Flow on the Internet: a longitudinal study of Internet addiction symptoms during adolescence

Internet Addiction (IA) constitutes an excessive Internet use behavior with a significant impact on the user’s well-being. Online flow describes the users’ level of being absorbed by their online activity. The present study investigated age-related, gender, and flow effects on IA in adolescence. The sample comprised 648 adolescents who were assessed twice at age 16 and 18 years. IA was assessed using the Internet Addiction Test and online flow was assessed using the Online Flow Questionnaire. A three-level hierarchical model estimated age-related, gender, and online flow effects on IA symptoms and controlled for clustered random effects. IA symptoms decreased over time (for both genders) with a slower rate in males. Online flow was associated with IA symptoms and this remained consistent over time. Findings expand upon the available literature suggesting that IA symptoms could function as a development-related manifestation at the age of 16 years, while IA-related gender differences gradually increase between 16 and 18 years. Finally, the association between online flow and IA symptoms remained stable independent of age-related effects. The study highlights individual differences and provides directions for more targeted prevention and intervention initiatives for IA.     

Effect of crosslinking on the positive temperature coefficient stability of carbon black‐filled HDPE/ethylene‐ethylacrylate copolymer blend system

Carbon black‐filled high‐density polyethylene (HDPE)/ethylene ethylacrylate copolymer (EEA) blends were prepared and the effect of crosslinking of the blends on the positive temperature coefficient (PTC) stability was investigated. By irradiation and silane‐crosslinking methods, crosslinked composites with various degrees of crosslinking were obtained. Crosslinking of the matrix polymer led to the disappearance of the negative temperature coefficient (NTC) phenomenon. Also, the PTC intensity increased with an increasing degree of crosslinking. The PTC stability of silane‐crosslinked samples was notably improved at heat cycles of 140°C. This was sufficiently improved by both the silane‐ and radiation‐crosslinking methods when they were treated at 85°C. Therefore, the limiting temperature of self‐regulating heat is about 85°C. Both radiation‐ and silane‐crosslinked samples are thought to be of use to the industry.     

Influence of Fe3+-doping on optical properties of CeO2−y nanopowders

Ce_1?xFe_xO_2?y (0≤x≤0.05) nanopowders were synthesized using hydrothermal method at low calcination temperature and low doping regime. Structural and morphological characterization has been carried out by the X-ray diffraction method and non-contact atomic force microscopy. Vibrational properties were investigated by Raman spectroscopy. It was observed that the content of oxygen vacancies increased significantly with Fe doping up to 3 mol%. For higher dopant concentration, phase separation was detected. The optical properties of pure and Fe³⁺-doped CeO_2?y samples were investigated by spectroscopic ellipsometry. Several analytical models were applied to analyze the optical absorption onset of ceria defective structure. It was found that, Cody–Lorentz model most suitably described the sub-band gap region of CeO_2?y nanopowders and consequently gave more accurate band gap values, which are closer to the direct band gap transitions than to the indirect ones. The increased content of localized defect states in the ceria gap and corresponding shift of the optical absorption edge towards visible range in Fe-doped samples can significantly improve the optical activity of nanocrystalline ceria.     

Analysis of fluid–elastic-structure interactions in an impinging jet with a dynamic 3D-PTV and non-contact 6D-motion tracking system

Measurements on pulsed impinging jets with 3D-particle tracking velocimetry (3D-PTV) system and 6-degree-of-freedom (DOF)-motion tracking system were carried out. Pulsed round jets were impinged on an elastic plate and the flow field near the plate was measured with a 3D-PTV system while the motions of the flexible plate was measured with 6D-motion tracking system. The measurement system consists of four cameras, light sources (Nd-Yag laser, Ar-ion laser, Black lamp) and a host computer. The nozzle diameter is D = 15 mm and two major experiments have been carried out for the cases of the distances between the nozzle tip to the elastic wall are z/D = 2.3 and 6.0. The pulsed jets were controlled by a solenoid valve and were impinged onto an elastic plate (material: silicon, diameter: 350 mm, thickness: 0.5 mm, hardness: 15). The measurement system was synchronized with the valve opening time. The Reynolds numbers were 20,000 and 24,000 when the jets were impinged with the volume velocities. In the first experiments a macroscopic interprets on the flow–structure interactions (FSI) was made using three-dimensional vector fields of the flow and three-dimensional displacements of the elastic plate. In the second experiments a microscopic interprets on the FSI was made using two-dimensional velocity vectors and three-dimensional displacements of the elastic plate. Experimental results showed that the elastic plate moved slightly to the opposite direction of the jet direction at the time of valve opening. It has been shown that the vortices travelling over the surface of the wall made the elastic wall distorted locally.     

Rapid synthesis and consolidation of nanostuctured Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgSiO<Subscript>3</Subscript> composites by high frequency induction heated sintering

Nanopowders of MgO, Al₂O₃ and SiO₂ were made by high energy ball milling. The rapid sintering of nanostuctured Al₂O₃-MgSiO₃ composites was investigated by the high-frequency induction heating sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and inhibits grain growth. Highly dense nanostructured Al₂O₃-MgSiO₃ composites were produced with the simultaneous application of 80 MPa pressure and the induced output current of total power capacity (15 kW) within 2 min. The sintering behavior, grain size and mechanical properties of Al₂O₃-MgSiO₃ composites were investigated.     

Development of a concentration measurement technique for steady state solid-liquid mixing using a neural network

A measurement technique that can measure the concentration of the solid particles in liquid flow was developed.The measurement system consists of a color camera and three LCD displays.The solid particles were put at the bottom of a cylindrical mixing tank in which JetA1 oil was filled.Transient mixing of the solid particles was performed by rotating a propeller type agitator with three different rotation speed(500,600,700 r/min).Mixing state was visualized by the LCD displays and a color camcorder.The color intensity of the glass particles changes with their concentration.The color information was decoded into three principle colors R,G,and B so that,the calibration curve of color-to-concentration was performed using these information.A neural network was used for this calibration.The transient concentration field of the solid particles was quantitatively visualized.     

Toward a Full Simulation of the Basic Oxygen Furnace: Deformation of the Bath Free Surface and Coupled Transfer Processes Associated with the Post-Combustion in the Gas Region

The present article treats different phenomena taking place in a steelmaking converter through the development of two separate models. The first model describes the cavity produced at the free surface of the metal bath by the high-speed impinging oxygen jet. The model is based on a zonal approach, where gas compressibility effects are taken into account only in the high velocity jet region, while elsewhere the gas is treated as incompressible. The volume of fluid (VOF) method is employed to follow the deformation of the bath free surface. Calculations are presented for two- and three-phase systems and compared against experimental data obtained in a cold model experiment presented in the literature. The influence on the size and shape of the cavity of various parameters and models (including the jet inlet boundary conditions, the VOF advection scheme, and the turbulence model) is studied. Next, the model is used to simulate the interaction of a supersonic oxygen jet with the surface of a liquid steel bath in a pilot-scale converter. The second model concentrates on fluid flow, heat transfer, and the post-combustion reaction in the gas phase above the metal bath. The model uses the simple chemical reaction scheme approach to describe the transport of the chemical species and takes into account the consumption of oxygen by the bath and thermal radiative transfer. The model predictions are in reasonable agreement with measurements collected in a laboratory experiment and in a pilot-scale furnace.     

Parametric and comparative study of spandrel beam effect on the punching shear strength of reinforced concrete flat plates

The safe and efficient construction of reinforced concrete flat plate systems requires an accurate, reliable and universally applicable procedure for the punching shear strength design. A nonlinear layered finite element method (LFEM) capable of analysing the punching shear strength of such system has been developed. Based on the LFEM, a parametric study is undertaken to evaluate some of the factors influencing punching shear strength of reinforced concrete flat palate with spandrel beams. This is done by varying the depth and the width of the spandrel beam while keeping other variables constant. The numerical results obtained by the LFEM are also compared with those predicted by the recommendations of the Australian Standard (AS3600‐2009) and the Wollongong‐Griffith (W‐G) semi‐empirical method. The results confirm that the Australian Standard is inadequate in predicting the punching shear strength at the corner and edge column connections of flat plates with spandrel beams or torsion strips. Copyright © 2010 John Wiley & Sons, Ltd.     

Development and ejection behavior of different material-based electrostatic ink-jet heads

There has been growing interests in direct patterning of metallic contents on the surface of the substrate without including complex steps of the microfabrication lithography process. The direct fabrication process using electrostatic ink-jet printing can be expected to be a powerful tool for both nanotechnology research and applications such as microelectronics. The droplet ejection voltage, meniscus, cone-jet behavior, and counter electrode distance depends on the ink properties such as surface tension, viscosity, and percentage of metallic pigments. In this paper, 2-μm level needle-type electrostatic head designs for contact-less fabrication of printed electronics, composed of differently treated surface materials, have been studied and analyzed. The electrostatically actuated ink-jet heads were tested and compared for low power and high resolution on ink containing metallic nano-particle particles as pigments. The two laboratory-fabricated discrete and electrostatically actuated ink-jet heads, one made by poly di-methyl siloxane modeling process and other through micro-electrical discharge machine techniques, were compared, and their orifice outlet surface (hydrophobic and hydrophilic) condition influence has been discussed. The paper also investigates different dripping behaviors of metallic ink under the influence of counter electrode distance, voltages, and materials. The observation of droplet ejection with high-speed camera revealed that in the case of hydrophobic head, better meniscus shape and ejection was achieved even at low voltage compared to the hydrophilic head. It was also found that the less flow rate is required in hydrophobic head. Printing characteristic of the hydrophilic nozzle head was also compared with the hydrophobic head on PET substrate.     

Properties and consolidation of nanocrystalline WSi2-SiC composite from mechanically activated powders by pulsed current activated combustion synthesis

Dense nanostructured WSi₂-SiC composite was synthesized by pulsed current activated combustion synthesis method within 2 min in one step from mechanically activated powders of WC and 3Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense WSi₂-SiC with relative density of up to 99.8% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. The average grain size and mechanical properties of the composite were investigated.