Acta Polytechnica最新文献_第8页

Applicability of Secondary Denitrification Measures on a Fluidized Bed Boiler 流化床锅炉二次反硝化措施的适用性

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Acta Polytechnica Pub Date : 2022-06-30 DOI: 10.14311/ap.2022.62.0341

Jitka Jeníková, Kristýna Michaliková, F. Hrdlička, J. Hrdlička, L. Pilař, Matěj Vodička, Pavel Skopec

引用次数: 1

Theoretical and experimental study of water vapour condensation with high content of non-condensable gas in a vertical tube 高不凝性气体水蒸气在垂直管内冷凝的理论与实验研究

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Acta Polytechnica Pub Date : 2022-06-30 DOI: 10.14311/ap.2022.62.0352

J. Krempaský, J. Havlík, T. Dlouhý

{"title":"Theoretical and experimental study of water vapour condensation with high content of non-condensable gas in a vertical tube","authors":"J. Krempaský, J. Havlík, T. Dlouhý","doi":"10.14311/ap.2022.62.0352","DOIUrl":"https://doi.org/10.14311/ap.2022.62.0352","url":null,"abstract":"This article deals with the possibility of separating water vapour from flue gases after oxyfuel combustion using condensation processes. Those processes can generally be described as condensation of water vapour in the presence of non-condensable gases. Hence, the effect of noncondensable gas (NCG) on the condensation process has been theoretically and experimentally analysed in this study. The theoretical model was developed on the basis of the heat and mass transfer analogy with respect to the effect of the NCG, the flow mode of the condensate film, the shear stress of the flowing mixture, subcooling and superheating. Subsequently, an experimental analysis was carried out on a 1.5m long vertical pipe with an inner diameter of 23.7mm. The mixture of vapour and air flowed inside the inner tube with an air mass fraction ranging from 23% to 62%. The overall heat transfer coefficients (HTC) from the theoretical model and experimental measurement are significantly lower than the HTC obtained according to the Nusselt theory for the condensation of pure water vapour. The overall HTC decreases along the tube length as the gas concentration increases, which corresponds to a decrease in the local condensation rate. The highest values of the HTC are observed in the condenser inlet, although a strong decrease in HTC is also observed here. Meanwhile, there is a possibility for an HTC enhancement through turbulence increase of the condensing mixture in the condenser outlet. Results also showed that the heat resistance of the mixture is several times higher than the heat resistance of the condensate film. The developed theoretical model based on heat and mass transfer analogy is in good agreement with experimental results with the standard deviation within +25% and −5%. The model is more accurate for lower NCG concentrations.","PeriodicalId":45804,"journal":{"name":"Acta Polytechnica","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49642895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Measurement of solid particle emissions from oxy-fuel combustion of biomass in fluidized bed 流化床中生物质全氧燃烧固体颗粒排放的测量

IF 0.8

Acta Polytechnica Pub Date : 2022-06-30 DOI: 10.14311/ap.2022.62.0337

Ondřej Červený, P. Vybíral, J. Hemerka, Luďek Mareš

引用次数: 0

Exact solutions for time-dependent complex symmetric potential well 时变复对称势阱的精确解

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Acta Polytechnica Pub Date : 2022-06-09 DOI: 10.14311/AP.2023.63.0132

B. Khantoul, Abdelhafid Bounames

引用次数: 0

Assessment of Granite – Kaolin Composite Bricks as Storage Barrier Facility for Liquid Radioactive Waste 花岗岩-高岭土复合砖作为放射性液体废物贮存屏障设施的评价

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Acta Polytechnica Pub Date : 2022-05-09 DOI: 10.1007/s41050-022-00036-2

E. Echeweozo, E. Efurumibe, A. D. Asiegbu, L. Nnanna, H. K. Idu

引用次数: 2

A mindlin shell finite element for stone masonry bridges with backfill 填土砌石桥梁的壳壳有限元

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Acta Polytechnica Pub Date : 2022-05-05 DOI: 10.14311/ap.2022.62.0293

P. Řeřicha

引用次数: 0

Results of research on backlash compensation in a power electric drive by low-power electronic device 利用低功率电子器件对电力传动装置齿隙补偿的研究结果

IF 0.8

Acta Polytechnica Pub Date : 2022-05-05 DOI: 10.14311/ap.2022.62.0303

S. Samsonovich, B. K. Fedotov, N. Rozhnin, R. Goryunov

{"title":"Results of research on backlash compensation in a power electric drive by low-power electronic device","authors":"S. Samsonovich, B. K. Fedotov, N. Rozhnin, R. Goryunov","doi":"10.14311/ap.2022.62.0303","DOIUrl":"https://doi.org/10.14311/ap.2022.62.0303","url":null,"abstract":"This article considers the feasibility of restoring and maintaining the kinematic accuracy of the support-rotary device drives by introducing a backlash compensation device into the control system. The power electromechanical drives of support-rotary device considered in this article contain two motors, the summation of the torques of which is carried out on a common output shaft. It is shown that the restoration of the required kinematic accuracy of the drives can be achieved by introducing one of two variants of an electronic device for backlash compensation into the control system. In the first variant, equal and opposite displacement signals are introduced into the control signals of the motors. The second variant introduces an electronic cross-connections backlash compensation scheme was into the control system. The study of the operation of the support-rotary device drive system with two backlash compensation devices carried out by a simulation method showed that the use of a cross-connection scheme is the most preferable and effective.As a result of the research, it was shown that the introduction of an electronic backlash compensation device into the control system makes it possible to ensure the operability of the power electromechanical drives of a support-rotary device with initial kinematic accuracy.","PeriodicalId":45804,"journal":{"name":"Acta Polytechnica","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48378847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Improvement of spectrum sensing performance in cognitive radio using modified hybrid sensing method 改进混合感知方法提高认知无线电频谱感知性能

IF 0.8

Acta Polytechnica Pub Date : 2022-05-05 DOI: 10.14311/ap.2022.62.0228

H. Abed, Hikmat N. Abdullah

{"title":"Improvement of spectrum sensing performance in cognitive radio using modified hybrid sensing method","authors":"H. Abed, Hikmat N. Abdullah","doi":"10.14311/ap.2022.62.0228","DOIUrl":"https://doi.org/10.14311/ap.2022.62.0228","url":null,"abstract":"Cognitive radio (CR) is a wireless technology for increasing the bandwidth usage. Spectrum sensing (SS) is the first step in CR. There are three basic techniques in SS, energy detection (ED), matched filter (MF), and cyclostationary detection (CFD). These techniques have many challenges in performance detection (Pd) and computational complexity (CC). In this paper, we propose a hybrid sensing method that consists of MF and CFD to exploit their merits and overcome their challenges. The proposed method aims to improve Pd and reduce CC. When MF hasn’t had enough information about PU, it switches to CFD with a reduction of CC in both MF and CFD. The proposed method is simulated under fading with cooperative and non-cooperative scenarios, measured using Pd and CC ratio Cratio, and evaluated by comparing it with traditional and hybrid methods in the literature. The simulation results show that the proposed method outperforms other methods in Pd and Cratio. For example, at Eb/No equal to 0 dB under the Rayleigh fading channel, the Pd in the proposed method increased by 38 %, 28 %, 28 %, and 18 % as compared with the modified hybrid method, traditional hybrid method, traditional CFD method, and traditional MF method in the literature, respectively.","PeriodicalId":45804,"journal":{"name":"Acta Polytechnica","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41725537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Analysis of factors affecting the efficiency of Jatropha curcas oil as an asphaltene stabiliser 麻疯树油作为沥青质稳定剂的影响因素分析

IF 0.8

Acta Polytechnica Pub Date : 2022-05-05 DOI: 10.14311/ap.2022.62.0283

Tomás Darío Marín Velásquez, Dany Day Josefina Arriojas Tocuyo

引用次数: 0

Analysis of output voltage ripple for dual randomized PWM buck converter operating in continuous and discontinuous conduction modes 连续和断续导通模式下双随机化PWM降压变换器输出电压纹波分析

IF 0.8

Acta Polytechnica Pub Date : 2022-05-05 DOI: 10.14311/ap.2022.62.0262

Aimad Boudouda, N. Boudjerda, F. Nafa

{"title":"Analysis of output voltage ripple for dual randomized PWM buck converter operating in continuous and discontinuous conduction modes","authors":"Aimad Boudouda, N. Boudjerda, F. Nafa","doi":"10.14311/ap.2022.62.0262","DOIUrl":"https://doi.org/10.14311/ap.2022.62.0262","url":null,"abstract":"Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations.","PeriodicalId":45804,"journal":{"name":"Acta Polytechnica","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41481589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0