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Synthesis of Cadmium Sulfi de Quantum Dots with Simultaneous Desulfurization of Kerosene Oil
Get PDFCadmium sulfi de (CdS) quantum dots (QDs) were synthesized by a standard hydrothermal method with simultaneous desulfurization of kerosene oil. Sulfur containing kerosene oil was treated with cadmium chloride (CdCl2) in the presence of sodium hydroxide (NaOH) at 120 °C for 1.5 to 5 h. CdS was formed and sulfur content of oil gradually decreased. Thus, desulfurization of the oil occurred with the formation of the CdS QDs. The concentration of sulfur decreased to a minimum of 0.055% after 5 h of the reaction. In addition, the particle size of QDs increased from 5.4 nm to 8.1 nm as the reaction time was increased from 1.5 to 5 h. Transmission electron microscopy (TEM) study revealed the formation of CdS QDs of particle size 5.4–8.1 nm
Structural Damage Detection Using a Modified Artificial Bee Colony Algorithm
Get PDFAn optimization approach based on Artificial Bee Colony (ABC) algorithm is proposed for structural local damage detection in this study. The objective function for the damage identification problem is established by structural parameters and modal assurance criteria (MAC). The ABC algorithm is presented to solve the certain objective function. Then the Tournament Selection Strategy and chaotic search mechanism is adopted to enhance global search ability of the certain algorithm. A coupled double-beam system is studied as numerical example to illustrate the correctness and efficiency of the propose method. The simulation results show that the modified ABC algorithm can identify the local damage of the structural system efficiently even under measurement noise, which demonstrates the proposed algorithm has a higher damage diagnosis precision
A Homogenized Function to Recover Wave Source by Solving a Small Scale Linear System of Differencing Equations
Get PDFIn order to recover unknown space-dependent function G(x) or unknown time-dependent function H(t) in the wave source F(x; t) = G(x)H(t), we develop a technique of homogenized function and differencing equations, which can significantly reduce the difficulty in the inverse wave source recovery problem, only needing to solve a few equations in the problem domain, since the initial condition/ boundary conditions and a supplementary final time condition are satisfied automatically. As a consequence, the eigenfunctions are used to expand the trial solutions, and then a small scale linear system is solved to determine the expansion coefficients from the differencing equations. Because the ill-posedness of the inverse wave source problem is greatly reduced, the present method is accurate and stable against a large noise up to 50%, of which the numerical tests confirm the observation
Metamaterial Inspired Radar Absorbers: Emergence, Trends and Challenges
Get PDFThe advances in metamaterial science and technology have raised the expectations of camouflage or stealth researchers to one order higher in terms of absorption characteristics. As metamaterial inspired radar absorbing structures are proving themselves as a good candidate with near unity absorption, feasibility towards hardware realization is necessary. Hence an extensive literature survey of metamaterial inspired radar absorbing structure has been carried out and reported in this paper along with the challenges and material issues. The various types of metamaterial structures that can be used as absorber have been provided along with simulation figures. To make the review more useful, graphene and carbon nanotube (CNT) based radar absorbing structures are also included along with their simulation and fabrication techniques
The Correlation Between Texture Features and Fibrous Cap Thickness of Lipid-Rich Atheroma Based on Optical Coherence Tomography Imaging
Get PDFFibrous cap thickness (FCT) is seen as critical to plaque vulnerability. Therefore, the development of automatic algorithms for the quantification of FCT is for estimating cardiovascular risk of patients. Intravascular optical coherence tomography (IVOCT) is currently the only in vivo imaging modality with which FCT, the critical component of plaque vulnerability, can be assessed accurately. This study was aimed to discussion the correlation between the texture features of OCT images and the FCT in lipid-rich atheroma. Methods: Firstly, a full automatic segmentation algorithm based on unsupervised fuzzy c means (FCM) clustering with geometric constrains was developed to segment the ROIs of IVOCT images. Then, 32 features, which are associated with the structural and biochemical changes of tissue, were carried out to describe the properties of ROIs. The FCT in grayscale IVOCT images were manually measured by two independent observers. In order to analysis the correlation between IVOCT image features and manual FCT measurements, linear regression approach was performed. Results: Inter-observer agreement of the twice manual FCT measurements was excellent with an intraclass correlation coefficient (ICC) of 0.99. The correlation coefficient between each individual feature set and mean FCT of OCT images were 0.68 for FOS, 0.80 for GLCM, 0.74 for NGTDM, 0.72 for FD, 0.62 for IM and 0.58 for SP. The fusion image features of automatic segmented ROIs and FCT measurements improved the results significantly with a high correlation coefficient (r= 0.91, p<0.001). Conclusion The OCT images features demonstrated the perfect performances and could be used for automatic qualitative analysis and the identification of high-risk plaques instead manual FCT measurements
Preparation of β-Cyclodextrin/Latex Dispersion for Coating of Cellulose Fabric
Get PDFIn recent years there has been an increasing demand for the application of natural products to address problems in the environment. The use of products derived from renewable resources can provide a sustainable strategy to replace totally or partially synthetic products. Cymbopogon, commonly known as lemongrass, is a tropical grass cultivated mostly for its essential oil, which has demonstrated several bioactivities, including antibacterial and antifungal properties. In the present work the formation of inclusion complex between β-cyclodextrin (β-CD) and lemongrass essential oil (LGEO) as well as its fi xation onto cotton fabric were investigated. Inclusion complex was prepared through solution method followed by freeze-drying. The starting materials and inclusion complex were characterized by FTIR, TG/DTG and SEM. The cotton fabric incorporated with inclusion complex was investigated by FTIR and XRD. The results suggested the success of complexation in the molar ratio of 0.015:0.018 mol/L (LGEO:β-CD) and the viability of fi xing the inclusion complex leading to a potential functional textile
Ultrasound-Assisted Synthesis of Sucrose and Fructooligosaccharides Esters as Bio-Plasticizers
Get PDFThis article presents the results obtained by the ultrasound-assisted synthesis of sucrose and fructooligosaccharides (FOS) esters with fatty acids (palmitic and 10-undecylenic), the identifi cation of the products and the study of their possible application as plasticizers in plastics processing. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H and 13C NMR) spectroscopy were used to identify the synthesized carbohydrate esters. The plasticizing effect of the sucrose palmitate applied in polyvinyl chloride (PVC) was evaluated by the glass transition temperatures; the decrease of the Tg with the increase of the ester content could be accepted as confi rmation of the esters’ plasticizing effect.
The antimicrobial activity of the synthesized sucrose and FOS esters was evaluated; the results allowed us to conclude that the 10-undecynoyl esters of sucrose and fructooligosaccharides could be successfully applied as potential antimicrobial agents, as well. The sucrose palmitate plasticizing effect was evaluated by determining the glass transition temperatures of thin polyvinyl chloride fi lms on the basis of differential scanning calorimetry (DSC) and changes of mechanical properties. The results showed a decrease of the glass transition temperature with the increase of the ester content, which confirmed the plasticizing effect of the obtained esters
Mechanical and Thermal Properties of High-Density Rigid Polyurethane Foams from Renewable Resources
Get PDFThe most common sustainable solution for polyurethane (PU) materials is their production using renewable resources. Polyols derived from biomass and recycled polymers are the most promising way to do that. This study compares five different sustainable polyols as a possible raw material for production of highdensity rigid PU foams for automotive application. The goal of our study was to show that biobased polyols are a suitable replacement for polyols derived from petrochemical products. The influence of the chemical structure of polyols on the PU polymer matrix and foam properties was investigated. Two sources of PU raw material feedstock were studied: the plant biomass and the side stream of poly(ethylene terephthalate) (PET) production. Three different polyols from renewable resources were investigated as well as two aromatic polyester polyols. High-density rigid polyurethane foams were developed from these raw materials. This was done to choose a material, which could be used as the core of structural elements for lightweight vehicles. The focus was put on the sustainability and competitive properties of the developed materials. The obtained results led to the conclusion that recycled PET polyols show a higher mechanical strength. Nevertheless, renewable resources are closely matched
Effect of Epoxidized Jatropha Oil on the Cure, Thermal, Morphological and Viscoelastic Properties of Epoxy Resins
Get PDFThis article reports the effect of epoxidized jatropha oil (EJO) on the thermal, cure and viscoelastic properties of epoxy resins. Epoxidized jatropha oil with an oxirane value of 5.0 was prepared and epoxy formulations containing different concentrations of EJO were evaluated for cure, morphology, thermal and viscoelastic properties. The curing temperature of the formulations increased with increasing EJO content. The glass transition temperature of the cured films decreased from 56 °C for unmodified epoxy resin to 23 °C for the sample with 60 wt% EJO reactive diluent, suggesting good plasticizing action. The thermal decomposition was only marginally affected
Synthesis and Thermal Characterization of Polyurethanes Obtained from Cottonseed and Corn Oil-Based Polyols
Get PDFThe use of vegetable oils to replace fossil feedstock has become an area of opportunity and a priority for study in the field of polymer science. Vegetable oils are considered as renewable resources with high potential, low cost and full availability. The aim of this study is the synthesis of biobased polyols from cottonseed oil (Gossypium barbadanse) and corn oil (Zea mays) as feedstock. Their synthesis was successfully performed, as can be concluded from the determination of their hydroxyl index as well as the structural and thermal characterization carried out in this work. Polyurethanes from biobased polyols were synthesized with two different isocyanates (HDI and MDI) and variable polyol/isocyanate ratio and they were further characterized by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy, concluding that cottonseed and corn oils could be considered as valid alternatives for the synthesis of biobased polymeric materials