Degradability and biocompatibility of bioglass/poly(amino acid) composites with different surface bioactivity as bone repair materials

Bioglass (BG) possesses excellent bioactivity and has been widely used in the manufacture of biomaterials. In this study, a composite with different surface bioactivity was fabricated via in situ melting polymerization by incorporating BG and poly(amino acid) (PAA) at a suitable ratio. The structure of the composite was characterized by Fourier transform infrared spectroscopy and XRD. The compressive strength of the BG/PAA composites was 139 MPa (BG:PAA = 30:70). The BG/PAA composites were degradable, and higher BG in composite showed higher weight loss after 4 weeks of incubation in simulated body fluid. In addition, the BG/PAA composite maintained adequate residual compressive strength during the degradation period. The SEM results showed the differences in surface bioactivities of the composites directly, and 30BG/PAA composite showed thicker apatite layer and higher Ca/p than 15BG/PAA. in vitro MG-63 cell culture experiments showed that the composite was noncytotoxic and thus allows cells to adhere, proliferate, and differentiate. This indicates that the composite has good biocompatibility. The implantations in the bone defects of rabbits for 4 and 12 weeks were studied. The composites had good biocompatibility and were capable of guiding new bone formation without causing any inflammation. The composite may be successfully used in the development of bone implants.     

Synthesis and characterization of eugenol-based silicone modified waterborne polyurethane with excellent properties

A eugenol-based silicone-containing monomer 4,4′-(1,1,3,3-tetramethyldisiloxane-1,3-dipropyl)bis-2-methoxyphenol(EUSi) was synthesized from eugenol and 1,1,3,3-tetramethyldisiloxane via the hydrosilylation reaction. And waterborne polyurethane (WPU) with excellent properties was obtained by using EUSi as a type of diol chain extender. The unique combination of rigidity and flexibility in the chemical structure of EUSi greatly facilitated the mechanical properties, thermal properties, and water resistance of WPU. With only a 3% dosage of EUSi, the maximum tensile strength was increased from 6.2 to 22.4 MPa, while the water absorption was decreased from 31.3% to a surprisingly 7.6%. Our work provides a new convenient strategy for the preparation of organosilicon-modified WPU with improved performance.     

Preparation and characterization of high strength and high modulus PVA fiber via dry-wet spinning with cross-linking of boric acid

To improve the mechanical properties of polyvinyl alcohol (PVA) fibers, a series of PVA fibers were prepared via dry-wet spinning with cross-linking of boric acid (BA) (PVA/BA fibers), and using the mixed solvent of dimethyl sulfoxide and water. Moreover, the final PVA/BA fibers were characterized by Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), differential scanning calorimetery (DSC), thermogravimetric analyzer (TGA), powder X-ray diffraction (XRD) and yarn strength tester. Furthermore, with the increasing of BA content, FTIR analysis showed that the degree of crosslinking of BA with PVA increased. SEM images of final PVA/BA fibers presented smooth surfaces, and the diameters decreased firstly and then increased. DSC, TGA, and XRD analysis indicated that the melting temperatures, thermal properties and crystallinities first increased and then decreased with the increasing of BA content. In addition, mechanical properties measurements illustrated that the cross-linking existed at an optimal BA content of 0.3 wt%, and PVA/BA-0.3 fiber had the highest tensile strength and Young's modulus of 13.1 ± 0.4 and 360.2 ± 10.4 cN/dtex, respectively.     

A Cross-sectional Study on the Relationship Between Homocysteine and Lipid Profiles Among Chinese Population from Hunan

Previous studies have explored the relationship between homocystein (Hcy) and lipid profiles. However, the results from these studies have been inconsistent. The current study investigated the correlation between Hcy and lipid profiles in Chinese community-based population. The participants were composed of 4012 Chinese people aged 30–92 years old, who were recruited from rural and urban communities in the Hunan Province. Non-parametric test and logistic regression were used to examine the distribution of Hcy and lipid profiles (triglyceride [TG], total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C]) and the relationship between them. The median age of subjects was 54.50 years old, and 40.98% were male. Median Hcy was 13.20 μmol/L, and 35.39% had hyperhomocysteinemia (HHcy). Median TG was 1.51 mmol/L, TC was 4.77 mmol/L, LDL-C was 2.62 mmol/L, and HDL-C was 1.27 mmol/L. In multivariable logistic regression analysis, HHcy was associated with high levels of TG (OR_male = 2.240, p < 0.001; OR_female = 2.539, p < 0.001), TC (OR_male = 2.237, p < 0.001; OR_female = 2.202, p < 0.001), and LDL-C (OR_male = 1.413, p = 0.010; OR_female = 1.617, p < 0.001) in the different sexes population and low level of HDL-C in females (OR = 1.326, p = 0.023) after adjusting for confounders. HHcy was independently associated with an increasing risk of low HDL-C among females. The regression analysis showed that HHcy was also associated with hypertriglyceridemia, hypercholesterolemia, and high level of LDL-C in males and females from Chinese community-based population, which provides a basis for the treatment and prevention of abnormal lipid metabolism.     

Study on polyurethane-acrylate/cerium dioxide modified by 3-(Methylacryloxyl)propyltrimethoxy silane and its UV absorption property

Firstly, cerium dioxide(CeO₂) was modified by 3-(Methylacryloxyl)propyltrimethoxy silane (KH-570), and modified CeO₂ (mCeO₂) was prepared. Then poly (urethane-acrylate) was modified by mCeO₂, and poly (urethane-acrylate)/modified CeO₂ (PUA/mCeO₂) composites with ultraviolet absorption property were prepared. The morphology, thermal hydrophobicity, mechanical properties, optical properties, and UV-absorption properties of PUA/mCeO₂ composites were studied. XRD and SEM analysis showed that the modified CeO₂ had better dispersion in the matrix than that of pure CeO₂. Ultraviolet–visible spectrum and thermogravimetric analysis were used to characterize the optical properties and thermal stability of PUA/mCeO₂ composites. The results showed that with the increasing of the mCeO₂ content, the UV-absorption property of PUA/mCeO₂ composites was improved gradually. When the content of mCeO₂ is 3%, the absorption of ultraviolet of PUA/mCeO2 composites is about 5 times of pure PUA film, and the absorption band is mainly in the UVA section. The thermal stability of PUA/mCeO₂ composites was improved with the adding of mCeO₂. With the increasing of mCeO₂ content, the contact angle of PUA/mCeO₂ composites increased significantly. And the UV-absorption mechanism of PUA/mCeO₂ Composites was studied. UV-curable PUA/mCeO₂ composites have good UV absorption property and water resistance. They will be used in the sun screen and protect people's skin.     

微波化学反应的无量纲准数动力学模型研究：以偶氮二异丁脒盐酸盐（AIBA）分解反应为例

微波辅助化学已成为备受关注的研究课题,但微波反应动力学模型缺乏系统的研究严重阻碍了微波在化学工业化上的应用,微波化学反应在化学工程化的放大设计及应用缺乏基础依据。以偶氮二异丁脒盐酸盐（AIBA）分解反应为例,通过选择合适的溶剂调整其复配比例,得到一系列具有不同沸点的混合溶剂作为反应介质,使反应在混合溶剂沸点下进行,以保证反应过程中微波的持续作用来研究微波反应动力学。从微波作用下动量传递、热量传递和质量传递的影响因素进行考虑,选择了对微波化学反应必须和充分的因素,包括微波功率密度 p、黏度 μ、密度ρ、反应物的浓度 C_A、温度 T、热导率 λ、损耗角正切δ 和微波辐射频率f。采用量纲分析方法,通过模型分析建立了微波分解反应动力学模型。通过大量的实验数据进行拟合,回归出特定反应的模型参数。该模型估算值与实验值的误差较小,相关性较高,具有一定的预测能力可解决微波反应过程放大的基础性问题,有望用于指导微波工业化生产。     

基于深度学习的锂离子电池SOC和SOH联合估算

锂离子电池常被作为储能元件以实现电能的存储和转化,然而其荷电状态(state of charge,SOC)和健康状态(state of health,SOH)无法被直接测量。为了实现锂离子电池SOC和SOH联合估算,该文分析SOC和SOH之间的关联性,并提出一种基于深度学习的锂离子电池SOC和SOH联合估算方法。该方法能够基于门控循环单元循环神经网络(recurrent neural network with gated recurrent unit,GRU-RNN)和卷积神经网络(convolutional neural network,CNN),利用锂离子电池电压、电流、温度,实现锂离子电池全使用周期内SOC和SOH的同时估算,而且由于将锂离子电池的SOH估算值考虑到SOC估算中,能够消除锂离子电池老化因素对锂离子电池SOC估算造成的负面影响,从而提升SOC估算精度。两个锂离子电池测试数据集上的实验结果表明,提出的估算方法能够在不同温度和不同工况下实现锂离子电池全使用周期SOC和SOH联合估算,且获得较高的精度。     

输出并联型双有源全桥变换器控制技术研究综述

输出并联型双有源全桥(dual-active-bridge,DAB)DC-DC变换器具备电气隔离、模块化扩展简单、高变比升降压及功率双向传输等优势,近年来得到国内外专家学者的广泛关注。首先,分析和归纳该类变换器功率平衡的典型控制方案,并从动态特性、模块化程度、传感器数量等方面,对不同控制方案下的研究策略进行多方面对比分析;然后,基于DAB变换器效率和动态性能优化方法,从多模块角度出发,分析组合系统功率平衡与DAB变换器性能优化相结合的一些典型混合控制策略,并从工程角度给出混合控制其他衍生思路及控制策略选取时,需考虑的实际因素;最后,从开关、桥臂、模块和拓扑等方向,对输出并联DAB变换器的容错控制方案进行详细概述并总结全文。     

高速航空燃油泵水力设计及两相流场数值模拟

为了满足下一代飞机发动机燃料供给的需求,根据供油系统的性能指标,确定燃油泵结构型式,基于速度系数法计算燃油泵的主要结构参数,完成高速燃油泵水力设计,建立其三维模型并进行网格划分.借助ANSYS-CFX仿真软件,基于RNG k-ε湍流模型及Zwart空化模型,实现燃油泵非空化及空化状态下的内流场数值模拟,分析其外特性变化趋势及压力、速度分布规律并预测其空化性能.结果表明:高速燃油泵扬程、效率、功率随流量的变化符合离心泵性能变化规律,且在设计点附近达到最高效率82.76％;有效汽蚀余量较大时,燃油泵扬程基本不发生变化,当有效汽蚀余量减小到一定值,扬程开始缓慢下降而后急剧减小,扬程下降3％对应的临界汽蚀余量为12.7m.     

变电站设备状态智能识别系统技术研究

针对目前变电站采用人工巡检判断设备状态的方式存在作业效率低、工作质量不高、巡检人员的安全难以保障的问题,集成应用开关状态综合判断技术、刀闸状态综合判断技术、智能巡检技术和视频联动技术等关键技术,研制了变电站设备状态智能识别系统,通过与数据采集与监视控制(SCADA)系统的信息交互,实现了变电站开关、刀闸设备状态的远程智能识别.该系统可在变电设备倒闸操作、定期巡检、专项巡检以及日常设备状态监视中代替人工巡检开关、刀闸设备状态,及时发现并预警设备状态隐患,提高了巡检效率和质量,降低了运行人员的劳动强度,保障了人身及设备安全.通过在500 kV文山变电站的应用实例表明,应用该系统在单台主变停电倒闸操作中可节省5.63工时,验证了系统的实用性和有效性.