Brute Force Technique Research Articles

A new algorithm for encryption/decryption for field applications

This paper proposes a novel scheme where the key k is generated as discrete logarithm of indices involving prime modulus p and any base value q. This base value q is an element of Z p . The Discrete logarithm values are substituted for k in the encryption equation. During decryption the corresponding k’s are used to recover the plaintext. The sender embeds the p, q values along with the encrypted message and transmits it. This obviates the need for sending the full-length key along with the encrypted message. The proposed method ensures higher security in the transmission. The strength of the method lies in the difficulty of guessing p, q values, the entire key need not be transmitted and the full set of ASCII values of the Z 256 plane figure in the encryption process. The paper also discusses the difficulty of attempting brute force technique to discover p, q values. As an extension of this work, the authors are exploring the possibility of using the full set of UNICODE values instead of the restricted 8-bit ASCII set.

NMR Spectroscopy of Adsorbed 129Xe at Low Temperatures and High Magnetic Fields

In this paper we report measurements of the nuclear magnetic resonance (NMR) spectrum of 129Xe adsorbed on silica gel and Grafoil® substrates in a 15 tesla magnetic field and temperatures in the range 10 mK to 1 K. Liquid 3He is used to shorten the spin lattice relaxation time of the 129Xe spins and obtain a high degree of spin polarization of over 40% in around a day. The 129Xe NMR spectrum generally exhibits two lines. We show that one line corresponds to the monolayer of surface xenon atoms and the other line to the monolayers of bulk solid xenon between the substrate and the surface monolayer. By comparing the spectra and relaxation rates for xenon of different 129Xe concentrations and by adding 4He we were able to investigate the 129Xe interlayer coupling. The work has important implications in the study of porous materials using hyperpolarized gases, the study of surface atoms by NMR and the production of hyperpolarized species by the brute force technique.

Uncoded Symbol Error Rate Estimation: Methods and Analysis

In wireless communications systems, channel quality estimates are often used to provide a measure of the quality of service or to enable resource allocation techniques that improve system capacity and/or user quality. The uncoded bit or symbol error rate (SER) is specified as a channel quality metric in second and third generation cellular systems (e.g., general packet radio service (GPRS), enhanced general packet radio service (EGPRS), and universal mobile telecommunications system (UMTS). Nonetheless, techniques to estimate the uncoded SER are typically outside the scope of these wireless standards and are not specified. In this paper, we analyze the performance of a number of uncoded SER estimation techniques, including a novel technique in which we use the soft information of the received symbols to obtain a fast and accurate estimate of the uncoded SER. The technique we introduce has been found to outperform, in terms of accuracy and required estimation interval, conventional hard-decision based techniques that use test-patterns, or use a decode/re-encode/compare approach . Our technique also outperforms the brute-force technique, which is to send a known test-pattern, demodulate it at the receiver, and count the observed discrepancies.

Brute Force Polarization of 129Xe

Hyperpolarized 129Xe has numerous applications in Nuclear magnetic resonance (NMR) and magnetic resonance imaging(MRI). As an alternative to the laser optical pumping method of production of hyperpolarized 129Xe gas, we have investigated the brute force technique which uses a very high magnetic field and millikelvin temperatures. One obstacle to this technique is the extremely long spin lattice relaxation times of nuclei in solids at very low temperature. We exploit the fact that liquid 3He can be used as an effective relaxant to enable 129Xe to be spin polarized on a high surface area substrate in a few hours. We are able to identify the contributions of different atomic layers to the magnetization by analyzing the 129Xe NMR spectrum. Furthermore, the addition of 4He allows us to turn off the relaxation mechanism, thereby preserving the polarization. The technique could be applied to nuclei other than 129Xe.

Review of chaos in the dynamics and rheology of suspensions of orientable particles in simple shear flow subject to an external periodic force

We review results obtained over a period of about a decade on a class of technologically and fundamentally important problems in suspension rheology viz., the dynamics and rheology of dipolar suspensions of orientable particles in simple shear flow. The areas explored in this review include effects such as the fluid flow field, external forcing, Brownian diffusion, hydrodynamic interactions and their impact on the rheological properties of the suspension. The main feature of the presentation is the use of a uniform framework in which one or more of the above effects can be studied, based on Langevin type equations for particle orientations combined with a brute-force technique for computing orientational averages. These models are capable of capturing complex dynamical behaviour in the system such as the presence of subharmonics or chaos, both in the dynamics and rheology. The tools developed allow for investigating how chaos in the system is affected by Brownian diffusion and hydrodynamic interactions. The presence of chaos opens up a number of novel possibilities for dynamical and rheological behaviour of the system, which can be put to efficient use in many ways, e.g. in separating particles by aspect ratio and possibly developing computer controlled intelligent rheology. The results also have implications for certain areas of chaos theory, such as a new intermittency route to chaos and the possibility of non-trivial collective behaviour in spatially extended systems. These studies highlight certain deficiencies in current techniques in the literature for handling the rheology of dilute and semi-dilute suspensions. In the presence of Brownian motion the proposed method computes the averages by simulating a set of deterministic ordinary differential equations rather than stochastic differential equations. The systems considered may also serve as a paradigm for analysing how microscopic chaotic fluctuations in spatially extended systems affect macroscopic averages. We also attempt to put our results into context with respect to recent work on rheochaos in complex fluids such as liquid crystals and nematic polymers.

Counting and automata

Counting is widely acknowledged to be one of the most difficult areas of Mathematics. As a result, many programming solutions to counting problems tend to revolve around the brute-force technique o...

Integral expressions for the numerical evaluation of product form expressions over irregular multidimensional integer state spaces

We consider stochastic systems defined over irregular, multidimensional, integer spaces that have a product form steady state distribution. Examples of such systems include closed and BCMP type of queuing networks, polymerization and genetic models. In these models the system state is a vector of integers, n=[n 1,...,n M ] and the steady state solution has product form of the type ?(n)=? i=1 M f i (n i ). To obtain useful statistics from such product form solutions, ?(n) has to be summed over some subset of the space over which it is defined. We consider situations when these subsets are defined by a set of equalities and inequalities with integer coefficients, as is most often the case and provide integral expressions to obtain these sums. Typically, a brute force technique to obtain the sum is computationally very expensive. Algorithmic solutions are available for only specific forms of f i (n i ) and shapes of the state space. In this paper we derive general integral expressions for arbitrary state spaces and arbitrary f i (n i ). The expressions that we derive here become especially useful if the generating functions f i (n i ) can be expressed as a ratio of polynomials in which case, exact closed form expressions can be obtained for the sums. We demonstrate the wide applicability of the integral expressions that we derive here through three examples in which we model finite highway cellular systems, copy networks in multicast packet switches and a BCMP queuing network modeling a multiuser computer system.

Connectors for bridging mismatches between the components of a software engineering environment

Software engineering environments (SEEs) are complex systems, for which configurability is an important requirement. Constructing SEEs out of existing tools is evidently desirable. During such a composition, mismatches between the data models of different tools will arise. The brute-force technique of hacking data translators into the implementation of individual tools has severe drawbacks regarding the modularity, maintainability and extensibility of the composed system. This paper proposes a novel technique for designing SEEs that uses explicit language constructs for bridging the mismatches in the data models, called dynamic view connectors. It shows how the separation of tool functionality from the concerns of bridging data-model mismatches improves the configurability and maintainability of an existing SEE.

Greens function modified spherical harmonic analysis

In an effort to develop a model for impulse responses in reverberant spaces, techniques for source radiation modeling were explored. One method of decomposing a source field involves an analysis based on spherical harmonic expansions of the field. Spherical harmonic decomposition is a powerful tool, but it is a mathematical approach which is completely independent of the type of source that creates the field. As a consequence, this technique cannot, in general, be used to gain insight into the underlying physical nature of the source. Moreover, because this is a brute force technique, the analysis can be extremely inefficient. In this presentation, modifications to the spherical harmonic analysis and synthesis equations are made to overcome these problems. These are based on the (theoretical) source types associated with the individual spherical harmonic expansion coefficients, and determination of the location of the primary components of the (physical) source. These modifications can greatly improve the computational efficiency and allow the source to be described by a set of coefficients which is more directly related to actual source types present. Illustrative examples will be shown. [Work supported by the Applied Research Laboratory at Penn State University under the Educational and Foundational Research Program.]

Dynamically negotiated resource management for data intensive application suites

In contemporary computers and networks of computers, various application domains are making increasing demands on the system to move data from one place to another, particularly under some form of soft real-time constraint. A brute force technique for implementing applications in this type of domain demands excessive system resources, even though the actual requirements by different parts of the application vary according to the way it is being used at the moment. A more sophisticated approach is to provide applications with the ability to dynamically adjust resource requirements according to their precise needs, as well as the availability of system resources. This paper describes a set of principles for designing systems to provide support for soft real-time applications using dynamic negotiation. Next, the execution level abstraction is introduced as a specific mechanism for implementing the principles. The utility of the principles and the execution level abstraction is then shown in the design of three resource managers that facilitate dynamic application adaptation: Gryphon, EPA/RT-PCIP, and the DQM architectures.

Steric effects and vector correlations in reactions of K atoms with brute force oriented aromatic molecules

In a crossed molecular beam experiment we have measured the angular and time-of-flight (TOF) distributions of the products formed in the reaction K+IR→KI+R, at collision energies of around 3 eV, where IR was systematically varied from iodobenzene to 2-, 3- and 4-iodotoluene. From these data we have deduced the double-differential reaction cross-section in the center-of-mass (CM) frame. All the reactions exhibit preferred sideways and backward scattering of products. Around 70% of the available energy is channeled into the internal degrees of freedom of the products. Orientation of the molecules has been achieved by application of the brute force technique. We have measured differential parallel and perpendicular steric effects over a wide range of scattering angles. The shape and magnitude of both steric effects indicate the existence of a strong vector correlation between the directions of the C–I bond and the recoil velocity. The extent of the correlation depends on the presence and the position of the methyl group on the phenyl ring: it is largest for iodobenzene and weakest for 2-iodotoluene. Also the head (I end) vs. tail (R end) reactive asymmetry depends on the methyl group: it ranges from 5:1 (for 2-iodotoluene) to 12:1 (for 4-iodotoluene). All the reactions proceed via a linear K–I–R transition state. The findings have been rationalized on the basis of simple dynamical models.

Reactive Scattering from Brute Force Oriented Molecules: K + IR → KI + R (R = i-C3H7 and t-C4H9)

We report results of a crossed molecular beam study on the reactions K + i-C3H7I → KI + i-C3H7 (R1) and K + t-C4H9I → KI + t-C4H9 (R2) performed at an elevated collision energy of 1.55 eV for both nonoriented and oriented reagent molecules. Orientation was achieved by using the brute force technique. The most important results are the following: (i) The flux of scattered products of R2 consists of a dominant fast and a minor slow component; the two reaction channels occur with a branching ratio of 100:2. In R1 the fast component only has been observed. (ii) In the center-of-mass frame the dominant component is preferentially scattered into the backward hemisphere with a propensity for sideways and backward scattering while the minor one is sharply forward scattered and travels on the average with the spectator stripping velocity. (iii) The parallel and perpendicular differential steric effects in both R1 and the dominant channel of R2 are very substantial and amount to a size close to the theoretical upper boundary. The parallel steric effect in the minor channel of R2 is rather weak, and the sign is likely to be opposite to the one of the dominant channel. (iv) From the differential steric effects we have deduced the moments J10 and J11 of an expansion of the orientation-dependent double-differential cross section in a series of real spherical harmonics. (v) Shape and magnitude of the moments are consistent with a tight vector correlation between the directions of the main product flux and the molecular principal a-axis. (vi) The steric opacity functions for R1 and the dominant channel of R2 indicate that attacks of the K atoms to the I end of the reagent molecules are favorable for the formation of the fast products. The favored end for the production of the minor component of R2 is likely to be the alkyl group. (vii) The emergence of the minor slow component in R2 has been qualitatively rationalized on the basis of the harpooning mechanism and electronic structure arguments. The model identifies the slow products as KI and electronically excited t-C4H9.

Reactive Scattering from Brute Force Oriented Asymmetric Top Molecules: K + C6H5I → KI + C6H5

In a crossed molecular beam experiment, we have measured angular and time-of-flight (TOF) distributions of products formed in the reaction K + C6H5I → KI + C6H5 at a collision energy of Etr = 1.9 eV. From these data we have extracted the double-differential reaction cross section in the center-of-mass frame. The brute force technique has been applied to orient for the first time an asymmetric top, namely the reagent molecule C6H5I. The effect of molecular orientation on the angular distribution of products has been investigated. We determined the difference of product intensity for (a) preferred encounters with the I end and the phenyl end (parallel steric effect) and (b) side-on attacks with the axis pointing in two opposite directions (perpendicular steric effect). We find (i) preferred sideways scattering of KI with a mean recoil energy of 31.6% of the totally available energy; (ii) an additional reaction channel with a branching ratio of 0.65% by which a flux of slow products, most likely KI, is formed; (iii) the transformation of the data to a more adapted coordinate frame reveals that backward rather than sideways scattering reflects the dynamics of the reaction; (iv) a tight correlation between the direction of the product flux and the orientation of the molecular axis; (v) the experimental results can be rationalized by the direct interaction with product repulsion (DIPR) model; (vi) the ratio of product yield for attacks of the K atoms to the I end (head) and the phenyl end (tail) amounts to ≈28:1; (vii) the full apex angle of the cone-of-acceptance amounts to ≈110°; (viii) the harpooning mechanism and simple molecular orbital arguments rationalize the impulsive reaction mechanism implicit to the DIPR model and offer an explanation for the existence of a channel for slow KI products.

Data mining of inputs: analysing magnitude and functional measures.

The problem of data encoding and feature selection for training back-propagation neural networks is well known. The basic principles are to avoid encrypting the underlying structure of the data, and to avoid using irrelevant inputs. This is not easy in the real world, where we often receive data which has been processed by at least one previous user. The data may contain too many instances of some class, and too few instances of other classes. Real data sets often include many irrelevant or redundant input fields. This paper examines the use of weight matrix analysis techniques and functional measures using two real (and hence noisy) data sets. The first part of this paper examines the use of the weight matrix of the trained neural network itself to determine which inputs are significant. A new technique is introduced and compared with two other techniques from the literature. We present our experience and results on some satellite data augmented by a terrain model. The task was to predict the forest supra-type based on the available information. A brute force technique eliminating randomly selected inputs was used to validate our approach. The second part of this paper examines the use of measures to determine the functional contribution of inputs to outputs. Inputs which include minor but unique information to the network are more significant than inputs with higher magnitude contribution but providing redundant information, which is also provided by another input. A comparison is made to sensitivity analysis, where the sensitivity of outputs to input perturbation is used as a measure of the significance of inputs. This paper presents a novel functional analysis of the weight matrix based on a technique developed for determining the behavioral significance of hidden neurons. This is compared with the application of the same technique to the training and test data. Finally, a novel aggregation technique is introduced.

Orientation and Alignment in Reactive Beam Collisions: Recent Progress

The concept of directional axis distributions and orientation-dependent reaction cross sections is used to describe the effect of the mutual orientation of reagents on the outcome of reactive beam collisions. The axis distributions and cross sections are expanded in series of Legendre polynomials and real spherical harmonics, respectively, and characterized by the expansion coefficients (moments). The interrelations between the moments of the cross sections and the directionally dependent experimental data (steric effects) on the one hand and the anisotropic properties of the potential energy surfaces on the other hand are presented. Recent progress in the field of dynamical stereochemistry results from the prep- aration of molecular orientation and alignment by using the novel brute force technique and an optical method, respectively. The theories of both methods are summarized, and typical experimental arrangements are presented. All experimental results based on these techniques are reviewed. Among the most important ones are the first orientation effects observed in a reaction with a (1)Σ: molecule (K + ICl) and the alignment effects found in the bench mark reaction Li + HF → LiF + H.

The design, analysis and simulation of a fault-tolerant interconnection network supporting the fetch-and-add primitive

The combining multistage interconnection network uses 4*4 switches as switching elements and introduces an extra stage of such switches and links to create four independent paths between any source-destination pair. Four copies of every message are sent through the network simultaneously. The scheduling discipline, the design of the switching elements to support the discipline, and the theoretical proof of correctness of the design constitute the key contributions of this study. Estimates are provided of various network parameters as a function of the workload, using analytical models and detailed network simulations. It is shown that the proposed design for fault tolerance is more cost-effective than the brute-force technique of having multiple copies of the network. >

An Efficient Tree-Generation Algorithm

An algorithm for generation of trees of a connected, non-oriented, and simple graph is presented in this paper. The space complexity of the algorithm is independent of the number of trees and the time complexity is drastically reduced compared to the brute-force technique. The algorithm is easily programmable. Experimental results for several graphs are presented.

Analysis of Some Techniques Used in Modern LF-VLF Radiation Systems

A technique for radiating relatively broad-band pulses from narrow-band antennas is presented and analyzed. Good efficiency and bandwidth are obtained through the techniques of 1) forcing the antenna current to rise to the required level within the required time, and 2) feedback of stored energy from the high-Q antenna to the power supply during the pulse decay. A sample computation is made on a Loran-type pulse having a peak radiated power of 3 kW from a 3O0-foot umbrella antenna. This system has an antenna broad-banding transmitter efficiency product of over three times that of a system using the brute force technique of resistance loading.