Search results for "Temperature a"

(Ag)Pd-Fe3O4 Nanocomposites as Novel Catalysts for Methane Partial Oxidation at Low Temperature

2020

Nanostructured composite materials based on noble mono-(Pd) or bi-metallic (Ag/Pd) particles supported on mixed iron oxides (II/III) with bulk magnetite structure (Fe3O4) have been developed in order to assess their potential for heterogeneous catalysis applications in methane partial oxidation. Advancing the direct transformation of methane into value-added chemicals is consensually accepted as the key to ensuring sustainable development in the forthcoming future. On the one hand, nanosized Fe3O4 particles with spherical morphology were synthesized by an aqueous-based reflux method employing different Fe (II)/Fe (III) molar ratios (2 or 4) and reflux temperatures (80, 95 or 110 &deg

Apparent molar volumes of 1-pentanol in water fromT=298 K toT=413 K atp=0.1 MPa andp=19 MPa

1996

Abstract Densities of 1-pentanol aqueous solutions were measured by using a vibrating tube densimeter especially designed and equipped to perform accurate measurements from ambient conditions up toT=423 K andp=80 MPa. The densimeter was tested by measuring densities of NaCl (aq). A comparison with the most reliable literature data showed very good agreement with differences lower than (0.03 and 0.1) kg·m−3for molalities below and above 0.5 mol·kg−1, respectively. From the density measurements, the apparent molar volumes of 1-pentanol in water,Vφwere determined as a function of molalitymat temperatures fromT=298 K toT=413 K atp=0.1 MPa andp=19 MPa. At a given temperature and pressure, and pa…

Mössbauer effect study of the temperature and pressure dependence of the singlet-quintet intersystem crossing dynamics in an iron(II) spin crossover …

1988

The lineshapes of Mossbauer spectra of the iron(II) spin crossover complex [Fe(6-mepy)3 tren] (PF6)2 are affected by the dynamics of the HS⇌LS equilibrium. The lineshapes are reproduced with a stochastic two-state-relaxation-model yielding rate constants similar to those determined for related complexes in solution. Application of an external pressure of 150 MPa increases the relaxation rate.

Effects of pressure and temperature on the dielectric constant of GaS, GaSe, and InSe:  Role of the electronic contribution

1999

In this work we report on direct measurements of the temperature and pressure dependences of the low-frequency dielectric constant along c axis $({\ensuremath{\varepsilon}}_{\ensuremath{\parallel}})$ of GaS, GaSe, and InSe. The temperature dependence of both the ordinary and extraordinary refractive indexes is also presented. A large increase of ${\ensuremath{\varepsilon}}_{\ensuremath{\parallel}}$ under pressure has been observed. In the framework of a rigid ion model, the lattice contribution to ${\ensuremath{\varepsilon}}_{\ensuremath{\parallel}}$ is shown to increase slightly under pressure, due to the change of the angle between the anion-cation bond and the layer plane. Consequently, …

Temperature and pressure dependence of the viscosities of perfluoropolyether fluids

1987

The viscosities of two structurally different perfluoropolyether fluids were determined at a series of temperatures and pressures, from 25 to 100°C and from 1 to 1000 bars. Flow activation energies and volumes as well as their temperature and pressure coefficients were derived. An attempt was made to relate measured and derived quantities to the compound structures.

Ab initio study on the mechanism of the HCO+O2→HO2+CO reaction

2003

Abstract The gas-phase reaction HCO+O 2 →CO+HO 2 has been investigated by means of ab initio calculations. The mechanism can proceed through either a direct hydrogen abstraction or addition of O 2 to the formyl radical. The energy barriers calculated at the QCISD(T)/6-311G(2df,2p) level of theory upon QCISD/6-311G(d,p) optimized structures are, respectively, of 2.98 kcal mol −1 for the direct abstraction and of 2.26 kcal mol −1 for the addition. Thus, the results obtained show that there is not a dominant pathway in the HCO+O 2 reaction under atmospheric conditions of temperature and pressure.

Suicide and Ambient Temperature: A Multi-Country Multi-City Study

2019

Background: Previous literature suggests that higher ambient temperature may play a role in increasing the risk of suicide. However, no multi-country study has explored the shape of the association and the role of moderate and extreme heat across different locations. Objectives: We examined the short-term temperature–suicide relationship using daily time-series data collected for 341 locations in 12 countries for periods ranging from 4 to 40 y. Methods: We conducted a two-stage meta-analysis. First, we performed location-specific time-stratified case-crossover analyses to examine the temperature–suicide association for each location. Then, we used a multivariate meta-regression to combine t…

Greenhouse climate control using wireless sensors

2008

Coexistence of active Brownian disks: van der Waals theory and analytical results

2020

At thermal equilibrium, intensive quantities like temperature and pressure have to be uniform throughout the system, restricting inhomogeneous systems composed of different phases. The paradigmatic example is the coexistence of vapor and liquid, a state that can also be observed for active Brownian particles steadily driven away from equilibrium. Recently, a strategy has been proposed that allows to predict phase equilibria of active particles [Solon et al., Phys. Rev. E 97, 020602(R) (2018)2470-004510.1103/PhysRevE.97.020602]. Here we elaborate on this strategy and formulate it in the framework of a van der Waals theory for active disks. For a given equation of state, we derive the effecti…

Simplified Hybrid PD Model in Voids

2011

In this paper a novel approach to model partial discharges (PD) activity taking place inside a spherical void in epoxy resin system has been traced. The approach is based on a time varying conductance of the inner void, subjected to multistress conditions: voltage, temperature and pressure. A simple lumped circuit macro-model simulates the global effects of PD activity: the different parameters influencing the discharge phenomenon in the void are taking into account by using a physical approach resulting in a time varying conductance inside the circuit. The evaluated PD activity has been compared with experimental and simulated one for the accessible and inaccessible part of the system. A d…