Abstract: The objective of this research is to develop a general technique so that one may predict the dynamic behaviour of a three-dimensional scale crane model subjected to time-dependent moving point forces by means of conventional finite element computer packages. To this end, the whole scale crane model is divided into two parts: the stationary framework and the moving substructure. In such a case, the dynamic responses of a scale crane model can be predicted from the forced vibration responses of the stationary framework due to actions of the four time-dependent moving point forces induced by the moving substructure. Since the magnitudes and positions of the moving point forces are dependent on the relative positions between the trolley, moving substructure and the stationary framework, it can be found from the numerical results that the time histories for the moving speeds of the moving substructure and the trolley are the key factors affecting the dynamic responses of the scale crane model.
Abstract: This research paper portrays a comparative analysis of
thermomechanical behaviour of Shielded Metal Arc Welding
(SMAW) and Gas Tungsten Arc Welding (GTAW) of low carbon
steel of AISI 1020 grade butt joints. The thermal history has been
obtained by experimental work. We have focused on temperature
dependent cooling rate as depicted by Adam’s two-dimensional
model. The effect of moving point heat source of SMAW and GTAW
on mechanical properties has been judged by optical and scanning
electron micrographs of different regions in weld joints. The
microhardness study has been carried to visualize the joint strength
due to formation of different phases.
Abstract: In this research article a comprehensive investigation
has been carried out to determine the effect of thermal cycle on
temperature dependent process parameters developed during gas
tungsten arc (GTA) welding of high carbon (AISI 1090) steel butt
joints. An experiment based thermal analysis has been performed to
obtain the thermal history. We have focused on different
thermophysical properties such as thermal conductivity, heat transfer
coefficient and cooling rate. Angular torch model has been utilized to
find out the surface heat flux and its variation along the fusion zone as
well as along the longitudinal direction from fusion boundary. After
welding and formation of weld pool, heat transfer coefficient varies
rapidly in the vicinity of molten weld bead and heat affected zone. To
evaluate the heat transfer coefficient near the fusion line and near the
rear end of the plate (low temperature region), established correlation
has been implemented and has been compared with empirical
correlation which is noted as coupled convective and radiation heat
transfer coefficient. Change in thermal conductivity has been
visualized by analytical model of moving point heat source. Rate of
cooling has been estimated by using 2-dimensional mathematical
expression of cooling rate and it has shown good agreement with
experimental temperature cycle. Thermophysical properties have been
varied randomly within 0 -10s time span.
Abstract: Recognizing human action from videos is an active
field of research in computer vision and pattern recognition. Human
activity recognition has many potential applications such as video
surveillance, human machine interaction, sport videos retrieval and
robot navigation. Actually, local descriptors and bag of visuals words
models achieve state-of-the-art performance for human action
recognition. The main challenge in features description is how to
represent efficiently the local motion information. Most of the
previous works focus on the extension of 2D local descriptors on 3D
ones to describe local information around every interest point. In this
paper, we propose a new spatio-temporal descriptor based on a spacetime
description of moving points. Our description is focused on an
Accordion representation of video which is well-suited to recognize
human action from 2D local descriptors without the need to 3D
extensions. We use the bag of words approach to represent videos.
We quantify 2D local descriptor describing both temporal and spatial
features with a good compromise between computational complexity
and action recognition rates. We have reached impressive results on
publicly available action data set
Abstract: The velocity of a moving point in a general path is the vector quantity, which has both magnitude and direction. The magnitude or the direction of the velocity vector can change over time as a result of acceleration that the time rate of velocity changes. Acceleration analysis is important because inertial forces and inertial torques are proportional to rectilinear and angular accelerations accordingly. The loads must be determined in advance to ensure that a machine is adequately designed to handle these dynamic loads. For planar motion, the vector direction of acceleration is commonly separated into two elements: tangential and centripetal or radial components of a point on a rotating body. All textbooks in physics, kinematics and dynamics of machinery consider the magnitude of a radial acceleration at condition when a point rotates with a constant angular velocity and it means without acceleration. The magnitude of the tangential acceleration considered on a basis of acceleration for a rotating point. Such condition of presentation of magnitudes for two components of acceleration logically and mathematically is not correct and may cause further confusion in calculation. This paper presents new analytical expressions of the radial and absolute accelerations of a rotating point with acceleration and covers the gap in theoretical study of acceleration analysis.