不同电结构雷暴中的地闪特征

对观测资料的分析表明,甘肃地区和海南岛的地闪特征具有很大差异。海南岛负地闪（P型）首次回击前的电场变化波形与国外的报道类似,而甘肃地区仅有30％左右的负地闪属P型,约70％的负地闪首次回击前的电场变化波形具有明显的云闪特征（C型负地闪）。海南岛没有发现正地闪,甘肃地区有正地闪。该两地区存在两类电结构不同的雷暴,两类雷暴中地闪放电过程及特征的很大差异,说明我国的防雷规范及措施很可能需要考虑雷暴的地区差异性。     

激光显微探针~(40)Ar/~(39)Ar定年进入了人类历史领域——评美国伯克莱地质年代学中心最新研究成果和年轻火山岩的定年极限

美国伯克莱地质年代学中心P.R.Renne等(1997)对采自意大利维苏威火山公元79年爆发喷出物中的透长石,进行了激光显微探针~(40)Ar/~(39)Ar定年,从46个分析数据中得到了~(40)Ar/~(39)Ar等时线年龄为1925±94 a,接近于与现今使用的格里历1918年前一致。这证明激光显微探针~(40)Ar/~(39)Ar定年法的可信度已扩展到记录人类历史的时间范畴。Renne等的最新研究成果把30多年来K-Ar地质年代学者对特别年轻火山岩的定年研究带入了一个新阶段,它为与晚新生代地质年代学有关的各种研究提供了一有力工具。     

广东珠海双胞旋沟藻Cochlodinium geminatum赤潮事件分析

多环旋沟藻Cochlodinium polykrikoides赤潮在全球频繁爆发。2006年10—11月间, 在广东珠海海域爆发的双胞旋沟藻Cochlodinium geminatum赤潮则较为少见。双胞旋沟藻赤潮发生于富营养的近岸水体, 赤潮发生区内水温变化范围23.41—27.54℃, 盐度变化范围15.49—17.92。双胞旋沟藻的细胞密度随温度和盐度的升高而显著升高, 最高细胞密度达1.6×106个.L-1。在赤潮发生后期, 海区水温下降及群落中红色中缢虫Mesodinium rubrum数量的上升, 可能是导致双胞旋沟藻赤潮衰亡的重要原因。     

基于BP神经网络的机载高分辨率SAR图像分类方法研究

研究可用于机载高分辨率SAR图像分类的灰度共生矩阵惯性矩、能量等纹理特征量以及灰度特征量.提出特征提取和统计分析选取特征向量的方法,基于BP神经网络对图像进行临督分类,最后对分类结果采用数学形态学算法进行开运算去除细小区域.由于该方法充分考虑到SAR图像灰度特征和纹理特征信息,与传统的仅仅考虑纹理特征方法相比,具有较好的分类性能,实验结果表明该方法能够获得较好的分类效果.     

Dietary guaiacol improves the growth of juvenile abalone, <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> Ino

We conducted a preliminarily study on the effects of dietary guaiacol on growth performance of abalone, Haliotis discus hannai Ino. Seven semi-purified diets were formulated with graded levels of guaiacol (0, 5, 10, 50, 100, 500, and 1 000 mg kg⁻¹). Abalone (initial weight: 0.29 ± 0.01 g; initial shell length: 8.55 ± 0.27 mm) were fed with these diets in a re-circulated water system for 152 days. Guaiacol significantly improved the specific growth rate (SGR) (P<0.05); excessive dietary guaiacol (1 000 mg kg⁻¹) led to significantly high mortality (P<0.05), and lipid content in the soft body increased significantly after dietary guaiacol (P<0.05). Activities of catalase and phenoloxidase (PO) in the viscera were significantly stimulated by dietary guaiacol (P<0.05). Broken-line analysis based on SGR indicated that the minimum dietary guaiacol for the optimal growth of juvenile abalone is 15.43 mg kg⁻¹.     

Review on retrieval of lunar regolith thickness by active and passive microwave measurements

It is one of the imPortant methods to retrieve lunar regolith thickness using active and passive microwave techniques. The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulation in the regolith media. The lunar regolith model is first introduced, and the features of the involved physical parameters are indicated thereafter, such as dielectric constants, surface roughness, particle size and thermal grads of the lunar regolith. The time delay and the migration of the radar echoes from the different interfaces is the key problem for active microwave measurement. And the simulation of the microwave radiative transfer in the regolith media is the important technique for the passive microwave measurement. The important parameters and the physical mechanism for the two measurements are also presented.     

Multivariate probabilistic estimates of heat stress for rice across China

Heat stress, a major threat to rice (Oryza sativa) production across China, would tend to increase in frequency and intensity under warming climate. Unlike probabilistic analysis via a univariate character, heat stress events, characterized by three variables (i.e., duration, peak and accumulated detrimental intensity), were identified in the past years. Nine distribution functions (i.e., Beta, Cauchy, Logistic, Normal, Exponential, Gamma, Lognormal, Weibull and Generalized Extreme Value) were firstly introduced and compared to select the best-fit marginal distribution of univariable by using Kolmogorov–Smirnov test, and seven copula functions (i.e., Normal and t, Gumbel–Hougaard, Clayton, Frank, Joe, Ali-Mikhail-Haq) were applied in the distributions of multivariables by Akaike Information Criterion statistics. It was obvious that higher magnitude was in the eastern parts in the context of heat stress frequency and characteristic variables. Critical values of heat stress variables corresponding to the certain return periods (i.e. 5, 10, 20 and 50 years) successively expanded in intensity and spatial scope. Inter-correlations of heat stress variables were significant, enlightening the importance of copula in connecting heat stress variables. The combined and co-occurrence bivariate and trivariate return period at certain univariate value corresponding to the given return periods, were consistent at the spatial scale. Accordingly, it was highlighted that eastern parts, especially Zhejiang, central-northern Fujian and eastern Jiangxi, were prone to heat stress, as a consequence of not only univariate but also multivariate probabilistic analysis. These results can be helpful in quantitatively assessing the vulnerability of rice to heat stress and provide us desired information of prevention strategies for heat stress.     

西南天山地区长时间尺度重力场变化特征

利用西南天山地区2007至2016年共20期流动重力观测资料,分析该地区一年、两年尺度和累积重力变化特征,探讨区域构造活动、地震孕育发生与重力场变化特征的关系。结果表明:西南天山地区迈丹断裂带、柯坪塔格断裂带等大型断裂带影响该区域的重力场分布,使该地区较多出现NEE向的重力梯度分布特征。塔里木盆地和西南天山重力变化有明显的差异性,2个不同的构造块体在重力分布上呈现相对反向变化,塔里木盆地和西南天山地区的重力变化界线不在塔里木盆地边缘的山前地带,而较多出现在柯坪推覆体中北缘地带。西南天山地区的地震大部分发生在重力正值变化区域的零线附近,震中及附近地区重力异常分布与构造特征有较好的一致性。在活动断裂带附近同时出现重力变化零线以及与断裂走向一致的重力变化高梯度带,可作为中短期前兆异常。     

A deep water shelly fauna from the uppermost Ordovician in northwestern Hunan,South China and its paleoecological implications

It is the first time to document the trilobite Mucronaspis(Songxites) wuningensis and the brachiopod ParomalomenaAegiromenella Assemblage from the Xinkailing Bed(Hirnantian, uppermost Ordovician) in Taoyuan and Cili counties,northwestern Hunan Province. Synecological analysis shows that this is a deep water shelly fauna of South China during the Hirnantian. It lived on the upper Jiangnan Slope in northwestern Hunan, adjacent to the southeast margin of the Upper Yangtze Region, and belongs to the Hirnantia fauna with cool and deep water, and low diversity affinity, similar to its contemporary shelly faunas from the southern Shaanxi Slope adjacent to the north margin of the Upper Yangtze Region, the northern Chongqing depression(new name), and the Jiangxi-Anhui-Jiangsu gentle slope of the Lower Yangtze Region. Paleoecologically,it could be attributed to the BA 4–5 benthic regime(about 60–150 m deep, and deepest to 200 m), and was significantly different from the trilobite M.(S.) mucronata and the typical Hirnantia fauna while the latters may have habited in BA 2–3 benthic regimes(about 5–60 m deep). A new paleogeographic distribution pattern of the Hirnantian shallow and deep water shelly faunas of South China is herein proposed for the first time. Assuming that the depositional rate was constant in northwestern Hunan during the end Ordovician, the duration of the Xinkailing Bed might be only 12 thousand years according to the thickness of the Wufeng Formation and the absolute age values of those relevant graptolitic biozones. Such a short time interval may indicate that the global environmental change during the crisis was much shorter than previously thought, and its influence on the deep water regime was significantly shorter than that on the shallow water regime.