bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design, Analysis and Comparison of Insulated Metal Substrates for High Power Wide-Bandgap Power Modules
Authors: Gurpinar Emre , Ozpineci Burak , Chowdhury Shajjad 
Published: December 2019

Abstract
In this technical paper, design, analysis and comparison of insulated metal substrates for high power wide-bandgap semiconductor-based power modules is discussed. The paper starts with technical description and discussion of state-of-the-art direct bonded copper substrates with different ceramic insulators such as AlN, Al2O3 and Si3N4. This is followed by introduction of insulated metal substrates, material properties and options on each layer, and design approach for high power applications. The properties of dielectric thickness, and impact on power handling capability of the substrate are discussed. Insulated metal substrate design approach for SiC MOSFET based power modules is presented. Finite element analysis-based characterization and comparison of different designs including steady-state and transient thermal response is presented. The results show that IMS is a promising alternative to DBC in high power modules with improved transient thermal performance. IMS provides flexible building structure with multi-layer stacking options and variable thicknesses at different layers.
Optimal Design and Modeling of Server Cabinets With In-Row Coolers and Air Conditioning Units in a Modular Data Center
Authors: Chowdhury Uschas , Hendrix Walter , Craft Thomas , James Willis , Sutaria Ankit , Agonafer Dereje 
Published: December 2019

Abstract
In a data center, electronic equipment such as server and switches dissipate heat and the corresponding cooling systems contribute to typically 25–35% of total energy consumption. The heat load continues to increase as there is a greater need for miniaturization and convergence. In 2014, data centers in the U.S. consumed an estimated 70 billion kWh, representing about 1.8% of total U.S. electricity consumption. Based on current trend estimates, U.S. data centers are projected to consume approximately 73 billion kWh in 2020 [1]. Many research and strategies are adopted to minimize energy cost. The recommended dry bulb temperature for long-term operation and reliability for air cooling is between 18–27°C and the largest allowable inlet temperature range to operate at is between 5°C and 45°C with American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) enabling much broader allowable zones) [2]. But understanding a proper cooling system is very important especially for thermal management of IT equipment with high heat loads such as 1U or 2U multi-core, high-end servers and blade servers which provide more computing per watt. Many problems like high inlet temperature due to the mixing of hot air with cold air, local hot spots, lower system reliability, increased failure, and downtime may occur. Among many other approaches to managing high-density racks, in-row coolers are used in between racks to provide cold air and minimize local hot spots. This paper describes a computational study being performed by applying in-row coolers for different rack power configuration with and without aisle containment. The power, as well as the number of racks, are varied to study the effect of raised inlet temperature for the IT equipment in a Computational Fluid Dynamics (CFD) model developed in 6SigmaRoom with the help of built-in library items. A comparative analysis is also performed for a typical small-sized non-raised facility to investigate the efficacy and limitations of in-row coolers in thermal management of IT equipment with variation in rack heat load and containment. Several other aspects like a parametric study of variable opening areas of duct between racks and in-row coolers, the variation of operating flow rate and failure scenarios are also studied to find proper flow distribution, uniformity of outlet temperature and predict better performance, energy savings and reliability. The results are presented for general guidance for flexible and quick installation and safe operation of in-row coolers to improve thermal efficiency.
Impact of Immersion Cooling on Thermo-Mechanical Properties of PCB’s and Reliability of Electronic Packages
Authors: Ramdas Shrinath , Rajmane Pavan , Chauhan Tushar , Misrak Abel , Agonafer Dereje 
Published: December 2019

Abstract
Immersion cooling is highly efficient thermal management technique and can potentially be used for thermal management of high-density data. However, to use this as a viable cooling technique, the effect of dielectric coolants on the reliability of server components needs to be evaluated. Previous work reported contradicting findings for Young’s modulus of PCBs, providing motivation for this work. This study focuses on effect of immersion cooling on the mechanical properties of printed circuit board (PCB) and its impact on reliability of electronic packages. Changes in thermo-mechanical properties like Young’s modulus (E), Glass transition temperature (Tg), of PCB and its layers due to aging in dielectric coolant are studied. Two types of PCBs using different material namely 370HR and 185HR are studied. To characterize Young’s modulus and Tg dynamic mechanical analyzer (DMA) is used. Major finding is Young’s modulus is decreasing for PCBs after immersion in dielectric coolant which is likely to increase reliability of electronics package.
Evolution of Anand Parameters With Elevated Temperature Aging for SAC Leadfree Alloys
Authors: Lall Pradeep , Yadav Vikas , Suhling Jeff , Locker David 
Published: December 2019

Abstract
Electronic components in downhole oil drilling and gas industry applications, automotive and avionics may exposed to high temperatures (&gt; 150°C) and high strain rates (1–100 per sec) during storage, operation and handling which can contribute to the failures of electronics devices. Temperatures in these applications can exceed 200°C, which is closed to melting point for SAC alloys. The microstructure for lead free solder alloys constantly evolves when subjected to thermal aging for sustained periods with accompanying degradation in mechanical properties of solder alloys. In this paper, evolution of microstructure and Anand parameters for unaged and aged SAC (SAC105 and SAC-Q) lead free solder alloys at high strain rates has been investigated induced due to thermal aging. The microstructure of the SAC solder is studied using scanning electron microscopy (SEM) for different strain rate and elevating temperature. The thermal aged leadfree SAC solder alloys specimen has been tested at high strain rates (10–75 per sec) at elevated temperatures of (25°C–200°C). The SAC leadfree solder samples were subjected to isothermal aging at 50°C up to 1-year before testing. To describe the material constitutive behavior, Anand Viscoplastic model has been used. Effect of thermal aging on Anand parameters has been investigated. In order to verify the accuracy of the model, the computed Anand parameters have been used to simulate the uniaxial tensile test. FEA based method has been used to simulate the drop events using Anand constitutive model. Hysteresis loop and Plastic work density has been computed from FEA.
CFD Analysis of Thermal Shadowing and Optimization of Heatsinks in 3rd Generation Open Compute Server for Single-Phase Immersion Cooling
Authors: Shah Jimil M. , Dandamudi Ravya , Bhatt Chinmay , Rachamreddy Pranavi , Bansode Pratik , Agonafer Dereje 
Published: December 2019

Abstract
In today’s networking world, utilization of servers and data centers has been increasing significantly. Increasing demand of processing and storage of data causes a corresponding increase in power density of servers. The data center energy efficiency largely depends on thermal management of servers. Currently, air cooling is the most widely used thermal management technology in data centers. However, air cooling has started to reach its limits due to high-powered processors. To overcome these limitations of air cooling in data centers, liquid immersion cooling methods using different dielectric fluids can be a viable option. Thermal shadowing is an effect in which temperature of a cooling medium increases by carrying heat from one source and results in decreasing its heat carrying capacity due to reduction in the temperature difference between the maximum junction temperature of successive heat sink and incoming fluid. Thermal Shadowing is a challenge for both air and low velocity oil flow cooling. In this study, the impact of thermal shadowing in a third-generation open compute server using different dielectric fluids is compared. The heat sink is a critical part for cooling effectiveness at server level. This work also provides an efficient range of heat sinks with computational modelling of third generation open compute server. Optimization of heat sink can allow to cool high-power density servers effectively for single-phase immersion cooling applications. A parametric study is conducted, and significant savings in the volume of a heat sink have been reported.
Forming sulfate- and REE-rich fluids in the presence of quartz
Authors: Cui Hao , Zhong Richen , Xie Yuling , Yuan Xueyin , Liu Weihua , Brugger Joël , Yu Chang 
Published: December 2019

Abstract
The presence of sulfate-rich fluids in natural magmatic hydrothermal systems and some carbonatite-related rare earth element (REE) deposits is paradoxical, because sulfate salts are known for their retrograde solubility, implying that they should be insoluble in high-temperature geofluids. Here, we show that the presence of quartz can significantly change the dissolution behavior of Na2SO4, leading to the formation of extremely sulfate-rich fluids (at least 42.8 wt% Na2SO4) at temperatures &gt;∼330 °C. The elevated Na2SO4 solubility results from prograde dissolution of immiscible sulfate melt, the water-saturated solidus of which decreases from ≥∼450 °C in the binary Na2SO4-H2O system to ∼270 °C in the presence of silica. This implies that sulfate-rich fluids should be common in quartz-saturated crustal environments. Furthermore, we found that the sulfate-rich fluid is a highly effective medium for Nd mobilization. Thermodynamic modeling predicts that sulfate ions are more effective in complexing REE(III) than chloride ions. This reinforces the idea that REEs can be transported as sulfate complexes in sulfate-rich fluids, providing an alternative to the current REE transport paradigm, wherein chloride complexing accounts for REE solubility in ore fluids.
How do undergraduate nursing students learn in the hospital setting? A scoping review of conceptualisations, operationalisations and learning activities
Authors: Stoffels Malou , Peerdeman Saskia M , Daelmans Hester E M , Ket Johannes C F , Kusurkar Rashmi A 
Published: December 2019

ObjectivesAlthough clinical learning is pivotal for nursing education, the learning process itself and the terminology to address this topic remain underexposed in the literature. This study aimed to examine how concepts equivalent to ‘learning in practice’ are used and operationalised and which learning activities are reported in the nursing education literature. The final aim was to propose terminology for future studies.DesignThe scoping framework proposed by Arksey and O’Malley was used to answer the research questions and address gaps in the literature. Two systematic searches were conducted in PubMed, EBSCO/ERIC and EBSCO/CINAHL between May and September 2018: first, to identify concepts equivalent to ‘learning in practice’ and, second, to find studies operationalising these concepts. Eligible articles were studies that examined the regular learning of undergraduate nursing students in the hospital setting. Conceptualisations, theoretical frameworks and operationalisations were mapped descriptively. Results relating to how students learn were synthesised using thematic analysis. Quality assessment was performed using the Critical Appraisal Skills Programme checklist.ResultsFrom 9360 abstracts, 17 articles were included. Five studies adopted a general, yet not explained, synonym for learning in practice, and the other approaches focused on the social, unplanned or active nature of learning. All studies used a qualitative approach. The small number of studies and medium study quality hampered a thorough comparison of concepts. The synthesis of results revealed five types of learning activities, acknowledged by an expert panel, in which autonomy, interactions and cognitive processing were central themes.ConclusionsBoth theoretical approaches and learning activities of the current body of research fit into experiential learning theories, which can be used to guide and improve future studies. Gaps in the literature include formal and informal components of learning, the relation between learning and learning outcomes and the interplay between behaviour and cognitive processing.
Simultaneous resection of the primary tumour and liver metastases after conversion chemotherapy versus standard therapy in pancreatic cancer with liver oligometastasis: protocol of a multicentre, prospective, randomised phase III control trial (CSPAC-1)
Authors: Wei Miaoyan , Shi Si , Hua Jie , Xu Jin , Yu Xianjun 
Published: December 2019

IntroductionApproximately 50% of pancreatic ductal adenocarcinoma (PDAC) patients are diagnosed with distant metastasis, especially liver metastasis. The current standard treatment for these stage IV patients is palliative chemotherapy. There is increasing agreement that synchronous PDAC and liver metastasis resection may benefit highly selected patients. Thus, the Chinese Study Group for Pancreatic Cancer (CSPAC)−1 trial is being launched to establish a strategy for selecting PDAC patients with liver oligometastases who may benefit from synchronous resection after conversion chemotherapy.Methods and analysisIn this study, liver oligometastasis is defined as no more than three metastatic lesions irrespective of their distribution within the liver lobes. The trial contains two steps. In the first step, 1000 to 1200 needle biopsy-confirmed PDAC patients with liver oligometastases are eligible for inclusion. Candidates will receive first-line chemotherapy. The RECIST V.1.1 criteria combined with tumour markers will be applied to evaluate the tumour response to chemotherapy every two cycles. Pancreatic cancer and hepatic metastasis resectability will be identified by multidisciplinary teams. Approximately 300 patients who meet our criteria will enter the second step and be randomly assigned at a 1:1 ratio to simultaneous resection of the primary pancreatic cancer lesion and liver oligometastases if no extensive metastatic sites are found during surgery or standard chemotherapy. Postoperative chemotherapy is recommended, and regimen selection should be based on the preoperative chemotherapy regimen. The primary endpoint is real overall survival (from enrolment to death). This study was activated in July 2018 and is expected to complete accrual within 5 years.Ethics and disseminationThis trial has been approved by the Clinical Research Ethics Committee of Fudan University Shanghai Cancer Centre. Written informed consent will be obtained from all participants. Serious adverse events will be reported. Trial results will be submitted for peer-reviewed publication.Trial registration numberNCT03398291; Pre-results.
Relationship between visual acuity and muscle mass in the Korean older population: a cross-sectional study using Korean National Health and Nutrition Examination Survey
Authors: Moon Ji Hyun , Oh Yun Hwan , Kong Mi Hee , Kim Hyeon Ju 
Published: December 2019

ObjectivesWe aimed to assess the effects of visual acuity on muscle mass, which is an important indicator of health in older populations.DesignPooled-sample cross-sectional study.SettingNationally representative population survey data.ParticipantsThe present study analysed men aged 65 years or older who participated in the Korea National Health and Nutrition Examination Survey (KNHANES, 2008–2011).Primary and secondary outcome measuresMuscle mass was measured by dual-energy X-ray absorptiometry scan, and low muscle mass was defined as appendicular skeletal mass divided by height squared (kg/m2) <6.43 kg/m2 (lowest quintile of the older population in KNHANES, 2008–2011). Visual acuity was evaluated based on best-corrected visual acuity of the better eye.ResultsOf the 1733 participants, 89.9% had good visual acuity. After adjusting for age, the height-adjusted appendicular skeletal muscle mass values were 7.16 and 7.00 kg/m2 in the good and poor vision groups, respectively (p=0.042). According to our criterion for low muscle mass, the prevalence of low muscle mass was 16.4% and 34.7% in the good and poor vision groups, respectively. After adjusting for age, smoking status, alcohol consumption status, frequency of physical activity, educational level, the status of basic livelihood recipient and history of stroke, the poor visual acuity group had higher odds of low muscle mass than the good visual acuity group (OR=1.60; 95% CI 1.02 to 2.50; p=0.040).ConclusionsOlder men with decreased visual acuity have low muscle mass. Poor vision might be an indicator of low muscle mass.
Benzodiazepines for cancer dyspnoea: a nationwide survey of palliative care physicians
Authors: Matsuda Yoshinobu , Matsunuma Ryo , Suzuki Kozue , Mori Masanori , Watanabe Hiroaki , Yamaguchi Takashi 
Published: December 2019

ObjectivesIt is unclear whether patients with non-specific dyspnoea are suitable candidates for studies investigating the effectiveness of benzodiazepines against dyspnoea. The objective of this survey was to investigate suitable subjects for studies of benzodiazepines for cancer dyspnoea.MethodsA nationwide questionnaire survey was conducted among 536 Japanese-certified palliative care physicians. We randomly selected 268 physicians and inquired about their approach to dyspnoea management in patients with cancer, with and without anxiety, as follows: (1) Administration of a benzodiazepine. (2) Administration or titration of an opioid. We also asked them to consider their approach in the following situations: (1) Opioid-naïve. (2) Low-to-moderate baseline opioid dose. (3) High baseline opioid dose. We assessed the use of specific benzodiazepines separately.ResultsOverall, 192 physicians responded to the questionnaire (71.6%). For patients without anxiety, the proportion of participants reporting that they frequently or very frequently ‘administer a benzodiazepine’ increased with baseline opioid dose (opioid-naïve: 5.2%, low-to-moderate: 11.5%, high: 26.0%). The proportion of participants reporting that they frequently or very frequently ‘administer or titrate an opioid’ decreased with baseline opioid dose (opioid-naïve: 83.3%, low-to-moderate: 73.4%, high: 41.1%). The pattern was similar for patients with anxiety, although more respondents said they prescribe benzodiazepine for these patients (naïve: 22.4%, low-to-moderate: 34.4%, high: 45.8%) and fewer prescribed an opioid. Alprazolam and lorazepam are frequently used.ConclusionPatients with anxiety or receiving a high baseline opioid dose could be potential candidates for future studies investigating the effectiveness of benzodiazepines against cancer dyspnoea.
Discriminating hypothalamic oligomenorrhea/amenorrhea from hyperandrogenic oligomenorrhea/amenorrhea in exercising women
Authors: Koltun Kristen J. , Williams Nancy I. , Scheid Jennifer L. , De Souza Mary Jane 
Published: December 2019

The mechanism underlying oligo/amenorrhea in exercising women is often presumed as hypothalamic inhibition secondary to energy deficiency; however, hyperandrogenism may provide an alternative mechanism in some exercising women. Our purpose was to compare reproductive, metabolic, and androgen profiles of exercising women with eumenorrheic, ovulatory menstrual cycles (n = 91), oligo/amenorrhea without evidence of hyperandrogenism (Oligo/Amen; n = 83), and oligo/amenorrhea with evidence of hyperandrogenism (Oligo/Amen-HA; n = 17), and determine the prevalence of oligo/amenorrhea with evidence of hyperandrogenism in exercising women. Self-reported menstrual history and quantification of daily estrogen and progesterone urinary metabolites determined reproductive status. Resting energy expenditure, body composition, and metabolic hormone concentrations determined metabolic status. Serum androgens and calculated free androgen index (FAI) determined androgen status. Groups were similar in age (22.4 ± 0.3 years), height (165.1 ± 0.5 cm), resting energy expenditure (1198.4 ± 12.0 kcal/day), and total triiodothyronine (85.0 ± 1.5 ng/dL) concentration. Oligo/Amen-HA had greater weight (60.0 ± 1.6, 56.1 ± 0.7 kg), body mass index (22.3 ± 0.4, 20.6 ± 0.2 kg/m2), percentage body fat (27.3% ± 1.4%, 24.4% ± 0.6%), fat mass (16.2 ± 1.0, 13.8 ± 0.4 kg), insulin (5.8 ± 0.7, 4.2 ± 0.3 μIU/mL), leptin (12.2 ± 2.3, 6.6 ± 0.7 ng/mL), FAI (6.1 ± 0.3, 1.7 ± 0.1), and luteinizing hormone/follicle-stimulating hormone (1.9 ± 0.3, 1.3 ± 0.2) compared with Oligo/Amen, respectively. In our sample, 17% of those with oligo/amenorrhea had concurrent hyperandrogenism. This study supports that oligo/amenorrhea in some exercising women is related to hyperandrogenism. Novelty Caution must be utilized when discriminating hypothalamic oligo/amenorrhea from hyperandrogenic oligo/amenorrhea. In our sample, 17% of those with presumed hypothalamic oligo/amenorrhea had concurrent hyperandrogenism. Exercise and/or mild energy deficiency may be protective against developing severe hyperandrogenic symptoms.
Quantifying echo chamber effects in information spreading over political communication networks
Authors: Cota Wesley , Ferreira Silvio C. , Pastor-Satorras Romualdo , Starnini Michele 
Published: December 2019

AbstractEcho chambers in online social networks, in which users prefer to interact only with ideologically-aligned peers, are believed to facilitate misinformation spreading and contribute to radicalize political discourse. In this paper, we gauge the effects of echo chambers in information spreading phenomena over political communication networks. Mining 12 million Twitter messages, we reconstruct a network in which users interchange opinions related to the impeachment of the former Brazilian President Dilma Rousseff. We define a continuous political leaning parameter, independent of the network’s structure, that allows to quantify the presence of echo chambers in the strongly connected component of the network. These are reflected in two well-separated communities of similar sizes with opposite views of the impeachment process. By means of simple spreading models, we show that the capability of users in propagating the content they produce, measured by the associated spreading capacity, strongly depends on their attitude. Users expressing pro-impeachment leanings are capable to transmit information, on average, to a larger audience than users expressing anti-impeachment leanings. Furthermore, the users’ spreading capacity is correlated to the diversity, in terms of political position, of the audience reached. Our method can be exploited to identify the presence of echo chambers and their effects across different contexts and shed light upon the mechanisms allowing to break echo chambers.