scholarly journals Dynamic characteristics of frequency-locked autodynes

2019 ◽  
Vol 30 ◽  
pp. 12009 ◽  
Author(s):  
Vladyslav Ya. Noskov ◽  
Kirill A. Ignatkov ◽  
Kirill D. Shaidurov
Keyword(s):  
Experimental Data ◽  
Numerical Modelling ◽  
Response Time ◽  
Dynamic Characteristics ◽  
Gunn Diode ◽  
Time Constants ◽  
Microwave Oscillators ◽  
Fast Movement ◽  
Signal Period

The results of research into the dynamic characteristics of microwave oscillators under the influence of both their own reflected radiation and external synchronising effect are presented. The basic relations for the analysis of signals during fast movement of the target are obtained, when the signal period is comparable to the autodyne response time constants. The results of numerical modelling of the characteristics are confirmed by the experimental data obtained on the example of an oscillator based on the Gunn diode of the 8-mm range.

scholarly journals Autodyne signal features of frequency-locked microwave oscillators

2019 ◽  
Vol 30 ◽  
pp. 12012 ◽  
Author(s):  
Vladyslav Ya. Noskov ◽  
Kirill A. Ignatkov ◽  
Kirill D. Shaidurov
Keyword(s):  
Experimental Data ◽  
Signal Analysis ◽  
Gunn Diode ◽  
Theoretical Research ◽  
Research Results ◽  
Microwave Oscillators ◽  
Signal Features ◽  
External Frequency ◽  
Autodyne Signal ◽  
The Impact

The research results on the autodyne signal formation in microwave oscillators, which are exposed under the impact of the proper reflected emission and, at the same time, of the external frequency-locked signal are presented. The basic relations are obtained for signal analysis under the condition of the quasistatic target movements. The theoretical research results are confirmed by experimental data obtained on the example of an oscillator made on the basis of the 8mm-range Gunn diode.

Scanning HEPA Filters with Photometers

1994 ◽  
Vol 37 (5) ◽  
pp. 46-52
Author(s):  
Bruce McDonald
Keyword(s):  
Experimental Data ◽  
Response Time ◽  
High Efficiency ◽  
Experimental System ◽  
Scanning Speed ◽  
Exponential Process ◽  
Time Constants ◽  
Response Characteristics ◽  
Counting Methods ◽  
Many Particles

High-efficiency particulate air (HEPA) filters and ultra low penetration air (ULPA) filters such as those used in cleanrooms and clean benches are frequently scanned or probed for leaks. Historically, filters were scanned with a light-scattering photometer that measures the light scattered from many particles simultaneously. While particle counting methods have been introduced, the photometer methods are still used in many cases. There has not been a documented basis for the scanning speed when using photometers. The photometer response time and the time that the probe is over a leak affects the magnitude of the meter response. This paper sets forth a model for the photometer response characteristics. Photometer response to a leak while scanning is modeled as a simple exponential process. The model is verified with experimental data. Time constants for the experimental system were determined. The effect of the response time on the ability to detect leaks is discussed. Methods to compenstate for the loss of sensitivity during scanning are presented.

scholarly journals Spatiotemporal dynamic characteristics of typical temperate glaciers in China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wang Shijin ◽  
Che Yanjun ◽  
Wei Yanqiang
Keyword(s):  
Mass Balance ◽  
Dynamic Characteristics ◽  
Flow Speed ◽  
Hydrothermal Conditions ◽  
Humid Climate ◽  
Ice Flow ◽  
Change Rate ◽  
Fast Movement ◽  
The 1950S ◽  
Yulong Snow Mountain

AbstractChina’s temperate glaciers have a relatively warm and humid climate and hydrothermal conditions at low latitudes. Temperate glaciers, however, have larger ablation, higher ice temperatures, relatively fast movement speeds, and a significant sliding process at the bottom. As a result, these glaciers are more significantly affected by climate change. On the basis of topographic maps, aerial photography, and Landsat OLI images, and combined with existing research results, this paper systematically analyzed the temporal and spatial dynamic characteristics of typical temperate glaciers. The results are as follows: (1) From the 1950s to the 1970s, compared with other types of glaciers, temperate glaciers showed strong retreat and ablation trends in terms of area, length, speed, and mass balance. (2) The reduction rates of glacier areas of Kangri Garpo, Dagu Snow Mountain, Yulong Snow Mountain (YSM), and Meili Snow Mountain (MSM) in China’s temperate glacier areas all exceeded 38%, which was far above the national average of 18% from the 1950s to the 2010s. (3) The recent length retreat rates of Azha Glacier, Kangri Garpo, and Mingyong Glacier, MSM, Hailuogou Glacier (HG), Gongga Snow Mountain (GSM), and Baishui River Glacier No. 1 (BRGN1), YSM were above 22 m/a, which was faster than the retreat rates of other regions. (4) Consistent with glacier retreat, temperate glaciers also had a faster ice flow speed. The ice flow velocities of the BGN1, HG, Parlung River Glaciers No. 4 and 94, and Nyainqêntanglha were, respectively, 6.33–30.78 m/a, 41–205 m/a, 15.1–86.3 m/a, and 7.5–18.4 m/a, which was much faster than the velocity of other types of glaciers. (5) Mass loss of temperate glaciers was most dramatic during the observation period (1959–2015). The annual mass balance from eight typical temperate glaciers fluctuated between − 2.48 and 0.44 m w.e., and the annual average change rate of mass balance (− 0.037 m w.e./a) was much higher than that in China (− 0.015 m w.e./a, p < 0.0001) and globally (− 0.013 m w.e./a, p < 0.0001).

FEA Tire Modeling and Validation Techniques

2015 ◽  
Author(s):  
Mehrsa Marjani ◽  
Moustafa El-Gindy ◽  
David Philipps ◽  
Fredrik Öijer ◽  
Inge Johansson
Keyword(s):  
Experimental Data ◽  
Dynamic Characteristics ◽  
Rolling Resistance ◽  
Vertical Acceleration ◽  
Virtual Model ◽  
Static And Dynamic Characteristics ◽  
Modeling Methods ◽  
Truck Tire ◽  
Tire Modeling ◽  
Tire Models

Recent advances in power and efficiency of computerized modeling methods has made it easier to develop accurate tire models. These newer models are now created with such accuracy that it has become easy to predict the experimental tire’s behavior and characteristics. These models are helpful with determining tire, tire-road, and tire-soil interaction properties. By creating virtual models, the overall capital for research and development can be reduced as well as replacing unavailable experimental tires for research. This research paper mainly focuses on the validation of computer generated FEA tire models which are then used for the prediction of the experimental tire’s rolling resistance, static and dynamic characteristics. Experimental data, such as rolling resistance and vertical acceleration are used in validation simulations in order to tune the virtual model to match the experimental tire’s behavior. The tire that was used for this research is a six-groove 445/50R22.5 FEA truck tire, which was constructed and validated over the course of this research.

Research on dynamic characteristics and fatigue robust optimization of integrated vehicle model

2018 ◽  
Vol 232 (14) ◽  
pp. 1982-1999
Author(s):  
Bobo Li ◽  
Huiqun Yuan ◽  
Tianyu Zhao ◽  
Guangding Wang
Keyword(s):  
Experimental Data ◽  
Robust Optimization ◽  
Dynamic Characteristics ◽  
Six Sigma ◽  
Multiple Frequency ◽  
Heavy Duty ◽  
Vehicle Model ◽  
Design For Six Sigma ◽  
Frequency Components ◽  
Simulation Results

This paper investigates the dynamic characteristics and fatigue robust optimization of heavy-duty tractor. First, this paper presents a vehicle model with sub-structure method. Based on the theory of base motion, the structure dynamic characteristics are analyzed. Second, the accuracy of the method is verified by comparing the experimental results with the simulation results. Also, the dynamic response and the transfer function of vehicle are obtained using the above methods. Combined with the experimental data, the methods of random multiple frequency components and multi-axial fatigue life are adopted to analyze the fatigue damage of the heavy-duty tractor under different road conditions. Finally, the Design for Six Sigma is used to optimize the vehicle’s structure. The results show that by using the proposed method, the dynamic characteristics of the vehicle can be analyzed accurately and effectively, robustness of the vehicle can be improved, and mass of the vehicle can be reduced.

Response time constants of two commonly used dose-rate meters

1977 ◽  
Vol 50 (590) ◽  
pp. 149-150
Author(s):  
P. J. Gillespie ◽  
J. L. Alexander
Keyword(s):  
Response Time ◽  
Dose Rate ◽  
Time Constants

Numerical Modelling of Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Square Arrangements

2016 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arnsten
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Wave Interaction ◽  
Wave Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters and an accurate numerical modelling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source (Computational Fluid Dynamics) CFD model REEF3D is used to simulate the breaking wave interaction with the multiple cylinders. The numerical model is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations, the level set method for the free surface and the k–ω model for turbulence. The model uses a 5th-order conservative finite difference WENO scheme for the convective discretization and a 3rd-order Runge-Kutta scheme for time discretization. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is seen between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. The breaking wave forces on each cylinder in the group are computed for the two cases and the results are compared with the breaking wave force on a single isolated cylinder. Further, the study investigates the water surface elevations and the free surface flow features around the cylinders. In general, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. The results of the present study show that the interference effects from the neighbouring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

Numerical Modelling in Turbines for OWC Systems: Application to a Radial Impulse

2010 ◽  
Author(s):  
Juan G. Gonza´lez ◽  
Bruno Pereiras ◽  
Francisco Castro ◽  
Miguel A. Rodri´guez
Keyword(s):  
Experimental Data ◽  
Numerical Modelling ◽  
Cfd Analysis ◽  
Oscillating Water Column ◽  
Impulse Turbine ◽  
One Dimensional ◽  
Directional Flow ◽  
Axial Turbines ◽  
D Model ◽  
Reaction Degree

This work is focused on radial impulse turbines for an Oscillating Water Column (OWC) which is one of the alternatives to the Wells turbines traditionally installed in the OWC systems. All self-rectifying turbines work under special conditions due to the bi-directional flow caused by OWC. But a radial impulse turbine has another special point: it works alternatively as an inflow/outflow turbine, so that its behavior is not symmetrical as is expected in axial turbines for OWC (Wells and axial impulse turbines). The complete CFD analysis we have made of a radial impulse turbine is described. The model was created for a specific turbine but can be adapted for any self-rectifying turbine. We have studied the turbine by means of a one-dimensional study and a 3-D model solved with FLUENT® software, and the results were validated with experimental data extracted from the bibliography. This model allowed us to analyse both the classical dimensionless parameters and the flow pattern. Moreover, we have introduced a special definition for the reaction degree in order to analyse the process of the energy conversion.

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