• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.237-254
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• 2005

The vast mechanical systems could be classified as closed loop system, open loop system and open & closed (switching) system. In the closed loop system, the kinematics and dynamics of 3-D mechanisms will be reviewed and closed form solutions using the direction cosine matrix method and reflection transformation method will be introduced. In the open loop system, kinematic & dynamic analysis methods regarding the redundant system which has more degrees of freedom in joint space than those of task space are reviewed and discussed. Finally, switching system which changes its phase between closed and open loop motion is investigated with the principle of dynamical balance. Among switching systems, the human gait in biomechanics and humanoid in robotics are presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.435-449
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• 2023

The state-of-the-art video-based point cloud compression(V-PCC) has a high efficiency of compressing 3D point cloud by projecting points onto 2D images. These images are then padded and compressed by High-Efficiency Video Coding(HEVC). Pixels in padded 2D images are classified into three groups including origin pixels, padded pixels and unoccupied pixels. Origin pixels are generated from projection of 3D point cloud. Padded pixels and unoccupied pixels are generated by copying values from origin pixels during image padding. For padded pixels, they are reconstructed to 3D space during geometry reconstruction as well as origin pixels. For unoccupied pixels, they are not reconstructed. The rate distortion optimization(RDO) used in HEVC is mainly aimed at keeping the balance between video distortion and video bitrates. However, traditional RDO is unreliable for padded pixels and unoccupied pixels, which leads to significant waste of bits in geometry reconstruction. In this paper, we propose a new RDO scheme which takes 3D-Distortion into account instead of traditional video distortion for padded pixels and unoccupied pixels. Firstly, these pixels are classified based on the occupancy map. Secondly, different strategies are applied to these pixels to calculate their 3D-Distortions. Finally, the obtained 3D-Distortions replace the sum square error(SSE) during the full RDO process in intra prediction and inter prediction. The proposed method is applied to geometry frames. Experimental results show that the proposed algorithm achieves an average of 31.41% and 6.14% bitrate saving for D1 metric in Random Access setting and All Intra setting on geometry videos compared with V-PCC anchor.

• International Journal of Aeronautical and Space Sciences
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• 제14권1호
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• pp.30-45
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• 2013

The present work focuses on the unsteady aerodynamics and aeroelastic properties of a small-medium sized wind-turbine blade operating under ideal conditions. A tapered/twisted blade representative of commercial blades used in an experiment setup at the National Renewable Energy Laboratory is considered. The aerodynamic loads are computed using Computational Fluid Dynamics (CFD) techniques. For this purpose, FLUENT$^{(R)}$, a commercial finite-volume code that solves the Navier-Stokes and the Reynolds-Averaged Navier-Stokes (RANS) equations, is used. Turbulence effects in the 2D simulations are modeled using the Wilcox k-w model for validation of the CFD approach. For the 3D aerodynamic simulations, in a first approximation, and considering that the intent is to present a methodology and workflow philosophy more than highly accurate turbulent simulations, the unsteady laminar Navier-Stokes equations were used to determine the unsteady loads acting on the blades. Five different blade pitch angles were considered and their aerodynamic performance compared. The structural dynamics of the flexible wind-turbine blade undergoing significant elastic displacements has been described by a nonlinear flap-lag-torsion slender-beam differential model. The aerodynamic quasi-steady forcing terms needed for the aeroelastic governing equations have been predicted through a strip-theory based on a simple 2D model, and the pertinent aerodynamic coefficients and the distribution over the blade span of the induced velocity derived using CFD. The resulting unsteady hub loads are achieved by a first space integration of the aeroelastic equations by applying the Galerkin's approach and by a time integration using a harmonic balance scheme. Comparison among two- and three- dimensional computations for the unsteady aerodynamic load, the flap, lag and torsional deflections, forces and moments are presented in the paper. Results, discussions and pertinent conclusions are outlined.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.324-335
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• 2024

The container package type sealed water electrolysis production system installs mechanical balance of plant and electrical balance of plant as an integrated unit to enable independent operation within the package module. The auxiliary equipment required to operate the water electrolysis system must be integrated to reduce the installation area and shorten the installation time. At this time, as leak risk factors are placed in a dense space, when a hydrogen gas leak accident occurs, it can have a mutual influence on other adjacent facilities, so it contains various risk factors. In this study, when a gas leak occurs in a container packaged water electrolysis system, possible sources of leakage in the system according to the KS C IEC 60079-10-1:2015 and KGS GC101 standards were identified, and the leak rate and leak characteristics were calculated. did. The hazardous area and its range were calculated according to ventilation and dilution characteristics. In order to optimize ventilation characteristics, design of experiment was used to analyze the influence to evaluate the adequacy of ventilation, and overseas ventilation standards were analyzed and compared. In addition, the optimal ventilation structure and characteristics of the container packaged water electrolysis system were presented according to the results of the experimental design method.

• 한국항해항만학회지
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• 제28권6호
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• pp.531-539
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• 2004

본 논문에서는 다양한 종류와 다양한 크기의 화물에 대해 3차원 적재 방법으로서 휴리스틱 기법을 이용한 해법을 제안하였다. 먼저, 컨테이너 비용을 적재비용, 수송비용 및 처리비용의 합으로 나타내었으며, 화물 간 우선순위 및 화물 내에서의 개수 간 우선순위를 적용하였다. 주어진 화물을 적재 공간 및 중량을 만족하면서 전체 컨테이너 비용을 최소화하는 컨테이너 종류 및 개수의 순위를 산출하였으며, 이때 컨테이너 개수는 사용자의 입장에서 1∼10순위 중 하나를 선택할 수 있도록 하였다. 적재 시 화물의 팔레타이저 및 디팔레타이져로서 컨테이너 내의 공간 이용률을 극대화시켰다. 마지막으로 컨테이너의 무게 균등화를 고려하여 취급중의 화물의 무게 불균등으로 인한 화물의 손상을 방지하였다. 제안된 휴리스틱 기법을 프로그램 언어를 이용한 시뮬레이션을 통해 그 유효성을 증명하였다.

• 약학회지
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• 제40권5호
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• pp.550-557
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• 1996

One of therapeutics in liver disease (morbus wilson) is D-penicillamin (D-pen: D-3-mercapto-valin). Especially the cross-linking of collagen molecules could be inhibited by D-pe n in extracellular space. In this study we investigated the antifibrotic effects of D-pen in rats that were induced the liver fibrosis by bile duct ligation and scission (BDL/S). Rats were treated for 4 weeks with D-pen after BDL/S operation or sham operation. The balance between fibrogenesis-marker (PNIIIP) and the fibrolysis-maker (PNIVP) were observed in sera by RIA (radioimmunoassay), and the parameter of collagen deposition in liver tissue (hydroxyproline: HYP) was measured by colorimetry. The weight of liver in BDL/S operated group was increased significantly in compared with sham operation group (15.2g${\pm}$1.1, vs 11.9g${\pm}$3.9: p<0.005, p<0.05). The rats group treated by D-pen showed the lower level of PNIIIP (6.7ng/ml${\pm}$1.5, vs 9.5ng/ml${\pm}$2.8) and the higher value of PIVCP (14.0ng/ml${\pm}$1.9, vs 7.9ng/ml${\pm}$1.5) in sera that compared to untreated rats. The content of HYP was decreased by 141% in BDL/S with D-pen treated group than that of it in BDL/S group. No correlation was revealed between collagen parameters in sera and HYP in liver tissue of BDL/S operated and D-pen treated rats. The group treated with D-pen showed the lower value of clinical biochemistry parameters (GOT: glutamate oxalacetate transaminase, Total-Bilirubin) in compared with only BDL/S operated rats, but the value of GPT (glutamate pyruvate transaminase) and Alkaline phosphatase in two BDL/S groups was nearly same. In the histological finding, we observed mild bile duct proliferation, weak inflammation and fibrosis in BDL/S with D-pen treated group, but BDL/S operated group showed the formation of septum (island of hepatocytes), massive bile duct proliferation. This result represents that the BDL/S operation induces liver fibrosis (cirrhosis) in 4 weeks, and D-pen inhibits the synthesis of collagen weakly and stimulates the degradation of collagen in the extracellular space. We conclude that the monitoring of PNIIIP, PIVCP in sera is useful parameter for screening of antifibrotic effect, and D-pen delay the liver fibrosis.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.75-82
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• 2002

A simultaneous optimal design problem of structural and control systems is discussed by taking a 3-D truss structure as an object. We use descriptor forms for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. We consider a minimum weight design problem for structural system and disturbance suppression problem for the control system. The structural objective function is the structural weight and the control objective function is $H_{\infty}$ norm from the disturbance input to the controlled output in the closed-loop system. The design variables are cross sectional areas of the truss members. The conditions for the existence of controller are expressed in terms of linear matrix inequalities (LMI) By minimizing the linear sum of the normalized structural objective function and control objective function, it is possible to make optimal design by which the balance of the structural weight and the control performance is taken. We showed in this paper the validity of simultaneous optimal design of structural and control systems.

• 한국운동역학회지
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• 제23권4호
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• pp.369-376
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• 2013

The purposes of this study were to assess dynamic stability toward pelvis-spine column distortion during running and to compare the typical three-dimensional angular kinematics of the trunk motion; cervical, thoracic, lumbar segment spine and the pelvis from the multi-segmental spine model between exercise group and non-exercise group. Subjects were recruited as exercise healthy women on regular basis (group A, n=10) and non-exercise idiopathic scoliosis women (group B, n=10). Data was collected by using a vicon motion capture system (MX-T40, UK). The pelvis, spine segments column and lower limbs analysiaed through the 3D kinematic angular ROM pattern. There were significant differences in the time-space variables, the rotation motion of knee joint in lower limbs and the pelvis variables; obliquity in side bending, inter/outer rotation in twisting during running leg movement. There were significant differences in the spinal column that is lower-lumbar, upper-lumbar, upper-thoracic, mid-upper thoracic, mid-lower thoracic, lower thoracic and cervical spine at inclination, lateral bending and twist rotation between group A and group B (<.05, <.01 and <.001). As a results, group B had more restrictive motion than group A in the spinal column and leg movement behaved like a 'shock absorber". And the number of asymmetry index (AI) showed that group B was much lager unbalance than group A. In conclusion, non-exercise group was known to much more influence the dynamic stability of equilibrium for bilateral balance. These finding suggested that dynamic stability aimed at increasing balance of the trunk ROM must involve methods and strategies intended to reduce left/right asymmetry and the exercise injury.

• 한국터널지하공간학회 논문집
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• 제16권2호
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• pp.213-224
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• 2014

최근, tunnel boring machine (TBM)을 이용한 도심지 지중 전력구 터널 건설이 증가하고 있다. 쉴드 TBM을 이용한 기계화 터널 굴착 공법은 재래식 공법에 비해 지반침하를 최소화 하고 발파에 의한 진동을 줄일 수 있는 장점이 있다. 국내에서는 earth pressure balance(EPB) 쉴드 TBM이 주로 사용되고 있다. 그러나 전력구 터널 굴착을 위한 쉴드 TBM 공법이 증가함에도 불구하고, 전력구 쉴드 TBM 터널의 거동 분석에 관한 연구는 미비한 실정이다. 본 연구에서는 후방주입 거리에 따른 전력구 쉴드 TBM 터널의 거동 특성을 분석하고, 굴착면 지반 손실과 후방주입 거리와의 상관관계를 도출하고자 한다. 쉴드 TBM을 이용한 터널 굴착은 3D FEM을 이용하여 시뮬레이션 하였다. 뒷채움 그라우트가 설치되는 거리의 변화에 따른 축력, 전단력, 휨 모멘트와 같은 단면력을 검토하고 지표면에서의 연직 변위를 분석하였다. 또한, 유한요소해석으로 얻어진 결과와 안정성 분석에 기초하여, 지반과 터널 구조물의 안정성을 확보할 수 있는 뒷채움재 주입시기를 결정할 수 있다.

• 한국주거학회논문집
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• 제22권1호
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• pp.105-114
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• 2011

There are various kinds of Large-Scale apartment sites in Seoul. There are more households in apartment sites than single family houses. Nowadays, it is easy to find a lot of apartment sites built in the style of a high rise building. On the matter of space, a building is influenced by the buildings near it. The influence a building has to another is different in both qualitative and quantitative ways. Therefore, in the case of apartment sites, the environmental surroundings of each household is affected by the nearby buildings. For these reasons, the environment is having more and more influence on the price of each household in apartment sites. This paper has defined Sunshine and Sky as the major environmental elements. In order to be analyzed, they have to be measurable. Thus, there are two types of variables in environmental surrounding of apartment sites, -the Duration of Sunshine and the possible amount of visible Sky- the significant variables which influence the housing price. This paper deals with the relationship between the possible duration of sunshine and the possible amount of sky a household is visible to. It focused on 62 different apartment sites which were built after 1990. It is based on the 3-dimensional Geographic Information System & Computer Aided Engineering for analyzing the sunshine simulation and the viewing simulation. This paper will be helpful for designing the apartment sites considering the balance between sunshine and sky.