• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.5
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• pp.390-394
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• 2002

Spikelet number per unit area(SPN) is a major determinant of rice yield. Nitrogen nutrition status and biomass during reproductive stage determine the SPN. To formulate a model for estimating SPN, the 93 field experiment data collected from widely different regions with different japonica varieties in Korea and Japan were analyzed for the upper boundary lines of SPN responses to nitrogen nutrition index(NNI), shoot dry weight and shoot nitrogen content at panicle initiation and heading stage. The boundary lines of SPN showed asymptotic responses to all the above parameters(X) and were well fitted to the exponential function of $f(X)=alphacdot{1-etacdotexp(gamma;cdot;X)}$. Excluding the constant, from the boundary line equation, the values of the equation range from 0 to 1 and represent the indices of parameters expressing the degree of influence on SPN. In addition to those indices, the index of shoot dry weight increase during reproductive stage was calculated by directly dividing the shoot dry weight increase by the maximum value ($800 extrm{g/m}^{-2}$) of dry weight increase as it showed linear relationship with SPN. Four indices selected by forward stepwise regression at the stay level of 0.05 were those for NNI ($I_{NNI}_P$) at panicle initiation, NNI($I_{NNI}_h$) and shoot dry weight($I_{DW}_h$) at heading stage, and dry weight increase($I_{DW}$) between those two stages. The following model was obtained: SPN=48683ㆍ $I_{DWH}$$^{0.482}$ㆍ $I_{NNIp}$$^{0.387}$ㆍ $I_{NNIH}$$^{0.318}$ㆍ $I_{DW}$ $^{0.35}$). This model accounted for about 89% of the variation of spikelet number. In conclusion this model could be used for estimating the spikelet number of japonica rice with some confidence in widely different regions and thus, integrated into a rice growth model as a component model for spikelet number estimation.n.n.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.2
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• pp.143-148
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• 1999

Soil moisture condition is an important limiting factor in growth and yield in rice culture. The purpose of this study was to compare the influence on the growth, yield and Quality of rice subjected to soil moisture stress (SMS) at different growth stages. Ajaponica rice cultivar, Dongjinbyeo, was cultured under flooded conditions in a plastic container filled with silty loam soil. The container was subjected to SMS until the initial wilting point (IWP) coincided with about 10% in soil moisture content and about-200 kPa in soil matric potential, and was then irrigated again, at 6 and 5 of main growth stage in 1996 and 1997, respectively. At maturity, the plant height, tiller number, leaf area and top dry weight were decreased more in SMS treatments at the early stage than the late stage. The averaged yield index of SMS to control in both years was lowest at meiosis (62.5%), which primarily resulted from lower percent ripened grain and 1,000 grain weight, and second＇ reduced the spikelet number per panicle and panicle number per hill, and followed at tillering stage (68.5%) which resulted from the lower production in tiller number and top dry matter during and after SMS treatment. The percent-age of read rice in SMS plants varied with the treatment stage as order of lower at meiosis (44.0%), heading (53.9%), panicle initiation (70.1%), tillering (72.1%), ripening (75.8%) and 5 days after transplanting (DAT) (79.0%). Protein content in brown rice was slightly larger in SMS at late growth stage than the control, while the contents of fat and ash differed very little between SMS and control. Contents of Mg and K and Mg/K in brown rice with SMS were lower at some treatment stages such as at ripening or panicle initiation.

• Communications for Statistical Applications and Methods
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• v.23 no.1
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• pp.47-55
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• 2016

Stratified cluster sampling has been widely used for effective parameter estimations due to reductions in time and cost. The probability proportional to size (PPS) sampling method is used when the number of cluster element are significantly different. However, simple random sampling (SRS) is commonly used for simplicity if the number of cluster elements are almost the same. Also it is known that the ratio estimator produces a good performance when the total number of population elements is known. However, the two stage cluster estimator should be used if the total number of elements in population is neither known nor accurate. In this study we suggest a composite estimator by combining the ratio estimator and the two stage cluster estimator to obtain a better estimate under a certain population circumstance. Simulation studies are conducted to compare the superiority of the suggested estimator with two other estimators.

• Journal of Korean Society for Quality Management
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• v.45 no.1
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• pp.65-92
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• 2017

Purpose: The performance of global major airports is evaluated and several research questions are examined relative to the measures characterizing airport performance. Methods: The two-stage internal structure of airport performance is considered by decomposing it into physical operations and revenue generation. In the physical operations stage, operating costs, number of runways, terminal area and number of employees are used as inputs, while passenger throughput, cargo throughput and aircraft movements are taken as outputs. Subsequently, in the revenue generation stage, the outputs from the preceding stage are taken as inputs, while revenue is used as output. Results: Based upon this two-stage modeling of airport performance, a multiplicative two-stage network data envelopment analysis model is employed to calculate the overall and stage efficiencies of 59 airports using the recent data in the 2014 Airport Benchmarking Report published by the Air Transport Research Society. Several internal and external factors are also considered such as airport size, airport geographical location, proportion of international passengers, ownership (listed or not) and management style, and statistical analysis is performed to examine their impacts on airport performance. Conclusion: It is shown that the airports exhibit statistically significant difference across regions, and also some statistically significant factors affecting airport performance are identified.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.8
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• pp.1093-1098
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• 2017

Objective: The aim of the current study was to describe the relationship between milk yield and lactation number, stage, length and milking frequency in Korean Holstein dairy cows using an automatic milking system (AMS). Methods: The original data set consisted of observations from April to October 2016 of 780 Holstein cows, with a total of 10,751 milkings. Each time a cow was milked by an AMS during the 24 h, the AMS management system recorded identification numbers of the AMS unit, the cow being milking, date and time of the milking, and milk yield (kg) as measured by the milk meters installed on each AMS unit, date and time of the lactation, lactation stage, milking frequency (NoM). Lactation stage is defined as the number of days milking per cows per lactation. Milk yield was calculated per udder quarter in the AMS and was added to 1 record per cow and trait for each milking. Milking frequency was measured the number of milkings per cow per 24 hour. Results: From the study results, a significant relationship was found between the milk yield and lactation number (p<0.001), with the maximum milk yield occurring in the third lactation cows. We recorded the highest milk yield, in a greater lactation length period of early stage (55 to 90 days) at a $4{\times}$ milking frequency/d, and the lowest milk yield was observed in the later stage (>201 days) of cows. Also, milking frequency had a significant influence on milk yield (p<0.001) in Korean Holstein cows using AMS. Conclusion: Detailed knowledge of these factors such as lactation number, stage, length, and milking frequency associated with increasing milk yield using AMS will help guide future recommendations to producers for maximizing milk yield in Korean Dairy industries.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2697-2711
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• 2023

In this study, the validity of reducing the number of gas turbine stages designed for a nitrogen Brayton cycle coupled to a sodium-cooled fast reactor was assessed. The turbine performance was evaluated through computational fluid dynamics (CFD) simulations under different off-design conditions controlled by a reduced flow rate and reduced rotational speed. Two different multistage gas turbines designed to extract almost the same specific work were selected: two- and three-stage turbines (mid-span stage loading coefficient: 1.23 and 1.0, respectively). Real gas properties were considered in the CFD simulation in accordance with the Peng-Robinson's equation of state. According to the CFD results, the off-design performance of the two-stage turbine is comparable to that of the three-stage turbine. Moreover, compared to the three-stage turbine, the two-stage turbine generates less entropy across the shock wave. The results indicate that under both design and off-design conditions, increasing the stage loading coefficient for a fewer number of turbine stages is effective in terms of performance and size. Furthermore, the Ellipse law can be used to assess off-design performance and increasing exponent of the expansion ratio term better predicts the off-design performance with a few stages (two or three).

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.63-63
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• 2022

Wheat flour can be categorized into bread, all-purpose, cake flour according to its protein content. Since optimal wheat flour protein content is different for each end use, it is necessary to diversify the nitrogen fertilizer methods depending on the end use and cultivar. Optimal wheat flour protein content of soft wheat (for cake flour) is lowest (<=10%) among all end use, it is necessary to develop nitrogen fertilizer methods for high yield and low protein content. In order to analyze the yield and quality changes of soft wheat as nitrogen fertilizer amount and splitting timing, soft wheat cultivar 'goso' was sown on paddy soil in jeunju, Republic of Korea ('21.10). the amount of nitrogen fertilizer was divided into 4 levels by adjusting 2kg/10a increments from 5.1 to ll.lkg/lOa, and in the N 7.1 and 9.1 kg/1 Oa(standard) treatment, N amount divided into sowing date:regrowing stage=3:7,4:6(standard), 5:5. In regrowing stage, Tiller number and N fertilizer amount at sowing date showed a correlation; y=-121.14x²+792.66x-525.41 (R²=0.77^*, y: Tiller number/m², x: N amount at sowing date(kg/10a)). Tiller number in regrowing stage was the highest when the nitrogen fertilizer amount at sowing date was 3.23kg/10a. spike number per m² was the highest when N fertilizer was divided into sowing date:regrowing stage=3:7(N amount: 9.1kg/10a). If N fertilizer amount was fixed, grain yield was also the highest when N fertilizer was divided into sowing date :regrowing stage=3:7. Also, N amount at sowing date and grain yield showed no correlation, but N amount at regrowing stage and grain yield showed significant correlation. As N amount increased, protein content also showed a tendency to increase.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.62-62
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• 2022

Among annual precipitation in Korea (1306.3 mm), 54% of it falls intensively in summer, and only about 12.4% falls in April and May, when the water requirement of wheat is the highest. Korean wheat also could be damaged by soil water excess stress as frozen soil thaws after winter (late Feb-Mar). This study was conducted to evaluate effect of soil water stress on yield and quality of Korean wheat cultivar 'Saegeumgang'. Soil water treatments consisted of 4 treatments; water excess treatment in tilling stage (3.23-3.30), drought treatment in ripening stage (Apr-Jun), irrigation treatment in ripening stage (5.10) and standard condition. There was no significant difference between the treatment conditions for culm length, and the number of spike number was the highest in the order of irrigation in the ripening period (951)> standard cultivation (876)> excess water treatment in the tilling stage (752)> drought treatment in the ripening stage (767/m²). Test weight and Thousand grain weight were 548g/L and 22. lg respectively, which were lower than other treatments, and there was no significant difference between the other treatments. Abortive grain was 5.4kg/10a which was lower than other treatment, and there was no significant difference between the other treatment than other treatments. In drought treatment, protein content was 11.9% which is the highest among all treatments, and SDS-sedimentation value was 27.2ml under drought treatment which was very low compared to other treatments. Therefore, wheat yield and spike number were decreased in excess water condition at tilling stage and drought condition at ripening stage. Furthermore, wheat quality became deteriorate in drought condition at ripening stage.

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1279-1287
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• 2012

We particularly emphasized how to determine the number of replications with sequential and multistage procedures. So, the t-test is used to achieve some predetermined level of accuracy efficiently with loss function in the case of normal, chi-squared, an exponential distributions. We provided that the relevance of procedures are sequential procedure, two-stage procedure, modified two-stage procedure, three-stage procedure and accelerated sequential procedure. Monte Carlo simulation is carried out to obtain the stopping sample size that minimizes the risk.

• Clinical and Experimental Reproductive Medicine
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• v.24 no.3
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• pp.377-383
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• 1997

The effects of embryo number and incubation volume on the development of mouse embryos were evaluated. The growth rate of two-cell mouse embryos to attached blastocyst stage and the growth rate of blastocysts to early somite stage were assessed after culture in different incubation volumes and embryo densities. Embryos were collected from ICR female mice superovulated with pregnant mare serum gonadotropin and human chorionic gonadotropin and mated by ICR males. In experiment 1, groups of one, five, ten, twenty 2-cell embryos were cultured in 10-, 50-, 500-, 1000-${\mu}l$ drops of BWW media under mineral oil at $37^{\circ}C$ in a humidified atmosphere of 5% $CO_{2}$ and 95% air. As the incubation volume decreased, significantly (p<0.05) higher rates of embryos reached morular and blastocyst stage on day 3 and 4 culture, respectively. In experiment 2, groups of one, five, ten, twenty blastocysts were cultured in 1- and 2-ml volumes of CMRL 1066 media under same condition as in experiment 1. However the reverse was the result. Decreasing the number of embryos incubated per volume from 1 to 20 significantly (p<0.05) increased the number of blastocysts reaching the late egg cylinder (LEC) and early somite (ES) stage on day 6 and 8 culture, respectively, regardless of incubation volume. Blastocysts cultured in 2ml had higher (p<0.05) development rates to LEC and ES stage on day 6 and 8 culture, respectively, than embryos cultured in 1ml. Our results suggest that the effects of embryo number and incubation volume on the development of mouse embryos are stage specific and the shifting point was between hatching and EEC stage.