Test of a convectively forced gravity wave drag parameterization in a general circulation model

The influence of gravity wave drag induced by cumulus convection (GWDC) on a simulated boreal summer climate was evaluated in a general circulation model. For this, the GWDC scheme developed by Chun and Baik was implemented into a version of the National Centers for Environmental Prediction (NCEP) global spectral model (GSM). Ensemble simulations with the two different convection schemes, the simplified Arakawa-Schubert (SAS) scheme and Community Climate Model (CCM) convection scheme, were conducted for the boreal summer of 1996. A cloud factor to modulate the stress intensity with respect to the cloud type was introduced in this study, in order to prevent unrealistic behaviors of the GWDC scheme in GSM. The effect of gravity wave drag on the zonal mean of wind and temperature fields was focused. On the whole, the effect of GWDC in this study is positive on the simulated seasonal climate. It is evident that biases in temperature in the polar region as well as in the zonal and meridional winds in the upper atmosphere are reduced. The percentage of reduction of the bias in zonal winds is about 10–20%. Such a response of the GWDC forcing widely appears not only in tropical regions but also in mid-latitude regions. These characteristics are prominent in the case of the SAS scheme, which is due to the various convective cloud types. The magnitude of GWDC forcing is generally small, but still positive, in the case of the CCM scheme, which is due to rather homogeneous cloud types. It is also found that the role of a particular GWDC forcing depends upon the inherent systematic biases of a particular model. It is concluded that incorporation of the GWDC parameterization in GCMs should be taken into account to improve the seasonal prediction.     

台阶式沉井等效墩宽计算方法探究

桥梁工程中存在形状各异的桥墩,在研究不同截面桥墩的局部冲刷特性时,桥墩尺寸的定量描述非常重要。以台阶式沉井结构为研究对象,梳理并分析了国内外相关等效桥墩宽度计算方法,发现各类公式本质上为计算不同条件下的桥墩平均阻水宽度。开展了台阶式沉井局部冲刷试验研究,基于试验数据对比分析了各类等效墩宽计算方法的计算结果,发现Melville和Raudkivi的等效墩宽计算公式能够较好地估算考虑动床条件下台阶式沉井的平均阻水宽度;进一步收集了国内外193组台阶式沉井类结构的局部冲刷试验数据,数据集统计分析结果显示Melville和Randkivi的等效墩宽计算公式能够较为准确且保守地量化大多数台阶式沉井类结构的截面非均匀性;最后基于数据集冲深墩宽比统计结果对该公式近似方法的合理性进行了讨论。     

A public Cloud-based China’s Landslide Inventory Database (CsLID): development,zone, and spatiotemporal analysis for significant historical events, 1949-2011

Landslide inventory plays an important role in recording landslide events and showing their temporal-spatial distribution. This paper describes the development, visualization, and analysis of a China's Landslide Inventory Database (CsLID) by utilizing Google’s public cloud computing platform. Firstly, CsLID (Landslide Inventory Database) compiles a total of 1221 historical landslide events spanning the years 1949-2011 from relevant data sources. Secondly, the CsLID is further broken down into six zones for characterizing landslide cause-effect, spatiotemporal distribution, fatalities, and socioeconomic impacts based on the geological environment and terrain. The results show that among all the six zones, zone V, located in Qinba and Southwest Mountainous Area is the most active landslide hotspot with the highest landslide hazard in China. Additionally, the Google public cloud computing platform enables the CsLID to be easily accessible, visually interactive, and with the capability of allowing new data input to dynamically augment the database. This work developed a cyber-landslide inventory and used it to analyze the landslide temporal-spatial distribution in China.     

Position-domain integrity risk-based ambiguity validation for the integer bootstrap estimator

Integrity monitoring for ambiguity resolution is of significance for utilizing the high-precision carrier phase differential positioning for safety–critical navigational applications. The integer bootstrap estimator can provide an analytical probability density function, which enables the precise evaluation of the integrity risk for ambiguity validation. In order to monitor the effect of unknown ambiguity bias on the integer bootstrap estimator, the position-domain integrity risk of the integer bootstrapped baseline is evaluated under the complete failure modes by using the worst-case protection principle. Furthermore, a partial ambiguity resolution method is developed in order to satisfy the predefined integrity risk requirement. Static and kinematic experiments are carried out to test the proposed method by comparing with the traditional ratio test method and the protection level-based method. The static experimental result has shown that the proposed method can achieve a significant global availability improvement by 51% at most. The kinematic result reveals that the proposed method obtains the best balance between the positioning accuracy and the continuity performance.     

Geochronology, Fluid Inclusions and Isotopic Characteristics of the Dongjun Pb-Zn-Ag Deposit, Inner Mongolia, NE China

The Dongjun Pb-Zn-Ag deposit in the northern part of the Great Xing’an Range (NE China) consists of quartz-sulfide vein-type and breccia-type mineralization, related to granite porphyry. Hydrothermal alteration is well-developed and includes potassic-silicic-sericitic alteration, phyllic alteration and propylitic alteration. Three stages of mineralization are recognized on the basis of field evidence and petrographic observation, demarcated by assemblages of quartz-pyrite-arsenopyrite (early stage), quartz-polymetallic sulfide (intermediate stage) and quartz-carbonate-pyrite (late stage). Zircon LA-ICP-MS U-Pb dating indicates that the granite porphyry was emplaced at 146.7 ± 1.2 Ma (Late Jurassic). Microthermometry and laser Raman spectroscopy shows that ore minerals were deposited in conditions of intermediate temperatures (175–359°C), low salinity (0.5–9.3 wt% NaCl eqv.) and low density (0.60–0.91 g/cm3). Ore-forming fluids were derived largely from magmatic hydrothermal processes, with late-stage addition of meteoric water, belonging to a H2O-NaCl-CO2 ± CH4 system. The δ34SV-CDT values range from 0.75‰ to 4.70‰. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the ore minerals are in the ranges of 18.240–18.371, 15.542–15.570, and 38.100–38.178, respectively. Data for the S and Pb isotopic systems indicate that the ore-forming metals and sulfur were derived from Mesozoic magma. Based on the geological characteristics and geochemical signatures documented in this study, we conclude that the Dongjun deposit is a mesothermal magmatic hydrothermal vein-type Pb-Zn-Ag deposit controlled by fractures and related to granite porphyry, in response to Late Jurassic tectonic–magmatic–hydrothermal activity. We further conclude that fluid immiscibility, fluid mixing and fluid-rock interactions were the dominant mechanisms for deposition of the ore-forming materials.     

Early solar system aqueous activity: K isotope evidence from Allende

The alkali element K is moderately volatile and fluid mobile; thus, it can be influenced by both primary processes (evaporation and recondensation) in the solar nebula and secondary processes (thermal and aqueous alteration) in the parent body. Since these primary and secondary processes would induce different isotopic fractionations, K isotopes could become a potential tracer to distinguish them. Using recently developed methods with improved precision (0.05‰, 95% confidence interval), we systematically measured the K isotopic compositions and major/trace elemental compositions of chondritic components (18 chondrules, 3 CAIs, 2 matrices, and 5 bulks) in the carbonaceous chondrite fall Allende. Among all the components analyzed in this study, CAIs, which formed initially under high‐temperature conditions in the solar nebula and were dominated by nominally K‐free refractory minerals, have the highest K₂O content (average 0.53 wt%) and have K isotope compositions most enriched in heavy isotopes (δ⁴¹K: ?0.30 to ?0.25‰). Such an observation is consistent with previous petrologic studies that show CAIs in Allende have undergone alkali enrichment during metasomatism. In contrast, chondrules contain lower K₂O content (0.003–0.17 wt%) and generally lighter K isotope compositions (δ⁴¹K: ?0.87‰ to ?0.24‰). The matrix and bulks are nearly identical in K₂O content and K isotope compositions (0.02–0.05 wt%; δ⁴¹K: ?0.62 to ? 0.46‰), which are, as expected, right in the middle of CAIs and chondrules. This strongly indicates that most of the chondritic components of Allende suffered aqueous alteration and their K isotopic compositions are the ramification of Allende parent‐body processing instead of primary nebular signatures. Nevertheless, we propose the small K isotope fractionations observed (< 1‰) among Allende components are likely similar to the overall range of K isotopic fractionation that occurred in nebular environment. Furthermore, the K isotope compositions seen in the components of Allende in this study are consistent with MC‐ICP‐MS analyses of the components in ordinary chondrites, which also show an absence of large (10‰) isotope fractionations. This is not expected as evaporation experiments in nebular conditions suggest there should be large K isotopic fractionations. Nevertheless, possible nebular processes such as chondrules back exchanging with ambient gas when they formed could explain this lack of large K isotopic variation.     

互联网影响下的“网剧”与传统“台剧”生产网络的结构差异

选取2016—2017年最具代表性的“网剧”和“台剧”各318部,运用社会网络分析法探讨互联网影响下的“网剧”与传统“台剧”生产网络的结构差异。研究表明：① 空间分布上看,相对于“台剧”生产网络,“网剧”生产网络中的企业区位、核心城市节点和城市间强联系更加集聚,尤其是向京津冀和长三角两大城市群集聚。② 网络结构上看,相对于“台剧”生产网络,“网剧”生产网络的规模小、联系数量少、分工粗略、中心势低,核心企业节点多为民营互联网影视企业,最强凝聚子群更为开放。最后,从互联网发展的地理格局、互联网带来的消费习惯改变、互联网引发的自由竞争,以及互联网视频平台企业的崛起四个方面分析了产生上述网络结构差异的原因。     

基于GIS的高校物流代理点选址研究

随着电子商务在社会生活中的广泛兴起,校园物流代理点也随之产生;物流代理点在很大程度上方便了师生快递领取,但由于高校物流代理点选址普遍存在随意性和不合理性,导致师生快递领取时浪费过多时间和精力。针对此问题,本研究结合GIS空间分析技术,通过对广西师范大学雁山校区学生宿舍、教学楼、食堂和道路分布数据的分析,利用缓冲区分析和叠置分析优选出物流代理点最佳分布区域,并对校园中现有的物流代理点分布合理性做出评价,进而给出合理的校园物流代理点选址区域建议,旨在为学校物流代理点科学选址及改善和提升校园人文品质提供合理建议,同时为物流企业规划选址及GIS空间分析应用提供参考。     

区域可持续发展能力的能值与(火用)耦合分析模型构建

可持续发展能力评价方法是识别人地协同规律、支撑科学决策的重要工具和热点需求。通过文献回顾与理论分析框架构建,耦合能值及?方法,提出自组织能力指数（SO）、生态压力指数（EP）、可持续发展能力指数（SC）构成的,基于热力学理论的可持续发展能力分析模型,利用文献荟萃法筛选17个典型发达国家1985年状态值计算SO与EP阈值,划分了4个阶段。利用中美两国1985-2015年特征对比验证,结果显示：① 2005年以前中国属“低自组织能力、低生态压力”阶段,之后进入“低自组织能力、高生态压力”阶段,存在低生态效率、规模扩张驱动特征;美国一直属“高自组织能力、高生态压力”阶段,存在高生态效率驱动、经济与生态脱钩特征,与全球生态足迹网络和世界自然基金会等的研究结果一致,模型具有较好适应性和可靠性。② 模型利用“获得?量/输入能值量”表达经济社会生态效率、“经济社会?损耗量/生态系统年产?量”表达生态压力,连接了经济社会对生态基底的熵化路径,可识别区域所处可持续发展阶段、分析水平变化和驱动因素。③ 模型以人类与生态并重的视角,从深度上反映经济社会的生态效率、从广度上评价生态空间被占用比例,具有宏观规模与微观效率分析相结合的优势,是对经典方法的补充。