Resonance neutron capture in 52Cr

Neutron capture γ-ray measurements have been performed upon a natural sample of Cr. Twenty-six γ-rays were observed from the 1626 eV resonance of the ⁵²Cr(n, γ)⁵³Cr reaction, and twenty-four of them were assigned to a level scheme. A value of $\text{3}\text{2}$^? was determined for the spin-parity of this resonance. The neutron separation energy, derived from a separate thermal measurement with an enriched (99.9 %) ⁵²Cr sample was determined to be 7939.1 ± 0.2 keV. The high (n, γ) (d, p) correlation found for thermal capture is absent for the p-resonance, however the γ-ray intensities from thermal and resonance capture are correlated, with r = 0.86_?0.11^+0.06.     

A 2D honeycomb-shaped network based on a starburst cluster: [Ag4(micro3-Cl)(PPh2(CH2)2PPh2)1.5{S2P(OR)2}3](R = Et, Pri)

The first 2D metal-organic framework utilizing PPh2(CH2)2PPh2 (dppe) units as the linkers and tetranuclear silver clusters, [Ag4(micro3)-Cl){S2P(OR)2}3], as the network nodes in the formation of the honeycomb-shaped layer structure is reported.     

Influence of Scholarships on STEM Teachers: Cluster Analysis and Characteristics

Science, technology, engineering, and mathematics (STEM) teachers' perceptions about the influence of scholarship on their decision to teach and to teach in a high‐needs school were examined using cluster analysis. Three hundred and four STEM scholars, who were currently teaching, and who received funding from 45 institutions located throughout the United States responded to this national survey that was part of a larger cross‐sectional program evaluation. Three disparate clusters were identified: less committed to becoming a teacher and teaching in a high‐needs school, highly committed to becoming a teacher but not to teaching in a high‐needs school, and highly committed to becoming a teacher and teaching in a high‐needs school. Furthermore, the results indicated that the recipient's race and the time when the scholar learned about the scholarship were related to cluster membership. These results can be used to target STEM majors who may be influenced by scholarships to enter teaching and to teach in high‐needs schools.     

Modeling complexity in musical rhythm

This article constructs a tree structure for the music rhythm using the L‐system. It models the structure as an automata and derives its complexity. It also solves the complexity for the L‐system. This complexity can resolve the similarity between trees. This complexity serves as a measure of psychological complexity for rhythms. It resolves the music complexity of various compositions including the Mozart effect K488. © 2009 Wiley Periodicals, Inc. Complexity, 2010     

New fitness sharing approach for multi-objective genetic algorithms

A novel fitness sharing method for MOGA (Multi-Objective Genetic Algorithm) is proposed by combining a new sharing function and sided degradations in the sharing process, with preference to either of two close solutions. The modified MOGA adopting the new sharing approach is named as MOGAS. Three different variants of MOGAS are tested; MOGASc, MOGASp and MOGASd, favoring children over parents, parents over children and solutions closer to the ideal point, respectively. The variants of MOGAS are compared with MOGA and other state-of-the-art multi-objective evolutionary algorithms such as IBEA, HypE, NSGA-II and SPEA2. The new method shows significant performance improvements from MOGA and is very competitive against other Evolutionary Multi-objective Algorithms (EMOAs) for the ZDT and DTLZ test functions with two and three objectives. Among the three variants MOGASd is found to give the best results for the test problems.     

Comparative analysis of the machine repair Problem with imperfect coverage and service pressure condition

In this paper we analyze the warm-standby M/M/R machine repair problem with multiple imperfect coverage which involving the service pressure condition. When an operating machine (or warm standby) fails, it may be immediately detected, located, and replaced with a coverage probability c by a standby if one is available. We use a recursive method to develop the steady-state analytic solutions which are used to calculate various system performance measures. The total expected profit function per unit time is derived to determine the joint optimal values at the maximum profit. We first utilize the direct search method to measure the various characteristics of the profit function followed by Quasi-Newton method to search the optimal solutions. Furthermore, the particle swarm optimization (PSO) algorithm is implemented to find the optimal combinations of parameters in the pursuit of maximum profit. Finally, a comparative analysis of the Quasi-Newton method with the PSO algorithm has demonstrated that the PSO algorithm provides a powerful tool to perform the optimization problem.     

Numerical prediction of interfacial instabilities: Sharp interface method (SIM)

We introduce a sharp interface method (SIM) for the direct numerical simulation of unstable fluid–fluid interfaces. The method is based on the level set approach and the structured adaptive mesh refinement technology, endowed with a corridor of irregular, cut-cell grids that resolve the interfacial region to third-order spatial accuracy. Key in that regard are avoidance of numerical mixing, and a least-squares interpolation method that is supported by irregular datasets distinctly on each side of the interface. Results on test problems show our method to be free of the spurious current problem of the continuous surface force method and to converge, on grid refinement, at near-theoretical rates. Simulations of unstable Rayleigh–Taylor and viscous Kelvin–Helmholtz flows are found to converge at near-theoretical rates to the exact results over a wide range of conditions. Further, we show predictions of neutral-stability maps of the viscous Kelvin–Helmholtz flows (Yih instability), as well as self-selection of the most unstable wave-number in multimode simulations of Rayleigh–Taylor instability. All these results were obtained with a simple seeding of random infinitesimal disturbances of interface-shape, as opposed to seeding by a complete eigenmode. For other than elementary flows the latter would normally not be available, and extremely difficult to obtain if at all. Sample comparisons with our code adapted to mimic typical diffuse interface treatments were not satisfactory for shear-dominated flows. On the other hand the sharp dynamics of our method would appear to be compatible and possibly advantageous to any interfacial flow algorithm in which the interface is represented as a discrete Heaviside function.     

Efficient acid catalytic synthesis of pyrazolopyrimidines from 1H-pyrazol-5-yl-N,N-dimethylformamidines with cyanamide

The efficient acid catalytic synthesis of pyrazolo [3,4-d]pyrimidine was developed by treating 1H-pyrazol-5-yl-N,N-dimethylformamidine with various aminating agents including N,O-bis(trimethylsilyl)hydroxylamine (NHSiMe₃(OSiMe₃)), cyanamide (NH₂CN), hydroxylamine (NH₂OH), methoxyamine (NH₂OMe), hydrazine (NH₂NH₂), and urea (NH₂C(O)NH₂) in acidic solution at reflux. Based on the experimental result, cyanamide (NH₂CN) and methanesulfonic acid were indicated the best aminating agent and acid mediated solvent. On the other hands, the reactivity tendency was involved the activity of original leaving species grafting on the aminating agents, such as –OH, –OMe, –OSiMe₃, –NH₂, –OSiMe₃, –C(O)NH₂, and –CN, in acid catalytic heterocyclic reaction.     

Preparation and properties of new soluble aromatic polyimides from 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride and aromatic diamines

A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic polyimides having inherent viscosities up to 0.66 dL/g were obtained by the conventional two-step procedure starting from the dianhydride monomer and various aromatic diamines. Most of the polyimides were readily soluble in amide-type solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. The aromatic polyimides had glass transition temperatures in the range of 205–242°C, and began to lose weight around 415°C, with 10% weight loss being recorded at about 500°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2021–2027, 1998     

The effect of crosslinking on thermal and mechanical properties of perfluorocyclobutane aromatic ether polymers

As the minimum features in semiconductor devices decrease, it is a new trend to incorporate copper and polymers with dielectric constant less than 3.0 to enhance the performance of the devices. Two fluorinated polymers, poly(biphenyl perfluorocyclobutyl ether) (BPFCB) and poly(1,1,1-triphenyl ethane perfluorocyclobutyl ether) (PFCB), are newly developed polymers with dielectric constants below 3.0. These two polymers have a similar backbone structure, but PFCB has the capability of crosslinking. To know the implications of these two polymers in the semiconductor industry, properties that are important for the integral reliability of Integral Circuits (IC), such as thermal and mechanical properties, should be understood. This comparative study shows that the crosslinking in perfluorocyclobutane aromatic ether polymer can reduce vertical thermal expansion and increase glass transition temperature (T_g) while water absorption, crystalline-like phase, and dielectric constant are slightly increased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1383–1392, 1998