Low-thrust spacecraft trajectory optimization is often a difficult and time-consuming process. One alternative is to instead use a closed-loop, feedback-driven control law, which calculates the control using knowledge of only the current state and target state, and does not require the solution of a nonlinear optimization problem or system of nonlinear equations. Though generally suboptimal, such control laws are attractive because of the ease and speed with which they may be implemented and used to calculate feasible low-thrust maneuvers. This thesis presents the theoretical foundations for seven modern low-thrust control laws based on control law "blending" and Lyapunov control theory for a particle spacecraft operating in an inverse-square gravitational field. The control laws are evaluated critically to determine those that present the best combinations of thoroughness of method and minimization of user input required. The three control laws judged to exhibit the most favorable characteristics are then compared quantitatively through three numerical simulations. The simulations demonstrate the effectiveness of feedback-driven control laws, but also reveal several situations in which the control laws may perform poorly or break down altogether due to either theoretical shortcomings or numerical difficulties. The causes and effects of these issues are explained, and methods of handling them are proposed, implemented, and evaluated. Various opportunities for further work in the area are also described. / text

Σκοπός της μελέτης ήταν να εξετάσουμε, σε ένα πειραματικό μοντέλο πειραματικής ηπατεκτομής (70%) αφ’ ενός και παροδικής απόφραξης του ηπατοδωδεκαδακτυλικού συνδέσμου (χειρισμός Pringle) αφ’ ετέρου, το φαινόμενο της βακτηριακής μετακίνησης, της ενδοτοξιναιμίας, καθώς και τις μεταβολές οι οποίες συμβαίνουν στην εντερική χλωρίδα και τον εντερικό βλεννογόνο. Σε αυτά τα δύο μοντέλα προσπαθήσαμε κατ’ αρχήν να πιστοποιήσουμε την αυξημένη μετακίνηση των εντερικών βακτηρίων στους μεσεντέριους λεμφαδένες και την διαπίδυση ενδοτοξινών από τον αυλό του εντέρου στην πυλαία και την αορτή. Στα ίδια μοντέλα προσπαθήσαμε να αναστείλουμε τα ανωτέρω φαινόμενα με φαρμακολογικούς χειρισμούς, μελετώντας πρώτον τη χορήγηση λακτουλόζης από το στόμα, η οποία έχει την ικανότητα να δεσμεύει την ενδοτοξίνη και να σχηματίζει σύμπλεγμα που δεν απορροφάται από το έντερο, με σκοπό τη μείωση της ενδοαυλικής απορροφήσιμης ενδοτοξίνης και δεύτερον τη χορήγηση δυσαπορρόφητων αντιβιοτικών από το στόμα, με σκοπό την ποσοτική ελάττωση του πληθυσμού της μικροβιακής χλωρίδας στον αυλό του εντέρου. Τα αποτελέσματα κάθε φάσης της μελέτης της ηπατεκτομής (70%) και του χειρισμού Pringle είχαν ως εξής: Η ηπατεκτομή (70%), προάγει την εντερική βακτηριακή μετακίνηση στους μεσεντέριους λεμφαδένες και στο ήπαρ, αυξάνει την ενδοτοξιναιμία και επιφέρει ιστολογικές αλλαγές στο ύψος των λάχνων. Η χορήγηση λακτουλόζης δημιουργεί τις κατάλληλες συνθήκες που επιφέρουν την μείωση των θετικών καλλιεργειών ιδιαίτερα αυτών του ήπατος και ελαττώνει την ενδοτοξίνη στην πυλαία. Η αποστείρωση του εντέρου με τη χορήγηση δυσαπορρόφητων αντιβιοτικών, μειώνει την εντερική βακτηριακή μετακίνηση στους μεσεντέριους λεμφαδένες και την ενδοτοξιναιμία. Ο χειρισμός Pringle, προάγει την εντερική βακτηριακή μετακίνηση και την ενδοτοξιναιμία, ενώ η απόπτωση ελαττώνεται με την αποστείρωση του εντέρου και τη χορήγηση λακτουλόζης μόνο άμεσα μετά τον χειρισμό. Η εξασφάλιση της ανατομικής και λειτουργικής ακεραιότητας του εντερικού βλεννογόνου έχει ιδιαίτερη σημασία στη διατήρηση του βλεννογόνιου εντερικού φραγμού και αποτρέπει την ενδοτοξιναιμία και τη βακτηριακή μετακίνηση. Η αποκατάσταση της δομικής και λειτουργικής ακεραιότητας του εντερικού βλεννογόνου, στην εκτεταμένη ηπατεκτομή, με τη χορήγηση μη απορροφήσιμων αντιβιοτικών και λακτουλόζης, αναστέλλει σημαντικά τα ανωτέρω φαινόμενα. / The purpose of this study is to investigate on an experimental model of extended hepatectomy(70%) and temporary occlusion of the hepatoduodenal ligament (Pringle maneuver), the phenomenon of bacterial translocation, endotoxaemia as well as the changes that are taking place, both in the intestinal flora and intestinal mucosa. In both models we attempt to demonstrate the increase translocation of intestinal bacteria to mesenteric lymph nodes (MLNs) and increase of endotoxin in the systemic and portal circulation. Using the same models, we attempted to inhibit the above phenomena with pharmacological manipulation. We examined the decrease of the endotoxins translocation, by administering per.os lactulose, which has the property to bind the endotoxin formatting a nonabsorbable comlex in the gut lumen. We also investigated the effect of nonabsorbable antibiotics per. os on reducing the intestinal flora. Our results indicated that, extended hepatectomy (70%) increased translocation of intestinal bacteria to mesenteric lymph nodes and liver and increased the endotoxaemia inducing the decrease of intestinal villus height. The administering of lactulose created the proper conditions which decreased positive liver cultures and reduced the endotoxin concentrations in portal blood. Gut decontamination by administration of nonabsorbable antibiotics reduced the intestinal flora, the intestinal bacteria translocation to MLNs and endotoxaemia. Pringle maneuver promoted the intestinal bacterial translocation and endotoxaemia. Apoptosis decreases, by gut decontamination and administration of lactulose only immediately after Pringle maneuver. The anatomic and functional integrity reassurance, of intestinal mucosa, has strong significance for the preservation of intestinal mucosal barrier to prevent endotoxaemia and bacterial translocation. The structural and functional establishment of enteric mucosa integrity, after extended hepatectomy, by administration of nonabsorbable antibiotics and lactulose, inhibit considerably the above phenomena.

Sedan helikopterns introduktion har den använts på en olika sätt i många olika militäroperationer. Dess unika egenskaper gör den till en bra vapenplattform. Trots detta har dess roller inom modern krigföring aldrig riktigt definierats. Studien syftar till att ta reda på vilka roller helikoptern kan ha inom manöverkrigföring. Detta görs genom att analysera manöverkrigföringens utmärkande drag mot helikopterns utmärkande drag. Därefter används fallstudier av Operation Desert Storm och Operation Iraqi Freedom för att se hur helikoptern har använts. Studien visar att helikopterns viktigaste roller inom manöverkrigföring är att stödja markförbanden med rörlighet och verkan. / Since the introduction of the helicopter it has been used in a variety of ways in many different military operations. Its unique properties make it a good weapon platform. Despite this, its roles in modern warfare have never really been defined. This study aims to find out what roles the helicopter may have in maneuver warfare. This is done by analyzing the characteristics of maneuver warfare and comparing it to the helicopter's characteristics. The study will use case studies of Operation Desert Storm and Operation Iraqi Freedom to see how the helicopter has been used. This study shows that the helicopter's main roles in maneuver warfare are to support ground troops with mobility and firepower

Thesis (M.S.)--University of Michigan, 1987.

Thesis (M.S.)--University of Michigan, 1988.

Thesis (M.S.)--University of Michigan, 1988.

Thesis (M.S.)--University of Michigan, 1987.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): Gerald G. Brown. Includes bibliographical references (p. 39). Also available online.

Manöverkrigföring är en central del i Försvarsmaktens syn på stridens genomförande och nyttjandet av sina väpnade resurser. Manöverkrigföring och manövertänkande tillmäts också stort utrymme i den militärstrategiska doktrinen. Med anledning av beslut om tillämpning för Militärstrategisk doktrin 2012 och därmed upphävandet av Militärstrategisk doktrin 2002 fann jag det värdefullt att analysera utvecklingen inom förhållningssättet till manöverkrigföring i doktrinen. Med kvalitativ textanalys som metod jämförde jag de båda doktrinerna i hänseende till manöverkrigföring och manövertänkande för att se om det skett någon utveckling. Jag belyste även möjliga påverkande faktorer på doktrinutvecklingen i två internationella insatser, nämligen KFOR och Isaf. Jag fann att en utveckling har ägt rum i förhållningssättet till manöverkrigföring och manövertänkande och att Militärstrategisk doktrin 2012 har ett mer nyanserat förhållningssätt än sin föregångare som hade ett mer okritiskt och föråldrat förhållningssätt till manöverkrigföring. / Maneuver warfare is a central part of the Swedish armed forces way of conducting battle and its use of its armed resources as a whole. Maneuver warfare and maneuver thinking is also an extensive part of the strategic doctrine. Due to the decision to implement the 2012 edition of the strategic doctrine and thereby to withdraw the 2002 edition I found it of value to analyze the development of the attitude towards maneuver warfare in the strategic doctrine. By the method of qualitative text analysis I compared the two strategic doctrines with maneuver warfare and maneuver thinking as the point of view to establish whether a change had taken place. I also illuminated possible factors in the doctrinal development by pointing out two international operations, KFOR and Isaf, as influential factors. I found that a developmental change had taken place in the attitude towards maneuver warfare and maneuver thinking. The 2012 edition of strategic doctrine had a more nuanced attitude than its predecessor that had a more uncritical and dated view concerning maneuver warfare.

Made available in DSpace on 2014-06-11T19:25:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-19Bitstream added on 2014-06-13T19:12:14Z : No. of bitstreams: 1 jacob_rr_me_guara.pdf: 637187 bytes, checksum: 24c38b78cd04acc4d1694e9912f95502 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / No presente trabalho é abordada a manobra orbital Terra-Lua - Terra com o objetivo de um menor consumo de combustível. Inicialmente o satélite executa uma órbita em torno da Terra. Em um certo instante um impulso é efetuado para efetuar uma manobra não con-focal em que o satélite é transferido para uma órbita de transferência geocêntrica até um ponto da esfera de influência da Lua. A partir deste ponto o satélite é transferido para uma órbita hiperbólica em torno da Lua, e, no perilúnio desta órbita um novo impulso é dado transferindo o satélite para uma órbita lunar. A seguir é efetuada a manobra de volta em que o satélite é transferido para a órbitra geocêntrica de transferência, e no pericentro desta o satélite é transferido para a sua órbita inicial em torno da Terra. O caso não coplanar e a influência das perturbações devidas ao achatamento da Terra e a atração gravitacional da Lua também são analisados. / In the present work an Earth-Moon-Earth orbital maneuver is studied with the purpose of minimum fuel consumption. Initially it is considered an artificial satellite orbiting around the Earth. In a certain instant an impulse is effected to effect a not cofocal maneuver where the satellite is transferred to an orbit of geocentric transference until a point of the sphere of influence of the Moon. From this point the satellite is transferred to a hyperbolic orbit around the Moon, and, in the perilúnio of this orbit a new impulse is given transferring the satellite to a lunar orbit. To follow the maneuver is effected in return where the satellite is transferred to geocentric orbit of transference, and in pericentro of this the satellite is transferred to its initial orbit around the Earth. The non-coplanar case and the influence of the disturbances due to the flattening of the Earth and the gravitational attraction of the Moon also are analyzed.