Electrooptic electric field sensor for dc and extra-low-frequency measurement

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The thesis reports the results of the research carried out towards the development of an electrooptic sensor for DC and extra low frequency electric field measurement. Available cubic electrooptic crystals were compared from the sensor sensitivity point of view. A new figure of merit was used taking into account the attenuation of the electric field in the dielectric crystal and its shape. The effect of optical activity in 23 cubic crystals was analyzed using the concept of Poincare sphere. The cubic crystals were further characterised for the charge relaxation time constant to estimate their performance in DC field measurements. Crystals of Bismuth Germanate and Lithium Niobate were identified as suitable materials for the DC field sensor. The selected crystals were found suitable at extra-low-frequencies. DC field measurements, without the rotation of the crystal, were possible only with Lithium Niobate. However, its performance was influenced to a great extent by the effect of stimulated conductivity. The quarter-wave plate and the crystal of Lithium Niobate were identified as the main sources of temperature instability. A new method of temperature compensation of the quarter-wave plate is proposed. Due to the temperature instability of Lithium Niobate, mainly attributed to the pyroelectric effect and natural birefringence, it is difficult to use the sensor in practical applications. The performance of the sensor is significantly affected by the presence of an external space charge. The proposed method of its elimination using an artificial extension of the sensing element did not reduce the space charge effect adequately. The response of the sensor in a space charge environment was found to be linear and independent of the space charge density. This enabled measurements of static fields in a unipolar environment. The direct field measurements in bipolar environment suffered from a drift which is intolerable in practical measurements. The minimum detectable electric field of this sensor in the frequency range from 1 to 200Hz was 1V/m, with a signal to noise ratio equal to 0dB and a resolution of 1V/m. The static field measurements were limited to measurements of pulses with a duration of 200s, due to a long term drift of photodetectors. The minimum detectable level of DC electric field was 2.4kV/m.EPSR

Communicative strategies of modern university education

Peer Reviewe

Estimating the Spatial Distribution of Groundwater Demand In the Texas High Plains

Developing groundwater management plans requires a good understanding of the interdependence of groundwater hydrology and producer water use behavior. While state-of-the-art groundwater models require water demand data at highly disaggregated levels, the lack of producer water use data has held up the progress to meet that need. This paper proposes an econometric framework that links county-level crop acreage data to well-level hydrologic data to produce heterogeneous patterns of crop choice and irrigation practices within a county. Together with agronomic data on irrigation water requirements of various crops and irrigation practices, this model permits estimation of the water demand distribution within a county. We apply this model to a panel of 16 counties in the Southern Texas High Plains from 1972 to 2000. The results obtained not only are consistent with those from the traditional multinomial logit land use model, but also indicate the presence of large intra- and inter-county heterogeneity in producer water use behavior.Discrete Choice Model, Random-coefficients Discrete Choice Model, Crop Choice, BLP, Groundwater, Texas High Plains, Ogallala Aquifer, Crop Production/Industries, Resource /Energy Economics and Policy,

Problems and Tasks of Higher Pedagogical Education at the Present Stage of Country’s Development

The analysis of the reasons why numerous attempts to update the Russian education system do not lead to the desired result and cause increasing criticism is carried out. One of the main reasons is seen in the violation of the systematic approach in solving the issues of the development of education in modern conditions. It is pointed out that the educational sphere, in fact, is always based on solving three problems: “what to teach”, “how to teach”, “why to teach”.The key question, that illuminates everything else, is the main question – in what social, economic and technological structure of society a person who receives education at any level, from preschool to university, has to live and work. Violation of the sequence of solving these problems, their inconsistency and the lack of a scientific justification ahead of the decisions made, inevitably lead to internal contradictions in the system being built and reduce its effectiveness.The analysis of why the Bologna system, which is widespread in a large number of countries with different levels of socio-economic status, turned out to be ineffective in Russia was made. It is shown that this system in its origin is a system of general higher non-professional education and an attempt to adapt it for receiving professional education in our country cannot be successful by its definition. It is said about the need of building a domestic multi-level system of professional higher education in modern conditions

Activity-Based Costing System Required For Successful Customer Relationship Management

The purpose of this paper is to discuss the importance of Activity-Based Costing to successful Customer Relationship Management.  The value a customer adds to a company through customer loyalty, using Customer Profitability Analysis

New Irrigation System Design for Maximizing Irrigation Efficiency and Increasing Rainfall Utilization

A new concept in irrigation system design, which has the potential of significant savings in both water and energy requirements, has been developed and is under evaluation. The system is characterized by and has been labeled a low energy-precision application (LEPA) system, which rather than spraying water into the air at moderate to high pressures, distributes it directly to the furrow at very low pressure through drop tubes and orifice controlled emitters. This occurs as the system continuously moves through the field in a rectilinear fashion. The system is used in conjunction with micro-basin land preparation which also optimizes the utilization of rainfall. The combined system minimizes the effect of soil and climatic variables which adversely influence furrow and sprinkler irrigation efficiencies. Significant savings of both water and energy resources are indicated from results of the limited testing to date

Dryland Wheat Response to Nitrogen and Phosphorus Fertilization.

8 p

CFD Simulation and Measurement of Flow Forces Acting on a Spool Valve

Directional control valves are widely used in hydraulic systems to control the flow direction and the flow rate. In order to design an actuator for such a valve a preliminary analysis of forces acting on the spool is necessary. The dominant axial force is the so called steady flow force, which is analysed within this study. For this purpose a 2/2-way spool valve with a sharp control edge was manufactured and investigated. CFD simulations were carried out to visualize the fluid flow inside the valve. The measured and simulated axial forces and pressure drops across the test valve are compared and show good qualitative correlation. However, the simulated values of axial forces are in average by 32 % lower compared with the measured ones. Therefore, the components of the axial force were scrutinized revealing a dominancy of the pressure force acting on ring areas in the spool chamber. Although CFD simulations are preferably used to save resources, the results of this study emphasise the importance of the experiments

Maintaining Subsurface Drip Irrigation Systems

6 pp., 3 tables, 1 illustration, 6 color photosA subsurface drip irrigation system should last more than 20 years if properly maintained. Important maintenance procedures include cleaning the filters, flushing the lines, adding chlorine and injecting acids. Details of these procedures are presented in a practical format