A Cow's ruminant behavior can provide information about a cow's health. Monitoring a cow's ruminant behavior could therefore be of use when assessing its health. However, it is difficult to simultaneously monitor multiple target cows' ruminations simultaneously without any contact-type equipment. A method for monitoring multiple target cows' ruminant behavior based on an optical flow method and an inter-frame difference method is proposed here in. The optical flow method is used to obtain the optical flow fields of the ruminant cows' mouth areas in the first 60 frames of a video. The optical flow values with large changes are selected from the first 60 frames of the test video and these values are superimposed to obtain the candidate ruminant cows' mouth areas. The candidate ruminant cows' mouth areas are magnified 1.5 times, and the inter-frame difference method is used to track the real cows' mouth areas in the new magnified areas. According to the ''center error'' and ''overlap rate'' indexes, the tracking result for the 15 videos is evaluated. The results show that the average successful tracking rate reaches 89.12%, demonstrating that the algorithm could be applied for the automatic monitoring of multiple target ruminant cows' mouth areas.INDEX TERMS Inter-frame difference method, optical flow method, ruminant behavior. III. RESULTS A. RESULTS OF COW RUMINATION MONITORING
Terahertz (THZ) band stop filter can be used to filter interference signals in a filter pass band. The quality factor (Q) is the most important index to evaluate the transmission performance of filter. Usually, the high Q, the narrow bandwidth and the large slope of the stop band will promise the good filtering accuracy and transmission response. However, the Q value taken from metamaterial structures designed on the plane is always only in the single digit, resulting in less than satisfactory in filtering performance. Herein, a high Q terahertz band stop filter based on metamaterials was proposed. To fabricate this three-dimensional (3D) metamaterial structure, a microtopographic substrate guided method with feasible and high accuracy capacities was proposed. As a result, the device is measured to be in the filtering state in 1.038-1.102 THz while it is stopped in 1.062-1.066 THz. The similarity between the experimental and simulated transmission is up to 86.32%, indicating the fabricating method possesses a high accuracy. Accordingly, the Q value was calculated to be as high as 532. The band stop filter with this record Q value can be widely used in THZ detection, imaging and sensing in future. Meanwhile, the proposed fabrication method is effectively applied in 3D metamaterial and THZ device as well.
electromagnetic waves change from transmission to reflection, and the change process is reversible. Due to the phase change properties, VO 2 is often embedded in a metamaterial structure to fabricate a THz modulator, and other materials which have the same phase change properties (e.g., bismuth, graphene, and gyroelectric) can be used to fabricate the THz modulator too. [12][13][14][15][16] As ref. [17] shown, an active and smart electro-optic THz modulator based on a strongly correlated electron oxide VO 2 was proposed. The metamaterial structure of the THz modulator is composed od three layers, the materials of each layer are silver (Ag), silicon dioxide (SiO 2 ), and VO 2 , respectively. With milliampere current excitation on the VO 2 film, the transmission, reflection, absorption, and phase of THz waves can be modulated efficiently. In particular, the antireflection condition can be actively achieved and the modulation depth reaches 0.99. As ref. [18] shown, an optically and thermally controlled THz modulator based on silicon (Si) and VO 2 hybrid meta surface is proposed to improve the ability of flexibly manipulating THz waves, and the modulator can bring a deep MD of 0.97 at 0.9 THz. There are other phase-change materials used in the modulator to modulate THz waves except VO 2 . As ref. [19] shown, a faraday modulator based on graphene, gyroelectric (InSb), SiO 2 , and Si materials was proposed. Finally, the THz signal transmission can be modified from 0 to 0.8 by varying applied static magnetic fields. As ref. [20] shown, a high-performance, broadband THz modulator based on the photo-induced transparency of carbon nanotube films was proposed. The modulation depth of this modulator can reach +0.8 with modulation speeds of 340 GHz under femtosecond pulsed illumination. In summary, the metamaterial structures are used to realize the transmission and reflection, and phasechange materials (PCM) are inserted in the metamaterial structures to modulate the transmission and reflection. Generally, all the structures are prepared by photolithography, etching, or liftoff technologies. As the feature size of metamaterials reduces to micro and nano scale, the cost rises at an exponential rate, and the accuracy of insertion of PCM is difficult to control.A deep MD of the modulator will bring a large-scale modulation, which means lots of signals can be controlled, thereby the diversity of modulation can be improved. Meanwhile, high rising and falling slopes of the filtering band, leading to a short time from filtering pass to blocking thereby an improvement of transmission response. Herein, a THz multiband amplitude Terahertz (THz) modulator can be used to modulate the amplitude and frequency of THz wave. A THz multiband amplitude modulator based on temperature control is proposed in this study. The metamaterial structure of proposed modulator is a double-layer cross structure which attached on a silicon substrate, and the cross-distribution of different materials in top and middle layer is Cu @ SiO 2 and SiO 2 @ VO 2 , r...
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