Modeling and multiresolution characterization of micro/nano surface for novel tailored nanostructures

Nanofabrication is state of the art technology. Various chemical, mechanical, biochemical and semiconductor products have characteristics controlled by the nanostructures of the surface and interphase. Surface microscopic imaging is generally used to capture different surface features. By properly analyzing the surface image, valuable information regarding manufacturing process and product performance can be extracted. While microscopy measurements can offer very accurate qualitative information about surface features, for many applications, it is critical to obtain a quantitative description of the surface morphology. Various statistical features can be used to characterize the surface in quantitative way. Such an analysis can be done by the multi-resolution capabilities of wavelet transforms (WT). A multi-scale molecular simulation can help to investigate the physical and chemical mechanism in manufacturing process. Multiresolution characterization was performed on the model structure to compare with image analysis. In our research, we have used a soft polymeric surface used in microfabrication application and a hard surface used for catalysis, and applied multiresolution characterization for surface feature extraction and multiscale modeling for optimizing system variables to get desired surface characteristics. In microfabrication, the efficiency of the product reduced by line-edge roughness (LER) created on the polymer surface. Off-line LER characterization is usually based on the top-down SEM image. We have shown a wavelet based segmentation method for edge searching region. There was no external decision involved in the wavelet based edge detection and characterization. Ab-initio atomistic based simulations are generally used for polymer material design in atomic scale. For mesoscale modeling we use the coarse graining of the molecules and use the Flory-Huggins mean field interaction parameters of the clusters of atoms or molecules obtained from ab-initio simulations. In our research we have used coarse grained lattice based important sampling Monte Carlo (MC) and kinetic Monte Carlo (kMC) methods for mesoscale simulation. We have identified the phase separation by spinodal decomposition resulting in the formation of LER. The kinetics of the process is found and the process variables are identified that can reduce the roughness. Surface of a transition metal have been analyzed in a similar way for enhanced catalytic performance

Impact of sampling technique on the performance of surrogate models generated with artificial neural network (ANN): A case study for a natural gas stabilization unit

Data-driven models are essential tools for the development of surrogate models that can be used for the design, operation, and optimization of industrial processes. One approach of developing surrogate models is through the use of input-output data obtained from a process simulator. To enhance the model robustness, proper sampling techniques are required to cover the entire domain of the process variables uniformly. In the present work, Monte Carlo with pseudo-random samples as well as Latin hypercube samples and quasi-Monte Carlo samples with Hammersley Sequence Sampling (HSS) are generated. The sampled data obtained from the process simulator are fitted to neural networks for generating a surrogate model. An illustrative case study is solved to predict the gas stabilization unit performance. From the developed surrogate models to predict process data, it can be concluded that of the different sampling methods, Latin hypercube sampling and HSS have better performance than the pseudo-random sampling method for designing the surrogate model. This argument is based on the maximum absolute value, standard deviation, and the confidence interval for the relative average error as obtained from different sampling techniques.Qatar UniversityScopu

DYNAMIC MODELING AND PROTOTYPING FOR LOW-FREQUENCY PIEZOELECTRIC MEMS VIBRATION ENERGY SCAVENGING: VIBES

ABSTRACT The advancement in the field of wireless electronics for use in embedded systems and control system technologies is limited by the availability of efficient and portable power generation system. Harvesting ambient energy provides an excellent option to energize these low power wireless electronic applications. Low frequency vibrational energy scavenging of microelectromechanical system (MEMS) utilizing piezoelectric power generation can effectively serve this purpose. Initial fabrication has been carried out in terms of PZT film characterization, initial testing to verify the piezoelectric nature of the as coated PZT film, optimization of 125 µm thick nickel electroplating, and innovative cantilever release process based on inductively coupled plasma etching (Bosch Process) to increase the yield of working cantilever arrays on a die. An optimized process flow for the prototype fabrication was proposed and lead zirconium titanate (PZT) thin film deposition by sol-gel was characterized on three different bottom electrodes. The net effective yield in terms of working cantilevers on a die was increased to about 80% of over 500 cantilevers on a die. X-ray diffraction results revealed the perovskite phase formation of the as-coated PZT film with a [111] predominant crystal orientation. The ascoated PZT film was poled and the initial testing confirmed the piezoelectric nature of the film. The desired cantilever configuration was modeled such that its natural frequency lies approximately in the 200 Hz range while ensuring that the maximum stress generated in the structure does not exceed the yield strength of the material both in the static stage and in the dynamic stage. It was observed that positioning of the mass was a significant factor influencing the natural frequency of the structure. The analysis was performed for cantilever configurations made of silica, PZT, and nickel in which the effect of the thinner layers (electrodes) has been ignored. It was found that this configuration yields a natural frequency of 255 Hz which lies in the desired range of frequency (100-500 Hz). INTRODUCTION The advancement made in very large scale integration (VLSI) design technology in the recent past has resulted in an increasing demand of low power digital signal processing (DSP) and remote sensing applications requiring short duty cycles. Novel energy sources have been exploited so as to generate sufficient power in the microwatt range to energize these low duty cycle applications Several different types of energy scavenging methods have been exploited in the current state of the art that utilize energy sources such as solar energy, mechanical vibrations, temperature gradient, electromagnetic field, pressure gradient, wind energy, acoustic energy, human power, etc. One of the potential sources for ambient energy scavenging is the mechanical vibration, the implementation of which is compatible with MEMS [1-4, 6, 9, 10]. Energy scavenging using mechanical vibrations can be implemented in three different methods which include the piezoelectric, electrostatic, and electromagnetic principles. This paper investigates the piezoelectric mode of scavengin

Large scale synthesis of 2D graphene oxide by mechanical milling of 3D carbon nanoparticles in air

Graphene oxide (GO) is one of the important functional materials. Large-scale synthesis of it is very challenging. Following a simple cost-effective route, large-scale GO was produced by mechanical (ball) milling, in air, of carbon nanoparticles (CNPs) present in carbon soot in the present study. The thickness of the GO layer was seen to decrease with an increase in milling time. Ball milling provided the required energy to acquire the in-plane graphitic order in the CNPs reducing the disorders in it. As the surface area of the layered structure became more and more with the increase in milling time, more and more oxygen of air got attached to the carbon in graphene leading to the formation of GO. An increase in the time of the ball mill up to 5 hours leads to a significant increase in the content of GO. Thus ball milling can be useful to produce large-scale two-dimensional GO for a short time.Comment: 23 pages, 10 figure

Microbial Extraction of Cobalt and Nickel from Lateritic Chromite Overburden using Aspergillus wentii

ABSTRACT Low-grade nickeliferous lateritic ore from Sukinda region of Orissa, India, was subjected to biohydrometallurgical treatment for the extraction of nickel and cobalt. The mineralogical studies reveal that nickel is entrapped in goethite matrix while cobalt is associated with the manganese phase. Aspergillus wentii NCIM 667, a citric acid producing fungal strain, was used for direct (one step and two step) and indirect (using culture filtrate) leaching of the metals under different conditions. The effect of varying pulp density (2%, 5%, 8%) and culture medium composition (viz. molasses and sucrose media) was investigated and the leaching conditions optimized. It was found that a maximum of 49.29% Ni and 35.18% Co could be recovered from the heat-treated lateritic chromite overburden by the culture filtrate bioleaching at 80°C with 2% pulp density

Case Report: “Spina Ventosa” Tuberculous Dactylitis in a 2 Year Old Boy - A Very Rare Disease

Tuberculous infection of metacarpals, metatarsals and phalanges is known as tuberculous dactylitis. There is a spindle shaped expansion of the short tubular bones due to tuberculous granuloma. Hence it is also known as spina ventosa. In our case, a two year old boy with a swelling in the metacarpal was provisionally diagnosed as enchondromata while the possibility of spina ventosa was kept in mind. He was posted for excision of the metacarpal followed by bone grafting. Histopathological examination report confirmed it as spina ventosa

Non-Circular beam correction to the CMB power spectrum

In the era of high precision CMB measurements, systematic effects are beginning to limit the ability to extract subtler cosmological information. The non-circularity of the experimental beam has become progressively important as CMB experiments strive to attain higher angular resolution and sensitivity. The effect of non-circular beam on the power spectrum is important at multipoles larger than the beam-width. For recent experiments with high angular resolution, optimal methods of power spectrum estimation are computationally prohibitive and sub-optimal approaches, such as the Pseudo-Cl method, are used. We provide an analytic framework for correcting the power spectrum for the effect of beam non-circularity and non-uniform sky coverage (including incomplete/masked sky maps). The approach is perturbative in the distortion of the beam from non-circularity allowing for rapid computations when the beam is mildly non-circular. When non-circular beam effect is important, we advocate that it is computationally advantageous to employ `soft' azimuthally apodized masks whose spherical harmonic transform die down fast with m.Comment: 12 pages, 2 figures; Proceedings of the Fundamental Physics With CMB workshop, UC Irvine, March 23-25, 2006, to be published in New Astronomy Review