A new efficient lightweight and secure image cipher scheme

Multimedia Tools and Applications - The protection of multimedia content has become a key area of research, since very often a user’s privacy and confidentiality can be at risk. Although a...     

The Virtual Laboratory Environment – An operational framework for multi-modelling,simulation and analysis of complex dynamical systems

The cross-disciplinary activity of modelling and simulation is the core of the scientific activities addressing the complexity of nature. In this context, we need reliable computational environments to integrate heterogeneous representations coming from different scientific fields. Therefore, such environments must be able to integrate heterogeneous formalisms in the same model and assist the modeller for the design and implementation of models, the definition of the experimental frames and the analysis of simulation results. The aim of this article is to introduce a tool supporting all these features, the Virtual Laboratory Environment (VLE). VLE is a software and an API which supports multi-modelling, simulation and analysis. It addresses the reliability issue by using recent developments in the theory of modelling and simulation proposed by Zeigler. We present VLE in the context of the modelling and simulation cycle and show the effectiveness of the tool with a multi-model of fireman fighting a fire spread.     

FAKIR: An algorithm for revealing the anatomy and pose of statues from raw point sets

3D acquisition of archaeological artefacts has become an essential part of cultural heritage research for preservation or restoration purpose. Statues, in particular, have been at the center of many projects. In this paper, we introduce a way to improve the understanding of acquired statues representing real or imaginary creatures by registering a simple and pliable articulated model to the raw point set data. Our approach performs a Forward And bacKward Iterative Registration (FAKIR) which proceeds joint by joint, needing only a few iterations to converge. We are thus able to detect the pose and elementary anatomy of sculptures, with possibly non realistic body proportions. By adapting our simple skeleton, our method can work on animals and imaginary creatures.     

Endoluminal high-resolution MR imaging protocol for colon walls analysis in a mouse model of colitis

Objective

An endoluminal magnetic resonance (MR) imaging protocol including the design of an endoluminal coil (EC) was defined for high-spatial-resolution MR imaging of mice gastrointestinal walls at 4.7 T.

Materials and methods

A receive-only radiofrequency single-loop coil was developed for mice colon wall imaging. Combined with a specific protocol, the prototype was first characterized in vitro on phantoms and on vegetables. Signal-to-noise ratio (SNR) profiles were compared with a quadrature volume birdcage coil (QVBC). Endoluminal MR imaging protocol combined with the EC was assessed in vivo on mice.

Results

The SNR measured close to the coil is significantly higher (10 times and up to 3 mm of the EC center) than the SNR measured with the QVBC. The gain in SNR can be used to reduce the in-plane pixel size up to 39 × 39 µm² (234 µm slice thickness) without time penalty. The different colon wall layers can only be distinguished on images acquired with the EC.

Conclusion

Dedicated EC provides suitable images for the assessment of mice colon wall layers. This proof of concept provides gains in spatial resolution and leads to adequate protocols for the assessment of human colorectal cancer, and can now be used as a new imaging tool for a better understanding of the pathology.

     

Calcium‐Iron Oxide as Energy Storage Medium in Rechargeable Oxide Batteries

Rechargeable oxide batteries (ROB) comprise a regenerative solid oxide cell (rSOC) and a storage medium for oxygen ions. A sealed ROB avoids pumping loss, heat loss, and gas purity expenses in comparison with conventional rSOC. However, the iron oxide base storage medium degrades during charging–discharging cycles. In comparison, CaFe₃O₅ has improved cyclability and a high reversible oxygen storage capacity of 22.3 mol%. In this study, we analyzed the redox mechanism of this compound. After a solid‐state synthesis of CaFe₃O₅, we verified the phase composition and studied the redox reaction by means of X‐ray diffraction, Mössbauer spectrometry, and scanning electron microscopy. Results show a great potential to operate the battery with this storage material during multiple charging–discharging cycles.     

The Complexity of Flood Filling Games

We study the complexity of the popular one player combinatorial game known as Flood-It. In this game the player is given an n×n board of tiles where each tile is allocated one of c colours. The goal is to make the colours of all tiles equal via the shortest possible sequence of flooding operations. In the standard version, a flooding operation consists of the player choosing a colour k, which then changes the colour of all the tiles in the monochromatic region connected to the top left tile to k. After this operation has been performed, neighbouring regions which are already of the chosen colour k will then also become connected, thereby extending the monochromatic region of the board. We show that finding the minimum number of flooding operations is NP-hard for c≥3 and that this even holds when the player can perform flooding operations from any position on the board. However, we show that this ‘free’ variant is in P for c=2. We also prove that for an unbounded number of colours, Flood-It remains NP-hard for boards of height at least 3, but is in P for boards of height 2. Next we show how a (c−1) approximation and a randomised 2c/3 approximation algorithm can be derived, and that no polynomial time constant factor, independent of c, approximation algorithm exists unless P=NP. We then investigate how many moves are required for the ‘most demanding’ n×n boards (those requiring the most moves) and show that the number grows as fast as Q(?c n)\Theta(\sqrt{c}\, n). Finally, we consider boards where the colours of the tiles are chosen at random and show that for c≥2, the number of moves required to flood the whole board is Ω(n) with high probability.     

From Dedicated Grid to Volunteer Grid: Large Scale Execution of a Bioinformatics Application

Large volunteer desktop platforms are now available for several kind of applications. More and more scientists consider this type of computing power as an alternative to the classical platforms such as dedicated clusters aggregated into Grids. This paper presents the work we did to run the first phase of the Help Cure Muscular Dystrophy project to run on World Community Grid. The project was launched on December 19, 2006, and took 26 weeks to complete. During this time frame, 123 GB of results were produced by volunteers who share their idle CPU time to compute a cross docking experiment over 168 proteins. We present performance evaluation of the overall execution and compare the World Community Grid volunteer Grid with a dedicated one.