Three-dimensional space-vector modulation algorithm for four-leg multilevel converters using abc coordinates

In this paper, a novel three-dimensional (3-D) space-vector algorithm for four-leg multilevel converters is presented. It can be applied to active power filters or neutral-current compensator applications for mitigating harmonics and zero-sequence components using abc coordinates (referred from now on this paper as natural coordinates). This technique greatly simplifies the selection of the 3-D region where a given voltage vector is supposed to be found. Compared to a three-level modulation algorithm for three-leg multilevel converters, this algorithm does not increase its complexity and the calculations of the active vectors with the corresponding switching time that generate the reference voltage vector. In addition, the low-computational cost of the proposed algorithm is always the same and it is independent of the number of levels of the converter.     

Comment on "From the summation-by-parts algorithm to Pi"

Comments on the paper by Mosig (IEEE Antennas and Propagation Magazine, vol.47, p.38-40, 2005 December). The paper by Mosig discussed acceleration of convergence of series. Without commenting on either the validity or efficiency of his method, the present author would like to draw attention to an existing method, published long ago by D. Shanks (1955). Briefly stated, this method takes a sequence and defines partial sums, which is described in this paper.     

Local structural characterization of Zn:Cd:Se ternary semiconductors

We have studied the local atomic structure around Zn and Cd, in CdSe, ZnSe, and ordered and disordered Zn_0.5Cd_0.5Se thin films, grown by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE) using X-ray absorption spectroscopy (XAS). Zn K-shell X-ray absorption fine structure (XAFS) shows that the Zn–Se pair nearest neighbor distance is the same in both ordered and disordered ternary samples. This result shows that the ordered (or disordered growth) does not have a significant effect in the nearest neighbor Zn environment. However, results from K-shell Cd XAFS show that the Cd–Se pair nearest neighbor distance in the Zn_0.5Cd_0.5Se ordered film exhibits a contraction compared to the same pair distance in the disordered Zn_0.5Cd_0.5Se sample and the binary CdSe compound. This suggests that the shortest Zn–Se nearest neighbor distance regulates the Cd–Se nearest neighbor distance in the ternary compounds, when these are grown in an ordered, layer by layer, fashion.     

Switching and PI control of walking motions of planar biped walkers

A companion paper has addressed the problem of designing controllers that induce exponentially stable, periodic walking motions at a fixed walking rate for a planar, biped robot with one degree of underactuation. This note provides two additional control features: 1) the ability to compose such controllers to obtain walking at several discrete walking rates with guaranteed stability during the transitions; and 2) the ability to regulate the average walking rate to a continuum of values.     

Practical implementation of possibilistic probability mass functions

 Probability assessments of events are often linguistic in nature. We model them by means of possibilistic probabilities (a version of Zadeh's fuzzy probabilities with a behavioural interpretation) with a suitable shape for practical implementation (on a computer). Employing the tools of interval analysis and the theory of imprecise probabilities we argue that the verification of coherence for these possibilistic probabilities, the corrections of non-coherent to coherent possibilistic probabilities and their extension to other events and gambles can be performed by finite and exact algorithms. The model can furthermore be transformed into an imprecise first-order model, useful for decision making and statistical inference.     

Synchronized world embedding in virtual environments

We introduce a novel distributed approach that lets users copy a given CVE section and keep it consistent with all its other copies and its original CVE area. Although 3D world modeling tools such as Alias' Maya and Discreet's 3DS Max already use object embedding, our method is the first to introduce it in a functioning CVE system. We also expand the traditional object-embedding concept by introducing a mutual synchronization function between the source and destination worlds. The mutual synchronization scheme propagates events $such as changes in an object's color, shape, or position - to other copies of a world. This synchronized world embedding thus offers a new way to expand worlds. Our method is built on existing CVE functionality, which lets us deploy it without significantly interfering with existing CVE designs. We've also altered the method so that it's usable when consistency needs are more relaxed.     

Piezoelectric paint: Ceramic-polymer composites for vibration sensors

A piezoelectric ceramic-polymer composite has been developed for use as a novel thick film strain sensor for vibration monitoring of structures. The material is in the form of a paint that can be applied to a wide range of substrates using conventional spraying equipment. The sensor properties depend on the morphology of the composite and on the electrodes that are used to couple it to the charge amplifier. Electrodes of various kinds have been tested. Interaction between the electrode and the piezoelectric paint sometimes occurs (for example, the organic vehicle for spray-coated electrodes may interact with the paint binder). The morphologies of the piezoelectric paint and of the electrode materials have been studied using light optical microscopy and scanning electron microscopy to investigate the effect of different compositions and of different processing conditions (e.g., paint mixing schedule). Preliminary work is reported on the characteristics of the piezoelectric particles and on the effect of heat treatment applied to anneal out defects produced by milling. X-ray analysis and particle size analysis have been used to characterize the changes that take place on heat treatment. X-ray diffractometry has also been used to follow the effect of poling on the paint sensors. At the present state of development, sensors made using the paint have a dynamic range of at least 40–4000 microstrain and a bandwidth of at least 1 Hz–2 kHz, and piezoelectric coefficient d ₃₁ of approximately 20 pC/N. The sensors are resistant to outdoor exposure and a successful field trial has been conducted.     

A reconfigurable high-frequency phase-locked loop

Reconfigurable phase-locked loops (PLLs) present the advantage of fast-frequency acquisition combined with narrow-noise bandwidth, since their parameters can be dynamically adjusted. High-frequency PLLs are generally implemented by means of analog circuits which are not easily reconfigured during operation. However, the five-port technique allows the discrimination of the phase difference between two microwave signals using a mixed circuit. In this paper the design of a PLL comprising a five-port based phase detector is presented. This system benefits from the phase-detector digital circuit to carry out the loop filtering. Simulation results for different conditions of noise and frequency acquisition are shown. We also present measurement results to confirm the simulations.     

Antitumor effect of plant lectins

BACKGROUND: Staff development experts in a tertiary-care hospital were searching for a holistic approach to facilitating improved outcomes. METHOD: Staff development experts, clinical nurse specialists, and clinical managers developed a model that provides a framework for educators to integrate their energies with those of other leaders in order to create a holistic approach to the goal of achieving excellence. RESULTS: The model that is proposed links strategies for change with outcome evaluation. CONCLUSIONS: The model provides a conceptual lens that helps nurse leaders focus on organizational assessment, strategies to improve the work environment, and the evaluation of outcomes. The model is useful for guiding practice as well as research.     

A new look at British graduate students.

Discusses findings of a survey of British graduate students in psychology conducted in late 1972 and 1973. Responses were obtained from 34 of the 89 British departments offering advanced courses or supervision for research leading to the PhD in psychology or one of its subspecialties. The total enrollment of all postbaccalaureate students in psychology was 1,112, but only 277 of these were in PhD programs; the number is almost 8 times higher in the US. UK postgraduate training in psychology seems to be conducted on a much smaller scale than in the US, the students enter doctoral training at an earlier age than American students, and females and non-White minority students are well represented in UK doctoral training programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)