The simulation of a twelve pulse diode rectifier with saturable reactors

A twelve pulse diode rectifier with saturable reactors to allow a degree of phase control is simulated using mathematical software. First order differential equations are solved numerically to allow calculation of line current. Application of the fast Fourier transform to line current provides harmonic current magnitudes. Line current waveforms and harmonic magnitudes from the simulation agree with expected results. The simulation is to be used as part of a harmonic analysis of multiple parallel connected diode rectifier

Enzymatic hollow fiber membrane bioreactor for penicilin hydrolysis

Continuous enzymatic reaction has been proven as an efficient technique for several industrial applications. In this study, a type of hollow fiber membrane bioreactor where penicillin acylase entrapped within membrane pores was applied to continuously hydrolyze Penicillin G The influences of various operating conditions on immobilization and enzymatic reaction processes were assessed. Amathematical model of the reactor behaviour at steady state condition was also developed. The immobilization results show that penicillin acylase was entrapped more than 90% (100,000 u.a m-?). Due to the much smaller size of 6-APA compared to the membrane pore, the solute diffuses freely through the membrane. However, the immobilized enzyme membrane retained around 35% of the solute. In addition, K,,, of immobilized penicillin acylase (8.04 mM) was slightly higher than that of free penicillin acylase (7.75 mM). The theoretical results indicated that convective transport was the main mechanism of mass transport even in the case where flux was very low. Low flux rate is important to avoid gel formation or enzyme release from membrane pores and to maximize the degree of conversion

Mathematical Tools for Calculation of the Effective Action in Quantum Gravity

We review the status of covariant methods in quantum field theory and quantum gravity, in particular, some recent progress in the calculation of the effective action via the heat kernel method. We study the heat kernel associated with an elliptic second-order partial differential operator of Laplace type acting on smooth sections of a vector bundle over a Riemannian manifold without boundary. We develop a manifestly covariant method for computation of the heat kernel asymptotic expansion as well as new algebraic methods for calculation of the heat kernel for covariantly constant background, in particular, on homogeneous bundles over symmetric spaces, which enables one to compute the low-energy non-perturbative effective action.Comment: 71 pages, 2 figures, submitted for publication in the Springer book (in preparation) "Quantum Gravity", edited by B. Booss-Bavnbek, G. Esposito and M. Lesc

Performance modelling of the Cambridge Fast Ring protocol

The Cambridge Fast Ring is high-speed slotted ring. The features that make it suitable for use at very large transmission rates are the synchronous transmission, the simplicity of the medium-access-control protocol, and the possibility of immediate retransmission of erroneous packets. A novel analytical model of the Cambridge Fast Ring with normal slots is presented. The model is shown to be accurate and usable over wide range of parameters. A performance analysis based on this model is presented

Warm Inflation with a General Form of the Dissipative Coefficient

We propose and investigate a general form of the dissipative coefficient $\Gamma=C_{\phi}T^{m}/\phi^{m-1}$ in warm inflation. We focus on discussing the strong dissipative processes $r=\Gamma/3H\gg1$ in the thermal state of approximate equilibrium. To this toy model, we give the slow-roll conditions, the amplitude and the index of the power spectrum under the general form of dissipative coefficient. Furthermore, the monomial potential and the hybrid-like potential are analyzed specifically. We conclude that the $m=0,3$ cases are worthy further investigation especially.Comment: 24 pages, no figures, to be published on JCA

A Simple Method to Check the Reliability of Annual Sunspot Number in the Historical Period 1610-1847

A simple method to detect inconsistencies in low annual sunspot numbers based on the relationship between these values and the annual number of active days is described. The analysis allowed for the detection of problems in the annual sunspot number series clustered in a few specific periods and unambiguous, namely: i) before Maunder minimum, ii) the year 1652 during the Maunder minimum, iii) the year 1741 in Solar Cycle -1, and iv) the so-called "lost" solar cycle in 1790s and subsequent onset of the Dalton Minimum.Comment: 15 pages, 3 figures, to be published in Solar Physic

A study on the growth of Pseudotolithus elongatus, Chrysichthys nigrodigitatus and Cynoglossus goreensis occurring in the Cross River Estuary

Samples of Pseudotolithus elongatus, Chrysichthys nigrodigitatus and Cynoglosus goreensis obtained from the Cross River Estuary (which is most probably the largest estuary water system along the coast of West Africa) between January 1980 and May 1981 were evaluated on basis of population dynamic analytical method postulated by Pauly (1980) for tropical fish stocks. Growth parameters were obtained for the fish species. Wherever possible, these results were compared to those obtained by Longhurst (1964d) and LeGuen (1971) in other West African waters. On the whole, results obtained in this study tend to indicate that the growth of the croaker, bagrid catfish and the sole in the Cross River Estuary is allometric, the third and fourth year-classes of P. elongatus the second and third class-year of C. nigrodigitatus and the fourth, fifth and sixth year classes of C. goreensis dominated in the age distribution of these fish specie

Studies of Pedestrian Amenity.

This report, produced for the Transport and Road Research Laboratory, summarises the results of an extensive literature search in two areas of pedestrian research: (I) Estimating the Number of Pedestrian Journeys (2) Pedestrian Amenity The report identifies gaps in current knowledge from the revealed literature and makes recommendations for best practice. Research proposals are made, to help alleviate such revealed gaps, in a companion report

Contributions of the seasonal and long term flood patterns of River Niger to the development and control of water hyacinth (Eichhornia crassipes) in Kainji Lake, Nigeria

(6 page document

Cameras and carcasses: historical and current methods for using artificial food falls to study deep-water animals

Deep-ocean animals remain poorly understood compared to their shallow-water relatives, mainly because of the great cost and difficulty involved in obtaining reliable ecological data. This is a serious issue as exploitation of deep-water resources progresses without sufficient data being available to assess its risks and impacts. First described almost 40 years ago, the use of baited cameras was pioneered by deep-sea biologists and is now a widely used technique for the assessing patterns of animal behaviour, abundance and biodiversity. The technique provides a non-destructive and cost-effective means of collecting data, where other techniques such as trawling are difficult or impractical. This review will first describe the evolution of baited camera techniques in deep-sea research from the early deployments, through recent programs to investigate trends in animal distribution with depth, latitude, and ocean basin. In the second section the techniques used for imaging, baiting, and analysis are synthesized, with special consideration for the modeling techniques used in assessing animal abundance and biomass