Dynamically tunable phase shifter with commercial graphene nanoplatelets

In the microwave frequency band the conductivity of graphene can be varied to design a number of tunable components. A tunable phase shifter based on commercial graphene nanoplatelets is introduced. The proposed configuration consists of a microstrip line with two stubs connected with a taper. On each side of the stubs there is a gap, short circuited through a via, where the commercial graphene nanoplatelets are drop casted. By applying a DC bias voltage that alters the graphene resistance the phase of the transmitted signal through the microstrip line can be varied. In order to maximize the phase shift of the transmitted signal and minimize the insertion loss, the length of the taper and the stubs are optimized by the help of circuit model and full-wave simulations. A prototype working at 4GHz is fabricated and measured. A phase variation of 33 degrees is acquired with an amplitude variation of less than 0.4dB

Impact of Processing Costs on Service Chain Placement in Network Functions Virtualization

The Network Functions Virtualization (NFV) paradigm is the most promising technique to help network providers in the reduction of capital and energy costs. The deployment of virtual network functions (VNFs) running on generic x86 hardware allows higher flexibility than the classical middleboxes approach. NFV also reduces the complexity in the deployment of network services through the concept of service chaining, which defines how multiple VNFs can be chained together to provide a specific service. As a drawback, hosting multiple VNFs in the same hardware can lead to scalability issues, especially in the processing-resource sharing. In this paper, we evaluate the impact of two different types of costs that must be taken into account when multiple chained VNFs share the same processing resources: the upscaling costs and the context switching costs. Upscaling costs are incurred by VNFs multi-core implementations, since they suffer a penalty due to the needs of load balancing among cores. Context switching costs arise when multiple VNFs share the same CPU and thus require the loading/saving of their context. We model through an ILP problem the evaluation of such costs and we show their impact in a VNFs consolidation scenario, when the x86 hardware deployed in the network is minimized

Empathy and self-efficacy, and resiliency: an exploratory study of counseling students in Turkey

AbstractThe purpose of this study was to explore the degree of empathy, self-efficacy, and resiliency among first grade counseling students. Participants consisted of 132 students enrolled in guidance and psychological counseling programs at three different universities in Turkey. The participants completed the Interpersonal Reactivity Index, Self-Efficacy Scale, Resiliency Scale and Information Sheet. Results show that most of the participants preferred the department of psychological counselling and guidance in the first row in the university entrance exam. Students’ career preferences differentiated significantly according to gender

State Aggregation-based Model of Asynchronous Multi-Fiber Optical Switching with Shared Wavelength Converters

Cataloged from PDF version of article.This paper proposes new analytical models to study optical packet switching architectures with multi-fiber interfaces and shared wavelength converters. The multi-fiber extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and performance for asynchronous traffic. In addition to using Markov chains and fixed-point iterations for modeling the mono-fiber case, a novel state aggregation technique is proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy of the performance models is validated by comparison with simulations in a wide variety of scenarios with both balanced and imbalanced input traffic. The proposed analytical models are shown to remarkably capture the actual system behavior in all scenarios we tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in the number of wavelength converters employed and their range. In addition, the SPIW solution allows to save, in particular conditions, a significant number of optical gates compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential complexity and cost reduction compared to SPN, while providing similar performance. (C) 2013 Elsevier B.V. All rights reserved

Public Sector Reform in Estonia: Views and Experiences from Senior Executives

Introduction: Coordinating for Cohesion in the Public Sector of the Future (COCOPS), as one of the largest comparative public management research projects in Europe, intends to provide a comprehensive picture of the challenges facing the public sector in European countries and to systematically explore the impact of New Public Management (NPM)-style reforms in Europe. The project brings together public administration scholars from eleven universities in ten countries2 and is funded as part of the European Union’s 7th Framework Programme between January 2011 and June 2014.3 The research is comparative and evidence-based, drawing on both existing data and innovative new quantitative and qualitative data collection, at both national and policy sector levels. A cornerstone of the project is the COCOPS Executive Survey on Public Sector Reform in Europe: an original, large-scale survey of public sector top executives in ten European countries, exploring executives’ opinions and experiences with regards to public sector reforms in general government, as well as more particularly in the health and employment policy sectors. Scholars within the public administration discipline have long underlined the need for more quantitative and rigorous comparative research, going beyond single-country and single-organization approaches (see Derlien 1992; Fitzpatrick et al 2011; Pollitt 2011; Raadschelders and Lee 2011). Moreover, few research initiatives have explored in depth the transformation of public administrations as triggered by NPM reform discourses in a systematic comparative form (Van de Walle and Hammerschmid 2011). Responding to such concerns, this survey offers systematic evidence regarding the dynamics of public administration reform in Europe, with the goal to create an encompassing and systematic picture of public administration after more than two decades of NPM reforms

Evaluation of the Precision-Privacy Tradeoff of Data Perturbation for Smart Metering

Abstract: Smart grid users and standardization committees require that utilities and third parties collecting metering data employ techniques for limiting the level of precision of the gathered household measurements to a granularity no finer than what is required for providing the expected service. Data aggregation and data perturbation are two such techniques. This paper provides quantitative means to identify a tradeoff between the aggregation set size, the precision on the aggregated measurements, and the privacy level. This is achieved by formally defining an attack to the privacy of an individual user and calculating how much its success probability is reduced by applying data perturbation. Under the assumption of time-correlation of the measurements, colored noise can be used to even further reduce the success probability. The tightness of the analytical results is evaluated by comparing them to experimental data

Commercial graphene nanoplatelets-based tunable attenuator

A commercial graphene nanoplatelets based tunable attenuator is proposed. The attenuator comprises of a couple of microstrip lines connected through a gap where the commercial graphene nanoplatelets are drop casted. The transmitted signal through the microstrip line can be varied by an applied DC bias voltage that alters the graphene resistance. The DC resistance of commercially acquired graphene is higher than labgrown graphene and so is the resulting minimum attenuation of the transmitted signal. The proposed structure is designed to reduce both the minimum graphene resistance and the transmission. The resultant dynamic range of attenuation is more than twice as compared to other series attenuators designed with lab grown graphene nanoplatelets. The operating frequency of the attenuator is from 1 GHz to 5 GHz with maximum dynamic range of attenuation almost 10 dB

Risk assessment in avalanche-prone areas

AbstractThis paper addresses the problem of defining a proper method for formal risk analysis in avalanche-prone areas. In this study, risk is defined as the annual probability of being killed by an avalanche for someone living or working permanently in a building under a hazardous hillside. A new methodology to estimate the hazard component of avalanche risk based on the use of dynamic models is introduced. This approach seems to have some advantages over the current methods based on statistical analysis of historic avalanche data. The vulnerability component of risk is formulated as a function of avalanche velocity, according to previous formulations. However, given the lack of knowledge on how avalanche impact damages structures and causes fatalities, the effect on the resulting risk mapping of using different vulnerability relations is explored. The potential of the proposed approach for evaluating the residual risk after the implementation of defensive structural work is discussed

Energy-Efficient VoD content delivery and replication in integrated metro/access networks

Today's growth in the demand for access bandwidth is driven by the success of the Video-on-Demand (VoD) bandwidth-consuming service. At the current pace at which network operators increase the end users' access bandwidth, and with the current network infrastructure, a large amount of video traffic is expected to flood the core/metro segments of the network in the near future, with the consequent risk of congestion and network disruption. There is a growing body of research studying the migration of content towards the users. Further, the current trend towards the integration of metro and access segments of the network makes it possible to deploy Metro Servers (MSes) that may serve video content directly from the novel integrated metro/access segment to keep the VoD traffic as local as possible. This paper investigates a potential risk of this solution, which is the increase in the overall network energy consumption. First, we identify a detailed power model for network equipment and MSes, accounting for fixed and load-proportional contributions. Then, we define a novel strategy for controlling whether to switch MSes and network interfaces on and off so as to strike a balance between the energy consumption for content transport through the network and the energy consumption for processing and storage in the MSes. By means of simulations and taking into account real values for the equipment power consumption, we show that our strategy is effective in providing the least energy consumption for any given traffic load

Multi-Walled Carbon Nanotubes Composites for Microwave Absorbing Applications

The response of materials to impinging electromagnetic waves is mainly determined by their dielectric (complex permittivity) and magnetic (complex permeability). In particular, radar absorbing materials are characterized by high complex permittivity (and eventually large values of magnetic permeability), Indeed, energy dissipation by dielectric relaxation and carrier conduction are principally responsible for diminishing microwave radiation reflection and transmission in non-magnetic materials. Therefore, the scientific and technological community has been investigating lightweight composites with high dielectric permittivity in order to improve the microwave absorption (i.e., radar cross-section reduction) in structural materials for the aerospace industry. Multiwalled carbon nanotubes films and their composites with different kind of polymeric resins are regarded as promising materials for radar absorbing applications because of their high permittivity. Nanocomposites based on commercial multi-wall carbon nano-tube (MWCNT) fillers dispersed in an epoxy resin matrix were fabricated. The morphology of the filler was analyzed by Field emission scanning electron microscopy (FESEM) and Raman spectroscopy, while the complex permittivity and the radiation reflection coefficient of the composites was measured in the radio frequency range. The reflection coefficient of a single-layer structure backed by a metallic plate was simulated based on the measured permittivity. Simulation achievements were compared to the measured reflection coefficient. Besides, the influence of morphological MWCNT parameters (i.e., aspect ratio and specific surface area) on the reflection coefficient was evaluated. Results verify that relatively low weight percent of MWCNTs are suitable for microwave absorption applications when incorporated into polymer matrix (i.e., epoxy resin)