Damage to mangroves from extreme cold in early 2008 in southern China

通讯作者Author for correspondence (E-mail: [email protected])2008年初,我国南方19个省经历了50年一遇的持续低温雨雪冰冻天气。极端气候对华南沿海各省的红树林区造成不同程度的危害。2008年3月,在我国南方各省红树林区的10个代表性地点,对这次寒害造成的红树植物伤害程度进行了系统的调查。结果表明:冬季低温对红树林的影响极为显著,特别是在低纬度的海南、广西和广东湛江,由于极端低温正值夜间退潮,对红树林的影响更为显著;在纬度较高的福建,本地红树种类秋茄(Kandelia obovata)、桐花树(Aegiceras corniculatum)和白骨壤(Avicennia marina)及引种的木榄(Bruguiera gymnorrhiza)等,由于长期适应于冬季较低的气温或在种植前经过抗寒锻炼,具有较强的抗寒能力。各地主要红树植物中,广布种秋茄、桐花树和白骨壤最为耐寒,其耐寒性均大于红树科的木榄、海莲(Bruguiera sexangula)和红海榄(Rhizophora stylosa)。海桑(Sonneratia caseolaris)对温度的敏感性最强,抗寒能力最低,因此,即使在其原产地海南也受到较为严重的寒害,在纬度更高的引种地出现大面积受害甚至全部死亡,而从孟加拉国引种的无瓣海桑(Sonneratia apetala)却显示出一定的抗寒能力。同一地点的红树植物幼苗的抗寒能力低于大树。此次寒害也造成了苗圃场的种苗大量死亡,成熟的植株提前落花落果,这势必会影响后继一两年内红树林的自然更新和人工造林。因此,在未来红树林造林或人工引种中,一定要考虑到红树植物的抗寒能力。国家自然科学基金(30671646和30700092);厦门大学“闽江学者”启动基

Research on Characterization and Evaluation of Electro-Optical Imaging System Performance

光电成像系统性能表征与评估方法是系统论证、设计、测试、评价等环节的理论基础。随着光电成像探测技术的迅速发展，如何从系统角度建立性能模型、确立性能指标及评价方法，与构成光电成像系统的光学技术、电子技术、信息处理技术等单项技术一道，成为光电信息科学与光电工程领域的重要研究课题，具有重要的学术与应用价值。 本文以提高光电成像系统性能遇到的制约问题为牵引，开展光电成像系统性能表征与评估方法研究，旨在从系统总体的角度研究光电成像系统性能与光学系统、探测器、信息处理等分系统的物理模型与计算模型；并从系统使用角度建立人眼视觉和机器视觉两种工作模式下系统使用性能的计算模型。研究内容和成果包括： 1、成像传感器性能表征研究。通过研究成像过程的物理机理，以成像传感器的能量传递特性、空间分辨特性和极限探测能力为三条主线，分别给出了成像传感器的响应度、灵敏度和分辨率计算模型；研究了采样成像传感器客观存在的信号混叠问题，据此提出了精确的成像传感器最小可分辨对比度MRC计算模型。与此同时，对归一化探测率D*、噪声等效温差NETD、极限分辨率等关键性能指标提出了简化计算模型，为光电成像系统固有性能预计建立了较为完善的理论体系。 2、成像传感器性能模型的实验验证方法研究。针对各项性能表征模型设计了相应的物理验证实验，验证了模型的正确性。提出了两项创新的测量方法：一是针对调制传递函数MTF传统测量方法存在的采样相位效应问题，提出了一种基于累积直方图的MTF精确测量方法；二是设计了基于楔形条纹的MRC测试方案，通过计算机自动判读楔形条纹，实现了最小可分辨对比度的客观测量。利用噪声计算模型，提出了一种精确且简易的CCD满阱电荷和本底噪声的标定方法。 3、基于人眼视觉机理的性能表征研究。深入研究并完善了目标获取任务性能TTP模型，对TTP模型提出了修正、改进和扩展：根据帕萨瓦尔定理，推导出系统对比度阈值函数的计算模型，修正了TTP模型存在的时间采样积分问题；引入非均匀性噪声因素，改进了TTP模型，使模型对噪声预测更精确；联合了涵盖目标/背景材质、太阳-观测几何、大气传输特性等光电探测对象与条件，给出了目标/背景对比度计算模型，扩展了TTP模型。 4、面向机器视觉的性能表征研究。基于统计理论指出了成像探测识别与跟踪问题的数学内涵；提出了基于CRLB的目标-图像参数估计方法，实现了自动目标跟踪中图像匹配精度的预测；提出了基于最小错误概率准则的目标-图像假设检验方法，实现了成像探测错误率的预测

Performance Prediction Method of Photoelectric Imaging Detection System

提出一种光电成像探测系统的性能预测方法。介绍包含传感器、处理器的探测系统模型。根据信号检测理论,以最小错误概率准则设计似然比探测器,利用中心极限定理计算错误率。实验结果表明,随着量化位数的增大,系统错误率逐渐减少,且计算错误率与仿真错误率趋于一致

Infrared Image Non-uniformity Correction Based on Joint Surface of Radiation and Environment Temperature

在传统红外图像非均匀性校正方法中,探测器均处在常温环境下,当探测器的环温在一个较宽的范围内变化时,这些方法的校正效果便会恶化、不适应。针对此问题,本文在原常温多点标定法的基础上提出了一种基于曲面拟合的校正方法,把原先标定曲线加上探测器环温维度扩展成标定曲面。随后的纵向对比实验和横向对比实验表明该方法能够显著降低非均匀性,并能适应环温变化的情况

Non-uniformity correction in polarization imaging obtained with integrated microgrid polarimeters

针对传统的非均匀校正算法难以校正偏振成像的非均匀问题,提出了一种新的矩阵校正算法。分析了偏振成像与非偏振成像的非均匀性的不同表现,阐述了微偏振片阵列成像的非均匀产生机理,指出了采用非偏振成像非均匀校正方法的失效原因。在构建偏振成像系统对入射偏振光源的响应模型基础上,提出了矩阵校正法。实验部分给出了矩阵校正法对均匀偏振场本底图像和信息丰富场景图像的校正效果,定量分析结果表明,矩阵校正法将均匀本底图像的非均匀性降至校正前的10%左右

氰化磨矿浸出工艺优化试验研究

为了打破现有氰化生产中传统磨矿、分级及浸出工艺,达到提高磨矿效率、氰化回收率和降低生产能耗的目标,金翅岭金矿进行氰化磨矿浸出工艺的优化试验研究,通过对矿物进行一次性磨矿浸出试验与分段磨矿浸出试验对比发现,矿物一次性磨矿至合格细度-400目细度达到90%,浸出12 h时,氰化回收率可达到99.5%;分段磨矿分段浸出一次磨矿细度为-400目占75%,一次浸出时间为16 h,分级后+400目再磨细度为91%,浸出时间为12 h时,总回收率可达99.64%。分段磨矿浸出磨机节约能耗约15%,氰化回收率提高0.14%

Dim air target detection based on radiation accumulation and space Inversion

背景辐射嗓声是弱信号检测面临的难点问题。提出了一种显著提升信嗓比实现匀速运动弱目标的有效检测算法。建立目标坐标空间和速度空间，以不同速度矢量控制图像叠加，形成提升了信嗓比的新的图像序列并构成图像空间;利用恒虚警判决法在图像空间中检测候选目标点;根据候选目标点所对应的坐标向量和速度向量分别映射到坐标空间和速度空间，由两个空间中出现的峰值判定目标点。实际红外成像系统实拍实验表明，算法能将信嗓比提升至接近原图的倍，目标检测概率和虚警概率都明显优于所对比的弱目标检测算法。 <br type="_moz" /

Multiple dim targets detection in infrared image sequences

Strong noises interference is a difficult technical problem for signals detection. Multiple targets detection with strong noises makes the problem more complicated. Aiming at the difficulty of multiple uniform rectilinear motion targets detection in infrared (IR) image sequences with strong noises, this paper presents a multiple dim targets detection algorithm which improves signal-to-noise ratio (SNR). Firstly, we establish a velocity space and stack image sequences along different velocity vectors. Secondly, mean filtering in time-domain is applied to stacked images. Thirdly, quasi-target points in mean filtering images are selected by constant false-alarm ratio (CFAR) judging. Finally, coordinate vectors and velocity vectors of quasi-target points are mapped to location space and velocity space, respectively. As a result, local peaks from the two spaces will confirm target points; meanwhile, velocity vectors of targets can also be acquired. In addition, effect of velocity steps on SNR improvement is analyzed, which can guide the selection of steps and reduce computational burden. Both moving dim targets simulation experiment and real-world dim targets detection experiment have proved that this algorithm can effectively detect multiple dim targets under strong noise background

Calculating model for equivalent thermal defocus amount in infrared imaging system

The main effect of temperature change on infrared imaging system is the focus shift of infrared lenses. This paper analyzes the equivalent influence on imaging between the temperature change and the defocus at room temperature. In order to quantify the equivalence, we define an equivalent thermal defocus amount (ETDA). The ETDA describes the distance of the photosensitive surface shifting at room temperature, which has the same effect on imaging as the temperature changes. To model the ETDA, the expression of the focal shift as a function of temperature is obtained by solving partial differential equations for the thermal effect on light path firstly with some approximations. Then point spread functions of the thermal effect and defocus at room temperature are modeled based on wave aberration. The calculating model of ETDA is finally established by making their PSFs equal under the condition that the cutoff frequency of infrared imaging systems is much smaller than that of infrared lens. The experimental results indicate that defocus of ETDA at room temperature has the same influence on imaging as the thermal effect. Prospectively, experiments at high/low temperature can be replaced by experiments at room temperature with ETDA

ZnSe-material phase mask applied to athermalization of infrared imaging systems

This paper reports a ZnSe-material phase mask that is applied to athermalization of a conventional infrared imaging system. Its principle, design, manufacture, measurement, and performance validation are successively discussed. This paper concludes that a ZnSe-material phase mask has a permissible manufacturing error 2.14 times as large as a Ge-material phase mask. By constructing and solving an optimization problem, the ZnSe-material phase mask is optimally designed. The optimal phase mask is manufactured and measured with a form manufacturing error of 1.370 &mu;m and a surface roughness value of 9.926 nm. Experiments prove that the wavefront coding athermalized longwave infrared (LWIR) imaging system works well over the temperature range from -40&deg;C to +60&deg;C