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1.
基于西安城区与郊区两个环境路边站和区域气象站2016-2018年观测的逐小时气象、环保和交通监测数据,对西安尾气污染物、机动车流量和气象要素条件进行统计分析。结果表明:1)2016年以来,西安市冬季空气质量指数和主要污染物浓度整体呈逐年下降趋势,治污减霾成效明显。主要尾气污染物浓度月际变化趋势相同,冬季11月到次年1月的浓度均明显高于其他月份的,夏季6月到8月的浓度较低,冬季的约为夏季的2~4倍。西安冬季汽车尾气污染物中,氮氧化物(NO_x)、碳氧化物(CO)、碳氢化物(HC)日变化特征相似,但细颗粒物(PM_(2.5))空间差异大。2)NO_x和CO与汽车尾气排放关系密切,每日上午时段二者浓度随车流量增大而增大,车流量整体偏大40%的城区比郊区污染物偏多20%~30%。尾气污染物浓度分布与风频、风速等密切相关:西安城市道路风速较低,风向与汽车尾气污染物的扩散方向基本一致,较高污染浓度通常都出现在主导风向的下风向。城市建筑和道路规划建设中,要保留足够的"城市通风廊道"。3)西安尾气污染物浓度不存在明显的"周末效应",城区站NO_x浓度无明显起伏变化,郊区站道路环境中的NO_x浓度受柴油车通行量影响较大,说明重型车可能对污染的影响更大。4)降水对污染物稀释沉降效果明显,对NO_x作用不明显。前期超过60%以上的相对湿度是降水开始前出现颗粒物小时最大增幅超过200μg/m~3的有利条件,高湿环境是重污染天气过程颗粒物暴发式增长的有利气象条件,因此静风或小风大气环境下,通过水雾"高射炮式"播撒方式增加低层湿度并非是沉降稀释颗粒物的有效方法。  相似文献   
2.
Funiusaurus luanchuanensis gen. et sp. nov. was described on the basis of an incomplete skull from the Upper Cretaceous Qiupa Formation of the Tantou Basin in Luanehuan County, Henan Province. It is the second representative of lizards known from Luanchuan and adds a new member to the Luanchuan Fauna. F. luanchuanensis is a small-sized lizard and systematically assigned to the Polyglyphanodontidae of the Teiioidea because of the presence of a caniniform tooth and an elongate posterior process of the postorbital. It is distinctive in that the heterodont dentition bears 19 teeth in both the upper and lower jaws, the 3^rd maxillary tooth is large and caniniform, the post-caniniform teeth in maxilla and those posterior to the 3^rd dentary tooth are chisel-like in lateral view, the prefrontal possesses a fossa on its lateral surface, the postorbital with an extremely elongate posterior process and the well-developed retroarticular process has a deep fossa on its dorsal surface. In phylogeny, our analysis suggests a close relationship of Funiusaurus to the large-sized Tianyusaurus from the same basin within the Tuberocephalosaurinae. The discovery of Funiusaurus is significant in confirming the status of the Tuberocephalosaurinae, which includes a group of the Asian members of the Polyglyphanodontidae only.  相似文献   
3.
As indicated by observed X-ray flares,a great amount of energy can be intermittently released from the postburst central engine of gamma-ray bursts(GRBs).As a natural consequence,the GRB’s external shock could be repeatedly energized.With such a multiple energy injection model,we explore the unique X-ray afterglow light curve of GRB 050712,which exhibits four shallow decay plateaus.Together with three early X-ray flares,the central engine of GRB 050712 is believed to have released energy at least seven times after the burst.Furthermore,we find that the energies released during the four plateaus are all on the same order of magnitude,but the luminosity significantly decreased with time.These results may provide some interesting implications for the GRB central engine.  相似文献   
4.
5.
This paper describes a set of on-site earthquake safety evaluation systems for buildings, which were developed based on a network platform. The system embedded into the quantitative research results which were completed in accordance with the provisions from Post-earthquake Field Works, Part 2: Safety Assessment of Buildings, GB18208.2-2001, and was further developed into an easy-to-use software platform. The system is aimed at allowing engineering professionals, civil engineeing technicists or earthquake-affected victims on site to assess damaged buildings through a network after earthquakes. The authors studied the function structure, process design of the safety evaluation module, and hierarchical analysis algorithm module of the system in depth, and developed the general architecture design, development technology and database design of the system. Technologies such as hierarchical architecture design and Java EE were used in the system development, and My SQL5 was adopted in the database development. The result is a complete evaluation process of information collection, safety evaluation, and output of damage and safety degrees, as well as query and statistical analysis of identified buildings. The system can play a positive role in sharing expert post-earthquake experience and promoting safety evaluation of buildings on a seismic field.  相似文献   
6.
The optical observations of the type Ic supernova(SN Ic) SN 2012 ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012 ap is highly reddened(with E(B- V)host~0.8 mag) and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of ~-19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be attributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we estimate that SN 2012 ap produced a56 Ni mass of ~ 0.3 ± 0.1M in the explosion, with an ejecta mass of 2.4+0.7-0.7M and a kinetic energy of E5K= 1.1+0.4-0.4× 102 erg. The properties of its progenitor are also briefly discussed.  相似文献   
7.
Because of the strong uplift of the Qilian Shan since late Cenozoic,the drainage basins that are derived from the mountains have undergone strong tectonic deformation.So the typical geomorphology characteristics of these drainage basins may indicate the strong tectonic movement in the region.For example,the Shule River drainage basin,which originates from the western part of the Qilian Shan owns unique geomorphology characteristics which may indicate the neotectonic movement. Stream networks of the Shule drainage basin extracted from the DEM data based on GIS spatial analysis technology are graded into five levels using Strahler classification method.Four sub-catchments,numbered 1,2,3 and 4 are chosen for detailed analysis.Furthermore,the four sub-catchments,the hypsometric integral curves,Hack profiles,SL index and average slope of the Shule drainage basin are determined by GIS tools.In addition,we analyzed the slope spectrum of the Shule drainage basin. The average elevation of the Shule drainage basin is very high,however,the slope of the drainage basin is very low,the gentle slope occupies so large area proportion that the slope spectrum shows a unimodal pattern and a peak value is in low slope region (0°~5°),so tectonic movement has a strong influence on the drainage basin.Under the intensive impact of the tectonic movement of the active fault and regional uplift,the hypsometric integral curve is sigmoid,revealing that the Shule drainage basin is in the mature stage.The Hack profile is on a convex,the longitudinal profile is best fitted by linear fitting and the abnormal data of the SL index of the Shule River has a good fit with the section through which the active fault traverses,that means the tectonic movement of the active fault has strong influence on the river's SL index.It is worth noting that lithologic factors also have great impact on the river geomorphology in some sections. According to the above analysis,we recognize that in the interior of active orogen,the evolution of river geomorphology usually is influenced by tectonic movement and reveals the regional neotectonics in turn.  相似文献   
8.
The association of seasonal timing of stratospheric final warming events(SFWs) in spring and the occurrence of major and minor stratospheric sudden warming events(SSWs) in midwinter were investigated through statistical analysis, parallel comparison, and composite analysis, based on the NCEP-NCAR reanalysis dataset covering 1958–2012. It was found that the intensity and occurrence of winter SSW events can largely affect the timing of spring SFWs. Specifically, the SFW onset dates tend to be later(earlier) after the occurrence(absence) of winter major SSWs. However, the occurrence or absence of minor SSWs does not change the frequency of early and late SFWs. A parallel comparison of the temporal evolution of the anomalous circulation and planetary-waves between major SSW and minor SSW winters indicates that the stratospheric polar vortex(polar jet) will keep being anomalously stronger 30 days after major SSW onset. And the associated significant negative Eliassen-Palm(EP) flux anomalies can persist for as long as 45 days after major SSW events. In contrast, the circulation anomalies around the occurrence of minor SSW events can last only a few days. To further verify the possible influence of the occurrence of major SSWs on the seasonal timing of SFWs, composite analysis was performed respectively for the 21 major-SSW years, 15 minor-SSW years, and the 15 non-SSW years. Generally, planetary-wave activity in the extratropical stratosphere tends to be stronger(weaker) and the westerly polar jet is anomalously weaker(stronger) in major-SSW(non-SSW) winters. But in the following spring, the planetary-wave activity is weaker(stronger) accompanied with an anomalously stronger(weaker) stratospheric polar vortex. In spring after minor-SSW years, however, the stratospheric polar vortex and the westerly polar jet exhibit a state close to climatology with relatively gentle variations.  相似文献   
9.
In this study, we determined the cytotoxicity and genotoxicity of carbamate insecticide carbaryl to flounder gill(FG) cells and its teratogenicity to zebrafish embryos. The cytotoxicity of carbaryl to FG cells was determined with methods including MTT and neutral red uptaking(NRU), lactate dehydrogenase(LDH) releasing and Hoechst 33342 and propidium idodide(PI) double staining. Moderate cytotoxicity in a concentration-dependent manner was observed. The 24 h-IC50 value of 53.48 ± 1.21, 59.13 ± 1.19 and 46.21 ± 1.24 mg L-1 carbaryl was obtained through MTT, NRU and LDH assays, respectively. Double fluorescence staining demonstrated that carbaryl induced the death of FG cells mainly through necrosis. There was no significant genotoxicity found in the FG cells exposed to the highest testing concentration of carbaryl(20 mg L-1, P 0.05) as was demonstrated by Comet assay. Zebrafish embryos exposed to carbaryl at concentrations ≥10 mg L-1 displayed moderate toxic effects on the survival, spontaneous movement, hatching, heart rates of the embryos and their development, which were evidenced by yolk and pericardial sac edemas, body length reduction and tail flexure in time- and concentration-dependent manners at specific stages. The 24 h-, 48 h- and 96 h-LC50 values of carbaryl to zebrafish embryos were 41.80 ± 1.10, 17.80 ± 1.04 and 14.46 ± 1.05 mg L-1, respectively. These results suggested that carbaryl is moderately toxic to FG cells cultured in vitro and zebrafish embryos, and the FG cells were similar to zebrafish embryos in their sensitivity to carbaryl as 24 h-IC50 and LC50 indicated.  相似文献   
10.
Habitat plays a critical role in regulating fish community structure. Using the data collected from a monthly trammel net survey in Ma’an archipelago off the east coast of China, we evaluated impacts of five different habitats(artificial reefs, mussel farms, cage aquaculture, rocky reefs and soft bottom) on fish assemblages. This study suggests that artificial reefs(AR) have significantly higher species richness, abundance and diversity than mussel farms(MF) or soft bottom(SB) habitats during most seasons, and that fish taxa in the AR habitats are similar to those in the rocky reef(RR) habitats. Two different fish assemblage patterns were revealed in the study area using non-metric multidimensional scaling ordination: an assemblage dominated by reef fishes(especially by Scorpaenidae species) in AR, RR and cage aquaculture(CA) habitats and an assemblage dominated by Sciaenidae species in MF and SB habitats. We suggest that reef fishes play a key role in differentiating fish community structures in the study area. Although few differences in fish abundance and diversity were found between the CA and SB habitats, a more diverse age structure was observed in the CA habitats. A much more complex fish assemblage and enhanced population of local species were established as a result of the presence of both floating and fixed artificial structures, probably through improved survival rates.  相似文献   
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