• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1376-1377
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• 2008

가스절연변압기(GITr)는 우수한 절연내력과 높은 신뢰성을 장점으로 가지고 있지만, 제작과 운전 단계에서 절연 결함이 발생할 수 있고 이러한 결함들은 가스절연변압기 사고의 원인이 될 수 있다. 따라서 결함에 대한 상시 진단 및 원인 분석이 반드시 선행되어야 하며 이와 같은 진단 분석 기법의 하나로 내부 절연결함의 위치 판별에 대한 연구의 필요성이 절실히 요구되고 있다. 따라서 본 논문에서는 일반적으로 부분 방전의 위치 판별을 위한 time delay 측정법 중 하나인 Cross-correlation 방법과 함께 제안한 Threshold-Initial peak detection 방법을 적용하여 위치 데이터를 취득하고 신뢰구간 이내의 데이터만 사용하여 부분 방전 위치 판별 한 결과, 더욱 정확한 위치 판별이 가능하였다.

• Journal of Periodontal and Implant Science
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• v.29 no.2
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• pp.355-373
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• 1999

Many researches have been reported that collagen as cellular stroma, matrix of grafting materials, mediator of agents for the purpose of promoting healing process invivo, but the responses in vivo were seen various. The goal of this experiment is to assess the effect of collagen on bony healing, through histological evaluation of implanted collagen on the calvarial defect in rats. 2-month-old Sprague-Dawley, 24 rats were used and 12 rats assigned to each group of control and test. Defect of 5mm in diameter was made on the calvarial bone with trephine bur. Following thorough saline rinse, defect of control group was left in empty and that of experimental group was filled with fibrillar collagen($COLLATAPE^{(R)}$, COLLA-TEC. INC. U.S.A.) soaked in saline. 3 rats in each group were sacrificed at 3, 7, 14, 21 days after operation respectively, and the tissue blocks were prepared for light microscope with H-E for evaluation of overall healing, with TRAP(tartrate resistant acid phosphatase) for evaluation of osteoclastic activity and with immunohistochemical staining for macrophages. The results were as follows : 1. In the control group, inflammatory responses were disappeared at day 14, but, in the experimental group inflammatory infiltrates were reduced at day 21. Thus, the experimental group showed more severe soft tissue inflammation than control group. 2. Both control and experimental group showed slight appositional growth at day 7 and gradual bony growth to 21th day. But, complete bony healing of the defect was not shown. There was no significant difference in bony healing between control and experimental group 3. Specific response of macrophages for implanted collagen was observed at day 14 in the experimental group. In conclusion, although fibrillar collagen caused inflammation of soft tissue during initial healing period, inflammatory responses by fibrillar collagen didn't inhibit bony regeneration and implanted collagen was biodegradaded by macrophages. Thus, we expect that fibrillar collagen can be used for useful mediator of graft materials or growth factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.379-388
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• 2016

There are various system defects from weapons manufacturing due to the numerous production processes and various production environments. The first kind of defect is patent defects, which can be detected by visual inspection, functional testing, and existing quality control procedures during the manufacturing process. The second kind is latent defects, which cannot be detected though existing quality management approaches because of the complexity of the system and manufacturing process. To minimize the initial defect problems, environmental stress screening (ESS) is needed to detect the defects, remove them, and improve the product conditions based on the environmental stress conditions of temperature and vibration. We implemented a tool for quantitative ESS effectiveness analysis and profile design automation based on MIL-HDBK-344 and verified it using six scenarios with different temperature stress, vibration stress, and test designs.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.357-370
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• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.48-56
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• 1999

In this paper, we have investigated experimentally the effects of initial oxygen concentration on oxygen pileup phenomenon and the diffusion of implanted impurities. 1.2 MeV $^{11}B^{+}$ and 2.2 MeV $^{31}P^{+}$ ions were implanted into p-type (100) Si wafers with a dose of 1${\times}10^{15}$ / $\textrm{cm}^2$. Secondary ion mass spectrometry(SIMS) measurements were carried out to obtain depth distribution profiles for implanted impurities and oxygen atoms after two-step annealing of $700^{\circ}C$(20 hours)+$1000^{\circ}C$(10 hours). Residual secondary defect distribution and annealing behabiour were also studied by cross-sectional transmission electron microscopy(TEM) observations. Oxygen pileup nearly $R_p$(projected range) were observed by SIMS measurements and considerable amount of residual secondary defect layer were observed by TEM observations. It can be seen that oxygen atoms are trapped at the secondary defects by the experimental results. Enhanced diffusions of boron and phosphorus to the bulk direction were observed with the increasing of initial oxygen concentration.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.344-354
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• 2015

In order to study the development of partial discharge (PD) under typical protrusion defects in gas-insulated switchgear, we applied step voltages on the defect and obtained the ${\varphi}-u$ and ${\varphi}-n$ spectrograms of ultra-high frequency (UHF) PD signals in various PD stages. Furthermore, we extracted seven kinds of features to characterize the degree of deterioration of insulation and analyzed their values, variation trends, and change rates. These characteristics were inconsistent with the development of PD. Hence, the differences of these features could describe the severity of PD. In addition, these characteristics could provide integrated characteristics regarding PD development and improve the reliability of PD severity assessment because these characteristics were extracted from different angles. To explain the variation laws of these seven kinds of parameters, we analyzed the relevant physical mechanism by considering the microphysical process of PD formation and development as well as the distortion effect generated by the space charges on the initial field. The relevant physical mechanism effectively allocated PD severity among these features for assessment, and the effectiveness and reliability of using these features to assess PD severity were proved by testing a large number of PD samples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.253-261
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• 2005

In decades, a substantial body of work on a unified viscoplastic model which considers the mechanism of plastic deformation and creep deformation has developed. The systematic scheme for numerical analysis of unified model is necessary because the dominant failure mechanism is the defect growth and coalescence in materials. In the present study, the unified viscoplastic model for materials with defects suggested by Suquet and Michel was employed for numerical analysis. The constitutive equations are integrated based on the generalized mid-point rule and implemented into a finite element program (ABAQUS) by means of user-defined subroutine (UMAT). To evaluate the validity of the developed UMAT code and the assessment of the adopted viscoplastic model, the results obtained from the UMAT code was compared with the numerical reference solution and experimental data. The unit cell analysis also has been investigated to study the effect of strain rate, temperature, stress triaxiality and initial defect volume fraction on the growth and coalescence of the defect.

• Archives of Reconstructive Microsurgery
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• v.11 no.1
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• pp.1-10
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• 2002

Purpose : To analyze the clinical results of free vascularized osteocutaneous fibula graft to tibial defect combined with soft tissue defect and infection. Materials and Methods : In the retrospective study of 51 consecutive cases of vascularized osteocutaneous fibular graft, the length of the grafted fibula, size of the skin flap, anastomosed vessels, ischemic time of the flap, time for union, hypertrophy of fibula and the complications were evaluated. Results : Initial bony union of the grafted fibula was obtained at 3.74 months after operation, except 4 cases of nonunion and delayed union. The weight bearing without external supports was possible at 18 months after operation in average. The fracture of grafted fibula was most common complication(16 cases). Conclusion : The vascularized osteocutaneous fibula graft provided satisfactory bony union and functional results in the cases not responsible for conventional treatment methods.

• Archives of Plastic Surgery
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• v.35 no.6
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• pp.692-697
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• 2008

Purpose: Gluteal perforator flap has evolved to one of the standard tools for coverage of pressure sore. We used this flap to cover the defect adjacent to the buttock. Methods: From September 2004 to August 2006, gluteal perforator flaps were performed in 3 patients with sore and 9 patients with tumor. We made the rule for free style design of the flap. First, the defect should be covered fully regardless of the shape or area. Second, the location of perforators was decided to maximize flap mobility. Third, the donor-site should be closed directly. Results: Successful reconstruction was fulfilled. In 2 cases, initial flap congestion was observed but medical leech was applied and it was resolved. Partial flap loss occurred in one case. Infection was observed in one case. But there were no major complications. Conclusion: Gluteal perforator flap is very good option for the reconstruction of the defects adjacent to the buttock.

• Journal of Periodontal and Implant Science
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• v.44 no.6
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• pp.300-306
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• 2014

Purpose: A laterally positioned flap (LPF) combined with a subepithelial connective tissue graft (SCTG) is one of the conventional approaches for resolving gingival recession defects, with the advantages of flap flexibility and extended coverage of the tissue graft. However, thus far, evidence is lacking for the use of this technique for the treatment of advanced gingival recession defects. This report discusses three Miller class III cases with interproximal bone loss and wide and deep defects treated with a combination procedure of a modified laterally positioned flap (mLPF) and SCTG. Methods: mLPF combined with SCTG was performed for each case. The defect size and the degree of hypersensitivity at baseline and the final appointment in each case were documented. Results: The three cases had a mean initial defect of $7.7{\pm}1.5mm$ and a mean residual defect of $1.7{\pm}1mm$ at the 6-, 3-, and 36-month follow-up, respectively, after the root coverage surgery. The symptom of hypersensitivity was improved, and the patients were satisfied with the clinical outcomes. Conclusions: The results demonstrated that the combination of mLPF with SCTG is promising for treating these advanced cases with respect to obtaining the expected root coverage with the gingival tissue.