Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system

The 10m Prototype facility at the Albert-Einstein-Institute (AEI) in Hanover, Germany, employs three large seismic attenuation systems to reduce mechanical motion. The AEI Seismic-Attenuation-System (AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5Hz. This system provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4Hz and in the vertical direction at 9Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the system. These dampers reduce RMS motion substantially in the frequency range between 10 and 100Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances

Seismic noise analysis and isolation concepts for the ALPS II experiment at DESY

The ALPS II experiment at DESY is searching for new particles beyond the standard model of particle physics in a laboratory-based Light-Shining-through-a-Wall experi- ment, using high finesse optical resonators to reach the required sensitivity. The input and output mirrors on the optical tables have extremely accurate positioning and align- ment requirements, for which the analysis of ground vibration and seismic noise is essen- tial. This thesis, therefore, focuses on this analysis, its evaluation, and the development of future seismic isolations for the ALPS II and JURA experiments. This work describes mechanical vibrations, seismic noise sources, seismic isolation principles, and also the seismic devices used to perform seismic noise analysis with their methods of measuring, calibrating, and analysing the acquired data. It summarises the seismic noise studies carried out in the ALPS II laboratories at HERA West as well as in the hall and tunnels of HERA North at DESY in Hamburg. For a more accurate presentation of the prevailing noise frequencies a new method of the modal analysis, the MfwaFFT was developed. Here, a noise-independent procedure for more precise data analysis is implemented which accounts for the highly sensitive conditions on-site. Furthermore, a seismic isolation concept based on this analysis in connection with the ALPS II experiment is developed and presented

Photonic Sensors Based on Integrated Ring Resonators

This thesis investigates the application of integrated ring resonators to different sensing applications. The sensors proposed here rely on the principle of optical whispering gallery mode (WGM) resonance shifts of the resonators. Three distinct sensing applications are investigated to demonstrate the concept: a photonic seismometer, an evanescent field sensor, and a zero-drift Doppler velocimeter. These concepts can be helpful in developing lightweight, compact, and highly sensitive sensors. Successful implementation of these sensors could potentially address sensing requirements for both space and Earth-bound applications. The feasibility of this class of sensors is assessed for seismic, proximity, and vibrational measurements

Study of the dynamic soil-structure interaction of a building on elastic foundation

Tese de mestrado integrado. Engenharia Civil (Especialização em Estruturas). Faculdade de Engenharia. Universidade do Porto. 201

Numerical Analysis and Gravity

In this dissertation we apply techniques of numerical analysis to current questions related to understanding gravity. The first question is that of sources of gravitational waves: how can we accurately determine the intrinsic physical parameters of a binary system whose late inspiral and merger was detected by the Laser Interferometer Gravitational-Wave Observatory. In particular, state-of-the-art algorithms for producing theoretical waveforms are as many as three orders of magnitude too slow for timely analysis. We show that direct software optimization produces a two order of magnitude speedup. We also describe documentation efforts undertaken so that the software may be rewritten to enhance both performance and physical realism. The second question is that of measuring Newton\u27s gravitational constant G. In particular, the results of experiments measuring G have differed by as many as ten standard deviations. Measuring the oscillation frequency of a magnetically-levitated microsphere shows promise for sharpening the value of G, and the system for this measurement was found to accurately measure low-frequency accelerations. As such, this system forms a prototype for a room-temperature, low-mass accelerometer. At the center of the accelerometer and G measurements lies a new image analysis technique we developed for determining the position of the microsphere to 1.6 nm

Modelling and thermal analysis of a seismic borehole sensor: diploma 2015

Analysis and adaptation of an acquisition system for a seismometer to enable operation at high temperatures (up to 180 [°C]). The simulation software and thermal measurements are used to validate theoretical results

A system for the acquisition and processing of seismic data for refraction studies of the earths crust

The use of arrays of seismometers for seismic refraction measurements of crustal structure using explosions is reviewed, and the general factors to be considered in the design of equipment for the acquisition and processing of such data are discussed. The design and construction of a particular system using digital magnetic tape recording are described in detail. The three main modes of operation are the recording of ten channels of seismic information in the field, the replay in the laboratory of these ten channels to a multi-channel galvanometer oscillograph, and the transfer of the digital information to punched paper tape for input to a general purpose digital computer. The programmes that have been developed for handling this data on an Elliott 803 computer are described. The system was used during a crustal experiment using depth charges in September, 1%$. The performance during this test is evaluated. II - Stress systems in an inhomogeneous crust. The plane strain stress in an elastic half-space in which there are discrete variations in density over rectangular areas of the cross section is calculated by the double integration of .the result for a point force acting within an homogeneous elastic half-space. The resulting stress system is shown to be a valid solution of the equations of elasticity, and analytical results are derived for several special cases. The application of the theory of elasticity to crustal processes is reviewed, and numerical results are used to discuss the stress systems associated with isostatic compensation and with a crust of varying density

Measurement of low frequency mechanical vibrations based on an inverted magnetic pendulum

In this paper is presented the mathematical model, design and construction of a prototype of a  vibration frequency meter in an adjustable range of 2 Hz to 30 Hz; The experimental results and their analysis are also presented, making a comparative evaluation with the theoretical model. The device is based on the principle of resonance applied in an inverted magnetic pendulum whose natural frequency can be modified by variations of physical parameters. The oscillation of the pendulum is recorded detecting variations in the magnetic field using hall effect sensors; the data recorded with a microprocessor is analyzed and the results are simultaneously plotted in a computer interface. The data obtained were processed to be plotted in the frequency domain, facilitating its analysis. It was proved that the prototype can be used as a frequency meter and that the adjustable character of the device works according to the mathematical model. Finally, The effect of the friction force was studied, it was concluded that the friction force affects the measurement after a considerable period of time of oscillation, but not in the first moments

Vibration Isolation Using In-filled Geofoam Trench Barriers

A significant amount of numerical and experimental research has been conducted to study the vibration isolation by wave barriers considering open trenches, in-filled concrete or bentonite trenches, sheet-pile walls, and rows of piles. A few studies have investigated the use of expanded polystyrene (EPS) geofoam material as wave barriers, which indicated that in-filled geofoam trenches can be used as effective wave barriers. However, no engineering design method is available to date for the design of such type of wave barriers. This dissertation presents comprehensive experimental and numerical investigations on the use of in-filled geofoam trench barriers to scatter machine foundations vibration, in order to provide some recommendations and design guidelines for their implementation in design. Two- and three-dimensional time-domain finite element models have been developed utilizing the finite element package ABAQUS. The numerical models have been verified and then used to study the effectiveness of different configurations of in-filled geofoam wave barriers. All the proposed configurations performed well in scattering surface waves. However, the single-continuous wall system was considered to be more economic and practical alternative for wave scattering. Based on the findings of the preliminary numerical investigations, a full scale field experimental study has been conducted to investigate the performance of in-filled geofoam trenches. An innovative approach to construct geofoam trenches involving hydro-dig technology was utilized. A series of experimental tests have been conducted to evaluate the performance of both open and in-filled geofoam trench barriers considering their geometry and distance from the source of disturbance. The results of the field experimental investigations were analyzed and interpreted to provide recommendations for implementation in design. Experimental results confirmed that in-filled geofoam trench barriers can effectively reduce the transmitted vibrations and its protective effectiveness is comparable to the open trench barrier. An extensive numerical parametric study was conducted to investigate the behaviour of in-filled geofoam wave barrier under different soil conditions and to point out the key parameters that dominate the performance of in-filled geofoam trench barriers. The influence of various key parameters on the screening performance were carefully analyzed and discussed. A model using Multiple Linear Regression (MLR) analysis was developed for design purpose. Finally, an artificial neural network (ANN) model has been developed, which aims at extrapolating the parametric study results to predict the in-filled geofoam wave barrier protective effectiveness in different soil profiles with different geometric dimensions