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1.
Various kinds of aluminum species in dealuminated mordenite were investigated in detail, and the quadrupole coupling constants
(QCCs) for aluminum atoms associated with these species were obtained by means of the newly introduced1H/27 AI TRAPWR method as well as27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR). QCC values of 11.3, 15.3, 13.3 and (14.0± 0.6) MHz were determined
from the TRAPDOR profiles for Lewis acid sites, Bronsted acid sites (SiOHAl) and two kinds of non-framework aluminum species
Al(OH)
n
, respectively. The source of the “invisible Al” is discussed on the basis of the NMR experimental results. 相似文献
2.
Herein, we report an approach to combat counterfeiting and storage of valuable information based on the solid‐state fluorescence switching behavior of isoniazid functionalized naphthalene diimide (ISO_NDI) in response to an external stimuli (i. e., HCl vapor). The unique feature of ISO_NDI is further utilized to develop an invisible ink (ISO_NDI‐PVA) with commercial polymer polyvinyl alcohol (PVA). A solid‐state fluorescence recovery was observed while loading with HCl vapors. This exclusive property of the material could be applied directly as a security ink for confidential data storage purpose. Based on above strategy, we successfully realized the rewritable application by using ISO_NDI‐PVA ink and confirm its practical efficacy on various substrates by creating different patterns. The solid‐state fluorescence switching behavior of ISO_NDI‐PVA ink exhibited reversible on/off signal for multiple cycles under the influence of HCl/NH3 vapors. Mechanistic investigation supports a clear participation of intermolecular charge transfer (ICT) phenomenon in the solid‐state fluorescence switching property. The ease of fabricating the ink with invisible to visible characteristics in response to HCl vapors provides new opportunities for exploring the application of ISO_NDI‐PVA as invisible ink for targeted security applications. 相似文献
3.
像计算机、电视机、空调等这类具有物理变质的可能性很小,但生命周期较短、不断更新换代、价值不断贬值的电子产品会发生无形变质的现象.在假设无形变质率与需求率负相关,同时在产品的存储过程中,考虑库存水平对销售量的影响情况下,研究需求受库存水平影响、且缺货时存在延迟订货的短生命周期物品的库存管理问题.创新之处在于考虑了产品的缺货问题;在允许缺货的条件下,建立了短生命周期物品的库存模型;运用数值算例进行了求解和验证;并对各参数进行了敏感性分析. 相似文献
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5.
We demonstrate the possibility of creating a time gap in the slow light based on spectral hole burning in a fourlevel Doppler broadened sodium atomic system. A time gap is also observed between the slow and the fast light in the hole burning region and near the burnt hole region, respectively. A cloaking time gap is attained in microseconds and no distortion is observed in the transmitted pulse. The width of the time gap is observed to vary with the inverse Doppler effect in this system. Our results may provide a way to create multiple time gaps for a temporal cloak. 相似文献
6.
Transformation optics provides great versatility for precisely manipulating electromagnetic waves. It has been extended to other fields including acoustics, thermotics, and electrics. Taking advantage of the transformation electrics method, we demonstrate that the square-shaped cloak can guide electric current around the cloaked region smoothly without perturbing the exterior electric current. And the cylindrical rotator can rotate the electric current.Inside the enclosed domain of the rotator, the electric current from the outside will appear as if it is coming from a different angle. Finally, the related experimental realizations and potential applications are also discussed. 相似文献
7.
Design of square-shaped heat flux cloaks and concentrators using method of coordinate transformation
A square-shaped heat flux cloak and a square-shaped heat flux concentrator have been designed theoretically according to the invariance symmetry of steady state thermal conductive equation. The direction of heat flux in these devices can be modulated as desired. Using the method of coordinate transformation, the inhomogeneous and anisotropic thermal conductivity in the transformation region have been acquired. Two-dimensional finite element simulations were performed to confirm the theoretical results. 相似文献
8.
以小苏打溶液替代氢氧化钠和碳酸钠溶液作为隐形墨水,天然色素酒精浸取液为显色剂,以白醋替代盐酸作为消色剂,进行隐形墨水实验,实验操作安全、简单,字迹显示清晰,用时恰当,是一个合适的课外活动实验。 相似文献
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10.
《Laser \u0026amp; Photonics Reviews》2017,11(6)
A method is introduced for the design of invisibility cloaks inspired by fluid dynamics that is different from traditional transformation optics. The inhomogeneous refractive index of the liquid cloak controlled by the natural liquid diffusion is analogous to its counterpart designed by transformation optics. Here, a tunable liquid visible cloak is experimentally presented by the natural diffusion of miscible flows. This method avoids the use of complex nanostructures in its solid counterpart, and provides a simple and low‐cost approach. This implies that optofluidics can be used as a technology to make real‐time reconfigurable transformation optic devices. 相似文献