Decentralised decision-making with information sharing vs. centralised decision-making in supply chains

In recent years, implementing coordination mechanisms in decentralised supply chains to reduce the well-known negative effects of decentralisation, such as the ‘bullwhip effect’, has become a considerable challenge. Furthermore, with the dramatic developments in information and communication technologies, real-time information sharing has become increasingly easier to implement. In this work, we study a mono-product divergent supply chain composed of a supplier, a warehouse, retailers and customers in the context of decentralised and centralised decisions. The main objective of this study is to compare a decentralised supply chain combined with different scenarios of simultaneous upstream and downstream information sharing vs. a centralised supply chain. A mathematical model is developed to compare the logistics costs in the two decision contexts. The experimental results clearly show that the simultaneous sharing of customer demand and supplier-warehouse lead time information in a decentralised supply chain yields nearly equivalent logistics costs as the centralised supply chain context. However, the main beneficiary of the sharing is the warehouse, which receives approximately two-thirds of the benefit. Thus, incentives and revenue sharing contracts should be implemented to motivate and balance the benefits between supply chain partners.     

Efficient hardware architecture of 2D-scan-based wavelet watermarking for image and video

This paper describes an efficient hardware architecture of 2D-Scan-based-Wavelet watermarking for image and video. The potential application for this architecture includes broadcast monitoring of video sequences for High Definition Television (HDTV) and DVD protection and access control. The proposed 2D design allows even distribution of the processing load onto a set of filters, with each set performing the calculation for one dimension according to the scan-based process. The video protection is achieved by the insertion of watermarks bank within the middle frequency of wavelet coefficients related to video frames by their selective quantization. The 2-D DWT is applied for both video stream and watermark in order to make the watermarking scheme robust and perceptually invisible. The proposed architecture has a very simple control part, since the data are operated in a row-column-slice fashion. This organization reduces the requirement of on-chip memory. In addition, the control unit selects which coefficient to pass to the low-pass and high-pass filters. The on-chip memory will be small as compared to the input size since it depends solely on the filter sizes. Due to the pipelining, all filters are utilized for 100% of the time except during the start-up and wind-down times. The major contribution of this research is towards the selection of appropriate real time watermarking scheme and performing a trade-off between the algorithmic aspects of our proposed watermarking scheme and the hardware implementation technique. The hardware architecture is designed, as a watermarking based IP core with the Avalon interface related to NIOS embedded processor, and tested in order to evaluate the performance of our proposed watermarking algorithm. This architecture has been implemented on the Altera Stratix-II Field Programmable Gate Array (FPGA) prototyping board. Experimental results are presented to demonstrate the capability of the proposed watermarking system for real time applications and its robustness against malicious attacks.     

Oxy‐fuel combustion technology: current status,applications, and trends

The increased level of emissions of carbon dioxide into the atmosphere due to burning of fossil fuels represents one of the main barriers toward the reduction of greenhouse gases and the control of global warming. In the last decades, the use of renewable and clean sources of energies such as solar and wind energies has been increased extensively. However, due to the tremendously increasing world energy demand, fossil fuels would continue in use for decades which necessitates the integration of carbon capture technologies (CCTs) in power plants. These technologies include oxycombustion, pre‐combustion, and post‐combustion carbon capture. Oxycombustion technology is one of the most promising carbon capture technologies as it can be applied with slight modifications to existing power plants or to new power plants. In this technology, fuel is burned using an oxidizer mixture of pure oxygen plus recycled exhaust gases (consists mainly of CO₂). The oxycombustion process results in highly CO₂‐concentrated exhaust gases, which facilitates the capture process of CO₂ after H₂O condensation. The captured CO₂ can be used for industrial applications or can be sequestrated. The current work reviews the current status of oxycombustion technology and its applications in existing conventional combustion systems (including gas turbines and boilers) and novel oxygen transport reactors (OTRs). The review starts with an introduction to the available CCTs with emphasis on their different applications and limitations of use, followed by a review on oxycombustion applications in different combustion systems utilizing gaseous, liquid, and coal fuels. The current status and technology readiness level of oxycombustion technology is discussed. The novel application of oxycombustion technology in OTRs is analyzed in some details. The analyses of OTRs include oxygen permeation technique, fabrication of oxygen transport membranes (OTMs), calculation of oxygen permeation flux, and coupling between oxygen separation and oxycombustion of fuel within the same unit called OTR. The oxycombustion process inside OTR is analyzed considering coal and gaseous fuels. The future trends of oxycombustion technology are itemized and discussed in details in the present study including: (i) ITMs for syngas production; (ii) combustion utilizing liquid fuels in OTRs; (iii) oxy‐combustion integrated power plants and (iv) third generation technologies for CO₂ capture. Techno‐economic analysis of oxycombustion integrated systems is also discussed trying to assess the future prospects of this technology. Copyright © 2017 John Wiley & Sons, Ltd.     

Modeling of ion transport reactor for oxy‐fuel combustion

This paper aims at investigating the performance of a cylindrical ion transport reactor designed for oxy‐fuel combustion. The cylindrical reactor walls are made of dense, nonporous, mixed‐conducting ceramic membranes that only allow oxygen permeation from the outside air into the combustion chamber. The sweep gas (CO₂ and CH₄) enters the reactor from one side and mixes with the oxygen permeate, and the products are discharged from the other side. The process of oxygen permeation through the reactor walls is influenced by the flow condition and composition of air at the feed side (inlet air side) and the gas mixture at the permeate side (sweep gas side). The modeling of the flow process is based on the numerical solution of the conservation equations of mass, momentum, energy, and species in the axisymmetric flow domain. The membrane is modeled as a selective layer in which the oxygen permeation depends on the prevailing temperatures as well as the oxygen partial pressure at both sides of the membrane. The CFD calculations were carried out using fluent 12.1 (ANSYS, Inc., Canonsburg, PA, USA), whereas the mass transfer of oxygen through the membrane is modeled by a set of user defined functions. The model results were validated against previous experimental data, and the comparison showed a good agreement. The study focused on the effect of oxygen partial pressure and temperature on the resulting combustion zones inside the reactor for the two cases of co‐current and counter‐current flow regimes. The results indicated that the oxygen to fuel mass ratio increases as the percentage of CO₂ increases in the inflow sweep gas for both co‐current and counter‐current flows. The obtained sweep mixture ratio (CO₂/CH₄) of 24 is found within the stoichiometric limit over most of the reactor length in the co‐current configuration, whereas the sweep mixture ratio of 15.67 is found in the counter‐current configuration owing to the high O₂ permeation. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of relaxation and phase transition on the resistivity of chemically deposited Ni66B34 layers

The effects of thermal treatment on the conductivity and the temperature coefficient of resistivity of thin amorphous layers of Ni-B metallic glasses (66% Ni, 34% B) are analysed in terms of the dependence on thickness and ageing temperature. The layer exhibits a macroscopical structure consisting of clusters in an amorphous medium; it is assumed that the cluster resistivity is temperature independent up to 350° C and that the amorphous medium is altered markedly by the ageing processes. These consequences are deduced which are in agreement with a previously proposed model for a layer structure.     

First-principle calculations of elastic and electronic properties of the filled skutterudite CeFe4P12

A theoretical study of elastic and electronic properties of the filled skutterudite CeFe₄P₁₂ is presented, using the full-potential linear muffin–tin orbital (FP-LMTO) method. In this approach the local spin density approximation (LSDA) was used for the exchange-correlation (XC) potential. Results are given for lattice constant, bulk modulus, its pressure derivative and elastic constants. Our calculations performed for band structure and density of state show that this compound is an indirect band gap material (Γ–N). The results are compared with previous calculations and experimental data.     

Ice slurry: Pressure drop and deposition velocity

Ice slurries are used in indirect refrigeration systems. The storage tank of ice slurry systems decreases the maximum required cooling capacity of the equipment and smooths down the installation consumption. An advantage of ice slurry systems compared to chilled water systems is the higher cooling energy that can be delivered to customers using the same installed pipes. This paper gives a complete investigation of ice slurry pressure drops and deposition velocity. A model for the friction factor, obtained by empirical and semi-empirical approximation, is discussed. A new simple and efficient method is introduced to find the deposition velocity in an ice slurry fluid flow. Finally a variety of experimental results and some theoretical calculations of ice slurry flow patterns are shown.