Direct-Drive Synchronous Generators with Excitation from Strontium-Ferrite Magnets: Efficiency Improvement
The authors consider the possibility to raise the specific power of synchronous generators with excitation from inexpensive permanent magnets. For this purpose, it is proposed to use tooth-wise windings and permanent magnets based on inexpensive magneto-hard material, e.g. strontium-ferrite. The magnets are to be placed between the rotor teeth, the alternate polarity of which is facing the air-gap. This provides a simpler and cheaper technology of making such a generator and improves its reliability. The proposed rational bevelling of the stator teeth not only raises the specific power of the generator but also reduces the level of noise and vibrations, extends the longevity of the magnets and bearings as well as facilitates the starting torque of the electric machine, e.g. if it is employed as wind generator.
This report describes the most important details of elaboration of a versatile power module that can be utilized as a part of various converters. Two or more modules connected together can form a frequency converter or multilevel converter or 3-phase inverter/rectifier etc. Initially the module was developed for fast prototyping of uninterruptible power supplies and energy systems with alternative energy sources. The module can be used also as a basis for laboratory equipment of the power electronics course.
The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM) but close to boundary conduction mode (BCM). The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.
The authors present a small-scale wind turbine emulator based on the AC drive system and discuss the methods for power coefficient calculation. In the work, the experimental set-up consisting of an AC induction motor, a frequency converter, a synchronous permanent magnet generator, a DC-DC boost converter and DC load was simulated and tested using real-life equipment. The experimentally obtained wind turbine power and torque diagrams using the emulator are in a good agreement with the theoretical ones.
Application of wind generators opens wide possibilities for raising the efficiency of low- and medium-power wind generators (WGs). The mass of generators in the proposed version is smaller, their reliability higher, while maintenance costs are lower. At the same time, the use of high-energy permanent magnets in generators of enhanced power comes up against some obstacles, which can be overcome through proper orientation of magnetization at creation of a magnetic field in the airgap of electrical machine. In this regard, it might be preferable to use magnets with indirect action on the airgap instead of those with direct action. A convincing example of the former variant is a generator with tangentially oriented magnetization of permanent magnets. In the work, an attempt is done to prove the advantages of such installation in modern low- and medium-power WGs
Broadly educated professionals are a rely valuable resource for the Russian public health system in the current socio-economic conditions. Their capability to flexibly switch the focus and content of their activities in the changing and challenging environment is essential for successful performance.
The purpose of our study is to analyze the international evidence on managing the process of competencies’ development in healthcare managers.
Competence-oriented education and training of future health-care managers is of special interest. In light of this, the study of international data on the organization of the processes of key competence development is important. Here with, it is necessary to take into account the content of the studies, resources and technologies, factors that influence on this process, the development and evaluation of models aimed at improvement of the education of healthcare management professionals at medical schools.
We believe that the results of this review will help to develop and offer a number of practical steps aimed at optimizing the education and training of healthcare managers. In addition to a review of international data, this article presents an innovative project for the development of professional competencies of health managers – the Academy of Talent Development in Healthcare (ATDH). This project involves students of the Sechenov University who want to learn how to lead healthcare teams efficiently.
There are a lot of models and algorithms to minimize risks during dredging operations and they are not without drawbacks. The paper describes the authors’ approach to solving this problem. Mathematical models are proposed and on their basis software is developed. Methods of the risk theory are used to minimize the risks. In this paper a consequence of influence refers to the deviation from the goal expressed in the expected results and the deviation of certain criterion factors. In this case, we mean any measure of quality. In its turn, risk factors reduce criterion factors. These factors are divided into categories - general transportation risks and risks of transporting ground. In these categories, one may derive the following risks - incidents at transport resulting from the impact of a set of random factors including the human one. For risk analysis and management, in addition to identifying critical chains of risk situations, the stochastic model for evaluating the chains is set forth. In order to implement this algorithm, the mathematical package Maple is used, which allows for conducting the required calculations with a software package including the Graph Theory. The paper presents fragments of the code listing.
The trematode Amurotrema dombrowskajae Achmerow, 1959, is the type and the only species of the paramphistomoid genus Amurotrema Achmerow, 1959. This intestinal parasite of grass carp (Ctenopharyngodon idella) was introduced with host to the Volga River Delta. These naturalized trematodes were found by the authors in 2014 – 2015. In the present study the phylogenetic position of Amurotrema dombrowskajae is analysed using partial 28S rDNA nucleotide sequences. Bayesian inference and Maximum Likelihood analyses place this species in a clade with representatives of the family Cladorchiidae - Megalodiscus temperatus (Stafford, 1905) and Indosolenorchis hirudinaceus Crusz, 1951. Thus, molecular data are consistent with the traditional view on the position of A. dombrowskajae in this family.
Recently a big interest arises to the automated diagnosis and digitalization of clinical data. The purpose of this article is to present treatment algorithm and software system for Problematic Skin Wounds (PSW) by using Platelet-Rich Plasma (PRP), based on the first study on platelet-rich plasma application carried out in Bulgaria. PSW-PRP-Project software system was developed for entering and processing medical data during PRP treatment, visualization of general patient information, treatment trend, as well as a module for training specialists through the created database. For a period of seven years around 100 patients have been treatment at the Department of Orthopaedics and Traumatology, UMBAL KANEV Ruse AD, by applying platelet-rich plasma. The algorithm for the use of platelet-rich plasma for treating problematic skin wounds allows for the proper and accurate treatment of patients with various problematic skin wounds with the purpose of solving the therapeutic problem and their complete recovery. The procedure’s course is determined based on assessment on three digital criteria TWS, TAS and TSWD. The algorithms are based on our results, obtained for the first in Bulgaria while treating problematic skin wounds by using platelet-rich plasma and successfully treating 92.78% of patients to full recovery.