Correlation between electrical and rheological measurements on sewage sludge

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
E. Dieudé-Fauvel ◽  
J.-C. Baudez ◽  
P. Coussot ◽  
H. Van Damme
Keyword(s):  
Sewage Sludge ◽  
Rheological Parameters ◽  
Clear Correlation ◽  
Electrical Measurements ◽  
Rheological Measurements ◽  
Sludge Characterization ◽  
Relaxation Experiments ◽  
Rheological Experiments ◽  
The One ◽  
Microstructure Of The Material

In order to improve sewage sludge characterization for both dewatering and agricultural spreading, we have studied their electrical and rheological properties. On the one hand, electrical measurements give a picture of the microstructure of the material (charges, particles mobility), whereas on the other hand, rheological experiments describe its macrostructure (consistency). The interactions of the matter are the link between them. Our results showed that sludge becomes more conductive when its dry content (for a defined composition) or the temperature increases, and also during aging. In parallel its apparent viscosity increases with the dry content but decreases with the temperature or during aging. In each case a clear correlation was found between electrical and rheological parameters. This relationship clearly depends on sludge composition, and also on parameters such as the temperature, the observation frequency, the velocity range in the case of relaxation experiments. Finally, those types of experiments can be correlated to improve the comprehension of sludge structure and consistency characterization.

The Use of Rheology for Sludge Characterization

1982 ◽  
Vol 14 (6-7) ◽  
pp. 475-489 ◽  
Author(s):  
H W Campbell ◽  
P J Crescuolo
Keyword(s):  
Particle Size ◽  
Sewage Sludge ◽  
Test Procedures ◽  
Particle Size Reduction ◽  
Rotational Viscometer ◽  
Polymer Addition ◽  
Rheological Measurements ◽  
Acceleration Rate ◽  
Sludge Characterization ◽  
Potential Use

Rheological measurements were conducted on a variety of anaerobically digested sewage sludges to evaluate the potential use of rheology in describing the effects of chemical conditioning on the physical characteristics of sludges. The objectives of the study were to evaluate the influence of the method of chemical conditioning on rheological measurements; to determine the response of the viscometer system to changes in the instrument variables; and to evaluate interrelationships between rheology and other physical properties. All rheological measurements were made using a coaxial rotational viscometer. Evaluation of a variety of test procedures identified that both the method of adding chemical conditioners, and the acceleration rate of the rotational viscometer, could significantly alter the shape of the rheograms. A suggested methodology was identified and selected samples were analyzed in triplicate to test the reproducibility of the procedures. Existing mathematical models do not adequately describe the variety of flow behaviour patterns observed with sewage sludge. The concepts of yield stress and apparent viscosity also have limited value due to problems of definition and calculation. A parameter termed the “instantaneous viscosity”, defined as the derivative of the flow curve, is suggested as being more suitable for describing sludge behaviour. The relationships between chemical conditioning, particle size distribution and applied shear were explored. As polymer addition increased, the sludge particles became more susceptible to shear breakup. The extent of particle size reduction was a function of the rate of shear and the time during which the shear was maintained.

CBED study of low-temperature InP grown by gas source MBE

1993 ◽  
Vol 51 ◽  
pp. 810-811
Author(s):  
R. Rajesh ◽  
M.J. Kim ◽  
J.S. Bow ◽  
R.W. Carpenter ◽  
G.N. Maracas
Keyword(s):  
Low Temperature ◽  
Second Phase ◽  
Material System ◽  
Ion Milling ◽  
Electrical Measurements ◽  
Gas Source ◽  
Structural And Electrical Properties ◽  
The One ◽  
Lt Inp ◽  
Gas Source Mbe

In our previous work on MBE grown low temperature (LT) InP, attempts had been made to understand the relationships between the structural and electrical properties of this material system. Electrical measurements had established an enhancement of the resistivity of the phosphorus-rich LT InP layers with annealing under a P2 flux, which was directly correlated with the presence of second-phase particles. Further investigations, however, have revealed the presence of two fundamentally different types of precipitates. The first type are the surface particles, essentially an artefact of argon ion milling and containing mostly pure indium. The second type and the one more important to the study are the dense precipitates in the bulk of the annealed layers. These are phosphorus-rich and are believed to contribute to the improvement in the resistivity of the material.The observation of metallic indium islands solely in the annealed LT layers warranted further study in order to better understand the exact reasons for their formation.

Use of Viscosity Standard Fluid To Control Quality of Rheological Measurements for Characterizing Asphalt Binders

1997 ◽  
Vol 1586 (1) ◽  
pp. 24-31
Author(s):  
Raj Dongré ◽  
Satish Ramaiah ◽  
John D’Angelo
Keyword(s):  
Control Charts ◽  
High Viscosity ◽  
Asphalt Binders ◽  
Rheological Parameters ◽  
Reference Laboratory ◽  
Statistical Process ◽  
Standard Material ◽  
Rheological Measurements ◽  
Statistical Process Control Charts ◽  
Repeatability And Reproducibility

The results of a study to establish a protocol for calibrating and maintaining Superpave rheometers are described. The reference standard material used was supplied by Cannon Instrument Co. The material (high viscosity standard) is designated as N2700000 and is supplied with ASTM traceable values of steady shear viscosity at various Superpave specification temperatures. The main objective was to determine whether sound calibration practices and adequate training can improve the repeatability and reproducibility of the rheological parameters required in the Superpave binder specification. Ten laboratories participated in the study. The results indicate that the viscosity standard can be used as a standard fluid to calibrate and maintain the Superpave rheometers. The repeatability and reproducibility data were compared with similar estimates reported by the AASHTO Materials Reference Laboratory. It was found that the reproducibility (between-laboratory variation) improved by a factor of two and repeatability (within-laboratory variation) improved modestly. With these results, a protocol for using the standard was also developed. Further analysis of results is under way to determine the frequency of calibration and maintenance required to obtain consistent rheological measurements. The results of this analysis and efforts to implement statistical process control charts for calibration and maintenance of rheometers using the standard reference fluid (Cannon N2700000 viscosity standard) are discussed.

Physical changes in milk caused by the action of rennet: IV. Effects of varying rennet concentration and temperature.

1959 ◽  
Vol 26 (1) ◽  
pp. 58-62 ◽  
Author(s):  
G. W. Scott Blair ◽  
J. Burnett
Keyword(s):  
Relaxation Times ◽  
Rheological Parameters ◽  
Cube Root ◽  
Different Temperatures ◽  
Rigidity Modulus ◽  
Temperature Relaxation ◽  
Relaxation Experiments ◽  
Pass Through ◽  
Term Creep ◽  
Physical Changes

1. Under carefully standardized conditions, the increase in the over-all rigidity modulus of curd when the time after rennetting is doubled, varies inversely as the cube root of the rennet concentration. The intercepts of the extrapolated setting curves on the time axis and the observed coagulation times vary inversely as the concentration.2. With the same (normal) rennet concentration, some rheological parameters increase or decrease progressively as temperature is increased from 21° to 41° C.; others pass through maxima or minima, all between 29° and 35° C.3. Long-term ‘creep’ experiments have been done over the above temperature range, creep and slow recovery increasing progressively with temperature. Relaxation experiments, though showing the simplest distribution of relaxation times at about 32° C., are too greatly influenced by unavoidable differences in firmness at the different temperatures for it to be possible, at this stage, to draw conclusions about their temperature dependence.4. A comparison of some of these results with data published by a few other workers is attempted.

Flow of Viscoplastic Liquids Through a Planar Expansion Followed by a Contraction

2006 ◽  
Author(s):  
Moˆnica F. Naccache ◽  
Rafael S. Barbosa
Keyword(s):  
Pressure Drop ◽  
Creeping Flow ◽  
Viscoplastic Fluid ◽  
Rheological Parameters ◽  
Planar Channel ◽  
Generalized Newtonian Fluid ◽  
Viscosity Function ◽  
The One ◽  
Volume Method ◽  
Newtonian Behavior

In this work, the creeping flow of a viscoplastic fluid through a planar channel with an expansion followed by a contraction is analyzed numerically. The solution of the conservation equations of mass and momentum is obtained via the finite volume method. In order to model the non-Newtonian behavior of the fluid, it was used the Generalized Newtonian Fluid constitutive equation. The viscosity function was the one proposed by Souza Mendes and Dutra [1]. The yielded and unyielded regions are obtained for several combinations of rheological parameters. The influence of these parameters on pressure drop through the cavity is also obtained and analyzed.

Partitioning of Cr, Cu, Pb and Zn in sewage sludge incineration by rotary kiln and fluidized bed furnaces

2000 ◽  
Vol 41 (8) ◽  
pp. 61-68 ◽  
Author(s):  
G. Mininni ◽  
C. M. Braguglia ◽  
D. Marani
Keyword(s):  
Fly Ash ◽  
Sewage Sludge ◽  
Rotary Kiln ◽  
Bottom Ash ◽  
Point Of View ◽  
Fluidised Bed ◽  
Chlorinated Organic Compounds ◽  
Sludge Incineration ◽  
Significant Enrichment ◽  
The One

The behaviour of four metals (Cr, Cu, Pb, Zn) during sewage sludge incineration was studied in eight pilot plant tests performed with a rotary kiln (RK) and a fluidised bed (FB) furnace. To simulate sludge co-incineration with hazardous wastes, in three FB tests feed sludge was mixed with chlorinated organic compounds. Chromium and copper showed similar concentrations both in bottom or cyclone ash and in fly ash, even at high chlorine input and high combustion temperature. In contrast, zinc and lead concentrations in fly ash produced in RK tests are one or two orders of magnitude higher than those in bottom ash. However, not even these two metals showed significant enrichment in FB tests carried out at high chlorine input. The predictive capability of a thermodynamic model was checked by comparing predicted metal volatilisation in the combustion chamber with experimental metal enrichment in the fly ash. Large discrepancies were observed in FB tests carried out at high chlorine content, where Pb, Zn, and Cu are predicted to volatilise in great extent, andin RK tests where zinc volatilisation is not predicted. Likely explanations of these discrepancies are the very short solid residence times in the FB furnace (non equilibrium conditions) and the incomplete mixing conditions in the RK furnace (pyrolysis pockets). From the environmental impact point of view, the pilot tests suggest that sludge incineration with fluidised bed furnace is safer than the one using rotary kiln furnace.

A-Si:H Solar Cells Deposited Using VHF–PECVD

1996 ◽  
Vol 420 ◽  
Author(s):  
W. G. J. H. M. Van Sark ◽  
J. Bezemer ◽  
R. Van Der Heijden ◽  
W. F. Van Der Weg
Keyword(s):  
Solar Cells ◽  
Chemical Vapour ◽  
Clear Correlation ◽  
Rf Power ◽  
Material Quality ◽  
High Frequencies ◽  
Cell Parameters ◽  
The One ◽  
Very High Frequencies ◽  
Very High

AbstractA-Si:H p+-i-n+ solar cells have been made employing plasma enhanced chemical vapour deposition at frequencies between 30–80 MHz. Here, only the i-layer was fabricated at these very high frequencies (VHF). Both the p+- and n+-layer were made using 13.56 MHz. A previous study has shown the material quality to depend on mainly the applied rf-power, and only slightly on the frequency. It should be noted that for homogeneity reasons a certain optimized pressure is required for each frequency. There is a clear correlation between material quality and solar cell parameters. An initial efficiency of 10 % has been obtained for cells deposited at 65 MHz using a low power density, while the deposition rate still is 2–3 times higher than the one at 13.56 MHz. Light-soaking reveals stabilisation at 6 % for the best cell, which compares well to conventional 13.56 MHz cells.

Dynamics of propagating waves in the olfactory network of a terrestrial mollusk: an electrical and optical study

1994 ◽  
Vol 72 (3) ◽  
pp. 1402-1419 ◽  
Author(s):  
D. Kleinfeld ◽  
K. R. Delaney ◽  
M. S. Fee ◽  
J. A. Flores ◽  
D. W. Tank ◽  
...  
Keyword(s):  
Action Potentials ◽  
Field Potential ◽  
Longitudinal Axis ◽  
Optical Signal ◽  
Clear Correlation ◽  
Inhibitory Input ◽  
Electrical Measurements ◽  
Terrestrial Mollusk ◽  
Bursting Neurons ◽  
Intracellular Signals

1. The procerebral (PC) lobe of the terrestrial mollusk Limax maximus contains a highly interconnected network of local olfactory interneurons that receives ipsilateral axonal projections from superior and inferior noses. This network exhibits an approximately 0.7-Hz intrinsic oscillation in its local field potential (LFP). 2. Intracellular recordings show that the lobe contains at least two classes of neurons with activity phase locked to the oscillation. Neurons in one class produce periodic bursts of spikes, followed by a period of hyperpolarization and subsequently a depolarizing afterpotential. There is a small but significant chance for a second burst to occur during the depolarizing afterpotential; this leads to a double event in the LFP. Bursting neurons constitute approximately 10% of the neurons in the lobe. 3. Neurons in the other class fire infrequently and do not produce periodic bursts of action potentials. However, they receive strong, periodic inhibitory input during every event in the LFP. These nonbursting cells constitute the major fraction of neurons in the lobe. There is a clear correlation between the periodic burst of action potentials in the bursting neurons and the hyperpolarization seen in nonbursting neurons. 4. Optical techniques are used to image the spatially averaged transmembrane potentials in preparations stained with voltage-sensitive dyes. The results of simultaneous optical and electrical measurements show that the major part of the optical signal can be interpreted as a superposition of the intracellular signals arising from the bursting and nonbursting neurons. 5. Successive images of the entire PC lobe show waves of electrical activity that span the width of the lobe and travel its full length along a longitudinal axis. The direction of propagation in the unperturbed lobe is always from the distal to the proximal end. The wavelength varies between preparations but is on the order of the length of the preparation. 6. One-dimensional images along the longitudinal axis of the lobe are used to construct a space-time map of the optical activity, from which we calculate the absolute contribution of bursting and nonbursting neurons to the optical signal. The contribution of the intracellular signals from the two cell types appears to vary systematically across the lobe; bursting cells dominate at middle and proximal locations, and nonbursting cells dominate at distal locations. 7. The direction and form of the waves can be perturbed either by microsurgical manipulation of the preparation or by chemical modulation of its synaptic and neuronal properties.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Empirical evolution of credit risk over a decade in IBEX. 35 companies and its relationship with the qualification of its ratings

2020 ◽  
Vol 16 (2) ◽  
pp. 61
Author(s):  
Josep Patau
Keyword(s):  
Credit Risk ◽  
Credit Rating ◽  
Clear Correlation ◽  
Crisis Period ◽  
Rating Agencies ◽  
Credit Rating Agency ◽  
Rating Agency ◽  
Determining Factors ◽  
Commercial Loans ◽  
The One

Object: The present work responds to two objectives. On the one hand, it describes the evolution of the main economic-financial indicators that influence credit risk (insolvency) for a sample of 10 Spanish companies listed on the IBEX 35. This analysis is studied for a comparative period of 10 years, which coincides with a pre-crisis stage (2002-2005) and an economic post-crisis phase (2012-2015). On the other hand, it corroborates the relationship between the analysed insolvency and the rating or credit-risk rating published for these companies by an internationally recognized credit rating agency, Standard & Poor's (S & P).Design / methodology: A sample of 10 companies and a 10-year period including the years 2002-2005 (pre-crisis) and the years 2012-2015 (post-crisis) are chosen, omitting the Spanish economic crisis that occurred in the year 2008. For the study of its evolution, 6 ratios obtained from the scientific literature that relate to credit risk and its effects on investments and company results are calculated. Finally, the correlations of these variables with the ratings of credit risk assessment by the rating agency S & P are measured. Descriptive statistics will assign value and graphics to this ten-year evolution, and with the incorporation of a factorial analysis, the correlation between the ratios and the S & P rating will be determined. The statistical analysis explains this correlation to a greater extent.Contributions / results: The results show a clear increase in the value of the impairment variable due to credit risk ten years later that directly affects the results of the companies, despite these companies having significantly reduced their investments in commercial loans pending collection and drastically reduced the period means of collection of clients. In turn, there is a clear correlation between the insolvency studied and the variables used by the S & P rating agency for the assessment of credit risk.Added value / conclusions: The empirical study concludes that there is a correspondence between insolvency and the rating given by an internationally prestigious rating agency (S & P) for the sample of 10 companies studied. Three variables – customer balance-accounts receivable, investments and the net amount of turnover – are determining factors explaining this correlation, and these three variables are the same ones that decisively influence both the pre-crisis period and the post-crisis period 10 years apart. The rating agencies weigh the insolvency variable in their analyses.

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