Influence of the Cryogenic Treatment in Micro Structure, hardness and Micro hardness of the Brass 60-40 and Bronze SAE 64
Abstract— At the end of the 60’s with the beginning of the space missions it was observed, that once the airships were sent into space and when they entered at the atmosphere, they presented an increase at the wear resistance on the structure of the space shuttles. It was concluded that the low temperature would have influenced in such changes. Over the year’s liquid nitrogen, gaseous nitrogen, helium and dry ice were used on metals and tool that were submitted to high wear and fatigue periods in order to increase the useful life of the material, this procedure was called cryogenic treatment. Once it was identified that low temperatures generated improvements to certain materials as steels, aluminum and some a ceramic materials and the problem emerged to establish the effect of this phenomena in materials as brass and bronze, so it was take the decision to determine the influence of the low temperatures in this materials. What microstructural changes and mechanical behavior could the cooper alloys suffer as the brass 60-40 and bronze SAE 64? Taking into account the time spent in the steel a pilot test was done to evaluate the effect in the variation of grain size and micro hardness to the state of delivering of material through ANNOVA method determined the amount of tubes to study per each material and time. In this case, the effect in the microstructure is evaluated by metallographic and the effect in the mechanic behavior will be evaluated with micro hardness and hardness testing. Were spent four brass tubes were used per each time of exposition where 24, 48, 72 and 120 hours respectively and bronze’s tubes used were there per each time of exposition likewise to brass. Finally it was observed a microstructural change and variations of mechanical properties where it is possible to conclude that to longer exposure of cryogenic treatment the resistance of the material increases. With an improvement in it is microstructure showing a grain with major dimensional stability.
Keywords— space missions, microstructural changes, ANNOVA, SAE 64.
Abstract— Aerial vehicles as VTOL 's (VERTICAL TAKE OFF LANDING), who meet tasks such as exploration are costly in terms of maintenance and resource consumption, as commonly these work self -powered propellers, which generates high energy consumption. One solution is the use of dirigible, which are economical and effective for the task of exploration, these it possible to obtain aerial images accurately and less consumption of energy resources due to flying at a constant height and should not counteract weight, which facilitates the execution of tasks such as scanning and monitoring.
Keywords— Dirigible, IMU, consumption of energy resources, slenderness, complementary filter.
Abstract— Using chemical bath deposition (CBD) technique, (Cd-Zn)S:CdCl2 thin films were prepared on glass substrates. Room temperature photoluminescence analysis in the 400-700 nm emission wavelength ranges for the excitation energies 365nm show the ‘well known’ green emission band related to exciton-donor complexes formed in presence of S / excess Cd are observed in the PL emission spectra of various rare earth doped (Cd-Zn)S:CdCl2 films. In doped films, characteristic emissions of lanthanide such as Ce are observed. Some properties related to nanocrystalline effects are also found. The influence of variation of ratio of cadmium and sulphur was studied on the PL emission intensity of (Cd-Zn)S:CdCl2 thin films. In a selected ratio of cadmium and sulphur for which emission intensity was highest, the effect of impurity concentration on PL emission intensity was studied.
Keywords— Photoluminescence, Chemical Bath Deposition, Thin Films, CdS.
Abstract— The modification on the surface of the polyethylene terephthalate (PET) polymer as a result of ArF (193nm) laser irradiation was investigated. Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray (EDX) spectroscopy were employed for examination of the chemical composition of irradiated surface and conical structure. FTIR spectroscopy indicates that by irradiation of PET, hydrophobic groups of the polymer molecules in the polymer chain have more freedom of movement and prevents from the interaction between water molecules and the hydrophilic groups on the polymer surface, and PET surfaces after exposure have become more hydrophobic. While the PET is irradiated by more than 800 pulses, its surfaces become hydrophilic, so that the surface of PET after treated by 1500 pulses, even become more hydrophilic than that of untreated one.
Abstract—In this study, in order to reduce torque ripple of 5 phase-10/8 segmental type switched reluctance motor (SRM) a controller was designed and then performed. The SRM was controlled as a bipolar by H-bridge topology with flexible controller circuit. To determine the effectiveness of the designed driver circuit, the motor was operated at various conditions and the torque ripple of the motor was recorded. The SRM was driven by the H-bridge converter topology which can operate at both constant frequency signal and signal obtained from the encoder. The obtained results showed that the torque ripple of the SRM is reduced by using the encoder signals rather than the constant frequency signal. This control technique demonstrated that the torque ripple of the SRM can be kept within acceptable limits.
Keywords— dsPIC33, H-Bridge Converter, Segmental Type Switched Reluctance Motor, Torque Ripple.
Abstract— This study aims to develop a method for enhancing x-ray image’s resolution in radiology department, some fabricated grids with significant capability in reducing backscattered radiation are used to assessment its effectiveness in improving radiographic image resolution. The fabricated anti backscattered grids are designed from different materials with different geometric shapes. Image resolution test tool is exposed to produce x-ray images at different exposure parameters (kVp, mAs). The results of resolution indexes (LP/mm) illustrated remarkable effect of anti backscattered grids in improvement of x-ray image resolution up to 32%, with the use of crossed iron steel grid. Therefore, the effectiveness of fabricated grids in enhancing image resolution is dependent on the grid’s material and design, as well as the radiation exposure parameters.
Keywords— Resolution, Anti-backscattered grid, X-ray, Image quality.
A Novel Method for the Analysis of Gene Expression Microarray Data with K-Means Clustering: Sorted K-Means
Background: Microarray technology has revolutionized the way genomic analysis has been performed. High-throughput data acquisition, brought up a challenge in data comprehension i.e. in gene expression.
Methods: k-means cluster obtained after analysis of miRNA expression data have been sorted by an algorithmic procedure. Results: The proposed method managed to sort k-means centroids and manifest a more simple way of drawing conclusions on studied tumor samples. miRNAs were unraveled that changed in expression levels with respect to tumor aggressiveness. Conclusions: In the present work we presented a new and simple approach in data analysis using a new analysis approach, which we termed sorted-k-means analysis.
Keywords—k-means, microarrays, sorted k-means, gene expression, miRNA, tumors.
Abstract— The purpose of this study is to investigate the effectiveness of rice husk, saw dust and tea waste as adsorbent for the removal of cadmium, chromium and lead ions respectively. The main parameters that influenced heavy metal adsorption on bioadsorbent were adsorbent dosage, % removal and pH value. Using the initial concentrations of lead, cadmium and chromium solutions at 10 ppm, the analysis was continued using contact time 60 mins. Besides that the influences of adsorbent dosage also been studied in a range of 10mg to 30mg.After that contains of heavy metal ions were analyzed using Atomic Adsorption Spectrophotometre (AAS). The maximum % removal of cadmium is 95.7% at 20ppm of initial concentration and 20mg adsorbent dosage of rice husk at pH 6.The maximum % removal of chromium is 98.75% at 20ppm of initial concentration and 10mg adsorbent dosage of sawdust at pH 3.The maximum % removal of lead is 99.25% at 20ppm of initial concentration and 10mg adsorbent dosage of tea waste at pH 5.5 batches. The batch studies revealed that the adsorption was influenced by the initial metal concentration, the biomass dose and solution pH. Langmuir isotherm model (R2≈1) was used to analyze the equilibrium data.
Keywords— Bioadsorbent , Rice husk, saw dust, tea waste , Heavy metals, Isotherms, Kinetics.
Effect of the Parameters Variation for Induction Motor on its Performance Characteristics with Field Oriented Control Compared to Scalar Control
Abstract—With inventing the semiconductor devices and control theories, the induction motors are placed the DC motor in the industrial applications. There are many control methods are used to control the induction motor as scalar control and field oriented control. The motor parameters which used inside control must be matched with actual motor parameters to achieve high dynamic response. So this paper is used to study the effect of the parameters variation for induction motor on the performance characteristics of its with field oriented control compared to scalar control at starting point and at full load point. In this paper, the skin effect is taken into consideration. This study is occurred in the constant flux region and in the field weakening region. MATLAB program is used to simulate this study.
Keywords— Field oriented control, Induction motor, Parameters variation, Scalar control.
Improved Genetic Algorithm for Minimizing Periodic Preventive Maintenance Costs in Series-Parallel Systems
Abstract—This work presents an improved genetic algorithm (IGA) for minimizing periodic preventive maintenance costs in series-parallel systems. The intrinsic properties of a repairable system, including the structure of reliability block diagrams and component maintenance priorities are considered by the proposed IGA. The proposed component importance measure considers these properties, identifies key components, and determines their maintenance priorities. The optimal maintenance periods of these important components are then determined to minimize total maintenance cost given the allowable worst reliability of a repairable system. An adjustment mechanism is established to solve the problem of chromosomes falling into infeasible areas. An elitist conservation strategy is applied to retain superior chromosomes in the iterative breeding process and to accelerate the approach toward the global optimum. A response surface methodology is further used to systematically determine crossover probability and mutation probability in the GA instead of using the conventional trial-and-error process. A case study demonstrates the effectiveness and practicality of the proposed IGA for optimizing the periodic preventive maintenance model in series-parallel systems.
Keywords—genetic algorithms, importance measure, periodic preventive maintenance, reliability, response surface methodology.
Antimicrobial Activity of Lactococcus and Lactobacillus Species Isolated from Raw Goat Milk. San Luis Argentina
Abstract— The goat milk and their products are used to human consumption with health benefits. The lactic acid bacteria (LAB) have ability to produce bacteriocins that inhibit the growth of spoilage microorganisms or pathogens present in food. In this study, bacteriocins-producing strains were isolated from goat milk samples. The isolates were able to inhibit the growth of Listeria monocytogenes ATCC 74902, Enterococcus faecalis ATCC 29212, Escherichia coli and/or Pseudomonas aeruginosa strains with an average inhibition halo between 8 and 12 mm. The strains were identified as Lactococcus lactis ssp lactis 2 (gmSL3, gmSL9, gmSL11, gmSL12, gmSL15 and gmSL40), Lactobacillus fermentum (gmSL28), Lactobacillus paracasei ssp paracasei 1 (gmSL5, gmSL20 and gmSL23). The antimicrobial substances showed high stability at temperatures and/or pH extremes. The tested strains inhibit the growth of more than one pathogen, of both bacteria Gram (+) and Gram (-). By RT-PCR, one band of 136 bp was found, whose size corresponds to Nisin A.
Keywords— antimicrobial peptides, bacteriocins, Lactic Acid Bacteria (LAB), raw goat milk.
Abstract— Protein terminals have important roles in molecular structural stability and in some occasions they have regulatory roles in catalytic reaction. To expand our understanding on the influences of distal residues mutation, we explored the molecular stability and kinetics of mannanase Man1312 mutants. For Man1312, the N-terminal loop was more disordered and changeable; therefore the mutations on N-terminal should have significant effects on enzymic properties. The experiment was investigated by spectrophotometer, circular dichroism and differential scanning calorimetry assays. As a result, positive mutations were found from sites of T2 and Q9 and double-site mutant ManY9G2 showed increased catalytic activity by 7.7% higher than Man1312. Meanwhile, ManY9G2 had significantly increased thermostability with promoted Topt by 6oC and elongated t1⁄2 by 7 min, which was resulted from the optimized intermolecular forces and a newly-built hydrogen bond in ManY9G2. In our experiment, the specific residues were mutated from hydrophilic to hydrophobic and the improved hydrophobicity on N-terminal had a positive impact on the properties of mannanase Man1312.
We construct N-terminal multi-site mutants of mannanase Man1312.
We determine the enzyme activity and thermal dynamics of mannanase and its mutants.
Best mutations increase the hydrophobilicity of N-terminal.
N-terminal mutation significantly improves the thermo-stability and slightly increases activity of mannanase.
Keywords— Mannanase, N-terminal, multi-site mutation, structural stability, activity.
Abstract— As the quantity of Waste Foundry Sand (WFS) is generated in huge amount, only a part of WFS is considered as the hazardous waste and the rest of the part is considered as non-hazardous industrial waste foundry sand. The leachate from WFS may contain hazardous compounds, which may probably effect the environment. The random release of heavy metals into the soil and waters is a major health alarm worldwide, as they cannot be broken down to non-toxic forms and therefore have long-lasting effects on the ecosystem. Leaching characteristics are essential in understanding the environmental impact or toxicity, dumping and potential development of beneficial applications of WFS. This study investigates that a trial was done to find out a fungal species from dumped site of a local foundry located at Coimbatore (Tamilnadu, India). Isolation of different fungal species from soil sample was carried out. All the isolated fungal species were then screened for their organic acid production by using HPLC. The molecular characterization of 18S rRNA for the isolated fungus was matched with R. oryzae. Physiochemical Characterization of WFS was done. Assessment of impacts of using fungal treated WFS its leachate quality was done using atomic absorption spectroscopy.
Keywords— Waste Foundry Sand, Isolation, organic acid, molecular characterization, leachate.
Physical and Chemical Characteristics of Material Containing Non-Ferrous Metals and Inorganic Aqueous Solutions
Abstract— Kinetic studies were conducted on the process of the dissolution of non-ferrous metals with the use of sulfur-containing material as a source of leaching agent - sodium thiosulfate. It is shown that with increasing concentrations of sodium hydroxide in solution in the range of 0.1 - 1.0 M, copper recovery is increased from 21.5 to 46.2 %.
As the temperature increases from 25 to 45 0C, copper dissolution rate in the initial moment of the time increases, then over time this figure gradually decreases with decreasing the copper content in the initial product. The value of the reaction order is 0.39. The calculated value of the activation energy in the process of leaching copper is 12.01 kJ / mol, which suggests that the analyzed process is proceeds in the diffusion mode.
Keywords— complex and low-grade raw materials, the structure of condensed systems, structural-phase transitions, hydrometallurgy.
Abstract— This article investigates the performance of the generator excitation loop equipped with a PID controlled AVR system, and of the dam automaton consisting of a PID controlled water flow regulation system in the southern interconnected grid (SIG) of the Cameroonian power system, when subjected to small perturbations, using linearized state-space models of the power plant. A fifth order model of the synchronous generator with a high gain excitation system and AVR is considered. A detailed formulation of equations comprising the mechanical and electrical swing dynamics of the turbine-generator unit and the load is realized; a multivariable state-space non linear model of the one area single machine system model is obtained. For small-signal performance analysis, the model is linearized around an operating point. The article also presents a state-space model of the water flow system. The effects of PID controlled AVR and water flow regulation systems are examined through performing of extensive MATLAB simulations to analyze the behavior of the proposed models following small disturbances. The simulation results presented in this paper are obtained using a MATLAB computer program developped by the authors; they provide useful insight into the dynamic behavior of the Cameroonian SIG, including stability, speed of response and steady-state accuracy. The paper establishes that the classical control systems do not have very good performance: long settling time, high overshoot, relativly slow response, and many damped oscillations.
Keywords— AVR, excitation system, PID controller, state-space modeling, small-signal stability.
Abstract— Studies during the last ten years have demonstrated that it is difficult to deposit pure silicon nitride by Pulsed Laser Deposition (PLD) without oxygen contamination even using a pure nitrogen atmosphere and a pure silicon target. The difference in the reactivity of nitrogen and oxygen means that there is always a certain amount of oxidation during the film growth from the residual oxygen in the vacuum system; the oxygen content can be more than 20 at.%. The aim of this work was to study the deposition of silicon nitride thin films under different experimental conditions to determine whether oxidation during, or posterior, to the deposition where the principal processes. We used optical emission spectroscopy (OES) and Langmuir probe measurements to study the plasma species and the parameters of the plasma. The chemical composition and the deposition rate of the films were measured by Rutherford Back Scattering (RBS), x-ray photoelectron spectroscopy (XPS) and profilometry, respectively. The OES results showed that the signal from nitrogen reached a maximum at 0.4 Pa (N2+, 391.4 nm) and decreased if the nitrogen pressure was increased further. The maximum nitrogen concentration in the deposits was ~21 at.% at 1 Pa, with an oxygen content of 28 at%. For lower pressures the coatings were rich in silicon and the coatings deposited at higher pressure (>1Pa) were rich in oxygen up to 50 at.%.
Keywords— Laser ablation, oxidation, plasma, silicon nitride.
Abstract— Lutein ester was extracted from marigold petals under hexane reflux at 60°C. For protection from oxidation, the as-obtained lutein ester was clathrated with β-cyclodextrin (β-CD) using two methods, viz. grinding lutein ester with β-CD in the presence of ethanol and through the mixing of an ethanol solution of lutein ester with an aqueous solution of β-CD. The results of DSC, IR, H1NMR analyses suggest successful clathration of lutein ester in β-CD. In terms of inclusion efficiency, the former is better than the latter to achieve clathration. We studied factors that can affect the stability of lutein ester such as light, air and temperature change, and the results confirm good stability of the clathrated lutein ester. The toxicity and pharmacokinetic tests on mice showed that the lutein-β-cyclodextrin complex is non-toxic and has an efficient release rate that matches body physiology.
Keywords— Lutein ester; Marigold petals; β-Cyclodextrin; Clathrated compound; Toxicity test.