基于朴素贝叶斯分类器的公共自行车系统故障诊断方法

针对公共自行车没有安装车载检测传感器、流动及停放区域较大、管理部门无法及时发现自行车故障等问题，提出了基于朴素贝叶斯分类器的自行车故障诊断方法。通过分析公共自行车系统(PBS)租用记录、维修记录和用户评价，选取15个状态分类特征作为自行车故障检测的特征向量；根据朴素贝叶斯分类器后验概率，获取每个状态分类特征对类的贡献率；以召回率作为评价指标来预测诊断故障自行车。采用杭州市PBS 2016年的相关数据对模型进行实践验证，通过预测模型输入特征值的优化，测试样本的召回率达85.79%，精度较为理想。     

Influence of modified fiber–MHSH hybrids on fire hazards,combustion dynamics,and mechanical properties of flame-retarded poly(butylene succinate) composites

Environmental problems caused by polymers and polymers have historically dominated both academic and industrial attention. Sustainable biodegradable wood-plastic composites (WPCs) as an optimum can solve the environmentally critical problems caused by petroleum-based polymers. However, they are flammable, prone to fire accidents, and often have a contradiction between mechanical performance and flame-retardant properties, which limits their range of applications. Here, we reported a flame-retarded poly(butylene succinate) (PBS) WPC prepared with modified natural fiber-magnesium hydroxide sulfate whisker (MHSH) hybrids and intumescent flame retardant s (IFRs). The mechanical performance, flame-retardant properties , thermal stability, and actual fire simulation parameters of composites were investigated. Owing to the unique composition characteristics of modified cassava dregs-MHSH hybrids, the mechanical properties (70P/23I/5C/2M, flexural strength was 39.2 ± 1.960/MPa, impact strength was 7.95 ± 0.3975/ [KJ/m²]), flame retardant properties (70P/23I/5C/2M, the limiting oxygen index value was 39.6%, UL-94 was V0) and thermal stability of WPC have been improved. Thereby, the balance between mechanical performance and flame retardant properties of biocomposites has been achieved in the practical engineering requirements. Furthermore, cone calorimeter data indicated that modified cassava dregs–MHSH hybrids played a role in improving the fire safety of composites. The total heat release, total smoke produce, toxic gas release, and total oxygen consumed of 70P/23I/5C/2M were lowered compared with those of 70P/25I/5C. Dynamics analysis indicated that the addition of modified cassava dregs–MHSH hybrids increased the activation energy of composites. Based on the experimental and analyses data, especially the morphological characterization of char residue analysis, it illustrated that modified cassava dregs–MHSH hybrids have a reinforcement and flame-retardant effect. The combusted residue of the incorporated modified cassava dregs–MHSH hybrids could support the three-dimensional charred layer formed by the combustion products of the IFR and the PBS. Thus, the more stable three-dimensional charred layer could not only effectively reduce thermal conductivity of composites but also hinder the propagation of heat into the interior substrate, thereby improving the flame-retardant properties of the WPC. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48490.     

丙三醇对PBST共聚酯结构和性能的影响

基于生物可降解性聚酯——聚丁二酸-共-对苯二甲酸丁二醇酯(PBST),通过原位添加不同含量的丙三醇作为第四单体,制备出共聚改性的PBST共聚酯。通过核磁共振仪(NMR)、差示扫描量热仪(DSC)、广角X射线衍射仪(WAXD)及接触角测试,分别对PBST共聚酯的结构和性能进行了研究。结果表明:丙三醇的加入并没有改变PBST共聚酯的化学组成和结构;随着丙三醇含量的增加,共聚酯的玻璃化转变温度先上升后下降,而熔点是逐步降低的;改性前后和拉伸前后PBST的晶型均未发生变化,但分子结构的规整性受到破坏,且发生拉伸诱导取向;改性PBST共聚酯的亲水性能较纯PBST有明显提高。     

共聚酯的合成与性能表征

以对苯二甲酸、乙二醇为主要原料,添加共聚单体新戊二醇(NPG)、5-叔丁基间苯二甲酸(tBI),通过熔融缩聚合成了一系列不同组成比例的共聚酯,分析了共聚酯的化学结构与组成、特性黏度、热性能、结晶性能和动态热力学性能。结果表明:随着tBI和NPG含量的增加,共聚酯的熔点降低,结晶能力逐渐减弱;当tBI和NPG物质的量分数总和达到13%及以上时,共聚酯为完全无定形态;tBI单元的加入使共聚酯的玻璃化转变温度升高,弥补了PENT共聚酯玻璃化转变温度低于PET的缺点;共聚酯的初始分解温度高于PET,初始储能模量大于PET,而随着测试温度的升高,共聚酯的柔韧性大于PET材料。     

Stability and cytotoxicity study of NiFe2O4 nanocomposites synthesized by co-precipitation and subsequent thermal annealing

In this article, NiFe₂O₄ nanoparticles (NPs) were prepared by co-precipitation method with subsequent thermal annealing leading to obtainment NPs with average sizes of 78 nm. Structure and magnetic analysis were performed by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and vibrating sample magnetometry techniques. Stability of NiFe₂O₄ NPs was evaluated in PBS solution during 20 days. The toxicity of prepared NPs was evaluated in vitro using different cancer cell lines: HeLa (cervical cancer cell), PC-3 (prostate cancer cell). Fibroblasts like cells of L929 obtained from subcutaneous adipose tissue of mouse were used as normal cells. Results indicate successful synthesis of NiFe₂O₄ NPs that exhibit low cytotoxicity in concentration range from 1 to 100 μg/ml. Presented physical and biological results indicate the possibility of application investigated magnetic nanoparticles in hyperthermia, targeted drug delivery, magnetic resonance imaging or cell separation.     

低熔点共聚酯的研究进展

介绍了国内外对低熔点共聚酯的研究现状,着重论述了低熔点共聚酯的熔融结晶行为、流变性、热稳定性以及其纺丝工艺研究,并对其发展前景进行了展望。     

基于PBS的自动化集成设计项目WBS技术研究

自动化集成项目的工作分解准确和及时性是此类项目管理的基础和关键。通过分析研究自动化产品设计阶段的业务流程,在该领域使用基于PBS产品分解结构的工作分解技术,集合自动化集成产品设计阶段的特点,提出PBS模型,WBS模块和WBS模型,通过对PBS-WBS映射模型的分析,映射矩阵和映射方法的建立。从而实现快速、精确的WBS转换方法,并在某复杂曲轴自动化集成单元的设计项目工作中进行应用,并得到验证。     

Novel Copolyesters Based on s-Triazine Derivatives

Ten copolyesters have been synthesized by polycondensation of MPNCCT and different mixtures of diols, such as: BPA + BPC, BPA + BPS, BPA + 1,4-DHA, BPA + Ph, BPA + C, BPA + R, BPA + EG, BPC + Ph, BPC + R, and Ph + 1,4-DHA. All the copolyesters have been characterized by IR spectra, NMR spectra, solubility, density and viscosity measurements and thermogravimetric analysis, TGA.     

过氧化物对PBS/PLA共混物反应性增容研究

通过加入过氧化二苯甲酰(BPO)和过氧化二异丙苯(DCP)进行反应性增容来改善其相容性,并通过扫描电子显微镜(SEM)、偏光显微镜(PLM)、动态力学性能测试(DMA)以及差示扫描量热分析仪(DSC)等方法对共混体系相容性及力学性能进行了表征及测试。实验结果表明,加入过氧化物BPO或DCP可以使共混体系相结构均匀细化,共混体系的相结构由未加入过氧化物时的海岛相转为双连续相结构,同时由DSC测试还可以明显看出共混体系形成了共晶结构,说明共混体系的相容性得到了显著提高。     

与偏振无关1×2．2×2和2×4A由空间光开关在Clos光网络中的应用

首先,对无阻塞的Clos（2,4,2）光网络的拓扑结构和光学实现进行了理论分析;其次,利用偏振光分束器（PBS）、相位型空间光调制器（PSLM）和反射镜设计1×2、2×2和2X4光开关。进而设计无阻塞的Clos（2,4,2）光网络,并讨论了n×m型光开光的设计原则和升级能力。最后,通过实验测试,光开关的串扰最低可以达到...