Sensitivity analysis of a fiber ring resonator based on an air-core photonic-bandgap fiber

The fiber ring resonator (FRR) is the core sensing element in a resonator fiber optic gyroscope (R-FOG), and its sensitivity determines the performance of the R-FOG. This paper presents an in-depth analysis of the sensitivity of the FRR which is made of an air-core photonic-bandgap fiber (PBF), in which the characteristics of the FRR using PBF are compared with that of an FRR using a conventional single mode fiber. When using PBF instead of conventional fiber, it is found that the resonance curve is changed, and the sensitivity of the FRR is decreased a little when a narrow spectral linewidth laser is used. However, the degree of the decrease in sensitivity is not big enough to deny the advantages of PBF in improving the performance of the R-FOG considering that PBF is much better than conventional fiber in reducing the drift. Also, the optimal parameters of the directional coupler for sensitivity are discussed. It is found that the optimal intensity coupling coefficient when using PBF is nearly two times larger than that when using conventional fiber, and the optimal coupler intensity loss when using PBF is smaller than that when using conventional fiber.     

Nonvolatile floating-gate memory programming enhancement using well bias

A nonvolatile memory programming approach using ohmic and Schottky well bias contacts is proposed. Programming efficiency using positive and negative bias voltages are compared in addition to electric field differences between the biases and type of contacts using experimental data and simulations. High-injection efficiency of electrons to the floating-gate is achieved using a negatively biased Schottky contact and a positively biased ohmic contact. A low-injection efficiency is achieved using a negatively biased ohmic contact and a positively biased Schottky contact.     

桁架接头对遥感相机桁架的影响

桁架结构在大中型遥感相机中已被广泛应用。理想的桁架接头为铰接接头,但在实际工程应用中人们却经常采用刚性连接接头。为比较采用两种接头的桁架的整体刚度及支杆材料利用率,首先对桁架中常用的两脚架结构进行了分析。然后,以锯齿形四角架桁架为例,从理论上计算出了两种不同接头的桁架的基频及受前框自重时支杆的最大应力。结果表明,两种接头的桁架的整体刚度几乎一样,但采用铰接接头的桁架比采用刚性连接接头的桁架材料利用率高,支杆可节省重量约21.87%。最后,用Nastran软件进行了有限元分析。结果证明,该理论计算结果是正确的,两种计算结果的差别小于1.12%。     

Constant bandwidth current feedback amplifier from two operational amplifiers

In this article, a new constant bandwidth current feedback amplifier is demonstrated using two operational amplifiers and a few components. The circuit is accurate and achieves gains in excess of 20?dB with only a 2.94% change in bandwidth using discrete components in the inverting configuration. The bandwidth can also be accurately defined using two resistors. Experimental results using a dual operational amplifier integrated circuit confirm the measured results.     

The Effects of Three Types of Profane Language in Persuasive Messages

The present investigation was concerned with the effect of using profanity in a communication on receiver attitude change and speaker credibility ratings. Results of the investigation found no support for the superiority of a persuasive communication using profanity of a religious, excretory, or sexual nature over the same communication devoid of such profanity. It was found, however, that if one of the above three types of profanity is included in a communication, greater attitude change can be expected to occur if the communicator is a female using any one of the three profanity-types mentioned than if the communicator is a male using the same types of profanity. Finally, it was found that using profanity in a communication generally has a detrimental effect on the perceived credibility of the communicator.     

Comparison of the Acquisition Performance of the Matched Filter and Integrate-and-Dump Receivers in a Multipath Delay and Fading Environment

The Matched Filter and the Integrate-and-Dump circuit techniques are both attractive acquisition methods for CDMA systems. Acquisition using the matched filter technique has attracted considerable interest in recent years since it shows a better performance in the presence of Gaussian noise. On the other hand acquisition using an integrate-and-dump circuit is attractive because it is less complex to implement. However, the acquisition performance can be affected significantly by the channel characteristics. In this paper, a numerical method and a computer simulation have been developed in order to compare the two acquisition systems in different propagation environments. Results show that the acquisition using a matched filter is much faster than that using the integrate-and-dump circuit for the reception of spread-spectrum signals in the presence of Gaussian noise. However, in a multipath delay and fading environment, the results show that the mean acquisition time using the matched filter is not always faster than that using the integrate-and-dump circuit. The results show that it depends on the fading, the delay, the number of users and the signal-to-noise ratio.     

量子启发数学形态学的研究

本文在量子信息处理技术的启发下提出一种新的数学形态学结构元素,该结构元素不是传统的结构元素的简单线性组合,而是一种类似于量子叠加态的多态结构元素.利用此结构元素构成的形态学基本算子被定义,其运算意义被解释,并指出在特定的情况下,该算子对数字图像的处理结果能退化到对应的传统形态学算子的处理结果.本文还给出一个利用这种叠加态结构元素进行二值图像边缘检测的实例,并将其检测结果与对应的传统处理结果进行了比较.     

The analysis of medium-sized arrays of complex elements using acombination of FDTD and reaction matching

The analysis of medium-sized arrays of complex antenna elements by means of a full-wave technique often requires impractical amounts of computer power. Nevertheless, it is essential that all the mutual couplings between elements are taken into account. A technique is presented in which the individual element is characterized using the FDTD method and, using the information this provides, the behavior of the complete array is predicted using a method based on reaction matching. Results using this method are compared to measurement and to results obtained using a complete full-wave analysis for three- and five-element arrays of printed dipoles. The error introduced by the approximation is shown to be small in most cases. For arrays of between 10 and 50 elements, savings in computer time of several orders of magnitude can be achieved and, in addition, changes in array geometry do not always necessitate all the results being recalculated     

Usability testing a minimal manual for the Intel SatisFAXtionfaxmodem

Two versions of a manual for the Intel SatisFAXtion faxmodem-the original manual shipped with the product and a proposed shortened manual-are compared. It is found using either manual improves performance over using no manual; there is little difference in performance between the group using the original manual and the group using the proposed shortened manual; and documentation cannot completely compensate for inadequacies in the user interface     

The performance evaluation of MWD logging tools using magnetic andelectric dipoles by numerical simulations

Traditional measurement-while drilling (MWD) logging tools use magnetic dipoles (coils) as transmitting and receiving antennas and operate at a fixed frequency. In this paper, a new MWD tool using electrical dipoles and using pulses as transmitting signals is investigated and its performance is compared to the coil-type MWD tool in the same formation using a numerical simulation technique. The performances of these two different tools are compared both in the time domain and in the frequency domain. A time-domain transmission-line-matrix (TLM) method is used to perform the analysis. It is shown that a pulsed electric-dipole type MWD tool is superior to a coil-type MWD tool in detection of formation boundaries in all the tested cases. It is further suggested that an MWD tool using electric dipole antennas may be more sensitive in practical applications     

Human recognition system for outdoor videos using Hidden Markov model

Human recognition is an essential requirement for human-centric surveillance, activity recognition, gait recognition etc. Inaccurate recognition of humans in such applications may leads to false alarm and unnecessary computation. In the proposed work a robust background modeling algorithm using fuzzy logic is used to detect foreground objects. Three distinct features are extracted from the contours of detected objects. An unique aggregated feature vector is formed using a fuzzy inference system by aggregating three feature vectors. To minimize computation in recognition using Hidden Markov model (HMM), the length of final feature vector is reduced using vector quantization. The proposed method is explained using five basic phases; background modeling and foreground object detection, features extraction, aggregated feature vector calculation, vector quantization, and recognition using Hidden Markov model.     

车辆牌照字符的提取

车辆牌照字符的提取是牌照自动识别系统中几大关键步骤之一。本文先用小角度Hough变换对倾斜的牌照进行校正，再利用牌照字符的灰度特征，采用基于种子的区域增长方法二值化牌照图像，最后根据车辆牌照的制造标准，提取字符，大量实验证明本文具有很好的结果。     

Performance of single- and double-ring resonators using 3×3optical-fiber coupler

This paper investigates theoretically the transmission characteristics of single- and double-ring resonators using 3×3 optical-fiber couplers. Two configurations of a 3×3 coupler are considered: configuration A, with the three fibers centered at the vertices of an equilateral triangle, and configuration B, with their centers aligned in a straight line. It is found that a ring resonator using configuration A does not show any performance improvement over ring resonators using 2×2 couplers. On the other hand, a single-ring resonator using configuration B has a performance close to resonators using 2×2 couplers. It is also shown that a double-ring resonator using a 3×3 coupler exhibits resonance with a double peak, which may find application in the filtering of coherent frequency-shift keying (FSK) signals after optical amplification in an optical-fiber line repeater     

Sub-1 V CMOS large capacitive-load driver circuit using directbootstrap technique for low-voltage CMOS VLSI

A novel sub-1 V CMOS large capacitive-load driver circuit using a direct bootstrap technique for low-voltage CMOS VLSI is reported. For a supply voltage of 1 V, the CMOS large capacitive-load driver circuit using the direct bootstrap technique shows a 3.3 times improvement in switching speed in driving a capacitive load of 2 pF compared to the conventional bootstrapped CMOS driver circuit using an indirect bootstrap technique. Even for a supply voltage of 0.8 V, this CMOS large capacitive load driver circuit using the direct bootstrap technique is still advantageous     

基于DDS与USB技术的通信对抗教学演示系统中软件的设计与实现

介绍了一种用于通信干扰与抗干扰教学与科研实验的演示系统中软件的设计方案,并给出了此方案的具体实现。软件设计在侦察模块中采用一种基于FPGA的FFT-信道化电子侦察方案,在干扰模块中采用FPGA与DDS技术相结合的方案,在控制模块中采用了USB数据传输技术。该系统为通信干扰的各类教学和科研提供了一定的参考,并为寻求对跳频通信的最有效干扰方式提供了一定的依据。     

自由曲面在离轴光学系统中的应用

针对自由曲面能提升成像光学系统的性能和校正像差的特点,分析了自由曲面在离轴光学系统中的应用优势。光学系统选用视场角为30°×11°、焦距为150 mm、F数为3的Cook-TMA。本设计中,离轴三反光学系统的主反射镜采用自由曲面设计。分析了使用Zernike多项式曲面在大视场离轴反射式光学系统中对离轴光学系统性能的提升效果,并与使用常规非球面的情况进行了比较,分析了自由曲面的优缺点。结果表明,自由曲面在提高离轴光学系统的成像质量方面具有更大的优势,系统的平均传递函数比常规非球面提升了15.9%以上,系统接近衍射极限。Zernike多项式曲面在离轴三反系统中的应用效果良好,系统的成像性能得到了较大的提升。     

基于DDS与USB技术的通信对抗教学演示系统中软件的设计与实现

本文介绍了一种用于通信干扰与抗干扰教学与科研实验的演示系统中软件的设计方案,并给出了此方案的具体实现。软件设计在侦察模块中采用一种基于FPGA的FFT-信道化电子侦察方案,在干扰模块中采用FPGA与DDS技术相结合的方案,在控制模块中采用了U SB数据传输技术。该系统为通信干扰的各类教学和科研提供了一定的参考,并为寻求对跳频通信的最有效干扰方式提供了一定的依据。     

An efficient hybrid strategy for uplink channel estimation in massive MIMO systems based on spatially correlated channels

The channel estimation (CE) process is an important phase that has a considerable influence on the performance of massive multiple-input multiple-output systems, in particular, in a more realistic scenario where the channels are spatially correlated (ScD). Thereby, in this work, the uplink (UL) CE process and channel hardening (CH) feature is addressed for ScD Rayleigh fading channels using the statistical Bayesian minimum mean square error estimator. The spatial correlation (SC) of the channels is described using different models, namely, the Gaussian local scattering (GLS) model, the uniform local scattering model, and the proposed hybrid model. Each model (i.e., GLS model and the uniform local scattering model) is studied using two arrangements, that is, for a uniform linear array (ULA) and uniform planar array (UPA). Moreover, the CH feature is investigated under SC of the channels using different models. Furthermore, this study proposes an efficient hybrid strategy based on SC of the channels for UL CE; that is, this work proposes a hybrid covariance matrix (CM) for UPA arrangement by relying on the Kronecker product of the CMs generated through two ULA arrangements, where the first CM is generated through horizontal ULA using GLS model, whereas the second CM is generated through vertical ULA using uniform local scattering model (i.e., one-ring model). Numerical results regarding CE and CH are provided to assert the theoretical expressions, where the CE is evaluated using the normalized mean square error, whereas the CH is assessed using the variance of CH.     

Smart UWB System Based on STC and TR Techniques for BER Performance Enhancement and Interference Rejection

In this research, a novel smart UWB system is introduced. The proposed system is based on using an adaptive maximum ratio combining (MRC) Rake receiver. The proposed adaptive Rake receiver uses Genetic algorithm (GA) to adaptively select the delays of the fingers of the Rake receiver depending on the channel impulse response. It adaptively selects the delays that will allow the Rake receiver to capture most of the energy in the multipath components with minimum complexity. This adaptive Rake receiver is referred to as a GA Rake. The adaptive GA Rake is applied to a single-input single-output and space time coding (STC) multi-input single-output UWB systems. The performance of those systems using a GA Rake is compared to their performance when using a conventional MRC-Rake receiver and showed a great enhancement in performance with less receiver complexity. Also, in this paper, the smart UWB system using STC is modified by using the time reversal (TR) pre-coding technique. The modified system is referred to as a TR smart UWB system. This modification leads to more enhancements in performance and more reduction in receiver complexity over the smart UWB system. Moreover, this paper also shows the ability a TR smart UWB system in combating interference from other UWB systems.     

Measuring confidence in optical flow estimation

The performance of a number of techniques proposed for estimating the quality of optical flow estimates formed using differential methods is considered. The existence of a bias in the optical flow estimates computed using numerical derivatives is demonstrated, as well as the correlation between observed errors and predictions made by using a variety of published confidence estimates