Flexible jobshop scheduling problem with resource recovery constraints.

Objectives and methods of study: The general objective of this research is to study a scheduling problem found in a local brewery. The main problem can be seen as a parallel machine batch scheduling problem with sequence-dependent setup times, resource constraints, precedence relationships, and capacity constraints. In the first part of this research, the problem is characterized as a Flexible Job-shop Scheduling Problem with Resource Recovery Constraints. A mixed integer linear formulation is proposed and a large set of instances adapted from the literatura of the Flexible Job-shop Scheduling Problem is used to validate the model. A solution procedure based on a General Variable Neighborhood Search metaheuristic is proposed, the performance of the procedure is evaluated by using a set of instances adapted from the literature. In the second part, the real problem is addressed. All the assumptions and constraints faced by the decision maker in the brewery are taken into account. Due to the complexity of the problem, no mathematical formulation is presented, instead, a solution method based on a Greedy Randomize Adaptive Search Procedure is proposed. Several real instances are solved by this algorithm and a comparison is carried out between the solutions reported by our GRASP and the ones found through the procedure followed by the decision maker. The computational results reveal the efficiency of our method, considering both the processing time and the completion time of the scheduling. Our algorithm requires less time to generate the production scheduling (few seconds) while the decision maker takes a full day to do it. Moreover, the completion time of the production scheduling generated by our algorithm is shorter than the one generated through the process followed by the decision maker. This time saving leads to an increase of the production capacity of the company. Contributions: The main contributions of this thesis can be summarized as follows: i) the introduction of a variant of the Flexible Job-shop Scheduling Problem, named as the Flexible Job-shop Scheduling Problem with Resource Recovery Constraints (FRRC); ii) a mixed integer linear formulation and a General Variable Neighborhood Search for the FRRC; and iii) a case study for which a Greedy Randomize Adaptive Search Procedure has been proposed and tested on real and artificial instances. The main scientific products generated by this research are: i) an article already published: Sáenz-Alanís, César A., V. D. Jobish, M. Angélica Salazar-Aguilar, and Vincent Boyer. “A parallel machine batch scheduling problem in a brewing company”. The International Journal of Advanced Manufacturing Technology 87, no. 1-4 (2016): 65-75. ii) another article submitted to the International Journal of Production Research for its possible publication; and iii) Scientific presentations and seminars

Carbon Nanotubes Reinforced Natural Rubber Composites

Several advanced methods have been introduced to disperse CNTs in the NR matrix. Various aspects highlighted in this chapter include the mixing processes such as melt mixing and latex mixing methods. As well as, formations of functional groups on the surfaces of CNT using silane coupling agents (i.e., ex-situ and in-situ functionalization). Moreover, hybrid CNT are beneficial to achieve better electrical conductivity of NR/CNT composites. These efforts are aimed to reduce the percolation threshold concentration in the NR composites for application as conducting composites based on electrically insulating rubber matrix. Sensor application is developed based on conducting NR composites. NR composites showed changing of resistivity during elongation termed as piezoresistivity. The most commonly used rubber matrices such as NR, ENR and IR are mixed with a combination of CNT and CB fillers as hybrid filler. The presence of linkages in the ENR composites results in the least loss of conductivity during external strain. It is found that the conductivity becomes stable after 3000 cycles. This is found to be similar to the NR-CNT/CB composite, while a few cycles are needed for IR-CNT/CB owing to the higher filler agglomeration and poor filler-rubber interactions. This is attributed to the polar chemical interactions between ENR and the functional groups on the surfaces of CNT/CB

Towards Industry 5.0: Intelligent Reflecting Surface (IRS) in smartmanufacturing

Industry 5.0 envisions close cooperation between humans and machines requiring ultra-reliable and low latency communications (URLLC). The Intelligent Reflecting Surface (IRS) has the potential to play a crucial role in realizing wireless URLLC for Industry 5.0. IRS is forecast to be a key enabler of 6G wireless communication networks as it can significantly improve wireless network performance by creating a controllable radio environment. In this paper, we first provide an overview of IRS technology and then conceptualize the potential for IRS implementation in a future smart manufacturing environment to support the emergence of Industry 5.0 with a series of applications. Finally, to stimulate future research in this area, we discuss the strength, open challenges, and opportunities of IRS technology in modern smart manufacturing

The effect of cross-linking on the molecular dynamics of the segmental and β Johari–Goldstein processes in polyvinylpyrrolidone-based copolymers

The effect of the cross-link density on the molecular dynamics of copolymers composed of vinylpyrrolidone (VP) and butyl acrylate (BA) was studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). A single glass transition was detected by DSC measurements. The dielectric spectra exhibit conductive processes and three dipolar relaxations labeled as a, b and g in the decreasing order of temperatures. The cross-linker content affects both a and b processes, but the fastest g process is relatively unaffected. An increase of cross-linking produces a typical effect on the a process dynamics: (i) the glass transition temperature is increased, (ii) the dispersion is broadened, (iii) its strength is decreased and (iv) the relaxation times are increased. However, the b process, which possesses typical features of a pure Johari Goldstein relaxation, unexpectedly loses the intermolecular character for the highest cross-linker content.B.R.F., M.J.S., P.O.S. and M.C. gratefully acknowledge CICYT for grant MAT2012-33483. F.G. and J.M.G. acknowledge the Spanish Ministerio de Economia y Competitividad-FEDER (MAT2014-54137-R) and the Junta de Castilla y Leon (BU232U13).Redondo Foj, MB.; Sanchis Sánchez, MJ.; Ortiz Serna, MP.; Carsí Rosique, M.; García, JM.; García, FC. (2015). The effect of cross-linking on the molecular dynamics of the segmental and β Johari–Goldstein processes in polyvinylpyrrolidone-based copolymers. Soft Matter. 11:7171-7180. https://doi.org/10.1039/c5sm00714cS7171718011V. Bühler , Polyvinylpyrrolidone Excipients for Pharmaceuticals: Povidone, Crospovidone and Copovidone , Springer , Berlin , 2005Haaf, F., Sanner, A., & Straub, F. (1985). Polymers of N-Vinylpyrrolidone: Synthesis, Characterization and Uses. 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Effect of Thermal Aging and Chemical Treatment on Tensile Properties of Coir Fiber

Effect of thermal aging and chemical treatment on the physical properties of coir fiber was investigated. Coir fibers were treated with sodium hydroxide and glutaraldehyde for 2 h. The influence of alkali and aldehyde treatment on tensile strength and elongation at break was studied in detail. Enhancement in tensile strength of coir fiber was observed up to five days of aging at 50°C and further decreased. Thermal cross linking of cellulose present in the fiber may be the reason for the increase in tensile strength and thermal degradation due to the chain scission of cellulose reduced the tensile strength. Sodium-hydroxide-treated samples showed an increase in tensile strength and reduction in elongation at break. The removal of impurities such as waxy and fatty acid residues from the coir fiber by reacting with strong base solution improved the strength of fiber. Cross linking of cellulose with glutaraldehyde in the fiber reduced the elasticity and enhances the strength of the material. Scanning electron microscopy was employed to analyze the change in surface morphology upon chemical treatment. Improvement in the tensile strength suggests that NaOH and glutaraldehyde can be effectively used to modify coir fiber with excellent physical properties