• 한국자기학회지
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• 제16권5호
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• pp.234-239
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• 2006

교환 결합력을 갖는 CoFe/MnIr 박막 시료에서 100 MHz$\sim$9 GHz의 주파수 범위에서 마이크로파 투자율을 측정하였으며, 이들 결과는 Landau-Lifshitz-Gilbert 이론을 사용하여 분석 하였다. 초기투자율 및 강자성 공명주파수는 CoFe의 두께 및 일방이방성에너지(unidirectional anisotropy)에 따라서 조절이 가능하며, 특히 공명주파수는 최대 20 GHz까지 조율이 가능하다. 따라서 마이크로파 대역에서 고투자율 및 저손실 특성을 갖는 CoFe/MnIr 재료는 수 GHz 대역에서 작동하는 마이크로파 부품에 적용 가능하다.

• 한국컴퓨터정보학회논문지
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• 제25권6호
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• pp.119-129
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• 2020

소프트웨어 개발은 다양한 프로세스 변동을 포함하기 때문에, 결정론적 이론 보다는 확률론적 이론에 더 영향을 많이 받는다. 확률론적 방식은 결정론적 방식보다 프로젝트 활동과 관련된 불확실을 고려하고, 예상되는 결과에 대해서 확률 분포로 접근하는 장점이 있다. 그러므로 소프트웨어 프로젝트를 성공하기 위해서는 확률 분포에 기반하여 범위, 규모, 비용, 공수, 일정 그리고 품질 목표를 체계적으로 관리해야 한다. 소프트웨어 규모 산정은 불확실성이 큰 개발 초기의 활동임에도 불구하고, LOC, COCOMO, FP, SLIM과 같은 결정론적 산정 방식으로 수행되고 있다. 본 연구에서는 확률적 분포 기반의 기능 점수 프로세스를 수립하고, 효과를 검증하기 위해 몬테카를로 시뮬레이션 기반의 자동차 전기전자 제어시스템 소프트웨어 개발에 적용한 사례를 제시한다. 본 연구 결과가 조직 내 기능 점수 프로세스를 수립하기 위한 가이드 및 관리자들의 정확한 의사결정 도구로 활용될 것으로 기대한다.

• 한국광학회지
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• 제14권6호
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• pp.613-622
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• 2003

반도체 와이어 본딩(wire-bonding) 조립공정에 사용되는 검사용 다중배치 현미경 광학계를 설계하였다. 2배와 6배에 공통으로 사용되는 대물부를 통과한 광선은 광분할 프리즘으로 둘로 나뉘고 각각의 결상부에 의하여 물체의 주변부는 2배, 물체의 중심부는 6배로 결상하게 한다. 이 때 리드프레임의 와이어 구조 때문에 $\pm$3 mm의 높이차가 있어서 대물부에서 물체까지의 거리가 서로 다르다. 이러한 단차에 ,의해 물체거리가 바뀌더라도 동일한 결상 배율로 선명하게 관찰하기 위해 결상부를 기계 보정식 줌 렌즈와 같이 비선형 궤적으로 이동시켜야 한다. 이 궤적을 구하기 위해 가우스 괄호를 사용해 비선형 연립방정식을 세우고 풀었다. 또한 각 렌즈 군의 굴절능과 군간 간격을 구하는 군별 기초 설계는 등가렌즈에 대한 3차 수차 이론을 사용하였으며, 최종적으로 최적화 기법을 통하여 이러한 현미경 광학계를 얻었다.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.603-619
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• 2018

In this research, an effective computational technique is carried out for nonlinear and post-buckling analyses of cracked imperfect composite plates. The laminated plates are assumed to be moderately thick so that the analysis can be carried out based on the first-order shear deformation theory. Geometric non-linearity is introduced in the way of von-Karman assumptions for the strain-displacement equations. The Ritz technique is applied using Legendre polynomials for the primary variable approximations. The crack is modeled by partitioning the entire domain of the plates into several sub-plates and therefore the plate decomposition technique is implemented in this research. The penalty technique is used for imposing the interface continuity between the sub-plates. Different out-of-plane essential boundary conditions such as clamp, simply support or free conditions will be assumed in this research by defining the relevant displacement functions. For in-plane boundary conditions, lateral expansions of the unloaded edges are completely free while the loaded edges are assumed to move straight but restricted to move laterally. With the formulation presented here, the plates can be subjected to biaxial compressive loads, therefore a sensitivity analysis is performed with respect to the applied load direction, along the parallel or perpendicular to the crack axis. The integrals of potential energy are numerically computed using Gauss-Lobatto quadrature formulas to get adequate accuracy. Then, the obtained non-linear system of equations is solved by the Newton-Raphson method. Finally, the results are presented to show the influence of crack length, various locations of crack, load direction, boundary conditions and different values of initial imperfection on nonlinear and post-buckling behavior of laminates.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.355-366
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• 2019

Self-centering wall (SCW) is a resilient and sustainable structural system which incorporates unbonded posttensioning (PT) tendons to provide self-centering (SC) capacity along with supplementary dissipators to dissipate seismic energy. Hysteretic energy dissipators are usually placed at two sides of SCWs to facilitate ease of postearthquake examination and convenient replacement. To achieve a good prediction for the skeleton curve of the wall, this paper firstly developed an analytical investigation on lateral load responses of self-centering walls with distributed vertical dampers (VD-SCWs) using the concept of elastic theory. A simplified method for the calculation of limit state points is developed and validated by experimental results and can be used in the design of the system. Based on the analytical results, parametric analysis is conducted to investigate the influence of damper and tendon parameters on the performance of VD-SCWs. The results show that the proposed approach has a better prediction accuracy with less computational effects than the Perez method. As compared with previous experimental results, the proposed method achieves up to 60.1% additional accuracy at the effective linear limit (DLL) of SCWs. The base shear at point DLL is increased by 62.5% when the damper force is increased from 0kN to 80kN. The wall stiffness after point ELL is reduced by 69.5% when the tendon stiffness is reduced by 75.0%. The roof deformation at point LLP is reduced by 74.1% when the initial tendon stress is increased from $0.45f_{pu}$ to $0.65f_{pu}$.

• 대한간호학회지
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• 제49권2호
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• pp.191-202
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• 2019

Purpose: Patient-centered care is a widely utilized concept in nursing and health care. However, the key components of patient-centered nursing have not yet been reported. Moreover, previous studies on patient-centered care have mostly focused on components of nursing rather than organizational factors. Therefore, a comprehensive understanding of influential factors of patient-centered care is required. Methods: The purpose of this study was to develop a theoretical model based on person-centered care theory, and the relevant literature and to test the developed model with covariance structure analysis in order to determine the causal paths among the variables. Results: The model fit indices for the hypothetical model were suitable for the recommended level (goodness of fit index=.87, standardized root mean residual=.01, root mean square error of approximation=.06, Tucker-Lewis index=.90, comparative fit index=.92, parsimonious normed fit index=.75). In this study, five of the six paths established in the initial hypothetical model were supported. The variables of teamwork, self-leadership, and empathy accounted for 56.4% of hospital nurses' patient-centered care. Among these, empathy was the strongest predictor of patient-centered care. Conclusion: These results suggest that it is necessary to use strategies to improve self-leadership and empathy. In addition to enhancing the personal factors of nurses, nursing organizations should strive for effective multidisciplinary cooperation with active support for patient-centered care and openness to change.

• Journal of Information Science Theory and Practice
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• 제9권2호
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• pp.1-17
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• 2021

Pseudo relevance feedback (PRF) is a powerful query expansion (QE) technique that prepares queries using the top k pseudorelevant documents and choosing expansion elements. Traditional PRF frameworks have robustly handled vocabulary mismatch corresponding to user queries and pertinent documents; nevertheless, expansion elements are chosen, disregarding similarity to the original query's elements. Word embedding (WE) schemes comprise techniques of significant interest concerning QE, that falls within the information retrieval domain. Deep averaging networks (DANs) defines a framework relying on average word presence passed through multiple linear layers. The complete query is understandably represented using the average vector comprising the query terms. The vector may be employed for determining expansion elements pertinent to the entire query. In this study, we suggest a DANs-based technique that augments PRF frameworks by integrating WE similarities to facilitate Arabic information retrieval. The technique is based on the fundamental that the top pseudo-relevant document set is assessed to determine candidate element distribution and select expansion terms appropriately, considering their similarity to the average vector representing the initial query elements. The Word2Vec model is selected for executing the experiments on a standard Arabic TREC 2001/2002 set. The majority of the evaluations indicate that the PRF implementation in the present study offers a significant performance improvement compared to that of the baseline PRF frameworks.

• 한국해양공학회지
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• 제34권6호
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• pp.406-418
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• 2020

In this study, a nonlinear wave simulation code is developed using a higher-order spectral (HOS) method. The HOS method is very efficient because it can determine the solution of the boundary value problem using fast Fourier transform (FFT) without matrix operation. Based on the HOS order, the vertical velocity of the free surface boundary was estimated and applied to the nonlinear free surface boundary condition. Time integration was carried out using the fourth order Runge-Kutta method, which is known to be stable for nonlinear free-surface problems. Numerical stability against the aliasing effect was guaranteed by using the zero-padding method. In addition to simulating the initial wave field distribution, a nonlinear adjusted region for wave generation and a damping region for wave absorption were introduced for wave generation simulation. To validate the developed simulation code, the adjusted simulation was carried out and its results were compared to the eighth order Stokes theory. Long-time simulations were carried out on the irregular wave field distribution, and nonlinear wave propagation characteristics were observed from the results of the simulations. Nonlinear adjusted and damping regions were introduced to implement a numerical wave tank that successfully generated nonlinear regular waves. According to the variation in the mean wave steepness, irregular wave simulations were carried out in the numerical wave tank. The simulation results indicated an increase in the nonlinear interaction between the wave components, which was numerically verified as the mean wave steepness. The results of this study demonstrate that the HOS method is an accurate and efficient method for predicting the nonlinear interaction between waves, which increases with wave steepness.

• Computers and Concrete
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• 제27권3호
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• pp.199-210
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• 2021

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• 한국전자거래학회지
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• 제26권2호
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• pp.61-81
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• 2021

언택트 시대에 새로운 여행의 형태로 자동차를 숙박공간으로 활용하는 차박이 주목받고 있다. 저렴한 비용, 편의성, 안전성 등의 장점과 함께 독립적인 여행을 가능하게 하는 차박의 특징으로 인해 차박 수요는 지속적으로 증가하고 있다. 차박에 대한 인기와 관련 산업이 급격히 성장하고 있음에도 불구하고 차박 트렌드를 이해하기 위한 학술적 논의는 거의 이루어진 바가 없는 실정이다. 새로운 형태의 여행 문화로 자리 잡고 관련 산업의 지속적 성장을 위해서는 차박에 대한 대중의 인식의 이해가 필수적이다. 따라서 본 연구에서는 마케팅믹스 이론과 빅데이터 분석을 바탕으로 차박에 대한 대중의 인식을 분석한다. 분석 결과에 따르면 차박은 소비자 주도의 여행 문화로 자리 잡고 있고, 자동차 산업의 애프터마켓 성장에 기여하고 있는 것으로 나타났다. 또한 소비자들은 경제적이고 현명한 방법으로 여행을 즐기는 경향이 강해지고 있으며 소셜 미디어를 통해 정보 공유에 적극적이다는 것을 확인할 수 있었다. 본 연구 결과는 새로운 여행 트렌드인 차박에 대한 초기 연구로써 이론적 기반을 바탕으로 한 빅데이터 분석 연구라는 점에서 의의가 있으며 활성화 방안에 대한 실무적 논의를 하였다는 점에서도 의미가 있다.