Application experiment and numerical simulation analysis of oil–water separator with two-oriented corrugated coalescence plate

The new structure of two-oriented corrugated plate is developed in an oil–water separator. The surface of the corrugated plate is modified so that one side is provided with a hydrophobic property and the other side is provided with a hydrophilic property. The effect of feed flow rate and composition on the separation efficiency of the separator is analyzed by experiments. A three-dimensional model of the separator is established for simulation by using the fluent software. The separation effect is characterized by the maximum concentration and thickness of the two constituents. The simulation results are in good agreement with the experimental results. The feed composition and feed flow rate can be worked together in the coalescence process. Both in the experiment and in the simulation, the concentration of the outlet of this polynode separator can reach more than 99% in the treatment of oil-bearing rate from 30% to 60% and inlet flow rate at 800?L/h～2000?L/h, which confirms the high separation efficiency of the device structure. At the same time, it also can be concluded that the lower oil phase concentration is suitable for larger inlet flow, while higher oil phase concentration is more applicable for lower flow rate in the appropriate range.     

Modelling the molecular weight distribution in terpolymerization systems with donor–acceptor complexes

In this work we present, for the first time, a mathematical development of the moments of the molecular weight distribution in terpolymerization systems where donor–acceptor complexes are formed and the propagating reactions are carried out according to the complex participation model. The resulting set of equations is applied to the system formed by vinyl chloride (VC), vinyl acetate (VAc) and maleic anhydride (MA), in order to show the use of the equations and the type of information that might be obtained from them.     

Molecular dynamics simulation of the equilibrium liquid–vapor interphase with solidification

The equilibrium structure of the finite, interphase interfacial region that exists between a liquid film and a bulk vapor is resolved by molecular dynamics simulation. Argon systems are considered for a temperature range that extends below the melting point. Physically consistent procedures are developed to define the boundaries between the interphase and the liquid and vapor phases. The procedures involve counting of neighboring molecules and comparing the results with boundary criteria that permit the boundaries to be precisely established. Two-dimensional radial distribution functions at the liquid and vapor boundaries and within the interphase region demonstrate the physical consistency of the boundary criteria and the state of transition within the region. The method developed for interphase boundary definitions can be extended to nonequilibrium systems. Spatial profiles of macroscopic properties across the interphase region are presented. A number of interfacial thermodynamic properties and profile curve-fit parameters are tabulated, including evaporation/condensation coefficients determined from molecular flux statistics. The evaporation/condensation coefficients away from the melting point compare more favorably with transition state theory than those of previous simulations. Near the melting point, transition theory approximations are less valid and the present results differ from the theory. The effects of film substrate wetting on evaporation/condensation coefficients are also presented.     

Viscosity of liquid Co–Sn alloys: thermodynamic evaluation and experiment

Shear viscosity measurements were performed for liquid Co–Sn alloys over a wide temperature range above the respective liquidus temperatures. A high temperature oscillating-cup viscometer was used. It was found experimentally that viscosity as a function of temperature obeys an Arrhenius law. The data were compared with calculated values, obtained from different thermodynamic approaches. A good agreement was found between experimental results and calculated ones by the Budai–Benkö–Kaptay model.     

Virtual point detector for HPGe detectors for 26.6–1332 keV photon energies by experiment and Monte Carlo simulation

Variation of virtual point detector (VPD) position inside HPGe detector as a function of source photon energy for the energy range from 26.6 to 1,332 keV was investigated. Although VPD concept was well established for HPGe detectors from 59.5 to 10 MeV, a new attempt was made to obtain VPD positions for photon energies below 59.5 keV. It was found that VPD position shows different functional behavior for the energy ranges 26.6–59.5 keV and 59.5–1,332 keV. The VPD position decreases with increasing energy for 26.6, 31.7, 36.4, and 37.3 keV and increases with the energy until it reaches a plateau. The functional behavior of VPD position for the energy range 26.6–59.5 keV was attributed to the dead layer thickness of the Ge crystal. Monte Carlo simulations were performed to investigate the behavior of VPD position with various dead layer thickness ranging from 100 to 800 μm. It was seen that VPD position increases with increasing energy for 31.7, 59.5, and 80.1 keV more significant at relatively lower energies, but constant for the energies 661–1,332 keV.     

Highly sensitive determination of mercury using copper enhancer by diamond electrode coupled with sequential injection–anodic stripping voltammetry

A highly sensitive determination of mercury in the presence of Cu(II) using a boron-doped diamond (BDD) thin film electrode coupled with sequential injection–anodic stripping voltammetry (SI–ASV) was proposed. The Cu(II) was simultaneously deposited with Hg(II) in a 0.5 M HCl supporting electrolyte by electrodeposition. In presence of an excess of Cu(II), the sensitivity for the determination of Hg(II) was remarkably enhanced. Cu(II) and Hg(II) were on-line deposited onto the BDD electrode surface at −1.0 V (vs. Ag/AgCl, 3 M KCl) for 150 s with a flow rate of 14 μL s⁻¹. An anodic stripping voltammogram was recorded from −0.4 V to 0.25 V using a frequency of 60 Hz, an amplitude of 50 mV, and a step potential of 10 mV at a stopped flow. Under the optimal conditions, well-defined peaks of Cu(II) and Hg(II) were found at −0.25 V and +0.05 V (vs. Ag/AgCl, 3 M KCl), respectively. The detection of Hg(II) showed two linear dynamic ranges (0.1–30.0 ng mL⁻¹ and 5.0–60.0 ng mL⁻¹). The limit of detection (S/N = 3) obtained from the experiment was found to be 0.04 ng mL⁻¹. The precision values for 10 replicate determinations were 1.1, 2.1 and 2.9% RSD for 0.5, 10 and 20 ng mL⁻¹, respectively. The proposed method has been successfully applied for the determination of Hg(II) in seawater, salmon, squid, cockle and seaweed samples. A comparison between the proposed method and an inductively coupled plasma optical emission spectrometry (ICP-OES) standard method was performed on the samples, and the concentrations obtained via both methods were in agreement with the certified values of Hg(II), according to the paired t-test at a 95% confidence level.     

Electrochemical simulation of oxidation processes involving nucleic acids monitored with electrospray ionization–mass spectrometry

Oxidation is commonly involved in the alteration of nucleic acids giving rise to diverse effects including mutation, cell death, malignancy, and aging. We demonstrate that electrochemistry represents an efficient and fast method to mimic oxidative modification of nucleic acids occurring in biological systems. Oxidation reactions were performed in a thin-layer cell employing a conductive diamond electrode as the working electrode and were monitored with electrospray ionization–mass spectrometry. Mass voltammograms were acquired for guanosine, adenosine, cytidine, and uridine. The observed oxidation potentials increased in the order guanosine<<adenosine<cytidine<uridine. Oxidation products of guanosine were characterized using high-resolution (tandem) mass spectrometry performed with a quadrupole–quadrupole time-of-flight instrument. On the basis of these experiments, it was concluded that the initial electrode reaction involves a one-electron, one-proton step to give a free radical. The primary oxidation product represents the starting point for a number of follow-up reactions, including guanosine dimerization as well as further oxidation to 8-hydroxyguanosine. Similar results were obtained for guanosine monophosphate and the corresponding dinucleotide. Furthermore, the guanosine radical was identified as an important intermediate for the formation of a covalent adduct with acetaminophen. This observation sheds new light on the mechanism of adduct formation as it demonstrates that oxidative activation of both the nucleobase and the adduct-forming agent is necessary to observe a detectable amount of adduct species.     

Calculated ionization energies for a series of sesquiterpenes: comparisons with experimental vertical ionization energies and comments on related structure–activity relationships (SARs)

The energies of the highest-occupied molecular orbitals (HOMOs) are known to be excellent predictors of the reactivities of biogenic hydrocarbons, such as terpenes, with reactive atmospheric oxidants including O₃, OH, and NO₃. Structure–Activity Relationships (SARs) have also been effectively employed in such studies and related to HOMO energies and lowest ionization energies (ionization potentials). This study employs density function theory (DFT), at the B3LYP/6-31G** level, to predict vertical ionization energies (IP_v) for a structurally diverse group of sesquiterpenes, each of which has been reported in air samples collected in the lower troposphere. The availability of published UV photoelectron spectra for nine sesquiterpenes permits comparison of experimental and theoretical vertical ionization energy data. The experimental and theoretical data show a good correlation (average discrepancy ± 0.07 eV). This enables predictions of reactivities for sesquiterpenes whose tropospheric lifetimes may last only a few hours before their transformations into secondary organic aerosols (SOA) close to their emission sources.     

Modelling of the Plasma–Sheath Boundary Region in Wall-Stabilized Arc Plasmas: Unipolar Discharge Properties

A two-dimensional model of the non-equilibrium unipolar discharge occurring in the plasma–sheath boundary region of a transferred-arc was developed. This model was used to study the current transfer to the nozzle (1 mm diameter) of a 30 A arc cutting torch operated with oxygen. The energy balance and chemistry processes in the discharge were described by using a kinetic block of 45 elementary reactions and processes with the participation of 13 species including electronically excited particles. The nonlocal transport of electrons was accounted for into the fluid model. The dependence of the ion mobility with the electric field was also considered. Basic discharge properties were described. It has been found that a large part (~ 80%) of the total electric power (1700 mW) delivered in the bulk of the sheath region is spent in heating the positive ions and further dissipated through collisions with the neutral particles. The results also showed that the electron energy loss in inelastic collisions represents only ~ 25% of the electron power and that about 63% of the power spent on gas heating is produced by the ion–molecule reaction, the electron–ion and ion–ion recombination reactions, and by the electron attachment. The rest of the power converted into heat is contributed by dissociation by electron-impact, dissociative ionization and quenching of O(¹D). Some fast gas heating channels which are expected to play a key role in the double-arcing phenomena in oxygen gas were also identified.     

Modelling of reaction–diffusion processes: the theory of catalytic electrode processes at hemispheroidal ultramicroelectrodes

The transient chronoamperometric current for a catalytic electrode reaction (EC′ reaction) at a hemispheroidal Ultramicroelectrode is reported. This simple new approximate multidimensional analytical expression is valid for all values of time and all values of the rate constant. It is more accurate for all times and large K than for short times and small K. The analytical results are compared with recently presented digital simulation results (Galceran and co-workers, J. Electroanal. Chem 466 (1999) 15) for a disc electrode and are found to be in good agreement.     

Numerical simulation for Darcy–Forchheimer three-dimensional rotating flow of nanofluid with prescribed heat and mass flux conditions

Journal of Thermal Analysis and Calorimetry - Darcy–Forchheimer three-dimensional rotating flow of nanoliquid with prescribed heat and mass flux conditions is addressed. Flow is generated by...     

Electron–ion recombination in radiation tracks in liquid argon: a computer simulation study

A simulation method is proposed to model electron–ion recombination in radiation tracks in liquid argon at 87 K. The method is applied to calculate the electron escape probability in clusters of up to 20 pairs of electrons and cations that represent a fragment of the track. The results reproduce the basic features of the track recombination in liquid argon observed in experiment.     

Specific heat of ternary Ag–Si–Ge alloys from 123 K to high temperatures: experiment and prediction

Journal of Thermal Analysis and Calorimetry - The knowledge of specific heat for Ag–Si–Ge alloys in a broad temperature range would facilitate their practical applications in various...     

Modelling of high-pressure phase equilibria using the Sako–Wu–Prausnitz equation of state: II. Vapour–liquid equilibria and liquid–liquid equilibria in polyolefin systems

Phase equilibria in binary and ternary polyolefin systems are calculated using the cubic equation of state proposed by Sako–Wu–Prausnitz (SWP). Calculations were done for high-pressure phase equilibria in ethylene/polyethylene (LDPE) systems and for liquid–liquid equilibria (LLE) in systems containing either high-density polyethylene or poly(ethylene-co-propylene). The calculations for the copolymer/solvent systems are compared with those using the SAFT EOS. The two equations of state can describe UCST, LCST as well as U-LCST behaviour with similar accuracy. Whereas, the binary interaction parameter is temperature-independent for SAFT, it is found to be a function of temperature for the SWP model. Moreover, the influence of an inert gas on the LCST of the polyethylene/hexane system is investigated using the SWP EOS. The polydispersity of the different polyethylenes is considered in the phase equilibrium calculations using pseudocomponents chosen by the moments of the experimental molecular weight distributions.     

Unsymmetrical 1λ3-1,2,4,6-thiatriazinyls with aryl and trifluoromethyl substituents: synthesis, crystal structures, EPR spectroscopy, and voltammetry

A general synthetic route to 3-trifluoromethyl-5-aryl-1λ(3)-1,2,4,6-thiatriazinyl radicals was developed. X-ray structures were obtained for all five neutral radicals and show that they exist in the solid state as cofacial dimers linked by S···S contacts. X-ray structures were also obtained for two of the precursor chlorothiatriazines along with several aryl N-imidoylamidines, p-methoxybenzamidine, and N-chlorosulfonyl-N,N'-benzamidine. Cyclic voltammetric studies were performed on the [R(2)C(2)N(3)S](?) radicals in CH(3)CN and CH(2)Cl(2) with [(n)Bu(4)N][PF(6)] as the supporting electrolyte under vacuum conditions in an all-glass electrochemical cell. The results provide quasi-reversible formal potentials for the [R(2)C(2)N(3)S](-/0) process in the range of -0.61 to -0.47 V, irreversible peak potentials for the [R(2)C(2)N(3)S](0/+) process from 0.59 to 0.91 V at lower concentrations, and the appearance of a second, reversible oxidation process from 0.69 to 0.94 V at higher concentrations (versus the Fc(0/+) couple; Fc = ferrocene). This behavior was indicative of monomer-dimer equilibrium in solution, as ascertained from digital models of the voltammograms. There is a small but measurable trend in both the oxidation and reduction potentials with varying remote aryl substituents. EPR spectra were obtained for all five neutral radicals in CH(2)Cl(2) solutions, which confirm the concentration of the unpaired electron density on the heterocyclic core. Trends were also seen in the hyperfine splitting constants a(N) with varying remote aryl substituents. Calculations were performed for all three oxidation states of the [R(2)C(2)N(3)S](-/?/+) monomeric rings; the resulting theoretical redox energies correlate well with solution phase voltammetric data.     

Analyzing small samples with high efficiency: capillary batch injection–capillary electrophoresis–mass spectrometry

We present an experimental approach to conducting fast capillary electrophoresis-mass spectrometry (CE-MS) measurements of very small samples in the nanoliter range. This is achieved by injecting sample very efficiently into a CE-MS system. Injection efficiency represents the ratio of injected sample to the amount of sample needed for carrying out the injection process (v/v). In order to increase this injection efficiency from typical values of 10(-3) to 10(-7), the concept of capillary batch injection is used to build an automated, small-footprint injection device for CE-MS. This device is capable of running true multi-sample measurement series, using minimal sample volumes and delivering an injection efficiency of up to 100?%. It is compatible with both aqueous and non-aqueous background electrolytes. As an additional benefit, CE-MS separations of a catecholamine model system in capillaries of 15?cm length under conditions of high electric field strength could be accomplished in 20?s with high separation efficiency. This report details design and specifications of the injection device and shows optimal parameter choices for injections with both high injection efficiency and high separation efficiency. Furthermore, a procedure is presented to coat the tip of a fused silica capillary with a silicone elastomer which acts as a seal between two capillaries.