• Wind and Structures
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• v.30 no.2
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• pp.211-217
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• 2020

Vibrations of a wind turbine blade have a negative impact on its performance and result in failure of the blade, therefore an approach to effectively control vibration in turbine blades are sought by wind industry. The small domestic horizontal axis wind turbine blades induce flap wise (out-of-plane) vibration, due to varying wind speeds. These flap wise vibrations are transferred to the structure, which even causes catastrophic failure of the system. Shape memory alloys which possess physical property of variable stiffness across different phases are embedded into the composite blades for active vibration control. Previously Shape memory alloys have been used as actuators to change their angles and orientations in fighter jet blades but not used for active vibration control for wind turbine blades. In this work a GFRP blade embedded with Shape Memory Alloy (SMA) and tested for its vibrational and material damping characteristics, under martensitic and austenite conditions. The embedment portrays 47% reduction in displacement of blade, with respect to the conventional blade. An analytical model for the actuated smart blade is also proposed, which validates the harmonic response of the smart blade.

• Archives of Plastic Surgery
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• v.39 no.6
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• pp.649-654
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• 2012

Background Deep burns of the elbow lead to soft tissue necrosis and infection, with exposure of deep structures. Adequate wound coverage of this area requires thin, pliable, and durable tissue, while optimal functional recovery requires early coverage and functional rehabilitation. We have found 3 types of island flaps that provide reliable coverage for the elbow. Methods A retrospective study was performed on all patients who underwent flap coverage of an elbow defect at our hospital. The patients' data including age, sex, cause of injury, wound dimensions, timing of flap coverage, postoperative elbow motion, and complications were investigated. Results Between 2001 and 2012, 16 patients were treated at our hospital. The mean age was 53.3 years. Three kinds of flaps were performed: 9 latissimus dorsi flaps, 4 lateral arm flaps, and 4 radial forearm flaps. The average defect size was 183.5 $cm^2$ (range, 28 to 670 cm2). Wound coverage was performed at mean duration of 45.9 days (range, 14 to 91 days). The mean postoperative active elbow flexion was $98^{\circ}$ (range, $85^{\circ}$ to $115^{\circ}$). Partial flap failure occurred in 1 latissimus dorsi flap. Minor complications included partial flap loss (11.8%), hematoma (23.5%), seroma (35.3%), and wound infection (5.9%). Conclusions Flap selection for elbow reconstruction is determined by the defect size and the extent of the adjacent tissue injury. Elbow reconstruction using an island flap is a single-staged, reliable, and relatively simple procedure that permits initiation of early rehabilitation, thereby improving a patient's functional outcome.

• Archives of Plastic Surgery
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• v.37 no.6
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• pp.831-834
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• 2010

Purpose: Congenital absence of the vagina is a rare case. It occurs as a result of Mullerian duct aplasia or complete androgen insensitivity syndrome. The reconstructive modality includes skin graft, use of intestine and various methods of flap. We report a patient who underwent vulvoperineal fasciocutaneous flap to reconstruct congenital absence of the vagina, while the external genitalia and ovaries are normal. Methods: A 26-year-old woman presented with vaginal agenesis. Under general anesthesia, a U-shaped incision was made between the urethral meatus and the anus. The new vaginal pocket was created up to the level of the peritoneal reflection between the urinary structures and the rectum. Next, the vulvoperineal fasciocutaneous flaps were designed in a rectangular fashion. Flap elevation was begun at the lateral margin which the adductor longus fascia was incised and elevated, and the superficial perineal neurovascular pedicle was invested by the fascial layer. The medial border was then elevated. A subcutaneous tunnel was created beneath the inferior of the labia to rotate the flaps. The left vulvoperineal flap was rotated counterclockwise and the right was rotated clockwise. The neovaginal pouch was formed by approximating the medial and lateral borders. The tubed neovagina was then transposed into the cavity. Results: In 3 weeks, the vaginal canal remained supple After 6 weeks, the physical examination showed normalappearing labia majora and perineum with an adequate vaginal depth. A year after the operation, the patient had a 7 cm vagina of sufficient width with no evidence of contractures nor fibrous scar formation. The patient was sexually active without difficulty. Conclusion: Although many methods were described for reconstruction of vaginal absence, there is not a method yet to be approved as a perfect solution. We used the vulvoperineal fasciocutaneous flap to reconstruct a neovagina. This method had a following merits: a single-stage procedure, excellent flap reliability, the potential for normal function, minimal donor site morbidity and no need for subsequent dilatation, stents, or obturators. We thought that this operation has a good anatomic and functional results for reconstruction of the vagina.

• Current Industrial and Technological Trends in Aerospace
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• v.4 no.1
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• pp.34-43
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• 2006

헬기는 비행에 필요한 추력, 모멘트 및 조종력을 회전하는 로터시스템에서 발생시키기 때문에 근본적으로 진동이 많이 생기는 항공기이다. 로터시스템의 회전에 의해 발생되는 진동소스를 제어함으로써 헬기 동체에 전달되는 진동을 감소시키고자 하는 연구들이 지금까지 수많이 진행되었다. 이러한 연구들을 크게 두 가지로 분류하면, 수동적 진동제어 방법과 능동적 진동제어 방법으로 나눌 수 있다. 수동적 진동제어 방법은 그간 오랫동안 연구되어 현재 운용 헬기에 실제적으로 적용되고 있으나 능동적 진동제어 방법은 최근까지 활발한 연구가 진행되고 있는 상태이다. 본 논문의 서론에서는 헬기 진동제어를 위한 일반적인 방법에 대한 개요를 소개하였다. 본문은 로터시스템 진동제어 기술 중 최근까지 연구가 진행되고 있는 능동적 진동제어 방법을 중심으로 기술하였다. 특히 최근 비행시험에 성공하여 거의 실용화 단계에 이르고 있는 PZT를 이용한 Trailing Edge Flap 기술, Active Twist Rotor 등을 중점적으로 소개하였다. 마지막으로 유로콥터 BK117의 ADASYS 로터 시스템 성공사례 및 향후 해결해야 할 기술적 제한사항 등을 간략하게 기술하였다.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.115-121
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• 2007

The aeroelastic analysis of rotor blades with trailing edge flaps, focused on reducing vibration while minimizing control effort, are investigated using large deflection-type beam theory in forward flight. The rotor blade aerodynamic forces are calculated using two-dimensional quasi-steady strip theory. For the analysis of forward flight, the nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. The objective function, which includes vibratory hub loads and active flap control inputs, is minimized by an optimal control process. Numerical simulations are performed for the steady-state forward flight of various advance ratios. Also, numerical results of the steady blade and flap deflections, and the vibratory hub loads are presented for various advance ratios and are compared with the previously published analysis results obtained from modal analysis based on a moderate deflection-type beam theory.

• Journal of Korean Foot and Ankle Society
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• v.22 no.3
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• pp.127-130
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• 2018

A 3rd degree burn on the heel including the Achilles tendon is vulnerable and requires active treatment to improve the functional outcomes. Previously, there have been a few treatments on severe burns, such as amputation, debridement or simple skin graft. The cooperative technique of an anterior lateral thigh flap with Achilles tendon reconstruction can be an innovative procedure that preserves the major arteries. The authors review a case and report the clinical outcome.

• Archives of Reconstructive Microsurgery
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• v.14 no.1
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• pp.1-13
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• 2005

Purpose: The purpose of this study is to present extended indications for the use of arterialized venous flaps in reconstructing soft tissue, tendon, nerve, blood vessel, and composite tissue defects of the hand of various sizes based on researches and clinical experiences of the authors. Moreover, procedures to achieve complete flap survival and postoperative results are presented. Materials & methods: This study is based on 154 cases of arterialized venous flaps performed to reconstruct the hand during the past 11 years. The most common cause of injury was industrial accidents with 125 cases. One hundred thirty patients or 84% of the cases had emergency operation within 2 weeks of the injury. The flaps were categorized depending on the size of the flap. Flaps smaller than $10\;cm^2$ were classified as small (n=48), those larger than $25\;cm^2$ classified large (n=42) and those in between medium (n=64). Classified according to composition, there were 88 cases (57.1 %) of venous skin flaps, 28 cases of innervated venous flaps, 15 cases of tendocutaneous venous flaps, which incorporated the palmaris longus tendon, for repair of extensor tendons of the fingers, and 17 cases of conduit venous flaps to repair arterial defect. There were 37 cases where multiple injuries to multiple digits were reconstructed. Moreover, there were 6 cases of composite tissue effects that involved soft tissue, blood vessels and tendons. The donor sites were ipsilateral forearm, wrist and thenar area, foot dorsum, and medial calf. The recipient sites were single digit, multiple digits, first web space, dorsum and palm of hand, and wrist. Results: There were seven cases (4.5%) of emergent re-exploration due to vascular crisis, and 3 cases of flap failure characterized by more than 50% necrosis of the flap. The survival rate was 98.1 % (151/154). In small flaps, an average of 1.01 afferent arteries and 1.05 efferent veins were microanastomosed, and in large flaps, an average of 1.88 afferent arteries and 2.19 efferent veins were anastomosed. In 8 cases where innervated flaps were used for reconstructing the palm of the hand, the average static two-point discrimination was $10\;(8{\sim}15)\;mm$. In 12 cases where tenocutaneous flaps were used, active range of motion at the proximal interphalangeal joint was 60 degrees, 20 degrees at the distal interphalangeal joint, and 75 degrees at the metacarpophalangeal joint. Conclusion: We conclude that the arterialized venous flap is a valuable and effective tool in the reconstruction of hand injuries, and could have a more comprehensive set of indications.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.17 no.2
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• pp.109-129
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• 1995

Many patients with malignancies of the head and neck undergo radiation therapy, either as the only method of treatment or in combination with surgery. Radiation therapy has great effect in the case of fairly advanced malignancies which can't be operated radically. But the complication of radiation therapy arise because of damage to the peri- and operated area. It is fully known that irradiated tissue shows retarded healing process in the skin, mucosa and especially vascuslar tissue. The purpose of this study was to observe the healing process of irradiated free or island flap after operation. As Experimental Models, Femoral arterial and venous anastomosis (Group 1), Epigastric-island flap (Group 2) and free Epigastric falp(Group 3) with irradiated postoperative 24 hrs were made on 30 rats/group. As Control Model(Group 4), Free Epigastric flap was not irradiated after operation was chosen on 30 rats. The amount of irradiation was single fraction of 20 Gy using as linear megavoltage accelerator. Difference between Experimental and Control group was evaluated by the method of clinical examination, histopatholoical findings, biochemical analysis and DNA activity at postoperative 1, 3, 7, 14 and 28 days. The results were as follows, 1. Skin color and new epithelization in group 2 and 3 was similar to control group clinically. 2. Postoperarive patency of femoral artery and vien showed 5% and 22% of ischemity. 3. The externa, media and intima of irradiated femoral artery and vein were similar to control group histopathlogically. 4. Granulation and collagen tissue accumulation of irradiated groups were more active due to degenerative and fibrotic changes than control group at postoperative 7 days histopathologically. 5. The hydroxyproline content of all experimental groups were reduced till 14 days and the group 2 was most prominent at postoperative 7 and 28 days(p<0.05). 6. DNA activities of all groups were reduced till 3 days, but begun to recover at 7 days and more activities in control group than irradiated group(p<0.05). Based on the above results, the clinical healing process of free flaps with irradiated postoperative 24 hrs little difference from control group without complications.

• Current Industrial and Technological Trends in Aerospace
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• v.9 no.1
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• pp.77-89
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• 2011

The vibration and noise reduction issue is very important in helicopter since the thrust and flight control force of helicopter are generated by rotating drive system. In past, there was a passive method to reduce vibration and noise to focus on specified frequency. Now, there are various active method to reduce vibration and noise due to technology development. This paper describes the worldwide technology trend of vibration and noise active control in helicopter. At introduction, generalmethod of vibration and noise reduction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.649-660
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• 2021

Through analytical method based on S-76 model, the level of rotor hub vibration reduction was analyzed according to higher harmonic actuating by individual blade control. The higher harmonic actuating method for individual blades was divided into a method of generating an additional actuating force from the pitch-link in the rotating part and generating actuating force through the active trailing edge flap control of the blade. In the 100kts forward flight conditions, the hub load analysis was performed by changing the phase angle of 15 degree for the 2P/3P/4P/5P harmonic actuation for individual blades. Through the harmonic actuation results, the sensitivity of the rotor system according to the actuating conditions was analyzed, and the T-matrix representing the characteristics of the rotor system was derived based on this analysis result. And through this T-matrix, optimal higher harmonic actuating condition was derived to minimize hub vibration level for flight condition. In addition, the effect on the performance of the rotor system and the pitch-link load under minimum hub vibration condition, as well as the noise influence through the noise analysis were confirmed.