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Seismic vibrators are used to investigate the structure of the subsurface in the framework of soil and gas exploration, also to locate faults and rupture zones in earthquake investigations. Vibrators introduce seismic waves that propagate through the ground and are received by seismic sensors at some distance from the source. This enables interpretation of the sub-soil structure by inverse analysis. To analyze the behavior of the soil below a seismic vibrator, analytical models were developed in the past in which the behavior of the soil is simplified by linear elasticity. This assumption of linear elastic soil model does not describe real soil behaviors. In this research, a seismic vibrator standing on a homogeneous soil is simulated by means of an axisymmetric finite element model with an advanced soil model, i.e. Hardening Soil model with smallstrain stiffness, called HS-small model in which the non-linear, irreversible soil behaviors as well as small-strain stiffness effects below a seismic vibrator are taken into account. The sign and amplitude of displacements of the ground surface in the near field and the far field are observed for a homogeneous sand and homogeneous clay. A comparison between the linear elastic model and the HS-small model in simulation the soil response is made. The response of the sand and clay under delta-pulse load, minimum-phase-wavelet load, chirp load, and harmonic load with different frequencies (5Hz and 50Hz) and amplitudes (10kN/m2 and 20kN/m2) is simulated and evaluated. The influence of stress-strain dependent soil stiffness and porewater on seismic wave velocities is evaluated by means of seismograms.

The graduation project is a collective project between TUDelft and JAM visual thinking. This study is devoted to unveil the potential of Visual Thinking in business sessions and to eventually improve the effectiveness of the method. JAM visual thinking, a consultancy company based on the Netherlands, features in providing various products from visualization to suggestions of strategies with their drawings. This graduation project is conducted to help JAMmers to harness the magic power of Visual Thinking effectively.

Document(en) uit de collectie Chemische Procestechnologie

This thesis describes the design of a project management tool for multidisciplinary design teams. Background: Complex projects require multidisciplinary design teams, which are harder to manage than teams with people from one discipline. To control the resources within projects, an adequate software package is chosen for each issue. This kind of symptom management drives the introduction of resource management tools. This ad hoc behaviour results in different software packages that are not tailored to the people involved in the projects. The problem is that use of these tools requires extra effort and discipline from the people involved, with the consequence that some tools find only limited use or are not considered useful at all. Project managers and designers use a plethora of highly specialized software tools and can hardly be burdened to add another five just to check project progress; this is why integration of these systems is needed. A trend to take into account in designing an integrated solution is that people from the client side and the people involved in project management from the company side will use other devices than desktop PCs to stay involved in projects, such as smartphones and tablet computers. Goal: To improve project management in multidisciplinary design teams and prevent overspending of the resources of projects. Assignment: Design a tool that focuses on the core of the problem, with project management as a leading perspective and the people involved in the project management process as primary users. Method: The core of the problem is analysed through a short literature study on the general knowledge on project management, a survey and interviews on the internal context and people at the company and a short market study on available solutions. By being embedded in the target group, it was possible to follow an iterative process of ideation and evaluation with the target group. The design is evaluated through a presentation and a user test with a browsable prototype with actual project information. Research results: Project leaders are not motivated to use many software packages for project management, as they already have the different tools to do their work with. Because they only limitedly use the available tools and do not trust information, as it is not up-to-date, they are not conscious about the status of a project. This is the main cause of overspending of resources. To become conscious about the status of the project, the target group needs to reflect on relevant, up-to-date information. They need to be allowed and encouraged to input the most important information to be able to reflect on information. The following factors were identified as related to project management: money, time, activities, files, communication, decisions and general project-related information. Further in the report these will be called the resources of project management. Design: The design proposal focuses on the integration of the different resources of project management in a project-focused solution. It is built on two pillars: shown information depends 1) on the user and 2) on the level of detail. Showing only information that is relevant to the user reduces the amount of noise. Different levels in information, showing more detail when zooming in, prevent from information overkill for the user and enables the user to keep overview. Features like live tiles and semantic zoom known from Windows 8, speed up usage and fit the need for different levels of information. To ensure cross-device scalability, a web-based platform is proposed. The design provides a way of documenting important information on each topic of project management. Conclusions and recommendations: The target group thinks the tool will help prevent overspending but I advice a step by step introduction to let the user get used to the system and keep the costs limited and the advantages high. Due to the limited time frame and complexity of the project, testing the design with a real project was not possible yet. Furthermore optimization in the interactions of data entry should be made.

The thesis deals with wave-equation migration in a visco-acoustic medium, where an ambiguity appears when one tries to image simultaneous velocity and attenuation perturbations.

The performance of a multigrid solver for time-harmonic electromagnetic problems in geophysical settings was investigated. With the low frequencies used in geophysical surveys for deeper targets, the light-speed waves in the earth can be neglected. Diffusion of induced currents is the dominant physical effect. The governing equations were discretised by the Finite-Integration Technique. The resulting set of discrete equation was solved by a multigrid method. The multigrid method provided excellent convergence with constant grid spacings, but not on stretched grids. The slower convergence rate of the multigrid method could be compensated by using bicgstab2, in which case multigrid acted as a preconditioner. Still, the overall performance was less than satisfactory with substantial grid stretching.