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• A new kind of partially coherent crescent-like beams with off-axis vortex is proposed. • The partially coherent crescent-like beams with off-axis vortex is experimentally generated. • The intensity pattern of such off-axis vortex beam possesses additional dark cores. • The off-axis vortex provides an additional degree of freedom for focus shaping. Based on the integral superposition method of constructing partially coherent beam model, a partially coherent crescent-like multi-vortex-correlated Schell-mode beam is first proposed. Numerical simulation results show that the beam possesses a crescent-like intensity distribution with multiple off-axis vortices on the source plane. By means of digital holography, the spatial light modulator was loaded with holograms, which realized experimentally the generation of this beam. The experimental normalized intensity distribution is basically consistent with the theoretical results. Adjusting the parameter N 0 , off-axis distance s and phase angle φ 0 , one can precisely control the number and position of multiple off-axis vortices. The results obtained are of importance for adjusting the beam centroid and studying vortex optics. [ABSTRACT FROM AUTHOR]

• Radiation force of a special correlated beam with multiple vortices is first derived. • Four focused hollow spots with obvious boundaries are obtained in the focal plane. • The gradient force and capture stability range increase with the increase of topological charge. • Multiple vortex beams have more capture points than the beams without vortices. In order to explore the potential application of a superimposed Hermite-Gaussian correlated Schell-model beams with off-axis multi-vortices in optical trapping, based on the generalized Collins formula, the focused beam intensity and radiation force on particles are derived in detail. Numerical results show that the gradient force and capture stability range increase with the increase of topological charge. By changing the vortex off-axis distance, the precise position control of the particles can be made. Adjusting the number of vortices can control the existence of vortex singularity on the side lobe of the beam, and generate or close the optical potential well or optical cage in real time. By selecting the appropriate beam order, two kinds of particles with different refractive indexes can be captured. The beams are expected to be applied to optical trapping of multiple particles at different positions. [ABSTRACT FROM AUTHOR]

Volcanic eruptions can release a large amount of volatiles, including sulfur dioxide and carbon dioxide, into the atmosphere and trigger regional and/or global perturbations of the climate and environment. However, the potential effect of the Linzizong volcanism, the most intense and widespread magmatism in southern Tibet, is not yet known. Here, the systematic results of fieldwork, spatial distribution analysis (area and volume), and zircon U Pb age dating of 54 samples are reported from the Linzizong volcanic rocks (Dianzhong, Nianbo and Pana Formations) in the Linzhou and Pangduo basins, southern Tibet. Our new zircon U Pb ages of 40 samples and compilations of previous data indicated that the Pana Formation erupted rapidly ca. 52–50 Ma, consistent with the coeval "flare-up" (∼51 Ma) of the Gangdese batholith. The average eruption fluxes of the lower (Dianzhong Formation), middle (Nianbo Formation), and upper (Pana Formation) parts of the Linzizong volcanic sequence are 11.8, 1.44, and 3994 km3/Ma, respectively. Evidence including the high average eruption flux (3994 km3/Ma), large magnitude (M = 8.80), and Volcanic Explosivity Index (VEI = 8) of the Pana Formation in the Linzhou and Pangduo basins suggests that this may represent a "supereruption" event in the Early Eocene. The rapid eruption of the Pana Formation was pervasive across the Tibetan Plateau and potentially extends to Sumatra, Southeast Asia, with consequences for the release of a large amount of CO 2 that could drive the Early Eocene Climatic Optimum (EECO). • Pana Formation in the Linzhou and Pangduo basins records a potential supereruption event (manitude value, M = 8.80). • Carbon flux of the Early Eocene rapid eruption of the Pana Formation was well constrained by two different methods. • Rapid eruption of the Pana Formation (∼ 52–50 Ma) in southern Tibet may be the dominant mechanism driving the EECO. [ABSTRACT FROM AUTHOR]

The Gangdese arc underwent the most intense magmatic flare-up of southern Tibet in the early Eocene (peaked at ∼50 Ma), generating widespread plutonic and volcanic rocks both along and across the arc. However, the dynamic mechanism for the magmatic flare-up is mysterious. This paper systematically analyzed the petrology, mineralogy, geochronology, and geochemistry of the early Eocene volcanic and intrusive rocks in the Pangduo basin in the eastern Gangdese arc. These rocks yielded identical zircon U Pb ages of ∼50 Ma and similar isotopic compositions. The low-silica (< 60 wt%) rocks, including basalt andesite and trachyandesite, result from low degree (2–3%) partial melting of garnet-bearing lithospheric mantle. Based on textural observations and geochemical studies, coupled with Rhyolite-MELTS modeling and zircon trace elements Rayleigh fractionation models, the following research results were obtained. The high-silica rhyolite, ignimbrite, and granite porphyry are the product of limited melt extraction, while the quartz monzonite belongs to the associated residual silicic cumulates. The quartz monzonitic porphyry and trachydacite show a widespread dissolution structure and high formation temperature of ∼850 °C. Whole-rock geochemical mixing model results indicate that they are generated by mixing products of mafic magma, high-silica melts, and remelting melts of quartz monzonite. The volcanic and intrusive rocks in the Pangduo basin are considered as a volcanic-plutonic complex, resulting from the synergistic effect of melt extraction and cognate magma mixing. Both the complex magmatic processes and the early Eocene magmatic flare-up are attributed to mafic magma injection. • The Pangduo volcanic-plutonic complex with various rock types is well exposed in the Pangduo basin, southern Tibet. • The rhyolitic ignimbrite and the quartz monzonite are extracted melts and corresponding residual cumulates, respectively. • Melt extraction and magma mixing via mafic magma injection promote the large-scale magma formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Mengku dacites, Lincang granites and diorites are spatially and temporally related. • The Triassic Mengku dacites is characterized by rejuvenation of the Lincang crystal mush. • The thermal input was supplied by mafic magma represented by the Lincang diorites. • Magmatic evolution was related to mantle upwelling in the post-collisional setting. The tectono-magmatic event of the Changning-Menglian Paleo-Tethys orogen is an important process for understanding the tectonic evolution of the SE Tibetan Plateau. This orogen is composed of Changning-Menglian suture, Lancang group, Lincang batholith, and Yunxian volcanics. The Lincang batholith and its volcanic counterparts are part of Triassic magmatism in this orogen. The botholith is composed of biotite monzogranite, granodiorite and diorite. The Middle to Late Triassic volcanics include Manghuai rhyolite, Xiaodingxi basalt and Mengku dacite. The Mengku dacite is volcanic dome in west of the batholith. Lincang biotite monzogranite and Mengku dacite have similar geochemistry and are characterized by negative ε Hf (t) values (–13.2 to –5.2) and ε Nd (t) values (–14.7 to –8.8), whereas diorite dikes within the Lincang batholith have slightly high ε Hf (t) values (–8.3 to –4.9) and ε Nd (t) values (–6.9 to –6.7). Manifestations of resorption textures in quartz and reverse compositional zoning in feldspars are recognized from Mengku dacite. We consider that Mengku dacites resemble the erupted Lincang biotite monzogranite as they occur in the same tectonic settings and have similar geochemical features and mineral assemblages dominated by plagioclase, alkali-feldspar, quartz, and biotite. The evolution of the Mengku dacite magma is characterized by the rejuvenation of crystal mush represented by the Lincang batholith. The required thermal input was supplied by mafic magma, represented by diorite dikes and enclaves within the Lincang batholith. The Middle to Late Triassic magmatic event in this orogen likely resulted from lithospheric delamination and upwelling of the asthenosphere in a post-collisional environment. [ABSTRACT FROM AUTHOR]

A dynamic model for a hydro-turbine governing system is established that accounts for the periodic excitation caused by the dynamic transfer coefficient. The dynamic analysis shows that the turbine regulation system produces bursting oscillatory behaviors when its transmission coefficient changes. The bursting oscillation behavior can adversely affect its stable operation. In response to this challenge, a prescribed performance sliding mode controller based on the time-varying tangent barrier Lyapunov function is proposed. Specifically, a time-varying constraint function of the exponential decay type is initially established. This function is then combined with the prescribed performance constraint function and the dynamic sliding surface to construct the time-varying tangent barrier Lyapunov function. In addition, to ensure that the system output exhibits a slight overshoot and fast-tracking speed at the initial time while satisfying the steady-state index, the relevant parameters of the time-varying constraint function are presented. Finally, the stability of the proposed controller is rigorously proven, verifying the effectiveness of the controller under five working conditions. The simulation results demonstrate that the prescribed performance sliding mode control based on the time-varying tangent barrier Lyapunov function can enable the hydro-turbine governing system to quickly break away from the bursting oscillation state. The proposed control strategy achieves faster convergence times for the rotor angle and generator speed (0.3 s) as well as the guide vane opening (0.3 s) than the ordinary sliding mode controller. The proposed strategy is also superior in controlling the steady-state error, which means that the proposed controller has a faster response speed, higher control accuracy, and optimized transient performance of the system than the traditional controller. • The hydro-turbine regulation system under periodic excitation exhibits bursting oscillations. • Prescribed performance control to handle state constraint problems. • Indirect constraints on the state are achieved by constraining the sliding surface. • The controller still has better performance when the parameters change. [ABSTRACT FROM AUTHOR]

The similarity criterion for high speed or high enthalpy rarefied reaction flows is the binary scaling law, one of which is the product of the incoming flow density and the characteristic scale of the test model in a rarefied wind tunnel should be equal to that under the flight condition. This is to ensure that the ratio between the characteristic distance of the relaxation process and the characteristic length of the body is equal. However, in a rarefied wind tunnel, it is difficult to directly measure the flow density below 10−5 kg/m3 using common methods due to the relatively high rarefied degree, an indirect density estimation method based on force analysis of a pendulum sphere was proposed in this study. The oscillation trajectory of the pendulum sphere under ultrahigh-speed rarefied flow conditions was recorded and the corresponding aerodynamic drag force acted on the sphere along the trajectory was analyzed, based on which the density distribution of the flow was then estimated combined with DSMC simulations. The obtained results show that in the present study, the flow is in under-expanded condition and the measured density sharply decreased from 10−6 kg/m3 to 10−7 kg/m3 at 140–170 mm from the nozzle outlet. • An indirect density measurement method for ultrahigh-speed rarefied flow filed was presented. • The aerodynamic forces acting on a small pendulum sphere in a rarefied flow can be obtained quite precisely and easily by analyzing its oscillation trajectory experimentally. • By comparing the obtained forces with those simulated by DSMC, the flow density as low as 10-6- 10-7 kg/m3 could be estimated which is usually hard to be measured using conventional method. [ABSTRACT FROM AUTHOR]

Abstract: Molecule-based electrorheological (ER) materials as a novel type of ER materials, dicarboxylic acid [H2(β-CD-A)] of β-cyclodextrin (β-CD) and the rare earth (RE) complexes [(β-CD-A)3(RE)2] (RE=Y, La, Gd) materials, were synthesized, the ER performance and dielectric property of the materials were studied. Our results show that these molecule-based ER materials exhibit clear ER effect. The ER performance of β-CD can be enhanced with the formation of H2(β-CD-A) and RE complexes. The ER activity of the yttrium complex is the highest among these RE complexes. The dielectric property plays an important role in influencing the ER property of these materials. [Copyright &y& Elsevier]

Abstract: Nano-sized TiO2 particle materials doped with Na2O or ZrO2 have been synthesized. Their composition (including the composition in the surface layer of particles), microstructure and dielectric property have been studied by XRD, BET, XPS, TEM and dielectric analysis. The electrorheological (ER) properties of the materials have shown that both Na-doping and Zr-doping can effectively enhance the ER performance of TiO2 materials with suitable degree of doping. Especially, the composition in the surface layer of particles plays a dominant role in influencing the ER performance of the particle materials. [Copyright &y& Elsevier]

Abstract: Chitosan nitrate (CTS-HNO3) as an electrorheological (ER) material was synthesized by a simple method. The nontoxic and facile chitosan (CTS) as a substrate of the materials, as well as nitric acid were chosen as starting materials. The ER properties of the suspensions of the CTS and CTS-HNO3 materials were researched. The CTS-HNO3 suspension has much better ER performance than the CTS suspension. The ER effect (relative shear stress, τ r = τ E/τ 0) of the CTS-HNO3 suspension (25wt%) in silicon oil under a dc electric field reached 94 at a shear rate of 14.5s−1, which is eight times higher than that of the CTS suspension, where τ E and τ 0 are the shear stresses at the electric field strengths of 4.2 and 0.0kV/mm, respectively. The formation of chitosan nitrate helped to decrease effectively the shear stress at zero electric field, and to enhance the ER effect of chitosan material markedly. The influence of the surface energy, conductivity, dielectric constant and dielectric loss tangent on the ER property of the particle materials was investigated, and the results indicate that surface energy played a predominant role. Moreover, the magnitude of the ER effect of the CTS-HNO3 suspension was closely related to the shear rate. In addition, the chitosan nitrate had better thermal stability. The properties of CTS-HNO3 are advantageous in its application as an ER material. [Copyright &y& Elsevier]

Abstract: A new class of electrorheological (ER) material using rare earth yttrium oxide as the substrate, K2O-doped Y2O3 materials, have been synthesized using K2CO3 and Y(NO3)3 as starting materials. Their ER performance, dielectric property and microstructure have been studied. The results show that the K2O doping can markedly enhance the ER activity of the Y2O3 material. A clear dependence of the ER effect on the degree of K2O doping has been observed. The shear stress of the suspension (25wt%) of a K2O–Y2O3 material (K/Y=0.4, molar ratio) in dimethyl silicone oil reaches 1.6kPa at electric field strength E =4.2kV/mm and shear stress rate γ =300s−1, and its relative shear stress τ r, which is defined as the ratio of shear stress at E =4.2kV/mm to zero-field shear stress (τ r = τ E/τ 0), reaches 6.6, which is six times higher than that of pure Y2O3. Investigations on relationships between ER effect and the microstructure and dielectric property of the materials indicate that the microstructure plays an important role, and dielectric property is a dominant factor in the modification of the ER effect of the particle materials. The results obtained in the research for these new ER materials is helpful for understanding further the mechanism of the ER effect and improving the ER material. [Copyright &y& Elsevier]

Abstract: A new class of doped electrorheological (ER) materials with rare earth (RE), TiO2 material doped with Er2O3 that belongs to the heavy rare earth oxide, was synthesized by the means of the hydrolysis and their compositions were determined by elemental analyses. The effects of the microstructure including the surface areas, pore volumes, pore size and crystal structure of the particles on the ER property of the materials were investigated by X-ray diffraction (XRD) analyses, BET surface area analyses, dielectric property and rheological measurement. The new results have shown that the microstructure, especially crystal lattice state plays an important role in influencing the dielectric property and ER property of the particle materials, which is propitious to further understanding the mechanism of ER effect and enhancing the ER activity of a material. [Copyright &y& Elsevier]

Abstract: Electrorheological (ER) materials of pure SiO2 and SiO2 doped with rare earths (RE=Ce,Gd,Y) (non-metallic glasses (silicates)) were prepared using Na2SiO3 and RECl3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance. [Copyright &y& Elsevier]