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In 2021, COVID-19 has been widely spread worldwide. Few studies focused on infection risk in the different confined spaces on university campuses. However, obtaining the quanta value of SARS-CoV-2 ...

We investigate how the financialization of nonfinancial corporations (NFCs) affects corporate risk-taking. We find that NFCs’ financialization has an adverse effect on corporate risk-taking, suppor...

This study discusses, from the perspective of the supplier-customer relationship, whether and how firms’ customer concentration affects corporate tax avoidance in the context of China. The results ...

Simultaneous optimisation of machines and buffers in a large series-parallel production line is an NP-hard problem. The formulated optimisation model in this study is used to minimise the total inv...

Automated material handling systems play a crucial role in intelligent manufacturing workshops. The main difficulty in optimising buffer allocation in such systems is to provide good evaluation for...

Contact force between fibers in different scales, such as microfiber and nanofiber, is different with those in the same scale. In this work, based on an electrospinning nanofiber yarn system, three...

In many manufacturing contexts, performance modelling of an integrated production and material handling system is a complex problem. Existing research lacks an in-depth consideration of the integra...

This paper investigates whether the insiders strategically manage the disclosure and timing of media coverage to maximize their trading profits. Using a sample of Chinese A-listed firms during the ...

Solving the buffer allocation problem (BAP) in long production lines is difficult because it is an NP-hard problem. In this paper, we propose a new approach to solve the BAP for long series-paralle...

This paper analyses the value of Hubei Ancient Village as an example of urban villages by examining its historical evolution, cultural continuity, existing problems and corresponding connection to ...

To accommodate the diverse users demands for consumer products, enterprises need to design and develop different lines of products according to different groups of users. Dynamic internet data, inc...

Queuing network models have been extensively used for performance evaluation in many modern manufacturing and communication systems. The phenomenon of feedback reflects many practical situations, e.g. reworking in the production systems. However, existing research on open queuing network with feedback mainly concentrates on the models with infinite buffers or the models with finite buffers but exponentially distributed inter-arrival and service times. Research on open queuing networks with finite buffers, feedback and general inter-arrival and service times has not been reported. In this paper, a Rate Iterative Method embedded with the Generalised Expansion Method, is proposed for modelling this type of queuing network. System performance measures include the mean throughput, work-in-process and sojourn time all calculated by the proposed method. The accuracy and the efficiency of the proposed method are tested by comparing the results with other methods or simulation results from the experiments. Finally...

Against a background of heat-treatment operations in mould manufacturing, a two-stage flow-shop scheduling problem is described for minimizing makespan with parallel batch-processing machines and re-entrant jobs. The weights and release dates of jobs are non-identical, but job processing times are equal. A mixed-integer linear programming model is developed and tested with small-scale scenarios. Given that the problem is NP hard, three heuristic construction methods with polynomial complexity are proposed. The worst case of the new constructive heuristic is analysed in detail. A method for computing lower bounds is proposed to test heuristic performance. Heuristic efficiency is tested with sets of scenarios. Compared with the two improved heuristics, the performance of the new constructive heuristic is superior.

Blocking makes the analytical modelling of open queuing networks with finite buffers intractable because the product-form solutions are unavailable. In this paper, about mould manufacturing, a four-stage flexible flow shop with match processing constraint is first modelled as an open queuing network with finite buffers. According to the characteristics of the matching node, the inter-arrival time distributions of parts arriving at the nodes are assumed to be exponential or general. Next, based on approximation of queuing theory, the Decomposition of State Space Method and the Generalized Expansion Method are developed for system performance evaluation. Then, experiments to assess the accuracy of the proposed methods are reported by comparing the analytical results with simulations. Finally, a case of a real-life production system of mould manufacturing is studied to show the application of the proposed methods. The results of experiments reveal that the proposed methods are feasible and effective for syst...

Most of the research efforts in project scheduling assumed complete information about the scheduling problem to be resolved. But in the real world, there are various uncertainties during the project execution, which made the plan, become invalid. Concerned with this problem, firstly, we analyse several major random events which lead to the uncertainty of available resources in manufacturers with make-to-order production strategy and consider the stochastic resource-constrained multi-project scheduling problem (RCMPSP). Then, we establish a Markov decision processes model and relevant procedures for this stochastic RCMPSP. Moreover, in order to deal with the common problem in stochastic optimisation – the curse of dimensionality, we propose a strategy approximation method that to limit the action space and state space by utilising several existing efficient priority rules and predefined probability threshold, respectively. With that we search for the suboptimal strategy to minimise the excepted total tardi...

On the background of the shops in the mould manufacturers, in this paper, a two-stage flexible flow shop scheduling problem is first described to minimise the makespan with head group constraint and released time, where the first stage consists of unrelated parallel work centres. Next, this problem is proved to be NP-hard. After that, a constructive heuristic algorithm, named as H′, is proposed and then both its time complexity and worst-case bound are analysed in detail. In addition, three classical heuristics are improved for the solution of this problem and their time complexity is also given. In order to test the efficiency of the H′ algorithm, sets of instances are designed. Compared with the three improved heuristics by means of these sets of examples, the performance of the H′ algorithm is superior. Furthermore, the H′ algorithm can even solve large-size practical problems in a reasonable solution time, which is significant to the application in the shops of mould makers.

In this study, a bibliometric method was used to evaluate the global scientific production of risk assessment research for the last 16 years and provide insights into the characteristics of the risk assessment research activities and tendencies that may exist in the papers. Data were obtained on the online version of SCI, Web of Science from 1992 to 2007. Two important respects of the paper characteristics were analyzed: (i) performance of publication and (ii) research tendency and hotspots. The main results were as follows: English-language articles took the majority of all the publications. Number of articles in this field increased from 1 in 1968 to 1037 in 2007. Human and Ecological Risk Assessment published the most papers in this field, taking 3% of all. Research tendency was investigated by statistically analyzing the distribution of paper title, author keyword, and keyword plus. Furthermore, a new method named “word cluster analysis” was successfully applied to find the research hotspots ...

New blood vessels are formed through the assembly or sprouting of endothelial cells (ECs) and become stabilized by the formation of perivascular matrix and the association with supporting mural cells. To investigate the role of endothelial Smad4 in vascular development, we deleted the Smad4 gene specifically in ECs using the Cre-LoxP system. EC-specific Smad4 mutant mice died at embryonic day 10.5 due to cardiovascular defects, including attenuated vessels sprouting and remodeling, collapsed dorsal aortas, enlarged hearts with reduced trabeculae, and failed endocardial cushion formation. Noticeably, Smad4-deficient ECs demonstrated an intrinsic defect in tube formation in vitro. Furthermore, the mutant vascular ECs dissociated away from the surrounding cells and suffered from impaired development of vascular smooth muscle cells. The disturbed vascular integrity and maturation was associated with aberrant expression of angiopoietins and a gap junction component, connexin43. Collectively, we have provided direct functional evidence that Smad4 activity in the developing ECs is essential for blood vessel remodeling, maturation, and integrity.

This paper concerns linear and nonlinear nth order boundary value problems that contain a finite number of random variables in the boundary conditions or in the differential equation. The results extend methods previously known for corresponding initial value problems. Numerically implementable procedures are given for the determination of the joint density of the solution at an arbitrary point. The possible use of Liouvilleapos;s equation to reduce a random boundary value problem to a random initial value problem is also indicated.