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151.
ABSTRACTThis study was aimed at investigating the variations in the melt strength of polypropylene as a result of blending with another polymer having long side branches in the presence of multi-functional agent and radical initiator. The formation of long chain branches was confirmed by strain hardening behavior in extensional viscometry and grafting efficiency data obtained from FTIR spectroscopy. strain hardening behavior, rheological parameters and grafting efficiency kept their ever-increasing trends by increasing the concentration of Trimethylol-propane-trimethacrylate (TMPTMA) until 3 phr, and the inefficiency of TMPTMA in branching reactions at concentrations higher than 3 phr is rooted in homo-polymerization of TMPTMA. 相似文献
152.
Abbas Saeed Hakeem Jekabs Grins Saeid Esmaeilzadeh 《Journal of the European Ceramic Society》2007,27(16):4773-4781
The nitrogen-rich part of the glass forming region in the La–Si–O–N system has been the subject of a comprehensive study. Glasses were prepared by heating powder mixtures of La metal, Si3N4 and SiO2 in a nitrogen atmosphere at 1650–1800 °C. By this new synthesis route, glasses containing up to 68 e/o of N and 62 e/o of La were prepared, showing that the glass forming region is significantly larger than previously reported. The glasses were characterized by elemental analysis, differential thermal analysis, X-ray powder diffraction, and scanning electron microscopy. They were found to be X-ray amorphous and homogenous, with the majority of them containing small amounts of crystalline La silicides and elemental Si. Glass transition temperatures (Tg) were found to vary between 900 and 1100 °C and crystallization to occur typically 120 °C above Tg. The forming of the glasses was investigated by characterizing samples taken out at various steps of the heating cycle. The results indicate that the glass formation is strongly dependent on reaction kinetics. A strong exothermal reaction occurs at temperatures 900–1100 °C, leading to the formation of assemblies of amorphous and crystalline (oxy)nitride phases that melt upon further heating at 1650–1800 °C. 相似文献
153.
Saeid Soltani Razi Helfi Parisa Almasi Reza Modarres 《Water Resources Management》2017,31(13):4253-4273
Design storm is one of the most important tools to design hydraulic structures, hydrologic system and watershed management, mostly extracted by intensity- duration - frequency (IDF) curves for a given specific duration and return period. As for conventional methods to calculate IDF curves, the precipitation should be recorded for different durations so that foregoing curves can be extracted. Such data can be collected from rain gauge stations. In many areas, just daily precipitation data are available by which IDF curves cannot be extracted as per conventional methods. The aim of this research is to make IDF curves for short-term durations according to time scaling model as well as daily rainfalls. The relationships of this method are characterized with three variables including mean (μ 24) and standard deviation (σ 24) of daily rainfall intensity, and scaling exponent (H) by which all IDF curves might be drawn. The method used in present paper entails for less computational steps than conventional methods and by far has low parameters considerably than others in turn increases reliability. Scaling method is used to extract the IDF curves in rain-gauge stations in Khuzestan province located in southwest Iran and results proved the efficiency and robustness of the scaling method. Also ability of scaling concept method was examined in constructing of regional IDF. 相似文献
154.
Hamed Azami Saeid Sanei Karim Mohammadi Hamid Hassanpour 《Digital Signal Processing》2013,23(4):1103-1114
Automatic segmentation of non-stationary signals such as electroencephalogram (EEG), electrocardiogram (ECG) and brightness of galactic objects has many applications. In this paper an improved segmentation method based on fractal dimension (FD) and evolutionary algorithms (EAs) for non-stationary signals is proposed. After using Kalman filter (KF) to reduce existing noises, FD which can detect the changes in both the amplitude and frequency of the signal is applied to reveal segments of the signal. In order to select two acceptable parameters of FD, in this paper two authoritative EAs, namely, genetic algorithm (GA) and imperialist competitive algorithm (ICA) are used. The proposed approach is applied to synthetic multi-component signals, real EEG data, and brightness changes of galactic objects. The proposed methods are compared with some well-known existing algorithms such as improved nonlinear energy operator (INLEO), Varri?s and wavelet generalized likelihood ratio (WGLR) methods. The simulation results demonstrate that segmentation by using KF, FD, and EAs have greater accuracy which proves the significance of this algorithm. 相似文献
155.
Jahan Bakhsh RaoofAuthor Vitae Reza OjaniAuthor VitaeSeyed Mahdi GolabiAuthor Vitae Ezat Hamidi-AslAuthor VitaeMohammad Saeid HejaziAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(1):195-201
Development of an electrochemical biosensor based on peptide nucleic acid (PNA) probe for detection of target DNA sequence and single nucleotide mutation in p53 tumor suppressor gene corresponding oligonucleotide using methylene blue (MB) as an electrochemical indicator is described. The interaction between MB and short sequence of p53, one of the most important tumor suppressor genes due to its dysfunction in the majority of human cancers, was studied by differential pulse voltammety (DPV). Probe modified electrode was prepared by self-assembled monolayer (SAM) formation of thiolated PNA molecules on the surface of gold electrode (GE). The hybridization of PNA probe with target DNA was performed in solution to form PNA-DNA hybrid on the surface of the GE. A significant increase in the reduction signal of MB was observed upon hybridization of the probe with the complementary DNA. The selectivity of the biosensor was studied using noncomplementary oligonucleotides. Furthermore, our results confirmed the ability of the sensor to detect single base mismatch in the sample oligonucleotide. The influence of probe concentration on the effective discrimination against noncomplementary sequence and point mutation was also investigated. Diagnostic performance of the biosensor is described and the detection limit is found 6.82 × 10−10 M. The electrochemical impedance spectroscopy was also employed to further investigate the sensor function. 相似文献
156.
Hamed Mobki Morteza H. Sadeghi Saeid Afrang Ghader Rezazadeh 《Microsystem Technologies》2011,17(9):1447-1452
In this work a novel MEMS based variable capacitor has been presented. To increase the tunability and decrease the applied
voltage, the conventional fixed-fixed beam used in CPW lines has been changed to a fixed-simple supported beam. The proposed
structure is a simple cantilever micro-beam in the first step of deflection and is changed to a fixed-simple supported micro-beam
in the second step of motion. In the capacitive micro-structures increasing the applied voltage decreases the equivalent stiffness
of the structure and leads the system to an unstable condition by undergoing to a saddle node bifurcation. In the proposed
structure to avoid pull-in instability and increase the capacitance tuning range, mechanical stiffness of the structure is
increased by changing boundary conditions by locating a pedestal in the end of the cantilever beam. The governing nonlinear
equation for static deflection of the micro-beam, based on Euler–Bernoulli micro-beam theory has been presented. The results
show that the proposed structure increases the capacitance tuning range and decreases the applied voltage. The results also
show that the position of the pedestal affects the tunability and the threshold voltage of the structure. 相似文献
157.
Reza Davarnejad Meysam Sabzehei Fatemeh Parvizi Saeid Heidari Asma Rashidi 《化学工程与技术》2019,42(12):2717-2725
Due to its low viscosity, soybean oil is commonly used as edible oil. Its production is accompanied by a large amount of wastewater containing hazardous materials like phenolic compounds. In this study, the electro‐Fenton process with response surface methodology was applied for oil removal from wastewater of soybean oil plants. Five independent variables, including reaction time, pH, current density, molar ratio of H2O2 to Fe2+, and volume fraction of H2O2 to wastewater, were investigated for their effects on oil removal. The significant independent variables were optimized by the Box‐Behnken design. The optimum conditions were statistically obtained, and the results were confirmed by experiment. 92.66 % oil removal were experimentally found for the optimum conditions. 相似文献
158.
Huge energy consumption in cloud infrastructure has turned into a challenging problem. Virtualization technology, which can be regarded as the first step in energy conservation by offering benefits like on-demand resource provisioning and live migration, creates a platform on which different resource allocation and scheduling policies can be defined on how to accumulate VMs on fewer number of hosts while respecting performance metrics. In this paper, after presenting a classification on VM placement strategies, we propose different combinatorial placement policies that take load dispersion of hosts into account to dynamically adapt their placement decisions. Simulated experiments through Cloudsim showed noteworthy results concerning energy-performance tradeoff. 相似文献
159.
Yazici Adnan Koyuncu Murat Yilmaz Turgay Sattari Saeid Sert Mustafa Gulen Elvan 《Multimedia Tools and Applications》2018,77(2):2225-2260
Multimedia Tools and Applications - This paper introduces an intelligent multimedia information system, which exploits machine learning and database technologies. The system extracts semantic... 相似文献
160.
Shendy Saeid Ahmadizadeh Shahverdizadeh Gholam Hossein Babazadeh Mirzaagha Hosseinzadeh-Khanmiri Rahim Es′haghi Moosa 《SILICON》2020,12(7):1735-1742
Silicon - Magnetic materials grafted with acetic acid (Fe3O4@SiO2COOH MNPs) were successfully prepared from the incorporation of bromoacetic acid as a functional group on the surface of magnetite... 相似文献