自适应神经网络在确定落煤残存瓦斯量中的应用

落煤残存瓦斯量的确定是采掘工作面瓦斯涌出量预测的重要环节，它直接影响着采掘工作面瓦斯涌出量预测的精度，并与煤的变质程度、落煤粒度，原始瓦斯含量、暴露时间等影响因素呈非线性关系，人工神经网络具有表示任意非线性关系和学习的能力，是解决复杂非线性，不确定性和时变性问题的新思想和新方法，基于此，作提出自适应神经网络的落煤残丰瓦斯量预测模型，并结合不同矿井落煤残存瓦斯量的实际测定结果进行验证研究，结果表明，自适应调整权值的变步长BP神经网络模型预测精度高，收敛速度快，该预测模型的应用可为采掘工作面瓦斯涌出量的动态预测提供可靠的基础数据，为采掘工作面落煤残存瓦斯量的确定提出了一种全新的方法和思路。     

LAKE REHABILITATION TECHNIQUES AND EXPERIENCES1

ABSTRACT: The degradation of many lakes is the result of aging processes which have been accelerated by the activities of man. Where it is too late to prevent sedimentation and eutrophication problems, lake rehabilitation and protection comprise a resource management option warranting serious consideration. A Wisconsin Lake Renewal Demonstration Project has been evaluating several rehabilitation schemes for the past five years. A selected summary of Project lake rehabilitation activities, including nutrient inactivation, dilution, aeration, and several types of aquatic plant management, suggests the present status of lake rehabilitation.     

Regional Lake Trophic Patterns in the Northeastern United States: Three Approaches

N   = 11,076). Results were compared to a large, nonrandomly sampled data set for the same area compiled by Rohm and others and contrasted with lake trophic state information published in the National Water Quality Inventory: 1994 Report to Congress [305(b) report. Lakes across the entire Northeast were identified by EMAP data as 37.9% (±8.4%) oligotrophic, 40.1% (±9.7%) mesotrophic, 12.6% (±7.9%) eutrophic, and 9.3% (±6.3%) hypereutrophic. Lakes in the ADI and NEU generally are at a low, nearly identical trophic state (96% oligotrophic/mesotrophic), while those in the CLP are much richer (45% eutrophic). EMAP results are similar to results of the Rohm data set across the entire region. In the CLP, however, EMAP identified approximately 45% of the lakes as eutrophic/hypereutrophic, while the Rohm data set identified only 21% in these categories. Across the entire Northeast, the 305(b) report identified a much higher proportion (32.2%) of lakes in eutrophic condition and a much smaller proportion (19.8%) in oligotrophic condition than did the EMAP survey data (12.5% ± 7.9% and 37.9% ± 8.5%, respectively). Probability sampling has several advantages over nonrandom sampling when regional resource condition assessment is the goal.     

Statistical Estimation and Model Selection of Species-Accumulation Functions

Abstract:  Soberón and Llorente (1993) proposed pure-birth stochastic processes as theoretical models for species-accumulation curves, and these processes have frequently been used to describe the progress of biological inventories. We describe, in algorithmic form, an alternative statistical analysis based on a likelihood approach ( Díaz-Francés & Gorostiza 2002 ) that provides mathematical rigor to the ideas in Soberón and Llorente (1993) and improves the estimation of the models by incorporating the facts that the variance of the error is not constant and that the observations are correlated. Additionally, we used the likelihood ratios between candidate models as an objective procedure for model selection, allowing comparison between the goodness of fit of various models. The software for these statistical methods can now be downloaded off the Internet. We used two examples of butterfly data sets to illustrate the use of the methods and the software.     

A scanning electron microscope study of the mandibular morphology of boreal copepods

Morphological details of the mandibular blades of 11 species of copepods were examined with scanning electron microscopy. The micrographs improved our understanding of the complex toothed edge of the mandibular blade, which in turn aids in identification of the copepod prey of chaetognaths by gut-content analysis. Beklemishev's discovery of siliceous tooth crowns in calanoid copepods was confirmed for most of the species examined. Long, sharp projections on the crowns of herbivorous species, and the deep grooves into which they fit on the teeth of the opposite mandible, suggest a cracking rather than a grinding function for these teeth.     

Compensation for “Meaningful Participation” in Climate Change Control: A Modest Proposal and Empirical Analysis

The debate over an international climate change regime has thus far focused primarily on efficiency concerns in developed countries. This paper suggests a means by which equity concerns may be addressed in the ongoing negotiations. A system of transfers is developed that is motivated by the difference between the damage caused by a country and the damage suffered by that country as a result of climate change. Illustrative calculations of the magnitude and direction of these transfers are made. We find that in general transfers flow from temperate to tropical countries but that the degree of uncertainty associated with these calculations is very large.     

Impacts of flight distance on sex ratio and resource allocation to offspring in the leafcutter bee, Megachile rotundata

Fisher's theoretical prediction of equal investment in each sex for a panmictic population (The genetical theory of natural selection. Clarendon, Oxford, 1930) can be altered by a number of factors. For example, the sex ratio theory predicts variation in equal investment in each sex when the maternal fitness gains from increased investment differ between sexes. Changing sex allocation because of changing payoffs may result from different ecological situations, such as foraging conditions. We investigated the impact of foraging travel cost on relative investment in sons vs daughters. Field studies were carried out with the central-place-foraging leafcutter bee Megachile rotundata (Fabricius), which has smaller males than females. Therefore, less investment is required to produce a viable son compared with a daughter. We found that with increased flight distance to resources, females produced a greater proportion of sons. Females also invested fewer resources in individual sons and daughters and produced fewer offspring with increased flight distance.     

A case study of resources management planning with multiple objectives and projects

Each National Park Service unit in the United States produces a resources management plan (RMP) every four years or less. The plans commit budgets and personnel to specific projects for four years, but they are prepared with little quantitative and analytical rigor and without formal decision-making tools. We have previously described a multiple objective planning process for inventory and monitoring programs (Schmoldt and others 1994). To test the applicability of that process for the more general needs of resources management planning, we conducted an exercise on the Olympic National Park (NP) in Washington State, USA. Eight projects were selected as typical of those considered in RMPs and five members of the Olympic NP staff used the analytic hierarchy process (AHP) to prioritize the eight projects with respect to their implicit management objectives. By altering management priorities for the park, three scenarios were generated. All three contained some similarities in rankings for the eight projects, as well as some differences. Mathematical allocations of money and people differed among these scenarios and differed substantially from what the actual 1990 Olympic NP RMP contains. Combining subjective priority measures with budget dollars and personnel time into an objective function creates a subjective economic metric for comparing different RMP’s. By applying this planning procedure, actual expenditures of budget and personnel in Olympic NP can agree more closely with the staff’s management objectives for the park.     

Association between radioactive fallout from 1951–1962 US nuclear tests at the Nevada Test Site and cancer mortality in midwestern US populations

We determined the association between radionuclide deposition levels from nuclear testing at the Nevada Test Site (NTS) and cancer mortality rates in 513 counties of the Midwestern states of Iowa, Illinois, Kansas, Missouri, and Nebraska. The 10-day cumulative deposition for 54 radionuclides and 1-year cumulative deposition for 19 radionuclides were determined with isotope ratios based on each test and ¹³¹I levels in the 513 counties obtained from the US National Cancer Institute’s ¹³¹I fallout study. Deposition calculations were done for each test and each radionuclide. Age-adjusted cancer mortality rates for 84 organ-gender combinations for the periods 1950–1959, 1960–1969, 1970–1979, and 1979–1995 were used. Analyses included permutation-based randomization tests for Spearman rank correlation (adjusted for multiple testing). Age-adjusted cancer mortality rates for connective and soft tissue sarcoma, thymus, and female lymphosarcoma and cancer of the colon, brain, thyroid, and uterus were significantly correlated with total fallout and total precipitation during 1951–1957 and 1962. ¹⁸⁷W had the highest cumulative deposition density at 10 days postshot (2783 MBq/m²) among the NTS radionuclides considered. The most significant correlations were observed for 10-day cumulative deposition density of ¹⁸¹W, ¹⁸⁵W, ⁵⁴Mn, ¹⁸⁷W, ²⁴Na, ¹⁸⁵W, ¹⁹⁹Au, ⁷Be, ⁶⁰Co, and deposition density of ¹⁸⁵W, ⁵⁴Mn, ⁷Be, and ⁶⁰Co present at 1-year with mortality for cancers such as female connective and soft tissue sarcoma, male and female thymus, female colon, male and female thyroid, female brain, male multiple myeloma, female breast, and uterine cancer. Significant correlations included isotopic forms of mutagenic metals such as antimony, beryllium, cadmium, cobalt, cesium, manganese, rhodium, selenium, tellurium, and tungsten. The large number of significant correlation tests beyond expectation warrants deeper questions related to the toxicology of fission products and induced radionuclides, validity of kriging procedures, and new studies on core sampling of watersheds and trees in regions assumed to receive the greatest levels of environmental radiocontamination. The text was submitted by the authors in English.