低收缩剂含量对不饱和聚酯树脂固化收缩率和力学性能的影响

选择聚醋酸乙烯酯(PVAc)作为低收缩剂(LSA),以199#不饱和聚酯树脂(UPR)作为基体制备试验样品,通过测量添加不同含量(质量分数,全文同)LSA的树脂浇铸体的固化收缩率和抗弯强度,评价LSA含量对UPR固化收缩率的影响效果.试验结果表明:PVAc含量对树脂浇铸体的力学性能和收缩率均有很大影响,综合固化收缩率和力学性能,在199# UPR配方中添加含量15％的PVAc,试件的综合性能最优.     

不饱和聚酯树脂的固化收缩机理与收缩应力分析

本文用自由体积理论分析了不饱和聚酯树脂的固化收缩机理。理论计算与实验测定结果基本一致。用光纤应力传感器测定了不饱和聚酯树脂由于固化收缩而产生的内部应力,得出收缩应力与固化过程中降温阶段的收缩率成正比。     

聚氨酯改性不饱和聚酯树脂的研究

为了提高不饱和聚酯树脂（UPR）的韧性，降低它的体积收缩率，采用聚氨酯（PU）对UPR进行了改性，并研究了PU/UPR共混物的固化性能，z结果表明：当PU质量分数WPU≤10%时，UPR与PU间有较好的相容性；当WPU≥25%时，共混物表现出明显的相分离特征；WPU=36%时，UPR的各项力学性能都能维持在一个较高的数值，同时体系的固化收缩率也明显变小。     

低轮廓不饱和聚酯树脂一维固化应力的研究

研究了在低轮廓不饱和聚酯（UP）树脂体系固化时的一维固化应力及低收缩添加剂（LPA）对固化应力的影响,发现LPA对于减小UP树脂体系的固化收缩应力具有明显的效果,LPA的含量、温度及LPA的类型对固化应力的产生和发展均有较大的影响.通过对体积收缩和固化应力的研究,发现收缩与固化应力形成和发展的关系是非线性的.     

新型低压片状模塑料增稠方法的研究

研究了低压片状模塑料的3种单一增稠体系，讨论了各种增稠剂用量对不饱和聚酯树脂增稠性能的影响情况。分析对比了各种增稠剂在增稠过程中的优缺点，从而采用联合增稠剂的方法，即将碱金属氧化物或氢氧化物(一般用氧化镁)与结晶树脂、端异氰酸酯基化合物与结晶树脂联合增稠不饱和聚酯树脂体系。研究表明，联合增稠剂的增稠效果比单一增稠剂的增稠效果要好，更加符合低压模塑的粘度和工业化生产的低成本要求。     

不饱和聚酯/聚氨酯共混改性研究--红外光谱动态跟踪共混树脂固化反应的研究

运用红外光谱动态跟踪了端羟基不饱和聚酯/TDI共混树脂固化反应过程,研究表明固化过程中发生了端羟基不饱和聚酯树脂与异氰酸酯(TDI)的扩链交联反应.并借助红外光谱动态测试对固化体系作了优化选择.     

声频振动法测定LPA/UP固化物动弹模量-弯曲强度的试验研究

声频振动法为非破损测试方法。可在聚合物基辣材料同一试件上连续测定由内外因影响其弹性模量的变化规律，进而推算力学性能的变化。具有大大减少试验工作量缩短试验周期的显著优点。本文研究用声频振动法测定低收缩添加剂（LPA）与不饱和聚酯树脂（UP）固化后的动态弹性模量，试验建立动弹模量与弯曲强度的相关关系，并对其进行数学回归分析。据此可推算同类组成体系材料的弯曲强度。试验表明该测定方法经济便捷，并具相当精度。     

不饱和聚酯挡风抑尘板力学性能研究

以玻璃纤维毡为增强骨架,不饱和聚酯树脂为基体材料,制备挡风抑尘板,并对不饱和聚酯树脂与玻璃纤维的配比、玻璃纤维的种类和固化剂、促进剂含量对挡风抑尘板力学性能的影响进行了研究。结果表明,当不饱和聚酯与玻璃纤维毡的质量比达到3∶1时,其拉伸强度和冲击强度都达到最大。高碱、中碱和无碱的玻璃纤维毡增强的挡风抑尘板拉伸强度分别达到55.198,75.249,89.446MPa,冲击强度分别达到30.699,35.367,41.343kJ/m2。而无碱玻璃纤维毡其拉伸强度比高碱提高了62%,比中碱提高了18.8%。冲击强度比高碱提高了34.7%,比中碱提高了16.9%。当促进剂质量分数为0.5%、固化剂质量分数为1%时,挡风抑尘板的拉伸强度最大为89.446MPa,冲击强度最大为41.343kJ/m2。     

W/O型不饱和聚酯树脂乳状液固化体系的研究

对W/O型不饱和聚酯树脂乳状液的固化条件进行了研究,并对乳状液的固化机理进行了探讨.结果表明:乳状液热固化选用BPO较好,固化工艺参数为60℃,固化时间为1～2小时,室温固化则宜选用BPO-二甲基苯胺引发体系.     

不饱和聚酯／聚氨酯共混改性研究——红外光谱动态跟踪共混树脂固化反应的研究

运用红外光谱动态跟踪了端羟基不饱和聚酯TDI共混树脂固化反应过程,研究表明固化过程中发生了端羟基不饱和聚酯树脂与异氰酸酯（TDI）的扩链交联反应。并借助红外光谱动态测试对固化体系作了优化选择。     

浅析英语语音教学中的/n//l/发音错误

在大学英语教学过程中,有关/n/与/l/的发音错误很常见,原因是没有完全掌握它们的发音规则。/n//l/发音规则的相似性造成了/n//l/不分的情况,而且局部方言中这两个音也不作区分,使得/n//l/混淆的情况更加严重。在教学过程中,可以通过重点讲解区分/n/与/l/的发音规则及其区别来避免/n//l/发音错误。本文同时也分析了含糊/l/音的发音错误,通过对/n/与/l/相关的发音错误分析找出大学英语语音教学行之有效的途径:在完全把握单音的发音规则的基础上,进一步强调语调的掌握,使学生拥有良好的语音。     

一种基于 MXene 的Fe2O3/Nb2O5/Nb4C3Tx 高灵敏丙酮传感器

MXene 具有较大比表面积和优异的导电性, 当与金属氧化物半导体结合时可以抑制片层团聚, 还可以大大提高载流子转移速率, 提高气敏性能。通过简单的水热和煅烧两步法成功合成了Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 三元复合材料。通过表征, Fe₂O₃ 微米球分布在 MXene 纳米片层之间。气敏测试结果表明, 与原始Fe₂O₃相 比, Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器对丙酮的响应能力有明显的提高。传感器灵敏度高, 选择性较好, 对环境中 浓度为 5 ×10^?6 的丙酮响应高 (R_a /R_g = 7.81, 30% RH), 响应和恢复速度快, 具有出色的重复性和长期稳定性。Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器具有良好的气敏性能, 主要因为三元复合材料提供了较大比表面积和丰富的氧空位, 增强了活性位点, 使得气体易于在传感器表面扩散, 为开发丙酮敏感复合材料提供了参考。     

肼类燃料液滴的亚临界——超临界蒸发/分解燃烧理论

对肼、一甲基肼、偏二甲肼的亚临界－－超临界蒸发／分解燃烧进行了研究,计算了肼类燃料滴在不同压力下液滴温度和蒸发速度的变化历程,计算了蒸发常数、传热数和传质数,其结果和实验数据是吻合的。本文不但考虑了肼类燃料滴的亚临界蒸发／分解燃烧,还考虑到了其超临界蒸发／分解燃烧,并对达到超临界工况时的界限参数进行了计算。     

Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating

LiCo_1/3Ni_1/3Mn_1/3O₂ was coated by a layer of 1.0 wt% CeO₂ via sol-gel method. The bared and coated LiMn_1/3Co_1/3Ni_1/3O₂ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure, only coating on the surface; the 1.0 wt% CeO₂-coated LiCo_1/3Ni_1/3Mn_1/3O₂ exhibits better discharge capacity and cycling performance than the bared LiCo_1/3Ni_1/3Mn_1/3O₂. The discharge capacity of 1.0 wt% CeO₂-coated cathode is 182.5 mAh·g⁻¹ at a current density of 20 mA·g⁻¹, in contrast to 165.8 mAh·g⁻¹of the bared sample. The discharge capacity retention of 1.0 wt% CeO₂-coated sample after 12 cycles reaches 93.2%, in comparison with 86.6% of the bared sample. CV results show that the CeO₂ coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte, thus enhance the electrochemical performance of the coated material.     

RDSS/Doppler/GPS/SINS组合导航系统研究

针对双星定位系统(RDSS)存在的定位位置滞后的先天缺陷,根据组合导航定位系统输出速度误差小的特点,给出了一套消除RDSS位置滞后的方案,并对RDSS／SINS组合系统进行了建模,依据联邦滤波器理论,考虑到GPS的实际情况,提出了RDSS／Doppler／GPS／SINS多传感器组合导航系统的设想,仿真结果表明,该组合导航系统具有准确度高、自主性强的特点。     

Transport Properties of Polycrystalline La2/3Ca1/3Mn1-xCuxO3

The infuence of Cu dopant (x) and sintering temperature(Ts) on the troansport propeties of La2/3Ca1/3Mn1-xCuxO3 series samples prepared by Sol-Gel technique was investigated.X-ray diffraction patterns show that all the samples with different Cu dopant and sintering temperatures (Ts) are of single phase without obvious latice distortion.Experimental results indicate that the insulator-metal transition temperature is diectly related to the sintering temperature and Cu dopant x.It is interesting to observe that a proper amount of Cu dompant can substantially improve magnetoresistance effects.     

Low temperature properties of organic-inorganic Ag/ p -CuPc/ n -GaAs/Ag photoelectric sensor

A thin organic film of p-type semiconducting copper phthalocynanine (CuPc) was deposited by vacuum evaporation on an n-type GaAs single-crystal semiconductor substrate. The fabricated Ag/p-CuPc/n-GaAs/Ag sensor was carried through an ageing process to stabilize the parameters. Voltage-current characteristics and photoelectrical response of the sensor were investigated at a wide temperature range of 82 to 350 K. Photoelectric characteristics were measured under nonmodulated filament-lamp illumination. It was observed that such sensor parameters as rectification ratio, threshold voltage, junction, shunt and series resistances, open-circuit voltage and short circuit current are temperature-dependent. It was found that wide-range voltage-current characteristics of the sensor may be described similarly to that of a Schottky barrier diode. Using the experimental data on voltage-current characteristics and absorbance of the CuPc films, the energy-band diagram of the p-CuPc/n-GaAs heterojunction was developed. It was shown that data obtained from simulation of an equivalent circuit of photoelectric sensor agreed with experimental results. Supported by the National Engineering and Scientific Commission of Pakistan     

St/BA/MAA/AA/VAC复合乳液的合成及其应用

采用半连续乳液种子聚合法合成苯乙烯（St）、丙烯酸丁酯（BA）、甲基丙烯酸 （MAA）、丙烯酸（AA）、醋酸乙烯酯 （VAc）的复合乳液.分析了丙烯酸对乳液电解质性能的影响,引发剂对聚合反应转化率的影响及乳化剂含量对乳液粘度的影响.通过正交试验确定组分的适当配比.该共聚乳液的粘度及固体含量符合要求,稳定性好, 性能价格比高.应用表明：用此乳液配制成地毯乳胶,胶膜具有良好的机械性能.     

Reliability of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode that consisted of Au/PZT/BIT/p-Si multilayer configuration was fabricated by pulsed laser deposition (PLD) technique. The reliability issues (I-V characteristics, capacitance retention, fatigue and imprint) were investigated. The I-V curve showed the conventional Schottky diode characteristics with a small current density of - 5.3×10 -10 A/cm2 at a voltage of - 4 V and 6.7×10-8 A/cm2 at a voltage of + 4V, and this characteristic can be maintained below 50℃. The capacitance variety of the ferroelectric diode was only 5 % in 10 hours after withdrawing the applied bias of + 5 V or - 5 V, indicating the diode had good capacitance retention. By applying 100 kHz bipolar pulses of 5 V amplitude, the decay in remanent polarization was only 10% after 109 switching cycles, and meanwhile the increase in coercive field was 12%. After being irradiated for 20 min with a 200 W ultraviolet ray lamp, the remanent polarization and coercive field had both varied, and a voltage shift was obse     

亚锰酸盐La0.7-xYxCa0.3MnO3的电磁特性和磁电阻效应

研究了用固相反应法制备亚锰酸盐多晶样品La0.7-xYxCa0.3MnO3,并研究了Y的不同掺杂(x=0.1,0.2)对样品的晶体结构、电磁特性和磁电阻效应的影响.实验结果表明,随着温度的降低,x=0.1样品的R-T曲线没有出现峰值,而x=0.2样品出现了峰值,显示了复杂的输运特性.两种样品的磁电阻Rm都随着温度的降低而升高,但都没有出现峰值.x=0.2的样品在较宽的温区内,磁电阻效应都很显著,而且Y掺杂由x=0.1提高至x=0.2,磁电阻效应增强.