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191.
The study indicates that the relative content ratios of Cu, Pb and Zn in soils and sediments tend to have stability compared to those in meteorites, rocks and organisms. This stability is considered to be associated with their geochemical properties and has no relationship to the existing environments if it is not disturbed by an anthropogenic factor. In addition, it can serve as a background reference in determining the changes in environmental quality due to human activities.  相似文献   
192.
我国棉花主产省区比较优势分析   总被引:9,自引:0,他引:9  
1992-1998年平均,我国12个棉花主产省(区)的粮棉单产比和植棉相对效益分别为1.94-7.24和0.95-5.41,经统计分析,这一单产比和相对效益每上升1,一个省1999年与1992年棉花产量之比就分别下降34.0个百分点、上升48.3个百分比,据此比较优势分析,在1999年我国棉花总产下调的形势下,甘肃、新疆宜保持原有产量水平、江苏、浙江、山东、河北、四川5省宜适当下调,而江西、安徽、河南、湖南、湖北5省则宜酌情处理。基于近期国际棉花市场形势的变化,作者认为,与其它省份一样,2001年甘肃、新疆的棉花产量也有较大的上调空间。  相似文献   
193.
用代数重建法反演地震面波品质因数Q值空间分布   总被引:1,自引:0,他引:1  
本文用代数重建(简称ART)法,反演面波的品质因数Q值分布;作了模型正演计算求得吸收特征时间t^*,接着用这些t^*求反演的Q值分布作比较,求出Q值的相对误差的空间分布在6-8%,说明这种方法用于Q值反演的正确性。用中国地震台网观测报告中振幅和周期,对1966年以后的518个地震事件,共3000多条射线,基于S.J.Duda提出的由震级起算函数的方法,计算每一条射线的t^*,然后对中国中部地区,取  相似文献   
194.
通过对大棚内外大樱桃萌芽到成熟期间空气温度和湿度的观测 ,结合其物候期 ,分析了温湿度与樱桃生长发育及产量的关系。结果表明 ,棚内温度条件明显优越于露地 ,但温棚内温湿度调控是否得当是影响大棚樱桃产量的关键。  相似文献   
195.
使用DYL型地应力测量仪,利用天然场源在地面上探测地下5km、7km、10km深部地质体所随地应力的相对大小。通过探测的地应力值相对大小和绘制等值线图的方法研究地下应力分布状态,并确定了地震危险区的位置及震级等。  相似文献   
196.
Inter-laboratory and absolute calibrations of rock magnetic parameters are fundamental for grounding a rock magnetic database and for semi-quantitative estimates about the magnetic mineral assemblage of a natural sample. Even a dimensionless ratio, such as anhysteretic susceptibility normalized by magnetic susceptibility (Ka/K) may be biased by improper calibration of one or both of the two instruments used to measure Ka and K. In addition, the intensity of the anhysteretic remanent magnetization (ARM) of a given sample depends on the experimental process by which the remanence is imparted. We report an inter-laboratory calibration of these two key parameters, using two sets of artificial reference samples: a paramagnetic rare earth salt, Gd2O3 and a commercial “pozzolanico” cement containing oxidized magnetite with grain size of less than 0.1 μm according to hysteresis properties. Using Gd2O3 the 10 Kappabridges magnetic susceptibility meters (AGICO KLY-2 or KLY-3 models) tested prove to be cross-calibrated to within 1%. On the other hand, Kappabridges provide a low-field susceptibility value that is ca. 6% lower than the tabulated value for Gd2O3, while average high-field susceptibility values measured on a range of instruments are indistinguishable from the tabulated value. Therefore, we suggest that Kappabridge values should be multiplied by 1.06 to achieve absolute calibration. Bartington Instruments magnetic susceptibility meters with MS2B sensors produce values that are 2-13% lower than Kappabridge values, with a strong dependence on sample centering within the sensor. The Ka/K ratio of ca. 11, originally obtained on discrete cement samples with a 2G Enterprises superconducting rock magnetometer and a KLY-2, is consistent with reference parameters for magnetites of grain size <0.1 μm. On the other hand, Ka values from a 2G Enterprises magnetometer and K values from a Bartington Instruments MS2C loop sensor for u-channel and discrete cement samples, will produce average Ka/K values that are unrealistically high if not properly corrected for the nominal volume detected by the sensors for these instruments. Inter-laboratory measurements of K and Ka for standard paleomagnetic plastic cubes filled with cement indicate remarkable differences in the intensity of the newly produced ARMs (with a standard deviation of ca. 21%), that are significantly larger than the differences observed from the calibration of the different magnetometers employed in each laboratory. Differences in the alternating field decay rate are likely the major source of these variations, but cannot account for all the observed variability. With such large variations in experimental conditions, classical interpretation of a “King plot” of Ka versus K would imply significant differences in the determination of grain size of magnetite particles on the same material.  相似文献   
197.
Observations of the dispersion of a contaminant plume in theatmospheric boundary layer, obtained using a Lidar, are analysedin a coordinate frame relative to the instantaneous centre of massof the plume. To improve the estimates of relative dispersionstatistics, maximum entropy inversion is used to remove noise fromthe Lidar concentration profiles before carrying out the analysis.A parametric form is proposed for the probability density function(pdf) of concentration, consisting of a mixture of a betadistribution and of a generalised Pareto distribution (GPD). Thispdf allows for the possibility of a unimodal or bimodaldistribution, and is shown to give a satisfactory fit toobservations from a range of positions relative to the source. Thevariation of the fitted parameters with crossplume location isanalysed, and the maximum possible concentration is found todecrease away from the plume centre.  相似文献   
198.
模糊数学方法在城市环境噪声监测优化布点中的应用   总被引:1,自引:0,他引:1  
张存洁 《高原气象》2002,21(3):333-336
对兰州市1990-1993年的城市区域网格噪声监测数据,应用模糊论方法学进行相关聚类分析,计算近度及择近手段,对兰州市城市区域环境噪声布点进行了优化。用未参加优化运算的1994年和1995年的实测数据进行优化后的检验(F,t),以此验证测点优化的可靠性。研究结果表明,应用模糊论方法进行城市环境噪声监测优化布点是可行的,准确的,且具有明显的经济效益。  相似文献   
199.
黄玮琼  吴宣 《中国地震》2002,18(4):377-381
在地震危险性分析中,历史地震资料是确定地震活动性参数的关键。鉴于我国西部地震资料记载年限短,地震活动水平高的情况,本文提出一种对中国西部地区如何使用有限资料,确定未来地震活动水平和合理估计地震活动性参数的方法。该方法是引入相对应变这一物理量,通过分析各地震带中强以上地震在时间上的相对应变释放速率,达到尽可能合理估计地震活动性参数的目的。  相似文献   
200.
N. Kraeva   《Tectonophysics》2004,383(1-2):29-44
Application of Tikhonov's technique, using input errors for the parameter of regularization estimation, enhances the accuracy and stability of the reconstruction of a source time function (STF) by the empirical Green function (EGF) method that gives us an opportunity to use simultaneously for analysis body and surface waves data, and to estimate the horizontal and vertical directivity effects. Knowledge of the last is particularly useful for the choice of an active nodal plane of earthquakes with the dip slip fault orientation that allows us to classify these earthquakes to the interplate or intraplate types and thereby to reach the better understanding of tectonic processes in the region of interest.By way of illustration, an attempt to estimate average parameters of faulting in a first approximation is made herein for two Russian Far East large events with opposite types of focal mechanism orientation, strike slip and dip slip. The former is not a matter of interest in the context of vertical directivity effect but enables us to test the method.The directivity analysis of pulse durations and inverse amplitudes of the relative source time functions (RSTFs) restored at eight globally distributed stations IRIS indicates that the destruction in the source of the Neftegorsk earthquake (05/27/1995 MW=7.1) propagated roughly horizontally in the direction 8±11° during 19.2±0.4 s along the rupture extending 35.5±4.9 km. The calculated slip distribution along the rupture coincides within the error with the results of field geological measurements on the causal surface fault that proves that the Neftegorsk earthquake source is well described by the model of the linear unilateral fault and gives a good assessment of the method applied.The average parameters of faulting in the Kamchatka earthquake (03/08/1999 MW=6.9) have been determined from data of 13 station IRIS. It was shown that the destruction in its source propagated downward at an angle of about 60° with horizon, in the direction about S156° E, during 13.4±0.2 s, along the rupture totaling 25.5±2.3 km in length. Therefore, the nodal plane, steeply dipped to the SE, was active and this event can be regarded as an intraplate type. Two asperities can be selected; the first with the maximum slip 3.3 m located at a distance of about 7 km from the onset of rupture, and the second with the maximum slip about 0.9 m centered at approximately 19 km from that.  相似文献   
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