航空发动机进气总温传感器测温误差研究

航空发动机进口总温测量的准确性是优化发动机控制率、保障发动机飞行安全的关键因素之一。针对影响传感器测量准确性的响应时间、恢复系数，通过空气动力学和热力学理论，分析出具体的影响因素，设计了多种结构模型，并通过热风洞试验、FloEFD软件建模和热流体仿真，从材料及结构上系统地提出了优化途径和改善办法并进行了验证，尤其是分析了双余度传感器的响应一致性误差并提出改善方法。研究结果为同类传感器的设计提供了参考和借鉴。     

Microwave dielectric properties of SrLa[Ga1−x(Mg0.5Ti0.5)x]O4 and SrLa[Ga1−x(Zn0.5Ti0.5)x]O4 (x = 0.2-0.8) ceramics

SrLa[Ga_1−x(R_0.5Ti_0.5)_x]O₄ (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K₂NiF₄-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R_0.5Ti_0.5) and SrLaGaO₄ can form the unlimited solid solutions. With increasing x for R = Mg and Zn, ε_r increases monotonously, the Qf value first increases and then decreases, while τ_f increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: ε_r = 23.3, Qf = 89 400 GHz, τ_f = −0.8 ppm/°C for SrLa[Ga_0.6(Mg_0.5Ti_0.5)_0.4]O₄ and ε_r = 23.3, Qf = 76 200 GHz, τ_f = 0.2 ppm/°C for SrLa[Ga_0.7(Zn_0.5Ti_0.5)_0.3]O₄, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications.     

Sequence-Dependent Nanofiber Structures of Phenylalanine and Isoleucine Tripeptides

The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials.     

机械结构分层优化技术研究进展

复杂机械结构优化设计一般表现为多目标、多约束、多参数的优化问题,所以复杂结构优化设计过程通常存在计算复杂、不易收敛等困难。分层优化技术是复杂结构优化设计的一种有效途径,通过将优化问题中复杂的约束、设计变量以及功能目标合理分解为若干子层问题进行求解,然后通过协调得到复杂机械结构整体优化问题的结果。文章对机械结构分层优化技术的理论、应用研究现状进行了总结并探讨了其关键技术环节及发展趋势。     

TLCD基础隔震框架结构的减振控制研究

为了避免和减轻由过大隔震层位移引起的损害,对基础隔震框架结构装设调频液柱阻尼器(tuned liquid column damper,简称TLCD)后混合系统的减振效果进行研究。建立了单层和多层混合控制系统在地震作用下的运动方程,采用TLCD-结构体系转化为调频质量阻尼器(tuned mass damper,简称TMD)-结构体系的等效方法,利用TMD参数优化公式,得到单个TLCD初始设计参数,并采用状态空间方程得到多个TLCD最优设计参数。通过对某8层基础隔震结构进行模拟,证明了该理论设计方法的合理性。该混合结构不仅可以减小隔震层位移和加速度,而且对上部结构位移和加速度反应都能更有效的控制。     

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications.     

寒冷地区某既有办公建筑围护结构优化改造研究

既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。     

具有外套管的释热元件表面温度求解

为进行具有外套管的释热元件的性能分析，需准确计算元件包壳外侧的温度分布。由于套管结构内外均存在流体，传热情况较为复杂，因此本文基于传热基本方程和能量守恒关系，设计开发了专用的迭代算法和计算程序求解该结构温度分布，并采用典型算例，将计算结果与Fluent软件仿真结果进行对比。结果表明，本文程序计算结果与Fluent软件仿真结果的相对误差小于5%。基于本算法编写的程序模块与燃料元件性能分析程序相耦合，可提高燃料性能分析流程的独立性。     

Sensitivity of a solid Eu(III) complex towards acetonitrile vapor: Structural and spectroscopic characterization

The Eu(III) nitrate complex of the meso- N,N′-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine ligand was synthesized and characterized by single crystal and powder X-ray diffraction. The crystal lattice of the complex is capable of absorbing and desorbing selectively acetonitrile molecules, at 293 K upon an acetonitrile vapor pressure of ∼0.1 × 10⁵ Pa. This process, which is partially reversible, can be easily followed by both powder X-ray diffraction (P-XRD) and Eu(III) luminescence spectroscopy. The acetonitrile molecule, located in the outer coordination sphere of the metal ion, does not affect the radiative transition probability of ⁵D₀ level of Eu(III) and also it does not activate further non-radiative channels from this level. On the other hand, this molecule is capable of affecting the energy position and intensities of the crystal field components of the ⁵D₀→⁷F₂ transition. The complex in solid form can be considered a promising material for the optical sensing of acetonitrile vapors.     

热处理对挤压态Mg-6Gd-5Y-1Zn合金组织与性能的影响

通过对Mg-6Gd-5Y-1Zn(质量分数,%)合金在固溶和时效处理状态下显微组织和力学性能的研究发现,α-Mg基体、沿挤压方向分布的条状18R-LPSO相、少量的Mg₂₄(GdYZn)₅ 相以及细层片状的14H-LPSO相构成了挤压态合金的组成相。挤压态合金经固溶(T4)处理后,一部分18R-LPSO相溶入基体,并且基体中的14H-LPSO相伸长同时粗化。挤压态合金经过固溶加时效(T6)处理后,大量β′相从α-Mg基体中析出。T6态合金的室温力学性能最好,其屈服强度、抗拉强度及伸长率分别为272 MPa、406 MPa和6.1%。β′相沉淀也发生在挤压态合金的直接人工时效(T5)处理过程,但相比于T6处理,14H-LPSO相和β′相在基体中的体积分数均偏低。