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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.
51

Reverse engineering homeostasis in molecular biological systems

Quo, Chang Feng 15 May 2013 (has links)
This dissertation is an initial study of how modern engineering control may be applied to reverse engineer homeostasis in metabolic pathways using high-throughput biological data. This attempt to reconcile differences between engineering control and biological homeostasis from an interdisciplinary perspective is motivated not only by the observation that robust behavior in metabolic pathways resembles stabilized dynamics in controlled systems, but also by the challenges forewarned in achieving a true meeting of minds between engineers and biologists. To do this, a comparator model is developed and applied to model the effect of single-gene (SPT) overexpression on C16:0 sphingolipid de novo biosynthesis in vitro, specifically to simulate and predict potential homeostatic pathway interactions between the sphingolipid metabolites. Sphingolipid de novo biosynthesis is highly regulated because its pathway intermediates are highly bioactive. Alterations in sphingolipid synthesis, storage, and metabolism are implicated in human diseases. In addition, when variation in structure is considered, sphingolipids are one of the most diverse and complex families of biomolecules. To complete the modeling paradigm, wild type cells are defi ned as the reference that exhibits the "desired" pathway dynamics that the treated cells approach. Key model results show that the proposed modern engineering control approach using a comparator to reverse engineer homeostasis in metabolic systems is: (a) eff ective in capturing observed pathway dynamics from experimental data, with no signifi cant di fference in precision from existing models, (b) robust to potential errors in estimating state-space parameters as a result of sparse data, (c) generalizable to model other metabolic systems, as demonstrated by testing on a separate independent dataset, and (d) biologically relevant in terms of predicting steady-state feedback as a result of homeostasis that is verifi ed in literature and with additional independent data from drug dosage experiments.
52

High-speed analog-to-digital conversion in SiGe HBT technology

Li, Xiangtao 19 May 2008 (has links)
The objective of this research is to explore high-speed analog-to-digital converters (ADCs) using silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for wireless digital receiver applications. The stringent requirements of ADCs for the high-performance next-generation wireless digital receiver include (1) low power, (2) low cost, (3) wide input signal bandwidth, (4) high sampling rate, and (5) medium to high resolution. The proposed research achieves the objective by implementing high-performance ADC's key building blocks and integrating these building blocks into a complete sigma-delta analog-to-digital modulator that satisfies the demanding specifications of next-generation wireless digital receiver applications. The scope of this research is divided into two main parts: (1) high-performance key building blocks of the ADC, and (2) high-speed sigma-delta analog-to-digital modulator. The research on ADC's building blocks includes the design of two high-speed track-and-hold amplifiers (THA) and two wide-bandwidth comparators operating at the sampling rate > 10 GS/sec with satisfying resolution. The research on high-speed sigma-delta analog-to-digital modulator includes the design and experimental characterization of a high-speed second-order low-pass sigma-delta modulator, which can operate with a sampling rate up to 20 GS/sec and with a medium resolution. The research is envisioned to demonstrate that the SiGe HBT technology is an ideal platform for the design of high-speed ADCs.
53

Tvorba projektů PPP v rámci ČR / Creating of PPP in Czech republic

Šarochová, Petra January 2008 (has links)
PPP is a generally accepted way of ensuring public services or public infrastructure on the basis of long-term contractual relationship, where public and private sectors share mutual benefits and risks resulting from the effort to secure the public infrastructure or public services . According to the current financial crisis, I think that the issue of PPP projects will be more important not only in the area of the Czech republic, but also in the whole world. The public sector is for the private partner reliable contractual partner. In a situation where is a lack of orders, we can expect that implementation of PPP projects will increase. Any PPP project was successfully completed in the Czech republic, the reason can be insufficient information, political and legislative support.
54

Possibilities for PPP in the Czech Republic / Možnosti využití metody PPP v ČR

Jílek, Petr January 2008 (has links)
Government of Czech republic approved in May this year concession project in two pilot PPP projects, which opens up new possibilities of implementation and the provision of costly public goods in the Czech Republic. In his thesis, I will refer to the use of methods of public-private partnerships in the implementation of individual projects in the Czech Republic. In the theoretical description for the situation it is appropriate to this method (including the exact type) to use as a stage where it is better to use the method of procurement. Furthermore, I will give a legislative framework of PPP projects in EU countries and selected non-member countries. The practical part is focus on specific PPP projects that are in the Czech Republic are beginning to realize and I assess their risks, advantages and disadvantages in comparison with the already carried out projects in abroad and it is not convenient to deal with such projects through public-private partnerships. The aim of this thesis is to clarify the existing conditions of the possible impact on use of the PPP
55

Analysis and Design of a High-Frequency RC Oscillator Suitable for Mass Production / Analys och konstruktion av en högfrekvent RC-svängningskrets lämplig för massproduktion

Dai, Jianxing January 2017 (has links)
Oscillators are components providing clock signals. They are widely required by low-cost on-chip applications, such as biometric sensors and SoCs. As part of a sensor, a relaxation oscillator is implemented to provide a clock reference. Limited by the sensor application, a clock reference outside the sensor is not desired. An RC implementation of the oscillator has a balanced accuracy performance with low-cost advantage. Hence an RC relaxation oscillator is chosen to provide the clock inside the sensor. This thesis proposes a current mode relaxation oscillator to achieve low frequency standard deviation across different supplies, temperatures and process corners. A comparison between a given relaxation oscillator and the proposed design is made as well. All oscillators in this thesis use 0.18 μm technology and 1.8 V nominal supply. The proposed oscillator manages to achieve a frequency standard deviation across all PVT variations less than ±6.5% at 78.4 MHz output frequency with a power dissipation of 461.2 μW. The layout of the oscillator's core area takes up 0.003 mm2.
56

Indoor positioning system using ultrasound combined with multilateration

Eiselt, Jonas, Mahmoud, Danial January 2018 (has links)
Under det senaste decenniet har inomhuspositionering fått en ökad popularitet och stått i fokus för forskning och utveckling, eftersom det ger praktiska möjligheter till att spåra och navigera objekt och människor i inomhusmiljöer. Det finns ingen global lösning för inomhuspositionering baserat på en enstaka teknologi såsom det gör för utomhuspositionering med sin satellitbaserade globala positioneringssystem. Många inomhusteknologier står inför många utmaningar såsom låg positioneringsnoggrannhet samt dyr och stor hårdvara. Den här uppsatsen beskriver hur en simpel och kostnadseffektiv lösning, som addresserar problemen med noggrannheten och hårdvarukostnaden, genom en iterativ forskningsmetod, utvecklades. Vår lösning är ett ultraljudsbaserat passivt sändare-mottagare system som kombinerar multilateration som positioneringsteknik och tidsskillnad av ankomst (TDOA) som mätprincip för att beräkna en 3D-position inuti en 4x2x2 m testyta med en övergripande noggrannhet på 16 cm inom ett 95% konfidensintervall. Vi registrerade noggranna TDOA-värden med en komparatorkrets som fungerade som en amplitud-trigger. Det här tillvägagångssättet var mycket enklare än vad andra relaterade arbeten använde sig av, vilket var sampling för att bearbeta inkommande signaler från sändarna. / During the past decade, indoor positioning has gained more popularity and has become a focus of research and development as it provides practical possibilities to track and navigate objects and people in indoor environments. There is no overall solution for indoor positioning based on a single technology like the solution for outdoor positioning with its satellite-based global positioning system. Many indoor positioning technologies today face many challenges such as low positioning accuracy, expensive and large hardware. This thesis describes how a simple and cost-effective solution, that addresses the problem of accuracy and space cost with regards to hardware being used, was developed through an iterative research methodology. Our solution is an ultrasound-based passive receiver-transmitter system that combines multilateration as a positioning technique and time difference of arrival (TDOA) as a measuring principle. This combination is used to calculate a 3D position within a 4x2x2 m test area with an overall accuracy of 16 cm within a 95% confidence interval. We registered accurate TDOA values with a comparator circuit that acts as an amplitude trigger. This approach was much more simple than that of other related works which used sampling to process incoming signals from the transmitters.
57

On Process Variation Tolerant Low Cost Thermal Sensor Design

Remarsu, Spandana 01 January 2011 (has links) (PDF)
Thermal management has emerged as an important design issue in a range of designs from portable devices to server systems. Internal thermal sensors are an integral part of such a management system. Process variations in CMOS circuits cause accuracy problems for thermal sensors which can be fixed by calibration tables. Stand-alone thermal sensors are calibrated to fix such problems. However, calibration requires going through temperature steps in a tester, increasing test application time and cost. Consequently, calibrating thermal sensors in typical digital designs including mainstream desktop and notebook processors increases the cost of the processor. This creates a need for design of thermal sensors whose accuracy does not vary significantly with process variations. Other qualities desired from thermal sensors include low area requirement so that many of them maybe integrated in a design as well as low power dissipation, such that the sensor itself does not become a significant source of heat. In this work, we developed a process variation tolerant thermal sensor design with (i) active compensation circuitry and (ii) signal dithering based self calibration technique to meet the above requirements in 32nm technology. Results show that we achieve 3ºC temperature accuracy, with a relatively small design which compares well with designs that are currently used.
58

3D Micromachined Passive Components and Active Circuit Integration for Millimeter-wave Radar Applications

Oliver, John Marcus 03 May 2012 (has links)
The development of millimeter-wave (30-300 GHz) sensors and communications systems has a long history of interest, spanning back almost six decades. In particular, mm-wave radars have applications as automotive radars, in remote atmospheric sensing applications, as landing radars for air and spacecraft, and for high precision imaging applications. Mm-wave radar systems have high angular accuracy and range resolution, and, while susceptible to atmospheric attenuation, are less susceptible to optically opaque conditions, such as smoke or dust. This dissertation document will present the initial steps towards a new approach to the creation of a mm-wave radar system at 94 GHz. Specifically, this dissertation presents the design, fabrication and testing of various components of a highly integrated mm-wave a 94 Ghz monopulse radar transmitter/receiver. Several architectural approaches are considered, including passive and active implementations of RF monopulse comparator networks. These architectures are enabled by a high-performance three-dimensional rectangular coaxial microwave transmission line technology known as PolyStrataTM as well as silicon-based IC technologies. A number of specific components are examined in detail, including: a 2x2 PolyStrata antenna array, a passive monopulse comparator network, a 94 GHz SiGe two-port active comparator MMIC, a 24 GHz RF-CMOS 4-port active monopulse comparator IC, and a series of V- and W-band corporate combining structures for use in transmitter power combining applications. The 94 GHz cavity-backed antennas based on a rectangular coaxial feeding network have been designed, fabricated, and tested. 13 dB gain for a 2 x 2 array, as well as antenna patterns are reported. In an effort to facilitate high-accuracy measurement of the antenna array, an E-probe transition to waveguide and PolyStrata diode detectors were also designed and fabricated. AW-band rectangular coaxial passive monopulse comparator with integrated antenna array and diode detectors have also been presented. Measured monopulse nulls of 31.4 dB in the ΔAZ plane have been demonstrated. 94-GHz SiGe active monopulse comparator IC and 24 GHz RF-CMOS active monopulse comparator RFIC designs are presented, including detailed simulations of monopulse nulls and performance over frequency. Simulations of the W-band SiGe active monopulse comparator IC indicate potential for wideband operation, with 30 dB monopulse nulls from 75-105 GHz. For the 24-GHz active monopulse comparator IC, simulated monopulse nulls of 71 dB and 68 dB were reported for the azimuthal and elevational sweeps. Measurements of these ICs were unsuccessful due to layout errors and incomplete accounting for parasitics. Simulated results from a series of rectangular coaxial power corporate power combining structures have been presented, and their relative merits discussed. These designs include 2-1 and 4-1 reactive, Wilkinson, and Gysel combiners at V- and W-band. Measured back-to-back results from Gysel combiners at 60 GHz included insertion loss of 0.13 dB per division for a 2-1 combination, and an insertion loss of 0.3 dB and 0.14 dB for "planar" and "direct" 4-1 combinations, respectively. At 94 GHz, a measured insertion loss of 0.1 dB per division has been presented for a 2-1 Gysel combination, using a back-to-back structure. Preliminary designs for a solid-state power amplifier (SSPA) structure have also been presented. Finally, two conceptual monopulse transceivers will be presented, as a vehicle for integrating the various components demonstrated in this dissertation. / Ph. D.
59

Design and Verification of An Energy-Efficient Edge-Pursuit Comparator / Design och verifiering av en energieffektiv Edge-Pursuit-jämförare

Xie, Haiqin January 2022 (has links)
With the rapid development of mobile communication, sensors, and biomedical in recent years, the demand for accurate data information, highquality audio and image has become much more significant, which requires a high-precision Analog to Digital Converter (ADC) to process weak analog signals. As one of the core modules of ADC, the comparator’s precision, speed, stability, and noise play a key role in the performance of the whole circuit. Over the years, those performance has been improved a lot by both designing new architectures and using advanced fabrication technology. However, the conventional comparators occupy 50%-60% of the total energy consumption of EPC, even with advanced technology and lower supply voltage. In this thesis, a new type of energy-efficient comparator, called Edge-Pursuit Comparator (EPC), is proposed, which satisfies the need for low comparison energy. The design of EPC is based on a ring oscillator, when the EPC enters the evaluation mode, two signal edges with different propagation delays will chase in it until one overlaps the other, and finally generate a stable voltage level in each output node. The circuit is built and simulated in Cadence Virtuoso using cmos22fdsoi technology. The simulation results reveal that the energy consumed per comparison is dependent on the input differential voltage, and it can be as low as 7 fJ when vin = 50 mV, which is around ten times smaller compared with conventional comparators. In addition, as the power consumption is considerable when the two input voltages are very close, a promising improvement is applied to EPC, namely connecting every node with a variable capacitor, which is called Edge-Pursuit Comparator enhanced with Capacitor (EPCC). Cadence simulation results prove that EPCC can largely lower the energy consumption under a small vin while keeping input-referred noise the same. Therefore, a combination of EPC and EPCC is expected to have prospective applications in the energy-efficient area. / Med den snabba utvecklingen av mobil kommunikation, sensorer och biomedicin under de senaste åren har efterfrågan på korrekt datainformation, högkvalitativt ljud och bild blivit mycket mer betydande, vilket kräver en högprecision Analog till Digital Converter (ADC) för att bearbeta svaga analoga signaler. Som en av ADC:s kärnmoduler spelar komparatorns precision, hastighet, stabilitet och brus en nyckelroll i prestanda för hela kretsen. Under årens lopp har dessa prestanda förbättrats mycket genom att både designa nya arkitekturer och använda avancerad tillverkningsteknik. De konventionella komparatorerna upptar dock 50%-60% av den totala energiförbrukningen för EPC, även med avancerad teknik och lägre matningsspänning. I detta examensarbete föreslås en ny typ av energieffektiv komparator, kallad Edge-Pursuit Comparator (EPC), som tillgodoser behovet av låg jämförelseenergi. Designen av EPC är baserad på en ringoscillator, när EPC:n går in i utvärderingsläget kommer två signalkanter med olika utbredningsfördröjningar att jaga i den tills den ena överlappar den andra, och slutligen generera en stabil spänningsnivå i varje utgångsnod. Kretsen är byggd och simulerad i Cadence Virtuoso med hjälp av cmos22fdsoiteknik. Simuleringsresultaten visar att energiförbrukningen per jämförelse är beroende av ingångsdifferensspänningen och den kan vara så låg som 7 fJ när vin = 50 mV, vilket är cirka tio gånger mindre jämfört med konventionella komparatorer. Dessutom, eftersom strömförbrukningen är avsevärd när de två inspänningarna är mycket nära, tillämpas en lovande förbättring på EPC, nämligen att ansluta varje nod med en variabel kondensator, som kallas Edge-Pursuit Comparator förbättrad med kondensator (EPCC). Kadenssimuleringsresultat bevisar att EPCC till stor del kan sänka energiförbrukningen under en liten vin samtidigt som ingångsreferat buller hålls detsamma. Därför förväntas en kombination av EPC och EPCC ha potentiella tillämpningar inom det energieffektiva området.
60

Štúdia uskutočniteľnosti PPP projektu / A Study of the Feasibility of the PPP Project

Allouache, Diana January 2009 (has links)
The thesis explains the formation of the PPP project feasibility study as an essential document in the preparatory phase of the project lifecycle. Its closer focus is on the economic evaluation of the investment project implementation using the PPP compared to the implementation using public procurement. The practical part refers to a specific example of calculating of the public sector comparator that is compared with the referential project and a value of money is determined as an indicator of profitability of both forms of implementation.

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