循环流化床富氧气化实验研究

在循环流化床富氧气化实验台上,通过调节水蒸气流量使气化温度基本稳定在910℃,研究了不同氧气浓度及气化当量比对煤气组分、产气率、冷煤气效率及碳转化率的影响。结果表明,氧气浓度从25%增加至40%时,N2体积分数从48.82%降低至33.83%,H2从21.47%不断增加至27.59%,CH4基本不变;受水蒸气流量影响,氧气浓度高于35%时,CO体积分数降低,CO2体积分数增加;氧气浓度40%时的煤气热值为空气气化煤气热值的1.84倍,产气率随氧气浓度增加从2.35 m3/kg降至2.13 m3/kg,冷煤气效率和碳转化率不断增大;当气化当量比从0.20增加至0.29时,N2体积分数先降低后升高,H2体积分数从24.01%增加到25.46%后基本保持不变,CO和CH4持续减小,CO2不断增加,产气率由1.94 m3/kg升高到2.29 m3/kg;受水蒸气和气化当量比综合影响,冷煤气效率先增大后减小,碳转化率持续增加。     

“四模块”嵌入下的混合式教学设计与实践*——以功能材料专业物理化学基础课程为例

为建设适应新时代要求,突出高阶性、创新性、挑战度的一流本科课程,实现价值引领、能力培养和知识传授的教育教学目标,结合功能材料专业的特点和民族高等院校学生的学情,构建了物理化学基础课程的“四模块、三阶段、两时空、双平台”的混合式教学新模式,重塑了“价值引领模块、基础理论模块、多学科融合模块和虚拟仿真实验模块”的“四模块”内容体系。通过“四模块”嵌入下的混合式教学实践研究,结合学生的课前、课中、课后等学习成绩,多维度评价学习效果,并藉由调查问卷来分析学生对混合式教学的评价,最终研究结果表明学生的个性化自主学习能力有了显著提高、学生运用物理化学理论解决复杂问题的综合能力得到了提升,学生经过刻苦学习获得了素质提高的成就感。     

Reception pattern influence on magnetoacoustic tomography with magnetic induction

Based on the acoustic radiation theory of a dipole source,the influence of the transducer reception pattern is studied for magnetoacoustic tomography with magnetic induction(MAT-MI).Numerical studies are conducted to simulate acoustic pressures,waveforms,and reconstructed images with unidirectional,omnidirectional,and strong directional transducers.With the analyses of equivalent and projection sources,the influences of the model dimension and the layer effect are qualitatively analyzed to evaluate the performance of MAT-MI.Three-dimensional simulation studies show that the strong directional transducer with a large radius can reduce the influences of equivalent sources,projection sources,and the layer effect effectively,resulting in enhanced pressure and improved image contrast,which is beneficial for boundary pressure extraction in conductivity reconstruction.The reconstructed conductivity contrast images present the conductivity boundaries as stripes with different contrasts and polarities,representing the values and directions of the conductivity changes of the scanned layer.The favorable results provide solid evidence for transducer selection and suggest potential practical applications of MAT-MI in biomedical imaging.     

Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation

The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min⁻¹, which is two orders of magnitude faster than the α and β phases.     

Anisotropic Poisson Effect and Deformation-Induced Fluorescence Change of Elastic 9,10-Dibromoanthracene Single Crystals

Elastic organic crystals have attracted considerable attention as next-generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10-dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c-axes) of the crystal are contracted upon elongation along the long axis (a-axis). Moreover, we found that the Poisson's ratios along the b-axis and c-axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c-axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.     

Anisotropic Poisson Effect and Deformation‐Induced Fluorescence Change of Elastic 9,10‐Dibromoanthracene Single Crystals

Elastic organic crystals have attracted considerable attention as next‐generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10‐dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c‐axes) of the crystal are contracted upon elongation along the long axis (a‐axis). Moreover, we found that the Poisson's ratios along the b‐axis and c‐axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c‐axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.     

阻尼对空爆荷载等效静载动力系数的影响

为考查阻尼参数对空爆荷载等效静载动力系数的影响,理论推导了空爆荷载下结构等效单自由体系弹塑性位移解及延性比解,设计并计算了阻尼比0.000 1～0.1、延性比1～4的20种典型工况的动力系数,并与现行抗爆设计规范动力系数公式结果进行了对比。结果表明:阻尼比小于0.000 1时可基本代表无阻尼状态,阻尼比0.01的动力系数比无阻尼的最大降低幅度为2.08%,数值差异很小,因此阻尼比为0.01以内时,可忽略阻尼对动力系数的影响;阻尼比0.05的动力系数比无阻尼的降低幅度约9.92%,数值差异较大,认为阻尼比0.05以上时将具有明显的经济效益;现行设计规范动力系数更适用于柔性结构体系,运用于刚性结构抗爆设计时,计算误差较大,对阻尼比较小的结构设计更不利。     

Chain elastic modulus of polyethylene: A spectroscopically determined force field (SDFF) study

Our SDFF for linear saturated hydrocarbon chains has been used to calculate the chain modulus of isolated and crystalline chains of n-alkanes of varying lengths. This has been done for static deformations and for the dynamic deformation in the longitudinal acoustic mode (LAM). Extrapolation to infinite chain length gives a common value of the room-temperature crystal modulus of 303 GPa (also obtained in an infinite chain calculation). Experimental Raman LAM measurements, corrected for chain-end interactions, give a modulus of 305 GPa, in excellent agreement. Problems with the experimental values obtained by inelastic neutron scattering and x-ray diffraction are discussed. © 1996 John Wiley & Sons, Inc.     

MSC折纸结构设计及其双稳态解析与实验

折纸是一门古老艺术,其本质是将平面材料沿着事先设计好的折痕进行折叠,进而形成一个复杂的三维结构．柔性折纸结构是实现三维结构轻量化的重要途径．因此,解析折纸结构几何特性和力学性质十分必要．本文以MSC(Magic Spiral Cube)为研究对象,通过实际折痕和虚拟折痕的方法,建立了该结构的几何模型,确定了实现完全展开和完全折叠对刚性面和可变形面的设计条件,在虚拟折痕上引入了扭转刚度,证明了该扭转刚度与柔性面变形的等效性,从而得到了MSC 折纸结构的弹性势能,得到了使结构变形的力与位移本构．通过力学特性分析,发现了MSC折纸结构具有双稳态特性,这种特性是由面内变形诱发的,与虚拟折痕刚度与弹性折痕刚度的比值有直接的关系．最后,我们对MSC折纸结构进行设计和制备,通过实验,验证了理论 模型的准确性．本文的研究结果不仅进一步加深了我们对于MSC折纸结构力学特性的认识,同时也为其工程应用提供理论基础．