经ERCP联合SpyGlass DS治疗的74例不明原因胆管狭窄患者的临床特征分析

目的 分析经内镜逆行胰胆道造影(endoscopic retrograde cholangiopancreatography, ERCP)联合SpyGlass DS治疗的不明原因胆管狭窄(indeterminate biliary stricture, IBS)患者的临床资料,为IBS的诊疗提供更多临床数据参考。方法 回顾性分析2020年1月至2023年4月北京中医药大学东方医院消化内镜中心经ERCP联合SpyGlass DS治疗的74例IBS患者的临床资料,归纳采用SpyGlass DS直视下视觉印象评估良恶性狭窄的情况,总结SpyGlass DS引导下视觉印象和SpyGlass DS引导下活检(SpyBite活检)在诊断IBS的性能特点。结果 共纳入74例IBS患者,男49例,女25例,年龄(67±12)岁(26~94岁)。74例患者中,61例(82.4%)直视下考虑为恶性狭窄,其中40例(65.6%)病理诊断提示恶性,5例(8.2%)病理诊断未提示恶性,16例(26.2%)未取活检。随访过程中,有1例患者经影像学检查被诊断为恶性肿瘤,而其余患者未发现进展;13例(17.6%)SpyGlass DS直视下考虑为良性狭窄,其中3例(23.0%)病理诊断恶性,5例(38.5%)病理诊断未提示恶性,5例(38.5%)未取活检并在随访过程中均未发现狭窄处进展。SpyGlass DS直视下视觉印象为肿瘤血管、增生物、黏膜不规则/结节性/增生性改变、黏膜损伤、胆管内渗出物的表现而病理诊断提示恶性的占比分别为24.4%、20.0%、62.2%、2.2%、8.9%。SpyGlass DS直视下视觉印象的敏感度为88.9%,特异度为37.5%,准确度为81.1%,SpyBite活检的诊断敏感度为95.7%,特异度为66.7%,准确度为92.3%。结论 对IBS可采用ERCP联合SpyGlass DS进行诊断,可大大提高疾病确诊率。

DS/FH信号跟踪的频率相位修正技术

直序/跳频(direct sequence/frequency hopping,DS/FH)扩频信号的跟踪受到多普勒效应和电离层效应的严重影响,使其难以应用于卫星导航的抗干扰领域。为了解决该问题,提出将递归最小二乘滤波修正的方法应用在DS/FH信号跟踪上。将处于不同通道中心频率的多普勒频率估计转化到DS/FH信号的整体中心频率进行并滤波,在频率捷变时对载波数控振荡器进行修正。根据对频率跳变前后载波相位和码相位突变的观察,实时估计电离层的电子密度,在频率捷变时修正载波相位和码相位。仿真实验证明,所提方法能够有效地消除DS/FH信号跟踪中的频率相位不连续问题,其跟踪精度与直序扩频信号度基本是相同量级。

用Direct3D结合3DSMAX实现动画技术

系统介绍了Direct3D ,3DSMAX在动画技术方面的功能和作用 ,并为它们结合实现动画技术提供了一个基本框架。

一种突发DQPSK-DSSS信号解调方法

为了解决通信测控系统可靠性通信的问题,提出了一种将直接序列扩频和DQPSK相结合的通信方法。文章通过对突发信号的捕获、DQPSK解调两方面仿真和分析,验证了算法的性能。文章通过Vivado等工具进行了基于FPGA的硬件代码开发,在工程中实测,验证了算法的可行性,该方法具有很高的应用前景。

Approach to blind estimation of the PN sequence in DS-SS signals with residual carrier

This paper presents an approach of singular value de- composition plus digital phase lock loop to solve the difficult problem of blind pseudo-noise （PN） sequence estimation in low signal to noise ratios （SNR） direct sequence spread spectrum （DS-SS） signals with residual carrier. This approach needs some given parameters, such as the period and code rate of PN sequence. The received signal is firstly sampled and divided into non-overlapping signal vectors according to a temporal window, whose duration is two periods of PN sequence. An autocorrelation matrix is then computed and accumulated by those signal vectors one by one. The PN sequence with residual carrier can be estimated by the principal eigenvector of the autocorrelation matrix. Further more, a digital phase lock loop is used to process the estimated PN sequence, it estimates and tracks the residual carrier and removes the residual carrier in the end. Theory analysis and computer simulation results show that this approach can effectively realize the PN sequence blind estimation from the input DS-SS signals with residual carrier in lower SNR.

Low complexity method for spreading sequence estimation of DSSS signal in non-cooperative communication systems

It is a necessary step to estimate the spreading sequence of direct sequence spread spectrum （DSSS） signal for blind despreading and demodulation in non-cooperative communications. Two innovative and effective detection statistics are proposed to implement the synchronization and spreading sequence estimation procedure. The proposed algorithm also has a low computational complexity with only linear additions and modifications. Theoretical analysis and simulation results show that the algorithm performs quite well in low SNR environment, and is much better than all the existing typical algorithms with a comprehensive consideration both in performance and computational complexity.

Neural network approach to blindestimation of PN spreading sequence in lower SNR DS/SS signals

An approach based on discrete Karhunen-Loeve transformation of the DS/SS signals is proposed to estimate PN sequence in lower S/N ratio DS/SS signals. Characteristics of self-organization and principle components extraction of unsupervised neural networks are exploited adequately. Theoretical analysis and experimental results are provided to show that this approach can work well on the lower S/N ratio input signals.

Ultra-wideband direct-sequence design approach for multiple narrowb and interference suppression

A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implemented in practical systems. Simulation results prove that the proposed method is effective to suppress the narrowband interference. Therefore, the integrity of both the ultra-wide bandwidth and the narrowband systems can be highly enhanced.

Research on Estimator and Testing Acquisition Schemes in Direct Sequence Spectrum Spreading Systems

Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the locally optimal estimation scheme, the optimal testing searches and the locally optimal testing scheme. In the four kinds of parallel acquisition schemes, the expressions for the probability of error are given and compared with the actual error probabilities obtained via Monte Carlo simulation. We also outline a technique that can be suboptimal because of a large amount of hardware and computation when using the parallel acquisition schemes.

New Acquisition Algorithm for Direct Sequence Spread Spectrum Signals

Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.

Fast method for spreading sequence estimation of DSSS signal based on maximum likelihood function

To estimate the spreading sequence of the direct sequence spread spectrum (DSSS) signal, a fast algorithm based on maximum likelihood function is proposed, and the theoretical derivation of the algorithm is provided. By simplifying the objective function of maximum likelihood estimation, the algorithm can realize sequence synchronization and sequence estimation via adaptive iteration and sliding window. Since it avoids the correlation matrix computation, the algorithm significantly reduces the storage requirement and the computation complexity. Simulations show that it is a fast convergent algorithm, and can perform well in low signal to noise ratio (SNR).

A Neural Network Approach to Blind Estimation of PN Spreading Sequence in DS/SS Signals

In this paper, a new approach is proposed to estimate pseudo noise(PN) sequence in the lower SNR DS/SS signals blindly. This method utilizes the characteristics of self-organization, principal components analysis and extraction of unsupervised neural networks adequately, in addition to its higher-speed operation ability, successfully solve the difficult problem about PN sequence blind estimation. The theoretic analysis and experimental results show that this approach can work very well on lower SNR input signals.

QUASI-SYNCHRONOUS MULTICARRIER DS-CDMA USING Z-COMPLEMENTARY SEQUENCES

In this paper, a multicarrier DS-CDMA system which employs Z-Complementary Se- quences (ZCS) as spreading code is investigated. The new system can not only eliminate multipath interference and Multiple Access Interference (MAI), but also support flexible number of users com- pared with system using Orthogonal Complementary (OC) codes. Multicarrier DS-CDMA using OC codes can be regarded as a special case of our proposed system. Zero Correlation Zone (ZCZ) of ZCS can be flexibly adjusted to meet the requirements on the user number and maximum multipath and in- ter-user delay, in this way, more users can be supported without losing interference-free property. The effectiveness of the proposed system is validated through theoretical analysis and simulation results.

Several Modulation in Direct-Sequence Spectrum-Spread Systems

Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the criterion the power of original signal is the same, it is shown that complex quaternary modulation has the best performance, and dual quaternary modulation degrades 2dB. Moreover, the frequency efficient of the two modulations is 2bit/Hz. Balanced quaternary has the same performance as BPSK with frequency efficient 1bit/Hz.

Ternary Zero Correlation Zone Sequence Sets for Asynchronous DS-CDMA

In this paper we propose a new class of ternary Zero Correlation Zone (ZCZ) sequence sets based on binary ZCZ sequence sets construction. It is shown that the proposed ternary ZCZ sequence sets can reach the upper bound on the ZCZ sequences. The performance of the proposed sequences set in asynchronous Direct Sequence-Code Division Multiple Access (DS-CDMA) system is evaluated. In the simulation we used two types of channels: Additive White Gaussian Noise (AWGN) and frequency non-selective fading with AWGN noise. The proposed ternary ZCZ sequence sets show better results, in term of Bit Error Rate (BER), than Hayashi’s ternary ZCZ sequence sets.

复杂环境下的DSSS信号抗均匀频谱干扰研究

随着直接序列扩频(DSSS)信号的广泛应用,复杂环境下的DSSS信号抗干扰研究尤为重要。以直扩系统中常见的均匀频谱信号为例,进行信号抗干扰研究。首先分析均匀频谱信号特性,进而设计直扩信号同步环路模型,通过均匀频谱信号带宽、中心频偏、能量的有机配置,研究均匀频谱信号对DSSS信号同步环路的影响,给出不同条件下最佳抗干扰方案,为通信接收机抗干扰及保障技术提供理论基础。

基于可逆元胞自动机加密的扩展码索引调制方案

针对直接序列扩频系统伪随机(Pseudo Noise,PN)码资源有限且码索引调制系统误码率性能下降的问题,提出了一种基于可逆的初等元胞自动机加密的扩展码索引调制方案。首先,针对PN码资源有限的问题,提出使用混沌规则的初等元胞自动机对PN码进行迭代的方案,从而实现扩展PN码的目的;其次,针对码索引调制误码率性能下降的问题,提出了一种可逆元胞自动机加密的码索引调制方案,在发射端,把信息比特切割成调制比特和映射比特,并分别映射为调制符号和扩频码索引,使用对应索引的扩频码对同相分量进行扩频,同时使用可逆元胞自动机对映射比特进行加密,加密后的映射比特为调制符号的正交分量选取对应索引的扩频码进行扩频。仿真与分析结果表明,在相同频谱效率条件下,在加性高斯白噪声信道中,当误码率为10-5时,扩展码索引调制方案的误码率性能优于码索引调制和广义码索引调制方案约2~4 dB,优于非正交码移键控码索引调制方案约0.5 dB。

一种DS/SS信号PN码序列估计的神经网络方法

本文提出了一种利用神经网络（Ｎ．Ｎ．）完成直接序列扩频（ＤＳ／ＳＳ）信号 ＰＮ（伪噪声码）码序列估计的新方法。该方法充分利用了无监督Ｎ．Ｎ．的自适应主元提取特性，加上其高速运算能力，解决了传统方法在ＰＮ码的实时处理及实现上的困难，理论分析和数值结果表明了本方案能在较低的输入信噪比条件下完成对ＰＮ码的正确估计。

水稻Ac×Ds后代基因组DNA中Ds侧翼序列的扩增及其Ds插入分析

采用TAIL-PCR技术从经鉴定含Ac/Ds双元件的材料中扩增Ds侧翼序列并测序,对水稻Ac×Ds后代基因组DNA进行Ac和Ds插入的PCR分析。利用NCBI的BLAST软件,以Ds侧翼序列为待查询序列进行GenBank在线搜索比对,获得Ds插入相关基因的染色体定位和功能注释等信息。对扩增的93个有效Ds侧翼序列进行分析,结果显示,有21个水稻杂交后代中Ds插入于基因编码区,其余72个插入在基因间序列,其中12个插入在特定基因的上游3kb以内的间隔区。本研究强调了提高Ds侧翼序列扩增和Ac/Ds植株筛选效率的技术关键。

部分驻留时间干扰对FH/DS通信系统同步影响分析

为了提高对FH/DS通信系统的干扰效率,相继提出了一些新的干扰方法;然而,这些新的干扰方法在FH/DS通信系统每跳驻留时间内仅能干扰其中一小部分.为此,在对FH/DS通信系统研究基础上,重点分析了部分驻留时间干扰对FH/DS通信系统同步的影响.进一步进行了计算机仿真与分析,验证了在一定干信驻留时间比情况下部分驻留时间干扰的有效性.