289. Assessment of the Impact of Particle Size-Selective Sampling Criteria and Instrumentation for Inhalable Aerosol on Observed Workplace Exposure Levels

AbstractThe paper describes the so-called Waterfall Algorithm, which may be used to calculate a set of parameters characterising the spatial structure of granular porous media, such as shift ratio, collision density ratio, consolidation ratio, path length and minimum tortuosity. The study is performed for 1800 different two-dimensional random pore structures. In each geometry, 100 individual paths are calculated. The impact of porosity and the particle size on the above-mentioned parameters is investigated. It was stated in the paper, that the minimum tortuosity calculated by the Waterfall Algorithm cannot be used directly as a representative tortuosity of pore channels in the Kozeny or the Carman meaning. However, it may be used indirect by making the assumption that a unambiguous relationship between the representative tortuosity and the minimum tortuosity exists. It was also stated, that the new parameters defined in the present study are sensitive on the porosity and the particle size and may be therefore applied as indicators of the geometry structure of granular media. The Waterfall Algorithm is compared with other methods of determining the tortuosity: A-Star Algorithm, Path Searching Algorithm, Random Walk technique, Path Tracking Method and the methodology of calculating the hydraulic tortuosity based on the Lattice Boltzmann Method. A very short calculation time is the main advantage of the Waterfall Algorithm, what meant, that it may be applied in a very large granular porous media.

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Evaluation of Marblewood Dust’s (Marmaroxylon racemosum) Effect on Ignition Risk

Applied Sciences ◽

10.3390/app11156874 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6874

Author(s):

Miroslava Vandličkova ◽

Iveta Markova ◽

Katarina Holla ◽

Stanislava Gašpercová

Keyword(s):

Particle Size ◽

Dust Particles ◽

Wood Dust ◽

Sieve Analysis ◽

Granulometric Analysis ◽

Analysis Measurement ◽

Risk Research ◽

Minimum Ignition Temperature ◽

The Impact

The paper deals with the selected characteristics, such as moisture, average bulk density, and fraction size, of tropical marblewood dust (Marmaroxylon racemosum) that influence its ignition risk. Research was focused on sieve analysis, granulometric analysis, measurement of moisture level in the dust, and determination of the minimum ignition temperatures of airborne tropical dust and dust layers. Samples were prepared using a Makita 9556CR 1400W grinder and K36 sandpaper for the purpose of selecting the percentages of the various fractions (<63, 63, 71, 100, 200, 315, 500 μm). The samples were sized on an automatic vibratory sieve machine Retsch AS 200. More than 65% of the particles were determined to be under 100 μm. The focus was on microfractions of tropical wood dust (particles with a diameter of ≤100 µm) and on the impact assessment of particle size (particle size <100 µm) on the minimum ignition temperatures of airborne tropical dust and dust layers. The minimum ignition temperature of airborne marblewood dust decreased with the particle size to the level of 400 °C (particle size 63 μm).

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Mechanical Response of Porous Copper Manufactured by Lost Carbonate Sintering Process

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.1863 ◽

2007 ◽

Vol 539-543 ◽

pp. 1863-1867 ◽

Cited By ~ 6

Author(s):

X.F. Tao ◽

Li Ping Zhang ◽

Y.Y. Zhao

Keyword(s):

Particle Size ◽

Flexural Strength ◽

Relative Density ◽

Mechanical Response ◽

Compaction Pressure ◽

Absorption Capacity ◽

Energy Absorption Capacity ◽

Three Point Bending ◽

Porous Copper ◽

The Impact

This paper investigated the mechanical response of porous copper manufactured by LCS under three-point bending and Charpy impact conditions. The effects of the compaction pressure and K2CO3 particle size used in producing the porous copper samples and the relative density of the samples were studied. The apparent modulus, flexural strength and energy absorption capacity in three-point bending tests increased exponentially with increasing relative density. The impact strength was not markedly sensitive to relative density and had values within 7 – 9 kJ/m2 for the relative densities in the range 0.17 – 0.31. The amount of energy absorbed by a porous copper sample in the impact test was much higher than that absorbed in the three-point bending test, impling that loading strain rate had a significant effect on the deformation mechanisms. Increasing compaction pressure and increasing K2CO3 particle size resulted in significant increases in the flexural strength and the bending energy absorption capacity, both owing to the reduced sintering defects.

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Effect of Particle Size Distribution on Powder Packing and Sintering in Binder Jetting Additive Manufacturing of Metals

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4036640 ◽

2017 ◽

Vol 139 (8) ◽

Cited By ~ 53

Author(s):

Yun Bai ◽

Grady Wagner ◽

Christopher B. Williams

Keyword(s):

Particle Size ◽

Additive Manufacturing ◽

Large Degree ◽

Full Density ◽

Powder Particle Size ◽

Powder Mixtures ◽

Fine Powders ◽

Sintering Shrinkage ◽

The Impact ◽

Binder Jetting

The binder jetting additive manufacturing (AM) process provides an economical and scalable means of fabricating complex parts from a wide variety of materials. While it is often used to fabricate metal parts, it is typically challenging to fabricate full density parts without large degree of sintering shrinkage. This can be attributed to the inherently low green density and the constraint on powder particle size imposed by challenges in recoating fine powders. To address this issue, the authors explored the use of bimodal powder mixtures in the context of binder jetting of copper. A variety of bimodal powder mixtures of various particle diameters and mixing ratios were printed and sintered to study the impact of bimodal mixtures on the parts' density and shrinkage. It was discovered that, compared to parts printed with monosized fine powders, the use of bimodal powder mixtures improves the powder's packing density (8.2%) and flowability (10.5%), and increases the sintered density (4.0%) while also reducing the sintering shrinkage (6.4%).

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Quantifying The Impact That Coxswain Behaviour Has on Whole Body Vibration - Simulator Trial

The International Journal of Maritime Engineering ◽

10.5750/ijme.v163ia3.807 ◽

2021 ◽

Vol 163 (A3) ◽

Author(s):

T J Newman

Keyword(s):

Phase 1 ◽

Whole Body Vibration ◽

Whole Body ◽

Motion Platform ◽

Body Vibration ◽

Sea Trial ◽

Data Driven Approach ◽

Exposure Levels ◽

Transit Speed ◽

The Impact

A common risk to personnel is from Whole Body Vibration (WBV) and shock when transiting at speed in heavy seas, and much research has been done by maritime organisations to reduce this risk and the associated health impacts. It is well known that coxswain ‘driving style’ can radically affect exposure levels for a given sea state and sustained transit speed. A data-driven approach to define what makes a good coxswain from a WBV perspective is currently being developed by the Naval Design Partnering team (NDP). In phase 1, a systematic coxswain behaviour tracking methodology has been developed and demonstrated using a motion platform-based fast craft simulator at MARIN. The performance of several experienced volunteer coxswains from MOD, RNLI and KNRM has been evaluated based on a set pattern of tests. The advantages of using the simulator, over a sea trial, have been demonstrated: it is more repeatable, more controllable, accurate and more accessible. The potential disadvantages of the approach are also discussed with reference to feedback gathered from coxswains. Analysis has shown effective throttle control is much more important than steering to reduce WBV. Several interesting trends in WBV reduction potential have been shown which it is thought, with further validation, could aid mission planning, mission execution and provide data for training autonomous feedback/control algorithms. Further work is required before the findings of this study can be fully exploited. These subsequent phases, which include sea trials, aim to provide validation and further evidence to support the initial findings.

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Green Preparation, Spheroidal, and Superior Property of Nano-1,3,5,7-Tetranittro-1,3,5,7-Tetrazocane

Journal of Nanomaterials ◽

10.1155/2018/5839037 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Xinlei Jia ◽

Jingyu Wang ◽

Conghua Hou ◽

Yingxin Tan

Keyword(s):

Activation Energy ◽

Particle Size ◽

Fractal Dimension ◽

Particle Size Distribution ◽

Size Distribution ◽

Fractal Theory ◽

Crystal Form ◽

Decomposition Temperature ◽

Scanning Calorimetry ◽

The Impact

Herein, a green process for preparing nano-HMX, mechanical demulsification shearing (MDS) technology, was developed. Nano-HMX was successfully fabricated via MDS technology without using any chemical reagents, and the fabrication mechanism was proposed. Based on the “fractal theory,” the optimal shearing time for mechanical emulsification was deduced by calculating the fractal dimension of the particle size distribution. The as-prepared nano-HMX was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). And the impact sensitivities of HMX particles were contrastively investigated. The raw HMX had a lower fractal dimension of 1.9273. The ideal shearing time was 7 h. The resultant nano-HMX possessed a particle size distribution ranging from 203.3 nm to 509.1 nm as compared to raw HMX. Nano-HMX particles were dense spherical, maintaining β-HMX crystal form. In addition, they had much lower impact sensitivity. However, the apparent activation energy as well as thermal decomposition temperature of nano-HMX particles was decreased, attributing to the reduced probability for hotspot generation. Especially when the shearing time was 7 h, the activation energy was markedly decreased.

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Optimization of proppant parameters for CBM extraction using hydrofracturing by orthogonal experimental process

Journal of Geophysics and Engineering ◽

10.1093/jge/gxaa009 ◽

2020 ◽

Vol 17 (3) ◽

pp. 493-505 ◽

Cited By ~ 1

Author(s):

Haoze Li ◽

Bingxiang Huang ◽

Qingying Cheng ◽

Xinglong Zhao

Keyword(s):

Particle Size ◽

Orthogonal Test ◽

Coal Mass ◽

Tensile Fracture ◽

Experimental Conditions ◽

Embedded Value ◽

Fracture Area ◽

Creep Time ◽

Experimental Process ◽

The Impact

Abstract Proppant placement concentration, particle size and creep time are important factors that affect the embedment of proppant into coal. Based on multistage creep, an orthogonal test is conducted, and an optimal proppant scheme for different closure stresses obtained. The results show that with increased proppant placement concentration, the number of coal fractures increases and the elastic modulus of the fracture area decreases. As the proppant particle size decreases, the plasticity of fracture-proppant assemblies increases gradually. The yield limit is highest when the particle size is 20/40 mesh. During the proppant embedding process, localization or uneven distribution of proppant results in tensile stress parallel to the fracture surface, which induces tensile fracture in the coal. In the fracture-proppant assembly areas, proppant fractures are severe and yield lines appear. As proppant concentration increases, more energy is accumulated during the proppant compaction stage, resulting in energy release producing craters and crevasses. The energy released also causes increased stress in the proppant-coal contact area and fracturing to the coal mass. The longer the creep time, the weaker the impact and the smaller is fluctuation. Moreover, we find that the orthogonal test can effectively analyze the importance of each parameter. Proppant placement concentration was found to have the highest influence on the process of proppant embedding into coal, followed by particle size and then time. Under experimental conditions, the lowest proppant-embedded value in coal samples was observed with proppant placement concentration of 2 kg m−2 and particle size of 20/40 mesh.

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