Operation of an Ionization Gauge in Dense Nonstationary Hydrogen Flows

The operation of a fast, small in size open-type ionization gauge in a high-density nonstationary hydrogen jet outflowing in vacuum is investigated. The upper limit of the gauge's operating range is 6 × 10¹⁷cm^–3at a spatial resolution in the jet cross section of 0.5 mm and a temporal resolution of 15 s. In gauge calibration under static conditions, the gas temperature in the sensor volume should be taken into consideration. Otherwise, a systematic measurement error of up to 100% arises. Features related to the operation of the ionization gauge in gas impulse flows are studied in detail. The possibility of correct gas-concentration measurements is shown.     

A Charged-Particle Detector Based on Proportional Tubes with a Segmented Cathode and Cathode Readout

A charged-particle detector based on proportional tubes with cathode readout is described. The cathode is sectionalized into 2.2 × 2.2-cm pads. The detector was tested on high-energy particle beams. At an anode-to-cathode distance of 1.1 cm, the spatial resolution was 1.25 mm along the anode wire. A simulation model of the detector on the basis of the measured pad-response function was proposed, compared to the experimental data, and used to calculate the two-track resolution. The detector can be used in various experiments as a large-area multiparticle two-coordinate detector.     

Subnanometer three-dimensional atom-probe investigation of segregation at MgO/Cu ceramic/metal heterophase interfaces.

Three-dimensional atom-probe (3DAP) microscopy has been applied to the study of segregation at ceramic/metal (C/M) interfaces. In this article, results on the MgO/Cu(X) (where X = Ag or Sb) systems are summarized. Nanometer-size MgO precipitates with atomically clean and atomically sharp interfaces were prepared in these systems by internal oxidation. Segregation of the ternary component (Ag or Sb) at the MgO/Cu heterophase interface was enhanced by extended low-temperature anneals. Magnesia precipitates in the 3DAP reconstructions were delineated as isoconcentration surfaces, and segregation of each ternary component at the C/M interfaces was analyzed with the proximity histogram method developed at Northwestern University. This method allows the direct extraction of the Gibbsian interfacial excess of solute at the C/M interfaces from the experimental data. A value of (3.2+/-2.0) x 10(17)m(-2) at 500 degrees C is obtained for the segregation of Ag at a MgO/Cu(Ag) interface, while a value of (2.9+/-0.9) x 10(18) m(-2) at 500 degrees C is obtained for the segregation of Sb at a MgO/Cu(Sb) interface. The larger Gibbsian excess for Sb segregation at this ceramic/metal heterophase interface is most likely due to the so-called pdeltaV effect.     

Application of the low-loss scanning electron microscope image to integrated circuit technology part II--chemically-mechanically planarized samples.

Chemical-mechanical planarization (CMP) is a process that gives a flat surface on a silicon wafer by removing material from above a chosen level. This flat surface must then be reviewed (typically using a laser) and inspected for scratches and other topographic defects. This inspection has been done using both the atomic force microscope (AFM) and the scanning electron microscope (SEM), each of which has its own advantages and disadvantages. In this study, the low-loss electron (LLE) method in the SEM was applied to CMP samples at close to a right angle to the beam. The LLEs show shallower topographic defects more clearly than it is possible with the secondary electron (SE) imaging method. These images were then calibrated and compared with those obtained using the AFM, showing the value of both methods. It is believed that the next step is to examine such samples at a right angle to the beam in the SEM using the magnetically filtered LLE imaging method.     

Computational chemistry: a useful (sometimes mandatory) tool in mass spectrometry studies

In this review, we present a brief summary of the theoretical methods most frequently used in gas-phase ion chemistry. In subsequent sections, the performance of these methods is analyzed, paying attention to the reliability of geometries, vibrational frequencies, energies, and entropies. The possible pathologies of the different methods, in the form of instabilities of the wave function or spin contamination problems, are discussed. Several examples are presented to illustrate the usefulness of ab initio or density functional theory (DFT) methods to predict the existence of elusive molecules and/or to characterize non-conventional structures, and to rationalize the charge redistributions normally associated with ion-molecule interactions and which result in bond-weakening or bond-reinforcement effects. Finally, the role of non-classical structures in ion-molecule interactions is also illustrated with different examples.     

Comparison of analytical techniques for nonlinear vibrations of a parametrically excited cantilever

This paper is concerned with second-order approximations to the steady-state principal parametric resonance response of a vertically mounted flexible cantilever beam subjected to a vertical harmonic base motion. The unimodal form of the nonlinear equation describing the in-plane large amplitude parametric response of the beam, derived in Krishnamurthy (Ph.D. Thesis, Department of Mechanical Engineering, Washington State University, 1986) based on the previous analysis in Crespo da Silva and Glynn (Journal of Structural Mechanics 1978; 6:437–48), is analysed using the harmonic balance (HB) and the perturbation method of multiple time scales (MMS). Single term HB, two terms HB, and second-order MMS with reconstitution version I (Nayfeh and Sanchez, Journal of Sound and Vibration 1989; 24:483–97) and version II (Rahman and Burton, Journal of Sound and Vibration 1989; 133:369–79) approximations to the steady-sate frequency–amplitude curves of the principal parametric resonance for each of the first four natural modes of the cantilever beam are compared with each other and with those obtained by numerically integrating the unimodal equation of motion. The time transformation is used in obtaining these approximations; also detuning is used in obtaining the square of the forcing MMS approximations. The obtained results show that, for the problem under consideration, the MMS version II is, in comparison with MMS version I, simpler to apply and leads to qualitatively more accurate second-order results. These results, however, show that the MMS version II tends to produce appreciable over corrections to the first-order results and may breakdown at relatively low response amplitudes, whereas the two terms HB solutions tend to improve the first-order results and lead to fairly accurate results even for relatively large response amplitudes.     

Application of the singularity function method to semi-infinite orthotropic rectangular plates on an elastic foundation

The singularity function method is applied to solve the structural problems of semi-infinite orthotropic rectangular plates on a Winker-type elastic foundation. Previous application by Selek et al. (Int. J. Mech. Sci., 25 (1983) 397) of the singularity function to plates on an elastic foundation was limited only to isotropic cases. Foundation-free orthotropic plate problems have been previously solved Adewale et al. (Int. J. Mech. Sci., 31 (1989) 853). In this paper, the singularity function method technique is extended to orthotropic rectangular plate on Winkler-type foundation. The isotropic rectangular plate results of Selek et al. (Int. J. Mech. Sci., 25 (1983) 397) and the foundation-free orthotropic rectangular plate results provided by Adewale et al. (Int. J. Mech. Sci., 31 (1989) 853) are recovered as special cases.     

A low cost, high accuracy roundness measuring system

This work presents a new architecture of a roundness measuring system in which the roundness measuring accuracy is not dependent on motion accuracy of the rotary element. In this architecture, the influence of motion errors on roundness measurement is minimized by applying a new error separation technique developed by Horikawa et. al. [1 and 2], the improved Reversal Method — IRM. A prototype that uses: a rotary table supported by ball bearings, non-contact gap sensors and a computer system that collects and process sensor readings has been developed. Experimental results have shown that even using a rotary table supported by ball bearings, that has non-repetitive motion errors larger than 2μm, the final measurement repeatability is better than 0.3μm of peak-to-peak value. In order to ensure the same levels of accuracy of the proposed system, a traditional roundness measuring system design must use a more precise and therefore more expensive type of bearing with a motion error no larger than 0.1μm.     

Experimental methodology to study tribological aspects of deep drawing — application to aluminium alloy sheets and tool coatings

To optimise the contact between aluminium alloy sheets and coated HSS steel tools during deep drawing operation, we present an experimental methodology to decompose an extended slippage by using a strip drawing test with cylindrical tools in multipassing mode. We show in this paper the role of transfer films formed on the tool surface on the evolution of both friction coefficient and surface topography of the metal sheet.     

AN APPLICATION OF SIMULTANEOUS HEAT AND MASS TRANSFER IN A CYLINDER USING THE FINITE-DIFFERENCE METHOD

A study of simultaneous heat and mass transfer during drying an infinite cylinder shape material (twigs of ilex paraguayenais saint hilaire) was carried out. The finite-difference method was used to solve the drying model and a simultaneous heat and mass balance in each node was made. Models with different assumptions were tested and the external mass transfer coefficient was used as a parameter to fit the model to experimental data. The thickness of the node and the time step were selected considering the system stability.

Drying temperature, twig diameter and air velocity were selected as study variables. The models results were in good agreement with experimental measurements giving mass coefficient values between 1.97 10^-4and 9.55 10^-4 Kg/m² s.