• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.19-27
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• 2011

Due to the growth of optical fiber network technologies, most networks recently support several tens of Gb/s bandwidth. UDT(UDP-based Data Transfer protocol) is an optimized protocol for bulk data transmission on the network, which has the high bandwidth and long delay time. It periodically controls the sending rate on the fixed sync-interval, 0.01 sec. Here, if the network traffic status varies quickly, available network bandwidth is not able to be properly utilized in-between the sync-intervals. In this paper, we propose an adaptive rate control method with considering the network traffic status in-between the sync-interval periods. The network traffic status is determined based on the RTT variances. With dividing the network status into four classes, the proposed method performs a new rate control by adjusting the inter-packet sending period for a corresponding class. As a simulation result, the proposed method improves the message delivery throughput as well as stability than that of the existing UDT Protocol.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.3
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• pp.315-320
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• 1998

In this paper, we present the PID control method for the controlling flow rate of highly complicated nonlinear Left Ventricular Assist Device(LVAD) with pneumatically driven mock circulatory system. Beat Rate (BR), Systole-Diastole Rate (SDR) and flow rate are used as the main variables of the LVAD system. System modeling is completed using the neural network with input variables (BR, SDR, their derivatives, actual flow) and an output valiable(actual flow). Then, as the basis of this model, we perform the simulation of PID control to predict the performance and tendency of the system and control the flow rate of LVAD system using the PID controller. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated through computer simulation and experiments.

• Tribology and Lubricants
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• v.22 no.1
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• pp.47-52
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• 2006

It is very important to control pressure and flow rate distribution on each component of engine lubrication network. Sometimes many kinds of orifice are used to control flow rate in the hydraulic lubrication field. In this study orifices were adopted on the lubrication network to control oil flow rate distribution. And unsteady transient flow network analysis was carried out to find out the effects of orifices on the engine oil circuit system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1997.11a
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• pp.187-190
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• 1997

Test Model15, which is used widely for the MPEG-2 bit rate control, has several problems such as non-unform picture quality, scene change and buffer underflow. Therefore, various algorithms have been developed to solve these problems. In this paper, we study various algorithms for the MPEG-2 bit rate control and compare their performances using software simulations. We also propose a new bit rate control strategy based on coded types of macroblocks within a picture.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.652-657
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• 2004

As the real-time multimedia applications through Internet increase, the bandwidth available to TCP connections is oppressed by the UDP traffic, result in the performance of overall system is extremely deteriorated. Therefore, developing a new transmission protocol is necessary. The TCP-friendly algorithm is an example meeting this necessity. The TCP-friendly (TFRC) is an UDP-based protocol that controls the transmission rate based on the available round transmission time (RTT) and the packet loss rate (PLR). In the data transmission processing, transmission rate is determined based on the conditions of the previous transmission period. If the one-step ahead predicted values of the control factors are available, the performance will be improved significantly. This paper proposes a prediction model of transmission rate control factors that will be used for the transmission rate control, which improves the performance of the networks. The model developed through this research is predicting one-step ahead variables of RTT and PLR. A multiplayer perceptron neural network is used as the prediction model and Levenberg-Marquardt algorithm is used for the training. The values of RTT and PLR were collected using TFRC protocol in the real system. The obtained prediction model is validated using new data set and the results show that the obtained model predicts the factors accurately.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.5
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• pp.310-318
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• 2016

Emerging technologies such as the Internet of Things (IoT) and the Advanced Driver Assistant System (ADAS) often have image transmission functions with tough constraints, like low power and/or low delay, which require that they adopt line-based, low memory compression methods instead of existing frame-based image compression standards. Bit rate control in the conventional frame-based compression systems requires a lot of hardware resources when the scope of handled data falls at the frame level. On the other hand, attempts to reduce the heavy hardware resource requirement by focusing on line-level processing yield uneven image quality through the frame. In this paper, we propose a bit rate control that maintains consistency in image quality through the frame and improves the legibility of text regions. To find the line characteristics, the proposed bit rate control tests each line for ease of compression and the existence of text. Experiments on the proposed bit rate control show peak signal-to-noise ratios (PSNRs) similar to those of conventional bit rate controls, but with the use of significantly fewer hardware resources.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.122-130
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• 1997

Coastal diaster induced by waves and countermeasures were investigated in the viewpoint of reduction of overtopping rate with enviroment in fishing port. The reduction method of wave overtopping rate using ecosystem control structures was proposed and studied on the efficiency by hydraulic and numerical experiments. The estimation models on wave overtopping rate was proposed after comparing previous models with dimensional analysis and experimental results. Control function o fwave overtopping by use of ecosystem controlstructures was simulated and discussed with combining wave shoaling-dissipation-breaking deformation model around ecosystem control structures and newly proposed calculation model for wave overtopping rate. Feasiblilty of ecosystem control structures could be confirmed for reduction of wave overtopping and fisheries-based multipurpose development of coastal zone.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.293-301
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• 2014

We present a study of vertical dynamics control of an electrostatically levitated gyro-accelerometer considering the wobbling effect and propose a tilt stabilization method with newly introduced control electrodes. Typically, a rotor in a vacuum rotates at high velocity, which may create a drift rate and lead to displacement instability due to the tilt angle of the rotor. To analyze this, first we set up a vertical dynamic equation and determined simulation results regarding displacement control. After deriving an equation for drift dynamics, we analyzed the drift rate of the rotor and the wobbling effect for displacement control quantitatively. Then, we designed new sub-electrodes for moment control that will decrease the drift amplitude of wobbling dynamics. Finally, a simulation study demonstrated that the vertical displacement control with the wobbling compensation electrodes mitigated the rotor's drift rate, showing the effectiveness of the newly proposed control electrodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9B
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• pp.829-837
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• 2006

Due to the internet network congestion, packets may be dropped or delayed at routers. This phenomenon degrades the quality of streaming applications that require high QoS requirements. The proposed algorithm in this paper, called DBRC(Delay-Based Rate Control), tries to cause router queue occupancy to reach a steady state or equilibrium by throttling the transmission rate of the multimedia traffics when network delays tend to increase and also probing for more bandwidth when network delays tend to decrease. Simulation results show that the proposed algorithm provides smooth transmission rate, nearly constant delay and low packet loss rates, compared with TFRC(TCP Friendly Rate Control) that is one of dominant multimedia congestion control algorithms.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.5
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• pp.247-253
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• 2015

The presented work demonstrates the effects of flow rate on the secondary side of DHS (District Heating System). Increasing flow rate at the secondary side of DHS decreases energy consumption and time to reach the set-point of the heated room while increasing heat flux on the floor in the heating space. When flow rate increases, the overall heat transfer rate of radiant floor also increases. However, the results also show overall heat transfer rateto not increased linearly and thus the existence of an optimal flow rate for the secondary side of DHS. Control of the radiant floor with hot water may be more effectively accomplished with a combined control strategy that includes heat flux and a temperature set-point. This experimental analysis has been performed using a lab-scaled DHS pilot plant located at Jeonju University in Korea.