Rectangular Cell Research Articles

Numerical Investigation on Using MWCNT/Water Nanofluids in Photovoltaic Thermal System (PVT)

Photovoltaic thermal systems (PVT) are solar energy conversion systems that produce both electricity and heat simultaneously. PVT systems seeking to minimize temperature of solar cells become more significant with the increased thermal and electrical efficiency of the working fluids (water and nanofluids) employed in the solar thermal system. The major objective of this research is to investigate the thermal, electrical and overall performance of the photovoltaic thermal (PVT) system with different weight fractions of MWCNT/water nanofluids (φ = 0.3%, 0.6% and 1%) and water. A sheet and tube PVT system model geometry, which has been simplified to rectangular PV cell, absorber plate, cylindrical pipe, and fluid domain geometries to investigate outlet and PV cell temperature of photovoltaic thermal (PVT) system between different weight fractions of MWCNT/water nanofluids (φ = 0.3%, 0.6% and 1%) and water with varying fluid inlet velocities from 0.02 m/s to 0.08 m/s using ANSYS FLUENT. The results show that increasing the inlet fluid velocity and weight fraction of the working fluid improves thermal and electrical efficiency. The highest improvement in thermal and electrical efficiency at 0.08m/s inlet fluid velocity for the weight fractions, φ = 1% of MWCNT/water nanofluids is 7.8% and 0.03% compared to water. In addition, the weight fractions, φ = 0.3% of MWCNT/water nanofluids is 4.46% and 0.01% and the weight fractions, φ = 0.6% of MWCNT/water nanofluid is 6.72% and 0.02%. Additionally, the maximum increase of overall efficiency at 0.08m/s inlet fluid velocity for the weight fractions, φ = 1% of MWCNT/water nanofluids is 7.83% compared to water while the weight fractions, φ = 0.3% of MWCNT/water nanofluids is 4.43% and the weight fractions, φ = 0.6% of MWCNT/water nanofluid is 6.74% at inlet fluid velocity of 0.08 m/s. As a result of the research, it was discovered that using MWCNT/water nanofluids improves the performance of PVT systems.

Mathematical modeling of inhomogeneous electric field impact on a liquid crystal layer

AbstractThe authors analyze the Fréedericksz transition phenomenon of reorientation of molecules in the plane liquid crystal layer in inhomogeneous electric field generated by parallel plate capacitor using the Oseen–Frank mathematical model. The capacitor is a set of short metal plates periodically located on both sides of the extended liquid crystal layer, connected in series in two circuits. When electric charges of different signs appear on opposite plates of the capacitor, the electric field in the periodicity cell turns out to be significantly inhomogeneous both in length and in thickness of the layer. Governing equations of the model represent Euler's variational equations in the problem on minimization of the potential energy of liquid crystal. Numerical solution of the equations uses the authorial variational difference scheme. The Laplace equation for electric potential in the exterior of the liquid crystal layer is solved using the method of lines. The electric field and the patterns of orientation angles of molecules inside the layer are determined by iterating with numerical solution of Poisson's equation using the fast Fourier transform at each iteration step. The algorithm is implemented by means of CUDA technology for computing systems with graphics accelerators. The scale of the mesh to ensure the computation accuracy is selected from calculation of Tsvetkov's order parameter in a rectangular cell pattern. Verification of the algorithm and program is implemented by way of comparing the computational results and the exact solution of the problem on the homogenous electric field with the constant initial orientation angle of liquid crystal molecules. The computations accomplished yield the patterns of the electric potentials and orientation angles of molecules depending on the position of the capacitor plates at uniform and s‐shaped initial distribution of the orientation angles through the thickness of the liquid crystal layer.

Structure, development, and the salt response of salt bladders in Chenopodium album L.

Salt bladders are specialized epidermal structures that halophytes use to store and excrete excess salt. However, the cell wall composition during salt bladder development is unclear, and the functions of salt bladders in a few wild plants remain unexplored. Therefore, the present study examined salt bladder development, cell wall composition, and their roles under salt stress by employing bladder-brushed and unbrushed Chenopodium album plants. We found that the bladder cell of C. album was connected to the epidermal cells through a rectangular stalk cell and developed from the shoot tip and the young leaves. The polysaccharides of salt bladder cell wall showed dynamic distribution at different stages of development. Moreover, salt bladders affected Na+ and K+ accumulation, increased reactive oxygen species scavenging, and improved the osmoregulation and photosynthetic efficiency in leaves, subsequently enhancing the salt tolerance of plants. The findings strengthen our knowledge of the physiological mechanisms of the accessory structures in desert plants, which can be used as a reference for further research at the molecular level.

The theoretical study of the efficiency of diffusion deposition of nanoaerosols in the extended range of the Peclet numbers

The efficiencies of the diffusion deposition of nanoaerosols for a single fiber for the models of aerosol filter and wire mesh screen are studied numerically in the extended range of the Peclet number Pe. The rectangular periodic cell model for fluid flow and convective-diffusive transport of small aerosol particles is used. Most of the previous theoretical and experimental studies of single fiber diffusion deposition efficiency were for the case of Pe > 1. The array with uniform square or chess grid of fibers and of a row of circular cylindrical fibers are considered as the filter and wire mesh screen models. The flow and particles transport equations are solved numerically using the Boundary Element Method.The obtained numerical data are used to derive the approximate formulas for the deposition efficiency in the entire range of the Peclet number for the various porosities of the filter medium or distances between fibers in a wire mesh screen. The derived dependencies take into account nonlinearity of the deposition efficiency at the low Peclet numbers. The obtained analytical dependencies compare well with the numerical and experimental data.

Sandwich structure with negative Poisson’s ratio of periodic rectangular tube: Mechanical properties and energy absorption

Due to its unique deformation form, Negative Poisson’s ratio sandwich structure has excellent energy absorption, but the low load capacity limits its engineering applications. In this paper, we design a new negative Poisson’s ratio rectangular tube periodic sandwich structure. There are many beams in this structure which appear plastic hinges when compressed. After further compression, the rectangular tube wall buckles and the core shrinks inward, which realizes that the structure exhibits high-performance energy absorption ability and excellent mechanical properties. Three-dimensional finite element model of sandwich structure with negative Poisson’s ratio of periodic rectangular tube quasi-static compression test and low-velocity impact were investigated by the use of ABAQUS/Explicit software. The accuracy of the simulation method was verified by the comparison of test and simulation results. Based on the validated numerical models were further investigated to comprehensively understand the influence of rectangular tube unit cell wall thickness ( t) and cell height ( h) on the load capacity and energy absorption capacity of the specimen. The energy absorption capacity and mechanical properties of the proposed negative Poisson’s ratio sandwich structure could be enhanced by optimizing the design of rectangular tube unit cell wall thickness ( t) and rectangular tube unit cell height ( h). The present findings offer insights into the application of negative Poisson’s ratio sandwich structure impact energy-absorbing structures in aerospace, automotive and other fields.

Equivalent circuit analysis of a mode-converting metacell in a coaxial transmission line at microwave frequencies

To provide for an ever-increasing need for camouflage, experts in stealth have been envisioning for a few years to use metasurfaces and their unconventional electromagnetic properties to serve as efficient cloaking devices. To prepare for the use of surface-mounted electronic components, useful for frequency-selecting purposes, we take interest in an equivalent circuit analysis of metasurfaces. Indeed, metasurfaces using electronic components invite one to combine the passive behavior of the host structure with that of the lumped elements. The equivalent circuit analysis of the hosting surface deprived of electronic components has so far been dedicated to the case of metasurfaces constituted by rectangular or square unit cells. This work, therefore, aims at extending the former study on Cartesian unit cells to the coaxial geometry of interest. The validity of such a method is then assessed by comparison with the numerical simulation results obtained using a finite-element method.

Effects of cholesterol on the structure and collapse of DPPC monolayers

Cholesterol induces faster collapse by compressed films of pulmonary surfactant. Because collapse prevents films from reaching the high surface pressures achieved in the alveolus, most therapeutic surfactants remove or omit cholesterol. The studies here determined the structural changes by which cholesterol causes faster collapse by films of dipalmitoyl phosphatidylcholine, used as a simple model for the functional alveolar film. Measurements of isobaric collapse, with surface pressure held constant at 52 mN/m, showed that cholesterol had little effect until the mol fraction of cholesterol, Xchol, exceeded 0.20. Structural measurements of grazing incidence X-ray diffraction at ambient laboratory temperatures and a surface pressure of 44 mN/m, just below the onset of collapse, showed that the major structural change in an ordered phase occurred at lower Xchol. A centered rectangular unit cell with tilted chains converted to an untilted hexagonal structure over the range of Xchol = 0.0–0.1. For Xchol = 0.1–0.4, the ordered structure was nearly invariant; the hexagonal unit cell persisted, and the spacing of the chains was essentially unchanged. That invariance strongly suggests that above Xchol = 0.1, cholesterol partitions into a disordered phase, which coexists with the ordered domains. The phase rule requires that for a binary film with coexisting phases, the stoichiometries of the ordered and disordered regions must remain constant. Added cholesterol must increase the area of the disordered phase at the expense of the ordered regions. X-ray scattering from dipalmitoyl phosphatidylcholine/cholesterol fit with that prediction. The data also show a progressive decrease in the size of crystalline domains. Our results suggest that cholesterol promotes adsorption not by altering the unit cell of the ordered phase but by decreasing both its total area and the size of individual crystallites.

Phyto-pharmacognostical investigation w.s.r. Micrometric investigation of sheethavar seed (Celosia argentea linn.)

Celosia argentea Linn. is a leading leafy vegetable of Nigerian country and India. It is herb, ornamental plant which belongs to family Amaranthaceae also having medicinal use in antidiabetic, anti-inflammatory, antioxidant, anti-bacterial, antiapoptosis etc. For proper methodical evaluation, authentication, macroscopy, microscopy, physicochemical parameters, phytochemical screening and qualitative of seed of C. Argentea has been observed under standard approach. The morphological study showed small black shining spherical, lenticular 3mm in diameter, greyish black in color, slightly aromatic in odour and gritty in touch. Microscopical transverse section of cock’s comb seed showed outer layer of epidermis consisting radially elongated rectangular dark brown color cell, narrow collapsed celled band, outer epidermis of tegmen, followed by parenchyma zone with angular cells of perisperm loaded by starch grains and crystals. Cock’s comb inner cell consists of prismatic crystals and aleurone grains. The unplumbed physicochemical parameters and qualitative screening of seed of cock’s comb are as per standard procedure and useful for future analysis.

Foam in Absorption Columns with Structured Packings – Part 1: Characterization

AbstractFoam in absorption and distillation processes is one of the main reasons for malfunctions in columns including higher pressure loss, lower throughput, and lower mass transfer rates leading to a reduction in separation efficiency. Detailed investigations on the foam formation and its behavior in structured packings are conducted using two different scales: a transparent rectangular measurement cell and a DN300 column. The influence of maldistributions in structured packing is discussed along with a first‐time identified foam‐related hysteresis effect. Ad‐ and disadvantages of fully wetted film flow and partially wetted rivulet flow on foam formation are discussed in detail. Overall, structured packings without a microstructure show a reduced foam formation compared to structured packings with a microstructure.

Mathematical model of the extrusion process of grain crops during non-isothermal flow of crop melting to the temperature at the beginning of the Maillard reaction

To describe the non-isothermal flow of grain crops melt in the extruder, the equations of motion, the equation of continuity, the equation of energy (heat balance), and the rheological equation were chosen as initial equations. To solve the model, the following assumptions were made. The flow of a moving viscous medium is assumed to be laminar and steady. The forces of inertia and gravity are so small compared to the forces of friction and pressure that they can be neglected. A viscous medium (melt) is an incompressible liquid characterized by constant thermal conductivity and thermal diffusivity. The change in thermal conductivity in the longitudinal direction was neglected due to the fact that convective heat transfer in the direction of flow is higher than the heat transfer by thermal conductivity. Heat transfer in the direction perpendicular to flow of the melt occurs only due to thermal conductivity. To solve the system of equations taking into account convective heat transfer, a numerical finite difference method was used, according to which the considered area (extruder channel) is divided into computational cells using a grid. The grid consisted of rectangular cells with a constant step between nodes, which exactly lie on the boundaries of the integration region. In this case, the differential equations were transformed into difference equations by replacing the derivatives at a point with finite differences along the cell boundaries. As a result, a mathematical model of non-isothermal melt flow in the extruder channel was obtained. To solve a mathematical model of the grain crops extrusion process with a non-isothermal flow of their melts, a program in the programming language C++ was compiled. A non-isothermal mathematical model of the grain crops extrusion process at temperatures at the beginning of the Maillard reaction, i.e., up to 120-125 °C, was obtained, which makes it possible to reveal the nature of the temperature change along the length of the extruder. Comparative analysis of the results of the numerical solution and experimental data showed good convergence: the standard deviation did not exceed 12.7%.

Investigation of the Shielding and Attenuation Effects of a Dynamical High-Density Chaff Cloud on the Signal Based on Voxel Splitting

Chaff jamming is a widely used passive interference method. A chaff cloud diffusion model for the widespread chaff cloud was presented. The high-density chaff cloud aerodynamic model can rapidly predict the chaff elements’ time-varying spatial orientation, location, and overall spatial distribution. Basing on these pieces of information, the radar cross section (RCS) for the single chaff fibre can be obtained based on the method of moments (MoM). For high-density chaff clouds, the attenuation and shielding effects on the signal must be considered. This paper proposed a voxel splitting method in rotated coordinates, dividing the chaff cloud into rectangular cells with one side perpendicular to the direction of radar entry. The varied polarized RCS features of the chaff cloud were simulated and analysed on this foundation. By dividing the chaff cloud into dynamic voxels and considering the uneven density distribution of the chaff cloud and the signal attenuation in each segment caused by the continuous fluctuating shape, fine-grained simulations of the chaff cloud radar echoes can be performed.

M-VCUT level set method for the layout and shape optimization of stiffeners in plate

Stiffened plates are widely used in engineering due to their relatively high rigidly-to-weight ratio. The stiffener layout and shape can significantly affect the mechanical properties of the plate. In this paper, a novel approach is developed in the framework of the Multiple Variable Cutting (M-VCUT) level set method for optimizing the layout and shape of stiffeners based on the Mindlin plate theory. In this approach, the layout and shape of stiffener can be controlled by adjusting the lower and upper limits of the design variables (cutting heights of the cutting surfaces at the cell nodes) conveniently. The coordinate mapping technique from the rectangular cell to the quadrilateral cell enables the shape of design domain to be arbitrary. In addition, multi-node cell with high-order polynomial interpolation technique is also applied for generating more complex geometry of stiffener. The numerical examples meshed by rectangular and quadrilateral cells are conducted for verifying the effectiveness of the proposed approach.

Slot coupled dual band high gain circularly polarized metasurface antenna

This article presents a slot coupled dual-band metasurface (MTS) based antenna with high gain and circular polarization characteristics. The MTS consists of two different unit cells, which give rise to two operating bands. The metasurface is excited by the slot aperture fed by a 50 Ω microstrip feed-line. The circular polarization is achieved by the diagonally oriented rectangular patch-based unit cells on top of the square substrate. Two orthogonal modes of MTS are required to produce circularly polarized waves, and these modes are excited by the slot aperture. The proposed MTS-inspired antenna is fabricated and experimentally validated. The experimentally verified impedance bandwidth of 33.71% in the lower frequency band and 5.35% in the upper-frequency band is achieved. The measured 3 dB (AR <3 dB)axial ratio bandwidth of 6.22% and 0.98% with a peak gain of 8.89 and 6.32 dBic is achieved with respect to 4.8 and 6.4 GHz resonant frequencies.

Effect of additives and electrode roughness on the production of hypochlorite sanitizer by the electrolysis of NaCl solution in a batch recycle reactor

The present work aims at studying the effect of some of the variables such as solution flow rate, electrode surface roughness, current density, NaCl concentration and the presence of additives such as drag reducing polymers and surfactants on the performance of an electrochemical reactor which produces sodium hypochlorite by the electrolysis of NaCl solution. A rectangular undivided cell with a graphite anode and Ni plated steel cathode was used to conduct the present study. The performance of the batch recycle reactor was assessed by determining: (i) hypochlorite yield (ii) cell current efficiency and (iii) electrical energy consumption in kW•h/kg. The results revealed that the energy consumption of hypochlorite production increases by increasing current density and solution flow rate while it decreases by increasing NaCl concentration and electrode surface roughness. Electrode roughness improved the performance of the cell and decreased the energy consumption by an amount ranging from 23 to 39% compared to the smooth electrode surface depending on the operating conditions. The presence of additives such as drag reducing polymers or surfactants were found have beneficial effects on the cell performance and decreases the electrical energy consumption especially with rough electrodes.

Infrared small target detection based on gray intensity descent and local gradient watershed

Robust infrared (IR) small target detection is an essential part of infrared search and tracking systems. Existing IR target detection methods based on human visual system usually use statistical features of rectangular region to measure the difference between target and background. In the case that the dim target size is smaller than the rectangular window cell size, since the window cell contains both the target and the background pixels, the statistical features cannot well represent the target contrast. The use of a rectangular window structure for calculation reduces the statistical difference between the target and the background, that is, reduces the saliency of the target, resulting in a slow rise in the ROC curve of the HVS method. This paper proposes a novel non-window structure filter for small target detection. Firstly, we obtain candidate target points by combining the high-frequency information of the image with the local maximum points, and at the same time, calculate the Sobel gradient map to prepare for subsequent processing. Then, a filter is designed based on gray intensity descent and local gradient watershed (GID-LGW) characteristics of the target, and it is used to calculate the contrast of each candidate target point. Finally, an adaptive threshold operation is applied to extract the target. Experiments show that compared with several baseline methods, the proposed method has a better detection rate, lower false alarm, and high speed, especially for small and weak targets with a size smaller than 3 × 2.

МЕТОДЫ ПОВЫШЕНИЯ ИЗНОСОСТОЙКОСТИ РАБОЧИХ ОРГАНОВ РОТОРНО-ВИХРЕВОЙ МЕЛЬНИЦЫ

The article is aimed at increasing the durability of the working bodies of rotary-vortex mills, which are widely used in the production of dry building mixes. The description of the device of a rotary-vortex mill is given.&#x0D; The article proposes a new method developed by scientists of the V.G. Shukhov BSTU to increase the durability of the mill's working bodies by applying cells with dimensions on their surfaces that allow particles of the crushed material to be pressed into them, and thereby protect the surface from rapid wear. &#x0D; As a result of an analytical study of the force interaction of the crushed material with the surface of the beale cell, an equation was obtained to determine the geometric dimensions of the cell, allowing due to friction forces to keep the volume of particles of the pressed material from falling out of it. &#x0D; It is established that the dimensions of the cell are interconnected and are determined in such a way that the resulting pushing force is equal to or less than the holding force (friction force). It is proved that the pressing of particles of the crushed material, in rectangular cells of the deposited mesh on the working surface of the bat, is largely determined by the geometric dimensions of the cell, and also depends on the physical and mechanical characteristics of the crushed materials. The design of the bill is proposed, which allows to increase its durability by reducing the contact area of the crushed material with the working surface of the bill.

Behaviors and interactions of strengthening and constraint for ductile Nbss matrix in Nb–Si based alloys

The ductile matrix in composites could be strengthened by incorporating brittle inclusions, while the constraint effect for matrix would become more obvious and detrimental to material toughening. The balance between strengthening and toughening was crucial to achieve excellent comprehensive mechanical properties. Upon the basis of microstructure of Nb–Si in situ composites, a unit rectangular cell containing elastic and isotropic Nb5Si3 particles was modeled, the Niobium solid solution (Nbss) matrix according with the Ramberg-Osgood constitutive relation was recognized as elastic-plastic. For Nb–Si based alloys, the effects of volume fractions of Nb5Si3 reinforcements, stress states and interfacial characteristics on the stress-strain field, flow localization and damage evolution were investigated by the finite element method (FEM). Further, the normalized work of rupture (χ) was calculated quantitatively as a function of volume fractions of Nb5Si3 phase as well as yield strength of Nbss matrix. These results would contribute to acquire more fundamental understanding of the strengthening and constraint effects which were exerted by Nb5Si3 reinforcements to ductile Nbss matrix, also an instructive guidance for the optimum design of Nb–Si based alloys.

Contacts, motion, and chain breaking in a two-dimensional granular system displaced by an intruder

We investigate numerically how the motion of an intruder within a two-dimensional granular system affects its structure and produces drag on the intruder. We made use of discrete numerical simulations in which a larger disk (intruder) is driven at constant speed amid smaller disks confined in a rectangular cell. By varying the intruder's velocity and the basal friction, we obtained the resultant force on the intruder and the instantaneous network of contact forces, which we analyze at both the cell and grain scales. We found that there is a bearing network that percolates forces from the intruder toward the walls, being responsible for jammed regions and high values of the drag force, and a dissipative network that percolates small forces within the grains, in agreement with previous experiments on compressed granular systems. In addition, we found the anisotropy levels of the contact network for different force magnitudes and regions, that the force network can reach regions far downstream of the intruder by the end of the intruder's motion, that the extent of the force network decreases with decreasing the basal friction, and that the void region (cavity) that appears downstream of the intruder tends to disappear for lower values of the basal friction. Interestingly, our results show that grains within the bearing chains creep while the chains break, revealing the mechanism by which bearing chains collapse.

Clustering Methods Based on Stay Points and Grid Density for Hotspot Detection

With the widespread use of GPS equipment, a large amount of mobile location data is recorded, and urban hotspot areas extracted from GPS data can be applied to location-based services, such as tourist recommendations and point of interest positioning. It can also provide decision support for the analysis of population migration distribution and land use and planning. However, taxi GPS location data has a large amount of data and sparse points. How to avoid the influence of noise and efficiently detect hotspots in cities have become urgent problems to be solved. This paper proposes a clustering algorithm based on stay points and grid density. Firstly, a filtering pre-processing algorithm using stay points classification and stay points thresholds is proposed, so the influence of stop points is avoided. Then, the data space is divided into rectangular grid cells; each grid cell is determined to be a dense or non-dense grid according to the defined density threshold, and the cluster boundary points and noise points are judged in the non-dense grid cells to avoid normal sampling points being treated as noise. Finally, the associated dense grids are connected into clusters. The sampling points mapped to the grid cells are the elements in the clusters. Our method is more efficient than the DBSCAN algorithm because the grid cells are calculated. The superiority of the proposed algorithm in terms of clustering accuracy and time efficiency is verified in the real data set compared to traditional algorithms.

Comparative vegetative anatomy of Wrightia tinctoria R.Br. and the endemic Wrightia indica Ngan (Apocynaceae Juss.) occurring in peninsular India

• The vegetative anatomy of Wrightia tinctoria and Wrightia indica was examined. • Giant stomata were present in leaves of W. tinctoria . • Trichomes were absent in the stem of W. tinctoria but present in W. indica . • Gelatinous fibers present in roots of W. indica were absent in W. tinctoria . • Vegetative anatomy could be valuable in the pharmacognosy of the Wrightia species. Wrightia tinctoria R.Br. and the endemic Wrightia indica Ngan are important medicinal plants possessing novel therapeutic compounds. However, the anatomy of these medicinal plants is not well studied. Therefore, the present study illustrates the vegetative anatomy of the two Wrightia R.Br. species using light microscopy. The stomata in the leaves were paracytic/anomocytic type in W. tinctoria and of paracytic type in W. indica . The foliar cuticle was of varying thickness, and multicellular trichomes were distributed on the abaxial surface of W. tinctoria and both leaf surfaces of W. indica . The leaf anatomical characters like uniseriate epidermis, collenchymatous hypodermis, heterogeneous mesophyll, endarch xylem, idioblasts, starch grains, and raphides were common for both the Wrightia species. Stems of W. indica were sparingly covered by multicellular trichomes. The stems of both Wrightia species possess uniseriate epidermis, angular collenchymatous hypodermis, parenchymatous cortex, starch grains, bicollateral vascular bundles with endarch xylem, idioblasts containing calcium oxalate crystals and water-cells in the stelar region. Starch grains were abundant in the pith of W. indica . The root periderm consists of rectangular cells and the cortex was parenchymatous in both Wrightia species. Water-cells and sclereids were present in the cortex of W. tinctoria , whereas sclereids were absent in W. indica . Vascular bundles were amphicribral in both Wrightia species. Significant differences were evident in the cellular dimensions of vegetative parts of both the Wrightia species. The observations of the present study indicate that the vegetative anatomy could aid in the discrimination of these two Wrightia species.