• Journal of Mechanical Science and Technology
• /
• 제14권1호
• /
• pp.84-92
• /
• 2000

A new bounce back boundary method of the second order in error is proposed for the lattice Boltzmann fluid simulation. This new method can be used for the arbitrarily irregular lattice geometry of a non-slip boundary. The traditional bounce back boundary condition for the lattice Boltzmann simulation is of the first order in error. Since the lattice Boltzmann method is the second order scheme by itself, a boundary technique of the second order has been desired to replace the first order bounce back method. This study shows that, contrary to the common belief that the bounce back boundary condition is unilaterally of the first order, the second order bounce back boundary condition can be realized. This study also shows that there exists a generalized bounce back technique that can be characterized by a single interpolation parameter. The second order bounce back method can be obtained by proper selection of this parameter in accordance with the detailed lattice geometry of the boundary. For an illustrative purpose, the transient Couette and the plane Poiseuille flows are solved by the lattice Boltzmann simulation with various boundary conditions. The results show that the generalized bounce back method yields the second order behavior in the error of the solution, provided that the interpolation parameter is properly selected. Coupled with its intuitive nature and the ease of implementation, the bounce back method can be as good as any second order boundary method.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.776-777
• /
• 2017

고체 추진제의 성능을 계산하기 위해서는 그레인 burn-back 해석 과정이 필요하다. 기존의 그레인 burn-back 해석은 level set method를 사용하였으나 표면 이동 해석에서 문제가 발생 하였다. 이에 본 연구에서는 face offsetting method를 적용하여 표면 이동 해석을 수행 하였다. 해석 결과, face offsetting method가 그레인 burn-back 해석에 유용한 방법임을 확인 하였다.

• 한국지반신소재학회논문집
• /
• 제10권2호
• /
• pp.55-66
• /
• 2011

본 논문에서는 Back-to-Back(BTB) 보강토 옹벽의 파괴메커니즘에 관한 연구내용을 다루었다. 이를 위해 모형실험과 불연속체 해석(Discrete Element Method, DEM)을 도입한 수치해석을 수행하였다. 먼저 축소모형실험에서는 일반적으로 시공되는 Back-to-Back 보강토 옹벽을 1/10로 축소하여 1-g 모델을 구축한 후 자중만으로 파괴에 도달하도록 하였으며 보강재의 길이변화에 따른 파괴 메커니즘을 고찰하였다. 아울러 모형실험 결과를 토대로 검증된 DEM 해석모델을 이용하여 다양한 시공조건에 대한 해석을 수행하여 BTB 옹벽의 폭 및 보강재 길이에 따른 파괴 메커니즘을 고찰하고 그 결과를 현재 적용되는 FHWA 설계기준과 비교하였다.

• 여성건강간호학회지
• /
• 제10권1호
• /
• pp.8-14
• /
• 2004

Purpose: The purpose of this study was to look into back pain, pain disability, labour pain, and related areas of pain experienced by postpartum women. Method: A survey about pain including a Visual Analogue Scale (VAS), Oswestry pain disability, and pain drawing was used in a descriptive research method on 98 women 2-3 days after delivery. Result: 57.1% of those surveyed reported experiencing back pain before pregnancy. 75.5% reported experiencing back pain during pregnancy. The average starting time of back pain for pregnant women was 2.9 months into pregnancy. 48.8% reported the most severe back pain in the last trimester of pregnancy, while most women complained of left and right pubic pain and lumbar area pain during pregnancy. Statistical relations were calculated and menstrual symptoms (F=5.938, p=0.004), back pain prior to pregnancy (F=4.714, p=0.000), back pain during pregnancy (F=-3.429, p=0.001), and back pain disability prior to pregnancy (F=-1.994). Conclusion: There is a relation in postpartum women's back pain between back pain prior to pregnancy and back pain during pregnancy. Pelvic examinations early in pregnancy can determine if back pain will change for the worse or relapse. Therefore, the application of a pain relieving nursing intervention is needed.

• 한국추진공학회지
• /
• 제23권4호
• /
• pp.81-91
• /
• 2019

고체 로켓 모터 성능을 계산하기 위해 Face offsetting method를 사용하여 3차원 그레인 burn-back 해석을 수행하였다. 그레인 연소 형상 해석은 표면의 이동을 계산하는 이동 경계면 문제이다. 기존 연구에서는 다양한 이동 경계면 해석 기법이 그레인 burn-back 해석에 적용되었으나 결과가 불완전했다. 이에 본 연구에선 face offsetting method를 사용한 그레인 burn-back 해석 모듈을 개발하였다. Face offsetting method는 기존 해석 기법의 장점을 조합하여 강건하고 정밀한 이동 경계면 해석을 수행한다. 해석 결과, face offsetting method가 그레인 burn-back 해석에 유용함을 검증하였다.

• Geomechanics and Engineering
• /
• 제36권1호
• /
• pp.83-97
• /
• 2024

It is important to make reasonable prediction about the long-term deformation of high rockfill geostructures. However, the deformation is usually underestimated using the rockfill parameters obtained from laboratory tests due to different size effects, which make it necessary to identify parameters from in-situ monitoring data. This paper proposes a novel hybrid back-analysis method with a modified objective function defined for the time-dependent back-analysis problem. The method consists of two stages. In the first stage, an improved weighted average method is proposed to quickly narrow the search region; while in the second stage, an adaptive response surface method is proposed to iteratively search for the satisfactory solution, with a technique that can adaptively consider the translation, contraction or expansion of the exploration region. The accuracy and computational efficiency of the proposed hybrid back-analysis method is demonstrated by back-analyzing the long-term deformation of two high embankments constructed for airport runways, with the rockfills being modeled by a rheological model considering the influence of stress states on the creep behavior.

• 한국추진공학회지
• /
• 제18권3호
• /
• pp.40-47
• /
• 2014

우주발사체 최적 설계에 사용될 내탄도 해석 코드를 위한 그레인 Burn-back 연구를 수행하였다. 그레인 Burn-back은 내탄도 해석에 필수적인 그레인의 연소면적의 계산에 사용된다. 최적 설계에 사용될 내탄도 해석 코드는 설계 변수의 변경 및 반복계산을 통해 요구 성능을 만족할 때 까지 반복 계산을 수행한다. 따라서 내탄도 해석에 적용될 Burn-back 해석기법은 설계 변수의 변경이 용이하며 계산시간이 짧아야 한다. 이에 본 연구에서는 Analytical Method를 이용하여 Burn-back 해석코드를 개발하였으며, 그레인 형상에 대해 기하학적 변수를 선정 및 형상 변화에 대해 정리하였다. 개발된 코드는 Numerical Method로부터 산출된 값과 비교하여 검증을 수행하였다.

• 복식문화연구
• /
• 제28권1호
• /
• pp.1-14
• /
• 2020

This study is based on a representative body shape drawn from previous studies that classify adult male torso shapes. In this study, a design method is proposed by developing a tight-fit pattern that can be easily developed into various items and designs using the body surface development figure. This is obtained by converting the 3D body shape of the model representing the representative body shape. The specific design method was conducted as follows. Actual measurement values were used for waist back length, waist-to-hip length, shoulder length. The scye depth was determined as C/4-1.7 cm, and the front and back Interscye was set at (1/2 × actual measurements)-0.2 cm. The front-back neck breadth was set to (1/5 × base neck circumference)-1.3 cm and (1/5 × base neck circumference) cm. The front-back neck depth was set to (1/5 × base neck circumference)-1.2 cm and 3.5 cm. Front chest circumference was C/4-1 (front-back difference)cm; (1/4 × back chest circumference) was C/4 + 1 (front-back difference) + 0.3 (dart amount) cm. Front waist circumference was W/4-0.2 (front-back difference) + 2.2 (dart amount) cm; back waist circumference was W/4 + 0.2 (front-back difference) + 2.5 (dartamount) cm; front hip circumference was H/4 + 0.2 (ease) + 0.2 (front-back difference) cm; and back hip circumference was H/4 + 0.2 (ease)-0.2 (front-back difference) cm; Front droop was 1.6 cm. The newly developed tight-fit pattern is expected to be of great use as a basis for garment construction.

• 상하수도학회지
• /
• 제27권5호
• /
• pp.611-619
• /
• 2013

In this study, Back Tracing Calculation Method was developed to determine the leakage location and leakage amount. Previously developed determination method of monitoring location and newly developed Back Tracing Calculation Method were applied to the sample pipe network and real size pilot plant. After leakage was assumed in the pilot plant, leakage location and leakage amount could be traced by Back Tracing Calculation Method. From the results, it was found that Back Tracing Calculation Method can be applied for the leakage detection in water distribution system. Furthermore, this method can be applied for the pressure management or leakage detection as a pressure control method in water distribution system.

• 한국농공학회지
• /
• 제45권6호
• /
• pp.172-182
• /
• 2003

In this study, the back analysis was performed by means of stereo-net, plane failure and block failure method to collapsed fields among the rock slopes designed by standardized criterion, and the internal frictions from the back analysis were compared with those used to reinforcement design. It was concluded that in the result of the analysis by means of stereo net, plain failure and block failure methods, the internal frictions used to re-design of collapsed slope underestimated 10$^{\circ}$, 5$^{\circ}$ and 10$^{\circ}$ in average. At present, the internal friction on the design is used the experience value according to the state of weathering, but internal friction angle by the back analysis on collapsed slope with various methods were more reliable values than those from the present method. And it was concluded that re-design was made extravagantly because the internal friction used to re-design for reinforcement of the collapsed slope was less than back analysis.