Observability and estimability of passive radar with unknown illuminator states using different observations

Most existing studies about passive radar systems are based on the already known illuminator of opportunity(IO)states.However,in practice,the receiver generally has little knowledge about the IO states.Little research has studied this problem.This paper analyzes the observability and estimability for passive radar systems with unknown IO states under three typical scenarios.Besides,the directions of high and low estimability with respect to various states are given.Moreover,two types of observations are taken into account.The effects of different observations on both observability and estimability are well analyzed.For the observability test,linear and nonlinear methods are considered,which proves that both tests are applicable to the system.Numerical simulations confirm the correctness of the theoretical analysis.

Acceleration of optical coherence tomography signal processing by multi-graphics processing units

A multi-GPU system designed for high-speed,real-time signal processing of optical coherencetomography(OCT)is described herein.For the OCT data sampled in linear wave numbers,themaximum procesing rates reached 2.95 MHz for 1024-OCT and 1.96 MHz for 2048-OCT.Data sampled using linear wavelengths were re-sampled using a time-domain interpolation method and zero-padding interpolation method to improve image quality.The maximum processing rates for1024-OCT reached 2.16 MHz for the time-domain method and 1.26 MHz for the zero-paddingmethod.The maximum processing rates for 2048-0CT reached_1.58 MHz,and 0.68 MHz,respectively.This method is capable of high-speed,real-time processing for O CT systems.

Change of State of a Dynamical Unit in the Transition of Coherence

The change of state of one map in the network of nonlocal coupled logistic maps at the transition of coherence is studied. With the increase of coupling strength, the network dynamics transits from the incoherent state into the coherent state. In the process, the iteration of the map first changes from chaos to period state, then from periodic to chaotic state again. For the periodic doubling bifurcations, similar to an isolated map, the largest Lyapunov exponent tends to zero from a negative value. However, the states of coupled maps exhibit complex behavior rather than converge to a few fixed values. The behavior brings a new chimera state of coupled logistic maps. The bifurcation diagram is identical to the phase order of maps iterations. For the bifurcation between 1-band and multi-band chaos, the symmetry of chaotic bands emerges and the transition of the order of iteration direction occurs.

United Nations Environment Programme’s 2018 Observer Activities Report to the Arctic Council

I. The Organization’s contributions to the work of the Arctic Council’s Working Groups, Task Forces, and/or Expert Groups The United Nations Environment Programme (UN Environment) has been active as an Observer to the Arctic Council since 1996, taking part in the Council’s Ministerial, Senior Arctic Officials meetings and, together with its collaborating centre GRID-Arendal in Norway and the UN Environment World Conservation Monitoring Centre (UNEP-WCMC) in the UK, has engaged actively in the efforts of most of the Council’s scientific and technical working groups. As the United Nation’s organization setting the global environmental agenda and along with the Multilateral Environmental Agreement (MEA) it administers—including those on biological diversity, hazardous waste, chemicals and mercury—UN Environment has facilitated global outreach for some of the Council’s work. Notably, UN Environment continues to provide technical support on a number of assessment and monitoring activities as described below.

Notes of Observations at the General Election in the United Sates

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ESO-based decoupling control with multi-objective optimization for boiler-turbine unit

A model-assistant extended state observer(MESO)-based decoupling control strategy is proposed for boiler-turbine units in the presence of unknown external disturbance and model-plant mismatch. For ease of implementation, the decoupling compensator is reduced to the proportion integration(PI) decoupler with the frequency domain analysis, where the decoupling error in collusion of uncertainties and disturbances can be estimated by the proposed MESO and then compensated. To decrease the sensitivity of the dynamic error for the decoupling control and fulfill various requirements of constraints, such as safety operation, energy conservation, emission reduction, etc., the plant is transmitted through a scheduled steady state region which is achieved from the optimized reference governor in advance. Simulation results show that the proposed control strategy can well suppress various disturbances including a decoupling error, and multi-objective optimization can meet multiple requirements with the premise of safety production.

Soft Sensor for Inputs and Parameters Using Nonlinear Singular State Observer in Chemical Processes

Chemical processes are usually nonlinear singular systems.In this study,a soft sensor using nonlinear singular state observer is established for unknown inputs and uncertain model parameters in chemical processes,which are augmented as state variables.Based on the observability of the singular system,this paper presents a simplified observability criterion under certain conditions for unknown inputs and uncertain model parameters.When the observability is satisfied,the unknown inputs and the uncertain model parameters are estimated online by the soft sensor using augmented nonlinear singular state observer.The riser reactor of fluid catalytic cracking unit is used as an example for analysis and simulation.With the catalyst circulation rate as the only unknown input without model error,one temperature sensor at the riser reactor outlet will ensure the correct estimation for the catalyst circulation rate.However,when uncertain model parameters also exist,additional temperature sensors must be used to ensure correct estimation for unknown inputs and uncertain model parameters of chemical processes.

TIME-DOMAIN INTERPOLATION ON GRAPHICS PROCESSING UNIT

The signal processing speed of spectral domain optical coherence tomography(SD-OCT)has become a bottleneck in a lot of medical applications.Recently,a time-domain interpolation method was proposed.This method can get better signal-to-noise ratio(SNR)but much-reduced signal processing time in SD-OCT data processing as compared with the commonly used zeropadding interpolation method.Additionally,the resampled data can be obtained by a few data and coefficients in the cutoff window.Thus,a lot of interpolations can be performed simultaneously.So,this interpolation method is suitable for parallel computing.By using graphics processing unit(GPU)and the compute unified device architecture(CUDA)program model,time-domain interpolation can be accelerated significantly.The computing capability can be achieved more than 250,000 A-lines,200,000 A-lines,and 160,000 A-lines in a second for 2,048 pixel OCT when the cutoff length is L=11,L=21,and L=31,respectively.A frame SD-OCT data(400A-lines×2,048 pixel per line)is acquired and processed on GPU in real time.The results show that signal processing time of SD-OCT can befinished in 6.223 ms when the cutoff length L=21,which is much faster than that on central processing unit(CPU).Real-time signal processing of acquired data can be realized.

Observation of multi-Raman gain resonances in rubidium vapor

We present an experimental study of multi-Raman gain resonances in a hot rubidium vapor.The experiment is performed based on a high-efficiency four-wave mixing process due to the Raman-driven coherence in a double-A configuration.The Raman gain resonance for ^（85）Rb atoms under a bias magnetic field is shown to be split into five or six peaks,depending on the orientation of the magnetic field.The formed multi-Raman gain resonances have potential applications in measurement of magnetic fields and generation of multi-frequency correlated twin beams.

改良膜龈手术在牙龈退缩治疗中的应用

随着人们对美观需求的日益提升,治疗牙龈退缩已经成为牙周科临床常见的患者诉求。临床上主要通过手术的方式治疗牙龈退缩,常见的手术包括游离龈移植术、带蒂瓣技术和双层瓣技术,适应证选择恰当时,通常可以获得满意的效果,但上述术式仍存在一定的不足,如根面覆盖效果不理想等。近年来,学者们针对这些不足陆续提出了一些改良方案来治疗不同程度的牙龈退缩,如改良游离龈移植术,即包含龈乳头及游离龈的牙龈单元移植,可改善受体区血供,提高根面覆盖效果,其针对轻度退缩的部位可获得良好的根面覆盖,同时可增宽角化龈和加深前庭沟,但应用于上颌美学区时可能存在术后牙龈颜色、形态不协调,美学效果欠佳的问题。牙龈瓣采用半厚-全厚-半厚的技术进行制备的改良冠向复位瓣,用于多颗牙牙龈退缩时,以退缩最严重牙为中心的改良切口设计的冠向复位信封瓣技术,可提高根面覆盖效果。不离断龈乳头,使龈瓣形成隧道,以容纳移植物的隧道技术及各种改良的隧道技术,可以有效减少术区的组织损伤,并促进创面愈合。本文通过对各类术式的阐述和文献回顾,总结改良膜龈手术治疗牙龈退缩的临床应用及注意事项,并提出牙龈退缩的治疗方案建议,同时强调牙龈退缩的对因治疗,以达到稳定的根面覆盖效果。创伤小、疗效稳定的手术方式和治疗方法是今后膜龈手术的发展方向。

旧金山会议中共代表问题新探

1945年董必武出席在旧金山举办的联合国制宪大会是抗日战争史和中国近代外交史上的重要事件,而中共代表取得参会权的过程却历经波折。在抗战后期的国共谈判中,新任美国驻华大使赫尔利为了善后“史迪威事件”,偏袒国民党政府、反对中共代表参加旧金山会议。随着美苏双方在雅尔塔会议上就远东问题达成秘密协定,以及毛泽东、周恩来坚决反对国民党一党专政,美国高层最终改变态度,敦促蒋介石同意在中国代表团内列入一名中共成员。国民党政府妥协退让的背后蕴藏着遏制中共的复杂谋略,延安方面的因应策略则体现出抗战后期中共对国家发展前景的深层思考。

脑-运动单元功能耦合估计方法

针对现有脑肌功能耦合(CMC)估计方法仅能反映皮层活动与运动单元(MU)复合放电活动间耦合状态、无法反映皮层和各MU独立耦合作用的问题,提出了一种脑与MU之间独立交互作用的估计方法,并初步验证了脑-运动单元功能耦合(CMUC)作用的存在。首先,采用肌电分解技术获得各MU独立活动,即运动单元动作电位序列;然后,利用头皮表面拉普拉斯技术,获得头皮电流密度以表征皮层活动,并通过估计运动单元动作电位序列和头皮电流密度的频域相干性获得CMUC;最后,通过手指伸展实验对所提方法的有效性加以验证。实验结果表明:当被试者伸展手指时,指伸肌的MU和对侧运动皮层存在显著的β、γ频带耦合交互作用,且耦合强度显著高于其他皮层区域。这一结论与已有的CMC研究结论相一致,能够表明所提CMUC估计方法的有效性,同时也证明了脑和MU独立耦合交互作用的存在性。提出的CMUC估计方法可为进一步深入研究生理及病理条件下肌肉的神经控制机制提供有力指导。

基于相量测量单元优化配置的配电网谐波状态估计研究

随着大量电力电子设备的接入,配电网谐波问题愈发严重。谐波状态估计的准确性直接影响到后续的谐波治理效果。相量测量单元(phasor measurement unit,PMU)可以实时测量节点电压与支路电流,可借助其实现谐波状态估计。然而目前PMU价格较高,如何进行合理的优化配置保证全网谐波状态可观,同时提高谐波状态估计的准确性,是亟待解决的问题。首先构建以PMU经济配置和谐波状态估计精度最高为目标的PMU优化配置模型,并提出一种改进二进制粒子群-遗传混合算法用于求解。随后在实时仿真器中搭建IEEE14节点模型,选用均值插补法以及Vondrak滤波法进行数据处理并分析了优化所得多种PMU配置场景对谐波状态估计的影响。结果表明:所提算法从减少投资成本及降低谐波状态估计误差角度考虑,能够给出合理的PMU配置方案,有助于支撑工程决策。

The Educational Adaptive-optics Solar Telescope at the Shanghai Astronomy Museum

The Educational Adaptive-optics Solar Telescope(EAST)at the Shanghai Astronomy Museum has been running routine astronomical observations since 2021.It is a 65-cm-aperture Gregorian solar telescope for scientific education,outreach,and research.The telescope system is designed in an“open”format so that the solar tower architecture can be integrated with it,and visitors can watch the observations live from inside the tower.Equipped with adaptive optics,a high-resolution imaging system,and an integral field unit spectro-imaging system,this telescope can obtain high-resolution solar images in the TiO and Hαbands,and perform spectral image reconstruction using 400 optical fibers at selected wavelengths.It can be used not only in public education and scientific outreach but also in solar physics research.

基于扩展状态观测器的锅炉-汽轮机组模糊模型预测控制

针对锅炉-汽轮机组易受扰动、非线性等特点,提出一种基于扩展状态观测器的模糊模型预测控制方法。首先,基于实际被控对象的输入输出数据建立1 000 MW锅炉-汽轮机组的模糊模型;然后利用输出代价函数在模糊模型上设计一个稳定的模糊模型预测控制器,以实现节流蒸汽压力、分离器蒸汽焓和负荷的稳定、快速和准确跟踪。将一种改进的线性扩展状态观测器与预测控制器相结合,以增强其抗干扰性能,该观测器可以在线估计系统的行为变化和未知干扰,通过设计合适的李雅普诺夫函数证明了整个控制系统的闭环稳定性。在对某1 000 MW锅炉-汽轮机组模型的节流阀压力、蒸汽分离焓和有效功率(负荷)参数的仿真中,具有扩展状态观测器的模糊模型预测控制超调量和调节时间等指标均优于积分模型预测控制、稳定模型预测跟踪控制器(stable model predictive tracking controller,SMPTC)和广义扩展状态观测器的控制(generalized extended state observer control,GESOBC),证明了所提出方法的有效性。

基于火电燃烧机组中固态变压器改进LADRC协同优化控制策略

在火电燃烧机组中,固态变压器面临惯性大、滞后多和耦合强等问题,为提升其控制性能,研制了一种基于改进线性自抗扰的协同燃烧优化控制策略。该策略以参数解耦型观测器为核心,结合BP神经网络算法进行参数调节,将固态变压器逆变级数学模型改写为解耦自抗扰形式。经数字仿真实验验证,该策略能有效提升抵抗扰动的能力,稳定误差下降2.5%,控制误差在3%以内,优于传统的PI控制和LADRC控制方法。

健中益肾汤联合针刺治疗脾肾两虚型重症监护病区获得性肌无力的临床观察

目的:观察健中益肾汤联合针刺治疗脾肾两虚型重症监护病区获得性肌无力(Intensive Care Unit Acquired Myasthenia,ICUAW)的临床效果。方法:选取2020年1月-2022年1月龙岩市中医院收治的ICUAW患者90例,采用随机数字表法分为A组、B组、C组。A组采用西医常规治疗,B组在A组常规治疗的基础上联合应用健中益肾汤治疗,C组在西医常规治疗的基础上采用健中益肾汤联合针刺治疗。观察三组患者治疗前后中医证候积分、英国医学研究理事会量表(Medical Research Council,MRC)评分、改良Barthel指数量表(Modified Barthel Index,MBI)评分、机械通气时长、重症监护病区(ICU)住院天数,以及肿瘤坏死因子-α(Tumor Necrosis Factor-α,TNF-α)、白细胞介素-6(Interleukin 6,IL-6)水平。结果:三组患者治疗前中医证候积分、MRC评分、MBI评分及TNF-α、IL-6水平的差异无统计学意义(P>0.05)。治疗后,三组患者的中医证候积分、MRC评分、MBI评分、机械通气时长、ICU住院天数及TNF-α、IL-6水平与治疗前比较均改善(P<0.05),且C组的改善较A组、B组显著(P<0.05)。C组机械通气时长、ICU住院天数明显少于A组、B组(P<0.05)。结论:健中益肾汤联合针刺治疗脾肾两虚型ICUAW效果显著,可显著改善患者的临床症状,促进患者预后,其机制可能与减轻炎症反应有关。

同一测点不同地震动分量空间相干性分析

利用SMART-1台阵的3次地震记录计算了同一测点三平动地震动分量间的相干值,并提出了相干函数模型。分析表明,同一测点各地震动分量间是低相干的,随频率衰减不明显;两水平分量间的相干性比水平分量与垂直分量间的相干性大。因此在工程计算中不计相干函数随频率的变化不会带来太大的误差。

兼顾元件权重和发电机同调性的山东电网PMU布点方法

在稳定计算的基础上,对于相量测量单元(phasor measurement unit,PMU)最优配置问题,进行了可观性权重设置和机组同调性分析。首先把逐点法与穷举法结合到一起形成了一种新的静态可观性改进算法,并引入了元件权重的概念来区分对不同设备可观性要求的程度;然后考虑了发电机同调性的影响,以可观性布点为基础,形成了动态可观性的布点;最后根据山东电网2006年夏季大方式的稳定计算结果,结合可观性和发电机同调性,提出了一种分阶段实施的有效PMU布点方法。