Effect of physical, chemical and electro-kinetic properties of pumice on strength development of pumice blended cements

In the present study, the potential effects of physical, chemical and electro-kinetic properties of pumice on the strength development of pumice blended cements (PBC) were examined and documented. A significant relationship between zeta potential of pumice samples, setting time and water demand of PBC was found. A relationship between the chemical content of pumice samples and compressive strength of PBC was also observed. However, zeta potential of the pumice samples was found to be less effective in strength development. Despite the lower clinker content, the setting time of the PBC samples was shorter than control specimen. 30 % pumice replacement by clinker resulted in 5–28 % reduction in 28-day strength depending on the characteristics of the pumice samples and grinding time.     

Soft input soft output Kalman equalizer for MIMO frequency selective fading channels

We consider the Kalman filter for equalization of a multiple-input multiple-output (MIMO), frequency selective, quasi-static fading channel. More specifically, we consider a coded system, where the incoming bit stream is convolutionally encoded, interleaved and then spatially multiplexed across the transmit antennas. Each substream is modulated into M-ary symbols before being transmitted over a frequency selective channel. At the receiver, we propose to use the Kalman filter as a low complexity MIMO equalizer, as opposed to the trellis based maximum a-posteriori (MAP) equalizer whose computational complexity grows exponentially with the channel memory, the number of transmit antennas and the spectral efficiency (bits/s/Hz) of the system. We modify the structure of the Kalman filter and enable it to process the a-priori (soft) information provided by the channel decoder, thereby allowing us to perform iterative (turbo) equalization on the received sequence. The iterative equalizer structure is designed for general M-ary constellations. We also propose a low complexity version of the above algorithm whose performance is comparable to its full complexity counterpart, but which achieves a significant complexity reduction. We demonstrate via simulations that for higher order constellations, when sufficient number of receive antennas are available (e.g. for a 2 transmitter, 3 receiver system, QPSK), the performance of the proposed algorithms after 4 iterations is within 1.5 dB of the non-iterative MAP algorithm with close to an order of magnitude complexity reduction. By objectively quantifying the complexity of all the considered algorithms we show that the complexity reduction for the proposed schemes becomes increasingly significant for practical systems with moderate to large constellation sizes and a large number of transmit antennas     

CCII-based simulated floating inductor and floating capacitance multiplier

Analog Integrated Circuits and Signal Processing - In this work, a new lossless simulated floating inductor (SFI) and a new lossless floating capacitance multiplier (FCM) are proposed. Both...     

Evaluating a low exergy heating system from the power plant through the heat pump to the building envelope

This study deals with an exergetic analysis and assessment of a low exergy heating system from the power plant through the ground-source heat pump to the building envelope. The methodology used is based on a pre-design analysis tool, which has been produced during ongoing work for the International Energy Agency (IEA) formed within the Energy Conservation in Buildings and Community Systems Programme (ECBCSP) Annex 37 to increase the understanding of exergy flows in buildings and to be able to find possibilities for further improvements in energy utilization in buildings. The analysis is applied to a room with a volume of 105 m³ and a net floor area of 35 m² as an application place, while indoor and exterior air temperatures are 20 °C and −15 °C, respectively. The heat pump system used for heat production with a maximum supply temperature of 55 °C was designed, constructed and tested in Aksaray University, Aksaray, Turkey. In this context, energy and exergy flows were investigated, while exergy destructions in the overall system were quantified and illustrated. Total exergy input of the system was found to be 7.93 kW and the largest exergy destruction occurred in the primary energy transformation at 5.31 kW.     

The thermoluminescent properties of lithium triborate (LiB3O5) activated by aluminium

In this paper, the thermoluminescence (TL) dosimetric characteristics of Al-doped LiB₃O₅ compounds are presented. The powder samples were prepared by the solid-state reaction method and the formation of the compounds were confirmed by an X-ray diffraction study. The TL studies of undoped and Al-doped LiB₃O₅ samples showed similar glow curve structures. They have three TL glow peaks at about 60, 130 and 200 °C after heating at a constant heating rate of 1 °C/s. Their comparative TL studies indicated that 5 wt% Al-doped LiB₃O₅ compound was approximately 240 times more sensitive than undoped compound. The TL emission spectra of Al-doped LiB₃O₅ showed a maximum band at around 520 nm. The main dosimetric characteristics, which are namely the TL dose response, TL sensitivity, fading, minimum detectable dose, reproducibility, precision of dose measurement and annealing procedure, indicated that Al-doped LiB₃O₅ sample, can be used in dosimetric applications. The trap parameters namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the glow peaks in beta irradiated undoped and Al-doped LiB₃O₅ samples were obtained by glow curve deconvolution (GCD) program.     

Exergoeconomic analysis of a hybrid copper-chlorine cycle driven by geothermal energy for hydrogen production

In this study, we conduct an exergy, cost, energy and mass (EXCEM) analysis of a copper-chlorine thermochemical water splitting cycle driven by geothermal energy for hydrogen production. We also investigate and illustrate the relations between thermodynamic losses and capital costs. The results show that hydrogen cost is closely and directly related to the plant capacity and also exergy efficiency. Increasing economic viability and reducing the hydrogen production costs will help these cycles play a more critical role in switching to hydrogen economy.     

Detection of C. Botulinum Types in Honey by mPCR

The aim of this study was to determine the prevalence of Clostridium botulinum in honey samples using conventional methods and multiplex PCR (mPCR). A total number of 150 honey samples were randomly collected from apiaries, retail shops, weekly open bazaars, and supermarkets in Samsun, Turkey. Of 150 honey samples, 4 (2.6%) were positive for the botulinum neurotoxin gene by mPCR analysis. A total of 4 C. botulinum isolates were obtained from the mPCR positive samples, of which 3 were type A and 1 was type B. No samples were positive regarding the type E and type F neurotoxin genes. This is the first report of type A and type B spores of C. botulinum being detected and isolated in Turkey. This study revealed that some honey samples may present a potential hazard for food borne and infant botulism.     

Simplified Spreadsheet Solutions.?II: Overall Schedule Optimization

Overall schedule optimization, considering time, cost, and resource constraints is a difficult task due to the inherent complexity of projects, the difficulties associated with modeling all aspects combined, and the inability of traditional optimization tools to solve this large-size problem. In this paper, a practical approach is presented for the modeling and optimization of overall construction schedules. To simplify modeling, a spreadsheet-based model is developed to be easily usable by practitioners. The spreadsheet model integrates critical-path network scheduling with time-cost trade-off analysis, resource allocation, resource leveling, and cash flow management. The model uses the total project cost as the objective function to be minimized. To facilitate this large-size optimization, a nontraditional optimization technique, genetic algorithms, is used to locate the globally optimal solution, considering all aspects simultaneously. Details of the proposed model are described, and a hypothetical case study was used to experiment with it. Integration of the model with a simple information system is described to automate the development of optimal construction schedules.     

Influence of Deposition Pressure (O2) on the YBCO (Y123) Thin Films Prepared by Pulsed Laser Deposition

In this paper, the influence of oxygen pressure on film quality and superconducting properties of YBa₂Cu₃O_7?δ (YBCO-Y123) thin films prepared by Pulsed Laser Deposition (PLD) was investigated. For this purpose, YBCO thin films were deposited on polished LaAlO₃ (l00) (LAO) substrates at three different oxygen pressures (150, 200, and 250 mTorr). X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were used to make comparative studies of film microstructure. Except for oxygen pressures, all other variables such as number of pulses, repetition rate, deposition temperature, heating and cooling rate, target-substrate distance, laser excitation energy, annealing temperature, and annealing pressure were fixed. For this fixed set of parameters, SEM, XRD analysis, and AC susceptibility measurements of these films revealed that the crystal structure quality and superconducting properties of YBCO thin films are optimum at the oxygen deposition pressure of 150 mTorr. As the deposition pressure increased, Y₂BaCuO₅ (Y211) phase peaks were seen in XRD patterns. The reason for this was believed to be caused by decreased concentration of CuO and BaO as determined by Energy Dispersive X-Ray Spectroscopy (EDX) of thin films.     

Highly efficient resonant coupling of optical excitations in hybrid organic/inorganic semiconductor nanostructures

The integration of organic and inorganic semiconductors on the nanoscale offers the possibility of developing new photonic devices that combine the best features of these two distinct classes of material. Such devices could, for example, benefit from the large oscillator strengths found in organic materials and the nonlinear optical properties of inorganic species. Here we describe a novel hybrid organic/inorganic nanocomposite in which alternating monolayers of J-aggregates of cyanine dye and crystalline semiconductor quantum dots are grown by a layer-by-layer self-assembly technique. We demonstrate near-field photon-mediated coupling of vastly dissimilar optical excitations in the two materials that can reach efficiencies of up to 98% at room temperature. By varying the size of the quantum dots and thus tuning their optical resonance for absorption and emission, we also show how the ability of J-aggregates to harvest light can be harnessed to increase the effective absorption cross section of the quantum dots by up to a factor of ten. Combining organic and inorganic semiconductors in this way could lead to novel nanoscale designs for light-emitting, photovoltaic and sensor applications.