• International Journal of Internet, Broadcasting and Communication
• /
• 제11권3호
• /
• pp.27-33
• /
• 2019

Quadrature spatial modulation (QSM) utilizes the in-phase and quadrature spatial dimensions to transmit the real and imaginary parts, respectively, of a single signal symbol. Improved QSM (IQSM) builds upon QSM to increase the spectral efficiency by transmitting the real and imaginary parts of two signal symbols using antenna combinations of size of two. In this paper, we propose a double QSM (DQSM) scheme that transmits the real and imaginary parts of two signal symbols independently through any of the transmit antennas. The two signal symbols are drawn from two different constellations of the same size with the first symbol drawn from any of the conventional modulation sets while the second is drawn from an optimally rotated version of the first constellation. The optimum rotation angle is obtained through extensive Monte Carlo simulations to minimize the bit error rate (BER) of the system. Simulation results show that for a given spectral efficiency, DQSM performsrelatively close to IQSM while requiring a smaller number of transmit antennas, and outperformsIQSM by up to 2 dB when the same number of antennas are used.

• 한국전자파학회논문지
• /
• 제26권9호
• /
• pp.783-789
• /
• 2015

본 논문에서는 long term evolution(LTE) 통신을 위한 2.6 GHz 대역에서 동작하는 고효율 Doherty 전력증폭기를 설계하였다. 2차 및 3차 고조파 임피던스를 조정하기 위한 간단한 구조의 정합 네트워크를 통해 전력증폭기의 고효율 동작을 달성하였다. Doherty 전력증폭기는 다양한 측면에서 장점을 갖는 GaN-HEMT 소자를 이용하여 제작되었으며, 10 MHz의 대역폭 및 6.5 dB 첨두 전력 대 평균 전력비(PAPR)의 특성을 갖는 LTE downlink 신호를 이용하여 측정되었다. 평균 전력 33.4 dBm에서 13.1 dB의 전력 이득, 57.6 %의 전력부가효율(PAE) 및 -25.7 dBc의 인접채널누설비(ACLR) 특성을 갖는다.

• Journal of information and communication convergence engineering
• /
• 제6권1호
• /
• pp.47-50
• /
• 2008

A novel high channel efficiency transceiver based on a fast acquisition frequency synthesizer has been designed. The direct digital synthesis (DDS) technique is applied and a simple memory look-up table is incorporated to expedite channel acquisition. The technique simplifies the frequency control process in the transceiver and thus reduces the channel switching time. As a result, the channel efficiency is improved. The designed transceiver is ideal for frequency hopping mobile communication applications.

• Transactions on Electrical and Electronic Materials
• /
• 제18권2호
• /
• pp.70-73
• /
• 2017

We investigated n-i-p type single junction hydrogenated amorphous silicon oxide solar cells. These cells were without front surface texture or back reflector. Maximum power point efficiency of these cells showed that an optimized device structure is needed to get the best device output. This depends on the thickness and defect density ($N_d$) of the active layer. A typical 10% photovoltaic device conversion efficiency was obtained with a $N_d=8.86{\times}10^{15}cm^{-3}$ defect density and 630 nm active layer thickness. Our investigation suggests a correlation between defect density and active layer thickness to device efficiency. We found that amorphous silicon solar cell efficiency can be improved to well above 10%.

• Journal of the Optical Society of Korea
• /
• 제20권1호
• /
• pp.13-21
• /
• 2016

Since the direct-gradient (DG) method uses the Shack-Hartmann wave front sensor (SH-WFS), based on the phase-conjugation principle, for atmospheric compensation in free-space optical (FSO) communication, it cannot effectively correct high-order aberrations. While the stochastic parallel gradient descent (SPGD) can compensate the distorted wave front, it requires more calculations, which is sometimes undesirable for an FSO system. A hybrid compensation (HC) method is proposed by properly using the DG method and SPGD algorithm to improve the performance of FSO communication. Simulations show that this method can well compensate wave-front aberrations and upgrade the coupling efficiency with few computations, preferable correction results, and rapid convergence rate.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
• /
• pp.222-224
• /
• 2009

This paper proposes analysis data of generation efficiency with tracking method for solar tracking. Tracking algorithm of PV generation is divided the sensor method and program method. Generation efficiency is analyzed the three cases 1-high insolation, 2-low insolation, 3-rapidly changing insolation. Proposed data is possible to apply for development of novel algorithm with hybrid tracking method in this paper. Hereby, This paper is proved the benefit of analyzed data.

• ETRI Journal
• /
• 제41권3호
• /
• pp.326-336
• /
• 2019

A wireless power transfer technique can solve the power capacity problem in wireless rechargeable sensor networks (WRSNs). The charging strategy is a wide-spread research problem. In this paper, we propose a demand-based charging strategy (DBCS) for WRSNs. We improved the charging programming in four ways: clustering method, selecting to-be-charged nodes, charging path, and charging schedule. First, we proposed a multipoint improved K-means (MIKmeans) clustering algorithm to balance the energy consumption, which can group nodes based on location, residual energy, and historical contribution. Second, the dynamic selection algorithm for charging nodes (DSACN) was proposed to select on-demand charging nodes. Third, we designed simulated annealing based on performance and efficiency (SABPE) to optimize the charging path for a mobile charging vehicle (MCV) and reduce the charging time. Last, we proposed the DBCS to enhance the efficiency of the MCV. Simulations reveal that the strategy can achieve better performance in terms of reducing the charging path, thus increasing communication effectiveness and residual energy utility.

• 가족자원경영과 정책
• /
• 제15권1호
• /
• pp.117-136
• /
• 2011

This study examined the effects of the division of household labor on the marital satisfaction of husbands and wives in dual-earner families. Data were collected from 193 couples in dual-earner families; the questionnaire measurements were based on recommendations from the literature review. The questionnaire consisted of inquiries concerning gender role attitudes, marital communication efficiency, division of household labor, satisfaction in the division of household labor, and marital satisfaction. Each of these categories had an individual measurement scale that enabled measurement of its impact on marital satisfaction. The major findings of this study are as follows: The couples in dual-earner families showed egalitarian gender role attitudes and high levels of marital communication efficiency. They also reported high levels of satisfaction with their division of household labor and their marital lives. Wives in dual-earner families had more egalitarian gender role attitudes compared with their husbands, and husbands perceived themselves to be investing more time in performing household chores (that is, in the division of household labor) than was perceived by their wives. Husbands were also more satisfied with the division of household labor and marital life compared to their wives. Finally, hierarchical multiple regression analysis revealed that satisfaction in the division of household labor and in marital communication efficiency (as perceived by the couples) significantly predicted husbands' marital satisfaction. On the other hand, wives' age, marital communication efficiency, and the differences in the division of household labor (as perceived by the couples) significantly predicted wives' marital satisfaction.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
• /
• pp.280-284
• /
• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제6권5호
• /
• pp.1333-1353
• /
• 2012

The robustness of a network is usually measured by error tolerance and attack vulnerability. Significant research effort has been devoted to determining the network design with optimal robustness. However, little attention has been paid to the problem of how to improve the robustness of existing networks. In this paper, we investigate how to optimize attack tolerance and communication efficiency of an existing network under the limited link addition. A survival fitness metric is defined to measure both the attack tolerance and the communication efficiency of the network. We show that network topology reconfiguration optimization with limited link addition (NTRLA) problem is NP-hard. Two approximate solution methods are developed. First, we present a degree-fitness parameter to guide degree-based link addition method. Second, a preferential configuration node-protecting cycle (PCNC) method is developed to do trade-off between network robustness and efficiency. The performance of PCNC method is demonstrated by numerical experiments.