• 한국강구조학회 논문집
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• 제14권4호
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• pp.481-487
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• 2002

콘크리트충전 강관기둥의 외다이아프램 접합부형식에서, 철골보의 하중이 내부의 콘크리트로 전달되는 하중전달 메카니즘이 아직 명확하게 규명되지 않았다. 여기서 각 층에서 철골보의 전단력은 외부의 강관과 내부의 콘크리트 사이의 부착응력에 의해 전달된다고 본다. 따라서 본 연구는 콘크리트충전 강관기둥의 부착응력을 파악하기 위해, 콘크리트면에만 하중을 가하는 단순가력실험을 실시하였다. 콘크리트 종류, 강관의 형상/길이, 이음부의 유무/뒷댐재의 두께 등을 변수로 총 30개의 실험체를 제작하여 실험을 실시했으며, 각 변수에 따른 실험결과를 비교/분석하고자 했다.

• Journal of the Korean Wood Science and Technology
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• 제36권4호
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• pp.66-76
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• 2008

최근 국내에서 급격히 그 수요가 증가하고 있는 낙엽송과 북미산 SPF(spruce-pine-fir) 규격재의 구조부재로서의 이용에 있어서 가장 간단하면서 많이 이용되는 파스너(fastener)인 못을 이용한 접합에 대해 그 전단성능을 검토하였다. 못접합은 특히 경골목구조(light frame construction)에서는 최적의 시공법으로 인식되고 있으며, 북미와 일본을 중심으로 못접합부에 대한 연구는 많이 진행되어 왔다. 현재 국내의 경골목구조와 기둥-보 공법에서 많이 이용되고 있는 구조부재(축재와 면재)의 못을 이용한 못접합부에 대해 그 전단성능의 기초적인 검토를 행하였다. 못접합부는 면재를 개입한 상태에서 주부재와 측면부재의 방향성에 따라 구분하여 주부재의 방향, 측면부재의 방향, 못의 종류에 따라 전단시험을 행하여 각각의 방향에 따른 못접합부의 전단성능을 비교 검토하였다. SPF 스터드재에 있어서는 낙엽송 집성재나 낙엽송 소재에 비해 못의 종류, 주부재와 면재의 방향성에 따른 전단성능의 차이가 현저하게 나타났다. 또한, 항복내력 및 최대내력과 접합계수와의 관계는 부재간의 배치상태에 따라 다르게 나타났다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.709-730
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• 2017

To address the challenge of unprecedented growth in mobile data traffic, ultra-dense network deployment is a cost efficient solution to offload the traffic over some small cells. The overlapped coverage areas of small cells create more than one candidate access points for one mobile user. Signal strength based user association in IEEE 802.11 results in a significantly unbalanced load distribution among access points. However, the effective bandwidth demand of each user actually differs vastly due to their different preferences for mobile applications. In this paper, we formulate a set of non-linear integer programming models for joint user association control and user demand guarantee problem. In this model, we are trying to maximize the system capacity and guarantee the effective bandwidth demand for each user by soft-association control with a software defined network controller. With the fact of NP-hard complexity of non-linear integer programming solver, we propose a Kernighan Lin Algorithm based graph-partitioning method for a large-scale network. Finally, we evaluated the performance of the proposed algorithm for the edge users with heterogeneous bandwidth demands and mobility scenarios. Simulation results show that the proposed adaptive soft-association control can achieve a better performance than the other two and improves the individual quality of user experience with a little price on system throughput.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2356-2363
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• 2015

본 연구는 볼트강도등급 10.9에 의해 추천되는 조임 토크 640~800(Nm)가 볼트-너트 체결체에 가해졌을 때 풀림 방지를 위한 코일 스프링의 삽입 및 시뮬레이션 기반 설계 최적화에 관한 것이다. 먼저 볼트-너트-코일스프링으로 구성된 조립체에 대하여 등가응력에 기반을 둔 구조 안전성 판단을 위한 조립체 구조해석 시뮬레이션을 수행한다. 그리고 이러한 해석 시뮬레이션 결과로부터 설계 개선안 도출을 위한 설계전략을 수립한다. 또한 이 전략 안에서 기존 설계의 성능을 개선해 나가는 반복 과정을 제안한다. 이 과정에서는 먼저 반응표면법을 사용하여 설계 파라미터 후보점을 찾고, 그 후보점의 반응값과 실제 시뮬레이션 결과를 비교함으로써 설계 후보점(코일스프링 감감수 N = 6)이 최적인지를 검증한다.

• 화약ㆍ발파
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• 제17권4호
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• pp.8-17
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• 1999

Unfortunately leaks occur in heat exchangers periodically, usually at the tube to tubeplate joint. The usual method of repair is to plug off the defective area and isolate the tubes of concern from the circuit. If the leaks continua the thermal capacity of the units is progressively reduced and for this reason the alternative of using an internal bridging sleeve has been examined. This paper discusses the overall development activities that has been found necessary to bring this repair procedure to a successful conclusion for use on the nuclear steam generator. In this work we have investigated optimum explosives and explosive quality, explosive sleeving's thickness, the design of sheath stress relieving heat treatment pull-out load, hydraulic leakage, stress corrosion cracking properties. The results obtain are as follows : (1) The optimum explosives and explosive qualities are PETN and about 15~40 gr/ft of explosive sleeving in nuclear steam generator. (2) Explosive sleeving's thickness is 1.1~l.4mm, If groove of 0.35mm formed in sleeve outside existed, For the hydraulic leakage is go up, explosive sleeving of formed groove are applicate tube and turnplate. (3) If the stress relieving heat treatment are experiment in $750^\circ{C}$, $850^\circ{C}$, 15 minutes Pull-out strength of sleeving 1,500~2,300kg, hydraulic leakage is $250kg/cm^2$.

• 대한정형도수물리치료학회지
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• 제9권2호
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• pp.25-45
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• 2003

Sling exercise treatment(S-E-T) is a therapeutic exercise based on scientific studies for the purpose of treating musculoskeletal or neurological disorders thereby improving strength, endurance, and skills for sensory-motor integration. Exercise resistance and intensity can be modified in various ways by changing the length of rope, patient position, therapist's manual resistance, and using elastic rope. The therapist can also progress to successively higher levels of exercise resistance and intensity by changing the position of the hanging point: the subject of this article. In brief, there are three axial components in S-E-T; hanging point, motor axis, and suspension point. The hanging point can be changed in several ways in relation to the joint; axial, superior, inferior, medial, and posterior hanging points. The position of the hanging point affects the amount of load on agonist and antagonist muscles as well as on the range of motion. To create an advanced exercise program, selection of hanging point can be two-dimensional such as superior-lateral or anterior-medial. Therapists, therefore, can freely but carefully select the best hanging point based on the purpose of the exercise and their level of knowledge in S-E-T.

• 한국컴퓨터정보학회논문지
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• 제23권6호
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• pp.43-49
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• 2018

In this paper, we propose a taping therapy as effective intervention for patients with the back pain. The purpose of this study is to investigate the effects of taping intervention on the VAS evaluated score and he muscular activation degree among 119 paramedics with musculoskeletal injury. In order to achieve the purpose of the study, data was collected from 15 paramediecs in the paramedics department of 3 fire stations under J city's fire defense headquarters. The following results can be obtained by measuring the subjective, the back muscle strength and the buckling-anteflexion before and after the taping for 15 119 paramedics. Through the verification experiment of taping effect to paramedics during the stretcher lifting in this study the VAS evaluated score for the backache are $1.67{\pm}0.62$ before and $0.80{\pm}0.68$ after the application of taping which show statistically significant decrease(p<0.05). In the experimentof joint operation range the measured buckling anteflexion length are $14.62cm{\pm}4.89$ before and $16.41cm{\pm}4.11cm$ after the application of taping which show statistically meaningful difference(p<0.05). In the comparison of muscle activity about paramedics erector spinae(ES) shows the meaningful decrease and external obliques(EO) displays the significant increase. Erector spinae(ES) and internal obliques(IO) show the increasing trend in the muscle activity although they are not significant. the muscle activity for the erector spinae is lowered so that the contribution to the force required for the extensor during the stretcher lifting is resultingly reduced to have the effects of enhancing the activity of abdominal muscles.

• Steel and Composite Structures
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• 제19권6호
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• pp.1561-1580
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• 2015

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.116-125
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• 2018

Modified 9Cr-1Mo ferritic steel is a preferred material for steam generators in nuclear power plants for their creep strength and good corrosion resistance. Austenitic stainless steels, such as type 316LN, are used in the high temperature segments such as reactor pressure vessels and primary piping systems. So, the dissimilar joints between these materials are inevitable. In this investigation, dissimilar joints were fabricated by the Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. The notch tensile properties and Charpy V-notch impact toughness properties of various regions of dissimilar metal weld joints (DMWJs) were evaluated as per the standards. The microhardness distribution across the DMWJs was recorded. Microstructural features of different regions were characterized by optical and scanning electron microscopy. Inhomogeneous notch tensile properties were observed across the DMWJs. Impact toughness values of various regions of the DMWJs were slightly higher than the prescribed value. Formation of a carbon-enriched hard zone at the interface between the ferritic steel and the buttering material enhanced the notch tensile properties of the heat-affected-zone (HAZ) of P91. The complex microstructure developed at the interfaces of the DMWJs was the reason for inhomogeneous mechanical properties.

• 한국전산구조공학회논문집
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• 제21권4호
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• pp.307-315
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• 2008

PPS(Post-tensioned Precast concrete System)공법은 U자형 PC로 제작된 넓은 보와 PC또는 현장 타설 콘크리트로 제작한 기둥으로 구성되며, PC보와 기둥의 일체성 확보를 위하여 프리스트레스를 도입하였다. 본 연구에서는 포스트텐션을 도입한 넓은 보-기둥 접합부의 구조적 특성을 규명하고, 다양한 변수해석이 가능하기 위한 자료를 제공하고자 유한요소해석 프로그램인 ANSYS을 사용하여 비선형 해석을 수행하였다 콘크리트에 대한 해석요소는 8개의 절점을 가지며 각 절점이 3개의 자유도(X, Y, Z축에 대한 병진 변위)를 갖는 Solid 65요소를 사용하였다. Solid 65요소에서 전단전달계수(Shear-Transfer factor)는 실험값에 근사적으로 해석값을 맞추기 위한 영향 계수값으로 균열이 발생하는 위치에 대한 전단강도의 감소를 반영한다. 그 결과, 본 실험체에 대한 해석에서는 열려진 전단전달계수 0.125와 닫혀진 전달계수 0.85에 기초하여 해석한 결과 닫혀진 전단전달계수는 0.85에서 열려진 전단전달계수에서는 0.2일때 가장 실험값에 근사한 해석치를 보였다.