A high voltage programmable ramp generator

In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1 ns and provides continuous speed variation from 6 to 30 ns for a ramp of 500 V. This is being developed as a part of automated streak camera for deflection of electron beam.     

Observer design and stabilization for linear neutral delay systems

This paper focuses on the state observer design problem as well as the observer-based stabilization problem for linear neutral delay systems. The purpose of the former problem is to design an observer that guarantees the asymptotic stability of the estimation error dynamics. The existence condition for such an observer is established. The latter problem, which is the main problem studied in this paper, aims at designing an observer-based feedback controller, such that the closed-loop system is asymptotically stabilized. It is shown that the desired controller can be easily designed if there are solutions to several linear matrix inequalities. Finally, two simulation examples are given to demonstrate the validity and effectiveness of the proposed approach.     

Structural studies of pulsed-laser deposited nanocomposite metal-oxide films

Pulsed laser deposition in vacuum has been used to develop metal-oxide nanocomposite films with well controlled structural quality. Results for the copper–aluminium oxide (Cu:Al₂O₃) system are used to illustrate the main morphological and structural features of these films. High resolution transmission electron microscopy (TEM) analysis shows that the films consist of Cu nanocrystals with average dimensions that can be controlled between 2 nm and 10 nm embedded in an amorphous Al₂O₃ matrix. It is observed that the in-plane shape of the nanocrystals evolves from circular to elongated, and the number of nanocrystals per unit area decreases as their size increases. This evolution is explained in terms of nucleation at the substrate surface and coalescence during the later stages of growth. The thermal stability of the films has been studied by in situ TEM annealing and no transformation could be observed up to about 800 °C when partial crystallization of the Al₂O₃ starts.     

Multipurpose modular experimental station for the DiProI beamline of Fermi@Elettra free electron laser

We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi@Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi@Elettra free electron laser in 2011.     

Three-dimensional image correction of tilted samples through coordinate transformation

In scanned probe measurements of micrometer- or nanometer-scale lines, it is nearly impossible to maintain the sample in a perfectly level position, and even a small amount of tilt can contribute to the accuracy of the result of the measure such as linewidth or step height. The current practice in image processing to deal with this problem is to conduct a line-by-line analysis to find the best fit of the substrate profile and subtract this background from all data points, thus describing 3D plane turns as a series of lines and processing them in succession in the x- or y-direction.In this paper a coordinate transformation method is proposed. The new coordinate system can be established on the basis of the inclined angle of the sample as well as the translation of three axes between the old coordinate system and the new coordinate system. The method can mathematically derive and hence correct all tilts around the x-, y- and z-axes and produce a leveled image simultaneously. Feature dimensions such as width, height, sidewall angle and pitch are calculated on the basis of simulated images using the coordinate transformation method and other methods. The result shows the advantage of the proposed method.     

Subtleties in ADF imaging and spatially resolved EELS: A case study of low-angle twist boundaries in SrTiO3

A screw dislocation network at the low-angle SrTiO3/Nb:SrTiO3 twist grain boundary has been analyzed by annular dark field (ADF) imaging and spatially resolved electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). The cores of one set of dislocations running parallel to the beam direction appear dark in the ADF STEM images. EELS on the dislocation core reveals a reduced Sr/Ti ratio compared to the bulk suggesting Sr-deficient cores. The second set of dislocations, orthogonal to the latter, is imaged by its strain field using low-angle annular dark field (LAADF) imaging. Multislice image simulations suggest channeling of the electron probe on the atomic columns for small tilts, theta < 1 degree, where the Sr columns act as beam guides. Only for larger tilts is the channeling effect strongly reduced and the fringe contrast approaches the value predicted by a purely incoherent imaging model. Ti-L(2,3) EELS across the dislocation core shows an asymmetry between the EELS and the ADF signal which cannot be explained by the geometry or beam broadening. This asymmetry might be explained by an effective nonlocal potential representing inelastic scattering in EELS.     

Experimental research on a modular miniaturization nanoindentation device

Nanoindentation technology is developing toward the in situ test which requires miniaturization of indentation instruments. This paper presents a miniaturization nanoindentation device based on the modular idea. It mainly consists of macro-adjusting mechanism, x-y precise positioning platform, z axis precise driving unit, and the load-depth measuring unit. The device can be assembled with different forms and has minimum dimensions of 200 mm × 135 mm × 200 mm. The load resolution is about 0.1 mN and the displacement resolution is about 10 nm. A new calibration method named the reference-mapping method is proposed to calibrate the developed device. Output performance tests and indentation experiments indicate the feasibility of the developed device and calibration method. This paper gives an example that combining piezoelectric actuators with flexure hinge to realize nanoindentation tests. Integrating a smaller displacement sensor, a more compact nanoindentation device can be designed in the future.     

Optical temperature sensor based on ZnO thin film's temperature-dependent optical properties

A reflective fiber temperature sensor system based on the ZnO thin film is proposed. The transmittance spectra and temperature dependent optical property of the sensing head with ZnO thin film is investigated theoretically and experimentally, and the temperature resolution of ～1?°C is obtained in the temperature region of 300-773 K. The temperature sensing system is only related to the wavelength shift of transmittance spectra, and has a high stability without depending on the incident light intensity. This research results also indicate a fiber optical sensor with a broad temperature measurement range (10-1800 K) can be gained as a promising temperature sensing device, and can be applied into some extremely environments, such as aircraft, nuclear power station and power transmission system, and so on.     

Plasmon holographic experiments: theoretical framework

A theoretical framework is described to understand the results of plasmon holography experiments leading to insight in the meaning of the experimental results and pointing out directions for future experiments. The framework is based on the formalism of mutual intensity to describe how coherence is transferred through an optical system. For the inelastic interaction with the object, an expression for the volume plasmon excitations in a free electron gas is used as a model for the behaviour of aluminium. The formalism leads to a clear graphical intuitive tool for understanding the experiments. It becomes evident that the measured coherence is solely related to the angular distribution of the plasmon scattering in the case of bulk plasmons. After describing the framework, the special case of coherence outside a spherical particle is treated and the seemingly controversial idea of a plasmon with a limited coherence length obtained from experiments is clarified.     

双带式薄板坯连铸及直接热轧进度报告

双带式薄板坯连铸过程应用了长直武、全移动型结晶器。这两个主结晶表面由两条翱紧的薄盎属带准确地变撑，并且用高速冷却水冷却，以恒定速度传动。这两条基本平行的金属带之间的空同在边缘处由金属边缘挡块组成的连续封闭环封闭，封闭环与金属带同步运行。