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Structure of Measuring Systems
Published in Francis S. Tse, Ivan E. Morse, Measurement and Instrumentation in Engineering, 2018
A shielded cable is shown in Fig. 3-48. The signal lead is shielded when the shield in the form of a braided copper mesh is connected to ground. The shield minimizes the voltage pickup between the signal lead and the surrounding electric field. This is called an electrostatic shield. First, the shield intercepts the surrounding electric field and a voltage is induced in the shield due to the antenna effect. The voltage in the shield will also induce a voltage in the signal lead by virtue of the distributed capacitance between the shield and the lead. Second, the ground connection drains the charge in the shield to ground to render the shield at the ground potential. Hence the signal lead of a shielded cable is free of the surrounding electric field. An instrument is shielded in like manner by means of a metallic chassis.
Optimization of light absorption in ultrathin elliptical silicon nanowire arrays for solar cell applications
Published in Journal of Modern Optics, 2022
Seyedeh Leila Mortazavifar, Mohammad Reza Salehi, Mojtaba Shahraki, Ebrahim Abiri
Three methods are adopted for NWs to increase the bandwidth of their structures. Primarily, the impact of distortion of the structures on ENWs is studied. Next, semi-periodic and multiple methods are applied to ENW structures. Finally, every structure is optimized by the PSO algorithm. Compared with other structures, the irregular NWs record the highest degree of current density. Even Irregular NWs without any reflectors show better properties than thin-film SCs that used ARC. The efficient interaction between optical antenna and diffraction effects results in higher absorption of semi-periodic arrays compared with periodic arrangements. However, this study used periodic multiple and multiple arrays to obtain the highest increase of current density. These nanostructures are more susceptible to the optical antenna effect. The suggested multiple ENW arrays with ARC recorded a 127.85% increase in current density versus thin-film cells.
A luminescent Tb(III)-organic framework: Selective sensing of PO4 3– ions and important role on tuberculosis curing
Published in Journal of Coordination Chemistry, 2021
Xiaodan Zhu, Hong Wu, Xinyan Gong, Chun Li, Jianli Ma
Complex 1’s fluorescence performance in the solid state was explored at ambient temperature (Figure 2a). At 393 nm, the ligand spectrum possesses a wide emission peak with a 331 nm excitation wavelength which is associated with the π–π* transition for H4dpc. Under a 319 nm excitation, at 624 nm, 589 nm, 546 nm and 493 nm, 1’s fluorescence spectrum in the solid state reveals four Tb3+ emission peaks, respectively, assigned to the f–f transitions 5D4–7F3, 5D4–7F4, 5D4–7F5 and 5D4–7F6. Furthermore, as displayed in Figure 2b, under the irradiation of a portable ultraviolet lamp (with 254 nm excitation wavelength), 1 reveals strong green fluorescence. The relevant experiment has suggested that the ligand’s absorbed energy could be transferred into the central Tb3+ ion. This phenomenon indicates that the ligand can sensitize the central metal ion on the basis of an antenna effect. In addition, the Tb-MOF exhibits excellent chemical stability as shown by the relative fluorescence strength (Figure 2b).
Structural and optical features of lanthanide species-derived functional hydrogels
Published in Soft Materials, 2019
Qin Wen, Yiping Tang, Kai Li, Yuhui Zheng
Lanthanide ions possess very low molar absorption coefficients and they have difficulty in absorbing energy. Such light absorption could be circumvented by the well-known antenna effect. Upon the irradiation with UV lights, the organic chromophores would absorb the energy and transfer it to the excited states of lanthanide ions. Therefore, the investigation of suitable organic frameworks to sensitize lanthanide ions would be quite valuable. In this study, the organic ligand was prepared via a two-steps process based on diethyl ester of 5-hydroxyisophthalic acid, dibromomethane, and anhydrous K2CO3 as raw materials. Owing to the abundant carboxyl groups, this organic structure can coordinate with lanthanide ions through oxygen atoms and the formation of stable rare earth compound would be achieved. The obtained products were defined as EuL and TbL in the following section. Generally speaking, the organic ligand can only sensitize europium or terbium ions individually. But the incorporation of such organic chromophore could result in typical emissions for these two lanthanide elements simultaneously. As for the case of terbium complex, the compound may undergo the intramolecular energy transfer from the triplet state of the ligand to terbium ions. In the example of europium complex, the main bands would be contributed by direct excitation in the 4f levels. The overall quantum yields of the two complexes were evaluated and the determined values were 6.9% for europium complex (λex = 393 nm) and 7.8% for terbium complex (λex = 328 nm).