• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.940-948
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• 2012

In Korea, researches on the exposure assessment of the hand-transmitted vibration started from the mid-90, however, they were performed in the limited industries such as auto-assembly plants and the evaluation of the vibration was mostly conducted by ISO 5349(1986). Therefore, it was necessary to assess hand-transmitted vibration levels of workplace such as ship building/repairing industry or mining industry where occupational injuries are largely occurred and to evaluate the vibration levels using revised ISO 5349(2001). The SVAN 948 Four Channels Sound & Vibration Analyser was used for the measurement. The workers using a chain saw were exposed to 1.7~2.8 $m/s^2$ of daily vibration level. Workers using a rock drill in a coal mining were exposed to the highest vibration acceleration among workers and the levels were 7.1~10.8 $m/s^2$. Vibration levels of grinders were different according to the types of grinders. The hand-transmitted vibration of 3 types of grinders were measured and the levels were 3.3~11.1 $m/s^2$. Workers using a impact wrench were exposed to 1.5~1.6 $m/s^2$ of vibration. Out of 20 kinds of machines, only 4 tools provided the information of vibration acceleration on the instructions. In addition, the current condition of workplace to control vibration was not much different from the past because there are no vibration exposure limit.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.349-358
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• 2021

The Brazilian test has been widely used to determine the indirect tensile strength of rock, concrete and other brittle materials. The basic assumption for the calculation formula of Brazilian tensile strength is that the elastic moduli of rock are the same both in tension and compression. However, the fact is that the elastic moduli in tension and compression of most rocks are different. Thus, the formula of Brazilian tensile strength under the assumption of isotropy is unreasonable. In the present study, we conducted Brazilian tests on flat disk-shaped rock specimens and attached strain gauges at the center of the disc to measure the strains of rock. A tension-compression bi-modular model is proposed to interpret the data of the Brazilian test. The relations between the principal strains, principal stresses and the ratio of the compressive modulus to tensile modulus at the disc center are established. Thus, the tensile and compressive moduli as well as the correct tensile strength can be estimated simultaneously by the new formulas. It is found that the tensile and compressive moduli obtained using these formulas were in well agreement with the values obtained from the direct tension and compression tests. The formulas deduced from the Brazilian test based on the assumption of isotropy overestimated the tensile strength and tensile modulus and underestimated the compressive modulus. This work provides a new methodology to estimate tensile strength and moduli of rock simultaneously considering tension-compression bi-modularity.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.6
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• pp.387-397
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• 2020

The purpose of this study is to determine the effect of work motivation and leadership on job satisfaction and its implications on employee performance. A total of 355 samples of Bukit Asam Coal Mining Company Ltd. in Indonesia were selected proportionally with random sampling. Data were obtained through questionnaires. Data analysis technique employed structural equation modeling (SEM) with AMOS 22. The results of the study show that leadership and work motivation have a positive and significant effect on job satisfaction. Leadership has a more considerable influence (0.263) than work motivation (0.171) toward employee job satisfaction. The influence of leadership towards job performance is 0.175. The influence of work motivation towards job performance is 0.166. Job satisfaction has the most dominant influence (0.363) towards employee performance. The direct effect of leadership on employee performance is 0.175 greater than the indirect influence of leadership on employee performance through employee job satisfaction, which is only 0.096. Likewise, the direct effect of work motivation towards employee performance is 0.166 greater than the indirect effect of work motivation towards employee performance through employee job satisfaction, which is only 0.062. Thus, job satisfaction does not mediate the effects of leadership and work motivation toward employee performance.

• Korean Business Review
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• v.5
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• pp.31-65
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• 1992

석탄산업은 서민생활보호와 에너지 안보 등 국가정책 목표달성을 위하여 매우 중요한 역할을 하고 있다. 또한 태백지역의 경우에는 석탄산업의 존립이 지역사회의 생존과 직결되고 있어서 이의 활성화가 매우 긴요하다. 그러나 석탄산업은 작업환경이 나쁘고 임금수준 등의 제반 여건이 좋지 않고, 사양산업이라는 인식이 만연되어 있는 관계로 근로자들의 이직율이 높고 신규인력의 유입율도 낮아서 탄광의 운영에 커다란 애로요인으로 등장하고 있다. 본 연구는 이러한 상황에 직면해 있는 태백지역 탄광업체의 인력난을 해결해 보기 위하여 탄광근로자들을 대상으로 설문지를 배포하고 이를 분석하여 그 해결책을 모색해 보고자 했다. 이를 위해서 경로분석과 이원분산분석을 통해서 이직요인을 발견하고 이를 위한 다각적인 대응방안을 구상해 보았다. 연구결과 태백지역 인력난을 완화시키고 노동인력의 정착성을 제고시키기 위해서는 1) 기업내적(企業內的)인 방안(方案)으로 근로생활의 보람(quality of working life) 조성, 기업문화의 조성, 임금제도의 개선과 생산성 향상, 후생복지시설의 개선, 내부적 제도의 개선과 회사운영의 공개, 대외적 홍보, 2) 정부(政府)의 지원방안(支援方案)과 논의사항(論議事項)으로 석탄산업에 대한 재정적 지원, 소비성 서비스업에 대한 노동력 유출억제, 교육여건의 개선 그리고 해외광원수입에 관한 문제는 장애요인이 많으므로 가능한 신중한 검토가 수반되어야 한다는 것 등을 고려할 수 있을 것으로 사료된다.

• Geomechanics and Engineering
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• v.16 no.1
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• pp.35-47
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• 2018

This paper investigates the mechanisms of tunnel spalling and massive tunnel failures using fracture mechanics principles. The study starts with examining the fracture propagation due to tensile and shear failure mechanisms. It was found that, fundamentally, in rock masses with high compressive stresses, tensile fracture propagation is often a stable process which leads to a gradual failure. Shear fracture propagation tends to be an unstable process. Several real case observations of spalling failures and massive shear failures in boreholes, tunnels and underground roadways are shown in the paper. A number of numerical models were used to investigate the fracture mechanisms and extents in the roof/wall of a deep tunnel and in an underground coal mine roadway. The modelling was done using a unique fracture mechanics code FRACOD which simulates explicitly the fracture initiation and propagation process. The study has demonstrated that both tensile and shear fracturing may occur in the vicinity of an underground opening. Shallow spalling in the tunnel wall is believed to be caused by tensile fracturing from extensional strain although no tensile stress exists there. Massive large scale failure however is most likely to be caused by shear fracturing under high compressive stresses. The observation that tunnel spalling often starts when the hoop stress reaches $0.4^*UCS$ has been explained in this paper by using the extension strain criterion. At this uniaxial compressive stress level, the lateral extensional strain is equivalent to the critical strain under uniaxial tension. Scale effect on UCS commonly believed by many is unlikely the dominant factor in this phenomenon.

• The Journal of Asian Finance, Economics and Business
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• v.4 no.2
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• pp.5-17
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• 2017

The main objective of the study is to measure the vulnerability of Indonesia's financial system stability in response to external shocks, including from regional economies namely three biggest Indonesia major trading partners (China, the U.S and Japan) and other external factors (oil price and the federal funds rate). Using Autoregressive Distributed Lag (ARDL) model and Orthogonalized Impulse Response Function (OIRF) with quarterly data over the period Q4 2002 - Q1 2016, results confirm that, 1) oil price response has the largest effect to Indonesia financial stability system and the effect period is the longest compared to others, represented by NPL and IHSG; 2) among those three economies, only China's economic growth has significantly positive effect to Indonesia financial stability system. Based on the findings it is better for the authorities to: 1) Diversify international trade commodities by decreasing share of oil, gas, and mining export and boosting other potential sectors such as manufacture, and fisheries; 2) Ensure the survival of Indonesia large coal exporter companies without neglecting burden of national budget; and 3) Create buffer for demand shock from specific countries by diversifying and increasing share of trading from other countries particularly from ASEAN member states.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.31-38
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• 2002

Bacteria have evolved various types of resistance mechanism to toxic heavy metals, such as arsenic and antimony. An arsenical and antimonial resistant bacterium was isolated from a shallow creek draining a coal-mining area near Taebaek City, in Kangwon-Do, Korea. The isolated bacterium was identified and named as Pseudomonas sp. KM20 after biochemical and physiological studies were conducted. A plasmid was identified and its function was studied. Original cells harboring the plasmid were able to grow in the presence of 15 mM sodium arsenite, while the plasmid-cured (plasmidless) strain was sensitive to as little as 0.5 mM sodium arsenate. These results indicated that the plasmid of Pseudomonas sp. KM20 does indeed encode the arsenic resistance determinant. In growth experiments, prior exposure to 0.1 mM arsenate allowed immediate growth when they were challenged with 5 mM arsenate, 5 mM arsenite, or 0.1 mM antimonite. These results suggested that the arsenate, arsenite, and antimonite resistance determinants of Pseudomonas sp. KM20 plasmid were indeed inducible. When induced, plasmid-bearing resistance cells showed a decreased accumulation $of\;73^As$ and showed an enhanced efflux $of\;^73As$. These results suggested that plasmid encoded a transport system that extruded the toxic metalloids, resulting in the lowering of the intracellular concentration of toxic oxyanion. In a Southern blot study, hybridization with an E. coli R773 arsA-specific probe strongly suggested the absence of an arsA cistron in the plasmid-associated arsenical and antimonial resistance determinant of Pseudomonas sp. KM20.

• Geomechanics and Engineering
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• v.3 no.3
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• pp.219-231
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• 2011

Waste fills resulting from coal mining should consist of large, free-draining sedimentary rocks fragments. The successful performance of these fills is related to the strength and durability of the individual rock fragments. When fills are made of shale fragments, some fragments will be durable and some will degrade into soil particles resulting from slaking and inter-particle point loads. The degraded material fills the voids between the intact fragments, and results in settlement. A laboratory program with point load and slake durability tests as well as thin section examination of sixty-eight shale samples from the Appalachian region of the United States revealed that pore micro-geometry has a major influence on degradation. Under saturated and unsaturated conditions, the shales absorb water, and the air in their pores is compressed, breaking the shales. This breakage was more pronounced in shales with smooth pore boundaries and having a diameter equal to or smaller than 0.060 mm. If the pore walls were rough, the air-pressure breaking mechanism was not effective. However, pore roughness (measured by the fractal dimension) had a detrimental effect on point load resistance. This study indicated that the optimum shales to resist both slaking as well as point loads are those that have pores with a fractal dimension equal to 1.425 and a diameter equal to or smaller than 0.06 mm.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.75-80
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• 2002

Enormous volumes of mining wastes from the abandoned and closed mines are disposed without a proper treatment at Southeastern part of Kangwon Province. Erosion of these wastes contaminates soil, surface water, and sediments with heavy metals. Objectives of this research were to fractionate heavy metals in the mine waste and to assess the potential S. P. A. G.(Soil Pollution Assesment Guidance) of each metal fraction. Mine wastes analyzed for physical and chemical properties. pH of wastes ranged from 3.3 to 8.0. Contents of total N and loss on ignition matter were in the ranges of 0.2~5.6%, and 0.8~15.3%, respectively. Heavy metals in the wastes were higher in the coal mines than those in the other mine wastes. Total concentrations of metals in the wastes were in the orders of Pb > Zn > Cu > Cd, exceeded the corrective action level of the Soil Environment Conservation Law and higher than the natural abundance levels reported from uncontaminated soils. Relative distribution of heavy metal fractions was residual > organic > reducible > carbonate > adsorbed, reversing the degree of metal bioavailability. Mobile fractions of metals were relatively small compared to the total concentrations. Soil Pollution Assesment Guidance(SPAG) values were ranged from 0.08 to 9.14 based on labile fraction of metal concentrations. SPAG values of labile concentration were lower than those of total concentration.

• Journal of the Korean Professional Engineers Association
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• v.19 no.4
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• pp.11-21
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• 1986

Mine drainage from coal mines is mostly acidic, polluted and/or contaminated, even if its quantity has increased substantially during recent days. This causes two kinds of problems arising at mining districts; one is the environmental disruption and the other is insufficient water supply for living, employee's bathing and industrial purposes. In order to mitigate the aforementioned problems, a specific equipment of Korea type for mine drainage purification has been developed and its prototype manufactured, followed by its applicability tests implemented at mine site. The results of the tests indicates that the new equipment developed is much lower than and economical compared to, other existing neutralization facilities at home and abroad in capital investment at installation stage, the consumption of neutralizing chemicals at operation stage and the requirements of installation site. Whangji area where the prototype water treatment equipment is installed has been sustaining a short supply of usable water, especially in dry seasons and supplementing about 40㎥ of water brought from a location farther than 4km in distance to meet water requirements. The prototype water treatment equipment is however considered capable of providing compressor cooling water in sufficient amount from winter season In the future.