Industrial and mechanical engineering department

The steady state boundary layer equations around rotating pure hydrocarbon droplet are solved numerically. The droplet is simulated to behave as a hard sphere. The transfer equations are discretized using an implicit finite difference method where Thomas algorithm solves the system of algebraic equations. Moreover, dimensionless parameters of heat and mass transfer phenomena around a rotating hexane droplet concluded. The thickness of the boundary layer is unknown for this model and therefore, it is determined. Further, this work proposes correlations of Nusselt and Sherwood numbers for monocomponent hydrocarbon droplets in evaporation. These correlations consider the rotation phenomena and further, the variation of the thermophysical and transport properties in the vapour phase.

This paper explores the recent trends of research and development in modern manufacturing systems. Those trends happen to direct the business activities of this sector towards the globalisation of the usual markets and the creation of a new virtual, agile, and extended production environment whose purpose is to ensure fast, responsive, and adaptable reaction to the new market conditions. This paper also attempts to investigate the implications and consequences of the new trends on emerging and developing economies.

This paper explores the recent trends of research and development in modern manufacturing systems. Those trends happen to direct the business activities of this sector towards the globalisation of the usual markets and the creation of a new virtual, agile, and extended production environment whose purpose is to ensure fast, responsive, and adaptable reaction to the new market conditions. This paper also attempts to investigate the implications and consequences of the new trends on emerging and developing economies.

This paper explores the recent trends of research a nd development in modern manufacturing systems. Those trends happen to direct the business activities of this sector towards the globalisation of the usual markets and the creation of a new virtual, agile, and extended production environ ment whose purpose is to ensure fast, responsive, and adaptable reaction to the new market conditions. This paper also attempts to investigate the implica tions and consequences of the new trends on emerging and developing economies.

We introduce a new family of Markov processes called “Markov Interactive Processes” (MIP). Such a process consists of several variables or components. Jumps occur in one component at a time and the transition rates of each component depend on the current states of the remaining components. We show that the t-step transition probabilities of a MW have a product form when the transition rates of the jumps in one component are proportional to a function of the states of the remaining components. This yields a product form stationary distribution as well. Several standard network models including closed Jackson networks are MIP’s with product form distributions. In addition, we approximate the stationary distributions for three cases of general two-component MW’s that do not have tractable equilibrium distributions. The first approximation is for an MIP in which one of the components has either very sluggish or very frequent transitions relatively to the other. The second approximation is for an MIP in which one component has two states where one of them dominates the other in the sense that this component stays longer in the dominating state. The third approximation is for a MIP in which one component’s transition rates are independent of the state of the other and has many non-dominating states in that their equilibrium probabilities are approximately equal. We apply our results to develop several new models for queueing systems which can fit in the framework of MIP’s. Finally, we study a family of Markov processes whose state spaces are partitioned into subspaces where one of them is “central” in that transitions from a non-central subspace into another are only possible through one or more central states. We express the stationary distribution of such a process in terms of the distributions of Markov processes with the same transition rates of the original process but restricted to the states of a non-central and the central subspaces.

Strategies to control the Bullwhip effect in supply chains have been the focus of a substantial amount of research in the last few decades. Some strategies were based on the implementation of information sharing and collaboration with retailers. Other strategies suggested the use of the vendor-managed inventory (VMI) approach. VMI however, requires significant implementation challenges to gain the trust and acceptance of the retailers as it gives the full control of the retailer’s inventory to the supplier. New type of strategies has been recently suggested where the supplier can control retailers’ orders with replenishment decisions that can decrease the effect of the bullwhip phenomenon by controlling the replenishment orders to a pool of retailers and ended up with preference discrimination among the retailers. This paper proposes a strategy that controls the fulfillment quantities to individual retailer’s orders, independently of other retailers, in a way that conserves the expe...

To study the prevalence of severe social anxiety (SSA) among a group of adolescents during the coronavirus disease of 2019 (COVID-19) pandemic. A total of 178 adolescents attending the private clinics of the authors were screened online for the presence of SSA, by using the self-reporting format of the Liebowitz Social Anxiety Scale for children and adolescents (LSAS-CA). SSA defined as LSAS-CA scores of 80 or more was checked for statistical association with the adolescents’ sociodemographic data and knowledge about the COVID-19 infection. The 18% of our participants had SSA, no correlation was found between having SSA and ä acknowledging or fearing the COVID-19 morbidity. Factors associated with SSA included texting, using social media, and playing video games during the lockdown. Mitigating factors include high family socioeconomic status, history of socialization with friends, and the use of WhatsApp as a source of information about COVID-19 infection.