An optimal repeat inspection plan with several classifications

Multicharacteristic critical components exist in many systems. Such components could be a part of an aircraft, space shuttle or a gas ignition system. A component is critical if it causes disaster or a very high cost upon failure. In this paper, a new inspection plan for critical multicharacteristic components is presented. A mathematical model that depicts the plan is developed. An algorithm is proposed for finding the optimal number of repeat inspections and the sequence of characteristics for inspection that minimizes expected total cost per accepted component. The expected cost consists of the cost of inspection and the cost of misclassifications. The inspection plan and the model developed generalize existing models in the literature and provide a more realistic formulation. An example is given to demonstrate the plan and the model.     

Postmodification of poly(9‐alkyl‐9H‐carbazole‐2,7‐diyl)s as a route to new main‐chain‐functionalized carbazole polymers

The postmodification of poly[9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P1 ) upon its reaction with N‐bromosuccinimide affords exclusive and full bromination of the 3,6‐positions of the carbazole repeat units to yield poly[3,6‐dibromo‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P2 ). Brominated polymer P2 can be used as a precursor for further functionalization at the 3,6‐positions with the desired functional group to afford other useful polymers. Polymer P2 has hence been reacted with copper(I) cyanide to afford poly[3,6‐dicyano‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P3 ). Full substitution of the bromide groups with nitrile‐functional groups has been achieved. The preparation and structural characterization of polymers P2 and P3 are presented together with studies on their electronic conjugation and photoluminescence properties. Cyclic voltammetry studies on polymer P3 indicate that the new polymer is easier to reduce (n‐dope) but more difficult to oxidize than its unsubstituted counterpart ( P1 ) as a result of the introduction of the electron‐withdrawing nitrile‐functional groups at the 3,6‐positions on the carbazole repeat units on the polymer chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3336–3342, 2006     

Poly(ortho‐phenylene ethynylene)s: Synthetic accessibility and optical properties

Poly(ortho‐phenylene ethynylene)s (PoPEs) have been synthesized via an in situ activation/coupling AB′ polycondensation protocol. The resulting polymers have been characterized by several analytical methods and are shown to have no structural defects. Although the Sonogashira–Hagihara polycondensation reaction is less efficient than for the preparation of the corresponding meta‐ and para‐linked polymers, presumably because of steric hindrance caused by the ortho substituents, the process can be accelerated by the use of microwave irradiation. Optical spectroscopy indicates solvent‐dependent conformational changes between extended transoid and helical cisoid conformations, providing the first experimental evidence for solvophobically driven folding of the PoPE backbone. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1619–1627, 2006     

Fe2P2O7 and Fe2P4O12 studied between 5–800 K

Mössbauer spectra of triclinic Fe₂P₂O₇ indicate the existence of two crystallographic metal positions in the structure. In the paramagnetic region the two Mössbauer doublets are closely overlapping. The magnetic transition takes place at ≈ 21 K and the saturated fields are around 12 tesla for the two positions. In monoclinic Fe₂P₄O₁₂ the two octahedrally coordinated metal positions give quite different quadrupole splittings (1.5 and 3 mm/s at room temperature) and hyperfine field values (42 and 12.5 Tesla at 5 K). The transition temperature is at ≈ 18.5 K.     

Heat “polynomials” for a singular differential operator on (0, ∞)

We generalize the theory of the heat polynomials introduced by P. V. Rosenbloom and D. V. Widder for a more general class of singular differential operator on (0, ). The heat polynomials associated with the Bessel operator and studied by D. T. Haimo appear as a particular case in this paper. In the special cases of second derivative and Bessel operators the heat polynomials are in fact polynomials inx andt, however, this property does not hold in general.Communicated by Tom. H. Koornwinder.     

Differential oscillator strengths and dipole polarizabilities for transitions of the helium sequence

The dipole radial integral for an initial discrete 1s state and a final continuum state has been calculated under the screened hydrogenic model. In this model, single-electron hydrogenic wave functions are employed and the initial and the final states are treated by two different effective-charge parameters. Numerical values of differential oscillator strengths for transitions from 1s 21S to the continuum for the helium sequence ions are obtained. Also calculated are the dipole polarizabilities, which are found to be in excellent agreement with the results of other authors.     

Catalytic Para‐Xylene Maximization. V. Toluene Methylation with Methanol and Disproportionation of Toluene Using Pt/ZSM‐5 and Pt/Mordenite Catalysts

Toluene was methylated with methanol and disproportionated using catalysts containing different Pt contents (0.2, 0.4 and 0.6%) supported on H‐ZSM‐5 or H‐mordenite (H‐M) zeolites in a fixed‐bed flow‐reactor operated atmospherically at temperatures of 300–500 °C in a flow of hydrogen. Platinum dispersion in the zeolite supports and acid sites strength distribution were evaluated using hydrogen chemisorption (1:1 stoichiometry) and ammonia temperature programmed desorption (TPD) in a differential scanning calorimeter (DSC). Toluene methylation was much faster on all catalysts than toluene disproportionation (DISP). Both reactions were more accelerated using H‐ZSM‐5 containing catalysts than H‐M containing catalysts. The yield of xylenes, and in particular para‐xylene, was significantly influenced by the yield of trimethylbenzenes (TMBs) in product. The selectivities for para‐, ortho‐ and meta‐xylenes production were found largely dependent on the Pt content in the catalysts, particularly when supported on H‐ZSM5‐zeolite. However, using Pt/H‐M catalysts, these selectivities were not strictly controlled by Pt content in the catalysts.     

Natural and fallout radionuclide concentrations in the environment of Islamabad

A study on the concentration of natural and fallout radionuclides in environmental samples collected from different localities of Islamabad was performed. For the determination of gamma-emitters such as ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs high purity germanium (HPGe) detector was used while for the analysis of ⁹⁰Sr, a beta-emitter, liquid scintillation counting system was used. The indoor absorbed dose rate was measured by a CaF₂ : Dy thermoluminescence detector. Other radiation parameters were also determined to evaluate the radiation hazard. All the results were well within the permissible limits showing that there is no radiation hazard in the environment of Islamabad.     

Structural chemistry of azo complexes

Summary Complexes of Co^II, Ni^II, Cu^II, Pd^II, and Pt^IV with 2,4,5-trihydroxybenzoic acid and its substituted phenylazoderivatives have been prepared, together with some mixed-metal (Co, Cu or Ni, Cu) complexes of itsm-nitro,m-carboxy andm-hydroxyarylazo derivatives. The stereochemistries and the modes of bonding of the complexes were elucidated by spectral and magnetic susceptibility measurements.Abstracted from her Ph.D. thesis.