GaN HEMT栅驱动技术研究进展

GaNHEMT器件由于其击穿场强高、导通电阻低等优越的性能,在高效、高频功率转换领域中有着广泛的应用前景.栅驱动芯片对于GaN HEMT器件应用起着至关重要的作用.介绍了GaN HEMT器件特性和驱动要求,对其栅驱动芯片的典型架构和每种芯片架构各自的关键实现技术研究现状进行了综述.同时介绍了GaN基单片集成功率IC的发...     

带标志位的均匀性特征检测SIFT配准算法研究

针对尺度不变特征SIFT配准算法中检测到的特征点不具有均匀分布的特性,实现了均匀性特征检测方法,同时对像素点设置标志位对检测步长进行动态调整。均匀性特征检测方法能够检测到更有效、更具有代表性的特征点,从而得到更加精确的图像变换关系;设置标志位对动态步长进行调整,可以进一步减少检测的次数。将带标志位的均匀性特征检测SIFT算法应用于图像的配准,实验表明改进算法的性能得到了有效提高。     

Recent advances in acid-resistant zeolite T membranes for dehydration of organics

Zeolite membranes offer outstanding potentials in separation of many molecular mixtures due to their molecular sieving selectivity and the high thermal and mechanical stability that allow them to operate at harsh conditions.Development of durable and high separation performance membranes with lower fabrication and operation cost are highly demanded for industrial applications. Zeolite T membrane possesses good acid-resistance with excellent hydrophilic properties as compared to NaA zeolite membrane and can be extended to industrial organic dehydrations under an acidic environment. In the present review the research advances in development of zeolite T membranes for the dehydration of organic mixtures in acidic conditions are summarized. Especially the low temperature synthesis, and epitaxial growth of the zeolite membrane with high performance are well addressed, besides emphasis is particularly placed on ensemble synthesis of hollow fiber zeolite T membrane module and its future prospects for industrial separations.     

Imidazolate-bridged dinuclear copper(II) complex with new macrocyclic ligand bearing two 1H-imidazol-4-yl-pendants

A new imidazolate-bridged dicopper complex [Cu₂(L)(Im)](ClO₄)₃·H₂O has been synthesized by reaction of new macrocyclic ligand 6, 20-bis(1H-imidazol-4-ylmethyl)-3, 6, 9, 17, 20, 23-hexaazatricyclo[24.3.1.1^11,15]hentriaconta-1(29), 11, 13, 15(31), 26(30), 27-hexaene (L) with Cu(ClO₄)_2?6H₂O and imidazole, and structurally characterized as a model compound of Cu₂Zn₂-SOD. There is antiferromagnetic interaction with g = 2.08, ? 2 J = 66.5 cm^? 1 between the two imidazolate-bridged Cu(II) atoms. The complex displays moderate SOD activity with IC₅₀ of 1.42 μM.     

Synthesis,Crystal Structure and Luminescence Property of a New (6,3)-Connected Zn(II) Coordination Polymer

The 2D coordination polymer, [Zn(dpa)(bpp)] _n (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, bpp = 1,3-di(4-pyridyl)propane) was prepared by hydrothermal synthesis in the presence of NaOH and characterized by single-crystal X-ray diffraction, FTIR spectra, element analysis and thermal analysis. The crystal structure determination reveals that the carboxylate groups of 2,4′-biphenyldicarboxylic acid are acting as bridging ligands and adopt two coordination modes; bis-monodentate and bidentate chelating. The network consists of a 2D (6,3)-connected architecture. At room temperature the solid-state luminescence spectrum of [Zn(dpa)(bpp)] _n shows a blue emission at about 354 nm upon excitation at 333 nm.     

The large electro-strain in BNKT-BST-100xTa lead-free ceramics

0.94Bi_0.5(Na_0.78K_0.22)_0.5Ti_1-xTa_xO₃-0.06Ba_0.95Sr_0.05TiO₃ (BNKT-BST-100xTa, for x = 0,0.005, 0.010, 0.015, 0.020 and 0.025) lead-free ceramics were fabricated by the solid-state reaction technique. Microstructure, dielectric, ferroelectric and fatigue performances of BNKT-BST-100xTa ceramics had been systemically studied. The XRD patterns confirmed that Ta⁵⁺ ions had completely dissolved into the lattice of BNKT-BST-100xTa ceramics. Meanwhile, the temperature of R3c-PNRs (T_s) was found to shift towards room temperature in dielectric permittivity curves with the introduction of Ta⁵⁺ ions. In addition, the highest unipolar strain of 0.32% with the corresponding normalized strain of 458 pm/V was obtained for x = 0.020 under the applied electric field of 70 kV/cm. The large electro-strain was cause by intrinsic effect of the crystal and the external electric field. Moreover, the excellent strain fatigue resistance indicated the prepared ceramics are promising candidates for actuators and stress sensors.     

热镀锌机组沉没辊系受力模型及影响因素

热镀锌机组沉没辊系在锌锅内工作状态下受力情况复杂,受外界影响较大。充分考虑热镀锌机组设备与其工艺特点,首先分析沉没辊系在工作状态下受力情况,分别建立矫正辊插入量与包角的关系式、基于辊面锌渣沉积厚度的辊面摩擦因数经验模型。随后采用条元离散法建立沉没辊系辊面接触压力、摩擦驱动力矩模型,基于简支梁模型确定沉没辊系轴端支撑力、轴端摩擦阻力矩模型。最后将沉没辊系受力模型应用于国内某热镀锌机组镀锌工艺段,以典型规格带钢确定沉没辊系受力影响因素,并依据机组实际工况及板形要求来确定生产工艺参数的5种不同水平,来分析其对辊系受力状态的影响规律,为沉没辊系工艺优化提供指导依据。结果表明,4种工艺参数对辊系接触压力及摩擦力矩影响都存在差异性,矫正辊插入量与辊面接触压力呈现非线性关系;带钢张力对各辊接触压力影响程度不同,其中沉没辊受到的影响最大,而其余两辊受到张力几乎不影响;辊面平均摩擦因数、带钢速度对辊的接触压力几乎不影响;辊系摩擦驱动力矩、轴端摩擦阻力矩随着矫正辊插入量及辊面平均摩擦因数增大都呈现出不同程度增大。带钢张力与沉没辊摩擦驱动力矩、轴端摩擦阻力矩呈线性变化关系,而带钢张力对其余两辊影响很小。带钢...     

二维非线性光子晶体点缺陷的双稳态特性

采用时域有限差分技术分析了非线性光子晶体点缺陷的双稳态特性,选择一定频率失谐的连续波入射并观察透射现象.分析发现,当连续波功率增加到阈值点时透射率达到最大值.采用大功率脉冲辅助连续波的方式发现点缺陷的透射率一直处于高透射状态,直至连续波功率下降到很低时,透射率才迅速下降.双稳态特性由频率失谐δ、缺陷谐振频率ω0及非线性系数n2等3个参数决定.采用空间电磁场的摄动理论验证所得结果与数值模拟结果一致.     

A novel ((Bi0.5Na0.5)0.94Ba0.06)1-x (K0.5Nd0.5)xTiO3 lead-free relaxor ferroelectric ceramic with large electrostrains at wide temperature ranges

Novel ((Bi_0.5Na_0.5)_0.94Ba_0.06)_1-x(K_0.5Nd_0.5)_xTiO₃(x = 0.0, 0.02, 0.04, 0.06) lead-free ceramics (BNBT–xKN) were prepared by the solid-state reaction method. The effects of A-site (K_0.5Nd_0.5)²⁺ complex-ion substitution on their phase structure, dielectric, piezoelectric, and electromechanical properties were studied. The X-ray diffraction results indicate that all compositions are located in the morphotropic phase boundary (MPB) region where the tetragonal phase coexists with the rhombohedral phase. In addition, as the KN content increases, the ferroelectric order transform to relaxor order, which is characterized by a degeneration of maximum polarization, remnant polarization and correspondingly adjusts the ferroelectric-relaxor transformation temperature (T_F-R) to room temperature. Interestingly, the disruption of ferroelectric phase caused a significant improvement of strains. A maximum strain of ~ 0.52% corresponding to normalized strain of ~ 612 pm/V appeared at 85 kv/cm for the x = 0.04 composition. Particularly, the composition of x = 0.04 exhibited high electrostrains of temperature insensitivity, which remained above 0.4% and kept within 10% from ambient temperature up to 110 °C. It can be ascribed to the coexistence of non-ergodic and ergodic states in the relaxor region. As a result, the systematic investigations on the BNBT–xKN ceramics can benefit the developments of temperature-insensitive “on-off” actuators.     

一种基于双边假设检验的Contourlet域乘性水印盲检测算法

为解决Contourlet变换域中乘性水印的检测问题,根据广义高斯分布描述图像Contourlet变换高频方向子带系数的统计分布特征,在服从广义高斯分布的系数中,将水印的检测问题转化为了具有未知参数的确定性伪随机序列的检测问题,利用双边假设检验推导出了适用于Contourlet域乘性水印的盲检测器。实验表明,该盲检测器的判决准,对任何嵌入强度均有效,并且可以自适应地确定检测阈值。