• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.109-122
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• 2018

Domestic LPG meters are being tested for LPG quantification in accordance with the "Measures Act". The LPG meter is re-tested every three years in accordance with the "Enforcement Decree of the Measures Act". The maximum permissible error within the test is within ${\pm}1.0%$, and the tolerance is within ${\pm}1.5%$. For the quantitative measurement of LPG, a hydrometer for LPG, a balance, and a pressure vessel are used. The volume of LPG varies in depending on the temperature and pressure. The current quantitative measurement method of LPG requires the measurement of temperature, pressure and density in order to determine the volume of LPG, respectively, and some equipments are needed accordingly. Coriolis mass flowmeter, on the other hand, measure the mass flow, density and temperature at the same time, and can be converted and calculated to the required values using a computer program, also it is widely applied in the industrial field. In this study, the volume of LPG was measured using a Coriolis mass flowmeter as a basic study of LPG quantitative measurement. In addition, it is shown that it is possible to apply for the LPG quantitative measurement using the Coriolis mass flowmeter by comparing it with the conventional LPG quantitative measurement method.

• Journal of Korean Society of Forest Science
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• v.83 no.3
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• pp.299-310
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• 1994

This study was carried out to examine the optimal road spacing and road density to minimize the total harvesting cost(road construction cost plus yarding cost) for mechanized yarding system to roadside by one - and two-stage two-way in Forestry build-up region. Chunchon-kun, Kangwon-do. The estimated road construction costs were ranged from ten million won to sixty million won per km. The results have indicated that cable crane was appropriate for yarding machine by one-stage, two-way, and estimated optimal road spacing was 1,698m~4,192m, averaged 3,087m, and road density was 3.44m/ha~8.44m/ha, and averaged 5. 12m/ha. In hilly terrain, combination of medium yarder and Logging bogie was suited to yarding machine by two-stage, two-way, and calculated optimal road spacing was 1,483m~3,481m, averaged 2,589m, and road density was 4.05m/ha~9.46m/ha, averaged 5.90m/ha. In steep terrain, combination of medium yarder and jinsung winch was suited, and estimated optimal road spacing was 1,693m~3,982m, averaged 2,960m, and road density was 3.68m/ha~8.64m/ha, averaged 5.38m/ha.

• Korean Journal of Poultry Science
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• v.47 no.1
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• pp.1-7
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• 2020

The effect of stocking density on the growth and meat quality of native Korean chickens was investigated. A total of 364 one-day-old native Korean chickens were randomly assigned to one of 5 treatments, each of which was replicated 4 times. Five distinct stocking densities-14, 15, 16, 18, and 22 birds/㎡-were compared. The diet was fed ad libitum for 10 weeks. Results indicated that the final body weight, body weight gain, and feed intake were lower (P<0.05) for the 22 birds/㎡ stock density as compared to the other stock densities. There was no significant difference in the feed conversion ratio, proximate analysis (DM, crude protein, crude fat, and crude ash), water-holding capacity, and cooking loss among the different stock densities. These results indicate that increasing the stock density to 22 birds/㎡ elicits some negative effects on the growth performance and meat quality of Korean-native chickens.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.128-128
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• 2010

중적외선 영역은 장애물에 의해서 파장의 흡수가 거의 일어나지 않기 때문에 적외선 소자에서 널리 이용되고 있다. 현재 대부분의 중적외선 소자에는 HgCdTe (MCT)가 사용되고 있지만, 3성분계 화합물이 가지는 여러 문제를 가지고 있다. 반면에, 2성분계 화합물인 인듐안티모나이드 (InSb)는 중적외선 영역 ($3-5\;{\mu}m$) 파장 대에서 HgCdTe와 대등한 소자 특성을 나타냄과 동시에 낮은 기판 가격, 소자 제작의 용이성, 그리고 야전과 우주 공간에서 소자 동작의 안정성 때문에 HgCdTe를 대체할 물질로 주목을 받고 있다. InSb는 미국과 이스라엘과 같은 일부 선진국을 중심으로 연구가 되었지만, 국방 분야의 중요한 소자로 인식되었기 때문에 소자 제작에 관한 기술적인 내용은 국내에 많이 알려지지 않은 상태이다. 따라서 본 연구에서는 InSb 소자 제작의 기초연구로 절연막과 pn 접합 형성에 대한 연구를 수행하였다. 절연막의 특성을 알아보기 위해, InSb 기판위에 $SiO_2$와 $Si_3N_4$를 PECVD (Plasma Enhanced Chemical Vapor Deposition)로 증착을 하였다. 절연막의 계면 트랩 밀도는 77K에서 C-V (Capacitance-Voltage) 분석을 통하여 계산하였으며, Terman method 방법을 이용하였다.[1] $SiO_2$는 $120-200^{\circ}C$의 온도 영역에서 계면 트랩 밀도가 $4-5\;{\times}\;10^{11}cm^{-2}$범위를 가진 반면, $240^{\circ}C$의 경우 계면 트랩 밀도가 $21\;{\times}\;10^{11}cm^{-2}$로 크게 증가하였다. $Si_3N_4$는 $SiO_2$ 절연막에 비해서 3배 정도의 높은 계면 트랩 밀도 값을 나타내었으며. Remote PECVD 장비를 이용하여 $Si_3N_4$ 절연막에 관한 연구를 추가적으로 진행하여 $7-9\;{\times}\;10^{11}cm^{-2}$ 정도의 계면 트랩 밀도 값을 구할 수가 있었다. 따라서 InSb에 대한 절연막은 $200^{\circ}C$ 이하에서 증착된 $SiO_2$와 Remote PECVD로 증착 된 $Si_3N_4$가 적합하다고 할 수 있다. 절연막 연구와 더불어 InSb 소자의 pn 접합 연구를 진행하였다. n-InSb (100) 기판 ($n\;=\;0.2-0.85\;{\times}\;10^{15}cm^{-3}$ @77K)에 $Be^+$이온 주입하여 p층을 형성하여 제작 되었으며, 열처리 조건에 따른 소자의 특성을 관찰 하였다. $450^{\circ}C$에서 30초 동안 RTA (Rapid Thermal Annealing)공정을 진행한 샘플은 -0.1 V에서 $50\;{\mu}A$의 높은 암전류가 관찰되었으며, 열처리 조건을 60, 120, 180초로 변화하면서 소자의 특성 변화를 관찰하였다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.4
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• pp.328-333
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• 1990

In developing dynamic growth model of a crop, it is important to estimate accurate dry matter partition to different parts of crop plants. Two rice varieties, Samkang and Chucheong, were transnplanted with three planting densities of 72. 90 and 120 hills per 3.3㎡ on May 30 and June 15 in 1988 to study the effect of planting density on dry matter partition in rice plants. Total dry wight per square meter of two varieteis in May 30 transplanting were greater than those in June 15 transplanting. Total dry wights were increased as planting density was increased. The response of dry weights of differents parts of rice plants per hill were decreased as the density was increased. Although the difference in dry weights of leaf blade and stem and sheath between two varieties was not great, greater ear weight of Samkang resulted in greater total dry weight than that of Chucheong. Despite of transplant in date and planting density on dry weights, the ratio of dry matter partition to different parts of rice plants at a certain growth stage remained constant. Estimated dry weights of different parts at two stages of growth based on average ratio of dry matter partition over two transplantion dates and planting densities agreed well with those observed.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.809-817
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• 2010

The primary purpose of this study was to investigate high school students' conceptual understanding of density for solids and liquids in pure and mixed substances who had preceded formal school science instruction on density and related topics. A concept assessment on density was developed and administered by demonstrative experiments accompanied by a written assessment test method to 120 general high school students in a metropolitan city. The scientific conceptions and alternative conceptions from students' responses were identified and the percentages of them were calculated. Then, their alternative conceptions and implicit theories on density were analyzed. About half of the students couldn't differentiate weight-volume-density and regarded density as an innate property of matter. Furthermore, the greater the number of variables involved in an experimental condition of the question, the more complicated and undifferentiated students' density concepts were. Students employed more improper variables such as particle size, intermolecular distance, surface tension, polarity of the solvent, etc. in explaining counter-intuitive observations. The implications for school science instruction were discussed.

• Journal of the Korean Institute of Gas
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• v.9 no.3 s.28
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• pp.49-54
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• 2005

This work was to calibrate Anton Paar 512P vibrating tube densimeter which is a special type for density measurement under high pressure (up to 70 MPa) and temperature (up to 420 K) and checked the validity of the new apparatus. Calibration was peformed with water, nitrogen and water, vacuum as reference fluids. Temperature is measured from 313.15 K and 353.15 K at 10 K intervals, and pressure is measured up to 30 MPa at 5 MPa intervals, respectively. To check the validity of new apparatus and the calibration method we compared the values obtained by measuring density of carbon dioxide with those given by NIST Thermophysical Properties of Pure Fluids Database. The average deviations between the NIST and the experimental data were $0.3\%$ with water and nitrogen as reference fluids.

• Horticultural Science & Technology
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• v.19 no.2
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• pp.179-185
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• 2001

Throughout the world, physical and chemical analyses of horticultural substrates are carried out in many different ways at the different laboratories. In Europe, standardization in properties and analytical methods of horticultural substrates has been a topic over the last decades. As a result, the CEN methods as European standard methods for the physical and chemical analyses were introduced and the final draft was reported in 1999 by CEN(Committee for European Standardization). Dry matter and moisture content are analyzed after drying samples at $103^{\circ}C$. Laboratory compacted bulk density is analyzed by determining the weight of sample compacted in the test cylinder with constant volume. Dry bulk density, particle density, total pore space, water volume, air volume and volume shrinkage are determined by saturating, draining and drying the sample using double rings and a sand suction table. pH and EC are analyzed by 1:5(sample:distilled water) extraction method on the basis of volume. Organic matter and ash content are determined after drying and combusting the samples. Now, CEN methods are being regarded almost as European standard methods. Further study needs to be carried out for universal applicability of the CEN methods to all the substrates.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.201-209
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• 2024

This study investigates the operational facets of low-density urban air mobility (UAM) from an airline's perspective amid burgeoning concerns about urban congestion in megacities. UAM, employing electric vertical takeoff and landing (eVTOL) technology, emerges as a potential remedy to the challenges of traffic gridlock and environmental degradation. As the UAM market progresses from initial stages to maturity, tailored traffic control systems become paramount. Focused on the context of low-density environments during UAM's inception, this research scrutinizes operational frameworks, essential infrastructure, and likely scenarios. It aims to bolster the safety and efficiency of UAM operations by delving into the specifics of traffic control concepts designed for these unique settings. The study seeks to significantly contribute to optimizing UAM's initial phases, providing insights into crucial operational dynamics for a smoother integration of urban air mobility into contemporary urban landscapes.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.536-539
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• 2014

본 논문에서는 생명체 간의 상호작용으로 형성된 안정된 생태계의 요인을 분석할 수 있는 계산 시뮬레이션 모델을 제안한다. 그리고, 실제 시뮬레이션 프로그램을 개발하고 이를 통해 얻은 실험 결과를 제시함으로써, 계산 시뮬레이션 분야와 생명과학 분야의 융합 가능성을 보인다. 제시한 계산 시뮬레이션 모델은 1) 하나의 커다란 생태계로 이루어진 세계, 2) 다수의 작은 생태계로 이루어진 세계, 3) 생태계가 미형성된 세계를 유전 알고리즘을 사용하여 모델링 하였으며, 실험 결과는 2)번 모델이 생태계를 가장 안정적인 상태로 오래 유지하는 결과를 보였다. 이를 통해서 충분한 에너지가 존재하거나 공급되는 환경에서는 생물 밀도가 높으면서 에너지 순환이 빠른, 작은 규모의 생태계가 가장 안정적이라는 생물학적인 결론을 도출할 수 있었다.