Vol. 4, No. 3 (2020): Regular Issue

The spring-pendulum system has been of greet interest for a long time, and one tried to use the perturbation analysis to understand such a system. Until now, one cannot provide a satisfied result to explain the dynamics of the spring-pendulum system. In this paper, bifurcation trees of period-1 to period-2 motions in a periodically forced, nonlinear spring pendulum system are obtained through the discrete mapping method. The corresponding harmonic frequency-amplitude characteristics of period-1 to period-2 motions are presented, and the stability and bifurcations of period-1 to period-2 motions on the bifurcation trees are presented as well. From the analytical prediction, numerical illustrations of period-1 and period-2 motions are completed for comparison of numerical and analytical solutions. The results presented in this paper are totally different from the traditional perturbation analysis.

A subgrid stabilized method based on two local Gauss integrations is presented to the numerical simulation of 2-D steady incompressible lid-driven cavity flow at higher Reynolds numbers. The main idea of this method is to use the subgrid model based on two local Gauss integrations as a stabilized term on the finite element discretization. In this method, the discretization equation is solved by Oseen iterative scheme. It is shown that steady flow simulations of the lid-driven cavity problem are computable up to Re = 45000. This maximum Reynolds number has not been reached by other stabilized finite element methods reported. Moreover, the computed vorticity values at the center of the primary vortex agree well with previous analytical solutions in the limit of infinite Reynolds number, and the numerical results for the properties of the primary vortex and the velocity components are also in agreement with the benchmark data in earlier studies.

In the environment of severe nuclear radiation, remote operation often uses a camera to transmit pictures to the control room. Because the noise generated by the current electronic equipment under the interference of nuclear radiation is random and irregular, the traditional denoising methods cannot meet the requirement of denoising noisy image effectively. Aiming at this problem, a denoising method based on image restoration technology is proposed. Firstly, some representative images are intercepted from the video of actual nuclear radiation field as experimental objects. Then these images are smoothed to get the region A where the pixel difference between the noisy mage and the smoothed image is larger than the threshold and the region B where the pixel difference between the smoothed image and the clean image is greater than the threshold to form two regions to be restored. Finally, the process of image restoring is performed on the two regions respectively. The two images after restoration are fused to obtain the final image. The experiment shows that our method has good performance in protecting the details of the image while removing the nuclear radiation noise. Compared with other methods, our method can obtain a more clear image.

Rotating equipment like pump, blower, fan etc. are widely used in industries, where high vibration levels are observed specifically caused due to unbalance in rotating parts. A survey of literature has shown that, in spite of growing concerns about the effect of vibration levels on the power consumption, little research has been done to correlate the vibration level with power loss due to vibration. In a large refinery, with hundreds of pumps and motors, the wasted power cost, due to vibrations alone may run into thousands of dollars. The objective of this work is to propose a systematic mathematical analysis to predict the effect of unbalance on the power loss in a rotor-shaft system and validate with experiments performed on a laboratory setup at different speeds. It is observed that as rotational speed and degree of unbalance is increased, power consumption also increases. Power loss due to different degree of unbalance viz 60 gm.cm, 120 gm.cm and 180 gm.cm was measured experimentally on a test setup comprising of rotor-shaft system and mathematical validation is presented for the same. Power loss mainly takes place due to friction in bearings, which is attributed to centrifugal force produced by unbalance and displacement of rotor-shaft system. Calculated power loss is in close range of power loss determined experimentally.

Intracytoplasmic sperm injection (ICSI), microinjection of a single spermatozoon into an oocyte, is a routine procedure in assisted reproduction programs. This procedure uses fine control of small bore microinjection needles and precise volume control via hydraulic syringe pumps. In many early experiments mercury is placed within the injection system because its high surface tension in the system facilitates the injection procedure. However, mercury is cytotoxic and therefore alternative fluids or approaches are needed. Here we examine the main properties of mercury and their impact on the various aspects of ICSI. We conclude that the small momentum diffusivity of mercury is the most important contributing factor that facilitates the ICSI procedures.

Theoretical formulation, Navier’s solutions of rectangular plates based on a new higher order shear deformation model are presented for the static and dynamic analysis of functionally graded plates (FGPs). This theory enforces traction free boundary conditions at plate surfaces. Shear correction factors are not required because a correct representation of transverse shearing strain is given. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Numerical illustrations concern flexural behavior of FG plates with Metal–Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fraction profiles, aspect ratios and length to thickness ratios. Results are verified with available results in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static and dynamic behavior of functionally graded plates. This paper presents a theoretical investigation in free vibration of simply supported FG beam. Young’s modulus of beam varies in the thickness direction according to power law. Governing equations were found by applying Hamilton’s principle. Navier type solution method was used to obtain frequencies. Different higher order shear deformation theories and classical beam theories were used in the analysis. A free vibration frequency is given for different material properties.