1.2 kW beta type Stirling engine with rhombic drive mechanism

Because of some advantages such as higher theoretical thermal efficiency, lower pollutant release, working with lower noisy, working with any kind of thermal energy, and having longer life time, Stirling engines receive attentions of academic workers. The development studies related to the drive mechanism as well as the other components of Stirling engine are progressing. In the present study, a beta type Stirling engine with a rhombic‐drive mechanism was manufactured and tested. Tests were performed at hot end temperatures of 600 and 800°C for five different stages of charge pressure ranging from 1 to 5 bar with 1 bar increments. Torque and power characteristics of the engine were deduced. The maximum engine torque and power were obtained as 18 Nm and 1215 W at engine speeds of 612 and 722 rpm, respectively, at 4 bar charging pressure. The cyclic work generations of the engine, which is an important parameter indicating the engine performance, were determined as 19, 27, and 25 J corresponding to 1, 3, and 5 bar charging pressures, respectively. In the experiments, the cylinder pressure variation was also measured at various charging pressures. While the charge pressure increases from 1 to 5 bar, the location of the maximum cylinder pressure ranged from 86° to 74° of crankshaft angle, which may have a bit influence on the engine performance. Copyright © 2017 John Wiley & Sons, Ltd.     

Response of a tall building far from the epicenter of the 11 March 2011 M 9.0 Great East Japan earthquake and aftershocks

The 11 March 2011 M 9.0 Great East Japan earthquake generated significant long‐duration shaking that propagated hundreds of kilometers from the epicenter and affected urban areas throughout much of Honshu. Recorded responses of a tall building at 770 km from the epicenter of the mainshock and other related or unrelated events show how structures sensitive to long‐period motions can be affected by distant sources. Even when the largest peak input motions to the building is about 3% g, the strong‐shaking duration was about 140 s. The 300‐ to 1000‐s prolonged responses of the building are primarily due to a combination of site resonance (e.g. structural fundamental frequency ~0.15 Hz and site frequency ~0.13–0.17 Hz) and low damping (~1–2%) of the structure. Response modification technologies can improve the response of the building during future earthquakes. The need‐to‐consider risks to such built environments from distant sources are emphasized. Copyright © 2012 John Wiley & Sons, Ltd.     

Investigation of hydrogen production methods in accordance with green chemistry principles

Hydrogen, as a clean fuel of future, is always counted environmentalist. However, production of hydrogen is not always green. Therefore, a need appeared to re-design the processes for terminating non-renewable resource dependency, minimizing wastes, increasing efficiency, and becoming greener. A systematic approach, Green Chemistry, which is based on 12 principles can be an instructive. This paper aimed to investigate the hydrogen production methods in accordance with green chemistry principles. Each method was evaluated for 12 principles to decide if they could meet the requirements or not. Hydrogen production methods investigated were classified under 4 groups according to the energy sources: electrical, thermal, hybrid and biological. After an overview of the main hydrogen production processes, we show that water electrolysis among electrical methods, biomass gasification as being CO₂ neutral among thermal methods, photo-electrochemical production among hybrid methods and bio-photolysis and photo-fermentation among biological methods makes hydrogen production “green”.     

Multiple Antenna Spectrum Sensing Based on GLR Detector in Cognitive Radios

Wireless Personal Communications - As is known, eigenvalue based spectrum sensing for multi-antenna cognitive radio systems is a highly preferred method because it requires no priori knowledge...     

An eclectic approach to design tunable amplifiers

Broadband amplifiers that can accommodate commercial communication standards such as GSM, UMTS, Wi‐Fi, and Wi‐Max are extremely important for radio equipment manufacturers. To achieve this coverage, the amplifier should provide high gain and efficiency over a band from 800 to 5200 MHz. Although there are transistor devices that have cut‐off frequencies well over these frequencies, amplifiers covering such a broad‐bandwidth are difficult to design due to the requirement of broadband matching networks. In this work, design of broadband tunable matching networks is investigated using Real Frequency Direct Computational Technique (RF‐DCT). In order to be able to work on sample structures, impedance transforming filters are chosen and a broadband tunable matching network has been designed. Implementation of tunable inductors is investigated and the performance of a tunable matching network using tunable inductors and capacitors is demonstrated. Eventually a broadband frequency tunable amplifier has been designed using the tunable inductor concept. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Improvement of bitumen and bituminous mixtures performances by triethylene glycol based synthetic polyboron

This study investigates the modification of bitumen with triethylene glycol based polyboron (TEGPB). TEGPB is a new additive material which was chemically synthesized at laboratory conditions. Four different TEGPB concentrations were used to modify 50/70 penetration grade bitumen: 1%(w/w), 2%(w/w), 3%(w/w) and 5%(w/w). The effects of TEGPB modification on the bitumen and bituminous mixture properties were determined by means of softening point, Marshall stability, Nicholson stripping, rotational viscosity (RV), Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests. Amount of TEGPB to be used within the bitumen has been chosen as 2%(w/w) according to RV test results. BBR and Nicholson stripping test results have showed that creep properties and stripping resistance of the modified bitumen was not adversely affected. It was also found out that softening point and rutting resistance of the bitumen as well as Marshall stability of the bituminous mixtures were increased by TEGPB modification.