A concept design of supercritical CO2 cooled SMR operating at isolated microgrid region

Most of the small modular reactor (SMR) concepts developed in the past have compact size and a longer life reactor core than the conventional nuclear power plants. However, these concepts have not achieved the full modularization including power conversion system. This study suggests an innovative concept of a reactor cooled by supercritical state carbon dioxide (S‐CO₂). A reactor core with uranium carbide fuel controlled by drum type control rods was designed. The core has long life (20 years) without refueling or reshuffling as well as inherent safety features. The reactor can be used as a distributed power source and replace outdated fossil fuel power plants for small cities. Moreover, the authors propose the S‐CO₂ Brayton cycle as a power conversion system to achieve compact and lightweight module. Because of compact core and power conversion system, the entire system can be contained in a single module. The target of the system is to be able to transport a single core and power conversion system module via ground transportation. In order to meet this target, single module's total weight is minimized in the order of 100 tons. The external size of a module is less than 7 m in length and 4 m in diameter. It produces 12MWe electricity from 36MWt reactor core. The S‐CO₂ Brayton cycle was optimized, and the cycle components such as turbomachineries and heat exchangers were designed preliminarily to observe the potential to maximize the performance while minimizing the weight. Moreover, a dry air‐cooling option to reject waste heat for inland installation was selected for the suggested nuclear system. A concept of passive decay heat removal system was developed, and its performance was examined to determine the required heat removal capacity of the system to assure the system's safety under various anticipated accidents. Copyright © 2016 John Wiley & Sons, Ltd.     

Ubiquitous Overexpression of Chromatin Remodeling Factor SRG3 Exacerbates Atopic Dermatitis in NC/Nga Mice by Enhancing Th2 Immune Responses

The SWItch (SWI)3-related gene (SRG3) product, a SWI/Sucrose Non-Fermenting (SNF) chromatin remodeling subunit, plays a critical role in regulating immune responses. We have previously shown that ubiquitous SRG3 overexpression attenuates the progression of Th1/Th17-mediated experimental autoimmune encephalomyelitis. However, it is unclear whether SRG3 overexpression can affect the pathogenesis of inflammatory skin diseases such as atopic dermatitis (AD), a Th2-type immune disorder. Thus, to elucidate the effects of SRG3 overexpression in AD development, we bred NC/Nga (NC) mice with transgenic mice where SRG3 expression is driven by the β-actin promoter (SRG3^β-actin mice). We found that SRG3^β-actin NC mice exhibit increased AD development (e.g., a higher clinical score, immunoglobulin E (IgE) hyperproduction, and an increased number of infiltrated mast cells and basophils in skin lesions) compared with wild-type NC mice. Moreover, the severity of AD pathogenesis in SRG3^β-actin NC mice correlated with expansion of interleukin 4 (IL4)-producing basophils and mast cells, and M2 macrophages. Furthermore, this accelerated AD development is strongly associated with Treg cell suppression. Collectively, our results have identified that modulation of SRG3 function can be applied as one of the options to control AD pathogenesis.     

Porous Polydimethylsiloxane/Au Composites as Solar-Light Absorbers for Light-Driven Thermoelectric Applications

Solar thermoelectric (TE) generators may potentially provide a viable alternative to photovoltaic devices for producing electrical energy from renewable sources. In this approach, the conversion of solar radiation into heat is essential to enhance the performance of TE devices, which necessitates the development of efficient solar light absorbers. Metal nanoparticles (NPs) have gained much attention in this regard because they can convert light into heat via plasmon-mediated photothermal effects. In this study, porous nanocomposites comprising polydimethylsiloxane (PDMS) and Au NPs are prepared. In the PDMS/Au composites, the narrow extinction spectrum of Au NPs is extended over longer wavelengths by plasmonic hybridization to promote the light absorption property of the NPs. In addition, the porous structure induces strong scattering of incident light, which further enhances the absorption efficiency of the Au NPs. Consequently, the plasmon-mediated photothermal effects of Au NPs are noticeably enhanced and increased the temperature of the PDMS/Au composites to as high as 75.7 °C under artificial solar radiation, compared to 42.1 °C without the Au NPs. By applying the PDMS/Au composites to commercial TE devices, the electrical performance of the TE devices is enhanced by approximately threefold.     

Effects of institutional arrangements in local water supply services in Korea

In Korea, local governments are primarily responsible for providing water supply services to citizens. Since 2004, 15 local governments have contracted this service to the Korean Water Resources Corporation (K‐Water). This paper examines the effects of the two different institutional arrangements – direct public delivery versus contracting out to K‐Water – on cost savings and productivity. To do so, it employs a hybrid cost function approach and uses the panel data covering the nine years from 2000 to 2008 in local governments. Empirical findings show mixed evidence on the effects of the two institutional arrangements on cost savings and productivity gains. Water supply costs are significantly lower under contracting out than under direct public delivery. However, there are no significant differences in productivity gains between the two institutional arrangements. Local water supply systems need to further reduce the average water supply costs through increasing their size and magnitude.     

Polycrystalline tungsten oxide nanofibers for gas-sensing applications

Tungsten oxide nanofibers were successfully prepared via thermal treatment of electrospun composite nanofibers consisting of polyvinylpyrrolidone (PVP) and tungstic acid at 500 °C in air. The morphology, crystal structure, and chemical composition of the nanofibers were characterized by SEM, EDX, TEM, XRD, and FT-IR before and after the thermal treatment. It was confirmed that the calcination process was responsible for the removal of PVP component and the growth of crystalline WO₃. The resulting tungsten oxide nanofibers, which had a rough surface morphology and an average diameter of around 40 nm, were found to be formed by the axial agglomeration of prolate spheroid-like WO₃ nanoparticles with monoclinic crystalline phases. Gas-sensing measurements of the polycrystalline WO₃ nanofiber mats were performed upon exposure to ammonia gas. They demonstrated n-type sensing response and sensitive NH₃ detection up to 10 ppm with a well-defined relationship between the concentration and detection response at an operating temperature of 300 °C. These results were interpreted by applying the space-charge layer model used in the semiconducting metal-oxide sensor systems.     

Dynamic behavior of capillary-driven encapsulation flow characteristics for different injection types in flip chip packaging

This study investigated the influence of different injection types, such as I-type, L-type, and U-type, on the dynamic behavior of capillary-driven encapsulation flows for a commercially available flip chip. The dynamic filling behavior of underfill encapsulation was visualized experimentally, and numerical simulations were conducted for three-dimensional flows in a flip chip package by using commercial software (ANSYS FLUENT Ver. 13.0). Numerical results were compared with experimental data for the filling time and the rate of change in underfill volume fraction with different injection types. At the early stage of underfill injection, the estimated flow characteristics exhibited high capillary acceleration that rapidly decreased with time, which indicates that capillary force was dominant in underfill encapsulation. The capillary pressure drop effect was dominant at the early stage. Thus, the injection method for underfill encapsulation inside the flip chip should be carefully controlled for faster and more stable encapsulation to avoid void formation in the chips.     

Cross-sectional analysis of W-cored Ni nanoparticle via focused ion beam milling with impregnation

Tungsten and nickel bimetallic nanoparticle is synthesized by radio frequency thermal plasma process which belongs to the vapor phase condensation technology. The morphology and chemical composition of the synthesized particle were investigated using the conventional nanoparticle transmission electron microscopy (TEM) sample. A few part of them looked like core/shell structured particle, but ambiguities were caused by either TEM sample preparation or TEM analysis. In order to clarify whether a core/shell structure is developed for the particle, various methodologies were tried to prepare a cross-sectional TEM sample. Focused ion beam (FIB) milling was conducted for cold-compacted particles, dispersed particles on silicon wafer, and impregnated particles with epoxy which is compatible with electron beam. A sound cross-sectional sample was just obtained from cyanoacrylate impregnation and FIB milling procedure. A tungsten-cored nickel shell structure was precisely confirmed with aid of cross-sectional sample preparation method.     

OLED with a controlled molecular weight of the PVK (poly(9-vinylcarbazole)) formed by a reactive ink-jet process

An ink-jet printing method was proposed to solve several conventional problems of ink jet process. PVK (poly(9-vinylcarbazole)) thin film was synthesized and simultaneousely patterned by the reactive ink-jet process (RIP). Gel permeation chromatography shows a linear relationship between the molecular weight of the PVK and the reaction time. The as-synthesized PVK with a controlled molecular weight was applied to an OLED device. Most of the OLED with the RIP–PVK film performed better compared to the reference OLEDs. The luminance graphs indicated the existence of a proper molecular weight leading to the optimum structural conformity which was matched well to the modified OLED structure, showing a linear relationship with the reaction time in the turn-on threshold. This result implies that one can control the proper molecular weight of a polymer and thus the electrical properties of an OLED device via the RIP method.