Self-phase modulation via similariton solutions of the perturbed NLSE Modulation instability and induced self-steepening

The perturbed nonlinear Schrodinger equation (PNLSE) describes the pulse propagation in optical fibers, which results from the interaction of the higher-order dispersion effect, self-steepening (SS) and self-phase modulation (SPM). The challenge between these aforementioned phenomena may lead to a dominant one among them. It is worth noticing that the study of modulation instability (MI) leads to the inspection of dominant phenomena (DPh). Indeed, the MI triggers when the coefficient of DPh exceeds a critical value and it may occur that the interaction leads to wave compression. The PNLSE is currently studied in the literature, mainly on finding traveling wave solutions. Here, we are concerned with analyzing the similarity solutions of the PNLSE. The exact solutions are obtained via introducing similarity transformations and by using the extended unified method. The solutions are evaluated numerically and they are shown graphically. It is observed that the intensity of the pulses exhibits self steepening which progresses to shock soliton in ultra-short time (or near t = 0). Also, it is found that the real part of the solution exhibits self-phase modulation in time. The study of (MI) determines the critical value for the coefficients of SS, SPM, or high dispersivity to occur.     

Application of PWM dimming based on Grassmann optical model北大核心CSCD

针对发光二极管（light-emitting diode,LED）光源颜色和光通量精准调控难度高,在生产应用中,调控操作需在电脑等设备上进行的问题,基于格拉斯曼颜色混合定律,结合脉宽调制(pulse width modulation,PWM)调控LED的特性,建立表示PWM与LED照度关系的数学模型,以STM 32微控制器为核心设计了三基色LED调光调色系统。对系统分别进行单色、双色和3色的混光照度实验,数字照度计的测量值与光照数学模型的理论值对比结果表明,该系统在0~370 lx区间内系统的光源照度误差≤4%,合成光色共16 777 216种,且对光源颜色和光通量的调控操作可直接在系统上完成,无需接入其他设备,减少了操作流程,满足工业视觉检测、农作物补光照明和文化旅游对光源颜色和照度的需求。     

Protograph bit-interleaved coded modulation: A bandwidth-efficient design paradigm for 6G wireless communications

Bit-interleaved coded modulation (BICM) has attracted considerable attention from the research community in the past three decades, because it can achieve desirable error performance with relatively low implementation complexity for a large number of communication and storage systems. By exploiting the iterative demapping and decoding (ID), the BICM is able to approach capacity limits of coded modulation over various channels. In recent years, protograph low-density parity-check (PLDPC) codes and their spatially-coupled (SC) variants have emerged to be a pragmatic forward-error-correction (FEC) solution for BICM systems due to their tremendous error-correction capability and simple structures, and found widespread applications such as deep-space communication, satellite communication, wireless communication, optical communication, and data storage. This article offers a comprehensive survey on the state-of-the-art development of PLDPC-BICM and its innovative SC variants over a variety of channel models, e.g., additive white Gaussian noise (AWGN) channels, fading channels, Poisson pulse position modulation (PPM) channels, and flash-memory channels. Of particular interest is code construction, constellation shaping, as well as bit-mapper design, where the receiver is formulated as a serially-concatenated decoding framework consisting of a soft-decision demapper and a belief-propagation decoder. Finally, several promising research directions are discussed, which have not been adequately addressed in the current literature.     

集成滤光片型近红外光谱组件的时空域性能改善研究

提出针对线性渐变滤光片型近红外光谱组件的时空域性能改善方法,并通过研制微型化512×2元InGaAs光谱组件,结合多帧数据融合算法完成了实验验证。光谱通道采用基于多次测量的两列相邻光敏元动态组合实现,相比单个大光敏元作为光谱通道,可以改善探测器盲元引起的不良影响。波长标定和测试结果表明,该光谱组件在线性渐变滤光片的分辨率限制下,可以有效减小相邻光谱通道间的波长间隔。     

Calix[4]pyrrole‐Based Heteroditopic Ion‐Pair Receptor That Displays Anion‐Modulated,Cation‐Binding Behavior

A new ditopic ion‐pair receptor 1 was designed, synthesized, and characterized. Detailed binding studies served to confirm that this receptor binds fluoride and chloride ions (studied as their tetraalkylammonium salts) and forms stable 1:1 complexes in CDCl₃. Treatment of the halide‐ion complexes of 1 with Group I and II metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, and Ca²⁺; studied as their perchlorate salts in CD₃CN) revealed unique interactions that were found to depend on both the choice of the added cation and the precomplexed anion. In the case of the fluoride complex [ 1? F]^? (preformed as the tetrabutylammonium (TBA⁺) complex), little evidence of interaction with the K⁺ ion was seen. In contrast, when this same complex (i.e., [ 1? F]^? as the TBA⁺ salt) was treated with the Li⁺ or Na⁺ ions, complete decomplexation of the receptor‐bound fluoride ion was observed. In sharp contrast to what was seen with Li⁺, Na⁺, and K⁺, treating complex [ 1? F]^? with the Cs⁺ ion gave rise to a stable, receptor‐bound ion‐pair complex [Cs ?1? F] that contains the Cs⁺ ion complexed within the cup‐like cavity of the calix[4]pyrrole, which in turn was stabilized in its cone conformation. Different complexation behavior was observed in the case of the chloride complex [ 1? Cl]^?. In this case, no appreciable interaction was observed with Na⁺ or K⁺. In addition, treating [ 1? Cl]^? with Li⁺ produces a tightly hydrated dimeric ion‐pair complex [ 1? LiCl(H₂O)]₂ in which two Li⁺ ions are bound to the crown moiety of the two receptors. In analogy to what was seen in the case of [ 1? F]^?, exposure of [ 1? Cl]^? to the Cs⁺ ion gives rise to an ion‐pair complex [Cs ?1? Cl] in which the cation is bound within the cup of the calix[4]pyrrole. Different complexation modes were also observed when the binding of the fluoride ion was studied by using the tetramethylammonium and tetraethylammonium salts.     

Nano/Micro HKUST-1 Fabricated by Coordination Modulation Method at Room Temperature

A simple and fast route for the synthesis of metal-organic framework(MOF) particles was presented.Cu 3(BTC) 2(HKUST-1,BTC=1,3,5-benzenetricarboxylate),one of the most well-known MOFs,was synthesized at room temperature via coordination modulation method.By adding different modulators(monocarboxylic acids) into the reaction system,the morphologies of HKUST-1 crystals were tuned from nano spheres to micro octahedrons at room temperature without any complex equipment.X-Ray diffractions and gas sorption measurements revealed highly crystalline particles with large Brunauer-Emmett-Teller(BET) surface areas(1116―1273 m 2 /g) and total pore volumes(0.62―0.73 cm 3 /g).The significantly small particle sizes and high capacity of gas sorption are considered advantageous for envisaged application in practical industrial process.     

The effect of nitro substitution on the photochemistry of benzyl benozhydroxamate: Photoinduced release of benzohydroxamic acid

The redox congener of the important signaling agent nitric oxide (NO), nitroxyl or nitrosyl hydride (HNO) has also been demonstrated to induce distinct physiological effects. The aim of this study was to determine if benzohydroxamic acid, which was selected as a stable model compound of HNO donors, could be released by the o-nitrobenzyl photolabile protecting group (PPG) in a wavelength-dependent manner. It was expected that selective irradiation of the o-nitrobenzyl chromophore would favor the release of benzohydroxamic acid over undesired products associated with N-O bond cleavage. Quantum yields for the release of benzohydroxamic acid protected by the o-nitrobenzyl PPG increased at longer wavelengths, with a concomitant decrease in the yield of minor products. Through the use of triplet photosensitizers, triplet quenchers, computational methods, and the position of the nitro substituent, insights into the nature of the mechanism were suggested.     

Effects of wavelength and substituents on iron(III) photoreduction in trans-[Fe(R-sal-R‵-en)(CH3OH)(NCS)] complexes

Photoredox reactions in irradiated methanolic solutions of trans-[Fe(R′-sal-R₂-en) (CH₃OH)(NCS)] complexes, where R′-sal-R₂-en^2? are tetradentate open-chain N,N′-1,1-R₂-ethylenebis(R′-salicylideneiminato) ligands (R?=?H or CH₃; R′?=?H, 5-Cl, 5-Br, 3,5-Br₂, 3-OCH₃, 4-OCH₃), have been explored and a mechanism suggested. The complexes are redox-stable in the dark in methanol. Continuous irradiation of solutions in the region of intraligand (IL) or ligand-to-metal charge transfer (LMCT) transitions leads to photoreduction of Fe(III) to Fe(II) and formation of formaldehyde (CH₂O). Formation of polystyrene-containing bonded NCS, when irradiating the complexes in the presence of styrene used as a radical scavenger, indicates that the primary photoreduction of Fe(III) to Fe(II) is accompanied by oxidation of NCS^? to the ^?NCS radical. R′-sal-R₂-en ligands have little effect on the photoinduced redox processes. The quantum yield of Fe(II) formation, Φ_Fe(II), as a quantitative parameter of photoredox efficiency, decreases significantly with increasing wavelength of incident radiation, and is slightly influenced by the peripheral groups, R, of R′-sal-R₂-en.     

Simultaneous Analysis of Co2+, Cu2+ Mn2+, Ni2+ and Zn2+ in The Ultraviolet Region Using 4-(Pyridil-2-AZO) Resorcinol and Multivariate Calibration

ABSTRACT

A multicomponent spectrophotometric methodology for the simultaneous determination of Co²⁺, Cu²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ in aqueous solution is reported, using (4-(pyridil-2-azo) resorcinol), a diode array spectrophotometer and multivariate calibration by partial least-squares and principal component regerssions. Spectra are recorded in the UV region. The 225 – 320 nm range is selected as optimal, through a criterion based on tederivatives of the differences between individual spectra, which compares favorably with a genetic algorithm. The methodology is applied to the simultaneous determination of the five than 1.5 mgL^?1. The best result are obtanied at pH 9.0, with average absolute errors of prediction lower than 0.09 mgL^?1