Distribution of products around a burning droplet: an analytical approach

A knowledge of the concentration distribution around a burning droplet is essential if accurate estimates are to be made of the transport coefficients in that region which influence the burning rate. There are two aspects of this paper; (1) determination of the concentration profiles, using the simple assumption of constant binary diffusion coefficients for all species, and comparison with experiments; and (2) postulation of a new relation for the therinal conductivity, which takes into account the variations of both temperature and concentrations of various species. First, the theoretical concentration profiles are evaluated and compared with experimental results reported elsewhere [5]. It is found that the agreement between the theory and experiment is fairly satisfactory. Then, by the use of these profiles and the relations proposed in the literature for the thermal conductivity of a mixture of nonpolar gases, a new relation for thermal conductivity: K = (A1 + B1 T) + (A2 + B2 T) xr (21). is suggested for analytical solutions of droplet combustion problems. Equations are presented to evaluate A1, A2, B1, and B2, and values of these terms for a few hydrocarbons are tabulated.

Possible use of self-calibration to reduce systematic uncertainties in determining distance-redshift relation via gravitational radiation from merging binaries

By observing mergers of compact objects, future gravity wave experiments would measure the luminosity distance to a large number of sources to a high precision but not their redshifts. Given the directional sensitivity of an experiment, a fraction of such sources (gold plated) can be identified optically as single objects in the direction of the source. We show that if an approximate distance-redshift relation is known then it is possible to statistically resolve those sources that have multiple galaxies in the beam. We study the feasibility of using gold plated sources to iteratively resolve the unresolved sources, obtain the self-calibrated best possible distance-redshift relation and provide an analytical expression for the accuracy achievable. We derive the lower limit on the total number of sources that is needed to achieve this accuracy through self-calibration. We show that this limit depends exponentially on the beam width and give estimates for various experimental parameters representative of future gravitational wave experiments DECIGO and BBO.

Wood-inhabiting Basidiomycetes in the Caucasus Region : Systematics and Biogeography

The Caucasus region is a hotspot of biodiversity and is one of the few areas in the Northern Hemisphere which harbor Pleistocene glacial refugia. The region encompasses Armenia, Azerbaijan, Georgia, the southernmost European Russia, NE Turkey, and northern Iran. The study on fungal composition of the Caucasus region and its connection and possible contribution to the present mycota of Europe has largely escaped empirical scrutiny. Using taxonomic surveys, phylogenetic reconstruction methods, haplotype analysis, and similarity tests, this study has aimed to, 1) summarize the knowledge on the occurrence of corticioids and polypores in the Caucasus region, 2) resolve the phylogenetic relationships of selected, resupinate wood-inhabiting basidiomycetes for which the Caucasus region is currently the mere, or one of the noteworthy areas of distribution, and, 3) assess the similarity of Caucasian corticioid fungi to those of Europe and important areas in the Northern Hemisphere, and to examine the significance of the Caucasus region as a glacial refugium for these fungi. This study provides the first catalogue of corticioids and polypores (635 species) occurring in the Caucasus region. The phylogeny and systematics of the Caucasian resupinate taxa in focus has been resolved and the usefulness of some morphological characters has been re-evaluated. In this context, four new genera and two new species were described and five new combinations were proposed, two of which were supplemented with modern descriptions. The species composition of corticioids in the Caucasus region is found to be distinctly more similar to Europe and North America than to East Asia and India. The highest molecular diversity and within population pairwise distance for Peniophorella praetermissa has been detected in the Caucasus and East Asia, with the isolates of the latter area being highly divergent from the European ones. This, and the assignment of root haplotype to the Caucasian isolates in a haplotype network for Phlebia tuberucalta and P. livida, call attention to the role of the Caucasus region in shaping the current mycota of Europe.

Comparison of Multiclass SVM Classification Methods to Use in a Supportive System for Distance Relay Coordination

This paper aims at evaluating the methods of multiclass support vector machines (SVMs) for effective use in distance relay coordination. Also, it describes a strategy of supportive systems to aid the conventional protection philosophy in combating situations where protection systems have maloperated and/or information is missing and provide selective and secure coordinations. SVMs have considerable potential as zone classifiers of distance relay coordination. This typically requires a multiclass SVM classifier to effectively analyze/build the underlying concept between reach of different zones and the apparent impedance trajectory during fault. Several methods have been proposed for multiclass classification where typically several binary SVM classifiers are combined together. Some authors have extended binary SVM classification to one-step single optimization operation considering all classes at once. In this paper, one-step multiclass classification, one-against-all, and one-against-one multiclass methods are compared for their performance with respect to accuracy, number of iterations, number of support vectors, training, and testing time. The performance analysis of these three methods is presented on three data sets belonging to training and testing patterns of three supportive systems for a region and part of a network, which is an equivalent 526-bus system of the practical Indian Western grid.

Influence of propellant choice on MPD arcjet cathode surface current density distribution

The radial current density on an MPD arcjet cathode surface is theoretically investigated for five propellants. It is found that excessive current concentration at the upstream end of the cathode occurs in the case of hydrogen. This undesirable effect is traced to the higher electrical conductivity of hydrogen plasma.

Power and Distribution Network Structure in the People's Republic of China - The Case of an Inland City in Transition

The aim of the current study is to examine the influence of the channel external environment on power, and the effect of power on the distribution network structure within the People’s Republic of China. Throughout the study a dual research process was applied. The theory was constructed by elaborating the main theoretical premises of the study, the channel power theories, the political economy framework and the distribution network structure, but these marketing channel concepts were expanded with other perspectives from other disciplines. The main method applied was a survey conducted among 164 Chinese retailers, complemented by interviews, photographs, observations and census data from the field. This multi-method approach enabled not only to validate and triangulate the quantitative results, but to uncover serendipitous findings as well. The theoretical contribution of the current study to the theory of marketing channels power is the different view it takes on power. First, earlier power studies have taken the producer perspective, whereas the current study also includes a distributor perspective to the discussion. Second, many power studies have dealt with strongly dependent relationships, whereas the current study examines loosely dependent relationships. Power is dependent on unequal distribution of resources rather than based on high dependency. The benefit of this view is in realising that power resources and power strategies are separate concepts. The empirical material of the current study confirmed that at least some resources were significantly related to power strategies. The study showed that the dimension resources composed of technology, know-how and knowledge, managerial freedom and reputation was significantly related to non-coercive power. Third, the notion of different outcomes of power is a contribution of this study to the channels power theory even though not confirmed by the empirical results. Fourth, it was proposed that channel external environment other than the resources would also contribute to the channel power. These propositions were partially supported thus providing only partial contribution to the channel power theory. Finally, power was equally distributed among the different types of actors. The findings from the qualitative data suggest that different types of retailers can be classified according to the meaning the actors put into their business. Some are more business oriented, for others retailing is the only way to earn a living. The findings also suggest that in some actors both retailing and wholesaling functions emerge, and this has implications for the marketing channels structure.

Neural network approach for fault location in unbalanced distribution networks with limited measurements

This paper presents an Artificial Neural Network (ANN) approach for locating faults in distribution systems. Different from the traditional Fault Section Estimation methods, the proposed approach uses only limited measurements. Faults are located according to the impedances of their path using a Feed Forward Neural Networks (FFNN). Various practical situations in distribution systems, such as protective devices placed only at the substation, limited measurements available, various types of faults viz., three-phase, line (a, b, c) to ground, line to line (a-b, b-c, c-a) and line to line to ground (a-b-g, b-c-g, c-a-g) faults and a wide range of varying short circuit levels at substation, are considered for studies. A typical IEEE 34 bus practical distribution system with unbalanced loads and with three- and single- phase laterals and a 69 node test feeder with different configurations are considered for studies. The results presented show that the proposed approach of fault location gives close to accurate results in terms of the estimated fault location.

Hardness of approximation results for the problem of finding the stopping distance in Tanner graphs

Tanner Graph representation of linear block codes is widely used by iterative decoding algorithms for recovering data transmitted across a noisy communication channel from errors and erasures introduced by the channel. The stopping distance of a Tanner graph T for a binary linear block code C determines the number of erasures correctable using iterative decoding on the Tanner graph T when data is transmitted across a binary erasure channel using the code C. We show that the problem of finding the stopping distance of a Tanner graph is hard to approximate within any positive constant approximation ratio in polynomial time unless P = NP. It is also shown as a consequence that there can be no approximation algorithm for the problem achieving an approximation ratio of 2(log n)(1-epsilon) for any epsilon > 0 unless NP subset of DTIME(n(poly(log n))).

Transient signal detection using wigner-ville distribution and wavelet denoising

The problem of detecting an unknown transient signal in noise is considered. The SNR of the observed data is first enhanced using wavelet domain filter The output of the wavelet domain filter is then transformed using a Wigner-Ville transform,which separates the spectrum of the observed signal into narrow frequency bands. Each subband signal at the output of the Wigner-ville block is subjected kto wavelet based level dependent denoising (WBLDD)to supress colored noise A weighted sum of the absolute value of outputs of WBLDD is passed through an energy detector, whose output is used as test statistic to take the final decision. By assigning weights proportional to the energy of the corresponding subband signals, the proposed detector approximates a frequency domain matched filter Simulation results are presented to show that the performance of the proposed detector is better than that of the wavelet packet transform based detector.

Comparative study of filter-bank mean-energy distance for automated segmentation of speech signals

This paper describes a method of automated segmentation of speech assuming the signal is continuously time varying rather than the traditional short time stationary model. It has been shown that this representation gives comparable if not marginally better results than the other techniques for automated segmentation. A formulation of the 'Bach' (music semitonal) frequency scale filter-bank is proposed. A comparative study has been made of the performances using Mel, Bark and Bach scale filter banks considering this model. The preliminary results show up to 80 % matches within 20 ms of the manually segmented data, without any information of the content of the text and without any language dependence. 'Bach' filters are seen to marginally outperform the other filters.

Photophysics of conjugated polymers: interplay between Forster energy migration and defect concentration in shaping a photochemical funnel in PPV

Recent single molecule experiments have suggested the existence of a photochemical funnel in the photophysics of conjugated polymers, like poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] (MEH-PPV). The funnel is believed to be a consequence of the presence of conformational or chemical defects along the polymer chain and efficient non-radiative energy transfer among different chromophore segments. Here we address the effect of the excitation energy dynamics on the photophysics of PPV. The PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poisson distribution. We observe that the Poisson distribution of the segment lengths explains the photophysics of PPV better than the Gaussian distribution. A recently proposed version of an extended particle-in-a-box' model is used to calculate the exciton energies and the transition dipole moments of the chromophores, and a master equation to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Forster expression. The observed excitation population dynamics confirms the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The time scale of spectral shift and energy transfer for our model polymer, with realistic values of optical parameters, is in the range of 200-300 ps. We find that the excitation energy may not always migrate towards the longest chromophore segments in the polymer chain as the efficiency of energy transfer between chromophores depends on the separation distance between the two and their relative orientation.

Structure and dynamics of benzene in one-dimensional channels

Molecular dynamics investigation of benzene in one-dimensional channel systems A1PO(4)-5, VPI-5, and carbon nanotube is reported. The results suggest that, in all the three host systems, the plane of benzene is almost perpendicular to the channel axis when the molecule is near the center of the channel and the plane of benzene is parallel to the channel axis when the molecule is near the wall of the channel. The density distribution of benzene as a function of channel length, z and the radial distance, r, from the channel axis is also different in the three host structures. Anisotropy in translational diffusion coefficient, calculated in body-fixed frame of benzene, suggests that benzene prefers to move with its plane parallel to the direction of motion in A1PO(4)-5 and VPI-5 whereas in carbon nanotube the motion occurs predominantly with the plane of the benzene perpendicular to the direction of motion.;Anisotropy associated with the rotational motion is seen to alter significantly in confinement as compared to liquid benzene. In A1PO(4)-5, the rotational anisotropy is reversed as compared to liquid benzene thereby suggesting that anisotropy arising out of molecular geometry can be reduced. Reorientational correlation times for C-6 and C-2 axes Of benzene are reported. Apart from the inertial decay of reorientational correlation function due to free, rotation, two other distinct regimes of decay are observed in narrower channels (AIPO(4)-5 and carbon nanotube): (i) an initial fast decay (0.5-2 ps) and (ii) a slower decay (>2 ps) of reorientational correlation function where C-6 decays slower than C-2 Similar to what is observed in liquid benzene. In the initial fast decay, it is seen that the decay for C-6 is faster than C-2 which is in contrast to what is observed in liquid benzene or for benzene confined in VPI-5.

Comparison of ANN models for predicting water quality in distribution systems

Deterministic models have been widely used to predict water quality in distribution systems, but their calibration requires extensive and accurate data sets for numerous parameters. In this study, alternative data-driven modeling approaches based on artificial neural networks (ANNs) were used to predict temporal variations of two important characteristics of water quality chlorine residual and biomass concentrations. The authors considered three types of ANN algorithms. Of these, the Levenberg-Marquardt algorithm provided the best results in predicting residual chlorine and biomass with error-free and ``noisy'' data. The ANN models developed here can generate water quality scenarios of piped systems in real time to help utilities determine weak points of low chlorine residual and high biomass concentration and select optimum remedial strategies.

Unsteady mixed convection with double diffusion over a horizontal cylinder and a sphere within a porous medium

The combined effects of the permeability of the medium, magnetic field, buoyancy forces and dissipation on the unsteady mixed convection flow over a horizontal cylinder and a sphere embedded in a porous medium have been studied. The nonlinear coupled partial differential equations with three independent variables have been solved numerically using an implicit finite-difference scheme in combination with the quasilinearization technique. The skin friction, heat transfer and mass transfer increase with the permeability of the medium, magnetic field and buoyancy parameter. The heat and mass transfer continuously decrease with the stream-wise distance, whereas the skin friction increases from zero, attains a maximum and then decreases to zero. The skin friction, heat transfer and mass transfer are significantly affected by the free stream velocity distribution. The effect of dissipation parameter is found to be more pronounced on the heat transfer than on the skin friction and mass transfer