• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.86-91
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• 2005

Regarding some of tire important works in tire shipyard, like tire production process, quality control, and material handling, there are many elements that disturb tire work-flaw. For example, there are mistakes in manufacturing, delay of production, and poor quality. These kinds of disturbances are from tire delay of communication time between tire production field and tire management. Therefore, it would be possible to strengthen tire competitiveness of shipbuilding industries by applying tire information technology based on Wireless Local Area Network (Wireless LAN), in order to establish tire multi-possession of real time production information in limited large shipbuilding yard. In this study, tire construction concept of tire information system, based on Wireless LAN, is proposed to build communication infrastructures in shipyards. The various information regarding shipbuilding inspection, process management, and material flaw are analyzed and constructed to databases in tire middle ware system, as tire platform for using Personal Display Agent (PDA). At last, tire middle ware system, which delivers tire information, is developed by tire C$\sharp$ and Microsoft.net; also, tire PDA application system is structured in WinCE O/S, and is tested and evaluated under tire server linked condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1967-1978
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• 2003

Transparency has been considered as a performance measure in bilateral teleoperation system. Therefore, many issues of transparency have been studied. This paper investigates the transparency in two-channel control architectures. At first, we show the feasibility using analytic transparency-conditions and present the two classes of two-channel control architecture, which are perfectly transparent under ideal situation. In addition, remedies to problems due to impedance model estimation errors under real situation are introduced. They are as fellows; design guideline of control parameters to reduce the effect of model estimation error effect and introduction of time delay estimation for unknown dynamics. From these analyses, the systematic control scheme, which is stable and well transparent under real implementation, is proposed in two-channel control architecture. Finally, the proposed scheme is applied to a 2 D.O.F master-slave system and the experimental results show the validity of the theoretical work.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.29-36
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• 2016

The effect of high ambient temperature and pressure conditions on the combustion performance of n-butanol, n-heptane and its mixing fuel (BH 20) were studied in this work. To reveal this, the closed homogeneous reactor model applied and 1000-1200 K of the initial temperature, 20-30 atm of initial pressure and 1.0 of equivalence ratio were set to numerical analysis. It was found that the results of combustion temperature was increased and the ignition delay was decreased when the ambient conditions were elevated since the combustion reactivity increased at the high ambient conditions. On the contrary, under the low combustion temperature condition, the combustion pressure was more influenced by the ambient temperature in the same ambient conditions. In addition, the total mass and the mass density of tested fuels were influenced by the ambient pressure and temperature. Also, soot generation of mixing fuel was decreased than n-heptane fuel due to the oxygen content of n-butanol fuel.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.691-708
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• 2010

An important issue of supporting multi-users with diverse quality-of-service (QoS) requirements over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resource while, at the same time, to meet each communication service QoS requirement. In this work, we study the problem of a variety of communication services over multi-media heterogeneous cognitive OFDM system. We first divide the communication services into two parts. Multimedia applications such as broadband voice transmission and real-time video streaming are very delay-sensitive (DS) and need guaranteed throughput. On the other side, services like file transmission and email service are relatively delay tolerant (DT) so varying-rate transmission is acceptable. Then, we formulate the scheduling as a convex optimization problem, and propose low complexity distributed solutions by jointly considering channel assignment, bit allocation, and power allocation. Unlike prior works that do not care computational complexity. Furthermore, we propose the FAASA (Fairness Assured Adaptive Sub-carrier Allocation) algorithm for both DS and DT users, which is a dynamic sub-carrier allocation algorithm in order to maximize throughput while taking into account fairness. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.134-141
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• 2010

In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based wireless mesh networks using directional antenna. The performance is presented in terms of throughput of system and delay between each node by varying number of users. The result show that proposed scheduling algorithm improving the performance by reducing the delay of mesh network system. Our work may be useful as a guideline to control the fairness between SSs for multi-hop systems such as multi-hop relay and mesh networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.4 s.107
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• pp.393-399
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• 2006

In this paper we applied a ray tracing method to estimate the scattering characteristics from large scale random rough surfaces. For the electromagnetic field evaluation, we have used the diffracted coefficient of the knife edge diffraction for the diffracted rays and Fresnel's reflection coefficients in connection with reflected rays. In addition, we examine to search for the traced rays using the imaging method which can be obtained all rays to arrived at receivers accurately and the diffracted field from rough surfaces is considered. Numerical examples have been carried out for the scattering characteristics of an ocean wave-like rough surface and delay spread characteristics of a building-like surface. In the present work we have demonstrated that the ray tracing method is effective to numerical analysis of a rough surface scattering.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2E
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• pp.10-17
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• 1999

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

• Nuclear Engineering and Technology
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• v.25 no.3
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• pp.403-412
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• 1993

By making use of the microprocessor technology, instrumentation system becomes intelligent. In this study a programmable smart transmitter is designed and applied to the nuclear engineering measurements. In order to apply the smart transmitter technology to nuclear engineering measurements, the digital time delay compensation function and water level change detection function are developed and applied in this work. The time compensation function compensates effectively the time delay of the measured signal, but it is found that the characteristics of the compensation function should be considered through its application. It is also found that the water level change detection function reduces the detection time to about 7 seconds by the signal processing which has the time constant of over 250 seconds and which has the heavy noise.

• Journal of Construction Engineering and Project Management
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• v.4 no.4
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• pp.41-46
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• 2014

Indian Construction industry is large, volatile, and requires tremendous capital outlays. Typically, the work offers low rates of return in relation to the amount of risk involved. A unique element of risk in the industry is the manner in which disputes and claims are woven through the fibre of the construction process. Delay is generally acknowledged as the most common, costly, complex and risky problem encountered in construction projects. Because of the overriding importance of time for both the Owner and the Contractor, it is the source of frequent disputes and claims leading to lawsuits. The growing rate of delays is adversely affecting the timely delivery of construction projects. Presently construction industries are facing a lot of problems, considering that a paper assess construction stakeholder's perception to the causes of delays and its effects on project delivery. And also one case study is considered in this paper to elicit responses from construction stakeholders. The primary aim of this paper is to identify the perceptions of the different parties regarding causes of delays, the allocation of responsibilities and the types of delays, and method of minimizing the construction delays.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.59-60
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• 2018

Busan New Port has continued to expand its capacity to handle transshipment cargos exceeding 50 percent of its total volume, but it is considered inefficient because of the work scheduling based on the worker experience. In particular, depending on the transshipment task situation, which often requires an external truck, excessive congestion caused by the vehicle's delay can lead to increased logistics costs and social costs. One way to resolve this issue is to minimize the single transport of the truck and to maximize dual-cycle transport by putting the finished truck into another task. Therefore, we would like to study how to efficiently schedule transportation transshipment cargos between terminals considering dual-cycle.