Calibration of the Pulsed Electroacoustic Technique in the Presence of Trapped Charge

The influence of pulse voltage on the accuracy of charge density distribution in the pulsed electroacoustic technique (PEA) is discussed. It is shown that significant error can be introduced if a low dc voltage and high pulse voltage are used to calibrate charge density. However, our main focus in the present paper is to deal with one of the practical situations where space charge exists in the material prior to any measurements. The conventional calibration method can no longer be used to calibrate charge density due to the interference by the charge on the electrode induced by space charge. A method has been proposed which is based on two measurements. Firstly, the sample containing charge is measured without any applied voltage. The second measurement is carried out with a small external applied voltage. The applied voltage should be small enough so there is no disturbance of the existing charge in the sample. The difference of the two measurements can be used for calibration. An additional advantage of the proposed method avoids the influence of the pulse voltage on calibration and therefore gives a more accurate representation of space charge. The proposed method has been validated

Dirichlet Process Hidden Markov Multiple Change-point Model

This paper proposes a new Bayesian multiple change-point model which is based on the hidden Markov approach. The Dirichlet process hidden Markov model does not require the specification of the number of change-points a priori. Hence our model is robust to model specification in contrast to the fully parametric Bayesian model. We propose a general Markov chain Monte Carlo algorithm which only needs to sample the states around change-points. Simulations for a normal mean-shift model with known and unknown variance demonstrate advantages of our approach. Two applications, namely the coal-mining disaster data and the real United States Gross Domestic Product growth, are provided. We detect a single change-point for both the disaster data and US GDP growth. All the change-point locations and posterior inferences of the two applications are in line with existing methods.Comment: Published at http://dx.doi.org/10.1214/14-BA910 in the Bayesian Analysis (http://projecteuclid.org/euclid.ba) by the International Society of Bayesian Analysis (http://bayesian.org/

Transparent conducting oxides for active hybrid metamaterial devices

We present here a study of the combined nonlinear response of plasmonic antenna—transparent conducting oxide hybrids for activation of metamaterial devices. Nanoantenna layers consisting of randomly positioned gold nanodisk dimers are fabricated using hole-mask lithography. The nanoantenna layers are covered with a 20 nm thin layer of transparent conducting oxide (TCO). We investigate the response of atomic layer deposited aluminum-doped zinc oxide (AZO) next to indium–tin oxide (ITO) produced using sputter coating. We show that our results are in agreement with the hypothesis of fast electron-mediated cooling, facilitated by the Ohmic interface between the gold nanodisks and the TCO substrate, which appears a universal mechanism for providing a new hybrid functionality to active metamaterial device

Microfabricated Silicon Mixers for Submillisecond Quench-Flow Analysis

Elucidation of fast chemical reactions such as protein folding requires resolution on a submillisecond time scale. However, most quench-flow and stop-flow techniques only allow chemical processes to be studied after a few milliseconds have elapsed. In order to shorten the minimum observation time for quench-flow experiments, we designed a miniaturized mixer assembly. Two “T” mixers connected by a channel are etched into a 1 cm × 1 cm silicon chip which is interfaced with a commercially available quench-flow instrument. Decreasing the volume of the mixing chambers and the distance between them results in an instrument with greatly reduced dead times. As a test of submillisecond measurements, we studied the basic hydrolysis of phenyl chloroacetate. This reaction proceeds with a second-order rate constant, k = 430 M^(-1) s^(-1), and shows pseudo-first-order kinetics at high hydroxide concentrations. The chemical reaction data demonstrate that the silicon device is capable of initiating and quenching chemical reactions in time intervals as short as 110 μs. The performance of these mixers was further confirmed by visualization using acid-base indicators

Generalised Predictive Control of a 12-bus Network Using Neutral-Point Clamped Voltage Source Converter UPFC

The paper presents the application of a UPFC to a case study of a 12-bus high power network. The UPFC shunt converter employs 8 3-level Neutral Point Clamped (NPC) voltage source converters (VSC) and 12 single-phase three-winding phase shifting transformers (PST), generating a 48-pulse output voltage. The 3-phase H-bridge series converter shares the same dc-link with the shunt one. The novel feature of this work lies in the use of a model-based generalised predictive current control law to the shunt converter for voltage and power flow control which has shown superior performance without additional filters compared to a P+I control scheme. In addition with the phase shift and switching angle control of each NPC-VSC output voltage, the topology offers improved harmonic performance and a zero-sequence blocking transformer is used for total triplen harmonics elimination

Optimal Design of Series-Parallel Differential Power Processing Converters for Photovoltaic Array Energy Systems

A scheme is proposed for maximum power point tracking in series-parallel photovoltaic arrays using differential power processing, based on bidirectional Cuk converters and inverted buck converters for adjusting module current and voltage respectively. Converter transfer functions are derived using linearization and state space time averaging. These are used to develop design criteria for well-behaved transient response, and reduction of the effect of non-minimum phase. A representative design with about 10 ms settling is presented. It is shown that this can form the basis of a successful perturb-and-observe control system

Amnestic Mild Cognitive Impairment and Early Alzheimer's Disease in an Asian Memory Clinic – Evidence for a Clinical Spectrum

Objectives: To determine if mild cognitive impairment (MCI) represents a continuum of cognitive and functional deficits. Methods: Clinical data of 164 subjects with no dementia (ND, n = 52), uncertain dementia (n = 69), and mild probable Alzheimer’s disease (AD, n = 43) were reviewed. Uncertain dementia patients were classified as pre-MCI (n = 11), early amnestic MCI (e-aMCI, n = 15) and late amnestic MCI (l-aMCI, n = 15). Cognitive assessments [Chinese Mini-Mental State Examination (CMMSE) and a validated neuropsychological battery], functional assessments (Lawton’s scale for instrumental activities of daily living) and neuroimaging (ischemic lesions and medial temporal lobe atrophy) were reviewed. Results: ND, aMCI and mild AD subjects demonstrated a significant trend for worsening performance for all cognitive and functional measures (ANOVA, p Conclusions: Clinical delineation of aMCI allows the differentiation of those likely to progress for better correlation to biomarker development

Investigation of passive flow control techniques to enhance the stall characteristics of a microlight aircraft

This report investigates the enhancement of aerodynamic stall characteristics of a Skyranger microlight aircraft by the use of passive flow control techniques, namely vortex generators and turbulators. Each flow control device is designed and scaled to application conditions. Force balance measurements and surface oil flow visualisation are carried out on a half-model of the microlight to further investigate the nature of the flow on the aircraft with and without the flow control devices. The results indicate a clear advantage to the use of turbulators compared with vortex generators. Turbulators increased the maximum lift coefficient by 2.8%, delayed the onset of stall by increasing the critical angle by 17.6% and reduced the drag penalty at both lower (pre-stall) and higher angles of attack by 8% compared to vortex generators. With vortex generators applied, the results indicated a delayed stall with an increase in the critical angle by 2% and a reduced drag penalty at higher angles of attack

Deciphering food hawkerpreneurship: Challenges and success factors in franchising street food businesses in Malaysia

This study investigates the challenges and identifies the critical success factors in transforming traditional hawker food into a franchisable business, principally within the context of Malaysia. This study aims to provide guidelines that could support the process of enterprising traditional street food businesses, especially to assist the mobilization and promotion of hawkerpreneurship for existing traditional food hawkers and future adopters. A total of five hawkerpreneurs and four traditional hawkers were qualitatively assessed through semi-structured interviews. As a result, four critical challenges that both hawkerpreneurs and traditional hawkers encountered were identified, namely: (1) exploring the unknown (2) high capital investment for total “make-over” (3) lack of knowledge in brand repositioning, and (4) resistance to automation and standardization, particularly as a way to retain authenticity. By considering these concerns, young entrepreneurs and financial investors can assess the potentiality and feasibility of hawker food, and identify areas to focus on in running a successful traditional street food business. The results of this study could further assist in developing the support mechanisms and start-up strategies that encourage the adoption of hawker food entrepreneurship among Malaysians