• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.169-175
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• 2006

Rotating annular disks are widely used in data storage devices such as CDs, DVDs(digital versatile disks), and HDs(hard disks). Higher data transfer rate in data storage disks could not be achieved by polycarbonate disks in the present market. The problem can be solved by applying the fiber-reinforce composite materials to the disks. In this paper, an application of composite materials to rotating disks is proposed to increase the critical speed. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating composite disks by the Galerkin method. The orthogonal functions are used in series solution. A companion paper(Part II) presents and discusses the numerical results of vibration analysis and critical speed for rotating polar orthotropic disk using the formulation and solution method given in this paper (Part I).

• Journal of the Korean Society for Railway
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• v.5 no.3
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• pp.158-166
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• 2002

In this paper, we introduce the software and hardware of the measurement system for on-line testing and evaluation of high speed railway. The test items focus on the verification of the performance and acquirement of the technical data of the high speed railway system. The software controls the hardware of the measurement system, perform the analysis and calculation of measurement data and acts as interface between users and the system hardware. For this purpose, three programs a measuring program, a monitoring program and post-processing program are developed. The detailed test scenario is in the process of development to closely follow the process of development and design of the system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.558-560
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• 2019

Recently, there are steadily required more highly broadcasting service based on the broadcasting extension and improved quality. This paper proposed the method of the implemented above mentioned. The proposed high speed data link techniques method is more improved processing speed and more efficiently editing advantage compare with earlier methods.

• Journal of Wind Energy
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• v.9 no.4
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• pp.40-46
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• 2018

In this study, a three-dimensional Navier-Stokes simulation around Wido Island was performed to analyze the wake effect behind an island. A 10 m/s wind speed and pressure boundary conditions were assigned for the inflow and outflow boundary conditions, respectively. Wido Island was modeled using GIS data. A prevailing wind from the north-northwest direction was determined based on QuikSCAT satellite data. A computational domain of $40km{\times}20km{\times}5km$ covering Wido Island was applied for numerical analysis. Sixty points were specified to extract the wind speed data. A wind speed profile inside the atmospheric boundary layer was compared with a wind profile using a simple power law. It turns out that the wake effect decreases the mean wind speed by 5% more or less, which corresponds to a 14% decrease in wind energy. Thus, the installation of a meteorological mast or development of a wind farm behind Wido Island is not highly recommended.

• Journal of Information Processing Systems
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• v.13 no.4
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• pp.668-676
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• 2017

Recently, the importance of big data has been emphasized with the development of smartphone, web/SNS. As a result, MapReduce, which can efficiently process big data, is receiving worldwide attention because of its excellent scalability and stability. Since big data has a large amount, fast creation speed, and various properties, it is more efficient to process big data summary information than big data itself. Wavelet histogram, which is a typical data summary information generation technique, can generate optimal data summary information that does not cause loss of information of original data. Therefore, a system applying a wavelet histogram generation technique based on MapReduce has been actively studied. However, existing research has a disadvantage in that the generation speed is slow because the wavelet histogram is generated through one or more MapReduce Jobs. And there is a high possibility that the error of the data restored by the wavelet histogram becomes large. However, since the wavelet histogram generation system based on the MapReduce developed in this paper generates the wavelet histogram through one MapReduce Job, the generation speed can be greatly increased. In addition, since the wavelet histogram is generated by adjusting the error boundary specified by the user, the error of the restored data can be adjusted from the wavelet histogram. Finally, we verified the efficiency of the wavelet histogram generation system developed in this paper through performance evaluation.

• Journal of IKEEE
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• v.10 no.2 s.19
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• pp.128-133
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• 2006

This paper describes a high speed interface circuit using redundant multi-valued logic for high speed communication ICs. This circuit is composed of encoding circuit that serial binary data are received and converted into parallel redundant multi-valued data, and decoding circuit that converts redundant multi-valued data to parallel binary data. Because of the multi-valued data conversion, this circuit makes it possible to achieve higher operating speeds than that of a conventional binary logic. Using this logic, the proposed 1:4 DEMUX (demultiplexer, serial-parallel converter), was designed using a 0.35um standard CMOS technology. Proposed DEMUX is achieved an operating speed of 4.5Gb/s with a supply voltage of 3.3V and with power consumption of 53mW. The operating speed of this circuit is limited by the maximum frequency which the 0.35um process has. Therefore, this circuit is to achieve CMOS communication ICs with an operating speed greater than 10Gb/s in submicron process of high operating frequency.

• Journal of Internet of Things and Convergence
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• v.8 no.4
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• pp.9-15
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• 2022

NAND flash memory is used as a medium for various storage devices due to its high data processing speed with low power consumption. However, since the read processing speed of data is about 10 times faster than the write processing speed, various studies are being conducted to improve the speed difference. In particular, flash dedicated buffer management policies have been studied to improve write speed. However, SSD(solid state disks), which has recently been used for various purposes, is more vulnerable to read performance than write performance. In this paper, we find out why read performance is slower than write performance in SSD composed of NAND flash memory and study buffer management policies to improve it. The buffer management policy proposed in this paper proposes a method of improving the speed of a flash-based storage device by analyzing the pattern of read data and applying a policy of pre-reading data to be requested in the future from NAND flash memory. It also proves the effectiveness of the read-ahead policy through simulation.

• Atmosphere
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• v.21 no.4
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• pp.439-446
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• 2011

NCEP reanalysis data were analyzed in order to provide distribution of global wind resource and wind speed in the surface layer for the years 2000-2009. Wind speed at 10 m above ground level (AGL) was converted to wind speed at 80 m above the ground level using the power law. The global average 80 m wind speed shows a maximum value of $13ms^{-1}$ at the storm track region. High wind speed over the land exists in Tibet, Mongolia, Central North America, South Africa, Australia, and Argentina. Wind speed over the ocean increased with a large value in the South China Sea, Southeast Asia, East Sea of the Korea. Sea surface wind in Western Europe and Scandinavia are suitable for wind farm with a value of $7-8ms^{-1}$. Areas with great potential for wind farm are also found in Eastern and Western coastal region of North America. Sea surface wind in Southern Hemisphere shows larger values in the high latitude of South America, South Africa and Australia. The distribution of low-resolution reanalysis data represents general potential areas for wind power and can be used to provide information for high-resolution wind resource mapping.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.93-101
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• 2012

PURPOSES : Adverse weather conditions such as heavy rain, heavy snowfall, and thick fog and so on have highly affect on the change in traffic conditions on the road. In particular, heavy snowfall causes capacity reduction as well as crash occurrence. This study investigated the effects of snowfall on speed on a freeway. METHODS : Vehicle detection systems data were matched with corresponding weather station data by regression analysis. RESULTS : The results show that the travel speed is reduced by 6.7% under little snowfall and by 12.8% under heavy snowfall. Regarding the speed variation, 8.7% and 114.7% increases are observed under little snowfall and heavy snowfall, respectively. It is also found that 1 cm increase in snowfall leads to 0.4% decrease in travel speed. In addition, the travel speed increases by 0.4% when the temperature increases by $1^{\circ}C$. CONCLUSIONS : It is expected that the outcome of this study will be useful in establishing more effective strategies for winter operations and road maintenance in practice.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.183-190
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• 2012

PURPOSES : The fundamental diagram provides basic information necessary in the analysis of traffic flow and highway operation. When traffic flow is congested, the density-flow points in the fundamental diagram are widely scattered and move in a stochastic manner. This paper investigates the pattern of density-flow point transitions and identifies car-following behaviors underlying the density-flow transitions. METHODS : From a microscopic analysis of 722 fundamental diagrams of NGSIM data, a total of 20 transition patterns of fundamental diagrams are identified. Prominent features of the transition patterns are explained by the behavior of the leader and follower. RESULTS : It is found out that the average speed and the speed difference between the leader and the follower critically determine the density-flow transition pattern. The density-flow path is very sensitive to the values of vehicle speed and spacing especially at low speed and high density such that most fluctuations in the fundamental diagram in the congested regime is due to the noise of speed and spacing variations. CONCLUSIONS : The result of this study suggests that the average speed, the speed difference between the leader and the follower, and the random variations of speed and spacing are dominant factors that explain the transition patterns of a fundamental diagram.