Types Of Substructures Research Articles

Stability patterns and trophic structure in a Delaware Bay plankton community

Using qualitative loop analysis we have extended our examination of a Delaware Bay plankton community to include an investigation of the roles played by the various entities (population, guild or nutrient) in the community. IN an entity removal exercise, we used stability relationships as a probe into community structure. Six types of stability change are possible as a result of entity removal from the system: stable to stable (s → s); stable to unstable (s → u); stable to disconnected (s → d); unstable to stable (u → s); unstable to unstable (u → u); unstable to disconnected (u → d). Using these changes as an investigative tool, we found that in order to account for the stability-instability patterns, it was necessary to construct a refined trophic structure model. The observed connections between the entities in the larger model could be grouped into two different types of stability substructures: a simple pattern and a more complex branching pattern. These patterns map easily onto the refined trophic structure model. Using stability analysis it is also possible to model community structure in ways other than the traditional trophic approach. Patterns of system necessity and relative contribution to stability are observed. These patterns match the refined trophic structure model derived previously. The roles that the various entities play in the overall community were followed over an annual cycle. Entities were seen to change their roles as a function of time and status within a subgroup. These results show that stability determinations have the potential to be used as a valuable tool in community analysis.

The number of infinite substructures

AbstractGiven a relational structure M and a cardinal λ < |M|, let øλ denote the number of isomorphism types of substructures of M of size λ. It is shown that if μ < λ are cardinals, and |M| is sufficiently larger than λ, then øμ ≤ øλ. A description is also given for structures with few substructures of given infinite cardinality.

STUDY ON PRACTICAL EXPERT SYSTEM FOR SELECTING THE TYPES OF RIVER-CROSSING BRIDGES

This paper describes an expert system for selecting the types of superstructures and substructures of river-crossing bridges, and deals with the knowledge of expert designers and rules of Japanese codes as the knowledge base. This expert system can automatically determine span arrangements satisfying the River-Crossing Structure Law, and uses the fuzzy set theory for pile type selection to express the ambiguous knowledge of expert designers. Moreover, in this system, the online data communication system between workstation and host computer is utilized for more accurate evaluation of substructure construction costs.

Fatigue of Al-Li alloys: mechanical properties, microstructure (TEM and SEM) and strain localization

The fatigue behaviour of two binary AI-Li alloys (A, solid solution; B, containing δ′ precipitates) is studied by macroscopic fatigue tests, and microscopic (SEM and STEM) observations. Two types of strain localization are found, appearing as two types of slip band in SEM, and as two types of substructure in TEM. These characteristics are ascribed to strain localization processes governed by strain amplitude for the former and strain rate for the latter.

Radon Mitigation Choices in the United States - A Comparison of Private and Public Sector Developments

This paper compares private- and public-sector developments relating to radon mitigation in the U.S. In response to elevated radon levels in many U.S. houses, the Federal and State governments and the private sector have undertaken many varied mitigation and public-information efforts resulting in a range of radon reduction installations in the U.S. Government-sponsored research and development of radon-mitigation techniques in single-family detached houses is compared with radon mitigation approaches undertaken by the private sector. An attempt is also made to compare premitigation diagnostics, the application of mitigation techniques to various substructure types, the performance of mitigation installations, and the cost of the installations. The information collected indicates that subslab ventilation is the most common technique in both public- and private-sector radon mitigation; however, air-to-air heat exchangers and sealing are employed more frequently in the private sector than in government-sponsored mitigation.

The distribution of two hnRNP-associated proteins defined by a monoclonal antibody is altered in heat-shocked HeLa cells

A monoclonal antibody obtained after mice were immunized with hnRNP purified from HeLa cells recognizes two polypeptides of M r 35,000 and 37,000. By immunocytofluorescence, these antigens can be visualized only in cells previously heat shocked at 45 °C for 5 or 10 min, although they are present at the same level in unstressed and stressed cells. The signal, which is mostly concentrated in the interchromatin space, where hnRNP fibrils are located, does not accumulate with time and disappears 4 to 5 h after heat shock. Discrimination between the two types of hnRNP substructures, the 30–50 S monoparticles and the nuclear matrix fibrils, based on differential sensitivity to salt or ribonuclease treatment, showed that in unstressed cells the antigens behave as monoparticle proteins. In contrast, in heat-shocked cells, most 35–37K antigens behave as nuclear matrix proteins. Thus, heat shock seems to induce a rapid and reversible switch of these two antigens from hnRNP monoparticles to the nuclear matrix. The data demonstrate that heat shock, which was previously shown not to alter the overall RNA: protein packaging ratio of hnRNP, induces subtle modifications of their substructure. Such modifications might be of importance since heat shock is known for instance to affect pre-mRNA processing.

Evolution of the dislocation structure and the stage of work-hardening of Ni3Fe alloy with [001] orientation

Using transmission diffraction electron microscopy, the dislocation structure of work-hardened iron nickel alloy with the compression axis in [001] orientation is studied over a wide interval of gradual strain. A connection is established between the change of the flow curve and the type of substructure formed. The quantitative characteristics of the observed structural types are determined and their behavior at different stages of the strain curve is traced.

Filtering of nonstationary signals using predictor median hybrid structures

An approach to filtering of nonstationary signals that contain abrupt changes from one signal state to another is presented. Proposed nonlinear filters, the Predictor Median Hybrid (PMH) filters, contain substructures to estimate the current signal value using forward and backward prediction. The output of the overall filter is the median of the predicted values and the actual signal value. This kind of nonlinear filter structure is shown to have some interesting properties: (1) Due to the median operation, the filters do not disturb rapid changes from one stationary signal to another and yet they attenuate noise. (2) The predictive substructures can be chosen according to the application, thus greatly extending the class of signals where median type filters can be applied. (3) Due to the predictive nature of the substructures they adapt to the signal, thus simplifying the design of the filters. Two types of predictive substructures have been used: linear predictive substructures and curve fitting based predictors. The PMH filters with linear predictive substructures are shown to be especially useful for the restoration of deterministic and stochastic signals that contain impulse-like distortions. The curve fitting based substructures are shown to be useful for attenuation of Gaussian noise.

Biodegradation of two tetrameric lignin model compounds by a mixed bacterial culture

The ability of a mixed bacterial culture to decompose two tetrameric lignin model com-pounds as a sole source of carbon and energy was investigated. The mixed bacterial culture con-sisted mainly of Gram negative rods. The tetram-ers contained two types of lignin substructures, namely the most abundant β-O-4 ether structure in lignin and also the 5-5 biphenyl structure. The tetramer (MW 638) containing two phe-nolic hydroxyls was decomposed readily; after 13 days of incubation, all intermediate products formed were almost totally decomposed. The non-phenolic tetramer (MW 666) was decom-posed much more slowly; after 53 days of incuba-tion, 5% of the substrate was unchanged. When both tetramers were degraded simultaneously, the non-phenolic tetramer was decomposed similarly to the phenolic tetramer. Determination of molecular weights of cata-bolic products showed that the degradation of the non-phenolic tetramer had proceeded at least to dimer level. SKF 525A, inhibitor of cytochrome P-450, caused one catabolic product to accumulate in the culture medium. This indicates involvement of cy-tochrome P-450 in the degradation pathway of the model compounds used. We conclude that this mixed bacterial culture was able to degrade the lignin model compounds used and that free phenolic groups seem to in-crease the biodegradability significantly.

Ultrastructure and Phylogenetic Significance of Notaspidean Spermatozoa (Mollusca, Gastropoda, Opisthobranchia)

Spermatozoa of five notaspidean opisthobranchs [Berthellina citrina, Berthella ornata, Pleuro‐branchus peroni, Pleurobranchaea maculata, Umbruculum sinicum] were examined using TEM. In all five species, the acrosome (sensu lato) consists of an apical vesicle (the acrosomal vesicle) and acrosomal pedestal. The acrosomal pedestal overlaps the nuclear apex, and in P. peroni (and possibly B. ornata) is periodically banded—‐the first reported incidence of this type of substructure in any euthyneuran acrosome. Although sperm nuclei of P. peroni, B. ornata and B. citrina differ in length and also the number of keels present (nucleus 7 μm long with four/five keels present in Pleurobranchus; 17 μm long with one keel in Berthella; 15 μm long with a very weak keel in Berthellina), the basal invagination to which the centriolar derivative, axoneme and coarse fibres are attached is always poorly developed, and very little overlap between nucleus and midpiece occurs. In P. maculata and U. sinicum, the nucleus forms a helical cord around the axoneme and mitochondrial derivative such that it is not possible to recognize exclusively ‘nuclear’ and ‘midpiece’ regions of the spermatozoon. In all notaspideans investigated, (1) the axoneme, coarse fibres and glycogen helix are enclosed by the paracrystalline and matrix components of the mitochondrial derivative and (2) a dense ring structure (attached to the plasma membrane) and glycogen piece are observed. While the glycogen piece is very short (0.85–1.43 μm) with a very degenerate axoneme in B. citrina, B. ornata and P. peroni, this region of the spermatozoan is well developed (30–35 μm long) in U. sinicum and exhibits a fully intact 9 + 2 axoneme. The ‘glycogen piece’(or its presumed homologue) in P. maculata spermatozoa is very short (0.65 μm), devoid of any axonemal remnant and constructed of a hollow, internal cylinder attached to an outer (incomplete) shell, and contains scattered (glycogen) granules. Spermatozoal structure supports a close relationship between the genera Berthellina, Berthella and Pleurobranchus. These three genera have more distant links with Pleurobranchaea, while Umbraculum maintains an isolated, specialized position within the Notaspidea.

Large deflection analysis of beams, pipes, or poles

This paper describes an efficient algorithm for the analysis of flexible beams, pipes or poles. The algorithm has been applied to a wide variety of offshore systems in which flexible pipes or hoses are commonly used. The method can be used to study either a complete line-like flexible structure or to develop the properties of a ‘long flexible beam element’ which can be combined with other types of elements or substructures to model complex structural systems.

種々の下部組織を持つ工業用純アルミニウム溶接熱影響部の再結晶挙動

Recrystallization behaviour of commercial pure aluminium may be affected by the morphology of substructures.In this study, commercial pure Al of 10 mm thick plate was prepared. That was machined to the plates of various thickness, then these were full annealed at 600°C for 30 min.All plates were made equal to 2 mm thick plates by three kind of treatments, these were cold-rolling, cold-rolling and 200°C×30 min. annealing (in this report, quasi stabilized treatment=Q.S.T.) and hotrolling. Each treatment induced another type of substructure, i.e. tangled dislocations, statically recovered structure, and dynamically recovered structure.Recrystallization behaviour of these three types of substructure-induced specimens was studied by isothermal heat treatments at various temperatures.And, softened width and recrystallized grain diameter at the electron beam weld heat affected zone of substructure-induced plates were compared. Test plates were 100 mm×100 mm square plates of 2 mm thickness.Obtained results were as follows;(1)Annealing at 200°C for 30 min. after cold-rolling gave smaller recrystallized grain diameter and hieher recrvstallization temperature than cold-rolled test specimens.(2)The higher the hot-roing temperaturc, the higher the recrystallization tempcrature became, but slight change of recrystallized grain diaameter was observcd.(3)While hardness of substructure-induced test speciren was below 30, hot-rolled test specimens had higher recrystallization temperature and smaller grain diameter than cold-rolled with or without Q.S.T.specimens.(4)Softened width and grain diameter of electron beam weld heat affected zone of cold-rolled plates were larger than these of cold-rolled with Q.S.T.or hot-rolled plates.

An algebra of algorithms and its application to program design and maintenance

This paper presents a method, comprising a new algebra and a formal procedure, for restructuring irregular algorithms. The resulting regular structures contain only three types of substructures: ‘sequence’, ‘if’ and ‘while’, and preserve all constituent transformations of the original. The method is primarily an aid for the design and maintenance of large-scale software.

Effects of solidification substructure on the mechanical properties of a nickel base superalloy

Rod specimens of HASTELLOY alloy X were unidirectionally solidified by the floating zone method in an electron-beam zone melter. Temperature gradient (▽ T) and growth rate ( R) were controlled to produce three types of solidification substructures: cellular, cellular-dendritic, and dendritic. Qualitative agreement with the solidification treatment of Tiller and Rutter was obtained, in that a decrease in the parameter ▽ T/ R changed the solidification mode away from cellular toward dendritic. Room- and elevated-temperature tensile tests indicate that the dendritic form of the alloy is stronger and more ductile than the cellular form, probably because there is less tendency for brittle, low-melting grain-boundary phases to form during dendritic solidification.

Crystal morphology and the dissolution of goethite

An electron microscope has been used to examine the characteristics of goethite crystals and the nature of acid attack on these crystals in aqueous solutions. The (100) face of synthetic acicular goethite crystals makes up 50–60 per cent of the total surface area of a sample. The smaller the crystal, the greater is the contribution of the (010) and (001) faces to the surface area. Very large acicular goethite crystals have a type of substructure. Dissolution of synthetic goethite crystals is anisotropic, two of the faces, (010) and (001) dissolving more rapidly than (100), as a result of an unequal distribution of the reactive sites over the different crystal faces. Dissolution rates are related to the size and shape of the crystals. Star-shaped twinned crystals and the large acicular crystals are rapidly attacked along “grain” boundaries. Pronounced acid attack also occurs at the twin planes. Haematite-containing twins dissolve in two stages, an initial rapid removal of the haematite being followed by much slower dissolution of the goethite.

Suffixes of addressable data graphs

The notion of a self-insertion of a data graph yields a simple and natural definition of a suffix of a data graph. For addressable data graphs, addressing schemes yield a useful alternative definition of suffix, which also suggests a generalized version of suffix. Examples of addressable data graphs and their suffixes include: trees and their subtrees, and arrays with their (possibly lower dimensional) subarrays. Thus a suffix can be viewed as a highly structured type of substructure of a data graph. Necessary and sufficient conditions for a suffix of an addressable data graph to be addressable are derived. It is further shown that suffix data graphs, even when not addressable, often enjoy a slightly weaker property termed quasi-addressability; in fact suffixes of so-called deep-rooted data graphs are always quasi-addressable.

Dislocation structure during creep of MgO single crystals

Abstract The dislocation substructure generated during compressive creep of MgO single crystals has been investigated using both etch-pit and transmission electron microscopy techniques. The type of dislocation substructure is dependent on strain. During transient creep nearly parallel cell walls are found whereas in steady state creep a nearly equiaxed network of cells is built up. Measurements of the density ρ of dislocations not associated with cell walls and of the cell wall area per volume S v reveal the following trends: During primary creep both ρ and S v are functions of strain; ρ decreases while S v increases with increasing strain. During steady state creep ρ and S v are constant. The isothermal stress dependence of the steady state values of ρ and S v can be described by relations ρ ∼ σ1·4, and SV∼σ0·7.

Substructure formation and nonuniformity in strain during high temperature creep of copper single crystals

The change in substructure during high temperature creep of copper single crystals was examined to make clear the relation between the substructure and the creep rate. The structural observations by means of etch-pit technique were made in the same area of the specimen surface after successive straining by creep. Different types of substructures were formed in different localities at an early stage of transient creep. Small subgrains elongating in the direction of the deformation band were found in some regions (region A). Large subgrains containing cells within them were observed in other regions (region B). With the progress of creep, the substructures in both regions underwent gradual changes to become alike in their appearance with each other. The creep strains in regions A and B were examined at various creep stages. The ratio of creep strain to the average creep strain throughout the specimen,e/eav, was a few times larger in region B than in region A at an early stage of transient creep. With the structural changes mentioned above, the difference between the ratios in the two regions came to disappear, both becoming almost unity at the later stage of creep. These results suggest the close relation between the substructure and the creep rate.

Unstable flow in martensite and ferrite

It is proposed that unstable plastic flow of iron alloys containing carbon or nitrogen occurs when (∂ lnν/∂τ*)T becomes negative (v is the average velocity of the dislocations andτ* the effective stress acting upon them) at the maximum in the force-velocity curve deduced from either the Snoek or the Cottrell steady-state drag model. In addition, a nucleating event is necessary. A model is developed which predicts relationships between the applied stress, the strain rate and the temperature at the onset of unstable flow, and also the activation energy associated with the event. Experiments have been carried out on iron-carbon and iron-nickel-carbon alloys covering a range of carbon concentration in solution. The alloys were either annealed ferrite or martensite and, thus, the extremes of the range of possible dislocation density were examined. Two distinct types of plastic instability were identified: jerky flow, the result of Snoek interaction, and serrated flow due to Cottrell drag. All the qualitative and quantitative features of the phenomenon which were examined were found to be in complete accord with the model. The average velocity of the dislocations as a function of the temperature at the start of unstable flow has been deduced from the model and an estimate of the density of dislocations moving at the time has been made using measured values of the critical strain rate. The strain rate and temperature at which unstable flow disappears were measured as a function of the carbon concentration and the two types of substructure. The data show that an explanation based on the assumption that the phenomenon involved is the same as that producing the Koster internal-friction peak is untenable. An alternative suggestion, based on the relative stability of a Cottrell cloud and a carbide precipitate, is discussed briefly and qualitatively.

The strength of ferrous martensite

A series of iron-carbon and iron-nickel-carbon steels have been investigated in order to assess the relative contribution of the following to the strength of martensite : 1. (a) solid solution hardening by carbon, 2. (b) carbon in the form of precipitates or segregates, and 3. (c) the substructure of the martensite, i.e. dislocation tangles or internal twinning. The results for solid solution hardening are consistent with a linear variation of the flow stress with the square root of the carbon content. Precipitation hardening occurs during the quench, or in certain cages during subsequent ageing of the martensite, and the hardening contribution of this precipitation or segregation is found to be comparable with that due to carbon in solution. In the absence of carbon the type of substructure appears to have no appreciable effect on the strength of the martensite. In the presence of carbon, the type of substructure does however affect the strength in that solid solution hardening is more pronounced for twinned martensite and only this type of martensite shows any appreciable hardening during artificial ageing after the quench. The Fleischer theory of solid solution hardening is applied in detail to the movement of a 2 〈111〉 edge and screw dislocations on {110} and {112} slip planes in tetragonal martensite. A model for the passage of slip dislocations through internally twinned martensite is developed from the original suggestion of Sleeswyk and Verbraak and used to account for the difference in solid solution hardening behaviour of lath and twinned martensite. Experimental evidence in support of the proposed model is presented.