Photonic Demodulator With Sensitivity Control

A current assisted photonic demodulator for use as a pixel in a 3-D time-of-flight imager shows nearly 100% static demodulator contrast and is operable beyond 30 MHz. An integrated tunable sensitivity control is also presented for increasing the distance measurement range and avoiding unwanted saturation during integration periods. This is achieved by application of a voltage on a dedicated drain tap showing a quenching of sensor sensitivity to below 1%     

Training recurrent neurocontrollers for real-time applications.

In this paper, we introduce a new approach to train recurrent neurocontrollers for real-time applications. We begin with training a recurrent neurocontroller for robustness on high-fidelity models of physical systems. For training, we use a recently developed derivative-free Kalman filter method which we enhance for controller training. After training, we fix weights of our recurrent neurocontroller and deploy it in an embedded environment. Then, we carry out additional training of the neurocontroller by adapting in real time its internal state (short-term memory), rather than its weights (long-term memory). Such real-time training is done with a new combination of simultaneous perturbation stochastic approximation (SPSA) and adaptive critic. Our critic is also a recurrent neural network (RNN), and it is trained by stochastic meta-descent (SMD) for increased efficiency. Our approach is applied to two important practical problems, electronic throttle control and hybrid electric vehicle control, with apparent performance improvement.     

Dynamic Loading in High-Speed Ball Bearings

The numerical dynamic model of a ball-bearing with angular contact and oil lubricant, which allows to study movement of the bearing parts, having six degrees of freedom, is developed. The general parameters, characterizing loading of bearing retainer, are analyzed. The influence of general structural parameters of several ball-bearings on in-service operation conditions of their retainers is analyzed.     

Adjusting the linear expansion coefficient Lin Fe-Ni-Co-Ti invars by aging and phase hardening

The N30K10T3 and N40K10T3 invars with the Curie points θ_C ≈ 200°C and θ_C ≈ 310°C and the martensite temperatures M _s ≈ −80°C and M _s < −196°C, respectively, have been studied. The two alloys were hardened by quenching in the range of temperatures from 100 to 750°C. In addition, the first alloy was hardened by a combination treatment including phase-transformation-induced hardening and aging. The method of phase hardening consisted in the use of a forward (γ → α) and a reverse (α → γ_ph) martensitic transformations. It has been shown that the temperature dependences of the linear expansion coefficient and the dependences of the hardness on the temperature and time of aging are considerably different for both alloys upon decomposition of the supersaturated solid solution. Both the ordinary and the double aging have been studied.     

Short-term creep and strength of fibrous polypropylene structures

The short-term creep and strength of fibrous polypropylene structures are investigated. On the basis of these characteristics, we develop the models of linear and nonlinear viscoelastic deformation of materials, specify the fields of their applicability, and study criteria used for the evaluation of the static strength and durability of these composites. __________ Translated from Problemy Prochnosti, No. 6, pp. 77–90, November–December, 2007.     

Formation of a fine-grained structure of iron-nickel alloys by reversible martensite transformation

We have investigated the influence of multiple γ-α-γ transformations proceeding by the shear mechanism on the structural-phase state of austenite in iron-nickel alloys N28T2Yu2 and N32. It has been shown that it is possible to form, by cyclic γ-α-γ transformations, a fine-grained structure of austenite due to the fragmentation of the initial structure that develops under the conditions of progressing disorientation of the crystal lattice of the γ-phase. In the process of thermocycling, the reversed austenite was continuously strengthened under the condition of the development of disorientation of its lattice. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 602–606, May–June, 2008.     

Electroluminescent properties of heterostructures with GaInNas quantum wells

GaInNAs quantum wells were grown by metal-organic vapor-phase epitaxy. In order to improve the optical properties, the GaNAs barriers were incorporated on both sides of the quantum well; these barriers compensated the elastic stresses. Characteristics of the optical transitions were assessed from the measurements of photoluminescence and photocurrent. In order to fabricate light-emitting diodes, nonalloyed ohmic contacts based on heavily δ-doped layers were used. Electroluminescence was observed at a wavelength of ～1.2 μm at temperatures of 77 and 300 K; the electroluminescence intensity depended linearly on the injection current if the latter exceeded a certain threshold value.     

Structure and properties of manganese austenitic steels quenched from the melt

The precipitation-hardening manganese austenitic steels with different content of carbide-forming elements and carbon obtained by the method of rapid melt quenching have been considered. The influence of dispersion of the structure on the morphology of carbides, strengthening, and the magnitude of shape-memory effect has been investigated.     

GaAs–AlGaAs heterostructure thyristors with completely optical transfer of emitter current

Several variants of thyristors based on GaAs-AlGaAs heterostructures with optical transfer of the emitter current are considered. The possibility that thyristors with fully optical transfer of the emitter current can be, in principle, created is demonstrated by means of the results of a study of n-p-n and p-n-p optoelectronic transistors in which the emitter current is converted into light, this light, in turn, being converted into a collector current. Structures of optoelectronic switches of this kind are presented. A switch comprising three constituent transistors has been suggested and fabricated taking into account specific features of the technique for growth of undoped GaAs layers and fabrication of high-voltage p ⁰-n ⁰ junctions with back-ground impurities from these layers, which makes the turn-on delay cardinally shorter and raises the working frequency.     

MOVPE of structures with aluminum nanocluster layers in a GaAs matrix

Metalorganic vapor phase epitaxy (MOVPE) was used to grow semiconductor structures comprising a GaAs single crystal matrix with incorporated layers of aluminum nanoclusters (Al-NCs). A new regime of GaAs overgrowth on Al-NC layers is proposed, which ensures planarization of the semiconductor layer surface at a thickness comparable with the height of Al-NCs.