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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 51 (1999), S. 55-77 
    ISSN: 1573-4889
    Keywords: STEELS ; SULFIDATION ; SCALE STRESSES ; ACOUSTIC EMISSION ; THERMAL-EXPANSION COEFFICIENTS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several high-temperature processes in chemical,petrochemical, and energy-processing industry arecharacterized by H2S-containing atmospheres,confronting engineers with severe corrosion attack ofthe metallic components. Sulfidation is observed onmaterials used for heat exchangers within theheat-recovery zones. The damage is originated not onlyby the relatively fast growth rates of the sulfidescales, but is also due to the loss of their limitedprotective effect by cracking. Scale failure, as aconsequence of stresses generated during scale growthand by temperature changes, was investigated on a carbon steel, a low-chromium steel (1Cr-0.4Mo, T12),a ferritic-chromium steel (12Cr-1Mo), and on austeniticsteel (18Cr-9Ni, AISI 321). The experiments in thetemperature range 400-600°C (700°C), withsubsequent cooling to ambient temperature, wereaccompanied by acoustic-emission measurements in orderto detect scale cracking. Critical parameters for scalefailure are presented.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The journal of VLSI signal processing systems for signal, image, and video technology 21 (1999), S. 167-177 
    ISSN: 1573-109X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents a high-speed method for computing elementary functions using parallel table lookups and multi-operand addition. Increasing the number of tables and inputs to the multi-operand adder significantly reduces the amount of memory required. Symmetry and leading zeros in the table coefficients are used to reduce the amount of memory even further. This method has a closed-form solution for the table entries and can be applied to any differentiable function. For 24-bit operands, it requires two to three orders of magnitude less memory than conventional table lookups.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of VLSI signal processing systems for signal, image, and video technology 9 (1995), S. 181-191 
    ISSN: 1573-109X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract As developed by Wallace and Dadda, a method for high-speed, parallel multiplication is to generate a matrix of partial products and then reduce the partial products to two numbers whose sum is equal to the final product. The resulting two numbers are then summed using a fast carry-propagate adder. This paper presents Reduced Area multipliers, which employ a modified reduction scheme that results in fewer components and less interconnect overhead than either Wallace or Dadda multipliers. This reduction scheme is especially useful for pipelined multipliers, because it minimizes the number of latches required in the reduction of the partial products. The reduction scheme can be applied to either unsigned (sign-magnitude) or two's complement numbers. Equations are given for determining the number of components and a method is presented for estimating the interconnect overhead for Wallace, Dadda, and Reduced Area multipliers. Area estimates indicate that for non-pipelined multipliers, the reduction in area achieved with Reduced Area multipliers ranges from 3.7 to 6.6 percent relative to Dadda multipliers, and from 3.8 to 8.4 percent relative to Wallace multipliers. For fully pipelined multipliers, the reduction in area ranges from 15.1 to 33.6 percent relative to Dadda multipliers, and from 2.9 to 9.0 percent relative to Wallace multipliers.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Reliable computing 2 (1996), S. 47-62 
    ISSN: 1573-1340
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Description / Table of Contents: Abstract Представлены конструкция аппаратуры, испояьзуемые арифметические алгоритмы и приложения к решению численных задач для интервальных арифметических сопроцессоров переменной разрядности. Эти сопроцессоры позволяют программисту устанавливать начальную разрядность вычислений, определять точность результатов и заново вычислять неточные результаты с большей разрядностью. Для уменьшения времени выполнения в численных приложениях используются пнтервально-арифмети ческие алгоритмы переменной разрядности. Рассмотрены три аппаратные схемы с щиной данных щириной 16, 32 и 64 бита. Эти схемы сравниваются по требуемой площади крисгалла, продолжительности рабочего пикяа и быстродействию в различных численных приложениях. Каджый из этих сопроцессоров может быть реализован на одном кристалле с рабочей частотой, сравнимой с сопроцессорами плавающей точки двойной точности стандарта IEEE. В некоторых численных приложениях наши сопроцессоры на два-четыре порядка быстрее, чем распространенные программные пакеты, реализующие интервальную арифметику переменной разрядности.
    Notes: Abstract This paper presents hardware designs, arithmetic algorithms, and numerical applications for variable-precision, interval arithmetic coprocessors. These coprocessors give the programmer the ability to set the initial precision of the computation, determine the accuracy of the results, and recompute inaccurate results with higher precision. Variable-precision, interval arithmetic algorithms are used to reduce the execution times of numerical applications. Three hardware designs with data paths of 16, 32, and 64 bits are examined. These designs are compared based on their estimated chip area, cycle time, and execution times for various numerical applications. Each coprocessor can be implemented on a single chip with a cycle time that is comparable to IEEE double-precision floating point coprocessors. For certain numerical applications, the coprocessors are two to four orders of magnitude faster than a conventional software package for variable-precision, interval arithmetic.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Reliable computing 2 (1996), S. 133-138 
    ISSN: 1573-1340
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Description / Table of Contents: Abstract Компьютерная арифметика оперативного доступа с большим основанием системы счисления предоставляет эффективный метод для вычислений с переменной разрядностью. Ее можно реализовать на обычных микропроцессорах с помощью последовательностей инструкций с тремя операндами. В работе представлена программная поддержка для компьютерной арифметики оперативного доступа с большим основанием системы счисления. Программное обеспечение включает в себя модули эмуляции для операций с большим основанием системы счисления, а также программу анализа разрядности, служащую для задания лопусков на исходные и промежуточные переменные, обеспечивающих гарантированную точность результата на заданной области.
    Notes: Abstract High radix on-line arithmetic provides an efficient method for performing variable-precision arithmetic. It can be implemented on conventional microprocessors using sequences of three operand instructions. This paper presents software support for high radix on-line arithmetic. This software includes emulation modules for high radix operations, and a precision analysis program for setting the input and intermediate variable tolerances necessary for guaranteed result accuracy over a specified domain.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Reliable computing 5 (1999), S. 311-322 
    ISSN: 1573-1340
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Compiler support for intervals as intrinsic data types is essential for promoting the development and wide-spread use of interval software. It also plays an important role in encouraging the development of hardware support for interval arithmetic. This paper describes modifications made to the GNU Fortran Compiler to provide support for interval arithmetic. These modifications are based on a recently proposed Fortran 77 Interval Arithmetic Specification, which provides a standard for supporting interval arithmetic in Fortran. This paper also describes the design of the compiler's interval runtime libraries and the methodology used to test the compiler. The compiler and runtime libraries are designed to be portable to platforms that support the IEEE 754 floating point standard.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Reliable computing 1 (1995), S. 325-342 
    ISSN: 1573-1340
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Description / Table of Contents: Abstract Описываются программный интерфейс и конструкция аппаратуры для интервальной арифметики переменной разрядности. Программный интерфейс дает программисту возможность управлять разрядностью вычислений, определяя точность результата. Также предусмотрены специальные инструкции для векторных и матричных операций. Конструкция аппаратуры напрямую поддерживает интервальную арифметику переменной разрядности, что значительно повышает точность вычислений и обеспечивает выигрыш в скорости в сравнении с сушествуюшими программными методами управления величиной численных погрешностей. Представлены аппаратно реализованные алгоритмы для основных арифметических операций, точных скалярных произведений и элементарных функций. Оценки времени вычислений и требуемой площади кристалла покззывают, что соответствуюший процессор может быть реализован на одном кристалле с рабочей частотой, сравнимой с существующими процессорами плавающей точки двойной точности стандарта IEEE.
    Notes: Abstract This paper presents a software interface and hardware design for variable-precision, interval arithmetic. The software interface gives the programmer the ability to specify the precision of the computation and determine the accuracy of the result Special instructions for vector and matrix operations are also provided. The hardware design directly supports variable-precision, interval arithmetic. This greatly improves the accuracy of the computation and is much faster than existing software methods for controlling numerical error. Hardware algorithms are presented for the basic arithmetic operations, exact dot products, and elementary functions. Area and delay estimates indicate that the processor can be implemented on a single chip with a cycle time that is comparable to existing IEEE double-precision floating point processors.
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In connection with the proposed structure of a trans-membrane cellular ion channel consisting of a complex between poly[(R)-3-hydroxy butanoate] (P(3-HB)) and calcium polyphosphate, CaPPi (ca. 150 units each), which is supposed to contain s-cis-bonds or even more highly strained ester conformations, we have prepared and studied the properties of the cyclic dimer of 3-HB, the diolide 1. All possible forms of 1, the rac-, the meso-, and the enantiomerically pure (R,R)- and (S,S)-compounds were prepared, purified, and characterized. The synthesis (Scheme 1) started from dimethyl succinate with the key step being the Baeyer-Villiger oxidation of the rac- and meso-2,5-dimethylcyclohexane-1,4-diones 5. The rac-diolide 1 was resolved by preparative chromatography on a Chiralcel OD column (Fig.1). The crystal structures of rac- 1 (Fig.3) and of meso- 1 (Fig.5) were determined by X-ray diffraction: the diolides 1 contain s-cis-ester bonds and an ester group with a conformation half way to the transition state of rotation (Fig.2). Strain energies for the diolides 1 of up to 17.8 kcal/mol are suggested. Accordingly, these compounds show reactivities similar to those of carboxylic-acid anhydrides or even acid chlorides. They cannot be chromatographed on silica gel, and they react with primary, secondary, and tertiary alcohols, and with amines to form derivatives of open chain 3-HB ‘dimers’, hydroxy acids 6, esters 7, and amides 8 (Scheme 2). The rate of acid-catalyzed ring opening of the diolides 1 with alcohols has been measured (Fig.6 and 7). From the results described, we conclude that it is unlikely for strained and reactive ester conformations to occur as part of ion channels through phospholipid bilayers of cells.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Seit der Einführung stabiler chiraler stationärer Phasen (CSP) für die Hochleistungsflüssigchromatographie (HPLC) wird die präparative Chromatographie mehr und mehr als ein effizientes Verfahren zur Herstellung enantiomerenreiner Verbindungen im industriellen Maßstab angesehen. Die aus der Natur der klassischen Chromatographie resultierende Diskontinuität des Verfahrens, verlangt die Umwandlung des Prozesses in einen kontinuierlichen Betrieb. Fine intelligente Lösung dieses Problems ist mit der simulierten Gegenstrom-chromatographie (SMB) gelungen. Diese ermöglicht die kontinuierliche Trennung eines Gemisches in zwei Komponenten mit hoher Reinheit und hoher Ausbeute. Zudem werden im Vergleich zur klassischen Chromatographie große Einsparungen an mobiler und stationärer Phase erzielt. Durch die Komplexität des Verfahrens bedingt, ist eine Simulation der chromatographischen Bedingungen erforderlich. Es werden das Prinzip des Verfahrens, die technischen Ausgestaltungen der Anlagen und das Verfahren zur Ermittlung der Betriebsparameter vorgestellt. An einem Beispiel wird ein Vergleich zwischen verschiedenen chromatographischen Verfahren durchgeführt.
    Additional Material: 8 Ill.
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