The main objective of this thesis is to analyse the relationship between tribalism and modernity in Afghanistan. Focusing on Pashtuns, who constitute the largest ethnic group in Afghanistan, the thesis traces their transformation from a tribal confederacy into a central state that introduced modernity to Afghanistan. In this regard, the thesis is, basically, a discussion of the struggle for power between two institutions in Afghanistan: the tribe and the state. In an effort to reveal the relationship between the two, the thesis looks at the modern strategies and ideologies used by the Afghan state to beat the power of tribalism. Nationalism and Socialism, in this regard, come up as two modern ideologies that are discussed in relation to Pashtun Tribalism. Questioning the concepts of Afghan Nationalism and Pashtun Nationalism as well as their relation to Pashtun Tribalism, the thesis discusses the concept of a tribe within the frame of modern border demarcation, nation-building efforts and modernist reform programmes. Passing on to the discussion on Socialism, the thesis then addresses the question of tribe in relation to the idea of class struggle, a communist party, a modern coup d&rsquo / &eacute / tat and a communist revolution. Contrasting the concept of tribe with such modern notions, the thesis finally reveals how tribalism managed to survive within these modern ideologies by articulating into them in various ways.

This thesis presents a compact femtosecond laser amplifier design for optical preamplifiers and power amplifiers consist of theoretical perspective, simulations to analyze and optimize beam performance. The propagation through optical media is simulated for every optical component such as mirrors and nonlinear crystal separately and suggested realignment of these components required increasing amplifier performance. Finally Gaussian beam propagation and aberration compensation has been conducted.

The confocal laser-scanning microscope (CLSM), known simply as a confocal microscope, is an important instrument which allows us to observe an object or a surface in three-dimensions with confocal microcopy technique. The basic difference of confocal microscopy is detecting the in- focused light, while the out of focus light is blocked out by the help of a pinhole. By this optical dissection ability of confocal microcopy, CLSM provides the images of investigated object or the surface with higher resolution and contrast as against conventional microscopic systems. Various types of Laser Scanning confocal microscopes have been developed and due to its high resolution and contrast they have become an invaluable tool for investigations in many areas like biology and medicine. In addition to its wide range of use, confocal microscope can be used for detecting of possible defects on metal surfaces. In this thesis our goal was to develop the analytical and theoretical back ground necessary for the successful completion of a laser/optic system coupled to a fiber bundle waveguide based on confocal scanning principles to effectively image a non-uniform, metal surface with speed and precision in order to assess any surface damage. In addition to this analysis we demonstrate a working confocal microscopy set-up and investigate the factors which affect the image quality by the experiments conducted in METU (Middle East Technical University) Laser Laboratory

Today, riflescope systems are used widely, mostly by military forces. In this study, a riflescope working in the visible range (400-700 nm) will be designed. The riflescope will have 3 degrees field of view and maximum 15 cm total track. Total design length is limited to 15 cm because a short riflescope is more stabilized than a long one with respect to thermal instability and vibrational effects. Taken into account the cost factor, only two types of glasses will be used in the design. One of them is NBK7 a crown glass and the other is N-F2 a flint glass. Moreover, Schmidt-Pechan prism will be used to construct an erected image. The optical performance analysis of the design is also carried out for a production ready riflescope system.

Focal plane corrected Cassegrain type optical systems have been widely used in various fields. The axial alignment of complex optical systems is not easy and a practical alignment method is needed for such systems. Tilts, decenters and axial motion of elements or group of elements in the system are the typical alignment parameters. Interferometric measurement is an effective way to see the errors caused by the misalignment of each element in an optical system. In this thesis, alignment of a Cassegrain type telescope will be examined by using interferometric measurements and modulation transfer function simulations.

The construction of an optical experimental setup is the objective, to measure transmission coefficient of optical components used in plasma investigations. Thus, proper light source either with continuous or line radiation spectrum should be used. In addition, the detectors&rsquo / output signal is recorded on a PC based data recorder after being digitized by an analog to digital converter card.

This thesis explains low temperature operation of an InGaAs Avalanche Photo Diode (APD) cooled using thermoelectric coolers in order to utilize in the quantum cryptographic applications. A theoretical background for the equipment used in the experiment was provided. Circuitry and mechanics used for the low temperature operation were designed. Performance measures for APD were explained and experiment results were presented.

ABSTRACT PERFORMANCE PARAMETERS OF WIRELESS VIRTUAL PRIVATE NETWORK KZ, S&uuml / heyla Ms.c, Department of Information Systems Supervisor: Assoc. Prof. Dr. Nazife Baykal Co-Supervisor: Assist. Prof. Dr. Yusuf Murat Erten January 2006, 78 pages As the use of PC&rsquo / s and handheld devices increase, it expected that wireless communication would also grow. One of the major concerns in wireless communication is the security. Virtual Private Network (VPN) is the most secure solution that ensures three main aspect of security: authentication, accountability and encryption can use in wireless networks. Most VPNs have built on IP Security Protocol (IPSec) to support end-to-end secure data transmission. IPSec is a wellunderstood and widely used mechanism for wired network communication. Because, wireless networks have limited bandwidth and wireless devices have limited power and less capable CPU, the performance of the networks when VPN&rsquo / s are used is an important research area. We have investigated the use of VPNs in wireless LANs to provide end &ndash / to &ndash / end security. We have selected IPSec as the VPN protocol and investigated the effects of using IPSec on the throughput, packet loss, and delay of the wireless LANs. For this purpose, we have set up a test bed and based, our results on the actual measurements obtained from the experiments performed using the test bed. v The wireless LAN we have used is an 802.11g network and the results show that the performance of the network is adversely affected when VPN&rsquo / s are used but the degradation is not as bad as expected.

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FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / Os aÃos maraging sÃo materiais de ultra-alta resistÃncia sendo composto principalmente por uma base quaternÃria Ni-Co-Mo-Ti que possuem excelente tenacidade aliada com alta resistÃncia mecÃnica sendo utilizadas na indÃstria bÃlica, nuclear, componentes aeronÃuticos, vasos de pressÃo atà indÃstria esportiva. Uma de suas importantes aplicaÃÃes à na utilizaÃÃo nos motores de histerese os quais necessitam de materiais com caracterÃsticas de materiais magneticamente macios e elevada resistÃncia mecÃnica. Foram realizados ensaios de microdueza para determinar propriedades mecÃnicas nas diversas condiÃÃes de tratamento de envelhecimento e meios de resfriamento. Com o objetivo de descobrir as fases presentes no material nas diversas condiÃÃes de tratamento foram realizadas ensaios por difraÃÃo de raios-X bem como analisar a macrotextura atravÃs de FDOC`s. A microtextura foi analisada atravÃs da tÃcnica de EBSD (Electron Backscatterig Diffraction) com o intuito de estudar a influÃncia da textura da austenita na martensita nas determinadas condiÃÃes de envelhecimento e meios de resfriamento. Esta dissertaÃÃo à de grande relevÃncia para o desenvolvimento de novos produtos utilizando aÃos maraging, pois determina as condiÃÃes que oferecem as propriedades mecÃnicas, bem como as fases e textura presentes no material nas condiÃÃes de tratamento requeridas. / Maraging steels are materials of ultra high strength mainly composed of a base quaternary Ni-Co-Mo-Ti which have excellent toughness combined with high mechanical strength being used in war industry, nuclear, aircraft components, pressure vessels up to the sports industry . One of its important applications is in use in hysteresis motors which require materials with characteristics of magnetically soft materials and high mechanical strength. Microdueza tests were performed to determine mechanical properties in different treatment conditions of aging and cooling media. In order to discover the phases present in the material conditions in the various treatment trials were performed by X-ray diffraction as well as analyze the macrotexture through FDOC `s. The microtexture was examined using the technique of EBSD (Electron Diffraction Backscatterig) in order to study the influence of the texture of the austenite in the martensite aging in certain conditions and means of cooling. This thesis is of great importance for the development of new products using maraging steel, because it determines the conditions that provide the mechanical properties as well as the phases and texture present in the material conditions of treatment required.