Some Universal Constructions of Autonomic Systems

Self-* is widely considered as a foundation for autonomic computing. The notion of autonomic systems (ASs) and self-* serves as a basis on which to build our intuition about category of ASs in general. In this paper we will specify ASs and self-* and then move on to consider some universal constructions such as products, coproducts, finite limits and colimits of ASs. All of this material is taken as an investigation of our category, the category of ASs, which we call AS.     

Algorithms for supporting disconnected write operations for wireless Web access in mobile client-server environments

In a wireless mobile client-server environment, a mobile user may voluntarily disconnect itself from the Web server to save its battery life and avoid high communication prices. To allow Web pages to be updated while the mobile user is disconnected from the Web server, updates can be staged in the mobile host and propagated back to the Web server upon reconnection. In this paper, we analyze algorithms for supporting disconnected write operations for wireless Web access and develop a performance model to identify the optimal length of the disconnection period under which the cost of update propagation is minimized. The analysis result is particularly applicable to Web applications which allow wireless mobile users to modify Web contents while on the move. We show how the result can be applied to real-time Web applications such that the mobile user can determine the longest disconnection period such that it can still propagate updates to the server before the deadline so that a minimum communication cost is incurred.     

Information and Service Integration Based on Agent-Oriented Ubiquitous Computing

Ubiquitous computing for information and service integration is currently at crucial point in its evolution, marked by the increasing developments of agent-based ubiquitous computing systems for the information and service integration. Some major features of ubiquitous computing systems (UCSs) consist of heterogeneity, decentralization, nondeterminism and dynamicity. Hence, agent-based ubiquitous computing (AUC) is a form of distributed computing by which computational processes are executed concurrently by assigning each computational process to one of agents on a UCS. The overarching goal of AUC is to support the seamless integration of information and services. Meeting this grand challenge of AUC requires that agent-orientation not tackled before is necessarily featured. To this end, taking advantage of the categorical structures we establish, in this paper, a firm formal development for featuring agent-orientation of ubiquitous computing. In other words, all of these are to formalize the AUC for information and service integration.     

Different Directions of Switching of Chromium Oxide Thin Films

We have investigated the switching behavior of as-deposited CrO _x and post-annealed CrO _y films by use of a variety of electrodes (top electrode Ag, Ti; bottom electrode Pt, fluorine tin oxide (FTO)). Resistance switching is highly dependent on electrode material and post-annealing treatment. Among Pt devices, I–V hysteresis was observed for the Ag/CrO _x /Pt device only; no resistance switching was observed for Ag/CrO _y /Pt, Ti/CrO _x /Pt, and Ti/CrO _y /Pt devices. Among FTO devices, I–V hysteresis was observed for the Ag/CrO _x /FTO device whereas I–V hysteresis with the opposite switching direction was observed for Ag/CrO _y /FTO, Ti/CrO _x /FTO, and Ti/CrO _y /FTO devices. The direction of switching depends not only on electrode material but also on post-annealing treatment, which affects the density of grain boundaries. Thus, the density of grain boundaries determines the type of charge carrier involved in the switching process. For as-deposited CrO _x films with a high density of grain boundaries Ag filament paths mediated by electrochemical redox reaction were observed, irrespective of bottom electrode material (Pt or FTO). Post-annealed CrO _y films with a low density of grain boundaries suppressed electrochemical redox reaction in the Ag/CrO _y /Pt device but promoted short-range movement of O^2? ions through the bottom interface, resulting in resistance switching in the Ag/CrO _y /FTO device. Electrochemical redox reaction-controlled resistance switching occurred solely in oxides with a high density of grain boundaries or dislocations.     

User identification via neural network based language models

Identifying compromised accounts on online social networks that are used for phishing attacks or sending spam messages is still one of the most challenging problems of cyber security. In this research, the authors explore an artificial neural network‐based language model to differentiate the writing styles of different users on short text messages. In doing so, the aim is to be able to identify compromised user accounts. The results obtained indicate that one can learn the language model on one dataset and can generalize it to different datasets to identify users with high accuracy and low false alarm rates without any modification to the language model.     

Privacy Analysis of Forward and Backward Untraceable RFID Authentication Schemes

In this paper, we analyze the first known provably secure Radio Frequency Identification (RFID) authentication schemes that are designed to provide forward untraceability and backward untraceability: the L-K and S-M schemes. We show how to trace tags in the L-K scheme without needing to corrupt tags. We also show that if a standard cryptographic pseudorandom bit generator (PRBG) is used in the S-M scheme, then the scheme may fail to provide forward untraceability and backward untraceability. To achieve the desired untraceability features, we show that the S-M scheme can use a robust PRBG which provides forward security and backward security. We also note that the backward security is stronger than necessary for the backward untraceability of the S-M scheme.     

A Learning-Based Approach for Web Cache Management

Web caching has been widely used to alleviate Internet traffic congestion in World Wide Web (WWW) services. To reduce download throughput, an effective strategy on web cache management is needed to exploit web usage information in order to make a decision on evicting the document stored in case of cache saturation. This paper presents a so-called Learning Based Replacement algorithm (LBR), a hybrid approach towards an efficient replacement model for web caching by incorporating a machine learning technique (naive Bayes) into the LRU replacement method to improve prediction of possibility that an existing page will be revised by a succeeding request, from access history in a web log. The learned knowledge includes information on which URL objects in cache should be kept or evicted. The learning-based model is acquired to represent the hidden aspect of user request pattern for predicting the re-reference possibility. By a number of experiments, the LBR gains potential improvement of prediction on revisit probability, hit rate and byte hit rate overtraditional methods; LRU, LFU, and GDSF, respectively.     

Fullerene Additives Convert Ambipolar Transport to p‐Type Transport while Improving the Operational Stability of Organic Thin Film Transistors

Many high charge carrier mobility (μ) active layers within organic field‐effect transistor (OFET) configurations exhibit non‐linear current–voltage characteristics that may drift with time under applied bias and, when applying conventional equations for ideal FETs, may give inconsistent μ values. This study demonstrates that the introduction of electron deficient fullerene acceptors into thin films comprised of the high‐mobility semiconducting polymer PCDTPT suppresses an undesirable “double‐slope” in the current–voltage characteristics, improves operational stability, and changes ambipolar transport to unipolar transport. Examination of other high μ polymers shows general applicability. This study also shows that one can further reduce instability by tuning the relative electron affinity of the polymer and fullerene by creating blends containing different fullerene derivatives and semiconductor polymers. One can obtain hole μ values up to 5.6 cm² V^–1 s^–1 that are remarkably stable over multiple bias‐sweeping cycles. The results provide a simple, solution‐processable route to dictate transport properties and improve semiconductor durability in systems that display similar non‐idealities.     

Laser probe measurements of quality evolution of solder joints during thermal cycling ageing tests

We present the results of a non-destructive measuring method allowing us to characterize the evolution of solder joints during thermal cycling ageing tests. The method uses a high resolution optical probe to detect selectively pure Joule and Peltier thermal responses of the solder joint subject to a given current pulse. The results show the Peltier and Joule responses to be good indicators for the evaluation of the age and the degradation of solder joints.