Search

This study describes the function, optimization, and demonstration of a new class of passive, low-cost microfluidic flow meters based on birefringent chitosan biomembranes analyzed by polarized microscopy. We subjected the membrane to dynamic flow conditions while monitoring the real-time response of its optical properties. We obtained figures of merit, including the linear response operating range (0 to 65 μL min−1), minimum response time (250 ms), sensitivity (2.03% × 10−3 μL−1 min), and minimum sensor longevity (1 week). In addition, possible sources of interference were identified. Finally, we demonstrate the membrane as a low-cost flow rate measurement device for the close loop control of a commercial pressure-driven pump. Preliminary experiments using a basic PID controller with the membrane-based flow rate measurement device showed that stable control could be achieved and the system could reach steady-state behavior in less than 15 seconds. Analysis of fundamental limits to sensor response time indicate the potential for faster steady-state behaviour. [ABSTRACT FROM AUTHOR]

A particle damper is applied to suppress the longitudinal vibration of underwater vehicle shafting in order to reduce vibration level and improve silence and stealth of underwater vehicles. The model of rubber-coated steel particle damper was established with discrete element method and PFC3D simulation software, the damping energy consumption law of collision and friction between particle and damper and between particle and particle investigated, the effects of particle radius, mass filling ratio, cavity length, excitation frequency, excitation amplitude, rotating speed and both stacking and motion states of particles on the system vibration suppression were discussed, and the bench test was carried out to verify the law. It revealed the mechanism of longitudinal vibration suppression of particle damping, established the intrinsic relationship between of total energy consumption of particle and vibration of system, and put forward the evaluating method of longitudinal vibration suppression effect by total energy consumption of particle and vibration reduction ratio. The research results show that the mechanical model of particle damper is reasonable and the simulation data is reliable; the rotating speed, mass filling ratio and cavity length have significant effects on the total energy consumption of particle and vibration reduction ratio. [ABSTRACT FROM AUTHOR]

We present a generalizable fabrication method for a new class of analytical devices that merges virtually any microfluidic design with high-sensitivity on-chip attenuated total reflection (ATR) sampling using any standard Fourier transform infrared (FTIR) spectrometer. Termed "spectIR-fluidics", a major design feature is the integration of a multi-groove silicon ATR crystal into a microfluidic device, compared with previous approaches in which the ATR surface served as a structural support for the entire device. This was accomplished by the design, fabrication, and aligned bonding of a highly engineered ATR sensing layer, which con'''tains a seamlessly embedded ATR crystal on the channel side and an optical access port that matched the spectrometer light path characteristics at the device exterior. The refocused role of the ATR crystal as a dedicated analytical element, combined with optimized light coupling to the spectrometer, results in limits of detection as low as 540 nM for a D -glucose solution, arbitrarily complex channel features that are fully enclosed, and up to 18 world-to-chip connections. Three purpose-built spectIR-fluidic cartridges are used in a series of validation experiments followed by several point-of-application studies on biofilms from the gut microbiota of plastic-consuming insects using a small portable spectrometer. [ABSTRACT FROM AUTHOR]

Innovation in cold-formed steel framing systems is needed for opening flexibility and application in mid-rise buildings. Hence, this study proposes a closed built-up section using four cold-formed steel (CFS) open sections with a high load bearing capacity that potentially enables the development of high-performance cold-formed steel framing systems for these. The closed section by combining four open CFS sections using fasteners can effectively enhance the load capacity of the sections under axial loading. With a specially designed intersections gusset plate this built-up section offers more potential configurations of beam-column moment connections for CFS structures. First, a heuristic optimization was performed to identify a high-performance section based on the local and distortional buckling strengths using the finite strip method. Second, a test program was developed to investigate the load bearing capacity and failure behaviors of the optimized built-up closed section under axial and eccentric loading. Third, their load bearing capacities were compared with several other closed sections such as the rectangular hollow tube (RHS) of equal cross-sectional area or equal moment of inertia to highlight the high material efficiency. This study paved the groundwork for exploring high-performance cold-formed steel framing systems with this unique closed built-up section. • Proposed a closed built-up section for two-way cold-formed steel framing systems. • Investigated the compression behavior and strength of specimens under axial and eccentric loadings. • Achieved a high load-bearing capacity of the closed built-up section. • Conducted a comparable analysis with equivalent rectangular hollow tube sections numerically. [ABSTRACT FROM AUTHOR]

This paper aims to experimentally and numerically investigate the structural performance of speed-lock joints with split bolts in steel storage racks. There are no bolts in the typical speed-lock joint for its ease of installation, and the joint transmits and bears force through interactions of the tabs and upright beam holes. However, the joint under seismic loading shows large looseness and slippage with low stiffness. Also, the energy dissipation capacity is insufficient and the failure of tabs in the joints might lead to brittle behavior. In this study, new detail of the speed-lock joint with bolts is proposed by adding a pair of split bolts in the beam end plate while still preserving its merit of ease of installation. A double-cantilever beam test was designed to test this speed-lock joint with split bolts along with the typical speed-lock joint. Low cyclic loading tests were performed on both types of joints: with split bolts and without split bolts. The results revealed the benefits that the split bolts could bring to significantly enhance the performance of the joint in terms of the maximum bending moment, the initial stiffness, the displacement ductility coefficient, the equivalent viscous damping coefficient, and the energy consumption. In addition, a two-step analysis method was proposed for the high-fidelity finite element model of the joints to overcome the complex contact nonlinearity. The numerical model was then validated with the tests for further numerical studies on the performance of speed lock joints with/without bolts. • Experimental tests were designed and conducted on the typical speed-lock joint and proposed joint with added split bolts. • With split bolts, the joint has less slippage and looseness and effectively eliminates the brittle tab failure. • Speed-lock joints with split bolts possess an additional load bearing mechanism that improves the seismic performance. • Atwo-step analysis method was proposed for the finite element model of the joints to overcome the complex contact nonlinearity. • Stress distributions from experimental and numerical results reveal the joint's improved bearing mechanism. [ABSTRACT FROM AUTHOR]

Water-lubricated rubber slat bearing is the key part of the propulsion shafting of an underwater vehicle. Under low speed, overload special conditions, the rubber slat of the bearing is easy to produce boundary lubrication or mixed lubrication state and induce friction self-excited vibration that produces chattering and squealing, especially rubber slat wear, which can seriously affect the concealment, reliability and occupant comfort of the underwater vehicle. To solve this problem, surface texture is built on the friction surface of the rubber slat to explore the influence of the wear of the rubber slat with/without surface texture on frictional vibration suppression mechanism, and discuss the factors affecting rubber slat wear. The influence of the wear of the rubber slat with surface texture on vibration suppression mechanism was researched in experiment under different testing conditions such as speed, load, etc., and compared with the no-textured rubber slat to evaluate the frictional vibration suppression level of two kinds of worn surfaces. Wear test results show that with the increase of test time, the friction moment and friction coefficient of textured rubber slat sample is declined by 15.5%, the average hourly rate of wear reduced by 23.3% than those of no-textured rubber slat one. But overall, the surface texture can accommodate the abrasive dust and water storage function, which can effectively improve the wet conditions between two friction surfaces, reduce the friction coefficient, and inhibit the form of the frictional force with high frequency component. It contributes to improve the suppression level of the high frequency frictional vibration of water-lubricated rubber slat bearing. In wear test, under special working conditions such as pressure 0.6 MPa, water temperature 40 °C and rotary speed 185 r/min, the friction coefficient, the maximum vibration amplitude and gross value of the textured slat sample are lower than those of no-textured one, and the abnormal vibration and squealing of the textured slats does not occur. • A partial bearing was used to replace the whole bearing to carry out the suppression mechanism test and the influence of the wear of the rubber slat with surface texture on vibration suppression mechanism was researched. • Surface texture can improve the wear resistance. The friction moment and average hourly wear rate of the textured slat are lower than those of the no-textured one. • The surface texture is still of the function of accommodating wear debris and storing water unless the pit texture is completely flattened. [ABSTRACT FROM AUTHOR]