285,252 research outputs found
Optimized Superconducting Nanowire Single Photon Detectors to Maximize Absorptance
Dispersion characteristics of four types of superconducting nanowire single
photon detectors, nano-cavity-array- (NCA-), nano-cavity-deflector-array-
(NCDA-), nano-cavity-double-deflector-array- (NCDDA-) and
nano-cavity-trench-array- (NCTA-) integrated (I-A-SNSPDs) devices was optimized
in three periodicity intervals commensurate with half-, three-quarter- and one
SPP wavelength. The optimal configurations capable of maximizing NbN
absorptance correspond to periodicity dependent tilting in S-orientation
(90{\deg} azimuthal orientation). In NCAI-A-SNSPDs absorptance maxima are
reached at the plasmonic Brewster angle (PBA) due to light tunneling. The
absorptance maximum is attained in a wide plasmonic-pass-band in
NCDAI_1/2*lambda-A, inside a flat-plasmonic-pass-band in NCDAI_3/4*lambda-A and
inside a narrow plasmonic-band in NCDAI_lambda-A. In NCDDAI_1/2*lambda-A bands
of strongly-coupled cavity and plasmonic modes cross, in NCDDAI_3/4*lambda-A an
inverted-plasmonic-band-gap develops, while in NCDDAI_lambda-A a narrow
plasmonic-pass-band appears inside an inverted-minigap. The absorptance maximum
is achieved in NCTAI_1/2*lambda-A inside a plasmonic-pass-band, in
NCTAI_3/4*lambda-A at inverted-plasmonic-band-gap center, while in
NCTAI_lambda-A inside an inverted-minigap. The highest 95.05% absorptance is
attained at perpendicular incidence onto NCTAI_lambda-A. Quarter-wavelength
type cavity modes contribute to the near-field enhancement around NbN segments
except in NCDAI_lambda-A and NCDDAI_3/4*lambda-A. The polarization contrast is
moderate in NCAI-A-SNSPDs (~10^2), NCDAI- and NCDDAI-A-SNSPDs make possible to
attain considerably large polarization contrast (~10^2-10^3 and ~10^3-10^4),
while NCTAI-A-SNSPDs exhibit a weak polarization selectivity (~10-10^2).Comment: 26 pages, 8 figure
Improving the multi-objective evolutionary optimization algorithm for hydropower reservoir operations in the California Oroville-Thermalito complex
This study demonstrates the application of an improved Evolutionary optimization Algorithm (EA), titled Multi-Objective Complex Evolution Global Optimization Method with Principal Component Analysis and Crowding Distance Operator (MOSPD), for the hydropower reservoir operation of the Oroville-Thermalito Complex (OTC) - a crucial head-water resource for the California State Water Project (SWP). In the OTC's water-hydropower joint management study, the nonlinearity of hydropower generation and the reservoir's water elevation-storage relationship are explicitly formulated by polynomial function in order to closely match realistic situations and reduce linearization approximation errors. Comparison among different curve-fitting methods is conducted to understand the impact of the simplification of reservoir topography. In the optimization algorithm development, techniques of crowding distance and principal component analysis are implemented to improve the diversity and convergence of the optimal solutions towards and along the Pareto optimal set in the objective space. A comparative evaluation among the new algorithm MOSPD, the original Multi-Objective Complex Evolution Global Optimization Method (MOCOM), the Multi-Objective Differential Evolution method (MODE), the Multi-Objective Genetic Algorithm (MOGA), the Multi-Objective Simulated Annealing approach (MOSA), and the Multi-Objective Particle Swarm Optimization scheme (MOPSO) is conducted using the benchmark functions. The results show that best the MOSPD algorithm demonstrated the best and most consistent performance when compared with other algorithms on the test problems. The newly developed algorithm (MOSPD) is further applied to the OTC reservoir releasing problem during the snow melting season in 1998 (wet year), 2000 (normal year) and 2001 (dry year), in which the more spreading and converged non-dominated solutions of MOSPD provide decision makers with better operational alternatives for effectively and efficiently managing the OTC reservoirs in response to the different climates, especially drought, which has become more and more severe and frequent in California
State-of-the-art in aerodynamic shape optimisation methods
Aerodynamic optimisation has become an indispensable component for any aerodynamic design over the past 60 years, with applications to aircraft, cars, trains, bridges, wind turbines, internal pipe flows, and cavities, among others, and is thus relevant in many facets of technology. With advancements in computational power, automated design optimisation procedures have become more competent, however, there is an ambiguity and bias throughout the literature with regards to relative performance of optimisation architectures and employed algorithms. This paper provides a well-balanced critical review of the dominant optimisation approaches that have been integrated with aerodynamic theory for the purpose of shape optimisation. A total of 229 papers, published in more than 120 journals and conference proceedings, have been classified into 6 different optimisation algorithm approaches. The material cited includes some of the most well-established authors and publications in the field of aerodynamic optimisation. This paper aims to eliminate bias toward certain algorithms by analysing the limitations, drawbacks, and the benefits of the most utilised optimisation approaches. This review provides comprehensive but straightforward insight for non-specialists and reference detailing the current state for specialist practitioners
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