다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Positive ions that are available in soils absorb on grain surfaces. The total sum of cations that can be absorbed bij a soil/sediment at a certain PH is defined by the cation-exchange capacity (CEC, in meq g-1: mol equivalents per gram). The uptake of cations is an important parameter in agriculture and the larger the CEC, the more cations can be absorbed to the soil. The CEC depends highly on the pH of soil and sediments, where the CEC decreases with decreasing PH (increasing acidity). The exchange of ions on sediments occurs commonly fast on geological time scales, but the kinetics of adsorption in natural environments is still poorly understood. The strength of the bonding between the cations and the sediments varies from weak Van der Waals bondings (physical adsorption) to strong chemical bonds. The CEC is widely used for agricultural assessment because it is a measure of general soil fertility as well as an indicator of structural stability because CED is capabel of enhancing development of shrinkage cracks. The list below shows the CEC for different types of minerals. The data indicate that the CEC can vary over 2 orders of magnitude for various types of , minerals and can vary one order of magnitude within one soil type. Cation exchange capacity for different types of sediment (Eisma, 1992; Locher and de Bakker, 1990):

Cation exchange capacity.

A review of recent advances in thermophysical properties at the nanoscale: From solid state to colloids

Preparation and evaluation of stable nanofluids for heat transfer application: A review

Nanofluids are described as a relatively new kind of colloidal solutions with a particle size smaller than one billionth of a meter (1–100 nm) suspended in the base fluid so as to enhance the thermophysical properties, which makes them an obvious choice for use in number of commercial applications including engineering, medical sciences, biotechnology, agriculture technology, transportation etc. With the advancement in nanotechnology during last few years, scientific community focuses on improvising combustion behavior, stability aspects, various engine performance parameters and emission characteristics of conventional diesel engine using nanoparticle laden diesel biodiesel fuel blends. Most recently few experimental works on above issues using nanosized metallic, non-metallic, organic and mixed particles in the base liquid fuel for diesel engine have appeared in the open literature. The obtained results are very encouraging due to multifold enhancement in thermo physical and chemical properties of modified fuel such as high surface to volume ratio, high reactive medium for combustion, enhanced heat and mass transport properties due to high thermal conductivity, improvement in flash point, fire point, pour point etc depending upon the type of nanoparticles used, their particle size and concentration with base fuel. Despite having all superiorities, somewhat unclear and contradictory results are found in the literature, further the experimental results of different researchers are not generalized so far as to reach at common consensus about this new approach of fuel modification. Keeping all these facts in mind, a serious attempt has been made to summarize the important published work on combustion and stability aspects of nanoparticle laden diesel, biodiesel fuels and their blends, and its effects on fuel and engine overall characteristics with the objective to provide a pathway to conduct further research in this area for utilizing maximum potential of nanoparticle fuel emulsion technology and to provide a promising future fuel for diesel engine.

A comprehensive review on combustion and stability aspects of metal nanoparticles and its additive effect on diesel and biodiesel fuelled C.I. engine.

Recently, the study of transformer oil-based nanofluids became of great interest, due to their prospective properties as a dielectric and cooling medium. However, agglomeration of nanoparticles limits the beneficial properties that can be obtained from nanofluids. So, the work presented in this paper aims to get enhanced dispersion behavior of nanoparticles within transformer oil-based nanofluids. Then, breakdown strength with the enhanced dispersion behavior is evaluated. In order to get enhanced dispersion behavior, nanofluids were prepared using nanoparticles with a surfactant. The surfactant plays a role in the stabilization of nanoparticles and maintaining suspension stability. The considered type of nanoparticles is TiO2 nanoparticles. Two series of nanofluid samples were prepared. Through the first series, the effect of surfactant concentration on dispersion behavior and agglomerate size was studied. The dispersion of nanoparticles was characterized using three different techniques. These techniques are optical microscope analysis, transmission electron microscope (TEM) analysis and zeta potential measurements. Based on these techniques, the suitable concentration of surfactant was identified. The second series of nanofluid samples was prepared with different weight percents of nanoparticles for assessing the breakdown strength. Weibull distribution was used to calculate the breakdown probability for the base oil as well as nanofluid samples. The results showed an enhancement in the breakdown strength by about 27% in comparison to the base oil. Based on the obtained results, mechanisms behind the dispersion behavior and breakdown strength were proposed and discussed.

R.M. Khattab

Papers

Dispersion behavior and breakdown strength of transformer oil filled with TiO 2 nanoparticles

Stability and electrical conductivity of water-base Al2O3 nanofluids for different applications

Thermo-mechanical properties of mullite/zirconia reinforced alumina ceramic composites

Preparation and characterization of porous alumina ceramics through starch consolidation casting technique

Effect of surfactant types and their concentration on the structural characteristics of nanoclay.