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Search Results: 1 - 10 of 104220 matches for " Zhongqiang Zhang "
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New explicit balanced schemes for SDEs with locally Lipschitz coefficients
Zhongqiang Zhang
Mathematics , 2014,
Abstract: We introduce a class of explicit balanced schemes for stochastic differential equations with coefficients of superlinearly growth satisfying a global monotone condition. The first scheme is a balanced Euler scheme and is of order half in the mean-square sense whereas it is of order one under additive noise. The second scheme is a balanced Milstein scheme, which is of order one in the mean-square sense.
A Solvent-Free Protocol for the Green Synthesis of 5-Arylidene-2,4-thiazolidinediones Using Ethylenediamine Diacetate as Catalyst
Yuliang Zhang,Zhongqiang Zhou
Organic Chemistry International , 2012, DOI: 10.1155/2012/194784
Abstract: A simple and efficient synthesis of 5-arylidene-2,4-thiazolidinediones by the Knoevenagel condensation of aromatic aldehydes with 2,4-thiazolidinedione catalyzed by ethylenediamine diacetate under solvent-free conditions is described. The major advantages of this method are simple experimental and work-up procedures, solvent-free reaction conditions, small amount of catalyst, short reaction time, high yields, and utilization of an inexpensive and reusable catalyst. 1. Introduction 2,4-Thiazolidinedione and its derivatives exhibit a variety of pharmacological activities [1–3]. 5-Arylidene derivatives of 4-thiazolidinones have been found to be better fungistatic agents than the parent 4-thiazolidinones [4]. It was reported that 5-arylidene-2,4-thiazolidinediones can act as potentially promising aldose reductase inhibitors [5] and 15-hydroxyprostaglandin dehydrogenase inhibitors [6]. There is a great interest in 5-benzylidenethiazolidine-2,4-dione derivatives as promising inhibitors of MurD ligase [7]. Thus, the synthesis of 5-arylidene-2,4-thiazolidinediones is currently of much importance. There are several methods reported in the literature for the synthesis of 5-arylidene-2,4-thiazolidinediones such as sodium acetate in acetic acid under reflux conditions [8], sodium acetate in acetic acid under microwave irradiation [9], piperidine in ethanol under reflux conditions [5, 10–12], piperidinium acetate in toluene under reflux conditions [6, 13], piperidinium acetate in ethanol under microwave irradiation [7], piperidinium acetate in DMF under microwave irradiation [14], glycine and sodium carbonate in H2O under reflux conditions [15], grinding with ammonium acetate in the absence of solvents [16], KAl(SO4)2·12H2O in H2O at 90°C [17], baker’s yeast [18], KF-Al2O3 under microwave irradiation [19], glycine under microwave irradiation [20], and polyethylene glycol-300 at 100–120°C [21]. Recently, ionic liquids ([bnmim]Cl, C3[min]2·2[Br-]) catalyzed synthesis of 5-arylidene-2,4-thiazolidinediones have also been reported [22, 23]. Each of these methods have their own advantages but also suffer from one or more disadvantages such as long reaction times, low to moderate yields, tedious work-up procedures, requirement of special apparatus, use of organic solvents, requirement of excess of catalysts, and difficulty in recovery and reusability of the catalysts. Researches are still in progress to improve the preparation methods of 5-arylidene-2,4-thiazolidinediones. In recent past, ethylenediamine diacetate (EDDA) has emerged as an inexpensive and effective Br?nsted
Cartesian closedness of categories of completely distributive lattices
Dexue Zhang,Zhongqiang Yang
Chinese Science Bulletin , 1998, DOI: 10.1007/BF03183505
Abstract: The category of completely distributive lattices with Scott continuous functions is cartesian closed. Neither the category of completely distributive lattices with arbitrary union preserving mappings nor the category of completely distributive lattices with nonempty union preserving mappings is cartesian closed.
Application of Fractal Theory in Brick-Concrete Structural Health Monitoring  [PDF]
Changmin Yang, Xia Zhao, Yanfang Yao, Zhongqiang Zhang
Engineering (ENG) , 2016, DOI: 10.4236/eng.2016.89058
Abstract: In order to monitor and forecast the deformation of the brick-concrete building, by taking a brick-concrete building as research object, fiber grating sensors were used to collect the monitoring data and double logarithmic curve of limit value characteristic and monitoring data were obtained based on the fractal theory. Constant dimension fractal method cannot be used to analyze the data directly. With the method of variable dimension fractal, we accumulate data, and the double logarithmic curve is smooth. Piecewise fractal dimensions are close. The outer interpolation method is used to calculate the fractal dimension of the next point and then back calculate the vertical displacement. The relative errors are calculated by comparing the forecast values and monitoring values, and the maximum relative error is 5.76%. The result shows that the fractal theory is suitable to use in the forecast of the deformation and the accuracy is good.
Size and temperature effects on the viscosity of water inside carbon nanotubes
Ye Hongfei,Zhang Hongwu,Zhang Zhongqiang,Zheng Yonggang
Nanoscale Research Letters , 2011,
Abstract: The influences of the diameter (size) of single-walled carbon nanotubes (SWCNTs) and the temperature on the viscosity of water confined in SWCNTs are investigated by an "Eyring-MD" (molecular dynamics) method. The results suggest that the relative viscosity of the confined water increases with increasing diameter and temperature, whereas the size-dependent trend of the relative viscosity is almost independent of the temperature. Based on the computational results, a fitting formula is proposed to calculate the size- and temperature- dependent water viscosity, which is useful for the computation on the nanoflow. To demonstrate the rationality of the calculated relative viscosity, the relative amount of the hydrogen bonds of water confined in SWCNTs is also computed. The results of the relative amount of the hydrogen bonds exhibit similar profiles with the curves of the relative viscosity. The present results should be instructive for understanding the coupling effect of the size and the temperature at the nanoscale.
Evaluating Grayware Characteristics and Risks
Zhongqiang Chen,Zhanyan Liang,Yuan Zhang,Zhongrong Chen
Journal of Computer Networks and Communications , 2011, DOI: 10.1155/2011/569829
Abstract: Grayware encyclopedias collect known species to provide information for incident analysis, however, the lack of categorization and generalization capability renders them ineffective in the development of defense strategies against clustered strains. A grayware categorization framework is therefore proposed here to not only classify grayware according to diverse taxonomic features but also facilitate evaluations on grayware risk to cyberspace. Armed with Support Vector Machines, the framework builds learning models based on training data extracted automatically from grayware encyclopedias and visualizes categorization results with Self-Organizing Maps. The features used in learning models are selected with information gain and the high dimensionality of feature space is reduced by word stemming and stopword removal process. The grayware categorizations on diversified features reveal that grayware typically attempts to improve its penetration rate by resorting to multiple installation mechanisms and reduced code footprints. The framework also shows that grayware evades detection by attacking victims' security applications and resists being removed by enhancing its clotting capability with infected hosts. Our analysis further points out that species in categories Spyware and Adware continue to dominate the grayware landscape and impose extremely critical threats to the Internet ecosystem. 1. Introduction Grayware, an umbrella term for software with unwanted or undesirable features and functionalities, imposes serious security threats to Internet activities as it is mainly designed to profile users' computing habits, capture sensitive data, and steal business secrets [1, 2]. The information collected by grayware could be used to obtain financial assets, commit organized crimes, or trade for profits [3]. For instance, the world's largest attempted robbery against London offices of a Japanese bank is conducted via a spyware [4], while the keylogger surreptitiously implanted at some Kinko's stores exposes banking accounts and their passwords to attackers [5]. With its grayware products that track users' surfing behavior, a grayware company has established the seventh largest decision-support database in the world [6]. Motivated by financial gains, grayware typically attempts to infect as many hosts as possible through diversified penetration mechanisms such as drive-by download, deceptive installations, or vulnerability exploitations [7]. To generate a continuous revenue, grayware usually resides permanently on affected machines and deeply permeates into
A projective ternary phase diagram of stationary non-equilibrium states for low-pressure diamond growth
Jitao Wang,Zhongqiang Huang,Yongzhong Wan,Wei Zhang,Qinghe Yang
Chinese Science Bulletin , 1997, DOI: 10.1007/BF02882561
Abstract:
Wiener chaos vs stochastic collocation methods for linear advection-diffusion equations with multiplicative white noise
Zhongqiang Zhang,Michael V. Tretyakov,Boris Rozovskii,George E. Karniadakis
Mathematics , 2015,
Abstract: We compare Wiener chaos and stochastic collocation methods for linear advection-reaction-diffusion equations with multiplicative white noise. Both methods are constructed based on a recursive multi-stage algorithm for long-time integration. We derive error estimates for both methods and compare their numerical performance. Numerical results confirm that the recursive multi-stage stochastic collocation method is of order $\Delta$ (time step size) in the second-order moments while the recursive multi-stage Wiener chaos method is of order $\Delta^{\mathsf{N}}+\Delta^2$ ($\mathsf{N}$ is the order of Wiener chaos) for advection-diffusion-reaction equations with commutative noises, in agreement with the theoretical error estimates. However, for non-commutative noises, both methods are of order one in the second-order moments.
Prevalence and Associated Factors of Elder Mistreatment in a Rural Community in People's Republic of China: A Cross-Sectional Study
Li Wu, Hui Chen, Yang Hu, Huiyun Xiang, Xiang Yu, Tao Zhang, Zhongqiang Cao, Youjie Wang
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033857
Abstract: Background Current knowledge about elder mistreatment is mainly derived from studies done in Western countries, which indicate that this problem is related to risk factors such as a shared living situation, social isolation, disease burden, and caregiver strain. We know little about prevalence and risk factors for elder mistreatment and mistreatment subtypes in rural China where the elder population is the most vulnerable. Methods In 2010, we conducted a cross-sectional survey among older adults aged 60 or older in three rural communities in Macheng, a city in Hubei province, China. Of 2245 people initially identified, 2039 were available for interview and this was completed in 2000. A structured questionnaire was used to collect data regarding mistreatment and covariates. Logistic regression analysis was used to identify factors related to elder mistreatment and subtypes of mistreatment. Results Elder mistreatment was reported by 36.2% (95% CI: 34.1%–38.3%) of the participants. Prevalence rates of psychological mistreatment, caregiver neglect, physical mistreatment, and financial mistreatment were 27.3% (95% CI: 25.3%–29.2%), 15.8% (95% CI: 14.2%–17.4%), 4.9% (95% CI: 3.9%–5.8%) and 2.0% (95% CI: 1.3%–2.6%), respectively. The multivariate logistic regression analysis revealed that depression, being widowed/divorced/single/separated, having a physical disability, having a labor intensive job, depending solely on self-made income, and living alone were risk factors for elder mistreatment. Different types of elder mistreatment were associated with different risk factors, and depression was the consistent risk factor for the three most common mistreatment subtypes. Conclusion Older adults in rural China self-report a higher rate of mistreatment than their counterparts in Western countries. Depression is a main risk factor associated with most subtypes of mistreatment. Our findings suggest that prevention and management of elder mistreatment is a challenge facing a rapidly aging Chinese population.
A projective ternary phase diagram of stationary non-equilibrium states for low-pressure diamond growth

Wang Jitao,Huang Zhongqiang,Wan Yongzhong,Zhang Wei,Yang Qinghe,

科学通报(英文版) , 1997,
Abstract:
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