Automated X‐ray inspection method for fillet‐less mounted chip components

Chip components mounted on the printed circuit board are rapidly being miniaturized. Furthermore, the fillet‐less chip soldering technique, which does not use a solder fillet, is widely used in portable products such as mobile phones. However, there is no method to inspect the soldering of fillet‐less chip mounting. In this paper, we propose an automated X‐ray inspection technique for fillet‐less chip mounting. It extracts three inspection parameters from the X‐ray image. In the experiments, we evaluate the repeatability and inspecting ability of the technique and confirm that sufficient information for failure detection is obtained. An automated X‐ray inspection system using this technique is now in operation at some factories, so in conclusion our automated method would be useful in practice. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

X‐ray micrographic imaging system based on COTS CMOS sensors

This paper presents the use of commercial off the shelf CMOS image sensors for the acquisition of X‐ray images with high spatial resolution. The X‐ray images, with application in biology, electronic components inspection, and paleontology research, are obtained with 8‐keV photons from a Cu tube. The quantum efficiency of the detector is estimated using attenuation lengths of photons in the sensor and compared to traditional scintillator conversion layers. The spatial resolution observed with the sensor is limited by the charge redistribution produced after photon interaction with Si.     

A new algorithm for shot noise removal in medical ultrasound images based on alpha‐stable model

Ultrasonic images are generally affected by multiplicative shot noise. Shot noise filtering is thus a critical pre‐processing step in medical ultrasound imagery. This paper analyses and models the coefficients of 2‐D multi‐resolution wavelet decomposition of logarithmically transformed images using alpha‐stable distribution model. Consequently, we propose a new function that performs a non‐linear operation on the data of classifying the coefficients, thus achieving a novel form of noise removal based on multi‐resolution wavelet decomposition and the alpha‐stable model. We compare our new technique with current shot noise reduction methods applied on actual ultrasound medical images and simulations results show that the proposed new method is more robust than the methods based on Gaussian assumption. Copyright © 2006 John Wiley & Sons, Ltd.     

Design of A Soft X‐ray Source with Periodic Microstructure Using Resonance Transition Radiation for Tabletop Synchrotron

A soft X‐ray source with a periodic aluminum multilayer structure with vacuum layers in between for tabletop synchrotrons with low‐energy electrons was designed, and the dependence of radiation performance on structural parameters was clarified using a theoretical calculation of the resonance transition radiation. A photon density of 1 keV pr incident electron was calculated by optimizing the thickness of the aluminum and vacuum layers. Furthermore, the designed structure was fabricated by a microfabrication technique. The effects of dimensional error on the photon density are discussed on the basis of the calculated results and the prototype structure of a 6‐MeV synchrotron. It is clarified that dimensional errors of 1.5% in Al layers and of plus or minus a few dozen nanometers in the vacuum layers are negligible in obtaining a photon density of more than 90% of the maximum value. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于小样本学习的X光图像违禁物品识别

自动X光安检是维护公共安全的重要手段.现有X光违禁物品识别的研究仅针对数据集包含的类别,不能直接应用于未参与训练的类别.数据集各类别的数量不平衡也会影响模型的性能.针对以上问题,提出一种基于小样本学习的X光图像违禁物品分割方法.模型首先将测试图像与标注的支持图像映射至相同的特征空间,然后度量图像间的像素级相似度与区域级...     

Real-time removal of impulse noise from MR images for radiosurgery applications

In the recent years, image processing techniques are used as a tool to improve detection and diagnostic capabilities in the medical applications. Among these techniques, medical image enhancement algorithms play an essential role in the removal of the noise, which can be produced by medical instruments and during image transfer. Impulse noise is a major type of noise, which is produced by medical imaging systems, such as MRI, computed tomography (CT), and angiography instruments. An embeddable hardware module, which can denoise medical images before and during surgical operations, could be very helpful. In this paper, an accurate algorithm is proposed for real-time removal of impulse noise in medical images. Our algorithm categorizes all image blocks into three types of edge, smooth, and disordered areas. A different reconstruction method is applied to each category of blocks for noise removal. The proposed method is tested on MR images. Simulation results show acceptable denoising accuracy for various levels of noise. Also, an field programmable gate array (FPGA) implementation of our denoising algorithm shows acceptable hardware resource utilization. Hence, the algorithm is suitable for embedding in medical hardware instruments such as radiosurgery devices.     

High‐brightness electron sources for a next‐generation light source based on an energy recovery linac

A high‐brightness electron source of ultrasmall emittance and high average current is one of the most important components for next‐generation light sources based on an energy‐recovery linac (ERL). Such a high‐brightness electron source can be realized by a DC photocathode gun driven by laser pulses tailored in the temporal and spatial dimensions. We propose a novel photocathode based on a quantum cascade laser (QCL). Since the ultrafast response of photoelectron emission from QCL is compatible with the tailored laser pulses, it is a candidate electron source for ERLs. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 46–53, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21154     

A delta‐method technique in the wavelet domain to determine statistical quantities of the response of electromagnetic devices with uncertain parameters

In this paper a method to determine the mean value and the variance of the response of a system with uncertain parameters is proposed. With the term ‘response of a system’ we indicate either the value of a single parameter that represents a figure of merit of a device (e.g. the efficiency of a transmission system or the band width of a communication channel) or a characteristic function of the system (e.g. the impulse or the frequency response). In the latter case we estimate the mean value and the variance at every sample of the response. The estimate is performed by using the delta method, a technique for approximating expected values of functions of random variables when the direct evaluation is not feasible. Two examples of the application of the proposed procedure are reported and the results are compared with simulations performed by a Monte Carlo analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Additive noise reduction in natural images using second‐generation wavelet transform hidden Markov models

Noise reduction or denoising is required for visual improvement or as a preprocessing step for subsequent processing tasks, such as image compression and analysis. Therefore, denoising has become a highly desirable and essential process in multimedia applications. The aim of all denoising processes, especially in natural images, is to uncover the true image from the observed noisy image, ideally removing the additive white Gaussian noise (AWGN) while producing a sharp, useful image without losing finer details. Generally, most of the noise obtained during acquisition and transmission of the natural images is assumed to be AWGN. In this study, we propose a new adaptive denoising framework based on second‐generation wavelet domain using hidden Markov models (SGWD‐HMMs) with some new local structure, utilizing the fact that the images are nonstationary with singularities and some smooth areas that can be considered as stationary. The dependencies among wavelet coefficients can be efficiently captured by HMMs since the dependence between two wavelet coefficients dies down quickly as their distance becomes big. Quite remarkably, experimental results verify the effectiveness of SGWD‐HMMs in benchmark images when compared with other state‐of‐the‐art denoising algorithms. It gives competitive results in the subjective and objective assessments, but it is computationally more expensive. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A low‐power delay stage ring VCO based on wrap‐gate CNTFET technology for X‐band satellite communication applications

Over the past few years, with lower power consumption, reasonable layout area, and the ease of integration with standard circuit design technologies compared to the other counterparts, delay stage ring voltage‐controlled oscillators (VCOs) have been in the limelight of microelectronics scientists. However, few efforts have focused on representing high‐performance delay stage ring VCOs in the deep nanometric regime. In this regard, by virtue of outstanding electrical properties of carbon nanotube wrap‐gate transistors, this work aims to propose a carbon nanotube field‐effect transistor (CNTFET)–based delay stage ring VCO. After performing rigorous simulations, the proposed ring VCO which has been designed by 10‐nm gate‐all‐around (GAA) CNTFET technology shows suitable electrical performance metrics. The simulation results demonstrate that the proposed GAA‐CNTFET‐based ring VCO consumes 85.176 μW at with a 6.12‐ to 10.42‐GHz frequency tuning range. At the worst‐case noise conditions, the proposed design presents ‐90.747 dBc/Hz phase noise at 1 MHz offset frequency. With occupying 1.414 μm² physical area, the proposed VCO is appropriate for the ultracompact nanoscale radio frequency apparatus. Our simulation results accentuate that with further improvements and commercializing the fabrication techniques for CNTFET transistors, the proposed GAA‐CNTFET‐based VCO can be considered as a potential candidate for X‐band satellite communication applications.     

Propagation and radiation field characteristics of nanometer electromagnetic waves in x‐ray dielectric waveguides with random media

X‐rays in the nanometer electromagnetic region are useful for nanospace fabrication, information and high‐energy transmission and control techniques of angstrom‐size structures in biomedical sciences and technology. In this paper, the electromagnetic fields in X‐ray gradient fiber with random refractive index media are studied. Statistical mode conversion of beam propagation, beam broadening, and beam center are investigated by the stochastic process theory of electromagnetic fields. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(3): 53–61, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.10002/eej.1160     

Application of the wavelet transform to the low‐bit‐rate speech coding system

In the analysis‐synthesis coding of speech signals, realization of high quality in the low‐bit‐rate coding depends on the extraction of its characteristic parameters in the preprocessing. The precise extraction of the fundamental frequency, one of the parameters of the source information, guarantees quality in speech synthesis. But its extraction is difficult because of the influence of the consonant, nonperiodicity of vocal cord vibrations, the wide range of the fundamental frequency, and so on. In this paper we propose a new fundamental frequency extraction with the criterion based on its harmonics structure and low‐bit‐rate speech coding system using the wavelet transform. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 62–71, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10309     

A novel micromixer with three‐dimensionally cross‐linked capillary array structure fabricated by deep X‐ray lithography

A novel micromixer was proposed, fabricated and verified. The new concept of the micromixer is to cross‐link many capillaries in a three‐dimensional structure. The characteristic flow behaviors were simulated by using the “FLUENT” computational fluid dynamics (CFD) software. The results of the CFD showed unique mixing behavior in three‐dimensionally cross‐linked capillaries. The mixing performance of the micromixer is strongly influenced by controlling the three‐dimensional crossing conditions. The micromixer was fabricated by deep X‐ray lithography with multistep exposure. The cross‐linked capillary structures were successfully fabricated while controlling the cross‐link conditions. The performance of the micromixer was evaluated by using an enzyme reaction. By comparing the mixtures produced with a cross‐linked fluid filter and with a fluid filter without cross‐linked capillaries, we found that the reaction was accelerated by using the new micromixer. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(1): 26–31, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21157     

Low‐Noise Fully Differential Amplifiers Using JFET‐CMOS Integration Technology for Smart Sensors

In this paper, CMOS‐based low‐noise amplifiers with JFET‐CMOS technology for high‐resolution sensor interface circuits are presented. A differential difference amplifier (DDA) configuration is employed to realize differential signal amplification with very high input impedance, which is required for the front‐end circuit in many sensor applications. Low‐noise JFET devices are used as input pair of the input differential stages or source‐grounded output load devices, which are dominant in the total noise floor of DDA circuits. A fully differential amplifier circuit with pure CMOS DDA and three types of JFET‐CMOS DDAs were fabricated and their noise performances were compared. The results show that the total noise floor of the JFET‐CMOS amplifier was much lower compared to that of the pure CMOS configuration. The noise‐reduction effect of JFET replacement depends on the circuit configuration. The noise reduction effect by JFET device was maximum of about − 18 dB at 2.5 Hz. JFET‐CMOS technology is very effective in improving the signal‐to‐noise ratio (SNR) of a sensor interface circuit with CMOS‐based sensing systems. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Method for Diffusing Carrier Noise under Zero‐Speed Condition using a Zero‐Sequence Voltage

In this paper, a technique is proposed to reduce the carrier noise of pulse width modulation (PWM) inverters for a permanent magnet motor drive. The carrier noise is generated by the motor and the reactor driven by the inverter and affected by the switching frequency. When a motor rotates and drives a machine, the carrier noise is hidden by the machine noise. However, when the motor speed is approximately zero, the carrier noise becomes dominant and raucous. The typical method to reduce the noise employs a switching frequency higher than the audible frequency of human hearing. However, the increase in switching frequency results in the inverter suffering a higher switching loss and lower efficiency. In particular, when the permanent magnet motor operates at approximately zero‐speed and full‐load, for example, in the hill‐start conditions of electric vehicles and the start and stop conditions of elevators, the current flows in specific power devices and the switching loss further increases. The proposed technique uses a zero‐sequence voltage, which is generated randomly with the M‐sequence signal, and diffuses the frequency components of the ripple contained in the current. The technique is able to reduce the noise without increasing the switching frequency of the inverter when the motor speed is almost zero. Simulation and experimental results show that the proposed technique can diffuse the carrier noise and the cycle of the M‐sequence signal changes the diffusion effect of the carrier noise.     

Embedded coding of medical images with regions of interest based on 3-D zerotree

In order to satisfy the need of diagnoses, based on the characteristic of medical images that a sequence of frames are formed in one body inspection, a new strategy for medical images compression is proposed. The 3-D wavelet is adopted and the planar zerotree is extended to the 3-D zerotree. By making use of the 3-D zerotree structure, a simple method for region of interest (ROI) mask generation is put forward. Medical images are compressed by three-dimensional embedded coding with the compression of regions of interest. Simulation results have shown that it can efficiently improve the compression ratio without affecting the diagnoses. Translated from Journal of Xidian University, 2006, 33(2): 182–185 [译自: 西安电子科技大学学报]     

A new approach for flicker analysis using information‐theory‐based wavelet energy entropy

Flicker is one of the critical power quality disturbances seen in power distribution networks nowadays. Besides its effects on the human life, it causes malfunctioning and misoperation of sensitive electrical equipment. The measurement of the flicker level is defined in IEC 61000‐4‐15 standard by a flicker meter, which deals only with voltage signals and is not sufficient to understand the contribution of the load and background power systems separately. Therefore, in this letter we present a new approach to the evaluation of flicker characteristics in the light of multiresolution wavelet analysis and information‐theory‐based wavelet energy entropy analysis together. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Control Method for Harmonic Voltage Injection to Achieve Noise Reduction in Position‐Sensorless Control of Permanent‐Magnet Synchronous Motors at Low Speeds

In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position‐sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a four‐pole, 2‐kW, 2100‐rpm IPMSM (interior permanent‐magnet synchronous motor). © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 49–56, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21246     

抑制局部放电信号窄带干扰的快速算法

为消除与抑制窄带干扰对电力设备局部放电信号在线监测的影响,提出了一种将快速傅里叶变换（FFT）与小波变换相融合的快速算法,即先对信号进行FFT,从窄带干扰背景中有效提取局部放电信号,再利用小波变换对FFT处理后的局部放电信号进一步消噪。对仿真信号和实测信号的分析结果表明,该方法对窄带干扰有较好的消噪效果,并且得到的局部放电信号失真较小。