• Journal of the Korean Arthroscopy Society
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• v.6 no.1
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• pp.31-36
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• 2002

Objective : The purpose of this study was to evaluate the clinical and radiological results after treatment of old ACL(anterior cruciate ligament) avulsion fracture of tibia. Materials and Method : 11 cases who were followed up at least 2 years after treatment in chronic ACL avulsion fracture of tibia were included in this study. The average age of patients was 26(9-66) years and the mean period of follow up was 53(24-131) months. After evaluation of the lesion and treatment of associated lesion under arthroscope, open reduction and internal fixation or fragment removal was performed. Pull-out suture was performed in 8 cases, screw fixation in 2 cases. Results : The Lysholm knee score was 64.3 in average preoperatively and improved to 96.2 average at follow up. On the Lachman test, there were mild(+) instabilities in 7 cases, moderate(++) in 4 cases. On the postoperative Lachman test, there were no instabilities in 9 cases, mild(+) instabilities in only 2 cases. According to Meyers and Mckeever's evaluation protocol, 9 cases $(81.8\%)$ were excellent, 2 case $(18.2\%)$, good. On preoperative instrumented anterior laxity test with $Telos^{\circledR}$, side to side difference in 201b was 7.8(10-4) min in average and 2.1(6-0) mm in average at follow-up. Conclusion : In chronic ACL avulsion fracture, it is thought that combination of arthroscopic evaluation of associated injury and open reduction and fixation and fragment removal can bring about satisfactory results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.259-266
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• 2020

In this study, required drill bits and excavation methods were developed for an uneven drilling method that can solve the problem of performance degradation of rock bolts. The developed drill bit's excavation performance was verified using rock with a strength of 100 MPa or more. In addition, for the relative evaluation of the uneven excavation method, experimental specimens were prepared for models with and without irregularities, and tests were performed. As a result of the experiment, the model with unevenness exhibited an average critical draw resistance of 801.6 kN, which is about 1.7 times the value of 468.7 kN for the model without unevenness, thus confirming the effect sufficiently. Therefore, it is expected that the resistance performance will significantly increase despite an increase in the uneven hole diameter of 20 mm. In the future, the results of this study could be used as basic data when performing other studies using numerical analysis models and performance verification through experiments to obtain an optimized rock forming method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.45-45
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• 2009

원가 측면에서 유리한 저항점용접(Resistance Spot Welding)이 차체 용접에 80%이상으로 가장 많이 적용되고 있다. 첨단고강도강(Advanced High Strength Steel)의 저항점용접성 및 용접부 특성에 미치는 공정 변수의 영향에 대한 연구결과는 많으나, 합금원소의 영향에 대해서는 전무하다. 특히, Si는 DP(Dual Phase)강에 첨가 시 균일한 마르텐사이트의 분포를 촉진하는 원소로 저항 점용접성 및 용접부 특성에 영향을 미칠 것으로 예상되며, 이에 대한 연구는 보고된바 없다. 본 연구에서는 냉연 DP강의 저항 점용접시 중요한 인자 중 하나인 너깃경과 전단인장강도에 미치는 Si함유량의 영향을 검토하였다. 사용된 강재 및 용접기는 1.2mm 두께의 Si함유량(0, 0.5, 1.0, 1.5wt%)이 다른 인장강도 780~1000MPa급 냉연 DP강과 단상 AC용접기를 사용하였다. 용접조건은 ISO 18278-2규격에 따라 가압력 4kA, 초기가압시간 40cycle, 유지시간 17cycle로 고정하고, 용접전류만 변화하여 용접을 실시하였다. 너깃경은 용접부 단면을 컷팅 후 폴리싱 하여, 광학현미경과 Image Pro plus를 이용하여 측정했으며, 인장시편규격은 JIS Z 3137를 이용하였다. Si함유량이 증가에 따라 스패터 발생 전류는 감소했고, 너깃경은 직선적으로 증가했다. Si함유량 증가에 따른 너깃경 증가 이유는 저항(R) 측정결과, Si함유량 증가에 따라 모재의 저항이 높아져, 따라서 입열량($Q=I^2Rt$)이 많아지기 때문으로 판단되었다. 인정전단강도는 Si함유량 증가에 따라 직선적으로 증가했다. 이러한 이유는 Si함유량 증가에 따라 너깃경이 증가되기 때문으로 판단되었고, 너깃경과 인장전단강도 사이에 직선적 관계(PL(kN)=$3.2N_{dia.}$-0.81, $R^2$=0.93)를 가지고 있었다. 파단양상은 Si함유량에 상관없이 5.4kA이하에서는 계면파단이 일어났고, 6.0kA이상에서는 풀 아웃 파단이 일어났다. 계면파단주원인은 용접부 가장자리에 지름이 약 $5{\mu}m$이하의 예리한 노치가 존재하여 노치응력집중과 HAZ계면 근처에 미접합부가 존재하기 때문으로 판단되었다. 6.0kA이상에서는 예리한 노치가 없었고, HAZ부가 완전히 접합되어 있기 때문에 풀 아웃 파단이 일어난 것으로 판단되었다. 따라서, Si함유량 증가에 따라 적정용접전류 구간은 감소했고, 너깃경은 직선적으로 증가했다. 또한, Si함유량 증가에 따라 인장전간강도는 증가 했으며, 너깃경과 인장전단강도 사이에 직선적 관계를 가지고 있었다. 파단 양상은 Si함유량에 상관없이 5.2kA이하에서는 계면파단이, 6.0kA이상에서는 풀 아웃 파단이 일어났다.

• Clinics in Shoulder and Elbow
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• v.16 no.2
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• pp.107-114
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• 2013

Purpose: This study is designed to evaluate the clinical and radiographical results for the displacement of fracture fragments after interlocking intramedullary nailing in humeral shaft fractures. Materials and Methods: We retrospectively reviewed the results of 8 cases of humeral shaft fractures that have displacements of over 10 mm and under 20 mm after interlocking intramedullary nailing between July 2004 and August 2011. The mean age was 54.1 years (range, 43 to 70 years) and there were 3 male and 5 female patients. Radiographically, the time to bony union, change of displacement and angulation of the fracture site, and degree of improvement of these two factors were measured. Clinically, the range of motion of shoulder and elbow joints, postoperative pain and complications were evaluated. Results: All cases showed complete bony union in last follow-up. The mean time to bony union was 16.1 weeks. At the last follow-up, almost all cases had normal range of motion of shoulder and elbow joints. But, one case had stiffness of shoulder joint. Therefore, arthroscopic capsular release and manipulation was performed. One case had transient shoulder pain and the other case had transient elbow pain. In the two cases, pull-out of proximal interlocking screw were noted, but they finally had bony union. Conclusion: Although considerable displacement of fracture fragments after interlocking intramedullary nailing in humeral shaft fractures was present, we had excellent radiographical and clinical outcomes. Therefore, an additional procedure, such as open reduction or another fixation for the fracture site, was not necessary.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.15-29
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• 2005

Statement of problem. The adjustable dental impression trays were made for being adjusted their width automatically along the width of dental arch. Purpose. The purpose of this study was to investigate the best retentive form of adjustable dental impression tray, and so to make it a more satisfactory product. Material and methods. The eight pairs of adjustable trays were made of ABS(acrylonitrile butadiene styrene) with different distribution of holes and with or without the rim on the border area of them. The experiment was done with the horse-shoe shaped metal plate to pull out the set impression body from the tray, and the tray jig which was made for holding the tray on a lower part of Universal Testing Machine(UTM, Zwick Z020, Zwick Co., Germany). After the impression in the tray was allowed to set four minutes, a tensile force was applied at right angles to the tray which had been previously seated on the jig. The force was applied to measure a maximum retentive force by use of a UTM at a constant strain rate of 100mm per minute. A 2-factor analysis of variance (p<.05) was used to determine whether differences existed among distribution of retentive holes and between rim existing and not. Results. 1 The retentive force of the upper and lower resin tray with 2mm holes on the tray border was highest(25.83/24.98kg). (p<.05) 2. As the tray had more retentive holes, it was less retentive. 3. There was no significant difference in the retentive force of the varied hole intervals in the case of distributing all the area. (p>.05) 4. The rimless trays were more retentive generally, than the rimmed trays except 2 case: upper tray group-all area / 2 mm, intervals and lower tray group-margin only / 2 mm, intervals.(p<.05) 5. Most of the adjustable trays were showed higher retentive force than perforated metal tray except the lower group that perforated on the all area at intervals of 2 mm.

• Land and Housing Review
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• v.2 no.1
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• pp.61-68
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• 2011

In order to clarify the structural performances of Welded Deformed Steel Bar Mats (WDSBM), the research stated includes the tests for standard hook of top bars of slab in concrete slab-wall joints, the tests for embedment length of top bar of slab, and the development strength tests for standard hook. The test results are as follows; (1) For slab-wall joints using WDSBM as reinforcement in slab, if the top bars of WDSBM are spliced by ordinary bars with sufficient development length and size, it is enough for the strength and crack control. (2) When WDSBM of slab is spliced in joint, the strength is increased with the embedment of bars of this WDSBM into wall. Beyond peak strength, however, ductility is diminished to that as no splice due to pull-out failure. (3) For slab-wall system, ultimate strain of concrete for flexural compression zone in lower surface of slab seems much greater than that of normal concrete beam. The reason is that normal concrete beam has the joint with $180^{\circ}$, however slab-wall joint has the $90^{\circ}$ of which concrete can be confined.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.149-158
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• 2010

Recently, numerous construction techniques for repairing and strengthening methods for above ground or air exposed concrete structure have been developed. However repairing and strengthening methods for underwater structural members under continuous loading, such as piers and steel piles need the further development. Therefore, this study develops an aqua epoxy, which can be used for repairing and strengthening of structural members located underwater. Moreover, using the epoxy material and strengthening fibers, a fiber reinforced composite sheet called Aqua Advanced FRP (AAF) for underwater usage is developed. To verify and to obtain properties of the material and the performance of AAF, several tests such as pull-off strength test, bond shear strength test, and chemical resistance test, were carried out. The results showed that the developed aqua epoxy does not easily dissolve in wet conditions and does not create any residual particle during hardening. In spite of underwater conditions, it showed the superior workability, because of the high viscosity over 30,000 cps and adhesion capacity over 2 MPa, which are nearly equivalent to those used in dry conditions. In case of the chemical resistance test, the developed aqua epoxy and composite showed the weight change of about 0.5~1.0%, which verifies the superior chemical resistance.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.249-263
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• 2017

The expansion behavior of inflatable steel pipe rockbolt shows geometric nonlinearity due to its ${\Omega}-shaped$ section. Previous studies on the anchoring behavior of inflatable steel pipe rockbolt were mainly performed using theoretical method. However, those studies oversimplified the actual behavior by assuming isotropic expansion of inflatable steel pipe rockbolt. In this study, the anchoring behavior of the inflatable steel pipe rockbolt were investigated by the numerical method considering the irregularity of pipe expansion and other influencing factors. The expansion of inflatable steel pipe rockbolt, the contact stress distribution and the change of the average contact stress and the contact area during installation were analyzed. The contact stresses were developed differently depending on the constitutive behavior of rocks. Small contact stresses occurred in steel pipes installed in elasto-plastic rock compared to steel pipes installed in elastic rock. Also, the anchoring behaviors of the inflatable steel pipe rockbolt were different according to the stiffness of the rock. The steel pipe was completely unfolded in the case of the stiffness smaller than 0.5 GPa, but it was not fully unfolded in the case of the stiffness larger than 0.5 GPa for the given analysis condition. When the steel pipe is completely unfolded, the contact stress increases as the rock stiffness increases. However, the contact stress decreases as the rock stiffness increases when the steel pipe is not fully expanded.

• Journal of Adhesion and Interface
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• v.19 no.1
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• pp.13-18
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• 2018

At ruthenium (Ru) catalyst was exposed from the atmosphere, the degree of catalyst activation decreased. The change of catalyst activity with the number of days of exposure to air for the Ru catalyst was confirmed using the surface tension method quantitatively. Mechanical properties and surfactant change after polymerization by DCPD using Ru catalyst for each air exposure day was evaluated. The Ru catalyst mixed with a dilution agent was exposed in the air and color was monitored for each day. Surface tension was measured using Wilhelmy and PTFE and associated with different catalyst activities. Heat was measured in real time during polymerizing DCPD with Ru catalyst. After polymerization, tensile strength was measured for p-DCPD and the change of material property was measured. Interfacial properties were also evaluated via microdroplet pull-out tests between glass fiber and p-DCPD. The surface tension was stable until the 4 days (33 dyne/cm) whereas the surface energy increased at the 10 days (34 dyne/cm), which could be correlated with oxidation of the catalyst. Tensile property and interfacial shear strength (IFSS) was also stable until the 4 days (tensile strength: 38 MPa and IFSS: 26 MPa) whereas the mechanical property decrease at 10 days (tensile strength: 15 MPa and IFSS: 3 MPa) dramatically.