Papers by Keyword: Stability Analysis

Abstract: Flow instability is a major challenge experienced in medical, engineering and industrial settings globally. For instance, flow instability linked with irregular cardiac output of the heart leads to organ malfunctioning in the medical field, it also encourages mechanical vibrations in the case of fluctuating flow rate, and several other applications. In this study, linear stability analysis is conducted to monitor the behavior of a small disturbance that is imposed on hydromagnetic Casson fluid that flows steadily through a saturated porous medium. A new variant of the Orr-Sommerfield equation is obtained and solved numerically by using spectral point collocation weighted residual approach with eigenfunction expansion of the Chebyshev polynomial as the admissible trial function. Based on the QZ algorithm, numerical results are obtained for wave and Reynold’s numbers, wave velocity as functions of Magnetic field intensity and porosity shape parameters. Results are validated against previously released data. The biophysics of the heart, particularly in cardiac rhythm analysis, as well as several other medicinal and technical applications, is among the areas where the current work has applicability.

Abstract: SRAM (Static Random Access Memory) is an essential component of memory devices such as laptops, phones, etc., which act as a semiconductor memory. The “Carbon Nanotube Field Effect Transistor (CNTFET)” is silicon associated high-stability, low-power device with excellent performance. CNTFET has been verified to be very advantageous for Very large-scale integration circuit designs in the nanoscale range because of its remarkable properties of metal oxide semiconductor field effect transistor (MOSFET). The material was brought to light because of its genuinely incredible electrochemical performance. Carbon nanotubes have unique properties such as high charge carrier mobility, high voltage, small footprint, exceptionally short and high control over pulse duration, and large current densities. In traditional MOSFET, bulk silicon is used, which has high leakage current and high field-effect; thus, CNTFET has been used as an alternative in recent years. When compared to the 10T CNTFET SRAM Bit cell is designed using HSPICE Tool in 22nm technology. Long-term stability and significant process variable changes are significant challenges with nanoscale SRAM cells.

Abstract: There is no clear calculation method for rocky slope stability analysis, and there are some differences between survey and design and construction site. Taking a bridge platform slope in Taihang Mountain, Hebei Province as an example, a geological model combined with Hoek-Brown strength quasi-side is used for stability analysis and calculation to improve the accuracy of engineering rock mechanics calculation.

Abstract: Aiming at the thermocapillary convection stability of sapphire crystal grown by liquid-encapsulated Czochralski method, by non-linear numerical simulation, obtained the flow function and temperature distribution of R-Z cross section, as well as the velocity and temperature distribution at liquid-liquid interface and monitoring point of B₂O₃/sapphire melt in annular two liquid system, covered with solid upper wall and in microgravity. By means of linear stability analysis, obtained the neutral stability curve and critical stability parameters of the system, and revealed the temperature fluctuation of the liquid-liquid interface. The calculated results of B₂O₃/sapphire melt were compared with 5cSt silicone oil/HT-70. The results show that under the same geometrical conditions, the flow of B₂O₃/sapphire melt system is more unstable than 5cSt silicone oil/HT-70, there are two unstable flow patterns, radial three-dimensional steady flow cell and hydrothermal waves near the hot wall. The larger the ratio of Pr number of upper and lower fluid layers is, the better the effect of restraining the flow of lower fluid layers is.

Abstract: The buried pipelines or vessels and other similar structures made of homogeneous or advanced composite materials are commonly used in civil engineering and biotechnology. The radial stability problem of these structures was widely studied using the cylindrical shell model over the past years. In this paper, the linear stability of cylindrical shells resting on Winkler elastic foundation under uniformly distributed external pressure was analyzed with semi-analytical quadrature element method (QEM). As for the longitudinal direction, the radial deflection of shell was approximated by the quadrature element formulation. While the analytic trigonometric function was adopted for description of radial deflection in circumferential direction. The Numerical results of critical buckling load were compared with the semi-analytical FEM. It is found that the semi-analytical QEM possesses higher computational efficiency and applicability than semi-analytical FEM. Then, the effects of the shell length, radius, and thickness on the critical buckling pressures are systematically investigated through the parametric studies.

Abstract: The stress and strain of surrounding rock and the development of plastic zone in the process of excavation of large underground cavern group have been the main concern of the design unit. The numerical simulation software is used to analyze the stability of caverns of an underground pumping station. The stress and displacement of the surrounding rock and the development of the plastic zone in the process of excavation are analyzed in detail. The results show that the tensile stress is easily generated in the side wall, and the maximum value can reach 4 M Pa. Correspondingly, the maximum displacement of the side wall part can reach 4 cm. The plastic zone is mainly concentrated in the surrounding rock near the side wall, the thickness can reach about 9 m. In general, the excavation of underground caverns is basically stable.

Abstract: In this paper the problem of guiding a parabolic trough solar concentrator through a system based on a water displacement mechanism is addressed. The actuator mechanism consists of a set of four on/off electrovalves in ”H-bridge” configuration, a small water pump, a sun sensor and two containers half-filled with water, installed on the side ends of the concentrator. To guide and balance the concentrator, a sliding mode controller (SMC) to enable / disable the opening and closing of the valves that control the direction and flow of water between the two containers is proposed. The validity of the implementation of the proposed law of control applied to the actuator mechanism is verified with stability analysis and simulation results.

Abstract: With the slope unstable rock masses of a stope in Longsi mine, Jiaozuo City, China as the target, we computed and analyzed the stability of unstable rock masses using a limit equilibrium method (LEM) and a discrete element strength reduction method (SRM). Results show that the unstable rock masses are currently stable. Under the external actions of natural weathering, rainfall and earthquake, unstable rock mass 1 was manifested as a shear slip failure mode, and its stability was controlled jointly by bedding-plane and posterior-margin steep inclined joints. In comparison, unstable rock mass 2 was manifested as a tensile-crack toppling failure mode, and its stability was controlled by the perforation of posterior-margin joints. From the results of the 2 methods we find the safety factor determined from SRM is larger, but not significantly, than that from LEM, and SRM can simulate the progressive failure process of unstable rock masses. SRM also provides information about forces and deformation (e.g. stress-strain, and displacement) and more efficiently visualizes the parts at the slope that are susceptible to instability, suggesting SRM can be used as a supplementation of LEM.

Abstract: The numerical analysis of a single-layer latticed dome has been carried out by using ANSYS, in order to evaluate the effect of influencing factors, like semi-rigidity of joint, buckling in compressed bars, load distribution and initial imperfections, which can produce important reductions of the load bearing capacity of these kind of structures. As a case study, the use of Temcor joint has been investigated. The characterization of the Temcor joint behavior to be introduced in the global model of the dome has been done by a FE model implemented on ABAQUS. The effects of the analyzed factors on the load-carrying capacity of the dome have been identified and useful suggestions for the design of this type of structures have been given.

Abstract: The stability of slope in open-pit affects the economic benefits and safety production of mining enterprises. From the two aspects of internal factors and external factors, this paper analyses the factors affecting the slope stability of open-pit, discusses the basic theory of slope stability analysis, and puts forward the criterion of slope stability based on the safety coefficient. The limit equilibrium method is chosen to analyze the stability of the high and steep slope of open-pit in this paper, and the SLIDE software is used for numerical simulation according to the actual slope model of certain open-pit. The simulation results show that the slope safety coefficient of the instance is 1.01, which is unstable slope. When the number of the slope blocks is more than 40, the safety coefficient tend to be stable. Blasting vibration has a great influence on slope stability. The results of slope stability analysis provide a scientific guidance for the prevention and control of the slope instability.