• 대한족부족관절학회지
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• 제9권2호
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• pp.151-157
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• 2005

Purpose: To present our experience of distal chevron osteotomy utilizing one BOLD $screw^{(R)}$ as an alternative fixation method which has advantages over the Kirschner (K)-wire fixation. Materials and Methods: Between January 2001 and June 2003, 19 patients with a symptomatic hallux valgus deformity underwent 20 distal metatarsal chevron osteotomies with one BOLD $screw^{(R)}$ fixation. The mean age was 55.6 years with a minimum follow up period 12 months. For radiographical evaluation, hallux valgus angle (HVA) and intermetatarsal angle (IMA) were used. For clinical evaluation, we used AOFAS hallux metatarsophalangeal interphalangeal scale and overall satisfaction of the patients. Results: The AOFAS scores improved from mean 47.5 points to mean 68.1 points at postoperative 3 months and mean 86.0 points at last follow-up. The average HVA corrected from 25.3 degrees to 12.7 degrees. The IMA was corrected from 11.6 degrees to 7.6 degrees. The overall satisfaction of the patients was 85%. There was no major complication. Conclusion: We demonstrated that distal chevron osteotomy with one BOLD $screw^{(R)}$ fixation has advantages such as no additional procedure, no loss of correction, early rehabilitation, no prominent hardware and skin irritation. This method also showed excellent bone union, correction and patient satisfaction.

• 대한족부족관절학회지
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• 제13권2호
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• pp.124-128
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• 2009

Purpose: The authors intended to analyze the operative results of mild to moderate hallux valgus treated with distal chevron metatarsal osteotomy. Materials and Methods: Twenty six feet of twenty three patients were followed for more than 1 year after the distal chevron metatarsal osteotomy. Biplanar osteotomy with wedge resection was done when the distal metatarsal articular angle (DMAA) was increased. The mean age was 39 years, and the mean follow up period was 27 months. Clinically preoperative and postoperative AOFAS hallux MP-IP scale and satisfaction after the surgery were analyzed. Radiologically hallux valgus angle, the 1st intermetatarsal angle, DMAA and sesamoid position before and after the operation were analyzed. Results: Distal chevron osteotomy was done in 15 cases and biplanar osteotomy was done in 11 cases. Clinically AOFAS scale was increased from 65.3 points preoperatively to 92.2 points postoperatively. Two patients were not satisfied with the results. Radiologically hallux valgus angle was decreased from $21.9^{\circ}$ preoperatively to $8.5^{\circ}$ postoperatively. The first intermetatarsal angle was decreased from $11.8^{\circ}$ preoperatively to $6.7^{\circ}$ postoperatively. DMAA was decreased from $11.8^{\circ}$ preoperatively to $5.5^{\circ}$ postoperatively. There was one case of minor wound infection. Conclusion: Distal chevron metatarsal osteotomy appears to be safe and satisfactory procedure for mild to moderate hallux valgus.

• 대한족부족관절학회지
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• 제1권2호
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• pp.95-101
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• 1997

Hallux valgus has been characterized by a valgus deformity of the great toe at the metatarsophalangeal joint, along with medial deviation of the first metatarsal, and by three components. First, there is a valgus angle more than $20^{\circ}$ at the first, metatarsophalangeal joint. Second, there is a greater angle than $9^{\circ}$ between the first. and second metatarsals. Third, there is bursal hypertrophy at the medial eminence of the first metatarsals head. The etiology is multifactorial and many procedures have been reported in the treatment of hallux valgus. Most of the procedures are directed towards pain relief, correction of deformity, and preservation of dorsiflexion in the first metatarsophalangeal joint. One such treatment is the Modified chevron osteotomy. It is technically simple, and provides greater stability than a standard osteotomy, and allows early ambulation after surgery. We a reviewed 19 cases with 13 patients of hallux valgus deformity. They were all treated with the Modified chevron osteotomy at the Department of Orthopedic Surgery, Choong ang Gil Hospital, between June 1988 and May 1994. The results of the study were as follows; 1. The mean age was 36 years. Three patients(5 case) were male and ten patients(14 cases) were female. 2. The mean value of the hallux valgus angle was $34.1^{\circ}$, and the first to second intermetatarsal angle was $12.1^{\circ}$, preoperatively. These angles were corrected to $15.8^{\circ}$ and $8.5^{\circ}$, respectively. 3. The metatarsalgia subsided in 17 cases (89.5%). avascular necrosis, non union, and dorsal angulation complicatious were nonexistant. Early bone healing occurred in all cases. 4. The Modified chevron osteotomy is technically simple. It provides excellent pain relief, early ambulation, increased mechanical stability, and many avoids many complications such as AVN, non-union, and dorsal angulation.

• 대한족부족관절학회지
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• 제8권2호
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• pp.126-130
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• 2004

Purpose: In this study, we tried to develop the technique of osteotomy for hallux valgus. The new modified technique of osteotomy was accomplished with even more greater stability, accurate correction of the deformity and more effective than 'chevron' osteotomy in terms of correction of the deformity. Materials and Methods: Between March 1998 and December 2001, 55 cases of new modified osteotomy for hallux valgus were performed for 39 patients, 16 of whom underwent operation of both feet. Operations were made for 34 women and 5 men whose average age was 46 years old (range, $20{\sim}71$ years). Average follow up period was three years (range, $2{\sim}5$ years), and during the follow up, the patients underwent physical examination and assessment with use of the American Orthpaedic Foot and Ankle Society's hallux-metatarso-phalangealinterphalangeal scale and standard foot radiographic measurements. Results: 37 patients (53 cases) out of 39 patients (55 cases) had no pain, good cosmesis, and all of the patients were satisfied with the results of the operation. Two had occasional mild discomfort. The average score according to the hallux-metatarso-phallangeal-interphalangeal scale was 93.2 points (range, $78{\sim}100$ points). The average preoperative intermetatarsal angle was $14.4^{\circ}$, which was decreased to $7.9^{\circ}$ after the osteotomy with an average correction of $6.5^{\circ}$ and The average preoperative hallux valgus angle was $34.1^{\circ}$, which was decreased to $11.1^{\circ}$ after the osteotomy with an average correction of $23^{\circ}$. This new modified technique would prevent the angulation or shortening at the osteotomy site and it was also even more stable at osteotomy site, and could do even more effective and accurate correction of the deformity than conventional Chevron osteotomy. Conclusion: New modified chevron osteotomy for the treatment of symptomatic hallux valgus was done in 55 cases, and the results were satisfactory in all cases. This method was more stable at the osteotomy site than conventional Chevron osteotomy and was also possible to do more accurate and more effective correction of the deformity. It was also easy to control the distal fragment of first metatarsal bone.

• 한국정밀공학회지
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• 제21권2호
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• pp.203-209
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• 2004

Compliant bi-stable mechanism allows two stable states within its operation range staying at one of the local minimum states of the potential energy. Energy storage characteristics of the bi-stable mechanism offer two distinct and repeatable stable states, which require no power input to maintain it at each stable state. This paper suggests an equivalent model of the chevron-type bi-stable microactuator using the equivalent spring stiffness in the rectilinear and the rotational directions. From this model the range of spring stiffness where the bi-stable mechanism can be operated is analyzed and compared with the results of the FEA (Finite Element Analysis) using ANSYS for the buckling analysis, both of which show a good agreement. Based on the analysis, a newly designed chevron-type bi-stable MEMS actuator using hinges is suggested for the latch-up operation. It is found that the experimental response characteristics of around 36V for the bi-stable actuation for the 60$mu extrm{m}$ stroke correspond very well to the results of the equivalent model analysis after the change in cross-sectional area by the fabrication process is taken into account. Together with the resonance frequency experiment where 1760Hz is measured, it is shown that the chevron-type bi-stable MEMS actuator using hinges is applicable to the optical switch as an actuator.

• 한국수소및신에너지학회논문집
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• 제15권3호
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• pp.194-200
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• 2004

Thermal energy performance of a brazed plate heat exchanger has been evaluated experimentally. The effects of plate pitch as well as chevron angle of a plate heat exchanger on the heat transfer rate and pressure drop have been investigated in the wide range as mass flow rates in detail. This problem is of particular interest in the design of a plate heat exchanger. The results obtained indicate that both heat transfer rate and pressure drop are increased as mass flow rate is increased, as expected. It is also found that the heat transfer rate is increased with a decrease in the plate pitch while the heat transfer is decreased with a decrease in the chevron angle. Friction factor correlations are suggested based on the measured pressure drop and effectiveness of plate heat exchangers are also compared.

• 대한족부족관절학회지
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• 제14권1호
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• pp.31-35
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• 2010

Purpose: Painful plantar callosities under the second, third or fourth metatarsal head have been controverted about its treatment mordalities. We performed the vertical chevron osteotomy in patients with painful callosities on the second and third metatarsal head, and evaluated the outcome clinically. Materials and Methods: Fourteen cases from 10 patients who had plantar keratosis were operated by vertical chevron osteotomy from March 2005 to October 2008. We used K-wire fixation for all cases. We evaluated the clinical results by the patients' satisfaction and disappearance of plantar lesion. Results: The plantar keratosis was completely disappeared in 8 cases and partially in 5 cases. In 2 cases, patients expresses their pain caused by constant metatarsalgia that was suspected to be dorsal incisional pain and joint capsulitis. Transmetatarsalgia was not appeared. Conclusion: We consider vertical chevron osteotomy as a good surgical method for treatment of plantar keratosis.

• 소성∙가공
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• 제26권4호
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• pp.210-215
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• 2017

In this paper, utilizing the theory of ductile fracture a chevron crack in a 4-stage open cold extrusion process is predicted by the finite element methods and then compared with previous experiments. The normalized Cockcroft-Latham damage model is employed and the material is identified using a tensile test based material identification technique that gives fracture information as well as flow stress at large strain. A large difference between the predicted cracks and actual experiments is observed, specifically narrower width and greater maximum height of the crack. This reveals the limitation of this approach based on the conventional theory of ductile fracture. Based on the observations and the related criticisms, a new approach for predicting the chevron crack is proposed, suggesting that either the critical damage should not be a fixed material constant, or that the conventional fracture theory should be considered with the effects of embrittlement due to accumulated plastic deformation while the duration of crack generation and plastic deformation should be reduced.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.347-352
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• 2005

The objectives of this paper are to study the characteristics of heat transfer and pressure drop in plate heat exchangers for absorption applications, and to quantify the effect of mass flow rate, solution concentration, and geometric conditions such as chevron angle on the heat transfer coefficient and pressure drop in the plate heat exchangers. The working fluid is $H_2O$/LiBr solution with the LiBr concentration range of 53.2 - 62.5 % in mass. The results show that the overall heat transfer coefficient increases linearly with increasing Re. The heat transfer rate increases with increasing the chevron angle while it does not significantly depend on the LiBr concentration. The pressure drop also increases with increasing the chevron angle. The effect of the chevron angle on the pressure drop is more significant than that of the concentration.

• 대한족부족관절학회지
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• 제9권2호
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• pp.158-161
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• 2005

Purpose: To analyze the risk factors and the treatment results of the distal chevron osteotomy for the hallux valgus in young adult. Materials and Methods: Eleven cases of hallux valgus in 9 patients who underwent the distal chevron osteotomy between February 2000 and January 2004 were included for the study. For the clinical evaluation, we used hallux-metatarsophalangeal interphalangeal scale of American Orthopaedic Foot and Ankle Society (AOFAS). For radiological evaluation, we measured hallux valgus angle (HVA) and intermetatarsal angle (IMA). Results: Five patients had family history of hallux valgus. Symptoms were aggravated by military drill and sports activity. The average AOFAS scale was 62.5 preoperatively, and 88.4 at final follow-up. The HVA and IMA were $34.9^{\circ}$, and $15.8^{\circ}$ preoperatively, $16.3^{\circ}$ and $8.2^{\circ}$ at postoperative 6 weeks, and $19.9^{\circ}$ and $9.8^{\circ}$ at final follow-up. Conclusion: The symptoms of hallux valgus in young adults were aggravated by military drill and sports activity. Distal chevron osteotomy was useful for the treatment of the moderate to severe hallux valgus in young patients.