22 research outputs found
Numerical investigation of flow over a wall mounted circular cylinder with a finite free end
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Chemical transport modeling for predicting secondary fine particles generated from coal-fired power plant
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Numerical analysis of non-uniform Cu(In, Ga)Se2 growth in a selenization process on large-area substrates for mass production
No full textGrowth of a Cu(In, Ga)Se2 (CIGS) layer during a selenization process is numerically studied to understand mechanisms for formation of stains on large-area substrates batched. CIGS layers need to be uniformly deposited onto the substrates to obtain even conversion efficiency. However, it is difficult to control growth of large-area CIGS layers due to turbulent thermal-fluid flow leaving stains on the substrates. In the present research, the selenization process for an industrial-scale substrates of which sizes are order of square-meters is considered with integrated simulations of detailed key physical processes such turbulent convection, convective-radiative-conductive heat transfer, and chemical reactions. Ascending or descending gas generated by heaters is identified by the time-averaged velocity fields. Descending flow in the passages between substrates produces uneven flow rates across the substrates leading to inhomogeneous supply of heat energy and gas species to the surface chemical reactions. The uneven temperature distribution is the major cause for the stain formation on the substrates. Gross shapes of the stains are found to be well matched with the predicted velocity contour of gas flow above the substrate. The stains are expected to be alleviated by rectifying gas flow such that flow rates become uniform across substrates before entering the passages.11Nsciescopu
A numbering-up metal microreactor for the high-throughput production of a commercial drug by copper catalysis
No full textMicroreactors are emerging as an efficient, sustainable synthetic tool compared to conventional batch reactors. Here, we present a new numbering-up metal microreactor by integrating a flow distributor and a copper catalytic module for high productivity of a commercial synthetic drug. A flow distributor and an embedded baffle disc were manufactured by CNC machining and 3D printing of stainless steel (S/S), respectively, whereas a catalytic reaction module was composed of 25 copper coiled capillaries configured in parallel. Eventually, the numbering-up microreactor system assembled with functional modules showed uniform flow distribution and high mixing efficiency regardless of clogging, and achieved high-throughput synthesis of the drug "rufinamide", an anticonvulsant medicine, via a Cu(i)-catalyzed azide-alkyne cycloaddition reaction under optimized conditions.11Nsciescopu
Credit Constraints And Training After Job Loss
No full textIt is a widely held view that imperfect capital markets mean that individuals from poor backgrounds cannot borrow in order to finance educational investments. This view pervades policy formation, and is reflected in the fact that post-compulsory education processes in all countries involve considerable government intervention and large public subsidies. But are the existence of credit constraints an empirical reality? This paper uses unique data to take a new approach to this question. Specifically, the 1995 Canadian Out of Employment Panel (COEP) allows us to explore the financial resources and skill formation choices of a large number of recent job losers. This approach has several advantages, including: a direct test of the role of finances in determining training; the availability of considerable information concerning individual histories; and the fact that the unemployed are a particularly apposite group with which to explore the questions of credit constraints. We find that credit constraints do appear to limit the human capital investments of a significant minority of job seekers. In particular, controlling for a broad range of background characteristics (including past educational investments and labour market outcomes), the possession of liquid assets at the time of job loss is strongly associated with subsequent self-financed training. This basic finding is corroborated with several different kinds of evidence drawn from the survey. The data also allow us to make a rough estimate of the extent to which participation in training would have been increased, had no part of our sample been credit constrained.
Antimony Sulfobromide Nanowire Bundles Exhibiting Ambipolar Photoelectrochemical Photocurrent Switching
No full textChalcohalides have emerged as novel semiconducting materials for fabricating electronic, optoelectronic, and electrochemical devices. Particularly, antimony (Sb)-based chalcohalides have attracted attention as solar energy conversion and thermoelectrics. Herein, the first report on the colloidal synthesis of antimony sulfobromide (SbSBr) nanowire bundles (NBs) via a hot-injection method is reported. The as-synthesized SbSBr NBs exhibited high size and shape uniformity and excellent phase purity. The growth behavior of the SbSBr NBs is systematically investigated by varying the reaction time, revealing a sequential structure and phase transformation from amorphous spherical nanoparticles to crystalline NBs. The optical bandgap and energy levels of the conduction and valence band edges are characterized in conjunction with first-principles calculations to understand the energy diagram of SbSBr NBs. SbSBr NB-based photoelectrodes are fabricated via a solution-based fabrication process to investigate the photoelectrochemical properties of nanosized SbSBr. The fabricated photoelectrodes exhibited a photoelectrochemical photocurrent switching behavior under anodic and cathodic biases and simulated solar illumination, enabling the fabrication of a two-channel optoelectronic demultiplexer as a proof-of-concept application. The successful synthesis of colloidal SbSBr and systematic investigation of its photoelectrochemical properties open new opportunities for using Sb-based chalcohalide NBs in developing optoelectronic and photoelectrochemical devices.
Integrated simulation of turbulent convection, radiation and conduction during a selenization process for large-scale CIGS thin films
No full textA numerical methodology for simulations of multi-mode heat transfer during a selenization process for CIGS (Copper Indium Gallium Selenide) solar cell films has been developed. Turbulent fluid dynamics and convective heat transfer are simulated using a finite-volume large-eddy simulation (LES) technique while thermal conduction and radiation are predicted using finite-element methods. The computational methodology is validated for three heat transfer modes. Using the technique, a numerical study of heat transfer during the selenization process for deposition of a CIGS layer is performed to analyze the thermo-fluid phenomena occurring during the process. The present method is found to well predict temperature distribution on substrates as a function of both space and time. It is also analyzed that how turbulent fluid motions alter temperature distributions on the substrate during the selenization process. (C) 2018 Elsevier Ltd. All rights reserved.11Nsciescopu
A feasibility study of HFO refrigerants for onboard BOG liquefaction processes
No full textAs the global demand for natural gas continues to increase, the production of liquefied natural gas (LNG) and the demand for LNG carriers are also on the rise. Following the advent of LNG propulsion engines, there has been widespread adoption of systems that use LNG or boil-off gas (BOG) as fuel, and subsequently re-liquefy remaining gas thorough the re-liquefaction system. In this study, we investigated the feasibility of hydrofluro-olefins (HFO) refrigerants, the newly developed refrigerants having low flammability and low global warming potential (GWP), in BOG re-liquefaction systems for liquefied natural gas carriers. Simulations of BOG re-liquefaction process were conducted and optimized to minimize energy consumption. Then, the explosion risk and global warming potential during the lifespan of the re-liquefaction processes are also analyzed. The optimization results indicate that using HFO refrigerants in the re-liquefaction process yields comparable energy consumption to the conventional hydrocarbon refrigerants. Additionally, the use of HFO refrigerants can contribute to reducing explosion risk of liquefaction process. However, despite HFO refrigerants being considered an environmentally friendly refrigerant, it is important to note that global warming impact has not decreased as significantly as expected. This is primarily due to the fact that the GWP of the system is heavily influenced by energy consumption. © 2023 The Authors. Published by Elsevier Ltd.publishedVersio
