Influence of moisture and CO2 on the material behavior of thermoplastic elastomers for beer bottle closures

Metal closures with a polymer-based sealing for beer bottles have been known since the late nineteen-sixties. However, to what extent which parameter of the polymer sealing gasket plays a role in closure performance to keep the beer quality to a highest level possible is not fully understood. For this purpose three thermoplastic elastomer (TPE) liners were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM) and surface roughness in order to understand the effect of relative humidity (RH) and carbon dioxide (CO₂) on their physical and chemical properties as well as their macromolecular structures. The TPEs’ viscoelasticity in the frequency domain under different isothermal conditions was evaluated. RH and CO₂ were effective for changes in thermomechanical and surface properties. Liner C was found to have lower seal performance attributed to its relatively higher crystallinity, stiffness, weaker bond structure and rougher surface. Vibrations can lead to seal leakage in Liner B due to its higher damping behavior during production and transportation. Liner A outperforms others due to stabile behavior within the operational temperature range.     

Accelerated wear testing of polyurethane hydraulic seal

The wear characteristics of a polyurethane (PU) hydraulic seal were investigated using a hydraulic seal tester and a pin-on-plate reciprocating tribo-tester, and the results were compared to field data with the aim of developing an accelerated wear test method for hydraulic seals. Tests using a hydraulic seal tester and a pin-on-plate reciprocating tribo-tester were found to reproduce abrasive wear of PU from the field. However, a significant compression set was observed from the test using the hydraulic seal tester. Motivated by the occurrence of abrasive wear from the field, the discolored lubricant and the lubricant with alumina particles were further used for testing using the pin-on-plate reciprocating tribo-tester. The height decrease data of the sealing surface showed that the wear was accelerated by factors of 2.1–3.4 using these degraded lubricants. The outcomes of this work are expected to aid in the design of reliable accelerated life testing for hydraulic seals.     

单分散SiO_2无孔微球比表面积标准物质的研究进展

从单分散二氧化硅(SiO_2)微球的合成方法、粒度表征、定值及其组装体几何比表面积的计算等几个方面对SiO_2比表面积标准物质的合成进行了总结.这种类型比表面积标准物质的合成不仅可以扩展我国比表面积标准物质的种类,而且将有助于加深人们对物质真实比表面积的进一步认识.     

Structure and sensory equipment of the ovipositor of Habrobracon hebetor (Say) (Hymenoptera: Braconidae)

The microsculpture of various structures of the ovipositor of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is described from scanning and transmission electron microscopy. These include: the ovipositor egg canal, valvillus, seal of the first valvulae, interlocking mechanism (olistheter) connecting the first and second valvulae, an olistheter-like interlocking mechanism connecting the two pieces of the first valvulae, annulation, microtrichia of the third valvulae, and the ovipositor sensory equipment. Better understanding of the microsculpture of these components may make their roles in stinging, oviposition, and the host selection process more clear.     

“O”形密封圈在军用望远镜密封上的应用

本文以国外M22型7×50双简望远镜为例,论述了“O”形橡胶密封圈应用于军用望远镜的密封工作实例,对解决和改进现有军用双望密封结构,提高产品密封性能具有一定参考价值。     

海豹油成分及其脂肪酸的色谱分析

本文用高压液相色谱对海豹油的主要组分进行定性、定量分析；利用气相色谱-质谱联用仪定性分析了海豹油脂中的脂肪酸部分，并以硬脂酸为内标，用气相色谱方法对海豹油脂肪酸各组分进行了定量分析，分析结果表明海豹油中油脂部分占92％，烯醛类气味物质占6％；海豹油脂中不饱和脂肪酸占脂肪酸总量的82％以上，而且富含γ-亚麻酸。为开发海豹油，从海豹油中分离除去其中气味物质-烯醛类方法的选择提供了依据。     

Non-Linear Dynamics of a Rotor-Bearing-Seal System

The non-linear dynamic behaviors of a rotor-bearing-seal coupled system are investigated by using Muszynska’s non-linear seal fluid dynamic force model and non-linear oil film force, and the result from the numerical analysis is in agreement with the one from the experiment. The bifurcation of the coupled system is analyzed under different operating conditions. It is indicated that the dynamic behavior of the rotor-bearing-seal system depends on the rotation speed, seal clearance and seal pressure of the rotor-bearing-seal system. The system state trajectory, Poincaré maps, frequency spectra and bifurcation diagrams are constructed to analyze the dynamic behavior of the rotor center. Various non-linear phenomena in the coupled system, such as periodic motion and quasi-periodic motion are investigated. The results show that the system has the potential for chaotic motion. The study may contribute to a further understanding of the non-linear dynamics of such a rotor-bearing-seal coupled system.     

液氢截止阀故障分析与改进

介绍了火箭发动机试验系统高压液氢截止阀的结构和设计中的材质选择、密封、绝热等技术难点,针对其使用中的出现阀杆与阀体之间咬死而无法进行动作的问题进行了全面的分析,并提出了解决方案。该阀门改进后,工作性能可靠。     

Nonlinear dynamic behaviors of a rotor-labyrinth seal system

The nonlinear model of rotor-labyrinth seal system is established using Muszynska’s nonlinear seal forces. We deal with dynamic behaviors of the unbalanced rotor-seal system with sliding bearing based on the adopted model and Newmark integration method. The influence of the labyrinth seal one the nonlinear characteristics of the rotor system is analyzed by the bifurcation diagrams and Poincare’ maps. Various phenomena in the rotor-seal system, such as periodic motion, double-periodic motion, quasi-periodic motion and Hopf bifurcation are investigated and the stability is judged by Floquet theory and bifurcation theorem. The influence of parameters on the critical instability speed of the rotor-seal system is also included.     

Comparison of Three Techniques for Lipid Removal from Seal Blubber: Gel Permeation,Acid Treatment,and Dialysis with Semipermeable Membrane

Abstract

Harbor seal blubber samples were analyzed for PCDD/Fs and PCBs by splitting the initial extract into three aliquots and applying three different techniques for lipid removal (the first step of sample cleanup methodology for GC-HRMS analysis): gel permeation chromatography (GPC), sulfuric acid treatment, and dialysis through semipermeable membrane. Correlation coefficients of analyte concentrations obtained from three sets of replicate samples ranged from 0.965 to 0.994. In addition, a number of seal blubber samples were processed without pre-extraction using only the dialysis technique. The analyte concentrations in these samples correlated well with the analyte concentrations obtained from dialyzed blubber extracts (correlation higher than 0.998). For all analyses (PCDD/Fs, NO- and MO-PCBs) the average surrogate standard recoveries for the GPC and dialysis techniques varied from 68 to 111%. The recoveries for PCDD/Fs and MO-PCBs standards ranged from 61 to 89% and 36 to 43% for the NO-PCBs when the acid treatment technique was used. Dialysis was proven to be an efficient technique for lipid removal of biological samples in comparison with the GPC and acid treatment techniques.