Large Structural Elements Research Articles

The impact of design approach and contracting practices on cost and execution period of school buildings

More than two million school-age children in Yemen are unable to enroll in education because of a shortage of school buildings. This is one of the reasons the country missed the Millennium Development Goal of achieving Education for all by 2015. The struggle to afford school accommodation will continue, because of the lack of resources and high unit cost. Construction cost as time schedule for an identical school building vary by the implementing agency. This paper aims to study in-depth this multi-dimensional issue to find out the factors that lead to this variation, as well as the reasons for the high unit cost and lengthy periods of construction. To achieve this objective, comprehensive raw data that was resourced from agencies that are assigned to implement the largest part of the construction program along with data collected through questionnaires and semi-structured interviews were utilized. Complete sets of design and contracting documents of representative schools were used for deeper analysis and evaluation. The analysis shows that the employed design approaches lead to large structural elements and consequently to longer implementation period and 30% increase in cost. It also shows that contractors add up to 20% for the client’s procurement procedure, approvals, and payment cycle. Additionally, bidders price risks related to accessibility to building sites, availability of building materials, and how trouble-prone is the region. The findings are of relevance to researchers, education planners, and practitioners as they are of high importance to policy makers and financiers whose main concern is to meet the growing need for school accommodation.

Nucleation of Condensed Phase in Water Vapor on the Nanostructured Surface of a β-AgI Crystal. 2. Free Energy

The free energy and work of nucleation of condensed water phase from vapor on a nanostructured basal face of a silver iodide crystal at 260 and 400 K have been calculated from the first principles of statistical mechanics by the Monte Carlo bicanonical statistical ensemble method. Relatively large structural elements have been represented by regularly repeating truncated pyramids with a base size of 8 nm and a height of 3 nm. For the interactions, a detailed model has been employed, which comprises the Ewald summation of long-range electrostatic and polarization interactions with the substrate. The dependences of the free energy and work of nucleation on the sizes of nuclei have been compared with the corresponding dependences for a smooth basal face of the crystal. Surface nanostructuring increases the thermodynamic stability of the nuclei by an order of magnitude and “extends” the process of their growth by five to six orders of magnitude to the region of lower pressures. Relatively large sizes of the nanostructure elements promote a decrease in the free energy of the uptake of water molecules at an initial stage of nucleation.

Surface Morphology and Magnetic Properties of (Sm,Gd)Fe2 With Laves Phase Structure

The magnetic and magnetostrictive properties of single-phase SmFe 2 and GdFe 2 alloys made by induction melting were investigated and compared. Atomic force and magnetic force microscopy were used to study the surface features of the alloys. Both alloys were granular; large structural elements consisted of finer grains, 40 to 80 nm in size. On the surface of a polished section of GdFe 2 , several types of magnetic domains structure were evident. Some areas had an absence of magnetic structure. A polished section of SmFe 2 had a pronounced domain structure of complex shape, consisting of islands 6 to 12 μm in size and bands 3 to 5 μm wide.

Processing Ultrasonic Data by Coda Wave Interferometry to Monitor Load Tests of Concrete Beams.

Ultrasonic transmission measurements have been used for decades to monitor concrete elements, mostly on a laboratory scale. Recently, coda wave interferometry (CWI), a technique adapted from seismology, was introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete laboratory samples and even large structural elements without having a transducer directly at the place where the change is taking place. Here, several load tests until failure on large posttensioned concrete beams have been monitored using networks of embedded transducers. To detect subtle effects at the beginning of the experiments and cope with severe changes due to cracking close to failure, the coda wave interferometry procedures had to be modified to an adapted step-wise approach. Using this methodology, we were able to monitor stress distribution and localize large cracks by a relatively simple technique. Implementation of this approach on selected real structures might help to make decisions in infrastructure asset management.

The indicator side of tree microhabitats: A multi‐taxon approach based on bats, birds and saproxylic beetles

Abstract National and international forest biodiversity assessments largely rely on indirect indicators, based on elements of forest structure that are used as surrogates for species diversity. These proxies are reputedly easier and cheaper to assess than biodiversity. Tree microhabitats—tree‐borne singularities such as cavities, conks of fungi or bark characteristics—have gained attention as potential forest biodiversity indicators. However, as with most biodiversity indicators, there is a lack of scientific evidence documenting their quantitative link with the biodiversity they are supposed to assess. We explored the link between microhabitat indices and the richness and abundance of three taxonomic groups: bats, birds and saproxylic beetles. Using a nation‐wide multi‐taxon sampling design in France, we compared 213 plots located inside and outside strict forest reserves. We hypothesized that the positive effect setting aside forest reserves has on biodiversity conservation is indirectly due to an increase in the proportion of large structural elements (e.g., living trees, standing and lying deadwood). These, in turn, are likely to favour the quantity and diversity of microhabitats. We analysed the relationship between the abundance and species richness of different groups and guilds (e.g., red‐listed species, forest specialists, cavity dwellers) and microhabitat density and diversity. We then used confirmatory structural equation models to assess the direct and indirect effects of management abandonment, large structural elements and microhabitats on the biodiversity of the target species. For several groups of birds and bats, the indirect effect of management abandonment and large structural elements on biodiversity was mediated by microhabitats. However, the magnitude of the link between microhabitat indices and biodiversity was moderate. In particular, saproxylic beetles’ biodiversity was poorly explained by microhabitats, large structural elements or management abandonment. Synthesis and applications. Tree microhabitats may serve as indicators for bats and birds, but they are not a universal biodiversity indicator. Rather, compared to large structural elements, they most likely have a complementary role to biodiversity. In terms of forest management and conservation, preserving diversity of microhabitats at the local scale benefits several groups of both bats and birds.

GEOLOGICAL FACTORS AND PHYSICOCHEMICAL PROCESSES OF GROUNDWATER FORMATION IN THE TUNKA DEPRESSION

The article describes the complex hydrogeological conditions of the Baikal rift zone viewed as a large structural element and pioneers in distinguishing two independent hydraulic systems in the study area. Groundwater resources and compositions of groundwater in these two systems are generated in fundamentally different ways. In the deep sediment layers, groundwater generated due to sedimentation is at the stage of elision (exfiltration) water exchange. Active phase transition of clay minerals to hydromica causes an additional water release, and sedimentary water and regenerated groundwater infiltrate from the condensed clay strata to sandy horizons. This process is accompanied by decompaction, heaving sand, and high (extra-high) reservoir pressures. Nitrogen-rich water and carbonic thermal water associated with faults and fault nodes are widespread in the basement of the Tunka depression. The thermal water result from infiltration and, together with fresh water, represents a uniform hydraulic system. Its development is determined by the dynamics of infiltration water in the water-feeding area in the Tunka loaches. At different hypsometric levels of the hydrogeological section, nitrogen-rich water descends, while carbonic thermal water ascends, and these processes occur simultaneously. Our study is focused on the physicochemical processes of the interaction between groundwater and sedimentary and crystalline rocks. It shows that the ion-salt and gas compositions of not only nitrogen-rich thermal water, but also those of methane water and carbonic thermal water occur in the ‘water-rock’ system without involving any additional substance from external sources. Compared to other thermal water, the composition of carbonic water is formed in a more complex way: first, it goes through the stage of the nitrogen-rich thermal water while passing through the aluminosilicate rocks and only then interacts with the carbonate rocks and become carbonic. The formation of carbonic water is accompanied by intensive karst processes at depths, which are ceasing closer to the surface. As a result of degassing, an opposite process is activated: authigenic minerals and travertines are formed on the surface. Groundwater and its gas phase are involved in the formation of rocks with a negative temperature, which are abundant in the Tunka depression, as well as large positive forms of the relief. It is shown that the activity of groundwater is not limited to the role of a filler in the host rocks and an intermediary medium between different geospheres. Groundwater is an active agent that initiates, controls and implements many geological processes.

Delayed antibiotic prescription for upper respiratory tract infections in children under primary care: Physicians’ views

Background: Overprescribing antibiotics for common or inaccurately diagnosed childhood infections is a frequent problem in primary healthcare in most countries. Delayed antibiotic prescriptions have been shown to reduce the use of antibiotics in primary healthcare.Objective: The aim was to examine primary care physicians’ views on delayed antibiotic prescriptions to preschool children with symptoms of upper respiratory tract infections (URTIs).Methods: A questionnaire was sent to 1180 physicians working in general practice in the Capital Region of Denmark, between January and March 2015. The questions focused on physicians’ attitude and use of delayed antibiotic prescriptions to children with URTIs.Results: The response rate was 49% (n = 574). Seven per cent of the physicians often used delayed prescriptions to children with symptoms of URTI, but 46% believed that delayed prescription could reduce antibiotic use. The physicians’ views on delayed antibiotic prescription were significantly associated with their number of years working in general practice. Parents’ willingness to wait-and-see, need for reassurance, and knowledge about antibiotics influenced the physicians’ views. Also, clinical symptoms and signs, parents’ willingness to shoulder the responsibility, the capability of observation without antibiotic treatment, and structural factors like out-of-hour services were relevant factors in the decision.Conclusions: Most physicians, especially those with fewer years of practice, had a positive attitude towards delayed antibiotic prescription. Several factors influence the views of the physicians—from perceptions of parents to larger structural elements and years of experience.

Hierarchical stack filtering: a bitplane-based algorithm for massively parallel processors

With the development of novel parallel architectures for image processing, the implementation of well-known image operators needs to be reformulated to take advantage of the so-called massive parallelism. In this work, we propose a general algorithm that implements a large class of nonlinear filters, called stack filters, with a 2D-array processor. The proposed method consists of decomposing an image into bitplanes with the bitwise decomposition and then processes every bitplane hierarchically. The filtered image is reconstructed by simply stacking the filtered bitplanes according to their order of significance. Owing to its hierarchical structure, our algorithm allows us to trade-off between image quality and processing time, and to significantly reduce the computation time of low-entropy images. Also, experimental tests show that the processing time of our method is substantially lower than that of classical methods when using large structuring elements. All these features are of interest to a variety of real-time applications based on morphological operations such as video segmentation and video enhancement.

Responses of riparian plants to habitat changes following restoration of channelized streams

AbstractThe ecological effects of stream restoration were evaluated by comparing riparian vegetation, flooding, and habitat properties between channelized and two types of restored streams in northern Sweden. Channelized streams were straightened and cleared of in‐stream boulders and wood >50 years ago to facilitate timber floating. Basic restoration (performed 8–10 years ago) returned cleared material back to the channels, and enhanced restoration (3 years ago) added large structural elements (boulders and downed trees) to previously basic‐restored streams. Riparian inundation duration increased only after enhanced restoration. Similarly, enhanced‐restored reaches had the highest amount of substrate available for plant establishment compared to channelized and basic‐restored streams. In contrast, soil biochemical properties (pH and C:N ratio) did not improve following either restoration effort. Riparian plant cover was higher at both restored types than channelized reaches. Plant species richness was higher at plot‐scale level (0.25 m2) at both restored types in the most species‐rich elevation levels compared to channelized reaches, whereas at the reach‐scale (>700 m2 of riparian area), species richness did not differ among stream types. Similarly, species composition segregated between channelized and restored reaches only at the plot scale. We found no significant differences in riparian vegetation between the two restored types. The lack of positive responses of vegetation to enhanced restoration and to variables that changed immediately after restoration (inundation, habitat area) implies that responses were either slower than expected or the changes in hydrology and substrate availability were not as important for riparian flora as believed.

Grenville tectonic events and evolution of the Yenisei Ridge at the western margin of the Siberian Craton

Geological, petrologic, geochemical, and isotopic geochronological evidence for Grenville events at the western margin of the Siberian Craton are considered. These events were related to assembly of the Rodinia supercontinent. Multiple manifestations of riftogenic and within-plate magmatism at the final stage of orogenic evolution gave rise to breakdown of Rodinia and the formation of the Paleoasian ocean. The results allowed us to develop a new concept on the Precambrian geological evolution of the Yenisei Ridge and the processes that created its tectonic structure. The chronological sequence of events in the history of the Transangarian Yenisei Ridge is based on geological evidence and isotopic dating of Precambrian complexes variable in geodynamic nature. Four tectonic stages dated at 1.4−1.1, 1.1−0.9, 0.90−0.85, and 0.8−0.6 Ga were controlled by collision and extension recognized from large regional linear crustal structural elements. The evolution of the Transangarian Yenisei Ridge, which lasted for ∼650 Ma, corresponds in duration to supercontinental cycles that begin from rifting and breakdown of the predated supercontinent and was completed by orogeny and the formation of a new supercontinent. The regional geodynamic history correlates with the synchronous sequence and similar style of tectonothermal events at the periphery of the large Precambrian Laurentia and Baltica cratons. This is evidenced by paleocontinental reconstructions, which confirm close spatiotemporal links of Siberia with cratons in the northern Atlantic 1400−600 Ma ago and indicate incorporation of the Siberian Craton into the ancient Nuna and Rodinia supercontinents.

Size dependent response of large shell elements under in-plane tensile loading

Large-scale thin-walled structures with a low weight-to-stiffness ratio provide the means for cost and energy efficiency in structural design. However, the design of such structures for crash and impact resistance requires reliable FE simulations. Large shell elements are used in those simulations. Simulations require the knowledge of the true stress–strain response of the material until fracture initiation. Because of the size effects, local material relation determined with experiments is not applicable to large shell elements. Therefore, a numerical method is outlined to determine the effect of element size on the macroscopic response of large structural shell elements until fracture initiation. Macroscopic response is determined by introducing averaging unit into the numerical model over which volume averaged equivalent stress and plastic strain are evaluated. Three different stress states are considered in this investigation: uniaxial, plane strain and equi-biaxial tension. The results demonstrate that fracture strain is highly sensitive to size effects in uniaxial tension whereas in plane strain or equi-biaxial tension size effects are much weaker. In uniaxial and plane strain tension the fracture strain for large shell elements approaches the Swift diffuse necking condition.

Watershed segmentation based on gradient relief modification using variant structuring element

Watershed segmentation is suitable for producing closed region contour and providing an accurate localization of object boundary. However, it is usually prone to over-segmentation due to the noise and irregular details within the image. For the purpose of reducing over-segmentation while preserving the location of object contours, the watershed segmentation based on morphological gradient relief modification using variant structuring element (SE) is proposed. Firstly, morphological gradient relief is decomposed into multi-level according to the gradient values. Secondly, morphological closing action using variant SE is employed to each level image, where the low gradient level sets use the large SE, while the high gradient level sets use the small one. Finally, the modified gradient image is recomposed by the superposition of the closed level sets, and watershed transform to the modified gradient image is done to implement the final segmentation. Experimental results show that this method can effectively reduce the over-segmentation and preserve the location of the object contours.

Granitoids in the basement of the Kurile island arc system

The Kurile island arc system consists of three large structural elements: the frontal zone, the Greater Kurile Ridge, and the backrc zone adjacent to the latter on the side of the Sea of Okhotsk in the form of submarine volcanic ridges. The frontal zone includes the Pacific slope of the Kurile arc consisting of the underwater Vityaz Ridge and islands of the Lesser Kurile Ridge. It touches the Pacific Plate, and the sea bottom in this area hosts outcrops of the basement of the entire island system. The data on the composition and age of the basement are of importance for solving the problem of the origin of the island arc, since they allow the onset of its formation and evolution to be reconstructed. The evidence for interpreting the composition of the basement beneath the Greater Kurile Ridge was provided only by single finds of metamorphic and intrusive rocks occurring in the form of xenoliths in lavas of the Kurile Islands (1). Based on these findings, Sergeev (2) assumed the presence of the Hercynian or Mesozoic folded basement under this structure, while Vasil'ev (3) believes that the entire island block and Vityaz Ridge represent constituents of the folded domain formed at terminal stages of the Mesozoic orogeny.

A Novel Algorithm of Edge Location Based on Omni-directional and Multi-scale MM

In order to suppress image noise effectively and extract the edge clearly and accurately, a novel approach based on omni-directional and multi-scale mathematical morphology for edge detection is proposed in this paper. In order to compare different object geometries a modified Hausdorff distance application is composed. With a new moments rule used, Opening operation and closing operation of large scale structural elements are adopted for suppression of noise, while small scale structural elements are used for edge extraction. Finally, the weighting combination calculation of edge maps acquired under different directions is executed according to different weights. The experimental results show that the improved algorithm has a great promotion in extracting edge information compared with several reference algorithms.

Versatile Assembly Systems for Large Components on the Example of the Aircraft Structure Assembly

At present, large components in airplane structural assembly are assembled with the aid of large fixed or partly adjustable devices dedicated to the relevant version. Some of the disadvantages of these systems are the limited range of possible adjustments of the handling devices and low flexibility. This restricts the assembly of different versions or products because the equipment cannot be adequately adapted to the version-specific requirements and geometry of the product. This paper describes a solution for a versatile assembly system for large structural elements which can be configured according to specific requirements employing a modular mechatronic building block with reconfigurable handling modules (robots). Motivation

Fibroblast growth on micro- and nanopatterned surfaces prepared by a novel sol–gel phase separation method

Physical characteristics of the growth substrate including nano- and microstructure play crucial role in determining the behaviour of the cells in a given biological context. To test the effect of varying the supporting surface structure on cell growth we applied a novel sol-gel phase separation-based method to prepare micro- and nanopatterned surfaces with round surface structure features. Variation in the size of structural elements was achieved by solvent variation and adjustment of sol concentration. Growth characteristics and morphology of primary human dermal fibroblasts were found to be significantly modulated by the microstructure of the substrate. The increase in the size of the structural elements, lead to increased inhibition of cell growth, altered morphology (increased cytoplasmic volume), enlarged cell shape, decrease in the number of filopodia) and enhancement of cell senescence. These effects are likely mediated by the decreased contact between the cell membrane and the growth substrate. However, in the case of large surface structural elements other factors like changes in the 3D topology of the cell's cytoplasm might also play a role.

The first sanctuary of the second cathedral of Gyulafehérvár (Alba Iulia, RO)

Abstract The study focuses on some original parts of the second building of Gyulafehervar cathedral which are now missing, such as its original sanctuary, which was demolished soon after completion and replaced by another. Also discussed are a number of carvings used in a secondary or tertiary setting, as spolia, originally made around 1200 or at the beginning of the 13th century, and then removed from their original context. Fragments of chevron-decorated carvings can be arranged along an arch that, because of its size, can only be identified with the transverse arch of the original apse of the sanctuary. The transverse arch on the face of the Gyulafehervar apse, built around 1200, was – as far as we know today – the largest structural element in Central Europe decorated with a “Norman” chevron ornament. From the exterior decoration of the original apse a surprisingly large number of richly decorated details still survive. The entablature high on top of the polygonal apse of the present-day sanctuary is ...

Application of the morphological alpha shape method to the extraction of topographical features from engineering surfaces

In contrast to the mean-line based filters, morphological filters are function oriented and more suitable for the functional prediction of component performance. This paper presents a novel morphological method based on the alpha shape for the extraction of topographical features from engineering surfaces. Compared to the traditional implementation of morphological filters, the alpha shape method is more efficient in performance for large structuring elements. The resulting envelope follows the form of the surface all over such that the distortions caused the end effects are avoided. A series of measured surfaces from the automotive cylinder liner and the bioengineering artificial femoral heads are analyzed using the morphological alpha shape method. The topographical features are successfully extracted, enabling further physical and tribological analysis to the components.

Evolution of a new function in an esterase: simple amino acid substitutions enable the activity present in the larger paralog, BioH

Gene duplication and divergence are essential processes for the evolution of new activities. Divergence may be gradual, involving simple amino acid residue substitutions, or drastic, such that larger structural elements are inserted, deleted or rearranged. Vast protein sequence comparisons, supported by some experimental evidence, argue that large structural modifications have been necessary for certain catalytic activities to evolve. However, it is not clear whether these activities could not have been attained by gradual changes. Interestingly, catalytic promiscuity could play a fundamental evolutionary role: a preexistent secondary activity could be increased by simple amino acid residue substitutions that do not affect the enzyme's primary activity. The promiscuous profile of the enzyme may be modified gradually by genetic drift, making a pool of potentially useful activities that can be selected before duplication. In this work, we used random mutagenesis and in vivo selection to evolve the Pseudomonas aeruginosa PAO1 carboxylesterase PA3859, a small protein, to attain the function of BioH, a much larger paralog involved in biotin biosynthesis. BioH was chosen as a target activity because it provides a highly sensitive selection for evolved enzymatic activities by auxotrophy complementation. After only two cycles of directed evolution, mutants with the ability to efficiently complement biotin auxotrophy were selected. The in vivo and in vitro characterization showed that the activity of one of our mutant proteins was similar to that of the wild-type BioH enzyme. Our results demonstrate that it is possible to evolve enzymatic activities present in larger proteins by discrete amino acid substitutions.

THE EFFECT OF FOUNDATION ROCKING OF SHEAR WALLS ON THE BEHAVIOR OF DUAL SYSTEMS SUBJECTED TO EARTHQUAKE LOADS

In most design cases of buildings, design engineers assign shear walls the total seismic loads while the frames (columns and beams) take the gravity loads. It is customary to assume that cantilever model of the building structure is fully restrained against rotations at the base. It is recognized, however, that full base fixity for such large structural elements is very difficult, if not impossible, to achieve. Base rotation is a vital component of wall deformations. Therefore, it significantly affect the stiffness of cantilever walls and hence possibly their share in the lateral force resistance within elastic dual systems. The reluctance by designers to address the problem could be attributed to difficulties to estimate reliably stiffness properties of soils and to find a representative model of problems. The Dual systems of building are being studied by formulating several mathematical models covering buildings with shear walls and frames that have different heights and walls stiffness extending between high and low stiffness values relative to the total stiffness of the building. An equivalent static analysis has been carried out on these models to show the effect of shear wall-frame rocking on the wall-frame interaction in terms of internal forces and deformations. At the end of this study, the most important results and recommendations are summarized, especially the necessity of considering the interaction between frames system and shear walls system. It was proven that, the effect of shear walls rocking will be important when the stiffness of these walls is large relative to the stiffness of the building.