Consecutive Nodes Research Articles

Hybrid neural network/finite element modelling of wave propagation in infinite domains

The paper presents the method of formulation of a transmitting boundary using artificial neural network (ANN). The back-propagation neural networks (BPNN) [Comput. Struct. 79 (2001) 2261; S. Haykin, A Comprehensive Foundation, second ed., Prentice-Hall, 1999; Z. Waszczyszyn, in B.H.V. Topping (Ed.), Computational Mechanics for the Twenty-First Century, Civil-Comp Ltd., 2000, p. 479] are used for simulation of dynamic reactions on artificial boundary from an outside region. Neural networks are applied to all nodes on “artificial boundary”. The input vector for ANN is composed of (1) displacement, velocity and acceleration at time t−1 in node on the boundary, (2) displacements at time t−1 in three consecutive nodes on line perpendicular to the artificial boundary. The output vector determines the dynamic reactions at time t. Besides the displacements, velocities and accelerations at time t are computed. Three problems are discussed: (1) wave propagation in semi-infinite strip, (2) wave propagation in semi-infinite strip with notch, (3) acoustic radiation from nonconcentric radiator. Neural networks with one or two hidden layers were tested. Computations proved that BPNNs can be efficiently applied to the implementation of the approximate boundary condition on the artificial surface.

Deterministic Advection-Diffusion Model Based on Markov Processes

A new deterministic numerical formulation named DisPar-k based on particle displacement probability distribution for Markov processes was developed to solve advection-diffusion problems in a one-dimensional discrete spatial grid. DisPar-k is an extension of DisPar, and the major difference is the possibility of establishing a number of consecutive particle destination nodes. This was achieved by solving an algebraic linear system where the particle displacement distribution moments are known parameters taken from the Gaussian distribution. The average was evaluated by an analogy between the Fokker-Planck and the transport equations, being the variance Fickian. The particle displacement distribution is used to predict deterministic mass transfers between domain nodes. Mass conservation was guaranteed by the distribution concept. It was shown that, for linear conditions, the accuracy order is proportional to the number of particle destination nodes. DisPar-k showed to be very sensible to physical discontinu...

Optimal tree access by elementary and composite templates in parallel memory systems

In this paper, we study efficient strategies for mapping onto parallel memory systems complete trees that are accessed by fixed templates (like complete subtrees, paths, or any combinations their of). These mappings are evaluated with respect to the following criteria: (1) the largest number of data items that can be accessed in parallel without memory conflicts; (2) the number of memory conflicts that can occur when accessing templates of size equal to the number of available memory modules, thereby exploiting the full parallelism of the system; (3) the complexity of the memory addressing scheme, i.e., the cost of retrieving the module where a given data item is mapped. We show that there exist trade-offs between these three criteria and the performance of different mapping strategies depends on the emphasis given on each of these criteria. More specifically, we describe an algorithm for mapping complete binary trees of height H onto M memory modules and prove that it achieves the following performance results: (1) conflict-free access to complete subtrees of size K and paths of size N such that N + K - [log K] /spl les/ M; (2) at most 1 conflict in accessing complete subtrees and paths of size M; (3) O(K/M + c) conflicts when accessing a composite template of K nodes consisting of c disjoint subsets, each subset being a complete subtree, or a path or a set of consecutive nodes in a level of the tree.

End-to-end queuing delay assessment in multi-service ip networks

Packet-based networks are more and more used to transport interactive streaming services like telephony and videophony. To guarantee a good quality for these services, the queuing delay and delay jitter introduced in the transport of voice or video flows over the packet-based network should be kept under control. Because data sources tend to increase their sending rate until (a part of) the network is congested, mixing real-time traffic and data traffic in one queue would lead to unacceptable high delays for real-time services. Therefore, voice and video packets need to get preferential treatment ( e.g. head-of-line priority) over data packets in the network nodes. Therefore, the queuing behavior of the voice and video packets can be studied more or less independently from the traffic generated by data services. Simple methods to assess the end-to-end delay are primordial. Since it is well known that an aggregate of voice (and CBR video) sources is accurately modeled by a Poisson arrival process and that delays in consecutive nodes are more or less statistically independent, this boils down to developing methods to calculate quantiles of the total queuing delay through a system of N statistically independent M/G/1 nodes. This paper develops four methods to calculate quantiles of the total queuing delay: a Gaussian method, a method based on the numerical inversion of the moment generating function of the total queuing delay developed by Abate and Whitt and two methods based on the assumption that the tail distribution of the individual queuing delay of one node is approximately exponential. The Gaussian method is the simplest, but only gives crude results. The method of Abate and Whitt is the most complex and breaks down for large quantiles. The methods based on the assumption of an exponential tail produce results that are more or less equally accurate as long as there is a node where the load is high enough.

A fault‐tolerant connected‐cycle‐based mesh architecture

Four consecutive nodes in a conventional mesh structure are first organized as a connected‐cycle module. And then, multiple connected‐cycle modules are combined with multiple bus sets and spare nodes to form the fault tolerant connected‐cycle‐based mesh architecture (FTCCBM). With this architecture, two reconfiguration schemes, both based on the modular block, are developed. Both schemes can eliminate the spare substitution domino effect during the reconfiguration process. Simulation results show that it appears to be better to implement the FT‐CCBM with 3 or 4 bus sets, and that both schemes provide for an increase in reliability over the interstitial redundancy scheme (Singh, 1988) and the multi‐level fault tolerance mesh (MFTM) (Hwang, 1996), at the same redundant spare ratio. Especially, with global reconfiguration, the reliability improvement ratios per spare (RIPS) can be at least twice of that of the MFTM scheme. Furthermore, the lower port complexity in spare nodes as compared to those in both of the aforementioned schemes, and versatility in reconfiguration capability are two additional merits of the proposed architecture.

Individual energy level distributions for one-dimensional diagonal and off-diagonal disorder

We study the distribution of the $n$-th energy level for two different one-dimensional random potentials. This distribution is shown to be related to the distribution of the distance between two consecutive nodes of the wave function. We first consider the case of a white noise potential and study the distributions of energy level both in the positive and the negative part of the spectrum. It is demonstrated that, in the limit of a large system ($L\to\infty$), the distribution of the $n$-th energy level is given by a scaling law which is shown to be related to the extreme value statistics of a set of independent variables. In the second part we consider the case of a supersymmetric random Hamiltonian (potential $V(x)=\phi(x)^2+\phi'(x)$). We study first the case of $\phi(x)$ being a white noise with zero mean. It is in particular shown that the ground state energy, which behaves on average like $\exp{-L^{1/3}}$ in agreement with previous work, is not a self averaging quantity in the limit $L\to\infty$ as is seen in the case of diagonal disorder. Then we consider the case when $\phi(x)$ has a non zero mean value.

An adaptive grid technique for the vertical structure of shallow water models

The efficient resolution of the boundary layers occurring in geophysical flows has motivated the search for criteria to optimize the vertical nodal placement in three-dimensional (3D) shallow water models. This paper describes the implementation and testing of an adaptive grid technique for the internal mode of shallow water models. The technique uses an r-method in which the nodes are moved vertically based on the velocity gradients between consecutive nodes. One-dimensional (1D) tests show that the method behaves well in tidal- and wind-driven flows, both in well-mixed and stratified conditions. Average accuracy improvements of 50% were obtained relative to uniform grids, with a 15% CPU time increase. The adaptive technique accounts accurately for the space and time variability of the flow, thus being attractive for any type of problem. Furthermore, the technique does not require an a priori knowledge of the flow conditions, thus simplifying greatly the modeling procedure.

Efficient algorithms for wavelength rerouting in WDM multi-fiber unidirectional ring networks

In this article, we consider wavelength rerouting in wavelength-routed Wavelength-Division Multiplexed (WDM) multi-fiber unidirectional ring networks with circuit switching. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. Wavelength rerouting is a viable and cost effective mechanism that can improve the blocking performance by rearranging certain existing lightpaths to accommodate a new request. Recently, in Ref. [1], a rerouting scheme called ‘Parallel Move-To-Vacant Wavelenth Retuning (MTV-WR)’ with many attractive features such as shorter disruption period and simpler switching control has been proposed. A polynomial time rerouting algorithm has also been proposed in Ref. [1] to minimize the weighted number of rerouted lightpaths in WDM networks with the parallel MTV-WR rerouting scheme. However, this algorithm is not time optimal and works correctly when the fiber links, wavelength channels, and lightpaths are all bidirectional. We present here a time-optimal rerouting algorithm to minimize the number of rerouted lightpaths in wavelength-routed WDM multi-fiber unidirectional ring networks with parallel MTV-WR rerouting scheme. This algorithm requires only O( NFW) time units, where N is the number of nodes in the network, F is the number of fiber links between two consecutive nodes, and W is the number of wavelength channels available on a fibre link. We also present on O( NF 2 W) time rerouting algorithm to minimize the weighted number of rerouted lightpaths. The simulation results show that the rerouting algorithms improve the blocking performance considerably and only very few lightpaths are required to be rerouted per rerouting. The results also show that, for a given network load per wavelength per fiber, increasing the number of wavelengths or the number of fibers, leads to an improved performance by the networks with rerouting, without any rerouting and with full wavelength conversion capability at the routing nodes.

New integral equation formulation of the measured equation of invariance and the extension to analyze two‐dimensional cylinders with impedance boundary conditions

We have derived a new form of the integral equation formulation of the measured equation of invariance (IE‐MEI). The new formulation clarifies the existence of a relationship between scattered electric and magnetic fields at consecutive nodes in the IE‐MEI and indicates that the relationship in a problem for a perfect electric conductor (PEC) holds for a problem with arbitrary materials. In a scattering problem of a two‐dimensional cylinder with an impedance boundary condition (IBC), every matrix in the IE‐MEI is a band‐like sparse matrix. That is, the solution process in the IE‐MEI with an IBC is the same as that for a PEC. Therefore the IE‐MEI with an IBC has the same merits of the IE‐MEI for a PEC: The more efficient computation can be achieved with the smaller memory than those of the method of moments (MOM). The IE‐MEI with an IBC is validated by numerical examples for a circular cylinder and a square cylinder by comparison with a combined field MOM that satisfies exact boundary conditions. Numerical examples show that the IE‐MEI with an IBC is applicable to the case where the generalized skin depth is less than half the width of a scatterer.

Dynamics and conformation of polymer chains in a porous medium.

Conformational and transport properties of polymer chains in a porous medium are studied using computer simulations. Two types of links between the consecutive nodes of the self-avoiding walk (SAW) chains are considered: (i) constant bond and (ii) flexible (fluctuating) bond. In addition to normal diffusive motion for the global transport of chains, we observe unusual nondiffusive transport phenomena such as subdiffusive power-law dependence of the rms displacement (${\mathit{R}}_{\mathrm{rms}}$) of the chain with time (t), i.e., ${\mathit{R}}_{\mathrm{rms}}$=${\mathit{At}}^{\mathit{k}}$ with an exponent k less than 1/2 at low porosity. In two dimensions, we find that the power-law exponent k is nonuniversal as it depends on the barrier concentration (${\mathit{p}}_{\mathit{b}}$) and the chain length (${\mathit{L}}_{\mathit{c}}$) with the magnitude of k\ensuremath{\simeq}0.0-0.5. The chains with flexible bonds exhibit better relaxation with the value of k slightly higher than that for the chains with constant bonds at low porosities. The subdiffusion constant A shows a nonuniversal power-law dependence on the chain length, A\ensuremath{\sim}${\mathit{L}}_{\mathit{c}}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\alpha}}}$, with \ensuremath{\alpha}\ensuremath{\simeq}0.28-1.85 for chains with constant bond, and 0.33-1.27 for chains with flexible bonds. A similar but less pronounced effect of impurity barriers is also observed in three dimensions. The radius of gyration of the chains is affected by the presence of barriers; characteristics of the crossover from a SAW to collapse conformations are reported, along with the anomalous conformation as a function of barrier concentration. \textcopyright{} 1996 The American Physical Society.

Relationship between myelin sheath diameter and internodal length in axons of the anterior medullary velum of the adult rat

Relations between myelin sheath diameters and internodal lengths were measured in whole mounts of osmium stained intact anterior medullary velum (AMV) from glutaraldehyde perfused adult rats. The AMV is a sheet of CNS tissue which roofs the IVth ventricle and contains fascicles of myelinated fibres which arise mainly from the nucleus of the IVth cranial nerve. These fibres displayed a broad range of myelin sheath external diameters and internodal lengths, from < 1–12 μm and 50–750 μm, respectively. Myelin sheath external diameter was a measurement of the axonal diameter plus the thickness of its myelin sheath, while internodal length was measured as the distance between consecutive nodes. There was a broadly linear relationship between myelin sheath diameters and internodal lengths, with the smaller diameter sheaths tending to have shorter internodes than the larger. However, the correlation was weak and for any given diameter myelin sheaths displayed considerable variation in their internodal lengths. The smallest diameter myelin sheaths, < 4 μm, consistently had shorter internodes than predicted by a linear regression and, in an analysis of consecutive internodes in single fibres, the slope was flattened in fibres with a diameter > 4 μm. Our results indicated that small and large calibre fibres may have different myelin sheath diameter-internodal length interrelations.

Folding Back in Decision Tree Analysis

This note demonstrates that two minimal requirements of decision tree analysis, the folding back procedure and the interchangeability of consecutive event nodes, imply independence.

Folding Back in Decision Tree Analysis

This note demonstrates that two minimal requirements of decision tree analysis, the folding back procedure and the interchangeability of consecutive event nodes, imply independence.

Concurrent processing of linearly ordered data structures on hypercube multicomputers

The paper presents a simple and effective method for the concurrent manipulation of linearly ordered data structures on hypercube systems. The method Is based on the existence of an augmented binomial search tree, called the pruned binomial tree, rooted at any arbitrary processor node of the hypercube such that; every edge of the tree corresponds to a direct link between a pair of hypercube nodes; and the tree spans any arbitrary sequence of n consecutive nodes containing the root, using a fanout of at most [log/sub 2/ n] and a depth of at most [log/sub 2/ n]+1. Search trees spanning nonoverlapping processor lists are formed using only local information, and can be used concurrently without contention problems. Thus, they can be used for performing operations such as broadcast and merge simultaneously on sets with nonuniform sizes. Extensions of the tree to k-ary n-cubes and faulty hypercubes are presented. Applications of this concurrent data structure to low- and intermediate-level image processing algorithms, and for dictionary operations involving multiple keys, are also outlined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quadratic spline interpolation on uniform meshes

The interpolation of a discrete set of data on a uniform mesh, representing the derivative values of a smooth function f, between consecutive nodes, is considered using quadratic C 1-splines. An L ∞-error estimate for the constructed spline is also presented.

Trajectory Planning Method for Mobile Robots

This paper accounts for the development of an original trajectory generation method for a two-dimensional mobile robot (i.e. capable of planar movement) designed to operate in industrial environments. In the last stage, a graph is searched to find an optimal solution. The nodes of this graph consist of three parameters, which determine absolute position and orientation of the robot.A first issue is the generation of trajectories in collision-free space (union of consecutive nodes). Cubic-spline interpolation with optimization of the reference system with respect to a given cost function is used, where this cost or evaluation function has real physical meaning.Very efficient and computationally inexpensive algorithms were developed to determine the optimal reference system and the cost function of a given piece of trajectory.A second issue dealt with is that of graph-expanding. An on-line collision detection method is created, and subsequently, a method for generating intermediate nodes in the presence of a single obstacle.Finally, an A-type algorithm is used to perform an on-line graph search, in order to determine the lowest cost trajectory in a fixed environment with obstacles.The trajectories obtained offer an advantageous compromise between optimality and computational cost: while not sacrificing much of the first, possibility of on-line implementation is assured.

Difference in grain productivity of tillers among main stem nodes in rice plant. I. Effects of the number and position of tillering nodes on grain productivity.

ポットに1株1本立で直播した水稲主稈の第2節から第11節の範囲で特定の節位に分げつを1節あるいは2, 3, 5節組み合わせて残存させ, それ以外の節から出現する1次分げつを毎日除去して生育させ, 主稈の節位別分げつの子実生産力に及ぼす1次分げつ出現節数および節位の影響について検討した。1) 1次分げつ残存節数が少なく, 残存節位が上位の区ほど主稈葉数が多くなり, 主稈穂重は優った。2) 1次分げつの出現日および出現率は第6節までは分げつ残存節数および残存節位の影響を受けなかったが, それ以上の節位では下位節に出現節数の多い区ほど出現日が遅れ, 出現率も低下する傾向がみられた。また, 下位節の1次分げつほど出現から出穂まで日数あるいは止葉葉数は多くなったが, 穂重との間に明瞭な関係は認められなかった。3) 主稈の節位別分げつ穂重 (子実生産力) は, 一般に穂数の差により下位節ほど優るが, ある特定節位の分げつの子実生産力については1次分げつの出現数の多少, および他の1次分げつの出現節位によって著しく変化するものと考えられた。すなわち, 主稈第n節分げつの子実生産力は他節からの分げつ出現数が少なく, さらに分げつ出現節数が同一の場合には, 第n節位より上位に他節の分げつが位置するほどその子実生産力は大となった。4) 主稈の中, 上位節にのみ1～2節とごく少数の1次分げつが出現すると, 高次分げつの割合が高くなり株当り穂数は対照 (無処理) 区に比べて減少した。しかし, 平均1穂重は主稈および各次位別分げつとも対照区を上回り, 株当り穂重の低下はわら重に比べて小さくなり, その結果穂重/わら重比は向上した。

Phyllotactic Patterns in Some Members of the Vitaceae

Changing phyllotactic patterns are found in some members of the Vitaceae such as Vitis riparia and Vitis cv Vivant. In addition to two opposite cotyledons, germinating seedlings of V. riparia and cv Vivant display two other phyllotactic patterns: (1) immediately following the emergence of the cotyledons, leaves are initated individually in a spiral pattern, usually 2/5, (2) upon the initiation of the first tendril the phyllotactic pattern changes to alternate and opposite leaves (distichous) with leaf-opposed tendrils at two consecutive nodes out of three. This study documents the different phyllotactic patterns occurring in these seedlings, concentrating on the transition between spiral and distichous leaf arrangements. The mean divergence angle observed at the primordial level in young seedlings of V. riparia and cv Vivant with spiral phyllotaxy was different from the reported divergence angle of 144⚬ (2/5) observed between mature leaves. The measurement of divergence angles can therefore differ greatly at different levels of observation (primordial vs. mature structure). The transition between spiral and distichous leaf arrangement is abrupt, the first tendril being initiated opposite a leaf. Later in development, the tendrils are shifted to one side of the axis giving the shoot a dorsiventral symmetry. The distichous "mature" dorsiventrally symmetrical pattern in seedlings of V. riparia and cv Vivant was compared to other members of the Vitaceae, which did not show this striking dorsiventrality.

Mechanisms of differential axial blockade in epidural and subarachnoid anesthesia.

The mechanisms of persistent differential blocks that accompany subarachnoid and epidural anesthesia are clarified here with the aid of two principles derived from in vitro study of individual myelinated axons: 1) conduction can leap two consecutive blocked nodes but not three, and 2) a fiber length with more than three consecutive nodes bathed by weak anesthetic may block by decremental conduction, the requisite concentration varying inversely with the number of nodes bathed by anesthetic. Principle 1 applies in epidural blockade, where anesthetic bathes only a few millimeters of segmental nerve extradurally in the intervertebral foramen. Here, three-node block will be rare in large, long-internode fibers but likely in small, short internode fibers, thus explaining the differential retention of motor power in the presence of block of pain, which is achieved in epidural anesthesia when relatively weak solutions are used, as in obstetrics. Principle 2 may intervene in subarachnoid blockade where, cephalad to the site of puncture, increasingly concentrated anesthetic bathes increasing lengths of fibers in the craniocaudal succession of spinal nerve roots. This will produce decremental conduction block in increasingly long internode fibers in successive roots, reflected in a corresponding craniocaudal segmental sequence of blocked physiological functions: vasoconstriction, cutaneous temperature discrimination, pinprick pain sensibility, and skeletal motor activity. The segmental spatial differential sequence migrates with time but resembles the temporal differential sequence of loss seen at the onset of peripheral nerve blocks. Several other previously disparate clinical observations follow logically from the new interpretation.

Peroxidase activity at consecutive nodes of Ranvier in the nerve to the medial gastrocnemius muscle after intramuscular administration of horseradish peroxidase

The distribution of axoplasmic organelles at consecutive nodes of Ranvier was investigated light- and electronmicroscopically in horseradish peroxidase-transporting muscle nerve fibres of the adult cat. Three main and apparently temporally interrelated distribution patterns were noted. These patterns were referred to as A, B and C. The axoplasm of type-A and type-B nodes was highly segregated with regard to the proximodistal distribution of certain organelles. At type-A nodes horseradish peroxidase-positive membrane limited bodies and horseradish peroxidase-negative vesiculotubular membrane profiles were accumulated just distal and just proximal to the nodal mid-level, respectively. At B nodes a disc-like accumulation of enzyme activity, that was situated a few μm proximal to the mid-level, added to the type-A pattern. The type-C node showed a barely segregated axoplasm in which horseradish peroxidase-positive bodies were distributed randomly. We suggest, on the basis of the mutual order of the nodal types in a sequence of consecutive nodes and their appearance relative to the time after the administration of the HRP, that the different axoplasmic patterns reflect the operation of an ordered process that delays part of the retrogradely transported HRP for 2–3 days. The large number of lysosome-like HRP positive bodies that appeared at the nodes during this process indicates that the nodal axoplasm not only delays but also might take part in the degradation of the foreign protein.