T**********e
发帖数: 29576 | 1 靠风力产生晃动发电，可以安装得很密，不占多大地方。
Vortex bladeless turbines wobble to generate energy
Looking somewhat like a giant reed gently swaying in the wind, the new
Vortex
bladeless wind-driven generator prototype produces electricity with very
few moving parts, on a
very small footprint, and in almost complete silence. Designed to reduce
the
visual and aural impact of traditional spinning-blade turbines, this new
device
takes advantage of the power contained in swirling vortices of air.
Designed to reduce the ... 阅读全帖 |
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b**********g
发帖数: 32 | 2 Another question is to generate these so-called "vortices", does one need
different antennas for different vortices? And on receiving end,
can two Yagi antennas receive all the vortices?
Assuming the energy-per-bit must still be maintained, would the power
spectrum density increase to a level unsafe for humans? |
|
c****e
发帖数: 2127 | 3 D'Alembert说如果来流没有vorticity/circulation，就没有升力
实际上的确是没有vorticity/circulation的
但是vorticity/circulation从哪里来？机翼的倾角 |
|
c****e
发帖数: 2127 | 4 of
attack都不大。飞机的cruise speed大约0.8Mach, 属于low-speed aerodynamics。由于
airfoil trailing edge的设计是sharp-cornered的，加上气体有黏滞性，这保证了
airfoil在posotive AoA情况下运动时，气流平滑地离开trailing edge并且上下表面没
有压
~~~~~~~~~~~~
力差（即starting vorticity is shed into wake或者说starting vortex is cast
~~~~
off），即满足了Kutta条件，从而产生环流, 进而产生lift。
请问这个没有压力差是指哪个部位？trailing edge?
用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）； 同
样是军用
机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要垂直起降）
； 同样是军
用飞机，subsonic,trans... 阅读全帖 |
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b***y
发帖数: 14281 | 5 既然有人争论方的学术水平，就上网搜了一下。应该说这个水平对于一个junior
faculty来说可以算是很牛B了，但是对于老方这种senior的已经搞了一辈子的人来说，
就只能算so so。不要说是院士，离aps fellow的级别也还差了不少。引用率最高的一
篇文章还是95年到了arizona之后跟老外合作的，被引118次，这也是方唯一一篇被引用
上百次的文章。可见方励之89之前确实没有做出过什么重要的工作，他的名声和地位绝
对是靠政治得来的，当然其中部分的也是80年在中国搞科普所得，必须承认科普工作也是
有重要的社会意义的。
(BTW，有人说你这个搜索未必完整。不错，确实不能保证100％毫无遗漏。但是我
用的search engine is THE search engine everybody in this community uses today.
So, if any article is not found by this search engine, sadly, it simply doesn't matter,
because no one would ever n... 阅读全帖 |
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w***s
发帖数: 15642 | 6 刚刚看到一段挺有意思，借bos的帖子写几句笔记：
赫舍尔在1785年发表了一篇论文"On the Construction of the Heavens"。在这篇论文
里，Herschel对观察和推断有一段论述挺有意思：
“'If we indulge a fanciful imagination and build worlds of our own... these
will vanish like Cartesian vortices.' On the other hand, merely 'adding
observation to observation', without attempting to draw conclusions and
explore 'conjectural views', would be equally self-defeating.”
这段话不就是学而不思则罔，思而不学则殆吗？“vanish”和殆对应得还挺好。文里提
到的Cartesian vortices，原来是笛卡尔提出的一个解释星体运动的理论；笛卡尔生得
早啊，没有万有引力，只好发明带子... 阅读全帖 |
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g****d
发帖数: 64 | 7 Vorticity is generated due to shear stress, which viscosity plays a crucial
role. If the two flow has a velocity gradient, then vorticity could be
generated. Just my two cents.
大
式 |
|
l***o
发帖数: 7937 | 8 飞机为什么会飞？这个题目太大了，需要考虑的情况太多了。
从飞机类型考虑，Rotor aircraft和Wing aircraft不同； 同样是Wing aircraft，民用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）； 同样是军用机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要垂直起降）； 同样是军用飞机，subsonic,transonic, supersonic, hypersonic, high-hypersonic又不一样；同样是一般商用民航机，不同的angle of attack情况也会不同（随着AoA的增大，气流会与airfoil的上表面分离，出现turbulence甚至whirlpool）。（当然啦，如果你是一个aerodynimics的专家，你会以说，这些本质都一样，因为都是N-S方程govern的。）
就拿一个flight cycle来看,起飞、巡航、控制和降落也不一样。这个题目至少包含四层意思：（1）飞机怎么能飞起来？（takeoff）（2）飞机在天上巡航，为什么不掉下来（cruise)？（3）飞机如何调整高度和转向（... 阅读全帖 |
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b*p
发帖数: 242 | 9 赞！菠萝飞行器设计制造系的？
我想问一下又没有人考虑过设计仿hummingbird的飞行器？
民用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）；
同样是军用机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要
垂直起降）； 同样是军用飞机，subsonic,transonic, supersonic, hypersonic,
high-hypersonic又不一样；同样是一般商用民航机，不同的angle of attack情况也会
不同（随着AoA的增大，气流会与airfoil的上表面分离，出现turbulence甚至
whirlpool）。（当然啦，如果你是一个aerodynimics的专家，你: 会以说，这些本质
都一样，因为都是N-S方程govern的。）
四层意思：（1）飞机怎么能飞起来？（takeoff）（2）飞机在天上巡航，为什么不掉
下来（cruise)？（3）飞机如何调整高度和转向（flight control)?(4)飞机如何降落
（landing）？估计这些都不是楼主的意思。楼主要问的是：How is lift gener... 阅读全帖 |
|
d*********r
发帖数: 813 | 10 讲得的确非常好。
cruise speed大约0.8Mach, 属于subsonic and transonic aerodynamics,超出low-speed
aerodynamics范围了。飞机起飞着陆阶段属于low-speed aerodynamics。
民用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）；
同样是军用机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要
垂直起降）； 同样是军用飞机，subsonic,transonic, supersonic, hypersonic,
high-hypersonic又不一样；同样是一般商用民航机，不同的angle of attack情况也会
不同（随着AoA的增大，气流会与airfoil的上表面分离，出现turbulence甚至
whirlpool）。（当然啦，如果你是一个aerodynimics的专家，你: 会以说，这些本质
都一样，因为都是N-S方程govern的。）
四层意思：（1）飞机怎么能飞起来？（takeoff）（2）飞机在天上巡航，为什么不掉
下来（cruise)？（3）... 阅读全帖 |
|
D****R
发帖数: 6053 | 11 解释的好！
民用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）；
同样是军用机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要
垂直起降）； 同样是军用飞机，subsonic,transonic, supersonic, hypersonic,
high-hypersonic又不一样；同样是一般商用民航机，不同的angle of attack情况也会
不同（随着AoA的增大，气流会与airfoil的上表面分离，出现turbulence甚至
whirlpool）。（当然啦，如果你是一个aerodynimics的专家，你: 会以说，这些本质
都一样，因为都是N-S方程govern的。）
四层意思：（1）飞机怎么能飞起来？（takeoff）（2）飞机在天上巡航，为什么不掉
下来（cruise)？（3）飞机如何调整高度和转向（flight control)?(4)飞机如何降落
（landing）？估计这些都不是楼主的意思。楼主要问的是：How is lift generated?
对于这个问题的解释不是没有，而是很多，当然也有一些不完整（如airfl... 阅读全帖 |
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i*****e
发帖数: 1359 | 12 赞，原来我不懂kutta condition，现在了解了
民用机又和军用机不同（军用机的速度高很多，姿势要求多，甚至需要360度翻转）；
同样是军用机，陆地起飞的战机和母舰起飞的战机也不同（后者起飞距离短，甚至需要
垂直起降）； 同样是军用飞机，subsonic,transonic, supersonic, hypersonic,
high-hypersonic又不一样；同样是一般商用民航机，不同的angle of attack情况也会
不同（随着AoA的增大，气流会与airfoil的上表面分离，出现turbulence甚至
whirlpool）。（当然啦，如果你是一个aerodynimics的专家，你: 会以说，这些本质
都一样，因为都是N-S方程govern的。）
四层意思：（1）飞机怎么能飞起来？（takeoff）（2）飞机在天上巡航，为什么不掉
下来（cruise)？（3）飞机如何调整高度和转向（flight control)?(4)飞机如何降落
（landing）？估计这些都不是楼主的意思。楼主要问的是：How is lift generated?
对于这个问题的解释不是没... 阅读全帖 |
|
h******i
发帖数: 661 | 13 你们学校ap能发这么多paper?
1989
Cosmological implications of quasar-galaxy associations, L.Z.Fang, Y.Q.Chu
and X.F. Zhu, Mod. Phys. Lett., 4, 887.
Geometrical optics in an inhomogeneous universe, L.Z.Fang and X.P.Wu,
Chinese Phys. Lett., 6, 233.
Quasar clustering and its cosmological implication, L.Z.Fang, Inter. J. Mod.
Phys. A4, 3477.
L'Osservatorio astronomico di Pechino: la sua storia, il presente, L.Z.Fang,
Scienza e Tecnica, Annuario della EST 88/89 404.
Overview on the frontier of high energy astr... 阅读全帖 |
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b***y
发帖数: 14281 | 14 No. The search include his early works up to 1978. Here is the same list
sorted by year.
1) The Influence of Gravitation on the Vacuum State.
By Li-Zhi Fang.
Acta Phys. Sinica 27 ( 1978) 181-18.
2) THE STRUCTURE AND STABILITY OF THE ABNORMAL NEUTRON STAR.
By Li-Zhi Fang, Qin-Yue Qu, Zhen-Ru Wang, Tan Lu, Liao-Fu Luo.
Sci.Sin.22:187-198,1979.
3) Some Recent Developments in Astrophysics. (Talk).
By Li-Zhi Fang, A. Qadir, R. Ruffini.
In *Nathiagali 1980, Proceedings, Physics and Contemporary Needs... 阅读全帖 |
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h****h
发帖数: 123 | 15 还是google这个吧wingtip vortices |
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J****n
发帖数: 3011 | 16 你这个10^2哪儿来的？
Over a large Re range (47
continuously from each side of the body, forming rows of vortices in its
wake.
Reynolds |
|
S******8
发帖数: 24594 | 17 老方到美国后发的文章列表，你自己看吧：
1990
174. Biased clustering in a universe with hot dark matter and a cosmic
string, L.Z.Fang, S.P.Xiang and L.Yan, Astr. & Astrophys. 233, 1.
175. Periodicity of redshift distribution in a T-3 universe, L.Z.Fang, Astr.
& Astrophys. 239, 24.
176. An upper limit to quasar's peculiar velocity, L.Z.Fang, Y.Q.Chu, X.F.
Zhu and L.F. Wang, Inter. J. Mod. Phys., 5, 2993.
177. Quasar pair and quasar's peculiar velocity, L.Z.Fang, Developments in
general relativity, astrophysics and qu... 阅读全帖 |
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f***y
发帖数: 4447 | 18 http://view.sdu.edu.cn/info/1003/92502.htm
相对论量子流体极化领域取得新突破 山大学者参与该实验
发布日期：2017年08月03日 11:28 点击次数：
［本站讯］8月3日，由山大学者在内的中国科学家参加的美国布鲁克海文国家实验室
RHIC-STAR国际合作组最新研究成果作为封面文章发表在《Nature》杂志上。该研究在
重离子碰撞中首次观测到了夸克胶子等离子体（QGP）的“整体极化”（global
polarization），发现碰撞产生的Lambda超子相对于碰撞反应平面存在明显的自旋极化
。QGP“整体极化”理论最早由山东大学梁作堂教授和长江学者讲座教授王新年于2004
年提出，论文发表在美国《物理评论快报》（Phys. Rev. Lett. 94, 102301）上，开
创了QGP围绕自旋自由度相关物理研究的新方向。STAR实验组发表在《Nature》的实验
结果证实了该论文的预言。
位于纽约长岛的美国布鲁克海文国家实验室的相对论重离子对撞机(RHIC)利用两束接近
于光速的金核对撞来模拟宇宙大爆炸，产生类似于早期宇宙的夸克胶子物质形... 阅读全帖 |
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a******o
发帖数: 16625 | 20 丰田UR系列发动机每一个型号都很牛逼
Toyota UR engine
From Wikipedia, the free encyclopedia
Toyota UR engine
Toyota 1UR-FSE Engine.JPG
Overview
Manufacturer Toyota Motor Corporation
Production 2006–
Combustion chamber
Configuration DOHC 90° V8
Chronology
Predecessor Toyota UZ engine
The Toyota UR engine family is a 32-valve quad-camshaft V8 piston engine
series which was first introduced in 2006 as the UZ series it replaced began
phasing out. Production started with the 1UR-FSE engine with D4-S di... 阅读全帖 |
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W*****t
发帖数: 4595 | 21 赞
你要是说防止wingtip vortices就更赞了 |
|
发帖数: 1 | 22 Academic Position
Harvard University Rowland; Junior Fellow/Principal Investigator 09/2011 –
Present
University of California, Los Angeles; Postdoctoral Scholar (PI: Dino Di
Carlo Ph.D.) 06/2011 – 08/2011
Education and Training
University of California, Los Angeles Mechanical Engineering Ph.D. 2011
University of California, Los Angeles Mechanical Engineering M.S. 2007
University of California, Los Angeles Mechanical and Aerospace Engineering B
.S. 2005
Publication
13. Dwayne A. L. Vickers, Mengx... 阅读全帖 |
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g******o
发帖数: 7 | 23 We are seeking a post-doctoral fellow who is interested in pursuing
analytical and computational research in the area of combustion. Required
expertise include: liquid injection and sprays, fuel-air mixing, vortical
flow dynamics, combustion, and CFD. The position is for a period of 2 years
. Applicants who are interested can contact:
Dr. Randy Chue (Associate professor)
Nanyang Technological University, Singapore
Email: R*******[email protected] |
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M******0
发帖数: 1280 | 24 I know you are kidding, but you know there are small eddies (vortices)
in the wake of the flying ball, right? |
|
M******0
发帖数: 1280 | 25 yeah, you are right. But the complicated vortical structures around the ball
can cause very weird ball movements, I think. There could be strong vortex
in one side of the ball that counter-rotating the ball, and as it reach the
ground, the vortex could dissipate, and the initial rotation could become
dominant again. Just some guess. Maybe a computer aerodynamic simulation can
tell the truth, a funding for that will be great, haha.
|
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M******0
发帖数: 1280 | 26 Yeah, that's under an ideal condition, no air movement, and it's called
Bernoulli principle, which means velocity and pressure is inversely
proportional. While in top spin, top side of the ball spin direction against
the incoming air speed, while the bottom side of the ball spin the same
direction as the incoming air flow, causing the top side air having a slower
speed than the bottom side air, thus higher pressure on the top than the
bottom, causing the ball to drop. Again Bernoulli principle.
... 阅读全帖 |
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o*4
发帖数: 417 | 27 Matthiessen SP, IL
5D 17-40, CPL, 3stop ND
found a baby raccoon
two images stitched
one more vortices |
|
H********g
发帖数: 43926 | 28 If a new theory is correct, the same physics it identifies as responsible
for the origin of living things could explain the formation of many other
patterned structures in nature. Snowflakes, sand dunes and self-replicating
vortices in the protoplanetary disk may all be examples of dissipation-
driven adaptation. |
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r*c
发帖数: 16750 | 29 发信人: Closingbell (转我的贴记住给包子~), 信区: Military
标 题: 英特尔科学奖2016年40人决赛名单出炉 11名华裔学生入围
发信站: BBS 未名空间站 (Thu Jan 21 09:21:35 2016, 美东)
据英特尔科学奖官方网站消息。英特尔科学奖20日公布入围决赛名单。在这份40人的决
赛名单里，共有11名华裔学生入围。
占入围人数近三成的华裔学生分别来自加州，康州，马里兰州，宾州，纽约州和密苏里
州。其中加州和纽约州分别有三名华裔学生入围，马里兰州有两位。
英特尔科学奖（Intel Science Talent Search）是美国一个科学奖项，原本称为西屋
科学奖（Westinghouse Science Talent Search），颁发给优秀的高中学生。英特尔科
学奖是西屋公司于1942年所创设，1998年改称为英特尔科学奖。美国总统乔治•
赫伯特•沃克•布什曾说英特尔科学奖“是科学界的超级碗”。许多著名的
科学家都曾获得该奖，包含罗德•霍夫曼、戴维•芒福德、谢尔登... 阅读全帖 |
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i*********n
发帖数: 320 | 32
Vortex radio waves could boost wireless capacity “infinitely”
After four years of incredulity and not-so-gentle mocking, Bo Thide of the
Swedish Institute of Space Physics and a team in Italy have finally proven
that it’s possible to simultaneously transmit multiple radio channels over
exactly the same wireless frequency. In theory, according to Thide, we could
potentially transmit an “infinite number” of TV, radio, WiFi, and
cellular channels at the same time over the same frequency, blasting ... 阅读全帖 |
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c******y
发帖数: 8796 | 33 只能LOS。。。这个问题比较大。
The Venetian innovation, which comes by way of Fabrizio Tamburini and his
team of researchers, effectively takes radio waves and twists them into a
vortex. As a result, you’re able to send several discrete signals over the
same frequency, theoretically (though not practically) providing us with an
“infinite number of channels in a given, fixed bandwidth.”
Basically, the multiple signals are sent out with different degrees of spin
(“orbital angular momentum states”) and the recei... 阅读全帖 |
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l*******G
发帖数: 1191 | 34 I didn't do this kind of stuff, but what I think the best way is
to check
1) whether N-S equation or any other equation you want to use for momentum
balance of fluid assume constant viscosity or not. Seems to me that NS
equation can be used for non-homogeneous or non-constant viscosity problems
2) re-derive the vorticity equation by taking curl to the momentum equation
and find out which terms the viscosity will go in
3) take simple senarios, find out solutions such as shearing flow |
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t**********m
发帖数: 205 | 35 来自主题: Mathematics版 - 伟哥之乐 The joy of viXra
https://telescoper.wordpress.com/2011/05/19/
Posted in The Universe and Stuff with tags arXiv, astronomy, Cosmology,
Physics, scientific publishing, viXra on May 19, 2011 by telescoper
From time to time on this blog I post rants about the state of scientific
publishing, open access, the importance of the arXiv for astronomy and
cosmology, and so on.
This morning, however, I discovered an “alternative” side to the whole
business of online science, a site by the name of viXra. Mos... 阅读全帖 |
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w*q
发帖数: 1544 | 36 tao教授的意见来了：
Villatoro’s blog has some detailed analysis, and has recently raised some
serious issues with the paper as well, in the crucial Section 6. (It’s in
Spanish, but this is easy to translate online.)
I can’t read Russian either, so I am happy to defer the detailed checking
to others, but my feeling is that this sort of abstract approach to the
regularity problem, using only the energy identity and harmonic analysis
estimates on the nonlinearity rather than more precise geometric informat... 阅读全帖 |
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w*q
发帖数: 1544 | 37 Villatoro’s blog has some detailed analysis, and has recently raised some
serious issues with the paper as well, in the crucial Section 6. (It’s in
Spanish, but this is easy to translate online.)
I can’t read Russian either, so I am happy to defer the detailed checking
to others, but my feeling is that this sort of abstract approach to the
regularity problem, using only the energy identity and harmonic analysis
estimates on the nonlinearity rather than more precise geometric information
specific... 阅读全帖 |
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m***z
发帖数: 108 | 38 visualise下你的流场，比如streamline，vorticity... 看看有没有问题 |
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i*****e
发帖数: 1359 | 40 我想是因为有vorticity。因为如果只看potential flow的话，D'Alembert告诉大家是
没有力的 |
|
E**E
发帖数: 103 | 41 vorticity 不是在boundary layer么？ |
|
d*********r
发帖数: 813 | 42 vorticity/circulation是由粘性和压力梯度产生的。机翼的迎角使得上下翼面的流动
不再对称，从而压力梯度也不再对称。机翼一面压力梯度大，正向的壁面附着涡强一些
。积分的效果就是上翼面正的涡量大于下翼面负的涡量，从而环量为正，在儒可夫斯基
定律的指导下，升力出来了。
但这并不是问题的全部。尽管涡量与升力有关，但是升力产生的直接物理原因是机翼表
面的压强分布。ubcumn 网友给出的压强分布图解释了升力产生的直接原因： http://www.mitbbs.com/article_t/Physics/31210633.html |
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i*****e
发帖数: 1359 | 44 我知道来流没有vorticity啊…
我的意思就是说，机翼产生vortex，然后根据Kutta–Joukowski定理产生升力 |
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t**********m
发帖数: 205 | 45 The joy of viXra
https://telescoper.wordpress.com/2011/05/19/
Posted in The Universe and Stuff with tags arXiv, astronomy, Cosmology,
Physics, scientific publishing, viXra on May 19, 2011 by telescoper
From time to time on this blog I post rants about the state of scientific
publishing, open access, the importance of the arXiv for astronomy and
cosmology, and so on.
This morning, however, I discovered an “alternative” side to the whole
business of online science, a site by the name of viXra. Mos... 阅读全帖 |
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L*m
发帖数: 235 | 46 2015诺贝尔物理奖
获奖人：Arthur B McDonald、Takaaki Kajita
获奖领域：实验高能物理
获奖原因：发现了中微子震荡，并因此证明了中微子具有质量
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