scholarly journals Time-Varying Kelvin Wake Model and Microwave Velocity Observation

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1575 ◽  
Author(s):  
Jie Niu ◽  
Xingdong Liang ◽  
Xin Zhang
Keyword(s):  
Doppler Velocity ◽  
Time Varying ◽  
Millimeter Wave Radar ◽  
Proposed Model ◽  
Wave Radar ◽  
Application Potential ◽  
Wake Model ◽  
Simultaneous Switching ◽  
First Time ◽  
Good Agreement

In the synthetic aperture radar (SAR) imaging of ship-induced wakes, it is difficult to obtain the Doppler velocity of a Kelvin wake due to the lack of time-varying wake models and suitable radar equipment. The conventional Kelvin wake investigation based on the static Kelvin wake model failed to reflect time-varying characteristics, which are significant in the application of the Kelvin wake model. Therefore, a time-varying Kelvin wake model with consideration of geometric time-varying characteristics and the hydrodynamic equation is proposed in this paper, which reflects the wake’s time-varying change lacking in the conventional Kelvin wake investigation. The Doppler velocity measurement, measured by a specially designed radar, can be exploited to verify the time-varying model by the comparison of velocity fields. Ground-based multi-input multi-output (MIMO) millimeter wave radar imaging through the simultaneous switching of transceiver channels was used to obtain the Doppler velocity for the first time. Finally, promising results have been achieved, which are in good agreement with our proposed model in consideration of the experimental scene. The proposed time-varying model and radar equipment provide velocity measurements for the Kelvin wake observation, which contains huge application potential.

Dynamic Behavior of Helical Gears with Effects of Shaft and Bearing Flexibilities

2011 ◽  
Vol 86 ◽  
pp. 26-29
Author(s):  
Kai Feng ◽  
Shigeki Matsumura ◽  
Haruo Houjoh
Keyword(s):  
Experimental Tests ◽  
Time Varying ◽  
Gear Pair ◽  
Contact Ratio ◽  
Mesh Stiffness ◽  
Helical Gears ◽  
Shaft System ◽  
Proposed Model ◽  
Center Distance ◽  
Good Agreement

This study presents a numerical model of helical gears to consider the effects of shaft and bearing flexibility. A primary feature of this study is that the time-varying mesh stiffness is not just determined by the geometry of gear pair but also updated for each iteration according to the change of center distance. The effects of shaft and bearing flexibilities are discussed by comparing the dynamic response of gear pairs supported with a rigid and a flexible bearing-shaft system. The results show that the pressure angle and contact ratio are significantly changed due to the center-distance variation of gears and the gear pair with a flexible bearing-shaft system has much larger vibration. Finally, experimental tests are conducted to validate the proposed model. The predicted results show good agreement with the experimental data.

scholarly journals Prediction of Concrete Failure Time Based on Statistical Properties of Compressive Strength

2020 ◽  
Vol 10 (3) ◽  
pp. 815
Author(s):  
Jiao Wang ◽  
Weiji Zheng ◽  
Yangang Zhao ◽  
Xiaogang Zhang
Keyword(s):  
Compressive Strength ◽  
Failure Time ◽  
Reliability Evaluation ◽  
Structural Safety ◽  
Time Varying ◽  
Concrete Failure ◽  
Proposed Model ◽  
Compressive Strength Of Concrete ◽  
Mc Simulation ◽  
Good Agreement

Since the heterogeneity of the cement-based material contributes to a random spatial distribution of compressive strength, a reliability analysis based on the compressive strength of concrete is fundamental to carry out structural safety assessment. By analyzing 10,317 datapoints on compressive strength of concrete, a time-varying reliability evaluation based on the third-moment (TM) method was proposed to predict the service life of concrete. Unlike the second-moment (SM) method, skewness is taken into account in the TM; thus, the calculated result of concrete failure time based on the TM is more accurate. In this paper, the errors of the calculated results using time-varying reliability evaluation are within 3%, as shown by Monte Carlo (MC) simulation. In addition, the proposed model (aiming to calculate the equivalent design compressive strength) verifies the concrete failure time calculated by time-varying reliability. According to the results, concrete failure times calculated by these two models are in good agreement. Overall, based on the simple and effective methodology adopted in this paper, it is feasible to develop time-varying reliability based on other factors that might also lead to concrete failure, such as carbonation-induced corrosion, cracking, or deflection of the concrete.

scholarly journals Vertical Velocity and Buoyancy Characteristics of Coherent Echo Plumes in the Convective Boundary Layer, Detected by a Profiling Airborne Radar

2006 ◽  
Vol 45 (6) ◽  
pp. 838-855 ◽  
Author(s):  
Qun Miao ◽  
Bart Geerts ◽  
Margaret LeMone
Keyword(s):  
Boundary Layer ◽  
Great Plains ◽  
Convective Boundary Layer ◽  
Ambient Air ◽  
Doppler Velocity ◽  
Convective Boundary ◽  
Millimeter Wave Radar ◽  
Radar Echoes ◽  
Temperature Excess ◽  
Wave Radar

Abstract Aircraft and airborne millimeter-wave radar observations are used to interpret the dynamics of radar echoes and radar-inferred updrafts within the well-developed, weakly sheared continental convective boundary layer. Vertically pointing radar reflectivity and Doppler velocity data collected above and below the aircraft, flying along fixed tracks in the central Great Plains during the International H2O Project (IHOP_2002), are used to define echo plumes and updraft plumes, respectively. Updraft plumes are generally narrower than echo plumes, but both types of plumes have the dynamical properties of buoyant eddies, especially at low levels. This buoyancy is driven both by temperature excess and water vapor excess over the ambient air. Plumes that are better defined in terms of reflectivity or updraft strength tend to be more buoyant.

scholarly journals Linear Regression Technique for Improvement of Feet Position Estimation during Standing Balance Using a Cane with Millimeter Wave Radar

2020 ◽  
Vol 28 (S2) ◽  
Author(s):  
Ibai Gorordo Fernandez ◽  
Kodai Kitagawa ◽  
Kawthar Abdul Rahman ◽  
Azura Che Soh ◽  
Alpha Agape Gopalai ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Estimation Error ◽  
The Elderly ◽  
Position Estimation ◽  
Millimeter Wave Radar ◽  
Proposed Model ◽  
Wave Radar ◽  
Linear Regression Technique ◽  
Base Of Support ◽  
Foot Position

It is estimated that one in three seniors fall at least once a year. Falls are a global problem for the elderly that affects their quality of life and poses a great risk. In our research, we are trying to develop a system that could prevent falls by estimating the fall risk in real time. The system would measure the balance of the user by measuring the position of the Center of Gravity inside the Base of Support. In our previous research, we presented a system with a millimeter wave radar attached to a cane to measure the area of the Base of Support. However, the obtained results for the foot position estimation error were significantly worse than similar studies. One of the reasons was that the sensor was not really estimating the position of the feet but the position of the lower legs. Therefore, in this research we present a correction model to improve the feet position estimation. The proposed model was able to reduce the foot position estimation RMSE from 54 mm down to 34 mm, which is closer to the results of other similar studies measuring the position of the feet.

The Large Millimeter Wave Radar Phased Antenna Array

2000 ◽  
Vol 54 (10) ◽  
pp. 101-111
Author(s):  
Aleksey Alekseevich Tolkachev ◽  
Vasiliy Andreevich Makota ◽  
Mariya Petrovna Pavlova ◽  
Anatoliy Moiseevich Nikolaev ◽  
Vladimir Victorovich Denisenko ◽  
...  
Keyword(s):  
Antenna Array ◽  
Millimeter Wave ◽  
Millimeter Wave Radar ◽  
Wave Radar ◽  
Phased Antenna Array

Antenna for Navigational Shipborne Millimeter-Wave Radar

2006 ◽  
Vol 65 (16) ◽  
pp. 1453-1462
Author(s):  
A. N. Nechiporenko ◽  
L. D. Fesenko
Keyword(s):  
Millimeter Wave ◽  
Millimeter Wave Radar ◽  
Wave Radar
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