Shear yielding modes of polycarbonate

The modes of shear yielding in edge-notched sheets of polycarbonate have been studied under slow tensile loading. Optical microscope techniques were used to characterize the flow lines through the thickness of the plastically deformed region. Three modes are observed, namely core yielding, hinge shear and intersecting shear. Core yielding consists of two families of shear flow lines contained in the centre region where the stress is highest. In the nearly plane strain condition, the dominating shear mode is hinge shear which is through-thickness yielding on inclined planes above and below the notch. Intersecting shear dominates in the nearly plane stress condition. In this case, yielding occurs through the entire thickness by slip along planes parallel to the width direction that make an angle with the plane of the sheet. It produces a necking effect in front of the notch. The thickness dependent transition from hinge shear to intersecting shear follows conditions suggested by Hahn and Rosenfield.     

The effect of melt-flow properties of PVC plastisols during fusion cycle on flooring wear layer surface quality

A rheological test to characterize the melt in various vinyl coating resins in a flooring wear layer formulation shows that the surface quality (absence of orange-peel) of the resilient foamed flooring is associated with the viscoelastic nature of the wear layer resin during the cure cycle: Resins with high molecular weight of a sufficiently high melt viscosity showed no entrapment of air bubbles or tendency to orange-peel, while resins with low melt viscosity produced very severe orange-peel. Orange-peel is independent of the type of foam resin used. For a given formulation, the proper selection of wear layer resin or resin mixtures that will develop the desired hot melt strength to contain the gases given off by the decomposition of the blowing agent, will help to alleviate or minimize orange-peel.     

Tuberculous abscess in retromammary region: CT findings

PURPOSE: Our goal was to evaluate CT findings of tuberculous abscess in the retromammary region of the breast. METHOD: Four patients with tuberculosis extending from the retromammary region to the pleura were examined by CT and the findings were evaluated. All cases were also examined with mammography and two cases were evaluated with sonography. Diagnosis was confirmed by acid-fast bacillus stain, culture, and histologic examination. RESULTS: Mammography showed relatively smoothly marginated, round mass density in two cases, nodular density in one, and focal bulging of the pectoral wall in one. A sonogram demonstrated in two cases a fistulous connection from the heterogeneous, fluid-containing lesion with floating internal debris in the retromammary region to the thoracic cavity. In all four cases, CT showed relatively smoothly marginated, inhomogeneous, hypodense lesions with surrounding rims of the cold abscess type. A direct fistulous connection from the retromammary lesion through the thoracic wall into the pleura was seen in two cases. Destroyed rib fragments within the abscess were noted in two cases. CONCLUSION: A tuberculous abscess in the retromammary region usually showed on CT a focal, smoothly marginated, inhomogeneous, hypodense lesion with a surrounding enhancing rim. A direct fistulous connection with the pleura or a destroyed rib fragment in the abscess as revealed by CT can be helpful in the differential diagnosis of other infectious types of retromammary abscess.     

Observation of a fast-formed absorption grating and a slowly formed phase grating in undeveloped dichromated gelatin

Real-time diffraction efficiency is measured during hologram formation in undeveloped dichromated gelatin (DCG) film. The main features of real-time diffraction efficiency of undeveloped DCG reveal double peaks with increasing exposure time. Adopting the grating translation technique, we show that the first peak originates from the absorption grating and that the latter is related to the phase grating. To explain such complicated hologram-formation dynamics, we present a phenomenological model for mixed gratings associated with photoinduced refractive-index changes and absorption changes. We have compared the model results with the experimental results, which show good agreement.     

Controlling Threshold and Resistive Switch Functionalities in Ag-Incorporated Organometallic Halide Perovskites for Memristive Crossbar Array

Halide perovskites (HPs) can be the effective functional materials for the sneak-path current issue in the memristive crossbar array. Herein, an efficient strategy is proposed to integrate the HPs-based bidirectional threshold and bipolar resistive switches (TS and RS). The resistance change characteristics from volatile threshold to nonvolatile resistive switching are modulated by controlling Ag doping concentration in the MAPbI₃. HPs provide the diffusive condition and the quantity of Ag regulates the radius of its network. A low amount of Ag contributes to weak network with a short lifetime. However, when the amount of Ag increases, the conductive filament becomes more robust, showing a long lifetime. A MAPbI₃:Ag TS with a low Ag content is developed, showing a steep switching slope (1 mV per decade), fast switching speed (< 80 ns), and low off-current (10 nA). And, a MAPbI₃:Ag RS with a high Ag content is developed, showing multilevel storage capability and long retention time (1400 s). Finally, these TS and RS coupled into the 1S-1R integrated component, resulting the development of the maximum crossbar array size to 1.4 × 10¹². This study offers an efficient methodology for tailoring the resistance change characteristics and a promising strategy for practical HPs-based memristive crossbar application.