• Journal of Communications and Networks
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• 제18권3호
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• pp.320-326
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• 2016

In existing literature on multiple-input multiple-output (MIMO) relaying communication systems, antenna selection is often implemented by maximizing the channel capacity or the output single-to-noise ratio (SNR). In this paper, we propose an energy-efficient low-complexity antenna selection scheme for MIMO relaying communication systems. The proposed algorithm is based on beamforming and maximizing the Frobenius norm to jointly optimize the transmit power, number of active antennas, and antenna subsets at the source, relaying and destination. We maximize the energy efficiency between the link of source to relay and the link of relay to destination to obtain the maximum energy efficiency of the system, subject to the SNR constraint. Compared to existing antenna selection methods forMIMO relaying communication systems, simulation results demonstrate that the proposed method can save more power in term of energy efficiency, while having lower computational complexity.

• 한국산업융합학회 논문집
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• 제25권1호
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• pp.71-78
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• 2022

With the advent of cutting-edge technology, renewable energy is significantly considered as alternative resources to supply electric power. However, many barriers such as energy intermittency, high initial installation cost, and low-efficiency generation challenged building new infrastructure with clean energy. Efforts reducing greenhouse gas emissions and reliance on fossil fuels resulted in the decentralization of power generation like distributed energy resource (DER). This paper is to introduce and evaluate the feasibility of building-integrated photovoltaics (BIPV) in a high-rise building in Ulsan. To optimize BIPV, a variety of methods to minimize efficiency decrease and maximize electric power generation after installing BIPV on the building's facade are suggested. The variables causing power losses are analyzed. By utilizing System Advisor Model (SAM), actual power generated from solar panels is measured by Thin-film PV, Mono-crystalline PV, and Poly-crystalline PV.

• 한국전기전자재료학회논문지
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• 제37권4호
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• pp.439-444
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• 2024

This study investigates the post-thermal treatment effects on the efficiency of silicon heterojunction solar cells, specifically examining the influence of annealing on p-type microcrystalline silicon oxide and ITO thin films. By assessing changes in carrier concentration, mobility, resistivity, transmittance, and optical bandgap, we identified conditions that optimize these properties. Results reveal that appropriate annealing significantly enhances the fill factor and current density, leading to a notable improvement in overall solar cell efficiency. This research advances our understanding of thermal processing in silicon-based photovoltaics and provides valuable insights into the optimization of production techniques to maximize the performance of solar cells.

• 펄프종이기술
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• 제36권4호
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• pp.67-76
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• 2004

Because paper industry spends lots amount of water, the recycling of water is very important in economical as well as environmental aspects. In order to optimize the process water recycling system, the efficiency of unit operation for water circulation, such as save-all system, CDS and settling tank, plays an important role in. In this study, the sedimentation efficiency of process water was evaluated by SS measurement with the different amounts of flocculent addition. 3 different kinds of process water were collected from fine paper mill, and applied in laboratory sedimentation equipment for the measurement of settling efficiency of SS materials. The addition amounts of alum and PAC were resulted in optimum efficiency of sediments in the condition of 100 ppm of alum and 500 ppm of PAC respectively. In the comparison of sedimentation efficiency between alum and PAC, alum showed more economical and efficient results. The SS of spill water and the particle size of suspended materials treated by alum flocculents were below 50 ppm and about 1 $\mu$m. It would be considered that the spill water can be substituted to superclear water grade.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1934-1944
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• 2017

As a key component of high-voltage power conversion system for electric vehicles (EVs), bidirectional DC/DC (Bi-DC/DC) is required to have high efficiency and light weight. Conventional design methods optimize the Bi-DC/DC at the maximum power dissipation point (MPDP). For EVs application, the work condition of the Bi-DC/DC is not strict as the MPDP, where the design method using MPDP may not be optimal during travel of EVs. This paper optimizes the Bi-DC/DC converter targeting efficiency and weight based on the driving cycle. By analyzing the two-phase interleaved Bi-DC/DC for hybrid energy storage systems (HESS) of EVs, its power dissipation is calculated, and an efficiency model is derived. On this basis, weight models of capacitor, inductor and heat sink are built, as well as a dynamic temperature model of heat sink. Based on these models, a method using New European Driving Cycle (NEDC) for optimal design of Bi-DC/DC which simultaneously considered efficiency and weight is proposed. The simulation result shows that compare with conventional optimization methods revealed that the optimization approach based on driving cycle allowed significant weight reduction while meeting the efficiency requirements.

• 한국대기환경학회지
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• 제23권6호
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• pp.744-751
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• 2007

Wet scrubber is widely used to remove toxic gaseous contaminants in various industries such as semi-conductor industry, display manufacturing industry and so on. In this study, to optimize a packed bed scrubber as one of typical wet scrubber size while keeping its performance, four different packing materials were investigated at different air flow rates, liquid-gas ratios and pH values. Ammonia, hydrochloric acid and hydrofluoric acid were used as test gases to characterize the scrubber performance. Gas removal efficiency increased as the packing size decreased, which resulted in the increase of specific surface area. The increase of air flow rate led to the decrease of gas removal efficiency, while the increase of liquid-gas ratio led to the increase of gas removal efficiency. For the case of $NH_3$ gas, lower pH, and for the cases of HCl and HF, higher pH contributed to higher gas removal efficiency. Gas removal efficiency of a wet scrubber increased in the order of HCl < $NH_3$ < HF according to its water solubility.

• 한국재료학회지
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• 제24권9호
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• pp.458-464
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• 2014

Light scattering enhancement is widely used to enhance the optical absorption efficiency of dye-sensitized solar cells. In this work, we systematically analyzed the effects of spherical voids distributed as light-scattering centers in photoanode films made of an assembly of zinc oxide nanoparticles. Spherical voids in electrode films were formed using a sacrificial template of polystyrene (PS) spheres. The diameter and volume concentration of these spheres was varied to optimize the efficiency of dye-sensitized solar cells. The effects of film thickness on this efficiency was also examined. Electrochemical impedance spectroscopy was performed to study electron transport in the electrodes. The highest power conversion efficiency of 4.07 % was observed with $12{\mu}m$ film thickness. This relatively low optimum thickness of the electrode film is due to the enhanced light absorption caused by the light scattering centers of voids distributed in the film.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1356-1357
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• 2011

Interior permanent magnet synchronous motor(IPMSM) adjustable speed drives offer significant advantages over induction motor drives in a wide variety of industrial applications such as high power density, high efficiency, improved dynamic performance and reliability. This paper proposes on-line efficiency optimization of IPMSM drive using fuzzy logic control(FLC) and the loss minimization method. In order to optimize the efficiency the loss minimization algorithm is developed based on motor model and operating condition. The d-axis armature current is utilized to minimize the losses of the IPMSM in a closed loop vector control environment. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current. The minimization of loss is possible to realize efficiency optimization control for the proposed IPMSM. The optimal current can be decided according to the operating speed and the load conditions. The proposed control algorithm is applied to IPMSM drive system and the operating characteristics controlled by the loss minimization method and FLC control are examined in detail.

• 동력기계공학회지
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• 제16권1호
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• pp.38-43
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• 2012

This paper describes an analysis on performance of R744-R404A cascade refrigeration system with internal heat exchanger to optimize the design for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, internal heat exchanger and compression efficiency, evaporating and condensing temperature in the R744 low- and R404A high-temperature cycle and temperature difference of cascade heat exchanger. The main results are summarized as follows : COP of cascade refrigeration system increases with the increasing of compression efficiency, but decreases with the increasing temperature difference of cascade heat exchanger. Also, the COP increases with the increasing of internal heat exchanger efficiency in high-temperature cycle, but decreases with that in low-temperature cycle. Therefore, internal heat exchanger efficiency, compressor efficiency and temperature difference of cascade heat exchanger on R744-R404A cascade refrigeration system have an effect on the COP of this system.

• 전력전자학회논문지
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• 제8권3호
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• pp.211-220
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• 2003

본 논문은 직접 토오크 제어 (Direct Torque control, DTC)를 이용한 릴럭턴스 동기전동기 (Reluctance Synchronous Motor, RSM)의 최대 효율 제어에 관한 연구이다. 릴럭턴스 동기전동기의 등가모델 해석에 있어서 철손의 영향을 고려하여 이론적으로 분석하였으며, 최대효율제어를 위하여 토크 전류와 여자전류 사이의 최적 각을 유도하였다. 릴럭턴스 동기전동기의 경우는 자속이 전류에 비례하므로 유도전동기와는 달리 자속레벨을 제어하면서 토오크의 동특성을 유지할 수 있다는 특징을 가지고 있으며, 제시된 연구에서는 릴럭턴스 동기전동기의 이러한 특징을 적용하여 직접 토오크 제어의 장점인 빠른 토오크 응답특성을 유지하면서 최대 효율 제어가 이루어지도록 한다. d/q 릴럭턴스 비가 2.57인 1.0 Kw 릴럭턴스 동기전동기를 이용하여 실험을 통해 제안된 방법들의 정당성을 입증하였다.