Structural transformation in Mn-substituted Sr2Bi2Ta2TiO12 Aurivillius phase synthesized by hydrothermal method: A comparative study and dielectric properties

In this study, a hydrothermal method was applied to synthesize the three-layer Aurivillius phase Sr₂Bi₂Ta₂TiO₁₂ (SBTTO) and Mn-substituted Sr_1·5Bi_2·5Ta₂Ti_0·5Mn_0·5O₁₂ (SBTTMO), with the use of NaOH as a mineralizer. The crystal structure, morphology, dielectric properties, and the correlation between the structural transformation and dielectric properties were investigated. The XRD data reveal that the SBTTO sample adopts a tetragonal crystal structure with the I4/mmm space group and is then transformed into an orthorhombic structure with the B2cb space group for SBTTMO. The morphology of both samples was observed by SEM, which showed anisotropic plate-like grains. With the Mn substitution, the ferroelectric transition temperature (T_c) significantly increases as the influence of the 6s² lone pair of Bi³⁺ increases, and this in turn further induces the relaxor-ferroelectric behavior. Consequently, the increase in T_c confirms the structural transformation from the paraelectric-tetragonal to the ferroelectric-orthorhombic phase.     

Process design and techno‐economic analysis of ethyl levulinate production from carbon dioxide and 1,4‐butanediol as an alternative biofuel and fuel additive

Carbon dioxide capture, utilization, and storage (CCUS) is one of the promising negative emission technologies (NET). Within various CCUS routes available, CO₂ conversion into fuels is one of the attractive options. Currently, most of CO₂ conversion into fuels requires hydrogen, which is expensive and consume large energy to produce. Hence, a different route of producing fuel from CO₂ by utilizing 1,4‐butanediol as the raw material is proposed and evaluated in this study. This alternative route comprises production of levulinic acid from the reaction between CO₂ and 1,4‐butanediol and production of ethyl levulinate, an alternative biofuel and biofuel additive, via an esterification reaction of levulinic acid with ethanol. The process is designed and simulated according to the available data and evaluated in terms of its technical features. Because of the unavailability of reaction data for synthesis of levulinic acid from 1,4‐butanediol and CO₂, several assumptions were taken, which may implicate the accuracy of the studied design. This technical evaluation is followed by cost estimations and sensitivity analysis. Because of the free CO₂, the profitability of the plant depends strongly on the prices of the other chemicals and the price difference between 1,4‐butanediol (raw material) and ethyl levulinate (product). Monte Carlo simulation indicates that the proposed plant will always be profitable if the ethyl levulinate is slightly more expensive than the 1,4‐butanediol, highlighting that the process of producing ethyl levulinate from CO₂ is economically profitable. Future research should be directed towards a catalytic system that can effectively convert CO₂ into levulinic acid, by‐products produced from the two reaction steps, and reduce the excess ethanol used in the second reaction.     

Self-Sensing Actuation With Adaptive Control in Applications With Switching Trajectory

This paper presents the application of self-sensing actuation (SSA) to facilitate the implementation of piezoelectric actuator in an intelligent mechatronic system. SSA is a technique to employ smart materials, such as piezoelectric materials, simultaneously as a sensor and an actuator; thereby increasing the level of integration of the system. The piezoelectric actuator is equipped with an exclusive adaptive controller amidst its nonlinearities and system's disturbance. The application area to be discussed is a microdispensing system, which is an example of a micromanufacturing process, combining a fluidic system and a positioning system.     

Mineral filler reinforcement for commingled recycled‐plastic materials

Three types of mineral fillers, gypsum, wollastonite, and talc, were investigated for their ability to modify the mechanical properties of commingled recycled‐plastic composites containing 0.07–0.26 v/v of filler. Mechanical test results showed that the talc reinforced composites were significantly better in mechanical properties when compared with the gypsum and wollastonite composites. Scanning electron microscopy (SEM) showed that gypsum formed large agglomerates in the matrix. Interfacial adhesion between filler and matrix was evaluated using simple empirical models. To enhance the adhesion, talc, and wollastonite were pretreated with silane coupling agents, 3‐methacryloxypropyltrimethoxy silane (γ‐MPS) and 3‐aminopropyltriethoxy silane (γ‐APS). This did not result in any significant improvement to the material properties. The γ‐APS treatment, however, increased the tensile properties of the composites by ～ 5% when compared with the γ‐MPS treatment. The SEM investigations showed that the γ‐APS treatment provided better adhesion of filler particles and hence voids were less likely to form in the matrix when compared with the γ‐MPS composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modeling of vial and ball motions for an effective mechanical milling process

Mechanical milling (MM) is referred to a solid state size reduction process where work materials in the form of coarse particulates are broken into the ultimate fineness by means of mechanical impact created by collisions of the work materials and the milling media which are placed inside a reciprocating vial. Many milling techniques have been so far developed to improve the process. However, the efficiency of MM process is still below satisfactory in terms of energy balance, where the energy consumed by the process of reduction is still very low compared to the energy supplied to perform the milling process itself. This contributes to high energy losses and proportionally to the span of processing time. Other major problems inherent in the process are contamination by the balls and the vial materials into the work materials, and process temperature that could influence the properties of milled materials. Since MM process utilizes the energy generated by impact upon the collisions of the balls against the work materials, it is important to understand the motions of the balls, the work materials, and the vial, which are the sources of the generation of impact energy. To obtain an optimized processing condition, the motions of vial and ball in relationship with the work materials should be designed in such a way to ensure the optimum impact energy is consumed by the work materials for the size reduction purposes. This paper presents a physical model for work materials, balls, and vial collisions based on different ways of motions. Using this model, higher impact could be achieved. These would lead to the reduction of milling time, contamination, as well as milling temperature.     

Perceptual audio data concealment and watermarking scheme using direct frequency domain substitution

A method is described for perceptually transparent data concealment and watermarking in audio. The proposed system replaces redundant and imperceptible frequency components with hidden data. A psychoacoustic model is used to identify suitable frequency locations for data hiding. Such a method is complicated by the windowing and overlapping requirements used for signal conditioning. The proposed system uses data flipping in place of windowing and incorporates a novel data detection scheme with adaptive weighting to increase the robustness of the watermark transmission. The resistance of the watermarking system to filtering, amplitude scaling and additive white noise is measured and results presented.     

Visual Contact Angle Estimation and Traction Control for Mobile Robot in Rough-Terrain

For a wheeled mobile robot traversing a rough terrain, knowledge of terrain variables is very important for developing effective traction control algorithms. A key variable of the most prevalent information that should be taken into account is the contact angle between the robot wheels and the ground. This paper presents an algorithm for visual estimation of wheel-ground contact angle on uneven terrain. We call it the Visual Contact Angle Estimation (VCAE) method. Given a white LED light source, a monocular camera is required to be mounted on the front wheel and the rear wheel respectively, with a field of view containing the wheel-ground contact interface and its location relative to the wheel is known and fixed during robot travel. This arrangement is used to measure the contact angle with an edge detection strategy. Then a traction control methodology based on multi-objective optimization is presented. This exploits the wheel-ground contact angle obtained in the VCAE system to improve ground traction and reduce power consumption. Simulation and experiment results for a wheeled robot traversing a symmetrical uneven testbed demonstrate the effectiveness of the VCAE method and traction control algorithms.     

Validation of the in vivo intravascular ultrasound measurement of in-stent neointimal hyperplasia volumes

OBJECTIVES: This study was undertaken to validate the in vivo intravascular ultrasound (IVUS) measurement of in-stent neointimal hyperplasia (IH) volumes. BACKGROUND: Because stents reduce restenosis compared to balloon angioplasty, stent use has increased significantly. As a result, in-stent restenosis is now an important clinical problem. Serial IVUS studies have shown that in-stent restenosis is secondary to intimal hyperplasia. To evaluate strategies to reduce in-stent restenosis, accurate measurement of in-stent neointimal tissue is important. METHODS: Using a porcine coronary artery model of in-stent restenosis, single Palmaz-Schatz stents were implanted into 16 animals with a stent:artery ratio of 1.3:1. Intravascular ultrasound imaging was performed at 1 month, immediately prior to animal sacrifice. In vivo IVUS and ex vivo histomorphometric measurements included stent, lumen and IH areas; IH volumes were calculated with Simpson's rule. RESULTS: Intravascular ultrasound measurements of IH (30.4+/-11.0 mm3) volumes correlated strongly with histomorphometric measurements (26.7+/-8.5 mm3, r=0.965, p < 0.0001). The difference between the IVUS and the histomorphometric measurements of IVUS volume was 4.1+/-2.7 mm3 or 15.8+/-11% (standard error of the estimate=0.7). Both histomorphometry and IVUS showed that IH was concentric and uniformly distributed over the length of the stent. Intravascular ultrasound detected neointimal thickening of < or =0.2 mm in 5 of 16 stents. Sample size calculations based on the IVUS measurement of IH volumes showed that 12 stented lesions/arm would be required to show a 50% reduction in IVUS-measured IH volume and 44 stented lesions/arm would be required to show a 25% reduction in IH volume. CONCLUSION: In vivo IVUS measurement of IH volumes correlated strongly with ex vivo histomorphometry. Using volumetric IVUS end points, small sample sizes should be necessary to demonstrate effectiveness of strategies to reduce in-stent restenosis.