基于方向小波变换的镁熔液弱小气泡检测

运用方向小波的多尺度和多方向变换,对高温镁熔液表面弱小气泡进行检测。先对原始图像进行方向小波变换重构高频,抑制背景杂质,再作帧差和迭代阈值分割处理,最后运用数学形态学检测到弱小气泡,并将结果与传统小波检测进行比较。实验结果表明方向小波变换方法是有效的,而且方向小波更符合图像的方向特点,能够较好地检测出复杂背景中的弱小气泡。     

激光熔注中增强相颗粒对晶粒生长影响的CA模拟

基于元胞自动机法,结合Moore型邻居定义和晶粒生长理论,建立了增强相颗粒SiC对镁合金激光熔注中表层316L不锈钢晶粒生长的影响模型,模型考虑了晶界迁移率和晶界能等因素,实现了不同增强相颗粒体积分数和颗粒尺寸对晶粒生长影响的计算机模拟。结果表明,所建立的模型能较好的模拟晶粒生长过程,所得晶粒生长指数为0.42;增强相颗粒体积分数含量越高,晶粒生长越慢,晶粒尺寸越小;增强相颗粒尺寸越小,晶粒生长的越慢,晶粒尺寸越小,组织越均匀。     

Deep drawing formability of AZ31 magnesium alloy based on magnetorheological elastomer support

In this paper, the flexible support mould is designed by using magnetorheological elastomer (MRE) to assist in the deep-drawing of magnesium alloys. Based on the magnesium alloy mechanical tensile test and magnetorheological elastomer regular force experiments, the deep-drawing process of AZ31 magnesium alloy supported by support mould was numerically simulated by finite-element analysis software ABAQUS. By varying the current input to the excitation coil to change the magnetic induction intensity and thus adjust the magnetic normal force of the magnetorheological elastomer, then using magnetic normal force to complete the auxiliary sheet metal deep-drawing. The results show that, compared with the unsupported mould, the supported mould can effectively reduce the maximum thinning rate of magnesium alloy on the original basis, thus effectively increasing the ultimate depth of magnesium alloy deep-drawing. It can replace the original buffer device, effectively solution the problem of pulling and cracking at the bottom of magnesium alloy caused by the original excessive damping force, and improve the yield rate of workpiece.     

Detection of brain tumour from MRI image using modified region growing and neural network

Abstract

Region growing is an important application of image segmentation in medical research for detection of tumour. In this paper, we propose an effective modified region growing technique for detection of brain tumour. It consists of four steps which includes: (i) pre-processing; (2) modified region growing by the inclusion of an additional orientation constraint in addition to the normal intensity constrain; (3) feature extraction of the region; and (4) final classification using the neural network. The performance of the proposed technique is systematically evaluated using the magnetic resonance imaging (MRI) brain images received from the public sources. For validating the effectiveness of the modified region growing, we have considered the quantity rate parameter. For the evaluation of the proposed technique of tumour detection, we make use of sensitivity, specificity and accuracy values which we compute from finding out false positive, false negative, true positive and true negative. Comparative analyses were made of the normal and the modified region growing using both the Feed Forward Neural Network (FFNN) and Radial Basis Function (RBF) neural network. From the results obtained, we could see that the proposed technique achieved the accuracy of 80% for the testing dataset, which clearly demonstrated the effectiveness of the modified region growing when compared to the normal technique.     

一种基于支持向量机分类的瞬态信号检测方法

用支持向量机（Support Vector Machine,SVM）方法对水下运动目标辐射噪声的谱图进行高维空间下的最优划分,实现水下瞬态信号的有效检测。其基本思想是将时频谱图拆分成若干时频细胞单元（Time Frequency Cell,TFC）,选择合适的高斯核向量机,寻找时频细胞单元间的差异性,进而实现对瞬态信号的检测。海试数据处理表明该方法检测瞬态信号的有效性,运算量小且稳健性高;与常规能量检测方法相比,更易确定检测门限,减少虚警。     

铅离子对复合磷酸盐磷酸镁水泥水化硬化特性的影响

研究了铅离子对复合磷酸盐磷酸镁水泥水化硬化特性的影响及其在复合磷酸盐磷酸镁水泥中的稳定性。实验结果表明,复合磷酸盐磷酸镁水泥抗压强度随着铅离子掺量的增加而降低,其中硝酸铅掺量达到10%时,复合磷酸盐磷酸镁水泥的各个龄期的抗压强度发生明显下降。铅离子对复合磷酸盐磷酸镁水泥凝结时间没有明显影响。在复合磷酸盐磷酸镁水泥水化过程中,铅离子对水泥体系的pH值影响不大,但能够造成水泥水化放热峰出现的时间延迟,水化放热的总量减少并影响主要水化产物的结晶程度。在复合磷酸盐磷酸镁水泥水化反应后期,当硝酸铅掺量达到10%以上时,在水化产物中出现了较为明显的Pb2P2O7的衍射峰。复合磷酸盐磷酸镁水泥固化铅离子的浸出毒性试验结果(43μg/L)远低于国家标准要求(5mg/L)。     

注射剂可见异物检测气泡干扰消除方法的研究

介绍了自动检测系统的构成,并提出了一种消除图像气泡干扰的方法.首先,采用图像差分方法消除原始图像中的大部分静态背景,然后对处理后的图像进行阈值分割、边缘检测、特征提取,重点研究了基于透光度、长宽比、紧凑度三个判据综合的气泡干扰消除方法.结果表明,该方法可以有效检测出医药注射剂中微小可见异物,检测正确率达到93%以上.     

基于RQA与SVM的声发射信号检测识别方法

针对裂纹声发射信号检测问题,提出基于递归定量分析与支持向量机相结合的新型检测方法。利用小波阈值去噪原理,对采集的声发射信号进行去噪,将递归定量分析引入声发射信号检测,提取递归定量分析的量化特征参数,结合支持向量机对模拟裂纹声发射信号进行识别。并实验验证该方法的可行性。     

水下爆炸气泡运动对水面形态影响的数值模拟

为了研究水下爆炸气泡运动对水面形态的影响,使用LS-DYNA软件,基于ALE算法,建立了水下爆炸气泡运动模型,讨论了不同装药水深距离参数条件下,不同类型水冢的形成过程及其特性、气泡运动特性和产生的水面波动特征。结果表明:在水下爆炸过程中,随水深距离参数的增大,水下爆炸形成的水冢类型依次为零碎型、飞溅型、酒杯型、皇冠型;同时爆炸产生的气泡最大半径也是随着水深的增大而减小,气泡脉动周期则相反;水面波动的特征主要与水冢的形成过程密切相关,不同类型的水冢所产生的水面兴波的机理不同。     

基体对镁合金氧化膜性能影响的研究进展

阐述了镁合金应用前景,介绍了阳极氧化特点以及影响氧化膜性能的因素,主要包括基体材料、电参数、电解液的组成及其浓度等.全面综述了基体对镁合金氧化膜成膜过程、成分、表面形貌以及耐蚀性的影响,提出了由于工业上使用的材料绝大多数为镁合金而不是纯镁,因此,开展合金元素对氧化膜性能影响的研究非常必要.     

Comparison of modified injection molding and conventional machining in biodegradable behavior of perforated cannulated magnesium hip stents

In this study,perforated cannulated magnesium(Mg)hip stents were fabricated via modified Mg injection molding and conventional machining,respectively.Additionally,the stent canal was filled with paraffin to simulate injection of biomaterials.The microstructure,mechanical performance,corrosion behavior,and biocompatibility were comparably studied.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)showed higher affinity of interstitial element such as oxygen and carbon as consequences of routine molding process.After immersion in SBF,machining stents showed reduced degradation rate and increased deposition of calcium phosphate compared to molding stents.Corrosion resistance was improved via paraffin-filling.Consistently,the hemolysis and in vitro osteoblast cell culture models showed favourable biocompatibility in machining stents compared to molding ones,which was improved by paraffin-filling treatment as well.These results implied that the feasibility of the prepared machining stents as the potential in vivo orthopaedic application where slower degradation is required,which could be enhanced by designing canal-filling injection of biomaterials as well.