Nanoelectromechanical systems

Nanoelectromechanical systems (NEMS) are drawing interest from both technical and scientific communities. These are electromechanical systems, much like microelectromechanical systems, mostly operated in their resonant modes with dimensions in the deep submicron. In this size regime, they come with extremely high fundamental resonance frequencies, diminished active masses,and tolerable force constants; the quality (Q) factors of resonance are in the range Q~10^3–10^5—significantly higher than those of electrical resonant circuits. These attributes collectively make NEMS suitable for a multitude of technological applications such as ultrafast sensors, actuators, and signal processing components. Experimentally, NEMS are expected to open up investigations of phonon mediated mechanical processes and of the quantum behavior of mesoscopic mechanical systems. However, there still exist fundamental and technological challenges to NEMS optimization. In this review we shall provide a balanced introduction to NEMS by discussing the prospects and challenges in this rapidly developing field and outline an exciting emerging application, nanoelectromechanical mass detection

Some New Integral Inequalities for Several Kinds of Convex Functions

In this study, we obtain some new integral inequalities for different classes of convex functions by using some elementary inequalities and classical inequalities like general Cauchy inequality and Minkowski inequality

Ultimate limits to inertial mass sensing based upon nanoelectromechanical systems

Nanomechanical resonators can now be realized that achieve fundamental resonance frequencies exceeding 1 GHz, with quality factors (Q) in the range 10^3<=Q<=10^5. The minuscule active masses of these devices, in conjunction with their high Qs, translate into unprecedented inertial mass sensitivities. This makes them natural candidates for a variety of mass sensing applications. Here we evaluate the ultimate mass sensitivity limits for nanomechanical resonators operating in vacuo that are imposed by a number of fundamental physical noise processes. Our analyses indicate that nanomechanical resonators offer immense potential for mass sensing—ultimately with resolution at the level of individual molecules

Inflation risk and default risk in a dynamic general equilibrium asset pricing model for an emerging market economy

Cataloged from PDF version of article.In this thesis, the difference between the T-Bill returns and common stock returns in Turkey is examined. It is observed that there is a bond premium in Turkey unlike the equity premium observed in developed countries. To understand this surprising observation, inflation-risk and default-risk are incorporated to the Mehra-Presscott (1985) dynamic asset pricing model. Inflation-risk alone is found to be insufficient to explain this bond premium. Only after allowing for a perceived default-risk, the observed bond premium of Turkish T-Bills over Turkish common stocks can be explained by such a model.Ekinci, M FatihM.S

Balanced electronic detection of displacement in nanoelectromechanical systems

We describe a broadband radio frequency balanced bridge technique for electronic detection of displacement in nanoelectromechanical systems (NEMS). With its two-port actuation-detection configuration, this approach generates a background-nulled electromotive force in a dc magnetic field that is proportional to the displacement of the NEMS resonator. We demonstrate the effectiveness of the technique by detecting small impedance changes originating from NEMS electromechanical resonances that are accompanied by large static background impedances at very high frequencies. This technique allows the study of important experimental systems such as doped semiconductor NEMS and may provide benefits to other high frequency displacement transduction circuits

Comment on "Evidence for Quantized Displacement in Macroscopic Nanomechanical Oscillators"

In a recent Letter, Gaidarzhy et al. [1] claim to have observed evidence for "quantized displacements" of a high-order mode of a nanomechanical oscillator. We contend that the methods employed by the authors are unsuitable in principle to observe such states for any harmonic mode

Intrinsic dissipation in high-frequency micromechanical resonators

We report measurements of intrinsic dissipation in micron-sized suspended resonators machined from single crystals of galium arsenide and silicon. In these experiments on high-frequency micromechanical resonators, designed to understand intrinsic mechanisms of dissipation, we explore dependence of dissipation on temperature, magnetic field, frequency, and size. In contrast to most of the previous measurements of acoustic attenuation in crystalline and amorphous structures in this frequency range, ours is a resonant measurement; dissipation is measured at the natural frequencies of structural resonance, or modes of the structure associated with flexural and torsional motion. In all our samples we find a weakly temperature dependent dissipation at low temperatures. We compare and contrast our data to various probable mechanisms, including thermoelasticity, clamping, anharmonic mode-coupling, surface anisotropy and defect motion, both in bulk and on surface. The observed parametric dependencies indicate that the internal defect motion is the dominant mechanism of intrinsic dissipation in our samples

Monocrystalline silicon carbide nanoelectromechanical systems

SiC is an extremely promising material for nanoelectromechanical systems given its large Young's modulus and robust surface properties. We have patterned nanometer scale electromechanical resonators from single-crystal 3C-SiC layers grown epitaxially upon Si substrates. A surface nanomachining process is described that involves electron beam lithography followed by dry anisotropic and selective electron cyclotron resonance plasma etching steps. Measurements on a representative family of the resulting devices demonstrate that, for a given geometry, nanometer-scale SiC resonators are capable of yielding substantially higher frequencies than GaAs and Si resonators

Effect of sand paper grading on the shear behaviour of fine-grained sand

This paper presents the results of direct shear test on sand paper reinforced and un-reinforced poorly graded fine-grained sand obtained from natural costal sand deposits of western shore of Cyprus Island. Mining of sand from natural deposits, including beaches, yields an inexpensive source of sand for construction or industrial uses. Samples prepared in identical densities with and without addition of different grading of discrete sand papers have been tested in order to assess the effect of sand paper grading on the shear strength parameters of soil. Laboratory testing program consisting 41 specimens were performed in circular shear box with 63 mm in diameter which were prepared regarding BS 1377-7. Tests are conducted with four vertical confining pressures: 100, 200, 300 and 400 kPa. The test results reveal that the sand paper grading play important role in the shear strength parameters of the soil. It was observed that the choose of grading close to the major percentage of sand particle size results to achieve increase in shear strength at all confining pressures which also results in increase of cohesion and friction angle