Hybrid modeling techniques for multilayered printed circuit board in power electronics: association of electromagnetic methods

With the fast development of power electronics circuits at increasing switching frequency (over 10 MHz), the multilayered printed circuits boards (PCBs) are being used more and more in the field of power electronics. In this paper, two main computational methods are presented to simulate the dynamic behavior of power electronics interconnection systems. Our aim is to present a methodology to analyze the electromagnetic (EM) behavior of power PCB regarding parasitic effects ( EM couplings) or dynamic effects (impedance): a general procedure is given to calculate EM couplings between strip conductors in multilayered configurations based on the principle of hybrid methods. Finally, we propose a new method to limit computation time based on matrix sparsification.     

1.04 GBd low EMI digital video interface system using small swingserial link technique

In a high-resolution flat panel system, a conventional interface that directly connects a liquid crystal display (LCD) controller to a flat panel cannot overcome the problems of excess EMI (electromagnetic interference) and power caused by full-swing transmission signals in parallel lines. This paper presents a high-speed digital video interface system implemented with a low-cost standard CMOS (complimentary metal-oxide-semiconductor) technology that can mitigate EMI and power problems in high-resolution flat panel display systems. The combined architecture of the high-speed, small number of parallel lines and low-voltage swing serial interface can support resolutions from VGA (640×480 pixels) up to XGA (1024×768 pixels) with significant power improvement and drastic EMI reduction. To support high-speed, low-voltage swing signaling and overcome channel-to-channel skew problems, a robust data recovery system is required. The proposed digital phase-locked loop enables robust skew-insensitive data recovery of up to 1.04 GBd     

Oscillation of the scattering time in a 2D electron system with oval antidots

Electron scattering by a single barrier is predicted to reveal singularities as the magnetic field is changed, because the number of electron collisions with the barrier dramatically increases as chaotic orbits around the barrier are changed into periodic orbits. To test this experimentally we have measured the magnetoresistance of AlGaAs/GaAs heterostructures with a two-dimensional electron gas and a lateral lattice containing a macroscopic number of oval-shaped antidots fabricated using electron lithography. Reproducible fluctuations in the magnetoresistance are observed at low field, which are due to the oscillations of the number of electron collisions with the antidots. The number of collisions N before the electron escapes from the antidot has been calculated as a function of B in an electric field. The position of the maxima in N(B) obtained from calculations and experiment are in reasonable agreement.     

Distribution of heat sources in vertical open channels with natural convection

In this paper we use the constructal method to determine the optimal distribution and sizes of discrete heat sources in a vertical open channel cooled by natural convection. Two classes of geometries are considered: (i) heat sources with fixed size and fixed heat flux, and (ii) single heat source with variable size and fixed total heat current. In both classes, the objective is the maximization of the global thermal conductance between the discretely heated wall and the cold fluid. This objective is equivalent to minimizing temperature of the hot spot that occurs at a point on the wall. The numerical results show that for low Rayleigh numbers (∼10²), the heat sources select as optimal location the inlet plane of the channel. For configuration (i), the optimal location changes as the Rayleigh number increases, and the last (downstream) heat source tends to migrate toward the exit plane, which results in a non-uniform distribution of heat sources on the wall. For configuration (ii) we also show that at low and moderate Rayleigh numbers (Ra_M ∼ 10² and 10³) the thermal performance is maximized when the heat source does not cover the entire wall. As the flow intensity increases, the optimal heat source size approaches the height of the wall. The importance to free the flow geometry to morph toward the configuration of minimal global resistance (maximal flow access) is also discussed.     

Study of the glucide fraction in ropy wines

Gas chromatography was used to study the polysaccharides present in samples that exhibited significant microbially induced viscosity values. Alterations in the media considered were related to the percentage glucose content and the total polysaccharide content.     

An Evolutionary Method for Synthesizing Low-Sensitivity Lossless Matching Networks

Whereas the present practice of designing matching networks for antennas is limited to conventional topologies, requiring a significant amount of domain knowledge, evolutionary algorithms can be used for automatically identifying unconventional designs that are more effective than would otherwise be developed. In this work, an automatic method to design lossless matching networks driven by an evolutionary algorithm (EA) that considers the sensitivities of the network parameters during the synthesis process is presented. To this end, a closed-form expression for the transducer power gain (TPG) sensitivity with respect to the component values is employed in such a way that the effects of the components tolerance on the matching network performance can easily be quantified. A 3D data structure based on the adjacency matrix is conveniently used to represent any type of network topologies. The proposed EA employs a novel set of topology variation operators, tailored for changing the circuit topology, and an association step, with the aim of reducing the number of nodes of the matching circuit. The efficiency of the proposed EA is tested in the synthesis of an impedance matching network for a VHF monopole whip antenna. This study’s results indicate a matching bandwidth improvement, a more uniformly distributed TPG along the operation frequency band and a more stable TPG regarding the components tolerance compared to the results obtained by previous approaches.     

为在巴西引入数字电视提交的"公开咨询报告"文稿第291号

1 引言 由"国家电信局"(National Telecommunications Agency,Anatel)主持的数字电视在巴西的首次"公开咨询报告"(Public Consultation)的一年后,我们注意到:在这种技术的领域内,已经出现很多不同的显著事实.除了"CPqD基金会"报告以外,新的对比性测试曾经在美国(ATSC对DVB-T)和中国香港(ATSC,DVB-T和ISDB-T)都进行过.还有一些报道表明:中国台湾也进行了对比性测试,目的是确立自己的数字电视标准.     

An Improved NER Methodology to the Portuguese Language

Mobile Networks and Applications - The text mining process typically involves the application of natural language processing (NLP) techniques, in order to obtain important information and extract...     

Thermal-lens and photo-acoustic methods for the determination of SiC thermal properties

In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρc_p, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (c_p) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments.     

Internationale Zusammenarbeit zum Nachweis bestrahlter Lebensmittel

Zusammenfassung Es wird eine Übersicht über die neuesten internationalen Entwicklungen, insbesondere die Programme von ADMIT (FAO/IAEA) und dem BCR (Europäische Gemeinschaft) zum Nachweis einer erfolgten Bestrahlung von Lebensmitteln gegeben. Eine Kontrolle bestrahlter Lebensmittel direkt am Produkt ist wünschenswert, um Kennzeichnung und eventuell bestehende Verbote zu überwachen, aber auch um das Vertrauen des Verbrauchers in eine korrekte Anwendung des Verfahrens zu stärken und sein Recht auf freie Wahl zwischen bestrahlten und unbestrahlten Lebensmitteln zu schützen. Auf internationaler Ebene haben bereits mehrere größere Ringversuche stattgefunden, z. B. Messung der Elektronen-Spin-Resonanz in Knochen von Geflügel, Schwein, Rind, Froschschenkeln und Fisch; Messung der Thermoluminescenz von unlöslichen Mineralien, isoliert aus Gewürzen und Kräutern; die gaschroma- tographische Analyse von Kohlenwasserstoffen und Alkylcyclobutanonen aus der Lipidfraktion von Hähnchen; und die mikrobiologische DEFT/APC-Analyse von Gewürzen. Diese Methoden sollen in naher Zukunft als internationale Standardmethoden etabliert werden.

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International co-operation in the field of detection of irradiated food

A survey over recent international developments to detect the irradiation treatment of foods is given, in particular the programmes of ADMIT (FAO/ IAEA) and of BCR (European Community). The need to detect radiation treatment by analysing the food itself is desirable to check compliance with existing regulations, such as the enforcement of labelling and control of prohibition, to enhance consumer confidence in the correct application of radiation processing, and to protect consumers' freedom of choice between irradiated or unirra-diated food products. Some larger collaborative studies on an international scale have already taken place, e.g. ESR measurements of bones from chicken, pork, beef, frog legs and fish, thermoluminescence of insoluble minerals isolated from herbs and spices, gas Chromatographic analysis of hydrocarbons and alkylcyclobutanones derived from the lipid fraction of chicken and the microbiological DEFT/APC procedure for spices. These methods could soon be implemented in international standard protocols.