Search

The transport of energetic charged particles through magnetized plasmas is ubiquitous in interplanetary space and astrophysics, and the important physical quantities are the parallel and perpendicular diffusion coefficients of energetic charged particles. In this paper, the influence of solar wind on particle transport is investigated. Using the focusing equation, we obtain parallel and perpendicular diffusion coefficients, accounting for the solar wind effect. For different conditions, the relative importance of the solar wind effect to diffusion is investigated. It is shown that, when energetic charged particles are close to the Sun, for parallel diffusion, the solar wind effect needs to be taken into account. These results are important for studying energetic charged particle transport processes in the vicinity of the Sun.

When the hydrostatic workbench is running under high-speed overload conditions, the friction by-product is partially placed, causing the micro-gap oil film to be smaller, and the tribology is exposed. The oil film morphology of hydrostatic workbench directly affects its lubrication performance, and the oil film morphology is determined by deformation of bearing friction pairs and the oil film morphology is extremely difficult to obtain. This study will provide an acquisition method for the oil film morphology through the deformation of the bearing friction pair, and the deformation prediction of hydrostatic workbench having double rectangular cavities in heavy type vertical lathe has studied based on ANSYS WORKBENCH, and these are helpful to further investigate oil film shape under the working conditions of high-speed and heavy-load. The oil film clearance test rig was established, and the simulation results were verified, which verified the effectiveness of the proposed numerical simulation method. It can be concluded that the rotational speed has a greater impact on the oil film thickness than that of load, and the oil film thickness of downstream side is smaller than that of upstream side, and oil film thickness changes more quickly inside of oil sealing edge than that of outside, and the friction behavior and failure mechanism of this kind of bearing are proved.

Piezoelectric materials possess excellent electromechanical coupling characteristics, which are functional and suitable in structural vibration control. This study investigates the active control of free and forced vibration for piezoelectric-integrated functionally graded carbon nanotube reinforced composite (FG-CNTRC) plate using the finite element method (FEM). Based on the first-order shear deformation theory (FSDT), the governing equations of the motion of a piezoelectric-integrated FG-CNTRC plate are derived by Hamilton’s principle. The convergence and accuracy of the numerical method is verified through the results of natural frequencies. The influences of CNT volume fraction, CNT distribution type, piezoelectric layer thickness-to-plate thickness ratio, and boundary condition on the natural frequencies are investigated. A constant gain velocity feedback algorithm is used to achieve the dynamic response control of the piezoelectric-integrated FG-CNTRC plate. In addition, the effects of dynamic load, feedback control gain, and boundary condition on the dynamic response of the plate are studied. Numerical results indicate that active control is promising for practical applications in civil and mechanical engineering.

In previous studies, a general spatial transport equation was derived from the Fokker–Planck equation. The latter equation contains an infinite number of spatial derivative terms T _n = κ _nz ∂ ^n F /∂ z ^n with n = 1, 2, 3, ⋯ . Due to the complexity of the general equation, some simplified equations with finitely many spatial derivative terms have been used by astrophysical researches, e.g., the diffusion equation, the hyperdiffusion equation, subdiffusion transport equation, etc. In this paper, the simplified transport equations with the spatial derivative terms up to the first, second, third, fourth, and fifth order are listed, and their transport coefficient formulas are derived, respectively. We find that most of the transport coefficients are determined by the corresponding statistical quantities. In addition, we find that the well-known statistical quantities, the skewness ${ \mathcal S }$ and the kurtosis ${ \mathcal K }$ , are determined by some transport coefficients. The results can help one to use various transport coefficients determined by the statistical quantities, including many that are relatively newfound in this paper, to study charged particle parallel transport processes.

In the research of various energy technologies, the direct-drive volume control flange-type rotary vane steering gear (DDVC-FRVSG) has become a promising component for controlling the course and posture of a vessel because of its superior energy-saving performance. However, nonlinear friction limits the ability of the DDVC-FRVSG to satisfy the efficient energy requirements of the vessel. This study proposes compensation methods to suppress nonlinear friction, such that the rudder can be efficiently controlled. Based on the principle of the DDVC-FRVSG, we establish a mathematical model and transfer function of the steering gear system along with a mathematical model of the impact of nonlinear friction on the rudder system. A friction model-based method using the integral back-stepping adaptive control strategy is proposed to suppress nonlinear friction, and both the models are studied theoretically and through simulation. Taking the no-compensation state as a benchmark, our measured results by prototype testing reveal that the method can compensate for nonlinear friction, achieving up to 73.08 % better performance on average and reducing the output power of the driving motor by 36.39 % on average. The findings of this research will contribute to the energy-saving performance and efficient energy requirement of the DDVC-FRVSG system.

Silicon (Si) could enhance plant tolerance to heavy metals; however, the mechanism of Si-mediated alleviation of cadmium (Cd) toxicity in Poa annua was not clear. In this study, we found that 100 μM Cd significantly inhibited the growth of Poa annua seedlings. Furthermore, Cd enhanced the H2O2 and malondialdehyde content. The activities of superoxide dismutase and ascorbate peroxidase were enhanced, but the catalase and peroxidase activities were reduced by Cd treatment. Cd also altered the activity and expression of glucose-6-phosphate dehydrogenase (G6PDH) in Poa annua roots. Application of Na3PO4, an inhibitor of G6PDH, decreased the activity of G6PDH, the expression of G6PDH, and increased the Cd toxicity, suggesting that G6PDH is involved in the regulation of oxidative stress induced by Cd. Application of 1 mM Si alleviated the inhibition of Cd on the growth of Poa annua seedlings. Si application not only led to reduced oxidative injuries but also decreased the accumulation of Cd in Poa annua seedlings under Cd stress. Furthermore, Si decreased the activity of G6PDH and the expression of G6PDH under Cd stress, which demonstrated that Si attenuates the Cd toxicity in Poa annua probably through decreasing the expression of G6PDH under Cd stress. When G6PDH was inhibited, the alleviation impact of Si on Cd stress was abolished. Taken together, these results demonstrated that the Cd tolerance in Poa annua enhanced by Si is mainly due to the decrease of Cd uptake in roots and lowering the oxidative stress induced by Cd.

Alternative respiration pathway (AP) is an important pathway which can be induced by environment stresses in plants. In the present study, we show a new mechanism involving the AP in nitrogen deprivation-induced tolerance of Poa annua callus to salt stress. The AP capacity markedly increased under a 600 mM NaCl treatment or nitrogen deprivation pretreatment and reached a maximum under the nitrogen deprivation pretreatment combined with the NaCl treatment (-N+NaCl). Malondialdehyde (MDA) and H2O2 content and Na+/K+ ratio significantly increased under the 600 mM NaCl treatment but less under the-N+NaCl treatment. Moreover, both the nitrogen deprivation and the NaCl stress stimulated the plasma membrane (PM) H+-ATPase activity and increased pyruvate content. The maximal stimulating effect was found under the-N+NaCl treatment. When the AP capacity was reduced by salicylhydroxamic acid (SHAM, an inhibitor of AP), content of MDA and H2O2 and Na+/K+ ratio dramatically increased, whereas PM H+-ATPase activity decreased. Moreover, exogenous application of pyruvate produced a similar effect as the nitrogen deprivation pretreatment. The effects of SHAM on the Poa annua callus were counteracted by catalase (a H2O2 scavenger) and diphenylene iodonium (a plasma membrane NADPH oxidase inhibitor). Taken together, our results suggest that the nitrogen deprivation enhanced the capacity of AP by increasing pyruvate content, which in turn prevented the Poa annua callus from salt-induced oxidative damages and Na+ over-uptake.

The validation of remote sensing products (RSPs) is fundamental work before the proper use of RSPs. This paper mainly introduces the technical specification for the validation of remote sensing product, which is used to guide user how to validate the available products. The validation of remote sensing products (VRSP) mainly there are two levels. The first level focuses on the validation at pixel scale and the other is the product level which contains a number of pixels that are distributed in different land use types which are selected to represent both the space-time characteristics of surface parameters investigated. At pixel scale, the validation procedure mainly consists of three steps: sampling design for ground observation, data collection and estimation the mean value at pixel scale. The data types of ground observation include the wireless sensor network, which are used to capture multi-scale heterogeneities of surface parameters, and the footprint which could be a flux observation such as eddy covariance (EC) and large aperture scintillometer (LAS). After finishing the validation at pixel scale, the second-level validation for the whole remote sensing product is followed. The assessment with indexes is then used to evaluate the performance of the validation. Last, a validation report on the description of the validation will be included in the technical specification.

During a reconnection event on 7 August 2004, Cluster and Double Star (TC-1) were near the neutral sheet and simultaneously detected the signatures of the reconnection pulses. AT 22:59 UT tailward flow followed by earthward flow was detected by Cluster at about 15 RE, while earthward plasma flow followed by tailward flow was observed by TC-1 at about 10 RE. During the flow reversal from tailward to earthward, the magnetic field Bz changed sign from mainly negative values to positive, and the X component of the magnetic curvature vector switched sign from the tailward direction to the earthward direction, which indicates that the reconnection site (X-line) moved tailward past the Cluster constellation. By using multi-point analysis and observation of energetic electron and ion flux, we study the movement and structure of the current sheet and discuss the braking effect of the earthward flow bursts in the inner magnetosphere.

In this paper we report new kinetic features of ions and electrons observed in the vicinity of the reconnection layer on 10 January 1997. This event has a three-dimensional magnetic field topological structure, which is much more complex than the previously suggested two-dimensional magnetic configuration. The ion distributions are non-gyrotropic and electrons show non-Maxwellian distribution functions. Acceleration of multiple ion beams, both parallel and perpendicular to the local magnetic field, have been observed. The perpendicular acceleration of the multiple ion beams can be explained by plasma mixing between the meandering ions accelerated around the ion diffusion region and the cold ions convected directly from the magnetosheath without passing through the X-line region. The parallel acceleration of the multiple ion beams can be understood by the fact that high-velocity ions ejected from the vicinity of the X-line mix with the plasma flowing directly across the boundary. We observed the kinetic effect of the separation of the electron and ion edges due to the time-of-flight effect. It is stressed that kinetic processes are the key to understanding these new observations that cannot be adequately explained by magnetohydrodynamic (MHD) models.Key words. Space plasma physics (magnetic reconnection; charged particle motion and acceleration) – Magnetospheric physics (magnetopause, cusp, and boundary layers)