Characterizing flat-top laser beams using standard beam parameters

2006 ◽  
Vol 84 (3) ◽  
pp. 223-240 ◽  
Author(s):  
S Saghafi ◽  
M J Withford ◽  
Z Ghoranneviss
Keyword(s):  
Near Field ◽  
Analytical Models ◽  
Model Parameters ◽  
Fourth Moment ◽  
Output Beam ◽  
Field Versus ◽  
Kurtosis Parameter ◽  
Beam Characteristic ◽  
Padé Method ◽  
Beam Parameters

We examine the correspondence between various models describing flat-top laser beam profiles using two standard parameters; namely, the M2 factor and the kurtosis parameter. Numerical expressions for M2, based on the second moment of the beam irradiance distribution in the near and far fields and for the kurtosis parameter, k, based on the fourth moment at the near field, are obtained. Plots of k in the near field versus M2 demonstrate the similarities between the different analytical models used to describe flat-top profiles. Using the Padé approximation, a relationship between k and M2, a new reference formula, is derived that predicts the values of M2 to within less than a percent for these flattened beams. This method is then extended to define numerical expressions relating the beam parameters (i.e., M2 and k) and the parameters describing the beam characteristic in each analytical model (model parameters). The results obtained using the Padé method are used to describe the output beam profiles for a high power copper vapour laser fitted with an unstable resonator.PACS Nos.: 42.55.–f, 42.55.Lt, 42.60.–v

Comparison of Analytical and Empirical Models to Capture Variations in Off-Road Vehicle Dynamics

2005 ◽  
Author(s):  
Paul J. Pearson ◽  
David M. Bevly
Keyword(s):  
Empirical Data ◽  
Vehicle Dynamics ◽  
Experimental Validation ◽  
Inertial Sensors ◽  
Analytical Models ◽  
Control Algorithms ◽  
Model Parameters ◽  
Steering Control ◽  
Steering Angle ◽  
Yaw Rate

This paper develops two analytical models that describe the yaw dynamics of a farm tractor and can be used to design or improve steering control algorithms for the tractor. These models are verified against empirical data. The particular dynamics described are the motions from steering angle to yaw rate. A John Deere 8420 tractor, outfitted with inertial sensors and controlled through a PC-104 form factor computer, was used for experimental validation. Conditions including different implements at varying depths, as would normally be found on a farm, were tested. This paper presents the development of the analytical models, validates them against empirical data, and gives trends on how the model parameters change for different configurations.

Characterization of Thermal and Acoustic Profiles of Potential Underwater Pipeline Leaks

2014 ◽  
Author(s):  
Shane Siebenaler ◽  
Eric Tervo ◽  
Mohan Kulkarni ◽  
Sandeep Patni ◽  
Glenn Gesoff
Keyword(s):  
Near Field ◽  
Thermal Response ◽  
Third Party ◽  
Analytical Models ◽  
Distributed Temperature Sensing ◽  
Offshore Installations ◽  
Underwater Pipeline ◽  
Optic Systems ◽  
Measurement Mechanism ◽  
Gas Leaks

Reliable detection of small potential leaks is a topic of significant interest for remote offshore pipelines. Potential leak cases of interest are pinhole leaks out of the bottom of the pipe due to corrosion, weld or seam cracks, or damage due to third-party contact. There are several emerging technologies that may have the potential to provide a means of detecting such leaks over long segments of underwater pipe. These technologies include distributed acoustic and distributed temperature sensing. A key element of evaluating the applicability of these systems is to characterize the behavior of leaks. It is critically important to understand how leaks behave when employing a technology that has only been previously used for other conditions. A joint-industry program was initiated to evaluate the thermal and acoustic behavior of hypothetical underwater leaks. The environments studied range from shallow, Arctic applications to deep offshore installations. Analytical models were assessed to predict the jetting behavior of simulated leaks and their near-field thermal response. This analysis was performed for both liquid and gas media. These models were validated by means of laboratory experiments. Acoustic characteristics of hypothetical liquid and gas leaks were determined by means of testing with hydrophones. This information can be leveraged by a number of technologies as the data are independent of the measurement mechanism. While the motivation of this work is to evaluate distributed fiber-optic systems, the data on leak characteristics may also provide indications on applicability of other techniques for detecting potential underwater leaks. The data from this project will allow the industry to improve the understanding of potential leaks from underwater pipelines and, hence, lay the foundation for determining appropriate detection systems.

scholarly journals An Updated Analytical Structural Pounding Force Model Based on Viscoelasticity of Materials

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Qichao Xue ◽  
Chunwei Zhang ◽  
Jian He ◽  
Guangping Zou ◽  
Jingcai Zhang
Keyword(s):  
Vibration Control ◽  
Viscoelastic Model ◽  
Control Process ◽  
Model Performance ◽  
Analytical Models ◽  
Model Parameters ◽  
Force Model ◽  
Control Analysis ◽  
Proposed Model ◽  
Force Calculation

Based on the summary of existing pounding force analytical models, an updated pounding force analysis method is proposed by introducing viscoelastic constitutive model and contact mechanics method. Traditional Kelvin viscoelastic pounding force model can be expanded to 3-parameter linear viscoelastic model by separating classic pounding model parameters into geometry parameters and viscoelastic material parameters. Two existing pounding examples, the poundings of steel-to-steel and concrete-to-concrete, are recalculated by utilizing the proposed method. Afterwards, the calculation results are compared with other pounding force models. The results show certain accuracy in proposed model. The relative normalized errors of steel-to-steel and concrete-to-concrete experiments are 19.8% and 12.5%, respectively. Furthermore, a steel-to-polymer pounding example is calculated, and the application of the proposed method in vibration control analysis for pounding tuned mass damper (TMD) is simulated consequently. However, due to insufficient experiment details, the proposed model can only give a rough trend for both single pounding process and vibration control process. Regardless of the cheerful prospect, the study in this paper is only the first step of pounding force calculation. It still needs a more careful assessment of the model performance, especially in the presence of inelastic response.

Influence of the active-medium inhomogeneity and of aperture stops on the output-beam parameters of a CO2laser

1982 ◽  
Vol 12 (5) ◽  
pp. 555-559
Author(s):  
V G Doronin ◽  
V I Novikov ◽  
V P Pipchenko ◽  
V A Stepanov
Keyword(s):  
Active Medium ◽  
Output Beam ◽  
Beam Parameters

Improved Analytical Models for Single- and Multi-layer Silver Superlenses

2009 ◽  
Vol 1182 ◽  
Author(s):  
Ciaran P Moore ◽  
Richard John Blaikie ◽  
Matthew D Arnold
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Single Layer ◽  
Analytical Models ◽  
Full Field ◽  
Accurate Performance ◽  
Imaging Performance ◽  
Performance Estimates ◽  
Continuous Metal ◽  
Good Agreement

AbstractSpatial-frequency transfer functions are regularly used to model the imaging performance of near-field �superlens� systems. However, these do not account for interactions between the object that is being imaged and the superlens itself. As the imaging in these systems is in the near field, such interactions are important to consider if accurate performance estimates are to be obtained. We present here a simple analytical modification that can be made to the transfer function to account for near-field interactions for objects consisting of small apertures in otherwise-continuous metal screens. The modified transfer functions are evaluated by comparison with full-field finite-element simulations for representative single-layer and multi-layer silver superlenses, and good agreement is found.

Research on output beam characteristic from unstable resonator of DF laser

2015 ◽  
Author(s):  
Wei-yan Ren ◽  
Hui Wang ◽  
Lei Cai ◽  
Song-qing Zhou ◽  
Zheng Zhang ◽  
...  
Keyword(s):  
Unstable Resonator ◽  
Output Beam ◽  
Beam Characteristic

scholarly journals Analytical calculation of intrinsic shielding effectiveness for isotropic and anisotropic materials based on measured electrical parameters

2014 ◽  
Vol 12 ◽  
pp. 83-89 ◽  
Author(s):  
M. Kühn ◽  
W. John ◽  
R. Weigel
Keyword(s):  
Near Field ◽  
Analytical Calculation ◽  
Anisotropic Materials ◽  
Electrical Circuit ◽  
Analytical Models ◽  
Shielding Effectiveness ◽  
Electrical Parameters ◽  
Measurement Systems ◽  
Definition Of ◽  
Adequate Measurement

Abstract. This contribution contains the mechanisms for calculation of magnetic shielding effectiveness from material samples, based on measured electrical parameters. For this, measurement systems for the electrical conductivity of high and low conductive material samples with respect to the direction of current flow are presented and discussed. Also a definition of isotropic and anisotropic materials with electrical circuit diagrams is given. For prediction of shielding effectiveness for isotropic and anisotropic materials, several analytical models are presented. Also adaptions to gain a near field solution are part of this contribution. All analytical models will also be validated with an adequate measurement system.

scholarly journals Kineto-elastic analysis of modular robot systems with component model updating

2021 ◽  
Author(s):  
Richard P. Mohamed
Keyword(s):  
Infinite Number ◽  
Model Updating ◽  
Experimental Tests ◽  
Analytical Models ◽  
Model Parameters ◽  
Elastic Analysis ◽  
Analysis Model ◽  
Worst Case ◽  
Structural Dynamic ◽  
Payload Capacity

This dissertation describes the kineto-elastic analysis and component structural dynamic model updating of serial modular reconfigurable robots (MRRs). In general, kineto-elastic analysis is concerned with the structural vibrations, elastic deflections, and torque transmissions of robots which undergo motion from one pose (position and orientation) to another. This work focuses on the kineto-elastic analysis of MRRs undergoing low-speed quasi-static motion. When determining an MRR's payload capacity, or designing MRR modules, the main difficulty is the large number of module configurations and the infinite number of poses within each configuration. Also, the kineto-elastic models of MRRs can become quite large with an increasing number of modules, thereby increasing the numerical complexity. Furthermore, the analytical models of individual MRR components may contain uncertainties, such as unknown stiffness and material parameters, which may lead to large errors for assembled MRR models. To alleviate these issues, a new framework was developed for the kineto-elastic analysis of MRR modules with an emphasis on assessing the worst-case poses. First, a combinatory search method was presented to reduce the computational burdens associated with determining the maximum payload capacity, and performing the module stiffness designs. This involved identifying the worst-case configuration and pose amongst a large number of configurations and infinite number of poses. Afterwards, it was demonstrated that the determination of an MRR's payload capacity, as well as the module stiffness designs, can be performed at the worst-case pose and configuration to satisfy a global set of kineto-elastic performance requirements for all remaining configurations. Next, a new component mode synthesis (CMS) model with fixed-free component boundaries was developed to reduce the sizes of kineto-elastic models, mimic natural link-joint connectivity, and allow experimental tests of joint modules in multiple poses to enable test-analysis model correlation. Finally, a novel method was created to update the uncertain model parameters of joint and link modules using frequency response data from component vibration tests in multiple poses (including the worst cases), with boundary conditions matching those from the CMS models. This procedure can completely avoid testing an entire assembly to perform model updating, and can provide accurate updated model results in any assembly pose.

scholarly journals Propagation of Vortex Hermite-Cosh-Gaussian Beams in a Gradient-Index Medium

2021 ◽  
Author(s):  
M. Lazrek ◽  
Z. Hricha ◽  
A. Belafhal
Keyword(s):  
Phase Distribution ◽  
Incident Beam ◽  
Propagation Distance ◽  
Gaussian Beams ◽  
Gradient Index ◽  
Output Beam ◽  
Propagation Equation ◽  
Intensity Pattern ◽  
Fiber Communications ◽  
Beam Parameters

Abstract Based on the Huygens–Fresnel integral, the propagation equation for a vortex Hermite-cosh-Gaussian beams (vHChGB) in gradient-index medium (GIM) is derived. From the obtained expression, the evolution of the intensity and the phase distributions of a vHChGB through a GIM are numerically demonstrated as a function of the gradient-index parameter β under the change of incident beam parameters. The results show that the characteristics of the output beam evolve periodically versus the propagation distance, and the period of evolution slows down when β is increased. Furthermore, it is demonstrated that the self-repeating properties of the intensity pattern and the phase distribution for the propagated vHChGB are altered by the incident beam parameters. The results obtained may be beneficial for applications in fiber communications and beam shaping.

Sign in / Sign up

Export Citation Format

Share Document