Disaster-survivable cloud-network mapping

Cloud-computing services are provided to consumers through a network of servers and network equipment. Cloud-network (CN) providers virtualize resources [e.g., virtual machine (VM) and virtual network (VN)] for efficient and secure resource allocation. Disasters are one of the worst threats for CNs as they can cause massive disruptions and CN disconnection. A disaster may also induce post-disaster correlated, cascading failures which can disconnect more CNs. Survivable virtual-network embedding (SVNE) approaches have been studied to protect VNs against single physical-link/-node and dual physical-link failures in communication infrastructure, but massive disruptions due to a disaster and their consequences can make SVNE approaches insufficient to guarantee cloud-computing survivability. In this work, we study the problem of survivable CN mapping from disaster. We consider risk assessment, VM backup location, and post-disaster survivability to reduce the risk of failure and probability of CN disconnection and the penalty paid by operators due to loss of capacity. We formulate the proposed approach as an integer linear program and study two scenarios: a natural disaster, e.g., earthquake and a human-made disaster, e.g., weapons-of-mass-destruction attack. Our illustrative examples show that our approach reduces the risk of CN disconnection and penalty up to 90 % compared with a baseline CN mapping approach and increases the CN survivability up to 100 % in both scenarios.     

Microwave dielectric properties of rubber and oil palm leaf samples: Measurement and modelling

This paper contains the results of measured dielectric constants of leaves of two tropical crops, rubber ( Heavea brasiliensis ) and oil palm ( Elaeis guineensis ) at microwave frequency region. Using a microcomputer-based automated system consisting of a Wiltron 360B vector network analyser,measurements are conducted based on the waveguide thin sheet technique. Leaf samples are inserted within waveguide sections, and the dielectric constants are calculated from the complex reflection coefficients. The measurements cover a frequency range of 4-18GHz. In general, the dielectric constant of a leaf sample is a function of water content and frequency. Theoretical calculations from three dielectric mixing models, i.e., the Debye-Cole Dual-Dispersion dielectric model by Ulaby and Rayes, Matzler's Model and Carlson's Model are compared with the measurements. From the comparisons, the dual-dispersion model is found to show more promise in prediction of the dielectric constants, if proper physical parameters of the model, such as bound and free-water volume fractions, are used.     

Acidity and porosity modulation of MWW type zeolites for Nopol production by Prins condensation

Prins condensation of β-pinene with paraformaldehyde was carried out over MCM-22, delaminated ITQ-2 and silica pillared MCM-36. The mesopore-containing MCM-36 and ITQ-2 catalysts exhibit higher conversion of β-pinene due to more exposed acid sites. Lewis acid sites are responsible for Prins condensation while Brønsted acid sites favor the isomerization of pinene. The Brønsted acid sites can be removed mostly by ion-exchanging the zeolites with sodium cations. Thus, NaMWW zeolites had a higher selectivity towards Nopol. Of these, NaITQ-2 showed the highest activity and selectivity, and is a stable and reusable catalyst for production of Nopol.     

Joint channel assignment and routing in multiradio multichannel wireless mesh networks with directional antennas

The aggregate capacity of a wireless mesh network (WMN) is severely affected by interflow interference. In this paper, we propose a network architecture that incorporates directional antennas with multiple orthogonal channels to effectively enhance the performance of WMNs. First, a sectored connectivity graph is introduced to model multiradio multichannel WMNs with directional antennas. Next we formulate the topology design, directional interface assignment, channel allocation, and routing mathematically as a mixed integer linear programming problem. This problem is solved using an iterated local search algorithm to obtain optimized network resource allocation. Simulation results indicate that the proposed architecture can achieve higher packet delivery ratio while providing better network fairness. Copyright © 2014 John Wiley & Sons, Ltd.     

Fair power control for wireless ad hoc networks using game theory with pricing scheme

Resource allocation in wireless ad hoc networks is usually modelled in a non-cooperative game theoretic framework with the objective of maximising individual utility. However, the selfishness of autonomous users under such framework may lead to throughput unfairness which only benefits certain users. To alleviate this unfairness problem, the authors propose a payment-based power control scheme using game theory where each user announces a set of price coefficients that reflects different compensations paid by other users for the interference they produce. Users who generate higher interference are required to pay more by transmitting at a lower power to give other users a fairer chance of sharing the throughput.Without any incentive to play fairly, users could misbehave by broadcasting high price coefficients to force other users to transmit at a lower power. The authors treat this problem casting it into a price game which resembles a Prisoner's Dilemma game. Users who play this game iteratively will behave cooperatively and broadcast the price coefficients truthfully. Together with analytical proof, the proposed approach is shown to converge to Nash equilibrium where at this point it is able to provide a fairer throughput share among users at the expense of a slight loss in total throughput.     

A study on an optimal approach temperature control strategy of condensing water temperature for energy saving

An optimal approach temperature (OAT) control strategy is proposed for resetting the condensing water temperature hourly, so to maximize the performance of the combined water chiller and cooling tower system. A system performance factor is introduced for evaluation of the system performance. A regression function is presented for the calculation of an optimal condensing water temperature at each hour of air-conditioning operation. The parameters in the regression function include the ambient wet bulb temperature, the chiller load ratio at the hour, and a dimensionless relative efficiency of chiller and cooling tower. The regression function has an R² close to 1 compared to the computed results. When applied to two cities in Taiwan, the OAT control strategy has a potential to save energy more than 4% on an annual basis. The OAT control strategy is most advantageous when applied to regions with large seasonal variation of wet bulb temperature.     

Radar backscatter from a dense discrete random medium

A dense medium phase matrix developed based on the concept of random lattice perturbation is employed in the radiative transfer theory to calculate the coand cross-polarized backscatter from a layer of randomly distributed spherical scatterers. The position randomness properties are characterized by the variance and correlation function of scatterer positions within the medium. The dense medium phase matrix differs from the conventional one in two major aspects, i.e., there is an amplitude and a phase correction. These corrections account for the effects of close spacing and position correlation between scatterers in a dense discrete random medium. This study shows that phase coherency and close-spacing amplitude modifications are two separate corrections necessary for an electrically dense medium. Results indicate that there is a need to distinguish between spatially and electrically dense medium. The phase correction is found to have a greater impact on cross-polarized than like-polarized backscatter coefficients; the converse is true of the amplitude correction. Backscattering calculations from the theory are compared with measurements from controlled microwave experiments on random media consisting of closely packed spheres, and from field measurements of dry snowpack. Predictions from such a theory agree well with the measured data     

Formation of Biocompatible Nanoparticles via the Self-Assembly of Chitosan and Modified Lecithin

ABSTRACT:  The formation of biocompatible nanoparticles via the self-assembly of chitosan (CHI) and modified lecithin (ML) was studied. Stable nanoparticles in the size range of 123 to 350 nm were formed at over a wide molar mixing ratios of CHI/ML solutions (amino group/phosphate group) (NH₃⁺/PO₃⁻) and total polyelectrolyte (PE) concentrations (0.1 to 1 wt%) except at intermediate molar ratios when the surface charge was close to neutrality. Zeta-potentials of the nanoparticles were found to be independent of the total PE concentrations. Nanoparticles exhibited excellent stability at over an extended pH (pHs 3 to 6) and ionic strength range (≤ 500 mM NaCl concentration). The particle size and zeta-potential of the nanoparticles increased with the molecular weight of CHI. Transmission electron microscopy suggested that nanoparticles were generally spherical in shape with CHI constituting the exterior of its surface at high molar mixing ratios. Dextran-fluorescein isothiocyanate, bovine serum albumin, and Coomassie brilliant blue as models of nonionic, positively and negatively charged compounds were encapsulated within the nanoparticles at between 8.7% and 62.7% efficiency. The ability of the nanoparticle suspensions to be converted to lyophilized powder or concentrated suspension was also demonstrated.