• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.100-109
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• 2012

In this paper, some ideas are proposed to establish the infrastructure of all-electric houses which are able to reduce primary energy consumption and $CO_2$ emission by adopting heat pump systems and induction heating cookers excluding the use of fossil fuel energy. This electrification concept is based on the consumption of only one type of energy which means electricity as secondary energy and the conventional fossil fuel energy is just consumed to generate electricity as primary energy. All-electric house is laid on the extension of the hydrogen economy in a long-term viewpoint so that the effectiveness of this new conceptual house is estimated analyzing the reduction of $CO_2$ emission. In this analysis, the balance of electricity supply and demand is considered including the construction of new power plants by renewable energy such as nuclear, IGCC and fuel cell because decarbonization is an essential element of hydrogen technology and economy and this action is accomplished in both supply and demand side of electricity. The results are able to contribute to develop various useful hydrogen policies and strategies and some detail researches are required previously to make the best application of this new conceptual house.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.43-50
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• 2011

The monitoring system for link travel speed using taxi probe is one of key sub-systems of ITS. Link travel speed collected by taxi probe has been widely employed for both monitoring the traffic states of urban road network and providing real-time travel time information. When sample size of taxi probe is small and link travel time is longer than a length of time interval to collect travel speed data, and in turn the missing state is inevitable. Under this missing state, link travel speed data is real-timely not collected. This missing state changes from single to multiple time intervals. Existing single interval prediction techniques can not generate multiple future states. For this reason, it is necessary to replace multiple missing states with the estimations generated by multi-interval prediction method. In this study, a multi-interval prediction method to generate the speed estimations of single and multiple future time step is introduced overcoming the shortcomings of short-term techniques. The model is developed based on Non-Parametric Regression (NPR), and outperformed single-interval prediction methods in terms of prediction accuracy in spite of multi-interval prediction scheme.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.743-749
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• 2010

This paper proposes a derating design method for improving system reliability by using a probabilistic approach. In the proposed design, the focus is upon system levels in determining derated levels of stresses such as temperature and current, unlike recent design approaches that focus on component levels. System reliability is evaluated using component reliability metrics that are given as functions of time and unknown stresses; this evaluation is based on a series system-reliability model. The variation in stress, which was not considered in previous derating designs, is introduced in the present design to account for the uncertainty in both environmental and operating conditions at the customer' hands. Optimization problems for system reliability improvement are formulated and solved using FORM to determine the best derating design. An example of a derating design for an electrical system shows the details of the proposed method and its applicability to systems design for reliability improvement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.55-61
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• 2017

In DVB-S3 standard of satellite broadcasting systems, FTN technique is applied to LDPC codes with (1+7) PSK modulation. In standard, BICM-ID and BCJR decoding method are considered to alleviate performance degradation due to FTN processing. BICM-ID method improves performance by calculating a new LLR from hard-decision value of decoder output. BCJR also improves performance by calculating forward and backward matrix each other. However these two methods require high computational complexity. Therefore this paper proposed modified decoding method in order to reduce computational complexity without performance degradation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.4
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• pp.390-402
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• 2009

This study aimed to examine the general characteristics of individual workers, psychosocial working environment, and ergonomic risk factors which affect the status of musculoskeletal disorders. Self-report was carried out for musculoskeletal symptoms and ergonomic risks in working environment in 856 production workers in 16 small to medium sized manufacturing companies. Musculoskeletal symptoms were examined with a standardized questionnaire, and ergonomic risks were evaluated with a qualitative self-administered instrument for the tasks related to musculoskeletal disorders. Major findings were as follows: 1) Complaint rate for musculoskeletal symptoms was higher in female, aged, married workers with longer working hours, less leisure/hobby activity, longer household working hours and history of disease or accident. 2) Complaint rate for musculoskeletal symptoms was significantly higher in workers with dissatisfaction, difficult tasks, and no self-control at work. 3) Complaint rate for musculoskeletal symptoms was significantly higher in workers involved in tasks with major ergonomic risk factors, and handling heavy equipment. 4) Explanatory power increased the model with the musculoskeletal symptoms as dependent variable and demographic variables, psychosocial working environment and ergonomic risk factors included, and total explanatory power of 18.6% revealed the significant effect. Based on the results, we can conclude that musculoskeletal symptoms in manufacturing workers are associated with individual demographic characteristics, psychosocial working environment and ergonomic risk factors.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.112-119
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• 2001

Parameter tuning methods by Ziegler-Nickels for control systems are generally classified into Z-N(1) and Z-N(2). The purpose of this paper is to describe what relations exist between methods of Z-N(1) and Z-N(2), or how Z-N(1) method can be originated from Z-N(2) method by analyzing one loop control system of P or PI controller and time delay process. The formulas of Z-N(1) consist of process parameters, L(time delay), $K_m$(gain) and $T_m$(time constant), but Z-N(2) method is based only on the ultimate gain $K_u$ and the ultimate period $T_u$ acquired normally by practical trial without any parameters of Z-N(1). In this paper, for the first step to seek mutual relations, the simple formulas of Z-N(2) are transformed into the formulas composed of the same parameters as Z-N(1) which is derived from the analysis of frequency characteristics. Then, the approximation of the actual ultimate frequency is proposed as important premise in the translation between Z-N(1) and (2). Such equalization and approximation brings a simple approximated formula which can explain how Z-N(1) is originated from the Z-N(2) in the form of formula. And a model system is adopted to compare the approximated formula to Z-N(1) and Z-N(2) methods, the results of which show the effectiveness of the proposals.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.897-904
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• 2012

The rifling design problem has continuous-type shape variables and an integral number of riflings. In addition, it requires considerable time for analysis because its behavior should be described by a nonlinear finite element model (FEM). Therefore, this study presents an efficient design process for rifling based on a design of experiment (DOE) approach. First, Bose's orthogonal array is used to represent 25 runs for four design variables including three shape variables and one integer variable. Then, nonlinear FE analyses are performed. Next, to minimize the bullet resistance without affecting the bullet velocity and bullet rotational angle immediately before a bullet leaves the gun barrel, a what-if design is performed. In the proposed what-if design, a functional including the design objective and constraints is constructed and effect analysis is performed by using the functional. It is found that the new design obtained from the what-if design shows better results than the current one.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.2
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• pp.197-215
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• 2015

Modeling water flow in variably saturated, porous media is important in many branches of science and engineering. Highly nonlinear relationships between water content and hydraulic conductivity and soil-water pressure result in very steep wetting fronts causing numerical problems. These include poor efficiency when modeling water infiltration into very dry porous media, and numerical oscillation near a steep wetting front. A one-dimensional finite element formulation is developed for the numerical simulation of variably saturated flow systems. First order backward Euler implicit and second order Crank-Nicolson time discretization schemes are adopted as a solution strategy in this formulation based on Picard and Newton iterative techniques. Five examples are used to investigate the numerical performance of two approaches and the different factors are highlighted that can affect their convergence and efficiency. The first test case deals with sharp moisture front that infiltrates into the soil column. It shows the capability of providing a mass-conservative behavior. Saturated conditions are not developed in the second test case. Involving of dry initial condition and steep wetting front are the main numerical complexity of the third test example. Fourth test case is a rapid infiltration of water from the surface, followed by a period of redistribution of the water due to the dynamic boundary condition. The last one-dimensional test case involves flow into a layered soil with variable initial conditions. The numerical results indicate that the Crank-Nicolson scheme is inefficient compared to fully implicit backward Euler scheme for the layered soil problem but offers same accuracy for the other homogeneous soil cases.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.231-237
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• 2008

One of the basic requirements for the most advanced countries would be the well-planned traffic infrastructures. For such traffic safety systems, foreign countries follow the current tendency to which they manage the traffic facilities and equipments based on the objective assessment for the state of every traffic safety facility in terms of Asset Management(AM). As the road safety facilities related among them are very diverse, and their functions are very important as well, the regulations and directions for installing them are enacted. However, despite the standards and directions for the installations, sometimes, the facilities are not installed in accordance with the standards, not only causing inconvenience to the users but also negatively affecting the safety for them. In the study, for the facilities in which the installation interval and height are standardized according to the designed speed and geometrical structure of the road among the various road safety facilities, the image analysis model capable of measuring them with a line scanning camera was developed. In addition, the program systematically analyzing this was also developed and applied to the field and, as the result of that, the size and installation interval of the facilities could be measured fast and accurately.

• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.61-77
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• 2003

Due to the wide expansion of the internet, people can freely get information what they want with lesser efforts. However without adequate forms or rules to follow, it is getting more and more difficult to get necessary information. Because of seemingly chaotic status of the current web environment, it is sometimes called "Dizzy web" The user should wander from page to page to get necessary information. Therefore we need to construct system which properly recommends appropriate information for general user. The representative research field for this system is called Recommendation System(RS), The collaborative recommendation system is one of the RS. It was known to perform better than the other systems. When we perform the web user modeling or other web-mining tasks, the continuous feedback data is very important and frequently used. In this paper, we propose a collaborative recommendation system which can deal with the continuous feedback data and tried to construct the web page prediction system. We use a sojourn time of a user as continuous feedback data and combine the traditional model-based algorithm framework with the Support Vector Regression technique. In our experiments, we show the accuracy of our system and the computing time of page prediction compared with Pearson's correlation algorithm.algorithm.