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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

H I line profiles of galaxies: tilted ring models

Nelson, Erica 08 May 2008 (has links)
Two-dimensional information on the kinematics and spatial distribution of gas in spiral galaxies is encoded in radio observations of their one-dimensional 21-cm neutral hydrogen (HI) line profiles. More than ten thousand HI profiles have been published and are publicly available. In order to explore the parameter space mapped out by the 21-cm neutral hydrogen line pro file, we have modified and run a FORTRAN-based computer simulation code. We have identified 7 control parameters that define the morphology of the modelled galaxy: they describe the neutral hydrogen gas distribution (density and spatial location of the gas), characteristics of its rotation curve, warps, asymmetries, and finally, the viewing angle. All except the last of these parameters tell us significant physical information about the galaxy but a determination of them is not immediately apparent from the two-dimensional 21-cm line profile. Hence, the goal of this exploration is to find meaningful correlations between the observed 21-cm line profile features and the underlying physical parameters.
2

On the interaction between modal behaviour and shear force behaviour of a pneumatic tyre

Tsotras, Achillefs January 2010 (has links)
The in-plane phenomena of interaction between the tyre structural response and contact force generation are investigated in this work. The challenges of the physical tyre simulation are identified, primarily associated with the computational load imposed by the need to capture the space distributed mechanisms that prescribe the above interaction. The method of modal expansion and reduction is proposed for the moderation of this load. The theoretical framework for the transformation of a tyre modal representation into a transient contact and shear force generation model is developed. Various modelling approaches are examined with regards to their modal prediction characteristics. Linear and non linear structural features as well as the physical properties that define the broad range modal behaviour are identified. A discretised form of the ring model is derived and combined with a foundation of viscoelastic tread elements for simulating the transient contact behaviour of the tyre. The resulting pattern of the modes' excitation justifies the validity of the modal reduction method and reveals the relative importance of various mechanisms and physical properties in tyre contact behaviour. The interaction between the friction controlled shear slip of the tread, the belt compliance and the sidewall buckling is found to be reflected on the two-dimensional contact pressure distribution patterns. A method able to simulate the dynamic transient rolling and slipping operating conditions is developed, although the small displacement assumption of the modal approach is dropped. The method, which is based on the combined modal-time and space-time domain solutions, is applied on the study of the physical mechanism of the launch process. The examination of the model under steady state kinematic conditions reveals the saturation of the traction force for profound levels of slip, which highlights the contribution of the structural mechanisms on the macroscopically observed shear force performance of the tyre. The variation of the modes' level of excitation, as induced by the operating conditions, is proposed for the capture of the physical properties effect on tyre behaviour and performance.
3

H I Line Profiles of Galaxies: Tilted Ring Models

Nelson, Erica 08 May 2008 (has links)
Two-dimensional information on the kinematics and spatial distribution of gas in spiral galaxies is encoded in radio observations of their one-dimensional 21-cm neutral hydrogen (HI) line profiles. More than ten thousand HI profiles have been published and are publicly available. In order to explore the parameter space mapped out by the 21-cm neutral hydrogen line pro file, we have modified and run a FORTRAN-based computer simulation code. We have identified 7 control parameters that define the morphology of the modelled galaxy: they describe the neutral hydrogen gas distribution (density and spatial location of the gas), characteristics of its rotation curve, warps, asymmetries, and finally, the viewing angle. All except the last of these parameters tell us significant physical information about the galaxy but a determination of them is not immediately apparent from the two-dimensional 21-cm line profile. Hence, the goal of this exploration is to find meaningful correlations between the observed 21-cm line profile features and the underlying physical parameters.
4

Implementation of E-Government services : Analysis of factors in case of Ukraine

Nesterenko, Mykola January 2014 (has links)
Electronic services have become a vital part in the implementation of electronic government. Government electronic services are significant tools for effective cooperation in any country between government, authorities, citizens, organisations, and so on. In order to implement these services it is necessary to know possible barriers and obstacles – factors, which can influence on the implementation process. Study in this field of research showed that a well-structured list of the factors that can influence on this implementation process is absent now. The purpose of this research is to identify and collect, analyse and structure different factors that can influence the implementation process of electronic government services. The collected list of factors have studied in the case of Ukraine. This research was conducted within the scope of Master’s level program in Linnaeus University, Sweden. In this research was used the mix method approach. The qualitative study was conducting through literature review and six interviews with people related to electronic government services. At the same time, as quantitative study was a survey with 131 answers from citizens. For analysing and structuring were using the Onion Ring Model of electronic government systems (Heeks, 2006) and the STEPLED analysis. The philosophical worldview of the research paper is social constructivism. During the research, I have studied more than 200 factors from different works of authors, which worked in this field. All collected factors were analysed and adapted in accordance to the Onion Ring Model. In addition, this model was modified by adding interlayers (additional rings) and extended in the Environment ring (with the usage of the STEPLED analysis). From the collected list were highlighted factors that influence on the implementation process in the case of Ukraine.
5

K-theory of theories of modules and algebraic varieties

Kuber, Amit Shekhar January 2014 (has links)
No description available.
6

Mindre nationers användande av luftmakt : En teorikonsumerande fallstudie av sexdagarskriget

Nilsson, Tim January 2017 (has links)
On 5 June 1967, the Israeli Air Force launched a surprise attack against the Egyptian Air Force and started what was to be known as the Six Day War. The Six Day War is a good example of when a small nation manages to singlehandedly defeat a superior adversary. The purpose of this paper is to analyze the success of the Israeli Air Force and their contribution to the victory. The use of air power in the Six Day War will be analyzed, using John Warden’s Five Ring Model and Shaun Clarke’s theories about risk-based coercion and SPOT-bombing. Research findings indicate that Shaun Clarke’s theories about coercion may to some extent explain the success of the Israeli Air Force. Attacking the armed forces created the threat of further violence against more valuable and vulnerable targets causing the Arabic leaders to choose peaceful solutions instead of continued fighting. Furthermore, the SPOT-bombing analyzes show that the psychological effect that the Israeli Air Force had on their adversary played a significant role in the campaign against Egypt. However, Warden’s model could not explain the reasons behind the outcome of the war.
7

Development of a 3D Ring Dynamics Model For a Heavy-Duty Piston Ring-Pack

Akurati, Parthasri, Kumar, Karan January 2021 (has links)
With the increasing restrictions in emission legislations, the automotive industry aims to improve the efficiency of the lubricating system and to decrease fuel consumption. In the power cylinder unit (PCU), the piston rings are the major contributor to these consumptions. Hence, focus on the dynamic behaviour of the rings to reduce lube oil consumption (LOC) becomes a key factor in thriving towards sustainability. Several studies have been conducted on the piston ring-pack specifically using a 2D ring dynamics approach. This study focuses on developing a 3D ring dynamics model, in the software tool AVL EXCITE™ Piston&Rings, which is capable of observing the behaviour of the ring along the third dimension i.e. circumferential direction. A coordinated approach used in the methodology gives an insight into the parameters affecting the model behaviour. Within the PCU, wear on the cylinder liner surface and in the piston ring grooves can lead to accelerated LOC. This study further focuses on using the 3D model to analyse the friction and wear on the piston rings. Factors contributing towards LOC are individually studied and the results obtained are compared to the experimental engine test data. The outcome of the 3D numerical model developed shows promising results. The model can therefore be used to simulate different piston ring-packs and analyse the behaviour of the piston ring with a better prediction of friction, wear and LOC. Thus, the model will contribute to reducing the number of physical tests conducted, the expense involved in conducting those tests and would provide satisfactory products to the customer and would manage future emission requirements.
8

An Examination into the Statistics of the Singular Vectors for the Multi-User MIMO Wireless Channel

Gunyan, Scott Nathan 13 August 2004 (has links) (PDF)
Many capacity and near-capacity achieving methods in multiple-input-multipleoutput (MIMO) wireless channels make use of the singular value decomposition (SVD) of the channel matrix. For the multi-user case, the SVD of the channel matrix for each user may result in right and left singular vectors that are similar between users. This proposes another descriptive characterization of the multi-user MIMO channel. Closely aligned singular vectors between any two users could reduce the achievable signaling rates of signal processing communication methods as one user would be more difficult to resolve in space-time from another. An examination into how this alignment can be described in realistic MIMO multipath channels using a two ring channel model is presented. The effects of correlation between singular vectors on achievable signaling rates is shown for one existing algorithm that approaches the sum capacity known as block-diagonalization. Analyzed is actual data collected in several indoor and outdoor experiments performed using newly constructed measurement hardware that extends the capabilities of an existing MIMO measurement system.
9

Attention: A Complex System / From the Intricate Modulation of Tuned Responses Towards a Layered Cortical Circuit Model

Helmer, Markus 11 September 2015 (has links)
No description available.

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