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Search Results: 1 - 10 of 120211 matches for " Aijun Wang "
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Study on Occupational Health and Safety Impact of Surfactant-Grafted Polyacrylamide Used in Oilfields  [PDF]
Tingting Jiang, Baohui Wang, Aijun Wang, Hongjing Han, Hongjun Wu
Occupational Diseases and Environmental Medicine (ODEM) , 2015, DOI: 10.4236/odem.2015.33006
Abstract: Surfactant-grafted Polyacrylamide (S-PAM) serves as a novel oil displacement agent in oilfield. Its toxicity and the impact on the occupational safety are unclear. The analysis on composition and chemical structure of S-PAM shows that due to its instability the harmful ammonia gas may be generated during the operation of S-PAM or high temperature. The toxicity and safety evaluation of the S-PAM were analyzed, and suggestions on the protection were proposed. It can provide a safe and healthy working environment for the operators with enormous social and economic benefits.
Geodesic and Contour Optimization Using Conformal Mapping
Ricky Fok,Aijun An,Xiaogong Wang
Statistics , 2015,
Abstract: We propose a novel optimization algorithm for continuous functions using geodesics and contours under conformal mapping.The algorithm can find multiple optima by first following a geodesic curve to a local optimum then traveling to the next search area by following a contour curve. To improve the efficiency, Newton-Raphson algorithm is also employed in local search steps. A proposed jumping mechanism based on realized geodesics enables the algorithm to jump to a nearby region and consequently avoid trapping in local optima. Conformal mapping is used to resolve numerical instability associated with solving the classical geodesic equations. Geodesic flows under conformal mapping are constructed numerically by using local quadratic approximation. The parameters in the algorithm are adaptively chosen to reflect local geometric features of the objective function. Comparisons with many commonly used optimization algorithms including gradient, trust region, genetic algorithm and global search methods have shown that the proposed algorithm outperforms most widely used methods in almost all test cases with only a couple of exceptions.
Optimization of Joint Power and Bandwidth Allocation in Multi-Spot-Beam Satellite Communication Systems
Heng Wang,Aijun Liu,Xiaofei Pan
Mathematical Problems in Engineering , 2014, DOI: 10.1155/2014/683604
Abstract: Multi-spot-beam technique has been widely applied in modern satellite communication systems. However, the satellite power and bandwidth resources in a multi-spot-beam satellite communication system are scarce and expensive; it is urgent to utilize the resources efficiently. To this end, dynamically allocating the power and bandwidth is an available way. This paper initially formulates the problem of resource joint allocation as a convex optimization problem, taking into account a compromise between the maximum total system capacity and the fairness among the spot beams. A joint bandwidth and power allocation iterative algorithm based on duality theory is then proposed to obtain the optimal solution of this optimization problem. Compared with the existing separate bandwidth or power optimal allocation algorithms, it is shown that the joint allocation algorithm improves both the total system capacity and the fairness among spot beams. Moreover, it is easy to be implemented in practice, as the computational complexity of the proposed algorithm is linear with the number of spot beams. 1. Introduction In recent years, the multi-spot-beam technique has played an important role in the satellite communication systems, as it can not only supply higher power density to a particular spot beam but also construct flexible service networks. However, the satellite power and bandwidth resources are scarce and expensive in multi-spot-beam satellite communication systems. As a result, it is crucial to make effort to enhance the utilization efficiency of power and bandwidth resource. Because the coverage of each spot beam is different, the real traffic demand of each spot beam is different and time varying. In addition, the channel condition of each spot beam is also affected by the weather condition. Therefore, it is important to dynamically allocate the bandwidth and power resource to each spot beam to meet its traffic demand. In the previous work, separate optimal power or bandwidth allocation algorithms were proposed in [1–4] and [5], respectively. The work in [1] emphasized the mathematical formulation and analytic solutions of the optimum power resource allocation problem and explained the tradeoff between the total system capacity and fairness among all spot beams with different traffic demands and delay constraints. The optimization problem is solved based on the Karush-Kuhn-Tucker (KKT) condition. However, the works in [1] did not provide the way to find the optimal Lagrangian multipliers. Therefore, the methods of bisection and subgradient were applied to search
Interpreting grain-size trends associated with bedload transport on the intertidal flats at Dafeng, central Jiangsu coast
Jianjun Jia,Yaping Wang,Shu Gao,Aijun Wang,Zhanhai Li
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-0341-z
Abstract: A MIDAS-400 customized data acquisition system has been used for the high-resolution sediment dynamic measurements over the Dafeng intertidal flats of northern Jiangsu during 6 tidal cycles from July 3 to July 10, 2003. The bed shear stress and bedload transport rates, in response to wave-current interactions, are calculated, which indicate that wind waves enhance the bottom shear stress and bedload transport rates. At the station for measurements, bedload transport was directed to seaward, with a sediment discharge of 30–150 kg·m-1 per tidal cycle. The surficial sediment samples were collected from a grid with 10 m spatial intervals over a rectangle 2 × 104 m2 experimental area, near the MIDAS-400 during the spring tide of July 4, 2003, and the neap tide of July 9, 2003. In addition, leveling survey was undertaken to obtain the detailed topography of the sampling area. Grain-size trend analysis of the sediment samples shows that the bedload transport patterns are complex, mainly controlled by the hydrodynamics and local geomorphology (e.g. tidal creeks) over the intertidal flats. Furthermore, the grain-size trends pattern during the neap tide rather than during the spring tide is consistent with the calculated bedload transport, and the grain-size trend vectors for the spring tide are larger than those for the neap tide, indicating that the sampling thickness of surficial sediment during the neap tide may contain the information on the geomorphological evolution (or sediment deposition/erosion) from the spring to the neap tide.
Sediment dynamic responses of coastal salt marsh to typhoon “KAEMI” in Quanzhou Bay, Fujian Province, China
AiJun Wang,Shu Gao,Jian Chen,DongYi Li
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0365-7
Abstract: In order to understand the mechanisms of coastal protection by salt marshes during typhoon events, in situ measurements of water level, tidal current speed and direction, and suspended sediment concentration (SSC) were carried out using Electromagnetic Current Meter (EMCM, AEM HR), miniature pressure sensor (MkV/D) and Seapoint Turbidity Meter (STM) sensor on a tidal flat in Quanzhou Bay, during the period when the typhoon “KAEMI” was passing through the region. The analysis of the data obtained shows that the near-bed current speed within the Spartina alterniflora marsh was generally below 5 cm s 1, which was apparently smaller than on the adjacent bare flat (i.e. 5–30 cm s 1). The change in the near-bed current speed in response to the typhoon event was not significant within the S. alterniflora marsh, but the current direction was influenced by the typhoon. The effect of the typhoon on the SSC was highly significant, with the SSC reaching 13 to 19 times the values on the bare flat or within the marsh under fair weather conditions; the near-bed SSC within the marsh was higher than on the bare flat, after the typhoon landed. The near-bed suspended sediment fluxes within the marsh and on the bare flat during the typhoon event were both enhanced, i.e., 4 times larger than under fair weather conditions. During the ebb, the bottom shear stress on the bare flat exceeded the critical shear stress for sediment motion for most of the ebb duration of the tide and, therefore, the bed sediment was eroding, with the erosion flux after the typhoon landed being around 2 to 3 times the value associated with fair weather conditions. In contrast, within the S. alterniflora marsh, the bottom shear stress was mostly lower than the critical shear stress for sediment motion, or lower than the critical shear stress for the maintenance of suspension; hence, the marsh surface was dominated by settling processes, with a settling flux during the typhoon being 3 to 6 times compared with the fair weather situations. The settling flux during the ebb was up to twice the magnitude for the flood. The comparison of sediment dynamic processes between the S. alterniflora marsh and the bare flat demonstrates that during the typhoon event the bare flat was dominated by erosion, whilst the presence of S. alterniflora favored the accretion of suspended sediment.
Numerical Simulation on Climate Effects of Freezing-Thawing Processes Using CCM3

Chenghai Wang,Guodong Cheng,Aijun Deng,Wenjie Dong,

寒旱区科学 , 2008,
Abstract: A parameterization of soil freezing-thawing physics for use in the land-surface model of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is developed and evaluated. The new parameterization scheme has improved the representation of physical processes in the existing land surface model. Numerical simulations using CCM3 with improved land-surface processes and with the original land-surface processes are compared against the NCEP reanalysis. It is found that the CCM3 version using the improved land surface model shows significant improvements in simulating precipitation in China during the summer season, the general circulation over East Asia, and wind fields over the Tibet Plateau. For the summer season, the improved model was able to better simulate the Indian summer monsoon components, including the mean northerly wind in the upper troposphere and mean southerly wind in the lower troposphere.
Sedimentation rates in the Wanggang salt marshes, Jiangsu

WANG Aijun,GAO Shu,JIA Jianjun,PAN Shaoming,

地理学报 , 2005,
Abstract: Coastal salt-marshes represent an important coastal wetland system. The total area of coastal wetlands exceeds 5000 km2 in Jiangsu Province, China, but it is decreasing rapidly in response to the intense reclamation activities and coastal erosion along a part of the coastline. Hence, two types of plants, Spartina angelica and Spartina alterniflora, were introduced successively into the Jiangsu coastal areas, in order to protect the coastline from erosion and to increase the accumulation rate. Pb-210 and Cs-137 analyses were carried out for sediment samples from the salt-marshes of Wanggang to determine the sedimentation rate, on the basis of an evaluation of the background activity values and the factors affecting the enrichment of Pb-210. Analysis of a typical sediment column of the tidal flat shows that there is weak absorption of Pb-210 in the silt-dominated sediment. Because of the influences of factors such as storm events, bioturbation, material sources and analytical error, some abnormal data points appear in the Pb-210 record. After ignoring these data the calculated sedimentation rate was 3.3 cm yr-1 on average. Based upon analysis of the Cs-137 dating, the rate since 1963 was 3.1 cm yr-1 on average, similar to the data by Pb-210 dating and the previous studies. The dating results show that there were three stages of sedimentation, with the most rapid accretion being taking place after Spartina angelica was introduced into the area. The study also shows that at the stage of Spartina alterniflora growth, the accretion rate was higher than on the flat surface with the same elevation without the cover of this plant.
Sediment dynamic responses of coastal salt marsh to typhoon “KAEMI” in Quanzhou Bay, Fujian Province, China

AiJun Wang,Shu Gao,Jian Chen,DongYi Li,

科学通报(英文版) , 2009,
Abstract: In order to understand the mechanisms of coastal protection by salt marshes during typhoon events, in situ measurements of water level, tidal current speed and direction, and suspended sediment concentration (SSC) were carried out using Electromagnetic Current Meter (EMCM, AEM HR), miniature pressure sensor (MkV/D) and Seapoint Turbidity Meter (STM) sensor on a tidal flat in Quanzhou Bay, during the period when the typhoon “KAEMI” was passing through the region. The analysis of the data obtained shows that the near-bed current speed within the Spartina alterniflora marsh was generally below 5 cm s 1, which was apparently smaller than on the adjacent bare flat (i.e. 5–30 cm s 1). The change in the near-bed current speed in response to the typhoon event was not significant within the S. alterniflora marsh, but the current direction was influenced by the typhoon. The effect of the typhoon on the SSC was highly significant, with the SSC reaching 13 to 19 times the values on the bare flat or within the marsh under fair weather conditions; the near-bed SSC within the marsh was higher than on the bare flat, after the typhoon landed. The near-bed suspended sediment fluxes within the marsh and on the bare flat during the typhoon event were both enhanced, i.e., 4 times larger than under fair weather conditions. During the ebb, the bottom shear stress on the bare flat exceeded the critical shear stress for sediment motion for most of the ebb duration of the tide and, therefore, the bed sediment was eroding, with the erosion flux after the typhoon landed being around 2 to 3 times the value associated with fair weather conditions. In contrast, within the S. alterniflora marsh, the bottom shear stress was mostly lower than the critical shear stress for sediment motion, or lower than the critical shear stress for the maintenance of suspension; hence, the marsh surface was dominated by settling processes, with a settling flux during the typhoon being 3 to 6 times compared with the fair weather situations. The settling flux during the ebb was up to twice the magnitude for the flood. The comparison of sediment dynamic processes between the S. alterniflora marsh and the bare flat demonstrates that during the typhoon event the bare flat was dominated by erosion, whilst the presence of S. alterniflora favored the accretion of suspended sediment. Supported by National Natural Science Foundation of China (Grant No. 40606012) and the Natural Science Foundation of Fujian Province (Grant No. D0510025)
Vertebral artery dissection associated with viral meningitis
Pan Xudong,Ma Aijun,Wang Kun,Nie Shumin
BMC Neurology , 2012, DOI: 10.1186/1471-2377-12-79
Abstract: Background Vertebral artery dissection (VAD) is often associated with trauma or occurs spontaneously, inevitably causing some neurological deficits. Even though acute infection can be related to the development of spontaneous VAD (sVAD), VAD associated with viral meningitis has never been reported in the literature. Case presentation A 42-year-old man with fever, sore throat, and runny nose developed sudden onset of occipital headache, vertigo, transient confusion, diplopia, and ataxia. Brain stem encephalitis was diagnosed initially because the cerebrospinal fluid (CSF) study showed inflammatory changes. However, subsequent diffusion-weighted (DWI) magnetic resonance imaging of his brain demonstrated left lateral medullary infarction, and the digital subtraction angiography (DSA) confirmed VAD involving left V4 segment of the artery. Consequently, the patient was diagnosed as VAD accompanied by viral meningitis. Conclusion This case suggests that viral meningitis might lead to inflammatory injury of the vertebral arterial wall, even sVAD with multiple neurological symptoms.
Linear Equalization Combined with Multiple Symbol Decision Feedback Detection for Differential Space-Time Modulation
Xiang-Gen Xia,Aijun Song,Genyuan Wang
EURASIP Journal on Advances in Signal Processing , 2002, DOI: 10.1155/s1687617202203091
Abstract: Differential space-time modulation (DSTM) for multiple antenna communication systems has been recently proposed for frequency-nonselective fading channels. In broadband multirate systems, frequency-selective fading may occur. In this paper, the DSTM in frequency-selective fading channels is considered. A linear equalizer for the DSTM is proposed over frequency-selective fading channels. Furthermore, the multiple symbol decision feedback detection is used to improve the performance of the linear equalizer.
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