Influence of temperature and humidity on the angle of repose of wood bulk materials

2016 ◽  
Author(s):  
И.В. Бачериков ◽  
Б.М. Локштанов
Keyword(s):  
Field Experiments ◽  
Bulk Material ◽  
Average Particle Size ◽  
Operating Conditions ◽  
Angle Of Repose ◽  
Wood Dust ◽  
Average Particle ◽  
Bulk Materials ◽  
Technical Literature ◽  
The Impact

При проектировании открытых и закрытых хранилищ измельченных сыпучих материалов древесных материалов, таких как щепа и опилки, большое значение имеет угол естественного откоса (статический и динамический) этих материалов. В технической литературе приводятся противоречивые сведения о величине этих углов, что приводит к ошибкам при проектировании складов. В справочных данных не учитываются условия, в которых эксплуатируются емкости для хранения сыпучих материалов, свойства и состояние этих сыпучих материалов. В свою очередь, ошибки при проектировании приводят к проблемам (зависание, сводообразование, «затопление» и т. д.) и авариям при эксплуатации бункеров и силосов на производстве. В статье представлены сведения, посвященные влиянию влажности и температуры на угол естественного откоса сыпучих материалов. На основании лабораторных и натурных экспериментов, проведенных с помощью специально разработанных методик и установок, была скорректирована формула для определения углов естественного откоса (статического и динамического) для измельченных древесных материалов в зависимости от их фракционного и породного состава, влажности (абсолютной и относительной) и температуры. При помощи скорректированной формулы можно определить угол естественного откоса древесных сыпучих материалов со среднегеометрическим размером частицы от 0,5 мм до 15 мм (от древесной пыли до технологической щепы) в различных производственных условиях. Статья может быть полезна проектировщикам при расчете угла наклона граней выпускающей воронки бункеров и силосов предприятий лесной отрасли и целлюлозо-бумажной промышленности. In the design of open and closed storage warehouses chopped wood materials for bulk materials such as wood chips and sawdust, great importance has an angle of repose (static and dynamic) of these materials. In the technical literature are conflicting reports about the magnitude of these angles, which leads to errors in the design of warehouses. In the referencesdoes not take into account the conditions under which operated capacities for storage of bulk materials, and properties and condition of the bulk material. The design errors lead to problems (hanging, arching, «flooding», etc.) and accidents in the operation of hoppers and silos at the mills. The article provides information on the impact of humidity and temperature on the angle of repose of granular materials. On the basis of laboratory and field experiments, conducted with the help of specially developed techniques and facilities has been adjusted formula for determining the angle of repose (static and dynamic) for the shredded wood materials depending on their fractional and species composition, humidity (absolute and relative) and temperature. It is possible, by using the corrected formula, to determine the angle of repose of loose wood materials with average particle size of from 0.5 mm to 15 mm (wood dust to pulpchips) in various operating conditions. The article can be helpful to designers in the calculation of the angle of inclination of the funnel faces produces bunkers and silos forest industries and pulp and paper industry.

Toughening of Polypropylene-Ethylene Copolymer with Nanosized CaCO3 and Styrene-Butadiene-Styrene

2007 ◽  
Vol 121-123 ◽  
pp. 1451-1454
Author(s):  
Jian Feng Chen ◽  
Guo Quan Wang ◽  
Xiao Fei Zeng ◽  
Hong Ying Zhao
Keyword(s):  
Average Particle Size ◽  
Average Particle ◽  
Single Screw Extruder ◽  
Roll Mill ◽  
The Matrix ◽  
Ethylene Copolymer ◽  
Styrene Butadiene Styrene ◽  
Styrene Butadiene ◽  
The Impact ◽  
Butadiene Styrene

Nanocomposites of nanosized-CaCO3/polypropylene-ethylene copolymer (PPE) and nanosized CaCO3/ PPE/ styrene-butadiene-styrene (SBS) were prepared by using two-roll mill and single screw extruder. The average particle size of nanosized CaCO3 was determined to be about 30 nm. By adding nanosized CaCO3 into PPE matrix, the toughness of the matrix improves significantly. At nanosized CaCO3 content of 12 phr (parts per hundred PPE resin by weight), the impact strength of CaCO3/PPE at room temperature reaches 61.6 KJ/m2, which is 3.02 times that of unfilled PPE matrix. In addition, the synergistic toughening effect of nanosized CaCO3 and SBS particles on PPE matrix was investigated.

scholarly journals Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

2022 ◽  
Vol 8 ◽  
Author(s):  
Ao Li ◽  
Aixia Zhu ◽  
Di Kong ◽  
Chunwei Wang ◽  
Shiping Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Soybean Lecithin ◽  
Average Particle Size ◽  
Soy Protein Isolate ◽  
In Vitro Digestion ◽  
Bimodal Distribution ◽  
Average Particle ◽  
Food Ingredients ◽  
The Impact

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

scholarly journals Effect of adding TiO2 nanoparticles on the SEM morphology and mechanical properties of conventional heat-cured acrylic resin

2019 ◽  
Vol 13 (3) ◽  
pp. 234-240
Author(s):  
Elnaz Moslehifard ◽  
Mahmood Robati Anaraki ◽  
Saeed Shirkavand
Keyword(s):  
Impact Strength ◽  
Tio2 Nanoparticles ◽  
Cross Sections ◽  
Average Particle Size ◽  
Acrylic Resin ◽  
Mechanical Tests ◽  
Average Particle ◽  
Sem Images ◽  
Tio2 Nps ◽  
The Impact

Background. The current study evaluated the compressive, flexural and impact strengths of heat-cured acrylic resins reinforced by TiO2 nanoparticles (NPs). Methods. TiO2 NPs were provided and characterized using scanning electron microscopy (SEM) to determine their morphology and crystalline structure. For three mechanical tests, 12 acrylic resin groups (n=9), totaling 108 specimens, were prepared using a special mold for each test, with TiO2 nanoparticle contents of 0, 0.5, 1 or 2 wt% in different groups. After curing, the compressive, flexural and impact strengths of the specimens were examined according to ISO 1567. Results. In the SEM and XRD study of TiO2 NPs, anatase was identified as the major crystalline phase followed by rutile (average particle size: 20.4 nm). SEM images showed that the nanocomposite with 1 wt% NPs had a more homogenized blend. 1 wt% TiO2 nanocomposite exhibited a higher, but non-significant, impact strength compared to the controls. ANOVA showed significant differences in the impact and flexural strengths between nanocomposites with various contents of TiO2 NPs. Conclusion. The nanocomposite with 1 wt% TiO2 NPs exhibited fewer micro-pores and micro-cracks in the SEM cross-sections. A non-significant increase was also observed in the impact strength with TiO2 NPs at 1 wt%. Further increase in TiO2 NPs decreased both the impact and flexural strengths. The compressive strength of the heat-cured acrylic resin was not affected by the incorporation of NPs.

Experiment and analysis on chaotic characteristics vibration mill with variable rotational speed

2021 ◽  
pp. 2150052
Author(s):  
Xiaolan Yang ◽  
Yuan Gao ◽  
Minping Jia
Keyword(s):  
Chaotic Motion ◽  
Average Particle Size ◽  
Engineering Application ◽  
Operating Conditions ◽  
Average Particle ◽  
Maximum Lyapunov Exponent ◽  
Motor Speed ◽  
Low Efficiency ◽  
Motion Characteristics ◽  
Vibration Mill

In an attempt to improve the current low efficiency and high consumption situation of vibration mills, this paper analyses the chaotic motion characteristics of the system and the movement of vibration mill. The complex stiffness-dispersion coupling of the system is also studied, so as to investigate the effect of the system’s chaotic motion characteristics on the efficiency improvement and energy consumption reduction. Based on the ADAMS software, this paper establishes a simplified vibration mill mechanical model, analyzes the singularity and stability of the system, and determines the critical speed at which the vibration motor becomes chaotic according to the bifurcation diagram. Then the chaotic state of the grinding machine with sinusoidal variation in its motor speed is studied based on the Poincaré principle, singular attractor and maximum Lyapunov exponent. Lastly, a 200[Formula: see text]h vibration test on diamond powder with an average particle size of 10 [Formula: see text]m was carried out. Test results under the two operating conditions of variable and constant speeds are compared and analyzed. Our results show that with variable speed the vibration mill achieved higher grinding efficiency but smaller particle grain size. The research elaborated in this paper provides a valuable reference for the engineering application of the chaotic characteristics of vibration mill.

scholarly journals Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 320 ◽  
Author(s):  
Dries Devlaminck ◽  
Paul Van Steenberge ◽  
Marie-Françoise Reyniers ◽  
Dagmar D’hooge
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Miniemulsion Polymerization ◽  
Monomer Conversion ◽  
Water Soluble ◽  
Explicit Calculation ◽  
Average Particle ◽  
Intermediate Radical ◽  
Raft Agent ◽  
The Impact

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical. To allow the identification of the nature of the RAFT retardation it is recommended to experimentally investigate in the future the impact of the average particle size (dp) on both the monomer conversion profile and the average polymer properties for a sufficiently broad dp range, ideally including the bulk limit. With decreasing particle size both a slow RAFT fragmentation and a fast RAFT cross-termination result in a stronger segregation and thus rate acceleration. The particle size dependency is different, allowing further differentiation based on the variation of the dispersity and end-group functionality. Significant RAFT cross-termination is specifically associated with a strong dispersity increase at higher average particle sizes. Only with an ideal exchange it is afforded in the modeling to avoid the explicit calculation of the RAFT intermediate concentration evolution.

scholarly journals Magnetic and Structural Studies of CoFe2O4Nanoparticles Suspended in an Organic Liquid

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Branka Babić-Stojić ◽  
Vukoman Jokanović ◽  
Dušan Milivojević ◽  
Zvonko Jagličić ◽  
Darko Makovec ◽  
...  
Keyword(s):  
Room Temperature ◽  
Bulk Material ◽  
Organic Liquid ◽  
Average Particle Size ◽  
Hydrodynamic Diameter ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Ferrite Nanoparticle ◽  
Nanoparticle System

We present a study of magnetic and structural properties of CoFe2O4nanoparticles suspended in an organic liquid. Transmission electron microscopy shows that the nanoparticles have a narrow size distribution of average particle size 5.9 ± 1.0 nm. X-ray diffraction shows that the particles are of cubic spinel crystal structure. Dynamic light scattering measurements reveal the existence of an organic shell around the CoFe2O4nanoparticles with an average hydrodynamic diameter of 14.4 nm. Coercive magnetic field atT=5 K is found to be 11.8 kOe. Disappearance of the coercive field and remanent magnetization at about 170 K suggests that the CoFe2O4nanoparticles are superparamagnetic at higher temperatures which is confirmed by the room temperature Mössbauer spectrum analysis. Saturation magnetization of the nanoparticles of 80.8 emu/g(CoFe2O4) at 5 K reaches the value detected in the bulk material and remains very high also at room temperature. The cobalt ferrite nanoparticle system synthesized in this work exhibits magnetic properties which are very suitable for various biomedical applications.

Mechanical Properties of AA 5754 Hybrid Metal Matrix Composite Fabricated through Rheo-Squeeze Casting

2020 ◽  
Vol 979 ◽  
pp. 10-15
Author(s):  
K. Sekar ◽  
K. Jayakumar
Keyword(s):  
Particle Size ◽  
Tensile Strength ◽  
Metal Matrix ◽  
Squeeze Casting ◽  
Base Alloy ◽  
Average Particle Size ◽  
Casting Process ◽  
Matrix Alloy ◽  
Average Particle ◽  
The Impact

Hybrid metal matrix composites (MMCs) were prepared with AA 5754 as matrix and B4C (fixed with 1 wt.% and average particle size as 25 μm) and Al2O3 reinforcements (varied from 0.5 to 2 wt. % with the interval of 0.5 and average particle size as 50 nm) using Rheo-squeeze casting process. Microstructure images were taken to observe the uniform distribution of reinforcement particles on the matrix alloy. The tensile strength for AA 5754 with 1 wt.% B4C and 2 wt.% Al2O3 hybrid composite showed higher value compared to base alloy and other composites. The wt. % of Al2O3 in the composite is increased to 2 %, the tensile strength and compressive strength were also increased due to combined Rheo-squeeze casting. AA 5754 reinforced with 1 wt.% B4C and 1.5 wt.% Al2O3 MMC indicated the Impact strength value of 30 Joules which is higher than AA 5754 matrix alloy and other compositions.

Obtaining and Research of Additive Products from Electro-Erosive Cobalt-Chrome Powders

2020 ◽  
Vol 989 ◽  
pp. 801-805
Author(s):  
Evgeniy V. Ageev ◽  
O.G. Loktionova ◽  
A.Y. Altukhov
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Average Particle Size ◽  
Experimental Studies ◽  
Average Particle ◽  
Cobalt Chromium ◽  
Technical Literature ◽  
Specific Particle ◽  
Cobalt Chrome

The main requirement for powders for additive machines is the spherical shape of the particles. Such particles most compactly fit into a certain volume and provide the “fluidity” of the powder composition in the material supply systems with minimal resistance. Based on the peculiarities of the methods of obtaining spherical powders in order to obtain spherical granules of a regulated grain size, the technology of electroerosive dispersion, which is distinguished by relatively low energy costs and ecological cleanliness of the process, is proposed. The main advantage of the proposed technology is the use of waste as raw materials, which is much cheaper than the pure components used in traditional technologies. In addition, this technology is powder, which allows to obtain powder-alloys. The widespread use of the method of EED for the processing of metal waste into powders for the purpose of their reuse and application in additive technologies is hampered by the lack of complete information in the scientific and technical literature on the influence of the original composition, modes and media on the properties of powders and technologies of practical application. Therefore, the development of technologies for the reuse of EED powders and the evaluation of the effectiveness of their use requires the conduct of comprehensive theoretical and experimental studies. The purpose of this work was to obtain and study additive products from electroerosive cobalt-chromium powders of a specific particle size distribution and to study their microstructure. The granulometry of the obtained powders was determined on a laser analyzer of particle sizes “Analysette 22 NanoTec”. The microstructure of additive samples from cobalt-chromium powders (by transverse polishing) was investigated by optical microscopy on an inverted optical microscope OLYMPUS GX51. On the basis of completed studies, aimed at obtaining and studying additive products from electroerosive cobalt-chrome powders of a specific particle size distribution, and studying their microstructure, it was found that additive samples, obtained from a cobalt-chrome powder with an average particle size of 35,68 microns, have practically no pores.

Mechanical retention – Influence of filler floc size and grammage of the fibre web

2012 ◽  
Vol 27 (2) ◽  
pp. 202-207 ◽  
Author(s):  
Karin Athley ◽  
Lars Granlöf ◽  
Daniel Söderberg ◽  
Mikael Ankerfors ◽  
Göran Ström
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Pilot Trial ◽  
Average Particle ◽  
Paper Machine ◽  
Quartz Particle ◽  
Drainage Time ◽  
Fibre Layer ◽  
Filler Retention ◽  
The Impact

Abstract An investigation of the impact of particle size on the mechanical retention of particles in a fibre network has been conducted. The particles used were five sets of quartz particle fractions having fairly narrow particle size distributions with average particle size ranging from a few μm to around 100 μm. The particles were used to model flocculated filler aggregates as part of a larger study of the effect of pre-flocculation on mechanical retention. Pre-flocculation of the filler is a possible strategy to increase the filler content of paper without deterioration of strength properties. A modified laboratory hand sheet former, known as the Rapid Drainage Device (RDD) was used. The major modification consisted of a long pipe that acted as a suction leg, which provides a dewatering vacuum at the same level as on a paper machine. The experimental results showed that mechanical filler retention increased linearly with particle size and grammage of the fibre layer above a critical grammage which depended on particle size. The linear relation was also seen in a pilot scale trial on the FEX pilot-paper machine at Innventia. During this trial fine paper was produced using pre-flocculated filler where the mean particle size of the flocs and fibres was measured in the flow to the headbox. The results from this pilot trial show that mechanical retention is an important part of the total filler retention. Drainage time and therefore drainage resistance increased with the grammage of the fibre layer and amount of quartz particle added. Drainage time, compared at total grammage (i.e. the sum of fibre and quartz particle grammage) was lowest for a fraction of medium-sized particles, with a median size of 35 mm. There was no obvious effect on retention or drainage resistance of a change in the dewatering pressure from 27.5 to 41.5 kPa.

Structure and magnetic properties of 4H-SrMnO3-δ(δ=0.0 and 0.18) nanoparticles synthesized by thermal decomposition of appropriate precursor

2014 ◽  
Vol 1708 ◽  
Author(s):  
M. Parras ◽  
I. N. González-Jiménez ◽  
A. Torres-Pardo ◽  
A. E. Sánchez-Pelaez ◽  
A. Gutiérrez ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Structural Information ◽  
Bulk Material ◽  
Oxygen Deficiency ◽  
Average Particle Size ◽  
Reduction Process ◽  
High Energy ◽  
Structural Features ◽  
High Energy Resolution ◽  
Average Particle

ABSTRACTStoichiometric 4H-SrMnO3.0 nanoparticles have been successfully synthesized for the first time from thermal decomposition of a new heterometallic precursor [SrMn(edta)(H2O)5]·3/2H2O. From this precursor, highly homogeneous 4H-SrMnO3.0 nanoparticles with average particle size 70 nm are obtained. Local structural information, provided by atomically-resolved microscopy techniques, shows that 4H-SrMnO3.0 nanoparticles exhibit the same general structural features than the bulk material, although structural disorder, due to edge-dislocations, is observed. The nanometric size of particles enables a topotactic reduction process at low temperature stabilizing a metastable 4H-SrMnO2.82 phase. The oxygen deficiency is accommodated through extra cubic layers breaking the …hchc… 4H-sequence. These defect areas are Mn3+ rich as evidenced by high energy resolution EELS data. Magnetic characterization of nano-4H-SrMnO3-δ shows significant variations with respect to the bulk material.

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