Formation Mechanism Of Structures Research Articles

Scalable Multi-Material Additive Manufacturing of Bioinspired Polymeric Material With Metallic Structures Via Electrically Assisted Stereolithography

Abstract Heterogeneous material systems consisting of metallic structures and polymer matrixes are of significance for applications such as integrated circuits, microelectromechanical devices, antennas, sensors, actuators, and metamaterials. Scaly-foot snail which lives in the deep ocean exhibits high strength and temperature resistance due to unique shells made of metal and polymer. Recently, different multi-material structures have been fabricated with metal deposition using multiple manufacturing processes. However, using these complicated hybrid processes is challenging to construct complexthree-dimensional (3D) structures of heterogeneous material with enhanced properties, high resolution, and time efficiency. Here, we establish a novel manufacturing strategy to build bioinspired hierarchical structures with heterogeneous material systems using electrically assisted stereolithography. The photocurable printing solution that can act as an electrolyte for charge transfer was developed, and the curing characteristic of the printing solution was further investigated. A fundamental understanding of the formation mechanism of metallic structures on the polymer matrix was studied through physics-based multi-scale modeling and simulations. The correlation between metallic structures morphology, printing solution properties, and printing process parameters, and their effects in building bioinspired hierarchical structures with heterogeneous materials were identified. Demonstrative test cases were built to verify the printing performance of the proposed approach. This research work will deliver a scalable additive manufacturing (AM) process that can facilitate various interesting applications based on bioinspired heterogeneous material and structures.

Formation, evolution and characterization of nanoporous structures on the Ti6Al4V surface induced by nanosecond pulse laser irradiation

Manipulating materials at nanoscale is challenging but rewarding. Nanostructures exhibit some unique properties distinguished from macroscopic bulk materials, so fabrication of nanostructures on the material surface is beneficial to broaden their functional applications. In this study, by nanosecond pulse laser irradiation in nitrogen atmosphere, it was found that unique nanoporous structures could be formed on the Ti6Al4V surface. The effects of laser parameters including the laser power, overlap rate, scanning speed, and repetition frequency on the formation and evolution of the nanoporous structures were systematically investigated. By changing the laser parameters, the nanoporous structures with various porosities could be easily achieved on the Ti6Al4V surface. According to the structural evolution and chemical composition, the formation mechanism of the nanoporous structures was discussed. Furthermore, by characterizing the micro-mechanical properties and wettability, it was found that the surface with nanoporous structures exhibited similar surface hardness but improved tribological performances compared to the original Ti6Al4V surface, and the surface wettability could be tuned. This study provides a simple method for fabricating nanoporous structures on the Ti6Al4V surface, which would broaden its functional applications.

Alloy-Type Lithium Anode Prepared by Laser Microcladding and Dealloying for Improved Cycling/Rate Performance.

Nanosized alloy-type materials (Si, Ge, Sn, etc.) present superior electrochemical performance in rechargeable batteries. However, they fail to guarantee cycling capacity and stability under high mass loading required by industrial applications due to low electric contact and adhesive strength, which has long been a challenge. This work proposes a rational design for an alloy-type anode via facile and versatile laser microcladding and dealloying. The proposed anode features a large-area porous network composed of continuous nano-ligaments, which consist of evenly distributed nanosized alloy-type material metallurgically bonded with conductive material. The fabrication of the structure is validated using Ge-Cu and Sn-Cu anodes, both exhibiting enhanced cycling stability at high areal capacity and rate performance in lithium-ion batteries. The enhancement is attributed to the structural features, which contribute to lithiation-delithiation stability and intact electron/Li ion transference path, as verified by in situ and ex situ transmission electron microscopy observations. More importantly, the critical solidification conditions of laser microcladding are provided by a multiphysics simulation, allowing for a thorough understanding of the structural formation mechanism. The study provides a possible approach to improve mass loading and performance of an alloy-type anode for practical application.

Structure, phase composition and mechanical characteristics of layered composite materials based on TiB/xTi-Al/α-Ti (x = 1, 1.5, 3) obtained by combustion and high-temperature shear deformation

The effect of the ratio of titanium and aluminum in the Ti–Al intermetallic layer on the microstructure, phase composition, and mechanical characteristics of layered composite materials based on TiB/xTi-Al/α-Ti (x = 1, 1.5, 3) is studied systematically. The layered composite materials are obtained by combustion and high-temperature shear deformation. The green sample is a compressed sandwich blank consisting of two Ti–B and Ti–Al powder layers and an α-Ti titanium sheet. The mechanisms of phase and structure formation that occur during synthesis and subsequent high-temperature shear deformation in ceramic and intermetallic layers are described. It is shown that the synthesis between the initial components proceeds according to the reaction-diffusion mechanism. It has been found that the structure, grain size (from 200 nm to 15 μm), phase composition, and mechanical characteristics of the composite can be tuned by changing the initial composition and the delay time before applying external pressure. It is shown that the mechanical characteristics of the resulting composites depend on the location of macrolayers relative to the applied load during high-temperature shear deformation and have the following values: composite surface hardness up to 1800 HV, elastic modulus up to 300 GPa, elastic recovery up to 43, stress intensity factor up to 25.3 MPa m1/2, bending strength up to 650 MPa. The mechanical characteristics of the obtained composites are compared with known analogs, and the advantages are revealed.

Three-Dimensional Numerical Simulation of Grain Growth during Selective Laser Melting of 316L Stainless Steel.

The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental method alone. In this study, we presented a high-fidelity 3D numerical model to address the grain growth mechanisms during the selective laser melting of 316 stainless steel, including two heating modes, i.e., conduction mode and keyhole mode melting. In the numerical model, the powder-scale thermo-fluid dynamics are simulated using the finite volume method with the volume of fluid method. At the same time, the grain structure evolution is sequentially predicted by the cellular automaton method with the predicted temperature field and the as-melted powder bed configuration as input. The simulation results agree well with the experimental data available in the literature. The influence of the process parameters and the keyhole and keyhole-induced void on grain structure formation are addressed in detail. The findings of this study are helpful to the optimization of process parameters for tailoring the microstructure of fabricated parts with expected mechanical properties.

A novel Ba2SrWO6:Mn4+/Dy3+ red phosphors for warm WLED applications

A novel non-rare-earth red-emitting phosphor of Ba2SrWO6:Mn4+ with a double-perovskite structure was synthesized via a solid-state reaction method at high temperatures, and the mechanism of structural formation was systematically investigated. Moreover, Dy3+co-dopant ions were exploited to develop a white-light phosphor of Ba2SrWO6:Mn4+/Dy3+. Excitation spectra of Ba2SrWO6:Mn4+ and Ba2SrWO6:Mn4+/Dy3+ were both in a wavelength range of 250–550 nm. Under 325 nm excitation, the Ba2SrWO6:Mn4+ phosphors showed a red emission with a peak at 693 nm because of the 2E → 4A2 transition of Mn4+ ions. The Mn4+ ion concentration in the Ba2SrWO6:Mn4+ phosphors was optimized at 0.6 mol%, and the corresponding CIE (Commission International de I’Edairage) chromaticity coordinate was determined at about (0.7238, 0.2762), locating in the deep-red-light region. Meanwhile, the white-light Ba2SrWO6:Mn4+/Dy3+ phosphors displayed a wide emission band, including a blue emission at 492 nm (attributed to 4F9/2 → 6H15/2), a yellow emission at 582 nm (owing to 4F9/2 → 6H13/2), and the red emission at 693 nm. By varying the Dy3+ ion concentration, the emission color of the co-doped phosphors can be tuned from white light (0.3365, 0.3493) to warm white-light (0.4263, 0.3778), qualifying the phosphorous materials as a potential candidate for white-light- or warm white-light-emitting diode applications.

Structural Characteristics and Formation Mechanism of Microbiota Related to Fermentation Ability and Alcohol Production Ability in Nongxiang Daqu.

Fermentation ability and alcohol production ability are important quality indicators of Chinese liquor Daqu, reflecting microbial growth and metabolic capacity and ethanol production capacity of Daqu microbiota, respectively. However, information on the microbial community related to the fermentation ability and alcohol production ability is unclear. In this study, fermentation functional microbiota (FFM) and alcohol functional microbiota (AFM) were obtained by correlating fermentation ability and alcohol production ability with Daqu microbiota. FFM and AFM consisted of 50 and 49 genera, respectively, which were basically the same at the phylum level but differed at the genus level. Correlation analysis showed that FFM and AFM were mainly affected by moisture, acidity, and humidity in the early stage of Daqu fermentation, and oxygen content was a critical factor for microbial succession in the middle stage of fermentation. FFM and AFM had commensal or synergistic interactions with multiple microbes. Function predictions indicated that fermentation functional bacterial microbiota was active in product synthesis and transport-related metabolic functions, and alcohol functional bacterial microbiota was very active in raw material utilization and its own metabolic synthesis. This study reveals the structural characteristics and formation mechanism of FFM and AFM, which is important for control of Daqu quality.

Simple Quaternary Templating Systems for Direct Synthesis of Unique SBA-15 Mesopore Frameworks Embedded with High-Content TiO2 Nanoparticles as High-Performance Photocatalysts.

This work presents a simple P123-based quaternary templating system using titanyl sulfate (TS) as the TiO2 precursor and self-contained sulfuric acid as the catalyst (TS/TEOS/P123/H2O). A unique structural configuration of SBA-15-type mesopore frameworks embedded with high-content TiO2 nanoparticles can be directly obtained. Even with a high TiO2 content (29.1 wt %), well-defined mesostructures free of pore blocking can be secured. A new structural formation mechanism is unveiled: a self-assembly process between inorganic species and P123 micelles yields ordered mesostructures catalyzed by self-contained TS in the low-temperature step, while sol-gel reaction and crystallization of TS coincide with processes of mesostructural re-organization and partial evacuation of P123 from mesopores. The incorporation of high-content TiO2 nanoparticles into mesopore frameworks mainly happens during the hydrothermal treatment step. Not surprisingly, thanks to well-defined mesostructures containing high-content accessible TiO2 nanoparticles, such TiO2/SBA-15 composites show high activity and good reusability in photodegrading Rhodamine B and humic acids and photoreducing highly toxic Cr6+ in water under UV irradiation.

Controlled impacts for structure formation and properties of cement concretes

Objective. The paper considers controlled effects on changes in the properties of components and the control effect of technological methods and techniques for obtaining composite building materials with a set of specified properties.Method. Methods of mechano-physical, physicochemical, nanotechnological influence were applied.Result. The system-structural approaches are systematized and generalized by control actions at the stage of structure formation, technological stages, formation of the optimal structure and properties of cement concrete. The physicochemical principles and mechanisms of structure formation are given, based on establishing the role of controlling the mechano-physical, physico-chemical, nanotechnological methods of influencing the cement-water system. The possibility of controlling structural transformations in binder systems, including through the use of technological influences, has been revealed.Conclusion. The implementation of the impacts on the components of cement concretes will ensure the targeted design of the structures of modern building materials.

Investigation of the Mechanism of SiO2 Particle and Capsule Formation at the Oil-Water Interface of Dye-Stabilized Emulsions.

In a previous contribution we described the formation of silica nanostructures in dye-stabilized nanoemulsions from tetraethyl orthosilicate droplets in water. Depending on the type of dye, either capsules (crystal violet, CV) or nanoparticles (congo red, CR) are formed. The thorough study of the sol-gel process uses a combination of time- and/or temperature-resolved small-angle X-ray scattering, transmission electron microscopy, and 1H NMR spectroscopy to elucidate the detailed kinetics and mechanism of structure formation. In both cases, small nuclei of 1.5-2 nm are formed, followed by either a fast cluster-cluster (CV) or a much slower monomer-cluster aggregation (CR). The former leads to a cross-linked network and finally to patchy capsules, while the latter leads to individual nanoparticles (SNPs). From an Avrami plot it can be deduced that the SNPs are formed by an interface-controlled one-dimensional growth process. The mechanisms are based on the different local environments at the oil-water interface, which is either slightly acidic (CV) or fairly basic (CR). The kinetics differ by a factor between 3 and 20 and are presumably caused by the different mobility of the catalyzing species H+ or OH-.

Ultrafast pulsed laser stealth dicing of 4H-SiC wafer: Structure evolution and defect generation

Ultrafast pulsed laser for wafer processing has been promising in the semiconductor industry due to its high precision and low thermal effect. The microstructure and defect during the stealth dicing process is critical to controlling the desired quality of the wafer. The structural evolution and defect formation mechanisms during stealth dicing of 4H-SiC with femtosecond and picosecond lasers were investigated. In order to understand the ultrafast pulsed laser interaction with 4H-SiC wafer, we studied the laser intensity dependence of the nonlinear refractive index, the propagation of laser beam focusing in 4H-SiC, the laser absorption, electron concentration evolution and energy deposition. The effect of two significant processing factors was discussed, including laser fluence and laser scribing times. The propagation paths and energy deposition of femtosecond and picosecond lasers in the internal processing of 4H-SiC were calculated by finite element method. The evolution of electrons temperature, lattice temperature and free electron concentration in the material during laser processing was analyzed. Femtosecond laser stealth dicing had higher processing accuracy due to minimal thermal effects. The defect induced by femtosecond laser was dominated by nanovoids and micro-cracks. The defect structure was affected by laser processing parameters such as scanning passes and laser power density. Multi-focusing of ultrafast pulsed lasers in transparent materials was generally considered to be a dynamic balance of nonlinear self-focusing and plasma defocusing. Picosecond laser processing resulted a higher processing efficiency under the same laser energy density comparing with femtosecond laser processing. However, defects during picosecond laser dicing were dominated by thermal ablation, which impaired the processing accuracy.

(Invited) Light-Emitting Devices Based on Defect-Enhanced Group-IV Nanostructures

Combining Si-based integrated optics with Si-based microelectronics is crucial for next-generation applications ranging from data transfer on short distances to sensing and, potentially, to quantum cryptography at telecom wavelengths. However, Si's intrinsically poor light-emitting properties, i.e., its indirect energy bandgap, inhibit a straightforward implementation of telecom devices such as light-emitting diodes and lasers operating at room temperature.We argue that adding Ge heterostructures, nanostructures, intentionally-induced defects, and defects within nanostructures to the Si platform can be a viable way to overcome the limitations of Si as a light-emitting material [1]. Significant progress for light-emission from group-IV nanostructures can be achieved by intentionally incorporating extended point defects inside the QDs upon in-situ low-energy ion implantation [2],[3]. This work discusses the superior light-emission properties from such defect-enhanced quantum dots (DEQDs) and our present understanding of their structural formation and light-emission mechanisms [4], indicating that optically direct recombination paths play a role in room-temperature light emission.As compared to other group-IV systems with pronounced optical emission, contact doping and hence fabrication of electrically driven devices is relatively straightforward in this nanosystem since DEQDs are embedded into a defect-free Si matrix [5],[6]. We show that useful electrically driven devices, such as light-emitting diodes (LEDs), can be fabricated employing optically active DEQD material. These LEDs exhibit exceptional temperature stability of their light-emission properties even up to 100°C, unprecedented for purely group-IV-based optoelectronic devices [7]. We discuss the role of vital parameters, such as the temperature stability of the structural properties [8],[9], the scalability of the light-emission with the nanostructure density [6], and passivation schemes to further improve the optical properties [8],[10]. Additionally, we elaborate on schemes for advanced layouts for electrically-pumped devices.References[1 ] M. Brehm, Silicon Photonics IV, 67-103, Silicon Photonics IV: Innovative Frontiers, edited by David J. Lockwood and Lorenzo Pavesi, Springer series Topics in Applied Physics (2021).[2] M. Grydlik et al., ACS Photonics 3, 298–303 (2016).[3] M. Grydlik et al., Nano Lett. 16, 6802–6807 (2016).[4] F. Murphy-Armando et al., Phys. Rev. B 103, 085310 (2021).[5] M. Brehm and M. Grydlik, Nanotechnology 28, 392001 (2017).[6] H. Groiss et al., Semicond. Sci. Technol. 32, 02LT01 (2017).[7] P. Rauter et al., ACS Photonics 5, 431-438 (2018).[8] L. Spindlberger et al., Crystals 10, 351 (2020).[9] L. Spindlberger et al., Physica Status Solidi (a) 216, 1900307 (2019).[10] L. Spindlberger et al., Appl. Phys. Lett. 118, 083104 (2021).

Vacuum wetting of Ag/TA2 to develop a novel micron porous Ti with significant biocompatibility and antibacterial activity

· A simple approach to fabricate micron-scale porous Ti was developed. · A surface-layered porous structure dispersing with AgNPs was obtained on TA2. · Volatilization/sublimation of Ag in TA2 promotes forming the pores and AgNPs. · The porous Ti has excellent biocompatibility and bio-corrosion resistance. · The porous Ti has an excellent antibacterial activity. Porous Ti with low modulus, excellent bio-corrosion resistance, biocompatibility, and antibacterial activity is highly pursued as advanced implant materials. In this work, a new approach to prepare micron porous structures on the surface layer of a grade 2 commercially-pure Ti (TA2) was proposed, which utilized a simple vacuum wetting process of pure Ag on the surface of TA2. The microstructure, corrosion resistance, biocompatibility, mechanical properties, antibacterial ability, and formation mechanism of the as-fabricated porous Ti were studied. The results show that the pores (with average pore sizes of 0.5–5 μm) are distributed on the surface layer of the TA2 with a depth of ∼10 μm. In particular, a large number of silver nanoparticles (AgNPs) form which are dispersed on the porous structures. The formation mechanisms of the porous structures and AgNPs were elucidated, suggesting that the volatilization/sublimation of Ag in TA2 is crucial. The porous Ti possesses excellent bio-corrosion resistance, surface wettability, biocompatibility, antibacterial activity, and a relatively low elastic modulus of 40–55 GPa, which may have a promising future in the field of orthopedic implants. This work also provides a novel idea for the development of advanced porous Ti materials for orthopedic-related basic research and biomedical applications.

İdrisyayla (Kırka-Eskişehir) Batısında Gözlenen Sferulitik Riyolitlere ait İlk Petrografik Dokusal Veriler

Spherulitic structures are classically defined as concentrically zoned crystal clusters that form in igneous systems (especially in alkaline igneous rocks), and usually occur as different mineral layers or shells.
 The volcano-sedimentary series observed in the Kırka region, south of Eskişehir, within the Kırka-Afyon-Isparta Volcanic Province, Western Anatolia, consists predominantly of Lower Miocene volcanic and pyroclastic sequences with rhyodacitic-rhyolitic in composition, lacustrine limestones, borate-bearing claystones, tuff, stromatolitic limestones and basalts. The formation mechanisms of the spherulitic structures observed in the marginal zone of the sub-alkaline rhyolitic lava dome outcropping within the Neogene series in the west of İdrisyayla in Kırka (Eskişehir) region were described for the first time with this study. The rhyolites are grayish light brown in color, have hypocrystalline hyalopilitic-holohyaline texture and present spherical structures defined as spherulites. These rocks present a completely flowing structure and are composed of volcanic glass containing rarely euhedral plagioclase and quartz microcrystals, The spherical structures observed on the surface of the rhyolites are up to 10-15 cm in size. The spherulites, which are almost round in shape, appear as concentric rings within the lava flow bands. The flow band texture of the volcanic glass phase presents continuity in the inner texture of the spherulitic structures.
 This study suggests that the sferulitic structures in the İdrisyayla (Kırka-Eskişehir) region were formed by the devitrification mechanism as a result of high temperature and rapid cooling. The petro-mineralogical features of the spherulitic rhyolites show that during the early magmatic stage, the oversaturated liquid crystallized in silica-rich fluid phases of relatively different densities, and radial quartz-feldspar crystal growths from a center, caused the formation of the spherulitic structure. It is also suggested that the lithophysae-like structures formed by the crystal growths representing the solid phase in the axial cavities due to the locally folding of the flow bands and the following radial mineral growths representing the liquid phase, were also changed the laminated texture in the marginal phase of the rhyolite.

Two-dimensional electrical resistivity structure of the crust and upper mantle across the North-South Gravity Lineament in NE China

The North-South Gravity Lineament (NSGL) is a large anomalous gravity zone that traverses several tectonic units with different properties in northeastern China. Its deep structural features and formation mechanism have long been a topical area of deep geophysical research. This study presents a magnetotelluric profile that extends from the Dongwuqi to Tongliao in Inner Mongolia and passes through geological structures such as the NSGL. Dimensional analysis of the profile data reveals good overall 2D features. 2D nonlinear conjugate gradient inversion of the profile data produced a model of the deep electrical structure. Horizontally, the electrical structure along the profile displays different characteristics in different blocks. The NSGL serves as a boundary for the change in the depth of the Moho discontinuity. Specifically, the Moho discontinuity is deep on the west side of the NSGL and shallow on its east side. Overall, the thickness of the lithosphere varies nonsignificantly, except in the western part of the profile, where the presence of a large low-resistivity anomaly in the shallow layer obscures the boundary of the lithosphere. The large high-resistivity anomaly in the center of the profile may be an indication that the partial delamination of the lithosphere caused by the convection of mantle materials and the upwelling of high-density mantle materials under the action of the westward subduction of the Pacific plate were the major causes of large positive gravity anomalies on the east side of the NSGL. The west side of the NSGL was predominantly controlled by the closure of the Mongol-Okhotsk Ocean, resulting in an increase in the thickness of the crust, which led to the formation of large negative gravity anomalies. These two factors collectively led to the formation of the NSGL.

The effects of ultrasonic treated whey on the structure formation in food systems based on whey in combination with pectin and agar-agar

We studied the effects of ultrasonicated whey in food systems with the structure-forming additives such as pectin and agar-agar. The high-intensity (45KHz, 40 W with cavitation) ultrasonic treated whey was used. The conditions and optimal modes of cavitation based ultrasonic processing of curd milk whey have been determined. The mechanism of structure formation has been studied in detail.From the studies carried out, the scientific basis for the choice of structure-forming agents in food systems was established along with the range of rational concentrations of pectin and agar-agar. It was shown that in the case of processing milk curd whey by the cavitation method, the concentration of the structure former can be reduced by 2 times compared to using non-sonicated whey in the food system thus saving costs on the raw materials.It was established that high-purity cavity treatment minimizes gel-like food systems set time up to 20% compared to the control within 15 min. The duration of high-purity treatment within 15 min contributes to an increase in penetration pressure, which characterizes the texture of the gel-like food two times.

Self-propagating high-temperature synthesis of MoAlB boride ceramics based on MAB-phase

This study focuses on the combustion kinetics and mechanisms of reaction mixtures in the Mo–Al–B ternary system taken so that the MoAlB MAB phase was formed. The effect of the initial temperature on the key combustion parameters was demonstrated. Reaction mixture preheating was found to weakly affect the maximum combustion temperature. The effective activation energy of self-propagating high-temperature synthesis (SHS) was calculated. Phase diagrams in the Mo–Al–B system were built using the AFLOW and Materials Project databases. The phase composition and structure of the synthesized ceramics with MoAlB lamellar grains 0.4 μm thick and ~2–10 μm long as a main component were studied. The DXRD lines of MoB and Mo2B5 intermediate borides with their total content of ≤3 % were also identified. Scanning electron microscopy and energy dispersive spectroscopy studies revealed that the Al2O3 phase was present in the intergranular pores. A sequence of chemical transformations in the combustion wave was studied, and a hypothesis about the structure formation mechanism was put forward. MoO2 and Al2O3 can be the primary phases during SHS, and the MoAlB phase is formed from the boron-containing aluminum–molybdenum melt. Submicron-sized MoB precipitates are formed in the post-combustion zone due to the partial oxidation of aluminum by the dispersion strengthening mechanism.

Dynamic Transcriptome-Based Weighted Gene Co-expression Network Analysis Reveals Key Modules and Hub Genes Associated With the Structure and Nutrient Formation of Endosperm for Wax Corn.

The endosperm of corn kernel consists of two components, a horny endosperm, and a floury endosperm. In the experiment, a kind of floury endosperm corn was identified. The result of phenotypic trait analysis and determination of amino acid content showed that the floury endosperm filled with the small, loose, and scattered irregular spherical shape starch granules and contained higher content of amino acid. The starch biochemical properties are similar between floury corns and regular flint corn. By using dynamically comparative transcriptome analysis of endosperm at 20, 25, and 30 DAP, a total of 113.42 million raw reads and 50.508 thousand genes were obtained. By using the weighted gene co-expression network analysis, 806 genes and six modules were identified. And the turquoise module with 459 genes was proved to be the key module closely related to the floury endosperm formation. Nine zein genes in turquoise module, including two zein-alpha A20 (Zm00001d019155 and Zm00001d019156), two zein-alpha A30 (Zm00001d048849 and Zm00001d048850), one 50 kDa gamma-zein (Zm00001d020591), one 22 kDa alpha-zein 14 (Zm00001d048817), one zein-alpha 19D1 (Zm00001d030855), one zein-alpha 19B1 (Zm00001d048848), and one FLOURY 2 (Zm00001d048808) were identified closely related the floury endosperm formation. Both zein-alpha 19B1 (Zm00001d048848) and zein-alpha A30 (Zm00001d048850) function as source genes with the highest expression level in floury endosperm. These results may provide the supplementary molecular mechanism of structure and nutrient formation for the floury endosperm of maize.

Spatial Structure Dynamics and Maintenance of a Natural Mixed Forest

Spatial structure dynamics play a major role in understanding the mechanisms of forest structure and biodiversity formation. Recently, researches on the spatial structure dynamics utilizing multi-period data have been published. However, these studies only focused on comparative analyses of the spatial structure of multi-period living trees, without an in-depth analysis of the change processes. In this study, we propose a new comprehensive analysis method for dynamic change of the spatial structure at the individual level, which includes three processes (living trees’ flow, mortality process and recruitment process) that have not been considered in previous researches. Four spatial structural parameters (SSSPs, Uniform angle index, Mingling, Dominance and Crowding) and a natural spruce-fir-broadleaf mixed forest with two-phase data were taken as an example to find out the laws of the spatial structure dynamics. All types of dynamic change were named and their proportions were analyzed. The proportion of changes in the SSSPs of individuals was relatively high, even though the mean values of the stand did not change considerably. The five values (0, 0.25, 0.5, 0.75, 1) of the SSSPs are in mutual flow, and the flows are typically one-step, with three-steps and four-steps changes being uncommon. The processes of mortality and recruitment have a higher influence on the spatial structure than the flow of living trees. The dynamic change of spatial structure analysis method created in this study can capture more features not discovered in earlier approaches, as well as guiding forest management in some ways. Understanding the nuances of these changes is a critical part of reasonable spatial structure and biodiversity maintenance, and should be the focus of future research efforts.

Numerical Study of Vortex Flow in a Classifier with Coaxial Tubes

Centrifugal air classifiers are one of the most used separation devices in particle technology. The study aims to obtain a detailed description of the bulk material classification mechanism in the developed centrifugal classifier. The classifier design and the mechanism of the stable vortex structure formation in the inter-tube space of the device are described. Velocities within and between the vortices are studied to identify regions with inverse flows, which serve as transport channels for particles. The computational fluid dynamics modeling results indicate three channels with negative or near-zero axial velocities: between the vortices, near the outer wall of the internal tube, and the inner wall of the external tube. The selectivity of the device decreases when transport channels are disrupted due to flow mixing, which is caused by the height shifting of the vortex centers.