An efficient green route for hexamethylene-1,6-diisocyanate synthesis by thermal decomposition of hexamethylene-1,6-dicarbamate over Co3O4/ZSM-5 catalyst:An indirect utilization of CO2

The utilization of CO2 as rawmaterial for chemical synthesis has the potential for substantial economic and green benefits. Thermal decomposition of hexamethylene-1,6-dicarbamate (HDC) is a promising approach for indirect utilization of CO2 to produce hexamethylene-1,6-diisocyanate (HDI). In this work, a green route was developed for the synthesis of HDI by thermal decomposition of HDC over Co3O4/ZSM-5 catalyst, using chlorobenzene as lowboiling point solvent. Different metal oxide supported catalysts were prepared by incipientwetness impregnation (IWI), PEG-additive (PEG) and deposition precipitation with ammonia evaporation (DP) methods. Their catalytic performances for the thermal decomposition of HDC were tested. The catalyst screening results showed that Co3O4/ZSM-525 catalysts prepared by different methods showed different performances in the order of Co3O4/ZSM-525(PEG) N Co3O4/ZSM-525(IWI) N Co3O4/ZSM-525(DP). The physicochemical properties of Co3O4/ZSM- 525 catalyst were characterized by XRD, FTIR, N2 adsorption-desorption measurements, NH3-TPD and XPS. The superior catalytic performance of Co3O4/ZSM-525(PEG) catalyst was attributed to its relative surface content of Co3+, surface lattice oxygen content and total acidity. Under the optimized reaction conditions: 6.5% HDC concentration in chlorobenzene, 1 wt% Co3O4/ZSM-525(PEG) catalyst, 250 °C temperature, 2.5 h time, 800 ml·min?1 nitrogen flow rate and 1.0 MPa pressure, the HDC conversion and HDI yield could reach 100% and 92.8% respectively. The Co3O4/ZSM-525(PEG) catalyst could be facilely separated from the reaction mixture, and reused without degradation in catalytic performance. Furthermore, a possible reaction mechanism was proposed based on the physicochemical properties of the Co3O4/ZSM-525 catalysts.     

Electrochemical removal of the insecticide imidacloprid from water on a boron-doped diamond and Ta/PbO<Subscript>2</Subscript> anodes using anodic oxidation process

The removal of pesticides from water is a major environmental concern. This study investigates the electrochemical removal of the insecticide imidacloprid (IMD) from aqueous solutions on a boron-doped diamond (BDD) and Ta/PbO₂ anodes under galvanostatic electrolysis. The influence of operating parameters, such as applied current density (50–100 mA cm^?2), initial chemical oxygen demand COD (0) (281–953 mg L^?1), temperature (25–65 °C) and pH (3.0–10.0) on COD and instantaneous current efficiency (ICE), was studied using the BDD electrode. The degradation efficiency of IMD increased by increasing current density and temperature, but noticeably decreased by the increase of initial pH value and initial concentration of IMD. The COD decay follows a pseudo-first-order kinetic, and the process was under mass transport control. COD removal reaches 90% when using an apparent current density of 100 mA cm^?2, initial COD of 953 mg L^?1, pH of 3.0 and at 25 °C after 4.5 h electrolysis time. Compared with Ta/PbO₂, BDD anode has shown better performance and rapidity in the COD removal using the same electrolysis device.     

Stabilisation of a wave equation with localised memory term and boundary frictional damping

This paper is devoted to the study of uniform decay of a wave equation with dynamical boundary conditions, localised memory term and frictional dampings. We prove that a localised memory term combined with frictional dissipations is strong enough, via transmission process (u|_Γ = v), to assure the asymptotic stability of the whole system.     

Miniaturized planar filters exhibiting flexible placement of three transmission zeros suitable for duplexer design

In this work, we show that a stub‐loaded open‐loop double resonator filter can produce three transmission zeros at finite frequencies close to the passband when designed using our proposed asymmetric feed point topology. We demonstrate that by selecting the length of the stub, the placement of double transmission zeros on either the high side of the passband or the low side of the passband can be selected. This selection can be achieved by using a single design parameter: the stub length. The flexibility in the double zero placement makes these filters particularly advantageous for duplexer designs. Two duplexers are fabricated using the proposed filter topology in a microstrip on a duroid substrate and substrate‐embedded stripline via Low‐Temperature Cofired Ceramic technology (LTCC). The measurements show steep attenuation of approximately 30 dB, close to the filters' passband as well as a compact size down to 0.075λ × 0.17λ.     

A robust multimedia surveillance system for people counting

Closed circuit television cameras (CCTV) are widely used in monitoring. This paper presents an intelligent CCTV crowd counting system based on two algorithms that estimate the density of each pixel in each frame and use it as a basis for counting people. One algorithm uses scale-invariant feature transform (SIFT) features and clustering to represent pixels of frames (SIFT algorithm) and the other uses features from accelerated segment test (FAST) corner points with SIFT features (SIFT-FAST algorithm). Each algorithm is designed using a novel combination of pixel-wise, motion-region, grid map, background segmentation using Gaussian mixture model (GMM) and edge detection. A fusion technique is proposed and used to validate the accuracy by combining the result of the algorithms at frame level. The proposed system is more practical than the state of the art regression methods because it is trained with a small number of frames so it is relatively easy to deploy. In addition, it reduces the training error, set-up time, cost and open the door to develop more accurate people detection methods. The University of California (UCSD) and Mall datasets have been used to test the proposed algorithms. The mean deviation error, mean squared error and the mean absolute error of the proposed system are less than 0.1, 16.5 and 3.1, respectively, for the Mall dataset and less than 0.07, 5.5 and 1.9, respectively, for UCSD dataset.

     

On the Weighted Pseudo-Almost Periodic Solution for BAM Networks with Delays

In this paper, a class of Bidirectional Associative Memory neural networks with time-varying weights and continuously distributed delays is discussed. Sufficient conditions are obtained for the existence and uniqueness of weighted pseudo-almost periodic solution of the considered model and numerical examples are given to show the effectiveness of the obtained results.     

Large‐signal modeling methodology for GaN HEMTs for RF switching‐mode power amplifiers design

A large‐signal model for GaN HEMT transistor suitable for designing radio frequency power amplifiers (PAs) is presented along with its parameters extraction procedure. This model is relatively easy to construct and implement in CAD software since it requires only DC and S‐parameter measurements. The modeling procedure was applied to a 4‐W packaged GaN‐on‐Si HEMT, and the developed model is validated by comparing its small‐ and large‐signal simulation to measured data. The model has been employed for designing a switching‐mode inverse class‐F PA. Very good agreement between the amplifier simulation and measurement shows the validity of the model. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Fast-flux hunter: a system for filtering online fast-flux botnet

Fast-flux networks is a domain name system (DNS) technique used by botnets, which is hiding some attack like phishing and malware delivery sites behind associate dynamical network of compromised hosts acting as proxies, that sometimes hosts malicious content. Detection of fast-flux networks continues to be a difficult issue attributable to the similar behavior between these networks and alternative legitimate infrastructures, like server farms and content distribution networks. This study seeks to improve the detection and prediction of the unknown “zero-day” online fast-flux botnet. This improvement will be achieved using a new system called the fast-flux hunter (FFH), which supports a new adaptive evolving fuzzy neural network algorithm. The FFH system is a hybrid between the supervised and unsupervised online knowledge-based learning systems. The core mechanism of the FFH is based on the inherent feature of the fast-flux networks. It uses a collection of DNS traffic information. The FFH is able to scan over 7615 domain records and extract 14 distinct features for each domain. The FFH decreases the classification method’s error rate. The FFH has a detection accuracy rate of approximately 98 % and is compatible with life-long learning systems, footprint-consuming memory, and high-speed systems.

     

Inter-domain policy violations in multi-hop overlay routes: Analysis and mitigation

The Internet is a complex structure arising from the interconnection of numerous autonomous systems (AS), each exercising its own administrative policies to reflect the commercial agreements behind the interconnection. However, routing in service overlay networks is quite capable of violating these policies to its advantage. To prevent these violations, we see an impending drive in the current Internet to detect and filter overlay traffic. In this paper, we first present results from a case study overlay network, constructed on top of PlanetLab, that helps us gain insights into the frequency and characteristics of the different inter-domain policy violations. Further, we investigate the impact of two types of overlay traffic filtering that aim to prevent these routing policy violations: blind filtering and policy-aware filtering. We show that such filtering can be detrimental to the performance of overlay routing. We next consider two approaches that allow the overlay network to realize the full advantage of overlay routing in this context. In the first approach, overlay nodes are added so that good overlay paths do not represent inter-domain policy violations. In the second approach, the overlay acquires permits from certain ASes that allow certain policy violations to occur. We develop a single cost-sharing framework that allows the incorporation of both approaches into a single strategy. We formulate and solve an optimization problem that aims to determine how the overlay network should allocate a given budget between paying for additional overlay nodes and paying for permits (transit and exit) to ASes. We illustrate the use of this approach on our case study overlay network and evaluate its performance under varying network characteristics.