一米望远镜低色散光谱仪试验

本文介绍了云南天文台一米望远镜附属的一台低色散光谱仪实验装置,介绍了该装置的设计原理、系统结构参数及试观测情况,并讨论了存在的问题和解决问题的设想。我们已用该装置观测到19m左右的具有大红移的类星体光谱。该类低色散光谱仪,将为我国星系研究工作者提供实测条件。     

2009年秋季南京地区一次持续性灰霾天气过程研究

2009年10月14—27日,南京地区发生了一次持续性的灰霾天气过程。利用气象观测资料和污染物浓度监测资料,结合焚烧点监测、后向气流轨迹模拟,分析了颗粒物和气态污染物的浓度演变特征、气象要素特征及产生持续灰霾天气的可能原因。研究表明,该次过程中绝大部分时间能见度低于10 km,空气污染指数最大时达到195。地面PM2.5质量浓度有显著增长,在26日达到最大值为0.782 mg/m3。NO2质量浓度日均值在24日和27日超过了环境空气质量二级标准,其含量分别为0.094和0.099 mg/m3,对应NOx质量浓度分别为0.105和0.108 mg/m3。SO2质量浓度在22日达到峰值,最大值为0.161 mg/m3,平均值为0.083 mg/m3,低于环境空气质量二级标准。分析显示:近半个月内南京地区天气形势稳定,处于持续温度偏高、干燥无雨的状态,非常有利于灰霾天气的发生。卫星监测发现24、25、26日江淮之间中部均有火点,其中24日有50个着火点,25日增加为85个,26日减少为38个,表明有秸秆焚烧现象存在。从后向气流轨迹分析来看,在秸秆焚烧最为严重的3 d内,南京地区主要受到来自东到东北方向气流的影响,有利于秸秆焚烧形成的污染物经气流输送影响南京,造成严重灰霾天气。     

静载作用下土工格栅加筋拓宽路堤土中应力特征试验研究

为探究荷载作用下软土地基直接拼接拓宽路堤受力和变形特征,利用自行设计制造的模型试验系统,通过改变软土地基差异沉降、土工格栅加铺层数对软土地基高速公路直接拼接路堤进行一系列模型试验,研究各种工况下旧路与新拓宽路堤土中应力变化。试验结果表明,拓宽路堤在荷载作用下新旧路各断面土中竖向应力随着荷载的增大而增大,受路堤填土边坡与下伏地基侧向约束条件的影响,荷载作用下土中竖向应力在填土路堤与地基内沿深度方向呈现先减小、后增大、再减小的分布特征;软土地基拓宽路堤差异沉降对新旧路结合部位土中竖向应力影响较大,土中竖向应力随着差异沉降增大而增大;旧路范围内土中竖向应力受差异沉降的影响不大;在拓宽路堤填土的顶部和底部各布设一层土工格栅加筋层时可明显减小路堤土中竖向应力和路堤沉降：相同荷载作用下对比无加筋路堤,铺设2层土工格栅加筋路堤的顶面沉降最大可以减少62%,土工格栅加筋对软土地基拓宽路堤沉降有较好的控制作用。     

Development characteristics of cloud-to-ground lightning with multiple grounding points

Using the optical images of a cloud-to-ground lightning flash with multiple grounding points obtained by a highspeed video system in the Qinghai Province of China along with synchronous radiated electric field information, the propagation characteristic and the electric field change features of the leaders and the grounding behavior of discharge channels are analyzed.In addition, the two-dimensional velocity of the leader was estimated and its correlation with the time interval of the corresponding subsequent return stroke, and that with the peak current of return stroke are investigated. The results show that the average distance between the three obvious grounded points of the first return stroke channel is about 512.7 m, and the average time interval between the pulses of the corresponding electric field fast changes is 3.8 μs. Further, the average time interval between electric field pulses from the stepped leader is smaller than that of normal single grounding lightning. The observed lightning in our study has two main channels, namely the left and right channels. Based on our observations, it is clear that the dart leader comes close to the ground in case of the left channel after the first return stroke, but it fails to form a return stroke.However, the right channel exhibits a relatively rare phenomenon in that the subsequent return stroke R2 occurred about 2.1 ms after the dart leader arrived at the ground, which was unusually long; this phenomenon might be attributed to the strong discharge of the first return stroke and insufficient charge accumulation near the grounded point in a timely manner. The two-dimensional velocities for the stepped leader of the two main channels are about 1.23×105 and 1.16×105 m s-1, respectively. A sub-branch of stepped leader for the left channel fails to reach the ground and develops into an attempt leader eventually; this might be attributed to the fact that the main branch connects considerably many sub-branches, which leads to the instantaneous decline of the potential difference between the sub-branch and ground. Furthermore, it might also be because the propagation direction of this sub-branch is almost perpendicular to the atmospheric electric field direction, which is not conducive to charge transfer. The two-dimensional velocities for the dart leaders of five subsequent return strokes are all in the normal range, and they positively correlate with the peak current of the subsequent return stroke.     

Transportation characteristics change under rapid urban expansion: A case study of Shanghai

This paper focuses on the economic development and urban morphology as well as its impact on the transportation system during the urban expansion of Shanghai in the last more than 20 years(1986-2008).Based on data from 3 comprehensive transport surveys of Shanghai since 1986,the changes in residential trip demand,vehicle use,and the spatial distribution of trips were studied to understand the demands on the transportation system.The factors contributing to those changes in transportation demand were discuss...     

Shear deformation and strength of the interphase between the soil–rock mixture and the benched bedrock slope surface

A series of benched excavations were typically carried out on the bedrock slope surface to improve the stability of the soil–rock mixture (S–RM) fill slope. It is difficult to devise an in situ, large-scale direct shear test for the interphase between the S–RM fill and the benched bedrock slope surface. This study introduced a comprehensive approach to investigate the shear deformation and strength of the interphase. First the soil–rock distribution characteristics were analyzed by test pitting, image analysis, and sieve test. Then the PFC2D random structure models with different rock block size distributions were built, and large-scale numerical shear tests for the interphase were performed after calibrating model parameters through laboratory tests. The stress evolution, damage evolution and failure, deformation localization (based on a principle proposed in this paper), rotation of rock blocks, and shear strength were systematically investigated. It was found that as the rock block proportion and rock block size (rock block proportion of 50 %) increase, the fluctuations of the post-peak shear stress–displacement curves of the interphase become more obvious, and the shear band/localized failure path network becomes wider. Generally, smaller rock blocks are of greater rotation angles in the shear band. The peak shear stress and internal friction angle of the interphase increase, while the cohesion decreases with growth of the rock block proportion. However, all these three parameters increase as the rock block size (rock block proportion of 50 %) increases.     

影响中国煤炭行业产业内贸易发展的因素分析

为探讨影响产业内贸易发展的各项因素在我国煤炭行业的作用情况,在总结煤炭行业产业内贸易产生机制和前人研究成果的基础上,运用产业内贸易理论,对可能影响煤炭产业内贸易的主要现实因素进行了总结分析,根据分析结果发现行业产业内贸易发展中存在着整体水平较低、企业规模不经济、专业化分工低、科学技术水平落后、全员劳动生产率低等问题。据此提出提高行业集中度、技术革新、优化企业组织等政策建议。     

攀西地区基性-超基性岩地球化学及嵌套韵律层的分形动力学研究

攀西地区层状基性 -超基性岩体从下到上具有套叠式韵律结构的特征 ,这种韵律由岩石的颜色、矿物的成分、结构等表征。在长期的地球重力作用下 ,物质的液态分异或固相结晶分异为层状岩体韵律成因的关键。提出用类似于 Cantor分形集合法构筑重力分异时空分形集合 ,结果以色谱条带图和直方图表达 ,并与攀枝花层状岩体的野外岩石观察的颜色韵律以及岩体实测的矿物成分、长石的 An号码进行了对比 ,表明岩体实测数据与构筑的重力分异时空分形理论图式很相似 ,揭示了攀西层状基性 -超基性岩体的套叠式韵律结构在成因上具有时空分形的特征     

新虚拟单能量图像对早期胃癌的诊断价值

目的:探讨新虚拟单能量图像在早期胃癌中的应用价值。方法:回顾性分析29例在双源CT行腹部双期双能量增强扫描的早期胃癌病人,并经手术证实病理资料。采用双源CT后处理工作站(Dual energy Mono+,syngo IPIPE,Siemens)使用100和Sn 140kV图像产生40keV、60keV、80keV三组新虚拟单能量图像(AMEIs),并与常规120kVp图像(PEIs)对照,比较各组对早期胃癌的检出率及CNR差异。结果:AMEIs 40keV组具有最高检出率(86.21%),但与PEIs组无统计学差异(相似文献