Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.     

Development of a Laser Interferometric Dilatometer for Measurements of Thermal Expansion of Solids in the Temperature Range 300 to 1300 K

A laser interferometric dilatometer has been developed for measuring linear thermal expansion coefficients of reference materials for thermal expansion in the temperature range 300 to 1300 K. The dilatometer is based on an optical heterodyne interferometer capable of measuring length change with an uncertainty of 0.6 nm. Linear thermal expansion coefficients of silicon were measured in the temperature range 700 to 1100 K. The performance of the present dilatometer was tested by a comparison between the present data and the data measured with the previous version of the present dilatometer and the data recommended by the Committee on Data for Science and Technology (CODATA). The present data agree well with the recommended values over all the temperature range measured. On the other hand, the present values at lower temperatures are in poor agreement with the previous experimental data. The combined standard uncertainty in the present value at 900 K is estimated to be 1.1×10^–8 K^–1.     

Investigation of the Precision of an Algebraic Algorithm for the Reconstruction of Tomograms from Projections Given in a Limited Range of Angles

The solution of the problem of reconstructing an image of the cross-section of an object with a limited set of data is considered. A program developed on the basis of the ART3 algebraic algorithm for reconstruction of tomograms is described. Results from a computational experiment are presented; in the course of the experiment the precision of a two-dimensional tomographic reconstruction as a function of the range of angles and number of projections obtained for models of cells with and without a nucleus is studied. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 34–37, August, 2005.     

An improvement of the EDI method in linear elastic fracture mechanics by means of an a posteriori error estimator in G

In this paper, an error estimator that quantifies the effect of the finite element discretization error on the computation of the stress intensity factor in linear elastic fracture mechanics is presented. In order to obtain the proposed estimator, a shape design sensitivity analysis (SDSA) is applied to the fracture mechanics problem. Following this approach, one of the most efficient post‐processing techniques for computing the strain energy release rate G, the well‐known EDI method, may be interpreted as a continuum method of the SDSA. The proposed error estimator is based on the recovery of the gradient fields and its reliability has been checked by means of numerical problems, yielding very good estimations of the true error. The new estimator remarkably improves the results given by a previous error estimator, which is based on a discrete analytical approach of SDSA. As a consequence, the combination of the new error estimator and the result given by the EDI method provides a much more accurate estimation of G. Copyright © 2003 John Wiley & Sons, Ltd.     

Use of a field lens for improving the overlap function of a lidar system employing an optical fiber in the receiver assembly

This paper presents a method to compute the overlap function of a lidar system in which a step-index optical fiber (or a bundle of such fibers) is used to carry the light collected by the telescope to the photoreceiver and a field lens is placed between the telescope and the optical fiber to increase the receiver field of view (FOV). The use of field lenses is a classical way to increase the FOV of radiometric systems (such as the receiving part of a lidar) when there is no numerical aperture (NA) limitation after the lens. However, when such a limitation exists, as in the case studied here, it will place a limit on the maximum attainable FOV. In the case of lidars, which have range-resolution capabilities, the limited FOV has an effect on the fraction of power coming from scattering volumes at different ranges that actually reaches the photodetector. This fraction is a function (the so-called overlap function) of the range of the scattering volume and its behavior has an impact on the accuracy of the retrievals. The application of the method developed in this paper shows that, in spite of the fiber NA limit, in practical situations the goal is attained of making the overlap function steeper and reaching higher values by using a field lens.     

An Estimation Method for the Total Quantity of Goods in Distribution by the Use of a Regression Curve

A method for estimating the total quantity of goods distributed in a market is presented by the use of a polynomial regression curve on the plane where the y-coordinate consists of the rates of goods for their product numbers.

Two kinds of estimators for the above-mentioned total quantity are proposed with investigating their asymptotic properties.

As a practical example, estimating the total quantity of beer cases in a market is considered.

     

Use of plasma impedance monitoring for the determination of SF6 reactive ion etch process end points in a SiO2/Si system

It is shown here that plasma impedance monitoring can be used successfully to determine the end point of reactive ion etching of a SiO₂ layer lying on a Si substrate in SF₆ plasma. The usefulness of this technique is demonstrated using a commercial Plasma Impedance Monitoring (PIM) system. The end point conditions are tested by monitoring changes in the fundamental and the first four harmonic components of the RF current, RF voltage, phase between RF voltage and current, RF discharge power and RF impedance. The best process monitoring parameter found in this work is modeled as a polynomial equation of RF input power, chamber pressure and gas flow rate, from which the end point can be predicted with good precision and easily detected by the PIM. The end point conditions are confirmed by both Fourier Transform Infrared Spectroscopy (FTIR) measurements and via observation of plasma color changes. Received:15 June 2001 / Accepted: 18 June 2001     

钛合金薄板激光和钨极氩弧焊残余应力测试研究

采用小孔释放法对钛合金薄板激光焊和钨极氩弧焊(TIG焊)的焊接残余应力进行了测试，并分析了焊接方法、焊接线能量和焊后热处理对残余应力分布规律的影响。研究结果表明：激光焊残余应力分布规律与普通熔焊方法相似，但其分布区域较窄；在热影响区内，激光焊残余拉应力值比TIG焊的约低100MPa；在焊缝及其熔合线附近，激光焊残余应力却比TIG焊的高。对于不同线能量激光焊接，线能量越大，焊缝越宽，热影响区的残余应力也越大。焊后真空热处理能降低残余应力90％。     

A differential-equation method for the computation of the electromagnetic scattering by an inhomogeneity in a cylindrical waveguide

Summary In this paper an exact method is described for computing numerically the scattering by an inhomogeneity in a cylindrical waveguide. The Generalized Telegraphist's Equations are used to transform the electromagnetic-field equations into a system of ordinary differential equations. The latter system behaves numerically unstable. A method is given to cope with this difficulty. Numerical results are presented for two- and three-dimensional obstacles in a waveguide of rectangular cross-section and they are compared with those obtained by other methods. Our method requires, in general, a relatively small amount of computation time and storage capacity. Another advantage of the method is its flexibility.     

Calculation of the critical conditions for a thermal explosion in an inhomogeneous medium by a method of integral relations

We develop a method of integral relations for problems of thermal explosion. We find the condition for ignition of a turbulent reactive stream in a pipe.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 1, pp. 95–98, January, 1980.     

Use of a Plackett-Burman design with multivariate calibration for the analysis of polycyclic aromatic hydrocarbons in micellar media by synchronous fluorescence

This work describes the use of a multilevel Plackett-Burman design (PB) for the creation of a calibration set for partial least square regression (PLS). The PB calibration set was compared to a collinear analogue by testing these two PLS models for the analysis of six polycyclic aromatic hydrocarbons (PAHs). These compounds were analyzed in micellar media by synchronous fluorescence after determination of the experimental conditions (choice of surfactant, analytical conditions such as deltalambda, step, and scan range). The external validation shows that the collinear set is inappropriate to quantify PAH in real samples, but the PB calibration set affords optimal results.     

空分流程传统的膨胀机制冷量估算方法的改进

分析了传统膨胀机制冷量估算的不足 ;提出利用流程计算软件来计算膨胀机的制冷量的方法 ;最后 ,介绍了一个计算实例。     

Detailed study of an efficient blue laser source by second-harmonic generation in a semimonolithic cavity for the cooling of strontium atoms

We have constructed a blue laser source consisting of an amplified, grating tuned diode laser that is frequency doubled by a KNbO3 crystal in a compact standing wave cavity and produces as much as 200 mW of internal second-harmonic power. We have analyzed the unusual characteristics of this standing wave cavity to clarify the advantages and disadvantages of this configuration as an alternative to a ring cavity for second-harmonic generation. We emphasize its efficiency and stability and the fact that it has an inherent walk-off compensation, similar to twin crystal configurations. We demonstrate its utility for laser cooling and trapping of earth alkalis by stabilizing the laser to the 461-nm transition of strontium, using a heat pipe, and then forming a magneto-optic trap of strontium from a Zeeman-slowed atomic beam.     

Sub-second adsorption for the fast sub-nanomolar monitoring of Clindamycin in its pure and pharmaceutical samples by fast Fourier transformation with the use of continuous cyclic voltammetry at an Au microelectrode in a flowing system

For the first time the fast Fourier adsorptive stripping voltammetry at a microgold electrode for the determination of Clindamycin in flow injection systems has been developed. The principal advantages of the method are that it is rapid, simple, and possesses low detection limit. Some investigations were also done, to find the effects of various parameters on the sensitivity of the proposed method. The conditions producing the performance were the pH value of 2, the scan rate value of 40 V/s, accumulation potential of (300 mV), and accumulation time of 0.3 s. Some of the advantages of the proposed method are as follows: the removal of oxygen from the test solution is not required any more, the detection limit of the method is sub-nanomolar and finally, the method is fast enough for determination of such compounds, in a wide variety of chromatographic methods. We also introduce a special computer based numerical method, for calculation of the analyte signal and noise reduction. After subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, to obtain a sensitive determination. The waveform potential was continuously applied on an Au disk microelectrode (with a 12.5 μm in radius). The method was linear over the concentration range of 4–42,498,400 pg/ml (r = 0.9957) with a limit of detection and quantitation 1.3 and 4 pg/ml, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay Clindamycin in capsules.     

Study on the interaction between a dislocation and impurities in KCl : Sr2+ single crystals by the Blaha effect Part I Interaction between a dislocation and an impurity for the Fleischer's model taking account of the Friedel relation

It has been previously reported for KCl : Sr²⁺ (0.035, 0.050, 0.065 mol% in the melt) single crystals that the interaction between a dislocation and the impurity can be approximated to the Fleischer's model. From the values of ₀ for the specimens, however, it was confirmed that the Friedel relation can be taken into the Fleischer's model. The ₀ is the bending angle at which the dislocation embraces the impurities under the effective shear stress at 0 K. Furthermore, the interaction between a dislocation and the impurity could be approximated to the Fleischer's model taking account of the Friedel relation. This was examined on the basis of the dependence of strain-rate sensitivity due to the impurities on temperature at about 100–200 K. Then, the critical temperature, at which the effective shear stress is zero, was determined to be 282 K. In addition, the values of the enthalpy and the Gibbs free energy of activation for the breakaway of the dislocation from the impurity were obtained for the specimen.     

Comments on the paper “an analysis of the relationship between driver injury and vehicle age for automobiles involved in North Carolina accidents during 1966–1970” by G.G. Koch and D.W. Reinfurt

Although the Koch/Reinfurt paper does not find significant increase in injury severity with vehicle age, the conclusion that there is “no important relationship between vehicle age at time of accident and severity” is not justified.