Analysis and design of an isolated single-phase power factor corrector with a fast regulation

This paper presents an analysis and a modeling approach to obtain a small-signal model design and the digital implementation of a linear control technique for single-phase boost power factor correctors (PFC). Such converters present nonlinear characteristics and approximations of them are used to drive the models. The proposed circuit significantly improves the dynamic response of the converter to load steps without the need of a high crossover frequency of the voltage loop by adding low-pass filter. So, a low distortion of the input current is easily achieved. This controller has been verified via simulation in Simulink using a continuous time plant model and a discrete time controller. Real-time implementation is performed on an experimental test bench utilizing a rapid prototyping tool. The controller is experimentally confirmed for steady-state performance and transient response.     

Radioiodination of 3-amino-2-quinoxalinecarbonitrile 1,4-dioxide and its biological distribution in Erhlich ascites cancer bearing mice as a preclinical tumor imaging agent

3-Amino-2-quinoxalinecarbonitrile 1,4-dioxide (QN) was labeled with ¹²⁵I, and the biological distribution of the product was studied. ¹²⁵I-QN was prepared by direct electrophilic substitution reaction using N-bromosuccinimide (NBS) as an oxidizing agent. The radiochemical yield of 92% was reached under the following optimum conditions: pH 7, 15 min, 100 μg of QN, and 75 μg of NBS. The labeled QN was stable for up to 12 h post labeling. Biodistribution study of ¹²⁵I-QN in tumor-bearing mice reflected that it accumulated in tissues with high proliferation rate with preferential accumulation in tumor sites. ¹²⁵I-QN was incorporated rapidly in the tumor site (T/NT = 4 at 2 h post injection), and then its content slowly decreased, whereas in the other tissues it decreased rapidly. The results obtained encourage the use of ¹²³I-QN as a tumor imaging agent.     

Experimental Study of Boiling Heat Transfer on Multiple and Single Nucleation Sites Using a Boiling-Meter

The general objective of this study is to contribute to a better understanding of heat transfer in a nucleate boiling regime. The aim is to determine the heat transfer characteristics under controlled operating conditions (thermodynamics of the fluid, noncondensable gas, surface state). Experimental investigations have been carried out in natural convection and nucleate boiling regimes. An experimental device was realized to perform boiling experiments using a boiling-meter, allowing investigations for different orientations of the wall. The boiling-meter is designed to investigate boiling for single and multiple nucleation sites. The purpose of this paper is to detail the experimental setup as well as the boiling-meter. This device allows the determination of the temporal heat transfer characteristics evolutions. In particular, this new device allows bringing to light the phenomenon of nucleation, growth, and detachment of generated vapor bubbles on a single artificial nucleate site, as well as for multiple natural nucleation sites. First results of the influence of the orientation of the heating wall for multiple and single nucleation sites on heat transfer are presented and analyzed.     

Nonenzymic browning. IX. Correlation of autoxidation and browning reactions in lipid-protein mixtures

Summary Polyunsaturated esters prepared from cod fish oil were rapidly oxidized in mixtures with casein but the peroxides formed as primary reaction products were rapidly destroyed. The carbonylic oxidation products reacting with benzidine or with 2-thiobarbituric acid behaved in the same manner. On the contrary, the browning proceeded slowly and the course was independent of changes of peroxides and carbonyl derivatives, so that some colourless intermediary products were obviously first formed which were then transformed into brown pigments. After reduction of peroxides with potassium iodide the extent of browning was much reduced but the reaction of remaining benzidine-active substances correlated well with browning reactions in mixture with protein. Most of the browning in lipid-protein mixtures was due to the reactions of peroxides, probably through some decomposition products.

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Nichtenzymatische Bräunung. IX. Korrelation zwischen Autoxydation und Bräunungsreaktionen in Lipid-Protein-Mischungen

Zusammenfassung Mehrfach ungesättigte Ester von Dorschleberöl wurden im Gemisch mit Casein schnell oxydiert, aber die als primäre Reaktionsprodukte gebildeten Peroxide wurden schnell zersetzt. Die carbonylhaltigen Oxydationsprodukte, die mit Benzidin oder mit 2-Thiobarbitursäure reagierten, verhielten sich auf derselben Weise. Zum Unterschied von den Oxydationsreaktionen verlief die Bräunung nur langsam und war von den Veränderungen der Peroxide und Carbonylderivate unabhängig. Es wurden zuerst farblose intermediäre Produkte gebildet, die dann in braune Stoffe umgewandelt wurden. Nach der Reduktion der Peroxide mit Kaliumjodid wurde die Bräunungsintensität erheblich erniedrigt, jedoch war die Reaktion von den zurückgebliebenen benzidinaktiven Stoffen in einer guten Korrelation mit der Geschwindigkeit der Bräunungsreaktionen im Gemisch mit Protein. Die Bräunung in Lipid-Protein-Gemischen ist also meistens durch die Reaktion von Peroxiden, weniger durch die Reaktion der Carbonylderivate, verursacht. Die Peroxide reagieren wahrscheinlich über einige ihrer Zersetzungsprodukte.

     

Four Voltmeter Vector Impedance Meter Based on Virtual Instrumentation

In this paper, a digital vector impedance half-bridge meter based on virtual instruments is designed, implemented and tested. Here, not only the accuracy of the magnitude of the impedance is considered but, more importantly, its phase measurement accuracy. The meter utilizes a four-voltmeter method which is a basic modification of the well-known three-voltmeter method. The half-bridge is constructed with commercially available data acquisition (DAQ) board in the form of peripheral control interconnect cards incorporated in personal computers. The DAQ board is used only to acquire the voltages instead of using four separate voltmeters, while the excitation signal is produced by an integrated circuit signal generator. The main error in this method arises from the error in measuring the voltage values. Since the resolution of the DAQ board used here is 16 bits; expect that absolute errors due to A/D conversion will be around 0.305 mV for ±10 V range. Detailed error analysis of the method is included in the context of the paper. It is found that the errors in the impedance magnitude is fairly small and relatively less sensitive on the resolution of the voltmeters because of the relative measurements in the half bridge with a precise reference resistance. The original three voltmeter vector impedance meter has relatively large error in the phase especially in the small phase angles. To decrease the phase error to an acceptable range, one has to increase the resolution of the voltmeter appreciably, which makes them expensive. The other solution to reduce the error in the phase angle with less cost is to add a fourth voltmeter which acquires directly the small phase angles. In this case, it is found that, a much lower resolution voltmeter can be utilized while achieving an acceptable measurement accuracy of the impedance.     

Phenomenological parameters of the spreading velocity in thyristors

Contents In this paper the propagating wave nature of plasma spreading in thyristors was resolved by measuring the current density distribution at consecutive instants during spreading. An analytical model for the plasma spreading velocity was developed. According to this model the spreading velocity is determined by the ratio of the characteristic lengthL* of the exponential decay of the current density in the transition region to the time constant of current rise* of the current density at certain location. It is found that* decreases with the current densityJ in the turn-on area because of the accelerating ohmic field in then-base whileL* is almost independent of the current densityJ in the operating current range. Theoretical expressions were derived forL* and* and compared with those measured. Satisfactory agreement was found between them.

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Phänomenologische Parameter der Plasma-Ausbreitungsgeschwindigkeit in Thyristoren

Übersicht In der vorliegenden Arbeit wurde der fortschreitende Wellencharakter des Ausbreitungsvorgangs in Thyristoren durch die Messung der Anodenstromdichte in fortlaufenden Zeitpunkten während der Ausbreitung untersucht. Ein analytisches Modell für die Ausbreitungsgeschwindigkeit wurde entwickelt. Nach diesem Modell ist die Ausbreitungsgeschwindigkeit durch das Verhältnis der charakteristischen LängeL* der exponentiellen Stromdichteabnahme im aktiven Übergangsbereich zur Zeitkonstante* des Stromdichteanstiegs bestimmt. Die Ergebnisse zeigen, daß* mit der Anodenstromdichte im leitenden Gebiet abnimmt. Das ist auf das beschleunigende ohmsche Feld in dern-Basis zurückzuführen. Die charakteristische LängeL* ist im Arbeitstrombereich näherungsweise unabhängig von der Anodenstromdichte. Theoretische Ausdrücke wurden fürL* und* hergeleitet und mit den gemessenen Werten verglichen. Gute Übereinstimmung zwischen Theorie und Messung wurde festgestellt.