The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry

We present the thermal expansion coefficient （TEC） measurement technology of compensating for the effect of variations in the refractive index based on a Nd： YA G laser feedback system, the beam frequency is shifted by a pair of aeousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-refiectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 29-748K, confirming not only the precision within 5 × 10-7 K-1 and the accuracy within 0.4% from 298K to 448K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.

An Integrated Agent-Based Framework for Assessing Air Pollution Impacts

Air pollution has considerable impact on human health and the wellbeing. Thus many regions of the world have established air pollution standards to ensure a minimum level of air quality. Precise assessment of the health and socio-economic impacts of air pollution is, however, a complex task;indeed, methods based within an epidemiological tradition generally underestimate human risk of exposure to polluted air. In this study, we introduce an agent-based modeling approach to ascertaining the impact of changes in particulate matter (PM10) on mortality and frequency of hospital visits in the greater metropolitan region of Sydney, Australia. Our modeling approach simulates human movement and behavioral patterns in order to obtain an accurate estimate of individual exposure to a pollutant. Results of our analysis indicate that a 50% reduction in PM10 levels (relative to the baseline) could considerably lower mortality, respiratory hospital admissions and emergency room visits leading to reduced pressure on health care sector costs and placing lower stress on emergency medical facilities. Our analysis also highlights the continued need to avoid significant increases in air pollution in Sydney so that associated health impacts, including health care costs, do not increase.

Probe Selection for Over-the-Air Test in 5G Base Stations with Massive Multiple-Input Multiple-Output

In 5G systems, massive multiple-input multiple-output (MIMO) has been adopted in base stations (BSs) to improve spectral efficiency and coverage. The traditional conductive performance test techniques are challenging due to the unaffordable cost and high complexity when testing a large number of antennas. To solve this problem, the over-the-air (OTA) test has been presented, in which probe selection is the key to reduce the number of channel emulators and probes. In this paper, a novel artificial bee colony (ABC) algorithm is introduced to enhance the efficiency and accuracy of probe selection procedure. A sectoring- based multi-probe anechoic chamber (MPAC) is built to evaluate the throughput performance of massive MIMO equipped in 5G BS. In addition, link level simulation is carried out to evaluate the proposal’s performance gain under the commercial network assumptions, where the average throughput of three velocity is given with different SNR region. The results suggest that OTA chamber and multi-probe wall are available not only for 5G BSs, but also for user equipments (UEs) with end-to-end communication.

Regional air quality prediction models using the knowledge－based system approach

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Thermal Decomposition of Mg-PTFE Based Pyrolant in Nitrogen and Air Environments

In order to analyze the thermal decomposition of MT based pyrolant in nitrogen and air environments,the thermal analysis experiments of MT and MTV pyrolants were carried out by TG-DTA and DSC.The results show that,in nitrogen environment,the spectrum result of Grignard-type reaction~[6] is verified by the decomposition characteristics of MT and MTV pyrolants.8.71% of Mg is consumed in the intermediate reaction of MT at 500-596 ℃ and the heat release of reaction is 31.93 k J/g.The endothermic decomposition of the intermediate product is at 684-740 ℃.In MTV,the intermediate reaction is at 435-595 ℃ and the heat release of reaction are increased by the addition of fluororubber.The intermediate product degrades at 677-745 ℃.In air environment,the decomposition of MT and MTV show the different reaction mechanism from the nitrogen environment.The presence of oxygen is involved in the reaction of Mg,and inhibits the intermediate reaction process of Mg and PTFE.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Human Memory/Learning Inspired Control Method for Flapping-Wing Micro Air Vehicles

The problem of flapping motion control of Micro Air Vehicles (MAVs) with flapping wings was studied in this paper.Based upon the knowledge of skeletal and muscular components of hummingbird, a dynamic model for flapping wing wasdeveloped.A control scheme inspired by human memory and learning concept was constructed for wing motion control ofMAVs.The salient feature of the proposed control lies in its capabilities to improve the control performance by learning fromexperience and observation on its current and past behaviors, without the need for system dynamic information.Furthermore,the overall control scheme has a fairly simple structure and demands little online computations, making it attractive for real-timeimplementation on MAVs.Both theoretical analysis and computer simulation confirms its effectiveness.

Long-term Durability of Cement-based Materials with Very Low w/b

To investigate the durability, especially the long-term stability of cement-based materials with very low w/b, the air permeability test, carbonation test, capillary absorption rate test and dilation potential test were adopted under long-term heat treatment condition. Microstructure of these materials is also analyzed by scanning electronic microscopy （SEM） and mercury intrusion porosimeter （MIP） in order to further unveil its mechanism and interrelation between microstructure and its properties. The results indicate that in the area investigated, cement-based material with w/b 0.17, like RPC, possesses low porosity and excellent durability. Moreover, its porosity will further decrease under long-term heat treatment compared with normal heat treatment. Its long-term durability is much superior to that of other cement-based materials with w/b 0.25 or 0.35 as high strength concrete（HSC）.

Development of flexible zinc–air battery with nanocomposite electrodes and a novel separator

In this paper, we present the development of flexible zinc–air battery. Multiwalled carbon nanotubes(MWCNTs) were added into electrodes to improve their performance. It was found that MWCNTs were effective conductive additive in anode as they bridged the zinc particles. Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate(PEDOT:PSS) was applied as a co-binder to enhance both the conductivity and flexibility. A poly(acrylic acid)(PAA) and polyvinyl alcohol(PVA) coated paper separator was used to enhance the battery performance where the PVP–PAA layer facilitated electrolyte storage. The batteries remained functional under bending conditions and after bending. Multiple design optimizations were also carried out for storage and performance purposes.

Simply air:Vanadium-catalyzed oxidative kinetic resolution of methyl o-chloromandelate by ambient air

Vanadium-catalyzed oxidative kinetic resolution（OKR） of methyl o-chloromandelate 2a,key intermediate of the well-known oral antiplatelet agent（S）-clopidogrel,was achieved by ambient air for the first time.The air oxidation system,which was composed of vanadium and tridentate Schiff base ligands derived from amino alcohols and salicylaldehyde derivatives,afforded an efficient and economic approach to the target intermediate with high enantioselectivities（99%ee）.

On the Accuracy Assessment of the Latest Releases of GOCE Satellite-Based Geopotential Models with EGM2008 and Terrestrial GPS/Levelling and Gravity Data over Egypt

The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to compare the free-air gravity anomalies and quasi geoid heights determined from several recent GOCE-based GGMs with the corresponding ones from the Earth Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with ground-based measurements on the other hand. The results regarding to the comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data provide better improvement with respect to EGM2008. The 4th release GOCE-based GGM developed with the use of space-wise solution strategy (SPW_R4) approximates the gravity field well over the Egyptian region. The SPW_R4 model is accordingly suggested as a reference model for recovering the long wavelength (up to SH d/o 200) components of quasi geoid heights when modelling the gravimetric quasi-geoid over the Egypt. Finally, three types of transformation models: Four-, Five- and Seven-parameter transformations have been applied to reduce the data biases and to provide a better fitting of quasi geoid heights obtained from the studied GOCE-based GGMs to those from GPS/levelling data. These models reveal that the standard deviation of vertical datum over Egypt is at the level of about 32 cm.

Predicting air pressure in drainage stack of high-rise building

It is necessary to understand the features of air pressure in a drainage stack of a high-rise building for properly designing and operating a drainage system. This paper presents a mathematical model for predicting the stack performance. A step function is used to describe the effect of the air entrainment caused by the water discharged from branch pipes. An additional source term is introduced to reflect the gas-liquid interphase interaction （GLII） and stack base effect. The drainage stack is divided into upper and base parts. The air pressure in the upper part is predicted by a total variation diminishing （TVD） scheme, while in the base part, it is predicted by a characteristic line method （CLM）. The predicted results are compared with the data measured in a real-scale high- rise test building. It is found that the additional source term in the present model is effective. It intensively influences the air pressure distribution in the stack. The air pressure is also sensitive to the velocity-adjusting parameter （VAP）, the branch pipe air entrainment, and the conditions on the stack bottom.

空战目标轨迹预测技术研究综述

信息化空战对抗中,快速获取和有效利用对手信息的一方,能够准确地预测对手的运动轨迹,更加迅速地完成OODA循环,进而取得空战优势。本文研究空战目标轨迹预测技术,以时序变化特征为研究视角,分别对基于物理、机器学习和深度学习的轨迹预测技术开展分析和总结,进一步归纳物理因素、空战因素和交互因素等作为轨迹预测模型的输入,单模态轨迹、多模态轨迹和行为意图三类作为模型的输出,并对未来智能化空战中的目标轨迹预测技术进行展望。

基准排放因子更新对隧道需风量的影响研究

为解决交通车辆持续更新导致的城市隧道内通风系统设计浪费和运营闲置,研究基准排放因子更新对隧道需风量的影响,并建立2种应对车辆更新的基准排放因子计算方法.首先,通过理论分析明确需风量计算式中随时间更新的关键参数为基准排放因子;随后,根据定量分析得到基准排放因子和纵坡-车速系数更新对需风量的影响;最后,结合国外理念和实际设计经验,提出2种考虑时间更新的基准排放因子计算方法.研究结果表明:我国道路隧道通风设计规范在制定基准排放因子时参考了世界道路协会(PIARC)通风报告,并分析得到了参考理由;与2000年相比,2021年的CO、NOx和PM基准排放限值分别降低了81.6%、76.7%和97.9%;建立了使用机动车污染物排放限值作为基准排放因子的最不利设计方法,计算出2018年各污染物基准排放因子(CO为0.0011 m^(3)/(辆·km),PM为0.4610 m^(2)/(辆·km)),相比于2014年《细则》分别降低84.3%和77.0%.建立并验证了基准排放因子计算方法,为城市道路隧道通风系统设计提供参考.

面向月球科研站任务的地月准实时遥操作模拟验证系统设计与关键技术研究

针对月球科研站任务地月遥操作需求和特点,设计地月准实时遥操作模拟验证系统,对其中的关键技术海量多尺度遥感数据环境感知、空地协同高精度定位、基于混合现实的预测仿真等进行了研究。提出了基于海量多尺度遥感数据的联合处理方法,环境感知数据融合可处理米级至厘米级环境感知结果;设计基于空地多运动平台协同定位的原型软件,空地协同地标约束下,定位精度不低于轨道器影像1个像素;开发了带有力觉反馈的预测仿真验证平台,在2~3 s变时延约束下可在仿真环境下协同演示遥操作过程,真实还原从端的遥操作作业场景,提高遥操作的执行效率和安全性。为地面人员的方案设计、操作手训练、故障处置等提供实时支持,为我国未来实施月球科研站任务筑牢基础。

基站空调在640层CT数据机房的使用效果

目的探讨基站空调在640层CT数据机房的使用效果。方法640层CT正常开机时,分别记录并比较基站空调和普通空调开启后数据机房温度由28℃降至24℃所需时间、正常运行必需后勤维护项目及次数、整体价格。结果室外温度为-5~30℃时,两种空调达到设定温度所需时间比较,差异无统计学意义(P>0.05),后勤维护项目次数相同;室外环境温度为31~42℃时,基站空调机房降温时间短于普通空调(P<0.05);普通空调需完成后勤维护项目一2次和项目二1次,基站空调需完成项目一2次;在室外环境温度为-6~-15℃时,普通空调故障停机,基站空调达到设定温度需要(12.4±1.5)min;基站空调整体价格高于普通空调;基站空调的整机性价比、操作使用、降温效率、故障报警和环境影响评分高于普通空调(P<0.05)。结论基站空调虽整体价格偏贵,但制冷速度快、可靠性高、维护简单,更适用于640层CT数据机房。

空基激光通信大气湍流传输的HARQ方案性能分析

大气湍流信道所引起的激光链路信号功率随机衰落是影响空基激光链路通信质量的重要因素。针对空基激光通信链路受大气湍流影响在短时间随机衰落导致的通信性能恶化情况开展HARQ传输能力仿真和性能分析。分析了不同编码码率、重传帧结构对误码纠错性能的影响,通过调整HARQ传输策略,对误码率性能改善以及通信带宽利用率等传输性能结果进行比较。根据仿真结果可知,较精细化的重传控制以及改变纠错编码码率能够有效提高激光链路的误码纠错能力。通过平衡HARQ重传过程中的编码码率和重传帧长度,可以在不影响链路传输效率的情况下明显改善激光链路传输性能。

基于简化人工蜂群算法的地面防空火力拦截设备部署方法

针对地面防空火力拦截设备部署问题中部署方案产生速度慢、不符合战场实际环境问题,提出了一种基于简化人工蜂群算法的地面防空火力拦截设备部署方法。本方法在地面防空火力拦截设备部署方案制定过程中,将人工蜂群算法分为初始化阶段和优化阶段。从专家知识辅助的视角出发,初始化阶段利用专家知识对可部署位置进行了寻优处理并结合随机初始化,优化阶段利用简化型邻域优化对初始化阶段产生的方案进行优化。2个阶段均对产生的部署方案进行校验,若方案达到给定突防概率指标则直接保存输出,大大提高了收敛速度,且产生的部署方案符合实际。仿真结果表明:提出的方法相比于传统蜂群算法在收敛速度方面具有明显优势。

Observation of selective surface element substitution in FeTe_(0.5)Se_(0.5) superconductor thin film exposed to ambient air by synchrotron radiation spectroscopy

A systematic investigation of oxidation on a superconductive Fe Te_（0.5）Se_（0.5）thin film,which was grown on Nb-doped SrTiO_3（001） by pulsed laser deposition,has been carried out.The sample was exposed to ambient air for one month for oxidation.Macroscopically,the exposed specimen lost its superconductivity due to oxidation.The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy（PES） and x-ray absorption spectroscopy（XAS） measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air.By the spectroscopic measurements,we found that the as-grown FeTe_（0.5）Se_（0.5）superconductive thin film experienced an element selective substitution reaction.The oxidation preferentially proceeds through pumping out the Te and forming Fe–O bonds by O substitution of Te.In addition,our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials.

TBO模式下终端区容量评估与优化

随着航空运输业的快速发展,航班量逐渐增加,造成了终端区可用空域资源饱和、空中交通拥堵、航班延误等现象。基于未来空中交通管理模式向着基于航迹运行(TBO)模式转变的趋势,考虑了机场、管制部门、航空公司这三个容量管理参与方,即在不同的协同决策下,建立终端区容量优化模型。运用基于滑动时间窗的优化-反馈算法和元启发式模拟退火算法,并以广州终端区作为实验案例进行验证。研究结果表明,模型在不同的协同决策下可以有效提高空域资源的利用率,对于增加终端区的运行容量具有一定效果。