• Interaction and multiscale mechanics
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• 제1권1호
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• pp.1-31
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• 2008

The present paper presents multiscale modelling via coupling of the discrete and finite element methods. Theoretical formulation of the discrete element method using spherical or cylindrical particles has been briefly reviewed. Basic equations of the finite element method using the explicit time integration have been given. The micr-macro transition for the discrete element method has been discussed. Theoretical formulations for macroscopic stress and strain tensors have been given. Determination of macroscopic constitutive properties using dimensionless micro-macro relationships has been proposed. The formulation of the multiscale DEM/FEM model employing the DEM and FEM in different subdomains of the same body has been presented. The coupling allows the use of partially overlapping DEM and FEM subdomains. The overlap zone in the two coupling algorithms is introduced in order to provide a smooth transition from one discretization method to the other. Coupling between the DEM and FEM subdomains is provided by additional kinematic constraints imposed by means of either the Lagrange multipliers or penalty function method. The coupled DEM/FEM formulation has been implemented in the authors' own numerical program. Good performance of the numerical algorithms has been demonstrated in a number of examples.

• 한국분말재료학회지
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• 제24권3호
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.2075-2092
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• 2017

Person re-identification is to match pedestrians observed from non-overlapping camera views. It has important applications in video surveillance such as person retrieval, person tracking, and activity analysis. However, it is a very challenging problem due to illumination, pose and viewpoint variations between non-overlapping camera views. In this work, we propose a viewpoint invariant method for matching pedestrian images using orientation of pedestrian. First, the proposed method divides a pedestrian image into patches and assigns angle to a patch using the orientation of the pedestrian under the assumption that a person body has the cylindrical shape. The difference between angles are then used to compute the similarity between patches. We applied the proposed method to real-time global multi-object tracking across multiple disjoint cameras with non-overlapping field of views. Re-identification algorithm makes global trajectories by connecting local trajectories obtained by different local trackers. The effectiveness of the viewpoint invariant method for person re-identification was validated on the VIPeR dataset. In addition, we demonstrated the effectiveness of the proposed approach for the inter-camera multiple object tracking on the MCT dataset with ground truth data for local tracking.

• 한국컴퓨터그래픽스학회논문지
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• 제8권4호
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• pp.1-7
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• 2002

본 논문에서는 3차원 인체 형상 스캔 데이터로부터 팔, 다리형상을 복원하는 방법을 제시한다. 이 방법에서는 팔, 다리 스캔 데이터의 대략적인 형상을 나타내는 기반 곡면과 자세한 세부 현상을 나타내는 displacement 맵의 이중구조로 형상을 복원한다. 팔, 다리 부분의 스캔 데이터 형상은 골격을 따라 스윕하는 타원체로 근사되며, 이 타원체 스윕을 부드럽게 감싸는 envelope 곡면으로 기반 곡면을 생성한다. 타원체 스윕의 envelope 곡면은 빠른 계산을 위해 골격을 따라 추출되는 타원의 스윕 곡면으로 근사된다. 기반 곡면에 대한 스캔 데이터 점들의 displacement는 각 단면 타원으로의 매핑을 통해 스칼라 값으로 구해지며, 다단계 스플라인 함수를 이용하여 매개화된 displacement 맵을 구성한다. 이 과정에서 복원된 형상 위의 점들은 해당하는 타원체 상으로 매핑된다. 본 방법을 통하여 팔, 다리의 간결한 형상 표현을 추출할 수 있으며, 매핑된 타원체를 이용하여 형상을 빠르고 사실적으로 변형할 수 있다.

• 연구논문집
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• 통권27호
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• pp.127-139
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• 1997

투포원 연사기는 스핀들 1회전에 2회의 꼬임을 부가하여 실의 신축성과 인장강도 및 내마모성을 증가시키며, 특수한 목적의 의장사를 만드는 섬유기계이다. 스핀들 유니트는 고속 회전중에 안정화된 운동이 지속되도록 구조설계가 요구되는 핵심장치로서 스핀들 유니트의 동특성 해석은 고속 스핀들 유니트설계의 최적화를 도모할 수 있을 것이다. 스핀들 유니트는 블레이드와 로타리 디스크로 구성되어 있으며, 스핀들 축에 대하여 회전체 형상을 유지 하고 있다. 동특성 해석을 수행하기 위하여 전달 매트릭스 해석법을 정의하고 해석용 프로그램인 SPINDLE을 이용하여 비틀림과 굽힘 고유진동수를 해석하였으며, 운전회전수에서 변위모우드를 분석하였다.

• 한국기계가공학회지
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• 제13권1호
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• pp.107-114
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• 2014

A friction hinge system which moves without power was designed and developed using the principle of friction force, which is caused by interference between the inner diameter of a silicon cap and the outer diameter of a cylindrical roller bearing with one-way rotation in a counterclockwise direction. The system was applied to the lid of buffet ware, which moved up by external force and moved down by gravitational force. However, design conditions which included a rotation angle of the hinge of more than 80 degrees and a closing time of more than 20 seconds were required when the lid of the buffet ware closed due to gravitational force. The design safety of the friction hinge body connected to the lid of the buffet ware from the hinge system was checked on the basis of structural, fatigue and thermal analyses. The material of the shaft, cap and flange among the hinge elements was changed to polyethylene from steel to reduce the weight of the friction hinge system. An injection molding simulation was performed and injection molds of the shaft, cap and flange were created. The weight of the hinge system was decreased from 805g to 219g.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.463-471
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• 2013

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.

• 대한가정학회지
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• 제36권10호
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• pp.119-130
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• 1998

This is on the dance costume of ancient Greece. The present study classified the characteristics of Greek dance and dance costume according to the silhouette, quality of material, color and ornaments. Materials of the study are the pictures and figures presented in literatures, sculptures, crockeries, murals, coins. The dances of Greece can be classified into religious dance, educational dance, recreational dance, dramatic dance and various forms of dance on each dances were developed. Especially, it is the greatest character that Greeks gave dances educational value and created composit art including song, lines and dance. As dance costume, Himation, Chiton, Chlamys which Greeks generally wore were widely worn. Also, the beauty of dance costume was maximized by the changes of basic costumes and development of various ways of wearing. Especially, professional dancers wore costumes shorter than knee-length ones forming a A-line silhouette different from a cylindrical one. Thin cloth revealing body silhouette such as fiax hemp, linen, silk were used as materials of dance costumes. As for colors, white was mainly used, But orange, blue and green were used, too. They wore band, scarf, bonnet on the head and seldom used any ornaments except for fibula. They wore the same sandals which Greeks wore, Crepis, front-heeled shoes which is thought to be the origin of modern ballet shoes for the technique of toe in dance. As mentioned above, as the dance costume of Greece were mainly worn as the similar forms of the dance costume of Greeks, various forms of costumes were worn with the development of dance and bold ways of wearing and silhouette were developed unlike the costume of common people.

• Smart Structures and Systems
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• 제16권3호
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• pp.479-496
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• 2015

In this work, a novel artificial circular muscle based on shape memory alloy (S.M.A.) is proposed. The design is inspired from the natural circular muscles found in certain organs of the human body such as the small intestine. The heating of the prestrained SMA artificial muscle will induce its contraction. In order to measure the mechanical work provided in this case, the muscle will be mounted on a silicone rubber cylindrical tube prior to heating. After cooling, the reaction of the rubber tube will involve the return of the muscle to its prestrained state. A finite element model of the new SMA artificial muscle was built using the software "ABAQUS". The SMA thermomechanical behavior law was implemented using the user subroutine "UMAT". The numerical results of the finite element analysis of the SMA muscle are presented to shown that the proposed design is able to mimic the behavior of a natural circular muscle.

• Journal of Plant Biology
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• 제16권1_2호
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• pp.1-5
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• 1973

Six young trees of Alnus tinctoria grown in isolation, each having different growing stage, were selected and the surface area of their roots, stems and leaves was determined. Each of the roots of more than 0.2mm in diameter and stems was cut at intervals of 10cm and their surface area was calculated with 2$\pi$rl from the average diameter (2r) of both sections (upper and lower) by making cylindrical estimation of the cut pieces. The leaf area measured was only one side area, and the volume of cut piece and amount of dry matter of each organ were also measured. The percentage to the surface area of the whole plant body by each organ was 4-12% in root, 7-9% in stem and 69-89% in leaf, respectively. There was relatively a little individual difference. However, the surface area ratios of root and stem showed a slightly increasing tendency while that of leaf decreasing according to the growing stage. The ratio of sum leaf area index (LAIi) was 2.3-4.0$m^2$/$m^2$-and that of the surface area index(SaIi) was 0.16-0.33$m^2$/$m^2$, respectively. It has been known that the stem surface area(SAI) to the leaf area index(LAI) is within the range of 31-53%, but the SAIi is within the range of 8-11% of the LAIi.