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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 电气工程代写|通讯系统作业代写communication system代考|Bolometers Detectors

Bolometers are detectors very sensitive to thermal radiation and are among the most widely used infrared detectors in the IR spectrum including the $\mathrm{THz}$ frequency range. The detector element is extremely sensitive to temperature change. Their principle of operation is such that the thermal radiation that hits the detector causes a temperature change. This will then lead to a change in resistance which gives access to a variation in the measurement of the voltage across an external reading circuit (Wheatstone Bridge). There are several types of bolometers [35]: – Metallic: the typical metals used in this type are nickel, bismuth, platinum, and titanium. They operate at room temperature and are easily integrated with CMOS technology. They are characterized by low noise, on the other hand, their temperature coefficient is low which decreases their performance.

The semiconductors used amorphous silicon, germanium, and alloys such as SiGe. Their temperature coefficient depends on the manufacturing process but it is of the order of 10 times higher than that of metals. Semiconductor oxides are also used such as GexSi1-xOy or vanadium oxide (V0x). * Hot electron superconductors: For a better bolometer sensitivity, the resistivity of the thermistor material must show a strong temperature dependence. The known high dependence of the resistivity of a superconductor on temperature makes it a natural choice for a thermistor material in bolometers. Note that unlike the other two types of bolometers where the resistance of their thermistor decreases with temperature, here the resistance of a superconductor increases with temperature (Fig. 6).

Golay cells and pyroelectrics are the most widely used commercial detectors due to their reasonable sensitivities. On the other hand, their response speeds are too slow (generally of the order of a few milliseconds), and they are very difficult to arrange in matrices which is a handicap for applications such as in imaging; Bolometers although they are capable of detecting frequencies above $2 \mathrm{THz}$, they require a response time of a few milliseconds, an electrical polarization but also sometimes a cryogenic temperature.

## 电气工程代写|通讯系统作业代写communication system代考|SDI Versus EOS Detection

In Sect. 4, we have described several detection methods, the most common of which is electro-optical sampling (EOS). EOS, however, is limited by over-rotation for strong THz fields. While various methods exist for circumventing the over-rotation limit, the latter always have drawbacks such as the reduction of the signal-to-noise ratio, a limited time acquisition length, or the deformation of the detected pulse $\mathrm{THz}$. An alternative electro-optical detection method would therefore be advantageous for the measurement of intense $\mathrm{THz}$ fields.

In 2012, Sharma et al. [36] developed a new electrooptic detection method based on an SDI system. The technique makes it possible to measure the phase change undergone by the probe wave when it passes through the electro-optical crystal by interferometry instead of measuring its polarization change with a polarizer.

During THz SDI detection, the probe pulse is temporally divided in half before reaching the detection crystal. The division is carried out using a glass plate: The laser pulse reflects first on the outer face of the glass plate, and then on its inner face, which creates two consecutive pulses. The first pulse reaches the crystal 3 ps before the second pulse. By adjusting the lengths of the probe and THz optical paths, it is possible to obtain that the first probe pulse passes through the crystal before the $\mathrm{THz}$ pulse while the second probe pulse passes at the same time as the THz pulse (see Fig. 7). The first pulse serves as a reference, while the second probe pulse is phase shifted by the birefringent crystal and therefore contains the information to be measured. The two probe pulses are then directed to a spectrometer consisting of a diffraction grating, a cylindrical lens, and a CCD camera. The two probe pulses are diffracted by the grating, after which they interfere together. Fringes are therefore observed on the camera, with an intensity given by the Formula (14). Here, it is the instantaneous phase differences between each of the Fourier components of the two probe pulses that it is desired to extract since they are induced by the THz field and proportional to the latter. Instantaneous phase differences can be extracted as follows:
$$\vartheta=\arctan \left(\frac{\operatorname{Im}(F(I(k)))}{\Re(\mathrm{F}(\mathrm{I}(\mathrm{k})))}\right)$$
where $\vartheta$ is the instantaneous phase difference between the two probe pulses, $\operatorname{Im}($. is the imaginary part, $\Re($.$) is the real part, and F(I(k))$ is the Fourier transform of the intensity of the fringes $I(k)$ (see Formula (14)).

For the calculation of the instantaneous THz field, the value of the phase shift corresponding to the center frequency of the probe pulse is generally selected. As mentioned in Sect. $4.5$ and observed in Fig. 7, the probe pulse is much shorter than the THz pulse, and therefore, it can be approximated that the calculated phase corresponds to a single point of the THz wave. To measure the complete $\mathrm{THz}$ wave, the glass plate is placed on a delay line that makes it possible to vary the optical path difference between the probe and THz pulses. For each position of the delay line and therefore for each point of the pulse $\mathrm{THz}$, the phase must be calculated. It is noted that, since the phase is calculated using an inverse tangent function, the result is always between $-\pi / 2$ and $\pi / 2$. To avoid phase jumps and thus obtain a continuous waveform, a standard phase unwinding algorithm is used.

# 通讯系统代考

## 电气工程代写|通讯系统作业代写communication system代考|SDI Versus EOS Detection

2012 年，Sharma 等人。[36] 开发了一种基于 SDI 系统的新型电光检测方法。该技术可以通过干涉测量法测量探测波通过电光晶体时所经历的相位变化，而不是用偏振器测量其偏振变化。

ϑ=反正切⁡(在里面(F(我(ķ)))ℜ(F(我(ķ))))

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

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