• Journal of Korean Foot and Ankle Society
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• v.11 no.2
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• pp.177-181
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• 2007

Purpose: The purpose of this study is to compare the two prosthesis that used for total ankle arthroplasty. Materials and Methods: From Sept. 2003 to Jun 2006, 13 patients and 14 ankles that could be follow up more than 1 months. Semiconstrained type (Group I, 7 cases) and Unconstrained type (Group II, 7 cases) were used for total ankle arthroplasty. Mean age was 63.2 year-old, 12 ankles are men and 2 ankles were women. Mean follow up periods were 29 months. The criteria to compare the clinical result were postoperative range of motion, AOFAS score and residual bone stock of medial malleolus. Results: Postoperative range of motion of group I was $43.6{\pm}9.4$ degrees and of group II was $50.7{\pm}7.3$ degrees (p=0.115). Postoperative AOFAS score of group I was $77.1{\pm}13.0$ points and of group II was $86.0{\pm}5.7$ points (p=0.094). Resected bone stock in medial malleolus of group I was $10.7{\pm}2.5\;mm$ and of group II was $5.1{\pm}1.2\;mm$ (p=0.003). Total number of complication in our study was 9 cases. 3 cases were a malleolar fracture, two occurred at intra-operation, the other at follow-up period. Re-operation was done in 6 cases, 3 cases were calcaneal corrective osteotomy, 2 cases were resection of a heterotopic bone and one case was pedicular flap operation for skin problem. Conclusion: In our hospital, mobile bearing type prosthesis shows good result than a semiconstrained type in respect of residual bone stock in medial malleolus. Postoperative range of motion and AOFAS score between two groups shows no significant difference. But small number of patients and short term follow up period is a defect in our study, afterward more population and long term follow up period are needed.

• Clinics in Shoulder and Elbow
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• v.2 no.1
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• pp.14-20
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• 1999

Purpose: Despite of the popular use of the reconstruction plate for the fixation of clavicular shaft fractures, some disadventages have been raised such as long period of immobilization, long skin incision, loosening of plate and screws, and increased chance of nonunion due to severe periosteal injury. Thus, the authors have performed intramedullary multiple Steinmann pins fixation that could reduce the disadvantages of plate fixation in order to compare the treatment results between the two groups. Materials & Methods: From 1994. Jan. to 1997. Dec. the department of orthopaedic surgery of the Kwak's hospital treated operatively for 56 cases of the clavicular shaft fractures in adult. 39 cases of them were treated with the plate fixation and 17 cases with the intramedullary multiple Steinmann pins fixation(SP group). Reconstruction plates(Plate group) were used for 26 out of 39 patients treated with plate fixation. Among the Plate group and SP group, each 15 cases were selected by age and sex and compared each other according to the bone union time, union rate, complication, and functional results. The follow-up period was 12 months at the shortest and 48 months at the longest and the average was 16 months. Results: The Plate group showed that the bone union time was 7 weeks and the bone union rate was 93%. The SP group showed 6.5 weeks and 100% respectively. In complication, the Plate group had 1 case of loosening of plate and screws and delayed union; SP group had 1 case of pin migration. The functional results according to Kang's criteria, 87% of the Plate group and 93% of the SP group showed good or excellent. Conclusion : The SP group showed very comparable results in terms of the bone union time, bone union rate, complication, and functional results comparing to the Plate group. The intramedullary multiple Steinmann pins fixation showed several advantages over the reconstruction plate fixation, which were simple operative technique, easy removal of pins, being able to perform immediate postoperative full range of motion exercise. Therefore, the intramedullary multiple Steinmann pins fixation is thought to be one of the useful operative techniques in treatment of the clavicular shaft fractures in adult.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.431-440
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• 2013

In this study, a standard tensile welded-joint test was conducted to select a welding electrode suitable for recently developed HSA800 steel. Two welding electrodes were available at the time of this study; one was GMAW-based and the other FCAW-based. The tensile test specimens were fabricated by joining 60mm-thick HSA800 plates according to the AWS-prequalified groove welded joint details. Specimens which violate the standard root opening distance (ROD) were also included to see if poor construction tolerance could be accommodated. During fabrication, serious concerns about the welding efficiency of the GMAW-based product were raised by a certified welder. Both welding electrodes showed satisfactory and similar performance from welded joint strength perspective. But groove welded joints made by using the FCAW-based rod consistently showed more ductile and stable behavior. The AISC provisions for PJP joint strength were shown to be very conservative under direct tensile loading. Violating the AWS prequalified ROD by 100% apparently passed the strength criteria, but unusual crater-like fracture surface was observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.843-850
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• 2020

The purpose of this study is to evaluate the structural risk and weakness of a railway tank car through nonlinear collision analysis according to overseas collision safety standards. The goal is to propose a crash safety design guideline for railway tank cars for transporting dangerous goods in Korea. We analyzed the buffer impact test procedure of railway freight cars prescribed in EN 12663-2 and the tank puncture test criteria prescribed in 49CFR179. A nonlinear finite element model according to each standard was modeled using LS-DYNA, a commercial finite element analysis solver. As a result of the buffing impact test simulation, it was predicted that plastic deformation would not occur at a collision speed of 6 km/h or less. However, plastic deformation was detected at the rear of the center sill and at the tank center supporting the structure at a collision speed of 8 km/h or more. As a result of a head-on test simulation of tank puncture, the outer tank shell was destroyed at the corner of the tank head when 4% of the kinetic energy of the impacter was absorbed. The tank shell was destroyed in the area of contact with the impacter in the test mode analysis of tank shell puncture when the kinetic energy of the moving vehicle was reduced by 30%. Therefore, the simulation results of the puncture test show that fracture at the tank shell and leakage of the internal material is expected. Consequently, protection and structural design reinforcement are required on railway tank cars in Korea.

• Journal of Navigation and Port Research
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• v.28 no.6
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• pp.481-489
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• 2004

Ship collisions and grounding continue to occur regardless of continuous efforts to prevent such accidents. With the increasing demand for safety at sea and for protection of the environment, it is of crucial importance to be able to reduce the probability of accidents, assess their consequences and ultimately minimize or prevent potential damages to the ships and the marine environment. Numerical simulations for actual collision problem are conducted with a special attention with respect to finite element size, fracture criteria and material properties, which require a careful consideration to improve the accuracy. A parametric analysis varying colliding speed, angle, design loading condition is conducted using nonlinear finite element analysis method for 46,00 dwt Product/chemical carrier. The relationship between the absorbed energy and indentation are derived quantitatively using the insights observed from this study, and a novel design concept for assessing the anti-collision performance are proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.263-274
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• 2018

In this study, the applicability and external/internal stability of a MSEW abutment with a slab were investigated. Structural analysis of slab bridges between 10 ~ 20.0 m and thicknesses of 0.7 ~ 0.9 m was carried out to calculate the reaction forces due to dead and live loads acting on the bridge supports. The slab bridge with a length of 20.0 m satisfied the allowable contact pressure of 200 kPa for the true MSEW abutment. Because the external stability of the true MSEW abutment was dominated by the geometry of the MSE wall, the change in the factor of safety due to the load of the super-structure is small. Because the stiffness of the foundations is fixed and the load of the super-structure is increased, the factor of safety of the bearing capacity was reduced. As the load of the super-structure was increased, the horizontal earth pressure of the true MSEW abutment increased greatly. As a result, the pullout and fracture of the uppermost reinforcement, which are the factors of safety, did not meet the design criteria. Therefore, it is necessary to increase the pullout resistance and the long-term allowable tensile force of the reinforcement placed on the top of the reinforced soils to ensure efficient design and performance of a true MSEW abutment.

• Journal of dental hygiene science
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• v.14 no.4
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• pp.461-467
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• 2014

The objective of this study was to evaluate the impact of the Q-ray view, a novel optical device on reliability of assessing a tooth status by dental hygiene students in the training for dental hygiene process. Twenty patients were enrolled in this study. Oral examinations were conducted by both seventeen third-year dental hygiene students and a trained faculty member. Traditional visual inspection was performed in phase I and then re-examined with Q-ray view in phase II. Restoration codes and lesion codes for each tooth were recorded separately according to the predefined criteria. As a measure of reliability, percent agreement and Cohen's kappa were determined. Agreements for each intraoral regions and types of lesion and restoration were calculated. Paired t-test and Pearson chi-square test for two proportions were used to compare mean Cohen's kappa and percent agreement at each phase. For the lesion code, mean kappa values of phase II for intraoral regions were significantly greater than that of phase I (p=0.017). For the both of the lesion code and restoration code, percent agreements of phase II for each types of lesion and restoration were significantly greater than that of phase II (p<0.001 and p<0.001, respectively). Especially difference of percent agreements between phase I and II for incipient caries, caries and fracture were significant for the lesion code (p=0.046, p<0.001, and p=0.029, respectively) and for not restored or sealed, tooth-colored restoration were significant for the restoration code (p<0.001 and p=0.011, respectively). The reliability of assessing a tooth status was improved when the Q-ray view used in dental hygiene student with beginner level of expertise. Q-ray view can be a promising device for conducting and educating the dental hygiene process better.

• Journal of Korean Medicine Rehabilitation
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• v.23 no.4
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• pp.185-194
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• 2013

Objectives The aim of this study was to evaluate the efficacy and safety of micro current taping therapy (MTT) on patients with chronic low back pain (CLBP). Methods We included 50 participants who met the inclusion criteria and 5 participants dropped out during the sessions due to the following reasons: 3 participants were personal reasons, 1 participant was taking medication, 1 participant was fore arm fracture. We attached "I" shaped 40 cm, 2 tapes along the erector muscles of the spine starting from both iliac crest and another "I" shaped 30 cm, 1 tape on the painful site horizontally. This procedure was done 8 times and participants visited a total of 9 times including a final visit for evaluation. We measured visual analog scale (VAS), range of motion (ROM) and schober's test on every visit. Participants completed a questionnaire of oswestry disability index (ODI) and Beck's depression inventory (BDI) on the first and last visits. Results In VAS for pain intensity and bothersomeness, there were significant decreases after 1st, 6th treatments. In range of extension, there was significant increase after 3rd treatment at first. In range of flexion, there was significant increase after 2nd treatment at first. In range of left flexion, there was significant increase after 4th treatment at first. In range of right flexion, there was significant increase after 3rd treatment at first. in schober's test, there was significant increase after 2nd treatment at first. In VAS, ROM, schober's test, BDI, ODI, there were significant improvement after all treatments had done. Conclusions There was a significant effect of MTT on CLBP. And there was no adverse effect.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.89-102
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• 2004

The generated blasting pressure wave initiated under decoupled-charge condition is a function of peak blasting pressure, rise time, and wave-shape function. The peak blasting pressure and the rise time are also the function of explosive and rock properties. The probabilistic distributions of explosive and rock properties are derived from the results of their property tests. Since the probabilistic distributions of explosive and rock properties displayed a normal distribution, the peak blasting pressure and the rise time can also be regarded as a normal distribution. Parameter analysis and uncertainty analysis were performed to identify the most influential parameter that affects the peak blasting pressure and the rise time. Even though the explosive properties were found to be the most influential parameters on the peak blasting pressure and the rise time from the parameter analyses, the result of uncertainty analysis showed that rock properties constituted major uncertainties in estimating the peak blasting pressure and the rise time rather than explosive properties. Damage and overbreak of the remaining rock around the excavation line induced by blasting were evaluated by dynamic numerical analysis. A user-subroutine to estimate the rock damage was coded based on the continuum damage mechanics. This subroutine was linked to a commercial program called 'ABAQUS/Explicit'. The results of dynamic numerical analysis showed that the rock damages generated by the initiation of stopping hole were larger than those from the initiation of contour hole. Several methods to minimize those damages were proposed such as relocation of stopping hole, detailed subdivision of rock classification, and so on. It was found that fracture probability criteria and fractured zones could be distinctively identified by applying fuzzy-random probability.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.1
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• pp.73-83
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• 1997

Most of the materials used in various industrial fields and also in our daily life are multi-component materials or composite materials, and it is well known that there are many cases where adhesion between the constituents within the bonded systems plays an important role. There are various types of performance evaluation tests for the bonded materials, among which tests for evaluating the bond performance under various conditions may be regarded as the most interesting ones for those engaged in work related to adhesion. I have studied on the mechanism of adhesion form the rheological standpoint with my colleagues, including some students from Korea, and I am very happy to be able to have a talk on some of our research works. In Japan, the so-called "adhesives" are usually classified into two categories;adhesives and pressure sensitive adhesives (PSA). Adhesives are the materials which solidify after bonding and are after used as the structural adhesives because the adhesive strength is comparatively strong. On the other hand, the pressure sensitive adhesives never solidify and are used as PSA tapes, labels or decals. About the adhesives, we have examined the dependence of adhesive strength(shear, tensile, peel) upon both temperature and rate of deformation, and found out some empirical rules which are applicable to most of the adhesive systems. We have also developed a simplified theory of adhesion, which is deseribed in terms of mechanical equivalent mode1 and a few failure criteria. Although some of the common rules can be accounted for according to this theory, it must be pointed out that a fracture mechanical approach ms inevitable especially in the region where the meehanical relaxation time of the adhesive is extremely large [W. W. Lim and H. Mizumachi]. About the pressure sensitive adhesives, we have studied on the PSA performance (peel, tack, holding power) as a function of both the viscoelastic properties and surface chemical properties of the materials, and found out some rules, and again we have developed a theory which deseribes the mechanism. And in addition, we have studied on the miscibility between linear polymers and oligomers, because PSA is generally manufactured by blending gums and tackifier resins. Many phase diagrams have been found and some of them have been analyzed on thermodynamic basis, and it became evident that the miscibility is a very important factor in PSA [H. J. Kin and H. Mizumachi]. In this presentation, I want to emphasize the fact that the adhesion performance is closely related to the structure/property of the adhesives.adhesives.