Modeling and Parameter Sensitivity Analysis of Valve-Controlled Helical Hydraulic Rotary Actuator System

As a type of hydraulic rotary actuator, a helical hydraulic rotary actuator exhibits a large angle, high torque, and compact structure; hence, it has been widely used in various fields. However, its core technology is proprietary to several companies and thus has not been disclosed. Furthermore, the relevant reports are primarily limited to the component level. The dynamic characteristics of the output when a helical rotary actuator is applied to a closed-loop system are investigated from the pe...     

Nanoparticles of polystyrene latexes by semicontinuous microemulsion polymerization using mixed surfactants

Nanosized polystyrene (PS) latexes stabilized by the mixture of cationic/cationic, anionic/anionic, or anionic/cationic surfactants of various types with high weight ratios of PS to surfactant (ca. 10:1) have been successfully synthesized by a semicontinuous microemulsion polymerization process. For cationic or anionic systems, spherical latex particles with a weight-averaged diameter (Dw) ranging from about 22 to 53 nm were nearly linearly dependent on the weight ratio of the mixed surfactants with similar charges. Their particle size distributions were rather uniform (Dw/Dn < 1.20). For a system with oppositely charged surfactants at nonequimolar ratios, it could produce stable PS particles up to 94 nm in diameter. High molar masses (Mw) of PS ranging from 1.1 to 1.9 x 10(6) g/mol could easily be obtained for all three systems investigated. For both cationic/cationic and anionic/anionic surfactant systems, the number of PS particles per milliliter of latex (Np) generated in the very early stage of O/W' microemulsion remained rather constant throughout the polymerization. This was controlled by using only 1 wt% of mixed surfactants and the continuous addition of a small amount of styrene. The present polymerization method allows one to synthesize nanoparticles of PS or other polymers of high polymer/surfactant weight ratios at some particle sizes that are unable to achieve them with a single type of surfactant.     

Tunable three-dimensional intensity distribution by a pure phase-shifting apodizer

The three-dimensional distribution of light intensity that is modulated by a pure phase-shifting apodizer is studied. Results show that the Strehl ratio can be altered by the proposed apodizer and by the waist width of incident Gaussian beams. By changing geometrical parameters of the proposed apodizer, we can increase the focal depth to several times that of the original system. The proposed apodizer can also be used to realize focal splitting and local minimum of intensity, which may be advantageous for constructing an optical trap. Furthermore, the local minimum of intensity number is tunable by changing the parameters of the apodizer.     

Fast algorithm for chirp transforms with zooming-in ability and its applications

A general fast numerical algorithm for chirp transforms is developed by using two fast Fourier transforms and employing an analytical kernel. This new algorithm unifies the calculations of arbitrary real-order fractional Fourier transforms and Fresnel diffraction. Its computational complexity is better than a fast convolution method using Fourier transforms. Furthermore, one can freely choose the sampling resolutions in both x and u space and zoom in on any portion of the data of interest. Computational results are compared with analytical ones. The errors are essentially limited by the accuracy of the fast Fourier transforms and are higher than the order 10(-12) for most cases. As an example of its application to scalar diffraction, this algorithm can be used to calculate near-field patterns directly behind the aperture, 0 < or = z < d2/lambda. It compensates another algorithm for Fresnel diffraction that is limited to z > d2/lambdaN [J. Opt. Soc. Am. A 15, 2111 (1998)]. Experimental results from waveguide-output microcoupler diffraction are in good agreement with the calculations.     

First-principles study of heat transport properties of graphene nanoribbons

We use density-functional theory and the nonequilibrium Green's function method as well as phonon dispersion calculations to study the thermal conductance of graphene nanoribbons with armchair and zigzag edges, with and without hydrogen passivation. We find that low-frequency phonon bands of the zigzag ribbons are more dispersive than those of the armchair ribbons and that this difference accounts for the anisotropy in the thermal conductance of graphene nanoribbons. Comparing our results with data on large-area graphene, edge effects are shown to contribute to thermal conductance, enhance the anisotropy in thermal conductance of graphene nanoribbons, and increase thermal conductance per unit width. The edges with and without hydrogen passivation modify the atomic structure and ultimately influence the phonon thermal transport differently for the two ribbon types.     

Mn²+-bonded reduced graphene oxide with strong radiative recombination in broad visible range caused by resonant energy transfer

The photoluminescence (PL) characteristics of Mn(2+)-bonded reduced graphene oxide (rGO) are studied in details. The Mn(2+)-bonded rGO is synthesized using MnO(2)-decorated GO as the intermediate products and ideal tunable PL is obtained by enhancing the long-wavelength (450-550 nm) emission. The PL spectra excited by different wavelengths are analyzed to elucidate the mechanism, and the resonant energy transfer between Mn(2+) and sp(2) clusters of the rGO appears to be responsible for the enhanced long-wavelength emission. To examine the effect of Mn(2+) on the long-wavelength emission from the Mn(2+)-bonded rGO, the PL characteristics of Mn(2+)-bonded rGO with smaller Mn concentrations are studied and weaker emission is observed. Our theoretical calculation corroborates the experimental results.     

Variable projection algorithms with sparse constraint for separable nonlinear models

Separable nonlinear models are widely used in various fields such as time series analysis, system modeling, and machine learning, due to their flexible structures and ability to capture nonlinear behavior of data. However, identifying the parameters of these models is challenging, especially when sparse models with better interpretability are desired by practitioners. Previous theoretical and practical studies have shown that variable projection (VP) is an efficient method for identifying separable nonlinear models, but these are based on L2 penalty of model parameters, which cannot be directly extended to deal with sparse constraint. Based on the exploration of the structural characteristics of separable models, this paper proposes gradient-based and trust-region-based variable projection algorithms, which mainly solve two key problems: how to eliminate linear parameters under sparse constraint; and how to deal with the coupling relationship between linear and nonlinear parameters in the model. Finally, numerical experiments on synthetic data and real time series data are conducted to verify the effectiveness of the proposed algorithms.     

我国透辉石和透闪石的开发利用

透辉石和透闪石都是含钙镁链状结构硅酸盐,典型的变质岩,重要的节能非金属工业矿物。 透辉石的化学式为CaMg(Si_2O_6),其理论化学成分为:CaO 25.9％,MgO 18.5％,SiO_255.6％。 透闪石的化学式为Ca_2Mg_6(Si_4O_11)_2(OH)_2,其理论化学成分为;CaO 13.8％,MgO24.6％,SiO_2 58.8％。     

GreaterChinaCRM—— 阻碍CRM的两大综合病症

现在有大量言过其实的报道声称CRM已经死亡，然而笔者认为其实CRM并没有走到尽头。但是，由于以下两大顽症的阻碍，CRM确实已进入了膏肓状态，大家必须对此加以认识并避免其死亡的发生。