Frequency-modulated continuous-wave multiplexed gas sensingbased on optical frequency comb calibration

Laser absorption spectroscopy has proven to be an effective approach for gas sensing, which plays an important rolein the fields of military, industry, medicine and basic research. This paper presents a multiplexed gas sensing system basedon optical frequency comb (OFC) calibrated frequency-modulated continuous-wave (FMCW) tuning nonlinearity. Thesystem can be used for multi-parameter synchronous measurement of gas absorption spectrum and multiplexed opticalpath. Multi-channel parallel detection is realized by combining wavelength division multiplexing (WDM) and frequencydivision multiplexing (FDM) techniques. By introducing nonlinear optical crystals, broadband spectrum detection is simultaneouslyachieved over a bandwidth of hundreds of nanometers. An OFC with ultra-high frequency stability is used asthe frequency calibration source, which guarantees the measurement accuracy. The test samples involve H13C14N, C_(2)H_(2)and Rb vapor cells of varying densities and 5 parallel measurement experiments are designed. The results show that themeasurement accuracies of spectral absorption line and the optical path are 150 MHz and 20 m, respectively. The schemeoffers the advantages of multiplexed, multi-parameter, wide spectrum and high resolution detection, which can realize theidentification of multi-gas components and the high-precision inversion of absorption lines under different environments.The proposed sensor demonstrates great potential in the field of high-resolution absorption spectrum measurement for gassensing applications.

Dynamics of a Nonautonomous SIR Model with Time-Varying Impulsive Release and General Nonlinear Incidence Rate in a Polluted Environment

In a polluted environment, considering the biological population infected with a kind of disease and hunted by human beings, we formulate a nonautonomous SIR population-epidemic model with time-varying impulsive release and general nonlinear incidence rate and investigate dynamical behaviors of the model. Under the reasonable assumptions, the sufficient conditions which guarantee the globally attractive of the disease-free periodic solution and the permanence of the infected fish are established, that is, the infected fish dies out if , whereas the disease persists if . To substantiate our theoretical results, extensive numerical simulations are performed for a hypothetical set of parameter values.

融入文献实例剖析的有机合成设计课教学实践

研究型人才是目前高校人才培养的重要目标之一,在本科生基础和专业选修课教学当中融入与课程内容紧密结合的文献教学,能够在巩固学生所学基础知识的同时,激发学生对相关专业领域的学习热情,培养学生的科学研究思维。围绕这一教学目标,探索了如何在本科生有机合成设计课教学中加入最新文献实例剖析,包括对文献内容的选择和采用的教学方法。

Global Dynamic Analysis of a Vector-Borne Plant Disease Model with Discontinuous Treatment

This paper proposes a vector-borne plant disease model with discontinuous treatment strategies. Constructing Lyapunov function and applying non-smooth theory to analyze discontinuous differential equations, the basic reproductive number R0 is proved, which determines whether the plant disease will be extinct or not. If R0 R0 > 1 , there exists a unique endemic equilibrium which is globally stable. The numerical simulations are provided to verify our theoretical results, which indicate that after infective individuals reach some level, strengthening treatment measures is proved to be beneficial in controlling disease transmission.

Dynamical Analysis of a <i>Schistosomiasis japonicum</i>Model with Time Delay

In this paper, a Schistosomiasis japonicum model incorporating time delay is proposed which represents the developmental time from cercaria penetration through skins of human hosts to egg laying. By linearizing the system at the positive equilibrium and analyzing the associated characteristic equations, the local stability of the equilibria is investigated. And it proves that Hopf bifurcations occur when the time delay passes through a sequence of critical value. Furthermore, the explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions are derived by using techniques from the normal form theory and Center Manifold Theorem. Some numerical simulations which support our theoretical analysis are also conducted.

Cobalt-nanoparticle catalysts derived from zeolitic imidazolate framework@MXene composites for efficient oxidative self-coupling of benzylamines

In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene.The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine,where atmospheric oxygen(1 atm)is used as the oxidant.Based on the results,the catalyst displayed impressive catalytic activity,achieving 95.4%yield of the desired imine at 383 K for 8 h.Furthermore,the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups.The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support,while also benefiting from the three-dimensional porous structure.Additionally,a preliminary investigation of potential reaction mechanisms is conducted.

Reversible generation of dissipative Kerr solitons in a microresonator by the backward tuning method

Soliton generation schemes have attracted considerable scholarly attention.This paper introduces a novel backward tuning method for the reversible generation of dissipative Kerr solitons(DKSs).Reversible soliton generation relies on the thermal stabilization of the auxiliary laser,coupled with backward tuning of the pump laser,significantly increasing the range of soliton steps by over 10 times.Moreover,the method alleviates the stringent auxiliary laser detuning requirement.By adjusting the detuning of the auxiliary laser,diverse numbers of solitons can be deterministically generated,enhancing both flexibility and precision.

Linear group delay spectral interferometry for full-range precision absolute length metrology

The optical frequency comb serves as a powerful tool for distance measurement by integrating numerous stable optical modes into interferometric measurements,enabling unprecedented absolute measurement precision.Nonetheless,due to the periodicity of its pulse train,the comb suffers from measurement dead zones and ambiguities,thereby impeding its practical applications.Here,we present a linear group delay spectral interferometer for achieving precise full-range distance measurements.By employing a carefully designed linear group delay(LGD)device for phase modulation of the comb modes,interference can occur and be easily measured at any position.Our approach effectively eliminates the dead zones and ambiguities in comb-based ranging,without the need for cumbersome auxiliary scanning reference devices or reliance on complex high-repetition-rate combs or high-resolution spectrometers.We conducted length metrology experiments using a mode-locked comb referenced to a rubidium clock,achieving a large nonambiguity range up to 0.3 m,covering the entire measurement period.The maximum deviation compared to a laser interferometer was less than 1.5μm,and the minimum Allan deviation during long-term measurements reached 5.47 nm at a 500 s averaging time.The approach ensures high accuracy while maintaining a simple structure,without relying on complex external devices,thereby propelling the practical implementation of comb-based length metrology.

Distributed field mapping for mobile sensor teams using a derivative‐free optimisation algorithm

The authors propose a distributed field mapping algorithm that drives a team of robots to explore and learn an unknown scalar field using a Gaussian Process(GP).The authors’strategy arises by balancing exploration objectives between areas of high error and high variance.As computing high error regions is impossible since the scalar field is unknown,a bio-inspired approach known as Speeding-Up and Slowing-Down is leveraged to track the gradient of the GP error.This approach achieves global field-learning convergence and is shown to be resistant to poor hyperparameter tuning of the GP.This approach is validated in simulations and experiments using 2D wheeled robots and 2D flying mini-ature autonomous blimps.

可充气球囊压迫辅助下硬化剂注射治疗38例食管-胃底静脉曲张的疗效评价

目的探讨可充气球囊压迫辅助下硬化剂注射治疗(bc-EIS)对食管-胃底静脉曲张(EGV)的疗效和安全性。方法前瞻性选择2020年6月12日至9月12日于安徽医科大学第一附属医院行bc-EIS的38例EGV患者,统计硬化剂使用量、硬化剂注射点数,观察术中注射点是否出血(不出血、渗血、喷血或射血)、是否需要压迫止血(无需压迫止血、针鞘压迫止血、透明帽压迫止血),术后早期(术后72 h~6周)再出血、迟发性(术后6周后)出血情况,并记录达到静脉曲张完全消失的治疗次数。术后随访1、3、6个月,评估bc-EIS的疗效和术后并发症。采用描述性方法进行统计学分析。结果38例EGV患者中,男24例,女14例,年龄(范围)为(53.2±11.3)岁(30~79岁)。bc-EIS术中,每例患者硬化剂使用量(范围)为(20.03±7.49)mL(6~40 mL),硬化剂注射点数(范围)为(4.97±1.83)点(2~10点)。第1、2、3次bc-EIS后静脉曲张完全消失率分别为71.1%(27/38)、89.5%(34/38)、100.0%(38/38)。38例EGV患者均未发生术后静脉曲张相关再出血。随访发现2例患者于术后1个月出现呕血、黑便,内镜诊断为贲门下方胃底静脉曲张出血,经内镜下组织胶注射治疗后好转。所有患者bc-EIS术后均未发生发热、自发性细菌性腹膜炎、肝性脑病、异位栓塞和死亡等严重不良反应。结论bc-EIS的硬化剂用量较指南推荐量约减少1/2,注射点出血少,特别是1次治疗后静脉曲张完全消失率>70%。

Long-distance ranging with high precision using a soliton microcomb

Laser-based light detection and ranging(lidar)plays a significant role in both scientific and industrial areas.However,it is difficult for existing lidars to achieve high speed,high precision,and long distance simultaneously.Here,we demonstrate a high-performance lidar based on a chip-scaled soliton microcomb(SMC)that can realize all three specialties simultaneously.Aided by the excellent properties of ultrahigh repetition rate and the smooth envelope of the SMC,traditional optical frequency comb(OFC)-based dispersive interferometry is heavily improved and the measuring dead zone induced by the mismatch between the repetition rate of the OFC and resolution of the optical spectrum analyzer is totally eliminated.Combined with an auxiliary dual-frequency phase-modulated laser range finder,the none-dead-zone measurable range ambiguity is extended up to 1500 m.The proposed SMC lidar is experimentally implemented in both indoor and outdoor environment.In the outdoor baseline field,real-time,high-speed(up to 35 k Hz)measurement of a long distance of^1179 m is achieved with a minimum Allan deviation of 5.6μm at an average time of 0.2 ms(27 nm at an average time of 1.8 s after high-pass filtering).The present SMC lidar approaches a compact,fast,high-precision,and none-dead zone long-distance ranging system,aimed at emerging applications of frontier basic scientific research and advances in industrial manufacturing.

Fabrication of MIL-100（Fe）@SiO2@Fe3O4 core-shell microspheres as a magnetically recyclable solid acidic catalyst for the acetalization of benzaldehyde and glycol

Abstract Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magnetic MIL-100 （Fe）@SiO2@Fe3O4 microspheres with a novel core-shell structure were fabricated by the in-situ self-assembly of a metal-organic MIL- 100（Fe） framework around pre-synthesized magnetic SiO2@Fe3O4 particles under relatively mild and environmentally benign conditions. The catalytic activity of the MIL-100（Fe）@SiO2@Fe3O4 catalyst was tested for the liquid-phase acetalization of benzaldehyde and glycol. The MIL-100（Fe）@SiO2@Fe3O4 catalyst has a significant amount of accessible Lewis acid sites and therefore exhibited good acetalization catalytic activity. Moreover, due to its superparamagnetism properties, the heterogeneous MIL-100（Fe）@SiO2@Fe3O4 catalyst can be easily isolated from the reaction system within a few seconds by simply using an external magnet. The catalyst could then be reused at least eight times without significant loss in catalytic efficiency.

Autonomous flying blimp interaction with human in an indoor space

We present the Georgia Tech Miniature Autonomous Blimp(GT-MAB), which is designed to support human-robot interaction experiments in an indoor space for up to two hours. GT-MAB is safe while flying in close proximity to humans. It is able to detect the face of a human subject, follow the human, and recognize hand gestures. GT-MAB employs a deep neural network based on the single shot multibox detector to jointly detect a human user's face and hands in a real-time video stream collected by the onboard camera. A human-robot interaction procedure is designed and tested with various human users. The learning algorithms recognize two hand waving gestures. The human user does not need to wear any additional tracking device when interacting with the flying blimp. Vision-based feedback controllers are designed to control the blimp to follow the human and fly in one of two distinguishable patterns in response to each of the two hand gestures. The blimp communicates its intentions to the human user by displaying visual symbols. The collected experimental data show that the visual feedback from the blimp in reaction to the human user significantly improves the interactive experience between blimp and human.The demonstrated success of this procedure indicates that GT-MAB could serve as a flying robot that is able to collect human data safely in an indoor environment.

PdZn intermetallic compound stabilized on ZnO/nitrogendecorated carbon hollow spheres for catalytic semihydrogenation of alkynols

Enhancing the selectivity of noble metal catalysts through electronic modulation is important for academic research and chemical industrial processes.Herein,we report a facile sacrificial template strategy for the synthesis of PdZn intermetallic compound(3-4 nm)highly distributed in ZnO/nitrogen-decorated carbon hollow spheres(PdZn-ZnO/NCHS)to optimize the selectivity of Pd catalysts,which involves carbonization of a core-shell structured polystyrene(PS)@ZIF-8 precursor in an inert atmosphere,impregnation Pd precursor,and subsequent H2 reduction treatment.Due to the unique structural and compositional features,the developed PdZn-ZnO/NCHS delivers an excellent catalytic performance for the semihydrogenation of 2-methyl-3-butyn-2-ol(MBY)to 2-methyl-3-buten-2-ol(MBE)with high activity(>99%),high selectivity(96%),and good recyclability,outperforming the analog Pd on ZnO(Pd/ZnO)as well as the supported Pd nanoparticles(Pd/C and Pd/NC).Density functional theory(DFT)calculations reveal that the presence of Znδ+species in PdZn-ZnO/NCHS alters the adsorption modes of reactant and product,leading to a decrease of the adsorption strength and an enhancement of the energy barrier for overhydrogenation,which results in a kinetic favor for the selective transformation of MBY to MBE.In addition,PdZn-ZnO/NCHS was also very effective for the partial hydrogenation of dehydrolinalool to hydrolinalool.

Marine information technology:the best is yet to come

Marine information technology(MarineIT)involves marine information gathering,transmission,processing,and fusion.Traditionally,this topic has been referred to in the context of acoustic,optical,and electromagnetic sensing of the ocean environment,most notably sonar/radar processing and satellite remote sensing.As its embodiment becomes enriched and its scope extends,particularly accompanied

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO_(2) reduction: A review

Photocatalytic CO_(2)reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels.Numerous attempts have been made to produce effective and efficient photocatalysts for CO_(2)reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO_(2)reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO_(2)reduction performance in order to achieve a long-term sustainability. Metalorganic frameworks(MOFs) are recently emerging as a new type of photocatalysts for CO_(2)reduction due to their excellent CO_(2)adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO_(2)reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO_(2)reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers,and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles(NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO_(2)reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO_(2)conversion.

Visible-light-induced photocatalytic CO_(2)reduction over zirconium metal organic frameworks modified with different functional groups

The reduction of CO_(2)into high value-added chemicals and fuels by a photocatalytic technology can relieve energy shortages and the environmental problems caused by greenhouse effects.In the current work,an amino-functionalized zirconium metal organic framework(Zr-MOF)was covalently modified with different functional groups via the condensation of Zr-MOF with 2-pyridinecarboxaldehyde(PA),salicylaldehyde(SA),benzaldehyde(BA),and trifluoroacetic acid(TA),named Zr-MOF-X(X=PA,SA,BA,and TA),respectively,through the post-synthesis modification.Compared with Zr-MOF and Zr-MOF-TA,the introduction of PA,SA,or BA into the framework of Zr-MOF can not only enhance the visible-light harvesting and CO_(2)capture,but also accelerate the photogenerated charge separation and transfer,thereby improving the photocatalytic ability of Zr-MOF for CO_(2)reduction.These results indicate that the modification of Zr-MOF with electron-donating groups can promote the photocatalytic CO_(2)reduction.Therefore,the current work provides an instructive approach to improve the photocatalytic efficiency of CO_(2)reduction through the covalent modification of MOFs.

Construction of isolated Ni sites on nitrogen-doped hollow carbon spheres with Ni-N_(3) configuration for enhanced reduction of nitroarenes

Designing and synthesizing high-efficiency non-precious metal-based catalysts having uniform active sites increases the reactivity and selectivity of materials and provides a platform for an in-depth understanding of their catalytic reaction mechanism.In this study,we provided an approach for fabricating isolated nickel single-atom sites(Ni SAs)with high loading(4.9 wt.%)stabilized on nitrogen-doped hollow carbon spheres(NHCS)using a core–shell structured Zn/Ni bimetallic zeolitic imidazolate framework(ZIF)composite as the sacrificial template.The as-fabricated Ni SAs/NHCS catalyst shows superior activity,selectivity,and recycling durability for the catalytic transfer hydrogenation of nitrobenzene to aniline,thus achieving 100%yield of aniline with a turn-over frequency(TOF)value as high as 29.9 h^(−1) under mild conditions.This TOF value is considerably superior to the supported Ni nanoparticle catalysts.The experiments designed show that the hollow structure feature of NHCS facilitates accessible active sites and mass transfer,which thus contributes to the enhancement of the catalytic performance of Ni SAs/NHCS.Density functional theory calculations show the high chemo-selectivity and activity of the Ni SAs catalyst,arising from the unique role of the single Ni-N3 site on simultaneously activating the H donor(N_(2)H_(4))and substrate,as well as the hydrogenation of the–NOH group as the rate-determining step.

Role of vector resistance and grafting infection in Huanglongbing control models

Citrus huanglongbing(HLB)is one of the most devastating diseases affecting citrus almost worldwide due to the lack of a cure.To better understand the impact of insecticide resistance and grafting infection on the spread of HLB disease,a vector-borne compartmental model is formulated to describe the transmission dynamics of HLB between citrus and Asian citrus psyllid(ACP).The basic reproduction number R0 is computed by using the next generation matrix approach,which is a threshold value of the uniform persistence and disappearance of HLB disease.By applying the sensitivity analysis of R0,we obtain some parameters with the most significant influence on the transmission dynamics of HLB.Moreover,we also obtain that grafting infection has the least influence on the transmission dynamics of HLB.Additionally,a time-dependent control model of HLB to minimize the cost of implementing control efforts and infected trees and ACPs is formulated.By using Pontryagin's Minimum Principle,we obtain the optimal integrated strategy and prove the uniqueness of optimal control solution.The simulation results illustrate that the strategy involving two time-dependent optimal controls is the most effective to suppress the spread of the disease.However,insecticide spraying is more effective measure compared with infected tree removing.

Analysis and optimal control of a Huanglongbing mathematical model with resistant vector

Huanglongbing(HLB)is an incurable disease that affects citrus trees.To better understand the transmission of HLB,the mathematical model is developed to investigate the transmission dynamics of the disease between Asian citrus psyllid(ACP)and citrus trees.Through rigorous mathematical derivations,we derive the expression of the basic reproduction number(R_(0))of HLB.The findings show that the disease-free equilibrium is locally asymptotically stable if R_(0)<1,and if R_(0)>1 the system is uniformly persistent.By applying the global sensitivity analysis of R_(0),we can obtain some parameters that have the greatest influence on the HLB transmission dynamics.Additionally,the optimal control theory is used to explore the corresponding optimal control problem of the HLB model.Numerical simulations are conducted to reinforce the analytical results.These theoretical and numerical results provide useful insights for understanding the transmission dynamics of HLB and may help policy makers to develop intervention strategies for the disease.