• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.218.1-218.1
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• 2014

In order to measure the absolute plasma density, various probes are proposed and investigated and microwave probes are widely used for its advantages (Insensitivity to thin non-conducting material deposited by processing plasmas, High reliability, Simple process for determination of plasma density, no complicate assumptions and so forth). There are representative microwave probes such as the cutoff probe, the hairpin probe, the impedance probe, the absorption probe and the plasma transmission probe. These probes utilize the microwave interactions with the plasma-sheath and inserted structure (probe), but frequency range used by each probe and specific mechanisms for determining the plasma density for each probe are different. In the recent studies, behaviors of each microwave probe with respect to the plasma parameters of the plasma density, the pressure (the collision frequency), and the sheath width is abundant and reasonably investigated, whereas relative diagnostic characteristics of the probes by a comparative study is insufficient in spite of importance for comprehensive applications of the probes. However, experimental comparative study suffers from spatially different plasma characteristics in the same discharge chamber, a low-reproducibility of ignited plasma for an uncertainty in external discharge parameters (the power, the pressure, the flow rate and so forth), impossibility of independently control of the density, the pressure, and the sheath width as well as expensive and complicate experimental setup. In this paper, various microwave probes are simulated by finite-different time-domain simulation and the error between the input plasma density in FDTD simulations and the measured that by the unique microwave spectrums of each probe is obtained under possible conditions of plasma density, pressure, and sheath width for general low-temperature plasmas. This result shows that the each probe has an optimum applicable plasma condition and reliability of plasma density measurement using the microwave probes can be improved by the complementary use of each probe.

• 천문학회보
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• 제42권2호
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• pp.48.3-49
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• 2017

Interplanetary space of the solar system contains a large number of dust particles, referred to as Interplanetary Dust Particles (IDPs) cloud complex. They are observable through meteors and zodiacal lights. The relative contribution of possible sources to the IDPs cloud complex was an controversial topic, however, recent research (Yang & Ishiguro, 2015 and references therein) suggested a dominance of cometary origin. In this study, we numerically investigated the orbital evolution of cometary dust particles, with special concerns on different evolutionary tracks and its consequences according to initial orbits, size and particle shape. The effect of dust particle density and initial size-frequency distribution (SFD) were not decisive in total cloud complex mass and mass supply rate, when these physical quantities are confined by observed zodiacal light brightness and dust particle SFD at 1 au. We noticed that, if we assume the existence of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko, the required mass supply rate decreases significantly. We also found out that close encounters with planets (mostly Jupiter) are the dominating factor of the orbital evolution of dust particles, as the result, the lifetime of cometary dust particles are shorter than Poynting-Robertson lifetime (around 250 thousand years). As another consequence of severe close encounters, only a small fraction of cometary dust particles can be transferred into the orbit < 1 au. This effect is significant for large size particles of ${\beta}$ < 0.01. The exceptional cases are dust particles ejected from 2P/Encke and active asteroids. Because they rarely encounter with Jupiter, most dust particles ejected from those objects are governed by Poynting-Robertson effect and well transferred into the orbits of small semimajor axis. In consideration of the above effects, we directly estimated probability of mutual collisions between dust particles and concluded that mutual collisions in the IDPs cloud complex is mostly ignorable, except for the case of large sized particles from active asteroids.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4675-4681
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• 2014

본 연구는 흡착제 Zeolite 3A와 DETOX에 대하여 $H_2S$의 유입농도와 흡착온도를 공정변수로 하여 포화시간, 흡착량, 흡착속도 등의 $H_2S$ 흡착 제거특성을 평가하기 위하여 수행되었다. $H_2S$의 유입질량유속이 증가함에 따라 Zeolite 3A의 흡착용량은 증가되었으나 포화시간은 감소되었다. 한편 DETOX의 흡착용량과 포화시간은 $H_2S$의 유입질량유속의 증가에 따라 감소되었다. 흡착온도가 상승함에 따라 Zeolite 3A의 흡착용량과 포화시간은 감소한 반면에, DETOX에 대한 이들 값은 증가하였다. DETOX의 $H_2S$흡착용량은 Zeolite 3A의 2.5~16.4배 정도 높게 나타났다. 이는 흡착에서 활성화에너지장벽을 넘어설 충돌빈도는 흡착온도가 증가함에 따라 증가한 것에 기인한 것으로 해석된다. Zeolite 3A와 DETOX에 대하여 $H_2S$의 흡착속도는 $H_2S$의 유입질량유속과 흡착온도가 증가함에 따라 증가하였다. $H_2S$의 흡착속도는 Zeolite 3A가 DETOX의 4배로 나타났다. DETOX는 Zeolite 3A에 비하여 온도 308~318K에서 포화시간은 더욱 길어지고 흡착용량은 더욱 커진다. 바이오가스 중의 $H_2S$제거에 있어서 DETOX는 Zeolite 3A에 비하여 유리한 것으로 나타났다.

• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.81-89
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• 2011

수중 모바일 ad-hoc 네트워크는 수중환경 감시, 재난방지, 해양자원 탐사, 해양생명체 탐구, 그리고 침몰선박 탐색과 같은 수중환경의 다양한 분야에서 유용하다. 수중 환경에서 다중 데이터 통신을 하기 위해서는 효율적인 Medium Access Control (MAC) 프로토콜의 설계가 필요하다. Aloha 프로토콜은 기본적이고 간단한 프로토콜의 하나지만, 충돌이 자주 발생하는 단점이 있다. 만약 RF 통신에서 충돌이 발생한다면, 재전송을 하여 이 문제를 해결할 수 있지만, 저주파를 사용하는 수중에서는 전송 속도가 느리기 때문에 재전송에 많은 어려움이 따른다. 따라서 충돌을 피하기 위해 MAC 프로토콜 기반의 Time Division Multiple Access(TDMA)가 사용되고 있지만, 기존 TDMA는 보낼 데이터가 없을 경우, 타임 슬롯을 쓰지 않는 문제점이 있다. 따라서, 본 논문에서는 보낼 데이터가 없을 경우, 짧은 "I Have No Data"(IHND)를 보냄으로써 타임 슬롯을 단축시키는 동적 TDMA 프로토콜 방식을 제안한다. 또한, 본 논문에서는 데이터 처리량과 채널 효율에 관련된 수학적 분석 모델을 제시하고 기존 TDMA 프로토콜과 비교함으로써 성능의 우수성을 검증한다.

• Journal of Trauma and Injury
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• 제37권1호
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• pp.67-73
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• 2024

Purpose: Posttraumatic stress disorder (PTSD) is prevalent and is associated with protracted recovery and worse outcomes after injury. This study compared PTSD prevalence using the PTSD Checklist for DSM-5 (PCL-5) with the prevalence of PTSD risk using the Injured Trauma Survivor Screen (ITSS). Methods: Adult trauma patients at a level I trauma center were screened with the PCL-5 (sample 1) at follow-up visits or using the ITSS as inpatients (sample 2). Results: Sample 1 (n=285) had significantly fewer patients with gunshot wounds than sample 2 (n=45) (8.1% vs. 22.2%, P=0.003), nonsignificantly fewer patients with a fall from a height (17.2% vs. 28.9%, P=0.06), and similar numbers of patients with motor vehicle collision (40.7% vs. 37.8%, P=0.07). Screening was performed at a mean of 154 days following injury for sample 1 versus 7.1 days in sample 2. The mean age of the patients in sample 1 was 45.4 years, and the mean age of those in sample 2 was 46.1 years. The two samples had similar proportions of female patients (38.2% vs. 40.0%, P=0.80). The positive screening rate was 18.9% in sample 1 and 40.0% in sample 2 (P=0.001). For specific mechanisms, the positive rates were as follows: motor vehicle collisions, 17.2% in sample 1 and 17.6% in sample 2 (P>0.999); fall from height, 12.2% in sample 1 and 30.8% in sample 2 (P=0.20); and gunshot wounds, 39.1% in sample 1 and 80.0% in sample 2 (P=0.06). Conclusions: The ITSS was obtained earlier than PCL-5 and may identify PTSD in more orthopedic trauma patients. Differences in the frequency of PTSD may also be related to the screening tool itself, or underlying patient risk factors, such as mechanism of injury, or mental or social health.

• Advances in nano research
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• 제5권4호
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• pp.359-372
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• 2017

Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of $CuCl_2$ (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of $30-80^{\circ}C$. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at $400^{\circ}C$ and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metalli-ccopper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of $50^{\circ}C$.

• 상하수도학회지
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• 제31권5호
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• pp.389-395
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• 2017

In this paper, we investigate the characteristics of membrane fouling caused by water temperature in the Membrane bioreactor(MBR) process and try to derive the membrane fouling control by chemical enhanced backwashing(CEB). The extracellular polymeric substances(EPS) concentration was analyzed according to the water temperature in the MBR, and the membrane fouling characteristics were investigated according to the conditions, with sludge & without sludge, through a lab-scale reactor. As shown in the existing literature the fouling resistance rate was increased within sludge with the water temperature was lowered. However, in the lab-scale test using the synthetic wastewater, the fouling resistance increased with the water temperature. This is because that the protein of the EPS was more easily adsorbed on the membrane surface due to the increase of entropy due to the structural rearrangement of the protein inside the protein as the water temperature increases. In order to control membrane fouling, we tried to derive the cleaning characteristics of CEB by using sodium hypochlorite(NaOCl). We selected the condition with the chemicals and the retention time, and the higher the water temperature and the chemical concentration are the higher the efficiencies. It is considered that the increasing temperature accelerated the chemical reaction such as protein peptide binding and hydrolysis, so that the attached proteinaceous structure was dissolved and the frequency of the reaction collision with the protein with the chemical agent becomes higher. These results suggest that the MBRs operation focus on the fouling control of cake layer on membrane surface in low temperatures. On the other hand, the higher the water temperature is the more the operation strategies of fouling control by soluble EPS adsorption are needed.

• Transactions on Electrical and Electronic Materials
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• 제8권1호
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• pp.5-10
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• 2007

Using a reference slurry, ammonium dodecyl sulfate (ADS), an anionic and environmentally friendly surfactant, was investigated as an alternative to BTA for its inhibition and lubrication characteristics. Results demonstrated that the inhibition efficiency of ADS was superior to that of BTA. Coefficient of friction (COF) was the lowest when the slurry contained ADS. This suggested that adsorbed ADS on the surface provided lubricating action thereby reducing the wear between the contacting surfaces. Temperature results were consistent with the COF and removal rate data. ADS showed the lowest temperature rise again confirming the softening effect of the adsorbed surfactant layer and less energy dissipation due to friction. Spectral analysis of shear force showed that increasing the pad-wafer sliding velocity at constant wafer pressure shifted the high frequency spectral peaks to lower frequencies while increasing the variance of the frictional force. Addition of ADS reduced the fluctuating component of the shear force and the extent of the pre-existing stick-slip phenomena caused by the kinematics of the process and collision event between pad asperities with the wafer. By contrast, in the case of BTA, there were no such observed benefits but instead undesirable effects were seen at some polishing conditions. This work underscored the importance of real-time force spectroscopy in elucidating the adsorption, lubrication and inhibition of additives in slurries in CMP.

• 멤브레인
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• 제24권1호
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• pp.20-30
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• 2014

C/N 비가 낮은 농촌마을 하수의 고도처리를 위하여 $0.4{\mu}m$의 세공크기를 갖고 있는 평막이 침지된 연속회분식 반응기를 사용하였다. 분말활성탄의 투입, 폭기량 및 유입 유기물 농도가 처리효율과 여과 성능에 미치는 영향을 조사하였다. 54일 이내의 조업 초기에서는 C/N 비가 증가할수록 COD, T-N 및 T-P의 제거율과 MLSS 농도는 증가하였다. 조업 89일 후의 COD, T-N 및 T-P의 제거율은 각각 97.1%, 75.0% 및 48.3%이었다. 막여과에 의해 처리수에서 SS는 검출되지 않았으며, T-P의 제거율이 낮게 나온 이유는 과잉의 슬러지를 배출하지 않았기 때문이다. 분말활성탄을 투여한 경우 조업이 진행됨에 따라 분말활성탄의 혼합강도와 충돌빈도가 증가하여 슬러지의 입자크기가 감소하였으며, 이로 인해 분말활성탄을 투여하지 않은 경우에 비해 TMP 상승이 크게 나타났다.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.468-474
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• 2019

우리나라는 2018년 OECD 회원국 가운데 인구 10만명 당 8.4명으로 35개국 중 4위로 높은 사고율을 보이고 있으며, 그 중 어린이나 고령자와 같은 교통약자의 사망률은 42.2%로 OECD회원국 중 가장 높은 수준에 있다. 이에 어린이 및 노인 등 교통약자에 대한 보행 중 교통사고를 감소시킬 수 있도록 기존에 설치된 수동적인 교통안전시설물에서 보행자 및 운전자를 감지하고 차량과 보행자간에 정보를 인지하여 상호 인식하는 ICT기반 능동형 교통시설물 개발하였으며, 본 연구에서는 관련 문헌 검토 및 교통사고분석시스템 자료를 이용하여 스쿨존 및 고령자와 같은 교통약자의 사고 발생 시 사고요인을 분석하였으며, 교통사고 특성 분석 등을 통하여 교통약자의 보행 중 교통사고 저감을 위한 맞춤형 교통안전시설물을 개발하였다. 또한, 테스트베드를 설치하여 교통안전시설물의 시인성 측정을 통해 주행 중 전방주시빈도 및 차량주행속도를 측정하였으며, 속도감속에 따라 보행자사고 중상률을 예측하기 위하여 한국교통안전공단에서 실행한 속도별 "자동차 대 보행자 인체모형" 충돌실험모델을 적용한 결과, 시설물 설치 후 중상가능성은 4.6%로 크게 감소됨을 예측하였다. 이와 같이 테스트베드를 통해 교통안전시설물의 시인성 및 차량통행속도 저감 효과를 검증하였고, 보행자대 차량사고의 중상률을 예측하여 상호인식 교통안전시설물을 효과검증을 시행한 결과, 상호인식 교통안전시설물을 설치함에 따라 교통약자의 교통사고에 대한 저감효과를 기대한다.