• Journal of Astronomy and Space Sciences
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• 제20권1호
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• pp.63-82
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• 2003

Schwarzschild의 선형 계획법을 사용하여 평형상태에서의 구형은하를 기술하는 비 충돌 볼쯔만 방정식의 일반적인 해를 얻었다. 이 계산으로부터 de Vaucouleurs의 광도 법칙을 만족하고 무거운 헤일로를 포함하는 등방성 구형은하의 존재를 확인할 수 있었다. 타원은하에서 속도 분산 곡선이 편평하거나 서서히 증가하는 현상은 암흑물질에 의한 질량대 광도비의 증가로 해석할 수 있다. 이런 경우 암흑물질의 밀도 분포는 core반경이 은하의 유효반경보다 훨씬 작은 값을 갖는다는 사실을 확인할 수 있었다.

• 한국농공학회지
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• 제42권5호
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• pp.114-124
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• 2000

The method to estimate agricultural organic matter flow on the regional scale was established and applied to a rural area in Chongwon-gun, Chungbok in 1996. The study area is of about 67$\textrm{km}^2$ and its population is about 7,000. The stocks and flows of organic matter are represented in dry weight per unit area and dry weight per unit area per year, respectively. the amount of inflow of organic matter indicates a possibility to cause environmental pollution. the amount of animal waste 767 kg/ha/yr account for 42 percent of total amount of organic waste 1,834 kg/ha/yr and therefore the environment in study area is greatly influenced by livestock. The decrease in recycling rate of animal waste form 100% to 70% has greatly increased the amount of disposal waste nearly twice, i.e., from 267 kg/ha/yr to 497kg/ha/yr . The results of this study demonstrate that appropriate animal population, increase in recycling of animal waste and preservation of agricultural land are necessary for environmental conservation of the study area.

• 한국초지조사료학회지
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• 제17권1호
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• pp.35-42
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• 1997

Many farmers apply cattle slurry on grassland, often in excess of crop N requirements, resulting in groundwater contamination. Our research objective was the development of grassland management systems that reduce undesirable sideeffects on other compartment of the ecosystem. Field experiment was conducted during 1991~1993 on sandy loam soil at AllgZiu south western Germany. Different sets of conditions were tested such as : zero fertilization, reduced sluny application$(l20kg N ha^{-1}yr^{-1})$, intensive sluny application(conventional sluny application, $240kg N ha^{-1}yr^{-1}$). The plots of the reduced slurry application had no significant effect on dry matter yields, digestible dry matter and net energy of herbage. Dry matter yield of zero fertilization was significantly lower than that of usual slurry application, however the content of Ca and Mg in herbage tended to increase. We conclude that reduced sluny application can be applied on grassland without adverse effects on dry matter production and quality of herbage.

• Communications for Statistical Applications and Methods
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• 제25권5호
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• pp.545-557
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• 2018

The inclusion of covariates in the model often affects not only the estimates of meaningful variables of interest but also its statistical significance. Such gap between statistical and subject-matter significance is a critical issue in huge sample studies. A popular huge sample study, the sample cohort data from Korean National Health Insurance Service, showed such gap of significance in the inference for the effect of obesity on cause of mortality, requiring careful consideration. In this regard, this paper proposes a sample size calibration method based on a Monte Carlo t (or z)-test approach without Monte Carlo simulation, and also proposes a test procedure for subject-matter significance using this calibration method in order to complement the deflated p-value in the huge sample size. Our calibration method shows no subject-matter significance of the obesity paradox regardless of race, sex, and age groups, unlike traditional statistical suggestions based on p-values.

• 한국축산시설환경학회지
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• 제6권1호
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• pp.37-44
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• 2000

A new hose slurry spreader with improved spreading uniformity is developed to distribute the slurrynear to the soil surface and to reduce odor problems. The precision of distributed slurry was investigated using 3 types of slurry and found to be dependent on the rotor speed. For the solid matter separated fluid containing 0.1% of dry matter rotor speed of 150 rpm showed best uniformity with CV of 10% In the case of slurry from dairy cattle which contains 8.2% of dry matter high rotor speed of 330 rpm showed best result with CV of 7.2% Also swine slurry which has a 13.6% of dry matter content showed the best result of 8.1% CV at the high rotor speed of 250rpm. A high rotor speed generates enough pressure in the central distributor and as a result uniform distribution of slurry can be achieved. In conclusion it is highly recommended rotor speed of 300 rpm to get the best performance.

• 한국초지조사료학회지
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• 제17권4호
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• pp.387-398
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• 1997

This experiment was to investigate the surface coverage, sward height and dry matter yield of 63 perennial ryegrass cultivars with control cultivar, orchardgrass(Potomac) at different cutting dates(May 25, July 5, August 20 and October 5), in order to select the adaptable cultivars of perennial ryegrass in the middle region of Korea. Four perennial ryegrass cultivars, E.V. Meadea, Aberystwyth S101, Raidor and Real, didn't survive afler sowing. Surface coverage of perennial ryegrass cultivars cut in August 20 was lower than others. Sward height of perennial ryegrass cultivars at each cutting dates was lower than that of orchardgrass. There were no significant differences in sward heights of each cutting date. Dry matter yield of perennial ryegrass cultivars cut in August 20 was lower than others. Total dry matter yield of Oakpark 6% Viktoria, Petra, G. Manawa, and Kangaroo Valley was fell in the range of 11.76 and 10.37t/ha while that of orchardgrass was 12.09t/ha. On the basis of total annual dry matter yield, the adaptability of perennial ryegrass cultivars was classfied as following.

• Environmental Analysis Health and Toxicology
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• 제13권1_2호
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• pp.27-31
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• 1998

Motor vehicle exhaust is the major cause to the air contamination in Seoul. It includes many toxic chemicals to human health such as aidehyde, PAHs, benzene, xylene, toluene, benzo[a]pyrene, nickel, arsenic and cadmium in gasoline exhaust and formaldehyde, PAHs, 1,3-butadiene, benzene and particulate matter in diesel exhaust. Some chemicals out of them are classified as a human carcinogen. Many large diesel vehicles such as buses and trucks are drivened frequently in Seoul so that the air in Seoul is seriously contaminated by diesel exhaust, especially particulate matter. The amounts of particulate matter from large diesel vehicles may be estimated to be more than 50% of small dust in Seoul. The particles of particulate matter are coated with many toxic chemicals and some of these are considered as a human carcinogen. The cancer risk has to be throughly managed because the population density of Seoul is very high. Government should list hazardous air pollutants in Seoul, assess the exposure of people to toxic pollutants, especially carcinogens and manage human health risk.

• Environmental Engineering Research
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• 제18권4호
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• pp.259-265
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• 2013

This study was conducted June 2011 at Gamo Lagoon, after tsunami of March 2011, to estimate food sources and utilization. The results show that the tsunami affected the sediment properties by changing the physical environmental alterations. The fatty acids of the gut content of Nuttallia olivacea mostly comprised the same organic matter found in the sediment. Fatty acids in the tissues showed mainly diatoms, bacteria, and dinoflagellates. That is, most of the food sources (i.e., diatoms, bacteria, dinoflagellates, macroalgae, and terrestrial organic matter) probably pass through the digestive system unharmed; however, terrestrial organic matter, which is refractory to biochemical degradation, indicated a different assimilation trend between the gut content and the tissue. This result suggests that input of labile organic matter from the sediment may control selective metabolism in N. olivacea. From these results, although the physical environment of sediment characteristics by tsunami changed, the food utilization of N. olivacea suggested a better assimilation of selected components from the gut content, irrespective of physical alteration.

• 한국환경과학회지
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• 제8권1호
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• pp.69-74
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• 1999

Soil properties which affect the retention of Pb(I) were investigated in the laboratory. It was determined, through selective removal, that organic matter and Fe-oxides are of lesser importance in influencing Pb retention than are soil clay minerals. The following trend : clays ＞ organic matter ＞ Fe-oxides represents the relative importance of each constituent in the adsorption of Pb by soils. The consistently greater Pb uptake by surface over subsurface samples was apparently due to differences in organic matter content, inasmuch as organic matter removal from both resulted in similar adsorption characteristics. All five soils stooled exhibited a pH-dependent trend of adsorption. The extent of Pb adsorption was least at low pH values(4~5), was maximum in the neutral pH range, and leveled off or diminished under more alkaline conditions. There was no strong correlation between Pb uptake and soil cation exchange capacity as routinely measured by the NH$_4$OAc method. A knowledge of clay mineralogy in conjunction with soil pH is suggested as being the most reliable guide to predicting Pb retention by soils.

• 한국입자에어로졸학회지
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• 제16권1호
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• pp.9-17
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• 2020

The characteristics of particulate matter made from daily cooking at a Korean residential apartment house with three dwellers had been investigated for about 3 months. All data were recorded by an optical particle counter every minute at the kitchen. Types of cooking such as boiling, frying, and grilling that performed in the house were listed. Boiling only was used in 32% cases among total 234 meals. Frying and grilling were 14% and 11%, respectively. From an initial indoor particulate matter smaller than 10 ㎛ in diameter, the increases due to cooking are reported by size. In case of boiling, PM at 1-10 ㎛ size and under 1 ㎛ size little increased. Normally, particles from oil or combustion in a process of frying or grilling increased indoor PM. In a case of grilling, particle mass concentration in a region of 1-10 ㎛ in diameter increased as much as 295 ㎍/㎥. Mass concentration of particles smaller than 1 ㎛ increased as much as 33 ㎍/㎥.