Random Shape Research Articles

Physicochemical characterization and rheological behavior of hemicelluloses isolated from sorghum bran, sorghum bagasse and sorghum biomass

The molecular characterization and rheological properties of hemicellulose B (Hemi. B) fractions isolated from sorghum bran (SBR), sorghum bagasse (SBA) and sorghum biomass (SBI) were undertaken. The monosaccharide analysis results confirmed that these polysaccharides had a typical arabinoxylan structure. High performance size exclusion chromatography study indicated that Hemi. B from SBR and SBA had a higher weight average molar mass (Mw) (383–397 kDa), radius of gyration (Rgz) (34.7–34.9 nm), intrinsic viscosities (ηw) (1.25–1.29 dL/g) and lower polydispersity index (Mw/Mn) (2.76–2.79) than Hemi. B from SBI. The Mw, Rgz, ηw and Mw/Mn of the Hemi. B from SBI were 261 kDa, 31.6, 0.931 and 6.01 respectively. The Hemi. B from SBR and SBA had a similar random coil shape, while the Hemi. B from SBI was more like a compact sphere in shape. The Hemi. B isolated from SBR showed a typical shear thinning behavior at all concentrations. But the Hemi. B from other two sources (SBA and SBI) exhibited a shear shinning behavior at high concentration, showing Newtonian behavior at lower concentration. The critical concentration was also calculated to evaluate the molecular properties. The lower Mw of Hemi. B shows a highest value of critical concentration (c∗), which was in coordinate with the negative correlation between c∗ values and Mw of different arabinoxylan varieties.

MilliBack

Real-time handwriting tracking is important for many emerging applications such as Artificial Intelligence assisted education and healthcare. Existing movement tracking systems, including those based on vision, ultrasound or wireless technologies, fail to offer high tracking accuracy, no learning/training/calibration process, low tracking latency, low cost and easy to deploy at the same time. In this work, we design and evaluate a wireless backscattering based handwriting tracking system, called MilliBack, that satisfies all these requirements. At the heart of MilliBack are two Phase Differential Iterative (PDI) schemes that can infer the position of the backscatter tag (which is attached to a writing tool) from the change in the signal phase. By adopting carefully-designed differential techniques in an iterative manner, we can take the diversity of devices out of the equation. The resulting position calculation has a linear complexity with the number of samples, ensuring fast and accurate tracking. We have put together a MilliBack prototype and conducted comprehensive experiments. We show that our system can track various handwriting traces accurately, in some testings it achieve a median error of 4.9 mm. We can accurately track and reconstruct arbitrary writing/drawing trajectories such as equations, Chinese characters or just random shapes. We also show that MilliBack can support relatively high writing speed and smoothly adapt to the changes of working environment.

Investigation on polyaniline with manganese dioxide nanostructure by using an in situ oxidative polymerization method

Polyaniline with 1 and 10 wt% of MnO2 nanoparticles (PANI/MnO2) was prepared by using in situ oxidative polymerization. The prepared polymer nanocomposite samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), impedance analysis (IA), and thermogravimetry (TG). X-ray diffraction patterns confirmed the tetragonal structure having an average crystalline size around 70 nm for MnO2 nanoparticles. SEM and TEM images showed that the particles are agglomerated due to van der Waals force. The particles have random spherical shape. FTIR revealed the interaction of functional groups between PANI and MnO2 nanoparticles. The conductivity of the nanocomposites was found to be of the order of 10−4S cm−1. The dielectric curves showed the low-frequency β relaxation peak pronounced at high temperature, which may be caused by side group dipoles. The thermal stability is improved compared with that of pure PANI. Suitable proportions of MnO2 in the PANI matrix can be applied for electrode materials for various applications.

Modeling the shock-induced multiple reactions in a random bed of metallic granules in an energetic material

An investigation of shock–particle interactions in reactive flows is performed using an Eulerian hydrodynamic method with a hybrid particle level-set algorithm to handle the material interface dynamics. The analysis is focused on the meso- to macro-scale numerical modeling of a granular metalized explosive containing randomly distributed metal particles intended to enhance its blast effect. The reactive flow model is used for the cyclotrimethylene-trinitramine (RDX) component, while thermally induced deflagration kinetics describes the aerobic reaction of the metal particles. The complex interfacial algorithm, which uses aligned level sets to track deforming surface between multi materials and to generate the random shape of granule elements, is described for aluminized and copperized RDX. Then, the shock-induced collapse of metal particles embedded in the condensed phase domain of a high explosive is simulated. Both aluminized and copperized RDX are shown to detonate with a shock wave followed by the burning of the metal particles. The energy release and the afterburning behavior behind the detonating shock wave successfully identified the precursor that gave rise to the development of deflagration of the metal particles.

Beam‐space direct localisation using passive arrays with random shape errors

Passive localisation with high accuracy is attractive in numerous fields. Beam-space direct position determination (BS-DPD) using antenna arrays is a promising positioning method which possesses both excellent performance and moderate complexity. Optimised beam-space design is a vital ingredient for practical BS-DPD systems. In this work, BS-DPD schemes using receiving arrays with random shape errors have been investigated. Performance limits are derived by using Fisher information analysis. Besides, robust formulation based on the compressed Taylor approximation is proposed to counter the randomness existing in antenna positions. Simulation results are provided to reveal the information loss induced by the non-idealities in receiving arrays and also to validate the robustness of the proposed BS-DPD algorithm.

Morphology of the palate, palatal rugae pattern, and dental arch form in patients with schizophrenia.

This study aimed to investigate the morphology of the palate, palatal rugae pattern, and dental arch form in patients with schizophrenia. An observational case-control study was designed following the STROBE statement and checklist. The sample consisted of 132 patients (39 diagnosed with schizophrenia and 93 controls). Dental casts of the patients were classified based on the pattern of their palatal rugae, their dental arch form, and the area of their palate. The palatal rugae in patients with schizophrenia had a more random distribution and shape compared to the control group (P=.027). Oval dental arches were the most prevalent in both groups (P=.473). The palate area was slightly larger in the control group (3.2318 ± 0.549 mm2 ) compared with the group of patients with schizophrenia (3.060 ± 0.470 mm2 ) (P=.090). Palatal rugae pattern may feature as a potential minor physical anomaly for schizophrenia. Additional studies with alternative sampling and classification systems are necessary to understand this finding and its applications in practice.

Sedimentation of gas-fluidized particles with random shape and size

Observations of the settling velocity of suspensions of irregular particles are found to depend on (i) the difference of density between the particles and the suspension and (ii) a viscosity which depends on the ratio of the concentration to the loose packing concentration.

Sorption of carbon dioxide by chickpeas packaged in modified atmospheres

Modified atmospheres (MAs) with high CO2 concentrations are used for packaging several commodities with different purposes, including as an alternative method for pest control. When used in gas-tight flexible packages, sorption by the commodity produces a vacuum effect that causes the package to adopt a random shape and makes it impossible to reshape it without opening the package. Other than storage problems in retail storehouses, sorption can affect the amount of gas inside the packages needed for pest control. This study reports the amount of CO2 sorption by chickpeas packaged with different MAs and the negative pressure produced due to the decrease in the partial pressure of the gas. Trials were conducted in 710 mL semi-rigid plastic containers filled up to 24%, 48% and 96% of their capacity (filling ratios). Three MAs (90%, 70% and 50% CO2 with a residual of 3%, 6% and 10% O2, respectively, and balanced by N2) were used during 24 h, 48 h, 240 h and 384 h of exposure at 20 °C. The maximum sorption (1.28 g CO2/kg of chickpea) was obtained with the lower filling ratio (24%) and with an initial concentration of 90%. Sorption decreased with the decline in the initial CO2 concentration and with the rise in the filling ratio. The time needed to reach the equilibrium sorption varied between 141 h and 27 h, depending on the initial CO2 concentration and the filling ratio of chickpeas. The vacuum effect produced inside the containers by sorption produced a negative pressure that increased with the increase in the filling ratio and the initial CO2 concentration. Whether the amount of CO2 available in packages after gas sorption is still effective for controlling chickpea pests remains to be tested.

Strip-loaded nano-photonics on horizontal slot waveguide

BackgroundA strip-loaded slot waveguide is a waveguide platform allowing a large amount of degrees of freedom in terms of fabrication. Contrary to other waveguide types where the guiding layer has to be patterned, only the shape of the top layer, usually a polymer, dictates the response of this platform.MethodsWe use the Finite Difference Time Domain method to study the field distribution and the modal behavior of light inside such a waveguide when the loading strip is patterned.ResultsWe present an overview of several photonic-crystal-based structures on a strip-loaded slot waveguide platform. This theoretical study shows how the fundamental mode confined in the horizontal slab slot waveguide interacts with the dielectric loading structures. By investigating the field confinement, one determines the importance of the longitudinal shape over the lateral shape of the loading structure. Through the examples of sidewall corrugation, row of cylindrical or elliptical holes, and random shapes, we show how such a platform can help integration of complex functions in waveguides.ConclusionsAlthough the spectral features depend strongly on the period and fill factor of the Bragg gratings studied in our case, the material distribution plays a key-role in the mode behavior. This impacts directly on the applications of such a platform for further modulators and sensors, for instance.

Inducing surface nanoporosity on Fe-based metallic glass matrix composites by selective dealloying

Nanoporosity (i.e. nanohole formation) is induced at the surface of Fe-based metallic glass matrix composites by selective chemical or electrochemical (at 1 V) etching of a Fe65Cu10Zr10B15 composite material using a 0.065 M HNO3 aqueous electrolyte. While electrochemical treatments are found to remove the Cu-rich precipitates present at the surface of this alloy, chemical etching (in absence of applied potential) only causes partial dissolution of the Fe-rich amorphous matrix. In both cases, the resulting pores exhibit random shapes and their lateral size ranges from a few tens to hundreds of nm. The investigated material is ferromagnetic at room temperature, both before and after dealloying and it does not crystallize during the (electro)chemical etching process. The contact angle in deionized water decreases in the dealloyed states in comparison with the as-spun ribbon. This procedure is appealing for applications that could benefit from the combination of increased surface area and the amorphous character (lack of crystallinity) at the surface of dealloyed metallic glass composite materials.

Thermal conductivity in disordered porous nanomembranes

In this work we study the effects of disorder on the thermal conductivity of porous 100 nm thick silicon membranes, in which the size, shape and position of the pores were varied randomly. Measurements using two-laser Raman thermometry on both non-patterned and porous membranes revealed more than a 10-fold reduction of the thermal conductivity compared to that of bulk silicon and a six-fold reduction compared to non-patterned membranes for the sample with random pore shapes. Using Monte Carlo methods we solved the Boltzmann transport equation for phonons and compared different possibilities of pore organization and its influence on the thermal conductivity of the samples. The simulations confirmed that the strongest reduction of thermal conductivity is achieved for a distribution of pores with arbitrary shapes that partially overlap. Up to a 15% reduction of the thermal conductivity with respect to the purely circular pores was predicted for a porous membrane with 37% filling fraction. The effect of the pore shape and distribution was further studied. Maps of temperature and heat flux distributions clearly showed that for particular pore placement heat transport can be efficiently blocked and hot spots can be found in narrow channels between pores. These findings have an impact on the fabrication of membrane-based thermoelectric devices, where low thermal conductivity is required. This work shows that for porous membranes with a given filling fraction the thermal conductivity can be further modified by introducing disorder in the shape and placement of the pores.

Connectivity and Blockage Effects in Millimeter-Wave Air-To-Everything Networks

Millimeter-wave (mmWave) offers high data rate and bandwidth for air-to-everything (A2X) communications including air-to-air, air-to-ground, and air-to-tower. MmWave communication in the A2X network is sensitive to buildings blockage effects. In this paper, we propose an analytical framework to define and characterise the connectivity for an aerial access point (AAP) by jointly using stochastic geometry and random shape theory. The buildings are modelled as a Boolean line-segment process with fixed height. The blocking area for an arbitrary building is derived and minimized by optimizing the altitude of AAP. A lower bound on the connectivity probability is derived as a function of the altitude of AAP and different parameters of users and buildings including their densities, sizes, and heights. Our study yields guidelines on practical mmWave A2X networks deployment.

Re-recognizing the impact of particle shape on physical and mechanical properties of sandy soils: A numerical study

The particle shape created by geological processes is an essential characteristic that determines the physical and mechanical properties of sandy soils. However, the nature of the arbitrary shape and the individual volume of particles in natural sand have been given scant regard. In this study, we constructed a particle flow code (PFC) model using a number of clumps with random irregular shapes (called “Irreg-Sam”), and simulated direct shear tests on silica sand. Further, particle shapes were investigated via a series of numerical tests on Irreg-Sams and comparative models with rounded particles (called “Reg-Sam”). The results indicate that Irreg-Sam can form a lower minimum void ratio and interval of extreme void ratios than Reg-Sam. Conversely, Reg-Sam has a greater peak shear strength than Irreg-Sam when the normal stress is less than 200 kPa. However, there was no noticeable difference in the critical shear strengths of these two samples. Because of the higher dilatancy angle under relatively low stress levels, sand with irregularly shaped particles will exhibit a greater peak shear strength than sand with rounded particles. The nature of the arbitrary shape and the individual volume of particles in sandy soils were found to be two important factors that cannot be ignored when studying the effect of particle shape. This research will facilitate better understanding of the role of particle shapes in sandy soils.

Neutronics modeling of bubbles in bubbly flow regime in boiling water reactors

Abstract This study mainly focused on the neutronics modeling of bubbles in bubbly flow in boiling water reactors. The bubble, ring and homogenous models were used for radial void fraction distribution. Effect of the bubble and ring models on the infinite multiplication factor and two-group flux distribution was investigated by comparing with the homogenous model. Square pitch unit cell geometry was used in the calculations. In the bubble model, spherical and non-spherical bubbles at random positions, sizes and shapes were produced by Monte Carlo method. The results show that there are significant differences among the proposed models from the viewpoint of physical interaction mechanism. For the fully-developed bubbly flow, k inf is overestimated in the ring model by about 720 ± 6 pcm with respect to homogeneous model whereas underestimated in the bubble model by about −65 ± 9 pcm with a standard deviation of 15 pcm. In addition, the ring model shows that the coolant must be separated into regions to properly represent the radial void distribution. Deviations in flux distributions principally occur in certain regions, such as corners. As a result, the bubble model in modeling the void fraction can be used in nuclear engineering calculations.

Generalized Model of Section Two-Roll Rolling - Geometry of the Zone of Deformation

A universal geometric model of the deformation zone during rolling of a "random shape" workpiece in a two-roll groove of a "random shape" is considered in this paper. The level of simplicity of the model should provide, on the one hand, a sufficiently detailed and accurate description of the deformation zone geometry and, on the other hand, ensure the possibility of implementing "fast" algorithms for calculating the necessary characteristics of the rolling process.

Ground state magnetic properties in AA-stacking bilayer graphene quantum dots using Lieb’s theorem

Abstract We have studied magnetic properties of ground state in perfect AA-stacking bilayer graphene quantum dots. Our main model is the single-orbital tight-binding Hamiltonian that is supplemented with a mean field Hubbard term. In addition, density functional method has been exploited to gain more confidence in our findings. The calculations are performed for some random and triangular shape of AA-stacking bilayer quantum dots and always yield an antiferromagnetic ordering with a total spin S = 0 ground state. Despite computational results of Hubbard model is admirably compatible with Lieb’s theorem, conventional crystallographic sublattices are not appropriate to interpret our computational results in terms of the theorem. Therefore, we have suggested a new sublattice decomposition to settle our numerical output to the consequences of Lieb’s theorem. Especially we demonstrate some characteristic including polarization of local magnetization, degeneracies in the energy spectrum, the ferromagnetic and antiferromagnetic coupling of vacancies in our system have decisive compatibility with new proposed sublattice decomposition.

Crack image detection based on fractional differential and fractal dimension

In civil engineering, crack detection using image processing has gained much attention among researchers and transportation agencies. As the crack image often presents a fuzzy boundary and random shape, it is difficult to achieve satisfactory detection performance. This study proposes a crack detection method based on the fractional differential and fractal dimension. This method achieves image enhancement and crack extraction in two stages. First, an image enhancement algorithm based on the fractional differential is applied to solve the fuzzy crack boundary. This algorithm can enhance the crack boundary information significantly while simultaneously maintaining texture details. Second, an improved extraction algorithm based on the fractal dimension is studied. This algorithm can effectively accomplish crack extraction according to shape features. Last, upon comparisons with classic and state‐of‐the‐art methods, the experiment shows that the proposed method can achieve satisfactory results for crack image detection.

Wideband High-Absorption Electromagnetic Absorber With Chaos Patterned Surface

A resistive metasurface featured by the Rossler chaos reaction-diffusion system patterns is proposed and realized in a wideband electromagnetic absorber. The chaos surface consists of units with both random shapes and dimensions. Simulation results show absorption phenomenon, and correlation function analysis indicates new wave-absorbing mode can be generated when correlation of the edges of the chaos patterns matches geometrical size of chaos units. Experimental results indicate unconventional bandwidth ratio with reflectivity lower than –10, –15, and –19 dB reaches 96.84%, 80.1%, and 56.1%, respectively. A high-absorption nature makes this structure have application potential in a modern anechoic chamber or other electromagnetic wave absorbers.

PhaseNet: A Deep Convolutional Neural Network for Two-Dimensional Phase Unwrapping

Phase unwrapping is a crucial signal processing problem in several applications that aims to restore original phase from the wrapped phase. In this letter, we propose a novel framework for unwrapping the phase using deep fully convolutional neural network termed as PhaseNet. We reformulate the problem definition of directly obtaining continuous original phase as obtaining the wrap-count (integer jump of 2 $\pi$ ) at each pixel by semantic segmentation and this is accomplished through a suitable deep learning framework. The proposed architecture consists of an encoder network, a corresponding decoder network followed by a pixel-wise classification layer. The relationship between the absolute phase and the wrap-count is leveraged in generating abundant simulated data of several random shapes. This deliberates the network on learning continuity in wrapped phase maps rather than specific patterns in the training data. We compare the proposed framework with the widely adapted quality-guided phase unwrapping algorithm and also with the well-known MATLAB's unwrap function for varying noise levels. The proposed framework is found to be robust to noise and computationally fast. The results obtained highlight that deep convolutional neural network can indeed be effectively applied for phase unwrapping, and the proposed framework will hopefully pave the way for the development of a new set of deep learning based phase unwrapping methods.

Coherent optical coupling of plasmonic dipoles in metallic nanoislands with random sizes and shapes

Coherent coupling of plasmonic dipoles of metallic nanoislands with random sizes and generation of surface lattice resonances via photonic lattices.