《多普勒效应》教学设计

【教学说明】 本课采用人民教育出版社《物理》选修3—4教材，对第十二章第五节“多普勒效应”进行了如下设计，学生尽管学习了机械波的产生、传播的基本规律，但关于多普勒效应学生尚缺乏相应的感性认识，而且这部分知识是比前面所学基础知识稍深一层的具有综合性的波的现象，学生学习中是具有相当大的难度。教学中没有必要给出多普勒效应中接收者接收到的频率公式，以免增加学生学习的心理负担和理解难度。笔者按照学生的认知规律，设计力求落实新课标的理念，从实验现象激发学生兴趣引出课题，使学生感受奇妙的物理现象。从学生身边的现象出发，通过实验以及多媒体演示，为学生认识多普勒效应提供充分的感性素材，

高中物理课堂的有效性——以《多普勒效应》为例

高中物理课堂教学自内容学习转变为思维锻炼,培养学生核心素养。让学生在课堂中学习丰富的物理知识,并将知识回归于生活,这是高中物理教学中的必要思路。对此,本文基于多普勒效应探究高中物理高效教学策略。主要是自教学思维及物理问题、学生思维、教学设计、定性定量分析等角度着手,培养学生物理综合素质。

《多普勒效应》教学探究活动

“多普勒效应”是人教版2005年初审通过的物理选修的学习内容。描述的是在波源与观察者之间有相对运动时产生的物理现象，它比波动现象又复杂了些。我在组织学生进行学习的实际过程中体会到，要掌握多普勒效应必须让学生明确：在多普勒效应中，波源的频率是不变的，由于波源与观察者之间有了相对运动，观察者接收到的频率才发生变化。这是学习本节课的关键。为顺利完成本节课的教学，我认为需做好如下五个环节。

多普勒效应的演示

在《多普勒效应》一节的教学中，课文中介绍火车向你驶来，音调变高。火车驶离你远去，音调变低，由于没有比较，学生一般都没有注意到这种现象，学生理解起来比较困难，实验室又没有专门的演示仪器，为了方便教学，我制作了此演示仪器，它演示现象明显，容易制作，现将器材、制作和演示操作介绍如下。

运用科学探究方式 启迪创新思维

本文通过《多普勒效应》一节为例,设计探究性方案,让学生自主思维、动手实验,体验探究过程的曲折和乐趣,发展其科学探究能力,增强他们的创新意识。

TRANSVERSE VELOCITY ESTIMATION BASED ON HIGH-ORDER DOPPLER EFFECT OF MOVING OBJECT

The one-order phase of the echo changes if there is relative radial moving between the object and the radar, i.e. , the Doppler effect. The Doppler effect is widely used in radar signal processing. The transverse motion of the object cannot change the one-order phase of the echo, but the high-order phase. The high-order Doppler effect of the transverse moving target is presented and a new algorithm for obtaining the transverse velocity is given. The scalar velocity of a target moving steadily in any direction can be calculated with one-order and two-order items of the echo phase. The calculating method and simulating results are given. As the transverse speed is 900 km/h, the speed calculation error is less than 0. 06% if SNR of echo signal is higher than 0 dB.

Analysis of Short-term Heavy Precipitations in a Regional Heavy Rainstorm in Shannxi Province

[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.

Research on integrated navigation method for AUV

The principles of the SINS/DVL integrated navigation system are introduced, and the compass status accuracy is compared. When the heading is changed, the dead reckoning algorithm using the heading information of the SINS (Strapdown inertial navigation systems) and DVL (doppler velocity log) is adopted to substitute the SINS/DVL integrated system. The simulation results show that the method can improve the accuracy of integrated navigation system when AUV (autonomous underwater vehicle) is in motion.

Radar target recognition based on micro-Doppler effect

Mechanical vibration of target structures will modulate the phase function of radar backscattering,and will induce the frequency modulation of returned signals from the target. It generates a side bands of the target body Doppler frequency shift,which is helpful for target recognition. Based on this,a micro-Doppler atomic storehouse is built for the target recognition,and four kinds of common classifiers are used separately to perform the classified recognition. The simulation experimental results show that this method has high recognition rate above 90%.

Analysis of external noise spectrum of high-speed railway

A schematic to make the spectra of the exterior noise of high speed railway was put forward. The exterior noise spectrum was defined based on the characteristics of the high-speed train exterior noise. Its characteristics considered here include identifying the exterior main sources and their locations, their frequency components including the Doppler effect due to the noise sources moving at high speed, the sound field intensity around the train in high-speed operation, the sound radiation path out of the train, and the pressure level and frequency components of the noise at the measuring points specified by the International Organization for Standardization(ISO). The characteristics of the high-speed train exterior noise of the high speed railways in operation were introduced. The advanced measuring systems and their principles for clearly indentifying the exterior noise sources were discussed in detail. Based on the concerned noise results measured at sites, a prediction model was developed to calculate the sound level and the characteristics of the exterior noise at any point where it is difficult to measure and to help to make the exterior noise spectrums. This model was also verified with the test results. The verification shows that there is a good agreement between the theoretical and experimental results.

Interfacial Shear Stress of Stratified Flow in a Horizontal Pipe

Experimental data are presented for the void fraction and the shear stresses of stratified gas-liquid flow in a pipe. A new technique was used to measure the interface shear stress. The interfacial shear stress was determined by using two methods: a momentum balance of gas and an extrapolation of the Reynolds shear stress profile at the gas-liquid interface. A new formula , relating to the interfacial friction factor with the void fraction and superficial gas Reynold number, was developed to predict the interface shear stress . The predicted values are in good agreement with experimental data.

Sliding speed calculation of the Wenchuan earthquake fault using the Doppler effect

Currently,the fault sliding speed functions or source–time functions used in theoretical seismogram calculations have only produced theoretical results;that is,the results of the fault speed–time functions have been obtained only from theoretical studies,and have not been validated using the measured data.This paper signifi cantly improves the method for calculating fault sliding speed using the Doppler eff ect,from the following four perspectives.First,the paper theoretically demonstrates how to confirm that the seismic waves received in some frequency bands by two diff erent receivers are emitted by the same source.Second,the paper proposes a method to determine the similarity of seismic waves received by two diff erent receivers in some frequency bands;it applies the relative change at the two receivers in Fourier amplitude standard deviation in some frequency bands,and determines that similar seismic waves are emitted by the same frequency bands.Third,to eliminate the interference of reflected and refracted waves,this study uses fault sliding time S-wave records for data processing.Finally,the paper replaces the long-time Fourier transform with short-time Fourier transform to enhance the positioning accuracy of fault sliding times.Based on these perspectives,the paper systematically summarizes a general methodology for calculating the fault sliding speed using the Doppler effect.This method is employed to calculate the fault sliding speed of the Wenchuan earthquake;the calculations reveal that there is a general correlation between the fault sliding speeds of the Wenchuan earthquake and the seismic moment changes.The results confi rm that the sliding speed of the Wenchuan earthquake fault possesses the characteristics of abrupt change,whereby a sudden increase in the sliding speed is followed by a rapid decrease.Generally,the sliding speed is not fast,and sometimes,no sliding occurs.There are obvious diff erences from the currently used sliding speed functions,such as the Haskell function,bell-shaped function,exponential function,and triangular function.To determine the fault sliding speed using the Doppler eff ect,only the earthquake records and locations of the epicenter and receivers are required,instead of using unknown crust parameters.In short,the proposed calculation method has clear physical meaning,and the required parameters are easier to obtain.

Model for Interaction Between Photon and Cold Atom in QED Cavity

A model has been established for the interaction between a single-mode optical field and a 2-energy-level cold atom with exact analytic solutions given. The processes of momentum and energy exchanges between the optical field and the cold atom due to the interaction between them are discussed in detail, and a formula has been given for the variation of momentum and energy exchange volumes with time t in dress state while both the effects of photon recoil and Doppler effect are taken into consideration.

ANALYSIS AND PROCESSING OF LMF-COSTAS STEPPED FREQUENCY RADAR SIGNAL

Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened.

TCD study of hemodynamic changes in PCA response to photic stimulation

Objectives: During visual stimulation, the elevated metabolism rate will coupl e with increase of blood flow velocity(BFV) in posterior cerebral artery(PCA). T his study with TCD was aimed to investigate whether the coupling might change ac cording to the different vasoneuronal conditions. Methods: Ninety-nine voluntee r s including 24 hypertension(HT) patients and 2 patients suffering from both HT a nd diabetes mellitus(DM) were enrolled in this trial. BFV and pulse indexes(PI) in P2 segments of PCA on both sides were monitored during visual stimulation. Re sults: In all subjects, Mean BFV increased and PI went down in response to visua l stimulation. The percentages of changes (ΔV and ΔP) of both mean BFV and PI we re larger in young group(<55 years old) than in old one(≥55 years old). There w a s significant positive correlation between ΔV and ΔP. Multivariated re gression a nalysis did not show HT and DM, but age related to ΔV(ΔP). We did not find signi ficant difference of ΔV(ΔP) between left and right sides. Conclusions: Blood flo w velocity in PCA P2 segment increased due to decreased cerebrovascular resistan ce during visual stimulation and the response weakened with aging of the patient .

Development of High-precision Rotary Encoder Using Semiconductor Laser

In this paper, the operation principle of laser rotary encoders is expounded and the optical quadruple frequency technology used in laser rotary encoders is explained, and the design idea of optical system in φ66 mm laser rotary encoder is mainly introduced, as well as the choice of principal devices.

Experimental Verification of Doppler Effect with the Refraction Method

The traditional method of measuring Doppler Effect is either reflection or dispersiion. This article clarifies that it can also verify the Doppler Effect with the refraction method. We have designed the experimental system with the method of optical heterodyne, using the refraction light beam from a prism, and made the experiment. The experimental results are in accordance with the theoretical calculation. It is very useful in some particular case, such as in Negative- Index Materials（NIM）, to verify the Doppler Effect with this method.

Study on intercarrier interference in mobile MIMO-OFDM based on the geometrical one-ring model

This paper investigates the distribution of intercarrier interference （ICI） in multiple-input multiple-output orthogonal frequency division multiplexing （MIMO-OFDM） systems based on the geometrical one-ring model. Using the spatial and temporal correlation of a geometrical one-ring model, a close-formed expression of intercarrier interference due to the Doppler effect caused by the movement of receiver is derived under the isotropic scattering conditions and non-isotropic scattering conditions. The analytical results are verified by Monte Carlo simulations. We use the generated channels to investigate MIMO-OFDM intercarrier interference under various channel parameters. It can be shown that more than 95% oflCI power comes from five neighboring subcarriers.

Spectral Studies of Oscillations Observed by the High-Latitude Radar and Magnetometers

A comparative spectral analysis of high-latitude magnetic and Doppler radar measurements is presented. The analysis takes into account the Doppler effect that is inherent in magnetic observations. The frequency shifts between the magnetic and radar data are estimated （removed） indirectly by formulating the spectral analysis of magnetic data as the Schuster problem of hidden periodicities. There is a satisfactory agreement between the basic frequencies of equidistant spectra found in the magnetic data and frequencies found in the corresponding Doppler radar data. Some conclusions relevant to these findings are discussed.