• Journal of Communications and Networks
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• v.16 no.5
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• pp.548-558
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• 2014

Load distribution is vital to the performance of multipath transport. The task becomes more challenging in real-time multimedia applications (RTMA), which impose stringent delay requirements. Two key issues to be addressed are: 1) How to minimize end-to-end delay and 2) how to alleviate packet reordering that incurs additional recovery time at the receiver. In this paper, we propose sub-packet based multipath load distribution (SPMLD), a new model that splits traffic at the granularity of sub-packet. Our SPMLD model aims to minimize total packet delay by effectively aggregating multiple parallel paths as a single virtual path. First, we formulate the packet splitting over multiple paths as a constrained optimization problem and derive its solution based on progressive approximation method. Second, in the solution, we analyze queuing delay by introducing D/M/1 model and obtain the expression of dynamic packet splitting ratio for each path. Third, in order to describe SPMLD's scheduling policy, we propose two distributed algorithms respectively implemented in the source and destination nodes. We evaluate the performance of SPMLD through extensive simulations in QualNet using real-time H.264 video streaming. Experimental results demonstrate that: SPMLD outperforms previous flow and packet based load distribution models in terms of video peak signal-to-noise ratio, total packet delay, end-to-end delay, and risk of packet reordering. Besides, SPMLD's extra overhead is tiny compared to the input video streaming.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.909-914
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• 2007

Today's dynamic nature of the construction environment requires management systems to be active enough to take real-time decisions. For real-time decision making, effective 3D spatial information acquisition is imperative. Various 3D data acquisition technologies are being developed and tested for 3D spatial information acquisition and its use for wide range of areas in the construction industry, however, there are shortcomings in these technologies. The major problems are long processing time and high cost which make current technologies impossible to be used for real-time applications. Laser-based Flash LADAR that illuminates the entire scene with diffuse laser light is comparatively fast and cost effective, therefore it is well suited for 3D spatial modeling of dynamic environment on a construction site. This paper presents experimental results to evaluate the performance of flash LADAR and discuss issues of applicability of Flash LADAR to 3D spatial modeling on a construction site.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1976-1981
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• 2003

Except a desktop computer and workstation, an embedded system is a system containing microprocessors. While a desktop computer and a workstation are designed for a general purpose, an embedded system is designed for a dedicated purpose. Thus, an embedded system must meet some constraints such as low power consumption, low cost, small size, real-time, or user-defined ones. A simple and low cost embedded system may be able to be designed without using embedded operating systems (OS). However, considered design time and effort, some embedded system had better be designed with using embedded OS. Under given constraints and purpose of some embedded systems, one embedded OS can save more time, cost, and effort in designing those embedded systems than others. This paper compares four embedded OSs, Windows CE, Embedded Linux, pSOS, and uC/OS. It analyzes several issues of embedded OS such as process scheduling, inter-process communication (IPC), memory management, and network support. Also, it describes the product of each embedded OS.

• Research in Mathematical Education
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• v.6 no.1
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• pp.53-63
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• 2002

This study investigates the impact of Calculator-Based Ranger (CBR) activities in the performance of middle school students' graphing abilities of physical phenomena. Two issues about CBR activities on graphing abilities were addressed in this study; (1) the effect of CBR activities on graphing abilities, and (2) the influence of instructional styles on students' graphing abilities. Following the use of CBR activities, students' graphing abilities were significantly more developed in three components-interpreting, modeling, and transforming. Significant differences were found in students' achievement depending on instructional styles related to differentiation, which is closely connected to transforming distance-time graphs to velocity-time graphs. The findings of this study indicate that CBR activities may enhance students in constructing appropriate webs of related concepts and ability to qualitatively interpret graphs. Using collaborative CBR activities to introduce and explore graphing of physical phenomena is, therefore, recommended for inclusion in the secondary mathematics curriculum.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.166-171
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• 2010

Wired monitoring systems have been used for damage detection and dynamic analysis of large structures(bridges, dams, plants, etc.). However, the real-world applications still remain limited, mainly due to time and cost issues inherent to wired systems. In recent years, an increasing number of researchers have adopted WSN(wireless sensor network) technologies to the field of SHM(structural health monitoring). Accurate time synchronization is most critical for the wireless approach to be feasible for SHM purpose, along with sufficient wireless bandwidth and highly precise measuring resolution. To satisfy technical criteria stated above, a wireless vibration monitoring system that uses high-precision MEMS(micro-electro-mechanical system) sensors and A/D convertor is discussed in detail. It was found experimentally that the level of time synchronization fell within $200\;{\mu}sec$.

• Journal of the Korea Safety Management & Science
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• v.10 no.1
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• pp.139-144
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• 2008

Recently, a multi-facility, multi-product and multi-period industrial production-distribution planning problem has been widely investigated in Supply Chain Management (SCM). One of the key issues in the current SCM research area involves reducing both production and distribution costs. We have developed an optimization model to tackle the above problems under the restricted conditions such as transportation time and a zero inventory. Computational experiments using commercial tool Ms-Excel Solver show that the real size problems we encountered can be solved in reasonable time. The model can be used to decide an appropriate production-distribution planning problem in SCM research area.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.8
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• pp.629-639
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• 1989

One of the major issues of the industrial vision systems is lengthy processing time due to bulky data for image coding. To reduce the processing time, a modified chain coding algorithm is proposed in such a way that it is more suitable for hardware implementation. A hardware chain coder is developed and used for learn and recognizing objects by extracting several features. It is shown that the desired vision system is much faster than a typical software based system so that it may be applicable to real-time industrial operations.

• Journal of Internet Computing and Services
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• v.6 no.6
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• pp.1-12
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• 2005

The number of web contents is enormous in the billions and rapidly growing, Most contents are state, but an increasing number are generated dynamically, Therefore, Internet-based client/server architecture of Contents Delivery Service System suffers from frequent disconnections and security threats casused by dependency of the server or overload. Idle computing resources in Internet are used for sloving these issues, In this paper, We implement and design the Content Delivery Service System for cyber education system using idle Computing Power in P2P computing to share computing resources, We implement not only internet infrastructure but also satellite infrastructure system. and designed to transfer real-time or non real-time contents.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.137-139
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• 2012

This paper presents a system architecture and database of construction quality management system which encourages real time information tracking and monitoring. It improves the real time quality record tracking by using QR code technology in the project delivery. The advantages and issues relative to QR code and the database structures of the tracking system are presented. Conventional project scheduling system, operation modeling and analysis system, and quality management system are hybridized using QR code technology. The system improves project quality management by tracking the atomic tasks which consists of a construction process at the lowest level of construction hierarchy. It analyzes the quality records to determine the causes of abnormality and/or nonconformity. Using QR code technology, the construction quality management system may be more effective than the conventional one. It was confirmed that the quality management processes in construction project delivery can be more visible and controllable by integrating QR code technology, project scheduling system, and quality management system.

• The Journal of Information Systems
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• v.19 no.1
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• pp.79-96
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• 2010

The organizations in the competitive business environment are under pressure of handling internal management processes as well as external supply chain issues. In addition, the paradigm of supply chain management (SCM) has been shifted from static to dynamic problems. For the efficient SCM, organizations should be a RTE (Real Time Enterprises) that views entire supply chains as a single entity. In this paper, the agent system that makes RTE and dynamic supply chains possible is developed. Then, the developed agent system is verified in the TAC SCM(Trading Agent Competition Supply Chain Management) experimental environment and a dashboard is also developed for monitoring management activities of supply chains. The contributions of this paper are as followings. First, unlike the previous agent systems, the suggested agent system in this paper provides autonomy and scalability using SOA. Second, this suggested model for dynamic environment can be applied for the development of software supporting a SCM.