• 한국지반신소재학회논문집
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• 제12권3호
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• pp.15-22
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• 2013

도상구조의 자갈(연성)에서 콘크리트(강성)로의 변화는 이를 지지하는 철도 노반구조에서도 보다 엄격한 변형 규제에 적합한 신형식 철도보강노반 구조를 요구하고 있다. 본 논문에서는 공용 후 잔류침하를 최소화할 수 있으면서도 대용량 반복하중이 작용하는 철도노반 영구구조물로서의 기능을 유지할 수 있는 강성벽 일체형 철도보강노반의 설계 특성을 평가하기 위한 민감도 분석을 실시하였다. 개발한 설계프로그램을 이용하여 단보강재와 장보강재의 간격, 보강재 강성 등 설계 입력변수 변화에 따른 원호활동, 전도 및 활동파괴에 대한 안전율 및 발생 부재력을 평가하였다. 이를 통하여 철도보강노반에서는 높이의 40%(0.4H)의 짧은 보강재를 연직간격 0.4m로 적용할 수 있으며 보강노반 적용을 위한 원지반 조건 등을 평가할 수 있었다. 또한, 철도보강노반을 구성하는 벽체와 보강재 연결구조의 중요성, 벽체 경계조건에서의 변위 허용구조 적용을 통한 하중 재하 시 발생 최대휨모멘트를 저감시키는 설계상의 특징을 파악할 수 있었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권1호
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• pp.60-69
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• 2005

Orthopedic rapid maxillary expansion(RME) has been a common treatment modality used to widen narrow maxillae in young children. However, since more skeletally matured adolescents or adults has closed midpalatal suture, the result of RME was undesirable because of dental tipping with little or no basal skeletal movement and resulted to many other complications. After such treatment, complications often occurred such as alveolar bending, compression of periodontal ligament, extrusion, buccal tipping, and severe relapse. Thus, surgically assisted rapid maxillary expansion(SA-RME) is required, especially for patients over 14 years old, to skeletally release maxillary expansion. We used two methods of maxillary expansion surgery. Surgically assisted rapid maxillary expansion(SA-RME) & surgically assisted posterior segmental expansion(SA-PSE) were used for narrow maxilla. The study was divided into two groups(SA-RME group and SA-PSE group). SA-RME group was consisted of 2 males and 4 females, and the ages of materials ranged from 15 years to 25 years with a mean of 20.2 years. SA-PSE group was consisted of 1 male and 5 females, and the ages ranged from 13 years to 23 years with a mean of 18.7 years. Dental study models were fabricated before starting the expansion and immediately after the expansion was completed. It was fabricated again 1 month later, 3 months later when the expansion device was removed, and 6 months later after the expansion was completed. A repeated measures analysis of variance(ANOVA) test was applied to assess changes between each groups over time. The amount of expansion and the amount of tipping movement each in both groups were compared by using paired t-test and it was also compared between each subjects within the group by using independent t-test. Both SA-RME and SA-PSE group showed stable results, but SA-PSE group showed statical significance in tipping movement of second premolar. We compared 6 patients who recieved SA-RME with 6 patients who received SA-PSE, and appraised the clinical usefulness.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제42권3호
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• pp.144-150
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• 2016

Objectives: We compared the transbuccal and transoral approaches in the management of mandibular angle fractures. Materials and Methods: Sixty patients with mandibular angle fractures were randomly divided into two equal groups (A, transoral approach; group B, transbuccal approach) who received fracture reduction using a single 2.5 mm 4 holed miniplate with a bar using either of the two approaches. Intraoperatively, the surgical time and the ease of surgical assess for fixation were noted. Patients were followed at 1 week, 3 months, and 6 months postoperatively and evaluated clinically for post-surgical complications like scarring, infection, postoperative occlusal discrepancy, malunion, and non-union. Radiographically, the interpretation of fracture reduction was also performed by studying the fracture gap following reduction using orthopantomogram tracing. The data was tabulated and subjected to statistical analysis. A P -value less than 0.05 was considered significant. Results: No significant difference was seen between the two groups for variables like surgical time and ease of fixation. Radiographic interpretation of fracture reduction revealed statistical significance for group B from points B to D as compared to group A. No cases of malunion/non-union were noted. A single case of hypertrophic scar formation was noted in group B at 6 months postsurgery. Infection was noted in 2 patients in group B compared to 6 patients in group A. There was significantly more occlusal discrepancy in group A compared to group B at 1 week postoperatively, but no long standing discrepancy was noted in either group at the 6 months follow-up. Conclusion: The transbuccal approach was superior to the transoral approach with regard to radiographic reduction of the fracture gap, inconspicuous external scarring, and fewer postoperative complications. We preferred the transbuccal approach due to ease of use, minimal requirement for plate bending, and facilitation of plate placement in the neutral mid-point area of the mandible.

• 대한정형도수물리치료학회지
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• 제14권1호
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• pp.48-60
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• 2008

Purpose : The purpose of this study was to compare the effects of Joing Mobilization and Group back Pain Exercise Program on the disability level and the pain of flexibility and the back muscle strength in the hearing impairment patients with Low back pain. Methods : The subjects of this study were 12 patients, 8 males and females. They visited clinic for physical treatment within 6 months after onset of low back pain. One group was applied with Joing Mobilization and other group was with Group back Pain Exercise Program. The patient were treated special program 3 times session weekly. And treatment 2 times session was 15min with physiotherapy weekly. The muscle strength was measured by Cybex 660, the level of disability by Oswestry low back pain disability scale, the intensity of pain by visual analogue scale (VAS). The data was analysed by paired T-test and independent T-test. Results : The results of this study were summarized as follow : 1. The Oswestry disability score of experimental and control group were significantly decreased and there was no difference in the Oswestry disability score change between joint mobilization group and back pain exercise group. 2. The pains in anterior, postrior, lift lateral and right lateral bending and in rotation of back pain exercise group were significantly increased compared with those of joint mobilization group. 3. The flexors and extensors peak torque of back pain exercise group were significantly increased at test velocities $30^{\circ}$/sec, $60^{\circ}$/sec compared with those of the joint mobilization group. There was no significant difference in extensors and flexors peak torque at $30^{\circ}$/sec, $60^{\circ}$/sec between two group. The results showed that the back pain exercise group were effective in decreasing disability score and pain of trunk activity, increasing trunk extension and flexion peak torque. Conclusion : It is suggested theat the back pain exercise program could be an essential factor for the effective intervension to the hearing impairment patients suffere from low back pain.

• 대한치과보철학회지
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• 제44권3호
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• pp.295-313
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• 2006

Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveola. bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of load-ing offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with in-creasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

• 대한치과보철학회지
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• 제45권5호
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• pp.589-600
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• 2007

Statement of Problem: Titanium has many advantages of high biocompatibility, physical porperties, low-weight, low price and radiolucency, but it is incompatible with conventional dental porcelain due to titanium's oxidative nature. Many previous studies have shown that they used the method of sandblast surface treatment prior to porcelain application, the researchs are processing about the method of acid etching or surface coating. Purpose: The purpose of this research is to study the effect on bond strength between titanium and porcelain when using macro-surface treatment and micro-surface treatment and macro and micro surface treatment. Material and method: In this study, we evaluated the bond strength by using 3-point bending test based on ISO 9693 after classified 7 groups-group P : polished with #1200 grit SiC paper, group SS : sandblasted with $50{\mu}m$ aluminum oxides, group LS : sandblasted with $250{\mu}m$ alumium oxides, group HC : treated with 10% hydrochloric acid, group NF : treated with 17% solution of fluoric acid and nitric acid, group SHC : treated with 10% hydrochloric aicd after sandblsting with $50{\mu}m$ alumium oxides, group SNF treated with 17% solution of fluoric acid and nitric acid. Results : Within the confines of our research, the following results can be deduced. 1. Group SS which was sandblasted with $50{\mu}m$ aluminum oxides showed the highest bond strength of 61.74 MPa and significant differences(P<0.05). The bond strengths with porcelain in groups treated acid etching after sandblasting decreased more preferable than the group treated with sandblasting only. It gives significant differences(P<0.05). 2. After surface treatments, the group treated with sandblasting showed irregular aspect formed many undercuts, in the SEM photographs. The group treated with hydrochloric acid had the sharp serrated surfaces, the group treated with the solution of fluoric acid and nitric acid had the smooth surfaces, the group with sandblasting and hydrochloric acid had irrigular and porous structure, the group with sandblasting and the solution of fluoric acid and nitric acid had crater-like surfaces. But all of the groups treated with acid etching was not found and undercut. Conclusion: In above results, average surface roughness increase, bond strength also increase, but surface topographs influences more greatly on bond strengths.

• 해양환경안전학회지
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• 제24권2호
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• pp.133-139
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• 2018

해상교량 하부의 직선항로 길이 확보는 선박 통항 안전을 위한 중요한 요소 중 하나이다. 그러나 항만 및 어항 설계기준에 따르면 해상교량 하부 직선항로 길이는 선박길이의 8배로 획일적인 가이드라인을 적용하고 있다. 본 연구는 적정 해상교량 하부직선길이를 도출하기 위해 ES 모델을 이용하여 항로폭, 통항량, 항로의 곡률, 직선항로길이에 따른 위험도 비율을 확인했다. 확인 결과 항로의 곡률이 $45^{\circ}$의 경우 항로길이가 3L에서 10L로 길어짐에 따라 위험도 비율이 2.27 % 감소했다. 곡률에 따른 위험도는 직선항로의 길이가 3L의 경우 곡률이 $45^{\circ}$에서 $0^{\circ}$로 변하면서 위험도 비율이 4.83 % 감소하는 것을 확인했다. 또한 항로폭 400 m, 시간당 발생선박이 20척의 조건에서 항로의 곡률별, 직선항로에 따른 위험도 비율은 최대 1.45 % 감소하는 것을 확인했다. 이를 통해 해상 교량 건설 시 항로의 혼잡도 및 곡률에 따라 일정 길이 이상의 직선항로가 필요함을 검증했다.

• 한국철도학회논문집
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• 제18권3호
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• pp.261-269
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• 2015

자갈궤도에서 레일과 침목을 연결하는 체결장치의 레일패드 강성이 증가함에 따라 윤중이 증가하고 궤도틀림진전이 증가되어 궤도유지보수비가 증가하게 된다. 반면에 레일패드강성이 감소하면 차량운행에 따른 전력소모비가 증가하게 된다. 따라서 자갈궤도 설계 시에 차량과 궤도 및 운영조건을 고려하여 궤도유지보수비와 전력소모비를 가급적 작게 할 수 있는 적정 레일패드강성을 결정하는 것은 철도 경제성 확보차원에서 중요한 과제라 할 수 있다. 본 연구에서는 $L{\acute{o}}pez$ Pita 등이 제시한 자갈궤도에서의 최적레일패드 강성을 평가하는 프로세서를 기초로 적정 레일패드강성 범위를 구하였다. 연구결과에 중요한 영향을 주는 레일패드강성에 따른 윤중변화를 보다 정확하게 평가하기 위하여 궤도구성품의 거동특성을 보다 상세하게 고려할 수 있는 고도화된 수치해석적 기법을 사용하여 평가하였다. 또한 국내에서의 차량, 궤도 운영조건을 고려함으로써 국내에서 궤도설계에 적용할 수 있는 적정 레일패드강성 범위를 도출하였다.

• Corrosion Science and Technology
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• 제9권4호
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• pp.147-152
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• 2010

Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer$^{(R)}$) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after $180^{\circ}$ bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.

• 농업과학연구
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• 제25권2호
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• pp.285-292
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• 1998

이 연구는 보통 포틀랜드 시멘트와 천연골재 및 볏짚재를 혼입한 볏짚재 콘크리트의 공학적 성질을 실험적으로 구명한 것으로써, 이 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 1. 볏짚재를 혼입한 콘크리트의 단위중량은 $2,250{\sim}2,335kgf/m^3$으로써 보통 시멘트 콘크리트에 비해 1~5% 정도 감소되었다. 2. 각 강도는 볏짚재를 결합재량의 5% 혼입한 콘크리트에서 가장 크게 나타났으며, 보통 시멘트 콘크리트에 비해 압축강도는 17%, 인장강도는 30%, 휨강도는 21% 증가되었다. 3. 볏짚재를 혼입한 콘크리트의 초음파진동속도는 4,059~4,360m/s로써 보통 시멘트 콘크리트와 유사하게 나타났으며, 볏짚재를 5% 혼입한 콘크리트에서 가장 큰 값을 보였다. 4. 내산성은 볏짚재의 혼입량이 많을수록 증가되었으며, 볏짚재를 5% 혼입한 콘크리트와 10% 및 15% 혼입한 콘크리트의 내산성은 보통 시멘트 콘크리트보다 각각 1.15배와 1.45배 및 1.60배 정도 크게 나타났다. 5. 적정량의 볏짚재를 혼입하여 콘크리트를 제조할 경우, 볏짚재 콘크리트의 공학적 성질이 보통 시멘트 콘크리트보다 우수할 뿐만 아니라, 농업부산물의 활용으로 인한 경제적 측면에서도 많은 기여를 할 수 있을 것이다.