IEEE Richard Harold Kaufmann Award Call for Nominations

This letter further discusses the difference between different definitions of voltage unbalance. Contrary to an earlier letter (see P. Pillay et al., ibid., vol.5, p.50-1, 2001), it is concluded that different definitions may give significantly different results. The two IEEE definitions that were not discussed in the earlier letter give different results and both deviate significantly from the true value (ratio of negative, and positive-sequence voltage) when a zero-sequence component is present.     

Laminar-turbulent transition behavior of fully developed air flow in a heated horizontal tube

I have experimentally studied the influence of the buoyancy force and inlet flow conditions on the laminar-turbulent transition process of fully developed air flow in a heated horizontal tube with uniform wall heat flux at modified Rayleigh number 3.1×10⁶. Eight time-series of the air temperature were simultaneously obtained using eight thermocouples positioned within the tube along a vertical line passing through the tube's axis. I have studied the time and space dependence of the transition behavior by analyzing these instantaneous time-series. By calculating a set of Lyapunov exponents and the correlation dimension of the time-series of a single thermocouple, these transitional flows are found to be chaotic.     

Collision Detection and Multitone Tree Search for Multiple-Access Protocols on Radio Channels

The carrier sense multiple access with collision detection (CSMA-CD) protocol cannot be applied directly to radio channels because of the difficulty in sensing remote carrier in the presence of local transmission. Only recently, a new protocol called the CSMA with timesplit collision detection (CSMA-TCD) was introduced to overcome this problem on radio channels. This paper presents an extension of the CSMA-TCD protocol, called CSMA-TCD with multitone tree search (CSMA-TCD-MTTS). In CSMA-TCD, a preamble is transmitted before data transmission. For CSMA-TCD-MTTS, the preamble is modulated with one out ofNtones. In case of a collision, a resolution algorithm splits the terminals involved into anN-degree tree according to the tone chosen. This paper presents the throughput and approximate delay analysis of the CSMA-TCD-MTTS protocol.     

Front Cover

In this paper, the authors present the results of experiments which clearly demonstrate a technical basis confirming that the carrier frequency harmonics data can be used for diagnostics relative to motor stator insulation degradation.     

MetaModel: a program for modelling and control analysis of metabolic pathways on the IBM PC and compatibles

MetaModel is a user-friendly program for calculating steady-state fluxes and metabolite concentrations of metabolic systems on the IBM PC and compatible computers. For any steady state that is obtained, one can then calculate a matrix of elasticity coefficients at that steady state, or a matrix of control and response coefficients. It thus offers a simple way to calculate the control structure of a pathway: it provides not only an educational tool that allows the student to verify empirically the classic summation relationships of metabolic control analysis but also a research tool for addressing 'what if?' questions about the behaviour of metabolic systems. Results can not only be printed or stored in a file, but can also be written to a special file that can be read by popular spreadsheet programs, thereby giving access to rapid, flexible and powerful methods for subsequent analysis and plotting of these results.     

Modeling and assimilation of root zone soil moisture using remote sensing observations in Walnut Gulch Watershed during SMEX04

Soil moisture status in the root zone is an important component of the water cycle at all spatial scales (e.g., point, field, catchment, watershed, and region). In this study, the spatio-temporal evolution of root zone soil moisture of the Walnut Gulch Experimental Watershed (WGEW) in Arizona was investigated during the Soil Moisture Experiment 2004 (SMEX04). Root zone soil moisture was estimated via assimilation of aircraft-based remotely sensed surface soil moisture into a distributed Soil-Water-Atmosphere-Plant (SWAP) model. An ensemble square root filter (EnSRF) based on a Kalman filtering scheme was used for assimilating the aircraft-based soil moisture observations at a spatial resolution of 800 m × 800 m. The SWAP model inputs were derived from the SSURGO soil database, LAI (Leaf Area Index) data from SMEX04 database, and data from meteorological stations/rain gauges at the WGEW. Model predictions are presented in terms of temporal evolution of soil moisture probability density function at various depths across the WGEW. The assimilation of the remotely sensed surface soil moisture observations had limited influence on the profile soil moisture. More specifically, root zone soil moisture depended mostly on the soil type. Modeled soil moisture profile estimates were compared to field measurements made periodically during the experiment at the ground based soil moisture stations in the watershed. Comparisons showed that the ground-based soil moisture observations at various depths were within ± 1 standard deviation of the modeled profile soil moisture. Density plots of root zone soil moisture at various depths in the WGEW exhibited multi-modal variations due to the uneven distribution of precipitation and the heterogeneity of soil types and soil layers across the watershed.     

Anfangsvorgänge bei Lichtenbergschen Figuren

Zusammenfassung Aufnahmen von Lichtenbergschen Figuren mit kurzen Spannungsstößen zeigen, daß bisher bekanntgewordene Bilder solcher Entladungsfiguren bereits ein verhältnismäßig weit vorgeschrittenes Stadium darstellen. Es gelingt mittels kurzer Stöße erste lawinenartige Anfänge der Figuren festzuhalten und einiges über Vorgänge im Anfangsstadium herauszulesen. Die negative Figur beginnt lawinenförmig an bevorzugten Stellen der Kathode. Bei nebeneinander entstandenen Lawinen ist sehr gut die gegenseitige Abstoßung infolge gleicher Ladung zu beobachten. Die Entladung hat einen geschichteten Aufbau. Die positiven Figuren bilden sich später aus. Es sprechen jedoch bisher keinerlei Anzeichen für ein Hinwachsen der Fäden zur Anode. Die Kanäle verjüngen sich zur Anode hin und selbst bei kurzen Stoßzeiten endet kein einziger vor der Anode. Auch die Art der gegenseitigen Abstoßung der positiven Fäden spricht mehr für ein Vorwachsen von der Anode aus. Aus den Farbaufnahmen ergibt sich für die filmschwärzende Strahlung eine Wellenlänge unter 450 m.