Energy price forecasting - problems and proposals for such predictions

This paper discusses the value of price forecasting in the electricity market during bidding or hedging against volatility. When bidding in a pool system, the market participants are requested to express their bids in terms of prices and quantities. Since the bids are accepted in order of increasing price until the total demand is met, a company that is able to forecast the pool price can adjust its own price/production schedule depending on hourly pool prices and its own production costs. This paper also discusses the challenges of price forecasting and describes some of the proposed methods for meeting these challenges.     

Simulated extreme value fatigue sensitivity to inclusions and pores in martensitic gear steels

The objective of this work is to model the sensitivity of high cycle fatigue resistance of secondary hardening martensitic gear steels to variability in extrinsic inhomogeneities such as primary inclusions, and pores, coupled with intrinsic microstructure variability. A simplified approach is presented to quantify the variability in the driving force for fatigue crack formation in the matrix at non-metallic inclusions and pores in lath martensitic gear steels using a three-dimensional crystal plasticity constitutive model. The utility of a simulation-based strategy for exploring sensitivity of minimum fatigue lifetime (low probability of failure) to microstructure lies in its inherent capability to consider parametric simulations of hundreds of inclusions and microstructures in contrast to limited numbers of physical experiments. Experiments are used to calibrate the polycrystalline cyclic stress–strain response and mean (50% probability) fatigue crack formation life. Several remote loading conditions are considered in the high cycle fatigue (HCF) regime relevant to typical gear applications. Idealized inhomogenieties (spherical) in the form of hard (Al₂O₃), soft inclusions (La₂O₂S), and pores are systematically investigated in this parametric computational study. Relations between remote loading conditions and local plasticity are discussed as a function of stress amplitude and microstructure. The maximum plastic shear strain range is used in the modified form of Fatemi–Socie parameter evaluated at the grain scale as a measure of the driving force for fatigue crack formation (nucleation and early growth to lengths on the order of several times the average grain size). Multiple realizations of the polycrystal microstructure are considered to obtain a statistical distribution of this fatigue indicator parameter (FIP). The results are used to construct an extreme value Gumbel distribution of the FIPs for the selected microstructures. Subsequently, a computational micromechanics based minimum life estimate that corresponds to 1% fatigue crack formation probability is calculated.     

TiO(2) fibers enhance film integrity and photovoltaic performance for electrophoretically deposited dye solar cell photoanodes

Nanoparticulated TiO(2) fibers as one-dimensional long structures were introduced into TiO(2) P25 nanoparticle films using coelectrophoretic deposition. This prevented the usual crack formation occurring in wet coatings, and resulted in less porosity and higher roughness factor of the films that provided more favorable conditions for electron transport. The films used as the photoanode of a dye solar cell (DSC) produced 65% higher photovoltaic efficiency. TiO(2) fibers can be excellent binders in single-step, organic-free electrophoretic deposition of TiO(2) for DSC photoanode.     

Effects of Kenaf core on properties of poly(lactic acid) bio‐composite

In this study, biodegradable poly(lactic acid) (PLA)/Kenaf core composites with different amount of Kenaf core were prepared using screw extrusion. The Structure, thermal stability, mechanical properties, and biodegradation of bio‐composites are evaluated. FTIR result shows the possible interaction between the Ken core and PLA matrix. The FESEM result showed that Kenaf core was uniformly disperse in PLA matrix. Tensile and flexural strength of PLA was improved Up to the 30%vol of kenaf core content. Young's modulus and hardness properties were improved by adding kenaf core into PLA matrix. Bio‐composite density has been decreased by adding more kenaf core and water absorption of the compound was increased linear. High Kenaf core content was also found to increase the rate of biodegradability of PLA/kenaf core. It can be proven by exposure of the samples to the environment and weight loss in soil burial analysis. POLYM. COMPOS., 35:1220–1227, 2014. © 2013 Society of Plastics Engineers     

Poly(ε-caprolactone) scaffolds of highly controlled porosity and interconnectivity derived from co-continuous polymer blends: model bead and cell infiltration behavior

Porous structures destined for tissue engineering applications should ideally show controlled and narrow pore size distributions with fully interconnected pores. This study focuses on the development of novel poly(ε-caprolactone) (PCL) structures with fully connected pores of 84, 116, 141, and 162 μm average diameter, from melt blending of PCL with poly(ethylene oxide) (PEO) at the co-continuous composition, followed by static annealing and selective extraction of PEO. Our results demonstrate a low onset concentration for PEO continuity and a broad region of phase inversion. A novel in vitro assay was used to compare scaffold infiltration by 10-μm diameter polystyrene beads intended to mimic trypsinized human bone marrow stromal cells (hBMSCs). Beads showed a linear increase in the extent of scaffold infiltration with increasing pore size, whereas BMSCs infiltrated 162 and 141 μm pores, below which the cells aggregated and adhered near the seeding area with low infiltration into the porous device. While providing a baseline for non-aggregated systems, the beads closely mimic trypsinized cells at pore sizes equal to or larger than 141 μm, where optimal retention and distribution of hBMSCs are detected. A cytotoxicity assay using L929 cells showed that these scaffolds were cytocompatible and no cell necrosis was detected. This study shows that a melt blending approach produces porous PCL scaffolds of highly controlled pore size, narrow size distribution and complete interconnectivity, while the bead model system reveals the baseline potential for a homogeneous, non-aggregated distribution of hBMSCs at all penetration depths.     

Pulverization of rubber using modified solid state shear extrusion process (SSSE)

The challenge of reusing scrap rubber material is mainly due to its crosslinked/vulcanized structure, which prevents the material from melting and from being melt processed into new items. The most feasible recycling approach is believed to be a process in which the vulcanized rubber is first pulverized into a fine powder and then incorporated into new products. Solid state shear extrusion (SSSE), developed at Illinois Institute of Technology, is a process for continuous pulverization of rubber materials into a fine powder (Aratoopour, H. U.S. Pat. 5,704,555 15 ; Arastoopour, H.; Schocke, D. A.; Bernstein, B.; Bilgili, E. U.S. Pat. 5,904,885 11 ; Ivanov, G. Polym Eng Sci 18 ). In this work, the design of the SSSE apparatus was modified to overcome heat generation due to pulverization and the limitation from the torque/feeding rate relation and, thus, to increase the efficiency of the process in the production of finer particles at higher throughput. The modification was achieved by separating the original process into the extrusion section and the pulverization section. The extrusion section is dedicated to convey material to the pulverization section, which consists of a cylindrical housing and a rotatable cylindrical element that rotates independent of the extruder's screw. The rotatable cylindrical element can be treaded or flightless. Both sections are connected with an adapter. This new approach to the design allowed us to apply a more efficient cooling system, capable of removing the heat of pulverization and, in turn, results in the production of finer rubber particles. Furthermore, separation of the conveying process from the pulverization process resulted in a reduction in extruder's torque and a significant increase in the throughput. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 119–127, 2006     

Artificial neural networks modelling of the performance parameters of the Stirling engine

The Stirling engine can theoretically be very efficient to convert heat into mechanical work at Carnot efficiency. Various parameters could affect the performance of the addressed Stirling engine which is considered in optimisation of the Stirling engine for designing purpose. Through addressed factors, torque has the highest effect on the robustness of the Stirling engines. Due to this fact, determination of the referred parameters with low uncertainty and high precision is needed. To solve the mentioned obstacle, throughout this paper, a generation of intelligent model called ‘artificial neural network’ (ANN) was implemented to estimate the torque of the Stirling heat engine. In addition, highly accurate actual values of the required parameters which were gained from open literature surveys from previous studies were implemented to develop a robust intelligent model. Based on the outcomes of the ANN approach, the output results of an ANN model were close to relevant actual values with a high degree of performance.     

Divided-wall distillation column design using molecular tracking

Divided-wall column (DWC) is an intensified separation process and so far developing a simple procedure for designing these units has been challenging. In this work, the concept of molecular tracking has been integrated with conventional methods to build a simple and easy-to-use methodology for designing DWCs for multicomponent separations. Application of the proposed approach is highlighted through several three- and four-component mixtures. The configuration obtained using molecular tracking gives a design with lower energy demands for the column reboiler, compared to other design methodology, which directly impacts the OPEX of the system.     

Optimized structure of AlGaAs/GaAs double junction solar cells

In this paper, the sub-layers of AlGaAs/GaAs double junction (DJ) solar cell have been redesigned in order to achieve an optimum cell structure. It has been deduced with cooperation of detailed balance limit theory and structural behaviour of AlGaAs, that the Al_0.45Ga_0.55As is the best choice for top cell’s material in AlGaAs/GaAs DJ solar cell. Also, there is a trade-off between peak tunnelling current and transparency in tunnel junction which makes Al_0.07Ga_0.93As as the optimum tunnel junction of AlGaAs/GaAs cell. Finally, a smoothed reflectance senary-layer structure based on modified-DBR has been proposed to be used as anti-reflection coating of proposed structure. Also, the thickness and doping concentration level of different layers have been optimized.