Range Of Design Specifications Research Articles

Multifeature-Assisted Neuro-transfer Function Surrogate-Based EM Optimization Exploiting Trust-Region Algorithms for Microwave Filter Design

This article proposes a multifeature-assisted neuro-transfer function (neuro-TF) surrogate-based electromagnetic (EM) optimization technique exploiting trust-region algorithms for microwave filter design. The proposed optimization technique addresses the situation where the response of the starting point is far away from the design specifications. We propose to utilize multiple feature parameters to help move the passband of the filter response into the range of design specifications. The pole–zero-based neuro-TF is introduced in this article to help extract the multiple feature parameters when the feature parameters of filter responses are not explicitly identified. Furthermore, we propose to derive new optimization objective functions to involve the multiple feature parameters. A new trust-region updating formulation for the modified optimization objective functions is derived to guarantee the optimization convergence. With the assistance of multiple feature parameters, the proposed surrogate-based EM optimization has a better capability of avoiding local minima and can reach the optimal EM solution faster than the surrogate-based EM optimizations without feature assistance. Three examples of EM optimizations of microwave filters are used to demonstrate the proposed technique.

A novel design of a low-voltage low-loss T-match RF-MEMS capacitive switch

This paper presents a novel design, optimization and analysis of capacitive radio frequency (RF) micro-electromechanical system (MEMS) switch. The design incorporates a novel membrane and beams' structure with two short high-impedance transmission-line (T-line) sections added on either side of the switch (namely T-match switch) to improve its RF performance, while maintaining low-actuation voltage. The short high-impedance T-line section has narrower width and higher impedance than the coplanar waveguide (CPW)'s signal line, behaves as series inductor to compensate the switch's up-state capacitance and provides excellent matching at the design frequency. This high-impedance T-line section was designed, simulated and optimized using finite-element-modelling (FEM) tool of electromagnetic (EM) simulator of AWR Design EnvironmentTM. The optimized T-line section's width and length is 10 µm and 70 µm, respectively. The RF-MEMS switch is actuated by electrostatic force with low-actuation voltage of 2.9 V, has maximum von Mises stress of 13.208 MPa which is less than aluminium's yield stress and can be operated in robust conditions. Compared to the normal capacitive RF-MEMS switch, this T-match capacitive RF-MEMS switch with two sections of optimized high-impedance T line has improved the performance of return loss and insertion loss, at switch-on state, by 45.83% and 55.35%, respectively; while at the switch-off state, the isolation is increased by 24.05%; only the switch-off return loss is degraded by 11.7% but the value (ź 0.5519 dB) is still located in the range of design specifications. The RF-MEMS switch's actuation time was simulated to be ~ 27 µs with amplitude of 5 V up-step voltage.

Remediating Large Plumes: Overcoming the Scale Challenge

Introduction The remediation industry, now three decades old, continues to evolve. This is driven by many factors: technological developments, a need to address emerging contaminants, regulatory changes, economic factors, and sustainability considerations. These have created both challenges and opportunities at different stages of the industry’s evolution. Although many things have changed with time, one of the most difficult practical challenges remains—namely, how to deal with large dissolved plumes (referred to as “large plumes” throughout this article). Presumptive thinking emphasizes containment and management of these large plumes rather than focusing on mass removal and site closures. The term large plume obviously highlights scale as being the critically defining attribute; however, it is worth identifying other attributes that are discussed in this article:

Interval mathematics for knowledge-based computer aided design in magnetics

The use of interval mathematics in a knowledge-based system for electromagnetic device design is discussed. It is shown that, through interval propagation, the expert designer can observe the consequences of imposing interval bounds on parameters so that the nonexpert user can then receive advice regarding the legal range of design specifications. However, there are some problems in utilizing interval mathematics within a network of design equations exhibiting complex parameter dependencies. Constraint propagation methods involving single-valued quantities cannot be substituted directly. Interval techniques have proved to be valuable at various stages of the design process as a knowledge integrity tool and as an aid to end-users of the CAD (computer-aided design) system. The usage of these methods in electromagnetics is not restricted to expert systems, however. They may also find applications in low-level numerical algorithms for electromagnetics. >

Fuel elements of the high temperature pebble bed reactor

This work is devoted to spherical fuel elements for the high temperature pebble bed reactor, their manufacture and the conditions which they must satisfy for use in a process-heat reactor with an average gas outlet temperature T G, out of 950°C. The positive results known from the operation of the AVR with T G,out = 950°C and from extensive irradiation tests of the THTR-300 element with BISO coated mixed-oxide particles, even beyond the range of design specifications, and possible damage mechanisms are described in detail. They show that a spherical fuel element already exists, for which only a short-term development is needed to produce a coolant temperature of 950°C in a process-heat reactor. Further developments will be characterized by the use of a pebble bed HTR for high conversion rates ( c ≈ 0.95) or for average gas outlet temperatures of more than 950°C. At higher temperatures the increased demands, mainly with regard to the release of fission products, can be fulfilled through the application of TRISO-coated fuel particles and the doping of the fuel kernels with Al 2O 3 SiO 2 . The reprocessing programme for fuel elements in the Federal Republic of Germany is mentioned briefly.