• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.84-92
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• 2023

As temporary storage facilities for spent nuclear fuels in domestic nuclear power plants are expected to be saturated, external intermediate storage facilities would be required in the future. Spent nuclear fuels are stored in metal canisters and then placed in a dry environment within concrete or metal casing for operation. In the United States, the dry storage method for spent nuclear fuels has been operated for an extended period. Based on the corrosion experiences of dry storage canisters in chloride environments, numerous studies have been conducted to reduce corrosion in welds. With the construction of intermediate storage facilities in Korea for spent nuclear fuels expected near coastal areas adjacent to nuclear power plants, there is a need for research on the corrosion occurrence of welds and mitigation methods for canisters in chloride environments. In this paper, we measured and compared the residual stresses in the Heat-Affected Zones (HAZ) after electron beam welding (EBW) and gas tungsten arc welding (GTAW) processes for candidate materials such as 304L, 316L, and duplex stainless steel(DSS). We investigated the possibility of microstructure control through the application of surface modification processes using friction stir processing (FSP). Corrosion tests on each welded specimen revealed a higher corrosion rate in EBW welds compared to GTAW. Furthermore, it was confirmed that corrosion resistance improved due to phase refinement and redistribution of precipitates when FSP was applied.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.102-108
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• 2023

A Chloride-induced stress corrosion cracking (CISCC) of austenite stainless steel in dry cask storage system (DCSS) can occur with extending service time than originally designed. Cold spray coating (CSC) not only form a very dense microstructure that can protect from corrosive environments, but also can generate compressive stress on the surface. This characteristic of CSC process is very helpful to increase the resistance for CISCC. CSC with several powders, such as 304L, 316L and Ni can be optimized to form very dense coating layer. In addition, the impact energy generated as the CSC powder collides with the surface of base metal at a speed of Mach 2 or more can remove the residual tensile stress of welding area and serve the compress stress. CSC layers include no oxidation and no contamination with under 0.2% porosity, which is enough to protect from the penetration of corrosive chloride. Therefore, the CSC coating layer can be accompanied by a function that can be disconnected from the corrosive environment and an effect of improving the residual stress that causes CISCC, so the canister's CISCC resistance can be increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.131-131
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• 2016

기원전 5000년 이집트에서부터 시작된 도금은 시간이 지남에 따라 점점 발전하여, 1900년대에 들어 전기를 이용한 도금공정이 개발되었고, 현재 뿌리산업으로써 각종 제조업에 널리 이용되고 있다. 도금 공정은 금속을 부식으로부터 보호하고, 제품의 심미성과 기능성, 생산성 등을 높이기 위해 주로 이용된다. 전주도금 공정은 완벽하게 동일한 형태의 생산품을 다량으로 제작 할 수 있기 때문에, 그 높은 생산성으로 주목 받고 있다. 특히, 나노/마이크로 크기의 정밀 소자 등을 가공하는 차세대 기술인 LIGA공정과 접목이 가능하다는 장점이 있다. 몰드를 이용하여 복제하는 방식인 전주 도금은 도금공정이 끝난 후 몰드와 완성된 제품을 분리해내는 추가공정이 필연적으로 발생하게 되는데, 둘 사이의 접착력을 낮추기 위하여 몰드의 표면에 이형박리제를 도포하게 된다. 이형박리제로는 전기가 잘 흐르면서 접착력이 낮은 이산화 셀렌이나 중크롬산이 주로 이용되지만, 원활한 박리를 위해서는 그 두께가 30 um 이상 확보되어야 하기 때문에 정밀한 미세구조 전주도금이 어렵다는 문제점이 있다. 또한 이와 같은 화학 약품들은 매우 유독하기 때문에 추가적인 폐수 처리 공정이 필요하며, 작업자의 안전을 위협하고 심각한 환경 오염을 초래한다는 추가적인 문제가 발생한다. 따라서, 매우 얇고 친 환경적이며 안전한 전주도금 이형박리제에 대한 연구가 요구되고 있다. 본 연구에서는 전주도금 몰드로 사용한 구리의 표면에 TCVD를 이용하여 단일 층 그래핀을 성장시킨 후, 그래핀이 코팅된 몰드에 구리를 전주도금하여 박리하였다. 박리 후 그래핀은 몰드에 손상 없이 남아있는 것을 Raman microscopy를 통해서 확인하였고, 몰드와 그래핀 사이의 접착력 (약 $0.71J/m^2$)에 비해 그래핀과 전주도금 샘플간에 낮은 접착력 (약 $0.52J/m^2$)을 갖는 것을 확인하였다. 이와 같이 낮은 접착력을 통해 박리 시 표면구조의 손상 없이 정밀한 구조의 미세 패턴구조를 형성할 수 있었다. 전주도금을 이용한 전극 형성과 고분자와의 융합을 통해 유연기판을 제작하여 bending 실험을 진행하였다. $90^{\circ}$의 bending 각도로 10000회 이하에서는 저항의 변화가 없었고, LED chip을 mounting한 후 곡률반경 4.5 mm까지 bending을 진행하여도 이상 없이 LED가 발광하는 것을 확인하였다. 위와 같은 전주도금 공정을 이용하여 고집적 전자기기, 광학기기, 센서기기 등의 다양한 어플리케이션의 부품제조에 활용될 수 있을 것으로 기대한다.

• Journal of radiological science and technology
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• v.41 no.6
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• pp.587-594
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• 2018

The purpose of this study was to develop the indirect dosimetry by calculation (IDC) method for diagnostic X-ray equipment. The experiments were performed with inverter type X-ray tubes: Toshiba (E7252X, Japan) and Varian (RAD-14, USA). For the development method, we first applied the standard quality of X-ray beam shown in the TRS457 document, and second, to produce the constants of trendline for the IDC, the total filtration on X-ray beam was subdivided. Third, in order to increase the precision, the energy region was divided into the high energy region and the low energy region and developed by the IDC. In order to verify the IDC, mean dose (mR) values were measured for three Toshiba X-ray tubes and three Varian X-ray tubes at clinical medical institutions and then compared with the IDC on the 2013. As a result, compared with the previous study, the accuracy of the IDC of this study were improved by 2.71% and 9.91% in Toshiba and Varian X-ray tubes, respectively.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.1-7
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• 2021

In order to acquire an image in a positron emission tomography, it is necessary to draw the position coordinates of the scintillation pixels of the detector module measured at the same time. To this end, in a detector module using a plurality of scintillation pixels and a small number of photosensors, it is necessary to obtain a flood image and divide a region of each scintillation pixel to obtain a position of a scintillation pixel interacting with a gamma ray. Alternatively, when the number of scintillation pixels and the number of photosensors to be used are the same, the position coordinates for the position of the scintillation pixels can be directly acquired as digital signal coordinates. A method of using a plurality of scintillation pixels and a small number of photosensors requires a process of obtaining digital signal coordinates requires a plurality of photosensors and a signal processing system. This complicates the signal processing process and raises the cost. To solve this problem, in this study, we developed a method of obtaining digital signal coordinates without performing the process of separating the planar image and region using a plurality of flash pixels and a small number of optical sensors. This is a method of obtaining the position coordinate values of the flash pixels interacting with the gamma ray as a digital signal through a look-up table created through the signals acquired from each flash pixel using the maximum likelihood function. Simulation was performed using DETECT2000, and verification was performed on the proposed method. As a result, accurate digital signal coordinates could be obtained from all the flash pixels, and if this is applied to the existing system, it is considered that faster image acquisition is possible by simplifying the signal processing process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.427-432
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• 2024

The polymer crystallization process, promoting the formation of ferroelectric β-phase, is essential for developing polyvinylidene fluoride (PVDF)-based high-performance piezoelectric energy harvesters. However, traditional high-temperature annealing is unsuitable for the manufacture of flexible piezoelectric devices due to the thermal damage to plastic components that occurs during the long processing times. In this study, we investigated the feasibility of introducing a flash lamp annealing that can rapidly induce the β-phase in the PVDF layer while avoiding device damage through selective heating. The flash light-irradiated PVDF films achieved a maximum β-phase content of 76.52% under an applied voltage of 300 V and an on-time of 1.5 ms, a higher fraction than that obtained through thermal annealing. The PVDF-based piezoelectric energy harvester with the optimized irradiation condition generates a stable output voltage of 0.23 V and a current of 102 nA under repeated bendings. These results demonstrate that flash lamp annealing can be an effective process for realizing the mass production of PVDF-based flexible electronics.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.537-543
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• 2020

The elderly population in the modern society is growing rapidly due to advance medical technology and minimally invasive surgery. Therefore, as the tendency to use medical device is increasing, pathogenic infection is a concern. Therefore, the first aim of modern medicine is infection prevention in medical place. Recently, patient implants are increasing using 3D printing. Hydroxyapatite is used as a representative material. And, there haven't had currently absorbed dose standard for sterilization of hydroxyapatite discs. Escherichia coli and Streptococcus mutans contaminated on the surface of hydroxyapatite discs were irradiated at each absorbed dose of 0, 0.5, 1.0, 3.0, 5.0 kGy using Gamma-ray of cobalt and Electron-beam of linear accelerator. Then, the number of bacteria was measured in the sample by the decimal dilution method. After sterilization, a non-parametric testing method was performed to compare the survival of Escherichia coli and Streptococcus mutans. As a result, Escherichia coli was sterilized at 1 kGy or more and Streptococcus mutans at 3 kGy or more on absorbed dose. It is considered possible to perform sterilization at a lower value than the recommended absorbed dose of radiation sterilization.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.207-217
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• 2010

Recently, the use of DC power increased due to the increased use of digital load. Power factor of input current decrease and input current harmonics increase, and conversion loss which is occurred in the AC / DC converter is a problem to provide the proper DC voltage to the device equipped with an internal AC / DC converter. Hybrid system supplies the AC power and DC power to AC load (motor load and the transformer load) and DC loads (computers, TV, LED fluorescent light) at the same time it supplies the renewable energy and utility energy taken power from Utility to user for improving the efficiency and renewable energy improvements in ease of use. This paper studies DC characteristics of traditional AC load for Hybrid distributions.

• Applied Biological Chemistry
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• v.43 no.3
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• pp.174-178
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• 2000

To search CDK4/Cyclin D1 enzyme inhibition materials, methanol extracts of native eighty seven plant species in thirty seven families were screened in vitro for their inhibiting activities against CDK4/Cyclin D1 enzyme which are control to the normal cell division cycle in human body. Extracts of Paeonia suffruticosa, Saurus chinensis, Sanguisorba officinalis and Celastrus orbiculatus among them significantly inhibited above fifty percent $(in\;5\;{\mu}g/ml)$ against CDK4/ Cyclin D1 enzyme. Especially, the extracts of P. suffruticosa and S. officinalis showed moderately strong inhibition. Also, cryptotanshinone was identified as active compound from a extracts of Salvia mitiorrhiza by spectroscopic analyses including 2D NMR experiments.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.11a
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• pp.153-156
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• 2007

임상 프로토콜은 의료 서비스의 질을 향상시키는데 매우 중요한 수단 중 하나이다. 하지만 대부분의 임상 프로토콜이 텍스트 기반으로 되어 있을 뿐만 아니라 텍스트 기반의 임상 프로토콜들이 실행 가능한 형태로 시스템화가 되었더라도 치료를 하는 전문의의 관점에서만 기술되어 왔다. 한편 최근의 임상 연구는 유비쿼터스 헬스케어 서비스를 이용한 환자 개인의 맞춤형 의료서비스에 관한 연구가 진행되고 있다. 이와 같은 유비쿼터스 헬스케어 환경에서는 환자가 병원에서 뿐만 아니라 시간과 장소의 제약을 받지 않고 휴대용 단말기나 진단기기를 이용하여 효과적으로 의료 서비스를 제공 받을 수 있기 때문에 전문의뿐만 아니라 환자와 시스템도 헬스케어에 참여를 하게 된다. 따라서 전문의 중심의 임상 프로토콜 기술로부터 참여자 중심의 임상 프로토콜 기술이 절실히 요구된다. 본 논문에서는 전문의, 환자, 그리고 시스템의 역할에 따라 프로토콜 상에서 수행되어야 할 태스크들과 참여자들의 상태정보를 태스크 튜플 형태로 표현하였다. 하지만 태스크 튜플 기반의 표현 방법은 임상 프로토콜올 직관적으로 이해하는 데는 한계 있어 이러한 단점을 보완한 패트리 넷 기반의 유비쿼터스 헬스케어 프로토콜 기술 방법을 제안한다.