Traversable wormhole in logarithmic f(R) gravity by various shape and redshift functions

In this paper, we study the traversable wormhole solutions for a logarithmic corrected [Formula: see text] model by considering two different statements of shape [Formula: see text] and redshift [Formula: see text] functions. We calculate the parameters of the model including energy density [Formula: see text], tangential pressure [Formula: see text] and radial pressure [Formula: see text] for the corresponding forms of the functions. Then, we investigate different energy conditions such as null energy condition, weak energy condition, dominant energy condition and strong energy condition for our considered cases. Finally, we explain the satisfactory conditions of energy of the models by related plots.

Water lifting and outflow gain of kinetic energy in tropical cyclones

While water lifting plays a recognized role in the global atmospheric power budget, estimates for this role in tropical cyclones vary from no effect to a major reduction in storm intensity. To better assess this impact, here we consider the work output of an infinitely narrow thermodynamic cycle with two streamlines connecting the top of the boundary layer in the vicinity of maximum wind (without assuming gradient-wind balance) to an arbitrary level in the inviscid free troposphere. The reduction of a storm’s maximum wind speed due to water lifting is found to decline with increasing efficiency of the cycle and is about 5% for maximum observed Carnot efficiencies. In the steady-state cycle, there is an extra heat input associated with the warming of precipitating water. The corresponding positive extra work is of an opposite sign and several times smaller than that due to water lifting. We also estimate the gain of kinetic energy in the outflow region. Contrary to previous assessments, this term is found to be large when the outflow radius is small (comparable to the radius of maximum wind). Using our framework, we show that Emanuel’s maximum potential intensity (E-PI) corresponds to a cycle where total work equals work performed at the top of the boundary layer (net work in the free troposphere is zero). This constrains a dependence between the outflow temperature and heat input at the point of maximum wind, but does not constrain the radial pressure gradient. We outline the implications of the established patterns for assessing real storms.

Viscoacoustic squeeze-film force on a rigid disk undergoing small axial oscillations

This paper investigates the air flow induced by a rigid circular disk or piston vibrating harmonically along its axis of symmetry in the immediate vicinity of a parallel surface. Previous attempts to characterize these so-called ‘squeeze-film’ systems largely relied on simplifications afforded by neglecting either fluid acceleration or viscous forces inside the thin enclosed gas layer. The present viscoacoustic analysis employs the asymptotic limit of small vibration amplitudes to investigate the flow by systematic reduction of the Navier–Stokes equations in two distinct flow regions, namely, the inner gaseous film where streamlines are nearly parallel to the confining walls and the near-edge region of non-slender flow that features gas exchange with the surrounding stagnant atmosphere. The flow in the gaseous film depends on the relevant Stokes number, defined as the ratio of the characteristic viscous time across the film to the characteristic oscillation time, and on a compressibility parameter, defined as the square of the ratio of the acoustic time for radial pressure equilibration to the oscillation time. A Strouhal number based on the local residence time emerges as an additional governing parameter for the near-edge region, which is incompressible at leading order. The method of matched asymptotic expansions is used to describe the solution in both regions, across which the time-averaged pressure exhibits comparable variations that give opposing contributions to the resulting time-averaged force experienced by the disk or piston. A diagram structured with the Stokes number and compressibility parameter as coordinates reveals that this steady squeeze-film force, typically repulsive for small values of the Stokes number, alternates to attraction across a critical separation contour in the parametric domain that exists for all Strouhal numbers. This analysis provides, for the first time, a unifying viscoacoustic theory of axisymmetric squeeze films, which yields a reduced parametric description for the time-averaged repulsion/attraction force that is potentially useful in applications including non-contact fluid bearings and robot locomotion.

Ageing of climbing ropes with and without hydrophobic coating

The effects of 4 months of weather exposure on the ageing of dynamic climbing ropes made of polyamide 6 were studied and differences between ropes with and without hydrophobic coating were examined. The polyamide degradation of the rope yarns was studied using infrared spectroscopy and a quasi-static tensile test. The number of falls to failure and the maximum force on the climber in a fall were evaluated with a drop test according to the UIAA 101 standard. Moreover, changes in the length of the ropes due to weathering were measured. The following results were found. After 4 months of weathering, sheath yarns of the coated rope showed a greater decrease in breaking force than those of the uncoated rope, which might be due to reactions of polyamide with radicals formed during the photo-induced oxidation of the coating. In contrast, the core yarns from the uncoated rope showed a greater decrease in breaking force than those from the coated rope, probably due to prolonged exposure of the uncoated core to water with possibly dissolved atmospheric acids. Furthermore, the decrease in the number of falls to failure was greater in the uncoated than in the coated rope. This difference was explained by a mechanism of changes in radial pressure of the sheath on the core. Regarding the maximum force on the climber, no significant changes due to ageing were observed during the drop test. Thus, it was concluded that 4 months of weather exposure do not pose a safety risk for climbing ropes, but the negative effect of coating on the ageing of polyamide might be detrimental when it comes to static personal safety equipment, such as slings or accessory cords.

A study of anisotropic compact stars in f(R,ϕ,X) theory of gravity

In this paper, we investigate the behavior of anisotropic compact stars in generalized modified gravity, namely [Formula: see text] gravity, where [Formula: see text] represents the Ricci scalar, [Formula: see text] is the scalar potential function and [Formula: see text] is a kinetic term of [Formula: see text]. We consider the spherically symmetric spacetime to analyze the feasible exposure of compact stars. We observe the behavior of anisotropic compact stars which includes Her X1, SAX J 1808.4-3658 and 4U 1820-30. From the graphical evaluation of energy density, tangential pressure, radial pressure, equilibrium conditions, energy conditions, mass–radius relationship, compactness and stability analysis of compact stars, it is concluded that the behavior of candidates of compact stars is regular in [Formula: see text] gravity for the considered parameter.

Non-Invasive radial pressure wave analysis may digitally predict women’s risks of type 2 diabetes (T2DM): A case and control group study

Background Women not only have worse diabetes complications, but also have menstrual cycle, pregnancy, and menopause which can make managing diabetes more difficult. The aim of this study was to investigate if radial pressure wave analysis may non-invasively screen for women’s risk of type 2 diabetes. Methods Spectrum analysis of the radial pressure wave was performed to evaluate the first five harmonic components, C1 to C5. The study consisted of a total of 808 non-pregnant female subjects aged 20–95 over the period of 4 years, and 404 of them were diagnosed with Type 2 diabetes as the case group. Result The first five harmonic components are significantly different in a comparison of the case group and the control group. In the logistic regression analysis, T2DM was found to be associated with C1 (OR = 1.055, CI = 1.037–1.074, p < 0.001), C2 (OR = 1.051, CI = 1.019–1.085, p = 0.002), and C3 (OR = 0.972, CI = 0.950–0.994, p = 0.013). In the Receiver Operating Characteristic curve analysis, the Area Under Curve of using C3 only (70%, p <0.05), weighted C1, C2 and C3, (75%, p < 0.05), and weighted C1, C2 and C3 and Body mass Index (84%, p <0.05) were tested for the accuracy on how well these tests separate the women into the groups with and without the T2DM. Conclusion We thus concluded that pulse spectrum was a non-invasive predictor for women’s risk of T2DM.

Treatment of an Unyielding Central Vein Stenosis using Valvuloplasty Balloon in a Young Female Presenting with Ineffective Hemodialysis

Percutaneous balloon venoplasty is widely employed for the management of central vein stenosis (CVS), a condition frequently encountered in patients on maintenance hemodialysis (MHD). The hypertrophied and fibrotic venous stenotic lesions often pose a challenge for interventionists, due to resistance to dilatation and high-elastic recoil. We report here successful utilization of mitral valvuloplasty balloon for percutaneous treatment of an unyielding brachiocephalic vein stenosis. Repeated failure of conventionally used peripheral balloon dilatation catheter prompted the use of a mitral valvuloplasty balloon that could exert higher radial pressure while preventing melon-seeding and hence successfully achieve stenosis dilatation. The mitral valvuloplasty balloon can be effectively and safely used for lesions resistant to repeated dilatations by conventional peripheral balloons. Rheological stress on central veins from ipsilateral arteriovenous fistula (AVF) may result in development of stenotic lesions, even in the absence of prior venous catheterization of the affected vein; therefore, in the presence of relevant symptoms, this diagnosis should not be excluded on the basis of absence of prior direct trauma at the stenosis site.

Determination of aortic pulse transit time based on waveform decomposition of radial pressure wave

Carotid-femoral pulse transit time (cfPTT) is a widely accepted measure of central arterial stiffness. The cfPTT is commonly calculated from two synchronized pressure waves. However, measurement of synchronized pressure waves is technically challenging. In this paper, a method of decomposing the radial pressure wave is proposed for estimating cfPTT. From the radial pressure wave alone, the pressure wave can be decomposed into forward and backward waves by fitting a double triangular flow wave. The first zero point of the second derivative of the radial pressure wave and the peak of the dicrotic segment of radial pressure wave are used as the peaks of the fitted double triangular flow wave. The correlation coefficient between the measured wave and the estimated forward and backward waves based on the decomposition of the radial pressure wave was 0.98 and 0.75, respectively. Then from the backward wave, cfPTT can be estimated. Because it has been verified that the time lag estimation based on of backward wave has strong correlation with the measured cfPTT. The corresponding regression function between the time lag estimation of backward wave and measured cfPTT is y = 0.96x + 5.50 (r = 0.77; p < 0.001). The estimated cfPTT using radial pressure wave decomposition based on the proposed double triangular flow wave is more accurate and convenient than the decomposition of the aortic pressure wave based on the triangular flow wave. The significance of this study is that arterial stiffness can be directly estimated from a noninvasively measured radial pressure wave.

Turbulence Calculations of a Dual-Structure Oxygen Lance for Converter Based on Hydrodynamics

The oxygen lance is a piece of special equipment in the converter steelmaking process for blowing oxygen into the molten steel. After more than 80 years of development, the structure and function of the oxygen lance have undergone many changes. In this paper, based on the theory of hydrodynamics, the jet behavior characteristics of a dual-structure oxygen lance for the converter are determined and optimized by CFD simulations and compared with those of the traditional-structure oxygen lance. The research results show that multiple jets deflect to the central axis of the oxygen lance during movement and the inclination angle of the nozzle holes influences the jet deflection. A decrease in the nozzle hole angle results in an increase in the mutual suction between the streams. With the increasing flow rate through the large holes in the new dual-structure oxygen lance, the dynamic radial pressure increases at the middle of the jet. The jet flow characteristics of the new dual-structure oxygen lance are better than those of the traditional oxygen lance. Its impact on the molten pool includes greater momentum, a larger impact area, and a more uniform and powerful stirring of the molten pool. A nozzle angle of 14° combined with a flow rate ratio of 65% and a nozzle angle of 17° combined with a flow rate ratio of 35% are the optimal parameters for the new dual-structure oxygen lance.

Nonlinear Postbuckling of Auxetic-Core Sandwich Toroidal Shell Segments with CNT-Reinforced Face Sheets Under External Pressure

Nonlinear buckling analysis for honeycomb auxetic-core sandwich toroidal shell segments with CNT-reinforced face sheets surrounded by elastic foundations under the radial pressure is presented in this study. The basic equation system of shells is established based on the von Kármán–Donnell nonlinear shell theory, combined with Stein and McElman approximation. Meanwhile, the foundation-shell elastic interaction is simulated by the foundation model based on the Pasternak assumption. The Galerkin procedure is utilized to achieve the pre-buckling and post-buckling responses for the shell, from which the radially critical buckling load is determined. Numerical analysis shows the various influences of auxetic-core layer, CNT-reinforced face sheets, and elastic foundation on the pre-buckling and postbuckling behavior of sandwich shells with CNT reinforced face sheets.