• The Journal of Engineering Geology
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• v.30 no.2
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• pp.161-173
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• 2020

This study is to examine the engineering characteristics of colunmar joints in Mudeugsan National Park, a global geopark. For these purposes, physical and mechanical properties of Mudeungsan Tuff, evaluation for the weathering degree of columnar joints, and crack behavior monitoring in columnar joints were conducted. The physical properties of Mudeungsan tuff were 1.02% for the average porosity, 0.38% for the average absorption, 2.69 g/㎤ for the average specific gravity, and 4,948 m/s for the average elastic wave velocity. Its mechanical properties were 337 MPa for the average uniaxial compressive strength, 68 GPa for the average elastic modulus, 0.29 for the average Poisson's ratio, 41.3 MPa for the average cohesion strength, and 62.8° for the average friction angle. the average rebound Q-value of the silver Schmidt hammer for the three columnar joint blocks at the Ipseok-dae was shown as 49.3. when this value is converted into uniaxial compressive strength, it becomes 70.5 MPa, which is about 21% of the uniaxial compression strength of Mudeungsan tuff. In addition, according to the results of crack monitoring measurements for the three columnar joint blocks at the Ipseok-dae, the crack behavior is less than 1 mm, so it is believed that its behavior in Ipseak-dae columnar joints has hardly occured to date.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.229-236
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• 1991

A study on the estimation of the stock density and biomass of Perinereis aibuhitensis in the tidal zone in Sosan, Chungchongnam-do, Korea was carried out from June to July 1988. A preliminary survey was conducted to determine the distribution pattern of the species and the optimum sample size for setting up the sampling design. The stock densities of the species by stratum and by subarea were estimated using the stratified random sampling method, based upon the results of preliminary survey. The differences in density between strata as well as among subareas were tested to decide whether they can be combined together for estimating the overall stock biomass or not. The results of the survey showed that p. aibuhitensis were randomly distributed(Poisson distribution) and the number of quadrats which satisfies a reasonable level of precision was determined to be five by stratum. The densities between strata were not significantly different, while densities among subareas were different. Subarea C showed the highest density with the mean of $53.9g/m^2$ and followed by subarea B. The density of subarea A was the lowest with the mean of $18.2g/m^2$. The overall mean density from the study area was $32.4g/m^2$ with the coefficient of variance(CV) of $6.8\%$ The overall stock biomass was estimated to be 147.5mt in this area.

• Geophysics and Geophysical Exploration
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• v.20 no.4
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• pp.207-215
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• 2017

To develope shale play which is one of unconventional energy resources, horizontal drilling and hydraulic fracturing are necessary and those are applied to the place where the differential horizontal stress ratio (DHSR) is low. The differential horizontal stress ratio is generally calculated by the minimum and maximum horizontal stress, but it is also calculated from dynamic elastic constants and anisotropic parameters. In this study we analyzed anisotropic properties through the core samples from Danyang limestone and calculated DHSR. The three types of core samples shaped in three directions (vertical, parallel and 45 degree to bedding) were used for laboratory test. We measured P-, S-wave velocities, and density and then calculated dynamic elastic constants, compliance and DHSR. According to the results of the core sample analysis the calculated DHSR is 0.185. Thomsen parameters of the Danyang limestone used in this study are characterized by the P- and S-wave velocities varying along the bedding symmetry axis. It is observed that the DHSR value is more affected by the change in compliance value than the Poisson's ratio. It is necessary to measure SH-wave velocity for more correct petrophysical properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.389-398
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• 2006

Structural optimization design has been developed with finite element analysis using effective and fast computational technology. Especially topology optimization design has been recently often used since it yields an optimal topology as well as an optimal shape under satisfied constraints. In general in finite element analysis, it is assumed that the structural material properties such as Young's modulus and Poisson's ratio and the variable of applied loading are fixed with obvious values in structure. However practically these values may take uncertainties because of environmental effect or manufactural error of structures. Therefore static or dynamic analysis of the structures may make an error, then finally it may have an influence on qualify of optimal design. In this study, the topology optimization design of structure is carried out using so called the interval finite element method, and the analysis method Is proposed. The results are also validated by comparing with conventional topology optimization results of density distribution method and finite element analysis results. The present method can be used to predict the optimal topology of linear elastostatic structures with respect to structural uncertainty of behavior.

• Korean Journal of Agricultural Science
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• v.25 no.2
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• pp.271-277
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• 1998

This study was performed to evaluate the stress-strain properties of surlightweight polymer concrete using synthetic lightweight aggregates. The following conclusions were drawn; 1. The dynamic modulus of elasticity was in the range of $1.514{\times}10^5{\sim}1.916{\times}10^5kgf/cm^2$, which was approximately 48~96% of that of the normal cement concrete. It was showed larger with the decrease of synthetic lightweight fine aggregate. 2. The static modulus of elasticity was in the range of $2.552{\times}10^4{\sim}4.386{\times}10^4kgf/cm^2$, which was showed lower compared to that of the normal cement concrete. The poisson's number of surlightweight polymer concrete was less than that of the normal cement concrete. 3. The stress-strain curves of surlightweight polymer concrete were showed smaller with the increase of expanded clay.

• Journal of Wetlands Research
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• v.16 no.3
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• pp.327-336
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• 2014

Submerged thin walls are extreme case of submerged rectangular blocks, and could be used for many purposes in rivers or coastal zones, e.g. to tsunami. To understand flow characteristics including flow and pressure fields around a specific submerged thin wall a numerical model was applied which includes computation of hydrodynamic pressure on ${\sigma}$-coordinate. ${\sigma}$-coordinate has strong merits for simulation of subcritical flow over mild-sloped beds. On the other hand ${\sigma}$-coordinate is quite poor to treat sharp structures on the bed. There have been a few trials to incorporate dynamic pressure in ${\sigma}$-coordinate by some researchers. One of the previous approaches includes process of sloving the Poisson equation. However, the above method includes many high-order terms, and requires long cpu for simulation. Another method SOLA was developed by Hirt et al. for computation of dynamic pressure, but it was valid for straight grid system only. Previous SOLA was modified for ${\sigma}$-coordinate for the present purpose and was adopted in a model system, CST3D. Computed flow field shows reasonable behaviour including vorticity is much stronger than the upstream and downstream of the structure. The model was verified to laboratory experiments at a 2DV flume. Time-average flow vectors were measured by using one-dimensional electro-magnetic velocimeter. Computed flow field agrees well with the measured flow field within 10 % error from the speed point of view at 5 profiles. It is thought that the modified SOLA scheme is useful for ${\sigma}$-coordinate system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.8-8
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• 2001

초고속 증착은 짧은 시간에 박막 형성을 가능하게 하므로 window glass 코팅등의 대면적 코팅에 있어서 비용을 절감 시키고, 대량생산을 가능하게 만들기 때문에 관심이 집중되고 있다. 고속증착 공정으로는 high current arc, laser arc, hollow cathode discharge ion plating 그리고 마그네트론 스퍼터링법 등이 있다. 특별히 마그네트론 스퍼터링법은 3m이상의 넓이에 코팅을 할때 두께가 매우 균일하며, 증착율은 evaporation 공정에 비해 경제적, 기능적인 면에서 효율적이다. 그리고 증착된 박막은 매우 조밀하고 좋은 밀착력을 갖고 있으며, 고융점 금속을 포함하여 금속 합금 및 혼합물의 비율을 조정 및 금속 산화물, 질화물, 탄화물 등과 같은 금속의 증착도 stoichiometry를 조정하여 박막을 합성 시키는데 있어서 효과적이다. 이러한 초고속 증착을 만들기 위한 마그네트론 스퍼터링법의 요건은 마그네트론 원이 높은 타켓 power density를 가져야 하며, 타켓에서 효율적으로 플라즈마를 구속하여 스퍼터 되는 이온의 양을 최대화 시킬 수 있어 한다. 따라서 본 실험에서는 초고속 증착을 위해서 직경 50mm 타켓의 UBM magnetron원을 설계 제작하였다. 고밀도의 플라즈마를 형성시키기 위해서, Poisson simulation c code를 이용하여 자기장의 방향, 세기 및 밀도를 측정 하였고, 자기장 측정기(Gauss meter)를 이용하여 실제 자장을 측정 비교 분석하였다. 상기의 data를 바탕으로 여러 형상의 마그네트론원을 설계, 제작하였고. 마그네트론 원의 특성 분석을 위해 I-V 방전 특성을 평가하였고 substrate ion current density와 박막의 증착율을 측정하였다.duty-on 시간의 증가에 따라 $Cr_2N$ 상의 형성이 점점 많아져 80% duty-on 시간 경우에는 거의 CrN과 $Cr_2N$ 상이 공존하는 것으로 나타났다. 또한 duty-on 시간이 증가할수록 회절피크의 세기가 증가하여 결정화가 더 많이 진행되어짐을 알 수 있었다. 마찬가지로 바이어스 펄스이 주파수에 다른 결정성의 변화도 펄스의 주파수가 증가할수록 박막이 결정성이 좋아지고 $Cr_2N$ 상이 쉽게 형성되었다. 증착 진공도에 따른 결정성은 상대적으로 질소의 농도가 높은 낮은 진공도에서는 CrN 상이 주로 형성되었으며, 반대로 높은 진공도에서는 $Cr_2N$ 상이 많이 만들어졌다. 즉 $1.3{\times}10^{-2}Torr$의 증착 진공도에서는 CrN 상만이 보이는 반면 $9.0{\tiems}1-^{-2}Torr$ 진공도에서부터 $Cr_2N$ 상이 형성되기 시작하여 $5.0{\tiems}10^{-2}Torr$ 진공도에서는 두개의 상이 혼재되어 있음을 알 수 있었다. 박막의 내마모성을 조사한 결과 CrN 박막의 마찰 계수는 초기에 급격하게 증가한 후 0.5에서 0.6 사이의 값으로 큰 변화를 보이지 않았으며, $Cr_2N$ 박막도 비슷한 거동을 보였다.차 이, 목적의 차이, 그리고 환경의 의미의 차이에 따라 경관의 미학적 평가가 달라진 것으로 나타났다.corner$적 의도에 의한 경관구성의 일면을 확인할수 있지만 엄밀히 생각하여 보면 이러한 예의 경우도 최락의 총체적인 외형은 마찬가지로 $\ulcorner$순응$\lrcorner$

• The Journal of the Korea Contents Association
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• v.19 no.12
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• pp.84-92
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• 2019

The deterioration of the urban heat environment due to climate change and the occurrence of heat-related diseases have emerged as one of the major social problems. This has led to more research on climate change, including heat waves, but it is mainly focused on climate factors. However, the urban heat island phenomenon accelerates the summer heat wave, and the increasing trend of heat-related patients in urban areas suggests the impact of the city's environment. Thus, this study analyzed the effects of physical and social characteristics of urban areas on heat-related patients in Seoul and Gyeonggi-do. The analysis showed that the ratio of the total area of residential, commercial and industrial facilities, the main source of heat energy locality, among the land use statuses, was not statistically significant, but the road area and the green area were found to have a positive and negative The population density and the percentage of people aged 65 or older, the percentage of people living alone and the proportion of people receiving basic living were all shown to be significant, with only the ratio of elderly living alone and the ratio of population density having negative effects. The results of the study can be used to develop urban policy alternatives related to local warming patients.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.9
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• pp.15-22
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• 2000

The effects of carrier transport and input power on the extinction ratio was theoretically analyzed in a 1.55${\mu}m$ InGaAsP/InGaAsP multiple-quantum-well(MQW) electroabsorption(EA) modulator. Poisson's equation, current continuity equations for electrons and holes, and optical field distribution were self-consistently solved by considering electric field dependent absorption coefficients. The field screening effect due to the carrier accumulation in heterointerface and the space-charge region occurred more seriously at the input side of modulator as input optical intensity increased. It was revealed that extinction ratio could be steeply degraded for modulator with the length of 200${\mu}m$ when an input power exceeds 10mW. A degradation of extinction ratio due to the field screening effect would be more significantly at high-performance devices such as a 1.55${\mu}m$DFB-LD/EA-modulator integrated source where optical coupling efficiency is almost complete or a very high-speed modulator with its length as short as a few tens ${\mu}m$.

• Journal of the Korean Data and Information Science Society
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• v.28 no.2
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• pp.297-307
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• 2017

The epidemic model is used to model the spread of disease and to control the disease. In this research, we utilize SEIR model which is one of applications the SIR model that incorporates Exposed step to the model. The SEIR model assumes that a people in the susceptible contacted infected moves to the exposed period. After staying in the period, the infectee tends to sequentially proceed to the status of infected, recovered, and removed. This type of infection can be used for research in cases where there is a latency period after infectious disease. In this research, we collected respiratory infectious disease data for the Middle East Respiratory Syndrome Coronavirus (MERSCoV). Assuming that the spread of disease follows a stochastic process rather than a deterministic one, we utilized the Poisson process for the variation of infection and applied epidemic model to the stochastic chemical reaction model. Using observed pandemic data, we estimated three parameters in the SIER model; exposed rate, transmission rate, and recovery rate. After estimating the model, we applied the fitted model to the explanation of spread disease. Additionally, we include a process for generating the Exposed trajectory during the model estimation process due to the lack of the information of exact trajectory of Exposed.