Unlicensed motorcycling of high school adolescents in Dehaghan county (Isfahan Province of Iran)

Background

Unlicensed motorcycling increases the chances of accidents in adolescents. There are many behavioral and non-behavioral factors involved in adolescents’ unlicensed motorcycling which were not addressed in research yet completely.

Methods

The cross-sectional study aimed to determine prevalence and related factors of unlicensed motorcycling on 500 unlicensed male high school adolescents in Dehaghan, who entered in the study by census. Demographic and motorcycling information were collected via self-report questionnaire, and its content validity was approved by a panel of experts. The statistical analyses of the data included Pearson Correlation Coefficient, chi-square, independent samples t-test and ANOVA with Tukey post hoc test.

Results

The prevalence of unlicensed motorcycling among participants was 74.2% and mean age at first motorcycling experience was 11.97 ± 1.97 years ranged from 8 to 17. Of the motorcyclist participants, 59.6% owned their personal motorcycle. Most motorcycle passengers (62.8%) were adolescent’s friends, and the most frequently expressed reason for use of motorcycle was fun and entertainment (54.2%). Age at first motorcycling experience was lower among rural adolescents than urban adolescents. However, unlicensed motorcycling was more prevalent among urban adolescents than rural ones. The relationship between living status, father’s job, mother’s job and age at first motorcycling experience was insignificant (P > 0.05). However, mean age at first motorcycling experience among students of humanities, technical disciplines, and general first year was lower than that among students of natural sciences and math.

Conclusion

High prevalence of unlicensed motorcycling and significant role of family and social environments on adolescents’ high-risk motorcycling without license, is indicative of the need for interventions at all levels of peers, family, and schools and also establishing new driving regulations in Iran.     

An efficient synthesis of 2,4,6-triarylpyridines catalyzed by heteropolyacid under solvent-free conditions

Preyssler type heteropolyacid is found to be an efficient catalyst for the synthesis of 2,4,6-triarylpyridines in good yields. The catalyst is recycled and reused several times.     

TERNARY NaCl+LiCl+H2O MIXED ELECTROLYTE SYSTEM: DETERMINATION OF ACTIVITY COEFFICIENTS BASED ON POTENTIOMETRIC METHOD

The mean activity coefficients for NaCl in a ternary electrolyte system were determined by the potentiometric method, at 25°C, using a solvent polymeric (PVC) sodium-selective membrane electrode (Na⁺ ISE), containing N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide as ionophore, and combined with an Ag/AgCl electrode. The potentiometric measurements were performed at the same ionic strengths in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m₁/m₂ = 1, 10, 50, 100). The nonideal behavior of the ternary NaCl(m₁) + LiCl(m₂) + H₂O electrolyte system was described based on the Pitzer ion-interaction model for mixed salts over the ionic strength ranging from 0.01 up to about 4 mol/kg. Two- and three-particle Pitzer interaction parameters for a mixed electrolyte system were determined based on potentiometric data, and the critical role of potentiometric selectivity coefficient (K ₁₂) of ISE as limiting factor in the potentiometric measurements was analyzed.     

Microstructure and Reliability Comparison of Different Pb-Free Alloys Used for Wave Soldering and Rework

This paper describes the results of an intensive microstructural and reliability study of pin-through-hole (PTH) and surface mount technology (SMT) components which were wave solder assembled using three groups of alloys: (1) near-eutectic Sn-Ag-Cu alloys such as SAC405 and SAC305, (2) low-Ag off-eutectic Pb-free alloys with an Ag content of about 1% and lower, and (3) eutectic Sn-Cu alloys with Ni and other additives. Both primary attach and reworked solder connections using solder fountain and hand rework were studied. The PTH connector types and SMT components were wave solder assembled on a test vehicle. Accelerated thermal cycling (ATC) was conducted at 0°C to 100°C for 6000 cycles. The difference in microstructures, intermetallic formation, Cu dissolution, grain coarsening, and crack formation is shown. The influence of the microstructure after assembly and rework on Weibull plot parameters and failure modes is described for 2512 resistors. Interconnect defects such as nonuniform phase distribution and void formation are discussed. The Sn-Cu-Ni- and Sn-Cu-Ag-Bi-based alloys tested in this study are recommended as potential suitable replacements for SAC305/405 in the wave solder process; no failure was detected up to 6000 cycles at 0°C to 100°C. Although SAC405 demonstrated better barrel fill and lower rate of crack propagation during ATC, after PTH rework, both of the alternative Pb-free alloys have a much lower Cu dissolution rate and definitely outperform SAC405 in ATC. SAC405 glue and wave resistors after primary attachment and rework demonstrate higher reliability than alternative alloys. Early failures relate to alternative alloy characteristics and should be considered for some applications.     

A synthesis of (arylthio-ethylidene)indolin-2-ones via S-arylation of oxoindolin-ethanethiolates with aryl halides

Aryl-sulfur bond formation between aryl halides and 1-(2-oxoindolin-3-ylidene)-2-aroylethanethiolates, prepared from isatin, 1-aryl-2-thiocyanatoethan-1-ones, and aryl halides, catalyzed by copper(I) iodide in DMF at 80°C afforded a nearly 1:1 mixture of (Z/E)-3-(2-oxo-2-aryl-1-(arylthio)ethylidene)indolin-2-ones, in good yields. The stereochemistry of these products has been confirmed by X-ray diffraction studies.     

The effects of SiO2 and K2O on glass forming ability and structure of CaOTiO2P2O5 glass system

The effects of SiO₂ and K₂O were investigated on the glass forming ability (GFA) and structural characteristics of CaOTiO₂P₂O₅ system. Differential thermal analyzer (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR and ³¹P magic angle spinning NMR methods were applied for characterizations of the system.Unwanted crystallization in the initial three components base glass composition was observed by adding SiO₂ and crystalline phases such as TiP₂O₇, rutile (TiO₂) and cristobalite (SiO₂) were formed in it.The results showed that K₂O prevents crystallization of glasses and promotes the formation of glass. FT-IR and X-ray diffraction showed that the addition of K₂O caused the formation of phosphate–silicate network as POSi, and formation of isolated droplet phases (rich of Si and P) separated from the phosphate matrix.The optimum amounts of SiO₂ and K₂O in phosphate structure were respectively 6 and 2 wt.%, 0 in accordance with glass forming ability (GFA) parameters. Despite addition of SiO₂ along with K₂O; the ³¹P MAS NMR and infrared spectrums of glasses show that no Q² sites were in the phosphate network. The Q¹ and the pyrophosphate groups was the predominant structural unit in these glasses.     

Effect of Cold Rolling Parameters on Bond Strength of Ti Particle Embedded Al Strips

Bond strength of cold roll bonded Al layers with and without Ti particles was studied. The effect of particle’s content that was placed between aluminium sheets and rolling reduction on weld efficiency and bonding was studied. Peel test was used to measure the adhesive strength between the bonded Al strips. The weld efficiency \(\eta\) of the roll bonding process was calculated. The results showed that the weld efficiency in the presence of Ti is lower than that in the absence of Ti. The surface conditions of the peeled surfaces were inspected by scanning electron microscopy. It could be concluded that by enhancing the rolling reduction up to 70%, the bonded area on the interface is increased and bonds with higher strength are produced. However, the addition of Ti particles leads to reduction of the bonded area and bond strength. Also, presence of Ti powders up to 0.5 wt%, lead to the increase of threshold deformation to 45%.     

Shear stress distribution prediction in symmetric compound channels using data mining and machine learning models

Shear stress distribution prediction in open channels is of utmost importance in hydraulic structural engineering as it directly affects the design of stable channels. In this study, at first, a series of experimental tests were conducted to assess the shear stress distribution in prismatic compound channels. The shear stress values around the whole wetted perimeter were measured in the compound channel with different floodplain widths also in different flow depths in subcritical and supercritical conditions. A set of, data mining and machine learning algorithms including Random Forest (RF), M5P, Random Committee, KStar and Additive Regression implemented on attained data to predict the shear stress distribution in the compound channel. Results indicated among these five models; RF method indicated the most precise results with the highest R² value of 0.9. Finally, the most powerful data mining method which studied in this research compared with two well-known analytical models of Shiono and Knight method (SKM) and Shannon method to acquire the proposed model functioning in predicting the shear stress distribution. The results showed that the RF model has the best prediction performance compared to SKM and Shannon models.