Heat transfer augmentation by swirl generators inserted into a tube with constant heat flux

A novel conical injector type swirl generator (CITSG) is devised in this study. Performances of heat transfer and pressure drop in a pipe with the CITSG are experimentally examined for the CITSGs' angle (α) of 30°, 45° and 60° in Reynolds number (Re) range of 10,000–35,000. Moreover, circular holes with different numbers (N) and cross-section areas (A_h) are drilled on the CITSG. In this way, total areas (A_t = N · A_h) of the holes on the CITSG are equaled each other. Besides, flow directors having three different angles (β = 30°, 60° and 90°) to radial direction are attached to every one of the holes. This study is a typical example for decaying flow. All experiments were conduced with air accordingly; Prandtl number was approximately fixed at 0.71. The local Nusselt number (Nu_x), heat transfer enhancement ratio (Nu_ER) and heat transfer performance ratio (Nu_PR) are calculated and discussed in this paper. It is found that the Nu_ER decreases with increase in Reynolds number, the director angle (β), the director diameter (d), and with decrease in the CITSG angle (α). Likewise, variation of Nu_PR and Nu_ER is also essentially similar for the same independent parameters.     

A different method for producing a flexible LiMn2O4/MWCNT composite electrode for lithium ion batteries

A flexible lithium manganese oxide (LiMn₂O₄)/multi-wall carbon nanotube (MWCNT) composite electrode was produced by casting a slurry-containing powdered LiMn₂O₄ on a previously prepared MWCNT paper. The structure of this new LiMn₂O₄/MWCNT composite electrode was characterized using scanning electron microscopy and X-ray diffraction patterns. Furthermore, the surfaces of these electrodes were coated with gold–palladium alloy using an RF magnetron sputtering technique to prevent Mn dissolution. To investigate the electrochemical performance of this flexible LiMn₂O₄/MWCNT composite electrode, a bare-LiMn₂O₄ electrode was prepared. The discharge capacity of the produced LiMn₂O₄/MWCNT nanocomposite electrode was cyclically tested, and the charge transfer resistance of the electrodes was studied using electrochemical impedance spectroscopy. Consequently, the Au–Pd-coated LiMn₂O₄/MWCNT had a 120 mAh g^?1 discharge capacity and 90 % capacity retention after 100 cycles.     

Ion nitriding of explosively-clad titanium/steel tandems

Ti-6Al-4V, that was explosively welded to a 304 stainless steel plate, was ion nitrided in a d.c. plasma. An effective nitriding was achieved due to the high dislocation density and vacancy concentration that emaneted from the shock wave exposure of explosive welding which, in turn, accelerated diffusion of nitrogen into the titanium matrix. Processed Ti-6AI-4V developed a surface layer of TiN () followed by a Ti₂N () and interstitial nitrogen containing diffusion layer of -titanium. The growth rate of compound layer ( + ) and case depth were found to be controlled by the diffusion of nitrogen. Depending on the temperature of ion nitriding, high Knoop hardness values, between 800 and 2520, were obtained and these values show two to sixfold increase in the hardness when compared with unprocessed samples. XRD results showed VN formation also, together with TiN and Ti₂N nitrides and a preferred TiN growth in (002) orientation. Interfaces between Ti-6Al-4V and 304 stainless steel showed higher hardnesses as was seen following explosive welding than associated cores and a small amount of recrystallization was observed in the Ti-6Al-4V layer at the higher temperature processing. Nitriding of clad-Ti-6Al-4V thus provides an excellent opportunity of cladding surfaces with titanium alloys, in advanced structural applications without the expense of their monolithic counterparts.     

Checking sequences for distributed test architectures

Controllability and observability problems may manifest themselves during the application of a checking sequence in a test architecture where there are multiple remote testers. These problems often require the use of external coordination message exchanges among testers during testing. However, the use of coordination messages requires the existence of an external network that can increase the cost of testing and can be difficult to implement. In addition, the use of coordination messages introduces delays and this can cause problems where there are timing constraints. Thus, sometimes it is desired to construct a checking sequence from the specification of the system under test that will be free from controllability and observability problems without requiring the use of external coordination message exchanges. This paper gives conditions under which it is possible to produce such a checking sequence, using multiple distinguishing sequences, and an algorithm that achieves this.     

Exploring the types and reasons of Internet-triggered academic dishonesty among Turkish undergraduate students: Development of Internet-Triggered Academic Dishonesty Scale (ITADS)

Internet contributes to the development of science and facilitates scientific demeanors while it also serves as a ground for academic misdemeanors. Recent studies indicate that Internet facilitates and spreads academic dishonesty. The purpose of the current study is to investigate the extent of involvement of Turkish university students in academic dishonesty practices facilitated through Internet (i.e. e-dishonesty) and to question the conditions which lead to e-dishonesty. Three hundred and forty nine education faculty students from the most populated state university in Turkey were administered two Likert-Scale questionnaires developed by the researchers. After the reliability and validity conditions were met, two exploratory factor analyses were conducted. The first one revealed the factors constituting common types of e-dishonesty among undergraduate students which were fraudulence, plagiarism, falsification, delinquency, and unauthorized help. The second factor analysis exhibited individual and contextual factors triggering e-dishonesty which were named as individual factors, institutional policies and peer pressure. Results of both analyses are discussed and suggestions for further research are provided.     

Three-dimensional, parallel, finite element simulation of fatigue crack growth in a spiral bevel pinion gear

This paper summarizes new results for predicting crack shape and fatigue life for a spiral bevel pinion gear using computational fracture mechanics. The predictions are based on linear elastic fracture mechanics theories combined with the finite element method, and incorporating plasticity-induced fatigue crack closure and moving loads. We show that we can simulate arbitrarily shaped fatigue crack growth in a spiral bevel gear more efficiently and with much higher resolution than with a previous boundary-element-based approach [Spievak LE, Wawrzynek PA, Ingraffea AR, Lewicki DG. Simulating fatigue crack growth in spiral bevel gears. Engng Fract Mech 2001;68(1):53-76] using the finite element method along with a better representation of moving loads. Another very significant improvement is the decrease in solution time of the problem by employing a parallel PC-cluster, an approach that is becoming more common in both research and practice. This reduces the computation time for a complete simulation from days to a few hours. Finally, the effect of change in the flexibility of the cracking tooth on the location and magnitude of the contact loads and also on stress intensity factors and fatigue life is investigated.     

A conducting composite of polythiophene: synthesis and characterization

Conducting polymer composites of polythiophene, using a polyamide as the insulating matrix, were prepared via electrochemical methods. The characterization of the composite was done by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared and pyrolysis studies. The conductivities were measured by a four-probe technique. The cited methods revealed that the composites have properties different from those of simple mechanical mixtures of the two polymers.     

Removal of phosphate from aqueous solutions by electro-coagulation

The aim of this paper was to investigate the feasibility of the removal of phosphate from aqueous solution by electro-coagulation (EC). The current density (CD) between 2.5 and 10 mA cm(-2) and duration in the limits of 5-20 min were tried for different concentrations. In order to determine optimal operating conditions, the EC process used for the phosphate removal was examined in dependence with the CD, initial concentrations and time. The results of the experimental batch processing showed high effectiveness of the EC method in removing phosphate from aqueous solutions.