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Search Results: 1 - 10 of 92728 matches for " Di Liu "
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Methanol Steam Reforming over Na-Doped ZnO-Al2O3 Catalysts  [PDF]
Di Liu, Yong Men, Jinguo Wang, Xin Liu, Qiuyan Sun
American Journal of Analytical Chemistry (AJAC) , 2016, DOI: 10.4236/ajac.2016.77052
Abstract: In this study, the catalyst composition in binary ZnO-Al2O3 catalyst was initially evaluated and optimized for methanol steam reforming. Then different Na contents were loaded by an incipient wetness impregnation method onto the optimized ZnAl catalyst. It was found that the activity was greatly enhanced by the modification of Na, which depended on the Na content in the catalyst. The methanol conversion was 96% on a 0.1 Na/0.4 ZnAl catalyst (GHSV = 14,040 h-1, S/C = 1.4, 350°C), which was much higher with respect to a Na-free 0.4 ZnAl catalyst (74%). The remarkable improvement of activity was attributed to a weakening of the C-H bonds and clear of hydroxyl group by the Na dopant leading to an accelerated dehydrogenation of the reaction intermediates formed on ZnAl2O4 spinel surface and thus the overall reaction.
Infinitely many solutions for the p-Laplace equations with nonsymmetric perturbations
Disheng Liu,Di Geng
Electronic Journal of Differential Equations , 2008,
Abstract: In this article, we study Dirichlet problems involving the p-Laplacian with a nonsymmetric term. By using the large Morse index of the corresponding Laplace equation, we establish an estimate on the growth of the min-max values for a functional associated with the problem. The estimate is better than the given result in some range. We show that the problem possesses infinitely many weak solutions.
A calculation method for low dynamic vehicle velocitybased on fusion of optical flow and feature point matching
Liu Di, Chen Xiyuan
- , 2017, DOI: 10.3969/j.issn.1003-7985.2017.04.006
Abstract: Aiming at the problem of the low accuracy of low dynamic vehicle velocity under the environment of uneven distribution of light intensity, an improved adaptive Kalman filter method for the velocity error estimate by the fusion of optical flow tracking and scale invariant feature transform(SIFT)is proposed. The algorithm introduces a nonlinear fuzzy membership function and the filter residual for the noise covariance matrix in the adaptive adjustment process. In the process of calculating the velocity of the vehicle, the tracking and matching of the inter-frame displacement and the vehicle velocity calculation are carried out by using the optical flow tracing and the SIFT methods, respectively. Meanwhile, the velocity difference between the outputs of these two methods is used as the observation of the improved adaptive Kalman filter. Finally, the velocity calculated by the optical flow method is corrected by using the velocity error estimate of the output of the modified adaptive Kalman filter. The results of semi-physical experiments show that the maximum velocity error of the fusion algorithm is decreased by 29% than that of the optical flow method, and the computation time is reduced by 80% compared with the SIFT method.
FDI, Institutional Change, Employment and Services Growth in Megalopolises  [PDF]
Di Shang, Liyan Liu
Journal of Service Science and Management (JSSM) , 2019, DOI: 10.4236/jssm.2019.125047
Abstract: This study was set out to identify the linkages between FDI, institutional change, employment and services growth in megalopolises in China. We choose the four super cities in China, Beijing, Shanghai, Guangzhou and Shenzhen, take government interference and openness as the proxy variable of institutional change, based on Douglas production function and using data from Year 2006 to 2017, we investigated the relations between FDI, institutional change, employment, and services growth with fixed effect panel data model. Findings show that FDI presented a significant positive impact on the service economic growth of the four megalopolises, while the number of employees in the service industry has a negative effect on the growth of the service industry, which is contrary to the common sense; With respect to institutional change, openness presented a strong positive effect and effect of government intervention is not significant; the city’s fixed investment and R & D investment of service sectors also presented an unclear effect.
Research of Drainage Gas Recovery Technology in Gas Wells  [PDF]
Shuren Yang, Di Xu, Lili Liu, Chao Duan, Liqun Xiu
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.42014
Abstract: Drainage gas recovery technology is the main method of gas recovery process in gas field, which has domestically and internationally been the main gas recovery processing measure in later stage of gas field production. In this context, produced water or condensate liquid will not be carried out of pit shaft by natural gas with the gradual drop of gas reservoir pressure and natural gas flow velocity, thus they will remain in pit shaft and form the so-called “gas well gathered liquid”. This fluid severely affects natural gas output and leads to the decline of oil field economic benefits, thus drainage gas recovery measure must be taken to increase gas well or even gas field output. It becomes the primary problem to be solved to select the best drainage gas recovery measure which can maximize gas field benefits and optimize gas well safety.
A Robust Optical Encryption Method for Three-Dimensional Object Based on the Fresnel Transform  [PDF]
Yinghong Liu, Weimin Jin, Xin Yang, Di Wu, Hongbo Zhang
Optics and Photonics Journal (OPJ) , 2015, DOI: 10.4236/opj.2015.511029
Abstract: An optical encryption of three-dimensional (3D) object with digital holography was implemented. In the process of encryption, two holograms involved recording key information and 3D object were obtained. In the process of decryption, the 3D object was reconstructed from the two holograms by extracting the object and key information, followed by multiplication of the two holograms and inverse Fresnel transform numerically. The robustness of the method was also tested for different occlusions attacks and Gaussian noises. The results showed that the method was able to encrypt and decrypt the 3D object while being robust under different occlusions attacks and Gaussian noises.
Forecasting S&P 500 Stock Index Using Statistical Learning Models  [PDF]
Chongda Liu, Jihua Wang, Di Xiao, Qi Liang
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.66086
Abstract: Forecasting the movement of stock market is a long-time attractive topic. This paper implements different statistical learning models to predict the movement of S&P 500 index. The S&P 500 index is influenced by other important financial indexes across the world such as commodity price and financial technical indicators. This paper systematically investigated four supervised learning models, including Logistic Regression, Gaussian Discriminant Analysis (GDA), Naive Bayes and Support Vector Machine (SVM) in the forecast of S&P 500 index. After several experiments of optimization in features and models, especially the SVM kernel selection and feature selection for different models, this paper concludes that a SVM model with a Radial Basis Function (RBF) kernel can achieve an accuracy rate of 62.51% for the future market trend of the S&P 500 index.
Effects of second hand smoke on airway secretion and mucociliary clearance
Yanyan Liu,Y. Peter Di
Frontiers in Physiology , 2012, DOI: 10.3389/fphys.2012.00342
Abstract: The airway acts as the first defense against inhaled pathogens and particulate matter from the environment. One major way for the airway to clear inhaled foreign objects is through mucociliary clearance (MCC), an important component of the respiratory innate immune defense against lung disease. MCC is characterized by the upward movement of mucus by ciliary motion that requires a balance between the volume and composition of the mucus, adequate periciliary liquid (PCL) volume, and normal ciliary beat frequency (CBF). Airway surface fluid (ASL) is a thin layer liquid that consists of the highly viscous mucus upper “gel” layer, and the watery lubricating lower “sol” layer. Mucus production, secretion and clearance are considered to play a critical role in maintenance of airway health because it maintains hydration in the airway and traps particulates, bacteria, and viruses. Different types of epithelial cells, including secretory cells, and ciliated cells, contribute to the MCC function. Cigarette smoke (CS) contains chemicals and particulates that significantly affect airway secretion. Active and passive CS-induced chronic obstructive pulmonary disease (COPD) is frequently associated with hyperplasia of goblet cells and submucosal glands (SMGs), thus increasing the secretory capacity of the airways that impairs MCC.
Energy conditions bounds on f(T) gravity
Di Liu,M. J. Reboucas
Physics , 2012, DOI: 10.1103/PhysRevD.86.083515
Abstract: In standard approach to cosmological modeling in the framework of general relativity, the energy conditions play an important role in the understanding of several properties of the Universe, including singularity theorems, the current accelerating expansion phase, and the possible existence of the so-called phantom fields. Recently, the $f(T)$ gravity has been invoked as an alternative approach for explaining the observed acceleration expansion of the Universe. If gravity is described by a $f(T)$ theory instead of general relativity, there are a number of issues that ought to be reexamined in the framework of $f(T)$ theories. In this work, to proceed further with the current investigation of the limits and potentialities of the $f(T)$ gravity theories, we derive and discuss the bounds imposed by the energy conditions on a general $f(T)$ functional form. The null and strong energy conditions in the framework of $f(T)$ gravity are derived from first principles, namely the purely geometric Raychaudhuri's equation along with the requirement that gravity is attractive. The weak and dominant energy conditions are then obtained in a direct approach via an effective energy-momentum tensor for $f(T)$ gravity. Although similar, the energy condition inequalities are different from those of general relativity (GR), but in the limit $f(T)=T$ the standard forms for the energy conditions in GR are recovered. As a concrete application of the derived energy conditions to locally homogeneous and isotropic $f(T)$ cosmology, we use the recent estimated value of the Hubble parameter to set bounds from the weak energy condition on the parameters of two specific families of $f(T)$ gravity theories.
Analysis of the Force Acting on the Sucker Rod by Polymer Solution  [PDF]
Lili Liu, Shuren Yang, Lihui Wang, Di Xu, Liang Zhao, Yue Cui
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.42009

With selecting lower-convected Maxwell constitutive equation, polymer solution flow equation in eccentric annulus is established. And the distribution rule of the force acting on the sucker rod by polymer solution has been gained. The result shows the eccentric ratio and the movement velocity of the sucker rod are major influence factors on the radial force. The greater the ratio is, the greater the force of sucker rod is. Then the eccentric wear is easier to appear.

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