• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.313-318
• /
• 1996

In this paper, a parametric study of the unbalance response and the stability is carried out to show the influence of seal parameters on the response of rotor. The seal parameters optimized are the seal clearance and the seal length. The minimum quantity of a Q factor in the critical speed and the maximum quantity of a logarithmic decreement in the operating speed, avoiding the reign of resonance, are the objective function. This paper describes a new approach to find a seal parameter of rotor system. The optimization method is used genetic algorithms, which are search algorithms based on the mechanics of natural selection and natural genetics. The results show the capability of this method and indicate that an optimal design of seals can improve the unbalance and the stability of rotor.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.9
• /
• pp.1596-1612
• /
• 2011

Coordinated Multi-Point (CoMP) transmission / reception is being studied in Long Term Evolution-Advanced (LTE-A) for future evolution of the $3^{rd}$ Generation Partnership Project (3GPP) LTE. Support of soft handover is essential for improving the performance of cell edge users. CoMP provides a natural framework for enabling soft handover in the LTE system. This paper evaluates the soft handover gain in LTE-A downlink. Mathematical analysis of signal to interference plus noise ratio (SINR) gain and the handover margins for soft handover and hard handover are derived. CoMP system model is developed and an inter-cell and intra-cell interference model is derived, taking into account the pathloss, shadowing, cell loading, and traffic activity. Reference signal received power (RSRP) is used to define the triggers and the measurements for soft handover. Our results indicate that parameter choices such as handover margin and the CoMP set size impact CoMP performance gain.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1994.06a
• /
• pp.919-924
• /
• 1994

The use of adaptive feedback cancellation to prevent howling requires a reference signal that is correlated with the feedback signal by is not correlated with the input signal. Such a signal is hard to obtain in hearing aids. In this paper, the use fo frequency compression to decorrelate the output signal with input signal for use as reference is presented. Performance evaluation results indicate that with the proper choice of system parameters, the use of this system can provide a significant increase in howling margin with minimal deterioration in output signal quality.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.03a
• /
• pp.473-480
• /
• 2003

A new semiactive control strategy for seismic response reduction using a neuro-controller and a magnetorheological (MR) fluid damper is proposed. The proposed control system adopts a clipped algorithm which induces the MR damper to generate approximately the desired force. The improved neuro-controller, which was developed by employing the training algorithm based on a cost function and the sensitivity evaluation algorithm replacing an emulator neural network, produces the desired active control force, and then by using the clipped algorithm the appropriate command voltage is selected in order to cause the MR damper to generate the desired control force. The simulation results show that the proposed semiactive neuro-control algorithm is quite effective to reduce seismic responses. In addition, the semiactive control system using MR fluid dampers has many attractive features, such as bounded-input, bounded-output stability and small energy requirements. The results of this investigation, therefore, indicate that the proposed semiactive neuro-control strategy using MR fluid dampers could be effective used for control seismically excited structures.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.99-108
• /
• 2018

An oil-tolerant and salt-resistant aqueous foam system was screened out as a possible lubricant to enable cold heavy oil transportation. The microstructures and viscoelasticity and effects of heavy oil, salt and temperature on the foam stability were investigated and new rheological and drainage models were established. The results indicate the foam with multilayered shells belongs to a special microcellular foam. The viscoelasticity could be neglected due to its low relaxation time. The drainage process can be divided into three stages. The foam with quality of 67.9% maintains great stability at high oil and salt concentrations and appropriate elevated temperature.

• International Journal of Reliability and Applications
• /
• v.14 no.2
• /
• pp.71-78
• /
• 2013

The problem of designing an experiment to estimate the reliability of a system that has N subsystems connected in series where each subsystem n has n $T_n$ components connected in parallel is investigated both theoretically and by simulation. An accelerated sampling sheme is introduced. It is shown that the accelerated sampling scheme is asymptotically optimal as the total number of units goes to infinity. Numerical comparisons for a system that has two subsystems connected in series where each subsystem has two components connected in parallel are also given. They indicate that the accelerated sampling scheme performs better than the batch sequential sampling scheme and is nearly optimal.

• Journal of the Korea Safety Management & Science
• /
• v.5 no.4
• /
• pp.157-167
• /
• 2003

More and more many people show a keen interest in the ergonomics application car. One of the recent trends of cockpit development is to integrate fore part of whole cockpit and compartment. The goal of this study is to develop and Analysis of User's Convenience a cockpit prototype based on the design guide of cockpit integration module. The process of this study has been followed analyzing development trend of next generation Automotive cockpit, extracting the design factor needed to making integration module and laying down the design guide of cockpit integration module. Finally, this study is indicate an instance that evaluation of utilization with Integrated Automotive Cockpit Module System.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.13 no.4
• /
• pp.217-224
• /
• 2005

The purpose of this study was to develop a cooler/heater using a thermoelectric module combined with a parallel flow type pulsating heat pipe with R-142b as a working fluid. The experiment was performed for 16 thermoelectric modules (6A/15V, size: $40\times40\times4mm$), varying design parameters of the heat pipe (inclination angle, working fluid charging ratio, etc.). Experimental results indicate that the optimum charging ratio and the inclination angle of the parallel flow type pulsating heat pipe were $30\%$ by volume and $30^{\circ}$, respectively. The maximum cooler/heater capacity were 479 W (COP: 0.47) and 630 W (COP: 0.9), respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.3
• /
• pp.1345-1362
• /
• 2019

Most active queue management algorithms manage network congestion based on the size of the queue but ignore the network environment which makes queue size change. It seriously affects the response speed of the algorithm. In this paper, a new AQM algorithm named CT-AQM (Change Trend-Adaptive Queue Management) is proposed. CT-AQM predicts the change trend of queue size in the soon future based on the change rate of queue size and the network environment, and optimizes its dropping function. Simulation results indicate that CT-AQM scheme has a significant improvement in loss-rate and throughput.

• Journal of Korean Living Environment System
• /
• v.24 no.3
• /
• pp.360-367
• /
• 2017

Although the elderly collecting and selling wastepaper is one of the most vulnerable groups in society, this group has not been studied specifically. Subjective health status is an important aspect of quality of life in old age. The purpose of this study is to examine factors affecting subjective health status among the elderly collecting and selling wastepaper. Analyses are based on data from 2014 Korean Elderly Survey. Multiple regression analysis showed that gender, depression, and fear of falling were associated with subjective health status. The results of this study suggest that gender and mental health aspects should be considered in making intervention plan for assessments and providing services for health among the elderly collecting and selling wastepaper. The study findings also indicate that efforts to improve safety in worksite of elderly persons collecting and selling wastepaper are needed.