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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Identification of an Unsteady Aerodynamic Model up to High Angle of Attack Regime

Fan, Yigang 12 December 1997 (has links)
The harmonic oscillatory tests for a fighter aircraft configuration using the Dynamic Plunge-Pitch-Roll (DyPPiR) model mount at Virginia Tech Stability Wind Tunnel are described and analyzed. The corresponding data reduction methods are developed on the basis of multirate digital signal processing techniques. Since the model is sting-mounted to the support system of DyPPiR, the Discrete Fourier Transform (DFT) is first used to identify the frequencies of the elastic modes of sting. Then the sampling rate conversion systems are built up in digital domain to resample the data at a lower rate without introducing distortions to the signals of interest. Finally linear-phase Finite Impulse Response (FIR) filters are designed by Remez exchange algorithm to extract the aerodynamic characteristics responses to the programmed motions from the resampled measurements. These data reduction procedures are also illustrated through examples. The results obtained from the harmonic oscillatory tests are then illustrated and the associated flow mechanisms are discussed. Since no significant hysteresis loops are observed for the lift and the drag coefficients for the current angle of attack range and the tested reduced frequencies, the dynamic lags of separated and vortex flow effects are small in the current oscillatory tests. However, large hysteresis loops are observed for pitch moment coefficient in the current tests. This observation suggests that at current flow conditions, pitch moment has large pitch rate and alpha-dot dependencies. Then the nondimensional maximum pitch rate q_<sub>max</sub> is introduced to characterize these harmonic oscillatory motions. It is found that at current flow conditions, all the hysteresis loops of pitch moment coefficient with same nondimensional maximum pitch rate are tangential to one another at both top and bottom of the loops, implying approximately same maximum offset of these loops from static values. Several cases are also illustrated. Based on the results obtained and those from references, a state-space model is developed to describe the unsteady aerodynamic characteristics up to the high angle of attack regime. A nondimensional coordinate is introduced as the state variable describing the flow separation or vortex burst. First-order differential equation is used to govern the dynamics of flow separation or vortex bursting through this state variable. To be valid for general configurations, Taylor series expansions in terms of the input variables are used in the determination of aerodynamic characteristics, resembling the current approach of the stability derivatives. However, these derivatives are longer constant. They are dependent on the state variable of flow separation or vortex burst. In this way, the changes in stability derivatives with the angle of attack are included dynamically. The performance of the model is then validated by the wind-tunnel measurements of an NACA 0015 airfoil, a 70 degree delta wing and, finally two F-18 aircraft configurations. The results obtained show that within the framework of the proposed model, it is possible to obtain good agreement with different unsteady wind tunnel data in high angle-of-attack regime. / Ph. D.
2

Investigations to identify the influence of the inhalation manoeuvre on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of dry powder inhalers : studies to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of dry powder inhalers

Yakubu, Sani Ibn January 2009 (has links)
Currently available dry powder inhalers (DPIs) for drug delivery to the lungs require turbulent energy to generate and disperse aerosol particles in the respirable range ≤5μm during inhalation. The patient's inspiratory effort together with the resistance inside the device creates this energy. Different inhalers provide varying degrees of resistance to inhalation flow and require different inhalation techniques for the generation and delivery of drug fine particles in respirable size range to the lungs. The aim of this research programme was to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of the salbutamol Accuhaler®, Easyhaler®, and Clickhaler® and the terbutaline Turbuhaler® DPIs. A high-performance liquid chromatography method for the assay of salbutamol sulphate and terbutaline sulphate in aqueous samples was modified and accordingly validated. In-vitro dose emission of the four different DPIs was measured using the pharmacopoeia method with modifications to simulate varying inhalation flows within patient and between patients. The ranges of the total emitted dose (% nominal dose) at the inhalation flow range of 10 - 60 Lmin-1, following one and two inhalations per metered dose for 2L and 4L inhaled volumes were as follows: the Accuhaler (52.64- 85.11; 61.88-85.11 and 59.23-85.11; 62.81-85.11); the Easyhaler (68.35-91.99; 79.94-91.99 and 73.83-92.51; 80.40-92.51); the Clickhaler (46.55-96.49; 51.12-96.49 and 51.18-101.39; 59.71-101.39) as well as the Turbuhaler (46.08-88.13; 51.95-88.13 and 48.05-89.22; 48.64-89.22). The results highlight that the four inhalers have flow-dependent dose emission property to a varying degree using 2L and 4 L inhaled volumes. There was no significant difference in the total emitted dose between a 2L inhaled volume and a 4L inhaled volume at each inhalation flow. Furthermore, the total emitted dose from the Easyhaler®, Clickhaler®, and Turbuhaler® was significantly (p≤0.001) greater with two inhalations than one inhalation per metered dose across the range of inhalation flow (10-60) Lmin-1. This effect was only observed at inhalation flow less than 30 Lmin-1 with the Accuhaler®. Overall there is a significant difference in the total emitted dose. The ex-vivo dose emission of the four different DPIs has been determined using the In- Check Dial device to train twelve non-smoking healthy adult volunteers to inhale at slow (30 Lmin-1) and fast (60 L min-1) inhalation flows through the device with its dial set corresponding to each inhaler. Subsequently each volunteer inhaled at the trained inhalation flows through each active inhaler. The local ethics committee approval was obtained prior to the study and all volunteers gave signed informed consent. The results obtained demonstrate that the studied inhalers have flow-dependent dose emission, thereby enhancing confidence in the use of the In-Check Dial® to identify a patient's inhalation flows through a variety of DPIs. Also the total emitted dose determined by ex-vivo methodology was significantly (p≤0.05) greater with two inhalations than one inhalation per metered dose. The results of the in-vitro aerodynamic dose emission characteristics highlight that the fine particle dose (FPD) from the four studied inhalers is flow dependent. Also the minimum inhalation flow to generate the (FPD) with the appropriate characteristics for lung deposition has been identified to be 20 L min⁻¹ for the Accuhaler®, Easyhaler® and Clickhaler®, while that for the Turbuhaler® is about 30 L min⁻¹. Also the inhalation volume above 2L and the number of inhalations for each dose have respectively no significant (p≤0.05) influence on the FPD emitted from the four studied inhalers. The results support the present instructions to patients using these inhalers to inhale once for each dose as fast as they can.
3

Investigations to identify the influence of the inhalation manoeuvre on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of dry powder inhalers: Studies to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of dry powder inhalers.

Ibn Yakubu, Sani January 2009 (has links)
Currently available dry powder inhalers (DPIs) for drug delivery to the lungs require turbulent energy to generate and disperse aerosol particles in the respirable range ¿5¿m during inhalation. The patient's inspiratory effort together with the resistance inside the device creates this energy. Different inhalers provide varying degrees of resistance to inhalation flow and require different inhalation techniques for the generation and delivery of drug fine particles in respirable size range to the lungs. The aim of this research programme was to identify the influence of inhalation flow, inhalation volume and the number of inhalations per dose on the ex-vivo dose emission and the in-vitro aerodynamic dose emission characteristics of the salbutamol Accuhaler®, Easyhaler®, and Clickhaler® and the terbutaline Turbuhaler® DPIs. A high-performance liquid chromatography method for the assay of salbutamol sulphate and terbutaline sulphate in aqueous samples was modified and accordingly validated. In-vitro dose emission of the four different DPIs was measured using the pharmacopoeia method with modifications to simulate varying inhalation flows within patient and between patients. The ranges of the total emitted dose (% nominal dose) at the inhalation flow range of 10 - 60 Lmin-1, following one and two inhalations per metered dose for 2L and 4L inhaled volumes were as follows: the Accuhaler (52.64- 85.11; 61.88-85.11 and 59.23-85.11; 62.81-85.11); the Easyhaler (68.35-91.99; 79.94-91.99 and 73.83-92.51; 80.40-92.51); the Clickhaler (46.55-96.49; 51.12-96.49 and 51.18-101.39; 59.71-101.39) as well as the Turbuhaler (46.08-88.13; 51.95-88.13 and 48.05-89.22; 48.64-89.22). The results highlight that the four inhalers have flow-dependent dose emission property to a varying degree using 2L and 4 L inhaled volumes. There was no significant difference in the total emitted dose between a 2L inhaled volume and a 4L inhaled volume at each inhalation flow. Furthermore, the total emitted dose from the Easyhaler®, Clickhaler®, and Turbuhaler® was significantly (p¿0.001) greater with two inhalations than one inhalation per metered dose across the range of inhalation flow (10 ¿ 60) Lmin-1. This effect was only observed at inhalation flow less than 30 Lmin-1 with the Accuhaler®. Overall there is a significant difference in the total emitted dose. The ex-vivo dose emission of the four different DPIs has been determined using the In- Check Dial device to train twelve non-smoking healthy adult volunteers to inhale at slow (30 Lmin-1) and fast (60 L min-1) inhalation flows through the device with its dial set corresponding to each inhaler. Subsequently each volunteer inhaled at the trained inhalation flows through each active inhaler. The local ethics committee approval was obtained prior to the study and all volunteers gave signed informed consent. The results obtained demonstrate that the studied inhalers have flow-dependent dose emission, thereby enhancing confidence in the use of the In-Check Dial® to identify a patient¿s inhalation flows through a variety of DPIs. Also the total emitted dose determined by ex-vivo methodology was significantly (p¿0.05) greater with two inhalations than one inhalation per metered dose. The results of the in-vitro aerodynamic dose emission characteristics highlight that the fine particle dose (FPD) from the four studied inhalers is flow dependent. Also the minimum inhalation flow to generate the (FPD) with the appropriate characteristics for lung deposition has been identified to be 20 L min-1 for the Accuhaler®, Easyhaler® and Clickhaler®, while that for the Turbuhaler® is about 30 L min-1. Also the inhalation volume above 2L and the number of inhalations for each dose have respectively no significant (p¿0.05) influence on the FPD emitted from the four studied inhalers. The results support the present instructions to patients using these inhalers to inhale once for each dose as fast as they can.
4

Investigation to Identify the Influence of Mannitol as a Carrier on the Ex-Vivo Dose Emission and the In-Vitro Aerodynamic Dose Emission Characteristics of Dry Powder Inhalers of Budesonide

Aloum, Fatima January 2020 (has links)
This study provides, for the first time, an ex vivo comparative evaluation of formulations of budesonide with crystallised β-form mannitol, commercial DPI grade mannitol and lactose. The lactose-budesonide was the marketed Easyhaler® 200 g formulation. Ex vivo assessment of deposition using the Easyhaler® multi-dose high resistance inhaler with reservoir was compared with the RS01® single dose capsule low resistance inhaler at two different inhalation rates. Aerodynamic characteristics, flow and surface energies were investigated together with in vitro and ex vivo assessment of drug deposition. Dose emission was greater for all formulations with higher inhalation flow, indicating greater detachment of drug from carrier, and greater with the Easyhaler®, highlighting the importance of correct device for formulation. Emission was lowest at both inhalation rates for crystallised mannitol due to poor flowability associated with elongated particle shape which resulted in interception deposition. Surface energies were also implicated; closely matched polar surface energy of carrier and drug may be an important inhibiting factor. The promising aerodynamic characteristics of crystallised mannitol with the RS01® inhaler and lactose-budesonide from in vitro assessment were not supported by ex vivo results, highlighting the need for careful selection of device.
5

The rational design of drug crystals to facilitate particle size reduction : investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution

Shariare, Mohammad Hossain January 2011 (has links)
Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.
6

Koncepční návrh malého letounu s důrazem na jednoduchost stavby / Conceptual design of small aircraft with emphasis on structure simplicity

Rajnštajn, David January 2020 (has links)
This thesis relates to a conceptual design of a light aircraft considering its easy manufacturability in non-professional workshop, for example at home. It is divided into three main parts. At the beginning there is mentioned a summary of existing light airplanes which determines the conceptual frame of the designed aircraft. The next part describes more detailed draft of different functional units, taking into consideration the constructional and manufacturing issues. The final part then contains basic equations to verify and define the most important characteristics of the designed aircraft.
7

The rational design of drug crystals to facilitate particle size reduction. Investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution.

Shariare, Mohammad H. January 2011 (has links)
Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.
8

Desenvolvimento de perfis aerodin?micos a partir de suas caracter?sticas utilizando redes neurais artificiais

Diniz, Bruno da Cunha 15 February 2013 (has links)
Made available in DSpace on 2014-12-17T14:58:20Z (GMT). No. of bitstreams: 1 BrunoCD_DISSERT.pdf: 4492853 bytes, checksum: 8fad50750c043cd4dab6a1e27f414d81 (MD5) Previous issue date: 2013-02-15 / One of the current major concerns in engineering is the development of aircrafts that have low power consumption and high performance. So, airfoils that have a high value of Lift Coefficient and a low value for the Drag Coefficient, generating a High-Efficiency airfoil are studied and designed. When the value of the Efficiency increases, the aircraft s fuel consumption decreases, thus improving its performance. Therefore, this work aims to develop a tool for designing of airfoils from desired characteristics, as Lift and Drag coefficients and the maximum Efficiency, using an algorithm based on an Artificial Neural Network (ANN). For this, it was initially collected an aerodynamic characteristics database, with a total of 300 airfoils, from the software XFoil. Then, through the software MATLAB, several network architectures were trained, between modular and hierarchical, using the Back-propagation algorithm and the Momentum rule. For data analysis, was used the technique of cross- validation, evaluating the network that has the lowest value of Root Mean Square (RMS). In this case, the best result was obtained for a hierarchical architecture with two modules and one layer of hidden neurons. The airfoils developed for that network, in the regions of lower RMS, were compared with the same airfoils imported into the software XFoil / Uma das maiores preocupa??es atuais na Engenharia ? o desenvolvimento de aeronaves que possuam baixo consumo e alto desempenho. Para isso, s?o estudados e projetados perfis aerodin?micos que tenham um valor elevado de coeficiente de sustenta??o e um valor baixo para o coeficiente de arrasto, gerando um perfil de alta efici?ncia. Quanto maior o valor da efici?ncia, menor ser? o consumo de combust?vel da aeronave, melhorando assim, o seu desempenho. Neste sentido, este trabalho objetiva desenvolver uma ferramenta para cria??o de perfis aerodin?micos a partir de caracter?sticas desejadas, como coeficiente de sustenta??o e de arrasto e efici?ncia m?xima, utilizando-se um algoritmo baseado em uma Rede Neural Artificial (RNA). Para isso, inicialmente foram coletados uma base de dados de caracter?sticas aerodin?micas de um total de 300 perfis, a partir do software XFoil. Ent?o, atrav?s de uma rotina implementada no software MATLAB, foram treinadas diversas arquiteturas de redes, entre modulares e hier?rquicas, utilizando-se o algoritmo de Retropropaga??o e a regra do Momento. Para an?lise dos resultados, foi utilizada a t?cnica de valida??o cruzada, avaliando a rede que possuiu o menor valor de Erro M?dio Quadr?tico (EMQ). Neste caso, o melhor resultado obtido foi para uma arquitetura hier?rquica com dois m?dulos e uma camada de neur?nios ocultos. Os perfis aerodin?micos desenvolvidos por essa rede, nas regi?es de menor EMQ, foram comparados aos mesmos perfis importados ao software XFoil. O presente trabalho oferece como contribui??o, em rela??o a outros trabalhos que envolvem RNA aplicada ? mec?nica dos fluidos, o desenvolvimento de perfis aerodin?micos a partir de suas caracter?sticas aerodin?micas
9

Návrh dvoumístného kovového letounu s ohledem na nízkou cenu a jednoduchost stavby / Design of the two seater ultralight aircraft with consideration the price and simplicity of the construction

Machala, Martin January 2012 (has links)
The object of the diploma thesis is a conceptual layout of two-seater metal ultralight aircraft which has simple construction and with respect to low price. The preamble of the work deals with concept, layout and technology of aircraft. As next part are solved an aerodynamic characteristics, a determinative of centre of gravity position and a performance. Last of all is strength of wing.
10

Identifikace aerodynamických charakteristik atmosférického letadla z výsledků letových měření / Aerodynamic Characteristics Identification of Atmospheric Airplane from Flight Measurement Results

Zikmund, Pavel Unknown Date (has links)
The thesis deals with aerodynamic characteristics identification from flight measurement. The topic is part of flight mechanic – handling qualities. The first theoretic part consists of three identification methods description: Error equation method, Output error method and Filter error method. Mathematical model of an airplane is defined and restricted to the motion with 3 degree of freedom. There is also introduced simulation of flight measurement for identification software validation. Practical part is focused on experiment preparation, execution and evaluation. The airplane VUT 700 Specto had been chosen to carry out flight tests. The airplane was modified to the new electric powered VUT 700e Specto after first measurement flights with combustion engine. Data record from on-board measurement unit was completed by telemetric data from autopilot and remote control system. Flight tests were carried out in stabilised mode of autopilot in symmetric flight. The results were confronted with analytical analysis results and DATCOM+ software parameter estimation.

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