System Figure Of Merit Research Articles

Pre-conceptual high temperature gas-cooled microreactor design utilizing two-phase composite moderators. Part I: Microreactor design and reactor performance

In this work, an approach is demonstrated for designing a microreactor based on a High Temperature Gas-Cooled Reactor (HTGR) platform intended for use in remote regions or for emergency response. The pre-conceptual microreactor design generated in this study is based on the Idaho National Laboratory's High Temperature Gas-Cooled Test Reactor (HTGTR) point design. Major design changes to the HTGTR were made to transform the design to a microreactor based on constraints inspired by open literature information from the Office of Secretary of Defense (OSD)/Strategic Capabilities Office (SCO) Pele Program. The primary purpose of this study is to compare reactor performance by evaluating key figures of merit for systems employing two-phase composite moderators (magnesia matrix with either an entrained beryllium or hydride containing moderating phase) relative to a reference graphite moderated case. Design parameters were selected to maximize reactor cycle performance for a given microreactor design with additional performance metrics such as natural resource requirement and fuel cycle costs also calculated. Our results demonstrate that a microreactor design based on the HTGR can be achieved by implementing a high fuel density. By using two-phase composite beryllium- or hydride-based moderators instead of graphite, substantial improvements can be realized in the reactor cycle performance, natural resource utilization, and fuel cycle cost.

Systematic Optimization of Multiple-Output DC Distribution Architectures

Complex electronic systems often require a power distribution architecture that provides multiple, separate voltage domains for various subsystem loads, such as microprocessor cores, interface, memory, analog, and radio frequency components. The multiple point-of-load regulated voltages are typically generated using multiple dc–dc converters operating from a single input dc voltage. This article introduces the permutation-graph (PG) method to systematically optimize multiple-voltage-domain dc distribution architectures using commercially available or custom single-input single-output dc–dc converter building blocks. The PG method enumerates possible converter arrangements and selects the converter blocks to achieve the best system figure of merit (FOM) in terms of system efficiency, size, cost, power density, or a combination of these metrics. In representative case study examples, considering a system operating from 48-V input dc voltage and requiring seven regulated point-of-load dc voltages {1, 1.3, 3.3, 5, 12, 24, and 40} V, it is shown how the proposed approach can improve the system FOM by more than 50% compared with solutions offered by a commercially available tool using standard dc–dc blocks. It is also shown how the inclusion of custom dc–dc blocks results in a different optimal arrangement, which yields further system FOM improvements. The approach is validated by experimental results on two 120-W system prototypes, providing five regulated dc voltages {1, 3.3, 5, 12, and 24} V from a 48-V dc bus.

Wideband Microwave Frequency Distribution for Multi-Access Along a Single Fiber Link

In this paper, a fiber-optic signal access method is proposed for stable wideband microwave frequency distribution. Incorporating with the tapped counter-propagating reference signals and variable optical delay lines (VODLs), a stable wideband microwave frequency signal can be obtained at any access point (AP) along the main fiber link. Moreover, all the phases of received wideband microwave frequency can be aligned. In this way, the whole system complexity can be dispersed as the central station only stabilizes the main fiber link delay, and the access ends (ANs) operate independently. Experimentally, a multi-access wideband microwave frequency distribution is demonstrated over a 50 km dispersion-compensated fiber link. A system figure of merit is investigated in detail. The results show that the fiber-optic wideband microwave frequency transmission system can operate for the frequency over 40 GHz. The additive phase noises of -125 dBc/Hz for the remote end (RN), and -131 dBc/Hz for the AN, respectively, are achieved at the 1 kHz offset frequency for a 1 GHz frequency signal. Thanks to the active delay stabilization, the Allan deviation (ADEV) of 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> /s and 2.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> /100 s for the RN, and the one of 8.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup> /s and 4.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> /100 s for the AN, respectively, are acquired.

Active Delay Stabilization of a 440-km Fiber Link in a Wideband Microwave Delay System

In this paper, a wideband microwave delay system with an equivalent 440-km fiber link is presented. The fiber link propagation delay fluctuation, suffering from temperature variation, is detected incorporating with a reference RF signal. With the help of a variable optical delay line, the wideband microwave frequency output is phase-stabilized. A system figure of merit is investigated in detail. The results show that, with dispersion compensation, the fiber-optic delay system can operate for the frequencies up to 38 GHz. Moreover, the fiber-optic system can provide a noise figure of below 40 dB, a signal-to-noise ratio of above 51 dB and a spur level of less than -56 dB for the delayed wideband microwave frequency signal. An additive phase noise of -116 dBc/Hz at the 10 kHz offset frequency can be guaranteed for a 1 GHz frequency. With active delay stabilization, the 38 GHz frequency delayed achieves an Allan deviation of 5.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> /s and 5.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> /10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s, respectively.

수신 코일 권선 수 변화에 의한 무선전력전송 최적 부하 구현

본 논문에서는 최대 무선전력전송 효율 구현에 필요한 최적 부하저항을 수신기 입력 임피던스(통상 <TEX>$50{\Omega}$</TEX>)에 바로 정합하기 위하여 수신 코일의 권선 수를 제어하는 방법을 제안한다. 수신 코일 권선 수와 도선 사이의 근접 효과가 고려된 최적 부하저항의 수식에 따라 수신 코일을 설계, 제작 및 측정하였다. 이론과 EM 시뮬레이션, 측정을 통하여 최적 부하 저항과 효율을 비교한 결과 비교적 잘 일치함을 확인할 수 있었다. 본 논문의 결과를 활용하면 별도의 급전 루프 없는 단순하고 부피가 작은 2-coil 시스템으로도 허용된 최대 전력을 구현할 수 있다. In this paper, we propose the method of controling the turns of a receiving coil for the matching directly to the receiver input impedance(typically <TEX>$50{\Omega}$</TEX>) with a maximum wireless power transfer(WPT) efficiency. Based on the presented the expression of the optimum load depending on a system figure of merit, number of the turns of a receiving coil, and proximity effect between conducting lines, the theoretical efficiencies have been compared with the measured ones with a good agreement. The results of this work may be used to realize a allowable maximum efficiency with a simple and low-profile 2-coil WPT system not requiring a separate feeding loop.

Access Point Density and Bandwidth Partitioning in Ultra Dense Wireless Networks

This paper examines the impact of system parameters such as access point density and bandwidth partitioning on the performance of randomly deployed, interference-limited, dense wireless networks. While much progress has been achieved in analyzing randomly deployed networks via tools from stochastic geometry, most existing works either assume a very large user density compared to that of access points, which does not hold in a dense network, and/or consider only the user signal-to-interference-ratio as the system figure of merit, which provides only partial insight on user rate as the effect of multiple access is ignored. In this paper, the user rate distribution is obtained analytically, taking into account the effects of multiple access as well as the SIR outage. It is shown that user rate outage probability is dependent on the number of bandwidth partitions (subchannels) and the way they are utilized by the multiple access scheme. The optimal number of partitions is lower bounded for the case of large access point density. In addition, an upper bound of the minimum access point density required to provide an asymptotically small rate outage probability is provided in closed form.

Multiobjective Optimization in Multifunction Multicapability System Development Planning

Properly allocating resources to achieve system development objectives has remained a challenge in systems engineering management. Various optimization models have been developed to optimize respective figures of merit (FOMs) subject to development constraints. System readiness level (SRL) is a system FOM that was originally introduced to assess the maturity of a system during its development lifecycle and has evolved to cover the development of multifunction multicapability (MFMC) systems. Optimization models which include SRL as either the objective or a constraint have been proposed for system development planning. Building on the definition of the recently enhanced MFMC SRL, this paper proposes a multiobjective optimization model, called MO_SRL, to simultaneously optimize the following: 1) the maturity of the system's selected functions or capabilities and 2) the consumption of development resources. An evolutionary algorithm is used to obtain a Pareto set of optimal solutions, where each solution represents a development plan informing which system components should be advanced to which maturity levels without exceeding a certain amount of resource consumption. With the consideration of SRL correlation to typical system development lifecycle, this model can identify several development alternatives for improving the system maturity to more advanced phases with minimum resource consumption, and these multiple alternatives provide systems engineering managers with flexibility in planning system development.

System Optimization Methodology for Integrated Piezoelectric MEMS Resonator Biochemical Sensors

Abstract While microelectro-mechanical (MEMS) resonators are increasingly being considered in biochemical sensing applications, the complexity of the system results in a need for a system level optimization in which the readout circuit and the MEMS components should carefully be co-optimized. Here, we present systematic optimization approach that highlights the trade-offs between the MEMS resonator and the accompanying oscillator-based integrated readout circuit. A system figure of merit is formulated to account for resonator modal frequency, equivalent electrical characteristics, sensitivity, readout circuit bandwidth, frequency resolution and power consumption. While the methodology can be adapted to study of various MEMS-based resonators coupled to oscillator-based readouts, for clarity, we analyze here the specific case of polymer-coated piezoelectric microbridge resonators sensitive to volatile organic compounds.

TU-C-I-609-07: Optimization of a Real Time Dual-Energy Subtraction Technique Based On a Flat Panel Detector

Purpose: To determine the optimal x-ray spectra for dual-energy subtraction with a flat panel detector (FPD), and to quantify the effects of dynamic filtration and FPD gain settings on image quality, tube loading, patient exposure, and overall system performance. Method and Materials: A simulation study was performed using available empirically determined data of x-ray spectra. The lungs and mediastinum of the chest were modeled with 12.5 cm and 20 cm thick regions of Lucite, respectively. Coronary calcification was modeled with a 1 mm thickness of bone-equivalent plastic. The FPD was modeled as an ideal detector with a 600 micron thick layer of CsI. Scatter was not considered in this study. Low and high energy images were normalized to a desired energy deposit in the detector dependent on FPD gain. A figure-of-merit (FOM) was used t6o quantify the overall system performance. The effects of various silver filter thicknesses (0–1000 microns), high to low energy image signal ratios (1–8), and two dual-energy noise reduction algorithms were evaluated for their effect on image quality, patient entrance exposure, tube loading, and FOM improvement. Results: As the thickness of the high-energy filter increased, image contrast, contrast-to-noise ratio, FOM and tube loading increased. Patient exposure was reduced by approximately 10% for the range of filter thicknesses studied. The FOM was maximized with a FPD signal ratio of approximately 3 without application of dual-energy noise reduction. However, dual gain operation did not show any improvement after noise reduction. Conclusion: An optimal dynamic filter combined with dual-energy noise reduction can improve the system FOM by a factor of 5. There is no further improvement in the system FOM when dual detector gain is used in conjunction with dual-energy noise reduction.