Privacy Loss in Distributed Constraint Reasoning: A Quantitative Framework for Analysis and its Applications

It is critical that agents deployed in real-world settings, such as businesses, offices, universities and research laboratories, protect their individual users’ privacy when interacting with other entities. Indeed, privacy is recognized as a key motivating factor in the design of several multiagent algorithms, such as in distributed constraint reasoning (including both algorithms for distributed constraint optimization (DCOP) and distributed constraint satisfaction (DisCSPs)), and researchers have begun to propose metrics for analysis of privacy loss in such multiagent algorithms. Unfortunately, a general quantitative framework to compare these existing metrics for privacy loss or to identify dimensions along which to construct new metrics is currently lacking. This paper presents three key contributions to address this shortcoming. First, the paper presents VPS (Valuations of Possible States), a general quantitative framework to express, analyze and compare existing metrics of privacy loss. Based on a state-space model, VPS is shown to capture various existing measures of privacy created for specific domains of DisCSPs. The utility of VPS is further illustrated through analysis of privacy loss in DCOP algorithms, when such algorithms are used by personal assistant agents to schedule meetings among users. In addition, VPS helps identify dimensions along which to classify and construct new privacy metrics and it also supports their quantitative comparison. Second, the article presents key inference rules that may be used in analysis of privacy loss in DCOP algorithms under different assumptions. Third, detailed experiments based on the VPS-driven analysis lead to the following key results: (i) decentralization by itself does not provide superior protection of privacy in DisCSP/DCOP algorithms when compared with centralization; instead, privacy protection also requires the presence of uncertainty about agents’ knowledge of the constraint graph. (ii) one needs to carefully examine the metrics chosen to measure privacy loss; the qualitative properties of privacy loss and hence the conclusions that can be drawn about an algorithm can vary widely based on the metric chosen. This paper should thus serve as a call to arms for further privacy research, particularly within the DisCSP/DCOP arena.     

Research directions for service-oriented multiagent systems

Today's service-oriented systems realize many ideas from the research conducted a decade or so ago in multiagent systems. Because these two fields are so deeply connected, further advances in multiagent systems could feed into tomorrow's successful service-oriented computing approaches. This article describes a 15-year roadmap for service-oriented multiagent system research.     

Building agent teams using an explicit teamwork model and learning

Multi-agent collaboration or teamwork and learning are two critical research challenges in a large number of multi-agent applications. These research challenges are highlighted in RoboCup, an international project focused on robotic and synthetic soccer as a common testbed for research in multi-agent systems. This article describes our approach to address these challenges, based on a team of soccer-playing agents built for the simulation league of RoboCup—the most popular of the RoboCup leagues so far.To address the challenge of teamwork, we investigate a novel approach based on the (re)use of a domain-independent, explicit model of teamwork, an explicitly represented hierarchy of team plans and goals, and a team organization hierarchy based on roles and role-relationships. This general approach to teamwork, shown to be applicable in other domains beyond RoboCup, both reduces development time and improves teamwork flexibility. We also demonstrate the application of off-line and on-line learning to improve and specialize agents' individual skills in RoboCup. These capabilities enabled our soccer-playing team, ISIS, to successfully participate in the first international RoboCup soccer tournament (RoboCup'97) held in Nagoya, Japan, in August 1997. ISIS won the third-place prize in over 30 teams that participated in the simulation league.     

Modifications of Tapioca Starch Properties by Polyethylene Glycol (4000) and Polyethylene Glycol (4000) Stearate Additives

Changes in crystallinity, iodine binding capacity and infrared spectral characteristics of tapioca starch on incorporation of polyethylene glycol (4000) and polyethylene glycol (4000) distearate additives into gelatinised starch have been investigated. A plausible explanation for the appearance of crystallinity for gelatinised starch on incorporation of the additives is given. The additives were also shown to influence the gelatinisation temperature of native tapioca starch. The DSC studies indicating this effect are discussed in detail.     

Structure–property relationship studies in amine functionalized multiwall carbon nanotubes filled polypropylene composite fiber

Amine functionalized multiwalled carbon nanotubes (a‐MWNT) based polypropylene (PP) composite fibers were prepared in the presence of polypropylene‐g‐maleic anhydride (PP‐g‐MA) by melt‐mixing followed by melt‐spinning with subsequent post‐drawing of the as‐spun fibers of varying draw ratio (DR). In order to enhance the interfacial interaction, a‐MWNT were utilized in combination with PP‐g‐MA during melt‐mixing. Fourier transform infrared spectroscopic analysis revealed the formation of imide bonds between MA functionality of PP‐g‐MA and amine functional group of a‐MWNT. Higher tensile properties of PP/a‐MWNT/PP‐g‐MA composite fibers were registered with varying DR of the as‐spun fiber. Orientation factors of a‐MWNT and PP chains along the fiber axis were correlated with the higher tensile modulus and tensile strength of PP/a‐MWNT/PP‐g‐MA composite fiber of varying DR. Crystallization studies indicated the role of hetero‐nucleating action of a‐MWNT in PP/a‐MWNT/PP‐g‐MA composite fiber. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Compact high-gain composite horn antenna for space-borne beacon application

ABSTRACT

The growing interest in higher capacity communications satellite necessitates the development of compact and lightweight other antennas (such as beacon horn antenna) at Earth-viewing deck due to crowded accommodation and weight limitation. In this article, we describe an innovative and compact high-gain composite horn antenna for space-borne beacon application. We have designed, manufactured and measured beacon horn antenna operating from 10.7 GHz to 12.5 GHz. The beacon horn antenna is devised by combining stepped section at input, axial corrugated in mid and finally radial corrugated sections. This engineered multiple sections provide extra flexibility of optimisation, leading to high edge of coverage (EoC) gain for Indian mainland, Lakshadweep Islands and Andaman & Nicobar Islands. The radial corrugated section is specially profiled using multi-profile subsections. The mode-matching technique (MMT)-based software CHAMP and ‘minimax optimiser’ have been used to analyse and optimise the Beacon horn antenna. Manufacturing of the horn using a turning machine over aluminium alloy helps to reduce its cost. Characterisation of the beacon antenna confirm predicted electrical results (return loss> 17 dB, cross-polarisation discrimination < ?40 dB, EoC gain > 24 dB). The Accommodation of the Ku-Beacon antenna on spacecraft is discussed with help of its near field from the scattering point of view and its tilt.     

High-Performance Photodetector and Angular-Dependent Random Lasing from Long-Chain Organic Diammonium Sandwiched 2D Hybrid Perovskite Non-Linear Optical Single Crystal

3D organic-inorganic metal halide perovskites are excellent materials for optoelectronic applications due to their exceptional properties, solution processability, and cost-effectiveness. However, the lack of environmental stability highly restricts them from practical applications. Herein, a stable centimeter-long 2D hybrid perovskite (N-MPDA)[PbBr₄] single crystal using divalent N1-methylpropane-1,3-diammonium (N-MPDA) cation as an organic spacer, is reported. The as-grown single crystal exhibits stable optoelectronic performance, low threshold random lasing, and multi-photon luminescence/multi-harmonic generation. A photoconductive device fabricated using (N-MPDA)[PbBr₄] single crystal exhibits an excellent photoresponsivity (≈124 AW⁻¹ at 405 nm) that is ≈4 orders of magnitudes higher than that of monovalent organic spacer-assisted 2D perovskites, such as (BA)₂PbBr₄ and (PEA)₂PbBr₄, and large specific detectivity (≈10¹² Jones). As an optical gain media, the (N-MPDA)[PbBr₄] single crystal exhibits a low threshold random lasing (≈6.5 µJ cm⁻²) with angular dependent narrow linewidth (≈0.1 nm) and high-quality factor (Q ≈ 2673). Based on these results, the outstanding optoelectronic merits of (N-MPDA)[PbBr₄] single crystal will offer a high-performance device and act as a dynamic material to construct stable future electronics and optoelectronic-based applications.     

Investigation of effect of protonic acid media on the optical and thermal properties of chemically synthesized poly(o-toluidine)

Conducting polymer, Poly(o-toluidine) was synthesized by chemical oxidative polymerization method using different inorganic acids such as HCl, H₂SO₄, HClO₄, HNO₃, H₃PO₄ and H₃BO₃ as protonic acid media. Synthesized polymers were characterized by UV-Visible and FT-IR spectroscopy. Conducting emeraldine salt phase of the polymer has been confirmed with the help of spectroscopic analysis. Thermal stability of these polymers were investigated by thermogravimetric (TG/SDTA) analysis. Increase in conductivity with increase in temperature was observed in all the samples.     

Nanoscale friction and wear maps

Friction and wear are part and parcel of all walks of life, and for interfaces that are in close or near contact, tribology and mechanics are supremely important. They can critically influence the efficient functioning of devices and components. Nanoscale friction force follows a complex nonlinear dependence on multiple, often interdependent, interfacial and material properties. Various studies indicate that nanoscale devices may behave in ways that cannot be predicted from their larger counterparts. Nanoscale friction and wear mapping can help identify some 'sweet spots' that would give ultralow friction and near-zero wear. Mapping nanoscale friction and wear as a function of operating conditions and interface properties is a valuable tool and has the potential to impact the very way in which we design and select materials for nanotechnology applications.     

Aerobic in-vessel composting versus bioreactor landfilling using life cycle inventory models

Potential environmental impacts associated with aerobic in-vessel composting and bioreactor landfilling were assessed using life cycle inventory (LCI) tool. LCI models for solid waste management (SWM) were also developed and used to compare environmental burdens of alternative SWM scenarios. Results from the LCI models showed that the estimated energy recovery from bioreactor landfilling was about 9.6 megajoules (MJ) per kilogram (kg) of waste. Air emissions from in-vessel composting contributed to a global warming potential (GWP) of 0.86 kg of CO₂-equivalent per kg of waste, compared to 1.54 kg of CO₂-equivalent from bioreactor landfill. Waterborne emissions contributing to aquatic toxicity is less coming from in-vessel composting than from bioreactor landfilling. However, emissions to air and water that contribute to human toxicity are greater for the composting option than for the landfill option. Full costs for in-vessel composting is about 6 times greater than for the landfilling alternative. Integration of individually collected commingled recyclables, yard wastes, and residual wastes with windrow composting and bioreactor landfilling produces airborne and waterborne emissions with the least environmental effects among the alternatives considered. It also yields greater energy savings due to the conversion of the landfill gas (LFG) to electrical energy than the option that diverts yard waste, food waste and soiled paper for aerobic in-vessel composting. However, this scenario costs 68% more than that where the commingled collection of wastes is integrated with in-vessel composting and conventional landfilling, owing to increased collection costs.