Transient Stream Research Articles

WITHDRAWN: Transient unidirectional acoustic streaming in annular resonators

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SQL Extensions to Enable Decision Support within Database Systems

Modern organizations store massive amount of information within their data warehouses to carry out complex analysis and decision support, such as identifying interesting trends, making unusual patterns to stand out and verifying hypotheses. Besides traditional data warehousing applications, a new class of data-intensive systems is emerging: applications in which the data is modeled not as persistent relations but rather as transient data streams. In this article we approach decision support from the database viewpoint. We briefly mention SQL features – the standard query language of database systems – and review several proposed extensions to make it a decision support-oriented language. Special emphasis is given to EMF SQL, an approach that has proven very useful in complex querying over traditional data ware-housing applications. We argue that this extension can also be useful in the context of stream data. Finally, we review and discuss decision support challenges over data stream systems.

Numerical analysis of the transient turbulent flow in a fuel oil storage tank

The filling process of a fuel oil storage tank containing a higher temperature fuel oil is numerically analysed. A k– ε model, which is developed by some modifications to those existing in the literature, is employed in order to take into account the turbulent effect for low- Re flow phenomena. A transient stream function–vorticity formulation is used for predicting streamlines and temperature distribution. The streamlines, the isotherms and the transient average temperature variations are presented for three different inflow velocities and for three different cases of heating.

STAND, a dynamic model for sediment transport and water quality

We introduce a new model–STAND (Sediment-Transport-Associated Nutrient Dynamics)–for simulating stream flow, sediment transport, and the interactions of sediment with other attributes of water quality. In contrast to other models, STAND employs a fully dynamic basis for quantifying sediment transport, thus distinguishing it from the well-known HEC-6 model. This latter, in particular, computes a steady-state form of sediment transport based on an approximation of transient flow regimes by a sequence of steady-state hydraulic conditions. STAND has a three-level structure. The first level accounts for the hydraulics of open-channel flow, using the conventional St Venant equations. The second level computes sediment transport potential and actual transport rates based on the information provided by the first level. In the third level (not discussed herein), changes of nutrient concentrations along the studied river can be computed as a function of nutrient transport, adsorption/desorption of nutrients to suspended sediment, and releases from bed-sediment pore water. Having introduced STAND and compared and contrasted its structure with HEC-6, STAND's performance is evaluated against a comprehensive data set obtained from a section of the Weihe River, a major tributary of the Yellow River, in China, and compared to results from HEC-6. From both visual evaluation and the statistics of the residual time series, it can be concluded that STAND provides the better simulation, notably under conditions of strongly transient stream behavior.

Development of a salt and water balance model for a large partially cleared catchment

A salt and water balance model was developed to represent stream flow and salinity generation processes following land use changes. At first a fundamental building-block model was developed based on the ‘downward approach’. The building-block model was tested and validated with data from six experimental sub-catchments within the Collie River basin in Western Australia. The approach requires specification of five physically meaningful key parameters, most of which can be obtained a priori or easily calibrated.Streamflow and salinity from the Collie River catchment, with an area of2,545 km2, has increased significantly due to clearing of 26% of the area during 1940–70s. For this study the catchment was divided into 91 sub-catchments and the building-block model was applied to each of the sub-catchments. Most of the known catchment attributes such as stream length, average slope, soil type, profile thickness and salt storage were incorporated into the model. Parameter values obtained from experimental sub-catchments were appropriate for representing the daily streamflow generation processes of the whole catchment. However, the prediction of stream salinity and salt loads was improved by running the model a number of times and taking the final values of the transient stream zone stores as an initial condition. The modelled daily stream flow, salinity and salt load hydrographs matched very well for all gauged sub-catchments.

Solar and heliospheric causes of geomagnetic perturbations during the growth phase of solar cycle 23

A database is compiled for the study of solar and heliospheric causes of geomagnetic perturbations with the daily average index Aр > 20 that were observed in the period 1997–2000. The number of such events (more than 200) progressively increased and fluctuated as the current solar cycle developed. It is established that geomagnetic storms are generated by dynamical processes and structures near the center of the solar disk in a zone of several tens of degrees, and these processes are responsible for the appearance in the Earth's region, within several tens of hours, of quasistationary and transient solar wind streams with a sufficiently strong southward component of the heliospheric magnetic field. These streams lasted more than a few hours. The following structures can serve as morphological indicators for the prediction of the appearance of such streams: (1) active and disappearing filaments derived from synoptic Нα-maps of the Sun, (2) solar flares, (3) coronal holes and evolving active regions, and (4) the heliospheric current sheet. The geometry of coronal mass ejections needs further observational study.

Effects of a porous manifold on thermal stratification in a liquid storage tank

A numerical model for a porous manifold has been developed to study its effects on thermal stratification in a typical storage tank. The tank considered has a capacity of 300 l and a height-to-diameter ratio of 2. The numerical model employs a transient stream function-vorticity formulation to predict the development of flow and temperature fields in a charging process. The Reynolds number of the inlet flow is fixed at 200 and a wide range of the Richardson number (0.01≤ Ri≤100) is considered. Other parameters considered include the Biot number (i.e. heat loss from the tank), the Darcy number (permeability of the porous manifold), the location of baffle, and the thickness of the porous tube. The results show that all these factors should be taken into account for a better design of a thermal storage tank. In addition, the results provide an envelope for these design parameters.

Neural dynamics of perceptual order and context effects for variable-rate speech syllables.

How does the brain extract invariant properties of variable-rate speech? A neural model, called PHONET, is developed to explain aspects of this process and, along the way, data about perceptual context effects. For example, in consonant-vowel (CV) syllables, such as /ba/ and /wa/, an increase in the duration of the vowel can cause a switch in the percept of the preceding consonant from /w/ to /b/ (J.L. Miller & Liberman, 1979). The frequency extent of the initial formant transitions of fixed duration also influences the percept (Schwab, Sawusch, & Nusbaum, 1981). PHONET quantitatively simulates over 98% of the variance in these data, using a single set of parameters. The model also qualitatively explains many data about other perceptual context effects. In the model, C and V inputs are filtered by parallel auditory streams that respond preferentially to the transient and sustained properties of the acoustic signal before being stored in parallel working memories. A lateral inhibitory network of onset- and rate-sensitive cells in the transient channel extracts measures of frequency transition rate and extent. Greater activation of the transient stream can increase the processing rate in the sustained stream via a cross-stream automatic gain control interaction. The stored activities across these gain-controlled working memories provide a basis for rate-invariant perception, since the transient-to-sustained gain control tends to preserve the relative activities across the transient and sustained working memories as speech rate changes. Comparisons with alternative models tested suggest that the fit cannot be attributed to the simplicity of the data. Brain analogues of model cell types are described.

Temperature Model for Highly Transient Shallow Streams

The development and application of a one-dimensional heat transport model in highly transient streams governed by unsteady flow is described here. The resultant framework consists of two modules called the hydrodynamic and heat transport modules. In the hydrodynamic module, the hydraulic variables such as flow depth and velocity are simulated. Based on this information, the heat transport module is executed to calculate temperatures. A new approach—coupling heat transport in the surface water and diffusion in the sediment zone—is developed and applied for this module. In this approach, an interaction term accounts for the flux of heat energy between the water and sediments, which affects the distribution of water temperature in clear and shallow streams. Implicit finite difference methods called the Preissmann four-point and the Crank-Nicolson schemes are used to solve each module. Application of this framework demonstrates that the model effectively simulates the hydraulic variables and temperatures.

Turbulent buoyant flows into a two dimensional storage tank

A numerical model was developed to simulate the turbulent mixing processes that occur when a cold fluid flows into a two dimensional tank containing a warmer fluid. The process simulates the charging of a chilled water thermal energy storage tank. The numerical model employs a transient stream function-vorticity formulation to predict the streamline and temperature distributions in the tank. The turbulent effect was modeled by a two equation turbulent model using the turbulent kinetic energy and turbulent length scale equations. The results for a lower corner inlet flow show that the cold fluid will not extensively mix with the warmer fluid in the tank for Archimedean number greater than five and inlet Reynolds number less than 1000. The warm and cold fluids will thermally stratify under these conditions and limitations.

Cosmic Ray Modulation by Transient and Corotating High Speed Streams in the Heliosphere

Cosmic Ray Modulation by Transient and Corotating High Speed Streams in the Heliosphere

Numerical Computation of Laminar Separation and Reattachment of Flow Over Surface Mounted Ribs

Numerical results are presented concerning the fluid characteristics of steady-state laminar flow over surface mounted ribs. Computations are carried out using a false transient stream function-vorticity form. The effects of the aspect ratios (width-to-depth) of the ribs and Reynolds numbers as well as initial boundary-layer thickness on entire flow field, separated region, and reattachment length are presented and discussed. The computed reattachment distance compares reasonably well with those data reported by previous studies. A correlation is provided in terms of the rib aspect ratio, Reynolds number, and the ratio of boundary-layer thickness and rib height. The pressure drop is excessive along the upstream vertical step face and it recovers thereafter, which agrees qualitatively with those of the previous studies for the flow over backward-facing steps.

An estimate of the maximum speed of the solar wind, 1938–1989

Beginning with a list of severe geomagnetic storms, we obtain an estimate of the maximum solar wind flow speed at Earth during the past ∼50 years. We do this by (1) focusing on the subset of severe storms that followed major proton flares (since large proton events are strongly associated with fast coronal mass ejections), (2) calculating the average speed of the associated interplanetary shocks from the time intervals between the flares and the onsets of the storms, and (3) using an empirical relationship between the average shock speed and the maximum flow speed of the associated transient stream to infer a peak flow velocity for each event. We find no evidence for bulk flow velocities greater than the ≳2000‐km/s value deduced from Prognoz 2 and HEOS 2 in situ plasma measurements for the August 4, 1972, event. The ≳2000‐km/s speed for that event does not appear to be anomalously high, however; there are other credible events, occurring before 1960, with inferred flow speeds approaching this value. The ≳2000‐km/s value lies at the high‐speed edge of a reasonable single distribution of peak solar wind speeds for a representative sample of the most energetic solar‐terrestrial events observed from 1938 to 1989.

The effects of blue and red light on Acetabularia mediterranea after long exposure to darkness

After Acetabularia mediterranea cells were kept in darkness for 2–8 weeks, all the cellular processes were arrested and the algae did not grow. In particular, the transcellular electrical potential (VAB) decreased to almost zero and cytoplasmic streaming was arrested. Upon illumination with continous blue light (BL), the first events were (as with white light (WL)), immediate increase in VAB and movements of water, followed, after a lag period of 1–3 min, by transient recovery of cytoplasmic streaming which lasted about 16 min. After 10 min (earlier than in WL), the frequency of the spontaneous action potentials increased much more than in WL. Then, after 1.5–4 hr during which VAB often decreased to zero while the cytoplasmic movements stopped, both activities resumed with diurnal oscillations. BL stimulated (as WL) rRNA synthesis, migration of rRNA from nucleus towards apex and cell growth. Upon illumination with red light (RL), VAB also increased, but water movements were much less pronounced than in BL. The transient streaming phase was shorter. The spontaneous action potentials increased in frequency much later (several hr) and much less than in BL or WL. VAB did not decreased at any time and was maintained at particularly high values. Cytoplasmic streaming resumed, but showed very attenuated or no rhythm. rRNA synthesis and migration remained low. Cell growth did not resume during the experiments. By comparing our results with those of other studies relating to growth, morphogenesis and photosynthesis, we suggest that BL and RL could affect all these processes by differentially modifying the cytoplasmic concentrations of ions which may influence the functions of the cytoskeleton.

The effects of blue and red light on Acetabularia mediterranea after long exposure to darkness

After Acetabularia mediterranea cells were kept in darkness for 2–8 weeks, all the cellular processes were arrested and the algae did not grow. In particular, the transcellular electrical potential (VAB) decreased to almost zero and cytoplasmic streaming was arrested. Upon illumination with continous blue light (BL), the first events were (as with white light (WL)), immediate increase in VAB and movements of water, followed, after a lag period of 1–3 min, by transient recovery of cytoplasmic streaming which lasted about 16 min. After 10 min (earlier than in WL), the frequency of the spontaneous action potentials increased much more than in WL. Then, after 1.5–4 hr during which VAB often decreased to zero while the cytoplasmic movements stopped, both activities resumed with diurnal oscillations. BL stimulated (as WL) rRNA synthesis, migration of rRNA from nucleus towards apex and cell growth. Upon illumination with red light (RL), VAB also increased, but water movements were much less pronounced than in BL. The transient streaming phase was shorter. The spontaneous action potentials increased in frequency much later (several hr) and much less than in BL or WL. VAB did not decreased at any time and was maintained at particularly high values. Cytoplasmic streaming resumed, but showed very attenuated or no rhythm. rRNA synthesis and migration remained low. Cell growth did not resume during the experiments.By comparing our results with those of other studies relating to growth, morphogenesis and photosynthesis, we suggest that BL and RL could affect all these processes by differentially modifying the cytoplasmic concentrations of ions which may influence the functions of the cytoskeleton.

Solar activity and heliosphere‐wide cosmic ray modulation in mid‐1982

A major episode of flare activity in June and July of 1982 was accompanied by a pair of heliosphere‐wide cosmic ray modulation events. In each case, a large Forbush decrease (FD) at earth was followed in turn by apparently related decreases at Pioneer 11 (P11) and Pioneer 10 (P10). The Pioneer spacecraft were separated by ∼155° in ecliptic longitude. We reviewed white light coronagraph and near‐sun (≤1 AU) satellite data to identify plausible solar origins of these modulation events. The first widespread intensity decrease (FD 1) can be attributed to the combined effects of a backside flare on June 3 from solar active region 18382/18383, located 23° in ecliptic longitude from Pioneer 10, and a visible disk flare from 18405 on June 6, when this region was 9° from Pioneer 11. The second widespread modulation event during this period (FD 2) may be linked to flares from active region 18474 on July 12 and 22. The July 12 flare was located 34° in azimuth from Pioneer 11, and the July 22 flare was 24° from Pioneer 10. Since even fast shocks would take ∼1 month to propagate to Pioneer 11 (12 AU) and ∼2 months to reach Pioneer 10 (28 AU) in mid‐1982, these “one‐to‐one” associations must be regarded with caution. The processes of entrainment and coalescence can cause a given traveling interplanetary disturbance to lose its identity enroute to the outer heliosphere. The fact that we were able to identify plausible solar flare candidates for each of the four Forbushlike decreases observed at the Pioneer satellites (two each at P10 and P11), however, removes the need to invoke a shock from a single flare as the sole cause of either FD 1 (at both P10 and P11) or FD 2. Such single‐flare scenarios have recently been suggested by several investigators to account for the widespread intensity decreases in mid‐1982. Instead, the heliosphere‐wide modulation during this period appears to result primarily from a sustained episode of powerful flares from a relatively narrow range of active solar longitude. A significant fraction (1/2 to 3/4) of the major coronal mass ejections (CMEs) and near‐sun shocks observed during June and July 1982 originated in flares occurring in a 45° band of Carrington longitude. Because of solar rotation these flares occur over the full range of ecliptic longitude and can generate an outward propagating shell of CMEs and shocks that encompasses the sun to produce the observed azimuthal symmetry in the cosmic ray modulation. The prolonged high‐speed wind stream at P10 in the second half of 1982 may have resulted, at least in part, from the coalescence of a series of fast transient streams directed toward that distant spacecraft into an extended compound stream.

Formation of a compound stream between 0.85 AU and 6.2 AU and its effects on solar energetic particles and galactic cosmic rays

During September 1979, Helios B (HB) and Voyager 1 (V1) were near 0.85 AU and 6.2 AU, respectively, and they were radially aligned with respect to the sun within 20°. A slow transient stream, two corotating streams, and two unusually fast transient streams passed HB during a 17‐day interval in that order. (A stream is defined here as a flow in which the speed is always greater than 475 km/s.) As the streams moved outward from HB to V1, they coalesced to form a single large “compound stream” which moved past V1 in 20 days. The compound stream was produced by motion of fast plasma away from slower plasma behind and by the interaction of the fast streams with slower streams ahead. The maximum speed observed was 1270 km/s at HB and 860 km/s at V1. Closely associated with this compound stream was one of the largest solar energetic particle events (protons 0.4–69 MeV) observed beyond 5 AU. The maximum intensity was in the region of increasing speed. The intensity‐time profile of the solar energetic particles was closely related to the speed profile. There is evidence of channeling and trapping of particles in a region following the highest speeds, where the magnetic field was strong and the magnetic field lines were nearly radial. The high‐energy protons (>150 MeV) and MeV electrons are believed to be accelerated in solar flare events. Interplanetary acceleration appears to play a major role in the low‐energy particle population. The galactic cosmic ray intensity remained low throughout the passage of the compound stream, recovering slowly as the speed decreased. The long “recovery time” is thus related to the large extent of the flow.

Cosmic ray variations and turbulent flow systems: 0.3–1.0 AU; 1977–1980

Relations among the relative counting rates of cosmic ray protons and the magnetic fields and flows observed by Helios 1 between 0.3 AU and 1 AU in the period January 1977 to August 1980 are discussed. Isolated corotating or transient flows are associated with short‐term depressions in cosmic ray intensity, but the effects are localized in longitude. Systems of corotating streams do not produce a long‐term modulation effect, although temporary, short‐term depressions in cosmic ray intensity are associated with individual streams and interaction regions. Spectra of fluctuations of the magnetic field and magnetic helicity for systems of corotating flows often do not have the form f−5/3 at frequencies ≥10−5 Hz, and accordingly, the hydromagnetic fluctuations in corotating streams near the sun do not appear to represent fully developed turbulence at low frequencies. Systems of transient streams containing shocks that might encircle the sun are associated with long‐lasting decreases in cosmic ray intensity. The magnetic field fluctuations in such flow systems are often turbulent, with f−5/3 spectra extending from below 10−5 Hz to the Nyquist frequency of the data. The turbulence is likely to be confined to sheets with thicknesses of the order of 0.1 AU, possibly associated with shocks. We conclude that long‐term modulation of cosmic rays inside 1 AU is associated with turbulence in transient disturbances that probably encompass a large longitudinal extent around the sun. In mixed flow systems the effects are intermediate between those of corotating and transient systems. The net modulation may be relatively small, with large short‐term variations associated with individual streams.

Discussion of “ Numerical Alternatives in Transient Stream Response ” by Rodney J. Sobey (June, 1984)

Discussion of “ <i>Numerical Alternatives in Transient Stream Response</i> ” by Rodney J. Sobey (June, 1984)

Closure to “ Numerical Alternatives ind Transient Stream Response ” by Rodney J. Sobey (June, 1984)

Closure to “ <i>Numerical Alternatives ind Transient Stream Response</i> ” by Rodney J. Sobey (June, 1984)