Control versus Data Flow in Parallel Database Machines

The execution of a query in a parallel database machine can be controlled in either a control flow way, or in a data flow way. In the former case a single system node controls the entire query execution. In the latter case the processes that execute the query, although possibly running on different nodes of the system, trigger each other. Lately, many database research projects focus on data flow control since it should enhance response times and throughput. The authors study control versus data flow with regard to controlling the execution of database queries. An analytical model is used to compare control and data flow in order to gain insights into the question which mechanism is better under which circumstances. Also, some systems using data flow techniques are described, and the authors investigate to which degree they are really data flow. The results show that for particular types of queries data flow is very attractive, since it reduces the number of control messages and balances these messages over the node

An Evaluation of Physical Disk I/Os for Complex Object Processing

In order to obtain the performance required for nonstandard database environments, a hierarchical complex object model with object references is used as a storage structure for complex objects. Several storage models for these complex objects, as well as a benchmark to evaluate their performance, are described. A cost model for analytical performance evaluation is developed, and the analytical results are validated by means of measurements on the DASDBS, complex object storage system. The results show which storage structures for complex objects are the most efficient under which circumstance

Persuasive Ways to Change Entrance Use of Buildings

People tend to use the same door every time they enter and exit a building. When certain entrances are widely preferred over others, congestion can occur. This paper describes two interventions to persuade visitors to use another entrance. The first intervention used sensory deprivation (darkness), and the second used guidance paths. The first intervention on sensory deprivation had the expected outcome. This intervention resulted in an avoidance of the darkened door. The second intervention had a result contrary to the expectations; it resulted in an increased preference for the door without guidance paths

Increasing Performance of Professional Soccer Players and Elite Track and Field Athletes with Peak Performance Training and Biofeedback:A Pilot Study

The aim of this pilot study was to investigate the effects of an intervention consisting of mental coaching combined with either electro encephalogram (EEG) alpha power feedback or heart rate variability (HRV) feedback on HRV, EEG outcomes and self-reported factors related to stress, performance, recovery and sleep quality in elite athletes. A prospective pilot study was performed with two distinct cohorts. Soccer players were provided with four sessions of mental coaching combined with daily HRV biofeedback (Group A); track and field athletes were provided with four sessions of mental coaching in combination with daily neurofeedback (Group B). Measurements were performed at baseline, post intervention and at 5 weeks follow-up. Objective measures: EEG and ECG. Subjective measures: Numeric Rating Scale for performance, Pittsburgh Sleep Quality Index, Rest and Stress Questionnaire and Sports Improvement-60. Group characteristics were too distinct to compare the interventions. Linear mixed models were used to analyze differences within groups over time. In Group A, significant changes over time were present in alpha power at 5 of 7 EEG locations (p <0.01-0.03). LF/HF ratio significantly increased (p = 0.02) and the concentration (p = 0.02) and emotional scale (p = 0.03) of the SIM-60 increased significantly (p = 0.04). In Group B, the HRV low frequency power and recovery scale of the REST-Q significantly increased (p = 0.02 and <0.01 resp.). Other measures remained stable or improved non-significantly. A mental coaching program combined with either HRV or EEG alpha power feedback may increase HRV and alpha power and may lead to better performance-related outcomes and stress reduction. Further research is needed to elucidate the effects of either type of feedback and to compare effects with a control group

Samenwerken en zakendoen via het Internet

In de Internetwereld zien we een nieuwe paradigma ontstaan: de ‘retailer’. Ook al is niet helemaal duidelijk wie deze rol gaat invullen, duidelijk is wel dat eindgebruikers een éénduidige ingang wensen voor een scala aan diensten. Transparantie van, onder andere, kosten is hierbij gewenst. Een dienstenaanbieder wil zich ook niet langer zorgen hoeven maken over generieke functionaliteit zoals authenticiteit en autorisatie van gebruikers, transacties, ‘application hosting’, betaling, of andere zaken die de zogenoemde retailer voor hem kan oplossen. Zo’n retailer past in een dienst-, in plaats van productgerichte aanpak. Het retailer paradigma wordt ondersteund door technische ontwikkelingen rondom het ASP model, de programmeertaal Java, ‘interoperabiliteit’, component software (hergebruik) en ‘netwerkcomputers’. Gebaseerd op het bovenstaande paradigma heeft FRIENDS een geïntegreerd platform ontwikkeld dat ondersteuning biedt aan zowel eindgebruikers, als ontwikkelaars, als aanbieders van on-line gedistribueerde diensten

Situational awareness for health and safety

Beyond Horizons: the future of applied research in Europa Situational Awareness for health and safet

Event Information System voor Military Boekelo

Event Information System voor Military Boekel