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Optimization of Technological Parameters for Preparation of Geopolymers Fabricated with Pulverized Fly Ash
Get PDFGeopolymer is widely considered as an important direction for the comprehensive utilization of fly ash with its production increasing sharply year by year. The effect of mixing proportion including SiO2/Al2O3 molar ratio, Na2O/SiO2 molar ratio and water-solid ratio on the performances of geopolymer fabricated with pulverized fly ash with a median particle size of 3.3 μm was investigated by an orthogonal test in this work, and the optimum preparation technics were also obtained. Results indicated that the compressive strength of geopolymer reached the maximum of 61.0 MPa when SiO2/Al2O3 molar ratio was 3.3, Na2O/SiO2 molar ratio was 0.11 and the W/S ratio was 0.30 under the optimum preparation technics of aging time of 3h, mixing time of 3min and curing at 80℃ for 24h. Overall, Na2O/SiO2 molar ratio played the most important role on the compressive strength of geopolymer, but SiO2/Al2O3 molar ratio had a minimal impact. FTIR spectrum demonstrated that the sample with the optimum proportion exhibited a more complex asymmetric stretching vibration peak, which indicated that there were more activated silicon/aluminum monomers and dimers in fly ash depolumerized and repolymerized and tetrahedral phase transitions, and then geopolymer paste with denser microstructure was formed
Synthesis, Structural and Luminescence Studies of Europium Doped Borate Glasses
Get PDFDifferent concentration of (0.1, 0.2, 0.3, 0.4, 0.5, 1.0 & 1.5) mol% of europium doped lead borate lithium glasses were prepared by melt quenching method. The properties of thermal, photoluminescence & structural were analyzed using DTA, FTIR and emission spectra. Emission spectra was used to evaluate the Judd-Ofelt (JO) parameters. Radiative parameters like stimulated emission cross-sections (σe), effective band width (∆λeff), transition probabilities (A), optical gain bandwidths (σe x ∆λeff), radiative lifetime (τrad) and optical gain (σe x τrad) values were evaluated for the transition 5D0→7Fj (j=1, 2, 3 and 4) of Eu3+ ions. The outcome of transition 5D0→7F4 at its highest value of branching ratios and stimulated emission cross-section are evaluated with the literature. Hence we can could the prepared host glass doped with Eu3+ ions are good fibre amplifiers and it can be used as a red laser
Investigation of the Hall-Petch Relationship Using Strain Gradient Plasticity Model for Finite Deformation Framework
Get PDFThe Hall-Petch relationship in metals is investigated using the strain gradient plasticity theory within the finite deformation framework. For this purpose, the thermodynamically consistent constitutive formulation for the coupled thermomechanical gradient-enhanced plasticity model is developed. The corresponding finite element method is performed to investigate the characteristics of the Hall-Petch relationship in metals. The proposed model is established based on an extra Helmholtz-type partial differential equation, and the nonlocal quantity is calculated in a coupled method based on the equilibrium conditions. An excellent agreement between the simulation results and the test data is resulted in the Hall-Petch graph. Furthermore, it is observed that the Hall-Petch constants do not remain unchanged but vary with the strain level
Optimization of Processing Parameters to Achieve Superior Quality and Maximum Recovery of Canola Oil
Get PDFAim of the present study was to improve the efficiency of processing to achieve a superior quality of canola oil with better recovery. Three sets of canola oil containing crude, neutralized, bleached, deodorized oils and deodorizer distillates (DD) were collected from edible oil processing industries. Important physicochemical properties of the oil were evaluated in all three sets including unsaponifiable matter, phosphorus content and soap content. The industrial processing of set I and II was found to be satisfactory as compared to set III. Therefore, set III was selected for the optimization of different processing parameters during each stage of processing. For neutralization, bleaching and deodorization different parameters were optimized to achieve a better quality of the finished product, good recovery and control of the processing cost. After optimization, physicochemical characteristics of neutralized, bleached, deodorized oil and its DD were evaluated. Also, the loss and recovery of neutral oil were calculated in each processing stage. The results of the present study showed that a slight variation of processing parameters leads to a great impact on the quality and recovery of the canola oil. High contents of free fatty acids (FFA) in DD indicated that it could be used as a potential source of biodiesel production
Optical Properties of Bismuth Borate Glasses Doped with Zinc and Calcium Oxides
Get PDFSome bismuth-borate oxide glass' samples were prepared by the fast quenching method, where B2O3 was replaced with equal concentrations of ZnO and CaO. X-ray diffraction (XRD) was used to examine the internal structure and Fourier transform infrared (FTIR) to identify building units and bonds throughout the studied structural matrices. XRD showed that all samples have short range order structural nature, while FTIR demonstrated some of Zn2+ acted as glass network formers and all Bi3+ acted as glass. UV-visible measurements and calculations showed a decreasing in the energy band gap from 3.83 eV to 1.73 eV with decreasing B2O3 content. Also with decreasing B2O3 content, both real refractive index and metallization factor decreased from 3.1 to 1.9 and from 0.56 to 0.71, respectively. For the studied glass' samples, density and molar volume showed inverted behaviors, where the density decreased while the molar volume increases with decreasing B2O3
Time-resolved and Temperature-dependent Broadband Emission of Plasmon-coupled Quantum Dots
Get PDFThe broadband photoluminescence (PL) emissions from CdSe QDs and plasmon-coupled QDs were characterized with time-resolved and temperature-dependent spectroscopy for the application of solid-state white light. The origin of broad spectral emission includes the transitions from bandedge and surface-trapped states. The emission intensity enhancement of plasmon-coupled QDs with respect to that of bare QDs is attributable to the reduction of nonradiative decay and the local field enhancement with plasmon-exciton coupling through the Coulomb interaction. The temperature-dependent and time-resolved PL spectroscopy revealed the existence of selective contribution strength of both the local field enhancement and the reduction of nonradiative decay with plasmon-exciton coupling at different spectral regions
Dibenzoylhydrazines as Insect Growth Modulators: Topology-Based QSAR Modelling
Get PDFDibenzoylhydrazines Xa-(C6H5)a-CO-N-(t-Bu)-NH-CO-(C6H5)b-Yb are efficient insect growth regulators with high activity and selectivity toward lepidopteran and coleopteran pests. For 123 congeneric molecules, a quantitative structure activity relationship model was built in the framework of the QSARINS package using 2D, Topology-based, PaDEL descriptors. Variable selection by GA-MLR allows building an efficient multilinear regression linking pEC50 values to nine structural variables. Robustness and quality of the model were carefully examined at various levels: data-fitting (recall), leave-one (or some) - out, internal and external validation (including random splitting), points not in depth investigated in previous works. Various Machine Learning approaches (Partial Least Squares Regression, Projection Pursuit Regression, Linear Support Vector Machine or Three Layer Perceptron Artificial Neural Network) confirm the validity of the analysis, giving highly consistent results of comparable quality, with only a slight advantage for the three-layer perceptron
Delaying the Ripening of Banana (Musa sp.) cv Kandula through the Application of 1-Methylcyclopropane (1-MCP)
Get PDF Climacteric fruits are treated with 1-Methylcyclopropene (1-MCP) to delay the ripening process, thereby to reduce postharvest losses. This study evaluated the effectiveness of level of 1-MCP on delaying the ripening of Kandula banana. Banana hands were exposed to three levels of 1-MCP concentrations (0.5, 1.0 and 2.0 ppm) for 6 h and stored at 14±10C and 85-90% Relative Humidity (RH). The untreated samples (control) were stored under similar conditions. Peel colour, pulp firmness, total soluble solids (TSS), physiological weight loss and pulp to peel ratio were measured at initial stage and during storage at 4-day intervals. Peel colour of banana samples treated with different levels of 1-MCP remained light green in colour even on day 29 in storage whereas untreated samples fully ripened on day 21 in storage. Further, samples treated with different levels of 1-MCP (0.5, 1.0 and 2.0 ppm) resulted in a least change in a* and b* values compared to the control. Initial a* value (19.63±0.95) of the samples treated with 0.5, 1.0 and 2.0 ppm and the control reduced to -17.63±0.32, -17.30±0.53, -18.47±0.31 and -4.16±0.76 respectively on day 21 in storage. Initial b* value (36.36±1.15) of the samples treated 0.5, 1.0 and 2.0 ppm and the control changed to 37.13±0.32, 34.80±0.00, 36.40±0.35 and 49.26±1.61 respectively on day 21 in storage. Initial pulp firmness (29.20±1.68) of the samples treated with 0.5, 1.0 and 2.0 ppm and the control reduced to 28.10±2.91, 23.90±2.50, 25.20±2.05 and 5.00±0.70 N respectively on day 21 in storage. The TSS of the samples treated with 0.5, 1.0 and 2.0 ppm and the control were 4.80±0.50, 5.20±0.25, and 5.10±0.35 and 15.10±1.00 brix respectively on day 21 in storage. Percentage weight loss of the samples treated with 0.5, 1.0 and 2.0 ppm and the control were 2.08±0.05, 1.93±0.24, 2.04±0.14 and 2.56±1.70% respectively on day 21 in storage. Pulp to peel ratio of the treated samples and the control was not significantly (p˃0.05) different on day 21 in storage. Treating banana hands with 1- MCP was found to be successful in delaying of ripening. However, as no significant effect of different levelsof 1-MCP on delaying of ripening was evident, 0.5 ppm 1- MCP can be recommended to extend the postharvest life of Kandula banana beyond 29 days when stored at 14±10C
Artificial Neural Network Simulations of Human Learning Suggest the Presence of Metastable Attractors in Visual Memory
Get PDFThe attractor hypothesis states that knowledge is encoded as topologically-defined, stable configurations of connected cell assemblies. Irrespective to its original state, a network encoding new information will thus self-organize to reach the necessary stable state. To investigate memory structure, a multimodular neural network architecture, termed Magnitron, has been developed. Magnitron is a biologically-inspired cognitive architecture that simulates digit recognition. It implements perceptual input, human visual long-term memory in the ventral visual pathway and, to a lesser extent, working memory processes. To test the attractor hypothesis a Monte Carlo simulation of 10,000 individuals has been run. Each simulated learner was trained in recognizing the ten digits from novice to expert stage. The results replicate several features of human learning. First, they show that random connectivity in long-term visual memory accounts for novices’ performance. Second, the learning curves revealed that Magnitron simulates the well-known psychological power law of practice. Third, after learning took place, performance departed from chance level and reached a minimum target of 95% of correct hits; hence simulating human performance in children (i.e., when digits are learned). Magnitron also replicates biological findings. In line with research using voxel-based morphometry, Magnitron showed that matter density increases while training is taken place. Crucially, the spatial analysis of the connectivity patterns in long-term visual memory supported the hypothesis of a stable attractor. The significance of these results regarding memory theory is discussed
A Comparative Study of the Pliability of Separate Auxetic Architectonic Structures by Means of CAD
Get PDFIf a lengthened structure gets fat in all directions and the same structure gets narrower when it is pressed, it is an auxetic structure. This happens because these kinds of structures have a negative Poisson's ratio (NPR). In this paper a comparative study of unity patterns of CAD auxetic geometries is presented. A Computer Aided Design library of auxetic geometries will be developed to apply them to architecture. The geometric behavior of the eighteen auxetic separate patterns is tested from the developed library in order to develop a systematic comparison, analyzing properties of these forms, such as their maximum achievable area reductions in relation with the total length of bars of the structure, in order to obtain a growth factor