Showing papers on "Water flow published in 1985"

Mechanical Limits to Size in Wave-Swept Organisms

Abstract: Plants and animals that inhabit the intertidal zone of wave—swept shores are generally small relative to terrestrial or subtidal organisms. Various biological mechanisms have been proposed to account for this observation (competition, size—specific predation, food—limitation, etc.). However, these biological mechanisms are constrained to operate within the mechanical limitations imposed by the physical environment, and these limitations have never been thoroughly explored. We investigated the possibility that the observed limits to size in wave—swept organisms are due solely or in part to mechanical, rather than biological, factors. The total force imposed on an organism by breaking waves and postbreaking flows is due to both the water's velocity and its acceleration. The force due to velocity (a combined effect of drag and lift) increases in strict proportion to the organism's structural strength as the organism increases in size, and therefore cannot act as a mechanical limit to size. In contrast, the force due to the water's acceleration increases faster than the organism's structural strength as the organism grows, and thus constitutes a potential mechanical limit to its size. We incorporated this fact into a model that predicts the probability that an organism will be destroyed (by breakage or dislodgement) as a function of five parameters that can be measured empirically: (1) the organism's size, (2) the organism's structural strength, (3) the maximum water acceleration in each wave, (4) the maximum water velocity at the time of maximum acceleration in each wave, and (5) the probability of encountering waves with given flow parameters. The model was tested using a variety of organisms. For each, parameters 1—4 were measured or calculated; the probability of destruction, and the size—specific increment in this probability, were then predicted. For the limpets Collisella pelta and Notoacmaea scutum, the urchin Strongylocentrotus purpuratus, the mussel Mytilus californianus (when solitary), and the hydrocoral Millepora complanata, both the probability of destruction and the size—specific increase in the risk of destruction were determined to be substantial. It is conjectured that the size of individuals of these species may be limited as a result of mechanical factors, though the case of M. complanata is complicated by the possibility that breakage may act as a dispersal mechanism. In other cases (the snails Thais canaliculata, T. emarginata, and Littorina scutulata; the barnacle Semibalanus cariosus), the size—specific increment in the risk of destruction is small and the size limits imposed on these organisms are conjectured to be due to biological factors. Our model also provides an approach to examining many potential effects of environmental stress caused by flowing water. For example, these methods may be applied to studies of: (1) life—history parameters (e.g., size at first reproduction, age at first reproduction, timing of reproductive cycles, length of possible reproductive lifetime), (2) the effects of gregarious settlement on the flow encountered, (3) the physical basis for patterns of disturbance, (4) the optimum (as opposed to the maximum) size of organisms, and (5) the energetic cost of maintaining a skeleton with an appropriate safety factor. A definitive answer regarding the possibility of mechanical limits to size depends both upon an accurate measurement of the probability of encountering a wave of specific flow parameters and upon factors that are external to the model considered (e.g., life—history parameters). Further, due to their ability to move with the flow, organisms that are sufficiently flexible can escape the size limits imposed on more rigid organisms. Thus, some macroalgae attain large sizes (2—3 m in maximum dimension). The precise role of these factors awaits further research.

Prediction of soil water properties for hydrologic modeling

Abstract: Water flow in soils can be characterized for many boundary and initial conditions by solving governing differential equations. Thus, a physically consistent means of quantifying water flow in soils in terms of the soil properties governing the movement of water and air exists. One reason why this state-of-the-art technology is not yet fully utilized is the difficulty of obtaining the required inputs which are the relationships between matric potential and hydraulic conductivity as a function of soil water content. Approximate water flow models based on physical principles or empirical results may simplify the computational requirements, however, inputs are still required. This paper presents procedures to (1) estimate input parameters for the Brooks-Corey, Campbell, and Van Genuchten soil water retention and hydraulic conductivity functions based on readily available soil properties, and (2) to estimate infiltration parameters.

Canopy transpiration and water fluxes in the xylem of the trunk of Larix and Picea trees - a comparison of xylem flow, porometer and cuvette measurements

Abstract: Leaf gas exchange, transpiration, water potential and xylem water flow measurements were used in order to investigate the daily water balance of intact, naturally growing, adult Larix and Picea trees without major injury. The total daily water use of the tree was very similar when measured as xylem water flow at breast height or at the trunk top below the shade branches, or as canopy transpiration by a porometer or gas exchange chamber at different crown positions. The average canopy transpiration is about 12% lower than the transpiration of a single twig in the sun crown of Larix and Picea. Despite the similarity in daily total water flows there are larger differences in the actual daily course. Transpiration started 2 to 3 h earlier than the xylem water flow and decreased at noon before the maximum xylem water flow was reached, and stopped in the evening 2 to 3 h earlier than the water flow though the stem. The daily course of the xylem water flow was very similar at the trunk base and top below the lowest branches with shade needles. The difference in water efflux from the crown via transpiration and the water influx from the trunk is caused by the use of stored water. The specific capacitance of the crown wood was estimated to be 4.7 x 10-8 and 6.3 x 10-8 kg kg-1 Pa-1 and the total amount of available water storage was 17.8 and 8.7 kg, which is 24% and 14% of the total daily transpiration in Larix and Picea respectively. Very little water was used from the main tree trunk. With increasing transpiration and use of stored water from wood in the crown, the water potential in the foliage decreases. Plant water status recovers with the decrease of transpiration and the refilling of the water storage sites. The liquid flow conductance in the trunk was 0.45 x 10-9 and 0.36 x 10-9 mol m-2s-1 Pa-1 in Larix and Picea respectively. The role of stomata and their control by environmental and internal plant factors is discussed.

The Influence of Macropores on the Transport of Dissolved and Suspended Matter Through Soil

Abstract: This article is concerned with the predominantly vertical movement of water through soils that to some degree have a network of large channels (macropores) and the consequences of this movement for the convective transport of solutes and suspended matter. Beven and Germann (1982) have reviewed the experimental evidence indicating that infiltration and redistribution of water in soils containing macropores are not adequately described by theories that treat the soil as a homogeneous medium conforming to Darcian principles of water flow. Such theories, developed for the mixing of solutions in hallow tubes (Taylor, 1953) and porous rock strata (Brigham et al., 1961), have been applied to miscible displacement experiments with columns of sand, resins, glass beads, or finely sieved and repacked soil. The underlying assumptions are that an unreactive solute moves through the medium at the same velocity as the water and all the analysis and interpretation of these experiments have been reviewed several times (Gardner, 1965; Biggar and Nielsen, 1967; Biggar and Nielsen, 1980; Wagenet, 1983) and will not be repeated here.

Recirculation in swirling flow - A manifestation of vortex breakdown

Abstract: The addition of a sufficiently high degree of swirl to flow going into a circular pipe produces a limited region of reversed flow. Such a vortex breakdown, as it is termed, represents a zone of transition from a supercritical to a subcritical flow state. If the flow remains subcritical, an unavoidable consequence is that the geometry and conditions downstream directly affect the upstream flow up to, and including, the breakdown region. Laser Dopper anemometer measurements of the swirl and axial velocity components, as well as the corresponding streamline patterns, are presented for water flow in a model based upon the geometry of a swirl combustor. It is shown that a strong exit contraction (55 percent of the diameter) has practically no influence on a flow which reverts to supercritical, whereas even a weak contraction (15 percent of the diameter) has a significant influence on a flow which remains subcritical. It is argued that a cold flow is likely to be totally unrepresentative of a reacting flow through the same geometry, and, also, that great care has to be taken over the boundary conditions to be imposed for the numerical computation of subcritical flows. 20 references.

Water Temperature as the Primary Influence on Timing of Seaward Migrations of Atlantic Salmon (Salmo salar) Smolts

Abstract: Using multiple regression models we tested if water temperature, water flow, cloudiness, and lunar cycle were significantly correlated with the timing of the yearly descent of Atlantic salmon (Salm...

Adaptive strategies of woody species in neotropical savannas

Abstract: Summary 1. In this review we discuss the adaptive strategy of woody species in tropical savannas. The low, evergreen, broadleaved, sclerophyllous tree is considered as the typical woody representative in these ecosystems. The discussion is largely based on data concerning four widespread neotropical species: Curatella americana, Byrsonima crassifolia, Bowdichia virgilioides and Casearia sylvestris, together with more fragmentary information available on other American and African savanna woody species. 2. Several types of savanna ecosystems with contrasting ecological features have to be distinguished. Our discussion refers to tree species in one of these types: seasonal savannas, that occur in a tropical wet and dry climate, with constantly high temperature, and on well-drained soils. Most of these savannas are normally burned once a year, towards the end of the dry season. 3. Woody species in seasonal savannas exhibit a quite distinctive morphology. They have low, tortuous trunks, deep and extensive root systems, relatively high R/S and L/S ratios, and large, highly scleromorphic leaves. Their annual phenodynamics appears somewhat puzzling since leaf renewal and expansion, as well as blooming, take place during the dry, apparently less favourable, part of the year. 4. Savanna trees maintain high leaf conductance throughout the year. Some species show a moderate midday decrease in leaf conductance suggesting partial stomatal closure, particularly under very high atmospheric water demands, or in young, developing leaves. However, given the steep vapour density gradient, transpiration flux density tends to be high, especially on clear dry-season days. 5. There is no drastic drop in leaf water potential, as might be expected with a high transpiration rate. The most negative values attained in either season only rarely exceed the leaf turgor loss point. This moderate fall in ψ permits leaf expansion in the dry season. Variable hydraulic resistance contributes to maintain high water flow when steep ψ gradients between soil and leaves are produced. 6. When all factors are taken into account, it seems that savanna trees maintain a favourable water budget all the year, thanks to their extensive root systems that may extract soil water from deep layers, thus allowing the maintenance of a high water flux through the soil-plant-atmosphere system even during the dry season. In this way, these trees have the least seasonal behaviour of all plant components in the seasonal savanna ecosystem. 7. Seasonal savannas occur on extremely poor, nutrient-deficient soils. As an apparent consequence of this nutrient stress, the concentration of nitrogen, phosphorus, potassium, calcium and magnesium in leaves tends to be significantly lower than in forest trees or in drought-deciduous species. 8. Two mechanisms contribute to improve the nutrient economy. One is the reallocation of absorbed nutrients between old and young tissues; the other, the minimization of nutrient losses due to low leaf wettability, low leaf cuticular conductance, and leaf renewal in the rainless season. 9. Savanna trees have low photosynthetic capacity. This is probably due to high internal resistance of leaves induced by their low nitrogen concentration. However, under field conditions rates of CO2 uptake may be maintained near their optimum because leaf conductance is high all day, and leaf temperature closely matches air temperature, remaining therefore within the optimal range for photosynthesis. 10. All in all, it appears that the physiological behaviour of savanna trees favours a continuously high water flux through the plant that, even if it lowers water-use efficiency, maintains leaf temperatures near optimum for CO2 uptake, prevents sharp drops in leaf water potential, and induces a high passive uptake of soil nutrients. In this way, the close interaction between water, carbon and nutrient economies leads to the increased fitness of these populations in the seasonal savanna environment.

Direct measurements of secondary currents in a meandering sand-bed river

Abstract: Natural channels often adopt a meandering course Water flow in meander bends is three-dimensional, consisting of primary velocities which are tangential to the bend, and secondary velocities, which are in the radial plane The pattern of secondary flow strongly affects the distribution of primary velocities This in turn affects the distribution of erosion and deposition in the bend and the way in which the channel shifts and changes shape Measurements of primary and secondary flows in a meandering gravel-bed river1,2 show that, in addition to the widely recognized main secondary circulation driving surface water outwards and bed water inwards, there can be a small cell of reverse rotation at the outer bank Further data have been collected in a sand-bedded river at low, intermediate and high discharges The results confirm the existence of the main and outer bank cells but also indicate that in some bends the main cell does not extend to the inner bank In fact, secondary flow at the inner bank of wide, shallow bends is directed radially outwards over the whole flow depth at all in-channel flows This indicates that some models of bend flow and channel development may be significantly in error

Wall-layer structure and drag reduction

Abstract: When drag-reducing additives are confined entirely to the linear sublayer of a turbulent channel flow of water, both the spanwise spacing and bursting rate of the wall-layer structure are the same as those for a water flow and there is no evidence of drag reduction. Drag reduction is measured downstream of the location where the additives injected into the sublayer begin to mix in significant quantities with the buffer region (10 y + The superscript + denotes a dimensionless quantity scaled with the kinematic viscosity ν and the wall shear velocity v * = (τ w /ρ) ½ . of the channel flow. At streamwise locations where drag reduction does occur and where the injected fluid is not yet uniformly mixed with the channel flow, the dimensionless spanwise streak spacing increases and the average bursting rate decreases. The decrease in bursting rate is larger than the corresponding increase in streak spacing. The wall-layer structure is like the structure in the flow of a homogeneous, uniformly mixed, drag-reducing solution. Thus, the additives have a direct effect on the flow processes in the buffer region and the linear sublayer appears to have a passive role in the interaction of the inner and outer portions of a turbulent wall layer.

Chapter 12 Multiple use management of public forestlands

Abstract: Publisher Summary This chapter focuses on the multiple-use management of public forestlands. The managers of these lands must, in addition to considering the value of timber harvests, consider various nonmarket amenity services, such as recreation, water flow, and wildlife, which are influenced by alterations in the standing stocks of timber. The chapter discusses research results on the relation of such multiple-use management to single-purpose timber management. The presentation is motivated by a number of issues of current concern, including (1) the withdrawal of lands from timber management, (2) the specialization or diversification of land use, (3) the level and stability of timber supply, and (4) the wisdom of certain accepted rule-of-thumb principles of public forestland management related to the age and level of harvests. The principles of public forestry in the United States have often been driven by the fear of timber shortage and the destabilizing effects on employment and prices arising from fluctuations in the supply of timber. The chapter describes the institutional setting for multiple-use management within the U.S. Forest Service.

Uptake of CO2 by aquatic vegetation

Abstract: Photosynthesis by aquatic plants based on the supply of CO2 from air-equilibrated solutions may be limited by the low diffusion coefficient of CO2 in water. For plants in which the transport of CO2 from the bulk medium is by diffusion, and the initial carboxylation uses RUBISCO, CO2 supply can be increased by growth in habitats with fast water flow over the surface (reducing unstirred layer thickness), or with heterotrophically-augmented CO2 levels, including the direct use of sediment CO2. Many aquatic plants using RUBISCO as their initial carboxylase counter the limitations on CO2 supply via the operation of biophysical CO2 concentrating mechanisms which are based on active transport of HCO−3, CO2 or H+ at the plasmalemma, and use bulk-phase HCO−3 or CO2 as the C source. A final group of aquatic plants use biochemical CO2 concentrating mechanisms based on auxiliary carboxylation by PEPc: C4-like and Crassulacean Acid Metabolism–like processes are involved. These various mechanisms for increasing CO2 supply to RUBISCO also help to offset the low specific reaction rate of aquatic plant RUBISCOs at low [CO2] and low [CO2]: [CO2]. In addition to overcoming restrictions on CO2 supply, the various methods of increasing inorganic C availability may also be important in alleviating shortages of nitrogen or photons.

Qollahuaya-Andean Body Concepts: A Topographical-Hydraulic Model of Physiology

Abstract: Ritual, pathological, and ethnopharmacological data indicate that Qollahuaya Andeans have a topographical-hydraulic model for understanding thephysiology of their bodies. Qollahuayas look to their ayllu, a mountain with three ecological levels, and its waterways for understanding their physiology. Analogously, Qollahuayas understand the body as a vertically layered axis with a system of ducts through which air, blood, fat, and water flow to and from the sonco (heart). Blood and fat, principles of life and energy, come together at the heart and flow to the members of the body in a hydraulic cycle of centripetal and centrifugal motion. The sonco is also a distillation center that combines respiratory, digestive, and reproductive functions. Within this distillation process, secondary fluids (bile, feces, gas, milk, phlegm, semen, sweat, and urine) are produced that need to be eliminated. If these fluids accumulate, they become noxious and must be purgedfrom the body with carminatives, emetics, enemas,fastings, dietary restrictions, and baths. Basically, the body is a hydraulic system with distillation, circulation, and elimination processes, which operate by the centripetal and centrifugal forces of liquids.

Analysis of River Wave Types

Abstract: In this paper we consider long-period, shallow-water waves in rivers that are a consequence of unsteady flow. River waves result from hydroelectric power generation or flow control at a dam, the breach of a dam, the formation or release of an ice jam, and rainfall-runoff processes. The Saint-Venant equations are generally used to describe river waves. Dynamic, gravity, diffusion, and kinematic river waves have been defined, each corresponding to different forms of the momentum equation and each applying to some subset of the overall range of river hydraulic properties and time scales of wave motion. However, the parameter ranges corresponding to each wave description are not well defined, and the transitions between wave types have not been explored. This paper is an investigation into these areas, which are fundamental to river wave modeling. The analysis is based on the concept that river wave behavior is determined by the balance between friction and inertia. The Saint-Venant equations are combined to form a system equation that is written in dimensionless form. The dominant terms of the system equation change with the relative magnitudes of a group of dimensionless scaling parameters that quantify the friction-inertia balance. These scaling parameters are continuous, indicating that the various river wave types and the transitions between them form a spectrum. Additional data describing the physical variability of a river and wave are incorporated into the analysis by interpreting the scaling parameters as random variables. This probabilistic interpretation provides an improved estimate of the friction-inertia balance, further insight into the continuous nature of wave transitions, and a measure of the reliability of wave type assessments near a transition. Case studies are used to define the scaling parameter ranges representing each wave type and transition and to provide data with which to evaluate the usefulness of the analysis for general application.

Oil-generating coals

Abstract: Coals are oil source rocks in many of the Tertiary basins of Southeast Asia. The precursors of these hydrogen-rich and oxygen-poor coals are coastal plain peats which have mainly developed in an everwet and tropical climate. In these environments water flow and reworking can concentrate liptinitic kerogen in preference to vitrinitic kerogen. The distribution, petrography and chemistry of the coaly Miocene source rocks present in the Kutai Basin are described. Studies of Tertiary and contemporaneous coastal plain deposits can be applied to trends in source rock distribution in offshore Norway. Comments on the environment of deposition of coaly sediments in the basins of the Norwegian Sea are discussed with reference to their possible oil and/or gas sourcing potential. The Triassic—Jurassic coals of the Haltenbanken area may become more oil-prone towards the delta margins, and facies mapping could aid oil exploration in this area.

Hand-held appliance for personal hygiene

Abstract: A hand-held appliance for mouth and tooth care with a grip portion having a manipulating element that is designed as a sliding switch and that is capable of being shifted in an axial direction. A push button is guided on inclined surfaces in the interior of the shell of the grip portion and reaches through a slot in the shell as well as through a cutout in the manipulating element. In the interior of the grip portion the push button rests on a pinch tube via a ball. The provision of the inclined surfaces results in the push button increasingly moving into the grip portion and increasingly squeezing off a pinch tube when the manipulating element is pushed forward. Independently thereof, the push button is at any given moment capable of being moved into the grip portion far enough to interrupt the water flow.

Quantifying Apoplastic Flux through Red Pine Root Systems Using Trisodium, 3-hydroxy-5,8,10-pyrenetrisulfonate

Abstract: The fluorescent compound trisodium, 3-hydroxy-5,8,10-pyrenetrisulfonate (PTS) was used to quantify the apoplastic flux through red pine (Pinus resinosa Ait.) root systems-that portion of the total water flux reaching the xylem without ever crossing a semipermeable membrane. Flow was induced by pressure through detopped root systems, and by transpiration through intact seedlings. Apoplastic flux was determined by multiplying total flux by the ratio of PTS concentration in the xylem exudate to PTS concentration in the bathing medium.Under aeration, apoplastic flux was less than 1% of total flux. Under anaerobic conditions, up to 50% of total flux was apoplastic suggesting that anaerobic conditions change the pathway of water flow into root xylem. The change under anaerobic conditions was reversible. Detopped root systems under pressure and intact seedlings under transpiration gave similar results. In detopped root systems, the magnitude of the pressure gradient may alter the apoplastic contribution to total flux.

On non-Darcian water flow in peat.

Abstract: (1) The movement of water through mires is a controlling ecological factor, since the transport of solutes by advection can dominate nutrient fluxes, determine the growth rates or survival of plants, and profoundly influence peat redox status and decomposition rates. Modelling and measuring subsurface water flows in mires requires a sound understanding of flow processes through peat. (2) The existing literature suggests that such flow violates Darcy's Law in humified peats, and casts doubt on the applicability of existing models for flow through porous media when applied to peatlands. (3) It is shown here that a large component of the reported 'non-Darcian' behaviour of peat can be explained by the elastic proporties of peat compression and the effective stress principle. We argue that Darcy's Law remains an appropriate tool for use in wetland hydrologic modelling.

Water purification and sterilization system

Abstract: A device for filtering and sterilizing potable water for household use which may be connected in the water line at a faucet or ahead of the automatic ice-making mechanism of a refrigerator. The water is purified in two stages: The first stage uses an activated carbon filter to remove solid particles, dissolved gases and colloidal particles from the water; the second state uses intensive ultraviolet radiation provided by a mercury vapor lamp to kill essentially all bacteria, viruses and any other organisms which are not trapped by the activated carbon filter. The lamp is mounted concentrically within a cylindrical tube having a water inlet at one end and an outlet at the other end, so that the water is sterilized as it passes through the annular chamber defined by the lamp and the outer wall of the cylindrical tube. A solenoid-activated shut-off valve cuts off the water flow from the device whenever a control circuit detects a failure of the lamp or a loss of line power. The filtering and sterilization process does not remove essential minerals from the water, an advantage of this device over distillation-based systems.

Water relations of white spruce (Piceaglauca (Moench) Voss) at tree line in north central Alaska

Abstract: Factors affecting xylem pressure potential and stomatal behavior during the growing season were studied on white spruce (Piceaglauca (Moench) Voss) at tree line in the central Brooks Range of northern Alaska. Leaf conductance and xylem pressure potentials were low during days of moderate and high evaporative demand, even though soil moisture was near field capacity. Boundary line diagrams, regression analysis, and laboratory experiments indicate that stomata are sensitive to changes in vapor pressure deficit and xylem pressure potential. A correlation between resistance to water flow through the tree and soil temperature suggests that soil temperatures less than 9 °C are associated with increased resistance to water flow and may partially explain the position of white spruce tree line in northern Alaska.

Determination of sap flow in Douglas-fir trees using the heat pulse technique

Abstract: A modified heat pulse technique was used to determine volumetric sap flow in 15–17 m tall Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees. Laboratory calibration of the heat pulse technique, accomplished by passing water through 200 mm long by 77 mm diameter stem sections with a gas pressure apparatus, showed an underestimation of the actual water flow rate by 47%. Using a six-thermistor temperature sensing probe inserted radially to a depth of 60 mm, field measurements of sap flux density were found to change with depth into the sap wood. Simultaneous measurements using the temperature sensing probes inserted in three azimuthal directions (0, 120, and 240°) showed good agreement during the daytime in three trees, while in another tree the ratio of the three sap flux densities gradually changed during the daytime. Hourly values of sap flow rate in two different trees, obtained using the laboratory calibration factor were 29 and 53% larger than corresponding foliar transpiration rates estimated usi...

The Role of Specific Yield in Ground-Water Recharge Estimations: A Numerical Study

Abstract: This paper numerically demonstrates and quantifies the importance of capillary-fringe and variable specific yield phenomena in ground-water recharge estimations. A one-dimensional numerical experiment consisting of a soil either with a capillary fringe or without it was set up using a finite-element code. A prescribed infiltrating flux was superimposed on top of the soil column, and the resulting unsaturated-saturated water flow was observed. By assuming a single value for specific yield, recharge is usually overestimated. For two cases considered in this study, the errors involved in ground-water recharge estimations by using such an assumption ranged from 88 to 330 times the simulated recharge, when variable specific yield is considered. This study also clearly demonstrates the effect of a constant specific yield value on the behavior of the water table rise, the total amount of which as well as the rate of such rise are underestimated under that assumption. In addition, under that assumption, the timing of the water table rise is out of phase with the timing of recharge events.

Washing machine with a turbidimeter and method of operating the same

Abstract: A washing machine uses a turbidimeter to measure turbidity of cleaning water for controlling the duration of its washing and cleaning cycles. Quality of this control is improved by taking measurements when the water flow is weak so that the effects of foams are negligible and waiting until turbidity drops at the beginning of the cycle to detect the initial value used in subsequent steps. Sensitivity of the turbidimeter is automatically adjusted for accuracy when the operation is temporarily stopped and restarted during a cycle.

Self-fill system

Abstract: In connection with a beverage dispensing machine, an automatic self-fill control apparatus for the machine for controlling the filling of the liquid tank, which liquid tank is fed with a combination of water and a concentrate syrup adapted to be mixed with the water within the tank. A sensor member is disposed in the tank in a position so as to be responsive to the rise and fall of liquid in the tank. Pump means are provided adapted to pump the syrup to the tank. Control of water flow to the tank is also carried out. The sensor member has a low probe for detecting a low predetermined level of liquid in the tank and a high probe for detecting a high predetermined level of liquid in the tank and adapted to respectively generate low and high probe signals. Control circuit means is provided receiving and responsive to these low and high probe signals for controlling the pump to operate when the low probe is uncovered and terminating the pumping action when the liquid level reaches the high probe position so that the liquid level in the tank is always maintained at a level between the low and high probes. Also provided is a third sensor for determining an unsafe condition referred to herein as a system override to shut the system down in the event that the high probe is covered and that the liquid level proceeds to the even higher third probe. Also in the system of the present invention, there is provided a sensor for detecting an out-of-syrup condition.

Numerical studies of the spectrum of low‐intensity ultrasound scattered by bubbles

Abstract: The magnitude of the nonlinear effect in the scattering of ultrasound by nitrogen bubbles in water is examined numerically, for ultrasonic frequencies and amplitudes typical of diagnostic medical devices, to determine the suitability of this effect for the detection of bubbles in blood or tissue for application in decompression research. Numerical solutions of the modified ‘‘Rayleigh’’ equation, including the effects of acoustic, thermal, and viscous damping, and the dependence of the polytropic exponent on frequency are presented for pulsed ultrasound. For the chosen conditions, it is shown that nonlinear scattering is significant only for the population of bubbles which are smaller than, or close to, resonance size, and primarily for those bubbles that are one‐half resonance size.