Suspended Mass Research Articles

Near-source observations of aerosol size distributions in the eruptive plumes from Eyjafjallajökull volcano, March–April 2010

Near-source observations of aerosol size distributions ( 1 [mu]m) ash particles. The number ratio of fine and coarse particles fluctuated strongly within short intervals of time, indicative of changes in the fragmentation energy. The near-source ash fallout was poorly sorted (interquartile range 16-80 [mu]m); ash grains sized <1 [mu]m contributed up to 7% of total volume. The high water content and electrical charge in the plume are believed to have enhanced the deposition through particle aggregation. In Phase III the eruption became drier and less explosive. The suspended aerosol mass was strongly bimodal with high particle abundances at ~0.2 and 1-4 [mu]m. The ash fallout was better sorted (interquartile range 60-120 [mu]m; no grains <1 [mu]m), attributed to limited particle aggregation.

Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer

[1] The goal of this study was to test the hypothesis that the aggregated state of natural marine particles constrains the sensitivity of optical beam attenuation to particle size. An instrumented bottom tripod was deployed at the 12-m node of the Martha's Vineyard Coastal Observatory to monitor particle size distributions, particle size-versus-settling-velocity relationships, and the beam attenuation coefficient (cp) in the bottom boundary layer in September 2007. An automated in situ filtration system on the tripod collected 24 direct estimates of suspended particulate mass (SPM) during each of five deployments. On a sampling interval of 5 min, data from a Sequoia Scientific LISST 100x Type B were merged with data from a digital floc camera to generate suspended particle volume size distributions spanning diameters from approximately 2 μm to 4 cm. Diameter-dependent densities were calculated from size-versus-settling-velocity data, allowing conversion of the volume size distributions to mass distributions, which were used to estimate SPM every 5 min. Estimated SPM and measured cp from the LISST 100x were linearly correlated throughout the experiment, despite wide variations in particle size. The slope of the line, which is the ratio of cp to SPM, was 0.22 g m−2. Individual estimates of cp:SPM were between 0.2 and 0.4 g m−2 for volumetric median particle diameters ranging from 10 to 150 μm. The wide range of values in cp:SPM in the literature likely results from three factors capable of producing factor-of-two variability in the ratio: particle size, particle composition, and the finite acceptance angle of commercial beam-transmissometers.

Sodium Aerosol Studies for Fast Reactor Safety

Abstract Generation and characterization of sodium aerosols contribute significantly towards safety studies of fast reactors and it is useful to assess the environmental source term. The characterization include both chemical and physical characteristics of sodium aerosols that are generated in the case of release of hot sodium into the atmosphere and causing sodium fire which causes dense sodium fumes. In IGCAR, an aerosol test facility, having 1 m3 volume with controlled humidity for carrying out physical and chemical characteristics of sodium aerosols, is in operation. In this paper the suspended mass concentration of sodium aerosols inside the closed environment (inside the aerosol chamber) and its theoretical predictions are presented. The experimental results are used for the theoretical determination of suspended mass concentration of sodium aerosols inside RCB in the case of CDA, using HAARM code and these results are also presented.

In-situ estimations of the density and porosity of flocs of varying sizes in a submarine canyon

This paper introduces a new method to estimate in-situ floc density and porosity of three particle-size classes: 0.45–10, 10–63 and, 63–250 μm. LISST-100 and CatNet (a novel on-board filtration system of nested filters) were used to measure suspended particle volume and mass concentrations of 32 and 3 size-classes, respectively. Two field experiments were conducted in 2004 and 2006 in the head region of Gaoping Submarine Canyon (GPSC) to test this method. In each experiment CTD and LISST-100 profiling and simultaneous water sampling were carried out on board R/V Ocean Research III. In 2004, the water samples were filtered in the laboratory after the cruise using traditional methods. CatNet was used in 2006 and the seawater filtration was done on board. Assuming the observed suspended particles were all flocs composed of primary particles (with assumed density of 2.65 g/cm 3) and interstitial water (with assumed density of 1.025 g/cm 3) we estimated the volume of primary particles. The volume difference between flocs (measured from LISST-100) and primary particles is the interstitial pore space in flocs. Subsequently, the porosity of a floc particle is the ratio of the volume of the interstitial pore space to that of the floc particle. Results for 2004 show erroneous values of estimated floc porosities, which do not appear in 2006. The major difference is that the seawater was filtered immediately on board using CatNet in 2006. After removing erroneous data related to after-cruise filtering, the averaged floc porosity and density in the three grain-size classes were 47.0, 64.0, 85.9% and 1.89, 1.61, 1.25 g/cm 3, respectively. There is a trend that larger particles have lower density, which is supported by literature. The temporal variations of floc density and porosity of all three particle-size groups were larger in the surface than near the bottom of the submarine canyon. This vertical variability resulted from flocculation and biogenic processes in the surface of the coastal ocean, and the terrestrial source of the Gaoping River. Floc density is an important physical parameter to evaluate the settling flux of suspended sediments in estuarine and marine environments. This approach provides direct in-situ floc bulk densities of different grain-size classes, which has advantages over conventional methods.

Fully three-dimensional analysis of high-speed train–track–soil-structure dynamic interaction

In this paper, a general and fully three dimensional multi-body-finite element-boundary element model, formulated in the time domain to predict vibrations due to train passage at the vehicle, the track and the free field, is presented. The vehicle is modelled as a multi-body system and, therefore, the quasi-static and the dynamic excitation mechanisms due to train passage can be considered. The track is modelled using finite elements. The soil is considered as a homogeneous half-space by the boundary element method. This methodology could be used to take into account local soil discontinuities, underground constructions such as underpasses, and coupling with nearby structures that break the uniformity of the geometry along the track line. The nonlinear behaviour of the structures could be also considered. In the present paper, in order to test the model, vibrations induced by high-speed train passage are evaluated for a ballasted track. The quasi-static and dynamic load components are studied and the influence of the suspended mass on the vertical loads is analyzed. The numerical model is validated by comparison with experimental records from two HST lines. Finally, the dynamic behaviour of a transition zone between a ballast track and a slab track is analyzed and the obtained results from the proposed model are compared with those obtained from a model with invariant geometry with respect to the track direction.

Characterization of silver–gallium nanowires for force and mass sensing applications

We investigate the mechanical properties of cantilevered silver–gallium (Ag2Ga) nanowires using laser Doppler vibrometry. From measurements of the resonantfrequencies and associated operating deflection shapes, we demonstrate that theseAg2Ga nanowires behave as ideal Euler–Bernoulli beams. Furthermore, radial asymmetriesin these nanowires are detected through high resolution measurements of thevibration spectra. These crystalline nanowires possess many ideal characteristics fornanoscale force and mass sensing, including small spring constants (as low as10 − 4 N m − 1), high frequency bandwidth with resonance frequencies in the0.02–10 MHz range, small suspended mass (picograms), and relatively highQ-factors(∼2–50) under ambient conditions. We evaluate the utility ofAg2Ga nanowires for nanocantilever applications, including ultrasmall mass and high frequencybandwidth piconewton force detection.

Spatially distributed modeling of surface water flow dynamics in the Everglades ridge and slough landscape

Summary A two-dimensional, spatially distributed flow dynamics model was developed and tested for a 1.5 by 4 km area of the patterned ridge and slough landscape of the Florida Everglades. This model is intended to support a deepened understanding of the system ecohydrological dynamics, and provide a useful tool for management decision support. The model was constructed with a fine enough mesh structure to ensure proper representation of ridge and slough topographic detail as well as capture local hydrologic influences. Upstream and downstream stage data collected near the study area in central Water Conservation Area 3A were used to establish the initial and boundary conditions. Water velocities measured in the ridges and sloughs over a 3-year period were used to calibrate and verify the model. Hydraulic resistance was computed using a power-law relationship with water depth. The simulated water levels, water depths, and flow velocities showed good agreement with the 3-year field-monitored data with percent model errors of approximately 4%, 12%, and 10%, respectively. Computed differences in hydraulic resistance between ridge and slough were reduced significantly during the storm season compared to the dry season. This suggests that more solute and suspended solid mass can be redistributed from the sloughs to the ridges in particular during wet seasons, due to the weakened heterogeneity of hydraulic resistance during high flows.

Influence of talc concentration in oil lubricant on the wear response of a bronze journal bearing

This study pertains to the examination of the effects of dispersing talc particles in an oil lubricant towards controlling the sliding wear characteristics of a journal bearing (bush) fabricated using a leaded-tin bronze. Influence of the content of the suspended mass in the oil and applied load on the wear behavior was also investigated. Properties evaluated were wear loss, frictional heating and friction coefficient. Addition of talc particles to the oil lubricant decreased the wear loss, frictional heating and friction coefficient while the applied load produced a reverse effect. Further, increasing content of talc up to 3–5% led to a decrease in the observed properties; the trend reversed at higher concentrations of the suspended mass in the oil. The increasing test duration caused the frictional heating and friction coefficient to increase at a high rate initially. The rate of increase lowered down at longer test durations. The observed wear behavior of the samples has been substantiated through the characteristics of wear surfaces and subsurface regions. The latter also enabled to understand the operating wear mechanisms.

Gravitational-wave detector realized by a superconductor

In this article, we present a new gravitational-wave detector based on superconducting magnetic levitation and results of its prototype test. Our detector is composed of the suspended test mass that is rotated by gravitational waves. Gravitational wave signals are readout by monitoring its angular motion. Superconducting magnetic levitation is used for the suspension of the test mass, since it has many advantages, such as zero mechanical loss and resonant frequency around its suspension axis in an ideal situation. For the study of actual performance of such gravitational-wave detector, a prototype detector has been developed. Using the prototype detector, the actual loss factor and resonant frequency are measured as 1.2×10−8Nms/rad and 5mHz respectively. A detector noise is also evaluated. The current noise level is determined by the magnetic coupling with external magnetic field and mechanical coupling between translation and angular motion. The prototype detector has already one of the lowest noise levels for gravitational waves at 0.1Hz among current gravitational-wave detectors. We have succeeded at the demonstration of the advantages of our torsion gravitational-wave detector.

Size and settling velocities of cohesive flocs and suspended sediment aggregates in a trailing suction hopper dredge plume

A field experiment was conducted to quantify settling velocities, aggregate states, and flocculation within a hopper dredge plume. Particular interest was in determining the abundance of dense, bed aggregates suspended from the consolidated bed during dredging. A suspended sediment plume from the hopper dredge Essayons was sampled for a period of 90 min after dredging. Settling velocities and suspended particle sizes were quantified through sampling with the Particle Imaging Camera System (PICS) and automated image processing routines. The sediment plume was identified and a profiling instrumentation frame was positioned within the plume using Acoustic Doppler Current Profiler (ADCP) backscatter. Results indicated that suspended bed aggregates (defined by densities of 1200–1800 kg m −3) represented 0.2–0.5 of total suspended mass, and flocs (densities<1200 kg m −3) represented 0.5–0.8 of total suspended mass. The peak diameter of bed aggregates and flocs occurred near 90 and 200 μm, respectively, corresponding to peak settling velocities of about 1 mm s −1 in each case. Floc settling velocities increased with particle size d 1.1, while bed aggregate settling velocity increased like d 1.3.

In-plane and out-of-plane MEMS motion sensors based on fringe capacitances

New MEMS motion sensors have been developed. These prototypes are based on a sensing technique that exploits the fringe capacitance between two co-planar electrodes designed over a thin oxide layer covering a grounded wafer substrate. A relevant fraction of the electric-field streamlines, generated by the readout voltage applied between the electrodes, develops in the air (or vacuum) volume over the electrodes. A grounded suspended mass moving within this volume modifies the streamlines configuration, causing relative changes in the capacitance between the electrodes as large as the ∼80% of the initial value. Two types of devices based on the described concept have been designed and built in an industrial surface micromachining process, to sense acceleration in the direction both parallel and orthogonal to the substrate surface. The realized devices have been tested and a sensitivity of ∼0.9 fF/g and ∼0.2 fF/g has been obtained for the in plane and for the out-of-plane structures respectively.

Improved Understanding of Vibrating-Wire Viscometer−Densimeters

The vibrating-wire technique has been widely applied in measurements of both viscosity and density. When tensioned by a suspended mass or sinker, the device may be used to measure these properties simultaneously. The sensitivity to density arises mainly from the effect of buoyancy on the tension and hence the resonance frequency of the vibrating wire. Earlier studies have used simplified working equations to relate the resonance frequency and the tension. In this work, we have employed the exact equations describing forced simple harmonic oscillations of a stiff wire under tension and also a second-order analytical solution of those equations. We show that the exact working equation describes the actual resonance frequency of tensioned tungsten wires with improved accuracy. This finding has been validated by means of experimental measurements of the resonance frequency at prescribed tensioning forces and at temperatures in the range (293 to 473) K. One consequence of this is that the true independently measured sinker volume may be used in preference to one obtained by calibration of the assembled sensor. The remaining parameters to be obtained are then the radius of the wire, Young’s modulus E for the wire, and an empirical parameter that accounts for the remaining departure from the theoretical expression. The values of wire radius obtained by calibration in a liquid of known viscosity have been compared with those from independent mechanical measurements having a relative uncertainty of 0.2 %. These comparisons have been made for both drawn wires and for a centerless ground rod with a diameter of 0.15 mm, and the differences are discussed in the light of scanning electron microscopy (SEM) studies of the circularity and uniformity of the wire. Finally, we provide experimental evidence that rough drawn wires may yield inaccurate viscosity measurements when applied to fluids having viscosities very different to the one used for calibration; conversely, a centerless-ground rod gave good results even when the viscosity to be measured was 60 times that of the calibration fluid.

Controls of Suspended Sediment Concentration, Nutrient Content, and Transport in a Subtropical Wetland

Redistribution of largely organic sediment from low elevation sloughs to higher elevation ridges is a leading hypothesis for the formation and maintenance of the native ridge and slough landscape pattern found in peat wetlands of the Florida Everglades. We tested this redistribution hypothesis by measuring the concentration and characteristics of suspended sediment and its associated nutrients in the flowpaths of adjacent ridge and slough plant communities. Over two wet seasons we found no sustained differences in suspended sediment mass concentrations, particle-associated P and N concentrations, or sizes of suspended particles between ridge and slough sites. Discharge of suspended sediment, particulate nutrients, and solutes were nearly double in the slough flowpath compared to the ridge flowpath due solely to deeper and faster water flow in sloughs. Spatial and temporal variations in suspended sediment were not related to water velocity, consistent with a hypothesis that the critical sheer stress causing entrainment is not commonly exceeded in the present-day managed Everglades. The uniformity in the concentrations and characteristics of suspended sediment at our research site suggests that sediment and particulate nutrient redistribution between ridges and sloughs does not occur, or rarely occurs, in the modern Everglades.

Full activated sludge model no. 1 calibration experience at a medium-size WWTP in Mexico

As part of the efforts done to introduce the practice of modeling in Latin America, this research carried out at the North-East WWTP of Monterrey represents the first comprehensive modeling case in Mexico. The main objective was to reproduce the organic carbon removal and sludge production rates of the plant, based on ASM1. Different intermediate studies were performed prior to the calibration of the model: influent characterization, tracer tests and hydraulics modeling, sludge settling tests and respirometry. Two fractionation methods (STOWA protocol and Influent-advisor) were compared, showing no equivalent patterns. A stepwise sequence of calibration was developed and successfully applied. The hydraulics of the reactors at the plant was reproduced by use of a series of 3 to 5 CSTRs. The waste and return activated sludge flowrates (Q(WAS) and Q(RAS)) were corrected based on the inorganic and total suspended solids mass balances. The Vesilind settling constants were measured (V(o) and r(hind)), while the flocculent zone settling parameter (r(floc)) was adjusted to calibrate the secondary clarifier. In ASM1, the adjusted parameters were the COD soluble inert fraction (frS(I)) and the particulate substrate fraction (FrX(S)). All other ASM1 parameters were kept at their default values. The steady-state calibrated model (in GPS-X) adequately described the quality of the effluent (carbon and nitrogen) as well as the sludge composition (M. Liquor and WAS). This case study provides voluntarily detailed data to allow its wide use for training and teaching purposes.

Determination of aerosol yields from 3-methylcatechol and 4-methylcatechol ozonolysis in a simulation chamber

Abstract Secondary Organic Aerosol (SOA) formation during the ozonolysis of 3-methylcatechol (3-methyl-1,2-dihydroxybenzene) and 4-methylcatechol (3-methyl-1,2-dihydroxybenzene) was investigated using a simulation chamber (8 m3) at atmospheric pressure, room temperature (294 ± 2 K) and low relative humidity (5–10%). The initial mixing ratios were as follows (in ppb): 3-methylcatechol (194–1059), 4-methylcatechol (204–1188) and ozone (93–531). The ozone and methylcatechol concentrations were followed by UV photometry and GC–FID (Gas chromatography–Flame ionization detector), respectively and the aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted methylcatechol concentrations assuming a particle density of 1.4 g cm−3. The aerosol formation yield increases as the initial methylcatechol concentration increases, and leads to aerosol yields ranging from 32% to 67% and from 30% to 64% for 3-methylcatechol and 4-methylcatechol, respectively. Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. These data are comparable to those published in a recent study on secondary organic aerosol formation from catechol ozonolysis. To our knowledge, this work represents the first investigation of SOA formation from the ozone reaction with methylcatechols.

Seasonal distribution and relationship of water mass and suspended load in North Yellow Sea

The concentration of suspended load can be determined by its linear relationship to turbidity. Our results present the basic distribution of suspended load in North Yellow Sea. In summer, the suspended load concentration is high along the coast and low in the center of the sea. There are four regions of high concentration in the surface layer: Penglai and Chengshantou along the north of the Shandong Peninsula, and the coastal areas of Lushun and Changshan Islands. There is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west. And there is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west. The distribution features in the 10 m and bottom layer are similar to the surface layer, however, the suspended load concentration declines in the 10 m layer while it increases in the bottom layer. And in the bottom layer there is a low suspended load concentration water mass at the region south of 38°N and east of 123°E extending to the southeast. In general, the lowest suspended load concentration in a vertical profile is at a depth of 10 to 20 m, the highest suspended load concentration is in the bottom near Chengshantou area.

Biaxial and Uniaxial Epoxy Accelerometers

This paper discusses biaxial and uniaxial optical accelerometers featuring polymer waveguides. They are fabricated by lithographic wafer scale micromachining techniques. These waveguides are employing relatively new epoxies: EpoClad and EpoCore. The accelerometers are based on the movement of a spring suspended seismic mass that embeds one or two waveguides. These waveguides are coupled with fixed waveguides on a frame. This induces light intensity variations due to deviations from the (initially) straight optical path. This phenomenon is used to measure acceleration. The fabrication process developed is solely surface micromachining, so no bulk or back-end etching is required, making it simple, versatile and low cost.

TSP, PM depositions, and trace elements in the vicinity of a cement plant and their source apportionments using chemical mass balance model in Izmir, Turkey

Total suspended particles mass concentrations (TSP) and bulk depositions of particulate matter (PM depositions) were measured around a cement plant located in the multi-impacted area to assess the affect of the plant on the ambient air in the vicinity in Izmir, Turkey. TSP samples were collected five times a month whereas PM depositions were sampled monthly at four sites between August 2003 and January 2004. The concentrations of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V, and Zn in TSP and PM depositions (except Cu) were reported. Chemical mass balance (CMB) receptor model with local source profiles was run in order to calculate the source contributions of the PM sources to the concentrations of TSP, PM depositions, and trace elements. Traffic was found to be the major contributor to TSP whereas PM depositions dominantly result from area sources including several stone quarries, concrete plants, lime kilns, and asphalt plants in the region. CMB model results indicate that the cement plant is a significant contributor to TSP, PM depositions, and trace elements, particularly Cd.

Biological treatment of benzene in a controlled trickle bed air biofilter

Trickle bed air biofilters (TBABs) are suitable for treatment of relatively high volumes of volatile organic compounds due to their controlled environment. A laboratory-scale TBAB was used for the treatment of an air stream contaminated with benzene under different loading rates (LRs) ranging from 7.2 to 76.8 g m −3 h −1. The TBAB was operated at pH 7 and 25 °C. Consistent long-term performance of the benzene TBAB depends on various factors one of which is the excess amount of biomass accumulated within the bed. Three experimental strategies for biomass control were employed in the study: weekly backwashing for 1 h, starvation (no benzene feed for a period of 2 d/week) and stagnation (no benzene, air and nutrient flow for a period of 2 d/week). The experimental plan was designed to investigate the long-term performance of the TBAB with emphasis on the empty bed resident time (EBRT), different benzene LRs, removal efficiency with TBAB depth, volatile suspended solids and carbon mass balance closure. For benzene loading up to 34.1 g m −3 h −1, removal efficiency consistently over 98% was achieved. At the maximum LR 76.8 g m −3 h −1 the removal efficiency was still above 80% by utilizing stagnation strategy for 2 d and gas flow switching once per week as means of biomass control. Backwashing once per week provided less efficient performance as compared to stagnation while starvation showed the worst performance. EBRT at 120 s provided the best performance while EBRT at 90 s showed slightly lower performance.

Aerosol formation yields from the reaction of catechol with ozone

The formation of secondary organic aerosol from the gas-phase reaction of catechol (1,2-dihydroxybenzene) with ozone has been studied in two smog chambers. Aerosol production was monitored using a scanning mobility particle sizer and loss of the precursor was determined by gas chromatography and infrared spectroscopy, whilst ozone concentrations were measured using a UV photometric analyzer. The overall organic aerosol yield ( Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses ( M o) to the total reacted catechol concentrations, assuming a particle density of 1.4 g cm −3. Analysis of the data clearly shows that Y is a strong function of M o and that secondary organic aerosol formation can be expressed by a one-product gas–particle partitioning absorption model. The aerosol formation is affected by the initial catechol concentration, which leads to aerosol yields ranging from 17% to 86%. The results of this work are compared to similar studies reported in the literature.