HCMU metric is an extremal Kähler metric with singularities on a compact Riemann surface. It is important to study the existence of HCMU metrics. Through studying the sufficient and necessary condition of Chen and Wu(Pacific J Math,2009,240(2):267-288) for the existence of HCMU metrics on S2, we show that there must exist a non-CSC HCMU metric on S2 which has N conical singularities and at least (N-1) saddle points.
By using the method of weight function and the techniques of real analysis and functional analysis and by introducing some special functions to jointly score the constant factor, a Hilbert-type integral inequality with multi-parameters is given. Its equivalent form is considered, and their constant factor is proved to be the best. Some meaningful results are obtained by choosing the special parameter values.
In this study we investigate the P-convergence of random sum(say ξn) of a double random sequence of random variables {Xn,i:n≥1,i≥1} in two cases. The first case is that {ξn:n≥1} is independent of Xn,i:n≥1,i≥1},and the second case is that {ξn:n≥1} is not necessarily independent of the double sequence {Xn,i:n≥1,i≥1}.These results include P-convergence of a branching process in varying environments.
In this study, a novel approach to single image resolution reconstruction is proposed based on nonlocal means, total variation-regularization, and sparse coding. Firstly, low-resolution (LR) image is denoised by nonlocal means which preserves geometric structure well. Then, high-resolution (HR) regularization-based component is obtained from up-scaling the LR image by using a reconstruction model. Image generation process is combined with total-variation regularization so that new image maintains part of the sharpness of the edges and some details. Meanwhile, the HR learning-based component is reconstructed by exploring the sparse coding which explores the co-occurrence relationship between LR training patches and their corresponding HR high-frequency patches. The regularization-based component and the learning-based component are combined to obtain an initial HR image. Finally, the global reconstruction constraint is applied to the initial image for making the final HR image natural. Experimental results show that our method is natural and robust.
An unconstrained optimization method is proposed to attack the double phase encryption system.Under the condition of knowing the plaintext, the new attack method builds an unconstrained optimization model and gets the accurate phase key via this model. Using the acquired phase key, the attacker decrypts the followed cipher. The new attack method transforms the problem of attacking the double phase encryption system into an unconstrained optimization model. The new attack method replaces Hessian matrix by quasi-Newton matrix to avoid computation of the reverse of Hessian matrix. The new attack method has fast convergence speed and strong robustness, and it is not too sensitive to the original values of the variables. This attack method can be applied to other encryption systems.
We propose a method for optical image encryption based on Fourier ptychography (FP).On the basis of 4f double random phase encoding system, the filter aperture (probe) is placed at the Fourier plane, so that the object support constrains for phase retrieval of FP are imposed by the confined optical-transfer-functions in the Fourier domain. Furthermore, we adopt the low numerical aperture objective lens and the variable-angle illumination, which simplifies the device effectively. Numerical simulation results show that the method has the merits of high convergence speed, feasibility, robustness, decryption quality,and security.
In order to study available injection speeds in velocity sensitive experiment for low permeability cores,a capillary model is built based on pore throat radius and distribution,and the finite difference method is used to resolve the equations.The effects of particle release, surface deposition, and particle plugging of three different kinds of low permeability cores on permeability damage are simulated.The influences of different injection solutions for ultralow permeability cores on critical speed are also simulated. Simulation results show that particle release and particle deposition are the primary damage mechanisms for low permeability cores.The lower the permeability of cores, the more remarkable the permeability damage and the stronger the effects of the bridge plug and singlehole blockage on the permeability damage. For the core with permeability smaller than 1×10-3 μm2, the injection solution according to SYT5358-2010 is not reasonable and two points should be added under 0.1mL/min. The model results provide a theoretical foundation for injection solution in velocity sensitive experiment for low permeability cores.
ZPF1 is a new formula that is composed of L-Arg and several natural antioxidants. In this study, the cardioprotective effect of ZPF1 has been investigated. It was found that ZPF1 promotes H9C2 cell growth and decreases intracellular ROS level in phenylephrine-treated cells. ZPF1 also attenuates isoprenaline-induced cardiac hypertrophy and dysfunction in mice, which is due to SERCA2a up-regulation.Our findings suggest that the combination of NO and natural antioxidants serves possible therapeutic intervention against heart failure.
Based on the stochastic frontier analysis and Cobb-Douglas production function,we use the panel data (2004-2013) of 34 prefectural cities of the three provinces to empirically investigate output efficiency and promoting effect on economy of scientific and technological resources (STR). The results are given as follows.1)The STR output efficiency has been continuously improved from 0.274 in 2004 to 0.341 in 2013. Liaoning province has high output efficiencies.Output efficiencies of three-quarters of the cities in Jilin province are lower than 0.250.Output efficiencies of most of the cities in Heilongjiang province are concentrated from 0.250 to 0.375. In spatial distribution, the cities with high-level output efficiencies are located in central-southern Liaoning and Harbin-Changchun urban agglomerations.2)STRs have positive functions on economic development in core cities such as Shenyang, Dalian, and Changchun and in resource-oriented cities such as Benxi,Fuxin, and Huludao.
In this study, the method of logarithmic mean Divisia index and vector autoregression model were used to analyze the influence factors of coal consumption in Shanxi province during 1988-2013. The results are as follows. 1) The wealth effect is the main driver of growth in total coal consumption. 2) In the short term technological progress suppresses coal consumption, but there exists "rebound effect" in the long run. 3) Population plays a weak role in promoting flow growth of coal consumption while the contribution rate of urbanization to coal consumption of the stock is up to 30.91%. 4) The impact of industrial structure adjustment on coal consumption in Shanxi is very weak, and variance decomposition shows that the average contribution rate is only 3.98%.
Roughness is an important design parameter of debris flow control engineering and it directly affects the resistance strength of the residual layer. To study the residual layer drag reduction mechanism, we simulated viscous residual layer by performing 40 groups of egg white tests. The glass ball motion on the viscous residual layer was observed and the relationship between resistance reduction of the viscous residual layer and roughness was studied. On the basis of the experimental data, the relationships of roughness with residual layer thickness, density, and slope gradient were analyzed, and the conclusions are given as follows. Roughness is proportional to the residual layer thickness and density and it is inversely proportional to the slope gradient. These results provide a theoretical basis for the future design of debris flow control project.
An SAR autofocus algorithm based on hybrid model is proposed. The hybrid model is a polynomial specially designed for focus filter. The hybrid model consists of two parts. The first part is a fixed-order Taylor polynomial to estimate the low frequency phase errors. The second part is an adaptive-order sinusoidal polynomial to estimate the high frequency phase errors. Through searching the hybrid model parameters, a better focus result is achieved when the phase errors contain more high frequency components. The simulation and experiment on real airborne SAR data demonstrate the validity and effectiveness of the proposed algorithm.
In this study, low sampling rate digital dechirp is used in SAL to decrease AD sampling rate of the system. On this basis, signal sampling and imaging processing are analyzed. To depress the influence of time delay error, a method for time delay error estimation is proposed. This method estimates time delay through dechirp with part of echo signal. To ensure the quality of pulse compression, a method based on RVP filtering is used to correct nonlinear distortion of the LFM signal. The feasibility of applying the low sampling rate digital dechirp in SAL is verified by simulations.
Machine-to-machine (M2M) communication is one of the major drivers in the cellular network evolution towards 5G system. A major problem is the access congestion since massive machine type communication devices (MTCDs) initiate random access simultaneously. To increase the access success probability we divide the preamble source and distinguish new MTCDs from backlog MTCDs to reduce the estimation error.We use ACB (access class barring) strategy to optimize the number of access attempt MTCDs. Simulation results show that the proposed optimization scheme increases the access success probability while decreases the access delay.
We present our study on SAR image segmentation based on K-means clustering. We analyze dynamical K-means clustering algorithms and improve the adaptation degree function computation method which divides the raw adaptation degree function by a direct ratio function of the sample number in clustering. Millimeter SAR image segmentation results verify that, for urban area, road, and bridge scenes segmentation, dynamical K-means clustering algorithm and adaptive dynamical K-means clustering algorithm with the improved adaptation degree function computation method have the same segmentation quality while the segmentation efficiency is higher than before.
It is very important to accurately acquire information of the web server and deployed application for website security testing. Since the web server's Banner was apt to be modified, we used the black-box testing method to analyze major web servers, and then selected web server's fingerprint which could prevent Banner cheating. Since the web application's keywords were apt to be deleted, we used the source code audit method to analyze major web applications, and then selected web application's fingerprint, which was associated with its function, and built a web fingerprint database. Furthermore, a web fingerprint identifying tool WebEye was designed and implemented. Experimental results show that WebEye faster and more accurately identifies the web server and application than similar tools, and it has good scalablity.
With the increase of internet video contents, the method of distributively storing these videos has attracted much attention. In the distributed storage system, storage balance will make a system more robust. However traditional distributed storage systems always adjust the storage imbalance after it happens, which might cause more IO cost. This study focuses on distributed video file storage and proposes a kind of storage system based on Hash and Bloom Filter, namely HBF. It balances the storage when a file is being stored into the system. The system contains different nodes and the files are distributively stored on these nodes. The ability to easily add and remove nodes makes capacity of the system more scalable. In addition, improvments in storage balance have also been achieved, which keeps the usage of nodes storage relatively consistent. The experiments indicate that HBF achieves a good balance of nodes storage as well as the high performance of the distributed video files storage system. Thus the load balance could be greatly improved, and meanwhile the ultilization of resources would be more reasonable.
Instrument Booking and Billing System of Chinese Academy of Sciences Version 2.0(IBBS@CAS) is a web application for instrument reservations and management, and it increases facility utilization, reduces operating cost and realizes engineering innovation. During about six years running, it provides an exceptional functional service, but its performance needs are not reached yet. In this study, under the condition of system limits, we carry out experiments on simulation environment to find out performance bottleneck by performance testing and log analysis. Then we propose a solution to enhance the IBBS@CAS. The solution ensures that the performance of system improves to meet user requirements in simulation environment. The experimental results show that the system response time is reduced by about thirty-five percents in a specific scenario.
Pollution-intensive industry development is a principal source of pollution emissions. The Yangtze River Delta(YRD) is one of the most developed areas in China and also one of areas facing great pressure of environmental pollution. We studied spatial distribution of pollution-intensive industries (PⅡ) and pullution emissions (PE) from 1999 to 2013 in the YRD. Results are shown as follows. 1) As the whole PⅡ and PE present diffusion process from regional core cities to edge cities. Industrial sectors and pollution factors are different. 2) Spatial distribution patterns of PⅡ and PE show consistence. Cities with high share and intensive pollution locate along the Shanghai-Nanjing line and in Hangzhou-Ningbo region. Cities with increasing PⅡ and PE shares locate in Suzhou, Ningbo, Nantong, etc. 3) PⅡ's effect on PE reflects differences between production technology and policy regulation. Policies and measures of promoting clean production and strengthening environmental regulation is the key to achieve a coordinated and win-win regional industry development and environmental protection.
The scientific data of solar-terrestrial space science has huge volume, wide variety, and complex structure. The correlations between different domain concepts and astro-events put forward high requirements of the scientific data retrieval in this field. However, the scientific data retrieval modules on the mainstream data share and publishing systems in this field are still built on the conventional keyword-based retrieval method. We present a semantic retrieval approach for the solar-terrestrial space system scientific data. Based on the semantic information extracted from scientific metadata of each scientific dataset, we get the TF-idf matrix using traditional text processing methods. Then latent semantic indexing further analyzes this matrix, and a similarity value is obtained to rank the relevance of a result to its search request. The experimental results show that the approach has a higher recall rate than conventional methods and maintains a high precision. This approach can be applied in other disciplines as well.