首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
My family     
My name is Zhong Xin.I am eleven years old.I have a happy family.My mother is a teacher.She is a beautiful woman in my father’s heart.I have the same opinion with my father.She likes watching TV and cooking.The food she cooked is delicious for us every day.My father is a power engineer.He is a good husband and a great father.He is very strict with me.But sometimes he is tender to my mother and me.He likes playing computer  相似文献   

2.
Nature Park     
My pet is a rabbit. Her name is Mimi. She is two years old. She is white. She likes snow in winter. She has two red eyes, two long ears, a short tail and four legs, jump with her legs. She can run fast. She likes to eat grass and carrots. She can play with me. She is lovely and small. I am very happy with my rabbit.  相似文献   

3.
My Sister     
Do you have some1sisters or brothers?I have one.She is a lovely girl.Her name is Lily.Lily is a pretty girl.She likes smiling.Her smile is sunny,beautiful and warm.She looks like a2angel.She likes watching TV and playing with me.If I have time,I always play with her.We are happy when we are together.She likes eating chickens3,chocolate,meat,and potatoes best.She is a good student at school.Her teachers and  相似文献   

4.
A novel posture alignment system for aircraft wing assembly   总被引:2,自引:0,他引:2  
A novel 6-degree of freedom (DOF) posture alignment system, based on 3-DOF positioners, is presented for the assembly of aircraft wings. Each positioner is connected with the wing through a rotational and adsorptive half-ball shaped end-effector, and the positioners together with the wing are considered as a 3-PPPS (P denotes a prismatic joint and S denotes a spherical joint) redundantly actuated parallel mechanism. The kinematic model of this system is established and a trajectory planning method is introduced. A complete analysis of inverse dynamics is carried out with the Newton-Euler algorithm, which is used to find the desired actuating torque in the design and path planning phase. Simulation analysis of the displacement and actuating torque of each joint of the positioners based on inverse kinematics and dynamics is conducted, and the results show that the system is feasible for the posture alignment of aircraft wings.  相似文献   

5.
This paper presents an optimal production model for manufacturer in a supply chain with a fixed demand at a fixed interval with respect to the learning effect on production capacity.An algorithm is employed to find theoptimal dela time for production and production time sequentially.It is found that the optimal delay time for production and the production time are not static,but dynamic and variant with time.It is important for a manufacturer to schedule the production so as to prevent facilities and workers from idling.  相似文献   

6.
A dual structure of composite right/left handed (CRLH) transmission line (TL) is analyzed in which an inductance LR is in parallel with a capacitance CL and a shunt capacitance CR is in series with an inductance LL. Both the distributed and lumped cases are considered. The dispersion diagram and transmission properties of the dual CRLH TL are given and compared with those of a standard CRLH TL. Contrary to the frequency response of a standard CRLH TL, a dual CRLH TL has a left-handed (negative phase shift) band at higher frequencies and a right-handed (positive phase shift) band at lower frequencies. A novel dual-band balun is presented as an application.  相似文献   

7.
In the present paper,a new image processing method for photocarrierspeckle fringe is proposed.A simple and fast filter is designed for different kinds of specklefringe with certain direction to eliminate the speckle effect.Fringe multiplication is carriedout with personal computer.The procedure of photocarrier speckle image collecting,pro-cessing,calculating and verifying is described with a practical example.  相似文献   

8.
河马     
The hippopotamus is a big animal. It feeds on plants. It is a hoofed mammal. It has thick, hairless skin, short legs and a large head with an enormous mouth.The hippopotamus is found in and near lakes and rivers in tropical Africa . The Africans call it 'River Horse'. It swims about with its whole body under water, but it keeps its eyes and nostrils above the water at all times. It does this to breathe and look around while it is swimming.  相似文献   

9.
In this paper,the control of complex delayed networks with different nodes is proposed.Firstly,the stabilization of coupled networks with time delay is investigated.By constructing a Lyapunov function,a linear feedback controller design procedure for the networks is converted to the problem of solving a set of linear matrix inequalities.Then the results are extended to networks with both delayed dynamical nodes and delayed couplings.It is shown that the stabilization of complex networks is determined by the dynamics of each uncoupled node,coupling matrix and feedback gain matrix of networks.Two examples are simulated.In the first example,a network with 10 nodes consisting of Lorenz systems and systems proposed by Zhang in 2009 is given.It is found that the network states are divergent without control,and convergent under designed linear feedback controllers.In the second example,a larger network with 100 nodes consisting of delayed Chen systems and delayed Lorenz systems is given.The proposed method is also effective for large scale networks.  相似文献   

10.
Two numerical simulations were performed to investigate the protective effect of the foam cladding. One simulation is based on a previous experimental study, which is a ballistic pendulum with and without a foam cladding subjected to close-range blast loading. The other model is a steel beam with and without a foam cladding under blast loading. The overpressure due to the blast event can be calculated by the empirical function ConWep or by an arbitrary Lagrangian-Eulerian (ALE) coupling model. The first approach is relatively simple and widely used. The second approach can model the propagation of the blast wave in the air and the interaction between the air and the solid. It is found that the pendulum with the foam cladding always swings to a larger rotation angel compared to a bare pendulum. However, the steel beam with an appropriate foam cladding has a smaller deflection compared to the bare beam without a foam cladding. It is concluded that the protective effect of the foam cladding depends on the properties of the foam and the protected structure.  相似文献   

11.
This paper presents an investigation of inverter fault-tolerant operation for a permanent magnet synchronous motor (PMSM) direct torque control (DTC) system under various inverter faults. The performance of a faulty standard 6-switch inverter driven PMSM DTC system is analyzed. To avoid the loss or even disaster caused by the inverter faults, a topology-modified inverter with fault-tolerant capability is introduced, which is reconfigured as a 3-phase 4-switch inverter. The modeling of the 4-switch inverter is then analyzed and a novel DTC strategy with a unique nonlinear perpendicular flux observer and feedback compensation scheme is proposed for obtaining a continuous, disturbance-flee drive system. The simulation and experimental results demonstrate that the proposed inverter fault-tolerant PMSM DTC system is able to operate stably and continuously with acceptable static and pretty good dynamic performance.  相似文献   

12.
Two numerical simulations were performed to investigate the protective effect of the foam cladding. One simulation is based on a previous experimental study, which is a ballistic pendulum with and without a foam cladding subjected to close-range blast loading. The other model is a steel beam with and without a foam cladding under blast loading. The overpressure due to the blast event can be calculated by the empirical function ConWep or by an arbitrary Lagrangian-Eulerian (ALE) coupling model. The first approach is relatively simple and widely used. The second approach can model the propagation of the blast wave in the air and the interaction between the air and the solid. It is found that the pendulum with the foam cladding always swings to a larger rotation angel compared to a bare pendulum. However, the steel beam with an appropriate foam cladding has a smaller deflection compared to the bare beam without a foam cladding. It is concluded that the protective effect of the foam cladding depends on the properties of the foam and the protected structure.  相似文献   

13.
圣诞大餐     
It is interesting to see how different countries celebrate Christmas.Belgium On Christmas Eve, it starts with a drink and "nibbles", followed by a "starter" course such as seafood, and then stuffed turkey. The dessert is a kind of cake made with cream.  相似文献   

14.
In this paper, an electrical resistance tomography(ERT) imaging method is used as a classifier, and then the Dempster-Shafer's evidence theory with fuzzy clustering is integrated to improve the ERT image quality. The fuzzy clustering is applied to determining the key mass function, and dealing with the uncertain, incomplete and inconsistent measured imaging data in ERT. The proposed method was applied to images with the same investigated object under eight typical current drive patterns. Experiments were performed on a group of simulations using COMSOL Multiphysics tool and measurements with a piece of porcine lung and a pair of porcine kidneys as test materials. Compared with any single drive pattern, the proposed method can provide images with a spatial resolution of about 10% higher, while the time resolution was almost the same.  相似文献   

15.
My Teacher     
Miss Lin is my English teacher. She is tall and slim. She has watery eyes, a high-bridged nose and a small mouth. She is very friendly. She is a humourous woman. She often jokes with us. She works hard. She is very responsible and kind, She usually helps those students who are poor at Eng-  相似文献   

16.
Virtual environment has been widely applied in scientific research and considered as an important tool of exploring science.But constructing a real virtual environment is rather difficult.The difficulty cannot be compared with developing general software,It has a high demand for sofware technology,Obviously traditional methods are not competent for the job.Fortunately with the development of agent-oriented technologies ,all problems seem to be solved.By classifying a virtual environment into four layers corresponding with real world and considering it as a collection of agents,the virtual objects can be mapped into agents and an agent model can be designed.Based on the idea that the state change of a system is caused by that of in dividuals and the mutual effect among them,a theory of agent behavior driven by event and belief is put for ward.Such agent-oriented modeling method can cope with the demand for handling multi-dimension information.It is an effective technique for constructing a large and complex virtual environment.  相似文献   

17.
My Pet Cat     
I have a cute cat named Lily.She was only three months old when she came into my home as my birthday gift.She is black and white with two big black eyes.As a baby cat,she is quite energetic and naughty,running here and there.I often play with her.  相似文献   

18.
欧阳美  张雅娜 《海外英语》2013,(7X):122-123
Culture,which is one of characteristics of a nation,plays an important role in translation.There is a relationship be tween culture and translation and the ways for cultural transmitting from one language to another language.So,the translator has to capture and project the special cultural quality properly in the target language.Cultural transfer is all about a multi-pronged ap proach,focusing on the author’s relationship with his subject and that with the reader,which should be expressed in a good work.  相似文献   

19.
This paper concerns with modeling and design of an algorithm for the portfolio selection problems with fixed transaction costs and minimum transaction lots. A mean-variance model for the portfolio selection problem is proposed, and the model is formulated as a non-smooth and nonlinear integer programming problem with multiple objective functions. As it has been proven that finding a feasible solution to the problem only is already NP-hard, based on NSGA-II and genetic algorithm for numerical optimization of constrained problems (Genocop), a multi-objective genetic algorithm (MOGA) is designed to solve the model. Its features comprise integer encoding and corresponding operators, and special treatment of constraints conditions. It is illustrated via a numerical example that the genetic algorithm can efficiently solve portfolio selection models proposed in this paper.This approach offers promise for the portfolio problems in practice.  相似文献   

20.
A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching (ZVS) PWM converter based on phase and amplitude control (PAC), when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号