基于激活函数四参可调的BP神经网络改进算法

为改善BP神经网络的性能,以标准Sigmoidal函数为基础,提出了一种四参数可调的激活函数模型.在学习过程中,它能同时对激活函数的陡度、位置及映射范围进行调节,具有更强的非线性映射能力.并推导出其在BP神经网络中的学习算法.仿真结果显示,改进后的激活函数与传统的标准Sigmoidal函数相比,收敛速度能提高10倍以上,收敛精度误差可减小到传统误差的0.4%以下,而且可以有效地减少隐层的结点数,学习能力可得到较大的提高.     

Catalytic Dehydrogenation of o‐Alkylated or o‐Alkoxylated Iodoarenes with Concomitant Hydrogenolysis

Palladium‐catalyzed dehydrogenation of suitable chains bonded to an ortho position of an iodoarene has been achieved by two methods both involving oxidative addition of the iodoarene to palladium(0) and palladacycle formation under mild conditions.     

Highly Efficient Alkyne Hydroarylation with Chelating Dicarbene Palladium(II) and Platinum(II) Complexes

1 We report on a novel reaction protocol for the coupling of arenes with alkynes (the Fujiwara reaction), yielding products of formal trans‐hydroarylation of the triple bond. The protocol makes use of a chelating N‐heterocyclic dicarbene palladium(II) complex as catalyst and allows us to perform the reaction in a few hours with only 0.1 mol % catalyst yielding the trans‐hydroarylation product in high yields and with excellent selectivity. We discuss the applicability of this reaction protocol, which appears at present quite general with respect to the alkyne, albeit limited to electron‐rich arenes. We also present the results of catalyst optimisation with respect to the nature of the nitrogen substituents in the carbene units, of the bridging group between the carbene units and of the coordinated anionic ligands. Finally, we also discuss the catalytic performance of a related chelating dicarbene complex of platinum(II).     

终端镍氢电池充放电智能管理系统的应用研究

电力设备终端在使用过程中会经常面临长时间备货存储不工作或者长时间工作不停电这样的问题,这都会导致终端内的电池性能下降,而电力部门要求镍氢电池在任何使用情况下都要保持足够的剩余电量和活性。针对终端使用的这些问题,在现有终端的平台上设计了新的硬件电路和软件算法,增加了镍氢电池的自我管理功能,使电池可以具有自动进行充放电、激活等能力。     

含油浮渣与高粱秆协同制备活性炭的研究

以含油浮渣和高粱秆为原料协同制备活性炭,制备过程分为低温炭化制备炭前体和高温活化制备活性炭两个阶段。炭前体的制备条件为含油浮渣与高粱秆质量比3∶1,炭化温度450℃,炭化时间2h。制备的炭前体表面具有一些孔道,其浸出液重金属含量不超标,使用过程中不会造成重金属污染。利用正交实验和单因素实验对炭前体高温活化制备活性炭的影响因素进行了深入研究,确定的最佳活化条件为以KOH为活化剂,炭前体与KOH质量比1∶4,活化温度800℃,升温速度15℃/min,活化保温时间1h。制备的活性炭表面分布着众多孔隙,大孔深处可见若干层小孔,孔径分布以微孔和介孔为主。比表面积、孔隙体积、平均孔径和碘吸附值分别达到1 648.74m~2/g、1.84cm~3/g、1.76nm和957.82mg/g,均超过了市售的木质商品活性炭。     

表面活性剂改性磁性氧化石墨烯共价固定脂肪酶CRL

采用化学共沉淀法制备磁性氧化石墨烯（MGO）,直接在反应体系中加入Span系列表面活性剂,一锅法制备得到表面活性剂改性磁性氧化石墨烯（SMGO）。X射线衍射仪（XRD）、扫描电镜（SEM）和傅里叶变换红外光谱（FTIR）表征结果表明SMGO制备成功,且具有良好的磁分离性能。以1,5-戊二醛（GA）为交联剂,褶皱假丝酵母脂肪酶（CRL）为模型酶,共价固定CRL于SMGO载体上。Span40 MGO固定化酶酶活回收率为116.5%±1.7%,为MGO固定化酶的6倍;比活可达32.5U/mg,为游离酶的1.6倍;k_cat/K_m也有较大的提升,高于游离酶50%。储存稳定性及热稳定性得到提高,用于水解反应6批次后仍然保留73.6%的相对酶活力。初步分析认为MGO经改性后表面从亲水性转为强疏水性,使得共价固定化过程中同时发生疏水性界面活化,这是酶活性提高的原因之一。文章所报道的改性策略可为类似载体改性提供新思路。     

Nonisothermal crystallization kinetics and stability of leucite and kalsilite from K2O-Al2O3-SiO2 glasses

The crystallization mechanisms and elemental stability of leucite and kalsilite formed from K₂O-Al₂O₃-SiO₂ glasses were investigated by X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Raman spectroscopy and differential scanning calorimetry (DSC). Glass samples with compositions along the leucite-kalsilite tie-line were produced by melt processing and were then heat-treated at 850, 950, and 1250°C for times ranging from 5 minutes to 1000 hours. Kalsilite is an unstable phase that behaves as an intermediate precursor to leucite. Crystalline materials in which kalsilite is the major phase lose potassium upon prolonged heat treatment (1000 hours at 1250°C), in contrast to those with leucite, in which little or no compositional alteration is detected. The formation of leucite from stoichiometric kalsilite is accompanied by the formation of potassium-doped alumina. The activation energies for leucite and kalsilite crystallization, determined via application of the Kissinger equation to thermal analysis data, were 579 and 548 kJ/mol, respectively. Finally, production of pure leucite can be achieved with more favorable crystallization kinetics when starting with off-stoichiometric compositions.     

Structure and enhanced antimicrobial activity of mechanically activated nano TiO2

Titanium dioxide is a photocatalyst, known not only for its ability to oxidize organic contaminants, but also for its antimicrobial properties. In this article, significant enhancement of the antimicrobial activity of TiO₂ (up to 32 times) was demonstrated after its activation by ball milling. The antimicrobial activity was analyzed for one fungal and 13 bacterial ATCC strains using the microdilution method and recording the minimum inhibitory concentration (MIC) values. In order to further investigate the correlation between the mechanical activation of TiO₂ and its antimicrobial activity, the structure, morphology and phase composition of the material were studied by means of Electron Microscopy, X-ray diffraction and nitrogen adsorption-desorption measurements. UV-Vis diffuse reflectance spectra were recorded and the Kubelka-Munk function was applied to convert reflectance into the equivalent band gap energy (E_g) and, consequently, to investigate changes in the E_g value. X-ray photoelectron spectroscopy was used to analyze the influence of mechanical activation on the Ti 2p and O 1s spectra. The presented results are expected to enable the development of more sustainable and effective advanced TiO₂-based materials with antimicrobial properties that could be used in numerous green technology applications.     

Influence of rapid thermal annealing at varied temperatures on conductivity activation energy and structural properties of Si-doped β-Ga2O3 film grown by pulsed laser deposition

Si-doped β-Ga₂O₃ was generally activated by high-temperature annealing (over 600?°C) due to its strong bonding energy. Considering the electronic applications using β-Ga₂O₃ such as various power devices with low power consumption, it is strongly required to decrease the device process temperature including the impurity activation process. In this article, in order to decrease the impurity activation process temperature, we proposed the rapid thermal annealing (RTA) treatment to activate the Si atoms in the β-Ga₂O₃ films since RTA treatment can give the high thermal energy to specimen in a short time and investigated the influence of RTA treatment with various temperatures on conductivity activation energy, and structural properties of Si-doped β-Ga₂O₃ film. Si-doped β-Ga₂O₃ films were hetero-epitaxially grown on c-plane sapphire substrate by pulsed laser deposition method. Crystallinity, surface roughness, and electrical properties of specimens were investigated by changing the RTA temperatures. Crystallinity and surface roughness of Si-doped β-Ga₂O₃ films were not significantly influenced by RTA treatment at temperatures range of 100–700?°C. Conductivity activation energy of specimens with RTA treatment was about 50–100?meV and did not depend on RTA temperatures. As a result, even Si-doped β-Ga₂O₃ film with RTA treatment at 100?°C showed a relatively good conductivity. Based on the experimental results in this study, it can be said that RTA treatment is useful method to decrease the temperature of activation process for Si-doped β-Ga₂O₃ thin films without serious structural degradations.     

五彩湾煤和吐鲁番煤热解动力学模型评估与应用

煤热解是煤热加工利用的基础反应,热解动力学模型有助于预测煤在热解过程中挥发分脱除规律,当前文献中已报道了多种热解动力学模型,厘清不同热解模型参数选择的差异,评估不同模型对煤种及热解反应适应性可为热解工艺设计提供参考。采用¹³C NMR核磁共振测量了五彩湾煤和吐鲁番煤的碳化学结构,并使用热重法测量了不同加热速率下的两种低阶煤失重曲线,结合分段式单一速率扫描法、等转化率法和3段式高斯分布活化能模型（3-DAEM）分析热重实验数据。结果表明单一速率扫描法得出的动力学参数难以准确揭示热解反应机理;等转化率法可以较好地得出热解活化能及指前因子分布图;将等转化率方法获得的指前因子赋值给分布活化能模型,可以避免分布活化能模型指前因子选择的盲目性;3-DAEM模型仅需要一条TGA曲线便可获得适用于整个加热速率的动力学参数,其预测结果与实验数据吻合最好,且模拟得出的活化能分布图很好地反映了煤热解三个阶段特征。