Crystallization and morphological features of syndiotactic polystyrene induced from glassy state

Spherulitic growth rates and microstructure of syndiotactic polystyrene (sPS) cold-crystallized isothermally at various temperatures, T_c (115–240 °C), have been investigated by small-angle light scattering (SALS), optical microscopy and transmission electron microscopy. The derived activation energy for sPS chain mobility at the crystal growing front is 5.4 kJ/mol, which is relatively lower than that of isotactic polystyrene, 6.5 kJ/mol. In addition, the Hv scattering invariant (Q_Hv) measured by SALS on the crystallized sPS samples displays a pronounced minimum at 150 °C. Despite a wide range of T_c used, however, the sample crystallinity estimated by Fourier transformation infrared spectroscopy remains unchanged. Prior to crystallization, the correlation length derived from the Vv patterns on the basis of Debye–Bueche model is ca. 1.13 μm regardless of T_c used. Interconnected domains with a width of ca. 1.8±0.5 μm are readily observed in all the crystallized samples under phase contrast microscopy and the phase-separated structure is conserved within sPS spherulites whose diameters are increased with increasing T_c.

Based on the above facts, we conclude that the presence of a Q_Hv minimum is ascribed to the resultant events of the two competitive transitions i.e. liquid–solid crystallization, and liquid–liquid demixing resulting from the spinodal decomposition (SD). At lower T_c, the unstable SD transition overwhelms the crystallization. Despite the low chain mobility, the coarsening process driven by the interfacial energies has reached a certain level before crystalline nucleation takes place. At higher T_c, on the other hand, cold crystallization becomes the dominant process due to the enhanced chain mobility, leading to the suppression of ongoing SD coarsening process. At an intermediate T_c range, comparable competition of the phase separation and crystallization prohibits the development of ordered symmetry within spherulites, giving the presence of Q_Hv minimum.     

就地复合冷再生路面设计参数及工艺参数

就地复合冷再生层技术是在现场将部分旧沥青层与基层一同再生后,形成既具有一定柔性又具较大刚性的新型路面层结构的一种技术。结合渝涪高速公路沥青路面病害处治工程,研究了就地复合冷再生层的结构厚度和组合、材料参数和工艺参数以及受力分析,并取得了成功的应用经验。研究结果认为：1）在复合铣刨和再生沥青面层和水泥稳定上基层条件下,为了确保就地复合冷再生层的压实质量,其厚度应控制在26cm以内比较适宜;2）复合冷再生层的空隙率应控制小于12％;3）复合冷再生层上应设置一层防水层,而且新铺沥青混凝土厚度应不小于9cm;4）复合冷再生层混合料的主要技术性能宜采用马歇尔流值（3～5mm）、浸水劈裂强度（大于0．45MPa）、冻融劈裂强度比（大于50％）和-10℃弯曲应变（大于1800με）来控制,而动稳定度（大于2000次／mm）仅作为次要技术指标。     

爪形大分子CBC—NO的合成、表征及降滤性能研究

以1,3-丁二醇、柠檬酸为原料、甲苯为溶剂,在120℃油浴中反应,合成了柠檬酸-1,3-丁二醇-柠檬酸（CBC）爪状物小分子;然后,以甲基苯磺酸为催化剂,使CBC依次与环烷酸、十八醇分别在140℃和180℃油浴下接枝,合成了新型的爪形大分子柠檬酸-1,3-丁二醇-柠檬酸-环烷酸-十八醇（CBC—NO）。采用^1H—NMR及IR对合成的两种化合物进行了结构表征。结果表明,合成的CBC和CBC—NO与所设计的分子结构相吻合。用元素分析确定了CBC的化学组成为C16H22O14。合成的CBC—NO溶于有机溶剂,不溶于水。将CBC—NO按600μg／g的加剂量添加到不同的轻柴油中,柴油的冷滤点最大可降低8℃。     

手指静脉图像感兴趣区域提取研究综述

近年全球的疫情促使生物识别技术进一步发展,指静脉识别作为第二代生物识别技术因其具有极高的安全性等优点而被应用于各个领域。指静脉图像感兴趣区域提取作为指静脉识别系统至关重要的一部分,是识别系统性能与适应不同应用场景的保证。分别介绍了商用指静脉识别产品与科研用指静脉采集设备,对其公开数据集进行了整理与分析;重点论述了指静脉图像预处理中感兴趣区域提取的主要工作,对各个步骤的代表性方法进行了深入梳理与分析,并对指静脉特征提取与匹配认证进行了概述;最后对其今后的发展与应用进行了总结与展望。     

燃料电池发动机冷启动进气预热系统性能研究

为了分析冷启动过程中质子交换膜燃料电池发动机的空气加热系统的工作性能,采用ε-NTU方法和CFD仿真技术得到了双流程换热器内部的温度分布,研究了冷却液温度和流量对整体散热器的换热性能的影响。通过比较发现模拟值与测试数据的误差小于10%,表明仿真模型和采用多孔介质模型的研究方法的可行性。根据仿真结果,采用遗传算法得到了该系统采用的铝制散热器的冷却液的最优参数组合,研究结果为优化空气预热系统,提高散热器的冷却效率提供了指导。     

相邻锅炉一次热风联络技术在CFB锅炉上的应用

针对循环流化床锅炉冷态启动用油量较大的问题,采用两台相邻锅炉一次热风风道联络的方法,实践中利用邻炉一次热风进行锅炉冷态启动,以煤代油缩短锅炉点火投油时间。结果表明:此方法使锅炉冷态启动时的用油量大幅下降,达到了显著的节能效果,并在此基础上展望了一次热风联络技术在锅炉防腐保养、冬季防冻等方面的应用前景。     

间歇式用能模式下墙体热分析

针对夏热冬冷地区间歇式用能特点,采用ANSYS软件对外墙内外保温墙体进行热分析。通过间断式施加温度荷载模拟空调运行,分析两种保温形式的墙体内温度变化情况。研究结果表明,受墙体内侧温度荷载的影响,内保温墙体内表面温度变化明显,且热量集中分布在内侧保温层部分,不易散失;外保温墙体受内侧温度荷载的影响较小,热量在墙体内分布均匀。在相同时间内,内保温需要施加荷载的时间明显比外保温的少。     

Cold Plasma Treatment of Soybean Oil with Hydrogen Gas

High-voltage atmospheric cold plasma (HVACP) treatment generates reactive gas species that induce inter- and intramolecular reactions in soybean oil. The goal of this study is to analyze the effect of HVACP treatment on the chemical structure of soybean oil in a hydrogen gas environment at atmospheric pressure. HVACP was used to treat soybean oil (15 g) for up to 6 hours by triplicate. Plasma-generated reactive gas species interact with the sample, producing three distinct fractions identified as a liquid, gel, and solid. Fatty acid profile, Fourier-transform infrared spectroscopy, proton and carbon nuclear magnetic resonance, size-exclusion chromatography, thermal properties, and peroxide value were used to characterize the chemical structure. Results indicated a lower content of polyunsaturated fatty acids, increased content of saturated fatty acids, and the presence of isomers. An insoluble portion was observed in the solid fraction and increased with treatment time up to 42% in the 6-h treated samples. Plasma species may cause two main reactions: polymerization and hydrogenation.     

Cold gas dynamic manufacturing: A non-thermal approach to freeform fabrication

This paper reports on the development of a novel freeform fabrication technique using a cold spray (CS) system. In the CS process, metallic powder particles are accelerated in a supersonic gas jet and impacted with a substrate at speeds in excess of 600 m/s. The non-melting nature of its deposition mechanism ensures that the sprayed material is free from thermally induced tensile stresses, while the underlying substrate remains unchanged. The process is seen as a viable method for additive manufacturing because of its high deposition rates and controllable spray jet. A process was developed to investigate the potential of non-thermal freeform fabrication and was coined Cold Gas Dynamic Manufacturing (CGDM). Here, additive and subtractive techniques were combined to enable the production of complex geometries. Whereas most CS facilities concentrate on the application of wear or corrosion-resistant coatings, CGDM is dedicated to the production of freeform components, whilst still retaining an inherent coating ability. The process can produce functional forms using novel manufacturing strategies that are unique to CS. This paper presents information on the process, and details the various strategies employed during component fabrication. It was possible to construct components from many materials, including titanium, which exhibited freeform surfaces, internal channels and embedded devices. A breakdown of the process economics is also provided, with and without helium recycling.     

The effect of neutral red on the corrosion inhibition of cold rolled steel in 1.0 M hydrochloric acid

The corrosion inhibition of neutral red on the corrosion of cold rolled steel in 1.0 M hydrochloric acid (HCl) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that neutral red is an effective inhibitor. It was found that the adsorption of neutral red could prevent steel from weight loss and the adsorption accorded with the Langmuir adsorption isotherm. Potentiodynamic polarization studies showed that neutral red mainly acted as a mixed-type inhibitor for steel in 1.0 M hydrochloric acid. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C. The most suitable range of inhibitor concentration was discussed. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and neutral red was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.