Experiment and simulation of electrolytic hydrogen production: Case study of photovoltaic-electrolyzer direct connection

Hydrogen as an energy currency, carrier and storage medium can contribute to solve the problem of intermittent availability of renewable energies. In this paper, we study the production of hydrogen by a proton exchange membrane (PEM) electrolyzer (WE) using photovoltaic energy (PV) as source of electricity. Experiments were performed to model and optimize the direct-coupling system. Mathematical and empirical models based on experiments were used to simulate the system. RMSE was about 2% for the PV and WE. Optimization of direct connection was carried out to improve the system efficiency. However, it was noticed that the simulation of the system does not fit well the experimental results. Nevertheless, the RMSE is about 7%. In this study, we emphasize the need to develop appropriate models for hydrogen production system that operates in direct connection mode.     

A fuzzy clustering-based genetic algorithm approach for time–cost–quality trade-off problems: A case study of highway construction project

Recently government agencies have started to utilize innovative contracting methods that provide incentives for improving construction quality. These emerging contracting methods place an enormous pressure on the contractors to improve construction quality. For a general contractor, which subcontracts most tasks of a project and invites a number of bids, choosing an appropriate bid which satisfies the time, cost and quality of construction project is complex and challenging. To solve this problem involving conflicting objectives, a fuzzy clustering-based genetic algorithm (FCGA) approach is proposed in this paper. A case study of highway construction is used to demonstrate the applicability of the proposed approach. A comparative study is conducted over three test cases involving varying dimensions and complexities to test performance of the proposed FCGA against existing approaches. Results reveal that the FCGA is capable of generating better Pareto front than other existing approaches.     

Dynamics of micromechanisms controlling the mechanical behaviour of industrial single crystal superalloys

When deforming bulk material, micromechanisms involving moving defects result in mechanical characteristics observed at a macroscopic scale.In situ straining of microsamples in a Transmission Electron Microscope, provides the unique advantage of observing the dislocation dynamics involved in such micro-deformation processes under the combined effects of stress and temperature. Here the efficiency of this technique is illustrated by describing the different obstacles controlling the movement of dislocations in a two-phase industrial single crystal superalloy. At 25‡ and 850‡C, different core structures of the moving dislocations as well as several ways of crossing obstacles are described, which concern the movement of dislocations inγ channels, at γ/γ′ interfaces and while shearing γ′ precipitates. From these observations, a quantitative analysis is developed leading to the evaluation of the critical propagation stresses involved in the channels of the matrix and when crossing the interfaces. This allows to discuss the various sites of resistance opposed to the dislocation movements and controlling the macroscopic deformation.     

Developing a reconfigurability index using multi-attribute utility theory

Reconfigurable manufacturing systems (RMSs) have been acknowledged as a promising means of providing manufacturing companies with the required production capacities and capabilities. This is accomplished through reconfiguring the system elements over the time for a diverse set of individualised products often required in small quantities and with short delivery lead time. This necessitates the requirement of mapping the manufacturing system capabilities and other characteristics by developing a suitable index. In this paper an index has been developed to measure the reconfigurability of RMSs keeping in mind their various core characteristics such as modularity, scalability, convertibility and diagnosability. These characteristics have been mapped together using multi-attribute utility theory. One could easily use this index to find the reconfigurability of a system possessing different characteristics. An illustrative example is provided to reveal the application of the proposed methodology on a given system. Insight gained would be of much interest to the decision makers managing the complexity of a manufacturing system for diversified products.     

Supply chain network design with unreliable suppliers: a Lagrangian relaxation-based approach

This paper deals with the integrated facility location and supplier selection decisions for the design of supply chain network with reliable and unreliable suppliers. Two problems are addressed: (1) facility location/supplier selection; and (2) facility location/supplier reliability. We first consider the facility location and supplier selections problem where all the suppliers are reliable. The decisions concern the selection of suppliers, the location of distribution centres (DCs), the allocation of suppliers to DCs and the allocation of retailers to DCs. The objective is to minimise fixed DCs location costs, inventory and safety stock costs at the DCs and ordering costs and transportation costs across the network. The introduction of inventory costs and safety stock costs leads to a non-linear NP-hard optimisation problem. To solve this problem, a Lagrangian relaxation-based approach is developed. For the second problem, a two-period decision model is proposed in which selected suppliers are reliable in the first period and can fail in the second period. The corresponding facility location/supplier reliability problem is formulated as a non-linear stochastic programming problem. A Monte Carlo optimisation approach combining the sample average approximation scheme and the Lagrangian relaxation-based approach is proposed. Computational results are presented to evaluate the efficiency of the proposed approaches.     

Simulation based fuzzy TOPSIS approach for group multi-criteria supplier selection problem

Supplier selection is nowadays one of the critical topics in supply chain management. This paper presents a new decision making approach for group multi-criteria supplier selection problem, which clubs supplier selection process with order allocation for dynamic supply chains to cope market variations. More specifically, the developed approach imitates the knowledge acquisition and manipulation in a manner similar to the decision makers who have gathered considerable knowledge and expertise in procurement domain. Nevertheless, under many conditions, exact data are inadequate to model real-life situation and fuzzy logic can be incorporated to handle the vagueness of the decision makers. As per this concept, fuzzy-AHP method is used first for supplier selection through four classes (CLASS I: Performance strategy, CLASS II: Quality of service, CLASS III: Innovation and CLASS IV: Risk), which are qualitatively meaningful. Thereafter, using simulation based fuzzy TOPSIS technique, the criteria application is quantitatively evaluated for order allocation among the selected suppliers. As a result, the approach generates decision-making knowledge, and thereafter, the developed combination of rules order allocation can easily be interpreted, adopted and at the same time if necessary, modified by decision makers. To demonstrate the applicability of the proposed approach, an illustrative example is presented and the results analyzed.     

Optical properties of a wrinkled nanomembrane with embedded quantum well

A wrinkled nanomembrane with embedded quantum well (QW), fabricated by the partial release and bond back of epitaxial layers upon underetching, is investigated by spatially resolved micro-photoluminescence spectroscopy. From the observed QW transition energies and calculations based on the linear deformation potential theory, we find that the bonded back regions are fully relaxed and act on the strain state of the wrinkled QW. Light emission enhancement observed in the wrinkled QW is explained by interference contrast theory.     

Synthesis,Characterization and Conducting Properties of Nanocomposites of Intercalated 2-Aminophenol with Aniline in Sodium-Montmorillonite

A simple method was used to synthesize poly(2-aminophenol), poly(2-aminophenol-co-Aniline) and polyaniline nanocomposites with sodium-montmorillonite (Na-M) using in situ intercalative oxidative polymerization. Morphology and thermal properties of the synthesized nanocomposites were examined by transmission electron microscopy (TEM) and thermogravimetric analysis. The thermal analysis shows an improved thermal stability of the nanocomposites in comparison with the pure poly(2-aminophenol). The intercalation of polymers into the clay layers was confirmed by X-ray diffraction studies, TEM images and FTIR spectroscopy. In addition, the room temperature conductivity values of these nanocomposites varied between 8.21 × 10^?5 and 6.76 × 10^?4 S cm^?1. The electrochemical behavior of the polymers extracted from the nanocomposites, has been analyzed by cyclic voltammetry. Good electrochemical response has been observed for polymer films; the observed redox processes indicate that the polymerization into Na-M produces electroactive polymers.     

Assessment of Oxytetracycline Residue in Cooked and Raw Meat of Chicken Broilers Before and After the End of Official Withdrawal Period

The aim of this study was to determine and to compare the presence of oxytetracycline (OTC) residues in raw and cooked (boiled) meat before and after withdrawal period with the Maximum Residue Limits (MRL) using biological and physicochemical techniques. In animal building of 2000 broiler chickens (Gallus domesticus, breed ISA F15) and under the same conditions, 12 healthy adult chickens were selected and divided in two groups (n?=?6 in each group). The sample was treated by Oxytetracycline® 20% (0.4 g/kg) during 3 days. Juices and muscles tissues were sampled twice for this assay: first, the broiler chickens were slaughtered (n?=?6) 24 h after the third day of treatment. However, the second sampling (n =?6) was performed 24 h after the end of the withdrawal period. For each portions of sample, the juice meat and muscle tissues samples were collected after cooking at 80 °C during 45 min and after freezing/defrosting for the raw meat. Biological methods consisted of using four plates test (FPT) to pre-screening and Premi®Test to screening. Finally, to confirm and to quantify the accurate level of OTC in positive samples, ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) measurements were conducted. The FPT test showed that all samples were positive. While the Premi®Test analysis showed negative results for raw meat tested and positive results for juice of meat cooked in both samples. The obtained results using UHPLC-MS/MS methods confirmed the previously results. Thus, the presence of such toxic substances in our diet constitutes a major health risk for consumers, requiring the establishment of an adequate monitoring system. There is a paucity of official withdrawal periods for veterinary medicinal products in cooking meat; a relationship between the concentrations of residues of antibiotics after waiting period and cooking is not established since meat is always cooked before consumption.