Wireless power transfer (WPT) is a promising charging technology for battery-limited sensors. In this paper, we study the use of an unmanned aerial vehicle (UAV) as a charger for WPT. Unlike the ...previous works, our study takes into account the power consumption of the UAV (power consumption during hovering and flight), the charging process from a base station (BS) to the UAV and the conversion loss of the energy harvester. Both one-dimensional (1D) and two-dimensional (2D) WPT systems are considered. The sum-energy received by all sensors is maximized to find the optimal strategy for UAV deployment. Two different charging schemes are proposed. Numerical results show that the sum-energy received by all sensors is determined by sensors' topology, the flight speed of the UAV and the transmit power. They also show that, when the BS charging process and the UAV power consumption are considered in the optimization, the optimal location of the UAV in the 1D and 2D WPT systems is closer to the BS than in the previous works that ignore these two practical factors.
A zigbee-based home automation system Gill, Khusvinder; Yang, Shuang-Hua; Yao, Fang ...
IEEE transactions on consumer electronics,
05/2009, Volume:
55, Issue:
2
Journal Article
Peer reviewed
Open access
In recent years, the home environment has seen a rapid introduction of network enabled digital technology. This technology offers new and exciting opportunities to increase the connectivity of ...devices within the home for the purpose of home automation. Moreover, with the rapid expansion of the Internet, there is the added potential for the remote control and monitoring of such network enabled devices. However, the adoption of home automation systems has been slow. This paper identifies the reasons for this slow adoption and evaluates the potential of ZigBee for addressing these problems through the design and implementation of a flexible home automation architecture. A ZigBee based home automation system and Wi-Fi network are integrated through a common home gateway. The home gateway provides network interoperability, a simple and flexible user interface, and remote access to the system. A dedicated virtual home is implemented to cater for the system's security and safety needs. To demonstrate the feasibility and effectiveness of the proposed system, four devices, a light switch, radiator valve, safety sensor and ZigBee remote control have been developed and evaluated with the home automation system.
Lithium-ion batteries are considered as one of the most promising power sources for energy storage system for a wide variety of applications such as electric vehicles (EVs) or hybrid electric ...vehicles (HEVs). The anode material often plays an important role in the determination of the safety and cycling life of lithium-ion batteries. Among all anode materials, spinel Li
4
Ti
5
O
12
has been considered as one the most promising anode candidates for the next-generation large-scale power lithium-ion batteries used for HEVs or EVs because it has a high potential of around 1.55 V (
vs.
Li/Li
+
) during charge and discharge, excellent cycle life due to the negligible volume change, and high thermal stability and safety. In this review, we present an overview of the breakthroughs in the past decade in the synthesis and modification of both the chemistry and morphology of Li
4
Ti
5
O
12
. An insight into the future research and further development of Li
4
Ti
5
O
12
composites is also discussed.
This review highlights breakthroughs in the past decade in the synthesis and the modification of both the chemistry and morphology of Li
4
Ti
5
O
12
.
Efficient and durable electrocatalysts from earth-abundant elements play a vital role in the key renewable energy technologies including overall water splitting and hydrogen fuel cells. Here, ...generally used CoFe based layered double hydroxides (LDHs) were first delaminated and exfoliated in the DMF-ethanol solvent (CoFe LDH-F), with enhancement both in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The exfoliation process creates more coordinatively unsaturated metals and improves the intrinsic electronic conductivity, which is important in water electrolyzer reactions. In the basic solution, the CoFe LDH-F catalyst outperforms the commercial iridium dioxide (IrO2) electrocatalyst in activity and stability for OER and approaches the performance of platinum (Pt) for HER. The bifunctional electrocatalysts can be further used for overall water splitting, with a current density of ∼10 mA/cm2 at the applied voltage of 1.63 V for long-term electrolysis test, rivalling the performance of Pt and IrO2 combination as benchmarks. Our findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting.
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By using the real-place Recursion method,the effects of alloying additions (Nb, Ta, Y, La) on glass forming ability(GFA) and corrosion resistance of bulk Zr-based amorphous alloys are studied. An ...atomic group model in the Zr2Ni primary crystalline phase centered to Ni atom are constructed by computer programming. We have calculated the total bond order integral (£BOI) between Ni atom and its neighbor elements (Nb, Ta, Y, La), also calculated the Fermi energy level of alloying elements. The calculation results show that the XBOI and the glass forming ability are greatly enhanced after Y substitution. Nb, Ta, La decrease the GFA and La has little influence on the GFA of the alloys.Nb, Y, La enable Zr-based amorphous easy to passive and increase corrosion resistance. Therefore, Y and La are most effective on glass forming ability and corrosion resistance of Zr-based amorphous alloys. By addition of minor Y and La can produce the new bulk amorphous alloys with good corrosion resistance.
Through a dual-ligand strategy, three mixed ligands metal–organic frameworks (MOFs), namely, {Zn2(Py2TTz)2(BDC)2·2(DMF)·0.5(H2O)} n (1), {Cd2(Py2TTz)2(BDC)2·2(DMF)} n (2), and ...{Co2(Py2TTz)2(BDC)2·2(DMF)·0.5(H2O)} n (3) (where Py2TTz = 2,5-bis(4-pyridyl)thiazolo5,4-dthiazole, BDC = 1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized under solvothermal conditions. The single-crystal X-ray diffraction analyses reveal that the three MOFs possess similar 2-fold interpenetrated three-dimensional framework structures with pcu topology. The fluorescence properties of compounds 1 and 2 were investigated systematically. The results show that compounds 1 and 2 display good fluorescent properties, which can be efficiently quenched by a trace amount of nitroaromatics 2,4,6-trinitrophenol (TNP) and antibiotics nitrofurazone (NZF) in water media. The large K sv value and small limit of detection demonstrate that compounds 1 and 2 can serve as good fluorescent sensors for TNP and NFZ detection in an aqueous system. Density functional theory calculations and spectral overlap experiments, coupled with luminescence decay experiments, confirm that the luminescence quenching mechanism involves a dynamic and static quenching mechanism and is dominated by the photoinduced electron transfer process and the Förster resonance energy transfer process simultaneously.
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With high thermal and mechanical stability, glass artificial compound eyes have great potential applications in wide field‐of‐view (FOV) imaging and fast detection. However, the rapid fabrication of ...large‐area, high integration, uniform, and well‐designed three‐dimensional (3D) glass compound eyes is still a great challenge. Here, a dry‐etching‐assisted femtosecond laser machining (DE‐FsLM) technology is proposed for fabrication of cm‐sized concave compound eye from a curved sapphire substrate, with which the fabrication efficiency can be improved by over two orders of magnitude compared with direct laser ablation. With high hardness and thermal stabilities, the sapphire concave compound eyes can be used as high‐temperature and hard‐casting templates for the replication of convex compound eyes on K9 glass. The replicated cm2‐size all‐glass compound eye consists of a spherical macrolens (1 cm diameter and 2.3 mm height) and over 190 000 close‐packed ommatidia (≈20 µm diameter and 1.5 µm height). The compound eyes exhibit excellent optical properties with wide FOV (up to 90°) imaging and focusing. These results indicate that the DE‐FsLM and casting replication technology will open new opportunities in micro‐/nanofabrication of hard materials.
Dry‐etching‐assisted femtosecond laser machining is proposed for the rapid fabrication of large‐scale uniform and smooth sapphire concave compound eye templates. K9 glass compound eyes are fabricated by high‐temperature casting replication from the sapphire concave compound eyes, which exhibit a wide field‐of‐view (up to 90°) for practical applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In order to improve the teaching effect of English writing, this paper combines the intelligent text semantic analysis algorithm to construct an English writing correction model. Moreover, this paper ...deduces the relationship formula between the range of English semantic information cloud drop and the evaluation word through the contribution of cloud drop group to qualitative concepts, the association between cloud drop central area and evaluation words, and the relationship between cloud drop ring area and evaluation word. In addition, this paper uses the word selection probability results obtained from the preference evaluation. The simulation results show that the English writing correction model based on intelligent text semantic analysis proposed in this paper can play an important role in the intelligent teaching of English writing.
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Passivation of electronic defects at the surface and grain boundaries of perovskite materials has become one of the most important strategies to suppress charge recombination in both polycrystalline ...and single-crystalline perovskite solar cells. Although many passivation molecules have been reported, it remains very unclear regarding the passivation mechanisms of various functional groups. Here, we systematically engineer the structures of passivation molecular functional groups, including carboxyl, amine, isopropyl, phenethyl, and tert-butylphenethyl groups, and study their passivation capability to perovskites. It reveals the carboxyl and amine groups would heal charged defects via electrostatic interactions, and the neutral iodine related defects can be reduced by the aromatic structures. The judicious control of the interaction between perovskite and molecules can further realize grain boundary passivation, including those that are deep toward substrates. Understanding of the underlining mechanisms allows us to design a new passivation molecule, D-4-tert-butylphenylalanine, yielding high-performance p-i-structure solar cells with a stabilized efficiency of 21.4%. The open-circuit voltage (V OC) of a device with an optical bandgap of 1.57 eV for the perovskite layer reaches 1.23 V, corresponding to a record small V OC deficit of 0.34 V. Our findings provide a guidance for future design of new passivation molecules to realize multiple facets applications in perovskite electronics.
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Two-dimensional (2D) perovskites have been shown to be more stable than their three-dimensional (3D) counterparts due to the protection of the organic ligands. Herein a method is introduced to form ...2D/3D stacking structures by the reaction of 3D perovskite with n-Butylamine (BA). Different from regular treatment with n-Butylammonium iodide (BAI) where 2D perovskite with various layers form, the reaction of BA with MAPbI3 only produce (BA)2PbI4, which has better protection due to more organic ligands in (BA)2PbI4 than the mixture of 2D perovskites. Compared to BAI treatment, BA treatment results in smoother 2D perovskite layer on 3D perovskites with a better coverage. The photovoltaic devices with 2D/3D stacking structures show much improved stability in comparison to their 3D counterparts when subjected to heat stress tests. Moreover, the conversion of defective surface into 2D layers also induces passivation of the 3D perovskites resulting in an enhanced efficiency.
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