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NewZigzag指标

  1. sigmoid函数饱和使梯度消失(Sigmoidsaturate and kill gradients)。 我们从导函数图像中可以看出sigmoid的导数都是小于0.25的,那么在进行反向传播的时候,梯度相乘结果会慢慢的趋*于0。这样,几乎就没有梯度信号通过神经元传递到前面层的梯度更新中,因此这时前面层的权值几乎没有更新,这就叫梯度消失。除此之外,为了防止饱和,必须对于权重矩阵的初始化特别留意。如果初始化权重过大,可能很多神经元得到一个比较小的梯度,致使神经元不能很好的更新权重提前饱和,神经网络就几乎不学习。
  2. sigmoid函数输出不是“零为中心”(zero-centered)。 一个多层的sigmoid神经网络,如果你的输入x都是正数,那么在反向传播中w的梯度传播到网络的某一处时,权值的变化是要么全正要么全负。

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תרגום "价格浮动" לאנגלית

We would also like to see the perennial problem of commodity price fluctuations given much greater attention.

From a human rights perspective, it will be important that NewZigzag指标 NewZigzag指标 trade rules guarantee flexibility to take remedial action to ensure that price fluctuations do not negatively affect the availability or accessibility of food.

Look at the tourist routes and the peak season travel vehicles nervous situation, season price fluctuation is bigger.

Each transaction (buying or NewZigzag指标 selling) always ends with the making of the opposite deal. It means that when you buy a CFD contract for a share, you turn into a company shareholder and can gain profit from the price fluctuation of NewZigzag指标 the chosen financial instrument.

An investment strategy used to reduce risk by locking in the price to protect against future price changes.

Looking at consumption, total retail sales of consumer goods increased 15.0% year on year in the first half, and real growth adjusted for price changes accelerated to 16.6%.

Related to NewZigzag指标 NewZigzag指标 this was the problem of lack of export diversification in many developing economies, where primary commodity exporters were vulnerable to demand and price fluctuations beyond their control.

Particular attention should be paid to the problem of market NewZigzag指标 volatility and price fluctuations, which prevented most developing countries NewZigzag指标 from achieving sustainable development.

Reviewed and streamlined product specifications and supply chain requirements in 10 new tenders for engineering contracts, including risk management procedures related to price NewZigzag指标 fluctuations in raw materials

世纪彩票Commonly used materials are stocking inventory, NewZigzag指标 to avoid short-term material price fluctuations or lack of material

Finally, it discussed national and international policy measures that might be needed to reduce the vulnerability of African NewZigzag指标 economies to commodity price fluctuations.

Because of considerable price fluctuations over the years and the ease of storage, it is believed that large quantities of opiates are stockpiled in Afghanistan.

6.2 Returns the price to follow the raw material price fluctuations, such as the same price in accordance with the purchase price or both NewZigzag指标 parties negotiated.

The price fluctuations were a direct result of the surplus opium on the market. For 1999 and 2000, the total income from opium should not be much higher for Afghanistan.

For example, the Zig Zag indicator, which you can find in the list of customs indicators, weeds out any minor price fluctuations and shows only the clear direction of the trend.

Finally, short-term price fluctuations could be minimized by adequately-funded international NewZigzag指标 buffer stocks; alternatively, the adverse impact of such fluctuations could be avoided if exporters in developing countries were to use commodity-linked financial instruments to hedge their commercial risks.

It was stressed that approaches to dealing with commodity problems should take into account the low levels of real prices for commodities, the long-term declining trend in terms of trade, excessive price fluctuations and difficulties associated NewZigzag指标 with market access and market entry conditions, as well as effective participation in supply chains.

the Department is NewZigzag指标 increasing its use of renewable energy supplies and reducing energy demand to improve operational effectiveness, reduce greenhouse gas emissions in support of U.S. climate change initiatives, NewZigzag指标 NewZigzag指标 NewZigzag指标 and protect the Department from energy price fluctuations

To lessen NewZigzag指标 the impact of oil price fluctuations and to correct fiscal imbalances, oil-dependent ESCWA States should adjust their fiscal policies by making their tax systems more progressive and broadening their tax base.

Manufacturing is also one of the main vehicles for technological development and innovation, and an NewZigzag指标 economy with a higher share of manufacturing in total value added is generally less exposed to external shocks, price fluctuations, climatic conditions and unfair competition policies.

הדוגמאות NewZigzag指标 משמשות רק כדי לעזור לך לתרגם את המילה או הביטוי שחיפשת בהקשרים שונים. הן לא נבחרות או מאומתות על ידינו ויכולות להכיל מונחים או רעיונות לא הולמים. אנא דווח על דוגמאות שיש לערוך או שאין להציגן. תרגומים גסים או לא פורמליים בדרך כלל מסומנים בצבע אדום או כתום.

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深度学习中几种常见的激活函数理解与总结

  1. sigmoid函数饱和使梯度消失(Sigmoidsaturate and kill gradients)。 我们从导函数图像中可以看出sigmoid的导数都是小于0.25的,那么在进行反向传播的时候,梯度相乘结果会慢慢的趋*于0。这样,几乎就没有梯度信号通过神经元传递到前面层的梯度更新中,因此这时前面层的权值几乎没有更新,这就叫梯度消失。除此之外,为了防止饱和,必须对于权重矩阵的初始化特别留意。如果初始化权重过大,可能很多神经元得到一个比较小的梯度,致使神经元不能很好的更新权重提前饱和,神经网络就几乎不学习。
  2. sigmoid函数输出不是“零为中心”(zero-centered)NewZigzag指标 。 一个多层的sigmoid神经网络,如果你的输入x都是正数,那么在反向传播中w的梯度传播到网络的某一处时,权值的变化是要么全正要么全负。

如上图所示:当梯度从上层传播下来,w的梯度都是用x乘以f的梯度,因此如果神经元输出的梯度是正的,那么所有w的梯度就会是正的,反之亦然。在这个例子中,我们会得到两种权值,权值范围分别位于图8中一三象限。当输入一个值时,w的梯度要么都是正的要么都是负的,当我们想要输入一三象限区域以外的点时,我们将会得到这种并不理想的曲折路线(zig zag path),图中红色曲折路线。假设最优化的一个w矩阵是在图8中的第四象限,那么要将w优化到最优状态,就必须走“之字形”路线,因为你的w要么只能往下走(负数),要么只能往右走(正的)。优化的时候效率十分低下,模型拟合的过程就会十分缓慢。

(2)tanh

优点 :tanh解决了sigmoid的输出非“零为中心”的问题

缺点 :(1)依然有sigmoid函数过饱和的问题。(2)依然进行的是指数运算

(3)ReLU

*年来,ReLU函数变得越来越受欢迎。全称是Rectified Linear Unit,中文名字:修正线性单元。ReLU是Krizhevsky、Hinton等人在2012年《ImageNet Classification with Deep NewZigzag指标 Convolutional Neural Networks》论文中提出的一种线性且不饱和的激活函数。它的数学表达式如7所示

优点: (1)ReLU解决了梯度消失的问题,至少x在正区间内,神经元不会饱和;(2)由于ReLU线性、非饱和的形式,在SGD中能够快速收敛;(3)算速度要快很多。ReLU函数只有线性关系,不需要指数计算,不管在前向传播还是反向传播,计算速度都比sigmoid和tanh快

缺点: (1) ReLU的输出不是“零为中心”(Notzero-centered output)。(2)随着训练的进行,可能会出现神经元死亡,权重无法更新的情况。这种神经元的死亡是不可逆转的死亡

引出的问题: 神经网络中ReLU是线性还是非线性函数?为什么relu这种“看似线性”(分段线性)的激活函数所形成的网络,居然能够增加非线性的表达能力?

(4)Leaky ReLU

ReLU是将所有的负值设置为0,造成神经元节点死亡情况。相反,Leaky ReLU是给所有负值赋予一个非零的斜率。Leaky ReLU激活函数是在声学模型(2013)中首次提出来的。它的数学表达式如公式8所示:

优点:

缺点: (1). Leaky ReLU函数中的α,需要通过先验知识人工赋值。

总结: Leaky ReLU很好的解决了“dead ReLU”的问题。因为Leaky ReLU保留了x小于0时的梯度,在x小于0时,不会出现神经元死亡的问题。对于Leaky ReLU给出了一个很小的负数梯度值α,这个值是很小的常数。比如:0.01。这样即修正了数据分布,又保留了一些负轴的值,使得负轴信息不会全部丢失。但是这个α通常是通过先验知识人工赋值的。

(5)RReLU

RReLU的英文全称是“Randomized Leaky ReLU”,中文名字叫“NewZigzag指标 随机修正线性单元”。RReLU是Leaky ReLU的随机版本。它首次是在Kaggle的NDSB比赛中被提出来的,其图像和表达式如下图所示:

特点:

(6)ReLU、Leaky ReLU、PReLU和RReLU的比较

总结:

(7)ELU

ELU的英文全称是“Exponential Linear Units”,中文全称是“指数线性单元”。它试图将激活函数的输出*均值接*零,从而加快学习速度。同时,它还能通过正值的标识来避免梯度消失的问题。根据一些研究显示,ELU分类精确度是高于ReLU的。公式如12式所示。

优点:

缺点:

(8)Maxout

Maxout “Neuron” 是由Goodfellow等人在2013年提出的一种很有特点的神经元,它的激活函数、计算的变量、计算方式和普通的神经元完全不同,并有两组权重。先得到两个超*面,再进行最大值计算。激活函数是对ReLU和Leaky ReLU的一般化归纳,没有ReLU函数的缺点,不会出现激活函数饱和神经元死亡的情况。Maxout出现在ICML2013上,作者Goodfellow将maxout和dropout结合,称在MNIST,CIFAR-10,CIFAR-100,SVHN这4个数据集上都取得了start-of-art的识别率。Maxout公式如13所示。

优点: NewZigzag指标 NewZigzag指标

缺点:

4.如何选择合适的激活函数?

(2)如果使用ReLU,那么一定要小心设置学习率(learning rate),并且要注意不要让网络中出现很多死亡神经元。如果死亡神经元过多的问题不好解决,可以试试Leaky ReLU、PReLU、或者Maxout。