• Geomechanics and Engineering
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• 제19권3호
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• pp.241-254
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• 2019

A finite element approach is presented to examine ground vibration characteristics under various moving loads in a homogeneous half-space. Four loading modes including single load, double load, four-load, and twenty-load were simulated in a finite element analysis to observe their influence on ground vibrations. Four load moving speeds of 60, 80, 100, and 120 m/s were adopted to investigate the influence of train speed to the ground vibrations. The results demonstrated that the loading mode in a finite element analysis is reliable for train-induced vibration simulations. Additionally, a three-dimensional finite element model (3D FEM) was developed to investigate the dynamic responses of a track-ballast-embankment-ground system subjected to moving loads induced by high-speed trains. Results showed that vibration attenuations and breaks exist in the simulated wave fronts transiting through different medium materials. These tendencies are a result of the difference in the Rayleigh wave speeds of the medium materials relative to the speed of the moving train. The vibration waves induced by train loading were greatly influenced by the weakening effect of sloping surfaces on the ballast and embankment. Moreover, these tendencies were significant when the vibration waves are at medium and high frequency levels. The vibration waves reflected by the sloping surface were trapped and dissipated within the track-ballast-embankment-ground system. Thus, the vibration amplitude outside the embankment was significantly reduced.

• 대한환경공학회지
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• 제36권4호
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• pp.295-302
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• 2014

본 연구는 물 재이용을 위한 하수고도처리공정으로서 이단유로 축전식 탈염공정의 적용 가능성을 평가하였다. 일반적으로 축전식 탈염장치는 전극이 병렬식으로 단순 적층되어 있는 반면에 이단유로 축전식 탈염장치는 분리판에 의해 모듈이 2개의 단으로 구분되어 1단과 2단이 수리학적 직렬연결이 되도록 고안되었다. 동일한 유입조건에서 전산유체역학 분석결과 이단유로 모듈이 단일유로 모듈에 비해 스페이서에서 보다 균등하고 빠른 유속분포를 보였고, 사영역도 상대적으로 작게 나타났다. 하지만 입구와 출구 간 압력강하는 단일유로 모듈이 0.4 bar인 반면 이단유로 모듈은 0.7 bar로 높게 나타났다. NaCl용액을 원수로 사용한 단위셀 테스트 결과, 단일유로와 이단유로의 최대 탈염효율은 유입유량 10 mL/min/cell pair에서 각각 88%, 91%이었다. 유량증가에 따른 단위셀 압력강하의 증가는 이단유로가 단일유로보다 높게 나타났으며, 유입유량 70 mL/min/cell pair에서 이단유로의 압력강하는 1.67 bar로 단일유로의 압력강하보다 2배 높게 나타났다. 이단유로의 압력강하를 완화시키기 위하여 전극 간 간격을 100에서 $200{\mu}m$으로 늘린 결과, 탈염효율은 유사하게 유지하면서 압력강하는 최대 0.87 bar로 낮게 유지할 수 있었다. Proto-type 축전식 탈염장치에 하수처리수를 주입하여 연속 운전한 결과, TDS 제거효율은 평균 78%로 나타났으며, 특정이온의 경우, $NH_4{^+}$-N, $NO_3{^-}$-N 및 $PO_4{^{3-}}$-P 제거효율이 각각 50%, 93% 및 50%로 나타나 질소제거 관점에서 CDI기술의 하수고도처리공정 활용가능성이 높을 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1651-1664
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• 2023

It is very difficult to capture the multi-dimensional phenomena such as asymmetric flow and temperature distributions with the one-dimensional (1D) model, obviously, due to its inherent limitation. In order to overcome such a limitation of the 1D representation, many state-of-the-art system codes have equipped a three-dimensional (3D) component for multi-dimensional analysis capability. In this study, a standard multi-dimensional analysis model of APR1400 (Advanced Power Reactor 1400) has been developed using TRACE (TRAC/RELAP Advanced Computational Engine). The entire reactor pressure vessel (RPV) of APR1400 has been modeled using a single 3D component. The fuels in the reactor core have been described with detailed and coarse representations, respectively, to figure out the impact of the fuel description. Using both 3D RPV models, a comparative analysis has been performed postulating a double-ended guillotine break at a cold leg. Based on the results of comparative analysis, it is revealed that both models show no significant difference in general plant behavior and the model with coarse fuel model could be used for faster transient analysis without reactor kinetics coupling. The analysis indicates that the asymmetric temperature and flow distributions are captured during the transient, and such nonuniform distributions contribute to asymmetric quenching behaviors during blowdown and reflood phases. Such asymmetries are directly connected to the figure of merits in the LBLOCA analysis. Therefore, it is recommended to employ a multi-dimensional RPV model with a detailed fuel description for a realistic safety analysis with the consideration of the spatial configuration of the reactor core.

• 대한원격탐사학회지
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• 제29권4호
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• pp.375-387
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• 2013

이중차분간섭기법(Double-Differential Interferometric SAR; DDInSAR)을 이용하여 빙하의 조위반응을 정확히 해석하기 위해서는 극지 해양에 대한 조위모델의 정밀도 평가가 수행되어야 한다. 이 연구에서는 동남극 테라노바 만에서 TPXO7.1, FES2004, CATS2008a, Ross_Inv 조위모델의 정밀도를 평가하기 위해 2년 동안 획득된 16쌍의 one-day tandem COSMO-SkyMed SAR 간섭영상으로부터 생성한 120개의 DDInSAR 영상과 수압식 파고계로 11일 동안 실측한 조위를 이용하였다. 먼저, DDInSAR 영상과 조위모델로 추출된 조위의 이중차분값(${\Delta}\dot{T}$)을 비교하였으며, 실측조위와 조위모델의 조위(T), 그리고 실측조위와 조위모델 조위의 24시간 차분값($\dot{T}$)을 비교하였다. ${\Delta}\dot{T}$와 T, $\dot{T}$의 평균제곱근오차(root mean square error; RMSE)는 조위모델의 역기압 효과(inverse barometer effect; IBE) 보정 후에 감소하였고, 이로부터 조위모델의 IBE는 필수적으로 보정되어야 함이 확인되었다. $\dot{T}$와 ${\Delta}\dot{T}$는 T보다 작은 RMSE를 보였다. 이는 SAR 간섭쌍의 시간차(24시간) 동안의 차분값인 에 조위모델과 실측조위의 평균해수면 오차와 조위모델이 사용하는 조화상수 중 $S_2$, $K_2$, $K_1$, $P_1$의 오차가 상쇄되기 때문이다. 따라서 IBE가 보정된 조위모델의 $\dot{T}$와 ${\Delta}\dot{T}$가 DDInSAR 기법에 사용될 수 있음을 확인하였다. 단기간 실측된 조위로는 최적의 조위모델 선정에 어려움이 있었으나, DDInSAR를 이용한 정밀도 평가에 의하면 Ross_Inv가 4.1 cm의 RMSE를 보여 테라노바 만의 DDInSAR에 가장 적합한 조위모델로 확인되었다.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.248-262
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• 1991

Simulation model was developed to analyze drying process for tray type red pepper dryer and validated by experiments. This model could predict satisfactorily temperatures and moisture contents of red pepper and temperatures of drying air during drying. Optimize algorithm was developed to search control valiables (drying air temperature, air recycle ratio and air flow rate) of red pepper dryer based on a criterion of minimizing energy consumption under the constraint conditions that statisfied carotenoid retension of at least 210mg per 100g dry matter, the moisture content of bottom layer of 15% (d.b) and drying time of less than 35 hours. Step changes in drying air temperature and air recycle ratio were considered in the optimization. In single step in control variables, the difference of the moisture content between top layer and bottom layer was great and more fan power was required. As the drying trays were exchanged when the moisture content of bottom layer reached to 100% (d.b), fifty percent of energy was saved and the difference of moisture content was little. In double step changes in control variables, optimal conditions were found by changing the step when the moisture content of bottom layer reached to 100% (d.b) (about 19.8 hours from starting drying). Optimum air flow rate was $18.1cmm/m^2$. Optimum drying air temperature and air recycle ratio in the first step was $55.8^{\circ}C$ and 0.80, and in the second step $65.6^{\circ}C$ and 0.88, respectively. In triple step changes in control variables, the optimal conditions were found by changing the steps when the moisture content of bottom layer reached to 250% (d.b) and 150% (d.b). Optimal air temperatures were $66.2^{\circ}C$, $58.4^{\circ}C$ and $66.9^{\circ}C$, and optimal air recycle ratios were 0.778, 0.785, 0.862 at each step, respectively. Optimal air flow rate was $18.9cmm/m^2$. The best operating mode was triple step mode considering energy consumption, drying time, fan power, and quality of dried red pepper. When the triple step mode was used to dry the red pepper, the energy consumption was about 16.5%~57.2% less than that of the single step mode and the drying time was 6.6 hours shorter than that of the double step mode.

• Journal of Acupuncture Research
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• 제27권1호
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• pp.117-127
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• 2010

Background : To demonstrate the efficacy of moxibustion therapy, randomized controled trials are required. But, clinical trials of moxibustion had limitations due to the absence of a sham moxibustion model for an appropriate placebo. Objectives : To develop a new sham moxibustion model based on the thermal characteristics of commercial indirect moxibustion, especially temperature, and to evaluate whether it could be applied in clinical trials. Methods : By applying heat insulation, we created a sham moxibustion device that was indistinguishable from a real one with the naked eye. It also stimulated heat but had inert remedial value. A clinical trial was performed on subjects to test double blinding. The subjects were randomly assigned into two groups, a treatment group and a sham group. Acupoint Zusanli($ST_{36}$) was used in each group for 3 times. A sham acupuncture credibility questionnaire was modified into a moxibustion credibility questionnaire and was filled out after treatment. Results : No major difference was detected in the subjects' baseline data. Most subjects and practitioners could not distinguish the sham moxibustion device from the real one. But, subjects who had experience of moxibustion therapy more likely to distinguish the sham moxibustion device from the real one than subjects who didn't have experience of moxibustion therapy. The treatment group showed a significant difference in the VAS(Visual Analog Scale) for intensity of sensation during treatment than that of the sham group. Conclusions : The sham moxibustion device in this study is proved sufficient and credible to be applied in investigations of the effect of moxibustion. But it is more appropriate for the people who don't have experience of moxibustion therapy.

• Journal of Welding and Joining
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• 제31권1호
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• pp.65-70
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• 2013

Finite element analysis and welding experiments were performed to evaluate deformation aspect for Flux Cored Arc Welding(FCAW) and Electro Gas Welding(EGW). Numerical researches of FCAW and EGW were performed considering the difference of number of welding pass and welding direction to arc flow. To perform the numerical study of FCAW and EGW, number of welding pass and welding direction to arc flow were considered in the finite element model. FCAW process requires multi pass and its welding direction is vertical to welding torch. On the other hand, EGW process requires single pass and its welding direction is parallel to welding torch. The difference of welding direction and heat input was considered in the finite element analysis. In FCAW process, Goldak's double ellipsoidal heat input model was adopted. In the EGW process, Hemi-spherical power density distribution was adopted. In the results of experiment and finite element analysis, angular deformation of FCAW process is larger than that of EGW process.

• 한국측량학회지
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• 제39권5호
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• pp.279-288
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• 2021

In the era of the 4th industrial revolution, smart construction, in which new technologies such as UAV (Unmanned Aerial Vehicle) are fused, is attracting attention in the construction field. However, the method of estimating earthwork volume using DEM generated by UAV survey according to practical regulations such as construction design guidelines or standard product counting is not officially recognized and needs to be improved. In this study, different types of UAV were measured and DEM was obtained using this data. The DEM (Digital Elevation Model) thus obtained was analyzed for changes in the amount of earthworks according to the size of the GSD (Ground Sample Distance). In addition, the amount of earthwork by DEM and the amount of earthwork by existing design drawings were compared and analyzed. As a result of the study, it was suggested that images with a GSD of 5cm or less are effective to generate a high-quality DEM. Next, as a result of comparing the earthwork volume calculation method using DEM and the earthwork volume based on the existing 2D design drawings, a difference of about 1% was shown. In addition, when the design earthwork amount calculated by the double-section averaging method was compared with the designed earthwork amount using DEM data by UAV survey, a difference of about 1% was found. Therefore, it is suggested that the method of calculating the amount of earthworks using UAV is an efficient method that can replace the existing method.

• 한국인구학
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• 제8권2호
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• pp.46-67
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• 1985

In this paper, an attempt has been made to examine the pattern of mortality in Korea during 1970~80. By applying the age-sex specific mortality rates quoted from 1978~79 life tables for Korea published by NBOS, EPB to those of the West pattern of regional model life tables and the far eastern pattern of model life tables for developing countries, life expectancy at birth were calculated. Also the author reviewed the trends of death rates, life expectancy and cause of death using vital registration data and other materials. Summarized results are as follows; 1. Crude death rates in Korea was reduced to one fifth in the 1983 compared to that in 1920's. Life expectancy also improved to almost double in 1985 compared to 1920's. But the difference in the life expectancy between male and female increased during that period and it was recorded as 6.4 years in 1985. This discrepancy was mainly due to the different tempo of decreasing in mortality level by sex, particularly, for the age 40 and above. 2. For the pattern of mortality in Korea, it showed that female mortality could accounted closer to the West pattern model life tables. There were high similarity between actual pattern prevalent in Korea and West pattern. And its coefficient of variance was also very low. However for the case of male, it was difficult to find the exact model life tables for explaining the actual situation on the male mortality pattern which means exist considerable dissimilarity in older ages. The Far eastern pattern of U.N. model life tables show better results than West pattern, however, the deviation of the pattern to actual was severe. Also in Far eastern pattern, high coefficient of variance was existed. Furthermore it was found in the paper that the mortality level of Korean male for the age 40 and above were much higher than that of Far eastern pattern which was reflected the high mortality of the male adult in Far east region. 3. The analysis of cause of death showed that circulatory disease such as cerebrovascular disease and hypertensive disease accounted for the leading cause of death in Korea for the age 40 and above. There should he paid special attention to chronic retrogressive diseases for the older age groups. For younger age groups, injury and poisoning were reported as important cause of death.

• 한국ITS학회 논문지
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• 제14권6호
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• pp.50-59
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• 2015

본 연구에서는 가치추정방법의 하나인 조건부 가치측정법(Contingent Valuation Method : CVM)을 이용하여 교통사고 긴급통보시스템 도입을 위한 지불의사액을 산정하고자 하였다. 분석을 위해 이중양분선택법 질문양식을 이용하여 긴급통보시스템에 대한 이용자들의 지불의사액(Willingness to Pay : WTP) 추정방안을 제시하였다. 기존 연구들의 경우 지불의사액 산정에 사용되는 질문 유형별 분석 모델별로 지불유무에 따른 절단데이터가 다르게 처리되고 있음을 알 수 있었다. 이에 따라 본 연구에서는 이중양분 선택법으로 구성된 절단 데이터를 처리하는 방법으로 모형별 지불의사액의 차이를 비교하였다. 연구에 사용된 설문지는 약 500부 수준으로 응답자의 지역적인 편차(bias)가 반영되지 않도록 온라인과 오프라인에서 동시에 진행하였으며, 연령대별 편차를 고려하기 위해 2010년 인구주택 총 조사 결과를 참조하여 자료를 구성하였다. 최종적으로 더 나은 자료의 해석을 위해 생존분석, 다중회귀분석, 토빗분석 등 다양한 통계기법을 적용하여 결론을 도출하였다.