THE LINEAR NORMALIZATION TECHNIQUE—AN ALTERNATIVE PROCEDURE FOR DETERMINING J-R CURVES FROM A SINGLE SPECIMEN TEST RECORD BASED ON LANDES' NORMALIZATION METHOD

An alternative approach for determining J-R curves from a single specimen test based on the normalization technique is proposed. The procedure requires only the load versus load-line displacement record and the final crack length in order to derive the J-R curve. The method has been applied to metal and polymers of various geometries and was verified by comparison with J-R curves obtained from potential drop and multiple specimen techniques.     

Statistical properties of out-of-frame detection schemes fordigital transmission systems

The importance of the misframe times for DS1 frame synchronization has often been addressed in designing and using network elements and mediation units. By extending the work of J. H. Eu and W. W. Rollins (1991), Markov chain first passage time analysis is used to derive higher moments of the misframe times in both random and burst error environments. This methodology is of great value in evaluating frame synchronization techniques for digital transmission systems. By experimenting with several out-of-frame detection schemes and reasonable values for bit error ratio (BER), it is shown that misframe times are always approximately exponentially distributed for all schemes     

Gain optimization for Yagi-Uda arrays

The author presents a personal account of the search for a design procedure for Yagi-Uda antenna arrays yielding a maximum gain, or directivity if element losses are neglected. Results on current distributions in the array are briefly reviewed. The analytical approach used to achieve gain optimization by means spacing and length perturbations is sketched. By using both spacing and length perturbations, it was possible to find the optimized array analytically in a systematic way, some examples having gain increases of nearly 80%. The effects of finite dipole radius and mutual coupling were included in the theoretical treatment     

An investigation of the use of heat pipes for machine tool spindle bearing cooling

The results of an experimental investigation into the practicality of using a heat pipe installed in the spindle of a milling machine to remove the heat produced in the spindle bearings which is capable of causing thermal distortion and cutting error are presented in the paper. Measurements of the variation of bearing temperature with time are reported at four different spindle speeds when there was no heat pipe installed, when the heat pipe was cooled by air and when the heat pipe was cooled by an ice/water mixture. Analysis of the results by a simple heat transfer model indicates that the particular heat pipe used was capable of removing up to 160 W with a corresponding 50% reduction in the rise of the bearing temperature above the temperature of the surrounding air at steady operating conditions.     

Pyrene oxidation as a model reaction for characterizing the mechanism of coke oxidation on Y zeolites

The same effect of temperature on the production of CO, CO₂ and H₂O was found during oxidative treatment of HY zeolites either impregnated with pyrene or coked. Therefore, pyrene oxidation can be used to specify the mechanism of coke oxidation. Three types of reactions can be distinguished: (a) condensation of polyaromatic molecules, (b) oxidation of polyaromatics into aldehydes, ketones, acids and anhydrides and (c) decarbonylation or decarboxylation of oxygenated compounds, all these reactions involving protonic sites.     

Korrosionsuntersuchungen an ausgewählten metallischen Werkstoffen im System Essigsäure/Esigsäureanhydrid

Corrosion tests of selected metallic materials in the system acetic acid/acetic anhydride The corrosion behaviour of the ferritic austenitic stainless steels X2 CrNiMoN 22 5 (UNS S31803) and X2 CrNiMoN 25 7 4 (UNS S32750), the nickel base alloy NiMo16Cr16Ti (alloy C-4) and the titanium grades Ti2 (Grade 2) and Ti2Pd (Grade 7) was investigated by immersion tests in boiling mixtures of acetic acid and acetic anhydride in the presence of air. All materials tested were corrosion resistant in acetic acid and acetic anhydride but were corroded rapidly by the mixtures with a corrosion loss up to 1 mm/a, except the nickel base alloy (alloy C-4). It was corrosion resistant in all solutions with a corrosion loss not exceeding 0.01 mm/a. Electrochemical tests show that all materials tested exhibit stable passivity in glacial acetic acid and active corrosion in the presence of 10% acetic anhydride.     

Corrosion morphologies on magnesium alloy AZ 91

Initiation and early propagation of pitting and filiform corrosion on bare alloy AZ91 (9% Al, 1% Zn) are investigated by natural immersion corrosion tests, electrochemical measurements and microanalytical studies. Initiation sites are few. Corrosion spreads from these sites first in the form of filiform corrosion for a limited period of time and pitting which later develops into a cellular type of etching. The important factors affecting filiform corrosion are temperature, material structure and degree of polarization at the anodic sites. Filiform attack on AZ91, unlike the classical mechanisms of filiform corrosion on coated metals, is driven by hydrogen evolution reaction on the cathodic sites of the surface, occurs under significant anodic control, propagates at a high, constant speed independent of degree of polarization along preferential paths determined by compositional and crystallographic factors, and is a temporary phenomenon under open circuit conditions. Pitting corrosion is more predominant with decreasing anodic polarization.     

Practical accuracy analysis of some existing effective channellength and series resistance extraction methods for MOSFET's

A method to analyze the accuracy of the extracted values for the channel length (L_eff) and series resistance (R_s) of MOSFET devices is presented. The analysis is based on a statistical argument being the variance σ of the extracted results. This variance is found to be a good measure for the accuracy of the particular extraction method used. It is shown that, in the case of deep submicron technologies, errors as large as 200 nm for ΔL can be made for these extraction methods depending on the process design and the process control. The use of a single transistor method is suggested as a possible solution to the low accuracy of the L-array methods