Application of Wavelet in Highly Ill-Posed Inverse Heat Conduction Problem

In this work, the prefiltering of the sensor data is taken into consideration when solving an inverse heat conduction problem. The temperature data obtained from each sensor is considered as a discrete signal, and discrete wavelet transform in a multi-resolution filter bank structure is utilized for the signal analysis, after which wavelet denoising algorithm is applied to remove noise from data signal. Subsequently, noisy and denoised temperatures are separately used as input data to an inverse heat conduction problem for comparison. The inverse heat conduction problem considered in this article is an inverse volumetric heat source problem, and it is solved using the conjugate gradient method along with the associated adjoint problem used to obtain the gradient of the objective function. Three sets of results in two case studies are compared (i.e., the result obtained from non-noisy data, noisy data, and denoised data). In the case of noisy data, iterative regularization is used to regularize the solution. The root mean square error of the estimated heat source from denoised data is reduced approximately by a factor of seven to nine as compared to those obtained from noisy data.     

Polyacrolein/mesoporous silica nanocomposite: Synthesis,thermal stability and covalent lipase immobilization

In this work, new polyacrolein/MCM-41 nanocomposites with good phase mixing behavior were prepared through an emulsion polymerization technique. Mesoporous silica was synthesized by in situ assembly of tetraethyl orthosilicate (TEOS) and cetyl trimethyl ammonium bromide (CTAB). The structure and properties of polyacrolein containing nanosized MCM-41 particle (5 and 10 wt%), were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, Dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption techniques, and thermogravimetric (TGA) analyses. The SEM images from the final powder have revealed good dispersion of the MCM-41 nanoparticles throughout polymeric matrix with no distinct voids between two phases. The results indicated that the thermal properties of the nanocomposite were enhanced by addition of MCM-41. Thermomyces lanuginosa lipase (TLL) was used as a model biocatalyst and successfully immobilized with polyacrolein and the nanocomposite via covalent bonds with the aldehyde groups. The activity between free enzyme, polyacrolein, and MCM-41 nanocomposite (10 wt%)-immobilized TLL was compared. The immobilized lipase with the nanocomposite shows better operational stability such as pH tolerance, thermal and storage stability. In addition, the immobilized lipase with the nanocomposite can be easily recovered and retained at 74% of its initial activity after 15 time reuses.     

Adaptive fault-tolerant DVFS with dynamic online AVF prediction

Advances in silicon technology and shrinking the feature size to nanometer levels make random variations and low reliability of nano-devices the most important concern for fault-tolerant design. Design of reliable and fault-tolerant embedded processors is mostly based on developing techniques that compensate reliability shortcomings by adding hardware or software redundancy. The recently-proposed redundancy adding techniques are generally applied uniformly to all parts of a system and lead to heavy overheads and inefficiencies in terms of performance, power, and area. Efficient employment of non-uniform redundancy becomes possible when a quantitative analysis of a system behavior while encountering transient faults is provided. In this work, we present a quantitative analysis of the behavior of an embedded processor regarding transient faults and propose a new approach that accurately predicts the architecture vulnerability factor (AVF) in real-time. Another critical concern in design of new-silicon processors is power consumption issue. Dynamic voltage and frequency scaling (DVFS) is an effective method for controlling both energy consumption and performance of a system. Since rate of radiation-induced transient faults depends on operating frequency and supply voltage, DVFS techniques are recently shown to have compromising effects on electronic system reliability. Therefore, ignoring the effects of voltage scaling on fault rate could considerably degrade the system reliability. Here, by exploiting the proposed online AVF prediction methodology and based on analytic derivation, we propose a reliability-aware adaptive dynamic voltage and frequency scaling (DVFS) approach in case study of Multi-Processor System on Chip (MPSoC) with Multiple Clock Domain (MCD) pipeline architectures in which the frequency and voltage are scaled by simultaneously considering all three of power consumption, reliability, and performance. Comparing to the traditional methods of reliability-aware DVFS systems, the proposed reliability-aware DVFS method yields 50% better power saving at the same reliability level.     

Controller design based on μ analysis and PSO algorithm

In this paper an evolutionary algorithm is employed to address the controller design problem based on μ analysis. Conventional solutions to μ synthesis problem such as D–K iteration method often lead to high order, impractical controllers. In the proposed approach, a constrained optimization problem based on μ analysis is defined and then an evolutionary approach is employed to solve the optimization problem. The goal is to achieve a more practical controller with lower order. A benchmark system named two-tank system is considered to evaluate performance of the proposed approach. Simulation results show that the proposed controller performs more effective than high order H_∞ controller and has close responses to the high order D–K iteration controller as the common solution to μ synthesis problem.     

A kinetic study of Pd–Au catalyzed synthesis of vinyl acetate from oxidation of ethylene and acetic acid in heterogeneous gas reaction

While qualitative interpretation of the experimental results is often limited to the identification of global mechanistic phenomena, kinetic modeling is a more powerful tool for the identification of the chemical reaction network that can describe the experimental results. In this paper, kinetic study of vinyl acetate (VA) synthesis was performed in a fixed bed reactor with oxidation of ethylene and acetic acid in gaseous phase over Pd/Au/SiO₂ catalyst under the industrial relevant reaction condition as follows: temperature of 120–165 °C, at constant pressure of 8 bar and the ratio of catalyst mass to the feed (W/F) was maintained at 70 g/mol min. Variation in partial pressure and concentration of reactants have led us to determine the rate limiting step and therefore proposing a new rate low based on Langmuir-Hinshelwood–Hougen–Watson (LHHW) approached consistent with experimental observation while adapted through mathematical formulation with high reliance. So, the kinetic parameters were determined by the Levenberg–Marquardt algorithm. Effect of temperature has also been surveyed showing a decreased in selectivity due to the difference in reaction constants of main and side reaction rate and an increase rate due to the increase in apparent activation energy.     

Buckling analysis of structural steel frames with inelastic effects according to codes

Steel building frames are often analyzed for stability in an elastic way, while most of their columns behave inelastically at the buckling stage. Most column design provisions allow for inelastic behavior, but overall inelastic stability analysis is rarely performed. In this study the analysis philosophy is centered on the overall frame stability and its true safety factor. As many columns show inelastic behavior at the buckling stage, the proposed procedure takes due consideration of this fact. Once the overall buckling factor for the frame is obtained, individual column effective length factors, and their true slenderness ratios are computed, and used in the design relationships. This procedure circumvents the use of design nomographs and numerous formulas proposed in the past to alleviate their shortcomings. The procedure proposed based on the overall safety factor concept is an iterative one. It starts with a stability analysis and gradually modifies the structural properties to take account of inelasticity and eventually converges to the final buckling factor and mode shape. Any type of lateral restraint can be exactly modeled and taken into consideration without the need for approximate simplifying assumptions. The design philosophy proposed herein is that all columns must have their design parameters as related to buckling capacity must be derived from a single buckling analysis valid for the whole structure, and not considered separately and isolated from the rest of the structure as is currently practiced. Examples are worked out to illustrate the procedure and the results are compared to those of others.     

A multi-path cognitive resource management mechanism for QoS provisioning in wireless mesh networks

In a Wireless Mesh Network (WMN), achieving acceptable Quality of Service (QoS) levels requires distributed control over network resources and subsequent awareness of the dynamically changing conditions of the WMN. In this paper, for facilitating such control, a cognitive mechanism is introduced, which facilitates cooperation and cognition among multiple Mesh Access Points and edge routers called Mesh Portals for routing client traffic via multiple paths. The aim of the cognition is to reasonably maximize the fulfillment of the clients from the achieved QoS (e.g., end-to-end delay and bandwidth). The cognitive process consists of three cycles. In the first cycle, the Perception Cycle, the current performance status of the WMN is continuously perceived through feedback loops. The perceived information is further processed and fed into the second cycle, the Learning Cycle, in order to understand the network conditions. This results in the prediction of the performance of the paths and estimation of the path delay for various load conditions. The third cycle, the Decision Cycle, is a game theoretic coalition formation algorithm, that results in path selection and data rate assignment. This algorithm is modeled as a cooperative game theory, which incorporates the Bilateral Shapley Value to find the best coalition from available paths, whereupon a bargaining game theory formulates the data rate assignment. Extensive simulations are performed for evaluating the proposed cognitive mechanism under various load conditions and results demonstrate the evident enhancement of the achieved end-to-end QoS of the clients and the network performance compared with non-cognitive scenarios, specifically in congested conditions.     

Estimation of Micellization Parameters of SDS in the Presence of Some Electrolytes for Emulsion Polymerization Systems

The critical micelle concentration and the effective degree of dissociation of micelles (α) of sodium dodecyl sulfate, which is the most extensively used surfactant in emulsion polymerization systems, were determined in the presence of various amounts of sodium carbonate and potassium persulfate, and some monomers, such as methyl methacrylate, butyl acrylate, and styrene by means of the conductometric procedure at 25 °C. In addition, the other micellization parameters, such as aggregation number and number of counter-ions per micelle, were computed directly from the obtained conductivity measurements data. The effect of the combination of sodium carbonate and potassium persulfate, on the critical micelle concentration of the sodium dodecyl sulfate solutions was studied at 60 °C (emulsion reaction temperature). The empirical formulations derived provide an easy way to estimate the critical micelle concentration and the effective degree of dissociation of micelles of a system at a given electrolyte and monomer concentration.     

Three-stage hybrid osmotic–intermittent microwave–convective drying of apple at low temperature and short time

ABSTRACT

In recent years, intermittent microwave coupled with hot air-drying has been used increasingly, thanks to considerable improvements observed in drying properties. The aim of this study was to investigate the effect of process of drying apple pretreated osmotically with sucrose solution at five concentrations of 0 (control), 10, 30, 50, and 70% (w/w), using intermittent microwave at four power levels of 0 (control), 360, 600, and 900?W, four pulse ratios of 1, 2, 3, and 4, and convective hot air (40°C) on drying kinetics, effective moisture diffusion coefficient, shrinkage, bulk density, rehydration ratio, and energy consumption. Results showed that the three-stage hybrid osmotic–intermittent microwave–convective drying of apple at low temperature yielded higher drying rates (with 41.5% decrease in drying time) and improved quality of final product. The effective moisture diffusion coefficient increased with an increase in power, pulse ratio, and the concentration of osmotic solution. Furthermore, shrinkage, bulk density, and energy consumption of the samples decreased with an increase in power, pulse ratio, and the concentration of osmotic solution. In summary, the use of intermittent microwave coupled with forced convection of hot air (at low temperature) in drying of apple pretreated by sucrose osmotic solution led to products with improved properties in terms of both quality and quantity.