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Numerical exploration on jet oscillation mechanism of counterflowing jet ahead of a hypersonic lifting-body vehicle

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Science China(Technological Sciences) 2018年第7期61卷 1056-1071页

作者： DENG Fan XIE Feng HUANG Wei dong hao ZHANG dong Science and Technology on Space Physics Laboratory China Academy of Launch Vehicle TechnologyBeijing 100076China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000China Science and Technology on Scramjet Laboratory National University of Defense TechnologyChangsha 410073China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical UniversityXi'an 710072China

Numerical investigation of a supersonic jet from the nose of a lifting-body vehicle opposing a hypersonic flow with the freestream Mach number being 8.0 at 40 km altitude was carried out by solving the three-dimensional, time-accurate Navier-Stokes equations with a hybrid meshes approach. Based on the analysis of the flow field structures and aerodynamic characteristics, the behaviours relevant to the LPM jet were discussed in detail, including the drag reduction effect, the periodic oscillation and the feedback loop. The obtained results show that the flow oscillation characteristic of the LPM jet is low-frequency and high-amplitude while that of the SPM jet is high-frequency and low-amplitude. Compared with the clearly dominant frequencies of the LPM jet, the SPM jet exhibits a broad-band structure. The LPM jet can sustain drag reduction effect until the angle of attack is 8°, and the lift-to-drag ratio of the vehicle is effectively improved by 6.95% at angle of attack of 6°. The self-sustained oscillation process was studied by a typical oscillating cycle of the drag force coefficient and the variation of the instantaneous pressure distribution,which reveals an off-axial flapping motion of the conical shear layer. The variation of the subsonic recirculation zone ahead of the vehicle nose strengthens the understanding of the jet behavior including the source of instability in the long penetration mode and the mechanism of the feedback loop. The aim of this paper is to advance the technology readiness level for the counterflowing jet applied as an active control technology in hypersonic flows by gaining a better insight of the flow physics.

关键词： hypersonic lifting-body vehicle counterflowing jet LPM periodic oscillation

Energy Scattering of a Generalized Davey–Stewartson System in Three Dimension

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Acta Mathematica Sinica,English Series 2017年第9期33卷 1206-1224页

作者： Jing LU Xing dong tang School of Mathematical Sciences Beijing Normal UniversityBeijing 100875P.R.China Institute of Applied Physics and Computational Mathematics Beijing 100088P.R.China

In this paper, we study the global scattering result of the solution for the generalized Davey-Stewartson system The main difficulties are the failure of the interaction Morawetz estimate and the asymmetrical structure of nonlinearity （in particular, the nonlinearity is non-local）. To compensate, we utilize the strategy derived from concentration-compactness idea, which was first introduced by Kenig and Merle .

关键词： Davey-Stewartson system scatter global well-posedness

Comparison and analysis of dislocation density,morphology and evolution in mi-crostructure of low-carbon steel produced using different technologies

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Journal of University of Science and Technology Beijing 2006年第5期13卷 406-410页

作者： hao Yu Yonglin Kang Hongbo dong Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China Jinan Iron ＆ Steel Group Co. Jinan 250101 China

Three kinds of specimens were produced from hot strips of similar composition and same thickness （nominal gauge 4.0 mm） but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9 mm hot strip using CSP （compact strip production） technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.

关键词： compact strip production (CSP) microstructure dislocation positron annihilation technique finite element simulation

A Degree Condition for Graphs Having All(a,b)-parity Factors

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 656-664页

作者： hao-dong LIU Hong-liang LU School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China

Let a and b be positive integers such that a≤b and a≡b(mod 2).We say that G has all(a,b)-parity factors if G has an h-factor for every function h:V(G)→{a,a+2,…,b-2,b} with b|V(G)| even and h(v)≡b(mod 2) for all v∈V(G).In this paper,we prove that every graph G with n≥2(b+1)(a+b) vertices has all(a,b)-parity factors if δ(G)≥(b^(2)-b)/a,and for any two nonadjacent vertices u,v ∈V(G),max{d_(G)(u),d_(G)(v)}≥bn/a+***,we show that this result is best possible in some sense.

关键词： degree condition all(a,b)-factors

Optimal Assimilation of Microwave Upper-Level Sounding Data in CMA-GFS

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Advances in Atmospheric Sciences 2024年第10期41卷 2043-2060页

作者： Changjiao dong hao HU Fuzhong WENG School of Atmospheric Physics Nanjing University of Information Science and TechnologyNanjing 210044China CMA Earth System Modeling and Prediction Centre(CEMC) China Meteorological AdministrationBeijing 100081China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China

Various approaches have been proposed to minimize the upper-level systematic biases in global numerical weather prediction(NWP)models by using satellite upper-air sounding channels as ***,since the China Meteorological Administration Global Forecast System(CMA-GFS)has a model top near 0.1 hPa(60 km),the upper-level temperature bias may exceed 4 K near 1 hPa and further extend to 5 *** this study,channels 12–14 of the Advanced Microwave Sounding Unit A(AMSU-A)onboard five satellites of NOAA and METOP,whose weighting function peaks range from 10 to 2 hPa are all used as anchor observations in *** is shown that the new“Anchor”approach can effectively reduce the biases near the model top and their downward propagation in three-month assimilation *** bias growth rate of simulated upper-level channel observations is reduced to±0.001 K d^(–1),compared to–0.03 K d^(–1)derived from the current dynamic correction *** relatively stable bias significantly improves the upper-level analysis field and leads to better global medium-range forecasts up to 10 days with significant reductions in the temperature and geopotential forecast error above 10 hPa.

关键词： CMA-GFS upper-level model bias anchoring bias correction satellite microwave data assimilation

Vacuum degree effects on betavoltaics irradiated by ^(63)Ni with differently apparent activity densities

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Science China(Technological Sciences) 2017年第2期60卷 282-288页

作者： LIU YunPeng XU ZhiHeng WANG hao tang XiaoBin Department of Nuclear Science and Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China jiangsu Key Laboratory of Material and Technology for Energy Conversion Nanjing 210016 China

For many current betavoltaics, beta sources and PN junction energy conversion units are separated. The air gap between the two parts could stop part of decay beta particles, which results in inefficient performance of the betavoltaic. By employing 63Ni with an apparent emission activity density of 7.26×10~7 and 1.81×10~8 Bq cm^(-2), betavoltaic performance levels were calculated at a vacuum degree range of 1×10~5 to 1×10^(-1) Pa and measured at 1.0×10~5 and 1.0×10~4 Pa, respectively. Results show that betavoltaic performance levels improve significantly as the vacuum degree increases. The maximum output power (P_(max)) exhibits the largest change, followed by short-circuit current (I_(sc)), open-circuit voltage (V_(oc)), and fill factor. The vacuum degree effects on Isc, Voc,and Pmax of the betavoltaic with low apparent activity density 63Ni are more significant than those of the betavoltaic with high apparent activity density ^(63)Ni. Moreover, the improved efficiencies of the measured performances are larger than the calculated efficiencies because of the low ratio of Isc and reverse saturation current (I_0). The values of I0, ideality factor, and shunt resistance were estimated to modify the equivalent circuit model. The calculation results based on this model are closer to the measurement results. The results of this research can provide a theoretical foundation and experimental reference for the study of vacuum degree effects on betavoltaics of the same kind.

关键词： vacuum degree betavoltaic apparent activity density energy conversion unit MCNP5

Investigation and assessment of micropollutants and associated biological effects in wastewater treatment processes

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Journal of Environmental Sciences 2020年第8期32卷 119-127页

作者： Xiaoyan Y.Ma Ke dong Lei tang Yongkun Wang Xiaochang C.Wang Huu hao Ngo Rong Chen Na Wang International Science&Technology Cooperation Center for Urban Alternative Water Resources Development Key Lab of Northwest Water ResourceEnvironment and EcologyMOEEngineering Technology Research Center for Wastewater Treatment and ReuseShaanxi ProvinceShaanxi Key Laboratory of Environmental EngineeringXi’an University of Architecture and TechnologyXi’an 710055China School of Civil and Environmental Engineering Faculty of Engineering and Information TechnologyUniversity of Technology SydneyBroadwayNSW 2007Australia School of Architecture and Civil Engineering Xi’an University of Science and TechnologyXi’an 710054China

Currently,the wastewater treatment plants(WWTPs)attempt to achieve the shifting from general pollution parameters control to reduction of organic micropollutants ***,they have not been able to satisfy the increasing ecological safety *** this study,the removal of micropollutants was investigated,and the ecological safety was assessed for a local *** the total concentration of 31 micropollutants detected was reduced by 83%using the traditional biological treatment processes,the results did not reflect chemicals that had poor removal efficiencies and low *** the five categories of micropollutants,herbicides,insecticides,and bactericides were difficult to remove,pharmaceuticals and UV filters were effectively *** specific photosynthesis inhibition effect and non-specific bioluminescence inhibition effect from wastewater were detected and evaluated using hazardous concentration where 5%of aquatic organisms are *** photosynthesis inhibition effect from wastewater in the WWTP was negligible,even the untreated raw ***,the bioluminescence inhibition effect from wastewater which was defined as the priority biological effect,posed potential ecological *** decrease non-specific biological effects,especially of macromolecular dissolved organic matter,overall pollutant reduction strategy is ***,the ozonation process was used to further decrease the bioluminescence inhibition effects from the secondary effluent;≥0.34 g O 3/g DOC of ozone dose was recommended for micropollutants elimination control and ecological safety.

关键词： Micropollutants Biological effect Wastewater treatment Ecological safety Ozonation

Distinct effect of preparation methods on reaction efficiency of Mn-Ce/Al_(2)O_(3) catalysts in low-temperature NH_(3)-SCR

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Journal of Rare Earths 2024年第10期42卷 1865-1872页

作者： Shijie hao Yandi Cai Wei Wei Yanan Lv Jiawei Ji Wei Tan Jingfang Sun Liwei Jia Changjin tang Lin dong State Key Laboratory of Pollution Control and Resource Reuse School of EnvironmentJiangsu Key Laboratory of Vehicle Emissions ControlCenter of Modern AnalysisKey Laboratory of Mesoscopic Chemistry of MOESchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing210023China Wuxi Weifu Environmental Catalysts Co. LtdWuxi214028China School of Environment Nanjing Normal UniversityNanjing210023China

In this study,a series of Mn-Ce/Al_(2)O_(3) catalysts was prepared by different methods of depositionprecipitation(MnCeAl-DP),impregnation(MnCeAl-IM) and citric acid(MnCeAl-CA),and the distinct effect of preparation methods on NO_(x) removal performance at low temperature was *** show that MnCeAl-DP exhibits not only the best activity but also the highest resistance against SO_(2)/H_(2)*** the assistance of comprehensive characterizations from scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-te mperature programmed deso rption(NH_(3)-TPD),and X-ray photoelectron spectroscopy(XPS),it is revealed that the MnCeAl-DP sample owns admired features of large surface area and pore volume,enriched Mn^(4+) and chemisorbed oxygen species originating from enhanced interaction between MnO_x and CeO_(2),as well as improved adsorption capacity to NH_(3) and *** these factors contribute to activity *** in-situ DRIFTS studies reveal that the improvement of NH_(3)-SCR performance over MnCeAI-DP is related to the formation of abundant nitrate species,which is beneficial to the "NH_(4)NO_(3)" reaction pathway and thus enhances low-temperature activity.

关键词： Mn-Ce/Al_(2)O_(3)catalysts NH_(3)-SCR Low temperature NH_(4)NO_(3) Fast SCR Rare earths

Controller area network node reliability assessment based on observable node information

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Frontiers of Information Technology & Electronic Engineering 2017年第5期18卷 615-626页

作者： Lei-ming ZHANG Long-hao tang Yong LEI State Key Laboratory of Fluid Power Transmission and Mechatronics Zhejiang UniversityHangzhou 310027China

Controller area network(CAN) based fieldbus technologies have been widely used in networked manufacturing systems. As the information channel of the system, the reliability of the network is crucial to the system throughput, product quality, and work crew safety. However, due to the inaccessibility of the nodes' internal states, direct assessment of the reliability of CAN nodes using the nodes' internal error counters is infeasible. In this paper, a novel CAN node reliability assessment method, which uses node's time to bus-off as the reliability measure, is proposed. The method estimates the transmit error counter(TEC) of any node in the network based on the network error log and the information provided by the observable nodes whose error counters are ***, a node TEC estimation model is established based on segmented Markov chains. It considers the sparseness of the distribution of the CAN network errors. Second, by learning the differences between the model estimates and the actual values from the observable node, a Bayesian network is developed for the estimation updating mechanism of the observable nodes. Then, this estimation updating mechanism is transferred to general CAN nodes with no TEC value accessibility to update the TEC estimation. Finally, a node reliability assessment method is developed to predict the time to reach bus-off state of the nodes. Case studies are carried out to demonstrate the effectiveness of the proposed methodology. Experimental results show that the estimates using the proposed model agree well with actual observations.

关键词： Controller area network(CAN) Transmit error counter(TEC) TEC value estimation Bayesian network Bus-off hitting time