Volume Holes Research Articles

Numerical study of the effect of hole arrangement on thermal efficiency of a pipe containing perforated porous media

In this study, fluid flow and heat transfer in a round tube containing perforated porous media are investigated numerically. The flow is laminar and the tube is exposed to a constant heat flux in the wall. Numerical simulation is performed in three dimensions with finite volume method. The number of holes is considered to be between 5 and 9, one of which is located in the center and the other near the inner surface of the pipe wall and around the central hole. The fluid transport in porous region is modeled using the Darcy–Brinkman–Forcheimer model and the fluid–solid thermal energy exchange is simulated by means of the local thermal equilibrium model. Effects of various parameters affecting the heat transfer and pressure drop in perforated porous medium such as number of holes, distance between holes, volume of holes, Darcy number, porosity, and thermal conductivity have been discussed. Based on the results, the arrangement and the number of holes as well as the characteristics of porous media greatly affects the heat transfer and pressure drop. Under the same conditions, for example, a certain amount of porous material and a certain number of holes, the efficiency of the porous medium, i.e. higher heat transfer and lower pressure drop, can be significantly increased by proper arrangement of the holes. For the conditions used in this study, the Nusselt number can be increased by more than four times the value of the empty tube from the porous medium.

Calculating Soft-Sphere Ionic Radii for Solid-State Arrangements from Solution Measurements

Despite extensive conceptualization of ions as hard spheres in most textbooks, solid-state structures are more accurately modeled as overlapping soft spheres that better reflect the size of the ions. The corresponding soft-sphere ionic radii of alkali and halide ions can be empirically established from the partial molar volume of the ions in aqueous solution. Partial molar volumes for 15 alkali halide solutes are calculated from the slope of solution density (g/L) versus the solution molarity (mol/L) at the infinite dilution limit. The set of resulting ion sizes for the lithium, sodium, potassium, rubidium, cesium, chloride, bromide, and iodide is both self-consistent, being composed of quantities that are mathematically additive, and physically meaningful. Upon setting the volume of Li(I) to 5.2 mL/mol, the solid-state structures of all 15 alkali halides, whether rock salt or CsCl, can be constructed to accurately model ion overlap as well as hole volume, though the size ordering of the ions is different than the ordering found for hard spheres. This new conceptual and empirical bridge between the solution and solid phases should help advance the teaching of these commonly disparate subjects by reinforcing aspects of both while drawing new connections between them.

Stability of horizon with pressure and volume of d-dimensional charged AdS black holes with cloud of strings and quintessence

In this paper, the thermodynamics and the stability of horizon of the charged AdS black hole surrounded by quintessence and cloud of strings in d-dimensional spacetime are studied via the scalar field scattering and the charged particle absorption. The cosmological constant is interpreted as the thermodynamic pressure in the black hole. During the study, we consider the case where the energy of the particle (scalar field) is related to the internal energy of the black hole. Furthermore, we also consider another assumption, which is proposed in Hu et al. (2019). This assumption considers that the energy of the particle (scalar field) is related to the enthalpy of the black hole. In addition, we compare and discuss the results obtained under these two assumptions. At the same time, we also consider the effect of the dimension. The thermodynamics of black holes in different dimensions has also been studied and compared.

Effect of L-shaped slots on scour around a bridge abutment

Abstract Local scour is the most significant cause of bridge failure. Providing a short abutment with a straight slot has proved to be an effective method for reducing scour at this abutment. In this study, laboratory experiments have been conducted to investigate the effectiveness of using L-shaped slots in comparison to the commonly used straight slot, on the scour reduction at short vertical-wall abutment under clear-water flow conditions and uniform bed materials. The slots were just above the bed and their diameters equal to half the abutment's length. The results illustrated that it is essential to have a straight slot in any combination of slots, as any configuration without one is inefficient. Also, a combination of a straight slot with one side slot in the middle of the abutment's width gives better performance than an individual straight slot, as it reduces the depth, area, and volume of the scour hole by about 32.6, 26.8, and 43.6% respectively, in comparison to 23.2, 20.7, and 35.3% for the straight slot alone.

Improving the yield of GaAs nanowires on silicon by Ga pre-deposition

GaAs nanowire (NW) arrays were grown by molecular beam epitaxy using the self-assisted vapor−liquid−solid method with Ga droplets as seed particles. A Ga pre-deposition step is examined to control NW yield and diameter. The NW yield can be increased with suitable duration of a Ga pre-deposition step but is highly dependent on oxide hole diameter and surface conditions. The NW diameter was determined by vapor-solid growth on the NW sidewalls, rather than Ga pre-deposition. The maximum NW yield with a Ga pre-deposition step was very close to 100%, established at shorter Ga deposition durations and for larger holes. This trend was explained within a model where maximum yield is obtained when the Ga droplet volume approximately equals the hole volume.

Water impact of a surface-patterned disk

Abstract

Nanometer Pore Structure Characterization of Taiyuan Formation Shale in the Lin-Xing Area Based on Nitrogen Adsorption Experiments

Ordos Basin is an important continental shale gas exploration site in China. The micropore structure of the shale reservoir is of great importance for shale gas evaluation. The Taiyuan Formation of the lower Permian is the main exploration interval for this area. To examine the nanometer pore structures in the Taiyuan Formation shale reservoirs in the Lin-Xing area, Northern Shaanxi, the microscopic pore structure characteristics were analyzed via nitrogen adsorption experiments. The pore structure parameters, such as specific surface area, pore volume, and aperture distribution, of shale were calculated; the significance of the pore structure for shale gas storage was analyzed; and the main controlling factors of pore development were assessed. The results indicated the surface area and hole volume of the shale sample to be 0.141–2.188 m2/g and 0.001398–0.008718 cm3/g, respectively. According to the IUPAC (International Union of Pure and Applied Chemistry) classification, mesopores and macropores were dominant in the pore structure, with the presence of a certain number of micropores. The adsorption curves were similar to the standard IV (a)-type isotherm line, and the hysteresis loop type was mainly similar to H3 and H4 types, indicating that most pores are dominated by open type pores, such as parallel plate-shaped pores and wedge-shaped slit pores. The micropores and mesopores provide the vast majority of the specific surface area, functioning as the main area for the adsorption of gas in the shale. The mesopores and macropores provide the vast majority of the pore volume, functioning as the main storage areas for the gas in the shale. Total organic carbon had no notable linear correlation with the total pore volume and the specific surface area. Vitrinite reflectance (Ro) had no notable correlation with the specific surface area, but did have a low “U” curve correlation with the total pore volume. There was no relationship between the quartz content and specific surface area and total pore volume. In addition, there was no notable correlation between the clay mineral content and total specific surface area and total pore volume.

Holographic Complexity and Thermodynamic Volume.

We study the holographic complexity conjectures for rotating black holes, uncovering a relationship between the complexity of formation and the thermodynamic volume of the black hole. We suggest that it is the thermodynamic volume and not the entropy that controls the complexity of formation of large black holes in both the complexity equals action and complexity equals volume proposals in general. Our proposal reduces to known results involving the entropy in settings where the thermodynamic volume and entropy are not independent, but has broader scope. Assuming a conjectured inequality is obeyed by the thermodynamic volume, we establish that the complexity of formation is bounded from below by the entropy for large black holes.

Experimental study of the effect of the length-to-width ratio and skewness angles of the pier installed at the bend on scour pattern

One of the causes of the destruction or damage of many bridges in the world is the local scour around the bridge piers. Accordingly, research on effective factors on the scouring pattern around the bridge piers is a necessity. In this study, the parameters of the scour hole created around rectangular piers, such as the depth, area and volume of the scour hole, and the effects of increasing the rectangular pier’s length-to-width ratio and its skewness angle towards the banks on scour hole parameters, bed topography changes and the downstream straight path in a 180° sharp bend has been investigated. The results showed that in a 180° sharp bend, the length of the rectangular pier should be at least 3 and at most 5 times its width. The pier with a length-to-width ratio of 3 had a better performance in terms of reducing scouring along the bend. The maximum depth of the scour hole around the piers occurs when the piers are located at 90°. Increasing the angle of attack caused by skewing the pier towards the inner and outer bank at 90° increases the depth and volume of the scour hole.

Effect of Copper Sulfate and Sulfuric Acid on Blind Hole Filling of HDI Circuit Boards by Electroplating

Here, in a certain high density interconnect (HDI) printed circuit board, the effect of copper sulfate and sulfuric acid on the filling effect of a blind hole with a certain diameter and depth was investigated by making a blind hole using a CO2 laser drilling machine, filling the blind hole via electroplating by simulating the electroplating line in a Halin cell, and observing the cross-section of a micro blind hole after polishing using metallographic microscope, as well as the effect of hole filling, are evaluated. The results show that, under the conditions of a certain plating solution formula and electroplating parameters (current density and electroplating time), the sag degree decreases with the increase in the copper sulfate concentration. When the concentration of copper sulfate increases from 210 g/L to 225 g/L, the filling effect is good and the sag degree is about 0. However, with the increase in sulfuric acid concentration, the sag increases gradually. When the sulfuric acid concentration is 25–35 g/L, both the sag and copper coating thickness are in a small range. Under appropriate electroplating conditions, a better blind hole filling effect can be obtained. The volume of blind hole has a certain effect on the diffusion and exchange of copper sulfate and sulfuric acid, as well as on the concentration distribution of additives.

Experimental study of the effect of submergence ratio of double submerged vanes on topography alterations and temporal evaluation of the maximum scour in a 180-degree bend with a bridge pier group

ABSTRACT Various protective methods are incorporated in order to change the flow pattern and reduce the intensity of the vortices around the piers with the aim of reducing scour at bridge piers. One of these methods is the employment of submerged vanes at the upstream side of the bridge piers. This study investigated the effect of the submergence ratio of the submerged vanes in scour reduction around a single pier and a group of piers. The results indicated that the greatest reduction in the maximum scour depth, the scour hole volume, the maximum sedimentary bar, and the scour hole area around the piers occurred in experiments with a single pier and triad piers with a longitudinal direction in combination with 75%-submerged vanes. At this submergence ratio, the maximum scour depth and the scour hole volume decreased by nearly 30 and 59% respectively in the single pier test including the submerged vanes, and by nearly 23 and 37% respectively in the triad pier group test with a longitudinal direction including the submerged vanes in comparison to the test with no submerged vane installed.

Kinetic Monte Carlo simulation of the growth of In nanostructures by droplet epitaxy on AlGaAs nanopatterned surfaces

In this paper, the results of the simulation of the In/AlGaAs growth on nanopatterned surfaces using modified analytical–Monte Carlo model are presented. The surface density of nanostructures is demonstrated to slightly decrease with increasing Al content. A decrease of an interhole distance leads to the occupation of a small part of a hole which can be prevented by a decrease of the hole volume. The best localization of In nanostructures on AlGaAs surfaces nanopatterned with holes at a distance of more than 125 nm can be achieved at a temperature of 300°C or higher. A decrease in temperature requires a sufficient decrease of an interhole distance to avoid nucleation beyond predefined positions.

Thermal Expansion of the Free Volume in Poly(vinyl alcohol) Using Positron Annihilation Technique and Group Contribution Method

Positron annihilation lifetime (PAL) as a function of temperatures were measured to determine the thermal expansion coefficient () of the ortho-positronium (o-Ps) hole volume for poly(vinyl alcohol), PVA. On the other hand, the thermal expansion coefficient ( of the bulk volume of PVA has been calculated from measuring the bulk volume as a function of temperature. The group contribution method is used for the calculation of the fractional of the free volume in the glassy and the rubbery states. For the glassy and rubbery states, the ratio of the thermal expansion coefficient of the bulk volume to that of the total free volume is calculated. There is an agreement between these ratios in glassy and rubbery states and those outcomes acquired from the PAL and the substance volume information. This indicated that the o-Ps lifetime is a sign to the free volume in the sample which is also proportional to the total free volume.

Innovative designed fuel pin of conceptual semi-heavy water research reactor with improved reactor safety

Improving thermal hydraulic parameters such as axial power distribution and decrease maximum fuel temperatures lead to higher reactor safety. In this study, with the variation of fuel pellet central hole (1UTVS) volume along the fuel pin axis, have achieved improvements of thermal hydraulic parameters of the semi-heavy water research reactor. The new design of fuel pin has contain fuel pellets with different radii central hole along the fuel pin axis. Calculations with the new design of fuel pin are carried out by coupling of neutronic (WIMS-D5+CITATION) and thermal hydraulic (COBRA-EN) codes for a conceptual high neutron flux semi-heavy water research reactor. As a result, the axial Power Peaking Factor (PPF) decreased from 1.2827 to 1.2118 and minimum Departure from Nucleate Boiling Ratio (DNBR) has increased from 5.31 to 5.583. Maximum fuel temperature is decreased from 1595 to 1499.6 °C and core average thermal flux is increased from 1.1607 × 1014 to 1.2447 × 1014 n/cm2.s at the Beginning of Cycle (BOC). These improvement which are the consequence of applying the new innovative design of the fuel pin lead to higher safety. This new idea of designed fuel pin with different radii central hole fuel pellets along the fuel pin axis can be used for nuclear reactors in order to improve their safety.

The entropy evolution of a noncommutative black hole under Hawking radiation

By calculating the entropy of a scalar field in the interior volume of noncommutative black holes and considering an infinitesimal process of Hawking radiation, a proportion function is constructed that reflects the evolution relation between the scalar field entropy and Bekenstein–Hawking entropy under Hawking radiation. Comparing with the case of Schwarzschild black holes, the new physics of this research can be expanded to the later stage of Hawking radiation. From the result, we find that the proportion function is still a constant in the earlier stage of Hawking radiation, which is identical to the case of Schwarzschild black holes. As Hawking radiation goes into the later stage, the behavior of the function will be dominated by the noncommutative effect. In this circumstance, the proportion function is no longer a constant and decreases with the evaporation process. When the noncommutative black hole evolves into its final state with Hawking radiation, the interior volume will converge to a certain value, which implies that the loss of information of the black hole during the evaporation process will finally be stored in the limited interior volume.

Integration of close‐range underwater photogrammetry with inspection and mesh processing software: a novel approach for quantifying ecological dynamics of temperate biogenic reefs

AbstractCharacterizing and monitoring changes in biogenic 3‐dimensional (3D) structures at multiple scales over time is challenging within the practical constraints of conventional ecological tools. Therefore, we developed a structure‐from‐motion (SfM)‐based photogrammetry method, coupled with inspection and mesh processing software, to estimate important ecological parameters of underwater worm colonies (hummocks) constructed by the sabellariid polychaete Sabellaria alveolata, using non‐destructive, 3D modeling and mesh analysis. High resolution digital images of bioconstructions (hummocks) were taken in situ under natural conditions to generate digital 3D models over different sampling periods to analyse the morphological evolution of four targeted hummocks. 3D models were analysed in GOM Inspect software, a powerful and freely available mesh processing software to follow growth as well as morphology changes over time of each hummock. Linear regressions showed 3D models only slightly overestimated the real dimensions of the reference objects with an average error < 5% between measured and model‐estimated dimensions for both length and volume. Manual inspection of models and semi‐automated surface‐to‐surface comparison allowed the computation of important metrics linked to the ecology of temperate reefs such as volume, surface area, surface complexity/rugosity, number and size of holes and creeks and the mean density of living worms per colony. Moreover we demonstrated the reliability of 3D surface complexity estimates against two linear rugosity measures: a traditional and a virtual variant of the ‘chain‐and‐tape’ method. Finally, besides 3D models deviation analysis via surface comparison, a Bayesian latent variable model approach was adopted to highlight the significative effects of sea state conditions on S. alveolata hummocks metrics. We demonstrated without damaging the benthic organisms that SfM approach allow continuous study of temperate bioconstruction leading to a fine description of short‐term structural modification mediated by hydrodynamics, making this technique accessible and repeatable to many other areas of ecological research.

Hydrodynamics of a bordered collar as a countermeasure against pier scouring

An experimental campaign on long-term clear-water scour at bridge piers with different configurations was performed in a laboratory to investigate the effects of different countermeasures. Tests were performed in a flume with a movable sediment bed for an unprotected cylindrical pier, a cylindrical pier with a standard collar and a cylindrical pier with a bordered collar. The scoured beds at the equilibrium stage were acquired through the photogrammetry technique and the efficiencies of the tested countermeasures were measured. Results showed a reduction in the maximum scour depth as well as in the scour hole volume with respect to the unprotected pier. The maximum scour depth was reduced by 59.63% with the standard collar and by 63.51% with the bordered collar. The scoured volume was reduced by 43.80% with the standard collar and by 60.00% with the bordered collar. The three-dimensional Reynolds-averaged Navier–Stokes equations were solved numerically to reproduce the hydrodynamics of the experiments. The volume of fluid technique was used to reproduce the free surface. For each test, the results of the simulations were analysed to investigate the flow field around the pier both at the initial (flat-bed) and at the equilibrium stages, highlighting the changes in the velocity field owing to the presence of the standard collar and of the bordered collar.

Interior volume of Kerr-AdS black holes

The interior volume of black holes as defined by Christodoulou and Rovelli exhibits many surprising features. For example, it increases with time, even under Hawking evaporation. For some black holes, the interior volume is not even a monotonic increasing function of its area, which means one cannot infer how large a black hole is by just looking from the outside. Such a notion of volume, however, turns out to be useful in the context of holography, as it seems to be dual to the complexity of the boundary field theory. In this study, we investigate the properties of the interior volume of 4-dimensional Kerr-AdS black holes, fixing either the mass parameter $M$ or the physical mass $E$, whilst varying the values of the cosmological constant. We found that the volume as a function of the radial coordinate features a "double lobe" while fixing $M$, whereas fixing $E$ yields behaviors that are qualitatively similar to the asymptotically flat case. We briefly comment on the holographic complexity of Kerr-AdS black holes.

Исследование электроэрозионной обрабатываемости жаропрочных сплавов применительно к технологии прошивки отверстий малого диаметра

This article presents a method of obtaining and analyzing a single electroerosion hole for a group of heat-resistant chromium-nickel alloys. The study of the geometric parameters of the hole allows us to calculate experimentally the coefficient of erosion of the workpiece material, which characterizes the efficiency of converting the electrical energy into the fracture work of a solid body. When a single erosion pulse is applied to the interelectrode gap, a single hole is formed on the electrode surface. The geometric parameters of the hole (diameter, depth, height of the collar) depend on many factors: the pulse energy, the composition of the working fluid, the material of the electrodes, the value of the interelectrode gap, etc. This study establishes the dependence of the volume of the removed material on the pulse energy, with other conditions being equal. Experimental studies are conducted in accordance with a well-known method, and photographs of individual holes are obtained for different pulse durations. Ball segment and ellipsoid models are proposed for calculating the volume of the removed metal. It is shown that the ball segment model yields the smallest calculation error. The volume of individual holes is calculated using the selected ball segment model.

Effect of Duration and Pattern of Hydrographs on Scour Around Pier in Sharp Bend Under Incipient Motion and Live Bed Conditions

In the present study, the effect of peak occurrence time and flood duration on the scour around the bridge pier installed in a sharply bended channel was investigated. For this purpose, several simple single-peaked hydrographs with the same durations and different peak occurrence times were produced in laboratory. In addition, hydrographs having two consecutive peaks with a steady flow discharge at the first peak and an unsteady-flow discharge at the second peak and vice versa were investigated. The flow velocity range began from incipient motion conditions and steeply increased to live bed conditions. In each experiment, the temporal variations of the maximum local scour depth were measured. In single-peaked experiments, by increasing hydrograph duration from 25 to 100 min, the maximum scour depth increased by 20%, and the progression of sediments along the downstream straight path increased by 150%. For hydrographs with two non-equal and the same duration peaks, at a constant discharge for the first peak and a decrease in the second peak discharge from 70 to 60, 50, and 45 (L s−1), the volume of the scour hole around the pier was decreasing 15, 40, and 60%. Its area fell by 10, 40, and 55%, respectively. When the rising and falling limb time of hydrographs were equal, the maximum sedimentation height increased by 2.7, 3.5, and 5 times, respectively by increasing test duration from 25 to 50, 75, and 100 min.