201 research outputs found
Congruences concerning Jacobi polynomials and Ap\'ery-like formulae
Let be a prime. We prove congruences modulo for sums of the
general form and
with . We also consider the
special case of the former sum, where the congruences hold
modulo .Comment: to appear in Int. J. Number Theor
Group method of data handling to predict scour depth around vertical piles under regular waves
AbstractThis paper presents a new application of the Group Method Of Data Handling (GMDH), to predict pile scour depth exposed to waves. The GMDH network was developed using the Levenberg–Marquardt (LM) method in the training stage for scour prediction. Scour depth due to regular waves was modeled as a function of five dimensionless parameters, including pile Reynolds number, grain Reynolds number, sediment number, Keulegan–Carpenter number, and shields parameter. The testing results of the GMDH-LM were compared with those obtained using the Adaptive Neuro-Fuzzy Inference System (ANFIS), Radial Basis Function-Neural Network (RBF-NN), and empirical equations. In particular, the GMDH-LM provided the most accurate prediction of scour depth compared to other models. Also, the Keulegan–Carpenter number has been determined as the most effective parameter on scour depth through a sensitivity analysis. The GMDH-LM was utilized successfully to investigate the influence of the pile cross section and Keulegan–Carpenter number on scour depth
Paleoearthquakes and slip rates of the North Tabriz Fault, NW Iran: preliminary results
The North Tabriz Fault is a major seismogenic fault in NW Iran. The last damaging earthquakes on this fault
occurred in 1721, rupturing the southeastern fault segment, and in 1780, rupturing the northwestern one. The
understanding of the seismic behavior of this fault is critical for assessing the hazard in Tabriz, one of the major
cities of Iran; the city suffered major damage in both the 1721 and 1780 events. Our study area is located on the
northwestern fault segment, west of the city of Tabriz. We performed geomorphic and trenching investigations,
which allowed us to recognize evidence for repeated faulting events since the Late Pleistocene. From the trenches,
we found evidence for at least four events during the past 3.6 ka, the most recent one being the 1780 earthquake.
On the basis of different approaches, horizontal slip per event and slip rates are found in the ranges of 4 ± 0.5 m
and 3.1-6.4 mm/yr, respectively. We also attempted an estimate of the average recurrence intervals which appears
to be in the range 350-1430 years, with a mean recurrence interval of 821 ± 176 years. On the basis of these results,
the northwestern segment of the North Tabriz Fault does not appear to present a major seismic potential for
the near future, however, not enough is known about the southeastern segment of the fault to make a comparable
conclusion
Paleoearthquakes and slip rates of the North Tabriz Fault, NW Iran: preliminary results
The North Tabriz Fault is a major seismogenic fault in NW Iran. The last damaging earthquakes on this fault occurred in 1721, rupturing the southeastern fault segment, and in 1780, rupturing the northwestern one. The understanding of the seismic behavior of this fault is critical for assessing the hazard in Tabriz, one of the major cities of Iran; the city suffered major damage in both the 1721 and 1780 events. Our study area is located on the northwestern fault segment, west of the city of Tabriz. We performed geomorphic and trenching investigations, which allowed us to recognize evidence for repeated faulting events since the Late Pleistocene. From the trenches, we found evidence for at least four events during the past 3.6 ka, the most recent one being the 1780 earthquake. On the basis of different approaches, horizontal slip per event and slip rates are found in the ranges of 4 ± 0.5 m and 3.1-6.4 mm/yr, respectively. We also attempted an estimate of the average recurrence intervals which appears to be in the range 350-1430 years, with a mean recurrence interval of 821 ± 176 years. On the basis of these results, the northwestern segment of the North Tabriz Fault does not appear to present a major seismic potential for the near future, however, not enough is known about the southeastern segment of the fault to make a comparable conclusion
Bacterial colonisation of collagen-coated polypropylene vaginal mesh: are additional intraoperative sterility procedures useful?
Air pollution perception in ten countries during the COVID-19 pandemic
As largely documented in the literature, the stark restrictions enforced worldwide in 2020 to curb the COVID-19 pandemic also curtailed the production of air pollutants to some extent. This study investigates the perception of the air pollution as assessed by individuals located in ten countries: Australia, Brazil, China, Ghana, India, Iran, Italy, Norway, South Africa and the USA. The perceptions towards air quality were evaluated by employing an online survey administered in May 2020. Participants (N = 9394) in the ten countries expressed their opinions according to a Likert-scale response. A reduction in pollutant concentration was clearly perceived, albeit to a different extent, by all populations. The survey participants located in India and Italy perceived the largest drop in the air pollution concentration; conversely, the smallest variation was perceived among Chinese and Norwegian respondents. Among all the demographic indicators considered, only gender proved to be statistically significant
Electoral Competition and Endogenous Political Institutions: Quasi-Experimental Evidence from Germany
Overlapping political budget cycle
We advance the literature on political budget cycles by testing for cycles in expenditures for elections to the legislative and the executive branches. Using municipal data, we identify cycles independently for the two branches, evaluate the effects of overlaps, and account for general year effects. We find sizable effects on expenditures before legislative elections and even larger effects before joint elections to the legislature and the office of mayor. In the case of coincident elections, we show that it is important whether the incumbent chief executive seeks reelection. To account for the potential endogeneity of that decision, we apply an IV approach using age and pension eligibility rules
Reliability, risk and lifetime distributions as performance indicators for life-cycle maintenance of deteriorating structures
This is the author’s version of a work that was accepted for publication in Reliability Engineering & System Safety. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ress.2013.09.013Structural capacity deterioration is among the main causes of increasing failure probabilities
of structural systems, thus maintenance interventions are a crucial task for their rational
management. Several probabilistic approaches have been proposed during the last decades for
the determination of cost-effective maintenance strategies based on selected performance
indicators. However, benefits and drawbacks of each performance indicator with respect to
the others should be further analyzed. The objective of this paper is to investigate
probabilistic approaches based on the annual reliability index, annual risk, and lifetime
distributions for life-cycle maintenance of structural systems. Maintenance schedules are
obtained for representative series, parallel, and series-parallel systems considering total
restoration of component resistances whenever a prescribed threshold, based on a selected
performance indicator, is reached. Effects related to different structural configurations and
correlation among failure modes are investigated. The superstructure of an existing bridge is
used to illustrate the presented approaches
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