On the Disappearance of Kilohertz Quasi-periodic Oscillations at a High Mass Accretion Rate in Low-Mass X-Ray Binaries

We here investigate the possibility that the ultra-high-energy cosmic-ray (UHECR) events observed above the Greisen-Zatsepin-Kuzmin (GZK) limit are mostly protons accelerated in reconnection sites just above the magnetosphere of newborn millisecond pulsars that are originated by accretion-induced collapse (AIC). We formulate the requirements for the acceleration mechanism and show that AIC pulsars with surface magnetic fields 1012 G/=10(20) eV. Because the expected rate of AIC sources in our Galaxy is very small ( approximately 10(-5) yr(-1)), the corresponding contribution to the flux of UHECRs is negligible and the total flux is given by the integrated contribution from AIC sources produced by the distribution of galaxies located within the distance that is unaffected by the GZK cutoff ( approximately 50 Mpc). We find that reconnection should convert a fraction xi greater, similar0.1 of magnetic energy into UHECRs in order to reproduce the observed flux.     

COMBINATION OF ECMWF REANALYZED DAILY RAINFALL AND PENTAD CMAP IN CHINA

In this study, 16 combinations of the ECMWF (European Centre for Medium-Range Weather Forecast) reanalyzed daily rainfall and the pentad CMAP in China for the period 1980- 1993( 1May - 31 Dec. ) were calculated. Correlation analysis was used to roughly evaluate daily rainfall for the whole of China and a combination of RPC (rotated principal component) and wavelet analyses was applied to data on observed and combined daily rainfall to obtain a detailed evaluation of the quality of these combined datasets in 6 selected major rainfall regions of eastern China. The results showed that except for intraweekly fluctuation, the best combination was roughly similar to or accorded well with observation in the aspects of space variation patterns and long period rainfall fluctuations related to monsoon onset and serious meteorologic disasters, indicating that this combination yielded better values of long term daily mean and standard deviation through the pentad CMAP ( CPC Merged Analysis of Precipitation), and can also represent rainfall fluctuations through the reanalyzed daily rainfall.     

关于垃圾填埋场渗滤系统渗透性能经时变化的研究

利用模拟实验对垃圾填埋场中渗滤系统的渗透性能与填埋时间的关系进行了研究。采用焚烧灰、土工织物和碎石导流层组成渗透系统,研究了实验时间对渗滤系统的渗透系数以及结晶物颗粒直径的影响。结果表明:由于垃圾焚烧灰中硅酸钙和铝酸钙的结晶作用,随着渗透时间的增加,吸附在土工织物表面的物质逐渐增多,使颗粒之间更紧密,导致空隙减小影响渗滤系统的渗透性能。根据研究结果,在垃圾焚烧灰填埋时,垃圾焚烧灰压实密度不要太高,这样有利于渗滤液的排放。     

Exercise in downscaling on sea surface temperature along Chinese coast

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川渝地区夏季降水变化气候特征分析

利用川渝地区34站1960—2006年共计47年的逐月降水量资料,采用经验正交函数（BOF）分解、旋转经验正交函数（REOF）分解、小波分析等方法详细讨论了川渝地区夏季降水量的时空变化特征。结果表明：川渝地区夏季降水量时空分布不均,川渝地区夏季降水量可以分为3个区,分别是川西高原区、盆地中部区和盆地东部区。近50年来,川渝地区夏季降水量具有显著不同的年代际变化特征,川西高原和盆地东部夏季降水量长期变化呈增加的趋势,而盆地中部呈减少的趋势。川渝各区夏季降水量具有显著不同的多时间尺度的周期变化特征,其中川西高原具有准15年和准5年的周期变化特征,盆地中部具有准14年、准6年和准3年的周期变化,盆地东部具有准16年、准8年和准3年的周期变化特征。     

基于Item2Vec负采样优化的专题地图产品个性化推荐方法研究

建立适用于专题地图产品检索的用户偏好推荐模型是提高专题地图质量的有效方式之一,在专题地图产品推荐场景中,存在严重的内容冷启动和评论数据稀疏问题,现有的推荐算法无法为特定类用户推荐不同特征的专题地图产品,导致用户从专题地图中获取偏好信息受到限制。因此,本文构建基于负采样的连续词袋模型和基于Word2Vec的Item2Vec相结合的用户偏好推荐方法,用于专题地图产品推荐。① 计算用户行为日志文件中交互行为数据的隐性评分,以代替专题地图推荐信息流场景中稀疏的用户评论数据;② 基于负采样的连续词袋模型提取目标专题地图的前后地图序列感知特征信息,通过控制正负样本比例为1:2,提升目标专题地图潜在评分的预测精度;③ 通过Item2Vec将带有用户行为特征信息的专题地图映射到向量空间,计算用户对专题地图的相似度矩阵,根据用户偏好程度完成推荐。在构建的专题地图评分实验数据集Thematic CMaps和4个公开验证数据集MovieLens上的测试结果表明:与LFM、Personal Rank、Content Based和SVD 4种传统推荐算法相比,本文所提方法可有效提高潜在评分的预测精度,推荐性能最高达到27.85%;与以霍夫曼采样方式的Item2Vec基础方法和YouTubeNet 2种神经网络推荐算法相比,评分预测精度有一定提高,且推荐性能不断提升,最高达到2.97%和5.78%。以经典算法奇异值分解（SVD）为例,将MovieLens-20M数据集切分后,在数据量不断增大的数据子集中,本文所用方法的评分预测精度和性能均优于SVD方法。     

黄河北岸兰州段丘陵区土壤生态化学计量与空间变异北大核心CSCD

为探究黄河北岸兰州段丘陵区土壤碳、氮、磷含量及化学计量比的空间变异特征,基于12个样地数据,采集1 m剖面内不同发生层土壤进行土壤含水率(SWC)、pH、有机碳(SOC)、全氮(STN)和全磷(STP)的测定。分析了研究区土壤碳、氮、磷含量及其生态化学计量特征在植被和土层上的差异及空间变异特征。结果表明:(1)研究区SOC、STN、STP均值分别为4.53、0.74、0.13 g·kg^(-1),C∶N、C∶P、N∶P均值分别为7.85、55.17、8.40;(2)研究区SOC、STN、C∶N和N∶P的块基比C_(0)/(C_(0)+C)<0.25,主要受气候、植被、地形等自然因素影响;STP、C∶P则C/(C+C)>0.75,主要受退耕还草等人为因素影响;(3)研究区土壤整体受到氮限制,与此同时有机碳更为匮乏,磷则在短期内不会成为限制因子。在黄河流域兰州段北岸丘陵区北岸的生态治理与恢复中,应重视有机肥和氮肥的配置与施加,同时需减少人为干扰,这对于植被的快速恢复与养分的固定具有重要意义。     

1208-1369年陕甘宁交界地区干湿变化

More than 240 items of historical records containing climatic information were retrieved from official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using moisture index and flood/drought (F/D) index obtained from the above information, the historical climate change, namely wet-dry conditions in borderland of Shaanxi Province, Gansu Province and Ningxia Hui Autonomous Region (BSGN, mainly included Ningxialu, Hezhoulu, Gongchanglu, Fengyuanlu and Yan’anlu in the Yuan Dynasty) was studied. The results showed that the climate of the region was generally dry and the ratio between drought and flood disasters was 85/38 during the period of 1208–1369. According to the frequencies of drought-flood disasters, the whole period could be divided into three phases. (1) 1208–1240: drought dominated the phase with occasional flood disasters. (2) 1240–1320: long-time drought disasters and extreme drought events happened frequently. (3) 1320–1369: drought disasters were less severe when flood and drought disasters happened alternately. Besides, the reconstructed wet-dry change curve revealed obvious transition and periodicity in the Mongol-Yuan Period. The transitions occurred in 1230 and 1325. The wet-dry change revealed 10- and 23-year quasi-periods which were consistent with solar cycles, indicating that solar activity had affected the wet-dry conditions of the study region in the Mongol-Yuan Period. The reconstructed results were consistent with two other study results reconstructed from natural evidences, and were similar to another study results from historical documents. All the above results showed that the climate in BSGN was characterized by long-time dry condition with frequent severe drought disasters during 1258 to 1308. Thus, these aspects of climatic changes might have profound impacts on local vegetation and socio-economic system.     

郑州望京楼遗址二里头文化时期植物资源的利用——来自石器残留淀粉粒的证据

通过对郑州望京楼遗址出土的二里头文化时期石杵和石臼进行淀粉粒分析,发现了5类可鉴定的不同形态淀粉粒,主要为粟黍类、小麦族(Triticeae)、薏苡属(Coix)、栎属(Quercus)和豆科(Fabaceae)等,以及部分未知种属的淀粉粒。石臼和石杵的使用部位形态多样的淀粉粒表明此类工具在当时被用于加工处理多种植物种子或果实。望京楼遗址二里头文化时期石器上粟、黍以及小麦等多种农作物淀粉粒的发现,同时结合二里头、南洼、皂角树等二里头文化遗址植物浮选结果,表明二里头文化时期中原腹心地区已普遍存在多品种的农作物种植。     

泰山旅游环境承载力及其时空分异特征与利用强度研究

旅游环境承载力作为一种稀缺性非实物资源具有空间分异和时间变化规律;文章采取静态的模型研究方法,对泰山主景区的旅游环境承载力作出了系统测算,揭示了其时空分异规律,剖析了旅游环境承载力资源的利用强度,提出了旅游调控策略。