• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.205-208
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• 2006

Similar friction welding were produced using 15 mm diameter solid bar in Ni-base superalloy(alloy718) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, AE total counts and ultrasonic attenuation coefficient. The specimens were tested as welded, not heat-treated. The tensile strength of the friction welded joints was increased up to 90% of the alloy718 base metal under the condition of all heating time. Optimal welding conditions were n=2,000 (rpm), $P_1=200$ (MFa), $P_2=200$ (MFa), $t_1=8$ (s), $t_2=5$ (s) when the total upset length is 4.4(mm). The weld interface of similar friction welded steel bars was mixed strongly.

• 상하수도학회지
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• 제7권2호
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• pp.9-23
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• 1993

Emission of hazardous and volatile organic chemicals from solid waste landfill site was become to important issue because of environmental pollution and health risk by such chemicals. Laboratory batch and continuous experiments were conducted respectively to elucidate isothermal sorption behaviors and transport phenomena(by gas through unsaturated solid waste layer) in wet solid waste-gas system. Source separated and size reduced refuse(bulky waste) and incinerated ash were used after controlling water content, and trichloroethylene(TCE) was chosen among many such chemicals because of it's generality among those man-created pollutants. Isothermal TCE sorption equilibria wet solid waste-gas system can be described in linear equation and partition coefficient in this system can be estimated approximately by the simple equation derived from schematic structure of the system. Transport equation modified by instantaneous equilibrium sorption fraction and kinetic sorption rate(overall mass transfer capacity coefficient) simulated well the column experiment results.

• 대한기계학회논문집
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• 제13권2호
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• pp.265-270
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• 1989

본 연구에서는 복사강도를 반구에 대하여 적분하여 비정상 미분방정식의 형태로 로 얻어지는 2-유속 회매질복사모델을 사용하여 복사전달방정식을 구성하고, 전술한 Yoshizawa 등의 가정을 배제하면서, 다공매질의 물리적 길이, 흡수계수 및 혼합기체의 당량비(equivalenceratio) 등을 변화시킴으로써 매질 내의 열적 구조를 분석하여 그들의 의 연구를 확장, 해석한다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권4호
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• pp.192-199
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• 2004

Elastic-factor of elastic epoxy were investigated by TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis), TGA (Thermogravimetric Analysis) and FESEM (Field Emission Scanning Electron Microscope) for structure-images analysis as toughness-investigation to improve brittleness of existing epoxy resin. A range of measurement temperature of the TMA and DMTA was changed from -20($^{\circ}C$) to $200^{\circ}(C)$, and TGA was changed from $0^{\circ}(C)$ to $600^{\circ}(C)$. Glass transition temperature (Tg) of elastic epoxy was measured through thermal analysis devices with the content of 0(phr), 20(phr) and 35(phr). Also, thermal expansion coefficient (a), high temperature, modulus and loss factor were investigated through TMA, TGA, and DMTA. In addition, the structure of specimens was analyzed through FESEM, and then elastic-factor of elastic epoxy was visually showed by FESEM. As thermal analysis results, 20(phr) was more excellent than 30(phr) thermally and mechanically. Specially, thermal expansion coefficient, high temperature, modulus, and damping properties were excellent. By structure-images analysis through FESEM, we found elastic-factor of elastic epoxy that is not existing epoxy, and proved high impact.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.200-202
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• 1996

MgO film was deposited on the glass substrate by the hollow cathode discharge ion plating method and the characteristics of the MgO thin film such as deposition rate, crystalline orientation, surface morphology and secondary electron coefficient were investigated. The deposition rate of MgO thin films were $430^{\sim}1270{\AA}$/min at various temperatures and biases. The crystalline orientation of the MgO thin film changed from (200) to (220) upon increasing the HCD current from 100A to 200A. These results indicated that the crystallin orientation of the MgO thin film was determined by the super-saturation ratio. The (200) peak decreased and the (220) peak increased as the substrate bias increased, while both peaks increased as the substrate temperature increased. The grain size increased as the substrate bias increased and the secondary electron emission coefficient increased as the substrate bias increased.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.801-805
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• 2018

In this study, an underwater radiation detector was built using a GAGG(Ce) scintillator and silicon photomultiplier to establish an underwater radiation exposure monitoring system. The GAGG(Ce) scintillator is suitable for small radiation detectors as it strongly absorbs gamma rays and has a high light emission rate with no deliquescent properties. Additionally, the silicon photomultiplier is a light sensor with characteristics such as small size and low applied voltage. Further, a program and mobile app were developed to monitor the radiation coefficient values generated from the detector. According to the results of the evaluation of the characteristics of the underwater radiation monitoring system, when tested for its responsiveness to radiation intensity and reactivity, the system exhibited a coefficient of determination of at least 0.99 with respect to the radiation source distance. Additionally, when tested for its underwater environmental temperature dependence, the monitoring system exhibited an increase in the count rate up to a certain temperature because of the increasing dark current and a decrease in the count rate because of decreasing overvoltage. Extended studies based on the results of this study are expected to greatly contribute to immediate and continuing evaluation of the degree of radioactive contamination in underwater environments.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1364-1371
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• 2018

An extensive investigation of photon interaction properties has been made for $Zn_xTe_{100-x}$ alloys (where x = 5, 20, 30, 40, 50) to explore its possible use in sensing and shielding gamma radiations. The results show better and stable response of ZnTe alloys for various photon interaction properties over the wide energy range, with an additional benefit of ease in fabrication due to lower melting points of Zn and Te. Mass attenuation coefficient values show strong dependence on photon energy as well as composition. Effective atomic number has maximum value for $Zn_5Te_{95}$ and lowest for $Zn_{50}Te_{50}$ in the entire energy region. The alloy sample with maximum $Z_{eff}$ shows minimal value of $N_e$ and vice versa. Mean free path follows inverse trend as observed for mass attenuation coefficient. The exposure and energy absorption buildup factors depend upon photon energy, penetration thickness and composition (effective atomic number) of $Zn_xTe_{100-x}$ alloys. It finds its application for sensing and shielding from highly energetic and highly penetrating photons at sites where radioactive materials were used and visibility of material is not a big constraint. Further, energy down conversion property of ZnTe alloys with subsequent emission in green band suggests its potential use in sensing gamma photons.

• 한국대기환경학회지
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• 제33권5호
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• pp.497-514
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• 2017

This study quantitatively analyzes the effects of emission inventory choices on the simulated particulate matter (PM) concentrations and the domestic/foreign contributions in the Seoul Metropolitan Area (SMA) with an air quality forecasting system. The forecasting system is composed of Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emissions (SMOKE)-Community Multi-Scale Air Quality (CMAQ). Different domestic and foreign emission inventories were selectively adopted to set up four sets of emissions inputs for air quality simulations in this study. All modeling cases showed that model performance statistics satisfied the criteria levels (correlation coefficient >0.7, fractional error <50%) suggested by previous studies. Notwithstanding the apparently good model performance of total PM concentrations by all emission cases, annual average concentrations of simulated total PM concentrations varied up to $20{\mu}g/m^3$ (160%) depending on the combination of emission inventories. In detail, the difference in simulated annual average concentrations of the primary PM coarse (PMC) was up to $25.2{\mu}g/m^3$ (6.5 times) compared with other cases. Furthermore, model performance analyses on PM species showed that the difference in the simulated primary PMC led to gross model overestimation in general, which indicates that the primary PMC emissions need to be improved. The contribution analysis using model direct outputs indicated that the domestic contributions to the annual average PM concentrations in the SMA vary from 44% to 67%. To account for the uncertainty of the simulated concentration, the contribution correction factor method proposed by Bae et al. (2017) was applied, which resulted in converged contributions(from 48% to 57%). We believe this study shows that it is necessary to improve the simulated concentrations of PM components in order to enhance the accuracy of the forecasting model. It is deemed that these improvements will provide more accurate contribution results.

• 감성과학
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• 제13권4호
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• pp.687-692
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• 2010

본 연구에서는 원적외선 방출 직불 소재를 개발하기 위해서 나노사이즈 게르마늄 업자와 PET chip을 마스터 배치 칩으로 제조하고 이를 PET와 용융 방사하여 sheath-core conjugate 복합사를 제조하여 이들의 물성과 이들 복합사로 제조한 직물의 원적외선 방출특성을 측정 분석하였다. 또한 게르마늄을 함유한 필라멘트와 직물의 물성을 측정하고 이들 물성이 사가공 공정의 중요공정 인자인 벨트각과 사속비 등의 공정인자와 직물 설계에서의 경사와 위사의 밀도에 관계하는 직물 밀도 계수 등의 설계 조건에 의해 직물 역학 특성과 직물 촉감등의 물성이 어떠한 변화를 가져 오는가에 대한 분석을 하였다. 최적 방사조건에 의한 core부에 게르마늄이 함유된 sheath-core형 PET복합사를 제조하였으며 이들의 절단강신도 모두 일반 PET계(系)의 물성치를 보였으며 DTY는 제직성에 문제가 없는 강신도를 보였고 습건열 수축률은 일반 PET사 보다 높은 값을 보였다. 게르마늄 함유 직물의 원적외선 방사강도는 $5{\sim}20{\mu}m$ 파장 영역에서 $3.53{\times}10^2W/m^2$을 보였으며 방사율은 0.874를 보였다. 그리고 최적 사가공 공정 조건 설정과 최적 직물밀도 설계로 직물의 역학 특성치와 촉감 특성의 저하를 막을 수 있음을 확인할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.433-433
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• 2012

As the requirement in patterning geometry continuously shrinks down, the termination of etch process at the exact time became crucial for the success in nano patterning technology. By virtue of real-time optical emission spectroscopy (OES), etch end point detection (EPD) technique continuously develops; however, it also faced with difficulty in low open ratio etching, typically in self aligned contact (SAC) and one cylinder contact (OCS), because of very small amount of optical emission from by-product gas species in the bulk plasma glow discharge. In developing etching process, one may observe that coupon test is being performed. It consumes costs and time for preparing the patterned sample wafers every test in priority, so the coupon wafer test instead of the whole patterned wafer is beneficial for testing and developing etch process condition. We also can observe that etch open area is varied with the number of coupons on a dummy wafer. However, this can be a misleading in OES study. If the coupon wafer test are monitored using OES, we can conjecture the endpoint by experienced method, but considering by data, the materials for residual area by being etched open area are needed to consider. In this research, we compare and analysis the OES data for coupon wafer test results for monitoring about the conditions that the areas except the patterns on the coupon wafers for real-time process monitoring. In this research, we compared two cases, first one is etching the coupon wafers attached on the carrier wafer that is covered by the photoresist, and other case is etching the coupon wafers on the chuck. For comparing the emission intensity, we chose the four chemical species (SiF2, N2, CO, CN), and for comparing the etched profile, measured by scanning electron microscope (SEM). In addition, we adopted the Dynamic Time Warping (DTW) algorithm for analyzing the chose OES data patterns, and analysis the covariance and coefficient for statistical method. After the result, coupon wafers are over-etched for without carrier wafer groups, while with carrier wafer groups are under-etched. And the CN emission intensity has significant difference compare with OES raw data. Based on these results, it necessary to reasonable analysis of the OES data to adopt the pre-data processing and algorithms, and the result will influence the reliability for relation of coupon wafer test and whole wafer test.