Effect of Tuned Spring on Vibration Control Performance of Modified Liquid Column Ball Damper

This paper reports the theoretical findings of the new modified type of tuned liquid column ball damper (TLCBD), called a tuned liquid column ball spring damper (TLCBSD). In this new modified form, the ball inside the horizontal section of the damper is attached to the spring. Furthermore, two types of this modified version are proposed, known as a tuned liquid column ball spring sliding damper (TLCBSSD) and a tuned liquid column ball spring rolling damper (TLCBSRD). In the former, the rotational motion of the ball attached to the spring is restricted, whereas in the latter, the ball attached to the spring can translate as well as rotate. Mathematical models and optimum design parameters are formulated for both types. The performance of these new modified damper versions is assessed numerically and subjected to harmonic, seismic, and impulse loadings. The results show that the performance of the newly proposed dampers is relatively better than traditional TLCBDs in harmonic and seismic excitations. The peak response reduction soon after the impact load becomes zero is comparatively better in TLCBSDs over TLCBDs. Overall, the newly proposed passive vibration control devices performed excellently in structure response reduction over TLCBDs.

Sensitivity of the Spool Rate on the Dynamic Response of the System

In rotodynamic systems, the rotor is spooled up from zero speed to its operating speed during the engine start. One of the considerations in design of rotating systems is the placement of rotor critical speed. It is vital to ensure that the rotor critical speeds are not close to the engine operating speed. However, it is not always possible to isolate all the frequencies above the operating speed. So, during the engine start to full speed, rotor system does travel through the mode. Therefore, to avoid a large system response, the rotor is spooled up quickly through the critical speed. In addition to the rotor critical speeds, the natural frequencies of the static structures may also get excited during the rotor spool up and spool down. The static structure response is one of the important considerations in designing a system for dynamic loading condition. It has been observed that the rotor spool rate affects the static structure response. This paper focuses on effect on system’s response under various spool rate. It has also been shown that the natural frequency of the system and damping in the system are two of the major factors towards sensitivity of system response with spool rate. Additionally, it has been observed that the presence of non-linearities shifts the peak response away from the natural frequency depending on the spool rate and spool direction.

Negative series resistance and photo-response properties of Au/PPY-MWCNTs composite /TiO2/Al2O3/n-Si/Al photodiode

The paper addresses a novel approach concerning the appearance of negative series resistance (Rs) at high frequencies for both temperatures and voltages. Most of the previous studies have focused on the relationship between voltage and current (I - V) to determine the value of Rs using several methods. By measuring capacitance and conductance as a function of voltage, we were able to develop a systematic analysis of series resistance. At high frequencies of 2×107, 107 Hz, Rs has negative values however, at frequency 106Hz it takes both positive and negative values, whilst from (105 - 10) Hz it has positive values. Here in this article, we synthesized Au/PPY-MWCNTs/TiO2/Al2O3/n-Si/Al structure which can be used in a variety of applications such as supercapacitors, and diodes. We investigated the electrical properties such as ideality factor (n), barrier height (фb), series resistance using several approaches such as conventional, Chueng, and Nord methods. The structure has shown rectification with a good response to daylight illumination. The structure response to daylight illumination indicates that photodiodes have the potential to be used as solar detectors.