Fundamental Issues of Nanofluid Behavior

2006 ◽  
Author(s):  
Wesley C. Williams
Keyword(s):  
Base Fluid ◽  
Colloid Stability ◽  
Particle Loading ◽  
Volume Percentage ◽  
Conductivity Enhancement ◽  
Metallic Oxides ◽  
Basic Understanding ◽  
The Common ◽  
The Stability ◽  
Abnormal Conductivity

This paper will elucidate some of the behaviors of nanofluids other than the abnormal conductivity enhancement, which are of importance to the experimental and engineering use of nanofluids. Nanofluid is the common name of any sol colloid involving nanoscale (less than 100nm) sized particles dispersed within a base fluid. It has been shown previously that the dispersion of nano-particulate metallic oxides into water can increase thermal conductivity up to 30–40% over that of the base fluid and anomalously more than the mere weighed average of the colloid. There is a great potential for the use of nanofluids as a way to enhance fluid/thermal energy transfer systems. Due to the recentness of nanofluid science, there are still many issues which have not been fully investigated. This paper should act as a primer for the basic understanding of nanofluid behavior. Particle size and colloid stability are of key importance to the functionality of nanofluids. The pH and concentration/loading of nanofluids can alter the size of the nanoparticles and also the stability of the fluids. It will be shown through experiment and colloid theory the importance of these parameters. Furthermore, most of the existing literature uses volume percentage as the measure of particle loading, which can often be misleading. There will be discussion of this and other misleading ideas in nanofluid science.

An Experimental Investigation on Thermal Conductivity and Viscosity of Graphene doped CNTs /TiO2 Nanofluid

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
A.M. Zetty Akhtar ◽  
M.M. Rahman ◽  
K. Kadirgama ◽  
M.A. Maleque
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Minimum Quantity Lubrication ◽  
Cutting Fluid ◽  
Cutting Zone ◽  
Observation Method ◽  
The Stability ◽  
The Relationship ◽  
Zeta Potential Analysis

This paper presents the findings of the stability, thermal conductivity and viscosity of CNTs (doped with 10 wt% graphene)- TiO2 hybrid nanofluids under various concentrations. While the usage of cutting fluid in machining operation is necessary for removing the heat generated at the cutting zone, the excessive use of it could lead to environmental and health issue to the operators. Therefore, the minimum quantity lubrication (MQL) to replace the conventional flooding was introduced. The MQL method minimises the usage of cutting fluid as a step to achieve a cleaner environment and sustainable machining. However, the low thermal conductivity of the base fluid in the MQL system caused the insufficient removal of heat generated in the cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. The ethylene glycol used as the base fluid, titanium dioxide (TiO2) and carbon nanotubes (CNTs) nanoparticle mixed to produce nanofluids with concentrations of 0.02 to 0.1 wt.% with an interval of 0.02 wt%. The mixing ratio of TiO2: CNTs was 90:10 and ratio of SDBS (surfactant): CNTs was 10:1. The stability of nanofluid checked using observation method and zeta potential analysis. The thermal conductivity and viscosity of suspension were measured at a temperature range between 30˚C to 70˚C (with increment of 10˚C) to determine the relationship between concentration and temperature on nanofluid’s thermal physical properties. Based on the results obtained, zeta potential value for nanofluid range from -50 to -70 mV indicates a good stability of the suspension. Thermal conductivity of nanofluid increases as an increase of temperature and enhancement ratio is within the range of 1.51 to 4.53 compared to the base fluid. Meanwhile, the viscosity of nanofluid shows decrements with an increase of the temperature remarks significant advantage in pumping power. The developed nanofluid in this study found to be stable with enhanced thermal conductivity and decrease in viscosity, which at once make it possible to be use as nanolubricant in machining operation.

Soil Strength Reduction Method Induced by Variation of Water Content

2012 ◽  
Vol 170-173 ◽  
pp. 847-852
Author(s):  
Peng Ming Jiang ◽  
Zhong Lei Yan ◽  
Peng Li
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Strength Reduction ◽  
Actual State ◽  
Soil Slope ◽  
Simple Method ◽  
The Common ◽  
The Stability

As the complexity of unsaturated soil theory, and it must have a long test period when we study the unsaturated soils, so the conventional design analysis software does not provide such analysis, so we can imagine that such a slope stability analysis does not accurately reflect the actual state of the slope. Based on the known soil moisture content，this paper use the soil water characteristic curve and strength theory of unsaturated soil to calculate the strength reduction parameters of soil which can calculate the stability of the soil slope when using the common calculation method. It is noticeable that this method can be extended and applied if we establish regional databases for this simple method, and these databases can improve the accuracy of the calculation of slope stability.

scholarly journals The Stability of the Aggregate Loss Distribution

Risks ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 91 ◽  
Author(s):  
Riccardo Gatto
Keyword(s):  
Stability Analysis ◽  
Survival Function ◽  
Saddlepoint Approximation ◽  
Computational Formula ◽  
Important Indicator ◽  
The Common ◽  
Infinitesimal Perturbation ◽  
Aggregate Loss ◽  
Aggregate Loss Distribution ◽  
The Stability

In this article we introduce the stability analysis of a compound sum: it consists of computing the standardized variation of the survival function of the sum resulting from an infinitesimal perturbation of the common distribution of the summands. Stability analysis is complementary to the classical sensitivity analysis, which consists of computing the derivative of an important indicator of the model, with respect to a model parameter. We obtain a computational formula for this stability from the saddlepoint approximation. We apply the formula to the compound Poisson insurer loss with gamma individual claim amounts and to the compound geometric loss with Weibull individual claim amounts.

Zambia's Second Republic —the Establishment of a One-Party State

1974 ◽  
Vol 12 (2) ◽  
pp. 231-244 ◽  
Author(s):  
Jan Pettman
Keyword(s):  
Political Development ◽  
Political System ◽  
The State ◽  
Second Republic ◽  
National Unity ◽  
Common Enemy ◽  
The Common ◽  
The Government ◽  
The Stability ◽  
Party State

Zambia inherited a system of government and administration in 1964 which was ill-suited to the tasks of political development to which her new leaders were dedicated. What little national unity and mobilisation had been achieved in the independence struggle declined with the removal of the common enemy. The Government rested on a fragile base, without the support of agreed rules and practices to limit and contain conflict, and without adequate instruments available for the implementation of its policies. So the search began for a more suitable political system, which could cope with the new needs of independence, and provide for the stability of the state and the survival of the Government.

scholarly journals Nodes, paranodes and neuropathies

2017 ◽  
Vol 89 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Janev Fehmi ◽  
Steven S Scherer ◽  
Hugh J Willison ◽  
Simon Rinaldi
Keyword(s):  
Peripheral Nerves ◽  
Clinical Importance ◽  
Specific Cell ◽  
Peripheral Neuropathies ◽  
Autoimmune Neuropathy ◽  
Basic Understanding ◽  
Clinical Variants ◽  
Inflammatory Neuropathies ◽  
The Common ◽  
Treatment Responsiveness

This review summarises recent evidence supporting the involvement of the specialised nodal and perinodal domains (the paranode and juxtaparanode) of myelinated axons in the pathology of acquired, inflammatory, peripheral neuropathies.The identification of new target antigens in the inflammatory neuropathies heralds a revolution in diagnosis, and has already begun to inform increasingly targeted and individualised therapies. Rapid progress in our basic understanding of the highly specialised nodal regions of peripheral nerves serves to strengthen the links between their unique microstructural identities, functions and pathologies. In this context, the detection of autoantibodies directed against nodal and perinodal targets is likely to be of increasing clinical importance. Antiganglioside antibodies have long been used in clinical practice as diagnostic serum biomarkers, and associate with specific clinical variants but not to the common forms of either acute or chronic demyelinating autoimmune neuropathy. It is now apparent that antibodies directed against several region-specific cell adhesion molecules, including neurofascin, contactin and contactin-associated protein, can be linked to phenotypically distinct peripheral neuropathies. Importantly, the immunological characteristics of these antibodies facilitate the prediction of treatment responsiveness.

Ba-, Si- and vacancy-rich phlogopites from the talc-bearing sulfide ore deposit of La Creuse, Beaujolais, France

2018 ◽  
Vol 82 (5) ◽  
pp. 1187-1210
Author(s):  
Marie-Lola Pascal ◽  
Michel Fonteilles ◽  
Véronique Tournis ◽  
Benoît Baptiste ◽  
Jean-Louis Robert ◽  
...  
Keyword(s):  
Goodness Of Fit ◽  
Monoclinic Space Group ◽  
Excess Charge ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Ore Deposit ◽  
Sulfide Ore ◽  
The Common ◽  
The Stability ◽  
High Level

ABSTRACTBa-rich and Si-rich phlogopites occur in the talc-bearing rocks of the La Creuse sulfide ore deposit in Beaujolais, France. They form a group of compositions completely separated from the common Al-rich phlogopites that occur in the surrounding talc-free metasiltites and metarhyolites, with higher Ba and Mg and lower Al contents. The Ba-rich phlogopites have a relatively narrow compositional range (0.24 to 0.80 Ba per formula unit, for 44 valencies) with high and constant Si (5.8 atoms per formula unit, apfu) and Mg + Fe (5.6 apfu), probably buffered by the presence of talc. Compared to low-Al phlogopites from talc-free rocks, the excess charge introduced by the BaK–1 substitution is compensated by interlayer vacancies. Such a high level of interlayer vacancy (0.56 pfu), related to the talc-producing metasomatic conditions, is essential for the stability of this special group of Ba-rich and Si-rich phlogopites.Single crystal X-ray diffraction analyses were performed. Ba-rich and Si-rich phlogopite is monoclinic, space group C2/m, (R = 5.31%) with a = 5.3185(5), b = 9.2136(9), c = 10.1349(11) Å and β = 100.131(11)°. The occupancies of Mg/Fe and K/Ba were refined exploring different vacancies. The solutions giving the best R factor (4.77%) and goodness-of-fit (1.06) are obtained with 15% < vacancy < 40% at the interlayer site.

Stability Analysis for a Class of Linear Switched Positive Systems

2012 ◽  
Vol 562-564 ◽  
pp. 2084-2087
Author(s):  
Hui Ding ◽  
Xu Yang Lou
Keyword(s):  
Lyapunov Functions ◽  
Dwell Time ◽  
Positive Systems ◽  
Time Analysis ◽  
Arbitrary Switching ◽  
The Family ◽  
The Common ◽  
The Stability ◽  
Switched Positive Systems ◽  
Explicit Relation

This paper addresses stability properties of linear switched positive systems composed of continuous-time subsystems and discrete-time subsystems. Based on the common linear copositive Lyapunov functions, stability of the positive systems is discussed under arbitrary switching. Moreover, a sufficient condition on the minimum dwell time that guarantees the stability of linear switched positive systems. The dwell time analysis interprets the stability of linear switched positive systems through the distance between the eigenvector sets. Thus, an explicit relation in view of stability is obtained between the family of the involved subsystems and the set of admissible switching signals.

scholarly journals Dispersion stability and rheological characteristics of water and ethylene glycol based zinc oxide nanofluids

2020 ◽  
pp. 187-187
Author(s):  
Adnan Qamar ◽  
Attique Arshad ◽  
Zahid Anwar ◽  
Rabia Shaukat ◽  
Muhammad Amjad ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ethylene Glycol ◽  
Industrial Applications ◽  
Deionized Water ◽  
Rheological Characteristics ◽  
Particle Loading ◽  
Viscosity Models ◽  
Vis Spectroscopy ◽  
Settling Speed ◽  
The Stability

With advancement of nanoscience, ?nanofluids? are becoming quite popular among thermal engineers. High thermal conductivity, relatively less settling speed, and higher surface area of nanoparticles are a few key promoting properties. The last two decades have seen dramatic progress towards using nanoparticles in industrial applications. However, the stability and rheological characteristics of prepared nanofluids have serious effects on their transport characteristics, but unfortunately, this has not found proper attention from researchers. In this study, stability and rheological characteristics of ZnO nanoparticles within deionized water, ethylene glycol, and their blends have been extensively tested. Stability was observed using UV-vis spectroscopy, while the viscosity was measured with the help of a rheometer. The data was collected with 0.011-0.044 wt. % loading of nanoparticles, while experiments were conducted within 15-55oC temperature range. Better stability was recorded when nanofluids were prepared with pure ethylene glycol. Experiments showed that the viscosity increased with particle loading, whereas the effect of surfactants appeared to be insignificant. Research results were used to assess predictions of different viscosity models. Experimental data was overpredicted by Einstein, Brinkman, and Batchelor?s models.

scholarly journals Study the Effect of Gum Arabic and Triton X-100 on Stability and Thermal Conductivity of ZnO/ethylene glycol Nanofluids

2021 ◽  
Vol 72 (1) ◽  
pp. 18-24
Author(s):  
Noor Sabeeh Majeed ◽  
Hussein A. Alabdly ◽  
Hussam Nadum Abdalraheem Al Ani ◽  
Dumitru Pascu ◽  
Aurelia Cristina Nechifor
Keyword(s):  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Zeta Potential ◽  
Ethylene Glycol ◽  
Base Fluid ◽  
Thermal Conductivity Coefficient ◽  
Uv Spectroscopy ◽  
Gum Arabic ◽  
The Stability ◽  
Triton X

Stability of nanofluids is one of the most important factors to ensure the most benefit of the properties of nanoparticles. Zinc oxide was used in the research with concentration between (0.2-1) wt. % with ethylene glycol base fluid. The stability of ZnO nanofluid was enhanced by adding two types of surfactants Tx-100 and Gum Arabic with concentration of (0.1-0.5) vol. % to stabilize the ZnO nanoparticles in the base fluid. The results showed that the Gum Arabic surfactant led to more stable fluid than that of Tx-100; this was shown from zeta potential and UV spectroscopy measurements. The thermal conductivity coefficient was also measured, and the results showed that the thermal conductivity increased with adding surfactant than without using a stabilizer.

Study on Stability of Highway Subgrade Slope in Desert Region

2013 ◽  
Vol 639-640 ◽  
pp. 974-977
Author(s):  
Jing Yu He ◽  
Guo Hua Liu
Keyword(s):  
Rapid Development ◽  
Construction Cost ◽  
Geological Environment ◽  
Highway Infrastructure ◽  
Desert Region ◽  
Environment Characteristic ◽  
Desert Areas ◽  
The Common ◽  
The Stability ◽  
Desert Highway

With the rapid development of economy, highway infrastructure is gradually extended to desert region. But at present, affected by the special engineering geological environment in desert areas, the work must be majorly planned and considered before the highway project is set that how to reduce the construction cost while ensuring the desert highway construction quality, and maximizing the maintainance and further improvement of desert environment. The wind and sand environment characteristic of desert areas is analyzed in this paper, then the common types of desert highway subgrade slope are investigated and the stability of wind-blown sand subgrade slope is studied, finally the theories and methods according to the characteristics of the desert subgrade are proposed.

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