Humidity sensing by optically interfacing with spectrally absorptive materials

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The measurement of humidity is rapidly increasing in importance in physical, chemical and biological processes as industry attempts to improve quality and production rates by better control of relative humidity (RH). A novel optical fibre humidity sensor suitable for use in an optical fibre multi-point distributed sensing system has been developed, thus for the first time allowing multipoint measurements of humidity along an optical fibre which can be distributed within an industrial plant or machine without the need for electrical power supplies. The novel point sensor is based on the principle of using the absorption spectrum of a colorimetric reagent (cobalt chloride) immobilised on the surface of the core of a multimode optical fibre by employing a thin gelatin film. The single point sensor has an insertion loss of less than 0.2 dB. Two-wavelength detection is employed to provide referencing to eliminate common mode intensity variation. The basic design, construction and testing of an experimental sensor in the humidity region 20 to 80% RH and temperature range 25 to 50 °C is described. Resolution and Repeatability can be better than 2% RH with a time constant of 0.5 second. A two-wavelength optical time domain reflectometer (OTDR) has been developed and a four-sensor network has been built. The resolution of measurement on the network can be better than 4% RH, but because of noise in the OTDR the resolution value is dependent on averaging time in the instrument.Funding was obtained from EPSRC

Timing error detection and correction for power efficiency: an aggressive scaling approach

Low-power consumption has become an important aspect of processors and systems design. Many techniques ranging from architectural to system level are available. Voltage scaling or frequency boosting methods are the most effective to achieve low-power consumption as the dynamic power is proportional to the frequency and to the square of the supply voltage. The basic principle of operation of aggressive voltage scaling is to adjust the supply voltage to the lowest level possible to achieve minimum power consumption while maintaining reliable operations. Similarly, aggressive frequency boosting is to alter the operating frequency to achieve optimum performance improvement. In this study, an aggressive technique which employs voltage or frequency varying hardware circuit with the time-borrowing feature is presented. The proposed technique double samples the data to detect any timing violations as the frequency/voltage is scaled. The detected violations are masked by phase delaying the flip-flop clock to capture the late arrival data. This makes the system timing error tolerant without incurring error correction timing penalty. The proposed technique is implemented in a field programmable gate array using a two-stage arithmetic pipeline. Results on various benchmarks clearly demonstrate the achieved power savings and performance improvement.N/

Towards wireless technology for safety critical systems.

Wireless technology provides an unprecedented level of design flexibility for new system designs and legacy system updates. However, there are several challenges which present themselves when adopting wireless technologies for use in safety systems. This paper elaborates on available design techniques which can resolve the implementation issues for a given application, to ensure data communication between nodes is safe (deterministic), secure, reliable and available.N/

A novel structure of a modular interleaved DC/DC converter for renewable street lighting systems

The conventional structure of the renewable street lighting systems required two converters. A buck converter used for battery charging during the day, and a boost converter used to supply power to the lighting system from the battery during night. Combining the two converters is desirable as both cost and size are reduced. In this paper, a novel structure of a modular interleaved DC/DC converter with PWM/PID control technique for renewable street lighting system is presented. During the day, the proposed converter works in a buck mode and is used to charge the battery. at night, the converter works in a boost mode to provide power to the lighting system. Analysis of the converter is carried out in order to achieve the required system stability and to improve its dynamic performance. The operating principle and boundary conditions are discussed too. All the advantages of interleaving technique, such as higher efficiency and reduced ripple for voltage/current, are also maintained. The simulation results are presented to show the performance of the proposed converter.N/

Impact of loads on power flow in power systems using PowerApps and ETAP

This paper presents a study of the impact of loads on power flow in power system. It deals with the impact of both the voltage nodes and the transmission of active and reactive power in lines, and therefore the loss of active and reactive power in the system. Flexible Alternating Current Transmission System (FACTS) devices are found to be encouraging in improving voltage stability limit in power systems. This paper investigates the application of FACTS devices (Static Var Compensator, SVC) on a 9-bus multimachine power system, it deal with the line losses and improving voltage stability limit. Amount of increased reactive power generation and line losses are taken as indicators of stressed conditions of a power system. The use of SVC is identified by PowerApps and ETAP software packages. Both software are used for IEEE 9 bus test system and the results obtained are presented and interpreted. Streszczenie. Analizowano wpływ napięć w węzłach i przepływ mocy biernej i czynnej na pracę systemu energetycznego. Artykuł przedstawia badania zastosowania urządzeń FACTS w dziewi1)ęcioszynowym, wielomaszynowym systemie. Wykorzystano oprogramowanie ETAP. Wpływ obciążeń na przepływy mocy w systemie wykorzystującym PowerApps i oprogramowanie ETAP Keywords: Power Flow, FACTS, SVC, PowerApps, ETAP. Słowa kluczowe: przepływy mocy, FACTS, Etap Introduction Load flow study in power system parlance is the steady state solution of the power system network [1]. The main information obtained from this study comprises the magnitudes and phase angles of load bus voltages, reactive powers at generators buses, real and reactive power flow on transmission lines [2], other variables being known. Usually a generating station is not situated near the load centre, but it may be away from load centre due to various circumstances