Interdependence of flow and pipe characteristics in transient induced contamination intrusion: numerical analysis

Abstract Contaminant intrusion in pipelines during transients is a remarkable mechanism, which leads to a decline in the quality of the contained water. The negative pressure of water hammer pressure waves is the trigger for the suction of pollution from the surrounding leak area, and hence deteriorating water quality. The volume of contamination intruded into the pipeline is investigated using mathematical and numerical modeling of the phenomenon. To elucidate this phenomenon in real pipe systems, the intrusion amount is estimated for 72 different scenarios including: two lengths of pipeline (i.e. short and long), three different leak locations, three different fluid velocities in the pipe, two leak diameters and two pipeline materials (elastic and viscoelastic). The results showed that the amount of intrusion in viscoelastic pipes was clearly less than that in elastic pipes, especially in long pipelines. The critical zone of high intrusion risk is identified close to the downstream valve for small leak sizes, nevertheless, it is difficult to estimate this zone in the case of large leaks due to significant interactions between nodal components (valve, leak, reservoir)

Comparison between doxycycline–rifampin–amikacin and doxycycline–rifampin regimens in the treatment of brucellosis

SummaryBackgroundCombination drug therapy of brucellosis leads to recovery of symptoms, shortening of symptomatic interval, and decrease in morbidity rate, but single drug therapy is associated with more relapse episodes and a higher rate of drug resistance. Different drug combinations have been evaluated in the treatment of brucellosis. Considering the failure of treatment and relatively high rate of relapse of the disease with the World Health Organization's (WHO) recommended therapeutic regimen, we evaluated a new regimen that we assumed would increase the success of treatment and decrease the rate of relapse. In this study we compare the standard regimen of the WHO, doxycycline–rifampin (DR), to triple therapy with doxycycline–rifampin–amikacin (ADR).MethodsTwo hundred and twenty-eight consecutive patients with brucellosis, who attended Hamedan Sina Hospital between 1999 and 2001, whether seen as outpatients or as inpatients, were enrolled in the study. The participants were randomly allocated to the DR group (receiving doxycycline 100mg twice a day and rifampin 10mg/kg body weight/day every morning, both taken orally for eight weeks) or the ADR group (receiving doxycycline 100mg twice a day and rifampin 10mg/kg body weight/day every morning, both taken orally for eight weeks, plus 7.5mg/kg amikacin intramuscularly twice a day for seven days). The patients were checked for the relief of symptoms, drug side-effects, and relapse of disease during the treatment and follow-up.ResultsOf the 228 patients enrolled, eight were withdrawn – four patients from the DR group and four from the ADR group. Of the remaining 220 participants (110 in the ADR group and 110 in the DR group), 107 were male (48.6%) and 113 were female (51.4%). Mean age was 35.7±17 years in the ADR group and 37±18.4 years in the DR group (p=0.5). In the DR group, 97 (88.2%) and in the ADR group, 106 (96.4%) of the patients had relief of symptoms (a significant difference by Chi-square test (p=0.04)). After completion of treatment, and at the sixth month follow-up, nine (9.3%) patients in the DR group and six (5.7%) in the ADR group experienced a relapse of the disease, with no significant difference (p=0.4). Mild side-effects were found in only 10 patients, and none required discontinuation of the therapeutic regimen. Of these patients, four were from DR group and six from ADR group; no significant difference was observed (p=0.7).ConclusionsGiven the fact that the ADR regimen had a higher efficacy and more rapid action in terms of relief of symptoms compared to the DR regimen, and that no significant difference in drug side-effects and disease relapse existed in the patients of either group, adding amikacin to the DR standard treatment regimen seems beneficial

A Study on Drying Kinetics of Rhubarb Medical Plant by an Infrared Dryer

Rhubarb is a mountain plant that contains many antioxidants and various vitamins, including A, B1, B2 and C, and is an extremely healthy product and a rich source of antioxidants and dietary fibers. Today, it is important to dry medicinal plants and agricultural products in order to achieve better product quality, so that minimal physical, chemical and biological changes made in the product. In this research, the drying kinetics of rhubarb medicinal plant with an infrared dryer conducted at three temperature levels of 50, 60, and 70 ℃ in the skin and without skin for 2 and 5 cm pieces of the product. By increasing the drying temperature and reducing the length of the parts and removing the skin of the samples, the drying speed and mass transfer increased and the drying time decreased. The values of activation energy ranged from 32.18 to 45.09 kJ/mol and the values of moisture diffusion coefficient ranged from 2.45 x 10-9 to 5.97 x 10-10 square meters per second. The overall color change of the product at all three temperatures was insignificant and the color of the rhubarb product changed little during the drying process. Using the intensity of low infrared radiations kept the color characteristics of rhubarb samples .Due to the low cost and high speed of drying, infrared dryer recommended as an economic method with high productivity for drying rhubarb medicinal plant

Fluid-structure interaction with pipe-wall viscoelasticity during water hammer

Fluid-structure interaction (FSI) due to water hammer in a pipeline which has viscoelastic wall behaviour is studied. Appropriate governing equations are derived and numerically solved. In the numerical implementation of the hydraulic and structural equations, viscoelasticity is incorporated using the Kelvin-Voigt mechanical model. The equations are solved by two different approaches, namely the Method of Characteristics - Finite Element Method (MOCFEM) and full MOC. In both approaches two important effects of FSI in fluid-filled pipes, namely Poisson and junction coupling, are taken into account. The study proposes a more comprehensive model for studying fluid transients in pipelines as compared to previous works, which take into account either FSI or viscoelasticity. To verify the proposed mathematical model and its numerical solutions, the following problems are investigated: axial vibration of a viscoelastic bar subjected to a step uniaxial loading, FSI in an elastic pipe, and hydraulic transients in a pressurized polyethylene pipe without FSI. The results of each case are checked with available exact and experimental results. Then, to study the simultaneous effects of FSI and viscoelasticity, which is the new element of the present research, one problem is solved by the two different numerical approaches. Both numerical methods give the same results, thus confirming the correctness of the solutions. Keywords: water hammer; fluid transient; pressure surge; fluid-structure interaction; pipe vibration; plastic pipe; viscoelasticit

INVERSE TRANSIENT ANALYSIS FOR PIPELINE LEAK DETECTION IN A NOISY ENVIRONMENT

International audienceIn the transient-based leak detection methods in the time domain, the solution parameter set is determined by minimizing an objective function that fits the numerically modeled pressures to measured pressures. If the measurement is contaminated with noise, then the optimum decision parameters may be some fictitious leaks whose computed pressure head is best matched to the noise not the reflections from leaks. This issue is explained in detail and then a different merit function to decline it, is suggested. It is based on maximizing the signal-to-noise ratio (SNR) which in literature usually termed as Matched Field Processing. This function is then compared with the conventional least square objective function and its efficiency subject to noise is assessed. It was found that the efficiency of each method mostly depends on the variance of noise and the system properties which may change from case to case. More specifically, the proposed merit function is more robust when its optimal variance is smaller than that of the least square cost function

Investigation of the Effects of Viscoelastic Support Properties Simulated by the Generalized Kelvin-Voigt Model on the Axial Vibration of a Rod

The application of Viscoelastic (VE) supports in order to dampening dynamic forces and energy dissipation has been investigated herein. Properties of viscoelastic substances are important in the quality and quantity of the dissipation. The viscoelastic materials were described using the generalized Kelvin-Voigt mechanical model and the resulting governing equations were solved using the finite element method in time domain. To investigate the effects of the viscoelastic characteristics of supprots on axial vibration, dynamic and quasi-steady analysis of a rod subject to axial step excitations was carried out. Finally, some important criteria were presented to improve the performance of these substances in energy dissipation. In addition, axial vibration of an elastic and a viscoelastic rod with end and middle VE supports subject to harmonic excitations were investigated. It reveals that the use of VE supports considerably damps out structural vibrations, especially at low frequencies. Whereas in high frequencies, the amount of the energy dissipation depends on the retardation times of the Kelvin-Voigt elements

Fluid-Structure Interaction in Transient-Based Extended Defect Detection of Pipe Walls

This paper investigates the effect of fluid-structure interaction (FSI) on the efficiency of transient-based reflections analysis (TBRA) applied to the detection of extended deteriorations in a reservoir-pipe-valve system. A waterhammer-with-FSI solver, based on the method of characteristics (MOC) and the finite-element method (FEM), is used and validated against available numerical and experimental results. Analytical expressions for the magnitudes of pressure reflections caused by FSI are derived. They tell how the system parameters affect FSI. The results obtained for the considered situation reveal that both pipe wall vibration (FSI) and pipe wall deteriorations may affect transient pressure in a similar, and possibly indistinguishable, way. Neglecting FSI in TBRA would skew the estimated locations, lengths, and numbers of the deteriorations in systems with considerable pipe wall axial vibration, thus making TBRA a more complicated method in flexible pipe systems

Correction the Bias of Odds Ratio resulting from the Misclassification of Exposures in the Study of Environmental Risk Factors of Lung Cancer using Bayesian Methods

Background & Objective: Inability to measure exact exposure in epidemiological studies is a common problem in many studies, especially cross-sectional studies. Depending on the extent of misclassification, results may be affected. Existing methods for solving this problem require a lot of time and money and it is not practical for some of the exposures. Recently, new methods have been proposed in 1:1 matched case–control studies that have solved these problems to some extent. In the present study we have aimed to extend the existing Bayesian method to adjust for misclassification in matched case–control Studies with 1:2 matching. Methods: Here, the standard Dirichlet prior distribution for a multinomial model was extended to allow the data of exposure–disease (OR) parameter to be imported into the model excluding other parameters. Information that exist in literature about association between exposure and disease were used as prior information about OR. In order to correct the misclassification Sensitivity Analysis was accomplished and the results were obtained under three Bayesian Methods. Results: The results of naïve Bayesian model were similar to the classic model. The second Bayesian model by employing prior information about the OR, was heavily affected by these information. The third proposed model provides maximum bias adjustment for the risk of heavy metals, smoking and drug abuse. This model showed that heavy metals are not an important risk factor although raw model (logistic regression Classic) detected this exposure as an influencing factor on the incidence of lung cancer. Sensitivity analysis showed that third model is robust regarding to different levels of Sensitivity and Specificity. Conclusion: The present study showed that although in most of exposures the results of the second and third model were similar but the proposed model would be able to correct the misclassification to some extent