A parallel algorithm for coverage optimization on multi-core architectures

Location siting is an important part of service provision, with much potential to impact operational efficiency, safety, security, system reliability, etc. A class of location models seeks to optimize coverage of demand for service that is continuously distributed across space. Decision-making and planning contexts include police/fire resource allocation for a community, siting cellular towers to support cell phone signal transmission, locating emergency warning sirens to alert the public of severe weather and other related dangers, and many others as well. When facilities can be sited anywhere in continuous space to provide coverage to an entire region, this is a very computationally challenging problem to solve because potential demand for service is everywhere and there are an infinite number of potential facility sites to consider. This article develops a new parallel solution approach for this location coverage optimization problem through an iterative bounding scheme on multi-core architectures. The developed approach is applied to site emergency warning sirens in Dublin, Ohio, and fire stations in Elk Grove, California. Results demonstrate the effectiveness and efficiency of the proposed approach, enabling real-time analysis and planning. This work illustrates that the integration of cyberinfrastructure can significantly improve computational efficiency in solving challenging spatial optimization problems, fitting the themes of this special issue: cyberinfrastructure, GIS, and spatial optimization.     

Contribution of phytoliths to total biogenic silica volumes in the tropical rivers of Malaysia and associated implications for the marine biogeochemical cycle

The contribution of phytoliths to total biogenic silica (BSi) volumes in rivers worldwide, and the associated implications for the biogeochemical cycle, require in-depth study. Based on samples from rivers in Peninsular Malaysia, this project investigated the source and characteristics of BSi found in Asian tropical rivers, as well as the process of reverse weathering taking place in these fluvial systems. Results indicated that BSi samples collected in sediments consisted of phytolith, diatom and sponge spicules. Phytoliths, predominantly of the elongate form, comprised 92.8%–98.3% of BSi in the Pahang River. Diatom BSi in this river consisted mainly of pennatae diatoms, but represented a relatively small proportion of the total BSi volume. However, diatom BSi (predominantly of the Centricae form) was more prevalent in the Pontian and Endau Rivers with shares of 68.8% and 79.3% of the total BSi volumes, respectively, than Pahang River. Carbon contents of the BSi particulates ranged from 1.85% to 10.8% with an average of 4.79%. These values are higher than those recorded in other studies to date, and indicate that BSi plays a major role in controlling permanent carbon burial. This study suggests that phytoliths from terrestrial plants are the primary constituents of BSi in the rivers of Peninsular Malaysia, and therefore represent a significant proportion of the coastal silica budget.     

伊宁地块早石炭世球泡流纹岩的发现及地球化学特征

伊宁地块西段中部阿腾套山一带发现的球泡流纹岩,多数产于早石炭世海相无球泡流纹岩夹层中,整体呈层状、互层状,球泡通气孔顺层平行于流纹构造定向分布,推断是海相极浅水环境下的产物,因而具有精细指相意义。该球泡流纹岩与同期A型花岗岩类共生,属碱性岩类,SiO_2含量为69.18%~77.69%,K_2O大于4%,Al_2O_3为11.32%~16.24%,Ga/Al×10~4=2.1~7.8,∑REE=85.22×10~(-6)~348.8×10~(-6),(La/Yb)_N=6.7~14.8,相对富集轻稀土,δEu具明显负异常,稀土配分及大离子元素蛛网图均与A型花岗岩类地球化学特征总体相同。ε_(Hf)(t)均大于0(+12.5~+15.5),两阶段锆石Hf模式年龄大于锆石U-Pb年龄,表明源区可能为早古生代新生地壳物质部分熔融演化而来。A型球泡流纹岩与同期A型花岗岩类均形成于拉张构造环境,是区内早石炭世大哈拉军山组中迄今唯一发现的显示拉张构造环境的珍贵实例。为揭示和探讨伊宁地块总体处于汇聚大背景下的局部拉张环境,以及东窄西宽之楔形构造形态提供了可能。     

Intraseasonal oscillation of the rainfall variability over Rwanda and evaluation of its subseasonal forecasting skill

非洲中东部地区的经济主要依靠自给农业支撑,该地区农业经济对降水的变化尤为敏感.本文以卢旺达为例,观测分析指出卢旺达的次季节降雨主要集中在10-25天;根据次季节尺度降水变率的单点相关方法,发现卢旺达的次季节降水变率和周围区域变化一致;进一步合成结果显示该地区次季节降水变率与异常西风有关,这可追溯到赤道地区西传的赤道Rossby波.最后,本文评估了当前动力模式ECMWF对 卢旺达地区(即非洲中东部)次季节降水变率的预报能力,发现EC模式在对该区域降水和相关风场指数的预报技巧都在18天左右,且预报技巧表现出一定的年际差异,这可能与热带太平洋的背景海温信号有关.该工作增进了当 前对非洲中东部地区的次季节降水变率和预测水平的认知,并且对该地区国家粮食安全和防灾减灾具有启示性意义.     

Performance of GPS and GPS/SINS navigation in the CE-5T1 skip re-entry mission

A CE-5T1 spacecraft completed a high-speed skip re-entry to the earth after a circumlunar flight on October 31, 2014. In addition to the strapdown inertial navigation system (SINS), a lightweight GPS receiver with rapid acquisition was developed as a navigation sensor in the re-entry capsule. The GPS receiver effectively solved the poor accuracy problem of long-term navigation using only the SINS. In contrast to ground users and low-earth-orbit spacecraft, numerous factors, including high altitude and kinetic characteristics in high-speed skip re-entry, are important for GPS positioning feasibility and were presented in accordance with the flight data. GPS solutions started at nearly 4900 km orbital altitude during the phases of re-entry process. These solutions were combined by an inertial measurement unit in a loosely coupled integrated navigation method and SINS navigation initialization. A simplified GPS/SINS navigation filter for limited resources was effectively developed and implemented on board for spacecraft application. Flight data estimation analyses, including trajectory, attitude, position distribution of GPS satellite, and navigation accuracy, were presented. The estimated accuracy of position was better than 42 m, and the accuracy of velocity was better than 0.1 m/s.     

武汉市城镇扩张适宜性与景观生态安全格局的时空耦合关系研究

城镇用地扩张与景观生态安全格局之间存在空间上的关联性与冲突性,为探究城镇扩张适宜性与景观生态安全格局的耦合关系,本文以武汉市为例,在2001、2007和2014年3期ETM遥感影像解译的基础上,结合武汉市高程、坡度、全国第二次土地调查与变更调查数据、道路交通网络数据等构建武汉市土地利用时空数据库。从自然环境因素与区位条件因素两大方面构建城镇扩张适宜性评价指标体系,利用GIS空间分析获取武汉市城镇扩张适宜性分布特征,采用最小阻力模型(MCR)构建武汉市景观生态安全格局。从空间分布特征与时间演变特征两个维度研究城镇扩张系统与景观生态系统之间的耦合关系。     

小冰期时中国南方地区降水模式的差异研究

小冰期是过去一千年中全球气候变化的重要事件之一。关于小冰期时中国季风区和西风影响区气候变化的对比研究众多,但是缺乏中国南方地区降水模式时空差异的研究,难以了解中国南方地区降水变化规律。为了系统地了解小冰期时中国南方地区降水的复杂性,本文将中国南方地区划分为东南—华南沿海地区、中部地区以及西南地区三个区域,总共选取了19条高分辨率的古气候记录进行对比研究,主要有以下几点认识:(1)相对于中世纪暖期而言,小冰期期间中国南方东南—华南沿海地区的气候偏湿,这可能与雨带在中国南方的滞留时间延长和沿海地区受台风的影响增强有关。(2)中国中部地区秦岭南麓和神农架高山林区在小冰期时期主要呈"冷湿"的模式,差异在于秦岭南麓区域主要在小冰期中后期偏湿,这与中部其他区域偏"冷干"的模式不同。这种区域差异可能是由于地形地势和大气环流的复杂性导致。(3)中国西南地区受印度夏季风和东亚夏季风的共同影响,且该区域地形复杂,其气候变化在小冰期时期存在更加明显的空间差异,没有呈现出比较一致的降水模式。与小冰期期间的降水变化不同的是,近30年东南—华南沿海地区除了台湾和雷州半岛,其他区域降水明显减少,可能受气温和人类活动等因素的影响。通过结合高分辨率的古气候记录,我们系统分析了中国南方小冰期的干湿模式在时空上的差异及其可能的影响因子,这对于认识小冰期时中国南方不同区域降水的复杂性及未来旱涝灾害的防控具有一定意义。     

班公湖-怒江缝合带东段丁青地幔橄榄岩成因:来自钻孔ZK02地幔橄榄岩矿物学及地球化学特征约束

丁青蛇绿岩位于班公湖-怒江缝合带东段,是该缝合带出露面积最大的蛇绿岩。为查明岩体成因,在丁青东岩体中实施了一口165.19m的钻孔。除最顶部有约0.5m厚的第四系残坡积物外,其余均为地幔橄榄岩。结合显微镜鉴定将岩心划分出17个岩性单元层,岩性主要以方辉橄榄岩为主,夹少量纯橄岩和含铬铁矿纯橄岩。地幔橄榄岩中橄榄石的Fo变化于88.79~93.73,铬尖晶石的Cr^#变化于44.33~81.66,揭示丁青地幔橄榄岩可能经历过约20%~40%的中高度部分熔融作用;全岩地球化学分析表明其具有富镁（MgO=45.98%~49.45%）、贫铝（Al₂O₃=0.19%~1.37%）和贫钙（CaO=0.28%~0.70%）的特点,属于熔融程度较高的地幔残余物质。岩石具有明显不同于阿尔卑斯蛇绿岩的轻稀土元素富集特征,指示区内地幔橄榄岩先经历了较强程度的部分熔融,后经历了俯冲消减过程中的流体交代。利用地幔橄榄岩中的铬尖晶石成分计算母熔体Al₂O₃含量对应的FeO/MgO值,与不同构造环境原始岩浆成分相比较,发现丁青地幔橄榄岩母熔体大多处于玻安岩中。纯橄岩氧逸度估算FMQ=-3.05~-0.71,方辉橄榄岩氧逸度FMQ=-3.89~+1.47,显示丁青地幔橄榄岩有俯冲作用的参与。通过丁青钻孔岩心的研究,提出丁青东岩体可能形成于俯冲带之上的弧前环境这一观点。     

二叠系火山碎屑岩气藏天然气地球化学特征及气源分析——以四川盆地成都—简阳地区永探1井为例

2018年12月底,在四川盆地二叠系火山岩发育地区部署的风险探井永探1井测试获得22.5万m³/d的高产工业气流,实现了二叠系火山碎屑岩的重大勘探突破,展现了火山碎屑岩气藏的巨大勘探潜力。本文根据该钻井成果资料,应用分析化验数据,采用不同地区气-气对比方法,开展了成都—简阳地区天然气地球化学特征分析、源-储接触关系解剖及气源综合对比。在此基础上,对二叠系火山碎屑岩气藏天然气成因进行了鉴别,对天然气来源进行了判识。结果表明：永探1井火山岩气藏天然气均为典型的干气,干燥系数达0.997,CH₄质量分数高,平均为99.03%,C₂H₆质量分数低,平均为0.35%,C₃H₈几乎没有,不含H₂S;天然气甲烷、乙烷碳同位素值均较轻,甲烷碳同位素平均值为-32.17‰,乙烷碳同位素平均值为-34.27‰,且岩心及镜下可见大量残余沥青,天然气成因鉴别分析表明永探1井火山岩气藏天然气为原油二次裂解气;通过源-储接触关系解剖以及天然气甲烷、乙烷碳同位素对比分析,表明永探1井火山碎屑岩气藏天然气主要来源于德阳—安岳台内裂陷内发育的巨厚下寒武统筇竹寺组优质烃源岩,部分来源于中二叠统。     

Effect of inherent anisotropy on the strength of natural granite residual soil under generalized stress paths

It is universally known that residual soils behave very differently from sedimentary soils. While the latter is widely known as cross-anisotropic, little is known regarding the strength anisotropy of residual soils. This study presents how the inherent anisotropy affects the strength of natural granite residual soils under generalized conditions, where intact specimens were carefully prepared and sheared under triaxial compression, extension, simple shear, and hollow cylinder torsional shear tests. The strength of natural residual soil, in terms of ultimate stress ratio M and undrained shear strength S_u, is found to be significantly anisotropic in a different way from normally consolidated clays with the maximum strength obtained under triaxial compression and the minimum under simple shear or at intermediate principal stress direction. As a result, the existing method failed to measure the anisotropy degree of the studied soil. Two parameters were proposed accordingly to quantify the anisotropic strength under general conditions, taking the special strength anisotropy pattern and cohesive-frictional nature of GRS into account. The proposed parameters enable the direct comparison of strength anisotropy among soils. This study serves as a data set to better understand residual soils regarding their anisotropic behaviors under generalized conditions. Although specific to granite residual soils in China, this study is expected to be more widely applicable to other weathered geomaterials.