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T. P. Singh 《Journal of Astrophysics and Astronomy》1999,20(3-4):221-232
This article gives an elementary review of gravitational collapse and the cosmic censorship hypothesis. Known models of collapse
resulting in the formation of black holes and naked singularities are summarized. These models, when taken together, suggest
that the censorship hypothesis may not hold in classical general relativity. The nature of the quantum processes that take
place near a naked singularity, and their possible implication for observations, is briefly discussed. 相似文献
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旱作莜麦的气象条件及适宜种植区域 总被引：2，自引：0，他引：2
根据我国莜麦主栽区－内蒙古乌兰察布盟３０余年的莜麦种植情况和气象资料，以及两个旗县近１０年的莜麦气象观测数据，全面分析了莜麦生长的气象条件，提出实现莜麦高产稳产的最佳光、水配置指标。 相似文献
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T. P. Singh 《Journal of Astrophysics and Astronomy》1997,18(4):335-338
We give an elementary overview of the subject of gravitational collapse in classical general relativity. Recent theoretical
evidence for the formation of black-holes and naked singularities is summarised. 相似文献
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We have determined chlorophyll a (Chla) concentration, primary productivity, cell density and species composition of diatoms, and the number of microzooplankton at the surface in the subarctic North Pacific in January 1996. The wet weight of copepods obtained by vertical tows from 150 m to the surface was also measured during the cruise. Chla concentration and primary productivity tended to be higher in the region west of 180°, the western subarctic North Pacific (WSNP), than east of 180°, the eastern subarctic North Pacific (ESNP). The same results were observed for the total diatom cell densities and for the genera Thalassiosira and Denticulopsis. Significant linear relationships were observed between the Thalassiosira cell density and Chla concentration and primary productivity, indicating that Thalassiosira contributes to the high-WSNP and low-ESNP distribution patterns of Chla concentration and primary productivity. Moreover, naked ciliate abundance tended to be lower in the WSNP than in the ESNP, whereas copepod biomass showed an inverse trend. Significantly negative Spearman rank correlations were found between the Thalassiosira cell density and the number of naked ciliates and between the number of naked ciliates and the wet weight of copepods. These results indicate that copepod grazing indirectly controls Thalassiosira cell density via predation on the naked ciliates. We conclude that the high copepod biomass in the WSNP is a factor controlling the high-WSNP and low-ESNP Thalassiosira abundance and hence Chla concentration and primary productivity patterns. 相似文献
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近年来,基于消费级无人机搭载专业相机开展摄影测量,精度已达到测量级要求,并在多个行业得到推广应用。本文以当前开展的房地一体化测量工作为研究对象,探索出利用消费级无人机搭载专业相机获取倾斜影像,自动生成实景三维模型,并利用EPS专业软件开展裸眼三维测图的技术路线,并对测量结果进行精度验证。结果表明,航高低于100m,影像分辨率优于3cm,成图精度能够满足1∶500房地一体测量规范要求。 相似文献
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We consider a scenario where the interior spacetime, described by a heat conducting fluid sphere is matched to a Vaidya metric
in higher dimensions. Interestingly we get a class of solutions, where following heat radiation the boundary surface collapses
without the appearance of an event horizon at any stage and this happens with reasonable properties of matter field. The non-occurrence
of a horizon is due to the fact that the rate of mass loss was exactly counterbalanced by the fall of boundary radius. Evidently
this poses a counter example to the so-called cosmic censorship hypothesis. Two explicit examples of this class of solutions
are also given and it is observed that the rate of collapse is delayed with the introduction of extra dimensions. The work
extends to higher dimensions our previous investigation in 4D. 相似文献
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瓯江口树排沙湿地不同生境大型底栖动物群落多样性研究 总被引：1，自引：0，他引：1
为了解瓯江口树排沙湿地不同生境大型底栖动物群落多样性,于2014年10月至2015年6月对红树林、互花米草及光滩3种生境开展大型底栖动物调查。共鉴定出大型底栖动物48种,隶属于5纲15目31科40属。大型底栖动物年平均栖息密度和生物量,红树林生境最高,互花米草生境次之,光滩生境最低。采用物种多样性指数和G-F多样性指数分析不同生境大型底栖动物群落多样性,发现红树林生境大型底栖动物的多样性高于互花米草生境和光滩生境。单因素方差分析表明:物种数、栖息密度、生物量及物种多样性季节间差异不显著,而物种数、Shannon-Wiener多样性指数与Margalef物种丰富度指数生境间差异显著。人工恢复红树林有助于提高大型底栖动物群落的多样性。 相似文献
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YuJiao Wang ZhangDong Jin Ling Zhou FuChun Li Fei Zhang LiuMei Chen XinNing Qiu RuGui Qi 《中国科学:地球科学(英文版)》2014,57(10):2512-2521
Otoliths are biogenic carbonate minerals in the inner ear of teleost fish, whose compositions can record the physical and chemical conditions of the ambient water environment inhabited by individual fish. In this research, the fishbones and otoliths of naked carp sampled near the Bird Island, offshore Lake Qinghai, were dated and analyzed for mineralogy and microchemical compositions. Comparing the microchemical compositions of ancient otoliths with those of modern otoliths, we conclude that the ancient naked carps inhabited a relict lake formed when the lake shrank from a high lake level, by combining with the AMS-14 C ages of fishbones and otoliths, the stratigraphy and surrounding topography of the sample site. AMS-14 C dating results of ancient fishbones and otoliths show that these naked carps lived from 680 to 300 years ago, i.e. during the Ming Dynasty of China. The X-ray diffraction(XRD) patterns demonstrate that the ancient lapillus is composed of pure aragonite, identical to modern one, indicating that the mineral of lapillus didn't change after a long time burial and that the ancient lapillus is suitable for comparative analysis thereafter. Microchemical results show that both ratios of Mg/Ca((70.12±18.50)×10?5) and ? 18O((1.76±1.03)‰) of ancient lapilli are significantly higher than those of modern lapilli(average Mg/Ca=(3.11±0.41)× 10?5 and ? 18O=(?4.82±0.96)‰). This reflects that the relict water body in which the ancient naked carp lived during the Ming Dynasty was characterized by higher Mg/Ca and ? 18 O ratios than modern Lake Qinghai, resulting from strong evaporation after being isolated from the main lake, similar to today's Lake Gahai. Based upon the stratigraphy and altitude of naked carp remains, it can be inferred that the altitude of lake level of Lake Qinghai reached at least 3202 m with a lake area of 4480 km2 during the Ming Dynasty, approximately ~5% larger than it is today. 相似文献