Study on synergistic system of energy-absorbing yielding anti-impact supporting structure and surrounding rock

Through the improvement of supporting structure and the utilization of the interaction between surrounding rock and supporting structure, the synergistic system of energy-absorbing yielding anti-impact supporting structure and surrounding rock is established. The process of energy absorption device, energy-absorbing yielding anti-impact supporting structure and synergistic system under impact is simulated to analyze the properties of them. The following conclusions could be drawn. The deformation and yielding process under compression of energy absorption device is divided into five stages. Compared with the traditional supporting structure, the energy-absorbing yielding anti-impact supporting structure has the reaction force with lower value and smaller fluctuation range before the deformation of the energy absorption device reaches the third ascending section. The synergy between surrounding rock and supporting structure plays an important role in roadway support. Compared with the supporting structure without surrounding rock, the reaction force of the supporting structure in the synergistic system is lower, and a stationary stage is added in the early stage of the reaction force curve.

Approximate Real-Time Force Spectroscopy Within Amplitude-Modulation Atomic Force Microscopy Topographical Imaging Using Few Harmonics and Fourier Methods

Quantitative measurement of the probe-sample interaction forces as a function of distance and time during imaging has been at the forefront of atomic force microscopy (AFM) research. This type of information is extremely valuable for understanding the material response to a variety of stimuli and interactions, such as mechanical deformations that vary in magnitude and rate of application, chemical interactions, or electromagnetic interactions. A variety of methods for performing such measurements simultaneously with topographical imaging is available, including methods based on Fourier analysis. Within these methods, reconstruction of the tip-sample force curve generally requires measurement of a large number of harmonics of the probe oscillation, which presents challenges such as the need for specialized hardware, low signal-to-noise ratio, and the need for extensive user expertise. In this paper, we present a simple method to perform a Gaussian-model-based fit of the tip-sample force curve across the surface, simultaneously with imaging, which requires measurement of only the first two or three harmonics for elastic materials. While such an approach only offers an approximate representation of the force curve, it can be highly accurate and fast, and has low instrumentation requirements, such that it can be relatively simple to implement on most commercial AFM setups.

Fitting of Atomic Force Microscopy Force Curves with a Sparse Representation Model

Atomic force microscopy (AFM) is a high-resolution scanning technology, and the measured data are a set of force curves, which can be fitted with a piecewise curve model and be analyzed further. Most methods usually follow a two-step strategy: first, the discontinuities (or breakpoints) are detected as the boundaries of two consecutive pieces; second, each piece separated by the discontinuities is fitted with a parametric model, such as the well-known worm-like chain (WLC) model. The disadvantage of this method is that the fitting (the second step) accuracy depends largely on the discontinuity detection (the first step) accuracy. In this study, a sparse representation model is proposed to jointly detect discontinuities and fit curves. The proposed model fits the curve with a linear combination of parametric functions, and the estimation of the parameters in the model can be formulated as an optimization problem with ℓ 0 -norm constraint. The performance of the proposed model is demonstrated by the fitting of AFM retraction force curves with the WLC model. Results shows that the proposed method can segment the force curve and estimate the parameter jointly with better accuracy, and hence, it is promising for automatic AFM force curve processing.

Simulation of metal microcomponents picking up by electrochemical based on ABAQUS

The development of micromanipulation technology has an important impact on the research in the microfield, which mainly focuses on the preparation and assembly of microcomponents, in which the microcomponent picking technology is used. The existing picking methods mainly use manipulation tools to clamp or adsorb components, which may destroy or fail to pick objects in the process of manipulation, and the efficiency is relatively low. In order to solve the problems in the existing manipulation methods, a new metal microcomponent picking method based on electrochemistry is proposed, which mainly uses the electrochemical principle to produce metal deposition, connect the manipulation tool and the object, and indirectly control the object by moving the manipulation tool. In this paper, the simulation software ABAQUS is used to pick up the microcopper wires with the length of 100, 200 and 300 [Formula: see text]m by using a pipette with a nozzle diameter of 15 [Formula: see text]m. The force curve between the tool and the object during the manipulation process is obtained. The feasibility of the method is verified by theoretical analysis and simulation experiments.

Dynamic analysis of semi-active MR suspension system considering response time and damping force curve

To obtain a good ride quality and smooth car body motion, many studies have focused on the damper. Passive dampers are unable to respond actively to changes in the environment; hence many studies are being conducted on semi-active dampers that use magnetorheological (MR) fluids. As the damping characteristics of the MR damper, such as the response time, control gain, and gradient of the damping force curve, can significantly affect the control performance of the vehicle, the damping characteristics of the MR damper should be carefully considered. Accordingly, in this study, we developed a method for selecting the damping characteristics of an MR damper for specific vehicle types and analyze the relation between the dynamic characteristics of MR damper and driving performances. To achieve this objective, we demonstrated that the damping characteristics can be tuned according to the additional flow path, groove, and core material. To confirm the enhancement of the ride quality, vibration control performance, and steering stability, the skyhook controller was considered. Since we obtained the suitable damping characteristics that met the requirements under random road profiles and bumpy roads, the realization of these characteristics will enable us to satisfy the driving requirements.

Research on erosion characteristics of a novel cavitation nozzle under nonsubmerged condition

When a cavitating jet enters the atmosphere directly, its cavitating effect weakens rapidly, and the erosion energy it produces cannot be fully utilized. Regarding the problem that existing cavitation nozzles are only used in submerged condition, methods to improve the erosion ability of cavitation jets under nonsubmerged condition are studied. The nozzle is visually simulated using Fluent software, and the results show that the dynamic submerged environment at the outlet effectively expands the nearby low-pressure cavitation area. The enhancement effect of the annular cavitation nozzle on the jet cavitation effect in the atmosphere domain is verified by measuring the impact force curve of the jet and through erosion tests on brass surface. Cleaning and derusting tests show that the annular cavitation nozzle has stronger derusting ability than the high-pressure nozzle under nonsubmerged condition and under the same pressure, demonstrating that the cleaning and derusting effect mainly comes from the collapse of cavitation bubbles.

Experimental and Modeling Analysis of the Cell-Wall Fracture of Nannochloropsis Oculata

ABSTRACTIn this study, a spherical indenter mounted on an atomic force microscope (AFM) was used to compress a Nannochloropsis oculata (N. oculata) cell on a poly-l-lysine coated slide. A mathematical model of the cell, which was derived by considering a fluid-filled spherical shell with axisymmetric compression between a sphere and an infinite flat plate, is proposed. In the construction of this mathematical model, the spherical shell was assumed to be a homogenous, isotropic, and elastic material. Thin-film theory was applicable to the spherical shell because the thickness of the shell was nearly negligible compared with its diameter. The governing equations of the contact and noncontact regions were converted from a boundary condition problem to an initial value problem. Then, the fourth-order Runge–Kutta method was applied to solve the transformed governing equations. The force curve obtained from the compression experiment was compared with the theoretical results derived from the proposed model. Furthermore, the numerical solution of the proposed model was verified to be consistent with the experimental data. The mechanical properties of cell walls were confirmed by applying the least square error method. Subsequently, the contact radius, inner pressure and tension distribution of the cell wall could be determined using the proposed model. The models proposed in other studies are suitable for analyzing the compression characteristics of cells whose size is of the order of tens of micrometers and millimeters. By contrast, the model proposed in this study can analyze the compression characteristics of N. oculata, which is only a few micrometers in diameter. Furthermore, a force curve that accurately describes the deformation behavior of N. oculata under strain levels of 25% was established.