• Archives of Plastic Surgery
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• v.40 no.5
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• pp.564-569
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• 2013

Background Scalp defects may be caused by various etiological factors, and they represent a significant surgical and aesthetic concern. Various surgical techniques can be applied for reconstructive work such as primary closure, skin grafting, pedicled or free flaps. In this article, the authors share their clinical experience with scalp operations using the technique of local flaps and discuss the application of this method from the perspective of not only the size of the defect, but also in relation to the anatomical area, quality of surrounding tissue, and patient's condition. Methods During the period from December 2007 to December 2012, 13 patients with various scalp defects, aged 11 to 86 years, underwent reconstruction with local pedicle flaps. The indications were based on the patients' condition (age, sex, quality of surrounding tissue, and comorbidities) and wound parameters. Depending on the size of the defects, they were classified into three groups as follows: large, 20 to 50 $cm^2$; very large, 50 to 100 $cm^2$; extremely large, 100 $cm^2$. The location was defined as peripheral (frontal, temporal, occipital), central, or combined (more than one area). We performed reconstruction with 11 single transposition flaps and 1 bipedicle with a skin graft on the donor area, and 2 advancement flaps in 1 patient. Results In all of the patients, complete tissue coverage was achieved. The recovery was relatively quick, without hematoma, seroma, or infections. The flaps survived entirely. Conclusions Local flaps are widely used in scalp reconstruction since they provide healthy, stable, hair-bearing tissue and require a short healing time for the patients.

• Archives of Reconstructive Microsurgery
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• v.18 no.1
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• pp.31-34
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• 2009

Purpose: Merkel cell carcinoma, also called neuroendocrine carcinoma, is a very rare type of skin cancer that develops as Merkel cells grow out of control. Merkel cell carcinoma is reported below 1% of whole skin neoplasms in the United States and is known that the 2-year survival rate is about 50~70%. The principles of treatment are wide excision of primary lesion with radiotherapy and/or chemotherapy that decrease the local recurrent rate. There has been no report of reconstruction with free flap after resection of Merkel cell carcinoma in Korea. Methods: We reconstructed the skin and soft tissue defect after wide excision of Merkel cell carcinoma with anterolateral thigh perforator free flap in two cases. No distant metastasis was found at the preoperative imaging work-up. In one case, preoperative chemotherapy was performed and the size of lesion was decreased. Results: There were no recurrence and significant complications. Functionally and aesthetically satisfactory results were obtained with reconstruction. Conclusion: Wide excision and reconstruction with anterolateral thigh perforator free flap for Merkel cell carcinoma patient is the first report in Korea. We regard this method as the treatment of choice in Merkel cell carcinoma.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.19-26
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• 2014

Concrete guide rail and median barrier are an attached RC member, however they are vulnerable to cracking due to slip form construction and large surface of member. In this study, causes and pattern of cracking are analyzed through assessment and NDT (Non-Destructive Technique) evaluation for concrete guide rail and median barrier on highway structure. For this work, analysis on drying shrinkage and hydration heat are performed considering installation period, and plastic shrinkage is also analyzed considering their environmental conditions. From the evaluation, plastic settlement around steel location, drying/ plastic shrinkage, and aggregate segregation are inferred to be the main causes of cracking in the structures. The crack causes and patterns are schematized and techniques of crack-control are suggested. Furthermore concrete guide rail/ median barrier in the bridge on the sea are vulnerable to cracking at early age so that special attentions should be paid at the stages of material selection and construction.

• Archives of Plastic Surgery
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• v.34 no.2
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• pp.269-273
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• 2007

Purpose: High-pressure injection(HPI) injury is an injury caused by accidental injection of substances by industrial equipment. HPI injury of the hand is a serious injury that can be potentially devastating. There have been a number of publications on the results of its treatment and its functional outcome of these hands. Unfortunately, the clinical outcomes were unsatisfactory following an initial treatment approach of digital expression of the injection material, elevation, soaks, dressing changes, and antibiotics. Methods: A 43-year-old right handed man sustained a high pressure injection injury to the tip of the left index finger. The injected material was industrial paint thinner. Tissue necrosis was noted at the pulp of the finger. Several debridements and irrigation were required. A pedicled chest flap transfer was performed on the eighteenth day after injury as the dorsal nail complex remained viable. This is a retrospective review of our experience with high-pressure finger injection injury caused by paint. A literature review, retrospective chart and radiologic review were presented. Results: Follow-up length was about 1 year. The injuried hand was left nondominant hand, the index. Patient complaints were cold intolerance, paresthesia, contact pain, and impairment of activities of daily living. Conclusion: The outcome of high-pressure injection injuries of the hand is affected by many factors. The time between injury and operative treatment has been regarded as a key determinant by a number of authors. The nature of the injected material is probably more important. It has been noted by many authors that injuries with paints have a worse outcome than those with oil or grease. This study confirms the fact that high-pressure injection injury caused by paint thinner to the hand is a significant problem. Virtually a patient suffers sequelae of this injury. The injury has significant repercussions for future function and reintegration into the work force.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.263-268
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• 2017

A hot forming process is required for Mg alloys to enhance the formability and plastic workability due to the insufficient formability at room temperature. Mg alloy undergoes dynamic recrystallization (DRX) during the hot working process, which is a restoration or softening mechanism that reduces the dislocation density and releases the accumulated energy to facilitate plastic deformation. The flow stress curve shows three stages of complicated strain hardening and softening phenomena. As the strain increases, the stress also increases due to work hardening, and it abruptly decreases work softening by dynamic recrystallization. It then maintains a steady-state region due to the equilibrium between the work hardening and softening. In this paper, an efficient optimization process is proposed for the material model of the dynamic recrystallization to improve the accuracy of the flow curve. A total of 18 variables of the constitutive equation of AZ80 alloy were systematically optimized at an elevated forming temperature($300^{\circ}C$) with various strain rates(0.001, 0.1, 1, 10/sec). The proposed method was validated by applying it to the constitutive equation of AZ61 alloy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1547-1551
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• 2010

We newly propose the silver alloys of Ag-5wt%Ge-2.5wt%Cu(Ge1) and Ag-5wt%In-2.5wt%(In1) to overcome the tarnish and mechanically weak problems of the conventional sterling silver Ag-7.5wt%Cu (Cu1). We check the castability, surface color stability during process and wearing, and work hardening with plastic deformation of all three silver alloys. Our newly proposed silver alloys of Ge1 and In1 showed improved castability, anti-tarnish stability, and work hardening property compared to the conventional sterling silver, which implied that these alloys might be more appropriate for the high-end silver jewelry.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.6
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• pp.18-25
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• 2007

In a plastic metal forming of thermally rate-sensitive material, the localized shear band stems from evolution of a narrow region in which intensive plastic flow occurs. And it give rise to fatal fracture with plastic instability. The objectives of this study are to investigate the localization behavior by using numerical method and predict the failure for WHA(Tungsten Heavy Alloy). In this work, the implicit finite difference scheme is used because of the advantage about convergence and the numerical stability. This study is based on an analysed material with hardening as well as thermally softening behavior which includes isotropic strain hardening and observed the extension of localization within shear band according to material properties.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.452-465
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• 2014

The application of friction stir welding (FSW) technology has been extended to all industries, including shipbuilding. A heat transfer analysis evaluates the weldability of a welded work piece, and elasto-plastic analysis predicts the residual stress and deformation after welding. A thermal elasto-plastic analysis based on the heat transfer analysis results is most frequently used today. However, its application to large objects such as offshore structures and hulls is impractical owing to its long computational time. This paper proposes a new method, namely an equivalent strain method using the inherent strain, to overcome the disadvantages of the extended analysis time. In the present study, a residual stress analysis of FSW was performed using this equivalent strain method. Additionally, in order to reflect the external constraints in FSW, the reaction force was predicted using a neural network, Finally, the approach was verified by comparing the experimental results and thermal elasto-plastic analysis results for the calculated residual stress distribution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.484-496
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• 1996

This paper presents an anlaysis on the thermodynamic performance of ice storage system. The primary interest in this work is the exergetic efficiency of the system. The ice storage system considered here is the capsule type system with the waste plastic bottle being used as a capsule. To examine the characteristics of irreversibility production and exergetic efficiency in detail the ice storage system to be analyzed has been separated from the refrigerator in this analysis. The analysis is based on the lumped model with 3 uniform temperatures. The results indicate that 3 dimensionless parameters can describe the exergetic efficiency of the system, from which the characteristics of irreversibilities and the ranges of these parameters to ensure the reasonable performance of the system can be found. Experiments also have been performed to demonstrate the feasibility of such a system. This analysis only shows the performance of ice storage side, with the refrigeration side excluded. However, the results can be interpreted as a total performance if the refrigerator coupled with the ice storage system operatres reversibly.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.587-593
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• 2017

The objective of this analytical study is to calculate the elasto-plastic stresses of Functionally Graded (FG) hyperbolic disc subjected to uniform temperature. The material properties (elastic modulus, thermal expansion coefficient and yield strength) and the geometry (thickness) of the disc are assumed to vary radially with a power law function, but Poisson's ratio does not vary. FG disc material is assumed to be non-work hardening. Radial and tangential stresses are obtained for various thickness profile, temperature and material properties. The results indicate that thickness profile and volume fractions of constituent materials play very important role on the thermal stresses of the FG hyperbolic discs. It is seen that thermal stresses in a disc with variable thickness are lower than those with constant thickness at the same temperature. As a result of this, variations in the thickness profile increase the operation temperature. Moreover, thickness variation in the discs provides a significant weight reduction. A disc with lower rigidity at the inner surface according to the outer surface should be selected to obtain almost homogenous stress distribution and to increase resistance to temperature. So, discs, which have more rigid region at the outer surface, are more useful in terms of resistance to temperature.