Permanent Magnet Flux Linkage Analysis and Maximum Torque per Ampere (MTPA) Control of High Saturation IPMSM

The maximum torque per ampere (MTPA) control is significant for improving the efficiency of the interior permanent magnet synchronous motor (IPMSM). However, for the high saturation IPMSM, the change of the permanent magnet (PM) flux linkage is more complicated, which can cause the MTPA control to deviate from the optimal solution. Therefore, an improved MTPA control method for the high saturation IPMSM is proposed in this paper. Compared with other methods, the proposed method improves the conventional models of flux linkage and torque by analyzing the nonlinear variation of the PM flux linkage with the dq-axis currents. Subsequently, an expression suitable for the MTPA control of high saturated IPMSM is derived based on the improved models. The proposed parameter fitting models are then fitted using data from 11 operating points and incorporated into the MTPA optimization algorithm to obtain the MTPA curve. Finally, the effectiveness of the proposed method in enhancing the control accuracy of the MTPA angle is verified through simulations and experiments

Dynamic Characteristics of Bubble Collapse Near the Liquid-Liquid Interface

Bubble collapse near the liquid-liquid interface was experimentally studied in this paper, and the dynamic evolution of a laser-induced bubble (generation, expansion, and collapse) and the liquid-liquid interface (dent and rebound) were captured by a high-speed shadowgraph system. The effect of the dimensionless distance between the bubble and the interface on the direction of the liquid jet, the direction of bubble migration, and the dynamics of bubble collapse were discussed. The results show that: (1) The jet generated during bubble collapse always directs toward the denser fluid; (2) bubble collapses penetrate the interface when the bubble is close to the interface; (3) three different shapes of the liquid-liquid interface—that is, a mushroom-shaped liquid column, a spike droplet, and a spherical liquid droplet—were observed

Sedimentation of Two Side-by-Side Heavy Particles of Different Density in a Shear-Thinning Fluid with Viscoelastic Properties

Particle sedimentation has widely existed in nature and engineering fields, and most carrier fluids are non-Newtonian. Recently, the manipulation of a settling particle in liquid has been a topic of high interest to those involved in engineered processes such as composite materials, pharmaceutical manufacture, chemistry and the petroleum industry. Compared with Newtonian fluid, the viscosity of non-Newtonian fluid is closely related to the shear rate, leading to a single settling particle having different dynamic behaviors. In this article, the trajectories and velocities of two side-by-side particles of different densities (heavy and light) settling in a shear-thinning fluid with viscoelastic property were studied, as well as that for the corresponding single settling particle. Regardless of the difference in the particle density, the results show the two-way coupling interaction between the two side-by-side settling particles. As opposed to a single settling particle, the wake of the heavier particle can clearly attract or rebound the light particle due to the shear-thinning or viscoelastic property of the fluid. Regarding the trajectories of the light particle, three basic path types were found: (i) the light particle is first attracted and then repelled by the wake of the heavy one; (ii) the light particle approaches and then largely traces within the path of the heavy one in the limited field of view; (iii) the light particle is first slightly shifted away from its original position and then returns to this initial position. In addition to this, due to the existence of a corridor of reduced viscosity and negative wake generated by the viscoelastic property, the settling velocity of a light particle can exceed the terminal velocity of a single particle of the same density. On the other hand, the sedimentation of the light particle can induce the distinguishable transverse migration of the heavy one

Cold Tolerance and Cold-Resistant Substances in Two <i>Tomicus</i> Species during Critical Transferring Periods

The pine shoot beetles Tomicus minor and Tomicus yunnanensis are important stem borers of Pinus yunnanensis in southwestern China. To determine strategies for cold resistance and changes in major cold-resistant substances in adults of two Tomicus species during two critical transferring periods, “shoot-to-trunk” and “trunk-to-shoot”, the insects’ supercooling point (SCP), freezing point (FP), and antifreeze protective substances were determined. The SCP and FP did not differ between female and male adults in the shoot-to-trunk phase, but were significantly lower in females in the trunk-to-shoot period. Although there was no difference in the SCP and FP between the two Tomicus species adults, both indexes were significantly lower in the shoot-to-trunk period than in the trunk-to-shoot period. The trehalose content in females of two Tomicus species was significantly lower than that in males in the trunk-to-shoot period, and the protein, glycerol, glycogen, fat, and sorbitol contents were different between the species in the same period. The protein and water content in adults of both species were significantly lower in the shoot-to-trunk period than in the trunk-to-shoot period, but the content of glycerol, trehalose, water, sorbitol, glycogen, and fat content were significantly higher in the shoot-to-trunk. Different types of cold-resistant substances regulating sex, species, and developmental stages were found, and the most abundant were cold-resistant substances regulating developmental stages

The underlying processes of a soil mite metacommunity on a small scale

<div><p>Metacommunity theory provides an understanding of how ecological processes regulate local community assemblies. However, few field studies have evaluated the underlying mechanisms of a metacommunity on a small scale through revealing the relative roles of spatial and environmental filtering in structuring local community composition. Based on a spatially explicit sampling design in 2012 and 2013, this study aims to evaluate the underlying processes of a soil mite metacommunity on a small spatial scale (50 m) in a temperate deciduous forest located at the Maoershan Ecosystem Research Station, Northeast China. Moran’s eigenvector maps (MEMs) were used to model independent spatial variables. The relative importance of spatial (including trend variables, i.e., geographical coordinates, and broad- and fine-scale spatial variables) and environmental factors in driving the soil mite metacommunity was determined by variation partitioning. Mantel and partial Mantel tests and a redundancy analysis (RDA) were also used to identify the relative contributions of spatial and environmental variables. The results of variation partitioning suggested that the relatively large and significant variance was a result of spatial variables (including broad- and fine-scale spatial variables and trend), indicating the importance of dispersal limitation and autocorrelation processes. The significant contribution of environmental variables was detected in 2012 based on a partial Mantel test, and soil moisture and soil organic matter were especially important for the soil mite metacommunity composition in both years. The study suggested that the soil mite metacommunity was primarily regulated by dispersal limitation due to broad-scale and neutral biotic processes at a fine-scale and that environmental filtering might be of subordinate importance. In conclusion, a combination of metacommunity perspectives between neutral and species sorting theories was suggested to be important in the observed structure of the soil mite metacommunity at the studied small scale.</p></div

Simple and partial Mantel tests of soil mite metacommunity dissimilarity against spatial and environmental distances (999 permutations).

<p>Simple and partial Mantel tests of soil mite metacommunity dissimilarity against spatial and environmental distances (999 permutations).</p

Species and individuals of soil mite metacommunities in 2012 and 2013.

<p>Species and individuals of soil mite metacommunities in 2012 and 2013.</p

The effect of environmental factors on the soil mite metacommunity structures analyzed by redundancy analysis and Monte Carlo permutation test (999 permutations)

<p>The effect of environmental factors on the soil mite metacommunity structures analyzed by redundancy analysis and Monte Carlo permutation test (999 permutations)</p