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.

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.

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.

장상피화생과 Helicobactor pylori와의 상관 관계에 관한 연구

이복희,김대수,이현숙,진영주,윤세진,송형근,성노현,정현용,이동호 충남대학교 의과대학 지역사회의학연구소 1994 충남의대잡지 Vol.21 No.2

In 1965 Lauren divided advanced gastric carcinoma into two main types-namely, "intestinal" and "diffuse" type carcinoma, which differ not only morphologically but also in their clinical and epidemiological characteristics. Moreover, a different histogenetic process has been postulated by many authors that intestinal type gastric carcinoma might arise from areas with intestinal metaplasia. Since Warren and Marshall reported the presence of Helicobacter pylori in the stomach in 1983, strong evidence has been obtained that there is a close relationship between Helicobacter pylori and chronic gastritis, atrophic gastritis, intestinal metaplasia, and intestinal type gastric carcinoma. To study the relationship between intestinal metaplasia and Helicobacter pylori infection, we performed gastroscopic biopsies and CLO tests taken from patients with epigastric pain. Only 87 patients with macroscopically suspected antral gastritis were included. The prevalence of intestinal metaplasia in gastric antral biopsies increased from 33.3% in the age group<30 years to 63.6% in the age group 60 years. When all patients were divided into two age groups-namely, (i)<50 years(n=41) and (ii)≥ 50 years(n-=46), intestinal metaplasia was found significantly more often in patients ≥ 50 years. ((i) 39.2%, (ii) 54.3%, p<0.0001). The prevalence of Helicobacter pylori in gastric antral biopsies decreased from 66.7% in the age group<30 years to 62.5%, in the age group in the age group 50 to 59 years. When all patients were divided into the same two age groups-namely(i)<50 years and (ii)≥50 years, the prevalence of Helicobacter pylori did not differ between two groups in a statistically significant way. The mean age of intestinal metaplasia positive patients who were also Helicobacter pylori positive was 48±11.0(mean±S.D.)years, whereas the mean age of intestinal metaplasia positive patients who were Helicobacter pylori negative was 52±9.7(mean±S.D.)years. In conclusion. although our data do not prove a causal relationship between Helicobacter pylori infection and the histogenesis of intestinal metaplasia, we suggest that Helicobacter pylori plays an important role in the development of intestinal metaplasia in the gastric mucosa. Whether Helicobacter pylori has to be present at all times during this process or is only necessary as a 'trigger', needs further research.

表面缺陷 形狀에 따른 疲勞龜裂進展 特性에 관한 實驗的 硏究

李龍福 弘益大學校 科學技術硏究所 1992 科學技術硏究論文集 Vol.2 No.-

In the current study, a general structural mild steel (SS41) was used of understand the characteristics of fatigue crack and its life evaluation on surface defect, which was machined for surface defect with different shapes. The characteristics of fatigue crack propagation and its life evaluation, during a surface crack initiation from the defect and its propagation, were understood. The experimental results are summarized as follows ; 1. For the surface crack propagation, due to a close relationships between crack length c and depth a, the change in aspect ratio as characteristics of surface crack propagation can be expressed by either the crack depth(a) or the length(c). 2. The aspect ratio of surface crack was varied with fatigue crack propagation. In other words, the ratio was affected by an initial aspect ratio (??) when the thickness ratio (a/t) was 0.4. And then its shape was changed into a semicircular and an ellipitcal one continuously. In this region the ratio the ratio was converged into the following equation regardless of initial defect shape. a/c = 1.4 - 1.43 (a/t) + 0.64 (a/t)² 3. For all initial defect shapes, the total fatigue life on stress ratio R is increased in the case of R=0.3 rather than in R=0.1. It was revealed that the effects of initial defect shape on the total fatigue life of a surface defected member was not constant. 4. In a stable crack growth region (region Ⅱ), the crack growth rates (dc/dN, da/dN) in a direction of length and depth, respectively, as a function of stress intensity factor range ΔK, were scattered over all ΔK range due to the effects of stress ratio R. The effect of stress ratio R were decreased with increase of ΔK. 5. The fatigue crack growth rates (dc/dN, da/dN) and stress intensity factor range ΔK can be related using Paris' equation. The values of index in the equation were in the range 2.54 - 6.89. The values in the direction of length ?? were larger than the value in the direction of depth ??.

정책북한의 대외교역 구조적 특징

이원복,이용삼 국제무역학회 2001 국제무역연구 Vol.7 No.2

북한의 대외경제정책은 국가독점의 원칙, 자급자족경제의 원칙에 입각하여 자립경제 건설의 완성을 위한 보조적 수단으로 간주해 왔으므로 무역의존도는 높지 않았다. 따라서 자립적 민족경제 건설을 상위개념으로 경제발전에 꼭 필요한 상품을 수입하고 그에 필요한 외화를 얻기 위해 상품을 수출하는 것을 기본으로 하고 있다. 그러나 사회주의권의 붕괴로 대외경제협력의 기반이 상실돼 대외무역액이 급격하게 감소하게 되고 북한의 주요 원조국이었던 러시아와 중국마저 구상무역에서 경화결제로 전환함에 따라 북한은 대외무역의 중요성을 점차 인식하게 되었다. 북한은 이러한 경제난을 극복하기 위하여 개방과 개혁을 통한 대외관계 개선으로 교역규모를 확대하고 있다. 북한의 대외교역 규모는 2000년도에 전년대비 33.1% 증가하여 북한경제의 회복을 보여주고 있으며 교역상대국의 다변화를 위하여 노력하고 있으나 수출입물자를 수송할 인프라구축이 열악하여 수송이 용이한 아시아, 유럽과의 교역이 98.5%로 지역별 편중이 심한 무역구조를 가지고 있다. 국가별로는 중국, 일본이외에 태국, 인도 등의 동남아시아 국가들과의 교역이 급속히 증대되고 있다. 그리고 북한의 주요수출상품은 섬유, 전기·전자, 기계류, 수산물, 비금속, 광물, 플라스틱, 농임 산물 등이며 주요수입상품은 기계 및 전기·전자, 섬유, 에너지물자, 식량, 운송기기, 플라스틱, 화학공업제품 등으로 구성되어 있다. This paper represents the structural characteristics on foreign economic policy of North Korea by analyzing the status of trade and relations with foreign countries. The trade dependence of North Korea has not been high until 1980's before destroying socialism system since they import only necessary commodities for building self-economy. However the economic conditions of North Korea have the experience of minus growth and serious difficulties economically which is caused due to inefficient economic policy and due to destroying socialism system. Therefore this paper analyzes the current status of trade and structural characteristics of North Korea to understand how they are going to overcome their difficulties economically by opening economy positively.

용접방법에 따른 하중전달 십자형 필렛 용접부의 피로특성

李龍福,吳炳德 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-

In this study, it was investigated about endurance limit and fatigue behavior of load carrying fillet welded cruciform joints according to welding methods of SMAW, SAW, MIG and FCAW commonly using for welding structures in present. Endurance limit carried out highly in the order of SMAW, MIG, SAW, FCAW and fatigue crack propagation ratio carried out lowly in the order of SMAW, MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures after due consideration about economic gains and operation efficiency of welding. Fatigue crack propagation ratio is more effected by strength of welding materials than endurance limit of welding materials according to welding methods.

강 봉 맞대기 용접부의 피로 및 파단 특성

이용복 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-

SM45C steel rods using generally for machine components was selected and welded by butt-GMAW method for this study. And then it was studied about characteristics of fatigue behavior and fracture surfaces by rotary bending test. Fatigue strength in weld zone presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. The region of infinite life by Haigh diagram presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. Fatigue cracks in unnotched specimens of base metal and weld zone introduces simultaneously from extensive out-side of circumferential cross-sections and propagates to the other side indicating beach markings and dimples according to consolidation of fatigue cracks. Fatigue cracks in all of notched specimens introduces simultaneously in out-side of circumferential cross-sections by high stresses and propagates to center of it indicating beach markings.

SICM616鋼 熔接部의 疲勞龜裂傳播速度에 있어서 殘留應力의 效果에 關한 實驗的 硏究

李龍福,金豪敬 弘益大學校 1984 弘大論叢 Vol.16 No.2

The following conclusions can be drawn from comparisons of fatigue crack growth rates in the weld metal and base metal of high strength steel. 1. Crack growth rates in weld metal are slower than those in base metal at low ΔK. 2. Crack growth rates in weld metal and base metal are almost identical at R=0.5. 3. The lower the stress ratio, the higher the residual stress effect, and higher stress ratio cause greater residual stress relaxation.

Al 2024-T4 熔接部의 殘留應力이 疲勞破壞擧動에 미치는 影響

李龍福,金鐘鉉 弘益大學校 1986 弘大論叢 Vol.18 No.2

Fatigue fracture behaviors were investigated by using the TIG welded aluminum alloy such as high-strength Al2024-T4 which are widely used in aero-space industry. The fatigue crack propagation was closely examined in both from tensile residual stress region towards compressive residual stress region and from compressive residual stress region towards tensile residual stress region. The experimental results are summarized as follows: 1. In case of fatigue crack propagation from tensile residual stress region, the values predicted by the Forman equation were found to be exactly corresponded to the experimental values. 2. In case of fatigue crack propagation from compressive residual stress region, the Forman equation was found improper to apply directly, but the equation was found proper, if the stress ratio was modified to zero. 3. It was found that crack propagation speed at tensile residual stress region was greater in restrained welding than in unrestrained welding, While crack propagation speed at compressive residual stress region was the same, both restrained welding and unrestrained welding.