• Steel and Composite Structures
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• 제49권4호
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• pp.441-456
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• 2023

Aiming at the development trend of light weight and high strength of engineering structures, this paper experimentally investigated the seismic performance of circular-in-square high-strength concrete-filled double skin steel tubular (HCFDST) stub columns with out-of-code width-to-thickness (B/t) ratios. Typical failure mode of HCFDST stub columns appeared with the infill material crushing, steel fracture and local buckling of outer tubes as well as the inner buckling of inner tubes. Subsequently, the detailed analysis on hysteretic curves, skeleton curves and ductility, energy dissipation, stiffness degradation and lateral force reduction was conducted to reflect the influences of hollow ratios, axial compression ratios and infill types, e.g., increasing hollow ratio from 0.54 to 0.68 and 0.82 made a slight effect on bearing capacity compared to the ductility coefficients; the higher axial compression ratio (e.g., 0.3 versus 0.1) significantly reduced the average bearing capacity and ductility; the HCFDST column SCFST-6 filled with concrete obviously displayed the larger initial secant stiffness with a percentage 34.20% than the column SCFST-2 using engineered cementitious composite (ECC); increasing hollow ratios, axial compression ratios could accelerate the drop speed of stiffness degradation. The out-of-code HCFDST stub columns with reasonable design could behave favorable hysteretic performance. A theoretical model considering the tensile strength effect of ECC was thereafter established and verified to predict the moment-resisting capacity of HCFDST columns using ECC. The reported research on circular-in-square HCFDST stub columns can provide significant references to the structural application and design.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.49-50
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• 2006

Photoelasticity is widely and conveniently used methods for whole field stress analysis. In this paper, 8-step photoelastic phase shifting method was performed by using a multi-purpose polariscope to measure the fringe orders along a specified line on the specimen containing a square hole. The material of the specimen is made of Polycarbonate. The measurement results by 8-step phase shifting method were compared with the those calculated by ABAQUS.

• International Journal of Advanced Culture Technology
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• 제7권4호
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• pp.32-39
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• 2019

The purpose of this study was to identify the effects of visual programs on job stress and burnout in emergency room nurses. This study used a nonequivalent control group pretest-posttest design. There were 26 participants in the experimental group and 27 in the control group. Data collection took place from December 12, 2017 to February 17, 2018. The program comprised eight weekly 120-minutes sessions, which included understanding and assessing job stress and burnout. Data were analyzed using the Chi-square test, paired t-test, and independent t-test. As a result, levels of job stress (t=-20.09, p<.001) and burnout (t=-22.31, p<.001) decreased significantly in the experimental group. The results suggest that the Visual Media Program could be an effective strategy for reducing job stress and burnout. Therefore, it is deemed a useful intervention for improving the quality of nursing care provided in emergency rooms.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.543-553
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• 2020

본 연구는 2018년 제7기 국민건강영양조사 결과를 이용한 2차 자료 분석이었다. 본 연구의 목적은 65세 이상 여성노인의 신체활동, 체질량지수, 우울이 건강관련 삶의 질에 미치는 영향을 파악하고 비교하기 위함이다. 구체적으로 연구대상자는 고혈압 진단을 받은 여성노인 550명, 고혈압 진단을 받지 않은 여성노인 375명으로 구성되었다. SPSS/WIN 22.0 프로그램을 이용하여 기술통계, chi-square test, t-test, multiple linear regression으로 분석하였다. 다중 선형 회귀 분석결과, 고혈압군에서 나이, 교육, 신체활동, 체질량 지수, 우울이 건강관련 삶의 질에 유의한 예측인자로 확인되었고 설명력은 26.9%였다(F=14.30, p<.001). 즉 신체활동량이 많을수록(t=3.02, p=.003), 체질량 지수가 낮을수록(t=-3.12, p=.002), 우울이 낮을수록(t=-7.69, p<.001) 건강관련 삶의 질이 높았다. 반면, 비고혈압군에서 교육과 우울이 건강관련 삶의 질에 유의한 영향인자로 확인되었고 설명력은 31.7%였다(F=5.37, p<.001). 즉, 우울이 낮을수록 (t=-5.53, p<.001) 건강관련 삶의 질이 높았다. 이러한 결과를 바탕으로 향후 고혈압 질환을 갖고 있는 여성노인을 대상으로 다른 구체적 신체활동의 특성을 비교하는 연구와 여성노인의 우울 및 비만 감소를 위한 신체활동 중재 프로그램의 개발이 필요하다.

• 한국정밀공학회지
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• 제28권4호
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• pp.391-397
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• 2011

Control of interior permanent magnet (IPMSM) is difficult because its nonlinearity and parameter uncertainty. In this paper, a fuzzy c-regression models clustering algorithm which is based on T-S fuzzy is used to model IPMSM with a series linear model and weight them by memberships. Lagrangian of constrained function is built for calculating clustering centers where training output data are considered. Based on these clustering centers, least square method is applied for T-S fuzzy linear model parameters. As a result, IPMSM can be modeled as T-S fuzzy model for T-S fuzzy control of them.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.727-745
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• 2005

The present study is an experimental investigation into the behaviour of high strength concrete square short columns subjected to biaxial bending moments and strengthened by GFRP laminates. The main objectives of the study are: to evaluate the improvement in the structural performance of HSC short square columns subjected to small biaxial eccentricity when strengthened by externally applied FRP laminates, and to investigate the optimum arrangement and amount of FRP laminates to achieve potential enhancement in structural performance especially ductility. The parameters considered in this study are: number of FRP layers and arrangement of wraps. The load eccentricity is kept corresponding to e/t = 0.125 in two perpendicular directions to the columns principal axes, and the wraps are applied in single or double layers (partial or full wrapping). In the present work, test results of five full scale concrete columns are presented and discussed. The study has shown that FRP wraps can be used successfully to enhance the ductility of HSC columns subjected to biaxial bending by 300%.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.380-385
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• 2001

In the present study, flow characteristics of turbulent oscillatory flow in a square-sectional $180^{\circ}$ curved duct are investigated experimentally. In order to measure wall shear stress and pressure distributions, experimental studies for air flow are conducted in a square-sectional $180^{\circ}$ curved duct by using the LDV system with the data acquisition and the processing system. The wall shear stress measuring point bend angle of the $150^{\circ}$ and pressure distribution of the inlet (${\phi}=0^{\circ}$) to the outlet (${\phi}=180^{\circ}$) at $10^{\circ}$ intervals of the duct. The results obtained from the experimentation are summarized as follows: A wall shear stress value in an inner wall is larger than that in an outer wall, except for the phase angle (${\omega}t/{\pi}/6$) of 3, because of the intensity of secondary flow. The pressure distributions are the largest in accelerating and decelerating regions at the bend angle(${\phi}$) of $90^{\circ}$ and pressure difference of inner and outer walls is the largest before and after the ${\phi}=90^{\circ}$.

• 사상체질의학회지
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• 제28권1호
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• pp.51-56
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• 2016

Objectives This study was to identify the types of errors in the statistical analysis and trends of previous reported papers that used various statistical techniques.Methods We have selected 118 original articles for statistical review from the OASIS(http://oasis.kiom.re.kr) and the Pubmed(http://www.pubmed.gov) in the field of Sasang constitutional medicine. Published year was restricted from 2011 to 2015.Results 1. The ANOVA(25.72%) was the statistic of choice overall, followed by the chi-square test(21.74%), regression analysis(14.13%), t-test(11.59%), and etc. 2. By examining the errors of the statistical methods, there were 42(59.2%) thesis with errors among 71 thesis using ANOVA, 19(31.7%) thesis among 60 thesis using chi-square test, and 35(89.7%) over 39 thesis using regression analysis.Conclusions To improve the quality of Sasang Constitution, the participation of statisticians in research design will reduce the significant errors in statistical interpretation of the results.

• 소성∙가공
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• 제16권6호
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• pp.457-462
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• 2007

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

• 한국전산유체공학회지
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• 제2권1호
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• pp.1-7
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• 1997

A FA-FD hybrid method, developed for solving three-dimensional incompressible Navier-Stokes equations, is applied to calculate three-dimensional laminar flows through a square duct with a 90° bend. The method discretizes the convective terms in the primary flow direction with 3rd-order upwind finite-differences and the convective and diffusive terms in the transverse directions with the two-dimensional finite analytic method. The non-staggered grid system is used and the pressure-velocity coupling is achieved by a global iteration procedure based on the PISO algorithm. Detailed comparisons between the computed solutions and the available experimental data are given mainly for the velocity distributions at cross-sections in a 90° bend of a square duct with both fully developed and developing entry flows. Although the computational result shows generally a good agreement with the experimental data, there are some significant discrepancies underlining the necessity of more accurate numerical methods as well as reliable experimental data for their validation.