bluuebunny/crossref_metadata_2025 huggingface dataset:
Issue framing within the climate debate: An analysis of US environmental policy outcomes
Authors: Badruzzaman Aeshna , Kushi Sidita , Marion Summer
Published: December 2022

This paper argues different policy issue framings of climate change—ranging from security to energy, economics, humanitarian response, and health frames—play critical roles in altering policy outcomes. Specifically, we focus on the several windows of opportunity that altered the pathway of the US climate change debates from 1985 to 2017. Progressing from the underpinnings of issue framing literature and public policy discourse, we conduct content analysis of news articles, academic papers, policy documents and other archival evidence, to show why and when environmental framings shift, and to what effect. Our innovative models provide generalization of these trends and their implications for environmental agenda setting, complemented by a qualitative section that contextualizes impact as well as the feedback mechanisms of issue framing on environmental politics in the United States. The findings highlight the need for future case study analysis to trace the causal mechanisms between climate change framings and US policy outcomes.
Serum estradiol to testosterone ratio as a novel predictor of severe preeclampsia in the first trimester
Authors: Shen Yongmei , Cao Jiasong , Yao Liying , Li Shanshan , Zhao Xiaomin , Li Wen , Wei Zhuo , Zhang Lei , Wang Jianxi , Chang Ying
Published: December 2022

Preeclampsia (PE) is the most common medical complication during pregnancy and the second leading cause of maternal death worldwide. However, a better predictive model of PE remains to be explored. A total of 15 severe preeclampsia (sPE) and 75 healthy control patients were included in this study. Patient data was obtained from September 2019 to September 2021. Nuchal translucency (NT) and crown‐rump length (CRL) of the fetus were acquired by ultrasound. Maternal blood samples were collected at 11+0 to 13+6 weeks of gestation. Chemiluminescent immunoassays were used to detect serum testosterone (T) and estradiol (E2) levels. Time‐resolved fluorescence analysis was used to examine the levels of serum pregnancy‐associated plasma protein A (PAPPA) and β‐human chorionic gonadotrophin (β‐HCG) protein. The sPE group exhibited increased T levels, and decreased E2 levels and E2/T ratios from 11 to 14 weeks of gestation, compared with the control group. E2 and the E2/T ratio showed positive linear correlation with CRL in pregnant women. Body‐mass‐index (BMI), T, and E2 were determined to be the main factors that affected the occurrence of sPE at the 12‐week gestation period time point. The receiver operating characteristic (ROC) curve revealed that the AUC of the E2/T ratio was .717. The imbalanced T and E2 levels in the patients had a specific intrinsic relevance with sPE, which suggests them as novel predictors of the sPE.
Circulating selenoprotein P levels predict glucose‐lowering and insulinotropic effects of metformin, but not alogliptin: A post‐hoc analysis
Authors: Takeshita Yumie , Tanaka Takeo , Takayama Hiroaki , Kita Yuki , Goto Hisanori , Nakano Yujiro , Saito Yoshiro , Takamura Toshinari
Published: December 2022

Aims/Introduction

Selenoprotein P (SeP; encoded by SEPP1 in humans) is a hepatokine that causes impaired insulin secretion and insulin resistance. Metformin downregulates SELENOP promoter activity through an adenosine monophosphate‐activated kinase–forkhead box protein O3a pathway in hepatocytes. This study aimed to test our hypothesis that circulating SeP levels are associated with the glucose‐lowering effect of metformin in humans.

Materials and Methods

A total of 84 participants with poorly controlled type 2 diabetes were randomly assigned to receive metformin (1,000 mg, twice daily) or a dipeptidyl peptidase‐4 inhibitor, alogliptin (25 mg, once daily) for 12 weeks. We tested metformin and alogliptin on SeP levels and factors associated therewith as a post‐hoc analysis.

Results

Both metformin and aloglipitin did not change the SeP levels. Although metformin significantly increased the insulin secretory index secretory units of islets in transplantation only in participants with higher baseline SeP (>3.87), both agents similarly reduced fasting plasma glucose and glycated hemoglobin. SeP levels at baseline were correlated negatively with changes in SeP (r = −0.484, P = 0.004) and fasting plasma glucose (r = −0.433, P = 0.011), and positively with changes in C‐peptide immunoreactivity (r = 0.420, P = 0.017) and secretory units of islets in transplantation (r = 0.388, P = 0.028) in the metformin, but not alogliptin, group.

Conclusions

Higher baseline levels of SeP significantly predicted metformin‐mediated, but not alogliptin‐mediated, glucose‐lowering and insulinotropic effects. Serum SeP levels might be a novel biomarker for predicting the outcomes of metformin therapy, which might be helpful in tailoring diabetes medication.
Health insurance coverage during the COVID‐19 pandemic: The role of Medicaid expansion
Authors: Mandal Bidisha , Porto Nilton , Kiss D. Elizabeth , Cho Soo Hyun , Head Lorna Saboe‐Wounded
Published: December 2022

Using data from the US Census Bureau's Household Pulse Survey, we analyzed the likelihood of loss of health insurance and enrollment into new health coverage during the early months of the COVID‐19 pandemic. Loss of employment was associated with a significant increase in the likelihood of loss of health insurance and, specifically, an increase in the likelihood of employer‐sponsored health insurance. However, individuals in Medicaid expansion states experienced a lower likelihood of loss of health insurance compared with individuals in nonexpansion states. At the same time, there was a statistically significant increase in Medicaid enrollment in expansion states, by 3.2 percentage points. Reemployment or acquiring employment was associated with a gain in health insurance coverage. During an economic downturn, eligibility, and coverage gaps leave many without affordable coverage options, and the pandemic will likely bring renewed attention to gaps in Medicaid coverage in nonexpansion states.
A brief assessment of eye blink drowsiness immediately prior to or following driving detects drowsiness related driving impairment
Authors: Cori Jennifer M. , Wilkinson Vanessa E. , Soleimanloo Shamsi Shekari , Westlake Justine , Stevens Bronwyn , Rajaratnam Shantha M. W. , Howard Mark E.
Published: December 2022

Drowsy driving is a major cause of fatal and serious injury motor vehicle accidents. The inability objectively to assess drowsiness has hindered the assessment of fitness to drive and the development of drowsy driving regulations. This study evaluated whether spontaneous eye blink parameters measured briefly pre‐ and post‐drive could be used to detect drowsy driving impairment. Twelve healthy participants (6 female) drove an instrumented vehicle for 2 h on a closed‐loop track during a rested (8–10 h awake) and an extended wake condition (32–34 h awake). Pre‐ and post‐drive, the participants completed a 5 min eye blink task, a psychomotor vigilance task (PVT), and the Karolinska sleepiness scale (KSS). Whole drive impairment was defined as >3.5 lane departures per hour. Severe end of drive impairment was defined as ≥2 lane departures in the last 15 min. The pre‐drive % of time with eyes closed best predicted the whole drive impairment (area under the curve [AUC] 0.87). KSS had similar prediction ability (AUC 0.85), while PVT reaction time (AUC 0.72) was less accurate. The composite eye blink parameter, the Johns drowsiness scale was the best retrospective detector of severe end of drive impairment (AUC 0.99). The PVT reaction time (AUC 0.92) and the KSS (AUC 0.93) were less accurate. Eye blink parameters detected drowsy driving impairment with an accuracy that was similar to, or marginally better than, PVT and KSS. As eye blink measures are simple to measure, are objective and have high accuracy, they present an ideal option for the assessment of fitness for duty and roadside drowsiness.
Silent HDV epidemics culminates in high levels of liver cirrhosis in endemic region despite 20 years of HBV vaccination
Authors: Isaeva Olga V. , Kyuregyan Karen K. , Karlsen Anastasia A. , Kuzmin Oleg V. , Potemkin Ilya A. , Kichatova Vera S. , Asadi Mobarkhan Fedor A. , Mullin Eugeniy V. , Kozhanova Tatyana V. , Manuylov Victor A. , Pochtovyy Andrey A. , Gushchin Vladimir A. , Saryglar Anna A. , Ilchenko Lyudmila Yu. , Mikhailov Mikhail I.
Published: December 2022

The hepatitis delta virus (HDV) is believed to be a vanishing infection in countries with successful hepatitis B virus (HBV) vaccination programs. We assessed the current status of HDV infection in Tuva, a region of the Russia that has been highly endemic for HBV. The proportion of HDV‐infected patients among HBsAg‐positive patients in the regional registry in 2020 was 32.7% (786/2401). An analysis of the medical records of 514 HDV patients demonstrated that 37.5% (193/514) had liver cirrhosis at the first doctor's visit, and 7.4% of patients lived in families where another family member had HDV. All HDV patients were infected with genotype HDV‐1, 94.5% had HBV genotype D, and 5.5% had genotype A. A serosurvey conducted among 1170 healthy volunteers showed that the average detection rate of HBsAg with anti‐HDV was 1.0% (95% CI: 0.57–1.81%). No anti‐HDV positive samples were detected in participants aged under 30 years. The HBsAg/anti‐HDV positivity rate peaked at 7.4% in patients aged 50–59 years, which was significantly higher than in a similar age cohort surveyed in 2008 (1.6%, p < .0001). A Bayesian analysis showed that HDV circulation in Tuva resulted from two waves of introduction, the first in the 1810s (95% HPD: 1741–1834) from Central Asia, and the second in the 1960s (95% HPD: 1953–1979) from Russia. HBV has a much longer history of circulation in Tuva with the MRCA for the predominant genotype HBV‐D dated to 972 (95% HPD: 535–1253) for subtype D1, 1274 (95% HPD: 936–1384) for D2, and 1173 (95% HPD: 1005–1618) for D3. A SkyGrid reconstruction of population dynamics showed an increase in the intensity of HDV spread in recent decades. This situation shows the need for HDV screening and prevention measures among people living with HBV.
Differences in medication adherence by sex and organ type among adolescent and young adult solid organ transplant recipients
Authors: Vaisbourd Yulia , Dahhou Mourad , Zhang Xun , Sapir‐Pichhadze Ruth , Cardinal Heloise , Johnston Olwyn , Blydt‐Hansen Tom D. , Tibbles Lee Anne , Hamiwka Lorraine , Urschel Simon , Birk Patricia , Bissonnette Janice , Matsuda‐Abedini Mina , BScPhm Jennifer Harrison , Schiff Jeffrey , Phan Veronique , De Geest Sabina , Allen Upton , Avitzur Yaron , Mital Seema , Foster Bethany J.
Published: December 2022

Background

Identification of differences in medication adherence by sex or organ type may help in planning interventions to optimize outcomes. We compared immunosuppressive medication adherence between males and females, and between kidney, liver and heart transplant recipients.

Methods

This multicenter study of prevalent kidney, liver and heart transplant recipients 14–25 years assessed adherence 3 times (0, 3, 6 months post‐enrollment) with the BAASIS self‐report tool. At each visit, participants were classified as adherent if they missed no doses in the prior 4 weeks and non‐adherent otherwise. Adherence was also assessed using the coefficient of variation (CV) of tacrolimus trough levels; CV < 30% was classified as adherent. We used multivariable mixed effects logistic regression models adjusted for potential confounders to compare adherence by sex and by organ.

Results

Across all visits, males (n = 150, median age 20.4 years, IQR 17.2–23.3) had lower odds of self‐reported adherence than females (n = 120, median age 19.8 years, IQR 17.1–22.7) (OR 0.41, 95% CI 0.21–0.80) but higher odds of adherence by tacrolimus CV (OR 2.50, 95% CI 1.30–4.82). No significant differences in adherence (by self‐report or tacrolimus CV) were noted between the 184 kidney, 58 liver, and 28 heart recipients.

Conclusion

Females show better self‐reported adherence than males but greater variability in tacrolimus levels. Social desirability bias, more common in females than males, may contribute to better self‐reported adherence among females. Higher tacrolimus variability among females may reflect biologic differences in tacrolimus metabolism between males and females rather than sex differences in adherence. There were no significant differences in adherence by organ type.
The novel HLA‐A*02:07:22 allele, identified by Sanger dideoxy nucleotide sequencing in a Chinese individual
Authors: Zhu Zun‐min , Zheng Zhong‐zheng , Du Ke‐ming , An Lin , Cheng Lin‐na
Published: December 2022

HLA‐A*02:07:22 differs from HLA‐A*02:07:01:01 by one nucleotide in exon 3.
Identification of the novel HLA‐DPB1*1328:01 allele by next‐generation sequencing
Authors: Galluccio Tiziana , Citterio Franco , Giustiniani Paola , Bianculli Antonio Giuseppe , Andreani Marco
Published: December 2022

The novel HLA‐DPB1*1328:01 allele differs from HLA‐DPB1*04:01:01:01 by one nucleotide substitution in exon 4.
Factors affecting time to treatment initiation after diagnosis for multidrug‐resistant/rifampicin‐resistant tuberculosis patients: A mixed‐methods study in Jakarta, Indonesia
Authors: Silitonga Permata , Jiang Weixi , Wyatt Sage , Burhan Erlina , Kes Esty Febriani M. , Long Qian
Published: December 2022

Objective

To investigate the time to treatment initiation (TTI) for multidrug‐resistant/rifampicin‐resistant tuberculosis (MDR/RR‐TB) patients after diagnosis in Indonesia and biological, psychological and social factors associated with the time interval.

Methods

This study was conducted in Persahabatan Hospital, Jakarta using a mixed‐methods approach. Registry data and medical records of MDR/RR‐TB patients were collected and matched (hospital dataset), and linked with psychosocial assessment results (linked dataset). Descriptive analysis was conducted to understand patient characteristics and the distribution of TTI after RR‐TB diagnosis by GeneXpert. Generalised linear regression was used to analyse factors associated with delay duration, and logistic regression to explore factors associated with the delay longer than the median duration for both datasets (basic vs. extended model). In‐depth interviews were conducted with patients and healthcare workers to understand the procedure of treatment initiation and how different factors led to delay.

Results

The hospital dataset included 275 patient‐matched cases, and 188 were further linked with psychosocial assessment results. The median time interval was 24 days [interquartile range (IQR) 23.5] and 26 days (IQR 21.25), respectively. Regression analysis showed that in the extended model, comorbidities (exp [coefficient]= 1.93), unemployment (exp [coefficient] = 1.80) and poor knowledge of MDR/RR‐TB (exp (coefficient) = 1.67) seemed to have the strongest effects on prolonging the time interval (p < 0.05). Unsuccessful TB treatment history was the only factor that significantly increased the risk of delay longer than the median duration (p < 0.05) in the basic model, while none of the factors were significant in the extended model. The qualitative study identified provider‐side factors (centralised service provision and insufficient human resources) and patient‐side factors (physical weakness, psychological stress and financial concern) associated with treatment delay.

Conclusion

MDR/RR‐TB patients in Persahabatan Hospital, Jakarta, Indonesia waited around 25 days for treatment initiation after RR‐TB diagnosis. Health system solutions are needed to address challenges facing both MDR/RR‐TB patients and healthcare providers to reduce delay in treatment initiation.
Platelet function of whole blood after short‐term cold storage: A prospective in vitro observational study
Authors: Kusudo Eriko , Murata Yutaka , Matsumoto Tsuguhiro , Kawamoto Shuji , Egi Moritoki
Published: December 2022

Background

There is no standardized storage temperature of whole blood for acute normovolemic hemodilution (ANH).

Study Design and Methods

We conducted a prospective observational study to examine the difference in platelet function between short‐term whole blood storage at 4 and 22°C. Venous blood (40 ml) was collected from seven healthy subjects who gave prior written consent. The samples were divided into three groups: before storage (group Pre), cold (4°C) storage (group C), and room temperature (22°C) storage (group R). Groups C and R were tested after 6 h of blood storage. Platelet aggregability, platelet factor 4 (PF4), β‐thromboglobulin (β‐TG), P‐selectin expression, pH, PO2, PCO2, glucose, lactate, blood count, and thromboelastography (TEG) parameters were measured. The percentage change in each parameter in groups C and R was calculated using the value in group Pre as a reference. These data were then compared between groups C and R using a Wilcoxon matched pairs test. p < 0.05 was considered to be statistically significant.

Results

Compared with group R, group C showed significantly higher platelet aggregability with adenosine diphosphate (ADP) 2, 4, and 6 μM (all p = 0.016) and collagen 1 μg/ml (p = 0.047) stimulation, and significantly lower PF4 and β‐TG elevation (both p = 0.031), glucose consumption (p = 0.031), and lactate production (p = 0.016). The ADP channel in TEG showed a significant increase in platelet aggregation rate in group C compared to group R.

Discussion

Cold storage of whole blood in ANH may provide improved storage conditions for platelets and contribute to improved hemostasis compared to room temperature storage.
Microwave Ablation Trocar Operated at Dual Tine Dual-Frequency: A Numerical Analysis
Authors: Satish Vellavalapalli , Repaka Ramjee
Published: December 2022

Microwave ablation (MWA) is a minimally invasive thermal ablation technique that has the advantages of obtaining high intratumoral temperatures, less treatment time, and large ablation region as compared to other thermal ablation techniques. The ablation region obtained during MWA procedure mainly depends on the design and type of the trocar being used. The trocar plays an essential role in the MWA system by governing the energy distribution during tissue ablation. In this study, a novel MWA trocar design has been considered to achieve concentrated ablation region along the tumor’s spatial distribution. A dual tine trocar with each tine supplied with energy at different frequencies (2.45 GHz and 6 GHz) has been considered for tumor ablation. Commercially available Finite Element based software has been used (comsol-multiphysics) to analyze the extent of ablation zone. Coupled bioheat and electromagnetic physics interfaces have been utilized. Results showed that the proposed trocar with tines operating at 6 GHz on both the tines leads to a large ablation region (3 cm in diameter) with spherical in shape. Irregularly shaped ablation region can also be achieved by this trocar with tines operating at different frequencies. The minimum time required for complete tumor ablation by the trocar operated at 6 GHz is 4 min, followed by 6 min for the trocar operated at 2.45 GHz. The proposed trocar can become a part of a better treatment planning system based on tumor shape, nearby blood vessel presence, and the trocar's precise insertion.
Transient Thermomechanical Stress Analysis of Hot Surface Ignition Device Using Sequentially Coupled Computational Fluid Dynamics–Finite Element Analysis Approach
Authors: Kang Sang-Guk , Ryu Je Ir , Motily Austen H. , Numkiatsakul Prapassorn , Lee Tonghun , Kriven Waltraud M. , Kim Kenneth S. , Kweon Chol-Bum M.
Published: December 2022

Energy addition using a hot surface ignition device is required for reliable ignition of aircraft compression ignition engines running on fuel variations and at altitude conditions. Thus, durability of the hot surface ignition device is crucial for application in these engines. Thermomechanical stress is one of the key parameters that determine durability, which requires an accurate prediction of the transient temperature field based on well-defined boundary conditions representing the dynamic and complex fluid flow inside engines. To meet this requirement, the present study focuses on transient thermomechanical stress analysis using a sequentially coupled computational fluid dynamics (CFD)–finite element analysis (FEA) approach to understand transient thermomechanical responses of the hot surface ignition device. A three-dimensional transient reacting flow simulation was conducted first using converge software, the results of which were exported to map thermal and pressure boundary conditions onto a structural finite element mesh. Transient thermomechanical stress analysis was performed sequentially using abaqus software utilizing the mapped boundary conditions. The results such as transient temperature history, resultant thermomechanical stress, displacement, potential failure modes, etc., were critically reviewed, which can provide helpful information for further design improvement.
Machine Learning Enables Autonomous Vehicles Under Extreme Environmental Conditions
Authors: Quach Nhi V. , Park Jewoo , Kim Yonghwi , Cheng Ruey-Hwa , Jenco Michal , Lee Alex K. , Yin Chenxi , Won Yoonjin
Published: December 2022

Autonomous vehicles are part of an expanding industry that encompasses various interdisciplinary fields including but not limited to dynamics and control, thermal engineering, sensors, data processing, and artificial intelligence. Autonomous vehicles require the use of various sensors, such as optical cameras, RADAR (radio detection and ranging), or LiDAR (light detection and ranging), to navigate on the road with the aim of self-driving. However, the exposures to environmental conditions related to the combination of surrounding temperature and humidity lead to challenges in sensor performance. For example, the sensor’s temperature will increase as the heat is generated during the vehicle’s usage. On the other hand, the sensor system will undergo thermal shock from the temperature difference the due to sudden changes in temperature, such as moving from an indoor garage at room temperature to −10°C environments. Furthermore, the consistent exposure to the cold weather may occur frosting, which can obstruct the optical sensor’s visibility. Those issues limit the potential of data processing from optical cameras and consequence autonomous driving reliability at extreme environmental conditions.

To review the requirements for sensor performance used in autonomous vehicles and to formulate solutions addressing potential concerns to improve autonomous driving safety, we simulate camera operating conditions in the real world. First, we correlate the common placements of optical sensors, mainly focusing on cameras, in autonomous vehicles to naturally occurring environmental conditions in relation to temperature and humidity. With this correlation, we aim to provide an understanding of potential areas on the vehicle that may be more prone to environmental factors of thermal shock or humidity variations. Second, we examine the condensation and frosting mechanism and formation sequence on the vehicle surfaces (e.g., windshield and camera lenses), which is then used to determine the level of water on the lenses before the sensor vision is impeded. Third, we introduce and conceptualize machine learning models that can extract features by employing object detection algorithms that perform image restoration to reconstruct areas with deterioration despite the presence of the droplets or frosts on the camera. With this research, we aim to provide a better understanding of the potential caveats and algorithm solutions that can help the capability for autonomous driving even under extreme environmental conditions.
Comparative Analysis of Direct and Indirect Cooling of Wide-Bandgap Power Modules and Performance Enhancement of Jet Impingement-Based Direct Substrate Cooling
Authors: Barua Himel , Gurpinar Emre , Xue Lingxiao , Ozpineci Burak
Published: December 2022

With the development of high-power and high-torque machines, requirements for high-power density electronics are increasing. Thermal management of such systems requires high heat extraction. Conventional air cooling based heat sinks and cold plate based liquid cooling have their own benefits for various applications but has limitations for high power density applications. The current study explores a jet impingement based direct substrate cooling system that was implemented for a SiC based direct bonded Cu substrate for various power losses. Numerical comparison between jet impingement cooling and conventional horizontal/indirect cooling (pin fin heat sink and genetic algorithm-optimized heat sink) showed that the area weighted average of the heat transfer coefficient (HTC) is high for both horizontal cooling designs, and the local HTC is higher for jet impingement. Design iterations were undertaken to resolve the bottleneck of this cooling system. Increasing the number of nozzles helped to cover more area at the direct bonded Cu bottom plate, which drops the chip temperature considerably. With a constant flow rate, increasing the number of nozzles would decrease local jet velocity, which reduces the heat extraction by jet impingement. This issue can be addressed by reducing the diameter of nozzle but doing so results in a high pressure drop where the design constraint is 2 psi. A flared nozzle design is proposed, which has a higher spreading angle of the jet that increases the flow coverage and reduces the pressure drop of the coolant loop.
AI/ML Applications for Thermally Aware SoC Designs
Authors: Norman Adam , Gallina Mark , Zhu Olena , Weiner Joyce , Garita Gonzalez Fabian
Published: December 2022

Thermal considerations are a critical facet in SoC and System design. There are numerous difficulties in performing comprehensive thermal analysis on modern SoC designs as well as considerable difficulty in moving towards a cross-discipline co-design strategy. The design space is large and growing more complex with each generation, coupled with long evaluation/simulation time for sufficiently accurate thermal response. Thermal feedback into design iterations were additionally slowed by the huge numbers of excitation (workloads) scenarios needed to provide design robustness. Augmented Intelligence and machine learning (ML) approaches are explored to address some of these difficulties, as well as development of a fast evaluation function to reduce total computation time. Various clustering and modeling techniques are used to improve stimulus/workload selection and coverage for analysis, which further reduces evaluation time. This huge enhancement in evaluation time has opened new opportunities for co-design work, ML optimization schemes are applied to address the high degrees of freedom present at the SoC level. The results have been impressive, showing huge potential for thermal improvements which translate directly into improved product performance.
Drop Durability of Printed Hybrid Electronic (PHE) Assemblies Under Extreme Acceleration Level
Authors: Abusalma Hisham , Dasgupta Abhijit , Bujanda Andres , Yu Jian , Tsang Harvey
Published: December 2022

In this paper, the drop durability of printed hybrid electronic (PHE) assemblies of various form factors is studied under extreme drop conditions with accelerations up to 20,000 G. Test specimens considered here include: circular disk, cantilever beam, and hemispherical dome samples.

The disk is made from a UV hardened resin material and mounted using a 3-point fixture. This specimen experienced overstress fracture at 20,000 G drops. Additionally, it was very susceptible to repetitive drop failure. The failure site was at the expected site of maximum flexure, as revealed by finite element modeling and by high-speed video recording.

The cantilever beam is a standard 1.6 mm thick FR4 substrate with printed silver traces. The substrate was durable but suffered from high strains near the clamp which are expected to cause damage to the silver conductive traces printed on them. The beam specimen was instrumented with strain gages and was also subjected to high-speed video recording of the drop event. The beam was found to vibrate in its first two bending modes when dropped at 10,000 G.

The hemispherical substrates for the dome specimens were made from several different polymeric materials and were mounted in a threaded fixture. Drop durability varied with choice of substrate material and fabrication method. Some showed catastrophic failures after 1–5 drops at 20,000 Gs while some survived more than 50 drops at 20,000 G. The failure site for all failed dome specimens was at the threads used for mounting to the fixture.
Liquid to Air Cooling for High Heat Density Liquid Cooled Data Centers
Authors: Heydari Ali , Radmard Vahideh , Eslami Bahareh , Tradat Mohammad I. , Manaserh Yaman , Miyamura Harold , Chowdhury Uschas , Shahi Pardeep , Hall Kevin Dave , Sammakia Bahgat , Rodriguez Jeremy
Published: December 2022

Growing demand for dense and high-performing IT compute capacity to support deep learning and artificial intelligence workloads necessitates data centers to look for more robust thermal management strategies. Today, data centers across the world are turning to liquid-based cooling solutions to keep up with the increased cooling demand for high power racks approaching 100kW of heat dissipation. Deploying direct-to-chip cold plate liquid cooling is one of the mainstream approaches which allows targeted cooling of high-power processors. This study provides the framework for a hybrid in row cooler (IRC) with liquid-to-air (L2A) heat exchanger (HX) system delivering chilled coolant to liquid-cooling cold plates mounted to the high heat dissipation electronics. This approach is useful for high heat density cooling of racks where no primary facility coolant is available at the data center. The present study aims to investigate the thermo-hydraulic performance of a distinct L2A IRC system that supplies cold secondary coolant (PG 25%) into the cooling loops of liquid-cooled servers in racks within an existing air-cooled data center. Thermal test vehicles (TTVs) are built to replicate actual high heat density servers. From the cold plate to data center level the proper choice of each level component was described based on their cooling performance and relevance. Three different cooling loop/rack designs are characterized experimentally, and detailed analytical and numerical (FNM) simulations are developed to analyze the heat exchanger performance. The FNM and CFD model of a data center are done in two steady and transient forms to study the performance of the L2A IRC in a data center.
Melt Front Enhancement of Phase Change Materials via Nanoparticle Inclusion for Improved Heat Transfer and Cyclability
Authors: Kasitz Joshua , Marshall Larry , Huitink David
Published: December 2022

Passive cooling techniques are widely sought-after solutions to thermal management issues in high power electronics due to increased energy dissipation in reduced areas. Phase change materials (PCMs) present a promising secondary passive thermal management opportunity by absorbing a large amount of energy as an isothermal process. This phenomenon can be utilized in various ways as a thermal management tool; including temperature spike alleviation, energy storage, and secondary passive cooling. Though PCMs have promising passive cooling ability, often it is difficult to select an appropriate or effective PCM for the specific application due to deficiencies in a particular material property. Previous studies have demonstrated the ability to alter PCM properties through the homogeneous inclusion of nanoparticles. Thermal conductivity is a particularly important metric for enhancement via nanoparticles due to the typically low conductivity of PCMs with high latent heats. Previous studies demonstrate the successful augmentation of this property. A large limiting factor to enhanced PCM passive cooling is related to the propagation of the melt front, representing the region of large energy absorption. In many cases, the melt front moves too slowly to effectively transfer energy away from the device. Slow material response time can also be problematic in the re-solidification process, limiting cyclability. Work has been conducted to monitor the melt front response to a thermal load. Early in the melting process, conduction dominates the heat transfer mechanism. This paper will examine the impact of nanoparticle inclusion as a means of controlling the melt front propagation. Using nanoparticles to control the composite thermal conductivity should lead to optimization ability of PCM melt characteristics to align with thermal management needs.
CFD Simulation-Based Comparative Study of Forced Convection Single-Phase Liquid Immersion Cooling for a High-Powered Server
Authors: Murthy Prajwal , Gupta Gautam , Herring Joseph , Lamotte-Dawaghreh Jacob , Sivaraju Krishna Bhavana , Bansode Pratik , Modi Himanshu , Agonafer Dereje , Mynampati Poornima , Sweeney Mike
Published: December 2022

Due to increasing computational workload and thermal design power requirements of high power-density microelectronics, low heat carrying capacity and poor thermal conductivity of air renders air-cooling insufficient to meet the cooling demands of component heat generation in high-performance servers. A more effective method of removing heat from these high-powered components is by using single-phase immersion cooling with a dielectric fluid of superior thermal properties and high boiling point. This study compares traditional forced-air cooling with forced convection single-phase immersion cooling to minimize chip junction temperatures of a 776 W high powered data center server using CFD simulations. The server is of spread-core configuration consisting of 2 CPU heatsink assemblies and 32 DIMM units with their specified chip thermal design power (TDPs). The first method consists of forced-air cooling with a 28°C air inlet supply and 110 CFM inlet air flowrate to establish baseline thermal performance. The second method is forced convection single-phase immersion cooling of the server in EC-110 dielectric fluid at 28 °C temperature and 2 GPM flow rate to observe server performance improvement in CPU case temperatures, maximum DIMM temperature, and server pressure drop through immersion cooling method. Lastly, CFD simulations are performed at different fluid inlet temperatures of 30, 40 and 50 °C, and 2 GPM fluid inlet flow rate, and the percentage change in the CPU case temperatures, server pressure drop and the maximum DIMM temperatures with fluid inlet temperature were studied.
Impact of Immersion Cooling on Thermomechanical Properties of Non-Halogenated Substrate
Authors: Bhandari Rabin , Lakshminarayana Akshay Boovanahally , Sivaraju Krishna Bhavana , Bansode Pratik Vithoba , Kejela Ephrem , Agonafer Dereje
Published: December 2022

Detailed study of material compatibility of the various electronics packaging materials for immersion cooling is essential to understand their failure modes and reliability. The modulus and thermal expansion are critical material properties for electronics mechanical design. Substrate is a critical component of electronic package and heavily influences failure mechanism and reliability of electronics both at the package and board level. This study mainly focuses on two major challenges. The first part of the study focuses on the impact of thermal aging in dielectric fluid for single-phase immersion cooling on the non-halogenate substrate’s thermo-mechanical properties. The second part of the study is the impact of thermal aging on thermo-mechanical properties of substrate in the air. The non-halogenated low Coefficient of Thermal Expansion (CTE) bismaleimide triazine (BT) resin laminate is used for its ultra-low CTE which in turn reduce the warpage of substrate. Moreover, the substrate has high glass transition temperature and high stiffness suitable for the application which requires high heat resistance. The substrate is aged in ElectroCool EC100 dielectric fluid, and air for 720 hours at three different temperatures: 22°C, 50°C, and 75°C. The complex modulus is characterized before and after aging for both parts and compared.
Evolution of Propensity for Chip-UF FCBGA Interface Delamination Under Fatigue-Loading and Sustained High Automotive Temperatures
Authors: Lall Pradeep , Pandurangan Aathi Raja Ram , Williamson Jaimal
Published: December 2022

Underhood applications in automotive are increasingly using electronics systems for safety and critical functions. In flip-chip ball grid array (FCBGA) packages, underfill (UF) forms the integral mechanical support between the substrate and die. In addition, underfills protect the chip against shock, vibration, moisture, and radiation. Underfills provide great mechanical support to the solder interconnects and limit the amount of plastic work during temperature excursions. Delamination is of the significant failure modes observed at chip-UF interfaces. Chip-UF interfaces have not been studied widely under cyclic fatigue loading with sustained high-temperature exposure. Chip-UF bi-material samples are prepared and subjected to long-term high-temperature aging at 100°C and then tested under four-point bend fatigue loading. The specimens have been exposed to isothermal aging for 30 days, 60 days, 90 days, 120 days, and 180 days. The interfacial crack growth rate with respect to the number of fatigue cycles has been determined from the experiment. The steady-state energy release rate and range of mode-I stress intensity values (ΔKI) have been computed for each of the test conditions. Paris power law has been used to establish the relationship between the crack growth rate and the range of stress intensity factors. Paris exponents (A,n) are determined from the relationship to understand the evolution in interfacial fracture toughness with respect number of days of aging under fatigue loading.
Experimental Study of Transient Hydraulic Characteristics for Liquid Cooled Data Center Deployment
Authors: Heydari Ali , Shahi Pardeep , Radmard Vahideh , Eslami Bahareh , Chowdhury Uschas , Sivakumar Akiilessh , Lakshminarayana Akshay , Miyamura Harold , Gupta Gautam , Agonafer Dereje , Rodriguez Jeremy
Published: December 2022

Increasing demands for cloud-based computing and storage, Internet-of-Things, and machine learning-based applications have necessitated the utilization of more efficient cooling technologies. Direct-to-chip liquid cooling using cold plates has proven to be one of the most efficient methods to dissipate the high heat fluxes of modern high-power CPUs and GPUs. While the published literature has well-documented research on the thermal aspects of direct liquid cooling, a detailed account of transient hydraulic investigation is still missing. In this experiment, a total of four 52U racks with four high-power TTV-servers (Thermal Test Vehicles) in each rack were designed and deployed. Each server consists of eight GPU TTVs and six NV switch heaters. Each of the two racks has a different vendor rack manifold and cooling loop modules (CLM). A 450 kW coolant distribution unit (CDU) is used to supply 25% propylene glycol coolant to these racks. Each rack has its own rack-level flow control valve to maintain the same flow rate. The present study provides an in-depth analysis of hydraulic transients when rack-level flow control valves are used with and without flow control. The operating conditions of the CDU are varied for different parameters, such as a constant flow rate, constant differential pressure, and constant pump speed. Furthermore, hydraulic transient is examined when the cooling loop modules are decommissioned from the rack one by one. The effect of this step-by-step decommissioning is assessed on the CDU operation and other racks. The pressure drop-based control strategy has been developed to maintain the same flow rate in the remaining servers in the rack when some cooling loop modules are decommissioned.
Deep Learning for Prediction of Print Parameters and Realized Electrical Performance and Geometry on Inkjet Platform
Authors: Lall Pradeep , Kulkarni Shriram , Soni Ved , Goyal Kartik , Miller Scott
Published: December 2022

A closed-loop deep learning approach for correlating the print parameters with realized electrical performance and geometry estimations on an inkjet platform has been presented in this paper. An estimate of the changes in the print parameters and the recognized print dimension is necessary to print reliable and fine conductive traces. The inks used for this analysis are both particle and particle-free silver inks, and the comparison of the same is also studied. A closed-loop control algorithm is used to attain the desired electrical and geometrical values by changing the print parameters without any user intervention. Sensing is achieved by an automatic print parameter sensing system using a camera that captures the print to identify the geometry and dimension of the same. Once the realized print parameters are determined, a deep learning neural network regression model based on these parameters is used to predict the desired input print parameters, which are used to achieve the desired geometry and dimension of the print. These new parameter values are passed on to the printing software to optimize the print and attain the desired geometry and characteristics.
Additively Printed Flexible Charging Circuits and Effect on Evolution of Line Resistance and Charging Current in Charging Thin Flexible Batteries
Authors: Lall Pradeep , Soni Ved , Miller Scott
Published: December 2022

Flexible electronics are increasingly finding commercial applications ranging from wearable activity tracking watches, rollable displays, foldable smartphones, and biometrics. There is an acceleration of effort in the research and development of additively printed electronics on flexible substrates. Aside from device flexibility, the usage of flexible electronics leads to weight and bulk miniaturization of the product leading to compact and sleek devices. In our previous works, we have successfully studied the effect of mechanical stresses on flexible batteries and their integration into the flexible format via battery lamination. However, in addition to the battery, the battery charging circuit is a key component that must be transferred from a rigid PCB to a flexible format. This study aims to employ electrically conductive ink to print a linear battery charging circuit on a flexible polyimide substrate using different additive printing technologies, namely, aerosol jet printing and direct ink writing (DIW). In aerosol jet printing, both the ultrasonic (AJU) and pneumatic atomization (AJP) technologies have been used for depositing ink, and their subsequent results have been compared. COTS have to be attached to the circuit using electronically conductive adhesives (ECA). The flexible charging circuit has been compared for the print platforms of aerosol-jet printing and direct-write during charging-discharge cycling of the circuit.
Effect of Property Evolution of Doped and Undoped SnAgCu Solder Alloys Under Shock and Vibration
Authors: Lall Pradeep , Yadav Vikas , Suhling Jeff , Locker David
Published: December 2022

Electronics may be required to operate in harsh environments in automotive, aerospace, and defense applications. Solder interconnects in harsh environments may be subjected to extremely-low and high temperatures in the range of −65C to +200C in conjunction with significant strain loads. Furthermore, electronic assemblies may be subjected to extended periods of non-climate-controlled storage prior to deployment. Prior studies have shown that lead-free solder materials continue to evolve under varied thermal loads, leading to deterioration in mechanical parameters such as Ultimate Tensile Strength and Elastic Modulus. The material characteristics for non-linear modeling and reliability prediction are required for risk minimization with the use of new alloy formulations in high-reliability applications. The current work fills this state-of-the-art gap by measuring the mechanical characteristics of undoped SAC105 and doped SAC-Q solder alloys at low operation temperatures (−65°C to 0°C) at high strain rate after varied thermal aging periods up to one year. In addition, the evolution of Anand parameters for SAC solder alloys after prolonged thermal aging has been studied. The Anand model’s reliability has been assessed by comparing experimentally observed data with forecasted data using determined model constants for both solder alloys. The Anand parameters were applied in a FE-framework to simulate drop events for a ball-grid array package on a printed circuit board assembly.
Influence of Cure-Reflow Profile and High-Temperature Operation of Additively Printed Conductive Circuits on Performance and Reliability
Authors: Lall Pradeep , Narangaparambil Jinesh , Hill Curtis
Published: December 2022

For many years, traditional rigid PCBs have been utilized in many applications and have been shown to be reliable in a number of applications. There hasn’t been much research on flexible electronics device attachment techniques and process reliability. There has been prior research done on copper sintering using various methodologies, but there is no prediction model to apply the underlying information directly for predicting the performance of the printed electronics. The sintering process determines the electrical performance of printed traces, and it is necessary to comprehend and estimate the resistivity of printed traces. This study developed a regression model based on an Artificial Neural Network (ANN) to predict resistivity. Because flexible substrates allow for more flexibility, it is critical to create a reliable way of attaching components to circuits that can endure various motions. Micro dispensing equipment was employed in this investigation to print conductive traces, an electrically conductive adhesive (ECA), and low-temperature solder (LTS) for component attachment pads. There is little understanding of SMD attachments’ behavior on additively printed flexible substrates, and we examined different aspects of their performance in this study.
Design of Buck Converter With Control System for Electric Vehicle Using SiC Device With Thermal Loss Model
Authors: Gupta Utsav , Vass-Varnai Andras
Published: December 2022

In today’s day and age, power electronic components are found in all areas of an electric vehicle, from power train to motors and from battery to ancillary loads. Power converters are used to optimize energy management in an automobile. While doing the electrical design of a power converter, the thermal aspects are usually neglected causing a vast difference in the simulation and real-life application. This paper aims to show how taking thermal characteristics into account for a power converter is beneficial and how it influences the results.
On the Viscoelastic Property Measurement of Filled Polymers by Dynamic Mechanical Analyzer (DMA)
Authors: Phansalkar Sukrut Prashant , Han Bongtae , Akbari Ehsan , Vaitiekunas Paulius
Published: December 2022

Dynamic mechanical analyzers (DMA) are routinely practiced in the semiconductor industry to measure the viscoelastic behavior of highly filled thermosetting polymers. The highly filled polymers possess unique challenges in viscoelastic property measurements where set-and-forget style of DMA operation do not always produce the most accurate data due to a large change in modulus over operating and/or manufacturing temperature excursions. This paper discusses the unique challenges associated with the highly filled polymers first and proposes a procedure to determine a proper set of testing parameters.