• Steel and Composite Structures
• /
• 제16권5호
• /
• pp.455-480
• /
• 2014

Sixteen concrete filled square CFRP-steel tubular (S-CFRP-CFST) stub columns under axial compression were experimentally investigated. The experimental results showed that the failure mode of the specimens is strength loss of the materials, and the confined concrete has good plasticity due to confinement of the CFRP-steel composite tube. The steel tube and CFRP can work concurrently. The load versus longitudinal strain curves of the specimens can be divided into 3 stages, i.e., elastic stage, elasto-plastic stage and softening stage. Analysis based on finite element method showed that the longitudinal stress of the steel tube keeps almost constant along axial direction, and the transverse stress at the corner of the concrete is the maximum. The confinement effect of the outer tube to the concrete is mainly focused on the corner. The confinements along the side of the cross-section and the height of the specimen are both non-uniform. The adhesive strength has little effect both on the load versus longitudinal strain curves and on the confinement force versus longitudinal strain curves. With the increasing of the initial stress in the steel tube, the load carrying capacity, the stiffness and the peak value of the average confinement force are all reduced. Equation for calculating the load carrying capacity of the composite stub columns is presented, and the estimated results agree well with the experimental results.

• 한국식품영양학회지
• /
• 제12권5호
• /
• pp.523-528
• /
• 1999

The influence of ginseng on the paste or gelatinization properties by amylograph and mixing properties by farinograph of wheat flour and on quality properties color cooking quality textural and sensory properties and reducing microbial population of LL(Long Life) noodles was studied. The contents of ginseng used were from 5% to 10% based on flour weight. The viscosity property of wheat flour with ginseng was increased the initial pasting temperature but the amylograph peak viscosity were decreased in vice versa. The farinograph absorption stability and breakdown were increased by ginseng. The whiteness of Ll nodles manufactured with ginseng was lower than that of control The shear extrusion force and hardness of LL noodles manufactured with ginseng were shown much higher value than those of control. At cooking quality examination of LL noodles manufactured with ginseng weight of cooked LL noodles was decreased but volum was appeared in ice versa,. Extraction amounts of LL noodles manufactured with ginseng during cooking were much smaller than those of control Total count of microorganism of Ll noodles manufactured with ginseng were decreased during storage at 3$0^{\circ}C$ Sensory properties of cooked LL noodles which was manufactured with ginseng showed quite acceptable. Based on the cooking and sensory evaluation test addition of 7.0% ginseng to wheat flour may be suitable for processing LL noodles.

• 한국식품영양학회지
• /
• 제12권3호
• /
• pp.252-257
• /
• 1999

In an attempt to evaluate the effects of calcium on paste or gelatinization properties by amylograph and mixing properties by farinograph of wheat flour and on viscosity property cooking quality textural and sensory properties of Ramyon were examined. The contents of calcium used were from 1.0% to 3.0% based on flour weight. The viscosity property of wheat flour with calcium was increased the initial past-ing temperature but the amylograph peak viscosity were decreased in vice versa. The farinograph absorp-tion stability and breakdown were increased by calcium. The shear extrusion force and hardness of Ram-yon manufactured with calcium were shown much higher value than those of control. At cooking quality examination of Ramyon manufactured with calcium weight of cooked Ramyon was increased by volume was decreased. Extraction amounts of Ramyon manufactured with calcium during cooking were much smaller than those of control. These changes will provided many advantages in the preparation of Ram-yon. The I2 reaction value of Ramyon manufactured with calcium and control were shown to almost same values. Sensory properties of cooked Ramyon which was manufactured with calcium showed quite acceptable. Based on the cooking and sensory evaluation test addition of 0.3% calcim to wheat flour may be suitable for processing Ramyon.

• 한국식품과학회지
• /
• 제28권1호
• /
• pp.58-65
• /
• 1996

탄산나트륨, 탄산칼륨과 이들의 혼합염(탄산나트륨/탄산칼륨=0.7-2.0)이 밀가루의 아밀로그래프에 의한 호화성질과 파리노그래프에 의한 반죽성질을 조사하였다. 알칼리제 혼합염(0.16%)이 국수의 성질에 미치는 영향도 아울러 검토하였다. 소금(0.17%)과 알칼리는 아밀로그래프의 호화개시 온도를 감소시켰고 최고점도를 증가시켰으며 그 효과는 탄산나트륨이 가장 현저하였다. 최고점도는 알칼리의 농도가 증가할수록 증가하였고 동일한 농도에서는 혼합비율에 따른 차이는 없었다. 파리노그래프의 흡수율은 소금에 의하여 감소되었고 알칼리제에는 영향을 받지 않았으나 소금과 알칼리제가 동시에 존재할 때는 소금의 효과가 감소하였다. 소금과 알칼리제는 반죽의 안정도를 크게 증가시켰으며 소금의 효과가 더욱 뚜렸하였다. 그러나 소금의 존재시 알칼리제 단독 또는 혼합 사용하였을 때는 농도에 관계없이 알밀로그람과 파리노그람 특성값은 큰 차이를 보이지 않았다. 알칼리제 혼합염의 첨가에 따라 건면의 황색도와 파쇄력이 증가하였고 파쇄력은 혼합비율 1.0에서 가장 큰 값을 보였다. 삶은 국수의 경우 무게와 부피증가 정도는 알칼리제 혼합염의 첨가에 따라 큰 변화가 없었으나 전단력과 압착력은 혼합비율 1.0에서 가장 높은 값을 보였다.

• 한국운동역학회지
• /
• 제16권2호
• /
• pp.145-151
• /
• 2006

A large interindividual variability and some abnormally kinematic patterns at the lower extremity were the main features of the gait in children with Down syndrome. The purposes of this study were to investigate the gait asymmetry and biomechanical difference between dominant leg and non dominant leg in children with Down syndrome. Seven boys with Down Syndrome(age: $120{\pm}0.9yrs$, weight $34.4{\pm}8.4kg$, leg length: $68.7{\pm}5.0cm$) participated in this study. A 10.0 m ${\times}$ 1.3 m walkway with a firm dark surface was built and used for data collection. Three-dimensional motion analyses were performed to obtain the joint angles and range of motions. The vertical ground reaction forces(%BW) and impulses($%BW{\cdot}s$) were measured by two force plates embedded in the walkway. Asymmetry indices between the legs were computed for all variables. After decision the dominant leg and the non dominant leg with max hip abduction angle, paired samples t-test was employed for selected kinematic and ground reaction force variables to analyze the differences between the dominant leg and the non dominant leg. The max hip abduction angle during the swing phase showed most asymmetry, while the knee flexion angle at initial contact showed most symmetry in walking and running. The dominant leg showed more excessive abduction of hip in the swing phase and more flat-footed contact than the non dominant leg. Vertical peak force in running showed more larger than those of in walking, however, vertical impulse showed more small than walking due to decrease of support time. In conclusion, the foot of dominant leg contact more carefully than those of non dominant leg. And also, there are no significant difference between the dominant leg and the non dominant leg in kinematic variables and ground reaction force due to large interindividual variability.

• 한국산학기술학회논문지
• /
• 제22권5호
• /
• pp.128-135
• /
• 2021

박판관은 충돌안전을 위한 에너지 흡수장치 중의 하나로써 가벼우면서도 에너지 흡수 효율이 좋아 널리 이용되어 왔다. 그러나 일반적인 박판관은 충돌 초기 피크하중(IPCF: Initial Peak Crushing Force)이 높게 유발될 뿐 아니라 반복적으로 나타나는 피크하중으로 인하여 충돌에너지 흡수장치로써의 안정성이 다소 떨어진다는 단점이 있다. 충돌 초기 피크하중을 감소시키고 충돌에너지 흡수장치의 안정성을 키우기 위하여 박판 파형관이 도입되었다. 파형관의 성능은 기하 형상에 큰 영향을 받기 때문에 최적설계 기법을 적용하여 파형관의 성능을 최적화할 수 있다. 본 논문에서는 충돌안전도 해석에 기반한 형상 최적설계를 수행하기 위하여 적응 근사모델(adaptive surrogate model)을 활용한 최적설계 기법을 활용하였다. 파형의 진폭 및 파장 뿐 아니라 형상의 곡률 변화를 설계 변수로써 고려하였다. 형상 설계 매개변수화를 수행하기 위하여 몰핑(morphing) 방법을 채택하였다. 수치 예제를 통해서 적응 근사모델에 기반한 최적설계 결과와 기존 근사모델에 기반한 최적설계 결과를 비교하고 적응 근사모델에 기반한 최적설계 방법이 좀 더 효율적인 결과를 도출함을 보였다.

• 한국운동역학회지
• /
• 제24권3호
• /
• pp.239-248
• /
• 2014

The purpose of this study was to quantify kinematic and kinetic characteristics of Yin-yang Bo gait according to their motor expertise, one of the Seokmun Ilwol martial art gait patterns. Yin-yang Bo gait pattern shows initial forefoot contact instead of heel contact, and increased time of stance phase time, internal-external rotation of ankle-knee-hip joints and pelvic. It aims to produce and store the more energy through continuous homeostasis of center of gravity (COG) and performance of stretch-shortening cycle. Some of these characteristics also were similar to the gait modification strategies for reducing knee adduction moment such as toe-out progression, medial thrust, internal rotation of hip joint. To identify the characteristics, four factors of expert Yin-yang Bo gait performance group were compared to that of none expert group; 1) angles of COG displacement and rotation 2) distal joint pre-rotation in internal-external rotation of ankle-knee-hip joints and pelvic, 3) invariability pelvic potential and pelvic segment total energy 4) knee abduction moment. Six healthy(three male) subjects participated in the experiment to perform Yin-yang gait pattern. Three-dimensional and force plate data were collected. Kinematic and kinetic data were compared between two groups using t-tests. Results showed that 1) the peak point of COG internal rotation angle was reduced in expert group, 2) kneeexternal and hip joint -internal and pelvic rotation angle peak frames were more near points in expert group.

• 한국공간구조학회논문집
• /
• 제18권3호
• /
• pp.37-44
• /
• 2018

A base isolation system is widely used to reduce seismic responses of low-rise buildings. This system cannot be effectively applied to high-rise buildings because the initial stiffness of the high-rise building with the base isolation system maintains almost the same as the building without the base isolation system to set the yield shear force of the base isolation system larger than the design wind load. To solve this problem, the mid-story isolation system was proposed and applied to many buildings. The mid-story isolation system has two major objectives; first to reduce peak story drift and second to reduce peak drift of the isolation story. Usually, these two objectives are in conflict. In this study, a hybrid mid-story isolation system for a tall building is proposed. A MR (magnetorheological) damper was used to develop the hybrid mid-story isolation system. An existing building with mid-story isolation system, that is "Shiodome Sumitomo Building" a high rise building having a large atrium in the lower levels, was used for control performance evaluation of the hybrid mid-story isolation system. Fuzzy logic controller and genetic algorithm were used to develop the control algorithm for the hybrid mid-story isolation system. It can be seen from analytical results that the hybrid mid-story isolation system can provide better control performance than the ordinary mid-story isolation system and the design process developed in this study is useful for preliminary design of the hybrid mid-story isolation system for a tall building.

• Computers and Concrete
• /
• 제24권1호
• /
• pp.73-83
• /
• 2019

Concrete reinforced with fiber reinforced polymer (FRP) bars (FRP-RC) has attracted a significant amount of research attention in the last three decades. A limited number of studies, however, have investigated the effect of bond slip on the performance of FRP-RC columns under eccentric loading. Based on previous experimental study, a finite-element model of eccentrically loaded FRP-RC columns was established in this study. The bondslip behavior was modeled by inserting spring elements between FRP bars and concrete. The improved Bertero-Popov-Eligehausen (BPE) bond slip model with the results of existing FRP-RC pullout tests was introduced. The effect of bond slip on the entire compression-bending process of FRP-RC columns was investigated parametrically. The results show that the initial stiffness of bond slip is the most sensitive parameter affecting the compression-bending performance of columns. The peak bond stress and the corresponding peak slip produce a small effect on the maximum loading capacity of columns. The bondslip softening has little effect on the compression-bending performance of columns. The sectional analysis revealed that, as the load eccentricity and the FRP bar diameter increase, the reducing effect of bond slip on the flexural capacity becomes more obvious. With regard to bond slip, the axial-force-bending-moment (P-M) interaction diagrams of columns with different FRP bar diameters show consistent trends. It can be concluded from this study that for columns reinforced with large diameter FRP bars, the flexural capacity of columns at low axial load levels will be seriously overestimated if the bond slip is not considered.

• 한국재료학회지
• /
• 제31권1호
• /
• pp.38-42
• /
• 2021

In this study, high temperature wetting analysis and AZ80/Ti interfacial structure observation are performed for the mixture of AZ80 and Ti, and the effect of Al on wetting in Mg alloy is examined. Both molten AZ80 and pure Mg have excellent wettability because the wet angle between molten droplets and the Ti substrate is about 10° from initial contact. Wetting angle decreases with time, and wetting phenomenon continues between droplets and substrate; the change in wetting angle does not show a significant difference when comparing AZ80-Ti and Mg-Ti. As a result of XRD of the lower surface of the AZ80-Ti sample, in addition to the Ti peak of the substrate, the peak of TiAl3, which is a Ti-Al intermetallic compound, is confirmed, and TiAl3 is generated in the Al enrichment region of the Ti substrate surface. EDS analysis is performed on the droplet tip portion of the sample section in which pure Mg droplets are dropped on the Ti substrate. Concentration of oxygen by the natural oxide film is not confirmed on the Ti surface, but oxygen is distributed at the tip of the droplet on the Mg side. Molten AZ80 and Ti-based compound phases are produced by thickening of Al in the vicinity of Ti after wetting is completed, and Al in the Mg alloy does not affect the wetting. The driving force of wetting progression is a thermite reaction that occurs between Mg and TiO2, and then Al in AZ80 thickens on the Ti substrate interface to form an intermetallic compound.