• Journal of Elementary Mathematics Education in Korea
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• v.19 no.3
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• pp.267-287
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• 2015

In this paper, based on the results of analysis on types and strategies of estimation in measurement in the textbooks according to 2009 revised elementary mathematics curriculum, the following four implications are suggested for curriculum development and textbook development for a later date. First, it is necessary to reconcile curriculum and textbooks in contents for estimation in measurement. In 2009 revised elementary mathematics curriculum, only estimation in length, estimation in capacity, estimation in weight, estimation in angular measure are presented. However, estimation in time and estimation in area are presented in textbooks. Second, it is necessary to introduce various strategies for estimation in measurement. In teacher's manual, three strategies like using referent, chunking, unitizing are illustrated. But in textbooks, such strategies are not illustrated properly. Third, the meaning of the 'estimate' need to be clarified. In textbooks, 'estimate' are used also in other contexts. Fourth, it is necessary to clarify whether or not to deal with estimation in time, estimation in area, and estimation in volume in the school curriculum. In 2009 revised elementary mathematics curriculum, estimation in time, estimation in area, and estimation in volume are not mentioned explicitly.

• Education of Primary School Mathematics
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• v.20 no.1
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• pp.1-18
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• 2017

The purpose of this study is the reorganization of the curriculum on the measurement, a part of the second grade math curriculum, for the improvement of the estimation capability in the elementary school students. Research questions were as follows: (1) how are the estimation capabilities of the students who have taken lessons on the diversified estimation strategies? and (2) how are the mathematical writing capabilities of the students who have taken lessons on the diversified estimation strategies? The study using reconstructed lessons was conducted on 18 second grade students in an elementary school located in Seoul. Results show that the students' estimation capabilities and have improved. They started to use 'about' when writing estimation results, different from writing the accurate measurements. Measurement errors were gradually reduced, ending up with a student who could accurately estimate exactly 1m. In addition, their estimation capabilities in using appropriate estimation strategy and writing skills describing the estimation strategy have improved.

• Journal of Elementary Mathematics Education in Korea
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• v.24 no.1
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• pp.53-87
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• 2020

The purpose of this study was to find a future direction for improving computational estimation instruction through examining the contents of computational estimation included in the 2015 revised elementary school mathematics curriculum and elementary school mathematics textbook and teacher's guide. Through this, several suggestions was made as follow. Firs, it is necessary to emphasize the computational estimation across all grade groups. Second, it is necessary to teach the computational estimation strategies systematically. It was found that it is necessary to reinforce the activities related to computational estimation in the computation related units.

• Journal of Animal Science and Technology
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• v.61 no.3
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• pp.122-137
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• 2019

Methane, one of the important greenhouse gas, has a higher global warming potential than that of carbon dioxide. Agriculture, especially livestock, is considered as the biggest sector in producing anthropogenic methane. Among livestock, ruminants are the highest emitters of enteric methane. Methanogenesis, a continuous process in the rumen, carried out by archaea either with a hydrogenotrophic pathway that converts hydrogen and carbon dioxide to methane or with methylotrophic pathway, which the substrate for methanogenesis is methyl groups. For accurate estimation of methane from ruminants, three methods have been successfully used in various experiments under different environmental conditions such as respiration chamber, sulfur hexafluoride tracer technique, and the automated head-chamber or GreenFeed system. Methane production and emission from ruminants are increasing day by day with an increase of ruminants which help to meet up the nutrient demands of the increasing human population throughout the world. Several mitigation strategies have been taken separately for methane abatement from ruminant productions such as animal intervention, diet selection, dietary feed additives, probiotics, defaunation, supplementation of fats, oils, organic acids, plant secondary metabolites, etc. However, sustainable mitigation strategies are not established yet. A cumulative approach of accurate enteric methane measurement and existing mitigation strategies with more focusing on the biological reduction of methane emission by direct-fed microbials could be the sustainable methane mitigation approaches.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.58-66
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• 2003

This paper discusses the practical issue of the bias estimation of the KOREASAT ground tracking data. First, a batch filter based orbit determination algorithm including the turn around range measurement in addition to the range, azimuth and elevation measurement is presented. Then the estimation performance is analyzed through simulation studies. Additionally, this paper proposes a tracking antenna bias estimation strategies using accurately tuned secondary ground tracking station. Finally the relationship between antenna biases are analyzed to give comprehensive tool for estimation results evaluation.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.427-434
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• 2003

This paper describes a new method of detecting rotor position in switched reluctance motor(SRM), Some strategies of position sensorless control methods for the motor include the measurement of phase current and applied pulse voltage in an unexcited phase. The principle of the estimation of a rotor position is based on the detection of inductance by pulse currents. This sensorless method is very simple to compute rotor position estimation and gives efficient control of drive system. Suggested method is verified by some experimental tests.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.228-230
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• 2004

This paper describes a new method of detecting rotor position in switched reluctance motor(SRM). Some strategies of position sensorless control methods for the motor include the measurement of phase current and applied pulse voltage in an unexcited phase. The principle of the estimation of a rotor position is based on the detection of inductance by pulse currents. Suggested method is verified by some experimental tests.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.159.2-159.2
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• 2012

In this study, we propose an effective strategy for precise orbital and geodetic parameter estimation using SLR (Satellite Laser Ranging) observations for ILRS AAC (Associate Analysis Center). The NASA/GSFC GEODYN II software and SLR normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 are utilized for precise orbital and geodetic parameter estimation. Weekly-based precise orbit determination strategy is applied to process SLR observations, and Precise Orbit Ephemeris (POE), TRF (Terrestrial Reference Frame), and EOPs (Earth Orientation Parameters) are obtained as products of ILRS AAC. For improved estimation results, selection strategies of dynamic and measurement models are experimently figured out and configurations of various estimation parameters are also carefully chosen. The results of orbit accuracy assessment of POE and precision analysis of TRF/EOPs for each case are compared with those of existing results. Finally, we find an appropriate strategy for precise orbital and geodetic parameter estimation using SLR observations for ILRS AAC.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.8
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• pp.1305-1318
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• 2007

On a global scale agriculture and in particular enteric fermentation in ruminants is reported to produce about one fourth (21 to 25%) of the total anthropogenic emissions of methane ($CH_4$). Methane is produced during the anaerobic fermentation of hydrolyzed dietary carbohydrates in the rumen and represents an energy loss to the host besides contributing to emissions of greenhouse gases into the environment. However, there appears to be uncertainty in the $CH_4$ estimation from livestock due to the limited availability of data to document the variability at the farm level and also due to the significant impact of diet on the enteric $CH_4$ production. The methane mitigation strategies require robust prediction of emissions from rumen. There are many methods available which would be suitable for measuring $CH_4$ produced from the various stages of animal production. However, several factors need to be considered in order to select the most appropriate technique like the cost, level of accuracy required and the scale and design of the experiments to be undertaken. Selection of any technique depends on the accuracy as each one has its advantages and disadvantages. Screening of mitigation strategies may be evaluated using individual animal before large-scale trials on groups of animals are carried out. In this review various methods for the estimation of methane production from ruminants as well as for the determination of methane production potential of ruminant feeds are discussed. The advantages and disadvantages of the methods starting from respiration chamber, ventilated hood, facemask, sulphur hexafluoride ($SF_6$) tracer technique, prediction equations and meteorological methods to in vitro methods are detailed.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.558-561
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• 2005

This paper describes a novel method of detecting excitation position in switched reluctance motor(SRM) drive. Some strategies of position sensorless control methods for the motor include the measurement of phase current and applied pulse voltage in an unexcited phase is suggested. The principle of the estimation of a rotor position is based on the detection of inductance by pulse currents. This sensorless method is very simple to detect excitation position estimation and gives efficient control of drive system. Suggested method is verified by some simulations.