• Nuclear Engineering and Technology
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• 제42권4호
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• pp.450-459
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• 2010

The present paper investigates the collapse pressure of cylinders with intermediate thickness subjected to external pressure based on detailed elastic-plastic finite element (FE) analyses. The effect of the initial ovality of the tube on the collapse pressure was explicitly considered in the FE analyses. Based on the present FE results, the analytical yield locus, considering the interaction between the plastic collapse and local instability due to initial ovality, was also proposed. The collapse pressure values based on the proposed yield locus agree well with the present FE results; thus, the validity of the proposed yield locus for the thickness range of interest was verified. Moreover, the partial safety factor concept based on the structural reliability theory was also applied to the proposed collapse pressure estimation model, and, thus, the priority of importance of respective parameter constituting for the collapse of cylinders under external pressure was estimated in this study. From the application of the partial safety factor concept, the yield strength was concluded to be the most sensitive, and the initial ovality of tube was not so effective in the proposed collapse pressure estimation model. The present deterministic and probabilistic results are expected to be utilized in the design and maintenance of cylinders subjected to external pressure with initial ovality, such as the once-through type steam generator.

• 한국강구조학회 논문집
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• 제15권1호
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• pp.25-31
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• 2003

본 연구는 데크플레이트의 모멘트 강도에 관한 실험적, 이론적 연구를 수행하였다. 실물크기의 14개 모멘트 실험을 행하였으며, 가력부의 국부좌굴을 방지하기 위해 1/4지점 집중하중을 가력하였다. 기준식들 간의 차이점을 이론적으로 비교분석하였다. 또한 미국 AISI, 유럽 EC3, 한국 기준과 실험값을 비교 평가하였다. 파괴모드는 보 중앙부의 국부좌굴 및 중간가력부의 국부좌굴에 의하여 형성되어 최대내력에 도달하였다. 인장측이 먼저 항복하는 경우 소성능력이 인장측에서 발휘되어 내력이 증대하였다. 설험결과는 인장측 부분 소성화를 고려한 EC 기준과 가장 잘 일치하였다. EC3 부록Z에 의한 통계학적 평가로부터 EC3 기준식이 목표로 하는 $^{\circ}{_M}=1.1$ 이내로 그 적용성이 만족되었다. AISI와 KS 기준에서도 소성화 개념을 추가한다면, 이론해석이 보다 더 개선될 것이다.

• 대한두경부종양학회지
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• 제25권2호
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• pp.119-122
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• 2009

Objectives : Ablation of carcinoma of the tongue leads to deficits in speech and swallowing, but none to date has provided all of the qualities of mobility and sensation to simulate the complex function of the tongue. The authors evaluated postoperative swallowing and pronouncing function in patients who underwent tongue reconstruction using free flap. Material and Methods : This is a retrospective review documenting the outcome of 42 patients between January of 1991 and August of 2008. We classified patients according to the size of resection of the tongue like as 7 partial glossectomy, 25 hemiglossectomy, 2 subtotal glossectomy, and 8 total glossectomy. Swallowing function was graded into 4 point scale and pronouncing function was analyzed using picture consonant articulation test. Aspiration was evaluated with videofluoroscopic swallowing study. Results : The average points for swallowing function were 3.43 in partial glossectomy, 3.52 in hemiglossectomy, 3 in subtotal glossectomy, and 2.63 in total glossectomy. The percentage of consonants correct showed 76.5% in partial glossectomy, 72.29% in hemiglossectomy, 47.69% in subtotal glossectomy, and 29.94% in total glossectomy. Aspiration was noted in 3 patients(1 hemiglossectomy and 2 total glossectomy) and 2 total glossectomy patients were taken permanent feeding gastrostomy. Conclusion : Free flap gave us proper volume in tongue reconstruction and showed good result in preserving swallowing function. Swallowing function difference according to the size of defect showed no statistical significance, whereas articulation function was shown to decrease in accuracy as the size of defect was larger.

• Archives of Plastic Surgery
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• 제46권1호
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• pp.88-91
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• 2019

The burn center in our hospital is a national and regional (Southeast Asia) center. Of all admissions, 10% are related to blast explosions, and 8% due to chemical burns. In the acute burn management protocol of Singapore General Hospital, early surgical debridement is advocated for all acute partial-thickness burns. The aim of early surgical debridement is to remove all debris and unhealthy tissue, preventing wound infection and thereby expediting wound healing. In chemical burns, there can be stubborn eschars that are resistant to traditional debridement. We would like to present a novel technique using the diathermy scratch pad as a cheap and efficient tool for the dual purpose of surgical debridement and dermabrasion.

• Archives of Plastic Surgery
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• 제35권3호
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• pp.295-302
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• 2008

Purpose: The lower leg often has poor vascularity, proximity to bone, and insufficient soft tissue. The island flaps offer a feasible one stage reconstruction and has a remarkable vascularization and high quality results for soft tissue defect with or without bony problems to occur on regions below the knee. So we reported our experience of island flaps with review of the literatures. Methods: We reconstructed 29 cases of soft tissue and 2 cases of bony defect on regions below the knee by using various island flaps at our hospital from December, 1991 to January, 2006. We used 2 fibular osteocutaneous island flaps, 15 reverse sural island flaps, 6 extensor digitorum brevis muscular island flaps, 2 medial plantar island flaps, 5 saphenous island flaps, and a dorsalis pedis island flap. Results: Partial necrosis was developed in 4 out of 15 reverse sural island flaps and 1 out of 5 saphenous island flaps, but they were healed with secondary skin graft. There was partial loss of skin graft on the donor sites in 2 cases. Conclusion: Island flaps are very useful for reconstruction of regions below the knee because island flaps have good vascularity and less risk of infection. Generous flap size, easy operative technique, lower cost, shorter operative time, and minimal morbidity at the donor site are other advantages. We attained satisfactory results.

• Archives of Plastic Surgery
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• 제41권6호
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• pp.668-672
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• 2014

Background Negative-pressure wound therapy (NPWT) is believed to accelerate wound healing by altering wound microvascular blood flow. Although many studies using laser Doppler have found that NPWT increases perfusion, recent work using other modalities has demonstrated that perfusion is reduced. The purpose of this study was to investigate the influence of NPWT on tissue oxygenation of the foot, which is the most sensitive region of the body to ischemia. Methods Transcutaneous partial pressure of oxygen ($TcpO_2$) was used to determine perfusion beneath NPWT dressings of 10 healthy feet. The sensor was placed on the tarso-metatarsal area of the foot and the NPWT dressing was placed above the sensor. $TcpO_2$ was measured until it reached a steady plateau state. The readings obtained at the suction-on period were compared with the initial baseline (pre-suction) readings. Results $TcpO_2$ decreased significantly immediately after applying NPWT, but gradually increased over time until reaching a steady plateau state. The decrease in $TcpO_2$ from baseline to the steady state was 2.9 to 13.9 mm Hg (mean, $9.3{\pm}3.6$ mm Hg; $13.5{\pm}5.8%$; P<0.01). All feet reached a plateau within 20 to 65 minutes after suction was applied. Conclusions NPWT significantly decrease tissue oxygenation of the foot by 2.9 to 13.9 mm Hg. NPWT should be used with caution on feet that do not have adequate tissue oxygenation for wound healing.

• Archives of Plastic Surgery
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• 제43권5호
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• pp.438-445
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• 2016

Background The goal of reconstruction is to provide coverage of exposed vital structures with well-vascularized tissue for optimal restoration of form and function. Here, we present our clinical experience with the use of the scapular fascial free flap to correct facial asymmetry and to reconstruct soft tissue defects of the extremities. Methods We used a scapular fascial free flap in 12 cases for soft tissue coverage of the extremities or facial soft tissue augmentation. Results The flaps ranged in size from $3{\times}12$ to $13{\times}23$ cm. No cases of total loss of the flap occurred. Partial loss of the flap occurred in 1 patient, who was treated with a turnover flap using the adjacent scapular fascial flap and a skin graft. Partial loss of the skin graft occurred in 4 patients due to infection or hematoma beneath the graft, and these patients underwent another skin graft. Four cases of seroma at the donor site occurred, and these cases were treated with conservative management or capsulectomy and quilting sutures. Conclusions The scapular fascial free flap has many advantages, including a durable surface for restoration of form and contours, a large size with a constant pedicle, adequate surface for tendon gliding, and minimal donor-site scarring. We conclude that despite the occurrence of a small number of complications, the scapular fascial free flap should be considered to be a viable option for soft tissue coverage of the extremities and facial soft tissue augmentation.

• Archives of Plastic Surgery
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• 제42권3호
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• pp.334-340
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• 2015

Background Full-thickness skin grafts (FTSGs) are generally considered unreliable for coverage of full-thickness finger defects with bone or tendon exposure, and there are few clinical reports of its use in this context. However, animal studies have shown that an FTSG can survive over an avascular area ranging up to 12 mm in diameter. In our experience, the width of the exposed bones or tendons in full-thickness finger defects is <7 mm. Therefore, we covered the bone- or tendon-exposed defects of 16 fingers of 10 patients with FTSGs. Methods The surgical objectives were healthy granulation tissue formation in the wound bed, marginal de-epithelization of the normal skin surrounding the defect, preservation of the subdermal plexus of the central graft, and partial excision of the dermis along the graft margin. The donor site was the mastoid for small defects and the groin for large defects. Results Most of the grafts (15 of 16 fingers) survived without significant surgical complications and achieved satisfactory functional and aesthetic results. Minor complications included partial graft loss in one patient, a minimal extension deformity in two patients, a depression deformity in one patient, and mild hyperpigmentation in four patients. Conclusions We observed excellent graft survival with this method with no additional surgical injury of the normal finger, satisfactory functional and aesthetic outcomes, and no need for secondary debulking procedures. Potential disadvantages include an insufficient volume of soft tissue and graft hyperpigmentation. Therefore, FTSGs may be an option for treatment of full-thickness finger defects with bone or tendon exposure.

• Archives of Plastic Surgery
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• 제40권5호
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• pp.575-583
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• 2013

Background The aim of lower-extremity reconstruction has focused on wound coverage and functional recovery. However, there are limitations in the use of a local flap in cases of extensive defects of the lower-extremities. Therefore, free flap is a useful option in lower-extremity reconstruction. Methods We performed a retrospective review of 49 patients (52 cases) who underwent lower-extremity reconstruction at our institution during a 10-year period. In these patients, we evaluated causes and sites of defects, types of flaps, recipient vessels, types of anastomosis, survival rate, and complications. Results There were 42 men and 10 women with a mean age of 32.7 years (range, 3-72 years). The sites of defects included the dorsum of the foot (19), pretibial area (17), ankle (7), heel (5) and other sites (4). The types of free flap included latissimus dorsi muscle flap (10), scapular fascial flap (6), anterolateral thigh flap (6), and other flaps (30). There were four cases of vascular complications, out of which two flaps survived after intervention. The overall survival of the flaps was 96.2% (50/52). There were 19 cases of other complications at recipient sites such as partial graft loss (8), partial flap necrosis (6) and infection (5). However, these complications were not notable and were resolved with skin grafts. Conclusions The free flap is an effective method of lower-extremity reconstruction. Good outcomes can be achieved with complete debridement and the selection of appropriate recipient vessels and flaps according to the recipient site.

• Archives of Plastic Surgery
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• 제47권1호
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• pp.54-61
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• 2020

Background Conventional methods of external bleeding for congested fingertip replants exhibit notable problems, including uncontrollable bleeding and unpredictable survival of the replant. We have added a local injection of heparin calcium to the routine use of systemic heparinization for inducing external bleeding. We retrospectively examined patients who underwent external bleeding using our method. Methods Local subcutaneous injections of heparin calcium were made in 15 congested replants in addition to systemic heparinization. Each injection ranged from 500 to 5,000 U. The average duration of the injections was 4.1 days. Surgical outcomes were analyzed and compared with a control group of patients who underwent external bleeding without heparin calcium. Results The overall survival rate was 93.3%, which was higher than that of the control group (83.3%), but the difference was not statistically significant (P=0.569). The survival rate for subzones I and II by the Ishikawa subzone classification was 100%, whereas it was 87.5% in subzones III and IV. No statistically significant difference was observed. The rate of partial necrosis was 0% in subzones I and II, whereas it was significantly higher (66.7%) in subzones III and IV (P=0.015). The mean total blood loss via external bleeding was 588 g in 10 fingers. No patients required blood transfusion. Conclusions Congestion of a replanted fingertip can be successfully managed without blood transfusion by our method. Although complete relief from congestion in replants in subzones I and II is achievable, there is a higher risk of partial necrosis in subzones III and IV.