Quick System-Level DDR3 Signal Integrity Simulation Research

Double data rate synchronous dynamic random access memory （DDR3） has become one of the most mainstream applications in current server and computer systems. In order to quickly set up a system-level signal integrity （SI） simulation flow for the DDR3 interface, two system-level SI simulation methodologies, which are board-level S-parameter extraction in the frequency-domain and system-level simulation assumptions in the time domain, are introduced in this paper. By comparing the flow of Speed2000 and PowerSI/Hspice, PowerSI is chosen for the printed circuit board （PCB） board-level S-parameter extraction, while Tektronix oscilloscope （TDS7404） is used for the DDR3 waveform measurement. The lab measurement shows good agreement between simulation and measurement. The study shows that the combination of PowerSI and Hspice is recommended for quick system-level DDR3 SI simulation.

Pedestrian perception-based level-of-service model at signalized intersection crosswalks

Pedestrian level of service(PLOS)is an important measure of performance in the analysis of existing pedestrian crosswalk conditions.Many researchers have developed PLOS models based on pedestrian delay,turning vehicle effect,etc.,using the conventional regression method.However,these factors may not effectively reflect the pedestrians'perception of safety while crossing the crosswalk.The conventional regression method has failed to estimate accurate PLOS because of the primary assumption of an arbitrary probability distribution and vagueness in the input data.Moreover,PLOS categories in existing studies are based on rigid threshold values and the boundaries that are not well defined.Therefore,it is an important attempt to develop a PLOS model with respect to pedestrian safety,convenience,and efficiency at signalized intersections.For this purpose,a video-graphic and user perception surveys were conducted at selected nine signalized intersections in Mumbai,India.The data such as pedestrian,traffic,and geometric characteristics were extracted,and significant variables were identified using Pearson correlation analysis.A consistent and statistically calibrated PLOS model was developed using fuzzy linear regression analysis.PLOS was categorized into six levels(A–F)based on the predicted user perception score,and threshold values for each level were estimated using the fuzzy c-means clustering technique.The developed PLOS model and threshold values were validated with the fieldobserved data.Statistical performance tests were conducted and the results provided more accurate and reliable solutions.In conclusion,this study provides a feasible alternative to measure pedestrian perception-based level of service at signalized intersections.The developed PLOS model and threshold values would be useful for planning and designing pedestrian facilities and also in evaluating and improving the existing conditions of pedestrian facilities at signalized intersections.

Weighted Multi-sensor Data Level Fusion Method of Vibration Signal Based on Correlation Function

As the differences of sensor＇s precision and some random factors are difficult to control,the actual measurement signals are far from the target signals that affect the reliability and precision of rotating machinery fault diagnosis.The traditional signal processing methods,such as classical inference and weighted averaging algorithm usually lack dynamic adaptability that is easy for trends to cause the faults to be misjudged or left out.To enhance the measuring veracity and precision of vibration signal in rotary machine multi-sensor vibration signal fault diagnosis,a novel data level fusion approach is presented on the basis of correlation function analysis to fast determine the weighted value of multi-sensor vibration signals.The approach doesn＇t require knowing the prior information about sensors,and the weighted value of sensors can be confirmed depending on the correlation measure of real-time data tested in the data level fusion process.It gives greater weighted value to the greater correlation measure of sensor signals,and vice versa.The approach can effectively suppress large errors and even can still fuse data in the case of sensor failures because it takes full advantage of sensor＇s own-information to determine the weighted value.Moreover,it has good performance of anti-jamming due to the correlation measures between noise and effective signals are usually small.Through the simulation of typical signal collected from multi-sensors,the comparative analysis of dynamic adaptability and fault tolerance between the proposed approach and traditional weighted averaging approach is taken.Finally,the rotor dynamics and integrated fault simulator is taken as an example to verify the feasibility and advantages of the proposed approach,it is shown that the multi-sensor data level fusion based on correlation function weighted approach is better than the traditional weighted average approach with respect to fusion precision and dynamic adaptability.Meantime,the approach is adaptable and easy to use,can be applied to other areas of vibration measurement.

New Method to Measure the Fill Level of the Ball Mill Ⅱ-Analysis of the Vibration Signals

The exact measurement of the fill level is the key and basic problem for automatic control and optimized operation of the coal pulverizing system. Because the ball mill pulverizing system is non-linearity, long time delay and time-varying, the reliable and effective method for measuring the fill level was lacked at present. In order to reduce the influence by various factors on measuring the fill level and improve the measuring accuracy of the fill level, a novel characteristic variable is proposed. A set of wireless transmission device was designed to record vibration signals, and an accelerometer with high accuracy and large measuring range was mounted directly on the mill shell to pick up the vibration signals from the mill shell. A series of data acquisition experiments under various ball load and water content of coal conditions were conducted in an industrial mill to investigate the relationship between the fill level and the angular position of the maximum vibration point of the mill shell through the analysis of the vibration signals. The analytical result of test data clearly show that the angular position of the maximum vibration point on the mill shell decreases as the fill level increases. At the same time, comparing with the traditional characteristic variable, the feature variable of the fill level proposed in this paper is not subject to the effect of the ball load and water content of coal, which provides a new solution and reliable basis for the accurate measurement of the fill level.

A new tracking error detection method using amplitude difference detection for signal waveform modulation multi-level discs

The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.

Radio Frequency Environment Effect Algorithms and Implementation in Signal-level Radar System Simulation

In radar system simulation,the reliability of simulation results depends not only on radar and target models,but also on radio frequency (RF) environment models,including clutter,multipath,diffraction,atmosphere refraction and attenuation.In traditional radar function simulation,all of these factors are grouped into a single pattern-propagation factor and can only give limited information for radar models.In signal-level simulation,radar models require simulated echoes should include information such as delay,doppler frequency,polarization,etc.By discussing and analyzing the principles and algorithms of RF environment effects (clutter,multipath,diffraction,atmosphere refraction and attenuation),this paper is supposed to provide a general RF environment model in signal-level.Algorithms for the Weibull clutter with Gaussian power spectral density (PSD) is discussed;A standard multipath and diffraction algorithm is analyzed,and the spherical earth and knife edge(SEKE)diffraction algorithm is introduced;The ray-tracing algorithm and the effective earth model are discussed;Algorithms for the absorption of oxygen and vapor are introduced;For certain algorithms,some practical advice is given.Finally,an object-oriented RF environment effects model is implemented,which has been dedicatedly designed for signal-level simulations and can provide relatively authentic simulated RF environment for the signal-level simulation of radar systems.Two simulation examples including clutter model and multipath and diffraction model are carried out and analyzed.

Tri-level programming model for combined urban traffic signal control and traffic flow guidance

In order to balance the temporal-spatial distribution of urban traffic flow, a model is established for combined urban traffic signal control and traffic flow guidance. With consideration of the wide use of fixed signal control at intersections, traffic assignment under traffic flow guidance, and dynamic characteristics of urban traffic management, a tri-level programming model is presented. To reflect the impact of intersection delay on traffic assignment, the lower level model is set as a modified user equilibrium model. The middle level model, which contains several definitional constraints for different phase modes, is built for the traffic signal control optimization. To solve the problem of tide lane management, the upper level model is built up based on nonlinear 0-1 integer programming. A heuristic iterative optimization algorithm(HIOA) is set up to solve the tri-level programming model. The lower level model is solved by method of successive averages(MSA), the middle level model is solved by non-dominated sorting genetic algorithm II(NSGA II), and the upper level model is solved by genetic algorithm(GA). A case study is raised to show the efficiency and applicability of the proposed modelling and computing method.

Read channel for signal waveform modulation multi-level disc

A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.

Improved partial response maximum likelihood method combining modulation code for signal waveform modulation multi-level disc

In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs partial response equalizer and adaptive viterbi detector combining modulation code. Compared with the traditional adaptive PRML detector, the improved PRML detector additionally employs illogical sequence detector and corrector. Illogical sequence detector and corrector can aw）id the appearance of illogical sequences effectively, which do not follow the law of modulation code for signal waveform modulation multi-level disc, and obtain the correct sequences. We implement the improved PRML detector using a DSP and an FPGA chip. The experimental results show good performance. The higher efficient and lower complexity can be obtained by using the improved PRML method than by using the previous PRML method. Meanwhile, resource utilization of the improved PRML detector is not changed, but the bit error rate （BER） is reduced by more than 20%.

基于经验小波变换的多通道微弱电流信号噪声控制

多通道微弱电流信号受很多噪声因素的干扰,导致输出的微弱电流信号与原始信号之间的相对误差增加,控制效果变差,为此提出基于经验小波变换的多通道微弱电流信号噪声控制方法;采集多通道微弱电流信号,利用经验小波变换技术分解采集到的微弱电流信号,判断电流信号中是否存在噪声并确定噪声类型;设计微弱电流信号噪声控制器,根据电流信号中的噪声量与噪声类型生成控制指令,对不同通道微弱电流信号噪声进行控制;在两种不同噪声强度的实验环境下,该方法控制下的多通道微弱电流信号信噪比较高,输出信号与原始信号间的相对误差较低,控制任务完成时间更短;以此证明该方法的多通道微弱电流信号噪声控制效果更好,可以广泛应用至电流信号噪声控制领域。

Noise level estimation method with application to EMD-based signal denoising

This paper proposes a new signal noise level estimation approach by local regions. The estimated noise variance is applied as the threshold for an improved empirical mode decomposition（EMD） based signal denoising method. The proposed estimation method can effectively extract the candidate regions for the noise level estimation by measuring the correlation coefficient between noisy signal and a Gaussian filtered signal. For the improved EMD based method, the situation of decomposed intrinsic mode function（IMFs） which contains noise and signal simultaneously are taken into account. Experimental results from two simulated signals and an X-ray pulsar signal demonstrate that the proposed method can achieve better performance than the conventional EMD and wavelet transform（WT） based denoising methods.

基于选频电平表设计的信号与系统综合实验

针对学生的工程实践能力培养,为信号与系统实验课程设计了项目驱动式综合实验“选频电平表设计”。基于CDIO工程教育模式设计了实验内容,指导学生通过团队协作完成电子产品从研发到运行的完整周期。实验项目涉及傅里叶变换、频谱搬移、滤波等信号的频域分析和处理方法,同时结合了模拟电路设计、单片机技术、 EDA技术、电路焊接与调试等内容,综合性强,紧贴工程实际。教学实践表明,该实验能帮助学生加深对理论知识的理解,积累实践经验,提高学习兴趣和实践能力。

白藜芦醇对膝骨关节炎模型大鼠关节液中氧化应激和炎症因子的调控作用

背景:膝骨关节炎是临床常见退行性关节疾病,主要表现为慢性炎症和氧化应激反应。白藜芦醇具有抗炎和抗氧化应激的生物作用,因此可对症进行治疗,有望为膝骨关节炎治疗提供新的策略。目的:探讨白藜芦醇通过沉默信息调节因子1(silence information regulator 1,SIRT1)/叉头框转录因子O1(forkhead transcription factor O1,FOXO1)通路对大鼠膝骨关节炎的作用机制。方法:40只SD大鼠随机分为对照组、模型组、白藜芦醇低剂量组和白藜芦醇高剂量组,每组10只,除对照组外均建立膝骨关节炎模型,分别在造模的第1,4,7天注射4%木瓜蛋白酶溶液与0.3 mol/L半胱氨酸溶液(1∶1混置0.5 h)的混合液20μL。造模成功后1 d开始给药,白藜芦醇低剂量组和白藜芦醇高剂量组大鼠经关节腔注射白藜芦醇25 mg/kg或100 mg/kg,对照组和模型组经关节腔注射等体积生理盐水。治疗28 d后,测定4组大鼠膝关节最大活动度;应用放射免疫法和ELISA法检测膝关节液中氧化应激指标和炎症因子水平;番红O-固绿染色分析膝关节中胶原纤维含量;采用Mankin组织学评分分析关节炎病变程度;蛋白质免疫印迹法检测膝关节SIRT1和FOXO1水平。结果与结论:①与模型组比较,白藜芦醇低剂量组和高剂量组大鼠膝关节最大屈伸角度明显增加,且高剂量组明显高于低剂量组(P<0.05);②与模型组比较,白藜芦醇低剂量组和高剂量组大鼠膝关节液中超氧化物歧化酶和谷胱甘肽过氧化物酶水平显著增加;而丙二醛水平显著下降,且高剂量组明显优于低剂量组(P<0.05);③与模型组比较,白藜芦醇低剂量组和高剂量组大鼠膝关节液炎症因子白细胞介素1β、白细胞介素6和肿瘤坏死因子α水平明显下降,且高剂量组明显低于低剂量组(P<0.05);④与模型组比较,白藜芦醇低剂量组和高剂量组大鼠膝关节胶原纤维含量增加,且高剂量组明显高于低剂量组(P<0.05);⑤与模型组比较,白藜芦醇低剂量组和高剂量组大鼠膝关节SIRT1表达水平显著增加,乙酰化FOXO1水平显著下调,且高剂量组变化幅度明显优于低剂量组(P<0.05);⑥提示白藜芦醇可显著改善膝骨关节炎大鼠关节液中的氧化应激和炎症因子水平,缓解关节炎症状,且呈剂量依赖性,可能是通过SIRT1/FOXO1通路实现的。

基于雷达对抗装备的信号级软件仿真模型设计

为了提高雷达对抗装备数字仿真的真实性,提升信号级软件模型研制效率,根据实际装备的工作原理,本文设计了一种“通用结构+专有特征”的信号级雷达对抗装备软件模型。按照实际雷达对抗装备的组成模块与运行原理构建通用基础框架,提高仿真模型复用性,根据不同雷达对抗装备专有功能特征,仿真模拟装备间的差异性,提升仿真模型的真实性与实现效率。

政策信号的多层级传递与市级政府行为合规:基于环境信息公开案例的实证研究

政策信号是传递上级政府治理意向、激励下级政府行为合规的重要手段。分析政策信号多层级作用机制下市级政府2008-2018年环境信息公开行为发现,政府组织中的上层与中层信号均会显著影响下层政府合规行为;在多层级传递过程中,政策信号的影响随行政级别差异的增加而减弱;中间环节传递的不一致信号会削弱上层政府信号效果;在交互作用中,上层政府的“强信号”将翻转中层政府的“不一致”信号,而“弱信号”则可能被后者抵消。在此基础上,提出研究结论与政策建议。

面向国产高性能加速器的LLVM编译器设计及优化

国防科技大学自主研制的高性能加速器采用中央处理器(CPU)+通用数字信号处理器(GPDSP)的片上异构融合架构,使用超长指令集(VLIW)+单指令多数据流(SIMD)的向量化结构的GPDSP是峰值性能主要支撑的加速核。主流编译器在密集的数据计算指令排布、为指令静态分配硬件执行单元、GPDSP特有的向量指令等方面不能很好地支持高性能加速器。基于低级虚拟器(LLVM)编译框架,在前寄存器分配调度阶段,结合峰值寄存器压力感知方法(PERP)、蚁群优化(ACO)算法与GPDSP结构特点,优化代价模型,设计支持寄存器压力感知的指令调度模块;在后寄存器分配阶段提出支持静态功能单元分配的指令调度策略,通过冲突检测机制保证功能单元分配的正确性,为指令并行执行提供软件基础;在后端封装一系列丰富且规整的向量指令接口,实现对GPDSP向量指令的支持。实验结果表明,所提出的LLVM编译架构优化方法从功能和性能上实现了对GPDSP的良好支撑,GCC testsuite测试整体性能平均加速比为4.539,SPEC CPU 2017浮点测试整体性能平均加速比为4.49,SPEC CPU 2017整型测试整体性能平均加速比为3.24,使用向量接口的向量程序实现了平均97.1%的性能提升率。

丽江黑龙潭泉群修复中地下水位作为补水控制信号的研究与应用

文章以丽江黑龙潭为例,研究岩溶地区泉水修复补水控制过程。基于九子海洼地为黑龙潭泉群主要补给来源这一基本判断,从宏观的地形地貌、地层岩性、地质构造、岩溶现象和地下水位动态变化规律入手,首先明确拟采用作为补水控制信号的水文观测井与目标泉群属于同一地下水系统,而后分析观测井地下水位变化规律与目标泉群流量变化规律具有良好的相关性,可作为补水控制井。通过泉群目标状态的拟定−对应补水控制井水位−考虑补水过程提前量时间−修正补水控制井水位这一过程,确定考虑补水时间过程的补水控制井信号水位为2409.41 m,最终实现对观测井水位数据为控制信号的补水过程的实时精准控制。

城市道路信号平面交叉口合理间距研究

平面交叉作为城市道路的关键节点,其合理净距的取值直接影响到整条路段车辆的行车安全和通行效率。文章统计分析了平面交叉口由于间距过短所引发交通事故的原因,基于交通流理论、车辆加减速方式、统计学和概率论原理、驾驶员操作习惯等建立了平面交叉口合理间距的计算模型,得到不同设计速度、车道数情况下平面交叉口合理间距的取值。

现代有轨电车平交路口信号系统控制方案研究

结合丽江市有轨电车1号线的线路特点及实际情况,对现代有轨电车平交路口信号系统控制方案进行研究,详细阐述路口控制系统结构、功能、接口,以及平交路口信号设备布置设计,对有轨电车通过平交路口的全过程进行深入分析。侧重介绍对于不同类型的路口,通过设备布置及有轨电车路口控制系统与市政交通控制系统完成信息交互,实现有轨电车安全高效的通过平交路口,对同一线路平交路口种类较多的情况提出解决方案,说明针对不同类型路口的不同路口通过处理逻辑,充分保障有轨电车行车安全和运营效率。

新型混合交通流场景下交叉口信号控制和轨迹控制协同优化方法

针对人类驾驶车辆(human driven vehicle,HDV)和智能网联车辆(connected and autonomous vehicle,CAV)组成的新型混合交通流场景,现有的交叉口协同控制方法中,集中控制和单车控制分别对中央控制器的算力和车载计算单元的算力要求较高。本文研究了1种将元胞传输模型(cell transmission model,CTM)与双层规划模型相结合的协同优化方法,利用可调整的元胞长度平衡求解信号控制与CAV轨迹优化2个问题所需的算力,从而灵活地根据中央控制器和车载计算单元的算力分配计算资源;通过上层模型预测交通流状态并优化信号控制参数,引入动态调整元胞长度规则,降低中央控制器的计算负担;基于上层的交通状态预测结果,利用下层模型对CAV轨迹进行全局规划,进一步提升交叉口通行效率。同时,为了提升解的最优性和求解的实时性,采用结合随机梯度下降法和遗传算法的迭代优化算法,避免陷入局部最优的同时提升求解效率。最后以无锡市先锋中路与春风南路交叉口数据为例,验证了不同CAV渗透率下优化的效果,结果表明:①相较于基准方案,本文提出的协同优化方案最高可以降低交叉口8.09%的车均行程时间,降低了交叉口拥堵向上游的传播;②当CAV渗透率为30%、60%和90%时,优化比例为2.51%、5.08%和7.88%;③在进口道流量大于3000 pcu/h时,仍能在100s内获得最优信号控制方案,可支持实时优化。该方法可以有效改善城市交通拥堵,提高新型混合交通流场景下交叉口的通行效率。