Development of a Flexible Laser Ultrasonic Probe

2002 ◽  
Vol 124 (2) ◽  
pp. 351-357 ◽  
Author(s):  
Sandra N. Hopko ◽  
I. Charles Ume ◽  
Dathan S. Erdahl
Keyword(s):  
Optical Fiber ◽  
Delivery System ◽  
Linear Array ◽  
Laser Ultrasonic ◽  
Ultrasonic Probe ◽  
Control Scheme ◽  
Inspection Systems ◽  
On Line ◽  
Directivity Patterns ◽  
Working Distance

Ultrasonics is a widely used nondestructive testing technique, which is often applied off-line for weld quality inspection. Laser ultrasonic (LU) inspection systems have the potential for on-line application, providing the means to identify unacceptable welds as they are formed. Because LU systems are non-contacting, they can be used for testing moving specimens or for operation in hazardous and/or high temperature environments. A highly versatile system can be created when an optical fiber delivery system is incorporated into the design. Introduction of a focusing objective increases the allowable working distance and permits stronger generation using material ablation as the generating mechanism. This paper describes the development of a laser ultrasonic probe using an optical fiber delivery system with a distal end, focusing objective. The optical fiber delivery system can be configured as a single fiber source, a linear array (fiber bundle) or a phased array. Results include experimentally obtained directivity patterns demonstrating ultrasonic generation using ablation sources. Thermoelastic source results are also included. This paper demonstrates the potential of the fiber tool and presents an overview of the weld control scheme.

Design of Laser Ultrasonic System for In-Process Weld Penetration Monitoring and Control

1999 ◽  
Author(s):  
Sandra N. Hopko ◽  
I. Charles Ume ◽  
Dathan S. Erdahl
Keyword(s):  
Optical Fiber ◽  
Delivery System ◽  
Monitoring And Control ◽  
Laser Ultrasonic ◽  
Ultrasonic Probe ◽  
Inspection Systems ◽  
On Line ◽  
Directivity Patterns ◽  
Working Distance ◽  
And Control

Abstract Ultrasonics is a widely used nondestructive testing technique, which is often applied off-line for weld quality inspection. Laser ultrasonic (LU) inspection systems have the potential for on-line application, providing the means to identify unacceptable welds as they are formed. Because LU systems are non-contacting, they can be used for testing moving specimens or for operation in hazardous and/or high temperature environments. A highly versatile system can be created when an optical fiber delivery system is incorporated into the design. Introduction of a focusing objective increases the allowable working distance and permits stronger generation using material ablation as the generating mechanism. This paper describes the development of a laser ultrasonic probe using an optical fiber delivery system with a distal end, focusing objective. The optical fiber delivery system can be configured as a single fiber source, a linear array (fiber bundle) or a phased array. Results include experimentally obtained directivity patterns demonstrating ultrasonic generation using ablation sources. Thermoelastic source results are also included. This paper demonstrates the potential of the fiber tool and presents an overview of the weld control scheme.

On-line tests of an optical fiber long-period grating subjected to gamma irradiation

2014 ◽  
Author(s):  
D. Sporea ◽  
A. Stancalie ◽  
D. Negut ◽  
G. Pilorget ◽  
S. Delepine-Lesoille ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Gamma Irradiation ◽  
Long Period Grating ◽  
Long Period ◽  
On Line

A Hierarchical Access Control Scheme Based on Lagrange Interpolation and ELGamal Algorithm with Numerical Experiments

2013 ◽  
Vol 385-386 ◽  
pp. 1705-1707
Author(s):  
Tzer Long Chen ◽  
Yu Fang Chung ◽  
Jian Mao Hong ◽  
Jeng Hong Jhong ◽  
Chin Sheng Chen ◽  
...  
Keyword(s):  
Access Control ◽  
Lagrange Interpolation ◽  
Control Mechanism ◽  
Key Generation ◽  
Electronic Documents ◽  
Control Scheme ◽  
Video Systems ◽  
Efficient Scheme ◽  
On Line ◽  
Access Control Mechanism

It is important to notice that the access control mechanism has been widely applied in various areas, such as on-line video systems, wireless network, and electronic documents. We propose an access control mechanism which is constructed based on two mathematical fundamentals: Lagrange interpolation and ElGamal algorithm. We conduct performance analysis to compare the efficiency of our proposed scheme with that of several related published schemes in both key generation phase and key derivation phase. Our new scheme is proven to be more efficient. It is shown, as expected, a more efficient scheme provides relatively less security and a more secure scheme is relatively less efficient for private keys of the same size.

The Optimization of Time-Frequency Control: Using Non-Autonomous Time-Delay Feedback Systems as Example

2016 ◽  
Author(s):  
Chi-Wei Kuo ◽  
C. Steve Suh
Keyword(s):  
Time Delay ◽  
Dynamic Instability ◽  
Frequency Control ◽  
Frequency Resolution ◽  
Control Technique ◽  
Time Step ◽  
Time Frequency ◽  
Control Scheme ◽  
Fxlms Algorithm ◽  
On Line

A novel time-frequency nonlinear scheme demonstrated to be feasible for the control of dynamic instability including bifurcation, non-autonomous time-delay feedback oscillators, and route-to-chaos in many nonlinear systems is applied to the control of a time-delayed system. The control scheme features wavelet adaptive filters for simultaneous time-frequency resolution. Specifically Discrete Wavelet transform (DWT) is used to address the nonstationary nature of a chaotic system. The concept of active noise control is also adopted. The scheme applied the filter-x least mean square (FXLMS) algorithm which promotes convergence speed and increases performance. In the time-frequency control scheme, the FXLMS algorithm is modified by adding an adaptive filter to identify the system in real-time in order to construct a wavelet-based time-frequency controller capable of parallel on-line modeling. The scheme of such a construct, which possesses joint time-frequency resolution and embodies on-line FXLMS, is able to control non-autonomous, nonstationary system responses. Although the controller design is shown to successfully moderate the dynamic instability of the time-delay feedback oscillator and unconditionally warrant a limit cycle, parameters are required to be optimized. In this paper, the setting of the control parameters such as control time step, sampling rate, wavelet filter vector, and step size are studied and optimized to control a time-delay feedback oscillators of a nonautonomous type. The time-delayed oscillators have been applied in a broad set of fields including sensor design, manufacturing, and machine dynamics, but they can be easily perturbed to exhibit complex dynamical responses even with a small perturbation from the time-delay feedback. These responses for the system have a very negative impact on the stability, and thus output quality. Through employingfrequency-time control technique, the time responses of the time-delay feedback system to external disturbances are properly mitigated and the frequency responses are also suppressed, thus rendering the controlled responses quasi-periodic.

Compact optical fiber components for a Nd:YAG laser delivery system

1994 ◽  
Author(s):  
Riccardo Falciai ◽  
Tania Pascucci ◽  
Alessandro Schena
Keyword(s):  
Optical Fiber ◽  
Delivery System ◽  
Nd:Yag Laser ◽  
Fiber Components
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