Weighted Self-Adaptive Threshold Wavelets for Interpolation Point Selection Used in Interconnect MOR

超高膨胀比涡轮噪声控制技术研究

赵辛午，黄洪雁

（哈尔滨工业大学 能源科学与工程学院，哈尔滨 150001）

中文说明：

气动噪声控制是提高鱼雷隐身性能的关键技术之一。本文讨论了局部进气的超高膨胀比涡轮气动噪声产生机理。相邻喷嘴与流道之间形成的三角形非出气区域引起的尾迹、圆周局部进气设计引起的不稳定性、喷嘴和转子之间区域形成的复杂激波系是这类涡轮气动噪声产生的三种主要来源。因此，本文提出了两种气动噪声控制方法，增加转静子之间的轴向间距，喷嘴下俯、双侧修型和尾缘吹气。数值模拟结果表明：在对原涡轮气动性能影响不大的情况下，优化后涡轮的气动噪声下降10 dB以上。

关键词：超高膨胀比涡轮、气动噪声、流动特性、优化

     

Microfluidic Tumor-on-a-Chip Model to Study Tumor Metabolic Vulnerability

Tumor-specific metabolic adaptations offer an interesting therapeutic opportunity to selectively destroy cancer cells. However, solid tumors also present gradients of nutrients and waste products across the tumor mass, forcing tumor cells to adapt their metabolism depending on nutrient availability in the surrounding microenvironment. Thus, solid tumors display a heterogenous metabolic phenotype across the tumor mass, which complicates the design of effective therapies that target all the tumor populations present. In this work, we used a microfluidic device to study tumor metabolic vulnerability to several metabolic inhibitors. The microdevice included a central chamber to culture tumor cells in a three-dimensional (3D) matrix, and a lumen in one of the chamber flanks. This design created an asymmetric nutrient distribution across the central chamber, generating gradients of cell viability. The results revealed that tumor cells located in a nutrient-enriched environment showed low to no sensitivity to metabolic inhibitors targeting glycolysis, fatty acid oxidation, or oxidative phosphorylation. Conversely, when cell density inside of the model was increased, compromising nutrient supply, the addition of these metabolic inhibitors disrupted cellular redox balance and led to tumor cell death.     

Comparison of throttle devices to measure two-phase flowrates of wet gas with extremely-low liquid loading

The online measurement of wet gas with extremely-low liquid loading (Lockhart-Martinelli parameter lower than 0.02) remains a challenge. In this study, three types of throttle devices, Venturi, orifice plate and cone, are compared experimentally with air-water two-phase flow in a horizontal pipe of inner diameter of 50 mm. High-precision correlations are established to measure the gas and liquid flowrates via a single throttle device. Results show that the two-phase mass flow coefficient (K) of the three throttle devices all increase linearly with the liquid densiometric Froude number and the K correlations are established respectively to correct the gas mass flowrate deviation. The pressure loss ratio (δ) for Venturi is sensitive and monotonous to the liquid loading, which contributes to the high accuracy of liquid flowrate measurement. By incorporating the K correlations, both the gas and liquid mass flowrates can be predicted precisely. The relative error of the gas mass flowrate predicted by the Venturi is within ±2.0% at 95% confidence level, and that of the liquid mass flowrate is within ±15% at 90% confidence level.     

一种X射线数字成像检测缺陷尺寸的测量方法

提出了一种X射线数字成像检测缺陷尺寸的测量方法。借鉴半波高法,以半波高法下的尺寸测量误差为基准,对不同缝隙尺寸试样在相同的检测条件下进行X射线数字成像检测,计算该检测条件下的总不清晰度,总结出缺陷尺寸与总不清晰度比值同波高比例的关系,并通过试验进行了验证。结果表明,该方法简单、实用性强,可为实现缺陷尺寸的准确测量提供技术支持。     

TA18钛合金管材织构对环向拉伸性能的影响

利用织构增强原理,开发出了TA18(Ti-3Al-2.5V)钛合金860 MPa级高强度管材,保证了管材的工艺性能,同时又具有优异的力学服役性能。标准规定反映径向织构的管材收缩应变比(CSR)大于1.3,但对上限值未作规定。本研究设计出小管径的环向拉伸夹具,测试了不同CSR管材的环向拉伸力学性能,分析织构对环向抗拉强度的影响,发现存在一个最有利的CSR值为1.75,大于或小于该CSR值时都会导致管材环向屈服强度下降。进一步测定了对应管材的极图和ODF图,从微观结构上可以解释这一规律和本质。环向抗拉强度下降会引起液压系统工作时疲劳强度降低,CSR值的上限在工艺设计时应当加以控制。本研究对发展安全可靠的航空液压系统具有十分重要的理论意义和工程应用价值。     

Poisson’s ratio of porous and cellular materials with randomly distributed isometric pores or cells

The porosity dependence of Poisson's ratio of materials with random microstructure is investigated via analytical and numerical modeling. It is shown that all analytical models predict porosity independence if the solid Poisson ratio is 0.2 and for low porosities a converging trend toward this value with increasing porosity. From all theory-based relations, only power-law and exponential relations allow for auxetic behavior. Numerical calculations on computer-generated digital microstructures (overlapping and isolated spherical pores, pores between overlapping spherical grains, wall-based cellular materials/closed-cell foams, and strut-based cellular materials/open-cell foams) confirm the general qualitative trends of the analytical models, although a closer look reveals significant quantitative differences. Cellular materials and foams exhibit similar features as porous materials in general, but lack their converging trend toward values around 0.2. Comparison of our results with the classical Roberts-Garboczi results shows good agreement, with subtle differences due to the different microstructures generated.     

Oxidative Stability of Chia (Salvia hispanica L.) and Sesame (Sesamum indicum L.) Oil Blends

Chia and sesame oils are important sources of essential fatty acids; however, their ω-3:ω-6 proportions do not comply with nutritional recommendation. A feasible approach to improve the ratio is to blend different oils, but only after understanding physical and chemical changes of the new matrix. Objective of the investigation was to determine the physico-chemical characteristics and the oxidative stability index (OSI), using the Rancimat method, of chia-sesame oil blends. The four ω-3:ω-6 blends tested (1:4, 1:6, 1:8, and 1:10) were exposed to temperatures of 110, 120, and 130 °C. The OSI values of the mixtures varied between 6.24–8.08, 3.07–4.00, and 1.62–2.01 hours for each temperature, respectively. In addition, their mean activation energy, enthalpy, entropy, and Q₁₀ were 88.4 kJ/mol, 85.2 kJ/mol, −41.1 J/mol K, and 2.0. Finally, a shelf life prediction performed at 25 °C indicated stability times between 80 and 123 days. Therefore, combining chia and sesame oils produced blends with a good balance of essential fatty acids.     

基于旋滚比的电主轴轴承预紧力优化研究

为研究不同工况下轴承预紧力对电主轴轴承动力学的影响规律，基于外轨道控制理论,建立了一种以旋滚比可优化的轴承预紧力动力学模型。通过分析高速状态下滚动体载荷和特征参数动态变化过程，构建综合考虑滚动体滚动、自旋转、陀螺运动和离心力的轴承动力学分析模型，在此基础上，计算旋滚比动态变化结果；研究Jones发现的阈值与旋滚比之间的动态定量映射关系；以轴承滚动体打滑状态为优化目标，使用MATLAB仿真分析不同工况下轴承最佳预紧力。建模分析表明，轴承旋滚比大小可以反映轴承预紧效果，也可实现轴承预紧力动态定量优化。     

双馈风机经VSC-HVDC接入弱受端系统运行特性分析

基于电压源换流器的高压直流输电(VSC-HVDC)是远距离风电并网的理想方案,同时可用于联接弱受端系统,但双馈风机经VSC-HVDC能够馈入多弱的受端系统仍待深入研究,有必要提出基于短路比的指标来衡量所能接入的受端系统。对此,基于定功率控制下VSC的稳定运行约束,分析系统稳态的临界运行点,总结出临界短路比的求解步骤。在此基础上,结合双馈风机的控制方程,详细讨论了风电场出力、弱交流系统等效阻抗和临界短路比的关系。仿真分析发现,受双馈风机无功特性的影响,接入受端系统的临界短路比未能达到理论值,引入基于无功补偿的有效短路比作为受端系统的强弱判断指标,使得所提临界短路比求解方法在此工况下依然成立。     

温度对膏体充填料浆流变特性影响试验研究

为了探究膏体的流变特性,取某尾砂制备不同质量浓度、灰砂比的尾砂料浆,采用Brookfield R/S+型流变仪和TC-550型制冷/加热式循环浴温度控制设备进行了膏体流变特性测试。结果表明,膏体料浆屈服应力和黏度随温度的变化与灰砂比和浓度有关。当灰砂比一定时,低浓度料浆屈服应力随温度增加不断减小,高浓度料浆屈服应力随温度升高先增加后减小; 当料浆浓度一定时,随着水泥比例增加,屈服应力随温度升高从不断减小到先增加后减小,且水泥比例越大,使屈服应力开始减小的温度越高。黏度变化情况与屈服应力类似。