蓬莱海市蜃楼形成的气象因素季节分布及征兆     

朱龙 《气象》2007,33(11):101-106

利用1980年以来蓬莱北部海域发生的37次海市蜃楼的数据,探讨了蓬莱海市形成的气象因素、季节分布及征兆。结果表明:蓬莱一年四季都能出现海市,绝大多数出现在5月上旬至8月上旬,因其气象条件最易满足海市形成。气层与海水温差达到8.5℃,风力2~4级,湿度较大,是蓬莱海市出现的必要条件;雨后或雪后天晴,伴有大的潮汐,骤冷骤热的异常气温变化,是海市出现的征兆。  相似文献   

对矿类专业毕业生“断层”现象的思考与对策     

张兴唐 《化工矿产地质》2006,28(2):121-123

在社会经济体制转型的过程中,矿类专业毕业生出现了人才的“断层”现象。通过对矿类专业人才“断层”现象形成的原因进行分析,认为缓解目前矿类专业人才短缺现象,要以矿山为主体采取内培外引、努力服务、“订单式”培养方式,长期克服类似的人才“断层”现象要以高校为主体,主动调整专业结构和招生规模,培养复合型人才校企合作,多形式、多渠道培养企业所需人才。  相似文献   

Detection of model voids by identifying reverberation phenomena in GPR records   总被引：2，自引：1，他引：2  

Lev Kofman  Amit Ronen  Sam Frydman   《Journal of Applied Geophysics》2006,59(4):284-299

In order to improve the reliability of the ground penetrating radar (GPR) method in identifying subsurface sinkholes and karst cavities, laboratory investigations have been performed. The main objective of this work was to examine the relationship between horizontal/vertical voids dimensions and wavelengths of various antennas, and the corresponding GPR responses. Emphasis was given to the investigation of the factors that cause the appearance of reverberation phenomena in the signal pattern.The tests were conducted in 5 m × 10 m area by 2-m-deep trench filled with homogenous, dry sand. The voids models (empty fiberglass cylinders in diameters of 0.6 m, 1.0 m, 1.5 m and 2.4 m, with various heights) were buried vertically with their tops at depths of between 0.7 and 1.5 m. Investigations were performed for the various model conditions by towing 500, 300 and 100 MHz antennas along a pre-established grid, for the various model conditions.The GPR data collected using the 500 MHz bistatic antenna above the 1.0-m- and the 1.5-m-diameter cylinders, and using the 300 MHz bistatic antenna above the 1.5-m-diameter cylinder, confirmed the presence of a reverberation phenomenon, i.e. a strong convex signal pattern, containing a series of high amplitude extending oscillations with reduced frequency.Based on past practical GPR experience of void detection and presently obtained experimental data, two rules of thumbs may be adopted for the prediction of the appearance of resonant radar pictures:

1. The void diameter larger than the wavelength in air of the antenna used.

2. The vertical size of the empty void not significantly smaller than its horizontal dimension.

The strong reverberations generated by the inner surface of the void targets were found to approximate standing waves generated in cylindrical waveguides and waveguide resonators. The theoretical, experimental and practical results obtained concur.  相似文献   

Prevalence of the terrain reversal effect in satellite imagery     

Miguel-Angel Bernabé-Poveda 《International Journal of Digital Earth》2015,8(8):640-655

The terrain reversal effect is a perceptual phenomenon which causes an illusion in various 3D geographic visualizations where landforms appear inverted, e.g. we perceive valleys as ridges and vice versa. Given that such displays are important for spatio-visual analysis, this illusion can lead to critical mistakes in interpreting the terrain. However, it is currently undocumented how commonly this effect is experienced. In this paper, we study the prevalence of the terrain reversal effect in satellite imagery through a two-stage online user experiment. The experiment was conducted with the participation of a diverse and relatively large population (n = 535). Participants were asked to identify landforms (valley or ridge?) or judge a 3D spatial relationship (is A higher than B?). When the images were rotated by 180°, the results were reversed. In a control task with ‘illusion-free’ original images, people were successful in identifying landforms, yet a very strong illusion occurred when these images were rotated 180°. Our findings demonstrate that the illusion is acutely present; thus, we need a better understanding of the problem and its solutions. Additionally, the results caution us that in an interactive environment where people can rotate the display, we might be introducing a severe perceptual problem.  相似文献   

伪权现象及抗差估计   总被引：1，自引：0，他引：1  

靳奉祥  王同孝 《测绘工程》1997,6(4):16-20

讨论了权与平差结果的关系，指出了残差向量与权之间不一定存在的一一对应的关系，对现行常用抗差估计方案用实例进行了研究，并建议抗差方案设计应对权函数的取值加以限制，以保证平差系统的稳健性。  相似文献   

初探地震活动的时间分维特征     

张勇利 《地震研究》1991,14(1):87-93

本文运用分维的概念和方法,对我国部分强震前地震活动时间分维,前震震群活动时间分维,7级以上大地震的余震活动时间分维和小震群活动时间分维进行了计算。初步结果表明,同一类型的地震活动(如强震前较大时空范围内地震活动、强震的余震、前震震群、小震群等类型)的时间分维十分相近,而不同类型地震活动的时间分维存在着差异,一般说来,强震前的地震活动比较普遍地存在降维现象,表现出临近强震时,震源及附近地区地震活动时间结构的有序性增强。这为地震预报开辟了一个新的途径。  相似文献   

遥感在河流谷坡工程地质环境评价中的应用     

甄春相 《遥感学报》1992,(1)

河流谷坡工程地质环境评价是水电工程的前期工作,直接关系到工程的选址、建设规模和水利资源的充分利用。 本文利用现有航空遥感资料,对四川雅砻江中游的鲜水河口至官地河段,约510 km河流谷坡的物理地质现象进行了判读,运用数理统计和工程地质综合分析的方法,对该河流区段的工程地质环境进行了评价,并对其发展趋势进行了预测,为该地区丰富的水利资源的开发利用提供了决策依据;对于区域工程地质环境评价,尤其是基础工作薄弱、自然条件恶劣、地面工作难以开展的高山峡谷地区的河流谷坡工程地质环境评价和发展趋势预测提出了新的方法。  相似文献   

黑河实验(HEIFE)能量平衡和水汽输送研究进展   总被引：7，自引：1，他引：7  

胡隐樵 《地球科学进展》1994,9(4):30-34

It is a review about advance of research on energy budget and transportation of water vapour in the HEIFE area. A basic model, the cold island in oasis and the inverse humidity phenomenon in desert, about interaction of oasis with desert environment is established. The major disturbance of the oasis to observation in the desert is the latent heat flux that is an ignored value in the energy budget on ground surface in the desert. Consequently, it is representative of the arid region to have measured energy budget at the gobi station and desert station in the HEIFE area.  相似文献   

Simulation of the Urban Heat Island Phenomenon in Mediterranean Climates   总被引：2，自引：0，他引：2  

G.?MihalakakouEmail author  M.?Santamouris  N.?Papanikolaou  C.?Cartalis  A.?Tsangrassoulis 《Pure and Applied Geophysics》2004,161(2):429-451

An intelligent data-driven method is used in the present study for investigating, analyzing and quantifying the urban heat island phenomenon in the major Athens region where hourly ambient air-temperature data are recorded at twenty-three stations. The heat island phenomenon has a serious impact on the energy consumption of buildings, increases smog production, while contributing to an increasing emission of pollutants from power plants, including sulfur dioxide, carbon monoxide, nitrous oxides and suspended particulates. The intelligent method is an artificial neural network approach in which the urban heat island intensity at day and nighttime are estimated using as inputs several climatic parameters. Various neural network architectures are designed and trained for the output estimation, which is the daytime and nighttime urban heat island intensity at each station for a two-year time period. The results are tested with extensive sets of non-training measurements and it is found that they correspond well with the actual values. Furthermore, the influence of several input climatic parameters measured at each station, such as solar radiation, daytime and nighttime air temperature, and maximum daily air temperature, on the urban heat island intensity fluctuations is investigated and analyzed separately for the day and nighttime period. From this investigation it is shown that heat island intensity is mainly influenced by urbanization factors. A sensitivity investigation has been performed, based on neural network techniques, in order to adequately quantify the impact of the above input parameters on the urban heat island phenomenon.  相似文献   

统计物理学在地震预报中的应用     

郭增建  秦保燕  吴瑾冰 《国际地震动态》2000,(8):1-7

将统计物理学中相变临界现象与震源孕育模式相结合,讨论了地震预报问题。这些临界现象是：长程关联、涨落加剧、奇异吸引子、岔点外敏、临界慢化、趋向分维、临界乳光、λ型、临界软模等。以上临界现象对应的前兆,是综合预报的物理基础。  相似文献