• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.4
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• pp.338-347
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• 1989

In this paper, the digital frequency synthesizer with the clock ccunting method is designed and implemented to increase the performace of the digital frequency synthesizer with pahse accumulating method which was developed before. Unlike an phase accumulating method, clock countind method is supplied a continually changeable clock frequency with PLL(Phase Locked Loop) and allocated a fixed phase step with N-ary counter. Form the experimenta results, it is confirmed that any periodic distorition phenomena are disappeared, and truncation harmonics are more reduced. But the output bandwidths are decreased in inverse proportion to the counter counting number and the circuits are somewhat complex than phase accumulating method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.61-68
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• 2015

Among comparison sorts, no algorithm excels a current set lower bound of O(nlogn) in operation. Quicksort, the fastest of its kind, has a complexity of O(nlogn) at its best and on average and $O(n^2)$ at worst. This paper thus presents two methods: first is an O(n+k) simple counting sort which operates much more speedily than an O(n+k), (k=maximum value) counting sort, and second is an O(ln) radix counting sort which counts the frequency of numbers in the digit l of a data and saves it in a corresponding virtual bucket in an array, only to virtually divide the array into radix digit numbers. For the 6 experimental data, the proposed algorithm makes O(nlogn) or $O(n^2)$ of Quicksort simple into O(n+k) or O(ln). After all, the proposed sorting algorithm has proved to be much faster than the counting sort and Quicksort.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.3
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• pp.222-235
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• 2015

The purpose of this study is to suggest guidelines for riser fatigue analysis in terms of selection of reasonable analysis method. Three analysis methods (spectral, regular wave, rain-flow counting) are introduced and compared. As the riser systems give non-linear response, the time-domain analysis method is more preferred than frequency-domain analysis method. The spectral fatigue analysis method, however, is still useful for identifying fatigue prone areas. Once stress RAO is established, fatigue damage can be calculated very quickly. The regular wave method and the rain-flow counting method are more time consuming but give more exact results compare to spectral method. In case of regular wave method, a set of regular waves which represent random sea states is considered for dynamic analysis. The rain-flow counting method is the most intuitive and exact method because it refers time history stresses containing most of non-linear effects of the riser system. However, it is not common for early design stage to use rain-flow counting method because of its high cost. In this study, it was confirmed that the regular wave method is the most cost effective way in specific cases. However, if the system is highly non-linear, it seems that the regular wave method gives less accurate results than rain-flow counting method. Therefore, it is imperative that the engineers select appropriate analysis method based on design stage and given engineering period. This paper also discusses the theoretical background of each calculation method and hydrodynamic aspects of marine riser systems. A steel catenary riser (SCR) line on FPSO was considered and marine dynamic program (OrcaFlex) was used for static and dynamic analysis.

• Fisheries and Aquatic Sciences
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• v.14 no.3
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• pp.218-225
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• 2011

Dual frequency identification sonar (DIDSON) is an imaging sonar that has been used for numerous fisheries investigations in a diverse range of freshwater and marine environments. The main purpose of DIDSON is fish counting, fish sizing, and fish behavioral studies. DIDSON records video-quality data, so processing power for handling the vast amount of data with high speed is a priority. Therefore, a semiautomated analysis of DIDSON data for fish counting, sizing, and fish behavior in Echoview (fisheries acoustic data analysis software) was accomplished using testing data collected on the Rakaia River, New Zealand. Using this data, the methods and algorithms for background noise subtraction, image smoothing, target (fish) detection, and conversion to single targets were precisely illustrated. Verification by visualization identified the resulting targets. As a result, not only fish counts but also fish sizing information such as length, thickness, perimeter, compactness, and orientation were obtained. The alpha-beta fish tracking algorithm was employed to extract the speed, change in depth, and the distributed depth relating to fish behavior. Tail-beat pattern was depicted using the maximum intensity of all beams. This methodology can be used as a template and applied to data from BlueView two-dimensional imaging sonar.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.577-582
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• 2010

The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with rainflow counting method. Also, The Modified Miner's rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.95-102
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• 2015

Generally, there is no sorting algorithm much faster than O(nlogn). The quicksort has a best performance O(nlogn) in best and average-case, and $O(n^2)$ in worst-case. This paper suggests virtual radix counting bucket sort such that counting the frequency of numbers in each radix digit, and moves the arbitrary number to proper virtual bucket in the array, and divides the array into radix digit numbers virtually. Also, this algorithm moves the data to proper location within an array for using the minimum auxiliary memory. This algorithm performs k-times such that the number of k digits in given data and the time complexity is O(n). Therefore, this algorithm has a O(kn) time complexity.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.3
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• pp.157-162
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• 2023

As a result of active geological investigation of faults in Korea, many Quaternary faults have been identified and some of them were judged to have potential to generate earthquakes. Those faults need to be considered as additional seismic sources in the seismic hazard analysis. When a fault is introduced as a new source, the earthquakes generated by the fault should be removed from the area sources that include any part of the fault, to avoid double counting. In practice, however, double counting cannot completely be avoided as the complete separation of the fault-generated earthquakes from the area sources is impossible due to uncertainties related to the earthquake location, subsurface structures of faults, etc. When a new fault source is introduced, the only constraint is the invariance of earthquake frequency. The maximum earthquake and the Richter-b value should also be subject to change, but there are no competent approaches to estimate the change due to incomplete separation of earthquakes. To gain insight into the effect of a new fault source, an example calculation of the seismic hazard were carried out. The example calculation shows that addition of a new fault source centers seismic hazard around the fault source.

• Phonetics and Speech Sciences
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• v.4 no.1
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• pp.111-118
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• 2012

The purpose of this study was to characterize and determine variances of speaking fundamental frequency and vocal intensity depending on gender and three utterance conditions (spontaneous speech, reading, and counting). A total of 65 undergraduate students (32 male students, 33 female students) attending universities in Daegu, South Korea participated in this study. The subjects were all in their 20s. This study used KayPENTAX's Visi-Pitch IV (Model 3950) to measure the variances of speaking fundamental frequency (SFF0) and vocal intensity (VI). As a result, this study came to the following conclusions. First, it was found that both males and females showed no significant difference in SFF0 and vocal intensity among three utterance conditions. Second, this study sought to analyze differences in the variances of SFF0 between males and females. As a result, it was found that females showed significantly higher levels of four measured variances (SFF0 $SD^{**}$, SFF0 $range^{***}$, Min $SFF0^{***}$ and Max $SFF0^{***}$) than males on spontaneous speech. However, it was found that there was no significant difference between males and females in SFF0 range on reading or in SFF0 SD and SFF0 range on counting. It was found that there was no significant difference between males and females in the level of measured variances of vocal intensity depending on utterance conditions. Finally, this study made a comparison and analysis on differences in the variances of SFF0 and vocal intensity among utterance conditions. As a result, it was found that all the measured variances of SFF0 in males were most significantly reduced depending upon spontaneous speech which was followed by reading and counting respectively (SFF0 SD: p<.001, SFF0 range: p<.05, Max SFF0: p<.05). Females however, show no significant difference in the measured variances of SFF0 depending upon three utterance conditions. It was also found that the measured variances of vocal intensity in females were most significantly reduced depending on spontaneous speech that was followed by reading and counting (VI SD: p<.001, VI range: p<.001, Min VI: p<.01 Max VI: p<.05), while males showed no significant difference in the measured variances of vocal intensity depending on three utterance conditions. In sum, these findings suggest that variances of SFF0 in males are affected by three utterance conditions, while variances of vocal intensity in females are affected by three utterance conditions.

• Wind and Structures
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• v.9 no.4
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• pp.255-270
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• 2006

Several analytical procedures available in literature, for the evaluation of wind induced fatigue damage of structures, either assume the wide band random stress variations as narrow band random process or use correction factors along with narrow band assumption. This paper compares the correction factors obtained using the Rainflow Cycle (RFC) counting of the measured stress time histories on a lamp mast and a lattice tower, with those evaluated using different frequency domain methods available in literature. A Bi-modal spectral method has been formulated by idealising the single spectral moment method into two modes of background and resonant components, as considered in the gust response factor, for the evaluation of fatigue of slender structures subjected to "along-wind vibrations". A closed form approximation for the effective frequency of the background component has been developed. The simplicity and the accuracy of the new method have been illustrated through a case study by simulating stress time histories at the base of an urban light pole for different mean wind speeds. The correction factors obtained by the Bi-modal spectral method have been compared with those obtained from the simulated stress time histories using RFC counting method. The developed Bi-modal method is observed to be a simple and easy to use alternative to detailed time and frequency domain fatigue analyses without considerable computational and experimental efforts.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.185-192
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• 2014

The riser systems for floating offshore structures are known to experience tri-modal dynamic responses. These are owing to the combined loadings from the low-frequency response due to riser tension behavior, middle-range frequency response coming from winds and waves, and high-frequency response due to vortex induced-vibration. In this study, fatigue damage models were applied to predict the fatigue damages in a well-separated tri-modal spectrum, and the resultant fatigue damages of each model were compared with the most reasonable fatigue damage calculated by the inverse Fourier transform of the spectrum, rain-flow counting method, and Palmgren-Miner rule as a reference. The results show that the fatigue damage models developed for a wide-band spectrum are applicable to the tri-modal spectrum, and both the Benasciutti-Tovo and JB models could most accurately predict the fatigue damages of the tri-modal spectrum responses.