Search

With the rapid growth of electric vehicles and hybrid electric vehicles, rigorous design targets in terms of cost, efficiency, and power density have been set for automotive power electronics. Novel power module and inverter technologies based on wide-bandgap semiconductors have been developed to meet these design targets. Compared with conventional cooling techniques, which are normally applied only on one side of the power module, a double-sided cooling approach enables higher power density and lower thermal resistance. In this work, we develop a three-phase power module that is double-side cooled using dielectric fluid jet impingement. In each phase, four silicon carbide power semiconductors are bonded to copper busbars without electrical insulation layers. A finite element analysis (FEA) model is created for thermal and thermomechanical analysis. Based on the modeling results, we develop a design space to correlate input and output parameters to generate response surfaces. We then use a multi-objective genetic algorithm-based optimization method to minimize the maximum junction temperature and thermal stresses within the power module. The multiphysics co-optimization approach enables an efficient design process of power modules with greatly reduced computational cost, as compared to conventional processes that rely on exhaustive numerical simulations and iterations.

This project describes the modeling process to design the packaging and heat exchanger for a half-bridge wide-bandgap (WBG) power semiconductor module. The module uses two silicon carbide, metal-oxide-semiconductor field-effect transistor (MOSFET) devices per switch position that are soldered to an aluminum nitride, direct-bond copper (DBC) substrate. A baseplate cooling configuration (e.g., no thermal grease) is used along with a water-ethylene glycol, jet-impingement-style heat exchanger. The heat exchanger was designed to be fabricated using prototyping equipment from the National Renewable Energy Laboratory, complies with automotive standards (for minimal channel sizes, flow rates, and coolant), and considers reliability aspects (i.e., erosion/corrosion). Device-scale computational fluid dynamics (CFD) is used first to design the slot jet impingement cooling configuration and compute the effective heat transfer coefficient (HTC) of the concept. The computed HTCs are then used as boundary conditions for a finite element study to optimize the package geometry (e.g., device layout and baseplate thickness) to minimize thermal resistance and minimize temperature variation between the module’s four devices. Finally, a fluid manifold is designed to generate the slot jets and cool the devices. Module-scale CFD predicts a relatively low junction-to-fluid thermal resistance of 16.7 mm2·K/W, a 1.4°C temperature variation between devices, and a total pressure drop of 5,860 Pa (0.85 psi) for the design. The thermal resistance of the module design is about 67% lower than the 2015 BMW i3 power electronics/modules thermal resistance.

BACKGROUND As the availability of Mohs micrographic surgery (MMS) continues to expand in Australia and incidence of keratinocyte cancer increases in adolescents and young adults, there has been rising interest in the use of MMS in this population. OBJECTIVE This study aimed to evaluate the characteristics of MMS cases in patients younger than 40 years. METHODS A review was performed of all MMS cases in patients younger than 40 years at the time of their surgery from 2012 to 2017 at the Skin and Cancer Foundation Australia, with comparison to a control group, aged older than 40 years. Patient, tumor and management characteristics were analyzed. RESULTS Four hundred ninety-three cases were eligible. Study and control groups differed significantly regarding gender (p < .001), tumor pathology (p < .001), anatomic site of tumor (p < .001), Mohs surgery stages (p = .039), defect size (p < .001), and repair method (p < .001). LIMITATIONS Retrospective study at a single institution. CONCLUSION Mohs micrographic surgery cases in patients younger than 40 years exhibit unique patient and tumor characteristics influencing choice of repair method.

One of the key challenges for the electric vehicle industry is to develop high-power-density electric motors. Achieving higher power density requires efficient heat removal from inside the motor. In order to improve thermal management, a multiphysics modeling framework that is able to accurately predict the behavior of the motor, while being computationally efficient, is essential. This paper first presents a detailed validation of a lumped parameter thermal network (LPTN) model of an Internal Permanent Magnet synchronous motor within the commercially available motor-cad modeling environment. The validation is based on temperature comparison with experimental data and with more detailed finite element analysis (FEA). All critical input parameters of the LPTN are considered in detail for each layer of the stator, especially the contact resistances between the impregnation, liner, laminations, and housing. Finally, a sensitivity analysis for each of the critical input parameters is provided. A maximum difference of 4%—for the highest temperature in the slot-winding and the end-winding—was found between the LPTN and the experimental data. Comparing the results from the LPTN and the FEA model, the maximum difference was 2% for the highest temperature in the slot-winding and end-winding. As for the LPTN sensitivity analysis, the thermal parameter with the highest sensitivity was found to be the liner-to-lamination contact resistance.

Background The availability of Mohs micrographic surgery (MMS) in Australia has increased dramatically since its inception in the 1980s. Objective This study aimed to describe the evolution of MMS practices at the Skin and Cancer Foundation Australia (SCFA) over the past 20 years (1997-2017). Methods Retrospective analysis of Mohs surgery cases at SCFA in 2017, 2007, and 1997, comparing data on sex, age, tumor type and site, initial tumor and final defect size, number of surgical stages and sections, and closure management. The present study is limited by being a retrospective analysis from a single institution. Results There was a 415% increase in the number of Mohs surgery cases from 1997 to 2017, and a significant increase in Mohs surgery-treated squamous cell carcinoma. The preoperative tumor and final defect size have decreased. More side-to-side closures and fewer grafts are being performed over time. Limitations Retrospective analysis from a single institution. Conclusion Over the last 20 years, MMS has remained appropriate in its application and is being increasingly used for treatment of squamous cell carcinoma suggesting improved access.

Experiments were conducted to measure the pool boiling performance of saturated R-245fa at low saturation temperatures (−30 °C, −40 °C, and −50 °C). Horizontally oriented cylindrical heat sources were used as the test samples and were intended to simulate a small section of a hydrogen-filled tube. Measurements evaluated the effects of saturation temperature and two microporous coatings on heat transfer coefficients (HTC), critical heat flux (CHF), and boiling incipient superheat. Results show that boiling performance decreases as the saturation temperature reduces—a result of less active nucleation sites and higher vapor coverage of the heated surface at lower temperatures. Microporous coatings increased HTCs and CHF values, but did not have a significant effect on reducing the boiling incipient superheat. The experimental results were used to develop correlations for nucleate pool boiling on plain and microporous surfaces that can be used to predict HTCs and CHF values at low saturation temperature conditions (down to −50 °C).

Effective thermal management of traction-drive power electronics is critical to the advancement of electric-drive vehicles (EDVs) and is necessary for increasing power density and improving reliability. Replacing traditional silicon devices with more efficient, higher temperature, higher voltage, and higher frequency wide-bandgap (WBG) devices will enable increased power density but will result in higher device heat fluxes. Compact packaging of high-temperature WBG devices near low-temperature-rated components creates thermal management challenges that need to be addressed for future power-dense systems. This paper summarizes the thermal performance of on-road automotive power electronics thermal management systems and provides thermal performance metrics for select vehicles. Thermal analyses reveal that the package resistance dominates the total thermal resistance (for existing automotive systems). Advanced packaging concepts were modeled and the results were compared with existing packaging designs to quantify their thermal performance enhancements. Double-side (DS)-cooled configurations that do not use thermal interface materials (TIMs) are package concepts predicted to provide a low junction-to-fluid thermal resistance (compared to current packages). Dielectric-fluid-cooled concepts enable a redesign of the package to reduce the package resistance, can be implemented in single- and two-phase cooling approaches, and allow for cooling of passive components (e.g., capacitors) and bus bars.

The future of electrification of vehicles and other systems will require the creation of high-power density power electronics with low junction-to-fluid thermal resistance cooling solutions. One way to create this solution is to move high-heat-flux liquid cooling (single- or two-phase) as close to the power electronics components as possible. One novel approach involves submersion in dielectric fluids as the cooling solution. We first provide the range of fluid properties and develop a figure of merit (FOM) to aid in dielectric fluid selection. Next, we perform computational fluid dynamics/heat transfer (CFD/HT) modeling using single-phase cooling (submerged jet impingement on an enhanced surface) to validate the dielectric fluid FOM. Results of the study show that the developed FOM is a good representation of the performance of the fluids when compared to the results of the CFD/HT analysis. Both FOM and the CFD/HT analysis show that based on pure thermohydraulic considerations, several commercially available fluids present higher performance, on the order of 5% of water. Finally, the FOM can be used to quickly assess the thermohydraulic performance of a dielectric fluid, as well as the secondary application-specific properties such as boiling point, saturation pressure, flash point, and global warming potential, thereby allowing for fluid candidates to be readily compared.

As quantum computers increase in size, the total energy used by a quantum data center, including the cooling, will become a greater concern. The cooling requirements of quantum computers, which must operate at temperatures near absolute zero, are determined by computing system parameters, including the number and type of physical qubits, the operating temperature, the packaging efficiency of the system, and the split between circuits operating at cryogenic temperatures and those operating at room temperature. When combined with thermal system parameters such as cooling efficiency and cryostat heat transfer, the total energy use can be determined. Using a first-principles energy model, this paper reports the impact of computer architecture and thermal parameters on the overall energy requirements. The results also show that power use and quantum volume can be analytically correlated. Approaches are identified for minimizing energy use in integrated quantum systems relative to computational power. The results show that the energy required for cooling is significantly larger than that required for computation, a reversal from energy usage patterns seen in conventional computing. Designing a sustainable quantum computer will require both efficient cooling and system design that minimizes cooling requirements.

One of the key challenges for the electric vehicle industry is to develop high-power-density electric motors. Achieving higher power density requires efficient heat removal from inside the motor. In order to improve thermal management, a multi-physics modeling framework that is able to accurately predict the behavior of the motor, while being computationally efficient, is essential. This paper first presents a detailed validation of a Lumped Parameter Thermal Network (LPTN) model of an Internal Permanent Magnet (IPM) synchronous motor within the commercially available Motor-CAD® modeling environment. The IPM motor’s stator is studied at steady state, and winding losses are generated by a constant DC current. The validation is based on temperature comparison with experimental data and with more detailed Finite Element Analysis (FEA). All critical input parameters of the LPTN are considered in detail for each layer of the stator, especially the contact resistances between the impregnation, liner, laminations and housing. Finally, a sensitivity analysis for each of the critical input parameters is provided. A maximum difference of 4% — for the highest temperature in the slot windings and the end windings — was found between the LPTN and the experimental data. Comparing the results from the LPTN and the FEA model, the maximum difference was 2% for the highest temperature in the slot windings and end windings. As for the LTPN sensitivity analysis, the thermal parameter with the highest sensitivity was found to be the liner-to-lamination contact resistance. The latter is often ignored in the literature, whereas its impact on temperature rise was found to be more significant than any other contact resistance within the stator.

High-frequency ultrasonography is a bedside tool increasingly used for the assessment of skin lesions, but there have been few reports about its importance in children with skin signs of hematologic disease. We present three cases to highlight the usefulness of high-frequency ultrasonography in assisting with the diagnosis of these skin lesions.

Fundamental research and development of ultra-wide bandgap (UWBG) semiconductor devices are under way to realize next-generation power conversion and wireless communication systems. Devices based on aluminum gallium nitride (AlxGa1−xN, x is the Al composition), β-phase gallium oxide (β-Ga2O3), and diamond give promise to the development of power switching devices and radio frequency power amplifiers with higher performance and efficiency than commercial wide bandgap semiconductor devices based on gallium nitride (GaN) and silicon carbide (SiC). However, one of the most critical challenges for the successful deployment of UWBG device technologies is to overcome adverse thermal effects that impact the device performance and reliability. Overheating of UWBG devices originates from the projected high power density operation and poor intrinsic thermal properties of AlxGa1−xN and β-Ga2O3. This Perspective delineates the need and process for the “electro-thermal co-design” of laterally configured UWBG electronic devices and provides a comprehensive review of current state-of-the-art thermal characterization methods, device thermal modeling practices, and both device- and package-level thermal management solutions.

As energy systems move towards wide-spread electrification, penetration of power semiconductor devices and power electronics continue to grow at a rapid pace. This paper attempts at reviewing the state-of-the-art in power semiconductor modeling and the existing state of modeling in general on the design of devices and systems. The modeling needs for semiconductor devices vary depending on the end-goal, and the level of abstraction needed towards model formulation also changes with the size and complexity of the system to be designed. Finally, key aspects of thermal design and modeling for power electronics are also discussed.

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%.

Gallium oxide is an emerging wide band-gap material that has the potential to penetrate the power electronics market in the near future. In this paper, a finite-element gallium oxide semiconductor model is presented that can predict the electrical and thermal characteristics of the device. The finite element model of the two-dimensional device architecture is developed inside the Sentaurus environment. A vertical FinFET device architecture is employed to assess the device’s behavior and its static and dynamic characteristics. Enhancement-mode device operation is realized with this type of device architecture without the need for any selective area doping. The dynamic thermal behavior of the device is characterized through its short-circuit behavior. Based on the device static and dynamic behavior, it is envisioned that reliable vertical transistors can be fabricated for the power electronics applications.

Due to the ever-increasing power density of the advanced electric machines (motors/generators) in electric vehicles and hybrid electric vehicles, thermal management of electric machines has become increasingly critical to permit high power output, enhanced reliability, and miniaturization. The cooling of electric machines is mostly accomplished by depositing fluids or oils directly onto the machine's coil windings to remove the excessive heat. As an efficient approach of direct cooling, jet impingement has been attracting significant attention from researchers and industry due to the high heat transfer rates and large cooling capacity. In this work, we present a study of fan jet impingement of automatic transmission fluid (ATF) on a target surface with a constant heat flux. Experiments were carried out with ATF temperatures varying from 50 °C to 90 °C and flow rates varying from 1 × 10−5 to 2.5 × 10−5 m3/s to encompass potential operating conditions within the automotive transaxle environment. A numerical model of the test section was developed and validated with experimental results and used to investigate the influence of flow parameters and nozzle geometry on the heat transfer characteristics of the impinging fan jet. Major controlling parameters studied in this work include flow rate, fluid temperature, nozzle-to-target distance, and incidence angles. Average heat transfer coefficients are calculated as the major metric to compare the impact from various controlling parameters. Correlation of flow and heat transfer characteristics of fan jet impingement is explored within the scope of this work. In addition, heat transfer coefficient results of fan jet impingement are compared with the circular jet, which is commonly applied to cool electric machines. At all flow velocities, circular jets yield heat transfer coefficients 20%–25% higher than those obtained from the fan jet impingement.

High-frequency ultrasonography (HFUS) can help improve dermatofibrosarcoma protuberans (DFSP) recognition. We present three cases of DFSP in which a "jellyfish-like" sonographic pattern was a useful adjunct in formulating the diagnosis. In addition, we review all DFSP ultrasound images available in the literature.

There is significant interest in the power electronics industry in transitioning from silicon to wide-bandgap devices. Gallium oxide devices have the potential to offer comparable or even superior performance than other wide-bandgap devices, but at a much lower cost. Recent breakthroughs include demonstration of a laboratory-scale gallium oxide transistors and diodes; however, a functional power electronics package for these devices is yet to be developed. In this paper, the research methodology in designing an electronics package for gallium oxide devices is outlined. Finite element-based thermal and thermomechanical modeling simulations were conducted to realize a package design that meets the combined target of minimal thermal resistance and improved reliability. Different package designs that include various material combinations and cooling configurations were explored, and their thermal and thermomechanical performance are reported. Furthermore, the short-circuit withstanding capabilities of gallium oxide devices were studied and compared with silicon carbide.

Background Streptococcus pneumoniae causes about 826,000 deaths of children in the world each year and many health facility visits. To reduce the burden of pneumococcal disease, many nations have added pneumococcal conjugate vaccines to their national immunization schedules. Nicaragua was the first country eligible for GAVI Alliance funding to introduce the 13-valent pneumococcal conjugate vaccine (PCV13) in 2010, provided to infants at 2, 4, and 6 months of age. The goal of this study was to evaluate the population impact of the first five years of the program. Methods Numbers of visits for pneumonia, pneumonia-related deaths, and bacterial meningitis in both children and adults, and infant deaths between 2008 and 2015 were collected from all 107 public health facilities in Leon Department. Vital statistics data provided additional counts of pneumonia-related deaths that occurred outside health facilities. Adjusted incidence rates and incidence rate ratios (IRRa) in the vaccine (2011–2015) and pre-vaccine periods (2008–2010) were estimated retrospectively using official population estimates as exposure time. Results The IRRa for pneumonia hospitalizations was 0.70 (95% confidence interval [CI]: 0.66, 0.75) for infants, and 0.92 (95% CI: 0.85, 0.99) for one year-olds. The IRRa for post-neonatal infant mortality was 0.56 (95% CI: 0.41, 0.77). In the population as a whole, ambulatory visits and hospitalizations for pneumonia, as well as pneumonia-related mortality and rates of bacterial meningitis were lower in the vaccine period. Conclusions During the first five years of program implementation, reductions were observed in health facility visits for pneumonia in immunized age groups and infant mortality, which would be hard to achieve with any other single public health intervention. Future study is warranted to understand whether the lack of a booster dose (e.g., at 12 months) may be responsible for the small reductions in pneumonia hospitalizations observed in one year-olds as compared to infants.

A high-fidelity computational fluid dynamics (CFD)-based model for bubble nucleation of the refrigerant HFE7100 on micrometer-featured surfaces is presented in this work. The single-fluid, incompressible Navier-Stokes equations, along with energy transport and natural convection effects, are solved on a featured surface resolved grid. An a priori cavity detection method is employed to convert raw profilometer data of a surface into well-defined cavities. The cavity information and surface morphology are represented in the CFD model by geometric mesh deformations. Surface morphology is observed to initiate buoyancy-driven convection in the liquid phase, which in turn results in faster nucleation of cavities. Simulations pertaining to a generic rough surface show a trend where smaller size cavities nucleate with higher wall superheat. This local-scale model will serve as a self-consistent connection to larger device scale continuum models where local feature representation is not possible.

We report the first case series of allogeneic haematopoietic stem-cell transplant patients with graft versus host disease who developed cutaneous non-tuberculous mycobacteria infection. A multidisciplinary approach, reduction of immunosuppressive medications, combination of antibiotics, close skin surveillance and excision of suitable lesions are recommended in this specific subgroup.

Leptospirosis is an epidemic-prone zoonotic disease that occurs worldwide, with more than 500,000 human cases reported annually. It is influenced by environmental and socioeconomic factors that affect the occurrence of outbreaks and the incidence of the disease. Critical areas and potential drivers for leptospirosis outbreaks have been identified in Nicaragua, where several conditions converge and create an appropriate scenario for the development of leptospirosis. The objectives of this study were to explore possible socioeconomic variables related to leptospirosis critical areas and to construct and validate a vulnerability index based on municipal socioeconomic indicators. Municipalities with lower socioeconomic status (greater unsatisfied basic needs for quality of the household and for sanitary services, and higher extreme poverty and illiteracy rates) were identified with the highest leptospirosis rates. The municipalities with highest local vulnerability index should be the priority for intervention. A distinction between risk given by environmental factors and vulnerability to risk given by socioeconomic conditions was shown as important, which also applies to the “causes of outbreaks” and “causes of cases”.

Increasing the number of electric-drive vehicles (EDVs) on America?s roads has been identified by the U.S. Department of Energy (DOE), the federal cross-agency electric vehicle (EV)-Everywhere Challenge, and the automotive industry as a strategy with near-term potential for dramatically decreasing the nation?s dependence on oil. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on the optimization of thermal management.

Thermal management strategies for automotive power electronic systems have evolved over time to reduce system cost and to improve reliability and thermal performance. In this study, we characterized the power electronic thermal management systems of two electric-drive vehicles—the 2012 Nissan LEAF and 2014 Honda Accord Hybrid. Tests were conducted to measure the insulated-gate bipolar transistor-to-coolant thermal resistances for both steady-state and transient conditions at various coolant flow rates. Water-ethylene glycol at a temperature of 65°C was used as the coolant for these experiments. Computational fluid dynamics and finite element analysis models of the vehicle's power electronics thermal management system were then created and validated using experimentally obtained results. Results indicate that the Accord module provides lower steady-state thermal resistance as compared with the LEAF module. However, the LEAF design may provide improved performance in transient conditions and may have cost benefits.

Background Streptococcus pneumoniae causes an estimated 826,000 deaths of children in the world each year and many health facility visits. To reduce the burden of pneumococcal disease, many nations have added pneumococcal conjugate vaccines to their national immunization schedules. Nicaragua was the first country eligible for funding from the GAVI Alliance to introduce the 13-valent pneumococcal conjugate vaccine (PCV13), provided to infants at 2, 4, and 6 months of age. The goal of this study was to evaluate the population impact of the first five years of the program. Methods Numbers of visits for pneumonia, pneumonia-related deaths, bacterial meningitis, and infant deaths between 2008 and 2015 were collected from all 107 public health facilities in León Department. Vital statistics data provided additional counts of pneumonia-related deaths that occurred outside health facilities. Adjusted incidence rates and incidence rate ratios (IRRa) in the vaccine (2011–2015) and pre-vaccine periods (2008–2010) were estimated using official population estimates as exposure time. Results The IRRa for pneumonia hospitalizations was 0.70 (95% confidence interval [CI]: 0.66, 0.75) for infants, and 0.92 (95% CI: 0.85, 0.99) for one year olds. The IRRa for post-neonatal infant mortality was 0.56 (95% CI: 0.41, 0.77). In the population as a whole, ambulatory visits and hospitalizations for pneumonia, as well as pneumonia-related mortality and rates of bacterial meningitis were lower in the vaccine period. Conclusion Five years following program introduction, reductions were observed in health facility visits for pneumonia in immunized age groups and infant mortality, which would be hard to achieve with any other single public health intervention. Future study is warranted to understand whether the lack of a booster dose (e.g.,, at 12 months) may be responsible for the small reductions in pneumonia hospitalizations observed in one year-olds as compared with infants. Disclosures S. Becker-Dreps, Pfizer: Consultant and Grant Investigator, Consulting fee and Research grant; D. J. Weber, Pfizer: Consultant and Speaker’s Bureau, Consulting fee and Speaker honorarium

Background—While the pentavalent rotavirus vaccine was highly efficacious against rotavirus diarrhea in clinical trials, the vaccine’s effectiveness under field conditions in the developing world is unclear. In October, 2006, Nicaragua became the first developing nation to implement universal infant immunization with the pentavalent rotavirus vaccine. To assess the impact of the immunization program, we examined the incidence of diarrhea episodes between 2003 and 2009 among children in the state of Leon, Nicaragua. Methods—We extracted data on diarrhea episodes from health ministry records. We used scaled Poisson regression models to estimate diarrhea incidence rate ratios (IRR) for the period following the program’s implementation to the period before implementation. Results—Following implementation of the immunization program, diarrhea episodes among infants were reduced (IRR 0.85, 95% confidence interval [CI] 0.71–1.02) during the rotavirus season, but appear to have increased during other months. Conclusions—While the immunization program appears effective in reducing diarrhea episodes during the rotavirus season, a large burden of diarrhea persists during the remainder of the year.

Parametric tests were experimentally conducted to observe the role of average nanoparticle size, pressure, heater orientation, and heater size during pool boiling of water using Al 2 O 3 nanoparticle coated flat heaters. Results indicate that pool boiling performance is dependent on the parameters tested, except the nanoparticle size, for both uncoated and nanocoated surfaces. The nanoparticle coated heater consistently produced dramatic Critical Heat Flux enhancement relative to the uncoated surface at all tested conditions. It was postulated that the better wettability in the nanocoating, especially its ability to continuously rewet the base of the growing bubbles, was the main cause of enhancement.

The pool boiling behavior of nanoparticle coated surfaces is experimentally studied in pure water. Nanoparticle coatings were created during nanofluid pool boiling experiments (Al 2 O 3 –water/ethanol). The nanocoatings developed can significantly enhance the critical heat flux. Ethanol nanofluids created more uniform nanocoatings which outperformed nanocoatings created in water nanofluids. The wetting and wicking characteristics of the nanocoatings are investigated through contact angle measurements and by conducting a dip test. A linear relationship between the CHF enhancement and the quasi-static contact angles of the nanocoatings was revealed. Additionally, a mechanism potentially responsible for nanocoating CHF enhancement is identified.

The pool boiling behavior of low concentration nanofluids (⩽1 g/l) was experimentally studied over a flat heater at 1 atm. Boiling of nanofluids produces a thin nanoparticle film, on the heater surface, which in turn is believed to increase the critical heat flux. The present study also indicates that the nanoparticle deposition results in transient characteristics in the nucleate boiling heat transfer. Finally, this study investigates possible causes responsible for the deposition of nanoparticle on the heater surface. Experimental evidence shows that microlayer evaporation, during nanofluid boiling, is responsible for the nanoparticle coating formed on the heater surfaces.

To characterize the production patterns of the dengue virus vector Aedes aegypti (L.) (Diptera: Culcidae), pupal surveys were conducted in selected neighborhoods of two major cities in Nicaragua. In Leon, 833 houses were visited in July and September 2003, corresponding to the beginning and middle of the dengue season; in Managua, 1,365 homes were visited in July 2003. In total, 7,607 containers were characterized, of which 11% were positive for Ae. aegypti larvae and 4% for pupae. In addition to barrels, potted plants and superficial water on tarps and in puddles were identified as highly productive sites. Univariate and multivariate analysis revealed frequency of container use, use of a lid, and rainwater filling as key variables affecting pupal positivity. Importantly, this survey demonstrated the risk associated with the presence of lids, the limited temporal efficacy of temephos, and the lack of association of water availability with risky water storage practices. Finally, we introduce the concept of an efficiency value and an accompanying graphical display system that can facilitate development of targeted pupal control strategies. These data underscore the importance of entomological surveillance of pupal productivity to gather information from which to derive streamlined, efficient, and effective vector control measures to reduce the density of Aedes mosquito larvae and pupae and thus the risk for dengue.

Thermal management for electric machines (motors/generators) is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. Cooling of the electric machine(s) in some electric vehicle traction drive applications is accomplished by impinging automatic transmission fluid (ATF) jets onto the machine’s copper windings. In this study, we provide the results of experiments characterizing the thermal performance of ATF jets on surfaces representative of windings, using Ford’s Mercon LV ATF. Experiments were carried out at various ATF temperatures and jet velocities to quantify the influence of these parameters on heat transfer coefficients. Fluid temperatures were varied from 50°C to 90°C to encompass potential operating temperatures within an automotive transaxle environment. The jet nozzle velocities were varied from 0.5 to 10 m/s. The experimental ATF heat transfer coefficient results provided in this report are a useful resource for understanding factors that influence the performance of ATF-based cooling systems for electric machines.Copyright © 2015 by ASME

We report the first case series of allogeneic haematopoietic stem-cell transplant patients with graft versus host disease who developed cutaneous non-tuberculous mycobacteria infection. A multidisciplinary approach, reduction of immunosuppressive medications, combination of antibiotics, close skin surveillance and excision of suitable lesions are recommended in this specific subgroup.

A study was conducted to experimentally characterize the pool boiling performance of hydrofluorocarbon (HFC)-245fa. The motivation for this research is to characterize the performance of candidate refrigerants for potential use in automotive power electronics two-phase cooling systems. The HFC-245fa pool boiling experiments were conducted using horizontally oriented 1-cm2 heated surfaces to quantify the effects of pressure and a microporous-enhanced coating on heat transfer coefficients and critical heat flux (CHF) values. Experiments were carried out at pressures ranging from 0.15 MPa to 1.1 MPa (reduced pressure range: 0.04–0.31). To enhance boiling heat transfer, a copper microporous coating was applied to the test surfaces. The coating was found to enhance heat transfer coefficients by as much as 430% and CHF by approximately 50%. Increasing pressure decreased the magnitude of the heat transfer coefficient enhancements but had minimal effect on CHF enhancements. The experimental data were then used to generate correlations for the boiling heat transfer coefficients and CHF values. Finally, the performance of HFC-245fa was compared to the performance of hydrofluoroolefin (HFO)-1234yf and HFC-134a at conditions of equivalent saturation temperatures and reduced pressures.Copyright © 2013 by ASME