19,354 research outputs found
Structural health monitoring and bridge condition assessment
Thesis (Ph.D.) University of Alaska Fairbanks, 2016This research is mainly in the field of structural identification and model calibration, optimal sensor placement, and structural health monitoring application for large-scale structures. The ultimate goal of this study is to identify the structure behavior and evaluate the health condition by using structural health monitoring system. To achieve this goal, this research firstly established two fiber optic structural health monitoring systems for a two-span truss bridge and a five-span steel girder bridge. Secondly, this research examined the empirical mode decomposition (EMD) method’s application by using the portable accelerometer system for a long steel girder bridge, and identified the accelerometer number requirements for comprehensively record bridge modal frequencies and damping. Thirdly, it developed a multi-direction model updating method which can update the bridge model by using static and dynamic measurement. Finally, this research studied the optimal static strain sensor placement and established a new method for model parameter identification and damage detection.Chapter 1: Introduction -- Chapter 2: Structural Health Monitoring of the Klehini River Bridge -- Chapter 3: Ambient Loading and Modal Parameters for the Chulitna River Bridge -- Chapter 4: Multi-direction Bridge Model Updating using Static and Dynamic Measurement -- Chapter 5: Optimal Static Strain Sensor Placement for Bridge Model Parameter Identification by using Numerical Optimization Method -- Chapter 6: Conclusions and Future Work
Advanced flight control system study
The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed
Basin scale assessment of landslides geomorphological setting by advanced InSAR analysis
An extensive investigation of more than 90 landslides affecting a small river basin in Central
Italy was performed by combining field surveys and remote sensing techniques. We thus defined the
geomorphological setting of slope instability processes. Basic information, such as landslides mapping
and landslides type definition, have been acquired thanks to geomorphological field investigations
and multi-temporal aerial photos interpretation, while satellite SAR archive data (acquired by ERS
and Envisat from 1992 to 2010) have been analyzed by means of A-DInSAR (Advanced Differential
Interferometric Synthetic Aperture Radar) techniques to evaluate landslides past displacements
patterns. Multi-temporal assessment of landslides state of activity has been performed basing
on geomorphological evidence criteria and past ground displacement measurements obtained by
A-DInSAR. This step has been performed by means of an activity matrix derived from information
achieved thanks to double orbital geometry. Thanks to this approach we also achieved more detailed
knowledge about the landslides kinematics in time and space
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Hydro-pneumatic pulse forming networks
A novel method that combines energy storage and power condition-
ing for renewable energy systems is presented. This method utilizes hydro-
pneumatic energy storage elements, also known as hydraulic accumulators,
as mechanical capacitors arranged in such a fashion as to create a hydro-
pneumatic pulse forming network (HPPFN) in a manner similar to sequen-
tially red pulsed formed networks (SFPFNs) used for electromagnetic railgun
launch. This pulse forming network has the ability to create a power output of
nearly constant amplitude for short durations, which is particularly well-suited
for supplying power to constant amplitude, duty-cycle-type loads.
The foundational principles are established herein for how HPPFN sys-
tems can be modeled and synthesized, so that systems can be designed and
scaled for practical applications. This foundation was established incremen-
tally in three parts. First, a working experimental test-bed system was con-
structed to prove the feasibility of operating a sequentially- red pulse forming
network using hydro-pneumatic energy storage elements in a manner analogous
to electromagnetic sequentially- red PFNs. Next, a modeling framework was developed for hydro-pneumatic pulse forming network synthesis. Finally, the
model-based synthesis approach was experimentally validated using the test-
bed to demonstrate that sizing and practical construction of HPPFN systems
can be accomplished. Suggestions for future work to extend these methods
and the applications of HPPFNs are provided.Mechanical Engineerin
Inorganic separator for a high temperature silver-zinc battery
Electrode design, inorganic separators, and performance tests of multiplate five ampere-hour silver-zinc battery cel
Guide for certifying pressure vessels and systems
This guide is intended to provide methodology and describe the intent of the Pressure Vessel and System (PV/S) Certification program. It is not meant to be a mandated document, but is intended to transmit a basic understanding of the PV/S program, and include examples. After the reader has familiarized himself with this publication, he should have a basic understanding of how to go about developing a PV/S certification program
On Collaborative Predictive Blacklisting
Collaborative predictive blacklisting (CPB) allows to forecast future attack
sources based on logs and alerts contributed by multiple organizations.
Unfortunately, however, research on CPB has only focused on increasing the
number of predicted attacks but has not considered the impact on false
positives and false negatives. Moreover, sharing alerts is often hindered by
confidentiality, trust, and liability issues, which motivates the need for
privacy-preserving approaches to the problem. In this paper, we present a
measurement study of state-of-the-art CPB techniques, aiming to shed light on
the actual impact of collaboration. To this end, we reproduce and measure two
systems: a non privacy-friendly one that uses a trusted coordinating party with
access to all alerts (Soldo et al., 2010) and a peer-to-peer one using
privacy-preserving data sharing (Freudiger et al., 2015). We show that, while
collaboration boosts the number of predicted attacks, it also yields high false
positives, ultimately leading to poor accuracy. This motivates us to present a
hybrid approach, using a semi-trusted central entity, aiming to increase
utility from collaboration while, at the same time, limiting information
disclosure and false positives. This leads to a better trade-off of true and
false positive rates, while at the same time addressing privacy concerns.Comment: A preliminary version of this paper appears in ACM SIGCOMM's Computer
Communication Review (Volume 48 Issue 5, October 2018). This is the full
versio
Integrated control and health management. Orbit transfer rocket engine technology program
To insure controllability of the baseline design for a 7500 pound thrust, 10:1 throttleable, dual expanded cycle, Hydrogen-Oxygen, orbit transfer rocket engine, an Integrated Controls and Health Monitoring concept was developed. This included: (1) Dynamic engine simulations using a TUTSIM derived computer code; (2) analysis of various control methods; (3) Failure Modes Analysis to identify critical sensors; (4) Survey of applicable sensors technology; and, (5) Study of Health Monitoring philosophies. The engine design was found to be controllable over the full throttling range by using 13 valves, including an oxygen turbine bypass valve to control mixture ratio, and a hydrogen turbine bypass valve, used in conjunction with the oxygen bypass to control thrust. Classic feedback control methods are proposed along with specific requirements for valves, sensors, and the controller. Expanding on the control system, a Health Monitoring system is proposed including suggested computing methods and the following recommended sensors: (1) Fiber optic and silicon bearing deflectometers; (2) Capacitive shaft displacement sensors; and (3) Hot spot thermocouple arrays. Further work is needed to refine and verify the dynamic simulations and control algorithms, to advance sensor capabilities, and to develop the Health Monitoring computational methods
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