• Latent Variable Modeling with R 英文无水印原版pdf pdf所有页面使用FoxitReader、PDF-XChangeViewer、SumatraPDF和Firefox测试都可以打开 本资源转载自网络，如有侵权，请联系上传者或csdn删除 查看此书详细...
• 本资料为纯英文版，是美国大学一元微积分入门教材 When the first edition of this book appeared twelve years ago, a heated debate about calculus reform was taking place. Such issues as the use of ...
• ## 什么是free variable

千次阅读 2019-09-27 14:19:28
但是有很多名词恰恰就是英文的，而我们因为英语水平的局限，很难将这些英文名词翻译到位，也就导致很容易理解的名词经常困扰着我们。 那今天的主角是free variable。 我把他叫为自由变量。 用英文可以这么解释它...
其实很多英文名词对应的中文名词我们很好理解，也很容易理解他的用处。但是有很多名词恰恰就是英文的，而我们因为英语水平的局限，很难将这些英文名词翻译到位，也就导致很容易理解的名词经常困扰着我们。
那今天的主角是free variable。
我把他叫为自由变量。
用英文可以这么解释它：
If a name is bound in a block, it is a local variable of that block. If a name is bound at the module level, it is a global variable. (The variables of the module code block are local and global.) If a variable is used in a code block but not defined there, it is a free variable.
最主要我觉得是最后一句，如果一个变量在一个代码块中使用，而没有在那里定义它，那它就是一个自由变量。
比如：
define(function(require, exports, module) {
// The module code goes here

});
这里的require,exports,module就是free variable.

又比如：
Gol.prototype._ensureInit = function() {
...
var _this = this;
var setDim = function() {
_this.w = _this.canvas.clientWidth;
_this.h = _this.canvas.clientHeight;
_this.canvas.width = _this.w;
_this.canvas.height = _this.h;
_this.dimChanged = true;
_this.draw();
};
setDim();
...
};
变量-this没有在setDim中声明，也没有传递。它是一个“自由变量”。
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• 本文转自...This tutorial conveys the basic ideas behind continuous-variable quantum key distribution (QKD). It is targeted at phys...
本文转自http://infiniquant.com/tutorial-continuous-variable-quantum-communication/。
This tutorial conveys the basic ideas behind continuous-variable quantum key distribution (QKD). It is targeted at physicists or engineers, preferably with a basic understanding of optics. Please share your thoughts if you have any comments or questions!
Terminology of continuous- and discrete-variable QKD
First, let us understand where the term “continuous-variable” comes from. It is the distinction to what is called “discrete-variable” quantum key distribution. Technically this can be understood as the difference between a single photon detector and a homodyne detector:
A single photon detector detects a click when a photon has hit the detector, or no click otherwise. Mathematically, this can be explained as the set of outcomes {click, no click}. The number of outcomes is discrete – therefore the term discrete-variable quantum key distribution, abbreviated DV-QKD.
A homodyne detector on the other hand measures the quadratures of the electric field of the incident light. The measurement outcomes of such a measurement are a projection of phase and amplitude of the electric field of light onto the quadrature axes. This projection yields a continuous value as a measurement result, therefore justifying the name continuous-variable quantum key distribution, or CV-QKD.
The classical phase space
A good tool to depict states of light is the optical phase space. To illustrate this basic concept of quantum mechanics, let us first make an analogy to classical mechanics and talk about the classical phase space instead: A pendulum has two major observable physical quantities: the position x of the pendulum, and its momentum p. If the motion of the pendulum is visualized in a 2D coordinate system with x and p along the two axes, then four interesting points can be identified along the pendulum’s path of evolution in this 2D phase space:

The pendulum is on the right side and stops, corresponding to maximal positive displacement and zero momentumThe pendulum is in the center on its way from right to left, has a position of 0 and has maximum velocity and thus momentumThe pendulum is on the left side and stops, corresponding to maximal negative displacement and zero momentumThe pendulum is in the center on its way from left to right, has a position of 0 and has maximum momentum
Connecting these points by letting the pendulum oscillate, will result in an ellipse as shown in the above figure on the right.
The optical phase space
States of light can also be depicted in such a phase space, only this time it is called the optical phase space. Light can be described as an electromagnetic wave. Its electric field component can be written as a function of sine and cosine. This makes it very similar to the periodic oscillation of the pendulum we just discussed.
In fact, even the same letters as for momentum and position are used to describe the electric field of light in the optical phase space. These variables are called the electric field quadratures X and P. Measuring these quantities, yields their marginal distributions. Combining these marginal distributions into one plot yields the optical phase space in analogy to the classical phase space composed of position and momentum for the example of the pendulum. The figure below shows a typical state of light, emitted by a laser. This state of light is called the coherent state and is parametrized by its amplitude and phase.

Why does the coherent state have a Gaussian distribution instead of a single point in the optical phase space diagram? The reason is Heisenberg’s uncertainty relation, which causes the exact position and momentum of classical mechanics to be a fuzzy probability distribution in quantum mechanics. Heisenberg’s uncertainty relation states that the simultaneous determination of certain physical properties is not possible with arbitrary precision. And these physical properties are called non-commuting observables. The most prominent pair of non-commuting observables is given by position x and momentum p. The optical analogue of this are the electrical field quadratures X and P. The result of this fact is that the expected measurement distribution of those observables is not a single point anymore, but instead a fuzzy version of that. For a coherent state, a two-dimensional Gaussian distribution in optical phase space.
Transmitting information using coherent states of light
It is long known that lasers can be used for communication. A simple definition of a good communication protocol is that it transmits information with minimal errors. As an example, one can turn a flash light on and off to transmit Morse code to someone else. An analogue in telecommunication is what is called “on-off-keying”, basically turning a laser on and off and encoding a 1 as on and a 0 as off to transmit information. Depicting this in the optical phase space, will yield a diagram with two coherent states, where one is centered in the coordinate system, corresponding to the laser being off and the other one with a certain amplitude and phase when the laser is on.

Communication only makes sense, if the information is transmitted over a certain distance. A typical way to cover the distance is transmission through glass fiber. Light propagation through such a fiber comes at the cost of a loss of intensity, exponentially tied to the distance. In logarithmic units, a typical value is 0.2 dB of loss per km of fiber. The effect on the original states prepared will bring the on-state closer to the center, since its amplitude is diminished by loss.
As we originally defined communication, it was our goal to achieve minimal errors when discriminating our measured states to recover the 0s and 1s from our measurement signal. This is achieved, when the loss of amplitude is kept such that the measurement distributions of the on-state and the off-state do not overlap significantly. In other words, discriminating the two states that transmit information, depends on the initial amplitude and the loss after propagation.
Eavesdropping the communication
An adversarial eavesdropper “Eve” is tapping in on the on-off-keying communication protocol we are running. Eve is tapping off the full amount of the transmitted light and is using a homodyne detector to establish measurement distributions constituting the optical phase space. The result of the measurement is two Gaussian distributions that can be well discriminated.

Eve does not want to get caught while performing the eavesdropping. As such, she has her own transmitter system and modulates coherent states with the amplitude and phase she detected. The receiver “Bob” will therefore think that no one was in the line, since the on-off-states arrive unchanged with respect to normal operation.
So what can we do against this situation?
Forcing Eve to leave a signature
Opposed to the communication goal of transmitting information with minimal errors, let us change the goal towards transmitting information with a fixed and non-negligible amount of errors. This can be achieved by lowering the amplitude of the on-state such that the two Gaussian distributions have a good overlap. The result for an eavesdropper will be that Eve cannot discriminate the two states without significant errors, unless she knew in the first place, which state was sent when. Note that this is not an argument about technical noise, but can be proven using quantum mechanics.

If Eve now wants to remain undetected, she has – again – to intercept and resend the states of light using her own detector and transmitter. However, this time, the states she prepared will not correspond to the original ones a certain fraction of the time, since she made errors discriminating them in the first place. This will leave Eve’s signature in the measurement distribution that Bob will later measure.
Detecting Eve’s signature
Since Bob is bound to the same state discrimination laws of quantum physics as Eve is, he also does not know, which of his measurements to assign to which state. However, Bob has help from Alice. Bob can disclose a random fraction of his measurements and Alice can tell him which state she sent for that random fraction. This allows Bob to properly assign his measurement values to the right state. He can then plot the distribution and calculate the variance of the distribution. If this variance is above the expected variance of a quantum noise-limited coherent state, he knows that something went wrong in the transmission and has to assume that Eve tampered with the quantum states along the way. The increased variance is indicated by the dotted red line in the picture below. This step is known as parameter estimation.

Handling the measurement data to generate a secret key
In case Alice and Bob do not detect an eavesdropper, they can continue to execute the protocol and move towards distilling a secret key from the measured data. Of course the publicly disclosed values in the previous step have to be thrown away, since they are no longer secret and can therefore not be used for a secret key.
The undisclosed part of the key may be used to generate a secret key. Bob’s measurement data can be seen as a version of Alice’s modulation but with added noise. He therefore does not have a perfect copy of Alice’s data, which he would need to have the same key as Alice. Speaking in terms of classical communication, a solution to this problem, would be to apply an error correction protocol. This is not possible for QKD, since Bob does not want to disclose any information that could compromise the secrecy of the key we are trying to generate.
The trick is now to only publicly disclose information, that does not tell Eve anything about the key, while still allowing Alice to correct Bob’s noise. We will not go into detail here on how this is done, but state that this can be done without leaking too much information. “Too much” means that the difference between the information leaked and the information gained through the quantum state exchange and the subsequent post-processing is still positive, allowing for a generation of a secret key rate greater than 0.
Finishing the protocol to get the final key
A few finishing touches are necessary to provide both parties with a final key. A confirmation step is necessary to ensure that the error correction worked correctly. After that, privacy amplification is performed to decrease the length of the error corrected key to a final key by reducing it by an amount that corresponds to the information leaked to Eve during the whole protocol. Finally, Alice and Bob authenticate themselves using a classical authentication method in order to ensure that they have established the secret key with the right person.
Here is a summary of the steps required to establish a key by performing a QKD protocol:
Quantum optical state exchange
Send a random sequence of overlapping (non-orthogonal) quantum states from Alice to Bob to establish a raw keyClassical post-processing
Parameter estimation to detect Eve and abort the protocol if an eavesdropper was detectedError correction to get an error corrected keyPrivacy amplification to reduce the information leaked to Eve to a negligible amountAuthenticate the communication
After these steps, a final secret key can be established between Alice and Bob, which is secret to Eve. This final key can now be used for encryption with encryption methods like the one-time pad or if no information-theoretic security level is required, AES.
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• 最后，总结一下国内目前的惯用法（英文取其一，序号对应上文）： field -> 成员变量， instance variable / non-static field -> 实例变量/非静态变量 class variable -> 静态变量 local variable -> 本地变量 ...

Having said that, the remainder of this tutorial uses the following general guidelines when discussing fields and variables. If we are talking about "fields in general" (excluding local variables and parameters), we may simply say "fields". If the discussion applies to "all of the above", we may simply say "variables". If the context calls for a distinction, we will use specific terms (static field, local variables, etc.) as appropriate. You may also occasionally see the term "member" used as well. A type's fields, methods, and nested types are collectively called its members.
先说一下 field 和 variable 之间的区别：
class variables and instance variables are fields while local variables and parameter variables are not. All fields are variables.
成员变量(field)是指类的数据成员，而方法内部的局部变量(local variable)、参数变量(parameter variable)不能称作 field。field 属于 variable，也就是说 variable 的范围更大。
术语解释：
域或字段、实例变量、成员变量(field, instance variable, member variable, non-static field)
field: A data member of a class. Unless specified otherwise, a field is not static.
非 static 修饰的变量。
虽然有如上定义，但是一般在使用时，成员变量(field)包括 instance variable 和 class variable。为了区分，个人认为，用实例变量/非静态变量(instance variable / non-static field)描述上面的定义更佳。
成员变量与特定的对象相关联，只能通过对象(new 出)访问。
声明在类中，但不在方法或构造方法中。
如果有多个对象的实例，则每一个实例都会持有一份成员变量，实例之间不共享成员变量的数据。
作用域比静态变量小，可以在类中或者非静态方法中使用以及通过生成实例对象使用。(访问限制则不可用)
JVM 在初始化类的时候会给成员变量赋初始值。
Example:

类字段、静态字段、静态变量(class variable, static field, staic variable)
使用 static 修饰的字段，一般叫做静态变量。
声明在类中，但不在方法或构造方法中。
多个实例对象共享一份静态变量
JVM在准备类的时候会给静态变量赋初始值。
作用域最大，类中都可以访问，或通过 类名.变量名 的方式调用(访问限制则不可用)。
Example:
局部变量(local variable)
定义在一个区块内(通常会用大括号包裹)，区块外部无法使用的变量。
定义在一个区块内(通常会用大括号包裹)，没有访问修饰符，区块外部无法使用的变量。
没有默认值，所以必须赋初始值
生命周期即为方法的生命周期
Example:
参数(input parameter, parameter (variable), argument)
这个就不多说了，要注意的是 argument 和 parameter 的区别(下文)。
另外，Oracle 官方文档中将参数分为了构造参数、方法参数和异常参数三部分。
Example:

Strictly speaking, a parameter is a variable within the definition of a method. An argument would be the data or actual value which is passed to the method. An example of parameter usage: int numberAdder(first, second) An example of argument usage: numberAdder(4,2)
不可变量、常量(final variable, constant)
即为使用 final 关键词修饰的变量。不可变量属于成员变量。
成员(member)
A field or method of a class. Unless specified otherwise, a member is not static.
指的是类中非静态的成员变量或方法。(用法同field)
属性(property)
Characteristics of an object that users can set, such as the color of a window.
可以被用户设置或获取的对象特征即为属性。
POJO 或 JavaBean 中的成员变量也称作属性(具有set、getter方法)。
最后，总结一下国内目前的惯用法(英文取其一，序号对应上文)：
field -> 成员变量， instance variable / non-static field -> 实例变量/非静态变量
class variable -> 静态变量
local variable -> 本地变量
input parameter -> 参数
final variable -> 常量
member -> 成员(用法同field)
property -> 属性返回搜狐，查看更多

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• 这是一个以前从没仔细想过的问题——最近在阅读《Java Puzzlers》，发现其大量使用了“域”这个词，这个词...先说一下 field 和 variable 之间的区别：class variables and instance variables are fields while loc...

这是一个以前从没仔细想过的问题——最近在阅读《Java Puzzlers》，发现其大量使用了“域”这个词，这个词个人很少见到，在这本书中倒是时常出现，所以在好奇心的驱使下搜索了一下相关的内容，顺便复习了一下基础，最后整理如下。
先说一下 field 和 variable 之间的区别：
class variables and instance variables are fields while local variables and parameter variables are not. All fields are variables.
成员变量(field)是指类的数据成员，而方法内部的局部变量(local variable)、参数变量(parameter variable)不能称作 field。field 属于 variable，也就是说 variable 的范围更大。
术语解释：
域或字段、实例变量、成员变量 (field, instance variable, member variable, non-static field)
field: A data member of a class. Unless specified otherwise, a field is not static.
非 static 修饰的变量。
虽然有如上定义，但是一般在使用时，成员变量(field)包括 instance variable 和 class variable。为了区分，个人认为，用实例变量/非静态变量(instance variable / non-static field)描述上面的定义更佳。
成员变量与特定的对象相关联，只能通过对象(new)访问。
声明在类中，但不在方法或构造方法中。
如果有多个对象的实例，则每一个实例都会持有一份成员变量，实例之间不共享成员变量的数据。
作用域比静态变量小，可以在类中或者非静态方法中使用以及通过生成实例对象使用。(访问限制则不可用)
JVM在初始化类的时候会给成员变量赋初始值。
Example:
public class FieldTest {
private int Xvalue; // Xvalue is a field
public void showX() {
System.out.println("X is: " + xValue);
}
}
2. 类字段、静态字段、静态变量(class variable, static field, staic variable)
使用 static 修饰的字段，一般叫做静态变量。
声明在类中，但不在方法或构造方法中。
多个实例对象共享一份静态变量
JVM在准备类的时候会给静态变量赋初始值。
作用域最大，类中都可以访问，或通过 类名.变量名 的方式调用(访问限制则不可用)。
Example:
System.out.println(Integer.MAX_VALUE);
3. 局部变量(local variable)
定义在一个区块内(通常会用大括号包裹)，没有访问修饰符，区块外部无法使用的变量。
没有默认值，所以必须赋初始值
生命周期即为方法的生命周期
Example:
if(x > 10) {
String local = "Local value";
}
4. 参数(input parameter, parameter (variable), argument)
参数，这个就不多说了，要注意的是 argument 和 parameter 的区别(下文)。
另外，Oracle 官方将参数分为了构造参数、方法参数和异常参数三部分。
Example:
public class Point {
private int xValue;
public Point(int x) {
xValue = x;
}
public void setX(int x) {
xValue = x;
}
}
Strictly speaking, a parameter is a variable within the definition of a method. An argument would be the data or actual value which is passed to the method. An example of parameter usage: int numberAdder(first, second) An example of argument usage: numberAdder(4,2)
5. 不可变量、常量(final variable, constant)
使用 final 关键词修饰的变量。不可变量属于成员变量。
6. 成员(member)
A field or method of a class. Unless specified otherwise, a member is not static.
指的是类中非静态的成员变量或方法。(用法同field)
7. 属性(property)
Characteristics of an object that users can set, such as the color of a window.
可被用户设置或获取的对象特征即为属性。
POJO 或 JavaBean 中的成员变量也称作属性(具有set、getter方法)。
最后，总结一下国内目前的惯用法(英文取其一，序号对应上文)：
field -> 成员变量， instance variable / non-static field -> 实例变量/非静态变量
class variable -> 静态变量
local variable -> 本地变量
input parameter -> 参数
final variable -> 常量
member -> 成员(用法同field)
property -> 属性
参考资料：
fields-vs-variables-in-java
http://docs.oracle.com/javase/tutorial/information/glossary.html
https://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.12

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• seaborn绘图时输入x,y值非实数，值可能为字符串，需要进行处理 解决： 绘图时记得去掉字符串类型比如名称的一列 将数字字符串转化为float类型 对于第二点： foo = pd.DataFrame(columns =['Names','Values']) ...
• 随时随地阅读更多技术实战干货，获取项目源码、学习资料，请关注源代码社区公众号(ydmsq666)、...from：https://stackoverflow.com/questions/38853027/webstorm-unresolved-variable-or-type-sails-module-export ...

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