모 연취급장 근로자들의 연폭로지표들과 혈압과의 관련성

임상복,김용배,이용진,리갑수,김화성,황규윤,장봉기,이성수,안규동,이병국 순천향대학교 산업의학연구소 1998 순천향산업의학 Vol.4 No.1

In order to investigate the relationship between blood lead with other lead exposure indices and blood pressure in occupationally lead exposed male workers, 629 workers(515 lead exposed workers and 114 non lead exposed workers) in a storage battery factory were studied. Blood lead(PbB), zinc protoporphyrin(ZPP) and urinary δ-aminolevulinic acid(ALAU) were selected as an index of lead exposure. Height and weight were also meaured with calibrated automatic height-weight machine to produce fatness index directly. Personal information on smoking and drinking history were also collected. Blood pressure was mearured by trained nurses with automatic sphingomanometer. All workers took at least 30 minute rest before their measurement of blood pressure. The results obtained were as follows: 1. The prevalence rate of hypertension of lead exposed and non-exposed workers were 3.5% in both group without any difference. 2. There were no differences of systolic and diastolic pressure between groups divided by lead exposure, smoking habit, drinking habit. but the increase of age group made the difference of diastolic pressure, and only differenct of systolic pressure observed in age group of less than 20 and that of more than 40. 3. In pearson's correlation analysis, PbB was correlated with systolic pressure significantly, but not with diastolic pressure. PbB was also correlated with pressure difference(systolic pressure-diastolic pressure). 4. There were no significant increase of systolic, diastolic pressure and pressure difference by the increase of PbB and ZPP grouping. 5. Stepwise multiple regression analysis using systolic pressure as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness (weight*0.9/height-100) as independent variables, revealed that PbB, age, drinking habit and fatness in order were significantly contributed to the dependent variable. 6. Stepwise multiple regression analysis using diastolic pressure as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness (weight*0.9/height-100) as independent variables, revealed that ALAU, age and fatness in order were significantly contributed to the dependent variable. 7. Stepwise multiple regression analysis using pressure difference as dependent variable and PbB, ZPP, ALAU, age, work duration, smoking habit, drinking habit and fatness(weight*0.9/height-100) as independent variables, revealed that PbB, age and fatness in order were significantly contributed to the dependent variable. 8. Logistic analysis of hypertensive conditions with categorized blood lead and other selected categorized independent variables indicated that only age(40> and 40≤) and fatness(1.0> and 1.0≤) were significantly contributed to dependent variable with 95% significant odd ratio confidence interval. With above results, lead exposure in terms of blood lead seemed to be minimally contributed to the raise of blood pressure, and the effect of blood lead was found to be more prominent on the pressure difference than the systolic and diastolic pressure themselves.

알루미늄合金(A5052-0) 熔接部의 疲勞破壤擧動에 關한 實驗的 硏究

李龍福,元光浩 弘益大學校 1985 弘大論叢 Vol.17 No.2

This research deals with Aluminum-Alloy (A5052-0) weldments. In this research the following conclusions are obtained. 1. when the fatique crack in heat affected zone propagates to base metal zone, total life is long in the following order, base metal, unrestrained weld metal, restrained weld metal, and fatigue crack growth rate is low in the same stress intensity factor range in the following order, base metal, unrestrained weld metal, restrained weld metal. 2. when the fatigue crack in base metal zone propagates to heat affected zone, total fatigue life is long in the following order, restrained weld metal, unrestrained weld metal, base metal, and at first time crack growth rate on base metal is higher than in weld metal but lower at the middle of specimen. 3. In E.C.T. specimen and C.C.T. specimen residual stresses in weldments largely act on fatigue behavior and in E.C.T. specimen mechanical properties of bead zone extend total fatigue life.

SM45C鋼 熔接部의 殘留應力에 依한 疲勞破壞擧動

李龍福,金鍾鉉,金相準 弘益大學校 1987 弘大論叢 Vol.19 No.2

Fatigue fracture behaviors of submerged arc welded SM45C steel were investigated when a crack propagated from tensile residual stress region. The experimental values were compared with the values expected by the Forman equation. The results are summarized as follows: 1. When the fatigue crack was propagated the experimental values were found to corresponded to the values predicted by Formane quation. 2. The experimental values in weld metals have a little difference to the values expected by Forman equation. It was assumed that residual stresses were relaxed by repeated tensile loading. 3. The higher stress ratios were, the larger the difference of fatigue crack growth rate always were in the Same stress intensity factor range for each stress ratios. Particularly, these differences of fatigue crack growth rates were smaller in weld metal than in base metal. It agrees with the fact of that the difference of .effective stress ratios for each stress ratios is small.

STS304 용접재의 피로거동에 관한 연구

李龍福,鄭鎭成,李柱翰 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.1

In this study, fatigue crack behaviors of STS304 weldment were invesgated when a crack propergated from tensile residual stress region or compressive residual stress region. Crack gowth rates were predicted and compares with experimental result. The experimental results are summarized as follows : 1. For the crack propagation from tensile residual stress region, the maximum residual stress at the crack tip redistributes greater than for the initial residual stress, and the point where the residual stress converted from tension to compression is transferred along the direction of cracking. 2. In the case of fatigue crack propagation from tensile residual stress region, the prediction line of crack growth rate by the initial residual stress declines sharply after middle region and the prediction line by the redistributed residual stress more approaches the experimental results. 3. The fatigue crack from compressive residual stress region has very low fatigue crack growth rate compare with the tensile residual stress region. Because it has low effective stress ratio in compressive residual stress region and it is not almost relaxed compressive residual stress during the cyclic loading. 4. The predicted fatigue crack growth rates considering effects of crack closure are in better agreement with the experimental results, in spite of variation of the residual stress. But there are regions where affected by material properties.

후방압출 공정에서 금형과 제품변형 관계에 대한 연구

이강희,박용복,박태식 公州大學校工科大學生産技術硏究所 1999 論文集 Vol.7 No.-

The die for cold forging gets a very high axial load and radial pressure during processing and hence deforms considerably in the radial direction. This radial deformation of die becomes a important factor influencing the dimensional accuracy of a product. In order to obtain a product with highly accurate dimension. Therefore, it is essential to acquire some information on elastic deformation of the die and the product. The study has been performed for the relation of the deformation between a die and a product in backward extrusion. The strain of the die has been given by the simple experiment using the strain gauges attached to the outer surface of the die. Also the history of the deformation of the die and the product has been given by the experiment and Lame's formula. The results has been compared with the previous another method. The study has given useful results for the deformation history of the die and the product through the experiment and Lame's formula in backward extrusion, which can be applied in the die design for the product with accurate dimension.

中炭素鋼 熔接部의 熱處理에 따른 機械的 性質에 관한 硏究

李龍福,金柄旭,康仁燦 弘益大學校 1982 弘大論叢 Vol.14 No.2

Strength of the weld zone is influenced by many complicated factors, such as welding conditions, constraint, materials, etc. Especially, Residual Stress plays an important role for mechanical properties in the weld zone. In this paper, the stress relief effect on the residual stress of the weld zone was examined under various annealing treatment. The results obtained are as follows. 1.Tensile strength on welding decreased 5.7%, 11.4% and 15.3% with increased annealing temperature from 650℃ to 850℃. 2.Absorbed lmpact energy increased in turns of Bond Zone, Base Metal, Fusion Zone and H.A.Z(Heat Affected Zone) and decreased with increasing of the annealing temperature 650℃, 850℃. 3.Reisdual Stress on welding was reduced by the ratio of 65%, 82.5%, 90% with the increased annealing temperature from 650℃ to 850℃. 4.It may be concluded that the best result of the annealing was obtained at 650℃.

Plasmid DNA의 세포전이에 대한 PEI 분자량의 영향

이경만,김인숙,이용복,신상철,오인준 한국약제학회 2005 Journal of Pharmaceutical Investigation Vol.35 No.1

Polyethylenimine (PEI) has been used as cationic polymers for efficient gene transfer without the need for endosomolytic agents. Various kinds of PEIs with different molecular weight were tested in order to investigate the effects of the molecular weight of PEI on the transfection efficiency and cell cytotoxicity. The [3-galactosidase expression (pCMV-13-gal) plasmid was used as a model DNA. Complex formation between PEI and pDNA was assessed by 1% agarose gel electrophoresis method. Particle size and zeta-potential of complexes were determined by electrophoretic light scattering spectrometer. In vino transfection efficiency was assayed by measuring (3-galactosidase activity. Cell cytotoxicity was deter-mined by MTT assay. Particle sizes of the complexes became smaller on increasing molecular weights of PEI and N/P ratios. Surface potential of complexes was increased as the molecular weight of PEI increased. Transfection efficiency of pCMV-[3-gal on the HEK 293 cells was greatest with PEI 25 K system but having the lowest cell viability. PEI with high molecular weight showed higher transfection efficiency and cell viability than PEI with low molecular weight.

龜裂닫힘 影響을 考慮한 表面疲勞龜裂 特性에 관한 硏究

李龍福 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.4 No.-

In this study, to evaluate the chraracteristics of fatigue crack propagation from the surface of material general structual rolled steel(ss41) was used, which was machined with surface pit shaped defects with different depths and radii. Surface fatigue crack characteristics considered crack closure effect could be well evaluated by experiments. The experimental results are summarized as follows: 1. The surface crack was varied to semicircular shape until a plate thickness ratio reachs 0.4 times and then become semi-elliptical shape. It could be expressed the fatigue crack shape by following equation. ?=1.0-0.67(?)+0.49(?)² 2. As the surface fatigue crack propargate, crack closure effect increases and has maximum value near crack depth with 0.5mm to 2mm and then decreases until it has bean constant value near crack depth ratio with 0.35 to 0.closure factor has 0.87 in the surface direction and 0.9 in the depth direction. 3. Considering the crack closure effect, it could be tacken crack closure ratio. ?=1.04 in both surface direction and depth direction and predicted characteristics of the surface fatigue crack correctly by using it.

고능률 소형 전자석에 의한 자왜 및 자기이방성 측정

이용호,신용돌,김병걸,민복기,송재성 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-

자왜 또는 자기이방성의 측정에 사용되는 전사석의 여자전류를 측정에 필요한 수초간만 흘려서 에너지 소모 및 측정시의 최대난점인 시료의 온도변화의 문제를 극소화하였다. 따라서 전자석의 냉각장치는 생략되고 크기와 전원의 용량도 극소화되었다. 공기간격 22㎜, 자극의 단면적 40 × 25㎟에서 0.5 T의 자장발생에는 180 W의 전원으로 족하였다. 시료의 자왜와, 자기이방성에 의한 토크를 전기용량센서에 의하여 측정하여 10^-8의 자왜분해능과 1 nJ의 토크 분해능을 얻었다. 0.02× 0.8× 10㎟의 연자성 리본의 형상이방성을 이용하여 이방성 측정시의 토크값을 교정하였다. A high efficiency small electromagnet(22㎜ air gap and 40 × 25㎟ core's cross section) suitable for measuring magnetostriction and magnetic anisotropy was built. The magnet could be miniaturized by reducing the measuring space and time. The excitation current of the electromagnet was supplied for only a few second of small. An 0.5 T magnetic field was generated with 180 W power consumption. The values of magnetostriction and magnetic anisotropy were measured with a very sensitive capacitance cell with resolution of 10^-8 and 1 no. The torque was calibrated using a soft magnetic ribbon's shape anisotropy.

FCAW 십자형 용접재의 피로거동에 관한 연구

李龍福,吳炳德 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

The influence of weld size(l/t) and specimen geometry(a/w) on fatique life and fatique crack growth rate of flux cored arc welded(FCAW) cruciform joints, containing lack of penetration(LOP) defects, has been studied experimentally. It was found that fatique life of the weld joint increases with the larger weld size(l/t) and the smaller specimen geometry(a/w) and exhibits significant variations in low stress region. the crack growth rates are relatively higher with the smaller weld size(l/t) for a constant stress intensity factor range(AK), and are faster with the larger stress intensity factor range. The longer weld leg length appears to be beneficial for the fatigue life in an allowable range of weldment size.