• Tunnel and Underground Space
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• v.8 no.2
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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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.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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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.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.69-78
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• 2004

In this study, the back analysis program was developed by applying the genetic algorithm, one of artificial intelligence fields, to the direct method. The optimization process which has influence on the efficiency of the direct method was modulated with genetic algorithm. On conditions that the displacement computed by forward analysis for a certain rock mass model was the same as the displacement measured at the tunnel section, back analysis was executed to verify the validity of the program. Usefulness of the program was confirmed by comparing relative errors calculated by back analysis, which is carried out under the same rock mass conditions as analysis model of Gens et at (1987), one of back analysis case in the past. We estimated the total displacement occurring by tunnelling with the crown settlement and convergence measured at the working faces in three tunnel sites of Kyungbu Express railway. Those data measured at the working face are used for back analysis as the input data after confidence test. As the results of the back analysis, we comprehended the tendency of tunnel behaviors with comparing the respective deformation characteristics obtained by the measurement at the working face and by back analysis. Also the usefulness and applicability of the back analysis program developed in this study were verified.

• Tunnel and Underground Space
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• v.6 no.1
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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.

• Korean Journal of Human Ecology
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• v.23 no.5
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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.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.71-78
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• 2002

This paper presents a back-calculation technique leer the prediction of the behavior of earth wall inserted in multi-layered soil deposit. The soil properties are back-calculated from the measured displacement at each construction stage and the behavior of earth wall far the next construction stage is predicted using back-calculated soil properties. For multi-layered soil deposit, the back-calculation would be very difficult due to the increase in the number of variables. In this study, to solve this difficulty, the back-calculation was performed successively from the lowest layer to the upper layers. An efficient elasto-plastic beam-column analysis was used for forward analysis to minimize the computation time of iterative back-calculation procedure. The coefficients of subgrade reaction and lateral earth pressure necessary for the formation of p-y curve were selected as back calculation variables, and to minimize the effect of abnormal behavior of the wall which might be caused by any unexpected action during construction, the difference between measured displacement increment and computed displacement increment at each construction stages is used as the objective function of optimization. The constrained sequential linear programming was used for the optimization technique to found values of variables minimizing the objective function. The proposed method in this study was verified using numerically generated data and measured field data.

• Women's Health Nursing
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• v.17 no.5
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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.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.4
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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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• v.21 no.2
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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.