双曲复数与时空球

利用Clifford代数的双曲虚单位引入双曲复数,双曲复平面,时空圆及时空球等概念,用于讨论狭议相对论中的物理问题.

静态球对称时空中Dirac方程分离变量及退耦

将一般静态球对称背景时空下的Dirac方程分离变量,得到退耦的径向方程和角向方程.从结果来看,不同的球对称时空其视界函数只影响径向方程,而不影响角向方程,这为进一步研究具有不同视界函数的静态球对称时空中Dirac粒子的行为提供了依据.

静态球对称时空中的标量场辐射

采用多项式函数代替乌龟坐标的方法,给出静态球对称时空中黑洞事件视界和宇宙视界区域内标量场方程的解,并对事件视界附近势垒的性质进行了讨论。发现对带电量不同的时空,标量场辐射的形式亦有所不同;势垒随宇宙学常数的减小而变窄、变高。

时空单位球与Lorentz变换

利用 Clifford代数的双曲虚单位 ,引入双曲复空间及时空单位球等概念 ,用于讨论Minkowski时空与 Lorentz变换 .

球对称稳态时空中标量场辐射的反射系数和透射系数

采用以方形势垒代替球对称稳态时空中视界附近的势垒的方法,计算了球对称稳态时空中标量场辐射的反射系数和透射系数,发现在此种类型的时空中,标量场的投射系数均接近于1,即所有的标量场都将透过势垒而传播到无穷远。

一般球对称动态时空中时间尺度变换的补偿效应

一般球对称动态时空中的Hawking效应可看作时间尺度变换下的补偿效应 .时间尺度变化率以规范势的形式出现 ,补偿场纯规范势的两个分量分别表征黑洞温度和温度变化率 .

动态球对称时空中的Dirac能级

本文准确地计算了动态球时空中的Ｄｉｒａｃ能级表达式，并对动态对称黑洞介附近的Ｄｉｒａｃ能级的性质进行了讨论。

时空代数的若干性质及应用

由Clifford代数引入时空代数 ,时空球 ,时空单位球 ,时空单位球面等概念 .利用时空单位球面的性质导出四维时空的一般Lorentz变换 .

黑洞附近修正的Stefan-Boltzmann定律

该文在一般球对称静态黑洞背景下,用WKB近似法得到黑洞附近修正的StefanBoltzmann定律.发现在黑洞事件视界附近,由于场自旋的存在,结果中除了类似于平直时空的主导项外,多了一个和局域温度二次方成正比的附加项.该项的出现暗示黑洞的辐射可能不是精确热的.

PC-based artif icial neural network inversion for airborne time-domain electromagnetic data

Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets.

Global Water Vapor Content Decreases from 2003 to 2012： An Analysis Based on MODIS Data

Water vapor in the earth′s upper atmosphere plays a crucial role in the radiative balance, hydrological process, and climate change. Based on the latest moderate-resolution imaging spectroradiometer(MODIS) data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor content declined from 2003 to 2012(slope b = –0.0149, R = 0.893, P = 0.0005). The decreasing trend over the ocean surface(b = –0.0170, R = 0.908, P = 0.0003) is more explicit than that over terrestrial surface(b = –0.0100, R = 0.782, P = 0.0070), more significant over the Northern Hemisphere(b = –0.0175, R = 0.923, P = 0.0001) than that over the Southern Hemisphere(b = –0.0123, R = 0.826, P = 0.0030). In addition, the analytical results indicate that water vapor content are decreasing obviously between latitude of 36°N and 36°S(b = 0.0224, R = 0.892, P = 0.0005), especially between latitude of 0°N and 36°N(b = 0.0263, R = 0.931, P = 0.0001), while the water vapor concentrations are increasing slightly in the Arctic regions(b = 0.0028, R = 0.612, P = 0.0590). The decreasing and spatial variation of water vapor content regulates the effects of carbon dioxide which is the main reason of the trend in global surface temperatures becoming nearly flat since the late 1990 s. The spatio-temporal variations of water vapor content also affect the growth and spatial distribution of global vegetation which also regulates the global surface temperature change, and the climate change is mainly caused by the earth's orbit position in the solar and galaxy system. A big data model based on gravitational-magmatic change with the solar or the galactic system is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatio-temporal variations of global water vapor content, vegetation and temperature at large spatio-temporal scale. This comprehensive examination of water vapor changes promises a holistic understanding of the global climate change and potential underlying mechanisms.

Detecting Global Vegetation Changes Using Mann-Kendal(MK) Trend Test for 1982–2015 Time Period

Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index(NDVI) from the Advanced Very High Resolution Radiometer(AVHRR) Global Inventory Modeling and Mapping Studies(GIMMS) time series(1982–2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal(MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends(P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types.

A New Upsurge in Global Seismicity

This paper studies the temporal and spatial distribution of great global earthquakes （Mw i〉 8.0） since 1900. We compare the two periods of upsurges of great earthquakes occurring in the middle of last century and beginning of this century. The former period took place between 1950 and 1965 during which 13 great earthquakes （Mw I〉 8.0） occurred, including three events with moment magnitude greater than 9. 0. The largest magnitude in this period reached 9.6. The latter period starts from the beginning of this century. In less than 12 years, 15 great earthquakes have attacked the world with the largest magnitude being Mw 9. 1. On the basis of comparison between these two upsurges of global earthquake activity, we infer that the ongoing high level of earthquake activity may continue for another five years or so. Numerous great earthquakes （Mw I〉8. 0） and many large earthquakes （Mw6.0 ~ 7. 0） will occur globally in these five years. In addition, this paper also discusses the relationships between earthquake activity along the Sumatra segment of the Indian-Australia plate boundary and that in the Bayankala block in the middle of Qinghai-Tibetan plateau as well as in the blocks of the southern plateau. The results indicate that the Qinghai-Tibetan plateau, in particular its middle and southern parts, is a likely place for future earthquakes of magnitude over 7.0.

Spatio-temporal Analysis of Urban Spatial Interaction in Globalizing China—A Case Study of Beijing-Shanghai Corridor

This paper aims to explore urban geography with a new perspective. Endowed with the urban geography connotations, an improved data field model is employed to integrate temporal dimension into spatial process of cities in a typical region in this article. Taking the Beijing-Shanghai Corridor including 18 cities as an example, the authors chose the city centricity index (CCI) and the spatial data field model to analyze the evolution process and features of sub-region and urban spatial interaction in this corridor based on the data of 1991, 1996 and 2002. Through the analy- sis, we found that: 1) with the improvement of the urbanization level and the development of urban economy, the cit- ies’ CCI grew, the urban spatial radiative potential enhanced and the radiative range expanded gradually, which reflects the urban spatial interaction’s intensity has been increasing greatly; 2) although the spatial interaction intensity among the cities and sub-regions in the Beijing-Shanghai Corridor was growing constantly, the gap of the spatial interaction strength among different cities and sub-regions was widening, and the spatial division between the developed areas and the less developed areas was obvious; and 3) the intensity of the spatial interaction of Beijing, Shanghai and their urban agglomerations was far greater than that in small cities of other parts of the corridor, and it may have a strong drive force on the choice of spatial location of the economic activities.

Spatio-temporal distribution of dissolved sulfide in China marginal seas

With sulfide increasingly recognized as an important parameter to assess the oxidation-reduction level in aqueous enviromnent, research on its geochemical behavior is becoming important. Water samples collected in Bohai Sea （1-19 August, 2010）, Yellow Sea （20-30 November, 2010） and East China Sea （3-17 June, 2010 and 1-10 November, 2010） were used to determine the occurrence and distribution of dissolved sulfide by methylene blue spectrophotometric method. Results show that： （1） horizontally, concentration of dissolved sulfide significantly varied from the coastal region to the open sea and profoundly influenced by physical processes. High values occurred in the river-sea boundary zone ＂marginal filter＂ due to rich riverine input, frequent upwelling and active exchange in shelf edge. Terrestrial input from adjacent rivers and the current cycling contributed to the high sulfide appeared in western Bohai Sea, eastern Shandong Peninsula, and northeast of Changjiang （Yangtze） River estuary. Especially, relative higher sulfide values occurred in Yellow Sea, which is consistent with the variation of salinity largely due to the hydrodynamic feature; （2） vertically, measurement of dissolved sulfide in bottom water was higher and more variable than that in surface water caused by the wind-induced resuspension and dissimilatory sulfate reduction. Moreover, nutrient-type profile clearly identified that oxidation plays a major role in the biogeochemistry cycle of sulfide in water; （3） seasonally, investigation for East China Sea in June and November reflected seasonal variation of Changjiang River Diluted Water, Kuroshio Current, and Taiwan Warm Current. Concentration in June was much higher than that sampled in November at most stations. Mean concentration of dissolved sulfide varied seasonally from 2.26 μg/L （June） to 1.16 μg/L （November） in surface and 3.00 μg/L （June） to 1.56 μg/L （November） in bottom. Progress in the field is slow and more effort is needed to ensure the accuracy and reliability of determination and estimate the natural or anthropogenic contribution of dissolved sulfide in ecosystems.

London Poems and History

In this article, I read different poems of London through the perspectives of time and the self. The city of London, as a physical space, a world in the Alfred Tennyson＇s Cleopatra＇s Nee history to Tennyson＇s Victorian Lo globe, is changing dle, the flow of tid ndon. The Needle through both inner time and outer time. Firstly, in Lord e symbolises the passing time, through the long Egyptian has been through different seas and places. The sense of history, a fusion of inner time and outer time, is claimed by the Needle＇s subjective self, seeing London as a ＂monster town＂. Secondly, Ahren Wamer＇s Greek titled poem is trying to locate the one in London, which cannot be localized, in the trend of globalization, as the gazer observed on the bus. Struggling between the self and the other, inner and outer existences, happiness and being unhappy, W. B. Yeats＇ from Vacillation comes to show the reader that through reflection and memory, the sense of one＇s own self can be reinforced and affirmed, while creating one＇s own personal history. Last but not the least, I read a part from T. S. Eliot＇s Four Quartets As the dialectic of light and shadow plays a sense of Beauty, the soul is aware of all fancy things, but only without any meanings. The question of the self and tradition, the poet and the world, somehow, is a timeless one

Remote sensing needs and capabilities in West Africa

The greatest advantage of remote sensing over conventional measurements lies in the opportunity to carry out detailed spatio-temporal analysis of land and ocean features on a very frequent basis. This paper analyses the contribution of satellite imagery to atmospheric, geophysical and ocean studies and management in West Africa since the early 1980s. The detailed application of data from optical sensors (e.g. Meteosat,NOAA/AVHRR, SPOT, Landsat TM, etc.) for weather prediction, hydrogeologicah landuse/cover and cartographic studies has been acknowledged. However, the use of microwave (e.g. SAR) and optical data for ocean monitoring and studies in the sub-region is still very limited. Even though sufficient remote sensing expertise and infrastructure is perceived in the region, no clearly defined networking or database exists.

轴对称黑洞的量子统计熵

避开了求解黑洞背景下波动方程的因难,应用量子统计方法,通过应用在量子引力中、由广义测不准关系得出的新态密度方程,直接求解轴对称Kerr黑洞背景下玻色场和费米场的配分函数.然后,在视界附近计算黑洞背景下玻色场和费米场的熵.得到用收敛级数表达的黑洞熵.在计算中不存在用brick wall模型计算黑洞熵时出现的发散项和小质量近似,使人们对非球对称时空中黑洞的统计熵有更深入的认识.

Spatio-temporal evolution of drought and flood disaster chains in Baoji area from 1368 to 1911

Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of drought and flood disaster chains in this area during the Ming and Qing dynasties using the methods of moving average, cumulative anomaly and wavelet analysis. The results are as follows:(1) We found a total of 297 drought and flood events from 1368 to 1911 in Baoji. Among these events, droughts and floods occurred separately 191 and 106 times, which accounted for 64.31% and 35.69% of the total events, respectively.(2) We observed distinct characteristics of flood and drought events in Baoji in different phases. The climate was relatively dry from 1368 to 1644. A fluctuant climate phase with both floods and droughts occurred from 1645 to 1804. The climate was relatively wet from 1805 to 1911. Moreover, we observed a pattern of alternating dry and wet periods from 1368 to 1911. In addition, 3 oscillation periods of drought and flood events occurred around 70 a, 110 a and 170 a, which corresponded to sunspot cycles.(3) We also observed an obvious spatial difference in drought and flood events in Baoji. The northern and eastern parts of Weihe River basin were regions with both frequent droughts and floods.(4) The sequential appearance of drought and flood disaster chains in Baoji from 1368 to 1911 was in response to global climate change. Since the 1760s, global climatic deterioration has frequently led to extreme drought and flood events.

Research into tritium and helium-3 contents distributions in steel wall of spherical pressure vessel

The tritium quantity stored in a steel pressure vessel decreases with time because of helium-3 decay and permeation of tritium into the steel wall of the pressure vessel.Meanwhile,the tritium quantity permeating into the steel wall also decreases with time due to helium-3 decay and diffusion in and out of the wall of tritium.Tritium and helium-3 in the steel wall will cause hydrogen and helium embrittlement of the wall material,respectively,and thereby change the carrying capacity of the vessel.Taking contemporarily both decay and permeation of tritium within the vessel and decay and diffusion of tritium having permeated into the wall into consideration,the governing equations of tritium and helium-3 contents in the wall were established and solved,and relevant formulas were deduced.Through analytical calculations,curves of tritium and helium-3 contents versus radius and time were theoretically plotted,the contents spatio-temporal distributions laws were obtained,and a law about helium-3 contents distribution in steel wall of a spherical pressure vessel was discovered which was called the law of double helium-3 content.