930 research outputs found
Considerations of uncertainty in robust optimisation of electromagnetic devices
No full textDue to unavoidable uncertainties related to material properties and manufacturing processes, the robustness of the optimal solution must be considered when designing electromagnetic devices. In this paper, the worst-case optimisation (WCO) and the worst-vertex-based WCO are proposed to evaluate the robustness of both performance and constraints under uncertainty. To reduce computing times when searching for the robust solution a predicted objective function is used, obtained with the help of a kriging algorithm which explores the searching space using the concept of rewards. Finally, to avoid some of the shortcomings of WCO, the concept of average performance evaluation is developed
Adaptive Weighted Expected Improvement With Rewards Approach in Kriging Assisted Electromagnetic Design
Get PDFThe paper explores kriging surrogate modelling combined with expected improvement approach for the design of electromagnetic devices. A novel algorithm based on the concept of rewards is proposed, tested and demonstrated in the context of TEAM Workshop Problem 22. Balancing exploration and exploitation is emphasized and robustness of the design considered
Next Generation of 100-μm-Pitch Wafer-Level Packaging and Assembly for Systems-on-Package
No full textAccording to the latest ITRS roadmap, the pitch of area array packages is expected to decrease to 100 µm by 2009. Simultaneously, the electrical performance of these interconnections needs to be improved to support data rates in excess of 10 Gbps, while guaranteeing thermomechanical reliability and lowering the cost. These requirements are challenging, thus, needing innovative interconnection designs and technologies. This paper describes the development of three interconnection schemes for wafer-level packages (WLPs) at 100-µm-pitch, involving rigid, compliant, and semicompliant interconnection technologies, extending the state of the art in each. Extensive electrical and mechanical modeling was carried out to optimize the geometry of the interconnections with respect to electrical performance and thermomechanical reliability. It was found that the requirements of electrical performance often conflict with those of thermomechanical reliability and the final “optimum” design is a tradeoff between the two. For the three interconnection schemes proposed, it was found that the electrical requirements can be met fairly well but acceptable mechanical reliability may require organic boards with coefficient of thermal expansion of 10 ppm/K or lower
Design and Analysis of a Novel Compact High Permittivity Dielectric Resonator Antenna
No full textA very compact and efficient dielectric resonator antenna is proposed and investigated. The novel structure is analyzed using two numerical methods and design guidelines are established. Moreover, it is shown that – by using very high permittivity materials and appropriate design of the resonator and its feeding structure – a wide frequency coverage is possible even at cellular frequencies. Simulation results are reported showing the effectiveness of the proposed antenna structure
SONATA-DIALOGUE FOR BASSOON AND PIANO BY V. ROTARU
No full textIn the pages of this article, the author analyzes the stylistic peculiarities of the Sonata-dialogue for bassoon and piano by Vladimir Rotaru, highlighting the composer’s predilection for the genre of instrumental chamber music, mostly for piano and wind instruments. Th e Sonata-dialogue in question is characterized by a musical language deeply rooted in folklore (with specifi c rhythms of the Moldovan folk dances), by using the principles of improvisation in developing the material and original virtuosity of the solo part. As a performer (soloist) of the sonata, the author suggests some methodical recommendations to bassoon-soloists in order to achieve a successful interpretation of the creation
An innovative method for highly-efficient fabrication of carbon fiber precursors via acrylonitrile emulsion copolymerization coupled to a chemical oscillator
No full textA new synthetic protocol to produce the carbon fiber precursor polyacrylonitrile (PAN) and its block copolymers with polyethylene glycol (PEG) is proposed here. The constant flux of radical species produced at low concentrations during the oscillating Belousov-Zhabotinsky (BZ) reaction was properly exploited to initiate the radical polymerization reaction. Compared with conventional methods, this oscillating initiation decreases the probability of chain termination, thus favouring the production of high molecular weight polymers, and it does not require an inert atmosphere and elevated temperatures to be produced. The solubility of the polymeric chains during the polymerization reaction was improved by adding the anionic micelle-forming surfactant sodium dodecyl sulphate (SDS). Following the initiation step, short oligomer chains are able to overcome the micellar interface, thereby reaching a favourable environment for the increase of the polymeric chains, thus strongly contributing to the increase of the molecular weight of the fibers' precursors. The synthesis was conducted by adding the monomer acrylonitrile (AN) to the unperturbed and PEG-perturbed BZ system after the onset of the oscillations, in the absence and presence of increasing amounts of the SDS surfactant. The potentiometric technique was utilized to detect the dynamics of the oscillatory reaction. Preliminarily, the response of the BZ system to the monomer addition was investigated. Additional information was provided from the study of the effect of the SDS and PEG concentration on the dynamics of the BZ reaction during AN polymerization, thus obtaining a deepening in the understanding of the BZ mechanism. The characterization of the obtained polymers and copolymers, by melting point measurements, molecular weight determinations, Fourier Transform Infrared (FTIR), X-ray diffraction (XRD) analyses, and thermal treatments, indicated that the proposed synthetic method produces carbon fiber precursors with high molecular weight and good thermal stability. The addition of the surfactant was revealed as a good method to improve and/or finely tune the precursor molecular weight. The proposed synthetic protocol represents a valuable alternative to conventional methods to produce highperformant precursors of carbon fibers
Electromagnetic Design of Dual Resonant Structures for Improved Sensitivity of Terahertz Label Free Bio-Sensing
Get PDFA design is proposed exploiting full wave numerical simulation of a dual resonant structure with an aim to sense small amounts of chemical and biochemical materials. The structure is energized with free space radiation in the terahertz regime. Thanks to its asymmetric geometry two close resonances are excited. The interference between these two resonances produces a sharp change in the frequency response of the system. By selectively loading the structure with only small amounts of probe material, a relatively large shift in the frequency response may be achieved. The concept is demonstrated through simulation, while optimization of the structure and the analyte loading is attempted
Two-stage distributed generation optimal sizing with clustering-based node selection
No full textNowadays, distributed generation (DG) is playing a significant role in the electrical energy systems. The diffusion of DG in the electrical networks could be beneficial to improve network operation, but excessive amounts of DG in operation could cause violations of the system constraints. This paper presents a new method to obtain the optimal size of DG sources in electrical distribution systems, taking into account the time-dependent evolution of generation and load. This method adopts a procedure composed of two nested calculation stages. The external stage is carried out by selecting a set of candidate nodes through a clustering-based approach based on normalized loss sensitivity factors and normalized node voltages. The internal stage is an exhaustive search driven by the calculation of an objective function with energy losses and voltage profile components, aimed at finding upgraded DG sizes using exhaustive search on a set of available sizes at the candidate nodes. The resulting method avoids the combinatorial explosion of the solutions to be analysed and determines pseudo-optimal DG sizing without violation of any of the system constraints under any operating condition. The proposed method is tested on a 20 kV rural distribution network, showing its effectiveness in obtaining the pseudo-optimal solution with a relatively low computational burden
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