Contents of Journal of Mechanical Engineering 58, 1 (2007) 




GHATAK, A., CHAKRABORTY, S.: Effect of external irreversibilities 
and variable thermal properties of working fluid on thermal 
performance of a dual internal combustion engine cycle                    1

ZAATRI, A., CHERFIA, A.: Emulation of a supervised intelligent 
robot                                                                    13

ABU-HILAL, M., BEITHOU, N.: Free transverse vibrations of 
a triple-beam system                                                     30

Abstracts



Effect of external irreversibilities and variable thermal properties of working fluid on thermal performance
of a dual internal combustion engine cycle

ARINDAM GHATAK, SUMAN CHAKRABORTY

This work presents the thermodynamic analysis of a realistic IC engine cycle (modelled as the dual combustion cycle) for effective performance estimation of the same. The effects of heat transfer through the cylinder walls are duly considered to formulate the pertinent mathematical model. The heat losses are considered to be proportional to the difference between the average temperature during the isobaric heat addition process and the ambient temperature. Moreover, effects of variation of specific heat of the working fluid with temperature are also taken into account while formulating the thermodynamic analysis. Effects of important system parameters such as pressure ratio, compression ratio, etc. on the overall efficiency and on the net work output of the system are also systematically studied, taking external irreversibilities into account. The results obtained from this work can be helpful in the design and performance evaluation of internal combustion engines in a more practical manner.

Emulation of a supervised intelligent robot

ABDELOUAHAB ZAATRI, ABDELHAKIM CHERFIA

This paper presents the design and the implementation of an intelligent mobile manipulator robot leading to emulate a human-like behaviour. The system is capable of using an autonomous strategy for searching modelled objects in its environment, localising their positions in 3D space, evaluating the safety of the intended actions by anticipation in virtual environments, and finally moving towards them safely for compliant contact and manipulation.

To work in all conditions, human intervention and human-robot co-assistance are provided through a multi-modal interface that enables a supervised autonomy. Moreover, a particular focus is afforded for designing a concurrent human-machine task allocator based on a Markov decision process.

The experiments carried out confirm the possibility to use the proposed framework into robotics systems for coping with various real-world applications.

Free transverse vibrations of a triple-beam system

MOHAMMED ABU-HILAL, NABIL BEITHOU

In this paper, the free vibration of an undamped triple-beam system on elastic foundation is analysed. The system consists of three Euler-Bernoulli beams of the same length that are arranged in parallel and continuously connected by elastic layers. The natural frequencies and the mode shapes of the system are determined. Furthermore, the initial value problem is solved to find the time-dependent free vibrations of the beams. Using a numerical example, the effects of the layer stiffnesses and those of the masses of the beams per unit length on the natural frequencies and the mode shapes are investigated in detail.