High mobility two-dimensional electron system on hydrogen-passivated silicon(111) surfaces

We have fabricated and characterized a field-effect transistor in which an electric field is applied through an encapsulated vacuum cavity and induces a two-dimensional electron system on a hydrogen-passivated Si(111) surface. This vacuum cavity preserves the ambient sensitive surface and is created via room temperature contact bonding of two Si substrates. Hall measurements are made on the H-Si(111) surface prepared in aqueous ammonium fluoride solution. We obtain electron densities up to $6.5 \times 10^{11}$ cm$^{-2}$ and peak mobilities of $\sim 8000$ cm$^{2}$/V s at 4.2 K.Comment: to appear in Applied Physics Letter

Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface

We report magneto-transport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors, is difficult to reconcile with non-interacting electron theory.Comment: 4 pages, 4 figures, to appear in Physical Review Letter

Modeling of micro- and nano-scale domain recording by high-voltage atomic force microscopy in ferroelectrics-semiconductors

The equilibrium sizes of micro- and nano-domains caused by electric field of atomic force microscope tip in ferroelectric semiconductor crystals have been calculated. The domain was considered as a prolate semi-ellipsoid with rather thin domain walls. For the first time we modified the Landauer model allowing for semiconductor properties of the sample and the surface energy of the domain butt. The free carriers inside the crystal lead to the formation of the screening layer around the domain, which partially shields its interior from the depolarization field. We expressed the radius and length of the domain though the crystal material parameters (screening radius, spontaneous polarization value, dielectric permittivity tensor) and atomic force microscope tip characteristics (charge, radius of curvature). The obtained dependence of domain radius via applied voltage is in a good quantitative agreement with the ones of submicron ferroelectric domains recorded by high-voltage atomic force and scanning probe microscopy in LiNbO3 and LiTaO3 crystals.Comment: 21 pages, 5 figure

Implementation of the Explicit Group Iterative Method for Solving Image Blurring Problem using Non-Linear Diffusion Equations

Diffusion equations have been known to solve various image processing problems. This study employs the diffusion equations as the partial difference equations (PDEs)-based image processing techniques for image blurring which also can be refer as the process of image smoothing. The solutions of diffusion equations were obtained using the iterative algorithms and thereafter applied in the image blurring processes. The images were blurred without destroying the crucial information of an image that need to be preserve such as sharp edges, lines and shapes as the diffusion occurs inside the image locations, where the images with different sizes were tested. In terms of performance comparison, the standard point Gauss-Seidel and two-point Explicit Group (2-EG) methods were considered to produce the same quality image of classical point iterative method which is Jacobi. The numerical results showed that 2-EG iterative method capable to smooth the inner region of the images faster compared to the standard point iterative method. It was shown that the 2-EG iterative method more efficient in reducing the number of iterations and computational time than the standard point iterative method

Sistem Informasi Pengelolaan Nilai SMPN 2 Mojolaban

Sistem Informasi Pengelolaan Nilai SMPN 2 Mojolaban merupakan sistem yang dibangun dengan tujuan untuk memudahkan pihak sekolah dalam proses pendataan siswa, pengolahan nilai siswa dan untuk memudahkan orang tua siswa untuk memantau hasil kegiatan belajar anaknya selama disekolah, sehingga para orang tua memperoleh informasi nilai siswa dengan lebih cepat dan efisien. Metode perancangan sistem yang digunakan adalah adalah SDLC (System Development Life Cycle) yaitu proses yang digunakan oleh analisis sistem untuk mengembangkan sistem informasi mulai dari analisis/penentuan kebutuhan, perancangan sistem, implementasi sistem, perawatan sistem dan kebijakan perencanaan sistem/penyerahan kepada konsumen. Dengan tahapan yang telah dibuat, Sistem Informasi Pengelolaan Nilai SMPN 2 Mojolaban berhasil diwujudkan. Serta system Informasi dapat berjalan sebagaimana mestinya yang diinginkan dan sesuai dengan tujuan system Informasi dibuat. Para guru lebih mudah mengelola nilai siswa dan tidak membutuhkan waktu yang lama sehingga siswa lebih cepat mengetahui informasi nilai mereka

Study of Magnetic Properties of A_2B^'NbO_6 (A=Ba,Sr, (BaSr): and B^'=Fe and Mn) double perovskites

We have studied the magnetic properties of Ba_2FeNbO_6 and Ba_2MnNbO_6. it is seen that Ba_2FeNbO_6 is an antiferromagnet with a weak ferromagnetic behaviour at 5K while Ba_2MnNbO_6 shows two magnetic transitions one at 45 K and the other at 12K. Electron spin resonance (ESR) measurements at room temperature show that the Mn compound does not show any Jahn-Teller distortion. It is also seen that the Neel temperature of the A_2FeNbO_6 (A=Ba,Sr, BaSr) compounds do not vary significantly. However variations in the average A-site ionic radius influence the formation of short range correlations that persist above T_N.Comment: 10 oages, 5 figures, MMM, to appear in J.Appl.Phy

OPTIMIZATION OF FLYING ROBOTS GROUP BASED ON UNMANNED AERIAL VEHICLES

LYSENKO, Dr. Sc., Senior lecturer Eng. Нelen TACHININA, PhD, N.A. TYMOSHENKO, post-graduate student National Aviation University, Ukraine REZUMAT. Este propusă o metodologie de conversie a sistemului compus dinamic într-un sistem discontinuu cu dimensiunea vectorilor de stare şi control care se schimbă în momentele de schimbare structurală. Cuvinte cheie: sistem dynamic, optimizare, traiectorie. ABSTRACT. The method of converting the compound dynamic system to the branching system with transient size of state and control vectors at a moment of structural changes is proposed

Temperature-dependent transport in a sixfold degenerate two-dimensional electron system on a H-Si(111) surface

Low-field magnetotransport measurements on a high mobility (mu=110,000 cm^2/Vs) two-dimensional (2D) electron system on a H-terminated Si(111) surface reveal a sixfold valley degeneracy with a valley splitting <= 0.1 K. The zero-field resistivity rho_{xx} displays strong temperature dependence for 0.07 < T < 25 K as predicted for a system with high degeneracy and large mass. We present a method for using the low-field Hall coefficient to probe intervalley momentum transfer (valley drag). The relaxation rate is consistent with Fermi liquid theory, but a small residual drag as T->0 remains unexplained.Comment: 5 pages, 4 figures; revised and slightly shortened for publication

Out of equilibrium electronic transport properties of a misfit cobaltite thin film

We report on transport measurements in a thin film of the 2D misfit Cobaltite $Ca_{3}Co_{4}O_{9}$. Dc magnetoresistance measurements obey the modified variable range hopping law expected for a soft Coulomb gap. When the sample is cooled down, we observe large telegraphic-like fluctuations. At low temperature, these slow fluctuations have non Gaussian statistics, and are stable under a large magnetic field. These results suggest that the low temperature state is a glassy electronic state. Resistance relaxation and memory effects of pure magnetic origin are also observed, but without aging phenomena. This indicates that these magnetic effects are not glassy-like and are not directly coupled to the electronic part.Comment: accepted in Phys Rev B, Brief report