铁路道床有砟-无砟过渡段动力特性的DEM-FEM耦合分析

针对铁路道床有砟-无砟过渡段的结构特点,采用离散元-有限元耦合模型分析散体道砟和无砟道床间过渡段的动力特性。散体道砟道床和无砟道床分别采用离散元方法 DEM和有限元方法 FEM模拟,而在过渡段将道砟颗粒嵌入无砟道床以增加道砟颗粒与无砟道床间的咬合力,并在离散元和有限元耦合区域实现了力学参数的传递。采用以上DEM-FEM耦合方法对有砟-无砟道床及其过渡段在列车荷载作用下的沉降过程进行了数值分析。计算结果表明,离散元方法中道砟颗粒间的力链呈现非对称梯形分布,其与有限元方法中的应力分布趋势一致;采用嵌入式道砟颗粒的方法可以增加有砟-无砟过渡段道砟间的咬合力,有效约束道砟颗粒的位移,减少有砟-无砟道床间的沉降差异。本文计算模型可以合理地分析有砟道床的力链分布以及无砟道床的应力分布,确定列车荷载下道床有砟-无砟过渡段的动力学行为。     

冲角工况下列车车轮损伤机理研究

曲线通过和蛇行运动时将会在轮轨间产生一定的冲角,为探究列车车轮在冲角工况下的损伤机理,利用JD-1轮轨模拟试验机对列车车轮进行滚动接触疲劳试验.结果表明:在冲角工况下车轮试件磨痕的不同区域存在不同的损伤机理,按损伤机理的不同可以将其分为塑性堆积区、疲劳损伤区和磨损区三个区域.在应力发生剧烈变化且应力方向由高应力区指向低应力区的区域将会出现材料的塑性堆积,并且在堆积处产生疲劳裂纹.滚动接触下的疲劳裂纹可以萌生于表面和亚表面,在较强应力作用下,车轮材料的晶粒发生了明显的细化,在横截面上呈现出纤维状组织.     

高速铁路连续箱型梁桥的动力响应与减振分析

根据列车具体的轴距和轴重,建立了和谐号动车组CRH380AL型列车简化模型;对高速铁路两跨连续梁桥采用多自由度欧拉伯努利梁单元进行主梁的模拟,并将液体黏滞阻尼器模拟为有限元阻尼单元;采用Newmark直接积分方法求解了高速列车作用下的连续梁桥运动方程,数值分析了列车车速以及液体黏滞阻尼器的阻尼系数对于高速铁路连续梁桥振动响应的影响。结果表明:黏滞阻尼器对于桥梁具有明显的减振效果,阻尼力不仅与阻尼系数有关还与列车时速有关;同一黏滞阻尼器条件下,桥梁的最大加速度并不随列车速度的增加而单调增加,而是在某些特定列车车速下桥梁的最大加速度出现了峰值,且随着黏滞阻尼器的阻尼系数增大,桥梁振动响应峰值处的最大加速度减幅不同;同一列车时速的条件下,桥梁的减振效果并不是随着阻尼系数的递增呈正比递增,而是随着阻尼系数的增大,阻尼器的减振效果增幅在减小。     

内埋武器高速风洞弹射投放模型试验关键技术研究

针对新一代战斗机超声速内埋武器弹射投放分离安全性问题,采用高速风洞投放实验技术研究内埋武器从开式武器舱弹射投放分离动态运动过程,风洞投放模型试验过程中采用除垂直加速度不足外,其余全部运动严格相似的轻模型相似设计方法,并针对轻模型法垂直加速度不足所导致的投放垂直位移偏离实物位移问题,采用一种简单易行的公式修正法进行补偿,试验给出了不同初始弹射投放分离条件下,内埋武器从载机投放分离后运动轨迹与姿态角随分离时间的变化规律,试验马赫数$Ma = 1.5$.研究结果表明:初始投放分离角速度对内埋武器投放分离后的运动轨迹及姿态角有较大的影响,当初始投放分离角速度$\omega _{z0}^s = 0^\circ/{\rm s}$时,内埋导弹出舱后先向下运动远离载机的流场干扰区,之后逐渐向载机方向抬升靠近并最终碰撞载机,高速风洞投放试验结果是不安全的,但经过公式修正后投放试验结果比较乐观,垂直方向运动仍然一直下降远离载机,这说明采用高速风洞投放试验得出的导弹不安全投放分离对真实载机来说不一定会出现,高速风洞投放试验结果比较保守. 当初始投放分离角速度$\omega _{z0}^s= 15^\circ/{\rm s}$和$\omega _{z0}^s = 30^\circ/{\rm s}$时,内埋导弹投放分离后运动趋势几乎一致, 均没出现向载机靠近的现象,内埋导弹具有一定的初始投放分离角速度有利于内埋武器的安全分离.      

Development of a general separation strategy by countercurrent chromatography using sanshools from Zanthoxylum bungeanum oleoresin as a case study

Three kinds of sanshools were separated from Zanthoxylum bungeanum oleoresin by high-speed countercurrent chromatography. Sanshools are a series of amide compounds extracted from the Zanthoxylum bungeanum. Due to similar structures, polarities, and dissociation constants, it was challenging to select an appropriate solvent system for their complete separation by countercurrent chromatography. To address this challenge, a solvent-system-selection strategy was proposed to identify a relatively suitable solvent system. Additionally, a separation procedure incorporating multi-elution modes selection was established to separate similar compounds in a logical order. Ultimately, a solvent system comprising n-hexane:ethyl acetate:methanol:water in a ratio of 19:1:1:5.67 was selected. Three amide compounds with high purity were obtained through the use of recycling elution mode to improve separation resolution: hydroxy-ε-sanshool (8.4 mg; purity: 90.64%), hydroxy-α-sanshool (326.4 mg; purity: 98.96%), and hydroxy-β-sanshool (71.8 mg; purity: 98.26%) were obtained from 600 mg sanshool crude extract. The summarized solvent-system-selection strategy and separation procedure incorporating multi-elution modes may instruct countercurrent chromatography users, particularly novices, seeking to separate compounds with highly similar chemical properties.     

An efficient high-speed counter-current chromatography method for the preparative separation of sesquiterpenoids from the rhizomes of Cyperus rotundus L. combined with evaluation of the anti-inflammation activity in vitro and molecular docking

Cyperus rotundus L. has been extensively used in ancient medication for the treatment of different disorders worldwide, in which sesquiterpenes are the most representative components. In this study, sesquiterpenes were effectively purified by two-dimensional counter-current chromatography in combination with continuous injection and inner-recycling mode with a solvent system of n-hexane/ethyl acetate/methanol/water (1:0.2:1:0.2, v/v/v/v). For one-dimension separation, continuous injection mode was used with three times injection and the inner-recycling mode was adopted for the separation of two mixtures for two-dimensional separation. Finally, four sesquiterpenoids, including scariodione ( 1 ), cyperenoic acid ( 2 ), scariodione ( 3 ), and α-cyperone ( 4 ), were obtained with purities over 98%. Mass spectrometry and nuclear magnetic resonance were applied to identify their structures. The results from the anti-inflammation effect with zebrafish demonstrated that cyperenoic acid exhibited stronger anti-inflammation activity. Molecular docking results suggested that cyperenoic acid possessed lower binding energies –9.4545 kcal/mol with 1CX2 to form formed hydrogen bond interaction with ARG120. In general, all the obtained findings proved that the strong anti-inflammation capacity of cyperenoic acid can have the potential of being adopted for treating diseases resulting from inflammation.     

Biphasic alcoholysis coupled with high-speed countercurrent chromatography for high performance on separating phorbol from Croton tiglium Linn extracts

Phorbol is a tetracyclic diterpenoid found in Euphorbia tirucalli, Croton tiglium, and Rehmannia glutinosa, and is nuclear of various phorbol esters. The rapid obtaining of phorbol with high purity highly contributes to its application, such as synthesizing phorbol esters with designable side chains and particular therapeutic efficacy. This study introduced a biphasic alcoholysis method for obtaining phorbol from croton oil by using polarity imparity organic solvents in both phases and established a high-speed countercurrent chromatography method for simultaneous separation and purification of phorbol. The optimized operation conditions of biphasic alcoholysis were a reaction time of 91 min, a temperature of 14°C, and a croton oil-methanol ratio of 1:30 (g:ml). The phorbol during the biphasic alcoholysis was 3.2-fold higher in content than that obtained in conventional monophasic alcoholysis. The optimized high-speed countercurrent chromatography method was using the ethyl acetate/n-butyl alcohol/water at 4.7:0.3:5 (v:v:v) with Na₂SO₄ at 0.36 g/10 ml as the solvent system, using the mobile phase flow rate of 2 ml/min, the revolution of 800 r/min, under which the retention of the stationary phase was achieved at 72.83%. The crystallized phorbol following high-speed countercurrent chromatography was obtained as high purity of 94%.     

Isolation of three glucaric acids from Leonurus japonicus Houtt. by using high-speed countercurrent chromatography combined with semi-preparative high-performance liquid chromatography

The isomerism of glucaric acids and the complexity of the composition of Leonurus japonicus Houtt. increased the difficulty of the separation of glucaric acids from the herb. In the present study, three glucaric acids were isolated from Leonurus japonicus Houtt. by using high-speed countercurrent chromatography combined with semi-preparative high-performance liquid chromatography. Cation exchange resin chromatography was applied to remove the alkaloids and enrich the glucaric acid fractions. Preliminary separation of the glucaric acid extract by high-speed countercurrent chromatography was carried out at 45℃ by using an optimized solvent system of ethyl acetate/n-butanol/formic acid/water (1:1:0.01:2, v/v/v/v) with satisfied stationary phase retention and separation factor. The semi-preparative high-performance liquid chromatography was used for further separation and purification of the target fractions, and three monomeric compounds were obtained with purities of 90.0, 91.0, and 95.3%. UV spectroscopy, NMR spectroscopy, and mass spectrometry were employed to identify their structures, which were assigned as 2-syringyl glucaric acid, 2,4-disyringyl glucaric acid, and 3,4-disyringyl glucaric acid, respectively, and 2,4-disyringyl glucaric acid was reported for the first time.     

Scale-Up Preparation of Crocins I and II from Gardenia jasminoides by a Two-Step Chromatographic Approach and Their Inhibitory Activity Against ATP Citrate Lyase

Crocins are highly valuable natural compounds for treating human disorders, and they are also high-end spices and colorants in the food industry. Due to the limitation of obtaining this type of highly polar compound, the commercial prices of crocins I and II are expensive. In this study, macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was used to purify crocins I and II from natural sources. With only two chromatographic steps, both compounds were simultaneously isolated from the dry fruit of Gardenia jasminoides, which is a cheap herbal medicine distributed in a number of countries. In an effort to shorten the isolation time and reduce solvent usage, forward and reverse rotations were successively utilized in the HSCCC isolation procedure. Crocins I and II were simultaneously obtained from a herbal resource with high recoveries of 0.5% and 0.1%, respectively, and high purities of 98.7% and 99.1%, respectively, by HPLC analysis. The optimized preparation method was proven to be highly efficient, convenient, and cost-effective. Crocins I and II exhibited inhibitory activity against ATP citrate lyase, and their IC₅₀ values were determined to be 36.3 ± 6.24 and 29.7 ± 7.41 μM, respectively.     

聚晶立方氮化硼刀具切削高锰钢的磨损机制

在半精加工试验条件(切削深度ap=0．5mm，进给量f=0．3mm／r，干切)下研究了聚晶立方氮化硼刀具切削奥氏体高锰钢时的磨损机制，用WDH-Ⅱ型光电温度计测量了切削温度，用工具显微镜测量后刀面磨损量，进而考察了切削时间和切削速度对后刀面磨损量的影响，采用S-250MK型扫描电子显微镜观察刀具前、后刀面的磨损形貌和组成变化．结果表明：当切削温度为400～750℃时，聚晶立方氮化硼刀具同高锰钢中的γ相及其析出相(Fe，Mn)3C之间产生严重的机械磨损；当切削温度超过800℃时，聚晶立方氮化硼刀具同高锰钢单一γ相之间产生扩散磨损；聚晶立方氮化硼刀具适合于高速切削.