Integer estimation in the presence of biases

 Carrier phase ambiguity resolution is the key to fast and high-precision GNSS (Global Navigation Satellite System) kinematic positioning. Critical in the application of ambiguity resolution is the quality of the computed integer ambiguities. Unsuccessful ambiguity resolution, when passed unnoticed, will too often lead to unacceptable errors in the positioning results. Very high success rates are therefore required for ambiguity resolution to be reliable. Biases which are unaccounted for will lower the success rate and thus increase the chance of unsuccessful ambiguity resolution. The performance of integer ambiguity estimation in the presence of such biases is studied. Particular attention is given to integer rounding, integer bootstrapping and integer least squares. Lower and upper bounds, as well as an exact and easy-to-compute formula for the bias-affected success rate, are presented. These results will enable the evaluation of the bias robustness of ambiguity resolution. Received: 28 September 2000 / Accepted: 29 March 2001     

Are managed retreat programs successful and just? A global mapping of success typologies,justice dimensions,and trade-offs

As managed retreat programs expand across the globe, there is an urgent need to assess whether these programs are reducing exposure to climatic hazards, enhancing adaptive capacity, and improving the living conditions of communities in a just and equitable manner or are they exacerbating existing risks and vulnerabilities? Strictly speaking, are retreat programs successful? Using an expansive intersectional justice approach to examine 138 post-resettlement case studies published between 2000 and 2021 across the Global North and South, we identified five typologies of success – techno-managerial, eco-restorative, compensatory, reformative, and transformative – and their trade-offs and synergies. Our meta-analysis incorporated a variety of metrics: relocation types, funding, decision making, socio-economic class, land use change, livelihood options, and social impacts. We found 26% of cases failed, 43% were successful, and 30% are on-going and therefore success was undetermined. The techno-managerial cases, while successful in the limited terms of relocating residents, paid little attention to equity and justice. The eco-restorative and compensatory cases reduced hazard exposure but revealed the synergies and tensions associated with social, ecological, and intergenerational justice. The reformative and transformative cases improved community wellbeing, rootedness, and access to livelihoods while incorporating diverse justice concerns to different degrees. By intersecting these typologies with multiple dimensions of justice, this study advances a novel planning and analytical tool for assessing the potential success or failure of current and future retreat programs.     

Single epoch ambiguity resolution for Galileo with the CAR and LAMBDA methods

This paper investigates single epoch ambiguity resolution performance using Galileo four frequency data. Two commonly used ambiguity resolution methods are used in the tests, including the Cascade Ambiguity Resolution (CAR) and the Least-Squares Ambiguity Decorrelation Adjustment (LAMBDA) methods. For CAR method, four optimal combinations are carefully selected according to their wavelength to noise ratios and success rate for ambiguity fixing. The test results show, in general, the LAMBDA method performs better than the CAR method. The speed of ambiguity resolution is closely related to the carrier phase measurement precision. With carrier phase measurement precision of 3 mm, single epoch ambiguity resolution can be achieved at every epoch with simulated 1-s interval 24-h Galileo data (total epochs 86,400). With the increase of carrier phase noise, ambiguity resolution performances become worse. When the noise level is increased to 12 mm, single epoch ambiguity resolution can only be achieved about 50% of epochs.     

华北地区高速公路沿线雾预报

在数值预报产品(MM5)的基础上,建立了华北高速公路沿线及邻近460个气象站的高影响天气一雾的统计预报模型.抽样检验系统运行2年多来所积累的预报和实况资料的结果表明,北京24 h能见度V≤5 km预报的年临界成功指数(CSI:Critical Success Index)为0.61,京津塘高速公路沿线的7个站为0.68...     

Probability Estimates of Field Areas and Trapped Oil Volumes

A portion of a sedimentary basin is subdivided conceptually into hexagons of equal area. The area of each hexagon is equal to the minimum area an oil field should have to be commercial. Hexagons can be full of oil or empty. A field size 1 consists of a cell with oil surrounded by six empty cells; a field size 2 consists of two adjacent cells with oil surrounded by eight empty cells, etc. Principles of Percolation Theory are used to determine the probability distribution of the areas of the oil fields existing in this portion of the basin. The only piece of information necessary to determine this probability distribution is the Success Ratio (number of successful exploration wells/total number of exploration wells drilled in this portion of the basin). This approach has several practical applications.A probabilistic model is introduced to predict to which extent potential oil traps are filled with oil. The model assumes that the probability that an oil unit will end up in a particular trap, is proportional to the surface area of the trap. The model predicts that independently of the distribution of the trap volumes, there will be a critical trap volume. All the traps having a volume less than this critical volume, will be filled to spill point. An equation is deduced to predict, for all traps having a volume greater than the critical, the volume of oil that can be encountered in the trap, provided the volume of the trap is known.     

资源评价特点与成矿带级资源评价的几个问题

近年来,铀资源评价在我国广泛开展,并取得丰硕成果。资源评价与传统地质预测不同,其主要差别是:资源评价应用了数学方法,它建立在对已有资料全面综合定量分析的基础上,对工作区的资源能作定质、定量、定位及定类型预测。矿田与矿带级资源评价也存在差别,矿带由于范围大,资料比例尺小,所以矿带资源评价是以评价成矿环境为主;而矿田资源评价则是以对预测资源定位、定量为主要宗旨。因此,两者在评价方法、预测模型建立、资料要求、变量选取等方面都存在很大差别。文章针对成矿带级资源评价各阶段经常遇到的问题,提出了多种处理办法,详细论述了矿床模型法用于矿带资源评价时所遇到的各种困难,最后作者提出在作成矿带或非总合式资源评价时采用矿床成因模型或成矿概念模型的建议。     

地质矿产部区域重力调查成果与展望

区域重力调查是一项基础地球物理调查工作。它的成果可用于研究地质构造、资源勘探、环境调查，地震灾害、地球形状、地球物理理论等方面。它象征着一个国家科学技术发展水平，特别是地学方面的水平。地矿部研究了国内外重力勘查情况，于１９７８年提出并组织、实施了全国范围的区域重力调查。通过十多年的工作，取得了丰硕成果。本文就地矿部区域重力调查成果与展望，予以论述。     

What drives the success of reforestation projects in tropical developing countries? The case of the Philippines

In response to substantial deforestation over many decades, large scale reforestation programs are being implemented across many tropical developing countries. Examples include the United Nations Billion Trees Campaign, the National Greening Program in the Philippines, and the 5 million ha reforestation program in Vietnam. However, while substantial investments are being made in reforestation, little information exists on the drivers influencing reforestation success and how these interact to determine environmental and socio-economic outcomes. In this study we surveyed 43 reforestation projects on Leyte Island, The Philippines to identify the drivers that most influence reforestation success as measured by key indicators drawn from the literature, including interactions between drivers and between drivers and indicators. We investigated 98 potential success drivers, including technical and biophysical factors; socio-economic factors; institutional, policy and management factors; and reforestation project characteristics. We also measured 12 success indicators, including forest establishment, forest growth, environmental and socio-economic success indicators. Stepwise multiple regressions were used to identify significant relationships among drivers and indicators and this analysis was used to develop a system of driver and indicator relationships. Based on this we found that revegetation method, funding source, education and awareness campaigns, the dependence of local people on forests, reforestation incentives, project objectives, forest protection mechanisms and the condition of road infrastructure were highly connected drivers that influenced multiple success indicators either directly or indirectly. We conclude that policies targeting revegetation methods, socioeconomic incentives, forest protection mechanisms, sustainable livelihoods, diversification of funding and partnerships, technical support, and infrastructure development are likely to have a broad systemic and beneficial effect on the success of reforestation programs in tropical developing countries.     

CSEM technology as a value driver for hydrocarbon exploration

The use of the controlled source electromagnetic (CSEM) method as a risk reduction tool in marine hydrocarbon exploration is gaining increased acceptance in the oil industry. This is related to the ability to map resistivity contrasts in the sub-surface and thus aid the detection of hydrocarbons which are typically more resistive than surrounding rocks. Whereas acoustic (seismic) energy allows for mapping sub-surface structures that may contain hydrocarbons, electromagnetic (EM) energy can often say something about the fluids contained within the structures. Numerous successful CSEM case stories have been published over the past several years. However, there are also quite a few stories about “failure”-cases, although not well documented in the literature. Such “failure”-cases may reflect the lack of understanding of the CSEM technology and how CSEM data can act as a value driver. In order to understand this, it is necessary to handle uncertainties and decisions associated with the technology, These include geological uncertainties, noise models, survey designs, forward modelling parameters, inversion/migration parameters and pre-processing of real data. A proper handling of these uncertainties and decisions will aid in defining and constraining the chance of geologic success and geologic-success-case net present value for prospects prior to drilling wells. As such, the CSEM technology has a significant potential to increase exploration efficiency, if applied correctly.     

资源评价的成功树法

成功树法是应用系统工程中的可靠性理论，将专家对成矿规律的认识系统工程化，改编为成功树的形式，通过计算成功树顶事件的成矿概率或成矿有利度，达到资源评价目的。文章详细介绍了成功树法的来源、原理、３种计算方法，具体说明了怎样建立综合铀矿成矿成功树，以及用它进行资源评价的步骤。由于本方法不受已知矿床数量、预测区面积大小的限制，适用于不同矿种、不同类型、不同比例尺的资源评价，具有良好的发展前景。