• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.989-995
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• 2009

Short-time Fourier transforms (STFT) are useful for analyzing signals with harmonics that vary with time. If the variation of the harmonics with time is smooth, such as in kinematic vibrations in vehicles, then it is possible to improve the STFT using order spectra and correlation analysis. In this paper, it is shown how correlation analysis can be performed when the speed signal is noisy or unknown and then it is shown how order spectra become simple to compute after this analysis. The results are illustrated by an analysis of axle and car body vibrations in the prototype high-speed train, HSR-350x.

• Earthquakes and Structures
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• v.3 no.6
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• pp.839-852
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• 2012

Earthquake records are often analyzed in various earthquake engineering problems, making time-frequency analysis for such records of primary concern. The best tool for such analysis appears to be based on wavelet functions; selection of which is not an easy task and is commonly carried through trial and error process. Furthermore, often a particular wavelet is adopted for analysis of various earthquakes irrespective of record's prime characteristics, e.g. wave's magnitude. A wavelet constructed based on records' characteristics may yield a more accurate solution and more efficient solution procedure in time-frequency analysis. In this study, a low-pass reconstruction filter is obtained for each earthquake record based on multi-resolution decomposition technique; the filter is then assigned to be the normalized version of the last approximation component with respect to its magnitude. The scaling and wavelet functions are computed using two-scale relations. The calculated wavelets are highly efficient in decomposing the original records as compared to other commonly used wavelets such as Daubechies2 wavelet. The method is further advantageous since it enables one to decompose the original record in such a way that a clear time-frequency resolution is obtained.

• The Journal of Information Systems
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• v.22 no.3
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• pp.25-42
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• 2013

Recently various kinds of Information Technology services are created and the quantities of the data flow are increase rapidly. Not only that, but the data patterns that we deal with also slowly becoming diversity. As a result, the demand of discover the meaningful knowledge/information through the various mining analysis such as linkage analysis, sequencing analysis, classification and prediction, has been steadily increasing. However, solving the business problems using data mining analysis does not always concerning, one of the major causes of these limitations is there are some analyzed data can't accurately reflect the real world phenomenon. For example, although the time gap of purchasing the two products is very short, by using the traditional sequencing analysis, the precedence relationship of the two products is clearly reflected. But in the real world, with the very short time interval, the precedence relationship of the two purchases might not be defined. What was worse, the sequence of the purchase intention and the sequence of the purchase realization of the two products might be mutually be reversed. Therefore, in this study, an expanded sequencing analysis methodology has been proposed in order to reflect this situation. In this proposed methodology, the purchases that being made in a very short time interval among the purchase order which might not important will be notice, and the analysis which included the original sequence and reversed sequence will be used to extend the analysis of the data. Also, to some extent a very short time interval can be defined as the time interval, so an experiment were carried out to determine the varying based on the time interval for the actual data.

• New & Renewable Energy
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• v.20 no.2
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• pp.17-25
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• 2024

In this study, the effect of the time step specified in a computational fluid dynamics (CFD) simulation on load response is analyzed and the drag coefficients of the floating body of floating offshore wind turbines (FOWTs) are estimated. By evaluating the error in the FOWT load response and the change in the drag-coefficient values based on the density of the time intervals, this study aims to establish a time-interval setting that minimizes the time and cost of CFD simulations for selecting drag-coefficient values. Practical CFD utilization strategies necessary for the calibration of medium-to high-fidelity analysis tools are presented. Based on a comparative analysis of CFD simulations conducted at various time intervals, the results confirmed that under a certain time interval that sufficiently considers various factors, the accuracy of the FOWT response with respect to density shows minimal differences, thereby providing an efficient utilization method for CFD simulations in FOWT design and analysis.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1269-1289
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• 2014

With the sub-stepping technique, the numerical analysis in real-time dynamic hybrid testing is split into the response analysis and signal generation tasks. Two target computers that operate in real-time may be assigned to implement these two tasks, respectively, for fully extending the simulation scale of the numerical substructure. In this case, the integration time-step of solving the dynamic response of the numerical substructure can be dozens of times bigger than the sampling time-step of the controller. The time delay between the real and desired feedback forces becomes more striking, which challenges the well-developed delay compensation methods in real-time dynamic hybrid testing. This paper focuses on displacement prediction and force correction for delay compensation in the real-time dynamic hybrid testing with a large integration time-step. A new displacement prediction scheme is proposed based on recently-developed explicit integration algorithms and compared with several commonly-used prediction procedures. The evaluation of its prediction accuracy is carried out theoretically, numerically and experimentally. Results indicate that the accuracy and effectiveness of the proposed prediction method are of significance.

• Journal of Families and Better Life
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• v.9 no.1 s.17
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• pp.95-112
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• 1991

This study is planned to provide the basic idea to seek for the appropriate Time Management Strategies and to investigate the Time Management Strategies and household work time of wives. For these research tasks, the data are collected through the questionnaire rand 479 respondents were housewives in seoul. Their data are analyzed using Frequency, ANOVA, Pearson's Correlation Analysis, Simple Regression Analysis, Multiple Regression Analysis. The Major findings of this study were as follows ; 1) There are significant differences in the time management strategies according to housewife's age, education level, and employment status, children's number, the type of housing, the type family, income and sex role attitude. 2) There are significant differences in the household work time according to housewife's age, education level, employment status, family size, children's number, type of housing, income, sex role attitude and time pressure perceptibility. 3) The Household work time is found to be negatively correlated to the Time Management Stategies except the adjustment of leisure and sleep time. 4) The Household work time is significantly related to housewife's employment status and the adjustment of leisure and sleep time.

• 전기의세계
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• v.31 no.2
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• pp.126-131
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• 1982

Induction motors are known to cause voltage dip, oscillating torque and inrush current on the dynamic period. To compensate for these undesirable effects, the prediction of dynamic performances is required. The dynamic performances are determinated by circuit time constants. From this point of view, in this paper, the dynamic equivalent circuit included only three time-constant parameters are presented. To predict more simply dynamic performances, the new characteristics time constant parameters are analyzed, and now these parameters are described as the function of circuit time constants. This paper reviews and analyzes the use of series capacitance compensations, and the use of this analysis can make simply a prediction about oscillating conditions.

• International Journal of Computer Science & Network Security
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• v.23 no.7
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• pp.165-170
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• 2023

Scheduling algorithms plays a significant role in optimizing the CPU in operating system. Each scheduling algorithms schedules the processes in the ready queue with its own algorithm design and its properties. In this paper, the performance analysis of First come First serve scheduling, Non preemptive scheduling, Preemptive scheduling, Shortest Job scheduling and Round Robin algorithm has been discussed with an example and the results has been analyzed with the performance parameters such as minimum waiting time, minimum turnaround time and Response time.

• Journal of Families and Better Life
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• v.7 no.2
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• pp.145-161
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• 1989

The objectives of this study are ; 1) To analyze the time use and the invironments of rural housewives household labor according to the characteristics of agriculture. 2) To investigate the factors influencing household labor time. In this study, the rural areas are divided into two groups according to characteristics of agriculture. One is traditional agricultural area-Seokchon Dong in Youngcheon Kun, and the other is commercial agricultural area-Dongpo 1 Dong in Sungju Kun. Two areas are located in Kyungpook Province. 145 housewives dwelling in above two villiages were interviewed. The statistics used for data analysis were frequency, percentile, T-test, x2-test, and multiple regression analysis. Results are as follows; 1) household labor time had not significant differences Hetween Youngcheon and Sungju. But agricultural labor time was longer in Sungju than in Youngcheon. 2) household labor environments in Sungju were better than those in Youngcheon. 3) household labor time was influenced by agricultural labor time and socio-cultural time.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.9-13
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• 2009

Recently, construction in downtown is often done closely at the adjacent building. In this case, underground construction need to Basement Composite Wall(BCW) construction. However, generally, during the construction process of BCW form works have many problems that are narrow working space and inefficient time consuming. Despite of these problems, there was no quantitative research for the work time of BCM assembly. Therefore, in this study, work time of CBW form assembly in underground construction is identified by the work analysis. The results of this study reveal that buttress work of basement form take lots of time in the entire work process of Basement Composite Wall form assembly.