An isolated ZVS/ZCS flyback converter using the leakage inductanceof the coupled inductor

This paper describes a simple and effective way to modify an existing hard-switched flyback power converter into a circuit with zero-voltage switching (ZVS) and zero-current switching (ZCS). The key improvement is to turn the unattractive features of the coupled inductor leakage inductance and snubber capacitor into attractive ones. The coupled inductor leakage inductance and snubber are used to form a quasi-resonant circuit to facilitate ZVS/ZCS of all power devices. The operating principles of the power converter and experimental results are presented     

Minimum entropy and information measure

Kapur et al. (1995) introduced the MinMax information measure, which is based on both maximum and minimum entropy. The major obstacle for using this measure, in practice, is the difficulty in finding the minimum entropy. An analytical expression has already been developed for calculating the minimum entropy when only variance is specified. An analytical formula is obtained for calculating the minimum entropy when only mean is specified, and numerical examples are given for illustration     

Evaluating the performance of flood-d: a tool for efficientlyreplicating Internet information services

Internet information services replicate their servers to improve availability, response time, and fault tolerance. Traditional replication algorithms do not address the scale and administrative decentralization of today's internetworks. We have proposed and implemented a scalable and efficient tool to replicate wide-area, autonomously managed services. We target replication degrees of thousands of weakly consistent replicas. The main goal of our replication tool is to make traditional replication services scale in today's exponentially growing, autonomously managed internetworks. Our tool, which we call flood-d, allows servers to be organized in multiple replication groups. For each replication group, flood-d builds a logical update topology that is resilient to server failure, and tries to minimize the communication cost and propagation time needed to transmit updates. Flood-d's logical topologies are computed based on communication latency and available network bandwidth. This paper describes flood-d, and presents simulation results obtained when using flood-d to extend existing replication algorithms. Our results show the gains of organizing service replicas into multiple, smaller replication groups, and using network-cognizant logical topologies to propagate updates. We argue that existing as well as emerging Internet information services can benefit from flood-d's services     

Benign postural vertigo and nystagmus of the horizontal semicircular canal

Benign paroxysmal vertigo and nystagmus are induced not only by the posterior but also by the horizontal semicircular canal. Benign positional nystagmus of the horizontal canal is more often observed than was previously thought. In 10 patients we analyzed the characteristics and the variability of nystagmus which accompanies positional vertigo of the horizontal canal. There are two forms of nystagmus: primary-geotropic, most often paroxysmal nystagmus (7 patients), and primary-apogeotropic, non-paroxysmal nystagmus (3 patients). Interestingly, in 2 patients with the primary-apogeotropic form the nystagmus converted during the examination into the primary-geotropic form. The reverse was not observed. We discuss the possible pathophysiological mechanisms which could be relevant for provoking manoeuvres.     

Thermodynamic assessment of the Hg–Tl system

The phase diagram and thermodynamic properties of the Hg–Tl binary system were modeled by means of the CALPHAD method, using experimental information as reported in the literature. A good agreement was observed between our calculated data and the existing experimental data. Also, an interesting result was established about the dependence of entropy and enthalpy of mixing functions on temperature, and at the same time, on practically ideal activity vs. concentration. The Gamma phase was described for the first time using the substitional RKMP model.     

The Silicon Graphics 4D/240GTX superworkstation

A class of machines known both as superworkstations and graphics supercomputers has become available. These workstations provide computing performance previously available only on supercomputers and graphics performance at levels never before available. The author presents a model that differentiates graphics architectures on the basis of graphics computation partitioning and places superworkstation architectures within the framework. He then presents the reasoning that resulted in the architecture of the Silicon Graphics 4D/240GTX superworkstation. The architecture and performance of the 4D/240GTX are discussed     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

Strain aging of tube steels during operation of overland oil pipelines

We applied the methods of fatigue failure in pure bending and of impact toughness to investigate the tube steels 17GS, 19G, 14GN, 14KhGS, 10G2S, and Kh52 (Czechoslovakia) of oil pipelines after different service times, and we also determined the stress intensity factors and strain aging co-effecients. The article shows that with loinger service time the tube steels become embrittled: the number of load cycles to failure decreases, impact toughness drops abruptly, and the strain-aging coefficient increases. In embrittled steels fatigue cracks become more ramified than in nonaged steels. It was established that in proportion to the length of operation of oil pipelines the residual life of the tube steels decreases in consequence of the embrittlement of structurally inhomogeneous regions of the metal. It is shown that specimens with welding seams fail 2–2.5 times more rapidly; this testifies to the intense aging in structurally inhomogeneous regions.All-Union Research Institute for the Construction and Planning of Oil Pipelines (VNIISPTnefti), Ufa. Translated from Problemy Prochnosti, No. 11, pp. 125–128, November, 1989.