基于MDP的无人机避撞航迹规划研究

无人机(UAV)进行避撞前提下的目标搜索航迹规划是指在复杂且众多的环境障碍约束中通过合理规划飞行路径,以更快、更高效的形式找到目标;研究了无障碍环境条件下有限位置马尔科夫移动的规律,构建了相应的马尔科夫移动分布模型;在借鉴搜索系统航迹规划的前沿研究成果之上,结合马尔科夫决策过程理论(MDP),引入了负奖励机制对Q-Learning策略算法迭代;类比“风险井”的可视化方式将障碍威胁区域对无人机的负奖励作用直观地呈现出来,构建了复杂障碍约束环境下单无人机目标搜索航迹规划模型,并进行仿真实验证明该算法可行,对航迹规划算法的设计具有一定的参考意义。

基于Simulink与Unity3D的制导弹药弹道可视化仿真

针对制导弹药的弹道可视化仿真中,观察视角单一,场景搭建简陋,无法模拟战场环境下制导弹药在攻击中的动态过程等问题,提出一种制导弹药弹道可视化模型的搭建方法;以某型激光制导弹药为对象,基于Simulink与Unity3D软件建立了联合仿真模型,采用Matlab/Simulink软件构建六自由度弹道仿真模型,采用Unity3D搭建包括制导弹药、目标和战场环境在内的三维场景,采用UDP通信协议将Simulink中的仿真数据传输到Unity3D中,提出一种数值可视化技术,能同时观察制导弹药的飞行姿态和仿真数值结果,实现制导弹药在战场环境下的弹道可视化仿真;将制导弹药参数加载到仿真模型中,对不同状态的目标进行了模拟攻击实验,实验结果显示,该仿真模型能够多视角、全方位地显示制导弹药的飞行姿态、弹道和过载情况,对于需要修改参数以逼近实战条件下的攻击过程,每次修正都能立刻通过可视化平台查看和验证修改结果;该可视化仿真模型为制导弹药的可视化仿真提供了便利的方法,对制导弹药的设计和作战使用具有一定的参考作用。

Towards Energy Efficient Shape Rolling:Roll Pass Optimal Design and Case Studies

Shape rolling is widely employed in the production of long workpieces with appropriate cross-section profiles for other industrial applications. In the development of shape rolling systems, roll pass design (RPD) plays an essential role on the quality control of products, service life of rolls, productivity of rolling systems, as well as energy consumption of rolling operations. This study attempts to establish a generic strategy based on hybrid modeling and an improved genetic algorithm, to support the optimizations of RPD and shape rolling operations at a systematic perspective. Objectives include improving the quality and efficiency of RPD, reducing energy consumption of shape rolling, as well as releasing the demands on costly trails and expert knowledge in RPD. Hybrid modeling based on cross-disciplinary knowledge is developed to overcome the limitations of isolated single-disciplinary models. And conventional genetic algorithm is improved for the implementation of optimal design. Targeting to integrate empirical data and published reliable solutions into optimizations, a parameters estimation method is proposed to transfer the initially misaligned models into a uniform pattern. A tool based on the Matlab platform is developed to demonstrate the optimal design operations, with case studies involved to validate the proposed methodology.

Parasitic Plants <i>Striga</i>and <i>Phelipanche</i>Dependent upon Exogenous Strigolactones for Germination Have Retained Genes for Strigolactone Biosynthesis

Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.

A New Diagnostic Method Applied to Gearbox Missing Gear Faults——LOD-ICA

With the increasingly stringent requirements for carbon emissions,countries have increased the scale of clean energy use in recent years.As an important new clean energy source,the ratio of wind power in energy utilization has been increasing.The horizontal axis wind turbine is the main form of wind power generation,which is subject to random wind loads during operation and is prone to various failures after a long period of operation,resulting in reduced power generation efficiency or even shutdown.In order to ensure stable external power transmission,it is necessary to perform fault diagnosis for wind turbines.However,the traditional time-frequency analysis method is defective.This paper proposes a new LOD-ICA method to realize the resolution of the vibration signals mode mixing problem incorporated the merits of both methods.The LOD-ICA method and the LOD method based on noise-assisted analysis decompose the same signal to produce different signal components.The feasibility of the LOD-ICA method was verified by comparing the correlation coefficients between each of the signal components generated by the two methods and the original signal.In the field of wind turbine fault diagnosis,the LOD-ICA method is employed to the fault characteristics of gearboxes to extract the fault signs of vibration signals,further demonstrated the superiority of the LOD-ICA method in processing vibration signals of rotating machinery.

Advances in coastal ocean boundary layer detection technology and equipment in China

Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of air pollution in land,sea,and atmosphere.We present an overview of coastal ocean boundary layer detection technology and equipment in China and summarize the progress and main achievements in recent years.China has developed a series of coastal ocean boundary layer detection technologies,including Light Detection and Ranging(LIDAR),turbulent exchange analyzer,air-sea flux analyzer,stereoscopic remote sensing of air pollutants,and oceanic aerosol detection equipment to address the technical bottleneck caused by harsh environmental conditions in coastal ocean regions.Advances in these technologies and equipment have provided scientific assistance for addressing air pollution issues and understanding land-sea-atmosphere interactions over coastal ocean regions in China.In the future,routine atmospheric observations should cover the coastal ocean boundary layer of China.

Development,verification and application of a versatile aerosol calibration system for online aerosol instruments

Traditional calibration methods mostly focus on the calibration of detection systems while the calibration from the sampling and pre-condition systems to the detection system is usually ignored.In this regard,a Primary Standard Aerosol Mass Concentration Calibration System(PAMAS)is developed for the whole-process calibration of time-resolved aerosol measurement instruments.PAMAS is composed of a particle generation chamber,an ultrasonic atomizer,a dilution system,and a syringe pump.It is designed to steadily generate standard aerosol particles of known concentrations(≤250μg/m^(3)),chemical compositions,and stable particle size distributions.Monodispersed aerosol can be generated in the size range of hundreds of nanometers to several micrometers with a narrow size distribution.The generated particles with different compositions generated by PAMAS have been well verified by the filter-based gravimetric method,yielding accuracy and R^(2) of more than 95%and 0.999 in a wide concentration range.The response time by changing the target concentration of reference particles is 1-2 min.PAMAS has been applied to various types of time-resolved aerosol measurement instruments,including particle mass concentration monitors(Beta Attenuation and Tapered Element Oscillating Microbalance),online Ion Chromatograph,and semi-continuous OCEC carbon aerosol analyzer.Very consistent results between PAMAS and calibrated instruments can be obtained if the instruments are functioning well.As for instruments with certain technical issues,PAMAS can serve as a good tool for performance evaluation and quality assurance of the instruments and the accuracy of the measurement data can be adjusted based on the calibration results.

Response of PM_(2.5)-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity

The coronavirus(COVID-19)pandemic is disrupting the world from many aspects.In this study,the impact of emission variations on PM_(2.5)-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic.Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown.After the lockdown,they rebounded rapidly,of which V and Ni even exceeded the levels before the lockdown,suggesting the recovery of both inland and shipping activities.Five sources were identified based on receptor modeling.Coal combustion accounted for more than 70%of the measured elemental concentrations before and during the lockdown.Shipping emissions,fugitive/mineral dust,and waste incineration all showed elevated contributions after the lockdown.The total non-carcinogenic risk(HQ)for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ.Whereas,the total carcinogenic risk(TR)for adults was above the acceptable level and much higher than that for children.Waste incineration was the largest contributor to HQ,while manufacture processing and coal combustion were the main sources of TR.Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk.From the perspective of health effects,priorities of control measures should be given to waste incineration,manufacture processing,and coal combustion.A balanced way should be reached between both lowering the levels of air pollutants and their health risks.

Aerosol oxalate and its implication to haze pollution in Shanghai,China

A total of 238 samples of PM2.5and TSP were analyzed to study the characteristics,sources,and formation pathways of aerosol oxalate in Shanghai in four seasons of 2007.The concentrations of oxalate were0.07–0.41 lg/m3in PM2.5and 0.10–0.48 lg/m3in TSP,respectively.Oxalate displayed a seasonal variation of autumn[summer[winter[spring in both PM2.5and TSP and was dominantly present in PM2.5in all samples.Correlation between oxalate and K?and high ratio of oxalate/K?suggested that biomass burning was a secondary source of aerosol oxalate in Shanghai,in addition to urban VOCs sources(vehicular and industrial emissions),especially in autumn.Secondary formation accounted for the majority of aerosol oxalate in Shanghai,which was supported by the high correlation of oxalate with nssSO42-,K?and NO3-,proceeding from different mechanisms.Relatively high ambient RH together with high cloud cover was found benefiting the secondary formation of aerosol oxalate.The in-cloud process(aqueous-phase oxidation)was proposed to be likely the major formation pathway of aerosol oxalate in Shanghai,which was supported by the high correlation of oxalate with nss-SO42-and K?,dominant residence of oxalate in droplet mode and result of favorable meteorological condition analysis.High correlation of oxalate and NO3-reflected the OH radical involved oxidation chemistry of the two species in the atmosphere and also suggested that gas-particle surface reactions and the evaporation–condensation process were both possible secondary formation pathways of aerosol oxalate in coarser particle mode([1.0 lm).As a major water-soluble organic compound in aerosols,concentration of oxalate showed a distinct negative correlation to the atmospheric visibility,which implied that aerosol organic compounds could play an important role in haze pollution as well as in air quality in Shanghai.

COVID-19 induces new-onset insulin resistance and lipid metabolic dysregulation via regulation of secreted metabolic factors

Abnormal glucose and lipid metabolism in COVID-19 patients were recently reported with unclear mechanism.In this study,we retrospectively investigated a cohort of COVID-19 patients without pre-existing metabolic-related diseases,and found new-onset in suli n resista nee,hyperglycemia,and decreased HDL-C in these patie nts.Mecha nistically,SARS-CoV-2 infecti on in creased the expression of RE1-silencing transcription factor(REST),which modulated the expression of secreted metabolic factors including myeloperoxidase,apelin,and myostatin at the transcriptional level,resulting in the perturbation of glucose and lipid metabolism.Furthermore,several lipids,including(±)5-HETE,(±)12-HETE,propionic acid,and isobutyric acid were identified as the potential biomarkers of COVID-19-induced metabolic dysregulation,especially in insulin resistance.Taken together,our study revealed insulin resistance as the direct cause of hyperglycemia upon COVID-19,and further illustrated the underlying mechanisms,providing potential therapeutic targets for COVID-19-induced metabolic complications.