Showing papers by "University of Architecture, Civil Engineering and Geodesy published in 2019"

Changing climate both increases and decreases European river floods

Abstract: Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere1. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe2. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe3, because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results—arising from the most complete database of European flooding so far—suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century4,5, suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management. Analysis of a comprehensive European flood dataset reveals regional changes in river flood discharges in the past five decades that are consistent with models suggesting that climate-driven changes are already happening.

Twenty-three unsolved problems in hydrology (UPH)–a community perspective

Abstract: This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

Effect of Selenium Biofortification and Beneficial Microorganism Inoculation on Yield, Quality and Antioxidant Properties of Shallot Bulbs

Abstract: Plant biofortification with selenium in interaction with the application of an arbuscular mycorrhizal fungi (AMF)-based formulate, with the goal of enhancing Se bioavailability, is beneficial for the development of the environmentally friendly production of functional food with a high content of this microelement. Research was carried out in order to assess the effects of an AMF-based formulate and a non-inoculated control in factorial combination with two selenium treatments with an organic (selenocystine) or inorganic form (sodium selenate) and a non-treated control on the yield, quality, antioxidant properties, and elemental composition of shallot (Allium cepa L. Aggregatum group). Selenocystine showed the best effect on the growth and yield of mycorrhized plants, whereas sodium selenate was the most effective on the non-inoculated plants. The soluble solids, total sugars, monosaccharides, titratable acidity, and proteins attained higher values upon AMF inoculation. Sodium selenate resulted in higher soluble solids, total sugars and monosaccharide content, and titratable acidity than the non-treated control, and it also resulted in higher monosaccharides when compared to selenocystine; the latter showed higher protein content than the control. Calcium, Na, S, and Cl bulb concentrations were higher in the plants inoculated with the beneficial microorganisms. Calcium and sodium concentrations were higher in the bulbs of plants treated with both the selenium forms than in the control. Selenocystine-treated plants showed enhanced accumulation of sulfur and chlorine compared to the untreated plants. The AMF inoculation increased the bulb selenium content by 530%, and the Se biofortification with selenocystine and sodium selenate increased this value by 36% and 21%, respectively, compared to control plants. The AMF-based formulate led to increases in ascorbic acid and antioxidant activity when compared to the non-inoculated control. The bulb ascorbic acid was increased by fortification with both selenium forms when compared to the non-treated control. The results of our investigation showed that both AMF and selenium application represent environmentally friendly strategies to enhance the overall yield and quality performances of shallot bulbs, as well as their selenium content.

Reaction products, structure and properties of alkali-activated metakaolin cements incorporated with supplementary materials – a review

Abstract: Incorporation of mineral blending and/or modifying additions which are single- or multi-component materials is one of the main trends in the development of both Portland clinker-based and non-clinker cements. There is an increasing scientific and industrial interest in alkali-activated binders as ecologically and technically promising inorganic materials. Progress in this area is also derived from advances in the technologies of production and processing of a wider range of mineral materials from natural and waste origins, and by constant expansion of the raw materials base of alkali-activated materials. This paper reviews (i) alkali-activated metakaolin-based cements incorporated with mineral supplementary materials from the point of view of the supplementary additions raw materials base, features of reaction products, structure, properties and formation process; (ii) a range and classification of mineral additions to alkali-activated metakaolin cements; (iii) the feasibilities of improving the structure and properties of mixed alkali-activated metakaolin cements.

Toward clean cement technologies: A review on alkali-activated fly-ash cements incorporated with supplementary materials

Abstract: The consistent development of the waste-minimisation and recycling-oriented technologies in the most resource- and energy-intensive industries is crucial for sustainable development. Chemical activation based on a non-fired or low-temperature approach for the production of binders from glassy aluminosilicates, including a wide range of wastes and by-products from different industries, is an intensively developing and promising clean technology that finds application in construction and building materials, management of hazardous and nuclear waste, etc. Blended binders are designed using a mixture of mineral materials as a tool, through the regulation of composition and structure, to obtain materials with controlled performance. The resulting materials in turn improve engineering performance and aid the valorisation of different types of wastes and by-products. This is one of the main trends in the development of the modern cement industry, including the alkali activation technology. Coal fly ash is one of the large-tonnage wastes that is effectively converted by alkali activation in binders and compatible with many mineral supplementary materials. This paper reviews (i) the supplementary mineral materials of natural and waste origin from different industries for alkali activated fly ash (class F) cements (AAFA); (ii) the composition, structure, and properties formation process of AAFA incorporated with blending and modifying materials, and (iii) the feasibility for improvement of the structures and properties of mixed AAFA.

Flexible PDMS-based triboelectric nanogenerator for instantaneous force sensing and human joint movement monitoring

Abstract: Flexible wearable sensors with excellent electric response and self-powered capability have become an appealing hotspot for personal healthcare and human–machine interfaces. Here, based on triboelectric nanogenerator (TENG), a flexible self-powered tactile sensor composed of micro-frustum-arrays-structured polydimethylsiloxane (PDMS) film/copper (Cu) electrodes, and poly(vinylidenefluoride–trifluoroethylene) (P(VDF-TrFE)) nanofibers has been demonstrated. The TENG-based self-powered tactile sensor can generate electrical signals through the contact-separation process of two triboelectric layers under external mechanical stimuli. Due to the uniform and controllable micro-frustum-arrays structure fabricated by micro-electro-mechanical system (MEMS) process and the P(VDF-TrFE) nanofibers fabricated by electrostatic spinning, the flexible PDMS-based sensor presents high sensitivity of 2.97 V kPa−1, stability of 40,000 cycles (no significant decay), response time of 60 ms at 1 Hz, low detection pressure of a water drop (~4 Pa, 35 mg) and good linearity of 0.99231 in low pressure region. Since the PDMS film presents ultra-flexibility and excellent-biocompatibility, the sensor can be comfortably attached on human body. Furthermore, the tactile sensor can recognize various types of human body movements by the corresponding electrical signals. Therefore, the as-prepared TENGs are potential on the prospects of gesture detection, health assessment, human-machine interfaces and so on.

Energy Parameters of the Binder during Activation in the Vortex Layer Apparatus

Abstract: Improving the efficiency of construction composites is a relevant problem for modern-day material science. One of the ways to solve the problem consists in activating the binders by means of vortex-layer devices. Mathematical transformations produced a formula for calculating the dependency of the number of ferromagnetic-particle collision on the number and velocity of such particles, as well as on the device chamber fill factor. The results obtained by applying the proposed formula differ from D.D. Logvinenko's model by 10% at max. We calculated the impact force, the impulse of the grinding body in the vortex-layer device, as well as the amount of applied energy per unit of mass of the ground material. It was found out that the impact force and the impulse of force were maximized in the test device. At the same time, energy applied over the grinding time necessary to even out the binder dispersion in the vortex-layer device was 2 to 4.8 times greater compared to conventional devices.

Modified Kantorovich operators with better approximation properties

Abstract: In the present paper, we study a new kind of Bernstein-Kantorovich-type operators. Here, we discuss a uniform convergence estimate for this modified form. Also, some direct estimates, which involve the asymptotic-type results, are established. Some numerical examples which show the relevance of the results are considered.

Literature Review of Advances in Materials Used in Development of Alkali-Activated Mortars, Concretes, and Composites

Abstract: Materials providing an improvement and conformance to increasing technical and ecological requirements plays a crucial role in the sustainable development of resource- and energy-intensive ...

SiO2 loading into polydopamine-functionalized TiO2 nanotubes for biomedical applications

Abstract: A recent advancement in bone therapies is the development of advanced implants from arrays of titania nanotubes, which are fabricated with self-ordering electrochemical anodization of a Ti substrate. We have fabricated a novel interface by coating an anodized Ti substrate with polydopamine. This interface is suitable for the efficient incorporation of SiO2 nanoparticles into the porous layer of TiO2 nanotubes formed on the underlying Ti substrate. The results of different characterization tests indicate that the nanoparticles are evenly incorporated into the titania nanotube arrays. Potentiodynamic polarization curves and electrochemical impedance spectra measurements in a solution of simulated body-fluid indicate that the composite layer of SiO2 nanoparticles and the titania-nanotube arrays were more corrosive-resistant than the layer of titania-nanotubes arrays. Its hydrophilic properties and surface roughness are enhanced with the incorporation of SiO2 nanoparticles. As shown by in-vitro cellular assays, cell attachment and alkaline phosphate activity on such composite layer improved. The polydopamine/anodization treatment of Ti substrates allows the quick integration of SiO2 with titania nanotubes to increase corrosive resistance and biocompatibility of the Ti substrate. This could be a new approach to investigating the collective effects of local chemistry of compounds, e.g., SiO2, and of local topography of titania nanotubes.

A new approach to predict the compression index using artificial intelligence methods

Abstract: The compression index is one of the important geotechnical parameters, essential for the structural design. Since the determination of the compression index based on oedometer tests is relatively expensive and time-consuming, different authors have proposed for its estimation models using regression analysis and artificial neuron networks. However, they have ignored several parameters that could have increased the predictive capability of models. Other studies have concluded that genetic programming could have yielded better results. Unfortunately, no compression index models or effective comparisons of different methods have been published. The aim of this study is to propose a novel approach for estimating the compression index more accurately. To test the approach, a comparison study using K-fold cross-validation technique was conducted utilizing several models of multilayer neural networks, genetic programming, and multiple regression analysis. These models have been applied to 373 oedometer t...

A refined sin hyperbolic shear deformation theory for sandwich FG plates by enhanced meshfree with new correlation function

Abstract: The moving Kriging interpolation-based (MKI) meshfree method is extended to mechanical behavior analysis of isotropic and sandwich functionally graded material plates. The MKI meshfree method, which is free of shear correction factors effect in plate analysis, is further enhanced by introducing a new multi-quadric correlation function, eliminating drawbacks of its conventional form, gaining accurate solution. In this paper, a new refined sin hyperbolic shear deformation plate theory (N-RSHSDT) is introduced for plate kinematics. The present theory gives rise to four governing equations only, and achieves the sin hyperbolic distribution of the transverse shear strains through the plate thickness. To show the accuracy and effectiveness of the developed method, numerical experiments are performed for both isotropic and sandwich composite plates.

Enhanced meshfree method with new correlation functions for functionally graded plates using a refined inverse sin shear deformation plate theory

Abstract: This paper presents a new numerical approach based on an effective meshfree method integrated with a refined inverse sin shear deformation plate theory to perform static bending, free vibration and buckling analysis of functionally graded plates. The present formulation is based on a refined inverse sin shear deformation theory (R-ISSDT). Unlike other traditional plate theories, the theory presented gives rise to only four governing equations, does not require shear correction factor , and captures the parabolic variation of the transverse shearing stresses through the thickness of the plate. In the formulation of the meshfree method a new correlation function is proposed which effectively eliminates the correlation parameters. After proposing the formulation of the problem, numerical examples are provided and the obtained results are compared with those found in literature.

Superconvergent gradient recovery for virtual element methods

Abstract: Virtual element method is a new promising finite element method using general polygonal meshes. Its optimal a priori error estimates are well established in the literature. In this paper, we take a...

Infrared small-target detection based on multi-directional multi-scale high-boost response

Abstract: As of late, infrared (IR) small-target detection technology is broadly utilized in low-altitude monitoring frameworks, target-tracking frameworks, precise guidance frameworks and forest fire prevention frameworks. In this paper, we propose an infrared small-target detection strategy based on multi-directional multi-scale high-boost response (MDMSHB). First, an eight-direction filtering template is proposed, which can consider the directional information of the image and significantly suppress heterogeneous background such as cloud, linear interference and interface like ocean–sky background. Then, a map based on multi-directional multi-scale high-boost response (MDMSHB map) is calculated. Finally, a straightforward threshold segmentation technique is utilized to get the detection result. The simulation results comparing this method with the four state-of-the-art strategies in six sequences demonstrate that the proposed strategy can adequately suppress heterogeneous background and arbitrary noise. The approach can improve detection rate and reduce false alert rate as well.

Specific absorption rate in Zn-doted ferrites for self-controlled magnetic hyperthermia

Abstract: In this paper, we study mixed ferrites nanoparticles with structure formula Me1−xZnxFe2O4 (Me = Co, Ni, Cu, Mn) appropriated for self-controlled magnetic hyperthermia (SMHT) for in vivo and in vitro applications. We discuss in details the influence of the size d, the Zn-ion concentration x on the magnetic characteristics: saturation magnetization MS, coercivity HC, effective anisotropy Keff and specific absorption rate (SAR). From a theoretical point of view we investigate monodispersed, non-interactive, single-domain spherical magnetic nanoparticles (MNPs). We propose a simple core–shell model with a constant thickness of the surface layer. We explain the behaviour of SAR as a function of size and dopping based on two thermal heating mechanisms: the mechanism leading to dynamic hysteresis loops of superparamagnetic origin and the heating mechanism via conventional metastable hysteresis. We investigate also a thermal heating efficiency based on the Zn-ion concentration. We show that whether SAR decreases (increases) when doping increases depends on whether the nanoparticle diameter d is smaller (larger) than the particle size dmax for which SAR has a maximum value. The numerical results are in qualitative agreement with many experimental data.

Distributed coordination control for suppressing circulating current in parallel inverters of islanded microgrid

Abstract: This study proposes a distributed hierarchical coordination control paradigm for parallel inverters, which not only enhances the flexibility of plug and play architecture but also strengthens the accuracy of current sharing with low sensitivity to the different line impedances and with fast response to the transient current change in islanded microgrid. Two kinds of distributed coordinated controller are designed to remove the voltage and frequency deviation from primary control. One is proportional-integral-derivative-based control, which detects the error between the segmented reference current and the actual measured current of the local inverter to calculate the compensating control input of the primary controller. The other is consensus-based control, which uses distributed control actions to spread local information among neighbouring distributed units. To improve the robustness of consensus algorithm, the authors take a relative value instead of absolute value from the primary control as the consensus variable to achieve accurate current sharing among different nominal power rating inverters. Then, a detailed small-signal state-space model is developed with the proposed secondary cooperated controller to achieve the stability analysis and parameters design purpose. Finally, an islanded MG test system is built in MATLAB/Simulink and control performances of two strategies are verified and compared.

Learning Behavior Analysis in Classroom Based on Deep Learning

Abstract: In this work, we study learning behavior analysis for automatic evaluation of the classroom teaching. We define five classroom learning behaviors including listen, fatigue, hand-up, sideways and read-write, and construct a class-room learning behavior dataset named as ActRec-Classroom, which includes five categories with 5,126 images in total. With the aid of convolutional neural network (CNN), we propose a classroom learning behavior analysis system framework. Firstly, Faster R-CNN is used to detect human body. Then OpenPose is used to extract key points of human skeleton, faces and fingers. Finally, a CNN based classifier is designed for action recognition. Extensive experiments validate the proposed system. The validation accuracy reaches 92.86% on average, and it meets the need of learning behavior analysis in the real classroom teaching environment.