Remote sensing of air pollution incorporating integrated-path differential-absorption and coherent-Doppler lidar

An innovative complex lidar system deployed on an airborne rotorcraft platform for remote sensing of atmospheric pollution is proposed and demonstrated.The system incorporates integrated-path differential absorption lidar(DIAL) and coherent-doppler lidar(CDL) techniques using a dual tunable TEA CO_(2)laser in the 9—11 μm band and a 1.55 μm fiber laser.By combining the principles of differential absorption detection and pulsed coherent detection,the system enables agile and remote sensing of atmospheric pollution.Extensive static tests validate the system’s real-time detection capabilities,including the measurement of concentration-path-length product(CL),front distance,and path wind speed of air pollution plumes over long distances exceeding 4 km.Flight experiments is conducted with the helicopter.Scanning of the pollutant concentration and the wind field is carried out in an approximately 1 km slant range over scanning angle ranges from 45°to 65°,with a radial resolution of 30 m and10 s.The test results demonstrate the system’s ability to spatially map atmospheric pollution plumes and predict their motion and dispersion patterns,thereby ensuring the protection of public safety.

Venous Doppler flow patterns,venous congestion,heart disease and renal dysfunction:A complex liaison

The World Journal of Cardiology published an article written by Kuwahara et al that we take the pleasure to comment on.We focused our attention on venous congestion.In intensive care settings,it is now widely accepted that venous congestion is an important clinical feature worthy of investigation.Evaluating venous Doppler profile abnormalities at multiple sites could suggest adequate treatment and monitor its efficacy.Renal dysfunction could trigger or worsen fluid overload in heart disease,and cardio-renal syndrome is a well-characterized spectrum of disorders describing the complex interactions between heart and kidney diseases.Fluid overload and venous congestion,including renal venous hypertension,are major determinants of acute and chronic renal dysfunction arising in heart disease.Organ congestion from venous hypertension could be involved in the development of organ injury in several clinical situations,such as critical diseases,congestive heart failure,and chronic kidney disease.Ultrasonography and abnormal Doppler flow patterns diagnose clinically significant systemic venous congestion.Cardiologists and nephrologists might use this valuable,noninvasive,bedside diagnostic tool to establish fluid status and guide clinical choices.

First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry

The first results of investigation of the turbulence structure using Doppler backscattering(DBS)on the Globus-M2 tokamak are presented.A one-channel DBS system with a variable probing frequency within the 18–26 GHz range was installed to investigate the edge plasma at normalized minor radiiρ=0.9–1.1.Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition.Correlation analysis was applied to the phase derivative of complex in-phase and quadrature(IQ)signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity.In L-mode,the radial correlation length L_(r)is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm.Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rate at the normalized minor radiusρ=0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient(ITG)mode.

Observation of Low-Level Jets in the Eastern Tropical Indian Ocean Based on Shipborne Coherent Doppler Lidar

In contrast to the Pacific and Atlantic Oceans,the Indian Ocean has lacked in-situ observations of wind profiles over open sea areas for decades.In 2021,a shipborne coherent Doppler lidar(CDL)was used to observe in-situ wind profiles in the eastern tropical Indian Ocean.This equipment successfully captured low-level jets(LLJs)in the region,and their characteristics were thoroughly analyzed.Results reveal that the observed wind speed of LLJs in the eastern Indian Ocean ranges from 6 m s^(-1) to 10 m s^(-1) during the boreal winter and spring seasons,showing a height range of 0.6 to 1 km and two peak times at 0800 and 2000 UTC.This wind shear is weaker than that in land or offshore areas,ranging from 0 s^(-1) to 0.006 s^(-1).Moreover,the accuracy of the CDL data is compared to that of ERA5 data in the study area.The results indicate that the zonal wind from ERA5 data significantly deviated from the CDL measurement data,and the overall ERA5 data are substantially weaker than the in-situ observations.Notably,ERA5 underestimates northwestward LLJs.

Comparison and Verification of Coherent Doppler Wind Lidar and Radiosonde Data in the Beijing Urban Area

As a new type of wind field detection equipment, coherent Doppler wind lidar(CDWL) still needs more relevant observation experiments to compare and verify whether it can achieve the accuracy and precision of traditional observation equipment in urban areas. In this experiment, a self-developed CDWL provided four months of observations in the southern Beijing area. After the data acquisition time and height match, the wind profile data obtained based on a Doppler beam swinging(DBS) five-beam inversion algorithm were compared with radiosonde data released from the same location. The standard deviation(SD) of wind speed is 0.8 m s^(–1), and the coefficient of determination R~2 is 0.95. The SD of the wind direction is 17.7° with an R~2 of 0.96. Below the height of the roughness sublayer(about 400 m), the error in wind speed and wind direction is significantly greater than the error above the height of the boundary layer(about 1500 m). For the case of wind speeds less than 4 m s^(–1), the error of wind direction is more significant and is affected by the distribution of surrounding buildings. Averaging at different height levels using suitable time windows can effectively reduce the effects of turbulence and thus reduce the error caused by the different measurement methods of the two devices.

Decoupling of temporal/spatial broadening effects in Doppler wind LiDAR by 2D spectral analysis

Pulse echo accumulation is commonly employed in coherent Doppler wind LiDAR(light detection and ranging)under the assumption of steady wind.Here,the measured spectral data are analyzed in the time dimension and frequency dimension to cope with the temporal wind shear and achieve the optimal accumulation time.A hardware-efficient algorithm combining the interpolation and cross-correlation is used to enhance the wind retrieval accuracy by reducing the frequency sampling interval and then reduce the spectral width calculation error.Moreover,the temporal broadening effect and spatial broadening effect are decoupled according to the strategy we developed.

Observation of Doppler shift f_(D) modulated by the internal kink mode using conventional reflectometry in the EAST tokamak

In this paper we present a new experimental observation using a conventional reflectometry technique,poloidal correlation reflectometry(PCR),in the Experimental Advanced Superconducting Tokamak(EAST).The turbulence spectrum detected by the PCR system exhibits an asymmetry and induced Doppler shift f_(D)during the internal kink mode(IKM)rotation phase.This Doppler shift f_(D)is the target measurement of Doppler reflectometry,but captured by conventional reflectometry.Results show that the Doppler shift f_(D)is modulated by the periodic changes in the effective angle between the probing wave and cutoff layer normal,but not by plasma turbulence.The fishbone mode and saturated long-lived mode are typical IKMs,and this modulation phenomenon is observed in both cases.Moreover,the value of the Doppler shift f_(D)is positively correlated with the amplitude of the IKM,even when the latter is small.However,the positive and negative frequency components of the Doppler shift f_(D)can be asymmetric,which is related to the plasma configuration.A simulated analysis is performed by ray tracing to verify these observations.These results establish a clear link between f_(D)and IKM rotation,and are helpful for studying the characteristics of IKM and related physical phenomena.

Opto-mechanical-thermal integration analysis of Doppler asymmetric spatial heterodyne interferometer

In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne(DASH)interferometer in harsh temperatures,an opto-mechanical-thermal integration analysis is carried out.Firstly,the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer.Secondly,the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed.The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis,and the phase error caused by thermal deformation is obtained by fitting.Finally,based on the wind speed error caused by thermal deformation of each component,a reasonable temperature control scheme is proposed.The results show that the interference module occupies the main cause,the temperature must be controlled within(20±0.05)℃,and the temperature control should be carried out for the temperature sensitive parts,and the wind speed error caused by the part is 3.8 m/s.The thermal drift between the magnification of the imaging optical system and the thermal drift of the relative position between the imaging optical system and the detector should occupy the secondary cause,which should be controlled within(20±2)℃,and the wind speed error caused by the part is 3.05 m/s.In summary,the wind measurement error caused by interference module,imaging optical system,and the relative position between the imaging optical system and the detector can be controlled within 6.85 m/s.The analysis and temperature control schemes presented in this paper can provide theoretical basis for DASH interferometer engineering applications.

Clinical Versus Doppler Based Assessment in Determining Amputation Level in Diabetic Foot Gangrene;A Prospective Cross-Sectional Study at Atbuth, Bauchi

Background: Amputation is defined as the surgical removal of a limb or part of a limb through the bone. If the amputation is done above or below the knee, they are termed major while minor amputations involve the partial removal of foot including forefoot resections, ray amputation of the digits or parts of the digits. Significant number of patients with diabetic foot ulcers end with amputations. In the past the amputation level was decided by clinical assessment alone, such as physical examination using color, temperature, peripheral pulses and wound bleeding during surgical procedure. The use of Doppler ultrasound to measure arterial blood pressure at the proposed amputation site has been advocated as a predictor of amputation success. An optimal choice of the level of amputation can reduce amputation complications. Methodology: A Prospective comparative randomized cross-sectional study carried out between 1st January 2022 and 1st January 2024 in ATBUTH, Bauchi amongst patients with diabetic foot Wagener stage IV and V scheduled for amputation. Outcome measures of wound break down, flap necrosis and re-amputation were assessed amongst the clinical based level assessment group and the doppler based level assessment group. Results: A total of 171 patients were recruited into the study. Males 103 and 68 are females, giving a male to female ratio of 1.5:1. mean age 47 years. There were 84 patients in the clinical based level assessment group and 87 patients in the doppler based level assessment. Conclusion: Diabetes mellitus foot disease is a significant risk factor for non-traumatic lower limb amputation and doppler level assessment is superior to clinical level in determining amputation level among diabetic patients scheduled for amputation. P-value 0.003.

Right-to-left shunt detection via synchronized contrast transcranial Doppler combined with contrast transthoracic echocardiography:A preliminary study

BACKGROUND Patent foramen ovale(PFO)-related right-to-left shunts(RLSs)have been impli-cated in cryptogenic stroke and migraine,with larger shunts posing a higher risk.When used individually to detect RLS,contrast transcranial Doppler(cTCD)and contrast transthoracic echocardiography(cTTE)may yield false-negative results.Further,the literature exposes gaps regarding the understanding of the limitations of cTCD and cTTE,presents conflicting recommendations on their exclusive use,and highlights inefficiencies associated with nonsynchronous testing.AIM To investigate the accuracy of multimodal ultrasound to improve diagnostic efficiency in detecting PFO-related RLSs.METHODS We prospectively enrolled four patients with cryptogenic stroke(n=1),migraine(n=2),and unexplained dizziness(n=1)who underwent synchronized cTCD combined with cTTE.The participants were monitored and followed-up for 24 months.RESULTS cTTE identified moderate and large RLSs in patients with recurrent cryptogenic stroke and migraines,whereas cTCD revealed only small RLSs.Moderate and large RLS were confirmed on combined cTTE and cTCD.After excluding other causes,both patients underwent PFO occlusion.At 21-and 24-month follow-up examinations,neither stroke nor migraine had recurred.cTTE revealed a small RLS in a third patient with unexplained dizziness and a fourth patient with migraines;however,simultaneous cTCD detected a large RLS.These patients did not undergo interventional occlusion,and dizziness and headache recurred at the 17-and 24-month follow-up examin-ations.CONCLUSION Using cTTE or cTCD may underestimate RLS,impairing risk assessments.Combining synchronized cTCD with cTTE could enhance testing accuracy and support better diagnostic and therapeutic decisions.

Abnormal Umbilical Doppler: Incidence and Neonatal Outcomes among Hypertensive Disorders in Pregnancy at KCMC: A Hospital-Based Prospective Cohort Study

Hypertensive disorders of pregnancy (HDP) are the most common maternal and perinatal health challenges. Globally, the incidence of HDP increased from 16.30 million to 18.08 million, with a total increase of about 10.9% from 1990 to 2019. Umbilical Doppler study in hypertensive disorders of pregnancy helps to predict neonatal outcomes and prevent neonatal and maternal morbidity and mortality. Objective: This study aims to determine the incidence of abnormal umbilical Doppler among hypertensive pregnant women, to identify the adverse neonatal outcomes associated with abnormal umbilical Doppler, and also to detect the diagnostic predictive values of umbilical Doppler to neonatal outcomes at KCMC. Material and methods: A hospital-based prospective cohort study included women with hypertensive disorders of pregnancy from the gestational age of 28 weeks and above, followed up to delivery during the study period from August 2022 to March 2023. Multivariate logistic regression analysis was used to determine the association between AUD and neonatal outcomes. Results: Out of 112 women with HDP, the incidence of abnormal umbilical Doppler was 38 (33.93%). Abnormal umbilical Doppler was associated with neonates with low birth weight aOR (95% of CI) of 4.52 (1.59 - 12.83) p = 0.005 and neonatal ICU admission 9.71 (2.90 - 32.43) p Conclusion: The incidence of abnormal umbilical Doppler is high in hypertensive disorders of pregnancy which is associated with an increase in neonatal low birth weight and neonatal ICU admissions, the sensitivity of abnormal umbilical Doppler in prediction of low birth weight and neonatal ICU admission is significant hence the routine use of umbilical Doppler assessment among hypertensive pregnant women is crucial.

高频波在IAR中传播的Doppler效应

根据高频波在电离层阿尔芬谐振器 (IAR)中的传播特性 ,将普适的Doppler频移公式具体化 ,以此为出发点 ,深入分析了IAR中产生Doppler效应的多种原因 ,尤其是IAR中粒子漂移 (包括电子和离子 )对产生Doppler频移的影响 ,并计算了相应的频移大小 .结果表明 :在IAR中 ,高频波Doppler频移可以达到几十Hz,其中电子漂移运动和飞船运动引起的高频波Doppler频移占主要地位 ,反射波相位变化引起的频移在入射波的频率足够高时只有0 .1Hz左右 ,可以忽略不计 ;这为高频波Doppler频移的实验观测结果提供了理论依据 .

青藏高原地面Doppler雷达与TRMM星载雷达测云比较

利用 1998年青藏高原地面Doppler雷达资料和TRMMPR资料进行对比分析 ,分别从不同角度出发 ,分析了Doppler雷达和TRMMPR所测云区在回波结构和回波强度等方面的相同和差异之处 。

基于微Doppler提取的具有旋转部件雷达目标成像

雷达运动目标部件的振动和旋转运动会对目标回波信号引入附加的频率调制并产生关于Doppler中心频率的附加边带效应.这种附加的谱效应会对目标主体的ISAR像造成污染,严重时无法对目标主体进行成像.文中提出了一种基于Hough变换的微Doppler信息分离与提取方法,基于旋转部件的微Doppler谱与目标主体谱在谱图域表现形式的不同,利用Hough变换和一种推广的Hough变换分别将目标主体谱与旋转部件的微Doppler谱提取后既获得了具有大旋转部件一类目标的清晰像、同时也获得了目标旋转部件的一些运动及结构信息.最后,仿真结果验证了该方法的有效性.

双选择性信道下联合Doppler分集的MIMO-OFDM系统研究

提出联合考虑空间分集与Doppler分集的方法来提高时变多径衰落信道下高速移动通信系统的性能。给出了联合考虑空间分集与Doppler分集的MIMO系统模型,推导出了时变多径衰落信道下系统所能获得的最大分集阶为MtMr(L+1)(Q+1),并提出了利用空时编码、预编码和OFDM技术相结合来提高系统性能的方法。通过仿真验证了分集技术的结合可以带来系统性能的提高。

GPS/Doppler导航随机模型的移动窗口实时估计算法

引进时间遗忘因子和观测冗余度因子,有效地平衡移动窗口内不同时刻的观测数据及其冗余情况对单位权方差估值的贡献,改进单位权方差的移动开窗实时估计算法。采用载噪比模型确定观测权阵,等价权抗差估计方法处理粗差。实测车载GPS/Doppler数据的处理结果表明:采用本文算法显著提高GPS/Doppler的导航精度与可靠性。

单Doppler雷达IVAP风场反演试验

单Doppler雷达风场反演技术对于扩大Doppler雷达在中尺度气象监测和预报中的应用范围具有重要的作用。通过采用“给定方位角内风场均匀假定”提出积分速度—方位处理技术IVAP(IntegratingVelocity-AzimuthProcessing),克服了VAP技术在单多普勒雷达风场反演中对Doppler速度小尺度脉动过分敏感的缺点,及VAD(Velocity-AzimuthDisplay,速度-方位显示)技术只能反演平均风矢量问题。利用2001-08-05上海特大暴雨时虹桥机场Doppler雷达速度资料进行中尺度风场反演试验。对均匀风方位角区间分别取9°,18°,45°和90°的反演结果的比较表明,采用较小的方位角区间可以反演出与这次暴雨有关的气旋式环流和中尺度辐合线。利用地面站实测风记录及风廓线数据对IVAP反演风的质量进行了评估。结果表明,反演风的风向和地面实测风的风向有很好的相关性,反演方位角区间越大,相关性越好。与20个时次同高度上风廓线仪探测的风速数据的对比表明,IVAP技术反演出的风速和它们也有很好的相关性,两者u、v分量均方误差在2m/s左右。由于IVAP技术风场反演无需事先对Doppler雷达原始的速度资料进行人为的滤波或平滑处理,所以具有较强的客观性,便于在气象雷达预报业务中应用。

阴茎动脉Doppler超声分析

目的研究健康成年男性阴茎背动脉(DA)、海绵体动脉(CA)PI、RI及S/D的正常值。方法将257名健康成年男性按年龄分为5组,分别为<30岁组65名,30～39岁组83名,40～49岁组61名,50～59岁组38名,60岁以上组10名。用Logidop!2型数字式Doppler超声血流仪检查双侧阴茎背动脉、双侧海绵体动脉PI、RI及S/D值。结果阴茎疲软状态下,阴茎背动脉、海绵体动脉PI、RI和S/D值个体左右比较无差异,各年龄组也无差异。建议正常参考值分别为:(1)LDA:PI1.43～3.43,RI0.72～0.92,S/D2.68～10.56。(2)RDA:PI1.47～3.47,RI0.73～0.93,S/D3.27～10.09。(3)LCA:PI1.49～3.21,RI0.74～0.90,S/D3.17～9.55。(4)RCA:PI1.93～3.27,RI0.72～0.90,S/D3.22～9.42。结论作为一种筛选手段,Doppler超声血流检测手段,有一定的应用价值。

连续波Doppler引信扫频波辐照效应

为研究扫频波对连续波Doppler引信的效应规律及作用机理,开展了典型引信扫频波辐照效应试验,结合现有文献研究结论,提出了普适的扫频波辐照下连续波Doppler引信效应规律及作用机理。试验结果表明:扫频波辐照下引信会意外发火,引信临界干扰电场强度与扫频频段有关;扫频步长、频点驻留时间与引信是否意外发火密切相关,受试引信意外发火时要求扫频步长≥7 k Hz,频点驻留时间≤483 ms;扫频参数不会影响受试引信临界干扰电场强度。扫频波辐照下连续波Doppler引信意外发火原因为:扫频波频率变化导致引信自差机振荡状态发生跳变,引起高频电路输出电压波动,从而推动执行级误动作。

二维光子晶体中反常Doppler效应的相位演变

光在具有负等效折射率的二维光子晶体中传输时会产生反常Doppler现象,为了分析光在该反常效应中传输时的相位变化,首先用时域有限差分(FDTD)法仿真了光经过静止光子晶体时的负折射现象,然后对光子晶体中沿光传输方向的Bloch波做快速傅里叶(FFT)处理。对滤波后的频谱,用iFFT反演出各平面波分量,并通过分析各平面波分量的相位演变,分离出与负折射产生有关的后退波分量。然后,将实验中的连续运动过程分解为各静止瞬间,分析了各相邻时刻探测面上信号光和参考光的相位变化,此处两束光的相位变化差随时间的变化量就是差频。静态FDTD方法仿真计算得到的差频与理论值的误差约为20%,能较好解释反常Doppler效应发生过程中光的相位变化。本文的研究揭示了反常Doppler效应发生时光子晶体中起作用的分量的相位变化,也为研究光在运动介质中的传输特性提供了新的思路。