a****o
发帖数: 42 | 1 【 以下文字转载自 Science 讨论区 】
【 原文由 amingo 所发表 】
偶正在搞纳米尺度下的扩散控制，简单说就是：
假定一个channel里在开始的时候在入口处注入少量的
tracer，同时假定channel内流体速度是微米每秒级
的，这样在过了很短的时间以后出现的情况将是，
在整个channel都存在tracer,原因是在扩散在这里对
tracer的分布起了重要的作用，典型的算例是：
channel length: 1 micro
channel width: 50 nano-meters
fluid velocity: 500 micro/s
passing time : 1/500s
tracer difussivity D : 1e-10
difussion length L_d : sqrt(D*t)= .5 micro
so, L_d is comparable with channel length
So, how to control such a serious difussion?
The first thing m |
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D*****r
发帖数: 1239 | 2 90%的话算是complication了，那医生的建议还是应该考虑的。生的时候如果宝宝8磅多
,是正常的，可以自己生的。一般医生不会直接建议刨是因为it may not be the best
interest in practice, 医生的guideline 鼓励 trial labor，说“every woman
deserves trial labor", 对母亲和宝宝都好。但如果你坚持刨，就和医生说，都是可
以讨论的嘛。如果怕疼的厉害就上epidural吧。网上也可以找找可以帮助放松的法子，
比如用 birth ball，跳belly dance（现在可以开始跳了，帮助打开骨盆，减轻腰痛）
，再带个lavender difusser熏香，可以帮助relax。都是网上看来的，我没实战经验啊
，祝福你和宝宝！
P.s. 你宝宝好可爱啊！确实胖乎乎的 XD |
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b**********8
发帖数: 1002 | 3 那个盘子估计是他自己做的difusser.光源越大，越接近被拍物体，光的质量就越好。
就是这个道理。
extension tube 也挺好玩，但是因为筒子太长了，viewfinder里会变得特别暗，对角
费劲。 |
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E********n
发帖数: 14662 | 4 罩子内面好像是反光面啊，是不是你说的difusser啊？ |
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s*******h
发帖数: 1361 | 5 Steve Zhu's paper is actually the easy part. The complexity can explode once
you try to implement it in real world. You are about to solve one of the
hardest yet mandatory cross-asset-class problems that each bank faces.
Smaller firms may not be able to set up the problem even if they want to.
- How can you generate scenarios across different asset classes and
instruments in each netting set and across all netting sets? Are simple
difussion processes enough to model individual assets, and are si... 阅读全帖 |
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x*t
发帖数: 30 | 6 I guess what the chemist and physicit could do is
just to control the difussivity D, as the D has
reflected all of chemistry and physics(not mechanics).
If we assume the N-S euqation is still applicalbe here,
the diffusion is proportinal to 1/(Re*Sc), Re=U.L/mu,
Sc=mu/D,
U, L :velocity and lengh scale respectively, mu, viscosity.
So we could enlarge the U, or L to reduce the diffusion as
well.
But maybe you don't like it.
So I suggest another wholly mechanical way(just rough
suggestion):
appyin |
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