Influence of kenaf form and loading on the properties of kenaf‐filled polypropylene/waste tire dust composites: A comparison study

Kenaf (KNF)‐filled polypropylene/waste tire dust (PP/WTD) composites containing different KNF loadings (0, 5, 10, 15, and 20 parts per hundred parts of resin (phr)) were prepared using a Thermo Haake Polydrive internal mixer. The influence of the KNF form (KNF short fiber (KNFs) and KNF powder (KNFp)) at different KNF loadings on properties of the composites was studied. Results showed that with increasing KNF loading, the stabilization torque, tensile modulus, water absorption, and thermal properties increased for both KNFp‐ and KNFs‐filled PP/WTD composites. However, the tensile strength and elongation at break decreased by 29.2% and 53.9%, respectively, for KNFp‐filled PP/WTD composites, whereas KNFs‐filled PP/WTD composites showed a decrement of 24.5% and 63.5%, respectively. The stabilization torque, tensile strength, and tensile modulus increased by 22.4%, 6.7%, and 2.6%, respectively, for KNFs‐filled PP/WTD composites at 20 phr KNF loading. The scanning electron microscopy morphological studies on the tensile fractured surfaces revealed poor adhesion between KNFp and PP/WTD matrices as compared to KNFs and PP/WTD matrices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40877.     

Microwave irradiated and thermally heated olive stone activated carbon for nickel adsorption from synthetic wastewater: A comparative study

In attempt to compare the removal efficiency and yield of the activated carbon prepared using the conventional and microwave‐assisted heating is the focus of this work. Toward this olive stone (a biomass precursor) is activated using the popular activating agent potassium hydroxide. The process optimization exercise is carried out by using the standard full factorial statistical design of experiments (response surface methodology). The activated carbons prepared under the optimized conditions are compared based on the adsorption capacity and yield. The adsorption capacity was found higher using microwave heating as compared with conventional heating. The microwave heating requires significantly lesser holding time as compared to conventional heating method to produce activated carbon of comparable quality, with higher yield. The BET surface area of carbon using microwave heating is significantly higher than the conventional heating. Although the mesopore surface area of carbon is not vary significantly, the activation time, power, and nitrogen gas consumption are significantly lower than the conventional heating rendering that the activation process via microwave is more economical than that via conventional heating. The adsorption isotherm data fitted the Langmuir isotherm well and the monolayer adsorption capacity was found to be 12.0 and 8.42 mg/g for microwave and thermally heated activated carbon, respectively. Regeneration studies showed that microwave‐irradiated and thermally heated olive stone could be used several times by desorption with an HCl reagent. Both carbons can be used for the efficient removal of Ni²⁺ (>99%) from contaminated wastewater. © 2013 American Institute of Chemical Engineers AIChE J, 60: 237–250, 2014     

Preparation of dendritic adamantane‐based polymers/layered silicate nanocomposites

An adamantane‐based atom transfer radical initiator (Adm‐Br) was prepared by the treatment of 1‐[[N‐[2‐Hydroxy‐l,l‐bis(hydroxymethyl)ethyl]amino]carbonyl]adamantane with bromopropionyl bromide. The resulting initiator was subsequently used in the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) to form (Adm‐p‐MMA), which was successfully used, as a macroinitiator, in further ATRP reactions with 3‐O‐methacryloyl‐1,2 5,6‐di‐O‐isopropylidene‐α‐d ‐glucofuranose (gly), a glycomonomer, to afford the Adm‐p‐MMA‐b‐gly polymer. The new Adm‐p‐MMA‐b‐gly polymer subsequently was employed to form a nanocomposite with chitosan‐modified, Nanofil clay (NC). The resulting Adm‐p‐MMA‐b‐gly/NC composite material was progressively hydrolyzed to regenerate the OH groups of the glucose units within the Adm‐p‐MMA‐b‐gly copolymer. The polymer/NC nanocomposites were characterized by X‐ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, and transmission electron microscopy. POLYM. ENG. SCI., 54:2669–2675, 2014. © 2013 Society of Plastics Engineers     

Porous polyethersulfone hollow fiber membrane in gas–liquid contacting processes

Porous polyethersulfone hollow fiber membranes were fabricated via dry–wet phase inversion method with the polymer concentration in the spinning dope either 13 wt% or 15 wt%. The fabricated hollow fiber membranes were characterized by different test methods and the performance of membranes in contactor applications was tested by CO₂ absorption. The mean pore size, effective surface porosity and membrane porosity decreased while the membrane density and Liquid Entry Pressure (LEPw) increased as polymer concentration increased. The CO₂ absorption flux of the fabricated membranes was measured in two cases; i.e. when the absorbent, distilled water, was in the lumen side or in the shell side. The CO₂ flux for the membrane, fabricated from 13 wt% PES solution, was compared with some commercial and in-house made membranes. The former membrane had 111% higher flux than a commercial PTFE membrane.     

Predicting the colour properties of viscose knitted fabrics using soft computing approaches

The aim of this paper was to predict the colour strength of viscose knitted fabrics by using fuzzy logic (FL) model based on dye concentration, salt concentration and alkali concentration as input variables. Moreover, the performance of fuzzy logic (FL) model is compared with that of artificial neural network (ANN) model. In addition, same parameters and data have been used in ANN model. From the experimental study, it was found that dye concentration has the main and greatest effects on the colour strength of viscose knitted fabrics. The coefficient of determination (R²), root mean square (RMS) and mean absolute errors (MAE) between the experimental colour strength and that predicted by FL model are found to be 0.977, 1.025 and 4.61%, respectively. Further, the coefficient of determination (R²), root mean square (RMS) and mean absolute errors (MAE) between the experimental colour strength and that predicted by ANN model are found to be 0.992, 0.726 and 3.28%, respectively. It was found that both ANN and FL models have ability and accuracy to predict the fabric colour strength effectively in non-linear domain. However, ANN prediction model shows higher prediction accuracy than that of Fuzzy model.     

Radio resource management for LTE-A relay-enhanced cells with spatial reuse and max–min fairness

One of the major issues in LTE-Advanced (LTE-A) systems is the poor capacity at the cell edge. This is mainly due to the interference experienced by the users as a result of the aggressive frequency reuse usually implemented. Relaying offers an attractive solution for this problem by offering better links than those with the eNodeB (eNB) for the terminals suffering from high path loss or high interference. However, adding relays complicates the resource allocation problem at the eNB and therefore the need for more efficient schemes arises. This is also aggravated by the reuse of resource blocks (RBs) by the relays to fully exploit the scarce spectrum, which, in turn, leads to intra-cell interference. In this paper, we study the joint power and resource allocation problem in LTE-A relay-enhanced cells that exploit spatial reuse. To guarantee fairness among users, a max–min fair optimization objective is used. This complex problem is solved using coordinate ascent and the difference of two convex functions (DC) programming techniques and the proposed scheme indeed converges to a local-optimum quickly. This is shown to be a satisfactory solution according to the simulation results that indicate an almost sevenfold increase in the 10th percentile capacity when compared to previously proposed solutions.     

High frequency response to the impedance complex properties of Nb-doped CaCu3Ti4O12 electroceramics

Impedance analyses was performed on undoped and Nb-doped CaCu₃Ti₄O₁₂ (CaCu₃Ti_4−xNb_xO_12+x/2; x = 0, 0.01, 0.03, 0.05, 0.1) to investigate their electrical properties. The pellet samples were prepared using the solid state reaction method. Silver electrode was deposited on both pellets’ surfaces for electrical measurement. The thermally etched samples showed tiny bumped domains within the grains. The existence of both domain and grain boundaries are believed to strongly influence the dielectric constant of CaCu₃Ti₄O₁₂ (CCTO). Undoped CCTO showed two arcs of impedance complex plane while Nb-doped samples have three arcs. Each arc represents the constituent elements of the CCTO. The highest frequency arc is evidence that CCTO consists of conductive domains which measure about 1 Ω and are insulated by two types of barriers, i.e. domain boundary and grain boundary.     

Reduction of EMI in AC Drives Through Dithering Within Limited Switching Frequency Range

In this paper, a method is presented to reduce electromagnetic (EM) emissions in AC drives. This method is applicable to many AC drives. It is proposed to dither the switching frequency of the power devices of an inverter in a pseudorandom way to spread out the emitted RF energy over a larger frequency range. The proposed method requires only software changes. Practical constraints to implement the frequency dithering approach are discussed. Simulation and measurement results show an improvement of more than 10 dB. The proposed method also converts specific spikes in the long-wave range from narrowband to broadband noise, which results in less stringent EM emission requirements for many applications.     

Sustainability of Groundwater Resources in the North-Eastern Region of Bangladesh

Water is essential for economic, social, and environmental development. Global water resources are vulnerable due to increasing demand related to population growth, pollution potential, and climate change. Competition for water between different sectors is increasing. To meet the increasing demand, the use of groundwater is increasing worldwide. In this paper, the water-table dynamics of the north-eastern region of Bangladesh were studied using the MEKESENS software. This study reveals that the depth to water-table (WT) of almost all the wells is declining slowly. In many cases, the depth will approximately double by the year 2040, and almost all will double by 2060, if the present trend continues. If the decline of the water-table is allowed to continue in the long run, the result could be a serious threat to the ecology and to the sustainability of food production, which is vital for the nation’s food security. Therefore, necessary measures should be taken to sustain water resources and thereby agricultural production. Demand-side management of water and the development of alternative surface water sources seem to be viable strategies for the area. These strategies could be employed to reduce pressure on groundwater and thus maintain the sustainability of the resource.