quantumet's New Writeupshttp://everything2.com/?node=New%20Writeups%20Atom%20Feed&foruser=quantumet2002-10-23T06:28:00ZWilliam Schickard (person)http://m.everything2.com/user/quantumet/writeups/William+Schickardquantumethttp://m.everything2.com/user/quantumet2002-10-23T06:28:00Z2002-10-23T06:28:00Z<b>Born:</b> 22 April 1592 in Herrenberg (near Tübingen), Württemberg (now Germany)<br>
<b>Died:</b> 24 Oct 1635 in Tübingen, Württemberg (now Germany)<br>
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William Schickard was the first man to create a mechanical calculating <a href="/title/device">device</a>, which he called a <i>calculation clock</i>. This <a href="/title/machine">machine</a>, constructed around 1623 C.E., aided in the <a href="/title/multiplication">multiplication</a> of large numbers. He was one of the first in the line of <a href="/title/inventors">inventors</a> leading to the eventual construction of modern-day <a href="/title/computer">computers</a>.
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He studied in the University of Tübingen, receiving his Master of Art degree in 1611. In 1613 he became a <a href="/title/Lutheran">Lutheran</a> minister for towns in the nearby region, working as a minister until 1619, when he was appointed a Professor of <a href="/title/Hebrew">Hebrew</a> at the University.
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Twelve years later, in 1631, he switched tracks and was appointed a Professor of <a href="/title/Astronomy">Astronomy</a>, a post he kept for the rest of his life.
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He studied various things, including <a href="/title/mathematics">mathematics</a>, <a href="/title/astronomy">astronomy</a>, <a href="/title/surveying">surveying</a>, and<!-- close unclosed tag --></p>…computer (thing)http://m.everything2.com/user/quantumet/writeups/computerquantumethttp://m.everything2.com/user/quantumet2002-09-03T01:27:20Z2002-09-03T01:27:20Z<p align="center"><big><big><big><strong>Computers</strong></big><br>
Or<br>
<em>From <a href="/title/steam+power">steam power</a> to <a href="/title/quantum+tunneling">quantum tunneling</a> in 150 years</em></big></big><br>
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<p>
A history and description of computers is immediately faced with a task of determining what truly constitutes a computer. A basic definition from typical web sources spits out:
<blockquote>
<b>com.put.er</b><i> Pronunciation Key (km-pytr)
n.</i><br>
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1. A <a href="/title/device">device</a> that computes, especially a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information.<br>
2. One who computes.
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This node concerns itself with definition 1, a broad category of machinery: mechanical, electrical, whatever. While most modern computers are purely electrical devices, the history of computers is steeped in mechanical contraptions of ever-increasing complexity. A full history would be excessive here, and is well<!-- close unclosed tag --></p>…chain story (thing)http://m.everything2.com/user/quantumet/writeups/chain+storyquantumethttp://m.everything2.com/user/quantumet2002-06-02T00:53:21Z2002-06-02T00:53:21Z<p><i>Susan gazed out the window of the <a href="/title/train">train</a>, the grimy panes distorting her view of the <a href="/title/nature">nature</a> flowing past outside. Sighing, she longed for beauty in her life, beauty that she had never known...</i></p>
<p><b>Her tiresome <a href="/title/introspection">introspection</a> was interrupted as the scoutship of the 3rd Imperial Galaxon Fleet landed on the tracks ahead of the train, causing the engineer to pull on the emergency brakes. Havoc ensued inside, as passangers and packages were thrown about in havoc. Fortunately, Lt. Dan "Dangerous" Lloyd, arriving through the <a href="/title/wormhole">wormhole</a> from the 31st century, was there...</b></p>
<p>Dan gazed upon the scene, and sighed, realizing the <a href="/title/futility">futility</a> of armed <a href="/title/conflict">conflict</a>, seeing <a href="/title/history">history</a> repeat itself yet again. And as he looked into the tired eyes of the Galaxons streaming from the scoutship, send on yet another endless task of <a href="/title/conquest">conquest</a>, he saw that they too were weary of the conflict...</p>
<p><b><i>Then, Ogar, the Giant of the North, <a href="/title/stepped">stepped</a> on all of them. Ogar then<!-- close unclosed tag --></i><!-- close unclosed tag --></b><!-- close unclosed tag --></p>…High-pass filter (thing)http://m.everything2.com/user/quantumet/writeups/High-pass+filterquantumethttp://m.everything2.com/user/quantumet2002-05-25T05:53:53Z2002-05-25T05:53:53ZThe <a href="/title/simplest">simplest</a> <a href="/title/high-pass">high-pass</a> <a href="/title/filter">filter</a> one can create using <a href="/title/discrete">discrete</a> <a href="/title/circuit">circuit</a> components is the first-order RC high-pass filter. It uses exactly one <a href="/title/resistor">resistor</a>, and one <a href="/title/capacitor">capacitor</a>.<br>
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<pre>
| |
Vin --| |----+--- Vout
| | |
C \
R /
\
|
Gnd
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A high-pass filter,roughly, is characterized by two things: its <a href="/title/corner+frequency">corner frequency</a>, and its <a href="/title/order">order</a>. The corner frequency of the above high-pass filter is fc = 1/(2πRC)</p>
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The corner frequency is where an input signal <a href="/title/power">power</a> will be cut down by a factor of 2. Typically, power is reported in <a href="/title/decibels">decibels</a> (dB); the corner frequency is the frequency at which the signal power is attenuated by 3 dB. The region above the corner frequency is called the <a href="/title/passband">passband</a>, the region below is called the <a href="/title/stopband">stopband</a>.</p>
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The order of the filter determines how steeply the <a href="/title/filter">filter</a> cuts off high frequencies; a first-order filter reduces signal power by 20 dB per<!-- close unclosed tag --></p>…Audio scrambling (idea)http://m.everything2.com/user/quantumet/writeups/Audio+scramblingquantumethttp://m.everything2.com/user/quantumet2002-05-08T08:38:39Z2002-05-08T08:38:39Z<small>Most of the information here gathered for a <a href="/title/analog">analog</a> <a href="/title/project">project</a> <a href="/title/class">class</a></small><br>
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Scrambling audio usually refers to somehow <a href="/title/garbling">garbling</a> a <a href="/title/sound">sound</a> signal being transmitted over some <a href="/title/insecure">insecure</a> medium (like a <a href="/title/phone+line">phone line</a>, a <a href="/title/walkie-talkie">walkie-talkie</a>, <a href="/title/cassette+tape">cassette tape</a>, etc) and ungarbling the sound at the receiving end, so that the intended <a href="/title/recepient">recepient</a> can understand the message. Typically, audio scrambling refers to mostly <a href="/title/analog">analog</a> <a href="/title/electronic">electronic</a> techniques; purely <a href="/title/digital">digital</a> setups like <a href="/title/encryption">encryption</a> are not considered scrambling.
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Scrambling is intended as a low-cost solution for defeating a casual or a limited-resource <a href="/title/eavesdropper">eavesdropper</a>. It won't stop someone truly determined from eventually figuring out what was said, but they can be slowed down for a while. A truly secure system would have to use aforementioned <a href="/title/encryption">encryption</a> techniques, which are expensive, requiring lots of computing power and circuitry to implement.
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There are various scrambling methods that are commonly used, and<!-- close unclosed tag --></p>…Laplace Transform (idea)http://m.everything2.com/user/quantumet/writeups/Laplace+Transformquantumethttp://m.everything2.com/user/quantumet2002-04-22T09:09:14Z2002-04-22T09:09:14ZAs an additional note, there are a few different <a href="/title/definitions">definitions</a> of the <a href="/title/Laplace">Laplace</a> <a href="/title/transform">transform</a>. The one that seems to appear in mathematics classes is the one listed above; the range of integration is from 0 to <a href="/title/infinity">infinity</a>.<br>
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However, some sources, such as my book for the Electrical Engineering Signals and Systems course I took, define the Laplace transform to range from <a href="/title/negative">negative</a> <a href="/title/infinity">infinity</a> to infinity. This is referred to as the <a href="/title/bilateral">bilateral</a> transform, as opposed to the unilateral transform described above. The two have identical properties; which to use depends on one's application. <a href="/title/Initial+value+problems">Initial value problems</a> require the unilateral transform; it seems the bilateral transform is more useful for <a href="/title/signals+and+systems">signals and systems</a>.<br>
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The <a href="/title/Fourier+transform">Fourier transform</a> and the Laplace transform are closely related; in a sense, the Fourier transform can be seen as a <a href="/title/special+case">special case</a> of the <a href="/title/bilateral">bilateral</a> Laplace transform, where the <a href="/title/complex+variable">complex variable</a> s in the integral is restricted to be on the imaginary axis. Because…