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	<title>Some stuff &#187; paper</title>
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	<description>here.</description>
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		<title>the disappearing retail</title>
		<link>https://blog.yhuang.org/?p=616</link>
		<comments>https://blog.yhuang.org/?p=616#comments</comments>
		<pubDate>Mon, 25 Jul 2011 05:24:07 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[bricks and mortar]]></category>
		<category><![CDATA[class]]></category>
		<category><![CDATA[latter class]]></category>
		<category><![CDATA[object]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[physical embodiment]]></category>
		<category><![CDATA[physical retail store]]></category>
		<category><![CDATA[property]]></category>
		<category><![CDATA[schadenfreude]]></category>
		<category><![CDATA[store]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=616</guid>
		<description><![CDATA[Borders the &#8220;bricks-and-mortar&#8221; bookstore went bankrupt last week. After more than a decade since the first online shopping sites opened up, the physical retail store is finally taking mortal blows. Well, not all physical retail stores &#8212; some survived by successfully running their own online sites. But let&#8217;s not overly distinguish between such apparent survival [...]]]></description>
			<content:encoded><![CDATA[<p>Borders the &#8220;bricks-and-mortar&#8221; bookstore <a href="http://www.slate.com/id/2299642/">went bankrupt</a> last week. After more than a decade since the first online shopping sites opened up, the physical retail store is finally taking mortal blows. Well, not all physical retail stores &#8212; some survived by successfully running their own online sites. But let&#8217;s not overly distinguish between such apparent survival and those that fail, since this mere issue of ownership doesn&#8217;t change the facts.</p>
<p>On the one hand, this development is a milestone triumph of digital efficiency and convenience, something I greatly appreciate. On the other hand, I &#8212; and it seems many others &#8212; can&#8217;t seem to muster the schadenfreude over the demise of a <em>bookstore</em>. Doesn&#8217;t seem right, but why?<br />
<span id="more-616"></span><br />
A digression. What exactly do retail stores sell? They sell objects of value. Some objects have value only in their physical form &#8212; food, clothes, utensils, machines, wood, whatever. Then there are objects that derive value primarily from the intellectual property embodied, the physical form being but a representation &#8212; books, newspapers, magazines, music, movies, even toys. Retail stores that sell the first class of objects haven&#8217;t gone out of business even now. There is some convenience to shopping online but there is still need to &#8220;check out&#8221; the object in question and take delivery of it, so the retail store isn&#8217;t superseded; some stores just made the retail locations a bona fide delivery point; over all the transition was incremental. Initially, retail stores that sell physical embodiments of intellectual property followed the same path. But then, purely digital devices happened &#8212; mp3 players, phones, e-readers, tablets &#8212; and the physical embodiment got stripped from the latter class of objects like chaff. I think it was this step that made the huge difference. Now what is sold is a digital object &#8212; in other words, the object sold got <em>swapped out</em>; the physical store became superfluous if you were only after the intellectual property, because it sold <em>something else</em>, and the differences in cost of delivery made physical stores untenable.</p>
<p>Back to why bookstores closing doesn&#8217;t feel great. Could it be nostalgia for the old fashioned paper form-factor? I&#8217;ve always felt that e-readers just aren&#8217;t that great yet, not a replacement of a book from many perspectives, except on the question of weight and volume. But this is minor. Then what about the next question, does a physical bookstore mean anything more than a warehouse of paper? The answer is affirmative. A bookstore, like a library, takes on the role of a commons.</p>
<p>If not enough people buy paper books, bookstores will close down, and that&#8217;s a shared loss. Whereas before, people pooled for a common good by paying more for paper books, now, for each person&#8217;s convenience, there will be something less for everyone. I don&#8217;t think this is the desired outcome. A lot of the conversion to electronic and digital forms is really a conversion to a more personal living style. Nowadays there is still the supermarket and coffee shops where you must get your objects in physical form, but imagine a day when none of these are necessary, when all objects have been digitized, Second Life style. Then there would be no physical stores for anything, and no need to physically be anywhere or interact. This social withdrawal is a profound yet perverse aspect of digitization, long predicted to happen, but the first steps of which we are seeing now. Is Google+ or Facebook going to be adequate replacement to glue people together? (If so, they had better get their <a href="?p=592">&#8220;entire social experience&#8221;</a> model right.)</p>
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		<item>
		<title>pessimism, or risk aversion?</title>
		<link>https://blog.yhuang.org/?p=517</link>
		<comments>https://blog.yhuang.org/?p=517#comments</comments>
		<pubDate>Sat, 18 Jun 2011 11:58:25 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[Bateson]]></category>
		<category><![CDATA[external rewards]]></category>
		<category><![CDATA[fashion]]></category>
		<category><![CDATA[negative fashion]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[referenced paper]]></category>
		<category><![CDATA[risk adjustments]]></category>
		<category><![CDATA[risk aversion]]></category>
		<category><![CDATA[stimulus]]></category>
		<category><![CDATA[type]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=517</guid>
		<description><![CDATA[I found the title of this article, &#8220;Honeybees might have emotions,&#8221; hard to believe. But then what is &#8220;emotion&#8221;? Bateson and Wright tested their bees with a type of experiment designed to show whether animals are, like humans, capable of experiencing cognitive states in which ambiguous information is interpreted in negative fashion. and from the [...]]]></description>
			<content:encoded><![CDATA[<p>I found the title of <a href="http://www.wired.com/wiredscience/2011/06/honeybee-pessimism/">this article</a>, &#8220;Honeybees might have emotions,&#8221; hard to believe. But then what is &#8220;emotion&#8221;?</p>
<blockquote><p>Bateson and Wright tested their bees with a type of experiment designed to show whether animals are, like humans, capable of experiencing cognitive states in which ambiguous information is interpreted in negative fashion.</p></blockquote>
<p>and from the <a href="http://www.cell.com/current-biology/abstract/S0960-9822%2811%2900544-6">referenced paper</a> itself:</p>
<blockquote><p>We show for the first time that agitated bees are more likely to classify ambiguous stimuli as predicting punishment. Shaken bees also have lower levels of hemolymph dopamine, octopamine, and serotonin.</p></blockquote>
<p>If an &#8220;ambiguous&#8221; stimulus is one that is unassociated with anything but is interpreted as a mixture of two known stimuli (or if it is explicitly some mixture-state stimulus&#8230; is it in this case?), then isn&#8217;t all this simply risk-aversion? If so, then basically bees have concave utility like probably all evolved organisms naturally should &#8212; to stay alive. Indeed, the fact that the actual chemical signaling mechanism for risk-aversion is associated with &#8220;pessimism&#8221; or &#8220;depression&#8221; in higher organisms is the more intriguing (but on second thought, obvious) result, suggesting that emotions are just internal (psychological) reward adjustments that drive external (behavioral) risk adjustments. Emotions bend the utility &#8220;function&#8221; into shape by applying compensatory rewards to the actual external rewards: a risk and reward add-on circuit.</p>
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		<item>
		<title>conformal cyclical cosmology</title>
		<link>https://blog.yhuang.org/?p=292</link>
		<comments>https://blog.yhuang.org/?p=292#comments</comments>
		<pubDate>Wed, 24 Nov 2010 06:05:42 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[cosmology]]></category>
		<category><![CDATA[cycle]]></category>
		<category><![CDATA[expansions]]></category>
		<category><![CDATA[massive particles]]></category>
		<category><![CDATA[mathematical sense]]></category>
		<category><![CDATA[news]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[penrose]]></category>
		<category><![CDATA[today]]></category>
		<category><![CDATA[understanding]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=292</guid>
		<description><![CDATA[Something in the news here today, referring also to Penrose&#8217;s paper from several years ago. In my limited understanding, Penrose suggests that the universe goes through these cycles of what can be interpreted as infinite expansions &#8220;followed by&#8221; big bangs, where the cycle renewal &#8220;happens&#8221; in a mathematical sense: in the way spacetime is metrized. [...]]]></description>
			<content:encoded><![CDATA[<p>Something in the news <a href="http://physicsworld.com/cws/article/news/44388">here</a> today, referring also to Penrose&#8217;s <a href="http://accelconf.web.cern.ch/AccelConf/e06/PAPERS/THESPA01.PDF">paper</a> from several years ago.</p>
<p>In my limited understanding, Penrose suggests that the universe goes through these cycles of what can be interpreted as infinite expansions &#8220;followed by&#8221; big bangs, where the cycle renewal &#8220;happens&#8221; in a mathematical sense: in the way spacetime is metrized. He says that in the infinite future, when all massive particles will have evaporated, we will be returned to a situation without a notion of space or time (since all things are lightlike, I suppose). From this, the very large scale of the given final universe can be reinterpreted as the very small beginning of the next universe. It&#8217;s an interesting thought.</p>
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		<title>Cell synthesized</title>
		<link>https://blog.yhuang.org/?p=269</link>
		<comments>https://blog.yhuang.org/?p=269#comments</comments>
		<pubDate>Thu, 20 May 2010 23:54:42 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[Cell]]></category>
		<category><![CDATA[cell cytoplasm]]></category>
		<category><![CDATA[computer]]></category>
		<category><![CDATA[computer dna]]></category>
		<category><![CDATA[first stored program computer]]></category>
		<category><![CDATA[genome sequences]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[proof]]></category>
		<category><![CDATA[sour grapes]]></category>
		<category><![CDATA[work]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=269</guid>
		<description><![CDATA[Scientists create synthetic cell, version 1.0 &#124; [paper] Our synthetic genomic approach stands in sharp contrast to a variety of other approaches to genome engineering that modify natural genomes by introducing multiple insertions, substitutions, or deletions (18–22). This work provides a proof of principle for producing cells based upon genome sequences designed in the computer. [...]]]></description>
			<content:encoded><![CDATA[<p><a href="http://news.cnet.com/8301-17938_105-20005533-1.html">Scientists create synthetic cell, version 1.0</a> | [<a href="http://www.sciencemag.org/cgi/rapidpdf/science.1190719v1.pdf">paper</a>]</p>
<blockquote><p>Our synthetic genomic approach stands in sharp contrast to a variety of other approaches to genome engineering that modify natural genomes by introducing multiple insertions, substitutions, or deletions (18–22). This work provides a proof of principle for producing cells based upon genome sequences designed in the computer. DNA sequencing of a cellular genome allows storage of the genetic instructions for life as a digital file.</p></blockquote>
<p>This seems significant, equivalent to booting up the first stored-program computer. </p>
<blockquote><p>Scientists who were not involved in the study are cautioning that the new species is not a truly synthetic life form because its genome was put into an existing cell.</p></blockquote>
<p>That&#8217;s sour grapes, because the original cell cytoplasm decays to zero exponentially fast in the number of replications, a point well made in the paper. It&#8217;s only needed for booting. What&#8217;s more useful to know is how much of the 1.08Mbp genome consists of existing genes. The paper says it&#8217;s a close copy of <em>M. mycoides</em>:</p>
<blockquote><p>The synthetic genome described in this paper has only limited modifications from the naturally occurring M. mycoides genome. However, the approach we have developed should be applicable to the synthesis and transplantation of more.</p></blockquote>
<p>The next step will be a basic cell with a minimal genome, a barebones cell OS, if you will. Then, on to synthetic functions. Pretty soon we&#8217;ll have cell API&#8217;s, fancy-pants programming frameworks, and bugs and viruses. I mean real ones.</p>
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		<item>
		<title>some science</title>
		<link>https://blog.yhuang.org/?p=260</link>
		<comments>https://blog.yhuang.org/?p=260#comments</comments>
		<pubDate>Fri, 09 Apr 2010 23:02:36 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[black body radiation]]></category>
		<category><![CDATA[equilbrium]]></category>
		<category><![CDATA[heat]]></category>
		<category><![CDATA[internal reflection]]></category>
		<category><![CDATA[law]]></category>
		<category><![CDATA[law of thermodynamics]]></category>
		<category><![CDATA[light bulbs]]></category>
		<category><![CDATA[opposite]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[radiation]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=260</guid>
		<description><![CDATA[Big bang an exploding white hole, opposite of a black hole? (paper) This sounds interesting and somehow satisfying. LED light bulbs coming, but incandescents being phased out by mandate in January, 2012? What?! Time to stockpile bulbs. I like my black-body radiation. Speaking of black-body radiation, suppose I have an enclosed system with a single [...]]]></description>
			<content:encoded><![CDATA[<p><a href="http://www.sciencedaily.com/releases/2010/04/100406172648.htm">Big bang an exploding white hole, opposite of a black hole?</a> (<a href="http://dx.doi.org/10.1016/j.physletb.2010.03.029">paper</a>) This sounds interesting and somehow satisfying.</p>
<p><a href="http://www.smartplanet.com/business/blog/smart-takes/ge-energys-smart-led-light-bulb-promises-17-years-of-service-nine-watt-draw/5830/">LED light bulbs coming</a>, but incandescents being phased out by mandate in January, 2012? <a href="http://en.wikipedia.org/wiki/Energy_Independence_and_Security_Act_of_2007#Incandescent_lights">What?!</a> Time to stockpile bulbs. I like my black-body radiation.</p>
<p>Speaking of black-body radiation, suppose I have an enclosed system with a single aperture for light and only light to pass through. Do I now have a system for converting heat to light, and therefore to electricity via bandgaps? Doesn&#8217;t that violate some law of thermodynamics?<br />
<span id="more-260"></span><br />
Okay, I guess the temperature of the photovoltaic converter (the heat sink) matters also, since photons incident on it need to find a site where the electron is in a low-energy state, so unless the converter is at absolute zero, there is some probability the photon will not be captured, which becomes waste heat.</p>
<p>Now what if we enclose the photovoltaic converter, too, so photons cannot escape? That won&#8217;t work, either, since at thermal equilbrium, the converter radiates as many photons as it captures, so no voltage develops. The converter just becomes hotter.</p>
<p>But wait, if the converter&#8217;s temperature rises above that of the radiating source, doesn&#8217;t that imply that the enclosed converter receives some kind of energy, even if it isn&#8217;t converted to electricity? Doesn&#8217;t that also violate a law of thermodynamics? Ah, but the radiating source and the converter are in optical contact. That must mean that no passive one-way optical material can exist, in which one side is totally opaque and absorptive and another side is totally transparent and reflective. Sounds like <a href="http://en.wikipedia.org/wiki/Kirchhoff's_law_of_thermal_radiation">Kirchhoff&#8217;s law</a>&#8230;</p>
<p>Yet, there are transparent optical interfaces that use total internal reflection on one side to achieve exactly this one-way effect, is there not? Okay, the optics also radiate, so no free lunch here.</p>
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		<title>senate voting model graph</title>
		<link>https://blog.yhuang.org/?p=240</link>
		<comments>https://blog.yhuang.org/?p=240#comments</comments>
		<pubDate>Wed, 17 Feb 2010 02:48:09 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[edge]]></category>
		<category><![CDATA[edge weights]]></category>
		<category><![CDATA[gaussian distributions]]></category>
		<category><![CDATA[Ghaoui]]></category>
		<category><![CDATA[graph structure]]></category>
		<category><![CDATA[independence relationships]]></category>
		<category><![CDATA[model]]></category>
		<category><![CDATA[model graph]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[today]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=240</guid>
		<description><![CDATA[There was a talk today that referenced this paper by Banerjee, El Ghaoui, and d&#8217;Aspremont on obtaining sparse graphical models for parameterized distributions. This undirected graphical model stating conditional independence relationships of senate voting behavior was shown. If two nodes A and B are connected only through a set of nodes C, then A and [...]]]></description>
			<content:encoded><![CDATA[<p>There was a talk today that referenced <a href="http://jmlr.csail.mit.edu/papers/volume9/banerjee08a/banerjee08a.pdf">this paper</a> by Banerjee, El Ghaoui, and d&#8217;Aspremont on obtaining sparse graphical models for parameterized distributions.</p>
<p>This undirected graphical model stating conditional independence relationships of senate voting behavior was shown.<br />
<img src="wp-content/uploads/images/voting.jpg" /></p>
<p>If two nodes A and B are connected only through a set of nodes C, then A and B are independent, conditioned on C. Basically it says if you want to predict anything about B from A and C, then C is enough, because A won&#8217;t tell you anything more. As pretty as the graph looks, this is a rather odd visualization. Without seeing the (Ising) model parameters, especially where the edge weights are positive or negative, this graph is hard to interpret, and the conclusions in the paper are especially questionable to me. In particular, being in the middle of this graph does not <em>necessarily</em> imply &#8220;moderation&#8221; or &#8220;independence&#8221;, (unlike in let&#8217;s say <a href="http://broadcast.oreilly.com/2009/05/us-senato-social-graph-1991--.html">this graph</a>). We would expect moderates to exhibit weak dependency to either party&#8217;s large cliques. But if, for example, the edge weight between Allen and B. Nelson is a strongly negative one (which it very well may be, since the two parties are not otherwise connected via negatively weighted edges), then the graph seems to imply that how the two parties vote can largely be predicted from the votes of the likes of Allen or B. Nelson; in that sense, they are the indicators for their parties, disagreeing on exactly those party-disambiguating issues.</p>
<p>There is some additional funny stuff going on. According to the paper, a missing vote counts as a &#8220;no&#8221; because they only solved the problem for binary and Gaussian distributions. I also count only about 80 nodes in there, while there are 100 senators. The graph structure also seems a bit too sparse, but this may be intentional, in order to drop weak dependencies from the graph. One does wonder though, whether the results weren&#8217;t really that good without manual fudging.</p>
<p>Unrelatedly, this reminds me of another famous academic <a href="http://www.sociology.columbia.edu/pdf-files/bearmanarticle.pdf">paper</a> graph, the high school dating graph:<br />
<img src="wp-content/uploads/images/highschool.jpg" /></p>
<p>If you look carefully, there is some oddball stuff going on here, too.</p>
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		<title>Middle Chinese and Old Chinese recitations</title>
		<link>https://blog.yhuang.org/?p=181</link>
		<comments>https://blog.yhuang.org/?p=181#comments</comments>
		<pubDate>Sun, 05 Apr 2009 11:09:38 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[book scheme]]></category>
		<category><![CDATA[classical texts]]></category>
		<category><![CDATA[guy]]></category>
		<category><![CDATA[Middle]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[poetry]]></category>
		<category><![CDATA[script]]></category>
		<category><![CDATA[southern dialects]]></category>
		<category><![CDATA[tang dynasty poetry]]></category>
		<category><![CDATA[tonal variations]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=181</guid>
		<description><![CDATA[There have long been Middle Chinese and Old Chinese reconstructions on paper, but since the Chinese script is not phonetic (although syllabic to a degree), it has been difficult to ascertain pronunciations. If one takes Classical Latin as an example &#8212; that is a reconstruction of fairly normal and believable speech of about 2000 years [...]]]></description>
			<content:encoded><![CDATA[<p>There have long been Middle Chinese and Old Chinese reconstructions on paper, but since the Chinese script is not phonetic (although syllabic to a degree), it has been difficult to ascertain pronunciations. If one takes Classical Latin as an example &#8212; that is a reconstruction of fairly normal and believable speech of about 2000 years ago if read aloud, yet there is nothing approaching that for Middle Chinese (about >1000 years ago) much less for Old Chinese (>2000 years ago). Recently though, a couple of funny videos cropped up on Youtube showing people making overly academic attempts at reading classical texts using reconstructed archaic pronunications.<br />
<span id="more-181"></span></p>
<p>Here&#8217;s a guy attempting to read Tang Dynasty poetry in Middle Chinese.<br />
<object type="application/x-shockwave-flash" data="http://www.youtube.com/v/sVw9iyq59zo" width="425" height="344"><param name="movie" value="http://www.youtube.com/v/sVw9iyq59zo" /><param name="FlashVars" value="playerMode=embedded" /></object></p>
<p>Here&#8217;s another guy attempting to read some of the oldest written poetry from the Zhou era in Old Chinese.<br />
<object type="application/x-shockwave-flash" data="http://www.youtube.com/v/twE4BYDlaxc" width="425" height="344"><param name="movie" value="http://www.youtube.com/v/twE4BYDlaxc" /><param name="FlashVars" value="playerMode=embedded" /></object></p>
<p>Generally I find these unbelievable and unnatural, probaby due to a combination of reconstruction error and bad or exaggerated intonation. Nobody can speak like this. For Middle Chinese it has been argued that the rhyme book scheme does not give one speech pattern and in any case the reconstruction has severe survivor bias toward modern southern dialects. For Old Chinese, I&#8217;m just speechless&#8230; I don&#8217;t think this guy even knows how to read Zheng Zhang Shang Fang&#8217;s phonetic notation, so he produces hilariously impractical initial and ending clusters with bizarre tonal variations to boot. Anyway, it&#8217;s a start.</p>
<hr />
Here&#8217;s an interesting article on the origins of <a href="http://culture.people.com.cn/GB/70485/70513/5216469.html">court dialects</a>.</p>
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		<title>Wired on the Gaussian copula</title>
		<link>https://blog.yhuang.org/?p=164</link>
		<comments>https://blog.yhuang.org/?p=164#comments</comments>
		<pubDate>Wed, 25 Feb 2009 04:37:47 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[covariance matrix]]></category>
		<category><![CDATA[default correlation]]></category>
		<category><![CDATA[Gaussian]]></category>
		<category><![CDATA[gaussian copula]]></category>
		<category><![CDATA[heck]]></category>
		<category><![CDATA[marginal distributions]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[pointless exercise]]></category>
		<category><![CDATA[structure]]></category>
		<category><![CDATA[technology]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=164</guid>
		<description><![CDATA[Because this article is spamming the internet today, I decided to read Li&#8217;s paper and learn what the heck is this Gaussian copula. For five years, Li&#8217;s formula, known as a Gaussian copula function, looked like an unambiguously positive breakthrough, a piece of financial technology that allowed hugely complex risks to be modeled with more [...]]]></description>
			<content:encoded><![CDATA[<p>Because <a href="http://www.wired.com/techbiz/it/magazine/17-03/wp_quant?currentPage=all">this article</a> is spamming the internet today, I decided to read Li&#8217;s paper and learn what the heck is this Gaussian copula.</p>
<blockquote><p>For five years, Li&#8217;s formula, known as a Gaussian copula function, looked like an unambiguously positive breakthrough, a piece of financial technology that allowed hugely complex risks to be modeled with more ease and accuracy than ever before. With his brilliant spark of mathematical legerdemain, Li made it possible for traders to sell vast quantities of new securities, expanding financial markets to unimaginable levels.</p></blockquote>
<p>And anyway, here is the <a href="http://www.defaultrisk.com/_pdf6j4/On%20Default%20Correlation-%20A%20Copula%20Function%20Approach.pdf">paper</a> referenced in the article.<br />
<span id="more-164"></span><br />
Firstly, so much for the sensationalism: so far as I can tell, the paper doesn&#8217;t say anything worthy of a Nobel Prize &#8212; but still it is mildly interesting. In fact, the whole point of the paper appears to be to introduce to the finance community an already known method for solving the inverse problem of distribution marginalization, that is, (non-uniquely) go from marginal distributions back to the joint distribution, by specifying a mediating copula that captures marginal-invariant joint structure. The technology is very straightforward, and Li didn&#8217;t invent it.</p>
<p>That aside, I did wonder, why the heck go through the motion of constructing a Gaussian copula (as in the article) if you assume your marginals and joint are all Gaussian to begin with and all you wanted to capture is the covariance matrix; you can just specify the joint Gaussian explicitly. It seems like a totally pointless exercise. After reading the paper though, I see that wasn&#8217;t really Li&#8217;s entire suggestion at all. He&#8217;s being descriptive rather than prescriptive of what his firm already did by casting it in the language of copulas, an interpretive generalization that allows for potentially more accurate modeling (of non-Gaussian marginals and complicated joint structure if so desired).</p>
<p>Now on to the accusations. The article says that Li tried to &#8220;model default correlation&#8221; using credit default swaps rather than ratings agency data. It turns out that wasn&#8217;t even a problem being solved in this paper. He suggested to use CDS market data to get implied <em>marginal</em> distribution, an established practice. As for how correlation is obtained from limited data, you&#8217;d have to blame one Greg Gupton:</p>
<blockquote><p>Having chosen a copula function, we need to compute the pairwise correlation of survival times. Using the CreditMetrics (Gupton et al. [1997]) asset correlation approach, we can obtain the default correlation of two discrete events over one year period.</p></blockquote>
<p>However, it is true that there is something funny going on with the concept of using market pricing to price other market instruments, when the only novel input for all of them must be what little information is collected from actual due diligence. A classic case of Garbage In Garbage Out in statistical modeling.</p>
<p>As somebody elsewhere wrote, this sort of thing would not pass muster in &#8220;real&#8221; engineering design. We&#8217;ve seen that dichotomy before between the absolutely error-free stricture of &#8220;hardware&#8221; design (chips and bridges) vs. the more lax attitude toward &#8220;software&#8221; design (operating systems and capital market systems). Maybe this dichotomy needs to go away.</p>
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		<title>On Penmanship in Chinese</title>
		<link>https://blog.yhuang.org/?p=154</link>
		<comments>https://blog.yhuang.org/?p=154#comments</comments>
		<pubDate>Thu, 29 Jan 2009 21:49:06 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[basis]]></category>
		<category><![CDATA[calligraphy]]></category>
		<category><![CDATA[first principle]]></category>
		<category><![CDATA[first principles]]></category>
		<category><![CDATA[matter]]></category>
		<category><![CDATA[muscle memory]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[penmanship]]></category>
		<category><![CDATA[result]]></category>
		<category><![CDATA[structure]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=154</guid>
		<description><![CDATA[I suppose good penmanship is the basis of good calligraphy, since calligraphy is mainly the addition of (variable) brush width to the structure of the characters. This bulk structure is really the key and it is particularly difficult to get correctly without muscle memory. That&#8217;s why they tell you to trace character books over and [...]]]></description>
			<content:encoded><![CDATA[<p>I suppose good penmanship is the basis of good calligraphy, since calligraphy is mainly the addition of (variable) brush width to the structure of the characters. This bulk structure is really the key and it is particularly difficult to get correctly without muscle memory. That&#8217;s why they tell you to trace character books over and over.</p>
<p>However, there is a way to figure this matter of structure from first principles (and perhaps generate a more unique style as a result), albeit with the tradeoff that you cannot be quick, you must be careful.<br />
<span id="more-154"></span><br />
The first principle for aesthetics is that the character must stand &#8230; this is something my old man told me, actually, so I didn&#8217;t figure this out myself, but it is very true. If you hold up the piece of paper and look at the strokes as struts of a building, it must look like the character is architecturally sound, i.e. reasonably symmetric if need be, balanced in weight so will not tip over, is not poorly supported with too small a bottom and too big a top, etc. This isn&#8217;t too difficult if the character is mechanically drawn, but the trick is to do it even with asymmetric calligraphic strokes and multi-part characters with asymmetric radicals and caps.</p>
<p>The second principle for aesthetics is about spacing, and this is much like optimal typography and typesetting. The strokes should be spread out evenly so that where they appear parallel, they appear to have nearly identical spacing as other such spaces. Otherwise there will be ugly bunching and voids. This is very difficult because the strokes are written in order so there is a pre-commitment issue. Once you commit to a particular stroke, it also commits the spacing requirements for the rest of the character. So one slightly off stroke and you are screwed. This is more a problem for large writing, since bigger mistakes are possible.</p>
<p>Then is the issue of multiple character layout. This wouldn&#8217;t be so much of an issue if all characters were the same shape and complexity, but they are not. Some are extremely sparse, and some are very dense. Some are tall and some are fat. They all have to be laid out on paper to look like they take up the same space and also evenly spaced from each other. There is also the compromise of making inter-stroke space appear similar in multiple characters. So one needs to deal with some visual artifacts and vision tricks. As a result, the characters will not all be the same size and will not be spaced evenly, so this is a very tricky thing to get right. You can have perfectly written individual characters but still a terrible collection.</p>
<p>And finally here is a side point: people say Simplified characters are uglier than Traditional characters for calligraphy. In fact this cannot be true. What happens is Simplified characters are sparser and sparser characters writ large are the most difficult to get correctly (not to mention there are no classic master&#8217;s character books to trace in Simplified). They are ugly only because (or to the extent that) they are not written well. The bastion of poor practioners (like me) is in small dense characters that distract from scrutiny and generally look pretty good no matter how you write them.</p>
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		<title>biometric authentication</title>
		<link>https://blog.yhuang.org/?p=139</link>
		<comments>https://blog.yhuang.org/?p=139#comments</comments>
		<pubDate>Thu, 04 Dec 2008 03:18:50 +0000</pubDate>
		<dc:creator>admin</dc:creator>
				<category><![CDATA[Uncategorized]]></category>
		<category><![CDATA[authentication protocol]]></category>
		<category><![CDATA[fingerprint reader]]></category>
		<category><![CDATA[paper]]></category>
		<category><![CDATA[paper templates]]></category>
		<category><![CDATA[pen]]></category>
		<category><![CDATA[problem]]></category>
		<category><![CDATA[random strings]]></category>
		<category><![CDATA[sort]]></category>
		<category><![CDATA[tablet mode]]></category>
		<category><![CDATA[Windows]]></category>

		<guid isPermaLink="false">http://scripts.mit.edu/~zong/wpress/?p=139</guid>
		<description><![CDATA[Now that I have gotten seriously addicted to Tablet PC (the faux paper templates in Windows Journal alone were enough to get me hooked), I&#8217;ve been pondering about some limitations of the platform. One is authentication. One of things you are not happy to do with a mouse &#8212; which the pen is, sort of [...]]]></description>
			<content:encoded><![CDATA[<p>Now that I have gotten seriously addicted to Tablet PC (the faux paper templates in Windows Journal alone were enough to get me hooked), I&#8217;ve been pondering about some limitations of the platform. One is authentication. One of things you are not happy to do with a mouse &#8212; which the pen is, sort of &#8212; is inputting random strings that have become of modern-day passwords.</p>
<p>So I understood the point of the fingerprint reader option on this build. Swipe and you can bypass having to type passwords in tablet mode when the keyboard is hidden. But I didn&#8217;t get the option, and I believe there are other alternatives.</p>
<p>There are many modes of biometric authentication, fingerprint, face recognition, handwriting, voice, etc., and getting nearly perfect reliability in each case is a difficult problem when used alone. State of the art is just not good enough. But combined into a multifactored authentication protocol, it may just work. Here is something that should work <em>today</em> with existing hardware:</p>
<table border="1" cellpadding="10" style="margin: 2 2 2 2; border-collapse: collapse; border-style: solid; border-color: #365873;">
<tr>
<td><strong>Look into the webcam, solve a quick reflexive cognition problem, and provide a handwriting sample.</strong></td>
</tr>
</table>
<p>That should do the trick for a quick keyboard-less authentication. Why hasn&#8217;t anybody written software to do this?</p>
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