Automated Detection and Characterization of Mesocyclones in X-band Radar Observations

Abstract On 20 May 2013, the cities of Newcastle, Oklahoma City, and Moore, Oklahoma, were impacted by a long-track violent tornado that was rated as an EF5 on the enhanced Fujita scale by the National Weather Service. Despite a relatively sustained long track, damage surveys revealed a number of small-scale damage indicators that hinted at storm-scale processes that occurred over short time periods. The University of Oklahoma (OU) Advanced Radar Research Center’s PX-1000 transportable, polarimetric, X-band weather radar was operating in a single-elevation PPI scanning strategy at the OU Westheimer airport throughout the duration of the tornado, collecting high spatial and temporal resolution polarimetric data every 20 s at ranges as close as 10 km and heights below 500 m AGL. This dataset contains the only known polarimetric radar observations of the Moore tornado at such high temporal resolution, providing the opportunity to analyze and study finescale phenomena occurring on rapid time scales. Analysis is presented of a series of debris ejections and rear-flank gust front surges that both preceded and followed a loop of the tornado as it weakened over the Moore Medical Center before rapidly accelerating and restrengthening to the east. The gust front structure, debris characteristics, and differential reflectivity arc breakdown are explored as evidence for a “failed occlusion” hypothesis. Observations are supported by rigorous hand analysis of critical storm attributes, including tornado track relative to the damage survey, sudden track shifts, and a directional debris ejection analysis. A conceptual description and illustration of the suspected failed occlusion process is provided, and its implications are discussed.

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Perfect metamaterial absorbers with polarization angle independency in X-band waveguide

Modern Physics Letters B ◽

10.1142/s0217984916501864 ◽

2016 ◽

Vol 30 (11) ◽

pp. 1650186 ◽

Cited By ~ 1

Author(s):

Cumali Sabah

Keyword(s):

Wireless Communication ◽

Frequency Region ◽

Polarization Angle ◽

Perfect Absorption ◽

Band Frequency ◽

X Band ◽

Resonance Frequencies ◽

Metamaterial Absorbers ◽

Space Boundary

The design and characterization of perfect metamaterial absorbers (MAs) based on simple configurations including square- and triangle-shapes, which operate in X-band frequency region are numerically and experimentally investigated. The proposed MAs provide perfect absorption with the polarization angle independency. In X-band waveguide, the absorption rates are 99.69% and 99.97% at the resonance frequencies of 10.57 GHz and 10.93 GHz for the square- and triangle-shaped MAs, respectively. In addition, the same configurations are numerically tested under free space boundary conditions to compare and discuss the obtained results. The suggested MAs enable myriad potential application areas for security and stealth technologies in X-band including wireless communication.

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Acoustic Features Characterization of Autism Speech for Automated Detection and Classification

2020 National Conference on Communications (NCC) ◽

10.1109/ncc48643.2020.9056025 ◽

2020 ◽

Author(s):

Abhijit Mohanta ◽

Prerana Mukherjee ◽

Vinay Kumar Mirtal

Keyword(s):

Automated Detection ◽

Acoustic Features

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Genesis, Maintenance and Demise of a Simulated Tornado and the Evolution of Its Preceding Descending Reflectivity Core (DRC)

Atmosphere ◽

10.3390/atmos10050236 ◽

2019 ◽

Vol 10 (5) ◽

pp. 236 ◽

Cited By ~ 1

Author(s):

Dan Yao ◽

Zhiyong Meng ◽

Ming Xue

Keyword(s):

Cloud Model ◽

Three Dimensional ◽

Radiosonde Data ◽

Phase Array ◽

Bottom Up ◽

Near Surface ◽

Radar Observations ◽

X Band ◽

Homogeneous Background ◽

Tornado Event

This study demonstrates the capability of a cloud model in simulating a real-world tornado using observed radiosonde data that define a homogeneous background. A reasonable simulation of a tornado event in Beijing, China, on 21 July 2012 is obtained. The simulation reveals the evolution of a descending reflectivity core (DRC) that has commonalities with radar observations, which retracts upward right before tornadogenesis. Tornadogenesis can be divided into three steps: the downward development of mesocyclone vortex, the upward development of tornado vortex, and the eventual downward development of condensation funnel cloud. This bottom-up development provides a numerical evidence for the growing support for a bottom-up, rapid tornadogenesis process as revealed by the state-of-the-art mobile X-band phase-array radar observations. The evolution of the simulated tornado features two replacement processes of three near-surface vortices coupled with the same midlevel updraft. The first replacement occurs during the intensification of the tornado before its maturity. The second replacement occurs during the tornado’s demise, when the connection between the midlevel mesocyclone and the near-surface vortex is cut off by a strong downdraft. This work shows the potential of idealized tornado simulations and three-dimensional illustrations in investigating the spiral nature and evolution of tornadoes.

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Characterization of Barium M-Hexaferrite with Doping Zn and Mn for Microwaves Absorbent

Materials Science Forum ◽

10.4028/www.scientific.net/msf.966.282 ◽

2019 ◽

Vol 966 ◽

pp. 282-289 ◽

Cited By ~ 2

Author(s):

Susilawati ◽

Aris Doyan ◽

Muhammad Taufik ◽

Wahyudi ◽

Eryn Ryantin Gunawan ◽

...

Keyword(s):

Calcination Temperature ◽

Ion Concentration ◽

Magnetic Minerals ◽

Natural Sand ◽

Band Frequency ◽

Absorbent Material ◽

Electrical And Magnetic Properties ◽

Magnetic Remanence ◽

X Band

The research was conducted to examine the content of Fe and other metal in natural sand of beach Ampenan, Mataram, Indonesia which is expected to be used as microwave absorbent material. Characterizations of the electrical and magnetic properties Barium M-Hexaferrite (BaM) with Zn-Mn doping (BaFe12-2xZnxMnxO19) are biosynthesized. Research carried out among others tested the metal content of Fe and other metals, synthesize BaFe12-2xZnxMnxO19. The samples were characterized using Vibrating Sample Magnetometer (VSM) and Network Vector Analyzer (VNA) for the test properties of electricity and magnetism, as well as the absorption of microwaves. The results from the AAS (Atomic Absorption Spectroscopy) testing showed that each gram of magnetic minerals in the natural sand containing 16.27 mg Fe, which states that the majority of metal components content is 69.80% Fe metal with the Magnetite and Hematite phases. The result from VSM showed that the coercivity value decreased when doping ion concentration and calcination temperature increased (0.16 Tesla at 600°C for x = 0.0 and 0.09 Tesla at 800°C for x = 1.0). Value of magnetic saturation and the magnetic remanence decreased with increasing ion concentration (Ms= 4.94 emu/g at x = 0.0 decreased to 0.31 emu/g at x = 1.0) and Mr = 3.43 emu/g for x = 0.0 decreased to 0.06 emu/g at x=1.0. These indicates that the sample has been soft magnetic. The result from VNA showed that the electrical conductivity values measured in the range 8.0-15.0 GHz indicate that the sample is a semiconductor (1.62×10-2 S/cm). The result from VNA showed that the microwave absorption properties increased at higher concentration of doping ions and the calcination temperature would increase the value of Reflection Loss (RL). Maximum RL value of the sample is -14.37 dB at 15 GHz and the absorption coefficient of 96.34%. These results indicate that the BaFe10.8Zn0.6Mn0.6O19 sample can be applied as a microwave absorbent material on X-band to Ku- band frequency. Keyword: Characterization, Barium M-Hexaferrite, doping, microwave, absorbent.

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