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To apply visible light communication systems in different scenarios, this article utilizes an excellent temperature-adjustable light source mixed with RGB LEDs and applies it in a visible light communication system. It uses color division multiplexing technology to achieve three-channel communication, thereby improving the communication bandwidth of the system. The communication system adopts three constant current driving circuits to control the duty cycle of Pulse Width Modulation (PWM) of each channel, thereby changing the proportion of RGB LEDs, and obtaining different color temperatures to achieve the purpose of color control for mixed-color LEDs. The experimental results show that when adjusting the color temperature, the change in luminous flux is very small, with fluctuations of less than 2.24%. When adjusting the brightness, the color temperature fluctuation is within 40 K, which is less than the 50 K color temperature limit that the human eye can distinguish, and the average color temperature error is 0.609%. Color tolerance less than 5.5 × 10−3 indicates good dimming effect, and the communication performance of the system is better in the high color temperature range, which is significantly superior to the low color temperature range. When the error rate is below 3.8 × 10−3, the total modulation bandwidth of the three channels reaches 11.7 MHz.

Multifunctional cotton fabric with adjustable color was simply fabricated by anchoring solid solution BiOBrxI1−x nanosheets on the surface of carboxymethylated cotton fabric for self-cleaning, UV protection, and near infrared reflection. The structure and morphology of prepared multifunctional cotton fabrics (BiOBrxI1−x-CCF (0 ≤ x ≤ 1)) were characterized by X-ray powder diffraction and scanning electron microscopy. Color, self-cleaning, UV protection, near infrared reflection, and acid and alkali resistance of these multifunctional cotton fabrics were systematically studied. With the increase of iodine content, the BiOBrxI1−x nanosheets with an average thickness of 40–50 nm and a size of 1–2 μm in the other two dimensions loaded on the cotton fabrics can extend the absorption edge of BiOBrxI1−x-CCF (0 ≤ x ≤ 1) from 430 nm to 630 nm, giving cotton fabric color and excellent UV protection property. Interlaced solid solution nanosheets on cotton fabric surface give BiOBrxI1−x-CCF hydrophobicity (contact angle: 139°–143°) and ability to photodegrade stain under the visible light irradiation. The near infrared reflectance of BiOBrxI1−x-CCF (0 ≤ x ≤ 1) is higher than that of the raw cotton, which gives it infrared reflection thermal isolation. BiOBrxI1−x-CCF (0 ≤ x ≤ 1) has a certain acid and alkali resistance in solution (pH 2.3–11.2). Thus, BiOBrxI1−x-CCF has great potential to be used as multifunctional fabric in self-cleaning and outdoor protection. Graphic abstract

In this study, a series of well-crystallized Yb3+/Er3+/Tm3+-tridoped Y2O3-ZnO ceramic nano-phosphors were prepared using sol–gel synthesis, and the phosphor structures were studied using X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The phosphors were well crystallized and exhibited a sharp-edged angular crystal structure and mesoporous structure consisting of 270 nm nano-particles. All phosphors generated blue, green, and red emission bands attributed to Tm: 1G4→3H6, Er: 2H11/2 (4S3/2)→4I15/2, and Er: 4F9/2→4I15/2 radiative transitions, respectively. Increasing in luminescent centers, weakening of lattice symmetry, and releasing of dormant rare earth ions can enhance all emissions. Er3+ can obtain energy from Tm3+ to enhance green and red emission. These colors can be tuned by optimizing the doping concentrations of the Er3+ ion. The color coordinates were adjusted by tuning both the Er3+ concentration and excitation laser pump power to shift the color coordinates and correlated color temperature. The findings of this study will broaden the potential practical applications of phosphors.

We discuss a two-color SASE free-electron laser (FEL) amplifier where the time and energy separation of two separated radiation pulses are controlled by manipulation of the electron beam phase space. Two electron beamlets with adjustable time and energy spacing are generated in an RF photo-injector illuminating the cathode with a comb-like laser pulse followed by RF compression in the linear accelerator. We review the electron beam manipulation technique to generate bunches with time and energy properties suitable for driving two-color FEL radiation. Experimental measurements at the SPARC-LAB facility illustrate the flexibility of the scheme for the generation of two-color FEL spectra.

Object-based manipulations, such as adding or removing objects for digital video, are usually malicious forgery operations. Compared with the conventional double MPEG compression or frame-based tampering, it makes more sense to detect these object-based manipulations because they might directly affect our understanding towards the video content. In this paper, a passive video forensics scheme is proposed for object-based forgery operations. After extracting the adjustable width areas around object boundary, several statistical features such as the moment features of detailed wavelet coefficients and the average gradient of each colour channel are obtained and input into support vector machine (SVM) as feature vectors for the classification of natural objects and forged ones. Experimental results on several videos sequence with static background show that the proposed approach can achieve an accuracy of correct detection from 70% to 95%.