MARCO POLO: near earth object sample return mission

MARCO POLO is a joint European–Japanese sample return mission to a Near-Earth Object. This Euro-Asian mission will go to a primitive Near-Earth Object (NEO), which we anticipate will contain primitive materials without any known meteorite analogue, scientifically characterize it at multiple scales, and bring samples back to Earth for detailed scientific investigation. Small bodies, as primitive leftover building blocks of the Solar System formation process, offer important clues to the chemical mixture from which the planets formed some 4.6 billion years ago. Current exobiological scenarios for the origin of Life invoke an exogenous delivery of organic matter to the early Earth: it has been proposed that primitive bodies could have brought these complex organic molecules capable of triggering the pre-biotic synthesis of biochemical compounds. Moreover, collisions of NEOs with the Earth pose a finite hazard to life. For all these reasons, the exploration of such objects is particularly interesting and urgent. The scientific objectives of MARCO POLO will therefore contribute to a better understanding of the origin and evolution of the Solar System, the Earth, and possibly Life itself. Moreover, MARCO POLO provides important information on the volatile-rich (e.g. water) nature of primitive NEOs, which may be particularly important for future space resource utilization as well as providing critical information for the security of Earth. MARCO POLO is a proposal offering several options, leading to great flexibility in the actual implementation. The baseline mission scenario is based on a launch with a Soyuz-type launcher and consists of a Mother Spacecraft (MSC) carrying a possible Lander named SIFNOS, small hoppers, sampling devices, a re-entry capsule and scientific payloads. The MSC leaves Earth orbit, cruises toward the target with ion engines, rendezvous with the target, conducts a global characterization of the target to select a sampling site, and delivers small hoppers (MINERVA type, JAXA) and SIFNOS. The latter, if added, will perform a soft landing, anchor to the target surface, and make various in situ measurements of surface/subsurface materials near the sampling site. Two surface samples will be collected by the MSC using “touch and go” manoeuvres. Two complementary sample collection devices will be used in this phase: one developed by ESA and another provided by JAXA, mounted on a retractable extension arm. After the completion of the sampling and ascent of the MSC, the arm will be retracted to transfer the sample containers into the MSC. The MSC will then make its journey back to Earth and release the re-entry capsule into the Earth’s atmosphere.     

金矿样品分析中相关问题讨论

依据金矿石特性,探讨样品在分析过程中要特别注意的加工、测试取样量、样品焙烧、载体灰化等几个关键问题,认为只有处理好以上几个关键问题才能得到准确、可靠检测结果。     

Simpson’s Paradox in Natural Resource Evaluation

Reversals of statistical relationships, when two or more groups of data in a cross tabulation are aggregated, were first revealed more than a century ago. The reversal was later named Simpson’s paradox after his reversal examples in a seminal paper drew the attention of the statistical community. However, almost all the published cases have been in sociology and biomedical statistics. Does Simpson’s reversal occur in geosciences? Various examples from petroleum geology and reservoir modeling will be shown in this paper. Boundary conditions for such a reversal will be discussed under a broader framework of sampling analysis. Ecological inference bias, change of support problem, modifiable areal unit problem, and reference class problem will be discussed in relation to the Simpson’s paradox in the framework of spatial statistics. It will be demonstrated that the traditional interpretation of the paradox as a result of disproportional sampling based on a contingency table is not always true in the framework of spatial statistics, and the reversal while theoretically benign is inferentially treacherous. Therefore, emphasis will be on the discussion of combining statistical and scientific inferences in geologic modeling and hydrocarbon resource evaluation under various sampling schemes or support effect with or without a Simpson’s reversal.     

Influence of sample size on line-based positional assessment methods for road data

Sample size influences considerably the variability of results of estimation processes, but this issue has never previously been analyzed for line-based positional assessment methods. The basis of the analysis is a simulation process which extracts homologous road axes from the product and from the control survey and applies the four methods. Sample sizes of road axes range from 10 Km up to 200 Km, and for each sample size 1000 simulations were run. Results for each sample size were compared to population parameters or population distribution functions by means of statistical tests. The variability of estimations was reduced in the order of 2.5-4.5 times when sample size increased from 10 Km to 200 Km.     

水氯镁石热分解尾气中氯化氢的回收研究

本文针对水氯镁石热分解尾气中含有的大量氯化氢气体进行尾气回收研究，设计完成了蒸馏吸收实验，单级吸收实验、二级吸收实验和连续实验，获得了相关实验数据，由此对设备的选型、实验条件的选择提供了依据。     

Measuring bedload in gravel-bed mountain rivers: averaging methods and sampling strategies

A dataset of more than 1,000 individual bedload samples coupled with hydraulic flow variables (water depth and velocity) was collected on two high mountain rivers the torrent de Saint Pierre, a proglacial gravel-bed river in the French Alps, in July 2002 and the Urumqi River, in the Chinese Tianshan mountains during summer 2005 and 2006.

Analysis of the dataset leads to question the usual section averaged sampling procedure of bedload using Helley-Smith type bedload sampler. It is shown that this procedure is inadequate to catch the full range of flow conditions. Comparison between moving averages on individual datasets and section averages furthermore show that this technique can lead to significantly different rating curves with predictions differing by more than an order of magnitude. Single point sampling is shown to be much more adequate than multiple point sampling and section averaging provided the dataset is sufficiently large.     

Benthic macroinvertebrate field sampling effort required to produce a sample adequate for the assessment of rivers and streams of Neuquén Province,Argentina

This multi-year pilot study evaluated a proposed field method for its effectiveness in the collection of a benthic macroinvertebrate sample adequate for use in the condition assessment of streams and rivers in the Neuquén Province, Argentina. A total of 13 sites, distributed across three rivers, were sampled. At each site, benthic macroinvertebrates were collected at 11 transects. Each sample was processed independently in the field and laboratory. Based on a literature review and resource considerations, the collection of 300 organisms (minimum) at each site was determined to be necessary to support a robust condition assessment, and therefore, selected as the criterion for judging the adequacy of the method. This targeted number of organisms was collected at all sites, at a minimum, when collections from all 11 transects were combined. Subsequent bootstrapping analysis of data was used to estimate whether collecting at fewer transects would reach the minimum target number of organisms for all sites. In a subset of sites, the total number of organisms frequently fell below the target when fewer than 11 transects collections were combined.Site conditions where <300 organisms might be collected are discussed. These preliminary results suggest that the proposed field method results in a sample that is adequate for robust condition assessment of the rivers and streams of interest. When data become available from a broader range of sites, the adequacy of the field method should be reassessed.     

Evaluating water quality for Amazonian streams along the interoceanic highway in Peru using macroinvertebrates collected by hand and with leaf packs

We assessed water quality using physical, chemical, and biological characteristics in 37 streams between Puerto Maldonado and Cusco in Peru. Study sites ranged from ∼200 to 4000 m in elevation, with streams selected as pairs (control/natural vs. human impacted) along this gradient. In general, temperature decreased (R² = 0.82) and other parameters increased [dissolved oxygen (R² = 0.19), conductivity (R² = 0.17), pH (R² = 0.37)] with elevation. Macroinvertebrates were hand collected by professional entomologists and using leaf packs implemented by conservation workers. The professionals identified 213 unique taxa from the hand collections, with 80 species collected only one time. Data from control streams showed that as elevation increased, total richness (p = 0.008) and EPT richness (p = 0.050) decreased whereas Diptera richness increased (p = 0.002). NMS ordination indicated significant differences in macroinvertebrate assemblages when control streams from low and high elevations were contrasted. Hand collections also revealed significant differences between control and impact streams for total richness, EPT richness and % Diptera, but not for % EPT, % EPT richness, or % Diptera richness. The majority of the deployed leaf packs were successfully retrieved and contained many macroinvertebrates (Avg. = 141 individuals per pack). There were 98 unique taxa (family level or higher) identified from the leaf packs by the trained conservation workers. Fourteen of 15 macroinvertebrate community metrics (at the family level) were able to detect significant differences between control and impact sites. All of the family level metrics responded similarly across the elevation gradient except total richness, EPT richness, EPT count, and % Hydropsychids. Both the Costa Rica and the Virginia Save Our Stream Indexes were able to differentiate control from impacted streams using leaf pack data. Although the diversity of macroinvertebrates was higher for hand collections relative to leaf packs (due to greater habitats sampled and higher taxonomic resolution), leaf pack samples were better able to distinguish control from impacted streams. Specifically, leaf packs were able to discern impacts in streams at low elevation better than those at high elevation. Generally, macroinvertebrates indicated impact from urbanization to be worse than impacts from other human activities (i.e., gold mining and agriculture). Overall, hand collections will serve as an important reference of species diversity going forward while leaf packs processed by trained conservation workers are a viable method to monitor stream water quality in Peru and perhaps elsewhere.     

Time-Dependent Reliability Analysis of Offshore Structures

During the life of an offshore structure,its structural strength declines due to various kinds ofdamages related to the time factor.In this paper,four major kinds of damages,including damages causedby fatigue,dent,corrosion and marine life,are discussed.Based on these analyses,formulas for theevaluation of the damaged structure reliability are derived.Furthermore the computer program ISM forthe analysis of structural reliability is developed by the use of Advanced First Order Second Moment meth-od and Monte-Carlo Importance Sampling method.The reliability of a turbular joint and a beam are stu-died as numerical examples.The results show that the theory and the analysis method given in this paperare reasonable and effective.     

Recent Developments in Marine Diamond Mining

The marine diamond deposits of southern Africa owe their existence to fluvial transport down the Orange River to the South Atlantic. On the coast, they were moved, sorted and concentrated by high-energy sea and wind conditions to create a veneer of diamondiferous gravels on the sea floor. Large scale, offshore production by De Beers Marine commenced in 1989 in Namibian waters. The company now acts as a contractor for Namdeb, a corporation owned jointly with the Namibian governments. Some junior public companies also produce diamonds by large-scale mechanized means and conduct extensive exploration programs. Two important developments have occurred recently. Firstly, equipment for the recovery of diamonds from the seabed has been successfully borrowed from other industries. Large drills from onshore civil engineering have been modified for marine sampling and mining. Remotely controlled, seabed-mounted, excavational systems have assumed a major role. The new systems allow both evaluation sampling and subsequent mining to be undertaken by similar or the same equipment, making the results compatible. They permit highly selective extraction and enhanced recovery of the gravels from irregular bedrock in water approaching 200 m deep. But none is universally applicable offshore, each being the preferred system under different conditions. Secondly, the total output of sea diamonds from Namibian waters has increased to 0.8 million carats annually and now exceeds that from all the country's onshore sources. An industry has become established. Corporate and individual perseverence, government encouragement, new technology, shareholders' risk finance, and De Beers' diamond marketing have all played a role in the success. Future diamond production may increase as companies meet the challenge of working lower grade, higher volume deposits, which will require new approaches to the mining process. With a decrease in the physical risk of marine mining, the most variable inputs in operational planning and production forecasting are recovered grade and throughout rate, together with equipment availability. The importance of reliable grade estimation from sufficient sampling density is widely perceived, but the greatest performance risk can involve the predicted excavation rate and 'mineability' of the seabed sediments. Published reserve statements would benefit from a requirement to specify the planned mining method, the consequent cutoff grade to be employed, and whether or not test mining has been undertaken.