基于近红外光谱技术的马铃薯叶片含水率高效预测

提出了运用近红外光谱技术检测新鲜马铃薯叶片中含水量的方法，并通过预测结果和运算量的对比得出一种高效率的预测方法。采集了900～2100 nm波段范围内110个新鲜马铃薯叶片的光谱反射率信息，经SG（Savitzky-Golay）平滑、多元散射校正（MSC）和标准正态变量变换（SNV）3种预处理后，分别建立偏最小二乘回归（PLSR）模型和BP神经网络模型，再运用回归系数（regression coefficients, RC）法在全波段光谱中提取特征波长，同样经3种预处理后分别建立预测模型。结果表明：在运用光谱全波段信息构建的模型中，经多元散射校正（MSC）预处理建立的BP神经网络模型预测效果最好，预测集决定系数R²为0.9791，均方根误差RMSE为0.3723；在基于特征波长构建的模型中，经SG平滑预处理建立的神经网络模型预测效果最优，预测集决定系数R²为0.9658，均方根误差RMSE为0.4759；验证了特征波段结合BP神经网络建立的模型与全波段建立的模型预测结果相差不大，因而能够极大地减少运算量，提高预测效率。     

基于亚波长光栅的负折射光子晶体成像研究

理论上折射率为-1的平板超透镜可以实现完美成像,但等效折射率为-1的光子晶体结构,不满足介电常数ε=-1和磁导率μ=-1的条件,光子晶体与自由空间阻抗不匹配,某些角度的入射光与光子晶体内布洛赫波不能耦合,致使该空间频率光信息丢失,限制了光子晶体成像分辨率。为了提高成像分辨率,在光子晶体表面设置亚波长光栅结构,利用光栅的增透减反和波矢匹配作用,提高光子晶体对入射光的耦合效率。通过调整光栅周期,使更多高空间频率分量参与成像,同时抑制低频分量的传输。设置亚波长光栅结构后,光子晶体成像分辨率由597 lp/mm提高到了850 lp/mm,突破了衍射极限。     

二维硅薄膜光子晶体波导的设计及制作

为了制作可用于通信波段的二维硅光子晶体波导,研究了光子晶体波导的设计方法及制作工艺。应用平面波展开法计算了两种空气孔型光子晶体结构的TE波禁带,经筛选采用了三角晶格空气孔结构。同样利用平面波展开法计算了引入缺陷后二维三角晶格空气孔型光子晶体波导结构的TE波禁带,经对比发现归一化频率为0.295 7的缺陷态最适宜用来制备光子晶体波导,并据此设计了用于1.55μm波长的二维三角晶格空气孔型光子晶体波导,其晶格周期为458nm,空气孔直径为339 nm。对设计的结构参数进行了容差计算,结果表明误差在-3.95~5.65 nm方能满足设计要求。最后使用聚焦离子束刻蚀工艺,制作了所设计的波导结构,并进行了测试。测试结果表明,样品实际晶格周期为463nm,空气孔直径为344 nm,比设计值大5 nm,在容差允许范围内,满足设计要求。     

弧矢聚焦双晶单色器聚焦误差分析

简单介绍了弧矢聚焦单色仪的分光原理及结构原理,分析了同步辐射弧矢聚焦双晶单色器实际转轴偏离理想转轴ΔS及晶面偏离与导轨的理想夹角Δα对出射光高度的影响,并对弧矢聚焦晶体压弯半径的压弯精度Δh对实验站聚焦光斑展宽的作用进行了理论推导.当ΔS≤31μm、Δα≤1′,就可以确保出射光线高度误差Δh≤25μm;当对称压弯第二晶体所需微位移器的行程≥1mm、精度≤1.25μm时,可满足聚焦光斑的展宽≤0.5mm要求,且当压弯半径R的弯曲精度在ΔR≤0.75%R的范围内不需对晶体压弯.     

基于Cantor结构的一维光子晶体耦合腔的光学特性

在N=3的三分Cantor多层结构的基础上设计了一种光子晶体耦合腔结构,用传输矩阵法研究了这种耦合腔结构的光学特性。结果表明,新结构有更宽的带隙,并在宽带隙中出现了一个损耗非常小的超窄透射窗口;保持缺陷层的几何厚度不变,改变缺陷层介质的折射率,该透射窗口位置能在很大的范围内移动。这种新的耦合腔结构可用作超窄带光子晶体滤波器或波长可调谐滤波器,在光通信超密集波分复用和光学精密测量等领域中有应用价值。     

基于正四边形晶格的微结构光子晶体光纤的特性分析

设计了基于正四边形晶格空气孔排列的光子晶体光纤,并在此基础上,通过在纤芯附近引入不同的微结构空气孔,运用全矢量有限元差分法,对不同微结构的光子晶体光纤的模式有效折射率、限制损耗、模场有效面积、非线性系数、波导色散系数等特性参数进行了仿真与分析。结果表明:引入不同的微结构,可以减小有效模场面积和增大非线性系数;引入正四边形微结构空气孔时,其限制损耗整体变化幅度较小;引入正八边形微结构空气孔时,其对应的波导色散系数在中波段变化比较平坦,且在波长为1 550nm处波导色散系数接近于零;引入正十二边形微结构空气孔时,其波导色散系数均为负值且变化幅度不大,可以应用于光纤的色散补偿。根据对引入不同微结构的光子晶体光纤的特性研究,为进一步研究光子晶体光纤提供一定的参考。     

基于光子晶体光纤的轨道角动量模式的产生

为了让光纤中产生轨道角动量 (orbital angular momentum,OAM) 模式更加集成化,提出了一种利用光子晶体光纤 (photonic crystal fiber,PCF) 产生轨道角动量模式的方法。通过设计特殊的PCF,使其本征模的奇偶模传输速度不同,在传输一段距离后形成π/2相位差,从而产生OAM模式。该PCF由中心空气孔、二氧化硅环形层和外包层构成,其中外包层由两层圆形空气孔组成,每层圆的数目为2n+2个,对应产生n阶OAM模式。采用有限元法对所设计光纤进行了三维数值仿真分析,成功产生了+2、+3、+4、+5阶OAM模式。该PCF产生OAM模式的方法,满足了未来光纤通信系统集成化、小型化的趋势,在全光纤模分复用系统中有着潜在的应用前景。     

光折变晶体两波耦合增益系数强度特性理论研究

对两中心模型光折变晶体两波耦合增益系数Γ,总的有效陷阱密度N_eff和强度特性因子η(I)的强度特性进行了理论研究。结果显示在两中心模型的光折变晶体中,Γ,N_eff和η(I)有着复杂的特性。当S_Dγ_T/S_Tγ_D小时,对于A类和B类两中心晶体,N_eff随强度的增加而增加最终趋于饱和,当S_Dγ_T/S_Tγ_D大时,对于A类晶体N_eff增加到一个最大值后稍有减少,而对于B类晶体,N_eff增加到最大值后然而有较大的减少。不同类型晶体增益系数Γ有着不同的强度特性是由于晶体中有着不同的能级结构。     

基于GaP光子晶体的平板超透镜设计与研究

超透镜是基于超表面对光场调控的成像器件，由于其具有体积小型化、工艺流程化的优势，在器件轻量化、便携性方面具有很好的应用前景。针对当前市场对透镜的体积需求，使用时域有限差分法模拟了一种新型结构的超透镜，它是基于光子晶体的平板超透镜，尺寸为长2μm，宽1μm，工作波长在717 nm可见光波段。该平板超透镜以TiO₂波导作为衬底，由Au和GaP两组周期相同的光子晶体呈相切的结构共同蚀刻在TiO₂波导上，模拟研究透镜成像效果。此外通过引入一系列不同形状的缺陷，研究其对平板透镜成像结果的影响，结果表明，当缺陷结构为矩形尺寸：Lx=0.5μm,Ly=0.8μm时，该平板超透镜呈现出最好的成像效果，达到了0.556λ数值的超分辨，极大地提高了成像质量。未来该平板超透镜在可便携的成像设备，AR,VR以及小型医疗设备等各个领域具有极大的发展潜力。     

固溶及时效温度对TC18 组织性能的影响

固溶及时效处理是实现钛合金强化的关键工艺,文中采用不同的固溶及时效温度对TC18钛合金进行了强化处理,对处理后合金的显微组织和性能进行了对比分析。在固溶过程中,随着温度的升高,亚稳β相生成量增加,使得后续时效过程的次生α相析出量增加,从而提高了合金强度,但塑性降低;在时效过程中,随着温度的升高,初生α相晶粒长大,次生α相析出量减少,合金强化效果降低而塑性提高。通过控制固溶及时效温度,调整初生α相与次生α相之间的数量及尺寸关系,可以达到调整合金性能的目的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.