Spatiotemporal Analysis of Droughts Over Different Climate Regions Using Hybrid Clustering Method

Assessment of spatiotemporal variations of drought is an efficient method for implementing drought mitigation strategies and reducing its negative impacts. This study aimed to assess the spatiotemporal pattern of short- to long-term droughts for an area with different climates. Therefore, 31 stations located in Iran were selected and the Standardized Precipitation Index (SPI) series with timescales of 3, 6, and 12 months were computed during the 1951-2016 period. A hybrid methodology including Maximal Overlap Discrete Wavelet Transform (MODWT) and K-means methods was used for obtaining the SPIs time-frequency properties and multiscale zoning of the area. The energy amounts of the decomposed subseries via the MODWT were applied as inputs for K-means. Also, the statistics in drought features (i.e. drought duration, severity, and peak) were assessed and the results showed that shorter term droughts (i.e. SPI-3 and -6) were more frequent and severe in the northern parts where the lowest values were obtained for drought duration. It was observed that the regions with more droughts frequency had the highest energy values. For shorter term droughts a direct relationship was obtained between the energy values and the mean SPIs, drought severity, and drought peak, whereas an inverse relationship was obtained for longer term drought. It was found that increasing the degree of SPI led to more similarity between the stations of each cluster. Also, the homogeneity of stations for the SPI-12 was slightly higher than the SPI-3 and -6.

     

Reinforcement learning for traffic light control with emphasis on emergency vehicles

The Journal of Supercomputing - Traffic lights are an important controlling factor in traffic flows, and good policies will facilitate traffic congestion. A car's waiting time is highly related...     

The effects of solvent and initiator on anionic ring opening polymerization of ϵ‐caprolactone: synthesis and characterization

Anionic ring opening polymerization of ?‐caprolactone was studied by using different amounts of two potassium activated initiators containing ethylene glycol (EG) and polyhedral oligomeric silsesquioxane (POSS) diol, in tetrahydrofuran and toluene as solvents. The synthesized hydroxyl terminated macromers and linear poly(?‐caprolactone) (PCL) were characterized by proton and carbon nuclear magnetic resonance and gel permeation chromatography (GPC) techniques. Results showed an increase in molecular weight as the monomer/initiator molar ratio increased from 100 to 151 and 202, while the molecular weight distribution (MWD) showed a minimum by monomer concentration increase. Moreover, POSS‐diol‐initiated PCLs showed a higher MWD than the polymers initiated with the EG initiator. This was attributed to the formation of a vesicular structure of POSS diols which was confirmed by optical microscopy. By deconvolution of GPC peaks, the best conditions to synthesize PCL with the narrowest MWD were selected. Finally, the effects of some other parameters were studied in more detail.     

Non-destructive ultrasonic evaluation of CFRP–concrete specimens subjected to accelerated aging conditions

The objective of this work is to utilize surface acoustic waves (SAWs) for non-destructive structural health monitoring of concrete specimens externally bonded with carbon fiber-reinforced polymer (CFRP) composites and subjected to accelerated aging conditions. Both experimental testing and signal processing schemes of ultrasonic wave propagation through the CFRP substrate are described. The surface waves are generated and received at the external face of the CFRP using narrow-band transducers with a 110-kHz center frequency. The received signals are filtered and amplified then digitized and processed to extract various parameters in both time and frequency domains including average power (P_Avg), maximum amplitude (V_max), and maximum power–frequency ratio ((P/F)_max). Changes in these parameters due to water-immersion aging at different temperatures were monitored over 12 weeks. Results indicated a marked decrease in measured ultrasonic parameters over time, particularly after the first 2 weeks, indicating a possible debonding or deterioration in the samples. Ultrasonic results showed good agreement with the findings of a parallel destructive study on mode-II fracture loading of CFRP–concrete samples, tested to obtain fracture energy (G_f) and define traction–separation response under temperature and water-immersion aging effects. It was observed that all ultrasonic parameters exhibit good correlations (|r|>0.5, P<0.05) with the fracture energy at all temperatures. Moreover, when the measurements at all temperatures were incorporated and linear relationships between destructive and non-destructive parameters were assumed, correlations of r=0.84, 0.80, and 0.80 were found between G_f and P_Avg, V_max, and (P/F)_max, respectively. This study paves the way for developing a non-destructive testing protocol for structural health monitoring of bridges and concrete structures undergoing repair and rehabilitation with CFRP composites.     

Properties of a hierarchical network based on the star graph

This paper introduces a new class of interconnection networks named star-pyramid. An n-level star-pyramid is formed by piling up star graphs of dimensions 1 to n in a hierarchy, connecting any node in each i-dimensional star, 1 < i ? n, to a node in the (i − 1)-dimensional star whose index is reached by removing the i symbol from the index of the former node in the i-dimensional star graph. Having extracted the properties of the new topology, featuring topological properties, a minimal routing algorithm, a simple but efficient broadcast algorithm, Hamiltonicity and pancyclicity, we then compare the network properties of the proposed topology and the well-known pyramid topology. We show that the star-pyramid has some more attractive properties than its equivalent pyramid. Finally, we propose two variants of star-pyramid, namely the generic star-pyramid and wrapped star-pyramid, as topologies with improved scalability, fault-tolerance, and diameter.     

Removal of toxic nitrate ions from drinking water using conducting polymer/MWCNTs nanocomposites

New application of conducting polymers as stable nanocomposites for nitrate ion exchange materials in water and wastewater treatment and for environmental protection is introduced in this work. The nanocomposites of multi-walled carbon nanotubes (MWCNTs) with different polymers such as: polyaniline (PANI), polypyrrole (PPY), poly(1,8-diaminonaphthalene) [P(1,8-DAN)] and poly(2-vinylpyridine) (P2VP) were synthesized with different dopants as effective and reusable nanocomposites for nitrate removal from drinking water. Nitrate anions at toxic concentrations were removed from water using ion exchange mechanism without any toxic byproducts. The obtained results demonstrate that effective ion exchange occurs between NO₃ ^? and Cl^?. There are some protonated heteroatoms in polymer chains that are bonded with anions of dopants and their counter ions in nanocomposites. These dopant anions on the =NH⁺– groups of polymers can be exchanged with NO₃ ^? in water. Adsorption of NO₃ ^? on polymer/MWCNTs nanocomposites showed dependency to some parameters. Different experimental parameters such as pH and temperature of the sample, polymers dopant, and the ratio of polymer to MWCNTs in nanocomposites affect the amount of nitrate removal. The highest removal efficiency was achieved at 1.20 g L^?1 of PANI/MWCNTs (3:1) nanocomposite, pH = 6.5 and ambient temperature. After five successive cycles of nitrate removal, this parameter was still up to 70 % compared to the first run (up to 80 %).     

Predictors of patients remaining anovulatory during clomiphene citrate induction of ovulation in normogonadotropic oligoamenorrheic infertility

The diagnostic criteria used to identify patients suffering from polycystic ovary syndrome remain controversial. The present prospective longitudinal follow-up study was designed to identify whether certain criteria assessed during standardized initial screening could predict the response to ovulation induction with clomiphene citrate (CC) in 201 patients presenting with oligomenorrhea or amenorrhea and infertility. Serum FSH levels were within the normal range (1-10 IU/L), and all patients underwent spontaneous or progestin-induced withdrawal bleeding. Initial CC doses were 50 mg daily for 5 days starting on cycle day 3. In the case of an absent response, doses were increased to 100 and 150 mg daily in subsequent cycles. First ovulation with CC was used as the end point. After a complete follow-up (in the case of a nonresponse, at least 3 treatment cycles with daily CC doses up to 150 mg), 156 patients (78%) ovulated. The free androgen index (FAI = testosterone/sex hormone-binding globulin ratio), body mass index (BMI), cycle history (oligomenorrhea vs. amenorrhea), serum androgen (testosterone and/or androstenedione) levels, and mean ovarian volume assessed by transvaginal sonography were all significantly different (P < 0.01) in responders from those in nonresponders. FAI was chosen to be the best predictor in univariate analysis. The area under the receiver operating characteristics curve in a multivariate prediction model including FAI, BMI, cycle history, and mean ovarian volume was 0.82. Patients whose ovaries are less likely to respond to stimulation by FSH due to CC treatment can be predicted on the basis of initial screening characteristics, such as FAI, BMI, cycle history (oligomenorrhea or amenorrhea), and mean ovarian volume. These observations may add to ongoing discussion regarding etiological factors involved in ovarian dysfunction in these patients and classification of normogonadotropic anovulatory infertile women.     

Preparation and evaluation of novel nano-bioglass/gelatin conduit for peripheral nerve regeneration

Peripheral nerves are exposed to physical injuries usually caused by trauma that may lead to a significant loss of sensory or motor functions and is considered as a serious health problem for societies today. This study was designed to develop a novel nano bioglass/gelatin conduit (BGGC) for the peripheral nerve regeneration. The bioglass nanoparticles were prepared by sol–gel technique and characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis. The interfacial bonding interaction between the nano-bioglass and gelatin in the developed conduits was assessed by FTIR. The surface morphology and pore size of the nanocomposite were investigated through scanning electron microscopy with the pore size of the conduits being 10–40 μm. Biocompatibility was assessed by MTT assay which indicated the BGGC to have good cytocompatibility. The guidance channel was examined and used to regenerate a 10 mm gap in the right sciatic nerve of a male Wistar rat. Twenty rats were randomly divided into two experimental groups, one with the BGGC and the other being normal rats. The gastrocnemius muscle contractility was also examined at one, two and three months post-surgery in all groups using electromyography (EMAP). Histological and functional evaluation and the results obtained from electromyography indicated that at three months, nerve regeneration of the BGGC group was statistically equivalent to the normal group (p > 0.05). Our result suggests that the BGGC can be a suitable candidate for peripheral nerve repair.