Having summarized cold chain logistics concept, characteristic of our country and analyzed the refrigerating transportation facilities and means of inside and outside.Describes the relationship between the environment and the application of thermal storage materials research, environmental regenerator material and cold chain logistics process, and application life cycle assessment (LCA) of content, technical framework for applications of thermal storage materials for a full range of analysis, the conclusion that regenerator material environment has a very important role and impact on the sustainable development of cold chain logistics conclusions.
Neural network is a very efficient method for vector quantization, and wavelet transform is a new algorithm developed rapidly in recent years. In this paper a kind of modified distortion competitive learning algorithm was proposed, image data after wavelet transform was analyzed, a new method of vector construction was proposed, and then a new vector quantization algorithm for image compression based on wavelet transform and distortion competitive learning (VQWDCL) was proposed, which is superior to the conventional vector quantization based on wavelet transform and LBG algorithm both on the experiments results and on the computation complication.
Abstract Near‐infrared (NIR)‐emitting phosphor materials have been extensively developed for optoelectronic and biomedical applications. Although Cr 3+ ‐activated phosphors have been widely reported, it is challenging to achieve ultra‐broad and tunable NIR emission. Here, a new ultra‐broadband NIR‐emitting LiIn 2 SbO 6 :Cr 3+ phosphor with emission peak at 965 nm and a full‐width at half maximum of 217 nm is reported. Controllable emission tuning from 965 to 892 nm is achieved by chemical unit cosubstitution of [Zn 2+ –Zn 2+ ] for [Li + –In 3+ ], which can be ascribed to the upshift of 4 T 2g energy level due to the strengthened crystal field. Moreover, the emission is greatly enhanced, and the FWHM reaches 235 nm. The as‐prepared luminescent tunable NIR‐emitting phosphors have demonstrated the potential in night‐vision and NIR spectroscopy techniques. This work proves the feasibility of chemical unit cosubstitution strategy in emission tuning of Cr 3+ ‐doped phosphors, which can stimulate further studies on the emission‐tunable NIR‐emitting phosphor materials.
Multichannel photoluminescence control from blue-to-green to red across the white region was achieved by solid solution evolution, valence mixing of Eu2+/3+ and Eu2+ → Mn2+ energy transfer.
Ce3+, Mn2+, and Tb3+-activated Mg2Y8(SiO4)6O2 (MYS) oxyapatite phosphors have been prepared via solid state reaction process. The Ce3+ emission at different lattice sites in MYS host has been identified and discussed. Under UV excitation, there exist dual energy transfers (ET), that is, Ce3+ → Mn2+ and Ce3+ → Tb3+ in the MYS: Ce3+/Mn2+/Tb3+ system. The energy transfer from Ce3+ to Mn2+ in MYS: Ce3+/Mn2+ phosphors has been demonstrated to be a resonant type via a dipole–quadrupole mechanism, and the critical distance (RC) calculated by quenching concentration method and spectral overlap method are 10.5 and 9.7 Å, respectively. The emitting colors of MYS: Ce3+/Mn2+/Tb3+ samples can be adjusted from blue to orange-red via ET of Ce3+ → Mn2+ and from blue to green via ET of Ce3+ → Tb3+, respectively. More importantly, a wide-range-tunable white light emission with high quantum yields (37–47%) were obtained by precise control of the contents of Ce3+, Mn2+, and Tb3+ ions. On the other hand, the CL properties of MYS: Ce3+/Mn2+/Tb3+ phosphors have been investigated in detail. The results indicate that the as-prepared MYS: Ce3+/Mn2+/Tb3+ phosphors have good CL intensity and CIE coordinate stability with a color-tunable emission crossing the whole visible light region under low-voltage electron beam excitation. In conclusion, the white light with varied hues has been obtained in Ce3+, Mn2+ and Tb3+-activated MYS phosphors by utilizing the principle of energy transfer and properly designed activator contents as well as the select of excitation wavelength under UV and low-voltage electron beam excitation.
Bismuth (Bi) is used for luminescent materials due to its unique optical performance, but deep-red light from Bi-doped materials is rarely reported. In particular, establishing a design principle for Bi-doped red materials is considered to be a significant challenge. Herein, using a deep-red SrSc2O4:Bi material featuring Bi–Bi pair emission, light-induced charge-transfer from BiSc3+–BiSr3+ to BiSc4+–BiSr2+ enables the realization of Bi2+2P3/2(1) → 2S1/2 deep-red emission. Intriguingly, SrSc2O4:Bi displays an excellent zero-thermal-quenching performance from 298 to 423 K, with a peak intensity that retains 98% of the intensity at 298 K and an integrated intensity at 423 K that even reaches 110% of the initial intensity. The intriguing spectroscopic characteristics of SrSc2O4:Bi make it a promising candidate in the agricultural field, night-vision security, and the medical treatment area. This work advances the understanding of red luminescence in Bi-activated luminescent materials and thus can initiate more exploitation of red materials for emerging applications.
Mixed-dimensional perovskite (MDP) heterostructures are promising optoelectronic semiconductors. Yet, the current preparation methods involve complex experimental procedures and material compatibility constraints, limiting their widespread applications. Here, we present a one-step room temperature solution-based approach to synthesize a range of 1D C4N2H14PbBr4 and 3D APbBr3 (A = Cs+, MA+, FA+) self-assembled MDP heterostructures exhibiting high-efficiency white light-emitting properties. The ultra-broadband emission results from the synergy between the self-captured blue broadband emission from 1D perovskites and the green emission of 3D perovskites, covering the entire visible-light spectrum with a full width at half-maximum exceeding 170 nm and a remarkable photoluminescence quantum yield of 26%. This work establishes a novel prototype for the preparation of highly luminescent MDP heterostructures, offering insights for future research and industrialization in the realm of white light LEDs.
High-performance and thermally stable phosphors play an important role in high-quality white light-emitting diode (pc-WLED) lighting. In this work, we proposed a cation substitution strategy to improve the luminescence performance of blue-emitting Bi3+-doped Ca4ZrGe3O12 (abbreviated as CZGO) phosphor. As expected, the introduction of Sr2+ and Si4+ can improve photoluminescence intensity and thermal stability. The photoluminescence intensity can be increased by 6.7 times. The internal quantum efficiency (IQE) can achieve 88.1%. Based on Rietveld refinement results, the corresponding enhancement mechanism is ascribed to the local lattice modification and the improved structure rigidity. In addition, controllable color tuning from blue to red light is successfully realized through designing Bi3+ → Eu3+ energy transfer. The energy transfer efficiency (ηT) is 0.55 in CZGO:2% Bi3+, 15% Eu3+ phosphor. The energy transfer mechanism is discussed in detail. The prototype pc-WLEDs with blue/red dual-emitting CZGO:2% Bi3+, 10% Eu3+ possess a high color rendering index (CRI = 90.8) and low correlated color temperature (CCT = 4372 K). The above investigations indicate that CZGO:Bi3+ and CZGO:Bi3+, Eu3+ are promising blue-to-red tunable phosphor candidates for pc-WLED applications.
Abstract Currently, Mn 4+ ‐activated red‐emitting materials are the research hotspot due to their promising application in phosphor‐converted white light‐emitting diodes (w‐LEDs). Here, a typical cation substitution strategy is reported to optimize Mn 4+ ‐doped germinate phosphor for improving luminescence performances. The effect of cation substitution for Ge 4+ ions by Ti 4+ , Sn 4+ , and Si 4+ ions on lattice structure, photoluminescence properties, and thermal stability of the as‐prepared Mn 4+ ‐doped germinates is systematically investigated. A significant improvement of emission intensity with Ti 4+ doping should benefit from the resonance emission enhancement effect. Some lattice distortion defects contribute to the thermal stability enhancement, which plays a role in driving the excited phonon traps to compensate the energy loss of nonradiative transition. Surprisingly, abnormal variation in intensity of anti‐Stokes and Stokes emission peaks with changing temperature is first observed, revealing a potential application in thermometry. The electroluminescence performances of as‐fabricated w‐LED devices using Mg 14 Ge 5 Ti 0.5 O 24 :Mn 4+ red phosphor are evaluated, which possess higher color rendering index ( R a = 87.3) and luminous efficiency (109.42 lm W −1 ) as well as lower color correlated temperature (3566 K) than those using Cs 2 GeF 6 :Mn 4+ and CaAlSiN 3 :Eu 2+ red phosphors. The results reflect the superiority of the studied phosphor in w‐LEDs and optical thermometry areas.
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