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Search Results: 1 - 10 of 240953 matches for " 刘宗昌 "
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淬火高碳马氏体沿晶断裂机制

金属学报 , 1989,
Abstract: 提出马氏体沿晶断裂机制粗大奥氏体晶粒转变为马氏体时,以晶粒为体积膨胀单元,必然产生不均匀应变,在晶界区形成显微局部应力,甚至产生应力集中,削弱晶界结合,有时出现微裂缝,在淬火第一类应力(或外力)作用下,形成沿原奥氏体晶界扩展的沿晶裂纹和冰糖状断口。
珠光体、贝氏体、马氏体相变的形核* Nucleation Mechanism of Pearlite, Bainite and Martensite*  [PDF]
,计云萍,任慧平
Material Sciences (MS) , 2013, DOI: 10.12677/ms.2013.32014
Abstract: 研究过冷奥氏体转变产物的形核规律具有重要理论价值。采用20MnCrMo、60Si2CrV等材料,奥氏体化后在不同温度进行等温处理,得珠光体、贝氏体、马氏体等产物,应用QUANTA-400型扫描电镜、JEM-2100透射电镜等观察各种相变的形核。发现:珠光体、贝氏体、马氏体均优先在奥氏体晶界处形核,下贝氏体、马氏体也在晶内形核。珠光体晶核由共析铁素体+共析渗碳体两相组成,共析共生,在700℃~650℃,珠光体临界晶核尺寸r* = 150~70 nm;临界形核功 155~292 J/mol。贝氏体在奥氏体的贫碳区形核,晶核是单相(BF),其临界尺度a* = 16.7~25 nm,临界形核功 2.7 × 102 J/mol。马氏体的临界晶核尺寸约为17~20 nm,形核功约为200~600 J/mol。表明随着温度的降低,临界晶核尺寸越来越小,而形核功越来越大。过冷奥氏体转变产物的形核是一个逐渐演化的过程,符合相变形核的一般规律。 It is significant theoretically to study the nucleation mechanism of the phase transformation products of the supercooled austenite. 20MnCrMo, 60Si2CrV and other material were respectively austenized and isothermal quenched at the different temperature to obtain pearlite, bainite and martensite. The nucleation of the phase transformation products was observed by QUANTA-400 environmental scanning electron microscope and JEM-2100 transmission electron microscope. It is found that pearlite, bainite and martensite can all nucleate at the crystal grain boundary of austenite preferentially, moreover, lower bainite and martensite can nucleate in the austenite crystal grain interior. The pearlite crystal nucleus consists of two phases of eutectoid ferrite and eutectoid cementite, which can coexist. At the temperature range of 700 C - 650 C, the dimension of the pearlite critical nucleus is about 150 - 70 nanometer and the critical nucleation energy is 155 - 292 J/mol. Bainite nucleates in carbon-poor region and the bainite crystal nucleus is single phase (BF). The dimension of the bainite ferrite critical nucleus is 16.7 - 25 nanometer and the critical nucleation energy is 2.7 × 102 J/mol. The dimension of the martensite critical nucleus is 17 - 20 nanometer and the critical nucleation energy is 200 - 600 J/mol. The results show that, with the decrease of the transformation temperature, the dimension of the critical nucleus is becoming smaller and smaller and the critical nucleation energy is getting larger and larger. The nucleation of the phase transformation products of the supercooled austenite is a gradual evolutionary process, which accords with the general rule of the phase transformation nucleation.
马氏体相变唯象“理论”的评述—五评马氏体相变的切变学说
The Commentary on Phenomenological Theory of Martensite Phase Transformation—The Fifth Commentary on Shear Theory
 [PDF]

, 计云萍, 任慧平
Material Sciences (MS) , 2014, DOI: 10.12677/MS.2014.44018
Abstract:
研究马氏体相变晶体学具有重要理论意义。本文简述并评价了唯象学说,指出:1) 以贝茵应变使母相转变为马氏体,缺乏热力学可能性,贝茵应变B作为计算数据,不可靠; 2) 马氏体浮凸是相变体积变化所致,与切变无关,浮凸普遍为帐篷型(∧),矩阵计算式中的形状应变F与马氏体相变晶体学没有直接的联系;3) 点阵不变切变缺乏热力学可能性,在实际的马氏体相变中不存在简单切变(S)。同样,刚性转动也是虚构的;4) 唯象学说与马氏体相变实际不符,应予摈弃。
It is of theoretical significance to study the crystallography of martensite phase transformation. The phenomenological theory was briefly described and evaluated. The proposed viewpoints are as follows. 1) The transformation from austenite to martensite through the Bain strain lacks of the thermodynamics possibility. Moreover, it is unreliable to use the Bain strain (B) as the calculating data; 2) The surface relief of martensite, which is generally in tent (∧) type, results from the bulk expansion during martensite phase transformation and has nothing to do with the shear. The shape strain (F) in the matrix calculation formula is not directly relevant to the crystallography of martensite phase transformation; 3) The lattice invariance shear is short of the thermodynamic feasibility. No simple shear (S) exists in the actual martensite phase transformation, similarly, the rigid rotation is imaginary; 4) The phenomenological theory doesn’t conform to the reality of martensite phase transformation and should be abandoned.
贝氏体相变时原子的位移
Atomic Displacement during Bainite Transformation
 [PDF]

, 计云萍, 任慧平
Material Sciences (MS) , 2013, DOI: 10.12677/MS.2013.36044
Abstract:
研究贝氏体相变过程中原子的位移具有重要理论意义。本文综合试验事实理论地分析了过冷奥氏体在中温区发生贝氏体相变时原子位移的方式,并指出在孕育期内,依靠浓度涨落,碳原子扩散位移形成了贫碳区和富碳区。在贫碳区中原子以新旧相化学势之差为驱动力,依靠热激活跃迁形成贝氏体铁素体晶核。从热力学上分析,贝氏体铁素体的形成不是切变过程,从相变动力学和扩散速度分析,也非扩散过程。贝氏体相变中,碳原子扩散,界面铁原子以非协同热激活跃迁方式形成贝氏体铁素体和贝氏体碳化物。
>It is significant theoretically to study the atomic displacement during bainite transformation. The atomic displacement mode during bainite transformation in medium temperature region was synthetically analyzed in theory. It is pointed out that, in incubation period, the carbon-poor areas come into being by carbon atoms diffusion displacement for the concentration fluctuation. In the carbon-poor area, the bainite ferrite crystal nucleus is generated by heat activation transition of the iron atoms under the driving force of the difference between the old and new phase chemical potential. From the view of thermodynamics, the formation of bainite ferrite is not shear. From the aspects of transformation kinetics and diffusion velocity, the formation of bainite ferrite is not diffusion either. In bainite transformation, the displacement mode of carbon atoms is diffusion, but that of the interface iron atoms is non-synergic thermal activation transition, which results in the formation of bainite ferrite and bainite carbide.
刺五加注射液的不良反应
,王德才
中国中医药信息杂志 , 2002,
Abstract:
钒在正火钢中的相分布及稀土的影响
,杨植玑
金属学报 , 1987,
Abstract: 对添加V,V-RE的中碳钢,应用物理化学相分析及电子显微分析法,研究了钒在正火状态下的分布及稀土的影响。试验钢用中频炉熔炼,锭重20kg,经1150—
一种低脉动度脉动发生机构的优化设计
,蓝兆辉,
福州大学学报(自然科学版) , 2014,
Abstract: 基于对心型低脉动度脉动式无级变速器的研究成果,提出一种用于此脉动式无级变速器的采用槽型凸轮连杆组合的脉动发生机构,详细阐述了其基本结构与工作原理,分析了该变速器的性能特征. 系统研究了脉动发生机构的目标函数、 设计变量和约束条件,建立其优化设计数学模型. 利用 Matlab 的优化工具箱对其进行优化设计,得到了更加紧凑的参数设计,达到了优化设计的目的.
基于提升树的自然场景中文文本定位算法研究
徐琼,,,
南京邮电大学学报(自然科学版) , 2013,
Abstract: 提出了一种新的基于提升树算法的自然场景中文文本定位技术。首先利用边缘特征进行文本区域的检测,即对下采样后彩色图像首先进行边缘提取、二值化处理,然后通过形态学运算以及连通区域分析去除大量的非字符连通域,获得候选的文本区域,最后,提取候选文本区域的phoggabor特征,通过提升树算法进一步确认是否为字符连通域。通过实验验证,该算法具有很高的召回率和准确率,综合性能较高。
基于主题相似度的视频分段
Video segmentation based on topic similarity

周敏,,,
- , 2016,
Abstract: 视频中的人体行为分析是计算机视觉领域的研究热点,视频分段是人体行为分析的基础。文中提出了基于主题相似度的视频分段方法,首先提取视频的时空特征,并利用词袋模型将视频中的人体行为表示成行为文档,对行为文档进行主题建模得到蕴含在文档中的主题特征,然后计算两个相邻滑动窗口内主题分布的相似度,绘制出相似度曲线,最后根据相似度曲线进行分段。实验结果表明,文中算法能够有效地将视频中的不同行为分割开来,提高后续行为识别工作的效率。
Human behavior analysis in video is the hottest field in computer vision.The video segmentation is the basis of human behavior analysis.The video segmentation based on topic similarity is presented.Firstly, the human behavior is expressed as a behavior document using space-time interest points and bag of words model.After representing the human behavior as document, a topic model is established to capture the topic features occurring in it.Then, the similarity of topic distribution between two side-by-side windows is calculated.With these topic similarities, the similarity curve is obtained.Finally, the human behavior in video is segmented according to the curve.Experimental results show that the video segmentation based on topic similarity can effectively separate different behaviors effectively, improving the efficiency of follow-up behavior recognition
基于运动和外形度量的多目标行人跟踪
Multi-object pedestrian tracking based on motion and appearance measurements

花景培,,,
- , 2016,
Abstract: 单目视觉的行人检测跟踪是计算机视觉领域研究的热点和难点之一。现有的检测跟踪算法对于遮挡情况的处理仍然不够理想,尤其是未经校正的缺少深度信息的单目场景。文中面向普通单目视频,针对行人的短暂遮挡情形,提出了一种基于运动外形信息融合的多目标行人跟踪方法。首先对视频序列中检测出的行人多目标提取其运动信息和外形信息,并根据信息的分布情况调整相应系数,将行人目标与各轨迹的距离度量融合为距离代价,构成代价矩阵,最终使用匈牙利算法实现任务分配,以此进行关联跟踪。PETS2009监控视频行人跟踪数据库的实验结果表明了文中算法对于行人目标短暂遮挡处理的可行性和有效性。
Monocular vision-based multi-objects pedestrian tracking is one of the hottest and most difficult research areas in computer vision.In pedestrian occlusion situations,existing tracking algorithms are not ideal,especially in an uncalibrated monocular camera setting losting depth information.Aimed at temporary pedestrian occlusion situations in ordinary monocular videos,a multi-object pedestrian tracking method based on motion and appearance information fusion is proposed.Firstly,motion and appearance distance measures are calculated between each detected pedestrian object and each track.Then,the weight coefficients are adjusted according to the distribution of the calculated distances,so that all the distances are fused to a single cost value,forming the cost matrix.Finally,Hungarian algorithm in assign problem is used to associate each pedestrian object to its track using the cost matrix above.Tracking results in performance evaluation of tracking and surveillance (PETS) 2009 dataset indicate the feasibility and the effectiveness of the proposed algorithm in temporary occlusion situations
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