Reliability and congestion control in cognitive radio sensor networks

Communication requirements for cognitive radio sensor networks (CRSN) necessitate addressing the problems posed by dynamic spectrum access (DSA) in an inherently resource-constrained sensor networks regime. In this paper, arising challenges for reliability and congestion control due to incorporation of cognitive radio capability into sensor networks are investigated along with the open research issues. Impact of DSA, i.e., activity of licensed users, intermittent spectrum sensing and spectrum handoff functionalities based on spectrum availability, on the performance of the existing transport protocols are inspected. The objective of this paper is to point out the urgent need for a novel reliability and congestion control mechanism for CRSN. To this end, CRSN challenges for transport layer are revealed and simulation experiments are performed to demonstrate the performance of the existing transport protocols in CRSN.     

Tenogenic Induction of Human MSCs by Anisotropically Aligned Collagen Biotextiles

A novel biofabrication modality, electrophoretic compaction with macromolecular alignment, is utilized to make collagen threads that mimic the native tendon's structure and mechanical properties. A device with kinematic electrodes is designed to fabricate collagen threads in continuous length. For the first time, a 3D‐biotextile is woven purely from collagen. Mechanical properties and load‐displacement behavior of the biotextile mimic those of the native tendon while presenting a porosity of 80%. The open pore network facilitates cell seeding across the continuum of the bioscaffold. Mesenchymal stem cells (MSCs) seeded in the woven scaffold undergo tenogenic differentiation in the absence of growth factors and synthesize a matrix that is positive for tenomodulin, COMP and type I collagen. Up‐regulation of tenomodulin, a tendon specific marker, is 11.6 ± 3.5 fold, COMP is up‐regulated 16.7 ± 5.5 fold, and Col I is up‐regulated 6.9 ± 2.7 fold greater on ELAC threads when compared to randomly oriented collagen gels. These results demonstrate that a bioscaffold woven using collagen threads with densely compacted and anisotropically aligned substrate texture stimulates tenogenesis topographically, rendering the electrochemically aligned collagen as a promising candidate for functional repair of tendons and ligaments.     

Extracting priority rules for dynamic multi-objective flexible job shop scheduling problems using gene expression programming

In this paper, two new approaches are proposed for extracting composite priority rules for scheduling problems. The suggested approaches use simulation and gene expression programming and are able to evolve specific priority rules for all dynamic scheduling problems in accordance with their features. The methods are based on the idea that both the proper design of the function and terminal sets and the structure of the gene expression programming approach significantly affect the results. In the first proposed approach, modified and operational features of the scheduling environment are added to the terminal set, and a multigenic system is used, whereas in the second approach, priority rules are used as automatically defined functions, which are combined with the cellular system for gene expression programming. A comparison shows that the second approach generates better results than the first; however, all of the extracted rules yield better results than the rules from the literature, especially for the defined multi-objective function consisting of makespan, mean lateness and mean flow time. The presented methods and the generated priority rules are robust and can be applied to all real and large-scale dynamic scheduling problems.     

Machinability of AA 2024 aluminum alloy by fiber laser engraving process

The main objective of the present study is to investigate the machinability of AA 2024-T351 aluminum alloy by laser beam-assisted engraving process. The surface in a defined area was machined with the engraving process parameters of scan speed, frequency, and pulse width. While surface roughness measurements were performed to characterize the texture of the processed surface with laser engraving parameters, machining depth measurements were carried out to determine the material removal capacity. In addition, a mathematical relation was built for engraving depth and surface roughness using the response surface methodology. An increase in scan speed and pulse width led to a decrease in engraving depth and surface roughness. Unlike the scan speed and pulse width, any increase in frequency led to increased surface roughness and decreased engraving depth. After processing with lower pulse width and scan speed, a chaotic topography was formed on the surface. The effects of process parameters on engraving depth and surface roughness were analyzed statistically using factorial analysis. Except for the frequency, all parameters for surface roughness were statistically significant, whereas all parameters for engraving depth were statistically significant.     

Virtual reality in requirement analysis for CIM system development suitable for SMEs

This paper presents a methodology, based on Virtual Reality (VR), for representing a manufacturing system in order to help with the requirement analysis (RA) in CIM system development, suitable for SMEs. The methodology can reduce the costs and the time involved at this stage by producing precise and accurate plans, specification requirements, and a design for CIM information systems. These are essentials for small and medium scale manufacturing enterprises. Virtual Reality is computer-based and has better visualization effects for representing manufacturing systems than any other graphical user interface, and this helps users to collect information and decision needs quickly and correctly. A VR-RA tool is designed and developed as a software system to realize the features outlined in each phase of the methodology. A set of rules and a knowledge base is appended to the methodology to remove any inconsistency that could arise between the material and the information flows during the requirement analysis. A novel environment for matching the physical and the information model domains is suggested to delineate the requirements.