Monday, March 24, 2008


FTP/SSL is a name used to encompass a number of ways in which FTP software can perform secure file transfers. Each way involves the use of a SSL/TLS layer below the standard FTP protocol to encrypt the control and/or data channels. It should not be confused with either SSH file transfer protocol (SFTP), or FTP over SSH (no acronym).

The most common uses of FTP and SSL are:

* AUTH TLS, Explicit FTPS or FTPES, named for the command issued to indicate that TLS security should be used. This is the preferred method according to RFC 4217. The client connects to the server port 21 and starts an unencrypted FTP session as normal, but requests that TLS security be used and performs the appropriate handshake before sending any sensitive data.

* AUTH as defined in RFC 2228.

* Implicit FTPS is an older, but still widely implemented style in which the client connects to a different port (usually 990), and an SSL handshake is performed before any FTP commands are sent.

Monday, March 17, 2008

Spiral model

The spiral model is a software development process combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts. Also known as the spiral lifecycle model, it is a systems development method (SDM) used in information technology (IT). This model of development combines the features of the prototyping model and the waterfall model. The spiral model is intended for large, expensive and complicated projects.

Sunday, March 09, 2008

NEC Display Solutions

NEC Display Solutions is a manufacturer of computer monitors and large-screen public-information displays, and has sold and marketed products under the NEC brand globally for more than twenty years. The company sells display products to the consumer, business, professional (e.g. financial, graphic design, CAD/CAM), digital signage and medical markets. The company became a wholly owned subsidiary of Japan-based NEC Corporation on March 31, 2005. Prior to that date, the company was known as NEC/Mitsubishi, a 50/50 joint venture between NEC Corporation and Mitsubishi Electric that began in 2000, and sold display products under both the NEC and Mitsubishi brands. The company, which is no longer affiliated with Mitsubishi, currently sells and markets products under the NEC brand only.

Tuesday, March 04, 2008

Molecular mechanics

In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. Molecular mechanics simulations, for example, use a single classical expression for the energy of a compound, for instance the harmonic oscillator. All constants appearing in the equations must be obtained beforehand from experimental data or ab initio calculations.

The database of compounds used for parameterization, i.e., the resulting set of parameters and functions is called the force field, is crucial to the success of molecular mechanics calculations. A force field parameterized against a specific class of molecules, for instance proteins, would be expected to only have any relevance when describing other molecules of the same class.