The Solar HepHep Process

The $Hep$ process is a weak-interaction reaction, $He3 + p \to He4 + e^+ + \nu_e$, which occurs in the sun. There is renewed interest in $Hep$ owing to current experimental efforts to extract from the observed solar neutrino spectrum information on non-standard physics in the neutrino sector. $Hep$ produces highest-energy solar neutrinos, although their flux is quite modest. This implies that the $Hep$ neutrios can at some level influence the solar neutrino spectrum near its upper end. Therefore, a precise interpretation of the observed solar neutrino spectrum requires an accurate estimate of the $Hep$ rate. This is an interesting but challenging task. We describe the difficulties involved and how the recent theoretical developments in nuclear physics have enabled us to largely overcome these difficulties. A historical survey of $Hep$ calculations is followed by an overview of the latest developments. We compare the results obtained in the conventional nuclear physics approach and those obtained in a newly developed effective field theory approach. We also discuss the current status of the experiments relevant to $Hep$.Comment: Published in Ann. Rev. Nuc. Part. Sci. vol. 54, 19 (2004). AR209 macros are include

Integration of knowledge-based system, artificial neural networks and multimedia for gear design

Design is a complicated area consisting of a combination of rules, technical information and personal judgement. The quality of design depends highly on the designer's knowledge and experience. This system attempts to simulate the design process and to capture design expertise by combining artificial neural networks (ANNs) and knowledge based system (KBS) together with multi-media (MM). It has been applied to the design of gears. Within the system the knowledge based system handles clearly defined design knowledge, the artificial neural networks capture knowledge which is difficult to quantify and multi-media provides a user-friendly interface prompting the user to input information and to retrieve results during design process. The finished system illustrates how features of different Artificial Intelligence techniques, KBS, ANNs and MM, are combined in a hybrid manner to conduct complicated design tasks

High-speed, solid state, interferometric interrogator and multiplexer for fiber Bragg grating sensors

We report on the design and prototyping of a robust high-speed interferometric multiplexer and interrogator for fiber Bragg grating sensors. The scheme is based on the combination of active WDM channel switching and passive, instantaneous interferometry, allowing the resolution of virgin interferometric interrogators to be retained at MHz multiplexing rates. In this article the system design and operation are described, and a prototype scheme is characterized for three sensors and a multiplexing rate of 4 kHz, demonstrating a noise floor of 10 nε/√Hz and no cross-sensitivity. It is proposed that the system will be applicable to demanding monitoring applications requiring high speed and high resolution measurements across the sensor array

Recent trends in power systems modeling and analysis

In recent years, the explosion of renewable energy sources, the increase in the demand for electrical energy, and several improvements in related technologies have fostered research in many relevant areas of interest

Estimation of the Default Risk of Publicly Traded Canadian Companies

Two models of default risk are prominent in the financial literature: Merton's structural model and Altman's non-structural model. Merton's structural model has the benefit of being responsive, since the probabilities of default can continually be updated with the evolution of firms' asset values. Its main flaw lies in the fact that it may over- or underestimate the probabilities of default, since asset values are unobservable and must be extrapolated from the share prices. Altman's nonstructural model, on the other hand, is more precise, since it uses firms' accounting data-but it is less flexible. In this paper, the authors investigate the hybrid contingent claims approach with publicly traded Canadian companies listed on the Toronto Stock Exchange. The authors' goal is to assess how their ability to predict companies' probability of default is improved by combining the companies' continuous market valuation (structural model) with the value given in their financial statements (non-structural model). The authors' results indicate that the predicted structural probabilities of default (PDs from the structural model) contribute significantly to explaining default probabilities when PDs are included alongside the retained accounting variables in the hybrid model. The authors also show that quarterly updates to the PDs add a large amount of dynamic information to explain the probabilities of default over the course of a year. This flexibility would not be possible with a non-structural model. The authors conduct a preliminary analysis of correlations between structural probabilities of default for the firms in their database. Their results indicate that there are substantial correlations in the studied data.Debt management; Credit and credit aggregates; Financial markets; Recent economic and financial developments; Econometric and statistical methods

A Software-Defined Multi-Element VLC Architecture

In the modern era of radio frequency (RF) spectrum crunch, visible light communication (VLC) is a recent and promising alternative technology that operates at the visible light spectrum. Thanks to its unlicensed and large bandwidth, VLC can deliver high throughput, better energy efficiency, and low cost data communications. In this article, a hybrid RF/VLC architecture is considered that can simultaneously provide light- ing and communication coverage across a room. Considered architecture involves a novel multi-element hemispherical bulb design, which can transmit multiple data streams over light emitting diode (LED) modules. Simulations considering various VLC transmitter configurations and topologies show that good link quality and high spatial reuse can be maintained in typical indoor communication scenarios

An investigation of the origin of soft X-ray excess emission from Narrow-line Seyfert 1 galaxies Akn564 and Mrk1044

We investigate the origin of the soft X-ray excess emission from narrow-line Seyfert 1 galaxies Akn564 and Mrk1044 using XMM-Newton observations. We find clear evidence for time delays between the soft and hard X-ray emission from Akn564 based on a 100ks long observation. The variations in the 4-10keV band lag behind that in the 0.2-0.5keV band by 1768+/-122s. The full band power density spectrum (PDS) of Akn~564 has a break at ~1.2e-3Hz with power-law indices of ~1 and ~3 below and above the break. The hard (3-10keV) band PDS is stronger and flatter than that in the soft (0.2-0.5keV) band. Based on a short observation of Mrk1044, we find no correlation between the 0.2-0.3keV and 5-10keV bands at zero lag. These observations imply that the soft excess is not the reprocessed hard X-ray emission. The high resolution spectrum of Akn564 obtained with the RGS shows evidence for a highly ionized and another weakly ionized warm absorber medium. The smeared wind and blurred ionized reflection models do not describe the pn data adequately. The spectrum is consistent with a complex model consisting of optically thick Comptonization in a cool plasma for the soft excess and a steep power-law, modified by two warm absorber media as inferred from the RGS data and the foreground Galactic absorption. The smeared wind and optically thick Comptonization models both describe the spectrum of Mrk1044 satisfactorily, but the ionized reflection model requires extreme parameters. The data suggest two component corona -- a cool, optically thick corona for the soft excess and a hot corona for the power-law component. The existence of a break in the soft band PDS suggests a compact cool corona that can either be an ionized surface of the inner disk or an inner optically thick region coupled to a truncated disk.Comment: Accepted for publication in ApJ, 19 page

Building Energy Modeling and Studies of Electric Power Distribution Systems with Distributed Energy Resources

There is significant opportunity for savings in energy and investment from improved performance of electric Power Distribution Systems (PDSs) through optimal planning and operation of conventional voltage-controlling devices. Novel multi-step model conversion and optimal capacitor planning (OCP) procedures are proposed for large-scale utility PDSs and are exemplified with an existing utility circuit of approximately 4,000 buses. Simulated optimal control and operation is achieved with a cluster-based approach that utilizes load-forecasting to minimize equipment degradation by intelligently dispersing device setting adjustments over time such that they remain most applicable. Improved performance may also be achieved through smart building technologies and Virtual Power Plant (VPP) control of increasingly more prevalent Distributed Energy Resources (DERs). The established simulation test bed for PDSs incorporates DERs to evaluate VPP implementations and an optimization process for control timing is proposed that minimizes targeted peak power and possible resulting increase in total daily energy. The advanced VPP controls incorporate the Consumer Technology Association (CTA) 2045 standard and EnergyStar performance characterizations to leverage HVAC systems as Generalized Energy Storage (GES) for load manipulation and to support the integration of demand-side generating DERs, such as local solar Photo-Voltaic (PV) systems