Mean response times for optimistic concurrency control in a multi-processor database with exponential execution times

Using a non-productform queueing network model, two approximations are developed for computing the average response time of transactions in a multi-processor shared-memory database system with optimistic concurrency control. The time and resources needed for the validation of transactions are explicitly taken into account in the queueing model, since they are not always negligible. The performance of the approximations, tested against a simulation of the queueing model, is very good

Stressor sensor and stress management system

A stressor detection system (100) comprises sensor means (101) arranged for being attached to a person for obtaining a time-varying signal representing a physical quantity relating to an environment of the person, and processing means (102) for deriving a stressor value from the obtained signal representing a degree to which the environment is inducing stress in the person. The processing means is arranged for deriving an amount of complexity comprised in the signal, and for deriving a higher stressor value for a larger amount of information. The processing means is further arranged for performing a spectral frequency analysis of the signal and for deriving the stressor value also in dependence on the spectral frequency analysis. The sensor means comprises a microphone (105), a camera (104), and a tri-axial accelerometer

The response time distribution in a multi-processor database with single queue static locking

A transaction scheduling mechanism is designed for a shared memory, multiprocessor database system. The scheduler used is a variant of static locking, adapted for real time and more than one processor. It is assumed that transactions arrive according to a Poisson process, execution times of transactions are independent and exponentially distributed and all transactions use the same number of data items. The system is then represented as a Markov model. A steady state is derived from this model. By examining the path through the system of a single transaction, a recursive relation that describes all moments of a transaction's response time is derived. The response time distribution is approximated by fitting a distribution to the first two moments. Simulation shows that this approximation gives excellent results

Autonomous wireless die

A wireless die (2) comprises an orientation detector (4) for determining an orientation of the die (2) and a transmitter (5) connected to the orientation detector (4) for transmitting die (2) orientation data to the receiver (3). The orientation detector (4) comprises at least two electromechanical detectors (6), the electromechanical detectors (6) being arranged for generating electrical power for the orientation detector (4) and transmitter (5), and for supplying gravity based orientation data