The aim of the diploma thesis is to design an algorithm for detection and recognition of the type of gun in the image. Firstly, the existing methods and techniques for detecting the various objects are briefly introduced in the text of the thesis however, the methods are primarily focused on guns. Next, the basics of neural networks are briefly outlined, followed by an overview of the most common detectors for deep neural networks. The second half of the thesis is devoted to the implementation of an application for generating images based on a 3D model of a gun, the creation of a data file and learning of a neural network. Finally, the results obtained, which clearly indicate that in order to cover a huge variation of real weapons, is necessary to generate a large amount of training data based on many different 3D models, are briefly summarized in the conclusion of the thesis.

Det svenska samhället har under de senaste åren bevittnat en förändring gällande samhällsvåldets karaktär och kontext. Det finns ett behov av effektiva preventiva åtgärder, vilket i sin tur kräver kunskap gällande det aktuella ämnet. Det huvudsakliga syftet med denna studie var därför att undersöka vilka möjliga faktorer som kan vara bidragande till samhällsvåldets eskalering med fokus på dess förändrade karaktär och kontext, med avgränsning på makronivå. Undersökningen utgick ifrån en kvalitativ ansats med semistrukturerade intervjuer som datainsamlingsmetod. Resultatet visar att orsakerna till samhällsvåldets kontext- och karaktärsförändring är mångfacetterade. Flertalet faktorer har betydelse för samhällsvåldets utveckling. De faktorer studien belyser är organiseringen inom svenska institutionen, förändringar i den kriminella miljön, narkotika samt media. Resultatet visar att dessa faktorer samspelar med varandra där organiseringen av Sveriges institutioner har en stor påverkan på hur de andra faktorerna uttrycker sig i samhället. / Swedish society has witnessed a change in recent years regarding the nature and context of community violence. There is a need for effective preventive measures, which in turn requires knowledge of the subject in question. The main purpose of this study was therefore to investigate what possible factors may be contributing to the escalation of community violence with focus on its changed character and context, with a definition at the macro level. The study was based on a qualitative approach with semi-structured interviews as a data collection method. The result shows that the causes of community violence´s context and character change are multifaceted. Several factors are important for the development of community violence. The factors the study highlights are the organization within the Swedish institution, changes in the criminal environment, drugs and the media. The results show that these factors interact with each other, where the organization of Sweden´s institutions has a major impact in how the other factors are expressed in society.

Ce travail a pour objectif d’étudier le comportement mécanique d’un fil de para-aramide en sollicitation longitudinale et dynamique. Pour ce faire, nous avons conçu un nouveau dispositif expérimental permettant de réaliser ces essais à l’aide d’un canon à gaz : le Dispositif de Traction par Impact sur Fil (DTIF). Ce dispositif a subi de nombreuses modifications dans le but d’obtenir des conditions d’essais optimales. Celui-ci est associé à un dispositif de mesure par laser permettant d’obtenir le profil de vitesse du projectile ainsi que les courbes caractéristiques de Force-Déformation du fil testé. La validité de la mesure est confirmée par comparaison aux résultats obtenus avec un vélocimètre à effet Doppler, dispositif permettant de mesurer directement et de façon précise le profil de vitesse du projectile. Plusieurs campagnes d’essais sont réalisées, à la fois dans le but d’identifier les caractéristiques dynamiques d’un fil seul, et dans le but de caractériser l’influence de l’arrangement structural d’un tissu sur le comportement dynamique d’un fil. Cette étude révèle l’intervention de trois principaux paramètres structuraux, qui sont la surface de contact inter-fils totale, le nombre de points de liage et les pressions inter-fils transverses et latérales au sein du tissu, influant sur quatre principaux critères de rupture du fil, qui sont les défauts de structure et les phénomènes d’hystérésis au sein du filament, les concentrations de contraintes ainsi que les forces de frottement au niveau des interactions entre le fil testé et le reste de la structure tissée. / This work aims at studying the mechanical behavior of a para-aramid yarn in dynamic and longitudinal load. To that end, we designed a new experimental device to achieve these tests with the use of a gas gun: the Tensile Impact Test for Yarn (TITY). This device met numerous modifications in the aim to reach optimal test conditions. It is associated with a measurement device using laser and allowing obtaining the velocity profile of the projectile and the Strength-Strain characteristic curves of the tested yarn. The validity of the measure is confirmed by comparing our results with those obtained with a laser Doppler vélocimètre, device allowing measuring directly and precisely the velocity profile of the projectile. Many test campaigns are performed. Both in the aim to identify the dynamic parameters of a single and virgin yarn, and in the aim to characterize the impact of the fabric structural arrangement on the dynamic behavior of a yarn. This study reveals the intervention of three main structural parameters, which are the total inter-yarns contact surface, the number of binding points and the transvers and lateral inter-yarns pressures, having an impact on four main yarn break criteria, which are the structural defects and hysteresis phenomena inside the filament, stress concentrations and frictional forces concerning the interactions between the tested yarn and the rest of the fabric.

The recent usage of presidential directives by President Barack Obama and President Donald Trump initiated debates around limits of presidential power. Research on the presidential power has shown lack of focus on the presidential directives, misinterpretation and wrong terminology which resulted in false accusations of presidential overreach and abuse of power. This thesis argues that the political gridlock and increasing passivity of Congress have contributed to a shift between the executive and legislative power of government. This thesis will trace the extent to which Congress has become resistant to pass two of the key priorities of President Obama's political agenda - immigration reform and gun regulation, after which the President had to act on the issues unilaterally. The main aim of the thesis is to show that presidential directives of President Obama were not issued in a vacuum and that there were debates, persuasion and negotiations preceding the executive actions in an attempt to advance President's agenda in a form of bipartisan legislation rather than unilateral presidential directive.

No description available.

The effects of a composite overwrapped gun barrel with viscoelastic damping layers are investigated. Interlaminar stresses and constrained layer damping effects are described. The Modal Strain Energy method is developed for measuring the extent to which the barrel is damped. The equations of motion used in the finite element analysis are derived. The transient solution process is outlined. Decisions for selected parameters are discussed. The results of the finite element analyses are presented using the program written in FORTRAN. The static solution is solved with a constant internal pressure resulting in a calculated loss factor from the Modal Strain Energy Method. The transient solution is solved using the Newmark-Beta method and a variable internal pressure. The analyses conclude that strategically placed viscoelastic layers dissipate strain energy more effectively than a thick single viscoelastic layer. The optimal angle for maximizing the coefficient of mutual influence in a composite cylinder is not necessarily the optimal angle when viscoelastic layers are introduced between layers.

In the traditional agenda-setting theory, the agenda-setters were the news media and the public has a minimal role in the process of agenda-setting, which makes the public a passive receiver located at the bottom in the top-down agenda-setting dynamics. This study claims that with the development of Information communication technologies, primarily social media, the networked public may be able to set their own agendas through connective actions, outside the influence of the news media agenda. There is little empirical research focused on development and dynamics of public agenda-setting through social media platforms. Understanding the development and dynamics of public agenda-setting may be key to accounting for and overcoming conflicting findings in previous reverse agenda-setting research. This study examined the public agenda-setting dynamics through a case of gun violence prevention activism Twitter network, the #MarchForOurLives Twitter network. This study determined that the agenda setters of the #MarchForOurLives Twitter network are the key Never Again MSD student leaders and the March For Our Lives. The weekly reflected important events and issues and the identified topics were highly co-related with the themes examined in the tweets created by the agenda setters. The amplifiers comprised the vast majority of the tweets. The advocates and the supporters consisted of 0.44% and 4.43% respectively. The tweets made by the agenda setters accounted for 0.03%. The young activists and the like-minded and participatory public could continuously make changes taking advantage of technologies, and they could be the hope in the current and future society.

Electron microscopy has become an essential component in many scientific fields, in which it contributes to new discoveries. The microscopy itself is continually being developed and the limits, which seemed to be insurmountable, have been overcome. The instruments have become user friendlier and their mobility enables flexible practical use in the field. The subject of this work is the design of a scanning electron microscope, the calculation of a magnetic curcuit of an immersion objective combined with standard lens, the theoretical calculation of a microscope resolution and the design solution of the mechanical parts of the microscope with a sample manipulator. The thesis includes a description of the electron microscopy development summarizing it briefly from the very beginning up to now. It also deals with electron sources, especially the Shottky cathode, which is to be the main object observed by the proposed device. The work also contains a description of the calculation of the microscope resolution as a function of the current density distribution. Another interesting issue included in the theoretical part is the signal detection, a description of several types of detectors and possible signal processing. The solution of the thesis includes a description of the concept of the scanning electron microscope with an explanation of the distribution of combined lens functions. The optical diagram shows the arrangement of the electron optics system and the distibution of pressure in the chamber of the microscope. The theoretical calculation is devoted to the magnetic curcuit design of the objective and to the resolution of the microscope for a given extent of working distances. Two modifications of the lens were designed – a standard simple objective and a combination of the standard objective with the immersion magnetic one. The results of both modifications are given for the parameters to be compared. The combined objective was designed with the possibility of use in two modes, as a standard and immersion lens. The deflection system is also divided into two modes, as a single deflection for the standard lens and as a two-dimension deflection for the immersion lens. Detectors for secondary electrons (SE) and detectors for back scattered electrons (BSE) will be used for the signal detection. The design of the microscope is another large part, which gives details on the most significant components of the microscope. The content of the technical solution is a three-dimensional computer model, created in Autodesk Inventor, which also includes a sample manipulator driven by piezoelectric actuators.

Syftet med studien var att undersöka hur olika brottsförebyggande aktörer ser på det 364 dagar långa uppehållet av skjutningar som varade i Linköping mellan 28 januari 2022 och 27 januari 2023. Syftet var även att studera hur aktörerna ser på förebyggande arbete mot skjutningar i Linköping på ett övergripande plan. För att studera detta har kvalitativa intervjuer genomförts med sex relevanta brottsförebyggande aktörer i kommunen. Resultatet visade att uppehållet utifrån informanternas beskrivning till stor del berodde på tillfälligheter som lett till avhållsamhet hos de som annars genomför skjutningar. Aktörerna hade dock tilltro till det egna och andra aktörers arbete på området, både preventivt och ingripande, och menade att samverkan mellan aktörerna är fundamentalt i arbetet mot skjutningar. De viktigaste slutsatserna var att det inte går att säkerställa varför uppehållet uppstod, men att aktörernas bilder av uppehållet och vilka åtgärder som fungerar var samstämmiga. Dessa åtgärder avser främst samverkan och närvaro. / The purpose of this study was to examine the perspectives of crime prevention actors regarding the 364-day absence of shootings in Linköping between January 28, 2022, and January 27, 2023. Additionally, the study aims to investigate how these actors perceive preventive efforts against shootings in Linköping. Qualitative interviews were conducted with six relevant crime prevention actors in Linköping to examine these aspects. The findings revealed that, according to the informants' descriptions, the absence of shootings during this period was largely due to coincidental factors that abstained potential perpetrators. Nevertheless, the actors expressed confidence in the effectiveness of their own and other actors' preventive and intervention initiatives, emphasizing the fundamental role of interagency collaboration in preventing shootings. The study concludes that while specific reasons for the absence cannot be determined, actors' perceptions and the importance of interagency collaboration was consistent. The findings highlight interagency collaboration and active presence in crime prevention.

<p>  </p> <p>Polymer bonded explosives (PBX) are a particle reinforced composite containing a high solids loading of explosive particulates bound in a polymer matrix. Commercially produced energetic particulates contain some percentage of flaws in the form of contaminants, porosity, and preexisting fractures. Additional large-scale porosity within the composite is generated during PBX formulation. The introduction of novel additive manufacturing techniques to the energetics field alters the known composite structure and introduces a porosity variable that has not been fully characterized. Porosity collapse during deformation is believed to be a predominant mechanism for hotspot formation, which dominates shock initiation behaviors. These phenomena are difficult to experimentally characterize due to inherent small spectral and temporal scales, and as such numerical and computational models are relied upon to inform fundamental physics. Experimental characterization of the behaviors of energetic materials during deformation is necessary to better inform computational studies and improve our understanding of hotspot formation mechanisms. </p> <p>This dissertation experimentally evaluates the high-rate deformation of porosity in individual explosive particulates and within the overall composite structure. This has included the development of a novel micromachining technique for pore generation in energetic single crystals using the focused ion beam (FIB), resulting in precise and controllable porosity generation that is easily reproducible in collaboration with computational studies. FIB was shown to be an effective pore generation technique, verified by assessing surface roughness and pore quality compared to contemporary manufacturing methods. Three experimental subsets are evaluated: surface cracks in HMX single crystals, polygonal pores in HMX single crystals, and large-scale porosity variations in mock vibration assisted print (VAP) produced composites of borosilicate glass beads and Sylgard 184® binder. A single stage light gas gun was used to impact the samples at 400 m/s and the impact event and resultant material response were observed in real time using x-ray phase contrast imaging (PCI). Machined surface cracks were shown to have negligible effect on the final fracture behaviors of HMX crystals. In polygonal pores fractures were shown to originate due to stress concentration during impact followed by otherwise expected brittle fracture behaviors. For wedge-like pores, the shockwave culminates on the front face of the pore and contributed to early fracture in some samples as well as a consistent open fracture opposite the impact along the shockwave direction in later stages of impact. For the blunt rectangular-like pores two differing behaviors were observed, wherein either the pore condensed and fracture at the pore was not seen during the impact event or large open fractures formed at the pore corners opposite the shockwave. The variance in response is attributed to the energy of fracture dissipating somewhere else in the material bulk, like the behaviors observed in the milled slot samples. Finally, additively manufactured PBX deformation behaviors were observed to be dominated by the collapse of the existing ordered porosity in the bulk which occurred at an increased rate relative to the bulk material compression. This resulted in a three-stage progression of deformation, consisting of a rapid collapse of large-scale ordered porosity, followed by the densification of the remaining features, and ultimately ending in compaction of the bulk as the impact projectile fully compressed the samples. Future work includes exploration of further FIB produced pore effects on dynamic fractures, evaluation of printed material deformation behaviors at additional rates, as well as application and evaluation of additional VAP printed material formulations.  </p>