Remote analysis of a distributed WLAN using passive wireless-side measurement

This paper presents network traffic measurements from a campus-wide wireless LAN (WLAN), with the data collected using remote passive wireless-side measurement. We used commercially-available monitoring devices to collect wireless traffic concurrently from 9 selected locations on the campus WLAN for 6 weeks. The aggregate trace contains almost 1 billion wireless frames, representing the WLAN activity generated by 6775 users and 97 access points. Analysis of the dataset identifies similarities and differences in the user behaviours across the observed WLAN locations, as well as emerging trends in WLAN usage regarding application usage and session mobility. Our study extends existing WLAN measurement studies by providing deeper insights into how WLANs are used, and by developing models of WLAN usage characteristics that are applicable in capacity planning, network testing, and network simulation studies.     

Myxobacteria ‐mediated synthesis of silver nanoparticles and their impregnation in wrapping paper used for enhancing shelf life of apples

The authors report Myxobacteria virescens (M. virescens) mediated synthesis of silver nanoparticles (AgNPs) and its efficacy against Staphylococcus aureus (ATCC‐33591), Salmonella typhi (ATCC‐51812), Escherichia coli (E. coli) (ATCC‐14948), Klebsiella pneumoniae (MTCC‐4030) and Pseudomonas aeruginosa (MTCC‐4673). The organism exhibiting resistance to various antibiotics showed remarkable sensitivity, when used in combination of antibiotics and AgNPs. Antimicrobial property of AgNPs is playing a significant role in medicine and food storage. In this study, they have used M. virescens for the synthesis of AgNPs, which were characterised by using UV‐Vis spectrophotometer, nano‐particles tracking and analysis, zeta potential, Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy. Synthesised AgNPs were impregnated into paper by three different methods, i.e. glass rod method (without binder), glass rod method (with binder) and direct synthesis of AgNPs on paper. Nanoparticles synthesis on paper showed the significant antimicrobial activity against Staphylococcus aureus (ATCC‐33591), Salmonella typhi (ATCC‐51812), E. coli (ATCC‐14948), Klebsiella pneumoniae (MTCC‐4030) and Pseudomonas aeruginosa (MTCC‐4673). Paper impregnated with AgNPs was used for wrapping of fruits (apples) which increases their shelf life up to 15 days. This study demonstrates a new method for wrapping of fruits, which increases the shelf life of apples.Inspec keywords: microorganisms, biotechnology, nanoparticles, wrapping, food packaging, antibacterial activity, ultraviolet spectra, electrokinetic effects, Fourier transform infrared spectra, X‐ray diffraction, transmission electron microscopy, food productsOther keywords: silver nanoparticles, wrapping paper impregnation, apple shelf life enhancement, Myxobacteria virescens mediated synthesis, glass rod method, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared, zeta potential, nanoparticle analysis, nanoparticle tracking, UV‐Vis spectrophotometer, antimicrobial property, antibiotic resistance, MTCC‐4673, Pseudomonas aeruginosa, MTCC‐4030, Klebsiella pneumoniae, ATCC‐14948, E. coli, Escherichia coli, ATCC‐51812, Salmonella typhi, ATCC‐33591, Staphylococcus aureus, M. virescens mediated synthesis     

Process parameters optimization for micro end-milling operation for CAPP applications

In Computer Aided Process Planning (CAPP), process parameters selection for the given manufacturing feature is the final activity and it is the key area for research and development. In this work, an attempt has been made to optimize parameters for micro end-milling operation as a part of CAPP system development for micromachining processes using Artificial Intelligence (AI) approach. Genetic Algorithm (GA) has been found to be the robust and efficient tool to solve nonlinear optimization problems involved in process planning. Microfeatures of size 0.7 and 1 mm are considered and polymethyl methacrylate is chosen as the work material due to its potential application in microparts fabrication. Initially, experimental investigation has been carried out to analyze the impact of process conditions such as spindle speed and feed rate on surface roughness and machining time. Further multiobjective optimization for minimization of responses is carried out using GA. Finally, confirmation experiments are carried out to validate the accuracy of GA results. The optimized process parameters are stored in the database and it ensures foolproof parameters for micro end-milling operation for CAPP applications apart from manuals and catalogues. The proposed approach can be repeated for various other end mill features and for different work and tool material combination to ensure a complete parameters selection module for CAPP system applications.     

3D‐Architected Soft Machines with Topologically Encoded Motion

The limited range of mechanical responses achievable by materials compatible with additive manufacturing hinders the 3D printing of continuum soft robots with programmed motion. This paper describes the rapid design and fabrication of low‐density, 3D‐architected soft machines (ASMs) by combining Voronoi tessellation and additive manufacturing. On tendon‐based actuation, ASMs deform according to the topologically encoded buckling of their structure to produce a wide range of motions (contraction, twisting, bending, and cyclic motion). ASMs exhibiting densities as low as 0.094 g cm^?3 (≈8% of bulk polymer) can be rapidly built by the stereolithographic 3D printing of flexible photopolymers or the injection molding of elastomers. The buckling of ASMs can be programmed by inducing gradients in the thickness of their flexible beams or by the localized enlargement of the Voronoi cells to generate complex motions such as multi‐finger gripping or quadrupedal locomotion. The topological architecture of these low‐density soft robots confers them with the stiffness necessary to recover their original shape even after ultrahigh compression (400%) and extension (500%). ASMs expand the range of mechanical properties currently achievable by 3D printed or molded materials to enable the fabrication of soft machines with auxetic mechanical metamaterial properties.     

Polyvinylpyrrolidone modified barium zirconate titanate /polyvinylidene fluoride nanocomposites as self-powered sensor

Highly flexible biocompatible nanocomposites comprising of Polyvinylpyrrolidone (PVP) modified Barium Calcium Zirconate Titanate (BCT-BZT) /Polyvinylidene fluoride (PVDF) were fabricated. The crystalline BCT-BZT powders were synthesized by a simple sol-gel method. Rietveld refinement analysis confirmed the coexistence of orthorhombic and tetragonal phase in the synthesized powders. The structural, dielectric and ferroelectric properties of the composites were analysed. Addition of PVP modified BCT-BZT powders was observed to enhance the polar phase in PVDF matrix. The piezoelectric output response as a function of different weight percentage of ceramic powders in the PVDF matrix was investigated. The optimal device with 60?wt% PVP modified BCT-BZT powders exhibited maximum peak to peak voltage of 23?V when tested for harnessing waste biomechanical energy (human hand palm force). The nanogenerator was easily scaled up to 4?×?4?cm and the stored power was utilized for powering fifty five LEDs. The fabricated device is flexible, light- weight and eco-friendly. Therefore, it can be explored as a potential candidate for application as self powered sensor.     

Touchy feely vectors: A compensatory design approach to support model-based reasoning in developing country classrooms

Educational technology designs in developing countries mostly focus on making knowledge resources widely available, through MOOCs, repositories and computer-based tutoring. The use of digital media for cognitive augmentation, particularly interactive designs that help learners understand modelling topics in STEM, is underexplored. We report a 3-year design study examining this potential in the Indian context, testing two iterations of an interactive system, Touchy-Feely Vectors (TFV). The design supports learning vectors, a modelling topic pre-university students struggle with. Virtual lesson-plans were co-designed with teachers to augment — but not replace — their existing practices, and to address classroom and resource constraints. Pre-post testing of TFV-1 (a computer-based prototype) showed that it helped students develop a more integrated vector concept, and improved their reasoning. Field-implementation of TFV-2 (a textbook-linked touch-screen based design) in 6-classrooms (3-Control, N=135; 3-Experimental, N=131) showed that it fostered cognitive engagement in average-students and geometry-algebra integration (model-based reasoning) in good-students. These results, along with a requirements analysis based on textbooks, indicate that the interaction possibilities supported by different representational media critically shape student reasoning. The study also illustrates a systematic approach to design and test digital media systems that support cognitive augmentation in developing countries.     

Characterizing the file hosting ecosystem: A view from the edge

We present a comprehensive, longitudinal characterization study of the file hosting ecosystem using HTTP traces collected from a large campus network over a one-year period. We performed detailed multi-level analysis of the usage behavior, infrastructure properties, content characteristics, and user-perceived performance of the top five services in terms of traffic volume, namely RapidShare, Megaupload, zSHARE, MediaFire, and Hotfile. We carefully devised methods to identify user clickstreams in the HTTP traces, including the identification of free and premium user instances, as well as the identification of content that is split into multiple pieces and downloaded using multiple transactions. Throughout this characterization, we compare and contrast these services with each other as well as with peer-to-peer file sharing and other media sharing services.     

Generalizing cryptosystems based on the subset sum problem

We identify a generic construction of cryptosystems based on the subset sum problem and characterize the required homomorphic map. Using the homomorphism from the Damg?rd-Jurik cryptosystem, we then eliminate the need for a discrete logarithm oracle in the key generation step of the Okamoto et al. scheme to provide a practical cryptosystem based on the subset sum problem. We also analyze the security of our cryptosystem and show that with proper parameter choices, it is computationally secure against lattice-based attacks. Finally, we present a practical application of this system for RFID security and privacy.