• Journal of Biosystems Engineering
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• 제28권2호
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• pp.97-106
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• 2003

One of the obstructing factors against managing dairy fm has been heavy labor requirement for feeding dairy cows. A Power-tiller TMF mixer was developed to reduce the cost and to provide economic benefit. The TMF mixer was desisted by the feeding capacity of 20∼30 heads at a batch with various functioning systems of auger type mixer, delivery conveyer, weighing console, pipe heater type heating system, power transmission train and mounting trailer. According to the study resulted, it showed that 1,200rpm, 1,600rpm, 2,000rpm and 2,300rpm were 6ps. Bps, lops and 12ps respectively. and that reduced shaft output by 15%. On the fodder mixer attached powertiller, initial output was necessary large torque. And the heating system was maintaining uniform temperature 60$^{\circ}C$ relatively.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.382-384
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• 2008

Hold-up time is a special requirement for the front end DC/DC converter in a server power supply. It forces the converter with the variable switching frequency to operate in a wide switching frequency range, which makes the regulation difficult and reduces the power density. In this paper a novel frequency controlled half bridge converter with the hold-up time extension circuit is proposed. During the hold-up time, the auxiliary switches are turned on, thus the resonant inductance is reduced and the voltage conversion ratio is increased. Therefore, the output capacitor of the power factor correction (PFC) circuit can be decreased, and the converter can have high power density. The proposed converter is verified by experimental results from a prototype with 700W, 400V input, and 12V output.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1322-1324
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• 2001

FuelCell/Battery hybrid power systems were studied to develop high efficient zero-emission fuel cell electric vehicles. Fuel cells were used as an auxiliary energy source and batteries were used as a transient power source. The fuel cell system is used to supply the average power demand. Dynamic response of the hybrid systems was simulated using PSPICE program and also tested experimentally. The results can be used to design the interface module and to determine the power requirement between the fuel cell unit and the battery pack.

• 한국통신학회논문지
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• 제21권5호
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• pp.1240-1255
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• 1996

This paper suggests power optimization technique in multi-level SCPC system as a method for efficient utilization of limited satellite power. The power optimization is realized by optimal assignment of satellite input carrier powers considering interference and noise generated in up-link and down-link. The Fletcher-Powell algorithm searching minimum(or maximum) point using gradient information is used to detemine the optimal input carrier powers. To apply Flectcher-Powell algorithm mathematical descriptions and their partial derivatives to interference and nose are presented. Because a target, which should be optimized, is satellite input carrier power, amplitude of each carrier group will be assumed to be an independent variable. The performance criterion for optimal power assignmentis classified into 4 categories with respect to CNR of destination receiver earth station to meet the requirement for various satellite link environment. Simulation results for two-level, four-level and six-level SCPC system are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.195-201
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• 1989

Voltage collapse is a serious concern to the electirc utility industry. It is common to associate steady-state stability with the ability of the transmission system to transport real power and to associate voltage collapse with the inability to provide reactive power at the necessary locations within the system. An algorithm to directly calculate the critical point of system voltage collapse was presented by the authors. The method (based on the ordinary power flow equations and explicit requirement of singularity of the Jacobian matrix) is basically one degree of freedom with proper load distribution factors. This paper suggests a modified algorithm to increase the degree of freedom, introducing the nonlinear programming technique. The objective function is a distance measure between the present operating point and the closest voltage collapse point. Knowledge of the distance and the most vulnarable bus from the voltage collapse point of view may be used as a useful index for the secure system operation.

• 한국세라믹학회지
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• 제47권1호
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• pp.1-7
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• 2010

Solid oxide fuel cells (SOFCs) have been under development for a variety of power generation applications. Power system sizes considered range from small watt-size units (e.g., 50-W portable devices) to very large multi-megawatt systems (e.g., 500-MW base load power plants). Because of the reversibility of its operation, the SOFC has also been developed to operate under reverse or electrolysis mode for hydrogen production from steam (In this case, the cell is referred to as solid oxide electrolysis cell or SOEC.). Potential applications for the SOEC include on-site and large-scale hydrogen production. One critical requirement for practical uses of these systems is long-term performance stability under specified operating conditions. Intrinsic material properties and operating environments can have significant effects on cell performance stability, thus performance degradation rate. This paper discusses potential applications of the SOFC/SOEC, technological status and current research and development (R&D) direction, and certain aspects of long-term performance degradation in the operation of SOFCs/SOECs for power generation/hydrogen production.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.1119-1120
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• 2008

배터리를 전원으로 사용하는 이동 통신 기기에서 전력 관리의 효율성은 전통적으로 중요한 요구조건 중의 하나이다. 특히 고성능과 고기능을 제공하면서도 더 긴 동작시간이 요구되는 최근의 이동 통신 기기들에서는 이러한 효율적인 전력 관리의 중요성이 더욱 크다. 본 논문은 전력 소모량과 시스템의 크기에서의 장점으로 인해 이동 통신 기기에 폭 넓게 적용되고 있는 embedded system 에서의 효율적인 전력 관리를 위한 CPU 소모 전력 관리 기법으로 적응적 동적 전력 관리 기법을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4331-4346
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• 2015

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each user's quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

• Journal of Information Processing Systems
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• 제7권1호
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• pp.93-102
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• 2011

In deeply scaled CMOS technologies, two major non-ideal factors are threatening the survival of the CMOS; i) PVT (process, voltage, and temperature) variations and ii) leakage power consumption. In this paper, we propose a novel post-silicon tuning methodology to scale optimum voltage and frequency "dynamically". The proposed design technique will use our PVT sensor circuits to monitor the variations and based on the monitored variation data, voltage and frequency will be compensated "automatically". During the compensation process, supply voltage is dynamically adjusted to guarantee the minimum total power consumption without violating the frequency requirement. The simulation results show that the proposed technique can reduce the total power by 85% and the static power by 53% on average for the selected ISCAS'85 benchmark circuits with 45 nm CMOS technology compared to the results of the traditional PVT compensation method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.301-305
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• 1998

The Power measurement that can measure a single quantity does not smooth to install a system, and are not convenient to use. These measuring values are vary difficult for mutual operation and analyzing, and that have too many problems to compile measured databases. If each single measured values are mutual assist, correction and reform, the system will be able to be improved by minimizing differences between measure quantities and as making many different measurement system (Voltage, Current, Power and Resistor) is installed in one system. This study is useful to develope the power measurement system that is easier to analyze and management by database all of the parameter values because the power measurement system is able to be interbased with PC as requirement of industralization and information age.