EXPERIMENT ON FLOW CHARACTERISTICS OF SYNTHETIC JET DRIVEN BY PIEZOELECTRIC MEMBRANE

The characteristics of the flowfields of a synthetic jet actuator are experimentally investigated with the slot-nozzle driven by the piezoelectric membrane. The particle image velocimetry （PIV） and the hot-wire anemometer are utilized to measure the flowfields and the velocity profiles of the actuator with different actuating factors. Analytical results show that pairs of counter-rotating vortices are generated near the nozzle. With the development of the synthetic ject, the synthetic jet rapidly spreads in the slot-width direction; while in the slot-length direction, it contracts firstly and slowly spreads. The centerline velocity distribution has a up-down tendency varying with axial distances, and accelerates to its maximum at z/b= 10. The transverse velocity profile across the slot-width is centro-symmetric and self-similar. However, the velocity profiles across the slot-length are saddle-like near the nozzle. It shows that there are two resonance frequencies for the actuator. If the actuator works with the resonance frequency, the vorticity and the velocity of the synthetic jet are higher than those of other frequencies. Compared with the continuous jet, the synthetic jet shows special flow characteristics.

The Dynamic Volt-Ampere Characteristics of a Vacuum Arc at Intermediate-Frequency Under a Transverse Magnetic Field

In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF and phase shift time were calculated by using the TMF contact model and the large phase shift of the magnetic field at a higher frequency was conductive to the dispersion process of residual plasma. The arc velocity was higher at 800 Hz than at 400 Hz. It can be inferred that TMF will encourage arc movement at 800 Hz. Moreover, the arc movement has an impact on the arc voltage. Because of the increasing length of the arc column with a high arc velocity, the elongated arc causes the arc voltage to increase. Specifically, the volt-ampere characteristics of the vacuum arc are divided into three stages in this paper. The higher the frequency, the greater the initial rate of rise in the arc voltage and the larger the area surrounded by arc volt-ampere characteristics. The correlations between the arc voltage and the amplitude and frequency of the current are also presented.

Synthetic Characteristics Associated with HIV Diagnosis through Voluntary HIV Testing among HIV-positive People with Non-marital and Non-commercial Heterosexual Transmission in China

The Joint United Nations program on HIV/AIDS reported that 53% of new infections globally in 2017 were beyond key populations and their sexual partners.In this report, although only 16% in Asia and the Pacific were people living with HIV (PLHIV) who did not report any HIV-risk behaviors (mainly including injective drug use, men who have sex with men, sexual workers, and their dients), increasing diag no sed cases who reported their own transmission as non-marital and non-commercial heterosexual con tact (non-M&C sex, defi ned as those heterosexuals who have unpaid sex with any other sexual partners whom they have never married) in China have indicated that the HIV epidemic is spreading to the general population by the bridge of key populations.

VOLT-AMPERE CHARACTERISTICS OF CIS-POLY(PHENYL ACETYLENE)

The volt-ampere (Ⅰ-Ⅴ) characteristics of the c/s-poly (phenyl acetylene) (PPA) of cis-transoidal structure has been studied in the temperature range of 253-288K. An ITO/ PPA/ Au sandwich configuration was used for the measurements. Under an applied field of less than 10~5V/ cm it showed ohmic behavior, while the space charge limited current (SCLC) was observed at applied fields above 5×10~5V/ cm. In the ohmic region a conductivity of 1.37×10^(-16)S/ cm was obtained at room temperature with an activation energy of 0.5eV. These data indicate that the conduction is not intrinsic one but is the result of thermal release of trapped carriers. In fact the data in the SCLC region treated according to the theory for a single Gaussian distribution of traps gave a mean trap energy of 0.48 eV with a half-width of 0.4 eV and a total density of trapping states of 5×10^(16)/cm^3.

Rheological and Tribological Characteristics of the Synthesized Lubricants Derived from Vegetable Oils

The double bonds in the vegetable oils can be conjungated and Diels-Alder react when they are heated in the existence of the catalyst. The percent of the double bond will decrease and the oxidative stability of the vegetable oils can be ameliorated. Dimmer acid can react with different carbon chain length of alcohols to form dimmer acid esters. A series of dimmer acid esters were synthesized and their rheological characteristics （viscosity, viscosity index, pour point） and tribological characteristics （the coefficient of friction at different load, the characteristic of extreine pressure （ PB ）, the wear scare diameter （ D30min^196N ） were evaluated and analyzed. The results showed that the characteristics of Di-iso-octanol dimmer acid ester were the best among the synthesized dimmer esters. It＇ s a lubricant with good properties（the viscosity is 94.5 mm^2/s, the viscosity index is high up to 141 and the pour point is - 49℃ ）. It is a kind of newly interesthing ester type lubricant. Its rheological and tribological characteristics are even better than those of the slap-up synthesized lubricant--pentaerythritol esters （C7-9 acidate）. The FT-IR spectrophotometer was used to analyze the structure of the synthetic esters. Their IR spectra are the same as the typical IR spectrum of ester. The test indicated that Di-iso-octanol dimmer acid ester could be used as a kind of base lubricant with excellent quantity.

Oil spill detection by a support vector machine based on polarization decomposition characteristics

Marine oil spills have caused major threats to marine environment over the past few years.The early detection of the oil spill is of great significance for the prevention and control of marine disasters.At present,remote sensing is one of the major approaches for monitoring the oil spill.Full polarization synthetic aperture radarc SAR data are employed to extract polarization decomposition parameters including entropy（H） and reflection entropy（A）.The characteristic spectrum of the entropy and reflection entropy combination has analyzed and the polarization characteristic spectrum of the oil spill has developed to support remote sensing of the oil spill.The findings show that the information extracted from（1-A）×（1-H） and（1-H）×A parameters is relatively evident effects.The results of extraction of the oil spill information based on H×A parameter are relatively not good.The combination of the two has something to do with H and A values.In general,when H〉0.7,A value is relatively small.Here,the extraction of the oil spill information using（1-A）×（1-H） and（1-H）×A parameters obtains evident effects.Whichever combined parameter is adopted,oil well data would cause certain false alarm to the extraction of the oil spill information.In particular the false alarm of the extracted oil spill information based on（1-A）×（1-H） is relatively high,while the false alarm based on（1-A）×H and（1-H）×A parameters is relatively small,but an image noise is relatively big.The oil spill detection employing polarization characteristic spectrum support vector machine can effectively identify the oil spill information with more accuracy than that of the detection method based on single polarization feature.

Experimental study on the jet characteristics of a steam plasma torch

Thermal steam plasma jet is promising for applications in environmental industries due to its distinctive characteristics of high enthalpy and high chemical reactivity. However, the performance of the steam plasma torch for its generation is limited by the problems of the large arc voltage fluctuation and serious erosion of the electrodes. In this study, a gas-stabilized steam plasma torch which can operate continuously and stably was designed. Experiments were conducted to reveal the effect of the different working parameters, including the anode diameter, the cooling water temperature, the arc current and the steam flow rate, on its Volt-Ampere characteristics, arc voltage fluctuation, thermal efficiency, jet characteristics and electrodes erosion. Results showed that the use of hot water to cool the electrodes can effectively prevent the condensation of steam on the inner wall of the electrodes, thus significantly reducing the arc voltage fluctuations and electrodes erosion. This is crucial for increasing the working life of the electrodes and ensuring long-term stability of the steam plasma torch. In addition, suitable anode diameter can greatly reduce the arc voltage fluctuation of the steam plasma torch and effectively improve the stability of the steam plasma jet. Furthermore, high arc current can effectively reduce the fluctuations of the arc voltage and increase the length and the volume of the steam plasma jet. Finally, using steam as the plasma forming gas can achieve higher thermal efficiency compared to air. An ideal thermal efficiency can be achieved by properly reducing the arc current and increasing the steam flow rate.

Electrical and Optical Characteristics of Electrodeless Lamp

In order to study the methods to enhance the efficacy of electrodeless lamp,volt-ampere characteristics,illuminance and emission spectrum have been investigated in home-built electrodeless lamp experimental system with an electrodeless lamp in shape like QL 85 lamp.The results show that lamp current increases as lamp voltage increases in non-discharge,the current decreases first and then increases as the voltage increases in discharge.The illuminance of electrodeless lamp increases linearly with discharge power increasing,and it decreases linearly with power decreasing.The emission spectrum is different for different bulb and lighting time.The spectrum of Ar 811.5 nm,76.5 nm,750.4 nm and Hg 313.2 nm decrease with lighting time.While the intensity of Hg 407.8 nm increases with lighting time.

Study on the Method of Short-Term Synthetic Earthquake Prediction in the North China Region

Based on the extraction and calculation of the short-term seismic precursory information magnitude from the 114 major precursory observations in the North China region, and together with consideration of factors such as geological structure, seismicity, crustal thickness, and in particular, the current geodynamics of the region, the authors studied the time-space evolution characteristics of the short-term earthquake precursory information magnitude and its relationship with earthquakes and proposed the index and method for the short-term synthetic prediction of earthquakes with M S≥5.0 in the North China region. The inspection through R-value shows that the method is effective to a certain extent for earthquake prediction.

一株新型高效聚磷菌Glutamicibacter sp.G2的分离鉴定及除磷特性

聚磷菌(Phosphorus accumulating bacteria,PAOs)在生物除磷系统(EBPR)的强化过程中发挥着重要作用。挖掘新型高效聚磷菌并优化其除磷工艺,对于废水生物除磷技术的发展具有重大意义。文章通过富集驯化、分离纯化,结合MOPS蓝白斑(10×)初筛、Albert异染颗粒复筛等方法从某污水处理厂污泥样品中筛选出一株高效聚磷细菌G2,将其鉴定为盐生谷氨酸杆菌(Glutamicibacter halophytocola),并通过单因素试验探究pH、温度、接种量、初始磷含量,以及水体中的阳离子浓度对菌株G2生长及除磷的影响。实验结果表明,该菌株在初始磷浓度为30 mg/L、pH为8.0、8.0%接种量、32℃的条件下发酵72 h后,磷去除率可达78.79%。同时,添加2.0%的Mg^(2+)可以将菌株G2在人工合成废水中的除磷率提高17.50%。文章所筛选出的盐生谷氨酸杆菌G2在人工合成废水中表现出了良好的除磷效果,有望为废水生物除磷技术提供优质菌种资源。

复杂地形条件下的PolInSAR森林模拟和特征参数分析

为了探究PolInSAR在不同地形条件下散射机理的变化规律,为后续开展PolInSAR技术在复杂地形条件下的森林参数估计和反演研究打下坚实的基础以欧洲空间局发布的PolSARPro软件中为PolInSAR森林模拟定制开发的PolSARprosim模拟器为基础,对模拟过程中的地形模型构建和森林位置图生成步骤进行改进,以适用于复杂地形条件下对森林场景的PolInSAR影像的模拟,实现了对平地、迎坡面和背坡面的完整三维地形场景的模拟。基于此模拟器生成了不同地形条件下的PolInSAR影像对的后向散射系数图、干涉相位图和相干系数图,均符合真实三维场景下的SAR的几何特性变化规律。通过对模拟的结果分析发现PolInSAR影像对的体相干系数随坡度增大而减小,干涉相位和垂直波数随坡度增大而增大,它们的灵敏度随着入射角增大而减小的变化规律。针对森林高度的反演研究发现,当考虑地形坡度对垂直波数的影响时,除了在较大的垂直波数条件以外整体的森林高度反演误差均比较稳定。

基于时序InSAR技术的中贵天然气管道天水市段沿线滑坡隐患识别与形变分析

中贵天然气管道天水市段沿线地处黄土高原,地貌类型多样、构造活跃、复杂地质条件下发育多种具有隐蔽性和潜伏性的地质灾害,其中滑坡灾害对中贵天然气管道的安全危害极大,因此,对中贵天然气管道天水段沿线滑坡隐患进行有效识别与分析具有重要意义。采用Sentinel-1A升降轨卫星数据,基于时序合成孔径雷达干涉测量(synthetic aperture radar interferometry,InSAR)对中贵天然气天水段沿线滑坡隐患进行了解译识别、现场复核、发育特征与典型滑坡形变分析。研究区共识别17处滑坡隐患点,现场复核最终确定13处,其余4处为人类工程活动区,其中常沟村和磨峪沟村滑坡形变受降雨影响。统计发现研究区管道沿线滑坡多发生在坡度40°~50°,高差400~600 m,东北坡向和距管道100~150 m范围内,且岩土体强度较低,地层以第四系全新统冲洪积层(Q_(4)^(a1+p1))为主。结果表明:联合升降轨的时序InSAR技术可以有效识别管道沿线滑坡隐患,为油气管线的安全运营及今后油气管道选线提供重要的科学依据和参考。

矩形射流口几何构型对合成双射流工作特性影响分析

合成双射流技术作为一种新型的主动流动控制技术,除具备常规合成射流结构简单、响应迅速等特点外,还能有效解决控制流场与环境流场间压差引起振膜失效的问题,兼具能量利用率高、结构灵活和易于一体化集成等优点。合成双射流工作特性易受射流口大小、形状等几何构型的影响,为进一步研究合成双射流工作特性,设计了25组不同矩形射流口几何参数的合成双射流激励器,通过PIV实验得到合成双射流激励器射流口处流场结构与频率特性的关系,分析射流口几何参数对激励器腔体亥姆霍兹共振频率的影响,并总结出最佳长宽比-深纵比关系;结合数值模拟研究激励器几何参数特性,探究射流口几何参数对射流速度分布与轴切换现象的影响规律,并与PIV实验结果进行对比验证。结果表明小长宽比矩形射流口所形成的射流在空间上的分布更集中,射流峰值速度更大;而大长宽比矩形射流口形成的射流的速度较低,且单股射流易受压力差作用发生偏转,但涡量分布更加均匀,与环境流体的能量交换更充分。

合成酚类抗氧化剂在我国室内灰尘中的污染特征及人体暴露风险

研究了来自我国17个省市的室内灰尘中13种合成酚类抗氧化剂(SPAs)及其4种转化产物污染特征.结果显示,我国室内灰尘中主要的SPAs污染物为传统SPAs 2,6-二叔丁基-4-甲基苯酚(BHT)和新型SPAs抗氧剂1010,两者的污染水平相当(BHT:165~1.10×10^(3)ng/g;抗氧剂1010:62.0~2.37×10^(3)ng/g),其浓度水平分别占所研究的SPAs总浓度的37.4%和36.0%.首次在室内灰尘中发现了抗氧剂330的存在,浓度水平最高为12.7ng/g.此外,灰尘中出现了一定浓度的SPAs转化产物,其中醌/醇化产物和醛化产物的占比较大,达到35.8%和56.9%,说明室内灰尘上的SPAs有一定的转化潜力.SPAs在室内灰尘中的浓度与采样点的经济发达程度有一定关联,东南沿海城市的SPAs浓度水平较高.受不同地区气候、地理条件影响,SPAs的浓度和组成体现出较大的空间差异.每日摄入量的评估结果显示,在高暴露情况下,成人和儿童对SPAs每日摄入总量分别为1.01×10^(-3)~0.54ng/(kg bw·d)和4.52×10^(-3)~2.39ng/(kg bw·d).虽然在目前的污染水平下,人们通过灰尘摄入途径的SPAs暴露量较小,但考虑到SPAs物质种类的快速更新换代和环境污染浓度的不断升高,其环境风险有待持续关注.

基于时频分析的SAR目标微波视觉特性智能感知方法与应用

合成孔径雷达(SAR)目标识别智能算法目前仍面临缺少鲁棒性、泛化性和可解释性的挑战,理解SAR目标微波特性并将其结合先进的深度学习算法,实现高效鲁棒的SAR目标识别,是目前领域较为关注的研究重点。SAR目标特性反演方法通常计算复杂度较高,难以结合深度神经网络实现端到端的实时预测。为促进SAR目标物理特性在智能识别任务中的应用,发展高效、智能、可解释的微波物理特性感知方法至关重要。该文将高分辨SAR目标的非平稳特性作为一种典型的微波视觉特性,提出一种改进的基于时频分析的目标特性智能感知方法,优化了处理流程和计算效率,使之更适用于SAR目标识别场景,并进一步将其应用到SAR目标智能识别算法中,实现了稳定的性能提升。该方法泛化性强、计算效率高,能得到物理可解释的SAR目标特性分类结果,对目标识别算法的性能提升与属性散射中心模型相当。

微生物胞外多糖的来源、生物合成及功能研究进展

胞外多糖是由微生物合成的一种功能多样的聚糖化合物。近年来研究发现,胞外多糖具有吸附性、亲水性、粘结性及免疫活性等特性,在多学科研究中受到广泛关注。目前胞外多糖的生产和提纯过程存在成本高、收率低等问题,阻碍了其规模化生产和商业应用。系统介绍了胞外多糖的微生物来源、生物学特征和生理功能,重点阐述了几种具有工业应用潜力的胞外多糖的生物合成机制,列举了胞外多糖最新的应用方向,并对胞外多糖的生物合成机制以及胞外多糖的规模化生产和多领域应用进行了展望。希望为进一步开发利用胞外多糖产生菌的菌种资源、深入研究微生物胞外多糖功能和活性机制以及发酵生产过程、以及对胞外多糖在多学科和多领域的广泛应用的优化提供参考。

四川雪宝顶白钨矿的矿物学及发光特征

本文通过对四川雪宝顶地区(瀑口梁、三道气、水晶镇、五铢堂)的白钨矿进行常规矿物学测试、LA-ICP-MS及光致发光光谱(PL光谱)测试,旨在获得其化学成分、矿物学与发光特征。通过高温固相法合成掺杂不同比例Sm、Eu、Dy元素的CaWO_(4)多晶,分析其光致发光光谱以探究Sm、Eu、Dy元素对其红色荧光的影响。结果显示,在中波紫外光(310 nm)照射下,四川雪宝顶地区白钨矿的荧光颜色有分区性,为红色和淡黄色;化学成分测试结果显示,样品含有Sr、Nb、Mn、Mo、稀土元素(REE)等微量元素,整体含有较高的REE总量(335.8-2243.0μg/g)和Sr元素(126.3~5188.2μg/g),在淡黄色荧光区域富集的Nb、Mn、Mo元素,说明白钨矿中Mn、Mo、Nb可提高作为激活剂的三价稀土离子(RE^(3+))的荧光发射强度。PL光谱测试表明,其红色荧光主要是Sm^(3+)、Eu^(3+)的贡献,其次还有Dy^(3+)、Tb^(3+)、Pr^(3+)的影响,淡黄色荧光主要是由Dy^(3+)导致,其次还有Sm^(3+)、Eu^(3+)的影响。本文通过分析合成白钨矿PL光谱得出,Dy^(3+)是Sm^(3+)、Eu^(3+)的敏化剂,Dy^(3+)对Sm^(3+)的荧光发射强度增强的更明显,尤其是Sm^(3+)的^(4)G_(5/2)→^(6)H_(7/2)跃迁(580~620 nm),在天然白钨矿中表现为Dy^(3+)阻碍了Sm^(3+)→Eu^(3+)的能量传递以及部分样品中Sm^(3+)最强发射峰从^(4)G_(5/2)→^(6)H_(9/2)跃迁(630~660 nm)变为^(4)G_(5/2)→^(6)H_(7/2)跃迁(580~620 nm)。

基于相位变化率的体目标与点源合成目标回波分辨

针对水下体目标与多点源合成回波信号的分辨问题,本文基于体目标与多点源合成回波信号的形成机理差异,表征分析了影响水下目标回波相位形成的关键因素及水下体目标与多点源合成回波相位形成的差异性,基于2类回波信号相位变化率的特征差异,提出并建立了基于相位变化率的体目标回波与多点源合成回波的分辨方法。通过Benchmark基准潜艇缩比模型和多点源合成目标模型的特性仿真和湖上对比测试对2类回波信号的分辨方法进行了验证,仿真和测试数据分析结果表明:通过对比同方位角度范围内的回波相位变化率,可以对体目标回波与多点源合成回波进行分辨,验证了基于相位变化率的水下体目标与多点源合成回波分辨方法的可行性。

一种综合多特征和超像素的SAR湿地水淹频率计算方法

湿地水域变化影响湿地生态功能发育,研究湿地水淹频率有助于湿地监测管理。为研究合成孔径雷达(SyntheticAperture Radar,SAR)多极化特征在湿地水淹频率中的应用,本文基于Sentinel-1雷达数据,提出一种综合多极化特征和超像素优化的SAR湿地水淹频率计算方法。该方法结合优化的雷达水体指数,采用统计投票,融合多极化特征和超像素空间上下文信息,能准确地识别水体,进而计算全年的湿地水淹频率。本文通过Google Earth Engine(GEE)平台,选取洞庭湖2020年的Sentinel-1 SAR数据展开试验,本文方法水体的提取精度为93.96%,计算的水淹频率分布与洞庭湖地势特点相符。

水平定向结晶法(HOC法)合成变石的宝石学及谱学特征

目前市场上合成变石中以提拉法合成产品为主,水平定向结晶法(HOC法)合成变石产品相对少见,其宝石学与谱学特征的研究资料仍有待补充。本文选择8颗来自俄罗斯厂家的HOC法合成变石样品为研究对象,采用折射仪等常规宝石学仪器、激光剥蚀电感耦合等离子体质谱仪、能量型色散X射线荧光能谱仪、紫外-可见光光谱仪、荧光光谱仪、拉曼光谱仪和傅里叶变换红外光谱仪对该类样品进行测试分析,探究其包裹体特征,微量元素组成、红外光谱、紫外-可见光光谱和荧光光谱等特征及与天然变石的差异。放大观察结果显示,HOC法合成变石样品的典型内含物为大量定向拉长空洞以及簇状金属包裹体。化学成分测试显示含有致色元素Cr和V,Cr含量较天然变石偏高;Fe元素含量极低,Mg、Ti、Ga等元素含量较天然变石低,且具有异常高的Mo含量,推测为金属Mo坩埚残余所致。紫外-可见光光谱仪测试结果显示为典型Cr谱,在橙黄光区与紫光区有两个宽的吸收带,645、656 nm处具有肩峰,680 nm处具有弱吸收峰。三维荧光光谱显示HOC法合成变石具有678、680 nm处强荧光峰以及690、696 nm处弱荧光峰,均为Cr元素所致,不具有天然变石中Ti和O元素的配合物所致460~550 nm处的发光中心。红外吸收光谱显示不具有天然变石特有的2160、2402 cm^(-1)处吸收峰以及3000~3500 cm^(-1)范围内与水有关的吸收。