基于BP神经网络的非线性组合预测模型在粮食物流需求预测中的应用

鉴于单项预测模型的局限性,在确定粮食物流需求量的基础上,建立了基于BP神经网络的非线性组合预测模型,并把这一模型应用于长春市粮食物流需求的预测。误差分析表明,该预测模型可以有效地提高粮食物流需求量的预测精度。     

Cadmium in edible crabs (Cancer pagurus L.) from Scottish coastal waters

Concentrations of cadmium in the hepatopancreas (0.1–61.3 mg kg⁻¹), gonad (0.15-11.0 mg kg⁻¹) and gills (0.2–10.7 mg kg⁻¹) of the edible crab Cancer pagurus L. from 16 sampling sites round the Scottish coast are reported, and compared with published elevated concentrations in crabs from the Orkney Islands. Geographical variations in the distribution of cadmium between organs indicate that the dietary uptake of cadmium is predominant in northern mainland and Orkney crabs, but that uptake from the water is more important in the south of Scotland. Mean dissolved cadmium concentrations in eastern coastal water increase from ∼10 ng dm⁻³ in northern waters to ∼25 ng dm⁻³ in the south. It seems likely that a regional contamination of the environment by cadium of geological origin occurs in the extreme north coast of Scotland, and in the Orkney and Shetland areas.     

Low temperature cleanup combined with magnetic nanoparticle extraction to determine pyrethroids residue in vegetables oils

To quantify trace pesticide residue in vegetable oil rapidly, low temperature cleanup combined with magnetic nanoparticle based solid phase extraction was developed to determine eight pyrethroids in vegetable oils, including tetramethrin, fenpropathrin, cypermethrin, decamethrin, fenvalerate, acrinathrin, permethrin and bifenthrin. Polystyrene coated magnetic nanoparticles were synthesised by a modified chemical coprecipitation combined with emulsion polymerisation method. The nanoparticles were afterwards characterised by Fourier transform-infrared spectroscopy, X-ray diffraction, transmission electron microscopy as well as vibrating sample magnetometer, and successfully employed as adsorbents for the magnetic solid phase extraction of pyrethroids which were cleaned up using low temperature approach in advance. Critical impact factors on the efficiency of the extraction method such as the mass of adsorbents used, volume and type of eluent solvent, extraction time as well as elution time were optimised subsequently. Regression analysis of the calibration curves of the eight pyrethroids yielded satisfactory correlation coefficients within the range of 0.980–0.998. Limit of detection and limit of quantification were calculated to be between 0.0290-0.0658 and 0.0890–0.1994 ng g⁻¹, respectively. Intra-day and inter-day reproducibility at different concentration levels also produced satisfactory recovery rates of 83.18–112.79% with relative standard deviations not exceeding 10.84% and 12.01%, respectively, suggesting desirable stability of the proposed method.     

静电拉伸薄膜反射镜成形机理研究

静电拉伸薄膜反射镜是利用静电场库仑力作用使薄膜产生面形变化,生成所需的光学曲面.由于薄膜反射镜成形过程中力场与静电场的相互耦合作用非常复杂,使其到目前为止在面形控制的理论分析上仍未有定量的结果.首先以平板电容理论为基础,对薄膜成形静电力场进行了近似分析,然后根据半球模型求解了薄膜结构变形,最终得到了薄膜反射镜面形尺寸与静电压参数的函数关系.所得结论对静电拉伸薄膜的研究工作具有一定的指导意义.     

压电式旋转驱动器的设计与实验

为了实现压电驱动器低频率、高效率的输出,设计了一种低频压电式旋转驱动器,这种旋转驱动器结构简单,由低频电源驱动。首先对旋转驱动器进行了结构设计与工作机理分析;然后建立了系统的动力学模型,得出系统输出位移和固有频率表达式;最后制作了实验样机进行实验测试,以微小物料为研究对象,测试驱动器的驱动能力。测试结果表明,当系统频率在91.5Hz时,旋转驱动器性能最佳,输出振动位移大致为45μm,物料移动最大速度为0.15cm/s。     

一种基于移动Agent的分布式通信算法

本文提出了一种基于移动Agent链接寻址分布式通信算法,通过分析通信位移延迟问题,对消息传递的寻址、消息排队的过程设置,实现了移动Agent的高速通信.     

Assessing the width of Gaussian density of states in organic semiconductors

The Density of States (DOS) is an ingredient of critical importance for the accurate physical understanding of the optoelectronic properties of organic semiconductors. The disordered nature of this class of materials, though, renders the task of determining the DOS far from trivial. Its extraction from experimental measurements is often performed by driving the semiconductor out of thermal equilibrium and therefore requires making assumptions on the charge transport properties of the material under examination. This entanglement of DOS and charge transport models is unfavorable since transport mechanisms in organic semiconductors are themselves still subject of debate. To avoid this, we propose an alternative approach which is based on populating and probing the DOS by means of capacitive coupling in Metal Insulator Semiconductors (MIS) structures while keeping the semiconductor in thermal equilibrium. Assuming a Gaussian shape, we extract the DOS width by numerical fitting of experimental Capacitance–Voltage curves, exploiting the fact that the DOS width affects the spatial distribution of accumulated charge carriers which in turn concurs to define the MIS capacitance. The proposed approach is successfully tested on two benchmark semiconducting polymers, one of n-type and one of p-type and it is validated by verifying the robustness of the extraction procedure with respect to varying the insulator electrical permittivity. Finally, as an example of the usefulness and effectiveness of our approach, we study the static characteristics of thin film transistors based on the aforementioned polymers in the framework of the Extended Gaussian Disorder transport model. Thanks to the extracted DOS widths, the functional dependence of current on the gate voltage is nicely predicted and physical insight on transistor operation is achieved.     

LTE-A网络中D2D通信的资源分配算法研究

该文研究了D2D通信使用LTE-A网络上行链路的资源分配问题。首先将问题建模为混合整数非线性规划问题(MINLP),其次根据待接入用户对各信道的青睐程度计算特征值列表并形成相应联盟。在保证各用户服务质量(QoS)的情况下,利用最大加权二部图匹配(MWBM)方法为待接入网络用户寻找合适的资源及复用的组合。仿真结果表明,该算法打破了D2D用户在数据传输过程中一直处于专用或者复用模式的束缚,扩大了D2D用户对可选用的资源范围,与现有算法相比,可有效提高系统的总速率。     

浮动式压电振动送料装置的试验研究

利用自行开发的自动测试与控制系统对浮动式压电振动送料装置的输送能力进行试验研究,分析了物料种类、振动角、工作电压、工作频率、限流板高度及料斗内物料高度等因素对输送效率的影响。确定了浮动式压电振动送料装置的工作电压和工作频率范围,可通过调节电压和频率中的任意一个来调节输送率。对玉米、大米、大豆及电子元件等不同的物料都有很好的输送效果。