• Title/Summary/Keyword: a longitudinal case study

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A study on the factor analysis by grade for highway traffic accident (고속도로 교통사고 심각도 등급별 요인분석에 관한 연구)

  • Lee, Hye-Ryung;Kum, Ki-Jung;Son, Seung-Neo
    • International Journal of Highway Engineering
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    • v.13 no.3
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    • pp.157-165
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    • 2011
  • With respect to the trend of highway traffic accident, highway accident is in decline, whileas, the fatality is on an increasing trend. Thus, many efforts to decrease highway traffic accidents and improve the safety, are required. In particular, in case of highway, the management standard by grade for accident black spot is designated. Thus, investing the effect factors by grade for highway traffic accident is required in detail. Thus, in this study, the factors affecting the traffic accidents among the environmental factors based on the graded data for the accident black spot in the applicable section targeting the Seoul-Pusan Express Highway, were reviewed; accident forecasting model which would analyze the characteristics of the accidents for determining the accident grade, was developed. As a result of establishing a model by using Quantification Theory of Type II, considering the characteristics of the dependent and independent variables based on the geometric structure, 'the fixed variable' among the variables relating to the accident, for the variables influencing over the accident grade, 'the type of vans, a chassis and people', 'the trailers, special vehicles and chassis people' and 'the negligence of watching and cloudy weather' were analyzed as common factors, in case of 'horizontal alignment', 'longitudinal slope' and, 'barricade' respectively.

A Study on the Composite Behavior of Simply Supported Composite Girders Considering the Partial Interaction (불완전 합성율을 고려한 단순합성형의 합성거동에 관한 연구)

  • Yong, Hwan Sun;Kim, Seok Tae;Park, Jae Yil
    • Journal of Korean Society of Steel Construction
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    • v.9 no.4 s.33
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    • pp.543-555
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    • 1997
  • Generally, in a steel-concrete composite gilder, the shear connector which was constructed between concrete deck and steel girder should have enough stiffness to behave as one body, because the conformity between plate and concrete deck is influences by the stiffness and spacing of the shear connectors. If the stiffness of shear connectors are insufficient, slip would happen at the contact surface. Partial interaction is the case that takes account of slips. In this paper, an easy method is presented to evaluate the stiffness or spacing of the shear connector according to the degree of imperfection without difficult calculations for a composite gilder with partial interaction. Also, the horizontal shearing force applied to the shear connector and the longitudinal axial force, which is occurs at contact surface between concrete deck and steel girder, have been presented in a simple influence line that is various to the parameters of sectional properties, degree of imperfection and applied load points. Furthermore, through the case study, it determined the relationships between the degree of imperfection and the follows 1) spring constants 2) axial force and horizontal shearing force 3) stress and neutral axis by using the partial differential equation based on Newmark's Partial Interaction Theory.

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Profile of sexual violence experiences among the survivors using victim support services in Korea (성폭력 피해특성에 따른 피해경험자 유형화와 지원 서비스 이용양태 연구)

  • Kim, Kihyun;Kim, Jae-Won;Park, Haeyoung;Ryou, Bee
    • Korean Journal of Social Welfare Studies
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    • v.47 no.4
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    • pp.255-280
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    • 2016
  • This study examined sexual violence characteristics among the individuals who utilized victim support services provided by National Rape Crisis Intervention Centers in Korea. The study is the part of a Korean longitudinal study on sexual assault characteristics and its implications for post-abuse adjustments, which is supported by Korean Mental Health Technology R&D Project. Eleven national rape crisis centers nationwide and 29 NGO's participated in the study. The participating centers provided the data on sexual abuse characteristics from their standardized case management system. The cases were randomly selected from the system. Total of 1077 cases were gleaned from the system and utilized for this analysis. Results indicated that the abuse characteristics differed by victims' age (children, adolescent vs. adults) as well as relationship with perpetrator. We could identify six different profile groups based on the detailed violence characteristics. The results assured us of the importance to understand the detailed characteristics of sexual violence and the old notion that 'one size may not fit all'. The results from the profile analyses may have important implication for developing victim support programs and appropriately allocating agency resources according to the different profiles of the service users.

Seismic response of skewed bridges including pounding effects

  • Kun, Chern;Yang, Ziqi;Chouw, Nawawi
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.467-476
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    • 2018
  • The seismic vulnerability of skewed bridges had been observed in many past earthquakes. Researchers have found that the in-plane rotation of the girders was one of the main reasons for the vulnerability of these types of bridges. To date, not many experimental works have been done on this topic, especially those including pounding between adjacent structures. In this study, shake table tests were performed on a bridge-abutment system consisting of a straight, $30^{\circ}$, and $45^{\circ}$ bridge with and without considering pounding. Skewed bridges with the same fundamental frequency and those having the same girder mass as the straight bridge were studied. Under the loadings considered, skewed bridges with the same frequency as the straight tend to have smaller responses than those with the same mass. The average maximum bending moment developed in the piers of the $30^{\circ}$ bridge with the same mass as that of the straight when pounding was not considered was 1.6 times larger than when the frequencies were the same. It was also found that the NZTA recommendations for the seat lengths of skewed bridges could severely underestimate the relative displacements of these types of bridges in the transverse direction, especially when pounding occurs. In the worst case, the average transverse displacement of the $45^{\circ}$ bridge was about 2.6 times the longitudinal displacement of the straight, which was greatly over the limit suggested by the NZTA of 1.25 times.

Wind Tunnel Test Study on the Wings of WIG Ship (WIG선의 날개에 대한 풍동실험 고찰)

  • Kim, S.K.;Suh, S.B.;Lee, D.H.;Kim, K.E.
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.1
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    • pp.60-67
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    • 1997
  • This paper presents the results of 3rd wind tunnel test for the wings of WIG R/C test models, 'Hanjin-1' & 'Hanjin-2'. We made 'Hanjin-1' in last May 1995 and had a success in test flight. And in order to grasp the aerodynamic characteristics of wings in ground effect, the measurements of lift and drag were carried out for the various kinds of wing. It was shown that lift and lift-drag ratio increase with decrease of the clearance, but the feature was considerably depended on the shape of wing section. In this case we select the three kind of wing. section, and then compare their characteristics especially for a stability in longitudinal motion. They are NACA6409 for 'Hanjin-1' and the two kinds of DHMTU for ekranoplans of Russia. Experimental results show that the pitching moments of DHMTU wing sections are smaller than NACA6409.

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Development of a Solar Collector Performance of Cylindrical Parabolic Concentrating Solar Collector (태양열(太陽熱) 집열기개발(集熱器開發)에 관(關)한 연구(硏究) - 포물반사곡면(抛物反射曲面)으로된 2차원(二次元) 집광식(集光式) 태양열(太陽熱) 집열기(集熱器)의 성능분석(性能分析) -)

  • Song, Hyun Kap;Yon, Kwang Seok;Cho, Sung Chan
    • Journal of Biosystems Engineering
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    • v.10 no.1
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    • pp.54-68
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    • 1985
  • It is desirable to collect the solar thermal energy at relatively high temperature in order to minimize the size of thermal storage system and to enlarge the scope of solar thermal energy utilization. So far the concentrating solar collector has been developed to collect solar thermal energy at relatively high temperature, but it has some difficulties in maintaining the volumetric body of solar collector for long term utilization. On the other hand, the flat-plate solar collector has been developed to collect the solar thermal energy at low temperature, and it has advantages in maintaining the system for long term utilization, since it's thickness is thin and not volumetric. In this study, to develop a solar collector that has both advantages of collecting solar thermal energy at high temperature and fixing conveniently the collector system for long term period, a cylindrical parabolic concentrating solar collector was designed, which has two rows of parabolic reflectors and thin thickness such as the flat-plate solar collector, maintaining the optical form of concentrating solar collector. The characteristics of the concentrating parabolic solar collector newly designed was analysed and the results are summarized as follows; 1. The temperature of the air enclosed in solar collector was all the same as $50^{\circ}C$ in both cases of the open and closed loop, and when the heat transfer fluid was not circulated in tubular absorber, the maximum surface temperature of the absorber was $118-120^{\circ}C$, this results suggested that the heat transfer fluid could be heated up to $118^{\circ}C$. 2. In case of longitudinal installation of the solar collector, the temperature difference of heat transfer fluid between inlet and outlet was $4^{\circ}-6^{\circ}C$ at the flow rate of $110-130{\ell}/hr$, and the collected solar energy per unit area of collector was $300-465W/m^2$. 3. The collected solar energy per unit area for 7 hours was 1960 Kcal/$m^2$ for the open loop and 220 Kcal/$m^2$ for the closed loop. Therefore it is necessary to combine the open and closed loop of solar collectors to improve the thermal efficiency of solar collector. 4. The thermal efficiency of the solar collector (C.P.C.S.C.) was proportional to the density of solar radiation, indicating the maximum thermal efficiency ${\eta}_{max}=58%$ with longitudinal installation and ${\eta}_{max}=45%$ with lateral installation. 5. The thermal efficiency of the solar collector (C.P.C.S.C.) was increased in accordance with the increase of flow rate of heat transfer fluid, presenting the flow rate of $110{\ell}/hr$ was the value of turning point of the increasing rate of the collector efficiency, therefore the flow rate of $110{\ell}/hr$ was considered as optimum value for the test of the solar collector (C.P.C.S.C.) performance when the heat transfer fluid is a liquid. 6. In both cases of longitudinal and lateral installation of the solar collector (C.P.C.S.C.), the thermal efficiency was decreased linearly with an increase in the value of the term ($T_m-T_a$)/Ic and the increasing rate of the thermal efficiency was not effected by the installation method of solar collector.

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Aeroelastic Behaviors of Self-anchored Suspension Bridge with Lateral Sag of Main Cable(II) - Focused on the Behavior of Tower - (횡방향 새그를 가진 자정식 현수교의 공탄성 거동(II) - 주탑의 거동을 중심으로 -)

  • Kwon, Soon Duck;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.9 no.2 s.31
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    • pp.269-275
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    • 1997
  • Wind tunnel test results and their interpretations, which were performed to study the aerodynamic stability of tower of self-anchored suspension bridge, are presented in this paper. Tower and full models were tested under smooth and turbulent flow conditions. In the case of the tower with inclined two columns, the vibration due to wakes were occurred at wide velocity zone because the wakes with various frequencies were generated by inclined upstream column. It has to be emphasized that the vibration characteristics of the tower in the self-anchored suspension bridge may be very sensitive to the longitudinal boundary conditions of the girder at the supports. Because of the two natural frequency of the tower, out-of-plane bending and torsional, were not well separated, coupled motions were observed in a wide range of wind velocity. The effectiveness of corner cut, countermeasure to reduce the tower vibrations, was also studied. It has been found that 1:10, comer cut size to column width, may be the most effective ratio for reducing the vibrations.

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Vibration and Ergonomic Exposures Associated With Musculoskeletal Disorders of the Shoulder and Neck

  • Charles, Luenda E.;Ma, Claudia C.;Burchfiel, Cecil M.;Dong, Renguang G.
    • Safety and Health at Work
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    • v.9 no.2
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    • pp.125-132
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    • 2018
  • Background: According to the US Bureau of Labor Statistics, musculoskeletal disorders (MSDs) accounted for 32% of all nonfatal injury and illness cases in 2014 among full-time workers. Our objective was to review and summarize the evidence linking occupational exposures to vibration and awkward posture with MSDs of the shoulder and neck. Methods: A literature search was conducted using the terms musculoskeletal disorders, vibration, and awkward posture. All types of observational epidemiologic studies, with the exception of case reports, published during 1998-2015 were included. Databases searched were MEDLINE (Ovid), Embase (Ovid), Scopus, Ergonomic Abstracts, NIOSHTIC-2, and Health and Safety Science Abstracts. Results: Occupational exposures to whole-body or hand-arm vibration were significantly associated with or resulted in MSDs of the shoulder and neck. Awkward postures while working were also associated with MSDs in these locations. These findings were consistent across study designs, populations, and countries. Conclusion: Occupational exposure to vibration and awkward posture are associated with shoulder and neck MSDs. Longitudinal studies are required to elucidate the mechanisms responsible for these associations, and intervention studies are warranted.

Nonlinear Analysis considered Confinement Effect of Precast Concrete Segment (프리캐스트 콘크리트 세그먼트의 구속효과를 고려한 비선형 해석)

  • Lee, Heon-Min;Kim, Tae-Hoon;Park, Jae-Keun;Kim, Young-Jin;Shin, Hyun-Mock
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.305-308
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    • 2008
  • The purpose of this study is to propose the confinement effectiveness of precast segmental concrete that binding by lateral confining steel in the method of precast segmental concrete pridge piers construction. Generally, the confinement effect of concrete that binding by lateral confining steel is defined by the confinement effectiveness coefficient and the confinement effectiveness coefficient is defined as the ratio of area of effectively confined concrete core to area of confined concrete core. The area of effectively confined concrete core is defined by Arching action occurred on a space of lateral confinement steel and The area of confined concrete core is defined by the ratio of area of longitudinal reinforcement to area of core of section. But in case of precast segmental concrete, concrete cover that exist on top and bottom of concrete segment should be considered.

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MHD WAVE ENERGY FLUXES GENERATED FROM CONVECTION ZONES OF LATE TYPE STARS

  • Moon, Yong-Jae;Yun, Hong-Sik
    • Journal of The Korean Astronomical Society
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    • v.24 no.2
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    • pp.129-149
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    • 1991
  • An attempt has been made to examine the characteristics of acoustic and MHD waves generated in stellar convection zones($4000\;K\;{\leq}\;T_{eff}\;{\leq}\;7000\;K$, $3\;{\leq}\;\log\;g\;{\leq}\;4.5$). With the use of wave generation theories formulated for acoustic waves by Stein (1967), for MHD body waves by Musielak and Rosner (1987, 1988) and for MHD tube waves by Musielak et al.(l989a, 1989b), the energy fluxes are calculated and their dependence on effective temperature, surface gravity and megnetic field strength are analyzed by optimization techniques. In computing magneto-convection models, the effect of magnetic fields on the efficiency of convection has been taking into account by extrapolating it from Yun's sunspot models(1968; 1970). Our study shows that acoustic wave fluxes are dominant in F and G stars, while the MHD waves dominant in K and M stars, and that the MHD wave fluxes vary as $T_{eff}^4{\sim}T_{eff}^7$ in contrast to the acoustic fluxes, as $T_{eff}^{10}$. The gravity dependence, on the other hand, is found to be relatively weak; the acoustic wave fluxes ${\varpropto}\;g^{-0.5}$, the longitudinal tube wave fluxes ${\varpropto}\;g^{0.3}$ and the transverse tube wave fluxes ${\varpropto}\;g^{0.3}$. In the case of the MHD body waves their gravity dependence is found to be nearly negligible. Finally we assesed the computed energy fluxes by comparing them with the observed fluxes $F_{ob}$ of CIV(${\lambda}1549$) lines and soft X-rays for selected main sequence stars. When we scaled the corrected wave fluxes down to $F_{ob}$, it is found that these slopes are almost in line with each other.

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