New Transformation (new + transformation)

Distribution by Scientific Domains


Selected Abstracts


ChemInform Abstract: Use of in situ Generated Ketene in the Wynberg ,-Lactone Synthesis: New Transformations of the Dichlorinated ,-Lactone Products.

CHEMINFORM, Issue 11 2001
Reginald Tennyson
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


A new space-vector transformation for four-conductor systems

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2000
A. Ferrero
Linear transformations are often employed in the study of three-phase systems, since they allow for simplifying the equations describing the system behaviour. Among them, the Fortescue, Clarke and Park transformations are very widely employed. In particular, the last one leads to the formulation of the Space-Vector theory, that is currently employed in the fields of AC machine theory, power definitions and active filtering. The greatest limitation in the use of these transformations is that they are restricted to systems with only three conductors. However, four-conductor systems are often present in the common practice of the electric systems and the application of the Space- Vector theory to such systems is not as straightforward as in the case of the three-conductor systems: a zero-sequence quantity must be considered separately. This paper proposes a linear transformation that extends the properties of the Space- Vector theory to four-conductor systems, and includes the Park transformation as a special case. The mathematical derivation of this new transformation is reported, and its application is discussed by means of some examples. [source]


Exact methods based on node-routing formulations for undirected arc-routing problems

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2006
R. Baldacci
Abstract This article proposes a new transformation of undirected arc-routing problems into equivalent node-routing problems, with emphasis on the transformation of Capacitated Arc Routing Problems (CARP) into Capacitated Vehicle Routing Problems (CVRP). For this last case, an analogue transformation has already been proposed in Pearn et al., where each required CARP edge is mapped onto a triplet of CVRP nodes. In our case, only two CVRP nodes are needed for every CARP required edge. The transformed instances have a structure and a dimension that make most CARP benchmarks solvable by state of the art CVRP techniques. We thus propose a general purpose transformation of arc into node-routing problems and new results on lower bounds and exact methods for CARP instances. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 47(1), 52,60 2006 [source]


Palladium-Catalyzed Cross-Coupling Reactions of Amines with Alkenyl Bromides: A New Method for the Synthesis of Enamines and Imines

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2004
José Barluenga Prof. Dr.
Abstract The palladium-catalyzed cross-coupling reaction of alkenyl bromides with secondary and primary amines gives rise to enamines and imines, respectively. This new transformation expands the applicability of palladium-catalyzed CN bond forming reactions (the Buchwald,Hartwig amination), which have mostly been applied to aryl halides. After screening of different ligands, bases, and solvents, the catalytic combination [Pd2(dba)3]/BINAP in the presence of NaOtBu in toluene gave the best results in the cross-coupling of secondary amines with 1-bromostyrene (dba=dibenzylideneacetone, BINAP=2,2,-bis(diphenylphosphino)-1,1,-binaphthyl). The corresponding enamines are obtained cleanly and in nearly quantitative yields. However, steric hindrance seems to be a limitation of the reaction, as amines carrying large substituents are not well converted. The same methodology can be applied to the coupling of secondary amines with 2-bromostyrene. Moreover, the reaction with substituted 2-bromopropenes allows regioselective synthesis of isomerizable terminal enamines without isomerization of the double bond. The best catalytic conditions for the cross-coupling of 1-bromostyrene with primary amines include again the use of the Pd0/BINAP/NaOtBu system. The reaction gives rise to the expected imines in very short times and with low catalyst loadings. A set of structurally diverse imines can be prepared by this methodology through variations in the structure of both coupling partners. However, 2-bromostyrene failed to give good results in this coupling reaction, probably due to product inhibition of the catalytic cycle. Competition experiments of vinyl versus aryl amination reveal that the reaction occurs preferentially on vinyl bromides. La reacción de acoplamiento cruzado de bromuros de alquenilo con aminas secundarias y primarias da lugar a enaminas e iminas respectivamente. Esta nueva transformación expande las aplicaciones de la reacción de formación de enlaces CN catalizada por paladio (aminación Buchwald,Hartwig), que se había limitado fundamentalmente a haluros de arilo. Después de un estudio de diferentes ligandos. bases y disolventes, los mejores resultados en la reacción de acoplamiento cruzado de aminas secundarias con 1-bromoestireno, se obtuvieron para el catalizador constituido por la combinación Pd/BINAP en presencia de NaOtBu en tolueno. Las correspondientes enaminas se obtienen limpiamente y con rendimientos prácticamente cuantitativos. Sin embargo, los impedimentos estéricos en la amina parecen ser una limitación de la reacción, puesto que aminas con sustituyentes voluminosos proporcionan conversiones bajas. La misma metodología puede aplicarse al acoplamiento de aminas secundarias con 2-bromoestireno. Además, la reacción con 2-bromopropenos sustituidos permite obtener de forma regioselectiva enaminas terminales isomerizables, sin que la isomerización del doble enlace tenga lugar. Las mejores condiciones catalíticas para el acoplamiento de aminas primarias con 1-bromoestireno incluyen de nuevo la utilización del sistema Pd(0)/BINAP/NaOtBu. La reacción proporciona las iminas esperadas en tiempos de reacción muy cortos y con baja carga del catalizador. Mediante esta metodología pueden prepararse un conjunto de iminas de gran diversidad estructural, permitiendo variaciones en ambos reactivos de acoplamiento. Sin embargo, la reacción con 2-bromoestireno no produce buenos resultados en este acoplamiento, probablemente debido a inhibición del ciclo catalítico por parte del producto de reacción. Finalmente, experimentos de competencia de aminación vinílica frente a aminación arílica, ponen de manifiesto que esta reacción se produce de forma preferente sobre los bromuros de vinilo. [source]


Revitalizing modifiability of legacy assets

JOURNAL OF SOFTWARE MAINTENANCE AND EVOLUTION: RESEARCH AND PRACTICE, Issue 4-5 2004
Niels Veerman
Abstract The modifiability of Cobol legacy code is discussed and an approach is proposed to improve the modifiability using automatic restructuring transformations. An algorithm is presented that enables the application of these transformations to large industrial Cobol systems. The transformations were adapted to a system of 80,000 lines of code by extending them with new transformations and transformation patterns. The resulting source code is analysed and discussed. Two case studies (over 5 million lines of code in total) with real-life Cobol programs show the large-scale application of the transformations. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Error estimates for mixed finite element approximations of the viscoelasticity wave equation

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 17 2004
Liping Gao
Abstract This paper studies mixed finite element approximations to the solution of the viscoelasticity wave equation. Two new transformations are introduced and a corresponding system of first-order differential-integral equations is derived. The semi-discrete and full-discrete mixed finite element methods are then proposed for the problem based on the Raviart,Thomas,Nedelec spaces. The optimal error estimates in L2 -norm are obtained for the semi-discrete and full-discrete mixed approximations of the general viscoelasticity wave equation. Copyright © 2004 John Wiley & Sons, Ltd. [source]