GPS动态监测形变信息提取技术

采用GPS技术对矿区地表移动进行动态监测,针对长距离差分动态定位精度受多因素残余误差的影响,利用主成分分析法(PCA)进行空间滤波,分离区域站点相关的共模误差,以提高坐标序列精度。为进一步分析矿区地表移动受多源影响,采用解决盲信号分离问题的独立分量分析法(ICA),提取各测站形变信息。通过实例与仿真分析,结果表明,利用PCA空间滤波可提高3个分量坐标序列精度分别为46.1%,71.0%及36.8%;基于特征矩阵联合似对角化算法(JADE)进行ICA分解,能够实现各测站形变信息的提取。     

基于云原生的时空大数据平台设计与实现

作为测绘地理信息工作实现"两支撑、一提升"定位的服务载体、自然资源管理的统一底板、智慧城市的时空基础设施、数字孪生城市的空间数字底盘等,时空大数据平台已成为城市信息化建设不可或缺的内容.时空大数据平台服务领域不断扩大,对其在时空大数据汇聚、融合、管理、共享、分析,以及高可用、高并发、高弹性等方面的要求也不断提升.本文基...     

Twenty-first century Arctic climate change in the CCSM3 IPCC scenario simulations

Arctic climate change in the Twenty-first century is simulated by the Community Climate System Model version 3.0 (CCSM3). The simulations from three emission scenarios (A2, A1B and B1) are analyzed using eight (A1B and B1) or five (A2) ensemble members. The model simulates a reasonable present-day climate and historical climate trend. The model projects a decline of sea-ice extent in the range of 1.4–3.9% per decade and 4.8–22.2% per decade in winter and summer, respectively, corresponding to the range of forcings that span the scenarios. At the end of the Twenty-first century, the winter and summer Arctic mean surface air temperature increases in a range of 4–14°C (B1 and A2) and 0.7–5°C (B1 and A2) relative to the end of the Twentieth century. The Arctic becomes ice-free during summer at the end of the Twenty-first century in the A2 scenario. Similar to the observations, the Arctic Oscillation (AO) is the dominant factor in explaining the variability of the atmosphere and sea ice in the 1870–1999 historical runs. The AO shifts to the positive phase in response to greenhouse gas forcings in the Twenty-first century. But the simulated trends in both Arctic mean sea-level pressure and the AO index are smaller than what has been observed. The Twenty-first century Arctic warming mainly results from the radiative forcing of greenhouse gases. The 1st empirical orthogonal function (explains 72.2–51.7% of the total variance) of the wintertime surface air temperature during 1870–2099 is characterized by a strong warming trend and a “polar amplification”-type of spatial pattern. The AO, which plays a secondary role, contributes to less than 10% of the total variance in both surface temperature and sea-ice concentration.     

Future changes of El Niño in two global coupled climate models

Idealized forcing experiments with 1% per year CO₂ increase to stabilized doubled and quadrupled CO₂, twenty-first century transient scenario experiments (SRES scenarios A1B and B1), and stabilized twenty-second century A1B and B1 experiments with two global coupled climate models (PCM and CCSM3) are analyzed for possible future changes of El Niño events. With increased CO₂ in the models, there is a reduction of amplitude of El Niño events. This is particularly apparent with larger forcing in the stabilized 4×CO₂ experiment in PCM and the stabilized greenhouse gas A1B experiment in CCSM3, where the reduction of amplitude is outside the range of the inherent multi-century variability of El Niño in the control runs of the models and is statistically significant. With moderately increased forcing (stabilized 2×CO₂ in PCM and the stabilized B1 experiment in CCSM3), the reduction in amplitude is evident, but it is not significant. The change in El Niño behavior with larger forcing is attributed to the change in base state temperature in the equatorial Pacific, which is similar with increased greenhouse gases (GHGs) in both models. Positive temperature anomalies in and below the thermocline, associated with a reduction of the trade winds, and weakened Pacific Ocean subtropical cells, produce a less intense thermocline, and consequently lower amplitude El Niño events. The previously noted intensification of El Niño tropical precipitation anomalies in a warmer mean base state that applied when there was no appreciable change in El Niño amplitude does not hold in the present study where the El Niño events decrease in magnitude in a future warmer climate. North American surface temperature anomalies associated with El Niño are reduced and become less significant in the future events, with the anomalously deepened Aleutian low in the North Pacific weakened and moved eastward with greater radiative forcing. Part of this is attributed to the smaller amplitude events and thus lower amplitude teleconnections as indicated by contrasting composites of medium and high amplitude El Niño events from the control runs. The change in midlatitude base state circulation also contributes to the change in El Niño teleconnections. The effects of this change in base state on the weakened El Niño teleconnections over North America are confirmed in sensitivity experiments with a version of the atmospheric model in which heating anomalies are specified to mimic El Niño events in a base state changed due to increased GHGs.     

The crust and upper mantle discontinuity structure beneath Alaska inferred from receiver functions

In this study, three receiver function stacking methods are used to study the detailed crust and upper mantle structure beneath south-central Alaska. We used teleseismic waveform data recorded by 36 stations in the Broadband Experiment Across the Alaska Range (BEAAR) and 4 permanent stations in Alaska. H − κ stacking method using P-to-S converted wave and its multiply reflected waves between the Earth's surface and the Moho discontinuity is adopted to estimate the crustal thickness (H) and average crustal V_P/V_S ratio (κ) in this region. The receiver function results for 24 stations show that the crustal thickness under Alaska ranges from 26.0 to 42.6 km with an average value of 33.8 km, and the V_P/V_S ratio varies from 1.66 to 1.94 with an average value of 1.81 which corresponds to an average Poisson's ratio of 0.277 with a range from 0.216 to 0.320. High Poisson's ratios under some stations are possibly caused by partial melting in the crust and the uppermost mantle. Common converted point (CCP) stacking results of receiver functions along three lines show clear Moho and slab images under this subduction zone. The depths of the slab from our CCP stacking images are consistent with those estimated from the Wadati–Benioff Zone (WBZ). In the area between two stations DH2 (147.8°W, 63.3°N) and DH3 (147.1°W, 63.0°N), a Moho depth offset of about 10 km is found by both the H − κ and CCP stacking techniques. Common depth point (CDP) stacking of receiver functions shows not only the 410-, 520- and 660-km discontinuities, but also significant variations (−30 to 15 km) in the transition zone thickness under the southwest and southeast parts of the study region. The transition zone becomes thinner by 20–30 km, indicating that the temperature there is 150–200 K higher than that of the normal mantle.     

稳定同位素53Cr在地下水污染研究中的应用

铬是地表水和地下水中的常见污染物，它被广泛应用于电镀、制革和防腐。在氧化条件下，Cr以Cr(Ⅵ)的阴离子铬酸盐（CrO2-4）和重铬酸盐（HCrO-4）形式存在，有很高的溶解性和流动性。Cr(Ⅵ)是一种可疑的致癌物。在还原条件下，Cr的分馏。所有地下水Cr(Ⅲ),它不溶解，并且强烈地吸附在固体表面上，而且毒性很小。Cr(Ⅵ)的还原作用可导致Cr稳定同位素轻同位素。因此，稳定铬同位素比值可以用作地下水中Cr(Ⅵ)还原程度的指示剂。笔者使用方程（1）确定了两个地下水样（MW-6和MW-12）的还原程度，它们分别为31%和68%。     

A study of the human-fatality rate in near-fault regions using the Victim Attribute Database

After the 1999 Chi-Chi earthquake, the Taiwanese government immediately issued new guidelines prohibiting the construction of structures for human occupancy within the Chelungpu fault zone. However, these guidelines were not based upon an in-depth hazard analysis of the near-fault regions. The positions of more than 80% of the 2,492 victims of the Chi-Chi earthquake were found by our research team. A Victim Attribute Database has been compiled that includes the GPS coordinates of the positioned victims as well as other attribute data associated with the victims. The human-fatality rates in the near-fault regions have been analyzed with regard to distances from the Chelungpu fault, the hanging-wall and footwall areas, as well as building type. The severity at the human-fatality rates in the near-fault regions is inversely proportional to distances from the causative fault, i.e., the closer the distance, the higher the human-fatality rate observed. The human-fatality rate for victims who lived in closer proximity to the hanging-wall areas is also significantly higher than those who lived in closer proximity to the footwall areas, especially in areas on either side of the fault and within 1,000 m of the fault surface trace. In terms of different building types, factors that include the capacity of the buildings to resistant strong shaking and the level of strong ground-motion greatly affected the human-fatality rates in the hanging-wall and footwall areas. Therefore simply prohibiting the construction of buildings within the active fault zone would be an insufficient method of reducing the number of potential victims; a nationwide effort should be undertaken to upgrade the capacity of buildings to resist strong shaking.     

精密单点定位中周跳探测与修复方法研究

分析了Geometr-Free以及Melbourne-Wubbena两种组合的性质,使用多种周跳探测方法对两种组合分别进行周跳的探测,计算了各个频率上发生的周跳大小,实现了周跳的修复.     

The sources,pathway, and preventive measures for fluorosis in Zhijin County,Guizhou, China

The F content of several materials from households of Zhijin County, one of the most severe endemic fluorosis-stricken areas in western Guizhou, was determined using the pyrohydrolysis/fluoride ion-selective electrode method to determine the sources of F and the pathways causing the disease. The average F content of the coal burned is 237 μg/g, the clay used as a binder for fine coal is 2262 μg/g, with 828 μg/g in the mixed coal and clay, while the F content of corn is 1419 μg/g, with 110 μg/g in chilies. The binder clay is found to be the main F source for the endemic fluorosis. Fluorine in the clay not only occurs in apatite and hornblende, but also is associated with illite and mixed-layer clay minerals of smectite and illite. About 80% of the F is released during combustion of the mixture. The F content of corn and chilies is about 1000 and 110 times higher, respectively, than the permitted level of F in foodstuffs according to the Chinese Standard GB 4809-84. Most of the F in corn and chilies probably occurs either in smoke dusts attached to the surface or is adsorbed onto the outer peel, rather than being absorbed by the inner part. Thus, in addition to developing F-sequestration technologies, changing the living habits of the residents in the endemic area, for example, washing corn and chilies before cooking and peeling corn before being pulverized into corn flour, will remove a large proportion of the F, and thus it can play an important role in endemic fluorosis prevention.