• 대한의용생체공학회:의공학회지
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• 제34권1호
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• pp.1-7
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• 2013

According to the frequent use of mobile devices, risk of repetitive strain injury for the finger joints was increasing recently. The purpose of this study was to investigate the difference of muscular endurance limit of the thumb between adults and children. A total of thirty subjects (15 adults: $41.0{\pm}7.9$ years and 15 children: $9.5{\pm}2.7$ years) was recruited for this experiment. Maximum voluntary contraction (MVC) of the thumb was measured for 100 trials for each subject by using a push-pull gauge. From the maximum peak value obtained, three main factors (MVC, endurance limit, and fatigue index) were defined to quantify fatigue characteristics of the thumb flexor muscle. The experimental results showed that the mean of MVC, endurance limit, and fatigue index of the children were approximately 50% compared to the adults (p < 0.001). From the results of Pearson correlation test, the endurance limit was highly correlated with weight, age, hand length rather than height. Based on this study, children are more vulnerable to repetitive task using the thumb such as text/SNS messaging, gaming, and scrolling.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.290-291
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• 2008

Recently High Temperature Superconductor(HTS) Tape is limelight of the applied superconducting machines. Mainly used superconducting tape are BSCCO tape and YBCO coated tape. These superconducting tape are applied such as SMES, superconducting generator and MAGLEV. Actually superconductor tape's experimental gauge is short. For this reason, experiment was conducted. Firstly length of 50cm BSCCO, YBCO Coated conductor@Cu and YBCO coated conductor@sus are prepared. and flow the over-current. Secondly, BSCCO and Coated conductor connected with lenth of 25cm and flow the over-current. Coupled line of HTS tape was compared with single line of HTS tape and these overcurrent characteristics was investigated.

• 한국구조물진단유지관리공학회 논문집
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• 제4권2호
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• pp.103-111
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• 2000

The objectives of the study are to know the strain distribution and modal dynamic behaviour of steel bridge girders by actual traffic load. The live load effect depends on many parameters including the span length, gross vehicle weight, axle weight, axle configuration so on. For the estimation of static and dynamic characteristic, strain data caused by moving loads and traffic characteristics of passing vehicle under actual traffic load have measured using Bridge Weigh in Motion. To confirm the reliability of BWIM system, strain data measured using the $120{\Omega}$ strain gauge under the same condition. It is considered that the data acquired from BWIM system have reliability through the analysis and comparison between stress measured by strain data from BWIM and computed by FEM. Additionally according to the measured strain data of up-line and down-line on the highway, the up-line bridge grows more faster than the down-line bridge and girder 4 and 5 carry more load when vehicles pass the inner line and girder 2 and 3 does when vehicles pass the outer line as this case(the bridge composed with 5 girders).

• Advances in aircraft and spacecraft science
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• 제6권3호
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• pp.225-238
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• 2019

A spike attached to a blunt nosed body significantly alters its flow field and influences the aerodynamic coefficients at hypersonic speed. The basic body is an axisymmetric, with a hemisphere nose followed by a cylindrical portion. Five different types of spikes, namely, conical aerospike, hemisphere aerospike, flat-face aerospike, hemisphere aerodisk and flat-face aerodisk are attached to the basic body in order to assess the aerodynamic characteristic. The spiked blunt body without the aerospike or aerodisk has been set to be a basic model. The coefficients of drag, lift and pitching moment were measured with and without blunt spike body for the length-to-diameter ratio (L/D) of 0.5, 1.0, 1.5 and 2.0, at Mach 6 and angle of attack up to 8 degrees using a strain gauge balance. The measured forces and moment data are employed to determine the relative performance of the aerodynamic with respect to the basic model. A maximum of 77 percent drag reduction was achieved with hemisphere aerospike of L/D = 2.0. The comparison of aerodynamic coefficients between the basic model and the spiked blunt body reveals that the aerodynamic drag and pitching moment coefficients decrease with increasing the L/D ratio and angle of attack but the lift coefficient has increasing characteristics.

• Advances in materials Research
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• 제11권1호
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• pp.59-73
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• 2022

In the construction industry, thin-walled frame elements with very slender open cross-sections and low torsional stiffness are often subjected to a complex loading condition where axial, bending, shear and torsional stresses are present simultaneously. Hence, these often fail in instability even before the yield capacity is reached. One of the most common instability conditions associated with thin-walled structures is Lateral Torsional Buckling (LTB). In this study, a first order Generalized Beam Theory (GBT) formulation and numerical analysis of cold-formed steel lipped channel beams (C80×40×10×1, C90×40×10×1, C100×40×10×1, C80×40×10×1.6, C90×40×10×1.6 and C100×40×10×1.6) subjected to uniform moment is carried out to predict pure Lateral Torsional Buckling (LTB). These results are compared with the Finite Element Analysis of the beams modelled with shell elements using ABAQUS and analytical results based on Euler's buckling formula. The mode wise deformed shape and modal participation factors are obtained for comparison of the responses along with the effect of varying the length of the beam from 2.5 m to 10 m. The deformed shapes of the beam for different modes and GBTUL plots are analyzed for comparative conclusions.

• Geomechanics and Engineering
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• 제35권1호
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• pp.1-11
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• 2023

A growing trend of utilizing helical piles for soft soil strata to support infrastructure projects is currently observed in Saemangeum, South Korea. Recognized mainly due to its ease of installation and reusability proves to be far more superior compared to other foundation types in terms of sustainability. This study applies modified p-y springs to characterize the behavior of a laterally loaded helical pile with a shaft diameter of 89.1 mm affixed with 3 helices evenly spaced along its embedded length of 2.5 m. Geotechnical soil properties are correlated from CPT data near the test bed vicinity and strain gauges mounted on the shaft surface. A modification factor is applied on the p-y springs to adjust the simulated data and match it to the bending moment, soil resistance and deflection values from the strain gauge measurements. The predicted lateral behavior of the helical pile through the numerical analysis method shows fairly good agreement to the recorded field test results.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.233-249
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• 1999

Primary fixation is one of the most important factor in establishing adequate osseointegration between implant and bone. To evaluate the initial healing response of bone around implants without primary bone contact, this study was designed to create considerable space between implant and bone in 5 mongrel dogs, about 1-year old. After 3 holes of 6.0mm in diameter were prepared at the femur neck of the dogs, commercially pure titanium thread type implants(STERI-$OSS^{(R)}$), 8mm in length and 3.8mm, 5.0mm and 6.0mm in diameter, were inserted. Implants were supported by only nonresorbable membrane($Teflon^{(R)}$), and the penetration of upper soft tissue into the gap was inhibited by it. The each implant was positioned in the center of the drilled hole. 9 implants with different diameters were inserted in 3 dogs for histologic observation, and 12 were inserted in 2 dogs for mobility test and removal torque test.Fluorescent dyes were injected in order of Doxycycline, Alizarin Red S, and Calcein at intervals of 2 weeks. At 4-, 8-, and 12-week after placement, 3 dogs were sacrificed for histologic observation, and at 8- and 12-week after placement, 2 dogs were sacrificed for mobility test using $Periotest^{(R)}$ (Simens AG, Bensheim, Germany) and torque test using Autograph AGS-1000D $series^{(R)}$(Japan). The result were as follows: 1. The wider the gap between bone and implant was, the less bone maturity was, and the later osseointegration was occurred. Trabecular direction of new bone around implant was changed from parallel to perpendicular to the implant, and the gap was filled with new bone, over time. 2. There was a decreasing tendency over time in the mobility of all implants, but the wider gap between bone and implant was, the smaller decrease of the mobility was. 3. There was a increasing tendency over time in the removal torque gauge of all implants, and the wider gap was, the smaller increase of the removal torque gauge was. The results suggest that osseointegration in case of implant without primary bone contact may be obtained by guided bone regeneration technique with prolonged healing period, but the time of second surgery should be considered carefully.

• 한국도로학회논문집
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• 제11권2호
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• pp.121-132
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• 2009

본 연구에서는 노후 콘크리트 포장의 효율적 유지보수를 위하여 국내 최초 적용된 Thin Bonded Continuously Reinforced Concrete Overlay (CRCO) 공법의 초기 공용성이 평가되었다. 서해안 고속도로의 표층 파손 구간에 Jointed Plain Concrete Pavement (JPCP) 덧씌우기와 CR8O 공법을 이용한 보수가 진행되었다. JPCP 덧씌우기 공법이 적용된 구간에서는 인접 슬래브가 완전히 분리되도록 덧씌워진 층의 줄눈을 완전히 커팅하였으며, CRCO 공법이 적용된 구간에서는 0.5% 종방향 철근과 위치 고정용 횡방향 철근을 설치한 후 그 위에 덧씌우기를 수행하였다. 두 구간 모두에서 3종시멘트가 이용되었다. 현장 강도 시험 결과, 1$\sim$3일 내에 교통개방이 가능한강도가 발현된 것이 확인되었으며, vibrating wire gauge (VWG) 데이터 분석 결과 CRCO 공법이 기존 포장의 줄눈 거동을 억제하는 것으로 나타났다. 부착강도 시험결과, 재령에 상관없이 높은 부착강도가 확인되었다. 한편 JPCP 덧씌우기 공법이 적용된 구간에서는 중앙부에서, CRCO 공법이 적용된 구간에서는 CRCO 포장과 같은 무작위 횡방향 균열이 관찰되었으며, CRCO 공법의 균열폭 거동이 JCP 보다 50% 정도 낮은 것으로 나타났다.

• 대한치과교정학회지
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• 제36권5호
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• pp.324-330
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• 2006

Sandblasted large grit, acid etched(SLA)표면처리 된 교정용 미니 임플랜트와 평활면을 가진 교정용 미니 임플랜트 사이에 제거회전력과 조직학적 소견을 통해 표면처리된 교정용 임플랜트의 임상적 가능성에 대하여 알아보고자 하였다. 실험재료로는 길이가 9.5 mm, 외경이 1.8 mm인 custom made, screw shaped, titanium implants가 사용되었다. 미니 임플랜트는 두개의 군으로 분류되었는데 SLA군은 20개의 SLA 표면처리된 미니 임플랜트이었고, 평활면군은 크기와 형태가 같지만 SLA처리공정이 생략되어 제작된 20개의 미니 임플랜트로 구성되었다. 이들은 10마리 가토의 경골에 식립되었다. 각각의 가토의 우측 경골에는 SLA군의 미니 임플랜트 2개가 식립되었고, 좌측 경골에는 평활면군의 미니 임플랜트 2개가 식립되었다. 각 군에는 식립 직후 Ni-Ti coil spring에 의해 약 150 g의 지속적인 견인력이 주어졌다. 식립 6주 후에 10마리의 가토를 희생하였고, 안정된 상태에서 Ni-Ti coil spring을 제거하였으며 digital torque gauge를 이용하여 제거 회전력을 측정하였다. 식립 6주 후에 SLA군의 경우 (8.29 Ncm) 평활면군 (3.34 Ncm)에 비해 더 높은 평균 제거회전력을 나타내었고 조직학적 소견에서도 screw 하방에서의 신생골 형성이 관찰되었다. SLA 표면처리된 미니 임플랜트는 평활면 미니 임플랜트에 비해 좀 더 강한 교정력에 저항할 수 있을 것으로 예상되었다.

• 한국강구조학회 논문집
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• 제17권6호통권79호
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• pp.681-688
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• 2005

본 연구는 광섬유 브래그 격자 (fiber Bragg grating, FBG) 센서를 이용하여 보강이 실시된 철도판형교의 수직처짐을 산정하고 이를 통해 교량의 정적 및 동적 거동을 모니터링 하는데 목적이 있다. 7개의 센서로 다중화(multiplexing)된 FBG 센서 2쌍을 지간 12.9 m인 철도 판형교의 상부와 하부 플랜지의 표면에 부착하였다. 이렇게 수평 배치된 FBG 센서로부터 직접 곡률을 측정하고 기하학적인 처짐-곡률관계와 회귀분석을 통해 교량의 처짐을 유추하였다. FBG 센서의 정확도를 검증하기 위해 교량의 중앙 지점에 기존의 전기식 변형률 센서와 처짐계를 설치하였다. 교량의 거동을 측정하기 위해 열차 재하실험과 증속실험을 실시하였다. 증속실험은 열차의 속도를 10 km/h 에서 90 km/h까지 10 km/h 씩 증가시키며 교량의 동적 거동을 분석하였다. 측정 변형률을 비교한 결과 FBG 센서와 전기식 센서가 최대오차 7%이내의 우수한 상관관계를 보였으며, 본 연구에서 제안된 실험법으로 유추된 최대처짐을 처짐계를 이용한 결과와 비교하였을 때 5% 이내의 오차를 보였다. 따라서 철도판형교의 안전성 평가를 위한 처짐 모니터링 시 FBG 센서의 적용성이 우수하다고 판단된다.