Numerous Experiments (numerous + experiment)

Distribution by Scientific Domains


Selected Abstracts


Top-down control of phytoplankton: the role of time scale, lake depth and trophic state

FRESHWATER BIOLOGY, Issue 12 2002
JÜrgen Benndorf
SUMMARY 1.,One of the most controversial issues in biomanipulation research relates to the conditions required for top-down control to cascade down from piscivorous fish to phytoplankton. Numerous experiments have demonstrated that Phytoplankton biomass Top-Down Control (PTDC) occurs under the following conditions: (i) in short-term experiments, (ii) shallow lakes with macrophytes, and (iii) deep lakes of slightly eutrophic or mesotrophic state. Other experiments indicate that PTDC is unlikely in (iv) eutrophic or hypertrophic deep lakes unless severe light limitation occurs, and (v) all lakes characterised by extreme nutrient limitation (oligo to ultraoligotrophic lakes). 2.,Key factors responsible for PTDC under conditions (i) to (iii) are time scales preventing the development of slow-growing inedible phytoplankton (i), shallow depth allowing macrophytes to become dominant primary producers (ii), and biomanipulation-induced reduction of phosphorus (P) availability for phytoplankton (iii). 3.,Under conditions (iv) and (v), biomanipulation-induced reduction of P-availability might also occur but is insufficient to alter the epilimnetic P-content enough to initiate effective bottom-up control (P-limitation) of phytoplankton. In these cases, P-loading is much too high (iv) or P-content in the lake much too low (v) to initiate or enhance P-limitation of phytoplankton by a biomanipulation-induced reduction of P-availability. However, PTDC may exceptionally result under condition (iv) if high mixing depth and/or light attenuation cause severe light limitation of phytoplankton. 4.,Recognition of the five different conditions reconciles previous seemingly contradictory results from biomanipulation experiments and provides a sound basis for successful application of biomanipulation as a tool for water management. [source]


Fretting behaviour of low-friction coatings

LUBRICATION SCIENCE, Issue 3 2005
C. Langlade
Abstract The choice of an appropriate low-friction coating for an industrial application is generally a difficult task. As many parameters are involved and are often unknown, selection criteria are hard to define. In order to elucidate the case of fretting conditions, a simulator has been used to reproduce the degradation mechanisms observed for real situations. Numerous experiments performed with this machine permit one to define endurance life criteria. The evolution of the life observed has been analysed as a function of the contact pressure and the film thickness. Using a Wöhler approach, endurance curves have been plotted that give useful information for selecting appropriate coatings. As other parameters may be of some interest, performance indices have been associated with them, and the results can be presented on a multi-axis (polar) diagram. [source]


Organizing for Radical Innovation: An Exploratory Study of the Structural Aspects of RI Management Systems in Large Established Firms

THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 6 2006
Gina Colarelli O'Connor
To escape the intense competition of today's global economy, large established organizations seek growth options beyond conventional new product development that leads to incremental changes in current product lines. Radical innovation (RI) is one such pathway, which results in organically driven growth through the creation of whole new lines of business that bring new to the world performance features to the market and may result in the creation of entirely new markets. Yet success is elusive, as many have experienced and scholars have documented. This article reports results of a three-year, longitudinal study of 12 large established firms that have declared a strategic intent to evolve their RI capabilities. In contrast to other academic research that has analyzed specific projects to understand management practices appropriate for RI, the present research reported explores the evolution of management systems for enabling radical innovation to occur repeatedly in large firms and reports on one aspect of this management system: organizational structures for enabling and nurturing RI. To consider organizational structure as a venue for capability development is new in the management of innovation and dynamic capabilities literatures. Conventional wisdom holds that RIs should be incubated outside the company and assimilated once they have gained traction in the marketplace. Numerous experiments with organizational structures were observed that instead work to manage the interfaces between the RI management system and the mother organization. These structures are described here, and insights are drawn out regarding radical innovation competency requirements, transition challenges, senior leadership mandates, and business-unit ambidexterity. The centerpiece of this research is the explication of the Discovery,Incubation,Acceleration framework, which details three sets of necessary, though not sufficient competencies, for building an RI capability. [source]


Position-sensorless direct-torque-controlled synchronous motor drive for ship propulsion

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2000
M. Niemelä
A new concept is proposedfor position-sensorless Direct-Torque-Controlled (DTC) synchronous motor drives for ship propulsion. The principles of determination of the initial rotor position at standstill or the position of a rotating rotor, the operation at zero speed and at low rotational speeds in general are described. The study introduces also a flux linkage estimate correction method for the DTC. Some of the results of the numerous experiments performed with a laboratory prototype drive are given. [source]