# 声能

$W=W_{\mathrm {potential} }+W_{\mathrm {kinetic} }=\int _{V}{\frac {p^{2}}{2\rho _{0}c^{2}}}dV+\int _{V}{\frac {\rho _{0}v^{2}}{2}}dV$

• $$V$$ – 流体的体积
• $$p$$ – 声压
• $$v$$ – 流体质点速度
• $$\rho_0$$ – 流体静态密度
• $$c$$ – 声速

## 声能密度

$\epsilon ={\frac {p^{2}}{2\rho _{0}c^{2}}}+{\frac {\rho _{0}v^{2}}{2}}$

## 平均声能量密度

${\bar {\epsilon }}={\frac {p_{e}^{2}}{\rho _{0}c^{2}}}$

## 参考

1.  L. E. Kinsler, A. R. Frey, A. B. Coppens, and J. V. Sanders, 1999. Fundamentals of Acoustics, fourth edition (Wiley).第5.8节。
2. ^ 杜功焕、朱哲明、龚秀芳，声学基础，第二版，第4.7节。

## 教程：如何DIY一台穿越机

Build a PRO FPV Racing Drone for ONLY $99 Full guide – 2018 UAVFUTURES$99 Build

Step by step guide showing you how to build an AWESOME FPV racing drone for around $99. This build is SIMPLE, CHEAP and most of all results in a crazy fast FPV racing quadcopter with awesome performance at an even better price. IMPORTANT. enjoy the videos and want to support UAVFUTURES . head to https://www.patreon.com/uavfutures every bit helps us make more content for you. GIVEAWAY details at bottom of description after component links. PARTS – things usually sell out after I make videos on them so I linked a ton of extra components below that people can use if something sells out. Pro Build Frame – http://bit.ly/2w97dVd SC/FC combo – http://bit.ly/2Na6RUT Motors – 2600kv – http://bit.ly/samguk2207 VTX – http://bit.ly/2BIq5zT also think about upgrading to the nice matek vtx to go full PRO – http://bit.ly/2ADgU1n Camera – http://bit.ly/2PB11Oe Props – http://bit.ly/2LpkHRI BASE Build Frame – http://bit.ly/2w97dVd ESCs – http://bit.ly/2od6o9T Flight controller- http://bit.ly/2BDY5x2 Motors DYS$10 – http://bit.ly/samguk2206
Motors cheap version http://bit.ly/2PAEnW4 but get the samguks VTX – http://bit.ly/2Lk6h5b
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IMPORTANT I know things sell out, A LOT and people might want other parts so there are some other links to new parts below. All of which will be great to build with.

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individual escs RS lite 35 amp – http://bit.ly/2BJvgzy Hacrc 35 amp – http://bit.ly/2OZgmH2 RS 20amp – http://bit.ly/2w7pkLu RS m series 35 amp – http://bit.ly/2LlHs93

combo ESCs with FC built in tattooF4 – http://bit.ly/2AGFvR7 Starf4- http://bit.ly/2Na6RUT DYS stack – http://bit.ly/2nGU18y

F4 Flight controllers DYS F4 – http://bit.ly/2OVTmZm HakRc – http://bit.ly/2w928MH Matek – http://bit.ly/2PAfrhc DalRc- http://bit.ly/2BJlMnY Speedybee – http://bit.ly/2w6pjHy

Other FPV Cameras Caddex micro – http://bit.ly/2iCTIGg Micro Arrow v2 – http://bit.ly/2o7SHsC eagle 2 – http://bit.ly/2PzqG9N Foxeer Falkor – http://bit.ly/2MwyYS3

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Props Avan Flows – http://bit.ly/2NdBo4k king kong – http://bit.ly/2w7svmo Cyclone – http://bit.ly/2BIeAsd 4blade RS – http://bit.ly/2o6z0S7

Antennas – pagoda – http://bit.ly/2My1DpE aomway omni – http://bit.ly/2NdifPT Aomway stick – http://bit.ly/2PxE26x UXII – http://bit.ly/2MS9yNU

FPV GOGGLES Aomway Commanders – http://bit.ly/CommandersAomway Viper goggles – http://bit.ly/FXTviper

DRONE RADIOS QX7 – http://bit.ly/2AXlich X-lite – http://bit.ly/Frskyxlite i6 – http://bit.ly/2w7vDi8

## 电脑技术：软路由搭建攻略——从小白到大白[转载]

• 软路由的定义
• 软路由的优缺点
• 什么人会使用软路由
• 软路由的挑选
• 软路由的组建
• 软路由的设置
• 硬路由桥接软路由发射WiFi

这篇文章不会涉及的知识点：

• 软路由虚拟机多系统（对于新手来说太麻烦而且我个人觉得暂时没有必要）
• 黑群晖之类的NAS搭建（三大妈已经有其他作者写过啦）

总的来说就是作者会尽可能的从新手的角度出发，尽量让各位小白都能看懂然后早日打造出自己的软路由

什么是软路由

在了解什么是软路由之前，我们先定义一下【硬路由】这个关键词，硬路由就是我们现在随便在京东淘宝搜索【路由器】搜出来的，从一开始就是按照路由器规范设计出来的硬件设备。而相对的【软路由】则是指，利用现有的硬件（可能是电脑或者树莓派之类的）配合软件来实现路由器的功能。

软路由对比硬路由优势在哪里？

## 硬件：摄像头的MIPI接口、DVP接口和CSI接口

DVP总线PCLK极限大约在96M左右，而且走线长度不能过长，所有DVP最大速率最好控制在72M以下，故PCB layout会较好画

MIPI总线速率随便就几百M，而且是lvds接口耦合，走线必须差分等长，并且注意保护，故对PCB走线以及阻抗控制要求高一点。

DVP是并口，需要PCLK、VSYNC、HSYNC、D[0：11]——可以是8/10/12bit数据，看ISP或baseband是否支持；

MIPI是LVDS，低压差分串口。只需要要CLKP/N、DATAP/N——最大支持4-lane，一般2-lane可以搞定。

MIPI接口和DVP接口的区别及优点 – 硬件综合 – 52RD研发论坛– http://bbs.52rd.com/Thread-214024-1-1.html