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Search Results: 1 - 10 of 264462 matches for " 刘云慧 "
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珠光体、贝氏体、马氏体相变的形核* Nucleation Mechanism of Pearlite, Bainite and Martensite*  [PDF]
宗昌,,
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]

宗昌,,
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]

宗昌,,
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.
北京东北旺农田景观步甲群落结构的时空动态比较
,宇振荣,
应用生态学报 , 2004,
Abstract: 2000年5~10月在北京海淀区东北旺实验基地,采用陷阱法对林地、农田边界和农田3类生境共14个处理的步甲进行了取样,并在此基础上分析了不同生境和不同季节步甲科昆虫群落的动态分布特征.结果表明,林地和农田边界类生境相对于农田类生境拥有更多的步甲个体数和物种数;无论是优势种还是稀有种都趋向于在林地和边界处生活;边界对相邻农田步甲群落的多样性有积极影响;对边界进行适度的干扰(秋季翻耕)有利于提高步甲群落的个体数量;农田生境中灌溉、施肥和秸秆还田对农田中步甲群落的个体数量和物种数量的空间分布均无显著影响.此外,还结合步甲的时空分布特性对步甲受威胁状况进行了初步的分析.
黑河中游绿洲灌溉区土地覆盖与种植结构空间格局遥感监测
王志,
地球科学进展 , 2013, DOI: 10.11867/j.issn.1001-8166.2013.08.0948
Abstract: 以高空间分辨率、高光谱分辨率CASI航空遥感数据作为采样带,对黑河中游绿洲灌溉区土地覆盖和农作物种植结构空间格局进行遥感监测。设计了分层分类方法,综合采用基于像素和基于对象的2种遥感图像分类方法对航空样带区域进行土地覆盖制图。根据实地土地覆盖类型调查与目视解译,对样带土地覆盖和农作物种植结构的分类结果进行精度评价,总体分类精度为84.2%,Kappa系数为0.793。与样带区域2007年LandsatTM/ETM+土地覆盖产品相比,高分辨率CASI航空数据能够对树木、草地与农作物类别进行有效监测。监测结果表明,中游绿洲灌溉区内接近59.1%的地区为裸地与建筑用地;植被覆盖区域占39.8%,其中,农田34.9%,树木5.3%,草地仅有0.1%;而在农田区域中玉米为大宗作物,分类成数占96.1%。研究结果表明高质量与高分辨率的航空遥感数据能够实现对流域下垫面异质性进行有效监测,为生态—水文过程研究提供高分辨率的下垫面类型信息。
基于加权Voronoi图的变电站优化规划
葛少,,
电力系统自动化 , 2007,
Abstract: 针对变电站优化规划这一城市电网规划工作中的重要环节,提出了一种基于加权Voronoi图的变电站规划方法,可以最终完成对变电站数量、容量、站址及供电范围的优化。该方法首先给出一种确定新建站容量组合的数学模型,并采用整数规划的优化技术同时得到其最优解和几组次优解。进而,根据是否含有已有站,分别给出利用常规Voronoi图法及综合考虑规划区域地形特点、区域面积和负荷分布情况的坐标几何方法产生初始站址。在此基础上,通过对Voronoi图进行加权来考虑负荷分布不均匀、各站额定容量和负载率不同对变电站供电范围的影响,进行变电站供电范围的整体优化,并确定新建站站址。实际算例表明,所提出的方法能够较好地满足变电站规划工作的要求。
传送带机械故障智能检测系统的设计
,杨婕,
南京林业大学学报(自然科学版) , 2003, DOI: 10.3969/j.jssn.1000-2006.2003.06.018
Abstract: <正>为区分机械与电气故障,提高检修效率,采用磁敏三极管、电子多路开关、单片机与字符型液晶显示模块构成具有声光报警和液晶汉字滚动显示的检测电路,以测定远程传送带上各主、从动轮的转速,从而可在线检测其机械故障。
基于硬约束调节的改进粒子群无功优化
,葛少,
天津大学学报(自然科学与工程技术版) , 2009,
Abstract: 在解决电力系统无功优化问题时,粒子群优化存在着处理离散变量困难、易陷入局部最优和不能完全满足不等式约束等情况.为此,在对连续变量进行离散对应的基础上,采用混沌策略增加其寻优性能,并针对边界约束问题提出了将越限的节点电压和功率因数进行“九宫”调节的特色改进方案,以保证粒子的飞行能被控制在可行解空间中,从而形成了新的改进粒子群优化算法.通过ieee标准节点系统和某地区实际电网的计算分析,表明该算法在寻优速度、寻优质量等方面均具有很好的效果.
电氧化湿法分解钼中矿工艺
徐海清,,
过程工程学报 , 2010,
Abstract: 采用电氧化法湿法分解低品位钼中矿,结果表明,电氧化分解钼中矿反应遵循一级反应动力学模型,其表观活化能为16.55kg/mol,最佳浸矿工艺条件为温度40℃、矿浆浓度(固液比)50g/L、电流密度1000A/m2、电解液NaCl浓度100g/L及pH10,在该条件下电解90min,钼中矿浸出率和电流效率分别为96.1%和50.7%.
低品位黄铜矿在嗜热布氏酸菌下的循环伏安分析
,魏振东,华美,
过程工程学报 , 2010,
Abstract: 电解液中含与不含布氏酸菌时,采用循环伏安法研究了黄铜矿-碳糊电极与电解液之间的电化学行为,并探讨了温度、阴极电位、Fe2+和Cu2+对循环伏安曲线的影响.结果表明,低品位黄铜矿在0.45V出现生成多硫化合物的氧化峰,在-0.25和-0.43V出现生成Cu5FeS4和Cu2S的还原峰.温度升高促进黄铜矿氧化分解,65℃时的峰电流为35℃时的2倍.添加适量Fe2+和Cu2+能促进黄铜矿的氧化分解.
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