等跨等截面连续体系频率的精确计算

大量的工程实践表明连续T梁桥(通常采用先简支后结构连续施工)的基频并不符合《公路桥涵设计通用规范》(JTG D60—2015)条文说明给出的连续梁桥基频计算公式。为此,本文首先采用多坐标法从理论上推导等截面多跨连续梁桥的基频计算公式;再结合某2及3跨等截面连续梁桥模型,对有限元分析、理论计算及规范公式的结果进行对比;最后对一座实际连续T梁桥的实验、有限元分析、理论计算结果进行比较。结果表明:等跨、等截面连续梁桥的基频符合相同跨径、相同截面简支梁桥的计算公式;等跨、等截面连续梁桥n(≥2)阶次的频率随着跨数的增加,逐渐减小,当跨数趋于无穷大时,趋近于基频。     

肉芝软珊瑚素全合成的研究：Ⅲ.肉芝软珊瑚素的合成

由3,7-二甲基-6,7-环氧-8-苯硫基-2-辛烯醛和6-甲基-8-三甲硅氧基-6-烯-2-酮-1-辛酸乙酯通过羟醛缩合、内酯化、Wittig反应、闭环等反应合成得肉芝软珊瑚素,总产率10.6％。其中的关键步骤是以硫稳定的碳负离子烷基化。讨论了合成品的立体化学。     

Influence of acid leaching and calcination on iron removal of coal kaolin

Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) demonstrated that 900℃ was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin (RCK), whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin (CCK). The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M?ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900℃. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.     

Simulation of wind gust structure in the atmospheric boundary layer with Lattice Boltzmann Method

Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation data shows that wind gust structure has coherent characteristics.This is important for entrainment of spring dust storms into the upper boundary layer,where they are transported great distances.The Lattice Boltzmann Method(LBM) is a computational fluid technique based on the Boltzmann transport equation.The LBM has been used to study complex motion such as turbulence,because it describes motion at the micro level.In this paper,Large eddy simulation is introduced in the LBM,enabling simulation of turbulent flow in the atmospheric boundary layer.The formation and development of wind gusts are simulated,and a coherent structure with a combination of wave and vortex is obtained.This explains the mechanism of soil erosion and sand entrainment by the coherent structure of wind gusts.     

利福定对果蝇寿命的影响

本文研究利福定喂饲果蝇对其寿命的影响。试验组液体饲料分别含利福定10、5和2.5ppm,结果发现这三个浓度的利福定对果蝇均有延寿效应,其中,10ppm的利福定对雄果蝇的延寿效果最好,平均寿命延长22.4％(p<0.05),5ppm的利福定对雌果蝇的延寿效果最好,平均寿命延长19.2％(p<0.05)。而且,它们的最高寿命也有显著延长,提示利福定是一种较好的抗衰老药物。     

高压除鳞喷嘴内部流场数值模拟与仿真分析

针对目前工厂广泛使用的高压除鳞喷嘴,应用前处理软件Gambit建立其内部流畅的三维模型,采用Fluent软件提供的Laminar层流模型对不同结构参数的喷嘴内部不可压缩、稳态、层流流场进行了数值模拟,并分析了各参数对其流场速度分布、压力分布和出口轴心速度的影响.仿真值与理论计算值十分接近,数值模拟结果表明,喷嘴收缩角和直径对其内部流场影响较大,而扩张角对其内部流场影响相对较小,但各参数都存在最优值,且各参数之间也存在着最优搭配使射流打击效果最好.     

Wigner-Ville distribution and cross Wigner-Ville distribution of noisy signals

The Wigner-Ville distribution （WVD） and the cross Wigner-Ville distribution （XWVD） have been shown to be efficient in the estimation of instantaneous frequency （IF）. But the statistical result of the IF estimation from XWVD peak is much better than using WVD peak. The reason is given from a statistical point of view. Theoretical studies show that XWVD of the analyzed signal can be estimated from XWVD of the noise-contaminated signal. The estimation is unbiased, and the variance is equal to that of noise. In this case, WVD cannot be estimated from W-VD of the noise-contaminated signal. Therefore, higher SNR is required when WVD is used to analyze signals.     

多群体优良模式自学习遗传算法

针对经典遗传算法存在的问题,提出了多群体优良模式自学习遗传算法.引入了迁移与学习算子,以提高遗传算法的有效性与收敛性.通过对Goldstein和Price函数的优化计算,说明了该方法具有良好的全局搜索能力和较快的收敛速度.     

特大规模组合电路测试数据产生方法研究

针对特大规模组合电路和全扫描设计电路提出了一种高速测试生成方法。该方法采用有限回溯测试模式产生方法生成测试码,采用ｎ（机器字长）个测试码并行的单故障传播方法模拟验证测试覆盖。测试生成与故障模拟为ｎ对１紧耦合集成方式。该方法运行１０个Ｂｅｎｃｈｍａｒｋ电路,取得了低测试长度、高故障覆盖、高效率的良好效果。     

就地城镇化地区耕地细碎化及其影响因素分析——以福建省晋江市为例

以福建省晋江市为研究区,基于2016年土地利用现状数据选取斑块面积指数、斑块形状指数和斑块分散指数3个景观指数构建耕地细碎化指标体系,从不同尺度对就地城镇化下晋江市耕地细碎化程度和空间分布进行了评价,然后基于耕地细碎化空间自相关特征并结合地理加权回归模型和地理探测器方法分析不同因素对耕地细碎化的影响.结果表明:1)晋江市耕地细碎化整体处于中度细碎化水平,其全局莫兰指数为0.382 7,具有一定的空间正相关,呈现出明显的空间集聚现象;2)高程、坡度和河流对耕地细碎化影响度以正影响为主,居民点和交通以负影响为主,土地利用类型中建设用地对耕地细碎化影响最为突出.细碎化高集聚区域基本处在各因素的主要影响度范围内,各个因素对耕地细碎化空间集聚产生显著影响;3)在选取的因素中自然因素(高程、坡度和河流)和人类干扰因子(居民点、交通和土地利用类型)对耕地细碎化的空间分异影响显著不同,自然因素(高程、坡度和河流)是晋江市耕地细碎化的主要原因,且居民点与自然要素共同作用会加剧耕地细碎化程度.