Stepped side shield writer for perpendicular recording

To increase the track density in hard disk drive (HDD), the write head fringing field should be controlled. The side shield is one of the candidates to reduce the fringing stray field. Although the wrap-around type [K. Nakamoto, et al., IEEE Trans. Magn. 41(10) (2005) 2914] and many other side shield structures [Y. Kanai, et al., IEEE Trans. Magn. 39(4) (2003) 1955; D.T. Wilton, D.J. Mapps, IEEE Trans. Magn. 29 (1993) 4182] were proposed, these side shield structures have a trade-off between the track edge field sharpness and the maximum write field strength on the center track. In this paper, we propose the new side shield writer called the stepped side shield (3S) head. The 3S head satisfies both the on-track write field strength and reduction of the adjacent track stray field. The track edge field sharpness is much improved especially in the high skew angle recording. We studied the 3S head effect by the statistic field simulation.     

Bit-array alignment effect of perpendicular SOMA media

One effective way to overcome the superparamagnetic limit of magnetic recording system is to reduce the grain number per bit at given signal-to-noise ratio (SNR) level by using uniformed media grains. The self organized magnetic array (SOMA) is designed to have uniform grains with perfect grain array structure. It is believed that high enough SNR with small number of grains per bit can be acheived. But in the engineering application, the recorded bit on SOMA media may align with the regular array at different locations and angles due to non-grain synchronized writing, skew angle, and circular track. This induces the bit-array alignment effect and degrades system performance of SOMA media. In this paper, the micromagnetic simulation results show that the bit array alignment effect causes large level SNR fluctuation on the same media. The SOMA media is not preferred to be used in the conventional recording configuration. It is only suitable for the configuration of patterned media.     

Dynamic optimization of track components to minimize rail corrugation

In this paper, the influence on corrugation of the most significant track parameters has been examined. After this parametric study, the optimization of the track parameters to minimize the undulatory wear growth has been achieved. Finally, the influence of the dispersion of the track and contact parameters on corrugation growth has been studied. A method has been developed to obtain an optimal solution of the track parameters which minimizes corrugation growth, thus ensuring that this solution remains optimum despite dispersion of track parameters and wheel–rail contact uncertainties. This work is based on the computer application RACING (RAil Corrugation INitiation and Growth) which has been developed by the authors to predict rail corrugation features.     

Corrigendum to: Optimum profile modifications of spur gears by means of genetic algorithms

The purpose of the present work is to correct some inaccuracies of the paper “Bonori, G., Barbieri, M., Pellicano, F., 2008, Optimum Profile Modifications of Spur Gears by Means of Genetic Algorithms, Journal of Sound and Vibration, 313, pp. 603–616”; in that work, the aim was the reduction of vibrations in spur gears by means of profile modifications. This goal was achieved by using an ad hoc genetic algorithm, where the objective function was the peak to peak or the harmonic content of the Static Transmission Error (STE) computed by Finite Element calculations.The efficiency in terms of vibration reduction of the optimized profile reliefs was checked using a one degree of freedom dynamic model. This dynamic model considers time varying mesh stiffness, backlash, and profile error. In the original paper the effect of intentional profile modifications was considered as part of the mesh stiffness, thus overestimating their effect in vibration reduction.In the present corrigendum, the dynamic model is updated, keeping into account profile deviations by means of an error function. Finally, the optimal profile modifications found in the original paper are checked using the updated model.     

在线诊断光谱仪用光栅制作误差对光谱成像的影响及补偿

为制作应用于在线诊断光谱仪的高分辨率光栅,通过分析记录参数误差对光栅刻线密度、聚焦曲线、谱像宽度等的影响及规律,提出相应的补偿方法是必要前提。基于费马原理、光程差理论及像差理论,分析了光栅光谱性能对记录参数误差的影响及其敏感性。在光栅使用参数固定的情况下,记录角度误差对光谱性能影响较大,在光栅设计时可通过对记录角度加权的方法来提高记录角度的取值的精确度;记录臂长误差对光谱性能影响较小;记录臂长和记录角度的相对误差决定了其对光栅光谱性能影响程度。结果表明,单侧记录臂长和角度误差对光谱性能的影响,可分别通过调节两臂臂长及角度的相对误差进行补偿。由此可以确定对应用于在线监测光谱仪光栅成像质量影响较大的误差因素,并给出制作误差的相应补偿方法,降低曝光系统的调试难度,为制作在线诊断光谱仪用高分辨率光栅提供理论指导。     

Adjacent track interference analysis of shielded perpendicular writers

In order to achieve high track density in perpendicular recording, write-field leakage from the main pole to adjacent tracks needs to be minimized. We used a 3-D finite-element method to investigate the optimal writer design, which minimizes fringing fields. We also confirmed the results using experimentally by studying adjacent track interference (ATI) on a spinstand. According to both modeling and experimental data, we found that ATI performance can be clearly improved with a wrap-around-shielded (WAS) writer while maintaining enough write-ability. In order to reduce the fringing field, a WAS having thick throat, high permeability and high saturated magnetic flux density was required. We also confirmed that variations of ATI performance due to flare length distributions can be effectively suppressed with the WAS writer.     

一种基因芯片光学扫描图像倾斜校正方法研究

针对在基因芯片光学扫描时产生的图像倾斜问题,提出了一种基于像素灰度的芯片图像倾斜校正方法。结合基因芯片图像的结构特点,基于行、列方向像素灰度定义芯片图像的校正指标。在角度检测范围内,利用折半搜索方法,基于校正指标来检测芯片图像的校正角度和芯片图像的校正位置。实验结果表明,该方法能有效地检测多类基因芯片图像的倾斜角度,具有较强的鲁棒性和实用性。     

Free Vibration Analysis of RC Box-Girder Bridges Using FEM

The free vibration analysis of simply supported box-girder bridges is carried out using the finite element method. The fundamental frequency is determined in straight, skew, curved and skew-curved box-girder bridges. It is important to analyse the combined effect of skewness and curvature because skew-curved box-girder bridge behaviour cannot be predicted by simply adding the individual effects of skewness and curvature. At first, an existing model is considered to validate the present approach. A convergence study is carried out to decide the mesh size in the finite element method. An exhaustive parametric study is conducted to determine the fundamental frequency of box-girder bridges with varying skew angle, curve angle, span, span-depth ratio and cell number. The skew angle is varied from 0° to 60°, curve angle is varied from 0° to 60°, span is changed from 25 to 50 m, span-depth ratio is varied from 10 to 16, and single cell & double cell are used in the present study. A total of 420 bridge models are used for parametric study in the investigation. Mode shapes of the skew-curved bridge are also presented. The fundamental frequency of the skew-curved box-girder bridge is found to be more than the straight bridge, so, the skew-curved box-girder bridge is preferable. The present study may be useful in the design of box-girder bridges.     

高速高分辨率圆感应同步器测角系统的研究

本文基于新的思路,突破纯开环或闭环的模式,采用总体开环和数字信号处理部分闭环的方案设计了圆感应同步器测角系统.讨论了其工作原理、硬件框架、典型电路分析,及系统在提高运行速度和减小动态误差方面所采取的措施.整个系统结构简单,并具有较高的跟踪速度、测角精度和工作稳定性.     

Wide viewing angle skewed effect of the point spread function in a wavefront coding system

The point spread function (PSF) of a wavefront coding (WFC) system with a cubic phase mask is analyzed with a wide viewing angle based on physical optics for what is believed to be the first time. Two coordinate transformations are made to generate a pupil function, from which we obtain the encoded PSF of the WFC system with defocus parameters W(020) and object angles alpha and beta. The encoded PSFs are further side extended as the object angles get wider. When alphabeta<0, the included angle ? of encoded PSF will skew to an obtuse angle. When alphabeta=0, ? remains orthogonal; when alphabeta>0, ? will skew to an acute angle. Furthermore, the effect of skew and side extension is even symmetric about W(020). As a result, the wide viewing angle has a bad effect on the imaging quality of the WFC system.     

飞秒光参量放大中三波群速失配的补偿

为了消除群速失配对参量放大的不利影响，描述了利用脉冲波面倾斜与非共线相位匹配相结 合，完全补偿飞秒光参量放大（OPA）中三波群速失配的新方法.计算了在BBOⅠ类、Ⅱ类相 位匹配条件下， 三波实现群速匹配时，相位匹配角、脉冲波面倾斜角以及非共线角随信号 光波长的变化.并分析了三波群速匹配对空间走离长度、参量增益和参量带宽的影响.结果表 明，在BBOⅠ类、Ⅱ类相位匹配条件下，利用该方法均能实现飞秒OPA连续调谐时三波的群速 匹配，从而大大增加了三波的有效互作用长度，为能够获得高增益，窄脉宽的参量光脉冲提 供了理论依据和指导. 关键词： 群速匹配 脉冲波面倾斜 非共线相位匹配 飞秒光参量放大     

Twisted transition of one bit written by trapezoidal single pole

This paper investigates bits transition shift written by a trapezoid single pole at a large skew angle. This work uses the even harmonic ripple effect to modulate the demagnetization field and observe the transition shape clearly. Experiment results indicate that the trapezoid single pole can produce a twisted transition at a large skew angle. This phenomenon is mainly due to the low-frequency data overwriting on the media. The twisted transition will limit the recording density in the perpendicular recording. Simulation work was completed to validate our experiment results. It suggests that the structure of single pole should be further improved to solve the twisted transition generated by the trapezoid single pole.     

用ZEMAX模拟五棱镜误差对平行度检测的影响

介绍了用五棱镜法检测大口径光束平行度的原理。分析了五棱镜加工的角度误差及面形误差对检测结果的影响，得出了五棱镜角度误差不影响检测结果，2个折射面的面形误差对检测结果的影响较小，2个反射面的面形误差对检测结果影响最大的结论。介绍了选择五棱镜的方法和减小面形误差影响的方法。最后，给出了用五棱镜法检测单星模拟器出射光束平行度的应用实例。     

SNR improvement by intergranular exchange coupling in CGC perpendicular magnetic recording media

Effect of intergranular exchange coupling in coupled granular and continuous (CGC) perpendicular media was investigated in terms of improvement of signal-to-noise ratio (SNR). The exchange coupling improves SNR and byte error rate (BER); however, it tended to widen the magnetic track width (MWW) of a track. That degradation is of concern for the CGC media. This paper discusses intergranular exchange coupling in CGC media to optimize track density and linear density to achieve high areal density.     

水声通信系统中双向turbo均衡算法研究（英文）

A direct-adaptation based bidirectional turbo equalizer for underwater acoustic communications is proposed.Abandoning the channel estimation process,the direct-adaptation based turbo equalizer embedded with digital phase-locked loop is adopted to track time-varying channel.The fast self-optimized algorithm is used to adjust the step size,thus a good tradeoff between the convergence speed and performance has been made.Furthermore,by minimizing the mean squared error,an optimal weighting factor is derived to exploit bidirectional diversity gain.The forward turbo equalizer is combined with the backward turbo equalizer to eliminate error propagation effect.Simulated and experimental results demonstrate that the bidirectional turbo equalizer outperforms the single directional one.It can be seen from the experimental results that,compared with the channel estimation based algorithm,the direct-adaptation based algorithm is less sensitive to the time-varying channel and has a lower bit error rate.     

Shingle magnetic recording assessment with spinstand measurement

Shingle Magnetic Recording (SMR) is a candidate to realize recording density of over 1 Tbit/in². At the cost of complex HDD firmware, we can expect many gains such as higher write-ability to break through the famous tri-lemma. In this paper, promising empirical data and concerns found on spinstand were introduced and discussed. More than 18 dB of better reverse overwrite (ROW) than conventional write recording (CWR) was confirmed at 40 nm of track pitch. Areal density capability (ADC) was improved by 25.5% by SMR. Another gain from SMR was observed at inner diameter (ID) and outer diameter (OD) that ADC loss due to skew effect was improved by using preferable side write pole edge. The dependence of ADC on magnetic read width measured with micro-track method (MRWu) indicates that side reading is limiting ADC. Reduction in side reading through narrower MRWu and inter-track interference cancellation technology are necessary to further improve ADC. BPI capability improvement by steeper down track field gradient at the track edge needs to be considered.     

Simulation of triaxial response of granular materials by modified DEM

A modified discrete element method(DEM)with rolling effect taken into consideration is developed to examine macroscopic behavior of granular materials in this study.Dimensional analysis is firstly performed to establish the relationship between macroscopic mechanical behavior,mesoscale contact parameters at particle level and external loading rate.It is found that only four dimensionless parameters may govern the macroscopic mechanical behavior in bulk.The numerical triaxial apparatus was used to study their influence on the mechanical behavior of granular materials.The parametric study indicates that Poisson’s ratio only varies with stiffness ratio,while Young’s modulus is proportional to contact modulus and grows with stiffness ratio,both of which agree with the micromechanical model.The peak friction angle is dependent on both inter-particle friction angle and rolling resistance.The dilatancy angle relies on inter-particle friction angle if rolling stiffness coefficient is sufficiently large.Finally,we have recommended a calibration procedure for cohesionless soil,which was at once applied to the simulation of Chende sand using a series of triaxial compression tests.The responses of DEM model are shown in quantitative agreement with experiments.In addition,stress-strain response of triaxial extension was also obtained by numerical triaxial extension tests.     

结合Sage-Husa滤波的合成孔径声呐多传感器组合运动补偿算法

在运动测量设备噪声统计特性不确定的情况下,提出结合Sage-Husa滤波的合成孔径声呐多传感器组合运动补偿方法。使用Sage-Husa卡尔曼滤波处理多种异类运动传感器的数据,自适应估计声呐速度的最优值,计算实际航迹与理想航迹之间的横荡误差和升沉误差,最后通过时延校正原始回波数据。仿真结果表明,Sage-Husa滤波对运动误差估计精度至少提高37%,运动补偿后,目标峰值旁瓣比和积分旁瓣比有所降低,峰值旁瓣比接近理论值.湖试数据处理结果表明,目标能量分散的情况有所改善,能量集中在主瓣,散焦得到抑制。Sage-Husa滤波在多传感器系统噪声先验知识缺失的条件下,能减小运动数据估计误差,提高运动补偿的准确性。     

Improving compatibility between thermoelectric components through current refraction

It is well known that components with dissimilar compatibility factors cannot be combined by segmentation into an efficient thermoelectric generator, since each component needs a unique optimal current density. Based on the complex variable method, the thermal-electric field within a bi-layered thermoelectric composite has been analyzed, and the field distributions have been obtained in closed-form. Our analysis shows that current refraction occurs at the interface, both the refraction angle and current density vary with the incidence angle. Further analysis proves that the current densities in two components can be adjusted independently by adjusting the incidence current density and incidence angle, thus the optimal current density can be matched in both components, and the conversion efficiency can be significantly increased. These results point to a new route for high efficiency thermoelectric composites.     

一种红外搜索系统的分布式多传感器航迹融合算法

红外搜索系统作为被动式搜索系统,一般只能获得目标所处位置的方位角和俯仰角信息,缺乏距离信息,在无测距装置的条件下,只能依靠角度信息进行数据融合。依据角度值的三角函数关系,提出了一种新的分布式多传感器航迹加权融合算法,算法经仿真验证有效,降低了融合航迹的误差。在对量测数据进行误差修正的基础上,算法效果更加显著。