Effects of hydrogen addition into liquefied petroleum gas reductant on the activity of Ag–Ti–Cu/Cordierite catalyst for selective catalytic reduction system

In this study, low temperature activity of Ag–Ti–Cu/Cordierite catalyst was investigated with liquefied petroleum gas (LPG) and hydrogen-liquefied petroleum gas (H₂-LPG) mixture as reductant. The selective catalytic reduction (SCR) catalyst was synthesized by impregnation method and characterized by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analyzes. BET analysis of the catalyst revealed surface area as 12.89 m²/g. Silver (Ag), titanium (Ti) and copper (Cu) nanoparticles were observed on the catalyst surface with SEM analysis. XRD analysis showed high dispersion of catalytic elements. The SCR performance tests were carried out at 170–270 °C temperature range, 30,000 h^?1 and 40,000 h^?1 space velocities, 1 kW, 2 kW, 3 kW and 4 kW engine loads with diesel engine real exhaust gas sample. NO_x conversion efficiency increased significantly in the presence of H₂, especially at low exhaust temperatures. The maximum NO_x conversion ratio was obtained as 89.53% with H₂-LPG reductant at 270 °C, 4 kW engine load and 30,000 h^?1 space velocity.     

Application of Continuous Parameter Genetic Algorithm to the Problem of Synthesizing Bandpass Distributed Amplifiers

Continuous parameter genetic algorithm (CPGA) is applied tosynthesis of monolithic GaAs FET bandpass distributed amplifiers for desired flat gain and maximum cutoff bandwidth. The results obtained by CPGA are compared with the results obtained by fuzzy genetic algorithm (FGA) and binary genetic algorithm (BGA).     

Finite element computation and experimental validation of sloshing in rectangular tanks

Finite element computation and experimental validation of sloshing in rectangular tanks near the primary and secondary resonance modes are presented. In particular, 2D free-surface evolution is studied. The computational analysis is based on solving the Navier-Stokes equations of incompressible flows with a monolithic solver that includes a stabilized formulation and a Lagrangian tracking technique for updating the free surface. The time-dependent behavior of the numerical and experimental wave heights at different control points are compared, where the experimental data is collected using ultrasonic sensors and a shake table that controls the motion of the rectangular container.     

Device characteristics of a 10.1% hydrazine‐processed Cu2ZnSn(Se,S)4 solar cell

A power conversion efficiency record of 10.1% was achieved for kesterite absorbers, using a Cu₂ZnSn(Se,S)₄ thin‐film solar cell made by hydrazine‐based solution processing. Key device characteristics were compiled, including light/dark J–V, quantum efficiency, temperature dependence of V_oc and series resistance, photoluminescence, and capacitance spectroscopy, providing important insight into how the devices compare with high‐performance Cu(In,Ga)Se₂. The record kesterite device was shown to be primarily limited by interface recombination, minority carrier lifetime, and series resistance. The new level of device performance points to the significant promise of the kesterites as an emerging and commercially interesting thin‐film technology. Copyright © 2011 John Wiley & Sons, Ltd.     

A high performance Σ-Δ readout circuitry for μg resolution microaccelerometers

This paper reports a second order electromechanical sigma-delta readout for micro-g resolution accelerometers in addition to other high-sensitivity capacitive microsensors with large base capacitance. The chip implements a switched-capacitor readout front-end and an oversampled sigma-delta modulator, and hence can be used for both open-loop analog readout and closed-loop control and readout with direct digital output. The readout circuit has more than 115 dB dynamic range and can resolve less than 3 aF/√Hz. Also this IC includes start-up circuit and feedback mechanism for closed-loop control of the accelerometer with a single 5 V supply in a ±4 g range. Together with the accelerometer, bandwidth of the overall system is limited with the sensor resonance frequency (1.53 kHz) in the open-loop mode. However in closed loop mode, oversampling of the acceleration data increases the bandwidth of the system up to few hundred kilohertz which is limited with the cut-off frequency of the low-pass filter placed at the output of the system. The start-up circuit allows rebalancing of a thick silicon proof mass with the limited 5 V supply after system start from power down or in the case of over-range input acceleration. The readout chip has been combined with a Silicon-On-Glass lateral accelerometer, which has a high sensitivity of 1.88 pF/g with large proof mass and long finger structures. A digital filtration and decimation circuitry is also implemented to signal process the output bit stream of the readout circuit. The complete module consumes 16 mW from a ±2.5 V supply and has an adjustable sensitivity up to 8 V/g with a noise level of 4.8 μg/√Hz in open-loop.     

The flame‐retardant effect of calcium hypophosphite in various thermoplastic polymers

The flame‐retardant behavior of calcium hypophosphite (CaHP) was investigated in different thermoplastic polymers including polyamide 6 (PA), poly (lactic acid) (PLA), thermoplastic polyurethane (TPU), and poly methyl metacrylate (PMMA). CaHP was used at three different amounts of 10, 20, and 30 wt%. The characterization of the composites was performed using limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis (TGA), and mass loss calorimeter test. According to the test results, CaHP enhances the fire‐retardant properties in different levels depending on the polymer type. The CaHP exhibits its flame‐retardant effect via the formation of foamed char structure in the condensed phase and via the dilution and radical scavenging effect in the gas phase.     

An Analytical Network Process (ANP) evaluation of alternative fuels for electricity generation in Turkey

In this paper, we present an Analytical Network Process (ANP) model to determine the best fuel mix for electricity generation in Turkey from a sustainable development perspective. The proposed model is implemented in two alternative scenarios. These scenarios are structured along the lines of classification between weak and strong sustainability, and therefore reflect two basic dimensions of sustainability of energy production—environmental protection and sustainable supply of energy resources. The results of the study indicate the gap between goals of sustainable development and energy policies of Turkey in terms of energy security and environmental degradation. Under all alternative scenarios of our model, the highest value alternative is hydropower—domestic, renewable source—while the Turkish electricity sector mainly relies on imported natural gas. The share of nuclear energy is in the range of 8.12–10.21% in our model results, although nuclear energy is not available yet. The calculated percentages of renewable fuels (biomass, geothermal, wind, solar) are 35.7% and 28.9% for Scenario 1 and Scenario 2, respectively, while the total percentage of these fuels is 0.18% of the installed capacity of Turkey. The results of our model suggest that the share of renewable fuels in installed capacity should be increased to achieve sustainable development.     

The impact of anthropogenic and biogenic emissions on surface ozone concentrations in Istanbul

Surface ozone concentrations at Istanbul during a summer episode in June 2008 were simulated using a high resolution and urban scale modeling system coupling MM5 and CMAQ models with a recently developed anthropogenic emission inventory for the region. Two sets of base runs were performed in order to investigate for the first time the impact of biogenic emissions on ozone concentrations in the Greater Istanbul Area (GIA). The first simulation was performed using only the anthropogenic emissions whereas the second simulation was performed using both anthropogenic and biogenic emissions. Biogenic NMVOC emissions were comparable with anthropogenic NMVOC emissions in terms of magnitude. The inclusion of biogenic emissions significantly improved the performance of the model, particularly in reproducing the low night time values as well as the temporal variation of ozone concentrations. Terpene emissions contributed significantly to the destruction of the ozone during nighttime. Biogenic NMVOCs emissions enhanced ozone concentrations in the downwind regions of GIA up to 25 ppb. The VOC/NO_x ratio almost doubled due to the addition of biogenic NMVOCs. Anthropogenic NO_x and NMVOCs were perturbed by ± 30% in another set of simulations to quantify the sensitivity of ozone concentrations to the precursor emissions in the region. The sensitivity runs, as along with the model-calculated ozone-to-reactive nitrogen ratios, pointed NO_x-sensitive chemistry, particularly in the downwind areas. On the other hand, urban parts of the city responded more to changes in NO_x due to very high anthropogenic emissions.     

LCC analysis for energy-saving in residential buildings with different types of construction masonry blocks

Space heating in cold climates requires large quantities of heat energy to be spent. Therefore, considerable energy-savings can be obtained using construction wall materials with low thermal conductivity in the buildings. In this study, an economic analysis (LCC analysis) was performed in order to estimate the optimum thickness, saving and pay-back period which minimizes the total cost including the masonry material and the energy consumption costs. The LCC analysis was carried out for external walls of buildings in Afyonkarahisar, Turkey. Considering long term and current outdoor air temperature records, degree-days (DD) values were used, and the variation of annual energy requirement of the building was investigated for various masonry (product) types for per unit area. Masonry products were block elements with one, two, three and four row-hollows, hollow-brick and aerated concrete. As the fuel types, fuel-oil, natural gas, coal and electricity were considered in the analysis. The functional unit of the LCC was the use of 1 m² of the building's living area over 50 year's period. As a conclusion, the highest energy-saving was obtained by the use of hollow blocks with 4 rows. Moreover, the most suitable fuels for all climate zones appear to be electricity and fuel-oil. But, the natural gas is a better choice when the atmospheric pollution is an important consideration.     

Self‐tuning PID control of a brushless DC motor by adaptive interaction

In this paper, a self‐tuning algorithm for proportional integral derivative (PID) control based on the adaptive interaction (AI) approach theory efficiently used in artificial neural networks (ANNs) is proposed. In this approach, a system is decomposed into interconnected subsystems, and adaptation occurs in the interaction weights among these subsystems. The principle behind the adaptation algorithm is mathematically equivalent to a gradient descent algorithm. The same adaptation as the well‐known backpropagation algorithm (BPA) can be achieved without the need of a feedback network, which would propagate the errors, by applying adaptive interaction. Thereby, the ANN controller can be adapted directly without wasting calculation time in order to increase the frequency response of the controller. The velocity control of a brushless DC motor (BLDCM) under slowly and rapidly changing load conditions is simulated to demonstrate the effectiveness of the algorithm. The AI tuning algorithm was used to tune up the PID gains, and the simulation results with PID adaptation process are presented by comparing the obtained results with the adaptive PID controller based on BPNN and a conventional PID controller. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.