[Note] Imperceptibility in Screen-Camera Communication


This note is about comparison among these paper in imperceptibility. I.e., we focus on the modulation part of the system design in each paper, neither the decoding or encoding part.

  • ImplicitCode Reading between Lines: High-rate, Non-intrusive Visual Codes within Regular Videos via ImplicitCode
  • ChromaCode ChromaCode: A Fully Imperceptible Screen-Camera Communication System
  • InFrame++ InFrame++: Achieve Simultaneous Screen-Human Viewing and Hidden Screen-Camera Communication
  • TextureCode High–Rate Flicker–Free Screen–Camera Communication with Spatially Adaptive Embedding
  • HiLight Real-Time Screen-Camera Communication Behind Any Scene
  • Kaleido Kaleido: You Can Watch It But Cannot Record It

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软件验证 – UPPAAL&Pacemaker- 学习笔记

[ 官网 ] http://www.uppaal.org/

[ 参考文档 ] http://www.it.uu.se/research/group/darts/uppaal/small_tutorial.pdf


Basic Concepts

To begin with, 理解一个简单的概念:时间自动机(Timed Automate)一个基于时钟(clocks)的有限状态机(Finite State Machine)。每个状态叫做 location

  • 状态之间的转换叫做 transitions
  • 去激活(fire)一个转换,需要有一个转换条件(guard) 和状态间的同步( synchronization
  • Guard: 满足时一个转换(中文版翻译为“使能迁移”)才可以执行
  • Synchronization: 是由一些广播信道broadcast chan构成,可以用于:
  • 接收到广播信号时进行转移
  • 转移时产生广播信号

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Computer Networks – Physical Links / Encoding

Demo: On-Off Modulation (Matlab)


  • Shannon-Hartley Theorem gives the theoretical throughput upper bound:
    • $C=Blog_2(1+\frac{S}{N})$
    • C: Channel Capacity, 带宽理论上限 (bps)
    • B: Bandwidth, 信道带宽 (Hz), limited by ADC, DAC rate
    • S: Signal Power, limited by safety concern
    • N: Noise Power
    • S/N or SNR: 信噪比(dB), SNR = 10 × log10(S/N)

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Advanced SQL Part 2

Views: Named Queries

Subqueries in FROM

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Advanced SQL

Run the query with an empty S:

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Database Intro & Basic SQL


  • A database is a large, organized collection of data.
  • A Database Management System (DBMS) is software that stores, manages and facilitates access to databases.
    • 传统DBMS即关系型数据库管理系统 Relational Database Management Systems (RDBMS)
    • SQL 数据描述和操作语言
    • ACID 数据库事务(Transaction)正确执行的四个基本要素的缩写:原子性(Atomicity)、一致性(Consistency)、隔离性(Isolation)、持久性(Durability)
  • Various levels of a database system


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python sklearn 无监督学习之降维 算法与应用


  • PCA(Principal Component Analysis) 主成分分析, 用于高维数据集的探索与可视化,还可以用作数据压缩和预处理等。
  • PCA可把具有相关性的高维变量合成为线性无关的低维变量,成为主成分。主成分能够尽可能保留原始数据的信息。
  • Terms:
    • 方差,各个样本和样本均值的差的平方和的均值,用来度量一组数据的分散程度。$s^2 = \frac{\sum_{i=1}^n (x_i – x)^2}{n-1}$
    • 协方差,用于度量两个变量之间的线性相关性程度。$Cov(X,Y)=\frac{\sum_{i=1}^n (X_i-\overline{X})(Y_i – \overline{Y})}{n-1}$
    • 协方差矩阵,变量的协方差值构成的矩阵。
    • 特征向量,描述数据集结构的非零向量 $A\overrightarrow{v}=\lambda \overrightarrow{v}$

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python-sklearn 机器学习导学&聚类入门实例

课程主页: https://www.icourse163.org/course/BIT-1001872001



  • 监督学习 Supervised Learning
    • 在给定人类标注的训练数据中学习函数
  • 无监督学习 Unsepervised Learning
    • 无人类标注的训练集
  • 增强学习/强化学习 Reinforcement Learning
    • 通过观察环境学习执行动作
  • 半监督学习 Semi-supervised Learning
  • 深度学习 Deep Learning

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