Entries from June 2007 ↓
June 30th, 2007 — Technical
Stirling Engines, not very popular, but really promising engines. Check out the features.
- Closed cylinder engine
- No Combustion and noise
- Works on heat exchange
- Any heat source can power the engine
- Most efficient of all engines
- Low Maintenance
- Most suitable for solar concentrators
This is a very simple but feasible and effcient technology, yet relatively untapped, why ? I can see only one reason. The Energy Lobby. Stirling engines will surely replace the concept of centralized power production. Every home will have its own energy source, a Stirling engine powered by either concentrated solar energy, waste wood, or even biogas from sewage.
The Germans have the technology, buy it from them, mass produce it cheaply in india, subsidize to promote like we do for inefficient solar cells, and we are self sufficient. 
I dream of having this on top of my house, my own powerhouse. A Solar concentrator and a Stirling engine. This is a 25KW station. Mine would be much smaller less than 5KW.
And Some interesting information - There was a company in Madras who manufactured 5KW Stirling engines for farmers. The fuel- wood, dried cow dung, and anything that burns and produces heat.
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June 21st, 2007 — Uncategorized
The google page rank is one of the most discussed topics in the SEO world. The PR of a page is a measure of the importance of a page.
How does google calculate PR ?
PR of a page is very much dependent on the number of pages referring to that page. Exactly the same way humans also rank other humans. One person is a great person if more people knows him. A page with reference from 10000 pages is a good page, similarly a person who is known to 10000 people is also a small celebrity.
The PR of a page is also affected by the PR of the pages that links to it. A reference from a higher PR page is very much more valuable than a lower PR page. Likewise a If a person is know to the Indian Prime minister, he definitely must be a celebrity or a politician or someone very important.
Keywords on higher PR pages are very likely to get search listings. We can see search listings as analogues to opinions. Opinions from higher PR pages are more important. Same is the case with humans also. The opinion of a person with lot of fans is very powerful. Politicians and movie stars become opinion formers like this.
The bottom like is that you can learn to become famous by observing the SEO world and finding the real world equivalent of it. Soon Ill come up with some ideas. If you happen to have some ideas regarding this, please comment.
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Google
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June 20th, 2007 — GSM/CDMA
Where ever you hear the name gateway, assume that we are talking about external connectivity. SMS gateway is used to provide SMS connectivity to third parties or solve protocol incompatibilities.
The SMSC is a part of the operators SS7 network. The SMS gateway is connected to the SMSC. In most cases the SMSC has inbuilt gateways. Any external connection from a network other than the SS7 network is handled through the gateway.
One major advantage of a gateway is that it supports TCP/IP based SMPP protocol. So we can access an SMS gateway from an IP network like the internet. Bulk SMS providers setup their own gateways or get connectivity to already set up gateways.
The SMS gateways provides SMS connectivity to third parties via many protocols, which includes HTTP, SMPP and XML. This allows a normal programmer to access SMS services very easily without having to worry about the telephone network protocols. If he is using the HTTP protocol to connect to an SMS gateway, he can send an SMS by calling an http request.
The only limitation of HTTP is that the number of SMS that can be send per second is less than 10. For higher throughput we need to use SMPP protocol. Its a bit more complicated, but many open source libraries are available to make the task easier.
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June 19th, 2007 — GSM/CDMA
Finally the picture is mine. Took me 30 mins.
BTS - Base Transceiver Station (Antenna)
BSC - Base Station Controller
MSC - Mobile Switching center
HLR- Home Location Register
VLR - Visitor Location Register
SMSC - Short Message Service Center
When a user sends an SMS, the request is placed via the MSC. The MSC forwards the SMS to the SMSC where it gets stored. The SMSC queries the HLR to find out where the destination mobile is and forwards the message to the destination MSC if the destination mobile is available. If the mobile is not available the message gets stored in the current SMSC itself. In most installations If a mobile is not available for SMS delivery the SMSC will not retry. Instead the destination MSC will inform the SMSC when the mobile comes back in range.
SMS handling is a store and forward operation unlike USSD.
SMS has got a validity period, for which it will wait for the destination mobile to the available. After that time the SMSC will delete the message. The validity period can be set by the user. Normal validity is 1 day.
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June 13th, 2007 — Technical
Sorry for the bad heading. Suggest me a good heading after reading the concept. Today I met a non tech person with a lot of ideas and this is one of his idea.
We all now have operator provided sim cards. His idea is to eliminate the concept of a personal mobile. One must be able to LOGIN to any mobile and use his connection. A concept very similar to email where we can use any computer or any internet service provider to access my email. All my contacts, and other mobile related data will be on an operator server and I will login to a mobile to use my connection. By this I will be able to attend my calls and make calls from my number using any mobile connection.
When wifi hotspots and wifi phones become popular we will see more of this concept in action. With the commercial operators such a concept is really hard to work out cos of the costs involved in setting up the additional infrastructure.
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