Tuesday, March 25, 2008


A computer database is a structured collection of records or data that is stored in a computer system. A database relies upon software to organize the storage of data. In other words, the software models the database structure in what are known as database models (or data models). The model in most common use today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships .

Tuesday, March 18, 2008

PL/SQL (Procedural Language/Structured Query Language)

PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's proprietary procedural extension to the SQL database language. Some other SQL database management systems offer similar extensions to the SQL language. PL/SQL's syntax strongly resembles that of Ada, and just like Ada compilers of the 80-s the PL/SQL runtime system uses Diana (intermediate language) as intermediate representation.

The key strength of PL/SQL is its tight integration with the Oracle database.

PL/SQL is one of three languages embedded in the Oracle Database, the other two being SQL and Java.

Monday, March 10, 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.

Wednesday, March 05, 2008

Ship transport

Ship transport is primarily used for the carriage of people and non-perishable goods, generally referred to as cargo.

Although the historic importance of sea travel for passengers has decreased, due to the rise of commercial aviation, it is still very effective for short trips and pleasure cruises. Sea transport remains the largest carrier of freight in the world.