6 results about "Spectral density function" patented technology

The present application provides a kind of quantitative evaluation method of the influence of wind tunnel inner surface roughness on airflow quality, belongs to the technical field of wind tunnel, the present application is collected by laser confocal scanner wall roughness multi-resolution point cloud data, high frequency, medium frequency and low frequency roughness component is extracted by wavelet decomposition, power spectral density function and fractal dimension are calculated to establish random roughness field probability distribution model, local velocity field and vorticity distribution are obtained by using lattice Boltzmann algorithm to simulate rough wall near flow field, the uniformity of airflow is calculated by generating equivalent random roughness field sample using Monte Carlo method for statistical analysis, the polynomial mapping function of roughness statistical characteristic parameter and airflow quality degradation index is established, when degradation index exceeds allowable threshold, wall roughness is over standard, solve the technical problems of low precision and insufficient calculation efficiency in quantitative evaluation of the influence of multi-scale random roughness on wind tunnel airflow quality.

A method of forming an illumination mode using an illumination system comprising an array of individually controllable reflective elements arranged to direct portions of a radiation beam to desired locations in a pupil plane. The method comprises allocating different reflective elements of the array to direct radiation to different locations in the illumination mode by: determining a desired power spectral density function of radiation directed by the array of reflective elements to the illumination mode, the desired power spectral density function including a cutoff frequency; applying different phases to frequency components of the power spectral density function; transforming the power spectral density function into a spatial domain signal that varies as a function of positions of the reflective elements; and using the spatial domain signal to allocate reflective elements that direct radiation to different locations in the illumination mode.

A kind of underwater vehicle noise prediction correction method based on bayesian inference, calculation model (1) includes Corcos autospectrum and Corcos normalized cross power spectral density function calculation model;According to calculation model (1), construct the schematic diagram (2) of bayesian network, the key factor identification and state analysis of the key factor of the modeling of the influencing factor of turbulent fluctuation pressure in bayesian network in schematic diagram (2) of bayesian network are built-in bayesian inference;According to the schematic diagram (2) of bayesian network, model in NETICA software, construct directed acyclic bayesian network (3);Reference calculation model (1) and directed acyclic bayesian network (3) are simulated setting (4) and noise signal comparison (5).The present application has the advantages of ensuring the precision of low-frequency noise prediction in sparse grid large size, improves the problem that the grid scale of finite element model and the space related scale of turbulent boundary layer pressure do not match and the calculation amount is too large when fine grid is used.

The present invention relates to a three-dimensional undulating green generation system for realistic putting simulation. The present invention comprises: an input module that sets terrain generation parameters of the green according to the difficulty or set value of the putting simulation; and a green generation module that generates a undulating surface in three-dimensional space based on the terrain generation parameters. In particular, the green generation module is characterized by generating a random field having an irregular height distribution using a spectral density function, and selectively superimposing tilting and stepping elements thereon to generate a three-dimensional green map similar to an actual field. Furthermore, the present invention provides a realistic putting physics environment by precisely tracking the altitude of the ball through natural coordinate calculations based on triangle elements and dynamically correcting the coefficient of friction according to the slope of the green.

This invention discloses a method and system for fatigue life analysis in multi-objective optimization design of pressure vessels. By constructing a parameterized model including structural parameters, material parameters, and cyclic load boundary parameters, stress response data at key locations are calculated, and a stress power spectral density function is generated. Based on the power spectral density function, spectral moment parameters and frequency domain characteristic parameters are extracted, and a probabilistic model is used to calculate the cyclic stress distribution, fatigue damage rate, and fatigue life. A multi-objective evaluation vector is constructed by combining structural design variables, stress response, and life results to uniformly evaluate structural quality, strength utilization, and fatigue life. An evolutionary optimization algorithm is used to introduce life contribution weights for iterative screening and updating of design variables. Through iterative control, model updates and optimization convergence are achieved, ultimately outputting a structural design scheme that meets multi-objective constraints and corresponding fatigue life analysis results, realizing the collaborative optimization of pressure vessel structural design and life assessment.

The present application relates to a kind of environmental microvibration evaluation method and storage medium for high-precision scientific device, the method comprises the following steps: collecting the environmental microvibration signal of environment to be evaluated;Power spectrum method is applied to the environmental microvibration signal processing, obtains corresponding first power spectral density function;The first power spectral density function is converted into the second power spectral density function of vibration velocity;According to second power spectral density function, the speed root mean square in the full frequency range of high-precision scientific device is calculated;The evaluation index of high-precision scientific device is converted into speed index;Based on the comparison of the speed root mean square and speed index, the environmental microvibration evaluation result of environment to be evaluated is obtained.Compared with prior art, the reliability of high-precision scientific device environmental microvibration analysis and evaluation is improved.