Total Mass Flux Research Articles

Observations of the 1996 Leonid meteor shower by radar, visual and video techniques

The activity of the 1996 Leonid shower from two radars, global visual and single-station low-light-level TV (LLTV) observations is presented and summarized. Radar observations from Ondřejov in the Czech Republic indicate a peak rate of (>+1) Leonids near λ⊙ = 235°2±0.1 (Equinox 2000). As observed by this radar, this peak interval was characterized by a significant increase in the number of bright Leonids as demonstrated by a noticeable lowering of the mass index near the peak. From radar observations in Ontario, Canada (using the CLOVAR system), a raw peak flux of 1.3±0.3×10−2 meteoroid km−2 h−1 brighter than radio magnitude +7.7 was reached at λ⊙ = 235°3±0.1, uncorrected for initial train radius effects. Single-station LLTV observations suggest a peak shower flux of 1.8±0.4×10−2 meteoroid km−2 h−1 brighter than absolute magnitude +5±0.5 between 235°3 and 235°39. The position of the radiant on the night of maximum of the shower is found to be α=152°9±1°0 and δ=22°1±1°0 from CLOVAR observations and α=153°3±1°7 and δ=22°1±1°7 from LLTV observations. Visual observations of the shower yield a peak zenithal hourly rate (ZHR) of 86±22 at 235°17±0°07 or an equivalent flux of 1.2±0.4×10−2 meteoroid km−2 h−1 brighter than absolute visual magnitude +6.5. The visual peak was short-lived (1.5 ± 0.5 h HWHM) and richer in fainter meteors than neighbouring intervals. Discrepancies in the estimated absolute Leonid flux found using differing methods are noted and possible reasons for the differences discussed. The stream in 1996 showed two distinct meteoroid populations: a population of recently ejected meteoroids rich in smaller particles near 235°17 which is very narrow in nodal extent (HWHM 0°07±0°02), and an older component (of order 10 revolutions in age) peaking near 235°4 which is rich in larger stream meteoroids, of long duration (FWHM 1°2 ±0°4), which contributed most to the total mass flux at Earth from the stream in 1996.

Sources of variability in geographical and seasonal differences in particulate fluxes from short-term sediment trap deployments, east of New Zealand

Free-floating sediment traps were used to measure total mass and particulate phosphorus fluxes from the upper ocean (>100–550 m) at two stations in each of three water types (subantarctic, Subtropical Convergence and subtropical), east of New Zealand, in winter and spring 1993. Despite marked changes in ecosystem community structure and function between water types and occasionally between stations, there were no significant differences in export flux either across water masses, between stations or with increasing water depth. One exception was in the Subtropical Convergence where significant increases in particulate flux with depth at one station in spring are inferred to be caused by tidal current resuspension of bottom sediments on the crest of the Chatham Rise. High degrees of variation between mass fluxes calculated from individual cylinders observed in winter (coefficients of variation ranging from 10 to 123%) may have been due to inter-trap hydrodynamic interactions or sample processing errors. In spring, overall coefficients of variation of mass flux were smaller than in winter (6–87%), but variations due solely to sub-sampling procedures were significant (<1–83%). The ranges of variability for the New Zealand traps are similar to other published sediment trap studies, suggesting that the use of single, free-floating sediment trap arrays to characterise fluxes for specific oceanic provinces is unlikely to be valid statistically. Based on the results from east of New Zealand, more than two arrays would be required to improve the power of the chosen statistical test in order to determine significant differences in particulate flux between physically and biologically distinctive oceanic water masses.

Short term variability of Particle fluxes and its relation to variability in sea surface temperature and chlorophylla field detected by Ocean Color and Temperature Scanner (OCTS) off Sanriku, northwestern North Pacific in the spring of 1997

A sediment trap experiment was carried out in conjunction with an over flight of Ocean Color Temperature Scanner (OCTS) on board Advanced Earth Observing Satellite (ADEOS) at 40°N, 143°E off Sanriku in April to May 1997. Short term variability of particle fluxes was examined at depths of 450 m and 600 m from April 6 to May 1 with a sampling interval of two days, and at 450 m with one day interval from 2nd to 10th May. Daily averaged mass flux at 450 m and 600 m was 815 mg m−2d−1 and 862 mg m−2d−1, respectively. A sharp increase in mass flux was observed during the period from April 26 to April 29 with the highest mass flux of 8 g m−2d−1. About 85% of the total mass flux for the entire duration (26 days) was collected within these 4 days. Trapped material during the peak flux period was mainly composed of diatoms dominated byThalassiosira spp. and resting spores ofChaetoceros spp. This suggested that the peak flux was the result of (a) diatom bloom(s) in the euphotic column. Current meter records at 420 m showed that on April 26 and 27, the period when the peak flux was observed, the southwestward current had diminished in strength and changed its direction northwestward. Low current speeds appeared to have enhanced trap efficiency to help form the peak flux. A time series of OCTS Intensive-LAC (Local Area Coverage: Region B) images from mid-March to early May was examined todetect phytoplankton bloom(s). In the March 26th Chl image, high concentration region was restricted to the southwest off Cape Erimo, but spread around the warm core ring (WCR) 93A by April 10. East of the WCR93A, high Chl concentration remained steady until May, but to the west of the WCR93A, Chl decreased rapidly before the 19th of April. From this observation we suspect that the peak flux observed at the end of April originated from a bloom, which ceased on the 17th or 18th of April, in the region north of 40°N and west of 143°E. Taking the current meter records into account, the source region for the trapped material is most likely around southwest of the Cape Erimo.

Seasonal and vertical variations of sinking particle fluxes in the West Caroline Basin

A sediment trap experiment was carried out in the West Caroline Basin, located in the equatorial western Pacific between influences of the Asian monsoon and the open ocean. Annual mass flux at the shallow trap at Site 1 was 57.10 g m -2 yr -1. Generally, the higher flux of organic matter was associated with higher activities of biogenic opal-producing and carbonate-producing plankton communities. In addition, as the organic matter content increases, the organic carbon/carbonate carbon ratio shows a tendency to increase. Carbonate-producing plankton was predominant during periods 1 and 3 (May to July and November to the beginning of December), which could be due to limited silica supply to the euphotic zone. On the other hand, surface sea water was more nutrient-rich during periods 2 and 4 (August to October and the end of December to April) at Site 1. These high total mass fluxes could be stimulated by wind. The amount of biogenic components collected in the sediment traps and the accumulation in surface sediments at Site 1 could be compared with primary productivity values. Carbonate and biogenic opal fluxes were 99% and 90% less, respectively, in the surface sediments compared to those in the shallow sediment trap. This could be due to the reaction of sinking particles with undersaturated deep sea water just above the sea floor, rather than with the water column during sinking. About 20% of the organic matter was decomposed between the shallow and deep sediment traps and more than 98% between the deep sediment trap and final burial in the surface sediments. The relative amount of organic carbon preserved in surface sediments was about 0.10% of annual primary productivity.

Temporal variability and composition of settling particle fluxes on the Barcelona continental margin (Northwestern Mediterranean)

The results of a year-long sediment-trap experiment provide the first direct observations of sediment fluxes to the seafloor on the Barcelona continental margin. Time-series of vertical particle fluxes and major constituents (organic carbon, biogenic silica, calcium carbonate and aluminosilicates) were determined inside and in the vicinity of the Foix submarine canyon from May 1993 to April 1994. The spatial and temporal variability of bi-weekly total mass fluxes indicate significant high frequency variability related to physical and biological processes at this site. The Foix submarine canyon acts as an actual conduit for transport of sediment from the shelf to the slope, and as a mid-slope sedimentary depocenter. The shelf-slope sediment transfer through this canyon is sporadic and takes place during and immediately after an important storm event or a river discharge increase. During periods of low cross-margin sediment transfer injected through the canyon, the vertical flux of particles is controlled by the along-slope geostrophic circulation. Breaking of the summer water stratification and vertical mixing also appears to be a major process which contributes to increasing the vertical flux of particles. Particle composition inside the Foix submarine canyon does not reflect any significant seasonal variations, but in the adjacent open slope, summer water stratification controls the composition of settling particulate matter. Retention of shelf-derived suspended particles along isopycnals in summer results in a decrease in total mass fluxes and an enrichment of organic carbon and clay mineral content in the settling particulate matter outside the canyon. During the spring biological bloom, the opal content increases particularly on the open slope, but the calcium carbonate does not because the high input of terrigeneous carbonate dominates that from biogenic carbonate production. The aluminosilicates fraction is the largest constituent of the vertical particle fluxes on the Barcelona continental margin, reaching higher percentages inside the Foix submarine canyon.

Mass transfer during gas absorption in a vertical gas-liquid slug flow with small bubbles in liquid plugs

A model is developed for the analysis of mass transfer during isothermal absorption in a vertical gas-liquid slug flow at large Reynolds numbers with liquid plugs containing small bubbles. Simple formulas for mass flux from the N-th unit cell of gas-liquid slug flow and for total mass flux from N unit cells are derived. In the limiting case the derived formulas for mass transfer during gas absorption in a slug flow with liquid plugs containing small bubbles recover the derived expressions for mass transfer in slug flow without small bubbles in the liquid plugs. Using the developed model recommendations concerning the design of the absorber operating in a slug flow regime are suggested.

A Finite-Volume Algorithm for Three-Dimensional Magnetohydrodynamics on an Unstructured, Adaptive Grid in Axially Symmetric Geometry

A new finite-volume algorithm for the solution of the time-dependent, nonideal magnetohydrodynamic (MHD) equations in cylindrical (r, φ,z) geometry is presented. The boundary geometry is assumed to be axially symmetric, but it can have arbitrary shape and connectivity in the poloidal (r,z) plane. The dynamics of the fluid is fully three-dimensional. A two-dimensional, unstructured, adaptive grid of triangles is used to describe the poloidal geometry. A pseudospectral algorithm with fast Fourier transforms is used for the periodic toroidal (φ) direction. The grid can be dynamically refined or coarsened by adding or deleting points to adapt to evolving fine-scale structures in the solution. The algorithm exactly conserves total mass, momentum, energy, and magnetic flux, and identically preserves the solenoidal properties of the magnetic field and the current density. Examples of the application of the algorithm to two-dimensional hydrodynamic and MHD shocks, the linear growth of a resistive tearing instability in a tokamak, and the linear growth and nonlinear saturation of three-dimensional kink instabilities in toroidal geometry are given.

Relation of vertical flux of particles smaller than 10 μm to total aeolian horizontal mass flux at Owens Lake

The vertical flux of particles smaller than 10 μm for a saline playa surface, the particle size composition of which was classified as loam‐textured, was estimated for a highly wind‐erodible site on the playa of Owens (dry) Lake in California. The ratio of this vertical flux to the horizontal flux of total airborne material through a surface perpendicular to the soil and to the wind, Fa/qtot, is 2.75×10−4 m−1. This is consistent with that ratio for sand‐textured soils and suggests that the binding energy and size of saltating particles for the tested surface material at Owens Lake is of the same order as that for sandier soils. The horizontal mass flux of saltating grains, q, in the reported wind erosion event is 51.3% of the total horizontal mass flux qtot. Therefore the ratio of Fa/q is 5.4×10−4 m−1.

Large‐scale variability of wind erosion mass flux rates at Owens Lake: 1. Vertical profiles of horizontal mass fluxes of wind‐eroded particles with diameter greater than 50 μm

A field experiment at Owens (dry) Lake, California, tested whether and how the relative profiles of airborne horizontal mass fluxes for &gt;50‐μm wind‐eroded particles changed with friction velocity. The horizontal mass flux at almost all measured heights increased proportionally to the cube of friction velocity above an apparent threshold friction velocity for all sediment tested and increased with height except at one coarse‐sand site where the relative horizontal mass flux profile did not change with friction velocity. Size distributions for long‐time‐averaged horizontal mass flux samples showed a saltation layer from the surface to a height between 30 and 50 cm, above which suspended particles dominate. Measurements from a large dust source area on a line parallel to the wind showed that even though the saltation flux reached equilibrium ∼650 m downwind of the starting point of erosion, weakly suspended particles were still input into the atmosphere 1567 m downwind of the starting point; thus the saltating fraction of the total mass flux decreased after 650 m. The scale length difference and ratio of 70/30 suspended mass flux to saltation mass flux at the farthest down wind sampling site confirm that suspended particles are very important for mass budgets in large source areas and that saltation mass flux can be a variable fraction of total horizontal mass flux for soils with a substantial fraction of &lt;100‐μm particles.

Optimization of gas hydrate reactors with slug flow

A model of heat transfer during gas hydrate formation at a gas-liquid interface in gas-liquid slug flow with liquid plugs containing small bubbles is suggested. Under the assumption of perfect mixing of liquid in liquid plugs, recurrent relations for temperature in the n-th liquid plug and heat and mass fluxes from the n-th unit cell in a gas-liquid slug flow are derived. The ratio of the total mass flux during gas hydrate formation in a cluster with N unit cells to the mass flux in a cluster with an infinite number of unit cells is determined. The number of unit cells that yield 95% of the total amount of gas hydrates in an infinite cluster of unit cells is calculated and formula for an optimal length of a gas hydrate slug flow reactor is derived.

Monitoring and modeling the mass, heavy metal and ion species dry deposition in central Taiwan

Dry deposition flux and particle concentration of mass, Ca2+, Mg2+, Cl− and SO4 2‐were measured by dry deposition plates and NRI (Noll Rotary Impactor), MOUDI (Micro‐Orifice Uniform Deposit Impactor), respectively in the ambient air of Chung‐Hsing University and Tung‐Hai University in central Taiwan from November 1995 to January 1996. AAA‐680/G flame atomic absorption spectrophotometer was used to measure the metals Ca2+ and Mg2+ and a I. C. (DIONEX DX‐100 Ion Chromatography) was used to measure the ions Cl− and SO4 2‐ species. The CHU sampling site was divided into two parts to discuss the influence of coarse particle on the concentration and deposition velocities. The average mass concentration (without NRI sampler) for thefine and coarse particles were 21.6, 23.8 and 19.8, 21.6 μg/m3 in CHU and THU sampling site, respectively. By the same token, the average mass concentration (with NRI sampler) for the fine and coarse particles were 26.4 and 30.9 μg/m3 in CHU sampling site, separately. The results indicated that the average deposition velocities were 1.34, 1.11, 1.19, 0.11 and 0.27 (cm/sec) for mass, Ca2+, Mg2+, Cl− and SO4 2‐, respectively in CHU area with NRI sampler. And the results also displayed the average deposition velocities were 1.58, 1.23, 1.64, 0.52 and 0.58 (cm/sec) for mass, Ca2+, Mg2+, Cl− and SO4 2‐, separately in CHU sampling site without NRI sampler. The deposition velocities were 3.93, 2.69 and 2.23 (cm/sec) for mass, Ca2+ and Mg2+, respectively in THU sampling site without NRI sampler. Thus, this study showed that the coarse particle did have significant influence on the urban and suburban area of central Taiwan. In the ambient air of CHU the correlation coefficient of average wind speed with average mass flux (R2) is 0.65 This phenomena can be further verified by the sampling site of THU (R2 = 0.76). The results indicated that fine particles (dp < 2.5 μm) occupied only about 4.65% and 7.20% for mass in CHU and THU sampling site, respectively. The calculated dry deposition coarse particle flux (dp > 2.5 μm) is much higher than dry deposition fine particle flux for mass even though the concentration distribution for the coarse and fine particle are insignificantly different. The calculated results displayed coarse particle occupied the majority (> 91.6%) of the total dry deposition in either urban or suburban area for mass, metal (Ca2+, Mg2+) and ions (Cl−, SO4 2‐). The correlation coefficient (R2) of total mass flux and coarse / fine particle concentration are 0.76 and 0.076, separately. And the results suggest that the magnitude of the flux is strongly dependent on coarse particle concentration and independent of the fine particle concentration.

Modeling convection/diffusion processes in porous textiles with inclusion of humidity-dependent air permeability

A set of partial differential equations describing time-dependent heat and mass transfer through porous hygroscopic materials was developed. Water in a hygroscopic porous solid may exist in vapor or liquid form in the pore spaces or in bound form when it has been absorbed by the solid, which is typically some kind of hydrophilic polymer. Factors such as the swelling of the solid due to water imbibition, and the heat of sorption evolved when the water is absorbed by the polymeric matrix, were incorporated into the appropriate conservation and transport equations. A numerical code to solve the set of nonlinear coupled equations was developed, and applied to an experimental apparatus designed to simulate transient and steady-state convection/diffusion conditions for textile materials. Experimental measurements of air permeability and diffusion properties as a function of relative humidity provided fundamental data on the changes in transport properties as hygroscopic textiles fibers swell and decrease the free gas phase volume within the porous structure. When these relations were incorporated into the numerical model, it was possible to directly compare the predictions of the numerical code with results generated in the experimental apparatus. Results are shown for hygroscopic porous textiles under several conditions. Under pure diffusion, with no convective flows across the sample, the temperature changes of hygroscopic textiles subjected to step changes in environmental relative humidity are shown to agree with the numerical predictions. These temperature changes are due to sorption of water vapor from the flows on the two sides of the material, and relate to textile fiber equilibrium sorption isotherms and sorption kinetics, as well as the physical structure and thermal properties of the textile. Under conditions of both a concentration gradient and a pressure gradient across the fabric, which results in combined diffusion and convection, it is shown that the effect of fiber swelling, which results in significant changes in the resistance to convective flow, also has an effect on the resulting total mass flux across the textile layer.

Steady-state performance in a thermosyphon with tube separator

A one-dimensional steady-state mathematical model describing natural circulation two-phase flow in a thermosyphon with tube separator is presented. The theoretical results show that a single liquid region in the lower part of the evaporator is available if the heat rate and operating temperature are low. At high performance operations the total mass flux changes weakly with variations in the operating temperature and heat rate. Void fraction distributions along the thermosyphon length are obtained under various operating conditions. Liquid fill ratios for steady flow are suggested.

Short‐term sediment trap fluxes from Chatham Rise, southwest Pacific Ocean

Sediment trap, nephelometer, and particulate matter (PM) data were collected in the vicinity of the Subtropical Convergence, north of Chatham Rise (42–43°S), southwest Pacific Ocean, in austral autumn 1992. Free‐floating cylindrical sediment traps were deployed below the euphotic zone at 200‐, 300‐, and 500‐m water depths. Increases in total mass flux and concomitant proportional decreases in other particulate fluxes (total carbon, nitrogen, and phosphorus) with depth reflected the collection of relatively refractory material, enriched in particulate carbon, as evinced by increases in C: N and C: P ratios below 300 m. Nephelometer and PM concentration profiles indicate that resuspension of sea‐floor sediments from the nearby submarine high (Chatham Rise) probably contributed to the observed increase in total mass flux with depth. Published pCO2 estimates, biological productivity data, and moderate particulate fluxes, as indicated by the present study suggest that oceanic water types east of New Zealand may be a biologically mediated regional sink for atmospheric CO2.

5593496 Slurry crystallization method using bubbles directed at a heat exchanger

A one-dimensional steady-state mathematical model describing natural circulation two-phase flow in a thermosyphon with tube separator is presented. The theoretical results show that a single liquid region in the lower part of the evaporator is available if the heat rate and operating temperature are low. At high performance operations the total mass flux changes weakly with variations in the operating temperature and heat rate. Void fraction distributions along the thermosyphon length are obtained under various operating conditions. Liquid fill ratios for steady flow are suggested.

SIMULATION OF WIND FORCES AND EROSION IN A FIELD WITH WINDBREAKS

A series of vegetative windbreaks across a field will reduce wind velocities near the surface, thus reducing the capacity of the wind to transport soil particles.The height, width, and projected stem and leaf surface area of windbreaks will determine the reduction in wind velocity and wind erosion. The objective of this study was to develop a model to assist in the design of barrier systems by considering the total mass flux of saltating particles across a uniform field consisting of a series of windbreaks. By assuming that the net force available to entrain grains varies linearly with total mass flux, a one-dimensional steady state equation is derived to predict the entrainment rate of saltation-sized particles across a field with windbreaks. Deposition of saltating particles is assumed to be a function of the mean trajectory length. The total mass flux of saltating particles is predicted for a series of sorghum windbreaks. For agricultural fields, the principal benefit of windbreaks is to reduce the total mass flux of saltating particles across a field since this would lead to the decreased emission of suspendible particles. For the field simulated in this study, the projected surface area of plant material and windbreak height, orientation, and width strongly influenced the predicted saltation flux and maximum deposition. The model also predicts a decrease in field-averaged saltation flux with decreasing barrier porosities and that, in a given field, a series of many short windbreaks is more effective in reducing saltation flux than a series of a few tall windbreaks.

Development of Cellulose Acetate Propionate Membrane for Separation of Ethanol and Ethyl tert-Butyl Ether Mixtures

For pervaporation separation of ethanol and ethyl tert-butyl ether mixtures, a cellulose acetate propionate membrane was chosen as the experimental membrane because of its high selectivity and good mass fluxes. The properties of the membranes were evaluated by the pervaporation separation of mixtures of ethyl tert-butyl ether/ethanol and the sorption experiments. The experimental results showed that the selectivity and the permeates depend on the ethanol concentration in the feed and the experimental temperature. With increases of the ethanol weight fraction in the feed and the temperature, the total and partial mass fluxes increased. With respect to the temperature, ethanol mass flux obeys the Arrhenius equation. The selectivity of this membrane decreases as the temperature and the ethanol concentration in the feed increase. This membrane shows special characteristics at the azeotropic composition. In the vicinity of the azeotropic point, minimum values of ethanol concentration in the permeate and in sorption solution are obtained. The swelling ratios increase when temperature and the ethanol concentration in the feed are increasing. The ethanol concentration in the sorption solution is also influenced by the temperature and the mixture's composition. When the temperature increases, the sorption selectivity of the membrane decreases.

Changes in the composition of fatty acids in sinking matter during a diatom bloom in a controlled experimental ecosystem

A controlled experimental ecosystem (CEE) was set-up in Saanich Inlet, British Columbia, Canada during the summer of 1986. A mixed phytoplankton bloom (predominated by diatoms) which rapidly resulted after addition of nutrients at the commencement of the experiment, led to high fluxes of total mass and organic carbon to the bottom of the CEE. Suspended particles settling to the bottom of the bag were collected from time to time and analysed for their fatty acids, particulate organic carbon and particulate organic nitrogen content. Fluxes of fatty acids were high when the bloom was in its exponential phase of growth whereas organic carbon increased when the bloom was in its decay phase. The major fatty acids were C14:0, tC16:0 and C16:1, but the overall composition of fatty acids changed extensively as growth of the bloom progressed. The fatty acid C20:5, for example, a characteristic of diatoms, increased rapidly and reached its maximum when the bloom attained its peak. On the other hand, C20:3 acid tended to increase towards the end of the bloom when nutrients in the water column of the CEE were already depleted and nanoflagellates dominated. These systematic changes in the abundance of C20:5 and C20:3 as well as those in the ratios of unsaturated fatty acids (UFA) to saturated fatty acids (SAFA) from the onset of the bloom until its end, suggest that the composition of fatty acids in sinking particles could serve as a useful biological indicator of diatom growth and ecophysiological state of the overlying diatom community.

Mathematical Modelling of the Primary and Secondary Drying Stages of Bulk Solution Freeze-Drying in Trays: Parameter Estimation and Model Discrimination by Comparison of Theoretical Results With Experimental Data

ABSTRACT A mathematical model was constructed and solved in order to describe quantitatively the dynamic behavior of the primary and secondary drying stages of the freeze-drying of pharmaceuticals in trays. The theoretical results were compared with the experimental data of the freeze-drying of skim milk, and the agreement between the experimental data and the theoretical results is good. Detailed model calculations have indicated that the contribution of the removal of hound (unfrozen) water to the total mass flux of the water removed during primary drying, is not significant. For this reason, it was found that one could not

Large-Scale Recirculation of Air over Southern Africa

Abstract Kinematic air parcel trajectory analysis is used to determine patterns of horizontal air transport in 2000 km × 2000 km areas over southern Africa. From these, composite zonal and meridional transport fields are derived for the subcontinent to estimate the extent to which recirculation of air and aerosols may take place in the lower troposphere between the surface and 500 hPa. The nature and degree of recirculation beneath the persistent 500-hPa absolutely stable layer is demonstrated, and transport by recirculation in discrete streams is shown to constitute 44% of the total transport over the region. From a determination of air volume fluxes and estimates of aerosol concentrations, the total mass flux of aerosols by direct transport and by recirculation in conditions during which semipermanent, subtropical, continental anticyclones prevail is estimated to be about 51 Mton yr−1 in the surface-to-hPa layer. Recirculation comprises approximately 22 Mton yr−1 of this amount. Of the recirculated tran...