Dynamic MmWave Channel Reconstruction of MIMO OTA Testing for Handover Scenarios

The evaluation of handover performance is essential for ensuring seamless user experience under innovative application scenarios in the fifth generation(5G)and beyond era,including autonomous driving,mobile augmented and virtual reality.However,due to the hardware constrains of a sectored multiprobe anechoic chamber(SMPAC),switching among multiple channel models is of low precision with a high cost in traditional over-the-air(OTA)test solutions.In this paper,we present an efficient and repeatable emulation strategy to reconstruct dynamic millimeter-wave(mm Wave)channels in laboratories for multiple-input multiple-output(MIMO)mobile devices.Firstly,we propose a novel evaluation metric,called average power angular spectrum similarity percentage(APSP),which minimizes the unexpected impact induced by the indefinite condition of adaptive antenna arrays in mm Wave terminals during handover process.Moreover,we propose a partitioned probe configuration strategy by designing a beam directivitybased switching circuit,which enables quick changes of probe configurations in SMPAC.Simulation results demonstrate the effectiveness of the proposed algorithms,thus providing a guideline for the reconstruction of the dynamic channel in different scenarios with resource limitation.

汽车软件OTA升级威胁分析及实测举隅

软件定义汽车是新一代汽车产业发展的必然趋势,汽车软件OTA升级是未来汽车软件升级的重要手段,在其带来便利的同时信息安全性值得重点关注。本文对汽车软件OTA升级进行资产识别、威胁场景识别、攻击路径及攻击可行性分析,提出汽车软件OTA升级信息安全测试指标,开展测试实践。本文给出测试过程中的重点问题分析,旨在通过完整的威胁分析,为汽车软件OTA升级体系研究提供参考。

Air pressure law of a reservoir constructed in karst sinkholes

Karst sinkholes with natural negative landform provide favorable conditions for the pumped storage reservoir construction for less excavation work.However,the construction of the reservoir would plug the natural karst channels for water and air,which would cause remarkable air pressure in karst channels when the groundwater level fluctuates.A large laboratory simulation test was carried out to study the air pressure variation of a reservoir built on the karst sinkhole.The air pressure in the karst channel and inside the model was monitored during the groundwater rising and falling process.Result showed that the variation of air pressure in the karst channel and the surrounding rock exhibited a high degree of similarity.The air pressure increased rapidly at the initial stage of water level rising,followed by a slight decrease,then the air pressure increased sharply when the water level approached the top of the karst cave.The initial peak of air pressure and the final peak of air pressure were defined,and both air pressure peaks were linearly increasing with the water level rising rate.The negative air pressure was also analyzed during the drainage process,which was linearly correlated with the water level falling rate.The causes of air pressure variation in karst channels of a pumped storage reservoir built on the karst sinkhole were discussed.The initial rapid increase,then slight decrease and final sudden increase of air pressure were controlled by the combined effects of air compression in karst channel and air seepage into the surrounding rock.For the drainage process,the instant negative air pressure and gradual recovering of air pressure were controlled by the combined effects of negative air pressure induced by water level falling and air supply from surrounding rock.This work could provide valuable reference for the reservoir construction in karst area.

Surface air temperature change in the Wuyi Mountains,southeast China

Detecting changes in surface air temperature in mid-and low-altitude mountainous regions is essential for a comprehensive understanding of warming trend with altitude.We use daily surface air temperature data from 64 meteorological stations in Wuyi Mountains and its adjacent regions to analyze the spatio-temporal patterns of temperature change.The results show that Wuyi Mountains have experienced significant warming from 1961 to 2018.The warming trend of the mean temperature is 0.20℃/decade,the maximum temperature is 0.17℃/decade,and the minimum temperature is 0.26℃/decade.In 1961-1990,more than 63%of the stations showed a decreasing trend in annual mean temperature,mainly because the maximum temperature decreased during this period.However,in 1971-2000,1981-2010 and 1991-2018,the maximum,minimum and mean temperatures increased.The fastest increasing trend of mean temperature occurred in the southeastern coastal plains,the quickest increasing trend of maximum temperature occurred in the northwestern mountainous region,and the increase of minimum temperature occurred faster in the southeastern coastal and northwestern mountainous regions than that in the central area.Meanwhile,this study suggests that elevation does not affect warming in the Wuyi Mountains.These results are beneficial for understanding climate change in humid subtropical middle and low mountains.

Investigation of the Film Formation in Dynamic Air Spray Painting

To accurately predict the film thickness distribution during dynamic spraying performed with air guns and support accordingly the development of intelligent spray painting,the spray problem was analyzed numerically.In particular,the Eulerian-Eulerian approach was employed to calculate the paint atomization and film deposition process.Different spray heights,spray angles,spray gun movement speeds,spray trajectory curvature radii,and air pressure values were considered.Numerical simulation results indicate that the angle of spray painting significantly affects the velocity of droplets near the spray surface.With an increase in the spraying angle,spraying height and spray gun movement speed,the maximum film thickness decreases to varying degrees,and the uniformity of the film thickness also continuously worsens.When the spray gun moves along an arc trajectory,at smaller arc radii,the film thickness on the inside of the arc is slightly greater than that on the outside,but the impact on the maximum film thickness is minimal.Increasing air pressure expands the coating coverage area,results in finer atomization of paint droplets,and leads to a thinner and a more uniform paint film.However,if the pressure is too high,it can cause paint splattering.Using the orthogonal experimental method,multiple sets of simulation calculations were conducted,and the combined effects of spraying height,spray angle,and spray gun movement speed on the film thickness distribution were comprehensively analyzed to determine optimal configurations.Finally,the reliability of the numerical simulations was validated through dynamic spray painting experiments.

C_(4)F_(7)N-air混合气体在稍不均匀和极不均匀电场中的工频绝缘特性分析

近年来,作为SF_(6)有效替代气体之一,七氟异丁腈(C_(4)F_(7)N)因其优异的电气性能和物化特性而受到关注与讨论,然而由于C_(4)F_(7)N的液化温度较高,需要与低液化温度的缓冲气体并用。选择空气作为缓冲气体,在稍不均匀电场与极不均匀电场下,通过工频击穿实验研究气压、混合占比和电极间隙对C_(4)F_(7)N-air混合气体工频击穿电压的影响。结果发现:C_(4)F_(7)N-air混合气体在两个电场下的工频击穿电压随着电极间隙的增大而近似线性增加,在极不均匀电场下,出现明显“驼峰”效应,混合比为8%~16%的C_(4)F_(7)N-air混合气体工频击穿电压可达到同条件下SF_(6)的67%~86%。在稍不均匀电场下,8%C_(4)F_(7)N/92%air混合气体的绝缘强度约为同条件下SF_(6)的0.8倍。混合比为12%~16%的C_(4)F_(7)N-air混合气体具备与SF_(6)相等的工频绝缘强度。总结:与SF_(6)对比,C_(4)F_(7)N占比为8%~16%的C_(4)F_(7)N-air混合气体具备替代SF_(6)气体的潜力。

Experimental Study on Purification Efficiency of Air Purifier for the Indoor Total Volatile Organic Compounds

By using total volatile organic compounds （TVOC） as the objective volatile pollutant, the purification efficiency of some representative air purifiers bought in the market was determined under the relatively independent and stable environmental conditions supplied by the self-made multi- functional environmental test chamber. Various evaluation parameters of TVOC were calculated based on the tested results, such as purification ef- ficiency and removal rate. The results showed that the TVOC purification efficiency increased with enhancing the temperature or lessening the rela- tive humidity, but this effect is not obvious. The air purifiers which use photocatalytic technology have higher TVOC purification efficiency than those which only use some adsorption technology. The purification efficiency and removal rate can be more accurate to evaluate the purification efficiency of air purifiers.

Orthogonal tests of lead-clad tin bimetal continuous casting by air pressure core-filling

To provide theoretical basis and practical guidance for preparing composite rods of external diameter no larger than 12 mm by directly continuous casting,low melting point materials of lead and tin were selected to prepare composite rods of external diameter 12 mm and inner diameter 8 mm with air pressing core filled continuous casting process.The orthogonal tests consisting of three factors and three levels were designed to investigate the parameters of melting lead temperature,continuous casting speed and air pressure that affect the performance of the composite rods.The results show that melting lead temperature is the most important factor that influences the solid/liquid interface location;continuous casting speed is the most important factor that influences the surface quality and lead and tin inter-diffusion amount;air pressure can improve the surface quality obviously and make the rods easily drawn out,but the surface quality cannot get obvious improvement when the air pressure is above 0.03 MPa.The composite rods have excellent surface quality,obvious intermediate layer,even thick clad,and metallurgical bonding interface under the condition of melting lead temperature of 375 °C,continuous casting speed of 10 mm/min,and air pressure of 0.03 MPa.

The Study of the Auto Disk Brake Air Test

In the paper weakness of air leakage system in our company is discussed firstly. Secondly the improved scheme of air leakage system including auto-control is designed. Then, the tooling with role of location and recovery is developed. At last the application of design optimization is processed. The result reveals that the system of air leakage detection is very valuable and important to manufacture.

Processing the rig test data of an air filling twin-tube shock absorber

A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.

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.

Test Apparatus for Performance Evaluation of Compressed Air End-Use Applications

Compressed air is an integral utility part of industrial utility systems. Any improvement in compressed air system will lead to reduction in utility cost. The effectiveness of utilization side of compressed air is usually dependent upon operator’s discretion. There are no performance testing methods available for testing existing end use equipments. A test apparatus for estimation of compressed air flow based on measurement of pressure reduction in a fixed volume cylinder in a given time is developed. The test apparatus is easy to build and simple to operate in an industrial environment. This can be used for measuring performance of any pneumatic end-use equipment and for benchmarking the performance. The test apparatus was used in a foundry for quantifying the performance of the old and new blow guns.

智能网联汽车OTA测试案例分析及对策研究

智能网联汽车的规模与日俱增,软件更新的需求也日益迅速,远程升级(OTA)技术为智能网联汽车的大规模更新提供了解决办法。文章从OTA的技术框架、安全技术和相关法规三个方面对OTA技术进行了概述,然后基于R156和《汽车软件升级通用技术要求》介绍了测试方法和测试案例。通过对测试案例进行分析,提出了存在的问题并给出了合理的对策。最后从智能网联汽车生产企业、OTA升级管理体系和第三方检测机构三个角度对网联汽车OTA升级安全技术提出了合理的建议。

Design and Characterization of an Aerosol Test Chamber for Emergency Response Patient Contamination Control Simulation and Research

Contaminated or infected patients present a risk of cross-contamination for emergency responders, attending medical personnel and medical facilities as they enter a treatment facility. The controlled conditions of an aerosol test chamber are required to examine factors of contamination, decontamination, and cross-contamination. This study presents the design, construction, and a method for characterizing an aerosol test chamber for a full-sized manikin on a standard North Atlantic Treaty Organization litter. The methodology combined air velocity measurements, aerosol particle counts and size distributions, and computational fluid dynamics modeling to describe the chamber’s performance in three dimensions. This detailed characterization facilitates future experimental design by predicting chamber performance for a variety of patient-focused research.

空空导弹海洋大气自然环境试验研究

针对空空导弹随航母服役需求和海洋大气自然环境适应性风险,结合相关标准和研制经验,对空空导弹海洋大气自然环境试验方案设计流程、方法及要点进行了研究。提出了一套空空导弹海洋大气自然环境试验方案,可用于指导新研型号科学有效地开展自然环境试验,为回答空空导弹海洋大气自然环境适应性指标提供了支撑。空空导弹应系统策划海洋大气自然环境试验,以尽早暴露问题,实现产品设计改进,为上舰环境适应性的提高奠定基础。同时,还应大力开展自然加速环境试验技术和动态自然环境试验技术研究工作。

通信产品OTA测试对无线电发射设备检测工作的影响分析

文章首先说明了OTA测试所遵循的原理,其次详细介绍了OTA测试所涉及测量指标、系统配置、具体测试方法,最后讨论了OTA测试对设备检测的影响,包括全面衡量设备性能、保障使用人员权益、提升设备整改速度等,供相关人员参考。

新能源汽车OTA方案及自动化测试方法

为了保证OTA功能可满足法规、功能性、稳定性、信息安全等要求,本文提出一种OTA自动化测试方法,能保障OTA功能的稳定性。

空气舵抖振载荷地面模拟试验技术研究

固体火箭的空气舵在挂机飞行中受到抖振载荷作用,出现了异常偏转现象,需要通过地面试验排查原因,并开展抖振载荷适应性考核。由于传统的试验方法未能复现故障,本文提出了一种新的抖振载荷地面模拟试验新技术,通过挂机飞行舵面实测数据计算舵面抖振载荷,并基于优化算法完成地面模拟试验条件制定,通过多激振器联合激励方法来完成抖振载荷加载。该试验技术在地面试验中成功实现了产品故障复现,大幅提高试验考核的真实性,该研究结果可以推广应用到其它舵产品气动载荷地面考核中。

轨道车辆空气弹簧刚度试验统型设计与研究

为实现轨道车辆空气弹簧静态和动态刚度试验模块化、标准化统型设计目标,对试验统型设计思路进行了分析;设计了一种新型的空气弹簧径向轴向组合密封模块化试验装置,并与传统密封装置进行了对比;重点利用新型装置探究了不同加载速度对刚度的影响,以及受迫和自由这两种不同振动方式对动刚度、阻尼、共振频率、共振倍率的影响。结果表明:统型试验装置能够满足试验要求,且装置数量减少了50%,存放空间缩减了50%,设计效率提高了60%,加载速度对静刚度的影响并不明显,受迫和自由这两种不同振动方式所测试的动态性能数据基本一致。

空间站舱内微量有害气体状态评价和流转分析

文章聚焦于中国空间站长期在轨运行中微量有害气体的整体状态和控制情况,阐述了微量有害气体随舱内物质循环向冷凝水回收净化以及CO_(2)去除和还原等环节流转的规律。通过在轨状态分析、地面比对评估试验结果和流转特性分析,说明中国空间站各净化系统对舱内微量污染物成分进行了有效控制,舱内空气中微量有害气体浓度保持在较低水平。研究旨在为后续微量有害气体净化环节的运行和监测提供指导。