Open Geometry Research Articles

Heat transport phenomena in Voronoi foam due to pulsating flow

Metal foam is of great interest to many researchers due to its heat transfer capabilities in transport phenomena. Metal foam has reduced weight and dimensions per meter of heat exchange surface. In this regard, the use of metal foam in transport cooling systems is relevant since the mass-dimensional characteristics of the components of vehicles are essential. This article numerically investigates heat transfer and pressure drop through open cell foam under pulsating flow. The pulsations were both symmetrical and asymmetrical. The pulsation frequency was varied in the range from 0.25 to 1.25 Hz; the dimensionless pulsation amplitude was constant at 28.6. Air was used as the working fluid. The Reynolds number corresponded to 30. Numerical analysis was carried out using Ansys Fluent. The 3D open cell foam geometry construction was based on the Laguerre Voronoi tessellations technique. The obtained data on heat transfer for a steady flow were compared with the experimental data. As a result of modeling, it was found that the heat transfer of open cell foam increases with increasing frequency for both symmetric and asymmetric flow pulsations. The heat transfer enhancement is always higher with asymmetric flow pulsations. Heat transfer at asymmetric pulsations with a frequency of 1.25 Hz improved by a factor of 1.41 compared to a steady flow. Open cell foam with asymmetric flow pulsations has a better thermal performance efficiency than symmetrical pulsations.

Minimizing plasma temperature for antimatter mixing experiments

The ASACUSA collaboration produces a beam of antihydrogen atoms by mixing pure positron and antiproton plasmas in a strong magnetic field with a double cusp geometry. The positrons cool via cyclotron radiation inside the cryogenic trap. Low positron temperature is essential for increasing the fraction of antihydrogen atoms which reach the ground state prior to exiting the trap. Many experimental groups observe that such plasmas reach equilibrium at a temperature well above the temperature of the surrounding electrodes. This problem is typically attributed to electronic noise and plasma expansion, which heat the plasma. The present work reports anomalous heating far beyond what can be attributed to those two sources. The heating seems to be a result of the axially open trap geometry, which couples the plasma to the external (300 K) environment via microwave radiation.

Three-Dimensional Atrial Wall Thickness Measurement Algorithm From a Segmented Atrial Wall Using a Partial Differential Equation

Despite advancements in high-precision segmentation technology for computed tomographic angiography (CTA)-based cardiac wall segmentation, the accurate detection of the endocardial (Endo) and epicardial (Epi) boundaries remains a prerequisite for automated measurements of the cardiac wall thickness (WT). We proposed a novel algorithm for automated three-dimensional (3D) atrial WT (AWT) measurements, including an automatic Endo-Epi boundary detection. We detected the boundaries that were topologically indistinguishable due to an open geometry at the anatomical boundaries using the combined Convex hull and Poisson solver methods. The Laplace equation for the WT measurement was solved by a partial differential equation combining the two detected boundaries of the myocardial wall. We verified the robustness of our algorithm in mask images of the atrial wall that were separated from the CTA images of 20 patients and a phantom model. The accuracy of the automatically detected Endo-Epi boundaries was acceptable as compared to that manually extracted from the phantom model (Dice coefficient = 0.979). The 3D AWTs calculated by the novel automated method from the CTA images obtained from 20 patients with atrial fibrillation had <10% error as compared to the conventional manual AWT measurement method for comparing the regional WT in all locations except the left antral area. The proposed algorithm’s AWT detection time was 27.15±6.99 s per patient, which was 1/40 that of the conventional method. Consequently, our results showed that the proposed automatic 3D AWT measurement algorithm had the potential to significantly improve the efficiency of calculating the AWT while maintaining the existing level of accuracy.

Open Geometry Prover Community Project

Mathematical proof is undoubtedly the cornerstone of mathematics. The emergence, in the last years, of computing and reasoning tools, in particular automated geometry theorem provers, has enriched our experience with mathematics immensely. To avoid disparate efforts,the Open Geometry Prover Community Project aims at the integration of the different efforts for the development of geometry automated theorem provers, under a common "umbrella". In this article the necessary steps to such integration are specified and the current implementation of some of those steps is described.

Isogeometric model reconstruction of open shells via Ricci flow and quadrilateral layout-inducing energies

Isogeometric analysis has received extensive attention in the last decade, but despite its merits, many isogeometric models are still produced manually or semi-manually. In this work, we introduce a new technique using Ricci flow and a carefully constrained minimization to convert trimmed and faceted open geometries into watertight spline models free of trim and suitable for isogeometric analysis with potential for automation. This technique is used to rebuild parts of the US Army’s DEVCOM Generic Hull vehicle and portions of a 1996 Dodge Neon finite element model into trim-free spline models. Isogeometric modal analysis is performed on each to show the viability of this reconstruction framework in generating IGA-suitable splines for shell analysis.

Barrow holographic dark energy in a nonflat universe

We construct Barrow holographic dark energy in the case of nonflat universe. In particular, considering closed and open spatial geometry we extract the differential equations that determine the evolution of the dark-energy density parameter, and we provide the analytical expression for the corresponding dark energy equation-of-state parameter. We show that the scenario can describe the thermal history of the universe, with the sequence of matter and dark energy epochs. Comparing to the flat case, where the phantom regime is obtained for relative large Barrow exponents, the incorporation of positive curvature leads the universe into the phantom regime for significantly smaller values. Additionally, in the case of negative curvature we find a reversed behavior, namely for increased Barrow exponent we acquire algebraically higher dark-energy equation-of-state parameters. Furthermore, we confront the scenario with Hubble parameter measurements and supernova type Ia data. Hence, the incorporation of slightly non-flat spatial geometry to Barrow holographic dark energy improves the phenomenology while keeping the new Barrow exponent to smaller values.

Shaping in the Third Direction; Synthesis of Patterned Colloidal Crystals by Polyester Fabric-Guided Self-Assembly.

A polyester fabric with rectangular openings was used as a sacrificial template for the guiding of a sub-micron sphere (polystyrene (PS) and silica) aqueous colloid self-assembly process during evaporation as a patterned colloidal crystal (PCC). This simple process is also a robust one, being less sensitive to external parameters (ambient pressure, temperature, humidity, vibrations). The most interesting feature of the concave-shape-pattern unit cell (350 μm × 400 μm × 3 μm) of this crystal is the presence of triangular prisms at its border, each prism having a one-dimensional sphere array at its top edge. The high-quality ordered single layer found inside of each unit cell presents the super-prism effect and left-handed behavior. Wider yet elongated deposits with ordered walls and disordered top surfaces were formed under the fabric knots. Rectangular patterning was obtained even for 20 μm PS spheres. Polyester fabrics with other opening geometries and sizes (~300–1000 μm) or with higher fiber elasticity also allowed the formation of similar PCCs, some having curved prismatic walls. A higher colloid concentration (10–20%) induces the formation of thicker walls with fiber-negative replica morphology. Additionally, thick-wall PCCs (~100 μm) with semi-cylindrical morphology were obtained using SiO2 sub-microspheres and a wavy fabric. The colloidal pattern was used as a lithographic mask for natural lithography and as a template for the synthesis of triangular-prism-shaped inverted opals.

Power exhaust concepts and divertor designs for Japanese and European DEMO fusion reactors

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan–Europe broader approach DEMO design activity (BA DDA). Common critical issues are the large power exhaust and its fraction in the main plasma and divertor by the radiative cooling (P rad tot/P heat ⩾ 0.8). Different exhaust concepts in the main plasma and divertor have been developed for Japanese (JA) and European (EU) DEMOs. JA proposed a conventional closed divertor geometry to challenge large P sep/R p handling of 30–35 MW m−1 in order to maintain the radiation fraction in the main plasma at the ITER-level (f rad main = P rad main/P heat ∼ 0.4) and higher plasma performance. EU challenged both increasing f rad main to ∼0.65 and handling the ITER-level P sep/R p in the open divertor geometry. Power exhaust simulations have been performed by SONIC (JA) and SOLPS5.1 (EU) with corresponding P sep = 250–300 MW and 150–200 MW, respectively. Both results showed that large divertor radiation fraction (P rad div/P sep ⩾ 0.8) was required to reduce both peak q target (⩽10 MW m−2) and T e,i div. In addition, the JA divertor performance with EU-reference P sep of 150 MW showed benefit of the closed geometry to reduce the peak q target and T e,i div near the separatrix, and to produce the partial detachment. Integrated designs of the water cooled divertor target, cassette and coolant pipe routing have been developed in both EU and JA, based on the tungsten (W) monoblock concept with Cu-alloy pipe. For year-long operation, DEMO-specific risks such as radiation embrittlement of Cu-interlayers and Cu-alloy cooling pipe were recognized, and both foresee higher water temperature (130 °C–200 °C) compared to that for ITER. At the same time, several improved technologies of high heat flux components have been developed in EU, and different heat sink design, i.e. Cu-alloy cooling pipes for targets and RAFM steel ones for the baffle, dome and cassette, was proposed in JA. The two approaches provide important case-studies of the DEMO divertor, and will significantly contribute to both DEMO designs.

Analysis of the safety of residential buildings under gas explosion loads

The phenomenon of a gas explosion, due to its complexity and possible effects, is the subject of numerous analyses. Gas explosions in a confined space can have various consequences both for users and for the structure itself. The aim of this study was to analyse the possibilities of protecting the structure of the building against the gas explosion effect. The analysis was conducted based on two accidents that occurred in residential buildings. In case of gas explosion in a building, it is crucial to mitigate its effect for both users and the structure. Venting of the explosion is highly effective method to protect the structures of buildings. This process is aimed to create semi-open space for flame propagation, which ensures the reduction of the peak pressure value. In residential buildings windows can be potential vent openings. This paper presents a comparison of four different regulations on the geometry of vent openings. The conducted analysis clearly shows that the safety of the structure is determined not only by the size of the vent openings, but also the strength of materials and construction solutions used in the building, which is not considered in any of the analysed regulations. • The backward analysis in assessing the effect of gas explosion in residential building. • Venting is an effective method of protecting structures against the effects of gas explosion. • Comparison of selected regulations for sizing potential vent openings. • Actual venting explosion regulations do not consider the material and construction solutions. • Properly designed vent openings allow to protect the structure of the building.

Solution of 2D nonstationary problem of hydrogeology for groundwater level detection in different phases of open pit mining

Solution of any problem of hydrogeology, especially pit wall slope stability design, needs information on groundwater levels in different phases of open pit mining. The groundwater level is mostly determined from the numerical modeling of fluid flows. The unsteady fluid flow modeling is a labor-consuming process and it often involves 3D methods of finite elements, finite volumes and finite differences, which requires much time and is sometimes impossible because of the lack of the source data. The fastest way of determining groundwater levels and fluid flow parameters in wanted directions at different times of open pit mining is the solution of 2D nonstationary problem of hydrogeology using the finite element method. The problem solving details are insufficiently described in technical literature, and the present authors instantiate the process by comparing the Rocscience Slide 2 application with the analytical solutions. The 2D unstable groundwater flow in the pit wall was modeled for 5 time periods: open pit mine life for 1460 days; every year until termination of open pit mining; time of the steady-state flow setting 25 years long. The modeling domain is found based on the open pit mine geometry, topography and impact radius. The impact radius is 1357 m. The model identifies a single aquifer with the permeability of 0.69 m/day. The model groundwater level deviates from the in-situ measurements taken in observation wells at a distance of 23 m by 2.5 %.

Experimental and analytical investigation on shear behavior of profiled steel sheet dry board composite wall system

Profiled steel sheet dry board (PSSDB) composite wall/panel system with advantages (like lightweight, enhanced flexibility, low-cost, simple pre-fabrication/erection process, no temporary formwork requirement etc.) is an innovative construction technology that has significant potential to be used as a viable alternative to its conventional counterparts in earthquake prone region. No significant research study is available on the structural behavior of PSSDB composite walls under in-plane shear loading. Nineteen PSSDB panels consisted of single profiled steel sheet (PSS) assembled with single or double plywood dry board (DB) are tested under shear loading to failure. The effects of boundary frame, central opening, concrete in-fill, fastener orientation, and panel geometry on load-deformation response, strength and failure modes are investigated and compared. Analytical models for shear capacities of PSSDB composite system of various configurations are developed based on modified code-based/existing equations and their performance validated using experimental results. These analytical models can be used by engineers in designing PSSDB composite system for practical construction.

Characterization of a Compound Heterozygous SLC2A9 Mutation That Causes Hypouricemia.

Renal hypouricemia is a rare genetic disorder. Hypouricemia can present as renal stones or exercise-induced acute renal failure, but most cases are asymptomatic. Our previous study showed that two recessive variants of SLC22A12 (p.Trp258*, pArg90His) were identified in 90% of the hypouricemia patients from two independent cohorts: the Korean genome and epidemiology study (KoGES) and the Korean Cancer Prevention Study (KCPS-II). In this work, we investigate the genetic causes of hypouricemia in the rest of the 10% of unsolved cases. We found a novel non-synonymous mutation of SLC2A9 (voltage-sensitive uric acid transporter) in the whole-exome sequencing (WES) results. Molecular dynamics prediction suggests that the novel mutation p.Met126Val in SLCA9b (p.Met155Val in SLC2A9a) hinders uric acid transport through a defect of the outward open geometry. Molecular analysis using Xenopus oocytes confirmed that the p.Met126Val mutation significantly reduced uric acid transport but does not affect the SLC2A9 protein expression level. Our results will shed light on a better understanding of SLC2A9-mediated uric acid transport and the development of a uric acid-lowering agent.

Study of the geometry of open channels in a layer-bed-type microfluidic immobilized enzyme reactor

This paper aims at studying open channel geometries in a layer-bed-type immobilized enzyme reactor with computer-aided simulations. The main properties of these reactors are their simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make these devices one of the simplest yet efficient enzymatic microreactors. The high surface-to-volume ratio of the reactor was achieved using narrow (25–75 μm wide) channels. The simulation demonstrated that curves support the mixing of solutions in the channel even in strong laminar flow conditions; thus, it is worth including several curves in the channel system. In the three different designs of microreactor proposed, the lengths of the channels were identical, but in two reactors, the liquid flow was split to 8 or 32 parallel streams at the inlet of the reactor. Despite their overall higher volumetric flow rate, the split-flow structures are advantageous due to the increased contact time. Saliva samples were used to test the efficiencies of the digestions in the microreactors.Graphical abstract

Investigation into the influence of macro-scale geometry on the stability of underground excavations in layered rock masses

Underground excavations for the development of infrastructure, mining operations, waste management etc. require support measures to ensure stability both during their construction and operational phases, which highly depends on the rock mass strength and deformability. Discontinuities within the rock mass are intrinsic features which determine said strength and deformability and affect the excavation stability. Several defining parameters demonstrate that rock mass variability has significant control in the material response during an excavation, especially in sedimentary rocks. In this paper, the Thornhill Sandstone is examined by applying numerical analysis and its mechanical response is investigated under several scenarios with varying excavation geometries, stress conditions while incorporating the influence of discontinuities explicitly within the numerical model. A two-dimensional parametric analysis is performed by applying the Finite Element Method (FEM) and integrating Discrete Fracture Networks (DFNs). More specifically, four different excavation geometries and three different in situ stress regimes are investigated. Drawing on the results, this paper provides insights for tunnel design optimisation when layered rock masses are encountered during an excavation in various underground stress environments with different opening geometries.

Rock engineering challenges in post-mining

A legacy of environmental challenges with abandoned mines remains for many generations. The challenges include among others: (i) danger from sinkholes above shallow old mine workings and (ii) effects of rising water level in deep mines. Abandoned shallow mines show after > 20 years no damaging subsidence. Sinkholes, however, may still develop by structurally controlled failure. Main contributing factors are the geometry of an underground opening. Geological factors include the resource type (orebody or seam), height of rock overburden and cohesive soil, water flow and discontinuity spacing. The latter determines the bulking factor of the displaced roof and thus the maximum caving height. For steeply inclined openings it must be considered whether the caved rock moves down the dip and prevents self-stabilization. Rising water levels in deep abandoned mines may induce seismic events. Despite significant progress in monitoring and numerical methods there is still no appropriate geological or rock mechanical basis for explaining or predicting water pressure induced seismic events. Some research topics are suggested to approach this issue.

On the use of effective thermophysical properties to predict the melting process of composite phase change materials with coarse structures

Composite PCMs combining metallic foam and paraffin are widely used as phase change materials (PCMs) to tailor the properties of pure PCMs and enhance the thermal energy storage/release. For the complex composites structures, the transient thermal response prediction by direct simulation (DS) is not easy in term of geometry generation and computation. The volume-averaged model (1T model) considering the composite PCMs as homogeneous media is sometimes used to deal with thermal transport in Composite PCMs, not always with a sufficiently good local description of non-steady conditions. The paper carries out a set of cases where a composite PCM modelled as an open-pore body-centred cell made of Aluminium (Al) filled with paraffin (i) to investigate the combined effects of the geometry of the unit cell (side length, porosity), the composite sample (sample height) and boundary conditions (heat input) on the heat response; (ii) to identify the local/overall errors in temperature and volume fraction of liquid PCM (and thus of stored heat) induced by the use of 1T model for various geometry/heat flux combinations. Analytical equations are proposed to predict the maximum temperature difference between Al and PCM as well as the maximum temperature difference calculated by applying the 1T or DS model as a function of the open cell structure geometry and heat flux. The main novelty introduced in the paper is the analytical model used to quantify the maximum local error on molten PCM volume fraction for the 1T model, and thus on heat stored/released. The model supplies good local thermal response predictions for fine structures and lower heat flux input. Nevertheless, errors in the volume fraction of molten PCMs predicted for the whole sample are far lower and the 1T model can be easily applied in a wider range of geometry/conditions.

Optimization of a diesel/natural gas dual fuel engine under different diesel substitution ratios

Dual fuel engines are attracting more and more attentions due to their low emissions and high efficiency compared with traditional single fuel engines. However, complex parameters coupling remains challengeable issues in dual fuel engine optimization. Here, the objective of this study is to optimize the diesel fuel ratio and the combustion parameters of a diesel/natural gas dual fuel engine by coupling the genetic algorithm with a 3D CFD engine combustion simulation. A total number of 9 parameters were optimized simultaneously. The results indicate that the optimized diesel injection timing is gradually postponed with the increase of the pilot diesel quantity. The indicated specific energy consumption (ISEC) can be achieved when the fuel ratio is in the range of 0.2 to 0.3 and injection timing is in the range of −30 to −15 °CA ATDC. The open bowl geometry is chosen in all the Pareto front solutions, which indicates the advantages of this chamber type for the dual fuel combustion mode. The compression ratios, exhaust gas recirculation (EGR) rates are gradually concentrated to several optimal values, while the swirl ratios are widely distributed in the range from 0.5 to 1.2. Furthermore, the temporal and spatial distribution of the cylinder temperature, NOx and CH4 emissions analysis showed that the higher diesel fuel ratio will generate a widely distributed high temperature region, which is beneficial for the methane oxidation. In addition, lower EGR rate and higher diesel injection quantity are beneficial to methane oxidation. This work illustrates a new optimization method for dual fuel engine complex parameters.

Tuning the CHA framework composition by isomorphous substitution for CO2/CH4 separation

Chemically and structurally flexible zeolites that adapt to coordinate extra-framework cations show a rich variety of gas adsorption behavior. Zeolite framework composition can be tuned to optimize pore geometry and host-guest interaction to improve selectivity. Herein, we report the study on the influence of zeolite framework nature on the separation of CO2/CH4, for CHA system containing variable isomorphously substituted heteroelements (none, B, Al, Ga, and Ti). Their performance has been evaluated by single-component isotherms and the overall separation ability was found to be related to both the geometry of 8-ring pore apertures in CHA and interaction between zeolite host and guest molecules, as revealed by Rietveld refinement of PXRD after dehydration and variable-pressure FTIR spectroscopy. Nearly isotropic geometry of the 8-ring pore opening in Al-CHA (3.84 × 3.89 Å) was obtained, while Ga-CHA exhibits the largest distortion (3.76 × 3.93 Å). Despite the smallest ionic radius of B, both the pore size of 8-ring (3.76 × 3.86 Å) as well as the unit cell volume are the smallest amongst the studied materials. Due to the combination of both the textural and the chemical factors, the maximum CO2 capacity and separation selectivity over CH4 follows the order Al-CHA > Ga-CHA > B-CHA ≈ Si-CHA > Ti-CHA. These observations suggest that tuning the framework composition of zeolite can strongly influence the separation of small molecules such as CO2 and CH4.

Biodegradable Elastic Sponge from Nanofibrous Biphasic Calcium Phosphate Ceramic as an Advanced Material for Regenerative Medicine

AbstractBiodegradable porous calcium phosphate (CaP) ceramics are widely used as synthetic graft substitutes for bone regeneration, owing to their chemical and structural similarity to bone and associated bioactivity in terms of bone‐bonding, osteoconductive, and even osteoinductive properties. Nevertheless, the intrinsic brittleness and poor processability of porous CaP ceramics strongly impair their clinical applicability. Herein, a biphasic calcium phosphate (BCP) sponge is developed that consists of a self‐supporting network of seamlessly interwoven hydroxyapatite nanowires and β‐tricalcium phosphate nanofibers and possesses a highly interconnected porous structure with open cell geometry and ultrahigh porosity. Owing to its unique properties, the ceramic sponge can be easily processed into various shapes and dimensions, such as cylindrical scaffolds and thin, flexible membranes. Moreover, the BCP sponge can be introduced into a bone defect in a compacted or folded state from a syringe and, upon wetting, expand to its original shape, thereby filling the cavity. The nanofibrous sponge gradually degrades in vitro and rapidly mineralizes when immersed in simulated body fluid. Moreover, it adsorbs significantly more proteins than a conventional porous BCP ceramic. Finally, the nanofibrous sponge supports the attachment, proliferation, and osteogenic differentiation of human mesenchymal stromal cells comparable to the conventional porous BCP ceramic.

HEE and HSC for flavors: perturbative structure in open string geometries

Introduction of electric field in the D-brane worldvolume induces a horizon in the open string geometry perceived by the brane fluctuations. We study the holographic entanglement entropy (HEE) and subregion complexity (HSC) in these asymptotically AdS geometries in three, four and five dimensions aiming to capture these quantities in the flavor sector introduced by the D-branes. Both the strip and spherical subregions have been considered. We show that the Bekenstein-Hawking entropy associated with the open string horizon, which earlier failed to reproduce the thermal entropy in the boundary, now precisely matches with the entanglement entropy at high temperatures. We check the validity of embedding function theorem while computing the HEE and attempt to reproduce the first law of entanglement thermodynamics, at least at leading order. On the basis of obtained results, we also reflect upon consequences of applying Ryu-Takayanagi proposal on these non-Einstein geometries.