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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

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Network Switching Services

Before we discuss communication protocols, let us take a detour and briefly discuss data transfer by a switching element. This is a technique by which data is moved from host to host across the length and width of the network mesh of hosts, hubs, bridges, routers, and gateways. This technique is referred to as data switching. The type of data switching technique used by a network determines how messages are transmitted between the two communicating elements and across that network. There are two types of data switching techniques: circuit switching and packet switching.

In circuit switching networks, one must reserve all the resources before setting up the physical communication channel needed for communication. The physical connection, once established, is then used exclusively by the two end systems, usually subscribers, for the duration of the communication. The main feature of such a connection is that it provides a fixed data rate channel, and both subscribers must operate at this rate. For example, in a telephone communication network, a connected line is reserved between the two points before the users can start using the service. One issue of debate on circuit switching is the perceived waste of resources during the so-called silent periods when the connection is fully in force but not being used by the parties. This situation occurs when, for example, during a telephone network session, a telephone receiver is not hung up after use, leaving the connection still established. During this period, while no one is utilizing the session, the session line is still open.

## 电子工程代写|计算机及网络安全代写Computer and Network Security代考|Network Connecting Devices

Before we discuss network connecting devices, let us revisit the network infrastructure. We have defined a network as a mesh of network elements. commonly referred to as network nodes, connected together by conducting media. These network nodes can be either at the ends of the mesh, in which case they are commonly known as clients or in the middle of the network as transmitting elements. In a small network such as a LAN, the nodes are connected together via special connecting and conducting devices that take network traffic from one node and pass it on to the next node. If the network is a big internetwork (large networks of networks like WANs and LANs), these networks are connected to other special intermediate networking devices so that the Internet functions as a single large network.

Now let us look at network connecting devices and focus on two types of devices: those used in networks (small networks such as LANs) and those used in internetworks.

This is the simplest in the family of network connecting devices since it connects the LAN components with identical protocols. It takes in imports and retransmits them verbatim. It can be used to switch both digital and analog data. In each node, presetting must be done to prepare for the formatting of the incoming data. For example, if the incoming data is in digital format, the hub must pass it on as packets; however, if the incoming data is analog, then the hub passes it as a signal. There are two types of hubs: simple and multiple port hubs, as shown in Figs. $1.23$ and $1.24 .$ Multiple port hubs may support more than one computer up to its number of ports and may be used to plan for the network expansion as more computers are added at a later time.

# 计算机及网络安全代考

## 有限元方法代写

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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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