Low power rf transceivers

This thesis details the analysis and design of ultra-low power radio transceivers operating at microwave frequencies. Hybrid prototypes and Monolithic Microwave Integrated Circuits (MMICs) which achieve power consumptions of less than 1 mW and theoretical operating ranges of over 10 m are described. The motivation behind the design of circuits exhibiting ultra low power consumption and, in the case of the MMICs, small size is the emerging technology of Wireless Sensor Networks (WSN). WSNs consist of spatially distributed ‘nodes’ or ‘specks’ each with their own renewable energy source, one or more sensors, limited memory, processing capability and radio or optical link. The idea is that specks within a ‘speckzone’ cooperate and share computational resources to perform complex tasks such as monitoring fire hazards, radiation levels or for motion tracking. The radio section must be ultra low power e.g. sub 1 mW in order not to drain the limited battery capacity. The radio must also be small in size e.g. less than 5 x 5 mm so that the overall speck size is small. Also, the radio must still be able to operate over a range of at least a metre so as to allow radio contact between, for example, rooms or relatively distant specks. The unsuitability of conventional homodyne topologies to WSNs is discussed and more efficient methods of modulation (On-Off Keying) and demodulation (non-coherent) are presented. Furthermore, it is shown how Super-Regenerative Receivers (SRR) can be used to achieve relatively large output voltages for small input powers. This is important because baseband Op-Amps connected at the RF receiver output generally cannot amplify small signals at the input without the output being saturated in noise (10mV is the smallest measured input for 741 Op-Amp). Instrumentation amplifiers are used in this work as they can amplify signals below 1mV. The thesis details the analysis and design of basic RF building blocks: amplifiers, oscillators, switches and detectors. It also details how the circuits can be put together to make transceivers as well as describing various strategies to lower power consumption. In addition, novel techniques in both circuit and system design are presented which allow the power consumption of the radio to be reduced by as much as 97% whilst still retaining adequate performance. These techniques are based on duty cycling the transmitter and receiver and are possible because of the discontinuous nature of the On-Off Keying signal. In order to ease the sensitivity requirements of the baseband receive amplifier a design methodology for large output voltage receivers is presented. The designed receiver is measured to give a 5 mV output for an input power of -90 dBm and yet consumes less than 0.7 mW. There is also an appendix on the non linear modelling of the Glasgow University 50nm InP meta-morphic High Electron Mobility Transistor (50nm mHEMT) and one on the non linear modelling of a commercial Step Recovery diode (SRD). Models for the 50 nm mHEMT and the SRD are useful in the analysis, simulation and design of oscillators and pulse generators respectively

A Study of the Histopathological Changes in the Retina and Late Changes in the Visual Field in Acute Methyl Alcohol Poisoning

Abstract Not Provided

Energy storage in the UK electrical network : estimation of the scale and review of technology options

This paper aims to clarify the difference between stores of energy in the form of non-rechargeable stores of energy such as fossil-fuels, and the storage of electricity by devices that are rechargeable. The existing scale of these two distinct types of storage is considered in the UK context, followed by a review of rechargeable technology options. The storage is found to be overwhelmingly contained within the fossil-fuel stores of conventional generators, but their scale is thought to be determined by the risks associated with long supply chains and price variability. The paper also aims to add to the debate regarding the need to have more flexible supply and demand available within the UK electrical network in order to balance the expected increase of wind derived generation. We conclude that the decarbonisation challenge facing the UK electricity sector should be seen not only as a supply and demand challenge but also as a storage challenge. (c) 2010 Elsevier Ltd. All rights reserved

Person Level Statistics Using Linked Employer-Employee Data

New statistical measures were published in a report by Statistics New Zealand on 24 October 2006 from the Linked Employer-Employee Data Set (LEED). LEED uses longitudinal information from existing taxation and Statistics NZ Sources to provides a range of information on the dynamics of the New Zealand labour market. New statistics have been produced for the first time on income transitions, job tenure, multiple job holding and the self-employed. The use of administrative data allows Statistics New Zealand to produce new statistics at level of regional and industry detail not available from existing sources. Detailed statistics from the 2000 to 2005 tax years are available on the Statistics New Zealand web-site. The statistics are mostly person-level statistics for the period to the end of the 2005 tax year. This paper provides highlight from this report, covering three areas: earnings transitions, multiple job holding as well as new information on self-employment. LEED can produce these outputs across time and three other dimensions, age, sex and regional council area. Not all of this information is provided in the annual release, but is available, free of change, on Statistics New Zealand’s web based Table Builder product

A Source of Polarised Electrons for the Study of Polarisation Effects in Polarised Electron-Atom Scattering

A source of polarised electrons suitable for use in a crossed-beam electron/atom scattering experiment has been built. The electrons were polarised by scattering them elastically from mercury atoms in a crossed-beam experiment. The electron polarisation was investigated for electron energies between 6 eV and 44 eV in the angular range from 30o to 130o. Spin analysis was performed by means of a 100 keV Mott scattering experiment from a gold target at a scattering angle of 120o. The intensity of the polarised electron beam was monitored simultaneously with the polarisation measurements. A maximum polarisation of (67.2 ± 8.2)% was obtained for an incident electron energy of 14 eV at a scattering angle of 95o. However, as a source of polarised electrons, the optimum conditions were obtained when the electron energy was 13 eV at a scattering angle of 95o. Under these conditions an electron polarisation of (62.7 ± 8.0)% was measured with an electron current in the alkali interaction region of 3.10-12A. Comparison with the results of previous theoretical and experimental studies of electron polarisation in low energy scattering from mercury show good agreement with the polarisation values and differential cross-sections

Theoretical and practical considerations in Z-plasty practice

The Z-plasty is used in 2 main sets of circumstances: in contractures and in facial scars. In these situations it functions for practical purposes in a single plane, or, more accurately. its theoretical basis can be discussed in terms of 2 dimensions. There is, however, a group of miscellaneous uses for the z-plasty which involve a third dimension, creating a curving Z-plasty. In all of these circumstances certain modifications of method are necessary to make full use of its virtues. Many of these modifications arose Initially in the context of hand surgery, because of the strict limitations Imposed by the anatomical factors operating in the hand. The theoretical background of the Z-plasty and the practical considerations arising therefrom are discussed In relation to these 4 aspects of its use. When the Z-plasty Is used in contractures the lengthening which relieves the contracture is achieved at the expense of shortening In the axis perpendicular to the contracture. The amount of lengthening and the corresponding amount of shortening is shown to result from variation in the size of the Z-plasty angles and the length of the Z-plasty limbs. Formulae are developed to prove this fact and derive quantitative results. The formulae also permit elucidation of the factors which limit angle size and limb length of the Z-plasty as used in practice. A rationale is also provided for the use of the multiple Z-plasty, a modification of standard Z-plasty technique used when tissue available for shortening is strictly limited. Used In scars, the Z-plasty, by virtue of the fact that the central limb of the completed Z-plasty lies at an angle to its pre-operative line, is able to break the continuous line of the scar. Assuming that it is possible to design the Z-plasty so that its central limb lies post-operatlvely on or parallel to a wrinkle the Z-plasty will have the effect of converting a long and relatively conspicuous scar Into a series of short and less conspicuous scars connected by lines (represented by each z-plasty central limb) lying In or parallel to the wrinkles. The method developed to enable the central limb to be placed with precision In terms of length, position and direction. Initially for the 6

Promoting Intercultural Competence in Professional Spaces: Education Abroad Experiences in England for Social Studies Pre-Service Teachers

This article presents a qualitative case study of U.S. social studies pre-service teachers (PSTs) interning in England. We explore how these experiences influence their teaching and their orientation towards culture and cultural difference, and how the structure of education abroad programs are designed to support growth in cultural competence and orientations towards teaching history. Participants are enrolled in a teacher education program that affords social studies PSTs an opportunity to study abroad in England post-student teaching. For this study the developmental model of intercultural sensitivity (DMIS) provided the conceptual frame to explore intercultural competence as it presents a continuum of ethnocentric to ethnorelative perspectives (Hammer & Bennett, 2003). Using this conceptual framework, data were collected from 32 social studies PSTs representing three annual cohorts who participated in the education abroad program from 2015-2017. Data from weekly student journals were captured and qualitatively analyzed. Participants wrote journal entries prior to departure, while abroad, and upon reentry to the United States in response to instructor generated prompts. Three broad themes emerged across the data: (1) living and interning in English society challenged facets of PSTs’ cultural identity and professional practices, (2) PSTs more critically examined their orientation towards social studies education as a discipline, and (3) PSTs expanded their awareness of broader educational issues and concerns. Implications offer insight to how education abroad programs impact pre-service social studies teachers’ pedagogical practices

Correlation clustering in data streams

In this paper, we address the problem of correlation clustering in the dynamic data stream model. The stream consists of updates to the edge weights of a graph on n nodes and the goal is to find a node-partition such that the end-points of negative-weight edges are typically in different clusters whereas the end-points of positive-weight edges are typically in the same cluster. We present polynomial-time, O(n·polylog n)-space approximation algorithms for natural problems that arise. We first develop data structures based on linear sketches that allow the “quality” of a given node-partition to be measured. We then combine these data structures with convex programming and sampling techniques to solve the relevant approximation problem. However the standard LP and SDP formulations are not obviously solvable in O(n·polylog n)-space. Our work presents space-efficient algorithms for the convex programming required, as well as approaches to reduce the adaptivity of the sampling. Note that the improved space and running-time bounds achieved from streaming algorithms are also useful for offline settings such as MapReduce models