Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by STM, RHEED and HRTEM

Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470--650C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH_4F aqueous solutions. It has been shown that smooth surfaces composed by wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures > 600C, whereas clean surfaces obtained at the temperatures < 600C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.Comment: 8 pages, 8 figures; version accepted to J. Appl. Phy

Real-Time Data Processing in the Muon System of the D0 Detector

This paper presents a real-time application of the 16-bit fixed point Digital Signal Processors (DSPs), in the Muon System of the D0 detector located at the Fermilab Tevatron, presently the world's highest-energy hadron collider. As part of the Upgrade for a run beginning in the year 2000, the system is required to process data at an input event rate of 10 KHz without incurring significant deadtime in readout. The ADSP21csp01 processor has high I/O bandwidth, single cycle instruction execution and fast task switching support to provide efficient multisignal processing. The processor's internal memory consists of 4K words of Program Memory and 4K words of Data Memory. In addition there is an external memory of 32K words for general event buffering and 16K words of Dual Port Memory for input data queuing. This DSP fulfills the requirement of the Muon subdetector systems for data readout. All error handling, buffering, formatting and transferring of the data to the various trigger levels of the data acquisition system is done in software. The algorithms developed for the system complete these tasks in about 20 microseconds per event.Comment: 4 pages, Presented and published at the 11th IEEE NPSS Real Time Conference, held at Santa Fe, New Mexico, USA, from June 14-18, 199

Fast electrochemical membrane actuator:Design, fabrication and preliminary testing

An actuator based on water electrolysis with a fast change of voltage polarity is presented. It demonstrates a new actuation principle allowing significant increase the operation frequency of the device due to fast termination of the produced gas. The actuator consists of a working chamber with metallic electrodes and supplying channels filled with an electrolyte. The chamber is formed in a layer of SU-8 and covered by a flexible polydimethylsiloxane membrane, which deforms as the pressure in the chamber increases. Design, fabrication procedure, and first tests of the actuator are described

Розробка алгоритму роботи автоматизованих механімів при виконанні оздоблювальних робіт на вертикальних поверхостях

The article shown light-machinery for tight spaces, limited spaces and at height. The uses of robotics is to allow for greater automation in various processes. Several variants of mechanisms were studied and considered. When comparing and selecting the most efficient equipment, a multicriterion analysis technique was used. The results confirmed that the robot can perform work not only on a vertical surface, but also in hard-to-reach places. Modern and perspective robotization of the total building process with minimum human intervention described. The article shown some groups by centered around the different types of robots: handling and  positioning of large elements,  interior finishing and connecting activities, finishing of large horizontal surfaces, finishing of exterior walls, the demolition process. Using algoritms of robatization and automatization, of building processes allows to reduce the duration of work, cost and increase productivity. The article indicate that robotization of the building activities, if pursued  with a rational and selective approach, may result in considerable productivity gains to the construction industry.У даній статті розглядається мала механізація, яку використовують в важкодоступних місцях, обмеженому просторі і на висоті. З цією метою були вивчені і розглянуті кілька варіантів механізмів. При порівнянні і виборі найбільш ефективного обладнання використовувалася методика багатокритеріального аналізу. Результати підтвердили, що робот може виконувати роботу не тільки на вертикальній поверхні, але і в важкодоступних місцях. Це дозволяє скоротити тривалість робіт, вартість і збільшити продуктивність. При цьому якість відповідає нормативу. Тому був розроблений алгоритм послідовності виконання робіт

The aerodynamics of a jet of particles in a channel

The main cause for dust discharge is ejection, i.e. formation of directional air flows in a stream of a bulk material due to the dynamic interaction of bombarding particles with air. Discovery of induced air flow occurrence regularities enables both forecasting the level of air pollutions with aerosol emission and choosing the optimum engineering solutions of air containment and dedusting. So far we have studied solid particles flowing in a chute and a jet of loose matter. Both situations represent extreme cases of the more general problem of material flowing through a duct with different distances between flow boundaries and duct walls. Without detriment to generality of the problem we shall consider a flat flow limited by vertical walls

Scaling Analysis of Defect Induced Structure of A6061 Alloy at Dynamic Strain Localization

Plastic strain localization and fracture of dynamically loaded metallic samples, occurred during plug formation, are investigated. These processes are closely related to the instability of plastic flow and can be attributed to structural-scaling transitions in mesodefect ensembles. The multiscale nature of defect structure allows us to use the fractal concept for quantitative analysis of both the fracture surface and the inner structure of a deformed material. The scaling properties of fracture surfaces are established in terms of the roughness index (Hurst exponent) as the characteristics of strain localization and fracture