敎育大學에 있어서 學生軍事敎育의 問題点과 그 改善方案 : RNTC制度를 中心으로

朴頭山 군산대학교 1976 論文集 Vol.9 No.2

職場民防衛隊 運營上의 問題點과 그 改善方案

朴頭山 群山敎育大學 1977 論文集 Vol.11 No.-

수치해석을 통한 반밀폐공간 내 수소가스 누출 시 농도변화에 관한 연구

백두산,김효규,박진욱,유용호,Baek, Doo-San,Kim, Hyo-Gyu,Park, Jin-Yuk,Yoo, Yong-Ho 한국터널지하공간학회 2021 한국터널지하공간학회논문집 Vol.23 No.1

온실가스 배출량을 줄이기 위해 내연기관 자동차에 대한 제한을 두고, 친환경자동차 보급 확대 정책을 내놓고 있다. 수소 전기자동차의 수소는 가연 범위 및 폭발 범위가 넓고, 폭발화염 전파속도가 매우 빠른 가연성 가스이기 때문에, 제조, 수송, 저장 시 누출, 확산, 점화 및 폭발 등의 위험성을 가지고 있다. 수소전기자동차의 연료탱크에는 폭발 등 위험성을 감소시키기 위해 온도감응식 압력방출장치(Thermally activate Pressure Relief Device, TPRD)가 있어, 사고가 발생했을 경우 폭발, 화재 등이 발생하기 전에 탱크 내부의 수소를 밖으로 방출한다. 그러나 지하주차장이나 터널과 같은 반밀폐공간에서 사고가 발생할 경우 공간 내 기류의 유동이 개방된 공간보다 미미하기 때문에 TPRD로부터 방출된 수소가스의 농도가 폭발하한계 이상으로 누적될 수 있는 등 문제가 발생할 수 있다. 따라서 본 연구에서는 TPRD의 노즐의 직경에 따라 시간에 따른 수소의 누출 유량을 분석하고, 반밀폐공간에서 수소가 누출될 경우 수소 농도변화를 수치해석으로 검토하였다. 노즐의 직경은 1 mm, 2.5 mm, 5 mm로 검토를 하였으며, 노즐 직경에 따라 지하주차장 내의 수소농도는 노즐의 직경이 클수록 빠른 시간에 농도가 높아지며, 최대값 또한 노즐 직경이 클수록 큰 것으로 분석되었다. 기류가 정체된 지하주차장에서는 노즐 주변에서 폭발하한계 이상의 수소 농도가 분포하는 것으로 분석되었으며, 폭발상한계를 넘지는 않는 것으로 분석되었다. Hydrogen in hydrogen-electric vehicles has a wide range of combustion and explosion ranges, and is a combustible gas with a very fast flame propagation speed, so it has the risk of leakage, diffusion, ignition, and explosion. The fuel tank has a Thermally active Pressure Relief Device (TPRD) to reduce the risk of explosion and other explosions, and in the event of an accident, hydrogen inside the tank is released outside before an explosion or fire occurs. However, if an accident occurs in a semi-closed space such as an underground parking lot, the flow of air flow is smaller than the open space, which can cause the concentration of hydrogen gas emitted from the TPRD to accumulate above the explosion limit. Therefore, in this study, the leakage rate and concentration of hydrogen over time were analyzed according to the diameter of the nozzle of the TPRD. The diameter of the nozzle was considered to be 1 mm, 2.5 mm and 5 mm, and ccording to the diameter of the nozzle, the concentration of hydrogen in the underground parking lot increases in a faster time with the diameter of the nozzle, and the maximum value is also analyzed to be larger with the diameter of the nozzle. In underground parking lots where air currents are stagnant, hydrogen concentrations above LFL (Lowe Flammability Limit) were analyzed to be distributed around the nozzle, and it was analyzed that they did not exceed UFL (Upper Flammability Limit).

中東戰의 敎訓을 通해서 본 北傀 軍事戰略의 問題点

朴頭山 群山敎育大學 1976 論文集 Vol.10 No.-

<i>In situ</i> dry cleaning of Si wafer using OF₂/NH₃ remote plasma with low global warming potential

Park, Jin Woo,Chae, Myeong Gyoon,Kim, Doo San,Lee, Won Oh,Song, Han Dock,Choi, Changhwan,Yeom, Geun Young IOP 2018 Journal of physics. D, applied physics Vol.51 No.44

<P>Dry cleaning technology is an essential technique that can be applied to remove native oxide and various contaminants during the semiconductor manufacturing for nanoscale electronic devices. In this study, the <I>in situ</I> dry cleaning of silicon dioxide (SiO<SUB>2</SUB>) with low global warming potential (GWP) gas mixtures has been investigated by sequential process steps composed of the reaction of SiO<SUB>2</SUB> surface by oxygen difluoride (OF<SUB>2</SUB>) (GWP:  <1)/ammonia (NH<SUB>3</SUB>) remote plasma and the removal of the reacted compound layer by lamp heating. By using the optimized OF<SUB>2</SUB>/NH<SUB>3</SUB> (2:1) mixture for the surface reaction followed by the lamp heating at 200 °C to remove the reacted compound layer, a high-SiO<SUB>2</SUB> cleaning rate and etch selectivity over silicon nitride (>30:1) could be obtained due to the formation of the highest HF concentration on the SiO<SUB>2</SUB> surface at the OF<SUB>2</SUB>/NH<SUB>3</SUB> (2:1) gas ratio. The compound layer formed during the reaction was (NH<SUB>4</SUB>)<SUB>2</SUB>SiF<SUB>6</SUB> observed for a previously investigated NF<SUB>3</SUB> (GWP: 17 200)/NH<SUB>3</SUB> plasma, but the dry SiO<SUB>2</SUB> cleaning rate and the etch selectivity over Si<SUB>3</SUB>N<SUB>4</SUB> obtained by the OF<SUB>2</SUB>/NH<SUB>3</SUB> plasma were higher than those by the optimized NF<SUB>3</SUB>/NH<SUB>3</SUB> plasma. The effects of OF<SUB>2</SUB>/NH<SUB>3</SUB> mixture dry cleaning on the electrical characteristics of metal-oxide-semiconductor (MOS) devices fabricated on the nano-scale trench patterned Si substrate with high aspect ratio were studied and compared with conventional wet and NF<SUB>3</SUB>/NH<SUB>3</SUB> mixture dry cleaning-based devices. Compared with other cleaning methods, OF<SUB>2</SUB>/NH<SUB>3</SUB> dry-cleaning shows the improved and reliable electrical characteristics such as sharper capacitance-voltage behavior, lower hysteresis, less interface trap charge and smaller contact resistivity. Therefore, it is believed that the <I>in situ</I> sequential dry SiO<SUB>2</SUB> cleaning with the OF<SUB>2</SUB>/NH<SUB>3</SUB> remote plasma can be applied as an essential cleaning method with extremely low GWP for fabricating next generation nano-scale devices.</P>

Effects of Discontinuous Percoll Gradient Containing Alpha-linolenic Acid on Characteristics of Frozen-thawed Boar Spermatozoa

Doo-San Kim,Yong Hwangbo,Hee-Tae Cheong,Choon-Keun Park 한국동물생명공학회(구 한국동물번식학회) 2020 Journal of Animal Reproduction and Biotechnology Vol.35 No.1

This present study was conducted to investigate protective effect of discontinuous Percoll gradient containing alpha-linolenic acid (ALA) before freezing process on viability, acrosome damage, mitochondrial activity, and oxidative stress of frozen-thawed boar spermatozoa. The separation of spermatozoa by discontinuous Percoll gradient was performed by different concentration of Percoll solution (45/90%) containing ALA combined with bovine serum albumin (BSA), and collected sperm in each Percoll layer was cryopreserved. To evaluate viability, acrosome damage, mitochondrial activity, and reactive oxygen species (ROS) level of frozen-thawed sperm, flow cytometry was used. Morphological abnormalities were observed under light microscope. In results, viability of sperm from 90% Percoll layer was higher than control and 45% Percoll group (p < 0.05). Separated sperm in 90% Percoll layer had lower acrosome damage and morphological abnormalities than control as well as viability, whereas 45% Percoll group was higher (p < 0.05). Similar with acrosome damage and abnormalities, mitochondrial activity was slightly enhanced and the population of live sperm with high ROS level was decreased by 90% Percoll separation, however, there was no significant difference. Supplementation of 3 ng/mL ALA into Percoll solution increased sperm viability and decreased population of live sperm with high ROS compared to control (p < 0.05). In conclusion, discontinuous Percoll gradient before freezing process could improve efficiency of cryopreservation of boar sperm through selection of sperm with high freezing resistance, and supplement of ALA during Percoll gradient might contribute suppression of ROS generation via stabilizing of plasma membrane during cryopreservation.

A Rule-based Optimal Placement of Scaling Shifts in Floating-point to Fixed-point Conversion for a Fixed-point Processor

Park, Sang-Hyun,Cho, Doo-San,Kim, Tae-Song,Paek, Yun-Heung The Institute of Electronics and Information Engin 2006 Journal of semiconductor technology and science Vol.6 No.4

In the past decade, several tools have been developed to automate the floating-point to fixed-point conversion for DSP systems. In the conversion process, a number of scaling shifts are introduced, and they inevitably alter the original code sequence. Recently, we have observed that a compiler can often be adversely affected by this alteration, and consequently fails to generate efficient machine code for its target processor. In this paper, we present an optimization technique that safely migrates scaling shifts to other places within the code so that the compiler can produce better-quality code. We consider our technique to be safe in that it does not introduce new overflows, yet preserving the original SQNR. The experiments on a commercial fixed-point DSP processor exhibit that our technique is effective enough to achieve tangible improvement on code size and speed for a set of benchmarks.

Layer-controlled thinning of black phosphorus by an Ar ion beam

Park, Jin Woo,Jang, Sung Kyu,Kang, Dong Ho,Kim, Doo San,Jeon, Min Hwan,Lee, Won Oh,Kim, Ki Seok,Lee, Sung Joo,Park, Jin-Hong,Kim, Kyong Nam,Yeom, Geun Young Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.41

<▼1><P>BP thinning was carried out using a monoenergetic Ar<SUP>+</SUP> ion beam and the BP could be thinned without damaging the surface.</P></▼1><▼2><P>Black phosphorus (BP) is one of the most interesting two-dimensional (2D) layered materials due to its unique properties, including a band gap energy change from 0.3 eV (bulk) to 2.0 eV (monolayer) depending on the number of BP layers, for application in nanoelectronic devices. In general, 2D layered materials including BP have limitations in terms of synthesis due to the process factors such as time, temperature, <I>etc.</I>, and thus, a thinning technique from the bulk material to a 2D material needs to be used while controlling the removed layer thickness. In this study, layer-controlled thinning of BP was performed by using a controlled Ar<SUP>+</SUP> ion beam method and the BP thinning characteristics were investigated. By using the near monoenergetic ion energy in the range of 45–48 eV, BP could be thinned with the thinning rate of ∼0.55 nm min<SUP>−1</SUP> down to bilayer BP without increasing the surface roughness and without changing the chemical binding states. The BP oxide on the pristine BP could also be successfully removed using the same Ar<SUP>+</SUP> ion beam. 2D BP field-effect transistors (FETs) fabricated with the thinned bilayer–10-layer BPs exhibited electrical characteristics similar to those of pristine BP FETs suggesting no electrical damage on the BP layers thinned by the controlled monoenergetic Ar<SUP>+</SUP> ion beam.</P></▼2>

Atomic layer etching of InGaAs by controlled ion beam

Park, Jin Woo,Kim, Doo San,Mun, Mu Kyeom,Lee, Won Oh,Kim, Ki Seok,Yeom, Geun Young IOP 2017 Journal of Physics. D, Applied Physics Vol.50 No.25

<P>Atomic layer etching (ALE) could be an important next-generation etching technique, applicable to various semiconductor materials including III–V compound materials such as indium gallium arsenide (InGaAs) which has high carrier mobility, an advantageous characteristic in nanoscale electronic devices. In this study, the ALE characteristics of InGaAs have been investigated using a reactive ion beam technique. For the ALE of InGaAs, chlorine radicals/low-energy (10–19 eV) reactive ions and low-energy (5–8 eV) Ar<SUP>+</SUP> ions were used for adsorption and desorption, respectively, during the etch cycle to precisely control the etch depth and to minimize the surface damage of the InGaAs. By using the ALE technique, a constant etch rate of 1.1 Å/cycle could be obtained for InGaAs, as well as an infinite etch selectivity of InGaAs over various materials such as photoresist, silicon, amorphous carbon layer, SiO<SUB>2</SUB>, and HfO<SUB>2</SUB>. The surface composition and surface roughness of the InGaAs after ALE were similar to those of as-received un-etched InGaAs.</P>

Data Cluster Detection for Low Power Embedded Memory Subsystems

Park, Dae Jin,Cho, Jeong Hun,Cho, Doo San Trans Tech Publications 2015 Applied Mechanics and Materials Vol. No.

<P>This work proposes a technique for optimizing data placement of application-wide reused data so that it resides in scratchpad memory of processing elements in multiprocessor system on chips. The proposed technique identifies data elements with fine granularity that can profitably be placed in the scratchpad memories to maximize performance and energy gains. We present a heuristic approach that efficiently exploits the scratchpad memories using memory access footprint. Our experimental results indicate that our approach is able to reduce energy consumption by 30% over cache based memory subsystems.</P>