Bytes Of Memory Research Articles

System architecture directions for networked sensors

Technological progress in integrated, low-power, CMOS communication devices and sensors makes a rich design space of networked sensors viable. They can be deeply embedded in the physical world and spread throughout our environment like smart dust. The missing elements are an overall system architecture and a methodology for systematic advance. To this end, we identify key requirements, develop a small device that is representative of the class, design a tiny event-driven operating system, and show that it provides support for efficient modularity and concurrency-intensive operation. Our operating system fits in 178 bytes of memory, propagates events in the time it takes to copy 1.25 bytes of memory, context switches in the time it takes to copy 6 bytes of memory and supports two level scheduling. The analysis lays a groundwork for future architectural advances.

HOW TO BREAK GIFFORD'S CIPHER

We present and implement a ciphertext-only algorithm to break Gifford's cipher, a stream cipher designed in 1984 by David Gifford of MIT and used to encrypt New York Times and Associated Press wire reports. Applying linear algebra over finite fields, we exploit a time-space tradeoff to determine key segments derived from a decomposition of the feedback function. This work, the first proposed attack on Gifford's cipher, illustrates a powerful attack on stream ciphers and shows that Gilford's cipher is ill-suited for encrypting broadcast data in the MIT-based Boston Community Information System (BCIS).Gifford's cipher is a filter generator—a linear feedback shift register with nonlinear output. Our cryptanalytic problem is to determine the secret 64-bit initial fill, which is changed for each news article. Representing the feedback function as a binary matrix F, we decompose the vector space of register states into a direct sum of four F-invariant subspaces determined from the primary rational canonical form of F. The attack computes segments of the key corresponding to these invariant subspaces, which have dimensions 24, 5, 6, and 29, respectively. Because the dimension-24 subspace corresponds to a nilpotent transformation, Gilford's cipher effectively uses only 40 bits of key. With a novel hashing technique, we search these 40 bits in only 227 steps. From the decomposition of F, we also compute the exact probability distribution of the leader and cycle lengths of all state sequences generated by Gifford's cipher.Our attack runs in 227 steps and 218 bytes of memory, which is a significant shortcut over the 264 steps required for a straightforward exhaustive search of all initial fills. Given ciphertext only from one encrypted article, our prototype implementation running on a loosely-coupled network of eight Sparcstations finds the article key within approximately four hours on average. Exploiting a key-management flaw of the BCIS, we also compute at no additional cost the corresponding master key, used for one month to encrypt all article keys in the same news section.

Durov Plot: A Computer Program for Processing and Plotting Hydrochemical Data

AbstractThe expanded Durov diagram has been widely used to represent the dissolved constituents of natural water and to show plausible hydrochemical processes occurring within the hydrological systems. Because of the time required to calculate Durov diagram coordinates and to plot the points, especially when dealing with large numbers of chemical analyses, the treatment of such data is often quite a tedious process. To alleviate this problem, DurovPlot program is designed to help users in calculating and plotting the diagram in a very short time. The program is written in BASIC as a special menu‐driven hydrochemical data analyses code. It was compiled using Microsoft QuickBASIC version 4.5 compiler. The utilization of this program requires the acquisition of an IBM‐PC or compatible with at least 512K bytes of memory, one disk drive (at least 360K bytes), a graphic card (EGA or VGA), and at least DOS version 5.0. DurovPlot possesses several advantages such as the ease with which the data can be entered, edited, and retrieved. The results of computation and plotting are obtained in seconds, depending on the amount of data analyzed and the speed of the computer processor.

High-Performance Three-Dimensional Electromagnetic Modelling Using Modified Neumann Series. Wide-Band Numerical Solution and Examples

We present a new, accurate, high-performance, wide-band three-dimensional (3-D) solver for the electromagnetic (EM) field scattering problem in an isotropic earth. The solver relates to those based on the volume integral equation (IE) approach and exploits a modified Neumann series (MNS) technique to solve Maxwell's equations. The solver allows for the conduction, polarization and displacement currents to be taken into account and admits for 3-D earth excitation by arbitrary electric or/and magnetic sources. We estimate the solver efficiency for scatterers discretized into Nx × Ny × Nz prisms, where it requires only about 6NxNyNz (log2(2Nx) log2(2Ny) + 6Nz) multiplications to get one term of the MNS expansion and about 200 NxNyNz2 bytes of memory. Our experience show that the number of terms N which are to be summed up to get the solution to 1% accuracy doesn't exceed fifty for the models with the conductivity contrast of up to 100. We demonstrate the solver versatility for magnetotellurics (MT) and controlled-source simulations. EM fields arising from a 3-D model with two high-contrast thin layers residing in layered earth were simulated due to a 10 Hz electric dipole located at the surface. When the layers were discretized into 16, 384 prisms our code on a Pentium-100 MHz took T ∼ 58 minutes, M ∼ 7 Mbytes and N ∼ 280. We also modeled the 0.1 Hz and 0.01 Hz MT responses within 3-D model with 1 Ω·m and 100 Ω·m blocks. When the blocks were discretized into 8, 000 prisms the code took T ∼ 5 minutes, M ∼ 8 Mbytes, and N ∼ 25. Finally fields for a crosswell model including a 3-D conducting target were simulated for 0.1 kHz and 10 kHz electric and magnetic dipoles in the wellbores. While the target was discretized into 6, 250 prisms the code took T ∼ 16 minutes, M ∼ 13 Mbytes, and N ∼ 24. All simulations showed from very good to excellent agreement with those of the other 3-D solvers.

On the implementation of minimum redundancy prefix codes

Minimum redundancy coding (also known as Huffman coding) is one of the enduring techniques of data compression. Many efforts have been made to improve the efficiency of minimum redundancy coding, the majority based on the use of improved representations for explicit Huffman trees. In this paper, we examine how minimum redundancy coding can be implemented efficiently by divorcing coding from a code tree, with emphasis on the situation when n is large, perhaps on the order of 10/sup 6/. We review techniques for devising minimum redundancy codes, and consider in detail how encoding and decoding should be accomplished. In particular, we describe a modified decoding method that allows improved decoding speed, requiring just a few machine operations per output symbol (rather than for each decoded bit), and uses just a few hundred bytes of memory above and beyond the space required to store an enumeration of the source alphabet.

Memory efficient ranking

Fast and effective ranking of a collection of documents with respect to a query requires several structures, including a vocabulary, inverted file entries, arrays of term weights and document lengths, a set of partial similarity accumulators, and address tables for inverted file entries and documents. Of all of these structures, the array of document lengths and the set of accumulators are the components accessed most frequently in a ranked query, and it is crucial to acceptable performance that they be held in main memory. Here we describe an approximate ranking process that makes use of a compact array of in-memory, low-precision approximations for the lengths. Combined with another simple rule for reducing the memory required by the partial similarity accumulators, the approximation heuristic allows the ranking of large document collections using less than one byte of memory per document, an eight-fold reduction compared with conventional techniques. Moreover, in our experiments retrieval effectiveness was largely unaffected by the use of these heuristics.

Real-Time Sleep–Wake Scoring in the Rat Using a Single EEG Channel

A new method of analysis of sleep in the rat based on the electrocorticogram (ECoG) is described. Three states, awake (W), nonrapid eye movement (NREM) and rapid eye movement (REM) sleep are automatically classified by the system. After amplification of the ECoG over a restricted bandwidth (3.18-25 Hz) and sampling at 512 Hz, the data are processed in 8-second epochs by a microcomputer, which generates three statistical and two harmonic variables. Each 8-second epoch is thus compressed into five numerical values occupying 10 bytes of memory. Epochs for each state of vigilance are identified by an expert observer to produce three reference models. The program classifies each epoch into the appropriate state by the least quadratic distance. The system was validated by comparing the results with a visual analysis of polygraph recordings. The agreement between the program and the two independent scorers for 24-hour tracings of six rats was 83% for REM sleep, 96% for W and 97% for NREM sleep.

True 3D Computer Modeling: Sculpture of Numerical Abstraction

True 3D Computer Modeling: Sculpture of Numerical Abstraction

A Star Pattern Recognition Algorithm for Autonomous Attitude Determination

A star pattern recognition algorithm is described enabling a state-of-the-art star tracker to quickly and reliably determine its attitude about all three axes without requiring any a-priori attitude knowledge. This device, referred to as a "Full-sky Autonomous Star Tracker (FAST)," can serve as a key sensor in future autonomous attitude control and navigation systems. Having a field of view of 11.5 by 11.5 degrees and an accuracy of 8 arcsec (1 sigma), the redundant, microcomputer equipped ASTROS II star tracker being developed by JPL for use with the Mariner Mark II planetary spacecraft is ideally suited to serve as a FAST. It is shown that an ASTROS II based FAST, integrated with an all-sky database of some 4,100 guide stars, and 810K bytes of memory, can deterrnine its attitude in approximately 1 second with a success rate very close to 100%. Its high speed is due to both the accuracy of the tracker and the efficiency of the algorithm which usually does not require any iterations.In addition to enabling a FAST, the recognition algorithm can also be used for automating the acquisition of celestial targets by astronomy telescopes, for updating the attitude of gyro based attitude control systems autonomously (planned for Mariner Mark II), and for automating ground based attitude reconstruction. Monte Carlo simulations and a much faster, highly accurate quasi-analytical method are used for predicting the success rate of the algorithm as a function of the many parameters required to define the sky, the star catalog from which the guide stars are extracted, the tracker, and the control parameters of the algorithm.

Instrumentation for High-Speed Digital Recording of Switching Surges

Three sophisticated monitoring systems were developed and used to make unattended measurements of over 600 switching surges on 33 motors at 11 different utilities. The authors describe in detail one of the recording systems which relies on ECL (emitted coupler logic) digital electronics and high-speed commercial digitizers to measure the multiple, fast-risetime, high-voltage surges typically created by vacuum circuit breaker switching operations. This three-channel monitoring system is capable of digitizing a voltage waveform at 5 ns intervals and has 64 K bytes of memory per channel. The digitizer sampling rate is varied in real time to allow high-speed recording of up to 256 transients. Wideband capacitive voltage dividers with a flat response from below power frequencies to 20 MHz were designed to bolt directly onto the motor terminals and were used to couple the surges to the monitoring system. Results from typical field measurements made with this system on motors controlled by vacuum switchgear are also reported. >

The influence of VLSI technology on computer architecture

Very-large-scale integration (VLSI) offers new opportunities in computer architecture. The cost of a processor has been reduced to that of a few thousand bytes of memory, with the result that parallel computers can be constructed as easily and economically as their sequential predecessors. In particular, a parallel computer constructed by replication of a standard computing element is well suited to the mass-production economics of the technology. The emergence of the new parallel computers has stimulated the development of new programming languages and algorithms. One example is the Occam language which has been designed to enable applications to be expressed in a form suitable for execution on a variety of parallel architectures. Further developments in language and architecture will enable processing resources to be allocated and deallocated as freely as memory, giving rise to some hope that users of general-purpose parallel computers will be freed from the current need to design algorithms to suit specific architectures.

Transputer network with flexible topology

A PC plug-in board has been designed containing 4 transputers (each with 1M bytes of memory) and a crossbar switch. Several such boards can be interconnected and arbitrary topologies can be made under software control. A high level powerful interface with the host PC allows for efficient host communication. Special attention has been paid to allow for testability of the system in a topology independent way.

The 5 minute rule for trading memory for disc accesses and the 10 byte rule for trading memory for CPU time

If an item is accessed frequently enough, it should be main memory resident. For current technology, “frequently enough” means about every five minutes. Along a similar vein, one can frequently trade memory space for CPU time. For example, bits can be packed in a byte at the expense of extra instructions to extract the bits. It makes economic sense to spend ten bytes of main memory to save one instruction per second. These results depend on current price ratios of processors, memory and disc accesses. These ratios are changing and hence the constants in the rules are changing.

Linked gas chromatography infrared mass spectrometry.

For almost 20 years the idea of linking a gas chromatograph with both an infrared and a mass spectrometer to form an integrated analysis system (GC/IR/MS) has intrigued analytical chemists. For example, in one of the earliest GC/IR papers, which reported GC/IR spectra of 10-18 wavenumber resolution with microgram-level sensitivity, Low and Freeman suggested the potential value of a GC/IR/MS system. Of course, it was obvious then (in 1968) that a number of significant improvements in both IR spectroscopy and computer technology would be required for the practical realization of this visionary suggestion. Although powerful and inexpensive computers easily capable of the experiment control and data reduction needs are readily available today, that was most emphatically not the case in 1968. In fact, at that time computer systems with 8K words (16K bytes) of 16-bit memory equipped with paper tape input-output, a teletype, and modest data acquisition and control capabilities were available for $35,000-$40,000exclamation Programming support was equally limited (e.g., multipass paper tape-oriented FORTRAN compilers, memory resident BASIC compilers that occupied most of memory, or assembly language). Consequently, development of requisite real-time control, data acquisition, data storage, and interpretation software would have been a formidable and extremely expensive undertaking. Mostmore » of these early difficulties have been overcome, and substantial progress has been made. It is therefore timely to review the current status and historical development of GC/IR/MS. The present article should complement the excellent related reviews by Griffiths and co-workers on chromatography-Fourier transform IR (FT-IR) spectrometry and Henion and co-workers on liquid chromatography-mass spectrometry (LC/MS). All these techniques are possible because of major technical advances made during the past 10 years or so.« less

Microcomputer Implemented PWM Inverter Using a Unique Pattern of Switching Angles

A method is proposed for implementing a PWM transistor inverter using a microcomputer. The control of the input de voltage to the inverter allows the use of a unique pattern of switching angles and a continuous variation of the output voltage. The periodically measured input de voltage defines completely the switching instants, which are inversely proportional to the measured dc voltage. A 10-bit A/D, converter allows a voltage and consequently a frequency resolution of 0.1 percent. Since the proposed method does not require extensive look-up tables, only about 700 bytes of memory were required for the inverter implementation using a TMS 9900 microprocessor.

SELECT-A-BERRY, a Small Fruit Cultivar and Nursery Database Program

Abstract Diverse geographical and climatic zones in North Carolina permit the culture of a full range of small fruit crops, including rabbiteye and highbush blueberries, strawberries, blackberries, and muscadine and bunch grapes. However, information on specific cultivars is scattered throughout various horticultural publications and nursery catalogs and is not readily available. We have developed an extension software program, SELECT-A-BERRY, which facilitates retrieval of small fruit cultivar and nursery information. The menu-driven program has been formatted for the Tandy 1000 (Radio Shack, a Division of Tandy Corp., Fort Worth, Texas) microcomputers recently installed in all North Carolina county extension offices, but it will also run on the IBM-PC and other MS-DOS systems with 256 K bytes of computer memory. Although the program is designed primarily to assist North Carolina commercial and home garden extension clienteles, SELECT-A-BERRY can be modified by agreement with us and the N.C. Agricultural Extension Service for use in other regions as well.

A model (WHTROOT) which synchronizes root growth and development with shoot development for winter wheat

A model has been developed of root growth in winter wheat based on cumulative thermal time with description of the extension and branching of individual age classes of seminal and crown root axes. The model requires, as input, the sowing date and average monthly mean air temperatures and gives, as output, the maximum depth of penetration of each age class of root and the root length density or root weight in any 10 cm layer of soil contributed by main axes, first-order and second-order laterals on any calendar date. The impact of soil temperature on root length density distributions with time was assessed by comparing a warm site (Perth, Australia) with a cool site (Rothamsted Experimental Station, England). Simulated values of root length density for plants with six leaves were consistently high when soil temperature was held constant at 10°C, but variable soil temperatures at each site resulted in rooting profiles characteristic for the two sites, although root length densities were larger than commonly observed at either location. The model simulates well described sequences of root production and permits calculation of maximal root development rates for unstressed plants growing in moist soil with no mechanical impedance to growth. It allows the co-development of root and shoot to be modelled and since it uses only about 5 K bytes of computer memory could be easily used for the assessment of management practices in the field.

A 32-Bit FASTBUS Computer

Los Alamos National Laboratory is building a 32-bit FASTBUS computer using the NATIONAL SEMICONDUCTOR 32032 central processing unit (CPU) and containing 16 million bytes of memory. The board can act both as a FASTBUS master and as a FASTBUS slave. It contains a custom direct memory access (DMA) channel which can perform 80 million bytes per second block transfers across the FASTBUS.

APCLUST: A versatile Apple II program to perform agglomerative hierarchical clustering analysis

A variety of algorithms for performing agglomerative hierarchical clustering analysis have been embodied in programs on mainframe computers (Blashfield, Aldenderfer, & Morey, 1982), but few clustering programs are available as yet for microcomputers (Whaley, 1982; recently Gilpin, 1985, described a program which performs hierarchical clustering analysis using a divisive procedure). Program APCLUST performs hierarchical clustering analyses on the Apple IT family of computers. Requirements. The program is written in APPLESOFf BASIC, a dialect of Microsoft BASIC, and should run without changes on other members of the Apple IT family (IT, ITe, and ITc), provided at least 48K bytes of RAM are available (the program requires 28K bytes of free memory). It is written to direct output to a printer if one is available, but may be used on systems lacking a printer as well. Conversion to other systems running Microsoft BASICs should be straightforward; a section of the APPLESOFf BASIC manual is devoted to relevant peculiarities of the Apple IT version. A disk drive running DOS 3.3 is necessary if the me input option, discussed below, is to be used. Input/Output Options. The program APCLUST requires as input the upper half (including diagonal) of a triangular matrix of values representing dissimilarities between pairs of up to 60 objects (variables). Data may be entered in three ways: (1) via DATA statements added to the program; (2) via entry from the keyboard during program execution; and (3) via a previously created data file on diskette (a utility program, APCLUSTFILEBUILDER, is provided to create the file). Output may be directed to the screen or to a printer in any slot (port) number. If desired, the program will pause periodically during output, awaiting a response from the user, to prevent results from scrolling off the screen. APCLUST assumes that the data matrix represents a single two/way

5.SPECTのイメージング技術(第41回総会)(I.核医学イメージング技術の標準化)

At present, a large number of SPECT systems are being widely used in Japan, hence, it is reasonable for us to know the physical and imaging characteristics of these SPECT devices, and also to recommend the optimum utility of SPECT systems. For this reason, a survey respect of characteristics of the commercialy available SPECT devices was carried out. In addition to this, various factors which have significant influence over SPECT image quality, such as, data acquisition matrix, reconstruction filter, γ-ray attenuation correction and daily quality control procedure, were also investigated. The materials used for this study are PET/SPECT phantom. Alderson liver phantom filled with Tc-99m solution, and either LFOV-E or ZLC-7500 interfaced to Scintipac 2400 minicomputer with 256 K byte of memory. Following are the results of this study. 1) The suitable data acquisition procedure was 128×128 matrix for linear sampling and approximately 64 views for angular sampling. 2) Reconstructed image using pre-processing filter with Wiener and Butterworth filters provided high quality image as compared with the Ramp filter. 3) Weighted backprojection method (WBP) proposed by Tanaka was superior to other methods, such as Sorenson method and Chang method in the object with non-uniform distribution of radionuclide. 4) It was found that uniformity correction of gamma camera and precise abjustment of the center of rotation are most important to maintain the images with a high quality.