• Journal of Mechanical Science and Technology
• /
• 제20권8호
• /
• pp.1118-1124
• /
• 2006

Recently, cavitation on the surface of mechanical heart valve has been studied as a cause of fractures occurring in implanted Mechanical Heart Valves (MHVs). It has been conceived that the MHVs mounted in an artificial heart close much faster than in vivo sue, resulting in cavitation bubbles formation. In this study, six different kinds of mono leaflet and bileaflet valves were mounted in the mitral position in an Electro-Hydraulic Total Artificial Heart (EHTAH), and we investigated the mechanisms for MHV cavitation. The valve closing velocity and a high speed video camera were employed to investigate the mechanism for MHV cavitation. The closing velocity of the bileaflet valves was slower than that of the mono leaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop areas is better able to prevent blood cell damage than the monoleaflet valves.

• 한국기계가공학회지
• /
• 제20권7호
• /
• pp.66-71
• /
• 2021

In this study, the shape design optimization of a refrigerator door hinge stopper was performed to reduce the discrepancy in the opening forces of the left and right doors of a double-door refrigerator. A finite element model was constructed and analyzed by quasi-static analyses to evaluate the structural performance of the door hinge stopper. The reaction moment calculated at the hinge axis was used as a measure of the door opening and closing forces. The design objective is to increase the door opening force by 50% while maintaining the door closing force and the maximum stress calculated in the body of the hinge stopper at the current level. A new design concept with a contacting slot was proposed to decouple the door closing and opening forces. Shape optimization was performed to determine the dimensions of the new design of the hinge stopper, and the rib pattern was determined by topological optimization to further increase the door opening force. It was observed that the new design met all design requirements.

• 한국정보과학회:학술대회논문집
• /
• 한국정보과학회 2001년도 봄 학술발표논문집 Vol.28 No.1 (A)
• /
• pp.355-357
• /
• 2001

HTTP/1.1 standard reduces latencies and overhead from closing and re-establishing connections by supporting persistent connections as a default, which encourage multiple transfers of objects over one connection. HTTP/1.1, however, does not define explicitly connection-closing time but specifies a certain fixed holding time model. This model may induce wasting server’s resource when server maintains connection with the idle-state client that requests no data for a certain time. This paper proposes the mechanism of a heuristic connection management supported by the client-side under persistent HTTP, in addition to HTTP/1.1’s fixed holding time model on server-side. The client exploits the tag information within transferred HTML page so that decides connection-closing time. As a result, the mechanism allows server to use server’s resource more efficiently without server’s efforts.

• Korean Journal of Acupuncture
• /
• 제39권2호
• /
• pp.23-33
• /
• 2022

Objectives : The purpose of this study is to establish a Korean medical perspective on the human body through understanding of the meridians according to the distribution of the three yin and three yang (삼음삼양) and the opening, closing and pivot (관합추) as defined in ≪Huangdi's Internal Classic≫. Methods : A total of 8 medical databases including KISS, Earticle, DBpia, RISS, OASIS, KMbase, and ScienceON were used to search studies published through July 2021, and literature was included without limitations on the publication period. The search terms were "(meridian OR acupoint OR meridian sinew) AND position" OR "Gwan-Hap-Chu" OR "Gae-Hap-Chu" OR "three yin and three yang". Two researchers independently made choices among the searched literature based on the preplanned selection/exclusion criteria. The search terms were"(meridian OR acupoint OR meridian sinew) AND position" OR "Gwan-Hap-Chu" OR "Gae-Hap-Chu" OR "three yin and three yang". Results : Of the 36 obtained from the survey, 19 (53%) followed the definitions of "internal diameter" for "three yin and three yang" and "the opening, closing and pivot," but 6 (about 16%) took a neutral position and 10 (22%) avoided mentioning. Therefore, it was judged that research was needed to end the debate on the distribution of 'three yin and three yang' and 'the opening, closing and pivot'. In order to apply the definition of ≪Huangdi's Internal Classic≫ on 'distribution of the three-yin and three-yang' and 'the opening, closing and pivot' to the upper limb and lower limb as well as the torso of the human body, this author proposed a human body model with both upper limb and lower limb attached, inspired by the posture of the fetus in the developmental stage. Conclusions : In this study, using a new human body model, it was revealed that the distribution of the three yin and three yang and the opening, closing and pivot' as defined in the ≪Huangdi's Internal Classic≫ can be applied not only to the torso of the human body, but also to the upper limb and lower limb. Based on the understanding of meridians, the selection of meridians in the clinical acupuncture should be made accurately, and continuous interest and research on this are expected.

• 대한족부족관절학회지
• /
• 제12권2호
• /
• pp.140-144
• /
• 2008

Purpose: The purpose of this study is to compare the treatment outcomes of distal chevron osteotomy with those of proximal metatarsal closing wedge osteotomy in patients with moderate severity hallux valgus. Materials and Methods: Forty-two patients (51 feet) who were underwent either distal chevron osteotomy (Group I, 22 patients, 27 feet) or proximal metatarsal closing wedge osteotomy (Group II, 20 patients, 24 feet) for the correction of moderate hallux valgus deformity were evaluated retrospectively. We assessed the radiographic results with several parameters including hallux valgus angle (HVA), intermetatarsal angle (IMA) and distal metatarsal articular angle (DMAA). And clinical results with modified AOFAS score at last follow-up. Results: There were no significant differences in IMA, HVA and DMAA between two groups preoperatively. We can achieve the good results with both procedures, but mean HVA and IMA of group II was significantly lower than those of group I. There was some loss of correction in group I at the last follow-up. There was no significant difference in clinical results according to modified AOFAS scoring between two groups at the last follow-up. Conclusion: The proximal metatarsal closing wedge osteotomy for the hallux valgus with moderate severity is better treatment option to achieve better radiographic correction and to prevent loss of correction or recurrence than distal chevron osteotomy.

• 대한소아치과학회지
• /
• 제42권3호
• /
• pp.233-241
• /
• 2015

본 연구는 학령 전 어린이의 정상적인 교합력과 구순 폐쇄력을 알아보기 위한 목적으로 수행되었다. 3-6세의 어린이 98명을 대상으로 하였고, 60명의 성인을 대조군으로 교합력과 구순 폐쇄력을 측정하였다. 좌우측 평균 교합력은 남아에서 217.69 N, 여아에서 205.05 N이었고, 평균 구순 폐쇄력은 남아에서 4.81 N, 여아에서 4.07 N이었다. 어린이는 연령이 증가함에 따라 교합력, 구순 폐쇄력 모두 증가하는 경향을 보였고, 성별에 따른 유의한 차이는 없었다. 성인에서는 교합력과 구순 폐쇄력 모두 남성이 여성보다 유의하게 큰 값을 보였다. 교합력과 구순 폐쇄력은 연령, 신장, 체중 모두에 대해 통계학적으로 유의한 양의 상관관계를 보였다. 그리고 어린이의 교합력과 구순 폐쇄력은 유의한 양의 상관관계를 나타내었다. 이상의 연구 결과 얻어진 정상적인 교합력 및 구순 폐쇄력은, 비정상적으로 낮은 값을 보이는 어린이를 감별하여 훈련을 통해 정상적인 성장을 유도하는데 사용될 수 있을 것이다.

• Bulletin of the Korean Chemical Society
• /
• 제11권5호
• /
• pp.399-402
• /
• 1990

Activation parameters of the exchange between two types of glycinate groups in (nitrilotriacetato)dioxovanadate(V) ion, $[VO_2(NTA)]^{2-}$, have been determined as the results of $^{13}C$ NMR measurements over a range of temperatures between 277 and 306$^{\circ}K$. The exchange mechanism is proposed on the basis of the chelate ring opening-closing process, assuming rupture of the metal-oxygen (glycinate) bond trans to V = O bond to give a five-coordinated intermediate.

• 대한족부족관절학회지
• /
• 제8권2호
• /
• pp.142-148
• /
• 2004

Purpose: We compared the results of three surgical procedures of the old neglected Freiberg's disease that was managed with metatarsal head reshaping, metatarsal head resection, and dorsal closing wedge osteotomy. Materials and Methods: From march 1996 to July 2002, five cases in six patients whose metatarsal head collapse already progressed underwent operative treatment. We compared the operative results in the view point of the radiographic follow-up and lesser toe metatrasophalangeal joint scale of AOFAS. Results: There were no further joint destruction and loose body formation. Also, lesser toe metatrasophalangeal joint scale of AOFAS improved from average score, 38.5 (range $22{\sim}49$) of preoperative one to average score, 86.6 (range, $72{\sim}100$). Especially, the 2 cases that underwent dorsal closing wedge osteotomy showed most favorable result and the 2 cases with metatarsal resection showed next favorable result. The 2 cases with intra-articular loose body removal and metatarsal reshaping showed the least effective result among three operative methods. Conclusion: Our Operative experiences of old neglected Freiberg's disease were all satisfactory irrespective of operative options and dorsal closing wedge osteotomy was thought to be most effective method.

• 대한족부족관절학회지
• /
• 제12권1호
• /
• pp.14-19
• /
• 2008

Purpose: We tried to understand the effects of the derotational closing wedge Akin osteotomy during the operation for the hallux valgus with pronation of great toe. Materials and Methods: Eighty five patients who had undergone Akin osteotomy among the eighty seven patients who had been treated with Scarf osteotomy with hallux valgus were included in this study. Derotational supination was added on the medial closing wedge Akin osteotomy at the base of proximal phalanx and it was secured with K-wire, headless screw or staple. We measured and analyzed pre- and post-operative hallux primus valgus angle and hallux pronational rotatory angle. Results: The hallux primus valgus angle improved an average of $14{\pm}2.98$ degrees to $-1{\pm}1.68$ degrees with the hallux pronational rotatory angle respectively from $24.8{\pm}7.64$ degrees to $4.7{\pm}4.22$ degrees. Conclusions: After the metatarsal osteotomy for the treatment of the hallux valgus with the pronation of great toe, derotational closing wedge Akin osteotomy can give us a belief that it can correct the hallux primus valgus angle and hallux pronational rotatory angle also and it can be a helpful method for minimizing the recurrence rate of the hallux valgus deformity.

• 대한족부족관절학회지
• /
• 제15권4호
• /
• pp.217-222
• /
• 2011

Purpose: The aim of this study was to evaluate the result of combined Weil and dorsal closing wedge osteotomy for Freiberg's disease. Materials and Methods: We performed combined Weil and dorsal closing wedge osteotomy of the second metatarsal under the diagnosis of Freiberg's disease in 7 patients, 7 feet (2 male and 5 female). The mean age at the time of operation was 29 years and the mean follow-up period was 31 months. Patients had no trauma history and no combined deformity of the foot. The surgical results were evaluated by VAS and weight bearing radiographs in antero-posterior and oblique projection. Results: According to Smillie staging system, there were 1 of stage II, 2 of stage III and 4 of stage IV patients. The osteotomy site was united at 8 weeks and the second metatarsal was shortened in length of average 2.8 mm. Remodeling of the metatarsal head was observed at 24 months. The mean VAS was decreased from 8.2 points preoperatively to 2.7 points at follow-up. And average range of motion of second metatarso-phalangeal joint was increased from 30o preoperatively to 45o at follow-up. There was no transfer metatarsalgia or arthritis of the metatarsal head during follow-up. Conclusion: Combined Weil and dorsal closing wedge osteotomy of the metatarsal appears to be an effective procedure for the treatment of Freiberg's disease with a view to shortening of metatarsal length and elevation of metatarsal head.