• Journal of Korean Institute of Industrial Engineers
• /
• v.22 no.3
• /
• pp.387-398
• /
• 1996

In this study the cell arrival processes from pre-buffer into multiplexer for MPEG(Motion Picture Experts Group) coding video sources are analyzed with consideration of the traffic periodicity in frame level. The analysis is performed by introducing the two arrival models, that is, periodic on/off source model and periodic uniform arrival model. Modulated $N^*D$/D/1 queueing system is utilized in periodic on/off source model, while ${\Sigma}{N_i}^*D_i$/D/1 queueing system is used in periodic uniform arrival model. The presented models are validated by comparing with computer simulations. Numerical results for periodic uniform arrival model are shown to be very accurate, but those of periodic on/off source model are shown to be inaccurate as the number of sources are increased.

• Journal of Applied Reliability
• /
• v.6 no.2
• /
• pp.151-161
• /
• 2006

This article is concerned with cost analysis model in periodic maintenance policy. The repair policy is differently applied according as unit importance during an item being used and unit restoration during an item being failed. So in this paper the repair policy with minimal repair is considered as follow : as the occurrence of failure between minimal repair and periodic interval time, unit is replaced by a spare unit until the periodic maintenance time arrived. Then total expected cost per unit time is calculated according to scale parameter of failure distribution in a view of customer's. The total expected costs are included repair and usage cost : operating, fixed, minimal repair, periodic maintenance and spare unit cost. Numerical example is shown in which failure time of item has Erlang distribution.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.603-606
• /
• 2006

In this study, we proposed a Modified Log-Periodic Tooth antenna structure with reflector for millimeter wave image sensor of PMMW(Passive Millimeter Wave). PMMW image sensor satisfy the requirements, such as, High Gain, Wideband, and Planar antenna structure.

• Journal of Mechanical Science and Technology
• /
• v.19 no.7
• /
• pp.1405-1413
• /
• 2005

Malfunctions or critical fatigue problems often occur in mistuned periodic structural systems since their vibration responses may become much larger than those of perfectly tuned periodic systems. These are called vibration localization phenomena and it is of great importance to accurately predict the localization phenomena for safe and reliable designs of the periodic structural systems. In this study, a simple discrete system which represents periodic structural systems is employed to analyze the vibration localization phenomena. The statistical effects of mistuning, stiffness coupling, and damping on the vibration localization phenomena are investigated through Monte Carlo simulation. It is found that the probability of vibration localization was significantly influenced by the statistical properties except the standard deviation of coupling stiffness.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.11 no.6
• /
• pp.175-180
• /
• 2001

Dynamic response localization of simple mistuned periodic structures is presented in this paper Mistuning in periodic structures can cause forced responses that are much larger than those of perfectly tuned structures. So mistuning results in the critical impact on high cycle fatigue of structures. Thus, it is of great importance to predict the mistuned forced response in an efficient way. In this paper, forced responses of coupled pendulum systems are investigated to identify the localization effect of periodic structures. The effects of mistuning and damping on the maximum forced response are examined. It is found that certain conditions of mistuning and coupling can cause strong localization and the localization becomes significant under weak damping. It is also found that the maximum forced response increases as the number of Periodic structures increases.

• Journal of Institute of Control, Robotics and Systems
• /
• v.11 no.2
• /
• pp.167-174
• /
• 2005

This paper experimentally validates the efficacy of scheduling method that satisfies the performance requirement of periodic data in the Foundation Fieldbus. The scheduling method allocates periodic data traffic to a bandwidth-limited fieldbus medium. The scheduling method generates schedule list that records schedule starting time and schedule period of each periodic data. This study developed an experimental model of a Foundation Fieldbus network system. Using the experimental model, this study showed that the scheduling method can be easily implemented in a practical Foundation Fieldbus network system. The results obtained from the experimental evaluation showed that the scheduling method restricts the delay of periodic data to a pre-specified bound.

• Advances in aircraft and spacecraft science
• /
• v.3 no.3
• /
• pp.299-315
• /
• 2016

In this work, a strategy for passive vibration control of periodic structures is proposed which involves adding a periodic array of simple resonant devices for creating band gaps. It is shown that such band gaps can be generated at low frequencies as opposed to the well known Bragg scattering effects when the wavelengths have to meet the length of the elementary cell of a periodic structure. For computational purposes, the wave finite element (WFE) method is investigated, which provides a straightforward and fast numerical means for identifying band gaps through the analysis of dispersion curves. Also, the WFE method constitutes an efficient and fast numerical means for analyzing the impact of band gaps in the attenuation of the frequency response functions of periodic structures. In order to highlight the relevance of the proposed approach, numerical experiments are carried out on a 1D academic rod and a 3D aircraft fuselage-like structure.

• Journal of the Chungcheong Mathematical Society
• /
• v.31 no.4
• /
• pp.511-518
• /
• 2018

We investigate periodicities of some hybrid cellular automata configured with rule 60 and 102 and periodic boundary condition.

• The Journal of Korean Obstetrics and Gynecology
• /
• v.30 no.1
• /
• pp.16-28
• /
• 2017

Objectives: This study was performed to review the research trends in the periodic therapy of dysmenorrhea in traditional Chinese medicine (TCM). Methods: We searched articles in Chinese Academic journal (CAJ). Search key words were 'dysmenorrhea' and 'periodic therapy or cyclic treatment'. Results: We selected 6 studies except unrelated studies. According to study design, study was classified into 1 single group before after study and 5 randomized controlled trials. According to dysmenorrheal type, study was classified into 4 studies on primary dysmenorrhea and 2 studies on secondary dysmenorrhea. In the selected studies, there were four studies in which the menstrual cycle was divided into 2 periods, one study divided into 3 periods, and one study divided into 4 periods. The most used herb was "Angelicae Gigantis Radix", "Cinnamomi Cortex Spissus". All studies showed effective results on dysmenorrhea. Conclusions: In TCM, Research on periodic therapy of dysmenorrhea was being conducted more actively than Korean medicine. The periodic therapy seems to be effective on dysmenorrhea from this research. It would be necessary to fulfill further clinical study with periodic therapy on dysmenorrhea in Korean medicine to establish standard evidence of them.

• Structural Engineering and Mechanics
• /
• v.16 no.1
• /
• pp.17-34
• /
• 2003

This paper presents a damage assessment procedure applied to periodic spring mass systems using an eigenvalue sensitivity-based method. The damage is directly related to the stiffness reduction of the damage element. The natural frequencies of periodic structures with one single disorder are found by adopting the transfer matrix approach, consequently, the first order approximation of the natural frequencies with respect to the disordered stiffness in different elements is used to form the sensitivity matrix. The analysis shows that the sensitivity of natural frequencies to damage in different locations depends only on the mode number and the location of damage. The stiffness changes due to damage can be identified by solving a set of underdetermined equations based on the sensitivity matrix. The issues associated with many possible damage locations in large structural systems are addressed, and a means of improving the computational efficiency of damage detection while maintaining the accuracy for large periodic structures with limited available measured natural frequencies, is also introduced in this paper. The incomplete measurements and the effect of random error in terms of measurement noise in the natural frequencies are considered. Numerical results of a periodic spring-mass system of 20 degrees of freedom illustrate that the proposed method is simple and robust in locating single or multiple damages in a large periodic structure with a high computational efficiency.