Size Homogenization Research Articles

Multi-scale experimental study on properties of compressed air foam and pressure drop in the long-distance vertical pipe

Compressed air foam has been gradually applied in super high-rise buildings due to its high extinguishing efficiency and great transportation ability. However, the transport characteristics of compressed air foam are unclear because the foam is a complex gas-liquid two-phase fluid. In this study, multi-scale experiments were conducted to investigate the foam properties of compressed air foam and pressure drop in the long-distance vertical pipe. The results show that the foam is compressed as a whole when pressure increases, resulting in a significantly increased foam density. At higher pressures, the bubble coarsening degree decreases, accompanied by a narrower particle size distribution and an increased foam size homogenization. Moreover, a critical pressure phenomenon is observed in foams with different foam expansion ratios. The average foam diameter stabilizes gradually with pressure changes after exceeding the critical pressure. A theoretical model for foam density is developed, considering various pressures, temperatures and foam expansion ratios. When the compressed air foam is transported in the vertical long-distance pipe, the pressure decreases in a slightly downward curve, which is due to the decrease in foam density. Finally, a prediction model for the pressure drop of compressed air foam in the long-distance vertical pipe is proposed, which considers changes in foam density. The accuracy of the prediction model is verified by the multi-scale experimental results. The results deepen the understanding of foam flow in the long-distance vertical pipe and provide useful guidance for applications of compressed air foam in super high-rise buildings.

Mechanical Dewatering of Homogeneous and Segregated Filter Cakes by Vibration Compaction

The solid volume fraction of a slurry requiring solid–liquid separation often fluctuates in industrial cake filtration processes. For low solid volume fractions, particle segregation arises, resulting in an inhomogeneous filter cake structure. Particle segregation has significant impacts on cake formation such as a longer cake formation time compared to homogeneous cakes. This work addresses the impact of this effect on vibration compaction, which is an alternative deliquoring method applying oscillatory shears to the filter cake. The dewatering results of homogeneous and segregated cakes made of the same material with a broad particle size distribution are compared. Although cake deliquoring is achievable despite particle segregation, vibration compaction is more effective for homogeneous cakes. The reason is that no particle size homogenization within segregated cakes occurs due to oscillatory shear, as particle size analyses indicate. The particle size measurements of cakes before and after vibration compaction reveal that the material’s particle size distribution is preserved despite vibration application. Vibration compaction achieves higher deliquoring than the common compaction method by squeezing, as elastic recovery effects after squeezing lead to the reabsorbing of liquid, already expressed and stored in the filter cloth. This demonstrates that vibration compaction is a real alternative for cake deliquoring.

Electromagnetic force behavior of high temperature superconducting coils coupled with multi-physics fields under different models

Rare earth barium copper oxide (REBCO) superconducting tape is the second generation of high temperature superconducting material with strong current carrying capacity and high mechanical strength, which has been studied most recently. In order to better investigate the electromagnetic force distribution characteristics of REBCO superconducting materials after electromagnetic excitation, firstly, the electromagnetic characteristics of superconducting tapes are numerically calculated by H method and T-A method on the basis of finite elements (FE) in this paper, and the effectiveness of T-A method is obtained. Based on this method, the influence of real size model (RS model) and homogenization equivalent model (HE model) on superconducting tape is further studied. The results show that the radial magnetic field reaches a peak of 1.01 T at the middle position of the upper surface of the pancake, while the axial magnetic field reaches a peak of 16.4 T at the inner side of the pancake, which indicates that the axial magnetic field contributes more to the total magnetic field. At the same time, the rationality of the equivalent method is obtained by comparing the calculation results of the RS and HE models. In addition, the mechanical changes of superconducting tapes are studied by T-A method under the HE model. It is found that the hoop stress and radial stress reach the peak values of 64.7 MPa and 6.84 MPa, respectively, and both are tensile stress, indicating that the hoop stress is more likely to cause damage to the superconducting tapes. Finally, the effect of different external tensile strains on the superconducting tape is discussed.

The Condition and Path of Effective Realization of Personalized Teaching in Intelligent Age

In the teaching situation of large class size and education homogenization, personalized teaching is difficult to achieve effectively. With the gradual penetration of intelligent technology into classroom teaching, the realization of personalized teaching has a new possibility. The effective realization of personalized teaching in the intelligent age needs the organic integration of intelligent technology and personalized teaching. Therefore, both intelligent technology and personalized teaching need to make necessary changes. Intelligent technology needs to deeply sketch students' learning portrait with big data, build personalized teaching resource library on cloud platform, enhance teachers' personalized teaching ability with artificial intelligence, and provide personalized teaching network environment with Internet, etc. Based on the integration of the two, the effective way to realize personalized teaching supported by intelligent technology is to establish differentiated teaching objectives, organize diversified teaching contents, select targeted teaching methods, integrate various learning organization forms and construct accurate teaching evaluation and feedback system.

Understanding the role of mechanical pretreatment before anaerobic digestion: Lab-scale investigations

Three successive mechanical pretreatments were applied at lab-scale in order to mimic the main functions of industrial mechanical pretreatments used for feedstock preparation in anaerobic digestion: particle size reduction (shredding), homogenization (mixing) and fiber alteration (blending). In parallel, full-scale mechanical devices have been investigated (two hammer mills and one chain mill). A physical and biochemical characterization was undertaken before and after each pretreatment. The results at lab-scale revealed that shredding reduced the size of coarse particles, smoothly increased solubilisation but did not affect much the methane yield. Mixing further improved the solubilisation and the water retention capacity of the investigated products. The most important effect was the improvement of the methane production rate rather than the methane yield. The results on full-scale pretreatments revealed that they behave as a combination of each function. Principal component analysis enabled to assign each full-scale device according to its effect on the investigated parameters.

A Novel Algorithm in Stochastic Chopped Carbon Fiber Composite Structure-A Study of RVE Size Effect and Homogenization Response of Directional Modulus

A Novel Algorithm in Stochastic Chopped Carbon Fiber Composite Structure-A Study of RVE Size Effect and Homogenization Response of Directional Modulus

Effects of freeze-thaw cycles on the erodibility and microstructure of soda-saline loessal soil in Northeastern China

Soda-saline loessal soils are distributed extensively in the Songnen Plain of Northeast China. Freeze-thaw effects on soil structure and mechanical properties are becoming more frequent and intense with global warming, which further affects soil erosion in cold regions. Quantifying the effects of freeze-thaw cycles (FTCs) on the erodibility of saline soils is challenging because of the abundant soluble salt content and complex soil mechanical responses. In this study, direct shear tests, disintegration tests, and scanning electron microscopy were conducted to investigate the effects of freeze-thaw action on the erodibility indicators (shear strength and disintegration velocity) of soda-saline loessal soils and their microscopic deterioration mechanisms. Four initial moisture contents (IMCs: 8%, 13%, 18%, 23%), three soluble salt contents (SSCs: 0.5%, 1.0%, 1.5%), and six FTCs (0, 1, 3, 6, 10, 15) were considered. The results showed that successive FTCs continued to degrade the erosion resistance of the soil until it stabilized after approximately 10 FTCs. After 15 FTCs, the shear strength and cohesion decreased by 8.6–19.8% and 24.1–59.2%, respectively, while the angle of internal friction was relatively unaffected. Meanwhile, the soil disintegration velocity increased by 52.3–208.8%. During the freeze-thaw process, the water-ice phase change and the crystallization of soluble salts both led to the continuous adjustment of the microstructure of soda-saline loessal soils. It was found that microcracks within the soil structural units increased significantly, cementation between the structural units weakened continuously, pore connectivity was enhanced, and pore size homogenization increased. Correlation analysis showed that IMC was the fundamental factor affecting the soil mechanical properties, whereas SSC mainly affected the soil's resistance to disintegration. The increase in IMC and SSC exacerbated the deterioration of the soil by freeze-thaw action. This paper presents a new understanding of the erosion characteristics and micromechanisms of soda-saline loessal soils in seasonally frozen regions under freeze-thaw action.

Effect of energy on Ti plate fabrication by vacuum selective laser melting for uniformity of grain size

Grain size homogenization by controlling heat input using modulated pulses in additive manufacturing was verified. A Ti plate was fabricated with a modulated pulsed laser by vacuum selective laser melting. 20-layer fabrication was performed with modulated pulsed laser and continuous wave laser. As a result of cross-sectional observation, it was found that the variation of the grain size was smaller when the modulated pulsed laser was used. These experimental results suggest that it is possible to control the grain size by using a modulated pulsed laser.

P–456 Impact of first-line chemotherapy prior to ovarian tissue cryopreservation on primordial follicle activation and survival in pre-pubertal and young adult patients

Abstract Study question How does chemotherapeutic regimen administered prior to ovarian tissue cryopreservation affect the signaling pathways regulating ovarian reserve and follicular survival in pre-pubertal and adult patients? Summary answer Chemotherapy induces key signaling processes of follicle activation and increases apoptosis in quiescent follicle. However, damages were different according to the age of the patient. What is known already Therapeutic regimen can damage the ovarian reserve leading to infertility of cancer survivors. Among fertility preservation options, cortical tissue banking appears to be an attractive alternative for patients who cannot delay their treatment or have already started chemotherapy. Though previous studies showed that first-line chemotherapy may induce follicular damages, the impact on follicle activation signaling pathways in human remains poorly understood. Deciphering the signaling modifications under chemotherapy is critical to have a better understanding of the follicle depletion process. Moreover, only few studies on cryopreserved tissue were conducted in children whereas follicle distribution differs compared to post-pubertal women. Study design, size, duration Cryopreserved ovarian tissue from young adult (16–27 years old, n = 6) and pre-pubertal (3–10 years old, n = 6) cancer patients were used as model. Fragments were thawed and cultured for 24 hours after size homogenization (4x2x0.5 mm). Patients who received chemotherapy before ovarian tissue cryopreservation were compared to non-exposed patients. PI3K/AKT/mTOR and Hippo pathways, as well as follicles and stroma survival, were assessed among the different groups at thawing and after culture. Participants/materials, setting, methods The impact of previous chemotherapy exposure on follicle activation, on the PI3K/AKT/mTOR and Hippo pathways was assessed at thawing and after 24 hours of culture by protein analyses (immunostaining and western blot). Histological analyses (follicular counting, immunostaining and TUNEL staining) were performed at the two timepoints to assess follicle distribution, morphology, stroma structure and apoptosis. Main results and the role of chance: The damage of chemotherapeutic regimen prior to cryopreservation was observed specifically on quiescent follicles after thawing by TUNEL staining in both adult and pre-pubertal patients. Surprisingly, apoptosis occurred more specifically in oocytes of pre-pubertal treated tissue while adult treated patients showed granulosa cells death. After culture, apoptosis was observed in the stroma but healthy follicles were observed in all conditions. Atretic follicles were observed similarly in pre-pubertal and adult cortex previously exposed to chemotherapy while not in the unexposed tissue. Protein analyses showed a higher expression of PI3K and Hippo proteins among all groups at thawing compared to cultured groups while difference was observed between pre-pubertal and adult cortex. At thawing, cortical tissues previously exposed to chemotherapy had a higher expression of phosphorylated forms of AKT and RPS6 compared to untreated groups, irrespective to the age. Moreover, immunostainings showed an oocyte-specific localization of p-AKT while p-RPS6 was more pronounced in the granulosa cells, suggesting an early process of follicle activation. Limitations, reasons for caution This study was limited to the evaluation of two major signaling pathways, PI3K/AKT/mTOR and Hippo. Moreover, considering the scarcity and the heterogeneity of our model, the number of patients included in this study is limited and the results should be interpreted with caution. Wider implications of the findings: Our results highlight the involvement of age and previous chemotherapeutic treatment in the regulation of signaling pathways regulating follicular activation, growth, and survival. Besides sustaining the chemotherapy-induced “burn out effect” theory, it opens perspectives to regulate the deleterious impacts of chemotherapy on follicles though molecular control of the altered pathways. Trial registration number Not applicable

Pore Size Control via Multiple-Site Alkylation to Homogenize Sub-Nanoporous Covalent Organic Frameworks for Efficient Sieving of Xenon/Krypton.

Among various fission products generated in nuclear reactors, xenon and krypton are two important fission gases with high flow, diffusivity, and radioactivity. Moreover, xenon isolated from these products is an expensive industrial resource with wide applications in medicine and lighting, which makes the development of efficient methods for separation of xenon/krypton significant. However, it is usually difficult for xenon/krypton to be adsorbed by chemical adsorbents due to their inert gas properties, and sub-nanoporous adsorbents proven to be workable for the separation of xenon/krypton are still hard to prepare and regulate the pore size. Herein, we report two novel sub-nanoporous covalent organic frameworks (COFs), which were applied to the sieving of xenon/krypton for the first time. The sub-nanoporous COFs were synthesized via aldehyde-amine polycondensation reactions and the subsequent pore size regulation and homogenization process by using a facile, operational, and efficient multiple-site alkylation strategy. Impressively, the as-prepared sub-nanoporous COFs realized the efficient adsorption and sieving of xenon/krypton owing to their slightly larger pore sizes (∼7 Å) than the dynamic diameters of xenon/krypton and their larger pore volumes. The maximum adsorption capacity for xenon is up to 85.6 cm3/g, and the xenon/krypton selectivity can reach to 9.7. Moreover, the as-prepared COFs possess good γ-ray irradiation stability, which endows them with great potentials for the sieving of radioactive xenon/krypton in the practical application. The multiple-site alkylation strategy proposed in this study provides a valuable approach for the pore construction and control of the porous materials, especially the sub-nanoporous adsorption materials.

Phase-field study on the effect of initial particle aggregation on the transient coarsening behaviors

The transient coarsening behavior of poly-disperse particles that aggregate into clusters was studied using a phase-field model in two dimensions. The effects of two characters of the cluster, i.e., particle number N c and particle density ρ c in a cluster, on the kinetics of transient coarsening are systematically investigated. The transient coarsening experiences two stages: the merging of multiple particles in a cluster into a single particle and further evolution towards the steady state. The evolutions of the scaled particle size distribution and the coarsening rate are non-monotonic during the transient stage. The length of the transient stage for the system with uniform cluster size increases with N c but is insensitive to ρ c. Reducing the cluster size homogenization can shorten the transient stage. Moreover, if the coarsening time is scaled by the moment at which multiple particles in all clusters complete the merging, the temporal evolutions of particle radius and particle size distribution are almost uniform for systems with different N c. This uniform relationship can be used to predict the long transient stage for the system with large N c, which cannot be directly obtained with limited simulation time.

Fabrication and Properties of Densified Tungsten by Magnetic Pulse Compaction and Spark Plasma Sintering

The present study demonstrates the effect of magnetic pulse compaction and spark plasma sintering on the microstructure and mechanical property of a sintered W body. The relative density of green specimens prepared by magnetic pulse compaction increases with increase in applied pressure, but when the applied pressure is 3.4 GPa or more, some cracks in the specimen are observed. The pressureless-sintered W shows neck growth between W particles, but there are still many pores. The sintered body fabricated by spark plasma sintering exhibits a relative density of above 90 %, and the specimen sintered at 1,600 oC after magnetic pulse compaction shows the highest density, with a relative density of 93.6 %. Compared to the specimen for which the W powder is directly sintered, the specimen sintered after magnetic pulse compaction shows a smaller crystal grain size, which is explained by the reduced W particle size and microstructure homogenization during the magnetic pulse compaction process. Sintering at 1,600 oC led to the largest Vickers hardness value, but the value is slightly lower than that of the conventional W sintered body, which is attributed mainly to the increased grain size and low sintering density.

Liquid Metal-Elastomer Soft Composites with Independently Controllable and Highly Tunable Droplet Size and Volume Loading.

Soft composites are critical for soft and flexible materials in energy harvesting, actuators, and multifunctional devices. One emerging approach to create multifunctional composites is through the incorporation of liquid metal (LM) droplets such as eutectic gallium indium (EGaIn) in highly deformable elastomers. The microstructure of such systems is critical to their performance; however, current materials lack control of particle size at diverse volume loadings. Here, we present a fabrication approach to create liquid metal-elastomer composites with independently controllable and highly tunable droplet size (100 nm ≤ D ≤ 80 μm) and volume loading (0 ≤ ϕ ≤ 80%). This is achieved through a combination of shear mixing and sonication of concentrated LM/elastomer emulsions to control droplet size and subsequent dilution and homogenization to tune LM volume loading. These materials are characterized utilizing dielectric spectroscopy supported by analytical modeling, which shows a high relative permittivity of 60 (16× the unfilled elastomer) in a composite with ϕ = 80%, a low tan δ of 0.02, and a significant dependence on ϕ and minor dependence on droplet size. Temperature response and stability are determined using dielectric spectroscopy through temperature and frequency sweeps with DSC. These results demonstrate a wide temperature stability of the liquid metal phase (crystallizing at <-85 °C for D < 20 μm). Additionally, all composites are electrically insulating across wide frequency (0.1 Hz-10 MHz) and temperature (-70 to 100 °C) ranges even up to ϕ = 80%. We highlight the benefit of LM microstructure control by creating all-soft-matter stretchable capacitive sensors with tunable sensitivity. These sensors are further integrated into a wearable sensing glove where we identify different objects during grasping motions. This work enables programmable LM composites for soft robotics and stretchable electronics where flexibility and tunable functional response are critical.

Effect of milling time and presence of Sn on the microstructure and porosity of sintered Ti-10Ta-8Mo and Ti-10Ta-8Mo-3Sn alloys

The aim of the present study was to assess the influence of the milling time (10 h, 15 h and 20 h) on the structure and properties of Ti-10Ta-8Mo (wt.%) and Ti-10Ta-8Mo-3Sn (wt.%) alloys for potential biomedical application. In addition, the influence of the addition of 3 wt% Sn on the structure and properties of the milled and sintered materials was investigated. X-ray diffraction confirmed the partial synthesis and formation of the β phase during the milling process. The transmission electron microscope analysis of the bright and dark field images and the diffraction image proved the nanocrystalline nature of the material after being subjected to 20h milling duration. The scanning electron microscope observation of the sintered samples confirmed the influence of the milling time and presence of Sn on the microstructure of the obtained material. Furthermore, a small addition of Sn led to better size homogenization by establishing a better balance between the cold-welding and agglomeration processes. At the same time yielding different structures of pores for the sintered samples. The dry sliding tests revealed the excellent friction properties and wear rate of the samples previously milled for 15 h, with the addition of Sn.

Porous structure uniformity investigation of tungsten matrix prepared by jet milled and annealed tungsten powder

The correlation between tungsten powder properties and porosity characteristics of porous tungsten matrix have been investigated in this paper. With the deagglomeration and classification, monodisperse tungsten powders of different particle size with narrow particle size distribution have been obtained. Multi-step annealing operation with continuously increasing temperature was taken to reduce the particle activity, which are conductive to particle size homogenization, shape modification and purification simultaneously. The press-sintered porous tungsten matrix prepared by jet milled and annealed tungsten powder presents homogeneous inter-connected pores with uniform pore size and distribution, indicating that low-activity monodisperse powder with narrow particle size distribution is required for manufacturing homogeneous porous tungsten matrix.

Characterizing the strange term in critical size homogenization: Quasilinear equations with a general microscopic boundary condition

Abstract The aim of this paper is to consider the asymptotic behavior of boundary value problems in n-dimensional domains with periodically placed particles, with a general microscopic boundary condition on the particles and a p-Laplace diffusion operator on the interior, in the case in which the particles are of critical size. We consider the cases in which {1&lt;p&lt;n} , {n\geq 3} . In fact, in contrast to previous results in the literature, we formulate the microscopic boundary condition in terms of a Robin type condition, involving a general maximal monotone graph, which also includes the case of microscopic Dirichlet boundary conditions. In this way we unify the treatment of apparently different formulations, which before were considered separately. We characterize the so called “strange term” in the homogenized problem for the case in which the particles are balls of critical size. Moreover, by studying an application in Chemical Engineering, we show that the critically sized particles lead to a more effective homogeneous reaction than noncritically sized particles.

Development of a novel one-step production system for injectable liposomes under GMP

There are few methods available for injectable liposome production under good manufacturing practices (GMP). Injectable liposome production processes under GMP generally consist of liposome formation, size homogenization, organic solvent removal, liposome concentration control and sterilization. However, these complicated and separate processes make it difficult to maintain scalability, reproducibility and sterility. To overcome these limitations, we developed a novel one-step in-line closed liposome production system that integrated all production processes by combining the in-line thermal mixing device with modified counterflow dialysis. To validate the system, we produced liposomal cyclosporine A (Lipo-CsA) and lyophilized the liposomes. The three independent pilot batches were highly reproducible and passed the quality specifications for injectable drugs, demonstrating that this system could be used under GMP. The accelerated stability test suggested that the liposomes would be stable in long-term storage. This one-step system facilitates a fully automated and unattended production of injectable liposomes under GMP.

The Addition of Zr in Nickel-Based Inconel 718 Superalloy to Prevent Hot Cracks Propagation

The Inconel 718 alloy owes high strength and ductility at high temperature due to precipitation strengthening. In order to upgrade productility of Inconel 718 alloy, the Inconel 718 alloy solve hot crackings through Zr additions. The result shows that, the Inconel 718 alloy with Zr addition achieves grain size refinement and homogenization effect. It is suggested that, homogenization process, such as temperature point and time control, realizes low content of Nb segregation which is the key to prevent hot crackings. At the same time, through dendrite space measurement, the grain refinement realize high productivity of forged Inconel 718 alloy, as a another method of soft effect. In conclusion, adding Zr element is one of dominant methods for producing high quality of Inconel 718 alloy.

Emulsification properties of pea protein isolate using homogenization, microfluidization and ultrasonication

Pea protein isolate (PPI) is used in many food formulations, due to its low cost, commercial availability and excellent amino acid profile. The objective of this study was to determine the emulsification properties of PPI. Particle size of PPI powders showed neither temperature (25–65°C) nor time (up to 24h) increased solubilisation of powder particles during mixing. Heating PPI dispersions (10%, w/w, protein) from 45 to 90°C led to an increase in storage modulus (G′; Pa) at 71°C, indicating the onset of protein aggregation. Gel formation occurred at 79°C (G′>1Pa). Pea protein-stabilised emulsions made using homogenization (15MPa; 1 pass) or microfluidization (50MPa; 1 pass) resulted in the formation of cold-set gels, with gel strength increasing with increasing oil concentration and fluidic pressure. Droplet size and viscosity of pea protein-stabilised emulsions decreased and increased, respectively, with increasing ultrasonication time. Overall, ultrasonication (<50°C) can create a uniform droplet size emulsion, while, homogenization and microfluidization can produce cold-set gels for use in a wide-range of food applications.

Template-free synthesis of hierarchically porous SiBCN monolith from organic gel precursors

A novel template-free method to synthesize hierarchically porous SiBCN monolith from a tailor-made organic gel precursor is proposed. The process includes four steps: the condensation reaction of tris[dichloromethylsilylethyl]borane and bis(trimethylsilyl)carbodiimide, the replacement of byproduct trimethylchlorosilane by styrene solution, the polymerization of styrene and the pyrolysis at 1000°C. The structures and thermal properties of organic gel precursors and SiBCN monolith, as well as the high temperature properties of SiBCN monolith were studied. This work demonstrates that the introduction of polystyrene is the key to obtain stable three-dimensional porous SiBCN network. The obtained SiBCN monolith displays a hierarchically porous structure with an average pore size of 1.95nm, a pore volume of 0.335cm3g−1 and a specific surface area of 31.78m2g−1. It is also observed that such hierarchically porous structure could be maintained after annealing at 1500°C. A pore size homogenization process is proposed to clarify the changes of porous architectures during the high temperature annealing.