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Special Thanks To:
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The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Featured Project
Duncan has done a lot of really great work on his latest project, and submitted it to be featured. Have a look at his thread and see for yourself what he's been up to!
Posted by Chris Russell on Monday 16 April 2007 - 01:17:10
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HvWiki Reaches 200!
That's right, HvWiki has reached the 200 article mark! Lots of interesting and valuable information has been added to the wiki, and many of the articles are truly in-depth and well-written. If you haven't stopped by lately, please have a look when you get a chance.
At this time, we'd like to encourage anyone and everyone to participate in the wiki. Even if all you do is correct a few typos, or add a few sentences here and there, every little bit helps. It's a community effort, after all. There are a lot of articles that need fleshing out, and some in need of a good overhaul. Tomorrow, February 2nd, the registrations will be opened, which means you don't have to ask to be registered. Everyone is encouraged to register. Due to problems with spam and other unwanted guests, the registrations will only be open for one week, so please avail yourself of this opportunity and sign up.
I've also started a new board, to assist in the development of the wiki. If you have any questions, comments, or anything else you'd like to say about the wiki, please stop by the board.
Thank you to everyone who has participated in the wiki's first 200 articles! 1,000 can't be far off!
Posted by Chris Russell on Thursday 01 February 2007 - 18:10:40
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New Board, Other News
There is now a new board in place, to ease communications with the moderating team. Please use this board as the central contact point when you need assistance from a moderator or administrator. Don't use the "report" button, and don't PM moderators who happen to be online. This will be the fastest, most reliable way to ensure you get a response, and a resolution.
In other news, if you filled out an application before the end of June, and haven't heard any kind of response from me, please try again. Your application may have been deleted by my spam filter.
I nearly forgot, 4hv.org turns five years old this month! The current total online presence of 4hv.org consists of 127,352 posts in 10199 threads. Fun fact: if you read 70 posts every single day, it would take almost five years to read the entire archive. Any ideas for a celebration?
Posted by Chris Russell on Sunday 16 July 2006 - 21:25:56
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Registrations Disabled
I've decided to disable registrations for the time being, while I work out a new system for handling new members. At the moment, I do not have an ETA for completion of the new system. There is, a workaround, however. If you'd still like to register, please send an email to **link**, titled "registration". Please include your desired username and real name, and at least a paragraph about why you'd like to join.
Please wait at least 7 days for a response. I will try to be much, much faster than that, but sometimes I do get busy.
Thank you for your understanding. I apologize for any inconvenience.
Posted by Chris Russell on Tuesday 04 April 2006 - 01:42:43
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Featured Project
Congrats to JimG on a project well done!
JimG wrote ...
Last October I was in a local surplus electronic parts store when I ran across a 1.375" x 3.5" 250V computer grade capacitor. Having just built two DRSSTCs I figured it might be cool to build a DRSSTC centered around this small capacitor. I then decided I would challenge myself with a few constraints.
1. The secondary shouldn't be any bigger than the capacitor. 2. The whole circuit should be kept small using SMT parts. 3. It should run off of a single power supply using a wall wart. 4. The interrupter should be on-board and easily updated. 5. It had to produce streamers, not just corona. 6. I wanted it to be a full bridge if possible.
This project is the first to be featured on the front page. If you'd like your project thread to be considered for a featured project, please make sure that your thread is in agreement with the project board rules, and contact me via PM.
Posted by Chris Russell on Friday 17 March 2006 - 01:12:41
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Strain rate sensitive materials
Your first introduction to such things was probably silly putty.
My first recollection was making something similar from a recipe in this book:
McGrath, Susan. Fun With Physics. Washington, DC: The National Geographic Society, 1986.
Good luck if you can find that book. It probably contributed much to my current inclinations in life... The silly putty alternative involved baking soda and vinegar ,I think. I do remember my mom hated making it. It was like pancake batter under no pressure, but like a rock if you tried to force it to do anything. The explantion the book gave was that the long polymer chains formed flowed across each other easily if not under pressure, but resisted moving if under pressure
In more recent news US and Canadian skiers have new clothes. After looking for more information about this I found this page too.
Posted by Ben on Tuesday 21 February 2006 - 08:13:17
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Fluid lenses feel the pressure
The new lens has been designed by Saman Dharmatilleke and colleagues at the Institute of Materials Research and Engineering (IMRE) in Singapore. It was made by housing a tiny drop of water -- or any other liquid with a high surface tension -- in the small aperture of a well. Applying pressure to the drop via an actuator changes the radius of curvature -- and hence the focal length -- of the drop. The focal length can therefore be tuned simply by varying the amount of pressure applied. The lenses can be made either from a liquid-air or a liquid-liquid interface.
Dharmatilleke and co-workers have been able to make two types of lenses with their technique: "bi-convex" lenses, in which both sides of the drop change shape, and "plano-convex" lenses, in which one side of the drop is planar and the other is convex. The latter are made by using one end of the aperture and sealing off the other with a thin transparent substrate. The new lenses can be made as small as 10 microns, making them the smallest lenses available today. They also consume very little power and are cheap to produce.
According to the team, the lenses would be ideal for devices that need to focus and zoom in on an object with precision, such as web cams, mobile phone cameras, bar-code scanners, and portable medical devices such as microscopes and endoscopes. The researchers have already licensed their technology to a Singapore engineering company PGS Precision Pte Ltd.
Although researchers at the electronics giant Philips developed a variable-focus fluid lens in 2004, it worked on different principles. It consisted of a drop of an electrically conducting aqueous solution surrounded by oil, the shape of which was changed by applying a voltage, rather than pressure. The voltage changed the extent to which the oil repelled the water.
Posted by Grant on Tuesday 14 February 2006 - 18:03:00
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Didn't get your confirmation email?
If you didn't get your confirmation email, it's probably because you are using an AOL or Netscape email address. For some unknown reason, AOL is refusing all mail from my server. The simple solution is to use a non-AOL email address to sign up, such as hotmail, gmail, or yahoo.
If you'd rather just be patient, I did (after much, much effort) get ahold of someone at the AOL postmaster department who admitted that there was no good reason that the server should be blocked. He's filed the necessary paperwork to get the block lifted, but the whole process may take up to a week to complete.
Posted by Chris Russell on Friday 10 February 2006 - 21:35:07
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We're open!
Yes, it's true, the site is open at last, with just an hour to spare before my self-imposed deadline!
Everything is obviously still not completely set up. I am working on a recent topics list, but it will take some time to set up. If there\'s anything else we need to do, please use the suggestion box. All I ask is that you be aware that we\'re going to be working on high-priority things first, so you might want to hold on to your other suggestions for a while, lest they get lost in the initial rush.
A few things you should be aware of: some of the rules have changed. Please re-read them, especially in regards to double-posting and image size restrictions. We have a news system in place. If you know of any news that would interest the community, or any upcoming events, please feel free to submit it to us.
I hope you all enjoy the new site. Please feel free to post your comments here, or use the forum.
Posted by Chris Russell on Thursday 09 February 2006 - 03:59:27
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We're Not Open Yet!
I'm glad that everyone is excited about the new forum being up, but please remember, it's not open for general use yet. Don't sign up unless you're currently a moderator, or you've talked to me about becoming a moderator. Otherwise, I'll just have to delete your account, and that's not fun for either of us.
Work on the site is progressing as expected, and we will be ready to open to everyone on February 8th. Unless something goes horribly, horribly wrong. Which it won't. In the meantime, please be patient, and feel free to have a look around.
Posted by Chris Russell on Thursday 02 February 2006 - 21:15:41
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