Comparative energetic and exergetic performance analyses for coal-fired thermal power plants in Turkey

The purpose of this study is to analyze comparatively the performance of nine thermal power plants under control governmental bodies in Turkey, from energetic and exergetic viewpoint. The considered power plants are mostly conventional reheat steam power plant fed by low quality coal. Firstly, thermodynamic models of the plants are developed based on first and second law of thermodynamics. Secondly, some energetic simulation results of the developed models are compared with the design values of the power plants in order to demonstrate the reliability. Thirdly, design point performance analyses based on energetic and exergetic performance criteria such as thermal efficiency, exergy efficiency, exergy loss, exergetic performance coefficient are performed for all considered plants in order to make comprehensive evaluations. Finally, by means of these analyses, the main sources of thermodynamic inefficiencies as well as reasonable comparison of each plant to others are identified and discussed. As a result, the outcomes of this study can provide a basis used for plant performance improvement for the considered coal-fired thermal power plants.     

C/C pattern of honey from Turkey and determination of adulteration in commercially available honey samples using EA-IRMS

Honey adulteration particularly by adding cheap sugars such as High Fructose Corn Syrup (HFCS) and cane sugar syrup into natural honey is widespread. This study reports (¹³C/¹²C, ‰) patterns of 31 authentic honey samples obtained from different sources and regions of Turkey as well as 43 commercial honey samples to determine the adulteration using mass spectrometer coupled to elemental analyzer (EA-IRMS). The analyses indicated that the ranges of (¹³C/¹²C, ‰) values of honey and protein fractions of Turkish honey are from −23.30 to −27.58‰ and −24.13 to −26.76‰, respectively. These values for commercial honey samples were determined to range from −11.28 to −25.54‰ and −19.35 to −25.61‰, respectively. The numbers of adulterated commercial honey samples were found to be 10, which corresponds to 23% of the total number of the samples. Diastase activity, HMF content, electrical conductivity and moisture content of honey samples were also determined. Method validation and uncertainty budget calculations were also reported.     

Seeding approach to noble metal decorated conducting polymer nanofiber network

Metal displacement reactions between conducting polymers-"synthetic metals"-and noble metals (Pt, Au and Ag) have been demonstrated using a seeding polymerization technique, to produce a synthetic metal nanofiber network decorated with noble metal nanoparticles, in one-step.     

Nail penetration test for determining the uniaxial compressive strength of rock

We offer a new and practical index test method, the nail penetration test (NPT), to estimate the UCS of intact rocks, to be used as alternative to the point load test (PLT) or Schmidt rebound hammer test (SRH). The major tools used in the investigation include a gasnailer with 130 J power and its nails ranging from 25 to 60 mm in length. The study material covers 65 rock blocks of gypsum, tuff, ignimbrite, andesite, sandstone, limestone, and marble. For the NPT, five nail shots were performed on each block sample and the average value was obtained. Two to three uniaxial compression tests were carried out on each specimen. Ten impacts were applied on rock blocks by using both the L- and N-types of SRH. Regarding the PLT, either 10 axial or 10 block tests was applied on each rock type.The average nail penetration depths were correlated with the UCS, I_S(50) and rebound number for both types of the SRH. Also, the measured UCS values were compared with those obtained from the empirical relationships using the data from the NPT, PLT, and SRH. It was found that the NPT provides better estimates for UCS than the PLT or SRH. Particularly applicable to weak to very weak rocks, the NPT is capable of indirectly estimating the UCS of intact rocks up to 100 MPa. The test is proposed for use in mainly in situ applications.     

Real-Time FFT Computation Using GPGPU for OFDM-Based Systems

In optical and wireless communications systems, the goal is to reach 10 Gbps or above data rates. In order to support such extremely high data rates, the physical layer generally uses orthogonal frequency division multiplexing (OFDM) modulation. Unlike serial transmission of symbols, the OFDM modulation transmits data with many parallel sub-carriers, which help to provide high bandwidth. Field programmable gate arrays (FPGAs) and digital signal processors (DSPs) are usually employed to process OFDM blocks in real time. However, FPGAs and DSPs are not cost effective, and they are difficult to adapt to new standards. One of the most computationally intensive functions in OFDM systems is the fast Fourier transform (FFT) computation process. This paper aims to accelerate the FFT process to achieve high communication throughput in real time. Two parallel approaches are implemented for two different NVIDIA graphics processing unit (GPU) architectures. To obtain the best performance values, several optimizations are implemented. Our general purpose graphics processing unit (GPGPU)-based FFT computation achieves up to 24 Gbps throughput in real time.     

A quality evaluation model for the design quality of online shopping websites

Design quality of websites is known to have a positive impact on user attention. Although there are lots of papers that investigate design qualities of websites in the literature, none of them takes into account interactions among design characteristics. The main objective of this study is to evaluate the perceived design quality of websites while considering the interactions among design characteristics. For this purpose, a new approach named the quality evaluation model (QuEM), which includes fuzzy set theory, the decision-making trial and evaluation laboratory method (DEMATEL), and generalized Choquet integral techniques, is proposed. The critical design characteristics of websites are determined based on interactions among them by using DEMATEL. Then, the degrees of importance are utilized in the generalized Choquet integral to evaluate the perceived design quality of website designs. Fuzzy set theory is utilized to cope with ambiguity in the linguistic evaluation of the different design characteristics and supports the analysis of the collected data. Finally, the proposed method is applied for the evaluation of the quality of the most used shopping websites in Turkey.     

Load-induced transitions in the lubricity of adsorbed poly(L-lysine)-g-dextran as a function of polysaccharide chain density

Chain-density gradients of poly(l-lysine)-graft-dextran (PLL-g-dex), a synthetic comblike copolymer with a poly(l-lysine) backbone grafted with dextran side chains, were fabricated on an oxidized silicon substrate. The influence of the changing dextran chain density along the gradient on the local coefficient of friction was investigated via colloidal-probe lateral force microscopy. Both in composition and structure, PLL-g-dex shares many similarities with bottlebrush biomolecules present in natural lubricating systems, while having the advantage of being well-characterized in terms of both architecture and adsorption behavior on negatively charged oxide surfaces. The results indicate that the transition of the dextran chain density from the mushroom into the brush regime coincides with a sharp reduction in friction at low loads. Above a critical load, the friction increases by more than an order of magnitude, likely signaling a pressure-induced change in the brush conformation at the contact area and a corresponding change in the mechanism of sliding. The onset of this higher-friction regime is moved to higher loads as the chain density of the film is increased. While in the low-load (and low-friction) regime, increased chain density leads to lower friction, in the high-load (high-friction) regime, increased chain density was found to lead to higher friction.