Heck and oxidative boron Heck reactions employing Pd(II) supported amphiphilized polyethyleneimine‐functionalized MCM‐41 (MCM‐41@aPEI‐Pd) as an efficient and recyclable nanocatalyst

A novel nanocatalyst was developed based on covalent surface functionalization of MCM‐41 with polyethyleneimine (PEI) using [3‐(2,3‐Epoxypropoxy)propyl] trimethoxysilane (EPO) as a cross‐linker. Amine functional groups on the surface of MCM‐41 were then conjugated with iodododecane to render an amphiphilic property to the catalyst. Palladium (II) was finally immobilized onto the MCM‐41@PEI‐dodecane and the resulted MCM‐41@aPEI‐Pd nanocatalyst was characterized by FT‐IR, TEM, ICP‐AES and XPS. Our designed nanocatalyst with a distinguished core‐shell structure and Pd²⁺ ions as catalytic centers was explored as an efficient and recyclable catalyst for Heck and oxidative boron Heck coupling reactions. In Heck coupling reaction, the catalytic activity of MCM‐41@aPEI‐Pd in the presence of triethylamine as base led to very high yields and selectivity. Meanwhile, the MCM‐41@aPEI‐Pd as the first semi‐heterogeneous palladium catalyst was examined in the C‐4 regioselective arylation of coumarin via the direct C‐H activation and the moderate to excellent yields were obtained toward different functional groups. Leaching test indicated the high stability of palladium on the surface of MCM‐41@aPEI‐Pd as it could be recycled for several runs without significant loss of its catalytic activity.     

Solving the nonlinear equations for one-dimensional nano-sized model including Rydberg and Varshni potentials and Casimir force using the decomposition method

The Adomian decomposition method has been applied to solve the nonlinear equations from the one-dimensional model for a nano-sized-oscillator. The model includes Rydberg and Varshni potentials as well as Casimir force with fractional damping. New approximate solution of the equations of motion for anharmonic vibrations of a nano-sized oscillator with the elastic force deriving from the Rydberg and Varshni potentials has been obtained.     

Using neural networks and genetic algorithms to enhance performance in an electronic nose

Sensitivity, repeatability, and discernment are three major issues in any classification problem. In this study, an electronic nose with an array of 32 sensors was used to classify a range of odorous substances. The collective time response of the sensor array was first partitioned into four time segments, using four smooth time-windowing functions. The dimension of the data associated with each time segment was then reduced by applying the Karhunen-Loéve (truncated) expansion (KLE). An ensemble of the reduced data patterns was then used to train a neural network (NN) using the Levenberg-Marquardt (LM) learning method. A genetic algorithm (GA)-based evolutionary computation method was used to devise the appropriate NN training parameters, as well as the effective database partitions/features. Finally, it was shown that a GA-supervised NN system (GANN) outperforms the NN-only classifier, for the classes of the odorants investigated in this study (fragrances, hog farm air, and soft beverages).     

Coupled pore network model for the cathode gas diffusion layer in PEM fuel cells

Acta Mechanica Sinica - A pore network model (PNM) is developed for gas diffusion layer (GDL) in the cathode side of polymer electrolyte membrane fuel cells (PEMFCs). The model is coupled to...     

INTREPID: an integrated network tool for routing, evaluation ofperformance, and interactive design

The network design problem discussed is that of selecting nodes and links in a network. This includes deciding where to place network processors and links and what capacity nodes and links to use at each location. At a higher level, these decisions also determine the network architecture. The focus is on a two-level network, backbone and local access. Although the selection of specific equipment or the detailed configuration of devices is not discussed, INTREPID is sufficiently fast and flexible to be of use in making such decisions. The principles used in the development of INTREPID and its components are described. A top-level view of INTREPID is followed by a discussion of the design flow, utility modules, and design algorithms. Experience with the tool is briefly described     

Application of modified magnetic nanoparticles with amine groups as an efficient solid sorbent for simultaneous removal of 2,4-Dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid from aqueous solution: optimization and modeling

In the present work, functionalized magnetic nano-adsorbent with amine groups (Fe₃O₄@SiO₂@NH₂) was prepared for the simultaneous removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution. Characterization such as Fourier transform infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscope confirmed that the magnetic nanoparticles structure of Fe₃O₄@SiO₂ nano-adsorbent was successfully functionalized by amine groups. The impact of some influencing parameters such as contact time, pH, adsorbent dosage, 2,4-D and MCPA initials concentration and solution temperature were studied. The equilibrium data were analyzed by Langmuir and Freundlich adsorption isotherms and also two models kinetically of pseudo-first-order and pseudo-second-order. Findings of the present study showed that the synthesized amino-functionalized MNPs will be helpful in use as an effective recyclable adsorbent for the removal of phenoxy acid herbicides from aqueous solution due to its advantages such as facile and rapid separation of target molecules from solution.     

Optimizing the choice of influential nodes for diffusion on a social network

An optimization approach is taken to locating the optimal set of initial contacts in a social network to maximize the number of total network members reached by a message. It is assumed that initial contacts are costly and that the number of initial contacts must be minimized simultaneously with maximizing the total number of network members contacted. A bi‐objective probabilistic integer programming model is developed that assumes that actors are heterogeneous in the probability that they will pass messages along their ego networks. Considering the complexity of solving the proposed model, it reformulated as a pure integer programming model. The algorithm is illustrated by the analysis of message passing in a short‐message system (texting) among university students. Copyright © 2015 John Wiley & Sons, Ltd.     

A Flexible Privacy-Enhanced Location-Based Services System Framework and Practice

Location based services(LBS) are becoming increasingly important to the success and attractiveness of next generation wireless systems. However, a natural tension arises between the need for user privacy and the flexible use of location information. In this paper we present a framework to support privacy enhanced location based services. We classify the services according to several basic criteria and we propose a hierarchical key distribution method to support these services. The key idea behind the system is to hierarchically encrypt location information under different keys, and distribute the appropriate keys only to group members with the necessary permission. Four methods are proposed to deliver hierarchical location information while maintaining privacy. We propose a key tree rebalancing algorithm to maintain the re-keying performance of the group key management. Furthermore, we present a practical LBS system implementation. Hierarchical location information coding offers flexible location information access which enables a rich set of location based services. Our load tests show such a system is highly practical with good efficiency and scalability.     

Dynamic Flow Control in Store-and-Forward Computer Networks

In a recent paper we presented an analysis of flow control in store-and-forward computer communication networks using a token mechanism. The analysis assumed equilibrium conditions for a selected set of system parameters which were not dynamically adjusted to stochastic fluctuations in the system load; this mechanism was referred to as "static flow control." In this paper we study a "dynamic flow control" in which parameters of the system are dynamically adjusted to match the availability of resources in the network. Based on Markov decision theory, an optimal policy to dynamically select the number of tokens is formulated. Because an exact solution to the problem is extremely difficult, an effective heuristic solution to the problem is presented. Numerical results are given and it is shown that the throughput-delay performance of a network is better with dynamic control than with static control.     

Efficient one-pot synthesis of polyhydroquinoline derivatives using Cs2.5H0.5PW12O40 as a heterogeneous and reusable catalyst in molten salt media

Polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using Cs_2.5H_0.5PW₁₂O₄₀ as a heterogeneous and reusable catalyst. The present method uses molten salt media instead of hazardous organic solvents. The present methodology offers several advantages such as simple procedure, excellent yields, and a short reaction time.