EVALUATION OF MODELS FOR ESTIMATION OF NET RADIATION FOR ALPINE SLOPING SURFACES          下载免费PDF全文

Huo Zonghui  W. G. Bailey 《Acta Meteorologica Sinica》1992,6(2):189-197

This paper describes and tests two models for estimating net radiation(or the radiation balance)on sloping surfacesof alpine environments.They are an empirical method based on the linear relationship between net radiation and globalsolar radiation and a flux-by-flux method involving the estimation of all the individual components of radiation budgetindependently.The results show that the empirical method is capable of predicting hourly net radiation on sloping sur-faces to within about±53 W m~(-2) under all sky conditions.During clear sky conditions,it could predict net radiation onslopes to within±58 W m~(-2) or 16% of the measured values.The flux-by-flux method,although it did not perform aswell as the empirical method,performed adequately and could give estimates of net radiation on slopes with root meansquare error of less than 74 W m~(-2)(20%)and a mean bias error of 27 W m~(-2)(7%).  相似文献   

Interpretation of S-wave data from Tai’an-Xinzhou DSS profile and its relationship with Xingtai earthquakes     

Song-Yan Song  Xue-Song Zhou  Chun-Yong Wang  Xian-Kang Zhang  Jian-Li Song  Yi Gong 《地震学报(英文版)》1997,10(1):15-25

On the basis of S wave information from Tai’an-Xinzhou DSS profile and with reference to the results from P-wave interpretation, the 2-D structures, including S-wave velocity V _s, ratio γ between V _p and V _s; and Poisson’ s ratio σ, are calculated; the structural configuration of the profile is presented and the relevant inferences are drawn from the above results. Upwarping mantle districts (V _s≈4.30 km/s) and sloping mantle districts (V _s≈4.50 km/s) of the profile with velocity difference about −4% at the top of upper mantle are divided according to the differences of V _s, γ and σ in different media and structures, also with reference to the information of their neighbouring regions; the existence of Niujiaqiao-Dongwang high-angle ultra-crustal fault zone is reaffirmed; the properties of low and high velocity blocks (zones) including the crust-mantle transitionalzone and the boudary indicators of North China rift valley are discussed. A comprehensive study is conducted on the relation of the interpretation results with earthquakes. It is concluded that the mantle upwarps, thermal material upwells through the high-angle fault, the primary hypocenter was located at the crust-mantle juncture 30.0∼33.0 km deep, and additional stress excited the M _S=6.8 and M _S=7.2 earthquakes at specific locations around 9.0 km below Niujiaqiao-Dongwang, the earthquakes took place around the high-angle ultra-crustal fault and centered in the brittle media and rock strata with low γ and low σ values. This subject is part of the 85-907-02 key project during the “8th Five-Year Plan” from the State Science and Technology Commission.  相似文献   

Experimental investigation of the harmonic generation by waves over a submerged plate   总被引：1，自引：0，他引：1  

J. Brossard  M. Chagdali   《Coastal Engineering》2001,42(4)

Experiments in a wave flume have been performed to analyse the nonlinear interaction between regular gravity waves and a submerged horizontal plate used as breakwater. A new method, based on the Doppler shift generated by a moving probes, has been used to discriminate the incident fundamental mode and the reflected fundamental mode. The relationships of the reflection and transmission coefficients to the wave number at different submergence depth ratios are presented. The accurate discrimination, by this method, of the phase-locked and free modes allows the quantification of the higher harmonics generated by the breakwater and the analysis of the nonlinear interaction between the waves and the submerged plate. The transfer of energy from the fundamental mode to higher harmonics is very large in the cases of small submergence depth ratios. The vortices produced at the edges take part in the production of higher harmonics by interaction with the free surface but involve, at the same time, a dissipation process that increases the efficiency of the breakwater.  相似文献   

The Implementation Effects of a Nationwide Sloping Farmland Soil Erosion Control Project in China     

FENG Wei  YANG Yunfen  ZHAO Yongjun  DI Baofeng  MA Changchen 《资源与生态学报(英文版)》2017,8(4):341-351

To understand implementation of a nationwide sloping farmland soil erosion comprehensive control project during China’s 12^th Five-Year Plan we used data collection and expert consultation. We selected 24 indexes across three aspects including project management, engineering construction and implementation benefit and used AHP-grey correlation analysis methods. We found that the scores for engineering construction were greater than 0.65 in most of the provinces, autonomous regions and municipalities. These scores are high and scores for project management and implementation benefit are between 0.45-0.65; however, overall scores are low. The comprehensive evaluation results are normally distributed. The composite scores for Sichuan, Yunnan and Guizhou are 0.71, 0.68 and 0.68 respectively, indicating that the implementation effects are good. The scores for Jilin and Liaoning are 0.38 and 0.42 respectively, indicating that the implementation effects need improvement. Scores for other provinces are between 0.45-0.65 and the effects are medium. The evaluation results show certain zonal rules spatially and the implementation effect in karst regions of Southwest China is the highest, followed by the purple soil region in Southwest China, Loess Plateau region of Northwest China, earth-rock mountain region of North China and red soil hilly region of South China. The implementation effect in the black soil region of Northeast China suggests that improvement is needed in this region.  相似文献   

Wave Interactions with Multiple Semi-Immersed Jarlan-Type Perforated Breakwaters     

Moussa S. ELBISY 《海洋工程》2017,31(3):341-349

This study examines wave interactions with multiple semi-immersed Jarlan-type perforated breakwaters. A numerical model based on linear wave theory and an eigenfunction expansion method has been developed to study the hydrodynamic characteristics of breakwaters. The numerical results show a good agreement with previous analytical results and experimental data for limiting cases of double partially immersed impermeable walls and double and triple Jarlan-type breakwaters. The wave transmission coefficient C_T; reflection coefficient C_R, and energy dissipation coefficient C_E coefficients and the horizontal wave force exerted on the front and rear walls are examined. The results show that C_R reaches the maximum value when B/L = 0.46n while it is smallest when B/L=0.46n+0.24 (n=0, 1, 2,...). An economical triple semi-immersed Jarlan-type perforated breakwater can be designed with B/L = 0.25 and C_R and C_T ranging from 0.25 to 0.32 by choosing a relative draft d/h of 0.35 and a permeability parameter of the perforated front walls being 0.5 for an incident wave number kh nearly equal to 2.0. The triple semi-immersed Jarlan-type perforated breakwaters with significantly reduced C_R, will enhance the structure’s wave absorption ability, and lead to smaller wave forces compared with the double one. The proposed model may be used to predict the response of a structure in the preliminary design stage for practical engineering.  相似文献   

堆石防波堤不规则波浪反射系数试验研究     

房伟  陈国平  严士常  钟雄华  王聪 《海洋工程》2017,35(5):125-131

结合物理模型试验,分析斜坡坡度、波陡、相对水深、护面类型和破波参数等因素对堆石防波堤不规则波浪反射系数的影响规律。将常用的Van der Meer公式,Seelig公式,Postma公式和Davison公式计算值和实测值进行比较,并结合试验数据,基于有效波高和平均周期定义的Iribarren数,得出堆石防波堤不规则波浪反射系数经验公式。结果表明,该公式能较好地计算不规则波作用下块石和扭王块体护面堆石防波堤波浪反射系数。  相似文献   

防波堤的人工神经网络Monte Carlo法可靠性分析     

张向东  董胜  张磊  张国伟 《中国海洋大学学报(自然科学版)》2012,42(4):82-86

防波堤建设费用巨大,且一旦遭到破坏,后果甚为严重,因此,如何准确地计算防波堤的可靠性意义重大.随着人工神经网络理论的快速发展,人工神经网络方法在结构可靠性分析中的应用逐渐得到重视.基于神经网络的Monte Carlo法计算直立式防波堤的可靠性,概率意义明确.以秦皇岛典型直立堤为算例,采用基于神经网络的Monte Carlo法对直立式防波堤进行可靠性分析时,将直立堤滑动破坏和倾覆破坏的极限状态方程中的所有参数均作为变量处理,并将计算结果与Monte Carlo模拟的直接抽样法、重要抽样法以及独立变量JC法的计算结果进行对比.结果表明:基于神经网络的Monte Carlo法和Monte Carlo模拟的直接抽样法、重要抽样法计算结果相近,而比独立变量JC法的计算结果略低.  相似文献   

The effects of tillage induced surface roughness,slope and discharge rate on soil detachment by concentrated flow: An experimental study     

Jiaqian Sun  Naichang Zhang  Mingxin Shi  Yanbin Zhai  Faqi Wu 《水文研究》2021,35(6):e14261

Soil erosion in sloping cropland is a key water and soil conservation issue in the Loess Plateau region, China. How surface roughness influences soil detachment remains unclear due to the inconsistent results obtained from existing studies. The objectives of the present study were to evaluate the effects of tillage practices on soil detachment rate in sloping cropland and establish an accurate empirical model for the prediction of soil detachment rates. A series of movable bed experiments were conducted on sloping surfaces under three different tillage practices (manual dibbling, manual hoeing, and contour drilling), with a smooth surface (non-tillage) as a control. The research indicated that soil detachment rate significantly increased with roughness (p < 0.05) since the average soil detachment rate was the highest under the contour drilling treatment (6.762 g m⁻² s⁻¹), followed by manual hoeing (4.180 g m⁻² s⁻¹), and manual dibbling (3.334 g m⁻² s⁻¹); the lowest detachment rate was observed under the non-tillage treatment (3.214 g m⁻² s⁻¹). Slope gradient and unit discharge rate were positively correlated with soil detachment rate and proved to be more influential than soil surface roughness. Four composite hydraulic parameters were introduced to estimate soil detachment rate on tilled surfaces. Regression analyses revealed that stream power was the most effective predictor of soil detachment rate compared with unit length shear force, shear stress, and unit stream power. By integrating surface roughness as a variable, the detachment rate could be accurately described as a nonlinear function of stream power and surface roughness. The results of the present study indicate that tillage practice could influence soil loss on sloping cropland, considering the higher soil detachment rates under all tillage practices tested compared with non-tillage. The results are attributed mainly to concentrated flow caused by the high water storage levels on tilled surfaces, which could damage surface microtopography and, subsequently, the development of headcuts.  相似文献   

可液化倾斜场地中桩基动力响应振动台试验研究   总被引：2，自引：1，他引：1       下载免费PDF全文

周恩全  伊思航  文艳  陆建飞 《地震工程学报》2020,42(3):732-741

为研究倾斜场地中桩基的动力响应,以2011年新西兰地震中受损的Dallington桥为原型,设计并完成可液化倾斜场地桥梁桩-土相互作用的振动台模型试验。试验再现了喷砂、冒水、地裂缝、场地流滑等宏观现象。试验结果表明,土层足够的液化势及惯性是造成倾斜场地侧向流滑的必要条件;浅层土相比深层土更易液化,液化层中的加速度由下至上呈现逐渐衰减的趋势,而未液化砂土层却表现为逐渐增大的特征;深部测点的桩侧土压力明显大于浅部测点,且土体的液化会弱化土对结构的压力;结构应变最大值位于上部桥台,而结构弯矩在桩身中部及土层分界面附近出现两个较大值,桩端嵌固及倾斜场地流滑是造成出现两个弯矩较大值的主要原因。  相似文献   

Artificial Marine Micro‐Reserves Networks (AMMRNs): an innovative approach to conserve marine littoral biodiversity and protect endangered species          下载免费PDF全文

José C. García‐Gómez  José M. Guerra‐García  Free Espinosa  Manuel J. Maestre  Georgina Rivera‐Ingraham  Darren Fa  Alexander R. González  Aurora Ruiz‐Tabares  Carlos M. López‐Fé 《Marine Ecology》2015,36(3):259-277

Coastal engineering works, especially the outer breakwaters of ports where environmental conditions are usually good, often constitute new habitats for marine littoral species. Their potential indirect contribution to the regeneration and conservation of protected species opens up a new perspective in protection of marine biodiversity. This is particularly true when these works harbour, as we show here, important reproductive populations of species that are threatened or even in danger of extinction. We provide integrated data on protected marine species in Southern Iberia established on different substrata (quarried dolomitic rocks, concrete cubic blocks, concrete tetrapods and vertical concrete walls) that are used in the construction of artificial levees that could potentially be Artificial Marine Micro‐Reserves (AMMRs). We also present the first evidence of the ‘reserve effect’ in potential AMMRs and we discuss the need for the creation of AMMRs including their effective networking (AMMRNs), supporting data for which has been observed by studying coastal facilities subjected to strict access restrictions (for security reasons, not conservation). These facilities have acted as valuable proxies and, in reality, potentially act as AMMRs, as well as having a role in helping to detect and control invasive species. We discuss the ecological engineering aspects related to the design and type of materials used in coastal constructions with a view to aiding the integration of these into existing coastal ecosystems as well as promoting greater settlement of species and therefore increases in biodiversity. Finally, the environmental implications of AMMRNs within the future implementation strategy of the Water Framework Directive 2000/60 EC are also discussed.  相似文献