Types Of Structural Elements Research Articles

A probabilistic approach for a T-stub ultimate strength assessment using response-surface approximation

The main goal of the study is to examine and demonstrate the application of a developed probabilistic framework to the analysis of a chosen general type of steel connection component in order to obtain the basic characteristics of its mechanical behaviour with regard to the chosen type of the input geometry and material properties. Accordingly, as a typical representative of the component method proposed by the Eurocode the equivalent T-stub was chosen as a subject of the study. This type of structural element has the capability to address the behaviour of several parts of the connection: column flange in bending, end plate in bending and flange cleat in bending. A method is proposed to determine the probability density function of the ultimate strength using a response-surface approach coupled with FEM applied to a stochastic structural model. The results of a study were processed by means of sensitivity analysis to determine the importance level of the input variables.

Intelligent Structural Elements Covered By Piezoelectric High-Polymer Film

Abstract If a piezoelectric material is deformed, the local electric field is caused by the electromechanical interaction. When a structural element with surface defects is subjected to the stress, the strain distribution appears also on the opposite surface to the defects. Such localized strain distribution can be measured by the electric potential distribution on a piezoelectric film mounted on the smooth surface. This paper shows that back-surface defects in typical structural elements can be visualized by mounted PVDF thin film

Development of an Automated Method for the Detection of Chronic Lacunar Infarct Regions in Brain MR Images

The purpose of our study is to develop an algorithm that would enable the automated detection of lacunar infarct on T1-and T2-weighted magnetic resonance (MR) images. Automated identification of the lacunar infarct regions is not only useful in assisting radiologists to detect lacunar infarcts as a computer-aided detection (CAD) system but is also beneficial in preventing the occurrence of cerebral apoplexy in high-risk patients. The lacunar infarct regions are classified into the following two types for detection: “isolated lacunar infarct regions” and “lacunar infarct regions adjacent to hyperintensive structures.” The detection of isolated lacunar infarct regions was based on the multiple-phase binarization (MPB) method. Moreover, to detect lacunar infarct regions adjacent to hyperintensive structures, we used a morphological opening processing and a subtraction technique between images produced using two types of circular structuring elements. Thereafter, candidate regions were selected based on three features — area, circularity, and gravity center. Two methods were applied to the detected candidates for eliminating false positives (FPs). The first method involved eliminating FPs that occurred along the periphery of the brain using the region-growing technique. The second method, the multi-circular regions difference method (MCRDM), was based on the comparison between the mean pixel values in a series of double circles on a T1-weighted image. A training dataset comprising 20 lacunar infarct cases was used to adjust the parameters. In addition, 673 MR images from 80 cases were used for testing the performance of our method; the sensitivity and specificity were 90.1% and 30.0% with 1.7 FPs per image, respectively. The results indicated that our CAD system for the automatic detection of lacunar infarct on MR images was effective.

New types of gold-bearing structures and rocks in ore fields of the western Mongolia-Okhotsk collisional suture

The Kariisky, Pil’nensky, and Pogromny gold deposits of the Shilka branch and the Ilinsky and Dybyksinsky deposits of the Onon-Tura branch of the Mongolia-Okhotsk Suture belong to the nappe-thrust type of ore fields. New types of gold-bearing structural elements are tectonic polymictic melange, serpentinite melange, autoclastic melange, losange (rhomb-shaped strike-slip duplexes), and mineralized sutures of low-amplitude thrust faults and detachments. It was established that such rocks of the dynamometamorphic complex as mylonites, cataclasites, pseudotachylites, and tectonic breccias may be gold-bearing.

Microstructural changes in Teruel dry-cured ham during processing

Dry-cured ham, “Protected Designation of Origin (PDO)” Teruel, is a high quality meat product processed using a traditional dry-curing procedure. The objective of this paper was to study the microstructure of the Biceps femoris and Semimembranosus muscles during “PDO Teruel” dry-cured ham processing using electron microscopy techniques (Cryo-SEM, SEM and TEM). The Semimembranosus and Biceps femoris muscles from raw ham show the typical structure of muscle tissue in meat. The muscle fibres appear firmly attached to one another by the endomysial connective tissue; the myofibrils inside the cells are strongly attached to each other and to the sarcolemma. In raw ham, the typical structural elements that constitute the sarcomere can be observed by TEM. Important microstructural changes are observed following salting; reflected in the fact that the Z-disks inside the myofibrils are no longer in line and there is important degradation of the cell membranes in this stage. At the end of the process, an accumulation of solutes, which could be products from proteolysis occurring mainly in the last stage of ripening, could be observed in both muscles. Thus the proteolysis and dehydratation phenomena that take place during “PDO Teruel” dry-cured ham processing occur at an ultrastructural level, and this is the basis to produce a product with the sensory features appreciated by consumers.

Formation of spectral lines in a dynamically active stochastic and multicomponent atmosphere

This paper is devoted to a determination of the statistical mean quantities describing spectral line radiation of dynamically active stochastic and multicomponent atmospheres. The lines in LTE are considered so that the effects of multiple scattering can be neglected. Two types of problem are discussed. In the first it is assumed that the realization of one or another type of nonthermal motion depends on the type of structural element and in the other this type of dependence is absent, i.e., it is supposed that the assumed random values of the velocity are distributed according to a law that is common to all the components. Particular attention is paid to a determination of the relative mean square deviation of the intensity of the observed radiation. It appears that the distinctive feature of the relative mean square deviation of the radiation in a line formed in a dynamically active stochastic atmosphere is local “spikes” (maxima) in the wings of the line. The theoretical results in this paper are compared with spectral observations of quiescent solar prominences obtained in framework of the SOHO space mission.

Statistical characters of mean backbone torsion angles of proteins

Based on the high resolution protein structures taken from the Protein Data Bank, the mean backbone torsion angle of each protein is calculated. Then the statistical characters of the mean backbone torsion angles of proteins are investigated. On φ – ψ plane, the representing points of the proteins, i.e., the mean backbone torsion angles ( φ ¯ , ψ ¯ ) , separate into four clusters according to four main structural classes. Each cluster has a determinate centroid, which associates to the relative content of two types of popular secondary structural elements, α -helices and β -strands. It is also found that α / β structural class exhibits greater concentricity of the partial mean backbone torsion angle relative to other classes. An intuitive explanation is that the α / β structural class has high level of average lengths of both α -helices and β -strands. These results provide a further understanding of protein structures.

Dispersion free wave splittings for structural elements

Wave splittings are derived for three types of structural elements: membranes, Timoshenko beams, and Mindlin plates. The Timoshenko beam equation and the Mindlin plate equation are inherently dispersive, as is each Fourier component of the membrane equation in an angular decomposition of the field. The distinctive feature of the wave splittings derived in the present paper is that, in homogeneous regions, they transform the dispersive wave equations into simple one-way wave equations without dispersion. Such splittings have uses both for radial scattering problems in the 2D cases and for scattering problems in dispersive media. As an example of how the splittings may be applied, a direct scattering problem is solved for a membrane with radially varying density. The imbedding method is utilized, and agreement is obtained with an FE simulation.

Elements, characteristics and character – Information functions of landscapes in terms of indicators

Abstract When monitoring landscape changes, the visual landscape should also be considered. This pertains to the information function of ecosystems and landscapes that refers to environmental structure and its function for satisfying needs. These needs of human perception include a certain equipment of landscape with stimuli, spatial orientation, as well as aesthetical-emotional needs. However, previous approaches of environmental monitoring and registration of landscape changes exclusively focus on the ecosystem; aesthetic and structural characteristics are evaluated, if at all, only via easily quantifiable variables in a data oriented manner that illustrates the diversity of individual landscape elements without theoretically grounding them based on general hypotheses and a theoretical concept. Based on results from perception research and information theory, therefore, a method for registering the visual landscape on different complexity levels is developed. This includes: - “elements” (i.e. “element level”), that is the description of the different types of land use and structure elements within a landscape unit. Furthermore, under these elements a variety of manifestations are also subsumed, such as small spatial dimensional relations, as well as individual synesthetic perceptions (noise and smells); - “characteristics” (i.e. “shape level”), that is the typical combinations of elements, design shapes and proportions; - and the overall area perception, that is the “character” (i.e. the space level) of a landscape as the result of a characterization process that classifies, illustrates and describes areas that are similar in appearance. One possible application of this approach can be demonstrated by the impacts of streets on the visual landscape. This example makes it evident that indicators for landscape diversity are only able to illustrate changes of individual elements but not of the character of landscapes themselves. This fact makes it necessary to additionally integrate aspects aside from quantitative ones when evaluating the visual landscape. Furthermore, it is necessary to empirically verify aspects that are significant for the perception of landscapes in order to make them more accessible than has been thus far for evaluations in the sense of indicators.

Stochastic structural model of rock and soil aggregates by continuum-based discrete element method

This paper first presents a stochastic structural model to describe the random geometrical features of rock and soil aggregates. The stochastic structural model uses mixture ratio, rock size and rock shape to construct the microstructures of aggregates, and introduces two types of structural elements (block element and jointed element) and three types of material elements (rock element, soil element, and weaker jointed element) for this microstructure. Then, continuum-based discrete element method is used to study the deformation and failure mechanism of rock and soil aggregate through a series of loading tests. It is found that the stress-strain curve of rock and soil aggregates is nonlinear, and the failure is usually initialized from weaker jointed elements. Finally, some factors such as mixture ratio, rock size and rock shape are studied in detail. The numerical results are in good agreement with in situ test. Therefore, current model is effective for simulating the mechanical behaviors of rock and soil aggregates.

COMPOSITE AND INTERACTION EFFECTS IN STEEL‐CONCRETE STRUCTURES FOR HIGHER FIRE RESISTANCE

Wide application of steel structures for office and industrial buildings is one of the main features of Lithuanian and world building industry. This fact is related to an essentially wider use of new structural solutions, new structural members and materials. Usage of different types of materials in one structural system for better utilisation of positive properties of each component is very popular in current building industry. Composite beams, columns, beams‐columns and composite floors can be mentioned. Structures that were designed and erected twenty or more years ago are mostly a collection of different types of structural elements. In general, interaction or composite effect is not taken into account, when designing such structures. Though a considerable number of roofs and ceilings made up of reinforced concrete slabs and steel beams or steel trusses are still in maintenance. Structural solution of the slabs, welding of embedded steel parts of slabs to steel structures, filling with concrete the joints between slabs create the conditions for interaction of slabs and steel structures. The result of this effect is that slabs take up a part of the internal forces of the steel structures and consequently diminish it in steel beams and trusses. It is obvious that this fact leads to the increase of load bearing capacity and fire resistance. The paper deals with the problem of evaluation of composite and structures interaction effect on fire resistance.

Analysis of the "thermodynamic information content" of a Homo sapiens structural database reveals hierarchical thermodynamic organization.

Classification of the amounts and types of lower order structural elements in proteins is a prerequisite to effective comparisons between protein folds. In an effort to provide an additional vehicle for fold comparison, we present an alternative classification scheme whereby protein folds are represented in statistical thermodynamic terms in such a way as to illuminate the energetic building blocks within protein structures. The thermodynamic relationship is examined between amino acid sequences and the conformational ensembles for a database of 159 Homo sapiens protein structures ranging from 50 to 250 amino acids. Using hierarchical clustering, it is shown through fold-recognition experiments that (1) eight thermodynamic environmental descriptors sufficiently accounts for the energetic variation within the native state ensembles of the H. sapiens structural database, (2) an amino acid library of only six residue types is sufficient to encode >90% of the thermodynamic information required for fold specificity in the entire database, and (3) structural resolution of the statistically derived environments reveals sequential cooperative segments throughout the protein, which are independent of secondary structure. As the first level of thermodynamic organization in proteins, these segments represent the thermodynamic counterpart to secondary structure.

Composite and interaction effects in steel‐concrete structures for higher fire resistance

Abstract Wide application of steel structures for office and industrial buildings is one of the main features of Lithuanian and world building industry. This fact is related to an essentially wider use of new structural solutions, new structural members and materials. Usage of different types of materials in one structural system for better utilisation of positive properties of each component is very popular in current building industry. Composite beams, columns, beams‐columns and composite floors can be mentioned. Structures that were designed and erected twenty or more years ago are mostly a collection of different types of structural elements. In general, interaction or composite effect is not taken into account, when designing such structures. Though a considerable number of roofs and ceilings made up of reinforced concrete slabs and steel beams or steel trusses are still in maintenance. Structural solution of the slabs, welding of embedded steel parts of slabs to steel structures, filling with concre...

Reliability of Frame and Shear Wall Structural Systems. I: Static Loading

A hybrid reliability evaluation approach is proposed, consisting of the response surface method, the finite-element method, the first-order reliability method, and the linear iterative scheme when the load is applied dynamically to a complicated structural system. The method is especially applicable for realistic structural systems consisting of different types of structural elements and materials. The method was specifically developed to evaluate the reliability of a steel frame and reinforced concrete shear wall structural system subjected to seismic loading. The unique feature of this algorithm is that the earthquake loading can be applied in the time domain, enabling a realistic representation of the seismic loading conditions. The steel members are represented by beam-column elements and the shear walls are represented by plate elements. The deterministic algorithm, discussed in detail in the companion paper, is then extended to consider the uncertainty in the random variables. The reliability of a frame without and with RC shear walls is evaluated for the serviceability performance functions. The results are verified using Monte Carlo simulation. The method estimates the probability of failure very accurately, and is very efficient compared to simulation. The algorithm can be used to estimate the reliability of complicated structural systems consisting of different types of structural elements and materials under dynamic including seismic loading applied in time domain.

Pumice concrete for structural wall panels

Some properties of lightweight pumice stone concrete (LWPSC) are discussed, on account of a possible structural use of this material. Then the results of an experimental investigation are described, in order to show that pumice can really be considered an alternative to common artificial lightweight aggregates, taking into account the performance pointed out by loading tests carried out on structural systems made of LWPSC. Three different kinds of reinforced wall panels were made using LWPSC, lightweight expanded clay concrete and normal weight concrete; then their structural responses under horizontal cyclic and constant vertical forces were compared, above all with reference to lateral stiffness, cracking pattern, ultimate strength and associated plastic deformations. This comparison shows the effectiveness of pumice as an aggregate in manufacturing concrete, at least for this type of structural element.

Encyclopedia of Vibration: Volumes 1, 2, and 3

5R10. Encyclopedia of Vibration: Volumes 1, 2, and 3. - Edited by SG Braun (Fac of Mech Eng, Technion-Israel Inst of Tech, Haifa, 32000, Israel), DJ Ewins (Dept of Mech Eng, Imperial Col of Sci, Tech and Med, Exhibition Rd, London, SW7 2BX, UK), and SS Rao (Dept of Mech Eng, Univ of Miami, PO Box 248294, Coral Gables FL 33124-0624). Academic Press, San Diego. 2001. 1595 pp. 3-vol set. ISBN 0-12-227085-1. $925.00.Reviewed by AW Leissa (Dept of Mech Eng, Ohio State Univ, 206 W. 18th Ave., Columbus OH 43210-1154).The title chosen for this three-volume set of information about vibrations is very appropriate, for it is indeed an encyclopedia, consisting of 168 short chapters, each treating a particular topic, arranged in alphabetical order. The individual chapters are written by persons who are known to be authorities on the topics. Altogether, 132 persons were contributors, writing chapters which are typically 7-12 pages long. The topics chosen take on a variety of forms. Some of them deal with long-standing vibration concepts (critical damping, dynamic stability, forced response, friction damping, hysteretic damping, etc), some consider types of structural or machine elements (beams, bearings, belts, blades and bladed disks, columns, disks, membranes, pipes, plates, etc), and some are brief summaries of methods of analysis (boundary elements, finite differences, finite elements, Krylov-Lanzos methods, linear damping matrix methods, etc). Current topics of considerable interest (active vibration suppression, actuators and smart structures, electrostrictive materials, laser based measurements, MEMS applications, etc) are also included. A typical chapter begins by describing the topic, and then defines and explains concepts and the terminology involved. Some interesting and useful results are then usually presented and discussed. Each chapter concludes with a list of publications which are recommended for further reading, for those who want to learn more about the topic. There is a wealth of useful information contained in this encyclopedia. This is due to not only the size of the compendium (1595 pages, 20×27cm), but also because each author had to try to condense the most important information into a limited space. It can only be a starting place for a reader interested in any topic, but it is a very good one. One can locate topics easily for, in addition to a complete Table of Contents at its beginning, a 31 page Index of topics and subtopics and their corresponding page numbers is included at the end of each volume. In the opinion of this reviewer, this three-volume encyclopedia is a collection of information which is very useful for all persons who want to know more about vibrations—students, engineers, researchers, and teachers. Those who can afford it will benefit significantly in having a personal copy. But every engineering library should definitely have it.

Two-dimensional supramolecular chemistry with molecular Tinkertoys

For some time now (1–5), we have worked on the development of a “molecular construction kit,” analogous to the children's Tinkertoy† construction set, which permits the assembly of complicated objects from a limited set of rods, connectors, and other simple building elements. The idea is to do civil engineering with individual molecular components ranging in size from a few to several dozen A. A somewhat related concept of “molecular Lego,” based on a different set of structural elements, was proposed (7) and developed (8) independently by Stoddard. Both belong to the wider category of “modular chemistry,” in which a small number of mid-sized rigid molecular structural elements are combined into complex structures (9). At the start of our project, a very limited selection of types and lengths of straight terminally functionalized molecular rods and connectors was available. We synthesized additional ones based on the oligomers of [1.1.1]propellane ([ n ]staffanes) (10) and on oligomeric 10-vertex and 12-vertex p -carboranes (11). Other laboratories produced polycubyls (12), oligomers of [2.2.2]propellane (13), additional oligomers of 12-vector carboranes (14), and many rods constructed from the more common p -phenylene and acetylene subunits. A combination of several types of such structural elements permits one to achieve an accurate match to a desired rod length. A recent comprehensive review (15) makes it abundantly clear that after a decade of effort, considerable flexibility exists in the choice of molecular rod lengths and properties. After some initial experiments with point (4) connectors, which function by forming bonds from a central atom to the termini of several rods, we turned our attention to star (4) connectors, which function by forming a bond between each of several star arm termini to the terminus of a rod or of another star arm. Various suitable star connectors such …

Bestandslücken in einem subalpinen Fichtenwald der Westkarpaten

The size, number, and enlargement of gaps as well as the process of gap formation were analyzed in a subalpine spruce forest in the Babia Gora massif, one of the highest in the western Carpathian Mountains. Openings in the forest canopy of up to one hundred square meters are typical structural elements of subalpine spruce forests. Gaps comprised 34% of the studied forest area of 14.4 ha. There were 38 gaps per ha, most of them <100 m2. Average gap size was 92 m2. Most gaps were environmentally heterogeneous as a result of their progressive and ongoing enlargement, which was evidenced in many gaps by snags and logs representing a wide spectrum of decomposition classes. The density of logs and the area covered by them were about two times larger in gaps than under spruce canop. Logs in gaps were of greater diameter. The mean gap size has increased in recent years. At the same time establishment of new gaps became rarer and enlargement of existing gaps took place more often. This suggests that the average area of gaps will further increase in the future. The closure of gaps resulting from the elongation of spruce branches on adjacent trees and through the development of young trees did not keep pace with the process of gap creation. It yielded a 0.3–0.4% increase of total gap area per year.

Molecular Characterization of the 56-kDa CYP153 from Acinetobacter sp. EB104

CYP153 a cytochrome P450 from Acinetobacter sp. EB104 catalyzes the hydroxylation of unsubstituted n-alkanes. We have decided to use the CYP153 system as a model for mechanistic studies on regioselective n-alkane oxidation and the interaction of hydrophobic substrates with soluble enzymes. Here the molecular cloning of the CYP153 gene is reported. Single specific primer PCR was applied to yield the whole gene sequence via chromosomal walks. CYP153 consists of 497 amino acids (Mr = 56 kDa) and thus represents an unusually long bacterial P450, containing all P450 typical structural elements. It constitutes the new P450 family CYP153. The prolonged N-terminus of about 90 amino acids does not contain a so far known membrane-anchoring sequence but a 28-amino acid long amphipathic helix. The relevance of the remarkably long N-terminus and of other sequence motives like the hydrophobic F-G loop is discussed with respect to substrate binding and recognition.

Dislocation dipoles in nanocrystalline films.

A theoretical model is suggested that describes the behavioral features and energetic characteristics of dipoles of grain boundary dislocations in nanocrystalline films. Such dislocation dipoles in nanocrystalline films are shown to play the role of misfit defect configurations that compensate, in part, for misfit stresses that occur due to a mismatch between crystal lattice parameters of films and substrates. Ranges of parameters (misfit parameter, grain size, etc.) are revealed at which the formation of dislocation dipoles is energetically favorable in nanocrystalline films. It is demonstrated that dislocation dipoles are typical structural elements of nanocrystalline films fabricated at highly nonequilibrium conditions.