A novel technique for residence time distribution (RTD) measurements in solids unit operations

This work presents a novel technique with fast response for Residence Time Distribution (RTD) measurements in gas-solid unit operations (e.g., fluidized bed reactors). This technique is based on an optical method which eliminates the requirement of knowing the velocity and concentration profiles at the exit section of the system. Experiments were carried out with SiC particles and a phosphorescent pigment used as a tracer. A concentration measurement system was developed to measure the tracer concentration in SiC/pigment mixtures. The corresponding pigment concentrations were evaluated at the bottom of this system using a photomultiplier. The pigment concentration was derived from the integral of the signal intensity received by the photomultiplier. Then, a calibration curve was established which provided the empirical relationship between the integral and pigment concentration. In order to validate this RTD measurement technique, a series of experiments was performed in a bubbling fluidized bed and the effect of the bed height was studied. It was shown that the experimental RTD curves were in good agreement with the theoretical RTD of bubbling fluidized beds. This solids RTD measurement technique can be used to provide a better understanding of the hydrodynamics of complex solids unit operations.     

Eu3+, Sm3+ Deep‐Red Phosphors as Novel Materials for White Light‐Emitting Diodes and Simultaneous Performance Enhancement of Organic–Inorganic Perovskite Solar Cells

The luminous efficiency of inorganic white light‐emitting diodes, to be used by the next generation as light initiators, is continuously progressing and is an emerging interest for researchers. However, low color‐rendering index (Ra), high correlated color temperature (CCT), and poor stability limit its wider application. Herein, it is reported that Sm³⁺‐ and Eu³⁺‐doped calcium scandate (CaSc₂O₄ (CSO)) are an emerging deep‐red‐emitting material with promising light absorption, enhanced emission properties, and excellent thermal stability that make it a promising candidate with potential applications in emission display, solid‐state white lighting, and the device performance of perovskite solar cells (PSCs). The average crystal structures of Sm³⁺‐doped CSO are studied by synchrotron X‐ray data that correspond to an extremely rigid host structure. Samarium ion is incorporated as a sensitizer that enhances the emission intensity up to 30%, with a high color purity of 88.9% with a 6% increment. The impacts of hosting the sensitizer are studied by quantifying the lifetime curves. The CaSc₂O₄:0.15Eu³⁺,0.03Sm³⁺ phosphor offers significant resistance to thermal quenching. The incorporation of lanthanide ion‐doped phosphors CSOE into PSCs is investigated along with their potential applications. The CSOE‐coated PSCs devices exhibit a high current density and a high power conversion efficiency (15.96%) when compared to the uncoated control devices.     

Influence of substitutional doping on the electronic properties of carbon nanotubes with Stone Wales defects: density functional calculations

Abstract

In this work, we implemented density function theory to investigate the structural and the electronic properties of nitrogen doped single walled carbon nanotube under different orientations of Stone Wales defect. We have found that, the doped defected structures are more stable than the non-doped defected structures. Furthermore, doping defected carbon nanotubes with a nitrogen atom has significantly narrowed the band gap and slightly shifted the Fermi level toward the conduction band. Moreover, nitrogen substitution creates new band levels just above the Fermi level which exemplifies an n-type doping. However, the induced band gap is indirect band gap compared to direct band gap as in pristine carbon nanotubes. Furthermore, the electronic and structural properties of nitrogen doped carbon nanotube with Stone Wales defects is crucially affected by the dopant site as well as the orientations of Stone Wales defects.     

H ∞ observer design for uncertain nonlinear discrete‐time systems with time‐delay: LMI optimization approach

We present a robust H _∞ observer for a class of nonlinear discrete‐time systems. The class under study includes an unknown time‐varying delay limited by upper and lower bounds, as well as time‐varying parametric uncertainties. We design a nonlinear H _∞ observer, by using the upper and lower bounds of the delay, that guarantees asymptotic stability of the estimation error dynamics and is also robust against time‐varying parametric uncertainties. The described problem is converted to a standard optimization problem, which can be solved in terms of linear matrix inequalities (LMIs). Then, we expand the problem to a multi‐objective optimization problem in which the maximum admissible Lipschitz constant and the minimum disturbance attenuation level are the problem objectives. Finally, the proposed observer is illustrated with two examples. Copyright © 2014 John Wiley & Sons, Ltd.     

Integrated supply chain and product family architecture under highly customized demand

Mass customization efforts are challenged by an unpredictable growth or shrink in the market segments and shortened product life cycles which result in an opportunity loss and reduced profitability; hence we propose a concept of sustainable mass customization to address these challenges where an economically infeasible product for a market segment is replaced by an alternative superior product variant nearly at the cost of mass production. This concept provides sufficient time to restructure the product family architecture for the inclusion of a new innovative product variant while fulfilling the market segments with the customer delight and an extended profitability. To implement the concept of sustainable mass customization we have proposed the notions of generic-bill-Of-products (GBOP: list of product variants agreed for the market segments), its interface with generic-supply-chain-structure and strategic decisions about opening or closing of a market segment as an optimization MILP (mixed integer linear program) model including logistics and GBOP constraints. Model is tested with the varying market segments demands, sales prices and production costs against 1 to 40 market segments. Simulation results provide us an optimum GBOP, its respective segments and decisions on the opening or closing of the market segments to sustain mass customization efforts.     

Hybrid Task and Message Scheduling in Hard Real Time Distributed Systems over FlexRay Bus

FlexRay is a vehicular communication protocol designed to meet growing requirements in hard real time automotive systems and to support time triggered as well as event triggered paradigms. Thus, there has been a lot of recent interest in timing analysis techniques in order to provide bounds for the message communication times on FlexRay. In this paper, we present an approach to compute the WCRT （worst case response time） for periodic and sporadic tasks, within a FlexRay node, responsible for sending messages on the FlexRay SS （static segment） and DS （dynamic segment）. On the other hand, we propose a scheduling table for messages transmitted over the FlexRay SS. An interesting innovation would be the use of a scheduling algorithm performed on a FlexRay node to guarantee the arrival of the right data on the right time and to ensure that every task meets its deadline. As application, we will use the extended SAE （society of automotive engineers） benchmark for the FlexRay network to identify the static and dynamic tasks, and calculate the response time, based on a hybrid scheduling model to further prove that the deadline of the SAE benchmark applications is insured.     

Nonlinear features of heart rate variability in paranoid schizophrenic

Cardiovascular mortality is significantly increased in patients suffering from schizophrenia. However, psychotic symptoms are quantified by means of the scale for the assessment of positive and negative symptoms, but many investigations try to introduce new etiology for psychiatric disorders based on combination of biological, psychological and social causes. Classification between healthy and paranoid cases has been achieved by time, frequency, Hilbert–Huang (HH) and a combination between those features as a hybrid features. Those features extracted from the Hilbert–Huang transform for each intrinsic mode function (IMF) of the detrended time series for each healthy case and paranoid case. Short-term ECG recordings of 20 unmedicated patients suffering from acute paranoid schizophrenia and those obtained from healthy matched peers have been utilized in this investigation. Frequency features: very low frequency (VLF), low frequency (LF), high frequency (HF) and HF/LF (ratio) produced promising success rate equal to 97.82 % in training and 97.77 % success rate in validation by means of IMF1 and ninefolds. Time–frequency features [LF, HF and ratio, mean, maximum (max), minimum (min) and standard deviation (SD)] provided 100 % success in both training and validation trials by means of ninefolds for IMF1 and IMF2. By utilizing IMF1 and ninefolds, frequency and Hilbert–Hang features [LF, HF, ratio, mean value of envelope ( \(\bar{a}\) )] produced 96.87 and 95.5 % for training and validation, respectively. By analyzing the first IMF and using ninefolds, time and Hilbert–Hang features [mean, max, min, SD, median, first quartile (Q1), third quartile (Q3), kurtosis, skewness, Shannon entropy, approximate entropy and energy, ( \(\bar{a}\) ), level of envelope variation ([ \(\dot{a}\) (t)]^2), central frequency \((\bar{W})\) and number of zero signal crossing \((\left| {\bar{W}} \right|)\) ] produced a 100 % success rate in training and 90 % success rate in validation. Time, frequency and HH features [energy, VLF, LF, HF, ratio and ( \(\bar{a}\) )] provided 97.5 % success rate in training and 95.24 % success rate in validation using IMF1 and sixfolds. However, frequency features have produced promising classification success rate, but hybrid features emerged the highest classification success rate than using features in each domain separately.     

Heat Treatment Improves Olive Oil Extraction

To determine the effect of hot water pre-treatment on olive oil extraction, six cultivars of olive fruit (Olea europaea L. cvs. “Arbequina”, “Hojiblanca”, “Lechín”, “Manzanilla”, “Picual”, and “Verdial”) were heated at 50, 55, and 60 °C prior to laboratory scale oil extraction. Heat treatment resulted in higher oil extraction than unheated control samples. Quality parameters of the oils were not significantly (P < 0.05) affected by these treatments; however, oil stability and bitterness intensity were reduced and pigment content was increased through pre-heat treatment. This process may be incorporated economically into olive oil processing.     

Electrochemical preparation and kinetic study of poly(o-tolidine) in aqueous medium

Poly(o-tolidine), PoT, film was prepared by electrochemical oxidation of the monomer, oT, in 0.1 M HCl + 0.1 M KClO₄. The presence of KClO₄ in the formation medium was found to be essential for the electropolymerization process to proceed. Increasing the upper potential limit up to +1.5 V, instead of +1.0 V, leads to appearance of a new anodic peak at +1.36 V and enhancement of the polymer formation of PoT without changing the film structure. The electrochemical behavior of the formed polymer films was investigated in 1.0 M HClO₄. The kinetic parameters were calculated from the values of the charge consumed during the electropolymerization process. The rate of the polymerization reaction was found to depend on the concentration of the monomer rather than the electrolyte. The polymerization rate is first order with respect to the monomer concentration and zero order with respect to the electrolyte. The electrolyte plays no active role in the kinetics of the electropolymerization process and its role is most likely limited to polymer doping.     

Chitosan graft copolymers‐HA/DBM biocomposites: Preparation,characterization, and in vitro evaluation

The combination of biopolymer with a bioactive component takes advantage of the osteoconductivity and osteoinductivity properties. The studies on composites containing hydroxyapatite (HA), demineralized bone matrix (DBM) fillers and chitosan biopolymer are still conducted. In the present study, the bioactive fillers were loaded onto p(HEMA‐MMA) grafted chitosan copolymer to produce a novel biocomposites having osteoinductive and osteoconductive properties. The produced composites were assessed by TGA, XRD, FTIR, and SEM techniques to prove the interaction between both matrices. In vitro behavior of these composites was performed in SBF to verify the formation of apatite layer onto their surfaces and its enhancement. The results confirmed the formation of thick apatite layer containing carbonate ions onto the surface of biocomposites especially these containing HA‐DBM mixture and pMMA having bone cement formation in their structure. These a novel biocomposites have unique bioactivity properties can be applied in bone implants and tissue engineering applications as scaffolds in future. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007