The Farmer, the Fairies, and the Computers

Using a temporary substitution of format, the author offers a fairy tale to demonstrate that we can’t expect understanding when computers take the place of humans in our interactions with service providers.     

Note on B-splines, wavelet scaling functions, and Gabor frames

Let g be a continuous, compactly supported function on such that the integer translates of g constitute a partition of unity. We show that the Gabor system (g,a,b), with window g and time-shift and frequency-shift parameters a,b>0 has no lower frame bound larger than 0 if b=2,3,... and a>0. In particular, (g,a,b) is not a Gabor frame if g is a continuous, compactly supported wavelet scaling function and if b=2,3,... and a>0. We give an example for our result for the case that g=B/sub 1/, the triangle function supported by [-1,1], by showing pictures of the canonical dual corresponding to (g,a,b) where ab=1/4 and b crosses the lines N=2,3,.     

Methods of Verifying Continuous Automatic Belt Weighers: State and Prospects

The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended.     

Experimental and modeling approaches of MR behaviors under large step strains

Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(t, γ), shows a decreasing trend with step strain. The experimental results indicate that G(t, γ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(t, γ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(t, γ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior.     

Java multimedia telecollaboration

Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use.     

A Digital Deformation Vacuum Gauge with an LC-Generator

The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 10⁵. The instruments developed cover the ranges 10³, 10⁴, and 10⁵ Pa.     

The effect of photon energy and temperature on the persistent tunneling photoconductivity effect in Al/δ(Si)-GaAs structures

The phenomenon of persistent tunneling photoconductivity was studied using the tunneling spectroscopy technique at liquid-helium temperature: the separation between the unoccupied levels in a δ-doped layer at the GaAs surface decreased after illumination. This decrease was due to an increase in the width of the quantum well of the δ-doped layer. For photon energies hv exceeding the GaAs band gap E _g , this increase in the width of the quantum well was related to the accumulation of positive charge in the depth of GaAs induced by the generation of the electron-hole pairs and photoionization of deep centers. For hv < E _g (including the case of CO₂ laser), only photoionization is important. The experimental data agree with the self-consistent calculations. The critical temperature for the effect has been determined (T _c = 45 K); at higher temperatures, the effect disappears.     

The radiation resistance of an arbitrarily oriented electric dipole exciting a corner antenna or a plane screen

Rigorous analytic expressions for radiation resistance R _Σ of an electric dipole are obtained for three mutually orthogonal orientations of the dipole’s axis with respect to a plane metal screen or right-angle corner of infinite dimensions. Radiation resistance R _Σ of the dipole oriented arbitrarily in space is calculated and analyzed as a function of the distance from the screen.     

Operation of the dam of the Bureiskaya HPP during filling of the reservoir

Operation of the dam in a transitional mode is described. __________ Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, January 2006, pp. 8–15.     

Dominant rock properties affecting the performance of conical picks and the comparison of some experimental and theoretical results

Conical picks are the essential cutting tools used especially on roadheaders, continuous miners and shearers and their cutting performance affects directly the efficiency and the cost of rock/mineral excavation. In this study, in order to better understand the effects of dominant rock properties on cutter performance, 22 different rock specimens having compressive strength values varying from 10 to 170 MPa are first subjected to a wide range of mechanical tests. Then, laboratory full-scale linear cutting tests with different depth of cut and cutter spacing values are realized on large blocks of rock specimens using one type of conical pick. Specific energy, cutting and normal force values for relieved and unrelieved cutting modes are recorded using a triaxial force dynamometer with capacity of 50 tonnes and a data acquisition system. Cutter force and specific energy values are correlated with rock properties and theoretical force and specific energy values obtained from widely used theoretical approaches.The results indicate that uniaxial compressive strength among the rock properties investigated is best correlated with the measured cutter performance values, which is in good agreement with previous studies. However, it is also emphasized in this study that Brazilian tensile strength, Schmidt hammer rebound values, static and dynamic elasticity modulus are also dominant rock properties affecting cutter performance.Theoretical specific energy defined by different researchers has a meaningful relationship with the experimental specific energy, which is an essential parameter for predicting the instantaneous cutting rates of mechanical excavation systems. It is also demonstrated that the experimental cutter forces obtained for 5 mm depth of cut are in good agreement with theoretical force values, if the friction angle between rock and cutting tool is included in the theoretical formulation. It is emphasized that, to some extend, laboratory tests can help to minimize high cost of a trial–error approach in the field.