薄壁件加工系统动态响应分析

薄壁件在铣削加工中容易产生共振或变形，直接影响加工稳定性及加工精度。采用主轴-刀具-工件整体铣削系统连续梁模型，系统研究在动态铣削力作用下，刀具端部与工件端部的动态响应之间的相互影响关系以及对整体系统动态响应影响较大的薄壁件尺寸。结果表明，工件横截面高度对系统共振的影响较为明显，当高度尺寸较小时，工件的低频共振会通过动态铣削力直接反映到刀具端部的振动频响上。工件横截面底边宽度尺寸的增大虽然对共振频率的改变不太明显，但会导致激发出来的刀具共振幅度出现明显降低。研究成果可以为薄壁件铣削加工系统的稳定性控制提供理论基础。     

Global Pathway Analysis: a hierarchical framework to understand complex chemical kinetics

An automated hierarchical framework, Global Pathway Analysis (GPA), is presented to understand complex chemical kinetics. The behaviour of the reacting system at macro level is bridged to the elementary reaction level by Global Pathways, which are the chemical pathways from an initial reactant species to a final product species. For each Global Pathway, its dominancy and effect on the system, such as those on the production or consumption of radicals, are quantified to understand its contribution to the system. Four examples are presented as demonstration: First, the classical second explosion limit of hydrogen is found to be resulted from the change of dominancy of a pressure-dependent Global Pathway, which consumes radical via H?+?O₂?+?M?=?HO₂?+?M reaction. Next, it is found that the negative temperature coefficient (NTC) regime of n-heptane is resulted from the competition between a low-temperature Global Pathway and a high-temperature Global Pathway. Third, a non-monotonic relation between autoignition delays and toluene ratio in toluene/n-decane mixture is analysed. This automated framework has been placed in public domain. Reduced kinetic models can be generated based on Global Pathways too. Finally, this methodology is demonstrated using DNS simulation results of the extinction and re-ignition of a turbulent non-premixed flame. The differences between simulation results are investigated using two different kinetics models via the analysis of global pathways.     

Screening and identification of Caulis Sinomenii bioactive ingredients with dual‐target NF‐κB inhibition and β2‐AR agonizing activities

Caulis Sinomenii (CS) is a valuable traditional medicine in China. Its extract can act as an anti‐inflammatory agent and a vascular smooth muscle relaxant. However, the underlying mechanisms remain unknown. In this study, we developed a simple dual‐target method based on ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry combined with a dual‐target bioactive screening assay for anti‐inflammatory and antispasmodic activities to characterize the chemical structure of various bioactive compounds of CS rapidly. Seven potential NF‐κB inhibitors were identified, including laudanosoline‐1‐O‐xylopyranose, 6‐O‐methyl‐laudanosoline‐1‐O‐glucopyranoside, menisperine, sinomenine, laurifoline, magnoflorine and norsinoacutin. Furthermore, IL‐6 and IL‐8 assays confirmed the anti‐inflammatory effects of these potential NF‐κB inhibitors, in which laudanosoline‐1‐O‐d ‐xylopyranose and menisperine were revealed as novel NF‐κB inhibitors. Among the seven identified alkaloids, three potential β₂‐adrenergic receptor agonists, including sinomenine, magnoflorine and laurifoline, were characterized using a luciferase reporter system to measure for the activity of β₂‐adrenergic receptor agonists. Finally, sinomenine, magnoflorine and laurifoline were identified not only as potential NF‐κB inhibitors but also as potential β₂‐adrenegic receptor agonists, which is the first time this has been reported. Molecular dynamic simulation and docking results suggest that the three dual‐bioactive constituents could not only inhibit Pseudomonas aeruginosa PAK strain‐induced inflammatory responses via a negative regulation of the Braf protein that participates in MAPK signaling pathway but also activate the β₂‐adrenegic receptor. These results suggest that CS extract has dual signaling activities with potential clinical application as a novel drug for asthma.     

Electric field assisted oxygen removal from the basal plane of the graphitic material

We provide a novel strategy to eliminate the epoxy group from the basal plane of graphene platelets. Given that the current reduction methods are unsatisfactory to clean the epoxides or sometimes cause undesirable structure deformations, the proposed strategy restores the original hexagonal carbon network without creating other new defects. To the best of our knowledge, the electric field mediated graphene oxide (GO) reduction has not yet been systematically investigated. The capability would permit the improvement of existing GO reduction methods and assist in the fabrication of high‐quality graphitic materials. © 2012 Wiley Periodicals, Inc.     

Cellular Fucosylation Inhibitors Based on Fluorinated Fucose-1-phosphates**

Fucosylation of glycans impacts a myriad of physiological and pathological processes. Inhibition of fucose expression emerges as a potential therapeutic avenue for example in cancer, inflammation, and infection. In this study, we found that protected 2-fluorofucose 1-phosphate efficiently inhibits cellular fucosylation with a four to seven times higher potency than known inhibitor 2FF, independently of the anomeric stereochemistry. Nucleotide sugar analysis revealed that both the α- and β-GDP-2FF anomers are formed inside the cell. In conclusion, we developed A2FF1P and B2FF1P as potent new tools for studying the role of fucosylation in health and disease and they are potential therapeutic candidates.     

An arsenate with the α‐CrPO4 structure type,NaCa1–xNi3–2xAl2x(AsO4)3 (x = 0.23): crystal structure,charge‐distribution and bond‐valence‐sum analyses

Since the discovery of electrochemically active LiFePO₄, materials with tunnel and layered structures built up of transition metals and polyanions have become the subject of much research. A new quaternary arsenate, sodium calcium trinickel aluminium triarsenate, NaCa_1–x Ni_3–2x Al_2x (AsO₄)₃ (x = 0.23), was synthesized using the flux method in air at 1023 K and its crystal structure was determined from single‐crystal X‐ray diffraction (XRD) data. This material was also characterized by qualitative energy‐dispersive X‐ray spectroscopy (EDS) analysis and IR spectroscopy. The crystal structure belongs to the α‐CrPO₄ type with the space group Imma . The structure is described as a three‐dimensional framework built up of corner‐edge‐sharing NiO₆, (Ni,Al)O₆ and AsO₄ polyhedra, with channels running along the [100] and [010] directions, in which the sodium and calcium cations are located. The proposed structural model has been validated by bond‐valence‐sum (BVS) and charge‐distribution (CHARDI) tools. The sodium ionic conduction pathways in the anionic framework were investigated by means of the bond‐valence site energy (BVSE) model, which predicted that the studied material will probably be a very poor Na⁺ ion conductor (bond‐valence activation energy ∼7 eV).     

高精度中小11径非球面修抛技术研究

为实现高精度中小口径非球面的加工，介绍了一种非球面修抛技术。基于Preston假设，将抛光过程描述成一个线性方程，计算得到材料的去除量与抛光时间、抛光压力和零件转速之间的函数关系。设计了整体修抛法和环带修抛法两种方法，在数控抛光的基础上，对口径为Ф117mm的凹抛物面和口径为Ф17mm凸双曲面进行修抛，修抛后非球面的面形精度PV值为0．184μm，RMS均小于0．032μm，达到了工程化应用要求，实现了中小口径非球面的高精度加工。     

二丙胺的结构微调对磷酸铝分子筛晶化过程影响的凝胶组成依赖性

以二丙胺异构体（二正丙胺DPA和二异丙胺D-iPA）为结构导向剂,在200℃加热2组反应原料物质的量之比不同的初始凝胶,合成出了高结晶度的磷酸铝分子筛AlPO₄-11。利用X射线粉末衍射分析、元素分析等表征手段,研究了凝胶的晶化过程和液相的pH值以及Al和P的浓度演化。初始凝胶各组分物质的量之比为n_Al2O3：n_P2O5：n_DPA/D-iPA：n_H2O2=1.0：1.0：1.2：75时,以DPA为结构导向剂,晶化过程中无中间相生成,而以D-iPA为结构导向剂时,晶化过程中生成了具有12元环孔道结构的磷酸铝分子筛AlPO₄-5中间相;初始凝胶各组分物质的量之比为n_Al2O3：n_P2O5：n_DPA/D-iPA：n_H2O2=1.0：1.0：1.0：75时,以DPA为结构导向剂,晶化过程中生成了具有18元环孔道结构的磷酸铝分子筛VPI-5中间相,而以D-iPA为结构导向剂时,晶化过程中同时出现了VPI-5及AlPO₄-5两种中间相。表明对于同一种有机胺,凝胶物质的量之比的改变影响了其结构导向效应。理论计算结果显示质子化的DPA及D-iPA中N原子上的电荷有差异,表明有机胺的结构微调影响其结构导向效应,但该影响依赖于凝胶组成。     

水分子对α相CL-20热分解机理影响的分子动力学研究

研究六硝基六氮杂异伍兹烷(CL-20)晶体不同晶型在不同温度下的反应机理, 对于深入认识含能材料在极端条件下的冲击起爆、冲击点火和爆轰过程等具有重要意义. 基于反应力场, 研究水分子在纯α相CL-20及其水合物的晶体结构中数量随时间的变换, 分析水分子对两种体系的初始分解和第二阶段的分解路径的影响. 计算结果表明: CL-20 分子的初始分解路径与水分子无关, 第二阶段的分解反应与水分子有关. 在低温(T<1500 K)下, 水分子对两种体系没有影响, 二者的初始分解路径均为N-NO₂键生成NO₂自由基; 在1500 K≤T≤2500 K时, 水分子作为反应物或与NO₂、、OH自由基等组成催化体系, 生成O₂、H₂O₂等产物, 加速水合物体系在高温下的第二阶段反应, 使得高温下水合物体系的化学反应速率和反应生成的NO₂自由基的数量比纯CL-20体系的化学反应速率和反应生成的NO₂自由基的数量大; 在T>2500 K时, 水分子的催化反应抑制CL-20初始分解反应, 使得在3000 K时纯CL-20体系的反应速率大于水合物体系中CL-20的反应速率.     

Amarusine A,a new dioxaspiro[4.4]nonane derivative with a butyrolactone ring from Pleioblastus amarus

Amarusine A (1), a new polyketide derivative possessing an unusual dioxaspiro[4.4]nonane derivative with a butyrolactone ring, was isolated from the leaves of Pleioblastus amarus. The structure and absolute stereochemistry of compound 1 were rigorously determined using UV, IR, HRESIMS, and 1D and 2D NMR techniques and by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Amarusine A (1) exhibits a good antioxidant activity for scavenging the DPPH radical. A possible biosynthetic pathway was postulated.