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.

Optical frequency comb technology: from ground to space

Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.

THE INFLUENCE OF COMBING ROLLER SPEED ON PURE RAMIE NOIL ROTOR YARN QUALITY AND SPINNING PERFORMANCE

This paper reports the optimum design of combing roller speed with reference to yielding 6-13 Ne(98.4—45.4 tex) pure ramie noil rotor-spun yarns. The universal rotatable composite design is adopted to get the highly precise regression equations, in which the variables are combing roller speed and yarn linear density considered to be the main technological parameters of combing roller and, the responses are the evaluation indexes concerning spinning stability, fiber length distribution of fibre ring from rotor groove and yarn properties. Based on these regression equations, the contours are plotted to analyse the influences of the parameters on the evaluation indexes; the optimization multicriteria mathematical model is simultaneously established to obtain the optimum parameters with the aid of Object Programming Approach along with Constrained Random Ray Method. Finally, an experiment is carried out to further test the acceptance of the calculated optimum values. It is shown that, for any yarn linear density within 6—13 Ne (98.4—45.4 tex), combing roller speed varying from 5000 to 9150 r/min affects content of extra-long fibre in fibre ring from rotor groove and yarn properties but does not significantly influence spinning stability; 7075 r/min, at which the SAQ-12 type of saw-toothed combing roller runs, is recommended to be the optimum combing roller speed for producing 6—13 Ne (98.4—45.4 tex) pure ramie noil yarns, where a compromise is achieved among the lowest content of extra-long fibre in fibre ring, the best spinning stability and the best yarn properties.

FUZZY DECISION-MAKING OF COMBING ROLLER COVERING FOR SPINNING PURE RAMIE NOIL ROTOR-SPUN YARNS

This paper deals with the types and specifications of combing roller covering for spinning pureramie noil rotor-spun yarns.A handling mode combining Fuzzy Decision-making and FuzzyCluster Analysis has been used for analyzing the experimental results.It is shown that,with regard to the specifications of the sawtooth clothing of the combing rol-ler,large working angle,large tooth pitch,fine tooth shape,short tooth height,smooth finish andgood wearability are of benefit to improving the spinning stability and the spun yarn properties.The pinned combing roller,however,regardless of its complicated process of production,is sug-gested to be preferred for spinning the pure ramie noil rotor-spun yarns.The handling mode used in this work is efficient in improving the reliability and objectivity ofthe conclusions and can be used for solving the similar problems.

Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

We investigated the interaction between DNA and hexammine cobalt III [Co（NH3）6]3＋ by a simple molecular combing method and dynamic light scattering. The average extension of A- DNA-YOYO-1 complex is found to be 20.9μm, about 30% longer than the contour length of the DNA in TE buffer （10 mmol/L Tris, 1 mmol/L EDTA, pH=8.0）, due to bis-intercalation of YOYO-1. A multivalent cation, hexammine cobalt, is used for DNA condensation. We find that the length of DNA-[Co（NH3）6]3＋ complexes decrease from 20.9 μm to 5.9μm as the concentration of the [Co（NH3）6]3＋ vary from 0 to 3 μmol/L. This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt. The results from the molecular combing studies are supported by dynamic light scattering investigation, where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions. It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.

Comb-Based Filter Design Using Sharpening Technique and Certain Palindromic Polynomial

This paper presents a novel approach to improve aliasing rejection in comb-based decimation filters. The method is established on certain palindromic polynomials with all zeros on the unit circle and the sharpening technique. As a result, aliasing rejection and the passband characteristic are improved. The method is illustrated with various examples and compared with the methods from the literature. .

Improved Multi-Path Routing for QoS on MANET

A Mobile Ad hoc NETwork(MANET)is a self-configuring network that is not reliant on infrastructure.This paper introduces a new multipath routing method based on the Multi-Hop Routing(MHR)technique.MHR is the consecutive selection of suitable relay nodes to send information across nodes that are not within direct range of each other.Failing to ensure good MHR leads to several negative consequences,ultimately causing unsuccessful data transmission in a MANET.This research work consists of three portions.The first to attempt to propose an efficient MHR protocol is the design of Priority Based Dynamic Routing(PBDR)to adapt to the dynamic MANET environment by reducing Node Link Failures(NLF)in the network.This is achieved by dynamically considering a node’s mobility parameters like relative velocity and link duration,which enable the next-hop selection.This method works more efficiently than the traditional protocols.Then the second stage is the Improved Multi-Path Dynamic Routing(IMPDR).The enhancement is mainly focused on further improving the Quality of Service(QoS)in MANETs by introducing a QoS timer at every node to help in the QoS routing of MANETs.Since QoS is the most vital metric that assesses a protocol,its dynamic estimation has improved network performance considerably.This method uses distance,linkability,trust,and QoS as the four parameters for the next-hop selection.IMPDR is compared against traditional routing protocols.The Network Simulator-2(NS2)is used to conduct a simulation analysis of the protocols under consideration.The proposed tests are assessed for the Packet Delivery Ratio(PDR),Packet Loss Rate(PLR),End-to-End Delay(EED),and Network Throughput(NT).

Multi-Path Attention Inverse Discrimination Network for Offline Signature Verification

Signature verification,which is a method to distinguish the authenticity of signature images,is a biometric verification technique that can effectively reduce the risk of forged signatures in financial,legal,and other business envir-onments.However,compared with ordinary images,signature images have the following characteristics:First,the strokes are slim,i.e.,there is less effective information.Second,the signature changes slightly with the time,place,and mood of the signer,i.e.,it has high intraclass differences.These challenges lead to the low accuracy of the existing methods based on convolutional neural net-works(CNN).This study proposes an end-to-end multi-path attention inverse dis-crimination network that focuses on the signature stroke parts to extract features by reversing the foreground and background of signature images,which effectively solves the problem of little effective information.To solve the problem of high intraclass variability of signature images,we add multi-path attention modules between discriminative streams and inverse streams to enhance the discriminative features of signature images.Moreover,a multi-path discrimination loss function is proposed,which does not require the feature representation of the samples with the same class label to be infinitely close,as long as the gap between inter-class distance and the intra-class distance is bigger than the set classification threshold,which radically resolves the problem of high intra-class difference of signature images.In addition,this loss can also spur the network to explore the detailed infor-mation on the stroke parts,such as the crossing,thickness,and connection of strokes.We respectively tested on CEDAR,BHSig-Bengali,BHSig-Hindi,and GPDS Synthetic datasets with accuracies of 100%,96.24%,93.86%,and 83.72%,which are more accurate than existing signature verification methods.This is more helpful to the task of signature authentication in justice and finance.

Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains

Frequency-comb emission via high-order harmonic generation(HHG)provides an alternative method for the coherent vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)radiation at ultrahigh repetition rates.In particular,the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission dynamics.Here we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse trains.We find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG,leading to suppression and enhancement of frequency-comb emission.The results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via HHG.The dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in detail.Our results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV–XUV regimes.

棉纺精梳机锡林不同梳理区梳理效果分析

为了研究棉纺精梳机锡林不同梳理区的精梳落棉率、棉结及纤维排除率的变化规律,使用5分区的整体锡林,并分别采用5个、4个、3个、2个、1个梳理区进行精梳试验,得到了5种不同试验方案的精梳落棉率、落棉中的棉结含量及纤维长度分布,并利用导出的公式计算得出锡林不同梳理区的落棉率、棉结排除率及不同长度纤维排除率的变化规律。结果表明:整体锡林的5个不同梳理区的落棉率、棉结排除率及不同长度纤维排除率的变化规律基本相同,即梳理区排序从大到小依次为第2梳理区、第3梳理区、第1梳理区、第4梳理区、第5梳理区。在锡林的同一梳理区内,当纤维长度小于钳板钳口外纤维丛长度时,纤维长度越短时排除率越高;当纤维长度大于钳板钳口外纤维丛长度时,随着纤维长度的增大纤维排除率有减小的趋势,并具一定的波动性。梳理隔距和锡林针齿深度是影响梳理效果的重要参数。

无轴泵喷叶片流激共振产生机理及其抑制

针对无轴泵喷异常高频梳状线谱噪声,本文研究了梳状线谱的产生原因及其噪声抑制特点。基于推进器实测噪声谱、振动谱梳状特征,初步定位梳状线谱与泵喷叶轮密切相关;进一步采用单向流固耦合分析方法,验证了无轴泵喷高频线谱来源于流激引起的叶轮面内2弯模态共振,并提出了一种在叶轮过流通道增设环筋以提高叶片支撑刚度的方案。流固耦合仿真及实测结果表明:带有环筋加强的泵喷叶轮对流激振动与噪声有明显抑制作用,梳状线谱噪声降幅达25.2~30.2 dB,且未向其他频段转移。

太阳系外行星探测技术概述

自20世纪90年代首次发现太阳系外行星(以下简称系外行星)以来,系外行星探测技术取得了飞速发展。目前已探测到超过5500颗系外行星,其中包括类地行星、超级地球、气态巨行星及冰巨行星等多种类型。这些发现极大地拓展了人类对自身周围环境和宇宙的认知,为理解行星形成和演化提供了宝贵的观测依据,也为寻找宜居行星和地外生命提供了重要线索。通过介绍系外行星探测的多种核心技术,包括原理和应用特点,旨在对比和分析不同探测方法的技术特征。通过分析多种探测技术的优势和局限性,为行星探测研究提供了实践参考和发展趋势展望。

提高微腔孤子光频梳泵浦能量转换效率技术研究进展

分析了孤子微梳泵浦能量转换效率低的原因,介绍了目前已提出的几种提高孤子微梳泵浦光能量转换效率的技术方案,包括激发孤子晶体光梳利用多孤子结构、正常-反常色散双腔耦合泵浦光循环存储结构、微腔-光纤/波导环泵浦光反馈耦合干涉结构、主-副微环腔耦合超模谐振峰劈裂结构等,并分析了这些方案的优缺点。在此基础上,给出了本课题组对反馈耦合腔的优化设计,仿真模拟结果显示,单孤子微梳的泵浦光转换效率可超过25%。最后,对孤子微梳的低能耗产生方案作出总结和展望,为微腔孤子光频梳泵浦能量转换效率提高技术的发展与应用提供理论参考。

梳状高度计编队探测海洋涡旋仿真分析

单颗星下点高度计卫星可进行一维海面高度测量,但时空分辨率较低,对涡旋的探测能力不足。梳状高度计卫星编队可提升海面高度时空分辨率,增强对涡旋的识别探测能力。为定量分析高度计编队下的涡旋探测能力,本文在黑潮延伸体海域开展观测仿真实验,对海平面高度进行沿轨采样,经优化插值算法处理后得到逐天海面高度异常数据场并进行涡旋识别与统计分析。此外,本文还同步开展了单颗星下点高度计和成像高度计卫星涡旋探测仿真实验及对比分析。结果表明,梳状高度计卫星编队在涡旋数量、极性、半径及振幅等方面识别效果较好,与成像高度计探测结果相近。

基于锁模光学频率梳的高速数据传输

大数据时代网络数据流量的爆炸式增长给通信系统的容量和数据传输速率带来极大的挑战.本文基于锁模光学频率梳的宽光谱范围和高相位相干性提出了一种高频正交幅度调制信号生成方法,通过电光调制器对光学频率梳进行幅度相位整形并下变频至射频域,生成携带编码信息的高速、高阶、低相位噪声的调制信号,再结合锁模光学频率梳窄线宽、多波长的特性,仅使用单个激光器即可实现基于波分复用技术的大规模并行高速通信.仿真验证了该方案的可行性,随后在100 m的自由空间光链路中使用光子微波信号进行16元正交幅度调制通信实验,实现了误码率低于10^(–6)的14 Gbit/s数据传输.

梳刷式枸杞采摘机的设计与理论分析

为了实现枸杞机械化采收,提高枸杞采摘的采净率、降低损伤率,提出一种柔性梳刷齿的梳刷式采摘机,该装置通过梳刷齿的冲击作用使得枸杞熟果脱落,完成采摘工作。通过对枸杞自然特征和物理参数测量分析,设置了梳刷器的各项参数,利用Solidworks软件搭建了样机模型,并选择了合适的材料制造了样机;通过静力学分析和赫兹碰撞理论推导出了梳刷齿速度与冲击力之间的关系式;使用Adams软件对梳刷过程进行了动力学分析,当滚筒转速为57 rpm时,枸杞果实的受力峰值为0.83 N,理论上满足了采摘的需求;在青海诺木洪农场对当地宁杞1号进行采摘实验,结果表明:采净率为96.84%,损伤率为8.76%,满足枸杞采收的工作要求。

国内外蜂蜜质量标准对比研究

我国的蜂群数量、蜂蜜产量、消耗量和出口量均居世界前列,但产业水平和经济效益与发达国家相比仍存在一定的差距。本文以蜂蜜进出口贸易为切入点,对比分析了我国与主要贸易国制定的蜂蜜质量标准,找出国内外蜂蜜质量评价中指标差异。针对现状,结合我国的蜂蜜质量问题,提出健全蜂蜜质量标准的合理建议,规范国内蜂蜜市场秩序,为提高我国蜂蜜国际竞争力提供技术支撑。

一种改进的Fixed-base Comb安全快速算法

本文从分析椭圆曲线上Fixed-baseComb算法出发,根据其特点,利用牺牲乘法操作以降低求逆操作的方法,分别用2kP、2P+Q的快速算法对Fixed-baseComb算法的预计算阶段和赋值阶段进行改进,极大地提高了计算效率:在素数域上预计算阶段提高70%～80%,而赋值阶段提高38%～43%,同时,改进算法通过对k的预处理,使得算法能够抵抗边际信道攻击.

光频梳下变频信号光纤延时频率恢复方法

针对光频梳下变频信号接收过程中存在的频率信息丢失问题,提出了一种基于频率-相位映射的信号频率恢复方法,该方法使用可调光纤延迟线在两路光频梳变频链路之间产生一组固定已知的时延,时延在信号原始频率与下变频信号相位差之间建立映射关系,利用该映射关系可以从测得的相位差计算出信号的原始频率。分析了时延值等参数对频率恢复的影响,估计了该方法对相位测量不确定度的限值要求,最后给出了该方法具体实施方案中关键参数的设置策略。所有下变频信号的相位差可以通过快速傅里叶变换等数据处理一次性得出,因此该方法的时间代价和计算成本几乎不随着信号个数增加而增加。在不考虑下变频信号混叠的情况下,本文所提出的方法在理论上对处理信号的数量没有限制,因此相比于已有的光频梳下变频信号频率恢复方法,在多信号频率恢复方面更具有优势。

金属离子对黑翅土白蚁消化代谢的影响

【目的】探究金属离子对黑翅土白蚁Odontotermes formosanus消化代谢过程的影响,挖掘黑翅土白蚁对含有金属离子的厨余垃圾和农林废弃物进行资源化处理的潜在价值。【方法】根据浓度梯度法,将含有不同质量分数Al^(3+)、Ca^(2+)、Fe^(3+)和Mg^(2+)的饵料供给黑翅土白蚁,确定黑翅土白蚁对饵料中金属离子的最大可取食质量分数。采用电感耦合等离子体发射光谱仪(ICP-OES)测定黑翅土白蚁虫体内及其新建菌圃内的对应金属元素质量分数,明确饵料中Al^(3+)、Ca^(2+)、Fe^(3+)和Mg^(2+)对虫体内及新建菌圃内对应金属元素质量分数的影响。采用试剂盒法测定黑翅土白蚁虫体内及其新建菌圃内漆酶和纤维素酶的活性,确定饵料中Al^(3+)、Ca^(2+)、Fe^(3+)和Mg^(2+)对上述酶活性的影响。【结果】黑翅土白蚁对饵料中Al^(3+)、Ca^(2+)和Fe^(3+)的最大可取食质量分数均为1.00 g·kg^(-1),对饵料中Mg^(2+)的最大可取食质量分数为10.00 g·kg^(-1)。黑翅土白蚁取食含有10.00 g·kg^(-1) Mg^(2+)的饵料后,其虫体内和菌圃内都发生了Mg的富集;取食含有1.00 g·kg^(-1) Fe^(3+)的饵料后,Fe仅在菌圃内富集。取食含有1.00 g·kg^(-1) Al^(3+)的饵料,会显著提高黑翅土白蚁虫体内的漆酶活性(P<0.05);取食含有1.00 g·kg^(-1) Ca^(2+)的饵料,会显著提高黑翅土白蚁虫体内的漆酶活性(P<0.05),但会显著降低纤维素酶活性(P<0.05);取食含有1.00 g·kg^(-1) Fe^(3+)的饵料,会显著提高黑翅土白蚁虫体内的漆酶活性和菌圃中的纤维素酶活性(P<0.05),但会显著降低菌圃中的漆酶活性和黑翅土白蚁虫体内的纤维素酶活性(P<0.05);取食含有10.00 g·kg^(-1) Mg^(2+)的饵料,会显著提高黑翅土白蚁虫体内的纤维素酶活性和菌圃中的漆酶活性(P<0.05),但会显著降低菌圃中的纤维素酶活性(P<0.05)。【结论】黑翅土白蚁可取食分别含有1.00 g·kg^(-1) Al^(3+)、Ca^(2+)和Fe^(3+)的饵料和含有10.00 g·kg^(-1) Mg^(2+)的饵料,1.00 g·kg^(-1) Al^(3+)可以提高黑翅土白蚁和菌圃微生物对木质素的联合降解能力。黑翅土白蚁具有资源化处理厨余垃圾和农林废弃物的应用潜力。