Internal Parallel Research Articles

Magnetic Configuration Scans in H-1 Heliac

The results of the experimental study of the magnetic configurations in the H-1 heliac are presented. The shape of the flux surfaces and the rotational transform in H-1 can be controlled by varying external coil currents. Electron beam magnetic mapping has been performed to show the existence of closed nested flux surfaces and to observe the effect of small errors in coil alignment on the vacuum magnetic structure in H-1. Langmuir probes have been used to study the electron density profiles in a current-free collisional RF-sustained plasma (n{sub e}<=4 x 10{sup 12} cm{sup -3}, T{sub e}<= 15 eV). In standard magnetic configuration and for the present moderate RF power levels, the highest central density is achieved at rather low magnetic field (0.07 T). This regime is characterized by peaked density profiles that appear to have a maximum coincident with the position of the vacuum magnetic axis. When a lowest-order m=1, n=1 resonance is introduced inside the outermost magnetic surface a strong asymmetry in both the vacuum magnetic structure and the plasma density profiles is observed. We observed low frequency (2-3 kHz) density fluctuations having low radial mode numbers and internal parallel plasma current localized in the regions of highest densitymore » gradient. These fluctuations are effectively suppressed by an increase of the magnetic field. 4 refs., 6 figs.« less

Parallel I/O subsystems in massively parallel supercomputers

Applications on MPPs often require a high aggregate bandwidth of low-latency to secondary storage. This requirement can met by internal parallel subsystems that comprise dedicated nodes, each with processor, memory, and disks.Massively parallel processors (MPPs), encompassing from tens to thousands of processors, are emerging as a major architecture for high-performance computers. Most major computer vendors offer computers with some degree of parallelism, and many smaller vendors specialize in producing MPPs. These machines are targeted for both grand-challenge problems and general-purpose computing.Like any computer, MPP architectural design must balance computation, memory bandwidth and capacity, communication capabilities, and I/O. In the past, most design research focused on the basic compute and communications hardware and software. This led to unbalanced computers that had relatively poor performance. Recently, researchers have focused on designing hardware and software for subsystems in MPPs. Consequently, most current MPPs have an architecture based on an internal parallel subsystem (the Architectures with parallel I/O sidebar describes some examples). In these computers, this subsystem encompasses a collection of nodes, each managing and providing access to a set of disks. The nodes connect to other nodes in the system by the same switching network that connects the compute nodes.In this article we'll examine why many MPPs use parallel subsystems, what architecture is best for such a subsystem, and how to implement the subsystem. We'll also discuss how parallel file systems and their user interfaces can exploit the parallel to provide enhanced services to applications.The systems discussed in this article are mostly tightly coupled distributed-memory MIMD (multiple-instruction, multiple-data) MPPs. In some cases, we also discuss shared-memory and SIMD (single-instruction, multiple-data) machines. We'll discuss three node types. Compute nodes are optimized to perform floating-point and numeric calculations, and have no local disk except perhaps for paging, booting, and operating-system software. nodes contain the system's secondary storage, and provide the parallel file-system services. Gateway nodes provide connectivity to external data servers and mass-storage systems. In some cases, individual nodes can serve as more than one type. For example, the same nodes often handle and gateway functions. The Terminology sidebar defines some other terms used in this article.

Performance evaluation of a massively parallel I/O subsystem

Presented are the trace-driven simulation results of a study conducted to evaluate the performance of the internal parallel I/O subsystem of the Vulcan MPP architecture. The system sizes evaluated vary from 16 to 512 nodes. The results show that a compute node to I/O node ratio of four is the most cost effective for all system sizes, showing high scalability. Also, processor-to-processor communication effects are negligible for small message sizes and the greater the fraction of I/O reads, the better the I/O performance. Worse case I/O node placement is within 13% of more efficient placement strategies. Introducing parallelism into the internal I/O subsystem improves I/O performance significantly.

An internal crack parallel to the boundary of a nonhomogeneous half plane under thermal loading

This paper considers the crack problem for a semi-infinite nonhomogeneous thermoelastic solid subjected to steady heat flux over the boundary. The crack faces are assumed to be insulated. The research is aimed at understanding the effect of nonhomogeneities of materials on stress intensity factors. By using the Fourier transform, the problem is reduced to a system of singular integral equations which are solved numerically. Results are presented illustrating the influence of the nonhomogeneity of the material on the stress intensity factors. Zero Mode I stress intensity factors are found for some groups of the material constants, which may be interesting for the understanding of compositions of advanced Functionally Gradient Materials.

Parallel rule firing in production systems

To improve the performance of forward chaining production systems, a new parallel execution model in which multiple production rules are fired in parallel in each production cycle is proposed. Solutions for three major problems in parallel rule firing are provided. The first solution, interference analysis, detects cases where a parallel firing result is different from the result of any sequential firing. Based on a data dependency graph of production systems, general techniques applicable to both compile- and run-time interference analyses are proposed. The second solution, parallel firing algorithms, achieve the parallel firing on multiple processor architectures. An efficient selection algorithm is provided to select multiple rules to be fired in parallel by combining the compile- and run-time interference analysis techniques. The parallel programming environment, the third solution, provides language facilities to enable programmers to make full use of potential parallelism without considering the internal parallel mechanisms. A parallel firing simulator is also implemented to estimate the effectiveness of parallel firings of production system programs. The effectiveness of parallel rule firings on several production system applications is evaluated. Results show that the degree of concurrency can be increased by a factor of 2-9. The sources of parallelism are investigated based on the evaluation results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Crystals of cellulose grown from TFA solution

Crystallization experiments starting from highly concentrated solutions of cellulose in trifluoroacetic acid (TFA) resulted in white crystalline particles with diameters of as much as 0.5 mm. The plate-like particles consist of lamellae arranged perpendicular to the surface. The lamellae are grown from thin scale-like platelets showing clear diffraction reflexes and an internal parallel structure. Parallel structures were also detected in partially hydrolyzed cellulose. It is concluded that cellulose chains of low DP tend to rearrange themselves by a side by side accumulation of extended molecules.

THE ROLE OF OXYGEN IN YBa2Cu3O7−δ

Five observations concerning the role of oxygen in the high-Tc superconductors YBa 2 Cu 3 O 7−δ are emphasized: (1) An internal electric field parallel to the c-axis constrains the redox reactions associated with the intercalation/disintercalation of oxygen primarily to the [ CuO 3−δ]3− layers located between Ba 2+ layers. (2) Intercalation of O 2− into the tetragonal YBa 2 Cu 3 O 6 phase results in an ordering onto one of the basal-plane axes of the Cu(1) layer, the b-axis of the orthorhombic phase. (3) Ordering between and within b-axis chains gives rise to discrete phases predicted to occur at O 6.875, O 6.75, O 6.5, O 6.25, and O 6.125. (4) An equilibrium oxidation state for the intercalation layer depends not only on the oxygen partial pressure and temperature, but also on the cations of the structure. (5) At higher oxidation states of the intercalation layer, any oxygen atom on the a-axis interacts with a near-neighbor oxygen on the b-axis to trap out holes in a peroxide ion ( O 2)2−.

Oxygen ordering, peroxide-ion formation, and polarization fluctuations in YBa 2Cu 3O 7− δ

It is argued that (1) an internal electric field parallel to the c-axis confines the redox reactions associated with oxygen intercalation/disintercalation to the intercalation layer, (2) coulombic interactions between intercalated oxygen introduce oxide-ion ordering within/between b-axis chains as well as ordering onto the b-axis, (3) peroxide-ion formation occurs between copper-bridging oxygen in contact with one another if the oxidation exceeds 7− δ = 6.5, and (4) an overlap of partially filled σ ∗ and π ∗ bands introduces polarization fluctuations that enhance the superconducting transition temperature.

Susceptibilité radiofréquence d'une jonction vis-à-vis d'un champ électrique parallèle au plan métallurgique

When an alternating electric field is applied parallel to a junction, the radiofrequency susceptibility gives an absorption having a maximum versus the direct current polarization of the junction; the real part of the susceptibility is negative. The explanation of both features involves an internal field parallel to the alternating field. The experiment allows the measurement of the concentration of minority carriers.

Unified optimal design of external and internal parallel indexing cam mechanisms

External and internal parallel indexing cam mechanisms have each been studied separately by other authors. In this paper, a unified analytic method and optimal design procedure are given. The objective function and constraints in optimization of the two kinds of parallel indexing cam mechanisms are discussed. A computer aided design program using a uniform algorithm proved rather effective in various cases, so that some new optimal results are obtained.

Influence of internal electric field on the transport properties of the magnetoplumbite system BaFe12-xMnxO19

Measurement of the room temperature conductivity and Seebeck coefficient for the magnetoplumbite system BaFe12-xMnxO19, 0<or=x<9, shows that Mn substitution increases the p-type conductivity caused by an enhancement of hole concentration, presumably Fe4+ or Mn4+ ions. This observation supports the deduction from neutron diffraction data that the Mn in the tetrahedral sites 4fiv of the spinel blocks is Mn2+. Such a formal-valence distribution is shown to be possible because of a lack of local charge neutrality in the structure. The intergrowth of (BaFe6O11)2- R blocks and (Fe6O8)2+ S blocks creates an internal electric field parallel to the c axis that shifts the redox potentials at 4e(1/2) sites relative to those at 4fiv sites. Measurement of the temperature dependence of the conductivity gives Arrhenius plots with two activation energies; E1 for T<Tc and E2 for T>Tc, where Tc is the Curie temperature. E1 approximately=0.37 eV appears to be a motional enthalpy which is essentially independent of x, but E2>E1 at x=0 changes to E2<E1 at larger x.

Magnetic thin films produced by sol-gel processes

Iron oxide films on borosilicate glasses were produced with the sol-gel method. The ESR spectra of the as-produced films exhibit two signals, one at g about 4.2 and the other at g about 2. A ferromagnetic signal was detected by heat-treating the samples in hydrogen atmosphere between 500 and 800 °C. Angular variation of the ferromagnetic resonance signals revealed an internal field parallel to the plane of the films. The internal field was about 3500 G in the film heat treated at 620 °C for 120 min. Scanning electron microscopy was also used for detailed surface characterization. Before treatments the film is characterized by a fine texture and a few voids whose dimensions are about 5×15 μ. After treatments the film contains particles about 15 μ in size.

Paleomagnetic constraints on the assembly of the Old Red Continent

A model is proposed on the basis of paleomagnetic and geological arguments for the assembly of the Old Red Continent, which in the Devonian comprised North America, the Baltic Shield and Russian platform, as well as a third element called “Armorica”. The latter is thought to have included most of Hercynian Europe and southern England and Wales, as well as possibly the Avalonian terranes of northeastern North America and perhaps some parts of the Atlas ranges and Moroccan Meseta. The model envisions a Late Ordovician (Taconic) collision of North America and Armorica, which are joined in the Late Silurian by the Baltic Shield and Russian platform. Not until the late Early Carboniferous did Gondwana join the Old Red Continent in a collision responsible for a large internal megashear parallel to the Caledonian orogenic belt as well as the Hercynian-Alleghenian orogeny. Subduction of the large Siluro-Devonian ocean between Gondwana and the Old Red Continent is held responsible for the mid-Devonian Acadian orogeny.

On the Stability Problem of Human Arm and Hand Movements Controlling External Load Systems

Different loads, controlled by a human operator effect different dynamic behaviour of the entire controlled Arm-Hand-Load (AHL) system. Thus, in terms of stability and optimal control, a human operator requires information about the AHL system to provide the Performance of a aiven task. Additionaly adaptive mechanisms must be present, to determine the properties of the closed loop system. It is shown, that the receptors of the neuromuscular system, muscle spindle and Golai tendon organs might have the functional role of an internal parallel model to the controlled AHL system. A parallel model of this kind is shown to be feasible to realize identification and compensatory mechanisms involved in the human motor control system.

A marine seismic study of late Quaternary sedimentaion and inferred glacier fluctuations along western Inverness‐shire, Scotland

A sparker survey was undertaken of the sea area inshore of the peninsula of sleat and the islands of Eigg and Muck in Western Scotland. This revealed major submarine moraines across the mouths of Loch Nevis and Loch Ailort, which help define the margin of a major glacier readvance phase, presumed to be equivalent to the late‐glacial Loch Lomond Readvance. Formation names are suggested for the seismic para‐stratigraphy. West of the moraines, there is a till (Minch Para‐formation) resting on bedrock, overlain by a stratum (Muck para‐formation) with well‐defined internal layering parallel to the substratum. The till is presumed to have been deposited by an ice cap which at its maximum reached the western edge of the continental shelf at some time after 27,000 B.P. The Muck para‐formation probably represents a glaciomarine unit deposited during the retreat of this ice cap, and has been deeply eroded. Above this erosion surface occur a series of sediments which infill local basins, and which appear to be of Flandrian age (Arisaig para‐formation). East of the moraines in Loch Nevis and Loch Ailort the draped sediments are missing and the till is overlain by apparent equivalents (Nevis para‐formation) of the marine sediments of Flandrian age to the west

The Coral Reef of Nijar, Messinian (Uppermost Miocene), Almeria Province, S. E. Spain

ABSTRACT The Nijar Reef is a thoroughly exposed and representative example of the Messinian coral reefs outcropping along the periphery of the western Mediterranean. Facies patterns in the Nijar Reef Complex are presented in this paper as a generalized guide or model for the study of other Messinian reefs. Messinian paleogeography of this area was characterized by an archipelago whose islands are present-day Sierras. At the beginning of the Messinian and before development of the reefs, marine terrigenous sediments (Marginal Terrigenous Complex) were deposited on an irregular erosion surface on the metamorphic basement. The Reef Complex developed as a belt, fringing the positive areas (islands) when terrigenous deposition decreased. The Reef Complex consists of: 1) reef-core, constructed by a framework of vertical, branching colonies of Porites coated by laminated micrite (probably submarine cements), which form pinnacles as well as thickets; and 2) fore-reef, made of sloping beds of broken skeletons and debris. The fore-reef is subdivided into: i) reef-talus slope, ii) proximal slope, and iii) distal slope. The reef talus forms massive strata with dips of 20-30° and abundant pebble-to-boulder size slumped blocks of reef-core and coral breccia. The proximal slope shows dips of 10-20° of well-bedded, thick strata with internal parallel layering of granule to sand-size skeletal calcarenites. The distal slope is made of predominant bioturbated skeletal calcisiltites and fine-grained calcarenites with ngles lower than 10°. The distal slope grades into the basinal pelagic marls of the Nijar plains. The original reef morphology is well-preserved in present-day topography, with relicts of pinnacles, reef valleys, and slopes. Messinian volcanic highlands located to seaward complicated the local paleogeography with atoll-like features. Reef growth was concomitant with a gradual fall of sea level and occurred before the Messinian gypsum was deposited on top of the basinal marls in what is now the plains area. The Reef Complex is partially truncated by a major erosion surface, and it is overlain by oolitic shoals and stromatolites of the so-called Terminal Carbonate Complex. The Terminal Complex is interpreted as an upslope equivalent (in age) to the Messinian Upper Evaporite, and it implies a new cycle of sea level rise.

Hanging roof with stiffening beams in the second order theory

The roof structure consists in several cables developing themselves in parallel vertical planes and directly bearing the roof deck. In both their ends, these cables are connected to two transverse beams supported by more cables starting by the ends of the parallel cables and anchoring themselves to several columns. In the transverse direction, besides the aforementioned two external beams, there are other internal parallel beams in order to stiffen the roof structure and to sustain the eventual service decks and the cranes. In this paper, an analytical method for this kind of roof is presented based on the deflection method. The deflection-load law is nonlinear and the deflection vector corresponding to a given load vector is found by means of the Newton-Raphson method, the solution is reached in an iterative way with successive tangent matrices. The numerical results for a simple example are given.

Models for parallel processing within programs

Approximate queueing models for internal parallel processing by individual programs in a multiprogrammed system are developed in this paper. The solution technique is developed by network decomposition. The models are formulated in terms of CPU:I/O and I/O:I/O overlap and applied to the analysis of these problems. The percentage performance improvement from CPU:I/O overlap is found to be greatest for systems which are in approximate CPU:I/O utilization balance and for low degrees of multiprogramming. The percentage improvement from I/O:I/O overlap is found to be greatest for systems in which the I/O system is more utilized than the CPU.

Chlorine-Nuclear-Magnetic-Resonance Study of the Ferromagnet Gadolinium Trichloride

We have utilized chlorine nuclear magnetic resonance to measure the magnetization as a function of temperature (0.032-4.2 K) and applied field (0-10 kOe) in the ferromagnet Gd${\mathrm{Cl}}_{3}$. Above the Curie temperature, 2.214 K, there is only one $^{35}\mathrm{Cl}$ pure-quadupole-resonance transition at 5314 kHz. Below the Curie temperature the internal field at the chlorine site splits the single transition line into three temperature-dependent transition lines. This observation is consistent with an internal field parallel to the symmetry axis ${C}_{3}$. Analysis based on the method of energy moments yields a quadrupole asymmetry parameter of 0.4265 \ifmmode\pm\else\textpm\fi{} 0.0001. The quadrupole Hamiltonian is diagonalized to give transition frequencies as a function of the pure-quadrupole-resonance transition frequency, the asymmetry parameter, and the magnitude of the internal field. A least-squares analysis is used to determine the magnitude of the internal field as a function of temperature. With an external magnetic field applied parallel to the direction of the magnetization for a spherical sample, the critical point at the field ${\stackrel{\ensuremath{\rightarrow}}{H}}_{\mathrm{int}}={\stackrel{\ensuremath{\rightarrow}}{H}}_{A}\ensuremath{-}\stackrel{}{\mathrm{D}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{M}(T)=0$ is used to measure the relationship between the internal field and the bulk magnetization. They are found to be simply proportional to within 0.5%, indicating a temperature-independent transferred hyperfine interaction. The transferred hyperfine field at the chlorine site is found to be antiparallel to the magnetization and equal to 1644 G at saturation. The $zz$ component of the transferred hyperfine interaction tensor is 685 kHz for the $^{35}\mathrm{Cl}$ nucleus. The zero-point magnetization defect $\frac{\ensuremath{\Delta}{M}_{0}}{{M}_{0}}$ is estimated at (1.31 \ifmmode\pm\else\textpm\fi{} 0.49)%. For $T&lt;0.5$ K the measurements show that the magnetization decreases faster than the predictions of Marquard and Stinchcombe and Cottam, based on the measured exchange constants. In the range $0.5&lt;T&lt;1.0$ K the internal field follows the equation $B(T)=4956.9\ensuremath{-}868.1{T}^{\frac{3}{2}}{e}^{\ensuremath{-}\frac{{E}_{min}}{\mathrm{kT}}}$, where $\frac{{E}_{min}}{k}=0.3586\ifmmode\pm\else\textpm\fi{}0.0026$ K. Near the Curie temperature the critical exponent $\ensuremath{\beta}$ is found to be 0.3904 \ifmmode\pm\else\textpm\fi{} 0.0060 with ${T}_{C}=2.2140\ifmmode\pm\else\textpm\fi{}0.0016$ K. The Green's-function predictions in the random-phase-approximation are compared to the magnetization measurements in zero and applied fields. The zero-field susceptibility is also calculated from the measurements.

Subcellular storage organelles for 5-hydroxytryptamine in parafollicular cells of drugs which deplete the amine.

A study was made of the effect of the administration of reserpine and parachlorophenylalanine, an inhibitor of 5-hydroxytryptamine (serotonin; 5-HT), on the capacity of thyroid parafollicular cells to synthesize and store 5-HT. The two drugs were given to nonhibernating bats in doses which produced an equivalent degree of depletion of 5-HT from the thyroid. Tritiated 5-hydroxytryptophan, the precursor of 5-HT, was then given intravenously to assess the ability of parafollicular cell granules to take up and retain newly synthesized 5-HT. Reserpine, but not parachlorophenylalanine, decreased the amount of labeled 5-HT found in the thyroid and prevented autoradiographic labeling of parafollicular cell granules. Quantitative ultrastructural and stereological analysis demonstrated that the granules in untreated animals appeared to be nearly spherical prolate ellipsoids, with a uniformly electron-opaque inner matrix. In animals given reserpine, the axial ratio of the ellipsoidal granules increased greatly and a faint internal striation parallel to the long axis of the granules became apparent. Similar changes were not induced by parachlorophenylalanine. No other morphological changes in the thyroid epithelium were detected after administration of reserpine. This study confirms the association of 5-HT with the mature small secretory granules of thyroid parafollicular cells.