A Formulation of the Potential for Communication Condition using C2KA

An integral part of safeguarding systems of communicating agents from covert channel communication is having the ability to identify when a covert channel may exist in a given system and which agents are more prone to covert channels than others. In this paper, we propose a formulation of one of the necessary conditions for the existence of covert channels: the potential for communication condition. Then, we discuss when the potential for communication is preserved after the modification of system agents in a potential communication path. Our approach is based on the mathematical framework of Communicating Concurrent Kleene Algebra (C2KA). While existing approaches only consider the potential for communication via shared environments, the approach proposed in this paper also considers the potential for communication via external stimuli.Comment: In Proceedings GandALF 2014, arXiv:1408.556

Exponential and power-law renormalization in phonon-assisted tunneling

We investigate the spinless Anderson-Holstein model routinely employed to describe the basic physics of phonon-assisted tunneling in molecular devices. Our focus is on small to intermediate electron-phonon coupling; we complement a recent strong coupling study [Phys.~Rev.~B {87}, 075319 (2013)]. The entire crossover from the antiadiabatic regime to the adiabatic one is considered. Our analysis using the essentially analytical functional renormalization group approach backed-up by numerical renormalization group calculations goes beyond lowest order perturbation theory in the electron-phonon coupling. In particular, we provide an analytic expression for the effective tunneling coupling at particle-hole symmetry valid for all ratios of the bare tunnel coupling and the phonon frequency. It contains the exponential polaronic as well as the power-law renormalization; the latter can be traced back to x-ray edge-like physics. In the antiadiabatic and the adiabatic limit this expression agrees with the known ones obtained by mapping to an effective interacting resonant level model and lowest order perturbation theory, respectively. Away from particle-hole symmetry, we discuss and compare results from several approaches for the zero temperature electrical conductance of the model.Comment: 11 pages, 6 figures, Published versio

Influence of phonon-assisted tunneling on the linear thermoelectric transport through molecular quantum dots

We investigate the effect of vibrational degrees of freedom on the linear thermoelectric transport through a single-level quantum dot described by the spinless Anderson-Holstein impurity model. To study the effects of strong electron-phonon coupling, we use the nonperturbative numerical renormalization group approach. We also compare our results, at weak to intermediate coupling, with those obtained by employing the functional renormalization group method, finding good agreement in this parameter regime. When applying a gate voltage at finite temperatures, the inelastic scattering processes, induced by phonon-assisted tunneling, result in an interesting interplay between electrical and thermal transport. We explore different parameter regimes and identify situations for which the thermoelectric power as well as the dimensionless figure of merit are significantly enhanced via a Mahan-Sofo type of mechanism. We show, in particular, that this occurs at strong electron-phonon coupling and in the antiadiabatic regime.Comment: 14 pages, 8 figures, Published versio

Nonequilibrium thermoelectric transport through vibrating molecular quantum dots

We employ the functional renormalization group to study the effects of phonon-assisted tunneling on the nonequilibrium steady-state transport through a single level molecular quantum dot coupled to electronic leads. Within the framework of the spinless Anderson-Holstein model, we focus on small to intermediate electron-phonon couplings, and we explore the evolution from the adiabatic to the antiadiabatic limit and also from the low-temperature non-perturbative regime to the high temperature perturbative one. We identify the phononic signatures in the bias-voltage dependence of the electrical current and the differential conductance. Considering a temperature gradient between the electronic leads, we further investigate the interplay between the transport of charge and heat. Within the linear response regime, we compare the temperature dependence of various thermoelectric coefficients to our earlier results obtained within the numerical renormalization group [Phys.~Rev.~B {\bf 96}, 195156 (2017)]. Beyond the linear response regime, in the context of thermoelectric generators, we discuss the influence of molecular vibrations on the output power and the efficiency. We find that the molecular energy dissipation, which is inevitable in the presence of phonons, is significantly suppressed in the antiadiabatic limit resulting in the enhancement of the thermoelectric efficiency.Comment: 11 pages, 7 figures, Published versio

The Role of Web 2.0 Technologies in Empowering Librarians: The Case Study of University Libraries in Iran

The present study aims to investigate the impact of Web 2.0 technologies on empowering the librarians of the Isfahan University of Medical Sciences and the University of Isfahan libraries. This applied research was conducted using a survey method. The population of the study consisted of 135 librarians in the the Isfahan University of Medical Sciences and the University of Isfahan libraries in Iran. Due to the limited number of participants, data were collected from the whole population and sampling was not carried out. Two questionnaires for assessing the Web 2.0 Library Tools and empowerment of staff were utilized to collect data. The analysis of the data was performed using descriptive and inferential statistical tests such as Kolmograph-Smirnov, Friedman, Pearson Correlation Coefficient, and Univariate Linear Regression in SPSS software version 22. The results revealed a statistically significant positive relationship between the use of Web 2.0 technologies and the empowerment of librarians (r=0.835). Also, statistically significant positive relationships were found between the use of Web 2.0 technologies and different dimensions of empowerment (i.e. independence and freedom of work, professional development and progress, self-control, Job satisfaction, and responsibility), with professional development and progress dimension had the highest (r=0.678, p=0.000) and independence and freedom of work had the lowest correlation (r=0.423, p=000) with the use of Web 2.0 technologies. The use of Web 2.0 technologies has also a statistically significant positive relationship with the librarians’ level of education (r=0.863, p=0.000) and their participation in training instructional courses on Web 2.0 and academic libraries (r=0.749, p=0.000)

Markov Chain Monte Carlo Methods for Exact Tests in Contingency Tables

This thesis is mainly concerned with conditional inference for contingency tables, where the MCMC method is used to take a sample of the conditional distribution. One of the most common models to be investigated in contingency tables is the independence model. Classic test statistics for testing the independence hypothesis, Pearson and likelihood chi-square statistics rely on large sample distributions. The large sample distribution does not provide a good approximation when the sample size is small. The Fisher exact test is an alternative method which enables us to compute the exact p-value for testing the independence hypothesis. For contingency tables of large dimension, the Fisher exact test is not practical as it requires counting all tables in the sample space. We will review some enumeration methods which do not require us to count all tables in the sample space. However, these methods would also fail to compute the exact p-value for contingency tables of large dimensions. \cite{DiacStur98} introduced a method based on the Grobner basis. It is quite complicated to compute the Grobner basis for contingency tables as it is different for each individual table, not only for different sizes of table. We also review the method introduced by \citet{AokiTake03} using the minimal Markov basis for some particular tables. \cite{BuneBesa00} provided an algorithm using the most fundamental move to make the irreducible Markov chain over the sample space, defining an extra space. The algorithm is only introduced for $2\times J \times K$ tables using the Rasch model. We introduce direct proof for irreducibility of the Markov chain achieved by the Bunea and Besag algorithm. This is then used to prove that \cite{BuneBesa00} approach can be applied for some tables of higher dimensions, such as $3\times 3\times K$ and $3\times 4 \times 4$. The efficiency of the Bunea and Besag approach is extensively investigated for many different settings such as for tables of low/moderate/large dimensions, tables with special zero pattern, etc. The efficiency of algorithms is measured based on the effective sample size of the MCMC sample. We use two different metrics to penalise the effective sample size: running time of the algorithm and total number of bits used. These measures are also used to compute the efficiency of an adjustment of the Bunea and Besag algorithm which show that it outperforms the the original algorithm for some settings

Interactive metadiscourse in dentistry research articles: Iranian vs non-Iranian academic writers

Linguistically, interactive metadiscourse devices are responsible for creating an unfolding and persuasive piece of writing. They help writers come up with a cohesive and reader-friendly text and highlight how they control the interactive meaning. This corpus-driven study is an attempt to explore the use of interactive metadiscourse markers in English dentistry research articles published in International ISI-indexed and Iranian local research-based journals. The aim was to see if interactive resources, as realized by rhetorical options, such as transitions, code glosses, endophoric markers, evidentials, and frame markers, are predisposed to discipline-specific rhetorical conventions. To this end, fourty dentistry research articles were analyzed using Hyland’s (2005) Interpersonal Model of Metadiscourse. The results disclosed similarities and differences in both the frequency and use of interactive resources between the two sets of research articles. The present results are expected to extend our understanding of authorial preferences for the use of metadiscourse markers in tandem with discourse functions in research articles in the selected discipline. The results of such studies may also improve different features of language pedagogy, such as teaching and learning academic writing, namely research articles