저주기 피로변형시 316L 스테인리스강의 비안정화 거동에 미치는 온도의 영향 : 반복응력거동 및 적정 피로수명인자 Cyclic Stress Response and a Suitable Fatigue Parameter

홍성구,이순복 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.1

In this study, cold worked (CW) 316L austenitic stainless steel was investigated by performing low-cycle fatigue test with varying temperature, strain amplitude, and strain rate. CW 316L stainless steel underwent additional hardening at room temperature and in the temperature range of 250-600℃: The hardening at room temperature came from plasticity-induced martensite transformation, and the hardening over 250-600℃ was attributed to dynamic strain aging. These hardening mechanisms competed with the softening mechanism which was induced by dynamic recovery, generally observed in cold worked materials, resulting in the cyclical non-stabilization of the material. Three fatigue parameters, such as stress amplitude, plastic strain amplitude, and plastic strain energy density, were evaluated. The results revealed that plastic strain energy density was nearly invariant through a whole life and, thus, recommended as a suitable fatigue parameter. (Received September 3, 2004)

316L 스테인리스강의 인장 및 저주기피로 변형시 관찰되는 동적변형시효 현상

홍성구,이순복 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10

Tensile and low-cycle fatigue (LCF) tests were carried out in a wide temperature range from 20℃ to 750℃ at strain rates of 1×10^(-4)~1×10^(-2)/s for 17% cold worked 316L stainless steel to investigate the conditions for the occurrence of dynamic strain aging (DSA) and its effects on material properties during tensile and LCF deformations. DSA introduced anomalous changes of tensile and LCF properties, and the DSA regimes under tensile and LCF loading conditions coincided with each other. During tensile deformation, DSA can be manifested in the forms of the plateau in the variation of strength with temperature, the minima in the variation of ductility with temperature, serrated yielding in the stress-strain curves, and the negative strain rate sensitivity (SRS). In case of LCF deformation, it can be manifested in the forms of the occurrence of the plateau or the peak in the variation of cyclic peak stress with temperature, the negative temperature dependence of plastic strain amplitude or softening ratio, the negative SRS, and the negative strain rate dependence of plastic strain amplitude or softening ratio.

316L 스테인리스강의 고온 저주기 피로저항에 미치는 동적변형시효의 영향

홍성구,이순복 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.2

Mechanism of dynamic strain aging (DSA) and its effect on the low-cycle fatigue (LCF) behavior in type 316L stainless steel were investigated by performing LCF tests in air in a wide temperature range from 20 to 650℃ with strain rates of 3.2x10^(-5)-1x10^(-2)/s. The regime of DSA was evaluated using the anomalies associated with DSA and was in the temperature range of 250-550℃ at a strain rate of 1x10/s, in 250-600℃ at 1x10^(-4)/s, and in 250-650℃ at 1x10^(-2)/s. The activation energies for each type of serration were about 0.57-0.74 times those for lattice diffusion indicating that a mechanism other than lattice diffusion is involved. It seems to be reasonable to infer that DSA is caused by the pipe diffusion of solute atoms through the dislocation core. Dynamic strain aging reduced the crack initiation and propagation life by way of multiple crack initiation, which comes from the DSA-induced inhomogeneity of deformation, and rapid crack propagation due to the DSA-induced hardening, respectively. (Received October 29, 2004)

하천수질조사에 있어서 시료채취빈도와 오염부하량

홍성구 안성산업대학교 1997 論文集 Vol.29 No.1

Sampling frequency is important in stream water quality monitoring and assessment, especially in small agricultural watersheds. Flow rates and water quality could change dramatically in the watersheds. In this study, two different sampling schemes were compared to evaluate the effects of the sampling frequency on stream water quality assessment. A year water quality data was used for this purpose that was a part of results obtained from a water quality monitoring project performed to evaluate the impact of best management practices on stream water quality for 10 years, in Nomini Creek watershed in the United States. The data was separated into two groups, a continuous sampling and a scheduled sampling. The continous sampling data was based on the samples taken by an automatic water sampler and the scheduled sampling was by visiting the watershed on every one or two-week intervals. The results showed that both flow-based average concentrations and loading of total suspended solids (TSS) and total Kjeldahl nitrogen (TKN) were significantly different between the two sampling schemes while those of nitrate nitrogen, ammonium nitrogen, and total phosphorus were not. These differences were apparently resulted from the fact that some water quality items such as TSS and TKN were sensitive to the rainfall events and the continuous sampling could catch the fluctuation of the changes in the concentrations during those events.

유압관로내의 동특성을 이용한 비정상 유량계측에 관한 연구

이홍구,윤석주,박성규,박길문 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

This paper describes an approach for estimating the unsteady flowrate through a hydraulic pipe lines and a components in real time. Concerning the dynamic characteristics of a hydraulic pipe lines, experimental research from the view point of focusing on the unsteady flowrate through a pipe is insufficient because of the lack of adequate flowmeters. In this experiment, a new instantaneous flowrate measurement system making use of a sharp-edged cylindrical choke and LDV has been proposed and developed by the authors. The unsteady flowrate is obtained from the measurements center-line velocity of a circular pipe using LDV and the pressure difference using a sharp-edged cylindrical choke, and experiments on the frequency characteristics are carried out. The results show a good agreement between the estimated and directly measured flowrate waveforms illustrates the validity of the method proposed here.

자기베어링시스템 강성의 실험적 고찰을 통한 안정화 특성에 관한 연구

강성구,강종규,홍준희 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

Due to the lack of stiffness and difficulties of control, it is hard to achieve well balanced magnetic levitation. In this paper, we analysis the current and position stiffness change according to bias current through experiment. Then, compensation equations were presented. After obtaining PD gain for each bias current and PD gain region through levitation experiment, we consider the characteristics.

과채류 잔류성 농약의 돌연변이 유발성

고용구,김성홍,오창경,오명철,김수현 濟州大學校 産業技術硏究所 1995 산업기술연구소논문집 Vol.6 No.-

Twelve residual pesticides which applied on the fruits and vegetables cultivation were tested for mutagenic activity using Salmonella typhimurium TA strain. Mutagenic activities against Tedion, Monopho, Danoton, Ometon and Captan of twelve pesticides tested were strong, Thalonil, Prosing, EPN, Phentoate, Dicopol and Captan were medium, and Dicopol were no. Tedion, hlonopho and Danoton showed strong mutagenic activities on TA98, Thalonil, Prosing, EPN, Phentoate, Parathion and Sappiran showed medium, and Danoton showed weak, while Dicopol and Sappiran showed no. At the other hand, Tedion, Danoton, Ometon and Captan showed storng mutagenic acitivities on TA100, Thalonil and Monopho showed medium and Prosing, Phentoate, Parathion and Sappiran showed weak, while EPN and Dicopol showed no. Therefore, EPN identified mutagen which induced only frameshift mutation, Sappiran was only base-substitution, and nine except these and Dicopol of twelve pesticides tested were mutagens which induced both frameshift and base-substitution mutation.

합성 펩티드를 이용한 Interleukin-2수용체 β-Chain에 대한 단일클론항체의 제작

이희구,이홍수,이인애,최용경,최인성,정태화,김길현 이화여자대학교 생명과학연구소 1995 생명과학연구논문집 Vol.6 No.-

Hybridoma producing monoclonal antibodies reactive with the β-chain of interleukin-2 receptor (IL-2R) were generated from mice immunized with a synthetic peptide of 19 amino acids. The synthetic peptide constitutes strongly hydrophilic region of extracellular domain of the IL-2R molecules(residues 32-50) as revealed by hydrophathy plot analysis. Hybridomas were screened by ELISA using Hut102 cells and the synthetic peptide as antigenic moiety, and by miasuring the binding activity of antivodies to the Hut102 cell surface that was monitored by a flow cytometer. The antibodies were further screened by their inhibitory effect against the interaction between IL-2R and interleukin-2(IL-2). Antibodies were further characterized by immunoprecipitation followed by autoradiography to reveal that the antibodies recongnize the 75 KD protein molecules expressed on the Hut102 cell surface and human peripheral blood mononuclear cells(PBMC) shich confirms the antigenic moiety to be β-chain of IL-2 recepter molecules.

합성 펩티드를 이용한 Interleukin-2수용체 β-Chain에 대한 단일클론항체의 제작

이희구,이홍수,이인애,최용경,최인성,정태화,김길현 梨花女子大學校 藥學硏究所 1995 藥學硏究論文集 Vol.- No.5

Hybridoma producing monoclonal antibodies reactive with the ß-chain of interleukin-2 receptor (IL-2R) were generated from mice immunized with a synthetic pepride of 19 amino acids. The synthetic peptide constitutes strongly hydrophilic region of extracellular domain of the IL-2R molecules(residues 32-50) as revealed by hydrophathy plot analysis. Hybridomas were screened by ELISA using Hut102 cells and the synthetic peptide as antigenic moiety, and by measuring the binding activity of antibodies to the Hut102 cell surface that was monitored by a flow cytometer. The antibodies were further screened by their inhibitory effect against the interaction between IL-2R and interleukin-2(IL-2). Antibodies were further characterized by immunoprecipitation followed by autoradiography to reveal that the antibodies recongnize the 75 KD protein molecules expressed on the Hut 102 cell surface and human peripheral blood mononuclear cells(PBMC) which confirms the antigenic moiety to be ß-chain of IL-2 recepter molecules.

1980년대(1981-1990) 전·후반기 피부과 외래환자의 통계적 비교 관찰

은 철,강승구,권상진,정성재,조지형,권철욱,김영진,김재홍 한양대학교 의과대학 1997 한양의대 학술지 Vol.17 No.1

To study the prevalence of common dermatoses 37,638 and 30,286 new outpatients who visited dermatology clinic with Hanyang University Hospital from January 1981 to December 1985 and from January 1986 to December 1990, respectively. Among the 37,638 outpatients in the first 5 years, the total number of male patients were 18,107(48.1%) and female patients were 19,531 (51.9%). Among the 30286 outpatients in the last 5 years, the total number of male patients were 14,705 (48.6%) and female patients were 15,581 (51.4%). In the both periods, the most frequent age groups was 21-30 (27.3%,25.2% respectively). The 15 common dermatoses, bacterial infection, seborreic dermatitis, drug eruption, verruca, syphilis, psoriasis, herpes zoster, and hypopigmentary disorder, in order of frequency. In thelast 5years, dermatophytosis, contact dermatitis, urticaria, acne, other eczema, atopic dermatitis, seborrheic dermatitis, bacterial infection, drug eruption, verruca, gerpes zoster, psoriasis, hypopigmentary disorder, scabies and syphilis were the 15 common dermatoses, as frequency. In both periods, the dermatosis which showed annually increasing tendency was dermatophytosis and those of decreasing tendency was bacterial infection. In the both periods, dermatophytosis, urticaria, bacterial infection, seborrheic dermatitis, verruca, and hypopigmentary disorder occurred most frequently during the summer season, and the incidence of other ecxema, scabies, atopic dermatitis, and herpes zoster increased during the winter season.