This dissertation describes two independent studies related to charged aerosols. The first study examines the role of electrical conductivity on the amounts of charge and mass emitted during the break-up of charged droplets via Coulombic fission. The second study examines the hygroscopic behavior of mixed particles. The results from both studies are presented here in detail along with an in-depth discussion of pertinent literature and applications in modern technologies. Charged droplets break-up via a process termed Coulombic fission when their charge density reaches a certain level during which they emit a portion of their charge and mass in the form of progeny microdroplets. Although Rayleigh theory can be used to predict the charge level at which break-ups occur, no equivocal theory exists to predict the amounts of charge or mass emitted or the characteristics of the progenies. Previous investigations have indicated that the electrical conductivity of a charged droplet may determine how much charge and mass are emitted during its break-up via Coulombic fission. To further examine this supposition, charged droplets having known electrical conductivities were observed through multiple break-ups while individually levitated in an electrodynamic balance. The amounts of charge and mass emitted during break-ups were determined using a light scattering technique and changes in the DC null point levitation potentials of the charged droplets. Here, electrical conductivity was found to increase and decrease the amounts of charge and mass emitted, respectively, while having no effect on the charge level at which break-ups occurred. The findings of this investigation have significant bearing in nanoparticle generation and electrospray applications. The hygroscopic behavior of atmospherically relevant inorganic salts is essential to the chemical and radiative processes that occur in Earth’s atmosphere. Furthermore, studies have shown that an immense variety of chemical species exist in the atmosphere which inherently mix to form complex heterogeneous particles with differing morphologies. However, how such materials and particle morphologies affect the hygroscopic behavior of atmospherically relevant inorganic salts remains mostly unknown. Therefore, the effects of water insoluble materials, such as black carbon, on the hygroscopic behavior of inorganic salts were examined. Here, water insoluble solids were found to increase the crystallization relative humidities of atmospherically relevant inorganic salts when internally mixed. Water insoluble liquids however, were found to have no effect on the hygroscopic behavior of atmospherically relevant inorganic salts. The findings of this investigation have significant bearing in atmospheric modeling.

Made available in DSpace on 2014-06-11T19:28:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-17Bitstream added on 2014-06-13T20:18:26Z : No. of bitstreams: 1 serra_me_me_botfca.pdf: 1870936 bytes, checksum: 12e9bbc49a2c704975691c8897a1ab0c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A pulverização é a mais importante técnica de aplicação de produtos fitossanitários na cultura do crisântemo. A otimização dessa tecnologia pode ser obtida com a transferência de carga elétrica às gotas, as quais são fortemente atraídas pelas plantas, minimizando a exposição dos aplicadores e as perdas para o ambiente. O trabalho objetivou avaliar a deposição das gotas de pulverização dotadas de carga elétrica (eletrostática) em comparação à técnica de pulverização convencional, bem como a eficiência dessas técnicas no controle de Tetranychus urticae na cultura do crisântemo. Os experimentos foram conduzidos no delineamento inteiramente ao acaso. No experimento para avaliação da deposição da pulverização foram realizados oito tratamentos com quatro repetições. Cada repetição foi representada por doze plantas às quais foram afixados papéis do tipo mataborrão na superfície abaxial e adaxial dos folíolos e em duas posições da planta: ápice e base. Foram utilizadas quatro pontas de pulverização (TXVK-3, AXI 110015, AXI 12002 TWIN e AXI 11003) combinadas às técnicas de pulverização eletrostática e convencional. Um corante marcador (Rodamina B) foi pulverizado na proporção de 5 gramas por 100 litros d água em cada um dos tratamentos. Os depósitos do corante marcador foram quantificados por 2 fluorometria. A eficiência dos tratamentos no controle do ácaro-rajado foi estabelecido pela combinação do tipo de ponta (AXI 110015, AXI 12002 TWIN e TXVK-3), da técnica de pulverização (eletrostática e convencional) e do produto para o controle do ácaro (azociclotina e espirodiclofeno, nas doses de 25 e 4,8 mL de i.a. por 100 L d água, respectivamente) mais dois tratamentos adicionais (testemunhas). Avaliações da população do ácaro foram realizadas antes e aos 3, 7, 11 e 15 dias após a pulverização pela contagem... / Spraying is the most important pesticide application technique for healthy development of chrysanthemum plants. The optimization of this technology can be obtained with the transference of the electric charge in the droplets. These droplets are strongly attracted by plants, minimizing the workers exposition as well as loss to the environment. The research aims to evaluate the spray deposition with electric charge (electrostatic) compared to conventional application technique. It also aims to evaluate the efficiency of these techniques in the Tetranychus urticae control of chrysanthemum plants. The experiments were carried out entirely at random. In the deposition experiment eight treatments were set with four repeats. Each repeat was represented by twelve chrysanthemum plants. Blotting paper was placed on the abaxial and adaxial surfaces of two leaves in different positions of the plants: top and bottom. Four spray nozzles (TXVK-3, AXI 110015, AXI 12002 TWIN and AXI 11003) were combined to different spraying techniques (electrostatic and conventional). A tracer dye (Rodamina B) was applied in the ratio of 5 grams per 100 L of water in each one of the treatments. Deposits of the tracer dye were quantified by fluorometery. The efficiency of treatments in the control of spider mite was established by combination of spray nozzle type (AXI 110015, AXI TWIN and TXVK-3), with different application techniques and the acaricides (azocyclotin and espirodiclofen, at the dosages 25 and 4,8mL of a.i. per 100 L of water, respectively), plus two additional treatments (checks). The evaluations of spider mite population were realized until and at 3, 7, 11 and 15 days after spraying by counting the number of mites in pre-established area of 1 4 cm2 in the top leaves of the plants. The percentage of efficiency of the control was calculated by the adapted formula of Henderson e Tilton... (Complete abstract click electronic access below)

The goal of this thesis is to study of the evolution of 3D electrically charged liquid droplets of fluid evolving under the influence of surface tension and electrostatic forces. In the first part of the thesis, an appropriate mathematical model of the problem is introduced and the linear stability analysis is developed by perturbing a sphere with spherical harmonics. In the second part, the numerical solution of the problem is described with the use of the boundary elements method (BEM) on an adaptive mesh of triangular elements. The numerical method is validated by comparison with exact solutions. Finally, various numerical results are presented. These include neck formation in droplets, the evolution of surfaces with holes, singularity formation on droplets with various symmetries and numerical evidence that oblate spheroids are unstable.

Orientador: Carlos Gilberto Raetano / Banca: Wilson Badiali Crocomo / Banca: Hamilton Humberto Ramos / Resumo: A pulverização é a mais importante técnica de aplicação de produtos fitossanitários na cultura do crisântemo. A otimização dessa tecnologia pode ser obtida com a transferência de carga elétrica às gotas, as quais são fortemente atraídas pelas plantas, minimizando a exposição dos aplicadores e as perdas para o ambiente. O trabalho objetivou avaliar a deposição das gotas de pulverização dotadas de carga elétrica (eletrostática) em comparação à técnica de pulverização convencional, bem como a eficiência dessas técnicas no controle de Tetranychus urticae na cultura do crisântemo. Os experimentos foram conduzidos no delineamento inteiramente ao acaso. No experimento para avaliação da deposição da pulverização foram realizados oito tratamentos com quatro repetições. Cada repetição foi representada por doze plantas às quais foram afixados papéis do tipo mataborrão na superfície abaxial e adaxial dos folíolos e em duas posições da planta: ápice e base. Foram utilizadas quatro pontas de pulverização (TXVK-3, AXI 110015, AXI 12002 TWIN e AXI 11003) combinadas às técnicas de pulverização eletrostática e convencional. Um corante marcador (Rodamina B) foi pulverizado na proporção de 5 gramas por 100 litros d’água em cada um dos tratamentos. Os depósitos do corante marcador foram quantificados por 2 fluorometria. A eficiência dos tratamentos no controle do ácaro-rajado foi estabelecido pela combinação do tipo de ponta (AXI 110015, AXI 12002 TWIN e TXVK-3), da técnica de pulverização (eletrostática e convencional) e do produto para o controle do ácaro (azociclotina e espirodiclofeno, nas doses de 25 e 4,8 mL de i.a. por 100 L d’água, respectivamente) mais dois tratamentos adicionais (testemunhas). Avaliações da população do ácaro foram realizadas antes e aos 3, 7, 11 e 15 dias após a pulverização pela contagem... (Resumo completo, clicar acesso eletrôncio abaixo) / Abstract: Spraying is the most important pesticide application technique for healthy development of chrysanthemum plants. The optimization of this technology can be obtained with the transference of the electric charge in the droplets. These droplets are strongly attracted by plants, minimizing the workers exposition as well as loss to the environment. The research aims to evaluate the spray deposition with electric charge (electrostatic) compared to conventional application technique. It also aims to evaluate the efficiency of these techniques in the Tetranychus urticae control of chrysanthemum plants. The experiments were carried out entirely at random. In the deposition experiment eight treatments were set with four repeats. Each repeat was represented by twelve chrysanthemum plants. Blotting paper was placed on the abaxial and adaxial surfaces of two leaves in different positions of the plants: top and bottom. Four spray nozzles (TXVK-3, AXI 110015, AXI 12002 TWIN and AXI 11003) were combined to different spraying techniques (electrostatic and conventional). A tracer dye (Rodamina B) was applied in the ratio of 5 grams per 100 L of water in each one of the treatments. Deposits of the tracer dye were quantified by fluorometery. The efficiency of treatments in the control of spider mite was established by combination of spray nozzle type (AXI 110015, AXI TWIN and TXVK-3), with different application techniques and the acaricides (azocyclotin and espirodiclofen, at the dosages 25 and 4,8mL of a.i. per 100 L of water, respectively), plus two additional treatments (checks). The evaluations of spider mite population were realized until and at 3, 7, 11 and 15 days after spraying by counting the number of mites in pre-established area of 1 4 cm2 in the top leaves of the plants. The percentage of efficiency of the control was calculated by the adapted formula of Henderson e Tilton... (Complete abstract click electronic access below) / Mestre