Stochastic Optimization in Econometric Models – A Comparison of GA, SA and RSG

This paper shows that, in case of an econometric model with a high sensitivity to data, using stochastic optimization algorithms is better than using classical gradient techniques. In addition, we showed that the Repetitive Stochastic Guesstimation (RSG) algorithm –invented by Charemza-is closer to Simulated Annealing (SA) than to Genetic Algorithms (GAs), so we produced hybrids between RSG and SA to study their joint behavior. The evaluation of all algorithms involved was performed on a short form of the Romanian macro model, derived from Dobrescu (1996). The subject of optimization was the model’s solution, as function of the initial values (in the first stage) and of the objective functions (in the second stage). We proved that a priori information help “elitist “ algorithms (like RSG and SA) to obtain best results; on the other hand, when one has equal believe concerning the choice among different objective functions, GA gives a straight answer. Analyzing the average related bias of the model’s solution proved the efficiency of the stochastic optimization methods presented.underground economy, Laffer curve, informal activity, fiscal policy, transitionmacroeconomic model, stochastic optimization, evolutionary algorithms, Repetitive Stochastic Guesstimation

SURVEY DESIGN USING INDIVIDUAL NUMERICAL SCALES IN THE FRAMEWORK OF ANALYTIC HIERARCHY PROCESSES

This paper discusses the adequacy of a generalization of Saaty’s 1-9 scale proposed by Liang at all (2008) in the attempt to identify individual scales. Several surveys in completely different areas were conducted on different topics. Comparisons among the consistency index-as a measure of a “good answer” and the previously mentioned scale reveal a non monotonic correspondence among those two criterions. Also, the individual scale considered – which is in itself a generalization of other similar scales for measuring individual responses – is not uniquely determined for a single respondent and is very often contradictory. Yet, the potential benefits in determining individual scales of measurement are enormous and maybe the most important one is getting rid of the myth of the good appliance of the “law of large numbers” in social sciences.Analytic Hierarchy Processes, knowledge sharing, mapping, numerical scale, simulated annealing, verbal responses.

Repetitive Stochastic Guesstimation for Estimating Parameters in a GARCH(1,1) Model

A behavioral algorithm for optimization - Repetitive Stochastic Guesstimation (RSG) - is adapted, with complete proofs for its global convergence, for estimating parameters in a GARCH(1,1) model, based on a very small number of observations. Estimators delivered by this algorithm for the example of a GARCH(1,1) model are dependent on some computational capabilities - namely number of iterations and replications performed. In this context, the Large Numbers Law might be applied in a completely different dimension. An alternative toward waiting until the historical data series are recorded (while the underling process may change several times) is to use computers for correctly extracting information from the most recent data. Given the existent computational support, it is also possible to determine estimates for the rates of convergence. As a result, potential benefits of this econometric technique can be gained in case of very young financial markets from Eastern European countries. Also, prediction and political decisions based on these estimations are properly grounded.RSG, GARCH Model, financial markets

Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins

Dinuclear nickel phenoxyiminato olefin polymerization catalysts based on rigid p-terphenyl frameworks are reported. Permethylation of the central arene of the terphenyl unit and oxygen substitution of the peripheral rings ortho to the aryl–aryl linkages blocks rotation around these linkages, allowing atropisomers of the ligand to be isolated. The corresponding syn and anti dinickel complexes (25-s and 25-a) were synthesized and characterized by single-crystal X-ray diffraction. These frameworks limit the relative movement of the metal centers, restricting the metal–metal distance. Kinetics studies of isomerization of a ligand precursor (7-a) allowed the calculation of the activation parameters for the isomerization process (ΔH^‡ = 28.0 ± 0.4 kcal × mol^(–1) and ΔS^‡ = −12.3 ± 0.4 cal mol^(–1) K^(–1)). The reported nickel complexes are active for ethylene polymerization (TOF up to 3700 (mol C_2H_4) (mol Ni)^(−1) h^(–1)) and ethylene/α-olefin copolymerization. Only methyl branches are observed in the polymerization of ethylene, while α-olefins are incorporated without apparent chain walking. These catalysts are active in the presence of polar additives and in neat tetrahydrofuran. The syn and anti isomers differ in polymerization activity, polymer branching, and polymer molecular weight. For comparison, a series of mononuclear nickel complexes (26, 27-s, 27-a, 28, 30) was prepared and studied. The effects of structure and catalyst nuclearity on reactivity are discussed

Bimetallic Effects on Ethylene Polymerization in the Presence of Amines: Inhibition of the Deactivation by Lewis Bases

Dinickel complexes supported by terphenyl ligands appended with phenoxy and imine donors were synthesized. Full substitution of the central arene blocks rotation around the aryl–aryl bond and allows for the isolation of atropisomers. The reported complexes perform ethylene polymerization in the presence of amines. The inhibiting effect of polar additives is up to 250 times lower for the syn isomer than the anti isomer. Comparisons with mononuclear systems indicate that the proximity of the metal centers leads to the observed inhibitory effect on the deactivation of the catalysts

Nickel-Mediated Hydrogenolysis of C–O Bonds of Aryl Ethers: What Is the Source of the Hydrogen?

Mechanistic studies of the hydrogenolysis of aryl ethers by nickel were undertaken with (diphosphine)aryl methyl ethers. A Ni(0) complex containing Ni–arene interactions adjacent to the aryl–O bond was isolated. Heating led to aryl–O bond activation and generation of a nickel aryl methoxide complex. Formal β-H elimination from this species produced a nickel aryl hydride which can undergo reductive elimination in the presence of formaldehyde to generate a carbon monoxide adduct of Ni(0). The reported complexes map out a plausible mechanism of aryl ether hydrogenolysis catalyzed by nickel. Investigations of a previously reported catalytic system using isotopically labeled substrates are consistent with the mechanism proposed in the stoichiometric system, involving β-H elimination from a nickel alkoxide rather than cleavage of the Ni–O bond by H_2

How calcium affects oxygen formation

Calcium is an essential component of the catalyst that forms oxygen from water during photosynthesis. It seems that part of calcium's job is to enable the release of oxygen from this catalyst

Intramolecular Arene C−H to C−P Functionalization Mediated by Nickel(II) and Palladium(II)

A tris(phosphine) ligand with a triarylbenzene backbone was employed to support mono-nickel(II) and -palladium(II) complexes. Two phosphine arms coordinated to the metal center, while the third phosphine was found to form a C–P bond with dearomatization of the central arene. Deprotonation effected the rearomatization of the central ring and metal reduction from M(II) to M(0). The overall conversion corresponds to a functionalization of an unactivated arene C–H bond to a C–P bond. This transformation represents a rare type of mechanism of C–H functionalization, facilitated by the interactions of the group 10 metal with the arene π system. This conversion is reminiscent of and expands the scope of recently reported intramolecular rearrangements of biaryl phosphine ligands common in group 10 catalysis