变截面涡旋盘高速铣削仿真加工与实验研究

为减小变截面涡旋盘涡旋齿的变形,提高加工精度,需确定合理的铣削参数。开展了变截面涡旋盘高速铣削仿真与实验研究以确定铣削参数的合理取值范围;选用HT250变截面涡旋盘为研究对象,研究了更接近实际的材料本构模型、刀-屑摩擦模型和热传导控制方程等关键技术;建立了变截面涡旋盘几何模型和简化后的二维铣削模型,利用ABAQUS软件仿真切屑成形过程及不同的铣削参数对铣削力、铣削热影响的变化曲线;通过多因素正交实验加工变截面涡旋盘。结果表明:当主轴转速为3500 r/min、每齿进给量为0.1 mm以及切削深度为2.5 mm时进行铣削更加合理。铣削变截面涡旋盘的研究为加工参数的选择提供了依据和参考;依据实验后所得的铣削参数进行铣削可减小铣削力、铣削温度及齿变形,提高了变截面涡旋盘的加工效率和质量。     

Measurements of thermal-neutron capture cross-section of Cesium-135 by applying mass spectrometry

ABSTRACT

The thermal-neutron capture cross-section (σ₀) and resonance integral (I₀) were measured for the ¹³⁵Cs(n,γ)¹³⁶Cs reaction by an activation method and mass spectrometry. Because of difficulty in the preparation of pure ¹³⁵Cs samples, we used ¹³⁵Cs contained as an impurity in a normally available ¹³⁷Cs standard solution. An isotope ratio of ¹³⁵Cs and ¹³⁷Cs in a standard ¹³⁷Cs solution was measured by mass spectrometry to quantify ¹³⁵Cs. Cesium-135 impurity along with the ¹³⁷Cs standard solution was irradiated at the hydraulic conveyer of the research reactor in the Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott’s indices at an irradiation position. A gadolinium filter was used to measure the σ₀, and a value of 0.133 eV was taken as the cut-off energy. Gamma-ray spectroscopy was used to measure induced activities of ¹³⁷Cs, ¹³⁶Cs and monitor wires. On the basis of Westcott’s convention, the σ₀ and I₀ values were derived as 8.57 ± 0.25 barn, and 45.3 ± 3.2 barn, respectively. The value of σ₀ obtained in the present study agreed within the limits of uncertainties with the past-reported value of 8.3 ± 0.3 barn.     

Ion mobility mass spectrometry in the omics era: Challenges and opportunities for metabolomics and lipidomics

Researchers worldwide are taking advantage of novel, commercially available, technologies, such as ion mobility mass spectrometry (IM-MS), for metabolomics and lipidomics applications in a variety of fields including life, biomedical, and food sciences. IM-MS provides three main technical advantages over traditional LC-MS workflows. Firstly, in addition to mass, IM-MS allows collision cross-section values to be measured for metabolites and lipids, a physicochemical identifier related to the chemical shape of an analyte that increases the confidence of identification. Second, IM-MS increases peak capacity and the signal-to-noise, improving fingerprinting as well as quantification, and better defining the spatial localization of metabolites and lipids in biological and food samples. Third, IM-MS can be coupled with various fragmentation modes, adding new tools to improve structural characterization and molecular annotation. Here, we review the state-of-the-art in IM-MS technologies and approaches utilized to support metabolomics and lipidomics applications and we assess the challenges and opportunities in this growing field.     

三角形微通道饱和沸腾传热系数的预测

基于以丙酮为工质的三角形截面微通道饱和沸腾传热的实验数据,通过最小二乘法对实验数据进行参数拟合,得到一组新的经验参数,结合Thome提出的预测圆形截面微通道饱和沸腾传热系数的三区模型,对微通道饱和沸腾的传热系数进行了预测。结果表明:该三区模型可以较好地预测出传热系数随着干度的变化趋势,并得到90.04%的实验值和预测值误差在30%之内,吻合度较好。     

浮法玻璃切裁横断面白碴的解决

针对玻璃横切出现白碴缺陷情况,分析其产生的原因,并提出有效的解决办法。     

综采大断面切眼一次成巷技术研究

为了解决潘三矿1642（1）大断面切眼的支护及施工技术难题,实现工作面的快速接替,分析了大断面切眼的支护原理,提出了锚网索、T3钢带和单体液压支柱配合工字钢挑梁的联合支护方式。同时根据一次成巷与二次成巷的优缺点对比,最终确定采用分次交替掘进、一次成巷的施工方案并取得了良好的社会经济效益,为类似条件下大断面切眼巷道的施工提供了很好的借鉴和参考。     

巷道截面变窄瓦斯爆炸传播特性的数值模拟

为获得井下巷道截面变窄对瓦斯爆炸传播特性的影响,利用Fluent流体力学软件建立相应的数值模型,对井下截面变窄的巷道瓦斯爆炸进行数值模拟研究。探讨了巷道截面变窄的大小对瓦斯爆炸的影响程度以及瓦斯爆炸后压力和温度的变化。巷道截面变窄对瓦斯爆炸有明显的激励作用,且巷道越窄,激励作用越明显。在此基础上,分析了巷道壁面和三波结构对瓦斯爆炸的影响。结果表明,经壁面反射后的反射波和三波点的碰撞使爆炸的压力和温度显著升高且持续时间较长。研究结果对矿井建设的安全设计与安全设施设备的实施有重要意义。     

大跨度变截面拱形立体管桁架施工技术

根据工程特点与场地条件,浙江财经学院体育中心24榀大跨度变截面拱形立体管桁架,采用地面拼装和空中拼装相结合的方法施工,拼装质量良好,焊接变形应力控制在设计要求范围内。     

非均匀变截面梁的等效梁解法

在阶梯折算法的基础上，用等效梁法给出了非均匀变截面梁的稳定性和自由振动问题的解，这是区别转换矩阵法的又一解法。     

基于网状含拓扑剖面的三维地质多体建模

针对传统的基于剖面建模方法使用平行的共面剖面的不足,提出基于网状含拓扑剖面的三维地质多体建模方法,利用一系列含有"结点–弧段–多边形"拓扑关系的、相互连接成网状的剖面,来进行多个地质体的三维模型构建,并且模型之间没有空隙和交叠。该方法将建模区域划分为若干网格分区,每个分区独立进行模型构建,最后将各分区模型拼合成为全区整体模型。建模过程中提供对模型的整体光滑。运用北京地区的实际数据,成功建立了北京市城市地质调查中的8个地质模型,证明该方法具有快速构建大区域高精度复杂地质模型的能力。