• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.390-397
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• 2019

A mechanical model of band sawing saw frame was established according to an analysis of a commonly used saw-frame structure diagram to overcome the problems of low service life, substandard cutting precision and efficiency, and high manufacturing cost caused by the unreasonable design of saw frame. Taking a particular type of sawing machine as an example, stress cycle analysis of the saw blade was carried out according to the mechanical model of the saw frame, and the fatigue analysis model of the most dangerous cross-section point that was most prone to fatigue failure of the saw blade was then established. The fatigue analysis result was used as the basis for the improved design of the saw frame, and the improved detailed saw-frame design parameters were obtained. The results suggested that the saw frame system is much more compact and the saw blade force met the fatigue strength requirements through the improved design. In addition, the service life of the saw blade and the cutting precision were increased. The established mechanical model of the saw frame in this paper is used widely and has high practical application values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.644-649
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• 2017

In the automobile industry, there is growing demand for lightweight vehicles due to environmental problems and rising oil prices. Therefore, aluminum alloys and special materials are being used to reduce the weight of vehicles, but there are still many difficulties to overcome in terms of cost and strength. Therefore, the application of advanced high strength steel (AHSS)is increasing. AHSS has good strength and formability.Safety regulations are becoming stricter, and 1.2-GPa super-high-strength steels are gradually being applied for the center pillar and roof rails. Thus, the application of different kinds of steels in automobile bodiesis also increasing gradually. This study evaluates the resistance point weldability and the characteristics of a welded part of SGAFC1180 1.2t steel. A simulation was used to observe the nugget formation and its growth behavior. The prediction performance showed a similar tendency within an error rate of 10%. Also, the effect of this behavior on the process resistance and dynamic resistance was investigated,along with the correlation between the shear tensile strength and nugget diameter.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.4
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• pp.246-252
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• 2015

In steel factory, hot roller cleaning process produces a lot of iron oxide particles called as mill scale. Major components of these particles are wustite (FeO), magnetite ($Fe_3O_4$), and hematite ($Fe_2O_3$). In this study, we tried to produce pure magnetite from the mill scale because of the largest phosphate adsorption capacity of the magnetite. The mill scale was treated with acid (HCl+$H_2O_2$), base (NaOH), and acid-base ($H_2SO_4$+NaOH). Batch adsorption tests showed the acid and/or base treatment could increase the phosphate adsorption capacity of the iron oxides from 0.28 to over 3.11 mgP/g. Magnetite, which could be obtained by acid and base treatment of the mill scale, showed the best adsorption capacity. From the kinetic analysis, both Freundlich and Langmuir isotherm well described the phosphate adsorption behavior of the magnetite. In Langmuir model, maximum phosphate adsorption capacity was found to be 5.1 mgP/g at $20^{\circ}C$.

• Journal of Preventive Medicine and Public Health
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• v.24 no.4 s.36
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• pp.496-506
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• 1991

A cross-sectional study was conducted to investigate the effect of long term noise exposure on blood pressure among steel mill workers. The workers participated in periodic medical examinations performed from August 27 to September 6 in 1990. Examined were 1,034 workers with high-level noise exposure(average $91.8{\pm}5.2dB(A)$) and 390 workers with low-level noise exposure(average $75.2{\pm}4.6dB(A)$). No significant difference was found in systolic or diastolic flood pressure between the two exposure groups. Prevalence of hypertension (${\geq}160mmHg\;systolic\;or{\geq}100mmHg\;diastolic$) was higher in a younger age group (${\leq}40$ years old) of high-level noise exposure than of low-level noise exposure. However, the difference was not statistically significant. Furthermore, in younger ages, prevalence of hypertension appeared to be higher in the hearing loss group (${\geq}25dB\;at\;1000Hz\;or{\geq}40dB$ at 4000Hz in at least one ear) than in the normal hearing group. From multiple regression analysis, hearing loss, body mass index, age, alcohol and family history of hypertension were proven to be predictors of diastolic blood Pressure (p<0.02). When regression was performed for each age group, hearing loss was a strong predictor of diastolic pressure in the younger age group (p<0.01).

• Journal of Preventive Medicine and Public Health
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• v.29 no.1 s.52
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• pp.113-131
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• 1996

This study was carried out to evaluate the relations among workers' general characteristics, work-related behaviors and health related behaviors in a steel industry with 1,134 workers in Pohang. The results were as follows; 1. The mean age of workers was 50 years old and working duration was 15 years and over. Most of them were married(94.5%) and had studied beyond high school (53.0%). They performed three shift work and most of them(63.0%) had experienced industial accidents. The frequency of noise and dust exposure was defined by a minimum of 6 hours per day, and workers complained about noise exposure(62.9%) and dust(55.6%). There were current smokers(67.7%), current drinkers(74.3%) and current exercising workers(32.3%) in the industry. The number of cigarette consumption in current drinkers was significantly high $(13.6{\pm}8.4\;pieces/day)$ and the alcohol consumption in current smokers was significantly high$(104.5{\pm}113.5\;g/wk)$. And the number of cigarette consumption of exercisers was significantly low and the alcohol consumption of exercisers was higher than non-exercisers. 3. The ratio of current smokers on frequent noise in exposed workers versus non-exposed workers was not significantly high but the current drinkers in frequent noise and dust exposed workers was significantly higher than non-exposed. 4. The normal levels of SGOT workers in non-smokers were significantly higher than in current smokers, and the normal levels of LFT (SGOT, SGPT, $\gamma-GTP$ workers in nondrinkers were significantly high. The normal levels of SBP and DBP workers in current smokers were not significantly high but were significantly high in non-drinkers. 5. The ratio of current smokers in voters unsatisfied with their job and working condition was higher than non-smokers, but the ratio of current drinkers in workers satisfied with their job and working condition were higher. 6. The significant factors for SGOT and $\gamma-GTP$ were age, the drinking amount and BMI. But the only significant factor for r-GTP was BMI. The significant factors for DBP were age, the alcohol consumption and BMI. And the significant factors for SBP were age, BMI.

• Journal of Preventive Medicine and Public Health
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• v.26 no.3 s.43
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• pp.371-386
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• 1993

This study was carried out to evaluate diagnostic criteria of noise-induced hearing loss (NIHL) among-workers in an iron foundry. Of 1,093 workers under the observation of noise-specific health examination, 184 workers were selected by way of first and second screening audiometric examination. A questionnaire survey, otological examinations, Rinne test and audiometric test were performed and the results were as follows ; The degree of hearing impairment in the left ear was more severe than in the right ear (p<0.05). The difference between hearing threshold of the first and the second hearing test at 1,000 Hz was about 5 dB with a narrow range of deviations while the difference at 4,000 Hz was about -7 dB with a wide range. Of the total study workers, 84.8% were tested within 15 hours away from noise exposure, and the rest after 16 hours. This study has identified that mean hearing loss at 4,000 Hz showed a significant statistical difference among the two study groups while mean hearing loss by 4-divided classification did not. The same phenomena were observed between the group with and without tinnitus and between the group with and without difficulty in hearing (p<0.05). Among 184 workers, 10 workers (5.4%) diagnosed as NIHL by old diagnostic criteria in contrast to 150 workers diagnosed as NIHL by the new diagnostic criteria. There was a significant difference between the two groups in the average hearing loss at 4,000 Hz and 4-divided classification (p<0.01), but there were no significant differences in age, the duration of employment, blood pressure and the duration wearing the personal hearing protector (p>0.05). If we apply Early Loss Index (ELI) method, some workers in younger age group diagnosed as NIHL by the new diagnostic criteria were fallen into within the normal range. In the mean time older age group show reverse results in contrast to the above finding. It is too early to confirm the value of the usage of the new diagnostic criteria in hearing examination. Further study is called for to verify the value of this criteria.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.315-319
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• 2015

A high-throughput electrorefiner has been developed for commercialization use by enhancing the uranium recovery from the reduced metal which is produced from the oxide reduction process. It is necessary to scrap and effectively collect uranium dendrites from the surface of the solid cathode for high yield. When a steel electrode is used as the cathode in the electrorefining process, uranium is deposited and regularly stuck to the steel cathode during electrorefining. The sticking coefficient of a steel cathode is very high. In order to decrease the sticking coefficient of the steel cathode effectively, vibration mode was applied to the electrode in this study. Uranium dendrites were scraped and fell apart from the steel cathode by a vibration force. The vibrational scraping of the steel cathode was compared to the self-scraping of the graphite cathode. Effects of the applied current density and the vibration stroke on the scraping of the uranium dendrites were also investigated.

• Journal of the Korean association of regional geographers
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• v.2 no.2
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• pp.19-36
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• 1996

This study is to examine the remained basis and the locational characteristics of manufacturing in Chonnam region. First, the locational characteristics of manufacturing in the peripheral region examined through theoretical discussions about manufacturing location. And the locational characteristics of the small and medium firms and large firms be studied as to understand the precedent characteristics of Chonnam region. Chonnam region have the precedent characteristics that the regional capital is not accumulated as Japen exploit agricultural products at a colonial period. And SOC, industry and technology are not developed as geographically Chonnam lesion turn aside the economics axis of Korea-Japen-America within a period of industrialization. Manufacturing firms have beer make up the traditional indigenous firms which base on local market, agriculture and marine products in Chonnam lesion. The characteristics of these firms mainly are food & drink, nonmetal industry that is composed of the small and medium sized firms. The industrial structure is changing to machinery, chemistry, electronics industry from food & drink, nonmetal industry. But these industry is making the simple products. In Chonnam region, these change of industrial structure was expanding to the inland or coast region from the neighhoring region of Kwangju metropolitan. The blanch factories of large enterprises that located in Chonnam region are not connected with small and medium sized firms. The small and medium sized firms are not developed. Because these large enterprises are the iron and steel industry or chemistry industry. So the large-manufacturing firms have characteristics of the capital intensive industry, and make up the monopolistic industrial space of fordist blanch factories.

• Economic and Environmental Geology
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• v.48 no.5
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• pp.391-400
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• 2015

Korea is a global steel producer and a major consumer while iron ore producing is very low compared to the demand. On the other hand, North Korea holds tremendous amount of iron reserves and, however, its producing rate is limited. Moreover, the data regarding mineral resources of North Korea is very limited and uncertain because of political isolation. This study estimated the amount of iron ore resource and production amount for the Musan Iron mine, the world-known open-pit mine of North Korea, using satellite imagery(Landsat MSS, ASTER) and digital maps between 1976 to 2007. As a result, the mining area of Musan mine was increased by $6.1km^2$ during the 30 years and the mining sector was estimated as $4.9km^2$. We estimated the iron resources and production amount of 0.7 and 0.2 billion metric tons, respectively based on 3D modeling and average iron ore density of Anshan formation in China. This amount indicates 8.1 million tons of annual average production and it coincides well with previous reports. We expect this study would be utilized significantly on inter-Korean exchange programs by providing trustable preliminary data.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.96-96
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• 2018

금속재료 중 알루미늄(Al)은 일반적으로 많이 사용되는 철강재에 비해 그 비중이 약 $1/3(2.7g/cm^3)$인 경량이고 열전도율이 약 3배($196kcal/^{\circ}C$, $20^{\circ}C$)로 높은 특성 등을 갖고 있다. 또한 대량생산에 의한 경제성을 가지기 때문에 건축 구조재, 전기 및 가전 등 다양한 산업 분야에서 널리 사용되고 있다. 특히, 위와 같은 특성으로 인해 열교환기의 종류에서 응축기(Condenser) 및 증발기(Evaporator)는 알루미늄(Al)을 널리 사용하고 있다. 하지만 단일 응축기 부품에도 이종 알루미늄 소재가 사용됨에 따라 갈바닉 부식이 발생할 수 있다는 단점이 있다. 따라서 본 연구에서는 현재 상용되고 있는 열교환기 중 응축기에서의 이종 알루미늄 재료로 인해 나타나는 갈바닉 부식 특성을 관찰-분석-연구 하였다. 본 연구에 사용된 알루미늄 재료는 현재 응축기 재료 중에서 각각 Tube와 Fin으로 널리 상용되고 있는 Al 1100과 Al 3003을 사용하였다. 표면 모폴로지는 SEM을 통해 관찰하였고 EDS를 통해 조성원소를 분석하였다. 또한 내식성 평가를 위해 5% NaCl 환경에서의 SST(Salt spray test, 염수분무시험) 시험과 3% NaCl 용액 내 자연침지 시험 및 탈기된 3% NaCl 용액 내 전기화학적 동전위 양극 분극 시험을 진행하였으며 더불어 갈바닉 부식 시험에 따른 혼합 전위 측정 및 외관 관찰을 하였다. 각 재료는 실험에 대해 동일한 표면적을 노출시켜 시험하였다. 5% NaCl 환경에서의 염수분무 시험 결과 Fin(Al 3003)의 경우에는 Tube(Al 1100) 보다 빠른 부식거동을 보이며 국부적인 공식부식(Pitting corrosion)이 촉진되었다. Tube(Al 1100)의 경우에는 치밀한 Al2O3 형성과 부식에 따른 Al(OH)3를 생성함에 따라 Fin(Al 3003)에 비해 느린 부식거동을 보였다. 3% NaCl 용액 내 자연 침지 및 전위 측정 결과 초기 전위는 Fin(Al 3003, 약 -0.85V/SCE)이 Tube(Al 1100, 약 -1.05V/SCE)에 비해 더 높은 값을 가지며 약 72시간 이후 Tube(Al 1100) 시편이 더 안정적인 전위 값을 나타냈다. 이는 안정적인 Al(OH)3 피막 형성에 기인한 것으로 사료된다. 탈기된 3% NaCl 용액 내 전기화학적 동전위 양극 분극 시험 결과 Fin(Al 3003) 시편에서 더 귀한 부식 전위 값을 나타냈지만 부식 전류는 더 낮은 값을 나타냈다. 상기 시험 결과를 바탕으로 Fin-Tube 간 장기간 접촉 시에는 갈바닉 부식이 발생할 수 있을 것으로 사료된다. 갈바닉 부식 시험 결과 초기 혼합 전위는 약 -1.05 V/SCE를 나타냈으며 약 288시간 경과 후 약 -0.85 V/SCE 값을 나타냈다. 이는 자연 전위 측정 및 동전위 양극 분극 시험에서의 부식 전위 값에서 알 수 있듯이 더 비한 전위인 Tube(Al 1100) 시편이 Fin(Al 3003) 시편에 대해 희생양극적(Sacrificial anode)인 역할을 한 것을 확인할 수 있었다. 또한 갈바닉 부식 전위 측정 간 외관 관찰에서도 Tube(Al 1100) 시편은 빠르게 흑변 하는 것을 확인할 수 있었으며 Fin(Al 3003) 시편은 침지 300시간 이후에도 초기와 유사한 표면 상태 및 광택을 유지하였다. 이상의 SST 시험, 자연 침지 시험, 전기화학적 양극 분극 시험 및 갈바닉 부식 시험 결과를 바탕으로 단일 부품 내 이종 알루미늄 소재 간 접촉 및 그에 따른 갈바닉 부식 발생을 확인할 수 있었다. 따라서 동종 성분이라고 할지라도 단일 부품 제작 시에는 그 사용 환경에 따라 이종 금속 재료의 사용에 대한 재고가 필요할 것으로 사료된다.