• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권5호
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• pp.1049-1068
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• 2011

In this paper a simple and effective call admission control (CAC) scheme is proposed for the emerging interleave-division multiple-access (IDMA) systems, supporting a variety of traffic types and offering different quality of service (QoS) requirements and priority levels. The proposed scheme is signal-to-interference-plus-noise ratio (SINR) evolution based CAC (SE-CAC). The key idea behind the scheme is to take advantage of the SINR evolution technique in the process of making admission decisions, which is developed from the effective chip-by-chip (CBC) multi-user detection (MUD) process in IDMA systems. By virtue of this semi-analytical technique, the MUD efficiency can be estimated accurately. Additionally, the computational complexity can be considerably reduced. These features make the scheme highly suitable for IDMA systems, which can combat intra-cell interference efficiently with simple CBC MUD. Analysis and simulation results show that compared to the traditional CAC scheme considering MUD efficiency as a constant, the proposed SE-CAC scheme can guarantee high power efficiency and throughput for multimedia traffic even in heavy load conditions, illustrating the high efficiency of CBC MUD. Furthermore, based on the SINR evolution, the SE-CAC can make accurate estimation of available resource considering the effect of MUD, leading to low outage probability as well as low blocking and dropping probability.

• 한국언론정보학보
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• 제55권
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• pp.164-183
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• 2011

디지털 컨버전스의 기술 혁신은 언론 부문에서 핵심적인 노동이라고 할 수 있는 기자노동에도 막대한 영향을 주고 있다. 노동과정론에 따르면, 자본주의적 생산양식에서 기술혁신으로 인해 노동자들은 노동에 대한 통제력을 상실해가면서 탈숙련화의 과정을 겪어 왔고, 경영진들은 억압적인 노동조건을 은폐하고 노동자들을 더욱 효율적으로 통제하기 위해 이데올로기적, 정치적 장치들을 도입해 왔다. 이러한 문제의식 위에서 본 연구는 뉴스룸 통합의 기술혁신이 기자노동의 숙련도에 어떠한 영향을 주는지, 또 경영진들이 기자들을 통제하기 위해 사용하는 전략이 무엇인지를 CBS 통합뉴스룸의 사례를 통해 실증적으로 분석하였다. 분석 결과, 통합뉴스룸 도입으로 인해 기자들은 숙련노동에 대한 통제력을 상실해가면서 탈숙련화되고 있었다. 또한, 경영진들은 새로운 뉴스생산관행, 가족주의 노사문화에 대한 노동자들의 동의를 획득해 나갔으며, 내부노동시장 분절화를 통해 기업권력의 강화와 노동사회의 고립화 전략을 취하고 있었다.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.460-474
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• 2023

A simple but accurate mathematical model is crucial for dynamic simulations and controller design of helical coil once-through steam generator (OTSG). This paper presents a three-region movable boundary dynamic model of the helical coil OTSG. Based on the secondary side fluid conditions, the OTSG is divided into subcooled region (two control volumes), two-phase region (two control volumes) and superheated region (three control volumes) with movable boiling boundaries between each region. The nonlinear dynamic model is derived based on mass, energy and momentum conservation equations. And the linear model is obtained by using the transfer function and state space transformation, which is a 37-order model of five input and three output. Validations are made under full-power steady-state condition and four transient conditions. Results show good agreements among the nonlinear model, linear model and the RELAP5 model, with acceptable errors. This model can be applied to dynamic simulations and controller design of helical coil OTSG with constant primary-side flow rate.

• 전자공학회논문지SC
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• 제43권1호
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• pp.45-52
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• 2006

본 논문에서는 새로운 무손실 스너버 회로를 설계하여 적용한 PWM-PFC 스텝-업 컨버터에 대해 제안한다. 제안된 컨버터는 전류불연속 제어모드에 의해 제어회로 구성이 간단하고 회로 구성소자의 용량을 줄일 수 있다. 또한 입력전류는 스위치의 듀티율 일정제어에 의한 교류 입력전압의 크기에 비례한 불연속적인 펄스열의 정현파상으로 된다. 그 결과 입력역률은 거의 단위역률로 주어지고 듀티율 일정제어에 의해서 제안된 컨버터는 제어기법이 간단하게 된다. 일반적으로 입력전류 불연속제어에 의한 컨버터의 경우, 사용된 스위치의 턴-온 동작은 영전류 스위칭으로 되는 장점이 있지만, 스위치의 턴-오프 동작은 최대 전류에서 스위칭되어 스위칭 손실을 증대시키고 스위치의 과중한 스트레스를 가져오게 된다. 이것은 컨버터의 효율을 저하 시키는 요인이다. 본 논문에서는 부분공진 회로로 동작되는 새로운 무손실 스너버 회로를 설계하여 스위치들의 턴-온, 턴-오프 동작을 소프트 스위칭으로 만들어 컨버터의 효율을 더욱 증대시킨다 제안된 PWM-PFC 스텝-업 컨버터는 컴퓨터 시뮬레이션과 실험을 통하여 그 타당성이 입증된다.

• 한국항공우주학회지
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• 제37권4호
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• pp.367-371
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• 2009

본 논문에서는 기존 연구결과들과 달리 비행체의 운동을 선형방정식으로 표현할 수 있다는 가정을 도입하지 않고 비례항법유도법칙의 최적성에 관한 해석 결과를 제시한다. 비례항법유도법칙은 비행체-표적 거리의 지수함수를 가중치로 갖는 제어 에너지를 최소화하는 최적의 유도법칙임을 비선형 방정식 기반으로 유도한다. 이때 가중함수의 지수와 비례항법상수와의 관계에 대해 설명한다. 또한 이러한 해석의 유효한 조건을 도출한다.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.593-600
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• 2010

In this paper, High brightness LED (light-emitting diodes) driver IC (integrated circuit) using new current sensing circuit is proposed. This LED driver IC can provide a constant current with high current precision over a wide input voltage range. The proposed current-sensing circuit is composed of a cascode current sensor and a current comparator with only one reference voltage. This IC minimizes the voltage stress of the MOSFET (metal oxide semiconductor field effect transistor) from the maximum input voltage and has low power consumption and chip area by using simple-structured comparator and minimum bias current. To confirm the functioning and characteristics of our proposed LED driver IC, we designed a buck converter. The LED current ripple of the designed IC is in ${\pm}5%$ and a tolerance of the average LED current is lower than 2.43%. This shows much improved feature than the previous method. Also, protections for input voltage and operating temperature are designed to improve the reliability of the designed IC. Designed LED driver IC uses 1.0 ${\mu}m$ X-Fab. BiCMOS process parameters and electrical characteristics and functioning are verified by spectre (Cadence) simulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.23-23
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• 2009

Recently, the nanowire configuration of GST showed nanosecond-level phase switch at very low power dissipation, suggesting that the nanowires could be ideal for data storage devices. In spite of many advantages of IST materials, their feasibility in both thin films and nanowires for electronic memories has not been extensively investigated. The synthesis of the chalcogenide nanowires was mainly preformed via a vapor transport process such as vapor-liquid-solid (VLS) growth at a high temperature. However, in this study, IST nanowires as well as thin films were prepared at a low temperature (${\sim}250^{\circ}C$) by metal organic chemical vapor deposition(MOCVD) method, which is possible for large area deposition. The IST films and/or nanowires were selectively grown by a control of working pressure at a constant growth temperature by MOCVD. In-Sb-Te NWs will be good candidate materials for high density PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 추계학술대회 논문집
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• pp.148-150
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• 2007

A novel torque sharing function (TSF) is presented. To improve efficiency and to reduce torque ripple in commutation region, only a phase torque under commutation is regulated to produce a uniform torque. And the torque developed by the other phase remains with the previous state under a current limit of the motor and drive. If the minimum change of a phase torque reference can not satisfy the total reference torque, two-phase changing mode is used. Since a phase torque is constant and the other phase torque is changed at each rotor position, total torque error can be reduced within a phase torque error limit. And the total torque error is dependent on the change of phase torque. To consider non-linear torque characteristics and to suppress a tail current at the end of commutation region, the incoming phase current is changed to torque increasing direction, but the outgoing phase current is changed to torque decreasing direction. So, the torque sharing of the outgoing phase and incoming phase can be smoothly changed with a minimum current cross over. The proposed control scheme is verified by some computer simulations and experimental results.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.1012-1020
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• 2013

In this work, Self-adaptive Differential Evolutionary (SaDE) algorithm is proposed to solve Optimal Location and Size of Capacitor (OLSC) problem in radial distribution networks. To obtain the SaDE algorithm, two improvements have been applied on control parameters of mutation and crossover operators. To expand the study, three load conditions have been considered, i.e., constant, varying and effective loads. Objective function is introduced for the load conditions. The annual cost is fitness of problem, in addition to this cost, CPU time, voltage profile, active power loss and total installed capacitor banks and their related costs have been used for comparisons. To confirm the ability of each improvements of SaDE, the improvements are studied both in separate and simultaneous conditions. To verify the effectiveness of the proposed algorithm, it is tested on IEEE 10-bus and 34-bus radial distribution networks and compared with other approaches.

• 전기학회논문지
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• 제61권4호
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• pp.612-616
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• 2012

This paper presents an active current regulator for LED driver IC. The proposed driver circuit is consists of DC-DC converter for supplying constant DC voltage to LED, active current regulator for compensating channel-to-channel current error from LED strings and feedback circuit for controlling duty ratio of the converter. The proposed active current regulator senses current of LED channels by equalizing both $V_{DS}$ and $V_{GS}$ at LED current control transistor. Because the proposed circuit directly measures the LED channel current without a sensing resistor and regulates all channel with same regulation loop, the power consumption and the current error are much small compared with previous works. The measured maximum efficiency of overall LED driver IC is approximately 94% and current error of LED channel-to-channel is under ${\pm}1.3%$. The proposed LED driver IC is fabricated Dongbu 0.35um BCD process.