A Novel Approach for Designing Generator Excitation controllers Using the IDA-PBC Technique

This paper presents a novel approach for designing of generator excitation controllers using Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) technique for a Single Machine Infinite Bus (SMIB) system that can also be directly used in a multi-machine environment. The generator system equations are modified by referencing the rotor angle with respect to the secondary of the transformer bus instead of the infinite bus. For the modified system equations, IDA-PBC is applied to stabilize the system around an operating condition. The IDA-PBC design results in a Lyapunov function for the modified system. The new control law is practically feasible and can be applied directly to multi-machine system without referring to external system parameters. The effectiveness of the proposed controller is tested on a SMIB and a 10 generator 39 bus test system for a range of operating conditions. The Proposed excitation controller has shown good performance for both small and large disturbances when compared to the performance of a conventional static exciter with power system stabilizer.

Spin distributions in antiferromagnetically coupled Mn2+Cu2+ systems: from the pair to the infinite chain

Probably the most informative description of the ground slate of a magnetic molecular species is provided by the spin density map. Such a map may be experimentally obtained from polarized neutron diffraction (PND) data or theoretically calculated using quantum chemical approaches. Density functional theory (DFT) methods have been proved to be well-adapted for this. Spin distributions in one-dimensional compounds may also be computed using the density matrix renormalization group (DMRG) formalism. These three approaches, PND, DFT, and DMRG, have been utilized to obtain new insights on the ground state of two antiferromagnetically coupled Mn2+Cu2+ compounds, namely [Mn(Me-6-[14]ane-N-4)Cu(oxpn)](CF3SO3)(2) and MnCu(pba)(H2O)(3) . 2H(2)O, with Me-6-[14]ane-N-4 = (+/-)-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, oxpn = N,N'-bis(3-aminopropyl)oxamido and pba = 1,3-propylenebis(oxamato). Three problems in particular have been investigated: the spin distribution in the mononuclear precursors [Cu(oxpn)] and [Cu(pba)](2-), the spin density maps in the two Mn2+Cu2+ compounds, and the evolution of the spin distributions on the Mn2+ and Cu2+ sites when passing from a pair to a one-dimensional ferrimagnet.

Generation of Minimum Leakage Input Vectors with Constrained NBTI Degradation

Technology scaling has caused Negative Bias Temperature Instability (NBTI) to emerge as a major circuit reliability concern. Simultaneously leakage power is becoming a greater fraction of the total power dissipated by logic circuits. As both NBTI and leakage power are highly dependent on vectors applied at the circuit’s inputs, they can be minimized by applying carefully chosen input vectors during periods when the circuit is in standby or idle mode. Unfortunately input vectors that minimize leakage power are not the ones that minimize NBTI degradation, so there is a need for a methodology to generate input vectors that minimize both of these variables.This paper proposes such a systematic methodology for the generation of input vectors which minimize leakage power under the constraint that NBTI degradation does not exceed a specified limit. These input vectors can be applied at the primary inputs of a circuit when it is in standby/idle mode and are such that the gates dissipate only a small amount of leakage power and also allow a large majority of the transistors on critical paths to be in the “recovery” phase of NBTI degradation. The advantage of this methodology is that allowing circuit designers to constrain NBTI degradation to below a specified limit enables tighter guardbanding, increasing performance. Our methodology guarantees that the generated input vector dissipates the least leakage power among all the input vectors that satisfy the degradation constraint. We formulate the problem as a zero-one integer linear program and show that this formulation produces input vectors whose leakage power is within 1% of a minimum leakage vector selected by a search algorithm and simultaneously reduces NBTI by about 5.75% of maximum circuit delay as compared to the worst case NBTI degradation. Our paper also proposes two new algorithms for the identification of circuit paths that are affected the most by NBTI degradation. The number of such paths identified by our algorithms are an order of magnitude fewer than previously proposed heuristics.

Mining sentiments from songs using latent dirichlet allocation

Song-selection and mood are interdependent. If we capture a song’s sentiment, we can determine the mood of the listener, which can serve as a basis for recommendation systems. Songs are generally classified according to genres, which don’t entirely reflect sentiments. Thus, we require an unsupervised scheme to mine them. Sentiments are classified into either two (positive/negative) or multiple (happy/angry/sad/...) classes, depending on the application. We are interested in analyzing the feelings invoked by a song, involving multi-class sentiments. To mine the hidden sentimental structure behind a song, in terms of “topics”, we consider its lyrics and use Latent Dirichlet Allocation (LDA). Each song is a mixture of moods. Topics mined by LDA can represent moods. Thus we get a scheme of collecting similar-mood songs. For validation, we use a dataset of songs containing 6 moods annotated by users of a particular website.

A stylometric study and assessment of machine translators

In this work we present a statistical approach inspired by stylometry -measurement of author style- to study the characteristics of machine translators. Our approach quantifies the style of a translator in terms of the properties derived from the distribution of stopwords in its output - a standard approach in modern stylometry. Our study enables us to match translated text to the source machine translator that generated them. Also, the stylometric closeness of human generated text to that generated by machine translators provides handles to assess the quality of machine translators.

Iminodiacetic acid functionalized polypyrrole modified electrode as Pb(II) sensor: Synthesis and DPASV studies

An electrochemical lead ion sensor has been developed by modification of carbon paste electrode (CPE) using polypyrrole functionalized with iminodiacetic acid (IDA-PPy) containing carboxyl group. The electrochemical response of Pb2+ ion on the IDA-PPy modified CPE has been evaluated and the controling parameters have been optimized using differential pulse anodic stripping voltammetry (DPASV). The IDA-PPy modified CPE shows a linear correlation for Pb2+ concentrations in the range of 1 x 10(-6) to 5 x 10(-9) M and the lower detection limit of Pb2+ has been found to be 9.6 x 10(-9) M concentration. Other tested metal ions, namely Cu2+, Cd2+, Co2+, Hg2+, Ni2+ and Zn2+, do not exhibit any voltammetric stripping response below 1 x 10(-7) M concentration. However, the Pb2+ response is affected in the presence of molar equivalents or higher concentrations of Cu2+, Cd2+ and Co2+ ions in binary systems with Pb2+, consequent to their ability to bind with iminodiacetic acid, while Hg2+, Ni2+ and Zn2+ do not interfere at all. A good correlation has been observed between the lead concentrations as analyzed by DPASV using IDA-PPy modified CPE and atomic absorption spectrophotometry for a lead containing industrial effluent sample. (C) 2014 Elsevier Ltd. All rights reserved.

Colorimetric detection of melamine based on the size effect of AuNPs

A simple colorimetric detection of melamine was studied using 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) citrate-capped gold nanoparticles (AuNPs). The AuNPs aggregated in aqueous solution in the presence of melamine, showing a visual color change from red to blue. This color change led to a shift in the absorption peak from 527 nm, 526 nm, and 525 nm to 638 nm, 626 nm, and 680 nm for AuNPs-I, AuNPs-II, and AuNPs-III, respectively. For all the three AuNPs, linearity was observed between the melamine concentration in aqueous solution and the absorbance ratios, A(638/527), A(626/525), and A(680/526), respectively. The limit of detection (LOD) for melamine for the AuNPs-II was found to be 2.37 x 10(-8) M (correlation coefficient R-2 = 0.9745), which showed better sensitivity as compared to the LOD of the AuNPs-I and AuNPs-III, which were 3.3 x 10(-8) M and 8.9 x 10(-8) M, respectively. The synthesis of AuNPs-II also involved a lower HAuCl4 concentration compared with the other two types of AuNPs, which may reduce the process cost. The AuNPs-II was selected to analyze melamine in pre-treated milk samples, and the recovery percentage was in the range of 91-106%. Thus, the efficient detection of melamine was possible using AuNPs-II for the on-site detection without the aid of expensive instruments.

An estimate of the number of tropical tree species

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between similar to 40,000 and similar to 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of similar to 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of similar to 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.