A high speed near infrared photometer for lunar occultation studies     

Ashok  N. M.  Chandrasekhar  T.  Ragland  Sam  Bhatt  H. C. 《Experimental Astronomy》1994,4(3-4):177-188

A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed.  相似文献   

董家山隧道小净距段爆破控制的数值模拟   总被引：11，自引：1，他引：11  

姚勇  何川  晏启祥  李玉文 《岩土力学》2004,25(Z2):501-506

结合都-汶高速公路董家山隧道小净距段的实际情况,应用数值模拟方法,对小净距段在爆破荷载作用下的相互影响问题进行了研究.结果表明在隧道爆破施工中应对迎爆侧进行重点监控,采用合理的开挖和加固方式将有效降低爆破施工对先建隧道的不利影响.研究结论可为类似小净距段隧道的爆破设计、施工及现场监控量测提供参考.  相似文献   

Temperature and heat flux spectra in the turbulent buoyancy subrange     

C. Sidi  F. Dalaudier 《Pure and Applied Geophysics》1989,130(2-3):547-569

The physical nature of motions with scales intermediate between approximately isotropic turbulence and quasi-linear internal gravity waves is not understood at the present time. Such motions play an important role in the energetics of small scales processes, both in the ocean and in the atmosphere, and in vertical transport of heat and constituents. This scale range is currently interpreted either as a saturated gravity waves field or as a buoyancy range of turbulence.We first discuss some distinctive predictions of the classical (Lumley, Phillips) buoyancy range theory, recently improved (Weinstock, Dalaudier and Sidi) to describe potential energy associated with temperature fluctuations. This theory predicts the existence of a spectral gap in the temperature spectra and of an upward mass flux (downward buoyancy and heat fluxes), strongly increasing towards large scales. These predictions are contrasted with an alternate theory, assuming energetically insignificant buoyancy flux, proposed by Holloway.Then we present experimental evidences of such characteristic features obtained in the lower stratosphere with an instrumented balloon. Spectra of temperature, vertical velocity, and cospectra of both, obtained in homogeneous, weakly turbulent regions, are compared with theoretical predictions. These results are strongly consistent with the improved classical buoyancy range theory and support the existence of a significant downward heat flux in the buoyancy range.The theoretical implications of the understanding of this scale range are discussed. Many experimental evidences consistently show the need for an anisotropic theory of the buoyancy range of turbulence.  相似文献   

COOLING RATES, SKY VIEW FACTORS AND THE DEVELOPMENT OF INTRA-URBAN AIR TEMPERATURE DIFFERENCES     

BJÖRN HOLMER  SOFIA THORSSON  INGEGÄRD ELIASSON 《Geografiska Annaler: Series A, Physical Geography》2007,89(4):237-248

Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter.  相似文献   

废物资源化利用的理论与方法——基于沱牌集团的应用分析     

李孔岳  金森 《地域研究与开发》2001,20(1):23-26

文章通过对废物资源化利用的历史回忆，从能量一经济－环境的复合系统，论述了能量的投入推动着经济的发展，经济发展又会带来环境的破坏，要在经济发展的同时减少环境的污染程度，不能采取简单的末端治理方式，而应从能量投入的源头开始治理，为此，要采取清洁的生产方式，减少废物排放量，并把真正的废物进行资源化利用，确保系统的完备性，做到能量投入减量化，经济发展,高速化，环境污染低量化，由此，结合沱牌集团的计划项目，我们模拟了沱牌集团废物资源化利用的框架，并用具体实例进行分析。  相似文献   

南京地区大气边界层晴空回波研究   总被引：10，自引：1，他引：10  

魏鸣  秦学  王啸华  蒋维楣 《南京气象学院学报》2007,30(6):736-744

以2005年6月23日南京多普勒雷达探测的晴空回波演变为例,分析了回波反射率与径向速度从夜间至上午的演变规律,利用实际的气象观测资料,对比了折射指数、地面温度、露点温度、水汽压和气压与回波强度的相关性,进一步探讨了边界层晴空回波与湍流混合特性之间的关系.研究表明:夜间大气的温、压、湿梯度使湍流出现,但湍流未充分混合使梯度维持,并导致折射指数的梯度增加,出现晴空回波;白天升温后湍流的增强使近地层大气充分混合,温、压、湿梯度减弱导致折射指数梯度减小,回波减弱消失.  相似文献   

极端干旱荒漠区典型晴天大气热力边界层结构分析   总被引：3，自引：1，他引：3  

张强  赵映东  王胜  马芳 《地球科学进展》2007,22(11):1150-1159

利用极端干旱区敦煌野外观测试验资料，分析了极端干旱荒漠区夏季典型晴天位温、风速、比湿等主要物理要素的垂直结构特征及其地表热力和近地层大气运动特征的日变化规律。发现在极端干旱地区夏季晴天大气热力边界层结构十分独特。在夜间，贴地逆温层最低在900 m以上，最厚可以达到1 750 m，逆温层上面的残余层一般能达到4 000 m左右的高度。在白天，位温超绝热递减层高达1 000 m，超绝热递减层上面的混合层最高达3 700 m，混合层顶上还有大约450 m甚至更厚的夹卷层。当白天对流层发展达到残余层以后，混合层的发展明显加快。风速和比湿垂直廓线特征很好地印证了大气热力边界层独特的结构特征，地表热力和近地层大气运动特征也为这种独特的大气热力边界层结构提供了较好的物理支持。  相似文献   

煤层气定向井的施工工艺     

吕利强 《中国煤田地质》2007,19(A01):21-23

沁煤盆地郑庄区煤层气井设计为丛式定向井，井身结构设计为直井段、造斜段、稳斜段。其中丛式井直井段设计为二开结构。在不同井段采用不同钻具组合，钻进参数及成井工艺也各不相同。在钻进过程中，为最大限度地发挥煤层气的开采效果，全孔采用清水作为钻井液，并使用了有线随钻测量系统和大功率钻探设备，钻进效果明显，全孔满足设计要求。  相似文献   

上海天文台佘山工作站夜天亮度的变化     

姚保安  毛亚庆 《中国科学院上海天文台年刊》2007,(1):17-22

使用1994—2007年在1．56m反射望远镜CCD照相机拍摄的资料，测定了上海天文台余山工作站夜天亮度的变化。由于上海城市的发展，佘山工作站的夜天亮度在V波段从每平方角秒约19mag变到15．8mag，也就是说，夜天亮度自1994年以来变亮了约20倍。国际上优良台站的夜天亮度在V波段等于或暗于21．5mag。上述夜天亮度是优良台站的200多倍。现在在佘山工作站使用1．56m反射望远镜对暗于V=14mag的星做精确测光已经很困难了。  相似文献   

基于晴空阈值法的全天空红外图像云量计算     

陈磊  张海波  石鹏飞  韩燕  关军 《沙漠与绿洲气象(新疆气象)》2015,9(3):50-56

为提高新疆戈壁地区云的自动化观测水平,基于全天空红外成像仪(WSIRCMS)获取的红外辐射图像,利用辐射传输模式SBDART分析了仪器测量波段对有云无云状况的敏感性并构建了拟合方程,同时利用典型季节的晴空辐射样本拟合了晴空曲线并统计形成了晴空阈值,最后利用统计晴空阈值对全天空红外辐射图像进行云像素识别和总云量计算。将不同季节总云量计算结果同人工观测结果对比验证表明：观测时段算法计算总云量和人工观测总云量差值在±2成以下的概率均在80%以上,说明该方法具有较高的准确度和较强的实用性,在观测业务中具有较好的应用前景。  相似文献