Mixed Volume Research Articles

Study of hydrogen bonding interactions in ethylene glycol-water binary solutions by Raman spectroscopy

EG (ethylene glycol) is a good model system for the study of the fundamental hydrogen bonds in aqueous solutions. Using Raman spectroscopy, we have investigated the EG volume fraction induced variation in the hydrogen bonding interactions and conformations of EG-H2O (water) binary solutions. New hydrogen bonding networks is evidenced by the appearance of remarkable changes in Raman spectra and the full width at half maximum (FWHM) when the mixing volume ratio is 0.5. The H-bond in water molecules firstly strengthened and then weakened with the increasing concentration of EG. Meanwhile, the dominant association structure also changed from H2O-H2O to EG-H2O in binary solutions in this process. We provide a simple but effective method for studying EG-H2O binary solutions. It also has exciting potential prospects and can be easily extended to other mixing situations.

Global random walk solvers for fully coupled flow and transport in saturated/unsaturated porous media

In this article, we present new random walk methods to solve flow and transport problems in saturated/unsaturated porous media, including coupled flow and transport processes in soils, heterogeneous systems modeled through random hydraulic conductivity and recharge fields, processes at the field and regional scales. The numerical schemes are based on global random walk algorithms (GRW) which approximate the solution by moving large numbers of computational particles on regular lattices according to specific random walk rules. To cope with the nonlinearity and the degeneracy of the Richards equation and of the coupled system, we implemented the GRW algorithms by employing linearization techniques similar to the L-scheme developed in finite element/volume approaches. The resulting GRW L-schemes converge with the number of iterations and provide numerical solutions that are first-order accurate in time and second-order in space. A remarkable property of the flow and transport GRW solutions is that they are practically free of numerical diffusion. The GRW solvers are validated by comparisons with mixed finite element and finite volume solvers in one- and two-dimensional benchmark problems. They include Richards’ equation fully coupled with the advection-diffusion-reaction equation and capture the transition from unsaturated to saturated flow regimes.

Microstructural Analyses of Cement-Based Binders in Stabilizing Champlain Sea Clay

This research investigated the strength development and the microstructural change in Champlain Sea clay when treated with five different cement-based binders. Champlain Sea clay, a marine clay, is commonly found in St. Lawrence Lowlands in eastern Canada. The unconfined compressive strength tests were conducted to measure the shear strength development of treated clay under different binder type, binder dosage, and curing time conditions. The scanning electronic microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to investigate the microstructural changes in the specimens. Based on the test results, it was found that cement is efficient to treat Champlain Sea clay with a significant strength improvement. For Champlain Sea clay used in this study, the optimum cement dosage was found to be around 100 kg/m3 per mixed volume in terms of strength improvement and cost-effectiveness. The clay samples treated with a mix of cement and cement kiln dust and a mix of cement with slag showed a substantial strength increase over time. These results proved the feasibility of using cement kiln dust mix or slag to replace a portion of cement in treating Champlain Sea clay. Based on SEM observations, a substantial transformation was observed in the microstructure of the clay due to cement mixing. A large amount of clay-binder aggregates were formed and the hydration products filled the porous network of the clay samples, which results in a strength improvement in the treated clay. Based on the XRD analysis, hydration products, such as calcium silicate hydrate and calcium tecto-dialumodisilicate tetrahydrate, were formed in the cement-treated clay specimens, which explains the strength improvement of Champlain Sea clay due to cement mixing.

Study of Jatropha curcas Linn and Olea europaea as Bio-Oil Lubricant to Physical Properties and Wear Rate

This paper presents a study on the effect of the mixed volume fraction of Jatropha curcas Oil (JCO) and Olea europea or extra virgin olive oil (EVOO) on the physical properties of the oil, especially viscosity, density and water content. This study also presents the mechanical properties examination result, especially its effect on the wear rate of the pin on disc tribometer results on ST 41 steel specimens, using optical microscopy. The independent variables used were variations of the oil mixture: 0, 20, 40, 60, 80 and 100% EVOO. With the increase in the percentage of the EVOO mixture in JCO, the density decreases. The result of water content in a higher percentage of JCO, the higher the water content value of 0.1217%. Pure JCO has the higher viscosity value of 1.9084 m2/s. The higher the percentage of JCO, the lower the wear rate value obtained. In the tribometer test, the pin on disk mixture of pure JCO has the lower wear value of 5.09 m2/s.

Local and Remote Influences on the Heat Content of Southern Ocean Mode Water Formation Regions

AbstractThe Southern Ocean (SO) is a crucial region for the global ocean uptake of heat and carbon. There are large uncertainties in the observations of fluxes of heat and carbon between the atmosphere and the ocean mixed layer, which lead to large uncertainties in the amount entering into the global overturning circulation. In order to better understand where and when fluxes of heat and momentum have the largest impact on near‐surface heat content, we use an adjoint model to calculate the linear sensitivities of heat content in SO mode water formation regions (MWFRs) to surface fluxes. We find that the heat content of these regions is, in all three basins, most sensitive to same‐winter, local heat fluxes, and to local and remote wind one to eight years (the maximum lead‐time of our simulations) previously. This is supported by sensitivities to potential temperature changes, which reveal the sources of the MWFRs as well as dynamic links with boundary current regions and the Antarctic Circumpolar Current. We use the adjoint sensitivity fields to design a set of targeted perturbation experiments, allowing us to examine the linear and non‐linear responses of the heat content to changes in surface forcing. In these targeted experiments, the heat content is sensitive to both temperature changes and mixed layer volume changes in roughly equal magnitude.

Experimental and modeling based dead-volume detection for externally stirred tanks

The role of homogenization in industrial systems is to provide proper feedstock and product properties to ensure the smooth operation of industrial systems. In this paper, an external recirculation mixing tank with unique construction for the homogenization of stratified liquids is investigated. The main focus of the work is to determine the relationship between tank geometry and dead volumes present in the unit. The unit’s geometry was altered by changing the volume of the tank during experimental work. Residence time based methods were applied for the investigation of the system. For a thorough investigation of the unit, computational fluid dynamics methods were employed in COMSOL Multiphysics to obtain data about the velocity field in the unit. Experimental and modeling data were compared and used to understand the impact of the tank geometry on the flow characteristics of the system, the dead volumes present and thus on the required homogenization time. Optimal tank geometry was chosen for the mixing process to minimize dead volume ratios and to allow more profitable operation. It was observed that the increase in the tank’s volume caused more significant amounts of dead volume to form with an increase in dead volume ratio from 20% to 27% for the smallest and largest geometries respectively. Thus, it was concluded that the geometry with the smallest volume is optimal for mixing since it encompasses the largest ratio of active mixing volumes. The methods provided can be used to analyze and optimize other mixing units in which stratified fluids are to be homogenized.

Influence of buoyancy force on Ag-MgO/water hybrid nanofluid flow in an inclined permeable stretching/shrinking sheet

The present work explored the heat transfer and boundary layer flow of a hybrid nanofluid past an inclined stretching/shrinking sheet with suction and buoyancy force effects. Silver (Ag) and magnesium oxide (MgO) are considered as the hybrid nanoparticles and suspended in water to form Ag-MgO/water hybrid nanofluid. The partial differential equations (PDEs) are converted into a system of ordinary differential equations (ODEs) by employing appropriate similarity transformation. The simplified mathematical model is then solved numerically using the bvp4c solver in the MATLAB software. The effects of governing parameters, namely the inclination angle, suction, stretching/shrinking, buoyancy or mixed convection and nanoparticle volume fraction parameters on the velocity and temperature profiles as well as skin friction coefficient and local Nusselt number are examined and presented graphically. The results are proven to have two solutions for both stretching and shrinking case, which consequently lead to the implementation of a stability analysis, hence confirming that only the first solution is stable. In addition, the local Nusselt number increases when the angle of inclination and suction parameters increase. The results also reveal that increasing values of Ag nanoparticle volume fraction in MgO/water nanofluid declines the local Nusselt number.

Application of bulk fluid volatile chemistry to exploration for metasedimentary rock-hosted orogenic gold deposits: An example from the Meguma terrane, Nova Scotia, Canada

Disseminated gold (Au) deposits hosted in metasedimentary rocks present unique exploration challenges because the Au is generally very fine-grained or refractory, and not vein-hosted. Exploration programs in such settings rely on extensive lithogeochemical surveys, lesser structural analysis, and little emphasis on ore-fluid geochemistry. The Moose River anticline (MRA) in the Lower Paleozoic Meguma terrane (Nova Scotia, Canada) hosts several high-tonnage (~10–20 Mt), low-grade (≤1–4 g/t Au) Au deposits comprised of disseminated ± quartz vein-hosted mineralization in metamudstones. Here, the Touquoy deposit hosted in the MRA is used to evaluate a new approach to geochemical exploration by examining if the volatile chemistry of host rocks preserves a signature related to Au mineralization, using a gas chromatographic (GC) technique that analyzes bulk volatiles released from crushed rock. Since GC is a bulk analytical technique, (i.e., multiple generations of fluid inclusion volatiles yielding a mixed analytical volume), the volatile composition of fluid inclusions were also investigated in-situ using laser Raman microspectroscopy to reconcile bulk analyses with the composition and abundance of different inclusion types. Inclusions in quartz pressure shadows associated with porphyroblasts host N2 ± CH4-dominant vapor phases and represent wall rock-equilibrated fluids. In comparison, fluid inclusion vapor phases in quartz veinlets crosscutting the metamudstones are more complex in composition and show a continuum between CO2-dominant and N2 ± CH4-dominant compositions; the former is interpreted as the fluid responsible for Au mineralization in the Meguma terrane (e.g., H2O-CO2 ± CH4 ± N2 fluids). GC shows statistically significant differences in the compostion of the bulk volatiles released from crushed metamudstones from the Touquoy deposit (n = 21) and barren (n = 24) settings. Whereas the former commonly contain detectable CO2 (50% of samples; LoQ(CO2) ~ 10−10 mol/g), only ~4% of metamudstones from barren settings along the MRA contain CO2, yielding a t-test p-value of 0.0103 between the two sample populations. Whereas the more frequent detection of CO2 in mineralized samples is related to increasing carbonate alteration proximal to Au mineralization, no correlation is observed between bulk CO2 abundance and Au grade. Additionally, anomalous differences in abundances of released C3 (t-test p-value = 0.043) and C4 (t-test p-value = 0.03) hydrocarbons (HC) are recognized between the two populations (LoQ(HC) ca. 10−13 to 10−12 mol/g), with Touquoy metamudstones having higher Σ(C3)/CH4 and Σ(C4)/CH4 ratios compared to barren equivalents. The compositional differences suggest that more aqueous-carbonic fluids infiltrated metamudstone units where locally favorable physical and/or chemical conditions were present, resulting in increased Au endowment. The relative increase in fluid flux, and thus Au grade, resulted in more trapped CO2 (i.e., resulting from more trapped inclusions and/or greater CO2 fluid component) and modification to hydrocarbon signatures through homologation and/or degradation reactions. Rigorous sample preparation ensures these compositional differences are related to paleofluids and not contamination.Tentatively, the results suggest that the bulk analysis of volatiles released from fluid inclusions in metamudstones may be a useful vectoring tool for disseminated Au mineralization in Meguma-type gold systems and similar environments (e.g., Carlin-type). This technique may be appropriately scaled to complement exploration drilling programs and may be more sensitive in determining ore proximity than often ambiguous pathfinder elements.

Phase Equilibrium and Density of CO2 + Acetic Acid Systems from 308.15 to 338.15 K and 15 to 45 MPa.

Using a high-pressure phase equilibrium apparatus and vibrating-tube densimeter, phase transition pressures of CO2 (1) + acetic acid (2) binary systems with x2 = 0.000, 0.107, 0.163, 0.222, and 1.000 were measured under temperatures from 308.15 to 338.15 K. Besides, the densities at the same composition and temperature under pressure from 15 to 45 MPa were also detected, and the volumes of mixing (ΔVm) were calculated. Three prediction models (SRK EOS, PC-SAFT EOS, and TS model) were introduced to predict and correlate the density of binary systems, which was found to have positive relationships with temperature and acetic acid concentration and a negative relationship with pressure. Thereinto, the variation trend of CO2 density with pressure tends to be flat under high pressure, and which of acetic acid density increased linearly with pressure. ΔVm are negative, and their absolute value increases with the increase of temperature and the decrease of pressure. The work herein could provide a theoretical guide and basic data for supercritical CO2 extraction technology and CO2 application in oil field development.

New insights and coupled modelling of the structural and thermodynamic properties of the LiF-UF4 system

LiF-UF4 is a key binary system for molten fluoride reactor technology, which has not been scrutinized as thoroughly as the closely related LiF-ThF4 system. The phase diagram equilibria in the system LiF-UF4 are explored in this work with X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The short-range ordering in the molten salt solution is moreover surveyed with Extended X-ray Absorption Fine Structure spectroscopy (EXAFS) and interpreted using a combination of standard fitting of the EXAFS data and Molecular Dynamics (MD) simulations with a Polarizable Ion Model (PIM) potential. The density, excess molar volume, thermal expansion, heat capacity, and enthalpy of mixing are extracted from the MD simulations across a range of temperatures and compositions; the behavior is non-ideal, with reasonably good agreement with the experimental data. Also calculated is the distribution of heteropolyanions in the liquid solution, and modelled using the quasi-chemical formalism in the quadruplet approximation taking into account the existence of the single-shell complexes [UF7]3−, [UF8]4−, and the dimeric species [U2F14]6−. Subjecting the optimization of the excess Gibbs energy parameters of the liquid solution to the constraints of the phase diagram data and local structure of the melt as derived from the EXAFS and coupled MD simulations, a CALPHAD-type assessment is proposed, linking structural and thermodynamic properties, with a rigorous physical description of the melt.

Numerical simulation of spherical bubble collapse by a uniform bubble pressure approximation and detailed description of heat and mass transfer with phase transition

A mathematical model for the simulation of the dynamics of spherical vapor-air bubbles and its numerical implementation is presented. Heat and mass transfer and phase transition in terms of evaporation and condensation as well as air absorption and desorption are considered. Flow variables are discretized by a mixed finite volume / finite difference scheme and solved either by a Crank-Nicolson or Runge-Kutta scheme. Due to the assumption of homogeneous bubble pressure (homobaricity), the solution of momentum equations is restricted to the Rayleigh-Plesset equation which makes the model computationally efficient. The model is validated by measurement data for bubble growth and applied to bubble collapse and rebound. By a comparison with Navier-Stokes results from literature, the homobaricity assumption is shown to be appropriate even in the last stage of bubble collapse. The relation of the local velocity and temperature field with heat and mass transfer is discussed. Equilibrium bubble interface conditions (liquid and gaseous side have the same temperature and chemical potential) are compared to non-equilibrium conditions and are shown to yield the same local velocity and temperature field for each stage of bubble collapse and rebound.

A new activity model for Fe\u2013Mg\u2013Al biotites: I\u2014Derivation and calibration of mixing parameters

A new activity model for Fe–Mg–Al biotites is formulated, which extends that of Mg–Al biotites (Dachs and Benisek, Contrib Mineral Petrol 174:76, 2019) to the K2O–FeO–MgO–Al2O3–SiO2–H2O (KFMASH) system. It has the two composition variables XMg = Mg/(Mg + Fe2+) and octahedral Al, and Fe–Mg and Mg–Al ordering variables resulting in five linearly independent endmembers: annite (Ann, K[Fe]M1[Fe]2M2[Al0.5Si0.5]2T1[Si]2T2O10(OH)2, phlogopite (Phl, K[Mg]M1[Mg]2M2[Al0.5Si0.5]2T1[Si]2T2O10(OH)2, ordered Fe–Mg biotite (Obi, K[Fe]M1[Mg]2M2[Al0.5Si0.5]2T1[Si]2T2O10(OH)2, ordered eastonite (Eas, K[Al]M1[Mg]2M2[Al]2T1[Si]2T2O10(OH)2, and disordered eastonite (Easd, K[Al1/3Mg2/3]M1[Al1/3Mg2/3]2M2[Al]2T1[Si]2T2O10(OH)2. The methods applied to parameterize the mixing properties of the model were: calorimetry, analysis of existing phase-equilibrium data, line-broadening in powder absorption infrared (IR) spectra, and density functional theory (DFT) calculations. For the calorimetric study, various biotite compositions along the annite–phlogopite, annite–siderophyllite (Sid, K[Al]M1[Fe]2M2[Al]2T1[Si]2T2O10(OH)2), and annite–eastonite joins were synthesized hydrothermally at 700 °C, 4 kbar and logfO2 of around − 20.2, close to the redox conditions of the wüstite–magnetite oxygen buffer at that P–T conditions. The samples were characterised by X-ray powder diffraction (XRPD), energy-dispersive scanning electron microprobe analysis, powder absorption IR spectroscopy, and optical microscopy. The samples were studied further using relaxation calorimetry to measure their heat capacities (Cp) at temperatures from 2 to 300 K. The measured Cp/T was then integrated to get the calorimetric (vibrational) entropies of the samples at 298.15 K. These show linear behaviour when plotted as a function of composition for all three binaries. Excess entropies of mixing are thus zero for the important biotite joins. Excess volumes of mixing are also zero within error for the three binaries Phl-Ann, Ann-Sid, and Ann-Eas. KFMASH biotite, therefore, has excess enthalpies which are independent of pressure and temperature (WGij = WHij). A least-squares procedure was applied in the thermodynamic analysis of published experimental data on the Fe–Mg exchange between biotite and olivine, combined with phase-equilibrium data for phlogopite + quartz stability and experimental data for the Al-saturation level of biotite in the assemblage biotite–sillimanite–sanidine–quartz–H2O to constrain enthalpic mixing parameters and to derive enthalpy of formation values for biotite endmembers. For Fe–Mg mixing in biotite, the most important binary, this gave best-fit asymmetric Margules enthalpy parameters of WHAnnPhl = 14.3 ± 3.4 kJ/mol and WHPhlAnn = −8.8 ± 8.0 kJ/mol (3-cation basis). The resulting asymmetric molar excess Gibbs free energy (Gex) departs only slightly from ideality and is negative at Fe-rich and positive at Mg-rich compositions. Near-ideal activity–composition relationships are thus indicated for the Ann–Phl binary. The presently used low value of − 2 kJ/mol for the enthalpy change of the reaction 2/3 Phl + 1/3 Ann = Obi is generally confirmed by DFT calculations that gave − 2 ± 3 kJ/mol for this ∆HFe–Mg order, indicating that Fe–Mg ordering in biotite is weak. The large enthalpy change of ∆HMg-Al disorder = 34.5 kJ/mol for the disordering of Mg and Al on the M sites in Eas (Dachs and Benisek 2019) is reconfirmed by additional DFT calculations. In combination with WHPhlEas = 10 kJ/mol, which is the preferred value of this study describing mixing along the Phl–Eas join, Mg–Al disordering over the M sites of biotite is predicted to be only significant at high temperatures > 1000 °C. In contrast, it plays no role in metamorphic P–T settings.

Density and viscosity of CO2 + ethyl acetate binary systems from 308.15 to 338.15 K and 15 to 45 MPa

Combined with a high-pressure vibrating-tube densimeter and capillary viscometer, the density and viscosity of CO2(1)+ethyl acetate(2) binary systems with x2 = 0.000, 0.036, 0.075, 0.117, 0.163, and 1.000 were measured under conditions of 308.15–338.15 K and 15–45 MPa. In addition, the volumes of mixing (ΔVm) and viscosity deviation (Δη) were also calculated. The results illustrate that the density and viscosity of all systems increased with decreasing temperature and increasing pressure. The viscosity of the binary systems increased with increasing ethyl acetate concentration, and the density reached a maximum point under high pressure conditions (40 and 45 MPa). Moreover, ΔVm was negative and found to be reduced with a temperature decrease and pressure increase. Δη was positive except for pressures at 15 MPa, and these were found to be improved when increasing the temperature and pressure. The PC-SAFT equation of state and the Toscani-Szwarc model were applied to predict and correlate the density of the systems. For viscosity, different types of models were used. The Chung-Lee-Starling model and TRAPP model were introduced to predict pure systems, the Song mixing rule was used for mixed system viscosity correlation, and the Baylaucq equation was applied for unitary and binary system viscosity correlation. Four types of statistical values (AAD, bias, SDV, and RMS) were used to evaluate these models for each system.

Investigation of the fabrication, characterization, protective effect and digestive mechanism of a novel Pickering emulsion gels

The current research provided a simple method to construct Pickering emulsion gels based on chitosan hydrochloride-carboxymethyl starch (CHC-CMS) nanogels stabilized Pickering emulsions and curdlan, which can offer a new strategy for the design of low-fat food. The hardness, elasticity, water holding capacity and swelling ratio of emulsion gels were influenced by the mixed volume ratios and curdlan concentration. The freeze-thaw stability of the emulsion gels was better than that of the Pickering emulsions. The shear-thinning property and solid-like behavior of Pickering emulsion gels were observed in the linear viscoelastic regions. Confocal laser scanning microscopy exhibited that most of emulsion droplets with a regular spherical shape were evenly distributed, indicating that little or no coalescence happened in the process of gelation. Moreover, emulsion gels displayed a smooth and dense wave-like structure. During the storage test at 55 °C for 14 days, emulsions gels provided the better protective effect on β-carotene than Pickering emulsions. Furthermore, the degradation behavior of β-carotene in emulsion gels conformed to a first-order kinetic model. The corresponding half-life time (t1/2) of β-carotene in the emulsion gels prepared by Pickering emulsions with 50% oil phase fraction increased from 19 days to 30 days with the concentration of curdlan increasing from 0 wt% to 3 wt%. The Pickering emulsion gels had the lower free fatty acid released compared to Pickering emulsions. Overall, these results demonstrated the potentials of Pickering emulsion gels in protecting bioactive components and designing low-fat food alternatives.

Multi-particle models of molecular diffusion for Lagrangian simulation coupled with LES for passive scalar mixing in compressible turbulence

Lagrangian simulation coupled with large eddy simulation (LES) is studied for turbulent scalar mixing in compressible flows, where Lagrangian simulation solves advection-diffusion equations with computational particles. In Lagrangian simulation, a molecular diffusion term needs to be modeled with a so-called mixing model, which also requires modeling the dissipation rate of scalar fluctuations. The present study extends a particle-based subgrid-scale model for the scalar dissipation rate to compressible flows, and its validity in compressible turbulence is examined with direct numerical simulation databases of a temporally evolving turbulent planar jet with a jet Mach number of 0.6 or 1.6. A priori test confirms that the model can well predict the mean scalar dissipation rate in the subsonic and supersonic turbulent jets. The model hardly depends on the spatial distribution of the particles when the number of particles used in the model is about 12. However, the scalar dissipation rate tends to be overestimated by the model in regions with large dilatation fluctuations although such regions with strong compressibility effects occupy only a small part of the flow. Lagrangian simulation coupled with LES of the turbulent jet is also performed with the scalar dissipation model combined with the mixing volume model. Lagrangian simulation with these models effectively predicts passive scalar statistics, such as averages, rms fluctuations, and turbulent fluxes, in the turbulent jet with both subsonic and supersonic jet velocities. The scalar dissipation model well predicts the coarse-grained scalar dissipation rate in Lagrangian simulation. The present results confirm that the mixing volume model combined with the particle-based model of the scalar dissipation rate is useful in Lagrangian simulation coupled with LES, which is a promising approach for simulating high-speed turbulent reacting flows as reaction terms appear in Lagrangian simulation in a closed form.

Consistency, convergence and error estimates for a mixed finite element–finite volume scheme to compressible Navier–Stokes equations with general inflow/outflow boundary data

Abstract We study convergence of a mixed finite element-finite volume scheme for the compressible Navier–Stokes equations in the isentropic regime under the full range $1<\gamma <\infty $ of the adiabatic coefficients $\gamma $ for the problem with general nonzero inflow–outflow boundary conditions. We propose a modification of Karper’s scheme (2013, A convergent FEM-DG method for the compressible Navier–Stokes equations. Numer. Math., 125, 441–510) in order to accommodate the nonzero boundary data, prove existence of its solutions, establish the stability and uniform estimates, derive a convenient consistency formulation of the balance laws and use it to show the weak convergence of the numerical solutions to a dissipative solution with the Reynolds defect introduced in Abbatiello et al. (2021, Generalized solutions to models of compressible viscous fluids. Discrete Contin. Dyn. Syst., 41, 1--28). If the target system admits a strong solution then the convergence is strong towards the strong solution. Moreover, we establish the convergence rate of the strong convergence in terms of the size of the space discretization $h$ (which is supposed to be comparable with the time step $\varDelta t$). In the case of the nonzero inflow–outflow boundary data all results are new. The latter result is new also for the no-slip boundary conditions and adiabatic coefficients $\gamma $ less than the threshold $3/2$.

Analysis of the effect of directional traffic volume and mix on road traffic crashes at three-legged unsignalized intersections

Traffic volume is the most common factor associated with road traffic crash frequency. Use of aggregate volume measures may lead to biased prediction of crash frequencies. Disaggregate analysis that involve hourly volumes can better explain this effect. In low and middle-income countries traffic mix may vary with respect to direction of travel on a road and such variation in proportion leads to crashes and conflicts among crossing vehicles at unsignalized intersections. This paper aims to explore the above relationship in the context of three-leg unsignalized intersections in Malaysia. First exploratory analysis of geometric and traffic variables was performed and their relationship with the crash frequency and type of conflicts was examined. Then probability of crashes was calculated with respect to the percentage of motorcycles that moved in a certain direction and proportion between volume in each direction. Segregation of the data with respect to traffic direction and traffic mix indicated that sites with less percentage of motorcycles moving in the far side direction experienced more crashes as compared to sites with greater percentage of motorcycles moving in the far side direction, given the condition that the volume ratio between each direction was larger than one. Results showed that the chances of crashes and serious conflicts increased upto 25% and 67% respectively; as the percentage of motorcycles that moved in the far side direction decreased from 31%, subject to the condition that the ratio of volume between each direction remained greater than one. It was concluded that traffic mix and traffic volume together influence the crash frequency at unsignalized intersections.

Volume preserving flow by powers of the $k$th mean curvature

We consider the flow of closed convex hypersurfaces in Euclidean space $\mathbb{R}^{n+1}$ with speed given by a power of the $k$‑th mean curvature $E_k$ plus a global term chosen to impose a constraint involving the enclosed volume $V_{n+1}$ and the mixed volume $V_{n+1-k}$ of the evolving hypersurface. We prove that if the initial hypersurface is strictly convex, then the solution of the flow exists for all time and converges to a round sphere smoothly. No curvature pinching assumption is required on the initial hypersurface.

Application of Tanks-in-Series Model to Characterize Non-Ideal Flow Regimes in Continuous Casting Tundish

This study describes a new tanks-in-series model for analyzing non-ideal flow regimes in a single-strand tundish. The tundish was divided into two interconnected tanks, namely an inlet tank and an outlet tank. A water model experiment was carried out to separately measure the residence-time distribution (RTD) of the two tanks. Drift beads were adopted in the water model experiment to simulate the non-metallic inclusions in molten steel. Dead volume fraction was evaluated by analyzing measured RTD curves. The ratio between mixed flow volume and plug flow volume was proposed as a new criterion to evaluate the inclusion removal. In the inlet tank, a higher mixed flow fraction was preferred to effectively release turbulent kinetic energy and enhance inclusion collision growth. In the outlet tank, a higher plug flow fraction was preferred to facilitate inclusion removal by flotation. The optimal positions of the weir were recommended based on the RTD analysis and the inclusion removal from the results of water model experiments. A theoretical equation was derived based on the tanks-in-series model, providing a good fitting function to analyze the experimental data. The confirmation test was performed by applying computational fluid dynamics simulations of liquid steel flow in the real tundish.

Strong quasi-stationary wintertime atmospheric surface pressure anomalies drive a dipole pattern in the Subantarctic ModeWater formation

AbstractThe deepest wintertime (Jul-Sep) mixed layers associated with Subantarctic Mode Water (SAMW) formation develop in the Indian and Pacific sectors of the Southern Ocean. In these two sectors the dominant interannual variability of both deep wintertime mixed layers and SAMW volume is a east-west dipole pattern in each basin. The variability of these dipoles are strongly correlated with the interannual variability of overlying winter quasi-stationary mean sea level pressure (MSLP) anomalies. Anomalously strong positive MSLP anomalies are found to result in the deepening of the wintertime mixed layers and an increase in the SAMW formation in the eastern parts of the dipoles in the Pacific and Indian sectors. These effects are due to enhanced cold southerly meridional winds, strengthened zonal winds and increased surface ocean heat loss. The opposite occurs in the western parts of the dipoles in these sectors. Conversely, strong negative MSLP anomalies result in shoaling (deepening) of the wintertime mixed layers and a decrease (increase) in SAMW formation in the eastern (western) regions. The MSLP variability of the Pacific and Indian basin anomalies are not always in phase, especially in years with a strong El Niño, resulting in different patterns of SAMW formation in the western vs. eastern parts of the Indian and Pacific sectors. Strong isopycnal depth and thickness anomalies develop in the SAMW density range in years with strong MSLP anomalies. When advected eastward, they act to precondition downstream SAMW formation in the subsequent winter.