Static and dynamic analysis of tunable two-section high-speeddistributed feedback laser utilizing the gain lever effect

Analysis of a novel semiconductor laser structure designed for obtaining wide tuning range along with high speed modulation response is presented. The laser consists of a composite cavity structure with two active (gain) sections. One of the sections has a grating corrugation while the other is flat. A detailed round-trip analysis is combined with the rate equations, which include sublinear gain/carrier relation, to perform steady-state and small-signal analysis. It is shown that the biasing (dc) condition of the different sections plays a critical role in the determination of the dynamic response of the device. In addition, we show that the gain-lever effect can be utilized for a considerable enhancement of the frequency modulation (FM) response. Other critical structural parameters such as the grating coupling coefficient and device geometry are discussed     

Crystallographic shear planes in nanocrystalline SnO2 thin films by high-resolution transmission electron microscopy

Atomic structures of crystallographic shear planes (CSPs) in nanocrystalline thin films of semiconductor SnO₂ were investigated by high-resolution electron microscopy. The films were prepared by electron beam evaporation in high vacuum (10^–6 torr) and followed by annealing in synthetic air at 700 °C for 1–2 H. CSPs with the displacement vector of [1/2 0 1/2] were observed in the planes parallel to (¯101), (110) and (¯3¯21). Most of the CPSs were found to terminate or interact with each other within SnO₂ crystallites. Partial dislocations exist at terminal places of CSPs or along intersecting lines of CSPs. CSP steps were also observed. Structural models of these defects have been proposed. Based on analysis of experimental data, it has been suggested that the Sn/O ratio at CSPs which are not parallel to their displacement vector, at cores of partial dislocations and at CSP steps, is higher than that of the perfect structure, that is, these defects are able to provide extra free electrons with the films.     

Method for monitoring positions in three dimensions

This article presents a fundamentally new method for controlling the position of an object in three-dimensional space by using a microinterferometer. This method assures high accuracy and efficiency. The method can be used for verifying accuracy of contact gauges in position-measuring machinery. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 17–18, April, 1996.     

Transition metal joints for steam generators—An overview

The transition metal joint (TMJ) between an austenitic stainless steel and a chromium-molybdenum (Cr-Mo) ferritic steel used widely in steam generators of power plants has for a long time presented problems relating to premature failures in service. The direct (bimetallic) TMJ presently in use is designed for a service life of about 200,000 h; but such TMJs with iron-base weld metals have been failing in service within about one-third of their design lifetime, while their counterparts with nickel-base weld metals fail within about one-half of their design lifetime. The causes for such premature service failures of these TMJs are discussed in detail, leading to the development of improved TMJs. One of the improved TMJs with a trimetallic configuration of austenitic stainless steel/Alloy 800/Cr-Mo ferritic steel is discussed in detail, covering its development, characterisation and evaluation. Accelerated performance tests in the laboratory have indicated a four-fold improvement in the service life of the TMJ with this trimetallic configuration compared to the bimetallic configuration. The metallurgical details of these studies are also discussed in this paper.     

Influence of body segment dynamics on loads at the lumbar spine during lifting.

Flexion-extension moments acting at the L5/S1 level and hip joints were calculated using three different techniques; a pure static analysis, a static analysis including the inertial force of the load, and a dynamic analysis. Ten subjects participated in the study and were asked to lift a box weighing either 50 N or 150 N, using a freestyle technique. The lifts were performed at normal and fast speed. The intra-subject lifting techniques were consistent when lifting the same loads. The moments predicted by the dynamic analysis and the static analysis were the same when holding weights in static postures. When performing the lifts, differences in the peak moments occurred between static and dynamic analyses. These differences were influenced by external load and by lifting speed. Taking the effect of the inertia of load into account in the static analysis resulted in an increase in the moment magnitude, but the predicted moment was still much less than in the dynamic analysis which yielded the largest moment magnitudes. The difference between dynamic and static analysis was greatest when lifting 50 N at fast speed; an 87% increase in L5/S1 moment and a 95% increase in hip moment was observed when replacing the pure static with a dynamic analysis.     

Dynamic arrays for fast, efficient, data manipulation during image analysis: a new software tool for exploratory data analysis.

Memory reallocation is used to construct a run-time data structure for fast/efficient storage of information during collection and analysis. The data structure presented uses dynamic memory but does not require the use of pointers to link nodes of information together. It allows for simple and efficient access to data via array indexing rather than through the use of lists or tree structures and it provides flexibility for competing storage requirements that are determined dynamically. The data structure is developed in the C programming language and a suite of ANSI standard C subroutines that make up a run-time data structure management system is provided.     

Quasi-optical multiplexer based on reflecting diffraction grating

The article presents results of theoretical and experimental investigation of quasioptical multiplexer based on reflecting diffraction grating. Diffraction losses caused by reflection into mirror harmonic, and by angle divergence of wave beams are calculated. In an experimental multiplexer, wave beams with the frequencies 70 GHz and 79 GHz were mixed with power losses less than 1%.     

New possibilities of chemical beneficiation of synnirites

Institute of Geology Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 106–109, January-February, 1992.     

Carrier multiplication in submicrometre pMOS transistors operated at cryogenic temperatures

The temperature and bias dependence of the carrier multiplication M(I/sub bulk//I/sub drain/) in submicrometre pMOS transistors has been characterised and studied over the temperature range of 30-300 K. In addition, a model which reproduces the bias dependence of M over the measured range of temperature can be extrapolated down to 4.2 K to predict the internal bulk potential and its related 'kink effect'. The agreement between data and the prediction of the model confirms that the gate voltage and temperature dependence of the mean free path plays the key role in determining the carrier multiplication characteristics of submicrometre pMOS transistors, operating in the temperature range of 4.2-300 K.<>