• 한국수정란이식학회지
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• 제14권2호
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• pp.93-97
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• 1999

The development potential of bovine somatic cells was evaluated using nuclear transfer. A single donor cell derived from fetus of HanWoo(Korean Native Cattle) was selected and deposited into perivitelline space of each enucleated oocyte before electrical fusion and activation. Nuclei of donor cells starved for 7 days (37%) tended to support the development of reconstitute embryo the blastocyst stage better than those of donor cells starved 3, 14 and 30 days. The cleavage rate was significantly lower(P<0.05) in reconstitute embryos derived from large size donor cells(51.2%), than those from small medium size donor cells(76.6 and 73.5, respectively). The developmental rate to blastocyst of reconstructed embryos from medium size donor cells was higher than those from small and medium size donor cells. This study demonstrates that an appropriate culture period for induction into quiescent stage and the size of donor cells effect on the efficiency of nuclear transfer using cultured bovine cells.

• 농업생명과학연구
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• 제52권6호
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• pp.111-125
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• 2018

본 연구에서는 변량방제기술을 적용한 농용 회전익기를 이용하여 살포한 입자의 구간비행 상태에서의 거리별 살포 패턴을 측정함으로써 무인 항공방제의 농약 부착률과 입자경의 분포 균일도를 평가하였다. 비행을 등속으로 유지하는 안내비행과 자동비행 모드에서 유효살포폭 3.6m로 인접비행 구간과 살포폭이 일부 중첩된 피복률에 대한 가로방향 분포의 변이계수는 30% 정도를 보였고, 비행방향 진로위치에 대한 피복률의 변이계수는 10% 미만으로 매우 균등한 것으로 평가되었다. 따라서 살포작업시 기체의 지면속도(ground speed)의 변이를 보상하는 변량살포기술은 균일도 측면에서 우수한 것으로 판명되었으며, 또한 입자경의 분포에 있어서 체적중위직경(VMD)과 개체중위직경(NMD) 모두 항공방제에 적절한 크기와 균일한 분포를 보였다. 따라서 농용 회전익기를 이용하여 소필지의 항공방제작업을 무인화 하는데 있어, 변량방제장치를 적용함으로써 소규모 필지의 균일 정밀방제를 도모하고자 하였다.

• 한국철도학회논문집
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• 제13권1호
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• pp.9-15
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• 2010

철도차량기지 중정비 공장의 규모를 설계할 때 최소 부지에 시설을 배치하여 검수효율을 향상시킬 필요가 있다. 본 연구에서는 중정비 공장 규모 산정 시에 적용되는 운행과 검수의 파동요인을 고려한 파동율(이하 "여유율")이 국내에서 아직 검증되지 않은 채 활용되는 외적인 요인을 중정비공장내 재장시간으로 흡수하기 위해 시설배치도 및 공정 작업의 시뮬레이션 분석에 의하여 합리적인 여유율을 산출하고 그 적정성을 검토하고자 한다. 본 연구는 공정의 작업시간이 평균값으로 되어있어 작업자 간의 편차를 고려, 공정작업시간에 표준편차를 10~20%로 주어 각각의 경우별로 시뮬레이션 결과치를 분석하여 가능 여유율을 도출하였다. 향후에는 차량의 운영 및 검수계획, 차량 예비율 및 중정비 공장의 설비능력, 공정외주비율, 표준인공 등 운영조건 등의 인자를 고려하여 과학적인 검토를 통해 적정 여유율을 적용함으로서 공장 규모를 최적화 할 필요가 있다.

• Journal of Biosystems Engineering
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• 제12권1호
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• pp.31-38
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• 1987

In order to improve the traditional post harvest system in Korea, a model for mechanized rice drying and storage system was developed and introduced as the first part of the study(Park, 1986). As the second part of the study, capital requirement and cost of the model system was analyzed. Also, optimum size of the model system was estimated by comparing with the traditional harvest system. From the study, the following results can be concluded: 1. The capital requirement of the model system decreases as the model size increases. For example, a model system having 500 ton storage capacity requires 439,000 Won/ton. However it requires 313,200 Won/ton only, if the model size increases to 1000 ton. 2. Also, total cost of the model system decreases as the model size increases. For example, total costs of the model system having 500 ton and 1000 ton storage capacity are 101,208 Won/ton and 69,320 Won/ton, respectively. 3. The breakeven point (optimum size) of the model can be estimated around 630 ton storage capacity if the operation rate is assumed as 100%. However, the optimum size of the model is 710 ton, if the operation rate it assumed 80%.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.674-677
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• 2002

Vertically aligned CNTs were grown on Fe-deposited $SiO_2$ substrates using thermal CVD of acetylene gas. The size of Fe particle is controlled by the flow rate of $NH_3$ and pretreatment time, which leads to control the diameter of CNTs. As the diameter of CNTs decreases, the growth rate is enhanced with an inverse dependence of the CNT diameter. The growth rate of CNTs increases linearly as the growth time increases until 30 min but is rapidly decreased over 40 min. We found an inverse relation between the diameter and growth rate of carbon nanotubes. As the diameter of CNTs increases, the compartment layers of bamboo-shaped CNTs appear more frequently. A base-growth model is suitable to explain the dependence of growth rate and structure of CNTs on the diameter size of catalytic particles.

• 보건행정학회지
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• 제14권2호
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• pp.1-16
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• 2004

The study purpose was to find which factors affect selection of hospital network types. This study used the 1998 American Hospital Association Annual Survey Database from Health Forum. Among these U.S. hospitals, the researcher selected hospitals located in Metropolitan Statistical Areas. Therefore the final observation cases for analysis are 1,971 Metropolitan Statistical Area hospitals in the United States. To identify significant variables influencing hospital network types, the study used proportional odds logistics regression model on population size, Health Maintenance Organization penetration rate, and market competition rate of area including a hospital, types of hospital ownership, hospital bed size, proportion of Medicare patients and Medicaid patients in total hospital patients, and occupancy rate. Contrary to conventional wisdom, selection of hospital network types was influenced by population size of area which a hospital located, types of ownership, hospital bed size, and proportion of medicare patients rather than Health Maintenance Organization penetration. Population size 1,000,000-2,499,999 had the highest probability of selecting type IV (clinical-vertical integration) from an independent hospital, and a religious group owned hospitals and for-profit owned hospitals had the highest probability of selecting Type IV (clinical-vertical integration) from an independent hospital. A bed size had positive relation on selecting Type IV (clinical-vertical integration) from an independent hospital. Unlikely general belief that the selecting types of hospital network was determined by the change of health insurance policy such as Health Maintenance Organizations and Preferred Provider Organizations, the types of hospital network were influenced by community characteristics such as population size, and hospital characteristics.

• Geomechanics and Engineering
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• 제14권2호
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• pp.151-159
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• 2018

Annually, the global production of construction aggregates reaches over 40 billion tons, making aggregates the largest mining sector by volume and value. Currently, the aggregate industry is shifting from sand to hard rock as a result of legislation limiting the extraction of natural sands and gravels. A major implication of this change in the aggregate industry is the need for understanding rock fragmentation and energy absorption to produce more cost-effective aggregates. In this paper, we focused on incorporating dynamic rock and soil mechanics to understand the effects of loading rate and water saturation on the rock fragmentation and energy absorption of three different sandstones (Red, Berea and Buff) with different pore sizes. Rock core samples were prepared in accordance to the ASTM standards for compressive strength testing. Saturated and dry samples were subsequently prepared and fragmented via fast and dynamic compressive strength tests. The particle size distributions of the resulting fragments were subsequently analyzed using mechanical gradation tests. Our results indicate that the rock fragment size generally decreased with increasing loading rate and water content. In addition, the fragment sizes in the larger pore size sample (Buff sandstone) were relatively smaller those in the smaller pore size sample (Red sandstone). Notably, energy absorption decreased with increased loading rate, water content and rock pore size. These results support the conclusion that rock fragment size is positively correlated with the energy absorption of rocks. In addition, the rock fragment size increases as the energy absorption increases. Thus, our data provide insightful information for improving cost-effective aggregate production methods.

• 한국세라믹학회지
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• 제44권2호
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• pp.98-102
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• 2007

The stability of slurry and removal rate during recycling of colloidal silica slurry was evaluated in silicon wafer polishing. The particle size distribution, pH, and zeta potential were measured to investigate the stability of colloidal silica. Large particles appeared as recycling time increased while average size of slurry did not change. Large particles were identified by EDS(energy dispersive spectrometer) as foreign substances from pad or abraded silicon flakes during polishing. As the recycling time increased, pH of slurry decreased and removal rate of silicon reduced but zeta potential decreased inversely. Hence, it could be mentioned that decrease of removal rate is related to consumption of $OH^-$ ions during recycling. Attention should be given to the control of pH of slurry during polishing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권12호
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• pp.4624-4642
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• 2014

Image compression is a popular research issue that focuses on the problems of reducing the size of multimedia files. Vector Quantization (VQ) is a well-known lossy compression method which can significantly reduce the size of a digital image while maintaining acceptable visual quality. A locally adaptive scheme (LAS) was proposed to improve the compression rate of VQ in 1997. However, a LAS needs extra indicators to indicate the sources, consequently the compression rate of LAS will be affected. In this paper, we propose a novel method to eliminate the LAS indicators and so improve the compression rate. The proposed method uses the concept of data hiding to conceal the indicators, thus further improving the compression rate of LAS. From experimental results, it is clearly demonstrated that the proposed method can actually eliminate the extra indicators while successfully improving the compression rate of the LAS.

• Journal of Advanced Marine Engineering and Technology
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• 제27권6호
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• pp.783-789
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• 2003

An experimental method to investigate the fracture strength and fracture toughness for the silicon nitrides sintered at various sintering temperature is established. The erosion rate for these materials in the various concentration of NaOH solution is also investigated. In result, the fracture strength of Si3N4 is decreased with the increase of sintering temperature. On the other hand, the fracture toughness KIC is increased with the increase of sintering temperature. The erosion rate of silicon nitride in the NaOH solution depend largely on the grain size and the concentration of NaOH solution. The erosion rate of silicon nitride sintered at $1800^{\circ}C$ was much higher than that at $1950^{\circ}C$. These results are due to the unique columnar structure of silicon nitride.