An optimization approach to the similarity criteria of flows and its application

In the present paper, we propose an optimization approach to investigate the similarity criteria of complex flows. With this approach, we may identify the dominant dimensionless variables governing complex flows by numerical sensitivity analysis. Firstly, we define the sensitivity factor and examine its dependence on the dimensionless variables. Then, we apply this approach to study the similarity criteria of porous media flow in a presumed oil reservoir. The similarity principle obtained from the numerical sensitivity analysis is in agreement with the theoretical law, thus demonstrating the feasibility of the proposed optimization approach. Further explanation is given by analyzing the deviation of pressure distribution in a model from its prototype. In addition, we examine the effects of flow parameter variation on the sensitivity factors and find that the dominant dimensionless variables may change from different sets of parameters.     

Diurnal variations of summer precipitation in Beijing

Climatic characteristics and secular trends of diurnal variations of summer precipitation in Beijing are studied using hourly self-recording rain-gauge data during 1961-2004. The results show that both rainfall amount and rainfall frequency present high values from late afternoon to early morning and reach the minima around noon. Two separate peaks can be identified in the high value period, one in the late afternoon and the other in the early morning. Taking the rainfall duration into account, it is found that the rainfall during late afternoon to midnight mainly comes from the short-duration rainfall events （an event of 1-6 hours in duration）, while the rainfall during midnight to early morning is accumulated mostly by the long-duration rainfall events （an event that lasts longer than 6 hours）. In the recent 40 years, the summer precipitation in Beijing has been considerably restructured. The total rainfall amount of short-duration events has increased significantly, while the total rainfall amount of Iong-duration events has decreased.     

A piecewise-integration method for simulating the influence of external forcing on climate

Climate drift occurs in most general circulation models （GCMs） as a result of incomplete physical and numerical representation of the complex climate system, which may cause large uncertainty in sensitivity experiments evaluating climate response to changes in external forcing. To solve this problem, we propose a piecewise-integration method to reduce the systematic error in climate sensitivity studies. The observations are firstly assimilated into a numerical model by using the dynamic relaxation technique to relax to the current state of atmosphere, and then the assimilated fields are continuously used to reinitialize the simulation to reduce the error of climate simulation. When the numerical model is integrated with changed external forcing, the results can be split into two parts, background and pertur- bation fields, and the background is the state before the external forcing is changed. The piecewise-integration method is used to con- tinuously reinitialize the model with the assimilated field, instead of the background. Therefore, the simulation error of the model with the external forcing can be reduced. In this way, the accuracy of climate sensitivity experiments is greatly improved. Tests with a simple low-order spectral model show that this approach can significantly reduce the uncertainty of climate sensitivity experiments.     

Ultrasound Imaging Signal Analysis of Underwater Topography in River Model Experiment

In this paper, we analyze the feature of ultrasonic image and investigate the effect of topography material, flow velocity and sediment concentration on the imaging of underwater topography by imaging experiments of model sands. These imaging experiments are conducted in river engineering physical model.The results show that the vertical distribution of pixel values is changed hugely at the position of imaging bright band of underwater topography. The imaging of underwater topography is not affected when flow velocity is below 40 cm/s and sediment concentration is below 5.0 ‰. The main influence factors of imaging signals are flow velocity and sediment concentration near the topographical bed. The resolution of ultrasound imaging signals is high, and the topography consisted of model sands with particle size smaller than 0.1 mm can be monitored well in the river model experiment.     

Social vulnerability for public safety: A case study of Beijing, China

Vulnerability to hazards includes not only components of a physical nature, but also those arising from social factors. In developing measures for disaster prevention or emergency response for disaster relief of big cities, an analysis of social vulnerability is very necessary but quite difficult. In order to address the problem, using Beijing as an example, we established a social vulnerability index system including 26 factors and developed an improved analytic hierarchy process (AHP) method. The weight of each factor was evaluated using the improved AHP process that obviously increased the passing rate of consistency of the experts’ questionnaire. The population, career, economy, infrastructure and social vulnerability distribution maps of Beijing were obtained. From them, it’s easy to see the characteristics of various vulnerability distributions. Through sensitivity analysis, the influencing factors of each area were listed in order of importance. The approach are useful for assessing, reducing the social vulnerability of big cities in China.     

Response of water budget to recent climatic changes in the source region of the Yellow River

Discharge in the source region of the Yellow River significantly declined after 1990.China Meteorological Administration(CMA) data show that precipitation in this region was low in the 1990s but returned to above normal after 2002;in recent decades there has been rapid warming of surface air,moistening and wind speed decrease.To investigate the influences of recent climatic changes on the water budget,this study simulates the surface water budget at CMA stations within and surrounding the source region during 1960-2006,using an improved land surface model.Results indicate that the spatial pattern of precipitation change is an important factor(except for precipitation amount and intensity) in determining the response of runoff to precipitation changes.Low runoff in the 1990s was consistent with precipitation amount and intensity.The recovery of precipitation after 2002 is mainly from increased precipitation in the dry area of the source region.Evaporation was mainly limited by water availability in this dry area,and thus most of the precipitation increase was evaporated.By contrast,energy availability was a more important influence on evaporation in the wet area.There was more evaporation in the wet area because of rapid warming,although precipitation amount partly decreased and partly increased,contributing to the reduction of runoff after 2002.This control on evaporation and its response,together with the modified spatial pattern of precipitation,produced a water budget unfavorable for runoff generation in the source region during recent years.     

Simulation study of discharge processes in thunderstorm

The discharge characteristics in thunderstorm have been calculated by using a numerical cloud model. The results indicate that discharge processes occur when simulated thunderstorm developed at the stage of 30-45 min and initial locations of discharge mainly distributes between 4.4-4.8 km and 6.4-6.8 km above the ground (corresponding to ambient temperature of - 10℃ and -25℃. In simulated thunderstorm with a tripole electric structure, 10% of discharges occur between upper positive charge area and middle negative charge area and propagate upwards (from middle negative charge area to upper positive charge area); while, 90% of discharges occur between lower positive charge area and middle negative charge area and propagate downwards (from negative charge area to lower positive charge area). There is a positive correlation between updraft and discharge. The occurrence of discharge process needs hydrometer with a specified concentration and size in cloud (corresponding to ≥ 5 mm/h for precipitation on the ground). The maximum value of precipitation lags the peak of discharge number by a period of about several minutes. The discharge and its variation in thunderstorm are an important factor for monitoring and forecasting thunderstorm.     

Interannual variation of annual precipitation and urban effect on precipitation in the Beijing region

The large scale character of the interannual variation of precipitation and the urban effect on local annual precipitation anomaly are investigated in this paper based on the 1960-2000 annual precipitation observations at 20 stations in the Beijing region.The results show that:the annual precipitation in the Beijing region possesses the large scale variation character with the linear trend of-1.197/10 yr,which corresponds to a total reduction of 27.82 mm in annual precipitation in the 41 years;the local annual precipitation anomalies(percent of the normal 1960-2000)show a positive center near the urban area,i.e.urban precipitation island(UPI),whose intensity increases with the linear trend of 0.6621%/10 yr,opposite to the interannual trend of large scale precipitation over the Beijing region;changes in the UPI are also associated with the intensity of synoptic processes of precipitation,and when the synoptic processes are strong(wet years),the intensity of UPI strengthens,while the synoptic processes are weak(dry years),and the UPI disappears in the Beijing region.     

Spatial hazard analysis and prediction on rainfall—induced landslide using GIS

The application of landslide hazard model cou-pled with GIS provides an effective means to spatial hazard analysis and prediction on rainfall-induced landslides.A modified SINMAP model is established based upon the sys-tematic investigation on previous GIS-hased landslide analy-sis models.By integrating the landslide deterministic model with the hydrological distribution model based on DEM,this model deeply studied the effect of underground water dis-tribution due to reinfall on the slope stability and landslide occurrence,including the effect of dynamic water pressure resulting from the dowm slope seepage process as well as that of static water pressure.Its applicability has been testified on the Xiaojiang watershed,the rainfall-induced landslides widespread area in Southeast China.Detailed discussion WAS carried out on the spatial distribution characteristics of landslide hazard and its extending trend,as well as the quantitative relationship between landslide hazard with pre-cipitation,slope angle and specific catchment area in the Xiaojiang watershed.And the precipitation threshold for landslide occurrence was estimated.These analytical results are proved useful for geohazard control and engineering decision-making in the Xiaojiang watershed.     

Connectivity of sparse vehicular ad hoc networks with channel randomness

<正> In this paper,we investigate the connectivity of vehicular ad hoc networks in free-flow traffic situationwith channel randomness.In order to illustrate the realistic environment,we consider that vehiclesare distributed in free-flow highway according to a Poisson point process,and signal propagation betweenconnected vehicles is subjected to log-normal shadowing effects.We obtain the distribution of the spaceheadway between successive vehicles and the distribution of signal coverage,which allows us to use theequivalent M/G/∞ queue theory to model the connectivity of VANETs in the form of average broadcastpercolation distance and average number of connected nodes.Then,extensive simulation studies are conductedto evaluate the obtained results.The analytical model presented here is able to describe the impactof various system parameters,including traffic parameters and signal propagation parameters on the connectivity.We use our analytical results,along with the common signal propagation data,to understandimpact of channel randomness on the connectivity of VANETs.     

Inductive transfer learning for unlabeled target-domain via hybrid regularization

Recent years have witnessed an increasing interest in transfer learning. This paper deals with the classification problem that the target-domain with a different distribution from the source-domain is totally unlabeled, and aims to build an inductive model for unseen data. Firstly, we analyze the problem of class ratio drift in the previous work of transductive transfer learning, and propose to use a normalization method to move towards the desired class ratio. Furthermore, we develop a hybrid regularization framework for inductive transfer learning. It considers three factors, including the distribution geometry of the target-domain by manifold regularization, the entropy value of prediction probability by entropy regularization, and the class prior by expectation regularization. This framework is used to adapt the inductive model learnt from the source-domain to the target-domain. Finally, the experiments on the real-world text data show the effectiveness of our inductive method of transfer learning. Meanwhile, it can handle unseen test points.     

Development of an Accurate Urban Modeling System Using CAD/GIS Data for Atmosphere Environmental Simulation

This paper presents an urban modeling system using CAD/GIS data for atmosphere environmental simulation, such as wind flow and contaminant spread in urban area. The CAD data is used for the shape modeling for the high-storied buildings and civil structures with complicated shape since the data for that is not included in the 3D-GIS data accurately. The unstructured mesh based on the tetrahedron element is employed in order to express the urban structures with complicated shape accurately. It is difficult to understand the quality of shape model and mesh by the conventional visualization technique. In this paper, the stereoscopic visualization using virtual reality (VR) technology is employed for the verification of the quality of shape model and mesh. The present system is applied to the atmosphere environmental simulation in urban area and is shown to be an useful planning and design tool to investigate the atmosphere environmental problem.     

Testing the ability of RIEMS2.0 to simulate multi-year precipitation and air temperature in China

RIEMS2.0 （Regional Integrated Environment Modeling System, Version 2.0） is now being developed starting from RIEMS1.0 by the Key Laboratory of Regional Climate Environment Research for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, China. In order to test RIEMS2.0’s ability to simulate long-term climate and its changes, as well as provide a basis for further development and applications, we compare simulated precipitation and air temperature from 1980 to 2007 （simulation duration from Jan. 1, 1979 to Dec. 31, 2007） under different cumulus parameterization schemes with the observed data. The results show that RIEMS2.0 can reproduce the spatial distribution of precipitation and air temperature, but that the model overestimates precipitation with the rainfall center moving northwestward and underestimates air temperature for annual simulations. Annual and interannual variations in precipitation and air temperature for different climate subregions are well captured by the model. Further analysis of summer and winter simulations shows that precipitation is overestimated, except for the Jianghuai-Jiangnan subregions in the winter, and the air temperature bias in the summer is weaker than in the winter. There are larger biases for precipitation and air temperature in semiarid subregions. Anomalies in precipitation and air temperature are also well captured by the model. Although a similar distribution can be found between observed data and simulated results under different cumulus parameterization schemes, these show differences in intensity and location. In sum, RIEMS2.0 shows good stability and does well in simulating the long-term climate and its changes in China.     

Interannual variation of annual precipitation and urban effect on precipitation in the Beijing region

The large scale character of the interannual variation of precipitation and the urban effect on local annual precipitation anomaly are investigated in this paper based on the 1960—2000 annual precipitation observations at 20 stations in the Beijing region. The results show that: the annual precipitation in the Beijing region possesses the large scale variation character with the linear trend of -1.197/10 yr, which corresponds to a total reduction of 27.82 mm in annual precipitation in the 41 years; the local annual precipitation anomalies (percent of the normal 1960—2000) show a positive center near the urban area, i.e. urban precipitation island (UPI), whose intensity increases with the linear trend of 0.6621%/10 yr, opposite to the interannual trend of large scale precipitation over the Beijing region; changes in the UPI are also associated with the intensity of synoptic processes of precipitation, and when the synoptic processes are strong (wet years), the intensity of UPI strengthens, while the synoptic processes are weak (dry years), and the UPI disappears in the Beijing region.     

Traffic Prediction in 3G Mobile Networks Based on Multifractal Exploration

Traffic prediction plays an integral role in telecommunication network planning and network optimization. In this paper, we investigate the traffic forecasting for data services in 3G mobile networks. Although the Box-Jenkins model has been proven to be appropriate for voice traffic (since the arrival of calls follows a Poisson distribution), it has been demonstrated that the Internet traffic exhibits statistical self-similarity and has to be modeled using the Fractional AutoRegressive Integrated Moving Average (FARIMA) process. However, a few studies have concluded that the FARIMA process may fail in modeling the Internet traffic. To this end, we conducted experiments on the modeling of benchmark Internet traffic and found that the FARIMA process fails because of the significant multifractal characteristic inherent in the traffic series. Thereafter, we investigate the traffic series of data services in a 3G mobile network from a province in China. Rich multifractal spectra are found in this series. Based on this observation, an integrated method combining the AutoRegressive Moving Average (ARMA) and FARIMA processes is applied. The obtained experimental results verify the effectiveness of the integrated prediction method.     

Simulation of the future change of East Asian monsoon climate using the IPCC SRES A2 and B2 scenarios

In this paper, we applied the newest emission scenarios of the sulfur and greenhouse gases, i.e. Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 and B2 scenarios, to investigating the change of the East Asian climate in the last three decades of the 21st century with an atmosphere-ocean coupled general circulation model. The global warming enlarges the land-sea thermal contrast and, hence, enhances (reduces) the East Asian summer (winter) monsoon circulation. The precipitation from the Yangtze and Huaihe river valley to North China increases significantly. In particular, the strong rainfall increase over North China implies that the East Asian rainy area would expand northward. In addition, from the southeastern coastal area to North China, the rainfall would increase significantly in September, implying that the rainy period of the East Asian monsoon would be prolonged about one month. In July, August and September, the interannual variability of the precipitation enhances evidently over North China, meaning a risk of flooding in the future.     

A Model Combining Discrete Event System Simulation and Genetic Algorithm for Buffer Allocation in Unreliable Large Production Lines

To solve the difficulties in allocating buffers for unreliable large production lines, this paper investigated a model combining the genetic algorithm with the discrete event system simulation method. In the simulation method, times-to-failure of an unreliable large production line is assumed to follow exponential distribution, whereas times-to-repair and times-to-processing are set to follow an Erlang-k distribution. Using a genetic algorithm based on special position-based mapping means and elitist protection strategy, the buffer configuration of an auto-body welding line is optimized. The simulation of the optimized configuration shows that the performance of the production line, such as productivity and the main average utilization of the workstations, is much improved. This model can optimize the allocation of buffers for unreliable large production lines effectively.     

A Novel Dynamic Decision Model in 2 player Symmetric Repeated Games

Considering the dynamic character of repeated games and Markov process, this paper presented a novel dynamic decision model for symmetric repeated games. In this model, players＇ actions were mapped to a Markov decision process with payoffs, and the Boltzmann distribution was intousluced. Our dynamic model is different from others＇ , we used this dynamic model to study the iterated prisoner＇ s dilemma, and the results show that this decision model can successfully be used in symmetric repeated games and has an ability of adaptive learning.     

Distribution Regularity of Debris Flow and Its Hazard in Upper Reaches of Yangtze River and Other Rivers of Southwestern China

In the upper reaches of Yangtze River and other rivers of southwestern China, the debris flows develop and lead to most serious disasters because of the various landforms, complex geological structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform, geological structure, and precipitation. The regularities of distribution of debris flows are as following： （1） distributed in transition belts of different morphologic regions; （2） distributed in the area with strong stream trenching; （3） distributed along fracture zones and seismic belts： （4） distributed in the area with abundant precipitation; （5） distribution of debris flow is azonal. The activity of abundant debris flows not only brings harm to Towns, Villages and Farmlands, Main Lines of Communication, Water-Power Engineering, Stream Channels etc., but also induces strong water and soil loss. According to the present status of debris flow prevention, the problems in disasters mitigation and soil conservancy are found out, and the key works are brought up for the future disasters prevention and soil conservancy.     

GIS-Based Spatial Analysis and Modeling for Landslide Hazard Assessment： A Case Study in Upper Minjiang River Basin

By analyzing the topographic features of past landslides since 1980s and the main land-cover types （including change information） in landslide-prone area, modeled spatial distribution of landslide hazard in upper Minjiang River Basin was studied based on spatial analysis of GIS in this paper. Results of GIS analysis showed that landslide occurrence in this region closely related to topographic feature. Most areas with high hazard probability were deep-sheared gorge. Most of them in investigation occurred assembly in areas with elevation lower than 3 000 m, due to fragile topographic conditions and intensive human disturbances. Land-cover type, including its change information, was likely an important environmental factor to trigger landslide. Destroy of vegetation driven by increase of population and its demands augmented the probability of landslide in steep slope.