• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.250-254
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• 2007

The reduction efficiency of air cleaner on particulate contaminants such as dust, airborne bacteria and fungi distributed in the office was relatively higher in case of office with workers than office without workers. This result would be attributed to workers' activities and physical characteristics of particulate contaminants. The air cleaner decreased a concentration of airborne bacteria more than airborne fungi, which implicates that difference of dust adsorption between airborne bacteria and fungi would affect an operation efficiency of air cleaner.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.28-37
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• 1988

Light scattering coefficient of visible light by atmospheric aerosol over the size range 0.01-10$\mu$m is determined from scattering efficiency and aerosol size distribution. Aerosol number distribution as a function of particle diameter dN/dlog D decreases rapidly as increasing particle size. Distribution of scattering coefficient d$\sigma_s/dlog$ D is mostly accumulated in diameter 0.1-2.0 $\mu$m showing its maximum in the vicinity of 0.6$\mu$m. This means that the visible light in the atmosphere is mainly scattered by these particles. Diurnal variation of scattering coefficient $\sigma_s$ appears its maximum in the morning, while minimum in the afternoon which agrees with the aerosol number distribution in the size range 0.1-2.0 $\mu$m.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1691-1701
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• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.

• KDI Journal of Economic Policy
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• v.26 no.2
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• pp.143-178
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• 2004

For a thorough accounting for economic growth, it is desired to include the working hours and the efficiency of labor as production factors in addition to the number of workers and human and physical capital stocks. This paper estimates the distribution of weekly working hours of total workers as a continuous variable using the maximum likelihood method, estimates the efficiency of labor as a function of working hours using wage statistics, and by combining these results, estimates the labor efficiency index in Korea for the period 1963~2003. Estimation results show that the efficiency of labor was maximized when the weekly working hours was 40 hours, and the average annual growth rate of the labor efficiency for the period 1963~2003 was 0.14 percent.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.76-83
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• 2009

In today's competitive power market, electric power utilities have strived to provide energy at an acceptable level of quality due to increased expectations from customers. For this reason, electric power utilities have invested in electric equipment and new techniques. That is the Distribution Automation System (DAS). A merit of DAS is the ability to reduce outage time because of fast service restoration. However, DAS is usually installed in outdoor environments. Therefore, their efficiency is affected by the external conditions. Lightning creates varying degrees of physical stress on DAS. This paper focuses on the reliability of DAS for lightning. Four application studies were performed to compare the reliability indices.

• The Journal of Industrial Distribution & Business
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• v.8 no.7
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• pp.63-70
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• 2017

Purpose - Due to the lack of physical activities and the increase of sedentary behaviors such as screen time, the health condition for contemporaries has been deteriorating. This study is designed to investigate how the use of worktable or tools unfit for body and sedentary behaviors can exercise influence on muscular skeletal disease and how it has an impact on lowering work efficiency and the quality of life with the medium of the muscular skeletal disease. Research design, data, and methodology - The research has developed a questionnaire with 5 hypothesis. The questionnaires were also made by interview and E-mail. 350 copies of questionnaires were distributed and 315 questionnaire were used for the analysis as valid data responses. SPSS ver.22.0 were used and made Cronbach's and reliability test, correlation, Baron & α Kenny 3 step mediated regression analysis. Results - The research has found that living environment factors have positive effect on the occurrence of musculosketal disease. Particularly, repeated use of unfit worktable or tools has a positive effect on the muscular skeletal disorder. And sedentary lifestyle also has a positive effect on the disease. The musculoskeletal disease caused by living environment has a positive impact on lowering the work efficiency. This study has also showed that the muscular skeletal disease has mediated the relationship between the living environment factors and the decrease of work efficiency due to musculoskeletal disease. The musculoskeletal disorders can effect the decrease of the quality of life as well, for the decrease of work efficiency has a positive effect on lowering the quality of life. Conclusions - Sedentary lifestyles, the use of worktable unfit for body, and the repeated use of a tool have caused the increase of muscular-skeletal diseases, and reduction of productivity as well as the hight cost of medical treatment for our contemporaries. Understanding the cause of disease morbidity, finding ways to prevent the disease, and educating people about them would contribute not only to improvement of individual health but also to the advancement of welfare for all.

• Journal of Korean Physical Therapy Science
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• v.1 no.2
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• pp.235-241
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• 1994

Myofascial pain syndrome is a common cause of physical disability and reduces the activity of the patient. The purpose of this study was review and analysis efficiency of myofascial pain syndrome with low back pain on 50 case who were treated at the Tae Jon Nam, Myung Ho rehabilitation clinic, from January 1, 1994 to May 31, 1994. The results of this study are as follows : 1. of the 50 cases, 24(48.0%) were male and 26(52.0 %) were female. The most common age group was 40 to 30 years old. 2. The most common duration of the treatment and onset were more than 25 months with 22(44.0 %) and less : 3. As for a major causative disease of low back pain with myofascial pain sndrome, without known cause(30.0 %), lifting object(16.0 %), post exercise(14.0 %) and heavy work(12.0 %). 4. Involved muscle with low back pain reviewed I. C. L(31.0 %), Q. L, Gluteus and others muscle(23.0 %). 5. Disease history and treatment duration were proportioned. 6. Involved muscle distribution for causative disease was 26.0 % post exercise to I. C. L, 33.5 % lifting object to Q. L, 40.0 % without known to gluteus. 7. Low back pain with syndrome was buttock and thigh Pain with 44.0 %, only low back pain with 36.0 %. 8. The improvement by physical therapy on the low back pain was good 24.0 %, fair 56.0 % etc respectively. * I.C.L : Iliocostalis lumborum * Q.L : Quadratus lumborum.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1203-1210
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• 2004

It was reported recently that the pump head degradation near the best efficiency point from single-phase flow to the break-down due to air entrainment became less in a screw-type centrifugal pump than in a general centrifugal pump. In this paper, I carried out internal pressure measurements and visualizations, and investigated the various physical phenomena occurring inside a screw-type centrifugal pump operated in air-water two-phase flow. The results could give some characteristics about the degradation of pump performance on air-water two-phase flow.

• Journal of the military operations research society of Korea
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• v.28 no.1
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• pp.1-16
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• 2002

The object of this study is to suggest the direction of building the defence logistics system of Korea Armed Forces in the future. For the purpose of this, we surveyed the best practices among the enterprises and U.S. Defence which reformed successfully the physical distribution and logistic in recent year. Also, we analyzed our current logistics system and suggested the vision, operational concept, and the way of building this system. This system is expected to reduce the total logistics cost, speed up the logistics velocity and increase the efficiency of the combat support.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.670-680
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• 2022

Owing to the lack of a cold-chain distribution system, most seafood is generally distributed under room temperature conditions. However the degradation of freshness during the distribution process can lead to disputes between sellers and consumers. The most widely used method for low-temperature distribution for seafood includes packaging it with styrofoam boxes and cold packs. In this study, vacuum-packed frozen fillets of four fish species of [white meat (Paralichthys olivaceus and Sebastes schlegelii) and red meat (Scomber japonicus and Scomberomorus niphonius)] were placed in styrofoam boxes with cold packs. Thereafter, changes in chemical (including pH, volatile basic nitrogen, and trimethylamine), physical (odor intensity, hardness, and chewiness), and microbial (viable cell count) characteristics of the fillets were measured during storage at 25℃. To identify the suitable method of determining freshness during the room-temperature distribution, several factors were considered, which included significant difference verification, correlation coefficients, and economic efficiency (experimental cost and time). Volatile basic nitrogen, pH, odor intensity, and viable cell count are the most rapid and accurate freshness indicators for determining freshness of frozen fish fillets during.