scholarly journals An analysis of possible assessment of hazards to ship shaft line, resulting from impulse load

2007 ◽  
Vol 14 (3) ◽  
pp. 12-20 ◽  
Author(s):  
Andrzej Grządziela
Keyword(s):  
Mathematical Model ◽  
Spectral Analysis ◽  
Underwater Explosion ◽  
Water Area ◽  
Elastic Deformations ◽  
Vibration Signals ◽  
Shaft Line ◽  
Hull Structure ◽  
Impulse Load ◽  
Critical Velocities

An analysis of possible assessment of hazards to ship shaft line, resulting from impulse load This paper presents a proposal of identification of a degree of hazard to ship shaft line due to impulse load caused by underwater explosion. A theoretical analysis was made of influence of changes in co-axiality of shafts on second-kind critical velocities resulting from elastic deformations of hull structure in vicinity of shaft bearing foundations. Results are presented of pilotage tests of underwater explosion performed on training water area. A preliminary mathematical model of underwater explosion is given with taking into account mass of explosives and distance from the tested object. The drawn conclusions show a way of identification of hazard to shaft line by using spectral analysis and time - runs of vibration signals recorded at shaft bearings.

Modeling the Effects of Underwater Detonation Wave

2013 ◽  
Vol 588 ◽  
pp. 175-183
Author(s):  
Andrzej Grządziela
Keyword(s):  
Vibration Spectrum ◽  
Water Environment ◽  
Underwater Explosion ◽  
Impulse Loading ◽  
Structure Model ◽  
Measuring Systems ◽  
Shaft Line ◽  
Hull Structure ◽  
On Line ◽  
Vibration Measuring

Minehunters are subjected to specific sea loads due to waving and dynamical impacts associated with underwater explosion. Sea waving can be sufficiently exactly modeled by means of statistical methods. Much more problems arise from modeling impacts due to underwater explosion. Knowledge of a character of impulse loading which affects ship shaft line can make it possible to identify potential failures by means of on-line vibration measuring systems. The problem of influence of sea mine explosion on hull structure is complex and belongs to more difficult issues of ship dynamics. Underwater explosion is meant as a violent upset of balance of a given system due to detonation of explosives in water environment. A paper presents a proposal of identification of a degree of hazard the ships hull forced from underwater explosion. A theoretical analysis was made of influence of changes of hull structure in vicinity of hull. The main problem of naval vessels is a lack of dynamical requirements of stiffness of the hull. Modeled signals and hull structure were recognized within sensitive symptoms of three sub models: model of hull structure, model of impact and model of propulsion system. All sub models allow testing forces and their responses in vibration spectrum using SIMULINK software and FEM models.

Modeling of the Minehunters Hull Strenght

2014 ◽  
Vol 1036 ◽  
pp. 189-194
Author(s):  
Andrzej Grządziela ◽  
Bogdan Szturomski ◽  
Marcin Kluczyk
Keyword(s):  
Shock Wave ◽  
Theoretical Analysis ◽  
Vibration Spectrum ◽  
Underwater Explosion ◽  
Virtual Model ◽  
Structure Model ◽  
Similar Nature ◽  
Underwater Explosions ◽  
Hull Structure ◽  
Impulse Load

The paper presents problems of modeling the ship’s hull subjected to the load of shock wave associated with non-contact underwater explosion. The article presents equations for describing the parameters of shock wave subjected to an impulse load. The paper presents a proposal of identification of a degree of hazard the ship’s hull forced from underwater explosion. A theoretical analysis was made of influence of changes of hull structure in vicinity of hull. Modeled signals and hull structure were recognized within sensitive symptoms of three sub models: model of hull structure, model of impact and model of propulsion system. All sub models allow testing forces and their responses in vibration spectrum using SIMULINK software and FEM models. The results of testing allowed performing simulations of a similar nature to the actual loads of underwater explosions. Virtual model of the hull of the ship responds in a similar manner to the real impacts.

scholarly journals Local and Global Gestalt Laws: A Neurally Based Spectral Approach

2017 ◽  
Vol 29 (2) ◽  
pp. 394-422 ◽  
Author(s):  
Marta Favali ◽  
Giovanna Citti ◽  
Alessandro Sarti
Keyword(s):  
Mathematical Model ◽  
Spectral Analysis ◽  
Group Theory ◽  
Visual Cortex ◽  
Connectivity Matrix ◽  
Spectral Approach ◽  
Good Continuation ◽  
Functional Architecture ◽  
Lie Group Theory ◽  
Gestalt Laws

This letter presents a mathematical model of figure-ground articulation that takes into account both local and global gestalt laws and is compatible with the functional architecture of the primary visual cortex (V1). The local gestalt law of good continuation is described by means of suitable connectivity kernels that are derived from Lie group theory and quantitatively compared with long-range connectivity in V1. Global gestalt constraints are then introduced in terms of spectral analysis of a connectivity matrix derived from these kernels. This analysis performs grouping of local features and individuates perceptual units with the highest salience. Numerical simulations are performed, and results are obtained by applying the technique to a number of stimuli.

scholarly journals Process modeling in sensor - object system when scanning underwater communications

2017 ◽  
pp. 84-94
Author(s):  
S. G. Cherny ◽  
A. A. Zhilenkov
Keyword(s):  
Mathematical Model ◽  
Process Modeling ◽  
Local Structure ◽  
Practical Importance ◽  
Underwater Vehicles ◽  
Water Area ◽  
Underwater Communication ◽  
Underwater Communications ◽  
Unmanned Underwater Vehicles ◽  
The Mathematical Model

The study focuses on the modeled processes describing the interaction of the scanning sensor with the element of underwater communication. This task is relevant in constructing the systems for automated monitoring of underwater objects by means of unmanned underwater vehicles. A simple model has been obtained that makes it possible to describe the structural properties of the object’s material or damage on its surface. The mathematical model of interaction between the object and the scanning sensor is presented as a sum of two series. The study shows that in problems of controlling the local structure of the object’s surface, it is possible to present the mathematical model in Kotelnikov expanded form. The obtained results are of high practical importance in solving the problems of laying specialized lines and highways in the territory of the Crimean water area of the Azov-Black Sea basin and regular monitoring their condition

scholarly journals A STUDY OF THE DEFLECTIONS OF METAL ROAD GUARDRAIL ELEMENTS

Transport ◽  
2009 ◽  
Vol 24 (3) ◽  
pp. 225-233 ◽  
Author(s):  
Olegas Prentkovskis ◽  
Andrey Beljatynskij ◽  
Rasa Prentkovskienė ◽  
Ivan Dyakov ◽  
Laima Dabulevičienė
Keyword(s):  
Mathematical Model ◽  
Finite Elements ◽  
Traffic Accidents ◽  
Statistical Data ◽  
Elastic Deformations ◽  
One Dimensional ◽  
First Order ◽  
Horizontal Beam ◽  
Deformation Processes ◽  
The Impact

Statistical data on traffic accidents in 2008 in Lithuania is presented. Referring to statistical data, grounding on an obstacle’ makes one‐tenth of all registered traffic accidents ‐ 9.4% (an obstacle may be a road guardrail, a lamp post, a tree, a bar, a gate, etc.). Road guardrails of various types are installed on the shoulders and dividing strips of urban and suburban roads. They are as follows: reinforced concrete guardrails, cable guardrails and metal guardrails. Metal guardrails, consisting of S‐shape metal posts and a protective W‐shape horizontal beam, are most popular. The authors of the present paper examine the deformation processes of the elements of the above mentioned guardrail. A mathematical model of metal road guardrail was developed. Metal road guardrail was modelled using one‐dimensional first‐order finite elements, taking into account only elastic deformations, as well as the effect of soil on the buried post section of the guardrail. Based on the developed mathematical model of metal road guardrail, the deflections of its elements caused by the impact of a vehicle moving at varying speed were determined. The obtained values of deflections of guardrail elements (a protective W‐shape horizontal beam and a S‐shape post) presented in paper do not exceed the admissible values (of beam deflections).

Spectral analysis of perturbed multiplication operators occurring in polymerisation chemistry

1989 ◽  
Vol 113 (1-2) ◽  
pp. 119-148 ◽  
Author(s):  
Niels Jørgen Kokholm
Keyword(s):  
Mathematical Model ◽  
Spectral Analysis ◽  
Equilibrium Distribution ◽  
Exponential Convergence ◽  
Adjoint Operator ◽  
Multiplication Operator ◽  
Multiplication Operators ◽  
Unique Equilibrium ◽  
Initial Value ◽  
Well Posed

SynopsisWe consider a mathematical model for the motion of a marked monomer in a system of reacting polymers at equilibrium. A well-posed integro-differential initial value problem for the probability of finding the marked monomer in a molecule of a given length is formulated. We prove exponential convergence of the probability to a unique equilibrium distribution. A quite complete spectral analysis is carried out for a self adjoint operator, which is a perturbation of a multiplication operator by an integral operator and is related to the generator of the time evolution.

Identification of Bearing Defects by Spectral Analysis

1980 ◽  
Vol 102 (2) ◽  
pp. 199-204 ◽  
Author(s):  
J. I. Taylor
Keyword(s):  
Spectral Analysis ◽  
Low Frequencies ◽  
Vibration Signals ◽  
Size Information ◽  
Spectrum Shape ◽  
Bearing Defects ◽  
Rolling Elements ◽  
Unique Signal ◽  
Moving Parts

This paper describes procedures for identifying defects in antifriction bearings from analyses of the low frequencies (up to 2,000 Hz) generated by the moving parts in the bearing. Defects on bearing raceways, the cage, or rolling elements, as well as excessive clearance, turning on the shaft and loose housing, cause unique vibration signals. A unique signal is also generated when bearings need lubrication. The spectrum shape, frequency, amplitude, and sum and difference frequencies are useful in identifying combinations of defects and their size. Information as to whether the bearing is in a thrust or radial loaded condition is presented.

scholarly journals Extension of Winding Function Theory for Modeling and Diagnosis of Partial Demagnetization Fault in PMSM Drive

2021 ◽  
Author(s):  
Zakaria Gherabi ◽  
Noureddine Benouzza ◽  
Azeddine Bendiabdellah ◽  
Djilali Toumi
Keyword(s):  
Mathematical Model ◽  
Spectral Analysis ◽  
Diagnostic Method ◽  
Function Theory ◽  
Permanent Magnet Synchronous Motor ◽  
Electrical Circuit ◽  
Spectral Content ◽  
Operating Modes ◽  
Stator Current ◽  
Electrical Circuit Model

This paper proposes the development of a new mathematical model dedicated to the diagnostic of the partial Demagnetization Fault (DF) in Permanent Magnet Synchronous Motor (PMSM). To do this, an extension of the Modified Winding Function Approach (MWFA) is proposed to accurately take into account the air gap asymmetry caused by the Demagnetization Fault (DF) in the PMSM inductances calculation. The calculated inductances are then used in the magnetically coupled electrical circuit model to simulate the PMSM behavior in the different operating modes. Finally, a diagnostic method based on the stator current spectral analysis is used to highlight the PMSM stator current spectral content in the various operating modes (with and without Demagnetization Fault).

scholarly journals Effects of Rotation in Low-Metallicity Stars

2004 ◽  
Vol 215 ◽  
pp. 220-221 ◽  
Author(s):  
Sara R. Heap ◽  
Thierry Lanz
Keyword(s):  
Spectral Analysis ◽  
Centrifugal Force ◽  
Massive Stars ◽  
Effective Gravity ◽  
The Core ◽  
Processed Material ◽  
Low Metallicity ◽  
Critical Velocities ◽  
Effects Of Rotation ◽  
Lines Of Evidence

We have carried out a spectral analysis of 17 O-type stars in the Small Magellanic Cloud (SMC). We find several lines of evidence that rotation plays an important role in massive stars in this low-metallicity galaxy (Z=0.2 Z⊙): (1) strong enrichment of nitrogen in half the program stars due to rotational mixing of processed material in the core up to the surface; (2) reduction of the effective gravity by the centrifugal force; (3) apparent anomalies in cluster isochrones that imply some stars are rotating at critical velocities.

Machinability of Heat-Resistant Titanium Alloys during Turning

2021 ◽  
Vol 1022 ◽  
pp. 62-70
Author(s):  
Tatyana Larionova ◽  
Sergei A. Lyubomudrov ◽  
Evgeniy Larionov
Keyword(s):  
Mathematical Model ◽  
Titanium Alloy ◽  
Titanium Alloys ◽  
Experimental Research ◽  
Cutting Tool ◽  
Technological System ◽  
Elastic Deformations ◽  
Heat Resistant ◽  
Processing Modes ◽  
Mechanical And Service Properties

The article discusses the properties and features of heat-resistant titanium alloys. The microstructure of a new titanium alloy VT41, its mechanical and service properties after various processing modes are presented. The main problems in the machining of difficult-to-machine titanium alloys are considered. The developed mathematical model of the formation of errors in turning titanium alloys, taking into account thermal deformations and dimensional wear of the cutting tool, elastic deformations of the technological system, is described. The paper presents the results of experimental research on turning of heat-resistant titanium alloy VT41 on a multi-parameter stand.

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