• 한국콘텐츠학회논문지
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• 제14권9호
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• pp.582-588
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• 2014

본 연구는 국가간 공동연구 네트워크가 기술 지식의 확산에 어떠한 영향을 미치는 가와 네트워크 상에서 중심성이 높은 국가가 새로운 기술을 얼마나 받아들이는지 분석하고 그 의미를 찾는 것을 목적으로 한다. 이를 위해 이차전지 분야와 전기 자동차 분야 논문 정보를 이용하여 연도별 국가간 공동연구 네트워크 밀도와 참여국가 수를 측정하고 변수간의 회귀분석을 수행하였다. 분석결과, 이차전지 분야 공동연구 네트워크 밀도가 증가할수록 참여국가 수는 선형관계로 증가하는 것으로 나타났다. 또한 공동연구 네트워크 상에서 연결정도 중심성이 높은 국가들이 중대형 이차전지 분야 개발을 주도하고 있는 것으로 나타났다. 반면에 전기 자동차 분야의 경우, 네트워크 밀도값은 증가 추세가 나타나지 않지만, 참여국가 수는 증가하고 있는 것으로 나타났다. 이는 기술 확산을 촉진하는데 있어서, 국가간 공동연구가 중요한 역할을 하지만 필요충분 조건은 아닌 것으로 분석되었다. 이러한 결과는 기술 성장에 있어서 반드시 필요한 기술 확산을 촉진하는 요인을 통계적으로 검증하였다는 점에서 의의가 있으나, 네트워크 상에서 중심적 역할에 대한 지표를 연결정도 중심성 만으로 측정하였다는 점과 네트워크 밀도가 행위자간 상호작용에 있어서 반드시 두 행위자간 관계만을 측정한다는 점에서 연구의 한계가 존재한다. 따라서 향후 다수의 연구자간 상호작용을 측정할 수 있는 방안에 대한 연구가 필요하다.

• 한국지반공학회논문집
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• 제15권5호
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• pp.229-240
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• 1999

본 논문에서는 유한차분법, 채널망 해석법 및 절리망 해석법 등 다양한 해석기법을 이용하여 개별 암석절리 및 절리암반에서의 지하수 유동과 주입재의 유동거동을 연구하였다. 유동거동은 두개의 상이한 관찰규모, 즉 변화하는 간극분포를 가진 실험실 규모의 거친 절리면과 3개의 절리군에 속한 단절된 절리들을 포함하고 있는 현장 규모의 절리암반에 대해 수행되었다. 단일절리에서의 유동해석결과 물과 주입재 모두 간극분포에 의존하는 채널흐름의 특성을 확인할 수 있었다. 유한차분법과 기존의 이론해에 의한 유량 계산결과를 비교 분석하였다. 절리암반의 경우 절리의 수와 굴착된 원형공동의 직경을 증가시키면서 공동내부로의 지하수 유입량을 분석하였다. 이 분석에는 절리망 해석법과 Goodman의 이론해를 사용하여 결과를 비교하였다. 또한 절리망 해석법의 경계효과, 절리망의 비균질성이 지하수 유동에 미치는 영향 등을 논의하였다.

• 한국해양공학회지
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• 제13권3호통권33호
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• pp.57-67
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• 1999

Welding is widely applicable and reliable process and is mainly adopted for fabricating heavy structures. Recently, weld metal transverse cracks in butt and fillet weld joint is a serious problem, and they must be eliminated for improving weld joint reliability. The weld metal transverse crack susceptibility of butt and fillet joint was carried out by cantilever type tensile crack testing jig and CTS test. In this view of point, this study investigated the potential factors for weld metal transverse crack. The main results obtained were as follows: 1. The content o fdiffusible hydrogen in weld metal played an important role for weld metal transverse cracks. 2. From cantilever type tensile crack tests, it was pointed out that the higher the diffusible hydrogen content and tensile restraint, the more susceptible to weld metal transverse craking. 3. The TSN(thermal severity number) and diffusible hydrogen were important factors for determining weld metal transverse cracks in fillet weld joints.

• 전자공학회논문지A
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• 제33A권7호
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• pp.143-148
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• 1996

Detailed analyses have been presentd for a basic single-electron-logic-cell consisting of two single-electron-transistors (SETs) in series. The interconnection between two SETs has been treated as a coulomb island and the joint probability density function of all three coulomb islands (two from the SETs and one form the interconnection) has been exactly calculated. The average number of electrons in each coulomb island and the steady-state ouptut voltage have been calculated and analyzed.

• Computers and Concrete
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• 제18권2호
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• pp.235-266
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• 2016

A rock mass containing non-persistent joints can only fail if the joints propagate and coalesce through an intact rock bridge. Shear strength of rock mass containing non-persistent joints is highly affected by the both, mechanical behavior and geometrical configuration of non-persistent joints located in a rock mass. Existence of rock joints and rock bridges are the most important factors complicating mechanical responses of a rock mass to stress loading. The joint-bridge interaction and bridge failure dominates mechanical behavior of jointed rock masses and the stability of rock excavations. The purpose of this review paper is to present techniques, progresses and the likely future development directions in experimental and numerical modelling of a non-persistent joint failure behaviour. Such investigation is essential to study the fundamental failures occurring in a rock bridge, for assessing anticipated and actual performances of the structures built on or in rock masses. This paper is divided into two sections. In the first part, experimental investigations have been represented followed by a summarized numerical modelling. Experimental results showed failure mechanism of a rock bridge under different loading conditions. Also effects of the number of non-persistent joints, angle between joint and a rock bridge, lengths of the rock bridge and the joint were investigated on the rock bridge failure behaviour. Numerical simulation results are used to validate experimental outputs.

• 한국표면공학회지
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• 제42권6호
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• pp.294-300
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• 2009

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, for effective application on thin aluminum alloy lap joint, non-heat treatment A5052 alloys were joined by FSLW with the length of probe 2.3 mm and 3.0 mm. Investigating the characteristics of joint area showed the results were as below ; When the length of probe was 2.3 mm, good joint area was formed at all welding condition except for 600 rpm-700 mm/min. In the case of 3.0 mm probe length, there was formed good joint area without defects at 1500 rpm-100 mm/min. The width of joint area, position and size of defects were very important factors for FSLW, due to heat input and stirring intensity.

• Advances in aircraft and spacecraft science
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• 제5권5호
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• pp.595-613
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• 2018

The objective of our study is to analyze the behavior of bonded, riveted and hybrid (bonded / riveted) steel / steel assemblies by tensile tests and to show the advantage of a hybrid assembly over other processes. the finite element method with the ABAQUS numerical code was used to model the fracture behavior of the different assemblies. Cohesive zone models (CZM) have been adopted to model crack propagation in bonded joints using a bilinear tensile separation law implemented in the ABAQUS finite element code. The riveted assemblies were modeled with the XFEM damage method identified in this ABAQUS numerical code. Both CZM and XFEM methods are combined to model hybrid assemblies. The results are consistent with the experimental results and make it possible to guarantee the validity of the applied numerical model. The use of a hybrid assembly shows a high resistance compared to other conventional methods, where the number of rivets has been highlighted. The use of the hybrid assembly improves mechanical strength and increases service life compared to a single lap joint and a riveted joint.

• The Korean Journal of Pain
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• 제18권2호
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• pp.151-155
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• 2005

Background: A significant number of patients complain of persistent pain or neurologic symptoms after lower back surgery. It is reported that facet joint pain plays a role in failed back surgery syndrome. To the best of our knowledge, there are few studies that have investigated the outcome of radiofrequency neurotomy in the patients with failed back surgery syndrome. Methods: The study group was composed of thirteen patients who were operated on due to their low back pain, and they displayed no postoperative improvement. All the patients underwent double diagnostic block of the lumbar medial branch of the dorsal rami with using 0.5% bupivacaine. The patients who revealed a positive response to the double diagnostic block were then treated with percutaneous radiofrequency neurotomy. The effect on their pain was evaluated with using a 4 point Likert scale. Results: Eleven patients revealed a positive response to the double diagnostic block. Ten patients were given percutaneous radiofrequency neurotomy. Nine patients showed sustained pain relief for 3 months after the percutaneous radiofrequency neurotomy. Conclusions: We found lumbar facet joint syndrome in the patients with failed back surgery syndrome by performing double diagnostic block and achieving pain relief during the short term follow-up after percutaneous radiofrequency neurotomy of the lumbar zygapophysial joints. This suggested that facet joint pain should be included in failed back surgery syndrome.

• 대한치과교정학회지
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• 제23권3호
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• pp.405-414
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• 1993

Among the radiographs for temporomandibular joint, transcranial radiograph is widely used for screening and diagnosing temporomandibular disorder because it has sharp image and it is easy to take. This study was performed to compare condylar position and image sharpness in standard and individually corrected transcranial radiographs using Accurad-200 headholder. Submentovertex view, Reverse-Towne view, Standard and individually corrected transcranial radiographs of 45 university students who were randomly selected were traced, measured and analyzed. The results were as follows : 1. The means of condylar axes and lateral slopes were $16.8^{\circ}\;and\;22.5^{\circ}$ respectively. There were no differences between male and female or right and left side. 2. Individually corrected radiographs showed smaller posterior joint ,space and larger anterior joint space than standard radiographs, but superior joint space did net show a statistical difference between standard and individually corrected radiographs. 3. While a large number$(42.2\%)$ of the standard radiographs showed concentric condylar position, lots of(57.8) condylar positions were retropositioned in the individually corrected radiographs. 4. The image sharpness was inferior in the individually corrected radiographs to that of the standard radiographs.

• Advances in concrete construction
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• 제14권5호
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• pp.317-330
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• 2022

This paper investigated computationally and experimentally the interaction here between a notch as well as a micropore under uniaxial compression. Brazilian tensile strength, uniaxial tensile strength, as well as biaxial tensile strength are used to calibrate PFC2d at first. Then, uniaxial compression test was conducted which they included internal notch and micro pore. Experimental and numerical building of 9 models including notch and micro pore were conducted. Model dimensions of models are 10 cm × 10 cm × 5 cm. Joint length was 2 cm. Joints angles were 30°, 45° and 60°. The position of micro pore for all joint angles was 2cm upper than top of the joint, 2 cm upper than middle of joint and 2 cm upper than the joint lower tip, discreetly. The numerical model's dimensions were 5.4 cm × 10.8 cm. The fractures were 2 cm in length and had angularities of 30, 45, and 60 degrees. The pore had a diameter of 1 cm and was located at the top of the notch, 2 cm above the top, 2 cm above the middle, and 2 cm above the bottom tip of the joint. The uniaxial compression strength of the model material was 10 MPa. The local damping ratio was 0.7. At 0.016 mm per second, it loaded. The results show that failure pattern affects uniaxial compressive strength whereas notch orientation and pore condition impact failure pattern. From the notch tips, a two-wing fracture spreads almost parallel to the usual load until it unites with the sample edge. Additionally, two wing fractures start at the hole. Both of these cracks join the sample edge and one of them joins the notch. The number of wing cracks increased as the joint angle rose. There aren't many AE effects in the early phases of loading, but they quickly build up until the applied stress reaches its maximum. Each stress decrease was also followed by several AE effects. By raising the joint angularities from 30° to 60°, uniaxial strength was reduced. The failure strengths in both the numerical simulation and the actual test are quite similar.