• Journal of KSNVE
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• v.4 no.3
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• pp.295-305
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• 1994

The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.118-120
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• 2023

Increasing port competition driven by the containerisation has motivated ports and terminals to focus on their performance to efficiently utilise the available resources and to make strategic decisions in port development and expansion. With both inter-port andintra-port competition increasing in the port of Colombo, this study aims to measure the efficiency of the container terminals in Colombo comparing to terminals in the port of Busan using the DEA window analysis to determine their operational efficiency and to provide suggestions for future port development activities. Multiple window analyses were conducted using CCR and BCC models with different orientations and window lengths to compare the efficiencies of 11 DMUs in both ports during the period from 2015-2019 to measure the efficiencies prior to the COVID-19 pandemic. Results revealed the largest terminal operator, PNC in Busan, to be the most efficient overall, while the second highest efficiency was recorded by one of the smallest terminal operators, SAGT in Colombo, among the sample. Although use of DEA in port performance measurement has been popular for many years, efficiency measurements in the port of Colombo, the main hub port in the South Asian region, has not been comprehensively studied so far.

• Journal of Information Processing Systems
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• v.2 no.1
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• pp.34-38
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• 2006

In the wireless network, TCP performs poorly because it was originally designed for wired networks and does not take into consideration wireless characteristics such as mobility, high-loss probability, and hidden-terminal problems. In particular, in the wireless multi-hop networks, a large congestion window increases the probability of contention and packet losses, and TCP performance is degraded severely as a result. So, it is necessary to limit the TCP congestion window size in order keep the probability of contention loss in the system to a minimum. In this paper, we propose a new scheme for determining the maximum congestion window size based on the measured bandwidth and Round-Trip-Time (RTT). Using ns-2 simulation, we show that the proposed scheme reduces the probability of packet contention and improves TCP performance.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.164-164
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• 2000

This paper proposes a moving window technique that extracts lanes and vehicles using the images captured by a CCD camera equipped inside an automobile in real time. For the purpose, first of all the optimal size of moving window is determined based upon speed of the vehicle, road curvature, and camera parameters. Within the moving windows that are dynamically changing, lanes and vehicles are extracted, and the vehicles within the driving lanes are classified as obstacles. Assuming highway driving, there are two sorts of image-objects within the driving lanes: one is ground mark to show the limit speed or some information for driving, and the other is the vehicle as an obstacle. Using characteristics of three-dimension objects, a neural network can be trained to distinguish the vehicle from ground mark. When it is recognized as an obstacle, the distance from the camera to the front vehicle can be calculated with the aids of database that keeps the models of automobiles on the highway. The correctness of this measurement is verified through the experiments comparing with the radar and laser sensor data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.888-894
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• 2007

The speech sound is detected by the vibration measurement of the window glass. In this study, we investigate the effect of the disturbing waves by background noise and window shaker excitation on the speech intelligibility of the detected sound. Based upon Modulation Transfer Function(MTF), speech intelligibility of the sound is objectively estimated by Speech Transmission Index(STI) As the level of the disturbing wave varies, variation of the speech intelligibility is examined. Experimental result reveals how STI is influenced by the level and frequency characteristics of the disturbing wave. By using a customized window shaker for disturbing sound, we evaluate the efficiency and the frequency characteristics of the anti-eavesdropping system. The purpose of the study is to provide useful information to prevent the eavesdropping through the window glass.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.519-526
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• 2005

Recently, the interest on the comfortable dwelling environment is increasing and the effort to solve the problem of exterior noise was tried. The propose of this study is to suggest the design of balcony window in apartment and to evaluate the sound insulation of it. So, we designed five types of balcony window which were considered not only sound insulation but ventilation. The sound reduction index of window was evaluated by the measurement in mock-up room. The results showed that case 2 improved about 6 dB in the weighted apparent sound reduction index than case 1, and case 3 reduced about $39 \%$ in construction cost than case 4.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.445-450
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• 2004

Recently, the interest on the comfortable dwelling environment is increasing and the effort to solve the problem of exterior noise was tried. The propose of this study is to suggest the design of balcony window in apartment and to evaluate the sound insulation of it. So, we designed five types of balcony window which were considered not only sound insulation but ventilation. The sound reduction index of window was evaluated by the measurement in mock-up room. The results showed that case 2 improved about 6dB in the weighted apparent sound reduction index than case 1, and case 3 reduced about 39% in construction cost than case 4.

• Journal of Environmental Health Sciences
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• v.44 no.4
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• pp.360-369
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• 2018

Objectives: Outdoor tobacco smoke can penetrate into the indoor environment through cracks in the building envelope. This study aimed to characterize the particle size distribution of infiltrated secondhand smoke (SHS) through the gap in a single glazed and a secondary glazed window according to pressure differences in a chamber. Methods: Two polyvinyl chloride sliding windows were evaluated for infiltration, one with a glazed window and the other with a secondary glazed window. Each window was mounted and sealed in a polycarbonate chamber. The air in the chamber was discharged to the outside to establish pressure differences in the chamber (${\Delta}P$). Outdoor smoking sources were simulated at a one-meter distance from the window side of the chamber. The particle size distribution of the infiltrated SHS was measured in the chamber using a portable aerosol spectrometer. The particle size distribution of SHS inside the chamber was normalized by the outdoor peak for fine particles. Results: The particle size distribution of SHS inside the chamber was similar regardless of window type and ${\Delta}P$. It peaked at $0.2-0.3{\mu}m$. Increases in particulate matter (PM) concentrations from SHS infiltration were higher with the glazed window than with the secondary glazed window. PM concentrations of less than $1{\mu}m$ increased as ${\Delta}P$ was increased inside the chamber. Conclusions: The majority of infiltrated SHS particles through window gap was $0.2-0.3{\mu}m$ in size. Outdoor SHS particles infiltrated more with a glazed window than with a secondary glazed window. Particle sizes of less than $1{\mu}m$ were associated with ${\Delta}P$. These findings can be a reference for further research on the measurement of infiltrated SHS in buildings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.600-605
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• 2000

The aim of this study is to compare the sound insulation performances of window depending on the measurement methods through the field test and analyze the factors that affect the sound insulation performances. Four measurement methods which are specified in the Koran Standard 2235 and the International Standard 140-5 were selected for the study; the outdoor sound source method which is classified the l000mm method and the 10mm method, the indoor sound source method, and the ISO method. The result of this study is that the sound insulation performance of the windows was the best when measured according to the ISO method and the worst the indoor sound source method. Through the study it was found that the main factors affecting the sound insulation performance of the windows were the correction of the specimen's area and the equivalent sound absorption area of the receiving room.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.722-725
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• 2013

In this work, we have been analyzed the characteristics of ReRAM with different annealing condition and temperature. The ReRAM devices with top electrode=150nm, bottom electrode=150nm, oxide thickness=70nm and annealing temperature=$500^{\circ}C$, $850^{\circ}C$ have been used in characterization. The Set/Reset voltage, sensing window and resistivity have been characterized. From the measurement results, the Set/Reset voltage and sensing window have been enhanced as the annealing temperature has been increased. But it has been decreased as the temperature performance has been increased. In case of the annealing temperature=$850^{\circ}C$, the variation of Set/Reset voltage was lower than that of other condition. But the variation of sensing window was the lowest when the annealing temperature was $500^{\circ}C$. With considering the variation of Set/Reset voltage and sensing window, the devices annealed at $850^{\circ}C$ showed the best performance to ReRAM.