Application of BDRM Theory in the Two-AXIS Underwater Channel

Two-axis underwater channel often exists in deep ocean. Because of the coupling between surface channel and SOFAR channel, sound propagation in the two-axis underwater channel is complex and so its calculations of acoustic fields are difficult. The beam-displacement ray-mode （BDRM） theory is a normal mode method for propagation modeling in the common horizontally stratified shallow water. We improve the theory, proposing a new method for computing the upper boundary reflection coefficient, and apply it to calculate the acoustic fields of two-axis underwater channel. Transmission losses in the two-axis underwater channel are calculated by the BDRM theory. The results are in good agreement with the KRAKEN code and the computational speed excels those of the other methods.

A Novel Roll Compensation Method for Two-Axis Transportable Satellite Antennas

Two-axis transportable satellite antennas(TATSAs) have been widely adopted owing to its simple structure and low cost. However, by searching in a wide range, it will take a very long searching time. Under extreme conditions, it will even fail to work. In this paper, we propose a novel roll compensation(RC) method for the low-cost TATSAs to achieve faster tracking even if when the antenna has no azimuth sensor. By analyzing the influence of roll axis on the system performance, details of the compensation method are derived. Simulation and measurement results indicate that the proposed RC method can effectively reduce the initial searching time for satellite communication. In addition, tracking along with the ellipse path with the RC method provides the highest tracking efficiency.

Sound propagation in two-axis underwater channel based on beam-displacement ray-mode theory

Sound propagation in a deep ocean two-axis underwater channel is often complex and difficult to simulate between surface channel and sound fixing and ranging (SOFAR) channel. The beam-displacement ray-mode (BDRM) theory is a normal mode method for propagation modeling in horizontally stratified shallow water. An improved method for computing the upper boundary reflection coefficient in the BDRM is proposed and applied to calculate the acoustic fields of a two-axis underwater channel. Transmission losses in the two-axis underwater channel are calculated in the new BDRM. The corresponding results are in good agreement with those from the Kraken code, and furthermore the computed speed of the new BDRM excels the other methods.

Tunable two-axis spin model and spin squeezing in two cavities

Multi-mode cavities have now attracted much attention both experimentally and theoretically. In this paper, inspired by recent experiments of cavity-assisted Raman transitions, we realize a two-axis spin Hamiltonian H = q（J_x^2＋ χJ_y^2） ＋ ω_0J_z in two cavities. This realized Hamiltonian has a distinct property that all parameters can be tuned independently. For proper parameters, the well-studied one- and two-axis twisting Hamiltonians are recovered, and the scaling of N^（-1） of the maximal squeezing factor can occur naturally. On the other hand, in the two-axis twisting Hamiltonian, spin squeezing is usually reduced when increasing the atomic resonant frequency ω_0. Surprisingly, we find that by combining with the dimensionless parameter χ（-1）, this atomic resonant frequency ω_0 can enhance spin squeezing greatly. These results are beneficial for achieving the required spin squeezing in experiments.

Research of the Data Processing Method in Two-Axis Servo Drift Testing

The theory and algorithm of Singular Value Decomposition(SVD) is introduced.The advantage of Singular Value Decomposition used in system identification is studied,compared and illustrated through analyzing the data of navigational gyroscopes drift in two-axis servo testing.

Endoscopic Optical Doppler Tomography Based on Two-Axis Scanning MEMS Mirror

We study the feasibility of endoscopic optical Doppler tomography with a micro-electro-mechanical system(MEMS) mirror based probe. The additional phase shifts introduced by the probe are tracked and formulated.The suppression method of the probe phase shifts is proposed and validated by fluid flow detection experiments.In vivo blood flow detection is also implemented on a hairless mouse. The velocities of the blood flow in two directions are obtained to be-8.1 mm/s and 6.6 mm/s, respectively.

Performance Indicators for Sun-Tracking Systems: A Case Study in Spain

Current PV cells technology takes advantage mainly from beam radiation. In this context the sun-trackers are such devices for efficiency improvement. On the other hand, projected shadows between devices make mandatory to increase the distances between mounting systems. Thus, the land’s capacity for mounting PV panels can be dramatically decreased. This fact conducts us to wonder where the optimum efficient point is. First, in this paper different types of sun-tracking systems are classified according to the movement they perform (cinematic classification). Further, three real PV installations-fixed, horizontal-axis tracking and dual-axis mount tracking—located in the same geographical area in Spain (they are approximately under the same weather conditions) are analyzed. These installations have been studied in order to establish which one is the most efficient and affordable—Specific Energy Production (SEP) and Performance Ratio (PR) analysis. PVGIS solar radiation estimate tool has been used for comparing the theoretical radiation potential on each plant. The land requirements have been considered in the analysis of the Ground Cover Ratio (GCR) and the Surface Performance Ratio (SPR). Moreover, comparing three main financial indicators let us carry out a financial study: Payback Time (PBT), Net Present Value (NPV) and Internal Rate of Return (IRR). In the case study, final annual energetic results demonstrate that the dual-axis plant shows a relevant SEP advantage, but if we take into account the land occupied for this sort of devices we find much more profitable the horizontal-axis sun-tracking system, with a SPR value 4.24% higher than the fixed system we have studied. Its PBT is also a 22% lower than the dual-axis tracking installation.

A new two-axis solar tracker based on the online optimization method:Experimental investigation and neural network modeling

This article presents a new two-axis solar tracker based on an online optimization algorithm so as to track the position of the sun without using its movement model.In this research,four well-known optimization algorithms are employed to find the two unknown parameters named azimuth and zenith angles,which determine the position of the sun.The magnitude of the sunray is considered as the cost function of all algorithms.Then,several experiments are carried out to find the best optimization algorithm with optimal population size,number of iterations,and also the best initialization method.Uniform initialization leads to faster convergence compared to random initialization.The results clearly show that the particle swarm optimization algorithm with a population size of 15 and 7 iterations using uniform initialization method has better performance than the other algorithms,with a convergence time of less than 40 s.The average fitness value or voltage received by the tracker is 2.4 Volts in this method,which is higher than other methods.TLBO also performs well with a population size of 15 and 7 iterations.Afterward,the artificial neural network with one hidden layer and 20 neurons is employed to predict these two parameters in each day and moment in a year in Shiraz city according to the experimental data extracted from PSO.Number of the day from January and the time are inputs and zenith and azimuth angles are considered the output of neural network modeling.The performance of the proposed ANN model is evaluated using regression plots,demonstrating a strong correlation between predicted and target outputs.Finally,the outcomes reveal the feasibility of using online optimization algorithms and neural network modeling in an effort to bypass the complex mathematical model of mechatronic systems and predict the movement of the sun automatically.

The WKBZ mode approach to sound propagation in the two-axis underwater channel

The two-axis underwater channel often exists in deep ocean. Sound propagation in the two-axis underwater channel is a benchmark problem for computational methods of underwater acoustics. In this paper, the generalized phase-integral (WKBZ) normal mo de approach is extended to deal with this kind of problem. Numerical results show that the extended WKBZ approach is effective.

Flight trajectory optimization of sun-tracking solar aircraft under the constraint of mission region

The optimal yawing angle of sun-tracking solar aircraft is tightly related to the solar azimuth angle,which results in a large arc flight path to dynamically track the sun position.However,the limited detection range of payload usually requires solar aircraft to loiter over areas of interest for persistent surveillance missions.The large arc sun-tracking flight may cause the target area on the ground to be outside the maximum coverage area of payload.The present study therefore develops an optimal flight control approach for planning the flight path of sun-tracking solar aircraft within a mission region.The proposed method enables sun-tracking solar aircraft to maintain the optimal yawing angle most of the time during daylight flight,except when the aircraft reverses its direction by turning flight.For a circular region with a mission radius of 50km,the optimal flight trajectory and controls of an example K-shaped sun-tracking solar aircraft are investigated theoretically.Results demonstrate the effectiveness of the proposed approach to optimize the flight path of the sun-tracking aircraft under the given circular region while maximizing the battery input power.Furthermore,the effects of varying the mission radius on energy performance are explored numerically.It has been proved that both net energy and energy balance remain nearly constant as the radius constraint varies,which enables the solar aircraft to achieve perpetual flight at almost the same latitude as the large arc flight.The method and results presented in this paper can provide reference for the persistent operation of sun-tracking solar aircraft within specific mission areas.