Calibration of an oscillating nozzle‐type rainfall simulator     

Bofu Yu  Cyril A. A. Ciesiolka  Paul Langford 《地球表面变化过程与地形》2003,28(13):1483-1490

Nozzle‐type rainfall simulators are commonly used in hydrologic and soil erosion research. Simulated rainfall intensity, originating from the nozzle, increases as the distance between the point of measurement and the source is decreased. Hence, rainfall measured using rain gauges would systematically overestimate the rainfall received at the ground level. A simple model was developed to adjust rainfall measured anywhere under the simulator to plot‐wide average rainfall at the ground level. Nozzle height, plot width, gauge diameter and height, and gauge location are required to compute this adjustment factor. Results from 15 runs at different rain intensities and durations, and with different rain gauge layouts, showed that a simple average of measured rain would overestimate the plot‐wide rain by about 20 per cent. Using the adjustment factor to convert measured rainfall for individual gauges before averaging improved the estimate of plot‐wide rainfall considerably. For the 15 runs considered, overall discrepancy between actual and measured rain is reduced to less than 1 per cent with a standard error of 0·97 mm. This model can be easily tested in the ?eld by comparing rainfall depths of different sized gauges. With the adjustment factor they should all give very similar values. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Fundamental study on the response characteristics of drivers during an earthquake based on driving simulator experiments     

Yoshihisa Maruyama  Fumio Yamazaki 《地震工程与结构动力学》2004,33(6):775-792

After the 1995 Kobe earthquake, the expressway structures in Japan were retrofitted and they will not now be seriously damaged under a certain level of strong earthquake motion. However, the stability of a moving vehicle has not been investigated yet. It has been reported that drivers feel seismically induced vibrations, especially in the transverse direction of vehicles. Owing to this phenomenon, drivers have some difficulty in controlling the vehicles during strong shaking. For further safety promotion of the expressway networks, it is important to understand the drivers' reactions to seismic motion. The present authors have performed a series of seismic response analyses of a moving vehicle to investigate its response characteristics based on numerical simulation. However, the responses of the driver were not considered in the simulation process. In order to investigate the drivers' reactions during an earthquake, a series of virtual tests were conducted using a driving simulator. This driving simulator has six servomotor‐powered electric actuators that control its motions. Several types of tests were carried out for different examinees to investigate drivers' responses while controlling the simulator under seismic motion. The results of this study showed that a larger response time lag to strong shaking and over turning of the steering wheel may shift the vehicle into the next lane. According to this finding, trafficaccidents could possibly occur under strong ground shaking in the case of heavy traffic. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

The influence of soil properties on the erodibility of Belgian loamy soils: A study based on rainfall simulation experiments     

Th. Verhaegen 《地球表面变化过程与地形》1984,9(6):499-507

Twenty soils from the Leuven region were tested in the laboratory with a rainfall simulator. Their texture varied from loam to loamy sand. On the basis of the results obtained, they were classified as a function of the runoff and splash erodibility. For every soil, several properties were determined and tentatively used to explain the classifications based on the runoff and splash erodibility. Significant negative correlations were found between silt content, aggregate stability, C_5–10 index, water content at saturation, and cohesion on the one side and erodibility on the other; a positive correlation was found between sand content and erodibility.  相似文献   

The study of the undiscovered mineral resources of the Tongass National Forest and adjacent lands,Southeastern Alaska     

David A. Brew  Lawrence J. Drew  Stephen D. Ludington 《Natural Resources Research》1992,1(4):303-322

The quantitative probabilistic assessment of the undiscovered mineral resources of the 17.1-million-acre Tongass National Forest (the largest in the United States) and its adjacent lands is a nonaggregated, mineral-resource-tract-oriented assessment designed for land-planning purposes. As such, it includes the renewed use of gross-in-place values (GIPV's) in dollars of the estimated amounts of metal contained in the undiscovered resources as a measure for land-use planning.Southeastern Alaska is geologically complex and contains a wide variety of known mineral deposits, some of which have produced important amounts of metals during the past 100 years. Regional geological, economic geological, geochemical, geophysical, and mineral exploration history information for the region was integrated to define 124 tracts likely to contain undiscovered mineral resources. Some tracts were judged to contain more than one type of mineral deposit. Each type of deposit may contain one or more metallic elements of economic interest. For tracts where information was sufficient, the minimum number of as-yet-undiscovered deposits of each type was estimated at probability levels of 0.95, 0.90, 0.50, 0.10, and 0.05.The undiscovered mineral resources of the individual tracts were estimated using the U.S. Geological Survey's MARK3 mineral-resource endowment simulator; those estimates were used to calculate GIPV's for the individual tracts. Those GIPV's were aggregated to estimate the value of the undiscovered mineral resources of southeastern Alaska. The aggregated GIPV of the estimates is $40.9 billion.Analysis of this study indicates that (1) there is only a crude positive correlation between the size of individual tracts and their mean GIPV's: and (2) the number of mineral-deposit types in a tract does not dominate the GIPV's of the tracts, but the inferred presence of synorogenic-synvolcanic nickel-copper, porphyry copper skarn-related, iron skarn, and porphyry copper-molybdenum deposits does. The influence of this study on the U.S. Forest Service planning process is yet to be determined.  相似文献   

Spatial averaging of hydraulic conductivity in three-dimensional heterogeneous porous media   总被引：4，自引：0，他引：4  

A. J. Desbarats 《Mathematical Geology》1992,24(3):249-267

Numerical models of groundwater flow require the assignment of hydraulic conductivities to large grid blocks discretizing the flow domain; however, conductivity data is usually available only at the much smaller scale of core samples. This paper describes a geostatistical model for hydraulic conductivity at both the core or point scale and that of grid blocks. Conductivity at the block scale is obtained empirically as a spatial power-average of point scale values. Assuming a multivariate Gaussian model for point log-conductivity, expressions are derived for the ensemble mean and variance of block conductivity. The expression for the ensemble mean of block scale conductivity is found to be similar to an expression for the ensemble effective conductivity of an infinite field derived analytically by earlier authors. Here, block conductivities obtained by power averaging are compared with effective conductivities obtained from a numerical flow model and are found to be in excellent agreement for a suitably chosen averaging exponent. This agreement deteriorates gradually as the log variance of conductivity increases beyond 2. For arbitrary flow field geometry and anisotropic conductivity covariances, the averaging exponent can be calibrated by recourse to numerical flow experiments. For cubic fields and an isotropic spatial covariance, the averaging exponent is found to be 1/3. In this particular case, it was found that flow field discretization at the block scale through local averaging of point conductivities gave similar results to those obtained directly using a point scale discretization of the flow field.  相似文献   

电子全站仪模拟器软件的开发原理与实现     

成方圆  童小华  周德意  程效军  钱俊 《测绘信息与工程》2007,32(6):45-47

在Visual Basic 6.0环境下,探讨了电子全站仪模拟器软件开发的基本原理,分析了系统设计的结构框架,并以坐标测量为例介绍了其实现的过程.  相似文献   

Three dimensional large scale earthquake simulator with six degrees of freedom     

Jun-Wei Han  Yu-Ting Li  Bao-Sheng Hu 《地震学报(英文版)》1998,11(3):387-390

Conclusions When the aseismic test of large scale structure is performed, it is a major performance that the actual response waveform is identical to the input signal waveform under the condition of analog control, especially when the damping of the structure tested is small. The rotational motions of the simulator are induced due to the structure inertia, so that it is a key technique for the simulator design that realizes independent control of the simulator with six degrees of freedom and suppresses the rotational motions. In the design, the modern control techniques are applied and a high performance of the three dimensional earthquake simulator is developed successfully. The simulator can simulate actual earthquake load and it is an important test device for aseismic research. This paper is a main project of the Eighth Five Plan, State Seismological Bureau.  相似文献   

1961–2005年中国陆地生态系统净初级生产力模拟（英文）     

苑全治  吴绍洪  赵东升  戴尔阜  陈力  张磊 《地理学报(英文版)》2014,(1)

Net primary productivity(NPP) is the most important index that represents the structure and function of the ecosystem.NPP can be simulated by dynamic global vegetation models(DGVM),which are designed to represent vegetation dynamics relative to environmental change.This study simulated the NPP of China's ecosystems based on the DGVM Integrated Biosphere Simulator(IBIS) with data on climate,soil,and topography.The applicability of IBIS in the NPP simulation of China's terrestrial ecosystems was verified first.Comparison with other relevant studies indicates that the range and mean value of simulations are generally within the limits of observations;the overall pattern and total annual NPP are close to the simulations conducted with other models.The simulations are also close to the NPP estimations based on remote sensing.Validation proved that IBIS can be utilized in the large-scale simulation of NPP in China's natural ecosystem.We then simulated NPP with climate change data from 1961 to 2005,when warming was particularly striking.The following are the results of the simulation.(1) Total NPP varied from 3.61 GtC/yr to 4.24 GtC/yr in the past 45 years and exhibited minimal significant linear increase or decrease.(2) Regional differences in the increase or decrease in NPP were large but exhibited an insignificant overall linear trend.NPP declined in most parts of eastern and central China,especially in the Loess Plateau.(3) Similar to the fluctuation law of annual NPP,seasonal NPP also displayed an insignificant increase or decrease;the trend line was within the general level.(4) The regional differences in seasonal NPP changes were large.NPP declined in spring,summer,and autumn in the Loess Plateau but increased in most parts of the Tibetan Plateau.  相似文献   

深海极端环境模拟装置设计   总被引：2，自引：0，他引：2       下载免费PDF全文

董贤信  蒋凯  陈杭  叶树明 《热带海洋学报》2014,33(2):101-108

为了满足深海极端环境科学研究的需求,设计了深海极端环境模拟装置。对系统结构以及工作原理进行分析,介绍了培养釜、温度控制子系统和压力控制子系统。重点针对当前模拟装置压力控制精度不高的问题,设计了高精度压力传感器,并提出一种迭代自学习PID压力控制算法,实现系统压力自动检测和连续控制,同时带有观察窗的培养釜结构可以实现微生物状况实时观测。实验结果表明,该系统能够实现深海极端环境参量高精度模拟,可以为深海极端环境科学研究提供很好的平台。  相似文献   

胡麻生理生化代谢指标对干旱胁迫的响应及其模拟模型的研究          下载免费PDF全文

康佳  李玥  康亮河 《干旱区地理》2022,45(3):879-889

为进一步研究胡麻生理生化代谢指标响应干旱胁迫时对胡麻产量的影响,采用盆栽控水法模拟胡麻干旱胁迫,依据2013—2014年甘肃省定西市西巩驿镇胡麻试验数据,建立并检验胡麻干旱胁迫模型,模拟干旱胁迫时对胡麻生理生化指标及产量影响,利用均方根误差（RMSE）和决定系数（R²）描述模型拟合度。结果表明：（1） 模型产量模拟值的RMSE为41.3159~155.6685 kg·hm^-2,平均值为80.1837 kg·hm^-2;R²为0.8929~0.9894,平均值为0.9387,该模型具有较好的拟合度、可行性也较强。（2） 在重度干旱胁迫下,抗氧化代谢指标——超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）中,CAT活性表现趋势为下降,终花期POD活性增幅（26.09%~28.00%）最大;渗透调节的3种物质含量均显著上升,其中脯氨酸增幅最大,达236.22%。（3） 呈现出极显著相关性的各指标有3组,分别是脯氨酸与叶绿素、丙二醛和CAT活性;可溶性蛋白与丙二醛和CAT活性;POD活性与SOD活性。胡麻生理生化指标响应不同程度干旱胁迫与胡麻的产量有极强的关联,此模型的建立是对胡麻生理生化指标响应干旱胁迫的科学补充,进一步为胡麻的高效生产管理及农业生产系统提供理论依据和支持。  相似文献