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Despeckling of Ultrasound Images Using Modified Local Statistics Mean Variance Filter
Get PDFThis article presents an improved method of despeckling the ultrasound medical images. In this paper a modified local statistics mean variance filter method has been proposed. In the proposed method, more consideration is given to local statistics since local statistical features are more important rather than global features.Various parameters like mean square error, peak signal to noise ratio, quality index, and structural similarity index measure are calculated to analyze the quality of the despeckled image
Preface to the Inaugural Issue of the Journal of Advanced Optics and Photonics
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Effects of Processing Parameters on Mechanical Properties and Structure of Banana Fiber-Reinforced Composites
No full textThe mechanical properties of unidirectional natural fiber-reinforced composites are generally affected by several processing parameters during compression molding. This study investigates the effects of processing temperature, time, and pressure on the tensile and flexural properties of acrylonitrile butadiene styrene reinforced by banana fibers. X-ray CT imaging was employed to find the relationship between the mechanical properties and structure of the processed composite. Besides, the water absorption of composites was observed and the way in which the mechanical properties evolved after water absorption was analyzed. The tensile and flexural properties of the unidirectional banana fiber-reinforced composite were found to be inversely proportional to the porosity. In addition, high-pressure compression molding might result in cracks and floating fibers that would significantly reduce its mechanical properties. The composite with the highest strength, smallest porosity and lowest water absorption was optimally prepared at T = 170 °C, t = 20 min, and P = 100 kg cm-2
Highly Functional Polyol Synthesis from Epoxidized Tall Oil Fatty Acids
No full textIn this work, free tall oil fatty acids were epoxidized with in-situ generated peroxyacetic acid. Reaction kinetics of epoxidation was investigated by oxirane content and iodine value titrimetric determination, as well as FTIR spectra analysis. A highly functional biobased polyol was synthesized by functionalizing epoxidized tall oil fatty acids with triethanolamine using Montmorillonite K10 as a catalyst. The obtained polyol was analyzed by FTIR and MALDI-TOF MS. The most common chemical and physical characteristics of obtained polyol were determined
Properties of Polyurethane Coatings Based on Linseed Oil Phosphate Ester Polyol
No full textLinseed oil was epoxidized using hydrogen peroxide (H2O2), acetic acid (AcOH) and ion exchange resin Amberlite IR-120 as a catalyst. Epoxidized oil was separately dissolved in isopropyl alcohol (IPA) or diethylene glycol butyl ether (DGBE) and phosphorylated with different amounts of phosphoric (H3PO4) acid (1%, 2%, 3% and 5%). The formation of phosphate polyesters was confirmed by Fourier-transform infrared (FTIR) and 31P nuclear magnetic resonance (NMR) spectra. Based on the synthesized polyols, polyurethane (PU) coatings were prepared. PU coating based on linseed oil diethylene glycol ester polyol was used as the reference. For the characterization of coatings, mechanical tests and thermogravimetric analysis (TGA) were used. The flammability parameters of wood samples with PU coatings at a heat flux of 35 kW/m2 were determined. It was found that PU coatings based on IPA polyols had higher mechanical characteristics, char residue upon thermal decomposition and flame retardancy
Modeling and Simulation of Human Cornea for the Measurement of Intraocular Pressure (IOP) through Eyelid
Get PDFThis article describes a study based on the use of an instrumented form of applanation and indentation tonometry through eyelid. The methods and devices which are available for the measurement of intraocular pressure (IOP) have their own limitations. These cause discomfort to the patients during IOP measurement. Also these methods, used to measure IOP over cornea, need anesthesia. In the present work, an attempt is made to develop a device for the measurement of IOP through eyelid which eliminates the need of anesthesia and enhance the patient’s comfort and convenience of the clinician. To represent the results of proposed technique, the human eye modeled with cornea, sclera and also with the eyelid, is used. Furthermore, simulation results of stress values for the range of IOP i.e. 5-40 mm of Hg are presented and discussed comparatively with eyelid and without eyelid i.e. directly ‘on cornea’ methods
On the Robustness of the xy-Zebra-Gauss-Seidel Smoother on an Anisotropic Diffusion Problem
Get PDFStudies of problems involving physical anisotropy are applied in sciences and engineering, for instance, when the thermal conductivity depends on the direction. In this study, the multigrid method was used in order to accelerate the convergence of the iterative methods used to solve this type of problem. The asymptotic convergence factor of the multigrid was determined empirically (computer aided) and also by employing local Fourier analysis (LFA). The mathematical model studied was the 2D anisotropic diffusion equation, in which ε > 0 was the coefficient of a nisotropy. The equation was discretized by the Finite Difference Method (FDM) and Central Differencing Scheme (CDS). Correction Scheme (CS), pointwise Gauss-Seidel smoothers (Lexicographic and Red-Black ordering), and line Gauss-Seidel smoothers (Lexicographic and Zebra ordering) in x and y directions were used for building the multigrid. The best asymptotic convergence factor was obtained by the Gauss-Seidel method in the direction x for 0 > 1. In this sense, an xy-zebra-GS smoother was proposed, which proved to be efficient and robust for the different anisotropy coefficients. Moreover, t h e c o nvergence factors calculated empirically and by LFA are in agreement
A New Encryption-then-Compression Scheme on Gray Images Using the Markov Random Field
Get PDFCompressing encrypted images remains a challenge. As illustrated in our previous work on compression of encrypted binary images, it is preferable to exploit statistical characteristics at the receiver. Through this line, we characterize statistical correlations between adjacent bitplanes of a gray image with the Markov random field (MRF), represent it with a factor graph, and integrate the constructed MRF factor graph in that for binary image reconstruction, which gives rise to a joint factor graph for gray images reconstruction (JFGIR). By exploiting the JFGIR at the receiver to facilitate the reconstruction of the original bitplanes and deriving theoretically the sum-product algorithm (SPA) adapted to the JFGIR, a novel MRF-based encryption-then-compression (ETC) scheme is thus proposed. After preferable universal parameters of the MRF between adjacent bitplanes are sought via a numerical manner, extensive experimental simulations are then carried out to show that the proposed scheme successfully compresses the first 3 and 4 most significant bitplanes (MSBs) for most test gray images and the others with a large portion of smooth area, respectively. Thus, the proposed scheme achieves significant improvement against the state-of-the-art leveraging the 2-D Markov source model at the receiver and is comparable or somewhat inferior to that using the resolution-progressive strategy in recovery
Unexpected Broadband Optical Limiting Properties of Antimonene Quantum Dots
Get PDFAntimonene has been found to possess excellent nonlinear refractive and saturable absorption properties recently. To further investigate its optical limiting properties, we prepared uniform antimonene quantum dots (AMQDs) via a facile ionic liquid-assisted exfoliation method. Thereafter the nonlinear absorption of the atomically thin AMQDs was studied using the open aperture Z-scan technique in the nanosecond laser pulse regime. Z-scan measurements indicate that the prepared AMQDs exhibited superior optical limiting properties at 532 nm and 1064 nm excitation, implying the antimonene hold potential for developing broadband nonlinear optical devices
Ductility and Ultimate Capacity of Concrete-Filled Lattice Rectangular Steel Tube Columns
Get PDFA kind of concrete-filled lattice rectangular steel tube (CFLRST) column was put forward. The numerical simulation was modeled to analyze the mechanical characteristic of CFLRST column. By comparing the load-deformation curves from the test results, the rationality and reliability of the finite element model has been confirmed, moreover, the change of the section stiffness and stress in the forcing process and the ultimate bearing capacity of the column were analyzed. Based on the model, the comparison of ultimate bearing capacity and ductility between CFLRST column and reinforced concrete (RC) column were also analyzed. The results of the finite element analysis show that the loading process of CFLRST column consists of elastic stage, yield stage and failure stage. The failure modes are mainly strength failure and failure of elasto-plastic instability. CFLRST column has higher bearing capacities in comparison with reinforced concrete columns with the same steel ratio. In addition, the stiffness degeneration of CFLRST column is slower than RC column and CFLRST column has good ductility