d*******2
发帖数: 340 | 1 http://www.edphoton.com/en
Wuxi OptonTech Ltd. specialises in diffractive optical elements (DOEs) and
computer generated holograms (CGHs) for flat-top (also referred to as top-
hat or super-Gaussain) beam shaping and other general beam shaping, beam
splitting, beam homogenizing (diffusing). Examples of general beam shaping
include multi-line patterns, square, view finder, crosshair, grids, rings,
etc. Typical applications of DOEs include phase gratings for optical linear
encoders, DOEs for motio... 阅读全帖 |
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a*****e
发帖数: 4577 | 2 如果讨论电磁波的话
按照wiki上的说法
Diffraction is normally taken to refer to various phenomena which occur when
a wave encounters an obstacle.
Scattering is a general physical process where some forms of radiation, such
as light, sound, or moving particles, are forced to deviate from a straight
trajectory by one or more localized non-uniformities in the medium through
which they pass.
如果平面波照射到一个点阵上，这个叫做diffraction还是scattering？ |
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G**Y
发帖数: 33224 | 4 From D800 Technical Guide:
Lesson 3: Don’t Stop Aperture Down Too Far
... Stop aperture down too far, however, and diffraction will cause the
image to actually lose definition. Optimal aperture—the aperture that
produces the greatest depth of fi eld with no loss of sharpness—varies from
lens to lens. In the case of the AF-S NIKKOR 14–24 mm f/2.8G ED lens used
in this example, an aperture f/8
will produce the sharpest image.... |
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d*h
发帖数: 2347 | 5 拍若干张用软件合成，现在这样的软件已经用在微距上了。
本来用残副18M pixels拍微距f8以上就已经有diffraction了，还没有用到D800呢——
用T3i+60mm macro有感。。 |
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z**h
发帖数: 224 | 6 【 以下文字转载自 Physics 讨论区 】
发信人: zzwh (微尺度爱情), 信区: Physics
标 题: international center for diffraction data 是要收费吗？
发信站: BBS 未名空间站 (Tue Mar 30 20:19:09 2010, 美东)
查一个化合物的XRD |
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d*******2
发帖数: 340 | 7 http://www.edphoton.com/Structured%20light%20by%20diffractive%2
Structured light is widely used for obtaining 3D depth imagery by projecting
a known pattern on to a scene. Specific applications include tracking a
moving object, motion sensing, gesture recognition, 3D sensing and mapping,
etc. Famous examples include the Radiohead's breakthrough cameraless music
video "House of Cards" and Microsoft's Kinect system.
Recently Wuxi OptonTech Ltd is proud to introduce new diffractive optical
element... 阅读全帖 |
|
l**n
发帖数: 908 | 8 对于你说的情况，即可以包括单晶的X-ray diffraction，也可以包括相应的Raman
scattering。
个人理解，diffration更强波的概念，scattering则更多强调个体（比如单个电子或光
子）的behavior，尤其是inelastic effect存在的时候。比如说，XRD关心的是反射光
形成的pattern所反映的点阵结构，而Raman谱则反映能量由于非弹性效应引起的变化。
当然，wave和个体之间是有联系的。 |
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l**n
发帖数: 908 | 9 有道理，diffraction确实是考虑从不同点出来的电磁波间相互作用的结果，所以说“
波”的概念在这里很重要，而在能量上一般都是属于弹性范畴。而scattering应该说考
虑的是单个的行为，其关注的可以是弹性行为，但更多的是非弹性行为。虽然说
scattering的研究是以统计为主，但各事件之间一般是看作相对独立，统计是在各结果
的基础上，而不涉及事件之间的相互作用。 |
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a*****e
发帖数: 4577 | 10 我觉得挺奇怪的一点就是
点阵如果是阵列，有一定的周期性， 一般就会成为diffraction
如果是随机点阵，就被成为scattering
按照你说的这个各事件独立为散射，事件相互关联为衍射的说法似乎比较套的上 |
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d*******2
发帖数: 340 | 12 http://www.edphoton.com/Structured%20light%20by%20diffractive%2
Structured light is widely used for obtaining 3D depth imagery by projecting
a known pattern on to a scene. Specific applications include tracking a
moving object, motion sensing, gesture recognition, 3D sensing and mapping,
etc. Famous examples include the Radiohead's breakthrough cameraless music
video "House of Cards" and Microsoft's Kinect system.
Recently Wuxi OptonTech Ltd is proud to introduce new diffractive optical
element... 阅读全帖 |
|
T*******I
发帖数: 5138 | 13 http://www.dantestella.com/zeiss/resolution.html
Resolution of camera lenses where are the limits – and why?
Some users of Zeiss lenses are so enthusiastic about these optics that they
believe Carl Zeiss can do won-ders. Well, this is not exactly true. The fact
is: Carl Zeiss has to adhere to nature's laws just as anybody else. So far,
Carl Zeiss's physicists have found no way around it.
One of these laws defines the resolution limit of any optical system, any
camera lens, even a perfect one wit... 阅读全帖 |
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b*s
发帖数: 82482 | 14 你说的是像素密度，这个密度（单个像素的大小）跟光学镜头的解像度，which is
really diffraction limited是两个独立元素，你这样说，就像是比较发动机马力和轮
胎的等级。虽然像素密度和镜头联合起来决定光学成像系统的总体性能，但是这两者之
间的联系跟发动机跟轮胎一样，完全不是一码事。
CCD的尺寸是由厂家决定的，单反的CCD像素比point and shoot的像素大得多，跟光学
系统没有什么关系。当然，CCD的选择跟镜头有关系，就如轮胎的选择和发动机是有关
系一样。
你首先混淆了resolution的定义：resolution是一个光学系统能够分开的两个点的最小
距离，跟最终的像素点没有一毛钱的关系。一台光学显微镜的分辨率是300-500 nm，跟
波长跟镜头的数值孔径有关，跟CCD无关。只要所选择的CCD的像素点符合成像面
Nyquist采样率即可
每个ccd element的尺寸决定了digital resolution，而前端的光学系统有自己的
diffraction limit，正比于波长，反比于aperture size。 ccd的尺寸基本由像素数... 阅读全帖 |
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r*s
发帖数: 2555 | 15 【 以下文字转载自 Joke 讨论区 】
发信人: rbs (jay), 信区: Joke
标 题: 诺委会太不像话了
发信站: BBS 未名空间站 (Wed Oct 4 10:23:52 2017, 美东)
尼玛87篇参考文献就不能加一篇施教授或能教授的CNS？
References
1. Ruska, E., Nobel Lectures, Physics 1981-1990, Tore Frängsmyr and
Gösta Ekspong, Eds. (1993) World Scientific Publishing, Singapore
2. Marton, L. (1934) Electron microscopy of biological objects. Nature
133, 911-911
3. Althoff, T., Mills, D. J., Popot, J. L., and Kühlbrandt, W. (2011)
Arrangement of electron transport chain compone... 阅读全帖 |
|
l*****o
发帖数: 19653 | 16 每个ccd element的尺寸决定了digital resolution，而前端的光学系统有自己的
diffraction limit，正比于波长，反比于aperture size。 ccd的尺寸基本由像素数目
（number of elements)决定的。比如，一平方厘米里如果有1万像素，那么每个像素的
面积就是1万分之一平方厘米，如果是正方形，就是边长为100微米。。。依次类推，如
果是1平方英寸ccd，有500万像素，那么每个像素对应的尺寸大概就是10微米一点儿。
。。
而光学系统的diffraction limit是1.22X波长/D（镜头直径），假设波长600nm，直径
35mm，那么它的diffraction limit大概是0.00025°，假设ccd距离镜头2厘米远，这个
limit就意味着大概5微米的成像尺寸。这是完全理想的情况。加上各种aberrations，
则接近10微米。。。
所以，如果像素高于500万（专业级别的相机基本都远大于），就可以说是超过了
diffraction limit, 其作用，我猜主要是用来经行数字图像处理。。。 |
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l*****o
发帖数: 19653 | 17 。。。。。。
照相机的像素，就是ccd sensor的数量，这个没什么好说的。每个ccd element就像一
个计数器，他的功能就是数有多少电子（光子，根据光电效应）在其中。。。
CCD的尺寸确实因为品牌不同而不同，但绝对不会有1平方寸和10平方寸那么远的差距。
我并不是狠确定那些厂家是否自己生产ccd，我猜想应该都是买的。如果你能证明每个
厂家都自己产ccd，我会狠吃惊。。。
没错，resolution是那么定义的。但不要忘记，beam optics是可逆的，也就是说，在
objective plane上的一点，要对应image plane上的一点，反之亦然。 当image plane
上两点之间间距小于diffraction limit所定义的尺寸（由diffraction limit(degree)
和于透镜的距离决定）时，同样，也就意味着它们所对应的objective plane上的两个
点不能被resolve。
换句话说，当由ccd像素大小决定的两个采样点间距小于由diffraction limit和景物距
离决定的resolution时，objective plane上的... 阅读全帖 |
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b*s
发帖数: 82482 | 18 请不要把CCD和CMOS厂家跟照相机厂家混为一谈。
成像系统的像素密度需要跟Nyquist采样率匹配才有效果，而Nyquist跟成像平面上的根
据镜头数值孔径和放大倍数所得到的像size有关。像素密度是需要相机厂商来选择的，
就像是轮胎是汽车厂商要选择搭配发动机的。但是轮胎厂商可以是独立厂商，所生产的
产品并不跟发动机直接联系，就像是CCD和CMOS厂商跟镜头厂商并不直接联系。照相机
厂商来决定正确的搭配和选材，正如汽车厂商要确定轮胎和发动机的搭配一样。
成像质量，特别是低光条件下的成像质量，跟CCD的full-well capacity还是很有关系
的，而full-well capacity跟CCD表面积直接相关，另外CCD的灵敏度还跟back-
illumination相关，虽然这个很少用在consumer级别的产品上。
另外，现在的CMOS芯片应用很广了，佳能的好几代产品都是CMOS主打了，CCD一统天下
的时代已经过去。CMOS现在已经进入Scientific-grade market了……
。。。。。。
照相机的像素，就是ccd sensor的数量，这个没什么好说的。每个c... 阅读全帖 |
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f**********c
发帖数: 651 | 19 据说这是好镜头的表现， quoted from ll:
Those "tiny black specks" are what you get when the lens is an odd number
of half-wavelengths out of focus. Note how both the foreground and
background point sources gradually show an increasing pattern of light and
dark rings - and more critically, how these ring patterns exhibit
identical shapes and intensities at a given degree of defocus in front of
and behind the plane of sharp focus? That beautiful symmetry, between
inside and outside focus, is a sign of near-pe... 阅读全帖 |
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c********y
发帖数: 30813 | 20 ☆─────────────────────────────────────☆
redskeleton (红骨架／白菜猪肉丸子汤) 于 (Wed Dec 22 23:40:22 2010, 美东) 提到:
带老婆孩子出去看灯展，照了不少照片，回来一看，我靠，这圈圈也太多了点，整个无
数同心圆套在一起，这焦外..............
☆─────────────────────────────────────☆
arsilverfox (Alli) 于 (Wed Dec 22 23:41:35 2010, 美东) 提到:
快做个桃心镜头盖拍心型bokeh~x]
☆─────────────────────────────────────☆
yuanwang (gauntlet) 于 (Wed Dec 22 23:42:20 2010, 美东) 提到:
我觉得还不错啊
☆─────────────────────────────────────☆
beetle1986 (beetle) 于 (Wed Dec 22 23:42:46 2010, 美东... 阅读全帖 |
|
r*s
发帖数: 2555 | 21 尼玛87篇参考文献就不能加一篇施教授或能教授的CNS？
References
1. Ruska, E., Nobel Lectures, Physics 1981-1990, Tore Frängsmyr and
Gösta Ekspong, Eds. (1993) World Scientific Publishing, Singapore
2. Marton, L. (1934) Electron microscopy of biological objects. Nature
133, 911-911
3. Althoff, T., Mills, D. J., Popot, J. L., and Kühlbrandt, W. (2011)
Arrangement of electron transport chain components in bovine mitochondrial
supercomplex I1III2IV1. The EMBO Journal 30, 4652-4664
4. Letts, J. A., Fied... 阅读全帖 |
|
s******y
发帖数: 17729 | 22 【 以下文字转载自 Military 讨论区 】
发信人: rbs (jay), 信区: Military
标 题: 诺委会太不像话了 (转载)
发信站: BBS 未名空间站 (Wed Oct 4 10:58:51 2017, 美东)
发信人: rbs (jay), 信区: Joke
标 题: 诺委会太不像话了
发信站: BBS 未名空间站 (Wed Oct 4 10:23:52 2017, 美东)
尼玛87篇参考文献就不能加一篇施教授或能教授的CNS？
References
1. Ruska, E., Nobel Lectures, Physics 1981-1990, Tore Frängsmyr and
Gösta Ekspong, Eds. (1993) World Scientific Publishing, Singapore
2. Marton, L. (1934) Electron microscopy of biological objects. Nature
133, 911-911
3. Althoff, T., Mi... 阅读全帖 |
|
l*********y
发帖数: 3447 | 23 it is more of diffraction limit, which is classical wave property of photon
instead of particle property.
I know little of photography but I think here the problem is a little more
complicated than diffraction limit. Basically the quality of image contains
both resolution and contrast. according to rayleigh criterion the closest
distance distinguished is when the maximum of diffracted pattern overlap
with first minimum diffracted pattern of adjacent point, but this
corresponds to minimum contras... 阅读全帖 |
|
s********n
发帖数: 2939 | 24 为什么一帮人就喜欢动嘴皮子不喜欢动手狗一下？明明说了是Fe4[Fe(CN)6]3，哪来的
钾？
https://en.wikipedia.org/wiki/Prussian_blue
Prussian blue
From Wikipedia, the free encyclopedia
This article is about the pigment. For the musical duo, see Prussian Blue.
See also: Midnight blue
Prussian blue
IUPAC name[hide]
Iron(II,III) hexacyanoferrate(II,III)
Other names[hide]
Berlin blue
Ferric ferrocyanide
Ferric hexacyanoferrate
Iron(III) ferrocyanide
Iron(III) hexacyanoferrate(II)
Parisian blue
Identifiers
CAS number 14038-43-8
PubChem ... 阅读全帖 |
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U*****g
发帖数: 366 | 25 My area: semiconductor device and physics / electrical engineering
CV:
QIUGUI ZHOU
Email: q**[email protected]
Phone: 1+(434) 243-2147
===========================================================================
EDUCATION
UNIVERSITY OF VIRGINIA
Charlottesville, VA
Ph.D. in Electrical Engineering
2011
UNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINA(中国科学技术大学)
Hefei, CHINA
Master of Science in Optics ... 阅读全帖 |
|
l****u
发帖数: 3449 | 26 感慨一下烙印的厚脸皮 -- 首先我根本不是faculty，这个烙印学生应该是搜了我以前
一篇paper，然后按照模板填上我文章名字和email就发过来了，贴出来奇文共欣赏。也
不知道这个烙印群发了多少封。请注意的他的研究兴趣是“Mechanical behavior of
Materials, Electronic and Magnetic Properties of Materials, Thin Films,
Phase Transformations,Thermodynamics,X-Ray Diffraction”，基本可以囊括材料系
所有方向了。
Respected Professor xxx
I am xxx, a pre-final year student currently pursuing B Tech in Materials
Science and Engineering at Indian Institute of Technology (I.I.T.), Kanpur,
India's premier technical institute. My rese... 阅读全帖 |
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a**e
发帖数: 427 | 27 理想diffraction limited下，大光圈的mtf应优于小光圈。但是往往大光圈下并不是
diffraction limited，反而mtf比小光圈的差。一般135镜头说f8最锐，就是因为它接
近diffraction limit，但光圈还不算太小。大光圈时的mtf更多取决于镜头设计时对色
散、中心边角、焦内焦外等等是怎么优化取舍的。 |
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f**********r
发帖数: 18251 | 28 【 以下文字转载自 Military 讨论区 】
发信人: smartkevin (PE), 信区: Military
标 题: Re: 普鲁士蓝解毒机理
发信站: BBS 未名空间站 (Wed May 1 11:49:11 2013, 美东)
为什么一帮人就喜欢动嘴皮子不喜欢动手狗一下？明明说了是Fe4[Fe(CN)6]3，哪来的
钾？
https://en.wikipedia.org/wiki/Prussian_blue
Prussian blue
From Wikipedia, the free encyclopedia
This article is about the pigment. For the musical duo, see Prussian Blue.
See also: Midnight blue
Prussian blue
IUPAC name[hide]
Iron(II,III) hexacyanoferrate(II,III)
Other names[hide]
Berlin blue
Ferric ferrocyanide
Ferric hexacy... 阅读全帖 |
|
J********n
发帖数: 534 | 29 其实protein crystallography的原理和显微镜的道理是一模一样的。
"But we can't build an X-ray microscope to look at molecules, for two
reasons. First, we don't have an X-ray lens. Second, even if we did have one
, it would have to be made with tolerances significantly less than the
distance between two atoms! However, we can (in effect) simulate an X-ray
lens on a computer. You can think of a microscope as working in two stages.
First, light strikes the object and is diffracted in various directions. The
lens collect... 阅读全帖 |
|
s*********a
发帖数: 113 | 30 d110:d101 = 3.248:2.488 in Rutile unit cell so it is quite distinguishable.
Better to have a diffraction pattern when you take high resolution TEM image
, actually it is just a 5 second job because you just need to put SAD
aperture in and push a button. FFT is not exactly the same as diffraction
pattern since it shows forbidden points or don't show double diffraction
points sometimes. |
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T*M
发帖数: 48 | 31 基本上你看D.B.Williams & C.B.Carter的那本TEM就可以了。
大家看你实在不懂都不知道怎么跟你说。你确实需要去上个TEM的课，带实验的那种。
如果你要的急呢，我简单跟你讲讲。
在TEM仪器的设置一定的情况下，你得到的reflection跟晶面间距的关系是一定的。怎
么去得到这个一定的关系呢？就是先用一个标准样品去标定一下，好象你照一朵花为了
说明它有多大需要放个手指在旁边一样。比如silicon. 在不同的camera length－－就
是diffraction mode的放大倍数下，不管你用什么记录，记录下一个硅的diffraction
pattern at zone(你要是zone也不知道，就需要先去学一下晶体学的课了). Si的
diffraction pattern是很好认的并且容易index，你量出一个reflection到(000)(
就是中心点，最强的那个)的长度。假如在CCD上Si(111)到(000)的距离在camera
length=20cm时是120 pixels, 对应～ 0.314 nm的晶面间距。那你就知道，以后在同样
的camera |
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d*******2
发帖数: 340 | 32 http://www.edphoton.com/Diffractive%20optical%20elements%20for%
Diffractive optical elements for motion sensing and gesture recognition
systems
For Infrared laser based human body motion sensing and gesture recognition
systems, diffractive optical elements (DOEs) are without doubt an ideal
solution. This is because DOEs can convert a laser beam to virtually
arbitrary intensity distribution that matches the requirements of customers
very well. |
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m****s
发帖数: 443 | 33 Franklin is best known for her work on the X-ray diffraction images of DNA,
which led to the discovery of the DNA double helix. According to Francis
Crick, her data and research were key in determining the structure[3] and
formulating Crick and James Watson's 1953 model regarding the structure of
DNA.[4] Franklin's images of X-ray diffraction, confirming the helical
structure of DNA, were shown to Watson without her approval or knowledge.
This image provided valuable insight into the DNA structu... 阅读全帖 |
|
发帖数: 1 | 34 【 以下文字转载自 EE 讨论区 】
发信人: lakeriver (), 信区: EE
标 题: Epi / Process/Device/ FA Engineer Openings
发信站: BBS 未名空间站 (Tue Jan 22 21:34:31 2019, 美东)
WinS (Shenzhen Institute of Wind bandgap Semiconductors深圳第三代半导体研究
院) is seeking the following job candidates. The R&D team consisting of
senior VPs /scientist/engineers/ with 10~20 years experiences in industry
from U.S. Candidates with semiconductor materials/device/process background
and FAB experience are highly recommended. Package is negotiable, benefit... 阅读全帖 |
|
b*****9
发帖数: 8922 | 35 ☆─────────────────────────────────────☆
ypockcalb (ypockcalb) 于 (Sun Aug 15 15:07:32 2010, 美东) 提到:
这家伙比较能吹！在bell lab 做了几年高级劳工，又在普林斯顿混了两年technical
staff就能千人,大家好好学学人家是怎么忽悠的！这家伙在bell lab的位置自己给出来
了，还算诚实，但是自己提高了在普林斯顿的位置。普林斯顿这个中红外材料实验室是
他老板Claire F. Gmachl离开bell lab后创建的，英文名称应该为MIRTHE（mid-
infrared technolies for health and evironments）,相关链接为
http://www.mirthecenter.org/。Claire F. Gmachl的主页为http://www.ee.princeton.edu/people/Gmachl.php。这家伙号称在量子级联激光器领域作出的贡献都是一些挂名的工作，从WEb of science 的搜索看，一共可以找到大概13篇... 阅读全帖 |
|
h****7
发帖数: 17 | 36 Please send a cover letter that addresses how you meet all of the required
skills when applying for the position. A current C.V. with the minimum
following information/sections is required: Educational background, degree
dates, GPAs with scales, name of advisor, citizenship; Relevant work
experience; Honors and awards; Invited presentations; Peer-Reviewed
Publications; Non-peer-reviewed Publications; Talks and Poster Presentations
; References. References will not be contacted without permission... 阅读全帖 |
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g******s
发帖数: 733 | 37 你确信在别的地区，用别人的电脑搜也是前三？
我用自己电脑 常用的浏览器搜beam shaping,我的网站排第一啊。
我的这个产品是diffractive optics或者diffractive optical elements,看了一下，
global search分别是3600和1300。不知道能不能从搜索估算出市场价值？ |
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E******y
发帖数: 614 | 38 10-05-11
Dan Shechtman, Nobel laureate. Larger photo. Photo courtesy of The Ames
Laboratory, USDOE.
Contacts:
Dan Shechtman, Materials Science and Engineering, Ames Laboratory, the
Technion -Israel Institute of Technology, 011-972-4-829-4299, dans@ameslab.
gov
Pat Thiel, Chemistry and Ames Laboratory, (515) 294-8985, t***[email protected]
Alex King, Ames Laboratory Director, (515) 294-2770, a******[email protected]
Steve Karsjen, Ames Laboratory, (515) 294-5643, k*****[email protected]
Mike Krapfl, News Ser... 阅读全帖 |
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e**n
发帖数: 5876 | 39 f2.0 zoom lens sounds fast? No thank you. You get diffraction as early as f/
8.
APS版的24m芯片一样的diffraction阿. 你要不也批判一下Nikon D5200和所有将要换装
24mp的机型
Because of that 2x crop factor you get DOF similar to high-end P&S. You
shoot the picture at f/2.8 and it looks like a picture from a FF body at f/5
.0. Great for macro but terrible for everything else.
m43的sensor面积是high-end P&S的5倍多, DOF相似, FF的面积是m43的4倍, DOF区别很
大. 恩. 非常公平, 非常的不bias.
Because of the tiny sensor, noise is always one stop or two stops worse ... 阅读全帖 |
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E********8
发帖数: 22 | 40 Definitely free electron laser is a much advanced x-ray source and it would
be likely to use micro-crystals. Nevertheless, we still need crystals, even
if they are small. I don't think small crystals are much easier to grow than
big ones.
In addition, how do you solve the structure once you obtain the diffraction
data? The key question is still to get the phases. I know there is a over-
sampling method for single particle diffraction. I don't think this method
can be applied to the crystal diffr |
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o2
发帖数: 2764 | 41 "小晶体容易拿到", based on this statement, I know you are not a
crystallographer. When "绝大部分不diffract", something is wrong with your
protein packing, which will cause poor resolution even the crystal is small.
Did the original group set up side by side control saying that the small
crystal diffracts better than the big ones from the same protein?
Again, I would say there is no magic here. Only big advantage I can think is
that your crystal will never grow bigger no matter what you do. But when
this hap |
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o2
发帖数: 2764 | 42 For the Single-particle diffraction technique, you need to combine both of x
-ray and electron diffraction patterns. And if the sample is noncrystalline,
you still need somehow separate it from the true solution. So I totally
agree with you, 1st it is very hard to reach angstrom range (right now we
are at nm range), 2nd it is sort of similar to cryo- EM. |
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i****g
发帖数: 3896 | 43 STORM的第一篇文章NATURE METHODS | VOL.3 NO.10 | OCTOBER 2006 Sub-diffraction
-limit imaging by stochastic optical reconstruction microscopy (STORM)是这样
写的
M.J.R. and M.B. conceived the STORM imaging concept. M.J.R., DNA imaging and
data analysis; M.B., RecA imaging and data acquisition. X.Z. supervised the
project.
如果要给这个炸药奖，只怕MJR和MB的贡献比Zhuang还大？
diffraction
and
the |
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P********n
发帖数: 372 | 44 PM if interested.
JOB DESCRIPTION:
Analytical Senior Scientist opening for someone with practical experience in
the area of microscopy, surface science, x-ray diffraction and other
material evaluation technologies. This position will be responsible for "
hands on" work leading the Analytical Science lab in the evaluation and
characterization of materials and products. This position is bonus eligible
and relocation is available for eligible candidates.
Responsibilities
•Lead the material ch... 阅读全帖 |
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发帖数: 1 | 45 WinS (Shenzhen Institute of Wind bandgap Semiconductors深圳第三代半导体研究
院) is seeking the following job candidates. The R&D team consisting of
senior VPs /scientist/engineers/ with 10~20 years experiences in industry
from U.S. Candidates with semiconductor materials/device/process background
and FAB experience are highly recommended. Package is negotiable, benefits
comparable to SUSTech University（南方科技大学）
Candidates with Ph.D from top 150 universities are qualified to get “孔雀计
划A/B/C” with 3.0 to 1.6... 阅读全帖 |
|
发帖数: 1 | 46 WinS (Shenzhen Institute of Wind bandgap Semiconductors深圳第三代半导体研究
院) is seeking the following job candidates. The R&D team consisting of
senior VPs /scientist/engineers/ with 10~20 years experiences in industry
from U.S. Candidates with semiconductor materials/device/process background
and FAB experience are highly recommended. Package is negotiable, benefits
comparable to SUSTech University（南方科技大学）
Candidates with Ph.D from top 150 universities are qualified to get “孔雀计
划A/B/C” with 3.0 to 1.6... 阅读全帖 |
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m******i
发帖数: 834 | 47 《近代X射线多晶体衍射——实验技术与数据分析》
（马礼敦著， 化学工业出版社，2002）的第一章。
第一章 绪论----X射线多晶体衍射的发展历程
X射线多晶体衍射(X-ray polycrystalline diffraction, XPD)，也称X射线粉末衍射(X-
ray powder diffraction, XPD)，是由德国科学家德拜(Debye)、谢乐(Scherrer)[1,2]
在1916年提出的。当时正值第一次世界大战，信息交流受阻，美国科学家Hull在1917年
又独立提出了这一方法[3]。所谓多晶体衍射或粉末衍射是相对于单晶体衍射来命名的，
在单晶体衍射中，被分析试样时一粒单晶体，而在多晶体衍射中被分析试样时一堆细小
的单晶体(粉末)。由于当时X射线的应用主要在解晶体结构，因此初期发展得并不快。
20
世纪30年代中期，Hanawalt和Rinn提出了用多晶体衍射在混合物中鉴定化合物的方法[4]
，接着又提出了包含1000种化合物参比谱的数据库[5]，使X射线多晶体衍射成为表征多
晶体聚集体结构的重要手段，开创了X射线多晶体衍射应用的新领域，吸引了很多人的注 |
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T****i
发帖数: 2190 | 48 我说的只是一个comment，不算问题。如果TEM image能够得出颗粒尺寸的话，这个尺寸
是可信的，但是要说明的是测量的误差有~10%，而且很大的颗粒（>um)要么在制样的时
候被不会被附着到C膜上（取决于你的制样方法），要么无法电子束穿透以至于无法成
像，所以这样的大颗粒是不会反应在你的size distribution上的。
至于Scherrer方程，本身推导的过程有不少的假设和近似(可以看Warren写的X-ray
Diffraction或者Cullity的Elements of X-ray Diffraction）。XRD谱的峰宽里面大颗
粒的权重要大于小颗粒，所以peak width是dominated by large particles。而且晶体
缺陷，应力还有仪器本身的峰宽都会对实验测得的半峰宽有影响，这些因素在计算的时
候得扣除。所以这个方程只能说是"估算"，它的误差来自于方程本身和实验的setup，
要使用的话尽量使用高角度的峰并一定要扣除instrument width。SAS也能得出尺寸信
息。但是这些方法的适用范围不尽相同。
如果你的TEM image已经 |
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s*********a
发帖数: 113 | 49 You should be able to see it if the zone axis for diffraction is right.
Actually for crystal, the first step for HRTEM is to tilt the sample to
the right zone axis, in which usually we use diffraction pattern for
reference.
Developing the films is somehow annoying, but can you just draw what you
saw
on the screen on some paper, at least it can give you some information. |
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T*M
发帖数: 48 | 50 恭喜啊。不过我说的imaging plates (IP)和TEM没有关系，
那就是一些和底片一样的东西，只是不用化学方法冲洗。
而且比CCD的dynamic range要高很多，如果有对electron diffraction
有特别的需要的，IP当然要好很多。
只要新的TEM还有可以装底片的空间，就可以用IP。
IP整套系统的价钱大约在$200K左右，每张IP大约$100,
可反复使用一万次。
不过大部分地方不需要quantitative electron diffraction,
所以就不用了。 |
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