BP神经网络结合变量选择方法在牛奶蛋白质含量检测中的应用北大核心CSCD

牛奶中的蛋白质含量会影响牛奶的品质,利用高光谱图像的光谱特征信息研究对牛奶蛋白质含量预测的可行性。本文提出一种基于竞争性自适应重加权算法(competitive adaptive reweighted sampling, CARS)和连续投影算法(successive projections algorithm, SPA)结合多层前馈神经网络(back propagation, BP)的预测建模方法,实验以含有不同浓度蛋白质的牛奶为对象,利用可见光/近红外高光谱成像系统共采集到5种牛奶共计250组高光谱数据,通过实验对比选择采用标准化方法对获取到的吸收光谱预处理,然后采用CARS结合SPA筛选特征波长,得到18个特征波长,建立CARS-SPA-BP模型,经过试验,CARS-SPA-BP模型的训练集决定系数和测试集决定系数R;和R;分别达到0.971和0.968,训练集均方根误差(root mean square error of calibration,RMSEC)和测试集均方根误差(root mean square error of prediction,RMSEP)达到了0.033和0.034。研究发现,采用CARS结合SPA筛选的牛奶特征波长建立的多层前馈神经网络模型,其模型预测结果与全波长建模相比并没有明显降低,因此将CARS结合SPA用于波长筛选并且结合BP神经网络基本可以完成对牛奶蛋白质含量的预测。为验证CARS-SPA-BP模型的预测能力,在相同数据环境下,使用较为传统的偏最小二乘回归(partial least squares regression, PLSR)进行建模,实验结果表明,CARS-SPA-BP相较于PLSR,R;和RMSEP均有明显提升。研究表明,CARS-SPA-BP可充分利用牛奶光谱特征信息实现较高精度的牛奶蛋白质含量检测。     

Effect of neighbouring village conditions and infrastructure interdependency on economic opportunity: A case study of the Yogyakarta region,Indonesia

To determine whether the inclusion of conditions in neighbouring villages and infrastructure interdependency are able to improve the performance of infrastructure–economy interaction models, we compare three related and progressive concepts. The first concept defines economic opportunity in a village as a function of available infrastructure within that village. The second concept includes the effect of economic opportunity in neighbouring villages in addition to available infrastructure within the village. In the third concept, we include the interdependency of infrastructures as another factor affecting the potential level of economic development in the village. We use Ordinary Least Squares (OLS) and a Geographic Information System (GIS) to model the first concept, and we add a spatial-lag model for the second. The third model expands on the second by introducing a Sugeno Fuzzy Inference System (FIS) and a rule-based OLS to capture the nature of infrastructure interdependency. The result of the three models is validated by a known spatial distribution of poverty levels and subjective well-being that serve as proxies for economic opportunity in the Yogyakarta region in Indonesia. The results demonstrate that the third model provides a more accurate prediction of the real conditions and performs consistently better than the other two models. We therefore conclude that conditions in neighbouring villages and infrastructure interdependency influence the economic opportunity of a village and should be considered in policy making regarding resource allocation in infrastructure development.     

Synthesis of magnetite nanoparticles by surfactant-free electrochemical method in an aqueous system

A simple surfactant-free electrochemical method is proposed for the preparation of magnetite nanoparticles using iron as the anode and plain water as the electrolyte. This study observed the effects of certain parameters on the formation of magnetite nanoparticles and their mechanism in the system, including the role of OH^? ions, the distance between electrodes and current density. We found that OH^? ions play an important role in the formation of magnetite nanoparticles. Particle size can be controlled by adjusting the current density and the distance between electrodes. Particle size increases by increasing the current density and by decreasing the distance between electrodes. Particle formation cannot be favored when the distance between electrodes is larger than a critical value. The magnetite nanoparticles produced by this method are nearly spherical with a mean size ranging from 10 to 30 nm depending on the experimental conditions. They exhibit ferromagnetic properties with a coercivity ranging from 140 to 295 Oe and a saturation magnetization ranging from 60 to 70 emu g^?1, which is lower than that of the corresponding bulk Fe₃O₄ (92 emu g^?1). This simple method appears to be promising as a synthetic route to producing magnetite nanoparticles.     

Experimental study of the natural organic matters effect on the power generation of reverse electrodialysis

In this paper, the effect of natural organic matters (NOMs), which are typically present in river and seawater, on the power generation of reverse electrodialysis was studied. Bovine serum albumin, humic acid, and sodium alginate were used as models of NOMs. A NOM model was added to concentrated salt water, diluted salt water, and/or both of them. Power density was used to measure the resulted power generation. Fourier transform infrared spectroscopy and scanning electron microscope were used to characterize the presence of NOMs on the membrane surfaces. The effect of NOMs on the generated power density was clearly observed. This effect was influenced by the NOM's type, the NOMs concentration, and the compartment in which NOMs are added. Fourier transform infrared spectroscopy and scanning electron microscope data confirmed that NOMs are deposited on both anion and cation exchange membrane surfaces. While all NOMs added to concentrated salt water did not influence the generated power density, different power density behavior was resulted from the different NOMs added to diluted salt water, where NOMs could increase or decrease or remain the generated power density. Thus, besides NOM's type, the salt concentration is very critical to determine the effect of NOMs on the generated power density. Copyright © 2017 John Wiley & Sons, Ltd.     

Axisymmetric alternating direction explicit scheme for efficient coupled simulation of hydro-mechanical interaction in geotechnical engineering—Application to circular footing and deep tunnel in saturated ground

Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical (H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit (ADE) scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in non-uniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourth-order finite difference (FD) approximation to the spatial derivatives of the axisymmetric fluid–diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps, giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua (FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%–50% that of FLAC's basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%–1.8%.     

基于变论域模糊控制的温室环境控制系统的设计

详细介绍了基于变论域模糊控制的温室环境控制系统,以温度控制系统为例进行设计。该系统以变论域模糊控制为核心算法,用BP神经网络改变模糊控制的论域。根据误差和误差变化率选择合适的论域,不仅克服了误差过大或过小时对温室控制的影响,还解决了温室多变量难以建立数学模型和隶属度函数选择较难的问题。     

Metabolomic Differentiation of Brassica rapa Following Herbivory by Different Insect Instars using Two-Dimensional Nuclear Magnetic Resonance Spectroscopy

The metabolic alterations of Brassica rapa (L.) leaves attacked by larvae of the specialist Plutella xylostella L. (Lepidoptera: Yponomeutidae) and the generalist Spodoptera exigua Hubner (Lepidoptera: Noctuidae) were investigated with nuclear magnetic resonance (NMR) spectroscopy, followed by a multivariate data analysis. The principal component analysis (PCA) of ¹H NMR spectra showed that metabolic changes in B. rapa leaves induced by the 2nd and the 4th instars were different from each other. However, the congestion of the one-dimensional ¹H NMR spectrum made it difficult to identify discriminating metabolites. To overcome the spectral complexity, several two-dimensional NMR techniques were applied. Of those evaluated, J-resolved spectroscopy, which affords an additional coupling constant, provided a wide range of structure information on differentiating the metabolites. Based on the J-resolved spectra combined with PCA, the major signals contributing to the discrimination were alanine, threonine, glucose, sucrose, feruloyl malate, sinapoyl malate, and gluconapin.     

Cooling Process and Cast Structure of Zr-Al-Ni-Cu–Based Bulk Metallic Glasses Produced in Various Atmospheres

Cooling process in the production of Zr₆₅Al_7.5Ni₁₀Cu_17.5-based bulk metallic glasses (BMGs) was investigated in various chamber atmospheres in Cu mold casting. Two different cooling modes, consisting of the direct heat transfer between the melt and Cu mold in the high temperature and indirect transfer via cavity in the low-temperature regions, are suggested. In the later case, the cooling effect should depend on the chamber atmosphere, which results in the formation of glassy structure with large relaxation enthalpy casting under the ambient Ar and He atmospheres due to a good thermal conductivity. The less relaxed BMGs produced by an improved cooling effect are also expected to contain a large amount of free volume for significant deformability. Actually, it is clarified that the compressive plastic deformation is improved with an increase of the relaxation enthalpy. The present study indicates a necessity of development of the glassy structure, i.e., relaxation state, and provides a new technique of the formation of less relaxed glassy structure for the improvement of plasticity in BMGs.     

Stereoselective Reduction of 1‐O‐Isopropyloxygenipin Enhances Its Neuroprotective Activity in Neuronal Cells from Apoptosis Induced by Sodium Nitroprusside

Genipin is a Chinese herbal medicine with both neuroprotective and neuritogenic activity. Because of its unstable nature, efforts have been to develop more stable genipin derivatives with improved biological activities. Among the new compounds reported in the literature, (1R)‐isopropyloxygenipin (IPRG001) is a more stable but less active compound compared with the parent, genipin. Here, two new IPRG001 derivatives generated by stereoselective reduction of the C₆=C₇ double bond were synthesized. The 1R and 1S isomers of (4aS,7S,7aS)‐methyl‐7‐(hydroxymethyl)‐1‐isopropoxy‐1,4a,5,6,7,7a‐hexahydrocyclopenta[c]pyran‐4‐carboxylate ( CHR20 and CHR21 ) were shown to be very stable both in high‐glucose cell culture medium and in mice serum at 37 °C. Evaluation using an MTT assay and Hoechst staining showed that CHR20 and CHR21 promote the survival of rat adrenal pheochromocytoma (PC12) and retinal neuronal (RGC‐5) cells from injury induced by sodium nitroprusside (SNP). The neuroprotective effects of CHR20 and CHR21 were greater than both isomers of IPRG001, the parent compounds. These results indicate that reduction of 1‐O‐isopropyloxygenipin enhances its neuroprotective activity without affecting its stability.     

基于FPGA的高速光谱采集与处理系统

为了实现光谱数据的高速采集与实时处理,研究了一种基于FPGA (Field-Programmable Gate Array)的高速光谱数据采集与分析系统.系统由光学模块和处理模块组成,光学部分由准直透镜、静态干涉具、CMOS探测器组成;处理模块由FPGA硬件编程实现.通过对所采集的干涉条纹进行切趾处理、FFT(fast Fourier transform)及光谱标定,并根据干涉具参数给出了光谱分辨率的函数关系,从而实现了对被测光谱的复现.采用了Moswlaim6.3f对处理模块进行了仿真分析,并计算了不同切趾方法对反演光谱的影响,验证了FFT时序逻辑关系符合设计要求.实验中搭建了光学模块和处理模块,完成了对660.0 nm激光的光谱分析.实验结果显示,该系统具有高速光谱数据采集与复现的能力,适用于高速光谱数据处理系统.