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.     

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     

Movement stability analysis of a pipe string in a thixotropic fluid

Features of movement of a drill pipe string in a well filled with a thixotropic fluid are analyzed taking into account inertial and elastic forces of the rope system. It is shown that processes of fluid structure degradation can lead to nonstationary movement of the pipes. In this case periodic and chaotic auto-oscillations are excited in the system.Bashkir State University, Ufa, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 4, pp. 405–411, April, 1994.     

Local staging with CT of tumors of the upper urothelium

OBJECTIVE: To evaluate the ability of computerized tomography (CT) to stage transitional cell carcinoma of the upper urinary tract. METHODS: 29 transitional cell carcinoma of the upper urinary tract submitted to nephroureterectomy were retrospectively evaluated. All 29 tumors had preoperative CT scans performed to stage the lesion. The pathological staging was compared to that of CT. RESULTS: 10 of the 29 tumors had CT evidence of tumor extension and 19 had localized noninvasive tumor on CT. Of the 10 patients with CT findings of tumor extension, 2 (20%) had superficial tumors and 8 (80%) had tumors that invaded into the adventitial fat, renal parenchyma or perirenal fat (pT3, pT4). Of the 19 patients with localized noninvasive tumor on CT, 13 (68%) had superficial tumors and 6 (32%) had pT3 or pT4 tumors. CT sensitivity for tumor invasion was 57% with a specificity of 87.5%. CONCLUSIONS: Our analysis shows that CT is of limited value in staging these tumors. When CT demonstrates direct tumor extension through the renal pelvic or ureteral wall, it is a sensitive indicator of high-stage tumor. However, the results obtained in low stage tumors must be viewed with caution.     

Pentacene-based organic thin-film transistors

Organic thin-film transistors using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active electronic material have shown mobility as large as 0.7 cm²/V-s and on/off current ratio larger than 10⁸; both values are comparable to hydrogenated amorphous silicon devices. On the other hand, these and most other organic TFT's have an undesirably large subthreshold slope. We show here that the large subthreshold slope typically observed is not an intrinsic property of the organic semiconducting material and that devices with subthreshold slope similar to amorphous silicon devices are possible     

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)     

Recrystallization/precipitation behaviour in microalloyed steels

Microalloyed high-strength low-alloy (HSLA) steels contain additions of Nb, V, Ti, or in combination, in amounts of 0.01 to 0.1 weight percent to improve mechanical properties, which are strongly dependent on the thermomechanical interaction taking place in the course of rolling mill processes. The recrystallizatian of hat-twisted austenite has been investigated in a cylindrical specimen (f 6×50 mm) machined from hat rolled plates of 0,052 wt % Niobium microalloyed steel. Continuous and interrupted torsion test were carried out in the temperature range 1123 K to 1173 K after a solution treatment of 1.5 minutes at 1423 K and torque-twist data were analysed. The various methods were discussed for obtaining results from torsion tests. The effect of precipitation kinetics was appreciated by way of connection t_p/t_p(red), where t_p is the experimental measured time for the peak stress and t_p(red) is the newly defined reduced time. The softening ratio X and time t_0.05R for start of static recrystallization were established.

The correlation between precipitation and recrystallization is presented as a graphs for chosen requirements (temperature of austenitization, carbon and niobium content and strain rate). If temperature goes below 850°C, the restoration processes are hardly suppressed, both are limited by diffusion and Nb(CN) precipitation, which are extended dynamically in the range of strains rates 10⁻² to 1 s⁻¹.

In the present paper, an attempt is made to derive the PRTT diagram and to define all mathematical equations for describing recrystallization times t_0.05R, t_0.5R, t_0.95R and t_0.05P for the start of precipitation. In real metal forming processes such as the hot rolling of plates or strips the knowledge of these parameters and results is extremely important for the the correct microstructure and sheet quality to be obtained.     

Crystallization and Drying in Thin Sucrose Films During Panning

Sucrose crystallization in thin films (50–55 μm) was studied, using a videomicroscopy technique, at conditions encountered during hard panning processes. No nucleation occurred in unseeded films, while a linear increase in seeded crystals occurred during drying. Crystal growth rate increased with temperature (25–30°C) and with air velocity (2.4–12.5 m/sec), but did not change with varying sucrose concentrations (70–76% w/w) and relative humidities (0–66% at 30°C). FD & C Yellow No. 5 food coloring in the dye form (0.05–0.5 g/100 mL) showed no effects while similar concentrations in the lake form inhibited crystal growth rate.     

EMULSION COATING TO EXTEND POSTHARVEST LIFE OF MANGO (MANGIFERA INDICA CV. MANILA)

A coating emulsion was prepared using maltodextrins, carboxymethylcellulose, propileneglycol and a mixture of s orbit an fatty acid esters with an HLB of 6. The emulsion was sprayed on fully mature, unripened manila mangoes, which were the stored at 15 and 25C and 80–85% R.H. At 25C it was observed that rate CO² production increased and lost in control fruits after 12 days of storage. Coated mangoes kept their rate CO² production and suffered only 8% weight loss after 21 days of storage. After storage, the coating was washed out and fruits were allowed to ripen naturally, which occurred in 3–4 days. The results obtained from this study indicate that application of the hydrophobic coating extended the postharvest storage of mangoes for at least 20 days more than uncoated fruits.