In this paper, a novel instantaneous control strategy for the AC control loop of voltage-type converter is proposed in which two switching vectors are selected sequentially in one sampling period. Vector selection is based on control error minimization theorem to bring both fast response and low ripple. Switching timing is determined in real time according to the THD(Total Harmonic Distortion) minimization theorem with instantaneous THD definition as a direct evaluation function. With this algorithm, instantaneous control can be realized in almost constant switching frequency. For DC output voltage control, voltage square feedback with load power compensated algorithm is introduced to obtain global stability with fixed gain. Experimental investigation confirmed the validity of proposed control algorithms.

Abstract The α-times integrated semigroups, α > 0, are introduced and analyzed. It is shown that suitable differential operators generate α-times integrated semigroups for α ∈ (1/2, 1).

By describing a large class of deep inelastic processes with standard parametrization for the different parton species, we check the characteristic relationship dictated by Pauli principle: broader shapes for higher first moments. Indeed, the ratios between the second and the first moments and the one between the third and the second moments for the valence partons is an increasing function of the first moment and agrees quantitatively with the values found with Fermi–Dirac distributions.

An HPLC procedure utilizing reversed-phase chromatography coupled with a coulometric array detection system was developed for the characterization of overall antioxidant status in fruits and vegetables. The method was reliable and sensitive (20 pg to 1 ng detection limit) and can also be used to identify and simultaneously quantify multi-antioxidants including vitamin C, glutathione, phenolic acids, and flavonoids in fruits and vegetables. Each fruit and vegetable aqueous extract showed an unique distribution of chromatographic peaks that could serve as a “fingerprint” for the fruit or vegetable. A significant positive linear correlation was demonstrated in fruit and vegetable aqueous extracts between the total antioxidant activities determined by using oxygen radical absorbance capacity (ORACROO•) assay and the electrochemical data generated from the coulometric array detectors. From these data, the ORACROO• assay appears to be a valid and useful procedure for measuring total antioxidant activity in extr...

The ICE-TEL project is a pan-European project which is building an Internet X.509-based certification infrastructure throughout Europe plus several secure applications that will use it. This article describes the trust model being implemented by the project. A trust model specifies the means by which a user may build trust in the assertion that a remote user is really who he purports to be (authentication) and that he does in fact, have a right to access the service or information he is requesting (authorization). The ICE-TEL trust model is based on a merging of and extensions to the existing pretty good privacy (PGP) web of trust and privacy-enhanced mail (PEM) hierarchy of trust models, and is called a web of hierarchies trust model. The web of hierarchies model has significant advantages over both previous models, and these are highlighted. The article further describes the way the trust model is enforced through some of the new extensions in the X.509 V3 certificates, and gives examples of its use in different scenarios.

The aim of this study was to determine whether the nitric oxide (NO) measured in exhaled air is produced at airway or alveolar level. Exhaled NO was measured using a chemiluminescence analyser, and carbon dioxide (CO2 concentration using a Morgan capnograph in single exhalations in 12 healthy subjects (mean age 32 yrs; 6 males and 6 females). For each subject, five exhalations were made directly into the NO analyser and five were made through a T-piece system, which allowed measurement of expiratory flow rate. The peak NO levels measured via the T-piece system were 41.2 (SEM 10.8) parts per billion (ppb), significantly lower than direct levels 84.8 (14.0) ppb (p<0.001). The levels of NO tended to rise to an early peak and plateau, while the CO2 levels continued to rise to peak late in the exhalation. The mean times to reach peak NO levels were 32.2 s (direct) and 23.1 s (T-piece), which were significantly different from that of peak CO2 levels 50.5 s (direct) and 51.4 s (T-piece) (p<0.001). At peak NO level, the simultaneous CO2 level mean 4.9% (SEM 0.14)%, was significantly lower than the peak CO2 reached, 5.8 (0.21)% (p<0.001). We conclude that peak nitric oxide levels are dependent on measurement conditions. There are significant differences between the time to peak of carbon dioxide and nitric oxide. Therefore, most nitric oxide, unlike carbon dioxide, is produced in airways and not at alveolar level.

In the “good old days” before automation became a way of life in the clinical laboratory, hand methods of analysis were sometimes capable of producing accurate as well as precise results-a highly gratifying situation to all concerned, especially the patient. Today in the U. S., 12,000 to 15,000 laboratories (depending upon the criteria used to define a clinical laboratory) are practicing clinical chemistry and turning out more than two billion results per year, according to a recent report from the Center for Disease Control (CDC). Somewhere in the transition from the widely used manual methods of yesterday to the extensive use of automated methods of today, accuracy as the predominant requirement for valid results was displaced by repeatability. Does one blame the engineers who adapted clinical methods to their ingenious machines in such a way as to produce highly replicable results, often at the expense of accuracy? Or does some of the fault lie with the professional clinical chemist who, under great pressure, started thinking more in terms of quantity than of quality? No matter what the historical reasons, there is little to be gained at this time in assigning blame. The goal in clinical chemistry today must be to reemphasize and recapture accuracy in analysis. At this point one may ask, “Why is accuracy in clinical chemistry necessary, anyway?” In all complex measurement systems, results, if they are to be comparable across time and distance, must be based on accuracy and not only on precision. Accuracy in measurement is related directly to the “true” value, the value that reflects reality in the most meaningful possible way. A measuring process is accurate (although not necessarily precise) if the average of a large number of replicate measurements obtained by this process is very close to the “true” value. Thus, accuracy involves traceability to the base system of units. If all practitioners agree on that base system of units, then results will be directly comparable and the bias of different methods becomes self-evident. Precision, by contrast, is only an expression of the reproducibility of a measurement system; it is not necessarily related to accuracy in any systematic way.

Abstract A large part of prior research about international performance involves a process of identifying the factors associated with enhanced performance. Such research addresses the relationship between past international strategy and performance. Stages-of-internationalization models, however, suggest that performance at a given stage has implications for the future behavior of exporting firms. Success at an early stage may move firms to more advanced stages. Conversely, failure at an internationalization stage may move firms to less advanced stages or to cease exporting altogether. The purpose of this inquiry is to draw upon for the first time, in a services marketing context, the customer satisfaction literature so as to examine the relationships between export performance, disconfirmation of prior expectations, satisfaction with export performance, the importance of exporting to the attainment of future firm goals, and future export intentions. Thus, it serves to further our understanding of the res...