Acoustic resonance detection using statistical methods of voltage envelope characterization in metal halide lamps

Acoustic resonance (AR) phenomenon occurs in metal halide lamps and can cause light flicker, lamp arc bending and rotation, lamp extinction, and in the worst case, arc tube explosion. This study takes place in the context of developing electronic ballasts with robust AR detection and avoidance mechanisms. To this end, a lock-in amplifier is used to measure and characterize lamp voltage root mean square (rms) short-term fluctuations. Statistical criteria based on the standard deviation of this rms value are proposed to assess AR presence and classify its severity. A set of metal halide lamps from different manufacturers and with different powers were tested. The average electrical power and AR level are controlled by adjusting the lamp operating frequency of high-frequency electronic ballast. The proposed criteria enable classifying healthy (without AR) and faulty (with AR) cases based upon either a two-dimensional plane or a boxplot. Regardless of lamp operating power, the results from this study show that the voltage rms variations and the defined criteria are significantly correlated with AR level

Innovative solutions for acoustic resonance characterization in metal halide lamps

Metal halide lamp is one kind of the most compact high-performance light sources. Because of their good color rendering index and high luminous efficacy, these lamps are often preferred in locations where color and efficacy are important, such as supermarkets, gymnasiums, ice rinks and sporting arenas. Unfortunately, acoustic resonance phenomenon occurs in metal halide lamps and causes light flicker, lamp arc bending and rotation, lamp extinction and in the worst case, arc tube explosion, when the lamps are operated in high-frequency bands. This thesis takes place in the context of developing electronic ballasts with robust acoustic resonance detection and avoidance mechanisms. To this end, several envelope detection methods such as the multiplier circuit, rectifier circuit, and lock-in amplifier, are proposed to characterize fluctuations of acoustic resonance. Furthermore, statistical criteria based on the standard deviation of these fluctuations are proposed to assess acoustic resonance occurrence and classify its severity. The proposed criteria enable classifying between no acoustic resonance and acoustic resonance cases based upon either a two-dimensional plane, a histogram or a boxplot. These analyses are confirmed by the study of spectral variations (variations of the spectral irradiance and colorimetric parameters) as well. Standard deviations and relative standard deviations of these variations are also correlated with the presence of acoustic resonance. The results from this study show that whatever voltage envelope variations or spectral variations are significantly influenced by acoustic resonance phenomena. A set of metal halide lamps from different manufacturers and with different powers are tested in our experiments. We concluded that our designed multiplier and rectifier circuits for acoustic resonance detection have the same sensitivity as the lock-in amplifier, paving the way for the implementation of this function directly into the ballast circuit board

A simple high-sensitivity acoustic resonance detection method for metal halide lamps

To detect acoustic resonance (AR) in metal halide (MH) lamps, a simple high-sensitivity method with a multiplier detector is presented in this paper. Voltage envelope variations are measured to evaluate whether AR occurs in MH lamps. The study is focused on improving the sensitivity of an AR detection method. Several manufacturers’ MH lamps are tested in our experiment. In addition, in order to verify the proposed method, the other method of voltage envelope detection is evaluated by a lock-in amplifier with high sensitivity and detection results are analyzed by statistical methods. The results show that the proposed circuit can provide similar sensitivity as the expensive lock-in amplifier to detect AR phenomena and the AR-free and the slight AR level can be easily distinguished

Electronic operation and control of high-intensity gas-discharge lamps

The ever increasing amount of global energy consumption based on the application of fossil fuels is threatening the earth’s natural resources and environment. Worldwide, grid-based electric lighting consumes 19 % of total global electricity production. For this reason the transition towards energy efficient lighting plays an important environmental role. One of the key technologies in this transition is High-Intensity Discharge (HID) lighting. The technical revolution in gas-discharge lamps has resulted in the highlyefficient lamps that are available nowadays. As with most energy efficient light solutions, all HID lighting systems require a ballast to operate. Traditionally, magnetic ballast designs were the only choice available for HID lighting systems. Today, electronic lampdrivers can offer additional power saving, flicker free operation, and miniaturisation. Electronic lamp operation enables additional degrees of freedom in lamp-current control over the conventional electro-magnetic (EM) ballasts. The lamp-driver system performance depends on both the dynamics of the lamp and the driver. This thesis focuses on the optimisation of electronically operated HID systems, in terms of highly-efficient lamp-driver topologies and, more specifically, lamp-driver interaction control. First, highly-efficient power topologies to operate compact HID lamps on low-frequency-square-wave (LFSW) current are explored. The proposed two-stage electronic lamp-driver consists of a Power Factor Corrector (PFC) stage that meets the power utility standards. This converter is coupled to a stacked buck converter that controls the lamp-current. Both stages are operated in Zero Voltage Switching (ZVS) mode in order to reduce the switching losses. The resulting two-stage lamp-drivers feature flexible controllability, high efficiency, and high power density, and are suitable for power sandwich packaging. Secondly, lamp-driver interaction (LDI) has been studied in the simulation domain and control algorithms have been explored that improve the stability, and enable system optimisation. Two HID lamp models were developed. The first model describes the HID lamp’s small-signal electrical behaviour and its purpose is to aid to study the interaction stability. The second HID lamp model has been developed based on physics equations for the arc column and the electrode behaviour, and is intended for lampdriver simulations and control applications. Verification measurements have shown that the lamp terminal characteristics are present over a wide power and frequency range. Three LDI control algorithms were explored, using the proposed lampmodels. The first control principle optimises the LDI for a broad range of HID lamps operated at normal or reduced power. This approach consists of two control loops integrated into a fuzzy-logic controller that stabilises the lamp-current and optimises the commutation process. The second control problem concerns the application of ultra high performance (UHP) HID lamps in projection applications that typically set stringent requirements on the quality of the light generated by these lamps, and therefore the lampcurrent. These systems are subject to periodic disturbances synchronous with the LFSW commutation period. Iterative learning control (ILC) has been examined. It was experimentally verified that this algorithm compensates for repetitive disturbances. Third, Electronic HID operation also opens the door for continuous HID lamp dimming that can provide additional savings. To enable stable dimming, an observer-based HID lamp controller has been developed. This controller sets a stable minimum dim-level and monitors the gas-discharge throughout lamp life. The HID lamp observer derives physical lamp state signals from the HID arc discharge physics and the related photometric properties. Finally, practical measurements proved the proposed HID lamp observer-based control principle works satisfactorily

Measurement techniques and instruments suitable for life-prediction testing of photovoltaic arrays

Array failure modes, relevant materials property changes, and primary degradation mechanisms are discussed as a prerequisite to identifying suitable measurement techniques and instruments. Candidate techniques and instruments are identified on the basis of extensive reviews of published and unpublished information. These methods are organized in six measurement categories - chemical, electrical, optical, thermal, mechanical, and other physicals. Using specified evaluation criteria, the most promising techniques and instruments for use in life prediction tests of arrays were selected

Variable Flux Profile Optimization of a High Flux Solar Simulator

A High Flux Solar Simulator (HFSS) provides artificial solar radiation using an array of high- intensity discharge lamps attached to ellipsoidal reflectors to focus their light to a point where high temperatures can be achieved. High flux solar simulators are used for solar thermal and thermochemical research. They provide high-flux radiation used for controlled lab-scaled experimentation as an alternative to concentrated solar power systems which depends on sunlight, which is intermittent. In this project, a HFSS model is developed consisting of ten 2.5 KW metal halide lamps mounted in a truncated ellipsoidal reflector with variable flux profile capability. The novel variability in flux profile is useful in achieving different ranges of temperatures with different flux profile configurations that can be used for a wide range of solar thermal, thermochemical, and photovoltaic research applications. The variation in the flux profile of the solar simulator model is achieved by changing the angle of the lamp module with respect to the target, changing the distance between the arc of the bulb and the focal point of the reflector and by varying the power of the lamps. Ray-tracing simulation software, Trace-Pro is used to analyze the variation in the flux profile with respect to the change in parameters of the solar simulator, and a relationship is determined by fitting various curve fit types, and a piecewise worked the best. This relationship is used to define the optimization model for obtaining the optimal configuration of the HFSS model using a trust-region reflective optimization method. The objective of the optimization model is to reduce the sum of the squared difference between the user-defined flux profile and the flux profile of the solar simulator model obtained by varying its parameters. Several user-defined flux profile configurations are tested. The optimization model was able to approximate the user-defined flux profile within the achievable limits of the flux profile of the solar simulator. Thus, reducing the effort in manually adjusting the parameters of the high flux solar simulator

Polychromatic fluence: calculation and application in ultraviolet reactors for water treatment

IIn recent decades the application of UV disinfection technology in water treatment has rapidly increased on a global scale, however important uncertainties remain regarding; the methods to achieve consistent and accurate measurement of polychromatic UV output, the fluence-response of microorganisms to UV wavelengths over the entire polychromatic lamp output range, and the optimal lamp conditions and compositions to optimise polychromatic UV disinfection performance. This research aimed to address each of these areas of uncertainty. First, limitations in the existing methods that are used for lamp output measurement were identified and quantified in terms of their potential to cause significant errors in polychromatic UV fluence calculation; solutions are proposed to overcome these limitations in future polychromatic fluence measurements. Next, a novel experimental apparatus was constructed, achieving the necessary spectral requirements to produce a high resolution action spectra for waterborne microorganisms over the 200-300 nm wavelength range. Application of this experimental setup to the comparison of the fluence-response of T1 and T1UV phage, common organisms used in UV reactor validation, identified important differences in UV sensitivity dependent on host selection, and high resolution action spectra were then produced for T1UV with two hosts over the full polychromatic UV range for the first time. Also, new viral surrogates were identified using a theoretical genomic model to predict their UV sensitivities, two of which were identified as having the potential to extend the upper UV fluence validation test limits. Finally, the production of a novel high pressure plasma discharge polychromatic lamp was achieved without the use of mercury, showing considerable potential for future applications.Open Acces

Smart Bagged Tree-based Classifier optimized by Random Forests (SBT-RF) to Classify Brain- Machine Interface Data

Brain-Computer Interface (BCI) is a new technology that uses electrodes and sensors to connect machines and computers with the human brain to improve a person\u27s mental performance. Also, human intentions and thoughts are analyzed and recognized using BCI, which is then translated into Electroencephalogram (EEG) signals. However, certain brain signals may contain redundant information, making classification ineffective. Therefore, relevant characteristics are essential for enhancing classification performance. . Thus, feature selection has been employed to eliminate redundant data before sorting to reduce computation time. BCI Competition III Dataset Iva was used to investigate the efficacy of the proposed system. A Smart Bagged Tree-based Classifier (SBT-RF) technique is presented to determine the importance of the features for selecting and classifying the data. As a result, SBT-RF is better at improving the mean accuracy of the dataset. It also decreases computation cost and training time and increases prediction speed. Furthermore, fewer features mean fewer electrodes, thus lowering the risk of damage to the brain. The proposed algorithm has the greatest average accuracy of ~98% compared to other relevant algorithms in the literature. SBT-RF is compared to state-of-the-art algorithms based on the following performance metrics: Confusion Matrix, ROC-AUC, F1-Score, Training Time, Prediction speed, and Accuracy

Time-Resolved Photoemission Electron Microscopy: Development and Applications

Time-resolved photoemission electron microscopy (TR-PEEM) belongs to a class of experimental techniquescombining the spatial resolution of electron-based microscopy with the time resolution of ultrafast opticalspectroscopy. This combination provides insight into fundamental processes on the nanometer spatial andfemto/picosecond time scale, such as charge carrier transport in semiconductors or collective excitations ofconduction band electrons at metal surfaces. The high spatiotemporal resolution also offers a detailed view of therelationship between local structure and ultrafast photoexcitation dynamics in nanostructures and nanostructuredmaterials, which is beneficial in exploring new materials and applications in opto-electronics and nano-optics.This thesis describes the investigation of ultrafast photoexcitation dynamics in metal- and III-V semiconductornanostructures using TR-PEEM. We investigate hot carrier cooling in individual InAs nanowires where we findevidence that electron-hole scattering strongly contributes to the intra-band energy relaxation of photoexcitedelectrons on a sub-picosecond time scale and we observe ultrafast hot electron transport towards the nanowiresurface due to an in-built electric field. We demonstrate the combination of TR-PEEM with optical time-domainspectroscopy to enable time- and excitation frequency-resolved PEEM imaging. The technique is applied to GaAssubstrates and nanowires. TR-PEEM is further used to investigate localized and propagating surface plasmonpolaritons. We explore the optical properties of disordered, porous gold nano-particles (nanosponges). Using TRPEEM,we can resolve several plasmonic hotspots with different resonance frequencies and lifetimes within singlenanosponges. We also explore excitation and temporal control of surface plasmon polaritons by means of singlelayeredcrystals of the transition metal dichalcogenide WSe2.In addition, this thesis includes developments in ultrafast optics, aiming to expand the capabilities of the TR-PEEMsetup. We present a setup for generating tunable broadband ultraviolet (UV) laser pulses via achromatic secondharmonic generation. The setup is suitable for operation at high repetition rates and low pulse energies due to its highconversion efficiency. Further, we describe a transmission grating-based interferometer for the generation of stable,phase-locked pulse pairs. Pulse shaping based on liquid crystal technology allows accurate control over the temporalshape of femtosecond laser pulses. We characterize Fabry-Perot interferences affecting the accuracy of such pulseshapers, and we demonstrate a calibration scheme to compensate for these interference effects

Electrophysiologic assessment of (central) auditory processing disorder in children with non-syndromic cleft lip and/or palate

Session 5aPP - Psychological and Physiological Acoustics: Auditory Function, Mechanisms, and Models (Poster Session)Cleft of the lip and/or palate is a common congenital craniofacial malformation worldwide, particularly non-syndromic cleft lip and/or palate (NSCL/P). Though middle ear deficits in this population have been universally noted in numerous studies, other auditory problems including inner ear deficits or cortical dysfunction are rarely reported. A higher prevalence of educational problems has been noted in children with NSCL/P compared to craniofacially normal children. These high level cognitive difficulties cannot be entirely attributed to peripheral hearing loss. Recently it has been suggested that children with NSCLP may be more prone to abnormalities in the auditory cortex. The aim of the present study was to investigate whether school age children with (NSCL/P) have a higher prevalence of indications of (central) auditory processing disorder [(C)APD] compared to normal age matched controls when assessed using auditory event-related potential (ERP) techniques. School children (6 to 15 years) with NSCL/P and normal controls with matched age and gender were recruited. Auditory ERP recordings included auditory brainstem response and late event-related potentials, including the P1-N1-P2 complex and P300 waveforms. Initial findings from the present study are presented and their implications for further research in this area —and clinical intervention—are outlined. © 2012 Acoustical Society of Americapublished_or_final_versio