Multiscale Analysis of Contact in Smooth and Rough Surfaces: Contact Characteristics and Tribo-Damage

This dissertation is comprised of two major interrelated foci. The first focus is to investigate the effect of surface roughness on the behavior of dry contacting bodies through both deterministic and statistical approaches. In the current research, different statistical micro-contact models are employed together with the bulk deformation of the bounding solids to predict the characteristics of the dry rough line-contact and elliptical point-contact including the apparent pressure profile, contact dimensions and real area of contact. Further, based on the results of numerical simulations, useful relationships are provided for the contact characteristics. In addition, a robust approach for the deterministic prediction of pressure and tangential traction distributions in dry rough contact configuration subjected to stick-slip condition is presented with provision for elastic-fully plastic asperity effects. The second focus of this research involves the assessment of three of the most common types of degradation processes that are observed in contact mechanics. The first contact failure mechanism studied is the rolling/sliding contact fatigue wear. In this research, the principles of continuum damage mechanics (CDM) are applied to predict the rolling/sliding contact fatigue crack initiation, and the effect of variable loading on the fatigue behavior of rolling contact with provision for non-linear damage evolution is investigated. The estimated numbers of cycles to crack initiation are compared to the available experimental results revealing good agreement. The second contact degradation phenomenon involves the study of the adhesive wear for unlubricated and lubricated contacts. A method is presented that applies the principles of CDM to predict the Archard adhesive wear coefficient for unlubricated contacts. By carrying out pin-on-disk experiments, wear coefficients for a specific material are obtained and compared with the predicted values showing good agreement. Further, the load sharing concept is applied to develop an engineering model for lubricated wear with the consideration of the thermal effects. The third type of degradation studied is the so-called fretting fatigue which is a failure phenomenon observed in contacting bodies subjected to very small amplitude oscillatory motion. Using the deterministic model developed for stick-slip contact condition, the effect of surface roughness on the crack initiation risk in a fretting contact is investigated and compared with experimental observations. In order to investigate the last two degradation phenomena, the results obtained from the first objective are directly utilized

An Elliptic Curve-based Signcryption Scheme with Forward Secrecy

An elliptic curve-based signcryption scheme is introduced in this paper that effectively combines the functionalities of digital signature and encryption, and decreases the computational costs and communication overheads in comparison with the traditional signature-then-encryption schemes. It simultaneously provides the attributes of message confidentiality, authentication, integrity, unforgeability, non-repudiation, public verifiability, and forward secrecy of message confidentiality. Since it is based on elliptic curves and can use any fast and secure symmetric algorithm for encrypting messages, it has great advantages to be used for security establishments in store-and-forward applications and when dealing with resource-constrained devices.Comment: 13 Pages, 5 Figures, 2 Table

Weighted triangular and circular graph products for configuration processing

In this paper new weighted triangular and circular graph products are presented for configuring the new forms of structural models. The graph products are extensively used in graph theory and combinatorial optimization, however, the weighted triangular products defined in this paper are more suitable for the formation of practical space structural models which are impossible to generate by the previous products. Here, the weighted triangular and circular products are employed for the configuration processing of space structures that are of triangular shapes or a combination of triangular and rectangular shapes and also of the solid circler shapes as domes and some space structural models. The covered graph products are represented for selecting or eliminating some parts or panels from the product graph by using the second weights for the nodes of the generators. Cut out products are other new types of graph products which are defined to eliminate all of the connected elements to a specified node, to configure the model or grid with some vacant panels inside of the model. This application can easily be extended to the formation of finite element models

The politics of cultural diversity : a survey in the liberal-communitarian debate

This thesis explores the politics of cultural diversity through a survey in the debate between liberal and communitarian thinkers. My aim is to show which side of the debate represents a more adequate position in relation to the politics of the existing cultural diversity in western liberal democracies compatible with the claims of multiculturalism which have emerged in the past two decades. In order to do so, I have chosen a selection of philosophers from each group: Alasdair Macintyre, Charles Taylor and Michael Walzer from the communitarians: and John Rawls, Joseph Raz and Will Kymlicka from the liberals. The critical examinations of their arguments which are presented here concern the normative aspects of the problem and concentrate on three main themes: (i) their concept of the self; (ii) their accounts of the foundations of political morality: and (iii) their suggestions for the politics of cultural diversity.Apart from the Introduction and the Conclusion, the thesis consists of two main parts: Part I contains an introduction to the communitarian critique of modernity and liberalism, followed by three chapters on the selected communitarians. In the same way, Part II consists of an introduction to liberal political thought and three chapters on the selected liberal thinkers.#In appreciation of the extent to which cultures may differ from each other in their ideal models of morality, the role which culture plays in constituting one's identity and the extent to which it is affected by communal relationships, and the significance of conceptions of the good life in political morality, communitarians' arguments seem more adequate and fruitful than those of their liberal counterparts, in respect of the politics of cultural communities. The politics of cultural diversity. i.e. the political relations between cultural communities, however, seems to be left with modus vivendi models which can be developed into a model of civil association of cultural communities

Offine/online Optimum Routing of a UAV using Auxiliary Points

This paper presents a method to determine the route of a three-dimensional UAV. Three criteria; the height, the length of flight path and the unauthorized areas are used as the constraints and combined in a fuzzy function as the evaluation function. The article aimed to discover a minimum cost route from source to destination considering the constrains. In this paper a new searching method is proposed, with use of auxiliary points. The auxiliary point method iteratively divides a straight line to two shorter lines with less cost of evaluation function. Implementation results show that the proposed method dramatically decreases the calculations; meanwhile the ight route is sub-optimum

Solutions to the GSM Security Weaknesses

Recently, the mobile industry has experienced an extreme increment in number of its users. The GSM network with the greatest worldwide number of users succumbs to several security vulnerabilities. Although some of its security problems are addressed in its upper generations, there are still many operators using 2G systems. This paper briefly presents the most important security flaws of the GSM network and its transport channels. It also provides some practical solutions to improve the security of currently available 2G systems.Comment: 6 Pages, 2 Figure

A Novel Hybrid Fuzzy Multi-Criteria Decision-Making Model for Supplier Selection Problem (A Case Study in Advertising industry)

Abstract Choosing the proper supplier has a critical role in designing of a supply chain. This problem is complex because each supplier may fulfill some of the manufacturer criteria and choosing the best supplier is a multi criteria problem. This paper proposes a novel hybrid approach to rank suppliers in advertising industry and considers two new criteria to evaluate the suppliers. The proposed approach combines Modified Digital Logic (MDL) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) using fuzzy theory. At the end, the results of the proposed approach are compared with a hybrid method using Fuzzy Analytical Hierarchy Process (FAHP) and Fuzzy TOPSIS on a real case study