• 터널과지하공간
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• 제8권2호
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• pp.139-145
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• 1998

The reliable estimation of the system parameters and the accurate prediction of the system behavior are important to design underground structures safely and economically. Especially, the elastic modulus and the in-situ stresses are very important parameters in predicting the behavior of the underground structure. Therefore, the back analysis using the field measurement data is developed to determine accurately the elastic modulus and the in-situ stresses of the underground structural system in this study. A back analysis using the combined finite and boundary element is developed. It can consider the far field boundary condition and is efficient in computation. In this study, a back analysis is performed to predict behaviors of underground structures for the real construction site. The comparison between the results of the back analysis with field measurement data and the obtained material properties from the field test shows good agreement for the real construction site.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.435-440
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• 2004

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.469-476
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• 2002

There are many methods to accelerate for consolidation of the soft ground but, in this study, only preloading method was used to improve the soft ground. To measure the settlement of soft ground, surface-settlement plates were installed at several points. To examine settlement behavior of soft ground, back analysis was done using the measured results. In the back analysis, consolidation parameter( $c_{v}$) were obtained and it was compared with test result for undisturbed sample.e.

• 한국지반공학회논문집
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• 제20권7호
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• pp.69-78
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• 2004

본 논문에서는 역해석 방법 중 직접법의 성능에 큰 영향을 미치는 최적화 과정을 인공지능의 한 기법인 유전자알고리즘을 이용하여 역해석 프로그램을 구성하였다. 유전자 알고리즘 및 역해석 기법의 효용성을 검증하기 위하여 과거 역해석 연구 사례 중의 하나인 Gens et al(1987)과 동일한 암반조건을 가진 모델에 대한 역해석을 실시하여 그 결과를 비교${\cdot}$검토하였다. 경부고속철도 터널 현장의 내공변위 및 천단침하에 대한 계측자료로부터 최종 내공변위의 예측함수를 결정하는 방법으로 터널의 총 변위를 분석하였다. 이를 역해석에 필요한 입력자료로 활용하여 역해석을 실시하고 터널 주변 암반의 거동을 반영할 수 있는 지반의 특성치를 구하였다. 각 현장 시험에서 얻어진 지반의 특성치와 비교한 결과 본 연구에서 적용된 유전자 알고리즘을 이용한 역해석 방법이 유의한 수준의 결과를 도출하고 있다는 사실을 확인하였다.

• 터널과지하공간
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• 제6권1호
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• pp.19-29
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• 1996

Back analysis model, capable of calculating the mechanical properties and the in-situ stresses of jointed rock mass, was developed based on the inverse method using a continuum theory. Constitutive equation for the behavior of jointed rock contains two unknown parameters, elastic modulus of intact rock and stiffness of joint, hence algorithm which determines both parameters simultaneously cannot be established. To avoid algebraic difficulties elastic modulus of intact rock was assumed to be known, since the representative value of which would be quite easily determined. Then, the ratio ($\beta$) of joint stiffness to elastic modulus of intact rock was assigned and back analysis for the behavior of jointed rock was carried-out. The value $\beta$ was repeatedly modified until the elastic modulus from back analysis became very comparable to the predetermined value. The joint stiffness could be calculated by multipling the ratio $\beta$ to the final result of elastic modulus. Accuracy and reliability of back analysis procedure was successfully testified using a sample model simulating the underground opening in the jointed rock mass. Applicability of back analysis model for the underground excavation in practice was also verified by analyzing the mechanical properties of jointed rock in which underground oil storage cavern were under construction.

• 한국생활과학회지
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• 제23권5호
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• pp.891-904
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• 2014

The objective of this study is to classify somatotypes of back-surface shape of women in their late 20s by using 3D body scan data(Size Korea 2010) in order to improve fitness of Hanbok Jeogori. The results were as follows: 1. According to the in-depth survey of the experienced expert's interview, most problems related to the fit were caused by the back area of Jeogori. 2. The result of factor analysis indicated that 6 factors were extracted and those factors comprised 82.85% of total variance. 3. According to the cluster analysis, back somatotypes of women in their late 20s were categorized by two types : straight type(54.1%) and bending type(46.9%). The results could be used as the Hanbok Jeogori to improve the fitness of back-surface shape.

• 한국지반공학회논문집
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• 제18권1호
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• pp.71-78
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• 2002

본 연구에서는 다층지반에 근입된 흙막이 벽의 단계별 계측변위로부터 각 층의 지반물성을 추정하고 이로부터 차기단계의 거동을 예측하기 위한 역해석 기법을 제안하였다. 지반이 다수의 층으로 구성되어 있을 경우 찾아야 할 대상변수가 많아지게 되며, 대상변수가 많아질수록 역해석에 상당한 무리가 따르게 된다. 이러한 층별 지반물성을 효율적으로 추정하기 위하여 최하단층부터 순차적으로 대상변수들을 찾아가는 방법을 이용하였다. 역해석은 상당량의 반복계산이 필요하기 때문에 정해석 방법으로는 해석시간이 짧고 시공단계 별 해석이 가능한 탄소성보법을 사용하였다. 역해석 대상변수는 탄소성 하중-변위 곡선의 구성요소인 지반반력계수와 수평토압계수들을 취하였으며, 목적함수는 이상변위에 의한 오차를 최소화시키기 위하여 단계별 계측변위 증분과 해석변위 증분의 차이로 구성하였다. 목적함수를 최소화 시키는 대상변수들을 찾기 위한 최적화 수법으로는 제약순차선형계획 법을 이용하였다. 본 연구를 통하여 제안된 방법을 수치해석자료 및 현장계측자료를 이용하여 검증하였다.

• 여성건강간호학회지
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• 제17권5호
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• pp.484-490
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• 2011

Purpose: This study was aimed to investigate the impact of job stress on low back symptoms among Clinical nurses (CNs) in university hospital. Methods: A total of 322 CNs employed in a hospital in Seoul were interviewed by a well-trained interviewer using the structured questionnaire. Data collected for this study includes demographics, social and work characteristics, low back symptoms, and job stress. To test the impact of job stress on low back symptoms, we used multiple logistic regression analysis. Results: The prevalence of low back symptoms was 25.8% in this study. Low back symptoms differed significantly by factors, such as physical work burden, past history of injury and work duration. Also low back symptoms differed significantly by organizational system among independent variables of job stress. In a multiple logistic regression analysis, the odds ratio of organizational system to low back symptoms was 2.07 after an adjustment. Conclusion: This study showed that organizational system among job stress was a significant variable in explaining low back symptoms. We suggest the improvement of organizational system category as a preventive strategy for low back pain in CNs working in hospital.

• 한국항공운항학회지
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• 제19권4호
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• pp.51-57
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• 2011

The spin-up and the spring-back are most severe load cases in the aircraft landing gear design. These load cases are caused by reciprocal action of complex physical phenomenon such as the friction between a tire and ground, inertia of the rotation of a tire and the flexibility of a landing gear structure. Generally, the empirical formula or the theoretical formula is used to calculate the spin-up and spring-back load in the early stage of the development program of the aircraft landing gear. After the materialization of the design of a landing gear, spin-up and spring-back load are acquired by the free drop test. In this study, the spin-up and the spring-back load of the rubber shock absorber type KC-100 nose landing gear are calculated by the explicit finite element analysis. Through this analysis, more accurate and realistic spin-up and spring back loads could be applied to the early phase of the development of the aircraft landing gear.

• The Journal of Korean Physical Therapy
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• 제21권2호
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• pp.79-85
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• 2009

Purpose: This study examined the characteristics of gait in patients with chronic low back pain. Methods: The subjects were out-patients suffering from chronic low back pain at the department of physical therapy, B hospital in Seoul. Gait analysis was performed by dividing the subjects into two groups. The study and control group comprised 15 chronic low back pain patients and 14 healthy people, respectively. Gait analysis was performed using a VICON 512 Motion Analysis System to obtain the spatio-temporal and kinematic parameters. Results: First, there was a significant difference in the spatio-temporal parameters between the two groups (p<0.05). Second, the study group showed significant differences in the kinematic parameters during the stance phase (p<0.05). Third, there were significant differences in kinematic parameters in the study group during the swing phase (p<0.05). Conclusion: The gait pattern of patients with chronic low back pain is characterized by more rigid patterns. Compared to the control group, there was a decrease in the spatio-temporal parameters and kinematic parameters in patients with chronic low back pain. These findings are expected to play a role as basic data and to form a rehabilitation program for low back pain patients.