Search results for "Oxidation rate"
showing 9 items of 9 documents
High temperature oxidation of Mg2(Si-Sn)
2016
Abstract High temperature oxidation of Mg 2 Si 1- x Sn x alloys ( x = 0.1 ⿿ 0.6) has been investigated. The oxidation rate was slow for temperatures below 430 °C. In the temperature range between 430⿿500 °C all the alloys exhibited breakaway oxidation. The onset temperature of the breakaway region in general decreased with increasing level of Sn in the alloy. The breakaway behavior is explained by a combination of the formation of a non-protective MgO layer and the formation of Sn-rich liquid at the interface between the oxide and Mg depleted Mg 2 Sn.
Effect of Temperature on N2O and NO Emission in a Partial Nitrification SBR Treating Reject Wastewater
2017
Temperature is a very important parameter during nitritation, having a direct effect on ammonia oxidation rate (AOR) and enzymatic activities which relate to both N2O and NO emission. This study aims at investigating the effect of temperature on AOR, N2O and NO production in an enriched ammonia oxidizing bacteria (AOB) sequencing batch reactor (SBR) performing partial nitrification (PN) of synthetic reject wastewater. To achieve that, a SBR was subject to several shifts in temperature (in the range of 30 to 15 °C, 5 °C for each decrease). Cycle studies, which contain two aeration phases, were conducted under each temperature. The results showed that AOR specific exponentially correlates wit…
RELATIONSHIP BETWEEN MAXIMAL FAT OXIDATION AND OXYGEN UPTAKE: COMPARISON BETWEEN PATIENTS WITH TYPE 2 DIABETES AND HEALTHY SEDENTARY SUBJECTS
2014
The contribution of fat oxidation to energy production during exercise is influenced by intensity of exercise. The aim of this study was to assess the relationship between the highest value of fat oxidation rate (FATmax) and the oxygen uptake (VO2) in sedentary type 2 diabetes (T2D) patients vs healthy sedentary subjects. Sedentary T2D patients and healthy sedentary subjects were evaluated to a graded exercise test, and oxygen uptake and fat oxidation rate were detected. Data show that in T2D patients fat oxidation rate is not impaired and the positive linear correlation between FATmax and both VO2 and VO2max suggests that even in T2D patients the muscle oxidative capacity might increase in…
Mechanistic aspects of oxalic acid oxidation by photocatalysis and ozonation
2008
Oxalic acid has been oxidised in acidic aqueous solutions (pH 3) using photocatalysis and ozonation alone or coupled. The simultaneous presence of ozone, titanium dioxide and near UV irradiation increases the oxidation rate of oxalic acid to values greater than those deriving from the single contributions of photocatalysis and ozonation. In particular in the present paper ozonation alone, heterogeneous photocatalysis and also combined ozonation with heterogeneous photocatalysis have been used for the oxidation of oxalic acid at acidic pH in the presence of TiO2 Degussa P25. A likely mechanism, able to explain both the homogeneous and heterogeneous processes, is discussed.
Influence of the Residual Stresses Induced by Shot-Peening on the Oxidation of Zr Plates
2014
The present study evaluates the influence of the residual stress on the oxidation rate of Zr at 650°C. It is shown that the oxidation rate can be substantially decreased by shot-peening. A systematic instigation of the various factors (such as the residual stress, the surface pollution and the chemical composition of the oxidation atmosphere) is realized to separate their influence on the oxidation. The influence of an annealing made after the shot-peening is also considered. One show that the pollution of the surface during the shot-peening process is not responsible for the oxidation rate decrease.
Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics
2009
Fe3Al intermetallics (Fe3Al, Fe3Al-Zr, Fe3Al-Zr,Mo and Fe3Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe3Al. Fe3Al showed massive spallation, whereas Fe3Al-Zr, Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air.
Effect of pH and nitrite concentration on nitrite oxidation rate
2011
The effect of pH and nitrite concentration on the activity of the nitrite oxidizing bacteria (NOB) in an activated sludge reactor has been determined by means of laboratory batch experiments based on respirometric techniques. The bacterial activity was measured at different pH and at different total nitrite concentrations (TNO 2). The experimental results showed that the nitrite oxidation rate (NOR) depends on the TNO 2 concentration independently of the free nitrous acid (FNA) concentration, so FNA cannot be considered as the real substrate for NOB. NOB were strongly affected by low pH values (no activity was detected at pH 6.5) but no inhibition was observed at high pH values (activity wa…
Relationship between maximal fat oxidation and oxygen uptake: comparison between type 2 diabetes patients and healthy sedentary subjects
2014
The contribution of fat oxidation to energy production during exercise is influenced by intensity of exercise. The aim of this study was to assess the relationship between the highest value of fat oxidation rate (FATmax) and the oxygen uptake (VO2) in sedentary type 2 diabetes (T2D) patients vs healthy sedentary subjects. Sedentary T2D patients and healthy sedentary subjects were evaluated to a graded exercise test, and oxygen uptake and fat oxidation rate were detected. Data show that in T2D patients fat oxidation rate is not impaired and the positive linear correlation between FATmax and both VO2 and VO2max suggests that even in T2D patients the muscle oxidative capacity might increase in…
Heart rate recovery after exercise and maximal oxygen uptake in sedentary patients with type 2 diabetes
2015
Aims: Heart rate recovery after exercise (HRR) is an estimate of autonomic modulation of the heart, and has been shown to be inversely associated with insulin resistance, metabolic syndrome, and type 2 diabetes [1]. Type 2 diabetes is associated with poor exercise tolerance and maximal aerobic capacity (VO2max) [2]. Aim of our study was to assess the relationship between HRR and VO2max in sedentary patients with type 2 diabetes. Methods: Maximal treadmill exercise testing using standard or modified Bruce protocol was performed in 16 (8 males and 8 females) sedentary patients with type 2 diabetes (T2D), and in 16 (9 males and 7 females) age-matched sedentary non-diabetic controls (ND). HRR (…