Optimal Design of Aperiodic Reconfigurable Antenna Array Suitable for Broadcasting Applications

An aperiodic reconfigurable microstrip antenna array is designed to serve as a DVB-T base station antenna operating in a single broadcasting channel. The antenna array is optimized at 698 MHz (center frequency of DVB-T channel 49) to concurrently achieve a particular radiation pattern shaping with high forward gain, main lobe tilting and null filling inside the service area, as well as low sidelobe level outside the service area, and low standing wave ratio at the inputs of all the array elements. To concurrently satisfy all the above requirements, both the geometry dimensions and the array feeding weights (amplitudes and phases) are optimized, thus leading to a complex multi-variable and multi-objective problem. The problem is solved by applying a recently developed particle swarm optimization (PSO) improved variant, called PSO with velocity mutation, in conjunction with the CST software package, which is employed by the PSOvm every time a full-wave analysis is required. Furthermore, all the optimization methods found in the CST environment are compared with the PSOvm. The results show that the PSOvm is capable of producing an antenna array geometry, which is closer to the predefined requirements than the geometries derived by the rest of the optimizers, in the least amount of computational time.

Numerical Simulation of the Influence of Gear Rotation Speed on the Gear Pump Flow Field

Gear pump has simple structure, long service life, strong self-priming capacity, high working reliability and other characteristics, which is widely used in various kinds of mechanical equipment. In order to study the influence of gear rotational speed on the internal fluid flow field change rule, the computational fluid dynamics software Fluent was used to simulate the gear pump flow field, while dynamic grid technique was carried on the numerical simulation of the gear pump under different rotation speed, and flow field characteristics were analysed. The results showed that with the increase of gear rotation speed, the area of pump fluid velocity mutation decreased, the area of pressure mutation reduced, and the larger volume of fluid closed to balance.

Experimental Study of Elastohydrodynamic Lubrication under Heavy Loaded and Variable Velocity Conditions

In order to reveal the elastohydrodynamic lubrication characteristics under heavy loaded and variable velocity conditions, We carried out the relevant experiments by the self-developed optical interference EHL experimental device. Improved apparatus substitute screw for the slider-crank, and driven by stepper motor. Velocity mutation experiment carried out to discuss features of the oil film while the stepper motor speed instantly changes from the velocity of 0.23mm/s, 0.38mm/s and 0.52mm/s. It shows that extrusion effect and oil film sag emerge in acceleration instantaneous similar to zero entrainment speed even it is not, and end of oil film has a necking phenomenon distinctly.

Design and Analysis of Timing Screw Based on B-Spline Curve

In order to reduce the vibration of the high speed timing screw and optimize the manufacturing process of classic three-section high speed timing screw. Mathematical model of three-section high speed timing screw is rebuilt based on B-spline curve and a general mathematical model for the screw. Thus result a new one-section form instead of old three-section type. Then the displacement and speed is simulated in MATLAB. After that,modal analysis and harmonic response analysis have been done in ANSYS. Whose results show that new one-section high speed timing screw which can meet the request of three-section. New one-section high speed timing screw has no velocity mutation, which reduces the vibration of the high speed timing screw. According to the result of modal analysis and harmonic response analysis, the vibration is reduced about 20%.

Particle Swarm Optimization Algorithms Applied to Antenna and Microwave Design Problems

Particle Swarm Optimization (PSO) is an evolutionary optimization algorithm inspired by the social behavior of birds flocking and fish schooling. Numerous PSO variants have been proposed in the literature for addressing different problem types. In this chapter, the authors apply different PSO variants to common antenna and microwave design problems. The Inertia Weight PSO (IWPSO), the Constriction Factor PSO (CFPSO), and the Comprehensive Learning Particle Swarm Optimization (CLPSO) algorithms are applied to real-valued optimization problems. Correspondingly, discrete PSO optimizers such as the binary PSO (binPSO) and the Boolean PSO with velocity mutation (BPSO-vm) are used to solve discrete-valued optimization problems. In case of a multi-objective optimization problem, the authors apply two multi-objective PSO variants. Namely, these are the Multi-Objective PSO (MOPSO) and the Multi-Objective PSO with Fitness Sharing (MOPSO-fs) algorithms. The design examples presented here include microwave absorber design, linear array synthesis, patch antenna design, and dual-band base station antenna optimization. The conclusion and a discussion on future trends complete the chapter.