Neural-Network-Introduction神经网络介绍大学毕业论文外文文献翻译及原文
神经网络 论文

摘要神经网络是一门发展十分迅速的交叉学科,它是由大量的处理单元组成非线性的大规模自适应动力系统。
神经网络具有分布式存储、并行处理、高容错能力以及良好的自学习、自适应、联想等特点。
目前已经提出了多种训练算法和网络模型,其中应用最广泛的是前馈型神经网络。
前馈型神经网络训练中使用最多的方法是误差反向传播(BP)学习算法。
但随着使用的广泛,人们发现BP网络存在收敛速度缓慢、易陷入局部极小等缺陷。
于是我们就可以分析其产生问题的原因,从收敛速度和局部极小两个方面分别提出改进的BP网络训练方法。
关键字:神经网络,收敛速度,局部极小,BP网络,改进方法AbstractNeural network is a cross discipline which now developing very rapidly, it is the nonlinearity adaptive power system which made up by abundant of the processing units . The neural network has features such as distributed storage, parallel processing, high tolerance and good self-learning, adaptive, associate, etc. Currently various training algorithm and network model have been proposed , which the most widely used type is Feedforward neural network model. Feedforward neural network training type used in most of the method is back-propagation (BP) algorithm. But with the use of BP network, people find that the convergence speed is slow, and easy fall into the local minimum. So we can analyze the causes of problems, from the two aspects respectively we can improve the BP training methods of neural network. Keywords:neural network,convergence speed,local minimum,BP neural network improving methods目录1 神经网络概述 (3)1.1生物神经元模型............................. 错误!未定义书签。
神经网络(NeuralNetwork)

神经⽹络(NeuralNetwork)1 引⾔机器学习(Machine Learning)有很多经典的算法,其中基于深度神经⽹络的深度学习算法⽬前最受追捧,主要是因为其因为击败李世⽯的阿尔法狗所⽤到的算法实际上就是基于神经⽹络的深度学习算法。
本⽂先介绍基本的神经元,然后简单的感知机,扩展到多层神经⽹络,多层前馈神经⽹络,其他常见的神经⽹络,接着介绍基于深度神经⽹络的深度学习,纸上得来终觉浅,本⽂最后⽤python语⾔⾃⼰编写⼀个多层前馈神经⽹络。
2 神经元模型这是⽣物⼤脑中的基本单元——神经元。
在这个模型中,神经元接受到来⾃n个其他神经元传递过来的输⼊信号,在这些输⼊信号通过带权重的连接进⾏传递,神经元接受到的总输⼊值将与神经元的阈值进⾏⽐较,然后通过“激活函数”处理以产⽣神经元的输出。
3 感知机与多层⽹络 感知机由两层神经元组成,输⼊层接收外界输⼊信号后传递给输出层,输出层是M-P神经元。
要解决⾮线性可分问题,需考虑使⽤多层神经元功能。
每层神经元与下⼀层神经元全互连,神经元之间不存在同层连接,也不存在跨层连接。
这样的神经⽹络结构通常称为“多层前馈神经⽹络”。
神经⽹络的学习过程,就是根据训练数据来调整神经元之间的“连接权”以及每个功能神经元的阈值;换⾔之,神经⽹络“学”到的东西,蕴涵在连接权与阈值之中。
4 误差逆传播算法⽹络在上的均⽅误差为:正是由于其强⼤的表达能⼒,BP神经⽹络经常遭遇过拟合,其训练过程误差持续降低,但测试误差却可能上升。
有两种策略常⽤来缓解BP⽹络过拟合。
第⼀种策略是“早停”:将数据分成训练集和验证集,训练集⽤来计算梯度、更新连接权和阈值。
第⼆种策略是“正则化”,其基本思想是在误差⽬标函数中增加⼀个⽤于描述⽹络复杂度的部分。
5 全局最⼩与局部极⼩若⽤Ε表⽰神经⽹络在训练集上的误差,则它显然关于连接权ω和阈值θ的函数。
此时,神经⽹络的训练过程可看作⼀个参数寻优的过程,即在参数空间中,寻找最优参数使得E最⼩。
神经网络(neuralnetwork(NN))百科物理

神经网络(neuralnetwork(NN))百科物理当今社会是一个高速发展的信息社会。
生活在信息社会,就要不断地接触或获取信息。
如何获取信息呢?阅读便是其中一个重要的途径。
据有人不完全统计,当今社会需要的各种信息约有80%以上直接或间接地来自于图书文献。
这就说明阅读在当今社会的重要性。
还在等什么,快来看看这篇神经网络(neuralnetwork(NN))百科物理吧~神经网络(neuralnetwork(NN))神经网络(neuralnetwork(NN))是由巨量神经元相互连接成的复杂非线性系统。
它具有并行处理和分布式存储信息及其整体特性不依赖于其中个别神经元的性质,很难用单个神经元的特性去说明整个神经网络的特性。
脑是自然界中最巧妙的控制器和信息处理系统。
自1943年McCulloch和Pitts最早尝试建立神经网络模型,至今已有许多模拟脑功能的模型,但距理论模型还很远。
大致分两类:①人工神经网络,模拟生物神经系统功能,由简单神经元模型构成,以图解决工程技术问题。
如模拟脑细胞的感知功能的BP(Back-Propagation)神经网络;基于自适应共振理论的模拟自动分类识别的ART(AdaptiveResonanceTheory)神经网络等;②现实性模型,与神经细胞尽可能一致的神经元模型构成的网络,以图阐明神经网络结构与功能的机理,从而建立脑模型和脑理论。
如基于突触和细胞膜电特性的霍泊费尔特(Hopfield)模型,以计算能量刻划网络整体的动态行为,可解释联想记忆;Ekeberg等人(1991)建立的基于Hodgkin-Huxley方程的四房室神经元模型等。
神经网络研究不仅为阐明脑功能机理,能是发展智能计算机和智能机器的基础。
这篇神经网络(neuralnetwork(NN))百科物理,你推荐给朋友了么?。
神经网络(NeuralNetwork)

神经⽹络(NeuralNetwork)⼀、激活函数激活函数也称为响应函数,⽤于处理神经元的输出,理想的激活函数如阶跃函数,Sigmoid函数也常常作为激活函数使⽤。
在阶跃函数中,1表⽰神经元处于兴奋状态,0表⽰神经元处于抑制状态。
⼆、感知机感知机是两层神经元组成的神经⽹络,感知机的权重调整⽅式如下所⽰:按照正常思路w i+△w i是正常y的取值,w i是y'的取值,所以两者做差,增减性应当同(y-y')x i⼀致。
参数η是⼀个取值区间在(0,1)的任意数,称为学习率。
如果预测正确,感知机不发⽣变化,否则会根据错误的程度进⾏调整。
不妨这样假设⼀下,预测值不准确,说明Δw有偏差,⽆理x正负与否,w的变化应当和(y-y')x i⼀致,分情况讨论⼀下即可,x为负数,当预测值增加的时候,权值应当也增加,⽤来降低预测值,当预测值减少的时候,权值应当也减少,⽤来提⾼预测值;x为正数,当预测值增加的时候,权值应当减少,⽤来降低预测值,反之亦然。
(y-y')是出现的误差,负数对应下调,正数对应上调,乘上基数就是调整情况,因为基数的正负不影响调整情况,毕竟负数上调需要减少w的值。
感知机只有输出层神经元进⾏激活函数处理,即只拥有⼀层功能的神经元,其学习能⼒可以说是⾮常有限了。
如果对于两参数据,他们是线性可分的,那么感知机的学习过程会逐步收敛,但是对于线性不可分的问题,学习过程将会产⽣震荡,不断地左右进⾏摇摆,⽽⽆法恒定在⼀个可靠地线性准则中。
三、多层⽹络使⽤多层感知机就能够解决线性不可分的问题,输出层和输⼊层之间的成为隐层/隐含层,它和输出层⼀样都是拥有激活函数的功能神经元。
神经元之间不存在同层连接,也不存在跨层连接,这种神经⽹络结构称为多层前馈神经⽹络。
换⾔之,神经⽹络的训练重点就是链接权值和阈值当中。
四、误差逆传播算法误差逆传播算法换⾔之BP(BackPropagation)算法,BP算法不仅可以⽤于多层前馈神经⽹络,还可以⽤于其他⽅⾯,但是单单提起BP算法,训练的⾃然是多层前馈神经⽹络。
神经网络理论及应用

神经网络理论及应用神经网络(neural network)是一种模仿人类神经系统工作方式而建立的数学模型,用于刻画输入、处理与输出间的复杂映射关系。
神经网络被广泛应用于机器学习、人工智能、数据挖掘、图像处理等领域,是目前深度学习技术的核心之一。
神经网络的基本原理是模仿人脑神经细胞——神经元。
神经元接收来自其他神经元的输入信号,并通过一个激活函数对所有输入信号进行加权求和,再传递到下一个神经元。
神经元之间的连接权重是神经网络的关键参数,决定了不同输入组合对输出结果的影响。
神经网络的分类可分为多层感知机、卷积神经网络、循环神经网络等等。
其中多层感知机(Multi-Layer Perceptron,MLP)是最基本的神经网络结构。
MLP由输入层、若干个隐藏层和输出层组成,每层包括多个神经元,各层之间被完全连接,每个神经元都接收来自上一层的输入信号并输出给下一层。
通过不断地训练神经网络,即对连接权重进行优化,神经网络能够准确地对所学习的模式进行分类、回归、识别、聚类等任务。
神经网络的应用非常广泛,涉及到各个领域。
在图像处理领域中,卷积神经网络(Convolutional Neural Network,CNN)是一种特殊的神经网络,主要应用于图像识别、图像分割等任务。
比如,在医疗领域中,CNN被用于对医学影像进行诊断,对疾病进行分类、定位和治疗建议的制定。
在语音处理领域中,循环神经网络(Recurrent Neural Network,RNN)因其能够处理序列数据而备受推崇,常用于文本生成、机器翻译等任务。
在自然语言处理领域中,基于预训练的语言模型(Pre-trained Language Models,PLM)在语言模型微调、文本分类和情感分析等方面表现出色。
尽管神经网络有诸多优点,但它也存在一些缺点。
其中最为突出的是过度拟合(overfitting),即模型过于复杂,为了适应训练集数据而使得泛化能力下降,遇到未知数据时准确率不高。
神经网络算法简介

神经网络算法简介神经网络(Neural Network)是模拟人类大脑神经学习和处理信息的一种计算机算法,它是深度学习领域的基础,被广泛应用于图像识别、语音识别、自然语言处理等各种场景中。
神经网络的发展和应用,为我们的生活带来了很多的变化和便利,今天我们来简单了解一下神经网络。
神经元模型神经元是神经网络的基本组成单元。
它接收到来自其他神经元传递过来的电信号,并且根据这些信号的相对强弱决定是否会向其他神经元发射信号。
在神经网络中,神经元的输入可以来自于其他神经元,也可以来自于外部输入,输出可以传递给后续的神经元或者被当做神经网络的最终输出。
神经网络结构神经网络的结构分为三层:输入层、隐藏层和输出层。
每一层都是由多个神经元组成,在前向传播过程中,从输入层的神经元开始向后传递信息,经过一系列的计算后,最后从输出层输出结果。
在隐藏层中,神经元的数量和层数可以根据需要进行设定。
随着神经网络层数的增加,模型的复杂度也会增加,能够表示的函数也更加复杂,从而提高了模型的准确度。
但是,如果层数过多或者神经元数量过多,就会导致模型出现过拟合的现象,出现这种情况时,就需要对模型进行优化调整。
神经网络的训练神经网络的训练需要大量的数据来进行模型的调整和学习,训练数据可以分为训练集、验证集和测试集三个部分。
其中,训练集用来训练模型,验证集用来验证模型的准确度,在训练过程中,如果出现了过拟合的现象,就需要通过验证集的误差来进行模型的调整。
最后,测试集是用来测试最终的模型精度的数据集。
神经网络的训练过程通常采用反向传播算法(Backpropagation Algorithm)。
它通过计算损失函数的梯度,从而进行网络参数的更新。
损失函数常用的有均值平方差(Mean Squared Error)和交叉熵(Cross-Entropy)等。
神经网络的优化神经网络优化是指在保持预测准确性的同时,降低模型的计算复杂度和训练时间。
在神经网络中,常用的优化算法有梯度下降法(Gradient Descent)、随机梯度下降法(Stochastic Gradient Descent)、自适应矩估计(Adaptive Moment Estimation,简称Adam)、自适应随机梯度下降法(Adaptive Stochastic Gradient Descent,简称AdaGrad)等。
神经网络的介绍范文

神经网络的介绍范文
神经网络(Neural Networks)是一种利用统计学习的方法,来解决
计算机视觉,自然语言处理,以及其他各种智能问题。
基本的神经网络架
构是由多个由具有可学习的权重的神经元构成的多层网络,每个神经元都
有一个可以被其他神经元影响的活动函数(例如逻辑函数或非线性函数)。
在简单的神经网络中,神经元可以接收输入信号并输出一个基于输入
信号。
输入信号可以是一维数组或多维数组,输出值可以是一维数组,也
可以是多维数组。
神经元可以有不同的连接强度,一些强连接的神经元可
以更大程度的影响输出,而连接弱的神经元则起到一个较小的作用。
神经
元之间的权重(weights)可以用梯度下降算法调整,以更精确的拟合数据。
分类器神经网络(Classifier Neural Networks)是使用神经网络来
实现分类任务的一种技术,类似于支持向量机(SVM)和朴素贝叶斯分类
器(Naive Bayes Classifier)。
该网络包含多个输入层,隐藏层和输出层。
输入层接收原始信号,隐藏层处理特征和聚类,然后输出层将结果转
换为有意义的分类结果。
神经网络简介

神经网络简介神经网络(Neural Network),又被称为人工神经网络(Artificial Neural Network),是一种模仿人类智能神经系统结构与功能的计算模型。
它由大量的人工神经元组成,通过建立神经元之间的连接关系,实现信息处理与模式识别的任务。
一、神经网络的基本结构与原理神经网络的基本结构包括输入层、隐藏层和输出层。
其中,输入层用于接收外部信息的输入,隐藏层用于对输入信息进行处理和加工,输出层负责输出最终的结果。
神经网络的工作原理主要分为前向传播和反向传播两个过程。
在前向传播过程中,输入信号通过输入层进入神经网络,并经过一系列的加权和激活函数处理传递到输出层。
反向传播过程则是根据输出结果与实际值之间的误差,通过调整神经元之间的连接权重,不断优化网络的性能。
二、神经网络的应用领域由于神经网络在模式识别和信息处理方面具有出色的性能,它已经广泛应用于各个领域。
1. 图像识别神经网络在图像识别领域有着非常广泛的应用。
通过对图像进行训练,神经网络可以学习到图像中的特征,并能够准确地判断图像中的物体种类或者进行人脸识别等任务。
2. 自然语言处理在自然语言处理领域,神经网络可以用于文本分类、情感分析、机器翻译等任务。
通过对大量语料的学习,神经网络可以识别文本中的语义和情感信息。
3. 金融预测与风险评估神经网络在金融领域有着广泛的应用。
它可以通过对历史数据的学习和分析,预测股票价格走势、评估风险等,并帮助投资者做出更科学的决策。
4. 医学诊断神经网络在医学领域的应用主要体现在医学图像分析和诊断方面。
通过对医学影像进行处理和分析,神经网络可以辅助医生进行疾病的诊断和治疗。
5. 机器人控制在机器人领域,神经网络可以用于机器人的感知与控制。
通过将传感器数据输入到神经网络中,机器人可以通过学习和训练来感知环境并做出相应的反应和决策。
三、神经网络的优缺点虽然神经网络在多个领域中都有着广泛的应用,但它也存在一些优缺点。
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毕业设计(论文)外文文献翻译文献、资料中文题目:神经网络介绍文献、资料英文题目:Neural Network Introduction文献、资料来源:文献、资料发表(出版)日期:院(部):专业:班级:姓名:学号:指导教师:翻译日期:2017.02.14外文文献翻译注:节选自Neural Network Introduction神经网络介绍,绪论。
HistoryThe history of artificial neural networks is filled with colorful, creative individuals from many different fields, many of whom struggled for decades to develop concepts that we now take for granted. This history has been documented by various authors. One particularly interesting book is Neurocomputing: Foundations of Research by John Anderson and Edward Rosenfeld. They have collected and edited a set of some 43 papers of special historical interest. Each paper is preceded by an introduction that puts the paper in historical perspective.Histories of some of the main neural network contributors are included at the beginning of various chapters throughout this text and will not be repeated here. However, it seems appropriate to give a brief overview, a sample of the major developments.At least two ingredients are necessary for the advancement of a technology: concept and implementation. First, one must have a concept, a way of thinking about a topic, some view of it that gives clarity not there before. This may involve a simple idea, or it may be more specific and include a mathematical description. To illustrate this point, consider the history of the heart. It was thought to be, at various times, the center of the soul or a source of heat. In the 17th century medical practitioners finally began to view the heart as a pump, and they designed experiments to study its pumping action. These experiments revolutionized our view of the circulatory system. Without the pump concept, an understanding of the heart was out of grasp.Concepts and their accompanying mathematics are not sufficient for a technology to mature unless there is some way to implement the system. For instance, the mathematics necessary for the reconstruction of images from computer-aided topography (CAT) scans was known many years before the availability of high-speed computers and efficient algorithms finally made it practical to implement a useful CAT system.The history of neural networks has progressed through both conceptual innovations and implementation developments. These advancements, however, seem to have occurred in fits and starts rather than by steady evolution.Some of the background work for the field of neural networks occurred in the late 19th and early 20th centuries. This consisted primarily of interdisciplinary work in physics, psychology and neurophysiology by such scientists as Hermann von Helmholtz, Ernst Much and Ivan Pavlov. This early work emphasized general theories of learning, vision, conditioning, etc.,and did not include specific mathematical models of neuron operation.The modern view of neural networks began in the 1940s with the work of Warren McCulloch and Walter Pitts [McPi43], who showed that networks of artificial neurons could, in principle, compute any arithmetic or logical function. Their work is often acknowledged as the origin of theneural network field.McCulloch and Pitts were followed by Donald Hebb [Hebb49], who proposed that classical conditioning (as discovered by Pavlov) is present because of the properties of individual neurons. He proposed a mechanism for learning in biological neurons.The first practical application of artificial neural networks came in the late 1950s, with the invention of the perception network and associated learning rule by Frank Rosenblatt [Rose58]. Rosenblatt and his colleagues built a perception network and demonstrated its ability to perform pattern recognition. This early success generated a great deal of interest in neural network research. Unfortunately, it was later shown that the basic perception network could solve only a limited class of problems. (See Chapter 4 for more on Rosenblatt and the perception learning rule.)At about the same time, Bernard Widrow and Ted Hoff [WiHo60] introduced a new learning algorithm and used it to train adaptive linear neural networks, which were similar in structure and capability to Rosenblatt’s perception. The Widrow Hoff learning rule is still in use today. (See Chapter 10 for more on Widrow-Hoff learning.) Unfortunately, both Rosenblatt's and Widrow's networks suffered from the same inherent limitations, which were widely publicized in a book by Marvin Minsky and Seymour Papert [MiPa69]. Rosenblatt and Widrow wereaware of these limitations and proposed new networks that would overcome them. However, they were not able to successfully modify their learning algorithms to train the more complex networks.Many people, influenced by Minsky and Papert, believed that further research on neural networks was a dead end. This, combined with the fact that there were no powerful digital computers on which to experiment,caused many researchers to leave the field. For a decade neural network research was largely suspended. Some important work, however, did continue during the 1970s. In 1972 Teuvo Kohonen [Koho72] and James Anderson [Ande72] independently and separately developed new neural networks that could act as memories. Stephen Grossberg [Gros76] was also very active during this period in the investigation of self-organizing networks.Interest in neural networks had faltered during the late 1960s because of the lack of new ideas and powerful computers with which to experiment. During the 1980s both of these impediments were overcome, and researchin neural networks increased dramatically. New personal computers and workstations, which rapidly grew in capability, became widely available. In addition, important new concepts were introduced.Two new concepts were most responsible for the rebirth of neural net works. The first was the use of statistical mechanics to explain the operation of a certain class of recurrent network, which could be used as an associative memory. This was described in a seminal paper by physicist John Hopfield [Hopf82].The second key development of the 1980s was the backpropagation algo rithm for training multilayer perceptron networks, which was discovered independently by several different researchers. The most influential publication of the backpropagation algorithm was by David Rumelhart and James McClelland [RuMc86]. This algorithm was the answer to the criticisms Minsky and Papert had made in the 1960s. (See Chapters 11 and 12 for a development of the backpropagation algorithm.)These new developments reinvigorated the field of neural networks. In the last ten years, thousands of papers have been written, and neural networks have found many applications. The field is buzzing with new theoretical and practical work. As noted below, it is not clear where all of this will lead US.The brief historical account given above is not intended to identify all of the major contributors, but is simply to give the reader some feel for how knowledge in the neuralnetwork field has progressed. As one might note, the progress has not always been "slow but sure." There have been periods of dramatic progress and periods when relatively little has been accomplished.Many of the advances in neural networks have had to do with new concepts, such as innovative architectures and training. Just as important has been the availability of powerful new computers on which to test these new concepts.Well, so much for the history of neural networks to this date. The real question is, "What will happen in the next ten to twenty years?" Will neural networks take a permanent place as a mathematical/engineering tool, or will they fade away as have so many promising technologies? At present, the answer seems to be that neural networks will not only have their day but will have a permanent place, not as a solution to every problem, but as a tool to be used in appropriate situations. In addition, remember that we still know very little about how the brain works. The most important advances in neural networks almost certainly lie in the future.Although it is difficult to predict the future success of neural networks, the large number and wide variety of applications of this new technology are very encouraging. The next section describes some of these applications.ApplicationsA recent newspaper article described the use of neural networks in literature research by Aston University. It stated that "the network can be taught to recognize individual writing styles, and the researchers used it to compare works attributed to Shakespeare and his contemporaries." A popular science television program recently documented the use of neural networks by an Italian research institute to test the purity of olive oil. These examples are indicative of the broad range of applications that can be found for neural networks. The applications are expanding because neural networks are good at solving problems, not just in engineering, science and mathematics, but m medicine, business, finance and literature as well. Their application to a wide variety of problems in many fields makes them very attractive. Also, faster computers and faster algorithms have made it possible to use neural networks to solve complex industrial problems that formerly required too much computation.The following note and Table of Neural Network Applications are reproduced here from the Neural Network Toolbox for MATLAB with the permission of the Math Works, Inc.The 1988 DARPA Neural Network Study [DARP88] lists various neural network applications, beginning with the adaptive channel equalizer in about 1984. This device, which is an outstanding commercial success, is a single-neuron network used in long distance telephone systems to stabilize voice signals. The DARPA report goes on to list other commercial applications, including a small word recognizer, a process monitor, a sonar classifier and a risk analysis system.Neural networks have been applied in many fields since the DARPA report was written. A list of some applications mentioned in the literature follows.AerospaceHigh performance aircraft autopilots, flight path simulations, aircraft control systems, autopilot enhancements, aircraft component simulations, aircraft component fault detectorsAutomotiveAutomobile automatic guidance systems, warranty activity analyzersBankingCheck and other document readers, credit application evaluatorsDefenseWeapon steering, target tracking, object discrimination, facial recognition, new kinds of sensors, sonar, radar and image signal processing including data compression, feature extraction and noise suppression, signal/image identificationElectronicsCode sequence prediction, integrated circuit chip layout, process control, chip failure analysis, machine vision, voice synthesis, nonlinear modelingEntertainmentAnimation, special effects, market forecasting。