copy and easy to authenticate) is the primary approach for resisting the increasing sophistication of counterfeiting. [1] Due to their visual identifiability, colorful light emissions of luminophors are considered to be ideal security elements. The luminescent patterns of banknotes under ultraviolet (UV) excitation are a well-known sample of this approach. In addition to the spatial spectral fingerprints displayed in emission colors, the excitation mode and emission lifetime of luminescence can be used as authentication information, providing higher coding levels. For example, photoluminescence (PL), upconversion luminescence (UCL), and long-lasting luminescence (LLL) are three quintessential modes for anticounterfeiting and information security. [2] The PL mode produces photons at longer wavelengths than the excitation wavelength, for example, downshifting UV excitation to visible emission. [3] The UCL mode converts longwavelength photons to short-wavelength ones, for example, in the upconversion of near-infrared (NIR) excitation to visible emission. [4] It is important to note that PL and UCL phenomena will disappear immediately once light excitation is stopped, showing a feature of pulse duration (so-called fluorescence). In contrast, LLL shows delayed initiation after the cessation of Optical characteristics of luminescent materials, including emission color (wavelength), lifetime, and excitation mode, play crucial roles in data communication and information security. Conventional luminescent materials generally display unicolor, unitemporal, and unimodal (occasionally bimodal) emission, resulting in low-level readout and decoding. The development of multicolor, multitemporal, and multimodal luminescence in a single material has long been considered to be a significant challenge. In this study, for the first time, the superior integration of colorful (red-orange-yellowgreen), bitemporal (fluorescent and delayed), and four-modal (thermo-/ mechano-motivated and upconverted/downshifted) emissions in a particular piezoelectric particle via optical multiplexing of dual-lanthanide dopants is demonstrated. The as-prepared versatile NaNbO 3 :Pr 3+ ,Er 3+ luminescent microparticles shown are particularly suitable for embedding into polymer films to achieve waterproof, flexible/wearable and highly stretchable features, and synchronously to provide multidimensional codes that can be visually read-out using simple and commonly available tools (including the LED of a smartphone, pen writing, cooling-heating stimuli, and ultraviolet/ near-infrared lamps). These findings offer unique insight for designing highly integrated stimuli-responsive luminophors and smart devices toward a wide variety of applications, particularly advanced anticounterfeiting technology.

A parallel 2D code for modeling nanosecond surface dielectric barrier discharge (nSDBD), combining a discharge description, detailed kinetics and hydrodynamics, is developed and validated. A series of experiments and numerical modeling for a single pulse nSDBD in atmospheric pressure air at a voltage amplitude of 24 kV have been performed. The measured and calculated velocity of the discharge front, electrical current, 2D map of N 2) emission and hydrodynamic perturbations caused by the discharge on the time scale -0.2 5 μs are compared. The data are presented and analyzed for the negative and positive polarity of the streamers. A set of parametric calculations with different dielectric permittivities and different dielectric thicknesses is presented.

The effect of heat release in reactions with charged and electronically excited species, or socalled fast gas heating (FGH), in nanosecond surface dielectric barrier discharge (nSDBD) in atmospheric pressure air is studied. Two-dimensional numerical simulations based on the PArallel Streamer Solver with KinEtics code are conducted. The code is based on the direct coupling of a self-consistent fluid model with detailed kinetics, an efficient photoionization model, and Euler equations. The choice of local field approximation for nSDBD modeling with simplified kinetics is discussed. The reduced electric field and the electron density are examined at both polarities for identical high-voltage pulses 24 kV in amplitude on a high-voltage electrode and 20 ns full width at half maximum. The distribution of the FGH energy and the resulting gas temperature field are studied and compared with findings in the literature. The input of different reactions to the appearance of hydrodynamic perturbations is analyzed.

Visually readable codes play a crucial role in anticounterfeiting measures. However, current coding approaches do not enable time-dependent codes to be visually read, adjusted, and differentiated in bright and dark fields. Here, using a combined strategy of piezoelectric lattice selection, oxygen vacancy engineering, and activator doping, a lanthanide ion-doped titanate is developed that integrates mechano-, thermo-, and photo-responsive color change (>18 h for bright field), persistent luminescence (>6 h for dark field), and stimulus-triggered multimodal luminescence. The feasibility of optical encoding, visual displaying, and stimulus-responsive encrypting of timedependent, dual-field information by using the developed material is demonstrated. In particular, the differentiated display of dual-field modes is achieved by combining mechanostimulated abolition of only the persistent luminescence and thermo-and photostimulated reversal of both the color change and persistent luminescence. The results provide new insights for designing advanced materials and encryption technologies for photonic displays, information security, and intelligent anticounterfeiting.

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For a long period, there was a resolution gap between numerical modeling and experimental measurements, making it hard to conduct a direct comparison between them, but they are now developing in parallel. In this work, we numerically study diffusive ionization wave and fast ionization wave discharge experiments using recently published electric-field-induced second-harmonic (E-FISH) data together with a classical fluid model. We propose a pressure-E/N range for the drift diffusion approximation and a pressure-grid range for the local field/mean energy approximation of the fluid model. The three-term Helmholtz photoionization model is generalized using parameters given for N 2 , O 2 , CO 2 , and air. The capabilities of the classical fluid method for modeling the inception, propagation, and channel breakdown stages are studied. The calculated electric field evolution of the ionization is compared with E-FISH measurements in the discharge development and gap-closing stages. The influence of electrode shape and predefined electron density on the streamer morphology and the long-standing inception problem of the ionization waves are discussed in detail. Within the application range of the classical fluid model, good agreement can be achieved between calculation and measurement.

The streamer-to-spark transition in a point-to-plane configuration in atmospheric pressure air is studied using a 2D–0D combined approach. A validated fluid code is used and improved to model the spark stage. 2D modeling of discharges at three different temperatures, 300, 600 and 800 K, are conducted; the spark transition occurs when the temperature reaches 800 K in the first pulse. A conservative criteria of spark transition temperature is proposed based on analytical solution and compared with experiments. Kinetics modeling of the post discharge stage is conducted with consistent input values extracted from the 2D model. Results show that the streamer-to-spark transition can be initiated at a lower temperature (600 K) and lower field (50–75 Td), and the long-lifetime O-atoms formed in previous pulses play an important role in ‘knocking off’ the electrons from negative charged species and maintaining the electron density in the post discharge stage. The dominating processes for electron production are electron detachment reactions from O 3 − , O 2 − and O−. The ionizations from excited species only accelerate the production of electrons when the plasma is already dense.

The characteristics of nanosecond-pulsed dielectric barrier discharge (nSDBD) in an anti-icing configuration is studied. The mechanisms and energy characteristics of the nSDBD-based plasma-assisted anti-icing are analyzed using a numerical model and existing experimental data. Two-dimensional simulations based on PASSKEy (PArallel Streamer Solver with KinEtics) code are conducted. The code couples a self-consistent fluid model with detailed kinetics, an efficient photo-ionization model, Euler equations and a heat transfer equation for solid materials. The results of icing wind tunnel experiments conducted by two groups are analyzed together. The reduced electric field and the electron density are examined for highvoltage pulses with 800 ns and 20 ns width. The 'merge' of counter-propagating surface streamers with the same polarity is numerically observed under high-voltage amplitude. The effects of gas heating and solid heating in time scales of one pulse and one duty cycle are compared, and the key mechanism for icing prevention is direct fast gas-heating energy transfer from gas to ice/water accumulated on the surface in each duty cycle.