船舶动力装置课程教学问题与改革研究

船舶动力装置是船舶的重要组成部分,船舶的性能很大程度由动力装置来保证。基于高校船舶动力装置课程教学改革中存在的问题及当前新工科对学生综合素质的要求,提出了改进教学的具体操作方法,以提高相关专业大学生专业基础理论水平,拓宽知识面,增强工程实践和解决工程问题的能力,为船舶行业的发展提供优秀人才。     

基于钢筋锈损截面面积的锈胀裂缝宽度计算模型

通过锈胀裂缝宽度预测混凝土结构中钢筋锈蚀程度是一种实用的非破损检测方法。然而,针对此问题的研究采用的方法不一、参数各异,所得的结论和所建立的计算模型之间也存在较大分歧。针对大量相关研究成果进行综合分析发现,锈胀裂缝的发展与局部区域内锈蚀产物的绝对生成量之间存在直接关系,锈胀裂缝宽度随着平均锈损截面面积的增大近似成线性增大,混凝土保护层厚度和钢筋直径对其无明显影响。通过锈蚀钢筋的三维扫描建立虚拟模型,建立区段最大截面锈蚀率与平均锈蚀率的转换关系。在此基础上综合已有自然锈蚀数据,建立了基于钢筋平均锈损截面面积的锈胀裂缝宽度计算公式,可对实际工程锈胀混凝土构件中的钢筋锈蚀程度给出合理估测。     

New vacancied and Dy3+-doped molybdates – Their structure,thermal stability,electrical and magnetic properties

Microcrystalline samples of new Cd_1–3xDy_2x⌷_xMoO₄ solid solution with limited homogeneity (0<x≤0.2222) and cationic vacancies (denoted as ⌷) were prepared by a high-temperature solid state reaction. The XRD data and SEM analysis showed that as-prepared ceramics crystallize in the tetragonal scheelite type symmetry (space group I4₁/a) with the crystallite size varying between ~2 and ~20 µm. A systematic change in lattice constants, a and c, as well as in lattice parameter ratio c/a with an increase of Dy content was observed. Dy-doped molybdates are paramagnets with the antiferromagnetic short-range interaction and spin-orbit coupling. Optical and electrical investigations proved Cd_1–3xDy_2x⌷_xMoO₄ solid solution to be in the insulating state of E_g>3 eV at room temperature and the thermally activated conduction of the Arrhenius-type above 350 K. Moreover, the I-V characteristics provided the evidence of symmetrical and non-linear behavior typical of charge carrier emission weakly induced by the temperature. Relative dielectric permittivity ε_r below 10 as well as loss tangent tanδ below 0.15 do not substantially depend both on the temperature in the range of 76–400 K and the frequency in the range of 5·10²–1·10⁶ Hz. These results are interpreted in the framework of the acceptor and donor vacancy centers.     

煤矿安全重在重塑煤炭行业管理体制

近几年我国矿难频发，有煤矿企业超能力生产、安全欠账多、人才匮乏、培训水平低和监管格局不当等原因。但其根本原因在于我国缺乏统一的煤炭行业管理机制。解决这一问题的根本途径在于重塑我国煤炭行业管理体制。     

Lattice dynamics and terahertz response of microwave dielectrics: A case study of Al-doped Ca0.6Sm0.27TiO3 ceramics

Low-loss microwave dielectric ceramics are of great significance for fifth-generation telecommunication (5G) devices used for higher frequencies, while reducing the dielectric loss in the microwave band is still a technical challenge. Lattice dynamics and terahertz response are closely related to the polarization of dielectrics, and can be used as effective methods to explore the loss mechanism of microwave dielectrics. Here, Al³⁺ was doped into the conventional high-permittivity (ε_r) Ca_1-xSm_2x/3TiO₃ (x = 0.4) ceramic system, enhancing the Q×f values significantly. Raman spectra, thermally stimulated depolarization currents (TSDC) and terahertz time-domain spectra (THz-TDS) together showed that the stiffness of cation vibration became stronger when z value was larger, indicating a smaller damping of the lattice vibration, and leading to lower extrinsic losses and higher Q×f values. The relationship between lattice dynamics, defect behavior and microwave dielectric loss will provide a significant reference for the development of low-loss microwave dielectric ceramics.     

助熔剂和密着剂对搪玻璃的作用机理及其研究进展

搪玻璃是一种在金属表面喷涂瓷釉(搪玻璃釉),经高温搪烧密着而成的复合材料,既具有玻璃的化学稳定性,又具有金属材料的硬度大、强度高等优良特性,同时表面光滑易清洗,因此在化工、医药等行业广泛应用。搪玻璃性能取决于搪玻璃釉的成分,搪玻璃釉包括基体剂、乳浊剂、助熔剂、密着剂等,其中助熔剂中含有低熔点物质,能够降低熔化温度,破坏搪玻璃釉连续的网络结构,形成新分子键,进而改良搪烧工艺;密着剂能够与金属基体发生化学反应,增强搪玻璃釉和金属基体的结合强度,进而提高力学性能。本文简要介绍了搪玻璃釉中的各类助剂,着重叙述了助熔剂和密着剂的组成及作用机理,为今后设计搪玻璃釉及提高搪玻璃设备性能提供了参考依据。     

Synthesis of 3D graphene/MnO2 nanocomposites with hierarchically porous structure for water purification

Journal of Porous Materials - In this work, a three-dimensional (3D) graphene/manganese dioxide nanocomposite (PGA/MnO2) with a hierarchically porous structure was prepared by facile steam...     

1',3-联吡咯-2-羧酸乙酯的合成

以异噁唑为原料,经碱性开环、亲核加成、成环脱羧、Clauson-Kaas四步反应合成了1',3-联吡咯-2-羧酸乙酯,其结构经1H-NMR确认。由于本方法中异噁唑碱性开环与加成两步反应实现一锅法,并对脱羧成环及Clauson-Kaas反应条件进行了优化,简化了工艺操作,降低了分离难度,提高了收率和产品纯度,适用于公斤级生产。     

One-pot synthesis of silver nanoparticle catalysts supported on N-doped ordered mesoporous carbon and application in the detection of nitrobenzene

Ag nanoparticles (Ag NPs) supported on nitrogen-doped ordered mesoporous carbon (N-OMC) were fabricated by one-pot synthesis strategy, in which 2D hexagonally ordered mesoporous SBA-15 and aniline were used as template and carbon precursor, respectively. Furthermore, the as-prepared composite of Ag NPs supported on N-OMC (Ag NPs/N-OMC) as electrochemical sensor towards the reduction of nitrobenzene (NB) was investigated, which displayed high sensitivity, fast response and good stability. The peak current of NB increased linearly with the concentration of NB in the range from 6.62 × 10⁻⁸ to 2.60 × 10⁻⁷ mol/L and 7.97 × 10⁻⁷ to 1.12 × 10⁻⁶ mol/L, and the low detection limit of 6.61 × 10⁻⁹ mol/L (S/N = 3) was obtained. Therefore, this work provides a new pathway to design and fabricate novel N-OMC composites, which have unique characteristics and hold numerous applications in the fields of sensors, electrocatalysis and others.     

超高效液相色谱-串联质谱法测定食用植物油中典型链格孢霉毒素

建立超高效液相色谱-串联质谱法测定食用植物油中典型链格孢霉毒素残留。正交试验确定最优提取条件为4 mL甲醇-乙腈溶液（1∶1,V/V）涡旋萃取10 s。选取Waters BEH C18(100 mm×2.1 mm,1.7μm)色谱柱,乙腈和1 mmol/L碳酸铵溶液为流动相,梯度洗脱,采用电喷雾离子源负离子多反应监测模式测定。细交链格孢菌酮酸在0.02～0.2 mg/L质量浓度范围内线性关系良好,链格孢酚、交链孢烯、腾毒素、交链格孢酚单甲醚4种毒素在0.002～0.2 mg/L质量浓度范围内线性关系良好,R2≥0.998。验证了5种毒素在葵花籽油和大豆油基质下方法准确性和精密度,在0.002～0.2 mg/kg添加量下,5种毒素的平均回收率为98%～118%,相对标准偏差为2.9%～17.4%,定量限为0.002～0.02 mg/kg。该方法能够满足食用植物油中典型链格孢霉毒素分析要求。