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Author

H. Zhang

Bio: H. Zhang is an academic researcher from Northwestern Polytechnical University. The author has contributed to research in topics: Airfoil & Attenuation coefficient. The author has an hindex of 2, co-authored 3 publications receiving 9 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the effects of numerical dissipation of spatial schemes, the third-order MUSCL and the fifth-order interpolation based on modified Roe scheme were implemented to simulate the flow past a three-element airfoil.
Abstract: Accurate prediction of the flow around multi-element airfoil is a prerequisite for improving aerodynamic performance, but its complex flow features impose high demands on turbulence modeling. In this work, delayed detached-eddy-simulation (DDES) and zonal detached-eddy-simulation (ZDES) was applied to simulate the flow past a three-element airfoil. To investigate the effects of numerical dissipation of spatial schemes, the third-order MUSCL and the fifth-order interpolation based on modified Roe scheme were implemented. From the comparisons between the calculations and the available experimental result, third-order MUSCL-Roe can provide satisfactory mean velocity profiles, but the excessive dissipation suppresses the velocity fluctuations level and eliminates the small-scale structures; DDES cannot reproduce the separation near the trailing edge of the flap which lead to the discrepancy in mean pressure coefficients, while ZDES result has better tally with the experiment.

7 citations

Journal ArticleDOI
TL;DR: Based on the forward scattering amplitude function for charged sand particles under the Rayleigh approximation and the effective permittivity method, a calculation model for microwave attenuation due to sand particles is given in terms of equal sized distribution and lognormal size distribution, and the attenuation is calculated and analyzed as mentioned in this paper.
Abstract: Based on the forward scattering amplitude function for charged sand particles under the Rayleigh approximation and the effective permittivity method, a calculation model for microwave attenuation due to charged sand particles is given in terms of equal sized distribution and lognormal size distribution, and the attenuation is calculated and analyzed. The results show that the attenuation with charged sand is greater than the case of no charge, and the more concentrative the surface charges on sand particles are, the greater are the influences on microwave attenuation. When the frequency is not too high, natural sand and vehicular sand have little effect on microwave attenuation, whereas the attenuation of explosive sand need be considered.

4 citations

Patent
10 May 2017
TL;DR: In this article, a fixed-wing UAV is used for large-stall vertical landing, where the wings are arranged on the vehicle body in a tool-free fast disassembly and assembly mode.
Abstract: A fixed wing unmanned aerial vehicle comprises a vehicle body, an electric propulsion mechanism arranged on the head of the vehicle body, wings arranged on the two sides of the vehicle body, and a horizontal tail arranged at the tail of the vehicle body. The wings are arranged on the vehicle body in a tool-free fast disassembly and assembly mode. During large-stall vertical landing, the wings can be taken off forwards along a chute of the vehicle body, energy of landing of the whole unmanned aerial vehicle is absorbed, so that according to stall decomposition technology of the fixed wing unmanned aerial vehicle provided by the invention, the influence of wind is small, and the landing precision is high.

1 citations

Proceedings ArticleDOI
28 Aug 2022
TL;DR: This paper presents the design of a leaky enhanced array architecture that surpasses the state of the art as it operates efficiently for frequencies up to 1THz, without excessive complications in the manufacturing.
Abstract: Photoconductive antennas are devices that provide power up to THz frequencies at a relatively low cost. However, the power radiated by each antenna is typically quite low and arrays have been proposed to increase it. In this paper we present the design of a leaky enhanced array architecture that surpasses the state of the art as it operates efficiently for frequencies up to 1THz, without excessive complications in the manufacturing. This architecture is compared with a ‘standard’ array, showing a broader bandwidth and a higher emitted detected signal.
Proceedings ArticleDOI
28 Aug 2022
TL;DR: In this paper , the authors designed and prepared the terahertz wave shielding and absorption materials based on organic aerogel, which has special advantage of low density and high electromagnetic wave reflection ability.
Abstract: With the development of terahertz technology, there is a booming demand of THz waves shielding and absorption materials to avoid electromagnetic interference or pollution. The electromagnetic interference shielding effectiveness not only depends on their composition, but also is influenced by their microstructures. Porous structure has special advantage of low density and high electromagnetic wave reflection’s ability. We design and prepare the THz wave shielding and absorption materials based on organic aerogel.

Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors present a survey of current understanding of the wave propagation during storms and present a detailed parametric assessment of some electrical and mechanical properties affecting wave propagation in sand and dust storms.
Abstract: Electromagnetic wave propagation in arid and semi-arid regions is influenced by sand and dust storms. Meagre information has hitherto been reported as to the effect of storms on telecommunication systems operating in such regions. This paper presents a survey of current understanding of the wave propagation during storms. In this first part of the review—Part I, detailed parametric assessment of some electrical and mechanical properties affecting wave propagation in sand and dust storms is given. The second part of the review—Part II describes the principle of approach and technology adopted for the investigation highlighting both strengths and drawbacks. The results demonstrate that most authors have calculated signal attenuation effect, revealing that it is not very significant unless during severe storms. A few papers indicate the possibility of more significant cross polarisation. Part I explicitly gives an account of the sand and dust storms' phenomenon, reviews the storms' parameters affecting electromagnetic wave propagations and discusses the microwave and millimeter wave bands.

29 citations

Journal ArticleDOI
TL;DR: In this paper, a realistic model is developed to predict the specific attenuation when electromagnetic signals propagate through dusty media (dust storms), based on Mie approximation for the scattering of electromagnetic signal by a spherical particle.
Abstract: A realistic model is developed to predict the specific attenuation when electromagnetic signals propagate through dusty media (dust storms). The model is based on Mie approximation for the scattering of electromagnetic signal by a spherical particle. Variation of the dust particles dimensions is considered in this model. Reliable published values for dust dielectric constant are used for computations over the frequency range from 2 GHz to 100 GHz, (i.e., S-band, X band, K-band, Ka-band, Ku-band and W-band). The model outcome is compared with the results from other models suggested in literature. The effect of air humidity on specific attenuation is also investigated.

28 citations

Journal ArticleDOI
TL;DR: The design results show that the robust design is capable of producing a set of robust solutions that are significantly less sensitive to input variations by capturing the Pareto-optimal front with respect to the criteria of aerodynamic performance and its stability.
Abstract: The fruit fly optimization algorithm (FOA) is a newly developed bio-inspired algorithm that has exhibited enormous values in engineering optimization. In this study, an effective multi-objective fruit fly optimization algorithm (MOFOA) incorporated with the Pareto dominance is investigated and applied to robust aerodynamic shape optimization considering uncertainties in the design process. In the MOFOA, the fruit flies are required to perform solution explorations within an adaptive search scope by flying around the Pareto non-dominated solutions. An enhanced clustering evolution mechanism of combining the cooperative local search and differential evolution operator is elaborately designed to enrich the exploratory capacities for complex optimization. Paired with the search strategy, the non-dominated sorting technique considering the quality as well as uniform distribution of Pareto solutions is adopted to deal with the multiple objectives. To generate high-quality and uniformly spread-out Pareto non-dominated solutions, the roulette wheel selection (RWS) operator based on crowding distance is employed to guide the selection processes of individuals throughout various stages of the MOFOA. The effectiveness and superiority of MOFOA are demonstrated by the comparative studies on several benchmark functions. Finally, a robust aerodynamic design system for combining the MOFOA optimizer with a Kriging-based surrogate model and full Navier–Stokes computation is advantageously implemented to perform shape optimization on a transonic airfoil using the Taguchi robust design methodology that emphasizes the inherent variability while improving engineering productivity. The design results show that the robust design, compared with the single-point design, is capable of producing a set of robust solutions that are significantly less sensitive to input variations by capturing the Pareto-optimal front with respect to the criteria of aerodynamic performance and its stability.

6 citations

Journal ArticleDOI
TL;DR: In this article, the expanding process of turbulent separation bubble induced by a horn ice on the leading edge of an airfoil for business jet was investigated numerically with IDDES.

6 citations

Proceedings ArticleDOI
01 Sep 2015
TL;DR: In this article, the authors deal with modelling and calculations of canting angle as input to the cross polarization discrimination by considering the forces influencing orientation of the falling particle and use of turbulence shear and inertial torque.
Abstract: In recent time, considerable interest has been shown to electromagnetic wave propagation in arid regions and the influence of sand and dust storms with emphasis on signal attenuation and cross polarization in dual polarized systems for frequency spectrum conservation. The realization of a dual-polarized system is, however, usually limited by degree of cross polar discrimination that can be achieved between the two orthogonal channels. Aside from non-sphericity of falling dust particles, cross polarization has been attributed to tendency of the falling particles to align in a particular direction (canting angle). While dust particle shape is yet to be well tackled, the existing works on cross polarization have only succeeded in guessing the canting angle. To this end, this work explicitly deals with modelling and calculations of canting angle as input to the cross polarization discrimination by considering the forces influencing orientation of the falling particle and use of turbulence shear and inertial torque. Results of the proposed model compared with some published results show close agreement.

5 citations