Vertical seismic absorber utilizing inertance and negative stiffness implemented with gas springs

A novel implementation of negative stiffness elements(NSEs)is proposed,utilizing industrial grade nitrogen gas springs as pre-stressed stiffness elements in a configuration with lever arms.This NSE is combined with an inerter to form a stiff dynamic absorber(SDA)for vertical seismic protection of structures with base isolation.The SDA is optimized to minimize vertical accelerations while ensuring static structural integrity,excellent damping performance and containment of relative displacements.The introduction of gas springs in place of conventional linear springs addresses important practical limitations through features of non-linearity and industrial grade manufacturing.The proposed implementation is dimensioned for a 50-ton structure and evaluated numerically for 25 actual earthquake records,in comparison with a linear SDA model and an equivalent conventional damper(CD).Individual and averaged results of acceleration and displacement time histories demonstrate vastly superior response compared to CD regarding induced accelerations for similar displacements.Performance equivalency with the linear SDA model indicates the stability of the gas spring implementation while guaranteeing predictability,tested endurance,proper tolerances,and off-axis motion resistance without requiring additional guiding components,as opposed to conventional springs.These features render the proposed implementation a promising solution for the realization of NSEs in seismic protection.

Helium,Argon and Carbon Isotopic Compositions of Spring Gases in the Hainan Island,China

Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.

TEM-SOFT:Academic Software for the Ergo-Mechanic Investigation of Tailgate Operation

Because of their technical advantages over ordinary metal springs, gas springs find usage in wide range of applications from furniture to aerospace industry as lifting, lowering or damping assists. Their integration to the tailgate operations in automotive industry is a challenging area, where not only the fundamental gas spring characteristics but also the mounting settings, working environment and tailgate body structure should be considered. The design and integration of these components will determine manual force exertion of operators thus the consideration of ergonomic characteristics of different populations is crucial. This paper introduces a recent visual academic software package, entitled TEM-SOFT, which is developed as a part of this research to perform ergo-mechanic simulations of tailgate operations with a fast, reliable and contemporary engineering approach and it is suitable for engineers and under-post graduate level students of mechanical and industrial engineering programs in the universities. The software developed and presented in this paper features all aspects of tailgate-gas spring operations considering the assembly scheme, tailgate mass center, gas spring type and working temperature in order to compute the required manual forces and the individual and combined impacts of acting parameters. Sufficient amount of scenarios were considered and the results were evaluated and discussed extensively. In addition to the other key findings, conducted research has shown that stronger gas springs, more effectively tend to move the critical tailgate position angle—where no operator force is needed to keep the tailgate opening—to the initial phases of the opening operation. A trade-off of this benefit is a superior initial manual force during closing.