居住区气温变化模型及应用

借助居住区热时间常数和地表热时间常数计算城市局地气温变化,给出的数学模型简单实用,但考虑了多项城市相关参数。结果表明实测值与预测值吻合较好。对部分城市参数作了敏感性分析,初步揭示了各参数变化对城市居住区气温的影响。     

基于无人机建模的尾矿库溃坝事故推演*

为诠释尾矿库溃坝后水砂演进过程,提升尾矿库事故灾害应急处置能力,采用无人机倾斜摄影技术获取尾矿库全息影像,建立尾矿库三维数字高程模型,导入三维流体计算软件对尾矿库进行溃坝事故推演。结果表明:尾矿库实景三维模型能高精度还原尾矿库实际情况,尾矿库溃坝将淹没库区临时厂房建筑及下游村落;其中,上游沟谷临时厂房建筑水位高程最大达8 m,尾砂淤积厚度最高达10.5 m,下游沟谷村落水位高程最大达10 m,尾砂淤积厚度最高达2.5 m;通过对库区下游布设监测点,得出各监测点处水位高程和尾砂淤积厚度变化规律,分析溃坝主要影响区域。研究结果可为尾矿库风险防控、应急响应工作提供借鉴。     

起重机在特殊工况下的静刚度与动刚度安全性分析

通过对一台桥式电磁起重机静刚度和动刚度的理论计算,以及对其主梁的探伤检查,分析了桥式起重机在特殊工况下的静刚度和动刚度,指出了在设计时应考虑的安全性问题。     

Decision making with option pricing and dynamic programming: development and application

In this study, an option pricing model and a dynamic programming model are developed. These models contribute to the improvement of the decision making process in two respects. First, these models allow for the own growth rate of mining costs to be incorporated into the analysis. Second, these models are developed to estimate the satisfactory gross revenue for investing, so that these models are helpful in analyzing multi-metal mines.The two models are applied to estimate the satisfactory revenue for investing in the Carlin east gold mine, Nevada, USA. The satisfactory revenue estimated by the option pricing model is found to be $42.2M, while that estimated by the dynamic programming model is found to be $44.4M. Since the revenue calculated on the basis of the current conditions is $36M, then the decision by option pricing and dynamic programming is to wait and not to invest now. Despite the difference between the two models in estimating and applying the discount rate, the two models generate the same decision.     

A CALIBRATION PROCEDURE USING TOPMODEL TO DETERMINE SUITABILITY FOR EVALUATING POTENTIAL CLIMATE CHANGE EFFECTS ON WATER YIELD1

ABSTRACT: An evaluation was conducted on three forested upland watersheds in the northeastern U.S. to test the suitability of TOPMODEL for predicting water yield over a wide range of climatic scenarios. The analysis provides insight of the usefulness of TOPMODEL as a predictive tool for future assessments of potential long-term changes in water yield as a result of changes in global climate. The evaluation was conducted by developing a calibration procedure to simulate a range of climatic extremes using historical temperature, precipitation, and streamfiow records for years having wet, average, and dry precipitation amounts from the Leading Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook (New Hampshire) Experimental Watersheds. This strategy was chosen to determine whether the model could be successfully calibrated over a broad range of soil moisture conditions with the assumption that this would be representative of the sensitivity necessary to predict changes in streamfiow under a variety of climate change scenarios. The model calibration was limited to a daily time step, yet performed reasonably well for each watershed. Model efficiency, a least squares measure of how well a model performs, averaged between 0.64 and 0.78. A simple test of the model whereby daily temperatures were increased by 1.7°C, resulted in annual water yield decreases of 4 to 15 percent on the three watersheds. Although these results makes the assumption that the model components adequately describe the system, this version of TOPMODEL is capable to predict water yield impacts given subtle changes in the temperature regime. This suggests that adequate representations of the effects of climate change on water yield for regional assessment purposes can be expected using the TOPMODEL concept.     

SELECTION AND SUSTAINABILITY OF LAND AND WATER RESOURCE MANAGEMENT SYSTEMS1

ABSTRACT: Most spatial decision support systems for natural resource planning and management are limited by their scenario-based (non-behavioral), deterministic (non-stochastic) structure. A spatial decision support system is developed that uses a multiple attribute decision-making model to explain how a property manager selects a land and water resource management system (LWRMS) based on its multiple, stochastic economic and environmental attributes. The decision support system assesses sustainable resource management at the property and watershed scales and identifies the most cost-effective policy for enhancing sustainable resource management. Economic attributes are determined with an economic model and environmental attributes are simulated with an environmental model. Input parameters for both models are generated with a geographic information system. The decision support system is used to rank five LWRMS for a sample of 20 farmers in Missouri's Goodwater Creek watershed and for two hypothetical watershed alliance groups. Results indicate that the average farmer and the two alliance groups would rank the five LWRMS in the same manner. From the viewpoint of the watershed alliance, the most preferred LWRMS for the average farmer in the watershed is sustainable.     

EVALUATION OF RUNOFF,EROSION, AND PHOSPHORUS MODELING SYSTEM—SIMPLE1

ABSTRACT: The purpose of this study was to evaluate the performance of Spatially Integrated Models for Phosphorus Loading and Erosion (SIMPLE) in predicting runoff volume, sediment loss, and phosphorus loading from two watersheds. The modeling system was applied to the 334 ha QOD subwatershed, part of the Owl Run watershed, located in Fauquier County, Virginia, and to the 2240 ha watershed, Battle Branch, located in Delaware County, Oklahoma. Simulation runs were conducted at cell and field scales, and simulation results were compared with observed data. Runoff volume and dissolved phosphorus loading were measured at the Battle Branch watershed. Runoff volume, sediment yield, and total phosphorus loading were measured at the QOD site. SIMPLE tended to underestimate runoff volumes during the dormant period, from November to March. The comparison between observed and predicted dissolved phosphorus showed better correlation than for observed and predicted total phosphorus loading. Cell level simulations provided similar estimates of runoff volume and phosphorus loading when compared to field level simulations for both watersheds. However, observed sediment yields better compared with the values predicted from the cell level simulation when compared to field level simulation. Finally, results of model evaluation indicated that SIMPLE's predictive ability is acceptable for screening applications but not for site-specific quantitative predictions.     

POTENTIAL EFFECTS OF CLIMATE CHANGE ON AGRICULTURAL WATER USE IN THE SOUTHEAST U.S.1

ABSTRACT: Climate change has the potential to have dramatic effects on the agricultural sector nationally and internationally as documented in many research papers. This paper reports on research that was focused on a specific crop growing area to demonstrate how farm managers might respond to climate-induced yield changes and the implications of these responses for agricultural water use. The Hadley model was used to generate climate scenarios for important agricultural areas of Georgia in 2030 and 2090. Linked crop response models indicated generally positive yield changes, as increased temperatures were associated with increased precipitation and CO2. Using a farm management model, differences in climate-induced yield impacts among crops led to changes in crop mix and associated water use; non-irrigated cropland received greater benefit since irrigated land was already receiving adequate moisture. Model results suggest that farm managers will increase cropping intensity by decreasing fallowing and increasing double cropping; corn acreage decreased dramatically, peanuts decreased moderately and cotton and winter wheat increased. Water use on currently irrigated cropland fell. The potential for increased water use through conversion of agriculturally important, but currently non-irrigated, growing areas is substantial.     

RESPONSE OF NORTH AMERICAN FRESHWATER LAKES TO SIMULATED FUTURE CLIMATES1

ABSTRACT: We apply a physically based lake model to assess the response of North American lakes to future climate conditions as portrayed by the transient trace-gas simulations conducted with the Max Planck Institute (ECHAM4) and the Canadian Climate Center (CGCM1) atmosphere-ocean general circulation models (A/OGCMs). To quantify spatial patterns of lake responses (temperature, mixing, ice cover, evaporation) we ran the lake model for theoretical lakes of specified area, depth, and transparency over a uniformly spaced (50 km) grid. The simulations were conducted for two 10-year periods that represent present climatic conditions and those around the time of CO₂ doubling. Although the climate model output produces simulated lake responses that differ in specific regional details, there is broad agreement with regard to the direction and area of change. In particular, lake temperatures are generally warmer in the future as a result of warmer climatic conditions and a substantial loss (> 100 days/yr) of winter ice cover. Simulated summer lake temperatures are higher than 30°C over the Midwest and south, suggesting the potential for future disturbance of existing aquatic ecosystems. Overall increases in lake evaporation combine with disparate changes in A/OGCM precipitation to produce future changes in net moisture (precipitation minus evaporation) that are of less fidelity than those of lake temperature.     

COMPARISON OF MODELS FOR ESTIMATING FLOOD QUANTILES IN NEW HAMPSHIRE AND VERMONT1

We develop and compare three regression models for estimating flood quantiles at ungaged stream reaches in New Hampshire and Vermont. These models emerge from systematic analysis and validation of relations between flood magnitude and six candidate predictors reflecting basin size, topography, and climate and channel size at 36 gaging stations with record lengths exceeding 20 years. Of the candidate predictors, bank full width is most highly correlated with flood magnitude and the best prediction equation is based on width. Thus channel geometry is closely related to the current hydrologic regime in spite of geologically recent glaciation and apparently non-alluvial bank materials. We also develop models that use information obtainable from maps or GIS. The best of these uses drainage area and drainage-basin elevation as predictors, but it is substantially less precise than the width-based relation. A third relation using only drainage area as a predictor is even less precise but may be useful for some purposes. No other single predictors or combinations yielded useful predictions, although some had been included in previously-established models for the region. Model comparison included examination of residuals generated by regression using one-at-a-time suppression of data points and comparison with precision obtainable with gaging records of varying lengths.