Chelated alkoxyalumoxanes and a silica-free binder based on them

Chelated alkoxyalumoxane oligomers have been synthesized through consecutive hydrolysis and alcoholysis of organoaluminum compounds stabilized by compounds capable of keto-enol tautomerism. The chelated alkoxyalumoxanes were used to prepare a silica-free binder for the fabrication of heat-resistant (up to 2050°C), chemically inert corundum ceramic composites. The likely structures of the synthesized preceramic alumoxane oligomers were inferred from physicochemical characterization results (¹H, ¹³C, and ²⁷Al NMR, IR spectroscopy, mass spectrometry, gel-permeation chromatography, thermal analysis, and elemental analysis).     

Signal processing using cellular neural networks

The cellular neural network (CNN) architecture combines the best features from traditional fully-connected analog neural networks and digital cellular automata. The network can rapidly process continuous-valued (gray-scale) input signals (such as images) and perform many computation functions which traditionally were implemented in digital form. Here, we briefly introduce the the theory of CNN circuits, provide some examples of CNN applications to image processing, and discuss work toward a CNN implementation in custom CMOS VLSI. The role of analog computer-aided design (CAD) will be briefly presented as it relates to analog neural network implementation.This work is supported in part by the Office of Naval Research under Contract N00014-89-J1402, and the National Science Foundation under grant MIP-8912639.     

89-GHz fT room-temperature silicon MOSFETs

The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f_T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region     

Special Features of Fracture of Steels from Partially-Alloyed Powders

Special features of fracture of structural steels 45N2D2M and 45N4D2M manufactured by pressing with subsequent sintering from partially alloyed iron powders are studied. Impact bending tests of specimens with different levels of retained porosity show two kinds of fracture, i.e., intraparticle cleavage and interparticle dimple fracture. In addition, the surfaces of the “initial” pores come out to the fracture surface. Other conditions being equal, growth in porosity decreases the proportion of the brittle component of fracture and decreases the critical brittle point.     

Metal fusion by laser radiation action in an oxidizing medium

Results are presented from a calculation of fusion of a massive zirconium plate under the action of laser radiation with consideration of simultaneous surface oxidation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 61, No. 1, pp. 11–14, July, 1991.     

Circular core polarization-maintaining optical fibers withelliptical stress-induced cladding

The reproducible technology for producing high-birefringence fibers with stress-induced elliptical cladding and circular core is described. The authors have obtained fibers that have a birefringence of about (1-3) 10^-4, a mode coupling parameter of about (2-7) 10 ^-5 m^-1, and loss of less than 0.5 dB/km at 1.6 μm. The authors have found effects restricting the capability of test fibers to maintain the state of linear polarization     

A methodology for the performance evaluation of data querystrategies in universal mobile telecommunication systems (UMTS)

The anticipated emergence of third-generation mobile systems, referred to as universal mobile telecommunication systems (UMTS), raises the problem of reconsidering the design of the databases destined to contain the user information. In particular, it is expected that the key concepts of the new database architectures will be high distribution and fast updating of information. So far, the problem of determining the most appropriate distributed database (DDB) architectures for third-generation mobile systems has not been widely dealt with in literature. This paper presents a methodology for evaluating hierarchical DDB architectures by means of an analytical model of the data querying operation. This methodology allows for structural alternatives, differing on account of the number of levels and branches in the hierarchy, to be evaluated in terms of query loads and mean response times, according to a given user mobility characterization and a given search protocol operation. By way of illustration, the paper discusses a case study, concerning a query operation arising from a location updating procedure and applied to a hierarchical tree-like DDB in which some structural alternatives are considered