Made available in DSpace on 2014-10-09T12:33:55Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:59Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:56Z (GMT). No. of bitstreams: 0 / Neste trabalho analisa-se o problema do transporte do feixe de elétrons em canhões de elétrons, estruturas periódicas de ímãs permanentes e em coletores de simples e múltiplos estágios. Essa análise é de relevância em projetos de dispositivos de micro-ondas de potência dos tipos amplicador klystron e válvula TWT. Determina-se a dinâmica das partículas a partir da solução da equação da trajetória que é derivada da força de Lorentz e da conservação de energia. A equação da trajetória obtida é diferencial de segunda ordem, não-linear e independentemente do tempo para o potencial generalizado. Utiliza-se o método de Runge-Kutta de 4a Ordem para integrar a equação da trajetória das partículas. Obtém-se o potencial escalar elétrico a partir da solução da equação de Poisson. Numericamente, obtêm-se os po- tenciais escalares elétricos e magnéticos, por meio do Método de Elementos Finitos (MEF). Ao longo do movimento de uma partícula, obtida a partir da solução da equação da trajetória, deposita-se carga elétrica. Utilizam-se macropartículas, uma vez que é praticamente impossível modelar cada partícula do problema, a partir do método Partícula na Célula (Particle in Cell - PIC). Neste caso, tem-se um problema acoplado para o potencial escalar elétrico e as trajetórias das macropartículas, uma vez que, as trajetórias das macropartículas dependem dos potenciais e estes, por sua vez, dependem das trajetórias. À convergência deste problema acoplado utiliza-se o Método das Aproximações Sucessivas (MAS). A plataforma desenvolvida, baseada nos métodos acima, compõe-se de duas ferramentas computacionais. A primeira, XMGUN, dedica-se ao projeto de: canhões de elétrons com grades e grades de sombreamento; e coletores de simples e múltiplos estágios considerando, ainda, a emissão de elétrons secundários. A segunda, XMAGUN, volta-se ao projeto de estruturas periódicas com ímãs permanentes. Afere-se o desempenho da ferramenta computacional XMGUN com o diodo plano de Pierce operando na condição em que a corrente é limitada pelas cargas espaciais. Por sua vez, verica-se o desempenho do XMAGUN por meio de simulações com estruturas do tipo PPM separadas pelo vácuo e na presença de pole pieces. Os resultados obtidos em todas as simulações convergiram satisfatoriamente para as soluções analíticas. Utilizando o XMGUN, projeta-se um canhão de elétrons com 30 kV de tensão de anodo e uma perveância de 1,37 Perv com capacidade de fornecer uma corrente elétrica de 7,1 A. Esse canhão tem uma malha com 2796 elementos e 5057 nós. As principais características geométricas do canhão de elétrons são: raio do catodo rc=14,6 mm; raio do disco do catodo rk =6,2 mm; e ângulo do eletrodo de focalização = 37. Neste caso, a velocidade transversal normalizada e o alcance do feixe zw observados são de 0,068 e 26,88 mm respectivamente. Obtém-se uma concordância superior a 93% em corrente e perveância com o EGUN. Utilizando, ainda, o XMGUN, são simulados coletores de simples e múltiplos estágios. O coletor de simples estágio apresenta 1612 nós e 2969 elementos, e o de 4 (quatro) estágios, 2496 nós e 4257 elementos. As tensões dos eletrodos do 1o, 2o, 3o e 4o estágio são de 9,45 kV, 8,65 kV, 6,45 kV e 3,45 kV respectivamente. Durante as simulações, devido à emissão de elétrons secundários, observa-se, para o coletor de simples estágio, macropartículas penetrando na região de deriva, fenômeno este indesejado, e não observado para o coletor de 4 (quatro) estágios. Considerando o XMAGUN, projeta-se um arranjo periódico com pole pieces e 5 (cinco) ímãs permanentes, capaz de fornecer um campo magnético, no centro da estrutura, de 0,42 T. Neste caso, a geometria do arranjo periódico obtida é: raio interno rm1 e externo rm2 do ímã permanente são iguais a 3,5 mm e 7,5 mm respectivamente; raio externo do pole piece r3 = 7,5 mm ; raio interno rf1 e externo rf2 da ponteira do pole piece são 1,6 mm e 3,05 mm respectivamente; espessura do ímã permanente T=2,95 mm; período magnético L =8,5 mm. A remanência do ímã permanente utilizada é de Br=0,85 T. A malha dessa estrutura periódica magnética apresenta pouco mais de 20.000 nós e 40.000 elementos. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:55Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:59Z (GMT). No. of bitstreams: 0 / A ciência forense moderna caminha lado a lado com a pesquisa científica. Os cientistas forenses se deparam diariamente com vários casos que requerem a análise de resíduos provenientes de disparos de arma de fogo (gunshot residues - GSR). Este trabalho contempla o desenvolvimento de uma metodologia para determinar assinaturas químicas de disparos de arma de fogo, medindo-se as concentrações de Pb, Ba e Sb presentes nos resíduos provenientes destes disparos depositados nas proximidades do orifício de entrada de projéteis, baseada na técnica de espectrometria de massas de alta resolução com fonte de plasma indutivamente acoplado (ICP-MS). Foram realizados disparos em cinco tipos de tecidos-alvos e coletados testemunhos em regiões próximas ao orifício de entrada dos projéteis. Os resultados demonstraram que o método possibilitou identificar e distinguir os resíduos de revólver calibre .38 ao de pistolas calibres .40 e 9 mm. O uso de gráficos ternários como ferramenta de análise dos dados coletados, permitiu identificar padrões específicos de distribuição de amostras em branco e dos resíduos depositados após disparos de revólveres e pistolas. A metodologia possibilitou a atribuição da origem dos disparos por meio de confirmação dos resíduos coletados também das mãos dos atiradores. Como conseqüência a metodologia representa um grande avanço nos procedimentos da polícia e visa adicionar uma contribuição valiosa às investigações forenses. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Gun violence is a pandemic problem in the United States, resulting in over two thirds of all homicides each year. Consequently, gun related policies have been fiercely debated within the political spectrum, with the 20th century seeing a dramatic increase in gun control legislation. Gun-free zones are designated areas that strictly prohibit all private citizens from carrying a firearm, even those with concealed weapon permits. The statistics indicate that numerous instances of gun related mass shootings have occurred within the confines of these gun-free zones (schools, movie theatres, government installations, etc.). However, little research exists to understand whether citizens actually feel any safer when they are in a gun-free zone. The purpose of this study was to explore citizens’ perceptions about gun control policies, specifically about using gun-free zones, who resided in the five states with the highest rates of gun violence per capitain descending order, these included Virginia, Florida, Texas, Nevada, and Connecticut. Moreover, these five states were the locations of the top five deadliest mass shootings in U.S. history to date. The researcher also discovered how residents felt about pro-gun areas, where responsible citizens could legally carry firearms, as well as determine whether gun-free zones influenced their likelihood of visiting a prescribed location. Finally, the study sought to understand residents’ perceptions regarding using gun-free zones pertaining to their impact on reducing incidents of mass shootings. The researcher filled the gap in the literature regarding knowledge pertaining to citizens’ perceptions about using specific gun control measures, such as gun-free zones, and the influence that the historical evidence had on their perceptions. The answer to RQ1 (do residents associate using gun-free zones with feelings of safety or feelings of concern?) was that participants were twice as likely to associate using gun-free zones with feelings of concern rather than feelings of safety. The answer to the first part of RQ2 (whether participants believed that gun-free zones reduced gun-related violence) was no, based on a 2-to-1 ratio. Responses to the impact of gun control measures on reducing gun violence were closely matched to perceptions of the role of gun-free zones in reducing gun violence. The answer to the second part of RQ2 (do residents believe that gun-free zones lower the occurrences of mass shooting incidents?) was no, again based on a 2-to-1 ratio. The answer to the third and final part of RQ2 (whether participants’ perceptions correlated to the historical/empirical evidence of the location of mass shootings as primarily inside of or outside of gun-free zones) was yes for participants from Florida, Texas, Nevada, and Connecticut and no for participants from Virginia.

Since the 75th anniversary of the 1928 Okeechobee Hurricane in 2003, a growing number of journalists and historians writing about the disaster have incorporated Zora Neale Hurston's 1937 novel Their Eyes Were Watching God as part of the official historical record of the hurricane. These writers often border on depicting Their Eyes as the authentic experience of black migrant workers impacted by the hurricane and subsequent flood. Within the novel itself, however, Hurston theorizes on the potential epistemic violence that occurs when a piece of evidence—a photograph, fallen body, or verbal artifact—is used to judge a person. Without a person's ability to use self-representation to give an "understandin'" (7) to go along with the evidence, snapshots or textual evidence threaten to violently separate people from their prior knowledge of themselves. By offering the historical context of photographs of African Americans in the Post-Reconstruction South, I argue that Janie experiences this epistemic violence as a young girl when seeing a photograph of herself initiates her into the racial hierarchy of the South. A few decades later, while on trial for shooting her husband Tea Cake, Janie again faces epistemic violence when the evidence of Tea Cake's body is used to judge her and her marriage; however, by giving an understandin' to go along with the evidence through self-representation, Janie is able to clarify that which other forms of evidence distort and is able to go free. Modern texts appropriating Their Eyes run the risk of enacting epistemic violence on the victims of the hurricane, the novel, and history itself when they present the novel as the complete or authentic perspective of the migrant workers in the hurricane. By properly situating the novel as a historical text that offers a particular narrative of the hurricane rather than the complete or authentic experience of the victims, modern writers can honor Hurston's literary achievement without robbing the actual victims of the hurricane of their voice.

There is a lack of consensus on the empirical findings in research examining the so-called ‘guns and butter’ argument – does military expenditure crowd out social expenditure or not? Feminist scholars have been arguing that militarism, affects women’s welfare in a negative way. This study investigates whether countries' increase in military expenditure leads to a deterioration in women's health and education, based on the guns and butter argument. The study intends to find out what a possible correlation looks like for two different models, one that represents the impact on women's health and another that represents the impact on women's education, by using maternal mortality and school enrollment (with a gender parity index) as dependent variables. The survey is conducted for a sampling of countries in Africa, the Middle East, and South Asia for the period 1988 to 2020. The main findings of this study indicate that increased military expenditure leads to increased maternal mortality, however, the study finds no linear relationship between military expenditure and girls' school enrollment. The study also finds no correlation between health care, education expenditure and maternal mortality. Nevertheless, it indicates that education expenditure has a positive effect on girls’ school enrollment, and health care expenditure has a negative effect on girls’ school registration.

The current study examines firearms’ impact on the relationship between illegal drug markets and homicide. At the county-level, Iowa and Virginia are analyzed using crime data from the National Incident Based Reporting System. More specifically, gun availability is tested as a mediator for county drug crime rates and homicide counts. Variable selection and prediction is based on routine activity and social disorganization theories. I argue that social disorganization allows the context for which criminal opportunity presents itself through routine activities. I posit gun availability mediates a positive relationship between illegal drug markets and homicide, with differences between urban and rural communities

Recent research has provided empirical support for counseling guidelines for pediatric gun safety and has demonstrated that some parental behaviors increase children's risk of gun injury. However, few data exist on patterns of gun-injury risks, especially for children younger than age 10, children from middle-class and non-urban families, and children of non-gun-owning vs. gun-owning parents. Part I of the study presents data on gun injury risks in a middle-SES sample of rural and suburban gun-owning and non-gun-owning parents and their 5-8-year-old children (N=60). Gun-owners (38.3% of the sample) endorsed an average of 10.57 out of 21 assessed gun injury risks, and evinced variable patterns of gun injury risks. Gun injury risks were much lower among non-gun-owners. However, a small number of non-gun-owners reported their children to have gun exposure risks more typical of gun-owners' children (e.g., child goes hunting/shooting). Part II of the study presents data on the children's responses to a crisis scenario involving a threat associated with defensive gun use (home intrusion). Children's crisis response plans were categorized as competent, passive, bold, or aggressive/gun. Competent plans were common (38.6%). However, most children generated non-competent crisis responses, including passive plans (21.1%), bold plans (19.3%), and aggressive/gun plans (21.1%). These results may help to identify styles of crisis response for targeted preventive interventions and emergency response training. The common theme in these results is that encouraging safe behavior, whether by young children responding to a crisis or by parents who own guns, requires an understanding of motivations for unsafe behavior and barriers to safer behavior. / Ph. D.

In late December 2000 the Ministry of Justice and Security of the Argentine province of Mendoza completed the first phase of the programme Canje de Armas por Mejores Condiciones de Vida, hereafter referred to as the Arms Exchange Programme, as part of a multi-faceted long-term approach to transform the public security climate. Two hundred eighty five pistols, revolvers and shotguns were voluntarily turned in by citizens for destruction in exchange for vouchers for foodstuffs and tickets to football games with values ranging from US $50 to $100. Participants were able to make contact with the programme organisers through a toll-free telephone line. Prior to the firearm turn-in component a public education effort was coordinated in the school system that culminated in a violent toy turn-in and destruction drive that brought in thousands of toy guns and video games for public destruction and incorporation into displays of art. The overwhelmingly positive response to the first phase of the programme inspired organisers to launch a second phase of weapons collection on 10 April 2001 including sectors of the province outside the Greater Mendoza area. Although the second phase was scheduled to end on 24 April 2001 it had to be extended on two separate occasions in response to enthusiastic requests from several localities that were not originally scheduled to host the Arms Exchange Programme. The second phase, which lasted six weeks, collected a total of 2,281 weapons and 6,547 rounds of ammunition, bringing in a total of 2,566 weapons and 8,262 rounds of ammunition for both phases combined. Arguably, the town of San Rafael, where 809 revolvers, pistols, shotguns and rifles were turned in over the course of four days, in the southern section of Mendoza province, saw more weapons turned in per capita than any other programme in the world to date.

Electrothermal (ET) Plasma Technology has been used for many decades in a wide variety of scientific and industrial applications. Due to its numerous applications and configurations, ET plasma sources can be used in everything from small scale space propulsion thrusters to large scale material deposition systems for use in a manufacturing setting. The sheer number of different types of ET sources means that there is always additional scientific research and characterization studies that can be done to either explore new concepts or improve existing designs. The focus of this work is to explore a novel electrothermal energetic plasma source (ETEPS) that uses energetic gas as the working fluid in order to harness the combustion and ionization energy of the subsequently formed energetic plasma. The goal of the work is to use computer code and engineering methods in order to successfully characterize the capabilities of the ETEPS concept and to then design a prototype which will be used for further study. This thesis details the background of ET plasma physics, the ETEPS concept physics, and the computational and design work done in order to demonstrate the feasibility of using the ETEPS source in two roles: space thrusters and electrothermal plasma guns. / Master of Science