Proving Distributed Algorithms by Combining Refinement and Local Computations

Distributed algorithms are considered to be very complex to design and to prove; our paper contributes to the design of correct-by-construction distributed algorithms. The main idea relies upon the development of distributed algorithms following a top/down approach, which is clearly well known in earlier works of Dijkstra, and to use refinement for proving the correctness of the resulting algorithms. However, the link between the problem and the first model remains to be expressed and the refinement is a real help to justify in a very progressive way the choices of design. We propose in this work a framework combining local computations models and refinement to prove the correctness of a large class of distributed algorithms. Local computations models define abstract computing processes for solving problems by distributed algorithms and can be integrated into a the Event-B modelling language to define proof-based patterns for the design of distributed algorithms. We illustrate our approach by examples like the leader election protocol or the distributed coloring algorithm. Our proposal is integrated into an environment called ViSiDiA

Mobile Agents For Implementing Local Computations in Graphs

Mobile agents are a recent paradigm to facilitate the design and programming of distributed applications. However, whilst their popularity continues to grow, a uniform theory of mobile agent systems is not yet sufficiently elaborated, in comparison with classical models of distributed computation. In this paper we show how to use mobile agents as an alternative model for implementing distributed local computation rules. In doing so, we approach a general and unified framework for local computations which is consistent with the classical theory of distributed computations based on graph relabeling systems

A Review of Tourism Development in Malaysia

This article looks into the development of tourism secor in Malaysia and sheds light on the efforts undertaken by successive governmets so far to set a comprhensive planning, build infrastructure and promote Malaysia as a  preffered destination internationally. The commitment of the government to the development of this sector and the improvement of the quality of tourism services and infrastructure are unlimited. Currently, tourism sector comes second after manufacturing in terms of contribution to GDP while the country is ranking among the top ten world tourist destinations. Such results indicate that government planning, which involves the interaction of all the influencing aspects and takes in consideration the breoad international context, proves successful and rightly guided. This unique experience can serve as a model to follow by other developing countries especially those countries with similar multicultral settings and natural potential. Keywords: Policy, Planning, Government, Malaysia, Tourism

Characterization And Evaluation Of Alkaline Activated Mortars Synthesized From Binary And Ternary Blends Of Palm Oil Fuel Ash, Ground Granulated Blast Furnace Slag And Fly Ash

Abu bahanapi kelapa sawit (POFA) dengan kehalusan yang berbeza (t-POFA, f-POFA dan u-POFA) memberi kesan kekuatan mampatan dan mikrostruktur mortar yang berasaskan POFA alkali teraktif. Campuran mortar ultrahalus POFA (u-POFA) alkali teraktif menunjukkan kekuatan mampatan yang tertinggi yang diukur antara 7 dan 28 hari. Pelbagai teknik penganalisaan (XRD, FTIR, dan FESEM-EDX) yang dilakukan pada sampel menunjukkan wujudnya pembentukan C-S-H dan N-A-S-H. Perbandingan telah dibuat secara individu untuk POFA, FA dan GGBFS sebagai mortar alkali teraktif menggunakan kaedah Taguchi. Keputusan kajian menunjukkan bahawa kekuatan mampatan tertinggi pada 28 hari rawatan secara individu POFA, FA dan GGBFS sebagai mortar alkali teraktif adalah masing-masing 41.20 MPa, 51.14 MPa dan 93.97 MPa. Kekuatan mampatan yang tinggi ini boleh dikaitkan dengan pembentukan pengikat gel (C-S-H dan N-A-S-H) dalam mortar alkali teraktif, seperti yang dibuktikan oleh analisis XRD, FTIR dan FESM-EDX. Mortar alkali teraktif binari dan ternari daripada tiga bahan (POFA, FA dan GGBFS) menunjukkan peningkatan kekuatan mampatan yang ketara apabila ditambah kepada kira-kira 25% berat u-POFA untuk campuran binari. Walau bagaimanapun, dalam ternari, kekuatan tertinggi diperolehi daripada 40% berat u-POFA, 20% berat FA dan 40% berat GGBFS. Kajian ini mengesahkan bahawa mortar alkali teraktif yang telah dibangunkan dalam kajian ini mempunyai prestasi yang amat baik apabila terdedah kepada pelbagai persekitaran yang agresif dan menunjukkan kestabilan terma yang tinggi apabila terdedah kepada suhu tinggi sehingga 1000 °C. _______________________________________________________________________________________________________ Palm oil fuel ash (POFA) with different fineness (t-POFA, f-POFA and u- POFA) has affected the compressive strength and the microstructure of the POFAbased alkaline activated mortars. The ultrafine POFA (u-POFA) alkaline activated mortar mixture exhibits the highest compressive strength measured between 7 and 28 days of age. Various analyses techniques (XRD, FTIR, and FESEM-EDX) were performed on the samples which showed the formation of C–S–H and N–A–S–H. Comparison has been made for individual POFA, FA and GGBFS as alkali activated mortars using Taguchi method. The results showed that the highest compressive strength at 28 days of curing individual POFA, FA and GGBFS as alkali activated mortars are 41.20 MPa, 51.14 MPa, and 93.97 MPa, respectively. This high compressive strength can be attributed to the formation of gel binder (C–S–H and N– A–S–H) in the alkali activated mortars, as proven by XRD, FTIR and FESM-EDX analyses. The binary and ternary blended alkaline activated mortars of three materials (POFA, FA and GGBFS) showed significant compressive strength improvement when added to about 25 wt% u-POFA for the binary blend. However, in ternary the highest strength obtained from 40 wt% u-POFA, 20 wt% FA and 40 wt% GGBFS. This research confirmed that the alkali activated mortar developed in this study has superior performance when exposed to various aggressive environments and exhibited high thermal stability when exposed to elevated temperature up to 1000 °C

Hypoxia inducible factor-1α accumulation in steatotic liver preservation: Role of nitric oxide

Open-Acces journal.-- et al.[Aim]: To examine the relevance of hypoxia inducible factor (HIF-1) and nitric oxide (NO) on the preservation of fatty liver against cold ischemia-reperfusion injury (IRI). Methods]: We used an isolated perfused rat liver model and we evaluated HIF-1α in steatotic and non-steatotic livers preserved for 24 h at 4°C in University of Wisconsin and IGL-1 solutions, and then subjected to 2 h of normothermic reperfusion. After normoxic reperfusion, liver enzymes, bile production, bromosulfophthalein clearance, as well as HIF-1α and NO [endothelial NO synthase (eNOS) activity and nitrites/nitrates] were also measured. Other factors associated with the higher susceptibility of steatotic livers to IRI, such as mitochondrial damage and vascular resistance were evaluated. [Results]: A significant increase in HIF-1α was found in steatotic and non-steatotic livers preserved in IGL-1 after cold storage. Livers preserved in IGL-1 showed a significant attenuation of liver injury and improvement in liver function parameters. These benefits were enhanced by the addition of trimetazidine (an antiischemic drug), which induces NO and eNOS activation, to IGL-1 solution. In normoxic reperfusion, the presence of NO favors HIF-1α accumulation, promoting also the activation of other cytoprotective genes, such as hemeoxygenase- 1. [Concluison]: We found evidence for the role of the HIF-1α/NO system in fatty liver preservation, especially when IGL-1 solution is used. © 2010 Baishideng.Supported by The Ministerio de de Sanidad y Consumo (PI 081988), CIBER-EHD, Instituto Carlos III, Madrid and Ministerio de Asuntos Exteriores y de Cooperación Internacionales (A/020255/08 and A/02987/09), MadridPeer Reviewe