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Rapid flow of granular materials
Published in M. Oda, K. Iwashita, Mechanics of Granular Materials, 2020
From these DEM results, the rapid granular flow assumptions work reasonably well, provided that the strain rate is high and solid concentration is low. The issue that requires most attention for future work appears to be particle rotation. From his DEM results Louge (1994) showed that the rotational temperature rose rapidly with increasing particle friction. At the moment, there is no complete theory for rapid granular flows that includes particle rotation. The effect of rotation not only may change the linear stress tensor, as shown in the work by Hopkins & Shen (1988), it also requires derivation of couple stresses. Although the framework for such theory is laid out as shown in Section 5.3, derivations of the couple stress tensors and the associated modifications in the balance equations still await future work.
Physical Processes
Published in Ralph L. Stephenson, James B. Blackburn, The Industrial Wastewater Systems Handbook, 2018
Ralph L. Stephenson, James B. Blackburn
The complete theory and application of that theory to shaft analysis will be covered later. The practical implication of a shaft analysis is that for a given power and shaft speed, there is a total shaft length that cannot be safely exceeded.
Effect of combined exhaust gas recirculation and retarded injection timing on diesel engine operated distilled waste plastic oil blend
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Mohanraj Chandran, Ramesh Chinnappan, Chun Kit Ang
The prediction of the complete theory of diesel engine combustion is more complex. Generally, the diesel engine combustion carried out through compression ignition method. Here the required quantity of air sucked by the engine during the intake stroke. Then, it is compressed up to 17 bar pressure during the compression stroke. At the end of compression, the injector can spray the fuel to the combustion chamber. And, the fuel droplets get mixed with air molecules. Due to peak pressure and temperature in the combustion chamber, the mixture is ignited and combustion is taking place. The energy released during combustion pushes the piston to BDC. The required quantity of air and fuel ratio is calculated based on the engine specifications. Chemically, the fuel is denoted in hydrocarbon number (C12H24 for diesel) and the air is acted as an oxidizer (23 vol% of O2 and 77 vol% of N2). After combustion, all the three components are reacted with each other and released the energy; then, products like CO, CO2, NOx, O2, and unburned HC are emitted in emissions.
A Review of Morton Effect: From Theory to Industrial Practice
Published in Tribology Transactions, 2018
Almost all of the case studies (or troubleshooting) reviewed previously attempted to solve ME-induced problems by reducing the differential heating of journals. The sole exception is the work by De Jongh and van der Hoeven (22). They utilized a heat barrier to isolate the journal from the differential heating generated in the fluid (De Jongh and van de Hoeven (22)). Little evidence of theoretical guidance could be traced during those case studies. This lack of theoretical guidance might sometimes have resulted in failure to eliminate ME-induced instability (Berot and Dourlens (5)). The theory-guided solutions greatly rely on the development of a more complete theory that can reflect the relationship between rotordynamics and the thermal field. Pragmatic guidance for field operators can be to provide a series of maps, tables, or plots that indicate the range of differential temperature for the most common rotor systems. Toward this end, various rotor systems—for example, with single or double overhung masses—of single or multiple stages, supported by plain journal bearings or tilting pad bearings, require intensive quantitative studies.
A new β-diketonate Dy(III) single‒ion magnet featuring multiple magnetic relaxation processes
Published in Journal of Coordination Chemistry, 2018
Peipei Cen, Xiufang Ma, Xiangyu Liu, Yi-Quan Zhang, Gang Xie, Sanping Chen
Investigations on existing mononuclear Dy(III)-based SMMs confirm that the anisotropic magnitude of Dy(III) ions is highly sensitive to fine tunings of local geometrical symmetry and ligand field [9]. Therefore, selecting proper ligands is a considerable point in organizing the desirable ligand fields and enhancing the anisotropy barriers for mononuclear Dy(III)-based SMMs. As a classical chelating ligand, β-diketonate and its derivatives have been extensively applied to drive the single-ion magnetic anisotropy in monometallic Dy(III) compounds [10] derived from their typical characteristics of stable bidentate patterns chelating to central ions and providing suitable ligand fields [11]. Consequently, increasingly, β-diketonate-Dy(III) SMMs or SIMs with eight-coordinate configuration have been developed [12] by way of modulating the coordination geometries around the Dy(III) centers through the addition of the capped coligands, such as 2,2′-bipyridine, 1,10-phenanthroline and their analogs [13]. The results indicated that the capped ligands effectively affect the anisotropy barriers of β-diketonate-Dy(III) SMMs. In spite of that, there is still no complete theory on the insight of the dynamics of the magnetization in Dy(III)-based SMMs. To further study the combination effect of β-diketonate and capped ligands on mononuclear Dy(III) SMMs, a β-diketonate analog, 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (TFNB), and auxiliary 2,2′-bipyridine (bpy) ligand were adopted in reaction with DyCl3·6H2O (Scheme 1). As a result, a monometallic dysprosium compound, [Dy(TFNB)3(bpy)] (1), has been prepared and isolated. The crystal structure has been characterized by X-ray diffraction. Magnetic investigations demonstrate that the compound behaves as a single-ion magnet and represents one of the few cases with well-defined multiple relaxation modes. The uniaxial magnetic anisotropies and magneto-structural correlations, as well as relaxation mechanism have been explored by ab initio calculations.