HS code-based negotiation with customs

List of Contents of this article:

• 1 ,HS code-based negotiation with customs Signal and signal period in the system
• 2, Given system differential equation d^2r(t)/dt^2+5dr(t)/dt+6r(t)=2d^2e(t)/dt+6de...
• 3, Signal And system professional questions
• 4, Signal and system topic solution:
• 5, Signal and System Problems: Solution

signal and signal period in the system

Your answer is correct! But it doesn't have to be as complicated as what you do. In fact, it is the common multiple of the period of two signals after multiplying two periodic signals.

Similarities and differences between the signal and the periodic signal expression and the communication principle expression in the system: the form of the expression is different. Periodic signal expressions generally take the form of trigonometric functions or exponential functions, such as sinusoidal functions, cosine functions, etc. Communication principle expressions mostly take the form of frequency domain analysis, such as Fourier transform, Laplace transform, etc.

Suppe the period of f(x) is a, the period of g(x) is b, and F(x)=f(x)+g(x). Proof: The period of F(x) is the least common multiple of a and b. F(x+a)=f(x), g(x+b)=g(x) is based on the meaning of the question, and set t as the period of F(x).

I'll tell you a very simple method. Sin (2πf×k) f is the frequency, and f can be obtained by bringing it into it, which is a natural period.

If it is a limited-period signal, each spectral line in the spectrum will be wide, and the envelope and spectral line interval are the same as above. Taking the periodic pulse modulation signal as an example, it is interesting that the minimum metric in the time domain: the intrapulse oscillation period, that is, the high or low of the carrier frequency, determines the maximum metric of the frequency domain: the position of the spectrum peak.

Given system differential equation d^2r(t)/dt^2+5dr(t)/dt+6r(t)=2d^2e(t)/dt+6de...

The meaning of the higher number is very clear: d^2r represents the second-order derivative of "r", and dt^2 indicates that it is derived from the time "t" twice. As for why we don't use d^2t, it is not easy to distinguish what to derive from.

is the second-order differentiation. d^2r divided by dt^2 is to find the second-order derivative of displacement to time, that is, acceleration. In uniformly variable speed linear motion, the ratio of velocity change to the time spent is called acceleration, and its international unit is meters/square seconds. Acceleration has size, direction, and is a vector.

Similarly, if you know the equation of motion r=r(t), you can find a according to the basic formula of kinematics, and then you can know the force of the object from Niu Er.) II: Special relativity mechanics: (Note:Γ=1/sqr (1-u^2/c^2), β=u/c, u is the inertial system velocity.) (I) Basic principle: (1) Principle of relativity: All inertial systems are equivalent.

Signal and System Professional Question

. A causal numerical sequence, if the pole of the system is located in the unit circle of the Z plane, then the system is a stable system. 2 Analog signals refer to continuous values of time and amplitude; digital signals are discrete values in time and amplitude; discrete time signals refer to continuous values in time and amplitude.

Lecturer: Example of time domain analysis of signals of Chen Houjin School of Electronic Information Engineering [Example 1] The waveform of the known signal x(t) is shown in the figure, (1) trial u(t) and r(t) represent x(t);(2) Write the x'(t) expression and draw the x'(t) waveform; (3) Draw the waveform of the signal x(-2t-4).

Single-choice question: 1 If the frequency band width occupied by the known continuous time signal is () A.400rad/sB. 200rad/sC. 100rad/sD.

In order to calculate the odd and even parts of the discrete signal x[n], we first need to understand the odd and even properties of the discrete signal.

Question 2: The Lashi transform exists, but the Fourier transform does not necessarily exist.

A. In general, the zero-state response has nothing to do with the system characteristics. B. If the starting state of the system is zero, the zero input response is equal to the zero state response. C. If the excitation signal of the system is zero, the zero input response is equal to the forced response.D. If the zero state response of the system is zero, the forced response is also zero.

Signal and System Question Solution:

1. In Oppenheimer's Signal and System, the underlined formula is the convolutional formula. Convolution is a basic operation in signal processing and system analysis, which is used to describe the interaction between two signals at a certain point in time.

2. Answer: B. The starting state is 0-state; the initial state is 0+ state; if the response interval of the equal solution is t≥0+, it should be determined by the 0+ state (initial state).

3. Consider the definition and properties of the shock signal, x(t)δ(t+3/2)-x(t)δ(t-3/2)=x(-3/2)δ(T+3/2)-x(3/2)δ(t-3/2), so it should be an excitation signal with an area of x (-3/2) and -x (3/2) respectively at t=-3/2 and t=3/2 respectively.

4. Signals and linear systems discuss the changes that occur after the signal passes through a linear system (that is, the mathematical relationship between input, output and the so-called system passed through).

Signal and System Problems: Solution

Answer: B. The starting state is 0-state; the initial state is 0+ state; if the response interval of the equal solution is t≥0+, it should be determined by the 0+ state (initial state).

The form of special solution is stimulated byThe excitation signal is determined, because the incitation signal only works when t=0, that is, in zhit, the input signal is 0 or it can be regarded as no input signal.

The most important situation of convolutional relations is the convolutional theorem in signal and linear systems or digital signal processing. Using this theorem, the convolutional operation in the time domain or space domain can be equivalent to the multiplication operation in the frequency domain, so as to use fast algorithms such as FFT to achieve effective calculations and save the cost of operation.

In Oppenheimer's Signals and Systems, the underlined formula is the convolutional formula. Convolution is a basic operation in signal processing and system analysis, which is used to describe the interaction between two signals at a certain point in time.

Consider the definition and properties of the shock signal, x(t)δ(T+3/2)-x(t)δ(t-3/2)=x(-3/2)δ(t+3/2)-x(3/2)δ(t-3/2), so it should be the impact of x(-3/2) and -x(3/2) respectively at t=-3/2 and t=3/2 respectively. Signal.

When doing specific questions, there are some specific situations that need to be considered: such as the concept of 0-state and 0+state, such as the situation where the input signal is an impact signal or a step signal. The problem of time domain response, the solution of differential equations, and the concepts of system excitation, response, initial state and initial conditions are clear.