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The drying process of electrode slurry for LiB should be crucial to obtain higher electrochemical performance, but it has been a black box. Furthermore, the lack of sufficient information on slurry microstructure complicates solving this issue. In this study, the cathode slurries having different internal structures are prepared and characterized by rheological properties. The drying process of the coating layer is evaluated in terms of film shrinkage. When the coarse particles of active material and the network structure of acetylene-black particles are uniformly mixed, a low drying rate results in extensive particle segregation and poor cycle performance. On the other hand, it is found that insufficient dispersion of active materials causes poor rate performance. Under the optimal drying condition, the slurry microstructure is found not to affect battery performance. However, the optimization of drying conditions requires consideration of material mobility during drying.

The packing density and stability of the aggregate mixtures significantly affect the quality of concrete, particularly in infrastructural applications. The Carneiro and Dinger-Funk (D-F) models are two of the tools utilized in the generation of aggregate grading for concrete applications. For the first time, this study aimed to develop a methodology for the determination of the Carneiro distribution modulus (Pr) and the D-F distribution modulus (q) for a given aggregate system that provides optimal packing characteristics considering the packing density and segregation potential. In this study, combinations of two coarse aggregate classes (19 to 4.75 mm and 9.5 to 2.36 mm) and two fine aggregates (4.75 to 0.15 mm and 600 to 75 μm) were generated using a number of trial values of Pr and q. The packing density and segregation potential of each aggregate mixture were then computed using the compressible packing model, considering equivalent idealized spherical aggregate particles. For the aggregates considered in this study, results indicated that the optimal mixtures result in the range 0.85 ≤ Pr ≤ 0.90 and 0.15 ≤ q ≤ 0.25 for Carneiro and D-F models, respectively. Although both models appear to produce equivalent aggregate mixture characteristics, the D-F model is less responsive to changes in the distribution modulus. Hence, it is more flexible for obtaining an aggregate mixture composition with optimal packing characteristics.

Made available in DSpace on 2021-06-25T11:07:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Enzymes production by solid-state cultivation in packed-bed bioreactor needs to be improved by mathematical modeling and also by experimentation. In this work, a mixture of sugarcane bagasse and wheat bran was used for the growth of the fungus Myceliophthora thermophila I-1D3b, able to secrete endoglucanase and xylanase, enzymes of interest in the second-generation ethanol production. Bench and pilot-scale bioreactors were used for the experiments, while critical parameters as bed porosity and airflow distribution were evaluated. Results showed enzymes with higher activities for the most porous medium, even though the less substrate amount to be cultivated. For the pilot-scale bioreactor, only the most porous medium was evaluated using different airflow distribution techniques. Using an inner tube for air supply resulted in more homogeneous enzyme production, with higher activities. The results here presented will be helpful for the scale-up of this class of bioreactor into industrial apparatuses. Food Engineering and Technology Department Institute of Biosciences Letters and Exact Sciences São Paulo State University (UNESP), Cristóvão Colombo, 2265, Jardim Nazareth Graduate Program of Chemical Engineering Federal University of São Carlos (UFSCar), Rod. Washington Luiz km 235, SP-310 Food Engineering and Technology Department Institute of Biosciences Letters and Exact Sciences São Paulo State University (UNESP), Cristóvão Colombo, 2265, Jardim Nazareth CNPq: 132957/2016-7 FAPESP: 2014/23453-3 FAPESP: 2018/00996-2 CNPq: 430786/2018-2

Excellent adsorption properties of porous metal-organic frameworks (MOFs) render them highly potential adsorbent for adsorption heat pump applications. However, their thermal properties are not quite satisfactory. Aluminium fumarate is a bioavailable ligand-based metal-organic framework with promising water uptake capacity. In this study, aluminium fumarate was synthesized following a green synthesis route and was doped with Nickel and Cobalt material at 10% and 20% concentration to create a mixed-valence complex system. Their thermal diffusivity and thermal conductivity were studied at different compression (7 MPa, 17 MPa and 27 MPa) pressure over a temperature range of 30 °C to 110 °C. Metal doping enhances the thermal conductivity of the doped aluminium fumarate MOFs. Doping of cobalt has a greater effect compared to nickel and 20% cobalt doped aluminium fumarate shows the highest thermal conductivity at 7 MPa compression pressure.

Concrete density is always a problem that occurs during concrete and it affects the strength, durability and apparent qualities of hardened concrete. Vibration is a practical thing that comes with a lot of noise and requires trained workers, and failure to do so will cause many problems. To overcome this problem, the development of self-compacting concrete has begun. This concrete, fills all the dimensions of the mould and is flowing through the use of more fine-grained and plastic shrinkage, without the need for vibration, without any parts being detached. The topics that have been considered for many years in concrete technology have been resilient and durable. For concrete having self-compacting and high resistance and durability, high- performance self-compacting concrete (HPSCC) has been created. The achievement of self-condensation requires the use of a large amount of powdered material, some of which are capable of replacing part of the cement, and replacing them is a step towards sustainable development. Also, using powder materials, the density of concrete aggregates increases and leads to improved strength and durability. The use of large quantities of powdered materials increases the need for mixing water and the likelihood of plastic shrinkage. Therefore, it is necessary to consider all items to enhance concrete performance, so that HPC can be designed and constructed. Therefore, in this research, a review of previous studies on the nature, mechanical properties and durability of highly capable HPSCC’s has been carried out and about 90 high citation articles have been considered, focusing on goals and results. The results of previous studies have shown that using SCC, concrete with similar strength of conventional concrete can be obtained. By reducing the proportion of water to cementicious materials, as well as using pozzolans, not only resistance but also concrete properties are enhanced and HPSCC is obtained.

The particle packing of cementitious materials is of essential importance to the performance of paste which constitutes the most uncertain part of mortar/concrete. Such importance is arising from the fact that the design of cementitious particle system inevitably involves the packing design, particularly for the emerging materials of 3D printable concrete and ultra-high performance concrete (UHPC). So far, scientific understanding of the particle packing in these emerging materials remains inadequate. In this regard, wet packing method (WPM) was used to measure the wet packing density (WPD) of ternary particle systems consisting of cement, pulverized fuel ash (PFA) and micro-silica (MS). The optimum ternary particle system in terms of WPD was determined. Comparison between the experimental results and Andreasen and Andersen (A&A) model revealed the limitations of A&A model. The design approach based on WPD contour shall advance particle packing-oriented cement and concrete science towards sustainable concrete design.

The electrical impedance characteristics of multi-walled carbon nanotube (MWCNTs) networks were studied as a function of CNT concentrations in the frequency range of 1 kHz–1 MHz. The novelty of this study is that the MWCNTs were not embedded in any polymer matrix and so the response of the device to electrical measurements are attributed to the CNTs in the network without any contribution from a polymer host matrix. Devices with low MWCNT packing density (0.31–0.85 µg/cm2) exhibit a frequency independent plateau in the low-frequency regime. At higher frequencies, the AC conductivity of these devices increases following a power law, characteristic of the universal dynamic response (UDR) phenomenon. On the other hand, devices with high MWCNT concentrations (>1.0 µg/cm2) exhibit frequency independent conductivity over the entire frequency range (up to 1 MHz), indicating that conduction in these devices is due to direct contact between the CNTs in the network. A simple single-relaxation time electrical equivalent circuit with an effective resistance and capacitance is used to describe the device performance. The electrical noise measurements on devices with different MWCNT packing densities exhibit bias-dependent low-frequency 1/f noise, attributed to resistance fluctuations.

The ternary blended cement with finer slag and silica fume (SF) could improve the packing density (PD) through the filling effect. The excess water (water more than needed for filling into voids between the cement particles) can be released to improve the fresh properties and densify the microstructure which is beneficial for improving the hardened properties. To verify the hypothesis and reveal how and why (cement + slag + SF) the ternary blends could bring such advantages, the binder pastes incorporating slag and SF with various water-to-binder ratios were produced to determine the PD experimentally. To evaluate the optimum water demand (OWD) for maximum wet density, the influence of the dispersion state of the binder on PD was investigated using the wet packing density approach. The effect of PD of various binary and ternary binder systems on water film thickness (WFT), fluidity, setting time, and compressive strength development of cement paste was also investigated. The results show that the ternary blends could improve the PD and decrease the water film thickness (WFT). The enhanced PD and altered WFT are able to increase fluidity and compressive strength. The ternary blends could improve the compressive strengths by increasing PD and exerting nucleation and pozzolanic effects.

From disaster prevention to mitigation, drug analysis to drug design, agriculture to food security, IoT to AI, and big data analysis to knowledge or sentiment mining, a high computation power is a prime necessity at present. As such, massively parallel computer (MPC) systems comprising a large number of nodes are gaining popularity. To interconnect these huge numbers of nodes efficiently, hierarchical interconnection networks are an attractive and feasible option. A Tori-connected flattened butterfly network (TFBN) has been proposed by the authors in a prior work for future generation MPC systems. In the previous study, the static network performance and static cost-effectiveness were evaluated. In this research, a novel trade-off factor named message traffic congestion vs. packing density trade-off factor has been proposed, which characterizes the message congestion in the network and its packing density. The factor is used to statically assess the suitability of the implementation of an interconnection network. The message traffic density, packing density, and new factor have been evaluated for the proposed network and similar competitive networks such as TTN, TESH, 2D-Mesh, 3D-Mesh, 2D-Torus, and 3D-Torus. It has been found that the performance of the TFBN is superior to the other networks.

This manuscript critically reviews the design and delivery of spray-dried particles for the achievement of high total lung doses (TLD) with a portable dry powder inhaler. We introduce a new metric termed the product density, which is simply the TLD of a drug divided by the volume of the receptacle it is contained within. The product density is given by the product of three terms: the packing density (the mass of powder divided by the volume of the receptacle), the drug loading (the mass of drug divided by the mass of powder), and the aerosol performance (the TLD divided by the mass of drug). This manuscript discusses strategies for maximizing each of these terms. Spray drying at low drying rates with small amounts of a shell-forming excipient (low Peclet number) leads to the formation of higher density particles with high packing densities. This enables ultrahigh TLD (>100 mg of drug) to be achieved from a single receptacle. The emptying of powder from capsules is directly proportional to the mass of powder in the receptacle, requiring an inhaled volume of about 1 L for fill masses between 40 and 50 mg and up to 3.2 L for a fill mass of 150 mg.

Active rheology control (ARC) or active stiffening control (ASC) is a concept with which the conflicting rheological requirements during different stages of concrete casting can be reconciled. For instance, formwork leakage could be reduced by actively controlling structuration at the formwork joints, without having the negative impact of increased structuration during pumping and form filling. Using the concepts of magnetorheology, an active control methodology was thus recently developed by the authors to study the control of formwork leakages under pressure. This was performed using a small-scale laboratory test setup, using cementitious pastes containing magnetisable particles. To upscale from paste to mortar, the effect of volume fraction of sand on the magnetorheological (MR) response and blocking mechanisms of mixtures containing Fe3O4 nanoparticles is thus investigated in the current study. The MR response is determined using storage modulus tests, and the impact of ASC for leakage reduction is investigated by measuring the flow rate. Experimental results show that increasing the sand volume beyond a threshold causes a reduction in mobility of the magnetic particles, and thus lowers the MR effect. Despite this reduction in the MR effect at high sand volume, the increased particle interactions induce clogging and filtration effects, drastically lowering the flow rate. Applying the ASC method refines the voids in the clog, thereby eliminating the filtration effect. It is concluded that ASC can be used on mortar, with the expectation that there would be a reduction in the magnetorheological effect with increasing volume of fine aggregates.

Packing density has a significant influence on the outcome of ensiling forage. In this study, we aim to investigate the effect of packing density on the ensiling properties, microbiome, and in vitro digestibility of barley silages. Barley was ensiled in polyethylene drum silos (30 L) with respective densities of 600, 650, 700, and 750 kg/m3 fresh matter (FM), and stored for 60 days. The bacterial communities, fermentation quality, and in vitro digestibility were analyzed. Fresh barley had a low count of lactic acid bacteria (LAB, 104 cfu/g of FM), and Lactobacillus was nearly undetectable (&lt, 1%). Increasing the packing density decreased the pH and the content of ammonia nitrogen (NH3-N), ethanol, neutral detergent fiber (NDF), and acid detergent fiber (ADF) of barley silage (p &lt, 0.05), and increased in vitro digestibility of dry matter, NDF, ADF, and DM recovery (p &lt, 0.05). A higher packing density decreased the abundances of Enterobacter (from 47.4% to 35.4%) and Clostridium (from 13.5% to 3.8%), and increased the abundance of Lactobacillus (from 1.8% to 17.0%). Thus, packing density positively correlated with Lactobacillus (p &lt, 0.05) but negatively correlated with Enterobacter (p &lt, 0.05). The pH and the content of ethanol were positively correlated with Enterobacter (p &lt, 0.05) but negatively correlated with Lactobacillus (p &lt, 0.05). In conclusion, the density of 750 kg/m3 FM resulted in the highest silage quality of the densities tested.

The glass transition is described as a time- and history-independent singular event, which takes place in an interval dependent on the distribution width of molecular vibration amplitudes. The intrinsic glass transition is not seen as a relaxation phenomenon, but is characterized by a fixed volumetric state at the glass temperature Tg0. The relaxation behavior of the transport properties depends on the distance to Tg0. Free volume is redefined and its generation is the result of the fluctuating transfer of thermal energy into condensed matter and the resulting combined interactions between the vibration elements. This creates vacancies between the elements which are larger than the cross-section of an adjacent element or parts thereof. Possible shifts of molecules or molecular parts through such apertures depend on the size and axis orientation and do not require further energetic activation. After a displacement, additional volume is created by delays in occupying abandoned positions and restoring the energetic equilibrium. The different possibilities of axis orientation in space result in the different diffusive behavior of simple molecules and chain molecules, silicate network formers, and associated liquids. Glass transformation takes place at a critical volume Vg0 when the cross-section of apertures becomes smaller than the cross-section of the smallest molecular parts. The glass transition temperature Tg0 is assigned to Vg0 and is therefore independent of molecular relaxation processes. Tg0 is well above the Kauzmann and Vogel temperatures, usually just a few degrees below the conventionally measured glass temperature Tg(qT). The specific volume at the two temperatures mentioned above cannot be achieved by a glass with an unordered structure but only with aligned molecular axes, i.e. in a crystalline state. Simple liquids consisting of non-spherical molecules additionally alter their behavior above Vg0 at Vgl where the biggest gaps are as small as the largest molecular diameter. Tgl is located in the region of the crystalline melting point Tm. Both regions, above and below Tm, belong to different physical states and have to be treated separately. In the region close to Vg0 respectively Tg0, the distribution of vibration amplitudes has to be taken into account. The limiting volume Vg0 and the formation of apertures larger than the cross-section of the vibrating elements or parts thereof, in conjunction with the distribution width of molecular vibrations as Vg0 is approached, and the spatial orientation of the molecular axes is key to understanding the glass transition.

Based on the available literature, a simple method was adopted to calculate the packing density of aggregates and thereby reduce their void content by optimising their packing aggregates and by using two different sizes of coarse aggregates and fine aggregates. This study provides an understanding of the way in which the shape of aggregates affects the properties of self-compacting concrete (SCC). The fresh, hardened, and durable properties of SCC with normal and lightweight fly ash coarse aggregates are found at the corresponding age of the curing. Their values were compared with respect to SCC containing normal aggregates. A mix with fly ash aggregates was found to have better fresh concrete properties due to the round shape of the aggregates. After the packing of the aggregates, this mix was found to have better mechanical and durability properties than all the other concrete mixes.

In the fabric industry, textile yarns are the fundamental building blocks. Hence, visualizing and studying yarn structure is essential to understand the structure and behavior of the fibers. Obtaining the yarn’s cross-section images is crucial in the calculations of yarn’s porosity; furthermore, a more precise expansion for the fiber’s migration can be concluded from the cross-sectional images. In this paper, three different methods (microtome, micro-computed tomography, and epoxy grinding–polishing methods) to image and visualize the yarn’s cross-section are presented. The experimental techniques are compared in terms of result useability, time of preparation, and overall outcome of the cross-sectional image. The images can be used for fiber distribution, air gap calculation, and twist analysis as well. The fiber diameter distribution of polyester yarn was measured based on the images obtained by the three different methods; the average fiber diameter measured based on the combined data from the three different methods was found to be 10.90 ± 0.30 µm. Published version

This paper describes the packing models that are fundamental for the design of ultra-high-performance concrete (UHPC) and their evolution. They are divided into two large groups: continuous and discrete models. The latter are those that provide the best method for achieving an adequate simulation of the packing of the particles up to nanometric size. This includes the interaction among the particles by means of loosening and wall coefficients, allowing a simulation of the virtual and real compactness of such particles. In addition, a relationship between virtual and real compactness is obtained through the compaction index, which may simulate the energy of compaction so that the particles are placed in the mold. The use of last-generation additives allows such models to be implemented with water–cement (w/c) ratios close to 0.18. However, the premise of maximum packing as a basic pillar for the production of UHPC should not be the only one. The cement hydration process affected by nanoadditives and the ensuing effectiveness of the properties in both fresh and hardened states according to the respective percentages in the mixture should also be studied. The characterization tests of the aggregates and additions (dry and wet compactness, granulometry, density and absorption) have been carried out in order to implement them numerically in the polydisperse packing model to obtain the compactness of the mixture. Establishing fixed percentages of nanoadditives in the calculation of the mixture’s compactness. The adequate ratio and proportion of these additions can lead to better results even at lower levels of compactness. The compressive strength values obtained at seven days are directly proportional to the calculated compactness. However, at the age of 28 days, better results were obtained in mixes with lower cement contents, fewer additions and lower compactness. Thus, mixes with lower cement contents and additions (silica fume and limestone filler) with a compactness of φ = 0.775 reached 80.1 MPa of strength at 7 days, which is lower than mixes with higher cement contents and number of additions (SF, limestone filler and nanosilica), which achieved a compactness of φ = 0.789 and 93.7 MPa for compressive strength. However, at 28 days the result was reversed with compressive strengths of 124.6 and 121.7 MPa, respectively.

For the requirement in container nursery culture that growing media should be achieved the appropriate degree compaction, this paper presents an experiment on the compaction dynamics of air-dried soil under repetitive drop shocks, as a preliminary step toward the mechanization of this compaction method. The drop height used to adjust the shock intensity included 2 mm, 4 mm, 5 mm and 6 mm. And the overall packing density of soil in a vertically stratified cylinder vessel and the local packing density in each layer were taken as indicators of soil compaction states. The stretched exponential function derived from KWW law than the empirical inverse-logarithmic function has been found to be more suitable for expressing the temporal evolution of soil compaction, according to the results of curve-fitting to test values of the overall and local density. It is inherent in this experimental configuration that the drop shock intensity even at a constant drop height varies with drop times, owing to the interaction between the soil packing itself and drop shocks caused by the combination of the packing and the container. But the function t/τf(t,H) is manifested as a straight line on the drop times t with the line slope related to the drop height H, so the soil compaction dynamics caused by its drop shocks and that under the condition with actively controlled intensity actually share the common relaxation law. In addition, the soil’s one-dimensional distribution of local packing density showed a slight positive gradient as similar as monodisperse particles did.

Porous materials are widely employed in a wide variety of industrial applications due to their advanced functional performance. Porous aluminum is among the most attractive metallic materials. It can be produced using repeatable methods involving a replicated Al foam that also provides porosity control. In this work, a highly porous replicated Al foam was fabricated. First, the model of multifunctional packing density was used and corrected to select the appropriate space holders. Then, Al foam was produced using a double-granular sodium chloride space holder. The obtained results showed a maximum porosity of 65% that was achieved using a mix of coarse, irregular granules with spherical granules of intermediate size. © 2021 by the authors.

To improve the environmental efficiency of the reverse filling system, three strategies aim to optimize the packing density, and the mechanical property were adopted in this study. Based on the compressive packing model (CPM), the relationship between the D50 ratio and maximum theoretical packing density for a reverse filling system with 25% and 30% superfine Portland cement was established. For comparison, silica fume and steel fiber were also added to the reverse filling system, respectively. The improvement of packing density by adjusting the D50 ratio was verified through the minimum water demand method, CPM, and modified Andreasen and Andersen (MAA) model. Compared to the reverse filling system added with 3 wt % silica fume, which possesses a comparable mechanical property with the optimized group (adjusted D50 ratio), the incorporation of steel fiber shows a more significant increase. The environmental efficiency of all the samples was quantified into five aspects through the calculation based on the mix proportion, compressive strength, and hydration degree. The comprehensive evaluation demonstrated that the optimized reverse filling system exerts a lower environmental impact and possesses a much higher cement use efficiency compared to the majority of ultra-high performance concrete (UHPC)/ ultra-high performance fiber-reinforced concrete (UHPFRC) reported in published papers.

Made available in DSpace on 2022-04-28T19:29:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Let p be an odd prime. Algebraic lattices of full diversity in dimension p are obtained from ramified cyclic extensions of degree p. The 3, 5, and 7-dimensional lattices are optimal with respect to sphere packing density and therefore are isometric to laminated lattices in those dimensions. Department of Mathematics and Statistics San Diego State University San Diego Department of Mathematics S˜ao Paulo State University University of Murcia Federal University of S˜ao Paulo

We use the Positions and Covering methodology to obtain exact solutions for the two-dimensional, non-guillotine restricted, strip packing problem. In this classical NP-hard problem, a given set of rectangular items has to be packed into a strip of fixed weight and infinite height. The objective consists in determining the minimum height of the strip. The Positions and Covering methodology is based on a two-stage procedure. First, it is generated, in a pseudo-polynomial way, a set of valid positions in which an item can be packed into the strip. Then, by using a set-covering formulation, the best configuration of items into the strip is selected. Based on the literature benchmark, experimental results validate the quality of the solutions and method’s effectiveness for small and medium-size instances. To the best of our knowledge, this is the first approach that generates optimal solutions for some literature instances for which the optimal solution was unknown before this study.

This work aimed to investigate the impact of Lead-fluoride based glasses via theoretical and simulation techniques on mechanical and radiation shielding parameters. Accordingly, Bi2O3 was blended with TeO2–B2O3–PbF2 glasses by using melt-quenching method. Using Fluka Monte Carlo code, the radiation shielding properties have measured. Moreover, Comparatively higher density PbF80 = 6.163 g/cm3 with 80 mol % Bi2O3, greater µ, µm and Zeff and lower T1/2, λ, tenth value layer values achieved for TeO2–B2O3– PbF2/Bi2O3 glass pointed it out as the best shield of gamma. Besides, the computed effective removal cross-sections against fast neutrons (ΣR) observed that the PbF80 sample has commensurately greater with a value 5.2954 (cm−1). The results observed that the variation PbF2/Bi2O3 improves the gamma protection ability of Lead-fluoride based glasses. The incremental of Bi2O3 at the expense of PbF2 increases the density and the packing density of the glasses and hence increase the longitudinal modulus-L, shear modulus-S, bulk modulus-K, and Young's modulus-Y from 15.89 to 25.9 GPa, from 8.49 to 12.09 -GPa, from 4.58 to 9.77 GPa, and from 15.74 to 25.69 GPa, respectively. The increase of the elastic moduli can be attrinuted to the glass former role of Bi2O3. The results indicate that the highest PbF2/Bi2O3 ratio encoded PbF00 has the best shielding and mechanical competence with measurable physical properties. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature. Taif University Researchers Supporting Project number (TURSP-2020/45) Taif University, Taif, Saudi Arabia.

Environmental considerations and technical benefits have directed research towards reducing cement clinker content in concrete, and one of the best ways to do this is to replace cement with supplementary cementitious materials. High calcium fly ash, ladle furnace slag, and limestone filler were investigated as supplementary cementitious materials in cement pastes, and binary mixtures were produced at 10%, 20%, and 30% cement replacement rates for each material. The water requirement for maximum packing and for normal consistency were obtained for each paste, and strength development was determined at 3, 7, 28, and 90 days for the 20% replacement rate. Furthermore, two ternary mixtures at 30% cement replacement were also prepared for maximum packing density and tested for compressive strength development. The results showed that high calcium fly ash decreased cement paste packing and increased water demand but contributed to strength development through reactivity. Ladle furnace slag and limestone filler, on the other hand, were less reactive and seemed to contribute to strength development through the filler effect. The ternary paste with 70% cement, 20% high calcium fly ash, and 10% limestone filler showed equivalent strength development to that of the reference cement paste.

Frass (fine powdery refuse or fragile perforated wood produced by the activity of boring insects) of larvae of the European house borer (EHB) and of drywood termites was tested as a natural and novel feedstock for 3D-printing of wood-based materials. Small particles produced by the drywood termite Incisitermes marginipennis and the EHB Hylotrupes bajulus during feeding in construction timber, were used. Frass is a powdery material of particularly consistent quality that is essentially biologically processed wood mixed with debris of wood and faeces. The filigree-like particles flow easily permitting the build-up of wood-based structures in a layer wise fashion using the Binder Jetting printing process. The quality of powders produced by different insect species was compared along with the processing steps and properties of the printed parts. Drywood termite frass with a Hausner Ratio HR = 1.1 with ρBulk = 0.67 g/cm3 and ρTap = 0.74 g/cm3 was perfectly suited to deposition of uniformly packed layers in 3D printing. We suggest that a variety of naturally available feedstocks could be used in environmentally responsible approaches to scientific material sciences/additive manufacturing.

International audience; Maximizing the transfer performances of heat and mass exchangers is a major target for process intensification purposes. Basically, flux enhancement can be achieved through increased specific surface area and/or increased transfer coefficients (e.g. Dean vortices generation in curved pipes), but this has to be balanced to energy requirement. In this study, novel performance criteria taking into account both specific surface area effects and the associated friction losses are proposed and applied to helical pipe exchangers covering a broad range of geometries. It is shown that most helical pipe geometries exhibit poor efficiencies in terms of volumetric transfer rates. Nevertheless, some very particular helix designs are shown to offer a huge potentiality for intensified heat/mass transfer performances. Surprisingly, a major volume reduction is indeed shown to be achievable together with a decreased energy requirement (pumping power). The performances of these novel designs are finally critically compared to alternative process intensification techniques

MSc (Mechanical Engineering), North-West University, Potchefstroom Campus A conventional bullet or projectile, driven by the rapidly expanding gas formed by the combustion of the propellant charge, accelerates in the barrel and reaches a certain muzzle velocity, spin, and propulsion energy. The geometric characteristics of the propellant grains are one of the primary factors which affect the performance of a projectile and its maximum achievable range. The geometric shape of the propellant grains is crucial to ensure simultaneous burnout of the entire charge before the projectile is discharged from the barrel to prevent unburnt propellant from forming residue inside the gun chamber. The geometrical shape of the propellant grains plays a significant role in the performance of a gun system. This also affects the packing density of the charge. In this research, a proposed propellant grain geometry for a 155 mm artillery gun system was investigated and compared to the rosette grain as a reference propellant grain. This was done to investigate and determine the effects of propellant geometry on the grain size, the packing density, the maximum pressure, and the muzzle velocity. the proposed propellant grain is outperformed by the rosette grain in term of performance. However, the developed propellant grain achieves higher packing density than the rosette grain. This research establishes a framework that to be used to develop any new propellant grain. Masters

The mechanical and radiation shielding features were reported for a quaternary Na2 O-CaO-SiO2-TiO2 glass system used in radiation protection. The fundamentals of the Makishima– Mazinize model were applied to evaluate the elastic moduli of the glass samples. The elastic moduli, dissociation energy, and packing density increased as TiO2 increased. The glasses’ dissociation energy increased from 62.82 to 65.33 kJ/cm3, while the packing factor slightly increased between 12.97 and 13.00 as the TiO2 content increased. The MCNP-5 code was used to evaluate the gamma-ray shielding properties. The best linear attenuation coefficient was achieved for glass samples with a TiO2 content of 9 mol%: the coefficient decreased from 5.20 to 0.14 cm−1 as the photon energy increased from 0.015 to 15 MeV. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: This research was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University through the Fast-Track Research Funding Program.

Pyrochlore titanate (Y2Ti2O7) is a promising material for a wide range of applications in optoelectronics and photocatalysis due to its advantageous chemical, mechanical, and optical properties. To enhance its potential for such uses, however, a high-quality and scalable synthesis method is required. We here investigate the crystallization of sol–gel produced Y2Ti2O7 layers. We observe a transition of the amorphous pyrochlore phase at annealing temperatures below 700 °C. The transmittances of the Y2Ti2O7 thin layers annealed at 400 to 700 °C are approximately 92.3%. The refractive indices and packing densities of Y2Ti2O7 thin layers annealed at 400–700 °C/1 h vary from 1.931 to 1.954 and 0.835 to 0.846, respectively. The optical bandgap energies of Y2Ti2O7 thin layers annealed at 400–700 °C/1 h reduce from 4.356 to 4.319 eV because of the Moss–Burstein effect. These good electronic and optical properties make Y2Ti2O7 thin layers a promising host material for many potential applications.

Powder packing in metal powders is an important aspect of additive manufacturing (otherwise known as 3-D printing), as it directly impacts the physical and mechanical properties of materials. Improving the packing density of powder directly impacts the microstructure of the finished 3D-printed part and ultimately enhances the surface finish. To obtain the most efficient packing of a given powder, different powder blends of that material must be mixed to minimize the number of voids, irrespective of the irregularities in the particle morphology and flowability, thereby increasing the density of the powder. To achieve this, a methodology for mixing powder must be developed, for each powder type, to obtain the maximum packing density. This paper presents a model that adequately predicts the volumetric fraction of the powder grades necessary for obtaining the maximum packing density for a given powder sample. The model factors in the disparity between theoretical assumptions and the experimental outcome by introducing a volume reduction factor. We outline the model development steps in this paper, testing it with a real-world powder system.

Separating finer particles from raw fly ash is a popular method to produce high-performance admixture of concrete. However, the supply of separated fly ash is obviously behind the demand and the residue fly ash is difficult to be disposed. Ground fly ash is another method to improve the particle size and reactivity, but the change of particle morphology during grinding may affect the rheological properties of cement paste and concrete, which limits the application of ground fly ash in concrete projects. In this study, the raw fly ash, separated fly ash, and ground fly ash of the same particle size range were studied and the particle morphology was analyzed by Image-Pro Plus process and spherical particles proportion calculation. On this basis, the fluidity and rheological properties of cement paste with different fly ash content were tested and the mechanism was discussed by packing density and zeta potential analysis. The results showed that the total amount of spherical particles in fly ash-cement paste system was reduced due to the spherical particles of ground fly ash being destroyed during the grinding process. Thus, compared with the separated fly ash of similar particle size range, the fluidity of ground fly ash was significantly decreased while the yield stress and plastic viscosity increased significantly, which indicated that the rheological properties of fly ash cement paste are closely related to the particle morphology of fly ash. The results provide theoretical basis and technology support to the application of ground fly ash.

In this work, we use contrast image processing to estimate the concentration of multi-wall carbon nanotubes (MWCNT) in a given network. The fractal dimension factor (D) of the CNT network that provides an estimate of its geometrical complexity, is determined and correlated to network resistance. Six fabricated devices with different CNT concentrations exhibit D factors ranging from 1.82 to 1.98. The lower D-factor was associated with the highly complex network with a large number of CNTs in it. The less complex network, having the lower density of CNTs had the highest D factor of approximately 2, which is the characteristic value for a two-dimensional network. The electrical resistance of the thin MWCNT network was found to scale with the areal mass density of MWCNTs by a power law, with a percolation exponent of 1.42 and a percolation threshold of 0.12 &mu, g/cm2. The sheet resistance of the films with a high concentration of MWCNTs was about six orders of magnitude lower than that of less dense networks, an effect attributed to an increase in the number of CNT&ndash, CNT contacts, enabling more efficient electron transfer. The dependence of the resistance on the areal density of CNTs in the network and on CNT network complexity was analyzed to validate a two-dimension percolation behavior.

In the additive manufacturing of metal materials, powder bed fusion 3D laser printing is the most widely used processing method. The density of the packed bed is another important parameter that can affect the part quality, however, it is the least understood parameter and needs further study. Aiming at addressing the problem of the powder packing density in the powder tank before powder spreading, which is neglected in the existing research, a combination of numerical simulation and experimental research was used to analyze the powder particle size distribution, powder stiffness coefficient, and vibration condition. Considering the van der Waals forces between the powders, a discrete element model suitable for fine metal powders for 3D printing is proposed. At the same time, a mathematical model that takes into account the vibration state is proposed, and the factors affecting the density of the powder were analyzed. A self-designed and manufactured three-dimensional vibration test rig was used to conduct physical experiments on spherical metal powders with approximately Gaussian distributions to obtain the maximum densities. The results obtained by the numerical simulation analysis method proposed in this paper are in good agreement with the experimental results. The influence of the amplitude and vibration frequency on the powder packing density is the same, that is, it increases with an increase in amplitude or frequency, and then decreases with a further increase in amplitude or frequency after reaching the maximum. It is unreasonable to discuss the packing densification only relying on the vibration intensity. Therefore, it is necessary to combine the amplitude and frequency to analyze the factors that affect the packing density of powders.

In this study, it was intended to investigate the effects of yarn spinning systems as well as yarn twist direction on some comfort and spirality performance properties of the fabrics. For this aim, interlock knitted fabrics made of 100% viscose yarns were produced with different spinning systems namely, ring, compact and siro at two twist directions; S and Z. The results indicate that the fabrics made of compact yarn possessed high water vapor and high air permeability values, but lesser vertical wicking values than ring yarn fabrics. However, both of the permeability values of the compact yarn fabrics markedly reduced when yarn twist direction was S. Generally, irrespective of yarn twist direction, the siro yarn fabrics exhibited better permeability but lesser wickability values as compared to ring yarn fabrics. Ring yarn fabrics displayed relatively highest wickability values and spirality percentages as compared to made from siro and compact yarns. In addition, samples produced from Z-twist yarn had higher air permeability values as well as water vapor permeability values but their vertical wicking values and spirality percentages were lesser than that of S-twisted ones. To sum up, it can be inferred that the spinning system has a profound influence on structural parameters of spun yarns. Bu çalışmada, iplik eğirme sisteminin yanı sıra iplik büküm yönünün kumaşların bazı konfor ve may dönmesi özellikleri üzerindeki etkileri araştırılmıştır. Bu amaçla, % 100 viskon elyafından üretilmiş interlok örme kumaşlar; ring, kompakt ve siro olmak üzere üç farklı eğirme sisteminde ve S ile Z olmak üzere iki farklı büküm yönünde üretilmişlerdir. Elde edilen sonuçlar, kompakt iplikten yapılan kumaşların su buharı ve hava geçirgenlik değerlerinin yüksek olduğunu, fakat kılcal ıslanma değerlerinin ise ring iplik sistemi ile üretilenlere kıyasla daha düşük olduğunu göstermiştir. Ayrıca, S büküm yönüne sahip kompak iplikten üretilmiş kumaşların hava ve su buharı geçirgenlik değerlerinin Z yönünde üretilmiş olanlara nazaran ciddi bir düşüş sergiledikleri görülmüştür. Genel olarak, iplik büküm yönüne bakılmaksızın, siro iplikten üretilmiş kumaşların geçirgenlik özelliklerinin ring iplik ile üretilenlere göre daha yüksek olduğu gözlenmiştir. Diğer taraftan, ring iplikten üretilmiş kumaşlar, siro ve kompakt ipliklerden yapılanlara göre nispeten en yüksek kılcal ıslanma ve may dönmesi sergilemişlerdir. Ayrıca, Z bükümlü iplikten üretilen numuneler daha yüksek hava ve su buharı geçirgenlik değerlerine sahipken, dikey kılcal ıslanma değerleri ve may dönmesi yüzdeleri S bükülmüş olanlardan daha düşüktür. Özetle, eğirme sisteminin ipliklerin yapısal parametreleri üzerinde derin bir etkiye sahip olduğu sonucuna varılmıştır.

Silica fume (SF) is the most commonly mineral admixture used for the production of high-strength concrete (HSC) due to its chemical characteristics of pozzolanic reactivity and physical filling effect. The objective of the present work is to compare the SF content by the chemical analysis of the pozzolanic reaction and the physical behavior by particle packing techniques. The first step of the study was to analyze the SF content to consume the calcium hydroxide (CH) produced during the hydration of Portland cement (PC), based on stoichiometric calculations. Then, the SF content for maximum packing density was obtained using analytical particle packing models and experimental tests. The compressive strength of the pastes was also measured. The results showed that the theoretical SF content for consuming CH is 15.6%, replacing PC. According to the packing density analytical models, the ideal SF content is 15% of the total fine materials. However, the experimental results indicated the use of a smaller SF content (10%). This difference between theoretical and experimental results is probably due to the high specific surface of the SF, which results in important surface forces between the grains, particle agglomeration and difficulty in SF densification with water.

Concrete with crushed concrete aggregates (CCA) shows lesser compressive strength than reference concrete with natural aggregates. The goal of this study is to improve the strength of structural concrete with 53% and 100% CCA replacements without increasing the cement content. Thus, improvements in CCA quality are induced by combining mechanical and pre-soaking pre-processing techniques. Mechanical pre-processing by rotating drum is separately pursued on fine and coarse CCA for 10 and 15 min respectively. Results show, adhered mortar content and CCA water absorption reduces as pre-processing duration increases. Pre-processing influences CCA particle grading, flakiness index, shape index, void-content, unit-weight and density, jointly seen as packing density, which increases with pre-processing duration. Water amount to pre-soak CCA before concrete mixing is stable despite grading modifications, due to reduced water absorption resulting from mechanical pre-processing. Compressive strength and workability for pre-processed CCA50 and CCA100 concrete are comparable to reference concrete and show similar trends of improvement with packing density. Packing density markedly shows the quality improvements induced by pre-processing on CCA, maybe considered as one of the quality assessment indexes for CCA. Packing density should be investigated for other recipes to see the stability of the trend with workability and compressive strength.

Some important properties of lattices are packing density and full diversity, which may be good for signal transmission over both Gaussian and Rayleigh fading channel, respectively. The algebraic lattices are constructed through twisted homomorphism of some modules in the ring of integers of a number field \begin{document}$ \mathbb{K} $\end{document}. In this paper, we present a construction of some families of rotated \begin{document}$ A_n- $\end{document}lattices, for \begin{document}$ n = 2^{r-2}-1 $\end{document}, \begin{document}$ r \geq 4 $\end{document}, via totally real subfield of cyclotomic fields. Furthermore, closed-form expressions for the minimum product distance of those lattices are obtained through algebraic properties.

Background: Endovascular therapy of intracranial aneurysms has a high recurrence rate. This study aimed to evaluate the risk factors of recurrence after endovascular coil embolization of intracranial aneurysms.Methods: From January 2014 to May 2015, 504 patients with 558 intracranial aneurysms who were treated by endovascular therapy were recruited from four high-volume centers. We used multivariate Cox proportional hazard regression to evaluate the risk factors associated with the angiographic recurrence of intracranial saccular aneurysms after endovascular coil embolization.Results: Angiographic follow-up was available for 504 patients (558 aneurysms), with a mean duration of 11.42 months. Of the 558 aneurysms, 57 (10.2%) aneurysms showed recurrence. Aneurysm size (p = 0.028), therapy (non-stent assisted coiling or stent-assisted coiling) (p = 0.008), the Raymond scale (p = 0.040), aneurysm rupture status (p < 0.001), and packing density (p < 0.001) showed significant associations with angiographic follow-up outcome. A low packing density was independently associated with aneurysmal recurrence after multivariate Cox proportional hazard regression analysis (p < 0.001).Conclusion: Endovascular treatment is effective for these lesions. Multiple factors could attribute to the aneurysmal recurrence after endovascular coil embolization. The low packing density is the independent risk factor for aneurysmal recurrence. These findings should be verified by larger multicenter and multi-population studies.

Concrete with crushed concrete aggregates (CCA) shows lesser compressive strength than reference concrete with natural aggregates. The goal of this study is to improve the strength of structural concrete with 53% and 100% CCA replacements without increasing the cement content. Thus, improvements in CCA quality are induced by combining mechanical and pre-soaking pre-processing techniques. Mechanical pre-processing by rotating drum is separately pursued on fine and coarse CCA for 10 and 15 min respectively. Results show, adhered mortar content and CCA water absorption reduces as pre-processing duration increases. Pre-processing influences CCA particle grading, flakiness index, shape index, void-content, unit-weight and density, jointly seen as packing density, which increases with pre-processing duration. Water amount to pre-soak CCA before concrete mixing is stable despite grading modifications, due to reduced water absorption resulting from mechanical pre-processing. Compressive strength and workability for pre-processed CCA50 and CCA100 concrete are comparable to reference concrete and show similar trends of improvement with packing density. Packing density markedly shows the quality improvements induced by pre-processing on CCA, maybe considered as one of the quality assessment indexes for CCA. Packing density should be investigated for other recipes to see the stability of the trend with workability and compressive strength.

The deformation law for axisymmetric deformation during the drawing of a core filled tube (CORFT) has been studied. However, the results of such studies could not be used in the flat rolling process of the CORFT, which is a plan deformation condition. In this paper, the inner core material and outer steel tube were successively analyzed based on the slab method during the flat rolling process (plan deformation) of the CORFT, and equations for wall thickness, core density, and roll force have been developed. The theoretical results solved by the developed equations were compared with the experimental results, revealing adequate accuracy for engineering requirements. The influences of rolling parameters on the roll force and the ultimate value of the relative density of the core material were studied, and the limiting condition for a larger roll force or higher value for relative density was obtained.

We construct some families of full diversity rotated [math] -lattices via [math] -modules for any [math] . We show that [math] -modules known in previous works to obtain rotated [math] -lattices with [math] an odd integer are ideals and we find a sufficient condition for such ideals to be principal ideals. We also present bounds and formulas for the minimum product distance of [math] and [math] restricted to some conditions.

Un nouveau Modèle d'Empilement Compressible (MEC), le MEC 4-paramètres, a été élaboré pour prédire la compacité d’empilements binaires en fonction de leur composition. L'effet de paroi est pris en compte grâce au calcul de la compacité locale dans une couche de fines particules sphériques situées contre la paroi d'une grosse particule. En faisant tendre le diamètre de cette dernière vers l'infini, on obtient un modèle géométrique permettant de quantifier l'effet d'une paroi plane et lisse sur un empilement partiellement ordonné de billes., Academic Journal of Civil Engineering, Vol 35 No 1 (2017): Special Issue - RUGC 2017 Nantes

We aimed to examine aneurysm hemodynamics with intra-saccular pressure measurement, and compare the effects of coiling, stenting and stent-assisted coiling in proximal segments of intracranial circulation. A cohort of 45 patients underwent elective endovascular coil embolization (with or without stent) for intracranial aneurysm at our department. Arterial pressure transducer was used for all measurements. It was attached to proximal end of the microcatheter. Measurements were taken in the parent artery before and after embolization, at the aneurysm dome before embolization, after stent implantation, and after embolization. Stent-assisted coiling was performed with 4 different stents: LVIS and LVIS Jr (Microvention, Tustin, CA, USA), Leo (Balt, Montmorency, France), Barrel VRD (Medtronic/ Covidien, Irvine, CA, USA). Presence of the stent showed significant reverse correlation with intra-aneurysmal pressure-both systolic and diastolic-after its implantation (r = -0.70 and r = -0.75, respectively), which was further supported by correlations with stent cell size-r = 0.72 and r = 0.71, respectively (P0.05). In conclusion, low-profile braided stents show a potential to divert blood flow, there was significant decrease in diastolic pressure after stent placement. Flow-diverting properties were related to stent porosity. Coiling does not significantly change the intra-aneurysmal pressure, regardless of packing density.

Toxoplasma gondiiis an obligate intracellular parasite infecting up to one third of the human population. The central event in the pathogenesis of toxoplasmosis is the conversion of tachyzoites into encysted bradyzoites. A novel approach to analyze the structure ofin vivo-derived tissue cysts may be the increasingly used computational image analysis. The objective of this study was to quantify the geometrical complexity ofT. gondiicysts by morphological, particle, and fractal analysis, as well as to determine if and how it is impacted by parasite strain, cyst age, and host factors. Analyses were performed on 31 images ofT. gondiibrain cysts of four type-2 strains (the reference Me49 strain and three local isolates, named BGD1, BGD14, and BGD26) using ImageJ software package. The parameters of interest included diameter, circularity, relative particle count (RPC), fractal dimension (FD), lacunarity, and packing density (PD). Although cyst diameter varied widely, its negative correlation withRPCwas observed. Circularity was remarkably close to 1, indicating that the shape of the brain cysts was a perfect circle.RPC,FD,andPDdid not vary among cysts of different strains, age, and derived from mice of different genetic background. Conversely, lacunarity, which is a measure of heterogeneity, was significantly lower for BGD1 strain vs. all other strains, and higher for Me49 vs. BGD14 and BGD26, but did not differ among Me49 cysts of different age, and derived from genetically different mice. This study is the first application of fractal analysis in describing the structural complexity ofT. gondiicysts. Despite all the differences among the analyzed cysts, most parameters remained conserved. Fractal analysis is a novel and widely accessible approach, which along with particle analysis may be applied to gain further insight intoT. gondiicyst morphology.

peer-reviewed Molecular separation of pharmaceutical contaminants from water has been recently of great interest to alleviate their detrimental impacts on environment and human well-being. As the novelty, this investigation aims to develop a mechanistic modeling approach and consequently its related CFD-based simulations to evaluate the molecular separation efficiency of ibuprofen (IP) and its metabolite 4-isobutylacetophenone (4-IBAP) from water inside a porous membrane contactor (PMC). For this purpose, octanol has been applied as an organic phase to extract IP and 4-IBAP from the aqueous solution due to high solubility of solutes in octanol. Finite element (FE) technique is used as a promising tool to simultaneously solve continuity and Navier-Stokes equations and their associated boundary conditions in tube, shell and porous membrane compartments of the PMC. The results demonstrated that the application of PMC and liquid-liquid extraction process can be significantly effective due to separating 51 and 54% of inlet IP and 4-IBAP molecules from aqueous solution, respectively. Moreover, the impact of various operational / functional parameters such as packing density, the number of fibrous membrane, the module length, the membrane porosity / tortuosity, and ultimately the aqueous solution flow rate on the molecular separation efficiency of IP and 4-IBAP is studied in more details

Over the last 20 years, remarkable advances have taken place in the research on reactive powder concrete (RPC). However, because of the high contents of cement and silica fume (SF) usually used in those types of concrete, the cost and environmental impact of RPC is considerably higher than conventional concrete. Hence, the use of supplementary cementitious materials as partial substitution of cement and SF has been an object of great interest by the scientific community. However, the replacement of cement and SF can result in the deterioration of certain properties of RPC, such as the early strength; however, RPC usually needs great amounts of cement and SF. This work presents a study to analyze the effect of metakaolin (MK) as a partial substitute of cement in a previously optimized mixture of RPC using statistical tools such central composite design, main effect plot analysis, and response surface methodology. In addition to MK, supplementary cementitious materials such as SF, limestone powder and recycled glass powder, and fine Type III cement were used. Based on the laboratory experiments results and statistical analysis, it was concluded than MK develops a high activity in the hydration process of RPC, helping it reach high strength at early ages, such as 1 and 7 days, which may be of interest for applications such as the connection of prefabricated elements or accelerated bridge construction. However, the effect of the partial substitution of Type III cement by MK on 28-day compressive strength was nonsignificant. Moreover, the MK inclusion in RPC provides a significant decrease in workability as the amount of MK increases., En los últimos 20 años se han producido notables avances en la investigación sobre el hormigón reactivo en polvo (RPC). Sin embargo, debido a los elevados contenidos de cemento y humo de sílice (SF) que suelen emplearse en esos tipos de hormigón, el coste y el impacto medioambiental del RPC son considerablemente superiores a los del hormigón convencional. De ahí que el uso de materiales cementantes suplementarios como sustitución parcial del cemento y el SF haya sido objeto de gran interés por parte de la comunidad científica. Sin embargo, la sustitución del cemento y el SF puede provocar el deterioro de ciertas propiedades del RPC, como la resistencia temprana; además, el RPC suele necesitar grandes cantidades de cemento y SF. Este trabajo presenta un estudio para analizar el efecto del metacaolín (MK) como sustituto parcial del cemento en una mezcla previamente optimizada de RPC utilizando herramientas estadísticas como el diseño compuesto central, el análisis de parcelas de efectos principales y la metodología de superficie de respuesta. Además del MK, se utilizaron materiales cementantes suplementarios como SF, polvo de caliza y polvo de vidrio reciclado, y cemento fino de tipo III. Basándose en los resultados de los experimentos de laboratorio y el análisis estadístico, se concluyó que el MK desarrolla una alta actividad en el proceso de hidratación del RPC, ayudando a que alcance una alta resistencia a edades tempranas, como 1 y 7 días, lo que puede ser de interés para aplicaciones como la conexión de elementos prefabricados o la construcción acelerada de puentes. Sin embargo, el efecto de la sustitución parcial del cemento Tipo III por MK sobre la resistencia a compresión a 28 días no fue significativo. Además, la inclusión de MK en el EPR proporciona una disminución significativa de la trabajabilidad a medida que aumenta la cantidad de MK.

AL-DAHAWI, Ali/0000-0001-7836-1525; Banyhussan, Qais/0000-0002-5927-0633; Abdulhameed, Ali A./0000-0002-6845-3669; Hanoon, Ammar/0000-0002-1369-9856 WOS: 000502361000022 Wet packing approach is recently used to design different kinds of concrete. To achieve an optimal particle packing density, the particles should be chosen in a way to fill the voids between larger particles with smaller ones for obtaining a dense and stiff particle structure. The majority of past research on packing density has focused on the evaluation of the particle size distribution of granular matrix to gain improvements in the packing density of cementitious materials, while limited attention has been paid to the construction of a model to estimate the packing density value. To serve that purpose, in this study, a series of 216 collected samples were used for proposing a model. The dataset was divided into two main sets for construction and verification of the model. As the basis for the packing density modeling, use of the gravitational search algorithm (GSA) was proposed. Design of experiment (DOE) software was used to evaluate the contribution of each variable on the proposed model. The outcomes indicate that among different parameters, water amount has the largest effect on the packing density value of cementitious pastes. Moreover, increases in the amounts of supplementary cementitious materials up to certain levels increase the packing density. The coefficient of variation (CoV) of the proposed model is 6.3% which reflects the accuracy and consistency of the model.

The treatment of wastewater from the iron and steel industry is difficult due to its complex and changeable characteristics. This paper introduces the application of polyvinylidene fluoride (PVDF)-pressurized ultrafiltration membrane with low packing density that produced via thermally induced phase separation (TIPS) in wastewater of iron and steel industry, to study the effects of packing density of ultrafiltration membrane modules as well as the membrane performance under different operation conditions, in order to provide guidance for the subsequent development of other ultrafiltration applications in wastewater of iron and steel. The results show a significant positive effect of smaller packing density on the transmembrane pressure difference (TMP) reducing and higher permeability. Under 30 min filtration cycle and 65 L m−2 h−1 (LMH) operation flux, the permeability can be stabilized to 200 L/(m2·h)/0.1 MPa, which is two times higher than that of the membrane module with 0.3 m2/m3 higher packing density under the same condition. It is obvious that compared with enhanced flux maintenance (EFM), chemically enhanced backwash (CEB) is a more effective cleaning method for iron and steel wastewater, which maintains TMP (30 kPa) without any significant increase under the premise of ensuring the high-flux (65 LMH) operation. The results also suggest reasonable parameters based on the test water quality, which include the filtration cycle and operation flux. The scanning electron microscopy (SEM) analysis and the turbidity of the permeate show that the ultrafiltration membrane has good intercept ability and high anti-pollution performance.

Storage is still limiting the implementation of hydrogen as an energy carrier to integrate the intermittent operation of renewable energy sources. Among different solutions to the currently used compressed or liquified hydrogen systems, physical adsorption at cryogenic temperature in porous materials is an attractive alternative due to its fast and reversible operation and the resulting reduction in storage pressure. The feasibility of cryoadsorption for hydrogen storage depends mainly on the performance of the used materials for the specific application, where metal-organic frameworks or MOFs are remarkable candidates. In this work, gravimetric and volumetric hydrogen uptakes at 77 K and up to 100 bar of commercially available MOFs were measured since these materials are made from relatively cheap and accessible building blocks. These materials also show relatively high porous properties and are currently near to large-scale production. The measuring device was calibrated at different room temperatures to calculate an average correction factor and standard deviation so that the correction deviation is included in the measurement error for better comparability with different measurements. The influence of measurement conditions was also studied, concluding that the available adsorbing area of material and the occupied volume of the sample are the most critical factors for a reproducible measurement, apart from the samples’ preparation before measurement. Finally, the actual volumetric storage density of the used powders was calculated by directly measuring their volume in the analysis cell, comparing that value with the maximum volumetric uptake considering the measured density of crystals. From this selection of commercial MOFs, the materials HKUST-1, PCN-250(Fe), MOF-177, and MOF-5 show true potential to fulfill a volumetric requirement of 40 g·L−1 on a material basis for hydrogen storage systems without further packing of the powders.

Purpose: A high packing density (PD) (i.e., coil volume per aneurysm volume) helps prevent recanalization after endosaccular embolization of cerebral aneurysms. We hypothesized that the use of soft coils may be useful to raise PD and retrospectively investigated the correlation between the ED coil volume rate (i.e., volume ratio of all placed coils) and PD in patients treated with endosaccular embolization using this coil. Methods: Excluding aneurysms treated with a stent, 292 aneurysms treated using ED coils were included in this study. The 292 aneurysms and aneurysms with ≥30%, ≥40%, and ≥50% ED coil volume rates (202, 168, and 129 aneurysms, respectively) underwent linear regression analysis of the following seven factors' influence on PD:ED ratio, aneurysm volume, neck width, height, maximum diameter, dome-to-neck ratio, and aspect ratio. Results: Independent factors of a high PD were high ED ratio and small neck width on analyses of aneurysms with an ED ratio of ≥40% and ≥50%. Only neck width was an independent factor on analyses of all 292 aneurysms and aneurysms with ED ratio of ≥30%. Conclusion: The use of ED coils in high volume rate correlated with a high PD and may contribute to prevent recanalization in small aneurysms.