• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.1001-1008
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• 2018

In this paper, we propose an efficient location tracking scheme using wireless signals for various situations in marine environment that requires location information for many reasons such as lifesaving, accident prevention, and facility management. Our proposed location tracking scheme not only monitors user's location, but also minimizes the risk under the user's limited battery power budget. The position of a user can be obtained at base stations from the strengths of the received signals from the user. In this case, it may require to prevent the user from getting out of the predetermined safe area. For each location in the safe area, we define a risk function, which is influenced by many factors such as location accuracy, depth, flow rate, and geometry. Our proposed scheme is based on finger printing technique and aims at minimizing the average risk of each user in the safe area.

• Convergence Security Journal
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• v.12 no.1
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• pp.27-33
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• 2012

VANET(Vehicular Ad-hoc Network) is a kind of ad hoc networks consist of intelligence vehicular ad nodes, and has become a hot emerging research project in many fields. It provide traffic safety, cooperative driving and etc. but has also some security problems that can be occurred in general ad hoc networks. Also, in VANET, vehiculars sho uld be able to authenticate each other to securely communicate with network-based infrastructure, and their location s and identifiers should not be exposed from the communication messages. This paper explains V2I authentication pr otocol using a hash function that preserves the user privacy. In addition, we analyze the security stability of the V2I authentication protocol using Casper in the formal verification technique. As a result, V2I authentication protocol us ing hash function prove a stability.

• School Mathematics
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• v.5 no.3
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• pp.343-360
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• 2003

In this paper, we deal with the teaching of algebra based on patterns and generalization. The past algebra curriculum starts with letters(variables), algebraic expressions, and equations, but these formal approaching method has many difficulties in the school algebra. Therefore we insist the new algebraic approaches should be needed. In order to develop these instructions, we firstly investigate the relationship of patterns and algebra, the relationship of generalization and algebra, the steps of generalization from patterns and levels of difficulties. Next we look into the algebra instructions based arithmetic patterns, visual patterns and functional situations. We expect that these approaches help students learn algebra when they begin school algebra.

• Journal of the Korean Institute of Gas
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• v.21 no.2
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• pp.41-49
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• 2017

Recently, as the number of facilities using chemicals is increasing, the amount of handling is rapidly increasing. However, chemical spills are occurring steadily, and if large quantities of chemicals are leaked in time, they are likely to cause major damage. These industrial complexes use information obtained from a number of sensors to detect and monitor leaking areas, and are used in industrial fields by applying existing fixed sensors to robots and drones. Therefore, it is necessary to propose a sensor placement method at the interface for rapid detection and response based on various leaking scenarios reflecting leaking conditions and environmental conditions of the chemical handling process. In this study, COMSOL was used to analyze the actual accident scenarios by applying the medium parameter to the case of chemical leaks. Based on the accident scenarios, the objective function is selected so that the velocity of each robot is calculated by attaching importance to each item of sensor detection probability, sensing time and sensing scenario number. We also confirmed the feasibility of this method of reliability analysis for unexpected leak accidents. Based on the above results, it is expected that it will be helpful to trace back the leakage source based on the concentration data of the portable sensor to be applied later.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.51-57
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• 2019

A plant layout problem has a large impact on the overall construction cost of a plant. When determining a plant layout, various constraints associating with safety, environment, sufficient maintenance area, passages for workers, etc have to be considered together. In general plant layout problems, the main goal is to minimize the length of piping connecting equipments as satisfying various constraints. Since the process may suffer from the heat and friction loss, the piping length between equipments should be shorter. This problem can be represented by the mathematical formulation and the optimal solutions can be investigated by an optimization solver. General researches have overlooked many constraints such as maintenance spaces and safety distances between equipments. And, previous researches have tested benchmark processes. What the lack of general researches is that there is no realistic comparison. In this study, the plant layout of a real industrial C3MR (Propane precooling Mixed Refrigerant) process is studied. A MILP (Mixed Integer Linear Programming) including various constraints is developed. To avoid the violation of constraints, penalty functions are introduced. However, conventional optimization solvers handling the derivatives of an objective functions can not solve this problem due to the complexities of equations. Therefore, the PSO (Particle Swarm Optimization), which investigate an optimal solutions without differential equations, is selected to solve this problem. The results show that a proposed method contributes to saving the capital expenditures.

• School Mathematics
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• v.15 no.1
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• pp.159-177
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• 2013

This study is a case study of STEAM education. We have developed teaching and learning materials, suggested teaching method, and analysed the result for exploring the potential and effect of STEAM. The content of this study is based on the history of mathematics. Science (S) is related to the 24 divisions of the year, the height of the sun, the movement of heavenly bodies. Technology (T) is related to the exploration with graphic calculators. Engineering (E) is related to design sundial and research on the design principles. Art (A) is related to literature review about mathematical history, the understanding of the value of the mathematics. Mathematics (M) is related to the trigonometric functions. We have considered that Project-Based Learning is proper teaching and learning for STEAM education, we have designed the STEAM PBL and analysed the results focused on the developing integrative knowledge, mathematical attitude including mathematical value, the competencies of 21 century. The result of this study is as follows. We find that STEAM education activates students' collaboration, communication skills and improves representation and critical thinking skills. Also STEAM education makes positive changes of students' mathematical attitudes including the values of the mathematics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.785-791
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• 2023

Risk management is essential for preventing accidents arising from uncertainties in TBM tunnel projects, especially concerning managing the risk of TBM tunnel collapse, which can cause extensive damage from the tunnel face to the ground surface. In addition, prioritizing risks is necessary to allocate resources efficiently within time and cost constraints. Therefore, this study aimed to establish a TBM risk database through case studies of TBM accidents and determine a risk priority for TBM tunnel collapse using the Bayes theorem. The database consisted of 87 cases, dealing with three accidents and five geological sources. Applying the Bayes theorem to the database, it was found that fault zones and weak ground significantly increased the probability of tunnel collapse, while the other sources showed low correlations with collapse. Therefore, the risk priority for TBM tunnel collapse, considering geological sources, is as follows: 1) Fault zone, 2) Weak ground, 3) Mixed ground, 4) High in-situ stress, and 5) Expansive ground. In practice, the derived risk priority can serve as a valuable reference for risk management, enhancing the safety and efficiency of TBM construction. It provides guidance for developing appropriate countermeasure plans and allocating resources effectively to mitigate the risk of TBM tunnel collapse.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.475-480
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• 2014

In the fields of researches associated with plant layout optimization, the main goal is to minimize the costs of pipelines for connecting equipment. However, what is the lacking of considerations in previous researches is to handle the multi floor processes considering the safety distances for domino impacts on a complex plant. The mathematical programming formulation can be transformed into MILP (Mixed Integer Linear Programming) problems as considering safety distances, maintenance spaces, and economic benefits for solving the multi-floor plant layout problem. The objective function of this problem is to minimize piping costs connecting facilities in the process. However, it is really hard to solve this problem due to complex unequality or equality constraints such as sufficient spaces for the maintenance and passages, meaning that there are many conditional statements in the objective function. Thus, it is impossible to solve this problem with conventional optimization solvers using the derivatives of objective function. In this study, the PSO (Particle Swarm Optimization) technique, which is one of the representative sampling approaches, is employed to find the optimal solution considering various constraints. The EO (Ethylene Oxide) plant is illustrated to verify the efficacy of the proposed method.

• Journal of Educational Research in Mathematics
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• v.18 no.2
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• pp.201-221
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• 2008

This study discusses how the humanity mathematics education can be realized in practice. The essence of mathematical concept is gradually disclosed revealing the ambiguities in the concept currently accepted and clarifying them. Historical development of mathematical concepts has progressed as such, exemplified with the group-theoretical thought and continuous function. In learning of mathematical concepts, thus, students have to recognize, reveal and clarify the ambiguities that intuitive and context-dependent definitions in school mathematics have. We present the process of improvement of definitions of a tangent and a polygon in school mathematics as examples. In the process, students may recognize the limitations of their thoughts and reform them with feelings of humility and satisfaction. Therefore this learning process would contribute to cultivating students' minds as the humanity mathematics education pursues.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3548-3557
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• 2010

Security enhancement technologies are required to preventing phishing and pharming attacks on Internet banking. One-time password(OTP) should be used with certificate for enhancing user authentication and security performance. However, existing OTP technique is weak on MITM(Man-In-The-Middle) attack and synchnonization should be provided on OTP system. Therefore, more advanced mechanism such as combining biometic data with OTP can be suggested to enhancing security on authentication system. In this paper, we designed and implemented a multifactor authentication system using one-time biometric template to generate unique authentication data after adapting biometric transform on each user's biometric data.