Odd-even effect in the synthesis of mesoporous silicate molecular sieves in the presence of alkyl cetyl dimethyl ammonium bromide

New quaternary ammonium salts with the formula, (C₁₆H₃₃)(C_nH_2n+1)(CH₃)₂N⁺Br (n =1 to 12) have been synthesized and used as templates to prepare crystalline mesoporous molecular sieves. The effect of the C_nH_2n+1 chain length on the nature of the obtained product and its d-distance has been investigated. A correlation between the nature of the obtained phases and the conformation of the carbon chain of the occluded surfactant was revealed by¹³C CP MAS NMR.     

Formation control of VTOL Unmanned Aerial Vehicles with communication delays

The formation control problem of a team of Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs) with communication delays is addressed. Based on the extraction algorithm presented in Abdessameud and Tayebi (2010a), we propose a new design methodology that simplifies the design of formation control laws with delayed communication for this class of under-actuated systems. Three control schemes are presented that provide delay-dependent and delay-independent results with constant and time-varying communication delays. The stability of the overall closed loop system in each scheme is established using Lyapunov–Krasovskii functionals. The proposed design methodology achieves global results in terms of the position and removes the requirement of the linear-velocity measurements. Simulation results are provided to show the effectiveness of the proposed control schemes.     

Delamination and Wrinkling of Flexible Conductive Polymer Thin Films

Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to the formation of blisters, wrinkles, and cracks. This is detrimental to their use especially in the case of multilayer devices. Here, it is shown that a simple water or solvent drop deposited on such films gives rise to a buckling instability and the formation of several folds due to the tendency of these films to swell in contact with the solvent. A phase diagram of the instability portraying its domain of existence, and thus the means to inhibit it, is proposed. By depositing drops on such films and observing the instability, material parameters such as the elastic modulus of the thin films or their energy of adhesion to the substrate can be estimated reliably. Further, the instability can be harnessed to pattern surfaces at low cost giving rise to percolated and more conductive pathways in the conductive polymer films under scrutiny.     

MFHS: A modular scheduling framework for heterogeneous system

Current innovative distributed architectures, proposing on-line services, involve more and more computing resources. From a provider point of view, the platform management leads to challenging problematic relating to resource allocation, which involve different kind of quality of service parameters, the provider has to focus on to keep his platform reliable and efficient. MFHS is a modular generic framework, which can be adapted to any distributed computing environment. Structured in modules, MFHS allows to discover the existing computing resources in terms of computing performance, network throughput and disk I/O speeds (Resources Discovery module) and to predict how the experiment should behave (P_i value). As the setting up of real experiments is often complex, MFHS allows: to make theoretical experimentation (based on models), to use any kind of distributed emulators, or to deploy experiments on real-experimental platforms. In this article, these three environments are used to highlight the reliability of MFHS (measured P_i=90% against 94% for the predicted P_i). Deployment and scheduling studies have also been achieved using an experimental Cloud based on OpenStack while Emulab test-bed has been used as emulator. During experiments, four QoS parameters are taken into account (Resources Monitoring module): energy consumption, cost, resource utilization, and makespan. These studies also includes a new heuristic called MMin, based on Max-Min and Min-Min algorithms. Experimentation section, proposes a detailed comparative analysis of these algorithms in terms of QoS results, while the abilities of the proposed heuristic MMin regarding the makespan metric is shown.     

CelloMOF: Nanocellulose Enabled 3D Printing of Metal–Organic Frameworks

3D printing is recognized as a powerful tool to develop complex geometries for a variety of materials including nanocellulose. Herein, a one‐pot synthesis of 3D printable hydrogel ink containing zeolitic imidazolate frameworks (ZIF‐8) anchored on anionic 2,2,6,6‐tetramethylpiperidine‐1‐oxylradical‐mediated oxidized cellulose nanofibers (TOCNF) is presented. The synthesis approach of ZIF‐8@TOCNF (CelloZIF8) hybrid inks is simple, fast (≈30 min), environmentally friendly, takes place at room temperature, and allows easy encapsulation of guest molecules such as curcumin. Shear thinning properties of the hybrid hydrogel inks facilitate the 3D printing of porous scaffolds with excellent shape fidelity. The scaffolds show pH controlled curcumin release. The synthesis route offers a general approach for metal–organic frameworks (MOF) processing and is successfully applied to other types of MOFs such as MIL‐100 (Fe) and other guest molecules as methylene blue. This study may open new venues for MOFs processing and its large‐scale applications.     

Screening of Fe–BEA catalysts for wet hydrogen peroxide oxidation of crude olive mill wastewater under mild conditions

A series of Fe–BEA catalysts, differing in the amount of iron have been characterized by XRD, BET surface area, UV–vis spectroscopy and chemical analysis. The zeolite samples have been tested as heterogeneous catalysts for the wet hydrogen peroxide oxidation of crude olive mill wastewaters (OMW) under very mild conditions (at 28 °C and atmospheric pressure). All experiments were performed on a laboratory scale set-up.BSE-1/3 catalyst with a moderate Fe content (Fe/Al = 1.19) showed the best results in terms of catalytic activity and loss of active species into the aqueous solutions. The stability of Fe species has been shown to be strongly dependent on the Fe environment into the zeolite framework.Over the selected catalyst, application of catalytic procedure on diluted OMW solution permitted high removal efficiencies of pollutants. The process produces a removal capacity of 28% of total organic carbon (TOC), 40% of total phenols, 30% of chemical oxygen demand (COD) and 59% of colour, just after 12 h. 5-Day biochemical oxygen demand (BOD₅), and toxicity towards the bioluminescent bacteria Vibrio fischeri were selected to follow the performance of this process in terms of reducing the ecotoxicity of OMW. Results showed an increase in the biodegradability of the treated sample and a decrease of the microtoxicity from 100% to 70% load towards V. fischeri.Occurrence of small catalyst deactivation by carbonaeous during the oxidation reaction was observed through scanning electron microscopy (SEM) and elemental analysis.     

Link failure resilience in the dynamic source routing protocol

Reactive routing protocols for mobile ad hoc networks reduce the routing cost in high mobility environments where link failures are frequent. However, route discovery in these protocols is typically performed via network‐wide flooding, which consumes a substantial amount of bandwidth and causes a significant latency to data packets. To improve the dynamic source routing (DSR) protocol and overcome these limitations, we propose two optimization techniques, viz. generalized salvaging mechanism and cache maintenance using a distributed topology discovery mechanism through mobile ant‐agents. We show, by simulations, that our contributions improve the DSR performance, and particularly in large scale networks with high mobility and heavy load that cause frequent link failures. Copyright © 2008 John Wiley & Sons, Ltd.     

Classical state feedback controller for nonlinear systems using mean value theorem: closed loop-FOC of PMSM motor application

The problem of state feedback controllers for a class of Takagi-Sugeno (T-S) Lipschitz nonlinear systems is investigated. A simple systematic and useful synthesis method is proposed based on the use of the differential mean value theorem (DMVT) and convex theory. The proposed design approach is based on the mean value theorem (MVT) to express the nonlinear error dynamics as a convex combination of known matrices with time varying coefficients as linear parameter varying (LPV) systems. Using the Lyapunov theory, stability conditions are obtained and expressed in terms of linear matrix inequalities (LMIs). The controller gains are then obtained by solving linear matrix inequalities. The effectiveness of the proposed approach for closed loop-field oriented control (CL-FOC) of permanent magnet synchronous machine (PMSM) drives is demonstrated through an illustrative simulation for the proof of these approaches. Furthermore, an extension for controller design with parameter uncertainties and perturbation performance is discussed.     

Identifying Root Causes of Construction Accidents

Construction accident investigation techniques and reporting systems identify what type of accidents occur and how they occurred. Unfortunately, they do not properly address why the accident occurred by identifying possible root causes, which is only possible by complementing these techniques with theories of accident causation and theories of human error. The uniqueness of the construction industry dictates the need to tailor many of the contemporary accident causation models and human error theories. This paper presents an accident root causes tracing model (ARCTM) tailored to the needs of the construction industry. ARCTM proposes that accidents occur due to three root causes: (1) Failing to identify an unsafe condition that existed before an activity was started or that developed after an activity was started; (2) deciding to proceed with a work activity after the worker identifies an existing unsafe condition; and (3) deciding to act unsafe regardless of initial conditions of the work environment. In addition, ARCTM emphasizes the need to determine how unsafe conditions exist before or develop after an activity is started and proposes that these unsafe conditions are due to four causes: (1) Management actions∕inactions; (2) unsafe acts of worker or coworker; (3) non-human-related event(s); (4) an unsafe condition that is a natural part of the initial construction site conditions. Thus, ARCTM acknowledges the possible contribution of both management and labor to the accident process. This perspective helps in better explaining accidents on construction sites and in identifying areas where prevention efforts should be directed, so that labor and management may provide more effective measures for preventing accident occurrence.     

Formation of Cobalt Phyllosilicate During Solid State Preparation of Co2+/ZSM5 Catalysts from Cobalt Acetate

When CO²⁺/ZSM5 catalysts are prepared by solid state exchange between H-ZSM5 and cobalt acetate, CO²⁺ ions form layered cobalt phyllosilicate at the surface of the zeolite grains, bringing about a reassessment of the chemistry involved in the preparation of catalytic systems by solid state exchange.