Densification Properties Research Articles

Convergence of the Incremental Projection Method Using Conforming Approximations

Abstract We prove the convergence of an incremental projection numerical scheme for the time-dependent incompressible Navier–Stokes equations, without any regularity assumption on the weak solution. The velocity and the pressure are discretized in conforming spaces, whose compatibility is ensured by the existence of an interpolator for regular functions which preserves approximate divergence-free properties. Owing to a priori estimates, we get the existence and uniqueness of the discrete approximation. Compactness properties are then proved, relying on a Lions-like lemma for time translate estimates. It is then possible to show the convergence of the approximate solution to a weak solution of the problem. The construction of the interpolator is detailed in the case of the lowest degree Taylor–Hood finite element.

Asymptotic Consistency for Nonconvex Risk-Averse Stochastic Optimization with Infinite-Dimensional Decision Spaces

Optimal values and solutions of empirical approximations of stochastic optimization problems can be viewed as statistical estimators of their true values. From this perspective, it is important to understand the asymptotic behavior of these estimators as the sample size goes to infinity. This area of study has a long tradition in stochastic programming. However, the literature is lacking consistency analysis for problems in which the decision variables are taken from an infinite-dimensional space, which arise in optimal control, scientific machine learning, and statistical estimation. By exploiting the typical problem structures found in these applications that give rise to hidden norm compactness properties for solution sets, we prove consistency results for nonconvex risk-averse stochastic optimization problems formulated in infinite-dimensional space. The proof is based on several crucial results from the theory of variational convergence. The theoretical results are demonstrated for several important problem classes arising in the literature.

Structure evolution and magnetization properties of FeSiBCCr amorphous alloys prepared by spark plasma sintering

FeSiBCCr bulk metallic glasses were prepared via spark plasma sintering, and the effects of holding time and heating rate on the structure and magnetization properties of powder compacts were investigated by SEM, TEM, XRD, DSC and VSM. The results show that when the holding time is increased from 10 min to 20 min, the internal porosity is reduced, and the amorphous fraction is decreased from 92.0 ± 1.7 % to 82.4 ± 4.3 % accompanied by the precipitation of fine nanocrystalline grains. When the holding time is increased to 30 min, the precipitation of the ferro-boron phase and growth of nanocrystalline grains lead to a significant deterioration of magnetization properties, although the compact density is significantly increased to 6.13±0.12 g/cm3. When the heating rate is increased from 20 K/min to 100 K/min, the activation energy of viscous flow is decreased and the compact density is improved due to the enhanced mass transfer. Moreover, the thermal stability of the amorphous material is also improved, effectively suppressing the grain coarsening and the precipitation of the ferro-boron phase. As a result, the saturation magnetic flux density is increased by 10 % and the coercivity is reduced by 83 %. The FeSiBCCr bulk metallic glasses prepared at a sintering temperature of 773 K, a heating rate of 100 K/min, and a holding time of 10 min contain an amorphous matrix with fine Fe2Si grains. And the compact has a density of 5.60±0.08 g/cm3, a saturation magnetic flux density of 1.03±0.03 T, and a coercivity of 15.9 ± 1.2 A/m, exhibiting promising magnetization properties and being expected to be used in medium and high frequency electronics.

Mechanical Properties and Dry–Wet Stability of Soda Residue Soil

To effectively utilize the effectively the solid waste-soda residue (SR) and fly ash (FA), a mixture of 70% SR, 20% FA, and 10% clay was formed to produce soda residue soil (SRS). By adding cement and/or lime, four different SRS proportions were prepared. The compaction properties, mechanical properties, and dry–wet stability. Furthermore, the mechanical mechanisms of SRS were explored, and the improvement effect and efficiency of cement and/or lime on the mechanical performance of SRS were analyzed. The results show that the SRS is lightweight and easy to compact and shape, which is conducive to construction. Compared to cement, lime has a greater impat on the compaction properties of SRS. The mechanical properties of SRS are enhanced after adding cement and/or lime; the unconfined compressive strength (UCS), California Bearing Ratio (CBR), and resilient modulus all increase significantly. The UCS, CBR, and resilient modulus of SRS with different proportions all increase with the increase of compaction degree; the CBR and resilient modulus can meet the requirements of the subgrade, and the UCS can meet the requirements of the base and sub-base. The contribution rate of cement per unit amount is better than that of lime to the mechanical performance of SRS. As dry–wet cycles increase, the dry–wet stability of SRS with different proportions first increases and then decreases, which is affected by hydration and dry–wet deterioration together, with a critical cycle number for the strength transition. The excellent mechanical performance of SRS benefits from the gradation and chemical action. The particles of SR, FA, and clay can complement each other and perform an interlocking action. Therefore, SRS has a good gradation and forms a dense and stable structure. Also, the chemical reactions between materials are very important. The cement and/or lime have a hydration and gelling effect, FA and clay participate in pozzolanic reactions, and SR and FA have certain alkali-activated effects.

Dielectric Properties of Compacts Sintered after High-Pressure Forming of Lithium Fluoride

High-pressure forming at 300 MPa and room temperature was applied before the sintering of a lithium fluoride (LiF) powder. The as-fired samples were tested as dielectrics and showed very interesting characteristics. The best sample, sintered at 750 °C for 8 h, had a relative permittivity of 12.1 and a loss tangent of 0.0006, both of them frequency-independent and temperature-independent up to at least 150 °C, and moreover, the volume DC resistivity was 27.4 × 1012 Ωm at room temperature. These parameters are comparable with oxide ceramics, processed at temperatures over 1300 °C, as for example, aluminum dioxide (Al2O3) or Y3Al5O12 (YAG). LiF material is advantageous because of its very low sintering temperature, which is only about one-half of typical oxide ceramic dielectrics.

Leveraging a multivariate approach towards enhanced development of direct compression extended release tablets

Extended release formulations play a crucial role in the pharmaceutical industry by maintaining steady plasma levels, reducing side effects, and improving therapeutic efficiency and compliance. One commonly used method to develop extended release formulations is direct compression, which offers several advantages, such as simplicity, time savings, and cost-effectiveness. However, successful direct compression-based extended release formulations require careful assessment and an understanding of the excipients’ attributes. The scope of this work is the characterization of the compaction behavior of some matrix-forming agents and diluents for the development of extended release tablets. Fifteen excipients commonly used in extended release formulations were evaluated for physical, compaction and tablet properties. Powder properties (e.g., particle size, flow properties, bulk density) were evaluated and linked to the tablet’s mechanical properties in a fully integrated approach, and data were analyzed by constructing a principal component analysis (PCA). Significant variability was observed among the various excipients. The present work successfully demonstrates the applicability of PCA as an effective tool for comparative analysis, pattern and clustering recognition and correlations between excipients and their properties, facilitating the development and manufacturing of direct compressible extended release formulations.

Study on Compaction Properties and Skeleton Structural Characteristics of Porous Asphalt Mixture

Porous asphalt pavements have a skeletal structure with a large number of interconnecting pores, which can improve drainage, ensure traffic safety, and reduce tire noise. However, it can weaken the mechanical properties of the pavement. One of the key factors affecting the performance of porous asphalt pavements is the quality of compaction, the assessment of which is difficult to accurately quantify. Therefore, Superpave gyratory compaction (SGC) and skeleton penetration tests of porous asphalt mixtures were carried out using three engineering-differentiated gradations in this paper to investigate the gyratory compaction characteristics and the skeleton contact state during penetration. The results show that obvious stages with the increase in number of cycles can be observed during the compaction process. All gradations can achieve the maximum porosity requirements within a reasonable number of compaction cycles, while only the medium and fine gradations can approximately meet the minimum porosity requirements. The coarse gradation takes too long to finish compaction and is almost impossible to meet the minimum porosity. The optimum match between the void ratio of the design gradation and the skeleton contact state can be verified using the VCA ratio and void ratio curves. This is a new method to determine the corresponding target compaction number that can ensure better accuracy and ease of engineering application. Moreover, medium-graded mixtures with better skeletal embedding exhibit greater skeletal strength than coarse-graded aggregates, which provide theoretical support for the establishment of material grade optimization methods.

COMPACTION CHARACTERISTICS AND WORKABILITY OF THE LATERITIC SOIL-IRON ORE TAILINGS IN PAVEMENT CONSTRUCTION

The mining waste deposit such as iron ore tailings (IOT) in Nigeria is a menace to the environment by constituting a nuisance to the mining industry, and its effect on lateritic soil as a compaction and plasticity reduction material for road pavement is considered in this study. The used natural lateritic soil was classified as A-7-6(11) or CL by the American Association of State Highway and Transportation Officials (AASHTO) and Unified Soil Classification System (USCS) respectively. Up to 16% of the soil’s dry weight was modified with iron ore tailings (IOT). Studying the effects of IOT on the altered soil focused on its cation exchange capacity, plasticity, compaction properties and California bearing ratio (CBR). British Standard Light (BSL) energy was used for the compaction process. However, the results of regression analysis showed that the optimum moisture content had a substantial impact on the soil CBR values. The results of the tests show that as the IOT content increased, plasticity and compaction characteristic values increased. Although an optimal 10% IOT treatment of lateritic soil significantly improved its strength properties, the plasticity characteristics recorded exceeded the requirement specified by the Nigerian General Specifications for direct use as a subbase or base material. Thus, reusing 10% iron ore tailings as filling materials required additional percentages of other pozzolanic materials to lessen the environmental problems associated with their deposition.

Exploring Design Optimization of Self-Compacting Mortars with Response Surface Methodology

The ever-evolving construction sector demands technological developments to provide consumers with products that meet stringent technical, environmental, and economic requirements. Self-compacting cementitious mixtures have garnered significance in the construction market due to their enhanced compaction, workability, fluidity, and mechanical properties. This study aimed to harness the potential of statistical response surface methodology (RSM) to optimize the fresh properties and strength development of self-compacting mortars. A self-compacting mortar repository was used to build meaningful and robust models describing D-Flow and T-Funnel results, as well as the compressive strength development after 24 h (CS24h) and 28 days (CS28d) of curing. The quantitative input factors considered were A (water/cement), B (superplasticizer/powder), C (water/powder), and D (sand/mortar), and the output variables were Y1 (D-Flow), Y2 (T-Funnel), Y3 (CS24h), and Y4 (CS28d). The results found adjusted response models, with significant R2 values of 87.4% for the D-Flow, 93.3% for the T-Funnel, and 79.1% for the CS24h. However, for the CS28d model, a low R2 of 39.9% was found. Variable A had the greatest influence on the response models. The best correlations found were between inputs A and C and outputs Y1 and Y2, as well as input factors A and D for responses Y3 and Y4. The resulting model was enhanced, thereby resulting in a global desirability of approximately 60%, which showcases the potential for the further refinement and optimization of RSM models applied to self-compacting mortars.

Set-based robust optimization of uncertain multiobjective problems via epigraphical reformulations

In this paper, we study a method for finding robust solutions to multiobjective optimization problems under uncertainty. We follow the set-based minmax approach for handling the uncertainties which leads to a certain set optimization problem with the strict upper type set relation. We introduce, under some assumptions, a reformulation using instead the strict lower type set relation without sacrificing the compactness property of the image sets. This allows to apply vectorization results to characterize the optimal solutions of these set optimization problems as optimal solutions of a multiobjective optimization problem. We end up with multiobjective semi-infinite problems which can then be studied with classical techniques from the literature.

Some generalized countably compact properties in topological groups

In this paper, firstly, we study strict q-spaces, strong q-spaces and point pseudocompact spaces in topological groups in terms of preimages of metrizable spaces. A continuous mapping f:X→Y is (strongly) sequential-perfect if f is closed and (f−1(F)) f−1(y) is a sequentially compact set for each (sequentially compact set F⊆Y) y∈Y. We give some characterizations as follows:(1)A topological group G is a strict q-space if and only if it is a sequential-perfect preimage of a metrizable space.(2)A topological group G is a strong q-space if and only if it is a strongly sequential-perfect preimage of a metrizable space.(3)A topological group G is a pointwise pseudocompact space if and only if there is a continuous open mapping f from G onto a metrizable space M such that f−1(F) is an r-pseudocompact set in G for each r-pseudocompact set F in M.Secondly, we study completeness of generalized countably compact topological groups in terms of preimages of completely metrizable spaces and obtain the following results:(4)A topological group G is strictly countably sieve complete if and only if G contains a closed sequentially compact subgroup H such that the quotient space G/H is completely metrizable and the canonical quotient mapping π:G→G/H is sequential-perfect.(5)A topological group G is countably sieve-s-complete if and only if G contains a closed sequentially compact subgroup H such that the quotient space G/H is completely metrizable and the canonical quotient mapping π:G→G/H is strongly sequential-perfect.(6)A topological group G is countably sieve-p-complete if and only if G contains a closed r-pseudocompact subgroup H such that the quotient space G/H is completely metrizable and the canonical quotient mapping π:G→G/H satisfies that π−1(F) is r-pseudocompact in G for each r-pseudocompact set F in G/H.

Shredded Waste Tyre General Approach as a Construction Material

The optimum percentage of shredded waste tyre was found out by addition of shredded waste tyre up to 20% at an increment of 5% to a lateritic soil and finding the Compaction properties, UCS and soaked CBR of lateritic soil-shredded waste tyre mixes. The optimum percentage of shredded waste tyre for stabilization of lateritic soil was found to be 10%. Compaction properties, UCS, soaked CBR, Hydraulic conductivity and Volumetric shrinkage strain of carbide sludge stabilized lateritic soil –shredded waste tyre mixes were found out.

In-cell investigation of the conformational landscape of the GTPase UreG by SDSL-EPR

UreG is a cytosolic GTPase involved in the maturation network of urease, an Ni-containing bacterial enzyme. Previous investigations invitro showed that UreG features a flexible tertiary organization, making this protein the first enzyme discovered to be intrinsically disordered. To determine whether this heterogeneous behavior is maintained in the protein natural environment, UreG structural dynamics was investigated directly in intact bacteria by in-cell EPR. This approach, based on site-directed spin labeling coupled to electron paramagnetic resonance (SDSL-EPR) spectroscopy, enables the study of proteins in their native environment. The results show that UreG maintains heterogeneous structural landscape in-cell, existing in a conformational ensemble of two major conformers, showing either random coil-like or compact properties. These data support the physiological relevance of the intrinsically disordered nature of UreG and indicates a role of protein flexibility for this specific enzyme, possibly related to the regulation of promiscuous protein interactions for metal ion delivery.

Standing waves for Schrödinger equations with Kato–Rellich potentials

We show the existence of standing waves for the nonlinear Schrödinger equation with Kato-Rellich type potential. We consider both resonant with the nonlinearity satisfying one of Landesman–Lazer type or sign conditions and non-resonant case where the linearization at infinity has zero kernel. The approach relies on the geometric and topological analysis of the parabolic semiflow associated to the involved elliptic problem. Tail estimates techniques and spectral theory of unbounded linear operators are used to exploit subtle compactness properties necessary for use of the Conley index theory due to Rybakowski. The obtained results extend those by Prizzi (2003) for the non-resonant case, resolve the existence problem at resonance and complete those from A. Ćwiszewski and W. Kryszewski (2019) where the bifurcation of stationary solutions from infinity was studied.

Active pullulan-based coatings incorporated with Auricularia auricular extracts for preserving potato fresh-cuts.

In the present study, Auricularia auricular polysaccharides (AAP) and Auricularia auricular proteins (AAPR) obtained from the waste products of Auricularia auricular were incorporated into pullulan (PUL) to obtain active packaging films/coatings. Results showed that incorporating AAP/AAPR into PUL-based films decreased their transparency, but increased the compactness, thermal stability, antioxidant, and antimicrobial properties. Adding 2% PUL films with 10%:10% of AAP/AAPR exhibiting good mechanical properties were applied to fresh-cut potatoes to avoid spoilage during eight days of storage, with significantly decreased in browning index, weight loss, microbial growth prevention and the total soluble solids was maintained. These results substantiated that pullulan containing AAP/AAPR as an active film/coating with antioxidant and antimicrobial properties has significant potential for maintaining safety and quality of fresh-cut potatoes and extending their shelf life.

Sustainable Use of Recycled Asphalt Pavement in Soil Stabilization

This study addresses unused recycled asphalt pavement (RAP) incorporated into sedimentary soil from the Guabirotuba Formation in Curitiba, Southern Brazil. Different percentages of RAP, ranging from 0% to 80% by weight, were mixed with the pure soil, with and without the addition of pozzolanic Portland cement. Tests were conducted to evaluate the mixtures' compaction properties, mechanical strength, and expansion after curing for up to 28 days. The results showed that adding RAP improved the mixtures' unconfined compressive strength (qu) and splitting tensile strength (qt). Up to 60% RAP, the qu increased by 260 kPa, and the qt increased by 340 kPa compared to the pure soil. The California Bearing Ratio (CBR) tests demonstrated an 18.62% improvement when 80% RAP was added to the untreated soil. In addition, the RAP also reduced the expansion of the compacted blends, with values decreasing from 1.19% to 0.88% with 80% RAP replacement. The expansion value was further reduced to 0.86% when the cement was added. The cement-soil-RAP compacted blends showed suitability for subgrade reinforcement, meeting the criteria of expansion <1% and CBR> 2%. Additionally, 3% cement and 40% RAP mixtures were suitable as a sub-base layer, with expansion <1% and CBR > 20%. The results provide valuable insights into utilizing RAP as an alternative material in soil improvement techniques employing the novelty porosity-to-cement index. Doi: 10.28991/CEJ-2023-09-09-016 Full Text: PDF

Converting optimum compaction properties of fine-grained soils between rational energy levels

This study introduces a practical energy conversion (EC)-type modeling framework capable of converting the optimum compaction properties of fine-grained soils between any two rational compaction energy levels (CELs). Model development/calibration was carried out using a database of 242 compaction test results — the largest and most diverse database of its kind, to date, entailing 76 fine-grained soils (covering liquid limits of 16–256%), with each soil tested for at least three different CELs. On establishing the framework, an independent database of 91 compaction test results (consisting of 34 fine-grained soils tested for varying CELs) was employed for its validation. The proposed EC-based models employ measured optimum water content (OWC) and maximum dry unit weight (MDUW) values obtained for a rational CEL (preferably standard Proctor) to predict the same for higher and/or lower compactive efforts (covering 214–5416 kJ/m3). The 95% lower and upper statistical agreement limits between the predicted/converted and measured OWCs were obtained as −2.16 wc % and +2.25 wc %, both of which are on par (in terms of magnitude) with the ASTM D1557 allowable limit of 2.1 wc %. For the MDUW predictions, these limits were calculated as −0.71 and +0.66 kN/m3, which can also be deemed acceptable when compared against ASTM’s allowable limit of ±0.7 kN/m3 (= ±4.4 lb/ft3). The proposed framework offers a reasonably practical procedure to accurately convert the optimum compaction parameters across different CELs (without the need for any soil index properties), and thus can be used with confidence for preliminary project design assessments.

The influence of directly compressible fillers/diluents on selected compact properties and drug dissolution: a case study of rivaroxaban

The influence of directly compressible fillers/diluents on selected compact properties and drug dissolution: a case study of rivaroxaban

Effects of Stearic Acid and Zein Incorporation on Refined Kappa Carrageenan-Based Composite Edible Film Properties

Incorporating hydrophobic materials into a polysaccharide-based film to form a composite edible film has been considered an effective way to strengthen the film properties, especially the water vapor resistance. Fatty acids, such as stearic acid, with long-chain and straight structures, exhibit strong hydrophobic performance to prevent water vapor diffusion through the film surface. Meanwhile, zein has been revealed as an encouraging material due to its compactness, less allergic, and gas barrier properties. The investigation of kappa-carrageenan/zein/stearic acid-based green composite edible film has been limited. Thus, this study aims to examine the effect of increasing stearic acid and zein concentrations on improving the moisture barrier and mechanical properties of kappa carrageenan-based composite edible film. Different concentrations of stearic acid (5, 10, and 15% w/w carrageenan) and zein (2.5, 5, and 7.5% w/w carrageenan) were applied to the composite edible film prepared using the solution casting method. The fabricated films have a thickness of 0.092–0.122 mm. The results indicated that increasing the concentration of stearic acid enhances the water vapor barrier and tensile strength of the edible film (p < 0.05). However, the increased zein concentration slightly weakened the water vapor barrier properties. Then, the elongation of the manufactured films was quite improved by the increment of stearic acid proportion, but neither by the increment of zein proportion nor the combination of these two substances. However, the incorporation of stearic acid and zein into refined-kappa carrageenan-based film remarkably improved the tensile strength, elongation, and water vapor barrier properties by 12–18%, 23–27%, and 43–44%, respectively, in comparison to the neat film. Based on the analysis result, the manufactured film which consists of 10% stearic acid and 2.5% zein is considered as the best film formula. This study, therefore, revealed the potentiality of stearic acid enforcement in food packaging applications.

Equivalence of minimax and viscosity solutions of path-dependent Hamilton–Jacobi equations

In the paper, we consider a path-dependent Hamilton–Jacobi equation with coinvariant derivatives over the space of continuous functions. Such equations arise from optimal control problems and differential games for time-delay systems. We study generalized solutions of the considered Hamilton–Jacobi equation both in the minimax and in the viscosity sense. A minimax solution is defined as a functional which epigraph and subgraph satisfy certain conditions of weak invariance, while a viscosity solution is defined in terms of a pair of inequalities for coinvariant sub- and supergradients. We prove that these two notions are equivalent, which is the main result of the paper. As a corollary, we obtain comparison and uniqueness results for viscosity solutions of a Cauchy problem for the considered Hamilton–Jacobi equation and a right-end boundary condition. The proof of the main result is based on a certain property of the coinvariant subdifferential. To establish this property, we develop a technique going back to the proofs of multidirectional mean-value inequalities. In particular, the absence of the local compactness property of the underlying continuous function space is overcome by using Borwein–Preiss variational principle with an appropriate gauge-type functional.