Current Issue : July - September Volume : 2018 Issue Number : 3 Articles : 5 Articles
The number of feature points on the surface of a non-cooperative target satellite used for\nmonocular vision-based relative navigation affects the onboard computational load. A feature point\nselection method called the quasi-optimal method is proposed to select a subset of feature points\nwith a good geometric distribution. This method, with the assumption that all of the feature points\nare in a plane and have the same variance, is based on the fact that the scattered feature points can\nprovide higher accuracy than that of them grouped together. The cost is defined as a function of\nthe angle between two unit vectors from the projection center to feature points. The redundancy\nof a feature point is calculated by summing all costs associated with it. Firstly, the feature point\nwith the most redundant information is removed. Then, redundancies are calculated again with\nthe second feature point removed. The procedures above are repeated until the desired number\nof feature points is reached. Dilution of precision (DOP) represents the mapping relation between\nthe observation variance and the estimated variance. In this paper, the DOP concept is used in a\nvision-based navigation system to verify the performance of the quasi-optimal method. Simulation\nresults demonstrate the feasibility of calculating the relative position and attitude by using a subset\nof feature points with a good geometric distribution. It also shows that the feature points selected by\nthe quasi-optimal method can provide a high accuracy with low computation time....
The application of the photonic crystal (PC) waveguide (WG) as the light delivery system in the heat-assisted magnetic recording\n(HAMR) system is demonstrated. The structure consists of a 90�° bending PC waveguide and a ridge dielectric waveguide taper\ncoupler. Three-dimensional (3D) models of structures are built and simulated in order to determine light coupling and\ntransmission efficiencies. Geometric parameters including the taper length (LTP), coupler inlet width (WFW), and PC waveguide\nwidth (WWG) are investigated. The initial simulation shows that the transmission efficiency of over 90% can be achieved with the\ncoupler integrated with the straight PC waveguide. However, the overall transmission efficiency is substantially reduced to 53.8%\nwhen the coupler is attached to the 90�° bending PC waveguide. Our analysis shows that the wave mode matching and light decay\nrate in the waveguide cavity are significant contributing factors. The transmission efficiency increases to around 60.8% after some\nmodification of the bending region....
Amicrowave brain imaging systemmodel is envisaged to detect and visualize tumor inside the human brain.Acompact and efficient\nmicrostrip patch antenna is used in the imaging technique to transmit equivalent signal and receive backscattering signal from the\nstratified human head model. Electromagnetic band gap (EBG) structure is incorporated on the antenna ground plane to enhance\nthe performance. Rectangular and circular EBG structures are proposed to investigate the antenna performance. Incorporation of\ncircular EBG on the antenna ground plane provides an improvement of 22.77% in return loss, 5.84% in impedance bandwidth,\nand 16.53% in antenna gain with respect to the patch antenna with rectangular EBG. The simulation results obtained from CST are\ncompared to those obtained from HFSS to validate the design. Specific absorption rate (SAR) of the modeled head tissue for the\nproposed antenna is determined. Different SAR values are compared with the established standard SAR limit to provide a safety\nregulation of the imaging system.Amonostatic radar-based confocal microwave imaging algorithm is applied to generate the image\nof tumor inside a six-layer human head phantom model....
Extending the data transfer rates through dense interconnections at inter- and intraboard levels is a well-established technique\nespecially in consumer electronics at the expense of more cross talk, electromagnetic interference (EMI), and power dissipation.\nOptical transmission using optical fibre is practically immune to the aforementioned factors. Among the\nmanufacturing methods, UV laser ablation using an excimer laser has been repeatedly demonstrated as a suitable technique to\nfabricate multimode polymer waveguides. However, the main challenge is to precisely control and predict the topology of the\nwaveguides without the need for extensive characterisation which is both time consuming and costly. In this paper, the authors\npresent experimental results of investigation to relate the fluence, scanning speed, number of shots, and passes at varying pulse\nrepetition rate with the depth of ablation of an acrylate-based photopolymer. The depth of ablation essentially affects total\ninternal reflection and insertion loss, and these must be kept at minimum for a successful optical interconnection on printed\ncircuit boards. The results are then used to predict depth of ablation for this material by means of adaptive neurofuzzy inference\nsystem (ANFIS) modelling. The predicted results, with a correlation of 0.9993, show good agreement with the experimental\nvalues. This finding will be useful in better predictions along with resource optimisation and ultimately helps in reducing cost of\npolymer waveguide fabrication....
Different lengths of WR3 (220ââ?¬â??330 GHz) and WR10 (75ââ?¬â??110 GHz)\nwaveguides are fabricated through direct metal laser sintering (DMLS). The losses\nin these waveguides are measured and modelled using the Huray surface roughness\nmodel. The losses in WR3 are around 0.3 dB/mm and in WR10 0.05 dB/mm. The\nHuray equation model is accounting relatively good for the attenuation in the WR10\nwaveguide but deviates more in the WR3 waveguide. The model is compared to finite\nelement simulations of the losses assuming an approximate surface structure similar\nto the resulting one from the DMLS process....
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