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An investigation of stresses and deformation states of clamped rotating functionally graded disks

Thawait A. K., Sondhi L., Sanyal S., Bhowmick S.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 1

189--198

EN

The present study deals with the linear elastic analysis of variable thickness rotating disks made of functionally graded materials (FGMs) by the finite element method. The disks have radially varying material properties according to an exponential law, which is achieved by the element based grading of the material properties on the meshed domain. The results are reported for three types of thickness profiles, namely, uniform, linearly varying and concave thickness, having their mass constant. The disks are subjected to the clamped boundary condition at the inner surface and the free boundary condition at the outer surface. The obtained results show that in a variable thickness rotating disk, deformation and stresses are less as compared to the uniform thickness disk.

2

Behavior based co-ordination of a troop of vehicles targeted to different goals in an unknown environment

Sanyal S., Barai R. K., Chakrabarti R., Chattopadhyay P. K.

Journal of Automation Mobile Robotics and Intelligent Systems

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2012

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Vol. 6, No. 4

20-26

EN

The issue of coordinated operation of multi-vehicle for a variety of tasks is getting increasing attention day by day and standing as a major research field due to their increased capacity and flexibility they can offer as a team. This paper presents a novel algorithm for multi-vehicle navigation, based on exhaustive search to avoid a set of randomly generated obstacles, predict the approximate position of other vehicles and thus keeping a safe distance to avoid collision and to maintain a formation amongst them while targeted towards the assigned goals. The proposed algorithm uses two optimizing functions in deriving drive commands, direction and turning, for a troop of vehicles. This particular algorithm is similar to the artificial potential field (APF) method which is widely used for autonomous mobile robot path planning due to its simplicity and mathematical elegance. In this work we have taken a behavior based reactive scheme together with artificially generated perturbation as the vehicles are running in a real time environment. Simulations have been carried out for a group of four vehicles, paired in two groups, approaching two different targets avoiding eight randomly generated obstacles, and keeping proper coordination between the members of intra and inter groups. The effectiveness of the proposed approach has been shown by some simulation results.

3

Hiding inside html and other source codes

Al-Quaheri H., Dey S., Sanyal S.

Image Processing & Communications

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2009

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Vol. 14, no 2-3

59-68

EN

Many steganographic techniques [1,2, 3, 4] were proposed for hiding secret message inside images, the simplest of them being the LSB data hiding [6, 7, 8, 9, 10, 11]. In this paper, we suggest a novel data hiding technique in an Html Web page [12] and also propose some simple techniques to extend the embedding technique to source codes written in any programming language (both case insensitive like Html, pascal and case sensitive languages like C, C++, Java) - an extension to [12]. We basically try to exploit the case-redundancy in case-insensitive language, while we try hiding data with minimal changes int the source code (almost not raising suspicion). Html Tags are case insensitive and hence an alphabet in lowercase and one in uppercase present inside an Html Tag are interpreted in the same manner by the browser, i.e., change in case in an web page is imperceptible to the browser. We first exploit this redundancy and use it to embed secret data inside an web page, with no changes visible to the user of the web page, so that he can not even suspect about the data hiding. The embedded data can be recovered by viewing the source of the Html page. This technique can easily be extended to embed secret message inside any piece of source-code where the standard interpreter of that language is case-insensitive. For case-sensitive programming languages we do minimal changes in the source code (e.g., add an extra character in the token identified by the lexical analyser) without violating the lexical and syntactic notation for that language) and try to make the change almost imperceptible.

4

A very simple approach for 3-D to 2-D mapping

Dey S., Abraham A., Sanyal S.

Image Processing & Communications

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2006

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Vol. 11, no 2

75-82

EN

Many times we need to plot 3-D functions e.g., in many scientific experiments. To plot this 3-D functions on 2-D screen it requires some kind of mapping. Though OpenGL, DirectX etc 3-D rendering libraries have made this job very simple, still these libraries come with many complex pre-operations that are simply not intended, also to integrate these libraries with any kind of system is often a tough trial. This article presents a very simple method of mapping from 3-D to 2-D, that is free from any complex pre-operation, also it will work with any graphics system where we have some primitive 2-D graphics function. Also we discuss the inverse transform and how to do basic computer graphics transformations using our coordinate mapping system.