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The effect of four elliptical cylinders with different aspect ratios on the natural convection inside a square enclosure

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2018年 122卷 491-503页

作者： Seo, Young Min Ha, Man Yeong Park, Yong Gap Pusan Natl Univ Sch Mech Engn Jang Jeon 2 Dong Busan 609735 South Korea Rolls Royce PLC Jang Jeon 2 Dong Busan 609735 South Korea Pusan Natl Univ Technol Ctr Thermal Management Jang Jeon 2 Dong Busan 609735 South Korea

This study conducted two-dimensional numerical simulations of the natural convection phenomena in a cold square enclosure containing four hot elliptical cylinders with a rectangular array. Rayleigh numbers in the range of 10(4) <= Ra <= 10(6) and a Prandtl number of Pr = 0.7 were considered. The immersed boundary method (IBM) was used to capture the virtual wall boundary of the cylinders based on the finite volume method (FVM). The main parameters investigated include the Rayleigh number and aspect ratio of the cylinders. The aspect ratio of the cylinders was varied in the range of 0.25 <= AR <= 4.00. The flow and thermal structures and corresponding heat transfer characteristics were investigated with respect to the transition of the flow regime from steady state to unsteady state. As a result, ((Nu(CYL)) over bar) increased by about 4.38% and ((Nu(EN)) over bar) increased by about 5.24% at AR = 4.00 with increasing AR compared to AR = 1.00 (Circular cylinder). Thus, the variation in AR has a remarkable influence on the heat transfer characteristics at the cylinder surfaces and the walls of the enclosure. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Natural convection Immersed boundary method Four elliptical cylinders rectangular array Heat transfer performance

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Sweep efficiency estimation for horizontal wells arranged in rectangular arrays

Sweep efficiency estimation for horizontal wells arranged in...

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2015 International Field Exploration and Development Conference (IFEDC 2015)

作者： M. M. Khasanov A. P. Roschektaev A. M. Andrianova O. M. Fuks LLC Gazpromneft Science & Technology Center Saint-Petersburg Russia

In the paper we propose the semianalytic method to estimate the dependence of the sweep efficiency on well spacing for the well pattern of horizontal wells with multiple hydraulic fractures. The method is based on the assumption that the sand body size distribution is the lognormal distribution. Parameters of this distribution are obtained through the analysis of statistical data on sand body sizes for the particular depositional environment of the oil field.

关键词： heterogeneous reservoir horizontal well sand-body distribution function sweep efficiency Horizontal wells SWEEP EFFICIENCY RESERVOIR HETEROGENEITY OIL FIELD rectangular array Statistical Data

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A compact closed-form Nusselt formula for laminar longitudinal flow between rectangular/square arrays of parallel cylinders with unequal row temperatures

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2016年 100卷 248-254页

作者： Sadeghifar, Hamidreza Djilali, Ned Bahrami, Majid Simon Fraser Univ LAEC Sch Mechatron Syst Engn Surrey BC V3T 0A3 Canada Univ Victoria Inst Integrated Energy Syst Victoria BC V8W 3P6 Canada Univ Victoria Energy Syst & Transport Phenomena Lab ESTP Victoria BC V8W 3P6 Canada Univ British Columbia Dept Chem & Biol Engn Vancouver BC V6T 1Z3 Canada Univ Victoria Dept Mech Engn Victoria BC V8W 3P6 Canada

Axial flows over cylinders are frequently encountered in practice, e.g. in tubular heat exchangers and reactors. Using the Integral method, closed-form relationships are developed for heat transfer coefficients or Nusselt number inside a fluid flowing axially between a rectangular/square array of parallel cylinders with unequal temperatures. The model considers the temperature variations of cylinders from one row to another while assuming the same temperature for all the cylinders in each row. The model could well capture several sets of numerical data, which can be regarded as excellent in light of the simplicity and comprehensiveness of the model. The compact and accurate formulae developed in this work can be readily employed, and also implemented into any software or tools, for the estimation of Nu in tubular heat exchangers, fins systems, porous media and composite manufacturing. (C) 2015 Elsevier Masson SAS. All rights reserved.

关键词： Nusselt number Heat transfer coefficient Laminar Parallel cylinders rectangular array Unequal cylinder temperatures

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Simple relaxed conditional likelihood

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BIOMETRIKA 2014年第3期101卷 726-732页

作者： Hanfelt, John J. Wang, Lijia Emory Univ Dept Biostat & Bioinformat Atlanta GA 30322 USA

When the data are sparse but not exceedingly so, we face a trade-off between bias and precision that makes the usual choice between conducting either a fully unconditional inference or a fully conditional inference unduly restrictive. We propose a method to relax the conditional inference that relies upon commonly available computer outputs. In the rectangular array asymptotic setting, the relaxed conditional maximum likelihood estimator has smaller bias than the unconditional estimator and smaller mean square error than the conditional estimator.

关键词： Asymptotic mean square error Nuisance parameter rectangular array Sparse data.

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Simulation and analysis of arrays formed by HF fishbone antenna

Simulation and analysis of arrays formed by HF fishbone ante...

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International Conference on Mechatronics Engineering and Computing Technology (ICMECT)

作者： Zhang, Zhigang Yin, Li Li, Ting Naval Univ Engn Coll Elect Engn Wuhan 430033 Peoples R China PLA Unit 91336 Qinhuangdao 066000 Peoples R China

ISBN: (纸本)9783038351153

This paper analyzes the radiation characteristics of fishbone antenna arrays and concludes its optimum set of array formation. In order to study the feasibility of apply fishbone antenna into pashed array, the common fishbone antenna array is analyzed and simulated by the method of moments. It mainly calculated the radiation properties of two-element array, four-element array and six-element array under the linear array, rectangular array and sector array respectively. Comparing characteristics of different number of array element under the same array type and the different array types under the same number of array element, it suggests that two-element array is the most appropriate array type when sector arrayed, and the array types of 3 x 2, 2 x 2 and 1 x 2 have relatively good effect of beam scanning in low frequency with phase shift.

关键词： Fishbone antenna moment method parallel array sector array rectangular array

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Location of Partial Discharges Sources Using Sensor arrays 4

Location of Partial Discharges Sources Using Sensor Arrays

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International Conference on High Voltage Engineering and Application (ICHVE)

作者： Polak, F. Sikorski, W. Siodla, K. Poznan Univ Tech Inst Elect Power Engn Piotrowo 3A PL-60965 Poznan Poland

ISBN: (纸本)9781479966134

Occurrence of partial discharges (PD) is one of the basic criteria of high voltage devices insulation evaluation. Precise PD source location is crucial for undertaking maintenance of mentioned equipment. This paper concerns the issue of partial discharges sources location using phased rectangular arrays technique and high-resolution direction of arrival estimation technology. In addition to the theoretical assumptions of both techniques, the simulation result, in which an Uniform rectangular array (URA) was used for registration of the electromagnetic signals generated by defects in power transformer insulation system, were shown. To estimate the Direction of Arrival (DOA) of electromagnetic signals, that propagate from the discharge-generating defect to the transducer array installed on transformer tank, Minimum Variance Distortionless Response (MVDR) algorithm was chosen. The location of defect was determined using two intersecting lines defined by the DOAs from two URAs. With the ability to locate multisource discharges (even at very low signal to noise ratio - SNR), the adopted solution has advantages over conventional techniques.

关键词： direction-of-arrival estimation partial discharges power transformer insulation sensor arrays transducers DOA MVDR algorithm URA defect location determination direction of arrival estimation technology discharge generating defect electromagnetic signal registration high voltage device insulation evaluation intersecting lines minimum variance distortionless response multisource discharge location partial discharge source location phased rectangular arrays technique power transformer insulation system transducer array transformer tank uniform rectangular array Direction-of-arrival estimation Insulation Noise Partial discharges Power transformers Sensor arrays Sensor arrays Partial discharges Direction of arrival estimation transformer insulation transformer oil tanks United States Department of Agriculture low SNR ELECTRIC TRANSFORMERS Insulation Transducers rectangular array intersecting line Noise

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Vector Vortex Beam Transmitarrays Composed of Split-ring Slot Elements

Vector Vortex Beam Transmitarrays Composed of Split-ring Slo...

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USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) Proceedings

作者： Guclu, Caner Veysi, Mehdi Capolino, Filippo Univ Calif Irvine Dept Elect Engn & Comp Sci Irvine CA 92695 USA

ISBN: (纸本)9781479978175

A novel birefringent transmitarray capable of local polarization conversion in infrared regime is presented. In particular an incident beam with linear polarization can be transformed into a radially or azimuthally polarized vector beam and in general a wide continuum of polarization states are realizable on the higher order Poincare spheres. The transmitarray is composed of a rectangular array of double-layer double split-ring slot nanoantennas. The double layer element, chosen here, enables high transmission coefficient amplitude, thus increases the efficiency of conversion to the vector vortex beams. The array element exhibits anisotropy with respect to the field polarization on the transmitarray plane, where the transmission coefficients for two orthogonal linear polarizations are almost equal in magnitude and have almost a 180¡ã phase difference. This transmission condition is crucial in the geometric phase control method employed here and it is satisfied in a certain frequency band. The local polarization transformation on the array is controlled through manipulating the angular orientation of the slot elements with respect to element centers. Locally the phase of circularly polarized transmitted waves are advanced or delayed with a phase equal to twice the rotation angle. This phase control method is purely geometrical and it is not frequency dependent. For a certain transmitarray, the generated beam's polarization map is also a function of incident beam polarization. We then study the interesting case of azimuthally E-polarized vortex beams which are a superposition of the Laguerre Gaussian (LG) beams carrying certain orbital angular momentum (OAM) states. Such beams have a strong longitudinally polarized magnetic field on the propagation axis of the beam where the total electric field vanishes. We demonstrate analytically and through numerical field calculations, the evolution of electric and magnetic fields as the beam propagates. These finding are- partic

关键词： Beams and girders Polarization BEAM Control Methods vortices array Element magnetic field angular orientation Elements rectangular array incident beam phase difference

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Parallel contextual array insertion deletion P systems and Siromoney matrix grammars

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INTERNATIONAL JOURNAL OF PARALLEL EMERGENT AND DISTRIBUTED SYSTEMS 2021年第4期36卷 335-358页

作者： Immanuel, S. James Jayasankar, S. Gnanaraj Thomas, D. Paramasivan, Meenakshi Thamburaj, Robinson Nagar, Atulya K. Sri Sairam Inst Technol Dept Math Chennai Tamil Nadu India Ramakrishna Mission Vivekananda Coll Dept Math Chennai 600004 Tamil Nadu India Saveetha Sch Engn Inst Sci & Humanities Dept Appl Math Chennai Tamil Nadu India Univ Trier FB 4 Informat Trier Germany Madras Christian Coll Dept Math Chennai Tamil Nadu India Liverpool Hope Univ Sch Math Comp Sci & Engn Liverpool Merseyside England

James et al. have introduced a variant of P systems called parallel contextual array insertion deletion P system and studied some of its properties. The family of array languages generated by this variant of PCAIDPS includes families of array languages like recognisable picture languages (REC) and context-sensitive matrix languages L(CSMG). In this paper we show that another interesting family L(CF : RIR) of Siromoney matrix languages is included in the family of array languages generated by PCAIDPS with two membranes. [GRAPHICS] .

关键词： P system rectangular array contextual array insertion and deletion Siromoney matrix grammar

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FAST ALGORITHM FOR TWO-DIMENSIONAL DETERMINISTIC NULLING

FAST ALGORITHM FOR TWO-DIMENSIONAL DETERMINISTIC NULLING

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IEEE Radar Conference (RadarConf)

作者： Fernandez, Manuel F. Yu, Kai-Bor Shanghai Jiao Tong Univ Shanghai Key Lab Intelligent Sensing & Recognit Shanghai Peoples R China

ISBN: (纸本)9781728116792

In the past few years, we have developed techniques for inserting multiple discrete and wide continuous nulls for uniform linear array (ULA), and introduced for this purpose the use of quasi- and mixed- matrices and their factorizations. The techniques give an optimal solution, based on least squares criteria and a low-rank approximation to balance the null-depth and pattern distortion. The technique is extended to two-dimensional (2-D) uniform rectangular array (URA) in this paper. A fast algorithm is developed based on some efficient matrix properties of the Kronecker Product (KP). Essentially, we have converted a MN x MN matrix problem to M x M and N x N matrix problems to enable efficient implementation of 2-D deterministic nulling where M x N is the dimension of the URA.

关键词： Antenna array response deterministic nulling quasi-matrix rectangular array Kronecker product

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Decoupled 2D Direction Finding Based on Sparse Signal Reconstruction 33

Decoupled 2D Direction Finding Based on Sparse Signal Recons...

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33rd Annual IEEE Military Communications Conference on Affordable Mission Success - Meeting the Challenge (MILCOM)

作者： Wang, Feng Cui, Xiaowei Lu, Mingquan Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China

ISBN: (纸本)9781479967704

A new two-dimensional direction finding algorithm called 2D-11-SVD is proposed in this paper. It is designed for rectangular arrays and can also be extended to rectangular arrays with faulty or missing elements. The key idea is to represent direction-of-arrival with two decoupled angles and then successively estimate them. Therefore two dimensional direction finding can be realized by applying several times of one dimensional sparse reconstruction based direction finding methods instead of directly extending them to two dimensional situation. Performance analysis and simulation results reveal that the proposed method has a much lower computational complexity and a similar performance compared with the wellknown 11-SVD algorithm, which has several advantages over conventional direction finding techniques due to the application of sparse signal reconstruction.

关键词： Direction-of-arrival estimation sparse signal reconstruction rectangular array faulty array

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