Halbach Magnets for Magnetic Resonance

This review is a compilation of relevant concepts in designing Halbach multipoles for magnetic resonance applications. The main focus is on providing practical guidelines to plan, design and build such magnets. Therefore, analytical equations are presented for estimating the magnetic field from ideal to realistic systems. Various strategies of homogenizing magnetic fields are discussed together with concepts of opening such magnets without force, or combining them for variable fields. Temperature compensation and other practical aspects are also reviewed. For magnetic resonance two polarities (di- and quadrupole) are of main interest, but higher polarities are also included.Comment: 37 pages, 17 Figure

Анализ электрической части Беловской ГРЭС и релейная защита блока генератор-трансформатор

Выпускная квалификационная работа 118 с., 24 рис., 21 табл., 17 источников, 6 прил. Объектом исследования является Беловская ГРЭС. Цель работы заключается в анализе электрической части Беловской ГРЭС (анализ структурной схемы, характеристики оборудования, расчет баланса мощностей и т.д.) и расчете релейной защиты блока генератор – двухобмоточный трансформатор. Для достижения поставленной цели использованы расчетные и графоаналитические методы, вычислительные расчетные комплексы CTCURR, программа для расчета продолжительных режимов электростанции «Исследование структурных схем КЭС с автотрансформаторами связи», пакеты программ Mathcad, Excel, графический редактор MS Visio. В процессе исследования проводились анализы продолжительных режимов электростанции и расчет токов коротких замыканий.Final qualifying work 118 p., 24 fig., 21 tab., 17 sources, 6 adj. The object of this study is to Belovo TPP. The purpose of work is to analyze the electrical Belovskaya GRES (analysis of structural scheme, the characteristics of the equipment, capacity balancing, etc.) and the calculation of relay protection unit generator - two-winding transformer. To achieve this goal and estimates used graphoanalitical method, computer systems design CTCURR, a program for calculating the continuous duty power "Research of structural schemes IES with autotransformers connection" packages Mathcad software, Excel, MS Visio editing. The study carried out extensive analyzes of power modes and calculation of short circuit currents

Схема управления системой термостатирования узлов скважинных приборов

Выпускная квалификационная работа 88 с., 12 рис., 20 табл., 53 источника. Ключевые слова: гироскопический инклинометр, система термостатирования, гироскопы, ШИМ-модуляция Объектом исследования являются системы термостатирования, применяемые в скважинном оборудовании Цель работы – разработка блока управления системой термостатирования гироинклинометра и проведение исследовании с его помощью В процессе исследования рассмотрены основные принципы построения систем термостатирования, выбраны оптимальные узлы. Разработана схема устройства и расчет основных элементов. В результате исследования был разработан и собран блок управления системой термостатироваия, проведена его настройка и тестирование в лабораторных условиях. Область применения: геофизика, системы ориентации и навигацииFinal qualifying work 88 p., 12 fig., 20 tab., 53 sources. Keywords: gyroscopic inclinometer, temperature control system, gyroscopes, PWM modulation The object of the study are temperature control systems used in the downhole equipment The purpose of work - development of a system control unit temperature control Gyroscopic inclinometers and conduct research with the help of The study describes the main principles of temperature control systems, selected the best sites. A diagram of the device and the calculation of the basic elements. The study was designed and assembled by a thermostatic control unit system, held its tuning and testing in the laboratory. Scope: Geophysics, orientation and navigation system

Microwave-free wide-field magnetometry using nitrogen-vacancy centers

A wide-field magnetometer utilizing nitrogen-vacancy (NV) centers in diamond that does not require microwaves is demonstrated. It is designed for applications where microwaves need to be avoided, such as magnetic imaging of biological or conductive samples. The system exploits a magnetically sensitive feature of NV centers near the ground state level anticrossing (GSLAC). An applied test field from a wire was mapped over an imaging area of $\approx 500 \times 470\,{\mu}\text{m}^2$. Analysis of the GSLAC lineshape allows to extract vector information of the applied field. The device allows micrometer-scale magnetic imaging at a spatial resolution dominated by the thickness of the NV layer (here $50\,{\mu}\text{m}$). For a pixel size of $4\,{\mu}\text{m} \times 3.8\,{\mu}\text{m}$ the estimated sensitivity is $4.8\,{\mu}\text{T}/\sqrt{\text{Hz}}$. Two modalities for visualizing the magnetic fields, static and temporal, are presented along with a discussion of technical limitations and future extensions of the method.Comment: 8 pages,6 figure

The interrelation between the electronic parameters of nitrogen atom and intramolecular interactions in ammonia derivatives

The electronic parameters and intramolecular interactions in the ground and transition states of inversion of the amines H₂NXHn (XHn=CH₃, NH₂, OH, F, SiH₃, PH₂, SH, Cl) were calculated using DFT (PBE96/def2-tzvpp) method. It was established that the electronacceptor properties of the XHn substituents has a prevailing influence on the change of the electronic parameters of nitrogen atom. Its increase leads to both a decrease of the charge on the nitrogen atom and an increase of the s-character and population of nitrogen lone pair (LP). All parameters under consideration correlate with the χ- and σᵢ-constants of the XHn substituents. The correlation coefficients increase when amines that contain X atoms only from one period are considered separately. It was found that the ρ values for amines containing X atoms from the second or third period are substantially different. The changes of the donor-acceptor interaction energies, s-character and LP population cannot be probable causes for different sensitivity of the electronic parameters of amines containing X atoms from different periods to the change of electron-acceptor properties of the XHn substituents. It was established that the mentioned parameters has only a subordinated influence in comparison with the influence of electron-acceptor ability of the XHn substituents. The negative charge on the nitrogen atom decreases with the increase of s-character and LP population and also with the decrease of energies of donor-acceptor interactions which lead to the withdrawal of electron density from the nitrogen atom. The s-character and LP population increase with the decrease of energies of donor-acceptor interactions which result in the reduction of electron density on the nitrogen atom. The total positive charges of the XHn groups and hydrogen atoms at the nitrogen atom decrease with increasing the electron-acceptor ability of the XHn substituents. The representation of the electron-acceptor properties of the substituents was shown to be more valid by using the χ-constants than by using the σᵢ-constants. The chlorine atom is a weak electron acceptor in comparison with an amino group