Based on multiteam system (MTS) theory and creativity theory, this study explores the influencing factor model of multiteam digital creativity (MTDC) in the action phase through two cross-validation ...studies, filling a theoretical gap and responding to the research call. Study 1 is a qualitative analysis method to fully explore the relevant influencing factors and enhance the theoretical saturation. Study 2 is an optimized DEMATEL method, known as the CL-WG DEMATEL analysis method, which cross-validates the new theoretical model and measures the centrality of the influencing factors. This study finds that the influence factor model of MTDC has eight major factors and distributes in four different levels. Further analysis shows that the three influences (team digital ability, multiteam digital sharing, and organizational digital resource matching) with the highest centrality of impact on MTDC all belong to the collective level, which indicates the uniqueness of the action phase of the performance episodes. The two cross-validation studies enhance the scientific validity of the new theoretical exploration. In addition, Theoretical and practical implications of the results are presented, and future directions for research are discussed.
In this letter, a printed broadband metasurface (MTS) antenna fed by an aperture coupling through a coplanar waveguide (CPW) is introduced. To achieve the wideband impedance matching, a technique of ...loading an MTS radiator formed by nonuniform patch elements above a stair-shape aperture is applied. The stair-shape aperture is attached to the end of the CPW. The proposed antenna is simple and low-profile in structure, which can be realized by a single-layer printed circuit board (PCB) substrate. To verify the concept, a prototype with an overall size of 1.28 λ 0 × 1.28 λ 0 × 0.09 λ 0 , where λ 0 is the free-space wavelength at 7 GHz, is fabricated. The proposed antenna realizes a wide impedance bandwidth of 67.3% with reflection coefficient ≤ -10 dB and peak gain of 9.18 dBi. The measurement results agree well with the anticipation.
•The mixed-mode fracture behavior of rock-type U-notched specimens is studied experimentally and theoretically.•The Brazilian disk weakened by the central U-notches were tested under mixed mode I/II ...loading.•Based on the maximum tangential stress (MTS) criterion, a new simple approach (MTS-FEM) is suggested to predict the fracture resistance of U-notched samples.•The tangential stress component at critical distance from the notch border is obtained from finite element analysis in the MTS-FEM criterion.•The value of the critical distance in MTS-FEM is determined corresponding to the fracture toughness for any arbitrary U-notched sample.•It is shown that the MTS-FEM criterion is able to estimate the fracture resistance of U-notched rock samples very well.
The aim of this paper is to present a new approach for predicting the mixed-mode fracture resistance of rock-type specimens containing U-shaped notches. The new approach is a modified form of maximum tangential stress (MTS) criterion which states the fracture takes place when the maximum tangential stress at the critical distance from the notch border attains critical value. The critical distance in rock-type specimen is relatively large and the formulations presented in the conventional MTS for characterizing the tangential stress component cannot provide good estimates. Therefore, the modified MTS (MTS-FEM) criterion proposes that the value of maximum tangential stress at the critical distance is determined directly from finite element analysis. Several mixed-mode fracture tests were conducted on the Brazilian disks weakened by central U notches in order to evaluate the MTS-FEM criterion. The comparison between the fracture loads obtained from experiments and those predicted by the MTS-FEM criterion shows that the MTS-FEM criterion can provide good estimates for fracture loads of rock-type U-notched samples under mixed mode loading.
The Pécs-Danitzpuszta sand pit is the most important outcrop of the oldest Pannonian (upper Miocene, Tortonian) deposits in southern Hungary. A trench excavated in 2018 exposed Lake Pannon deposits ...and underlying Paratethys strata down to the upper Badenian (Serravallian), and together with the sand pit they make up a continuous sedimentary succession with a true thickness of ~220 metres. Due to tectonic deformation, middle Miocene deposits and carbonates in the lowermost Pannonian are overturned. Layers become vertical close to the marl-sand boundary, then the dip changes to normal, with continuously decreasing dip angles. The exposed succession starts with 5 m of upper Badenian (13.8-12.6 Ma old) calcareous marls and sandy limestones with sublittoral, then littoral molluscs, which were deposited in the normal salinity seawaters of the Central Paratethys. The overlying 8 m of sand, silt, sandy breccia and conglomerate are fossil-free,; only the lowermost silt layer contains reworked Badenian microfauna. This unit probably accumulated from gravity-driven flows in a fan-like, probably terrestrial depositional setting. The next 7.5 m of frequently alternating thin-bedded limestones, marls and clays with sublittoral biota represent rapid transgression. Foraminifers, ostracods, molluscs and calcareous nannoplankton indicate late Sarmatian, then Pannonian age for this interval. However, the locations of the boundaries indicated by the various groups are not are not consistent, making the position of the Sarmatian/Pannonian boundary uncertain. The Sarmatian beds with marine fossils still accumulated in the Paratethys, between ~12.1–11.6 Ma, under varying salinities due among others to temporary freshwater input. The Pannonian strata already represent sediments of the brackish Lake Pannon. Above these beds, uniform calcareous marl becomes dominant with some clay layers and graded or structureless conglomerate to sandstone interbeds. The deposition of the overall 64- m- thick Pannonian calcareous marl section took place in the open, probably few -hundred -metres -deep water of the lake between ~11.62 and 10.5–10.2 Ma. It may represent a rare, well-exposed surface occurrence of the Endrőd Formation which is known from thousands of wells in the Pannonian Basin. Above this section, a 6-7 -m- thick transitional interval of silty marls and sands is followed by ~140 m of limonitic, pebbly sands. They have poor to moderate sorting and rounding, metre -thick beds with transitional boundaries and abundant fossils and clasts reworked from older Miocene units. Their accumulation took place between 10.2-10.5 and 9.6 Ma by gravity flows connected to deep-water portions of fan deltas.
Floods are among the most dangerous geohazards in Central Europe. Their occurrence is often the result of the cumulative contribution of sub-catchments in the culmination zone of a mountain range, ...which subsequently has a devastating effect in the foreland. However, data on discharges from gauging stations are mostly missing from these sites (high-gradient streams), which are crucial to understanding the origin of floods in low-lying populated areas where they can cause significant damage. Therefore, this study focuses on an extensive reconstruction of flood events in 13 sub-catchments in the culmination zone of the Orlicke hory Mts. Flood events were reconstructed using dendrogeomorphic approaches, currently the most accurate absolute dating method. The analysis revealed 111 floods in all sub-catchments during the 34 to 84 year period by dating 844 growth disturbances in a tree-ring series of 632 trees (Picea abies (L.) Karst.) damaged during the floods. Regional reconstruction across the mountain range revealed events of regional and local significance, with no direct link between event magnitude and areal extent. This is consistent with the two dominant rainfall patterns identified that likely triggered the floods (short-term extreme rainfall and medium-term above-average rainfall). In particular, however, the study revealed several patterns of spatial transformation of flood events from source sub-catchments to their form captured at gauging stations in the foreland. The combination of various lines of evidence (geomorphic mapping, growth disturbance patterns, spatial pattern of flooding) suggests a limited erosional effect of most of the reconstructed events. The findings thus shed new light on the overall dynamics of floods in the mountain massif and their impact on flood discharges in the foreland.
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•A floods chronology was compiled from 13 sub-catchments in the Orlicke hory Mts.•111 flood events were dated using data from 632 disturbed trees.•Short-term extreme and medium-term above-average precipitation are the main triggers.•Patterns of flood transformation from source watersheds to forefields were revealed.
•A novel piezoelectric energy harvester (PEH) device using simple fabricated structures was proposed based on pavement environment.•MTS loading tests and a theoretical electromechanical model were ...developed to comprehensively evaluate the effects of working parameters on energy harvesting efficiency of the PEH device.•A new scaling law was established to guideline the design of the PEH device for enhancing the efficiency of energy harvesting by properly selecting the system parameters.
The traffic environment contains tremendous mechanical energy due to the dynamic loads of moving vehicles which can be converted into electricity by using piezoelectric materials. Considering the road environmental characteristics, we propose here a piezoelectric energy harvester (PEH) consisting of piezoelectric ceramics that are encapsulated in epoxy resin filler between the MC nylon protective plates. As an illustration, periodic traffic loading is considered and is simulated by a controlled MTS loading, using which the effects of various system parameters on the efficiency of energy harvesting are examined. A theoretical electromechanical model is also developed to predict the energy harvesting behavior of the PEH device. The theoretical predictions agree very well with the experimental measurements, and they both suggest that various load, material, and circuit factors will have diverse effects on output power. To figure out the best collection of all factors and their simultaneous effect on the output performance, we also establish a simple and universal scaling law to reveal the underlying mechanism of the correlation between various systematic parameters. The normalized output power depends only on the normalized intrinsic impedance that consists of all material properties, geometrical, electrical circuit, and loading condition parameters. The optimization strategy may provide a useful tool to guide the design of the PEH device for enhancing the efficiency of energy harvesting by properly selecting the system parameters.
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The paper presents the results of a novel 3-D shared aperture 3 × 3 matrix antenna-array for 26 GHz band 5 G wireless networks. Radiation elements constituting the array are hexagonal-shaped patches ...that are elevated above the common dielectric substrate by 3.35 mm and excited through a metallic rod of 0.4 mm diameter. The rod protrudes through the substrate of 0.8 mm thickness. It is shown that by isolating each radiating element in the array with a wall suppresses unwanted electromagnetic (EM) wave interactions, resulting in improvement in the antenna’s impedance matching and radiation characteristics. Moreover, the results show that by embedding hexagonal-shaped slots in the patches improve the antenna's gain and radiation efficiency performance. The subwavelength length slots in the patches essentially transform the radiating elements to exhibit metasurface characteristics when the array is illuminated by EM-waves. The proposed array structure has an average gain and radiation efficiency of 20 dBi and 93%, respectively, across 24.0–28.4 GHz. The isolation between its radiation elements is greater than 22 dB. Compared to the unslotted array the improvement in isolation between radiating elements is greater than 11 dB, and the gain and efficiency are better than 10.5 dBi, and 25%, respectively. The compact array has a fractional bandwidth of 16% and a form factor of 20×20×3.35 mm3.
Alkali-activated lightweight aggregates (LWAs) made of alkali-activated aluminosilicate-rich mine tailings (MTs) offer a promising alternative to natural lightweight aggregates. The comprehensive ...investigation of lightweight aggregate production using aluminosilicate-rich MTs in combination with commercial slag as a reactive aluminosilicate remains largely unexplored. In this study, mixtures of MTs and slag were pelletized through the application of a pan pelletizer machine. The study focused on examining the impact of different slag concentrations on the chemical, physical, mechanical, mineralogical, and morphological properties of the produced LWAs. Furthermore, a comparison was made between the physical and mechanical characteristics of the resulting LWAs and those of flay-ash (FA)-based LWAs. The results revealed that the inclusion of slag in LWAs, as compared to FA, led to the production of LWAs with superior physical and mechanical properties. Specifically, as the slag content increases, the water absorption, dissolution, and porosity of LWAs significantly decreased, while the bulk density and compressive strength increased. It is important to note that these changes occur without affecting the specific gravity of the LWAs. The scanning electron microscope (SEM) images clearly showed that the addition of slag, similar to FA, especially at concentrations of more than 20% and higher, promoted uniform geopolymerization within the specimens. Furthermore, the energy-dispersive X-ray spectroscopy (EDS) analysis revealed that all LWAs with concentrations of 20% slag and higher exhibited a Si:Al ratio exceeding three, indicating a higher likelihood of geopolymer backbone formation. The X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses revealed that the alkali activation process led to the depletion of gypsum, originally present in the MTs, and the emergence of sodalite and zeolite in the LWAs. Thermogravimetric analysis (TGA) tests provided additional confirmation of the ongoing geopolymerization process in slag-based LWAs, particularly those containing 20% slag or higher.
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•10-30% slag addition increased LWAs' compressive strength by 22.38% and stiffness by 33.87%.•Geopolymerization in LWAs with ≤15% slag showed suboptimal results, with unreacted mica sheets present.•Successful geopolymerization is confirmed by the absence of clay mineral bands and the presence of Si-O bands in LWAs.•The slag-based LWAs exhibited superior physical and mechanical properties when compared to those made from FA.
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