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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

Automated system design optimisation

Astapenko, D. January 2010 (has links)
The focus of this thesis is to develop a generic approach for solving reliability design optimisation problems which could be applicable to a diverse range of real engineering systems. The basic problem in optimal reliability design of a system is to explore the means of improving the system reliability within the bounds of available resources. Improving the reliability reduces the likelihood of system failure. The consequences of system failure can vary from minor inconvenience and cost to significant economic loss and personal injury. However any improvements made to the system are subject to the availability of resources, which are very often limited. The objective of the design optimisation problem analysed in this thesis is to minimise system unavailability (or unreliability if an unrepairable system is analysed) through the manipulation and assessment of all possible design alterations available, which are subject to constraints on resources and/or system performance requirements. This thesis describes a genetic algorithm-based technique developed to solve the optimisation problem. Since an explicit mathematical form can not be formulated to evaluate the objective function, the system unavailability (unreliability) is assessed using the fault tree method. Central to the optimisation algorithm are newly developed fault tree modification patterns (FTMPs). They are employed here to construct one fault tree representing all possible designs investigated, from the initial system design specified along with the design choices. This is then altered to represent the individual designs in question during the optimisation process. Failure probabilities for specified design cases are quantified by employing Binary Decision Diagrams (BDDs). A computer programme has been developed to automate the application of the optimisation approach to standard engineering safety systems. Its practicality is demonstrated through the consideration of two systems of increasing complexity; first a High Integrity Protection System (HIPS) followed by a Fire Water Deluge System (FWDS). The technique is then further-developed and applied to solve problems of multi-phased mission systems. Two systems are considered; first an unmanned aerial vehicle (UAV) and secondly a military vessel. The final part of this thesis focuses on continuing the development process by adapting the method to solve design optimisation problems for multiple multi-phased mission systems. Its application is demonstrated by considering an advanced UAV system involving multiple multi-phased flight missions. The applications discussed prove that the technique progressively developed in this thesis enables design optimisation problems to be solved for systems with different levels of complexity. A key contribution of this thesis is the development of a novel generic optimisation technique, embedding newly developed FTMPs, which is capable of optimising the reliability design for potentially any engineering system. Another key and novel contribution of this work is the capability to analyse and provide optimal design solutions for multiple multi-phase mission systems. Keywords: optimisation, system design, multi-phased mission system, reliability, genetic algorithm, fault tree, binary decision diagram
242

A waste minimisation framework for the procurement of design and build construction projects

Withana-Gamage, Inoka S. January 2011 (has links)
Both construction Waste Minimisation (WM) and construction procurement activities play an effective role in attaining sustainability by giving due consideration to the environment, community and social conditions in delivering built assets. The construction industry has a major impact on the environment, both in terms of resource consumption and increasing waste production. Recent figures published by the UK government reveal that construction and demolition activities produce approximately 32% of total waste generated: three times the waste produced by all households combined. However, the current and on-going research in the field of construction WM and management focuses mainly on onsite waste quantification and management; and stakeholders‟ source identification. Little research has been undertaken to evaluate the relationship between Construction Procurement Systems (CPS) and construction waste generation. However, literature emphasises the need for research in this context. This research aims to develop a Procurement Waste Minimisation Framework (PWMF) to enhance WM practices by evaluating the relationship between CPS and construction waste generation. Objectives of the research include: examine construction WM drivers, WM approaches, waste origins and causes; critically review and evaluate current CPS and sustainable procurement practices in the UK; assess the relationship between CPS and construction waste generation; investigate and synthesis Procurement Waste Origins (PWO); examine the most suitable CPS that could potentially embed and sustain WM; develop and validate the PWMF. This research has adopted a survey research design and mixed methods sequential procedure. Data has been gathered through a cross sectional, self-administered postal questionnaire survey (N=258 distributed, n=65 received) and semi-structured interviews (N=17) with procurement managers and sustainability managers from the top 100 UK contracting organisations and quantity surveyors from the top 100 UK quantity surveying organisations. Data analysis techniques include: descriptive statistics; non-parametric tests; and constant comparative method. The PWMF has developed based on the findings of literature review, questionnaire survey and semi-structured interviews and adopting key concepts of problem solving methodology. The PWMF validation method includes: validation questionnaire (N=8) and follow-up semi-structured interviews (N=6) with procurement managers, sustainability managers and quantity surveyors. Key findings which emerged from the study include: CPS do have an impact on waste generation in construction; integrated CPS have major potential to integrate WM strategies; four PWO identified (i.e. uncoordinated early involvement of project stakeholders; ineffective communication and coordination; unclear allocation of WM responsibilities; and inconsistent procurement documentation) and associated sub-waste causes; and the developed PWMF enables to diagnose potential waste origins and causes, and WM improvement measures for design and build projects. The study has made recommendations which, if adopted, will lead to significant improvements in WM practices and sustainable procurement practices in construction. The content should be of interest to contractors, clients, and organisations dealing with procurement, waste and sustainability.
243

Respect : Challenge the norms and expand the idea of what is possible

Legeby, Matilda January 2017 (has links)
In this project I have explored the situation for unaccompanied refugees in the ages 15-22 years. Being seen as part of a homogenous group was something that the girls described as frustrating and prohibiting. They, as all youths, have a need to talk about them selves, on their own terms. My design proposal is an exercise for students and teachers in high school where you are given an arena in the class room to talk about your self, your values and the norms in society. By choosing a role model and create something to wear, challenge the preconceived ideas of what is expected, create positive forward looking conversations and an opportunity to give a glimpse of who you are.  I have looked at the relations between the individual, the unaccompanied refuge girl, and the people working in the Swedish welfare system. With the help of materiality I have explored the notion of individuality, personal space and respect.  How to challenge societal norms, prejudice and expand the idea of what is possible? / I detta projekt har jag undersökt situationen för ensamkommande flyktingtjejer i åldrarna 15-22 år. Tjejerna gav uttryck för att det var begränsande och frustrerande att bli sedd som en del av en homogen grupp. De, liksom alla ungdomar, har ett behov av att få prata om sig själva på sina egna villkor.   Projektet resulterade i ett designförslag i form av en övning för alla studenter och lärare på högstadiet som skapar ett utrymme för att prata om värderingar och de normer vi har i samhället. Genom att välja en förebild och att skapa något att bära, kan man i klassrummet utmana förutfattade meningar om vad som förväntas av en, skapa positiva framåtsyftande samtal och ge de personer som finns runt dig i vardagen en liten skymt av vem du är. Jag undersökt relationerna mellan de ensamkommande tjejernana och personer som jobbar i välfärdssystemet. Med hjälp av materialitet har jag utforskat begreppen individualitet, att ta plats och respekt. Hur kan vi utmana våra fördomar, rådande normer och vidga tanken på vad som är möjligt?
244

Erotetic logic as a specification language for database queries

Jason, Gary James. January 1986 (has links)
Call number: LD2668 .T4 1986 J37 / Master of Science / Computing and Information Sciences
245

Evaluating ARCADIA/Capella vs. OOSEM/SysML for System Architecture Development

Shashank Pramod Alai (6861410) 12 August 2019 (has links)
Systems Engineering is catching pace in many segments of product manufacturing industries. Model-Based Systems Engineering (MBSE) is the formalized application of modeling to perform systems engineering activities. In order to effectively utilize the complete potential of MBSE, a methodology consisting of appropriate processes, methods and tools is a key necessity. In the last decade, several MBSE projects have been implemented in industries varying from aerospace and defense to automotive, healthcare and transportation. The Systems Modeling Language (SysML) standard has been a key enabler of these projects at many companies. Although SysML is capable of providing a rich representation of any system through various viewpoints, the journey towards adopting SysML to realize the true potential of MBSE has been a challenge. Among all, one of the common roadblocks faced by systems engineers across industries has been the software engineering-based nature of SysML which leads to difficulties in grasping the modeling concepts for people that do not possess a software engineering background. As a consequence, developing a system (or a system of systems) architecture model using SysML has been a challenging task for many engineers even after a decade of its inception and multiple successive iterations of the language specification. Being a modeling language, SysML is method-agnostic, but its associated limitations outweigh the advantages. ARCADIA (Architecture Analysis and Design Integrated Approach) is a systems and software architecture engineering method based on architecture-centric and model-based engineering activities. If applied properly, ARCADIA allows for a very effective way to model the architecture of multi-domain systems, and overcome many of the limitations faced in traditional SysML implementation. This thesis evaluates the architecture development capabilities of ARCADIA/Capella versus SysML following the Object-Oriented Systems Engineering Method (OOSEM). The study focuses on the key equivalences and differences between the two MBSE solutions from a model development perspective and provides several criteria to evaluate their effectiveness for architecture development using a conceptual case of Adaptive Cruise Control (ACC). The evaluation is based on three perspectives namely, architecture quality, ability to support key process deliverables, and the overall methodology. Towards this end, an industry-wide survey of MBSE practitioners and thought leaders was conducted to identify several concerns in using models but also to validate the results of the study. The case study demonstrates how the ARCADIA/Capella approach addresses several challenges that are currently faced in SysML implementation. From a process point of view, ARCADIA/Capella and SysML equally support the provision of the key deliverable artifacts required in the systems engineering process. However, the candidate architectures developed using the two approaches show a considerable difference in various aspects such as the mapping of the form to function, creating functional architectures, etc. The ARCADIA/Capella approach allows to develop a ‘good’ system architecture representation efficiently and intuitively. The study also provides answers to several useful criteria pertaining to the overall candidate methodologies while serving as a practitioner’s reference in selecting the most suitable approach.
246

The production of software that aids in the design of low voltage distribution networks by optimising the locations of junctions

Apostolellis, Justin January 1996 (has links)
A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 1996 / The use of computer-based tools in the design of electrical distribution networks results in the cost effective production and implementation of designs. This is because they help automate time-consuming routine tasks and enable the optimisation of certain aspects of a network design. The production of a tool that performs an optimisation on the low voltage (LV) portion of a distribution network is discussed. It uses the influence that a network's topology has on its associated cost, by applying a search that modifies the topology to result in a minimum cost. The modification of the network's topology is achieved through changing junction positions to alternative locations. It operates on an entire radial LV network, and therefore considers the coupling between junctions in the same network. The user of the tool must specify the alternative locations for each junction in the network, as well as information about the network, such as cable lengths and cable types. The search algorithm is based on an adaptation of the branch and bound method, which is a reduced search algorithm. It has been chosen as opposed to an exhaustive search algorithm to reduce computational requirements. The tool Is most useful for optimising completely underground distribution systems. Test results revealed a 7% saving in the cost of cables for a specific case study. The software has been developed with the application of object-oriented analysis and design within an ISO 9001 accredited software development environment. iii / GR2017
247

Developing a photovoltaic MPPT system

Unknown Date (has links)
Many issues related to the design and implementation of a maximum power point tracking (MPPT) converter as part of a photovoltaic (PV) system are addressed. To begin with, variations of the single diode model for a PV module are compared, to determine whether the simplest variation may be used for MPPT PV system modeling and analysis purposes. As part ot this determination, four different DC/DC converters are used in conjunction with these different PV models. This is to verify consistent behavior across the different PV models, as well as across the different converter topologies. Consistent results across the different PV models, will allow a simpler model to be used for simulation ana analysis. Consistent results with the different converters will verify that MPPT algorithms are converter independent. Next, MPPT algorithms are discussed. In particular,the differences between the perturb and observe, and the incremental conductance algorithms are explained and illustrated. A new MPPT algorithm is then proposed based on the deficiencies of the other algorithms. The proposed algorithm's parameters are optimized, and the results for different PV modules obtained. Realistic system losses are then considered, and their effect on the PV system is analyzed ; especially in regards to the MPPT algorithm. Finally, a PV system is implemented and the theoretical results, as well as the behavior of the newly proposed MPPT algorithm, are verified. / by Thomas Bennett. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
248

Low-power front-end designs for wireless biomedical systems in body area network (BAN). / CUHK electronic theses & dissertations collection

January 2012 (has links)
近年來感測器、集成電路及無線通信的科技迅速發展,促使IEEE802.15工作小組6(TG6)致力硏究一個新的無線通信標準─人體區域網路(BAN)。這個新標準特別考量在人體上、人體內或人體周邊的應用。雖然BAN至今還未達成最後定案,不同類型的應用方案已被廣泛提出。這些方案可分為醫療應用(例如:生命徵象感測和植入式治療)及非醫療應用(例如:消費性電子、個人娛樂和遙遠控制)。無線感測節點〈WSN)的基本要求包括輕巧、廉價及低耗電量。因此,本論文提出了一個符合以上要求的注入式鎖態發射機。此外,我們設計了三個發射機的內部模組。由於BAN的物理層例如調變方式和頻譜配置還未完全製訂,本文的電路設計將基於IEEE802.15 TG6的初步建議。 / 第一個模組是一個利用同相位雙路輸入及電流再使用技術的次毫瓦、第一次諧波LC注入式鎖態振盪器〈ILO)。該振盪器操作範圍在醫療植入式通訊服務〈MICS)頻段,並已採用了0.13-μm CMOS工藝實現而僅佔有200 m x 380 m芯片面積。實驗結果表明,在輸入動力0 dBm時,其鎖定範圍可達800 MHz (150 950 MHz) 。最重要的是,該ILO擁有-30 dBm的高輸入靈敏度,同時在1-V供電下只消耗660 A靜態電流。超低的靜態電流使WSN能從人體收集能量而變得完全自主。 / 第二個模組是一個低功耗MICS非整數型頻率合成器,其目的在於選擇信道。雖然整數鎖相環由於其低複雜性而被廣泛使用,對MICS頻段而言並不是一項良好方案。主要原因在於其信道寬只有300 kHz,速度、頻率解析度和相位雜訊變得很難平衡。為此,我們採用0.13-μm CMOS製程設計了一個4階第二型和差積分〈Σ-)調變器分數鎖相環。為了抑制混附單頻信號,二階單迴路數字Σ-調變器加入了抖動。仿真結果顯示該頻率合成器能在15 s內鎖定,同時在1.5-V供電下只消耗4 mW功耗。 / 第三個模組是一個高效能、完全集成的E類功率放大器〈PA)。該PA採用了自給偏壓反相器作為前置放大器,操作範圍在MICS頻段及工業、科學和醫學〈ISM)頻段。在0.18-m CMOS工藝下實現的該PA佔有0.9 mm x 0.7 mm芯片面積。實驗結果表明,在1.2-V供電下及操作頻率是433 MHz時,該PA的漏極效率及輸出功率分別可達40.2 %和14.7 dBm。當操作頻率從380 MHz 到460 MHz,該PA仍能保侍最少34.7 %的漏極效率。此設計適用於低數據傳輸率、固定振幅調變,例如:QPSK、OQPSK等。 / Recent technological advances in sensors, integrated circuits and wireless communication enable miniature devices located on, in or around the human body to form a new wireless communication standard called wireless Body Area Network (BAN). Although BAN is still being investigated by the IEEE 802.15 Task Group 6 (TG6), a vast variety of applications has been proposed which can be categorized into medical applications (e.g. vital signs monitoring and implantable therapeutic treatment) and non-medical applications (e.g. consumer electronics and remote control). The basic requirements of each Wireless Sensor Node (WSN) include light weight, small form-factor, low cost and low power consumption. This thesis proposes an injection-locked transmitter which is a potential candidate to minimize the power consumption of the RF transmitter in WSNs. Three circuit blocks in the proposed injection-locked transmitter are designed and implemented. Since the physical layer of BAN, such as modulation scheme and frequency allocation, has still not been finalized yet, the prototypes in this thesis are designed based on the preliminary suggestions made by the IEEE 802.15 TG6. / The first circuit block is a sub-mW, current-reused first-harmonic LC injection-locked oscillator (ILO) using in-phase dual-input injection technique, operating in the Medical Implantable Communications Service (MICS) band from 402MHz to 405 MHz for medical implants. It has been fabricated in a standard 0.13-m CMOS technology; occupying 200 m x 380 m. Measurement results show that the proposed ILO features a wide locking range of 800 MHz (150-950 MHz) at input power of 0 dBm. More importantly, it has a high input sensitivity of -30 dBm to lock the 3-MHz bandwidth of the MICS band, while consuming only 660 W at 1-V supply. This ultra-low power consumption enables autonomous WSNs by energy harvested from the human body. / The second circuit block is a low power MICS fractional-N frequency synthesizer for channel selection. Although integer-N phase-locked loop (PLL) is widely used due to its low circuit complexity, it is not considered as a good solution for MICS band where the channel spacing is just 300 kHz, due to the severe trade-off between speed, frequency resolution and phase noise performance. To solve this issue, a 4th-order type-II Σ- fractional-N PLL is designed using a standard 0.18-m CMOS technology. A 2nd-order single-loop digital Σ- modulator with dither is designed to eliminate the spurious tones. Simulation results verify that the synthesizer achieves 15 s locking time and consumes 4 mW at a power supply of 1.5 V. / Finally, a power-efficient fully-integrated class-E power amplifier with a self-biased inverter used as a preamplifier stage has been implemented in a standard 0.18-m CMOS process, with 0.9 mm x 0.7 mm active area. It operates in both MICS band for implantable devices and Industrial, Scientific and Medical (ISM) band for wearable devices. Experimental results shows that it achieves 40.2 % drain efficiency while output power is 14.7 dBm at 433 MHz under 1.2-V supply. Moreover, the drain efficiency maintains at least 34.7 % over the frequency range from 380 MHz to 460 MHz. This design is suitable for low data-rate, constant envelope modulation, such as QPSK, OQPSK, etc. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Kwan Wai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract of thesis entitled: --- p.I / 摘要 --- p.IV / Contents --- p.VI / List of Figures --- p.XI / List of Tables --- p.XVII / Acknowledgement --- p.XVIII / Chapter CHAPTER 1. --- Introduction --- p.1 / Chapter 1.1 --- Motivation for body area network (BAN) --- p.1 / Chapter 1.2 --- Standardization of BAN and its positioning between different communication technologies --- p.3 / Chapter 1.3 --- Classification of BAN and its potential applications --- p.5 / Chapter 1.4 --- Requirements and challenges of BAN --- p.7 / Chapter 1.5 --- Research objectives and organization of this dissertation --- p.9 / References --- p.11 / Chapter CHAPTER 2. --- Background information of biomedical transceivers --- p.12 / Chapter 2.1 --- MICS band --- p.12 / Chapter 2.1.1 --- Frequency allocation --- p.12 / Chapter 2.1.2 --- Output power --- p.13 / Chapter 2.1.3 --- Transmit spectral mask --- p.14 / Chapter 2.1.4 --- Transmit center frequency tolerance --- p.14 / Chapter 2.1.5 --- Channel model --- p.15 / Chapter 2.1.6 --- Link budget --- p.17 / Chapter 2.2 --- Fundamental figure of merits for transceivers --- p.18 / Chapter 2.2.1 --- Noise figure, noise floor and receiver sensitivity --- p.18 / Chapter 2.2.2 --- Transmitter energy efficiency --- p.19 / References --- p.20 / Chapter CHAPTER 3. --- Review of transmitter architectures --- p.21 / Chapter 3.1 --- Overview --- p.21 / Chapter 3.2 --- Architectures --- p.22 / Chapter 3.2.1 --- Quadrature --- p.22 / Chapter 3.2.2 --- Polar --- p.23 / Chapter 3.2.3 --- PLL-based --- p.24 / Chapter 3.2.4 --- Injection-locked --- p.26 / Chapter 3.3 --- Radio architecture selection for biomedical systems in BAN --- p.27 / Chapter 3.3.1 --- Data-rate --- p.27 / Chapter 3.3.2 --- Modulation scheme --- p.28 / Chapter 3.3.3 --- Proposed transmitter architecture --- p.28 / References --- p.31 / Chapter CHAPTER 4. --- Design of sub-mW injection-locked oscillator --- p.33 / Chapter 4.1 --- Introduction --- p.34 / Chapter 4.2 --- Circuit design and analysis --- p.34 / Chapter 4.3 --- Experimental results --- p.47 / Chapter 4.4 --- Summary --- p.55 / References --- p.56 / Chapter CHAPTER 5. --- Design of low-power fractional-N frequency synthesizer --- p.58 / Chapter 5.1 --- Synthesizer architectures --- p.59 / Chapter 5.2 --- PLL design fundamentals --- p.63 / Chapter 5.2.1 --- Stability --- p.63 / Chapter 5.2.2 --- Phase noise --- p.65 / Chapter 5.3 --- Proposed architecture --- p.67 / Chapter 5.4 --- System design --- p.68 / Chapter 5.4.1 --- Stability --- p.68 / Chapter 5.4.2 --- Phase noise --- p.73 / Chapter 5.5 --- Σ modulation in fractional-N synthesis --- p.75 / Chapter 5.5.1 --- Basic operating principles --- p.76 / Chapter 5.5.2 --- An accumulator as a first-order Σ- modulator --- p.78 / Chapter 5.5.3 --- Noise analysis --- p.80 / Chapter 5.5.4 --- Architectures --- p.84 / Chapter 5.5.5 --- Design and modeling --- p.87 / Chapter 5.5.6 --- Digital circuit implementation --- p.99 / Chapter 5.5.7 --- Measurement results --- p.104 / Chapter 5.6 --- Time domain behavioral modeling --- p.104 / Chapter 5.7 --- Design of building blocks --- p.106 / Chapter 5.7.1 --- VCO --- p.107 / Chapter 5.7.1.1 --- Principles --- p.107 / Chapter 5.7.1.2 --- Circuit design --- p.111 / Chapter 5.7.2 --- PFD --- p.131 / Chapter 5.7.2.1 --- Principles --- p.131 / Chapter 5.7.2.2 --- Circuit design --- p.133 / Chapter 5.7.3 --- CP --- p.136 / Chapter 5.7.3.1 --- Principles --- p.136 / Chapter 5.7.3.2 --- Circuit design --- p.137 / Chapter 5.7.4 --- Frequency divider --- p.138 / Chapter 5.7.4.1 --- Principles --- p.138 / Chapter 5.7.4.2 --- Circuit design --- p.145 / Chapter 5.7.5 --- Loop filter --- p.148 / Chapter 5.8 --- Layout issues --- p.149 / Chapter 5.9 --- Overall simulation results --- p.150 / Chapter 5.1 --- Summary --- p.152 / References --- p.153 / Chapter CHAPTER 6. --- Design of high-efficient power amplifier --- p.154 / Chapter 6.1 --- Classification of PAs --- p.154 / Chapter 6.2 --- Circuit design considerations --- p.158 / Chapter 6.3 --- Experimental results --- p.160 / Chapter 6.4 --- Summary --- p.164 / References --- p.166 / Chapter CHAPTER 7. --- Conclusions and future work --- p.167 / Chapter 7.1 --- Conclusions --- p.167 / Chapter 7.2 --- Future work --- p.168 / References --- p.171
249

A low-cost active RFID indoor locationing system using phased array technology. / Low-cost active radio frequency identification indoor locationing system using phased array technology

January 2012 (has links)
近十年來,無線通訊技術、流動電話服務以及無線網絡的發展一日千里。不單止為社會帶來很多新的技術及先進的設備,更加帶來了許多新穎的應用構想。其中最被廣泛討論的要數室內無線實時定位系統。室內定位,顧名思義就是一種對一個或多個室內目標進行定位及追蹤的技術。這種技術的潛在應用非常多元化,例如倉庫管理、人力資源調配等等。透過這種技術可以使一些室內位置信息相關的服務更加自動化,從而提升服務效率。正因為市場狂熱的需求,近年來室內無線實時定位系統一直都是一個熱門的研究課題。 / 本論文的上半部主要是討論一種基於無線射頻識別技術的室內無線實時定位系統。這個系統的特點是在閱讀器的天線上應用了模擬一維綫相控陣列天線。系統的定位原理是基於三角測距法,透過相控陣的主波束掃描配合信號強度測量去估算出信號入射角。比較其他入射角測量的方法,應用這種方法的硬件成本更低而且能確保一定的精度。整個系統的開發包括有無線射頻標籤、閱讀器、模擬一維綫相控陣列天線、網絡控制器、數據庫、圖像應用界面及一種有效壓抑室內多徑問題的定位算法。這個系統的最大好處就是它不像其他一些現存的定位系統一樣,在安裝後需要進行大量的離線實地校準。我們進行了大量的實驗去客觀地驗證系統的定位性能,實驗的結果指出系統的定位誤差平均值小於一米。 / 為了控制系統的硬件成本,上述所提及到的模擬一維綫相控陣列天線會採用一種非常便宜的板材:FR4。但是FR4這種板材便宜的代價便是它相對較高的介質損耗。較高的介質損耗對模擬一維綫相控陣列天線的實現存在着一個重要的難題:模擬360º移相器的插入損耗相對電壓變化不平滑。有見及止,本論文的下半部會討論一種新穎而有效壓抑因高介質損耗而導致插入損耗不平滑的反射式移相器。新的移相器設計包含兩種壓抑插入損耗不平滑的技術。在仿真結果中,新的設計把傳統設計的插入損耗不平滑從1.4分貝大幅降低至0.3分貝。實驗的結果指出,在360o 的移相範圍內只存在着0.6分貝的插入損耗不平滑。 / 最後在此作一個總結。本論文主要是討論一種高效、低成本、基於無線射頻識別技術及模擬一維綫相控陣列天線技術的室內無線實時定位系統。大量的實驗數據證明了它良好的定位性能。而且系統的網絡設計使到它可以更彈性地應用到不同的場所。 / In recent years, the rapid development in wireless communication technologies, mobile computing devices and wireless networks has stimulated a fast growing interest in various location-aware systems that can provide real time information of physical locations of objects or persons. In this thesis, an active radio frequency identification (RFID) indoor positioning system utilizing analog linear phased array antenna (PAA) technology has been proposed and demonstrated. By using beam steering of an analog linear PAA and measuring the corresponding received signal strength indicator (RSSI), one can determine the angle of arrival (AoA) of the transmitted signal from a tag. In this work, a complete locationing system has been built, which includes RFID tag, reader integrated PAA, network controller and database with event driven functions. Besides that, a novel positioning algorithm that can effectively overcome indoor multipath effect is also proposed. The major advantage of the proposed system is that it doesn’t require any on-site calibration. Therefore, the setup of the proposed system is scenario-independent. A large number of experiments and results have demonstrated that the probabilities of spatial errors of less than 1 meter and 1.5 meters of the proposed system are about 80% and 95% respectively. / In order to have a cost-effective system, those analog linear PAAs are fabricated in FR4 substrate, with which constant insertion loss under phase steering of a 360º analog phase shifter is difficult to realize due to the substrate loss. In order to overcome this difficulty, a novel loss-compensated microstrip 360º reflection-type diode phase shifter with constant insertion loss has been proposed and concept proven. In this regard, two techniques have been investigated to reduce the insertion loss variation which is caused by using lossy substrate. As compared with the conventional design, simulation results have shown a considerable improvement on the insertion loss variation from 1.4dB to 0.3dB. Measurement results have demonstrated a 0.6dB insertion loss variation over 360º phase steering range. / In conclusion, a low-cost but with moderate performance RFID indoor locationing system based on analog linear PAA technology has been proposed and experimentally demonstrated. The prototype system has shown its high accuracy, flexibility in network deployment, and scenario-independent operation. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Hung, Wing Hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 85-87). / Abstracts also in Chinese. / ABSTRACT --- p.I / 論文摘要 --- p.III / ACKNOWLEDGEMENT --- p.V / TABLE OF CONTENT --- p.VI / LIST OF FIGURES --- p.IX / LIST OF TABLES --- p.XIII / LIST OF ABBREVIATIONS --- p.XIV / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1. --- RESEARCH MOTIVATION --- p.1 / Chapter 1.2. --- OVERVIEW OF THE THESIS ORGANIZATION --- p.5 / Chapter CHAPTER 2 --- FUNDAMENTALS IN LINEAR PHASED ARRAY ANTENNA AND REFLECTION-TYPE PHASE SHIFTER --- p.6 / Chapter 2.1. --- LINEAR PHASED ARRAY ANTENNA --- p.6 / Chapter 2.1.1. --- Operating Principle --- p.7 / Chapter 2.1.2. --- Simulation Example --- p.9 / Chapter 2.2. --- REFLECTION-TYPE PHASE SHIFTER --- p.10 / Chapter 2.2.1. --- Operating Principle --- p.10 / Chapter 2.2.2. --- Simulation Example --- p.12 / Chapter CHAPTER 3 --- CONVENTIONAL INDOOR POSITIONING METHODOLOGIES --- p.15 / Chapter 3.1. --- RSSI RANGING --- p.15 / Chapter 3.1.1. --- Radio Fingerprint --- p.15 / Chapter 3.1.2. --- Radio Propagation Model --- p.17 / Chapter 3.1.3. --- Reference Tags --- p.18 / Chapter 3.1.4. --- Ordered Signal Strength Sequence --- p.19 / Chapter 3.2. --- UWB RANGING --- p.20 / Chapter 3.3. --- NEAR FIELD ELECTROMAGNETIC RANGING (NFER) --- p.21 / Chapter CHAPTER 4 --- CONVENTIONAL 360º REFLECTION-TYPE PHASE SHIFTER DESIGNS --- p.23 / Chapter 4.1. --- PARALLELING TWO SERIES-RESONANT VARACTOR CIRCUIT --- p.23 / Chapter 4.1.1. --- 360º Phase Shift --- p.24 / Chapter 4.1.2. --- Constant Insertion Loss --- p.24 / Chapter 4.1.3. --- Performance --- p.25 / Chapter 4.2. --- PARALLELING TWO ARMS HAVING 180O PHASE CHANGE WITH 90º OUT OF PHASE --- p.27 / Chapter 4.2.1. --- Linearity and 180º Phase Shift --- p.27 / Chapter 4.2.2. --- Constant Insertion Loss --- p.29 / Chapter 4.2.3. --- 360º Phase Shift --- p.29 / Chapter 4.2.4. --- Performance --- p.30 / Chapter 4.3. --- CONNECTING TWO ARMS HAVING 180O PHASE CHANGE WITH 90O OUT OF PHASE IN-SERIES --- p.31 / Chapter 4.3.1. --- Constant Insertion Loss --- p.31 / Chapter 4.3.2. --- 360º Phase Shift --- p.32 / Chapter 4.3.3. --- Performance --- p.32 / Chapter CHAPTER 5 --- AN ACTIVE RFID INDOOR POSITIONING SYSTEM UTILIZING ANALOG LINEAR PHASED ARRAY --- p.34 / Chapter 5.1. --- POSITIONING METHODOLOGY --- p.35 / Chapter 5.2. --- SYSTEM ARCHITECTURE --- p.37 / Chapter 5.2.1. --- Analog Linear Phased Array Antenna --- p.39 / Chapter 5.3. --- POSITIONING ALGORITHM --- p.51 / Chapter 5.3.1. --- Zone Decision --- p.51 / Chapter 5.3.2. --- Point Location --- p.52 / Chapter 5.4. --- EXPERIMENTAL RESULT --- p.58 / Chapter CHAPTER 6 --- NOVEL 360º REFLECTION-TYPE DIODE PHASE SHIFTER WITH CONSTANT INSERTION LOSS UNDER LOSSY SUBSTRATE --- p.65 / Chapter 6.1. --- REVIEW --- p.66 / Chapter 6.2. --- PROBLEMS --- p.68 / Chapter 6.3. --- PROPOSED SOLUTIONS --- p.71 / Chapter 6.3.1. --- Closed Reflection Coefficient Circle --- p.71 / Chapter 6.3.2. --- Centered Reflection Coefficient Circle --- p.74 / Chapter 6.4. --- SIMULATION AND MEASUREMENT RESULT --- p.77 / Chapter CHAPTER 7 --- CONCLUSION --- p.83 / REFERENCES --- p.85 / AUTHOR’S PUBLICATIONS --- p.88 / Chapter APPENDIX 1: --- DESIGN OF RFID TAG --- p.89 / Chapter APPENDIX 2: --- DESIGN OF RFID READER --- p.98 / Chapter APPENDIX 3: --- DESIGN OF RFID CONTROLLER --- p.100
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Student experiences with instructional videos in online learning environments

Hibbert, Melanie C. January 2016 (has links)
Drawing upon qualitative methods of semi-structured interviews and observational talk-through interviews, this qualitative dissertation investigates the ways in which graduate students in an online course context experience online instructional videos. A conceptual framework of user experience and multimodality, as well as the framework of sense-making developed by McCarthy and Wright (2004) guided this study and data analysis. The findings of this dissertation have implications for how students are participating in, interacting with, and making sense of online learning environments. Some of the findings of this research include: (a) students do not necessarily experience course videos as discrete elements (or differentiate them with other aspects of the course); (b) the times and contexts in which students view instructional videos shifts (e.g., between home and commuting); (c) student motivations and expectations shape how they approach and orient themselves towards watching online course videos; and (d) multimodal design elements influence students’ meaning-making of online instructional videos. These data findings are all in support of the overarching conclusion of this dissertation, which is that students have significant agency in these online environments, and their meaning-making of online videos may not align with designers’ intentions. This conclusion argues against deterministic views of design. The emerging findings have design implications related to the creation of learning environments in online spaces, such as: (a) fully integrating videos within the broader instructional design of a course; (b) foregrounding the embedded context of instructional videos; and (c) accounting for the shifting times, places, and contexts in which viewers watch instructional videos. This dissertation is situated in the growing field of online education, in particular higher education, where significant money and resources are increasingly dedicated towards the development of online spaces while still much is unknown in relation to the design, experiences, and impact of these online learning environments.

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