Earticle

In this paper, we study secure energy efficiency (SEE) for simultaneous wireless information and power transfer (SWIPT) in a distributed antenna system (DAS) based IoT network. We consider a system in which both the legitimate user (Bob) and the eavesdropper (Eve) rely on the energy harvested from the received radio signal. Firstly, with perfect channel state information (CSI), we formulate the maximization of SEE as a constrained optimization problem. In this problem, we aim to highlight the advantage of SWIPT in exploiting the Eve’s energy harvesting requirement. This is achieved by defining a charge constraint in the SEE optimization problem which ensures that the Eve is deprived of its only energy source. Next, considering the fact that perfect CSI is hard to achieve in practice, we characterize the system performance in terms of the outage probability (OP) of SEE. For the given SWIPT-in-DAS setup, we derive the closed form expression for the OP of SEE and with the help of numerical results, we study the effect of transmit power levels, number of distributed antenna (DA) ports and the PS ratio of devices. To the best of our knowledge, this is the first attempt to define the OP of SEE for SWIPT-in-DAS.

With the growing number of devices, applications, and services, energy-efficient communication has become critical in next-generation wireless networks. Terahertz (THz) bands provide vast bandwidth for high data rates, but their poor penetration causes user blockage. To address this, we consider a massive MIMO (mMIMO) THz non-orthogonal multiple access (NOMA) system assisted by an IRS-mounted UAV that reflects signals toward blocked users. We formulate the UAV trajectory design as an NP-hard problem and propose a low-complexity Track Selection Scheme (TSS) that minimizes UAV energy consumption. We develop a Deep Q-Network (DQN)-based NOMA power allocation scheme to further enhance performance and formulate an energy-efficiency maximization problem. The latter is solved using a combination of the Dinkelbach method and the Concave?Convex Procedure (CCCP). Simulation results demonstrate that the proposed schemes significantly reduce UAV energy consumption and improve system sum-rate and energy efficiency compared with benchmark algorithms.

The differential global positioning system (DGPS) transmits a GPS enhancement signal using a top-loaded monopole antenna in the medium frequency range. The top-loaded antenna in the medium frequency band can attain a radiation efficiency on the order of 10%. The antenna ground plane characteristics affect the antenna radiation efficiency. To improve the radiation efficiency, it is necessary to install the antenna on a ground plane with large enough physical dimensions and good conductivity. The antenna radiation efficiency is a primary factor in determining the DGPS service area. The service area of the DGPS using a medium frequency band is dominantly affected by the antenna radiation efficiency. To determine antenna radiation efficiencies accurately, the antenna radiation efficiencies of DGPS are deduced from the propagation power in this paper. Based on the deduced antenna radiation efficiencies, the service area for the Korean nationwide-DGPS is analyzed and evaluated.

This study investigates the performance in output power and efficiency enhancements of Reversed Doherty Power Amplifiers (RDPA) compared to Conventional Doherty Power Amplifiers (CDPA) under varying Quarter-Wave Transformer Losses (QWTL) from 1 dB to 5 dB. The RDPA achieves a comparable maximum output power (Psat) of 47.55 dBm, with a 6 dB back-off point showing consistent performance superiority, maintaining a lead of 0.7–2.9 dB across QWTL conditions. Despite a 1.25 dB decrease in saturation power due to QWTL, RDPA demonstrates a notable improvement in Power Added Efficiency (PAE), achieving 43% at 6 dB back-off, compared to CDPA’s 35%. Efficiency at other load conditions (OBO) for RDPA also consistently outperforms CDPA, with PAE ranging from 3.79% to 25.83% depending on QWTL and Drain efficiencies (DE) of the carrier and peaking amplifiers. These results highlight the RDPA’s resilience to QWT losses and its potential for energy-efficient wireless applications, positioning it as a strong candidate for next-generation high-efficiency amplifier designs.

Non-contact power supply (NCPS), as a clean and safe energy supply concept has been applying wildly. Comparing with the conventional transformer the non-contact transformer has a large air gap between the long primary winding and the secondary winding. Due to it, the non-contact transformer has increased leakage inductance and reduced magnetizing inductance. So the high frequency series resonant converter has been widly used on the non-contact power supply system for transferring the primary power to the secondary one, from what a high influence voltage can be gained on the secondry coil even though the large air gap exists. However, it still has the disadvantages of the load sensitive voltage gain characteristics when load is changing. In this paper, we propose a fuzzy logic controller to adjust the frequency of the inverter to track the resonat which is changing when the load is change.

최근 러시아·우크라이나 전쟁 및 국제 에너지 가격의 상승으로 인해 전력 구입단가는 소비자에게 전력을 판매하는 단가에 비해 상당히 높은 편이다. 이러한 원인으로 한전의 경영악화가 발생하였고, 전력산업 및 경제 전반에 악영향을 미치고 있다. 국민들에게 부담이 전가되지 않도록 전력 생산 분야에서 더 나은 경영성과를 이끌어 낼 필요가 있다. 따라서 본 논문에서는 국내 발전회사 8곳을 대상으로 발전설비 용량, 인원의 투입대비 매출액의 효율성 및 생산성을 비교분석하였다. 분석결과 2개의 사기업은 효율성 이 최적의 상태인 것으로 나타났으며, 공기업은 사기업보다 효율성이 낮게 나타났다. 생산성을 분석한 결과 8개 기관 모두 증가하였다. 다만, 사기업의 상승률에 비해 공기업은 상대적으로 낮은 상승률을 보였다. 정부의 경영실적평가에 효율성 분석인 DEA를 포함하여 더 객관성 있고 신뢰성 있는 평가 방법을 고려할 필요가 있다.

Due to the recent wars in Russia and Ukraine and the rise in international energy prices, the unit cost of purchasing electricity is significantly higher than the unit cost of selling electricity to consumers. This has led to a deterioration in KEPCO's management, which is having a negative impact on the power industry and the economy as a whole. it is necessary to achieve better management performance in the field of electricity generation so that the burden is not passed on to the people. Therefore, this research aimed to analyze the efficiency and productivity of the amount of power generation facilities, personnel input, and sales for eight domestic power generation companies. The results showed that two private companies had optimal efficiency, while public companies were less efficient than private companies. When analyzing productivity, all eight organizations increased. However, compared to the increase of private companies, the increase of public companies was relatively low. There is a need to consider more objective and reliable evaluation methods, including DEA, an efficiency analysis, in the government's evaluation.

As the wireless power transfer (WPT) technology based on strongly resonance coupled method realizes large power charging without any wires through the air, there are advantages compared with the wired counterparts, such as convenient, safety and fearless transmission of power. From this reason, the WPT systems have started to be applied to the wireless charging for various power applications such as train, underwater ship, electric vehicle. This study aims for the effect and characteristics of different inserted resonance coil between Tx and Rx coils for charging system of superconducting magnetic levitation (MAGLEV) train. The transfer efficiency and effect are evaluated with helix type, rectangular type copper resonance coil, and HTS resonance coil under bulb and HTS magnet load, respectively. The input power is adapted with radio frequency (RF) power of 370 kHz below 500 W.

본 논문은 5G 시스템에 적용되어 인 빌딩, 지하철과 터널등에 사용되는 50 Watts급 중계기용 고효율 전력증폭기 설계 방법과 전기적 특성을 나타내었다. 여기서 설계된 전력증폭기의 종단 트랜지스터는 GaN(gallium nitride)을 사용하여 도허티방식으로 구성하였으며, 선형성을 만족시키기 위해서 DPD(digital predistortion)를 이용하여 혼변조 신호를 제거하였다. 또한, 5G 시스템에서 요구되는 증폭기의 이득 제어와 경보 처리등 다양한 요구사항을 처리하기 위해서 마이크로프로세서가 전력증폭기 내부에 존재하게 설계하였다. 통신사업자가 요구하는 규격의 전력증폭기는 46.5 dBm 출력전력과 증폭기 전체의 효율이 37%가 측정되었고, EVM(error vector magnitude)은 2.3% 그리고 ACLR(adjacent channel leakage ratio)은 52.8 dBc로 측정되어 요구되는 전기적 특성과 다양한 경보조건을 만족하는 것을 확인하였다.

This paper presents the design method and electrical characteristics of a high-efficiency power amplifier for a 50 Watts class repeater applied to a 5G system and used in in-building, subway, and tunnel. GaN was used for the termination transistor of the power amplifier designed here, and intermodulation signals were removed using DPD to satisfy linearity. In addition, in order to handle various requirements such as amplifier gain control and alarm processing required in the 5G system, the microprocessor is designed to exist inside the power amplifier. The amplifier manufactured to confirm the electrical performance of the power amplifier satisfying these conditions satisfied 46.5 dBm and the overall efficiency of the amplifier was 37%, and it was confirmed that it satisfied various alarm conditions and electrical characteristics required by telecommunication companies.

본 논문은 고효율 고선형 특성을 얻기 위하여 신테라사가 제공한 디지털로 제어되는 아날로그 전치왜곡 칩을 이용한 도허티 전력증폭기를 설계하였다. 여기서 사용된 아날로그 전치왜곡기는 입력과 출력신호를 비교하여 출력의 혼변조 신호 특성을 개선하기 위하여 입력 신호의 크기와 위상을 조절함으로서 선형성을 개선시켰다. 또한, 도허티 전력증폭기를 설계하여 이용함으로써 고효율의 특성을 얻었다. 제작된 전력증폭기는 중심주파수 2150 MHz에서 평형증폭기와 비교하여 11% 이상의 효율 개선 효과와 출력 전력 100W 이하에서 인접채널 전력을 15 dB 이상 개선시켰다.

This paper presents the Doherty power amplifier with a digitally controlled analog predistorter circuit of Scintera Corp. to produce high power efficiency and high linearity performance. The analog predistorter improves the linearity performance because of controlling amplitude and phase values of input signal in order to improve intermodulation performance of power amplifier. Also, the power amplifier is designed by the Doherty technology to obtain the high efficiency performance. To validate the Scintera's analog predistorter, we are implemented the power amplifier with Doherty method at center frequency 2150 MHz. Compared with the balanced amplifier, the power amplifier is improved above 11% enhanced efficiency and more than 15 dB ACPR improvement.

본 논문에서는 SLM(selective mapping)과 PTS(partial transmit sequence) 방식을 이용한 STBC MIMO-OFDM(space-time block code multi-input multi-output orthorgonal frequency division multiplexing) 시스템의 PAPR(peak-to-average power ratio) 성능을 분석한다. MIMO-OFDM 시스템에서 SLM과 PTS 방식은 비선형왜곡을 줄이고 비선형 HPA(high power amplifier)의 전력효율을 개선하기 위해 사용된다. 시뮬레이션 결과에서는 QPSK를 사용한 기존의 MIMO-OFDM 시스템과 비교하였을때, SLM의 PAPR이 3.5dB 정도 줄어드는 동안 PTS는 5dB 정도 감소되는 결과를 볼 수 있다. 또한, HPA의 앞단에 사전왜곡기의 유무에 따른 MIMO-OFDM 시스템의 BER 성능을 분석해 본 결과 사전 왜곡기를 사용하였을 때 선형 증폭기에 근접하기 위해서 SLM 방식에서 6dB IBO(input backoff)가 요구되고 PTS 방식에서는 4dB가 요구됨을 확인하였다. PAPR을 개선하는 방식을 사용하지 않으면 8dB의 IBO가 필요하다.

Tn this paper, we evaluate the peak-to-average power ratio (PAPR) performance in a space-time block code (STBC) multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system using selected mapping (SLM) and partial transmit sequences (PTS) approaches. SLM and PTS methods are used to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear high power amplifier(HPA) in the MIMO-OFDM system. In simulation result, when compared with the existing MIMO-OFDM system using QPSK, the PTS method reduces the PAPR about 5dB while the SLM method can reduce about 3.5 dB. Also, we find the BER performance of the MIMO-OFDM system with and without the predistorter in front of the HPA. When the predistorter is used, the input back-off (IBO) of 4 dB is required in the PTS method, and IBO of 6 dB in the SLM method to closely conform to the linear amplifier. If the method of improving the PAPR is not used, the value of IBO of 8 dB is required.

Continuously variable transmission(CVT) combined differential gear unit has many advantages, which are the decrease of CVT size, the increase of overall efficiency, the extension of speed ratio range, and the generation of geared neutral. It is known that such CVT can be classified into the input coupled type and the output coupled type according to the coupling location of continuously variable unit(CVU). In this paper, six different configurations of input coupled type CVT combined V-belt CVU and 2K-H I type differential gear unit are proposed. Some useful theoretical formula related to speed ratio, power flow and efficiency are derived and analyzed. The propriety of derived formula and theoretical analysis are proven by various experiments.

Blades of wind energy plants are exposed to external shocks or internal cracks during operation. Furthermore, the blade surfaces can be contaminated by substances such as dust, blood of birds, salt or insects which can decrease the electricity generation efficiency significantly. For this reason, many blade cleaning companies started to appear and a variety of methods for cleaning were suggested. Despite these diverse methods, there has been no study to investigate how effectively to clean the substances in quantitative manner. In this paper, the cleaning efficiency of two rotor blade cleaning methods, brush and water-jet, is examined through experiments by changing operating parameters. Then, the optimal operating conditions for both methods are derived.

In this paper, the high efficiency and linearity Doherty power amplifier using DGS and adaptive bias technique has been designed and realized for 2.3GHz WiBro applications. The Doherty amplifier has been implemented using silicon MRF 281 LDMOS FET. The RF performances of the Doherty power amplifier (a combination of a class AB carrier amplifier and a bias-tuned class C peaking amplifier) have been compared with those of a class AB amplifier alone, and conventional Doherty amplifier. The Maximum PAE of designed Doherty power amplifier with DGS and adaptive bias technique has been 36.6% at 34.01dBm output power. The proposed Doherty power amplifier showed an improvement 1dB at output power and 7.6% PAE than a class AB amplifier alone.

국내 원전은 방사능방재법에 의거하여 '정보시스템 보안규정'이 수립됨과 함께 조직구성부터 자산의 기술적/운영적/관리적 보안조치에 이르는 사이버보안 체계를 도입하여 운영하고 있다. 단계별 접근법, 물리적방호체계의 대안조치 등이 시도되고 있지만, 관리대상의 감소는 이루어지지 않기 때문에 현장의 한정된 인력으로 운영하기엔 보안 역량의 부담이 가중되고 있다. 본문에서는 원전 안전기능을 수행하는 A1 유형 자산에 대해 정비규정(MR, Maintenance Rule), EPRI 기술적 평가 방법론(TAM, Technical Assessment Methodology)를 활용하여 정비적인 측면과 기기 특성에 대한 측면으로 분석하였다. 이를 통해 사이버침해로 인한 자산기능의 영향을 재분석하는 방안을 제시한다.

Domestic nuclear power plants operate under the establishment of the "Information System Security Regulations" in accordance with the Nuclear Safety Act, introducing and implementing a cybersecurity system that encompasses organizational structure as well as technical, operational, and managerial security measures for assets. Despite attempts such as phased approaches and alternative measures for physical protection systems, the reduction in managed items has not been achieved, leading to an increased burden on security capabilities due to limited manpower at the site. In the main text, an analysis is conducted on Type A1 assets performing nuclear safety functions using Maintenance Rules (MR) and EPRI Technical Assessment Methodology (TAM) from both a maintenance perspective and considering device characteristics. Through this analysis, approaches to re-evaluate the impact of cyber intrusions on asset functionality are proposed.

국내 순환유동층보일러형 발전소에서 발생하는 석탄재의 재활용을 위해 석회석 미분말과 CFBC 비산재를 이용하여 0.2∼0.4 ㎜ 크기를 가지는 석회계 흡수제를 제조하였다. 석회계 흡수제에 소석회를 소량 혼합한 결과 칼슘실리케이트 성분이 입자 표면에 형성되어 강도가 향상되었으며, 탈황특성을 비교한 결과 상업적으로 사용되고 있는 로내탈황용 석회석보다 약 10% 정도 높은 전환율을가진 것으로 나타나 탈황 흡수제로 활용 가능함을 확인하였다.

For the recycling of coal ash from the domestic circulating fluidized bed boilers, a lime-based sorbent with 0.2~0.4 mm size was prepared by using limestone powder and CFBC fly ash. Mixing a small amount of slaked lime in the lime-based absorbent lead the formation of calcium silicate on the surface of the particle and the strength of absorbent particle was improved. As a result of comparing the desulfurization characteristics, it was found that the conversion rate was about 10% higher than that of commercially available limestone desulfurization used in the furnace, which is confirmed that it can be used as a desulfurization absorbent.

Recently, energy saving is a important concern. IT fields, also, are try to reduce the electricity during the IT service, that links to green IT. Especially, green data center is a hot issue, because there are many new projects to build large data center, that spends huge electricity. Even though there are many new projects, the process to build the green data center is not arranged. That depend on the personal experience during the data center construction. Especially, cooling is complex and many problem to reduce the electricity. So, this research provides the method, that is consisted of tasks, activities, and guideline to build the green data center.