor digital displays, but most CFD/HT software packages are limited in simulating solar irradiance through semi-transparent materials and multiple surfaces. Therefore, the contribution from solar irradiance must be treated with care when creating a CFD/HT model especially when an optimum number of mesh elements is to be used to minimize the necessary processing power and solution computation time. In the current study, we employ true solar testing to determine how much solar irradiance passes through the vandal glass assembly. In lieu of defining the solar irradiance as a heat flux, a methodology to determine the power that should be imposed on the sun-exposed vandal glass is described. As outdoor digital displays face harsher thermal challenges compared to the displays that are deployed indoors, it is necessary to come up with a display design that can best benefit from the cooling effect. There are numerous parameters that can be adjusted to optimize the display in terms of its thermal performance but in particular, this paper explores the effect of adjusting the gap distance between the vandal glass and the liquid crystal display (LCD) to see how the maximum LCD temperature and fan performance are influenced.
CFD Analysis of Molten Solder Flow Behavior and Bridging Mechanism During Solder Bump Formation
Authors: Miyazawa Risa , Okamoto Keishi , Mori Hiroyuki
Published: December 2019

Technology of fine pitch interconnect with lead-free solder joint has been developed to enhance the performance of flip-chip high density packages. This study presents an investigation of solder bump forming behavior by means of CFD simulation analysis. The flow motion of molten solder is analyzed with 3D model we developed, and the simulation result is validated with the experiment. Moreover, the investigation of factors affecting solder bridging across adjacent pads is also performed. It is revealed that wettability between liquid solder and organic insulator, which is represented as contact angle in the calculation has large effect on the solder bridging phenomena. The simulation result suggests that worsening the wettability of the insulator can reduce the occurrence of bridging.
Experimental Investigation of Single-Phase Cooling in Embedded Microchannels: 3D Manifold Heat Exchanger With R-245fa
Authors: Jung Ki Wook , Lee Hyoungsoon , Kharangate Chirag , Zhou Feng , Asheghi Mehdi , Dede Ercan M. , Goodson Kenneth E.
Published: December 2019

High performance and economically viable thermal cooling solutions must be developed to reduce weight and volume, allowing for a wide-spread utilization of hybrid electric vehicles. The traditional embedded microchannel cooling heat sinks suffer from high pressure drop due to small channel dimensions and long flow paths in 2D-plane. Utilizing direct “embedded cooling” strategy in combination with top access 3D-manifold strategy reduces the pressure drop by nearly an order of magnitude. In addition, it provides more temperature uniformity across large area chips and it is less prone to flow instability in two-phase boiling heat transfer. Here, we present the experimental results for single-phase thermofluidic performance of an embedded silicon microchannel cold-plate bonded to a 3D manifold for heat fluxes up to 300 W/cm2 using single-phase R-245fa. The heat exchanger consists of a 52 mm2 heated area with 25 parallel 75 × 150 μm2 microchannels, where the fluid is distributed by a 3D-manifold with 4 micro-conduits of 700 × 250 μm2. Heat is applied to the silicon heat sink using electrical Joule-heating in a metal serpentine bridge and the heated surface temperature is monitored in real-time by Infra-red (IR) camera and electrical resistance thermometry. The experimental results for maximum and average temperatures of the chip, pressure drop, thermal resistance, average heat transfer coefficient for flow rates of 0.1, 0.2. 0.3 and 0.37 lit/min and heat fluxes from 25 to 300 W/cm2 are reported. The proposed Embedded Microchannels-3D Manifold Cooler, or EMMC, device is capable of removing 300 W/cm2 at maximum temperature 80 °C with pressure drop of less than 30 kPa, where the flow rate, inlet temperature and pressures are 0.37 lit/min, 25 °C and 350 kPa, respectively. The experimental uncertainties of the test results are estimated, and the uncertainties are the highest for heat fluxes < 50 W/cm2 due to difficulty in precisely measuring the fluid temperature at the inlet and outlet of the micro-cooler.
Modeling and Analysis of a Shape Memory Alloy-Based Adaptive Regulator for Thermal Management
Authors: Liang Gary , Sadeghifard Ashkan , Krishna Anirudh , Lee Jaeho , Peraza Hernandez Edwin A.
Published: December 2019

The goal of this work is to develop and model an adaptive thermal management system formed by shape memory alloy (SMA) helical springs and stretchable selective emitters. Emitters are prepared by depositing a metallic layer on an elastomeric film (3M VHB 4910). Strain changes in the film induce alterations of the surface corrugation of the metallic layer, which enables adjustments of its emissivity spectrum. SMAs are materials that undergo moderate recoverable deformations driven by temperature changes. SMA springs are used here as adaptive deformation enablers (both as actuator and thermal sensor). The thermal management system is created by connecting stretchable emitters and SMA springs in series. When the temperature of the system is increased by sunlight irradiation, the SMA springs undergo contractions which elongate the stretchable emitters, flattening their corrugated metallic layer, thereby leading to an increase in their solar reflectivity and allowing radiative cooling. When the system temperature is decreased, the SMA springs relax and allow the emitters to recover their original surface corrugation, leading to an increase in their solar absorptivity and allowing radiative heating. This repeatable process allows the system to exhibit open-loop adaptive regulation of its temperature under varying solar irradiation. A reduced-order model of the system is derived to perform feasibility studies of the concept and results demonstrating the functionality of the system are presented.
Damage of Flexible Electronic Line Printed With Ag Nanoparticle Ink due to High-Current Density
Authors: Saito Daiki , Sasagawa Kazuhiko , Moriwaki Takeshi , Fujisaki Kazuhiro
Published: December 2019

Flexible printed circuits (FPCs) are widely used in electronic devices such as movable part line or wearable sensor. Photolithography is one of the most popular processes for fabricating electric interconnect lines. However, inkjet printing has attracted attention because the method can draw an arbitrary-shape electric lines without any mask. Therefore, nanoparticle metal ink is widely used for printing of conductive electric lines with lowering cost and small-lot production. The physical characteristics such as flexibility or durability of metal nanoparticle ink lines have been evaluated by bending or tensile tests. By contrast, the evaluation method has not been sufficiently established for the electrical characteristics of these lines, and the failure mechanism under high-current density has not been clarified. According to scaling down of electric devices, current density and Joule heating in device lines increase and electromigration (EM) damage becomes a serious problem. EM is a transportation phenomenon of metallic atoms caused by electron wind under high-current density. Reducing EM damage is extremely important to enhance device reliability. In this study, current loading tests of metal nanoparticle ink line were performed to discuss damage mechanism and evaluate electrical reliability under high-current density condition.

As the results of current loading tests, the thickness of cathode part of straight-test line was decreased. It is considered that atomic transport from the cathode to the anode occurred by EM phenomenon. The line surface became rough and aggregates of particles generated at middle or anode parts of straight-test line by high-current loading. Both of atomic transport and aggregate generation were closely related the changes of potential drop, their dominances were varied depending the current density value.
Evaluation of Thermal and Electrical Properties of Nano-Enhanced PCM for Usage in High-Voltage Systems
Authors: Iradukunda Ange-Christian , Kasitz Josh , Moreno Fernando , Huitink David
Published: December 2019

Rapid temperature transients sustained during operation of high voltage electronics can be difficult to manage by relying solely on uniform heat removal mechanisms. Phase Change Materials (PCMs) can be useful as a buffer against these intermittent temperature spikes when integrated into electronic packages. However, their integration poses challenges of both physical and electrical interactions within the package, particularly in high voltage systems. The present study aims to evaluate electrical and thermal properties of nano-enhanced PCMs to inform integration in high voltage systems. The nanocomposites are obtained by seeding 0.0006–0.12 wt% of Gold, Graphene Oxide, and Iron Oxide particles to Sorbitol. Improvements in thermal properties including latent heat as high as 15% are observed; however, this comes at the expense of dielectric strength of the PCM.
Stator Diagnosis in Permanent Magnet Synchronous Motor (PMSM)
Authors: Zholbaryssov Madi , Sarwar Azeem
Published: December 2019

GM has a vision of future with zero crashes, zero emissions, and zero congestion. Permanent Magnet Synchronous Motors will be integral part of an all-electric future, due to their excellent power to mass ratio and smaller size, which promises to deliver the zero emission world. Making sure that these motors do not fail abruptly without warning, will also reduce congestion caused on the roads by such incidents. Stator winding health monitoring presented in this article allows to detect a fault at its early stage, which greatly increases the chances of the customer being able to repair electric drive system before it completely fails. We present approach for detecting shorted turn faults in stator winding of permanent magnet synchronous motor. The approach is based on monitoring negative sequence admittance for certain operating conditions. Timely fault detection also allows to take preventive action to limit damage propagation across the electric drive, thus, reducing repair and warranty costs. The research presented in this article also furthers GM’s strategic initiative to develop Vehicle Health Management (VHM) technologies that positively impact customer ownership experiences and drive their long-term loyalty to GM brands.
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

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

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

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

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

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

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

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

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

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

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.
Outdoor Running Activities Captured Using Wearable Sensors in Adult Competitive Runners
Authors: DeJong Alexandra F. , Hertel Jay
Published: December 2019

Treadmill running analyses cannot adequately replicate outdoor running demands, and wearable sensors offer a means to overcome this clinical limitation. The purpose of this report is to describe five individual runners’ biomechanical outcomes during hill and track intervals, stroller running, and 5- and 21-K races using wearable sensors. Step rates and lengths increased while foot contact time decreased during sprints and 5-K race portions. Stroller running increased step rate, length, and pronation. Step length decreased and pronation and foot contact time increased over the 21-K race. Wearable sensors helped identify patterns in natural training environments as a basis for clinical application.
Inflammatory Monocytes and Neutrophils Regulate Streptococcus suis-Induced Systemic Inflammation and Disease but Are Not Critical for the Development of Central Nervous System Disease in a Mouse Model of Infection
Authors: Auger Jean-Philippe , Rivest Serge , Benoit-Biancamano Marie-Odile , Segura Mariela , Gottschalk Marcelo
Published: December 2019

Streptococcus suis
is an important porcine bacterial pathogen and zoonotic agent responsible for sudden death, septic shock, and meningitis. These pathologies are a consequence of elevated bacterial replication leading to exacerbated and uncontrolled inflammation, a hallmark of the
S. suis
systemic and central nervous system (CNS) infections. Monocytes and neutrophils are immune cells involved in various functions, including proinflammatory mediator production.
Molecular Mechanism for Antibody-Dependent Enhancement of Coronavirus Entry
Authors: Wan Yushun , Shang Jian , Sun Shihui , Tai Wanbo , Chen Jing , Geng Qibin , He Lei , Chen Yuehong , Wu Jianming , Shi Zhengli , Zhou Yusen , Du Lanying , Li Fang
Published: December 2019

Antibody-dependent enhancement (ADE) of viral entry has been observed for many viruses. It was shown that antibodies target one serotype of viruses but only subneutralize another, leading to ADE of the latter viruses. Here we identify a novel mechanism for ADE: a neutralizing antibody binds to the surface spike protein of coronaviruses like a viral receptor, triggers a conformational change of the spike, and mediates viral entry into IgG Fc receptor-expressing cells through canonical viral-receptor-dependent pathways. We further evaluated how antibody dosages impacted viral entry into cells expressing viral receptor, Fc receptor, or both receptors. This study reveals complex roles of antibodies in viral entry and can guide future vaccine design and antibody-based drug therapy.
Bottom-Up Fabrication of Protein Nanowires via Controlled Self-Assembly of Recombinant
Geobacter
Pilins
Authors: Cosert K. M. , Castro-Forero Angelines , Steidl Rebecca J. , Worden Robert M. , Reguera G.
Published: December 2019

The discovery in 2005 of conductive protein appendages (pili) in the metal-reducing bacterium
Geobacter sulfurreducens
challenged our understanding of biological electron transfer and pioneered studies in electromicrobiology that revealed the electronic basis of many microbial metabolisms and interactions. The protein nature of the pili afforded opportunities for engineering novel conductive peptides for the synthesis of nanowires via cost-effective and scalable manufacturing approaches. However, methods did not exist for efficient production, purification, and
in vitro
assembly of pilins into nanowires. Here we describe platforms for high-yield recombinant synthesis of
Geobacter
pilin derivatives and their assembly as protein nanowires with biochemical and electronic properties rivaling those of the native pili. The bottom-up fabrication of protein nanowires exclusively from pilin building blocks confirms unequivocally the charge transport capacity of the peptide assembly and establishes the intellectual foundation needed to manufacture pilin-based nanowires in bioelectronics and other applications.
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

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

Landscapes 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.
Digital dry gangrene as a primary manifestation of systemic lupus erythematosus
Authors: Sonkar Satyendra Kumar , Kumar Satish , Atam Virendra , Chaudhary Shyam Chand
Published: December 2019

Digital dry gangrene is commonly seen in cases of connective tissue disease such as systemic sclerosis. In systemic lupus erythematosus (SLE) digital gangrene is rare. As initial manifestation, it is again a rare phenomenon because it occurs late in the course of disease. Here we are reporting the case of a woman who was having extensive cutaneous gangrene of her fingers and toes, as a first and foremost presentation without any other typical signs and symptoms of SLE. Her serology was positive for SLE. The patient was treated conservatively and responded well.
Resection of a large mycotic aneurysm of the left anterior descending coronary artery
Authors: Ali Umar , Stamp Nikki , Larbalestier Robert
Published: December 2019

A 50-year-old Indigenous woman, on home haemodialysis, was found to have a large mycotic aneurysm of the proximal left anterior descending coronary artery at the site of a previous drug-eluting stent. Blood cultures grew methicillin-sensitiveStaphylococcus aureusbacteraemia. She underwent a complex operation involving resection of the mycotic aneurysm, removal of the stent and a coronary artery bypass graft to the distal left anterior descending (LAD) coronary artery using the left internal mammary artery. She had a complicated intensive care unit admission with pericardial tamponade on day 1 postoperatively requiring reopening and removal of clot and type 1 respiratory failure requiring reintubation on day 10 postoperatively. Once extubated, she developed prolonged hyperactive delirium and a significant decline in mobility. Over the course of a 6-week hospital admission, she received extensive multidisciplinary care and was discharged for rehabilitation to a peripheral hospital. She was discharged home after rehabilitation with ongoing follow-up with infectious diseases.