Role Of Geometry Research Articles

The roles of geometry and viscosity in the mobilization of coarse sediment by finer sediment

In rivers, the addition of finer sediment to a coarser riverbed is known to increase the mobility of the coarser fraction. Two mechanisms have been suggested for this: a geometric mechanism whereby smaller sizes smooth the bed, increasing near-bed velocity and thus mobility of the larger sizes, and a viscous mechanism whereby a transitionally smooth turbulent boundary layer forms, rendering the coarser grains more mobile. Here, we report on experiments using two sediment mixtures to better understand these proposed mechanisms. In Mixture 1, we used 0.5 and 5 mm grains, and in Mixture 2, we used 2 and 20 mm grains. If the entrainment of coarse gravel by finer sediment is a purely geometric effect, then the addition of finer material should produce the same effect on the mobility of the coarser material for both mixtures because they have the same size ratio. We show that addition of finer material has a different effect on the two mixtures. We observed an increase in the mobility of the coarse fraction for both mixtures, but the increase in coarse fraction mobility for Mixture 1 was almost twice that for Mixture 2. Our experiments show that in addition to the geometric effect, enhancement of coarse gravel transport by finer sediment is also driven by a viscous effect.

Role of geometry and coherent twin boundaries in mechanical response of Cu〈110〉 nanopillars under tensile loading: insights from molecular dynamics simulations

Role of geometry and coherent twin boundaries in mechanical response of Cu〈110〉 nanopillars under tensile loading: insights from molecular dynamics simulations

Wet foam flow for cleaning food industry equipment: Role of geometry in maintaining removal efficiency of Bacillus spores.

Wet foam flow for cleaning food industry equipment: Role of geometry in maintaining removal efficiency of Bacillus spores.

Interpretation of the Mathematical Geometry of the Roti Canai Structure in North Sumatra

This research was aimed at finding out the role of mathematical geometry in the process of making delicious Roti Canai. This research uses a literature review method or what is usually called library research which uses library materials such as books, magazines, documents, and journal articles. The results of this research show that there is a role of mathematical geometry in making Roti Canai, which includes a circular shape (π), structure, weight, and temperature measurement. From all the involvement of geometry in the process of making Roti Canai, delicious Roti Canai is created. So, it is concluded that the role of geometry is very important in the process of making Roti Canai.

A review of the recent advances in the heat transfer physics in latent heat storage systems

Overwhelming research interest in developing green and renewable energy systems has fostered the innovation of novel latent heat storage systems. Transport phenomena during phase transitions significantly influence the thermal energy transfer rates and the efficiency of charging and discharging such systems. Hence, a comprehensive elucidation of heat transfer physics is essential for researchers to develop the insight, model, experiment, and analyze a thermal system. This paper reviews the heat transfer mechanisms involved in phase-changing processes in various latent heat storage system configurations. At the outset, though the phase-changing process in latent heat storage systems appears simple, a critical observation unveils the complex evolution of various coupled fluid-thermal transfer processes. An astute examination of such phenomena is essential to effectively figure out the role of geometry, orientation, process variables and their dimensionless groups, boundary conditions, material property, etc., in developing accurate models and correlations. The presence of vortical flow structures and gradients of velocity and temperature lead to local variations in heat transfer coefficients in boundaries separating the heat transfer fluid (HTF) passages and phase-changing material (PCM). Gravity influences the Rayleigh–Bénard convection phase-changing process, which offers a higher energy transfer rate than heat diffusion-dominated melting/solidification. A wide variety of test cases are surveyed and conclusively figured out the role of geometry and orientation-dependent convection in the phase-changing process. The present overview of heat transfer physics shall provide a guideline for the system designers to fine-tune HTF flow path geometrical aspects and PCM confinement for improved heat transfer response and system performance.

Theoretical considerations and supporting evidence for the primary role of source geometry on field potential amplitude and spatial extent.

Field potential (FP) recording is an accessible means to capture the shifts in the activity of neuron populations. However, the spatial and composite nature of these signals has largely been ignored, at least until it became technically possible to separate activities from co-activated sources in different structures or those that overlap in a volume. The pathway-specificity of mesoscopic sources has provided an anatomical reference that facilitates transcending from theoretical analysis to the exploration of real brain structures. We review computational and experimental findings that indicate how prioritizing the spatial geometry and density of sources, as opposed to the distance to the recording site, better defines the amplitudes and spatial reach of FPs. The role of geometry is enhanced by considering that zones of the active populations that act as sources or sinks of current may arrange differently with respect to each other, and have different geometry and densities. Thus, observations that seem counterintuitive in the scheme of distance-based logic alone can now be explained. For example, geometric factors explain why some structures produce FPs and others do not, why different FP motifs generated in the same structure extend far while others remain local, why factors like the size of an active population or the strong synchronicity of its neurons may fail to affect FPs, or why the rate of FP decay varies in different directions. These considerations are exemplified in large structures like the cortex and hippocampus, in which the role of geometrical elements and regional activation in shaping well-known FP oscillations generally go unnoticed. Discovering the geometry of the sources in play will decrease the risk of population or pathway misassignments based solely on the FP amplitude or temporal pattern.

Role of geometry and adhesion in droplet freezing dynamics

We propose a thermal and geometrical analytical model for the freezing front dynamics of a spherical drop. The growth is characterized by an effective diffusion coefficient that increases as the substrate temperature decreases and a spherical front that meets the edges of the drop perpendicularly. We compare our model with experimental data for substrate temperature ranging from -9 to -80 \ifmmode^\circ\else\textdegree\fi{}C. We highlight the importance of heat diffusion in the liquid and the adhesion of drops to the substrate that decreases at low temperature.

On the role of geometry in statistical mechanics and thermodynamics. I. Geometric perspective

This paper contains a fully geometric formulation of the General Equation for Non-Equilibrium Reversible-Irreversible Coupling (GENERIC). Although GENERIC, which is the sum of Hamiltonian mechanics and gradient dynamics, is a framework unifying a vast range of models in non-equilibrium thermodynamics, it has unclear geometric structure due to the diverse geometric origins of Hamiltonian mechanics and gradient dynamics. The difference can be overcome by cotangent lifts of the dynamics, which leads, for instance, to a Hamiltonian form of gradient dynamics. Moreover, the lifted vector fields can be split into their holonomic and vertical representatives, which provides a geometric method of dynamic reduction. The lifted dynamics can be also given physical meaning, here called the rate-GENERIC. Finally, the lifts can be formulated within contact geometry, where the second law of thermodynamics is explicitly contained within the evolution equations.

On the role of geometry in statistical mechanics and thermodynamics. II. Thermodynamic perspective

The General Equation for Non-Equilibrium Reversible–Irreversible Coupling (GENERIC) provides the structure of mesoscopic multiscale dynamics that guarantees the emergence of equilibrium states. Similarly, a lift of the GENERIC structure to iterated cotangent bundles, called a rate GENERIC, guarantees the emergence of the vector fields that generate the approach to equilibrium. Moreover, the rate GENERIC structure also extends Onsager’s variational principle. The maximum entropy principle in the GENERIC structure becomes the Onsager variational principle in the rate GENERIC structure. In the absence of external forces, the rate entropy is a potential that is closely related to the entropy production. In the presence of external forces when the entropy does not exist, the rate entropy still exists. While the entropy at the conclusion of the GENERIC time evolution gives rise to equilibrium thermodynamics, the rate entropy at the conclusion of the rate GENERIC time evolution gives rise to rate thermodynamics. Both GENERIC and rate GENERIC structures are put into the geometrical framework in the first paper of this series. The rate GENERIC is also shown to be related to Grad’s hierarchy analysis of reductions of the Boltzmann equation. Chemical kinetics and kinetic theory provide illustrative examples. We introduce rate GENERIC extensions (and thus also Onsager-variational-principle formulations) of both chemical kinetics and the Boltzmann kinetic theory.

Acceleration waves and oscillating gas bubbles modelled by rational extended thermodynamics

The study of acceleration waves for a rarefied polyatomic gas is carried out in planar, cylindrical and spherical geometry referring to the rational extended thermodynamics theory with 14 moments. The case of a rarefied monatomic gas is determined as a limit case, and the role of geometry and molecular degrees of freedom is investigated. In addition, the behaviour of an acceleration wave travelling inside an oscillating gas bubble is modelled by the 14-moment PDE system under adiabatic condition. We show that dissipation combined with hyperbolicity tends to inhibit shock formation, and that the dynamic pressure cannot be zero inside the oscillating bubble. This fact can produce observable effects even in the Navier–Stokes approximation, if the gas exhibits high bulk viscosity.

The role of geometry on controlled cavity collapse and top jet drop

The contents of this work explore the influence of three geometric parameters on controlled cavity collapse at liquid interface and the subsequent ejected drop; the parameters are the angle of the ejecting nozzle plate (θ), the height (H), and the radius (R) of the vessel used to enclose the liquid within. The conducted computational modeling shows that changing the angle of the nozzle plate from a flat surface to inclined surface in one direction causes the droplet diameter to decrease, whereas an inclination in the opposite direction results in larger droplets. Moreover, changing the height of the fluid vessel does not actually influence the drop size and its velocity as long as the vessel height is much larger than the nozzle radius (R0). Below the limit H = 5R0, the droplet size starts to decrease and its velocity to increase by decreasing the vessel height. Finally, the droplet size decreases by increasing the radius of the fluid vessel even when R ≫ R0. This is attributed to the change in the displaced liquid volume and subsequently the cavity volume at the tip of the nozzle when the vessel radius is changed.

Heat transfer in a fracture embedded in a finite matrix: On the role of geometries and thermal dispersivity in the fracture

Understanding heat transfer in the discrete fracture embedded in a finite rock matrix is critical to the investigation of thermal energy transfer in the fracture network and the assessment of geothermal energy recovery in the enhanced geothermal system (EGS). In this study, an analytical model is proposed for transient and steady-state thermal energy transfer in a discrete fracture embedded in a finite rock matrix. The heat transfer model accounts for thermal convection, velocity-dependent thermal dispersion and longitudinal thermal conduction in the fracture, and thermal conduction in the rock matrix. The influence of the outer boundaries of the finite rock matrix will also be considered along with thermal exchange between the fracture and rock matrix. The thermal transfer processes in those two domains are coupled by assuming the continuity of temperatures and thermal fluxes along the fracture-rock matrix interfaces. The solutions are validated with the existing analytical solution and numerical model, and proved to be robust and accurate. The study implies that: 1) the geometries, such as the fracture aperture and thickness of the rock matrix, have an important influence on the temperature distribution. The fracture temperature will change in a greater range in the wider fracture and thicker rock matrix; 2) longitudinal thermal conduction in the fracture does not have a major influence on the temperature distribution in the system, and thus can be ignored; 3) thermal dispersivity in the fracture is an important mechanism to include. Ignoring thermal dispersion in the fracture will misestimate the temperature significantly. Also, thermal conductivity in the rock matrix is a key parameter for the thermal exchange between the rock matrix, surrounding environment and fracture. When the rock matrix has a greater thermal conductivity, the temperature in the fracture is observed to change less. The analytical model proposed in this study is implemented to analyze the thermal flow-through experiments in fractured core samples by Zhao (1987) and estimate the thermal dispersivity values in the fracture. The Morris global sensitivity analysis is conducted to identify the most influential input variables and estimate the interaction effects. The global sensitivity analysis is consistent with thermal breakthrough curve analysis and indicates that the temperature in the fracture is sensitive to fracture aperture, rock matrix radius, thermal dispersivity in the fracture and thermal conductivity in the rock matrix, and insensitive to longitudinal thermal conductivity in the fracture.

Operando electrochemical TEM, ex-situ SEM and atomistic modeling studies of MnS dissolution and its role in triggering pitting corrosion in 304L stainless steel

Insights into the roles of geometry, size, and composition on MnS inclusion dissolution to initiate pits in 304L SS were obtained by combining operando and ex-situ electron microscopy, EDS, and atomistic modeling. The majority of thirty MnS on SS surface did not undergo dissolution even after over a week of exposure, and only a small number caused an attack of SS. Operando TEM during potentiodynamic polarization confirmed that MnS attack was followed by corrosion of the nearby SS substrate. Atomistic modeling revealed that elemental variations in the surface composition may play a role in differentiating pitting initiation by sulfur species.

Disk wrinkling under gravity

We study the deflection by gravity of a circular elastic disk deposited on a rigid support. The axisymmetric deflection induces compressive orthoradial stresses which leads to a wrinkling instability above a critical threshold of the dimensionless gravity force. We study this instability by a combination of experiments, numerical simulations and analytical tools, with a particular focus on the role of geometry. We show that aspect ratio is a crucial parameter that controls both the threshold of instability and the most unstable mode. The influence of this parameter on the threshold can be caught by introducing a new nondimensionalization of the transverse load.

The Role of Geometry on a Self-Sustaining Bio-Receptive Concrete Panel for Facade Application

Bio-receptivity refers to the aptitude of a material to allow for the natural growth of small plant species on stony surfaces with minimum external influence. Despite the numerous associated environmental benefits, the growth of mosses and lichens on facades has always been viewed as a negative phenomenon due to the random and shabby growth conditions. This research dealt with the design of a self-sustaining bio-receptive concrete facade system with an aim to create a more sustainable and green concrete for the construction industry. The research used surface geometry as a design variable to facilitate moss growth on concrete panels in an ordered and systematic manner. The exercise was an attempt to not only address the functional aspect of bio-receptivity but also its aesthetical quality, which has a primary influence on people’s perception of bio-receptivity and can promote mass use of this type of concrete material. The research was conducted in a top-down approach, where first, through design by research, six distinctly designed concrete panels were fabricated using adapted material composition (blast furnace cement with 75% slag, 0.6 water/cement, sand 0–4 mm and gravel 5–8 mm) as the boundary condition. The concrete mixture together with no curing policy resulted in highly porous concrete panels, suitable for bio-receptive properties. Next in the design validation phase, the influence of surface geometry/roughness on the water retention ability of the panels and the subsequent moss growth on the panels were evaluated through in vitro experiments. The water retention experiment of the panels was based on quantitative measurements for weight, relative humidity and temperature at several time intervals. The moss-growing experiment was carried out within an ideal greenhouse condition where the panels were initially inoculated with moss spores; the results were based on qualitative observation for a period of 4 months. According to the comparative analysis of these results, with the same material composition, Panel 2 showed the highest bio-colonization owing to its prominent surface geometry, whereas Panel 5 showed the least bio-colonization owing to its plain surface despite high absorption capacity. Thus, the role of geometry has been extensively proven in this research and as an outcome a set of general design guidelines have been formulated for a self-sustaining bio-receptive concrete facade panel, using geometry as a design variable for bio-receptivity.

Application areas of the angle reflector

The article provides examples of how the device known as the «angle reflector» a few decades ago has been increasingly used in various fields of science and technology in recent years. Angle reflectors are designed to change (reflect) optical and radar rays in the direction, opposite to the original direction. At present, angle reflectors are widely used to ensure the safety of road transport on dangerous road sections. Radio wave reflectors have the same design as optical ones; therefore, in radio detection and location, angle reflectors are used to send warning signals to ship radars on bridge supports, beacons and buoys. Modern angle reflectors attached to meteorological probes allow determining the direction and speed of the wind at high altitude, which is especially important in the study of the outer space. In recent years, devices have been developed to improve the accuracy of radar stations calibration. The examples of graphical calculation of angle reflectors presented in the article clearly demonstrate the primary role of geometry in the design activity of an engineer. The graphical calculation is based on the theoretical positions of projective geometry. The design and calculation of optical systems is carried out by the graphoanalytic method, since only with a combination of graphical and analytical methods it is possible to accurately calculate the course of a light beam, laser, or radio wave and thereby determine the design parameters of the devices. The article focuses on a graphical method for calculating two types of angle reflectors using orthogonal projection, due to which modern engineers will be able to create more up-to-date designs of optical systems with a wide range of applications.

The role of geometry in the generation of a shock wave by a femtosecond laser pulse

Laser exposure at a sufficient intensity creates a shock wave (SW), propagating in the irradiated target. The process is used in many technological applications. As a result of femtosecond exposure, a warmed up layer with a thickness of d T ∼ 0.1 μm occurs. The radius of the heating spot R L varies from values of the order of a micron (focusing on the diffraction limit) up to tens or hundreds of microns depending on the experiment. As you can see, R L ≫ d T, therefore one-dimensional motion with a plane surface is generated. The quasi-plane SW stage ends when the SW moves away from the target surface to a depth of about RL. Then the stage of quasi-hemispherical propagation begins. The paper analyzes the transition from plane to hemispherical SW. The motion of the “wings” of a hemispherical wave on the target surface bordering on a gas or vacuum is investigated. Theoretical estimates and numerical simulation results are presented. Analysis of the movement of the “wings” on the surface is important for experimental diagnostics of phenomena inside the target.

On the role of geometry in geo-localization

Consider the geo-localization task of finding the pose of a camera in a large 3D scene from a single image. Most existing CNN-based methods use as input textured images. We aim to experimentally explore whether texture and correlation between nearby images are necessary in a CNN-based solution for the geo-localization task. To do so, we consider lean images, textureless projections of a simple 3D model of a city. They only contain information related to the geometry of the scene viewed (edges, faces, and relative depth). The main contributions of this paper are: (i) to demonstrate the ability of CNNs to recover camera pose using lean images; and (ii) to provide insight into the role of geometry in the CNN learning process.

Factors influencing the development of violent pyroconvection. Part II: fire geometry and intensity

Fire spread associated with violent pyrogenic convection is highly unpredictable and difficult to suppress. Wildfire-driven convection may generate cumulonimbus (storm) clouds, also known as pyrocumulonimbus (pyroCb). Research into such phenomena has tended to treat the fire on the surface and convection in the atmosphere above as separate processes. We used a numerical model to examine the effect of fire geometry on the height of a pyroconvective plume, using idealised model runs in a neutral atmosphere. The role of geometry was investigated because large areal fires have been associated with the development of pyroCb. Complementary results (detailed in Part I) are extended by considering the effect that fire shape can have on plume height by comparing circular, square, and rectangular fires of varying length and width, representing the difference between firelines and areal fires. Results reveal that the perimeter/area ratio influenced the amount of entrainment that the plume experiences and therefore the height to which the plume rises before it loses buoyancy. These results will aid in the prediction of blow-up fires (whereby a fire exhibits a rapid increase in rate of spread or rate of spread) and may therefore be useful in determining where fire agencies deploy their limited resources.

Dent Imperfections in Shell Buckling: The Role of Geometry, Residual Stress, and Plasticity

Abstract Departures of the geometry of the middle surface of a thin shell from the perfect shape have long been regarded as the most deleterious imperfections responsible for reducing a shell’s buckling capacity. Here, systematic simulations are conducted for both spherical and cylindrical metal shells whereby, in the first step, dimple-shaped dents are created by indenting a perfect shell into the plastic range. Then, in the second step, buckling of the dented shell is analyzed, under external pressure for the spherical shells and in axial compression for the cylindrical shells. Three distinct buckling analyses are carried out: (1) elastic buckling accounting only for the geometry of the dent, (2) elastic buckling accounting for both dent geometry and residual stresses, and (3) a full elastic–plastic buckling analysis accounting for both the dent geometry and residual stresses. The analyses reveal the relative importance of the geometry and the residual stress associated with the dent, and they also provide a clear indicator of whether plasticity is important in establishing the buckling load of the dented shells.