Measurements of electron density and Stark width of neutral helium lines in a helium arc plasma

Electron densities in an atmospheric helium arc plasma have been measured with the Stark broadening parameters of helium spectral lines. The spatially distributed radiation intensities are converted to plasma emission coefficients at every wavelength by means of Abel inversion. From the inverted profiles of He I lines of 4713 ?, 5016 ?, and 6678 ? electron density has been calculated, which ranges from 0.5 ×10¹⁶ to 4 ×10¹⁶ cm^-3 for a helium arc with current 200 A. Stark widths of He I lines of 3889 ? and 7065 ? are determined based on the measurements and compared with existing data.     

Diode laser spectroscopic measurements and theoretical calculations of line parameters of nitrogen-broadened water vapor overtone transitions in the 818-834 nm wavelength region

Nitrogen-broadened water vapor line parameters of the (2 1 1) ← (0 0 0) overtone band transitions in the 818-834 nm wavelength region are measured by using a tunable diode laser spectrometer. Water vapor is kept at its saturated vapor pressure at room temperature within a sample cell. Use of a balanced detector and a lock-in amplifier helps to increase the detection efficiency and the signal-to-noise ratio. The collisional broadening coefficients are extracted from the fitting of the experimental data by using a standard Voigt line profile. Collisional half-widths of water vapor lines perturbed by nitrogen are evaluated using the complex-valued implementation of the Robert-Bonamy (CRB) formalism. The rotational wave functions and the energy eigenvalues in the (2 1 1) vibrational state of water molecule are assumed on the basis of symmetry properties. Hence the outcome of this work also tests the validity of the theoretical approximations. The experimental data are compared with the corresponding theoretical values and the possible causes of deviation between the two have also been discussed.     

Experimental and theoretical study of line shift and mixing in the ν4 band of NH3 perturbed by N2

The shift coefficients and line-mixing parameters of rovibrational-inversion transitions in the ν₄ band of ammonia (NH₃) perturbed by nitrogen (N₂) have been measured at room temperature with a high-resolution Fourier transform spectrometer. The collisional shift and line mixing are obtained from the non-linear least-square multi-pressure fitting techniques. Comparison is made with the results of theoretical calculation based on semi-classical model extended to the case of symmetric top molecule with inversion motion. The shifts and the line-mixing parameters are calculated using, respectively the approach developed by Robert and Bonamy and the state-to-state cross-section. The agreement is satisfactory on the average. Good agreement is also obtained for line mixing with previous measurements.     

Scattering polarization in the presence of magnetic and electric fields

The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under Zeeman effect, and Hanle effect in weak magnetic fields are discussed. The theory is general enough to handle scattering in intermediate magnetic fields (Hanle-Zeeman effect) and for arbitrary orientation of magnetic field. The quadrupolar electric field produces asymmetric line shifts, and causes interesting level-crossing phenomena either in the absence of an ambient magnetic field, or in its presence. It is shown that the quadrupolar electric field produces an additional depolarization in the Q/I profiles and rotation of the plane of polarization in the U/I profile over and above that arising from magnetic field itself. This characteristic may have a diagnostic potential to detect steady-state and time-varying electric fields that surround radiating atoms in solar atmospheric layers.     

A Lattice Model for the Line Tension of a Sessile Drop

Within a semi-infinite three-dimensional lattice gas model describing the coexistence of two phases on a substrate, we study, by cluster expansion techniques, the free energy (line tension) associated with the contact line between the two phases and the substrate. We show that this line tension, is given at low temperature by a convergent series whose leading term is negative, and equals 0 at zero temperature.     

Coupling and ionization effects on hydrogen spectral line shapes in dense plasmas

A study of hydrogen lines emitted in dense and low temperature plasmas is presented. Coupling and ionization effects in a transition from impact to quasi-static broadening for electrons are analyzed with the help of the Frequency Fluctuation Model (FFM). Electron broadening of Balmer series lines is studied for different densities and temperatures spanning a wide domain from impact to quasi-static limit. It is shown that electronic broadening makes a transition from impact to quasi-static limit depending on plasma conditions and principal quantum number. Even for the Balmer alpha line, at a density equals 10¹⁸ cm^-3 and a temperature equals 1 eV, this transition occurs both in the wings and the core of the line.     

汽车发动机多模式自动生产输送线控制系统的研发

发动机的制造技术对汽车的质量至关重要。汽车发动机生产输送线采用顺序作业的流水线工艺过程。其自动控制系统采用德国Siemens公司的PLC-300系列控制器作为整个输送线的主体控制器,I/O系统作为控制信号的采集系统,采用Profibus现场总线技术进行通讯,自动完成将发动机部件进行直线移动、旋转、举升,翻转等操作。采用WinCC人机界面软件组建成系统的操作监控站进行产品数量、生产节拍的监视。本项目组成员在此基础之上又根据生产实际制作了相应的适合学校教学自动线实训系统,进行教学设备的开发。     

Performance improvement on OVSB based WDM RoF-EPON link using SOA with DCF and FBG

Performance of four channel WDM RoF-EPON link based on OVSB transmission using SOA is enhanced by compensating dispersion and FWM with DCF and FBG by 10.95% for equal channel spacing and further improvement has been shown up to 23.61% by using unequal spacing for the same transmission link. The performance enhancement by using DCF and FBG is ascertained by evaluating Q factor and eye opening.     

Measurements of O2-broadening and -shifting parameters of water vapor spectral lines in the second hexad region

Oxygen pressure induced broadening and shifting coefficients for water vapor absorption lines in the 8600–9010 cm⁻¹ region have been measured and calculated. The spectra were recorded with a Bruker IFS 125HR spectrometer at a spectral resolution of 0.01 cm⁻¹ for lines with angular moment of the upper states up to 10. Calculations of line broadening and shifting coefficients are performed using a semi-empirical approach. The method is based on the impact theory of broadening, and includes the correction factors whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data. The comparison of our calculations with the experimental values argues that the semi-empirical method is quite acceptable for the determination of the water vapor absorption line profile parameters.