Analysis of electrical switching in sub-micron KNO3 thin films

The coercive field of KNO₃ films 75 to 400nm thick is found to satisfy the empirical relation E_C ∼d ^-1.3, where d is the thickness, in agreement with earlier work on BaTiO₃ by Stadler and on TGS by Hadni et al. The switching times for large area devices (20Ox200μm) vary as E^-1.5 in agreement with early work on BaTiO₃ by Stadler and Zachmanidis, and indicate that the limiting parameter is the velocity of domain growth perpendicular t o the applied field.     

Buckling analysis of multi-walled carbon nanotubes under combined loading considering the effect of small length scale

The torsional and axially compressed buckling of an individual embedded multi-walled carbon nanotube (MWNTs) subjected to an internal and/or external radial pressure was investigated in this study. The emphasis is placed on new physical phenomena which are due to both the small length scale and the surrounding elastic medium. Multiwall carbon nanotubes which are considered in this study are classified into three categories based on the radius to thickness ratio, namely, thin, thick, and almost solid. Explicit formulas are derived for the van der Waals (vdW) interaction between any two layers of an MWNT based on the continuum cylindrical shell model. In most of the previous studies, the vdW interaction between two adjacent layers was considered only and the vdW interaction among other layers was neglected. Moreover, in these works, the vdW interaction coefficient was treated as a constant that was independent of the radii of the tubes. However, in the present model the vdW interaction coefficients are considered to be dependent on the change of interlayer spacing and the radii of the tubes. The effect of the small length scale is also considered in the present formulation. The results show that there is a unique buckling mode (m,n) corresponding to the critical shear stress. This result is obviously different from what is expected for the pure axially compressed buckling of an individual multi-walled carbon nanotube.     

Design of CMOS three-stage amplifiers for fast-settling switched-capacitor circuits

In this paper, a time-domain design procedure for fast-settling three-stage amplifiers is presented. In the proposed design approach, the amplifier is designed to settle within a specific time with a given settling accuracy and circuit noise budget by optimizing both the power consumption and silicon die area. Both linear and nonlinear settling regions of three-stage amplifiers are considered and optimal values of the amplifier stages transconductance and compensation capacitors are obtained using the genetic algorithm optimization. Detailed design equations are provided and circuit level simulation results using a 90 nm CMOS technology are presented to evaluate the usefulness of the proposed design scheme respected to the previously reported design approaches.     

Reversible robust data hiding based on wavelet filters modification

Multimedia Tools and Applications - In this paper, a new robust reversible data hiding method is proposed. The method is designed based on wavelet modifications which result in a scalable data...     

Investigating elastic stability of cylindrical shell with an elastic core under axial compression by energy method

In this paper, the elastic axisymmetric buckling of a thin, isotropic and simply supported cylindrical shell with an elastic core under axial compression has been analyzed using energy method. The nonlinear strain-displacement relations in general cylindrical coordinates are simplified using Sanders kinematic relations (Sanders, 1963) for axial compression. Equilibrium equations are obtained by using minimum potential energy together with Euler equations applied for potential energy function in cylindrical shell. To acquire stability equation of cylindrical shell with an elastic core, minimum potential energy theory and Trefftz criteria are implemented. Stability and compatibility equations for an imperfect cylindrical shell with an elastic core are also obtained by the energy method, and the buckling analysis of shell is carried out using Galerkin method. Critical load curves versus the aspect ratio are obtained and analyzed for a cylindrical shell with an elastic core. It is concluded that the application of an elastic core increases elastic stability and significantly reduces the weight of cylindrical shells.     

Effect of stiffness ratio of piezoelectric patches and plate on stress concentration reduction in a plate with a hole

The effect of piezoelectric patches and plate stiffness on placement and power of piezoelectric actuators for reduction of the stress concentration factor around a hole in a plate under tension is investigated. For this purpose, two conditions are considered: patches are softer than the plate and the plate is softer than the patches. Patches are located at the top/bottom and left/right of a hole. Results show that the stiffness ratio of patches and the plate can affect the best location to reduce the stress concentration factor. Next, by comparing the results, some suggestions are presented for locating the patches. Results are validated by some experimental tests.     

Composting of Disposal Organic Wastes: Resource Recovery for Agricultural Sustainability

One of the major problems of agricultural soils in the tropical regions of the Pacific is the low organic matter content. Because of the hot and humid environment, the soil organic matter (SOM) is minimal due to rapid decomposition. Composted organic material is being applied on agricultural fields as an amendment to provide nutrients and enhance the organic matter content for improving the physical and chemical properties of the cultivated soils. In addition land application of composted material as a fertilizer source effectively disposes of wastes that otherwise are buried in landfills. In our soil program at the University of Guam, we are evaluating the use of organic material as an alternative to synthetic fertilizers. Its goal is to develop management strategies and use available resources for improving crop production while conserving resources and preserving environmental quality. Our case study project is designed to improve soil fertility status by using composted organic wastes and assessing how the nitrogen and other essential nutrients contribute to long-term soil fertility and crop productivity without application of synthetic fertilizers. In our pilot project, compost is produced from wood chips, grinded typhoon debris mixed with animal manure, fish feed, shredded paper and other organic wastes. Mature compost is then applied on the field at the rates of 0, 5, 10 and 20 t/ha as a soil amendment on the eroded cobbly soils of southern Guam. Corn is planted and monitored for growth performance and yield. The effect of land application of composted material on the SOM content and overall soil quality indices are being evaluated in this pilot study.     

Electrochemical detection and discrimination of single copy gene target DNA in non-amplified genomic DNA

A sensitive, fast and inexpensive method for direct electrochemical detection of target DNA sequences in non-amplified genomic DNA samples is described. Hybridization detection relies on the alteration in guanine oxidation signal following hybridization of the probe with complementary genomic DNA. Initially, the method was tested to detect target DNA on low cycle number PCR amplicons. Having obtained promising detection results from only 5 cycles product, the feasibility of target sequence detection in extracted genomic DNA without PCR amplification, but with the vortex mediated fragmentation of the large genomic DNA into small pieces was examined. Experimental variables affecting the efficiency of sensor were investigated. Detection experiments with various non-complementary genomic DNAs as well as a proper probe, non-specific with respect to all genomic samples confirmed the excellent selectivity of the approach. The sensitivity of the method for analyzing the vortex mediated fragmentized genomic DNA samples is estimated to be approximately of 0.58 ng/μl.     

H ∞ Control of T-S Fuzzy Singularly Perturbed Systems Using Multiple Lyapunov Functions

In this paper, H _∞ controller synthesis of T-S fuzzy singularly perturbed systems based on fuzzy and non-fuzzy multiple Lyapunov functions is discussed. By assuming some lower bounds for the grades of fuzzy membership functions and using the elimination lemma, the design conditions are presented in the form of linear matrix inequalities (LMIs). Considering ε as the singular perturbation parameter, it is shown that the ε-dependent controller in the absence of disturbances, results in an asymptotically stable closed-loop system, and in the presence of disturbances, satisfies the H _∞-norm condition for all ε∈(0,ε ^?]. The resulting LMIs are feasible for larger values of ε ^? compared to those of the previous methods. Moreover, for the case that the value of ε is not available for feedback, Finsler’s lemma is used to separate the controller gains and the ε-dependent Lyapunov matrix, and to achieve an ε-independent control. An example is presented to illustrate the validity of the design techniques.     

FEM Simulation of the Bending Angle During the Laser Forming of FGM Plates

Functionally graded material (FGM) plate forming by using a modern laser technique is taken into consideration in this article. By using finite element simulation, the effects of movement speed, laser diameter, laser power, plate thickness, and the number of passes on the value of the FGM plate transverse bending angle are investigated. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. By comparing the simulation with analytical formulas, it is observed that the FE results are in good agreement with the analytical results.