• Journal of Information Technology Applications and Management
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• 제13권3호
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• pp.89-105
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• 2006

Information revolution shifted the meaning of education from traditional face-to-face education to technology integrated virtual one, namely cyber education. A new way of education, however, has not constituted its methodological standards either performance measurement scheme. The study probes the critical factors that influence students' achievement and satisfaction especially in the cyber education environment. Using hierarchical regression, important factors for students' achievement and satisfaction in the management education environment are presented. The results indicate that students' individual characteristics are relatively less influential for cyber education success. Rather, institutional supports including provision of in-depth interaction among students and with the instructor are more critical. We can infer that cyber education essentially requires three factors: in-depth interactions with instructor collaborative environment among peer students technical support from the institution.

• Geomechanics and Engineering
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• 제20권4호
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• pp.333-343
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• 2020

Preventing or reducing the damage impact of lateral soil movements on piled foundations is highly dependent on understanding the behavior of passive piles. For this reason, a detailed experimental study is carried out, aimed to examine the influence of soil density, the depth of moving layer and pile spacing on the behavior of a 2×2 free-standing pile group subjected to a uniform profile of lateral soil movement. Results from 8 model tests comprise bending moment, shear force, soil reaction and deformations measured along the pile shaft using strain gauges and others probing tools were performed. It is found that soil density and the depth of moving layer have an opposite impact regarding the ultimate response of piles. A pile group embedded in dense sand requires less soil displacement to reach the ultimate soil reaction compared to those embedded in medium and loose sands. On the other hand, the larger the moving depth, the larger amount of lateral soil movement needs to develop the pile group its ultimate deformations. Furthermore, the group factor and the effect of pile spacing were highly related to the soil-structure interaction resulted from the transferring process of forces between pile rows with the existing of the rigid pile cap.

• 한국정밀공학회지
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• 제18권8호
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• pp.139-149
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• 2001

The effects of the cutting conditions on the surface roughness of workpiece in turning were studied in this paper. The workpieces made of carbon steel SM20C and SM45C were tamed without the support of the tailstock center. Cutting conditions were changed in three or flour steps in each parameter and cutting fluid was used. The surface roughness results of tests were measured and the effects of the cutting conditions were analyzed by the method of analysis of variance. The summary of the experimental research is as follows. The main parameters were cutting speed, fred-rate, depth of cut, and the interactions between speed and fled-rate, speed and depth of cut, and fred and depth of cut. As cutting speed increased, surface roughness showed lower value. The surface roughnesses of feed-rate 0.102 mm/rev and 0.147 mm/rev were better than those of feed-rate 0.05 mm/rev and 0.2 mm/rev.

• 대한조선학회논문집
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• 제42권5호
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• pp.427-434
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• 2005

The free surface influenced the wake behind a rotating propeller and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique and ensemble-averaged to study the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is affected only by the propeller rotation speed, the leading on the blades and the proximity of the propeller to the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. The presence of the free surface greatly affected the wake structure, especially for propeller immersion depth of 0.6D. At small immersion depths, the free surface modified the tip and trailing vortices and the slipstream flow structure downstream of X/D = 0.3 in the propeller wake.

• 대한기계학회논문집B
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• 제21권2호
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• pp.316-328
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• 1997

There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for passive control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by passive cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable "passive" effect than the cases of its opposite. opposite.

• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1904-1907
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• 2018

We designed a depth-encoding positron emission tomography (PET) detector by using a bottom and side readout method with a cross-arranged scintillator array. To evaluate the characteristics of the novel detector module, we used the DETECT2000 simulation tool to perform the optical photon transport in the crystal array. The detector module consists of an $M(column){\times}N(row)$ cross-arranged crystal array composed of M/3 sub-arrays consisting of $N{\times}3$ crystals. The second column of the sub-array is arranged perpendicular to the first and the third columns. The crystal is optically coupled to the crystals of the other columns; however, the surfaces between the crystals in the same column are treated as reflectors. A $6{\times}5$ crystal array consisting of two sub-arrays was considered for proof of concept. The two multi-pixel photon counter (MPPC) arrays are coupled to the bottom and one side of the crystal array, respectively. The x-y position is determined by the bottom MPPC array, and the side MPPC array gives depth information. All pixels in the x-y plane and the z direction were clearly distinguished.

• 경영과학
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• 제22권2호
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• pp.35-49
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• 2005

When new services are introduced, interaction among existing and new services has to be considered. The interaction can be characterized by the substitution or complementary effect among services. This paper analyzes how the interaction among services affects the customers' subscription decision in telecommunication services industry. Based on a face-to-face in-depth survey from a sample of 1,200 respondents, a new wireless internet access service or WiBro is analyzed to identify the substitution/complementary effect in relation to the existing other telecommunication services. Additionally, the important factors explaining both customers' subscription and substitution decisions are identified. The analysis results indicate that males and students are more likely to subscribe WIBro service. Interestingly, family size positively affects the subscription decision. However, heavy users of on-line game are reluctant to subscribe WiBro service. Among the potential WiBro subscribers, the customers who are less satisfied with the existing fixed line broadband internet access service are more likely to stop subscribing the fixed line service, which implies substitution by a new service. We believe that the consideration of the interactions among services is essential to devise a winning strategy for the new services in the highly uncertain telecommunications business environment.

• 지질공학
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• 제18권1호
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• pp.103-115
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• 2008

이 연구의 목적은 경남 북서부 화강암 분포지역 지하수의 지구화학적 특징 및 불소의 원인을 물-암석반응으로 이해하는 데 있다. 이를 위하여 지하수의 수질과 모암인 화강암의 주요 성분간의 부화경향성을 검토하였으며, 변질된 암석내 광물의 미세조직을 전자현미경으로 관찰하고 화학성분을 분석함으로써 물-암석반응에 따른 지하수내 불소의 용존 원인을 해석하였다. 불소함량과 경도를 비교한 결과 이들 간에는 뚜렷한 상관성은 나타나지 않는다. 그러나 불소함량과 pH는 대체로 서로 비례하는 경향을 보이며, 공의 심도가 깊어질수록 불소함량도 증가한다. 흑운모의 변질작용은 벽개를 따라 일어나거나, 결정의 가장자리 부분에서 가장 우세하게 일어난다. 물-암석반응에 의하여 흑운모가 쉽게 변질되므로 본 연구지역의 지하수내 불소의 주공급원이 될 가능성이 가장 높다.

• Steel and Composite Structures
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• 제41권5호
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• pp.761-773
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• 2021

This study presents a 3D non-linear finite element (FE) assessment of dynamic soil-structure interaction (SSI). The numerical investigation has been performed on the time domain through a Finite Element (FE) system, while considering the nonlinear behavior of soil and the multi-directional nature of genuine seismic events. Later, the FE outcomes are analyzed to the recorded in-situ free-field and structural movements, emphasizing the numerical model's great result in duplicating the observed response. In this work, the soil response is simulated using an isotropic hardening elastic-plastic hysteretic model utilizing HSsmall. It is feasible to define the non-linear cycle response from small to large strain amplitudes through this model as well as for the shift in beginning stiffness with depth that happens during cyclic loading. One of the most difficult and unexpected tasks in resolving soil-structure interaction concerns is picking an appropriate ground motion predicted across an earthquake or assessing the geometrical abnormalities in the soil waves. Furthermore, an artificial neural network (ANN) has been utilized to properly forecast the non-linear behavior of soil and its multi-directional character, which demonstrated the accuracy of the ANN based on the RMSE and R² values. The total result of this research demonstrates that complicated dynamic soil-structure interaction processes may be addressed directly by passing the significant simplifications of well-established substructure techniques.

• 한국해안·해양공학회논문집
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• 제21권3호
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• pp.216-223
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• 2009

수면보다 높은 사각기둥 저항체가 등간격으로 배치되어 있는 경우의 상당저항계수 식의 횡방향에 따른 항력상호작용계수를 연구하여 제안하였다. 저항체의 횡방향 이격거리에 따른 에너지 손실이 오리피스의 공극률에 따른 에너지 손실과 동일하다고 가정하고 오리피스의 에너지 손실계수를 차용하여 횡방향 항력상호작용계수를 제안하였다. 이 항력상호작용계수를 사용하는 상당저항계수 식을 김 등(2008)에 의해 사용된 수리조건에 대해 그 해석능력이 검증된 FLOW-3D를 이용하여 수치실험한 결과와 비교하였다. 그 결과가 잘 일치하였고 이로부터 바닥마찰뿐만 아니라 수면보다 높은 정방형 다열기둥의 종방향 및 횡방향 이격거리에 따라 변화되는 저항정도를 고려할 수 있는 제안된 상당저항계수 식의 타당성을 검증하였다.