• Geomechanics and Engineering
• /
• 제16권4호
• /
• pp.449-461
• /
• 2018

The load sharing ratio (${\alpha}_{pr}$) of piles is one of the most common problems in the preliminary design of piled raft foundations. A series of 3D numerical analysis are conducted so that special attentions are given to load sharing characteristics under varying conditions, such as pile configuration, pile diameter, pile length, raft thickness, and settlement level. Based on the 3D FE analysis, influencing factors on load sharing behavior of piled raft are investigated. As a result, it is shown that the load sharing ratio of piled raft decreases with increasing settlement level. The load sharing ratio is not only highly dependent on the system geometries of the foundation but also on the settlement level. Based on the results of parametric studies, the load sharing ratio is proposed as a function of the various influencing factors. In addition, the parametric analyses suggest that the load sharing ratios to minimize the differential settlement of piled raft are ranging from 15 to 48% for friction pile and from 15 to 54% for end-bearing pile. The recommendations can provide a basis for an optimum design that would be applicable to piled rafts taking into account the load sharing characteristics.

• 대한의용생체공학회:의공학회지
• /
• 제30권1호
• /
• pp.10-17
• /
• 2009

Accurate electroencephalography (EEG) forward calculation is of importance for the accurate estimation of neuronal electrical sources. Conventional studies concerning the EEG forward problems have investigated various factors influencing the forward solution accuracy, e.g. tissue conductivity values in head compartments, anisotropic conductivity distribution of a head model, tessellation patterns of boundary element models, the number of elements used for boundary/finite element method (BEM/FEM), and so on. In the present paper, we investigated the influence of modeling errors in the boundary element volume conductor models upon the accuracy of the EEG forward solutions. From our simulation results, we could confirm that accurate construction of boundary element models is one of the key factors in obtaining accurate EEG forward solutions from BEM. Among three boundaries (scalp, outer skull, and inner skull boundary), the solution errors originated from the modeling error in the scalp boundary were most significant. We found that the nonuniform error distribution on the scalp surface is closely related to the electrode configuration and the error distributions on the outer and inner skull boundaries have statistically meaningful similarity to the curvature distributions of the boundary surfaces. Our simulation results also demonstrated that the accumulation of small modeling errors could lead to considerable errors in the EEG source localization. It is expected that our finding can be a useful reference in generating boundary element head models.

• 대한기계학회논문집A
• /
• 제27권5호
• /
• pp.724-733
• /
• 2003

Fatigue design rules for welds in the ASME Boiler and Pressure Vessels Code are based on the use of Fatigue Strength Reduction Factors(FSRF) against a code specified fatigue design curve generated from smooth base metal specimens without the presence of welds. Similarly, stress intensification factors that are used in the ASME B3l.1 Piping Code are based on component S-N curves with a reference fatigue strength based on straight pipe girth welds. But the determination of either the FSRF or stress intensification factor requires extensive fatigue testing to take into account the stress concentration effects associated with various types of component geometry, weld configuration and loading conditions. As the fatigue behavior of welded joints is being better understood, it has been generally accepted that the difference in fatigue lives from one type of weld to another is dominated by the difference in stress concentration. However, general finite element procedures are currently not available for effective determination of such stress concentration effects. In this paper, a mesh-insensitive structural stress method is used to re-evaluate the S-N test data, and then more effective method is proposed for pressure vessel and piping fatigue design.

• 대한족부족관절학회지
• /
• 제12권1호
• /
• pp.86-92
• /
• 2008

Purpose: To evaluate the safety and prognostic factors of intramedullary nailing of distal tibia fractures in terms of function and symptoms of the ankle joint. Materials and Methods: We retrospectively analyzed 22 distal tibial fractures with intramedullary nailing. The mean duration of follow-up was 43 months. We reviewed medical records to describe each case. We measured radiographic parameters such as fracture configuration, arthritic change of the ankle joint and status of reduction. We also assessed clinical results by AOFAS ankle hind foot scoring system, degree of pain by VAS and range of motion to find out prognostic factors for functional result of the ankle joint. Results: Bone healing was obtained in all cases without any wound complications. Mean AOFAS ankle score was 94. There were 4 cases with mild (VAS<3/10) ankle pain and 2 cases with mild limitation of ankle motion. The comminution of fracture had a significant relationship with delayed angular deformity of ankle joint (p=0.032). There was no other significant parameter affecting ankle joint function except the location of nail-end. Conclusion: Intramedullary nailing in distal tibia fracture is a safe and effective procedure. But further study may need to evaluate the relationship between the position of nail-end and the function of ankle joint.

• 한국군사과학기술학회지
• /
• 제18권5호
• /
• pp.594-601
• /
• 2015

The purpose of this research is to propose a maintenance support system for deciding assembly sequence of the product and appropriate tools that are used to assembly and disassembly of parts in the product when geometric properties of the product. The digital maintenance system (DMS) is developed to generate the maintenance guideline and the initial experiment is conducted especially for an underwater weapon system with cylindrical structure. DMS considers four factors to find the efficient assembly and disassembly procedure automatically: (1) assembly tree, (2) properties of each part, (3) distance from the center of the product, and (4) volume. Based on the factors, DMS simulate the movement of each tool virtually and the properties of tools are investigated to find an appropriate tool for using assembly and disassembly of each part in the product. The proposed approach integrates modeling, simulation, data configuration, and virtual reality to allow a development of preliminary maintenance guidance.

• 대한기계학회논문집
• /
• 제9권1호
• /
• pp.71-80
• /
• 1985

본 연구에서는 이중관 열교환기의 내관의 바깥 벽면에 반지 형태의 원형돌기 를 부착하여 굵기와 피치를 변화시키면서 압력손실과 열전달계수의 변화를 실험적으로 고찰하였다.

• Ocean Systems Engineering
• /
• 제8권3호
• /
• pp.313-327
• /
• 2018

Meeting the touchdown point (TDP) target box is one of the challenges during catenary riser installation, especially for deep water or ultra-deep water riser systems. TDP location mismatch compared to the design can result in variation of riser configuration, additional hang-off misalignment, and extra bending loads going into the hang-off porch. A good understanding of the key installation parameters can help to minimize this mismatch, and ensure that the riser global response meets the design criteria. This paper focuses on investigating the potential factors that may affect the touchdown point location, and addressing the challenges both in the design stage and during installation campaign. Conventionally, the vessel offset and current are the most critical factors which may affect the TDP movement during installation. With the offshore exploration going deeper and deeper in the sea (up to 10,000ft), other sources such as the seabed slope and seabed soil stiffness are playing an important role as well. The impacts of potential sources are quantified through case studies for steel catenary riser (SCR) and lazy wave steel catenary riser (LWSCR) in deep water application. Investigations through both theoretical study and numerical validation are carried out. Furthermore, design recommendations are provided during execution phase for the TDP mismatch condition to ensure the integrity of the riser system.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.622-627
• /
• 2001

The object of this paper is to compare stress intensity factor that be calculated by Raju-Newman's equation, finite element method, and Vessel INTegrity analysis inner flaws(VINTIN) program for longitudinal semi-elliptical cracks in cylindrical vessel under inner pressure. For this, three-dimensional finite-element analyses were performed to obtain the stress intensity factors for various surface cracks with t/R = 0.1. The finite element meshes were designed for various crack shapes with t/R of 0.1. The crack depth to thickness ratio, a/t, was set to 0.2 and 0.5 matching Raju-Newman's equation. The crack depth to length ratio, a/c, was set to 0.2 and 0.4 in the same way and 0.33 was added to extend the range of crack configuration. Finite Element Analyses(FEA) were performed using the commercial FEA program ABAQUS. The results showed that the Raiu-Newman solutions were about 4-10% lower than FEA's using symmetric model of one-eighth of a vessel and close to those of FEA using symmetric model or one-forth or a vessel. Ana VINTIN solutions were nearly equal to those or Raju-Newman.

• KIEAE Journal
• /
• 제9권1호
• /
• pp.23-30
• /
• 2009

A lightcourt design is typically used to address issues concerning aesthetics, feeling, and mood. From the view point of environmental aspect, as an ecological shaft space, it plays a key role in controlling inner quality. In particularly, the lightcourt concept allows the exploitation of daylighting by bring natural light into the center of the building, thus eliminating dark deep spaces. Additionally, the lightcourt shades the inner space in summer. The amount of light available at the base of the lightcourt depends on a number of factors; translucency of the top, reflectance and the geometry of the space. In this paper is to exemplify a lightcourt configuration with a sloped wall. It promises the maximized a sense of freedom and daylighting availability. It is a matter of course that the lightcourt with open-top plays a role as a light source for the adjacent space to the lightcourt. A series of lighting simulation provides performance data of daylighting with changing photometric factors. For the case that a skylight is not available, an electric lighting design with metal halide lamps has been established to create luminous ceiling. As expected, a sloped lightcourt with open-top exposes its superiority of daylighting source. Ancillary considerations to enhance of daylighting potential for the adjacent space have been issued with performance data.

• 한국추진공학회지
• /
• 제4권4호
• /
• pp.26-35
• /
• 2000

본 연구에서는 어떤 2차목을 가지는 축대칭 아음속/음속 이젝터 유동을 조사하기 위하여, 수치해석법을 이용하였다. 수치계산은 2차 정체실에서 이젝터 디퓨저 출구까지의 넓은 계산영역에 대하여, 압축성 Reynolds-Averaged Navier-Stokes방정식에 완전 음적 유한 체적법을 적용하였다. 축대칭 아음속/음속 이젝터 시스템에 대한 실용적 설계 인자를 얻기 위해서, 이젝터 목면적, 혼합부의 형상, 그리고 이젝터 목 길이를 변화시켜, 비교적 낮은 작동압력비로 운전되는 이젝터 유동특성의 변화를 조사하였다 계산 결과들은 2차 정체실의 진공성능에 미치는 작동압력비와 아젝터 형상의 영향을 조사하는데 활용되었다.