• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.6
• /
• pp.1480-1489
• /
• 1996

In ATM networks there are two methods in traffic control as schemes advancing the quality of service. One is reactive control after congestion and the other which is generally recommended, is preventive control before congestion, including connection admission control on call leel and usage parameter control, network parameter control, priority control and congestion control on cell level. In particular, usage parameter control is required for restricting the peak cell rate of bursy tracffic to the parameter negotiated at call set-up phase since the peak cell rate significantly influences the network quality of service. The scheme for progressing quality of service by usage parameter control is themethod using VSA(Virtual Scheduling Algorlithm) recommended ITU-T. The method using VSSA(Virtual Scheduling Suggested Algorlithm) in this paper is suggested by considering cell delay variation and token rate of leaky bucket, compared VSA and VSANT(Virtual Scheduling Algolithm with No Tolerance) with VSSA which polices violated cell probability of conformed peak cell rate and intentionally excessive peak cell rate. VSSA method using IPP(Interruped Poisson Process) model of input traffic source showed more quality of service than VSA and VSANT methods as usage parameter control because the suggested method reduced the violated cell probability of contformed peak cell rate and intentionally excessive peak cell rate.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.1004-1005
• /
• 2006

This paper investigates a speed sensorless control of induction motor. The control strategy is based on MRAS (Model Reference Adaptive System) using load-torque observer as a reference model for flux estimation. The speed response of conventional MRAS controller characteristics is affected by variations of load torque disturbance. In the proposed system, the speed control characteristics using a load-torque observer control isn't affected by a load torque disturbance. Simulation results are presented to prove the effectiveness of the adaptive sliding mode controller for the drive variable load of induction motor.

• Steel and Composite Structures
• /
• v.19 no.3
• /
• pp.697-711
• /
• 2015

It is well known the importance of considering hysteretic energy demands for the seismic assessment and design of structures. In such a way that it is necessary to establish new parameters of the earthquake ground motion potential able to predict energy demands in structures. In this paper, several alternative vector-valued ground motion intensity measures (IMs) are used to estimate hysteretic energy demands in steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure Sa($T_1$) as first component. As the second component, IMs related to peak, integral and spectral shape parameters are selected. The aim of the study is to provide new parameters or vector-valued ground motion intensities with the capacity of predicting energy demands in structures. It is concluded that spectral-shape-based vector-valued IMs have the best relation with hysteretic energy demands in steel frames subjected to narrow-band earthquake ground motions.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1299-1319
• /
• 2015

This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength ($f_{cu}$). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load-moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.

• Journal of Satellite, Information and Communications
• /
• v.5 no.2
• /
• pp.87-91
• /
• 2010

The IEEE 802.15.4 and IEEE 802.15.7 standard are the typical of low rate wireless and Visible Light Wireless personal area networks. Its Medium Access Control protocol can support the QoS traffic flows for real-time application through guaranteed time slots (GTS) in beacon mode. However, how to achieve a best allocation scheme is not solved clearly. The current analytical models of IEEE 802.15.4 MAC reported in the literature have been mainly developed under the assumption of saturated traffic or non-bursty unsaturated traffic conditions. These assumptions don't capture the characteristics of bursty multimedia traffic. In this paper, we propose a new analytical model for GTS allocation with burst Markov modulated ON-OFF arrival traffic.

• Korean Journal of Child Studies
• /
• v.35 no.2
• /
• pp.171-189
• /
• 2014

This study examined the influences of parent-child conflict and conflict resolution on behavior problems experienced in early adolescence by both boys and girls, and investigated whether conflict resolution had any moderating effects upon the relation between parent-child conflict and these behavior problems. The participants of this study were 397 first and second graders (193 boys and 204 girls) from three middle schools located in Seoul and Gyoung-gi province. To measure the research variables, the Korean-Youth Self Report by Oh et al. (2010), the short version of Conflict Behavior Questionnaire (Homes, 2012), and the Thomas Kilman Conflict Mode Instrument (Cha & Cheon, 2011) were used. The data were analyzed by means of descriptive statistics, t-test, multiple regression analysis, and hierarchical regression analysis. The results indicated that both for boys and girls, the level of parent-child conflict increased the levels of both externalizing and internalizing behavior problems whereas conflict resolution had no significant effect on behavior problems. In addition, in the case of boys only, conflict resolution moderated the effect of father-child conflict on internalizing behavior problems.

• Journal of Korean Public Health Nursing
• /
• v.19 no.1
• /
• pp.64-73
• /
• 2005

The purpose of this study was to discuss the difference of stress by the grade, examine the relationship between characteristics and main stress, and to investigate the effect of the National Examination of Registered Nurses on stress by using the stress self-rating scale targeting university nursing students (n=314), The stress self-rating scale consists of three subscales: stress responses, stressors and coping parts, such as perceived social support and a sense of humor. The data were analyzed by descriptive statistics, t-test, Pearson's correlation coefficient and regression analysis. The results showed that passing the National Examination of Registered Nurses was the first problem among the stressors. Stressors of the living factors and nursing factors, and subjective stressors of the surveyed nursing students were the highest among the senior students, but stressors of nursing factors increased according to the grade of the nursing students. Perceived stress responses were high in psychological responses of other aspects, and perceived stress responses increased according to the grade (p<.001). Senior students had a high weight of perceived stress responses (problem-focused, emotion-focused). and active and negative coping modes. Significant factors that explained the stressors were coping mode(r=.62-82. p<.01) and cognition(r=.19. p<.01). including the social support. These findings suggest that social support was very important for seniors. and that we have to develop approaches to decrease stress according to the student grade for nursing education process.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.2 s.69
• /
• pp.1-7
• /
• 2006

This paper, presents a comparison between numerical analysis and field test on a real offshore platform in Bohai Bay, China. This platform is a steel jacket offshore platform with vertical piles. The field testing under wave-induced force and wind force etc. was conducted, in order to obtain the dynamic parameters of the structure, including the frequencies of the jacket platform, as well as the corresponding damping ratios and mode shapes. The natural excitation technology (NexT) combined with eigensystem realization algorithm (ERA) and the peak picking (PP) method in frequency domain are carried out for modal parameter indentification under operational conditions. The three-dimeansional finite element model (FEM) is constructed by ANSYS and analytical modal analysis is performed to generate modal parameters. The analytical results were compared with experimental results. A good agreement was achieved between the finite element and analysis and field test results. It is further demonstrated that the numerical and experimental modal analysis provide a comprehensive study on the dynamic properties of the jacket platform. According to the analysis results, the modal parameters identification under ambient excitation can calibrate finite element model of the jacket platform structures, or can be used for the structural health monitoring system.

• Journal of the Korean Ceramic Society
• /
• v.28 no.1
• /
• pp.20-28
• /
• 1991

Fracture of Al2O3 tubes for different loading path under combined tension/torsion was investigated. Macroscopic directions of crack propagation agreed well with the maximum principal stress criterion, independent of the loading path. However, fracture strength from the proportional loading test($\tau$/$\sigma$= constant) showed either strengthening or weakening compared to that from uniaxial tension, depending on the ratio $\tau$/$\sigma$. The Weibull theory was capable to predict the strengthening of fracture strength in pure torsion, but not the weakening in the proportional loading condition. The strengthening or weakening of fracture strength in the proportional loading condition was explained by the effect of shear stresses in the plane of randomly oriented microdefects. Finally, a new empirical fracture criterion was proposed. This criterion is based on a mixed mode fracture criterion and experimental data for fracture of Al2O3 tubes under combined tension/torsion. The proposed fracture criterion agreed well with experimental data for both macroscopic directions of crack propagation and fracture strengths.

• Journal of the Korean Society of Safety
• /
• v.27 no.3
• /
• pp.111-116
• /
• 2012

This study is about the quantitative safety assessment of hydrogen station in Korea operating with on-site type. This was written by background information that before qualitative safety assessment to write. For the qualitative safety assessment method, the study used FMEA(failure mode & effect analysis) and HAZOP(hazard & operability), and adopted the FTA(fault tree analysis) as the quantitative safety assessment method. To write the FTA, we wrote FT by Top event that hydrogen leakage can be called most serious accident of hydrogen station. Each base event collect reliability data by reliability data handbook, THERP-HRA and estimation of the engineering. Assessment looked at the high frequency and the possible risk through Gate, Importance, m.cutsets analysis.