A Scalable Middleware Solution for Advanced Wide Area Web Services

To alleviate scalability problems in the Web, many researchers concentrate on how to incorporate advanced caching and replication techniques. Many solutions incorporate object-based techniques. In particular, Web resources are considered as distributed objects offering a well-defined interface. We argue that most proposals ignore two important aspects. First, there is little discussion on what kind of coherence should be provided. Proposing specific caching or replication solutions makes sense only if we know what coherence model they should implement. Second, most proposals treat all Web resources alike. Such a one-size-fits-all approach will never work in a wide-area system. We propose a solution in which Web resources are encapsulated in physically distributed shared objects. Each object should encapsulate not only state and operations, but also the policy by which its state is distributed, cached, replicated, migrated, etc

Optimal methods for coordinated en-route web caching for tree networks

Web caching is an important technology for improving the scalability of Web services. One of the key problems in coordinated enroute Web caching is to compute the locations for storing copies of an object among the enroute caches so that some specified objectives are achieved. In this article, we address this problem for tree networks, and formulate it as a maximization problem. We consider this problem for both unconstrained and constrained cases. The constrained case includes constraints on the cost gain per node and on the number of object copies to be placed. We present dynamic programming-based solutions to this problem for different cases and theoretically show that the solutions are either optimal or convergent to optimal solutions. We derive efficient algorithms that produce these solutions. Based on our mathematical model, we also present a solution to coordinated enroute Web caching for autonomous systems as a natural extension of the solution for tree networks. We implement our algorithms and evaluate our model on different performance metrics through extensive simulation experiments. The implementation results show that our methods outperform the existing algorithms of either coordinated enroute Web caching for linear topology or object placement (replacement) at individual nodes only.Keqiu Li, Hong Shen, Francis Y. L. Chin, Si Qing Zhen

Adaptation-Aware Web Caching: Caching in the Future Pervasive Web

In the upcoming world of Pervasive Computing, content adaptation is an essential concept to meet the heterogeneous requirements of web users using various web access technologies. However, content adaptation interferes with the effectiveness of web caching. Leveraging the advantages of web caching even in the world of Pervasive Computing is the subject of this paper. We presen

Ecofriendly alkali metal cations diffusion improves fabrication of mixed-phase titania polymorphs on fixed substrate by chemical vapor deposition (CVD) for photocatalytic degradation of azo dye

Controlling the nanoscale synthesis of semiconductor TiO2 on a fixed substrate has fascinated the curiosity of academics for decades. Synthesis development is required to give an easy-to-control technique and parameters for TiO2 manufacture, leading to advancements in prospective applications such as photocatalysts. This study, mixed-phase TiO2(B)/other titania thin films were synthesized on a fused quartz substrate utilizing a modified Chemical vapor depodition involving alkali-metal ions (Li+, Na+, and K+) solution pre-treatment. It was discovered that different cations promote dramatically varied phases and compositions of thin films. The films had a columnar structure with agglomerated irregular-shaped particles with a mean thickness of 800–2000 nm. Na+ ions can promote TiO2(B) more effectively than K+ ions, however Li+ ions cannot synthesize TiO2(B). The amounts of TiO2(B) in thin films increase with increasing alkali metal (K+ and Na+) concentration. According to experimental and DFT calculations, the hypothesized TiO2(B) production mechanism happened via the meta-stable intermediate alkaline titanate transformation caused by alkali-metal ion diffusion. The mixed phase of TiO2(B) and anatase TiO2 on the fixed substrate (1 × 1 cm2) obtained from Na+ pre-treated procedures showed significant photocatalytic activity for the degradation of methylene blue. K2Ti6O12, Li2TiO3, Rutile TiO2, and Brookite TiO2 phase formations produced by K+ and Li + pretreatment are low activity photocatalysts. Photocatalytic activities were more prevalent in NaOH pre-treated samples (59.1% dye degradation) than in LiOH and KOH pre-treated samples (49.6% and 34.2%, respectively). This revealed that our developed CVD might generate good photocatalytic thin films of mixed-phase TiO2(B)/anatase TiO2 on any substrate, accelerating progress in future applications