• Geomechanics and Engineering
• /
• 제24권6호
• /
• pp.505-518
• /
• 2021

The present paper has been carried out to understand the effects of impact loading on the rock tunnels, constructed in different region corresponding to varying unconfined compressive strength (UCS), through finite element method. The UCS of rockmass has substantial role in the stability of rock tunnels under impact loading condition due to falling rocks or other objects. In the present study, Dolomite, Shale, Sandstone, Granite, Basalt, and Quartzite rocks have been taken into consideration for understanding of the effect of UCS that vary from 2.85 MPa to 207.03 MPa. The Mohr-Coulomb constitutive model has been considered in the present study for the nonlinear elastoplastic analysis for all the rocks surrounding the tunnel opening. The geometry and boundary conditions of the model remains constant throughout the analysis and missile has 100 kg of weight. The general hard contact has been assigned to incorporate the interaction between different parts of the model. The present study focuses on studying the deformations in the rock tunnel caused by impacting load due to missile for tunnels having different concrete grade, and steel grade. The broader range of rock strength depicts the strong relationship between the UCS of rock and the extent of damage produced under different impact loading conditions. The energy released during an impact loading simulation shows the variation of safety and serviceability of the rock tunnel.

• 대한기계학회논문집A
• /
• 제24권11호
• /
• pp.2705-2712
• /
• 2000

In meshless methods some techniques to impose essential boundary conditions have been developed since the approximations do not satisfy Kronecker delta properties at nodal points. In this study, new scheme for imposing essential boundary conditions is developed. Weight functions are modified by multiplying with auxiliary weight functions and the resulting shape functions satisfy Kronecker delta property on the bound ary nodes. In addition, the resulting shape functions possess and interpolation features on the boundary segments where essential boundary conditions are prescribed. Therefore the essential boundary conditions can be exactly satisfied with the new method. More importantly, the impositions of essential boundary conditions using the present method is relatively easy as in finite element method. Numerical examples show that the method also retains high convergence rate comparable to Lagrange multiplier method.

• 한국농촌생활과학회지
• /
• 제5권1호
• /
• pp.31-41
• /
• 1994

The purpose of this study is to analyze the changes of rural housing conditions by comparing the general housing indicators of rural area and those of urban. For those purposes, the indicators that present the housing conditions are set up, and the changes of average housing conditions are analyzed by a region : Shis(cities), Ups, Myons. For the analysis, Population and Housing Census Report and related data were used. Rural housing conditions have become better since the 1960s in the aspect of quality. They are, however, relatively much worse than those of urban areas. The gap of housing conditions between urban and rural housing is big, especially in qualitative indicators, which are housing facilities. Quantitative indicators, which are housing supply rate and ownership rate, are better than urban conditions.

• 대한수학회논문집
• /
• 제16권2호
• /
• pp.265-275
• /
• 2001

In the previous paper we studied n-dimensional CR-submanifolds of (n-1) CR-dimension immersed in a complex projective space CP(sup)(n+p)/2, and especially determined such submanifolds under curvature conditions related to vertical direction; In the present article we determine such submanifolds under curvature conditions related to horizontal directions.

• 대한수학회지
• /
• 제46권6호
• /
• pp.1193-1206
• /
• 2009

C. Guenther studied the stability of DeTurck flows by using maximal regularity theory and center manifolds, but these arguments can not solve the stability of Ricci flows because the Ricci flow equation is not strictly parabolic. Recognizing this deficiency, the present paper considers and obtains the stability of Ricci flows, and of quasi-Ricci flows in view of some Killing conditions.

• 호남수학학술지
• /
• 제41권2호
• /
• pp.227-242
• /
• 2019

In the present paper, we derive several sufficient conditions for $Carath{\acute{e}}odory$ functions in the open unit disk ${\mathbb{D}}:=\{z{\in}{\mathbb{C}}:{\mid}z{\mid}<1\}$ under the constraint that the second coefficient of the function is preassigned. And, we obtain some sufficient conditions for strongly starlike functions in ${\mathbb{D}}$.

• 대한물리의학회지
• /
• 제7권4호
• /
• pp.459-469
• /
• 2012

PURPOSE: The purpose of the present study was to examine changes caused by asymmetric bag carrying methods to carry the bag with one shoulder only to plantar pressure during walking. METHODS: Twenty three normal adults without any gait problem participated in the present study. Experimental conditions used consisted of walking without carrying any bag(condition 1), walking wearing a bag on both shouders (condition 2), and walking wearing a bag on the right shoulder(condition 3) and the weight of the bag was set to 15% of each subject's body weight. All the subjects were instructed to participate in all experiments under these three conditions and plantar pressures were measured from the subjects' right and left feet using an F-scan system while the subjects were walking under the three conditions. To analyze the measured plantar pressure, the sole was divided into seven areas (Hallux, Toe, Met1, Met23, Met45, Mid foot and Heel) and maximum plantar pressures in individual areas were measured. RESULTS: The results of measurement of plantar pressures under three walking conditions did not show significant changes in any areas of the left and right feet except for the mid foot area of the right food. The asymmetry between the left and right feet was examined and the results showed significant differences only in area Met23 under condition 2 and did not show significant differences in any other areas. CONCLUSION: On comprehensively considering the results of the present study, it could be seen that asymmetric bag carrying did not have large effects on changes in plantar pressure during walking compared to symmetric carrying. The reason for this is considered to be posture adjusting mechanisms against load positions.

• 한국항공우주학회지
• /
• 제47권11호
• /
• pp.761-767
• /
• 2019

본 연구에서는 전산유체역학과 6자유도 운동 해석을 결합하여 사출 조건 변화에 따른 공중 발사 운동체의 초기 거동에 관한 해석이 수행되었다. 해석 결과를 실험 측정 데이터와 비교함으로써 해석 기법의 정확성을 검증하였다. 다양한 사출 조건에 대한 사출 안정성 해석이 수행되었으며, 사출 운동체의 초기 거동에 지배적인 영향을 미치는 주요 인자로써 운동체의 무게, 전방 및 후방 사출력의 크기를 고려하였다. 이들 인자의 변화 범위에 대한 운동체의 사출 안정성 반응 곡면이 도출되었다. 모든 조건에서 후방 사출력이 작용하지 않는 경우에는 운동체의 안정 사출이 불가한 것으로 나타났다. 또한 운동체의 무게가 감소될수록 불안정 사출 영역이 확대되었다.

• 한국산림과학회지
• /
• 제87권4호
• /
• pp.590-600
• /
• 1998

본 연구에서는 규범적 접근방법을 이용하여 무등산 도립공원의 주요 시설물에 대한 평가기준을 설정하고, 설정된 평가기준을 토대로 공원의 현 시설물 관리상태를 평가하였으며, 여기에서 발견된 문제점을 해결하기 위한 개선방안을 제시하였다. 데이터는 1996년 8월 중 무등산 도립공원에서 현지설문조사와 우편설문조사에 의하여 수집되었으며, 총 1,173명의 조사대상자 중 519명(44.2%)이 본 연구의 분석에 이용되었다. 결과에 따르면, 선정된 5개 지표항목 중 '쓰레기통 충분여부'와 '등산로 안내시설 충분여부'를 제외한 3개 지표항목(화장실 충분여부, 화장실 청결상태, 대중교통수단을 이용하기 위하여 기다려야 하는 시간)에서 현 상황이 명가기준보다 불량한 것으로 나타났다. '등산로 안내시설 충분여부'에 대한 현 상황은 평가기준과 동일하였다. 문제점이 있는 것으로 밝혀진 지표항목에 대해서는 이를 개선하기 위한 관리대안을 제시하였으며, 이러한 자료들이 공원 시설물관리를 위하여 어떻게 이용될 수 있을 것인가를 소개하였다.

• Steel and Composite Structures
• /
• 제25권6호
• /
• pp.693-704
• /
• 2017

In this research, a simple hyperbolic shear deformation theory is developed and applied for the bending, vibration and buckling of powerly graded material (PGM) sandwich plate with various boundary conditions. The displacement field of the present model is selected based on a hyperbolic variation in the in-plane displacements across the plate's thickness. By splitting the deflection into the bending and shear parts, the number of unknowns and equations of motion of the present formulation is reduced and hence makes them simple to use. Equations of motion are obtained from Hamilton's principle. Numerical results for the natural frequencies, deflections and critical buckling loads of several types of powerly graded sandwich plates under various boundary conditions are presented. The accuracy of the present formulation is demonstrated by comparing the computed results with those available in the literature. As conclusion, this theory is as accurate as other theories available in the literature and so it becomes more attractive due to smaller number of unknowns.