We analyzed the weather situation, boundary layer structure, and PM_2.5 concentration during the haze-fog event of 27 to 31 Jan 2013 occurred in the North China plain(NCP). The weather conditions indicated that latitudinal circulation and weak pressure system controlled the NCP area during that period. There were continuous inversion layer and stable structure within the boundary layer. The surface and lower level wind was usually less 2 m/s, and relative humidity was higher. Such stable weather situation and high emissions were favorable to pollutant accumulation and fine aerosol's formation. Then, the high PM_2.5 concentration directly leaded to low visibility and heavy fog-haze. Real-time WRF-Chem model made a good forecast for the PM_2.5 concentration and the haze spatio-temporal distribution and evolution in the NCP area. The wind convergence and pollutant accumulation usually occurred along the mountain edge and in the NCP area.

Due to the time-varying characteristics of length-of-day (LOD), it is difficult to model LOD variations with a deterministic model. We employ a new type of artificial neural networks (ANN)-extreme learning machine (ELM) to predict LOD variations. In order to solve the problems of embedding dimension selection and network topology design, a training algorithm for ELM based on grey relational analysis (GRA) is first proposed. It optimizes the input and hidden layers simultaneously. Secondly, the values of LOD variation are preprocessed and a GRA-ELM model is then set up to accurately forecast LOD variation in near real-time. Finally, the prediction results are analyzed and compared with those obtained by the back propagation neural networks, generalization regression neural networks and Earth orientation parameters prediction comparison campaign. The results show that the prediction accuracy of our method is equal to or even better than those of the other prediction methods. The developed method is easy to use.

In this paper, an application-layer QoS(quality of service) control method for real-time video transmission based on 3G network is proposed. This method calculates packet loss rate using a linear prediction algorithm, and it introduces a self-designed SILD(strict increase loose decrease) congestion control algorithm to adjust the transmission bit rate of video streams. Experimental results show that the performance parameters, such as transmission delay and jitter, meet the industrial standard requirements and that the utilization of network bandwidth is improved. Therefore, the proposed QoS control method is suitable for real-time video transmission over 3G network and has good practicality and feasibility.

Dust emission has significant influences on the air quality of Nanjing. Annual emissions of soil, paved road, and construction dusts in 2010 were estimated by using AP-42 methods and their spatial distributions with a 3 km×3 km grid resolution are given. Results showed that the emissions of PM₁₀ in Nanjing were 261, 67 270, and 7 540 tons, respectively. The largest dust emission was from the paved road, and the emission value gradually decreased from downtown to suburban area. Overall, the dust emission of PM₁₀ in Nanjing was less than that in Shanghai and was about 67.3% of the local industry emission.

An adaptive-energy-threshold-based energy-efficient on-demand multicast routing protocol (EMRP) for wireless Ad Hoc and sensor networks is proposed to prolong the network lifetime. Based on the network energy status, EMRP adaptively calculates an energy threshold which protects the nodes with low remaining energy by discouraging their engagement in multicast tree. Further, it adopts destination-driven strategy to efficiently reduce the multicast tree size to save the energy for a multicast task. EMRP does not require nodes to keep global or local network state information. It has low overheads and is easy to implement. Simulation results show that EMRP greatly reduces the energy cost for per-packet delivery and prolongs the network lifetime.

In this work, Wuhu City in China was selected as the studied area. NDWI, MNDWI, LBV_B, KT₃+TM₄>TM₂+TM₇, and a new model KT₃+TM₂>TM₄+TM₃ were used to extract water body information based on Landsat TM data. Qualitative and quantitative comparisons were made. The results show that the new water information extraction model, KT₃+TM₂>TM₄+TM₃, is the most accurate(with a total accuracy of 93%), and its accuracy is less affected by vegetation and buildings.

Different emission inventories were applied to investigate the spatial distribution and temporal variation of anthropogenic emission in China during the period from 2000 to 2010. The analysis results indicate that the total anthropogenic emission generally increased during the past 10 years. NO_x emission increased continuouslly and it exceeded SO₂ emission in 2010. From 2006 to 2010, PM₁₀ and SO₂ emissions decreased by 76% and 10%, respectively. From 2000 to 2010, the emissions of SO₂, NO_x, and BC increased by 5.6 Tg (25%), 13.1 Tg (85%), and 0.3 Tg (20%), respectively, but OC emission decreased by about 0.7 Tg (17%), PM₁₀ emission largely decreased by 12.4 Tg (74%), and there was no obvious change in NMVOC emission. There are quite large differences in the temporal variations of emissions among different regions of China.

To improve the accuracy of voice activity detection (VAD) under noisy environments, a VAD algorithm based on Mel frequency cepstrum coefficients (MFCC) distance with an order statistics filter (OSF) is proposed. First, the MFCC for each frame of the signals is extracted. Then, the background noise is estimated using the headmost sixteen frames. Finally, the MFCC cepstrum distance between each frame and the background noise is calculated. An order statistics filter is applied to a sequence of the estimated cepstrum distances to obtain the weighted cepstrum distance of each frame. The speech/non-speech classification is based on the weighted cepstrum distance. The experimental analysis carried out on the TIMIT speech corpus shows that the proposed algorithm is effective under white noise, pink noise, car noise, and fighter noise conditions even at low ratio of signal to noise.

Asian options are path dependent contingent claims whose terminal payoff depends on the average of underlying asset price over some period prior to maturity. Using change of numéraire as a tool, we illustrate how to derive price formulae for the discrete and continuous geometric average Asian options with floating strike price by risk-neutral valuation approach.

Relief degree of topography is a significant factor to affect the development of economy and society.By using window analysis theory and mean change-point analysis method, the optimal statistical unit of relief amplitude is extracted based on ASTER GDEM data, and then the classification and correlation analyses on relief degree of topography are carried out.It is shown that 0.202 5 km² is the best measuring unit.The differences in relief amplitude between different provinces are obvious, and the differences are not obvious in each province.Meanwhile, the relationships of relief degree of topography with population and economy are analyzed by using spatial analysis technique,statistical method, and PCA sorting method.The results show that population density gradually decreases with relief degree of topography and it reaches a fixed value when relief degree of topography is 3.7.The negative correlation degree of relief degree of topography with the proportion of the third industry is large, the degree with urbanization rate is less, and the degree with per capita GDP is the least.

Ninety-nine volatile organic compounds (VOCs) species were measured in autumn in Beijing. The average concentration of VOCs was 54.6 ppb. The average concentiations of NMHCs and oxygenated VOCs were 38.0 ppb and 10.04 ppb, respectively. The pollution status of VOCs was evaluated based on the diurnal variation and ratio between typical VOCs species(E/E and B/T). The air masses observed were characterized to photochemical-aged and supposed to be affected mainly by traffic emission sources. The same conclusion was reached by the co-analysis of air mass backward trajectory and B/T value at noon.

An adversary can infiltrate online social networks (OSNs) on a large scale by deploying socialbot network, which is an army of socialbot accounts. This will endanger the information security of online social network and users. To solve the problem, we propose a detection method based on the population characteristics. We extract the following population characteristics: centralized created time, similar screen names, and coincident active time. On the basis of the extracted charateristics and by using date mining method, the method is proposed to detect socialbots networks. The method is used in a data set of 480 000 users of sina microblog and detects many socialbots networks which include 6 899 socialbots accounts. The low false negative rate and false positive rate indicate that the method is feasible and effective.

Single screw water vapor compressor is applied in the mechanical vapor recompression heat pump (MVR) system. Analysis of the working process of the compressor is carried out. Experiments for the MVR systems with closed cycle and open cycle are performed under different evaporation temperature conditions. The results show that the volume efficiency of the compressor is larger than 0.73 and the adiabatic efficiency is larger than 0.5 when the evaporation temperature is higher than 80 ℃. The largest practical COP of the system reaches 12.5 and the highest actual SMER reaches 20 kg/(kW·h) in the present experiments. The high efficiency and energy-saving features of the MVR system driven by single screw water vapor compressor are fully shown in this study.

Based on HJ-CCD remote image data, object-oriented technology was applied into the land-cover extraction in Hunan Province. We mainly focus on land-cover survey method using HJA/B remote sensing images on large scale and explore a set of approaches to get land-cover information using object-oriented technology. The overall accuracy of the results is 84.99% and Kappa coefficient is 82.79%. The research results show that land-cover survey method using HJ-CCD remote sensing images and object-oriented classification technology is feasible and effective on large scale.

The hexavalent chromium transport in groundwater in Jiaozuo part of the middle route of south to north water transfer project was investigated by using the numerical simulation technology. The simulation results show that hexavalent chromium contamination plume may migrate to the area beneath the main canal about 20 years later, which will place a threat to the security of water quality of the main canal. Furthermore, the primary factors controlling the hexavalent chromium transport in groundwater were identified for different simulation periods. The investigation results may have implication on protection of water quality of the main canal.

The 95 alien invasive plants of 23 families were identified in Northeast China based on field investigation and reported data. Based on comprehensive analysis of the previous risk assessment methods of alien invasive species, a risk assessment model of alien invasive plants in Northeast China was established. We assess the alien invasive plants in Northeast China using this model, and 25, 53, and 17 species are identified as the species of the risk levels of A, B, and C, respeetively. Some control measures were presented for each risk level.

This study focuses on the pore structure and gas migration in tight sandstone reservoir in Kuqa depression of Tarim basin, based on microscopic observation and laboratory experiments. Results indicate that main pore types of tight sandstone in the study area are disslolved pores and slot pores, and the pore-throat radiuses are about 0.1 μm; there is no obvious correlation between permeability and porosity; gas migration in tight sandstone requires a certain starting pressure gradient; and the process of gas migration and accumulation in tight sandstone can be divided into the following three stages: accumulation of gas bubbles, formation of continuous state gas, and migration of the continuous state gas through pore system.

The daily averages of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated in several years in China. A radiative transfer model (SBDART) was utilized to simulate the solar irradiance values at the surface and TOA by using as input aerosol properties retrieved from AERONET sun photometer measurements. At the AERONET stations at SACOL, Xianghe, and Taihu, the daily mean ARF values were (-7.2±7.1), (-11.7±9.5), and (-14.9±8.3) W/m² at the TOA; (-21.9±12.2),(-36.5±29.5), and (-42.2±21.0) W/m² at the surface; and (14.7±9.7), (24.8±23.0), and (27.3±16.5) W/m² in the atmosphere, respectively. The surface cooling and the atmosphere warming caused by aerosol at Xianghe and Tiahu stations were greater than at SACOL. The daily ARF of the desert dust aerosol was significantly greater than the total average of aerosol, especially at the surface and in the atmosphere, showing that dust can produce more obvious surface cooling and atmosphere warming.

As the collision theory for raindrop and aerosol particle is important in below-cloud scavenging, collision efficiency as a function of raindrop diameter (D_p) and aerosol diameter (d_p) is discussed. The scavenging coefficient (SC) under thundercloud is 5 to 6 times higher than those under non-thundercloud when d_p is less than 1 μm. Field measurements of aerosol number concentration at bottom and top of Huangshan mountain from June to August of 2011 were used to analyze the variation characteristics of observed and theoretical SCs. The results show that observed SC variation for ultrafine-sized particle is in reasonable agreement with the theoretical one, and the observed SC is 5 to 6 times higher than the theoretical SC. Submicron-sized particle SC is higher under thundercloud than that under non thundercloud. Based on the observations, exponential relationship between the hour-averaged SC and rainfall intensity is derived, in which the correlation coefficient is 0.81.

Samples of ambient fine particulate matter were collected using Andersen cascade sampler. The contributions of secondary organic carbon (SOC) to particulate matter in different sizes were determined by the "OC/EC minimum ratio" technique. The sources of size-resolved fine particulate matter in Hangzhou were analyzed using the CMB model. The results showed that secondary aerosol and vehicle exhaust were the major sources in small-size segment. The contribution of suspended dust, cement dust, and fly ash gradually increased in coarse segment, and the contribution of secondary particles and vehicle exhaust dropped to about 50%.