Structural studies of TiN/ZrN multilayer coating deposited by physical vapour deposition

Multilayer coatings have been produced using unbalanced magnetron physical vapour deposition in which discrete layers of TiN and ZrN were co-deposited. It has been shown that the multilayers exhibited two-fold periodicity having values of 13 and 2.8 nm. This periodicity, measured both by cross-sectional transmission electron microscopy and low-angle X-ray diffraction, has been precisely related to the process parameters used. Analysis has shown that a third, previously unreported, phase existed within the coating having a lattice parameter comparable to that of TiN and a well-defined orientation relationship with the primary phases. The existence of this phase has been explained in terms of variations in the stoichometry of the coating due to non-uniform metal to nitrogen deposition rates within the chamber. Textural studies revealed that preferred orientation existed in the coating; the degree of which was greater in the ZrN layers than the TiN layers.     

Breaking substitution cyphers using stochastic automata

Let Λ be a finite plaintext alphabet and V be a cypher alphabet with the same cardinality as Λ. In all one-to-one substitution cyphers, there exists the property that each element in V maps onto exactly one element in Λ and vice versa. This mapping of V onto Λ is represented by a function T*, which maps any v∈V onto some λ∈Λ (i.e., T*(v)=λ). The problem of learning the mapping of T* (or its inverse (T *)^-1) by processing a sequence of cypher text is discussed. The fastest reported method to achieve this is a relaxation scheme that utilizes the statistical information contained in the unigrams and trigrams of the plaintext language. A new learning automaton solution to the problem called the cypher learning automaton (CLA) is given. The proposed scheme is fast, and the advantages of the scheme in terms of time and space requirements over the relaxation method have been listed. Simulation results comparing both cypher-breaking techniques are presented     

Scan performance of infinite arrays of microstrip patch elementsloaded with varactor diodes

The analysis and scanning characteristics of an infinite array of rectangular microstrip patches each loaded with a varactor diode is presented. The analysis is based on full-wave moment method theory and uses attachment modes to accurately model the current through the feed and the diode. The effect of the biased varactor diode on the scan performance is presented, and it is shown that the impedance mismatch caused by a scan blindness can be eliminated. Other characteristics are also given such as: the active element gain, the efficiency of each loaded microstrip element, and the level of cross polarization generated by the loading of the patch. The effect of the diode biasing level as well as the position of the diode on each radiating element on these scan characteristics is also considered     

A channel model for characterization of the error data recoveredfrom compact discs

The data recovered from compact discs are contaminated with errors that exhibit a bursty behavior. A channel model is developed to characterize the error bursts and good-data gaps that occur in actual data recovered from compact discs. The probability of having m erroneous symbols in a data block of length n symbols is calculated using the channel model. This probability can be used to evaluate the performance of the error-correction code (ECC) used in the compact disc system     

Influence of the purity of the starting materials on the recording of dynamic holograms in Bi12TiO20 crystals

The parameters of Bi₁₂TiO₂₀ crystals grown with bismuth oxide of different degrees of purity were measured by a holographic recording technique in an external ac electric field and were compared with a crystal specially doped with chromium. Various crystal parameters such as the diffusion length of the photoexcited carriers and the Debye screening length were determined. It was found that the absorption spectrum of the material and the holographic recording efficiency were strongly influenced by light chromium doping and by insufficient purity of the starting mixture. Pis’ma Zh. Tekh. Fiz. 23, 27–32 (March 12, 1997)     

Intracavitary afterloading therapy as a new technique of boost irradiation in anal canal carcinoma

PURPOSE: There are different techniques of boost irradiation in the treatment of patients with anal carcinoma. A new system of applicators is presented, which can be used for an intracavitary afterloading therapy. MATERIAL AND METHODS: Three different applicators are available, the first with a central catheter (K1), a second with 5 semicircular fixed catheters (K2) and an eccentric shield, a third with 8 circular fixed catheters and a central shield (K3). RESULTS: The adequate choice of applicator and catheters takes into consideration the individual localisation and extension of anal carcinoma in planning therapy. Thus, in circular growing tumors, an irradiation of the whole circumference of the anal canal is possible. In non-circular growing tumors, the dose applied in the non-affected part of the anal canal can be reduced to a quarter of the dose applied at the tumor. CONCLUSION: The new system of intracavitary afterloading therapy is a good alternative to previous techniques of boost irradiation in the treatment of anal carcinoma. By means of this technique, irradiation can be highly individualized, the tumor better included and non-affected sections of the anal canal saved.     

Energy Value of Resistant Starch

Resistant starch was evaluated for energy value using fine silica and normal starch as controls and young rats as a test model. The net increase in rats' carcass energy due to the test materials fed over a 3-wk period formed the basis for assessing energy value. Rats fed normal starch deposited about twice as much fat and significantly more protein in the carcass than those fed either resistant starch or silica. Rats fed resistant starch or silica showed similar growth responses and increases in components of body composition and carcass energy content. This suggested that resistant starch provided, like silica, no energy.