The soroban (算盤, そろばん?, counting tray) is an abacus developed in Japan. It is derived from the suanpan, imported from China to Japan around 1600.[1] Like the suanpan, the soroban is still used today, despite the proliferation of practical and affordable pocketelectronic calculators.


Contenido movil

Published on May 1, 2013
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Pagina de compatibilidad de kernel con tun.ko:

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Herramientas gratuitas para UML

Existen herramientas gratuitas de buena caliadad para UML. Tanto Netbeans como Eclipse soportan esta funcionalidad con el ciclo completo de desarrollo desde generación de código hasta reingenieria. Esto, claro, si se quiere trabajar en Java. En .Net no he encontrado este grado de funcionalidad en herramientas Open Source. Una opción de bajo costo, relativo a RUP y similares, es Visual UML. Visual Paradigm tiene una edición limitada sin costo, Smart Development Environment Community Edition for Visual Studio.

UML, ejemplo sencillo sobre Modelado de un Proyecto Introducción a UML


1: Motor radial de un avión

2: Distribución oval

3: Principio de la máquina de coser

4: Movimiento de Cruz de Malta – de la mano del segundero, que controla al reloj

5: Mecanismo de cambio de velocidades (automóvil)

6: Junta universal para velocidad constante automática

7: Sistema de carga de proyectiles

8: Motor giratorio – motor de combustión interna, el calor y no el movimiento del pistón, causa el movimiento giratorio

9: Motor en línea – cilindros alineados en forma paralela

limited unlimited

AT&T Inc. is effectively ending unlimited data plans, saying that it will no longer let customers use more than a set amount of data per month without penalty.
Under a new policy, AT&T will slow download speeds for unlimited 3G and 4G smartphone customers who exceed three gigabytes and 4G LTE users who exceed five gigabytes of data in a given month. AT&T had previously been slowing speeds, or throttling, customers who were in the top 5% of data users in their respective market.

AT&T has been trying to manage capacity on its network in the face of heavy data consumption by Apple Inc. iPhone users and a limited supply of wireless airwaves, or spectrum. The carrier is spending billions to build out a new fourth-generation mobile-broadband network that can handle more data traffic.
A spokesman, Mark Siegel, said the new guidelines were necessary because of confusion among unlimited customers over when their download speeds would be slowed. He declined to say by how much the speeds would be decreased.
Now, AT&T says customers will get a text message when their usage approaches 3GB in one billing cycle. AT&T will slow customers’ data speeds for the rest of that billing cycle.
After that, speeds go back to normal if customers stay under the limit. But if they exceed the limit again, customers’ speeds get slowed without receiving another text-message reminder.
In 2010, AT&T was the first carrier to introduce so-called tiered pricing plans which capped customers’ data use. It allowed existing customers to keep their unlimited data plans indefinitely. About 56% of AT&T’s smartphone customers are on the tiered plans, the carrier said Wednesday.
The Dallas-based carrier in January boosted the prices of the tiered plans by as much as 33% while increasing the amount of data allowed per month.
AT&T and other carriers have been pushing Congress and the Federal Communications Commission to release more licenses for wireless airwaves to help stave off a capacity crunch as more customers download video, music and photos to their smartphones.
The data caps aren’t the only moves the Dallas-based telecommunications giant is taking to manage its network. In recent weeks, the carrier has begun sending out notices to some customers still using cellphones on its older 2G cellular network to swap out their devices for newer ones that can run on 3G networks.
“Your current, older-model 2G phone might not be able to make or receive calls and you may experience degradation of your wireless service in certain areas,” AT&T cautioned in the letter. Mr. Siegel said the carrier hoped to use some of the 2G spectrum for new technologies, though it would still offer 2G services to those who want them.
“We’re simply urging them to upgrade to a new device if they want to,” Mr. Siegel said.
Mr. Siegel said the carrier sent the notices to customers in the New York metropolitan area and may send them to other customers. He noted the program was voluntary and affected a small number of subscribers and most 2G phones would continue to work.
AT&T is offering the users one of four free phones, such as the Samsung Electronics Co. Evergreen or the LG Electronics Inc. GU295.

Jane Foody’s iPhone is practically her personal assistant. 
The 27-year-old physical therapist and yoga instructor from Yonkers, NY, uses her iPhone for everything, from scheduling appointments, to streaming music during lessons, to showing her clients how to properly strike a downward dog pose.
But last month, AT&T threatened to shut down Jane’s personal assistant. AT&T sent Jane a text message saying that she was using too much data on her unlimited data plan, and that they could block her access to high-speed data. Jane says her iPhone would be useless for anything but making phone calls and sending text messages, and she’s not happy about it.
Jane started a petition on Change.org calling on AT&T to stop slowing down data and respect the unlimited data plans paid for by customers. AT&T is digging in its heels after 10,000 people already signed Jane’s petition. The company responded to the campaign by saying customers with unlimited plans can only access three gigabytes of data per month — meaning unlimited plans no longer exist!
Jane isn’t the only AT&T customer being accused of using “too much” data on unlimited plans. A huge article from the Associated Press revealed just weeks ago that AT&T is similarly targeting the top 5% of its “unlimited” data customers, or nearly 850,000 people. 
Jane says she tried to file a complaint with AT&T about being unable to use her unlimited data, but the only responses she says she got were from sales representatives pushing her to pay more money to be able to use as much data as she wants. “I told them, ‘I shouldn’t need to do that since I have unlimited data,'” Jane said.
Cell phone companies have listened to customer outrage before: in December, more than 166,000 Change.org members successfully pushed Verizon to cancel a new fee to pay bills online. Jane hopes that if enough people speak out to AT&T, the cell phone company will also buckle and listen to their customers.
Thanks for being a change-maker,
– Jon, William, Jess, Tim, Michael, and the Change.org team

La escalabilidad del computo

Cuando estaba en la escuela, hace algunos años, había gran efervescencia sobre el tema del computo paralelo, de hecho mi tesis doctoral es sobre este tema. Recuerdo que comentado sobre   las posibilidades del paralelismo con mi asesor, me dijo que desde un punto de vista teórico el  computo paralelo no era importante porque no cambiaba los limites de escalabilidad impuestos por los problemas NP.

Ahora nos encontramos en un resurgimiento de los enfoques del computo distribuido debido al abaratamiento del hardware y la cada vez mayor disponibilidad de conexiones de banda ancha. Por lo tanto la cuestión de algoritmos eficientes para problemas NP y la corroboración teórica de NP ǂ P se ha convertido en uno de los problemas primordiales de la teoría y practica del computo.