Physical Layer Security with Threshold-Based Multiuser Scheduling in Multi-antenna Wireless Networks

In this paper, we consider a multiuser downlink wiretap network consisting of one base station (BS) equipped with AA antennas, NB single-antenna legitimate users, and NE single-antenna eavesdroppers over Nakagami-m fading channels. In particular, we introduce a joint secure transmission scheme that adopts transmit antenna selection (TAS) at the BS and explores threshold-based selection diversity (tSD) scheduling over legitimate users to achieve a good secrecy performance while maintaining low implementation complexity. More specifically, in an effort to quantify the secrecy performance of the considered system, two practical scenarios are investigated, i.e., Scenario I: the eavesdropper’s channel state information (CSI) is unavailable at the BS, and Scenario II: the eavesdropper’s CSI is available at the BS. For Scenario I, novel exact closed-form expressions of the secrecy outage probability are derived, which are valid for general networks with an arbitrary number of legitimate users, antenna configurations, number of eavesdroppers, and the switched threshold. For Scenario II, we take into account the ergodic secrecy rate as the principle performance metric, and derive novel closed-form expressions of the exact ergodic secrecy rate. Additionally, we also provide simple and asymptotic expressions for secrecy outage probability and ergodic secrecy rate under two distinct cases, i.e., Case I: the legitimate user is located close to the BS, and Case II: both the legitimate user and eavesdropper are located close to the BS. Our important findings reveal that the secrecy diversity order is AAmA and the slope of secrecy rate is one under Case I, while the secrecy diversity order and the slope of secrecy rate collapse to zero under Case II, where the secrecy performance floor occurs. Finally, when the switched threshold is carefully selected, the considered scheduling scheme outperforms other well known existing schemes in terms of the secrecy performance and complexity tradeoff

Rethinking the Eclectic Paradigm: Explaining MNE E-Commerce Corporations' Activity in the Chinese Digital Sector

We use the eclectic paradigm as an analytical framework to explain the MNE e-commerce company’s activities in China. Grounded in the rich data, we argue that the dynamic interplay between the ownership advantage and local institutional context that have emerged—particularly in the information age—plays a significant role in explaining the trajectory of MNE e-commerce companies in China. We propose On, Ln and In by embedding network-based advantages within the OLI paradigm. With the acceleration of technological change and non-ergodic uncertainty, such a network-embedded eclectic paradigm will lead to MNE e-commerce companies’ sustainable development in the emerging economy.

The use of motivational interviews by nurses to promote health behaviors in adolescents: A scoping review protocol

Abstract The developmental changes during adolescence may affect subsequent risk for diseases and health-related behaviors. Motivational Interview (MI) may be taken as an essential tool in the provision of nursing care to adolescents, being itself a workspace with possible therapeutic effects. At this context, it is important to examine and map the use of MI by nurses in their clinical practice with adolescents to promote health behaviors. Objetives A scoping review has been currently undertaking to find out what is the current extent of the use of nurse-led MI; which adolescent populations were included; in which contexts nurses use MI; which MI techniques/strategies have been used and what outcomes on health behaviors promotion have been reported. The first task was to develop a search strategy to identify relevant studies for this review. It is described here the experience in constructing a search strategy for this review. Methodology This scoping review will be informed by JBI methodology. An initial search of MEDLINE and CINAHL was undertaken. An analysis of the text words contained in the title and abstract, and of the index terms used to describe the searched articles were retrieved and these were then used to construct a search strategy for use in Medline and Cinahl. Results Analysis of the text words and the index terms generated 19 keywords: It was identified 5 synonyms for "Adolescents", 12 for "MI" and 2 for "nurse". A new research formula was designed using the text words identified. Adolescen*[Title/Abstract]) OR Younger*[Title/Abstract]) OR Youth*[Title/Abstract]) OR Teen*[Title/Abstract]) OR Adolescent[MeSH Terms])) AND (((((((((((("Motivational interview"[Title/Abstract]) OR "Motivational intervention"[Title/Abstract]) OR "Motivational interviews"[Title/Abstract]) OR "Motivational interventions"[Title/Abstract]) OR "motivational interviewing"[Title/Abstract]) OR "motivational counseling"[Title/Abstract]) OR "motivational support"[Title/Abstract]) OR "Motivational enhancement"[Title/Abstract]) OR "Brief intervention"[Title/Abstract]) OR "Brief interventions"[Title/Abstract]) OR Motivational Interviewing[MeSH Terms]) OR Directive Counseling[MeSH Terms])) AND ((nurs*[Text Word]) OR Nurses[MeSH Terms]). Limiters - Language: English, Portuguese, Spanish. In MEDLINE this research formula generated 125 results. Other 16 databases referenced at the protocol will be searched to identify additional studies. Articles identified from the final search will be assessed for relevance to the review, based on information provided in the title and abstract. The full article will be retrieved for all studies that meet the inclusion criteria of the review. Conclusions It was presented here the initial results of this search. Next steps of this study will be to develop and refine the search strategy for use in other databases. It is expected that findings from this Scoping Review provide needed information to nurses related to the use of MI to promote health behaviors in adolescents and inform opportunities for future development in nursing practice.

Shape and chemically anisotropic colloidal particles: A theoretical study of their structure, phase behavior, and slow dynamics

A detailed non-equilibrium state diagram of shape-anisotropic particle fluids is constructed. The effects of particle shape are explored using Naive Mode Coupling Theory (NMCT), and a single particle Non-linear Langevin Equation (NLE) theory. The dynamical behavior of non-ergodic fluids are discussed. We employ a rotationally frozen approach to NMCT in order to determine a transition to center of mass (translational) localization. Both ideal and kinetic glass transitions are found to be highly shape dependent, and uniformly increase with particle dimensionality. The glass transition volume fraction of quasi 1- and 2- dimensional particles fall monotonically with the number of sites (aspect ratio), while 3-dimensional particles display a non-monotonic dependence of glassy vitrification on the number of sites. Introducing interparticle attractions results in a far more complex state diagram. The ideal non-ergodic boundary shows a glass-fluid-gel re-entrance previously predicted for spherical particle fluids. The non-ergodic region of the state diagram presents qualitatively different dynamics in different regimes. They are qualified by the different behaviors of the NLE dynamic free energy. The caging dominated, repulsive glass regime is characterized by long localization lengths and barrier locations, dictated by repulsive hard core interactions, while the bonding dominated gel region has short localization lengths (commensurate with the attraction range), and barrier locations. There exists a small region of the state diagram which is qualified by both glassy and gel localization lengths in the dynamic free energy. A much larger (high volume fraction, and high attraction strength) region of phase space is characterized by short gel-like localization lengths, and long barrier locations. The region is called the attractive glass and represents a 2-step relaxation process whereby a particle first breaks attractive physical bonds, and then escapes its topological cage. The dynamic fragility of fluids are highly particle shape dependent. It increases with particle dimensionality and falls with aspect ratio for quasi 1- and 2- dimentional particles. An ultralocal limit analysis of the NLE theory predicts universalities in the behavior of relaxation times, and elastic moduli. The equlibrium phase diagram of chemically anisotropic Janus spheres and Janus rods are calculated employing a mean field Random Phase Approximation. The calculations for Janus rods are corroborated by the full liquid state Reference Interaction Site Model theory. The Janus particles consist of attractive and repulsive regions. Both rods and spheres display rich phase behavior. The phase diagrams of these systems display fluid, macrophase separated, attraction driven microphase separated, repulsion driven microphase separated and crystalline regimes. Macrophase separation is predicted in highly attractive low volume fraction systems. Attraction driven microphase separation is charaterized by long length scale divergences, where the ordering length scale determines the microphase ordered structures. The ordering length scale of repulsion driven microphase separation is determined by the repulsive range. At the high volume fractions, particles forgo the enthalpic considerations of attractions and repulsions to satisfy hard core constraints and maximize vibrational entropy. This results in site length scale ordering in rods, and the sphere length scale ordering in Janus spheres, i.e., crystallization. A change in the Janus balance of both rods and spheres results in quantitative changes in spinodal temperatures and the position of phase boundaries. However, a change in the block sequence of Janus rods causes qualitative changes in the type of microphase ordered state, and induces prominent features (such as the Lifshitz point) in the phase diagrams of these systems. A detailed study of the number of nearest neighbors in Janus rod systems reflect a deep connection between this local measure of structure, and the structure factor which represents the most global measure of order.

Minimalist Hardware Architectures for Agent Tracking and Guidance

The philosophy of minimalism in robotics promotes gaining an understanding of sensing and computational requirements for solving a task. This minimalist approach lies in contrast to the common practice of first taking an existing sensory motor system, and only afterwards determining how to apply the robotic system to the task. While it may seem convenient to simply apply existing hardware systems to the task at hand, this design philosophy often proves to be wasteful in terms of energy consumption and cost, along with unnecessary complexity and decreased reliability. While impressive in terms of their versatility, complex robots such as the PR2 (which cost hundreds of thousands of dollars) are impractical for many common applications. Instead, if a specific task is required, sensing and computational requirements can be determined specific to that task, and a clever hardware implementation can be built to accomplish the task. Since this minimalist hardware would be designed around accomplishing the specified task, significant reductions in hardware complexity can be obtained. This can lead to huge advantages in battery life, cost, and reliability. Even if cost is of no concern, battery life is often a limiting factor in many applications. Thus, a minimalist hardware system is critical in achieving the system requirements. In this thesis, we will discuss an implementation of a counting, tracking, and actuation system as it relates to ergodic bodies to illustrate a minimalist design methodology.

Obtenção de óxidos a base de níquel e cobalto para reação de oxidação parcial do metano

Nickel-based catalysts supported on alumina have been widely used in various reactions to obtain synthesis gas or hydrogen. Usually, higher conversion levels are obtained by these catalysts, however, the deactivation by coke formation and sintering of metal particles are still problems to be solved. Several approaches have been employed in order to minimize these problems, among which stands out in recent years the use of additives such as oxides of alkali metals and rare earths. Similarly, the use of methodologies for the synthesis faster, easier, applicable on an industrial scale and to allow control of the microstructural characteristics of these catalysts, can together provide the solution to this problem. In this work, oxides with spinel type structure AB2O4, where A represents divalent cation and B represents trivalent cations are an important class of ceramic materials investigated worldwide in different fields of applications. The nickel cobaltite (NiCo2O4) was oxides of spinel type which has attracted considerable interest due to its applicability in several areas, such as chemical sensors, flat panel displays, optical limiters, electrode materials, pigments, electrocatalysis, electronic ceramics, among others. The catalyst precursor NiCo2O4 was prepared by a new chemical synthesis route using gelatine as directing agent. The polymer resin obtained was calcined at 350°C. The samples were calcined at different temperatures (550, 750 and 950°C) and characterized by X ray diffraction, measurements of specific surface area, temperature programmed reduction and scanning electron microscopy. The materials heat treated at 550 and 750°C were tested in the partial oxidation of methane. The set of techniques revealed, for solid preparations, the presence of the phase of spinel-type structure with the NiCo2O4 NixCo1-xO solid solution. This solid solution was identified by Rietveld refinement at all temperatures of heat treatment. The catalyst precursors calcined at 550 and 750°C showed conversion levels around 25 and 75%, respectively. The reason H2/CO was around 2 to the precursor treated at 750°C, proposed reason for the reaction of partial oxidation of methane, one can conclude that this material can be shown to produce synthesis gas suitable for use in the synthesis Fischer-Tropsch process

I. Quantal effects in biochemical cooperativity and a proposed mechanism for the differentiation of calcium signaling in synaptic plasticity. II. Evolutionary algorithms for the optimization of methods in computational chemistry

In Part 1 of this thesis, we propose that biochemical cooperativity is a fundamentally non-ideal process. We show quantal effects underlying biochemical cooperativity and highlight apparent ergodic breaking at small volumes. The apparent ergodic breaking manifests itself in a divergence of deterministic and stochastic models. We further predict that this divergence of deterministic and stochastic results is a failure of the deterministic methods rather than an issue of stochastic simulations.

Ergodic breaking at small volumes may allow these molecular complexes to function as switches to a greater degree than has previously been shown. We propose that this ergodic breaking is a phenomenon that the synapse might exploit to differentiate Ca$^{2+}$ signaling that would lead to either the strengthening or weakening of a synapse. Techniques such as lattice-based statistics and rule-based modeling are tools that allow us to directly confront this non-ideality. A natural next step to understanding the chemical physics that underlies these processes is to consider \textit{in silico} specifically atomistic simulation methods that might augment our modeling efforts.

In the second part of this thesis, we use evolutionary algorithms to optimize \textit{in silico} methods that might be used to describe biochemical processes at the subcellular and molecular levels. While we have applied evolutionary algorithms to several methods, this thesis will focus on the optimization of charge equilibration methods. Accurate charges are essential to understanding the electrostatic interactions that are involved in ligand binding, as frequently discussed in the first part of this thesis.

Radio Frequency Superconducting Quantum Interference Device Meta-atoms and Metamaterials: Experiment, Theory, and Analysis

Metamamterials are 1D, 2D or 3D arrays of articial atoms. The articial atoms, called "meta-atoms", can be any component with tailorable electromagnetic properties, such as resonators, LC circuits, nano particles, and so on. By designing the properties of individual meta-atoms and the interaction created by putting them in a lattice, one can create a metamaterial with intriguing properties not found in nature. My Ph. D. work examines the meta-atoms based on radio frequency superconducting quantum interference devices (rf-SQUIDs); their tunability with dc magnetic field, rf magnetic field, and temperature are studied. The rf-SQUIDs are superconducting split ring resonators in which the usual capacitance is supplemented with a Josephson junction, which introduces strong nonlinearity in the rf properties. At relatively low rf magnetic field, a magnetic field tunability of the resonant frequency of up to 80 THz/Gauss by dc magnetic field is observed, and a total frequency tunability of 100% is achieved. The macroscopic quantum superconducting metamaterial also shows manipulative self-induced broadband transparency due to a qualitatively novel nonlinear mechanism that is different from conventional electromagnetically induced transparency (EIT) or its classical analogs. A near complete disappearance of resonant absorption under a range of applied rf flux is observed experimentally and explained theoretically. The transparency comes from the intrinsic bi-stability and can be tuned on/ off easily by altering rf and dc magnetic fields, temperature and history. Hysteretic in situ 100% tunability of transparency paves the way for auto-cloaking metamaterials, intensity dependent filters, and fast-tunable power limiters. An rf-SQUID metamaterial is shown to have qualitatively the same behavior as a single rf-SQUID with regards to dc flux, rf flux and temperature tuning. The two-tone response of self-resonant rf-SQUID meta-atoms and metamaterials is then studied here via intermodulation (IM) measurement over a broad range of tone frequencies and tone powers. A sharp onset followed by a surprising strongly suppressed IM region near the resonance is observed. This behavior can be understood employing methods in nonlinear dynamics; the sharp onset, and the gap of IM, are due to sudden state jumps during a beat of the two-tone sum input signal. The theory predicts that the IM can be manipulated with tone power, center frequency, frequency difference between the two tones, and temperature. This quantitative understanding potentially allows for the design of rf-SQUID metamaterials with either very low or very high IM response.

O Emprego Operacional das Unidades de Reconhecimento Blindado na Guerra de África (1961-1975)

Com esta investigação pretende-se avaliar se as missões, a organização, os sistemas de armas, a instrução ou o treino das Unidades de reconhecimento, originalmente vocacionadas para atuar em operações convencionais, se constituíram como fatores limitadores do seu emprego na Guerra de África. Na realização desta investigação foi feito um estudo pormenorizado dos fatores em cima referidos. Quanto às missões, organização, instrução e treino foi realizado um estudo comparativo entre aquilo que existia, e que era praticado, com aquilo que foi executado e utilizado na guerra de África. Este estudo pretendia perceber as diferenças que existiram, e se estas foram de facto uma influência limitadora ao emprego destas unidades. Quanto aos sistemas de armas, foram analisados aqueles que foram empregues em África, pretendendo-se assim perceber quais é que foram as restrições destes sistemas. Para a realização desta investigação utilizamos o procedimento histórico e comparativo para realizarmos à comparação entre aquilo que existia e o que se executou no terreno, nos fatores missões, organização e instrução e treino. Na análise dos sistemas de armas utilizámos o procedimento histórico para a enumeração dos sistemas empregues e suas limitações. No final do estudo de cada fator deduzimos mediante os dados que foram sendo apresentados, se estes foram limitadores ao emprego destas unidades. Na recolha de dados utilizámos a pesquisa documental para a consulta de Quadros Orgânicos (QO), relatórios das unidades, relatórios das regiões militares, bem como manuais doutrinários das unidades de reconhecimento blindado. Utilizámos também a pesquisa bibliográfica para a consulta de teses sobre o reconhecimento blindado, artigos da Revista da Cavalaria, resenhas das campanhas de África, bem como livros alusivos à subversão e às campanhas de África. No final deste trabalho verificámos que os sistemas de armas foram a maior limitação destas unidades, pelo simples facto de terem influenciado todos os outros fatores em análise. Contudo vemos que as razões desta influência sobre os outros fatores poderiam verificar-se em qualquer tipo de conflito, visto serem derivadas dos problemas de sustentação das viaturas. Realmente existiram pequenas limitações em todos os fatores de análise neste conflito, em relação ao convencional, sendo que nos parece que foram contornadas com dedicação, e capacidade de improvisação das forças Portuguesas, para as ultrapassar.

The use of motivational interviews by nurses to promote health behaviors in adolescents: developing a search strategy for this review

Introduction: The developmental changes during adolescence may affect subsequent risk for diseases and health-related behaviors. Motivational Interview (MI) may be taken as an essential tool in the provision of nursing care to adolescents, being itself a workspace with possible therapeutic effects. At this context, it is important to examine and map the use of MI by nurses in their clinical practice with adolescents to promote health behaviors. Objectives: A scoping review has been undertaking to find out what is the current extent of the use of nurse-led MI; which adolescents were included; in which contexts nurses use MI; which MI techniques/strategies are used and what outcomes have been reported. The first task was to develop a search strategy to identify relevant studies for this review. It is described here the experience in constructing the search strategy review. Methodology: This scoping review will be informed by JBI methodology. An initial search of MEDLINE and CINAHL was undertaken. An analysis of the text words contained in the title and abstract, and of the index terms used to describe the searched articles were retrieved and these were then used to construct a search strategy for use in Medline and Cinahl. Results: Analysis of the text words and the index terms generated 19 keywords: It was identified 5 synonyms for "Adolescents", 12 for "MI" and 2 for "nurse". A new research formula was designed using the text words identified. Adolescen*[Title/Abstract]) OR Younger*[Title/Abstract]) OR Youth*[Title/Abstract]) OR Teen*[Title/Abstract]) OR Adolescent[MeSH Terms])) AND (((((((((((("Motivational interview"[Title/Abstract]) OR "Motivational intervention"[Title/Abstract]) OR "Motivational interviews"[Title/Abstract]) OR "Motivational interventions"[Title/Abstract]) OR "motivational interviewing"[Title/Abstract]) OR "motivational counseling"[Title/Abstract]) OR "motivational support"[Title/Abstract]) OR "Motivational enhancement"[Title/Abstract]) OR "Brief intervention"[Title/Abstract]) OR "Brief interventions"[Title/Abstract]) OR Motivational Interviewing[MeSH Terms]) OR Directive Counseling[MeSH Terms])) AND ((nurs*[Text Word]) OR Nurses[MeSH Terms]). Limiters - Language: English, Portuguese, Spanish. In MEDLINE this research formula generated 125 results. Other 16 databases referenced at the protocol will be searched to identify additional studies. Articles identified from the final search will be assessed for relevance to the review, based on information provided in the title and abstract. The full article will be retrieved for all studies that meet the inclusion criteria of the review. Conclusions: It was presented here the initial results of this search. Next steps of this study will be to develop and refine the search strategy for use in other databases. It is expected that findings from this Scoping Review provide needed information to nurses related to the use of MI to promote health behaviors in adolescents and inform opportunities for future development in nursing practice.

Convergence time to equilibrium distributions of autonomous and periodic non-autonomous graphs

We present some estimates of the time of convergence to the equilibrium distribution in autonomous and periodic non-autonomous graphs, with ergodic stochastic adjacency matrices, using the eigenvalues of these matrices. On this way we generalize previous results from several authors, that only considered reversible matrices.