Effect of close-fit sliplining on the hydraulic capacity of a pressurized pipeline

A full-scale laboratory testing setup was used to examine the flow conditions through a new steel pipe with relatively smooth interior (no tubercles, encrustations, holes, scales, etc.) before and after sliplining with a high density polyethylene (HDPE) liner. Results of the tests indicate that the relative roughness of the lined pipe section was generally lower than that of the new steel pipe at Reynolds Numbers of 200,000 to 500,000. The average friction factor (Swamee–Jain) for the lined pipe was 0.0180 compared to 0.0185 for the original steel pipe. The minimum and maximum friction coefficients were 0.0146 and 0.0208 for the lined pipe and 0.0148 and 0.0241 for the new steel pipe, respectively. This indicates that a deteriorated pipe with significant roughness could be restored back to its original condition using close-fit sliplining. Meanwhile, installation of the 6.35 mm (1/4 in.) thick liner in the 152.4 mm (6 in.) pipe reduced its cross-sectional flow area by about 16% and, accordingly, would decrease the flow by about 20% under the same head loss. To further explore this condition, two design parameters, the liner thickness and its buckling resistance, were examined analytically using a practical application of 152.4 mm (6 in.) pipeline with an internal negative pressure due to a water hammer. Results of the analysis indicate that a 3.4 mm (1/8 in.) thick HDPE liner with average quality installation would provide about 100 kPa ( 10 m or 33 ft water column) of buckling resistance, but would also reduce the flow capacity by about 12.7%. While the laboratory tests were only performed on one type of liner material (i.e., HDPE), the general concepts and findings of this study would apply to other types of polymeric liners.     

Magnetic resonance imaging-compatible posterior cervical implant for occipitocervical stabilization. Technical note

Posterior cervical stabilization was accomplished in 30 patients (19 females and 11 males) by using sublaminar titanium cables and a new titanium bullet-shaped implant. Seventeen patients underwent occipitocervical fixation and 13 others were treated subaxially. These patients have been followed for 18 to 52 months (mean 36 months), and no implant has failed during the follow-up period.     

Superconducting energy storage technology-based synthetic inertia system control to enhance frequency dynamic performance in microgrids with high renewable penetration

With high penetration of renewable energy sources (RESs) in modern power systems, system frequency becomes more prone to fluctuation as RESs do not naturally have inertial properties. A conventional energy storage system (ESS) based on a battery has been used to tackle the shortage in system inertia but has low and short-term power support during the disturbance. To address the issues, this paper proposes a new synthetic inertia control (SIC) design with a superconducting magnetic energy storage (SMES) system to mimic the necessary inertia power and damping properties in a short time and thereby regulate the microgrid (µG) frequency during disturbances. In addition, system frequency deviation is reduced by employing the proportional-integral (PI) controller with the proposed SIC system. The efficacy of the proposed SIC system is validated by comparison with the conventional ESS and SMES systems without using the PI controller, under various load/renewable perturbations, nonlinearities, and uncertainties. The simulation results highlight that the proposed system with SMES can efficiently manage several disturbances and high system uncertainty compared to the conventional ESS and SMES systems, without using the PI controller.     

Study for Corrosion and Hydrogen Evolution Behavior of Ti-6Al-4V Alloy in Simulated Acid Rain Water

The electrochemical behavior of Ti-6Al-4V alloy was investigated using electrochemical impedance spectroscopy (EIS) measurements at the open circuit potentials and potentiodynamic polarization measurements in a simulated acid rain containing inorganic additives. The ac circuit model for Ti-6Al-4V alloy at corrosion interface in simulated acid rain containing inorganic additives was proposed, which was based on two time constants equivalent circuit. Ti-6Al-4V alloy in a simulated acid rain of pH 1.5 containing inorganic additives showed a characteristic of a capacitive behavior. The effect of different concentrations of the inorganic additives (iodate, dichromate, phosphate, and nitrate) on the corrosion of the alloy in acid rain water (ARW) was also studied. It was found that the corrosion rate decreases drastically in the solution containing iodate, dichromate, and phosphate anions; however, nitrate anions increase the corrosion rate of the alloy. The investigated inorganic additives had inhibiting effect on the corrosion of the alloy in ARW, and their efficiency decreases according to the order: iodate > dichromate > phosphate > blank > nitrate. Polarization data results are in good agreement with EIS.     

Effect of silicon alloying addition on the corrosion behaviour of aluminium in some aqueous media

The corrosion behaviour of three Al–Si alloys was studied after galvanostatic passivation in 0.1 M sodium tartrate, sulfate and borate solutions using EIS techniques. The degree of passivation depends on the anion type, the degree of polarization and the alloy composition. It was also found that increase in pH led to a decrease in polarization resistance R _p. The effect of formation voltage, V _f, on the growth and dissolution kinetics of the oxide grown on the alloys was studied. The polarization resistance value increases as V _f increases up to a certain value; above this the R _p value decreases. This critical V _f depends on the alloy composition and the test solution. The kinetics of oxide layer dissolution in the absence and presence of Cl^– ions was also studied. Increase in immersion time leads to a more severe attack by Cl^– ions as shown by the decrease in the value of R _p. At low Cl^– ion concentration the value of R _p is higher than that in chloride ion free sulfate solutions, because the rate of passive film repair is much higher than that of barrier layer dissolution. However, at high Cl^– ion concentration penetration of Cl^– through defects in the barrier layer leads to formation of an oxyhalide layer.     

Theoretical Verification of Existing Solutions on Lateral Loading of Masonry Infill Walls

The present contribution is the first part of a research work aimed to check the infill masonry walls according to the new German wind code. An assessment for the existing design methods of masonry walls under lateral loading has been performed based on definition of the upper bound values of moment bending coefficients. The assumption of orthotropic brittle failure has been adopted to define failure criterion in terms of the bending moments. The failure criterion implemented into ANSYS to produce moment coefficients following this method. The characteristics of the function of bending moment coefficient are defined to be used in the assessment of existing solutions. To overcome the shortcomings in the application of yield line method on masonry, modifications have been introduced based on the length of the first crack. The moment coefficient values from different sources have been compared with the proposed methods. The differences and similarities between the results have been explained. Theoretische Beurteilung von Lösungsansätzen zu Ausfachungswänden unter Plattenbeanspruchung. Der Beitrag ist der erste Teil einer Forschungsarbeit, die darauf abzielt, Ausfachungswände ent sprechend der neuen deutschen Windnorm zu überprüfen. Dabei ist eine Einschätzung der vorhandenen Bemessungsmethoden von Mauerwerkswänden unter Plattenbeanspruchung, basierend auf der Definition eines oberen Grenzwertes des Koeffizienten zur Berechnung des Biegemomentes, durchgeführt worden. Um eine Beurteilung im Hinblick auf die Biegemomente definieren zu können, wurde ein sprödes Versagen in senkrechter Richtung angenommen. Das hier zur Bestimmung der Momentkoeffizienten in der Software ANSYS implementierte Kriterium berücksichtigt dieses Versagen. Die Eigenschaften des Kurvenverlaufes des Biegemomentkoeffizienten werden definiert und bei der Beurteilung von vorhandenen Lösungen verwendet. Um die Defizite im Zusammenhang mit der Bruchlinientheorie von Mauerwerk zu überwinden, sind Modifizierungen basierend auf der Berücksichtigung der Länge eines Erstrisses eingeführt worden. Die Werte der Momentkoeffizienten aus unterschiedlichen Quellen wurden mit dem vorgeschlagenen Vorgehen verglichen sowie die Unterschiede und Ähnlichkeiten zwischen den Ergebnissen erläutert.     

Arching effect in case of exterior walls with low surcharge under wind action / Ausbildung der Bogentragwirkung bei Außenwänden mit geringer Auflast unter Windbeanspruchung

It is very important to have a minimum surcharge on external masonry walls to help the wall resisting wind actions. The present contribution describes the behaviour of masonry wall under wind action with low surcharge. The behaviour has been investigated using a finite element non‐linear model that considers the large displacement non‐linearity. An increasingly wind load has been applied and the deformation state and the thrust line within the wall have been investigated. The results of the analysis show that the behaviour of the wall under low surcharge was greatly characterized by the arching effect. Due to the low surcharge the influence of the second order effect was very small and can be neglected.     

Corrosion and impedance studies on magnesium alloy in oxalate solution

Corrosion behavior of AZ91E alloy was investigated in oxalate solution using potentiodynamic polarization and electrochemical impedance measurements (EIS). The effect of oxalate concentration was studied, where the corrosion rate increases with increasing oxalate concentration. The effect of added ions (Br⁻, Cl⁻ or SiO₃²⁻) on the electrochemical behavior of magnesium alloy in 0.1 M Na₂C₂O₄ solution at 298 K, was investigated. It was found that the corrosion rate of 0.1 M oxalate solution containing silicate ion is lower than the blank (0.1 M Na₂C₂O₄). This was confirmed by scanning electron microscope (SEM) observations. However, for the other added ions Br⁻ or Cl⁻, the corrosion rate is higher than the blank.