• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.780-788
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• 2011

The lack of QoS (Quality of Service) support functionalities in IEEE 802.11 DCF mode makes it difficult to provide real-time multimedia services in WLANs. In this paper, we propose an effective available bandwidth measurement method in IEEE 802.11b DCF environments. The proposed method measures the total channel idle time and the collision probability during each measurement period. Then, the available bandwidth is calculated by considering those measured information and the transmission overheads at MAC and PRY layers. The performances of the proposed method are evaluated using OPNET simulator. The simulation results show that the proposed method provides more exact results than existing comparable schemes.

• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.24-29
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• 2014

In general, a large-capacity axial flow fan is used for industrial processes or ventilation in a social overhead capital infrastructure. The main characteristics of the large axial-flow fan need a lot of electrical power consumption and operate 24 hours a day, 365 days a year. Since the large axial flow fan consumes several hundreds to thousands kW per hour, both manufacturer and consumer are struggling to select high efficiency products for saving energy and reducing operation cost. Therefore, the performance testing should be accurately conducted in experimental equipments. The performance estimation and uncertainty of measurement of the axial-flow fan gathered from the result from nozzle shaped testing equipments certified with ANSI/AMCA standard and duct shaped testing equipment under the same experimental condition. The experimental results from both facilities have maximum 17% differences in performance evaluation and uncertainty of measurement. As considering that the differences, it is doubt about the reliability of testing result. The test was repeated with the specific term during 12 months because it is important to fully reflect the real conditions and to decide the repeatability of data. The evaluation of duct type testing facilities was failed to get an uncertainty measure. Testing results were previously published. As a series of previous paper, axial fan (∅1690 mm) and duct type testing facilities were fabricated. The purpose of fabricating testing equipment was testing an uncertainty measurement under the controlled environments.

• ETRI Journal
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• v.43 no.3
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• pp.377-388
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• 2021

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1331-1345
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• 2017

Binary instrumentation has been developed for monitoring and debugging executables without their source codes. Previous efforts on the binary instrumentation are mainly focused on its capability and accuracy, but not on efficiency for practical application. In particular, criteria and measurement methodologies for evaluating and comparing the efficiency of binary investigation tools and algorithms do not estimated yet. In this paper, we propose the instrumentation primitives which are a unit functionality and measurement methodology. Through the empirical experiments by adopting the proposed methodology on DynamoRIO and Pin, we show the feasibility of the proposal.

• Journal of Information Processing Systems
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• v.6 no.2
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• pp.147-162
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• 2010

In this paper, we present a fine-grained localization algorithm for wireless sensor networks using a mobile beacon node. The algorithm is based on distance measurement using RSSI. The beacon node is equipped with a GPS sender and RF (radio frequency) transmitter. Each stationary sensor node is equipped with a RF. The beacon node periodically broadcasts its location information, and stationary sensor nodes perceive their positions as beacon points. A sensor node's location is computed by measuring the distance to the beacon point using RSSI. Our proposed localization scheme is evaluated using OPNET 8.1 and compared with Ssu's and Yu's localization schemes. The results show that our localization scheme outperforms the other two schemes in terms of energy efficiency (overhead) and accuracy.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1918-1923
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• 2010

In electic railway, 25kV is applied to AC sections of overhead contact lines and pantographs of Korea Train eXpress(KTX) make contact at speeds of 300km/h. Thus, there is a need to utilize wireless, optic, contact-less sensors to implement condition monitoring systems. This paper is based on describing and analyzing the condition monitoring system implementation technologies for efficient catenary current ratio characteristic assessment. The conclusion of this paper should be widely applied to design, diagnosis, completion of construction, current collection status, fault diagnosis, and selection of contact wires and suspension wires.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.491-495
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• 2004

Harbor and bay is essential social overhead capital to our country economy national security. This harbor and bay is ever-present danger of marine accident by massed sea traffic discharge. A nautical mark in sea maintains safety of sea traffic and establishes in sea for increase of efficiency of ship service to prevent this sea accident. In this study, position of light buoy that establish for safety of harbor and bay that decided adjacent district along the coast base point by utilization method of intersection and evaluated and compares with DGPS measurement techniques.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.205-207
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• 2003

The line impedance is important data that is applied in all analysis fields of electric power system like power flow, fault current, stability and relay calculation etc. Usually, impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistance. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Therefore, the line impedance were measured for this study in an actual power system of underground cables, and were analyzed by a generalized circuit analysis program EMTP for comparison with the measured value. These analysis result is considered to become foundation of impedance calculation for underground cable.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.470-472
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• 2003

This paper presents the measurement results and the statistical analysis of electrical and magnetic fields in the vicinity of overhead distribution lines. The maximum values of electrical and magnetic fields are 0.042kV/m and 8.3mG. The median values are 0.005kV/m and 1.3mG. The electrical and magnetic fields of distribution lines are compared to those of transmission lines and home appliances.

• Journal of International Society for Simulation Surgery
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• v.1 no.2
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• pp.83-86
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• 2014

Purpose This paper was purposed to suggest the method to produce the supportive helmet (head correction) for the infants who are suffering from plagiocephaly and to evaluate the level of transformation through 3D model. Method Either of CT or X-ray restored images has been used in making the supportive helmet (Head correction) in general, but these methods of measuring have problems in cost and safety. 3D surface measurement technology was suggested to solve such matters. Results It was to design the transformed model of the head within 0.7cm in average by scanning the surface of head and performing 3D restoration with marching cube and the changing rate of the head was compared in numerical data with 3D model. Conclusion The suggested methods displayed the better performance than the conventional method in respect of the speed and cost.