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IBM Journal of Research and Development

Issue 2 • Date March 1979

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Displaying Results 1 - 16 of 16
  • HeNe Parallel Plate Laser Development

    Page(s): 108 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (845 KB)  

    A parallel plate format is used for fabricating “hard” sealed HeNe lasers. The new packaging geometry and construction process are suitable for large scale manufacturing. Cut plate, molded plate, and folded beam lasers have been built and tested. Several changes from conventional lasers, such as evaporated film cathode and anode, square cross section bore, glass sealed Brewster windows, and “soft” glass bore materials, are discussed. The power output capability, measurements of gain and loss parameters, and the reliability of these lasers are also considered. View full abstract»

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  • Cathodes for HeNe Lasers

    Page(s): 119 - 127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (493 KB)  

    Vapor deposited aluminum cathodes for parallel plate HeNe lasers have been used with considerable success. It is shown that the aluminum cold cathode is improved by the addition of copper and that other alloying elements of bulk Al 2024 do not contribute to cathode performance. The plasma oxidation process of Hochuli improves cathode performance by cleaning the surface and optimizing the oxide film for maximum efficiency. There appears to be a trade-off between life and electron tunneling efficiency for optimum oxide thickness. Auger electron spectroscopy, ellipsometry, and scanning electron microscopy are the techniques used for surface characterization. View full abstract»

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  • Nondestructive Analysis for HeNe Lasers

    Page(s): 128 - 131
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (330 KB)  

    The methods used to measure the gas properties in sealed helium-neon lasers are described. Such parameters as total gas pressure, minor constituent concentration (i.e., He/Ne ratio), and gas purity can be measured using spectral emission methods. How these parameters and measurement techniques relate to the electrical operating characteristics of the laser is described. View full abstract»

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  • Polarization Problems of Parallel Plate Lasers

    Page(s): 132 - 139
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    Parallel plate laser technology requires that the plasma envelope and particularly the Brewster windows be “hard sealed.” The first part of this study reports the effects of misalignments of the Brewster windows on laser performance. This turned out not to be a serious problem. In the second part the increase in the birefringence of the Brewster windows resulting from the hard seal technique is examined. We found that this problem, which is serious, can be eliminated by careful control of the temperature during sealing and the annealing process. View full abstract»

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  • Reduction of Storage Fragmentation On Direct Access Devices

    Page(s): 140 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    A technique is described for partially reorganizing the contents of disk storage so as to reduce the level of fragmentation. The method entails choosing that fraction of the contents which is estimated to have the greatest impact on the free space distribution, followed by the relocation of these data to more favorable locations, subject to the system integrity requirements. View full abstract»

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  • Arithmetic Coding

    Page(s): 149 - 162
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (963 KB)  

    The earlier introduced arithmetic coding idea has been generalized to a very broad and flexible coding technique which includes virtually all known variable rate noiseless coding techniques as special cases. An outstanding feature of this technique is that alphabet extensions are not required. A complete decodability analysis is given. The relationship of arithmetic coding to other known nonblock codes is illuminated. View full abstract»

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  • High-Speed Programmable Logic Array Adders

    Page(s): 163 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (909 KB)  

    Programmable Logic Array (PLA) adders are described which perform an addition in one cycle with a single pass through a PLA and require a reasonable number of product terms for an 8-, 16-, or even a 32-bit adder. The PLA features two- bit input decoders feeding an AND array followed by an OR array whose outputs are pairwise EXCLUSIVE-ORed. Carry-look-ahead adder equations, adapted to the PLA to require relatively few product terms, are adjusted for maximum sharing of product terms. The number of unique product terms is a relative measure of one of the physical dimensions of the PLA. Equations for contiguous sum bits are grouped into strings, each using a common input carry. A procedure optimally assigns sum bits to strings to further minimize the total number of unique product terms. The methods are extended to PLAs with decoders of increased inputs and substantially reduced product terms. They can serve as dedicated macro functions on a chip, using special decoders relevant to adders. As a result, the other PLA dimension comprising the number of outputs from all input decoders increases only moderately, and can even decrease, with larger decoders. Finally, the PLA adder can be further substantially compressed by splitting the OR array into two parts such that a row of the AND array is shared between two product terms, and an OR array column is shared between two sums of product terms. View full abstract»

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  • Thermal Stress in Bonded Joints

    Page(s): 179 - 188
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (591 KB)  

    This paper considers the stress distributions in bonded materials induced by differential expansion or contraction of these materials. The analytical approach is similar to the lap joint theories attributed to Volkersen and expanded by Goland and Reissner. Several simple and typical analytical models are presented to bring out the relative importance of different geometrical and material parameters and to give some insight into different modes in which the bonds might fail. View full abstract»

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  • Implications of a Selective Acknowledgment Scheme on Satellite Performance

    Page(s): 189 - 196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (550 KB)  

    Data link response time is becoming more of a concern today with the onset of satellite transmissions of computer data. The long propagation delay inherent to satellite communications may lead to a degradation in data link response time as compared to the same transmission over purely terrestrial links. Furthermore, data link errors need be considered in any such study of response time of satellite data links. A model has been developed to study data link response time under a selective acknowledgment retransmission protocol. The model not only calculates mean link response time, but also the second moment of the response time. This model is then applied to various interactive data transmission schemes over a half-duplex (HDX) satellite link with terrestrial tails, although modifications can easily be made to analyze pure terrestrial or satellite links. The model parameters include bit error rate (BER), terrestrial as well as satellite propagation delay, modem transit delay, MAXOUT (maximum number of unacknowledged data frames), frame size (bits), and message size (bits). View full abstract»

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  • Study of Head-Tape Interaction in High Speed Rotating Head Recording

    Page(s): 197 - 205
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (610 KB)  

    The steady state tape dynamics resulting from the interaction of a high speed rotating head and a flexible recording tape are formulated within the framework of linear shell theory. Tape displacements in the area above the head are coupled with the solution to the Reynolds equation in order to calculate the film thickness (flying height) between head and tape. Simulated results for spherical heads are compared to observed behavior on experimental systems. View full abstract»

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  • Rapid and Precise Method for Analysis of Energy Dispersive X-Ray Spectra

    Page(s): 206 - 213
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A new, precise, and rapid method for the analysis of energy dispersive x-ray spectra generated by electron beam or x-ray excitation is presented. It includes the use of Gaussian profiles and a polynomial of 1/E (where E is the x-ray energy) to represent the observed x-ray characteristic lines and background, automatic sectioning of the entire spectrum, and a figure of merit to estimate goodness of fit. Details of the method and its programming techniques are given. Results of analyzing complicated energy dispersive x-ray (EDX) spectra of multi-element alloys are presented. View full abstract»

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  • Contrast Attenuation Factors for Remote Sensing

    Page(s): 214 - 224
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (738 KB)  

    Attenuation factors for the contrast of objects lying on the earth's surface and observed through five different atmospheric models are calculated as a function of the wavelength (0.31-0.9935 µm), solar zenith angle, ground reflectivity, and the nadir and azimuth angles of view. The first model is free of aerosols and absorbing gases. Absorption by average amounts of oxygen, ozone, and water vapor is included in the remaining four models. The second model is also free of aerosols, but the last three models contain aerosols in the form of a spherical polydispersion made from a substance with a spectrally independent refractive index of 1.5-0.01 i. Models 3 and 4 are expected to represent, respectively, the average and strong turbid conditions encountered over large continental areas. Models 3 and 5 contain aerosols with different size distribution characteristics, but have the same amount of aerosol mass loading per unit horizontal area. The contrast attenuation factor is found to increase with an increase in wavelength and reflectivity of the surrounding surface, and a decrease in the atmospheric turbidity and gaseous attenuation. It also depicts strong azimuthal dependence especially for models illuminated by low-altitude solar radiation of longer wavelengths. View full abstract»

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  • On the Application of Coding Theory to Hashing

    Page(s): 225 - 226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (167 KB)  

    Quick proofs are given for the characterization (due to Schay, Raver, Hanan, and Palermo) of the collision distance of a linear hashing function and for a dual notion (called the restriction distance), which relates to the accessibility of addresses by sets of keys and the uniform distribution of sets of keys over addresses. View full abstract»

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  • Recent papers by IBM authors

    Page(s): 227 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    Reprints of the papers listed here may usually be obtained by writing directly to the authors. The authors' IBM divisions are identified as follows: CHQ is Corporate Headquarters; DPD, Data Processing Division; DSD, Data Systems Division; FED, Field Engineering Division; FSD, Federal Systems Division; GPD, General Products Division; GSD, General Systems Division; OPD, Ofice Products Division; RES, Research Division; SCD, System Communications Division, and SPD, System Products Division. Journals are listed alphabetically by title; papers are listed sequentially for each journal. View full abstract»

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  • Recent IBM patents

    Page(s): 233 - 234
    Save to Project icon | PDF file iconPDF (154 KB)  
    Freely Available from IEEE
  • Authors

    Page(s): 235 - 238
    Save to Project icon | PDF file iconPDF (347 KB)  
    Freely Available from IEEE

Aims & Scope

The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

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Meet Our Editors

Editor-in-Chief
Clifford A. Pickover
IBM T. J. Watson Research Center