• 한국구조물진단유지관리공학회 논문집
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• 제27권5호
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• pp.120-129
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• 2023

행어케이블의 장력은 현수교의 건전성과 안전성을 확인할 수 있는 주요 응답 중 하나이다. 일반적으로 공용 중인 현수교에서 행어케이블의 장력을 추정하기 위해 진동법이 주로 사용되고 있다. 진동법은 행어케이블에서 고유진동수들을 측정하고 행어케이블의 형상 조건을 이용하여 간접적으로 장력을 추정하는 방법이다. 이 연구에서는 영상계측시스템을 이용하여 팔영대교의 행어케이블에 대하여 장력을 추정하였다. 영상계측시스템은 측정의 편의성과 경제성을 고려하여 디지털 캠코더와 삼각대를 사용하였다. 영상계측시스템을 이용하여 측정된 행어케이블의 응답은 변위 기반이므로 진동법을 적용하기 위한 고차모드의 고유진동수는 측정하기 어려울 수 있다. 이 연구에서는 저차모드의 고유 진동수를 이용하여 장력을 추정할 수 있는 역해석 기법을 적용하였다. 역해석 기법은 현장에서 측정된 행어케이블의 고유진동수들과 유한요소해석을 이용하여 산정된 고유진동수들의 오차를 목적함수로 정의하여 최적화를 수행하였다. 최적화 방법은 목적함수의 편미분이 필요 없는 직접탐색법을 적용하였다. 역해석 기법을 이용하여 산정된 장력과 진동법을 이용하여 추정된 장력을 비교 분석하여 역해석 기법에 대한 신뢰도와 정확도를 확인하였다. 그 결과 역해석 기법을 적용하면 저차모드의 고유진동수를 이용하여도 신뢰성 있는 장력의 추정이 가능하였다.

• 대한물리의학회지
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• 제14권3호
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• pp.55-62
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• 2019

PURPOSE: Text-mining has been shown to be useful for understanding the clinical characteristics and patients' concerns regarding a specific disease. Low back pain (LBP) is the most common disease in modern society and has a wide variety of causes and symptoms. On the other hand, it is difficult to understand the clinical characteristics and the needs as well as demands of patients with LBP because of the various clinical characteristics. This study examined online texts on LBP to determine of text-mining can help better understand general characteristics of LBP and its specific elements. METHODS: Online data from www.spine-health.com were used for text-mining. Keyword frequency analysis was performed first on the complete text of postings (full-text analysis). Only the sentences containing the highest frequency word, pain, were selected. Next, texts including the sentences were used to re-analyze the keyword frequency (pain-text analysis). RESULTS: Keyword frequency analysis showed that pain is of utmost concern. Full-text analysis was dominated by structural, pathological, and therapeutic words, whereas pain-text analysis was related mainly to the location and quality of the pain. CONCLUSION: The present study indicated that text-mining for a specific element (keyword) of a particular disease could enhance the understanding of the specific aspect of the disease. This suggests that a consideration of the text source is required when interpreting the results. Clinically, the present results suggest that clinicians pay more attention to the pain a patient is experiencing, and provide information based on medical knowledge.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 1998년도 추계학술발표논문집
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• pp.254-259
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• 1998

오늘날 컨테이너의 과다한 물동량 증가로 인하여 수작업으로 이루어지는 컨테이너 식별자를 처리하는데 어려움을 겪고 있는 가운데, 이를 자동으로 인식하고 그 결과를 항만 물류 처리 자동화 시스템에 적용하고자 하는 필요성이 대두되고 있다. 이에 본 논문에서는 컨테이너의 인식 처리를 자동화하기 위한 방안으로 컨테이너의 식별자 인식에 신경망 알고리즘의 하나인 Back-propagation을 적용하였으며, BP 알고리즘을 적용하기 위해서 적절한 scaling 비율을 구하고, 학습 DB를 구축하여 기존의 식별자 인식보다 신속하고 정확한 처리가 가능하도록 구현하였다.

• 오토저널
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• 제16권1호
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• pp.10-21
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• 1994

본 연구에서는 현재 자동차의 좌, 우측 Back Mirror의 부품중의 하나인 Frame을 현재 Zinc Diecasting 제품을 플라스틱으로 대체하는데 따른 여러가지 문제점을 플라스틱으로 대체하는데 따른 여러가지 문제점을 플라스틱 사출성형 CAE 해석을 이용하여 검증한 뒤 그 결과를 토대로 실제 제품개발 및 금형개발 등에 응용하기 위하여 연구를 행하는데 그 목적이 있다.

• 대한안전경영과학회지
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• 제16권1호
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• pp.119-127
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• 2014

This study tried to develop a basis for quantitative index of working postures associated with WMSDs (Work-related Musculoskeletal Disorders) that could overcome realistic restriction during application of typical checklists for WMSDs evaluation. The baseline data(for a total of 603 jbs) for this study was obtained from automobile manufacturing company. Specifically, data for back posture was analyzed in this study to have a better and more objective method in terms of job relevance than typical methods such as OWAS, RULA, and REBA. Major statistical tools were clustering, logistic regression and so on. The main results in this study could be summarized as follows; 1) The relationship between working posture and WMSDs symptom at back was statistically significant based on the results from logistic regression, 2) Based on clustering analysis, three levels for WMSDs risk at back were produced for flexion as follows: low risk(< $18.5^{\circ}$), medium risk($18.5^{\circ}{\sim}36.0^{\circ}$), high risk(> $36.0^{\circ}$), 3) The sensitivities on risk levels of back flexion was 93.8% while the specificities on risk levels of back flexion was 99.1%. The results showed that the data associated with back postures in this study could provide a good basis for job evaluation of WMSDs at back. Specifically, this evaluation methodology was different from the methods usually used at WMSDs study since it tried to be based on direct job relevance from real working situation. Further evaluation for other body parts as well as back would provide more stability and reliability in WMSDs evaluation study.

• Steel and Composite Structures
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• 제33권1호
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• pp.37-66
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• 2019

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless-steel lipped channels as compression members are becoming increasingly popular. The advantages of using stainless-steel as structural members are corrosion resistance and durability, compared with carbon steel. The AISI/ASCE Standard, SEI/ASCE-8-02 and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element analyses have been reported in the literature for such back-to back cold-formed stainless-steel channels. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (gAS/NZS) standards for built-up carbon steel sections only describe a modified slenderness approach, to consider the spacing of the intermediate fasteners. Thus, this paper presents a numerical investigation on the behavior of back-to-back cold-formed stainless-steel built-up lipped channels. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404 have been considered. Effect of screw spacing on the axial strength of such built-up channels was investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns, failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines by AISI and AS/NZS. In total, 647 finite element models were analyzed. From the results of the parametric study, it was found that the AISI & AS/NZS are conservative by around 10 to 20% for cold-formed stainless-steel built-up lipped channels failed through overall buckling, irrespective of the stainless-steel grades. However, the AISI and AS/NZS can be un-conservative by around 6% for all three grades of stainless-steel built-up channels, which failed by local buckling.

• Physical Therapy Rehabilitation Science
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• 제10권1호
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• pp.64-68
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• 2021

Objective: In clinical practice, there are a lot of exercise to reduce body weight or reduce the amount of body fat in order to solve back pain. However, many studies have contradicted the relationship between back pain and weight or body fat mass. The purpose of this study was to investigate the relationship between fat mass, body mass index and low back pain of office worker. Design: Crossed-sectional study Methods: Among the white-collar workers diagnosed with non-specific back pain by doctors, subjects who were not included in the exclusion criteria were selected to measure the subject's body fat mass, body mass index, pain intensity, and disability index due to back pain. The NPRS was used for the intensity of back pain of office workers, and the ODI was used for the degree of disability due to back pain. A body composition analyzer was used to measure the body fat mass and body mass index of white-collar workers. Results: There was no significant difference between the two groups in the comparison between the normal group and the excessive group according to the criteria of fat mass and body mass index. In the correlation analysis of fat mass, body mass index, pain intensity, and disability index, it was found that there was a significant correlation between fat mass and body mass index. However, neither fat mass nor body mass index had a significant correlation with pain intensity and disability index. Conclusions: The fat mass and body mass index of office worker do not affect low back pain.

• Geomechanics and Engineering
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• 제31권6호
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• pp.599-614
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• 2022

One of the methods of stabilizing retaining walls, embankments, and deep excavations is the implementation of plate anchors (like the Geolock wall anchor systems). Back-to-back Mechanically Stabilized Earth (BBMSE) walls are common stabilized earth structures that can be used for bridge ramps. But so far, the analysis of the interactive behavior of two back-to-back anchored walls (BBAW) by double-plates anchors (constructed closely from each other and subjected to the limited-breadth vertical loading) including interference of their failure and sliding surfaces has not been the subject of comprehensive studies. Indeed, in this compound system, the interaction of sliding wedges of these two back-to-back walls considering the shear failure wedge of the foundation, significantly impresses on the foundation bearing capacity, adjacent walls displacements and deformations, and their stability. In this study, the effect of horizontal distance between two walls (W), breadth of loading plate (B), and position of vertical loading was investigated experimentally. In addition, the comparison of using single and equivalent double-plate anchors was evaluated. The loading plate bearing capacity and displacements, and deformations of BBAW were measured and the results are presented. To evaluate the shape, form, and how the critical failure surfaces of the soil behind the walls and beneath the foundation intersect with one another, the Particle Image Velocimetry (PIV) technique was applied. The experimental tests results showed that in this composite system (two adjacent-loaded BBAW) the effective distance of walls is about W = 2.5*H (H: height of walls) and the foundation effective breadth is about B = H, concerning foundation bearing capacity, walls horizontal displacements and their deformations. For more amounts of W and B, the foundation and walls can be designed and analyzed individually. Besides, in this compound system, the foundation bearing capacity is an exponential function of the System Geometry Variable (SGV) whereas walls displacements are a quadratic function of it. Finally, as an important achievement, doubling the plates of anchors can facilitate using concrete walls, which have limitations in tolerating curvature.

• Geomechanics and Engineering
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• 제11권4호
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• pp.571-585
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• 2016

The crest of the Pubugou central core rockfill dam (CCRD) cracked in the first and second impounding periods. To evaluate the safety of the Pubugou CCRD, an inversion analysis of the constitutive model parameters for rockfill materials is performed based on the in situ deformation monitoring data. The aim of this work is to truly reflect the deformation state of the Pubugou CCRD and determine the causes of the dam crest cracks. A novel real-coded genetic algorithm based upon the differences in gene fragments (DGFX) is proposed. It is used in combination with the radial based function neural network (RBFNN) to perform the parameters back analysis. The simulated settlements show good agreements with the monitoring data, illustrating that the back analysis is reasonable and accurate. Furthermore, the deformation gradient of the dam crest has been analysed. The dam crest has a great possibility of cracking due to the uncoordinated deformation, which agrees well with the field investigation. The deformation gradient decreases to the value lower than the critical one and reaches a stable state after the second full reservoir.

• 한국방재학회 논문집
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• 제8권1호
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• pp.81-87
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• 2008

본 연구는 복개터널 안정해석시 이용되는 불확실한 지반물성값을 계측자료로부터 최적화하는 역해석에 관한 연구이다. 이 문제에 적합한 최적화 알고리즘을 선택하기 위하여 Simplex방법, Powell방법, Rosenbrock방법, Leverberg-Marquardt방법의 최적화 알고리즘을 가상의 지반굴착문제에 적용하여 소정의 정확성으로 최적해를 구할 수 있는 신뢰도와 변수평가에 소요되는 연산속도에 관하여 비교분석하였다. 해석결과 각 방법모두 허용규준을 만족한 후 정해에 수렴하였고, 함수평가에 소요되는 연산속도에서 최소자승법의 Levenberg-Marquardt방법과 Rossenbrock방법이 효율적으로 수행되는 것으로 나타났다. 한편 복개터널의 탄성계수와 포아송비를 역해석한 결과 역해석시 고려되는 계측점의 수가 증가할수록 설계변수를 정확하게 평가할 수 있었으며 소요되는 연산속도도 개선되는 것으로 나타났다.