A new automatic measurement system for high-speed railway substructure settlement based on hydrostatic pressure difference levelling

Exact settlement measurement of substructures plays an important role in their status detection throughout all-life-cycle of high-speed railway. A Hydrostatic Pressure Difference Levelling system (HPDL) is developed based on the mechanism that pressures of any two points at different elevations in incompressible static liquid are different. The approach accounts for a hyperbolic variation in the density of the pressure transmission liquid with temperature, variation in the earth’s gravitational field and the elevation at the measurement point. High accuracy capacitive differential pressure transmitters are adopted owing to their high sensitivity, temperature-insensitive, low energy consumption, and sensing stability. The HPDL results are verified with settlement values measured by the precise level. It was demonstrated that the HPDL results correlate well with the precise level and can be considered as an effective method to measure the settlement of high-speed railway substructures.

Free Surface of the Liquid-Gas Phase Separation as a Measuring Membrane of a Device for Measuring Small Hydrostatic Pressure Difference Values / Powierzchnia Swobodna Rozdziału Faz Ciecz-Gaz Jako Membrana Pomiarowa Urządzenia Do Pomiaru Małych Wartości Różnicy Ciśnienia Hydrostatycznego

To obtain a correct reading of fluid flow through a porous medium, it is necessary to know the pressure distribution. While in the case of large Reynolds numbers (turbulent flows) finding pressure measurement devices on the market is not a major problem, there are currently no available devices with sufficient accuracy for measurement of laminar flows (i.e. for Re numbers (Bear, 1988; Duckworth, 1983; Troskolański, 1957) in the range from 0.01 to 3). The reasons of this situation has been discussed in a previous articles (Broda & Filipek, 2012, 2013). Therefore, most of the work on this issue relates to testing velocity distribution of the filter medium (Bear, 1988) or pressure distribution at high hydraulic gradient levels (Trzaska & Broda, 1991, 2000; Trzaska et al., 2005). The so-called measurements of the lower limit of the applicability of Darcy’s law for liquid, as well as determining a threshold hydraulic gradient J0 (Bear, 1988) tend to cause especially great difficulty. Such measurements would be particularly important application in determining the infiltration of water into the mine workings, filtering through the foundations of buildings, etc. For several years, the authors (Broda & Filipek, 2012, 2013) have been engaged in the development of methods and measuring instruments (patent applications: P.407 380 and P.407 381), which would allow for measurement of hydrostatic pressure (differences) below 1 Pa. In the course of research, a new concept of methodology for measuring low values of hydrostatic pressure differences was developed, which is the subject of this article. This article seeks to introduce a new concept of using the free surface of liquid-gas separation as the measuring membrane of a device used in measurement of small values of hydrostatic pressure. The focus is mainly on the possibility of building such a device - describing the technical difficulties that occurred during the execution of the idea. Consequently, less attention was paid to the broader considerations related to uncertainty of the proposed method’s measurements, due to the authors’ awareness that this is the first prototype of such a device and, on the basis of this experience, another one will be built and tested. The observations and numerical analysis of the image formed on the screen by the passage of a laser beam through the free surface of the liquid-gas separation show that at low values of pressure difference, the bubble acts as a membrane shifting in the direction of lower pressure, in such way that the displacement is proportional to the pressure difference at both ends of the bubble. The proprietary method of numerical data processing presented in this article, based on analysis of the intensity of color change in a frame moving along a selected line outside of visual changes in the image of the laser beam after passing through the test structure, provided a tool to create first mathematical models to describe the observed changes (2),(3). Presented in this article method of measuring the difference between the free surface levels in two containers, and hence the measurement of hydrostatic pressure difference provides a new tool for laboratory measurements in the fields of science, which were previously unattainable.

Droplet Detachment Mechanism in a High-Speed Gaseous Microflow

This paper experimentally investigates the mechanism of water droplet detachment in a confined microchannel under highly inertial (10 < Re < 200) air flow conditions. Experimental observations show that as the Reynolds number of the continuous phase is increased, the droplet transitions from an elongated slug to a nearly uniform aspect ratio droplet. Supporting scaling arguments are then made that examine the relevant forces induced by the continuous phase on the droplet at the point of detachment. The inertial, viscous, and hydrodynamic pressure forces that result as the air flow is confined in the small gap between droplet and channel walls are compared to the surface tension force pinning the droplet at the injection site. The results indicate that the dominant detachment mechanism transitions from the hydrostatic pressure difference to inertial drag as the continuous phase velocity is increased.

TRANSMURAL PRESSURE THROUGHOUT A PRE-STRESSED HOLLOW CONDUIT WHEN SUBMITTED TO COMBINED LARGE SOLID DEFORMATIONS

In the human body, water passes continuously from the bloodstream across the walls of the blood vessels to the regional lymphatic as a result of a hydrostatic pressure difference. Then, as an illustrative example, our model involves application of a transmural pressure and the resulting transmural filtration of fluid through a pre-strained hollow cylinder subjected to combined finite deformations. Some results that can provide additional useful insight can help in improving the method for performing prosthesis conduit material for use with living tissue, understanding problems which involves the diffusion of fluid-saturated wall for various mechanical parameters such as the pre-stress/strain, the material parameters ratio and applied or induced twist angle are discussed.

There Is No Transmantle Pressure Gradient in Communicating or Noncommunicating Hydrocephalus

OBJECTIVE: To examine whether a transmantle pressure gradient exists in adult patients with communicating and noncommunicating hydrocephalus. METHODS: Ten patients participated in the study. The mean patient age was 57 ± 18 years (range, 20–80 yr); seven patients had communicating hydrocephalus, and three had noncommunicating hydrocephalus. Microsensors were used to measure the intracranial pressure (ICP), for 17 to 24 hours during sleeping and waking periods, in the right lateral ventricle (ICPIV) and in the subarachnoid space (ICPSAS) over the right cerebral convexity simultaneously. Patient activities and body positions were documented. The hydrostatic pressure difference between the two sensors was calculated from cranial x-rays for four basic body positions and compared with the actual body positions of the patients and the measured difference between the two sensors. For three 10-minute periods, the exact transmantle pressure gradient was calculated for each patient as ICPIV − ICPSAS, adjusted for the hydrostatic pressure difference. RESULTS: The measured pressure difference between the two sensors was always within the limits of the maximal possible hydrostatic pressure difference, and it correlated well with the expected difference for the various body positions: mean correlation coefficient, 0.79 ± 0.10 (range, 0.65–0.92). The exact mean transmantle pressure was −0.01 ± 0.24 mm Hg (range, −0.4 to 0.4 mm Hg). ICP waves caused by cardiac pulse, respiration, and B waves were identical in both spaces. CONCLUSION: This study demonstrates no factual support for existence of a transmantle pressure gradient in nonacute communicating or noncommunicating hydrocephalus.

Renal adrenergic effector mechanisms: glomerular sites for prostaglandin interaction

Micropuncture experiments were performed in Munich-Wistar rats to ascertain the renal microcirculatory sites at which prostaglandins interact with the renal nerve and angiotensin II. Renal nerve stimulation (RNS) of 3 Hz alone decreased single-nephron glomerular filtration rate (SNGFR) by 30%, the consequence of 10 and 35% reductions in the glomerular capillary hydrostatic pressure difference (delta P) and the single-nephron plasma flow (SNPF), respectively. Pre- and postglomerular vascular resistances increased. RNS during prostaglandin inhibition (indomethacin) resulted in a 70% reduction in SNGFR, secondary to 1) a further diminution in delta P and in SNPF, via heightened pre- and postglomerular vasoconstriction and 2) a marked decline in the glomerular ultrafiltration coefficient (LpA), from 0.058 +/- 0.006 to 0.027 +/- 0.002 nl.s-1.mmHg-1.g kidney wt-1 (P less than 0.005). Acute angiotensin II inhibition (MK-421 and [Sar1,Ala8]angiotensin II) in rats pretreated with indomethacin partially attenuated the effects of RNS on vascular resistances and therefore on delta P, SNPF, and SNGFR and prevented the reduction in LpA. Thus vasodilatory prostaglandins act as local modulators of both renal nerve and angiotensin II constrictive actions on glomeruli and renal microcirculation.

Applied pressures and net water flux across in vitro frog gastric mucosa.

The effects of hydrostatic pressure differences up to 0.4 atm/413 cmH2O were studied on frog gastric mucosa in vitro. Net water flux, transmucosal electrical potential difference, and acid secretion were measured. A significant correlation between hydrostatistic pressure difference and net water flow (r=0.77) was obtained. The intercept of the regression line, at zero hydrostatic pressure difference, is 9.3 +/- 0.5 microliter/cm2.h, and the slope 42.9 +/- 3.2 microliter/cm2.atm.h. No significant correlation was obtained between the hydrostatic pressure difference and the transmucosal potential difference (P greater than 0.20), the acid secretion (P greater than 0.20), or the nonacidic chloride transport, measured as short-circuit current (P greater than 0.20). Hydrostatic water flux is compared to osmotically induced flux previously reported. It is proposed that the difference between hydrostatic and osmotic induced water fluxes is due to the area of cells exposed to the pressures. Only part of surface cells are directly exposed to the osmotic pressure due to the presence of restricted extracellular compartments.

PATHS OF TRANSTUBULAR WATER FLOW IN ISOLATED RENAL COLLECTING TUBULES

The cells of perfused rabbit collecting tubules swell and the intercellular spaces widen during osmotic flow of water from lumen to bath induced by antidiuretic hormone (ADH). Ouabain had no influence on these changes. In the absence of net water flow intercellular width was unaffected when tubules were swollen in hypotonic external media. Therefore, during ADH-induced flow widening of intercellular spaces is not a consequence of osmotic swelling of a closed intercellular compartment containing trapped solutes, but rather is due to flow of solution through the channel. Direct evidence of intercellular flow was obtained. Nonperfused tubules swollen in hypotonic media were reimmersed in isotonic solution with resultant entry of water into intercellular spaces. The widened spaces gradually collapsed completely. Spaces enlarged in this manner could be emptied more rapidly by increasing the transtubular hydrostatic pressure difference. In electron micrographs a path of exit of sufficient width to accommodate the observed rate of fluid flow was seen at the base of the intercellular channel. It is concluded that the intercellular spaces communicate with the external extracellular fluid and that water, having entered the cells across the luminal plasma membrane in response in ADH, leaves the cells by osmosis across both the lateral and basilar surface membranes.

Lithium-Induced Oscillations of Potential and Resistance in Isolated Frog Skin

The rhythmical variations of electrical potential and DC resistance resulting from the exposure of the anatomical outside of isolated frog skin to a concentration of lithium ion greater than 20 millinormal were reinvestigated. In general, the potential and resistance changes were in phase, although in some skins, a phase shift occurred after the first few waves. The mean level of the resistance declined during the exposure to lithium, returning to its former level upon reintroduction of sodium in place of lithium. The oscillations, with a period of from 3 to 15 minutes, could last for 2 hours or more before damping out; the amplitude of the waves could be altered during this time by the passage of direct current or by the introduction of a hydrostatic pressure difference across the skin. Even after the oscillations damped out, the system remained "excitable," responding to a step of direct current or hydrostatic pressure with an oscillatory train. The nature and magnitude of the response to current and pressure were dependent upon the "polarity" of the applied perturbation. Direct observation of the skin revealed no evidence of oscillatory water movement concomitant with the electrical events.