拟高粱单株农艺性状相关与通径分析

通过对拟高粱单株农艺性状间相关和通径分析看出,拟高粱农艺性状辅助选择育种中,分蘖数、株高作为拟高粱主要选择指标并兼顾茎粗是较合理的单株选择方法。     

金氰化浸出过程动力学反应速度估计

金氰化浸出过程中,动力学反应速度的不可测量给模型辨识带来了困难,而由浓度等可测变量估计动力学反应速度是一个不适定逆问题,极易将浓度测量数据中的噪声放大,造成估计结果不准确.采用Tikhonov正则化方法,去除了复杂的动力学反应模型,利用浓度、流量等测量数据和物质守恒方程来辨识金和氰根离子的动力学反应速度,有效地减少了测量数据中误差的传递.实验结果表明,该方法不但能很好地跟踪动力学反应速度的变化趋势,抑制噪声的放大,而且易于实现.与有限差分、平滑滤波估计方法相比,其估计效果明显得到了改善.     

Effects of alloying and high-temperature heat treatment on the microstructure of Nb–Ti–Si based ultrahigh temperatur e alloys

The phase co mpositions, microstructure and especi ally phase i nterfaces in the as-cast and heat-treated Nb– Ti–Si based ultrahigh temperature alloys have been investigated. It is shown that β(Nb,X)5Si3 and γ(Nb,X)5Si3 are the primary p hase s in the Nb–22Ti–16Si–5Cr–5Al (S1) (at%) and Nb–20Ti–16Si–6C r–4Al–5Hf–2B–0.06Y (S2) (at% ) alloys, respectively. The Nb solid solution (Nbss) is the primary phase in Nb–22Ti–14Si–5Hf–3Al–1. 5B –0.0 6Y (S3) (at%) alloy . An orientation relationship between Nbss and γ(Nb,X)5Si3 was determine d to be (1-10)Nb//(101-0)γ and [111]Nb//[0001]γ in the as-cast S2 and S3 alloys. Some original β(Nb,X)5Si3 transfor med into α(Nb,X)5Si3 because Al and Cr diffused from the β(Nb,X)5Si3 to Nbss during heattreatment at 1500 °C for 50 h in the S1 alloy. Mean while, Ti diffused from Nbss to β(Nb,X)5Si3, which induced a Ti to generate near the interface between Nbss and Ti-rich β(Nb,X)5Si3. The orientation relationship between the newl y-formed a Ti and previous Nbss was (110 )Nb//(1-10-1) αTi and [001]Nb//(12-3-1)αTi. Among the ( Nb,X)5Si3 phases , the contents o f Cr and Al in β(Nb,X)5Si3 are n earl y the same as those in γ(Nb,X)5Si3 but obviously hi gher than those in the α(Nb,X)5Si3, where as the content of Si in α(Nb,X)5Si3 is nearly the same a s that in γ(Nb,X)5Si3 but higher than that in the β(Nb,X)5Si3     

Effects of alloying and high-temperature heat treatment on the microstructure of Nb-Ti-Si based ultrahigh temperature alloys

The phase compositions,microstructure and especially phase interfaces in the as-cast and heat-treated Nb-Ti-Si based ultrahigh temperature alloys have been investigated.It is shown that β(Nb,X)5Si3 and...     

基于变换域形状描述子的图像检索方法的比较与分析

为了更好地了解变换域方法在图像检索中的检索效果,比较分析了Zernike矩、GFD、PCET、RCFT和RFMT等现有的5种基于变换域的形状描述方法.分别在不变性、计算复杂性、噪声鲁棒性、有效特征数的选取方面对其进行了深入的分析和比较.选用MPEG7 CE Shape-1Part B中的1 400幅图像构成的图像库对这些方法进行检索和性能测试,并实际应用于由500幅病例图构成的图像库的医学图像检索.在研究噪声影响时,对各测试集图片加上不同程度的高斯噪声.通过比较分析及实验结果验证,Zernike矩和GFD方法的检索性能最好,有良好的抗噪性,因而适合于医学图像检索的实际应用.     

分层网络频谱资源分配方案

提出一种频谱资源分配方案,以提升分层毫微微小区网络的期望吞吐量.该方案为每层下行传输分配部分共享频谱资源,在单个用户期望吞吐量满足服务质量需求时,通过动态调整共享频谱资源分配比例,能够最大化网络期望吞吐量.为进一步获得每层下行传输的期望吞吐量,基于Nakagami-m衰落信道推导了每层用户下行接收信干噪比的累积分布函数.理论分析和仿真表明,该频谱资源分配方案能够有效提升网络期望吞吐量,但服务质量需求参数的增长限制了吞吐量的提升.     

A novel lambda negative-resistance transistor in the 0.5 μm standard CMOS process

A novel negative-resistance transistor (NRT) with a Lambda shaped I-V characteristic is demonstrated in the 0.5 μm standard CMOS process. To save on the number of component devices, this device does not use standard device models provided by CMOS processes, but changes a MOSFET and a BJT into a single device by fabricating them in the same n-well, with a p-type base layer as the MOSFET’s substrate. The NRT has a low valley current of -6.82 nA and a very high peak-to-valley current ratio of 3591. The peak current of the device is -24.49 μA which is low enough to reduce the power consumption of the deivce, and the average value of its negative resistance is about 32 kΩ. Unlike most negative-resistance devices which have been fabricated on compound semiconductor substrates in recent years, this novel NRT is based on a silicon substrate, compatible with mainstream CMOS technology. Our NRT dramatically reduces the number of devices, minimizing the area of the chip, has a low power consumption and thus a further reduction in cost.     

一种机床固定结合部的动力学参数化建模方法

在全面分析机床固定结合部动力学特性的影响因素（结合面接触长、宽、粗糙度和预紧力）基础上,根据正交试验理论设计了结合面动力学特性实验试件.利用机床固定结合部动力学建模及其参数识别理论,识别各种工况下试件的动力学模型参数.在对结合面动力学模型参数深入分析的基础上,利用曲面响应法,建立了机床固定结合部动力学参数化数学统计模型.实验验证了该模型的有效性,为数控机床整机动力学精确建模提供了理论基础.     

黄瓜叶肉细胞壁的微观力学性能

以黄瓜叶肉组织为研究对象,经过固定—脱水—包埋—切片处理后,在纳米压痕仪上进行单轴压缩试验.试验结果表明:在应力小于1.0 MPa时,细胞壁发生弹性变形,当应力大于1.0 MPa时,细胞壁会产生塑性变形;同时可以看出在弹性变形范围内,当应力小于0.4 MPa时,应力-应变关系呈线性关系,而应力大于0.4 MPa时,应力-应变呈现非线性特征.为了精确地表述细胞壁材料的力学特性,在对应力-应变数据进行分析的基础上,采用2参数的Mooney-Rivlin模型对试验数据进行拟合,得到模型参数C1和C2分别为0.792,0.195 MPa.     

基于时间序列分析的滑坡位移预测-以尖山营古滑坡复活为例

为了深入研究滑坡位移的特点,以尖山营古滑坡复活为例,基于时间序列加法模型,结合尖山营古滑坡的复活背景,将古滑坡位移分解为趋势项与周期项。对趋势项位移使用等维新息灰色（1,1）（GM（1,1））模型进行分析,并提取周期项位移,建立一阶自回归（A R）模型对周期项进行预测。将两者预测结果相加,即可得到古滑坡预测总位移。结果表明：预测与实测值误差较小,模型精度较高,能够较好的描述尖山营古滑坡的位移特征,可用于古滑坡后续的监测预报预警中,具有一定的理论研究与工程价值。