Final Compaction Research Articles

Prediction model of compaction process parameters for pavement of cement emulsified asphalt mixture based on effective compaction work

Cement emulsified asphalt mixture (CEAM) is a semi-flexible pavement material, which is formed by the organic combination of aggregate, cement, emulsified asphalt and water. The compaction process of CEAM includes demulsification of emulsified asphalt, hydration of cement, evaporation of water, and formation of a three-dimensional interwoven network of aggregate, cement and asphalt. Therefore, it has different compaction deformation characteristics from the hot asphalt mixture. In order to explore the theoretical model of compaction process parameters for pavement (PCPP), which are based on compaction deformation characteristics and strain energy theory, effective compaction work (ECW) was defined as the compaction work consumed by viscoplastic compression displacement of the material. The mechanical response is studied by compressive testing and a calculation model for lab-scale effective compaction work (LECW) is established for CEAM. Furthermore, a calculation model for effective compaction work in pavement (PECW) is established based on the work-energy equivalence principle and roller compaction datas. In addition, a prediction model of PCPP for target dense degree (TDD) is obtained by the equivalence of LECW and PECW, and the introduction of energy absorption efficiency (EAE). Moreover, the PCPP combination modes during three stages, i.e., initial compaction, re-compaction and final compaction, of the roller are determined according to the compaction deformation characteristics of CEAM material. Based on the compaction combinations modes, the compaction process parameters combinations (CPPC) during the three compaction stages for the TDD are derived from the prediction model. The reliability of the proposed model is verified by a road compaction test. The CPPC results reveal the reliability of established LECW and PECW models. However, the EAE of vibration compaction in the prediction model is revised to be 76.05% after the road compaction test. The prediction model and introduction of EAE provide a theoretical baseline for the parametric design of compaction and construction process of CEAM and other pavement materials.

The mechanical property and microscopic deformation mechanism of nanoparticle-contained graphene foam materials under uniaxial compression

Nanoparticle-contained graphene foams have found more and more practical applications in recent years, which desperately requires a deep understanding on basic mechanics of this hybrid material. In this paper, the microscopic deformation mechanism and mechanical properties of such a hybrid material under uniaxial compression, that are inevitably encountered in applications and further affect its functions, are systematically studied by the coarse-grained molecular dynamics simulation method. Two major factors of the size and volume fraction of nanoparticles are considered. It is found that the constitutive relation of nanoparticle filled graphene foam materials consists of three parts: the elastic deformation stage, deformation with inner re-organization and the final compaction stage, which is much similar to the experimental measurement of pristine graphene foam materials. Interestingly, both the initial and intermediate modulus of such a hybrid material is significantly affected by the size and volume fraction of nanoparticles, due to their influences on the microstructural evolution. The experimentally observed ‘spacer effect’ of such a hybrid material is well re-produced and further found to be particle-size sensitive. With the increase of nanoparticle size, the micro deformation mechanism will change from nanoparticles trapped in the graphene sheet, slipping on the graphene sheet, to aggregation outside the graphene sheet. Beyond a critical relative particle size 0.26, the graphene-sheet-dominated deformation mode changes to be a nanoparticle-dominated one. The final microstructure after compression of the hybrid system converges to two stable configurations of the ‘sandwiched’ and ‘randomly-stacked’ one. The results should be helpful not only to understand the micro mechanism of such a hybrid material in different applications, but also to the design of advanced composites and devices based on porous materials mixed with particles.

Soil management in semi-arid vineyards: Combined effects of organic mulching and no-tillage under different water regimes

Optimizing water use in vineyards is crucial for ensuring the sustainability of viticulture in semi-arid regions, and this may be achieved by minimizing direct water evaporation from the soil through the use of mulching. In this context, the current study aimed at assessing the combined effects of the vine-row application of an organic mulch (vine prunings) and no-tillage under two water regimes on soil properties, plant water and nutritional status, yield and must composition of grapevine (Vitis vinifera L.) cv. Bobal grown under semi-arid conditions. For this purpose, a field experiment in a split-plot design was carried out for three years (2016–2018) in a mature Bobal vineyard located in Eastern Spain. Two soil management strategies (tillage and organic mulching with no-tillage) were assessed under two water regimes (rainfed and deficit drip irrigation) with four replications per combination. Vine responses were determined by measuring midday stem water potential, leaf nutrient concentrations, pruning weight, yield components and grape composition. Soil properties were assessed at the end of the experiment. Mulching and no-tillage positively affected vine water status under both water regimes, resulting in reductions in grape phenolic composition. Interactive effects of both water regime and soil management on water use efficiency were found. Regardless of soil management practice, irrigation increased yield and pruning weight when compared to rainfed conditions. Soil management had slight effects on vine nutritional status. At the end of the experiment, soil compaction increased and infiltration decreased as a consequence of mulching and no-tillage. Organic mulch and no-tillage improved vine water status, however, considering the final soil surface compaction and low water infiltration rate, longer-term studies are necessary to assess the sustainability of combining both practices.

Power‐controlled flash spark plasma sintering of gadolinia‐doped ceria

AbstractElectric field‐assisted sintering (FAST) is a rapidly growing scientific and engineering domain. In the present paper, we describe the process of flash sintering (FS) in a configuration of classical spark plasma sintering (SPS) (graphite punch and boron nitride (BN) die), also called flash spark plasma sintering (FSPS). The densification process of Gd0.1Ce0.9O2‐x powder is studied in detail with a focus on the transition from FAST to FS. We discuss the electrical, geometrical, and thermal evolution of the process and the characteristics of the final compacts. Low electrical fields are sufficient for the onset of FS. Ceria is a material difficult to sinter by FAST techniques due to its known mechanochemical transformations. We observed the disintegration of pellets after experiments with well‐pronounced flash event.

Meso-scale study on compaction characteristics of asphalt mixtures in Superpave gyratory compaction using SmartRock sensors

Compaction degree is an essential parameter to characterize the construction quality and performance of asphalt pavement. Under the same compaction conditions, asphalt mixtures with different aggregate sizes and gradation may exhibit different compaction characteristics. Accordingly, this paper aims to study the compaction characteristics of asphalt mixture at the meso-scale through particle response of the mixture by using SmartRock sensor. Firstly, a laboratory test scheme of the asphalt mixture is designed and the SmartRock sensors are used to obtain the internal stress of the mixture during compaction. By comparing the particle stress with the height of the specimen, it is inferred that the stress state of the particles can reflect the compactness of the compacted material, and the change rate of compaction degree in logarithmic coordinates is proposed to characterize the compaction performance of the asphalt mixture. Furthermore, the quantitative analysis is comprehensively conducted related to the different nominal maximum aggregate size (NMAS), locations and gradation types. The results reveal that the asphalt mixture with larger NMAS has a better compactibility in terms of forming a stable skeleton structure, and the mixture in the middle of specimen can be compacted more easily than that in the top and bottom area of specimen. It can be aslo found that the gradation type affects the compaction performance through the probability of coarse aggregates interlocking with each other. The open-graded mixture (i.e, PAC-16) is relatively faster to achieve the target compaction degree than gap-graded and dense-graded mixtures (i.e, SMA-16 and AC-16, respectively). Although the asphalt mixture with larger NMAS and coarser gradation can reach a certain compaction degree with a rapid speed, it doesn't mean the mixture can achieve higher compaction degree finally under the action of subsequent compaction work. The test result shows that the asphalt mixture with coarser aggreages is relatively difficult to compact with lower final compactness. The experimental research sheds substantial light on the internal relationships between the response of the particles and compaction charateristics of asphalt mixture at meso-scale.

Evaluation of a Novel Polymeric Flocculant for Enhanced Water Recovery of Mature Fine Tailings

The novel cationic flocculant, poly(lactic acid) choline iodide ester methacrylate (poly(PLA4ChMA)), has been shown to provide improved flocculation of 5.0 wt.% mature fine tailings (MFT) diluted in deionized water compared to commercial anionic polymers, with continued dewatering of the sediment occurring as the polymer undergoes partial hydrolytic degradation. However, the elevated dosages (10,000 ppm) required would make the polymer costly to implement on an industrial scale. With this motivation, the impact of MFT loading and the use of process water is explored while comparing the settling performance of poly(PLA4ChMA) to available commercial alternatives such as anionic FLOPAM A3338. Improved consolidation of 5.0 wt.% MFT diluted with process water could be achieved at reduced dosages (500 ppm) with poly(PLA4ChMA). However, the final compaction levels after polymer degradation were similar to those achieved with the nondegradable commercial flocculants. Flocculation-filtration experiments with undiluted MFT are also conducted to compare the performance of the polymers. Significantly faster rates of water release were observed with the cationic flocculants compared to FLOPAM A3338, but no improvement in the overall tailings compaction was found either before or after poly(PLA4ChMA) degradation. Thus, the improved dewatering observed with poly(PLA4ChMA) in dilute MFT suspensions does not extend to conditions that would be encountered in the field.

Crashworthiness of polystyrene foam and cardboard panels reinforced with carbon fiber reinforced polymer and glass fiber reinforced polymer composite rods

This article presents an experimental study on the quasi-static crushing performance of carbon fiber reinforced polymer (CFRP) rods consisting of unidirectional carbon fibers wrapped by braided glass fibers. Rods with and without a taper are tested and then inserted in extruded and expanded polystyrene foam and cardboard panels. Hybrid columnar aluminum tube–CFRP rod structures are also tested in all panel materials. These results are compared to those based on glass fiber reinforced polymer (GFRP) rods, GFRP rods in polystyrene foams, and to GFRP rods in cardboard from a previous study. Tapered CFRP rods exhibit progressive crushing behavior with specific energy absorption superior to GFRP rods, with values of 82 kJ/kg and 65 kJ/kg, respectively. Moreover, the highest specific energy absorption (111 kJ/kg) is obtained in hybrid columnar aluminum tube–CFRP tapered rods, exceeding values of aluminum tubes (89 kJ/kg) and equivalent structures containing GFRP rods (102 kJ/kg). Within panels, cardboard produces the largest increase in mean load of CFRP and GFRP rods due to most constraining fiber splaying during crushing, followed by extruded foam, and lastly expanded foam. However, crushing displacement is most restricted in cardboard due to earlier final compaction. The smallest variations in crushing load occur in extruded polystyrene due to greater homogeneity throughout the foam structure.

A High-performance Homogeneous Droplet Routing Technique for MEDA-based Biochips

Recent advancement of microelectrode-dot-array (MEDA)-based architecture for digital microfluidic biochips has enabled a major enhancement in microfluidic operations for traditional lab-on-chip devices. One critical issue for MEDA-based biochips is the transportation of droplets. MEDA allows dynamic routing for droplets of different size. In this article, we propose a high-performance droplet routing technique for MEDA-based digital microfluidic biochips. First, we propose the basic concept of droplet movement strategy in MEDA-based design together with a definition of strictly shielded zones within the layout in MEDA architecture. Next, we propose transportation schemes of droplets for MEDA architecture under different blockage or crossover conditions and estimate route distances for each net in offline. Finally, a priority-based routing strategy combining various transportation schemes stated earlier has been proposed. Concurrent movement of each droplet is scheduled in a time-multiplexed manner. This poses critical challenges for parallel routing of individual droplets with optimal sharing of cells formulating a routing problem with higher complexity. The final compaction solution satisfies the timing constraint and improves fault tolerance. Simulations are carried out on standard benchmark circuits, namely, Benchmark suite I and Benchmark suite III. Experimental results show satisfactory improvements and prove a high degree of robustness for our proposed algorithm.

Population balance modelling of ribbon milling with a new mass-based breakage function.

Dry granulation through roll compaction followed by milling is a widely used pharmaceutical process. The material properties of powders and the roll compaction process conditions affect the strength of ribbons, and subsequently the granule size distribution (GSD). Accurate prediction of the granule size distribution from milling of ribbons with different properties is essential for ensuring tablet quality in the final compaction stage. In this study, MCC, PH-102 ribbons with precisely controlled porosities were produced and milled in a cutting mill and granule size distribution was analysed using QicPic. A population balance model with a new breakage function based on the Weibull function was developed to model the ribbon milling process. Eight model parameters were initially obtained for each ribbon porosity and very good agreement between the model and experimental results was obtained. Sensitivity analysis was then performed and thus reduced the number of model parameters that changed with ribbon porosity to two in the breakage function. The refined model was able to predict the granule size distribution both within and outside the experimental boundaries. It was shown that the model developed in this study has a great potential for predicting granule properties and therefore the optimisation of the dry granulation process.

Multi-particle FEM modelling on hot pressing of TiC-316L composite powders

316L stainless steel (abbreviated by 316L) has been applied in many key industrial areas due to its outstanding properties like corrosion resistance, ductility and biocompatibility etc. However, the relatively low strength and wear resistance of this material restrict its further application. This problem can be solved by the introduction of TiC particulate reinforcement into 316L matrix, which can effectively improve the strength, stiffness, wear resistance and high temperature strength. In the present work, three-dimensional hot pressing (HPing) of TiC-316L composite powders in a closed die is numerically reproduced by multi-particle finite element method from particulate scale. The evolution of macro- and microscopic properties during HPing is systematically characterized and analyzed, and the densification dynamics and mechanisms are identified. The results show that HPing can not only significantly decrease the pressing pressure, but also alleviate the stress concentration in the final compacts. With the increase of pressing temperature, the equivalent von Mises stresses in the compacts get smaller and the equivalent strains of TiC-316L composite powders get larger. During HPing, the voids are mainly filled by particle rearrangement and plastic deformation of 316L particles. Meanwhile, the equivalent von Mises stresses concentrated within the 316L particles firstly increase and then decrease, and the equivalent von Mises stresses concentrated within the TiC particles increase monotonically. Large stresses are mainly concentrated within the TiC particles, which are decreasing from the surface to the center of each particle. Also, larger contact normal forces are mainly distributed within and around the TiC particles.

Conformational switches control early maturation of the eukaryotic small ribosomal subunit.

Eukaryotic ribosome biogenesis is initiated with the transcription of pre-ribosomal RNA at the 5' external transcribed spacer, which directs the early association of assembly factors but is absent from the mature ribosome. The subsequent co-transcriptional association of ribosome assembly factors with pre-ribosomal RNA results in the formation of the small subunit processome. Here we show that stable rRNA domains of the small ribosomal subunit can independently recruit their own biogenesis factors in vivo. The final assembly and compaction of the small subunit processome requires the presence of the 5' external transcribed spacer RNA and all ribosomal RNA domains. Additionally, our cryo-electron microscopy structure of the earliest nucleolar pre-ribosomal assembly - the 5' external transcribed spacer ribonucleoprotein - provides a mechanism for how conformational changes in multi-protein complexes can be employed to regulate the accessibility of binding sites and therefore define the chronology of maturation events during early stages of ribosome assembly.

Analysis of cold compaction for Fe-C, Fe-C-Cu powder design based on constitutive relation and artificial neural networks

The constitutive relations for Fe-C and Fe-C-Cu powder compactions were investigated with the three consitituents: i) powder design parameters, ii) material related properties, and iii) final compaction properties. With the concept of materials informatics, this approach enables to predict the final compaction properties depending on the material conditions. The correlations between powder design parameters (particle size, graphite content, lubricant content, particle size distribution, copper content) and material related properties (ρTap, γ, a, b, n) in Shima-Oyane model were characterized by the compaction experiments and artificial neural network (ANN) model. The ANN model was developed to predict the effect of powder design parameters on the material related properties. The average mean absolute percentage error of predicted material related properties was 2.194%. The final properties (green density, density gradient, effective stress, hydrostatic stress, effective strain, volumetric strain) were calculated by the compaction simulation based on the experimental and predicted material related properties.

A double-sigmoid model for grapevine bunch compactness development

AimBunch compactness is the result of a complex dynamic process in which many bunch, berry and rachis features interact during the whole grapevine reproductive cycle. The aim of this work is to identify the different developmental stages involved in bunch compactness determination during the second growing season, from full-flowering to harvest time.Methods and Results In this work, bunch features from ten wine grapevine cultivars with diverse bunch compactness (including very loose and very compact bunches) have been periodically described. Experimental data allowed us to quantify changes in bunch compactness from berry set until harvest time in an objective manner. Our results indicate that bunch compactness development follows a double-sigmoid model, characterized by two consecutive cycles, each one with a growing stage followed by a latent one. Differences in the slope factor of the growing stages and in the duration of each developmental phase can explain part of the bunch compactness variation observed in our set of cultivars.ConclusionsTwo consecutive sigmoid cycles with four different stages can be observed in the determination of grapevine bunch compactness. Bunch architecture before véraison plays an important role in the final compactness of the bunch at harvest time.Significance and impact of the studyThe double-sigmoid model for bunch compactness development, and the four different stages identified will aid in future analyses aimed to unravel the underlying mechanisms affecting this complex trait.

Nut Directs p300-Dependent, Genome-Wide H4 Hyperacetylation in Male Germ Cells

Nuclear protein in testis (Nut) is a universal oncogenic driver in the highly aggressive NUT midline carcinoma, whose physiological function in male germ cells has been unclear. Here we show that expression of Nut is normally restricted to post-meiotic spermatogenic cells, where its presence triggers p300-dependent genome-wide histone H4 hyperacetylation, which is essential for the completion of histone-to-protamine exchange. Accordingly, the inactivation of Nut induces male sterility with spermatogenesis arrest at the histone-removal stage. Nut uses p300 and/or CBP to enhance acetylation of H4 at both K5 and K8, providing binding sites for the first bromodomain of Brdt, the testis-specific member of the BET family, which subsequently mediates genome-wide histone removal. Altogether, our data reveal the detailed molecular basis of the global histone hyperacetylation wave, which occurs before the final compaction of the male genome.

Moving forward: why responding to migration, mobility and HIV in South(ern) Africa is a public health priority.

IntroductionGlobal migration policy discussions are increasingly driven by moral panics – public anxiety about issues thought to threaten the moral standards of society. This includes the development of two Global Compacts – agreed principles to guide an international response – for (1) “Refugees” and (2) “Safe, Regular and Orderly Migration.” While the need to address migration and health is increasingly recognized at the global level, concerns are raised about if this will be reflected in the final Compacts. The Compacts focus on securitization, an approach that aims to restrict the movement of people, presenting potentially negative health consequences for people who move. Globally, concern is raised that migration‐aware public health programming initiatives could be co‐opted through a global health security agenda to further restrict movement across borders. This is particularly worrying in the Southern African Development Community (SADC) – a regional economic community associated with high levels of migration and the largest population of people living with HIV globally; this case is used to explore concerns about the health implications of the Global Compacts.DiscussionCurrent HIV responses in SADC do not adequately engage with the movement of healthcare users within and between countries. This negatively affects existing HIV interventions and has implications for the development of universal HIV testing and treatment (UTT) programmes. Drawing on literature and policy review, and ongoing participant observation in policy processes, I outline how Global Compact processes may undermine HIV prevention efforts in SADC.ConclusionsThe global health imperative of developing migration‐aware and mobility‐competent health responses must not be undermined by moral panics; the resultant international policy processes run the risk of jeopardizing effective action at the local level. Globally, migration is increasingly recognized as a central public health concern, providing strategic opportunities to strengthen public health responses for all. Without mainstreaming migration, however, health responses will struggle. This is particularly concerning in SADC where HIV programmes – including UTT initiatives – will struggle, and key health targets will not be met. Globally, contextually appropriate migration‐aware responses to health are needed, including and a specific focus on HIV programming in SADC.

Medium-Frequency Electrical Resistance Sintering of Highly Oxidized Iron Powder

Highly oxidized iron powders were consolidated by means of the medium-frequency electrical resistance sintering technique (MF-ERS). In order to activate the powders and to disperse the oxides coating the particles, prior to the consolidation process, powders were milled in a high-energy mill for 7 minutes. Structural and mechanical characterisations of electrically consolidated compacts were carried out in order to study the effect of two main processing parameters (current intensity and heating time). The compact properties resulted to be very sensitive to these parameters, especially to the current intensity. A change from 5 kA to 10 kA in the current intensity makes the porosity to fall from 30% to 8%. Moreover, using a higher current intensity (10 kA) increases the mechanical properties of the final compacts: micro-hardness change in almost 50 HV, up to 104 HV 1, and compression resistance by around 500 MPa, up to 569 MPa.

Characterization of Post-Meiotic Male Germ Cell Genome Organizational States.

Dramatic and unique genome reorganizations accompany the differentiation of haploid male germ cells, characterized by a gradual loss of the vast majority of histones leading to a final tight compaction of the genome by protamines. Despite being essential for procreation and the life cycle, the mechanisms driving the transformation of nucleosomes into nucleoprotamines remain poorly understood. To address this issue, our laboratory has developed a number of specific approaches, ranging from the purification of spermatogenic cells at specific stages, the analysis of chromatin transitional states, the functional characterization of histone variants, histone-replacing proteins and their chaperones. This chapter will detail all related relevant techniques with a particular emphasis on methods allowing the functional studies of histone variants and the genome organizational states associated with the studied histones in spermatogenic cells undergoing histone-to-protamine exchange.

The importance of an initial aggregation step for the destabilization of an anatase colloidal suspension

The sedimentation rate is increased by aggregation of fine particles by flocculation. In colloidal suspensions, however, the floc formation is not sufficient for efficient sedimentation because the aggregates, even though containing large amounts of colloidal particles, still are very small and light, causing slow sedimentation rates. In colloidal systems, flocculation must be preceded by an initial aggregation step of the colloidal particles, using coagulation by an electrolyte or agglomeration by hydrophobic-association. This article compares the influence of initial aggregation through coagulation with aluminum chloride hexahydrated (IAHAC) and initial aggregation induced by dodecylamine (IADDA) on the flocculation of colloidal titanium dioxide particles (anatase) with a hydrolyzed polyacrylamide (HPAM). The results were evaluated in terms of turbidity and final compaction of the sediment. In both cases, the initial aggregation step provided a significant improvement in flocculation with HPAM. The IADDA generated relatively large flocs, the supernatant presented less turbidity, and the sediment was more compacted than with the flocs formed from IAHAC.

Spray freeze granulation of submicrometre alpha-alumina using ultrasonication

Granulation is a key factor towards improvement of the flowability of fine ceramic powders to make them suitable for industrial dry pressing. Controlled granulation of fine alumina particles with a primary particle size of ∼ 150 nm was carried out using spray-freeze drying, which led to the production of flowable granules with high crushability. The fracture surface of uniaxially die-pressed green bodies made from granules with density values of ≥ 50%of theoretical showed a uniform microstructure. Sintering experiments were performed using conventional single- and two-stage radiant heating methods followed by density and grain size measurement and characterisation of the final dense compacts to study the efficiency of two-stage sintering in grain growth elimination. The results have been compared with those of alumina bodies prepared using similar suspension by the slip-casting route.

Analysis of suspension sedimentation in fluids with rheological shear-thinning properties and thixotropic effects

Suspension sedimentation in fluids with shear-thinning properties is of interest in several industrial operations, such as oil and gas exploration. This paper offers new information about the behavior of a group of particles settling in shear-thinning fluids. The tests carried out in this work differ from those reported in earlier works, because they involved a quantitative analysis of the settling behavior of particulate materials in regions with high concentrations of solids (where sediment is formed). To this end, the gamma-ray attenuation technique was used to monitor the concentration of solids in different regions of the tube over time. The results revealed significant differences in the behavior of particles settling in Newtonian and non-Newtonian fluids. Sediment was formed faster in the shear-thinning fluid when compared to the Newtonian fluid of similar apparent viscosity. However, final sediment compaction took longer in the non-Newtonian fluid. Overall, this study provides relevant information about sedimentation in non-Newtonian fluids, and addresses a subject about which several aspects should be further explored and better understood.