Packing Volume Research Articles

A study on optical properties of MnO doped borobismuthate glasses

A series of borobismuthate glasses doped with MnO with 0, 0.2, 0.4, 0.6, 0.8 and 1 mol% were prepared by melt quenching technique. X-Ray Diffraction (XRD) studies confirms the amorphous nature of samples. The parameters density, molar volume, molar refraction and oxygen packing density (OPD) were calculated and it is observed that density decreases and molar volume increases with increase in MnO component due to formation of Non Bridging Oxygens (NBO). Optical absorption studies were done for glass samples and it shows that optical bandgap energy (Eopt) and metallization criterion (M) decreases with increase in MnO component indicates that these glasses can behave as amorphous semiconductors. Apart from this the optical parameters such as linear refractive index (n), coefficient of absorption (α), coefficient of extinction (K), optical conductivity (σop), optical polarizability (αo) and optical basicity (Λth) have also been evaluated for all samples and studied as a function of wavelength.

Physical, Mechanical and Structural Properties of Yttrium Oxide Doped Zinc Borate Glasses

In this project, the nominal glass composition with the form of (55-x) H3BO3-45ZnO-xY2O3 (x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) are synthesized by melt quenching techniques. The effect of Y2O3 on physical, mechanical and structural properties of glasses have been investigated using different characterization techniques. The parameters like density, molar volume and oxygen packing density have been calculated. Based on the micro hardness study, it has showed the decreasing trend from 518.80 N.mm-2 to 453.13 N.mm-2 with an increasing of Y2O3 content from 0.0 mol% to 2.5 mol%. The structural features of the yttrium oxide doped zinc borate glass were studied via X-Ray Diffraction (XRD) to confirm the amorphous nature of glass and Fourier Transforms Infrared Spectroscopy (FTIR) has been done to obtain the band positions and functional groups. FTIR spectral studies were recorded in the 400-4000 cm-1 wavenumber range at room temperature.

DC electrical conduction in strontium vanadium borate glasses

Abstract A series of borate glasses with the composition x(SrO)·(50 – x)V2O5·0.5(B2O3) where x = 0, 0.1, 0.2, 0.3 and 0.4 were prepared by melt-quenching technique. The non-crystalline nature of the glasses has been established by XRD studies. Room temperature density and DC electrical conductivity of the samples were investigated in the temperature range of 300 K to 443 K. The molar volume and oxygen packing density (OPD) were estimated. The results show that the density, molar volume and OPD decrease with the increasing of SrO mole fraction. The DC electrical conductivity data has been analyzed in the light of Mott’s small polaron hopping (SPH) model and the activation energies were estimated. The conductivity was observed to rapidly fall and activation energy was found to increase when SrO was incorporated into the glass network. This may indicate that Sr+ ions have not contributed to the total conductivity and the observed conductivity may be of polaronic type only, which is due to the hopping of electrons between multivalent states of vanadium. Various small polaron hopping parameters such as small polaron radius, rp, effective dielectric constant, ϵp, polaron band width, J, optical phonon frequency, υo, small polaron coupling constant, γp, density of states at Fermi level, N(EF) were estimated and discussed.

Effect of Fe2O3 Concentration on the Properties of Basalt Glasses

ABSTRACT Basalt fiber as a type of reinforced material has been widely used in fiber-reinforced polymer (FRP) composites. Iron oxide (Fe2O3) has a great influence on the thermal and elastic properties of basalt fiber. In this study, ultrabasic, basic, and intermediate basalt rocks were chosen as raw materials and the dependence of Fe2O3 content variations on the properties of basalt glass was explored. Results showed that the density, molar volume (Vm), and oxygen packing density (OPD) of basalt glasses increased with the increase of Fe2O3 content. The viscosity, as well as crystallization behavior, is dominated by Fe2O3 content. Besides, the addition of Fe2O3 contributed to increasing the elastic modulus and hardness of basalt glasses.

On the Interfacial Flow Over Porous Media Composed of Packed Spheres: Part 1-Identification of the Effective Slip Length

The effective slip length at the interface between pure fluid flow and porous media composed of packed spheres has been accurately characterized. In this study, as the first part of a two-part series, the slip length is obtained by matching the flow rate over the actual packed spheres from a direct simulation with that over an effective smooth surface using the Navier-slip boundary condition from analytic solution. Three classical packing structures, e.g., simple cubic (SC), face-centered cubic (FCC), and body-centered cubic (BCC), are employed. The accuracy of the slip length is validated by comparing the velocity field of flow over the actual porous architecture and over the effective smooth surface. We report that the slip length is best described as a function of the free slip area, rather than conventional variables such as solid volume fraction and packing structure, with the error less than 7.5%. Then, the effective smooth surface with the slip length is applied to describe two flow problems: a stick–slip–stick flow and channel flow. The slip velocity as well as its slope at the interface and the velocity profile within the pure fluid channel is accurately reproduced. In Part 2, effective slip length will be employed to characterize optimal effective viscosity and stress jump coefficient in the Stokes–Brinkman approach, which can be applied for industrial and natural flows in dual-scale porous media in predicting flow solutions inside and outside the porous media.

EFISIENSI PEMASARAN CABAI RAWIT MERAH DI DESA CIDATAR KECAMATAN CISURUPAN KABUPATEN GARUT

The research marketing efficiency of red cayenne pepper was located in the Cidatar part of Cisurupan regency Garut district purposed to know marketing channel, marketing margin, and farmer’s share. The research used descriptive analysis method. About 31 farmers were chosen with a random sampling method and with the snowball method to got 10 sellers. Interview and observation in collecting primary data while the documentation to retrieve secondary data. There are five red cayenne pepper marketing channels in Cidatar, Cisurupan District, Garut Regency. The marketing channels are, I) farmer – a collector – wholesaler Jakarta – retailer – consumer Jakarta; II) farmer – a collector – wholesaler Cikajang– retailer – consumer Cikajang; III) farmer – a collector – wholesaler Cikajang – wholesaler Jakarta – retailer – consumer Jakarta; IV) farmer – a collector – wholesaler Bandung – retailer – consumer Bandung; V) farmer – a collector – wholesaler Bandung – wholesaler Jakarta – retailer – consumer Jakarta. The margin analysis results that the smallest marketing margin is in marketing channel II at 52,3 per cent. The largest Farmer’s share is at 47 per cent in marketing channel II and the biggest ratio of πi/Ci is at 5,64 in marketing channel III. The suggestion that can be given to farmers is to choose marketing channel I because channel I am the channel with the great packing volume that may be delivered by the market and also the highest price compared to other marketing channels.

Surface atomic packing fraction as a figure of merit for the structural transition and the bulk-to-nano transformation of spherical FCC and BCC nanosolids

Abstract We report on the development of a simple and efficient method to predict the structural transition and the bulk-to-nano transformation of spherical FCC and BCC solid nanoparticles using the surface atomic packing fraction ( g s ). For both structures, g s ’s are maxima at radii equal to the nearest neighbor distances. These g s values are smaller than the maximum values of their bulk counterparts. Compared to the bulk phase, the volume packing fraction (f) of a FCC nanoparticle decreases with size and approaches 0.810 at shells greater than 208. Our predictions show that bulk-to-nano transition starts at N ~ 10 4 , in a good agreement with the relevant literature. The disturbing the spherical shape of small FCC nanoparticles is found to be easier than breaking them across {100} and {111} crystal planes. However, for BCC, small NPs are more difficult to break through {100} and {111} planes. The current results highlight possible mechanisms for controlling the physical properties of matter at the nanoscale through their morphological characteristics. This study demonstrates that the interplay between packing, structural transition and shape can be utilized to develop new nanomaterials with controlled properties.

Transient modelling and simulation of gas turbine secondary air system

The behaviour of the jet engine during transient operation and specifically its secondary air system (SAS) is the point of this work. This paper presents a methodological approach to develop a fast, one-dimensional transient platform for preliminary analysis of the flow behaviour in gas turbine engines secondary air system. For this purpose, different elements of the system including rotating chamber, pipe, turbine blade cooling, orifice, and labyrinth seal are modelled in a modular form. The validity of the developed models for each component is checked against experimental/publicly available data. Then, using a flow network simulation approach, the secondary air system of a two-spool turbofan engine is modelled and simulated in transient mode. The coupling effect between volume packing and swirl are considered in the simulation, under two pre-defined scenarios for step and scheduled boundary condition variations. In the step-change scenario, the boundary conditions are changed instantly to represent the flow behaviour of the SAS under extreme operating conditions (i.e. shaft fracture, flameout, etc.). In the scheduled scenario, the boundary conditions vary linearly with time to represent the performance of the SAS under normal operating conditions (i.e. acceleration and deceleration). The key findings include the fact that, under normal engine operation, the flow in the SAS varies smoothly and converges much faster than the primary flow by around one magnitude. Thus, it is reasonable to use steady-state SAS model to simulate SAS flow behaviour under these conditions. However, under extreme conditions (e.g. flameout), which could induce an abrupt change in the primary airflow properties (pressure, temperature), reverse airflow or choking conditions in SAS may be observed. This could result in a malfunction of the SAS, inducing further damages to the engine.

Theoretical and experimental analysis of the thermodynamic and economic performance for a packed bed humidifier

In this paper, the thermodynamic and economic performance of the humidifier, with a wire mesh corrugated packing, is investigated and evaluated with the defined evaluation criteria experimentally and theoretically. In view of the humidification characteristics of packings, the mathematical models based on mass and energy balance are established. Performance of the packed bed humidifier, evaluated by the unit humidification capacity of volume (UHCV) and the unit humidification capacity of cost (UHCC), is first studied experimentally with fixed packing volume. Moreover, the parametric analysis of the humidification performance is achieved. The maximum values obtained simultaneously from the experiment present as 3.82 × 10−2 kgs−1 m−3 for the UHCV and 12.74 kg$−1 for the UHCC, as the liquid–gas ratio is 2 and the inlet water temperature is 90 °C. The simulation results illustrate that a peak point appears separately at mr = 0.5 for the UHCV and mr = 3 for the UHCC with the increase of liquid-gas ratio. It is also found that a higher value of the inlet air and water temperature, as well as the wet-bulb temperature of inlet humid air, can enhance the UHCV and UHCC in varying extents, while the inlet relative humidity has a reverse influence on them. Furthermore, it is observed that the effects of the specific surface area on the UHCV and UHCC are contradictory, with a best thermodynamic performance of 43.3 × 10−2 kgs−1 m−3, while the maximum economic value presents as 13.3 kg$−1.

Synthesis, structure and properties of silver tellurite glasses**In memory of our beloved teacher, Professor DSc Yanko Dimitriev.

The present work is a continuation of our earlier investigations on synthesis of non-traditional tellurite glasses and study of their structure and properties. Several multicomponent glass compositions containing Ag2O (15, 25 mol%) have been selected for investigations. The glasses obtained were homogeneous and colored depending on composition. Some physical characteristics (density, molar volume, oxygen molar volume and oxygen packing density) of the amorphous samples were estimated. By IR spectroscopy was found that the addition of Ag2O, shifts the band 625–620 cm−1 to lower frequencies, due to the creation of Te—NBO bonds, which confirm it’s modifying role. XPS exhibited that the addition of Ag2O leads to the appearance of Te3+ and Te0 valence states and TeO3 structural units additional to the dominant Te4+ amount and TeO4 units, respectively. Formation of small silver clusters, covered by Ag1+ ions was supposed as well. The existing of bridging oxygen bonds, only which build up the amorphous network, were discovered. It was established by UV–vis that the absorption edge of the glasses varies from 350 nm to 450 mm and the addition of Ag2O caused a red shifting of the cut-off. It was also found that the silver plasmon resonance band appeared about 400 nm.

Simple Method for Rheological Determination of Surfactant Layer Thickness, Adsorbed on Soft Rubber Particles.

Natural rubber latex is a colloidal suspension of particles, which is very important for many industrial applications. These latex particles are not only polydispersed but also very soft and deformable, which makes the prediction of rheological properties much difficult. Herein, the rheology of natural rubber latex has been studied at high particle concentrations, analyzing the effects of surfactant addition on colloidal stability. A hydrophobically modified inulin surfactant (INUTEC NRA) was selected for this study since previous works had shown that this inulin surfactant imparts good colloidal stability to polystyrene latex particles. The most important objective was studying the influence of the surfactant on the particle adsorbed layer and determining the thickness of the adsorbed surfactant layer. The results showed that the relative viscosity increased as a function of latex volume fraction, and this increase became extremely sharp as the volume fraction approached the maximum packing volume fraction, as expected. This variation in viscosity with the volume fraction has a complex behavior, which could not be analyzed using conventional models based on hard rigid spheres, such as Krieger-Dougherty (K-D) or Maron-Pierce (M-P). Herein, we describe a simple semiempirical method to determine the surfactant adsorbed layer thickness, based on the linear dependence of intrinsic viscosity with 1/(ϕmax - ϕ)2, where ϕ is the volume fraction of rubber particles and ϕmax is the maximum volume fraction at which viscosity tends to infinity. The difference in the maximum packing fraction, with and without the surfactant, allows the calculation of the adsorbed layer thickness, δ ≈ 2.8 nm, which is a good estimate for the thickness of surfactant molecules adsorbed on latex particles. This surfactant thickness has been confirmed by direct measurements using dynamic light scattering (DLS), which gave a value of 3.1 nm. Viscoelastic oscillatory measurements have also been performed, showing that natural rubber particle suspensions are predominantly elastic above ϕ = 0.63 latex volume fractions. The elastic modulus has been analyzed as a function of surfactant concentration, confirming that the stability of latex particles is mainly controlled by the surfactant concentration.

An experimental analysis of deepest bottom-left-fill packing methods for additive manufacturing

The adoption of Additive Manufacturing (AM) technology requires the efficient utilisation of the avail- able build volumes to minimise production times and costs. Three-dimensional algorithms, particularly the Deepest Bottom-Left-Fill (DBLF) heuristic, have been extensively used to tackle the problem of packing arbitrary 3D geometries within the AM sector. A particularly common method applied to more realistic packing problems is the combination of DBLF and metaheuristics such as Genetic Algorithms (GAs). Through a series of experiments, this paper experimentally investigates the practical aspects, and comparative performance of different DBLF based methods including a brute force algorithm and GA combined with DBLF for AM build volume packing. The insights into the relationship between algorithm efficiency (in terms of volume utilisation), simulation runtime, and practical requirements, in particular geometry rotation constraints are investigated. In addition to providing an increased comprehension of the practical aspects of applying DBLF algorithms in the AM context, this study confirms the limita- tions of traditional DBLF and the requirements for more flexible and intelligent placement strategies while experimentally demonstrating that higher degrees of freedom for part rotation contribute to small improvements in volume density. The resulting additional computational effort discourages this strategy, however.

Effect of Tungsten on Physical and Optical Properties of Niobate Tellurite Glasses

In the present work, three optically transparent tungsten niobate tellurite glasses with compositions of (90-x)TeO2-10Nb2O5-xWO3 (x = 0, 6, 12 mol%) were synthesized by conventional melt quenching technique. For all these three glass samples, the structural and the compositional dependence of different physical parameters such as density, molar volume and ionic packing density have been analyzed. It been observed that the amorphous nature of the samples has been confirm by X-ray diffraction analysis. The physical properties of the glasses were evaluated and the change in density ( ), molar volume ( ) and ionic packing density ( ) in these glasses indicates the effect of WO3 different content registered on the glasses structure. The highest refractive indexes value 2.171 at 632.8 nm was measured for 78TeO2–10Nb2O5–12WO3 glass. It is found that the addition of WO3 concentration to TeO2-Nb2O5 glass system increase the value of density, molar volume as well as ionic packing density. The refractive index value of the glass increase with tendency for small optical energy band gap.

An International Laboratory Comparison Study of Volumetric and Gravimetric Hydrogen Adsorption Measurements.

In order to determine a material's hydrogen storage potential, capacity measurements must be robust, reproducible, and accurate. Commonly, research reports focus on the gravimetric capacity, and often times the volumetric capacity is not reported. Determining volumetric capacities is not as straight-forward, especially for amorphous materials. This is the first study to compare measurement reproducibility across laboratories for excess and total volumetric hydrogen sorption capacities based on the packing volume. The use of consistent measurement protocols, common analysis, and figure of merits for reporting data in this study, enable the comparison of the results for two different materials. Importantly, the results show good agreement for excess gravimetric capacities amongst the laboratories. Irreproducibility for excess and total volumetric capacities is attributed to real differences in the measured packing volume of the material.

Investigation of the free volume characteristics of PEO based solid state polymer electrolyte by means of positron annihilation spectroscopy

Ion conduction in poly (ethylene oxide), PEO, based electrolytes are explained considering the ion movement coupled with polymer segmental motions or free volume. Herein, we describe the application of positron annihilation spectroscopy to investigate the free volume structure of PEO-LiTFSI solid state electrolyte with varying electrolyte concentration. Addition of LiTFSI indicates plasticization effect through the increase in free volume size of polymer matrix. Depth dependent Doppler broadening measurements have shown a decrease in positron/positronium diffusion length and S-parameter value on addition of electrolyte. The observed decrease in S-parameter and positronium intensity could not be ascribed to positronium reaction (inhibition) with dissociated ions or salt aggregates as the variation does not follow the established inhibition expression. The SW correlation curves indicate that the chemical environment at positron/positronium annihilation sites in PEO-LiTFSI is similar to pristine PEO. It again confirms that reduction in positronium intensity and S-parameter cannot be attributed to positronium inhibition. The present study shows that resultant positron/positronium annihilation parameters can be directly attributed to the change in molecular packing or free volume structure of the solid state electrolytes.

Characterization of the wall effect of concrete via random packing of polydispersed superball-shaped aggregates

On the mesoscopic scale, concrete can be treated as a two-phase composite consisting of aggregates and mortar matrix. The geometrical feature of aggregate particles usually has significant impact on the structural evolution of concrete and then affects the macro-mechanical properties. To explore the relation between the aggregate characteristics and the macroscopic properties of material, a variety of packing models of particles such as spheres and ellipsoids have been widely applied in previous studies. In the paper, a family of polyhedron-like particles which are defined as the superball is applied to represent the aggregate particles. Based on the Monte Carlo simulation, the models of concrete mesostructure are generated in a random manner. By combining the semi-periodic models of these particles with the section analysis technique, three parameters (i.e., the volume fraction of aggregates VV, the specific surface area of aggregates SV and the mean free spacing between aggregates λ at the cross-section of the models) can be obtained. On the basis of different particle packing systems, we further study the effect of the aggregate characteristics (e.g., particle size distribution, particle shape, particle packing volume fraction, etc.) on the variation of the interfacial layers (which are caused by the wall effect) near the boundaries of formwork and a series of meaningful results are successively obtained. Based on the simulated results in the work, a more comprehensive insight into the phenomenon of the wall effect in concrete can be gained. It is hoped that the conclusions may provide a helpful guidance for the design of the composite materials.

Effect of barium addition and plasma nitriding treatment on chemical and physical properties of Al, Pb borate glass system as a developed radiation shield

The effect of the BaO addition of to aluminum, lead borate in a series of (BaO)x (B2O3)60-x (Al2O3)10 (Li2O)10 (PbO)20 glasses where x = 0 to 50 weight% have been studied through their shielding, mechanical, thermal and chemical properties. The physical parameters such as molar volume (Vm), density (ρ), and oxygen packing density (OPD) were evaluated and discussed. Moreover, the thermal stability of the investigated system increases with BaO content. The present study proved that each of the plasma nitriding treatments of the samples and/or increasing Ba content greatly improved their ability to resist scratching and corrosion. Therefore, the obtained results are candidates for the present glass system to be effectively used as a protective shield against nuclear radiations in many advanced domains.

Detecting microstructural white matter abnormalities of frontal pathways in children with ADHD using advanced diffusion models.

Studies using diffusion tensor imaging (DTI) have documented alterations in the attention and executive system in children and adolescents with attention-deficit/hyperactivity disorder (ADHD). While abnormalities in the frontal lobe have also been reported, the associated white matter fiber bundles have not been investigated comprehensively due to the complexity in tracing them through fiber crossings. Furthermore, most studies have used a non-specific DTI model to understand white matter abnormalities. We present results from a first study that uses a multi-shell diffusion MRI (dMRI) data set coupled with an advanced multi-fiber tractography algorithm to probe microstructural measures related to axonal/cellular density and volume of fronto-striato-thalamic pathways in children with ADHD (N = 30) and healthy controls (N = 28). Head motion was firstly examined as a priority in order to assure that no group difference existed. We investigated 45 different white matter fiber bundles in the brain. After correcting for multiple comparisons, we found lower axonal/cellular packing density and volume in ADHD children in 8 of the 45 fiber bundles, primarily in the right hemisphere as follows: 1) Superior longitudinal fasciculus-II (SLF-II) (right), 2) Thalamus to precentral gyrus (right), 3) Thalamus to superior-frontal gyrus (right), 4) Caudate to medial orbitofrontal gyrus (right), 5) Caudate to precentral gyrus (right), 6) Thalamus to paracentral gyrus (left), 7) Caudate to caudal middlefrontal gyrus (left), and 8) Cingulum (bilateral). Our results demonstrate reduced axonal/cellular density and volume in certain frontal lobe white matter fiber tracts, which sub-serve the attention function and executive control systems. Further, our work shows specific microstructural abnormalities in the striato-thalamo-cortical connections, which have not been previously reported in children with ADHD.

Colloidal dynamics and elasticity of dense wax particle suspensions over a wide range of volume fractions when tuning the softness by temperature

We report on the colloidal dynamics and rheology of liquid droplet emulsions and solid particle suspensions over a wide range of volume fractions. Diffusing wave spectroscopy and rheometry were utilized to study the micro/macroscale properties of 1-eicosene wax particles dispersed in water. By changing the temperature, the wax droplets change their properties from soft to hard or vice versa, which, depending on the density, may affect the system properties in a different way. Our measurements in the high volume fraction regime focus on the elasticity index and the plateau storage modulus, Gp′. The results show a more pronounced increase of the modulus for the wax particle suspensions around the random close packing volume fraction compared to the emulsion.

Physical and Structural Properties of Dysprosium Doped Barium Borate Glass

Five distinguish glass samples were prepared by melt quenching technique of the composition (81-x)H3BO3-19BaCO3-xDy2O3 with x = 0, 0.2, 0.4, 0.6 and 0.8 mol%. The effect of Dy3+ to the barium borate glass can be investigated in terms of their physical properties such as density, molar volume and oxygen packing density. The structural properties were analyzed by X-Ray Diffraction (XRD) technique and Fourier Transform Infrared Spectroscopy (FTIR). The result revealed that the increment of mol% of Dy3+ in the compound generally will increases the density and molar volume of the glass samples. The amorphous nature of the glass system was verified from the XRD spectra pattern. Meanwhile, the FTIR spectra shown the presence of Ba2+, BO3, BO4, B-O-B linkage, H-O-H and isolated borate in the glass network.