Re: [silk] More on invisibility cloaks
On Friday 23 July 2010 11:29 AM, Vinayak Hegde wrote: On Fri, Jul 23, 2010 at 9:38 AM, Udhay Shankar N ud...@pobox.com wrote: http://www.gizmag.com/invisibility-cloak-made-of-glass/15796 I don't buy it. I will believe it when I don't see it Aaahhh.. I feel a delicious headache coming on. Visions of a celebrated cat spinning/not spinning in its grave come to mind. Bharath
[silk] Gifts vs Choices
Very interesting way of putting it, from Amazon CEO Jeff Bezos. http://www.princeton.edu/main/news/archive/S27/52/51O99/index.xml We are What We Choose Remarks by Jeff Bezos, as delivered to the Class of 2010 Baccalaureate May 30, 2010 As a kid, I spent my summers with my grandparents on their ranch in Texas. I helped fix windmills, vaccinate cattle, and do other chores. We also watched soap operas every afternoon, especially Days of our Lives. My grandparents belonged to a Caravan Club, a group of Airstream trailer owners who travel together around the U.S. and Canada. And every few summers, we'd join the caravan. We'd hitch up the Airstream trailer to my grandfather's car, and off we'd go, in a line with 300 other Airstream adventurers. I loved and worshipped my grandparents and I really looked forward to these trips. On one particular trip, I was about 10 years old. I was rolling around in the big bench seat in the back of the car. My grandfather was driving. And my grandmother had the passenger seat. She smoked throughout these trips, and I hated the smell. At that age, I'd take any excuse to make estimates and do minor arithmetic. I'd calculate our gas mileage -- figure out useless statistics on things like grocery spending. I'd been hearing an ad campaign about smoking. I can't remember the details, but basically the ad said, every puff of a cigarette takes some number of minutes off of your life: I think it might have been two minutes per puff. At any rate, I decided to do the math for my grandmother. I estimated the number of cigarettes per days, estimated the number of puffs per cigarette and so on. When I was satisfied that I'd come up with a reasonable number, I poked my head into the front of the car, tapped my grandmother on the shoulder, and proudly proclaimed, At two minutes per puff, you've taken nine years off your life! I have a vivid memory of what happened, and it was not what I expected. I expected to be applauded for my cleverness and arithmetic skills. Jeff, you're so smart. You had to have made some tricky estimates, figure out the number of minutes in a year and do some division. That's not what happened. Instead, my grandmother burst into tears. I sat in the backseat and did not know what to do. While my grandmother sat crying, my grandfather, who had been driving in silence, pulled over onto the shoulder of the highway. He got out of the car and came around and opened my door and waited for me to follow. Was I in trouble? My grandfather was a highly intelligent, quiet man. He had never said a harsh word to me, and maybe this was to be the first time? Or maybe he would ask that I get back in the car and apologize to my grandmother. I had no experience in this realm with my grandparents and no way to gauge what the consequences might be. We stopped beside the trailer. My grandfather looked at me, and after a bit of silence, he gently and calmly said, Jeff, one day you'll understand that it's harder to be kind than clever. What I want to talk to you about today is the difference between gifts and choices. Cleverness is a gift, kindness is a choice. Gifts are easy -- they're given after all. Choices can be hard. You can seduce yourself with your gifts if you're not careful, and if you do, it'll probably be to the detriment of your choices. This is a group with many gifts. I'm sure one of your gifts is the gift of a smart and capable brain. I'm confident that's the case because admission is competitive and if there weren't some signs that you're clever, the dean of admission wouldn't have let you in. Your smarts will come in handy because you will travel in a land of marvels. We humans -- plodding as we are -- will astonish ourselves. We'll invent ways to generate clean energy and a lot of it. Atom by atom, we'll assemble tiny machines that will enter cell walls and make repairs. This month comes the extraordinary but also inevitable news that we've synthesized life. In the coming years, we'll not only synthesize it, but we'll engineer it to specifications. I believe you'll even see us understand the human brain. Jules Verne, Mark Twain, Galileo, Newton -- all the curious from the ages would have wanted to be alive most of all right now. As a civilization, we will have so many gifts, just as you as individuals have so many individual gifts as you sit before me. How will you use these gifts? And will you take pride in your gifts or pride in your choices? I got the idea to start Amazon 16 years ago. I came across the fact that Web usage was growing at 2,300 percent per year. I'd never seen or heard of anything that grew that fast, and the idea of building an online bookstore with millions of titles -- something that simply couldn't exist in the physical world -- was very exciting to me. I had just turned 30 years old, and I'd been married for a year. I told my wife MacKenzie that I wanted to quit my job and go do this crazy thing that probably wouldn't work since most
Re: [silk] Gifts vs Choices
Thanks. But why did his grandmother start crying? AB On 23 July 2010 12:15, Udhay Shankar N ud...@pobox.com wrote: Very interesting way of putting it, from Amazon CEO Jeff Bezos. http://www.princeton.edu/main/news/archive/S27/52/51O99/index.xml We are What We Choose Remarks by Jeff Bezos, as delivered to the Class of 2010 Baccalaureate May 30, 2010 As a kid, I spent my summers with my grandparents on their ranch in Texas. I helped fix windmills, vaccinate cattle, and do other chores. We also watched soap operas every afternoon, especially Days of our Lives. My grandparents belonged to a Caravan Club, a group of Airstream trailer owners who travel together around the U.S. and Canada. And every few summers, we'd join the caravan. We'd hitch up the Airstream trailer to my grandfather's car, and off we'd go, in a line with 300 other Airstream adventurers. I loved and worshipped my grandparents and I really looked forward to these trips. On one particular trip, I was about 10 years old. I was rolling around in the big bench seat in the back of the car. My grandfather was driving. And my grandmother had the passenger seat. She smoked throughout these trips, and I hated the smell. At that age, I'd take any excuse to make estimates and do minor arithmetic. I'd calculate our gas mileage -- figure out useless statistics on things like grocery spending. I'd been hearing an ad campaign about smoking. I can't remember the details, but basically the ad said, every puff of a cigarette takes some number of minutes off of your life: I think it might have been two minutes per puff. At any rate, I decided to do the math for my grandmother. I estimated the number of cigarettes per days, estimated the number of puffs per cigarette and so on. When I was satisfied that I'd come up with a reasonable number, I poked my head into the front of the car, tapped my grandmother on the shoulder, and proudly proclaimed, At two minutes per puff, you've taken nine years off your life! I have a vivid memory of what happened, and it was not what I expected. I expected to be applauded for my cleverness and arithmetic skills. Jeff, you're so smart. You had to have made some tricky estimates, figure out the number of minutes in a year and do some division. That's not what happened. Instead, my grandmother burst into tears. I sat in the backseat and did not know what to do. While my grandmother sat crying, my grandfather, who had been driving in silence, pulled over onto the shoulder of the highway. He got out of the car and came around and opened my door and waited for me to follow. Was I in trouble? My grandfather was a highly intelligent, quiet man. He had never said a harsh word to me, and maybe this was to be the first time? Or maybe he would ask that I get back in the car and apologize to my grandmother. I had no experience in this realm with my grandparents and no way to gauge what the consequences might be. We stopped beside the trailer. My grandfather looked at me, and after a bit of silence, he gently and calmly said, Jeff, one day you'll understand that it's harder to be kind than clever. What I want to talk to you about today is the difference between gifts and choices. Cleverness is a gift, kindness is a choice. Gifts are easy -- they're given after all. Choices can be hard. You can seduce yourself with your gifts if you're not careful, and if you do, it'll probably be to the detriment of your choices. This is a group with many gifts. I'm sure one of your gifts is the gift of a smart and capable brain. I'm confident that's the case because admission is competitive and if there weren't some signs that you're clever, the dean of admission wouldn't have let you in. Your smarts will come in handy because you will travel in a land of marvels. We humans -- plodding as we are -- will astonish ourselves. We'll invent ways to generate clean energy and a lot of it. Atom by atom, we'll assemble tiny machines that will enter cell walls and make repairs. This month comes the extraordinary but also inevitable news that we've synthesized life. In the coming years, we'll not only synthesize it, but we'll engineer it to specifications. I believe you'll even see us understand the human brain. Jules Verne, Mark Twain, Galileo, Newton -- all the curious from the ages would have wanted to be alive most of all right now. As a civilization, we will have so many gifts, just as you as individuals have so many individual gifts as you sit before me. How will you use these gifts? And will you take pride in your gifts or pride in your choices? I got the idea to start Amazon 16 years ago. I came across the fact that Web usage was growing at 2,300 percent per year. I'd never seen or heard of anything that grew that fast, and the idea of building an online bookstore with millions of titles -- something that simply couldn't exist in the physical world -- was very exciting to
Re: [silk] Gifts vs Choices
On Fri, Jul 23, 2010 at 4:56 PM, J. Alfred Prufrock another.prufr...@gmail.com wrote: Thanks. But why did his grandmother start crying? Are you serious? Because she knew smoking was bad for her health, she knew it would kill her, that she really wanted to quit and would if she could, but she couldn't. And now, her grandson was pointing out to her that she was a failure and a bad example. Essentially her grandson had just told her that she was doing something really stupid, and she knew it was true but couldn't change. -- Charles
[silk] UPS power consumption and battery charging
Hi. Does anyone here know how to calculate approximately how much power an online/double-converting/sine wave UPS consumes from the mains? I guess that, if it has to keep N 12V batteries charged, the most power it can consume is (a bit higher than, depending on efficiency) N*12V*c, where c is the maximum charging current. Am I missing anything? (For my 1KVA online UPS, which has 3 65AH/12V batteries and charges them at up to 6A, I speculate that the maximum power used is 6*3*12=216W, and when the charger is floating to keep the batteries charged, the power use is pretty much negligible.) Second, can anyone comment on the advisability of charging SLA (sealed lead acid) batteries at currents of =0.1C (i.e. 10% of their rated Ah capacity or more)? My UPS vendor says they've had problems with current that high, and the battery FAQ says 0.1C for SLAs, but battery vendors seem to recommend 10-20% even for SLAs. Does this differ significantly for VRLA batteries? Third, can anyone explain in detail the internals of a constant-voltage battery charger? I understand the basic idea: provide as much current as needed to maintain the voltage across the terminals at the recommended charging level, but I don't understand enough about how batteries work to figure out what happens when you apply a higher current, or how the voltage is measured or maintained. Also, does anyone know how much I should expect to spend on a basic DC ammeter (the nifty clamp-on hall effect ones, not an in-circuit one), preferably in India? -- ams
Re: [silk] Gifts vs Choices
Le 23 juil. 10 à 09:49, silklist-requ...@lists.hserus.net a écrit : At any rate, I decided to do the math for my grandmother. I estimated the number of cigarettes per days, estimated the number of puffs per cigarette and so on. When I was satisfied that I'd come up with a reasonable number, I poked my head into the front of the car, tapped my grandmother on the shoulder, and proudly proclaimed, At two minutes per puff, you've taken nine years off your life! interesting that this quick estimate agrees with both (a) cursory googling for current estimates of effect of smoking on life expectancy, and (b) country song lyrics. I doubt Hank Jr was ever published in the JAMA, but fwiw : Well I think I'll play the jukebox and light up another cigarette. They say for every puff of that loving smoke you get another minute closer to death. Well I smoke two or three packs a day and my arithmetic's not too sound But I know I'm getting hours closer to that cold, cold ground. -Dave
