Experimental and theoretical study of methane adsorption on granular activated carbons

The experimental and theoretical study of methane adsorption on granular activated carbons is presented. The adsorption data are modeled by various isotherm equations. Toth equation is found to have the best fit. The isosteric heat decreases with loading and increases weakly with temperature, which is an indication of heterogeneity of the methane and granular activated carbon system. Using optimized parameters from Toth equation, a novel procedure is developed to calculate the integral heat of adsorption, which is the total amount of isosteric heat of adsorption at a given temperature and pressure during the adsorption process. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

An improved delay‐dependent bounded real lemma (BRL) and H∞ controller synthesis for linear neutral systems

In this paper, a novel delay‐dependent bounded real criterion and an improved sufficient condition are derived for the design of an H_∞ state‐feedback controller for linear neutral time‐delay systems. On the basis of an augmented Lyapunov‐Krasovskii functional, a new bounded real lemma is introduced in terms of a convex linear matrix inequality (LMI) condition that can be solved using interior point algorithms. The bounded real lemma is extended to obtain a sufficient condition for the existence of a delay‐dependent H_∞ memoryless state‐feedback controller. Neither any model transformation nor bounding of any of the cross terms are utilized while deriving the bounded real lemma. Moreover, the use of any free slack matrix variable approach is avoided to a certain extent in order not to increase the complexity of the synthesis problem. A cone complementary nonlinear minimization algorithm is employed to achieve a feasible solution set for the synthesis conditions. Finally, seven numerical examples are given to illustrate the effectiveness of the proposed method. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Inactivation Kinetics of Polyphenol Oxidase in an Aqueous Model System under Stand-Alone and Combined Ultrasound and Ultraviolet Treatments

The objectives of this work were to study the ultrasound- and ultraviolet light-induced inactivation kinetics of polyphenol oxidase extracted from different sources in a model system. The polyphenol oxidase crude extract was obtained from bananas, apples, quince, eggplants, plums, dill, and cultured mushrooms, which exhibited high enzyme activity. The polyphenol oxidase crude extract was treated with ultrasound and ultraviolet light at 40°C temperature for 40 min. The study showed that the polyphenol oxidase enzyme was inactivated between 12 and 100% during ultrasound only treatment; between 4 and 29% during ultraviolet light only treatment; and between 80 and 100% during simultaneous ultrasound and ultraviolet light treatment. Based on the measurements, an exponential decay model for determining polyphenol oxidase inactivation kinetics was developed. The model provides high determination coefficients (R²): 0.968–0.999 with ultrasound only treatment, 0.881–0.990 with ultraviolet only treatment, and 0.975–1.000 with simultaneous ultrasound and ultraviolet treatment. The polyphenol oxidase kinetics evaluation showed that different treatments provided different inactivation times, or D-values. The D-values were 7.0–656.1 min for ultrasound only treatment (D_US), 251–1887 min for ultraviolet only treatment (D_UV), and 3.3–59.4 min for combined ultrasound and ultraviolet treatment (D_US+UV).     

Dynamic analysis of adsorption on bidisperse porous catalysts

In a variety of catalytic processes dealing with porous catalysts, bidisperse solids arc used. In such systems, it is important to know the adsorption rate together with the diffusion rate in the macro and micropores of the porous solid. In this work, the Dog'u-Smith (1975) single pellet pulse response method has been used for the simultaneous evaluation of the adsorption and the macro and micropore diffusion parameters in bidisperse porous catalysts. It has been shown that the method succesfully can be applied for fast and accurate evaluation of these parameters. Equations relating the adsorption and diffusion parameters to the measurable properties of the response peak have been derived for a bidisperse pellet. The method experimentally was tested for ethylene adsorption on α-alumina at 45°C and atmospheric pressure. For a pellet of total porosity 0.73 and macroporosity 0.32, the effective macro and micropore diffusivities and the adsorption equilibrium constant were determined as 0.0334 cm²/s, 8.9×10⁶ cm²/s and 25 cm³/g, respectively.     

Effects of Er,Cr:YSGG laser parameters on dentin bond strength and interface morphology

Previous studies have shown the effects of Er,Cr:YSGG laser irradiation on the dentin bond strength; but there are few reports that show the significance of the irradiation with different laser parameters on dentin bond strength and interface morphology. This in‐vitro study attempted to evaluate the microtensile bond strength (μTBS) and interface morphology of resin‐dentin interfaces, either followed by treatment with Er,Cr:YSGG laser irradiation with different parameters or not. The flattened dentin samples of 35 bovine teeth were embedded into acrylic blocks and randomly divided into seven groups according to surface treatments using Er,Cr:YSGG lasers with different parameters: 3 W/20 Hz, 3 W/35 Hz, 3 W/50 Hz, 1.5 W/20 Hz, 1.5 W/35 Hz, 1.5 W/50 Hz, or no laser treatment (n = 5). Composite buildups were done over bonded surfaces and stored in water (24 hours at 37°C). Specimens were sectioned into sticks that were subjected to μTBS testing and observed under FE‐SEM. Control groups (27.70 ± 7.0) showed statistically higher values than laser‐irradiated groups. There were no significant differences among laser groups. Despite that, increasing the pulse frequency yielded slightly higher bond strength. Depending on laser settings, Er,Cr:YSGG laser irradiation caused interfacial gaps and resin tags with wings morphology. With the parameters used in this study, Er,Cr:YSGG laser irradiation promoted morphological changes within resin‐dentin interfaces and negatively influenced the bond strength of adhesive systems. Microsc. Res. Tech. 78:1104–1111, 2015. © 2015 Wiley Periodicals, Inc.     

Experimental investigation of machining characteristics and chatter stability for Hastelloy-X with ultrasonic and hot turning

Ultrasonic-assisted machining is a machining operation based on the intermittent cutting of material which is obtained through vibrations generated by an ultrasonic system. This method utilizes low-amplitude vibrations with high frequency to prevent continuous contact between a cutting tool and a workpiece. Hot machining is another method for machining materials which are difficult to cut. The basic principle of this method is that the surface of the workpiece is heated to a specific temperature below the recrystallization temperature of the material. This heating operation can be applied before or during the machining process. Both of these operations improve machining operations in terms of workpiece-cutting tool characteristics. In this study, a novel hybrid machining method called hot ultrasonic-assisted turning (HUAT) is proposed for the machinability of Hastelloy-X material. This new technique combines ultrasonic-assisted turning (UAT) and hot turning methods to take advantage of both machining methods in terms of machining characteristics, such as surface roughness, stable cutting depths, and cutting tool temperature. In order to observe the effect of the HUAT method, Hastelloy-X alloy was selected as the workpiece. Experiments on conventional turning (CT), UAT, and HUAT operations were carried out for Hastelloy-X alloy, changing the cutting speed and cutting tool overhang lengths. Chip morphology was also observed. In addition, modal and sound tests were performed to investigate the modal and stability characteristics of the machining. The analysis of variance (ANOVA) method was performed to find the effect of the cutting speed, tool overhang length, and machining techniques (CT, UAT, HUAT) on surface roughness, stable cutting depths, and cutting tool temperature. The results show both ultrasonic vibration and heat improve the machining of Hastelloy-X. A decrease in surface roughness and an increase in stable cutting depths were observed, and higher cutting tool temperatures were obtained in UAT and HUAT compared to CT. According to the ANOVA results, tool overhang length, cutting speed, and machining techniques were effective parameters for surface roughness and stable cutting depths at a 1% significance level (p ≤ 0.01). In addition, cutting speed and machining techniques have an influence on cutting tool temperature at a 1% significance level (p ≤ 0.01). During chip analysis, serrated chips were observed in UAT and HUAT.     

ECM-aware cell-graph mining for bone tissue modeling and classification

Pathological examination of a biopsy is the most reliable and widely used technique to diagnose bone cancer. However, it suffers from both inter- and intra- observer subjectivity. Techniques for automated tissue modeling and classification can reduce this subjectivity and increases the accuracy of bone cancer diagnosis. This paper presents a graph theoretical method, called extracellular matrix (ECM)-aware cell-graph mining, that combines the ECM formation with the distribution of cells in hematoxylin and eosin stained histopathological images of bone tissues samples. This method can identify different types of cells that coexist in the same tissue as a result of its functional state. Thus, it models the structure-function relationships more precisely and classifies bone tissue samples accurately for cancer diagnosis. The tissue images are segmented, using the eigenvalues of the Hessian matrix, to compute spatial coordinates of cell nuclei as the nodes of corresponding cell-graph. Upon segmentation a color code is assigned to each node based on the composition of its surrounding ECM. An edge is hypothesized (and established) between a pair of nodes if the corresponding cell membranes are in physical contact and if they share the same color. Hence, multiple colored-cell-graphs coexist in a tissue each modeling a different cell-type organization. Both topological and spectral features of ECM-aware cell-graphs are computed to quantify the structural properties of tissue samples and classify their different functional states as healthy, fractured, or cancerous using support vector machines. Classification accuracy comparison to related work shows that the ECM-aware cell-graph approach yields 90.0% whereas Delaunay triangulation and the simple cell-graph approach achieves 75.0 and 81.1% accuracy, respectively.     

The effect of substrate and post annealing temperature on the electrical properties of polycrystalline InSe thin films

The correlation between the electrical properties of vacuum evaporated InSe thin films and the growth conditions as well as post depositional annealing has been investigated. The electrical properties of the deposited films have been studied in the temperature range of 50–320 K. The donor levels present in the InSe films have been analysed by applying the single donor-single acceptor model to the electrical data.     

Robust delay‐dependent ℋ︁∞ control of time‐delay systems with state and input delays

This paper studies the design problem of robust delay‐dependent ??_∞ controller for a class of time‐delay control systems with time‐varying state and input delays, which are assumed to be noncoincident. The system is subject to norm‐bounded uncertainties and ??₂ disturbances. Based on the selection of an augmented form of Lyapunov–Krasovskii (L‐K) functional, first a Bounded Real Lemma (BRL) is obtained in terms of linear matrix inequalities (LMIs) such that the nominal, unforced time‐delay system is guaranteed to be globally asymptotically stable with minimum allowable disturbance attenuation level. Extending BRL, sufficient delay‐dependent criteria are developed for a stabilizing ??_∞ controller synthesis involving a matrix inequality for which a nonlinear optimization algorithm with LMIs is proposed to get feasible solution to the problem. Moreover, for the case of existence of norm‐bounded uncertainties, both the BRL and ??_∞ stabilization criteria are easily extended by employing a well‐known bounding technique. A plenty of numerical examples are given to illustrate the application of the proposed methodology of this note. The achieved numerical results on the maximum allowable delay bound and minimum allowable disturbance attenuation level are exhibited to be less conservative in comparison to those of existing methods in the literature. Copyright © 2010 John Wiley & Sons, Ltd.     

Analytical models for risk-based intrusion response

Risk analysis has been used to manage the security of systems for several decades. However, its use has been limited to offline risk computation and manual response. In contrast, we use risk computation to drive changes in an operating system’s security configuration. This allows risk management to occur in real time and reduces the window of exposure to attack. We posit that it is possible to protect a system by reducing its functionality temporarily when it is under siege. Our goal is to minimize the tension between security and usability by trading them dynamically. Instead of statically configuring a system, we aim to monitor the risk level, using it to drive the tradeoff between security and utility. The advantage of this approach is that it provides users with the maximum possible functionality for any predefined level of risk tolerance.