Research for the Dynamic Range and Its Extension of Digital Intermediate Frequency Receiver

For the optimization of dynamic range and bandwidth of digital intermediate frequency receiver(DIFR), main factors affecting them and their relationships are studied. Firstly, the DIFR sensitivity, bandwidth, noise factor of radio frequency (RF) analog front-end (RFAF), and processing gain of intermediate frequency(IF) sampling are analyzed. Secondly, the constraint relationship of the noise factor of RFAF, the signal-to-noise ratio of ADC and the dynamic range of DIFR are studied. The relationship between the dynamic range and the RFAF gain, and that of the extended dynamic range and the RF AGC(automatic gain control) step are educed and simulated. These results can be used as theory foundations and design references for the implementation and optimization of the large dynamic range and wideband DIFR.

A Digital Photographic Technique for Knee Range of Motion Measurement: Performance in a Total Knee Arthroplasty Clinical Population

Background: Knee range of motion is an essential outcome measure following total knee arthroplasty and it is important to measure this outcome with a simple and accurate tool. Measurement from digital photographs could provide a superior clinical alternative to the common goniometer as devices for capturing digital photographs are becoming more accessible, measurement accuracy is assisted with the associated software and images can be saved and stored for later reference. This ability to store images with measurements could be particularly useful in research involving knee range of motion. This study evaluated the validity and reliability of a simple photographic measurement technique to measure knee flexion and extension of patients following knee arthroplasty.Methods: Knee flexion and extension of 38 subjects who had undergone total knee arthroplasty were assessed at the one year post-operative review with the digital technique and a universal goniometer as the criterion reference. Digital measurements were repeated one month later by the first assessor (intra-tester reliability) and another independent assessor (inter-tester reliability).Results: Validity: the digital technique was found to have a high level of agreement with the universal goniometer measurements (all MAD sion with almost perfect Intra-Class Correlations (Intra-tester;flexion 0.99, extension 0.96;inter-tester;flexion 0.97, extension 0.93).Conclusion: Measurement of knee range of motion from digital photographs can be used in routine clinical total knee arthroplasty follow-up instead of, or interchangeably with the universal goniometer.

Dynamic Free-Spectral-Range Measurement for Fiber Resonator Based on Digital-Heterodyne Optical Phase-Locked Loop

We propose a novel scheme, based on digital-heterodyne optical phase-locked loop with whole-fiber circuit, to dynamically measure the free-spectral-range of a fiber resonator. The optical phase-locked loop is established with a differential frequency-modulation module consists of a pair of acousto-optic modulators. The resonance-tracking loop is derived with the Pound-Drever-Hall technique for locking the heterodyne frequency of the OPLL on the frequency difference between adjacent resonance modes. A stable locking accuracy of about 7 × 10?9 and a dynamic locking accuracy of about 5 × 10?8 are achieved with the FSR of 8.155 MHz, indicating a bias stability of the resonator fiber optic gyro of about 0.1?/h with 10 Hz bandwidth. In addition, the thermal drift coefficient of the FSR is measured as 0.1 Hz/?C. This shows remarkable potential for realizing advanced optical measurement systems, such as the resonant fiber optic gyro, and so on.

Re-delineating mountainous areas with three topographic parameters in Mainland Southeast Asia using ASTER global digital elevation model data

Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However, there is no unified and explicit definition for mountainous areas. The local elevation range(LER) is a crucial structural parameter for delineating mountainous areas. However, current LER products are limited by the subjective selection of an optimum statistical window or coarser spatial resolution of topographical data. In this study, we presented an approach using thresholds for three topographic parameters, elevation, slope, and LER, derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM) to redelineate the vast mountainous areas of mainland Southeast Asia(MSEA). The mean change-point analysis method was applied to determine the optimum statistical window of the 1 arc second(approximately 30 m)-resolution GDEM LER. The results showed that: First, the optimum statistical window is 38 × 38 cell units(width × height) in a rectangular neighborhood, or an area of about 1.30 km^2 for calculating GDEM LER in MSEA. Second, the LER of more than 80% of the area ranges from 30 m to 499 m in MSEA. The LERs in the northern and northwestern MSEA are greater than their counterparts in the south and east. Third, the area of the re-delineated mountainous areas was 83.52 × 10~4 km^2, about 38.71% of the total area. Spatially, the mountainous areas are mainly distributed in the north and northeast of MSEA. The re-delineated 30-m resolution map of the mountainous areas will serve as a topographical dataset for monitoring mountainrelated land surface changes in MSEA. The parameter-modified mountain extraction procedure can be expanded to delineate global mountainous areas.

Distribution characteristics and impact on pump＇s efficiency of hydro-mechanical losses of axial piston pump over wide operating ranges

A novel performance model of losses of pump was presented,which allows an explicit insight into the losses of various friction pairs of pump.The aim is to clarify that to what extent the hydro-mechanical losses affect efficiency,and to further gain an insight into the variation and distribution characteristics of hydro-mechanical losses over wide operating ranges.A good agreement is found in the comparisons between simulation and experimental results.At rated speed,the hydro-mechanical losses take a proportion ranging from 87% to 89% and from 68% to 97%,respectively,of the total power losses of pump working under 5 MPa pressure conditions,and 13% of full displacement conditions.Furthermore,within the variation of speed ranging from 48% to 100% of rated speed,and pressure ranging from 14% to 100% of rated pressure,the main sources of hydro-mechanical losses change to slipper swash plate pair and valve plate cylinder pair at low displacement conditions,from the piston cylinder pair and slipper swash plate pair at full displacement conditions.Besides,the hydro-mechanical losses in ball guide retainer pair are found to be almost independent of pressure.The derived conclusions clarify the main orientations of efforts to improve the efficiency performance of pump,and the proposed model can service for the design of pump with higher efficiency performance.

A TECHNIQUE OF DIGITAL SURFACE MODEL GENERATION

It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.

What Is the Accuracy of Shoulder Range of Motion Measurements on Physical Exam?

The purpose of this study is to investigate a new method for measuring shoulder range of motion (ROM) in an orthopedic practice utilizing a smartphone application to improve accuracy from physical exam typically used in research. Our aim is to evaluate the application, Physio2Go (P2G), which uses a virtual goniometer, assessing validity by comparing its measurements to those taken by a universal goniometer (UG). Two observers of varying clinical experience, a research assistant and research fellow, compared measurements. Statistically, we used the intra-class correlation coefficient (ICC), standard error of measurement (SEM), and the Pearson correlation coefficient (PCC). Following validation we tested P2G in symptomatic postoperative shoulder patients measuring forward flexion (FF) and external rotation (ER). We compared P2G measurements to visual estimation (VE) done by a fellowship trained orthopedic surgeon. Statistically we used ICC, Bland- Altman plots with 95% limits of agreement (LOA), and scatter plots. We examined the impact of the application using Welch’s t-test comparing pre-to-postoperative ROM improvements using the values obtained by P2G and VE. We found high intra-rater reliability of P2G for both observers, substantial correlation between UG and P2G measurements, highly correlated inter-observer reliability for UG and P2G, and statistically significant PCC values (p < 0.05). As expected, ROM measurements of symptomatic patients comparing P2G and VE measurements demonstrated lower correlation. Bland-Altman plots demonstrated wide confidence intervals;scatterplots and histograms confirmed low agreement among measurement methods. Clinical application demonstrated varying statistical significance depending on whether measurements were done by P2G or VE. Our study found that P2G provided superior reliability compared to the customary physical exam routinely used for orthopedic research. The value of using this application instead of a UG is the ease of use and the ability for any member of the healthcare team, regardless of clinical experience to be able to produce reliable and valid measurements.

A Parallel Amplifier Structure for Increasing Dynamic Range of EW Receivers

In Electronic Warfare （EW） receivers, the desired Dynamic Range （DR） often far exceeds the dynamic range attainable with available Analog-to-Digital Converter （ADC） technology. ADC is the key bottleneck in achieving the needed dynamic range. In this paper, an approach for improving the effective DR by utiliTing multiple amplifiers is presented. The amplifiers, arranged in parallel channels with different gains, can increase the dynamic range greatly.

我国省际数字技术创新水平测算及区域差异研究

本文通过专利文本分析识别得到45万余条我国数字技术专利,构建二阶段时空极差熵值法测算我国2000—2020年31个省份的数字技术创新水平,采用Dagum基尼系数和方差分解方法,从空间和结构双重视角探究我国数字技术创新水平的区域差异及来源,并运用地理探测器探寻数字技术创新水平差异的驱动因素。研究发现,我国数字技术创新水平呈现波动上升趋势,2010年以后增长态势更为明显;广东、北京、江苏、上海和浙江是数字技术创新水平最高的5个省份;我国数字技术创新水平呈现“东高西低”“南高北低”的空间分布格局;“东–西”区域间差异是数字技术创新水平差异的主要空间来源,创新数量差异是数字技术创新水平差异的主要结构来源;从驱动因素看,研发人力投入是影响数字技术创新水平差异的主导因素,研发人力投入与信息基础设施的交互组合是关键性驱动因素,不同地区的驱动因素有所差异。本研究丰富了数字技术创新水平评价相关研究,对探索各地区数字技术创新水平具有借鉴意义。

提高LCL型并网逆变器鲁棒性的延时补偿策略

在LCL型并网逆变器中,数字控制延迟会影响传统电容电流反馈有源阻尼(CCFAD)的有效阻尼区间,LCL滤波器的谐振频率必须低于系统采样频率的1/6,否则虚拟阻抗对应的虚拟电阻为负值,影响系统的稳定性。针对此问题,提出了一种扩展CCFAD的有效阻尼区间的控制策略,在一阶相位超前补偿器的基础上加入积分环节,理论分析证明了所提控制策略可以将虚拟电阻呈正阻尼特性的区域扩展到(0,0.35fs),进一步扩大了有效阻尼区间。同时,提出了一套参数设计方法,根据稳定裕度约束条件得到补偿器参数的可取值范围。最后通过仿真和实验表明,在弱电网下该控制策略相比传统CCFAD控制策略具有更好的鲁棒性,验证了所提控制策略的正确性和有效性。

近距空战中目标飞机战术机动数学模型建模与仿真

作为空空导弹设计与验证的主要手段,数字仿真技术在制导系统性能评估、抗干扰性能评估、空战对抗仿真等领域发挥着重要的作用。为解决空空导弹数字仿真试验中目标飞机机动样式单一,不能反映近距格斗过程中目标姿态的变化问题,梳理了飞机机动数学模型在导弹总体性能评估与对抗推演等方面的应用背景需求。对六自由度飞机机动简化数学模型的建设进行了分析和论证。构建了飞机作战典型机动动作库、机动动作指令生成器,实现了以较少的参数刻画不同的机动动作。在三自由度质点运动模型基础上,考虑机动过载、目标攻角、横滚角变化,建立目标机动数学模型。根据所建模型,对几种典型机动教学模型进行数字仿真。仿真结果表明,目标机动轨迹与预期吻合,能够满足导弹总体设计、对抗推演对数字仿真的需求。

一种高帧频大动态范围像素级数字化读出电路设计

与短波和中波器件相比,长波红外探测器具有较大的光电流和暗电流,故需要强大的电荷存储能力。而使用传统的模拟像元读出电路技术会严重受限于电荷存储能力,使得长波探测器的动态范围和信噪比难以提升,从而制约着长波红外成像系统的发展和应用。提出一种像素级数字读出电路技术,通过数字积分克服了传统模拟积分方案电荷存储能力受限的缺陷,实现了探测器的数字信号输出,能够极大提高探测器的动态范围、抗干扰能力和帧频。该技术是提升长波探测器性能的有效途径。基于该技术设计了一款像元间距为30 m的320×256数字读出电路,其输出以低压差分信号(Low Voltage Differential Signal,LVDS)方式传输。仿真结果显示,该电路的最高帧频可达1000 Hz,动态范围大于95 dB。

一种面积与随机性均衡的DEM设计

针对高速电流舵数模转换器(Digital-to-Analog Conversion,DAC)中电流源阵列不匹配问题,提出了一种基于随机结合的分组译码动态元素匹配(Dynamic-Element Matching,DEM)结构以提升DAC的转换性能。所提结构是一种基于随机旋转(Random Rotation-based Binary-weighted Selection,RRBS)的改进结构。该结构首先将输入数据分成高位数据与低位数据,接着将低位数据经过RRBS结构处理所得的结果逐位与高位数据结合进行第二次处理并得到最终输出。该结构在输入数据为3位与输入数据大于3位这两种情况下存在差异。使用MATLAB对提出结构的无杂散动态范围(Spurious Free Dynamic Range,SFDR)进行了仿真。首先给出该结构在不同分段方式与不同误差情况下的SFDR对比图,接着将不同DEM结构在不同误差下进行对比,最后对该结构在不同输入频率与误差的情况进行仿真对比。同时,给出了该结构在tsmc65工艺下的综合结果。在相同的系统周期下,该结构所占用的面积相比于RRBS结构的更小。通过仿真与综合结果可以看出,提出的DEM结构电路减小了电路面积;相比于未使用DEM的14位DAC,本结构可以使SFDR提高15 dB以上。

基于数字孪生的水土流失防治责任范围变化预测模型

为建立实用、高效的水土流失防治责任范围变化预测模型,提高合规性判断的准确性,在总结水土流失防治责任范围可撤销性、时空交错性、临时性和条件适用性等4个主要动态特性的基础上,提出一种基于数字孪生的水土流失防治责任范围变化预测模型。数学模型为描述防治责任范围状态的虚拟模型,防治责任范围为物理实体,模型基于防治责任范围变化主要因素的孪生数据,对防治责任范围有效性状态进行评估和预测。结果表明:模型对防治责任范围变化进行预测的正确率提升约38%,具有良好的预测防治责任范围变化的性能,有助于进一步提升提高遥感监管成果的质量,在生产建设项目遥感监管应用领域有一定的借鉴意义。

基于无人机数字近景摄影测量的服役边坡监测方法

针对现有边坡变形监测技术自动化与智能化程度低及安设复杂且对边坡有损坏等问题,提出一种基于无人机数字近景摄影测量的服役边坡坡表变形监测方法。根据数字近景摄影测量的相关理论,确定了数码相机内参数标定和监测点坐标解算方法,研制出一种可布设在服役边坡坡表的数字近景摄影测量和全站仪测量通用的变形监测目标物,实现对边坡的联合监测。研究结果表明,数字近景摄影测量技术配合专门设计的变形监测目标物对边坡坡表变形较为敏感,第一期和第二期的监测点位中误差分别为3.3 mm和1.7 mm,水平位移监测的点位和垂直位移监测的高程中误差分别为3.5 mm和1.6 mm,达到毫米级的监测精度,满足滑坡监测标准的精度要求;同时变形监测目标物制作可靠、成本低廉,具有较高的应用价值。

一种用于音频应用的高动态范围高精度模数转换器

提出了一种应用于音频应用的Zoom型模数转换器,采用一个5位异步逐次逼近式(Successive Approximation Register,SAR)模拟数字转换器(Analog to Digital Converter,ADC)与3阶多位量化离散时间的Delta-Sigma调制器相结合,通过SAR ADC进行粗量化、Delta-Sigma调制器进行精细量化的方式,实现高的动态范围和精度。该Zoom型模数转换器采用0.18μm CMOS工艺实现,仿真结果表明,在1.8 V电源电压和3.072 MHz采样频率下,实现了109.34 dB的信号噪声失真比(Signalto-Noise-and-Distortion Ratio,SNDR),17.87 bits的有效位数(Effective Number of Bits,ENOB),112.7 dB的动态范围(Dynamic Range,DR),整体电路功耗为3.73 mW。

汾河上游兰村站径流及基流的趋势性分析

为揭示汾河流域径流及基流变化规律,基于汾河上游兰村站1956-2020年的径流序列资料,运用数字滤波法,将日径流量划分为直接径流量和基流量,通过M-K检验法判别径流和基流演变规律,采用重标度极差(R/S)分析法进行年径流和年基流的长程相关性分析。结果表明:兰村站基流指数(BFI)在不同年代间的变化表现为先减小后增加的趋势;基流深及径流深变化过程呈显著下降趋势,径流深的突变点出现在1974年,基流深的突变点是1972年;年径流深和基流深时间序列均呈现强的长期相关性,即未来有进一步下降的趋势。

基于区块链和SM9数字签名的代理投票方案

随着互联网的普及,电子投票技术逐渐替代传统纸质投票技术。然而,传统的电子投票方案主要针对一人一票制来设计方案,在一些特殊的投票场景下,一人一票制投票方式不再适用。例如,投票者不具备专业知识却也需要投票的场景,投票者由于不能理解选举的内容而消极投票,造成选举结果不专业和不公正等问题。此外,传统的电子投票技术还存在选举过程不透明和选票不可验证等问题。针对上述问题,文章提出一种基于区块链和SM9数字签名的代理投票方案。该方案首先使用区块链技术解决选票的全局可验证问题,其次使用零知识范围证明技术解决恶意选票值的问题,然后利用基于椭圆曲线的改进ElGamal算法的同态性质实现选票加密和自计票功能,最后使用SM9数字签名算法和变色龙哈希函数设计的代理投票凭证实现投票权的转让过程。通过安全性分析,证明了文章所提方案满足鲁棒性、合法性、机密性、全局可验证性和公平性。理论分析和实验数据表明,文章所提方案性能良好,适用于需要专业知识场景下的选举。

基于深度强化学习的数字电网数据安全迁移研究

数字电网数据时序均值在冗余状态下的动态发展特点,导致迁移过程中难以有效控制丢包率。为此,文章提出基于深度强化学习的数字电网数据安全迁移研究。从集群(Cluster)角度入手,开展基于深度强化学习数字电网数据建模,明确在数字电网集群Queue存在空位的情况下集群的具体状态。在具体的迁移过程中,引入纹理基元理论,计算得到数字电网数据在阈值范围内的变化特征后,为数字电网数据迁移设置敏感度参数,构建数字电网数据迁移函数。在此测试结果中,整个迁移过程的丢包率仅为6.75%,具体迁移过程中各个阶段的最高丢包率仅为2.03%。

Synthetic aperture radar tomography sampling criteria and three-dimensional range migration algorithm with elevation digital spotlighting

Based on the general geometric model of multi-baseline Synthetic Aperture Radar Tomography （TomoSAR）, the three-dimensional （3-D） sampling criteria, the analytic expression of the 3-D Point Spread Function （PSF） and the 3-D resolution are derived in the 3-D wavenumber domain in this paper. Considering the relationship between the observation geometry and the size of illuminated scenario, a 3-D Range Migration Algorithm with Elevation Digital Spotlighting （RMA-EDS） is proposed. With this algorithm 3-D images of the area of interest can be directly and accurately reconstructed in the 3-D space avoiding the complex operations of 3-D geometric correction. Finally, theoretical analyses and simulation results are presented to demonstrate the shift-varying property of the 3-D PSF and the spatialvarying property of the 3-D resolution and to demonstrate the validity of the 3-D RMA-EDS.