186,798 research outputs found
Crystal structure of 2,4-bis(2-chlorophenyl)-7-tert-pentyl-3-azabicyclo[3.3.1]nonan-9-one
No full textThe title compound, C25H29Cl2NO, which is a chloro analog of 2,4-bis(2-bromophenyl)-7-(tert-pentyl)-3-azabicyclo[3.3.1]nonan-9-one [Park, Ramkumar & Parthiban (2012). Acta Cryst. E68, o2946], exists in a twin-chair conformation with an equatorial orientation of the 2-chlorophenyl groups. The tert-pentyl group on the cyclohexanone adopts an exocyclic equatorial position and is disordered between two orientations in a ratio 0.520 (8):0.480 (8). The crystal packing shows no directional contacts beyond van der Waals contacts
Generalized drift-diffusion for microscopic thermoelectricity
Get PDFThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 191-193).Although thermoelectric elements increasingly incorporate nano-scale features in similar material systems as other micro-electronic devices, the former are described in the language of irreversible thermodynamics while devices such as heterojunction bipolar transistors and semiconductor lasers are often described with the drift-diffusion equations. We present a microscopic description of the thermoelectric effects using a generalization of the common drift-diffusion formulation of semi-classical transport. We then replicate these basic results in a commerical device simulation package to explore Peltier cooling at a basic p-n junction. This framework should enable the design of spatially-inhomogenenous thermoelectric elements and internally-cooled micro-electronic devices.by Parthiban Santhanam.S.M
A review of zirconium disulfide: Structural characterization, properties, applications, and prospects of dichalcogenide materials
No full textIn recent decades, two-dimensional (2D) materials have attracted significant attention for their unique electronic, optical, mechanical, and electrical properties, making them promising for applications in catalysis, solar cells, batteries, and superconductivity. Among 2D materials, transition-metal dichalcogenides (TMDCs) are noteworthy due to their tunable bandgap, high carrier mobility, and mechanical flexibility. Zirconium disulfide (ZrS2), a member of the TMDC family, stands out for its thermodynamic stability, environmental friendliness, and excellent thermoelectric properties. This paper provides an in-depth discussion of the synthesis of ZrS2 and its related materials, detailing various crystal structures and characterization methods. Additionally, the properties and applications of ZrS2 and its analogs are thoroughly reviewed, with a focus on their potential future developments
A geo-spatial approach to perceive the groundwater regime of hard rock terrain- a case study from Morappur area, Dharmapuri district, South India
No full textThe goal of the present study is to identify the groundwater regime of Morappur area at Dharmapuri district, India. The study area covers an area of 410 sqkm. The area belongs to a hard rock terrain where the primary porosity is feeble and the secondary porosity offered by fracture, joints and shear zones etc, contributes to the groundwater regime. The availability of surface water resources is sparse and hence the groundwater repositories are intensely utilized. In the current study area, the availability of groundwater is limited due to scanty rainfall and poor recharge. The entire study area underlain by hard crystalline rocks of Archaean age, Charnokite and Hornblende epidote gneiss are the main rock types encountered in the area. The over exploitation of these resources more than the adequate recharge has resulted to decrease in the groundwater level. In this context, it is very much important to identify and understand the groundwater regime of this area for the better groundwater monitoring and conservation of this precious resource. Remote Sensing and GIS are playing a vital role in the advancement of hydro-geological studies. The use of conventional methods alone has its own limitations in comprehending the groundwater regime of the area. The integrated study using remote sensing, field studies together with GIS has helped to understand the role of structural, lithological and geomorphic units in controlling the groundwater occurrence and movement in the present study area. Various thematic maps were prepared from the satellite images and they were integrated and incorporated in a GIS platform along with collateral information to study the groundwater regime of Morappur area. The outcome of this study clearly shows the importance of the geospatial studies in identifying the role of satellite imageries and geospatial techniques to understand the groundwater regime of a hard rock terrain
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Benchmark ab initio energy profiles for the gas-phase Y- + CH3X → CH3Y + X- (X,Y = F,Cl,Br): validation of hybrid DFT methods
No full textThe energetics of the gas-phase S(N)2 reactions Y- + CH3X- --> CH3Y + X- (where X,Y = F,Cl,Br), were studied using (variants on) the recent Wi and W2 ab initio computational thermochemistry methods. These calculations involve CCSD and CCSD(T) coupled cluster methods, basis sets of up to spdfgh quality, extrapolations to the one-particle basis set limit, and contributions of inner-shell correlation, scalar relativistic effects, and (where relevant) first-order spin-orbit coupling. Our computational predictions are in excellent agreement with experimental data where these have small error bars; in a number of other instances reexamination of the experimental data may be in order. Our computed benchmark data (including cases for which experimental data are unavailable altogether) are used to assess the quality of a number of compound thermochemistry schemes such as G2 theory, G3 theory, and CBS-QB3, as well as a variety of density functional theory methods. Upon applying some modifications to the level of theory used for the reference geometry (adding diffuse functions, replacing B3LYP by the very recently proposed mPW1K functional [Lynch, B. J.; Fast, P. L.; Harris, M.; Truhlar, D. G. J. Phys. Chem. A 2000, 104, 4811]), the compound methods appear to perform well. Only the "half-and-half" functionals BH&HLYP and mPWH&HPW91 and the empirical mPW1K functional, consistently find all required stationary points; the other functionals fail to find a transition state in the F/Br case. BH&HLYP and mPWH&HPW91 somewhat overcorrect for the tendency of B3LYP land, to a somewhat lesser extent, mPW1PW91) to underestimate barrier heights. The Becke97 and Becke97-1 functionals perform similarly to B3LYP for the problem under study, while the HCTH and HCTH-120 functionals both appear to underestimate central barriers. HCTH underestimates complexation energies; this problem is resolved in HCTH-120. mPW1K appears to exhibit the best performance of the functionals considered, although its energetics are still inferior to the compound thermochemistry methods. mPW1K, however, appears to be very suitable for generating reference geometries for more elaborate thermochemical methods in kinetics applications
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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