Mesut Pervizpour

Truly Distributed Fiber Vibration Sensor Using Pulse Base BOTDA With Wide Dynamic Range

We report on what we believe to be the first truly distributed fiber vibration sensor based on pulse base Brillouin optical time-domain analysis (BOTDA). The pulse base approach is used to realize one-end one-laser simplification of the BOTDA system, in which the modulated pulse creates the probe wave and interacts with the pulse pump. Short pulse ( 10 ns) is used to enhance the dynamic range for the sensed object. A signal acquisition system with a 1-GHz sampling rate and 2-kHz trigger rate is employed to measure the truly distributed vibrations along the sensing fiber. With 6.25-ns pulsewidth, 160-MHz dynamic range is verified and different vibrations with 0-, 1.4-, and 2.4-Hz frequency components are distinguished in a 168-m sensing range. The experimental results demonstrate that this proposed sensor may be applicable for distributed dynamic measurements of large structural components.

Distributed Temperature Sensing System Based on Rayleigh Scattering BOTDA

A distributed temperature sensor based on Rayleigh scattering Brillouin optical time domain analysis (Rayleigh-BOTDA) is proposed in this paper. The sensor uses Rayleigh backscattering effect of microwave modulated pulse base sidebands as probe wave and a high sensitive photon counting detector for Brillouin signal intensity detection. Compared with a conventional BOTDA system, the Rayleigh-BOTDA effectively suppresses polarization-induced signal fluctuation resulting in improved signal intensity. The experimental scheme presented is simplified by using a single laser with one-end access. The temperature accuracy of the new sensing system was demonstrated as 1°C on spatial resolution of 3 m.

Distributed fiber sensor based on modulated pulse base reflection and Brillouin gain spectrum analysis

In recent years, several distributed sensor systems based on stimulated Brillouin scattering in optical fibers have been proposed [J. Intell. Mater. Syst. Struct.10, 340 (1999); Proc. SPIE5855, 555 (2005)]. We propose a simpler scheme based on fiber-end reflection and Brillouin gain spectrum analysis. In this setup, only one optical source is necessary to provide both the pump and the probe wave; the latter is provided by the modulated pulse base. First, the physical mechanisms for two different Brillouin scattering processes in our sensor system are analyzed and an approximate theory model is proposed. In addition, it is demonstrated that the simple system configuration allows simultaneous acquisition of the time-domain and the frequency-domain information. It is experimentally demonstrated that this configuration is effective for strain measurements and could as well be applied to temperature monitoring.

Health monitoring for effective management of infrastructure

Significance of effectively managing civil infrastructure systems (CIS) throughout CIS life-cycles, and especially during and after natural or man-made disasters is well recognized. Disaster mitigation includes preparedness for hazards to avoid casualties and human suffering, as well as to ensure that critical CIS components can become operational within a short amount of time following a disaster. It follows that mitigating risk due to disasters and CIS managementare intersecting and interacting societal concerns. A coordinated, multi-disciplinary approach that integrates field, theoretical and laboratory research is necessary for innovating both hazard mitigation and infrastructure management. Health monitoring (HM) of CIS is an emerging paradigm for effective management, including emergency response and recovery management. Challenges and opportunities in health monitoring enabled by recent advances in information technology are discussed in this paper. An example of HM research on an actual CIS test-bed is presented.

Structural identification of phenomenological physical models with controlled mechanisms of uncertainty

Structural identification (St-Id) of constructed systems is of interest to researchers as well as civil infrastructure systems owners and operators. St-Id offers an objective, quantitative evaluation of constructed systems through effective and integrated utilization of state-of-the-art experimental and analytical technologies. During the past five years two test beds were created at the University of Cincinnati and Drexel University for the exploration of analytical and experimental barriers obstructing successful St-Id applications. The two physical models are plane-grid structures with different controlled mechanisms of uncertainty. The objective of this paper is to present the St-Id studies to the two physical models. The principal mechanisms of uncertainty that governed the global structure behavior of the first physical model were nonlinear visco- elastic boundaries. The second model incorporated a fiber- reinforced polymer composite deck and its connection details to the grid. The impact of these different mechanisms of uncertainty on the success of St-Id will be addressed.

Impact wave monitoring in soil using a dynamic fiber sensor based on stimulated brillouin scattering.

The impact wave response of soil due to a ball drop is monitored on a 30.5 cm by 30.5 cm square soil box using a fiber sensor with dynamic strain sensing capability. The experiments are conducted in real time using a simple one-laser one-modulator configuration with stimulated Brillouin scattering. The embedded BOTDA sensor grid successfully monitored the distribution and evolution of the inner strains of a sand bed during a mass impact on its surface. The measurement of the distributed dynamic strains was possible in several milliseconds and with 1 cm actual location resolution. This paper presents a time-domain signal analysis utilized for determining the dynamic strains in embedded fiber sensor. The results demonstrate the method to be a promising one for detection of subsurface vibration and movement in geotechnical Structure Health Monitoring (SHM).

Data processing and quality assurance in health monitoring of constructed system

This paper discusses a data quality control, handling, and assurance process for real-time on-line monitoring. It further displays the processing steps during a typical data quality assurance. Data process design and utilization varies with type of data and information to be presented. Design of a data-flow process that would lead to real-time visualization, engineering analysis, storage, and archival of data is quite challenging for real-time on-line monitoring applications. An existing system for continuous health monitoring of a ling-span bridge is described and the design of the data quality assurance (DQA) steps is discussed. Wind that is monitored at various stations at the bridge is processed using the DQA steps. This paper further illustrates the identification of stationary wind segments on the attempt to correlate this with the various responses obtained from the critical components of the bridge.

Mathematical Modeling of Electrically Assisted Hydrocarbon Transport in Porous Media

Electrically assisted mass transport of hydrocarbon compounds in natural porous media has gained much attention not only for environmental mitigation of contaminating oils, but also recovery of reservoir oils over the last two decades. Applying a direct current (DC) to activate ElectroKinetic (EK) phenomena near the solid-liquid interfaces inside the porous media constitutes the basic concept of this method. As a result, the water, solutes, micelles and colloids that reside in the pore space or in the vicinity of the pore walls are transported from one electrode to the other where it can be collected, treated or transformed. In electrically enhanced oil recovery applications, the phenomenon leads to oil transport under an applied electric field in reservoirs. Although there are numerous multi-phase flow models used to predict oil recovery rate under applied and reservoir pressures in petroleum engineering, there is no working model of this transport under an electrical gradient. In this paper, a mathematical model of electrically assisted mass transport of water and immiscible hydrocarbon liquid in water wet porous medium is proposed. The model accounts for contributions of electrokinetic transport and two-phase (oil-water) flow through coupling equations for a well-defined porous system.

On the controllability and observability of intelligent infrastructure systems

Intelligent infrastructure systems require the installation and operation of large suites of sensors and actuators. Implicit in the design of these suites is a tradeoff between hardware complexity and functionality, which can be described in terms of the degrees of controllability and observability. Schmittendorfs degree-calculation algorithms are a possible tool for intelligent infrastructure design. An array of single-degree-of-freedom mass-spring modules and a one-dimensional model of a multi-story building with passive tuned-mass dampers are used as examples to illustrate these concepts.