Scale characterizations in a DEA directional technology distance function framework

The present study extends prior research on data envelopment analysis (DEA)-based returns to scale in view of the fact that the standard methods are very restrictive. The extension is made in the context of the directional technology distance function that generalizes the Shephard input and output distance functions. The two main results in this extended setting are as follows. First, we show how Banker's most productive scale size (MPSS) concept is characterized. Second, we obtain scale elasticity measures and examine the properties and the relationships with standard scale elasticity measures.     

New route to optically active amine derivatives: ruthenium-catalyzed enantioselective hydrogenation of ene carbamates

The reaction of cyclic ketones with tert-butyl or benzyl carbamate under acidic conditions directly affords prochiral ene carbamates. Their enantioselective hydrogenation in the presence of a chiral ruthenium catalyst provides a new access to optically active carbamates easy to deprotect to the corresponding optically active amines.     

Have mirror planets been observed?

Over the last few years, several close orbiting (∼0.05 AU) large mass planets (M∼M_Jupiter) of nearby stars have been discovered. Their existence has been inferred from tiny doppler shifts in the light from the star. We suggest that these planets may be made of mirror matter. We also suggest that some stars such as our sun may also have a similar amount of mirror matter, which has escaped detection.     

On the integrable hierarchies associated with the N = 2 super Wn algebra

A new Lax operator is proposed from the viewpoint of constructing the integrable hierarchies related with the N = 2 super W_n algebra. It is shown that the Poisson algebra associated to the second Hamiltonian structure for the resulting hierarchy contains the N = 2 super Virasoro algebra as a proper subalgebra. The simplest cases are discussed in detail. In particular, it is proved that the supersymmetric two-boson hierarchy is one of the N = 2 supersymmetric KdV hierarchies. Also, a Lax operator is supplied for one of the N = 2 supersymmetric Boussinesq hierarchies.     

Modeling of pyridine synthesis process in a coupled fluidized bed reactor

To obtain the optimal operating conditions of a coupled reactor for pyridine synthesis, reactor modeling process is carried out in this paper. During the modeling process, the flow hydrodynamics, heat transfer behavior, inter-phase mass transfer behavior and reaction kinetics were taken into consideration consequently. Further, a regression program based on least square method was proposed to regress the model parameters. The prediction results agreed well with the experimental results with an average deviation of 5.9%. Finally, by setting suitable aim function, the optimal operating conditions of the coupled reactor for pyridine synthesis were determined.     

Rhodium dihydride complexes as models for the theoretical analysis of enantioselective hydrogenation reactions

A combination of molecular mechanics methods and extended Hückel calculations has been applied in order to have access to the more stable complexes expected to be involved as catalytic intermediates in the enantioselective hydrogenation of ketopantolactone (KPL) using chiral aminophosphine-phosphinite (AMPP) chlororhodium complexes. The product selectivity has been deduced from correlations between the prevailing configuration of the hydrogenated derivatives and the energetics of competing diastereomeric dihydride complexes of formula [RhCl(H)₂(AMPP)(KPL)] with the assumption that the enantioselectivity is controlled by the relative energies of such intermediates. The calculations have been obtained from the application of sequential and exhaustive search methodologies. The procedure has been applied to complexes bearing the aminophosphine-phosphinites (S)-Cp,Cp-ProNOP (IV) and (S)-Ph,Cp-ProNOP (V) and bis(aminophosphanes) derived from 2-(anilinomethyl)pyrrolidine (VI–IX). The latter induce a reversal of configuration of the major enantiomer of the hydrogenation product when varying specific substituents at the phosphorus atoms. Computations were carried out also for complexes bearing the two enantiomers (S)- and (R)-Ph,Cp-isoAlaNOP. The lowest energy complexes present enantiomeric structures. A novel insight into the local reactivity of the intermediates has been gained from determining the first migrating hydride according to the superdelocalizability parameter calculated for all isomers. Thus, the configurations of pantolactone arising from the alkoxyrhodium species obtained when assuming a nucleophilic attack of one of the hydrides to the carbonyl group of the ketone has been defined and are in total agreement with the experimental data.     

Markov-type fuzzy decision processes with a discounted reward on a closed interval

We formulate a new multi-stage decision process with Markov-type fuzzy transition, which is termed Markov-type fuzzy decision process. In the general framework of the decision process, both of state and action are assumed to be fuzzy itself. The transition of states is defined using the fuzzy relation with Markov property and the discounted total reward is described as a fuzzy number on a closed bounded interval. To discuss the optimization problem, a partial order of convex fuzzy numbers is introduced. In this paper the discounted total reward associated with an admissible stationary policy is characterized by a unique fixed point of the contractive mapping. Moreover, the optimality equation for the fuzzy decision model is derived under some continuity conditions. Also, an illustrated example is given to explain the theoretical results and the computation in the paper.     

Coupling a two-stage absorption heat transformer with finite heat sources and sinks

The coupling among a two-stage heat transformer (TSHT) and finite heat sources and sinks is considered. A novel configuration is proposed, in which the evaporator of the second stage is fed both by the absorber of the first stage and by the external source. A lumped-parameter mathematical model is used to compute the performance of the proposed TSHT. It has been found that the range of applicability is widened, when compared with the usual configuration. Moreover, the use of a two-stage apparatus allows one to noticeably increase the performance compared with that obtainable with a simpler single-stage transformer. Thus, it is possible to increase the output heat and/or the user temperature, to reduce the discharge temperature, or to use lower quality energy sources. The results also allow one to draw some more general conclusions on the applicability of absorption heat transformers of different configurations, when different heat sources/sinks are considered.     

Dynamic steady crack growth in elastic-plastic solids—propagation of strong discontinuities

The near-tip field of a mode I crack growing steadily under plane strain conditions is studied. A key issue is whether strong discontinuities can propagate under dynamic conditions. Theories which impose rather restrictive assumptions on the structure of an admissible deformation path through a dynamically propagating discontinuity have been proposed recently. Asymptotic solutions for dynamic crack growth, based on such theories, do not contain any discontinuities. In the present work a broader family of deformation paths is considered and we show that a discontinuity can propagate dynamically without violating any of the mechanical constitutive relations of the material. The proposed theory for the propagation of strong discontinuities is corroborated by very detailed finite element calculations. The latter shows a plane of strong discontinuity emanating from the crack tip (with its normal pointing in the direction of crack advance) and moving with the tip. Elastic unloading ahead of and/or behind the plane of discontinuity and behind the crack tip have also been observed.The numerical investigation is performed within the framework of a boundary layer formulation whereby the remote loading is fully specified by the first two terms in the asymptotic solution of the elasto-dynamic crack tip field, characterized by K₁, and T. It is shown that the family of near-tip fields, associated with a given crack speed, can be arranged into a one-parameter field based on a characteristic length, L_g, which scales with the smallest dimension of the plastic zone. This extends a previous result for quasi-static crack growth.