Development of Nb tube processed Nb3Al multifilamentary superconductor

The Nb tube process has recently been developed at NRIM (Japan) for fabricating Nb₃Al multifilamentary superconductors containing more than one million continuous ultrafine filaments of less than 0.1 m diameter. The adjustment of hardness of Al cores relative to Nb matrix by alloying Al cores with additives of Mg, Ag(-Ge), Cu(-Ge), Zn, etc. improved remarkably the cold workability of Nb/Al composites. Wires heat treated below 1000°C show superior properties to a commercial multifilamentary (Nb,Ti)₃Sn conductor: (1) higherJ _c (4.2 K) (1.5×10⁹ A/m² at 10 T), (2) smaller degradation inJ _c with mechanical strain, and (3) smaller ac loss (resulting from a smaller effective superconducting filament diameter: about 2 m). Furthermore, sensitivity to irradiation is nearly the same as that of (Nb,Ti)₃Sn. Other techniques to produce Nb₃Al are unsuitable for developing a conductor with multifilamentary structure, and thereby the Nb tube processed Nb₃Al multifilamentary conductors is the best available for fusion reactor magnets.     

A new method for determining the plasma electron density using three-color interferometer

A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO(2) laser. Short-time integrations of the fractional fringes enhance the reliability of this method.     

Piezoresistor-equipped fluorescence-based cantilever probe for near-field scanning

Scanning near-field optical microscopes (SNOMs) with fluorescence-based probes are promising tools for evaluating the optical characteristics of nanoaperture devices used for biological investigations, and this article reports on the development of a microfabricated fluorescence-based SNOM probe with a piezoresistor. The piezoresistor was built into a two-legged root of a 160-microm-long cantilever. To improve the displacement sensitivity of the cantilever, the piezoresistor's doped area was shallowly formed on the cantilever surface. A fluorescent bead, 500 nm in diameter, was attached to the bottom of the cantilever end as a light-intensity-sensitive material in the visible-light range. The surface of the scanned sample was simply detected by the probe's end being displaced by contact with the sample. Measuring displacements piezoresistively is advantageous because it eliminates the noise arising from the use of the optical-lever method and is free of any disturbance in the absorption or the emission spectrum of the fluorescent material at the probe tip. The displacement sensitivity was estimated to be 6.1 x 10(-6) nm(-1), and the minimum measurable displacement was small enough for near-field measurement. This probe enabled clear scanning images of the light field near a 300 x 300 nm(2) aperture to be obtained in the near-field region where the tip-sample distance is much shorter than the light wavelength. This scanning result indicates that the piezoresistive way of tip-sample distance regulation is effective for characterizing nanoaperture optical devices.     

Nitridation behavior of silicon powder compacts of various thicknesses with Y2O3 and MgO as sintering additives

The effects of the nitriding temperature (1300 and 1350°C), holding time (0‐4 hours), and thickness of Si powder compacts on the nitridation behavior of silicon were investigated by examining the nitridation rates, analyzing phase compositions, and observing the microstructures of nitrided compacts. Si powder compacts doped with Y₂O₃ and MgO as sintering additives were prepared with thicknesses of 3, 6, and 9 mm. The phases of nitrided compacts were transformed from Si to α‐Si₃N₄ and β‐Si₃N₄ with an increase in the nitriding temperature and holding time. The degree of nitridation increased with the nitriding temperature and holding time. The β/(α+β) ratio increased with the nitriding temperature and holding time, and with a decrease in the thickness of the Si powder compacts. However, all compacts exhibited the same tendency for a higher β/(α+β) ratio at the compact surface than in the bulk of the compact. The variation in the β/(α+β) ratio for each compact decreased with an increase in the nitriding temperature and holding time.     

Forward/backward prediction solution for adaptive noisy FIR filtering

An important and hard problem in signal processing is the estimation of parameters in the presence of observation noise. In this paper, adaptive finite impulse response (FIR) filtering with noisy input-output data is considered and two developed bias compensation least squares (BCLS) methods are proposed. By introducing two auxiliary estimators, the forward output predictor and the backward output predictor are constructed respectively. By exploiting the statistical properties of the cross-correlation function between the least squares (LS) error and the forward/backward prediction error, the estimate of the input noise variance is obtained; the effect of the bias can thereafter be removed. Simulation results are presented to illustrate the good performances of the proposed algorithms. Supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104), the Ministerial Foundation of China (Grant No. A2220060039) and the Fundamental Research Foundation of BIT (Grant No. 1010050320810)     

Dynamic surface control approach to adaptive robust control of nonlinear systems in semi-strict feedback form

This article considers the adaptive robust control of a class of single-input-single-output nonlinear systems in semi-strict feedback form using radial basis function (RBF) networks. It is well known that the standard backstepping design may suffer from “explosion of terms”. To overcome this problem, the recently developed dynamic surface control technique which employs a first-order low-pass filter at each step of the backstepping design procedure is generalized to the nonlinear system under study. Our attention is paid to achieve guaranteed transient performance of the adaptive controller. At each step of design, a feedback controller strengthened by nonlinear damping terms to counteract nonlinear uncertainties is designed to guarantee input-to-state practical stability of the corresponding subsystem, and then parameter adaptations are introduced to reduce the ultimate error bound. Furthermore, for the output trajectory tracking problem, it is recommended to adopt the partial adaptation policy to reduce the computational burden due to “curse of dimension” of the RBF networks. Finally, numerical examples are included to verify the results of theoretical analysis.     

Enhancing transparency on a ball screw teleoperation robot system using a novel velocity estimation method with FPGA

Applications are using force sensation in order to estimate real contact with the environment. In a bilateral control, force feedback is needed, but a force sensor is not suitable. Hence, the force sensation is improved by using a new velocity estimation that is programmed into the FPGA. The short processing time used in the FPGA improves the force sensation in the bilateral ball screw systems. The force sensation results are higher and faster than provided by the conventional method.     

Optimization of low‐temperature poly‐Si TFT‐LCDs and a large‐scale production line for large glass substrates

Abstract— An update of the progress of inherently low‐temperature poly‐Si (LTPS) technologies, such as ELA, ion doping, and activation in conjunction with chemical vapor deposition (CVD) and photolithography will be given. We will also discuss whether LTPS LCDs will be applied to a large‐scale production line using a large motherglass substrate. It was found that a more‐powerful excimer laser as well as photolithography with higher‐resolution and a more‐precise overlaid arrangement would enable a large‐scale production line handling motherglass of 4th generation size to be constructed in the very near future with reasonable investment and productivity costs.     

MALDI-MS derived prognostic protein markers for resected non-small cell lung cancer

Protein signals obtained directly from frozen lung tissue sections using MALDI-MS were used to predict nodal involvement and survival in resected non-small cell lung cancer (NSCLC). We have identified a list of these protein signals and further evaluated their prognostic values for NSCLC using immunohistochemistry (IHC). Kaplan-Meier analysis was used to assess the mortality risk associated with the prognostic protein IHC-staining intensities. The combined IHC scores of calmodulin, thymosin β4, and thymosin β10 were found to be correlated with NSCLC patient survival (p = 0.004). Furthermore, low cofilin-1 IHC-staining intensity was found to be correlated with a better outcome for patients with negative lymph node status (p = 0.006) while high cofilin-1 IHC-staining intensity was found to be correlated with a better outcome for patients with positive node status (p = 0.034). In conclusion, the prognostic protein signals selected using MALDI-MS can be identified and tested by IHC in formalin-fixed tissue samples. MALDI-MS-derived protein signals can be potentially translated to a conventional clinical setting to aid in the prognosis of patients with NSCLC at the molecular level.     

In situ mask designed for selective growth of InAs quantum dots in narrow regions developed for molecular beam epitaxy system

We have developed an in situ mask that enables the selective formation of molecular beam epitaxially grown layers in narrow regions. This mask can be fitted to a sample holder and removed in an ultrahigh-vacuum environment; thus, device structures can be fabricated without exposing the sample surfaces to air. Moreover, this mask enables the observation of reflection high-energy electron diffraction during growth with the mask positioned on the sample holder and provides for the formation of marker layers for ensuring alignment in the processes following the selective growth. To explore the effectiveness of the proposed in situ mask, we used it to grow quantum dot (QD) structures in narrow regions and verified the perfect selectivity of the QD growth. The grown QDs exhibited high optical quality with a photoluminescence peak at approximately 1.30 mum and a linewidth of 30 meV at room temperature. The proposed technique can be applied for the integration of microstructures into optoelectronic functional devices.