• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 433
  • 94
  • 81
  • 59
  • 37
  • 36
  • 12
  • 8
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 2
  • Tagged with
  • 972
  • 242
  • 179
  • 132
  • 110
  • 107
  • 102
  • 91
  • 87
  • 85
  • 78
  • 76
  • 76
  • 71
  • 69
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

Evaluating Cyber war

Lee, Jonathan Iming 21 February 2011 (has links)
Richard A. Clarke and Robert K. Knake’s book, Cyber war, claims to identify a new threat and vulnerability in the United States. By examining the points they make and evaluating them in the context of the first cyber attack, STUXNET, we shall conclude that the technical argument is correct; however the overall argument is incomplete. What they fail to emphasize is the amount of human intelligence involved in committing a successful cyber attack, and the extent to which having intelligence operations greatly enhances a state's cyber capabilities. / text
582

Η παράμετρος της κεντρικότητας σε ανεξάρτητα κλίμακας μεγάλα δίκτυα / The centrality metric in large scale-free networks

Γεωργιάδης, Γιώργος 16 May 2007 (has links)
Ένα φαινόμενο που έκανε την εμφάνισή του τα τελευταία χρόνια είναι η μελέτη μεγάλων δικτύων που εμφανίζουν μια ιεραρχική δομή ανεξαρτήτως κλίμακας (large scale-free networks). Μια παραδοσιακή μέθοδος μοντελοποίησης δικτύων είναι η χρήση γραφημάτων και η χρησιμοποίηση αποτελεσμάτων που προκύπτουν από την Θεωρία Γράφων. Όμως στα κλασικά μοντέλα που έχουν μελετηθεί, δυο κόμβοι του ίδιου γραφήματος έχουν την ίδια πιθανότητα να συνδέονται με οποιουσδήποτε δυο άλλους κόμβους. Αυτός ο τρόπος μοντελοποίησης αποτυγχάνει να περιγράψει πολλά δίκτυα της καθημερινής ζωής, όπως δίκτυα γνωριμιών όπου οι κόμβοι συμβολίζουν ανθρώπους και συνδέονται μεταξύ τους αν γνωρίζονται άμεσα. Σε ένα τέτοιο δίκτυο είναι αναμενόμενο δυο φίλοι κάποιου ατόμου να έχουν μεγαλύτερη πιθανότητα να γνωρίζονται μεταξύ τους από ότι δυο τυχαία επιλεγμένοι ξένοι. Αυτό ακριβώς το φαινόμενο ονομάζεται συσσωμάτωση (clustering) και είναι χαρακτηριστικό για τα εν λόγω δίκτυα. Είναι γεγονός ότι πολλά δίκτυα που συναντώνται στη φύση αλλά και πάρα πολλά ανθρωπογενή δίκτυα εντάσσονται σε αυτήν την κατηγορία. Παραδείγματα τέτοιων είναι τα δίκτυα πρωτεϊνών, δίκτυα τροφικών αλυσίδων, επιδημικής διάδοσης ασθενειών, δίκτυα ηλεκτρικού ρεύματος, υπολογιστών, ιστοσελίδων του Παγκόσμιου Ιστού, δίκτυα γνωριμιών, επιστημονικών αναφορών (citations) κ.α. . Παρότι φαίνεται να άπτονται πολλών επιστημών όπως η Φυσική, η Βιολογία, η Κοινωνιολογία και η Πληροφορική, δεν έχουν τύχει ευρείας μελέτης, καθώς μέχρι στιγμής έλειπαν πραγματικά μεγάλα δίκτυα για πειραματική μελέτη (κενό που καλύφθηκε με την ανάπτυξη του Παγκόσμιου Ιστού). Μέχρι σήμερα δεν έχουν φωτιστεί όλα εκείνα τα σημεία και τα μεγέθη που είναι χαρακτηριστικά για αυτά τα δίκτυα και που πρέπει να εστιάσει η επιστημονική έρευνα, παρόλα αυτά έχει γίνει κάποια πρόοδος. Μια τέτοια έννοια που μπορεί να εκφραστεί με πολλά μεγέθη είναι η έννοια της κεντρικότητας (centrality) ενός κόμβου στο δίκτυο. Η χρησιμότητα ενός τέτοιου μεγέθους, αν μπορεί να οριστεί, είναι προφανής, για παράδειγμα στον τομέα της εσκεμμένης «επίθεσης» σε ένα τέτοιο δίκτυο (π.χ. δίκτυο υπολογιστών). Η ακριβής όμως συσχέτιση της κεντρικότητας με τα άλλα χαρακτηριστικά μεγέθη του δικτύου, όπως η συσσωμάτωση, δεν είναι γνωστή. Στόχος της εργασίας είναι να εμβαθύνει στην έννοια της κεντρικότητας, και χρησιμοποιεί σαν πεδίο πειραματισμών τον χώρο της εσκεμμένης επίθεσης σε ανεξάρτητα κλίμακας δίκτυα. Στο πλαίσιο αυτό γίνεται μια συνοπτική παρουσίαση των μοντέλων δικτύων που έχουν προταθεί μέχρι σήμερα και αναλύεται η έννοια της κεντρικότητας μέσω των παραδοσιακών ορισμών της από την επιστήμη της Κοινωνιολογίας. Στη συνέχεια προτείνεται μια σειρά ορισμών της κεντρικότητας που την συνδέουν με μεγέθη του δικτύου όπως ο συντελεστής συσσωμάτωσης. Η καταλληλότητα των ορισμών αυτών διαπιστώνεται στην πράξη, εξομοιώνοντας πειραματικά επιθέσεις σε ανεξάρτητα κλίμακας μεγάλα δίκτυα και χρησιμοποιώντας στρατηγικές επίθεσης που βασίζονται σε αυτές. / A trend in recent years is the study of large networks which possess a hierarchical structure independent of the current scale (large scale-free networks). A traditional method of network modelling is the use of graphs and the usage of results based on Graph Theory. Until recently, the classical models studied, describe the probability of two random vertices connecting with each other as equal for all pairs of vertices. This modelling fails to describe many everyday networks such as acquaintance networks, where the vertices are individuals and connect with an edge if they know each other
583

Racial Disparities Study in Diabetes-Related Complication Using National Health Survey Data

Yan, Fengxia 15 December 2010 (has links)
The main aim of this study is to compare the prevalence of diabetes-related complications in white to the prevalence in other racial and ethnic groups in United States using 2009 Behavioral Risk Factor Surveillance System (BRFSS). By constructing the logistic regression model, odds ratios (OR) were calculated to compare the prevalence of diabetes complications in white and other groups. Compared to white, the prevalence of hypertension and stroke in African Americans were higher, while the prevalence of heart attack and coronary heart disease were lower. The Asian Americans or Pacific Islanders, African Americans and Hispanics were more likely to develop retinopathy compared to white. The prevalence of hypertension, hypercholesterolemia, heart attack, coronary heart disease, Stroke in Native Americans and “other” group were not significantly different from the prevalence in white. Asian or Pacific Islanders were less likely to experience stroke.
584

Sklandytuvo atakos ir slydimo kampų matavimo metodų tyrimas / Research of measurements of glider’s attack and slip angle

Lapinskas, Vytautas 15 June 2011 (has links)
Baigiamajame magistro darbe atliekamas sklandytuvo atakos ir slydimo kampo matavimo metodų tyrimas. Pirmoje darbo dalyje apžvelgiami atakos kampo matuokliai: virvutė, pritvirtinta ant stiklinio gaubto, atakos – slydimo kampo matuoklis su vėjarodžiu ir Pitoto vamzdelio tipo daviklis. Davikliai palyginami, aprašomi jų privalumai ir trūkumai lyginant su kitais davikliais. Antroje dalyje aprašomi alfa ir beta kampų matavimo metodai: matavimas vamzdelio tipo davikliu ir metodas, kai nenaudojami specialūs atakos, slydimo kampo davikliai. Toliau apžvelgiami veiksniai, turintys įtakos matavimo tikslumui. Pateikiamos kelių vamzdelio tipo daviklių kalibravimo kreivės. Paskutinėje dalyje programa Matlab kuriamas matematinis-dinaminis sklandytuvo modelis. Modeliu, pagal nustatytas sąlygas, skaičiuojami atakos ir slydimo kampai, analizuojami grafikai. / The thesis made the glider’s attack and slip angle measurement methods for the investigation. The first part gives an overview of measuring devices of angle of attack and slip angle: The side string, attached to the side of the canopy, vane mounted AOA sensor, Pitot-tube type sensor. The sensors are compared, describes their advantages and disadvantages compared with other sensors. The second part describes the alpha and beta angle measurement methods: measurement with the tube-type sensor, and the method without using the specific attack, slip angle sensors. The following gives an overview of factors affecting the measurement accuracy. Several tube-type sensor calibration curves are presented. The last part of thesis presents development of mathematical – dynamic model of the glider using Matlab software. The model calculates the angle of attack and slip using set conditions of flight.
585

Issues of cyber warfare in international law / Kibernetinio karo problematika tarptautinėje teisėje

Kazinec, Darius 05 July 2011 (has links)
Cyber has been around for over a decade and yet we are still faces with a situation of a very weak or rather no regulation. This is being heavily influenced by our weak technological development and due to the nature of cyberspace and the Internet. Cyber warfare poses interesting questions for us. It is one of a kind type of warfare, the one we cannot see or feel, but it‘s impacts are instantaneous and potentially devastating. States and scholars agree on that. This thesis attempts to explore possibilities of application of existing international laws to amend this situation and answer the questions if it is adequate or at all possible. While scholars are still arguing about the basics of what cyber warfare and cyberspace actually is, it keeps on evolving. States on the other hand have recognized the potential threat of cyber warfare a long time ago and are attempting to mend the existing legal void, however not successfully. The effects of their efforts are limited only to a small number of States. States who are not willing to give up their cyber capability would also stay clear from such international legislation. International treaties and State practice were analyzed in search of a way to accommodate cyber warfare under the current regime. The findings show that application of existing legal basis to cyber warfare is at best difficult and strained. The reality is that cyber warfare does not fit adequately under any of the legal umbrellas at the moment. Application of... [to full text] / Kibernetinis karas jau egzistuoja daugiau nei dešimtmeti tačiau mes vis dar turime labai silpną šio reiškinio reguliavimą. Tokia situacija yra stipriai įtakota mūsų silpnu techniniu galimybių bei interneto struktūros. Kibernetinis karas yra labai keblus. Tai yra naujoviškas kariavimo būdas kurio mes nematome, bet jo pasekmes gali būti žaibiškos ir niokojančios. Mokslininkai ir pasaulio valstybės tai jau seniai pripažino. Šis darbas bando atskleisti galimybes tarptautines teises reguliavimui kibernetinio karo atžvilgiu, jeigu tai iš viso yra įmanoma. Tačiau mokslininkai vis dar ginčijasi dėl kibernetinio karo ir kibernetines erdvės terminologijos, tuo tarpu kibernetinio karo grėsme tik didėja. Pasaulio valstybes tai suprasdamos bando ištaisyti teisės trukumus, tačiau nesėkmingai. Bet kokie pasiūlymai ir susitarimai galioja tik nedideliam valstybių ratui. O didžiosios valstybės tuo tarpu nenoriai atsisakytu savo kibernetinio pajėgumo. Darbe buvo išanalizuotos tarptautinės sutartys bei valstybių praktika bandant pritaikyti esamus režimus kibernetinio karo reguliacijai. Darytinos išvados, kad esamos tarptautinės teisinės bazės taikymas geriausiu atveju yra sudėtingas ir nenatūralus. Realybė yra tai, kad kibernetiniam karui netinka nei vienas režimas. O toks jo taikymas, deja sukelia daugiau problemų nei buvo prieš tai. Tačiau dar nėra išsemtos visos galimybės ir ateitis gali parodyti teisingą sprendimą. Tuo tarpu valstybes yra pasiruošusios vesti derybas dėl tarptautinės... [toliau žr. visą tekstą]
586

Application of continuous wavelet analysis to hyperspectral data for the characterization of vegetation

Cheng, Tao Unknown Date
No description available.
587

The cytoprotective role of Ras signaling in glomerular epithelial cell injury /

Huynh, Carl. January 2007 (has links)
In experimental membranous nephropathy, complement C5b-9-induced glomerular epithelial cell (GEC) injury leads to breakdown of glomerular peimselectivity and proteinuria. This study addresses mechanisms that limit complement-mediated injury, focusing on Ras. Complement-mediated injury was attenuated in cultured GEC expressing a constitutively active form of Ras (V12Ras), compared with Neo (control) GEC. V12Ras GEC showed constitutive activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase pathways, but inhibition of these pathways did not reverse the protective effect of Ras. V12Ras GEC showed smaller and rounder morphology, decreased F- to G-actin ratio, decreased activity of the Rho GTPase, Rac, and decreased Src activity. In V12Ras GEC, disruption or stabilization of the F-actin cytoskeleton reversed the protective effect of V12Ras on complement-mediated injury. Thus, the protective effect of V12Ras may be dependent on remodeling of the actin cytoskeleton. Furthermore, the reduction of Src activity due to Ras activation may alter the equilibrium in activities of Rho GTPases, a family of proteins known regulate the actin cytoskeleton. Activation of Ras signaling is a novel pathway to consider in developing strategies for cytoprotection in complement-mediated injury.
588

Aerodynamic Validation of Emerging Projectile Configurations

Sor, Wei Lun 01 November 2012
Approved for public release; distribution is unlimited. / Ever-increasing demands for accuracy and range in modern warfare have expedited the optimization of projectile design. The crux of projectile design lies in the understanding of its aerodynamic properties early in the design phase. This research first investigated the aerodynamic properties of a standard M549, 155mm projectile. The transonic speed region was the focus of the research as significant aerodynamic variation occurs within this particular region. Aerodynamic data from wind tunnel and range testing was benchmarked against modern aerodynamic prediction programs like ANSYS CFX and Aero-Prediction 09 (AP09). Next, a comparison was made between two types of angle of attack generation methods in ANSYS CFX. The research then focused on controlled tilting of the projectile’s nose to investigate the resulting aerodynamic effects. ANSYS CFX was found to provide better agreement with the experimental data than AP09.
589

Exploring the Relationship of Sleep-related Movement Disorders with Cerebrovascular Disease

Boulos, Mark Iskander 24 June 2014 (has links)
INTRODUCTION: The association of Sleep-Related Movement Disorders (SRMDs) such as Restless Legs Syndrome (RLS) and Periodic Limb Movements (PLMs) with cerebrovascular disease is underexplored. Emerging evidence links them to vascular disease, for which white matter hyperintensities (WMHs) are a well-recognized biomarker. METHODS: We conducted a cross-sectional hospital-based observational study in which high-risk TIA and minor stroke patients were assessed for vascular risk factors, WMHs and polysomnography-determined sleep variables. RESULTS: Ninety-seven patients were enrolled, of whom 44 completed polysomnography. Twenty-five percent had RLS, which was associated with lower quality of life. Independent of the effect of classical vascular risk factors, PLMs (but not RLS) were associated with WMHs on linear regression analyses (p=0.016). CONCLUSIONS: SRMDs are prevalent after minor stroke/TIA. RLS is associated with poor quality of life, while PLMs are associated with WMHs. Whether PLMs are implicated in the pathogenesis of WMHs or whether WMHs exacerbate PLMs remains uncertain.
590

Abstracting and correlating heterogeneous events to detect complex scenarios

Panichprecha, Sorot January 2009 (has links)
The research presented in this thesis addresses inherent problems in signaturebased intrusion detection systems (IDSs) operating in heterogeneous environments. The research proposes a solution to address the difficulties associated with multistep attack scenario specification and detection for such environments. The research has focused on two distinct problems: the representation of events derived from heterogeneous sources and multi-step attack specification and detection. The first part of the research investigates the application of an event abstraction model to event logs collected from a heterogeneous environment. The event abstraction model comprises a hierarchy of events derived from different log sources such as system audit data, application logs, captured network traffic, and intrusion detection system alerts. Unlike existing event abstraction models where low-level information may be discarded during the abstraction process, the event abstraction model presented in this work preserves all low-level information as well as providing high-level information in the form of abstract events. The event abstraction model presented in this work was designed independently of any particular IDS and thus may be used by any IDS, intrusion forensic tools, or monitoring tools. The second part of the research investigates the use of unification for multi-step attack scenario specification and detection. Multi-step attack scenarios are hard to specify and detect as they often involve the correlation of events from multiple sources which may be affected by time uncertainty. The unification algorithm provides a simple and straightforward scenario matching mechanism by using variable instantiation where variables represent events as defined in the event abstraction model. The third part of the research looks into the solution to address time uncertainty. Clock synchronisation is crucial for detecting multi-step attack scenarios which involve logs from multiple hosts. Issues involving time uncertainty have been largely neglected by intrusion detection research. The system presented in this research introduces two techniques for addressing time uncertainty issues: clock skew compensation and clock drift modelling using linear regression. An off-line IDS prototype for detecting multi-step attacks has been implemented. The prototype comprises two modules: implementation of the abstract event system architecture (AESA) and of the scenario detection module. The scenario detection module implements our signature language developed based on the Python programming language syntax and the unification-based scenario detection engine. The prototype has been evaluated using a publicly available dataset of real attack traffic and event logs and a synthetic dataset. The distinct features of the public dataset are the fact that it contains multi-step attacks which involve multiple hosts with clock skew and clock drift. These features allow us to demonstrate the application and the advantages of the contributions of this research. All instances of multi-step attacks in the dataset have been correctly identified even though there exists a significant clock skew and drift in the dataset. Future work identified by this research would be to develop a refined unification algorithm suitable for processing streams of events to enable an on-line detection. In terms of time uncertainty, identified future work would be to develop mechanisms which allows automatic clock skew and clock drift identification and correction. The immediate application of the research presented in this thesis is the framework of an off-line IDS which processes events from heterogeneous sources using abstraction and which can detect multi-step attack scenarios which may involve time uncertainty.

Page generated in 0.056 seconds