1,340 research outputs found
Analytical and Reliability Study of the Tunnel with Rockbolts in Rock Masses
Rockbolts are a critical reinforcement ways which widely used in tunnel engineering. In this paper, an analytical solution of circular tunnel with rockbolts was proposed based on homogenization method, and then the stability of a circular tunnel was investigated by considering the uncertainty based on the proposed analytical solution. Elastoplastic analytical solution for unsupported circular tunnel was presented briefly in hydrostatic stress field with a linear Mohr-Coulomb yield criterion and a non-associated flow rule. An analytical solution of circular tunnel with rockbolts was proposed through considering rock mass and rockbolts as a new homogeneous, isotropic, parameters strengthened equivalent composite material. A numerical example is used to verify the proposed analytical solution. The results show that the proposed solution can effectively characterize the mechanical behavior of rock mass and rockbolts in tunnel. Then, the proposed solution is adopted to calculate reliability index and failure probability of tunnel. The results show that the proposed method can also be effectively used to perform the stability and reliability analysis of tunnel and rockbolts have an important effect on plastic zone size and displacement of tunnel
A novel chaotic time series prediction method and its application to carrier vibration interference attitude prediction of stabilized platform
Aiming at the problems existing in previous chaos time series prediction methods, a novel chaos times series prediction method, which applies modified GM(1, 1) model with optimizing parameters to study evolution laws of phase point L1 norm in reconstructed phase space, is proposed in this paper. Phase space reconstruction theory is used to reconstruct the unobserved phase space for chaotic time series by C-C method, and L1 norm series of phase points can be obtained in the reconstructed phase space. The modified GM(1, 1) model, which is improved by optimizing background value and optimizing original condition, is used to study the change law of phase point L1 norm for forecasting. The measured data from stabilized platform experiment and three traditional chaos time series are applied to evaluate the performance of the proposed model. To test the prediction method, three accuracy evaluation standards are employed here. The empirical results of stabilized platform are encouraging and indicate that the newly proposed method is excellent in prediction of chaos time series of chaos systems
Chemical Synthesis and Applications of Colloidal Metal Phosphide Nanocrystals
Colloidal nanocrystals (NCs) have emerged as promising materials in optoelectronic devices and biological imaging application due to their tailorable properties through size, shape, and composition. Among these NCs, metal phosphide is an important class, in parallel with metal chalcogenide. In this review, we summarize the recent progress regarding the chemical synthesis and applications of colloidal metal phosphide NCs. As the most important metal phosphide NCs, indium phosphide (InP) NCs have been intensively investigated because of their low toxicity, wide and tunable emission range from visible to the near-infrared region. Firstly, we give a brief overview of synthetic strategies to InP NCs, highlighting the benefit of employing zinc precursors as reaction additive and the importance of different phosphorus precursors to improve the quality of the InP NCs, in terms of size distribution, quantum yield, colloidal stability, and non-blinking behavior. Next, we discuss additional synthetic techniques to overcome the issues of lattice mismatch in the synthesis of core/shell metal phosphide NCs, by constructing an intermediate layer between core/shell or designing a shell with gradient composition in a radial direction. We also envision future research directions of InP NCs. The chemical synthesis of other metal phosphide NCs, such as II–V metal phosphide NCs (Cd3P2, Zn3P2) and transition metal phosphides NCs (Cu3P, FeP) is subsequently introduced. We finally discuss the potential applications of colloidal metal phosphide NCs in photovoltaics, light-emitting diodes, and lithium ion battery. An overview of several key applications based on colloidal metal phosphide NCs is provided at the end
Development of a Vacuum Ultra-Violet Laser-Based Angle-Resolved Photoemission System with a Super-High Energy Resolution Better Than 1 meV
The design and performance of the first vacuum ultra-violet (VUV) laser-based
angle-resolved photoemission (ARPES) system are described. The VUV laser with a
photon energy of 6.994 eV and bandwidth of 0.26 meV is achieved from the second
harmonic generation using a novel non-linear optical crystal KBe2BO3F2 (KBBF).
The new VUV laser-based ARPES system exhibits superior performance, including
super-high energy resolution better than 1 meV, high momentum resolution,
super-high photon flux and much enhanced bulk sensitivity, which are
demonstrated from measurements on a typical Bi2Sr2CaCu2O8 high temperature
superconductor. Issues and further development related to the VUV laser-based
photoemission technique are discussed.Comment: 29 pages, 10 figures, submitted to Review of Scientific Instrument
Reversible shear thickening at low shear rates of electrorheological fluids under electric fields
Shear thickening is a phenomenon of significant viscosity increase of
colloidal suspensions. While electrorheological (ER) fluids can be turned into
a solid-like material by applying an electric field, their shear strength is
widely represented by the attractive electrostatic interaction between ER
particles. By shearing ER fluids between two concentric cylinders, we show a
reversible shear thickening of ER fluids above a low critical shear rate (<1
s-1) and a high critical electric field strength (>100 V/mm), which could be
characterized by a modified Mason number. Shear thickening and electrostatic
particle interaction-induced inter-particle friction forces is considered to be
the real origin of the high shear strength of ER fluids, while the applied
electric field controls the extent of shear thickening. The electric
field-controlled reversible shear thickening has implications for
high-performance ER/magnetorheological (MR) fluid design, clutch fluids with
high friction forces triggered by applying local electric field, other
field-responsive materials and intelligent systems.Comment: 29pages, 9 figure
Optimizing method of mechanism angle of upper limb rehabilitation robot at glenohumeral joint
At present, there are seventy million stroke patients in China and annual death toll of stroke is 1 million 650 thousand people. The survivors about 75% become disabled persons and lose the ability to move. To address this issue, a kind of rehabilitation exoskeleton robot called YANARM is proposed which for training of shoulder complex. This paper, a kind of method for optimizing the angle parameters of series dynamic axes under given workspace conditions is presented. The forward and inverse kinematics solutions of glenohumeral mechanism are solved based on the exponential product formula (POE) and the Paden-Kahan sub-problem. The range of joint rotation angle can be inversely solved according to the end of the arm position at the borderline of the workspace. A curve between the angle and the CP which equal mean variance of joint rotation range plus sum of all joint rotation ranges is solved. The mechanism angle of glenohumeral joint is optimized by this method
Development of a small-diameter and high-resolution industrial endoscopy with CMOS image sensor
In the industrial field, an endoscope is typically employed for the observation and inspection of internal defect and corrosion of an engine and chemical plant. Current industrial optical endoscopes normally use CMOS sensor which offers best performance as an image pickup device. Here we report experimental demonstration of an industrial endoscope modality consisting of a 5 mm diameter rigid tube and 1280 × 960 pixels CMOS camera, which enables accurate diagnosis of small-scale industrial components with hollow shape. As a proof of concept, we successfully perform arc-surface imaging at a resolution of 57 lp/mm and ± 30^o field of view. Finally, potentially applying the wavefront coding method to extend the depth of field of endoscopic system is comprehensively discussed
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