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71.
张晓红 《承德石油高等专科学校学报》2012,14(4):90-94
顶岗实习作为有效推进高职高专工学结合人才培养的重要途径,能大大提高学生的实践操作能力和职业素养。由于我院商务英语专业尚未开展顶岗实习,而旅游英语专业却已经实施了顶岗实习的人才培养方式,因此,为了更好地开展商务英语专业的顶岗实习,本研究通过对已完成顶岗实习的旅游英语专业的学生进行问卷调查,并通过反思顶岗实习中存在的问题,从而为研究我院开展商务英语顶岗实习提供建议和帮助。 相似文献
72.
73.
74.
WAVELET ALGORITHM FOR INTEGRAL OPERATOR EQUATION AND ITS APPLICATIONS TO ELECTROMAGNETIC PROBLEMS 总被引:1,自引:0,他引:1
A brief summary of the basic theory of wavelet is proposed. The properties of wavelet function are discussed. The possible applications of wavelet to electromagnetics are given. Examples show that the wavelet method is feasible and effective for solving electromagnetic problems. 相似文献
75.
76.
Solid expandable tubular technology has gained wide acceptance in the petroleum industry due to its operationally simplified and cost-effective solution in well drilling. The down-hole hydraulic expansion results in forward motion of a mandrel until it pops out of the tubular. The pop-out phenomenon, which occurs at the end of the tubular expansion process, leads to a sudden release of stored energy within a fluid-tubular system, causing unnecessary vibration. These vibrations can become severe and may cause permanent damage to the tubular. Hence, a complete understanding of the dynamics of the fluid-tubular system is essential to avoid premature failure.
This paper focuses on the development of a mathematical model describing the dynamics of a fluid-tubular system due to pop-out phenomenon. The coupling between tubular, fluids, and formation is incorporated. An analytical solution for the propagation of displacement, stress, and pressure waves, originating due to the excitation caused by pop-out, is obtained. The model also identifies the potential failure locations along the tubular. The coupling effect is more prominent if the tubular material is elastic as compared to elastic-perfectly plastic material. A sensitivity analysis showed that the coupling effects vanish with increase in tubular stiffness and reach an asymptotic value with an increase in formation stiffness. The quantification of coupling effects is important in order to see the effects of pressure waves on the other subsystems present down hole. 相似文献
This paper focuses on the development of a mathematical model describing the dynamics of a fluid-tubular system due to pop-out phenomenon. The coupling between tubular, fluids, and formation is incorporated. An analytical solution for the propagation of displacement, stress, and pressure waves, originating due to the excitation caused by pop-out, is obtained. The model also identifies the potential failure locations along the tubular. The coupling effect is more prominent if the tubular material is elastic as compared to elastic-perfectly plastic material. A sensitivity analysis showed that the coupling effects vanish with increase in tubular stiffness and reach an asymptotic value with an increase in formation stiffness. The quantification of coupling effects is important in order to see the effects of pressure waves on the other subsystems present down hole. 相似文献
77.
Adriana Brancaccio Giovanni Leone Rocco Pierri 《AEUE-International Journal of Electronics and Communications》2004,58(6):382-390
In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data. 相似文献
78.
Katalin Balla Galina A. Kurina Roswitha März 《Journal of Dynamical and Control Systems》2006,12(3):289-311
The index of DAE systems arising from linear quadratic optimal control problems is considered. Necessary and sufficient conditions
ensuring regularity with tractability index one are proved. Then, it is shown that if the control problem DAE is regular with
index one and if the leading term of the DAE to be controlled is given by one full-column-rank and one full-row-rank matrix,
then it has a Hamiltonian inherent explicit ODE. For problems with regular index zero or index one DAEs to be controlled,
the DAE of the control problem is shown to be regular with tractability index one or three, depending on whether the control
coefficient R is singular.
2000 Mathematics Subject Classification.
49N10, 49J15, 34A09.
Supported by the DFG research center MATHEON in Berlin. This work was partially
supported by the Russian Fundamental Research Foundation Project Nos. 02-01-00351
and 06-01-00296. 相似文献
79.
随着我国社会经济与科技的快速发展,电能越来越成为我国公民进行正常活动的重要因素,而电能表是作为电能计量的唯一设备,因此我国对电能表的需求数量也在不断增加.为了满足如今电力行业中对电能表准确性以及功能性的要求,我国电能表市场出现了多种多样电能表,这些电能表无论是在结构、准确度还是在功能上较之以前的都有了很大的进步,提升了我国电能计量的准确性以及功能性. 相似文献
80.
无线传感器网络的安全技术研究 总被引:2,自引:1,他引:2
无线传感器网络(WSN)是通过无线通信方式形成的一个多跳自组织网络,是集信息采集、信息传输、信息处理于一体的智能化信息系统。由于其本身资源方面存在的局限性和脆弱性,使其安全问题成为一大挑战。文中分析了无线传感器网络的安全需求、可能受到的安全攻击,给出了防御方法和解决方案。通过安全加密协议、认证流广播和多种密钥机制实现传感器网络的数据机密性、完整性和系统鲁棒性。 相似文献