Change in hydraulic resistance of water supply pipes being renovated with polyethylene pipes

Przeprowadzono analizę wpływu renowacji starych przewodów sieci wodociągowej na wartość oporów hydraulicznych. Rozważaniom poddano bezwykopową technologię renowacji i rekonstrukcji rurociągów metodą reliningu z zastosowaniem rur z polietylenu o mniejszej średnicy zewnętrznej od średnicy wewnętrznej przewodu poddanego renowacji. Przeprowadzono analizę hydrauliczną wpływu wartości współczynnika chropowatości na wartość współczynnika oporów liniowych, a także na przepuszczalność hydrauliczną przewodów o różnej średnicy wewnętrznej wykonanych z żeliwa i polietylenu. Wykazano, że wartość współczynnika chropowatości ma wpływ na wysokość strat ciśnienia odwrotnie proporcjonalnie do średnicy wewnętrznej przewodu. Na podstawie przeprowadzonych analiz oszacowano graniczną średnicę wynoszącą DN=800 mm jako tę, w przypadku której zmiana współczynnika chropowatości, przy zmniejszonej średnicy wewnętrznej przewodu, może prowadzić do wymiernych korzyści renowacji pod względem hydraulicznym.Effect of the existing water supply pipe renovation on hydraulic resistance was analyzed. Trenchless relining method of pipe renovation and reconstruction was considered, using polyethylene (PE) pipes of smaller outside diameter than the inside diameter of a renovated pipe. Hydraulic analysis was carried out of roughness coefficient influence on linear friction factor as well as on hydraulic conveyance of pipes of various inside diameters, made of cast iron and polyethylene. Roughness (k) was demonstrated to affect the head loss inversely proportionally to the inside diameter of the pipe. On the basis of the conducted analysis, an approximate threshold diameter DN=800 mm was estimated for which change in roughness (k), at the reduced inside pipe diameter, may lead to measurable hydraulic benefits of renovation

Optimal Estimators Of The Position Of A Mass Extinction When Recovery Potential Is Uniform

Numerous methods have been developed to estimate the position of a mass extinction boundary while accounting for the incompleteness of the fossil record. Here we describe the point estimator and confidence interval for the extinction that are optimal under the assumption of uniform preservation and recovery potential, and independence among taxa. First, one should pool the data from all taxa into one combined supersample. Next, one can then apply methods proposed by Strauss and Sadler (1989) for a single taxon. This gives the optimal point estimator in the sense that it has the smallest variance among all possible unbiased estimators. The corresponding confidence interval is optimal in the sense that it has the shortest average width among all possible intervals that are invariant to measurement scale. These optimality properties hold even among methods that have not yet been discovered. Using simulations, we show that the optimal estimators substantially improve upon the performance of other existing methods. Because the assumptions of uniform recovery and independence among taxa are strong ones, it is important to assess to what extent they are satisfied by the data. We demonstrate the use of probability plots for this purpose. Finally, we use simulations to explore the sensitivity of the optimal point estimator and confidence interval to nonuniformity and lack of independence, and we compare their performance under these conditions with existing methods. We find that nonuniformity strongly biases the point estimators for all methods studied, inflates their standard errors, and degrades the coverage probabilities of confidence intervals. Lack of independence has less effect on the accuracy of point estimates as long as recovery potential is uniform, but it, too, inflates the standard errors and degrades confidence interval coverage probabilities

Heavy metal content of water exposed to cement lining in the water pipe

Mechanizm wymywania z cementu toksycznych metali ciężkich nie został jeszcze dokładnie rozpoznany. Istnieje wiele czynników mających wpływ na ten proces, jak np. jakość przepływającej wody, a zwłaszcza jej pH, zasadowość, temperatura, zawartość chloru itp. Wpływ mają także skład i mikrostruktura wykładziny cementowej rur wodociągowych. W badaniach modelowych określono zawartość wybranych metali ciężkich (ICP-OES, ICP-MS) w wodzie przed i po 6-miesięcznym czasie eksploatacji rurociągu z żeliwa sferoidalnego z wykładziną cementową. Stwierdzono, że zawartość pierwiastków śladowych (Ba, Fe, K, Ni, Mg, Na, Sr, Zn, V, Cd, Pb, Mn, Cu i As) w wodzie kontaktującej się zarówno z nową wykładziną cementową, jak i po 6-miesięcznej eksploatacji przewodu była niewielka, w większości przypadków poniżej progu detekcji (ICP-OES). Badania strukturalne wykładziny cementowej wykonane za pomocą skaningowej mikroskopii elektronowej wykazały, że cienka warstewka kalcytowa pokrywająca zaczyn cementowy na wewnętrznej powierzchni rury bardzo szybko uległa zniszczeniu, jednakże jej skład chemiczny nie uległ zmianie po 6-miesięcznej eksploatacji układu badawczego. W miejscach zniszczenia wykładziny cementowej stwierdzono obecność znacznej liczby igiełek ettringitu, świadczących o rozpoczynającej się korozji betonu.The mechanism governing the release of toxic heavy metals from cement is still far from being well understood. The process is influenced by a diversity of factors such as the quality of the water flowing in the pipes (especially its pH, alkalinity, temperature and chlorine content), or the composition and microstructure of the internal lining applied. This paper reports on model investigations into the presence of selected heavy metals (determined by ICP-OES and ICP-MS) in the water before and after 6-month service. It has been found that in the majority of instances the trace element content (Ba, Fe, K, Ni, Mg, Na, Sr, Zn, V, Cd, Pb, Mn, Cu and As) was below the detection threshold (ICP-OES), regardless of whether the water was exposed to a fresh lining or after six months of service. Structural examinations of the cement lining by scanning electron microscopy (SEM) have produced the following findings: the thin calcite layer covering the cement paste on the internal surface of the pipe was destroyed within a very short time, the chemical composition of the layer, however, remained unchanged after 6-month service of the pipe being tested. At the points of cement lining destruction a large number of ettringite needles was detected, which is indicative of the onset of concrete corrosion

Data from: Adaptive credible intervals on stratigraphic ranges when recovery potential is unknown

Numerous methods exist for estimating the true stratigraphic range of a fossil taxon based on the stratigraphic positions of its fossil occurrences. Many of these methods require the assumption of uniform fossil recovery potential—that fossils are equally likely to be found at any point within the taxon's true range. This assumption is unrealistic, because factors such as stratigraphic architecture, sampling effort, and the taxon's abundance and geographic range affect recovery potential. Other methods do not make this assumption, but they instead require a priori quantitative knowledge of recovery potential that may be difficult to obtain. We present a new Bayesian method, the Adaptive Beta method, for estimating the true stratigraphic range of a taxon that works for both uniform and non-uniform recovery potential. In contrast to existing methods, we explicitly estimate recovery potential from the positions of the occurrences themselves, so that a priori knowledge of recovery potential is not required. Using simulated datasets, we compare the performance of our method with existing methods. We show that the Adaptive Beta method performs well in that it achieves or nearly achieves nominal coverage probabilities and provides reasonable point estimates of the true extinction in a variety of situations. We demonstrate the method using a dataset of the Cambrian mollusc Anabarella

Version of Fig. 6 accessible to color-deficient readers

Black and white version of Figure 6

R code

R code for Adaptive Beta Method (v38.0

Version of Fig. 5 accessible to color-deficient readers

Black-and-white version of Figure 5

Adaptive Credible Intervals On Stratigraphic Ranges When Recovery Potential Is Unknown

Numerous methods exist for estimating the true stratigraphic range of a fossil taxon based on the stratigraphic positions of its fossil occurrences. Many of these methods require the assumption of uniform fossil recovery potential—that fossils are equally likely to be found at any point within the taxon\u27s true range. This assumption is unrealistic, because factors such as stratigraphic architecture, sampling effort, and the taxon\u27s abundance and geographic range affect recovery potential. Other methods do not make this assumption, but they instead require a priori quantitative knowledge of recovery potential that may be difficult to obtain. We present a new Bayesian method, the Adaptive Beta method, for estimating the true stratigraphic range of a taxon that works for both uniform and non-uniform recovery potential. In contrast to existing methods, we explicitly estimate recovery potential from the positions of the occurrences themselves, so that a priori knowledge of recovery potential is not required. Using simulated datasets, we compare the performance of our method with existing methods. We show that the Adaptive Beta method performs well in that it achieves or nearly achieves nominal coverage probabilities and provides reasonable point estimates of the true extinction in a variety of situations. We demonstrate the method using a dataset of the Cambrian mollusc Anabarella