• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.45-46
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• 2015

본 논문에서는 무게중심좌표계에 의한 공간벡터 PWM의 간단한 구현방법을 제안한다. 무게중심좌표계를 사용하면 듀티비를 계산할 때 SIN, COS의 함수계산없이 단순한 사칙연산만을 사용하고 기준벡터가 속한 섹터에 따라 서로 다른 듀티비를 정하는 식을 유도할 필요가 없으며 듀티비가 어떻게 정해지는지에 대한 직관적인 이해를 할 수 있다. 본 논문에서는 무게중심 좌표계에서 공간벡터 PWM의 듀티비를 정하는 원리에 대하여 설명한다.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.445-450
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• 1998

In the present paper the effects of combined heat and mass transfer on the fin efficiency were calculated. Sector method was used for calculating the fin efficiency of the continuous fin. The parameter Lewis No. and C which describe the combined heat and mass transfer is derived by using the heat and mass transfer analogy and effects of Lewis No. and C on the fin efficiencies were calculated.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.8
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• pp.348-366
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• 2007

Capacity of modem storage devices is becoming larger than yesterday and integration of disk is increasing. It refers that physical errors can damage a lot of digital information on storage devices. So we propose file system test framework in this paper to test integrity and robustness of file systems. We develop the tool for generating bad sectors on disks and the tool which creates all physical errors defined in storage devices. We also develop the tool for immediately monitoring the condition of read and write execution on storage devices. So, by integrating those tools, we develop FORT, test framework for confirming robustness of file system. We analyze robustness of ext3 file systems by FORT. Lastly, we present draft of intelligent system merging file system and device driver's layer architecture.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.286-291
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• 2013

In this paper, a compact rectenna system is designed using a circular sector antenna with harmonic-rejecting characteristics and a direct impedance matching method. The system is designed with bandpass filtering performed by the harmonic-rejection of the circular sector antenna and without impedance matching circuit for the diodes by the direct impedance matching technique. Therefore, while the rectifying circuit of the proposed system can be implemented without a bandpass filter and a impedance matching circuit, it is integrated on the back side of the antenna using precise fabrication techniques for coaxial feedings without degrading the system performances corresponding to the feeding points. From the experimental results, the optimized rectenna system has presented excellent performances of a conversion efficiency of more than 52 % and a conversion voltages of more than 1.5 V at 2.5 GHz.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.161-168
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• 2015

Horizontally curved bridges are subjected to torsional loads by their vertical dead loads only as well as eccentric loads, which cause negative reactions at supports. In this paper, effects of bridge curvature on vertical reactions at supports are investigated for 48.8 m length simple span steel box girder bridges with elastomeric bearings by varying curvature angle from 0.49 to 1.35 rad. In order to expect magnitude and direction of reactions including possibility of negative reactions, reaction evaluation equations have been analytically developed by separating a superstructure of curved bridge into independent components. Concrete slabs and bottom flanges in steel box section are assumed geometrical annular sectors in area dimension, and top flanges and webs that have very narrow projected areas are assumed geometrical arcs in line dimension. Proposed equations have relatively simple forms and prediction values are on very good agreement with those from finite element analyses by difference of 1% order.

• Journal of the Korea Society of Computer and Information
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• v.19 no.7
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• pp.113-130
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• 2014

In this paper, we propose BLOCS algorithm to find sequence of data that should be saved in cache device of hybrid storage system which uses SSD as a cache device. BLOCS algorithm which uses a sequence pattern mining scheme, creates a set of frequently requested sectors with respect to requested order of sectors. To compare the performance of the proposed scheme, we introduce Distance (DIST) based scheme, Request Frequency (FREQ) based scheme, and Frequency times Size (F-S) based scheme. We measure the hit ratio and I/O latency of different caching schemes using hybrid storage caching simulator. We acquired booting workload along with ten scenarios of launching applications and use the workloads as input to the cache simulator. After experiment with booting workload, we find that BLOCS scheme gives hit ratio of 61% which is about 15% higher than the least performing DIST scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.611-619
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• 2005

The present paper proposes two different packet scheduling algorithms in the IEEE 802.16e type TDD-OFDMA downlink, which are the weighted fair scheduling(WFS) and the throughput guarantee scheduling(TGS). The performance of proposed scheduling algorithms are compared to some of conventional schedulers such as round robin(RR), proportional fair(PF), fast fair throughput(FFTH), and fair throughput(FH) in terms of service coverage, effective throughput and fairness at 64 kbps and 128 kbps minimum user throughput requirements. For a relatively smaller throughput(64 kbps) requirement, the proposed algorithms provide higher improvement in the number of users per sector within 95$\%$ service coverage while satisfying the lxEV-DV fairness criterion. For a relatively larger throughput(128 kbps) requirement, the proposed algorithms provide higher coverage enhancement while maintaining the same effective aggregate throughput over PF scheduler.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.1-7
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• 2009

In this paper, the author presents the MIMO(Multi-Input Multi-Output) receiver algorithm with the capability of inter-cell or inter-sector interference cancellation over multi-antenna OFDM(Orthogonal Frequency Division Multiplexing) systems. As contrast with the previous research dealing with the filtering scheme at the time domain, the proposed algorithm is presented as the pre-filtering scheme which can be applicable to the frequency domain. Note that the proposed one can be implemented only by pilot symbols which are used in the channel estimation. In addition, it is analytically confirmed that the proposed scheme can be applied for either MIMO( C-SM(Collaborative-Spatial Multiplexing)) interference or SIMO(Single-Input Multi-Out) interference. The proposed receiver algorithm is verified by simulations over UL-PUSC SR off in IEEE 802.16e standard. From simulation results, it is confirmed that the proposed one can be applicable regardless of the kind of interference. Furthermore, it is verified that the performance is guaranteed even under Ole severe effect of interference and the improvement of system throughput is guaranteed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.769-774
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• 2013

Turbine blades and disc, which are one of the most important rotating parts of a gas turbine engine, are required to have highly efficient performance in order to minimize the total life cycle costs. Owing to these requirements, these components are exposed to severe conditions such as extreme turbine inlet temperatures, high compression ratios, and high speeds. To evaluate the structural integrity of a turbine disc under these conditions, material modeling and finite element analysis techniques are essential; furthermore, shape optimization is necessary for determining the optimal solution. This study aims to generate 2D finite element models of an axisymmetry model and a sector one and to perform thermal-structural coupled-field analysis and contact analysis. Structurally vulnerable areas such as the disc bore and disc-blade interface region are analyzed by a parametric study. Finally, an improved design is provided based on the results, and the necessity of elaborate shape optimization is confirmed.

• Convergence Security Journal
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• v.8 no.4
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• pp.65-71
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• 2008

According to the capacity of hard disk drive is increasing day by day, the amount of data that forensic investigators should analyze is also increasing. This trend need tremendous time and effort in determining which files are important as evidence on computers. Using the file system APIs provided by Windows system is the easy way to identify those files. This method, however, requires a large amount of time as the number of files increase and changes the access time of files. Moreover, some files cannot be accessed due to the use of operating system. To resolve these problems, forensic analysis should be conducted by using the Master File Table (MFT). In this paper, We implement the file access program which interprets the MFT information in NTFS file system. We also extensibly compare the program with the previous method. Experimental results show that the presented program reduces the file access time then others. As a result, The file access method using MFT information is forensically sound and also alleviates the investigation time.