複合組織鋼의 摩擦 熔接部의 疲勞破壞特性에 관한 硏究

吳世旭,姜鎬珉,兪在煥,林東哲 東亞大學校 1988 東亞論叢 Vol.25 No.1

This study has been carried out to investigate the characteristics of fatigue crack of welded zone and heat affected zone of friction welded dual phase steel. The results obtained from the experiments are summarized as follows. Microstructure of welded zone is changed to ferrite and pearlite from ferrite and martensite by wel-ding heat. Micro-vickers hardness of welded zone is higher than that of base metal zone and heat affec-ted zone. Micro-vickers hardness of heat affected zone is lower than that of welded zone and microstructure of heat affected zone is changed to fine martensite and ferrite by heating cycle of welding. Fatigue limits of heat affected zone is a little higher than that of welded zone and base metal zone. There are no difference of fatigue limit of base metal zone and welded zone. Fatigue strength of welded zone is similar to that of base metal zone. At high △K region(△K>19MPa·??), fatigue crack propagation velocity of heat affected zone is slower than that of welded zone and base metal zone, and the difference of fatigue crack propagation velocity is smaller than that of high △K region. The crack occurs to the notch in heat affected zone first, but the final fracture surface is the surface of welded zone. It is abvious that heat affected zone of friction welded dual phase steel superior to welded zone and base metal zone in fatigue strength and resistance of fatigue crack propagation. The above mentioned facts are contrary to theory that heat affected zone of general metals is weaker than welded zone and base metal zone.

계장화충격시험에 의한 복합조직강의 파괴인성에 관한 연구

오세욱,유재환,박원조,이경봉 동아대학교 공과대학 부설 한국자원개발연구소 1989 硏究報告 Vol.13 No.1

The dynamic fracture toughness (K_(Id)) is measured using the precracked standard Charpy specimen with an instrumented impact machine. The value of K_(Id) is determined as a function of yield strength and microstructure, and correlations are established between K_(Id) and both energy of initial fracture and total energy of fracture. Since the K_(Id) values of the precracted impact specimens are in accordance with their theoretical ones, this test method is sufficiently practical.

Al-Ti-Cr 합금계 L1_2기지 합금의 800℃에서의 상안정성

오민욱,이재경,오명훈,위당문 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1

Relationship between the phase stability and the composition of L1_2-based Ti-Al-Cr alloys at 800℃ was investigated. It was found that the yield strength of Al-21Ti-23Cr and Al-21Ti-15Cr alloys with Ti-lean composition after exposure at 800℃showed a relatively small increase compared with that of alloys homogenized at 1150℃. However, yield strength of al-30Ti-15Cr alloy with Ti-rich composition after exposure at 800℃ increased very remarkably. The difference in strength increment after exposure at 800℃ was due to the partial decomposition of L1_2 phase in Al-21Ti-23Cr and Al-21Ti-15Cr alloys, and the complete decomposition of L1_2 phase in al-30Ti-15Cr alloy. Therefore, alloys with Ti-lean composition were expected more suitable for light heat resistant and oxidation resistant coating material with respect to stability of L1_2 phase. It was also revealed that the phase decomposition of L1_2 phase resulted from the shift of L1_2 phase region to Al-rich corner in Al-Ti-Cr phase diagram with decreasing temperature.

GMAHN 환경에서의 TCP 프로토콜 성능 분석

吳世德,金玄旭,李光培,張良根,裵振勝,金在浩 明知大學校 産業技術硏究所 2007 産業技術硏究所論文集 Vol.26 No.-

Recently, GMAHN that provides interface between MANET and Wired Network has been focused in Mobile Communication. It is necessary that The technology provide reliable data transmission technology between mobile node and wired network in MANET environment that varing by the node movement. In this paper, using the TCP protocol(Tahoe, Reno, Vegas, SACK)that increases reliability between source and destination, we applied the TCP protocol mechanism to various environment, and compared result, and also proposed the efficient TCP mechanism by comparing each mechanism.

최근 5년간 급성 A형 간염으로 입원한 환자들에 대한 입원 내용 분석

장재영,유병욱,조용진,오정은,홍성호,조주연 순천향대학교 의학연구소 2009 Journal of Soonchunhyang Medical Science Vol.15 No.1

Abstract Background : Due to improvements in Korea's sanitary conditions, antibody rates to the hepatitis A virus is decreasing rapidly and admission due to the disease is increasing, Patients who were admitted for hepatitis A during the last 5 years were selected and yearly differences in admission, clinical picture, medical fees, and differences according to age and gender were analyzed. Methods : Patients who were admitted to the Seoul Soonchunhyang University Hospital during the 5 year period between May of 2003 and April of 2008 and tested positive for IgM anti-HAV were selected and their medical records retrospectively analyzed. Results : 156 subjects [91 male (58%), 65 female (42%) were selected. The average age was 29.2 years (range; 21.4-37), average admission period 12.6 days (range; 12.5-1 7.7) days, and average medical fees 2,295,151 (range; 932,097-3,658,205) KRW(Korean Won), Yearly incidence rates were as follows : 10 for May, 2003 to April, 2004, 14 for May, 2004 to April, 2005, 23 for May, 2005 to April, 2006, 69 for May, 2006 to April, 2007, and 41 for May, 2007 to April, 2008, The maximum value median of AST, ALT, and bilirubin during admission was 989 IU/L, 1999 IU/L, and 5.6 mg/dL each, Each factors were all positively correlated with the patient's age. Conclusions : Recent decrease in antibody positivity of the hepatitis A virus and subsequent surge of acute hepatitis A is a cause of rising socioeconomic costs. A large scale epidemiologic research on whether HAV vaccination should be made mandatory and health insurance applied seems to be needed. Key words : Hepatitis A, Age, Medical fees, Vaccination

SB41鋼 潛弧熔接部의 平滑 및 側面홈에 관한 疲勞크랙 傳播特性 : 大氣雰圍氣下에서의 擧動 at Room Temperature in Air

吳世旭,金在喆,李祥源 동아대학교 공과대학 부설 한국자원개발연구소 1986 硏究報告 Vol.10 No.2

Fatigue test was conducted on the smooth and side-grooved specimens fabricated from submerged are welded plate of SB41 steel. Test conditions were constant-loan-amplitude fatigue crack growth test with stress ratio 0.1, loading frequency 5㎐, sinusoidal waveform at room temperature in air. The results are summarized as follows: 1) Fatigue crack growth rate of weld metal is slightly lower than that of base metal. 2) Due to the effect of plastic constraint, side-grooved specimen shows somewhat faster fatigue crack growth rate than smooth specimen. 3) Welding residual stress affects fatigue crack growth rate.

複合組織鋼이 腐蝕疲勞크랙傳播特性에 미치는 食鹽水 濃度의 影響

吳世旭,姜鎬珉,兪在煥 東亞大學校 海洋資源硏究所 1989 硏究論文集 Vol.2 No.1

The corrosion fatigue test was performed under rotated bending in salt solution having a concentration from 0.01 wt percent to 3.5 wt percent to investigate the corrosion fatigue crack propagation characteristics for dual phase steel. Corrosion pits were occurred in martensite, and microcracks occurred at corrosion pits were selectively propagated towared martensite because slip bands were not found in ferrite which were encapsulated by martensite. The number of corrosion pits, the diameter of corrosion pits and the length of corrosion cracks for M.E.F. and raw material(R.M)were increased with the concentration of salt solution and the number of cycles. The initiation of crack was almost same regardless of the concentration of salt solution; approximately N??/N??=20% in case of M.E.F. and N??/N??=14% in case of raw material (R.M.) The difference of corrosion fatigue crack propagation was increased with an increase in concentration of salt solution. The corrosion resistance effect of dual phase steel was smaller than that of raw material (R.M.) in corrosion fatigue crack propagation rate.

單一試驗片의 安定히스테리시스 曲線에서 金屬의 硬化指數 推定에 관한 硏究

吳世旭,金在喆 동아대학교 공과대학 부설 한국자원개발연구소 1986 硏究報告 Vol.10 No.1

Fully reversed pull-push low cycle fatigue test under triangle cyclic waveform mode of constant strain control were conducted for SM15C and copper at the room temperature in air. Cyclic strain hardening exponent, n' was obtained from the cyclic δ-ε curve defined as the locus of tips of the stable hysteresis loops. Equivalent cyclic strain hardening exponent, n'_(eq), was obtained from the outer trace of a single stable hysteresis loop. Modified equivalent cyclic strain hardening exponent, n'_(eqm) , was obtained from the outer trace of a single stable hysteresis loop in the modified coordinate system. The relationship between n'_(eq), n'_(eqm), and n' was investigated with the test results. Equivalent cyclic strain hardening exponent n'_(eq) is considerable dependent upon the controlled strain range Δ^(ε) and decrease with increase of Δ^(ε). If Modified equivalent cyclic strain hardening exponent n'_(eqm) is calculated from the stable hysteresis loop at the modified coordinate system translated along the elastic slope, it closely approach to cyclic strain hardening exponent n'.

準備運動과 回復技術이 反復出戰走者의 記錄에 미치는 影響

洪在郁,吳貞胤 淸州敎育大學校 1981 論文集 Vol.18 No.-

The purpose of this research was to determine the effects of an absence of a warm-up, a warm-up, and a warm-up Recovery techniques on repeated performances of three all-out trials in the 300m dash. the subjects were 15male college boys who run a total of nine 300 dashes consisting of three trials of each treatment with a 20 minutes rest period between trials on three different testing days Approximately two months later the same pattern of nine 300m dashes was administered a second time. The result of this study shed some new Light on the use of warm-up between repeated performances of events similar to the 300m dash. There is no doubt that the psychological factor plays an important role in affecting the physical subjects Consciously or subconsciously did notgo allout without the warm-up or the warm-up with recovery techniques, because they psychologically felt their performance would be adversely affected without them. of course, in no study can the psychological factor be Completely controlled. However, in this study all 15 subjects hadtwo practice administrations in running two heats of all-out 300m dashes during the conditioning program, before the testing started. The subjects knew how it felt to run this distance all-out and were instructed before the conditioning program that three were no physiological advantage to any one method. It is possible that in this study whatever physiological factors that operated in the warm-up, and warm-up and recovery techniques had a prime in fluence on attaining significant superior performances. One can only speculate what these warm-up may be beneficial are the increase in muscle temperature, the increased rate of blood volume Circulation, and the increase in the oxygen exchange system. The reasons the recovery techniques may have provided some performance advantage are the heart and three omplete removal of all body weight from the Legs during the 15 min rest period. This study indicated performance in repeated trials of the 300m dash does not deteriorate as fast if subject tselevated their Legs followedby a short warm-up than if they just sat for the rest period or sat and warm-up for the rest period. ① statistically significant differences at the .05 le uel were found between the overall means of the two administrations, the methods, and trials, a significant interaction effect was also found between method and trials. ② There are significant simple effects at the .01 level of significance between trials and methods 1, and 2 and between methods attrial3. ③ Tests for simple effects coupled with Tukey's HSD test revealed that by the fime trial3 Comes about, the warm-up with recovery techniques demonstrated significant superiority of performance over no warm-up ④ statistically significant diffenences at the .05 Level were found between the three methods, and among the means between the three trials a significant interaction among methods and trials was also found.

Pinus koraiensis와 Pinus parviflora의 樹高에 따른 氣孔數 變異에 關하여

權五容,辛昌男,吳炅煥,方在旭 충남대학교 자연과학연구소 1980 學術硏究誌 Vol.7 No.2

Stomata1 distribution in relation to the height of Pinus parviflora and Pinus koraiensis was studied 1. Stomata1 bands per needle of P parviflora and P koraiensis were 8.60±0.62 - 11.47±0.74, 14.07±1.03 - 16.60±0.99 and the number of stomata per band were 382.0±8.80 404.27±26.16, 1,326. 67±87.78 - 2,286.58±214.57, respectively 2. The number of stomatal band was significantly different between 3, 4m and 5, 6m in P parviflora and between 5, 6m and 7m in P. koraiensis Consequently, it is suggested that stomatal frequency gradient associated with increasing height above the ground is correlated with the greater degree of exposure to light.