Fabrication and characterization of injection molded poly (ε-caprolactone) and poly (ε-caprolactone)/hydroxyapatite scaffolds for tissue engineering

In this study, poly(ε-caprolactone) (PCL)/sodium chloride (NaCl), PCL/poly(ethylene oxide) (PEO)/NaCl and PCL/PEO/NaCl/hydroxyapatite (HA) composites were injection molded and characterized. The water soluble and sacrificial polymer, PEO, and NaCl particulates in the composites were leached by deionized water to produce porous and interconnected microstructures. The effect of leaching time on porosity, and residual contents of NaCl and NaCl/HA, as well as the effect of HA addition on mechanical properties was investigated. In addition, the biocompatibility was observed via seeding human mesenchymal stem cells (hMSCs) on PCL and PCL/HA scaffolds.The results showed that the leaching time depends on the spatial distribution of sacrificial PEO phase and NaCl particulates. The addition of HA has significantly improved the elastic (E′) and loss moduli (E″) of PCL/HA scaffolds. Human MSCs were observed to have attached and proliferated on both PCL and PCL/HA scaffolds. Taken together, the molded PCL and PCL/HA scaffolds could be good candidates as tissue engineering scaffolds. Additionally, injection molding would be a potential and high throughput technology to fabricate tissue scaffolds.     

Seismic response and stability of underground rock caverns: a case study of Baihetan underground cavern complex

The seismic stability of the underground cavern complex, which houses the Baihetan hydropower plant in Yunnan Province, China, currently the world’s 2nd largest underground rock cavern group, is studied in this article. A preliminary performance-based seismic assessment approach specified for underground rock caverns is firstly proposed. The seismic performance objectives are classified. Reference earthquake motions are specified with the determination of the seismic variables. Detailed dynamic response analyses (Method 2B) are conducted based on the parameters given by the cyclic dynamic loading tests with medium strain rate. The seismic response of acceleration, stress, displacement and failure zones are studied. In addition, the seismic spectrum characteristics are analysed with a newly introduced wavelet packet technique. The mechanism of the support measures for seismic stability is also discussed. The assessment for seismic performance of the underground cavern complex is obtained by integrating these results. Serviceability objective of the underground cavern complex under operating basis earthquake may be satisfied, and the safety objective be feasible but with the presence of the proposed reinforcement system. The seismic isolation design is preferred, yet not necessary. And if any seismic isolation design is to be adopted, the frequency absorption range of the isolation material is expected to be 1–4 Hz.     

硬壳电热暖手器取暖舒适温度范围研究

应用现场测试法调研了硬壳暖手器用于取暖舒适温度。首先,提出一个用于描述暖手器取暖时热感觉的"7点标度,"40名受试者按此标度描述其热感。分析受试者的性别、手部温度、气温(室温)以及成长所在分区有无集中供暖等几个因素对选取舒适温度的影响。实验结果表明,女性的手部对取暖舒适性的期望略比男性高1-2℃左右;气温越高,受试者选取的取暖温度也越高;受试者手部温度越高,其对于取暖的期望就越低;成长在有集中供暖地区的受试者选择用于手部取暖温度高1℃以上。最后,基于以上几个影响因子,总结出最适用于手部取暖的暖手器表面温度为50或者51℃。     

TiO2 nanotubes/MWCNTs nanocomposite photocatalysts: synthesis, characterization and photocatalytic hydrogen evolution under UV-vis light illumination

Nanocomposite of TiO2 nanotubes (TiO2NTs) and multiwalled carbon nanotubes (MWCNTs) has been synthesized by a hydrothermal method and firstly used in photocatalytic hydrogen production. The obtained TiO2 NTs/MWCNTs composites were characterized by X-ray diffraction, transmission electron microscopy, Raman spectrum and ultraviolet-visible diffuse reflectance spectroscopy. The experimental results revealed that the MWCNTs were decorated with well dispersed anatase TiO2 nanotubes with a diameter of 8-15 nm. A slight blue shift and weak symmetry was observed for the strongest Raman peak which resulted from strain gradients originating from interface integration between TiO2 nanotubes and MWCNTs. The photocatalytic activity of the as-prepared samples was evaluated by hydrogen evolution from water splitting using Na2S and Na2SO3 as sacrificial reagents under UV-vis light irradiation. Enhanced photocatalytic activity compared with P25 has been observed for the resulted samples. The nanocomposite with optimized MWCNTs content of 1% displayed a hydrogen production rate of 161 micromol x h(-1) x g(-1). Good photocatalytic stability of the as-synthesized samples was observed as well.     

Multi-walled carbon nanotubes as a new counter electrode for dye-sensitized solar cells

Airbrushed multi-walled carbon nanotube (MWNT) networks were investigated as a new counter electrode for dye-sensitized TiO2 photoelectrochemical solar cells. The structural and physical properties of the MWNTs were studied by various techniques including SEM, TEM, Raman, optical absorption, and electrochemical impedance spectroscopy (EIS). The MWNTs exhibited catalytic activity for the reduction of triiodide in the electrolyte as studied by EIS measurements. The performance of the dye-sensitized solar cells was improved by using MWNTs as counter electrodes. This observation is explained by the significantly increased contact area between the MWNT counter electrode and the electrolyte which facilitates efficient charge transportation in the solar cell. We demonstrated that the MWNTs are suitable for replacing expensive Pt electrodes for fabricating high efficiency dye-sensitized solar cells. The process used in this study is also technically attractive for large scale and economic production.     

采暖供热量数学模型的建立及求解

为简便、快速、准确计算年采暖供热量，有必要根据采暖热负荷的持续曲线图，确定全年供暖需量，它是进行集中供热规划，可行性论证和设计，确定热化系数最佳值等必不可少的基础工作。本文介绍了采暖供热量的数学模型的建立及其解法．     

磷钼酸盐玻璃的红外和拉曼光谱研究

本文系统地研究了ＣｕＩ－ＭｏＯ３－Ｐ２Ｏ５三元系玻璃和ＬｉＣｌ－Ｌｉ２Ｏ－ＭｏＯ３－Ｐ２Ｏ５四元系玻璃的红外和拉曼光谱。结果表明：当磷钼酸业系统玻璃中不存在Ｍｏ时，玻璃网络主要由链状偏磷酸盐基团组成。随着Ｍｏ含量的增加，偏磷酸盐基团向焦磷酸盐基团转化，同时出现ＭｏＯ和低聚合的钼氧四面体。而修饰体ＣｕＩ、ＬｉＣｌ和Ｌｉ２Ｏ并不进入网络，只是起断网和使网络结构松散的作用。     

铰接式车辆中双万向联轴节运动分析

从运动学的观点分析了铰接式车辆前传动轴和双万向节的布置原则，并进而分析了因制造和安装误差造成的传动不均匀性。     

亚磷酸三（2，4－二叔丁基苯）酯的合成

讨论了以２，４－二叔丁基苯酚、三氯化磷为原料合成抗氧剂１６８的方法。对催化剂的选择等工艺条件进行了对照试验，并对自合成品与进口品进行光谱、色谱分析比较     

用傅里叶分析法诊断电力电子电路的故障

本文提出了一种电力电子电路故障的在线诊断方法。由于电力电子电路中包含故障信息的关键点信号通常具有周期性，故可采用傅里叶变换将时域信息变换到频域中分析。采用本文的频域故障特征抽选方法，能够有效地实现故障诊断。