121,773 research outputs found
GAS-LIQUID-CHROMATOGRAPHY TOGETHER WITH C-13 NUCLEAR MAGNETIC-RESONANCE SPECTROMETRY IN THE ANALYSIS OF DIASTEREOMERIC MIXTURES OF ALCOHOLS AND DIOLS
No full textHYDRATED SIGMA-BONDED ORGANOMETALLIC CATIONS IN ORGANIC-SYNTHESIS .2. ALLYLSTANNATION OF ALDEHYDES BY CROTYLTIN CHLORIDES IN ACID-MEDIA
No full textAllylstannation of three aldehydes RCHO (RC2H5, (CH3)2CH, and (CH3)3C) with crotyltin chlorides Bu3-nClnSnCH2CHCHCH3, n = 1, 2, and 3, has been carried out in the presence of aqueous 0.1–4.0 M HClO4. The stereochemical course of these reactions, to give the threo / erythro alcohols RCH(OH)CH(CH3)CHCH2 and/or the E/Z alcohols RCH(OH)CH2CHCHCH3, depends on the number, n, of the chlorine atoms bonded to tin and on the concentration of perchloric acid. In 0.1 M HClO4, the threo / erythro isomer pair is obtained. With increasing acid concentration, the threo / erythro pair is gradually replaced by the E/Z isomer pair, which is the sole product in 4 M HClO4. However, in most of the examined cases the ratio anti / syn = (threo + E)/(erythro + Z) remains constant for any given aldehyde and crotyl compound. Stereoselectivity, which is fairly good in some cases, is determined by the nature of the aldehyde: syn-convergence occurs with pivalaldehyde, and anti-convergence with isobutyraldehyde. No stereoselection is found in the case of propanaldehyde
Organotin Halides as Catalytic Precursors in Dehydration Processes. Part 1. Acetalizations and Transacetalizations of Alicyclic Diols and Polyols
No full textA multigrid method for PDE-constrained optimization with uncertain inputs
No full textIn this manuscript, we present a collective multigrid algorithm to solve efficiently the large saddle-point systems of equations that typically arise in PDE-constrained optimization under uncertainty, and develop a novel convergence analysis of collective smoothers and collective two-level methods. The multigrid algorithm is based on a collective smoother that at each iteration sweeps over the nodes of the computational mesh, and solves a reduced saddle-point system whose size is proportional to the number N of samples used to discretized the probability space. We show that this reduced system can be solved with optimal O(N) complexity. The multigrid method is tested both as a stationary method and as a preconditioner for GMRES on three problems: a linear-quadratic problem, possibly with a local or a boundary control, for which the multigrid method is used to solve directly the linear optimality system; a nonsmooth problem with box constraints and -norm penalization on the control, in which the multigrid scheme is used as an inner solver within a semismooth Newton iteration; a risk-averse problem with the smoothed CVaR risk measure where the multigrid method is called within a preconditioned Newton iteration. In all cases, the multigrid algorithm exhibits excellent performances and robustness with respect to the parameters of interest.CSQ
A Multigrid Solver for PDE-Constrained Optimization with Uncertain Inputs
No full textIn this manuscript, we present a collective multigrid algorithm to solve efficiently the large saddle-point systems of equations that typically arise in PDE-constrained optimization under uncertainty, and develop a novel convergence analysis of collective smoothers and collective two-level methods. The multigrid algorithm is based on a collective smoother that at each iteration sweeps over the nodes of the computational mesh, and solves a reduced saddle-point system whose size is proportional to the number N of samples used to discretized the probability space. We show that this reduced system can be solved with optimal O(N) complexity. The multigrid method is tested both as a stationary method and as a preconditioner for GMRES on three problems: a linear-quadratic problem, possibly with a local or a boundary control, for which the multigrid method is used to solve directly the linear optimality system; a nonsmooth problem with box constraints and L1-norm penalization on the control, in which the multigrid scheme is used as an inner solver within a semismooth Newton iteration; a risk-averse problem with the smoothed CVaR risk measure where the multigrid method is called within a preconditioned Newton iteration. In all cases, the multigrid algorithm exhibits excellent performances and robustness with respect to the parameters of interest
Organotin halides as catalytic precursor in dehydration processes. V. Acetalization and transacetalization of alicyclic diols and polyols
No full textA Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
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