Relevant bibliographies by topics / Saturation function

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Saturation function'

Author: Grafiati
Published: 4 June 2021
Last updated: 26 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Saturation function.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Saturation function"

1

Jia, Lijie. "The processing of saturation function in saturation control system." IOP Conference Series: Materials Science and Engineering 631 (November 7, 2019): 052048. http://dx.doi.org/10.1088/1757-899x/631/5/052048.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Carpenter, Chris. "Reconciling Log-Derived Water-Saturation and Saturation-Height Function Results." Journal of Petroleum Technology 68, no. 08 (2016): 65–66. http://dx.doi.org/10.2118/0816-0065-jpt.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Diouf, C., A. Cros, S. Monfray, et al. "“Y function” method applied to saturation regime: Apparent saturation mobility and saturation velocity extraction." Solid-State Electronics 85 (July 2013): 12–14. http://dx.doi.org/10.1016/j.sse.2013.03.007.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Afrough, Armin, Mehdi Bahari Moghaddam, Laura Romero-Zerón, and Bruce J. Balcom. "Exponential Capillary Pressure Functions in Sedimentary Rocks." E3S Web of Conferences 89 (2019): 02005. http://dx.doi.org/10.1051/e3sconf/20198902005.

Full text
Abstract:
The Brooks-Corey power-law capillary pressure model is commonly imposed on core analysis data without verifying the validity of its underlying assumptions. The Brooks-Corey model, originally developed to model the pressure head during the drainage of soil, is only valid at low wetting phase saturations. However, such models are often applied in petroleum production simulations and may lead to erroneous recovery factors when the saturation range of interest is far from the end points. We demonstrate that exponential models work much better for capillary pressure compared to the Brooks-Corey model over a wide saturation range. Mercury injection porosimetry, petrographic image analysis, and magnetic resonance studies suggest that the pore and throat size distribution in many rocks are log-normally distributed. This fact was previously employed to calculate the capillary pressure function as a function of saturation for pore size distributions described by atruncated log-normal distribution. Employing a Taylor series expansion, we simplify the random fractal capillary pressure model of Hunt to Pc = exp(a − bS), where S is the wetting phase saturation, and a and b characteristic of the porous medium. An extensive dataset of seventeen centrifuge capillary pressure measurements were used in this research to demonstrate the merit of the new method. For both sandstones and carbonates, the logarithm of capillary pressure showed a linear relationship with saturation as observed by magnetic resonance imaging centrifuge capillary pressure measurements over a wide saturation range. This work demonstrates that: (a) in semi-log plots of capillary pressure as a function of saturation, capillary pressurewill vary linearly over a wide saturation range, (b) such a plot as described in (a) will show the uni-or bimodal pore size distribution of the rock, (c) the exponential capillary pressure function simplifies analytical modelsthat use the capillary pressure function, for example oil recovery models for fractured reservoirs.
APA, Harvard, Vancouver, ISO, and other styles
5

Imbert, Jean-Pierre, Salih-Murat Egi, and Costantino Balestra. "Vascular Function Recovery Following Saturation Diving." Medicina 58, no. 10 (2022): 1476. http://dx.doi.org/10.3390/medicina58101476.

Full text
Abstract:
Background and Objectives: Saturation diving is a technique used in commercial diving. Decompression sickness (DCS) was the main concern of saturation safety, but procedures have evolved over the last 50 years and DCS has become a rare event. New needs have evolved to evaluate the diving and decompression stress to improve the flexibility of the operations (minimum interval between dives, optimal oxygen levels, etc.). We monitored this stress in saturation divers during actual operations. Materials and Methods: The monitoring included the detection of vascular gas emboli (VGE) and the changes in the vascular function measured by flow mediated dilatation (FMD) after final decompression to surface. Monitoring was performed onboard a diving support vessel operating in the North Sea at typical storage depths of 120 and 136 msw. A total of 49 divers signed an informed consent form and participated to the study. Data were collected on divers at surface, before the saturation and during the 9 h following the end of the final decompression. Results: VGE were detected in three divers at very low levels (insignificant), confirming the improvements achieved on saturation decompression procedures. As expected, the FMD showed an impairment of vascular function immediately at the end of the saturation in all divers but the divers fully recovered from these vascular changes in the next 9 following hours, regardless of the initial decompression starting depth. Conclusion: These changes suggest an oxidative/inflammatory dimension to the diving/decompression stress during saturation that will require further monitoring investigations even if the vascular impairement is found to recover fast.
APA, Harvard, Vancouver, ISO, and other styles
6

Zhou, Yingfang, Dimitrios Georgios Hatzignatiou, Johan Olav Helland, Yulong Zhao, and Jianchao Cai. "Pore-Scale Modelling of Three-Phase Capillary Pressure Curves Directly in Uniformly Wet Rock Images." Geofluids 2021 (January 5, 2021): 1–15. http://dx.doi.org/10.1155/2021/6622079.

Full text
Abstract:
In this work, we developed a semianalytical model to compute three-phase capillary pressure curves and associated fluid configurations for gas invasion in uniformly wet rock images. The fluid configurations and favorable capillary entry pressures are determined based on free energy minimization by combining all physically allowed three-phase arc menisci. The model was first validated against analytical solutions developed in a star-shaped pore space and subsequently employed on an SEM image of Bentheim sandstone. The simulated fluid configurations show similar oil-layer behavior as previously imaged three-phase fluid configurations. The simulated saturation path indicates that the oil-water capillary pressure can be described as a function of the water saturation only. The gas-oil capillary pressure can be represented as a function of gas saturation in the majority part of the three-phase region, while the three-phase displacements slightly reduce the accuracy of such representation. At small oil saturations, the gas-oil capillary pressure depends strongly on two-phase saturations.
APA, Harvard, Vancouver, ISO, and other styles
7

Shen-Iuan Liu and Cheng-Chieh Chang. "Pseudo-exponential function for MOSFETs in saturation." IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing 47, no. 11 (2000): 1318–21. http://dx.doi.org/10.1109/82.885141.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Barale, Cristina, Rouslan Senkeev, Franca Napoli, et al. "Transferrin Saturation Inversely Correlates with Platelet Function." Thrombosis and Haemostasis 119, no. 05 (2019): 766–78. http://dx.doi.org/10.1055/s-0039-1681061.

Full text
Abstract:
Background The association between iron overload (IO) and risk of cardiovascular disease is controversial. Epidemiological studies have found a significant negative association of transferrin (Tf) saturation and cardiovascular events suggesting that higher body iron possibly confer a protective effect towards developing cardiovascular events. The biological mechanisms of this phenomenon are unknown. Objective This article investigates the role of IO on platelet reactivity. Materials and Methods This study was a prospective case–control study comparing 45 patients with IO, mostly characterized by the HFE gene mutations C282Y and/or H63D, with 32 healthy controls. We evaluated: (1) platelet aggregation in both platelet-rich plasma and whole blood, (2) platelet membrane expression of the activation marker CD62P, (3) activation of platelet signalling phosphoinositide 3-kinase /Akt and mitogen-activated protein kinase/extracellular signal-regulated kinases (Erk)-1/2 pathways, (4) a pattern of in vivo platelet activation markers, and (5) iron biomarker predictors of platelet reactivity. Results IO patients had significantly lower platelet aggregability, expression of CD62P and phosphorylation amounts of pAkt and pErk-2 in response to agonists. Furthermore, patients with higher Tf saturation levels were characterized by lower circulating levels of sCD40L, PDGF-BB and thromboxane B2. Platelet aggregation and activation parameters inversely correlated with Tf saturation and the stepwise multivariate regression analysis underlined the role of Tf saturation in predicting platelet reactivity. We also found that in vitro platelet exposure to diferric Tf, but not to iron-depleted TF, dose-dependently inhibited platelet function in all investigated subjects. Conclusion Tf saturation is inversely associated with platelet reactivity and this could explain, at least in part, the association of high Tf and lower risk of cardiovascular diseases in IO.
APA, Harvard, Vancouver, ISO, and other styles
9

Paquet, Catherine, Pierre Couture, Michel Carrier, Jean-Claude Tardif, and André Y. Denault. "Cerebral oxygen saturation and left ventricular function." Canadian Journal of Anesthesia/Journal canadien d'anesthésie 53, no. 1 (2006): 26417. http://dx.doi.org/10.1007/bf03017020.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Bohman, Tom, Maria Fonoberova, and Oleg Pikhurko. "The saturation function of complete partite graphs." Journal of Combinatorics 1, no. 2 (2010): 149–70. http://dx.doi.org/10.4310/joc.2010.v1.n2.a5.

Full text
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "Saturation function"

1

Lamendola, Joel E. "Limit Cycle PIO Analysis With Simultaneously Acting Multiple Asymmetric Saturation." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36767.

Full text
Abstract:
Pilot in-the-loop oscillation (PIO) is a phenomenon which occurs due to the dynamic interaction between pilot and aircraft. This detrimental aircraft handling quality appears through a variety of flight conditions and is very difficult to predict. Due to this complex behavior, PIO is not easily eliminated. This report describes a method of PIO analysis that is capable of examining multiple asymmetric nonlinearities acting simultaneously. PIO analyses are performed on a model based on the USAF NT-33A variable stability aircraft with nonlinearities including stick position limiting, elevator deflection limiting, and elevator rate limiting. These analyses involve the use of dual input describing functions which enable the prediction of frequency, amplitude, and mean point of oscillation.<br>Master of Science
APA, Harvard, Vancouver, ISO, and other styles
2

Alves, Jose Henrique Gomes de Mattos Mathematics UNSW. "A Saturation-Dependent Dissipation Source Function for Wind-Wave Modelling Applications." Awarded by:University of New South Wales. Mathematics, 2000. http://handle.unsw.edu.au/1959.4/17786.

Full text
Abstract:
This study reports on a new formulation of the spectral dissipation source term Sds for wind-wave modelling applications. This new form of Sds features a nonlinear dependence on the local wave spectrum, expressed in terms of the azimuthally integrated saturation parameter B(k)=k^4 F(k). The basic form of this saturation-dependent Sds is based on a new framework for the onset of deep-water wave breaking due to the nonlinear modulation of wave groups. The new form of Sds is succesfully validated through numerical experiments that include exact nonlinear computations of fetch-limited wind-wave evolution and hindcasts of two-dimensional wave fields made with an operational wind-wave model. The newly-proposed form of Sds generates integral spectral parameters that agree more closely with observations when compared to other dissipation source terms used in state-of-the-art wind-wave models. It also provides more flexibility in controlling properties of the wave spectrum within the high wavenumber range. Tests using a variety of wind speeds, three commonly-used wind input source functions and two alternative full-development evolution limits further demonstrate the robustness and flexibility of the new saturation-dependent dissipation source term. Finally, improved wave hindcasts obtained with an implementation of the new form of Sds in a version of the WAM model demonstrate its potential usefulness in operational wind-wave forecasting applications.
APA, Harvard, Vancouver, ISO, and other styles
3

Barbour, Michele Emily. "Human tooth enamel dissolution in citric acid as a function of degree of saturation and pH." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272036.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Zhu, En. "The role of US agricultural and forest activities in global climate change mitigation." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1406.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Laws, Eric L. "An Investigation of Color Memory as a Function of Hue, Saturation, Lightness and Observer Imagery Vividness for Blue, Green and Orange Test Hues." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26367.

Full text
Abstract:
Fifty-two college-aged observers participated in an experiment assessing color memory via a PowerPoint '97 computer display program which varied one of the three dimensions of hue, saturation and lightness at a time. Consistent with previous research, errors were greater for the lightness conditions followed by saturation, and least for hue conditions Additionally, a signal detection analysis indicated that d-prime was greatest for the hue conditions, less for saturation and lowest for lightness conditions. There were also significant but unpredicted differences in response criterion which may reflect task difficulty. Scores on the Vividness of Visual Imagery Questionnaire (Marks, 1973) were, in general, not correlated with performance on these color memory tasks, inconsistent with previous research. The role of complexity of neuronal circuitry, the significance for opponent-process, trichromatic and retinex color vision theories and the relationship to Sokolov's model of color memory were discussed. Also, it was concluded that investigators of color memory using a computer display are well-advised to calibrate the monitor with a colorimeter because the internal computer units may be unreliable indexes of changes in hue, saturation and lightness.<br>Ph. D.
APA, Harvard, Vancouver, ISO, and other styles
6

Andersson, Louise. "Kan syrgasmättnad, fysisk funktion och självupplevda symtom förbättrats hos personer med KOL, stadium 2, efter träning av bålstabilitet i kombination med sluten läppandning?" Thesis, Luleå tekniska universitet, Institutionen för hälsovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64153.

Full text
Abstract:
Sammanfattning Bakgrund: KOL är en obstruktiv lungsjukdom med luftflödesbegränsningar pga.  kronisk bronkit och emfysem. De patofysiologiska mekanismer är en progressiv inflammatorisk process som påverkar hela kroppen. De viktigaste behandlingsstrategierna är rökstopp, farmakologisk behandling samt fysisk träning.  Personer med KOL har ofta en nedsatt fysisk funktionsnivå, som inte behöver vara kopplad till sjukdomens svårighetsgrad.  De viktigaste fysioterapeutiska interventionerna för KOL är mätning av fysisk kapacitet, aerob- och muskelstärkande träning, tekniker för sekretmobilisering via motståndsandning samt undervisning i energibesparande arbetssätt. Interventionerna leder till förbättrad funktionsnivå, bromsar upp sjukdomen, minskar risken för samsjuklighet med andra icke smittsamma sjukdomar (NCD), minskar risken för execerbationer, förbättrad livskvalitet, samt minskar risken att dö för tidigt (6MWT &gt;350 m).     God bålkontroll är central för en effektiv biomekanisk funktion i syfte att maximera kraft och minimera skaderisker. En bra bålkontroll har hos friska personer visats ha en positiv effekt på diafragmas funktion, samt att bålkontrollen påverkas av andningen vilket blir extra tydligt vid fysiskt ansträngande arbete.     Sambandet mellan bålkontroll, syrgasmättnad, fysisk funktion och självskattade symtom hos personer med KOL har enligt författarens kännedom inte studerats tidigare. Syfte: Studien syftar till att undersöka om fysisk aktivitet, med fokus på förbättrad bålstabilitet och sluten läppandning, kan förbättra syrgasmättnad, fysisk kapacitet, benmuskelstyrka, balans och självskattade symtom hos personer med KOL, stadium 2. Metod: Single subject experimental design (SSED) med AB design (baslinje undersökning – intervention) användes. Primärt utfallsmått var saturation och gångsträcka mätt med 6MWT. Sekundära utfallsmått var enbensstående balans, CS-30 samt CAT. Data på kvotskalenivå analyserades visuellt med stöd av 2-SD-bands analys och celerationslinje analys. Förändringar i CAT före och efter interventionen redovisas i procent. Resultat: Fyra personer inkluderades i studien. Resultatet visar en möjlig interventionseffekt avseende gångsträcka vid 6MWT och enbensstående balans för två av deltagarna, som vid studiestart låg under eller tangerade förväntade normalvärden i samtliga parametrar. En av dessa stabiliserades avseende lägsta värde på saturation vid 6MWT. Det fanns en effekt/möjlig effekt på förbättrad benstyrka (CS-30) för de deltagare som vid studiestart låg över förväntade normalvärden i samtliga parametrar. Självskattade lungsymtom (CAT) förbättrades hos tre av deltagarna (31–55 procent) och försämrades hon en av deltagarna (-17 procent). Konklusion: Studien visar en möjlig positiv effekt av bålstabiliserande träning på gångsträcka (6MWT), enbensstående balans, antalet uppresningar vid CS-30 samt självupplevda lungsymptom (CAT) för personer med KOL, stadium 2. Fler studier behövs för att stärka validiteten av dessa fynd.<br>Abstract Background: COPD is an obstructive pulmonary disease with air flow constraints due to chronic bronchitis and emphysema. The pathophysiological mechanisms are a progressive inflammatory process that affects the entire body. The main treatment strategies are smoking cessation, pharmacological treatment and physical exercise. People with COPD often have a reduced physical function level, which not need to be linked to the severity of the disease. The most important physiotherapeutic interventions for COPD are measurement of physical capacity, aerobic and muscle strength training, techniques for mobilization of sputum through resistance breathing techniques and teaching in energy-saving work methods. The interventions lead to improved functional levels, slow down the disease, reduce the risk of comorbidity with other non-communicable diseases (NCD), reduce the risk of exacerbation, improve quality of life, and reduce the risk to die prematurely (6MWT&gt; 350m).     A well-functioning core stability is considered central to an effective biomechanical function to maximize strength and minimize risks of injury and has been shown by healthy individuals to have a positive effect on diaphragm function. It has also been shown that the ability to core-control is affected by deep breathing and especially during hard physical work.    A correlation between oxygen saturation, physical function, self-estimated symptoms and core stability in people with COPD, has to the knowledge of the author not been studied earlier.     Aim: The aim of the study was to investigate whether there are a correlation exercise together with improved core stability and pursed lip breathing, can improve oxygen saturation, physical capacity, leg muscle strength, balance and self-estimated symptoms in people with COPD in stage 2.Methodology: A single subject experimental design (SSED) with AB design (baseline survey - intervention) was used. As primary outcome saturation and walking distance measured at 6MWT were used. Secondary outcomes were CS-30, single balance and CAT. Data at nominal level were analyzed by using Two Standard Deviation Band Analysis and Celeration Line Analysis, Changes in CAT, pre- and post-intervention, was analyzed by percentage. Result: Four participants were included in the study. The result indicates a possible intervention effect regarding walking distance at 6MWT and single leg balance for two of the participants, who at study start were below or dropped below expected normal values in all parameters. One of these participants was stabilized for the lowest value of saturation at 6MWT. There was an effect/possible effect in the CS-30 for participants who at study start exceeded expected normal values in all parameters. Self-estimated symptoms (CAT) were improved in three participants (31–55 percent) and got worse in one participant (17 percent).Conclusion: The study indicates that core stability training focusing on improved motor control for stabilizing core muscles may have a positive effect on walking distance (6MWD) single leg balance, number of up rises in CS-30 and self-estimated lungsymptoms for people with COPD, stage 2. More studies are needed to validate these preliminary findings.
APA, Harvard, Vancouver, ISO, and other styles
7

Shahraeeni, Mohammad Sadegh. "Inversion of seismic attributes for petrophysical parameters and rock facies." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/4754.

Full text
Abstract:
Prediction of rock and fluid properties such as porosity, clay content, and water saturation is essential for exploration and development of hydrocarbon reservoirs. Rock and fluid property maps obtained from such predictions can be used for optimal selection of well locations for reservoir development and production enhancement. Seismic data are usually the only source of information available throughout a field that can be used to predict the 3D distribution of properties with appropriate spatial resolution. The main challenge in inferring properties from seismic data is the ambiguous nature of geophysical information. Therefore, any estimate of rock and fluid property maps derived from seismic data must also represent its associated uncertainty. In this study we develop a computationally efficient mathematical technique based on neural networks to integrate measured data and a priori information in order to reduce the uncertainty in rock and fluid properties in a reservoir. The post inversion (a posteriori) information about rock and fluid properties are represented by the joint probability density function (PDF) of porosity, clay content, and water saturation. In this technique the a posteriori PDF is modeled by a weighted sum of Gaussian PDF’s. A so-called mixture density network (MDN) estimates the weights, mean vector, and covariance matrix of the Gaussians given any measured data set. We solve several inverse problems with the MDN and compare results with Monte Carlo (MC) sampling solution and show that the MDN inversion technique provides good estimate of the MC sampling solution. However, the computational cost of training and using the neural network is much lower than solution found by MC sampling (more than a factor of 104 in some cases). We also discuss the design, implementation, and training procedure of the MDN, and its limitations in estimating the solution of an inverse problem. In this thesis we focus on data from a deep offshore field in Africa. Our goal is to apply the MDN inversion technique to obtain maps of petrophysical properties (i.e., porosity, clay content, water saturation), and petrophysical facies from 3D seismic data. Petrophysical facies (i.e., non-reservoir, oil- and brine-saturated reservoir facies) are defined probabilistically based on geological information and values of the petrophysical parameters. First, we investigate the relationship (i.e., petrophysical forward function) between compressional- and shear-wave velocity and petrophysical parameters. The petrophysical forward function depends on different properties of rocks and varies from one rock type to another. Therefore, after acquisition of well logs or seismic data from a geological setting the petrophysical forward function must be calibrated with data and observations. The uncertainty of the petrophysical forward function comes from uncertainty in measurements and uncertainty about the type of facies. We present a method to construct the petrophysical forward function with its associated uncertainty from the both sources above. The results show that introducing uncertainty in facies improves the accuracy of the petrophysical forward function predictions. Then, we apply the MDN inversion method to solve four different petrophysical inverse problems. In particular, we invert P- and S-wave impedance logs for the joint PDF of porosity, clay content, and water saturation using a calibrated petrophysical forward function. Results show that posterior PDF of the model parameters provides reasonable estimates of measured well logs. Errors in the posterior PDF are mainly due to errors in the petrophysical forward function. Finally, we apply the MDN inversion method to predict 3D petrophysical properties from attributes of seismic data. In this application, the inversion objective is to estimate the joint PDF of porosity, clay content, and water saturation at each point in the reservoir, from the compressional- and shear-wave-impedance obtained from the inversion of AVO seismic data. Uncertainty in the a posteriori PDF of the model parameters are due to different sources such as variations in effective pressure, bulk modulus and density of hydrocarbon, uncertainty of the petrophysical forward function, and random noise in recorded data. Results show that the standard deviations of all model parameters are reduced after inversion, which shows that the inversion process provides information about all parameters. We also applied the result of the petrophysical inversion to estimate the 3D probability maps of non-reservoir facies, brine- and oil-saturated reservoir facies. The accuracy of the predicted oil-saturated facies at the well location is good, but due to errors in the petrophysical inversion the predicted non-reservoir and brine-saturated facies are ambiguous. Although the accuracy of results may vary due to different sources of error in different applications, the fast, probabilistic method of solving non-linear inverse problems developed in this study can be applied to invert well logs and large seismic data sets for petrophysical parameters in different applications.
APA, Harvard, Vancouver, ISO, and other styles
8

Chan, Teck-Wai. "Proximity-to-separation based energy function control strategy for power system stability." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15840/1/Teck-Wai_Chan_Thesis.pdf.

Full text
Abstract:
The issue of angle instability has been widely discussed in the power engineering literature. Many control techniques have been proposed to provide the complementary synchronizing and damping torques through generators and/or network connected power apparatus such as FACTs, braking resistors and DC links. The synchronizing torque component keeps all generators in synchronism while damping torque reduces oscillations and returns the power system to its pre-fault operating condition. One of the main factors limiting the transfer capacity of the electrical transmission network is the separation of the power system at weak links which can be understood by analogy with a large spring-mass system. However, this weak-links related problem is not dealt with in existing control designs because it is non-trivial during transient period to determine credible weak links in a large power system which may consist of hundreds of strong and weak links. The difficulty of identifying weak links has limited the performance of existing controls when it comes to the synchronization of generators and damping of oscillations. Such circumstances also restrict the operation of power systems close to its transient stability limits. These considerations have led to the primary research question in this thesis, "To what extent can the synchronization of generators and damping of oscillations be maximized to fully extend the transient stability limits of power systems and to improve the transfer capacity of the network?" With the recent advances in power electronics technology, the extension of transfer capacity is becoming more readily achievable. Complementary to the use of power electronics technology to improve transfer capacity, this research develops an improved control strategy by examining the dynamics of the modes of separation associated with the strong and weak links of the reduced transmission network. The theoretical framework of the control strategy is based on Energy Decomposition and Unstable Equilibrium Points. This thesis recognizes that under extreme loadings of the transmission network containing strong and weak links, weak-links are most likely to dictate the transient stability limits of the power system. We conclude that in order to fully extend the transient stability limits of power system while maximizing the value of control resources, it is crucial for the control strategy to aim its control effort at the energy component that is most likely to cause a separation. The improvement in the synchronization amongst generators remains the most important step in the improvement of the transfer capacity of the power system network.
APA, Harvard, Vancouver, ISO, and other styles
9

Chan, Teck-Wai. "Proximity-to-Separation Based Energy Function Control Strategy for Power System Stability." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15840/.

Full text
Abstract:
The issue of angle instability has been widely discussed in the power engineering literature. Many control techniques have been proposed to provide the complementary synchronizing and damping torques through generators and/or network connected power apparatus such as FACTs, braking resistors and DC links. The synchronizing torque component keeps all generators in synchronism while damping torque reduces oscillations and returns the power system to its pre-fault operating condition. One of the main factors limiting the transfer capacity of the electrical transmission network is the separation of the power system at weak links which can be understood by analogy with a large spring-mass system. However, this weak-links related problem is not dealt with in existing control designs because it is non-trivial during transient period to determine credible weak links in a large power system which may consist of hundreds of strong and weak links. The difficulty of identifying weak links has limited the performance of existing controls when it comes to the synchronization of generators and damping of oscillations. Such circumstances also restrict the operation of power systems close to its transient stability limits. These considerations have led to the primary research question in this thesis, "To what extent can the synchronization of generators and damping of oscillations be maximized to fully extend the transient stability limits of power systems and to improve the transfer capacity of the network?" With the recent advances in power electronics technology, the extension of transfer capacity is becoming more readily achievable. Complementary to the use of power electronics technology to improve transfer capacity, this research develops an improved control strategy by examining the dynamics of the modes of separation associated with the strong and weak links of the reduced transmission network. The theoretical framework of the control strategy is based on Energy Decomposition and Unstable Equilibrium Points. This thesis recognizes that under extreme loadings of the transmission network containing strong and weak links, weak-links are most likely to dictate the transient stability limits of the power system. We conclude that in order to fully extend the transient stability limits of power system while maximizing the value of control resources, it is crucial for the control strategy to aim its control effort at the energy component that is most likely to cause a separation. The improvement in the synchronization amongst generators remains the most important step in the improvement of the transfer capacity of the power system network.
APA, Harvard, Vancouver, ISO, and other styles
10

Hillier, Heidi Therese. "How is substrate selectivity in hydride transfer decided in an alcohol dehydrogenase? : Directed evolution of alcohol dehydrogenase A from Rhodococcus ruber DSM 44541 through iterative saturation mutagenesis, a study to understand the structure and function relationship of enzymatic catalysis." Thesis, Uppsala universitet, Biokemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331683.

Full text
APA, Harvard, Vancouver, ISO, and other styles
More sources

Books on the topic "Saturation function"

1

Tanigaki, Miho. Saturation of the approximation by spectral decompositions associated with the Schrödinger operator. Tohoku University, 1998.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
2

Tanigaki, Miho. Saturation of the approximation by spectral decompositions associated with the Schrödinger operator. Tohoku University, 1998.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
3

Gert, Joshua. Color Constancy. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198785910.003.0006.

Full text
Abstract:
This chapter presents an account of color constancy that explains a well-known division in the data from color-constancy experiments: So-called “paper matches” exhibit a much higher level of constancy than so-called “hue-saturation matches.” It argues that the visual representation of objective color is the representation of something associated with a function from viewing circumstances to color appearances. Thus, a relatively robust constancy in the representation of objective color is perfectly consistent with a relatively less robust level of constancy in color appearance. The account also endorses Hilbert’s idea that we can represent the color of the illumination on a surface as well as the color of the surface itself. Finally, the chapter addresses an objection to the hybrid view that notes our capacity to make very fine-grained distinctions between the objective colors of surfaces.
APA, Harvard, Vancouver, ISO, and other styles
4

Peake, Sandra L., and Matthew J. Maiden. Management of septic shock in the critically ill. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0298.

Full text
Abstract:
The management of septic shock is a medical emergency. Following prompt recognition, treatment priorities are haemodynamic resuscitation, empirical antimicrobials, urgent control of the source of infection and monitoring the response to therapy. Haemodynamic resuscitation is focused on maintaining an adequate macrocirculation, while also ensuring adequacy of microcirculatory blood flow to the cells. Intravenous fluids and catecholamines have been the mainstay of therapy. However, the amount and type of fluids, choice of vasoactive medications, and the appropriate resuscitation endpoints have been questioned. Greater awareness of the importance of resuscitating the microcirculation and cell function have led to endpoints such as venous O2 saturation and changes in lactate levels becoming resuscitation targets. Urgent definitive treatment of the infection is also crucial. This requires prompt broad-spectrum empirical antimicrobial therapy, draining infected collections and removing infected medical devices. Despite extensive research, no new therapies have improved survival from septic shock.
APA, Harvard, Vancouver, ISO, and other styles
5

Shirodaria, Cheerag, and Sam Dawkins. Percutaneous coronary intervention. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0097.

Full text
Abstract:
Cardiac catheterization is a procedure by which information is obtained from the heart by passing fine plastic tubes (occasionally other instruments) either near to or within the heart, to introduce contrast to cardiac structures to understand their anatomy and function better, to measure pressures, and/or to measure oxygen saturations in different cardiac chambers. It is an extraordinarily useful diagnostic procedure. Percutaneous coronary intervention (PCI) is the modern term for an intervention on a coronary artery that relieves narrowing. It includes balloon angioplasty and stent insertion. PCI is a therapeutic procedure.
APA, Harvard, Vancouver, ISO, and other styles
6

Macdougall, Iain C. Iron management in renal anaemia. Edited by David J. Goldsmith. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0126.

Full text
Abstract:
Although erythropoiesis-stimulating agent therapy is the mainstay of renal anaemia management, maintenance of an adequate iron supply to the bone marrow is also pivotal in the process of erythropoiesis. Thus, it is important to be able to detect iron insufficiency, and to treat this appropriately. Iron deficiency may be absolute (when the total body iron stores are exhausted) or functional (when the total body iron stores are normal or increased, but there is an inability to release iron from the stores rapidly enough to provide a ready supply of iron to the bone marrow). Several markers of iron status have been tested, but those of the greatest utility are the serum ferritin, transferrin saturation, and percentage of hypochromic red cells. Measurement of serum hepcidin, which is the master regulator of iron homoeostasis, has to date proved disappointing as a means of detecting iron insufficiency, and none of the available iron markers reliably exclude the need for supplemental iron. Iron may be replaced by either the oral or the intravenous route. In the advanced stages of chronic kidney disease, however, hepcidin is upregulated, and this powerfully inhibits the absorption of iron from the gut. Thus, such patients often require intravenous iron, particularly those on dialysis. Several intravenous (IV) iron preparations are available, and they have in common a core containing an iron salt, surrounded by a carbohydrate shell. The IV iron preparations differ in their kinetics of iron release from the iron–carbohydrate complex. In recent times, several new IV iron preparations have become available, and these allow a greater amount of iron to be given more rapidly as a single administration, without the need for a test dose.
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Saturation function"

1

Yang, Hongjiu, Yuanqing Xia, and Qing Geng. "Saturation-Dependent Lyapunov Function." In Studies in Systems, Decision and Control. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-3660-7_8.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Lascelles, P. T., and D. Donaldson. "Vitamin C Saturation Test." In Diagnostic Function Tests in Chemical Pathology. Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1846-7_79.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Pliuškevičius, Regimantas. "On saturation with flexible function symbols." In Mathematical Foundations of Computer Science 1996. Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/3-540-61550-4_172.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Yates, G. K., C. D. Geisler, R. B. Patuzzi, and B. M. Johnstone. "Saturation of Receptor Currents Accounts for Two-Tone Suppression." In Cochlear Mechanisms: Structure, Function, and Models. Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5640-0_22.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Mantel, Charlie, Keisuke Miyazawa, and Hal E. Broxmeyer. "Physical Characteristics and Polymerization During Iron Saturation of Lactoferrin, A Myelopoietic Regulatory Molecule With Suppressor Activity." In Lactoferrin Structure and Function. Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2548-6_12.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Vigh, Laszlo. "Lipid Saturation by Catalytic Hydrogenation and Its Effect on Membrane Structure and Function." In The Metabolism, Structure, and Function of Plant Lipids. Springer New York, 1987. http://dx.doi.org/10.1007/978-1-4684-5263-1_26.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Sharma, Teena, Isha Agrawal, and Nishchal K. Verma. "Transmission Map Estimation Function to Prevent Over-Saturation in Single Image Dehazing." In Conference Proceedings of ICDLAIR2019. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67187-7_16.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Wang, Mengfei, Guangri Jin, and Yang Xiong. "Influence of different fine-grained soil content and saturation state on shear behavior of sandy soil." In Advances in Civil Function Structure and Industrial Architecture. CRC Press, 2022. http://dx.doi.org/10.1201/9781003305019-39.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Longo, Dario Livio, Pietro Irrera, Lorena Consolino, Phillip Zhe Sun, and Michael T. McMahon. "Renal pH Imaging Using Chemical Exchange Saturation Transfer (CEST) MRI: Basic Concept." In Methods in Molecular Biology. Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_14.

Full text
Abstract:
AbstractMagnetic Resonance Imaging (MRI) has been actively explored in the last several decades for assessing renal function by providing several physiological information, including glomerular filtration rate, renal plasma flow, tissue oxygenation and water diffusion. Within MRI, the developing field of chemical exchange saturation transfer (CEST) has potential to provide further functional information for diagnosing kidney diseases. Both endogenous produced molecules as well as exogenously administered CEST agents have been exploited for providing functional information related to kidney diseases in preclinical studies. In particular, CEST MRI has been exploited for assessing the acid-base homeostasis in the kidney and for monitoring pH changes in several disease models. This review summarizes several CEST MRI procedures for assessing kidney functionality and pH, for monitoring renal pH changes in different kidney injury models and for evaluating renal allograft rejection.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
APA, Harvard, Vancouver, ISO, and other styles
10

Hunt, Allen, Robert Ewing, and Behzad Ghanbarian. "Pressure Saturation Curves and the Critical Volume Fraction for Percolation: Accessibility Function of Percolation Theory." In Percolation Theory for Flow in Porous Media. Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03771-4_8.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Saturation function"

1

Mahinfalah, M., G. Nakhaie Jazar, M. Rastgaar Aagaah, and N. Mahmoudian. "Frequency Response of Vibration Isolators With Saturating Spring Elements." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84520.

Full text
Abstract:
An investigation using averaging method is carried out to obtain the frequency response of a class of vibration isolators with saturation spring. The saturation characteristics are modeled using a hyperbolic-tangent function. The hyperbolic-tangent saturation function is compared with other popular saturation functions, using piecewise nonlinear approximation. A parameteric study indicates that piecewise linear approximation of saturating functions provide results that are close enough to the results of hyperbolic tangent approximation. A sensitivity analysis of frequency response of the system is also investigated based on the piecewise linear approximation.
APA, Harvard, Vancouver, ISO, and other styles
2

Andersen, Pål Østebø. "Extended Fractional Flow Theory for Steady State Relative Permeability Experiments With Capillary End Effects – Transient Solutions and Time Scales." In 2022 SPWLA 63rd Annual Symposium. Society of Petrophysicists and Well Log Analysts, 2022. http://dx.doi.org/10.30632/spwla-2022-0031.

Full text
Abstract:
Steady state core flooding experiments are regularly performed for estimation of relative permeability functions which are key inputs for simulation of multiphase flow in porous media. Such tests can be time demanding, thus it is valuable to find the relation between fluid flow properties, injection conditions and the time for the desired measurements of stabilized average saturation and pressure drop to be obtained. The phases we consider are oil and water but could be any immiscible phases. An injection condition is specified by the total injected volumetric rate Qt and the fraction F of the total rate due to water. At steady state at these injection conditions there is no change with time in pressures or saturations. We consider the transition from the steady state of one injection condition, when one or both of Qt and F are changed, until the steady state of the new injection conditions have developed. The spatial saturation distributions at steady state are known analytically from solutions derived by Andersen (2021a). From the method of characteristics, a solution is constructed to describe the velocity of each saturation traveling between the two steady state profiles. The velocity for each saturation is estimated based on an effective fractional flow function that combines contributions of advective and capillary forces to one saturation dependent function. The solution allows us to interpret experimental data, forecast the time scale of the tests at each condition and suggest a more optimal scheme to conduct the experiments as they proceed. Assuming an imbibition setup, the solution implies frontal displacement and short time scales when increasing the fraction F where the flow function is convex. This is the case at sufficiently low saturations. At higher saturations the flow function becomes concave and the saturations travel with individual speeds proportional to the flow function derivative. The time scale is limited by the slowest saturation. At high saturations the saturation speed approaches zero giving an infinite time scale. In a water-wet case, capillary end effects shift the saturation profiles up to include slower high saturations and increase the time scale. In an oil-wet case the saturation profiles are shifted down such that the slowest saturations are faster or travel a shorter distance, thus reducing the time scale. The model is validated by comparing the proposed analytical solution with numerical solutions.
APA, Harvard, Vancouver, ISO, and other styles
3

Kumar, Rajesh, P. K. Cherukupalli, B. L. Lohar, and Dinesh Chandra. "Saturation Modeling in a Multilayered Carbonate Reservoir Using Log-Derived Saturation-Height Function." In SPE/DOE Improved Oil Recovery Symposium. Society of Petroleum Engineers, 2002. http://dx.doi.org/10.2118/75213-ms.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Kawai, Yuki, and Kenji Uchiyama. "Modified integral sliding mode controller with saturation function." In 2016 7th International Conference on Mechanical and Aerospace Engineering (ICMAE). IEEE, 2016. http://dx.doi.org/10.1109/icmae.2016.7549566.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Ma, Haifeng, Jianhua Wu, and Zhenhua Xiong. "PID saturation function sliding mode control for piezoelectric actuators." In 2014 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM). IEEE, 2014. http://dx.doi.org/10.1109/aim.2014.6878088.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Phu, Do Xuan, and Bien Minh Tri. "Adaptive Optimal Control for Upper Exoskeleton following Saturation Function." In 2021 24th International Conference on Mechatronics Technology (ICMT). IEEE, 2021. http://dx.doi.org/10.1109/icmt53429.2021.9687228.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Syofyan, Syofvas, Christophe Darous, Ishan Raina, et al. "A New Approach to Model Saturation Below Free Water Level, A Case Study From a Giant Reservoir in the Middle East." In 2022 SPWLA 63rd Annual Symposium. Society of Petrophysicists and Well Log Analysts, 2022. http://dx.doi.org/10.30632/spwla-2022-0058.

Full text
Abstract:
The calculation of oil saturation below the free water level is often disregarded, considering it relates to uncertainty in calculations, or non-exploitable isolated residual hydrocarbon. In this giant field of the Middle East exploited from crest wells, a recent campaign of flank appraisal wells revealed significant hydrocarbon saturation that is incompatible with the original free water level and existing saturation height modeling in drainage. A completely new thinking of the saturation height modeling involving an imbibition cycle became one of the reasonable options to model the phenomena. To include imbibition into the saturation height modeling process, two additional steps are required. The first step is the construction of the imbibition saturation function from available core Pc imbibition experiments. A saturation function fitted to the data and combined with end points relationships defines the scanning curves behavior of the imbibition process from any initial water saturation in drainage. The second step is the search of the Paleo-free water level position in each well that ultimately is mapped to implement the saturation modeling in 3D. The log saturation profiles in the new flank appraisal wells, mud logging and core saturations have confirmed that hydrocarbon is present at depth significantly below the initial free water level and only an imbibition cycle post initial accumulation can explain this observation. The fitting of the Pc imbibition core data with a Van Genuchten type of function is appropriate and more practical for the 3D implementation than using other non-linearizable functions. The mapping of the paleo-free water level revealed that the structure at the time of accumulation was similar in shape but flatter than today’s structure suggesting a compression post-migration. The match between the Sw from logs and the Sw from this new saturation modeling approach is very robust leading to a much better in-place estimation and prospectivity. This case study is certainly an eye-opener for fields with similar migration and post-migration history. The methodology honors the principles of capillary pressures to model saturations and can readily be implemented in 3D in the same way saturation height modeling with drainage only is implemented. The process also improves the understanding of the geological post migration structural events that impact reservoir performance. Finally, it opens the opportunity for tapping additional oil in place below initial free water levels.
APA, Harvard, Vancouver, ISO, and other styles
8

De Dominicis, Luigi, and Roberta Fantoni. "Saturation effects in degenerate four-wave mixing lineshape on FeI atomic vapors." In Medical Imaging 2003 Physiology and Function: Methods, Systems, and Applications, edited by Alexis Carabelas, Giuseppe Baldacchini, Paolo Di Lazzaro, and Dimitrios Zevgolis. SPIE, 2003. http://dx.doi.org/10.1117/12.513514.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Baig, Raheel, and Hasan Nooruddin. "Digitally Augmented Subsurface History Match (DASH-Sim): A New Frontier in Reservoir Simulation History Matching." In SPE Symposium: Leveraging Artificial Intelligence to Shape the Future of the Energy Industry. SPE, 2023. http://dx.doi.org/10.2118/214474-ms.

Full text
Abstract:
Abstract History matching is a long-standing industry challenge and resource-intensive process. In this paper, we introduce a new method in the area of automated history matching algorithms, called Digitally Augmented Subsurface History Match (DASH-Sim), that focuses on calibrating the permeability property at the field level. The new approach captures the global displacement mechanism as observed in the field by capitalizing on time-lapse surveillance data. Time-lapse surveillance data is used to derive an accurate representation of subsurface saturation as a function of time. We refer to this dynamic saturation distribution as the 4D saturation model. The DASH-Sim method minimizes the difference in saturation between the 4D model and the simulation model at all timesteps by adjusting the 3D grid-cell permeability values. A novel mathematical relationship is introduced that calculates the required permeability calibration in the simulation model as a function of the underlying rock quality and the difference in water saturation between the 4D saturation model and the simulation model. The algorithm considers the dynamic nature of saturation by successively updating the static permeability property at each timestep of the corresponding observed 4D saturation. A synthetic case study is presented in which the new algorithm is applied. First, a truth case simulation model was run using a permeability distribution from which water saturations were recorded as a function of time. The simulated water saturation over time using the truth case permeability was treated as the observed 4D saturation model. Next, a significantly modified permeability property was replaced in the simulation model resulting in a new water saturation distribution over time. The DASH-sim algorithm was then used as an inverse history match calibration process to generate permeability modifications guided by the objective function to minimize mismatch in saturations between the observed 4D saturation model and the numerical simulation model. Results indicate a very good history match is achieved in an automated manner, reducing the turnaround time for such tasks by orders of magnitude. The inverse problem of history matching subsurface reservoir models is a very challenging and time-consuming task. The DASH-Sim offers a new approach to automate this tedious task consistently by considering both surface-level production and subsurface time-lapse measured surveillance data.
APA, Harvard, Vancouver, ISO, and other styles
10

Khamaiseh, Samer Y., Izzat Alsmadi, and Abdullah Al-Alaj. "Deceiving Machine Learning-Based Saturation Attack Detection Systems in SDN." In 2020 IEEE Conference on Network Function Virtualization and Software Defined Networks (NFV-SDN). IEEE, 2020. http://dx.doi.org/10.1109/nfv-sdn50289.2020.9289908.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Reports on the topic "Saturation function"

1

Dougherty, J. H., Eckenhoff Jr., Hunter R. G., Jr W. L., J. W. Parker, and D. J. Styer. Hyperbaric and Hyperoxic Effects on Pulmonary Function During Air Saturation Dives. Defense Technical Information Center, 1985. http://dx.doi.org/10.21236/ada418606.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Shykoff, B. E. Pulmonary Function After Oxygen-Accelerated Decompressions from Repetitive Sub-Saturation Air Dives. Defense Technical Information Center, 2005. http://dx.doi.org/10.21236/ada442753.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Roberts, J. J., E. Carlberg, and W. Lin. Electrical properties of tuff from the ESF as a function of water saturation and temperature. Office of Scientific and Technical Information (OSTI), 1998. http://dx.doi.org/10.2172/652973.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

LANG, Philipp, and Stephan MATTHÄI. Fracture-Matrix Interface Area Contacted by Injected Fluid as a Function of Average Saturation, Mechanical Aperture and Counter-Current Imbibition. Cogeo@oeaw-giscience, 2011. http://dx.doi.org/10.5242/iamg.2011.0177.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Carlo Montemagno. Establishing a Quantitative Functional Relationship between Capillary Pressure Saturation and Interfacial Area. Office of Scientific and Technical Information (OSTI), 2002. http://dx.doi.org/10.2172/796249.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Montemagno, C. D. Establishing a quantitative functional relationship between capillary pressure, saturation and interfacial area. 1997 annual progress report. Office of Scientific and Technical Information (OSTI), 1997. http://dx.doi.org/10.2172/13606.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Montemagno, C. D., M. Celia, and W. G. Gray. Establishing a quantitative functional relationship between capillary pressure saturation and interfacial area. 1998 annual progress report. Office of Scientific and Technical Information (OSTI), 1998. http://dx.doi.org/10.2172/13607.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Russo, David, and William A. Jury. Characterization of Preferential Flow in Spatially Variable Unsaturated Field Soils. United States Department of Agriculture, 2001. http://dx.doi.org/10.32747/2001.7580681.bard.

Full text
Abstract:
Preferential flow appears to be the rule rather than the exception in field soils and should be considered in the quantitative description of solute transport in the unsaturated zone of heterogeneous formations on the field scale. This study focused on both experimental monitoring and computer simulations to identify important features of preferential flow in the natural environment. The specific objectives of this research were: (1) To conduct dye tracing and multiple tracer experiments on undisturbed field plots to reveal information about the flow velocity, spatial prevalence, and time evolution of a preferential flow event; (2) To conduct numerical experiments to determine (i) whether preferential flow observations are consistent with the Richards flow equation; and (ii) whether volume averaging over a domain experiencing preferential flow is possible; (3) To develop a stochastic or a transfer function model that incorporates preferential flow. Regarding our field work, we succeeded to develop a new method for detecting flow patterns faithfully representing the movement of water flow paths in structured and non-structured soils. The method which is based on application of ammonium carbonate was tested in a laboratory study. Its use to detect preferential flow was also illustrated in a field experiment. It was shown that ammonium carbonate is a more conservative tracer of the water front than the popular Brilliant Blue. In our detailed field experiments we also succeeded to document the occurrence of preferential flow during soil water redistribution following the cessation of precipitation in several structureless field soils. Symptoms of the unstable flow observed included vertical fingers 20 - 60 cm wide, isolated patches, and highly concentrated areas of the tracers in the transmission zone. Soil moisture and tracer measurements revealed that the redistribution flow became fingered following a reversal of matric potential gradient within the wetted area. Regarding our simulation work, we succeeded to develop, implement and test a finite- difference, numerical scheme for solving the equations governing flow and transport in three-dimensional, heterogeneous, bimodal, flow domains with highly contrasting soil materials. Results of our simulations demonstrated that under steady-state flow conditions, the embedded clay lenses (with very low conductivity) in bimodal formations may induce preferential flow, and, consequently, may enhance considerably both the solute spreading and the skewing of the solute breakthrough curves. On the other hand, under transient flow conditions associated with substantial redistribution periods with diminishing water saturation, the effect of the embedded clay lenses on the flow and the transport might diminish substantially. Regarding our stochastic modeling effort, we succeeded to develop a theoretical framework for flow and transport in bimodal, heterogeneous, unsaturated formations, based on a stochastic continuum presentation of the flow and a general Lagrangian description of the transport. Results of our analysis show that, generally, a bimodal distribution of the formation properties, characterized by a relatively complex spatial correlation structure, contributes to the variability in water velocity and, consequently, may considerably enhance solute spreading. This applies especially in formations in which: (i) the correlation length scales and the variances of the soil properties associated with the embedded soil are much larger than those of the background soil; (ii) the contrast between mean properties of the two subdomains is large; (iii) mean water saturation is relatively small; and (iv) the volume fraction of the flow domain occupied by the embedded soil is relatively large.
APA, Harvard, Vancouver, ISO, and other styles
9

Bradford, Joe, Itzhak Shainberg, and Lloyd Norton. Effect of Soil Properties and Water Quality on Concentrated Flow Erosion (Rills, Ephermal Gullies and Pipes). United States Department of Agriculture, 1996. http://dx.doi.org/10.32747/1996.7613040.bard.

Full text
Abstract:
Concentrated flow erosion in rills, pipes, ephermal gullies, and gullies is a major contributor of downstream sedimentation. When rill or gullies form in a landscape, a 3- to 5-fold increase in soil loss commonly occurs. The balance between the erosive power of the flow and the erosion resistance of the bed material determines the rate of concentrated flow erosion. The resistance of the bed material to detachment depends primarily on the magnitude of the interparticle forces or cohesion holding the particles and aggregates together. The effect of soil properties on bed material resistance and concentrated flow erosion was evaluated both in the laboratory and field. Both rill erodibility and critical hydraulic shear were greater when measured in 9.0 m long rills under field conditions compared with laboratory mini-flumes. A greater hydraulic shear was required to initiate erosion in the field compared to the mini-flume because of the greater aggregate and clod size and stability. Once erosion was initiated, however, the rate of erosion as a function of hydraulic shear was greater under field conditions because of the greater potential for slaking upon wetting and the greater soil surface area exposed to hydraulic shear. Erosion tests under controlled laboratory conditions with the mini-flume allowed individual soil variables to be studied. Attempts to relate rill erosion to a group soil properties had limited success. When individual soil properties were isolated and studied separately or grouped separately, some trends were identified. For example, the effect of organic carbon on rill erodibility was high in kaolinitic soils, low in smectitic soils, and intermediate in the soils dominated by illite. Slow prewetting and aging increased the cohesion forces between soil particles and decreased rill erodibility. Quick prewetting increased aggregate slaking and increased erodibility. The magnitude of the effect of aging depended upon soil type. The effect of clay mineralogy was evaluated on sand/clay mixtures with montmorillonite (M), Illite (I), and kaolinite (K) clays. Montmorillonite/sand mixtures were much less erodible than either illite or kaolonite sand mixtures. Na-I and Na-K sand mixtures were more erodible than Ca-I and Ca-K due to increased strength from ionic bonding and suppression of repulsive charges by Ca. Na-M was less erodiblethan Ca-M due to increased surface resulting from the accessibility of internal surfaces due to Na saturation. Erodibility decreased when salt concentration was high enough to cause flocculation. This occurred between 0.001 mole L-1 and 0.01 mole L-1. Measuring rill erodibility in mini-flumes enables the measurement of cohesive forces between particles and enhances our ability to learn more about cohesive forces resisting soil detachment under concentrated water flow.
APA, Harvard, Vancouver, ISO, and other styles
10

Snyder, Victor A., Dani Or, Amos Hadas, and S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580670.bard.

Full text
Abstract:
Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'Saturation function' for particular source types:
Journal articles Dissertations / Theses
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography