Energy harvesting devices based on the triboelectric and piezoelectric principles have been widely developed to scavenge wasteful and tiny mechanical energy into usable electrical energy. In ...particular, triboelectric energy harvesting generators with relatively simpler structure and piezoelectric fiber-based counterpart with extremely light weight compositions showed a very promising application in the self-powered sensors. In this paper, a novel hybridization of graphenebased piezoelectric generator (GBPG) and graphene-PET triboelectric generator (GPTG) were simultaneously packaged. The integrated structure, graphene-based hybridized self-powered sensor (GHSPS), was demonstrated to be optically transparent and mechanically robust. For the piezoelectrically harvesting device, an in-situ poling and direct-write near-field electrospinning (NFES) Poly(vinylidene fluoride) (PVDF) piezoelectric fibers were fabricated and integrated with a single layer chemical vapor deposition (CVD) grown graphene. On the other hand for GPTG counterpart, two composite layers of a single layer graphene/PET simultaneously served as triboelectrically rubbing layers as well as bottom/top electrode. This GHSPS successfully superimposed both piezoelectric and triboelectric electricity and the synergistically higher output voltage/current/power were measured as ~6 V/280 nA/172 nW in one press-and-release cycle of finger induced motion. The proposed GHSPS showed a promising application in the field of self-powered sensors to be ubiquitously implemented in the future Industry 4.0 scenarios.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We report on the phase stabilization of rhombohedral (rh-) In2O3 films on sapphire substrate deposited by metal organic chemical vapor deposition. With the help of a high-temperature nucleation layer ...and evolutionary structural selection of rhombohedral phase during the growth process, stable epitaxial growth of single crystalline rh-In2O3 is achieved. The mechanism of phase selective epitaxial growth is studied by means of high-resolution X-ray diffraction and transmission electron microscopy measurements. Furthermore, Raman spectroscopy measurements are carried out to investigate the phonon properties of rh-In2O3. Raman-active phonon modes of rh-In2O3 are first identified.
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IJS, KILJ, NUK, PNG, UL, UM
In this paper, a second-order, dual-band, band-pass frequency selective surface (FSS) with high selectivity is presented by cascading three-layers of periodic metallic arrays. The unit cell in both ...two exterior layers is composed of gridded-double square loops (G-DSLs) while the element in the middle layer is consisting of wire grid. The three layers are separated by two thin F4B-2 substrates with dielectric constant of 2.65 + 0.02
i
. The proposed FSS can provide multi-transmission poles and multi-transmission zeros. There are two transmission poles in each pass-band. The two pass-bands are separated by two transmission zeros. On the upper side of the second pass-band, other two transmission zeros are generated also. These transmission zeros lead to a wide out of band rejection and a fast fall off response on both sides of each pass-band. The simulation is implemented using full wave electromagnetic simulator CST Microwave Studio, the central frequencies of the two pass-bands are 12.7 and 17.4 GHz. In addition, the designed principle is described using equivalent circuit model (ECM). Furthermore, the prototype of the FSS is fabricated and measured. Both simulated and measured results demonstrated that the proposed FSS has the merits of incident angle stability from 0° to 60° for both TE and TM polarizations.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•The effect of in-situ TiB2 particles on microstructure evolution of AZ80 alloy during rolling was investigated.•The introduction of TiB2 particles can significantly improve the rolling ability of ...AZ80 alloy and inhibit edge crack.•TiB2 particles with fiber-like distribution improves the strength and ductility of AZ80 alloy simultaneously.•The strengthening and toughening mechanism of the TiB2/AZ80 composites was analyzed.
In-situ TiB2/AZ80 composite was prepared by a simple casting method, and then hot-rolling. Effects of TiB2 reinforcements on the microstructural evolution of composite were investigated. In-situ TiB2 particles could refine the as-cast grains of AZ80 alloy, and promote recrystallization through particle stimulated nucleation (PSN) effect. Due to the grain refinement and the PSN effect of TiB2, the twin induced recrystallization mode in AZ80 alloy is transformed into grain boundary and particle dominated recrystallization process in the TiB2/AZ80 composite, which suppresses the generation of coarse shear bands during rolling and improves the rolling ability. At the same time, the morphology of TiB2 particle clusters was continuously modified with the increase of rolling passes, and finally formed fiber-like distribution characteristics. Fine grain strengthening and thermal mismatch strengthening are the main strengthening mechanisms of the composite sheet. Internal toughening mechanisms are texture weakening, the proliferation of more<c+a>dislocations, higher Schmidt factor and more uniform strain distribution induced by the PSN effect. In addition, external toughening ones should attribute to bending and deflection of cracks resulting from fiber-like particle distribution characteristics. Thus, the strength and toughness of the TiB2/AZ80 composite were simultaneously enhanced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Insensitive munition assessments are required to carry out sympathetic detonation experiments, in which detonation of an explosive charge triggers detonation of another, and a chain reaction ...subsequency starts. In this paper, a numerical simulation method is developed to predict the sympathetic detonation behavior of fuze explosive trains, which includes the ignition and growth model, the Jones–Wilkins–Lee equations of state, and the constitutive relationship. The sympathetic detonation behaviors of a fuze is studied for a single donor and a single acceptor. The causes of sympathetic detonation of the fuze explosive trains are analyzed for different fragment and shock wave loading conditions. A sympathetic detonation criterion in different modes of loading is established, which provides a theoretical model for predicting the relationship between the detonation sequence and the placement distance of the fuze. The conclusions obtained in this paper can provide a reference for studying sympathetic detonation of fuze conditions.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The mechanism of oxygen exchange between the gas phase and Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxide was evaluated by considering the inhomogeneity of the oxide surface. The applicability of existing models for ...the analysis of the oxygen exchange mechanism was considered. A new model with a dissociation step was suggested. The rate-determining steps of the oxygen exchange process were revealed under different experimental conditions. The change in the rate-determining step occurred at 600–650 °C. The probable cause was considered taking into account the parameter of nonequivalency of adsorption centers. A relationship between the oxygen isotope redistribution rates and the rates of the elementary steps in a “gas phase–solid oxide” system was revealed.
It has already been proven that trees and shrubs, can efficiently remove particulate matter (PM) from air. However, almost nothing is known about PM accumulation by herbaceous plants (grasses and ...forbs) found in urban meadows. Meadows, unlike trees and shrubs, can be located close to roads, one of the main sources of PM in cites. The aim of this study was to investigate the tolerance to urban condition and PM accumulation in the immediate roads vicinity of selected plants species in urban meadows. PM accumulation of annual and perennial meadows was compared with that of lawns. Results were interpreted in the context of species composition, biomass production, soil conditions and ambient PM concentrations. Of the species grown in annual meadows, the highest PM accumulation was found in Achillea millefolium L., Chenopodium album L. and Echium vulgare L., while Centaurea scabiosa L., Echium vulgare L. and Convolvulus arvensis L. accumulated the largest amounts of PM in perennial meadows. PM deposition on plants was positively correlated with a feathery leaf shape. For species in the annual meadows, a positive correlation was also found between PM accumulation and the wax content on plants. The presence of hairs on leaves, leaf size and plant growth pattern had no effect on PM deposition on plants. PM accumulation in one square metre of urban meadow was on average greater than that of lawn, regardless of meadow species' composition, age and location. The greatest accumulation of PM was found in a perennial meadow with low biodiversity but the greatest biomass. It would appear that the biomass produced by meadows and canopy structure has a crucial impact on the amount of PM accumulated by meadow plants. The results obtained indicate that meadows could be an important element of nature-based solutions for mitigating air pollution in urbanised areas.
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•Urban meadows accumulate significant amounts of PM.•Meadows accumulate PM more effectively than traditional lawns.•Level of PM accumulation is determined by meadow biomass and architecture.•Morphology of herbaceous plants has little effect on PM accumulation.•Perennial herbaceous plants are well adapted to urban conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A numerical simulation is carried out to investigate the effect of the Helmholtz resonator capacity on the Hartmann whistle operating at high values of the nozzle pressure ratio using the turbulence ...model. The results of the present numerical simulations are compared to experimental data. The simulation results show that the frequency and amplitude of the Hartmann whistle with the Helmholtz resonator are obviously lower as compared to the conventional Hartmann whistle. Moreover, the Mach number contours and streamlines indicate that the Helmholtz resonator does not affect the shock-cell structure between the nozzle and the cavity, and the Hartmann whistle with the Helmholtz resonator has a. jet regurgitant mode that is different from the Hartmann whistle with a. straight resonator. The diameter of the Helmholtz resonator is an important factor affecting the fundamental frequency.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Urban meadow effectively phyto-cleaned the air throughout the year.•A dead urban meadow phyto-cleaned the air in autumn and winter.•An urban meadow phyto-cleaned air most effectively in summer.•The ...structure of the urban meadow determines its air phyto-cleaning potential.•Urban meadow phyto-cleaned the air more effectively than lawn.
Urban areas are characterised by polluted air which endangers the health and quality of life of city dwellers. Among the dangerous air contaminants is particulate matter (PM) and one of the main sources of PM in urban areas is road traffic. Studies have already shown that the air can be phyto-cleaned by plants, especially trees and shrubs. However, for safety reasons, planting trees and shrubs in some places is problematic, e.g. close to roads. These locations are usually occupied by lawns, which are plant communities of low ecological value. Unfortunately, too little attention has been paid so far to urban meadows. Therefore, this study (i) investigated for the first time the phyto-cleaning potential of an urban meadow all year round, including autumn–winter period, and (ii) compared the efficiency and mechanisms of PM phyto-cleaning by an urban meadow and lawn during the vegetative season. Plant material was harvested from urban meadow (in June, August, November and March) and lawns (in June and August) located by a busy road in Warsaw (Poland). PM was analysed in two categories (surface PM and in-wax PM) and two size fractions (fine: 0.2–2.5 µm, coarse: 2.5–10 µm). The results obtained suggested that accumulation of PM by urban meadow is possible even out of vegetative season. In autumn and winter, even though the meadow plants were physiologically not active, they still participated in air phyto-cleaning. Urban meadow phyto-cleaned air most effectively in summer when the vegetation was fully developed, and least effectively in autumn. During the vegetative season, the urban meadow accumulated more PM than lawns, mostly due to the greater height and complex structure. Therefore, urban meadow would appear to offer an promising solution to problem of phyto-cleaning of urban air in the immediate vicinity of roads throughout the year.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Development of new mixed conductors with both high oxygen permeability and phase stability under reducing atmosphere is indispensable for realizing practical MIEC systems of oxygen separation and ...membrane reactor. In this study, a family of Co-free Fe-based perovskite-type oxides, (Ba,Sr)(Fe,Mn)O
3−
δ
was prepared and their oxygen permeability and phase stability against reduction were examined. Optimum Ba doping concentration at A site was found around 30%, and Ba
0.3Sr
0.7FeO
3−
δ
showed highest oxygen permeability (3.0 cm
3(STP)cm
−
2
min
−
1
at 900 °C) in this study. Perovskite-type oxides of the Ba–Mn–Fe–O and Ba–Sr–Mn–Fe–O systems with appropriate compositions preserved the structure even after annealing in the reducing atmosphere of 5% H
2/N
2 at 1000 °C, showing their exceeding reduction tolerance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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