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Mastering Development

Error fetch from react to express without CRA(create-react-app)

import React,{Component} from ‘react’; import ‘../styles/App.css’; class App extends Component{ constructor() { super(); this.state = { products: [] }; } componentDidMount() { fetch(‘http://localhost:4000/products’, { method: ‘GET’, mode: “no-cors”, headers: {“Content-Type”: “application/json”} }).then(res => {console.log(res);res.json()}) .then(products => this.setState({products})); } render() { return ( <div> <h1>Hello, react.js!!!</h1> <ul> {this.state.products.map(product => <li>{product.product_name}</li>)} </ul> </div> ); } } export […]

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Ask Health Medical

What are the epidemiological basis (bases) of ceasing containment measures once an outbreak becomes epidemic/pandemic?

A previous question on SE has asked about whether testing, a part of the strategy of containment, can help reduce transmission enough such that it reduces the need for aspects of mitigation (Could increased testing for COVID-19 slow its spread enough to allow the relaxation of social distancing measures?) Here, I would like to ask […]

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Database Development

Build Indexes on Production Aurora MySQL Cluster

does anyone know of a strategy equivalent to https://docs.mongodb.com/manual/tutorial/build-indexes-on-replica-sets/ ?, that is, any procedure where the creation of indexes on the “read-write” instance and the read instances have the least possible impact (tables with about 50 million records). Thanks.

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Ask Engineering

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is quite safe, and it should not be kept above 40°. Why? I think the larger the protecting angle becomes, the longer will the \$L\$ be, that is, the range that shield […]

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Ask Engineering

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is quite safe, and it should not be kept above 40°. Why? I think the larger the protecting angle becomes, the longer will the \$L\$ be, that is, the range that shield […]

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Ask Engineering

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is quite safe, and it should not be kept above 40°. Why? I think the larger the protecting angle becomes, the longer will the \$L\$ be, that is, the range that shield […]

Categories
Ask Engineering

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is quite safe, and it should not be kept above 40°. Why? I think the larger the protecting angle becomes, the longer will the \$L\$ be, that is, the range that shield […]

Categories
Ask Engineering

Why should the protective angle on high voltage lines be kept as small as possible?

This website, https://circuitglobe.com/overhead-ground-wire-or-earth-wire.html, said for effective shielding, we should keep the protecting angle as small as possible, the angle between 20° and 30° is quite safe, and it should not be kept above 40°. Why? I think the larger the protecting angle becomes, the longer will the \$L\$ be, that is, the range that shield […]

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User Help

Adjust PDF colors on a dark document (for print)

Summary: Have to print several PDF’s coming with dark, dull colors, the printed result is very dark and often bleeding ink. I can compensate easily using the printer’s color adjustment on Canon Printers (brightness, intensity, contrast, etc), that’s awesome but I can’t do the same on HP printers as there is no color adjustment. I’m […]

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Ask Chemistry

Specific conductance of KCl

The question: A conductivity cell containing distilled water has a resistance of $454 k \Omega$, while the same cell containing KCl solution prepared in the same sample of water shows resistance of $2150 \Omega$. If the plates of the conductivity cell have area $0.5 cm^2$ each and are separated by $1cm$, find the cell constant […]