• Nuclear Engineering and Technology
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• 제26권4호
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• pp.548-554
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• 1994

Si (Li) 검출기의 full-energy peak 효율을 전기증착 선원을 사용하여 실험적으로 결정하였다. 효율 결정에 사용된 측정선원은 $^{51}$ Cr, $^{54}$Mn, $^{57}$ Co, $^{65}$ Zn 핵종으로서 전기증착 방법으로 제작하였으며, 검출기에 collimate를 설치하여 측정하였다. 산출된 효율값은 K X-선에의한 실리콘 결정에서의 탈출확률 및 측정선원과 검출기 사이의 관련 매질에 대한 감쇠효과에 대하여 보정하였으며, 보정된 효율값은 광자 에너지에 무관하게 일정하였다. 결과적으로 5-15 keV 에너지 영역에서 검출효율의 측정 정확도를 향상시킬 수 있었다.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.263-272
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• 2014

Scattering source calculations using conventional spherical harmonic expansion may require lots of computation time to treat full-coupled three-dimensional photon-electron transport in a highly anisotropic scattering medium where their scattering cross sections should be expanded with very high order (e.g., $P_7$ or higher) Legendre expansions. In this paper, we introduce a modified scattering kernel approach to avoid the unnecessarily repeated calculations involved with the scattering source calculation, and used it with parallel computing to effectively reduce the computation time. Its computational efficiency was tested for three-dimensional full-coupled photon-electron transport problems using our computer program which solves the multi-group discrete ordinates transport equation by using the discontinuous finite element method with unstructured tetrahedral meshes for complicated geometrical problems. The numerical tests show that we can improve speed up to 17~42 times for the elapsed time per iteration using the modified scattering kernel, not only in the single CPU calculation but also in the parallel computing with several CPUs.

• ETRI Journal
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• 제43권3호
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• pp.436-446
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• 2021

In this paper, we propose an energy-efficient unmanned aerial vehicle (UAV) relaying network. In this network, the channels between UAVs and ground transceivers are model-free. A UAV acting as a flying relay explores better channels to assist in efficient data delivery between two ground nodes. The full-duplex relaying mode is applied for potential energy efficiency (EE) improvements. With the genetic algorithm, we manage to optimize the UAV trajectory for any arbitrary radio map scenario. Numerical results demonstrate that compared to other schemes (eg, fixed trajectory/speed policies), the proposed algorithm performs better in terms of EE. Additionally, the impact of self-interference on average EE is also investigated.

• 대한전자공학회논문지TC
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• 제48권2호
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• pp.90-94
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• 2011

본 논문에서는 고주파 대역 중에서 에너지 전송과 관련되어 정류 회로의 구조와 특성을 분석하고, 최대의 효율을 이끌어 낼 수 있는 방안을 찾고자 한다. 13.56MHz에서의 입력 신호를 DC 변환하여 실험 및 측정을 하였다. 정류회로는 반파 정류회로, 전파정류회로 브릿지 정류회로로 나눌 수 있고, 최대 효율을 갖기 위해서 다양한 정류 회로를 전산 모의 실험하였다. 현재까지의 연구 내용은 passive 소자를 이용한 효율 개선에 중점을 두고 실험을 하였다. 정류 효율에 영향을 미치는 요소는 소자의 특성에 좌우하며, 이번 실험에서는 약 70%의 효율을 측정할 수 있었으며, 보다 개선된 소자를 사용함으로서 낮은 입력에서 높은 효율을 얻을 수 있었다.

• Journal of Power Electronics
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• 제9권5호
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• pp.809-821
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• 2009

This paper proposes a new phase-shift full-bridge DC-DC converter by applying energy recovery circuits to a conventional full-bridge DC-DC converter in plasma display panel applications. The converter can achieve soft-switching in main-switches by an extra auxiliary resonant network even with the wide operating condition of both output load and input voltage. The un-coupled design guidelines to the main bridge-leg component parameters for soft-switching operation contribute to conduction loss reduction in the transformer primary side leading to efficiency improvement. The auxiliary switches in the resonant network also operate in zero-current switching. This paper analyzes the operation modes of the proposed scheme and presents the key design guidelines through steady state analysis. Also, the paper verifies the validity of the circuits by hardware experiments with a 1kW DC/DC converter prototype.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권10호
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• pp.2732-2749
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• 2023

Device-to-Device (D2D) communication has received increasing attention and been studied extensively thanks to its advantages in improving spectral efficiency and energy efficiency of cellular networks. This paper proposes a novel relay selection algorithm for multi-hop full-duplex D2D communications underlaying cellular networks. By selecting the relay of each hop in a reverse manner, the proposed algorithm reduces the heavy signaling overhead that traditional relay selection algorithms introduce. In addition, the social domain information of mobile terminals is taken into consideration and its influence on the performance of D2D communications studied, which is found significant enough not to be overlooked. Moreover, simulations show that the proposed algorithm, in absence of social relationship information, improves data throughput by around 70% and 7% and energy efficiency by 64% and 6%, compared with two benchmark algorithms, when D2D distance is 260 meters. In a more practical implementation considering social relationship information, although the proposed algorithm naturally achieves less throughput, it substantially increases the energy efficiency than the benchmarks.

• International Journal of Naval Architecture and Ocean Engineering
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• 제1권1호
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• pp.29-38
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• 2009

A ship's screw-propeller produces thrust by rotation and, at the same time, generates rotational flow behind the propeller. This rotational flow has no contribution to the generation of thrust, but instead produces energy loss. By recovering part of the lost energy in the rotational flow, therefore, it is possible to improve the propulsion efficiency. The contra-rotating propeller (CRP) system is the representing example of such devices. Unfortunately, however, neither a design method nor a full-scale performance prediction procedure for the CRP system has been well established yet. The authors have long performed studies on the CRP system, and some of the results from the authors' studies shall be presented and discussed.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.425-428
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• 2017

본 논문에서는 진동 에너지를 이용하여 에너지를 수확하는 전파 정류 하베스팅 회로를 설계하였다. 설계된 회로는 저전압에서도 전력효율이 우수하도록 Beta-Multiplier를 이용하여 Body-Bias technique을 Negative Voltage Converter에 적용하였으며, Comparator를 Bulk-Driven type으로 설계하였다. 제안된 회로는 $0.35{\mu}m$ CMOS 공정으로 설계하였으며, 설계된 회로의 칩 면적은 $931{\mu}m{\times}785{\mu}m$이다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.53-56
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• 2002

Samsung's newly developed high luminance efficiency 42" VGA plasma display panel is introduced. A new discharge cell structure, SDR (Segmented electrode in Delta color arrayed Rectangular subpixel) has been applied to a full size panel for the first time. In this paper, we describe how this new discharge cell structure for high efficiency is integrated to an energy saving plasma display with better picture quality.

• Journal of Power Electronics
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• 제19권6호
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• pp.1337-1350
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• 2019

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.