• Korean Journal of Food Science and Technology
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• v.19 no.6
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• pp.463-470
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• 1987

In order to develop a rapid predicting method of the shelf-life of moisture sensitive foods and establish their proper packaging methods, the qualify changes and shelf-life of dired laver as a model food were studied by the computer simulation. A mathematical model of the relationship between the rate constants of chlorophyll a and water activity was established at $10^{\circ}C,\;25^{\circ}C$ and $40^{\circ}C$. Computer simulation to predict water activity and chlorophyll a was developed by considering the simultaneous influence of storage conditions such as water content of products, storage temperature and relative humidity, packaging materials. Simulated quality changes of dried laver was in good agreement with the experiment data. Chlorophyll a and sensory score decreased as the water activity increased. And correlation coefficient between the sensory scores and the contents of chlorophyll a was very high as 0.991. The critical water activity by sensory evaluation was around 0.55. The shelf-life of dried laver packaged with plastic films could be predicted from the above results in various storage conditions.

• Journal of the Korean School Mathematics Society
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• v.15 no.1
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• pp.109-135
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• 2012

In December of 2009, General Curriculum Revised in 2009 was announced and research on corresponding mathematics curriculum revision has been initiated from that period. Finally, in August 2011, Mathematics Curriculum Revised in 2009 was announced. In this new curriculum, Creativity is emphasized as the ability pursued in General Curriculum Revised in 2009. Accordingly, for the purpose of fostering students with creative and challenging minds, teaching and learning methods including the objectives and content should be more carefully implemented in math class. In case of the area of Probability and Statistics closely related to real life situations, it is suggested that school curriculum in mathematics would not deal with only mathematical problems on algorithm, but rather present teaching and learning materials related to the real life in order to recognize the usefulness of the content of Probability and Statistics and to learn how to think about it. In this paper, effective guidelines for teaching and learning the content of Probability and Statistics and its activities that follows the direction on Mathematics Curriculum Revised in 2009' are suggested based on the analysis of the PISA and TIMSS international assessments items. Thus, the guidelines suggested in this study would be used efficiently and appropriately for developing instructional materials or planning curriculum revision and setting its direction in the future.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.1
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• pp.26-33
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• 1999

Coastal sediments in polluted areas adsorb many hydrophobic pollutants such as PCBs. During environmental remediation projects like dredging, they can be resuspended and transported to less polluted areas. To assess the environmental impact, the author previously developed a mathematical model that can simulate the changes of particle size distribution (PSD) due to sedimentation, vortical dispersion and coagulation. In this research, the simulation results using this model were presented in conjunction with observed PSDs from a 2-m settling column simulating coastal environments. The simulations showed that the model predictions were in fairly good agreement with the observed data (changes of PSDs in terms of depths and times), and that the resuspended sediments coagulated during the vertical transport. So, this study showed that the developed model has a good ability to describe the very complicated phenomena of real aggregation and vortical transport dynamics of coastal sediments with various particle sizes.

• Journal of Cadastre & Land InformatiX
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• v.44 no.2
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• pp.139-153
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• 2014

The world geodetic system transformation of cadastral record have to minimize differences of boundary and area being in cadastral record according to transformation for that is direct connected with the land owner and property protection. However it is very difficult to accurately maintain the before and after transformation because coordinate transformation is generally using a mathematical conversion formula. At present, Helmert model by using 4-parameter is official coordinate transformation model for Cadastral Resurvey Project but scale factor is most sensitive to changes of area and relative position in the same parcel. In this study, it was proposed 3-parameter method using by scale factor fixing through the application of a Helmert in order to avoid changing the area difference and keeping the error within the tolerance range of the boundary which is related to the boundary point coordinate region.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.15-22
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• 2012

The variation in the wind speed with height above ground is called the wind shear profile. In the field of wind resource assessment, analysts typically use one of two mathematical relations to characterize the measured wind shear profile: the logarithmic profile (log law) and the power law profile (power law). The logarithmic law uses the surface roughness as a parameter, and the power law uses the power law exponent as a parameter. The shape of the wind shear profile typically depends on several factors, most notably the roughness of the surrounding terrain and the stability of the atmosphere. Since the atmospheric stability changes with season, time of day, and meteorological conditions, the surface roughness and the power law exponent also tends to change in time. For this study, Using the observed data from Met-mast, located in Pyeongdae, Handong in Jeju. we used the matlab and windograper to calculate roughness length and the law exponents. These calculations are similar to reference the data, but they have different ranges. In the ocean case, each reference data and calculated data was the same, but the crop area is higher than the earlier studies. In addition, the agricultural village is lower than the earlier studies.

• Communications of Mathematical Education
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• v.38 no.2
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• pp.93-120
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• 2024

On-line education in mathematics education changed in various aspects before and after COVID-19. This study conducted a systematic literature review of 98 academic papers on on-line education published from 2017 to 2023 in the field of mathematics education before and after COVID19. In particular, this study conducted content analysis to organize on the definitions of various similar terms related to online education. In addition, this study explored research trends on year, research subject, research method, on-line education type, and research topic by the pre-COVID-19, COVID-19, and post-COVID-19 era. Also, a comparative analysis was conducted on literatures on the effects of online education. As a result, first, it was confirmed that there is a need to organize the definitions of terms similar to online education. Also, the implications of identifying the differences and hierarchies between each term can be found. Second, it was confirmed that teachers' expertise for on-line mathematics education was emphasized based on the result of the rapid increase in the number of on-line education studies on teachers since COVID-19. Third, it was confirmed that the number of studies on blended and flipped learning was high in pre-COVID-19, but decreased in the COVID-19 era. Instead, in the COVID-19 era, studies on real-time interactive classes were rapidly active, and even in the post-COVID-19 era, studies on real-time interactive classes still occupied a large proportion. Finally, it was confirmed that the effectiveness of on-line education varies depending on the research background and model. Accordingly, the need to be cautious in interpreting the results of each study on the effectiveness of on-line education was confirmed. Based on these findings, this study presented implications for future research on on-line education in mathematics education.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.739-746
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• 2008

The aim of this study is finding the optimal design parameters and the optimal operation variables of a reactive distillation column. Different from steady state optimization, dynamic optimization makes it possible considering operation ability as well as design problems at process design step. For performing dynamic optimization, dynamic simulation should be done first. If dynamic simulation is already finished, dynamic optimization can be performed with less effort than that of dynamic simulation.Reactive distillation systems involving reaction and separation in a single unit have the potential to reduce capital and operating costs, particularly when reaction have conversion constraint or when azeotropes exist making conventional separation difficult and expensive. This study here present work on the continuous distillation process, the homogeneous catalyzed esterification of methanol and acetic acid, the synthesis of methyl acetate. Based on an equilibrium stage model of a reactive distillation column a dynamic optimization problem was formulated and solved. And the results were verified by performing dynamic simulation and showing the variation of conversion and purity as the variation of the operation variables. As the results of dynamic optimization, this study found optimal feed ratio, reflux ratio and reboiler duty of this system. And as this study applied it to dynamic simulations the dynamic characteristics of a reactive distillation column are showed under optimal operating condition.

• Journal of the Korean School Mathematics Society
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• v.11 no.3
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• pp.377-397
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• 2008

In today's secondary school mathematics curriculum, assessment is to be focused on evaluating the student's mathematical thinking rather than finding the correct solution to the problem. A descriptive evaluation method is therefore introduced to the school districts and suggested as an alternative assessment method in K-12 school mathematics. Descriptive evaluation method is widely available for use in schools, but there are barriers to using it since the teachers are forced to use the method by the school districts. In this research, we surveyed 120 secondary school mathematics teachers in Seoul and the surrounding metropolitan area to understand the status and the perception about using descriptive evaluation. The goal of the study was to find and understand the direct implications of using the new assessment method in secondary mathematics classes. The study showed that most of the mathematics teachers used the descriptive assessment method during their regular exam periods which is given twice per semester. Most of the open-ended problems used for descriptive evaluation were medium or high level math questions which were graded by the teachers at least 3 times to ensure objective evaluation. The teachers stated that objectivity in grading, administrative situation, and development of descriptive problems were the difficult barriers in descriptive evaluation. The teachers in the survey also commented that teachers' administrative responsibility should be reduced and that school environment in general should be improved for the new assessment method to become successful. Finally, the study showed that development of more descriptive problems with specific grading guidelines need to be developed for each grade level.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.545-552
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• 2015

Process modeling and simulation is a powerful methodology to quantitatively predict the change of process variables when operating and design conditions are changed. In this study, considering drawbacks of currently used process simulator for combined cycle plants, we developed process modeling system equipped with an ease of use and flexibility for model development. For this purpose, the analysis of combined cycle processes was carried out and consequently, mathematical models and libraries were developed. Furthermore, in view of the fact that the level of the abstraction of process models depends on the purpose of simulation as well as the available data, simple and rigorous models were also developed for some important units. In use of reference combined plant, we executed process simulation using the developed modeling system and the comparison was made between the results of simulation and the reference data. Less than 1% marginal error was identified and we concluded that the modeling system can be applied for commercial combined cycle processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.517-526
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• 2015

This paper presents the results of study for improving the reliability of quadrotor attitude control by applying a multi-sensor along with a data fusion algorithm. First, a mathematical model of the quadrotor dynamics was developed. Then, using the quadrotor mathematical model, simulations were performed using the improved reliability multi-sensor data as the inputs. From the simulation results, we designed a Gimbal-equipped quadrotor system. With the quadrotor in a hover state, we performed experiments according to the angle change of the user's specifications. We then calculated the attitude control data from the actual experimental data. Furthermore, with additional simulations, we verified the performance of the designed quadrotor attitude control system with multiple sensors.