Direct method for rotation estimation from spherical images using 3D mesh surfaces with SPHARM representation

Since a large field of view obviously bears important advantages, the use of spherical images is becoming increasingly important in various computer vision and image processing applications. This paper presents a novel rotation estimation approach for spherical images based on 3D mesh representation of gray level intensity. Once the 3D meshes of the underlying spherical images are obtained, the 3D rotation can be estimated directly and efficiently, without feature extraction and matching process. Subsequently, we propose a direct method for 3D object rotation estimation using spherical harmonics representation with SVD decomposition and ICP algorithm for estimation refinement. Experimental results validate our approach and prove its suitability and robustness for rotation estimation. Moreover, it performs well against noisy images, brightness changes, image compression and occlusions. A comparative study of our proposed approach with four similar methods for 3D rotation estimation between spherical images, is realized to prove its effectiveness.     

Lightweight digital video stabilization for small-size robot

Though constrained by payload and processing, small robots have gained applications in collecting visual information from the scene. Typically these small-size robots do not carry data loggers and send the video information to a hand-held device at a remote location for visual observations. Due to sophisticated processing and control limitations from mechatronics resources, the video captured by the robot is subjected to the effects of unintended motion, which requires digital methods for video stabilization. For a lightweight solution for video stabilization, we avoid use of any external hardware and develop a Singular Value Decomposition (SVD) based digital algorithm that avoids explicit feature tracking and motion estimation during stabilization. The process involves identifying a subspace with minimal dimensions that contains information of intentional motion alone. This work identifies the minimal subspace for video stabilization using the sliding window geometry method for practical implementation. Further, a shape-preserving filter is utilized to remove perturbations induced by the unintended motions, thereby resulting in the reconstruction of the stabilized video sequence. Experimental results on two different small-size robots viz spherical robot and Unmanned Aerial Vehicle (UAV) in indoor and outdoor settings, respectively, show quality outcomes without any change in parameters of the proposed filter design. Performance comparison with existing methods on the quality of stabilized video shows that the proposed stabilization method overcomes the non-availability of features for tracking due to large amplitudes and limited onboard resources. With the proposed video stabilization method, there is a potential for wider applicability of small-size robots in remote visual observations.     

基于似圆阴影的光学遥感图像油罐检测

针对光学遥感图像中受阴影干扰的油罐目标识别率低的问题,该文提出一种将改进的视觉显著模型与似圆阴影区域特征检测相结合的由粗到精的油罐目标检测方法。首先建立改进的视觉显著模型,将油罐从复杂背景中粗分离。然后对分离结果中由油罐产生的似圆阴影区域进行精检测,得到疑似油罐目标。再去除阴影,获得油罐目标的初步检测结果。最后基于图搜索策略及先验知识,确定油罐目标并定位油库区域。实验结果表明,该方法对检测光学遥感图像中存在似圆阴影的油罐目标具有较高的鲁棒性和准确率。同时,在不同环境的光学遥感图像中使用该方法可快速准确地定位油库区域。     

基于坐标变换下的球形机器人稳定平台控制

由于球形机器人内部构件相对于壳体需要保证全方位的运动,所以机器人内部的传感器以及探测设备常因缺乏稳定支撑而无法正常工作.基于此,探讨通过控制的方法使机器人内部形成稳定平台.利用基于能量耗散形式下的拉格朗日方程建立球形机器人前向滚动状态下的动力学模型,并根据实际运动情况对所推导的动力学方程进行线性化处理,接着通过坐标变换的方法,使方程在新的平衡点处转化为线性定常的状态空间形式.在整个变换过程中引入平衡摆角和平衡速度两个重要概念,为进一步分析机器人运动特征奠定基础.对于动力学方程中出现的循环坐标,采用减少状态变量的方式来保证系统的可控、可观性.针对机器人运动中所需要达到的具体性能指标要求,设计机器人的全状态反馈控制器,可对系统的极点进行任意配置.仿真结果表明了所设计的控制器的有效性.     

局部减薄储罐拱顶非线性稳定性分析

首先应用非线性有限元法进行局部均匀减薄拱顶的稳定性分析,计算结果表明,罐壁及罐壁油压对罐顶失稳的临界载荷影响很小.随后针对拱顶局部均匀减薄问题,提出一种近似的解析分析法,解析法将减薄部分分离出来,处理为受剩余部分弹性支撑的扁球壳,并导出相应的等效弹性支撑刚度计算公式,最后利用修正迭代法获得近似的失稳临界载荷计算公式.解析方法的计算结果与有限元法计算结果对比表明,文中提出的局部失稳临界载荷计算公式具有与有限元方法相一致的计算精度,可用于局部减薄拱顶储罐的局部稳定性评估,计算结果表明腐蚀区几何参数为9.5时最易出现局部失稳.     

装甲抗侵彻技术研究进展及对化工储罐保护层风险防控的借鉴

爆炸碎片对化工储罐的侵彻作用破坏性极强,储罐保护层技术作为侵彻事故风险防控的重要手段却仍处于起步阶段。典型的保护层技术,如军事装甲技术研究已经较为成熟,可为储罐保护层技术发展提供重要的借鉴意义。本文系统分析了国内外有关化工储罐保护层及军事装甲防护侵彻损伤的相关文献,指出化工储罐保护层技术研究亟待解决的问题,并参考装甲技术研究进展提出其进一步研究方向：在材料选取方面应考虑防弹金属、陶瓷以及一些新兴材料的应用及耦合设计;在结构设计方面可以采用实验及数值模拟两种方法,研究储罐保护层层数、各层厚度比、各层排列顺序、层间间隙等诸多关键参数对储罐保护层抗侵彻性能的影响。通过对侵彻事故发生概率及事故后果严重程度两方面的表征,为储罐保护层技术在爆炸碎片多米诺效应事故风险防控中的应用提供参考。     

The effect of reactor temperature gradient on microstructures of sodium borosilicate glass powders produced by ultrasonic spray pyrolysis technique

Sodium borosilicate glass powders were produced by ultrasonic spray pyrolysis technique for three different reactor temperature gradients and the effect of the reactor temperature gradient on the microstructures of the powders produced was investigated. A three-zone ultrasonic spray pyrolysis system reactor in which the temperatures of each zone could be controlled separately was designed for this purpose. When the drying speed is high, early shell formation was observed in the aerosol droplets due to the difference of the drying speed between inner and outer parts and hollow powders were produced. In order to produce dense powder particles, shell formation on the aerosol droplet should be prevented, therefore drying speed should be decreased. The powders produced were glass-structured, spherical shaped and with smooth surfaces. The density of the hollow powder particle was 1.9 g/cm³ while the density of the dense particle was 2.5 g/cm³.     

Large scale and environmentally friendly preparation of micro-submicron spherical silica and their surface effect in resin materials

Amorphous micro-submicron spherical silica powders with different particle sizes and surface properties were prepared by turbulent flow cycle method and characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MASS), X-ray diffraction (XRD), particle size distribution (PSD), specific surface area (SSA) analysis and scanning electron microscopy (SEM). The effects of particle size and surface property of different spherical silica on the fluidity of resin materials were conducted. The result showed that the spherical silica with the characterization of D₅₀ = 2.5 μm and the ratio of experimental specific surface area and calculated specific surface area is 2.38, played a better role in the flow ability of epoxy materials. So it may be a better choice for the preparation of epoxy materials used in IC packaging area and other high-tech fields.     

全压力式液化石油气储罐防泄漏注水工艺方案的探讨

对全压力式液化石油气储罐设置防止液化气泄漏的注水工艺方案进行了探讨,同时讨论了北方地区对注水管线防冻问题的解决措施。     

Yeast‐mediated stereo‐selective reduction of estrone by continuous cell culture with dual stirred tanks for product yield improvement

BACKGROUND: β‐Estradiol is an important hormone for the treatment of breast cancer and osteoporosis. β‐Estradiol can be produced via Saccharomyces cerevisiae mediated reduction of estrone. However, substrate inhibition and low production yield have been observed in the batch cell culture. RESULTS: An innovative continuous cell culture with dual stirred tanks in series was designed to solve the above problems. The growth medium was fed continuously to the incubation tank where the cells were incubated aerobically; the viable cells were then supplied continuously to the reaction tank in which the yeast‐mediated anaerobic reduction of estrone was performed with continuous feed of the substrate medium and continuous withdawal of the reaction cell culture. Thus, an increase in cell productivity from about 3‐fold to 7‐fold was obtained when compared with the batch cell culture. The β‐estradiol yield was improved to 64.8% on the second reaction day, accompanied by an accumulation of 12.9 mg β‐estradiol on the third reaction day. The yield was about 10% more and the accumulated recovery of β‐estradiol was 4.3‐fold better than with the batch cell culture. The diastereomeric excess value (%de) of β‐estradiol was more than 99%. CONCLUSION: A high product yield with excellent stereo‐selectivity was achieved in a short reaction period with the developed continuous cell culture and the dual stirred tank. Copyright © 2010 Society of Chemical Industry