<p>Aircrafttrajectory optimization is traditionally used forminimizing fuel consumption or time when going from one flightstate to another. This thesis presents a possible approach toincorporate tactical constraints in aircraft trajectoryoptimization.</p><p>The stealth technology of today focuses on making thetactics already in use more effective. Since tactics andstealth are closely interrelated, new and better results may beobtained if both aspects are considered simultaneously. Simplyreducing the radar cross section area in some directionswithout considering tactical aspects may result in little, ifany, improvement.</p><p>Flight tests have been performed in cooperation withEricsson Microwave Systems and the Swedish Air Force FlightAcademy. The aircraft used was the subsonic jet trainer Saab105, designated SK60 by the Swedish Air Force. The results showa decrease of 40% in the time interval between the instant theaircraft was first detected until it could pass above the radarstation. This corresponds to a reduced radar cross section(RCS) in the direction from the aircraft to the radar of almost90%, if classical RCS reduction techniques would have beenapplied.</p><p>If a modern aircraft with stealth properties would be used,the proposed methodology is believed to increase the possibleimprovements further. This is because the variation of themagnitude of RCS in different directions is greater for a shapeoptimized aircraft, which is the property exploited by thedeveloped method.</p><p>The methods presented are indeed an approach utilizing theideas of the network centric warfare (NCW) concept. Themethodology presented depends on accurate information about theadversary, while also providing up-to-date information to theother users in the information network.</p><p>The thesis focuses on aircraft but the methods are generaland may be adapted for missiles, shipsor land vehicles. Theproposed methods are also economically viable since they areuseful for existing platforms without costly modifications. Themethods presented are not limited to radar threats only. Thereasons for using radar in this thesis are the availablenon-classified data and that radar is known to pose a majorthreat against aircraft.</p>

<p>When simulating target seekers, there is a great need for computationally efficient, target models. This report considers a study of radar target modelling based on Inverse Synthetic Aperture Radar (ISAR) measurements of generic aircraft. The results underlie future modelling of full-size air targets. </p><p>A method is developed for two-dimensional modelling of aspect-dependent target scattering. The approach taken is to generate point-scatterer models of two targets, where each point scatterer is defined according to its position and radar cross section (RCS), estimated from ISAR images. The scattered energy contributions from all point scatterers are summed to simulate a radar return signal. To validate the models, the modelled radar target centre is compared to the true radar target centre, which is determined from ISAR images. </p><p>The method is presented to be promising for modelling air targets with large, persistent radar cross section.</p>

The collision probability approach to neutron transport can be used to obtain the energy-dependent neutron spectrum in nuclear reactor systems as well as other quantities of interest. This method makes the approximation that the neutron distribution is constant within homogeneous regions, or cells, in the system. This assumption restricts geometries that can be modeled by the collision probability approach. The geometry modeled is typically an infinite lattice of two homogeneous cells: a fuel pin cylinder and the coolant that surrounds it. The transport of neutrons between the homogeneous cells is done using probabilities describing the chance that a neutron having a collision in one cell has its next collision in another cell. These collision probabilities can be cast in terms of escape and transmission probabilities for each cell. Some methods exist that extend the collision probability approach to systems composed of more than two homogeneous cells. In this work, we present a novel collision probability method, based on previous work by Schneider et al. (2006a), for an arbitrary number of cells. The method operates by averaging the transmission probabilities across cells of the same shape, and thus assumes a certain level of homogeneity across all cells. When using multigroup cross sections, which the collision probability approach requires, it is necessary to consider the effect that a system's geometry and composition has on those multigroup cross sections. The cross sections must be computed in a way that accounts for the resonance self-shielding that may reduce the reaction rates in the resonance region. The process of developing self-shielded cross sections in a heterogeneous system utilizes an escape cross section. We compute this escape cross section using the same collision probabilities used to obtain the energy spectrum. Results are presented for simple two-cell systems, and preliminary results for four-cell simulations are also given. An extension to the method is provided that accounts for the fact that in thermal systems the assumption of homogeneity is not always valid. / text

The focus of this thesis is to improve upon the existing neutron cross section data for rhenium (Re) in the energy range 0.01 eV to 1 keV. Neutron transmission and capture yield measurements were performed using natural rhenium samples at the Rensselaer Polytechnic Institute Gaerttner Linear Accelerator Center. Measurements were performed using the time of flight method, in which neutron energies are differentiated using the elapsed times between neutron emission from a pulsed neutron source and the subsequent detector interactions. Transmission measurements were performed using ⁶Li glass scintillation detectors. Capture measurements were performed utilizing a 16-segment NaI(Tl) multiplicity detector. Most measurements were performed at a flight path length of 25 meters, with one set of experiments (thermal transmission) performed at 15 meters. The experiments used several metallic, elemental rhenium samples of various thicknesses, ranging from 1 mil to 100 mils. (1 mil = 0.001 inch = 0.0254 mm) Following the reduction of the experimental data, SAMMY was used to perform the data analysis. SAMMY is a shape-fitting Bayesian analysis code that determines resonance parameters by fitting neutron time of flight data using the Reich-Moore approximation of R-matrix theory. The combined transmission and capture yield data analysis determined resonance parameters for rhenium resonances in the energy range of 0.01 eV to 1 keV. The updated rhenium resonance parameters are compared to previously published parameters and ENDF/B-VII.1. / text

In this dissertation, we present a study of WZ production in proton-proton collisions at a center-of-mass energy of 7 TeV. The data analyzed was collected by the ATLAS detector and corresponds to an integrated luminosity of \(4.6 fb^{−1}\) provided by the Large Hadron Collider in 2011. We select WZ events in the fully leptonic decay mode with electrons, muons, and missing transverse energy in the final state. Events are required to have three isolated leptons with significant transverse momentum, a large missing transverse energy, a Z candidate reconstructed from two of the selected leptons, and a W candidate reconstructed from the missing transverse energy and third lepton. The major backgrounds to the WZ signal in the leptonic decay channel are Z+jets events, ZZ production, Z+photon events, and events with top quarks. We estimate the Z+jets and top quark background contributions from data and take the expected contribution for the other background processes from simulation. We observe 317 WZ candidates in data, with a background expectation of \(68\pm10\) events. The total production cross section is extracted from the selected sample using a maximum likelihood method and is determined to be \(19.0^{+1.4}_{-1.3} (stat) \pm0.9 (syst) \pm0.4 (lumi) pb\), which is consistent with the next-to-leading Standard Model prediction of \(17.6^{+1.1}_{-1.0} pb\). WZ production in the Standard Model includes a contribution from the WWZ triple gauge boson vertex. If new physics beyond the Standard Model exists and interacts with W and Z bosons, the coupling of the WWZ vertex could differ from the Standard Model prediction. We set limits on anomalous triple gauge boson couplings using the transverse momentum spectrum of Z bosons in the selected sample. We derive the 95% confidence interval for three model-independent anomalous triple gauge couplings using a frequentist approach and set the most stringent bounds to date on two of the three parameters. / Physics

The Neutrinos at the Main Injector (NuMI) facility at Fermi National Accelerator Laboratory (FNAL) produces an intense muon neutrino beam used by the Main Injector Neutrino Oscillation Search (MINOS), a neutrino oscillation experiment, and the Main INjector ExpeRiment [nu]-A, (MINER[nu]A), a neutrino interaction experiment. Absolute neutrino cross sections are determined via [mathematical equation], where the numerator is the measured number of neutrino interactions in the MINOS Detector and the denominator is the flux of incident neutrinos. Many past neutrino experiments have measured relative cross sections due to a lack of precise measurements of the incident neutrino flux, normalizing to better established reaction processes, such as quasielastic neutrino-nucleon scattering. But recent measurements of neutrino interactions on nuclear targets have brought to light questions about our understanding of nuclear effects in neutrino interactions. In this thesis the [nu subscript mu] inclusive charged current cross section on iron is measured using the MINOS Detector. The MINOS detector consists of alternating planes of steel and scintillator. The MINOS detector is optimized to measure muons produced in charged current [nu subscript mu] interactions. Along with muons, these interactions produce hadronic showers. The neutrino energy is measured from the total energy the particles deposit in the detector. The incident neutrino flux is measured using the muons produced alongside the neutrinos in meson decay. Three ionization chamber monitors located in the downstream portion of the NuMI beamline are used to measure the muon flux and thereby infer the neutrino flux by relation to the underlying pion and kaon meson flux. This thesis describes the muon flux instrumentation in the NuMI beam, its operation over the two year duration of this measurement, and the techniques used to derive the neutrino flux. / text

We review the Regge theory and the minijet model for pp and pp collisions. We show that, in the conventional minijet approach, the asymptotic behavior of the total cross section calculated using currently accepted gluon distribution function and perturbative QCD rises too rapidly when compared with the data and fails to satisfy Froissart bound. To tame the rise, we have developed a new formalism for the interaction between QCD gluon and the classical color field of the colliding nucleons, and show how the gluon propagator is modified. The corresponding gauge invariance condition of the propagator is derived and shown to be satisfied. The modified gluon propagator leads to a suppression of the minijet cross section due to the gg [rightwards arrow] gg sub-process in the small-x region. We show that the pp and pp total cross section from [square root]s = 5 GeV to 30 TeV can be described as a sum of a hard component contributed by the classical field modified minijet model and a soft component due to the exchange of the Pomeron and the I=0 exchange-degenerate [omega] and f Regge trajectories. The soft-component model is motivated by the notion of duality. The predicted total cross section has a ln s asymptotic behavior. / text

Σκοπός είναι η διερεύνηση της τεχνολογίας των χερσαίων (onshore) ανεμογεννητριών και συγκεκριμένα των πυλώνων των ανεμογεννητριών. Αν εξετάσουμε το αιολικό δυναμικό στις χερσαίες περιοχές της Ευρώπης, παρατηρούμε αμέσως τις τεράστιες δυνατότητες ανάπτυξης ανεμογεννητριών. Παρατηρούμε επίσης την πλεονεκτική θέση της χώρας μας που εμφανίζεται να διαθέτει στο Αιγαίο πέλαγος μια από τις πλουσιότερες, σε αιολικό δυναμικό, περιοχές της Ευρώπης. Για να έχουμε όμως μεγαλύτερη απόδοση στην ισχύ μιας ανεμογεννήτριας πρέπει να αυξήσουμε το ύψος της έτσι ώστε να εκμεταλλευτούμε τις υψηλότερες ταχύτητες ανέμου σε μεγαλύτερα ύψη. Αυτό με την σειρά του θα επιφέρει πιο μεγάλα φορτία και επομένως μεγαλύτερες καταπονήσεις (εντατικά μεγέθη) στην βάση του πυλώνα καθώς η ανεμογεννήτρια προσομοιώνεται με σύστημα προβόλου. Ως συνέπεια τούτου θα πρέπει να αυξήσουμε την αντοχή του πυλώνα είτε αυξάνοντας το πάχος του υλικού της διατομής (αποφεύγεται – απαιτούνται μεγάλα πάχη συνεπώς μεγάλα κόστη), είτε αυξάνοντας τη διάμετρο της διατομής (αποφεύγεται – περιορισμένο πλάτος οδικού δικτύου που αποτρέπει την μεταφορά τμημάτων του πυλώνα της ανεμογεννήτριας με μεγάλες διατομές), είτε αυξάνοντας την αντοχή του υλικού της διατομής (αντικείμενο διατριβής). Στην παρούσα διατριβή γίνεται μελέτη βελτιστοποίησης σχεδιασμού των πυλώνων των ανεμογεννητριών με σύμμικτη διατομή χάλυβα-σκυροδέματος η οποία οδηγεί σε σχετικά μικρά πάχη διατομών, μικρής διαμέτρου, μεγάλης επιθυμητής αντοχής και μειωμένου κόστους υλικά. Αρχικά γίνεται η ανάλυση διατομής με στόχο την βελτιστοποίηση - ελαχιστοποίηση του κόστους για δεδομένη αντίσταση και στη συνέχεια η ανάλυση επαναλαμβάνεται για την βελτιστοποίηση του κόστους για δεδομένη δυσκαμψία. Στη συνέχεια με τη βοήθεια του σχεδιαστικού αναλυτικού προγράμματος ANSYS θα γίνει η σχεδίαση του πυλώνα της ανεμογεννήτριας όπου θα εφαρμοστούν τα προβλεπόμενα φορτία. Κατόπιν αυτού του σχεδιασμού διεξάγουμε πείραμα στο εργαστήριο όπου προσομοιώνουμε την ανεμογεννήτρια ώστε να συγκρίνουμε τα πειραματικά αποτελέσματα με την αναλυτική διαδικασία στο πρόγραμμα ANSYS. Γίνεται παράθεση και σχολιασμός των αποτελεσμάτων ώστε να προκύψουν τα συμπεράσματά μας και τελικώς γίνονται προτάσεις για περαιτέρω έρευνα όσον αφορά τα υλικά της διατομής των πυλώνων καθώς και την καλύτερη αξιοποίηση της αιολικής ενέργειας. / The aim is to investigate the technology of land (onshore) wind turbines and specifically for the pillars of wind turbines. If we investigate the wind potential in inland areas of Europe, we see immediately the enormous growth potential of wind turbines. We also observe the vantage point of our country that appears to have the Aegean Sea, one of the richest in wind potential areas of Europe. In order to increase the power of a wind turbine we must increase its height so as to take advantage of higher wind speeds at higher altitudes. This leads to higher loads and thus higher stresses (section forces) at the base of the tower as the wind turbine system is simulated with the cantilever system. As a consequence we should increase the strength of the pillar by increasing the thickness of the section material (to be avoided - large thicknesses therefore high costs required) or by increasing the diameter of the cross section (to be avoided - narrow road network that prevents transfer of the turbine pillar parts with large cross-sections), or by increasing the strength of the section’s material (subject of thesis). This thesis deal with the Design Optimization of Composite Cross Section Steel – Concrete Wind Turbine Towers which leads to relatively low thickness cross-sections, with small diameters, desirable high strength and reduced cost of materials. Initially we conduct sectional analysis in order to optimize - minimize the cost for a given resistance, and then the analysis is repeated for cost optimization for a given stiffness. Then we develop equations which correlate the moment, the stiffness and the cost of the wind turbine tower with the thicknesses of the materials (steel – concrete) which the cross section is composed of. Consequently we plot the equations that give the materials’ dimensions ranges when both the moment and stiffness is modified. Also we can understand how all this procedure affects the whole cost of the cross section. Then we conduct analysis and design of the wind turbine pillar with the analytical program ANSYS according to the design loads. Afterwards, lab-scale tests are conducted in order to model the wind turbine behavior. The experimental results are compared to the analytical observations. Finally we display and comment the results of that research so as to draw conclusions regarding the pillar design and the efficient wind energy utilization and present suggestions to future research.

In real conditions, a great majority of machine and structure elements and parts (shafts, pins, axis, etc.) are subjected to bending. That’s why the study of elastic plastic bending has a wide engineering science background and a very broad field of application. This work presents analytical research of elastic plastic pure bending of rectangular cross-section element. The simple power relation expresses stress strain curve in the region of uniform plastic deformation. Derived mathematical relations allow to calculate deviation of dimensionless stress neutral axis from symmetry axis of an element and dimensionless pure bending moment versus monotonic strain. Theoretical curves for different material constants are drawn. Theoretical curves of dimensionless pure bending moment give tolerable coincidence with experimental date. Derived relationships can be also fitted to analysis of rectangular cross-section element loaded by low cycle pure bending.

Introduction All experimental studies involving charged particle induced nuclear reactions require a precise knowledge of monitor reactions. A number of well described proton induced monitor reactions exist in the lower energy range [1], which is covered by most medical cyclotrons. Concerning proton energies above 20 MeV, however, the accuracy of the monitor reactions declines as cross section data becomes scarcer. Furthermore, the growing interest in precise determination of projectile energies by comparing of ratios of monitor reaction cross sections demands new measurements and evaluations of known data for high threshold monitor radionuclides. In this work cross section measurements on the formation of 61Cu were done and energy de-pendent radionuclide ratios were calculated. Material and Methods For investigation of the natCu(p,x)61Cu reaction copper foils of natural isotopic composition (Goodfellow Ltd.) were irradiated. The targets were of 10 and 20 μm thickness, having a diameter of 15 mm. Proton bombardments up to 45 MeV incident energy were done in the stacked-foil arrangement at the accelerator JULIC of the Nuclear Physics Institute (IKP) of the Forschungszentrum Jülich. In addition to an internal irradiation possibility the cyclotron is equipped with an external target station which was used for most experiments. It can adapt standard and slanting solid target holders and is equipped with a water cooled four sector collimator and additional helium cooling of the entry foil. Several irradiations were executed. In each stack, besides copper samples, aluminium absorbers and additional nickel monitor foils were also placed, the latter for the determination of the respective beam current. The produced radioactivity of 61Cu was analysed non-destructively using HPGe γ-ray detectors (EG&G Ortec). Results and Conclusion Reaction cross sections of the natCu(p,x)61Cu process up to 45 MeV were measured and com-pared with existing data from the literature (FIG. 2). Except for the data of Williams et al. our results are in good agreement, showing a maxi-mum of about 165 mbarn at 37.5 MeV proton energy. The overall uncertainty of the new cross section data is between 8 and 10 %. In FIG. 3, the excitation functions of the relevant monitor reactions on Cu are shown. In combination with the excitation function of the natCu(p,xn)62Zn reaction, isotope ratios were calculated which can be used for determination of the proton energy within a target stack in the energy range of 22–40 MeV as described by Piel et al. [3]. FIGURE 4 shows the cross section ratio in dependence of the proton energy. Above this energy, 65Zn could be used to generate isotope ratios for energy determination, although the long half-life (T½ = 244.3 d) of that radionuclide may be a problem. Additional cross section measurements are planned in order to further strengthen the data base of this potential monitor reaction. The results of this work shall be evaluated in the framework of an ongoing Coordinated Research Project of the IAEA.