Cost benefit analysis of series systems with warm standby components

This paper deals with the cost benefit analysis of series systems with warm standby components. The time-to-repair and the time-to-failure for each of the primary and warm standby components is assumed to have the negative exponential distribution. We develop the explicit expressions for the mean time-to-failure, MTTF, and the steady-state availability, A _T () for three configurations and perform a comparative analysis. Under the cost/benefit (C/B) criterion, comparisons are made based on assumed numerical values given to the distribution parameters, and to the cost of the components. The configurations are ranked based on: MTTF, A _T (), and C/B where B is either MTTF or A _T ().     

Uniform convexity of ψ-direct sums of Banach spaces

Let X and Y be Banach spaces and ψ a continuous convex function on the unit interval [0,1] satisfying certain conditions. Let X⊕_ψY be the direct sum of X and Y equipped with the associated norm with ψ. We show that X⊕_ψY is uniformly convex if and only if X,Y are uniformly convex and ψ is strictly convex. As a corollary we obtain that the ?_p,q-direct sum (not p=q=1 nor ∞), is uniformly convex if and only if X,Y are, where ?_p,q is the Lorentz sequence space. These results extend the well-known fact for the ?_p-sum . Some other examples are also presented.     

直接缩聚法合成淀粉接枝可降解聚酯和聚酯酰胺及其表征

以可溶性淀粉、乳酸、乙醇酸和己内酰胺为原料在氯化亚锡催化下直接缩聚制备得到了淀粉接枝乳酸-乙醇酸共聚物及淀粉接枝乳酸-乙醇酸-己内酰胺共聚物。用核磁共振(NMR)、差热(DSC)及热重(TG)分析分别对产物的结构和热性能进行了表征。     

Direct alpha spectrometry for characterising hot particle properties

Non-destructive analysis methods, especially direct alpha spectrometry but also gamma ray spectrometry and scanning electron microscopy were applied to a nuclear bomb particle from the Thule accident. The use of high-resolution direct alpha spectrometry with the aid of Monte Carlo simulations was demonstrated here in order to determine the properties of this particle. In general, the information that can be obtained through direct alpha spectrometry depends on the information available a priori. For example, known elemental composition makes the assessment of particle dimensions possible even if scanning electron microscopy images are unavailable. Although direct alpha spectrometry may be applied for particle characterisation, further developments in spectrum analysis tools are necessary.     

Transient soot dynamics in turbulent nonpremixed ethylene-air counterflow flames

The dynamics of soot formation in turbulent ethylene-air nonpremixed counterflow flames is studied using direct numerical simulation (DNS) with a semi-empirical soot model and the discrete ordinate method (DOM) as a radiation solver. Transient characteristics of soot behavior are studies by a model problem of flame interaction with turbulence inflow at various intensities. The interaction between soot and turbulence reveals that the soot volume fraction depends on the combined effects of the local conditions of flow, temperature, and fuel concentration, while the soot number density depends predominantly on the high temperature regions. Depending on the relative strength between mixing and reaction, the effects of turbulence on the soot formation lead to three distinct paths in deviating the data points away from the laminar flame conditions. It is found that turbulence has twofold effects of increasing the overall soot yield by generating additional flame volume and of reducing soot by dissipating soot pockets out of high-temperature regions. The relative importance between the two effects depends on the relative length scales of turbulence and flame, suggesting that a nonmonotonic response of soot yield to turbulence level may be expected in turbulent combustion.     

Palladium(II)-catalyzed oxidative Heck coupling of thiazole-4-carboxylates

Oxidative Heck coupling of thiazole-4-carboxylates via palladium(II)-catalyzed C-H bond activation has been achieved in moderate to good yields. No ligand, and no acidic additive were used in the reaction. The results showed that this protocol tolerated a series of substitutions on the thiazole ring. A preliminary attempt of direct arylation with p-xylene via Pd(II)-catalyzed C-H bond activation has also been done.     

A biosensing platform based on horseradish peroxidase immobilized onto chitosan-wrapped single-walled carbon nanotubes

One-step, diameter-selective dispersion of single-walled carbon nanotubes (SWCNTs) has been accomplished through noncovalent complexation of the nanotubes with a water-soluble, biocompatible polymer chitosan at room temperature. Such chitosan-wrapped individual SWCNTs can be used for the immobilization of horseradish peroxidase (HRP) and be used to construct an electrode for direct bioelectrochemical sensing without an electron mediator. The direct electron transfer between HRP and the electrode surface was observed with a formal potential of approximately −0.35 V (vs. saturated calomel electrode) in phosphate buffer solution and the calculated heterogeneous electron transfer rate constant is approximately 23.5 s⁻¹. Experimental results indicate that the immobilized HRP retains its catalytic activity for the reduction of nitric oxide. Such an HRP–SWCNT–chitosan-based biosensor exhibited a rapid response time of less than 6 s and a good linear detection range for nitrite concentration, from 25 to 300 μM with a detection limit of 3 μM. The apparent Michaelis–Menten constant (K _m) and the maximum electrode sensitivity (i_max/K _m) are found to be 7.0 mM and 0.16 μA mM⁻¹, respectively. Both the unique electrical properties of SWCNTs and biocompatibility of chitosan enable the construction of an excellent biosensing platform for improved electrocatalysis of HRP, allowing, specifically, the detection of trace levels of nitric oxide.     

Cost efficiency measures in data envelopment analysis with data uncertainty

This paper extends the classical cost efficiency (CE) models to include data uncertainty. We believe that many research situations are best described by the intermediate case, where some uncertain input and output data are available. In such cases, the classical cost efficiency models cannot be used, because input and output data appear in the form of ranges. When the data are imprecise in the form of ranges, the cost efficiency measure calculated from the data should be uncertain as well. So, in the current paper, we develop a method for the estimation of upper and lower bounds for the cost efficiency measure in situations of uncertain input and output data. Also, we develop the theory of efficiency measurement so as to accommodate incomplete price information by deriving upper and lower bounds for the cost efficiency measure. The practical application of these bounds is illustrated by a numerical example.     

η-INVARIANT AND CHERN-SIMONS CURRENT

The author presents an alternate proof of the Bismut-Zhang localization formula of ηinvariants, when the target manifold is a sphere, by using ideas of mod k index theory instead of the difficult analytic localization techniques of Bismut-Lebeau. As a consequence, it is shown that the R/Z part of the aualytically defined η invariant of Atiyah-Patodi-Singer for a Dirac operator on an odd dimensional closed spin manifold can be expressed purely geometrically through a stable Chern-Simons current on a higher dimensional sphere. As a preliminary application, the author discusses the relation with the Atiyah-Patodi-Singer R/Z index theorem for unitary flat vector bundles,and proves an R refinement in the case where the Dirac operator is replaced by the Signature operator.     

Identifying the radiating core of Lighthill’s source term

A decomposition of the Lighthill source term is effected which yields ten sub-terms comprising velocity, vorticity, dilatation and density fields. An analysis methodology is then developed, aimed at understanding the respective roles played by these sub-terms in the production of sound. By Direct Numerical Simulation of a temporal mixing-layer—chosen both for its simplicity and its amenability to analysis in wavenumber space—the radiating components of the different sub-terms are isolated and studied. Interesting identities are observed between specific events in the evolution of the flow and the various sub-terms of the source, and the essence of the sound production mechanism is found to comprise subtle imbalances which disrupt inherent space–time symmetries which exist between the various sub-terms.