• Archives of Plastic Surgery
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• 제33권2호
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• pp.187-192
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• 2006

The perforator flaps are based on cutaneous vessels which are originated from a main pedicle and penetrate fascia or muscle to reach the skin. The lateral lower leg is one of the most suitable areas for harvesting perforator flaps because a number of perforator vessels exist. The authors applied peroneal perforator flaps in nine patients. Five flaps were reverse island flaps based on peroneal artery and septocutaneous perforator, and four flaps were free flap based on musculocutaneous perforator only. The recipient site was the posterior ankle in three patients, posterior heel in three patients, lateral malleolus, anterolateral ankle, and foot dorsum in one patient each. The flap size ranged from 5 to 12cm long, from 3 to 5cm wide, and the primary closure of the donor site was possible in most cases. All flaps, except for the flap in two patients in the reverse island flap series, survived completely. The peroneal perforator flap is a very thin, pliable flap with minimal donor site morbidity and is suitable for the reconstruction of small and medium sized superficial skin defects. Also, this flap may be considered as an alternative to radial forearm flap or other perforator flaps.

• 한국정밀공학회지
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• 제16권6호
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• pp.45-51
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• 1999

The semi-solid forging is a new forging technology in which the billet is heated to the semi-solid state coexisting liquid and solid phase for making globular microstructure and subsequently formed. As the semi-solid forging is compared with conventional casting such as die casting and squeeze casting for the characteristics of its process, the product without inner defects such as gas porosity and segregation can be obtained and its microstructure is globular grain. Simutaneously, its mechanical properties are improved by globular microstructure and the lower temperature of the slug causes the cycle time of manufacturing to be shortened and the die life to be lengthened. As it is compared with conventional cold and hot forging, it is possible to minimize the equipment of production owing to a lower forming load and reduce the number of process by a followed treatment for complex shaped product. Therefore it is needed to confirm the quality of a semi-solid forged product by defining its characteristics quantitatively under these advantages. This paper investigates the formability of a master cylinder by its forming variables. And the microstructural characteristics and mechanical property of it is also studied.

• 한국안전학회지
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• 제33권4호
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• pp.1-7
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• 2018

This paper is analyzed for the thermal characteristics(1 year) of the 6 components(DC breaker, DC filter(including capacitor and discharge resistance), IGBT(Insulated gate bipolar mode transistor), AC filter, AC breaker, etc.) of a photovoltaic power generation-based PCS(Power conditioning system) below 20 kW. Among the modules, the discharge resistance included in the DC filter indicated the highest heat at $125^{\circ}C$, and such heat resulting from the discharge resistance had an influence on the IGBT installed on the rear side the board. Therefore, risk priority through risk priority number(RPN) of FMEA(Failure modes and effects analysis) sheet is conducted for classification into top 10 %. According to thermal characteristics and FMEA, it is necessary to pay attention to not only the in-house defects found in the IGBT, but also the conductive heat caused by the discharge resistance. Since it is possible that animal, dust and others can be accumulated within the PCS, it is possible that the heat resulting from the discharge resistance may cause fire. Accordingly, there are two options that can be used: installing a heat sink while designing the discharge resistance, and designing the discharge resistance in a structure capable of avoiding heat conduction through setting a separation distance between discharge resistance and IGBT. This data can be used as the data for conducting a comparative analysis of abnormal signals in the process of developing a safety device for solar electricity-based photovoltaic power generation systems, as the data for examining the fire accidents caused by each module, and as the field data for setting component management priorities.

• 한국태양에너지학회 논문집
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• 제39권3호
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• pp.9-17
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• 2019

Laser cutting cell of solar cells can achieve high voltage and efficiency through more array than conventional 6 inch cell compared to same area. In this study, we fabricated c-Si cutting cell with various lasers and laser conditions such as power, speed, and number of times. In the case of picosecond laser, excellent surface characteristics were obtained due to small surface defects and low thermal damage at the output of 20W and the speed of 100 mm/s. However, it is not possible to fabricate a cutting cell having good characteristics due to nonuniform cutting inside the wafer when the processing for forming a cutting cell is not sufficiently performed. For nanosecond lasers, the best wafer characteristics were obtained for fabrication of excellent cutting cells at a frequency of 500 kHz and a laser speed of 100 mm/s. However, the nanosecond laser has not been processed sufficiently in the condition of a number of times. As a result, it was confirmed that the wafer thickness was cut by $63{\mu}m$ of the cell thickness of $170{\mu}m$ in the condition of five times of laser process. It was found that more than 30% of the wafer thickness had to be processed to fabricate the cutting cell. After cutting the 6-inch cell having the voltage of 0.65 V, we obtained the voltage of about 0.63 V.

• 비파괴검사학회지
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• 제29권5호
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• pp.450-457
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• 2009

열차폐 코팅 시편에 대하여 열충격을 주기적으로 가한 후 발생하는 결함을 관찰하였다. 실험에 사용 된 열차폐 코팅 시편은 인코넬-738로 제작된 모재 위에 CoNiCrAlY 본드 코팅층과 $ZrO_2-8wt%Y_2O_3$ 세라믹탑 코팅층이 플라즈마 용사 방법으로 올려진 형태로 되어있다. 열충격 시험은 $1000^{\circ}C$의 고온으로 가열했다가 상온으로 급격하게 냉각시키는 가혹한 조건으로 실행되었고, 사이클 수가 증가함에 따라 열충격의 피로도 또한 증가하였다. 시험후 시편 내부의 미세 조직 변화와 결함을 전자현미경으로 관찰하고, 시편의 기계적인 특성을 측정하여 그 변화 양상을 살펴보았다. 열충격 주기실험후 본드 코팅층과 세라믹 탑 코팅층 사이에 발생하는 TGO 산화물층에 대한 변화 양상과 이에 대한 와전류 신호를 측정하여 TGO층 성장 거동의 비파괴적인 평가를 위한 실험을 진행하였다. 본 연구를 통하여 마이크로 단위의 TGO층에 대한 와전류검사의 적용 가능성을 확인하고 열차폐 코팅의 수명을 예측할 수 있는 가능성을 제시하였다.

• Carbon letters
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• 제11권3호
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• pp.176-183
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• 2010

PAN precursor fibers were produced via wet-spinning process, and effects of polymerization and spinning processes, especially the stretching process, were investigated on mechanical properties and micro-morphologies of precursor fibers. An increase in molecular weight, dope solid and densification and a decrease in surface defects were possible by controlling polymerization temperature, the number of heating rollers for densification and the jet stretch ratio, which improved the mechanical properties of precursor fibers. The curves for strength, modulus, tensile power and diameter as a function of stretch ratio can be divided into three stages: steady change area, little change area and sudden change area. With the increase of stretch ratio, the fiber diameter became smaller, the degree of crystallization increased and the structure of precursor fibers became compact and homogeneous, which resulted in the increase of strength, modulus and tensile power of precursor fibers. Empirical relationship between fiber strength and stretch ratio was studied by using the sub-cluster statistical theory. It was successfully predicted when the strengths were 0.8 GPa and 1.0 GPa under a certain technical condition, the corresponding stretch ratio of the fiber were 11.16 and 12.83 respectively.

• Archives of Plastic Surgery
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• 제40권2호
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• pp.91-96
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• 2013

Background A thinned anterolateral thigh (ALT) flap is often harvested to achieve optimal skin resurfacing. Several techniques have been described to thin an ALT flap including an adipocutaneous flap, an adipofascial flap and delayed debulking. Methods By systematically reviewing all of the available literature in English and French, the present manuscript attempts to identify the common surgical indications, complications and donor site morbidity of the adipofascial variant of the ALT flap. The studies were identified by performing a systematic search on Medline, Ovid, EMBASE, the Cochrane Database of Systematic Reviews, Current Contents, PubMed, Google, and Google Scholar. Results The study selection process was adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, and 15 articles were identified using the study inclusion criteria. These articles were then reviewed for author name(s), year of publication, flap dimensions and thickness following defatting, perforator type, type of transfer, complications, thinning technique, number of cases with a particular area of application and donor site morbidity. Conclusions The adipofascial variant of the ALT flap provides tissue to fill large defects and improve pliability. Its strong and safe blood supply permits adequate immediate or delayed debulking without vascular complications. The presence of the deep fascia makes it possible to prevent sagging by suspending and fixing the flap for functional reconstructive purposes (e.g., the intraoral cavity). Donor site morbidity is minimal, and thigh deformities can be reduced through immediate direct closure or liposuction and direct closure. A safe blood supply was confirmed by the rate of secondary flap debulking.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.639-643
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• 2002

The main purpose of this study was to investigate the formation mechanisms of imperfections such as irregular humps, outer cavity and inner cavity in the laser fusion zone of diamond saw blade. Laser beam welding was conducted to join two parts of blade; mild steel shank and Fe-Co-Ni sintered tip. The variables were beam power and travel speed. The microstructure and elements distributions of specimens were analyzed with SEM, AES, EPMA and so on. It was found that these imperfections were responded to heat input. Irregular humps were reduced in 10.4∼17.6kJ/m heat input range. However there were no clear evidences, which could explain the relations between humps formation and heat input. The number of outer cavity and inner cavity decreased as heat input was increased. Considering both possible defects formations mechanisms, it could be thought that outer cavity was caused by insufficient refill of keyhole, which was from rapid solidification of molten metal and fast molten metal flow to the rear keyhole wall at low heat input. More inner cavities were found near the interface of the fusion zone and sintered segment and in the bottom of the fusion zone. Inner cavity was mainly formed in the upper fusion zone at high heat input whereas was in the bottom at low heat input. Inner cavity was from trapping of coarsened preexist pores in the sintered tip and metal vapor due to rapid solidification of molten metal before the bubbles escaped.

• Archives of Plastic Surgery
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• 제43권4호
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• pp.344-351
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• 2016

Background Xeroderma pigmentosum (XP) is an autosomal recessive disorder characterized by xerosis, ultraviolet light sensitivity, and cutaneous dyspigmentation. Due to defects in their DNA repair mechanism, genetic mutations and carcinogenesis inevitably occurs in almost all patients. In these patients, reconstruction of cutaneous malignancies in the head and neck area is associated with some challenges such as likelihood of recurrence and an aggressive clinical course. The aim of this study is to discuss the therapeutic options and challenges commonly seen during the course of treatment. Methods Between 2005 and 2015, 11 XP patients with head and neck cutaneous malignancies were included in this study. Demographic data and treatment options of the patients were evaluated. Results The mean age of the patients was 32 years (range, 10-43) (4 males, 7 females). The most common tumor type and location were squamous cell carcinoma (6 patients) and the orbital region (4 patients), respectively. Free tissue transfer was the most commonly performed surgical intervention (4 patients). The average number of surgical procedures was 5.5 (range, 1-25). Six patients were siblings with each other, 5 patients had local recurrences, and one patient was lost to follow-up. Conclusions Although genetic components of the disease have been elucidated, there is no definitive treatment algorithm. Early surgical intervention and close follow-up are the gold standard modalities due to the tendency toward rapid tumor growth and possible recurrence. Treatment must be individualized for each patient. In addition, the psychological aspect of the disease is an important issue for both patients and families.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.21-24
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• 2002

The main purpose of this study was to investigate the formation mechanisms of imperfections such as irregular humps, outer cavity and inner cavity in the laser fusion zone of diamond saw blade. Laser beam welding was conducted to join two parts of blade; mild steel shank and Fe-Co-Ni sintered tip. The variables were beam power and travel speed. The microstructure and elements distributions of specimens were analyzed with SEM, AES, EPMA and so on. It was found that these imperfections were responded to heat input. Irregular humps were reduced in 10.4∼l7.6kJ/m heat input range. However there were no clear evidences, which could explain the relations between humps formation and heat input. The number of outer cavity and inner cavity decreased as heat input was increased. Considering both possible defects formations mechanisms, it could be thought that outer cavity was caused by insufficient refill of keyhole, which was from rapid solidification of molten metal and fast molten metal flow to the rear keyhole wall at low heat input. More inner cavities were found near the interface of the fusion zone and sintered segment and in the bottom of the fusion zone. Inner cavity was mainly formed in the upper fusion zone at high heat input whereas was in the bottom at low heat input. Inner cavity was from trapping of coarsened preexist pores in the sintered tip and metal vapor due to rapid solidification of molten metal before the bubbles escaped.