A micromechanics based analysis of hollow fiber composites using DQEM

In this study, a generalized plane strain micromechanical model is presented to obtain micro-stress/strain fields within the unidirectional (UD) hollow fiber reinforced composites. In addition, the thermally induced residual stresses during cooling down process, overall elastic properties and energy absorption capability of hollow reinforced composite are studied. The representative volume element (RVE) of the composite consists of a quarter of the fiber surrounded by matrix to represent the real composite with repeating square array of fibers. Fully bonded fiber–matrix interface condition is considered and the displacement continuity and traction reciprocity are properly imposed to the interface. The cubic serendipity shape functions are used to convert the solution domain to a proper rectangular domain. A Least-squares based differential quadrature element method (DQEM) is used to obtain solutions for the governing partial differential equations of the problem. Results of the presented method for various stress and displacement components and thermal residual stresses show excellent agreement with finite element analysis. Furthermore, predicted overall properties also show good agreement with other available analytical and finite element results. Moreover, results also revealed that the presented model can provide highly accurate predictions with a few number of elements and grid points within each element.     

Effect of blend granulometry on calciothermic reduction of TiO2

Investigated was the effect of particle size of starting powder material on the calciothermic reduction of TiO₂ in the TiO₂-Ca system. According to XRD results, TiO₂ did not react with Ca after 40 h of ball milling. DTA data indicated that a decrease in the particle size of starting material resulted in lower reaction temperatures between molten Ca and TiO₂ (decrease from 1073 to 1044°C). The XRD results showed that titanium metal can be produced from nanosized starting material, and the reduction reaction progressed at lower temperatures upon a decrease in the particle size of TiO₂. Also, the particle size of the products decreased with decreasing particle size of starting TiO₂. The concentration of residual oxygen depended on the particle size of TiO₂ due to increasing surface of contact with deoxidizer (Ca).     

Antielectrostatic agent addition in low-dielectric-constant polymerization media

In the coordinative polymerization of α-olefin by a slurry process, a low-dielectric-constant suspending agent, such as hexane or heptane, must be used. As a result of solvent movement and its friction between system components, electrostatic charges are generated. Because of low electrical conduction of these solvents, the generated charges accumulate in the polymerization medium. Consequently, a repulsive force between same charges effects the growth of the polymer particles and causes them to form fine particles. In this article, we present research results on the effects of antielectrostatic agents on the increase of the electrical conduction of the polymerization medium, particle size distribution, and also the quantity of fine particles in the final polymer. Techniques gained from the fuel industry were applied to modify the subjected polymerization medium. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of the effects of Canadian climate conditions on the MEPDG predictions for flexible pavement performance

This study aims to investigate the quality of the recently developed Canadian climatic database and the effect of climatic factors on flexible pavement performance using the mechanistic-empirical pavement design guide (MEPDG). Two hundred and six Canadian climatic files were used to carry out the analysis. Freezing index and frost depth from the MEPDG were compared with the data available in Canadian databases. The sensitivity of pavement performance to climate conditions, predicted using the MEPDG, was also studied. The pavement performance predicted using the virtual weather station and existing weather station data was compared. From the pavement performance sensitivity study, it was found that the asphalt concrete, total pavement rutting and international roughness index show sensitivity to climate changes. It was also found that differences in the quality and duration of data for close-by stations can result in variation in the predicted performance. Overall, the study assists with facilitating the implementation of the MEPDG in Canada.     

Traffic inputs for mechanistic-empirical pavement design guide using weigh-in-motion systems in Alberta

Mechanistic-empirical pavement design guide (MEPDG) uses axle load spectra and the number of axle applications to characterise traffic loads for pavement design. Alberta Transportation installed weigh-in-motion (WIM) systems at six highway locations to characterise traffic loads in Alberta for MEPDG design. Seasonal and regional trends in traffic characteristics of the six WIM sites were investigated and compared with the default values in the MEPDG for the years 2009 and 2010. Truck traffic classification (TTC) and axle load distribution factor (ALDF) for the WIM sites showed deviations from the MEPDG defaults. Seasonal variations were also evident in the distribution of different classes of truck throughout the year. Differences are attributed to cold climate conditions and special truck traffic in Alberta because of local industries. Influence of the differences between site-specific traffic characteristics and the MEPDG defaults on the performance of both flexible and rigid pavements for Alberta conditions was investigated through a sensitivity analysis. It was found that the flexible pavement performance is sensitive to TTC and ALDF, and the rigid pavement performance is most sensitive to ALDF.     

A grasshopper optimizer approach for feature selection and optimizing SVM parameters utilizing real biomedical data sets

Neural Computing and Applications - Support vector machines (SVM) are one of the important techniques used to solve classifications problems efficiently. Setting support vector machine kernel...     

Electrocoalescence of binary water droplets falling in oil: Experimental study

The approaching movement and consequent coalescence of binary water droplets falling in stagnant oil and exposed to an external electric field are investigated using a high speed camera. Different situation of the droplets and electric field intensities are applied in the experiments. The qualitative results of the experimental observations are exhibited through the scaled images of the binary droplets snapshots in milliseconds. Furthermore, different approaching trends of the droplets are presented as quantitative plots and discussed based on the theoretical electrostatic and hydrodynamic models. The effect of the applied voltage amplitude, initial distance of the drop pair, and skew angle of the electric field are investigated. The experimental results prove the electrostatic theories; as acceleration in electrocoalescence demonstrated using a stronger electric field as well as closer distance between the droplets. It was also revealed that the skew angle of the electric field decelerates the electrocoalescence until alignment of the droplets.     

Synthesis of CL‐20 by a Greener Method Using Nitroguanidine/HNO3

CL‐20 is a nitramine applied in both explosives and propellants. The traditional nitrolysis of tetraacetyldibenzylhexaazaisowurtzitane (TADB), as the key precursor for the synthesis of CL‐20, requires the use of N₂O₄/HNO₃/H₂SO₄ (so‐called mixed acid) which has its drawbacks, especially at industrial scales. Herein, the nitrolysis of TADB with a one pot method was investigated using nitroguanidine (NQ) and guanidinium nitrate (GN)/HNO₃ as new system for the synthesis of CL‐20. Positive features of these nitro‐debenzylation/nitro‐deacetylation methods include lack of mixed acids, simple work‐up and less hazardous reagents. The maximum yield of reaction (72 %) was obtained under optimized conditions (NQ (3.48 mmol) and TADB (0.58 mmol) in 98 % HNO₃ (5 mL) at 85 °C and 24 h).     

Contribution to emission reduction of CO2 by a fluidized-bed membrane dual-type reactor in methanol synthesis process

In this work, a fluidized-bed membrane dual-type reactor was evaluated for CO₂ removal in methanol synthesis process. The feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. A two-phase dynamic model in bubbling regime of fluidization was developed in the presence of long-term catalyst deactivation. This model is used to compare the removal of CO₂ in a FBMDMR with a conventional dual-type methanol synthesis reactor (CDMR) and a membrane dual-type methanol synthesis reactor (MDMR). The simulation results show a considerable enhancement in the CO₂ conversion due to have a favourable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems.