Reduce Storage Requirements Research Articles

Biogas production from dairy manure: The effects of temperature perturbations

By taking advantage of a digester's microbial dynamics, gas production can be made to coincide more closely with gas utilization, thereby reducing storage requirements. At constant temperature, a 4-liter control digester with a detention time of 19 days, fed with diluted dairy manure (three parts tap water to one part manure), behaved dynamically like two three-liter digesters fed undiluted manure at a detention time of 15 days. A second 14-liter digester fed with the diluted manure was operated with three different phase relations between a 24 h temperature cycle and the time of the once-daily feeding. In all cases digester operation was stable. In this study, gas production dynamics were investigated using laboratory scale digesters fed daily with dairy manure and operated both at constant temperature and with programmed temperature fluctuations of ±3·3° C about a mean of 35·8°C. The data suggest that gas production can be manipulated by heating and cooling the digester contents. Thus it may be possible to reduce gas storage volume by matching a varying gas production with varying energy demand.

Fractal finite element mesh generation for vibration problems

A new approach for solving plate vibration problems has been formulated by using the Pascal–Sierpinski gaskets and finite element method. The Pascal–Sierpinski gaskets are geometric fractals that are self-similar under scale transformation. Modeling a finite plate element with the basic Pascal–Sierpinski gasket unit, the equations of motion of the basic unit are derived. A buildup process is formed by linking three identical units together. Finally, systematic recurrence relations are generated. The advantage of this approach is that the dynamic matrix of the system has the same dimension at each buildup step. The basic vibration properties, computation time, and memory requirements are discussed and critically compared with traditional finite element methods by discussing a specific example. In general, finite element mesh generation based on geometric fractals offers much promise in reducing storage requirements and computation times significantly.

A Fourier Series Approach to Skyline Generalization for Surface Irradiance Estimates in Alpine Terrain

The degree of generalization acceptable in defining alpine skylines in radiation budget components is explored using truncated Fourier series representations. Numerical simulations are performed for sites in the Teton range of Wyoming, U.S.A. The mean skyline approach performs poorly for all irradiances except the incoming longwave. To calculate direct and global solar and net radiation, more complex skylines are needed with several harmonics, although the requirements are less stringent if primary interest is focused on spatially-averaged radiation budgets. Nevertheless, the Fourier series approach shows promise as a means of reducing storage requirements for skyline data in computer programs to perform topoclimatic radiation calculations and as a method of generating conveniently and objectively a continuous skyline function from discrete data.

An Adaptive General Sparse Out-Of-Core Cholesky Factorization Scheme

A practical out-of-core Cholesky factorization scheme is introduced that is based on reorganizations of the matrix data structure during the factorization. It is applicable to the factorization of both dense and sparse matrices. The scheme can be regarded as a simple extension of the conventional in-core sparse factorization method. It is highly adaptive in the sense that it will run successfully in a range of storage sizes. Experimental results on some large sparse practical problems are provided; they show significant reduction in storage requirement for Cholesky factors with little increase (and sometimes decrease) in execution time.

Constrained Power System State Estimation

Abstract The structure of electrical power networks is such that there are a number of nodes for which the power injections are known to be exactly zero. These zero-power injections can be treated as equality constraints in the power system state estimation problem. This paper reviews the methods for handling equality constraints and presents a novel technique based on a direct elmination of the dependent variables. A general algorithm is presented which can be adapted to any Weighted Least-Squares (WLS) solution technique. A method based on Givens rotations is particularly suitable, and is described in detail in the paper. Since this method tends to be time-consuming, a hybrid method is also presented which can substantially improve the solution time and reduce storage requirements. The paper also presents some results on the use of the commonly employed weighting method. The conventional and proposed algorithms are tested using an IEEE power system and a New Brunswick Electric Commission transmission network.

B‐Spline Terrain Modeling on Personal Computer

The implementation on a personal computer of three-dimensional terrain modeling based on B-splines is described. Such models are useful for initial route location studies in highway planning and design. The model described makes use of B-spline-type surfaces defined on curved knot lines, which allows a large volume of survey data to be condensed to a significantly smaller number of parameters, which are then stored. These parameters may be used at a later time for the extraction of cross-sectional information or the reconstruction of three-dimensional images. This significant data reduction makes the modeling suitable for implementation on a personal computer because of reduced storage requirements and processing time. Timing for some examples is included.

WATOPT -- An Optimizer for Circuit Applications

A nonlinear constrained optimizer, WATOPT, targeted towards circuit applications is described. It utilizes a specially tailored quadratic program which reduces storage requirements and improves speed of computations. Three advanced designs in the frequency domain show application.

A new mode renumbering algorithm for bandwidth reduction

AbstractA new algorithm is presented for automatic renumbering of systems of interconnected nodes so as to minimize the bandwidth of the connectivity matrix. This is necessary to reduce storage requirements for banded matrix solution techniques. The method is based on those due to Cuthill and McKee1 and Gibbs, Poole and Stockmeyer.2 Under test against several other algorithms on a range of 20 examples of various types it always performed at least as well as, and in most cases better than, the best of the other methods. Seven examples are given in the paper, comparing final bandwidths with those produced by seven other algorithms.

A differential compiler for computer animation

A program for the real-time display of computer animation on a bit-mapped raster display is presented. The differential compiler performs temporal domain image data compression using frame replenishment coding on successive frames of animation stored in memory as bitmaps and saves only the differences. A small run-time interpreter then retrieves and displays the differences in real-time to create the animated effect. This results in a significant reduction in storage requirements, and allows animation on general purpose computers which would otherwise be too slow or have insufficient memory. Frame creation is both device and method independent. An animation environment supports interactive editing capabilities, reconstructing any arbitrary desired frame for later modification. Frames can be added, modified, or deleted, and the animated sequence can be viewed at any point during the session. The compiler is automatically called as needed; its operation is transparent to the user. The compiler is described in detail, both in terms of data compression and the requirements of interactive animation editing.

A Variable-Resolution Finite-Element Model of Frontogenesis

Abstract A frontogenesis model is formulated using the inviscid, adiabatic, Boussinesq, hydrostatic primitive equations and bilinear finite elements. Results of integrations of the model for a horizontal deformation flow are compared with the analytic solution obtained (using the “cross-front geostrophic approximation”) by Hoskins and Bretherton. For sufficient resolution the numerical solutions are almost identical to the analytic one in the region near the front, even though the front is well developed and only five hours away from becoming discontinuous at the surface. A substantial improvement in computational efficiency is achieved by using variable resolution away from the front instead of uniform resolution everywhere: as much as a factor of 25 reduction in CPU time and a factor of 5 reduction in storage requirements are observed. Contrary to the recent findings of Aksel et al., no difficulties are encountered in the application of open boundary conditions and neither is resolution limited by the u...

Fractal finite element mesh generation for vibration problems

A new approach for solving plate vibration problems has been formulated by using the Pascal–Sierpinski gaskets and finite element method. The Pascal–Sierpinski gaskets are geometric fractals that are self‐similar under scale transformation. Modeling a finite plate element with the basic Pascal–Sierpinski gasket unit, the equations of motion of the basic unit are derived. A buildup process is formed by linking three identical units together. Finally, systematic recurrence relations are generated. The advantage of this approach is that the dynamic matrix of the system has the same dimension at each buildup step. The basic vibration properties, computation time, and memory requirements are discussed and critically compared with traditional finite element methods by discussing a specific example. In general, finite element mesh generation based on geometric fractals offers much promise in reducing storage requirements and computation times significantly.

Extracting statistical data from free-form text

The authors describe a method for processing free-form text files. The method consists of segregating and separating four physically and logically identifiable regions. The four regions are postprocessed to update three history files that contain information about manufactured products over a period of time. The technique used in processing such files falls under the general category of data segregation and character recognition. It involves the use of logical and mathematical operations in recognizing region boundaries and types of data fields and establishing uniqueness in name recognition. Hashing methods are used, combined with logical matrix multiplication in updating the history files. Sparse formats are used to store multiple large arrays on disks, reducing storage requirements by more than a factor of two. The techniques are implemented using multiprogramming environments in an automated system.

On the Stability of Predictor-Corrector Methods for Parabolic Equations with Delay

Diffusion problems where the current state depends upon an earlier one give rise to parabolic equations with delay. The efficient numerical solution of classical parabolic equations can be accomplished via methods for stiff differential equations; one such class is predictor-corrcctor-type methods with extended real stability intervals and with reduced storage requirements. Analogous methods for equations with delay are proposed and analysed here. Our analysis will be based on the test equation y(t)=q 1 y(t)+q 2 y(t-ω), where, in view of the class of parabolic delay equations we want to consider, our main interest will be in the case |q 1 |≫|q 2 |. Implementational details of the methods developed are given and numerical results are presented.

Double encoding—a technique for reducing storage requirement of text

Many recent advances have been made in data storage and communications media. However, the explosive proliferation of information and the continuous growth of data applications are outgrowing any technological advances in storage devices and communications tools. Data compression offers an attractive approach to alleviate many of the problems associated with data proliferation. In this paper, we present a new double compression scheme for text, program source and documentation files. The first phase of compression is a dictionary-based method that also uses run-length encoding. The second phase of compression is based on utilizing the distributional and correlational properties of the output of the first phase. The technique achieves high degrees of compression and is further enhanced by the hardware assistance that VLSI technology will eventually offer to the realization of data compression techniques.

Multiple Generation Text Files using Overlapping Tree Structures

When repeatedly editing a text file, one is often faced with a choice of keeping previous generations for backup or deleting previous generations to reduce storage requirements. Since one generation of a text file is often very similar to the previous generation, the above conflict can often be resolved by sharing much of the common information. We propose using a tree structure to represent a text file. Common subtrees can be shared. Results of an experiment with one file are reported.

A prime number approach to biological sequencing

Computational sequencing of nucleic acid and amino acid sequences is placing increasing demands on computer resources. The use of prime numbers is explored as a convenient means of improving program speed and reducing storage requirements. It is concluded that the application of the prime number approach leads to significant increases in speed and some reduction in storage requirements.

Accelerated ‘relaxation’ or direct solution? Future prospects for fem

Abstract‘Dynamic’ or ‘viscous’ relaxation procedures have not gained much popularity in finite element analysis in which the direct (Gaussian elimination) solution dominates. Reasons for this are various—the most important being the rather slow convergence generally achieved for such procedures. However, it is possible to accelerate this quite dramatically and a method of doing so is shown in this paper. With the use of such acceleration and the inherent advantages of greatly reduced storage requirements and simplicity of programming, relaxation procedures promise an exciting possibility for the solution of large two‐ and three‐dimensional problems in both linear and nonlinear ranges.

Modelling the non-linear stochastic characteristics of EMG/tension relationship

A generalized non-linear mathematical model for the identification of EMG/tension relationship is developed. Volterra functional expansions are utilized for identification of the linearities as well as the non-linearities of the system, leading to the development of a generalized methodology. Kernels of the system are computed in the frequency domain using an efficient fast fourier transform (FFT) algorithm. The results obtained for the case of biceps brachii muscle are compared with the corresponding results obtained by using a stochastic state-space model : the Volterra approach appears to provide a more realistic characterization. Symmetry of the kernels reduces storage requirements and computation time on the digital computer considerably. Physiological interpretation of the results obtained reveals diagnostic information about certain pathologies related to human skeletal muscle.

Approximation of multipath planar shapes in pattern analysis

The concept of multipath approximation of two-dimensional images is introduced and an algorithm for the functional approximation of multipath curves is given. It is shown that application of this algorithm results in a significant reduction in storage requirements and an increase in the preservation of important features of the image.

A Simple theoretical model for calculating and parameterizing the ionospheric photoelectron flux

We have developed a simple method for calculating the ionospheric photoelectron flux that uses the concept of average electron energy loss to simplify the calculation of the degraded electron spectrum. This method, which requires only a knowledge of the total inelastic electron impact cross sections, rather than a detailed knowledge of the many partial cross sections can be used for the calculation of all secondary ion and excited state production rates. We estimate that the use of an average energy loss reduces the computation time by a factor of 10 and considerably reduces storage requirements. The simple model is designed to provide ionospheric chemistry workers with a convenient means of obtaining photoelectron spectra similar to that which is currently available for obtaining neutral densities. It is shown that the ionospheric photoelectron flux in the local equilibrium region is directly proportional to the attenuated solar EUV flux, which is a function only of the total neutral column density, and is independent of the neutral density composition. Therefore, electron impact cross sections can be chosen so that the simple method may also be used to parameterize the measured ionospheric photoelectron fluxes.