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1.
片状材料的径厚比是片状材料的一个重要特征参数。以片状云母为研究对象,引入形状明显区别于片状云母的聚苯乙烯球作为支撑材料。实验结果表明,当云母片与聚苯乙烯球混合质量比为1∶3时,呈竖立取向云母片的数量达到最大值,随机采集200个云母片的长径和厚度,其径厚比的统计样本均值为15.37。支撑材料聚苯乙烯球为片状云母带来大量支撑位点,显著提高片状云母呈竖立取向的概率,能够快速、直观地同时测量云母片的长径和厚度,有效提高云母片径厚比的测量效率和准确性。  相似文献   
2.
Yongtao Li 《中国物理 B》2022,31(5):54215-054215
A novel ultra-broadband polarization splitter based on a dual-core photonic crystal fiber (DC-PCF) is designed. The full-vector finite element method and coupled-mode theory are employed to investigate the characteristics of the polarization splitter. According to the numerical results, a graphene-filled layer not only broadens the working bandwidth but also reduces the size of the polarization splitter. Furthermore, the fluorine-doped region and the germanium-doped region can broaden the bandwidth. Also, the 4.78 mm long polarization splitter can achieve an extinction ratio of -98.6 dB at a wavelength of 1550 nm. When extinction ratio is less than -20 dB, the range of the wavelength is 1027 nm-1723 nm with a bandwidth of 696 nm. Overall, the polarization splitter can be applied to all-optical network communication systems in the infrared and near-infrared wavelength range.  相似文献   
3.
This paper expands the notion of robust profit opportunities in financial markets to incorporate distributional ambiguity using Wasserstein distance as the ambiguity measure. Financial markets with risky and risk-free assets are considered. The infinite dimensional primal problems are formulated, leading to their simpler finite dimensional dual problems. A principal motivating question is how distributional ambiguity helps or hurts the robustness of the profit opportunity. Towards answering this question, some theory is developed and computational experiments are conducted. Finally some open questions and suggestions for future research are discussed.  相似文献   
4.
猪肉内部结构成分复杂,各部位的成分相似,分辨较为困难。结合激光诱导击穿光谱技术,通过光谱分析的方式提高分类精度。以5种不同部位的长白山黑猪肉(里脊肉、梅花肉、后腿肉、前腿肉、五花肉)作为待测样品,通过冷藏、切片等预处理方法,探究激光诱导击穿光谱技术鉴别猪肉脂肪与肌肉及其不同部位的可行性。首先通过采集猪肉脂肪样品与肌肉样品的LIBS谱线信息发现,猪肉中Mg,K,Fe,Cu,Ca和Na等元素较为丰富,并在脂肪样品光谱中发现C-N键,与肌肉样品LIBS谱线信息相比,脂肪样品受其内部水分、有机质成分影响致使其谱线信息背景和噪声信号干扰较大,二者谱线信息存在一定差异,说明LIBS可对脂肪组织与肌肉组织进行鉴别。通过对目标元素Ca,Na,Mg,K和Al其LIBS特征谱线强度进行检测,计算Mg/Ca,Al/Ca,Na/Ca和K/Ca比值,发现与Al/Ca和Mg/Ca相比,Na/Ca和K/Ca各部位元素比值分布差异明显,在此基础上,根据Na/Ca和K/Ca比值,计算猪肉各部位元素分布决策阈值[(1-α)=90%]。发现与Al/Ca和Mg/Ca比值相比,Na/Ca和K/Ca更能明显的反应出各部位元素分布的不同。其比值分布阈值基本可对猪肉各部位进行区分。以前腿肉与后腿肉为例,前腿肉Na/Ca和K/Ca比值分别分布在1.29~1.58和0.31~0.42,后腿肉Na/Ca和K/Ca比值分别分布在0.98~1.18和0.15~0.23。其元素比值分布无明显重叠。最后,为提高LIBS技术对猪肉不同组织分类的可靠性,将光谱元素强度比值数据与主成分分析法相结合,基本可以实现对猪肉各部位的分类,说明元素特征谱线强度比值在对猪肉各部位分类时具有一定的预测精度。该工作证明,使用激光诱导击穿光谱技术对猪肉进行分类识别等定性分析时具有一定可行性,有望适用于其他生物组织检测分析。  相似文献   
5.
赵铭  王天枢 《应用光学》2021,42(1):194-199
介绍一种多波长掺铥主动锁模光纤激光器,增益介质为长2 m的掺铥光纤,主动锁模通过铌酸锂强度调制器实现。腔内加入基于双折射的光学滤波器,利用保偏光纤双折射滤波效应在滤除腔内多余超模噪声的同时,还可以实现多波长输出。基频下的锁模脉冲频谱信噪比可达68.48 dB,在稳定的锁模状态下波长信道数最大为5。此外,腔内偏振无关隔离器被替换为偏振相关隔离器后,将锁模脉冲加载数字信号同步调制,测得的眼图光信噪比提高了8.67 dB。测试结果表明,锁模脉冲的时间稳定性得到有效提升。  相似文献   
6.
This work studies the macroscopic and microscopic behaviors of ellipsoids under triaxial tests using 3D discrete element method (DEM) simulation. To avoid the boundary effect, a novel stress servo-controlled periodic boundary condition is proposed to maintain the confining pressure of samples during testing. The shape features of ellipsoids are investigated, including the aspect ratio of elongated/oblate ellipsoids and the initial arrangement directions of ellipsoids. The macroscopic properties of ellipsoidal particle samples, such as the deviatoric stress, volumetric strain, internal friction angle, as well as dilatancy angles are explored. Elongated and oblate ellipsoids with varying aspect ratios are investigated for the occurrence of stick-slips. In addition, it is demonstrated that the initial arrangement direction has a significant impact on the coordination number and contact force chains. The corresponding anisotropy coefficients of the entire contact network are analyzed to probe the microscopic roots of macroscopic behavior.  相似文献   
7.
In this study, a fingerprint-activity relationship modeling between chemical fingerprints and antirheumatic activity was established, and multivariate statistical analysis was used to evaluate the quality of Taxilli Herba (TH) from different hosts. Characteristic fingerprints of 20 batches of TH samples were generated by high-performance liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (HPLC-Triple TOF-MS/MS), and the similarity analysis was calculated based on thirteen common characteristic peaks by hierarchical clustering analysis (HCA). Subsequently, nine efficacy markers were discovered by combining fingerprints and antirheumatic activity through grey correlation analysis (GCA) and bivariate correlation analysis (BCA). Meanwhile, the content of 5 constituents in 9 markers was determined by high-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (HPLC-QTRAP-MS/MS). The comprehensive quality of TH was assessed using multivariate statistical analysis, including principal components analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS). The results showed that a high dose of TH extract could markedly ameliorate arthritis damage compared to other doses, with flavonoids playing an important role in the antirheumatic activity. The comprehensive quality of samples from Morus alba L. (SS) was superior to those from Liquidambar formosana Hance (FXS). The present study will demonstrate the markers associated with efficacy, and provide an applicable strategy for more comprehensive quality control and evaluation of TH.  相似文献   
8.
羟基磷灰石(HA)晶体的形核和生长与表面活性剂、初始钙-磷物质的量比值(nCa,0/nP,0)密切相关。因此,本研究以油酸为表面活性剂制备高柔韧超长HA纳米纤维,利用X射线衍射(XRD)、FTIR、场发射扫描电镜(FESEM)和能量色散X射线谱(EDS)探究了不同nCa,0/nP,0对HA纳米纤维微观结构的影响,并基于产物微观结构演变提出HA纳米纤维的形成机制。nCa,0/nP,0=0.8~1.2有利于高结晶超长柔韧HA纳米纤维的合成,而过高和过低的nCa,0/nP,0会导致油酸诱导HA沿c轴择优生长的作用减弱,进而导致非晶绳结状或低结晶纳米针束状产物的形成。HA晶体的择优生长方向随nCa,0/nP,0的降低由a轴向c轴转变,但过低的nCa,0/nP,0导致HA晶体倾向同时沿a轴和c轴生长。  相似文献   
9.
To date, luminescent materials have been preferably used for non-contact optical thermometers. In this manner, novel red-emitting Ba2Y0.8Eu0.2NbO6:Mn4+ (BYEN:Mn4+) phosphors were designed for multi-type non-contact luminescent thermometers based on the dual-emission states and temperature-dependent lifetime (TDL) models. In the temperature range of 303–483 K, the sensing sensitivities based on the dual-emission states of (5D07F2, 2Eg4A2g) and (5D07F1, 2Eg4A2g) were estimated. Especially, the maximum absolute sensing sensitivity (Sa) was found to be about 0.1558 K-1 for the BYEN:0.007Mn4+ phosphor based on the 5D07F1 and 2Eg4A2g positions. This phosphor also exhibited good relative sensing sensitivity (Sr) (0.0186 K-1) based on the 5D07F2 and 2Eg4A2g states. Besides, the relative sensing sensitivities (SR) at 5D07F1 and 2Eg4A2g transitions were estimated to be 0.0034 and 0.0194 K-1, respectively with the help of the TDL technique. In the light of these results, novel red-emitting Ba2Y0.8Eu0.2NbO6:Mn4+ phosphors are expected to be a potentially attractive candidate for applications in multi-type luminescent thermometers. Finally, a novel unique polydimethylsiloxane film exhibiting tricolor-luminescent emissions was introduced and further suggested for high-security anti-counterfeiting.  相似文献   
10.
采用简单的水热法合成了六角柱形NaErF_(4)和NaErF_(4)@NaYF_(4)核壳上转换发光材料,利用扫描电镜(SEM)、X射线粉末衍射(XRD)和荧光光谱(PL)等表征对材料的形貌、结构和上转换发光性能进行了研究。结果表明,纯NaErF_(4)样品为六角柱形,边长和厚度均为1μm左右,样品表面光滑。随着NaYF_(4)壳层的包覆,六角相NaErF_(4)周围出现了大量的立方相NaYF_(4)纳米颗粒,得到了NaErF_(4)@NaYF_(4)核壳结构。荧光光谱表明,通过在六角柱形NaErF_(4)表面包覆NaYF_(4)壳层,可以有效增强上转换发光强度,其中,位于527,543,663 nm处的3个发射峰分别对应于Er^(3+)的^(2)H_(11/2)→^(4)I_(15/2)、^(4)S_(3/2)→^(4)I_(15/2)和^(4)F_(9/2)→^(4)I1_(5/2)能级跃迁。随着壳层中Y∶F比例的增加,立方相NaYF_(4)的晶体衍射峰逐渐增强;同时,对应的NaErF_(4)@NaYF_(4)样品发射光谱中红绿比(R/G)逐渐增大,发光颜色也从绿色、经黄绿色逐渐向黄色过渡,实现了多色发光。  相似文献   
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