Motoro1a V8088

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Reliability of a k-out-of-n warm-standby system

A general closed-form equation is developed for system reliability of a k-out-of-n warm-standby system (dormant failures). The equation reduces to the hot and cold standby cases under the appropriate restrictions     

1/fand 1/?f noise produced by a radio-frequency current in a carbon resistor

The 1/f noise observed in carbon resistors under a.c. bias is found to have different properties from, and is not coherent with, the resistance fluctuations producing the 1/?f noise. Some thermal origin is suggested.     

Modeling a shared-load k-out-of-n:G system

A Markov model for analyzing the reliability and availability of an n-unit shared-load repairable k-out-of-n:G system with imperfect switching is presented. The equations for both time-dependent and steady-state system availability are given. An inverse Laplace transform is used to solve the simultaneous differential equations for the nonrepairable case. A generalized analytic function for system reliability is obtained. Examples are provided to demonstrate the model and the impact of a load-sharing strategy on the reliability. The load-sharing strategy can improve system reliability and availability, if the controller and switching parameters are adequate. The proposed approach and solution are helpful to system engineers and reliability analysts     

Reliability of a general consecutive-k-out-of-n:Fsystem

A linear (circular) consecutive-k-out-of-n:F system consists of n components ordered on a line (circle). Each component and the system have two states: good or failed. The system fails if and only if at least k consecutive components fail. The reliability of such systems is computed. The most general case is examined without any restriction on the components     

Reliability of a consecutivek-out-of-r-from-n:F system

The reliability of the consecutive k-out-of-r-from-n:F system is studied. For k=2 an explicit solution is given for n components in line or in cycle in the i.i.d. case. For k⩾3 sharp lower and upper bounds are given for the reliability of the system and demonstrated for different values of n, k, r, p. These bounds are exact for r=n, n-1, n-2, n-3, and for these values the exact analytic solution is also given     

Injection control of a multipass amplification of a dischargeexcited XeF (C→A) laser

The laser performance and kinetic properties of the broadband C→A transition of the XeF*-exciplex have been studied under discharge excitation. With a pulsed dye laser as the injection source, amplified output pulses with an energy of up to 4 mJ have been obtained in the wavelength range from 450 to 520 nm. Injection of a well-defined seed pulse in an unstable confocal cavity has been developed into a useful technique for identification of subtle kinetic details of the complicated lasing process in XeF*, such as the role of the competitive narrow-band B→X transition or the influence of the various buffer gases     

H-polarization diffraction by a thick metal-dielectricjoin

An analysis is presented of the H-polarization diffraction due to a material discontinuity formed by the junction of a thick dielectric half-plane with a metallic half-plane having the same thickness. This is accomplished by first considering the solution of several subproblems. These include the direct diffraction and coupling due to a plane wave incident on a loaded open-ended parallel plate waveguide and radiation and reflection by a waveguide mode. The final solution for diffraction by the metal-dielectric join is obtained by introducing a perfectly conducting stub within the loaded guide and subsequently using the generalized scattering matrix formulation with the stub brought to the waveguide opening. All the analysis relating to the subproblems is done by the dual integral equation approach. As expected, the final expressions involve several Wiener-Hopf split functions which are evaluated numerically or analytically     

Comment on `Modeling a shared-load k-out-of-n*Gsystem'

The commenter states that there is no reason to perform the steady-state analysis as attempted by J. Shao and L.R. Lamberson (see ibid., vol.40, no.2, p.205-9, June 1991) for a Markov chain that has an absorbing failure state. Corrected expressions are provided     

A personal communications network using a Ka-bandsatellite

The feasibility of a personal communications network using portable terminals that can provide 4.8 kb/s voice communications to a hub station via Ka-band geosynchronous satellite has been investigated. Tradeoffs are examined so that the combined system of hub and gateway earth stations, the satellite, and the personal terminals can provide a competitive service in terms of cost, availability, and quality. A baseline system that uses a spacecraft with approximately 140 spot beams to cover the contiguous US (CONUS) and 5 W power amplifiers in each beam is described. Satellite access in both the forward and return directions uses frequency-division multiple-access/code-division multiple-access (FDMA/CDMA) with a chip rate of 2.5 Mchip/s     

On computing MTBF for a k-out-of-n:G repairablesystem

It is often necessary to calculate the MTBF (mean time between failures) quickly in order to make timely design decisions. An important system for which such calculations must be made is a k-out-of- n:G parallel system with unlimited repair and exponential interfailure and repair times at the unit level. Although a general formula is known, it is not easily remembered or derived. A method for deriving a formula for MTBF in this situation that is easily reproduced quickly by remembering a few simple concepts is presented     

Pre-stack inversion of a 1-D medium

Assuming a one-dimensional (1-D) acoustic medium and a known density, we want to determine the velocity distribution from pre-stack surface seismic data. Basically, we have to identify a distributed parameter in the two-dimensional (2-D) wave equation. This inverse problem is set as an optimization problem. This allows us to expect that the information redundancy available in the data will provide an optimal signal-to-noise enhancement. Since the forward modeling we use gives a complete solution of the wave equation, all the events explained by acoustic wave propagation, such as guided waves or high-order multiples, will be used to infer information about the velocity distribution. From the above arguments we may expect an accurate result with high resolution, even with noise-corrupted data. Although the developed methodology is not optimal at all, the numerical experiments confirm this expectation and illustrate the power of the proposed inversion method.     

An O(kn) algorithm for a circularconsecutive-k-out-of-n:F system

An O(k×n) algorithm is described for evaluating the reliability of a circular consecutive-k-out- n:F system     

Preventive Replacement of a 1-Unit System with a Wearout State

This paper is concerned with a 1-unit system with 3 types of states: usual, wearout, and failure; the hazard rate is constant in the usual state and is monotonically increasing and unbounded in the wearout state. In order to deal with this system in detail, we introduce two models: model 1 in which the period of normal operation is fixed and model 2 in which it is a random variable with a negative exponential distribution function. The models have different preventive replacement policies based on both age and state. Moreover we give the conditions under which these policies are effective.     

Analysis and optimization of a nondissipative LC turn-offsnubber

A nondissipative LC turn-off snubber is used to reduce the voltage stress on a switching transistor, which is caused by the energy stored in the transformer leakage inductance. A detailed analysis of the fundamental characteristics of a buck-boost converter with an LC snubber is given, clarifying the effect of the snubber capacitance. In particular, it is found that the transformer current increases with the snubber capacitance, the transistor surge voltage and power loss are evaluated, and the optimum value of the snubber capacitance is derived. The most effective value of the snubber inductance is also discussed     

High-Tc superconductivity seeks a digital home

Two obvious applications of high-T_c superconductors are discussed: the use of Josephson technology at 77 K and the use of high-T_c lines for interconnects. The difficulties that must be addressed for each of these is discussed, and the prospects for overcoming them are assessed. The need to achieve full compatibility with polymers is stressed     

Efficient algorithm for reliability of a circular consecutive-k-out-of-n:F system

The time complexities of previously published algorithms for circular consecutive-k-out-of-n:F systems are O (nk²) and O(nk). The authors propose a method to improve the original O(nk² ) algorithm, and hence derive an O(nk) algorithm     

Dual-band RF receiver for GPS-L1 and compass-B1 in a 55-nm CMOS

A fully integrated dual-band RF receiver with a low-IF architecture is designed and implemented for GPS-L 1 and Compass-Bl in a 55-nm CMOS process. The receiver incorporates two independent IF channels with 2 or 4 MHz bandwidth to receive dual-band signals around 1.57 GHz respectively. By implementing a flexible frequency plan, the RF front-end and frequency synthesizer are shared for the dual-band operation to save power consumption and chip area, as well as avoiding LO crosstalk. A digital automatic gain control （AGC） loop is utilized to improve the receiver＇s robustness by optimizing the conversion gain of the analog-to-digital converter （ADC）. While drawing about 20 mA per channel from a 1.2 V supply, this RF receiver achieves a minimum noise figure （NF） of about 1.8 dB, an image rejection （IMR） of more than 35 dB, a maximum voltage gain of about 122 dB, a gain dynamic range of 82 dB, and an maximum input-referred 1 dB compression point of about -36.5 dBm with an active die area of 1.5 × 1.4 mm2 for the whole chip.     

A Case Study on a 2-1-1 Cascaded Continuous-Time Sigma-Delta Modulator

This paper intends to give an insight into the potentials and tradeoffs when designing cascaded, continuous-time (CT) sigma-delta modulators. Therefore, a case study is presented considering the implementation of a 2-1-1 CT modulator. The nonideal behavior is regarded in detail and an automatic gain-error cancellation is presented. Finally, a circuit board implementation is presented, which has been chosen to verify the automatic error correction. It turns out that despite a more critical behavior than in the discrete-time (DT) case, cascaded CT modulators have the potential, to realize high bandwidth, high resolution analog-to-digital (A/D) converters in future integrated designs.