• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.10
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• pp.843-850
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• 2013

Cognitive radio systems have been considered as a strong solution of frequency scarcity due to the limit of frequency resources. This paper proposed an active interference management scheme that the secondary system can coexist with the primary system in the same frequency band without interference. Using the proposed protocol, the secondary user acquires interference channel information and transmit/receive filter information and designs precoding matrix using these information. Since interference from the secondary systems are collected to unused subchannels of the primary system, the primary system can suppress interference without additional process. The secondary systems suppress interference from the primary system using whitening matched filter so that the spectral efficiency can be improved. Numerical results provides that the proposed scheme improves performance of the secondary systems without interference to the primary system and do not degrade performance of the primary system even if the number of the secondary systems increases.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.9-17
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• 2002

This analysis is aimed to find out how the conditions of secondary air injection affects the residence time and the turbulence energy of flue gas and flow field in a small incinerator. A commercial code, PHOENICS, is used to simulate the flow field of an Incinerator. The computational grid system is constructed in a cartesian coordinate system In this numerical experiment, an independent numerical variable is the conditions of secondary air injection and dependants are the residence time of flue gas and the mean value of turbulence energy in a primary combustion chamber. The flow field and the distribution of turbulence energy are analysed to evaluate the residence time of flue gas and the turbulence energy The computational results say that the tangential injection of secondary air make the residence time much longer than the radial injection and that the radial injection of secondary make turbulence much stronger than the tangential injection.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.786-791
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• 2017

In this paper, the run time of Li-polymer secondary cell with and without Active Balancing BMS is analyzed. The Active Balancing System using Flyback Converter with two-way power control facility, his designed for optimal characteristics of balancing. The run time of Li-polymer secondary cell is drastically increased employing the Flyback Convert Active Balancing BMS. The run time performance of Li-polymer secondary cell with or without Flyback Converter Active Balancing BMS is analyzed with the discharging and charging experiment of Li-polymer secondary cell.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.11
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• pp.62-74
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• 2012

This paper proposes a new secondary battery charger/discharger available for zero voltage discharge which is used for test equipments and formation process. The proposed system is a switching type converter, and thus the system is high efficiency and more compact as compared with linear type charger/discharger. Conventional switching type charger/discharger can not discharge secondary batteries to zero voltage because of voltage drops in the switching elements and long distributing line(typically 10m). However, the proposed system is able to discharge the battery to zero voltage in constant current mode regardless of the voltage drops. In this paper, we analyze the proposed charger/discharger and the validity of the system is verified by simulation and experiment.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.162-167
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• 2000

Construction machinery includes an engine enclosure separated from a cooling system enclosure by a wall to reduce noise and advance cooling system performance. For this structure, however, the axial fan cannot be of benefit to the engine room, and so the temperature rise in the engine room makes several bad conditions. This paper proposes that hot air in engine room is evacuated tv secondary pipe using jet pump. This paper demonstrates the structure and the effect of jet pump and useful guideline on design of area, length, and shape of secondary pipe to maximize the effect of jet pump.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1436-1445
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• 2021

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2015-2028
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• 2016

In this paper, we propose a sum transmission rate maximization based cooperative spectrum sharing protocol with quality-of-service (QoS) support for both of the primary and secondary systems, which exploits the situation when the primary system experiences a weak channel. The secondary transmitter ST_b which provides the best performance for the primary and secondary systems is selected to forward the primary signal. Specifically, ST_b helps the primary system achieve the target rate by using a fraction of its power to forward the primary signal. As a reward, it can gain spectrum access by using the remaining power to transmit its own signal. We study the secondary user selection and optimal power allocation such that the sum transmission rate of primary and secondary systems is maximized, while the QoS of both primary and secondary systems can be guaranteed. Simulation results demonstrate the efficiency of the proposed spectrum sharing protocol and its benefit to both primary and secondary systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.731-741
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• 2009

Optical repeater is often installed at the isolated area. Spatial separation makes it possible to reduce the inter-code interference when secondary scrambling codes are used for traffic connected through repeater. In this paper, we propose five secondary scrambling code usage scenarios with the aids of optical repeater to maximize the user capacity. In order to evaluate the performance, dynamic system level simulation is performed. We also propose a base station-repeater switching where each active users can change access points by comparing the channel condition from base station and repeater thorough secondary common pilot channel (S-CPICH) signal to noise-interference ratio (SINR). Moreover, primary-secondary scramble code replacing scheme is proposed which replaces secondary scramble code with primary scramble code when a call using primary scramble code is ended and its corresponding OVSF code is available to users using the secondary scramble code

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.354-361
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• 2011

In this paper, we propose a spectrum sharing system that enable secondary user's spectrum access in cooperative communication scheme. At phase 1, a transmitter in primary system broadcasts signals to the rest nodes. And then, at phase 2, a transmitter in secondary system combines the decoded signals after received from a transmitter in primary system and its own signal. And then transmitter of secondary system broadcasts the combined signals to receivers of primary and secondary systems. At this time, due to the process of combining signals, receivers of primary and secondary systems experiences a performance degradation. Therefore, we propose a novel adaptive incremental decode-andforward(AIDF) protocol to overcome this problem. By using AIDF protocol, we show performance improvement of total system through various simulations.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.5
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• pp.553-563
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• 2015

Reportedly the fatality rate from secondary collision is six times higher than the average fatality rate from all traffic accidents. So prevention of the secondary collision is attracting significant attention from automotive industries. However, the secondary collision prevention systems that have been developed are not considering possibility of brake actuator failure that can occur by the impact during the initial collision. In this paper, a new system has been developed that could prevent secondary collision even in case of brake actuator failure by taking advantage of still operating actuators. In this system, a steering control is performed for maintaining a lane by using linear quadratic regulator. Additionally, the system attempts differential brake control with the remaining braking capability to stop the vehicle in the shortest distance. Through simulation in various collision scenarios, the system has demonstrated significant potential of preventing secondary collision that could otherwise have resulted in severe fatality.