Estimates of B-decays into K-resonances and dileptons

Short and long distance contributions to the exclusive B-decays into various K-resonances and dileptons, i.e. $B \to K^i \ell \bar \ell (\ell = e,\mu ,\nu )$ , are examined. The heavy quark effective theory has been used to calculate the hadronic matrix elements. Substantial branching fractions are obtained for the dileptonic B-decays into some higher excited states of K-mesons. The long distance (resonance) contributions to these exclusive rare B-decay modes dominate the short distance contributions mostly by two orders of magnitude. It is pointed out that, excluding the resonance contributions, the P-wave channels are dominant, accounting for about 50% of the inclusiveB→X _s ? ⁺ ? ^? branching fraction.     

Elastodynamic analysis of a plane weakened by several cracks

The stress fields in an infinite plane containing Volterra type climb and glide edge dislocations under time-harmonic excitation are derived. The dislocation solutions are utilized to formulate integral equations for dislocation density functions on the surfaces of smooth cracks. The integral equations are of Cauchy singular type which are solved numerically for several different cases of crack configurations and arrangements. The results are used to evaluate modes I and II stress intensity factors for multiple smooth cracks.     

An approximate solution for the Couette–Poiseuille flow of the Giesekus model between parallel plates

An approximate analytical solution is derived for the Couette–Poiseuille flow of a nonlinear viscoelastic fluid obeying the Giesekus constitutive equation between parallel plates for the case where the upper plate moves at constant velocity, and the lower one is at rest. Validity of this approximation is examined by comparison to the exact solution during a parametric study. The influence of Deborah number (De) and Giesekus model parameter (α) on the velocity profile, normal stress, and friction factor are investigated. Results show strong effects of viscoelastic parameters on velocity profile and normal stress. In addition, five velocity profile types were obtained for different values of α, De, and the dimensionless pressure gradient (G).     

A hybrid imperialist competitive algorithm for minimizing makespan in a multi-processor open shop

In this paper a new mixed-integer linear programming (MILP) model is proposed for the multi-processor open shop scheduling (MPOS) problems to minimize the makespan with considering independent setup time and sequence dependent removal time. A hybrid imperialist competitive algorithm (ICA) with genetic algorithm (GA) is presented to solve this problem. The parameters of the proposed algorithm are tuned by response surface methodology (RSM). The performance of the algorithm to solve small, medium and large sized instances of the problem is evaluated by introducing two performance metrics. The quality of obtained solutions is compared with that of the optimal solutions for small sized instances and with the lower bounds for medium sized instances. Also some computational results are presented for large sized instances.     

On pressure-frequency relations in the excised larynx

The purpose of this study was to find relationships between subglottal pressure (P(s)) and fundamental frequency (F(0)) of phonation in excised larynx models. This included also the relation between F(0) and its rate of change with pressure (dFdP). Canine larynges were prepared and mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottal adduction was accomplished either by using two-pronged probes to press the arytenoids together or by passing a suture to simulate lateral cricoarytenoid muscle activation. The pressure-frequency relation was obtained through a series of pressure-flow sweep experiments that were conducted for eight excised canine larynges. It was found that, at set adduction and elongation levels, the pressure-frequency relation is nonlinear, and is highly influenced by the adduction and elongation. The results indicated that for the lower phonation mode, the average rate of change of frequency with pressure was 2.9+/-0.7 Hzcm H(2)O, and for the higher mode was 5.3+/-0.5 Hzcm H(2)O for adduction changes and 8.2+/-4.4 Hzcm H(2)O for elongation changes. The results suggest that during speech and singing, the dFdP relationships are taken into account.     

A lifetime model with increasing failure rate

This paper deals with a new two-parameter lifetime distribution with increasing failure rate. This distribution is constructed as a distribution of a random sum of independent exponential random variables when the sample size has a zero truncated binomial distribution. Various statistical properties of the distribution are derived. We estimate the parameters by maximum likelihood and obtain the Fisher information matrix. Simulation studies show the performance of the estimators. Also, estimation of the parameters is considered in the presence of censoring. A real data set is analyzed for illustrative purposes and it is noted that the distribution is a good competitor to the gamma, Weibull, exponentiated exponential, weighted exponential and Poisson-exponential distributions for this data set.     

Methane Conversion to Hydrogen and Carbon Black by DC-Spark Discharge

A continuous production of hydrogen and carbon black from methane without CO₂ emission in atmospheric pressure has been investigated by non thermal decomposition of methane using a system of direct current (DC)-spark discharge plasma, which has great advantages over other systems, like thermal plasma or catalytic conversion of methane in H₂ production. A plasma reactor with specific design of electrodes was employed to examine the reactor performance regarding operating conditions such as feed flow rate, input power and electrodes distance. The experimental results showed that designed reactor increases not only the concentration of the produced hydrogen in continues condition but also guarantees stable plasma. As the methane supply rate increased, the hydrogen concentration decreased but on the other hand the hydrogen volume flow rate increased. In general, under the specified operating condition (power?=?21 W and methane flow rate?=?150?ml/min), the plasma converter produced a hydrogen concentration of 45?% at hydrogen volume flow rate of 75?ml/min.     

Anti-plane elastodynamic analysis of cracked graded orthotropic layers with viscous damping

Stress analysis is carried out in a graded orthotropic layer containing a screw dislocation undergoing time-harmonic deformation. Energy dissipation in the layer is modeled by viscous damping. The stress fields are Cauchy singular at the location of dislocation. The dislocation solution is utilized to derive integral equations for multiple interacting cracks with any location and orientation in the layer. These equations are solved numerically thereby obtaining the dislocation density function on the crack surfaces and stress intensity factors of cracks. The dependencies of stress intensity factors of cracks on the excitation frequency of applied traction and material properties of the layer are investigated. The analysis allows the determination of natural frequencies of a cracked layer. Furthermore, the interactions of two cracks having various configurations are studied.     

Antiplane elastodynamic analysis of a strip weakened by multiple defects

The method of images is utilized to derive the solution of a screw dislocation under time-harmonic conditions for an elastic strip from the solution of infinite planes. The displacement and stress components are obtained for a strip under concentrated antiplane, time-harmonic traction. The dislocation solution is employed to formulate integral equation for a strip weakened by cracks and cavities. The effects of load frequency and crack orientation on the stress intensity factors are studied.