The accuracy of channel estimation is very important for Orthogonal Frequency Division Multiplexing (OFDM) systems. In a high speed wideband wireless communication, the channel can be modeled as a sparse one. Therefore, the Compressed Sensing (CS) technique can be used for the estimation of the channel. In this paper, the problem of deterministic pilot allocation in OFDM systems is considered and a new criterion which is based on minimizing the summation of the correlations between the columns of the Discrete Fourier Transform (DFT) sub-matrix is proposed. It will be shown that the proposed criterion is a simple version of the well-known but complex criterion, Restricted Isometry Property (RIP). In addition, the pilot pattern design, using our proposed scheme, indicates better recovery performance than other proposed coherence based criteria in terms of the reconstruction mean square error (MSE) and successful channel recovery percentage. Simulation results confirm our analysis. 相似文献
How to accurately recognize the mental state of pilots is a focus in civil aviation safety. The mental state of pilots is closely related to their cognitive ability in piloting. Whether the cognitive ability meets the standard is related to flight safety. However, the pilot's working state is unique, which increases the difficulty of analyzing the pilot's mental state. In this work, we proposed a Convolutional Neural Network (CNN) that merges attention to classify the mental state of pilots through electroencephalography (EEG). Considering the individual differences in EEG, semi-supervised learning based on improved K-Means is used in the model training to improve the generalization ability of the model. We collected the EEG data of 12 pilot trainees during the simulated flight and compared the method in this paper with other methods on this data. The method in this paper achieved an accuracy of 86.29%, which is better than 4D-aNN and HCNN etc. Negative emotion will increase the probability of fatigue appearing, and emotion recognition is also meaningful during the flight. Then we conducted experiments on the public dataset SEED, and our method achieved an accuracy of 93.68%. In addition, we combine multiple parameters to evaluate the results of the classification network on a more detailed level and propose a corresponding scoring mechanism to display the mental state of the pilots directly. 相似文献
Fast pyrolysis oil can be used as a feedstock for syngas production. This approach can have certain advantages over direct biomass gasification. Pilot scale tests were performed to investigate the route from biomass via fast pyrolysis and entrained flow gasification to syngas. Wheat straw and clean pine wood were used as feedstocks; both were converted into homogeneous pyrolysis oils with very similar properties using in-situ water removal. These pyrolysis oils were subsequently gasified in a pressurized, oxygen blown entrained flow gasifier using a thermal load of 0.4 MW. At a pressure of 0.4 MPa and a lambda value of 0.4, temperatures around 1250 °C were obtained. Syngas volume fractions of 46% CO, 30% H2 and 23% CO2 were obtained for both pyrolysis oils. 2% of CH4 remained in the product gas, along with 0.1% of both C2H2 and C2H4. Minor quantities of H2S (3 vs. 23) cm3 m−3, COS (22 vs. 94) cm3 m−3 and benzene (310 vs. 532) cm3 m−3 were measured for wood- and straw derived pyrolysis oils respectively. A continuous 2-day gasification run with wood derived pyrolysis oil demonstrated full steady state operation. The experimental results show that pyrolysis oils from different biomass feedstocks can be processed in the same gasifier, and issues with ash composition and melting behaviour of the feedstocks are avoided by applying fast pyrolysis pre-treatment. 相似文献
In recent years, the development of alternative fuels from renewable resources, like biomass, has received considerable attention. Biodiesel is defined as fatty acid methyl or ethyl esters from vegetable oils, when it is used as fuel in diesel engines and heating systems.
In this context, the cultivation of Brassica carinata as oilseed crop for biodiesel production in the south of Europe (Spain and Italy) and north of Africa has gained special interest, since it allows the use of set-aside lands, giving higher yields per hectare than the traditional Spanish crops.
Methyl or ethyl esters are the product of transesterification of vegetable oils with alcohol (methanol/ethanol) using an alkaline catalyst. In addition, the process yields glycerol, which has large applications in the pharmaceutical, food and plastics industries.
In the present work, the process of biodiesel production for pilot plant using B. Carinata oil as raw materials with methanol and using potassium hydroxide as catalyst has been studied.
The biodiesel quality meets European specifications defined by pr EN 14214:2002 (E). The obtained results have been used for industrial scale up of the process. 相似文献
Studies by the Rand Corporation in the 1980s identified substantial differences in the scale-up and start-up performance of plants processing particles versus those processing liquids or gases. These differences were inevitably unfavorable. Particulate process plants take longer to start up and are less likely to achieve desired production rates. Facility operators often underestimate the challenges involved. These problems generally relate to an inadequate understanding of the behavior of particle systems. Many of these behaviors are sensitive to process scale or process history in ways that would not be expected by engineers familiar only with liquid or gas systems. Empiricism must often substitute for first principles. Modeling provides some answers, but often not enough to eliminate the need to operate pilot plants. This paper reviews some of the unit operations involved in particle processing and highlights scale-up issues involved. The use of information from suppliers and other third parties is discussed, as well as scale-up strategies in competitive or regulated industries. 相似文献