• Journal of Korea Ship Safrty Technology Authority
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• no.7 s.25
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• pp.64-76
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• 2008

This paper describes the failure mechanism and Charpy impact test of Fiber glass Reinforced Plastic composites which it was actually used for side plate of vessel. There are two examinations. The examination I, the specimens which it given temperature range $-25^{\circ}C$-$50^{\circ}C$ and with different initial notch length did impact test and then it compared impact energy(Uc) and impact fracture toughness(GIC). The examination II, the specimens which it putted into fresh water and sea water for scheduled hours did impact test and it compared impact energy(Uc) and impact fracture toughness(GIC). From examination I, it showed that impact energy(Uc) and impact fracture toughness(GIC) were peak at ambient temperature and decrease as temperature reduced. Fracture toughness(GIC) showed increase as initial notch length reduced. From examination II, impact energy(Uc) and impact fracture toughness(GIC) tended to increase which specimens putted in fresh water compared with sea water and maximum tolerance rate tend to decrease as permeation hours will be long.

• Computers and Concrete
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• v.2 no.6
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• pp.499-516
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• 2005

A composite model is used to represent the heterogeneity of plain concrete consisting of coarse aggregates, mortar matrix and the mortar-aggregate interface. The composite elements of plain concrete are modeled using triangular finite element units which have six interface nodes along the sides. Fracture is captured through a constitutive single branch softening-fracture law at the interface nodes, which bounds the elastic domain inside each triangular unit. The inelastic displacement at an interface node represents the crack opening or sliding displacement and is conjugate to the internodal force. The path-dependent softening behaviour is developed within a quasi-prescribed displacement control formulation. The crack profile is restricted to the interface boundaries of the defined mesh. No re-meshing is carried out. Solutions to the rate formulation are obtained using a mathematical programming procedure in the form of a linear complementary problem. An event by event solution strategy is adopted to eliminate solutions with simultaneous formation of softening zones in symmetric problems. The composite plain concrete model is compared to experimental results for the tensile crack growth in a Brazilian test and three-point bending tests on different sized specimens. The model is also used to simulate wedge-type shear-compression failure directly under the loading platen of a Brazilian test.

• Communications for Statistical Applications and Methods
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• v.3 no.2
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• pp.275-282
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• 1996

A life distribution F with survival function $\overline{F}$=1-F, finite mean $\mu$ and mean residual life m(t) is said to be NBUE(NWUE) if m(t)$\leq$($\geq$) .$\mu$ for t$\geq$0. This NBUE property can equivalently be characterized by the fact that $\varphi$(u)$\geq$($\leq$)u for 0$\leq$u$\leq$1, where $\varphi$(u) is the scaled total-time-on test transform of F. A generalization of the NBUE properties is that there is a value of p such that $\varphi$(u)\geq.u$ for 0$\leq$u$\leq$p and $\varphi$(u)\leq$$\leq$u$\leq$1, or vice versa. This means that we have a trend change in the NBUE property. In this paper we point out an error of Klefsjo's paper (1988). He erroneously takes advantage of trend change point of failure rate to calculate the empirical test size and power in lognormal distribution. We solves the trend change point of mean residual lifetime and recalculate the empirical test size and power of Klefsjo (1988) in mocensoring case.

• The Korean Journal of Applied Statistics
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• v.22 no.4
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• pp.793-804
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• 2009

The hypotheses of difference, ratio and odds ratio between two proportions are used for the non-inferiority trial. The approximate unconditional test suggested by Kang and Chen (2000) based on difference and ratio have the potential problem against the failure rate. When the sample size is small, the type I errors of the asymptotic test using the normal approximation suggested by Chen et al. (2000) tends to exceed the nominal level. Therefore, we propose the approximate unconditional test based on odds ratio and compare the test with the asymptotic test. And we compare the three hypotheses used in the approximate unconditional tests of two proportions with respect to the type I errors and power.

• The KIPS Transactions:PartD
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• v.17D no.4
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• pp.271-282
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• 2010

Insufficient requirement management accounts for 54% ofunsuccessful software development projects and 22% of insufficient requirement management comes from requirement change management. Hence, requirement management activities are important to reduce failure rates and a tracing method is suggested as the major factor in requirements change management. A traceability table is easy to use because of its legibility accurate tracing. However, traceability tables of existing studies have failed to concretely suggest method of change management and effect of traceability. Also, studies of methods to estimate change impact is complex. Hence, this study suggests how to use a traceability table to manage changes in requirements. Together, in comparison to existing studies, this study suggests easier methods to estimate change rate and change impact. Also Fifteen projects were sampled to test the hypothesis that traceability table influences the success of projects and that it decreases the failure rate that comes from the insufficient requirements management.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.82-88
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• 2013

It is important to give lightning warning prior to a cloud-to-ground (CG) discharge within an Area of Concern (AOC) because most of lightning damage and victim are usually occurred by the first lightning in the AOC. The aim of this study is to find the optimal operation conditions of the automated lightning warning systems in order to make the best use of the available data. In this paper, the test-operated results of the automated lightning alert and risk management system (ALARM) based on detections of CG discharge and eletrostatic field and optimized at probability of lightning have been described. It was possible to obtain the following warning performance parameters: probability of detection (POD), false alarm ratio (FAR), probability of lightning (POL) and failure-to-warn rate (FTW). The data obtained from trial operation for 5months were not sufficient but the first analysis of domestic lightning warning was carried out. We have observed that the evaluated statistical results through trial operation depend on the various factors such as analysis methods and criteria, topographical conditions, etc. Also we suggest some methods for improvement of POL and POD including the finding of the optimal electric field threshold level to be used, based on the high values of FAR and FTW found in this work.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.109-124
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• 2014

Objective: This study was conducted for one-hand users including hemiplegic clients currently using general folding manual wheelchairs, so as to analyze their specific problems and recommend solutions regarding usage. Background: Traditional manual wheelchairs require considerable use and control of both hands for operation, thus adaptations become necessary for individuals with asymmetrical use of hands. Method: Thirty hemiplegic clients who were admitted to rehabilitation and convalescent hospitals participated as subjects. The research tools were general folding manual wheelchairs commonly used by people with impaired gait, and the Wheelchair Skills Tests (WST) WST-M/WCU 4.1 version was adopted as the assessment tool. All participants were asked to fill out questionnaires on demographics and wheelchair usage characteristics. Assessment procedures were performed with currently used manual wheelchairs and with/without the use of foot to control the wheelchair. Results: When the participants drove folding manual wheelchairs without the use of foot, even the lowest failure rate among the WST items tested recorded 96.7%. On the contrary, with the use of foot in maneuvering the wheelchairs, failure rates dropped noticeably and success rate among the WST items tested was as high as 86.7%. Conclusion: These findings imply that the use of one-arm (hand) propellable (drivable) wheelchair can be an active and effective solution in resolving problems for hemiplegic clients using existing manual wheelchairs. As such, the government should provide institutional support to further develop and distribute this device or technology, and promote relative research in tandem. For now, the supply of commercially available device to hemiplegic clients is deemed urgent and also a mechanism to provide the devices and relevant services. Application: This study offers viable solutions for hemiplegic clients who rely on existing manual wheelchairs to increase their mobility and occupational performance.

• Journal of Veterinary Clinics
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• v.30 no.6
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• pp.453-455
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• 2013

Heartworm infection is a fatal disease causing heart failure and pulmonary diseases in dogs. This heartworm infection can also occur in wild carnivores including Raccoon dogs. Recent study found that relatively high prevalence rate in wild Raccoon dog population. Therefore, this study was designed to evaluate the prevalence rate of D. immitis in free-roaming Raccoon dogs and the recovery rate of microfilariae in infected Raccoon dogs in Korea. Overall prevalence rate of D. immitis in Korean Raccoon dogs was 17.8%. Prevalence rate in male Raccoon dogs was 21.8%, while that in female Raccoon dogs was 12.8%. Microfilariae were not detected in 17 Raccoon dogs having positive in heartworm antigen test. Our study result suggested that the prevalence rate of D. immitis in Korea is twice higher than that of Japan. In addition, microfilaremia is rare in Raccoon dogs as commonly noticed in cats.

• Clinical and Experimental Reproductive Medicine
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• v.19 no.2
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• pp.169-174
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• 1992

Previous studies have indicated that immunological factor is responsible for the infertility. We have detected sperm antibodies in ZIFT patients which grouped as fertilization failure (A; n=18) and low fertilization rate (${\leq}50%$)(B; n=20). Patients, however, had normal oocytes and sperms. We collected serum from wives and semen from husbands and donors (fertile sperm), if it was needed. We examined class, binding patterns and amounts of antisperm antibodies(ASA) by direct and indirect immunobead binding assay. In group A, 11 husbands were ASA positive showing 62.2% and 61.1% binding with IgA and IgG, respectively, and two wives were ASA positive showing 70.0% and 71.0% binding with IgA and IgG, respectively. Binding sites were mainly at the head of sperms (84%). In group B, 8 husbands were ASA positive showing 37.5% and 40.0% binding with IgA and IgG, respectively, and two wives were ASA positive showing 41.3% and 42.0% binding with IgA and IgG, respectively. Binding sites were also mainly at the head of sperms (78%). For the treatment of ZIFT patients who had fertilization failure at the first trial, we used albumin fractionation method and dilution method with 30% fetal cord serum (FCS) to reduce the titer of ASA. We used partial zona dissection (P.Z.D.) method for wives who have antisperm antibodies in their serum. According to represented method, we could inhance the fertilization rate to 60.0% by albumin fractionation and 20.0% by P.Z.D., respectively. We concluded that the use of micromanipulation like P.Z.D. or the other sperm processing methods is required to increase a chance of fertilization. This result suggested that it should be a prerequisite to test antisperm antibodies prior to entering assisted reproductive technologies (ART) programs.

• Journal of Periodontal and Implant Science
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• v.44 no.1
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• pp.13-19
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• 2014

Purpose: The purpose of this study was to retrospectively evaluate the survival of periodontally hopeless teeth that were intentionally extracted and replanted after a delay and to compare the radiographic characteristics of the survival group with those of the failure group. Methods: The clinical and radiographic data from patients who underwent delayed intentional replantation between March 2000 and July 2010 were reviewed. Twenty-seven periodontally hopeless teeth were extracted and preserved in medium supplemented with antibiotics for 10-14 days. The teeth were then repositioned in the partially healed extraction socket and followed for 3 to 21 months. The radiographic parameters were analyzed using a paired t test and the cumulative survival rate was analyzed using Kaplan-Meier analysis. Results: Seven replanted teeth failed and the overall cumulative survival rate was 66.4%. In the survival group, the amount of bone loss was reduced from 68.45% to 34.66% three months after replantation. There was radiologic and clinical evidence of ankylosis with 5 teeth. However, no root resorption was found throughout the follow-up period. In the failure group, bone formation occurred from the bottom of the socket. However, a remarkable radiolucent line along the root of a replanted tooth existed. The line lengthened and thickened as time passed. Finally, in each case of failure, the tooth was extracted due to signs of inflammation and increased mobility. Conclusions: Delayed intentional replantation has many advantages compared to immediate intentional replantation and could serve as an alternative treatment for periodontally involved hopeless teeth. However, techniques for maintaining the vitality of periodontal structures on the tooth surface should be developed for improved and predictable results.