X射线衍射全谱拟合相定量分析新方法:Le Bail直接比对法

X射线衍射物相分析包括定性和定量分析。Rietveld全谱拟合法作为一种无标样定量方法正在取代传统的基于含量-强度方程的相定量法。然而,在用Rietveld法进行拟合时,因需要待测试样所有所含物相的晶体结构模型而使其应用受到限制。本文提出新的无标样定量分析法Le Bail直接比对法,该法仅仅需要晶胞参数和空间群信息,就能进行定量分析,这些数据都能从指标化中得到,扩展了全谱拟合定量分析的应用范围。结果与Rietveld结构精修相比较,相对误差在0.03%。     

衍射仪的机械制造误差对拟合可信度极限的影响

全谱结构拟合是获得研究对象精细结构的一种重要方法,X射线多晶衍射仪测试的角度准确度直接影响全谱结构拟合的正确性和可信度,而测角仪的机械制造误差是影响测量角度准确度不可忽视的因素。该文采用模拟计算方法对由蜗轮蜗杆系统的制造误差造成的X射线多晶衍射全谱拟合结果的可信度进行了分析,结果表明对theta-theta衍射仪而言,机械制造的角度准确度至少要达到±0.003°,拟合结果才是有可信度的,所以只有采用直接在衍射仪轴上安装有高准确度的圆光栅的方式,才能提供符合当前物质结构分析的要求。该文具体给出了圆光栅的准确度要求。     

晶体的X射线衍射谱仿真与实验研究

为了获取晶体初始X射线衍射谱,开展了晶体物质X射线衍射谱的仿真与实验研究。基于X射线衍射原理构建了晶体的X射线衍射谱仿真理论模型,仿真了Cu、Si和NaCl晶体的衍射强度分布,计算得到了晶体在5°和10°衍射角度时的衍射能谱。搭建了X射线衍射实验平台,实测了NaCl单晶的衍射能谱,校验了仿真模型,实测谱对应的能量和强度与仿真结果一致。解决了晶体的初始衍射谱受到仪器测量误差影响的问题,为晶体初始衍射谱的获取提供了一种有效的方法。     

(La(0.7-x)Y0.3)2/3 Ca1/3MnO3的晶体结构研究

利用标准的固相反应法制备了(La0.7Y0.3)2/3Ca1/3MnO3和La空位(La0.62Y0.3)2/3Ca1/3MnO3锰氧化物粉末样品。X射线衍射(XRD)测量分析表明样品均为单相,并且在300K到30K温度范围内结构没有发生改变,单胞仍然具有正交对称性(Pnma)。并用Rietveld全谱拟合法对X射线衍射测量所得的晶体结构衍射谱进行了拟合。结果表明,晶体结构参数(a,b,c)和晶胞体积(v)随温度发生了明显变化,Mn-O键长随温度减小单调增大,而Mn-O-Mn键角呈单调减小,这也说明存在静态的Jahn-Teller效应。     

圆环衍射中轴线上的光强分布

运用瑞利-索末菲衍射积分、菲涅耳衍射积分、夫琅和费衍射积分分别计算了圆环衍射在孔径轴线上的强度分布，并对计算结果进行了讨论。     

理论光学教学中标量和矢量成像理论的比较

为了探讨光学理论课程中标量理论的适用范围,以及超出标量理论范围后该如何处理等问题,本文使用菲涅尔衍射和透镜相位变化的标量成像理论与基于德拜近似的平面波角谱展开法的矢量成像理论做了比较。结果发现菲涅尔衍射的精度要求在实际使用中过于苛刻,当数值孔径小于0.4时,标量理论能获得精度很高的结果。     

台风“米雷”近地层风特性实测研究（英文）

目的:对台风"米雷"作用下上海浦东近海岸边近地风特性进行全场监测记录,获得10 m、20 m、30 m和40 m高度处的风速实测数据,以研究台风过程中的平均风速风向、湍流度、阵风因子、湍流积分尺度和脉动风速功率谱等近地风特性。创新点:1.利用浦东实测基地的测风塔,获得10 m、20 m、30 m和40 m高度处台风"米雷"的风速实测数据。2.对台风"米雷"作用下的近地风特性进行分析,并对不同风特性参数之间的相互关系进行研究。方法:1.在浦东实测基地建立40 m高的测风塔,利用现场实测的方法,研究台风"米雷"作用下的近地层风场特性;2.利用经验公式拟合的方法,将现场实测结果与经验公式所得结果进行比较,并分析它们之间的差异。结论:1.各向湍流积分尺度均呈现随平均风速的增大而增大的趋势,在10 m、20 m和40 m高度处各向湍流积分尺度的均值之比分别为1?0.69?0.08、1?0.61?0.09和1?0.65?0.13;2.当平均时距大于10 min时,u和v方向的湍流积分尺度随平均时距的增大而增大,但w方向的湍流积分尺度基本不随平均时距的改变而改变;3.台风初期惯性子区各湍流分量功率谱的分布斜率小于-5/3,随后逐渐满足Kolmogorov 5/3率,纵向脉动风速功率谱与von Karman经验谱吻合较好,而横向和竖向脉动风速功率谱与von Karman经验谱在高频段有所偏差。     

不同过程控制剂对TiC基金属陶瓷的影响

采用粉末冶金法制备了TiC-10%Mo-20%Ni金属陶瓷,研究了不同过程控制剂对组织性能的影响,采用Rietveld全谱拟合法对X射线衍射图谱进行分析,金属Mo和Ni与TiC发生固溶反应,形成了典型的芯-环结构,选用正己烷为过程控制剂时,在1 450℃烧结金属陶瓷的硬度最高达到1 432HV30,断裂韧性为10.47 MPa·m~(1/2)。     

高职定积分应用的教学研究举例

定积分是高职数学教学中非常重要的一部分教学内容,定积分应用的问题是对现代社会经济现象定性及定量分析的一个重要内容。这就要求学生不仅要学会定积分的基本计算,还要会用定积分处理相关的实际问题。本文以定积分教学为背景,给出定积分在社会生活中的一些实例,从实际应用的角度来说明定积分的应用和使用。     

Fresnel圆屏衍射的计算机模拟演示

基于Huygens-Fresnel衍射积分和Babinet原理,利用Hankel变换算法及球面波因子处理方法,在普通PC上使用MFC编程较好地实现了Fresnel圆屏衍射的计算机模拟演示。演示中,Fresnel圆屏衍射的光强剖面分布、衍射图样和中心光强分布分别随光的传输距离和波长及圆屏半径的改变而变化,光的传输距离和波长及圆屏半径由三个滚动条分别控制。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.