• 폴리머
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• 제30권6호
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• pp.498-504
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• 2006

물을 반응매체로 하고 스티렌을 단량체로 하는 현탁중합법을 이용하여 입경이 $1{\sim}20{\mu}m$에 이르는 입자를 합성하고자 시도하였다. 소수성 실리카를 안정제로, azobisisobutyronitrile(AIBN)을 개시제로 선택하였다. 반응은 65에서 $95^{\circ}C$ 사이의 선택된 온도에서 진행하였다. 안정제의 농도는 물에 대하여 0.17 wt%에서 3.33 wt%까지 변화시켰으며, 개시제는 단량체에 대하여 0.13 wt%에서 6.0 wt%까지 변화시켰다. 소수성 실리카의 수용액 내의 분산은 정확한 pH 조절을 통하여 이루어졌으며, pH 10에서 최적의 분산을 보였다. 안정제의 농도를 증가하는 경우 초기에는 평균입경이 감소하다 안정제의 농도가 1.67 wt%에서 최소 평균입경을 나타낸 후 증가하였다. 이는 과다한 안정제의 농도로 인한 반응매체 내에서의 이차반응과 이로 인한 입자간의 응집에 기인하는 것으로 사료된다. 안정제의 농도 증가에 따른 분자량은 안정제의 농도가 0.13 wt%에서 1.00 wt%의 사이에서는 일정하였으나, 안정제의 농도가 1.67 wt%를 초과하며 증가하였다. 이러한 분자량의 변화는 과다한 안정제로 인한 개시제의 활성 및 효율 저하, 그리고 반응매체 내에서의 이차반응에 그 원인이 있는 것으로 사료된다. 개시제의 농도 증가 및/혹은 반응온도의 증가는 반응속도와 입경을 증가시켰다. 그 결과, 소수성 실리카를 안정제로 하는 현탁중합반응에서 안정제의 농도, 개시제의 농도, PH 그리고 반응온도의 조절을 통하여 평균입경이 $1{\sim}20{\mu}m$ 영역에 포함되는 구형의 폴리스티렌 입자를 합성할 수 있다는 사실을 확인하였다.제를 일으키지 않도록 주의를 기울여야 한다.s}20cm$에 대해 $0.941{\pm}0.008,\;1.032{\pm}0.004,\;1.049{\pm}0.014$이다. 치료 계획용 시스템과 수 계산에 의한 MU값의 계산 비교결과 7개 기관의 값이 허용오차 범위를 벗어났다. 쐐기를 제외한 8가지 조건에서 계산된 평균 MU값들은 SAD 조건으로 출력 교정된 장비가 SSD 조건으로 교정된 장비에 비해 6 MV 광자선은 3 MU, 10 MV 광자선은 5 MU 정도 더 높았다. 쐐기를 사용할 경우 MU값은 Varian사 장비와 Siemens사의 장비에 따라 다르고 동일 각의 쐐기를 사용할 경우 Siemens사의 쐐기를 사용할 때 MU값이 크다. 결론: 수집된 광자선 빔 데이터를 분석하여 빔데이터의 정확성과 치료계획용 시스템의 계산 정확성을 대략적으로 점검 할 수 있는 기준 값을 제시하였다.동결이 요구되며 본 연구에서 이용된 OPS 동결 방법이 폭넓게 활용될 것으로 사료된다.며 이 때가 최상의 교배 적기로 사료되며, 혈장 progesterone농도가 4.0 ng/ml 이상으로 증가한 날(Bay 0)을 기준으로 하였을 때부터 CI는 혈장 estradiol-$17{\beta}$ peak 후 1일째인 최고치를 나타내었고, CI peak 후 1일째인 Day 0에 혈장 progesterone 농도가 최초로 4.0 ng/ml 이상으로 증가하여 CI가 90% 이상으로 지속된 시기가 최상의 교배 적기임이 확인되었다. 따라서 혈장 progesterone농도 측정으로 정확한 배란 시기 및 교배 적기를 판정할 수 있으나, 시설비가 저렴하고 검사 방법이 간단한 질 세포 검사가 Shih-tzu 견에서 발정 주기, 교배

• Safety and Health at Work
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• 제9권2호
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• pp.184-191
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• 2018

Background: Due to an increasing number of workers aged 50 years and above, the number of those employed is also on the rise, and those workers aged 50 and over has exceeded 50% of the total fatal occupational injuries. Therefore, it is necessary to implement the selection and concentration by identifying the characteristics of high-risk groups necessary for an effective prevention against and reduction of fatal occupational injuries. Methods: This study analyzed the characteristics of high-risk groups and the occupational injury fatality rate per 10,000 workers among the workers aged 50 and over through a multi-dimensional analysis by sex, employment status of workers, industry and occupation by targeting 4,079 persons who died in fatal occupational injuries from January 2007 to December 12. Results: The share of the workers aged 50 years and above is increasing every year in the total fatal occupational injuries occurrence, and the high-risk groups include 'male workers' by sex, 'daily workers' by worker's status, 'craft and related-trades workers' by occupation, and 'mining' by industry. Conclusion: The most frequent causal objects of fatal occupational injuries of the workers aged 50 years and above are found out to be 'installment and dismantlement of temporary equipment and material on work platforms including scaffold' in the construction industry and 'mobile crane, conveyor belt and fork lifts' in the manufacturing industry.

• 한국환경과학회지
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• 제25권5호
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• pp.737-744
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• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).

• Safety and Health at Work
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• 제12권2호
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• pp.174-183
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• 2021

Background: Toluene diisocyanate (TDI) is a highly reactive chemical that causes sensitization and has also been associated with increased lung cancer. A risk assessment was conducted based on occupational epidemiologic estimates for several health outcomes. Methods: Exposure and outcome details were extracted from published studies and a NIOSH Health Hazard Evaluation for new onset asthma, pulmonary function measurements, symptom prevalence, and mortality from lung cancer and respiratory disease. Summary exposure-response estimates were calculated taking into account relative precision and possible survivor selection effects. Attributable incidence of sensitization was estimated as were annual proportional losses of pulmonary function. Excess lifetime risks and benchmark doses were calculated. Results: Respiratory outcomes exhibited strong survivor bias. Asthma/sensitization exposure response decreased with increasing facility-average TDI air concentration as did TDI-associated pulmonary impairment. In a mortality cohort where mean employment duration was less than 1 year, survivor bias pre-empted estimation of lung cancer and respiratory disease exposure response. Conclusion: Controlling for survivor bias and assuming a linear dose-response with facility-average TDI concentrations, excess lifetime risks exceeding one per thousand occurred at about 2 ppt TDI for sensitization and respiratory impairment. Under alternate assumptions regarding stationary and cumulative effects, one per thousand excess risks were estimated at TDI concentrations of 10 - 30 ppt. The unexplained reported excess mortality from lung cancer and other lung diseases, if attributable to TDI or associated emissions, could represent a lifetime risk comparable to that of sensitization.

• Asian-Australasian Journal of Animal Sciences
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• 제19권2호
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• pp.160-164
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• 2006

Currently, boars selected for commercial use as AI sires are evaluated on grow-finish performance and carcass characteristics. If AI sires were also evaluated and selected on semen production, it may be possible to reduce the number of boars required to service sows, thereby improving the productivity and profitability of the boar stud. The objective of this study was to estimate genetic correlations between production and semen traits in the boar: average daily gain (ADG), backfat thickness (BF) and muscle depth (MD) as production traits, and total sperm cells (TSC), total concentration (TC), volume collected (SV), number of extended doses (ND), and acceptance rate of ejaculates (AR) as semen traits. Semen collection records and performance data for 843 boars and two generations of pedigree data were provided by Smithfield Premium Genetics. Backfat thickness and MD were measured by real-time ultrasound. Genetic parameters were estimated from five four-trait and one five-trait animal models using MTDFREML. Average heritability estimates were 0.39 for ADG, 0.32 for BF, 0.15 for MD, and repeatability estimates were 0.38 for SV, 0.37 for TSC, 0.09 for TC, 0.39 for ND, and 0.16 for AR. Semen traits showed a strong negative genetic correlation with MD and positive genetic correlation with BF. Genetic correlations between semen traits and ADG were low. Therefore, current AI boar selection practices may be having a detrimental effect on semen production.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1796-1816
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• 2007

Recently, started to apply a strategy of selection and concentration in the construction and transportation R&D for the effective utilization of limited R&D resources. The department of construction and transportation planned the construction and transportation R&D innovative road map by the future 10 years technical requirement under the first year on the innovation of the construction and transportation technology from last year. The innovative road map which is a strategic and long term master plan integrated a construction and transportation suggested a vision as value createar for a improvement of living quality in the future. And made a specific goal that is the seventh construction technology level and the fifth transportation technology level in the world. The department of construction and transportation is planning a mid- long range planing of the construction and transportation R&D as following measurement of innovative road map. KICTEP and KISTEP planned a mid- long range R&D planing of the transportation system, logistics, aviation, railway for the last year. Introducing a methodology used a mid- long range plan and main results of the future railway R&D plan. And suggesting a politic comments for the effectively propelling railway R&D projects.

• 한국산업보건학회지
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• 제26권3호
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• pp.367-376
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• 2016

Objectives: The production and use of nanoparticles have been increased. In 2014 Workplace Survey Results, 335 companies produce and treat nanoparticls. However, lack of data on nano-toxicity and a method for risk management and regulation on nanoparticles and the standard test method are not sufficient. Protective equipment selection guidelines for nanoparticles are not established. It is required to carry out respirator efficiency test against nanoparticles. This study was performed to evaluate filtration efficiency and manikin-based total inward leakage of particle filtering mask using in Korean country challenged with silver nanoparticles. Methods: We investigated filtration efficiency and total inward leakage of 7 respirator with silver nanoparticle. Results: The geometric mean diameters of Silver nanoparticles were 30 nm and number concentration were about $10^6{\sharp}/cm^3$. Filtration efficiency of six of the seven particle filtering masks was more than 98% and one particle filtering masks filtration efficiency was 94.9%. The filtration efficiency of particle filtering masks to 20 nm silver nanoparticels was highest. Artificial breathing machine with manikin based total inward leakage were 7.6% ~ 42.3%. Conclusions: The results of this study nano-silver filter efficiency was high but the total inward leakage was higher than filter penetration. Therefore, education on how to wear a respirator should be demanded. Especially for workers handling nanoparticles and toxic material, user seal checking and fit test must be performed.

• 한국조경학회지
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• 제27권5호
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• pp.38-47
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• 2000

Carbon dioxide is a major greenhouse gas causing climate change. This study quantified annual direct and indirect uptake of carbon by urban greenspace, and annual carbon release from vegetation maintenance and fossil fuel consumption. The study area was whole Chuncheon and Kangleung, and also two districts of Kangnam and Junglang in Seoul, cities located in middle Korea. Carbon uptake by urban greenspace played an important role through offsetting carbon release by 6-7% annually in Chuncheon and Kangleung. For Kangnam and Junglang, where the population density was relatively higher, urban greenspace annually offset carbon release by 1-2%. Future possible tree plantings could double annual carbon uptake by existing trees in urban lands (except natural and agricultural lands) of a study city. Based on study results, planning and management guidelines for urban greenspace were suggested to save energy and to reduce atmospheric $CO_2$ concentrations. They included selection of optimum tree species, proper planting location from buildings, design of multilayered planting, amendment of existing regulations for greenspace enlargement, avoidance f intensive vegetation maintenance, and conservation of natural vegetation.

• 동아시아경상학회지
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• 제5권2호
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• pp.1-11
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• 2017

This study attempts to verify effects of CEO' supports, compensation and educational training and those of individual annual salaries and company's sales on promotion of knowledge management expected to contribute to enhancing construction industry's competitiveness, from the perspective of person-organization fit. For the analysis, a total of 368 effective questionnaires were used to conduct independent sample t-test, regression analysis and hierarchical moderated regression analysis. The findings show that individual annual salaries have a positive relationship with company's performance and company's sales also have positive relationships with both knowledge management activities and company performance, and CEO's supports, compensation and educational training are important factors that can improve knowledge management activities. In addition, the principle that the rich get richer and the poor get poorer is also operated in construction industry, as in other industries. Therefore, members in a company should conduct optimal strategies to enhance the knowledge management activities through selection and concentration, while governmental agencies require the establishment of IT system for it and supports for related cost and consulting of it.

• Advances in materials Research
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• 제8권1호
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• pp.11-24
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• 2019

This paper presents a review study for energy-efficient gas turbines (GTs) with cycles which contributes significantly towards sustainable usage. Nonetheless, these progressive engines, operative at turbine inlet temperatures as high as $1600^{\circ}C$, require the employment of highly creep resistant materials for use in hotter section components of gas turbines like combustion chamber and blades. However, the gas turbine obtain its driving power by utilizing the energy of treated gases and air which is at piercing temperature and pushing by expanding through the several rings of steady and vibratory blades. Since the turbine blades works at very high temperature and pressure, high stress concentration are observed on the blades. With the increasing demand of service, to provide adequate efficiency and power within the optimized level, turbine blades are to be made of those materials which can withstand high thermal and working load condition for longer cycle time. This paper depicts the recent developments in the field of implementing the best suited materials for the GTs, selection of proper Thermal Barrier Coating (TBC), fracture analysis and experiments on failed or used turbine blades and several other designing and operating factors which are effecting the blade life and efficiency. It is revealed that Nickel based Superalloys were promising, Cast Iron with Zirconium and Pt-Al coatings are used as best TBC material, material defects are the foremost and prominent reason for blade failure.