Representing the mean residual life in terms of the failure rate

In survival or reliability studies, the mean residual life or life expectancy is an important characteristic of the model. Whereas the failure rate can be expressed quite simply in terms of the mean residual life and its derivative, the inverse problem—namely that of expressing the mean residual life in terms of the failure rate—typically involves an integral of a complicated expression. In this paper, we obtain simple expressions for the mean residual life in terms of the failure rate for certain classes of distributions which subsume many of the standard cases. Several results in the literature can be obtained using our approach. Additionally, we develop an expansion for the mean residual life in terms of Gaussian probability functions for a broad class of ultimately increasing failure rate distributions. Some examples are provided to illustrate the procedure.     

Hybrid mode-switched control of DC-DC boost converter circuits

This paper has proposed a new switching scheme for controlling dc-dc boost converter circuits. The converter is represented as a hybrid system with three modes of operation. The switching among these modes is governed by the adjustable reference voltage and a reference current which are calculated by an energy balance principle. The scheme has been applied to a realistic converter circuit modeled with various parasitic components. All the specifications related to the ripple voltage, line and load regulation are shown to be achievable by relating them to the switching surfaces, namely a reference voltage and a reference current. The state trajectories have been shown to reach a hybrid limit cycle already proved to be super-stable from consideration of chaos. Numerical results clearly bring out the advantages of the proposed control scheme.     

Scattering of a Monopolar TE-Polarized Electromagnetic Pulse on an Ideally Conducting Cylinder

Journal of Communications Technology and Electronics - Abstract—The problem of scattering on an ideally conducting infinite cylinder of a monopolar electromagnetic pulse, the electric field...     

Maximizing Parallel Testing in an FM Receiver

High volume production environments create great challenges for production testing and verification of Radio Frequency (RF) devices. In this environment, much emphasis is put on parallel testing, or the ability to test multiple devices at the same time using a single tester. In order for this parallelism to become a reality, there is a need for production RF tests to be simplified and reduced to requiring only the simplest test stimulus and analysis. In this paper, we present a new method of measuring the performance of a Frequency Modulation (FM) receiver that requires only a continuous wave signal input in order to eliminate the more costly Signal-to-Noise Ratio test. Using this new technique we will then demonstrate how simplifying this test and adding frequency diversity enables testing of up to 8 devices in parallel using a single tester.     

Analysis of anharmonic and thermoelastic properties of non-centrosymmetric crystals

In the present paper an analytical potential form is used for overlap repulsive energy, derived by Harrison from quantum mechanical considerations, along with the composite effect of three-body forces and intersublattice displacement. The short-range overlap parameters in Harrison's potential form have direct correlation with the valence state energies for outermost electrons. The potential model is applied to calculate the third and fourth order elastic constants, first and second pressure derivatives of second order elastic constants, Grüneisen parameter and its volume dependence, Anderson parameter, and thermal expansion coefficient for three non-centrosymmetric crystals, viz. CaF₂, SrF₂ and BaF₂. The calculated values of various physical quantities are found to be in good agreement with experimental data.The authors are grateful to Dr. Mansour Khalef, the Head of Physics Department, TNRC, Tajura (Tripoli) for the facilities and encouragements.     

Application of R-matrix method to electron-H<Subscript>2</Subscript>S collisions in the low energy range

Electron-H₂S collision process is studied using the R-matrix method. Nine low-lying states of H₂S molecule are considered in the R-matrix formalism to obtain elastic integral, differential, momentum transfer and excitation cross sections for this scattering system. We have represented our target states using configuration interaction (CI) wavefunctions. We obtained adequate representation of vertical spectrum of the target states included in the scattering calculations. The cross sections are compared with the experiment and other theoretical results. We have obtained good agreement for elastic and momentum transfer cross sections with experiment for entire energy range considered. The differential cross sections are in excellent agreement with experiment in the range 3–15 eV. A prominent feature of this calculation is the detection of a shape resonance in ²B₂ symmetry which decays via dissociative electron attachment (DEA). Born correction is applied for the elastic and dipole allowed transition to account for higher partial waves excluded in the R-matrix calculation. The electron energy range is 0.025–15 eV.     

A superdense star model as charged analogue of Schwarzschild’s interior solution

A charged analogue of Schwarzschilds interior solution has been derived by considering the non-gravitational energy density to be constant along with a special choice of electric intensity. The charged fluid sphere so obtained is seen to be more general than that of P.S. Florides and joins smoothly with the Reissner-Nordström metric at the pressure-free interface. Also the new charged fluid sphere is capable of representing a superdense star with surface density of 2×10¹⁴ g cm^–3 which can occupy maximum mass 1.502408 times the solar mass. In the process of deriving the solution, the authors have also come across A. L. Mehras gaseous charged fluid model which is found to be unphysical as it has negative pressure at least at the center of the model.This revised version was published online in April 2005. The publishing date was inserted.     

Low temperature thermoelectric properties of Cu intercalated TiSe2: a charge density wave material

Y₂O₃ nanoparticles and nanorods have been firstly synthesized in bulk Ti-Y films prepared by magnetron sputtering on Si (100) substrates at different temperatures. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) are used to characterize the structure, morphology, and composition of the as-synthesized nanoparticles and nanorods. The mechanical properties of the sputtered films are investigated using nanoindentation techniques. The results indicate that both the nanoparticles and nanorods have a pure cubic Y₂O₃ structure resulting from the reaction of Y atoms with the residual O₂ in the vacuum chamber, and are free from defects and dislocations with uniform diameters of about 30 nm. The Y₂O₃ nanoparticles mainly distribute at the grain boundaries of the Ti matrix and the nanorods have lengths ranging from 250 nm to more than 1 μm with the growth direction parallel to the (002) plane. As the growth temperature elevates, the nanoparticles turn to be coarsening while more and longer nanorods are inclined to form. Compared with the Ti film, the TiY films have a remarkable increase in hardness, but do not exhibit expected increase in elastic modulus. Finally, the growth mechanism is also briefly discussed.