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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

Model for Touchdown Dynamics of a Lander on the Solar Power Sail Mission

Gutierrez Ramon, Roger January 2016 (has links)
The ISAS/JAXA Solar Power Sail mission, bound to explore the Jupiter trojans, will face many challenges during its journey. The landing manoeuvre is one of the most critical parts of any space mission that plans to investigate the surface of celestial bodies. Asteroids are mostly unknown bodies and in order to plan a successful landing on their surface, a great number of landing scenarios need to be taken into account. For the future mission to the Jupiter trojans, a study of the landing dynamics and their effects on the lander has to be done. A simple model of a lander has been created based on a design for the ISAS/JAXA Solar Power Sail mission, and the possible landing scenarios have been simulated. For this case, only the last part of the landing, which will be a free-fall has been taken into account. The lander is modelled as a rigid structure with a landing gear composed of four legs. The surface has been modelled as a flat plane with different inclinations and the possibility of including small obstacles or terrain roughness has been implemented. In the model, the lander is allowed 6 degrees of freedom. Several landing possibilities are tested with residual velocities and deviations in the starting point, and the stability of the lander is evaluated respect its geometry. Damping strategies have been considered to protect the instruments and reduce the impact, allowing for a safer landing. The effect of including crushable honeycomb dampers in the legs is also implemented, simulated and evaluated, by using a model of crushable honeycombs with different characteristics. In addition, the model includes also the position, direction and characteristics of the thrusters. Thus, it could be used to study other phases of the landing sequence where active control of the lander is needed, and evaluate the behaviour and response of different control-loop algorithms for attitude and position control of the lander.
2

Do ISAs fulfil their aim in the audit of SMEs? : A study concerning how the implementation of ISAs in Sweden has affected audit quality and efficiency in the audit of small and medium-sized enterprises

Bokedal, Madeleine, Fågelsbo, Sofia January 2014 (has links)
Previous research noticed a conflict between audit quality and efficiency that has been discussed when applying International Standards on Auditing (ISAs) in the audit of small and medium-sized enterprises (SMEs). However, there is a lack of research that concerns ISAs affect on audit quality and efficiency in the same study. Hence, the following research question was formulated: How has the implementation of International Standards on Auditing in Sweden affected audit quality and efficiency in the audit of small and medium-sized enterprises? Based on the perceptions of the interviewees, the implementation of ISAs has resulted in clearer risk assessment and increased use of analytical procedures, thereby improved audit quality. Further, ISAs have increased the hours spent on internal control, which impair audit efficiency since this activity is not judged as important when gathering audit evidence. This conflict between audit quality and efficiency is mostly explained by the shall requirements of ISAs since many of these are not applicable in the audit of SMEs. Our findings indicate a need to adapt ISAs and to allow deviations from shall requirements. The outcome would be that ISAs are closer to fulfil their aim in the audit of SMEs, which is higher audit quality without the loss of efficiency.
3

An investigation into the Auditing Profession Regulatory Framework and the factors influencing the adoption of ISAs in the Libyan context

Eltweri, Ahmed Mohamed El Hadi January 2015 (has links)
Accounting information for decision making needs to be reliable, unless the information is audited, it cannot be regarded as reliable. Therefore, although extensive research in the area of accounting in general, and auditing in particular, has been conducted in the developed countries, similar investigations within developing countries have so far been relatively limited. Moreover, global financial crises, the most recent in 2007/8, have increased the pressures for better regulations with the aim of harmonising the auditing profession globally. This study therefore aims to help fill the gap in research and to provide recommendations to the governing body of the Libyan auditing profession, in order to address the difficulties faced by the profession, and advance and improve the quality of professional auditing practice. This study is predominantly positivist in essence, but, based on the nature of the problem and research questions, a mixed methods approach to gathering data from stakeholders in the auditing profession is adopted. A questionnaire (196 respondents), and a set of semi-structured interviews (nine participants), represent the quantitative and qualitative instruments of the study respectively. The research sample for both empirical exercises is comprised of individuals from five different groups representing the Libyan auditing profession stakeholders. This wide spread of participants is selected in order to generate valid, reliable, generalizable, and meaningful data, and conclusions. The overall conclusion drawn from the analysis is that the Libyan audit profession regulations are considered inadequate by the profession itself, since they fall short of meeting international standards, as supported by the fact that many foreign companies invest in Libya, and they insist on their auditing using ISAs as a guarantee of transparent and high quality auditing. The Libyan audit profession is unwilling to implement these international standards, and this weakness needs to be addressed. Furthermore, issues relating to licensing, accounting and auditing education, examination for entry to the profession, and Continuing Professional Development (CPD) must all be reviewed. In addition, a new regulatory framework, that involves government supervision, and the use of internationally-recognised standards in the performance of auditing duties, must be introduced. In terms of the most appropriate regulatory approach, the results indicated that the independent regulator model is preferred; and with respect to auditing standards, the study finds that the preferred approach is to harmonise all auditing standards used in Libya, and to adopt the ISAs with certain modifications that suit the Libyan context. Furthermore, the study sample identified six factors that impact positively on the adoption of the ISAs, and a further six factors that had negative influences. This research contributes to the body of literature by filling the gap regarding the Libyan auditing profession in general, and identifying factors that have an impact on the adoption of ISAs in particular. Recommendations are provided to the authority responsible for supervising the Libyan auditing profession that essentially require the upgrading of all professionals, and perseverance to ensure national and international development of the profession in particular, and to other countries with similar characteristics in general.
4

Estudo da variação espaço-temporal da Água Modal Subtropical do Atlântico Sul / Study of the spatio-temporal variation of the South Atlantic Subtropical Mode Water

Bernardo, Piero Silveira 20 October 2016 (has links)
Águas modais são formações oceânicas caracterizadas por camadas de propriedades praticamente homogêneas. Isso pode ser observada tanto através de baixos gradientes verticais de temperatura e salinidade, quanto de baixos valores de vorticidade potencial (VP). Portanto, para avaliarmos a formação da Água Modal Subtropical do Atlântico Sul (AMSTAS) foi utilizado o conjunto de dados In Situ Analysis System (ISAS - IFREMER) entre 2002 e 2014 para a região de 20ºS a 45ºS. Em conjunto aos critérios de Sato e Polito (2014) para a identificação da AMSTAS foram aplicados um novo intervalo de temperatura (13ºC a 16ºC) e a utilização de um gradiente vertical de temperatura (dT/dz = 0,02ºC m-1), tanto em superfície, de julho a novembro, quanto em subsuperfície durante todo o ano. Desse modo, os perfis selecionados foram utilizados para avaliar a variação do volume das camadas de AMSTAS. Na camada de superfície, buscou-se identificar os perfis que haviam sido recentemente afetados pela convecção local, que representa o principal mecanismo para a formação das águas modais, apenas entre julho e outubro. Para tanto, reduziu-se o valor máximo de VP dos perfis para 1,2 × 10-11 m-1 s-1. A partir da aplicação desse critério mais restritivo, calculou-se a taxa de formação de AMSTAS (Δ f) mensal, entre 2002 e 2009, para compararmos com a taxa de formação estimada (ΔF) pela teoria de Walin (1982), utilizando os dados do projeto Objectively Analyzed air-sea Fluxes (OAFlux). O Δ f apresentou média inferior a ΔF, indicando assim a necessidade de avaliarmos o conjunto de processos que afetam a formação da AMSTAS, em adição ao balanço de calor pela superfície. / Mode waters are oceanic formations characterized by layers of nearly homogeneous properties. This feature can be observed both at low temperature and salinity vertical gradients, as in low potential vorticity (PV) values. Therefore, to evaluate the formation of South Atlantic Subtropical Mode Water (SASTMW) the In Situ Analysis System (ISAS - IFREMER) data set was used for the period between 2002 and 2014 for the 20ºS to 45ºS region. Jointly with the criteria set by Sato e Polito (2014) for the identification of the SASTMW were applied a new temperature range (13ºC a 16ºC) and the use of a vertical temperature gradient (dT/dz = 0.02ºCm-1 both in surface, between June and November, as in the subsurface throughout the year. Thus, the selected profiles were used to evaluate changes in the volume of the layers of SASTMW. Within the surface layer data, we sought to identify profiles that had been recently affected by the local convection, which is the main mechanism for the formation of mode water, only between July to October. Thereby, we reduced the maximum PV value of the profiles to 1.2 × 10-11 m-1 s-1. From the application of this more restrictive criteria, we calculated the SASTMW monthly formation rate (Δf) between 2002 and 2009 to compare with the estimated formation rate (ΔF) from the Walin (1982) theory, using the data from the project Objectively Analyzed air-sea Fluxes (OAFlux). The Δ f showed a mean value lower than the ΔF rate, indicating the need to evaluate a broader set of processes that affect the SASTMW formation, in addition to the heat balance through the surface.
5

Estudo da variação espaço-temporal da Água Modal Subtropical do Atlântico Sul / Study of the spatio-temporal variation of the South Atlantic Subtropical Mode Water

Piero Silveira Bernardo 20 October 2016 (has links)
Águas modais são formações oceânicas caracterizadas por camadas de propriedades praticamente homogêneas. Isso pode ser observada tanto através de baixos gradientes verticais de temperatura e salinidade, quanto de baixos valores de vorticidade potencial (VP). Portanto, para avaliarmos a formação da Água Modal Subtropical do Atlântico Sul (AMSTAS) foi utilizado o conjunto de dados In Situ Analysis System (ISAS - IFREMER) entre 2002 e 2014 para a região de 20ºS a 45ºS. Em conjunto aos critérios de Sato e Polito (2014) para a identificação da AMSTAS foram aplicados um novo intervalo de temperatura (13ºC a 16ºC) e a utilização de um gradiente vertical de temperatura (dT/dz = 0,02ºC m-1), tanto em superfície, de julho a novembro, quanto em subsuperfície durante todo o ano. Desse modo, os perfis selecionados foram utilizados para avaliar a variação do volume das camadas de AMSTAS. Na camada de superfície, buscou-se identificar os perfis que haviam sido recentemente afetados pela convecção local, que representa o principal mecanismo para a formação das águas modais, apenas entre julho e outubro. Para tanto, reduziu-se o valor máximo de VP dos perfis para 1,2 × 10-11 m-1 s-1. A partir da aplicação desse critério mais restritivo, calculou-se a taxa de formação de AMSTAS (Δ f) mensal, entre 2002 e 2009, para compararmos com a taxa de formação estimada (ΔF) pela teoria de Walin (1982), utilizando os dados do projeto Objectively Analyzed air-sea Fluxes (OAFlux). O Δ f apresentou média inferior a ΔF, indicando assim a necessidade de avaliarmos o conjunto de processos que afetam a formação da AMSTAS, em adição ao balanço de calor pela superfície. / Mode waters are oceanic formations characterized by layers of nearly homogeneous properties. This feature can be observed both at low temperature and salinity vertical gradients, as in low potential vorticity (PV) values. Therefore, to evaluate the formation of South Atlantic Subtropical Mode Water (SASTMW) the In Situ Analysis System (ISAS - IFREMER) data set was used for the period between 2002 and 2014 for the 20ºS to 45ºS region. Jointly with the criteria set by Sato e Polito (2014) for the identification of the SASTMW were applied a new temperature range (13ºC a 16ºC) and the use of a vertical temperature gradient (dT/dz = 0.02ºCm-1 both in surface, between June and November, as in the subsurface throughout the year. Thus, the selected profiles were used to evaluate changes in the volume of the layers of SASTMW. Within the surface layer data, we sought to identify profiles that had been recently affected by the local convection, which is the main mechanism for the formation of mode water, only between July to October. Thereby, we reduced the maximum PV value of the profiles to 1.2 × 10-11 m-1 s-1. From the application of this more restrictive criteria, we calculated the SASTMW monthly formation rate (Δf) between 2002 and 2009 to compare with the estimated formation rate (ΔF) from the Walin (1982) theory, using the data from the project Objectively Analyzed air-sea Fluxes (OAFlux). The Δ f showed a mean value lower than the ΔF rate, indicating the need to evaluate a broader set of processes that affect the SASTMW formation, in addition to the heat balance through the surface.

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