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

Righe spettrali: formazione, shift ed allargamento

In questo breve elaborato si vuole spiegare l’importanza dello studio di un corpo celeste mediante l’osservazione del suo spettro ovvero un grafico del flusso emesso in funzione della frequenza o della lunghezza d’onda nel quale sono presenti righe spettrali, formate dall’interazione tra materia e radiazione, a causa dell’assorbimento od emissione di fotoni a seguito di transizioni elettroniche, ma anche vibrazionali e rotazionali per le molecole. In particolare, dall’analisi delle righe spettrali si traggono diverse informazioni sull’oggetto, quali, la composizione e l’abbondanza delle specie chimiche che lo compongono in base al tipo di righe presenti e alla loro intensità, si deduce la temperatura e la pressione dell’oggetto studiato dalla larghezza di queste, ancora, informazioni sul moto relativo e la distanza dall’osservatore misurando lo shift delle righe; infine densità e campi magnetici del mezzo interstellare. Per molti oggetti astronomici, troppo distanti, lo studio dello spettro è l’unico modo per trarre conclusioni sulla loro natura. Per questo, nel primo capitolo si ricava l’equazione del trasporto radiativo, soffermandosi sui processi che regolano l’assorbimento e l’emissione di energia. Il secondo capitolo invece, tratta il caso particolare delle atmosfere stellari, nel quale si ricava, con una serie di approssimazioni fatte sull’equazione del trasporto radiativo, quale parte osserviamo di una stella e dove si formano le righe spettrali. Successivamente ci si è concentrati sui meccanismi che portano alla formazione delle righe spettrali, analizzando sia le transizioni radiative con i coefficienti di Einstein, sia quelle collisionali, e distinguendo tra transizioni permesse o proibite con le regole di selezione. Infine si sono esaminate le informazioni che si possono ricavare dalle righe spettrali, approfondendo sui fenomeni di shift e modifica di queste, descrivendo più nel dettaglio la riga a 21 cm dell’atomo di idrogeno, fondamentale in astrofisica.

Scheduling di dispositivi in una casa intelligente su piattaforma Home Manager

Obiettivo di questa tesi è estendere la piattaforma sperimentale Home Manager e sviluppare il supporto alla schedulazione degli elettrodomestici. L’utente Home Manager notificherà al sistema la propria volontà di accendere un determinato dispositivo, delegando a quest’ultimo la scelta sul quando dovrà essere eseguito il compito corrispondente, sulla base delle politiche generali della Smart Home.

Accounting for the Multi-Period Impact of Service When Determining Employee Requirements for Labor Scheduling

Providing good customer service, inexpensively, is a problem commonly faced by managers of service operations. To tackle this problem, managers must do four tasks: forecast customer demand for the service; translate these forecasts into employee requirements; develop a labor schedule that provides appropriate numbers of employees at appropriate times; and control the delivery of the service in real-time. This paper focuses upon the translation of forecasts of customer demand into employee requirements. Specifically, it presents and evaluates two methods for determining desired staffing levels. One of these methods is a traditional approach to the task, while the other, by using modified customer arrival rates, offers a better means of accounting for the multi-period impact of customer service. To calculate the modified arrival rates, the latter method reduces (increases) the actual customer arrival rate for a period to account for customers who arrived in the period (in earlier periods) but have some of their service performed in subsequent periods (in the period). In an experiment simulating 13824 service delivery environments, the new method demonstrated its superiority by serving 2.74% more customers within the specified waiting time limit while using 7.57% fewer labor hours.

Shift from coral to macroalgae dominance on a volcanically acidified reef

Rising anthropogenic CO2 in the atmosphere is accompanied by an increase in oceanic CO2 and a concomitant decline in seawater pH (ref. 1). This phenomenon, known as ocean acidification (OA), has been experimentally shown to impact the biology and ecology of numerous animals and plants2, most notably those that precipitate calcium carbonate skeletons, such as reef-building corals3. Volcanically acidified water at Maug, Commonwealth of the Northern Mariana Islands (CNMI) is equivalent to near-future predictions for what coral reef ecosystems will experience worldwide due to OA. We provide the first chemical and ecological assessment of this unique site and show that acidification-related stress significantly influences the abundance and diversity of coral reef taxa, leading to the often-predicted shift from a coral to an algae-dominated state4, 5. This study provides field evidence that acidification can lead to macroalgae dominance on reefs.

Multi-stage scheduling problems with precedence constraints

Abstract not available

A heuristic algorithm for the two-machine re-entrant shop scheduling

Abstract not available

Heuristics for the two-stage job shop scheduling problem with a bottleneck machine

Abstract not available

Heuristics for short route job shop scheduling problems

Abstract not available

Scale and ecosystem services: how do observation, management, and analysis shift with scale—lessons from Québec

Ecosystem service assessment and management are shaped by the scale at which they are conducted; however, there has been little systematic investigation of the scales associated with ecosystem service processes, such as production, benefit distribution, and management. We examined how social-ecological spatial scale impacts ecosystem service assessment by comparing how ecosystem service distribution, trade-offs, and bundles shift across spatial scales. We used a case study in Québec, Canada, to analyze the scales of production, consumption, and management of 12 ecosystem services and to analyze how interactions among 7 of these ecosystem services change across 3 scales of observation (1, 9, and 75 km²). We found that ecosystem service patterns and interactions were relatively robust across scales of observation; however, we identified 4 different types of scale mismatches among ecosystem service production, consumption, and management. Based on this analysis, we have proposed 4 aspects of scale that ecosystem service assessments should consider.

International Law and Land Rights in Africa: The shift from states’ territorial possessions to indigenous peoples’ ownership rights

This is a pre-copyedited, author-produced PDF of a chapter published in Home, Robert, (ed.) Essays in African Land Law. Pretoria University Press, pp. 47-68. ISBN 9781920538002 Availiable at : http://www.pulp.up.ac.za/cat_2011_15.html

Teaching Rules or Teaching Creativity: a Paradigm Shift

Structure is everything in a screenplay we are told. If indeed there are any rules to screenwriting then this would be carved in tablets of stone. Within pedagogical frameworks we are diligent in our instruction of the three acts, advocating it as a paradigm. We pass on tools for the analysis of character that are gleaned from psychology. But I have seen students struggle with this toolbox. They feel constrained by concrete techniques. So often seeing principles as rules, structure as restriction. The stifling of free-form ideas is further compounded by the plethora of books that claim the path to glory lies only in structural devices. Some even purport to have a formula, a simple prescriptive model that will bestow almost certain success. Yet this is an industry that abhors formula, that hungers for the fresh and the new. Without bravado, imagination and experimentation with character and form, the best structured screenplay in the world is merely a typing exercise. As educators we have a duty to retain a balance between letting a student’s mind dance and keeping them to the tempo. This study will compare a variety of diverse structures, from Hegel to Alcoholics Anonymous, Kubler Ross to Jung. It will analyse recent journal articles, on both new techniques in teaching creativity and new approaches to the instruction of screenwriting, to suggest a model of how best to inform the application of structure to HE students and keep creativity uppermost. A structure of emotional truth. An equal appreciation of both the tools of our craft and an imaginative exploration of character and world that can unlock our originality and our artistry.

Two-stage open shop scheduling with a bottleneck machine

Abstract not available