• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1330-1338
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• 2015

In wireless communication network, the amount of packet data for the video streaming in the playout buffer of the receiver is changed with time according to network condition. If the amount of packet data is less than a specific buffer amount, the buffer underflow problem is generated. On the contrary, if the amount of packet data is more than a given buffer amount, the buffer overflow problem is occurred. When the playout of the video streaming is processed, these buffer underflow and overflow problems cause stop and skip phenomenons and then provide the discontinuity of playout. Therefore, to solve the buffer underflow and overflow problems of the video streaming in wireless communication network, This paper analyzes the combined effect of Token Bucket scheme, which controls the bursty traffic, and AMP(Adaptive Media Playout) scheme, which adaptively changes the playout speed of receiver. Through simulation, we found that the combination of Token Bucket and AMP schemes provides the superiority in terms of the occurrence number of buffer underflow and overflow, the stop duration time and the number of removed frames generated by underflow and overflow, and PSNR.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.31-40
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• 2012

The irregularity of railway track affects not only the comfort of ride such as noise or vibration but also the safety of train operation. For this reason, it is an interesting research area to design a reliable and sustainable railway track system and to analyze the train movement mechanism based on systematic approaches considering reasons of track irregularity possible in a specific local environment. Irregularity data inspected by EM-120, an railway inspection system in Korea includes unavoidable incomplete and erratic information, so it is encountered lots of problem to analyse those data without appropriate pre-data-refining processes. In this research, for the efficient management and maintenance of railway system, progress rate of standard deviation of irregularity is quantified. During the computation, some important components of railways such as rail joint, ballast, roadbed, and fastener have been considered. Probabilistic distributions of irregularity growth with respect to time are computed to predict the remaining service life of railway track and to be adapted for the safety assessment.

• Journal of Intelligence and Information Systems
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• v.18 no.1
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• pp.91-107
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• 2012

As the Internet becomes more popular, many people use it to communicate. With the increasing number of personal homepages, blogs, and social network services, people often expose their personal information online. Although the necessity of those services cannot be denied, we should be concerned about the negative aspects such as personal information leakage. Because it is impossible to review all of the past records posted by all of the people, an automatic personal information detection method is strongly required. This study proposes a method to detect or classify online documents that contain personal information by analyzing features that are common to personal information related documents and learning that information based on the Na$\ddot{i}$ve Bayes algorithm. To select the document classification algorithm, the Na$\ddot{i}$ve Bayes classification algorithm was compared with the Vector Space classification algorithm. The result showed that Na$\ddot{i}$ve Bayes reveals more excellent precision, recall, F-measure, and accuracy than Vector Space does. However, the measurement level of the Na$\ddot{i}$ve Bayes classification algorithm is still insufficient to apply to the real world. Lewis, a learning algorithm researcher, states that it is important to improve the quality of category features while applying learning algorithms to some specific domain. He proposes a way to incrementally add features that are dependent on related documents and in a step-wise manner. In another experiment, the algorithm learns the additional dependent features thereby reducing the noise of the features. As a result, the latter experiment shows better performance in terms of measurement than the former experiment does.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.87-92
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• 2010

As the Concept "how environmental friendly" becomes more and more important in road construction. However, so far there is no estimation method. Environmental friendly concept can be incorporated at the plan level in order to influence decision making, and support policies that affect environment. The overall goal of this study was to develop environmental friendly concept measures for the national highway and to develop a methodology to implement a more environmental friendly concept. The research identified 8 performance measures through a project analysis that could address environmental impact assessment system's ten strategic goals - Topography, Wildlife, hydrology, landuse, air quality, water quality, soil, waste, noise, landscape. The qualitatively and quantitatively evaluation approach was selected as the decision support framework and performance measure were investigated using the AHP(Analytic Hierarchy Process) and pilot corridor for a 10 section and calculate the index values. The methodology was applied to a pilot corridor comprised of a 120km section of national highway in korea. The methodology made it possible to identify the specific performance measures that need improvement to enhance the overall environmental friendly concept. It is fairly intuitive, based on readily available data, and is easy to apply. It provides a powerful tool for government to assess the relative environmental friendly conceptof their transportation corridors now and in the future. It allows for comparisons within a corridor and with other corridors and identifies the improvements needed to enhance the environmental friendly concept.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.15-21
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• 2004

It is possible to detect flaws in pipelines without interruption using all EMAT transducer because it is a non-contact transducer which can transmit ultrasonic waves into specimens without couplant. And it ran easily generate guided waves desired in each specific problem by altering the design of coil and magnet. In the present work, EMAT systems have been fabricated to generate surface waves, and selectively the plate wave of $A_1\;or\;S_1$ mode. The surface wave of 1.5MHz showed a good signal-to-noise ratio without distortion in its propagation along a pipeline, while the $S_1$ mode of 800kHz and the $A_1$ mode of 940kHz were distorted according to their dispersive properties. The wider the excitation pulse becomes, the better the mode selectivity of the plate waves becomes. A pipe of 256mm inner diameter and 5.5m thickness with 5 flaws was used for comparing the flaw detectability among the modes under consideration.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.10
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• pp.447-454
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• 2015

This paper proposes geographical name denoising by machine learning of event detection based on twitter. Recently, the increasing number of smart phone users are leading the growing user of SNS. Especially, the functions of short message (less than 140 words) and follow service make twitter has the power of conveying and diffusing the information more quickly. These characteristics and mobile optimised feature make twitter has fast information conveying speed, which can play a role of conveying disasters or events. Related research used the individuals of twitter user as the sensor of event detection to detect events that occur in reality. This research employed geographical name as the keyword by using the characteristic that an event occurs in a specific place. However, it ignored the denoising of relationship between geographical name and homograph, it became an important factor to lower the accuracy of event detection. In this paper, we used removing and forecasting, these two method to applied denoising technique. First after processing the filtering step by using noise related database building, we have determined the existence of geographical name by using the Naive Bayesian classification. Finally by using the experimental data, we earned the probability value of machine learning. On the basis of forecast technique which is proposed in this paper, the reliability of the need for denoising technique has turned out to be 89.6%.

• Journal of Korea Water Resources Association
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• v.52 no.8
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• pp.575-587
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• 2019

This study evaluated the effect of a mother wavelet in the wavelet analysis of various times series made by combining white noise and/or sine function. The result derived is also applied to short-memory arctic oscillation index (AOI) and long-memory southern oscillation index (SOI). This study, different from previous studies evaluating one or two mother wavelets, considers a total of four generally-used mother wavelets, Bump, Morlet, Paul, and Mexican Hat. Summarizing the results is as follows. First, the Bump mother wavelet is found to have some limitations to represent the unstationary behavior of the periodic components. Its application results are more or less the same as the spectrum analysis. On the other hand, the Morlet and Paul mother wavelets are found to represent the non-stationary behavior of the periodic components. Finally, the Mexican Hat mother wavelet is found to be too complicated to interpret. Additionally, it is also found that the application result of Paul mother wavelet can be inconsistent for some specific time series. As a result, the Morlet mother wavelet seems to be the most stable one for general applications, which is also assured by the recent trend that the Morlet mother wavelet is most frequently used in the wavelet analysis research.

• Journal of the Korea Institute of Building Construction
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• v.21 no.5
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• pp.483-493
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• 2021

Urban overcrowding has created an explosive supply and demand for high-rise buildings. High-rise buildings are contributing to enhancing the image of the city by serving as focal points, but due to the stack effect, malfunction of elevator doors, difficulties in opening and closing the doors and windows of the outer wall, smoke and odors spreading to the upper floors, noise, energy loss, fire and pollutants have been causing various unexpected problems such as rapid spread of fire. This study classified high-rise buildings according to their vertical zoning, analyzed the causes of and solutions to the stack effect, and derived design and construction methods. Through the initial plan to block the outside air and securing airtightness through precise construction, we sought ways to secure the airtightness inside and outside the building by actively blocking the airflow from the lower floors. In addition, the facility solution can be a measure to reduce the specific phenomena caused by the stack effect, but it should only be applied to the minimum extent because the potential for secondary damage is high. This study emphasized the need for systematic stack effect management by suggesting design and construction measures for each vertical zoning of the causes and countermeasures of the stack effect. It is expected that this study will be helpful not only for design and construction, but also for building maintenance.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.570-575
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• 2021

Since humans live while feeling rich in their five senses, care must be taken not to damage their hearing in order to lead a happy life. Hearing damage suffered in a living environment is common in a partial band where a specific frequency band is first damaged. However, since the initial pain of hearing damage does not appear much, it is difficult to determine the symptoms in the early stages. In this paper, we proposed a high-speed measurement method that can easily and quickly self-measure hearing damage through a simple app. In this method, 9 pure tones compensated for gain for each voice soub-band are alternately heard in both ears, so that one's own hearing damage can be detected at high speed. When 18 tone pulses were heard for 30 seconds per person, 1 out of 12 subjects was identified as suspected of partial hearing damage. And when the test subjects were informed of the hearing determination method for the number of hearings, the participants themselves immediately determined whether their hearing was damaged. This measurement method simply judges the hearing of both ears within 30 seconds with a smart phone, so that hearing measurements that took more than 10 minutes in hospitals are relatively accurate, and it was found that hearing health can be maintained while reducing time and costs.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.97-105
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• 2020

Recently, as the data speed and operating frequencies of Ethernet keeps increasing, electro magnetic interference (EMI) also becomes increasing. The generation of such EMI will cause malfunction of near electronic devices. In this study, EMI filters were applied to reduce the EMI generated by DC-DC SMPS (switching mode power supply), which is the main cause of EMI generation of Ethernet switch. As the EMI filter, MLCCs with excellent withstanding voltage characteristics were used, which had advantages in miniaturization and mass production. Two types of EMI MLCC filters were used, which are X-capacitor and X, Y-capacitor. X-capacitor was composed of 2 MLCCs with 10 nF and 100 nF capacity and 1 Mylar capacitor. Y-capacitor was consisted of 6 MLCCs with a capacity of 27 nF. When only X-capacitor was applied as EMI filter, the conductive EMI field strength exceeded the allowable limit in frequency range of 150 kHz ~ 30 MHz. The radiative EMI also showed high EMI strength and very small allowable margin at the specific frequencies. When the X and Y-capacitors were applied, the conductive EMI was greatly reduced, and the radiation EMI was also found to have sufficient margin. In addition, X, Y-capacitors showed very high insulation resistance and withstanding resistance performances. In conclusion, EMI X, Y-capacitors using MLCCs reduced the EMI noise effectively and showed excellent electrical reliability.