A MRAS-based adaptive pseudoreduced-order flux observer for sensorless induction motor drives

The performance of vector-controlled sensorless induction motor drives is generally poor at very low speeds, especially at zero speed due to offset and drift components in the acquired feedback signals, and the increased sensitivity of dynamic performance to model parameter mismatch resulting especially from stator resistance variations. The speed estimation is adversely affected by stator resistance variations due to temperature and frequency changes. This is particularly significant at very low speeds where the calculated flux deviates from its set values. Therefore, it is necessary to compensate for the parameter variation in sensorless induction motor drives, particularly at very low speeds. This paper presents a novel method of estimating both the shaft speed and stator resistance of an induction motor. In this novel scheme, an adaptive pseudoreduced-order flux observer (APFO) is developed. In comparison to the adaptive full-order flux observer (AFFO), the proposed method consumes less computational time, and provides a better stator resistance estimation dynamic performance. Both simulation and experimental results confirm the superiority of the proposed APFO scheme for a wide range of resistance variations from 0 to 100%.     

Next generation of 100-/spl mu/m-pitch wafer-level packaging and assembly for systems-on-package

According to the latest ITRS roadmap, the pitch of area array packages is expected to decrease to 100 /spl mu/m by 2009. Simultaneously, the electrical performance of these interconnections needs to be improved to support data rates in excess of 10 Gbps, while guaranteeing thermomechanical reliability and lowering the cost. These requirements are challenging, thus, needing innovative interconnection designs and technologies. This paper describes the development of three interconnection schemes for wafer-level packages (WLPs) at 100-/spl mu/m pitch, involving rigid, compliant, and semicompliant interconnection technologies, extending the state of the art in each. Extensive electrical and mechanical modeling was carried out to optimize the geometry of the interconnections with respect to electrical performance and thermomechanical reliability. It was found that the requirements of electrical performance often conflict with those of thermomechanical reliability and the final "optimum" design is a tradeoff between the two. For the three interconnection schemes proposed, it was found that the electrical requirements can be met fairly well but acceptable mechanical reliability may require organic boards with a coefficient of thermal expansion of 10 ppm/K or lower.     

Solving the inverse problem for aggregation in activated sludge flocculation using a population balance framework.

Many systems contain populations of individuals. Often, they are regarded as a lumped phase, which might, for some applications, lead to inadequate model predictive power. An alternative framework, Population Balance Models, has been used here to describe such a system, activated sludge flocculation in which particle size is the property one wants to model. An important problem to solve in population balance modelling is to determine the model structure that adequately describes experimentally obtained data on for instance, the time evolution of the floc size distribution. In this contribution, an alternative method based on solving the inverse problem is used to recover the model structure from the data. In this respect, the presence of similarity in the data simplifies the problem significantly. Similarity was found and the inverse problem could be solved. A forward simulation then confirmed the quality of the model structure to describe the experimental data.     

Antimicrobial activity and biodegradation behavior of poly(butylene adipate‐co‐terephthalate)/clay nanocomposites

Poly(butylene adipate‐co‐terephthalate) (PBAT) nanocomposites films are prepared by a solution intercalation process using natural montmorillonite (MMT) and cetyltrimethylammonium bromide (CTAB)‐modified montmorillonite (CMMT). Cation exchange technique has been used for modification of MMT by CTAB and characterized by Fourier transform infrared analysis, thermo‐gravimetric analysis, and X‐ray diffraction (XRD) studies. CMMT gives better dispersion in the PBAT matrix than MMT and is confirmed by XRD and transmission electron microscopy. Because of better compatibility of CMMT, water vapor transmission rate of PBAT decreases more in the presence of CMMT than MMT. The biodegradability of PBAT and its nanocomposite films are studied in compost and from the morphological analysis it is apparent that the PBAT/CMMT shows a lower biodegradation rate in comparison to the PBAT/MMT. The antimicrobial activity of PBAT and its nanocomposite films is tested by an inhibition zone method. Because of the presence of the quaternary ammonium group of CTAB‐modified MMT, PBAT/CMMT nanocomposites show adequate antimicrobial activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40079.     

Application of bi-orthogonal wavelet transform and genetic algorithm in image steganography

Multimedia Tools and Applications - The Internet is used for exchanging information. Sometimes it is required to transmit confidential data over the internet. Here the authors use image...     

Evaluation of wet air oxidation as a pretreatment strategy for bioethanol production from rice husk and process optimization

The pretreatment of rice husk by the wet air oxidation (WAO) technique was investigated by means of a statistically designed set of experiments. Reaction temperature, air pressure, and reaction time were the process parameters considered. WAO pretreatment of rice husk increased the cellulose content of the solid fraction by virtue of lignin removal and hemicellulose solubilization. The cellulose recovery was around 92%, while lignin recovery was in the tune of 8–20%, indicating oxidation of a bulk quantity of lignin. The liquid fraction was found to be rich in hexose and pentose sugars, which could be directly utilized as substrate for ethanol fermentation. The WAO process was optimized by multi-objective numerical optimization with the help of MINITAB 14 suite of statistical software, and an optimum WAO condition of 185 °C, 0.5 MPa, and 15 min was predicted and experimentally validated to give 67% (w/w) cellulose content in the solid fraction, along with 89% lignin removal, and 70% hemicellulose solubilization; 13.1 gl^?1 glucose and 3.4 gl^?1 xylose were detected in the liquid fraction. The high cellulose content and negligible residual lignin in the solid fraction would greatly facilitate subsequent enzymatic hydrolysis, and result in improved ethanol yields from rice husk.     

Self-adjoint operators from selected nonsymmetric matrices: application to kinetics and rectification

It is shown that two problems, one which has become a classic in chemical kinetics developed by Wei and Prater and the other a more prosaic development in multicomponent rectification, when cast in the proper mathematical framework become amenable to a more direct solution. This involves the selection of the proper inner product on a finite dimensional vector space so that the linear operators become self adjoint.