순수 Ti 용접재의 기계적 특성 및 피로크랙 성장특성에 관한 연구

최병희,이종범,정장만,장경천,최병기 朝鮮大學校 機械技術硏究所 2007 機械技術硏究 Vol.10 No.2

In this study, fatigue fracture often occurs due to the fatigue crack in the machine and welding structure and this is the result of severe operational environment, operational condition, and design condition caused by the large scaled and light weighted machine and structure in recent days. Therefore, safety and reliability should be secured to prevent the fatigue fracture of machine and structure, and the use of titanium has been increased in the metal material for the safety and reliability. The purpose of this thesis was to investigate the welding characteristics and fatigue crack growth characteristics of titanium, commonly using power station, aircraft and ship. The experimented material was TIG welded in order to look over the characteristics according to the notch position and compare with other material. The results, at the same welding condition, 4 pass specimen which had the smallest number of welding pass had the highest tensile strength with 51kgf/㎟ and the tensile strength of 4 pass specimen was 10% higher than the one of 7 pass specimen, and its elongation reduced about 30%. The initial fatigue crack growth characteristic is slower in this order, boundary zone < welding zone < HAZ < base metal. Especially boundary zone's growth speed is slower about 30 times than base metals.

잔류응력을 고려한 SS400재의 피로특성에 관한 연구

최병희,이종범,정장만,장경천,최병기 朝鮮大學校 機械技術硏究所 2007 機械技術硏究 Vol.10 No.2

In this study is about the fatigue characteristics which appears in the welding residual stress field. The welding residual stress takes place mostly at the portion where SS400 materials are automatical welded. The effects of the welding residual stress in the growth and propagation of fatigue crack, so as to study the fatigue behavior in the welding residual stress field. The results, in case of the load range is constant, as the stress ratio is changing to 0.1, 0.33. 0.5 the propagation life is constant but the growth life decreases. And than, when maximum load or minimum load is constant, as the stress ratio increases the growth life and propagation life increase. The fatigue crack propagations rate da/dN appears to accelerate when the stress intensity factor range △K is less than 15MPa-m^(1/2). The growing and propagation fatigue crack in the welding residual stress field is similar to original specimen after being passed the original residual stress field.

사내벤처캐피탈이 투자기업의 기술혁신에 미치는 영향

윤병섭(Yoon Byung-Seop),김정수(Kim Joung-Soo),장지인(Jang Jee-In) 한국국제회계학회 2012 국제회계연구 Vol.0 No.41

This study discusses Corporate Venture Capital's contributing role to the innovative venture business(VB) by analyzing its promoting effect on the "Technology Innovation" for the invested venture business. It has analyzed the number of patent registrations and amount of investment in intangible assets of the 52 companies invested by Corporate Venture Capital(CVC) during the period from January of 1999 to December of 2008. The results are as follows. First, the company has shown its growth in registering the patent after receiving the CVC's investment, which verifies the CVC's pumping-up role in technology innovation. The result shows that the formation of CVC motivates R&D and innovation will and has a postive influence on technology innovation by the complementary relationship with academic externality of existing knowledge capital. This study supports the works by Kortum and Lerner(2000), Hellman and Puri(2000), McNally(1997), Ki-whan Lee and Byung-seop Yoon(2007) asserting that CVC's investment influences the number of patent registration and it contributes to spreading the technology innovation. Second, it is found that the number of patent registrations from IT VBs invested by CVC is larger than that of Non-IT VBs. The result implies that the high-technologies of IT VB's play a critical role in registering more patent than low-technology Non-IT VBs. Third, it is found that the ratio of investment in intangible assets by the VBs has grown after receiving CVC's fund, which implies that the CVC's investment plays a stimulating role for the VBs to invest more budget into R&D so that they can accomplish technology innovation.

中小企業 技術開發의 成功要因에 관한 硏究

張炳輯 忠州大學校 1995 한국교통대학교 논문집 Vol.30 No.1

Our small and medium-sized enterprises were excessively dependent on foreign technologies in the past due to their relatively weak technological potentials. However, on the threshold of 1980, they have attempted to depart from their dependency on low-cost labor and poor-quaility production and to active introduction of advanced technologies; self-development of new technologies; training of skilled labor; enhancement, sophistcation, automation of production facilities, etc. After all, they are pursuing a technology-intensive industry. All such efforts are being focused on the technological development. According to academic theories, top lmanagement of our small and medium-sized enterprises should recognize the importance of technological development and its impact on international competitivemess if they want to respond effectively to the changing conditions and to survive in the ever-fierce competitions. With such basic concept in mind, this study was aimed at analyzing the factors of the successful technological development of our small and medium-sized enterprises positively and there by presenting a set of those factors. By analysis the effects of these facors and other conditions on the factors of the successful technological development of our small and medium-sized enterprises positively and there by presenting a set of those factors. By analyzing the effects of these facors and other conditions on the business performance the following conclusions were drawn: 1) The important factors of technological development have affected the business performance positively. 2) The most influential factors are top management's involvement and support followed up vby employees 'participation, the ability to predict the changing technological environments, and other institutions' cooperation. 3) The effects of these factors on the business performance vary depending on the conditions and environments with which the firm copes, and especially have an most important effect on the development of new products and responsiveness. 4) Although the performances of the technological development count on the business types, the motive and patterns of technological development don't relate to the performance of it.

Se/CS₂용액으로 처리한 n-GaAs 표면의 Photoreflectance 특성에 관한 연구

장광수,김인수,배인호,한병국,이정열 嶺南大學校 基礎科學硏究所 1997 基礎科學硏究 Vol.17 No.-

The surface of of n-GaAs(100) was treated using 1.5㎎/100ml solution of Se/CS₂. The passivation of the surface of this sample was investigated by photoreflectance(PR) experiment. After the surface treatment, the samples were annealed between 300 to 700 ℃ in a N₂atmosphere for 10 min. From the obtained Franz-Keldysh oscillations, we have evaluated the surface electric field(E?) and built-in voltage(V??). The density of surface states(Q??) and surface Fermi level(E??) of n-GaAs treated with CS₂and Se/CS₂solution were determined 1.78 ×10??㎝?? , 1.81×10?㎝? and 0.734 eV, 0.737 eV, respectively. After annealed at 600 ℃, These values were about 45% and 13% smaller than those in unannealed samples. It has found that the passivation of surface occured when the surface of the sample had been treated with Se/CS₂ solution and annealed from 400 to 600 ℃. This is ascribed to effects due to activation of elemental Se on the surface.

초등학생의 전류에 대한 오개념을 줄이기 위한 비유물의 효과

장병기,이준희 춘천교육대학교 과학교육연구소 2000 과학교육연구 Vol.23 No.-

NaC1 수용액과 실리콘 오일에 의한 성층유체의 저온거동에 관한 실험적 연구

장원택,전승배,김병철 朝鮮大學校 機械技術硏究所 2007 機械技術硏究 Vol.10 No.1

To study the influence of phase change of solution and fluid flow on low temperature in thermal storage, solar pond and removal of oil pollution at the sea, an experimental study was carried out in the square cavity filled with stratified fluids of silicone oil and aqueous sodium chloride. In the case of the lower cooling surface, the temperature of the system was dominated by conduction owing to the temperature and concentration fields stabilized by gravity. Liquid superheat influenced less in the lower part and the maximum density of sodium chloride became lower as the salt concentration got higher in the upper part. And the lower the initial temperature in the system the lower the temperature distributions were. When the actual liquid temperature was lower than the liquidus temperature with Ci = 15%, a supercooling phenomenon was observed But with Ci = 5% and Ci = 10% the actual liquid temperature was higher than the liquidus temperature and the temperature of upper fluid also got lower when the concentration of sodium chloride became lower. The influence of latent heat was less in the lower part and the raising ratio in temperature was higher when the initial concentration was lower in the upper part.

모 통신관련, 사업장 연작업자들의 건강수준 평가

장덕희,황보영,리갑수,김화성,이성수,안규동,이병국 순천향대학교 산업의학연구소 1997 순천향산업의학 Vol.3 No.1

To evaluate the health status of lead workers in telecommunication industry, author studied 369 male workers working in a telecommunication industry. Study variables chosen were blood zinc protoporphyrin(ZPP), hemoglobin, serum glutamic oxalacetic transaminase(SGOT), serum glutamic oxalacetic transaminase(SGPT), γ-glutamyltrans-peptidase(GGT) and hepatitis B virus antigen and antibody. Personal data such as smoking and drinking habit, work duration were also collected. 15 lead related symptom questionnaires were provided to all lead workers and filled up by themselves and reconfirmed by physician. The results were obtained as follow; 327 workers(89%) among 369 workers were healthy and 42(11%) workers abnormal health state. 9 workers were disease state among 42 workers those who were abnormal health state. The most frequent disease was liver disease(52.4%), and next was hypertension(26.2%) and then anemia(9.5%), hyperlipidemia(4.8%) and pulmonary tuberculosis(4.8%) in order of frequency. There was no case of lead intoxication. The mean of blood ZPP concentration of study subjects was 14.4±6.9㎍/㎗ and maximum blood ZPP concentration was 48.0㎍/㎗. The means of GOT, GPT and GGT were 29.4±10.0unit/L, 19.7±14.4unit/L and 38.7±31.5unit/L, respectively. The prevalence rate of hepatitis B virus antigen was 6.8% and the one of hepatitis B virus antibody was 43.6%. The symptoms with high prevalence rate above 40% were six; 'loss of appetite', 'frequent numbness of fingers or feet', 'feeling tired or fatigue generally', 'becoming nervous or sensitive to not important things', 'feel dizziness when standing up', and 'feel sleepy frequently'. The prevalence rate of symptoms were increased by the increase of age. The prevalence rate of symptoms were higher in smoking group and drinking group than non-smoking group and non-drinking group, respectively.

말뚝으로 보강된 탄성지반상에 놓여 있는 연속기초의 해석

장준환,신수곤,장병순 부산대학교 생산기술연구소 2000 生産技術硏究所論文集 Vol.59 No.-

지반이 다소 연약하여 건물 기초를 말뚝으로 보강된 연속줄기초로 설계할 경우, 탄성지반을 무시하고, 말뚝을 탄성지점으로 한 연속보로 처리하는 것이 보통이다. 그러나 실제 기초에서는 지반반력과 말뚝반력을 모두 무시할 수 없는 경우가 많다. 본 논문은 지반반력과 말뚝반력을 동시에 고려하고 n경간의 탄성지점을 가지는 탄성지반상의 보에 대한 해석을 반무한장보와 유한장보로 구분하여 계시하고, 하중 재하위치에 따라 반무한장보 및 유한장보로 해석해야 할 범위를 제시하였다 In this paper, the method of analysis for the girder supported with piles on the elastic soilmedium is proposed. The girder supports with piles on the elastic soil medium is often used as those of crane rail at a ship yard. For the purpose of practical design, these girders were often regarded as continuous beams elastically supported with piles. Actually, the method of ana1ysis for these girders should be considered as analysis of girder supported with piles on the elastic soil medium. From the proposed method, we can calculate bending moment and shearing force of these girders, after obtaining the reaction of piles by calculating the deflection of pile support point due to external load and pile reaction.

초등학교 과학영재아를 위한 특별 프로그램 개발 연구

장병기,이대형,김남일,이면우 춘천교육대학교 과학교육연구소 2000 과학교육연구 Vol.23 No.-