微型涡喷发动机燃烧室全覆盖气膜冷却

为了延长微型涡喷发动机燃烧室的使用寿命,针对燃烧室壁面高温区进行全覆盖气膜冷却研究. 在KJ-66微型涡喷发动机试车实验的基础上,比较实际燃烧工况下,排布方式和燃烧室外环的扩张孔对气膜冷却效果及燃烧室整体性能的影响. 结果表明,在实际微型涡喷发动机模型中,顺排的平均综合冷却效率低于叉排,但对壁面的综合降温效果优于叉排. 随着扩张孔出口直径的增大,气膜冷却效果逐渐改善,但会影响燃烧室出口温度分布的均匀性. 由于燃烧室后排冷却孔的影响,二次流射入主流会发生偏转,提升了气膜的冷却效果. 整体而言,全覆盖气膜冷却在实际燃烧工况下对燃烧室壁面有着很好的冷却作用,扩张型气膜孔能够有效改善燃烧室外环的气膜冷却效果.     

Pathways to eliminate carbon emissions via renewable energy investments at higher education institutions

Higher education institutions are among the many public and private sector entities that have committed to long-term sustainability goals in response to the threat of climate change. A key challenge for these institutions is establishing a commitment to make targeted investments in renewable energy technologies in support of emissions reduction goals. Such strategies require a vision to simultaneously coordinate strategic investments in renewable energy technologies with tactical operational decisions to achieve the desired benefits. In this paper, we formulate and solve a least-cost renewable energy capacity investment planning model to determine pathways to achieve emissions reduction strategies. Specifically, we apply our model to Rutgers University to evaluate its target of 100 % carbon neutrality. Using these insights, we share recommendations on how these strategies can be executed. This research serves as a springboard for administrators to assess and deploy their emissions reduction strategies, while ensuring system and financial constraints are satisfied.     

The high temperature phase transitions of orthorhombic La0.95MnO3

The high temperature phase transitions of orthorhombic La_0.95MnO₃ from room temperature to 1273 K were studied using high temperature XRD technique in air. Two-phase transitions were found in temperature ranges, 373–473 K and 973–1273 K, respectively. The crystal symmetry increases from orthorhombic to rhombohedral then cubic, while the second transition was not completed in the observation of the present study. The first transition could be due to the depression of Jahn–Teller distortion, while the second one could be caused by the ionic oscillation at high temperature. The lattice thermal expansion coefficients of rhombohedral La_0.95MnO₃ from 473 to 973 K were also calculated using lattice parameters.     

变薄拉伸工艺中凹模锥角的计算机模拟优化

在分析了变薄拉伸工艺应力性质的基础上 ,应用有限元模拟软件定量地分析了凹模锥角对拉伸工艺的影响 ,并给出了凹模锥角的合理范围 ,从而为优化模具设计 ,合理制定工艺提供了可靠的参考依据     

石墨化率不同的自焙炭块的热膨胀

采用精密垂直拉杆膨胀仪在１４～１０００℃范围内测量了具有不同石墨化率的自焙炭块的相对热伸长量，并由此获得了热线膨胀系数α。结果表明：石墨化率一定时，α值在较低温度下随温度升高而增加，在较高温度下，α值随温度变化不明显；恒温时，石墨化率越高，α值越低。讨论了单位热应力下的弹性模量概念     

First-principles calculation of phase equilibria and phase separation of the Fe-Ni alloy system

Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calculations have proved the stabilization of the LIE phase at 1：3 stoichiometry, which is in agreement with the experimental result, and predicted the existence of L1 0 as a stable phase below 550 K; this L1 0 phase has been missing in the conventional phase diagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L1 0 and L12Eorder-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion （CTE） is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye-Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed.     

中频炉酸性炉衬使用寿命的探讨

通过对炉衬材料的选择,作用机理及影响石英砂炉衬材料寿命的相关因素的阐述,说明了SD-T-A石英砂干振料可提高中频炉酸性炉衬使用寿命的原因.     

20CrNiMo牙轮牙爪锻造缺陷对力学性能的影响

KX-250三牙轮钻头上的牙轮牙爪可选用20CrNiMo钢锻造,但20CrNiMo牙轮牙爪在锻造过程中产生的缺陷严重影响产品的力学性能.为此对20CrNiMo牙轮牙爪进行质量跟踪,并对试样进行了力学性能的测试.结果表明：当锻造产生了白点和过热缺陷时,牙轮牙爪的力学性能明显下降,尤其是塑性指标和冲击韧度降低明显.为了防止这些缺陷的产生,还提出了一些对策,以提高牙轮牙爪的力学性能.     

高校扩招背景下大学生心理问题易发事件及其相关因素研究

本研究用高校学生心理问题调查问卷对 16 2 4名大学生进行调查 ,并用SCL - 90量表对其中 5 80名学生进行测评 ,同时测量学生的特质性应对方式 ,探讨高校扩招背景下大学生的心理问题易发事件及相关因素。扩招后大学生自感压力最大的心理问题易发事件是感到竞争激烈、择业困难、考试不过关等 ;大部分易发事件都和SCL - 90总分及各因子分存在着极显著相关 ;应对方式和易发事件及SCL - 90总分、各因子分存在着极显著的相关。扩招后和竞争、就业、学业相关的心理问题易发事件已成为影响大学生心理健康的首要因素     

镁渣膨胀性机理试验研究

通过镁渣形成过程、组成、粉化、颗粒分析和安定性试验,研究了镁渣产生体积膨胀性和膨胀滞后性的机理,提出了减轻或消除其膨胀性和膨胀滞后性危害的方法和措施,为镁渣在建筑、交通、水利等工程领域中的应用提供理论依据和指导。