A new mixed integer programming formulation for facility layout design using flexible bays

This paper presents a mixed-integer programming formulation to find optimal solutions for the block layout problem with unequal departmental areas arranged in flexible bays. The nonlinear department area constraints are modeled in a continuous plane without using any surrogate constraints. The formulation is extensively tested on problems from the literature.     

Quantum group invariant fermionic gases: GLp,q(2) and SUp/q(2) invariances

We first investigate the high-temperature behavior of a two-parameter deformed quantum group fermionic gas with GL_p,q(2) symmetry, where (p,q)C×C. We then discuss both the structural and thermodynamical differences between GL_p,q(2)- and SU_r(2)-fermions with r=p/q where (p,q)R×R.     

Extremely cold positrons for antihydrogen production

The storage of extremely cold (4 K) antiprotons in a Penning trap is an important step toward the creation and study of cold antihydrogen. The other required ingredient, the largest possible number of comparably cold positrons, is still lacking. These would be recombined in a high vacuum with the trapped antiprotons, already stored at a pressure below 5×10⁻¹⁷ Torr, thereby avoiding annihilation of the antihydrogen atoms before they can be used in high accuracy measurements or in controlled collision experiments. In an exploratory experiment, positrons from a 18 mCi²²Na source follow fringing field lines of a 6 T superconducting solenoid through tiny apertures in the electrodes of a Penning trap to strike a tungsten (reflection) moderator. The positron beam is chopped mechanically and a lock-in directly detects a positron current of 2.5×10⁶e⁺/s on the moderator. The use of a moderator, unlike an earlier experiment in which < 100 positrons were confined in vacuum, should greatly increase the number of positrons trapped in high vacuum.     

Synthesis and synthetic utility of 1-acyl-2-alkyl-4-trimethylstannyl-1,2-dihydropyridines

1-Acyl-2-alkyl-1,2-dihydropyridines were prepared from 4-trimethylstannylpyridine and Grignard reagents. This methodology was utilized in the synthesis of N-methyl-2-azatricyclo[5.3.1.0]undecane.     

New alkaloids from Phoebe grandis (Nees) Merr

The alkaloidal extract of the leaves of Phoebe grandis (nees) merr. have provided two new minor alkaloids; phoebegrandine D (1), a proaporphine-tryptamine dimer, and phoebegrandine E (2), an indoloquinolizidine. This is the first report on the occurrence of an indoloquinolizidine in the Phoebe species. The crude extract also exhibited antiplasmodial activity (IC50<8 microg mL-1). The structures of the novel compounds were elucidated by spectroscopic methods, notably 2D NMR and HRMS.     

X-ray attenuation around <Emphasis Type="Italic">K</Emphasis>-edge of Zr,Nb, Mo and Pd: A comparative study using proton-induced X-ray emission and <Superscript>241</Superscript>Am gamma rays

Mass attenuation coefficients (μ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd, Cd and Sn foils. The measurements were carried out at the K _α and K _β energy values of the target elements by two techniques: (1) Proton-induced X-ray emission (PIXE) and (2) ²⁴¹Am (300 mCi) source. In PIXE, 2 MeV proton-excited X-rays were detected by a Si(Li) detector. In the second case, X-rays excited by 59.54 keV photons from the targets were counted by an HPGe detector under a narrow beam good geometry set-up with sufficient shielding. The results are consistent with theoretical values derived from the XCOM package and indicate that the PIXE data have better statistical accuracy.     

Raman spectroscopic studies of vibrational relaxation and non‐coincidence effect in substituted benzaldehyde binary mixtures

The molecular interaction in the binary mixture of 3‐phenoxybenzaldhyde (3Phbz) and 4‐ethoxybenzaldehyde (4Etob) was analysed in four different solvents. The concentration dependence of vibrational relaxation of the CO stretching band of 3Phbz in different solvents was investigated by varying the concentration of the solute molecule in the solvents by performing Raman spectroscopic measurements. The self‐associated nature and the formation of hydrogen‐bonded complexes in the solute molecule, 4Etob, were considered to analyse the wavenumber separation between the peaks of hydrogen‐bonded and free carbonyl groups. Copyright © 2009 John Wiley & Sons, Ltd.     

Modeling and analysis of system reliability using phase‐type distribution closure properties

Phase‐type distribution closure properties are utilized to devise algorithms for generating reliability functions of systems with basic structures. These structures include series, parallel, K‐out‐of‐N, and standby structures with perfect/imperfect switch. The algorithms form a method for system reliability modeling and analysis based on the relationship between the system lifetime and component lifetimes for general structures. The proposed method is suitable for functional system reliability analysis, which can produce reliability functions of systems with independent components instead of only system reliability values. Once the system reliability function is obtained, other reliability measures such as the system's hazard function and mean time to failure can be obtained efficiently using only matrix algebra. Dimensional and numerical comparisons with computerized symbolic processing are also presented to show the superiority of the proposed method.     

On some constacyclic codes over $$\mathbb {Z}_{4}\left[ u\right] /\left\langle u^{2}-1\right\rangle $$, their $$\mathbb {Z}_4$$Z4 images,and new codes

In this paper, we study \(\lambda \)-constacyclic codes over the ring \(R=\mathbb {Z}_4+u\mathbb {Z}_4\) where \(u^{2}=1\), for \(\lambda =3+2u\) and \(2+3u\). Two new Gray maps from R to \(\mathbb {Z}_4^{3}\) are defined with the goal of obtaining new linear codes over \(\mathbb {Z}_4\). The Gray images of \(\lambda \)-constacyclic codes over R are determined. We then conducted a computer search and obtained many \(\lambda \)-constacyclic codes over R whose \(\mathbb {Z}_4\)-images have better parameters than currently best-known linear codes over \(\mathbb {Z}_4\).