Statistical inference for constant-stress accelerated life tests with dependent competing risks from Marshall-Olkin bivariate exponential distribution

This paper considers a constant-stress accelerated dependent competing risks model under Type-II censoring. The dependent structure between competing risks is modeled by a Marshall-Olkin bivariate exponential distribution, and the accelerated model is described by the power rule model. The point and interval estimation of the model parameters and the reliability function under the normal usage condition at mission time are obtained by using the maximum likelihood estimation method and the bootstrap sampling technique. Moreover, the pivotal quantities based estimation are adopted to estimate the model parameters and the generalized confidence intervals. As a comparison, we also consider the Bayes estimation and the highest posterior density credible intervals for the model parameters based on conjugate priors and importance sampling method, respectively. To illustrate the proposed methodology, a Monte Carlo simulation is used to study the performances of different estimation methods. Finally, a dataset is analyzed for illustrative purpose and a comparison with the original results is also given.     

Some node ordering methods for the K2 algorithm

Inferring Bayesian network structure from data is a challenging issue, and many researchers have been working on this problem. The K2 is a well‐known order‐dependent algorithm to learn Bayesian network. The result of the algorithm is not robust since it achieves different network structure if node orderings are permuted. Consequently, choosing suitable sequential node ordering for the input of the K2 algorithm is a challenging task. In this work, some deterministic methods for selecting a suitable sequential node ordering are introduced. The effectiveness of these methods benchmarked through the Asia, Alarm, Car, and Insurance networks. The results indicate that the methods based on the concept of mutual information and entropy are suitable for finding a sequential node ordering and considerably improves the precision of network inference. The source code and selected data sets are available on http://profiles.bs.ipm.ir/softwares/ordering/ .     

Numerical computation on Marangoni convective flow of two‐phase MHD dusty nanofluids under Brownian motion and thermophoresis effects

The current theoretical study describes the Marangoni thermal convective flow of magnetohydrodynamic dusty nanofluids along a wavy vertical surface. The two‐phase mathematical model is developed under the influence of thermal radiation and exponentially varying space‐dependent heat source. Pure and hybrid nanoparticles together with dust particle suspension in the base fluid are taken into consideration to characterize the behavior of the flow. Brownian motion and thermophoresis mechanisms are considered, since it enhances the convection features of dusty nanofluid. Appropriate transformations are adopted to modify the flow governing equations and boundary conditions to dimensionless form. The forward finite difference scheme is implemented to illustrate the resultant coupled partial differential equations. The Newton quasi‐linearization technique is utilized to reduce the nonlinear system into a linear form, which is solved thereafter by Thomas algorithm. The responses of velocity, temperature, concentration, friction factor, and heat and mass transfer rate profiles with various governing parameters are discussed and portrayed graphically. The study evidences that the radiation and space‐dependent heat generating parameters strengthen the temperature distribution. Also, the heat transfer rate appreciably rises with the increment in Marangoni convection. The solution methodology and accuracy of the model is validated by generating the earlier outcomes for nonradiating nanofluid flow without heat source/sink.     

Benzaldehyde Lyase‐Catalyzed Direct Amidation of Aldehydes with Nitroso Compounds

Benzaldehyde lyase from the Pseudomonas fluorescens catalyzes the reaction of aromatic aldehydes with nitroso compounds and furnishes N‐arylhydroxamic acids in high yields. Aromatic aldehydes and benzoins are converted into enamine‐carbanion‐like intermediates prior to their reaction with nitroso compounds. The kinetic resolution of rac‐2‐hydroxy‐1,2‐diphenylethanones furnished (S)‐benzoins and arylhydroxamic acids with high enantioselectivities and conversions.     

双非线性密度制约predator-prey系统的持久性

通过微分方程定性与稳定性理论和泛函分析中的Brouwer不动点定理.讨论了具有双非线性密度制约的Holling Ⅳ型功能反应的predator-prey非自治系统的一致持久性,并且当系统是周期系统时,得到该系统周期正解存在惟一且全局渐近稳定的充分条件.     

Jobshop lot streaming with routing flexibility,sequence-dependent setups,machine release dates and lag time

Lot streaming is a technique of splitting production lots into smaller sublots in a multi-stage manufacturing system so that operations of a given lot can overlap. This technique can reduce the manufacturing makespan and is an effective tool in time-based manufacturing. Research on lot streaming models and solution procedures for flexible jobshops has been limited. The flexible jobshop scheduling problem is an extension of the classical jobshop scheduling problem by allowing an operation to be assigned to one of a set of eligible machines during scheduling. In this paper we develop a lot streaming model for a flexible jobshop environment. The model considers several pragmatic issues such as sequence-dependent setup times, the attached or detached nature of the setups, the machine release date and the lag time. In order to solve the developed model efficiently, an island-model parallel genetic algorithm is proposed. Numerical examples are presented to demonstrate the features of the proposed model and compare the computational performance of the parallel genetic algorithm with the sequential algorithm. The results are very encouraging.     

A note on modelling the capacitated lot-sizing problem with set-up carryover and set-up splitting

The capacitated lot-sizing problem with set-up carryover and set-up splitting (CLSP-SCSS) is formulated as a mixed integer linear program. We define set-up carryover as the production of a product that is continued over from one period to another without incurring an extra set-up. Set-up splitting occurs when the set-up for a product is started at the end of a period and completed at the beginning of the next period. We allow product dependent set-ups. Initial experimentation highlights the importance of including set-up splitting in the CLSP model. In 12 out of the 18 problem instances tested, our model yielded better solutions or removed infeasibility when compared with a CLSP model without set-up splitting.     

A detailed description of the Gurson–Tvergaard–Needleman model within a mixed velocity–pressure finite element formulation

In an effort to implement Gurson‐type models into a mixed velocity–pressure finite element formulation with the MINI‐element P1 ⁺ ∕ P1, the algorithm proposed by Aravas (IJNME, 1987) to integrate the pressure dependent plasticity as well as the formulations of consistent tangent moduli have been analyzed. This work firstly reviews and clarifies the mathematical basis of the formulations used by Aravas (IJNME, 1987) and demonstrates the equality of the tangent moduli formulations proposed by Govindarajan and Aravas (CNME, 1995) and Zhang (CMAME, 1995), which are widely used in the literature. A unified formulation to calculate the tangent moduli is proven, and its accuracy is also investigated by the finite difference method. The implementation of the Gurson–Tvergaard–Needleman model is then detailed for the mixed velocity–pressure finite element formulation, which employs the MINI‐element P1 ⁺ ∕ P1. Due to the particularity of this element, one needs to calculate two tangent moduli instead of one. The formulas for calculating the ‘linear tangent modulus’ and the ‘bubble tangent modulus’ are then detailed. Finally, comparison tests are carried out with ABAQUS (Dassault System, Simulia Corp., Providence, RI, USA) in order to validate the present implementation for both homogeneous and heterogeneous deformations. Copyright © 2013 John Wiley & Sons, Ltd.     

Reaction Rate Calculation in Fast Reactor Blanket Using Multiband Sn Theory

A new method was applied to calculation of reaction rates in blanket of LMFBR using the multiband S_n theory. This procedure leads to the use of direction dependent total micro cross sections, which advances the penetration of neutrons into the blanket.

Test calculation with RZ model of a prototype fast reactor shows that reaction rates tend to rise with the penetration into blanket compared to the conventional multigroup calculation: the maximum difference was about 3% for ²³⁸U capture, 4% for ²³⁵U fission, 4% for ²³⁹Pu fission, and less than 1% for ²³⁸U fission. This tendency shows the same direction as the difference observed between the continuous energy Monte Carlo method and the conventional method.     

Optimal Feedback Control of a Nuclear Reactor as a Distributed Parameter System

The analytical treatment of a distributed reactor having spatially dependent parameters is presented. Both the modal expansion method and the function space method are applied successfully to obtain the optimal feedback system for the terminal cost problem. The explicitly posed control obtained by means of the function space method is particularly convenient for machine computation. A numerical example is presented to show the characteristics of the synthesized optimal feedback system.