基于能量特征的脑电信号特征提取与分类

为了快速、有效地提取脑电特征,提高分类正确率,采用带通滤波和小波包分析的方法提取Mu、Beta节律对应的脑电信号,在时域范围内,将信号幅度的平方作为能量特征值;在频域范围内,采用AR模型功率谱估计法所得的功率谱密度作为能量特征值.根据运动想象脑电信号特点,构造左右通道信号能量差值的符号特性作为分类判别依据,进行分类测试,方法简单.初步实验结果表明,所利用的两种方法的分类正确率达87.857%.     

Effect of electric charge accumulation on low energy ion implantation in insulators

Charge accumulation at the surface of insulators during low energy ion implantation is related to two processes: ion impinging on the sample and secondary electron emission. Samples composed of a piece of Si (having the size of the ion beam) fixed on the centre of polyethylene (PE) coupons have been implanted with 2.2 keV H₂ ions to a fluence of 2 × 10¹⁶ H/cm². ERD (Elastic Recoil Detection) depth profiles of the implanted ions are shallower with an increase of the PE coupon size. The relative critical Si/PE size to repel all the incident ions is around 1.1 × 1.1 cm²/2.5 × 2.5 cm². The potential of the secondary electron suppressor has been varied from −500 V to +500 V. It changes the secondary electron distribution around the implanted area and, consequently, affects the accumulation of charges at the sample surface. When the potential is 0 V, a uniform ion implantation with little effect of charge accumulation for all sizes of PE coupons is obtained. A two-dimension model has been performed and gives a good explanation for the mechanism of the electric charge neutralisation.     

EFFECT OF DRILLPIPE ROTATION ON BOREHOLE CLEANING FOR EXTENDED REACH WELL

Wellbore cleaning is a key technology for the Extended Reach Drilling (ERD). The success of drilling extended reach wells depends directly upon the quality of wellbore cleaning. The rotation of the drillpipe, and hydraulic and rheological parameters, are the key factors for wellbore cleaning. In this study, Computational Fluid Dynamics (CFD) is applied to simulate solid-liquid two-phase flows in wellbore annulus. The annual flow field with the presence of drillpipe rotation is described through analyzing various rotation conditions. The results indicate that the quasi-spiral flow is the main flow pattern for liquid-solid transport in the horizontal annulus. The influence of rotation on the cuttings transport is also investigated, as the rotation of drillpipe increases the disturbance of liquid to solid in annulus. As a result, the solid flow becomes favorable and the solid volume is reduced. Comparisons with previously published results are also performed to prove the importance of drillpipe rotation in the wellbore clearing for the ERD.     

Oscillatory neural activity associated with cognitive processes affected by spatial frequency

The spatial frequency contained in visual objects is known to affect human psychophysiology. In our previous study, we showed that event‐related potentials are affected by spatial frequency during a simple calculation task. In that study, however, we did not investigate the contribution of oscillatory neural activities. The purpose of the present study is to characterize the changes in oscillatory neural activity associated with cognitive processes, and to investigate how these signals are affected by the spatial frequency of a visual stimulus during simple calculation tasks. We investigate these issues by analyzing our previously collected electroencephalography (EEG) dataset using the same visual stimulus, tasks, subjects, and EEG recordings. In that study, four types of vertically striped visual stimuli were used. The visual stimuli contained embedded numbers (from 0 to 9) that possessed the following frequency (f) characteristics: white noise, 1/f, 1/f², and 1/f³. The subjects were instructed to perform two tasks: ‘add numbers’ (addition task) and ‘do not add numbers’ (reference task). EEG data were recorded, and event‐related synchronization (ERS) and desynchronization (ERD) for each visual stimulus were analyzed on the basis of the intertrial variances of wavelet coefficients for theta, alpha, low‐beta, and gamma band activity. Eight healthy men (21–23 years) were recruited to participate in the study. Our results suggest the presence of a frequency discrimination function in the theta band activity in the fronto‐central area at the latency of 198 ms during the addition task. The alpha‐band ERD during completion of the reference task also showed a spatial frequency dependency. This phenomenon was observed in the left temporal‐parietal area at a latency of 376 ms, and is thought to be related to the perceptual filter. We conclude that the observed changes in oscillatory neural activity associated with cognitive processes are affected by spatial frequency. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Ion beam analysis of hydrogen in advanced materials: Recent experience of Van de Graaff lab

Hydrogen is considered to be the ideal energy carrier in the near future. It would be of great importance to obtain experimental data regarding the interaction of hydrogen with materials as they could assist to better realize the occurring phenomena. More specifically, quantification of hydrogen in materials could help to modify the materials processing conditions in the field of hydrogen generation, storage and utilization for the final goal of energy generation. Measurement of hydrogen in materials has always been a challenge in front of researchers. In this research work, hydrogen analysis has been performed by “Elastic Recoil Detection” (ERD) technique using the α-beam of the Van de Graaff accelerator of Nuclear Science and Technology Research Institute (NSTRI). Capability of ERD for quantification of hydrogen in carbon nanotube, H-treated Ti thin layer as well as in semiconducting sample of Si single crystal – prepared under certain conditions – has been shown. Capability of ERD for characterization of advanced materials is shown by hydrogen quantification or hydrogen concentration depth profiling in each representative example.     

The development of a time of flight spectrometer for LARN

An elastic recoil detection time of flight system to depth profile light elements has been developed on ALTAÏS, the new Tandetron accelerator at LARN. The detector mounted at 45° from the beam axis consists of two isochronous electron detectors for the timing signal (START and STOP) and a 450 mm² heavy ion PIPS detector that detects the energy of the recoil atoms. The 2MV Tandem accelerator provides heavy ion beams with a maximum energy of 16 MeV depending on the charge transfer efficiency of the gas exchange canal located in the middle of the machine. A large variety of primary ion beams like ²⁸Si, ³⁵Cl, ⁶³Cu, ¹²⁷I or ¹⁹⁷Au can be produced with the SINIX heavy ion source and accelerated on the target. Typical current around 1 nA can be obtained. The energy transfer to the recoil atoms is typically in the MeV range and depends on the mass and the energy of the projectile. Some secondary effects like the energy loss in the carbon foils of the timing detector but also in the entrance window of the energy detector should not be neglected if we try to depth profile light elements with this technique. Time resolution of about 1 ns for the electrons detectors is suitable to obtain 1 amu mass resolution. Some examples of applications will be developed in this paper.     

大位移井井壁稳定三维弹塑性有限元分析

现有井壁围岩应力求解模型大都基于平面应变假设，相对岩石真实应力状态会有一定的误差。在空间坐标变换基础上建立了大位移井井壁稳定分析三维弹塑性有限元模型，将井斜角与方位角的变化转化为井轴坐标系下地应力场应力分量的变化，保证了模型的稳定性。利用所建模型对弹性和弹塑性条件下的大位移井井壁围岩稳定性进行了研究。计算结果表明：岩石在弹塑性条件下能够通过塑性变形吸收更多能量；在相同外载条件下，弹塑性岩石比脆性岩石更稳定。经过现场实例验证，在深部弹塑性地层钻进时，可以采取比常规设计稍低的泥浆密度，即能保持井壁稳定，又可以减少地层伤害。     

离子注入对超高分子聚乙烯磨损性能的影响

用８０ｋｅＶ不同剂量的Ｃ３Ｈ＾＋８,Ｎ＾＋２对超高分子聚乙烯样品进行离子注入,通过反冲探测分析表明注入层Ｈ含量的变化,对样品表面在离子注入前后的磨损性能进行了测试。实验结果显示,离子注入以后样品表面氢含量减少,磨损性能增强。     

载酶塑料填料的制备与优化

酶催化反应精馏（ERD）是使用酶作催化剂,将反应精馏（RD）与生物催化相结合的过程。近年来,该工艺过程因其高选择性和环境友好性而日益得到认可。本文研究了塑料填料固定化酶,将含有脂肪酶的溶胶-凝胶溶液喷涂到塑料填料表面,制备了载酶塑料填料。载酶填料作为精馏柱内不可或缺的结构单元,其稳定性是影响ERD发展的重要因素。溶胶-凝胶配方各组分的相对含量直接影响凝胶基质和被包埋酶的性能,因此,本研究对凝胶配方进行了优化,以改善塑料填料载酶涂层的开裂问题。用傅里叶红外光谱（FTIR）、扫描电镜（SEM）对样品进行了表征,并对黏附强度、循环稳定性、机械性能、酶活性和催化效率进行了研究。结果表明,塑料填料表面凝胶涂层的脆性开裂情况得到了改善,涂层与填料的结合强度提高了14.2%。溶胶-凝胶配方的优化可以改善凝胶基质的性能,提高载酶填料的机械稳定性,且优化配方制备的催化剂具有优异的酶学稳定性。这一工作证明了塑料填料固定化酶的可行性,为ERD的工业化打下基础。     

Depth profiling of Al2O3 + TiO2 nanolaminates by means of a time-of-flight energy spectrometer

Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al₂O₃ + TiO₂ nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20 nm and total thickness between 40 nm and 60 nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements ⁶³Cu, ³⁵Cl, ¹²C and ⁴He ions with energies ranging from 0.5 to 10 MeV, were used and depth profiles of the whole nanolaminate film could be analyzed down to 5 nm individual layer thickness.