Evaluation of greenhouse residues gasification performance in hydrogen production

In this study, a modeling study was carried out to investigate the potential of hydrogen production from greenhouse tomato and pepper residues blending in different rates (0%, 25%, 50%, 75% and 100%) by air-steam gasification. The numerical model developed for the gasification system assumes that all carbon in the mixture is gasified. Air to fuel rate and steam to fuel rates are 0.05 due to high content of O₂ in biomass residues. The gasifier temperature is 877 °C (1150 K) for developed model. According to the result of this study, increasing tomato residues blending rate increases hydrogen content of syngas. It is mainly caused by the content of O₂ in tomato residues being higher than content of O₂ in pepper residues. This study shows that the O₂ content of greenhouse residues is an important factor in syngas production, especially in H₂ production.     

Effects of operational parameters on emission performance and combustion efficiency in small-scale CFBCs

A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emissions. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (two-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO_x and SO₂ emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure at the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO₂ and NO_x emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO_x emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal.     

Strengthening the structural behavior of adobe walls through the use of plaster reinforcement mesh

This study presents an experimental investigation on the use of additives and plaster mesh in adobe wall panels. Three different groups of adobe soil mixture are considered for forming adobe blocks in wall panels with and without mesh placement along horizontal mortar joints. The groups consist of plain adobe blocks, blocks with 1% straw and 10% fly ash. Wall panels are loaded under diagonal compressive axial load in order to evaluate their ultimate load capacities, deformability, and energy absorption characteristics. According to the results obtained from tests, the combined use of plaster mesh with additives enhances the structural behavior significantly.     

Numerical integration of a class of 3d plastic-damage concrete models and condensation of 3d stress–strain relations for use in beam finite elements

This paper presents a method for the integration of a class of plastic-damage material models. The integration of the evolution equations results in a nonlinear problem, which is linearized and solved with the Newton–Raphson method using a sub-stepping strategy. The consistent tangent matrix can be formulated either in terms of the stress components in a general reference system or in terms of the principal stress and strain components with the former then transformed to the general reference system. In order to account for plane stress conditions, the stress–strain relations of the 3d material model are then condensed out. Plane stress conditions are imposed by the linearization of the stresses that need to be set equal to zero; thus the strain fields are updated in the corresponding directions. This solution method is extended to include transverse pressure and the effect of transverse reinforcing steel for a 3d concrete material model. The equilibrium of the stresses in the reinforcing steel and concrete is linearized and the strain fields are updated until the residual satisfies a specified tolerance. The consistent tangent matrix due to the condensation process is derived. The proposed algorithms are tested at the material and element level by comparison of numerical solutions with available experimental data.     

An evolutionary analysis of the innovation policy domain: Is there a paradigm shift?

Scientometrics - Researchers focus on understanding the nature of ecosystems and societies as well as explaining how paradigms change. These efforts are presented and disseminated through scholarly...     

A comparison of time series and machine learning models for inflation forecasting: empirical evidence from the USA

This study compares time series and machine learning models for inflation forecasting. Empirical evidence from the USA between 1984 and 2014 suggests that out of sixteen conditions (four different inflation indicators and four different horizons), machine learning models provide more accurate forecasting results in seven conditions and the time series models are better in nine conditions. Moreover, multivariate models give better results in fourteen conditions, and univariate models are better only in two conditions. This study shows that machine learning model prevails against time series models for the core personal consumption expenditure (core-PCE) inflation forecasting, and the time series model (ARDL) is better for the core consumer price (core-CPI) index inflation forecasting in all horizons.

     

Hydrodynamic modeling of a circulating fluidized bed

Hydrodynamics plays a crucial role in defining the performance of circulating fluidized beds (CFB). The numerical simulation of CFBs is very important in the prediction of its flow behavior. From this point of view, in the present study a dynamic two dimensional model is developed considering the hydrodynamic behavior of CFB. In the modeling, the CFB riser is analyzed in two regions: The bottom zone in turbulent fluidization regime is modeled in detail as two-phase flow which is subdivided into a solid-free bubble phase and a solid-laden emulsion phase. In the upper zone core-annulus solids flow structure is established. Simulation model takes into account the axial and radial distribution of voidage, velocity and pressure drop for gas and solid phase, and solids volume fraction and particle size distribution for solid phase. The model results are compared with and validated against atmospheric cold bed CFB units' experimental data given in the literature for axial and radial distribution of void fraction, solids volume fraction and particle velocity, total pressure drop along the bed height and radial solids flux. Ranges of experimental data used in comparisons are as follows: bed diameter from 0.05-0.418 m, bed height from 5-18 m, mean particle diameter from 67-520 μm, particle density from 1398 to 2620 kg/m³, mass fluxes from 21.3 to 300 kg/m²s and gas superficial velocities from 2.52-9.1 m/s.As a result of sensitivity analysis, the variation in mean particle diameter and superficial velocity, does affect the pressure especially in the core region and it does not affect considerably the pressure in the annulus region. Radial pressure profile is getting flatter in the core region as the mean particle diameter increases. Similar results can be obtained for lower superficial velocities. It has also been found that the contribution to the total pressure drop by gas and solids friction components is negligibly small when compared to the acceleration and solids hydrodynamic head components. At the bottom of the riser, in the core region the acceleration component of the pressure drop in total pressure drop changes from 0.65% to 0.28% from the riser center to the core-annulus interface, respectively; within the annulus region the acceleration component in total pressure drop changes from 0.22% to 0.11% radially from the core-annulus interface to the riser wall. On the other hand, the acceleration component weakens as it moves upwards in the riser decreasing to 1% in both regions at the top of the riser which is an important indicator of the fact that hydrodynamic head of solids is the most important factor in the total pressure drop.     

Artificial neural network and fuzzy expert system comparison for prediction of performance and emission parameters on a gasoline engine

This study is deals with artificial neural network (ANN) and fuzzy expert system (FES) modelling of a gasoline engine to predict engine power, torque, specific fuel consumption and hydrocarbon emission. In this study, experimental data, which were obtained from experimental studies in a laboratory environment, have been used. Using some of the experimental data for training and testing an ANN for the engine was developed. Also the FES has been developed and realized. In this systems output parameters power, torque, specific fuel consumption and hydrocarbon emission have been determined using input parameters intake valve opening advance and engine speed. When experimental data and results obtained from ANN and FES were compared by t-test in SPSS and regression analysis in Matlab, it was determined that both groups of data are consistent with each other for p > 0.05 confidence interval and differences were statistically not significant. As a result, it has been shown that developed ANN and FES can be used reliably in automotive industry and engineering instead of experimental work.     

Evolution of connected health: a network perspective

In this study, the evolution of the connected health concept is analysed and visualized to investigate the ever-tightening relationship between health and technology as well as emerging possibilities regarding delivery of healthcare services. A scientometric analysis was undertaken to investigate the trends and evolutionary relations between health and information systems through the queries in the Web of Science database using terms related to health and information systems. To understand the evolutionary relation between different concepts, scientometric analyses were conducted within five-year intervals using the VantagePoint, SciMAT, and CiteSpace II software. Consequently, the main stream of publications related to the connected health concept matching telemedicine cluster was determined. All other developments in health and technologies were discussed around this main stream across years. The trends obtained through the analysis provide insights about the future of healthcare and technology relationship particularly with rising importance of privacy, personalized care along with mobile networks and mobile infrastructure.