Eccentric compression behavior of FRP-concrete-steel tubular composite columns

FRP-concrete-steel tubular (FCS) composite columns are composed of the external tube, the internal steel tube, and the concrete between both tubes. They have been attracting the attention of many researchers due to their high ductility, lightweight, resistance to corrosion, and easiness of construction. However, there are few studies on FRP-concrete-steel tubular composite columns under eccentric load. To investigate the behavior of composite columns under the eccentric compression, a non-linear analysis program for FCS composite columns was compiled. The program was verified by existing tests, and the influences of eccentricity, FRP tube wall thickness, steel tube wall thickness, steel tube radius, slenderness ratio, and concrete strength grade on the eccentric compression performance were systematically analyzed. The results showed that the calculated results were in good agreement with the experimental results. It showed that the program can accurately reflect the deformation of FCS composite columns under various loads and estimate the ultimate load of FCS composite columns under eccentric compression. The eccentric ultimate load increased with the decrease of eccentricity and slenderness ratio, and with the increase of FRP tube wall thickness, steel tube wall thickness, and concrete strength grade. The ultimate eccentric load decreased with the increase of steel tube radius, but when the steel tube wall thickness reached a certain thickness, the ultimate eccentric load of FCS composite columns increases with the increase of steel tube radius. The conclusion can provide reference for the practical application of the structure.

Effects of Tube Radius and Surface Tension on Capillary Rise Dynamics of Water/Butanol Mixtures

Capillary-driven action is an important phenomenon which aids the development of high-performance heat transfer devices, such as microscale heat pipes. This study examines the capillary rise dynamics of n-butanol/water mixture in a single vertical capillary tube with different radii (0.4, 0.6, and 0.85 mm). For liquids, distilled water, n-butanol, and their blends with varying concentrations of butanol (0.3, 0.5, and 0.7 wt.%) were used. The results show that the height and velocity of the capillary rise were dependent on the tube radius and liquid surface tension. The larger the radius and the higher the surface tension, the lower was the equilibrium height (he) and the velocity of rise. The process of capillary rise was segregated into three characteristic regions: purely inertial, inertial + viscous, and purely viscous regions. The early stages (purely inertial and inertial + viscous) represented the characteristic heights h1 and h2, which were dominant in the capillary rise process. There were linear correlations between the characteristic heights (h1, h2, and he), tube radius, and surface tension. Based on these correlations, a linear function was established between each of the three characteristic heights and the consolidated value of tube radius and surface tension (σL/2πr2).

Terahertz Thermal Sensing by Using a Defect-Containing Periodically Corrugated Gold Waveguide

A terahertz (THz) thermal sensor has been developed by using a periodically corrugated gold waveguide. A defect was positioned in the middle of this waveguide. The periodicities of waveguides can result in Bragg and non-Bragg gaps with identical and different transverse mode resonances, respectively. Due to the local resonance of the energy concentration in the inserted tube, a non-Bragg defect state (NBDS) was observed to arise in the non-Bragg gap. It exhibited an extremely narrow transmission peak. The numerical results showed that by using the here proposed waveguide structure, a NBDS would appear at a resonance frequency of 0.695 THz. In addition, a redshift of this frequency was observed to occur with an increase in the ambient temperature. It was also found that the maximum sensitivity can reach 11.5 MHz/K for an optimized defect radius of 0.9 times the mean value of the waveguide inner tube radius, and for a defect length of 0.2 (or 0.8) times the corrugation period. In the present simulations, a temperature modification of the Drude model was also used. By using this model, the thermal sensing could be realized with an impressive sensitivity. This THz thermal sensor is thereby very promising for applications based on high-precision temperature measurements and control.

Correction to: Dewatering of foam-laid and water-laid structures and the formed web properties

In the original publication of the article, the sentences “Hirasaki and Lawson (1985) found a decrease by almost a factor of 104 occurring in the apparent viscosity of foam (air content 83%) in capillary tubes as the ratio of bubble radius to tube radius, , increased from 0.1 to 10.

HEART SOUND MODEL BASED ON CASCADED AND LOSSLESS ACOUSTIC TUBES

In order to further understand the generation mechanism of Heart Sound, we introduce a new method for simulating Heart Sound by using cascaded and lossless acoustic tubes. Based on the theory of acoustics, we abstract the ventricles and arteries inside of the heart as multistage tubes with equal length and different radii. By controlling the radii of tubes, we simulate the process of relaxation and constriction of the ventricles and arteries. Then, we calculate the transfer function of the tubes based on the theory of reflective transmission line. To gain the tubes’ radii, we use formant frequency as the model target parameters and put forward an approximation method. Finally, the experimental results show that compared with traditional model, the model based on cascaded and lossless acoustic tubes could better reflect the state of the ventricles and arteries. Meanwhile, by comparing the model tube radius of normal Heart Sound and pathological Heart Sound, we can give a better explanation to the cause of pathological Heart Sound.

Interlayer Attraction Force in Concentric Carbon Nanotubes

The interlayer attraction force between concentric carbon nanotubes (CNTs) plays an important role in CNT-based nanodevices. However, the precise measurement of the interlayer attraction force remains to date a challenge. Although theoretical investigations have identified the dependence of the interlayer attraction force on the tube radius, no explicit relation for such dependence has been established so far. Here, based on an analytical model, we find that the interlayer attraction force between two telescoping concentric CNTs is proportional to the mean (but not the inner nor the outer) radius of the contacting two tubes and consequently propose an explicit expression that relates the interlayer attraction force with the mean radius as well as the interlayer spacing. We also implement the effect of temperature in the present expression based on the linear dependence of the attraction force on temperature. The present expression can be compared with the existing theoretical and experimental results, offering an efficient way to evaluate the interlayer attraction force in the nanodevices composed of concentric CNTs.

Modeling membrane nanotube morphology: the role of heterogeneity in composition and material properties

Membrane nanotubes have been identified as dynamic structures for cells to connect over long distances. Nanotubes typically appear as thin and cylindrical tubes, but they may also have a beaded architecture along the tube. In this paper, we study the role of membrane mechanics in governing the architecture of these tubes and show that the formation of beadlike structures along the nanotubes can result from local heterogeneities in the membrane either due to protein aggregation or due to membrane composition. We present numerical results that predict how membrane properties, protein density, and local tension compete to create a phase space that governs the morphology of a nanotube. We also find that there is an energy barrier that prevents two beads from fusing. These results suggest that the membrane-protein interaction, membrane composition, and membrane tension closely govern the tube radius, number of beads, and the bead morphology.

Kinetic theory based multiphase flow with experimental verification

This review is an extension of our 2014 circulating fluidized bed (CFB) plenary lecture. A derivation of multiphase mass, momentum and energy balances is presented, with a review of elementary kinetic theory, to explain the concepts of granular temperature and pressure and the core-annular flow regime commonly observed in CFB. The kinetic theory shows that the particle concentration is given by the reciprocal of a fourth order parabola of dimensional tube radius, in agreement with experiments. Computed flow regimes and heat and mass transfer coefficients in fluidization are also discussed.