毫米波成像准光路设计与测量

为提高毫米波成像系统的空间分辨率,研究了毫米波成像准光路设计方法。讨论了聚焦元件的截断效应,研究了天线增益与束腰半径关系并利用高斯波束法设计了毫米波成像准光学系统,在系统参数确定的前提下对聚焦元件进行一体化设计。实验测量了准光路参数及透镜的聚焦效果,给出了实验结果并分析了透镜参数对实验误差的影响,证明了设计过程的有效性。设计过程步骤明确,设计结果与实测结果较为一致,对毫米波成像准光学系统的设计具有一定实用价值。     

火箭弹多模导引头对复杂气象环境适用性研究

目的计算分析火箭弹多模导引头对复杂气象的环境适用性,为作战使用提供参考。方法采用气溶胶衰减计算公式,建立探测距离与波长、相对湿度、能见度关系,运用MATLAB计算光学成像系统在雾霾条件下的探测距离。依据约翰斯顿准则计算光学探测设备一定高度上对目标的捕获识别概率,从而判断有云环境条件下,云底高度对探测设备的影响。根据毫米波雷达最大作用距离模型和雨滴特性,建立其降雨衰减模型,计算分析降雨率对毫米波雷达探测距离的影响。结果获取了雾霾条件下探测距离随相对湿度和波长的变化规律,确定了有云条件下导引头对云底高度的最低要求,绘制了降雨条件下毫米波雷达对不同目标的探测距离随降雨率的变化曲线。结论火箭弹多模复合导引头充分发挥了不同探测设备的优势,对复杂天气环境具有较好的适用性。     

高轨高时空分辨大气二氧化碳监测仪

与世界经济快速增长相伴的碳排放量增加导致了全球气候变暖加剧,已引起国际社会高度关注,减排的呼声高涨。卫星遥感具有宏观、快速、定量、准确等特点,是碳监测最可行、最有效的技术支撑手段之一。为解决现有低轨大气CO₂遥感探测中存在的时间分辨率低的问题,提出了一种地球静止轨道大气CO₂柱浓度探测的时空联合调制空间外差干涉成像光谱技术。基于该技术研制了高轨高时空分辨大气二氧化碳监测仪原理样机,具有O₂-A 0.76μm、CO₂弱吸收1.57μm和CO₂强吸收2.05μm 3个探测通道,空间分辨率优于3 km@36000 km,可实现CO₂探测精度优于2×10^-6,覆盖中国区域时间分辨率优于3.5 h的探测能力。基于原理样机开展了外场试验以及航飞试验,有效反演了不同目标区域的CO₂浓度信息,验证了高轨高时空分辨大气CO₂监测仪的技术可行性,为下一代碳监测载荷研制和数据应用提供技术基础。     

毫米波云雷达与激光云高仪气象探测性能对比分析

为评估毫米波云雷达及激光云高仪的探测性能,选取广州市气象局KA波段毫米波云雷达和激光云高仪云高观测数据,通过对比两种测云设备在相同条件下的差异,分析不同要素对观测设备的影响,结果表明：(1)毫米波云雷达与激光云高仪同时探测到有云时,二者在云底高度观测上吻合程度较高,相关系数为0.98;(2)在数据获取率上,云雷达对高云的探测能力明显优于激光云高仪,但在对低云的探测能力上还有待提高,和激光云高仪相比,云雷达对低云和中云的识别能力有待提高;(3)对于多层云的观测,低层云的遮挡降低了激光云高仪对中高层云的观测,激光云高仪探测的中高层云多数在云雷达的回波内部.(4)对于不同强度的降水,日降水量越多,该天所测得的高、中云层回波就越少.(5)通过边界层高度与污染物的关系分析可以得出,边界层高度与PM2.5浓度呈反比.这些研究能够对毫米波云雷达和激光云高仪的探测能力进行评估,为后续选择设备提供参考,也推动了云观测技术的发展.     

杭州市大气气溶胶光学特性研究

利用太阳分光光度计（CE-318）对杭州市地面的气溶胶光学特性进行观测,并对卫星反演的中分辨率成像光谱仪（Moderate Resolution Imaging Spectroradiometer,MODIS）气溶胶产品进行验证.结果表明,MODIS气溶胶产品在杭州地区的精度较高,3个站点全部数据回归曲线的斜率和截距分...     

三频卫星信标测量TEC方法探讨及数值模拟

针对三频信标高精度探测的特点,开展了部分比较和模拟工作,结果表明采用三频信标获得的TEC精度高于双频信标。电离层CIT成像的结果显示,采用三频信标能够探测出较小尺度的电离层扰动,而双频信标对小尺度扰动的探测结果往往无能为力。     

基于改进电法装置和深度神经网络的填埋场渗滤液水位探测

渗滤液水位检测和管控是填埋场环境风险管控的关键之一,高密度电法装置具有无损、快速和分辨率高等优点,但填埋场铺设的HDPE防渗膜的高阻特性掩盖了渗滤液的低阻特性,反演结果存在探测精度差、探测范围有限等问题,无法有效识别渗滤液水位. 为此,本文设计了改进的川字型采集装置并配套提出了基于深度神经网络的非线性反演算法——EConvNet-C,通过构建高仿真模拟模型获得了代表性场景下的学习样本,并进行学习训练得到了渗滤液水位与观测数据的非线性映射关系. 对上述改进的电法装置和配套的反演算法的有效性进行了验证,并开展了实际填埋场地的案例研究. 结果表明:①基于川字型装置的EConvNet-C反演的电阻率存在明显的分层特征,在场景A中EConvNet-C反演算法的均方误差(MSE)均在0.00230以下,渗滤液水位探测精度均在90.0%以上. ②以“浅层滞水”形式非正常积存情况下,EConvNet-C探测精度略有下降,但MSE仍在0.00420以下,水位探测精度仍在80.0%以上. ③基于传统探测装置的深度神经网络耦合方法得到的渗滤液水位探测精度略低于基于川字型装置的EConvNet-C,而基于传统探测装置的线性反演耦合方法在HDPE膜高阻特性的影响下无法有效识别渗滤液水位. 因此,基于川字型装置的EConvNet-C在填埋场渗滤液水位探测领域具有较大潜力,可为后期开展垃圾填埋场的性能和风险评估提供指导.      

基于热成像技术的污水排放源识别研究

污水暗排口是一种较难监测的污染源.为了更好地探索监测这种污染源的方法,本研究以北京市城区积水潭处的护城河为对象,利用热成像技术对模拟污水暗排口进行了探测.结果表明,模拟污水与河道中的原水的温度分布存在显著差异,原水温度分布均匀,而模拟污水排入后水面温度呈辐射状同心圆分布,从红外图像上可以明确地把两种水体区分开来.实验还研究了在异质水体排入时水面红外图像特征随时间的变化情况.结果表明,在有异质水体排入时,图像中会出现温度异常的水域;随着异质水体的持续排入,温度异常水域开始逐渐扩大.研究结果为利用热成像技术遥感监测污水暗排口提供了依据.     

基于毫米波的海上目标RCS测量标定分析

目的提高靶场毫米波海上目标RCS测量标定精度。方法针对海上目标的外场雷达目标特性(Radar Cross Section,RCS)测量系统动态标定问题,在给出了无源相对标校法的基础上,对毫米波RCS测量系统标定过程中云雾杂波、大气衰减、海面及地面杂波的影响进行详细分析。结果结合靶场外场实际测量,提出了衰减修正、合理选择标校气象条件等相应减小标定误差的措施。结论基于毫米波海上目标RCS测量标定的分析及其措施可极大地减小毫米波外场海面测量标校中气象环境、海面或地面杂波等对系统标定的影响,提高系统标定精度。     

激光雷达相干成像原理及其研究的若干问题

总结了激光雷达相干成像技术研究现状和进展,根据激光相干成像一般原理,针对2种最新激光雷达即距离高分辨多普勒和合成孔径相干成像技术,给出其系统技术框架和成像效果。分析了激光雷达相干成像特点及系统设计所必须解决的技术难点,指出解决问题的方案和注意问题,为我国进一步开展空间、空中和地基平台激光雷达相干成像试验研究和理论仿真奠定预先技术支持。     

Magnetic resonance spectroscopy of the fetal brain

Fetal magnetic resonance spectroscopy (MRS) is technically feasible in utero and demonstrates similar findings to those observed in neonatal populations. MRS can provide additional information to conventional T1- and T2-weighted imaging of the fetal brain. It is of particular use when subtle changes are present on conventional fetal MRI sequences, and when imaging fetuses at risk of brain injury and metabolic abnormalities. Copyright © 2009 John Wiley & Sons, Ltd.     

A selective N,N-dithenoyl-rhodamine based fluorescent probe for Fe3+ detection in aqueous and living cells

A novel N,N-dithenoyl-rhodamine based fluorescent and colorimetric Fe3+probe 1 was designed and synthesized by only one step from Rhodamine B hydrazide and 2-thiophenecarbonyl chloride.The structure of probe 1 was characterized by ~1 H NMR/~(13)C NMR spectroscopy,IR spectroscopy,and HRMS spectrometry.Accompanying with significant changes in visual color and fluorescent spectrum,probe 1 displayed good sensitivity for Fe~(3+)with an abroad pH span.The detection limit(3.76 μmol/L,0.2 mg/L) for Fe~(3+)was lower than WHO recommended value(0.3 mg/L) for drinking water.Using two thiophene carbonyl groups as coordinating functional recognition group,probe 1 showed excellent selectivity towards Fe3+over diverse coexistent metal ions and anions.The sensing mechanism between dithenoyl-substituted probe 1 and Fe~(3+)was further confirmed by ~1 H NMR and IR titration experiments,binding constants study,and Job's plot analysis.Furthermore,probe 1 also exhibited good cell membrane permeability and could be used as an efficient Fe~(3+) probe in living human cells.     

Prenatal diagnosis of tuberous sclerosis. Use of magnetic resonance imaging and its implications for prognosis

Tuberous sclerosis (TS) is an autosomal dominant disorder with a high rate of de novo mutation. The real difficulty is to ascertain the diagnosis and to give the neurological prognosis in each case. Prenatal diagnosis of TS is generally based on ultrasonographic signs of multiple cardiac tumours, i.e. rhabdomyomas. Recent progress in magnetic resonance imaging (MRI) enables the diagnosis in a large proportion of cases based on typical brain lesions. It may have a role in the prenatal management of TS, although MRI images seem to underestimate the anatomical findings. Two cases in which TS was diagnosed prenatally are presented with reference to the value of MRI in the prenatal management and comparison with anatomical findings.     

Postnatal investigation of fetal renal disease

The antenatal ultrasound diagnosis of renal tract abnormalities is now firmly established. Postnatal imaging protocols are constantly evolving and still many questions remain unanswered. Most infants are asymptomatic at birth and aggressive imaging is unwarranted both for the infant and overburdened Radiology departments. The urgency with which to undertake imaging relates to the suspected antenatal diagnosis and clinical scenario, with bilateral hydronephrosis, posterior urethral valves and complicated duplex systems taking a high priority. The main imaging modality postnatally remains ultrasound, and together with nuclear medicine gives a powerful combination of both anatomy and function. Intravenous urography is never indicated in the neonate. Copyright © 2001 John Wiley & Sons, Ltd.     

Three-dimensional ultrasound in evaluating the fetus

In recent years three-dimensional (3D) ultrasound has made a place in clinical practice and has become a major field of research in obstetrics. In this article we will review the diagnostic performance of the most widely used 3D ultrasound applications in the assessment of fetal anomalies, explain the technique to gain correct 3D images and offer some practical advice for their efficient use. Examples are given to demonstrate the applicability and vividness of 3D in daily routine. Copyright © 2010 John Wiley & Sons, Ltd.