• 한국산학기술학회논문지
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• 제17권1호
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• pp.544-552
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• 2016

본 연구는 다문화 청소년의 스트레스와 학교생활 적응 상태를 파악하고 자아존중감, 사회적 지원, 스트레스 대처에 따라 어떠한 변화가 나타나는 지를 확인하여 향후 다문화 청소년을 위한 프로그램 개발의 기초자료를 활용되고자 시도되었다. 이를 위해 구조방정식을 활용하여 다문화가정 청소년의 스트레스와 학교생활적응 간의 관계를 파악하고, 스트레스 대처, 사회적 지원, 자아존중감의 매개효과를 살펴보고자 하였다. 본 연구의 결과는 다음과 같다. 다문화가정 청소년의 스트레스는 사회적 지원과 자아존중감에는 음(-)의 영향을 미쳤다. 하지만 스트레스 대처는 통계적으로 유의한 영향이 발견되지 못했다. 이어서 분석한 스트레스 대처, 사회적 지원, 자아존중감은 모두 스트레스와 학교생활적응 간의 관계에서 정(+)의 매개효과가 있음이 나타났다.

• 화약ㆍ발파
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• 제33권4호
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• pp.14-24
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• 2015

근접발파진동이 흙막이 안정성에 미치는 영향을 알아보기 위해 3개 현장에서 시험발파를 시행하였다. 시험결과 동일거리의 지중에서 측정된 진동은 지표에서 측정된 진동의 10~52% 수준으로 작아 어스앵커 정착장 등 지중에 설치된 구조물은 지표에 있는 구조물에 비해 상대적으로 발파진동에 안전함을 확인하였다. 측정된 3개 현장의 지표 및 지중진동 PPV를 통합 회귀분석하여 진동추정식을 도출하였으며, 이를 활용 지중 및 지표에서 양생중인 콘크리트에 대해 양생시간별 허용진동기준을 만족하는 발파패턴별 최소이격거리를 산정하였다. 근거리 발파진동 측정, 흙막이 계측치 변화 확인, 구조물 변형여부 육안관찰을 통해 확인한 결과 특별히 흙막이 안정성에 불리한 불연속면이 발달하지 않는 한 지발당장약량 2.4kg 이하의 발파작업은 흙막이 안정성에 유의미한 영향을 미치지 않는 것으로 판단된다.

• 시큐리티연구
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• 제61호
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• pp.163-179
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• 2019

본 연구의 목적은 경비안전시스템 이용자들의 서비스품질이 기업이미지와 고객만족도에 미치는 영향을 분석하는데 있다. 이를 실증분석을 통해 확인하고자 전국적으로 이용자 200여명을 대상으로 2019년 5월 2일부터 6월 12일까지 약 40일 동안 설문조사를 실시하였다. 설문내용은 "서비스품질, 기업이미지, 고객만족도"로 구성하였다. 실증분석은 타당성과 중요도, 신뢰도, 연관성 분석을 중심으로 실행하였다. 설문조사를 통하여 탐색적요인 및 구조방정식 등을 추출하고자 SPSS WIN 18.0을 사용하였다. 연구 결과 경비안전시스템 이용자들은 서비스품질이 좋을수록 기업이미지가 좋아지고, 기업이미지가 좋을수록 고객만족도가 높아지는 것으로 나타났다. 또한 서비스품질이 좋을수록 고객만족도가 높아질 것으로 제시하였다. 따라서 각 경비안전시스템 업체들은 고객만족도 향상을 위해 서비스품질을 꾸준히 향상시켜 나가야 할 것이다.

• 한국강구조학회 논문집
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• 제23권2호
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• pp.229-236
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• 2011

본 연구는 폭두께비(W/T)에 따른 중심압축하중을 받는 SC(Steel Plate-Concrete)구조의 압축거동 특성을 파악하는 것이 주목적이다. SC구조는 전단 연결재를 갖는 샌드위치 강판 사이에 콘크리트를 타설하여 시공하는 구조이다. SC구조의 실험체는 폭두께비(W/T)가 1.60와 3.56인 실험체로 구분하였다. 실험을 통하여 다음과 같은 결과를 얻었다. SC구조 실험체의 파괴양상은 최대압축강도에 도달하기 전에 스터드와 스터드 사이 강판이 국부좌굴하고 콘크리트는 일부 균열 및 박리현상이 나타났다. 또한 SC구조 실험체의 최대압축강도는 기존 설계기준식(AISC 2005, ACI318-05 및 KBC 2005)에 의한 압축강도보다 거의 크게 나타났다. SC구조 실험체의 폭두께비(W/T)가 증가할수록 강판에 의한 SC구조 실험체의 콘크리트 구속효과는 감소하는 것으로 나타났다.

• 한국산업정보학회논문지
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• 제25권4호
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• pp.65-81
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• 2020

본 연구는 의료서비스 산업에서 역량을 의료기관 조직과 개인의 차원으로 분류하여 조직역량과 개인역량이 조직구성원들의 직무만족 및 업무수행에 미치는 영향 정도를 살펴보고자 하였다. 이를 위해 개인역량과 조직역량의 구성요인과 함께 직무만족, 업무수행에 대한 개념을 정립하고 이들간의 관계를 검증하여 의료기관에 필요한 역량이 무엇인지를 파악하였다. 본 연구는 국내의 한 의료기관에 근무하는 의사와 간호사 243명을 대상으로 하였으며, 설문 분석결과, 첫째, 조직역량은 직무만족 및 업무수행에 유의한 영향이 있는 것으로 나타났다. 둘째, 개인역량은 직무만족에 유의한 영향이 있는 것으로 나타났지만 업무수행에는 유의한 결과를 얻지 못했다. 셋째, 직무만족은 업무수행에 유의한 영향이 있는 것으로 나타났다. 이러한 결과는 의료기관 경영진 및 정책입안자에게 조직역량과 개인역량 개발의 중요성에 관한 기초적인 정보를 제공하였다.

• Earthquakes and Structures
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• 제13권4호
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• pp.353-363
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• 2017

The present study considers a multi-span continuous bridge, isolated by lead rubber bearing (LRB). Dynamic soilstructure interaction (SSI) is modelled with the help of a simplified, sway-rocking model for different types of soil. It is well understood from the literature that SSI influences the structural responses and the isolator performance. However, the abovementioned effect of SSI also depends on the earthquake ground motion properties. It is very important to understand how the interaction between soil and structure varies with the earthquake ground motion characteristics but, as far as the knowledge of the authors go, no study has been carried out to investigate this effect. Therefore, the objectives of the present study are to investigate the influence of earthquake ground motion characteristics on: (a) the responses of a multi span bridge (isolated and non-isolated), (b) the performance of the isolator and, most importantly, (c) the soil-structure interaction. Statistical analyses are conducted by considering 14 earthquakes which are selected in such a way that they can be categorized into three frequency content groups according to their peak ground acceleration to peak ground velocity (PGA/PGV) ratio. Lumped mass model of the bridge is developed and time history analyses are carried out by solving the governing equations of motion in the state space form. The performance of the isolator is studied by comparing the responses of the bridge with those of the corresponding uncontrolled bridge (i.e., non-isolated bridge). On studying the effect of earthquake motions, it is observed that the earthquake ground motion characteristics affect the interaction between soil and structure in such a way that the responses decrease with increase in frequency content of the earthquake for all the types of soil considered. The reverse phenomenon is observed in case of the isolator performance where the control efficiencies increase with frequency content of earthquake.

• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.363-383
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• 2018

One-dimensional (1D) models of incompressible flows, can be of interest for many applications in which fast resolution times are demanded, such as fluid-structure interaction of flows in compliant pipes and hemodynamics. This work proposes a higher-order 1D theory for the flow-field analysis of incompressible, laminar, and viscous fluids in rigid pipes. This methodology is developed in the domain of the Carrera Unified Formulation (CUF), which was first employed in structural mechanics. In the framework of 1D modelling, CUF allows to express the primary variables (i.e., velocity and pressure fields in the case of incompressible flows) as arbitrary expansions of the generalized unknowns, which are functions of the 1D computational domain coordinate. As a consequence, the governing equations can be expressed in terms of fundamental nuclei, which are invariant of the theory approximation order. Several numerical examples are considered for validating this novel methodology, including simple Poiseuille flows in circular pipes and more complex velocity/pressure profiles of Stokes fluids into non-conventional computational domains. The attention is mainly focused on the use of hierarchical McLaurin polynomials as well as piece-wise nonlocal Lagrange expansions of the generalized unknowns across the pipe section. The preliminary results show the great advantages in terms of computational costs of the proposed method. Furthermore, they provide enough confidence for future extensions to more complex fluid-dynamics problems and fluid-structure interaction analysis.

• Steel and Composite Structures
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• 제34권2호
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• pp.261-277
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• 2020

The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

• Geomechanics and Engineering
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• 제21권4호
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• pp.357-369
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• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.365-380
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• 2020

The focus of this paper is to develop an analytical approach based on an efficient shear deformation theory with stretching effect for bending stress analysis of cross-ply laminated composite plates subjected to transverse parabolic load and line load by using a new kinematic model, in which the axial displacements involve an undetermined integral component in order to reduce the number of unknowns and a sinusoidal function in terms of the thickness coordinate to include the effect of transverse shear deformation. The present theory contains only five unknowns and satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without using any shear correction factors. The governing differential equations and its boundary conditions are derived by employing the static version of principle of virtual work. Closed-form solutions for simply supported cross-ply laminated plates are obtained applying Navier's solution technique, and the numerical case studies are compared with the theoretical results to verify the utility of the proposed model. Lastly, it can be seen that the present outlined theory is more accurate and useful than some higher-order shear deformation theories developed previously to study the static flexure of laminated composite plates.