Optimizing vote and quorum assignments for reading and writingreplicated data

In the weighted voting protocol which is used to maintain the consistency of replicated data, the availability of the data to ready and write operations not only depends on the availability of the nodes storing the data but also on the vote and quorum assignments used. The authors consider the problem of determining the vote and quorum assignments that yield the best performance in a distributed system where node availabilities can be different and the mix of the read and write operations is arbitrary. The optimal vote and quorum assignments depend not only on the system parameters, such as node availability and operation mix, but also on the performance measure. The authors present an enumeration algorithm that can be used to find the vote and quorum assignments that need to be considered for achieving optimal performance. When the performance measure is data availability, an analytical method is derived to evaluate it for any vote and quorum assignment. This method and the enumeration algorithm are used to find the optimal vote and quorum assignment for several systems. The enumeration algorithm can also be used to obtain the optimal performance when other measures are considered     

Resource finding in store-and-forward networks

We present a model of searching for a resource in a distributed system whose nodes are connected through a store-and-forward network. Based on this model, we show a lower bound on the number of messages needed to find a resource when nothing is known about the nodes that have the current location of the resource. The model also helps us to establish results about the time complexity of determining a message optimal resource finding algorithm when the probability distribution for the location of the resource in the network is known. We show that the optimization problem is NP-hard for general networks. Finally we show that optimal resource finding algorithms can be determined in polynomial time for a class of tree networks and bidirectional rings. The polynomial algorithms can be used as a basis of heuristic algorithms for general networks.This work was supported in part by NSF grants CCR-8806358 and NCR-8604850     

Countering security information overload through alert and packet visualization

This article presents a framework for designing network security visualization systems as well as results from the end-to-end design and implementation of two highly interactive systems. In this article, we provide multiple contributions: we present the results of our survey of security professionals, the design framework, and lessons learned from the design of our systems as well as an evaluation of their effectiveness. Our results indicate that both systems effectively present significantly more information when compared to traditional textual approaches. We believe that the interactive, graphical techniques that we present will have broad applications in other domains seeking to deal with information overload.     

Mechanical characterization of glass/polyimide microjoints fabricated using cw fiber and diode lasers

This paper discusses the laser-irradiated microjoints between glass and polyimide for applications in neural implants. To facilitate bonding between them, a thin titanium film with a thickness of approximately 0.2 μm was deposited on glass wafers using the physical vapor deposition (PVD) process. Two sets of samples were fabricated where the bonds were created using diode and fiber lasers. The samples were subjected to tension using a microtester for bond strength measurements. The failure strengths of the bonds generated using fiber laser are quite consistent, while a wide variation of failure strengths are observed for the bonds generated with diode laser. Few untested samples were sectioned and the microstructures near the bond areas were studied using an optical microscope. The images revealed the presence of a sharp crack in the glass substrate near the bond generated with the diode laser. However, no such crack was observed in the samples made using fiber laser. To investigate the reasons behind such discrepancy in bond quality further, uncoupled three-dimensional finite element analyses (FEA) were conducted only for the samples created using diode laser. First, the transient heat diffusion-based FEA was conducted by using the laser power intensity distribution as a time dependent heat source. This model calculates the temperature distribution within the substrates as a function of time. Next, the structural model predicts the amount of residual stresses developed in the joint system as it is cooled down to room temperature. The out-of-plane normal component of residual stresses was within the failure strength range of glass that may have caused fracture initiation in the substrate.     

Erucic acid content in some rapeseed/mustard cultivars developed in Bangladesh

Seed samples of 21 indigenous and developed rapeseed/mustard cultivars (Brassica campestris, B. juncea and B. napus) were characterized for their fatty acid composition. Erucic acid was one of the main fatty acids, in proportions ranging from 21.59 to 51.57% followed by oleic acid ranging from 7.03 to 25.21%. The other major monounsaturated fatty acid was gadoleic acid, which accounted for 4.12–12.06%. The major polyunsaturated fatty acids were linoleic and linolenic acid, ranging from 11.79 to 16.89% and 6.29 to 11.15%, respectively. Among the saturated fatty acids, palmitic acid accounted for 1.20–3.36%. Erucic acid content was negatively correlated with all other major fatty acids. The cultivars Binasarisha‐3, Binasarisha‐4, Binasarisha‐5, MM 22‐12‐98, MM 2‐16‐98, MM 36‐6‐98, MM 49‐3‐98, MM 34‐7‐98 and Barisarisha‐8 of B. napus had significantly (P < 0.001) low levels of erucic acid and high levels of oleic, linoleic and linolenic acids among all the cultivars. These four cultivars and five advanced generation mutant lines may be exploited in breeding programmes for the development of nutritionally better‐quality locally adaptive cultivars. Copyright © 2005 Society of Chemical Industry     

Biocompatibility assessment of next generation materials for brain implantable microelectrodes

Proper interfacing between the microelectrode device and the cells is very important for functional stimulation of brain; the microelectrodes need to be in close proximity to the cells. The materials currently being used in device or research (silicon, polymer, platinum) do not support neuronal attachment on their surfaces. Here, we investigated primary neuronal cell attachment on Pyrex glass, sapphire, and iridium oxide as promising alternative materials. Sapphire was found to be an excellent substrate to support neuron attachment in serum free condition. Using micro-patterning, sapphire was shown to have great potential as a substrate for next generation neural implants.     

Isotope Engineered Fluorinated Single and Bilayer Graphene: Insights into Fluorination Selectivity,Stability, and Defect Passivation

Tailoring the physicochemical properties of graphene through functionalization remains a major interest for next-generation technological applications. However, defect formation due to functionalization greatly endangers the intrinsic properties of graphene, which remains a serious concern. Despite numerous attempts to address this issue, a comprehensive analysis has not been conducted. This work reports a two-step fluorination process to stabilize the fluorinated graphene and obtain control over the fluorination-induced defects in graphene layers. The structural, electronic and isotope-mass-sensitive spectroscopic characterization unveils several not-yet-resolved facts, such as fluorination sites and C F bond stability in partially-fluorinated graphene (F-SLG). The stability of fluorine has been correlated to fluorine co-shared between two graphene layers in fluorinated-bilayer-graphene (F-BLG). The desorption energy of co-shared fluorine is an order of magnitude higher than the C F bond energy in F-SLG due to the electrostatic interaction and the inhibition of defluorination in the F-BLG. Additionally, F-BLG exhibits enhanced light–matter interaction, which has been utilized to design a proof-of-concept field-effect phototransistor that produces high photocurrent response at a time <200 µs. Thus, the study paves a new avenue for the in-depth understanding and practical utilization of fluorinated graphenic carbon.     

CoSe2@N-Doped Graphene Nanocomposite High-Efficiency Counter Electrode for Dye-Sensitized Solar Cells

Journal of Inorganic and Organometallic Polymers and Materials - In present study, CoSe2, and CoSe2@N-doped graphene nanocomposite has been prepared in an inert atmosphere and used as a DSSC...     

Dust and water splashing models for hopping figures

To enhance the realism of computer animation sequences, the interaction between autonomous creatures and their environment needs to be modelled. Two such commonly occurring phenomena, dust and water splashing on impact, are presented in this paper. These pseudodynamic models, based on particle system concepts, are designed for hoppers with approximately elliptical bases. The proposed models can be extended for use with multi‐legged creatures. The dust model is parameterized by creature dimensions, soil particle dimensions and wind direction. The splash model is parameterized by creature dimensions and water film thickness. Explicit control of behavioural parameters of both models is also provided to allow application‐specific usage. Copyright © 1999 John Wiley & Sons, Ltd.