Bayesian inference approach for establishing efficient routes in wireless ad-hoc networks

Mobile ad hoc networks (MANETs) are dynamic wireless networks that have no fixed infrastructures and do not require predefined configurations. In this infrastructure-less paradigm, nodes in addition of being hosts, they also act as relays and forward data packets for other nodes in the network. Due to limited resources in MANETs such as bandwidth and power, the performance of the routing protocol plays a significant role. A routing protocol in MATET should not introduce excessive control messages to the network in order to save network bandwidth and nodes power. In this paper, we propose a probabilistic approach based on Bayesian inference to enable efficient routing in MANETs. Nodes in the proposed approach utilize the broadcast nature of the wireless channel to observe the network topology by overhearing wireless transmissions at neighboring nodes in a distributed manner, and learn from these observations when taking packet forwarding decision on the IP network layer. Our simulation results show that our routing approach reduces the number of control message (routing overhead) by a ratio up to 20 % when the network size is 60 nodes, while maintaining similar average route establishment delay as compared to the ad-hoc on demand routing protocol.     

Towards practical private processing of database queries over public data

Privacy is a major concern when users query public online data services. The privacy of millions of people has been jeopardized in numerous user data leakage incidents in many popular online applications. To address the critical problem of personal data leakage through queries, we enable private querying on public data services so that the contents of user queries and any user data are hidden and therefore not revealed to the online service providers. We propose two protocols for private processing of database queries, namely BHE and HHE. The two protocols provide strong query privacy by using Paillier’s homomorphic encryption, and support common database queries such as range and join queries by relying on the bucketization of public data. In contrast to traditional Private Information Retrieval proposals, BHE and HHE only incur one round of client server communication for processing a single query. BHE is a basic private query processing protocol that provides complete query privacy but still incurs expensive computation and communication costs. Built upon BHE, HHE is a hybrid protocol that applies ciphertext computation and communication on a subset of the data, such that this subset not only covers the actual requested data but also resembles some frequent query patterns of common users, thus achieving practical query performance while ensuring adequate privacy levels. By using frequent query patterns and data specific privacy protection, HHE is not vulnerable to the traditional attacks on k-Anonymity that exploit data similarity and skewness. Moreover, HHE consistently protects user query privacy for a sequence of queries in a single query session.     

Performance analysis of high-concentrated multi-junction solar cells in hot climate

Multi-junction concentrator solar cells are a promising technology as they can fulfill the increasing energy demand with renewable sources. Focusing sunlight upon the aperture of multi-junction photovoltaic (PV) cells can generate much greater power densities than conventional PV cells. So, concentrated PV multi-junction solar cells offer a promising way towards achieving minimum cost per kilowatt-hour. However, these cells have many aspects that must be fixed to be feasible for large-scale energy generation. In this work, a model is developed to analyze the impact of various atmospheric factors on concentrator PV performance. A single-diode equivalent circuit model is developed to examine multi-junction cells performance in hot weather conditions, considering the impacts of both temperature and concentration ratio. The impacts of spectral variations of irradiance on annual performance of various high-concentrated photovoltaic (HCPV) panels are examined, adapting spectra simulations using the SMARTS model. Also, the diode shunt resistance neglected in the existing models is considered in the present model. The present results are efficiently validated against measurements from published data to within 2% accuracy. Present predictions show that the single-diode model considering the shunt resistance gives accurate and reliable results. Also, aerosol optical depth (AOD) and air mass are most important atmospheric parameters having a significant impact on HCPV cell performance. In addition, the electrical efficiency (η) is noticed to increase with concentration to a certain concentration degree after which it decreases. Finally, based on the model predictions, let us conclude that the present model could be adapted properly to examine HCPV cells' performance over a broad range of operating conditions.     

Graph-based video sequence matching using dominant colour graph profile (DCGP)

This paper presents a fast and effective technique for videos’ visual similarity detection and measurement using compact fixed-length signatures. The proposed technique (dominant colour graph profile DCGP) extracts and encodes the spatio-temporal information of a given video shot into a graph-based structure (tree) that fully captures this vital information. The graph structured properties are utilized to construct a fixed-length video signature of 112 decimal values per video shot. The encoded spatio-temporal information is extracted following channelling each video frame into a block-based structure, where the positions of respective blocks are tracked across video frames and encoded into multiple DCGP trees. The proposed technique provides a high matching speed (>2000 fps) and robust retrieval performance. The experiments on various standard and challenging datasets shows the framework’s robust performance, in terms of both, retrieval and computational performances.     

Synthesis,characterization, and thermal analysis of two polymeric chromium ternary complexes with nitrilotriacetic acid and alanine or glycine

Two chromium ternary complexes with nitrilotriacetic acid as a primary ligand and alanine or glycine as secondary ligand were prepared in slightly acidic medium. The structure of these two complexes was characterized using elemental, thermal analysis, FTIR spectra, and the two complexes mass spectra. The spectroscopy data suggest that these two complexes were in polymeric form and have the monomeric unit H[Cr(HNTA)(Hala)(SO₄)] and H[Cr(HNTA)(Gly)(SO₄)] in which sulfate group act as a bidentate ligand linked between each monomeric unit for the same complex. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ground stabilization for tunnel construction in mixed-face conditions

A scheme for providing stability measures for a tunnel excavated in mixed-ground conditions using chemical grouting is described. Typical geotechnical problems encountered during excavation are highlighted. An analytical approach for calculating the required thickness of grouted soil was developed. Grout characteristics to achieve the required behaviour are described, along with the recommended sequence of construction. A methodology employing finite element analyses to predict the tunnel behaviour during construction is proposed. It was utilized in designing the excavation support. Predictions compared well with actual field measurements.     

Adaptive feedforward cancellation of sinusoidal disturbances in superconducting RF cavities

A control method, known as adaptive feedforward cancellation (AFC), is applied to damp sinusoidal disturbances due to microphonics in superconducting radio frequency (SRF) cavities. AFC provides a method for damping internal and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity for an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.     

Equivalent mechanical model for seismic forces in combined tanks subjected to vertical earthquake excitation

Liquid-storage tanks with circular cross sections are commonly built with a combined vessel consisting of a truncated cone and a superimposed top cylindrical cap. Unlike cylindrical tanks, combined tanks are characterized by the inclination of the walls of the conical segment. As a result, compressive meridional stresses are induced in the shell by the hydrostatic pressure of the contained fluid and the hydrodynamic pressure associated with vertical ground excitation. The current paper aims at identifying the dynamic characteristics of liquid-filled combined tanks subjected to vertical ground excitation. Numerical analysis is conducted based on a coupled finite-boundary element formulation that accounts for the associated fluid–structure interaction. An equivalent model is developed to duplicate forces induced in liquid-filled combined vessels subjected to vertical base excitation. The proposed model accounts for the flexibility of the vessel walls. Meanwhile, the contained fluid is idealized as rigid and flexible components. The proposed equivalent model provides a simplified tool to predict seismically-induced forces in liquid-filled vessels subjected to vertical earthquake excitation.     

A review on colorimetric indicators for monitoring product freshness in intelligent food packaging: Indicator dyes,preparation methods,and applications

Intelligent food packaging system exhibits enhanced communication function by providing dynamic product information to various stakeholders (e.g., consumers, retailers, distributors) in the supply chain. One example of intelligent packaging involves the use of colorimetric indicators, which when subjected to external stimuli (e.g., moisture, gas/vapor, electromagnetic radiation, temperature), display discernable color changes that can be correlated with real-time changes in product quality. This type of interactive packaging system allows continuous monitoring of product freshness during transportation, distribution, storage, and marketing phases. This review summarizes the colorimetric indicator technologies for intelligent packaging systems, emphasizing on the types of indicator dyes, preparation methods, applications in different food products, and future considerations. Both food and nonfood indicator materials integrated into various carriers (e.g., paper-based substrates, polymer films, electrospun fibers, and nanoparticles) with material properties optimized for specific applications are discussed, targeting perishable products, such as fresh meat and fishery products. Colorimetric indicators can supplement the traditional “Best Before” date label by providing real-time product quality information to the consumers and retailers, thereby not only ensuring product safety, but also promising in reducing food waste. Successful scale-up of these intelligent packaging technologies to the industrial level must consider issues related to regulatory approval, consumer acceptance, cost-effectiveness, and product compatibility.