• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1223-1234
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• 2022

Efforts for reducing greenhouse gas emission coping with climate change have also been performed in the field of water and wastewater works. In particular, the technical development for reducing energy has been applied in operating water distribution system. The reduction of energy in water distribution system can be achieved by reducing structural loss induced by topographic variation and operational loss induced by leakage and friction. However, both analytical and numerical approaches for analyzing energy budget of water distribution system has been challengeable because energy components are affected by the complex interaction of affecting factors. This research drew mathematical equations for 5 types of state (hypothetical, ideal, leak-included ideal, leak-excluded real, and real), which depend on the assumptions of topographic variation, leakage, and friction. Furthermore, the derived equations are schematically illustrated and applied into simple water network. The suggested method makes water utilities quantify, classify, and evaluate the energy of water distribution system.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.245-250
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• 2014

Addiction can be largely divided into two categories. One is called medium addiction in which medium itself causes an addiction. Another is called cause addiction that brings addiction through combination of sensitive self and latent personal action. The medium addiction involves addiction phenomena directly caused by illegal drugs, alcohol and various other chemicals. The cause addiction is dependent on personal sensitivities as a sensitive problem of personal and includes cyber addictions such as shopping, work, game, internet, TV, and gambling. In this paper we propose two-dimensional addiction model that are equivalent to using an R-L-C series circuit of Electrical circuit and a Spring-Damper-mass of mechanical system. We also organize a Duffing equation that is added a nonlinear term in the proposed two-dimensional addiction model. We represent periodic motion and chaotic motion as time series and phase portrait according to parameter's variation. We confirm that among parameters chaotic motion had addicted state and periodic motion caused by change in control coefficient had pre-addiction state.

• Journal of Navigation and Port Research
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• v.27 no.4
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• pp.375-381
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• 2003

The studies on automatic ship collision avoidance system, which have been carried out last 10 years, are facing on new situation due to newly developed high technology such as computer and other information system. It was almost impossible to make it used in real navigation 3-4 years ago because of the absence of the tool to get other ship's information, however recently developed technology suggests new possibility. This study is carried out to develop the algorithm of automatic ship collision support system. The NOMOTO ship's mathematic model is adopted in simulation for its simplicity. The fuzzy reason rules are used for course-keeping system and for the calculation of Collision Risk using TCPA/DCPA. Moreover ‘encounter type’ between two ships is analyzed based on Regulations for Preventing Collisions at Sea and collision avoidance action is suggested. Some situations are simulated to verity the developed algorithm and appropriate avoidance action is shown in the simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.115-126
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• 2018

The purpose of this study is to examine the effects of the factors that hinder innovation of SMEs on innovation activities of Korean firms. Many existing literature studies remain focused on factors that promote innovation activities. However, in order for companies to promote innovation, it is important to analyze the factors that hinder innovation as well as those that promote innovation. In this study, we analyzed the relationship between technological innovation inhibition factors and technological innovation performance of 4,075 SMEs in Korea using the Korea Institute of Science and Technology Policy statistical data. The research model and hypothesis test of this study consist of three stages. First, the reliability of the variables used was verified using exploratory factor analysis. Second, the proposed hypothesis was modeled using structural equation modeling. Finally, validity of the structural equation was verified using confirmatory factor analysis. As a result, the lack of need for innovation influenced innovation performance and the government support system mediated them. SMEs should establish technological innovation strategies to maximize the effect of technological innovation with limited resources, and government should make polices to promote innovation of SMEs. It's expected to be used in the case of establishing a support policy.

• Composites Research
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• v.32 no.5
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• pp.284-289
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• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.

• Journal of Navigation and Port Research
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• v.40 no.4
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• pp.213-222
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• 2016

Recently, as cases of organizations' information disclosure occur continuously, it is urgent to manage security of information and establish measures to enhance security of information by an organization itself. Especially, members of an organization should be prepared with measures for information security, and an organization should do its efforts to raise its members' awareness toward information security. I set a research model to verify what effects an organization's fulfillment of regulations to secure information brings to performance of information security and selected members from maritime and port organizations and financial and insurance institutes as sample. Results of the analysis to identify factors affecting information security performance among members of maritime and port organizations are as follows. Firstly, I found that the factors affecting information security awareness are information security attitude and information security standards. Secondly, the factor giving influence on information security policy of an organization was found to be information security standards. In contrast, information security punishments and information security training were verified not to give influence on compliance of information security policy. Thirdly, information security awareness was identified to give significant influence on compliance of information security policy, information security competence and information security behavior. Fourthly, compliance of information security policy was verified to be those factors that give influence on information security competence and information security behavior. Lastly, information security competence and information security behavior were found to be such factors that give influence on information security performance.

• Journal of Distribution Research
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• v.12 no.1
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• pp.85-104
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• 2007

The basic purpose of this study is to investigate service quality and relationship quality affecting the result of long-term relationship between service buyers and suppliers. This research presented a constructive model(service quality${\rightarrow}$relationship quality${\rightarrow}$customer's revisiting intention) and then propose the research model base on prior researches and studies about relationships among components of service. Data were gathered from respondents who visit traditional markets. For this study, data were analyzed by SPSS and AMOS 5.0. Data were gathered from 209 respondents in the Korean traditional market. This research proposed 6 hypotheses on 5 latent variables and tested through structural equation modeling. 5 alternative measurements were compared through statistical significance test of the paths of research model and the overall fitting level of structural equation model. and the result was successful. The results of the study indicate that service quality is properly modeled as an antecedent of relationship quality and revisiting intentions. We also discussed managerial implications of the study and its limitations.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.560-564
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• 2011

The objective of this study is to propose a mathematical model for a pervaporation process for concentrating hydrogen peroxide. The process was developed by NASA, which consists of a shell and membrane tubes, where a liquid hydrogen peroxide solution flows in the shell, and a sweep gas flows in the tubes countercurrent to each other. The liquid retentate is concentrated as more water molecules permeate and evaporate through the membrane than hydrogen peroxide. For this process, a mathematical model has been developed in the form of a system of nonlinear partial differential algebraic equations based on a sorption-diffusion mechanism for permeation, an Arrhenius relationship for the temperature dependency of the permeate flux, and mass and momentum balances for the liquid concentrations and flows in the membrane module. The dynamic behavior of the concentration of hydrogen peroxide in the retentate side has been simulated by solving a simplified version of the proposed model, and the result is compared with the experimental data reported in the NASA patent.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.137-149
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• 2012

Field measurements of resistance to flow are analyzed for 739 rivers vegetated with grass (281 channels), shrubs (150 channels) and trees (308 channels). The measured distribution of Manning roughness coefficients ranges from 0.015~0.250 for grass, 0.016~0.250 for shrubs, 0.018~0.310 for trees. Significant trends are obtained between Darcy-Weisbach (or Manning roughness coefficients) and flow discharge, friction slope, and relative submergence. The regression equations for Darcy-Weisbach and Manning roughness coefficients in vegetated rivers are: $f_{veg}=0.436Q^{-0.363}$, $f_{veg}=3.305S_f^{0.508}$, and $n_{veg}=0.061Q^{-0.124}$, $n_{veg}=0.144S_f^{0.199}$, $V=5.3(h/d_{50})^{1/8.3}{\sqrt{ghS_f}}$, $\sqrt{8/f}(=V/u*)=5.75log(5h/d_{50})$, respectively. These semi-empirical relationships should be useful for hydraulic engineering practice.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.623-628
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• 2006

This paper presents the characteristics of an antenna factor of two kinds of EMI dipole antennas with a coaxial cable balun used in the frequency range between 30 and 1,000 MHz. The integral equation for unknown current distribution is solved by the Galerkin's method of moments with piecewise sinusoidal functions. An antenna factor for EMI dipole antennas with the coaxial cable balun is derived by using the power loss concepts. We can realize two kinds of EMI dipole antennas with appropriate antenna factors in the frequency range from 30 to 1,000 MHz: 150-cm dipole length($30{\sim}300 MHz$) and 30cm dipole length($300{\sim}1,000 MHz$). To check th ε validity of the theoretical analysis, the complex antenna factor was measured using by reference antenna methods. It is shown that the calculated complex antenna factor is good agreement with experimental results.