ut | 易学教程

TTL

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数字集成电路概念：在一块半导体基片上制作一个完整的逻辑电路需要的全部原件和连线外接：使用时接电源，输入和输出特点：具有体积小，可靠性高，速度快，而且价格便宜的特点结构分析（1）任一输入为低电平（0V）时 uo=5-uR2-ube3-ube4=3.4V 高电平！逻辑关系：任0则1。 (2) 输入全为高电平（3.4V）时输入、输出的逻辑关系式：F=（ABC）’ 逻辑关系：全1则0 输出高电平UOH，输出低电平UOL UOH>=2.4V, UOL<=0.4V 便认为合格。典型值UOH=3.4V UOL=0.3V 。输入阈值电压UT ui<UT时，认为ui是低电平 ui>UT时，认为ui是高电平 UT=1.4V 输入，输出负载特性前级输出为低电平时级间电流：流入前级，记为IOL ，约 1.4mA 。称为灌电流。前级输出为高电平时级间电流：流出前级，记为IOH（拉电流）拉电流能力：维持UOH时，所允许的最大拉电流值。输入端通过电阻R接地 R 较小时：ui<UT ， T5不导通，输出高电平。 R增大时：R变大，–>ui变大–>ui=UT时，输出低电平。计算临界值：当R>=1.45千欧时，可以认为输入为“1”；当R<1.45千欧时，可以认为输入为“0”。来源： CSDN 作者： FANCYPANDAN 链接： https://blog.csdn.net

Every derived table must have its own alias error

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可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I get that error when running the following query: SELECT MAX( DateTime ) FROM ( ( SELECT DateTime FROM Class_Searches ) UNION ALL ( SELECT DateTime FROM Book_Searches ) ) WHERE User_Email = 'bla@blah.com' AND DateTime > NOW( ) - INTERVAL 30 DAY I know I need to add Aliases but I'm not sure where 回答1: You need an alias for the subquery, and you need to apply the conditions either to both queries that you union: SELECT MAX(DateTime) FROM ( SELECT DateTime FROM Class_Searches WHERE User_Email = 'bla@blah.com' AND DateTime > NOW( ) - INTERVAL

AWS store MQTT message to DynamoDB

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可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I built a python script that sends MQTT message periodically. This is the JSON string sent to the backend: {"Id": "1234", "Ut": 1488395951, "Temp": 22.86, "Rh": 48.24} On backend side, I want to store the MQTT message into DynamoDB table. I followed an Amazon tutorial and the data contained into the MQTT messages are stored into the table. My problem regards the table columns. The table has only 3 colums: Id: Partition Key Ut: Sort Key Payload: contains the mqtt message. It is possible to have columns for each key contained into MQTT message

html+css :时间轴布局

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<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>time line</title> <style type="text/css"> *{ margin: 0; padding: 0; box-sizing: border-box; } body{ background: #fff; font-family: "Helvetica Neue", sans-serif; margin: 50px; } #timeline{ margin-left: 30%; border-left: 10px solid #bce1fa; } #timeline li{ position: relative; list-style: none; display: block; width: 100%; clear: both; } #timeline li::before{ content: ''; display: block; width: 30px; height: 30px; border: 5px solid #bce1fa; border-radius: 50%; background: #3498DB; position: absolute; left: -25px; top: 0; /*box-sizing:

UT规则

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1：类名为ltc开头 2：当有测试方法时，类名才用 ltc_ut... 来源： https://www.cnblogs.com/liyafei/p/11458778.html