THE LIMIT CYCLES AND HOPF BIFURCATION OF A CLASS OF SIMPLIFIED HOLLING TYPE-IV PREDATOR-PREY SYSTEM WITH LINEAR STATE FEEDBACK

In this paper, a class of simplified Type-IV predator-prey system with linear state feedback is investigated. We prove the boundedness of the positive solutions to this system, and analyze the quality of the equilibria and the existence of limit cycles of the system surrounding the positive equilibra. By Hopf bifurcation theory, the result of having two limit cycles to the system is obtained.     

Photocatalytic Free Radical-Controlled Synthesis of High-Performance Single-Atom Catalysts

Single-atom catalysts (SACs) have emerged as crucial players in catalysis research, prompting extensive investigation and application. The precise control of metal atom nucleation and growth has garnered significant attention. In this study, we present a straightforward approach for preparing SACs utilizing a photocatalytic radical control strategy. Notably, we demonstrate for the first time that radicals generated during the photochemical process effectively hinder the aggregation of individual atoms. By leveraging the cooperative anchoring of nitrogen atoms and crystal lattice oxygen on the support, we successfully stabilize the single atom. Our Pd₁/TiO₂ catalysts exhibit remarkable catalytic activity and stability in the Suzuki–Miyaura cross-coupling reaction, which was 43 times higher than Pd/C. Furthermore, we successfully depose Pd atoms onto various substrates, including TiO₂, CeO₂, and WO₃. The photocatalytic radical control strategy can be extended to other single-atom catalysts, such as Ir, Pt, Rh, and Ru, underscoring its broad applicability.     

CO2和pH光纤化学传感器研究进展

本文简述了CO2和pH光纤化学传感器的最新研究进展,重点介绍了用于环境监测的基于pH指示剂的CO2和pH传感器。     

AC发泡剂中一种助发泡剂的鉴定

目前国内外通过在AC发泡剂中添加各种促进剂进而获得改性AC的方法已成为一种趋势。添加何种改性剂无疑是研究改性AC的关键。因此定性分析AC中的改性剂,对改性AC的研发将有极大的帮助。文章应用由作者在Vibrational Spectroscopy上首次提出的薄层色谱显微傅里叶红外联用的方法,鉴定出某改性AC中一种罕见添加剂的官能团,结合元素分析及化学物性分析等,推测出此添加剂的结构。通过对推测物质碎裂机理的解释和未知添加剂质谱图的分析,进一部验证了该添加剂为所推测的物质。这种鉴定方法同样适用于AC中其他无标准图谱的改性剂分析。     

基于模拟退火的CRS算法

本文是对非线性规划问题提出的一种算法,该算法把模拟退火算法应用到CRS算法中,根据模拟退火算法每一次迭代都体现集中和扩散两个策略的平衡的特点,使CRS算法更能够搜索到全局最优解,而不会陷入局部最优解。最后把提出的算法应用到两个典型的函数优化问题中,结果表明,算法是可行的、有效的     

ZSM-5 zeolite single crystals with b-axis-aligned mesoporous channels as an efficient catalyst for conversion of bulky organic molecules

The relatively small and sole micropores in zeolite catalysts strongly influence the mass transfer and catalytic conversion of bulky molecules. We report here aluminosilicate zeolite ZSM-5 single crystals with b-axis-aligned mesopores, synthesized using a designed cationicamphiphilic copolymer as a mesoscale template. This sample exhibits excellent hydrothermal stability. The orientation of the mesopores was confirmed by scanning and transmission electron microscopy. More importantly, the b-axis-aligned mesoporous ZSM-5 shows much higher catalytic activities for bulky substrate conversion than conventional ZSM-5 and ZSM-5 with randomly oriented mesopores. The combination of good hydrothermal stability with high activities is important for design of novel zeolite catalysts. The b-axis-aligned mesoporous ZSM-5 reported here shows great potential for industrial applications.     

混合氧化物掺杂电致变色

本文论述采用混合氧化物掺杂的新方法,对电致变色层和离子导电层分别掺入氧化物和金属,使电致变色器件响应速度、增大着色透过率变化等方面的特性得到很大改善.最后给出实验结果.     

奇摄动非线性系统的角层和冲击层现象

研究一类具有转向点的二阶非线性系统的角层和冲击层现象,在适当的假设条件下,利用微分不等式方法证明了解的存在性,并得到了解的按分量的一致有效的渐近估计.     

层状结构簇合物FeNb_2Te_4和Fe_2Nb_2Te_4的穆斯堡尔谱和晶体结构研究

测定了FeNb_2Te_4和Fe_2Nb_2Te_4的穆斯堡尔谱和晶体结构。它们的穆斯堡尔谱都是一组对称的四极分裂双峰。实验数据用最小二乘法计算机程序拟合。经计算机拟合后的穆斯堡尔参数(在77K时)为:对于FeNb_2Te_4,δ=0.409±0.004 mm/s,△F_Q=0.633±0.004 mm/s,线宽r=0.372±0.004 mm/s;对于Fe_2Nb_2Te_4,δ=0.425±0.004mm/s,△E_Q=0.671±0.004mm/s,r=0.404±0.004 mm/s。化学位移δ值是相对于α-Fe的。由X衍射单晶结构测定得出,FeNb_2Te_4属正交晶系,空间群Pmmn,晶胞参数:a=1.2432(4)nm,b=0.3796(1)nm,c=0.7314(4)nm,V=0.3452(4)nm~3,Z=2。Fe_2Nb_2Te_4也是属正交晶系,空间群Pma2,晶胞参数:a=0.7955(1)nm,b=0.6258(1)nm,c=0.7202(2)nm,V=0.3585(3)nm~3,Z=2。从穆斯堡尔参数可确定这两个簇合物的Fe原子都属高自旋+3价,而且都处在晶格中的等价位置,这与单晶结构测定的结果相一致。     

非线性对称平板光波导TE模色散特性的近似计算

本文利用微扰法,导出了克尔型非线性对称平板光波导TE模传播常数的近似计算公式。结果表明,本文公式得到的结果与精确结果吻合得很好。