Enhancement of electromechanical properties of natural rubber by adding barium titanate filler: An electro-mechanical study

Natural rubber is one of the most potential electro-active polymers for sensors, actuators, and energy harvesting applications. Enhancing the characteristic properties of polymers by reinforcing with fillers that possess multifunctional attributes have attracted considerable attention. In the present study, barium titanate reinforced natural rubber composite is prepared by using two-roll mill mixing. Afterwards, mechanical, electrical, and electromechanical properties of the composites are extensively analyzed by reinforcing different amounts of barium titanate into the matrix of natural rubber. The fabricated dielectric composite shows excellent properties such as high dielectric constant, low dielectric losses, high dielectric breakdown strength, and extreme stretchability. It is observed that as the filler loading reaches the value of 11 parts per hundred rubber (phr), maximum agglomeration of the particles occurs. Maximum stretchability and highest ratio of dielectric constant to elastic modulus are obtained at 8 phr of barium titanate fillers and at the loading, a maximum actuation strain of 11.24% is achieved. This study provides a simple, economical, and effective method for preparing enhanced mechanical, electrical, and electromechanical properties of natural rubber composites, facilitating the wide applications of dielectric materials as actuators and generators.     

Cutting force and hole quality analysis in micro-drilling of CFRP

Micro-drilling in carbon fiber reinforced plastic (CFRP) composite material is challenging because this material machining is difficult due to anisotropic, abrasive and non-homogeneous properties and also downscaling of cutting process parameters affect the cutting forces and micro-drilled hole quality extensively. In this work, experimental results based statistical analysis is applied to investigate feed and cutting speed effect on cutting force components and hole quality. Analysis of variance based regression equation is used to predict cutting forces and hole quality and their trend are described by response surface methodology. Results show that roundness error and delamination factor have similar trends to those of radial forces and thrust force, respectively. Non-linear trends of cutting forces and hole quality errors are observed during downscaling of the micro-drill feed value. Optimization results show that cutting forces and hole quality errors are minimum at a feed value which is almost equal to the tool edge radius rather than at the lowest feed value. Therefore, the presented results clearly show the influences of size effects on cutting forces and hole quality parameters in micro-drilling of CFRP composite material.     

Bubble interactions for the Mullins–Sekerka problem: Some case examples

The Mullins–Sekerka free boundary problem originates from the study of solidification and liquidation of materials where material is transported by diffusion. In the present paper we explore dynamics of bubbles for the Mullins–Sekerka problem. Using a set of ordinary differential equations for the radii and the centers, we numerically simulate the relevant interactions in both “two-dimensional” and “three-dimensional” settings. Our results illustrate how larger bubbles grow at the expense of smaller ones and highlight the role of additional factors such as the initial inter-bubble distance or weak asymmetries in the bubble position in the ensuing dynamics. One novel feature in comparison with earlier works is the possibility to continue for the three-dimensional case the simulation past the points where one of the bubbles disappears.     

A Comparative Evaluation of Scatter Correction Techniques in High-Resolution Detectors Based on PSPMTs and Scintillator Arrays

Single photon emission computed tomography images suffer from low contrast as a result of photon scatter. The standard method for excluding the scatter component in pixelized scintillators is the application of an energy window around the central photopeak channel of each crystal cell, but small angle scattered photons still appear in the photopeak window, and they are included in the reconstructed images. A number of scatter correction techniques have been proposed in order to estimate the scatter component, but they have not yet been applied in pixelized scintillators, where most groups use the standard one-photopeak window for scatter correction. In this paper, the author have assessed three subtraction techniques that use a different approach in order to calculate the scatter component and subtract it from the photopeak image: the dual energy window subtraction technique, the convolution subtraction technique, and a deconvolution technique. All these techniques are compared to the standard method     

Synthesis and anticonvulsant activity of new acylthiosemicarbazides and thiazolidones

A number of 1-(3-phenyl-4(3H)-quinazolinone-2-ylmercaptoacetyl)-4-substituted thiosemicarbazide and 2-(3-phenyl-4(3H)-quinazolinone-2-ylmercaptoacetylhydrazono)-3-sub stituted 4-thiazolidone derivatives were synthesized and evaluated for anticonvulsant activity. Some of the tested compounds showed significant activity against MES and ScMet induced seizures.     

FUZZY RADIAL BASIS FUNCTION (FRBF) NETWORK BASED TOOL CONDITION MONITORING SYSTEM USING VIBRATION SIGNALS

Thriving automation in industries leads to more research on the tool condition monitoring systems for better accuracy and fast recognition/evaluation of tool wear. Research on the applicability of the new advances in the soft-computing as well as in the signal processing fields is the inevitable consequence. In this work, a new soft-computing modeling technique, fuzzy radial basis function (FRBF) network has been applied to the prediction of drill wear using the vibration signal features. This work presents the wear prediction performance comparison of this new model with three other already tried and established soft-computing models, such as back propagation neural network (BPNN), radial basis function network (RBF) and normalized radial basis function network (NRBF), for both time-domain as well as wavelet packet approaches of feature extraction. Experimental results show that FRBF model with wavelet packet approach produces the best performance of predicting flank wear.     

Inherited Retinal Diseases Due to RPE65 Variants: From Genetic Diagnostic Management to Therapy

Inherited retinal diseases (IRDs) are a heterogeneous group of conditions that include retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA) and early-onset severe retinal dystrophy (EO[S]RD), which differ in severity and age of onset. IRDs are caused by mutations in >250 genes. Variants in the RPE65 gene account for 0.6–6% of RP and 3–16% of LCA/EORD cases. Voretigene neparvovec is a gene therapy approved for the treatment of patients with an autosomal recessive retinal dystrophy due to confirmed biallelic RPE65 variants (RPE65-IRDs). Therefore, the accurate molecular diagnosis of RPE65-IRDs is crucial to identify ‘actionable’ genotypes—i.e., genotypes that may benefit from the treatment—and is an integral part of patient management. To date, hundreds of RPE65 variants have been identified, some of which are classified as pathogenic or likely pathogenic, while the significance of others is yet to be established. In this review, we provide an overview of the genetic diagnostic workup needed to select patients that could be eligible for voretigene neparvovec treatment. Careful clinical characterization of patients by multidisciplinary teams of experts, combined with the availability of next-generation sequencing approaches, can accelerate patients’ access to available therapeutic options.     

Polystyrene Suspension Polymerization: The Effect of Polymerization Parameters on Particle Size and Distribution

Effects of polymerization parameters are studied to better understand interactions between parameters in stirred-tank polymerization reactors and to derive a regression model correlating polymer particle size and particle-size distribution with agitator speed, agitator diameter, tricalcium phosphate, dodecyl benzene sodium sulfonate concentrations, and mass cycle period. The derived equations give way to prediction of the polymerization conditions in order to obtain desired particle size and particle-size distributions which covers particle sizes between 0.3 and 5 mm. The roles of some other parameters and limiting agitation parameters are also investigated.