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Abstract

Dynamic contact and impact problems are widely applicable. An accurate solution method for these kinds of problems can be used in many fields of mechanical engineering (e.g., cutting metalwork, cogwheel drives, etc.). However, the proper handling of the contact is problematic, as there emerges a substantial amount of nonlinearity in the displacement field. Therefore, a spurious high frequency oscillation is present in the solution. These oscillations must be avoided, as divergence can easily occur in the contact algorithm due to them. In order to eliminate this effect, the applied numerical method must be chosen and set properly. In this study, a comprehensive guide is provided for the appropriate selection of the proper numerical method and its parameters.

Open access

Abstract

In the Hydraulic Laboratory of the Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava the distribution of the flow velocity in a shaft intake structure was investigated on a physical model. The homogeneity of the flow velocity distribution in the intakes of turbines has a great influence on the turbine performance. Modern optical methods, particle image velocimetry and laser Doppler anemometry, were used to measure the flow velocity distribution in the model of the turbine intake. The particle image velocimetry method provides a record of the velocity field, while the laser Doppler anemometry method provides an accurate indication of the velocity at a given point. The flow velocity distributions in the examined profiles were measured by the particle image velocimetry and laser Doppler anemometry methods and the results were compared with each other.

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Abstract

On the basis of elaborating the connotation of intensive city block, it is pointed out that the intensive structure organization is the key to realize intensive city block. The order complexity of the block structure is formed by the close connection, overlapping of elements, the depth difference and their compound association. This paper constructs the basic pedigree of block structure design from three levels of street configuration, plot organization and building layout, and forms the derivation and comprehensive application strategy of pedigree from the organic linkage and compound of each other.

Open access

Abstract

Algae are an evolutionary model of success and colonize all suitable ecological niches including building material surfaces that have favorable characteristics. In the last 25 years, building physics measures were developed to reduce water availability, especially on external thermal insulation composite systems.

Investigations into the influence of coating formulations have so far primarily focused on binder systems, biocides and hygrothermal properties. Research on the algal susceptibility due to the fillers is not to be found, but these regularly constitute a large proportion of final coatings. The present work investigates the influence of magnesium-containing fillers in the process of algal colonization of free-weathered façade coatings and a defense-strategy by water-activated pigment composition.

Open access
Pollack Periodica
Authors:
Athmar Thamer Naiyf
,
Fahad Mohanad Kadhim
,
Samah Falah Hasan
, and
Muhammad Safa Al-Din Tahir

Abstract

The aim of this study is to design a pylon with an engineering structure that gives it support and strength and manufacture a pylon characterized by low cost, lightweight, and bearing the patient's weight. This study designed two pylon models and fabricated by additive manufacturing techniques. The polylactic acid polymer is used as the filament for the 3D printing of pylons. A force plate and tensile test with finite element method simulation ANSYS software were applied to the pylons to evaluate their performance. The results showed that 3D printed pylon with Y-section has enough strength under stress and good safety factor, and the ability to bear a high patient load without buckling and exceed the requirements to become instead of the metallic prosthetic pylons.

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Abstract

With the rapid importance of high-performance energy modeling of buildings, whole-building energy simulation engines are rapidly used in the decision-making process. However, there are tens of engines in the market, which makes the choice of design engine very challenging. This article provides a comparison of the applications of whole-building energy simulation to predict a significant number of systems. As a result, the selected engines will be compared to establish their characteristics and abilities. Nevertheless, the focus will be placed on: generic criteria; envelope; lighting; service hot water; Heating-ventilation; and renewable systems. However, the authors found that an engine could be used extensively in one system and has limited capabilities in another system.

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Abstract

Concrete-filled steel tube columns are widely used in civil engineering structures due to their excellent ductility, energy absorption capacity, ultimate load-bearing capacity, and seismic behavior. In this paper, a numerical study modeling of eight lightweight concrete and conventional concrete filled steel tubes was carried out using ABAQUS software, and the lateral load-carrying capacity of square and circular steel tubes under cyclic load was compared. The quarter and one-third height of the tubes was filled with concrete with respect to the pier's height, to improve the base performance of the piers. The results show that the capacity of steel tubes filled with lightweight concrete increased by 40%–70% regarding energy absorption. The square tubes showed better performance than the circular tubes in terms of yielding load, yielding displacement, and energy dissipation.

Open access

Abstract

To estimate and model explosion pressure rise in closed volumes, industrial applications require a simple method. Ideal gas model is capable to assume pressure rise values to 10% above to initial pressure. However, most of the explosion venting devices opens higher than this pressure range.

Extension of ideal gas model was carried out in this paper. Authors made some experimental studies in 20 L explosion sphere at ambient temperature and atmospheric initial pressure, with propane-air mixtures at different concentrations between 2.8 and 6.3 vol%. They measured pressure values inside the chamber during explosion and recorded at 9,600 Hz. Based on experimental studies, authors extended ideal gas model application range to 1.5 barg.

Open access

Abstract

This study investigates teacher learning and professional development in school-university partnership in Myanmar. This study explores teacher learning and professional development through engaging in a school-university partnership through mentoring activity. Research studies have shown mentoring can improve teachers' learning and professional development (Hargreaves & Fullan, 2000). A sequential explanatory mixed-methods design was applied in this study. Participants were 120 schoolteachers in the quantitative part while 4 participants were interviewed. This study aimed to answer how the impact of school-university partnership on teacher learning and professional development can be understood. To answer this research question, two groups of schoolteachers (mentor and non-mentors) and three groups of teachers based on communication level with student teachers were compared. The results showed that teachers who had mentoring experiences improved their professional skills and competencies more than non-mentor teachers mainly in the areas: pedagogical content knowledge, knowledge about learners' behaviours and characteristics and cross-curricular skills. Furthermore, teachers who had intensive communication with student teachers showed higher mean values in self-confidence, enjoyment in teaching and reflection on teaching practices and feeling like a responsible person in education. Findings from the qualitative part showed that teachers learned these skills and competencies through intensive collaborative activities such as discussing teaching and learning, guiding student teachers in their classroom management and planning a lesson and having a friendly conversation with them. Overall, this study confirms that engaging in school-university partnership through mentoring enhances mentors develop their self-confidence, and enjoyment in teaching as well as their professional knowledge and skills.

Open access

Abstract

The basidiomycetes yeast Trichosporon is widespread in the natural environment, but can cause disease, mainly in immunocompromised patients. However, there have been only few studies about this infection in Thailand. In this study, we characterized 53 Trichosporon spp. isolated from urine samples from patients admitted to a single hospital in Bangkok, Thailand over a one-year period from 2019 to 2020. The strains were identified using colony morphology, microscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and nucleotide sequence analysis of intergenic spacer 1 (IGS1). Fifty-one isolates were Trichosporon asahii, and the remaining isolates were Trichosporon inkin and other Trichosporon species. Three genotypes of IGS1—1, 3, and 7 were observed among T. asahii. The sensitivity of the yeasts to the antifungal drugs amphotericin B, fluconazole, and voriconazole ranged from 0.25 to >16 μg ml−1, 0.5–8 μg ml−1, and 0.01–0.25 μg ml−1, respectively. We investigated biofilm formation by the isolates, and no biofilm production was found in one isolate, low biofilm production in forty-four isolates, and medium biofilm production in six isolates. T. inkin produced biofilms at low levels, and Trichosporon spp. produced biofilms at medium levels. This research increases our understanding of the molecular epidemiology of Trichosporon spp. isolated from one university hospital in Bangkok, Thailand, and reveals their genetic diversity, antifungal susceptibility profiles, and capacity for in vitro biofilm production.

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