• 대한조선학회논문집
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• 제42권5호
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• pp.479-486
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• 2005

The final goal of shift alignment design is that the bearing reaction forces or mean pressures are within design boundaries for various service conditions of a ship. However, it is found that calculated bearing load can be substantially variable according to the locations of the effective support points of after sterntube bearing which are determined by simple calculation or assumption suggested by classification societies. A new analysis method for shaft alignment calculation is introduced in order to resolve these problems. Key concept of the new method is featured by adopting both nonlinear elastic and multi-support elements to simulate a bearing support Hertz contact theory is basically applied for nonlinear elastic stiffness calculation instead of the projected area method suggested by most of classification societies. Three loading conditions according to the bearing offset and the hydrodynamic moment and twelve models according to the locations of the effective support points of sterntube bearings are prepared to carry out quantitative verifications for an actual shafting system of 8000 TEU class container vessel. It is found that there is relatively large difference between assumed and calculated effective support points.

• 한국항공우주학회지
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• 제47권9호
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• pp.678-685
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• 2019

미래 전장 환경의 변화와 항공무기체계의 기술적 발전에 따라 유인기와 무인기의 상호 보완적인 유무인기 복합 운용을 통한 임무 수행이 요구된다. 기존의 유무인기 전투체계는 항공작전임무에 따라 운용되었으며 유무인기의 성능에 따라 수행 가능한 임무가 제한된다. 본 논문에서는 유무인기 협업 기반의 임무 도출을 위해 미 국방성의 무인기 시스템 로드맵과 공군의 항공작전을 분석한 후 기존의 유무인기의 임무를 분석한다. 다음으로 임무를 수행하기 위해 필요한 유무인기의 기본 기능을 식별하고 유무인기 협업 기반의 임무를 적 방공제압 임무로 선정한 후 이 임무를 수행하기 위한 절차를 단계별로 분석한다. 본 논문은 유무인기 복합 운용 개념의 구체화를 위해 임무 단계별 절차를 물리적인 공간 및 시간 순서의 맥락으로 분석하여 제안한다.

• 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 $0.65f_{pu}$.

• Physical Therapy Rehabilitation Science
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• 제8권3호
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• pp.125-133
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• 2019

Objective: To compare the postural control between non-specific chronic low back pain (NSCLBP) subgroups and healthy people during dynamic balance performance using a modified Star Excursion Balance Test (mSEBT). Design: Cross-sectional study. Methods: Eighteen NSCLBP subjects (9 active extension pattern [AEP], 9 flexion pattern [FP]), and 10 healthy controls were enrolled in this study. All subjects performed mSEBT on their dominant leg on a force plate. Normalized reach distance and balance parameters, including the center of pressure (COP) displacement and velocity, were recorded. Results: There were significant differences in mean reach distances in both posterolateral and posteromedial (PM) reach directions between AEP and healthy subjects (p<0.001) and between FP and healthy subjects (p<0.001). However, there were no significant differences among the three groups in the anterior reach direction. Also, the results showed no significant differences in mean COP variables (velocity and displacement) between pooled NSCLBP and healthy subjects. However, the subjects were reclassified into AEP, FP and healthy groups and the results showed a significant difference in mean COP velocity in the PM direction between AEP and FP subjects (p=0.048), and between AEP and healthy subjects (p=0.024). Conclusions: The findings in this study highlight the heterogeneity of the individuals with NSCLBP and the importance of identifying the homogenous subgroups. Individuals with AEP and FP experience deficits in dynamic postural control compared to healthy controls. In addition, the findings of this study support the concept of the Multidimensional Classification System.

• Journal of the Korean Data Analysis Society
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• 제20권6호
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• pp.3049-3067
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• 2018

최근 조직몰입(organizational commitment) 3요인(정서적 몰입, 규범적 몰입, 지속적 몰입) 모델(Allen, Meyer, 1990, 1991) 관련 연구에서 사람중심 접근법(person-centered approach)이 많은 관심을 받고 있지만 아직 국내 연구자들에게는 크게 확산되지 못하고 있다. 이에 본 논문은 사람중심 접근법의 개념과 관련 자료분석 방법을 군집분석(cluster analysis)과 잠재프로파일분석(latent profile analysis)을 중심으로 소개하고자 한다. 또한 이러한 방법들의 실제 적용 사례를 제시하기 위해 국내 직장인들 349명으로부터 수집한 자료를 바탕으로 군집분석과 잠재프로파일분석을 각각 실행하여 각 분석으로부터 6개의 조직몰입 프로파일 유형들을 도출하였으며 그 결과를 비교하였다. 뿐만 아니라, 조직몰입 프로파일 유형 간 이직의도(turnover intention)의 차이를 살펴봄으로써 도출된 프로파일의 타당성을 확인하였다. 본 논문은 조직몰입에 대한 기존의 변수중심 접근법(variable-centered approach)에 대한 보완적 방법으로 사람중심 접근법이 갖는 의미를 이해하고, 나아가 국내 직장인들의 조직몰입 프로파일 유형을 살펴볼 수 있다는 점에서 국내 연구자들 뿐만 아니라 실무담당자들에게 시사하는 바가 크다고 할 수 있다.

• 정보보호학회논문지
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• 제21권5호
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• pp.83-94
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• 2011

RFID 요킹증명은 2004년 A. Juels에 의해 제안된 개념으로써, 한 쌍의 태그가 하나의 리더에 의해 동시에 스캔됐음을 증명하는 것이다. A. Juels가 최초로 제안한 요킹증명 프로토콜은 이 후 재생공격에 취약한 문제점이 지적되었고, 이를 개선하기 위해 여러 다른 요킹증명 프로토콜들이 제안되었다. 그러나 최초 제안된 기법이 태그의 낮은 성능을 고려해 프로토콜의 경량화를 중요한 이슈로 보았던데 비해, 현재까지 알려진 요킹증명 프로토콜들은 상대적으로 태그에 더 많은 연산량과 저장공간을 필요로 하는 단점이 있다. 우리는 요킹증명의 기본적인 조건을 모두 만족시키면서 성능이 낮은 수동형 태그를 고려한 안전한 프로토콜 두 가지를 제안한다. 제안하는 기법은 기존에 알려진 재생공격뿐만 아니라 전수공격에 있어서도 높은 안전성을 보장하며, 한 쌍 이상의 태그 그룹, 흑은 다수의 태그 그룹들을 한번의 프로토콜 수행으로 증명할 수 있도록 설계되었다.

• Smart Structures and Systems
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• 제26권6호
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• pp.693-701
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• 2020

The conventional Kalman Filter (KF) provides a promising way for structural state estimation. However, the physical parameters of structural systems or models should be available for the estimation. Moreover, it is not applicable when the loadings applied to the structures are unknown. To circumvent the aforementioned limitations, a two-stage KF with unknown input approach is proposed for the simultaneous identification of structural parameters and unknown loadings. In stage 1, a modified observation equation is employed. The structural state vector is estimated by KF on the basis of structural parameters identified at the previous time-step. Then, the unknown input is identified by Least Squares Estimation (LSE). In stage 2, based on the concept of sensitivity matrix, the structural parameters are updated at the current time-step by using the estimated structural states obtained from stage 1. The effectiveness of the proposed approach is numerically validated via a five-story shearing model under random and earthquake excitations. Shaking table tests on a five-story structure are also employed to demonstrate the performance of the proposed approach. It is demonstrated from numerical and experimental results that the proposed approach can be used for the identification of parameters of structure and the external force applied to it with acceptable accuracy.

• 산업경영시스템학회지
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• 제44권1호
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• pp.9-16
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• 2021

Modern combat has been extended to the concept of real-time response to a variety of threats simultaneously occurring in vast areas. In order to quick command determination and accurate engagement in these threats, the combat system has emerged in frigate. Frigates conduct anti-surface, anti-submarine, and anti-aircraft as the core forces of the fleet. In this study, the combat effectiveness measures naval frigates using AHP (analytic hierarchy process) method. A hierarchical structure for measuring the combat effectiveness was developed, and weights of criteria were calculated by expert surveys and pair-wise comparisons. In addition, the combat effectiveness of frigates was synthesized and compared. The weights for each attribute were calculated, and the weights for the three main attributes were in the order of act (0.594), evaluate (0.277), and see (0.129). As a result of calculating the weight, anti surface warfare (0.203) was the highest. The combat effectiveness of FFG Batch-III, which has advanced hardware and software and improved combat system capabilities, see (1.73 to 2.56 times), evaluate (1.68 to 2.08 times), and act (1.31 to 3.80 times) better than the comparative frigate. In summarizing the combat effects of the frigate, FFG Batch-III was 1.41~2.95 times superior to the comparative frigate. In particular, a group of experts evaluated the act importantly, resulting in better combat effectiveness.

• 한국항행학회논문지
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• 제26권5호
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• pp.312-318
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• 2022

현재 대한민국은 인구절벽 현상에 의한 병역자원의 감소 문제에 직면해 있으며 이에 대응하기 위해 군 구조 개편 및 전력 구조 변화를 추구하고 있다. 육군은 이런 상황 변화에 대한 대응으로 미래 전장을 주도할 드론봇 전투체계의 전력화를 추진하고 있다. 미래의 전장은 지휘통제, 감시정찰, 정밀타격이 결합된 통합 전장 개념으로 전환될 것이며 이러한 변화에 따라 드론봇을 포함한 무인 전투체계가 실전 배치되어, 위험도가 높고 인간이 수행하기 어려운 전투상황에 더욱 광범위하게 적용될 것이다. 본 논문에서는 이러한 변화에 대한 대응 방안의 하나로 BDI 아키텍처 기반의 의사 결정 시스템을 가진 자율행동 소프트웨어를 개발하였다. 자율행동 소프트웨어는 다 기종에 대한 적용성 확보를 위해 프레임워크 구조를 적용하였고 대상 무인기를 대대급 감시정찰 무인기로 가정하여 PC기반 환경에서 기능을 검증하였다.

• Geomechanics and Engineering
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• 제31권5호
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• pp.505-518
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• 2022

This study introduces soil resistance multipliers at locations encompassed by the zone of influence of the helix plate to consider the added lateral resistance provided to the helical pile. The zone of influence of a helix plate is a function of its diameter and serves as a boundary condition for the modified soil resistance springs. The concept is based on implementing p-multipliers as a reduction factor for piles in group action. The application of modified p-y springs in the analysis of helical piles allows for better characterization and understanding of the lateral behavior of helical piles, which will help further the development of design methods. To execute the proposed method, a finite difference program, HPCap (Helical Pile Capacity), was developed by the authors using Matlab. The program computes the deflection, shear force, bending moment, and soil resistance of the helical pile and allows the user to freely input the value of the zone of influence and Ω (a coefficient that affects the value of the p-multiplier). Results from ten full-scale lateral load tests on helical piles embedded at depths of 3.0 m with varying shaft diameters, shaft thicknesses, and helix configurations were analyzed to determine the zone of influence and the magnitude of the p-multipliers. The analysis determined that the value of the p-multipliers is influenced by the ratio between the pile embedment length and the shaft diameter (D_p), the effective helix diameter (D_h-D_p), and the zone of influence. Furthermore, the zone of influence is recommended to be 1.75 times the helix diameter (D_h). Using the numerical analysis method presented in this study, the predicted deflections of the various helical pile cases showed good agreement with the observed field test results.