• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.603-609
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• 2022

Passivation quality is mainly governed by epitaxial growth of crystalline silicon wafer surface. Void-rich intrinsic a-Si:H interfacial layer could offer higher resistivity of the c-Si surface and hence a better device efficiency as well. To reduce the resistivity of the contact area, a modification of void-rich intrinsic layer of a-Si:H towards more ordered state with a higher density is adopted by adapting its thickness and reducing its series resistance significantly, but it slightly decreases passivation quality. Higher resistance is not dominated by asymmetric effects like different band offsets for electrons or holes. In this study, multilayer of intrinsic a-Si:H layers were used. The first one with a void-rich was a-Si:H(I₁) and the next one a-SiO_x:H(I₂) were used, where a-SiO_x:H(I₂) had relatively larger band gap of ~2.07 eV than that of a-Si:H (I₁). Using a-SiO_x:H as I₂ layer was expected to increase transparency, which could lead to an easy carrier transport. Also, higher implied voltage than the conventional structure was expected. This means that the a-SiO_x:H could be a promising material for a high-quality passivation of c-Si. In addition, the i-a-SiO_x:H microstructure can help the carrier transportation through tunneling and thermal emission.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.803-811
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• 2024

Nuclear accidents such as Fukushima Daiichi have highlighted the potential of passive safety systems to replace or complement active safety systems as part of the overall prevention and/or mitigation strategies. In addition, passive systems are key features of Small Modular Reactors (SMRs), for which they are becoming almost unavoidable and are part of the basic design of many reactors available in today's nuclear market. Nevertheless, their potential to significantly increase the safety of nuclear power plants still needs to be strengthened, in particular the ability of computer codes to determine their performance and reliability in industrial applications and support the safety demonstration. The PASTELS project (September 2020-February 2024), funded by the European Commission "Euratom H2020" programme, is devoted to the study of passive systems relying on natural circulation. The project focuses on two types, namely the SAfety COndenser (SACO) for the evacuation of the core residual power and the Containment Wall Condenser (CWC) for the reduction of heat and pressure in the containment vessel in case of accident. A specific design for each of these systems is being investigated in the project. Firstly, a straight vertical pool type of SACO has been implemented on the Framatome's PKL loop at Erlangen. It represents a tube bundle type heat exchanger that transfers heat from the secondary circuit to the water pool in which it is immersed by condensing the vapour generated in the steam generator. Secondly, the project relies on the CWC installed on the PASI test loop at LUT University in Finland. This facility reproduces the thermal-hydraulic behaviour of a Passive Containment Cooling System (PCCS) mainly composed of a CWC, a heat exchanger in the containment vessel connected to a water tank at atmospheric pressure outside the vessel which represents the ultimate heat sink. Several activities are carried out within the framework of the project. Different tests are conducted on these integral test facilities to produce new and relevant experimental data allowing to better characterize the physical behaviours and the performances of these systems for various thermo-hydraulic conditions. These test programmes are simulated by different codes acting at different scales, mainly system and CFD codes. New "system/CFD" coupling approaches are also considered to evaluate their potential to benefit both from the accuracy of CFD in regions where local 3D effects are dominant and system codes whose computational speed, robustness and general level of physical validation are particularly appreciated in industrial studies. In parallel, the project includes the study of single and two-phase natural circulation loops through a bibliographical study and the simulations of the PERSEO and HERO-2 experimental facilities. After a synthetic presentation of the project and its objectives, this article provides the reader with findings related to the physical analysis of the test results obtained on the PKL and PASI installations as well an overall evaluation of the capability of the different numerical tools to simulate passive systems.

• Journal of Chest Surgery
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• v.38 no.1 s.246
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• pp.13-22
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• 2005

It has been known that pulsatile flow is physiologic and more favorable to tissue perfusion than nonpulsatile flow. The purpose of this study is to directly compare the effect of pulsatile versus nonpulsatile blood flow to renal tissue perfusion in extracorporeal circulation by using a tissue perfusion measurement system. Material and Method: Total cardiopulmonary bypass circuit was constructed to twelve Yorkshire swines, weighing 20$\~ $30 kg. Animals were randomly assigned to group 1 (n=6, non pulsatile centrifugal pump) or group 2 (n=6, pulsatile T-PLS pump). A probe of the tissue perfusion measurement system $(QFlow^{TM}-500)$ was inserted into the renal pa­renchymal tissue. Extracorporeal circulation was maintained for an hour at a pump flow of 2 L/min after aortic cross-clamping. Tissue perfusion flow of the kidney was measured at baseline (before bypass) and every 10 minutes after bypass. Serologic parameters were collected at baseline and 60 minutes after bypass. Result: Baseline parameters were not different between the groups. Renal tissue perfusion flow was substantially higher in the pulsatile group throughout the bypass (ranged 48.5$\~$ 64 in group 1 vs. 65.8$\~$88.3 mL/min/100 g in group 2, p=0.026$\~$ 0.45) The difference was significant at 30 minutes bypass $(47.5{\pm}18.3\;in\;group\;1\;vs.\;83.4{\pm}28.5$ mL/min/100 g in group 2, p=0.026). Serologic parameters including plasma free hemoglobin, blood urea nitrogen, and creatinine showed no differences between the groups at 60 minutes after bypass (p=NS). Conclusion: Pulsatile flow is more beneficial to tissue perfusion of the kidney in short-term extracorporeal circulation. Further study is suggested to observe the effects to other vital organs or long-term significance.

• Clean Technology
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• v.29 no.4
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• pp.255-261
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• 2023

Power semiconductors are semiconductors used for power conversion, transformation, distribution, and control. Recently, the global demand for high-voltage power semiconductors is increasing across various industrial fields, and optimization research on high-voltage IGBT components is urgently needed in these industries. For high-voltage IGBT development, setting the resistance value of the wafer and optimizing key unit processes are major variables in the electrical characteristics of the finished chip. Furthermore, the securing process and optimization of the technology to support high breakdown voltage is also important. Etching is a process of transferring the pattern of the mask circuit in the photolithography process to the wafer and removing unnecessary parts at the bottom of the photoresist film. Ion implantation is a process of injecting impurities along with thermal diffusion technology into the wafer substrate during the semiconductor manufacturing process. This process helps achieve a certain conductivity. In this study, dry etching and wet etching were controlled during field ring etching, which is an important process for forming a ring structure that supports the 3.3 kV breakdown voltage of IGBT, in order to analyze four conditions and form a stable body junction depth to secure the breakdown voltage. The field ring ion implantation process was optimized based on the TEG design by dividing it into four conditions. The wet etching 1-step method was advantageous in terms of process and work efficiency, and the ring pattern ion implantation conditions showed a doping concentration of 9.0E13 and an energy of 120 keV. The p-ion implantation conditions were optimized at a doping concentration of 6.5E13 and an energy of 80 keV, and the p+ ion implantation conditions were optimized at a doping concentration of 3.0E15 and an energy of 160 keV.