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

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

Theoretical and Experimental Investigation of the Dissipated and Stored Energy Ratio in Iron under Quasi-Static and Cyclic Loading

The problem of energy storing (cold work accumulation) in metals was intensively investigated both theoretically and experimentally during all last century but a general theoretical conception of the process was not created. This work is devoted to an experimental investigation of energy dissipation in metals under plastic deformation and to the development of a thermodynamic model to study the cold work accumulation under plastic deformation and failure. The proposed model is based on a statistical description of collective properties of mesoscopic defects and on dividing the plastic deformation into two parts (dissipative and structural). The structural plastic strain was considered as an independent thermodynamic variable that allowed us to determine the thermodynamic potential of the system. The derived constitutive relations were applied for numerical simulation of tensile and cyclic tests. The numerical results demonstrate a good agreement with experimental data.Экспериментально исследовано рассеяние энергии в металлах при пластическом де формировании и разработке термодинами­ческой модели для изучения накопления наклепа при пластическом деформировании и разрушении. Предлагаемая модель осно­вана на статистическом описании коллек­тивных свойств мезоскопических дефектов и на разделении пластической деформации на две части (диссипативную и общую). Общая пластическая деформация рассмат­ривалась как независимая термодинамическая переменная, что позволило опреде­лить термодинамический потенциал систе­мы. Полученные определяющие соотноше­ния применили для численного моделиро­вания результатов испытаний на растяжение и циклических испытаний. Численные ре­зультаты хорошо согласуются с эксперимен­тальными данными

Theoretical and Experimental Investigation of the Dissipated and Stored Energy Ratio in Iron under Quasi-Static and Cyclic Loading

The problem of energy storing (cold work accumulation) in metals was intensively investigated both theoretically and experimentally during all last century but a general theoretical conception of the process was not created. This work is devoted to an experimental investigation of energy dissipation in metals under plastic deformation and to the development of a thermodynamic model to study the cold work accumulation under plastic deformation and failure. The proposed model is based on a statistical description of collective properties of mesoscopic defects and on dividing the plastic deformation into two parts (dissipative and structural). The structural plastic strain was considered as an independent thermodynamic variable that allowed us to determine the thermodynamic potential of the system. The derived constitutive relations were applied for numerical simulation of tensile and cyclic tests. The numerical results demonstrate a good agreement with experimental data.Экспериментально исследовано рассеяние энергии в металлах при пластическом де формировании и разработке термодинами­ческой модели для изучения накопления наклепа при пластическом деформировании и разрушении. Предлагаемая модель осно­вана на статистическом описании коллек­тивных свойств мезоскопических дефектов и на разделении пластической деформации на две части (диссипативную и общую). Общая пластическая деформация рассмат­ривалась как независимая термодинамическая переменная, что позволило опреде­лить термодинамический потенциал систе­мы. Полученные определяющие соотноше­ния применили для численного моделиро­вания результатов испытаний на растяжение и циклических испытаний. Численные ре­зультаты хорошо согласуются с эксперимен­тальными данными

Aerodynamic properties of particles in the gravitational flow of a chuted bulk material

Chutes are a linking element of transportation lines used for transfers of reprocessed materials from one transporting group or equipment to another. The mode of the chuted material motion and the nature of the associated aerodynamic processes are determined by the aggregate physical and mechanical properties of the material being transferred and structural design of chutes. Structurally chutes are subdivided into prismatic, cylindrical and pyramid-shaped (bin) chutes by shape and into vertical, tip and kinked chutes by the bottom slope angle. The most common in practice are tip chutes of a prismatic or a pyramid shape. The purpose of this work was the study of particle movement of granular materials in the sloping chute. In the result of the research, we revealed the following

Collective Modes in the Microshear Ensemble as a Mechanism of the Failure Wave

Results of theoretical and experimental study of failure wave phenomena are presented. A description ofthefailure wavephenomenon wasproposed in terms ofa self-similar solutionfor the microshear density. The mechanisms offailure wave generation andpropagation were classified as a delayedfailure with the delay time corresponding to the time ofexcitation ofself-similar blow-up collective modes in a microshear ensemble. Experimental study of the mechanism of the failure wave generation andpropagation was carried out using afused quartz rod and included the Taylor test with high-speed framing. The results obtained confirmed the "delayed” mechanism of the failure wave generation and propagation.Представлены результаты теоретических и экспериментальных исследований явления волны разрушения. Предложено описание явления волны разрушения на основе авто­модельного решения для плотности микро­сдвигов. Механизмы возникновения и рас­пространения волны разрушения классифи­цировали как замедленное разрушение, при­ чем время задержки соответствовало времени возбуждения автомодельных взрывных коллективных колебаний во множестве микросдвигов. Экспериментальное исследо­вание механизма возникновения и распро­странения волны разрушения проводилось с использованием расплавленного кварцевого стержня и включало испытание по методу Тейлора с высокоскоростным фотографированием. Полученные результаты подтверди­ ли “замедленный” механизм возникновения и распространения волны разрушения

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