Presence Of Porous Material Research Articles

Monitoring of Sulfur Mustard (HD) Vapor in the Presence of Absorptive Building Materials.

In the event of an accidental or intentional release of a chemical warfare agent (CWA), environmental samples must be collected and analyzed to assess the level of the contamination. Equally important is an understanding of the fate and transport of a CWA in the presence of porous materials, which may impact the ability to collect environmental samples. Air monitoring techniques may be used to rule in/out the presence of a CWA. Here, relationships between the CWA sulfur mustard (HD) surface contamination levels and the associated HD vapor concentration were investigated. Results indicate that absorption of HD into vinyl, concrete, and sealed concrete followed by slow diffusion out of these materials significantly prolonged the presence of HD vapor concentrations. The extracted material recovery data suggest that positive correlations can be established between residual material contamination and vapor concentration but also that surface wiping alone would fail to detect absorbed HD.

Heat transport magnetization for Burgers fluid in a porous medium with convective heating and heterogeneous-homogeneous response

Many technical applications exist for porous material. In this paper, a new mathematical model for the Burgers fluid, which is sustained in the presence of porous material, is presented. The thermal energy transmission characteristics are investigated utilizing a heat source related to temperature. The homogeneous-heterogeneous reactions in the current work will demonstrate the characteristics of fluid concentration scrutiny. The similarity transformations are used to transform the system of partial differential equations (PDEs) into ordinary differential equations (ODEs). By introducing the ideas of the fourth and fifth Runge-Kutta-Fehlberg methods, developed ODEs are solved. The graphs demonstrate that the results are relevant. According to the relaxation time factor, the Burger's fluid properties thermal distribution is reduced by the relaxation time parameter. The behavior of the Biot number and retardation time factor is evaluated by comparing them to that of the material component of the Burgers fluid. Data utilizing the heterogeneous response will rise with a larger magnitude since the homogeneous strength response is diminished by the fluid concentration rate. When the porosity parameter increases, the velocity distribution decreases. The current findings are contrasted with published work as special examples in order to ensure accuracy and validity.

Combined effects of MHD and slip velocity on oscillatory mixed convective flow around a non-conducting circular cylinder embedded in a porous medium

The present analysis addresses the impact of magnetohydrodynamics and slip velocity on oscillating mixed-convective electrically-conducting fluid flow over thermally and horizontal non-conducting circular cylinder inserted in a porous medium. The fluid with a slip-boundary has a variety of uses in current technology, including the polishing of prosthetic heart valves and the interior heart cavities. The fluid motion is governed by connected nonlinear PDE's which are converted into convenient equations by applying finite-difference scheme with primitive transformation and Gaussian elimination technique. The numerical solutions of connected dimensionalized equations are obtained in the form of fluid velocity, temperature and magnetic profiles which are used to examined oscillating skin-friction, oscillating heat transfer and current-density for various emerging dimensionless parameters, slip number S L , Prandtl number Pr, porous number Ω and some other fixed parameters. The FORTRAN software is used for numerical results and displayed these results on Tech Plot. The novelty of the current work is to analyze mixed convective heat transfer analysis with MHD and slip velocity effects for oscillatory flow around a no-conducting horizontal circular cylinder embedded in a porous medium. First, the numerical solutions for steady part are secured and then these results are used in un-steady part, which make nonlinear coupled partial differential equation linear. It is pertinent to mention here that the convective heat transfer is practically associated with oscillatory flow behavior. It is observed that an increase in slip number S L leads to enhance the fluid velocity and temperature field. Transient current density and transient skin friction rate shows maximum magnitude of oscillation at both π / 6 and π / 3 stations in the presence of porous material.

Peroxone activated persulfate oxidation of 1,4-Dioxane under column scale conditions

The research presented herein investigates a peroxone activated persulfate (PAP) oxidant, commercialized under the trade name OxyZone®, and its effects on 1,4-Dioxane (dioxane) contaminated water under column scale conditions in the presence of porous material. There is a limited understanding of the underlying processes that govern PAP oxidation, including the oxidation rates in the presence of aquifer material, and how these reactions proceed once the oxidant is injected into a contaminant plume. Initial batch experiments with porous material (e.g. sand) provided data on the reaction rates of dioxane oxidation as a function of the oxidant: contaminant ratio. The observed degradation rates were approximately 4 times lower than those reported for aqueous solutions containing no porous media. Subsequent column experiments simulated two PAP injections schemes along the flowpath of a dioxane plume to study if the injection of one oxidant slug may yield different results than injecting the same oxidant volume at two separate locations. The injection of one oxidant slug was found more effective, resulting in near complete destruction of dioxane over a prolonged time at a rate more than an order of magnitude greater than in the two-slug injection scenario. Tracer test results suggest that the prolonged oxidant reactivity was in part caused by the high density of the injected oxidant solution. Overall, the results underline the importance of accounting for the properties of both the oxidant solution and the porous material when considering the injection of PAP oxidant into an impacted aquifer.

Effect of Porous Materials on Explosion Venting Overpressure and Flame of CH4/air Premixed Gas

ABSTRACT To understand the overpressure transient and flame behavior of CH4/air premixed gas explosion venting in the presence of porous materials, a series of explosion venting tests is conducted in a spherical vessel with a neck. The effects of pore size, porosity, thickness, and properties of porous material on Pstat, Pred, Pburst , and Pext are measured using pressure transmitters, and the image of an exploding venting jet flame passing through porous materials is captured using a high-speed camera. It is shown that the pressure wave at the high-pressure side of the explosion vent is in a critical state when the venting burst membrane ruptures without the porous materials, and the vented jet is confirmed to be under-expanded. The addition of porous materials does not significantly affect Pstat but results in the highest Pburst in porous material Al2O3 50PPI and the highest Pred in porous material SiC 20PPI. This is consistent with the assumption that Pred > Pburst , and that an increase in Pburst corresponds to a decrease in Pred . In addition, Pext is more likely to occur at a position 250–350 mm away from the vent, and as the thickness of the porous materials increases, the possibility of an external explosion overpressure will increase. Moreover, the porous material significantly affects the venting jet flame, and as the thickness of the porous material increases, the shape of the venting jet flame resembles that of a “broom,” owing to the dynamic overpressure generated from the flame-porous material interaction.

Effect of channel geometry and porous coverage on flame acceleration in hydrogen–air mixture

Flame propagation in a hydrogen–air mixture in the presence of porous materials was investigated experimentally in channels with different dimensions and cross–sections. In this study, experiments were performed in a rectangular channel with one or two walls covered with porous material to study flame propagation in stoichiometric hydrogen–air mixtures at room temperature and atmospheric pressure. Depending on the channel configuration, the porous coating of the internal walls ranged from 1/4 to 1/2 of the channel area. Four types of polyurethane foam with a number of pores per inch (PPI) ranging from 10 to 80 were used to cover the channel walls. Flame propagation was visualized using a Schlieren device and high-speed camera. The largest flame acceleration in the porous channel relative to the solid channel was observed in the 20×20mm channel. The ratio of the velocities in the porous channel to the velocity in the solid channels was 6–7 for the porous material with the largest (2.5mm) pores. In the case of a 10×10mm channel, the flame velocity in the porous channel was higher than the flame velocity in the solid channel after 350mm only when using porous coatings with 2.5mm and 1.3mm pores. When using a porous coating with smaller pores the flame velocity was lower than in the solid channel. Schlieren images show different stages of flame propagation from a turbulent flame to a supersonic flame with shock waves.

Thermophysical properties of the surface of asteroid 162173 Ryugu: Infrared observations and thermal inertia mapping

TIR, the thermal infrared imager on Hayabusa2, acquired high-resolution thermal images of the asteroid 162173 Ryugu for one asteroid rotation period on August 1, 2018 to investigate the thermophysical properties of the asteroid. The surface temperatures of Ryugu suggest that the surface has a low thermal inertia, indicating the presence of porous materials. Thermophysical models that neglect or oversimplify surface roughness cannot reproduce the flat diurnal temperature profiles observed during daytime. We performed numerical simulations of a thermophysical model, including the effects of roughness on the diurnal brightness temperature, the predictions of which successfully reproduced the observed diurnal variation of temperature. The global thermal inertia was obtained with a standard deviation of 225 ± 45 J m−2 s−0.5 K−1, which is relatively low but still within the range of the value estimated in our previous study (Okada et al., Nature 579, 518–522, 2020), confirming that the boulders on Ryugu are more porous in nature than typical carbonaceous chondrites. The global surface roughness (the ratio of the variance of the height relative to a local horizontal surface length) was determined as 0.41 ± 0.08, corresponding to a RMS surface slope of 47 ± 5°. We identified a slightly lower roughness distributed along the equatorial ridge, implying a mass movement of boulders from the equatorial ridge to the mid-latitudes.

The effect of porous coating on the flame acceleration in hydrogen–air mixture

Flame acceleration in the hydrogen–air mixture in the presence of porous materials was investigated experimentally. Polyurethane foam with different pore size placed on top and button sides of the channel was found to greatly affect flame acceleration in the channel. High–speed schlieren images showed, that polyurethane foam with larger pores leads to flame wrinkling. Dependencies of the flame velocity on the pore size were presented. It was found that final flame velocity by the end of the porous section can be up to 5 times higher while using polyurethane foam with 10 pores per inch compared to polyurethane foam with 80 pores per inch. The flame velocity in the smooth channel was lower than the flame velocity in the porous channel for all tested cases. Polyurethane foam with smaller pore size led to pressure decrease compared to solid channel. Supersonic combustion with velocity around 1600m/s was registered in the channel with PF10 on the walls. It was discovered, that the use of such a porous coating can lead to preventing the increase in the shock wave pressure during the combustion of hydrogen–air mixtures.

Effects of metal foam meshes on premixed methane-air flame propagation in the closed duct

In many practical applications, the comprehensive measures are needed to suppress the gas explosions, and lining the channel walls with porous materials before a special installation for flame résistance is an effective choice. The aim of the present work is to investigate the effect of porous materials on the premixed flame propagation process in a closed combustion tube. Experiments are carried out to examine the flame dynamics for the stoichiometric methane/air mixtures both in the empty tube and in the presence of porous materials. The results demonstrate that the flame propagation can be divided into five typical stages, and a tri-tulip flame is observed during the development of the classic tulip flame. The inversion distance L of the flame front is selected to characterize the tulip flame evolution. It is worth to notice that the flame tip fronts travel faster with smaller porous densities PPI(pores per inch) from the finger shape stages to flat shape stages. The explosion severity parameters, including peak pressure and maximum pressure growth rates, are compared for all configurations, and the porous density plays an important role on the explosion severity. The maximum rate of pressure rise decreases linearly with the porous densities. It is deduced that the metal foam meshes with the larger porous densities PPI have more significant impacts on suppressing the tulip formation. The coupling of the flame front with the pressure wave plays a significant role in the onset and evolution of the tulip flame. As a whole, the metal foam meshes can reduce the overpressures can reduce the overpressures by33.3%–46.6%, while they have little effect on the flame tip speeds and shapes.

Pyrogenic transformation of oil-bearing biomass into biodiesel without lipid extraction

This study mechanistically investigated the pseudo-catalytic transesterification of oil-bearing biomass through a thermo-chemical pathway. As a case study, all experimental work was conducted with sesame seed and sesame oil. The pseudo-catalytic transesterification occurred in the presence of porous material (silica) since porous material provided reaction space as a micro reactor and drove the heterogeneous reactions between the mobile phase of methanol and the stationary phase of triglycerides (TGs) in sesame. The experimental work verified that the main driving force of pseudo-catalytic transesterification was temperature in the presence of porous material, which led to the direct derivatization of oil-bearing biomass into fatty acid methyl esters (FAMEs). Thermal cracking was observed at temperatures higher than 350°C and the main experimental parameter initiating this thermal cracking was temperature and time. However, the optimal conditions identified in this study were temperatures lower than 350°C, where the total yield of FAMEs reached up to 96.4±0.3% of lipid in sesame seed. The introduced technology would be applicable to the production of biodiesel and comprehensive lipid analysis in oil-bearing biomass.

Pseudo catalytic transformation of volatile fatty acids into fatty acid methyl esters

Instead of anaerobic digestion of biodegradable wastes for producing methane, this work introduced the transformation of acidogenesis products (VFAs) into fatty acid methyl esters (FAMEs) to validate the feasible production of short-chained fatty alcohols via hydrogenation of FAMEs. In particular, among VFAs, this work mainly described the mechanistic explanations for transforming butyric acid into butyric acid methyl ester as a case study. Unlike the conventional esterification process (conversion efficiency of ∼94%), the newly introduced esterification under the presence of porous materials via the thermo-chemical process reached up to ∼99.5%. Furthermore, the newly introduced esterification via the thermo-chemical pathway in this work showed extremely high tolerance of impurities: the conversion efficiency under the presence of impurities reached up to ∼99±0.3%; thus, the inhibition behaviors attributed from the impurities used for the experimental work were negligible.

Analysis of the lipid profiles in a section of bovine brain via non-catalytic rapid methylation.

The main focus of this study is to mechanistically introduce a new qualitative and quantitative technique for mapping the lipid profile of a sectional brain via non-catalytic transesterification reaction (i.e., pseudo catalytic reaction in the presence of porous materials). One of the biggest technical advances achieved in this study is the qualitative and quantitative analysis of lipid from bovine brain in trace quantities in the magnitude of μg via the non-catalytic pathway. Moreover, newly introduced derivatization in this work showed high tolerance against impurities (i.e., water and extractives).

INFLUENCE OF NANOPOROUS MATERIALS ON THE CHEMICAL COMPOSITION OF MERLOT AND CABERNET SAUVIGNON WINES

The variation of the content of 12 phenolic compounds from 5 months aged Cabernet Sauvignon and Merlot wine samples treated with siliceous and aluminosiliceous porous materials was analysed through a HPLC method. The standard physical-chemical analyses (alcoholic concentration, total acidity, volatile acidity, relative density, reductive sugars, total dry extract, non-reductive extract, free SO2, total SO2, pH) were registered. The used nanomaterials: SBA-15, Al-MCM-41, KIT-6 were synthetized in the laboratory and were structurally characterized through the BET and SEM methods. The obtained results are in accordance to literature findings. The experimental results are proof that the maturation of wine, specifically Cabernet Sauvignon and Merlot, in the presence of porous materials modifies the physical-chemical composition as well as the phenolic content of wines.

Numerical Analysis of Aerodynamic Noise Reduction by Applying Porous Materials

Aerodynamic noise from bluff bodies is well reduced when they are covered with porous materials. In this study, presence of porous materials is modeled by momentum loss in the equation of fluid motion, and mathematical formulae for evaluating aerodynamic noise based on the theory of vortex sound are modified in order to include the effect. Flow around the cylinder covered with porous materials is calculated by LES techniques. When the inertial resistance factor C2 is set to 200[m-1], no vortex is shed periodically into the wake any longer and a region of zero-velocities is spread behind the cylinder, which forms stable shear layers. Time variations of the force exerted on the cylinder and the total momentum loss in the whole porous areas are also reduced at C2=200[m-1]. Flow through porous materials induces velocities in circumferential direction at the outer edge of the materials which weaken vortices of shear layers, and also induces velocities in radial direction which widen the space between two shear layers behind the model. Numerical analysis predicts the reduction of aerodynamic noise in the case of C2=200[m-1], which agrees qualitatively with experimental results. Although strong sound sources are formed around separation points in the case of the bare cylinder, stable flow around the cylinder with porous materials seems to suppress production of sound sources.

Use of Fly Ash as Bonding Material on Low Thermal Expansion Porous Materials

In this work it was determined the effect of fly ash (FA) as bonding material during the fabrication of low thermal expansion porous materials. SiC, fly ash, Vitrified Bonding Material (VBM), and LiAlSiO4 powders were used as raw materials. Porous materials were sintered at 850°C and 950°C after manual milling and mechanical milling in a planetary ball milling at 800 RPM. SEM micrographs showed the presence of porous materials, and it was observed that fly ash particles did not melt at 850°C. However if sintering temperature increases at 950°C, FA starts to melt and it is forming bridges between SiC particles. Thermal expansion values were around 3.0x10-6 K-1. According to these results, it seems that it is possible to have a favorable synergy between FA and VBM to fabricate SiC porous materials with low thermal expansion values.

Prediction of airborne sound and impact sound insulation provided by single and multilayer systems using analytical expressions

In this work, the authors use analytical solutions to assess the airborne sound and impact insulation provided by homogeneous partitions that are infinite along their plane. The algorithm uses Green’s functions, derived on the basis of previous work by the authors on the prediction of airborne sound insulation provided by single and double panels. The model is now extended to handle multilayer systems, allowing the simulation of three-dimensional loads applied in both the acoustic and solid media. The model is validated against experimental results and compared with simplified expressions for single, double and triple panels. The results provided by the analytical model were found to provide a good agreement with the experimental results, except in the vicinity of the coincidence effect in the presence of thicker panels. The applicability of the proposed tool is then illustrated by analyzing the acoustic behavior provided by single layers and by a suspended ceiling. Different variables are studied, such as the mass, the stiffness of the layers, the position and direction of the load within the elastic medium and the presence of porous material in the fluid layers. It was found that the model is able to simulate the acoustic phenomena involved in single and multilayer systems.

Diffuse scattering of radar on the surface of Venus: Origin and implications for the distribution of soils

Previous analysis of PV altimeter data has shown that ~25% of the surface of Venus is characterized by low values of reflectivity, interpreted as being due to the presence of porous materials such as soils. However, examination of a corrected reflectivity data set in combination with PV altimeter data suggests that no more than 5% of the surface of Venus is covered by soils more than several to tens of cm in depth. Most regions of apparent low reflectivity are instead interpreted to be due to the presence of small (5–50 cm) roughness elements on the surface that cause diffuse scattering at the 17 cm PV wavelength. Regions of low apparent reflectivity are of interest because of a correlation with tessera, a complex tectonic unit mapped from Venera 15/16 SAR data. Regions of tessera are characterized by a complex system of intersecting ridges and valleys thought to be of tectonic origin. Examination of possible models for the form of diffuse scatterers in the tessera suggests that they are rock fragments and originate from a mass-wasting process that is linked to the rugged nature of the terrain. Further, these diffuse scatterers are associated with other tectonic landforms, suggesting that they originate as part of tectonic deformation of the surface. Viewed from a geologic standpoint, the PV data sets are important tools for understanding tectonic, volcanic, and degradational processes on Venus, as well as for future interpretation of data from the Magellan mission.

ChemInform Abstract: NITRATION OF TOLUENE IN THE PRESENCE OF POROUS MATERIALS

AbstractDie Einwirkung von Salpetersäure auf Toluol in Gegenwart von porösen Materialien wie japanischem sauren Ton, Silicagel, Aktivkohle, Molekularsieben oder Diatomeenerde führt zu p‐ und o‐Nitrotoluol.

多孔性物質の存在下におけるトルエンのニトロ化

The p- to o-ratio of nitrotoluenes formed by nitration of toluene in the presence of porous materials, such as Japanese acid clay, silica gel, active carbon, molecular sieves or diatom earth, was compared with that obtained by the usual nitration with mixed acid. In general, p/o increased more or less by adding the porous materials and showed tendency to increase when the proportion of nitric acid to the porous materials was decreased. Moreover, in the nitration of toluene adsorbed on the porous materials, the maximum p/o of 1.56 (with silica gel) was obtained, while the p/o by the usual nitration was 0.71. A part of such effect may be attributed to the steric-hindrance against o-substitution at fine porous spaces on the materials.