Change In Aspect Ratio Research Articles

Study of effect of multiple recycling on the mechanical properties of Sisal Fiber and Fly ash Reinforced hybrid Composites

Introduction: Recycling and reuse of the polymer composites have been gaining popularity these days due to their environmental and disposable concerns. However, the recyclability of natural fiber and fly ash reinforced polymer composite is still not explored much which has restrained the industries not to use them at full potential. Recycling of polymers, polymeric composites, and their wastes are trending nowadays. Researchers have used both recycled reinforcements such as paper, fiber, etc., with matrix and fresh reinforcement with recycled matrix too. In this regard, limited reports have been found on the recycling of the natural fiber reinforced polymer composites. In spite of this, when it comes to the recycling of degradable materials, it is still in the nascent phase. Recycling of the biodegradable materials may lose some of their original properties after every cycle (1). These lost tensile and flexural properties may be exhibited due to the fiber breakage, fiber degradation, change in fiber aspect ratio, and polymer chain shortening. Reinforcement of the recycled composites with fresh fibers to restore their lost tensile and flexural properties could open a new window for the researchers. Current work focuses on the recycling and subsequent reinforcement of the recycled composites to enhance the tensile and flexural properties of the same. Methods: Hybrid composites with 15-30 wt.% sisal fibers and 5-15 wt.% fly ash were formulated with impact modified polypropylene. The impact on mechanical properties due to the recycling and reinforcement was investigated. All the tensile, flexural, and impact testing samples have been fabricated by using Hakke rheomix and Hakke Minijet II micro injection molding machine (2). Results & Discussion: Composite with 15 wt.% sisal fibers showed a minimal ~2 % and ~2 % loss in tensile and flexural strength while the one with 30 wt.% fiber showed a maximum ~10 % and ~4 % loss respectively. In order to restore the lost mechanical properties, recycled composite have been reinforced with 5 wt.% natural fiber. The establishment of a good interfacial adhesion between reinforcing filler and fiber has been confirmed from FTIR studies. Strong interfacial interaction among reinforced SSL fiber and the blended matrix leads to a strong polymer composite. Although there is a decrease in tensile and flexural properties of the hybrid composite due to the increased reinforcement of fly ash, these are the still close to the base matrix. Also, an improvement in notched impact strength of the composite has been observed (3). Recycled, polymer composite samples show that the hybrid composites with highest fly ash content show the least decrease in tensile and flexural properties due to the non-breakage of fly ash particles. However, an insignificant change was, observed in impact strength of the recycled and reinforced composites. Conclusions: Recycling and reinforcement with 5 wt.% of FA of hybrid PP composites consisting of sisal fiber and fly-ash were successfully completed and evaluated. Fly ash plays a vital role in restricting the damage to the mechanical properties due to the recycling. Furthermore, inclusion of 5 wt.% of SSL fiber to the recycled composites sample helped in reclaiming lost mechanical properties. Keywords: Composite Recycling, Hybrid composite, Natural fiber, Fly ash

VOID EVOLUTION BEHAVIOR AND CLOSURE CRITERION INSIDE LARGE SHAFT FORGINGS DURING A FORGING PROCESS

In this study, the effects of different void positions, void shapes and sizes on the evolution of voids were discussed in detail using experiments and simulations. The results show that the influence of the void size on the void closure can be ignored, while the void position and void shape have a great influence on the closure of a void. Considering the complexity of the void-shape change in a forging process, we proposed a quantitative expression of the void-shape coefficient, which is affected by the effective stress and effective strain. Meanwhile, the void-shape evaluation parameter, defined as a function of the stress deviator, effective strain and effective stress, was proposed to describe the changes in the void aspect ratio. Finally, WHF (wide die heavy blow) forging experiments were conducted using a 5MN hydraulic press to verify the numerical-simulation results. Based on the experimental and simulation results, a new mathematical model for void-closure determination was established during a forging process of large shaft forgings. The experimental results were consistent with the simulation results, showing that the void-closure model can accurately determine whether a void is closed or not.

VOID EVOLUTION BEHAVIOR AND CLOSURE CRITERION INSIDE LARGE SHAFT FORGINGS DURING A FORGING PROCESS

In this study, the effects of different void positions, void shapes and sizes on the evolution of voids were discussed in detail using experiments and simulations. The results show that the influence of the void size on the void closure can be ignored, while the void position and void shape have a great influence on the closure of a void. Considering the complexity of the void-shape change in a forging process, we proposed a quantitative expression of the void-shape coefficient, which is affected by the effective stress and effective strain. Meanwhile, the void-shape evaluation parameter, defined as a function of the stress deviator, effective strain and effective stress, was proposed to describe the changes in the void aspect ratio. Finally, WHF (wide die heavy blow) forging experiments were conducted using a 5MN hydraulic press to verify the numerical-simulation results. Based on the experimental and simulation results, a new mathematical model for void-closure determination was established during a forging process of large shaft forgings. The experimental results were consistent with the simulation results, showing that the void-closure model can accurately determine whether a void is closed or not.

Size-Dependent Vibration Problem of Two Vertically-Aligned Single-Walled Boron Nitride Nanotubes Conveying Fluid in Thermal Environment Via Nonlocal Strain Gradient Shell Model

The free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in thermal environments. It is supposed that the two adjacent boron nitride nanotubes are coupled with each other in the context of linear deformation by van der Waals interaction according to Lennard–Jones potential function. To achieve a more accurate modeling for low-scale structures, both hardening and softening effects of materials are considered in the nonlocal strain gradient approach. The motion equations and associated boundary conditions are derived by means of Hamilton’s variational principle, then solved utilizing differential quadrature method. Numerical studies are done to reveal the effect of different boundary conditions, size scale parameters, aspect ratio, inter-tube distance, and temperature change on the variations of dimensionless eigenfrequency and critical flow velocity.

Analysis of deformation behavior in various incremental tube forming processes

ABSTRACT Incremental Tube Forming (ITF) is a comparatively new forming process in which the ends of a tube are expanded into the desired shape using a hemispherical tool. ITF process finds its applications in various sectors like automotive, aerospace, and heavy industries for interconnection of the piping system, structural elements, etc. It is crucial to analyze the tube’s deformation behavior for its successful forming and good accuracy of the formed part. The current work investigates the tube’s deformation behavior during the grooving and tube end forming in single and multistage strategies. Both the experimental and simulations are performed to analyze the strain distribution, thickness variation, and formability of the AA6063 tube. The experimental and simulated strain distribution reveals that the bottom end of the tube where forming started is in the plane strain state and the free end of the tube is uni-axial tension. The thickness variation and reduction percentages for experimental and simulations are in agreement with each other. An error of less than 2% was found for thickness variation at all the considered wall angles. Finally, the microstructural analysis performed using electron back scattered diffraction (EBSD) technique has revealed the changes in grain size, local misorientations and grain aspect ratio formed at various wall angles.

Adaptive ensemble perception tracking

Recently, tracking models based on bounding box regression (such as region proposal networks), built on the Siamese network, have attracted much attention. Despite their promising performance, these trackers are less effective in perceiving the target information in the following two aspects. First, existing regression models cannot take a global view of a large-scale target since the effective receptive field of a neuron is too small to cover the target with a large scale. Second, the neurons with a fixed receptive field (RF) size in these models cannot adapt to the scale and aspect ratio changes of the target. In this paper, we propose an adaptive ensemble perception tracking framework to address these issues. Specifically, we first construct a per-pixel prediction model, which predicts the target state at each pixel of the correlated feature. On top of the per-pixel prediction model, we then develop a confidence-guided ensemble prediction mechanism. The ensemble mechanism adaptively fuses the predictions of multiple pixels with the guidance of confidence maps, which enlarges the perception range and enhances the adaptive perception ability at the object-level. In addition, we introduce a receptive field adaption model to enhance the adaptive perception ability at the neuron-level, which adjusts the RF by adaptively integrating the features with different RFs. Extensive experimental results on the VOT2018, VOT2016, UAV123, LaSOT, and TC128 datasets demonstrate that the proposed algorithm performs favorably against the state-of-the-art methods in terms of accuracy and speed.

The causal relationship between melt pool geometry and energy absorption measured in real time during laser-based manufacturing

During laser powder bed fusion additive manufacturing, laser power absorption is governed by a protean pool of molten metal that can present as a highly reflective surface, a deeply absorbing cavity, or some amalgamation thereof. These melt pool dynamics have been linked to defect creation, porosity, and surface finish quality. Although these are therefore critical for determining final part quality, their instantaneous influence on laser absorption have only been explored through simulation. To date, direct real-time observations have been elusive due to the locally extreme environment. In this work, we focus a laser on Ti-6Al-4V powder and bare plate while quantifying the time-dependent, absolute energy absorption by monitoring omnidirectional backscattered laser intensity. We also simultaneously record the projective melt pool geometries with high-speed synchrotron x-ray imaging. We find that laser absorption strongly reflects the stability of the vapor depression over a wide range of applied laser powers, oxygen content in the processing atmosphere, and with the presence of powder. During laser scanning of a powder bed surface, we find a significant absorption reduction after 400 µs due to a dramatic change in the vapor depression aspect ratio – an event known to create porosity. As several industrial scan strategies necessitate thousands of these events during a build, their identification and control is of significant practical importance. Lastly, a normalized enthalpy model is demonstrated to be effective in quantifying the relationship between the laser absorption and cavity depth, even under transient conditions. In addition to providing vital quantitative data for simulation calibration, the correlation of melt pool geometry with laser absorption during realistic processing conditions suggests the use of a total backscattered light detection system for real-time process control.

Sequential Superassembly of Nanofiber Arrays to Carbonaceous Ordered Mesoporous Nanowires and Their Heterostructure Membranes for Osmotic Energy Conversion.

The capture of sustainable energy from a salinity gradient, in particular, using renewable biomass-derived functional materials, has attracted significant attention. In order to convert osmotic energy to electricity, many membrane materials with nanofluidic channels have been developed. However, the high cost, complex preparation process, and low output power density still restrict the practical application of traditional membranes. Herein, we report the synthesis of highly flexible and mechanically robust nanofiber-arrays-based carbonaceous ordered mesoporous nanowires (CMWs) through a simple and straightforward soft-templating hydrothermal carbonization approach. This sequential superassembly strategy shows a high yield and great versatility in controlling the dimensions of CMWs with the aspect ratio changes from about 3 to 39. Furthermore, these CMWs can be used as novel building blocks to construct functional hybrid membranes on macroporous alumina. This nanofluidic membrane with asymmetric geometry and charge polarity exhibits low resistance and high-performance energy conversion. This work opens a solution-based route for the one-pot preparation of CMWs and functional heterostructure membranes for various applications.

Numerical study on duplex stainless-steel plate girder under simultaneous bending and shear

The use of stainless-steel results in significant life-cycling cost savings. It likewise has high-temperature properties, just as satisfactory weldability, and fracture toughness. This study investigates the behaviour ofstainless-steel plate girder under simultaneous bending and shear using commercial FE software Abaqus. For modelling stainless steel of grade Duplex EN 1.4462 (2205) was used, which possess twice the design strength of austenitic and ferritic stainless steels. Numerically validated models were used to conduct parametric study covering effect of flange slenderness and flange thickness to web thickness ratios. The results show a significant contribution of the flange on shear strength and bending moment capacity of stainless-steel plate girders. The contribution of the flange was also influenced by the presence of end rigid post and change in the panel aspect ratio.

‘Thrills Sweep Like Electric Currents through Multitudes’: Spectacle, Sociality, and Media Competition in Mid-Century America

This article analyses contemporaneous debates over the competing screen formats, venues, and technological platforms designed to deliver moving images to domestic and public audiences in mid-twentieth century America. The postwar crisis in the American theatrical box office witnessed changes in film gauges, aspect ratios, and theater sound as well as in the architectural design of motion picture theaters, and the article examines the failed innovation of theater television and the explosive growth of the drive-in theater in the 1950s as responses to rising competition from advertising-supported domestic television. Drawing upon the rich technical, trade, and popular press literature of the period, the author argues for the relevance of the postwar debates over moving image reception for contemporary controversies over the viability of theatrical exhibition in the era of streaming video and global pandemic.

Radar-Based Bayesian Estimation of Ice Crystal Growth Parameters within a Microphysical Model

Abstract The potential for polarimetric Doppler radar measurements to improve predictions of ice microphysical processes within an idealized model–observational framework is examined. In an effort to more rigorously constrain ice growth processes (e.g., vapor deposition) with observations of natural clouds, a novel framework is developed to compare simulated and observed radar measurements, coupling a bulk adaptive-habit model of vapor growth to a polarimetric radar forward model. Bayesian inference on key microphysical model parameters is then used, via a Markov chain Monte Carlo sampler, to estimate the probability distribution of the model parameters. The statistical formalism of this method allows for robust estimates of the optimal parameter values, along with (non-Gaussian) estimates of their uncertainty. To demonstrate this framework, observations from Department of Energy radars in the Arctic during a case of pristine ice precipitation are used to constrain vapor deposition parameters in the adaptive habit model. The resulting parameter probability distributions provide physically plausible changes in ice particle density and aspect ratio during growth. A lack of direct constraint on the number concentration produces a range of possible mean particle sizes, with the mean size inversely correlated to number concentration. Consistency is found between the estimated inherent growth ratio and independent laboratory measurements, increasing confidence in the parameter PDFs and demonstrating the effectiveness of the radar measurements in constraining the parameters. The combined Doppler and polarimetric observations produce the highest-confidence estimates of the parameter PDFs, with the Doppler measurements providing a stronger constraint for this case.

Two-Step Affine Transformation Prediction for Visual Object Tracking

The main drawback of correlation filter scheme is that it can only predict translation of the object, ignoring the other affine transformations such as rotation, aspect ratio change, and scale change. This paper tries to address this problem by a two-step affine transformation prediction method. The first step is to predict coarse target translation by the correlation filter model with adaptive model update rate generation. Compared with fixed update rate in existing correlation filter based trackers, the presented method generates the update rate by Long Short-Term Memory model with inputs of historical target templates. The second step maps well-designed features to affine transformation parameters. The designed features contain the information of affine transformation which makes the learning of non-linear mapping function possible. The training samples for on-line filter model update are transformed to the same pose, and they help the learnt filter to represent the object better than non-aligned samples. The proposed network is trained from end to end and achieves competitive performance when comparing with state-of-the-arts trackers on four benchmarks, OTB100, UAV123, VOT2018, and VOT2020.

Experimental analysis of aspect ratio in iliac vein stenosis

BackgroundVeins are thin-walled tubes. Their lumen is roughly circular with an aspect ratio close to 1:1 under physiologic pressures. When they collapse owing to decreased internal pressure or external compression, the aspect ratio changes. The vertical diameter is usually diminished more than the transverse, with a considerable decrease in the lumen area. The recent emergence of stent correction of many venous compression syndromes, particularly iliac vein stenosis, has brought attention to the importance of the aspect ratio, quite apart from an overall decrease in caliber. The iliac vein pressure is influenced not only by stenosis, but also intra-abdominal pressure, right atrial pressure, and collaterals. We investigated the impact of aspect ratio in an experimental model incorporating these factors. MethodsInflow was provided from a header tank at 25 mm Hg pressure into a Penrose tubing enclosed in a polyethylene cylinder pressurized (Starling pressure) to simulate intra-abdominal pressures of 5 and 10 mm Hg. The Penrose drained into an outflow tank with a pressure of 7 mm Hg, simulating right atrial pressure. Stenosis was simulated with a series of three-dimensional, printed plastic nozzles with caliber areas of 50, 100, and 200 mm2 and varying in aspect ratios of 1:1 to 1:4. The flow and pressure in this system was monitored with the use of overflow collaterals in some experiments. ResultsFree flow from the header tank through the Penrose (zero Starling pressure) with a 200 mm2 circle nozzle into the outflow tank with zero pressure resulted in flow pressure of approximately 1.5 mm Hg. Using nozzles of a smaller caliber or an increased aspect ratio resulted in an increase of flow pressures of up to approximately 3.7 mm Hg. Flow into an outflow tank of 7 mm Hg simulating right atrial pressure further increased flow pressures by approximately 7 mm Hg. The addition of Starling pressures of 5 and 10 mm Hg simulating abdominal pressure increased flow pressure even further to the 10 to 17 mm Hg range. When the Starling pressure was dominant, the additional contribution of nozzle caliber stenosis or aspect ratio reduction to the overall flow pressure ranged from 2 to 6 mm Hg. Collateral overflow varied inversely with collateral resistance. Some experiments yielded an anomalous flow/pressure phenomena known to occur in collapsible tube flows. ConclusionsA decrease in the caliber or the aspect ratio of iliac vein stenosis was among several other factors that generate peripheral venous hypertension in an experimental model. Increased intra-abdominal pressure is a major influence that amplifies the pressure effects of aspect ratio or caliber reduction.

Change of Microstructure and Hardness of Duo-Casted Al3003/Al4004 Clad Material during Extrusion Process

This study was carried out to observe and measure the microstructure, distance between dendrite arms, aspect ratio, and Knoop hardness change of extruded material formed by the hydro co-extrusion of Al3003/Al4004 clad material manufactured by the duo-casting method. The specimen of duo-casted Al3003/Al4004 clad materials was circle shaped; it was composed of Al3003 (outside) and Al4004 (inside) materials. The manufacturing conditions of the hydro co-extruded specimen were 423 K temperature and 6.5 ratio of extrusion. At the interface of the duo-casted Al3003/Al4004 clad material, a non-junction at the interface and non-metallic inclusions of Si- and Mn-based oxides were observed. Al3003 exhibits equiaxed crystals; Al4004 has a casted structure with dendrites before extrusion, showed slight deformation during extrusion, and then finally exhibited completely deformed structures after extrusion. In the cast material, the distance between dendrite arms increased, and the aspect ratio of dendrites tended to decrease from the surface to the center. However, in the case of the extruded material, neither Al3003 nor Al4004 changed significantly from the surface to the inside. As extrusion progressed, the Knoop hardness value at the interface of Al3003/Al4004 increased rapidly compared with those of Al3003 and Al4004 matrixes.

타원형 실린더의 종횡비의 변화가 Lid-driven 사각 밀폐계의 혼합 대류에 미치는 영향

타원형 실린더의 종횡비의 변화가 Lid-driven 사각 밀폐계의 혼합 대류에 미치는 영향

Helically Grooved Gold Nanoarrows: Controlled Fabrication, Superhelix, and Transcribed Chiroptical Switching

Plasmonic chiroptical materials, coupled by chirality and surface plasmons, have been attracting great interest due to their potential applications, such as photonics, chiral recognition, asymmetri...

Exploration of nontrivial topological domain structures in the equilibrium state of magnetic nanodisks

Topological magnetic domains exhibit many fascinating features and great potential in information storage and spintronics owing to their unique spin textures. In order to investigate the topological properties of the domain structures, the spontaneous evolutions of magnetic moments are evaluated by using Landau–Lifshitz–Gilbert equation. The equilibrium phase diagrams of the system with randomly, radial and axial distributed initial magnetic moments have been studied in detail. Simulation results show that the changes of quality factor (Q) and aspect ratio (T/D) lead to great differences in magnetization process under different initial magnetization states. Vortex, biskyrmion, skyrmion and bubble are formed as the value of Q gradually increases from 0 to 1. The system with Q 1.0 are arranged along the easy axis. When Q and T/D are in the range of 0.6 ~ 0.8 and 0.10 ~ 0.16, respectively, it is conducive to the formation of nontrivial topological domain. Biskyrmion is spontaneously formed in the system of Q = 0.6 and T/D = 0.12, proving that skyrmion-like domain can be generated in the absence of Dzyaloshinskii–Moriya interaction or external field.

Aeroelastic analysis of an idealized landing gear door in subsonic potential flow

Landing gear doors on aircraft have experienced flutter during preliminary flight testing. While designs vary widely, landing gear doors are typically plate-like structures with a relatively rigid actuator attached to their inside surface. To better understand the aeroelasticity of landing gear doors, this study investigates the aeroelastic stability of an idealized model. The model consists of a hinged plate with an interior constraint approximating the actuator attachment. The plate is subject to uniform flow, and an unsteady vortex lattice model is coupled to the structural model to predict critical flow velocities. The location and footprint area of the internal constraint, along with plate aspect and mass ratios, are varied to investigate a large parameter space. Results reveal that the critical flow speed and instability mechanism are sensitive to the postulated actuator placement. In general, flutter is the dominant mode of instability when the actuator is postulated in the leading quarter of the plate. In other postulated locations, divergence dominates. However, the exact shape and location of the boundary between flutter and divergence is configuration dependent and found to be especially sensitive to changes in aspect ratio.

Single Crystalline Higher Manganese Silicide Nanowire Arrays with Outstanding Physical Properties through Double Tube Chemical Vapor Deposition.

In this work, we report a novel and efficient silicidation method to synthesize higher manganese silicide (HMS) nanowires with interesting characterization and physical properties. High density silicon nanowire arrays fabricated by chemical etching reacted with MnCl2 precursor through a unique double tube chemical vapor deposition (CVD) system, where we could enhance the vapor pressure of the precursor and provide stable Mn vapor with a sealing effect. It is crucial that the method enables the efficient formation of high quality higher manganese silicide nanowires without a change in morphology and aspect ratio during the process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the HMS nanowires. High-resolution TEM studies confirm that the HMS nanowires were single crystalline Mn27Si47 nanowires of Nowotny Chimney Ladder crystal structures. Magnetic property measurements show that the Mn27Si47 nanowire arrays were ferromagnetic at room temperature with a Curie temperature of over 300 K, highly depending on the relationship between the direction of the applied electric field and the axial direction of the standing nanowire arrays. Field emission measurements indicate that the 20 μm long nanowires possessed a field enhancement factor of 3307. The excellent physical properties of the HMS nanowires (NWs) make them attractive choices for applications in spintronic devices and field emitters.

A new method to determine elasto-plastic J-integral for steel pipes with longitudinal semi-elliptical surface cracks

Steel pipes have been widely used in the water and petroleum industries where crack-like flaws have long been recognised as a major cause of their failures. This paper intends to develop a new method for determining the elasto-plastic J-integral of cracked pipes made of all types of steel. A solution to elasto-plastic J-integrals is derived for external longitudinal semi-elliptical surface cracks in pressurised steel pipes. A meshing technique is developed in the detailed three-dimensional finite element analysis that incorporates the mixed types of quadratic tetrahedron and hexahedron elements. The developed method is verified with detailed finite element results. It is found in the paper that the general trend of normalised fully plastic J-integral changes with the change of crack depths and aspect ratios, and the magnitude of normalised fully plastic J-integrals can be significantly affected by material properties and pipe dimensions. The developed method can provide a useful tool for the failure assessment of pressurized steel pipes, allowing for a wide range of pipe dimensions, crack geometries and material properties.