Mg-5wt%Al-0.6wt%Zr 합금의 용탕단조시 주조결함의 형성 및 방지

황영하,허승호,홍준표 ( Young Ha Hwang,Seung Ho Huh,Chun Pyo Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A The squeeze casting of a Mg-5wt%Al-0.6wt%Zr alloy was carried out to investigate the conditions for the formation and the prevention of macrodefects, such as macrosegregation and shrinkage defects. The effects of the process parameters, the applied pressure, the die temperature, and the pouring temperature on the formation of macrodefcts were investigated in correlation with the evolution of macrostructure. Three types of macrodefects were found; macrosegregation only, shrinkage defects only, both macrosegregation and shrinkage defects. It was found that the pouring temperature, the die temperature, and the applied pressure are closely related to the formation of macrodefects. Sound castings without macrosegregation and shrinkage defects can be obtained under the conditions of 80 MPa < P < 110 MPa, 730˚C < Tp < 760˚C, and 180˚C < Tp < 250˚C. (Received April 15, 1998)

전자문서 표준 컨테이너(DDC)의 권한 관리 방안에 대한 연구

국상진 ( Sangjin Kook ),허승호 ( Seung Ho Huh ),장혜란 ( Hyeran Jang ),원준열 ( Jun Yol Won ),원동호 ( Dong-ho Won ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.2

전자문서보관소와 같이 대규모의 전자문서가 저장되는 시스템은 어떤 특정한 방법을 기준으로 해당 데이터를 저장한다. 이는 데이터의 저장, 검색, 송수신, 보안 요소 등 여러 가지 요구사항에서 기인하며, 이를 근거로 설계 되어야 한다. 본고에서는 현재 이슈가 되고 있는 전자문서보관소의 적합한 데이터 저장 방법에 대하여 알아보고 이를 안전하게 관리하기 위한 방법을 접근제어 측면에서 생각하여 보기로 한다.

DVCS를 이용한 전자서명 유효성 연장 방법에 관한 연구

국상진 ( Sangjin Kook ),허승호 ( Seung Ho Huh ),민철홍 ( Cheolhong Min ),원동호 ( Dong-ho Won ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.1

전자서명의 안전성은 사용된 전자서명 알고리즘과 키 길이가 가장 중요한 요소이다. 안전한 알고리즘의 선택은 물론이고, 적당한 키 길이를 선택하여만 안전한 전자서명을 활용 할 수 있게 된다. 일반적으로 알고리즘과 키 길이에 따라서 키 사용기간은 결정이 되며, 이로 인하여 특정 기간을 주기로 인증서를 다시 발급 받아야 하는 문제점이 존재한다. 또한 사용하지 않는 키로 검증을 수행 할 경우 전자서명 된 내용을 신뢰 할 수 없음은 물론이다. 본고에서는 전자서명 된 데이터의 유효성을 연장하는 방법에 대하여 제안 한다.

고주파 전극도자 절제술의 임상적 경험

김윤년(Yoon Nyun Kim),배장호(Jang Ho Bae),신경목(Kyeung Mok Shin),한성욱(Sung Wook Han),허승호(Seung Ho Huh),김기식(Kee Sik Kim),김권배(Kweon Bae Kim) 대한내과학회 1997 대한내과학회지 Vol.52 No.1

N/A Objectives : Among the current therapeutic options for paroxysmal supraventricular tachycardias, only surgery and ablative techniques are curative. However, surgery is associated with substantial cost, morbidity, and rarely death. Recently, catheter ablation techniques have been developed to treat paroxysmal supraventricular tachycardias. These techniques are effective and low-risk curative treatment for supraventricular tachycardias. This article shall describe our clinical experiences in radiofrequency catheter ablation for supraventricular tachycardias and review the literature. Methods: The study population consisted of 154 patients with supraventricular tachycardias from January 1993 to August 1995. Eighty one patients were men and seventy three patients were women, and their mean age was 41.29±15.41 years. Radio-frequency currents(mean) were applied through a catheter electrode positioned against the mitral or tricuspid annulus or a branch of the coronary sinus or atrioventricular node. Results: Among 154 patients, the mechanisms for paroxysmal supraventricular tachycardias were found to be atrioventricular reentrant tachycardia involving a concealed accessory pathway in 51(33.1%), Wolff-Parkinson-White syndrome in 57(37%), and atrioventricular nodal reentrant tachycardia in 46 (29.9%). Successful outcomes were achieved in 46 of 46 patients(100%) with atrioventricular nodal reentrant tachycardia, 7 of 8 patients(87.5%) with double accessory pathways, 69 of 72 patients(95.8%) with left-sided accessory pathway, and 19 of 28 patients (67.9%) with right-sided accessory pathway. Total 141 of 154 patients(91.6%) with supraventricular had a successful outcome with radio- frequency current application(mean). Conclusions: Radiofrequency catheter ablation techniques are highly effective in ablating accessory pathways or modifying atrioventricular node, with low morbidity and no mortality.

인공 진피용으로 Polymer(polyglactin)의 이용 가능성에 관한 연구

김홍석,홍성표,박재경,허승호 大韓成形外科學會 1998 Archives of Plastic Surgery Vol.25 No.4

The result of artificial skins made with collagen is poor after grafting over the full thickness wounds due to their rapid degradation by enzymatic cleavage. This study is an in vivo study of an artificial skin made with a biodegradable polymer, which can better address the problem of the collagenous artificial dermis. To investigate the availability of a biodegradable polymer for an artificial dermis and to get an information about the optimal degradation rate of a polymer for an artificial dermis, we made an artificial dermis by seeding of fibroblasts within the vicryl mesh and made a bilayer artificial skin by covering the artificial dermis with cultured keratinocytes. And these artificial dermis and artificial skin were evaluated in a full thickness wound model. The results are as followings: 1. The artificial dermis was available for grafting for 1 week culture of vicryl mesh-fibroblast. 2. The artificial dermis retarded the contraction of full thickness wounds. 3. The artificial dermis generated the granulation tissue and accepted the STSG completely. 4. The generated tissue from the artificial dermis had incorporated into the surrounding tissue by 4 weeks postgrafting. 5. Vicryl in the artificial dermis became to biodegrade from the culture period and absorbed completely by 5 weeks. 6. The epidermal portion was poorly differntiated during in vitro culture period. In conclusion, the polymer-fibroblast graft can retard the wound contraction and generate a new tissue permitting a useful dermal replacement. And to get more optimal results, another polymer which has slower biodegradation rate than vicryl should be used for the artificial dermis and the epidermal portion should be differentiated after in vivo grafting.

확장된 안면경부 피판을 이용한 협부 재건

허승호,양원용,홍성표,이두형 대한미용성형외과학회 1997 Archives of Aesthetic Plastic Surgery Vol.3 No.1

Together, the cheek and neck can be considered as a single anatomic location because skin vascularity, texture and thickness are similar. The cervicofacial flap has been described as the treatment of choice for the cheek defect because of its good mobility and excellent cosmetic result. However, if the defects on the cheek are wider than the length of palpebral fissure or extended to the lower two thirds of the cheek, the conventional cervicofacial flaps would be inadequate in size without the benefit of expansion. Tissue expansion of the cheek and neck is distinguished by a particularly high rate of complication. Prevention of various complications require careful planning and certain modifications in technique. We have used the following modifications and measures to prevent the complications and to maximize the expansion. 1) Whenever possible, expanders were placed over the rigid foundation such as mandible or posterior neck area after wide undermining. 2) Expanders were placed deep to platysma in the neck area. 3)Following optimal expansion, the further dissection extending to the clavicle and the posterior neck area was performed for optimal mobilization and draping of the expanded skin. 4) The expanded skin was advanced upward on the cervical portion and rotated forward on the cheek portion. 5) The flap should not be draped above the inferior orbital rim and postoperatively the pressure garments were applied to prevent drooping of the expanded skin. We experienced 21 cases of the expanded cervicofacial flaps with above surgical modifications and the expanded cervicofacial flaps can resurface the 95% of cheek defects with munimal complications and excellent cosmetic results.

단순 안와골절의 골절부위에 따른 임상적 경과에 대한 연구

이두형,홍성표,양원용,허승호 大韓成形外科學會 1998 Archives of Plastic Surgery Vol.25 No.6

As the traffic accidents and occupational accidents increase, the pure blow out fracture has been increased. If we could know the prognostic information of the pure blowout fracture according to the fracture sites, it would be of benefit in consulting the patients preoperatively and in planning the treatment. In this study we defined the posterior wall fracture as that extending 2 cm from orbital rim and the anterior wall fracture as that presenting within 2 cm from orbital rim. These fractures were individually classified into inferior wall fractures, medial wall fractures, and combined inferior and medial wall fractures, based on the operative finding and the preoperative CT scanning. We experienced 76 cases of pure blowout fracture patients underwent surgical correction and followed up the subsidence of diplopia and extraocular muscle limitation with ophthalmic Hess test. The results obtained are as following: 1. Posterior wall fractures were improved more slowly than anterior wall fractures. 2. Combined inferior and medial wall fractures were improved more slowly than isolate inferior wall or medial wall fractures. These results may be related to the difference of the traumatic forces and the anatomical structure of the fracture sites. These results inform the importance of accurate anatomical reconstruction of fracture sites and can be used as a prognostic information of the pure blow out fractures.

Al - Si 합금의 수직원심주조시 응고조직의 형성

홍준표,허승호,장성락 한국주조공학회 2000 한국주조공학회지 Vol.20 No.3

Al-Si alloys were solidified in a rotating cylindrical mold by a vertical centrifugal casting process. Under a certain casting condition, there are four distinct zones such as the chill zone, the primary fine columnar zone, the equiaxed zone, and the secondary coarse columnar zone from the mold wall. The columnar-equiaxed transition (CET) and the equiaxed-columnar transition (ECT) were measured as functions of solute content, flow rate (mold velocity), pouring temperature and mold temperature. Within the critical value of solute content, as the flow rate increases, the columnar-equiaxed transition were found, but not the equiaxed-columnar transition. The aspect ratio of the primary columnar zone was more affected by the solute content than the flow rate. However the aspect ratio of the equiaxed zone was more affected by the flow rate than the solute content. The aspect ratio of the secondary columnar zone was affected by both the flow rate and the solute content.

가토에서 편측 삼각봉합선 조기유합이 두개 안면골 성장에 미치는 영향

이두형,이안나,허승호,양원용 大韓成形外科學會 1998 Archives of Plastic Surgery Vol.25 No.3

Immobilization of unilateral(right) lambdoid suture was produced in 9-day-old rabbits to determine its effect on subsequent craniofacial growth. The suture was immobilized by the topical application of methyl-2-cyanoacrylate adhesive, subsequent growth effects on the cranial vault, cranial base and facial skeleton were assessed by serial radiographic cephalometry. The statistically significant result(p < 0.05) were: 1. The growth of immobilized lambdoid suture was decreased accompanying compensatory growth at coronal suture bilaterally. 2. The length of anterior and posterior cranial base was increased. 3. Anterior midfacial height was increased. 4. Lower midfacial angle(angular relationship of cranial base to lower midface) was decreased. With the view of above findings, it is clear that restricted growth was seen at unilateral lambdoid suture accompanying compensatory growth at coronal suture and resulted in altered cranial base and facial growth.