• Nuclear industry
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• v.30 no.1
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• pp.76-87
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• 2010

• Tunnel and Underground Space
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• v.9 no.4
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• pp.350-363
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• 1999

The precision cyclic shear test system was established to investigate the mechanical characteristics of rough rock joints under cyclic loading conditions. Laboratory cyclic shear tests were conducted for saw-cut joints and artificial rough rock joints using Hwangdeung granite and Yeosan marble. Surface roughness and aperture characteristics of specimens were examined by measuring surface topography using the laser profilometer. Peak shear strength, phase difference during loading and unloading, and anisotropic shear behavior were investigated throughout the cyclic shear test results. These features and their subsequent variations in each loading cycle are significantly dependent upon the second order asperities and the strength of intact rock. It was observed that degradation of asperities for rough rock joints under cyclic shear loading followed the exponential degradation laws of asperity angle and that the mechanism for asperity degradation would be different depending upon the normal stress level, roughness of joint surface and the loading stage.

• Journal of KIISE
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• v.44 no.8
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• pp.760-766
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• 2017

Repetitive strings have been studied in diverse fields such as data compression, bioinformatics and so on. Recently, two problems of approximate periods of strings over integer alphabets were introduced, finding minimum ${\delta}-approximate$ periods and finding minimum ${\gamma}-approximate$ periods. Both problems can be solved in $O(n^2)$ time when n is the length of the string. In this paper, we present two parallel algorithms for solving the above two problems in O(n) time using $O(n^2)$ threads, respectively. The experimental results show that our parallel algorithms for finding minimum ${\delta}-approximate$ (resp. ${\gamma}-approximate$) periods run approximately 19.7 (resp. 40.08) times faster than the sequential algorithms when n = 10,000.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3188-3193
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• 2012

It is important to search a pitch for vocoder. The major drawback to vocoders is their large computational requirements in searching a pitch and a codebook. In this paper, a simple method is proposed to improve the pitch searching process in the pitch filter almost without degradation of quality. The period of speech signal is emphasized by using Dual Pulse technique, the same type of autocorrelation method, in pitch search. Sometimes the incorrect pitch can be obtained by halving, doubling and trifling, To solve it, before searching a pitch, we estimate energy rate in a frame and compensate envelop of signal with it. By using the proposed algorithm in pitch search, its required computation are reduced and searching pitch is improved.

• Journal of Convergence for Information Technology
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• v.8 no.5
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• pp.137-143
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• 2018

Generally, a radar signal is modulated and transmitted in order to avoid signal detection. In electronic warfare, the specification of a radar is recognized by analysing the received radar pulses. In this paper, we propose an algorithm to recognize the PRI (Pulse Repetition Interval) type of radar signals. This algorithm uses the autocorrelation technique applying different comparison ranges according to the PRI type. It applies a short comparison window to stable and staggered PRI, and a relatively large comparison range to jittered PRI. The experiment shows that the proposed algorithm can discriminate the PRI type of radar pulses correctly. For the more, it can find out the stagger level of staggered type of radar signals.

• The KIPS Transactions:PartD
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• v.10D no.2
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• pp.187-194
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• 2003

Main Memory storage system can increase the performance of the system by assigning enough slack time to real-time transactions. Due to its high response time of main memory devices, main memory resident data management systems have been used for location management of personal mobile clients to cope with urgent location related operations. In this paper we have developed a multi-threaded main memory storage system as a core component of real-time retrieval system to handle a huge amount of readers and writers of main memory resident data. The storage system is implemented as an embedded component which is working with the help of a disk resident database system. It uses multi-threaded executions and utilizes latches for its concurrency control rather than complex locking method. It only saves most recent data on main memory and data synchronization is done only when disk resident database asks for update transactions. The system controls the number of read threads and update threads to guarantee the minimum requirements of real-time retrievals.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.18-22
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• 2006

The transmission characteristics of multiply cascaded phase-shifted long-period fiber gratings(LPFGs) were investigated theo-retically and experimentally. Their passband can be changed by increasing the number of p-shifted LPFGs. When two p-shifted LPFGs with different grating lengths are cascaded in series, the bandwidth of the rejection band and passband can be controlled by the pristine characteristics of two gratings. We also investigate the transmission characteristics of phase-shifted LPFG by exposing the half of LPFG region to UV laser. The transmission characteristics strongly depend on the initial coupling strength of the LPFG.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.64-72
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• 2015

Risk Based Inspection (RBI) Period was proposed for highway bridges in Korea. Hazard factors affecting bridge condition deterioration were found by analyzing condition data from Highway Bridge Management System (HBMS). Certain level of correlations between those factors and condition deterioration were found. They are used to evaluate hazard score. Summarizing several hazard factors, final hazard is classified as three level;high, moderate, low. Vulnerability is assessed only by the current state of bridge. Then, risk matrix is suggested for inspection periods. Inspection periods of the bridges with grade C, D, and E are maintained the same as before. But, those of grade A and B with moderate and high hazard score are elongated to maximum 6 years while the maximum inspection period is three years at present. By adjusting inspection period according to risk assessment, it was shown that 27% of average inspection manpower can be saved.

• Plant Journal
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• v.9 no.4
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• pp.31-36
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• 2013

In order to extend a hot gas parts replacement cycle of a gas turbine, blade row 1 from low pressure turbine, which has a significant impact on the cycle, has been selected from stored set after one cycle use. Taking into account the status of the first stage moving blade in LP turbine operated more than 27,000 equivalent operating hours(EOH) and the replacement cycle in the same type of gas turbine, the replacement of the high temperature components installed on the GT, a study subject, can be extended from 24,000 to 27,000 EOH.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.291-296
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• 2008

For the past two decades, 3D/4D CAD research has heel mainly focused on the design and construction phase of a facility life-cycle. However, there has been a general notion that the strength of 3D/4D CAD lends itself to other phases such as planning, operation and maintenance. In this research, a 3D/4D CAD model was generated in a commercial software platform. Then, the traditional 1:fe cycle facility management procedures are reviewed to, see any possible improvement opportunity with the 3D/4D CAD model as an example. A focus group interview, in conjuction with an extensive literature review, produced the list of area where 3D/4D CAD model could significantly benefit the traditional life cycle facility practices. Finally, a questionnaire-based survey was conducted with 155 respondents to statistically verify the feasibility of 3D/4D CAD for life cycle facility management.