虚拟现实中的增强虚境技术

增强虚境技术在基于图形的建模与绘制(GBMR)框架下利用基于图像的建模与绘制(IBMR)方法描述复杂对象及加速场景绘制,可以解决虚拟现实研究中逼真绘制与实时显示间的矛盾.将国内外增强虚境方面的最新研究成果按融入合成场景中图像对象包含几何信息的比例划分成3大类,分别是在合成场景中融入纯图像对象、融入部分几何信息的图像对象及利用IBMR方法加速场景绘制,介绍了3类工作中新的研究成果,分析了这些成果的基本原理、方法、过程和优缺点,提出了该领域技术发展面临的5大问题及可能的解决方法．      

基于序列影像的小天体三维形状重建方法研究

提出了一种基于序列影像的小天体三维形状重建方法。利用小天体序列影像间的内在几何约束关系,在无精确位置、姿态数据的条件下,基于稀疏光束法平差求解小天体序列影像的相对位置、姿态。综合利用核线几何约束、半全局匹配、多视最小二乘匹配等策略进行小天体序列影像的密集匹配,重建小天体三维形状信息。由于小天体序列影像尺度变化大、纹理贫乏,导致影像匹配的误匹配率较高,在匹配过程中采用随机KD树搜索策略与拟合透视变换模型的RANSAC算法剔除粗差。利用"黎明号"探测器的绕飞段实测影像,对灶神星(VESTA)的三维形状重建进行了实验,结果证明了该方法的有效性。     

使用深度神经网络检测Cassini ISS图像中圆盘状星体轮廓

Cassini空间探测器光学成像系统（ISS）拍摄的图像中,很多卫星呈现为面元,其轮廓检测是天体测量的重要工作.使用神经网络方法进行ISS图像中面元轮廓检测.每个ISS图像的像素分为轮廓边缘和非轮廓两类.使用神经网络框架TensorFlow,输入每个像素的9个特征,输出每个像素的分类.利用约3.6万个像素训练该网络,通过380幅ISS图像进行测试.与人工标记结果相比,轮廓像素检测的平均精确率为78.26%,平均召回率为73.32%.以检出轮廓像素作为输入,通过椭圆拟合得到面元的轮廓,所得轮廓与面元真实轮廓吻合良好.研究结果表明该方案能够有效检测出面元轮廓,进而给出假图像星的排除范围.      

基于组字典学习的逆合成孔径雷达成像方法

基于压缩感知(compressive sensing, CS)的逆合成孔径雷达(inverse synthetic aperture radar, ISAR)成像方法可以使用非常少的数据来获得高质量的图像。但基于CS的ISAR成像方法中目标场景不准确的稀疏表示限制了成像方法的性能。结合字典学习(dictionary learning, DL)技术的CS ISAR成像方法能够寻找到目标场景图像块的最优稀疏表示,提高成像质量,但每一个图像块被单独考虑,而忽略了彼此之间的相互依赖关系。为了实现进一步提高成像质量的目标,针对ISAR图像分块重建的问题,首次提出一种基于组字典学习(group dictionary learning,GDL)的ISAR成像方法。将具有相似结构的图像块聚类并构建出多个图像块组,利用奇异值分解(singular value decomposition, SVD)从图像块组中学习出最优组稀疏变换字典。学习好的组稀疏变换字典可以寻找到待重建图像块组的最优稀疏表示,进而重建出高质量的目标场景图像。实验结果表明:与现有的CS ISAR成像方法相比,基于GDL的ISAR成像方法能获得更好的成像效果,并具有更高的计算效率。     

基于双边截断的双参数海上风电站 SAR图像 CFAR检测

文章提出了 1种基于双边截断的双参数海上风电站 SAR图像 CFAR检测器 DTCS-TPCFAR,目的是提高在具有多个目标海上区域和石油泄漏区域等环境下对海上风电站的检测性能。DTCS-TPCFAR所提出的双边截断杂波的方法,能够同时消除高强度和低强度异常值的干扰,同时保留真实的杂波样本。通过使用最大似然估计计算双边截断后样本的均值和标准差,然后通过这 2个参数估计值计算出截断阈值,最后再结合指定的虚警率(Probability of False Alarm,PFA)来对测试单元(Test Cell,TC)进行判断,完成最终的目标检测。这也是首次将 CFAR检测器用于检测海上风电站。文章通过 Sentinel-1数据集来验证该方法的有效性。实验结果表明,文章所提出的算法在相同指定虚警率下,具有更高的检测率(Detection Rate,DR)和更低的误报率(False Alarm Rate,FAR)。     

基于快速均值漂移和水平集方法的图像分割技术

通过加强边缘检测函数的约束作用,对L i提出的无需重新初始化的水平集方法进行了改进,用于提高水平集方法对弱边缘与低对比度图像的分割处理性能。同时,利用快速均值漂移法对图像进行预分割,将得到的轮廓作为水平集方法的初始轮廓,从而降低水平集函数的迭代次数。脑部M R图像的分割实验结果表明,该算法能够准确地提取相应的脑组织,同时大大地提高水平集函数的演化速度。     

月球主要构造特征：嫦娥一号月球影像初步研究

月球在31亿年前已基本停止地质活动,从而保留了其形成初期的信息．这些信息对于认识月球、地球乃至太阳系的形成演化具有重要意义．在已有研究成果的基础上,结合嫦娥一号探月卫星CCD影像数据,从月海穹窿、撞击坑、月岭、断裂、月坑链、月溪及月谷等方面介绍了月球主要构造形式的地质特征、形貌特征及遥感影像特征,对其成因以及所隐含的地质意义进行了分析．结果表明,嫦娥一号CCD影像信息丰富,影像清晰,利用其CCD影像数据进一步研究月球的构造现象是可行的．     

基于规则的航空发动机孔探图像诊断方法研究

针对军用航空发动机内部损伤频率高、诊断决策时间长的问题,运用基于规则的推理方法,结合案例推理,进行了航空发动机内部损伤维修决策的专家诊断研究,开发了基于孔探图像的航空发动机内部损伤维修决策专家系统。依据领域专家的经验,通过分析得到了对该型发动机的专家知识,并将其转换为if-then的知识规则存放于知识库中;利用图像处理方法,对损伤进行测量,得到损伤的尺寸参数;根据损伤尺寸,依据相应的知识规则,应用正向推理得到损伤的维修决策。运用多个航空发动机内部损伤实例验证了所开发的专家系统的有效性。     

3D information from 2D images recorded in the European Modular Cultivation System on the ISS

The European Modular Cultivation System (EMCS) on the ISS allows long-term biological experiments, e.g. on plants. Video cameras provide near real-time 2D images from these experiments. A method to obtain 3D coordinates and stereoscopic images from these 2D images has been developed and is described in this paper. The procedure was developed to enhance the data output of the MULTIGEN-1 experiment in 2007. One of the main objectives of the experiment was to study growth movements of the Arabidopsis plants and the effect of gravity on these. 3D data were important during parts of the experiment and the paper presents the method developed to acquire 3D data, the accuracy of the data, limitations to the technique and ways to improve the accuracy. Sequences of 3D data obtained from the MULTIGEN-1 experiment are used to illustrate the potential of this newfound capability of the EMCS. In the experiment setup, a positional depth accuracy of about ±0.4 mm for relative object distances and an absolute depth accuracy of about ±1.4 mm for time dependent phenomena was reached. The ability to both view biological specimens in 3D as well as obtaining quantitative 3D data added greatly to the scientific output of the MULTIGEN-1 experiment. The uses of the technique to other researchers and their experiments are discussed.     

Effects of lighting and air movement on temperatures in reproductive organs of plants in a closed plant growth facility

Temperature increases in plant reproductive organs such as anthers and stigmas could cause fertility impediments and thus produce sterile seeds under artificial lighting conditions without adequately controlled environments in closed plant growth facilities. There is a possibility such a situation could occur in Bioregenerative Life Support Systems under microgravity conditions in space because there will be little natural convective or thermal mixing. This study was conducted to determine the temperature of the plant reproductive organs as affected by illumination and air movement under normal gravitational forces on the earth and to make an estimation of the temperature increase in reproductive organs in closed plant growth facilities under microgravity in space. Thermal images of reproductive organs of rice and strawberry were captured using infrared thermography at air temperatures of 10–11 °C. Compared to the air temperature, temperatures of petals, stigmas and anthers of strawberry increased by 24, 22 and 14 °C, respectively, after 5 min of lighting at an irradiance of 160 W m⁻² from incandescent lamps. Temperatures of reproductive organs and leaves of strawberry were significantly higher than those of rice. The temperatures of petals, stigmas, anthers and leaves of strawberry decreased by 13, 12, 13 and 14 °C, respectively, when the air velocity was increased from 0.1 to 1.0 ms⁻¹. These results show that air movement is necessary to reduce the temperatures of plant reproductive organs in plant growth facilities.