Impact of Sky Conditions on Net Ecosystem Productivity over a “Floating Blanket” Wetland in Southwest China

Based on eddy covariance(EC) measurements during 2016–20, the effects of sky conditions on the net ecosystem productivity(NEP) over a subtropical “floating blanket ” wetland were investigated. Sky conditions were divided into overcast, cloudy, and sunny conditions. On the half-hourly timescale, the daytime NEP responded more rapidly to the changes in the total photosynthetic active radiation(PARt) under overcast and cloudy skies than that under sunny skies. The increase in the apparent quantum yield under overcast and cloudy conditions was the greatest in spring and the least in summer. Additionally, lower atmospheric vapor pressure deficit(VPD) and moderate air temperature were more conducive to enhancing the apparent quantum yield under cloudy skies. On the daily timescale, NEP and the gross primary production(GPP) were higher under cloudy or sunny conditions than those under overcast conditions across seasons. The daily NEP and GPP during the wet season peaked under cloudy skies. The daily ecosystem light use efficiency(LUE) and water use efficiency(WUE) during the wet season also changed with sky conditions and reached their maximum under overcast and cloudy skies, respectively. The diffuse photosynthetic active radiation(PAR_d) and air temperature were primarily responsible for the variation of daily NEP from half-hourly to monthly timescales, and the direct photosynthetic active radiation(PAR_b) had a secondary effect on NEP. Under sunny conditions, PAR_b and air temperature were the dominant factors controlling daily NEP. While daily NEP was mainly controlled by PAR_d under cloudy and overcast conditions.

Organizational Modes and Environmental Conditions of the Severe Convective Weathers Produced by the Mesoscale Convective Systems in South China

Composite radar reflectivity data during April-September 2011-2015 are used to investigate and classify storms in south China(18-27°N;105-120°E). The storms appear most frequently in May. They are either linear;cellular or nonlinear systems, taking up 29.45%, 24.51% and 46.04%, respectively, in terms of morphology. Linear systems are subdivided into six morphologies: trailing stratiform precipitation(TS), bow echoes(BE), leading stratiform precipitation(LS), embedded line(EL), no stratiform precipitation(NS) and parallel stratiform precipitation(PS). The TS and NS modes have the highest frequencies but there are only small samples of LS(0.61%) and PS(0.79%) modes.Severe convective wind(≥17m s-1at surface level) accounts for the highest percentage(35%) of severe convective weather events produced by cellular systems including individual cells(IC) and clusters of cells(CC). Short-duration heavy rainfall(≥50 mm h-1) and severe convective wind are the most common severe weather associated with TS and BE modes. Comparison of environmental physical parameters shows that cellular convection systems tend to occur in the environment with favorable thermal condition, substantial unstable energy and low precipitable water from the surface to300 hPa(PWAT). However, the environmental conditions favoring the initiation of linear systems feature strong vertical wind shear, high PWAT, and intense convective inhibition. The environmental parameters favoring the initiation of nonlinear systems are between those of the other two types of morphology.

Assessment of Meteorological Threats to the Coordinated Search and Rescue of Unmanned/Manned Aircraft

The architecture and working principle of coordinated search and rescue system of unmanned/manned aircraft,which is composed of manned/unmanned aircraft and manned aircraft,were first introduced,and they can cooperate with each other to complete a search and rescue task.Secondly,a threat assessment method based on meteorological data was proposed,and potential meteorological threats,such as storms and rainfall,can be predicted by collecting and analyzing meteorological data.Finally,an experiment was carried out to evaluate the performance of the proposed method in different scenarios.The experimental results show that the coordinated search and rescue system of unmanned/manned aircraft can be used to effectively assess meteorological threats and provide accurate search and rescue guidance.

Methodological Research in the Field of Civil Aviation Safety

In order to promote the application and development of civil aviation safety(CAS)in the field of safety and enrich the theoretical system of CAS research,the methodology of CAS was studied.The definition of CAS was reconstructed,its connotation was explained from four aspects,and its research object was clarified.This paper discussed the mechanism of CAS,that is,to maintain system security through the establishment of safety prevention and control system(SPCS),and explained the research content of CAS from theory and technology application.Five principles and applicable methods for CAS research were summarized.In addition,it put forward the general procedure of CAS research,explained the specific content and implementation method or basis of each step.The research results show that the methodology of CAS is a systematic theoretical system with certain guiding significance,combined with the mechanism,research content,research principles and methods,and research procedures of CAS.

SVR Recommendation Algorithm of Civil Aviation Auxiliary Service Based on Context-Awareness

Analysis of the particularity of the civil aviation passenger auxiliary service recommendation scenario.As application of the traditional recommendation algorithm has certain limitation in civil aviation auxiliary services recommendation,a SVR recommendation algorithm of auxiliary service of civil aviation based on context-awareness was proposed.Analysis of the civil aviation passenger travel data,construct the civil aviation passenger preference model,then recommend auxiliary service for passengers.Based on the traditional two-dimensional user-item recommendation,considering the user characteristics,item attributes and user contextual information in the process of recommendation,which can effectively reduce the data sparseness in some degree.In addition,when there is a new user or a new item,whose similar users or items can be found according to the user or item attributes,to some extent,which can solve the problem of cold start.The experimental results show that the algorithm can recommend auxiliary service for passengers more accurately,which can provide convenience for passengers as well as increase the quality of airlines’services.

Research on the evolutionary game of the supervision of civil aviation dangerous goods transportation training

This study is carried out to promote the precise supervision of dangerous goods transportation training,improve the efficiency of civil aviation supervision and further ensure the safety of air transportation.First,from the perspective of behaviour interaction and interest demands,evolutionary game theory is used to construct a tripartite evolutionary game model of dangerous goods transportation training institutions,the Civil Aviation Administration of China(CAAC)and the public.Then,the evolutionary game equilibrium of the system is further analysed under the joint action of the three parties.Finally,the influences of important parameters of the model on the behavioural strategy selection of the three parties are investigated via MATLAB numerical simulation.The conclusions reveal that the system has three evolutionarily stable strategies under different parameters,namely(non-compliant training,supervision,non-participation in supervision),(non-compliant training,supervision,participation in supervision)and(compliant training,supervision,non-participation in supervision).Moreover,the CAAC supervision cost,the fine amount,the supervision cost of public participation,the supervision success rate and the reporting reward amount are the main parameters that affect the behavioural strategy selection of the tripartite game players.The conclusions and suggestions of this study provide a decision-making basis and guidance for the supervision and management of civil aviation dangerous goods transportation training.

State of rare earth elements in the rare earth deposits of Northwest Guizhou,China

We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O,Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt.Rare earth elements were not detected by electron probe.(NH_4)_2 SO_4,(NH_4)Cl, NaCl, and H_2 SO_4 were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10%reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals.

THE INFLUENCES OF SSTA OVER KUROSHIO AND ITS EXTENSION ON RAINFALL IN NORTHEAST CHINA UNDER THE BACKGROUND OF TWO DIFFERENT EL NIO CASES

By using the gauged rainfall in 160 stations within China's Mainland and the NCEP/NCAR reanalysis data, the impacts of anomalous SST in Kuroshio and its extension on precipitation in Northeast China were investigated. The results show that a difference in the meridional circulation such as the East Asia/Pacific teleconnection pattern(EAP)may be responsible for the difference in rainfall between 1998 and 2010. In comparison with 1998, the anomalous meridional circulation pattern in 2010 shifted northeastward, and then the western subtropical high, the mid-latitudinal trough and the northeastern Asia blocking high also shifted northeastward, causing intensified convergence of the cold and warm air masses at the southern region and thus more rainfall in the southwestern region and less in the northwestern region. In 1998, the anomalous cyclone, one component of the meridional pattern, located at the Songhuajiang-Nengjiang River basin, resulted in more rainfall in the majority of the area. The results of observation and the model show that the difference in SSTA in Kuroshio and its extension under the background of different El Ni觡o events is the key point:(1) The anomalous warmth moved westward from the mid-Pacific to the east of the Philippine Sea during the central event, which led the heat resources shifting to the northeast in 2010; subsequently, a shift occurred to the north of the anomalous ascent and decent, followed by a warm SSTA in the region of Kuroshio's extension in 2010 and Kuroshio in 1998.(2) The warm SSTA in the Kuroshio extension causing the Rossby wave activity flux strengthened in 2010, and then the westerly jet shifted northward and extended eastward. A warm SSTA in Kuroshio and cold SSTA in its extension in 1998 caused the westerly jet to shift southward and weaken. As a result,the anomalous anticyclone and cyclone shifted northward in 2010, and the blocking high also shifted northward.

Sensitivity of warm-sector heavy precipitation to the impact of anthropogenic heating in South China

为探讨人为热(AH)对华南暖区暴雨的影响,该文利用WRF-SLUCM模式并考虑适当的AH释放,对2014年5月8日发生在珠江三角洲(PRD)的暖区暴雨进行了数值模拟。有无AH效应的模拟结果分析表明,降水对AH的影响敏感,AH效应使得城区总降水量减少约10%。影响的可能机制为:AH增加导致的热力场和流场再分布,使得局地辐合向PRD边界区域转移增强城乡边界的对流和降水;PRD城区内更为均质的城市热环境减小了热力对比削弱了辐合,从而降低了城区降水。

A NUMERICAL DIAGNOSIS OF LEADING SIGNALS FACILITATING A “NORTH-RIDGE SOUTH-TROUGH” DIPOLE FOR THE EARLY-2008 SOUTH-CHINA FREEZING-RAIN EVENTS

Previous studies emphasize the important role of a "north-ridge versus south-trough" dipole (affecting the latitudes from 20° to 75° N around the Tibetan Plateau) of anomalous geopotential height ( Z ) in the early-2008 abnormal cryogenic freezing-rain-and-snow events in the southern part of China. The present study intends to extract the leading signal facilitating the dipole based on the numerical outputs of a full Z-linear model for diagnosing the global Z . Using this model built on full primitive equations in spherical-isobaric coordinates, we can further split the anomaly of Z-Zfζ-uβ (representing the Z component not explicitly associated with the Coriolis parameter f and its meridional derivative β ) into 15 components. With the model-output Zfζ-uβ (mainly accounting for the dipole under the geostrophic balance) and Z-Zfζ-uβ matrices as the left and right singular vectors respectively, a maximum covariance analysis (MCA) is performed to extract the significant 2-4-day leading signal carried by the MCA Z-Zfζ-uβ mode in the upstream area of the dipole. This leading signal is mainly attributed to 1) the abnormally strong westerlies centered around the exit region of the Atlantic jet-stream and 2) the corresponding anomalous 950-300 hPa anticyclone to the south of the abnormally strong center of westerlies. The energy of the positive wave center around this jet exit region favors the downstream north-ridge while the energy of the negative wave center associated with the anomalous anticyclone favors the downstream south-trough.

Different Summer Rainfall Anomaly Patterns in Northeast China Associated with Two Kinds of El Ni?o Events

The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an atmospheric general circulation model(AGCM).It is shown that,for different types of El Ni?o events,there is different rainfall anomaly pattern in the following summer.In the following year of a typical El Ni?o event,there are remarkable positive rainfall anomalies in the central-western region of northeast China,whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki event.The reason for the distinct difference is that,associated with the different sea surface temperature anomalies(SSTA)along the equatorial Pacific,the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer after El Ni?o Modoki events.Influenced by the anomalous anticyclone in Philippine Sea,southwesterly anomalies over eastern China strengthen summer monsoon and bring more water vapor to northeast China.Meanwhile,convergence and updraft is strengthened by the anomalous cyclone right in northeast China in typical El Ni?o events.These moisture and atmospheric circulation conditions are favorable for enhanced precipitation.However,because of the northward shift,the anomalous anticyclone in the Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years,and the anomalous cyclone in northeast China in typical El Ni?o cases shifts to the north of northeast China,leading to the"dipole pattern"of rainfall anomalies.According to the results of numerical experiments,we further confirm that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in northeast China.

Vulnerability of Regional Aviation Networks Based on DBSCAN and Complex Networks

To enhance the accuracy of performance analysis of regional airline network,this study applies complex network theory and Density-Based Spatial Clustering of Applications with Noise(DBSCAN)algorithm to investigate the topology of regional airline network,constructs node importance index system,and clusters 161 airport nodes of regional airline network.Besides,entropy power method and approximating ideal solution method(TOPSIS)is applied to comprehensively evaluate the importance of airport nodes and complete the classification of nodes and identification of key points;adopt network efficiency,maximum connectivity subgraph and network connectivity as vulnerability measurement indexes,and observe the changes of vulnerability indexes of key nodes under deliberate attacks and 137 nodes under random attacks.The results demonstrate that the decreasing trend of the maximum connectivity subgraph indicator is slower and the decreasing trend of the network efficiency and connectivity indicators is faster when the critical nodes of the regional airline network are deliberately attacked.Besides,the decreasing trend of the network efficiency indicator is faster and the decreasing trend of the maximum connectivity subgraph indicator is slower when the nodes of four different categories are randomly attacked.Finally,it is proposed to identify and focus on protecting critical nodes in order to better improve the security level of regional airline system.

Analysis of a Large-Scale Heavy Precipitation Weather Process in Northern China from September 17 to 20, 2021

In the autumn of 2021, China’s precipitation appears the distribution characteristics of “more in the South and less in the north”. Compared with the same period in history, the precipitation is more. The analysis is based on a large-scale heavy precipitation weather process in the middle and late September. The atmospheric circulation situation and weather situation of this precipitation process are mainly discussed. The results show that the low-pressure trough between the Balkesh Lake and Baikal Lake area made the cold air move eastward, and the warm and humid air flow extending westward was conducive to the enhancement of precipitation. The anticyclone circulation in the Sea of Japan transported the cold and humid air to the northeast of China. The southeast air flow around the subtropical high in the Western Pacific, the southwest air flow in the bay of the Bengal Bay and the South China Sea met in the southwest to produce precipitation and continued to move northward. They merged with the cold and humid air flow in the Northeast in the north of the Yangtze River, resulting in large-scale precipitation in northern China.

Analysis of Rainfall Weather Process in Most of China from 3-6 October, 2021

Heavy rain is a common abnormal weather in China, which is prone to major natural disasters such as floods. By using China National Climate Center’s DERF2.0 (the second-generation product of monthly dynamic extended ensemble prediction) models and NCEP (National Centers for Environmental Prediction) data, and using synoptic and dynamic methods and other research methods, the rainfall weather process in most of China from October 3-6, 2021 is analyzed. The results show that: 1) this process had a long duration, large cumulative rainfall and strong extreme. 2) The warm and wet flow and the cold air intersected in the central and western regions of China and Northeast China, which resulted in a regional rainstorm process within ten days. 3) There was a low-level jet moving from Guizhou and Hunan to the south of Northeast China, bringing a lot of water vapor. To sum up, the rainfall process of this round has a certain relationship with the adjustment of atmospheric circulation.

Chemical Properties,Low-Temperature Performance,and Burning Performance of Bio-Jet Fuel

The effects of composition of bio-jet fuels on freezing point,smoke point,distillation range,and flash point are investigated.Performance tests using petroleum-based jet fuel with different compositions are conducted in line with standard test specifications.The results show that alkylbenzenes reduce the freezing point,with the amount of reduction becoming greater with increasing alkylbenzene content.For a 25%content of the C_8 aromatic xylene,the freezing point is in the range from-55.5℃to-60.1℃.The presence of monocyclic aromatic hydrocarbons leads to an increase in carbon deposition performance,especially when alkyl side chains are present.With cycloalkanes,carbon deposition is reduced,although alkyl side chains weaken this beneficial effect.Isomeric hydrocarbons are beneficial in reducing carbon deposition.The ASTM D7566 specifications for the distillation range are based on the average properties of petroleum-based aviation fuel,and if all the parameters governing the distillation range of an alternative jet fuel are at their lower limits,it is necessary to check whether other performance standards are met.Light components affect the flash point greatly,with 5%of benzene reducing the flash point by 17℃,whereas intermediate components(e.g.,xylene and ethylbenzene)and heavier components have less impact.Although alcohols provide better combustion performance,their content must be strictly limited owing to their effects in reducing the flash point.

An extended multiple-support response spectrum method incorporating fluid-structure interaction for seismic analysis of deep-water bridges

The effects of ground motion spatial variability(GMSV)or fluid-structure interaction(FSI)on the seismic responses of deep-water bridges have been extensively examined.However,there are few studies on the seismic performance of bridges considering GMSV and FSI effects simultaneously.In this study,the original multiple-support response spectrum(MSRS)method is extended to consider FSI effect for seismic analysis of deep-water bridges.The solution of hydrodynamic pressure on a pier is obtained using the radiation wave theory,and the FSI-MSRS formulation is derived according to the random vibration theory.The influence of FSI effect on the related coefficients is analyzed.A five-span steel-concrete continuous beam bridge is adopted to conduct the numerical simulations.Different load conditions are designed to investigate the variation of the bridge responses when considering the GMSV and FSI effects.The results indicate that the incoherence effect and wave passage effect decrease the bridge responses with a maximum percentage of 86%,while the FSI effect increases the responses with a maximum percentage of 26%.The GMSV and FSI effects should be included in the seismic design of deep-water bridges.

Visual Analysis for Civil Aviation Passenger Reservation Data Characteristics Based on Uncertainty Measurement

Aviation data analysis can help airlines to understand passenger needs,so as to provide passengers with more sophisticated and better services.How to explore the implicit message and analyze contained features from large amounts of data has become an important issue in the civil aviation passenger data analysis process.The uncertainty analysis and visualization methods of data record and property measurement are offered in this paper,based on the visual analysis and uncertainty measure theory combined with parallel coordinates,radar chart,histogram,pixel chart and good interaction.At the same time,the data source expression clearly shows the uncertainty and hidden information as an information base for passengers’service

Research on FMC analytic algorithm of PBN track transition coding

Airborne navigation database(NavDB)coding directly affects the result of analysis on the instrument flight procedure by the modern aircraft flight management computer(FMC).A reasonable flight track transition mode can improve the track tracking accuracy and flight quality of the aircraft.According to the path terminator(PT)and track transition characteristics of the performance based navigation(PBN)instrument flight procedure and by use of the world geodetic system(WGS)-84 ellipsoidal coordinate system,the algorithms for“fly by”and“fly over”track transition connections are developed,together with the algorithms for coordinates of fix-to-altitude(FA)altitude termination point and heading-to-an-intercept(VI)track entry point and for track transition display of the navigation display(ND).According to the simulation carried out based on the PBN instrument approach procedure coding of a certain airport and the PBN route data at a high altitude,the algorithm results are consistent with the FMC-calculated results and the actual ND results.

The Feasibility of Task-based Teaching Approach in Flight Attendants English Class in China

This paper study the feasibility of task-based teaching model in flight attendant oral English class in China. The problem of this research is to discuss why task-based teaching can be used in flight attendant oral English class to improve students' oral English and its advantage. The research results shows that TBT makes language learningcloser tolearners' real life. However, the drawbacks manifests that the task-based methodplaces high requirements on teachers and students since it is more flexible and cooperative, which calls for high control from teachers and good collaboration from students.