• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.208-222
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• 2021

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

• Korean Journal of Food Science and Technology
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• v.37 no.2
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• pp.194-198
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• 2005

Growth curves of Listeria monocytogenes in modified surimi-based imitation crab (MIC) broth were obtained by measuring cell concentration in MIC broth at different culture conditions [initial cell numbers, $1.0{\times}10^{2},\;1.0{\times}10^{3}\;and\;1.0{\times}10^{4}$, colony forming unit (CFU)/mL; temperature, 15, 20, 25, 37, and $40^{\circ}C$] and applied to Gompertz model to determine microbial growth indicators, maximum specific growth rate constant (k), lag time (LT), and generation time (GT). Maximum specific growth rate of L. monocytogenes increased rapidly with increasing temperature and reached maximum at $37^{\circ}C$, whereas LT and GT decreased with increasing temperature and reached minimum at $37^{\circ}C$. Initial cell number had no effect on k, LT, and GT (p > 0.05). Polynomial and square root models were developed to express combined effects of temperature and initial cell number using Gauss-Newton Algorism. Relative coefficients of experimental k and predicted k of polynomial and square root models were 0.92 and 0.95, respectively, based on response surface model. Results indicate L. monocytogenes growth was mainly affected by temperature and square root model was more effective than polynomial model for growth prediction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.15-16
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• 2014

As trade cross the world is increasing these days, safe and effective management of harbour system is becoming important issue. With this background, the development of automatic time-domain simulation programme for ship berthing operation has been being peformed and PD (Proportional Derivative) controller has been used to control the speed and the heading angle of ships. This paper provides feasibility study for developing the time-domain simulation programme for berthing operation of ships with analysing advantages and drawbacks of the two different mathematical models, one is for low advance speed of ships by Kose (1984) and the other is MMG model for normal advance speed, through the simulations with various initial heading angles and positions of the ship.

• The Journal of Korean Association of Computer Education
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• v.19 no.3
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• pp.21-34
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• 2016

This study aims to develop user experience based mathematical program for self-directed learning. To meet its aim this program is designed and developed according to the process and method of 'ADDIE', general design model of education program. The features of this program are as follows. First, teacher can set questions conveniently through intuitive system of web and learner can solve questions at anytime and anywhere through instant access to application. Second, learner can solve different types of questions based on powerful question database and teacher can provide instantaneous feedback on them. Third, learner's circulation learning can be possible by utilizing paper-video explanation and wrong answer note and teacher supports learner's active learning management though group achievement management.

• Communications of Mathematical Education
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• v.27 no.2
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• pp.121-134
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• 2013

Linear Algebra are arguably the most popular math subjects in colleges. We believe that students' learning and understanding of linear algebra can be improved substantially if we incorporate the latest advanced information technologies in our teaching. We found that the open source mathematics program 'Sage' (http://sagemath.org) can be a good candidate to achieve our goal of improving students' interest and learning of linear algebra. In particular, we developed a simple mobile content which is available for Sage commands on common cell phones in 2009. In this paper, we introduce the mobile Sage which contains many Sage functions on a smart-phone and the mobile linear algebra content model(lecture notes, and video lectures, problem solving, and CAS tools) and it will be useful to students for self-directed learning in college mathematics education.

• Education of Primary School Mathematics
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• v.14 no.2
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• pp.207-218
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• 2011

This research is to explore mathematics gifted education which considered individual difference of gifted students in elementary school-level. The purpose of this study is to develop a differentiated instruction model and mathematical materials for gifted students that consider students' individual difference. We also investigate effectiveness of differentiated instruction through change of self-directed learning ability and studying satisfaction of gifted students. The results of this study will provide basic information on the after research related with development and application of mathematics gifted education program and differentiated instruction.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.7
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• pp.50-61
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• 1999

\In this paper, we consider the optimal scheduling of detection and tracking parameters in phased array radars to minimize the radar energy required for track maintenance in a cluttered environment. We develop a mathematical model of target detection induced by a search process in phased array radars. In the mathematical development, we take into account the effect of unwanted measurements that may have originated from clutter or false alarms in the detection process. We use and analytic approximation of the modified Riccati equation of the probabilistic data association (PDA) filter to take into account the effect of clutter interference in tracking. Based on the search process and the tracking models, we formulate the optimal scheduling problem into a nonlinear optimal control problem. We solve a constrained nonlinear optimization problem to obtain the solution of the optimal control problem.

• Journal of the Korea Safety Management & Science
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• v.14 no.1
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• pp.23-31
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• 2012

Recent research on stand-alone focused on the improvement and development of functions for solving problems such as the limited operating time of stand-alone installed at dwelling and their low reliability caused by false alarms, but it is more urgent to study on the operating range of stand-alone sensor in consideration of the impacts of combustion products on residents because the primary goal of fire safety is minimizing casualties. This study purposed to propose the optimized operating range of stand-alone sensor in consideration of the impacts of combustion products on residents. For this purpose, we made a mathematical approach to the change of temperature over the lapse of time in compartment fires similar to house fires, and established the standards of the body's response against heat and smoke based on literature review. In addition, we surveyed domestic and foreign technological standards for stand-alone sensor, and converted them to standards for residents of the body's response against heat and smoke using mathematical model equations and analyzed them comparatively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.120-128
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• 2011

Recently, safety diagnosis of the existing structures has been emerged as important issue. In particular, systematical and precise safety diagnostics for steel structures for power substation, have been required. Steel structures for power substation are under the periodical impact loads from operations of gas insulated switchgear. These loading condition accelerates damage and aging of structure. The objective of this research is to evaluate damage of structure under periodical impact loads. To evaluate the integrity of structures as organizing mathematical models including the dynamic characteristics of structures, Frequency Domain Decomposition method was choiced and an algorism was proposed. For verifying this methods and algorism, a mathematical model is composed of the development of a variety of reverse analysis and a signal processing technology reflecting physical damage of structures. A series of analysis and test results indicatge that proposed method has a confidence for applying a filed test. Therefore, it is expected to be able to take advantage of system identification to detect damage for the maintenance and management of steel structures under periodical impact loads such as power substation.

• Communications of Mathematical Education
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• v.36 no.2
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• pp.201-227
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• 2022

The purpose of this study was to develop an instrument measuring mathematics anxiety suitable for Korean High school students. In order to achieve this study purpose, the study was conducted according to the procedure of setting components of mathematics anxiety, developing questions, and verifying validity and reliability. First, in order to set the components of mathematic anxiety, previous studies on mathematic anxiety. Through this, six factors of mathematic anxiety were derived. Next, new questions were developed for each of the six constituent factors. The 122 questions were revised and supplemented through two content validity tests, and the final instrument for mathematics anxiety consisted of 49 questions of 6 factors. Finally, to verify the validity and reliability of the measurement instrument for mathematics anxiety, a survey was conducted on 1,848 students from 16 universities in Seoul and the metropolitan area. Next, a validity analysis was conducted with the 1,645 responses, excluding students who answered that there was no mathematics anxiety. As a result of exploratory factor analysis, 15 out of 49 questions were removed. Six factors were named individual characteristics, pressure on achievement, abstraction in mathematics, teaching and learning style, parental attitudes, and cumulative mathematics subjects. As a result of confirmatory factor analysis, the model fit was found to be appropriate, and the convergence validity and discriminant validity were found to be good.