• 한국통신학회논문지
• /
• 제38B권10호
• /
• pp.843-850
• /
• 2013

인지 라디오 시스템은 1차 시스템이 사용 중인 주파수를 공유함으로써 지역 당 주파수 이용효율을 향상시킬 수 있는 중요한 기술로 인식되고 있다. 본 논문에서는 2차 시스템이 1차 시스템에 간섭을 미치지 않으며 주파수를 공유할 수 있는 보다 능동적인 간섭 관리 기법을 제안한다. 제안된 프로토콜을 통해 2차 사용자는 1차 시스템의 간섭 채널 정보 및 송 수신 필터 정보를 획득하고 이를 이용하여 프리코딩 행렬을 계산한다. 이때 2차 시스템으로부터의 간섭은 1차 시스템의 사용되지 않는 부채널로 모이기 때문에 1차 시스템은 추가적인 연산 없이 자동적으로 간섭을 제거한다. 그리고 2차 시스템은 백색화 정합 필터를 통해 1차 시스템으로부터의 간섭을 제거함으로써 스펙트럼 효율을 향상시킨다. 전산모의실험을 통해 제안된 기법이 1차 시스템에 간섭을 미치지 않는 동시에 2차 시스템의 성능을 향상시키고, 2차 시스템의 수가 증가하더라도 1차 시스템의 성능이 저하되지 않음을 보였다.

• 산업기술연구
• /
• 제22권A호
• /
• pp.9-17
• /
• 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.

• 전기학회논문지
• /
• 제66권5호
• /
• pp.786-791
• /
• 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.

• 조명전기설비학회논문지
• /
• 제26권11호
• /
• pp.62-74
• /
• 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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.162-167
• /
• 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
• /
• 제53권5호
• /
• pp.1436-1445
• /
• 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)
• /
• 제10권5호
• /
• pp.2015-2028
• /
• 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.

• 한국통신학회논문지
• /
• 제34권8C호
• /
• pp.731-741
• /
• 2009

최근 셀 커버리지 증대와 음영지역 및 핫스팟(hot spot) 지역의 서비스 공급을 위해 추가적인 기지국 설치를 하지 않고 중계기를 활용하고 있다. 중계기는 기지국과 지형적으로 떨어져 있기 때문에 중계기와 기지국이 서로 다른 스크램블 코드를 사용할 때, 코드간 간섭이 줄어들 수 있다. 본 논문은 이와 같은 사실을 이용하여 중계기를 활용한 primary-secondary 스크램블 코드 활용 방안을 연구한다.. 이를 위해서 다섯 가지의 시나리오를 제시하고, 각 시나리오 별 성능을 시스템 레벨 시뮬레이션을 통해 비교한다. 이에 더하여, secondary 스크램블 코드의 미치는 간섭을 줄이고, 아웃티지(outage) 성능을 향상시키기 위해서 기지국-중계기간 스위칭(switching) 기법과 primary-secondary 스크램블 코드간 리플레이싱(replacing) 기법을 제안한다.

• 한국전자파학회논문지
• /
• 제22권3호
• /
• pp.354-361
• /
• 2011

본 논문에서는 1차 시스템의 협력 통신에서 중계기가 2차 시스템의 송신단으로 동작함으로써 2차 스펙트럼 접근이 가능한 협력 통신 기법을 제안한다. 일반적인 협력 통신 시스템에서는 Phase 1에 1차 시스템의 송신단은 자신의 신호를 모든 노드에 브로드캐스트하고, 나머지 노드는 이 신호를 수신한다. 그런 다음, Phase 2에 1차 시스템의 중계기 역할을 하는 2차 시스템 송신단은 1차 시스템에서 수신 후 복호한 신호와 자신이 전송하고자 하는 신호를 결합하여 각 수신단으로 브로드캐스트 한다. 이를 수신하는 각 1차 및 2차 수신단에서는 큰 잡음을 가지는 신호를 수신하며, 이는 수신 성능 감소의 원인이 된다. 이를 극복하기 위해서 1차 시스템 수신단이 1 phase만에 수신에 성공할 시에 2차 시스템 송신단이 자신의 신호만을 전송하는 적응 증분형 복호 후 전송 프로토콜을 제안한다. 이를 이용하여 전체 시스템의 성능을 향상시킬 수 있음을 모의실험을 통해 보인다.

• 한국자동차공학회논문집
• /
• 제23권5호
• /
• pp.553-563
• /
• 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.