Vapor-air discharges between electrolytic cathode and metal anode at atmospheric pressure

Experimental investigation is performed of the structures and electrical characteristics of vapor-air discharges between a metal (solid, hollow, pointed) anode and an electrolytic cathode at atmospheric pressure. Singular features are revealed of free vapor-air discharges with an electrolytic cathode and their relative transition. Analysis and generalization of the experimental results enable one to reveal the basic physical processes which define the possible mechanism of maintaining a vapor-air discharge with an electrolytic cathode.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 005–010. Original Russian Text Copyright © 2005 by A. F. Gaisin and E. E. Son.     

Laminate thickness and resin pressure evolution during axisymmetric liquid composite moulding with flexible tooling

This paper presents experimental observations from the filling and post-filling stages of 1D axisymmetric Resin Infusion (VARTM) and RTM Light. A series of experiments have been performed to investigate the influence of mould flexural stiffness and fill mode on fluid pressure, cavity thickness, filling stage time, and post-filling stage time. Observations are also made on the effect of those parameters on the repeatability of nominally identical experiments. This paper helps identify the circumstances where a RTM simulation would be sufficiently accurate for an RTM Light process, and consequently where a full flexible tooling simulation is necessary.     

On the degradation of a shock wave in high-current radiating discharges in gases at atmospheric pressure

A theoretical study is made of the features of the radiational-plasmadynamic processes occurring in pulsed high-current radiating discharges in gaseous media at atmospheric pressure when a capacitive store is discharged across an extended interelectrode gap L=10–100 cm. Discharges of this kind are efficaciously employed as radiation sources and generators of strong shock waves in various scientific and practical applications [see A. F. Aleksandrov and A. A. Rukhadze, Physics of High-Current Electric-Discharge Light Sources [in Russian], Atomizdat, Moscow (1976), p. 181, and Radiational Plasmadynamics [in Russian], énergoatomizdat, Moscow (1991), p. 572]. Pis’ma Zh. Tekh. Fiz. 24, 71–75 (June 12, 1998)     

Non-invasive VHF injected signal monitoring in atmospheric pressure plasma and axial DC magnetron

A universal non-invasive real-time frequency domain reflectometry plasma process measurement that is independent of impedance matching network is described. The measurement is deployed on the main power transmission line of the plasma tool to detect both hardware and reflections form plasma. An illustration for atmospheric pressure plasma and axial DC magnetron plasma is given. Power handling capability is 20 (2 A×10 V) and 100 W (250 mA×400 V), respectively. Four simple equivalent electrical models in terms of transmission-line theory and frequency dependent reflection modulus (gain) are employed to analyze the DC magnetron measurement results. It is shown that the electrical length between the directional device measurement plane and the plane at which the transmission line is termination by the hardware and plasma determines the frequency response signal. The strength of the signal (depth of the zero) is found to be inversely related to the termination resistance. Information on hardware, and dynamic process-induced changes due to physical sputtering/erosion are accessible.     

Two-dimensional ultra-thin-layer chromatography and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry in bioanalysis

The feasibility of ultra-thin-layer chromatography (UTLC) and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) for bioanalysis was studied with benzodiazepines as model substances in human urine. Two-dimensional (2D) UTLC was shown to be an efficient technique for the separation of benzodiazepines. Separations occurred in 4-12 min, and the separated compounds were identified by AP-MALDI-MS. The limits of detection with AP-MALDI-MS and AP-MALDI-MS/MS were in the picomole range and thus low enough for bioanalysis. The applicability of the 2D UTLC-AP-MALDI-MS was demonstrated in detection of metabolites with an authentic biological urine sample.     

Deposition of the ZnO transparent electrodes at atmospheric pressure using a DC Arc Plasmatron

Structure and electrical properties of ZnO films deposited by a DC Arc Plasmatron were studied. Films were deposited at atmospheric pressure on a cold substrate. Effect of annealing and plasma treatment was investigated. It was shown that in the as-deposited state the films have an amorphous structure and resistance of about 2 MΩ/cm. Annealing in hydrogen atmosphere at 550 °C improves the crystalline structure and decreases the resistivity of the films down to 5 Ω/cm. Also treatment of surface by hydrogen-argon plasma can be used for decreasing of the resistance of the ZnO films.     

Two-dimensional and axisymmetric unit cell models in the analysis of composite materials

Unit cell models have been widely used for investigating fracture mechanisms and mechanical properties of composite materials assuming periodically arrangement of inclusions in matrix. It is desirable to clarify the geometrical parameters controlling the mechanical properties of composites because they usually contain randomly distributed particulate. To begin with a tractable problem this paper focuses on the effective Young’s modulus E of heterogeneous materials. Then, the effect of shape and arrangement of inclusions on E is considered by the application of FEM through examining three types of unit cell models assuming 2D and 3D arrays of inclusions. It is found that the projected area fraction and volume fraction of inclusions are two major parameters controlling effective elastic modulus of inclusions.     

Modeling of the chemical composition of DC atmospheric pressure air discharge plasma in contact with aqueous solutions of sodium dodecylbenzenesulfonate

The results of calculation of the chemical composition of plasma of the DC atmospheric pressure discharge in air in contact with aqueous solutions of sulfonol (C₁₂H₂₅C₆H₄SO₃Na) in the concentration range of 0–10 g/L at a discharge current of 40 mA are presented. At modeling, the combined solution of Boltzmann equation for the electron gas, equations of vibrational kinetics for ground states of N₂, O₂, H₂O, and NO molecules, equations of chemical kinetics and plasma conductivity equation were used. It was shown that sodium atoms appearing as a result of transfer processes from the liquid cathode affect the chemical composition of the plasma and the characteristics of the electron gas.     

Prebreakdown stage of a surface discharge fired by a pulse in the air at atmospheric pressure

Results of investigation of a high-current plane pulsed surface discharge with separated torches fired in the air at atmospheric pressure are presented. The dynamics of ignition and development of the discharge in the prebreakdown stage has been considered. The main parameters of the plasma in the prebreakdown stage (the stage of intense prebreakdown glow) have been determined by spectroscopic methods and the influence of the dielectric material of a substrate on the plasma parameters has been analyzed. It has been established that the duration of an intense prebreakdown glow depends on the experimental conditions. A physical pattern of formation of an intense prebreakdown glow is proposed.__________Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 1, pp. 178–185, January–February, 2005.     

Transverse electric discharges in supersonic air flows: Simulation of the effects influencing the heating of gas in discharge channel

The Navier-Stokes equations are used to numerically investigate the gasdynamic aspects of interaction between a transverse discharge and supersonic flow in a model of heat source. The effect made by the jet and by the gasdynamic interaction of discharge channels on temperature is analyzed for plane flows with a pair of identical heat sources. Axisymmetric flows are calculated for a uniform incident flow. A marked variation of the flow parameters in the discharge zone and in the wake is observed if the power of energy input corresponds to, or is higher than, the gas enthalpy flow incident via the characteristic cross section of heat source. The calculation results are compared with experimental data. Explanations are provided of the results of experiments in heating a supersonic flow by a transverse electric discharge.     

Performance analysis of and compensation for aspect-ratio effects of fast-fourier-transform-based simulations of large atmospheric wave fronts

Fast-Fourier-transform-based simulators of atmospheric wave fronts with a von Kármán turbulence spectrum were tested with reference to the phase-structure function and phase variance over a pupil on large square and rectangular formats. The symmetry and the accuracy of the phase-structure function were found to be limited by the aspect ratio and the size of the phase screen. The phase variance over a pupil is less sensitive to the aspect ratio than the phase-structure function and is dependent mainly on the size of the phase screen. Several tests are reported and discussed together with a method of compensation for the negative effects of rectangular formats.     

Micro-structured electrode arrays: Glow discharges in Ar and N2 at atmospheric pressure using a variable radio frequency generator

Micro-structured electrode (MSE) arrays consist of an interlocked, comb-like, capacitive electrode system with gap widths in the μm range. Large-area uniform glow discharges up to atmospheric pressure were penetrated with our arrays. In order to ignite glow discharges at atmospheric pressure this approach is established next to using dielectric barrier arrays and plasma jets. Because of the industrial, scientific and medical (ISM) limitation of available radio frequencies the usual frequency for experiments is 13.56 MHz. Using a variable radio frequency generator more information about the frequency dependent breakdown mechanisms are gained. The electric parameters of the non-thermal plasma system are characterized by a special probe with an upper frequency detection limit of 60 MHz.     

Determination of the cathode erosion and temperature for the phases of high voltage discharges using FEM simulations

A discharge produces an energy input in the cathode material, which causes the erosion of the material surface. The principal mechanism of erosion is the formation of craters mainly due to melting. From calorimetric results published in the literature, the amounts of energy delivered to the cathode for the different phases of the discharge (breakdown, arc and glow discharge) were calculated. A FEM model was developed to simulate the temperature distribution and the phase transitions, which allows the definition of molten and evaporated zones. These zones were compared with the volumes of craters done in Pt-samples at air with pressures ranging between 1 and 9 bar and static electrode gaps of 2 mm. The breakdown energy is enough to melt an amount of material, which is responsible for the formation of very flat craters. The formation of deeper overlapped craters observed in experiments can not be produced during the breakdown; they are produced by the arc phase of the discharge. The assumption of the crater area as the area for the energy exchange between plasma and material gives the best results in the simulation. The glow discharge produces only a light heating of the cathode, without any significant erosion.     

环境压力对低温容器蒸发流量的理论分析和试验验证

建立了用于计算低温容器蒸发流量的数学模型,得出了蒸发流量与环境温度、环境压力之间的关系。结果显示,瞬时蒸发流量变化不但受到环境压力影响,同时还受到环境压力变化率以及容器内液体量的影响。提出了衡量环境压力变化对蒸发流量影响程度的无因次量,讨论了在不同漏热、不同装载量情况下环境压力变化的影响程度。以液氮为工质,对35立方米高真空多层绝热低温容器在不同地点进行了试验,试验结果与计算结果符合较好。     

Stress-strain state of the cylindrical shell of a pressure vessel with local heating

Results of calculated and experimental investigations of the stress-strain state of a cylindrical shell subjected to local heating are presented. The solution is obtained by expanding the internal forces into a Fourier series for the circumferential coordinate of the shell. The method of full-scale high-temperature tensometry was used for the experimental investigations. Experimental data and calculation results are compared.Translated from Problemy Prochnosti, No. 10, pp. 85–88, October, 1990.     

Comparison of atmospheric pressure chemical ionization, electrospray ionization, and atmospheric pressure photoionization for the determination of cyclosporin A in rat plasma

Atmospheric pressure chemical ionization was compared with electrospray ionization and atmospheric pressure photoionization (APPI) as an interface of high-performance liquid chromatography (HPLC)-tandem mass spectrometry (MS/MS) for the determination of cyclosporin A (CsA) in biological fluids in support of in vivo pharmacodynamic studies. These ion sources were investigated in terms of their suitability and sensitivity for the detection of CsA. The effects of the eluent flow rate and composition as well as the nebulizer temperatures on the photoionization efficiency of CsA in the positive ion mode under normal-phase HPLC conditions were explored. The ionization mechanism in the APPI environment with and without the use of the dopant was studied using two test compounds and a few solvent systems employed for normal-phase chromatography. The test compounds were observed to be ionized mainly by proton transfer with the self-protonated solvent molecules produced through photon irradiation. Furthermore, ion suppression due to sample matrix interference in the normal-phase HPLC-APPI-MS/MS system was monitored by the postcolumn infusion technique. The applicability of these proposed HPLC-API-MS/MS approaches for the determination of CsA at low nanogram per milliliter levels in rat plasma was examined. These proposed methods were then compared with respect to specificity, linearity, detection limit, and accuracy.     

Gasdynamics and heat transfer during axisymmetric turbulent jet interaction with a normally disposed area

The influence of selecting the kind of turbulence model on the results of a numerical computation of turbulent jet interaction with an obstacle is analyzed.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 1, pp. 33–37, July, 1988.     

Rectilinear ion trap mass spectrometer with atmospheric pressure interface and electrospray ionization source

A rectilinear ion trap (RIT) mass analyzer was incorporated into a mass spectrometer fitted with an electrospray ionization source and an atmospheric pressure interface. The RIT mass spectrometer, which was assembled in two different configurations, was used for the study of biological compounds, for which performance data are given. A variety of techniques, including the use of a balanced rf, elevated background gas pressure, automatic gain control, and resonance ejection waveforms with dynamically adjusted amplitude, were applied to enhance performance. The capabilities of the instrument were characterized using proteins, peptides, and pharmaceutical drugs. Unit resolution and an accuracy of better than m/z 0.2 was achieved for mass-to-charge (m/z) ratios up to 2000 Th at a scan rate of approximately 3000 amu/(charge.s) while reduced scan rates gave greater resolution and peak widths of less than m/z 0.5 over the same range. The mass discrimination in trapping externally generated ions was characterized over the range m/z 190-2000 and an optimized low mass cutoff value of m/z 120-140 was found to give equal trapping efficiencies over the entire range. The radial detection efficiency was measured as a function of m/z ratio and found to rise from 35% at low m/z values to more than 90% for ions of m/z 1800. The way in which the ion trapping capacity depends on the dc trapping potential was investigated by measuring the mass shift due to space charge effects, and it was shown that low trapping potentials minimize space charge effects by increasing the useful volume of the device. The collision-induced dissociation (CID) capabilities of the RIT instrument were evaluated by measuring isolation efficiency as a function of mass resolution as well as measuring peptide CID efficiencies. Overall CID efficiencies of more than 60% were easily reached, while isolation of an ion with unit resolution at m/z 524 was achieved with high rejection (>95%) of the adjacent ions. The overall analytical capabilities of the ESI-RIT instrument were demonstrated with the analysis of a mixture of pharmaceutical compounds using multiple-stage mass spectrometry.