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Search Results: 1 - 10 of 37024 matches for " Fengying Yan "
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Study on the Workover Fluid Formula and Performance of the Prevention Reservoir
Fengying Zhang,Jienian Yan,Zhiyong Li
Modern Applied Science , 2009, DOI: 10.5539/mas.v3n12p9
Abstract: In the workover treatment of Yakela condensate gas field, the workover fluids are easily leaked, and many problems such as clay expansion, rate sensitivity, migration of fines, and change of wetting property will occur, which will induce serious reservoir harms. In the article, the performances of the existing workover fluid of the Yakela condensate gas field with high temperature and high pressure are evaluated, and the influencing factors harming the reservoir are analyzed and obtained, and the effective measures and methods preventing the reservoir harm are confirmed. The technical principle, material composing, performance index, and the evaluation of stratum liquid compatibility are introduced in the article. The result of performance evaluation indicates that the core return permeability of the workover liquid system can achieve above 80%, and it is an ideal low-harm workover fluid system.
Permanence and Globally Asymptotic Stability of Cooperative System Incorporating Harvesting  [PDF]
Fengying Wei, Cuiying Li
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.37082

The stability of a kind of cooperative models incorporating harvesting is considered in this paper. By analyzing the characteristic roots of the models and constructing suitable Lyapunov functions, we prove that nonnegative equilibrium points of the models are globally asymptotically stable. Further, the corresponding nonautonomous cooperative models have a unique asymptotically periodic solution, which is uniformly asymptotically stable. An example is given to illustrate the effectiveness of our results.

A Note on the Structure of Affine Subspaces of L2(Rd)  [PDF]
Fengying Zhou, Xiaoyong Xu
Advances in Pure Mathematics (APM) , 2015, DOI: 10.4236/apm.2015.52008

This paper investigates the structure of general affine subspaces of L2(Rd) . For a d × d expansive matrix A, it shows that every affine subspace can be decomposed as an orthogonal sum of spaces each of which is generated by dilating some shift invariant space in this affine subspace, and every non-zero and non-reducing affine subspace is the orthogonal direct sum of a reducing subspace and a purely non-reducing subspace, and every affine subspace is the orthogonal direct sum of at most three purely non-reducing subspaces when |detA| = 2.

Risk Decision Analysis of Logistics Purchasing Based on Mathematical Expectation  [PDF]
Fengying Wang, Zhixin Liang
Open Journal of Modelling and Simulation (OJMSi) , 2016, DOI: 10.4236/ojmsi.2016.42005
Abstract: The mathematical expectation value method is a commonly used method in risk decision-making. This paper studies the problem of how to arrange the purchase plan in order to get the maximum expected profit; considering the applicable principles of mathematical expectation, the decision method for getting the optimal decision scheme is given. Finally, we do simulation and stability analysis on an example and obtain the reasonable result. This result shows that mathematical expectation value method is effective in solving the problem of risk decision.
Research on the Personalized Recommendation Algorithm for Hairdressers  [PDF]
Zhixin Liang, Fengying Wang
Open Journal of Modelling and Simulation (OJMSi) , 2016, DOI: 10.4236/ojmsi.2016.43009
Abstract: In order to retain customers, hairdressers usually persuade customers to be their members by offering membership card. This paper studies how to set up their recommendation system in the hairdressers. According to the membership information and consumer behavior, the hairdresser provides personalized recommendation to different members and lets customers experience personalized choices. A recommendation algorithm based on customer ratings and a customer classification method based on Logistic Regression Model are discussed in this paper. The former is used to recommend hair style and color to a customer. The latter is used to determine whether to recommend some maintenance programs to a customer or not.
Improved isolation of good-quality total RNA from the optic stalk of Mud crab, Scylla paramamosain
Zhu,Houze; Jiang,Keji; Zhang,Fengying; Zhang,Dan; Pi,Yan; Ma,Lingbo;
Electronic Journal of Biotechnology , 2012,
Abstract: an improved and efficient protocol was developed based on the takara rnaiso plus kit (code: d9108a) for isolating good-quality total rna from the optic stalk of mud crab, scylla paramamosain. the protocol was based on the trizol method with modifications. the carapace overlapping the optic stalk was retained with rna in regular protocol. in order to remove the abundant deposition correlative with the carapace which makes the isolation of rna particularly difficult, 5m potassium acetate solution (ph = 6.0) was added before the precipitation of rna, and the temperature of rna deposition was also decreased to -70oc to ensure the stabilization of rna. good-quality total rna from the optic stalk of s. paramamosain could be easily isolated with this modified protocol and three conventional methods were also employed to confirm the quality of rna. this improved method would be helpful in facilitating molecular research of crabs involving rna from the optic stalk.
Large Essential norm of Toeplitz operators and Hankel operators on the weighted Bergman space
Fengying Li
Mathematics , 2012,
Abstract: In this paper, we show that on the weighted Bergman space of the unit disk the essential norm of a noncompact Hankel operator equals its distance to the set of compact Hankel operators and is realized by infinitely many compact Hankel operators, which is analogous to the theorem of Axler, Berg, Jewell and Shields on the Hardy space in Axler et al. (1979); moreover, the distance is realized by infinitely many compact Hankel operators with symbols continuous on the closure of the unit disk and vanishing on the unit circle.
An integrative estimation model of summer rainfall-band patterns in China
WEI Fengying,

自然科学进展 , 2007,
Abstract: Three variation indices are defined to objectively and quantitatively represent fluctuations of three rainfall-band patterns in summers in China for the period from 1951 to 2005, and the variation features of these indices are analyzed on both of interdecadal and interannual scales. A new method is proposed to establish an integrative estimation model based on the analysis of rainfall-band indices, and the model is applied to air, ocean factors to estimate their roles on variations of three rainfall-band patterns on different time-scales. The tests of estimation effects show that the fluctuations of three rainfall-band patterns are composed of variations on both significant interdecadal and interannual scales, of which the interannual variation is mainly influenced by the Elnino/Lanina events, the East Asia monsoon and the ridge locations of subtropical high pressures in western pacific, while the interdecadal variation is mainly controlled by the Pacific decadal oscillation and interdecadal oscillations of the Arctic oscillation, ENSO, Nino3 sea surface temperature and summer monsoon. The estimated results from the integrative estimation model of rainfall-band patterns suggest that the way of estimation first according to each time scale of both the interdecadal and interannual scales, then estimating with an integration, which is proposed in this paper, has an obvious improvement on that without separation of time scales.
Fuzzy Comprehensive Evaluation of Service Agent Based on Large-Scale Products of New Technology  [PDF]
Jianhui Kong, Fengying Zhang, Zongfang Zhou
Modern Economy (ME) , 2015, DOI: 10.4236/me.2015.64049
Abstract: For new-tech products manufacturing enterprises, good after-sale service plays an important role in the marketing of new-tech products and promoting the sustainable development. Therefore, how to select and evaluate the service agent will be an inevitable and important job for new-tech manufacturing enterprises. However, the evaluation process and results of the service agent always show fuzziness because of the uncertain evaluation factors. In order to solve this problem, the dissertation firstly introduced methods of fuzzy comprehensive evaluation and multiple attribute decision making from quantitative and qualitative views respectively. Secondly, a method of evaluation on “important” service agent based on fuzzy Borda method was constructed. By the numerical experiment, results show that the fuzzy comprehensive evaluation methods of service agent proposed in this paper are feasible and effective, which provides a new idea to address the problem of evaluating the service agent for new-tech products manufacturing enterprises.
A Class of Lie 2-Algebras in Higher-Order Courant Algebroids  [PDF]
Yanhui Bi, Fengying Han, Meili Sun
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.47131

In this paper, we study the relation of the algebraic properties of the higher-order Courant bracket and Dorfman bracket on the direct sum bundle TMpT*Mfor an m-dimensional smooth manifold M, and a Lie 2-algebra which is a categorified version of a Lie algebra. We prove that the higher-order Courant algebroids give rise to a semistrict Lie 2-algebra, and we prove that the higher-order Dorfman algebroids give rise to a hemistrict Lie 2-algebra. Consequently, there is an isomorphism from the higher-order Courant algebroids to the higher-order Dorfman algebroids as Lie 2-algebras homomorphism.

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