치과 급속 교정용 초내식성 스테인리스강 가공재의 특성

오근택,김영식,김경남 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1

When stainless steels are used in the human body, the nickel ion released from the alloys over a short or long term can cause such adverse effects as allergies, dermatitis, asthma. Although the higher the corrosion resistance of stainless steels and the lower the nickel content, the better it is for the human body, since nickel has an essential role in the stabilization of the austenitic phase and the corrosion resistance of stainless steels, it is difficult to remove nickel completely. In this regard, the purpose of this study was to investigate corrosion resistance, cytotoxicity and mechanical properties of super stainless steels, and upon this basis, to evaluate their potential for orthodontic applications. Super austenitic stainless steels had higher content of nickel(17~20 wt%) than super duplex stainless steels (7~10 wt%) or super ferritic stainless steels (lower than 3 wt%). Super austenitic and duplex stainless steels had nitrogen content of above 0.2 w%. These steels had high Mo or W contents of which synergistic effect together with N increases localized corrosion resistance. In terms of hardness, super stainless steels exhibited higher value than 316L S. S. and two times higher than cp Ti(grade II). Austenitic and duplex stainless steels exhibited better mechanical properties. Super stainless steels exhibited low passive current density (3~4 μA/㎠) and similar potentiodynamic polarization behaviors among themselves. Thus, these steels are considered to have high corrosion resistance in the human body-simulated solution. Pitting corrosion occurred in 316L S. S.. A3 containing the highest nickel content, as well as SAF2507 exhibited none cytotoxicity, and the others, slightly. This indicates that the cytotoxicity has no direct relation with nickel content itself in these alloys. Super stainless steels with both high corrosion resistance and good biocompatibility are expected to be used for orthodontic applications by virtue of the passive film attribute enhanced by synergistic effect of Mo+N or by high addition effect of Cr+W.

타이타늄 임플란트와 상부구조물의 갈바닉 쌍의 전기화학적 특성

오근택,김명화,최병갑,김경남 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.1

For the aesthetic and functional restoration of edentulous patients, recently dental implants have been used widely. Dental implants and restorative alloys are required with the high corrosion resistance. Suprastructure and implant with different compositions, which are in electrical contact, may develop galvanic or coupled corrosion problems. Besides galvanic corrosion, crevice and pitting corrosion may occur in the marginal gap or the gap between dental implant assemblies. In this study, Ti implants, gold, silver-palladium, cobalt-chromium and nickel-chromium suprastructures were used to investigate their galvanic and crevice corrosion of suprastructure/Ti implant couples. Potentiodynamic and potentiostaic testing were performed in artificial saliva at 37℃. Potentiodynamic testing was carried out at the potential scan rate of 1 ㎷/sec and in the range of -600∼1600 ㎷(SCE). Potentiostatic testing such as open circuit potential and current densities at -250, 0 and 250 ㎷(SCE) was performed for 5000 seconds in artificial saliva. After electrochemical testing, the surface and cross-sectional morphologies of the samples were observed using optical microscopy. Potentiodynamic test results indicated that suprastructure/Tim implant couples exhibited the passive current density range of 0.5∼12 ㎂/㎠, Ti abutment/Tim implant and gold/Tim implant couples exhibited relatively low passive current density, Co-Cr/Tim implant couples the highest. Co-Cr and Ni-Cr/Tim implant couples showed the breakdown potentials of 700 and 570 ㎷(SCE), respectively. Open circuit potentials of silver, Ti abutment, gold, Ni-Cr and Co-Cr/Ti implant couples were -93.2±93.9, -123.7±58.8, -140.0±80.6, -223.5±35.1, and -312.7±29.8, respectively and stable according to immersion time. The couples exhibited cathodic current densities at -250 ㎷(SCE), especially, gold and silver alloys showed the high cathodic current densities of ±3.18 and ±6.63 ㎂/㎠, respectively. At 250 ㎷(SCE), Ti abutment/Ti implant couples exhibited the lowest current density of 9.48×10^-2 ㎂/㎠, and gold, Ni-Cr, Co-Cr and silver/Ti implant couples exhibited 0.313, 1.27, 5.60 and 8.06 ㎂/㎠, respectively. The couples exhibited relatively low current densities at 0 ㎷(SCE). The photographs after electrochemical testing showed crevice or pitting corrosion in the marginal gap and suprastructure surface. Although Co-Cr/Ti implant couples among the tested samples had the possibility of the galvanic corrosion, its degree was not significant.

알루미늄 튜브 하이드로포밍에서의 예비 굽힘 공정의 효과에 관한 연구

임희택,박경창,김형종,김헌영 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.B

Recently social demands of fuel economy and environmental regulations require the development of lightweight components and new manufacturing technologies. The aluminum tube hydroforming is a manufacturing process which can provide lightweight components as automotive parts. In this paper, the hydroformability of aluminium tube in different condition of bending process is presented. An investigation has been conducted on how to control the deformed shape and its effect on thinning distribution after hydroforming by using finite element simulation. Finite element simulation of tube hydroforming for automotive trailing arm is carried out to explore the effect of 2-dimensional and 3-dimensional bending.

Counseling의 基本的 槪念 및 三學派에 관한 理論과 技術問題 比較考察

金慶澤 대구교육대학교 1971 論文集 Vol.7 No.-

Counseling is a central and momentous part of guidance. For, its purpose is to accelerate the client's growth of personality by professional and technical activities to help the adjustment of the client. In this thesis, I defined some major concepts of counseling-adjustment, needs, human relations, conflicts, self-expression, and self-concept-from my point of view. At the same time, I made clear some differences among the three theories of counseling-clinical, client-centred, and eclectic counseling. I discussed and compared the emphases and problems the three schools hold respectively. As a conclusion, I suggested what kind of theories and techniques would be the most desirable in our school setting.

어린이의 問題行動 治療를 위한 遊戱療法의 適用上 問題考察

金慶澤 대구교육대학교 1973 論文集 Vol.9 No.-

Children learn a number of things through plays because children express their natural feelings and thinkings by means of behaviors rather than their linguistic expressions. Some needs, attitude and feelings are shown by their plays. Then acceptive and receptive atmosphere are established. So the more they play the more rakedly they reveal their feelings. Through precise observation of their behaviors, we can understand the traits of their personality and gain several informations for diegnosing behaviors. Besides, if the children get some frustration on account of their limited circumstances, they are fallen into emotional stress. And according to the accumulation of this stress the maladjustment on the personal and behaviorial activities is often shown. In order to remove these maladjustments and maintain normal mental health by plays, this study will be concentrated on the catharsis of melancholy feelings and on the expression of their depressed feelings. In this article, the follwoings are investigated for applying for school education in an attempt to solve these problems. 1) The subject children on play therapy. 2) The theoretical point on play therapy. 3) The technical problem on play therapy. 4) The facilities and establishments on play theory.

폐흡충에 의한 무균성 노흉에 대한 돼지꼬리형 도관(pig-tail catheter)을 이용한 치료의 효과

한경택,권세훈,김형호,하재화,선길홍,권용은,윤성호,이승일 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.3

Background: Pulmonary paragonimiasis is caused by consumption of raw or improperlycooked crustacea infected with the laval stage (metacercaria) of Paragonimus westermani. The most characteristic symptoms were rust-colored sputum and cough. Paragonimiasis causes pleural thickening or effusion in 48% of the patients. Pleuro-pulmonary paragonimiasis can be easily overlooked by physicians who do not suspect this disease in the differential diagnosis. Method: We compared the outcomes of 11 patients with paragonimus empyema managed either through thoracotomy or pig-tail catheter drain. These patients were confirmed by food history, clinical and radiological findings, and laboratory data. Results: The male and female ratio was 1.75 : 1, and mean age was 40.0 ± 13.5 years. AII patients had pulmonary symptoms such as cough or chest pain. Serum-ELISA for paragonimiasis were all positive (mean titer was 0.57). AII patients had pleural effusion in radiological findings( 2 patients had bilateral pleural effusion). All patients received praziquantel (75 ㎎/㎏/day for 3days). Two patients were treated with thoracotomy and nine patients were treated with pig-tail drain. Hospital stay were 14.5 days in thoracotomy group and 5.6 days in pig-tail group respectively, Conclusion: Compared to the conventional thoracotomy grouP, the patients with paragonimus empyema who received pig-tail catheters had a significantly-decreased period of drain in situ, were clinically improved earlier, and were discharged earlier.

치과 재료용 NiTi 합금의 특성에 대한 Ag 첨가의 영향

오근택,박기호,심형민,황충주,김경남 大韓齒科器材學會 2001 대한치과재료학회지 Vol.28 No.4

Equiatomic and near-equiatomic nickel-titanium alloys have shape memory effect and superelasticity. However nickel-titanium alloys are extremely sensitive to the precise nickel-titanium ratio and alloying additions. There are many reports on the alloying additions such as Fe, Al, Cr, Co, V, Pt, Pd, Zr, Hf, Nb and Cu. The purpose of this study was to investigate the effect of silver addition to nickel-titanium alloy for dental and medical application.Arc melting process was used to fabricate nickel-titanium alloys. The casts were heat-treated in a vacuum furnace at 950℃ for 72 hours to homogenize their composition. Subsequently, they were hot-rolled at 950℃ to obtain the plate samples and annealed in a vacuum furnace at 950℃. To investigate the properties of nickel-titanium alloys, phases, transformation temperature, compositions, corrosion resistance and hardness were evaluated using X-ray diffractometer, differential scanning calorimeter, energy dispersive spectroscopy or atomic absorption spectroscopy, potentiostat and micro-vickers hardness tester, respectively. NiTiAg alloys showed the low silver recovery rate for the cast due to its low evaporation temperature, and showed low silver solubility to NiTi alloy. Silver addition to NiTi alloy increased transition temperature range (TTR) above 100℃ and stabilized martensitic phase(monoclinic structure) at room temperature because Ms temperature was above room temperature. Martensitic and austenitic phase existed in x-ray diffraction pattern of solution annealed NiTiAg alloys. The Silver addition is considered to improve corrosion resistance and change largely the mechanical properties depending upon the amount of alloying addition and types of addition elements.

XML/EDI기반 건설물류관리시스템

남경우,서용칠,구교진,현창택 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

Logistics in construction project includes purchase, procurement and transportation on the network consisting of contractor, subcontractor, supplier, manufacturer, carrier and so on. Collaborations and integrations among the each participants play a key role. It is necessary that we take advantage of recent information technology in order to optimize logistics and achieve collaborative integration. The use of extensible markup language(XML) has been continued increasingly in recent years. This research aims at presenting conceptual Logistics system based on XML/EDI. Various participant in construction project will have more efficient and malleable Logistics atmosphere.

초내식성 스테인리스강 선재와 브라켓의 내식성 및 금속 이온 용출 특성

오근택,정경진,황충주,박용수,김경남 大韓齒科器材學會 2001 대한치과재료학회지 Vol.28 No.4

Metallic orthodontic appliances are known to release metal ions in an oral cavity. It is not advisable that toxic corrosion products derived from the appliances is absorbed into the body. Metal ions release from orthodontic appliances is known to have large effects on the result of orthodontic treatment and systemic health. Metal bracket and wire were made of super stainless steel(S32050) with high corrosion resistance. The corrosion resistance and ion release property of S32050 and conventionally used appliances were examined. Four types of wire were ligated in either super stainless steel(SB) or Tomy bracket(TB) with O-ring, and then each group was immersed in an artificial saliva at 37℃ for 12 weeks. Amount of released metal ions was measured with immersion time by graphite furnace atomic absorption spectroscopy and surface morphology was investigated. S32050 showed the low passive current density of about 1 μA/㎠ and the stable passive region to a high potential in artificial saliva. S32050 appliances did hardly release nickel ions in artificial saliva. S32050 wire(SRW) and NiTi wire(NW) didn't show significant difference of Ni ion release with immersion time, meanwhile, Remanium wire(RW) showed significant difference in 12 weeks. Ni ion releasce from the brackets didn't show any significant difference with immersion time and between SB and TB. Amounts of Ni ion released from TB-SRW showed significant difference in 12 weeks, those from TB-RW showed significant difference from 4 weeks later and highest release among all groupsin12weeks. TB-NW released little Ni ion for all immersion time and showed significant difference from 4 weeks later, TB-TW(TMA wire) showed significant difference in 12 weks. SB-SRW didn't show any significant difference and SB-RW signigicant difference in 12 weeks,but lower compared with TB group. SB-NW and SB-TW didn't show any significant difference. Corrosion products didn't be observed in mostly groups during the immersion time, except that in TB-RW, they were observed on the bracket surface between O-ring and wire from 8 weeks later. Super stainless steel wire had good corrosion resistance compared with stainless steel wire, and it is believed that it can be used as orthodontic material for bracket and wire.

교정용 스테인리스강 선재의 내식성에 미치는 응력 제거 열처리 조건의 영향

오근택,전용석,황충주,김경남 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.2

Heat treatment is applied to orthodontic wires in order to relieve the stress that results from cold working and the orthodontists manipulations. In this study, 4 types of wires were heat-treated in an air, argon or vacuum environment, and were either cooled in a furnace or a water bath. Corrosion properties of the heat-treated wires were investigated by potentiodynamic method. The difference of corrosion resistance between the wires heat-treated in an ambient according to cooling methods was not significant. After heat-treated in an ambient, both water-cooled and furnace-cooled wires had a similar and low corrosion resistance. The difference of corrosion resistance between the wires heat-treated n a vacuum environment with cooling methods was significant. After heat-treated in a vacuum, the furnace-cooled wires had high corrosion resistance, but the water-cooled wires low. After heat-treated in a vacuum, argon, or air environments, the water-cooled wires had low corrosion resistance. It was considered because the irregular and unstable film was formed on the surface of the wires when cooled in a water bath. The control wires showed a low current density and high pitting potential, but most of the heat-treated wires did high current density and low pitting potential except for the wire heat-treated in vacuum and then cooled in a furnace. Conclusively, orthodontic wires are considered to have to be heat treated in vacuum condition or inert gas environment and then to be cooled in a furnace in order to inhibit surface oxidation, minimize the decrease of corrosion resistance and improve the mechanical properties.