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Search Results: 1 - 10 of 25609 matches for " Ling Hao "
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Improved Current Decomposition in Helical Antennas Using the Esprit Algorithm
Yang Li;Hao Ling
PIER , 2010, DOI: 10.2528/PIER10052811
Abstract: We apply the ESPRIT algorithm to decompose the currents on a helical antenna into different traveling wave modes. The strengths, phase velocities and decay constants of the various modes are extracted across frequencies. Their contributions to the antenna performance including gain, polarization and time-domain radiated pulse shape are investigated. Our results show that the mode is a dominant contributor to the helix gain at the low end of the frequency band while the mode contributes significantly to the gain at higher frequencies. It is also found that the reflected current modes from the open end reduce the circular polarization purity of the helix. Lastly, it is observed that the and modes contribute constructively to a low-dispersion pulse from the antenna.
Numerical Modeling and Mechanism Analysis of VHF Wave Propagation in Forested Environments Using the Equivalent Slab Model
Yang Li;Hao Ling
PIER , 2009, DOI: 10.2528/PIER09012306
Abstract: We study the radio wave propagation at VHF frequencies in a forested environment using a three-layer anisotropic slab model. The analytical solution to the slab model is implemented numerically to generate broadband data. The data are then transformed into the time domain. The various propagation mechanisms including the direct wave, the lateral wave, the multi-reflected slab waves and the multi-bounce lateral waves are investigated based on their respective times-of-flight. Our results show that the dominant propagation mechanisms are highly dependent on the effective permittivity and conductivity of the forest layer. We then utilize the numerical solution to extract the effective medium parameters of the forest based on the published measurement data of Hicks et al. Good agreement between the fitted model and the measurement data is achieved. The extracted effective permittivity and conductivity of the forest layer show considerable anisotropy and frequency dependence.
Direction of Arrival Estimation of Humans with a Small Sensor Array Using an Artificial Neural Network
Youngwook Kim;Hao Ling
PIER B , 2011, DOI: 10.2528/PIERB10100510
Abstract: An array processing algorithm based on artificial neural networks (ANNs) is proposed to estimate the directions of arrival (DOAs) of moving humans using a small sensor array. In the approach, software beamforming is first performed on the received signals from the sensor elements to form a number of overlapping beams. The received signals from all the beams produce a unique "signature" in accordance with the target locations as well as the number of targets. The target tracking procedure is handled by two separate ANNs in sequence. The first ANN determines the number of targets, and the second ANN estimates their respective DOAs. The ANNs are trained using simulation data generated based on a point scatterer model in free space. The proposed approach is tested using measurement data from two loudspeakers and two walking humans in line-of-sight and through-wall environments.
Investigation of the Mechanism of Tangent Bifurcation in Current Mode Controlled Boost Converter  [PDF]
Ling-ling Xie, Ren-xi Gong, Kuang Wang, Hao-ze Zhuo
Circuits and Systems (CS) , 2011, DOI: 10.4236/cs.2011.21007
Abstract: Tangent bifurcation is a special bifurcation in nonlinear dynamic systems. The investigation of the mechanism of the tangent bifurcation in current mode controlled boost converters operating in continuous conduction mode (CCM) is performed. The one-dimensional discrete iterative map of the boost converter is derived. Based on the tangent bifurcation theorem, the conditions of producing the tangent bifurcation in CCM boost converters are deduced mathematically. The mechanism of the tangent bifurcation in CCM boost is exposed from the viewpoint of nonlinear dynamic systems. The tangent bifurcation in the boost converter is verified by numerical simulations such as discrete iterative maps, bifurcation map and Lyapunov exponent. The simulation results are in agreement with the theoretical analysis, thus validating the correctness of the theory.
A q-analogue of Wolstenholme's harmonic series congruence
Ling-Ling Shi,Hao Pan
Mathematics , 2005,
Abstract: We establish a q-analogue of Wolstenholme's harmonic series congruence.
Jing-Hao Hao,Jian-Ling Wang
Acta Crystallographica Section E , 2011, DOI: 10.1107/s160053681104387x
Abstract: In the title compound, [Zn(C8H6N5O4)2(H2O)2], the six-coordinate ZnII ion, which is located on an inversion center, has a distorted octahedral configuration. Each 5-carboxy-2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-imidazole-4-carboxylate ligand chelates to the ZnII ion through a triazole N atom and a carboxylate O atom in the equatorial plane. The coordination sphere is completed by two water molecules in axial positions. There is an intramolecular O—H...O hydrogen bond in the ligand. In the crystal, molecules are linked via intermolecular O—H...O, O—H...N and N—H...N hydrogen bonds, forming a three-dimensional structure.
Tricuspid Valve Reconstruction in a Patient with Ventricular Septal Defect and Subacute Endocarditis  [PDF]
Hong-bin Wang, Min Li, Ming Zhang, Yan-ling Zhu, Hao Wen
Surgical Science (SS) , 2011, DOI: 10.4236/ss.2011.24035
Abstract: Objective Tricuspid valve reconstruction was advocated as the operative method for the treatment of tricus-pid valve endocarditis recently. Many people accept that valve replacement therapy should be performed if more than two valve leaflets are involved. The aim of the study to discuss if reconstructive surgery could be done to treat two valve leaflets involved in tricuspid valve endocarditis. Methods A 17-year-old boy with ventricular septal defect (VSD) and tricuspid valve subacute endocarditis was surgical treated through extra-corporeal circulation. two-thirds of the defective septal cusp, and half of the defective anterior cusp were ex-cised during operation. The tricuspid valve was reconstructed with autologous pericardial strip, cusp com-missuroplasty and 4-0 prolene sutures made as chordae tendineaes. VSD was repaired using a pericardial patch. Results The patient was discharged post-operation with excellent restoration of the tricuspid valve ac-tivity. Cardiac ultrasound revealed normal tricuspid valve activity and low degree of regurgitation two years follow-up. Conclusions It seems that tricuspid valve reconstruction could be performed for two defective leaflets or half of the tricuspid valve.
Doppler Features from Wind Turbine Scattering in the Presence of Ground
Aale Naqvi;Nick Whitelonis;Hao Ling
PIER Letters , 2012, DOI: 10.2528/PIERL12081004
Abstract: We study the Doppler features of electromagnetic scattering from a wind turbine with rotating blades in the presence of ground. Image theory in conjunction with a shooting-and-bouncing ray code, Ahilo, is used to carry out the dynamic signature simulation. The observed features in the simulation are corroborated with laboratory measurements. In addition, the Doppler features from a wind turbine in the presence of a moving ground is simulated and analyzed.
Simulation of Heating Cell in a New Integrated Solar Plate-fin Desalination Unit by Fluent
Shu Xu,Xiang Ling,Hao Peng
Information Technology Journal , 2011,
Abstract: Supply of adequate quantities of fresh potable water is one of the most serious problems confronting human. To resolve this crisis, solar distillation is a typical process where solar energy is used to distil fresh water from saline or brackish water for drinking purposes and other applications. It is generally classified into passive and active distillation systems. This study proposed a new solar plate-fin distillation system that was designed to increase the productivity and improve the efficiency of the solar plate-fin still. The solar still worked by virtue of the higher evaporation rate under vacuum conditions. A mathematical model was developed and used to optimize the design of the heating cell. Also, presented and discussed in a detail description of local and average heat transfer characteristics of the serrated fins. Results indicated different structure of heating cell has a significant effect on the characters of the new solar plate-fin desalination unit.
Electromagnetic Simulation of the Near-Field Distribution around a Wind Farm
Shang-Te Yang,Hao Ling
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/105071
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