Design of an anti-jamming GPS receiver based on orthogonal projection method

Code delay and Doppler shifted frequency could not be captured by using the conventional GPS receiver in strong interference environments because the received GPS signals which traveled a long distance are very weak. An anti-jamming GPS receiver is proposed. The interferences in the received signals are cancelled by using subspace projecting technique, and the resulting interference-free signals are processed by a weight vector which maximizes the signal-to-noise ratio. Simulation is conducted, and the resu...     

Research on the technology of femtosecond laser micromachining based on image edge tracing

Aiming at fabrication of complex microstructures and micro-patterns, a kind of femtosecond laser micromachining technology based on the BMP image edge tracing was proposed. We introduced the general principle of this technology and discussed the implementation of the machining paths extraction, optimization, tracing and the feedback of the machining procession in detail. On the basis of this technology, control software for femtosecond laser micromachining was developed. Furthermore, we have accomplished the fabrication of complicated two-dimensional (2D) micro-patterns on a copper thin film. The results indicate that this technology can be used for digital control micromachining of complex patterns or microstructures at micron and submicron scales by femtosecond laser.     

GN海带新品系脂肪酸的气相色谱-质谱联用分析

首次用乙醇提取、甲酯化处理的方法,对GN海带新品系脂肪酸的化学成分采用GC-MS技术进行分析研究。结果表明:海带中含有10种不饱和脂肪酸,占37.98%,其中亚油酸占9.29%,γ-亚麻酸占3.74%,EPA占1.12%,DHA占0.63%,花生四烯酸占4.9%;含有4种饱和脂肪酸,占56.22%的,其中棕榈酸(又名软脂酸)的含量高达36.23%。为海带新品系在生物制药和营养保健品领域的深度开发应用提供了科学依据。     

新型冷弯翼缘闭合压弯构件的力学性能

研究了两种新型(HF1、HF2)冷弯翼缘闭合截面在压弯荷载作用下的力学性能,采用非线性有限元数值方法,应用大型有限元通用程序ANSYS对新型截面构件的力学性能进行了模拟。分析了新型截面构件在压弯荷载作用下的屈曲模式、变形特征、承载力、刚度等方面力学性能,分析结果表明:新型冷弯截面构件具有截面平均应力高、相关曲线饱满、构件刚度大、弯曲变形小,板件不易局部屈曲等方面力学性能优势,新型冷弯翼缘闭合构件相关曲线饱满,适宜承受压弯荷载,具有多方面优良的力学性能,可以深入研究并合理推广使用。     

基于改进的卷积神经网络图像识别方法

当前的图像特征识别大多采用的是传统的机器学习方法与卷积神经网络方法。传统的机器学习对图像识别的研究,特征提取多是通过人工完成,泛化能力不够强。最早的卷积神经网络也存在诸多缺陷,如硬件要求高,需要的训练样本量大,训练时间长。针对以上问题,提出了一种改进的神经网络模型,在LeNet-5模型的基础上并在保证识别率的情况下,简化网络结构,提高训练速度。将改进的网络结构在MINIST字符库上进行识别实验,分析网络结构在不同参量中的识别能力,并与传统算法进行对比分析。结果表明提出的改进结构在当前识别正确率上,明显高于传统的识别算法,为当前的图像识别提供新的参考。     

基于模型缩聚-频响函数型模型修正的子结构损伤识别方法

由于大型复杂结构参数识别困难,提出将频响函数型模型修正方法与子结构方法结合进行损伤识别。构造一个关于损伤频响函数的优化方程。通过子结构有限元模型向损伤后频响函数修正的过程,识别损伤参数。以一个三层平面刚架为数值算例,计算结果表明该算法对损伤参数较为敏感,识别精度较高,可以准确识别出预设的子结构损伤单元和损伤程度。     

基于GA-SVM算法永磁同步直线电机变载荷进给位置误差预测

针对永磁同步直线电机精密进给过程中,受到齿槽效应、端部效应及摩擦力扰动等非线性因素的影响,位置误差难以预测问题,提出了一种基于遗传算法(GA)优化支持向量机(SVM)算法永磁直线电机变载荷位置误差预测模型的方法。通过测量各种情况下永磁直线电机在运动过程中的位置变化情况,利用遗传算法优化支持向量机算法建立预测模型。该模型采用实验台运行的正弦轨迹数据为训练样本,三角波轨迹数据为测试样本。选取各种情形的正弦波轨迹数据和三角波轨迹数据进行仿真预测和验证。以各种情况的正弦波信号的指令位置、指令速度和电流作为模型的输入,以三角波信号的位置误差作为输出。结果表明,经过遗传算法优化支持向量机建立的位置误差预测模型,在拟合和预测精度上要优于未经过算法优化的位置误差预测模型。     

Hydrogen absorption behavior of TA15 alloy

The hydrogen absorption kinetics of TA15 titanium alloy at 973–1123 K was studied using a tube-type hydrogen treatment furnace. The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found that only the second hydrogen absorption period exists in the hydrogen absorption process of TA15 alloy between 973 and 1123 K, and the activation energy is 54.889 kJ/mol for hydrogen absorption. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results demonstrate that δ hydride forms between 973 and 1123 K, and β phase decreases with the increase of temperature. Orthorhombic α″ martensite is generated at 1073-1123 K, and their amount increases with increasing temperature.     

Thermoelectric effect of silicon films prepared by aluminum-induced crystallization

Aluminum-induced crystallized silicon films were prepared on glass substrates by magnetron sputtering. Aluminum was added in the silicon films intermittently by the regular pulse sputtering of an aluminum target. The amount of aluminum in the silicon films can be controlled by regulating the aluminum sputtering power and the sputtering time of the undoped silicon layer; thus, the Seebeck coefficient and electrical resistivity of the polycrystalline silicon films can be adjusted. It is found that, when the sputtering power ratio of aluminum to silicon is 16%, both the Seebeck coefficient and the electrical resistivity decrease with the increasing amount of aluminum as expected; the Seebeck coefficient and the electrical resistivity at room temperature are 0.185-0.285 mV/K and 0.30-2.4 Ω·cm, respectively. By reducing the sputtering power ratio to 7%, however, the Seebeck coefficient does not change much, though the electrical resistivity still decreases with the amount of aluminum increasing; the Seebeck coefficient and electrical resistivity at room temperature are 0.219-0.263 mV/K and 0.26-0.80 Ω·cm, respectively.     

矮坨坨内生真菌Fusarium oxysporum代谢产物及其抗肝癌活性的研究

从矮坨坨根部分离得到的一株内生菌,经形态与分子生物学18S rDNA序列分析鉴定为尖孢镰刀菌(Fusarium oxysporum).运用中压柱色谱,高效制备液相色谱方法和现代波谱技术1HNMR、13CNMR以及LC-MS从其发酵液的乙酸乙酯部位分离鉴定了9个单体化合物,分别为4-氨基-2-羟基嘧啶(1),4,5-二氢-3H-吡唑-3-羧酸甲酯(2),4-羟基-7-(2-羟基-丁基)-3-甲基-氧杂环庚烷-2-酮(3),2-氨基-3-甲基戊酸(4),2,5-二氨基戊酸(5),2-氨基-3-甲基丁酸(6)4-羟基苯甲酸(7),脱氢镰刀菌酸(8),镰刀菌酸(9),其中化合物8对肝癌HepG2和Hep3B细胞具有较强的细胞毒活性,IC50值分别为23.9和29.1 μg/mL,而对正常肝细胞L-02未显示细胞毒性.