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991.
城市风环境是城市微气候研究的一个重要方向,对分析城市热岛效应、空气流通等具有重要意义。本文以郑州市市区为例,使用1971—2018年气象观测数据、2018年建筑分布数据(OSM)和2016年资源三号卫星数据作为数据源,通过运用气象学和GIS技术结合的方法,探究潜在通风廊道,科学量化城市形态对风环境的影响。研究首先借助WindNinja软件,对城市背景风环境进行模拟分析,该计算方法提高了风道定位的精度。然后利用卫星遥感数据制作了数字高程模型(DSM),结合OSM计算下垫面地表粗糙度。进一步借助ArcGIS软件,利用最小成本路径法(LCP)确定城市潜在通风廊道的位置。结果表明:① 郑州市近年来平均风速缓慢下降,平均每10年下降0.26 m/s;全年主导风向东北风进入城市后受城市形态影响在京广铁路线附近以西逐渐转为东北偏东风,其中在京广快速路以东风速较高,在京广快速路以西风速较低;② 金水区西部、中原区、二七区以及管城区的地表粗糙度较高,通风环境较差;金水区东部和惠济区的地表粗糙度较低,通风环境较好;③根据盛行风向模拟的潜在通风廊道,其共同特点是趋向于低粗糙度的地区。  相似文献   
992.
农田防护林是农田生态系统的屏障,其健康状况的监测与评估在我国北方农田林网管理中尤为重要。本文以新疆生产建设兵团第三师51团为研究区,使用复合翼无人机CW-20搭载Micro MCA12 Snap多光谱相机获取农田防护林的多光谱影像,经辐射校正、裁剪等预处理,通过优选有效特征和模型比较,提出农田防护林提取的有效方法。首先,基于原始12波段,依据相关性系数矩阵和最佳指数因子(Optimum Index Factor,OIF)选取最优3波段和植被指数特征进行组合,构建8种农田防护林提取方案;然后,通过建立语义分割Deeplabv3+模型进行精度评价,得到最优3波段组合6(波长710 nm)、8(波长800 nm)、 11(波长900 nm)波段为最佳特征组合;最后,以最优3波段为基础,将Deeplabv3+模型与U-Net、ENVINet5模型进行对比分析。结果表明:Deeplabv3+模型能够更深层次的挖掘光谱中潜在的信息,相比其他模型,能够较好地处理正负样本不均衡问题,获得最高MIoU值85.54%,比U-Net、ENVINet5的MIoU值则分别高出21.21%、27.19%。该研究结果可为基于多光谱遥感影像的语义分割在农田防护林提取及健康状况监测的应用提供借鉴和参考。  相似文献   
993.
A new species of cymothoid Isopeda, Nerocila donghaiensis, collected from the body of a sciaenid fish, Johnius sp., is described in the present paper. The new species can be distinguished from the other species of genus Nerocila by its endoped of uropods with deep notch, sharply serrated on the lateral margin and strongly serrated on the medial margin; antennule with 1 st article swollen; dactyli of pereopods Ⅰ, Ⅱ, Ⅳ, Ⅴ swollen.  相似文献   
994.
An in vivo fluorescence discrimination technique for phytoplankton population was developed by using Wavelet packet transform, cluster analysis and non-negative least squares. The technique was used to analyze water samples from different sea regions. For simulative mixtures, when dominant species account for 60%, 70%, 80%, 90% at the division level, the correct discrimination ratios (CDRs) are 83.0%, 99.1%, 99.7% and 99.9% with the relative contents of 58.5%, 68.4%, 77.7% and 86.3%, respectively; when the algae dominance are 60%, 70%, 80%, 90%, 100% at the genus level, the CDRs are 86.1%, 94.9%, 95.2%, 96.8% and 96.7%, respectively. For laboratory mixtures, the CDRs are 88.1% and 78.4% at the division and genus level, respectively. For field samples, the CDRs were 91.7% and 80% at the division and genus level, respectively (mesocosm experiments), and the CDRs were 100% and 66.7% at the division and genus level, respectively (Jiaozhou Bay). The fluorometric technique was used to estimate the phytoplankton community composition and relative abundance of different classes for the April 2010 cruise in the Yellow Sea with the results agreeing with those in published papers by other authors.  相似文献   
995.
Through the geochemical analysis of two hundred-meters cores KD4 and ZK3 from Laizhou Bay,in this study,we determined the distribution law and controlling factors of the geochemical elements.We analyzed 24 elements with respect to their R factors and major principal components,which were combined with the source discrimination functions DFCr/Th and DFCa/Al to obtain the sediment source index and its variation with depth for this area.A comparison of the changes in climate indicators suggests a clear correlation between the source and climate changes.The results show that the Yellow River and surrounding short-term rivers are the main sediment sources in this area.The PC3 of the KD4 core and PC2 of the ZK3 core(e.g.,CaO,MnO,SiO2)exhibit significant variations and reflect the relative contributions of Yellow River sources.The deposition process can be divided into six stages:in Phase I(MIS 5c–MIS 5a),the Yellow River formed,and the composition of the Yellow River had a greater influence on the sedimentary composition of the study area.In Phase II(MIS 5a–MIS 3),the sediment sources of the Yellow River and the short-term streams in this area were wavering,with the sediments derived from short-term rivers playing a more important role.In Phase III(MIS 3),with a sharp drop in temperature,the study area was in the process of retreat,and the sediment source changed from the Yellow River to short-term rivers,after which the Yellow River source material remained the main sediment source for the region.A similar process occurred three more times in Phase IV(MIS 3–MIS 2),Phase V(MIS 2–MIS 1),and Phase VI(MIS 1).With changes in climate,especially during alternating sea-land phases,the sediment source varied in marine-terrestrial-marine phases,and the changes are observed as Yellow River source-surrounding provenance-Yellow River source.However,this process of change is not synchronized with the sea-land strata alternation.  相似文献   
996.
The present work was carried out to evaluate the safety of shrimp(Solenocera crassicornis)treated with different concentrations of sodium metabisulfite(SMB)by soaking or spraying during frozen storage.Shrimps soaked in higher concentrations of SMB showed higher sensory scores,lower total color differences,and better anti-melanosis effects than shrimps in the control and other treatment groups throughout frozen storage(−18℃).Lower total volatile basic nitrogen and thiobarbituric acid reactive substances and higher salt soluble protein contents were detected in shrimp soaked with high doses of SMB compared with other samples.In addition,lower counts of total aerobic plates and psychrotrophic bacteria were observed in shrimp treated by soaking with higher doses of SMB than those in control shrimp and shrimp treated with other methods during frozen storage(−18℃).However,the SO2 content of 5%SMB-soaked samples exceeded the maximum allowable limit of 100mgkg−1.Overall,the use of 1.5%SMB soaking to treat shrimp results in good antioxidant and antimicrobial effects and,thus,may be suggested to preserve S.crassicornis under frozen conditions.The results of this study present important guidance on the use of SMB to maintain the quality of marine-trawling shrimp from manufacturing to consumption.  相似文献   
997.
我国东部中低山区第四纪冰川的存在与否一直存在争议,但冰川必然对山体进行冰蚀作用形成冰蚀地貌。为了分析我国东部中低山区的山体地貌是否具有冰蚀特征,该文选取了现代冰川集中发育区-喜马拉雅山脉作为冰蚀地貌的研究对象,通过宏观分析,除了由缩口、三角脊、残弧组成的冰斗系统外,还发现冰蚀作用过程存在避谷、吞脊、切壁、穿梁等特殊习性。分析认为冰蚀过程主要受制于雪线高程、积雪高程与坡向坡角三方面因素的控制。以此为基础,对我国东部的江西庐山、山东蒙山、大兴安岭主峰黄岗梁三个地区的山体地貌进行对比分析,发现这些山区的山体地貌与喜马拉雅山脉的冰蚀地貌具有一致性。文章从冰蚀过程的角度确认了我国东部中低山区存在第四纪冰川的事实。  相似文献   
998.
N-(2-hydroxy-1-naphthaldene)-4-aminoantipyrine has been synthesized. The structure is determined by X-ray diffraction method and elemental analysis. The crystal system belongs to orthorhombic space group P(2)2(1)2(1). The geometry has been ob-tained from the density functional theory (DFT) method and the B3LYP method employing the 6-31G* basis sets. The calculated results propose that the latter is close to the experimental data. The structural parameters from the theory are close to those of the crystal and the calculated total energy of coordination is -31677.172 eV. The energy of HOMO and LUMO and the energy gap are 5.179 eV, -1.603 eV and 3.577 eV, respectively.  相似文献   
999.
The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter (Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, Betula costata, and mixed litter), soil in humus horizon (0--5cm) and soil horizon (5-20cm), and soil macrofauna (Oligochaeta, Geophiloporpha and Juliformia) from 2001 to 2002. The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index (El). The results indicate that dynamic changes of various litters are very complicated. The contents of Fe in each kind of litter increase firstly, and then decrease in the study period. The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter, and the mixed litter is in the middle level, but the differences among them are not significant. The contents of Mg and Fe in humus are higher than those in soil, but the contents of Ca in soil are higher than that in humus. The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter. The diplopod presented obvious enrichment of Ca and Mg (E1〉1), but it does not significantly enrich Fe. Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra, but E1〈1. Soil fauna can make great influences on the material cycle of the subsystems.  相似文献   
1000.
采用柱色谱分离方法,分别以氧化铝(5g)、上部为氧化铝下部为硅胶(3g:2g)、上部为硅胶下部为氧化铝(3g:2g)和硅胶(5g)4种填充方法对原油和沥青砂岩抽提物进行族组成分析,对其饱和烃馏分进行气相色谱-质谱分析,对比剖析了饱和烃生物标志物组成特征。结果表明:这4种不同的填充方法对类异戊间二烯型烷烃、藿烷、规则甾烷等生物标志物的分子组成影响一般均较小,但对于高碳数正构烷烃和重排甾烷等化合物的影响则较明显。  相似文献   
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