A preventative approach to mitigating CW interference in GPS receivers

In the global positioning system (GPS), code division multiple access (CDMA) signals are used. Because of the known spectral characteristics of the CDMA signal, continuous wave (CW) interference has a predictable effect on the different pseudo random noise (PRN) spreading codes (unique to each satellite) depending on the Doppler frequency of the signal. The Doppler frequency for each signal is also predictable once the receiver position is known. As different satellite signals have different Doppler frequencies, the effect on the signal quality is also different. In this paper first the effect is studied analytically. The concept of an “exclusion zone” is defined and analyzed for each satellite. This exclusion zone, where that satellite should not be used due to interference degradation, is shown to be predictable for each satellite as a function of time. Using this prediction, the CW interference effect on the positioning quality of the receiver can be mitigated by ignoring the affected satellites within exclusion zones when performing position evaluation. The threshold beyond which a satellite should be excluded is then derived by studying the mutual effects of the geometry and the signal quality of that satellite on the positioning quality. Receiver autonomous integrity monitoring (RAIM) uses redundancy in measurements to perform an internal consistency check to see if all of the measurements are satisfactory. In this paper this technique is also used to mitigate the effect of CW interference on the positioning accuracy. Finally it is shown that the prediction of the exclusion zone for each satellite outperforms the RAIM algorithm in mitigation the effect of the interference when 5 satellites are visible. An erratum to this article can be found at     

响应面法优化鹿角菜中岩藻多糖的提取工艺

在单因素试验的基础上,利用Box-Benhnken中心组合实验设计,采用响应面法对鹿角菜(Pelvetia siliquosa)中岩藻多糖的提取工艺进行优化。结果表明,液料比、水浴温度和水浴时间对岩藻多糖提取率均有显著影响;最佳提取工艺条件为:液料比(m L/g)32、水浴温度90℃、水浴时间8.4 h,此时岩藻多糖最高提取率为5.2005%,与理论值5.2153%相比,相对误差很小。响应面模型与实际情况拟合良好,采用响应面法对鹿角菜中岩藻多糖提取条件进行优化合理可行。     

Utilization of high-resolution EGM2008 gravity data for geological exploration over the Singhbhum-Orissa Craton,India

High-resolution EIGEN6C4 and EGM2008 Bouguer gravity data of 2190 degree spherical harmonic over the Singhbhum-Orissa Craton, India, have been generated from the International Centre for Global Earth Models. The Bouguer gravity anomaly difference maps of (i) in situ and EIGEN6C4, (ii) in situ and EGM2008 and iii) EIGEN6C4 and EGM2008 of the study area are compared. It reveals that EIGEN6C4 has lesser systematic error than EGM2008. However, from different profile plots of Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of the in situ, EIGEN6C4 and EGM2008, it is observed that most of the signatures of lithounits and geological structural elements are delineated very well by EGM2008 and match 94–98% with those of EIGEN6C4. Further, the Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of EGM2008 data over the study area have been used effectively for identifying various lithounits and geological structural elements.     

Anomalous drip in the Punkva caves (Moravian Karst): relevant implications for paleoclimatic proxies

The anomalous drip in the Punkva caves (Moravian Karst) shows specific hydrogeochemical properties such as low SI_calcite ~ 0.14 ± 0.11 (standard deviation), low mineralization (4.53 ± 0.42) × 10^?3 mol l^?1, and enhanced values of δ¹³C (?7.85 to ?8.35‰ VPDB), Mg/Ca × 1000 ratio (45.7 ± 3.3), and Sr/Ca × 1000 ratio (0.65 ± 0.06). By these properties, the anomalous drip significantly differs from other regular drips in the same cave and other caves in the region. The study suggests that the anomalous drip properties are a consequence of prior calcite precipitation or/and water mixing along the water flow path. As the former processes are spatially controlled, the knowledge of dripwater flow path seems to be necessary for correct paleoclimatic/paleoenvironmental reconstructions. Copyright © 2015 John Wiley & Sons, Ltd.     

长江三峡非正常含炭粘土沉积及其地质灾害意义

在长江三峡工程库区巫山、奉节、云阳等新县城进行工程地质勘察过程中, 发现在长江岸坡地带存在含炭粘土沉积.对部分含炭粘土进行了14C年龄测定, 年龄测定结果与该含炭粘土层所在高程相当的阶地形成年代不一致, 含炭粘土为非正常沉积.非正常含炭粘土的存在与发现, 一方面揭示出巫山等移民新县城斜坡经历了非正常的形成演化; 另一方面说明长江三峡河谷演化过程中夹杂着突发的地质灾害事件.      

“死碳”对14C年代测定影响的初步研究

在回顾14 C测年技术发展的基础上,指出了影响14 C测年精度的各种因素,并初步讨论了“死碳”对14 C年代的影响。通过对岩溶区“死碳”的成因分析以及对碳酸盐样品的14 C年代学研究,认为酸的来源不同,是造成岩溶区样品14 C年代偏老的原因;局部环境中“死碳”释放是造成水生样品14 C表观年龄偏老的主要原因。由于影响岩溶区样品14 C年龄的因素是多方面的,目前尚无有效的校正办法。为此,作者在讨论了洞穴碳酸盐样品年代的可靠性及影响因素的基础上,提出了用交叉对比定年的方法解决“死碳”对14 C测年的影响问题和在岩溶地区谨慎使用14 C年龄的建议。      

区域气候模式对温室效应引起的中国西北地区气候变化的数值模拟

使用RegCM2区域气候模式,进行了CO₂加倍对中国区域气候影响的数值试验,对西北地区进行了重点分析.结果表明,在CO₂加倍的情况下,西北地区的气温将明显升高,年平均升高值为2.7℃,高于全国平均变化.同时降水也将明显增加,平均增加率达到25%,远高于全国平均,增加率的数值大小依次为冬季、春季、秋季和夏季.     

Late glacial to Holocene planktic foraminifera bioevents and climatic record in the South Adriatic Sea

Quantitative analyses of planktic foraminifera, sea‐surface temperatures (SSTs), oxygen isotope and radiocarbon dating from a deep‐sea core recovered in the South Adriatic Sea have been used to reconstruct a subcentennial climatic and biochronological record since the late glacial (the last 24 cal. ka BP). The identification and relative abundance of 25 species of planktic foraminifera along the core have provided a continuous record of the faunal changes over this time interval. These results have permitted the establishment of 10 biozones in the South Adriatic Sea based on the appearance and/or disappearance of the main specific taxa, from peaks of abundance and/or by modification in marine conditions. The robust chronology of the South Adriatic core allowed correlation of SST estimates to the GISP2 ice core record, indicating that the main climate changes recorded in Greenland ice cores over the last 24 ka are recorded and globally synchronous with those observed in the South Adriatic Sea. This finding further allows comparison of the planktic foraminifera record with the event stratigraphic scheme proposed by the INTIMATE group in order to better identify the relationship between past climatic changes and the response of microfaunal assemblages in the South Adriatic. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal stress assessment using carbon and oxygen isotopes from Scleractinia,Rocas Atoll,northeastern Brazil

More than 430 C and O isotope analyses were carried out on carbonates from six coral species collected during June 1995, July 1998 and February 1999 at Rocas atoll, offshore northeastern Brazil: Siderastrea stellata Verrill 1868, Porites branneri Rathbum 1887, Porites astreoides Lamarck 1816, Mussismilia hispida Verrill 1902, Madracis decactis Lyman 1859 and Montastrea cavernosa Linnaeus 1886. Samples were collected in pools within the ring of the atoll, at water depths from 1.0 to 7.0 m. Oxygen isotope chemistry demonstrated that the studied species experienced several periods of bleaching; calculated temperature for one species vary, suggesting important changes within the time scale of coral growth. The species P. branneri, P. astreoides, M. cavernosa and the Brazilian endemic species M. hispida registered temperature variations during coral growth more accurately than did S. stellata and M. decactis. Carbon isotope behaviour in coral skeletons of the species examined at this atoll seems to have maintained a close relationship between density and/or zooxanthelar productivity: the greater the algal density, the heavier the δ¹³C values in skeletons.     

Upper Campanian-Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin: Towards a standard δC curve for the Boreal Realm

High-resolution carbon isotope stratigraphy of the upper Campanian-Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-resolution δ¹³C profile from Rørdal, northwestern Denmark. A quantitative approach is used to test the reliability of Upper Cretaceous nannofossil bio-events and provides accurate biohorizons for the correlation of δ¹³C profiles. The Campanian-Maastrichtian boundary (CMB) is identified through the correlation of dinoflagellate biostratigraphy and δ¹³C stratigraphy between Stevns-1 and the Global boundary Standard Stratotype-section and Point at Tercis les Bains (SW France), allowing the identification of new chemical and biostratigraphic markers that provide a precise placement of the stage boundary on a regional scale. The boundary interval corresponds to the third phase of a stepwise 0.8‰ negative δ¹³C excursion, lies in calcareous nannofossil subzone UC16d^BP, and encompasses the last occurrence of nannofossil Tranolithus stemmerikii and first occurrence of nannofossil Prediscosphaera mgayae. Fifteen δ¹³C events are defined and correlated to sixteen reliable nannofossil biohorizons, thus providing a well-calibrated standard high-resolution δ¹³C curve for the Boreal Realm.