-
#1020 by Tellmeagain on 31 Dec, 2015 14:23
-
Allthough I do not side with this type of the conspiracy theories, I do feel that skepticism should apply to all information we get, unless it can be verified independantly by others.
...
As we have not identified the person who claimed to work with dr.Yang in the past, we can only ASSUME that information is correct, while keeping the notion , in the back of our mind, that this might be incorrect information.
...
I could not find any birth date, but considering she might have been around 25 when graduating in 1982, that puts her age around ±58 years. Is that a common age for a Chinese professor to retire? no idea, tbh...
The only certitude on her retirement we'll have is when the university updates their page...
She was not graduated in 1982. She was a freshwoman (likely with age 18 +- 1) in 1982. So she is around 51. Professors do not retire at 51. I highly doubt oyzw's statement about her retirement. His English is not good, obviously. He might mean that she is retired from the EmDrive work.
-
#1021 by Rodal on 31 Dec, 2015 14:25
-
...
What surprised me was the poster didn't know the Demonstrator rotary test rig videos were available on www.emdrive.com Found that a bit strange.
Someone with the same username oyzw has been active in Chinese forums and previously posted having knowledge of Shawyer's SPR rotary test rig, for example:
http://bit.ly/1R0zbbaQuoteoyzw published in 2015-9-19 10:54
...You downloaded complete experimental video SPR business? On the air suspension platform EMdrive microwave signal has been swept from the low frequency to high frequency
AlsoQuoteoyzw published in 2015-9-18 23:19
Oh, I have the support of entrepreneurs and postdoctoral experiment
Users oyzw and Wrought iron also wrote in a Chinese forum some time ago something to the effect that some EM Drive committee turned down something due to "air flow". (working from memory, can't recall the statement or where it is...)
http://lt.cjdby.net/thread-1788789-1-1.htmlQuoteWrought iron Posted at 2014-2-20 08:42
This is a good thing, ah, there is no experimental video ah, Yang did you move in?
No boat experiment can not be convincing.
Need TellMeAgain or someone else fluent in Chinese to provide better translation from the Chinese forums to interpret this information
-
#1022 by Rodal on 31 Dec, 2015 14:30
-
Your interpretation (that oyzw meant that Yang is retired from EM Drive work, as the main point of oyzw's statement was the cancellation of her EM Drive project) is sensible, because this would be consistent with Yang's post-2014 papers being devoted to conventional microwave ion thrusters using reaction with an on-board propellant (no further publications on propellant-less EM Drive from Yang, and instead concentrating on conventional microwave ion thrusters using propellants).
Allthough I do not side with this type of the conspiracy theories, I do feel that skepticism should apply to all information we get, unless it can be verified independantly by others.
...
As we have not identified the person who claimed to work with dr.Yang in the past, we can only ASSUME that information is correct, while keeping the notion , in the back of our mind, that this might be incorrect information.
...
I could not find any birth date, but considering she might have been around 25 when graduating in 1982, that puts her age around ±58 years. Is that a common age for a Chinese professor to retire? no idea, tbh...
The only certitude on her retirement we'll have is when the university updates their page...
She was not graduated in 1982. She was a freshwoman (likely with age 18 +- 1) in 1982. So she is around 51. Professors do not retire at 51. I highly doubt oyzw's statement about her retirement. His English is not good, obviously. He might mean that she is retired from the EmDrive work. -
#1023 by X_RaY on 31 Dec, 2015 14:30
-
May be you are right and this is a cone with small cone angle, hard to see in the video.
It looks like a cylindrical cavity resonator. The basic result for both orientations is almost the same (increasing weight measurement of the counterweight at the balance).i m Kyungpook National Univ student and i find this Thread to youtube.
https://www.youtube.com/watch?v=HJXO1wwppOE&google_comment_id=z12wtf4pqojutrpp304cerkwjqakj5wwh3k&google_view_type#gpluscomments
so glad to see it ! and i make a emdrive this youtube and with caption. (translation must need)
simple experiment. would like watch my video . Thank you.
Hello,
1. As far as I can see this experiment is similar to Iulian Berca's.
2. The thrust obtained at the scale is around 1.5g.
3. The lengths of the two arms of the lever are similar with the frustum's arms seems to be slightly longer.
Let's say the ratio is:
frustum's arm length / counterweight arm's length = 1.2
4. Therefore the thrust at the frustum is around:
1.5/1.2=1.25g
This is quite similar to Iulian's result which is encouraging.
So for me the big question is now:
Can the 1.2g of thrust (or weight imbalance) can be explained by effects like:
- thermal air flow effects
- electromagnetic (Lorentz) forces on the power supply cables
My uneducated guess:
- the Lorentz forces would be much smaller than 1.2g
- the thermal air flow effects: no idea
Can any of the physicists here give a rough estimate of the magnitude of those two effects for the conditions of this experiment ?
Looks strong like thermal effects like convection / ballooning...
Edit: This is an important test and must be compared with a similar but conical cavity! Maybe one can eliminate (most of) the thermal component going this way.
It looks like a frustum to me, not a cylinder.
But you're right that he obtains very similar values of thrust with the frustum pointing in opposite directions.
Therefore, it's not a confirmation of the EM drive effect.
If I remember correctly Iulian obtained different thrust numbers for the up/down directions.
However, if the thermal effect thrust with such a setup is indeed of the order of 1g, that casts a lot of doubts on Iulian's results too: they might also be explained by thermal effects.
More information about would be nice. -
#1024 by Flyby on 31 Dec, 2015 14:40
-
I was curious about how important the frustrum angle was, so I did a little radical experiment. I wrote a script that ran MEEP in a loop, changing the cone slope by one degree each time, keeping the small-end diameter, height, and frequency constant. height was about 2 wavelengths. So with each run the large end got bigger and bigger. End plates were flat.
Regardless the debate on the accuracy of MEEP, in modeling electromagnetic resonances, it should not come a surpise that the patterns are super - highly sensitive to changes.
To have this complete in a reasonable amount of time I also considerably simplified the model, taking advantage of "cylindrical symmetry", placing the signal source at the enter of the small end. For now it was a linear source, but I intend to do this over again using a circularly polarized source. The source was located on the central axis, one quarter wavelength from the small end.
Using cylindrical symmetry allowed me to generate pictures for Hr, Hz, Er, and Ez fields, for every angle from 0 to 45 degrees in under one hour. Using 3D cartestian coordinates and no symmetry this would have taken nearly two days. Four videos are shown below, showing how each field pattern changes as the angle increases, one degree per second. Use the zoom feature of your video playback software to make them bigger if necessary. The pictures are all trapezoidal in shape, and show only half of the frustrum. This is because MEEP knows that everything is symmetrical and so only computes that one view. The field names with "r" in them mean "radial".
Analysis: 1. the field patterns are extremely sensitive to cone angle. Radical changes were seen sometimes with only one degree of change. This suggests that experimenters should not choose cone angles at random.
2. The curvature of the fields due to the diverging frustrum walls was clearly evident even at this low resolution. And in some ranges of angle the fields were curved in the reverse direction! I expect this to be considerably affected by the flat end plate. I will do it again later using spherical end-plates. And also with exponential ("trombone") wall shapes.
3. At some angles the 'sign' of the fields reversed completely. (Indicated by blue vs red in the pictures.)
After all, using reflecting mirrors you double the sensitivity for each reflection, so imagine the consequences when a wave is reflected 10 000x times or more...
I think these (slow) spatial shifts of amplitudes is mainly caused by the shape of the cavity.
Because the resonance patterns (they are not static, as first expected) depend on the spatial cumulative amplitudes, the slightest change in spatial position of the amplitude spike of one or more waves, will cause different cause patterns.
According my uneducated guess, this is why it is so extremely hard to get consistent results from an EMdrive (IF there is any thrust signal to be found, that is)
The slightest change in frequency, cavity dimensions or angle of the frustum will wreck havoc on the apparent stable resonance pattern.
But then again...I'm unqualified in the matter on a theoretical level and can not prove it on an experimental way... sadly, my point of view has zero scientific value atm, but working on it...
-
#1025 by Flyby on 31 Dec, 2015 14:45
-
Allthough I do not side with this type of the conspiracy theories, I do feel that skepticism should apply to all information we get, unless it can be verified independantly by others.
...
As we have not identified the person who claimed to work with dr.Yang in the past, we can only ASSUME that information is correct, while keeping the notion , in the back of our mind, that this might be incorrect information.
...
I could not find any birth date, but considering she might have been around 25 when graduating in 1982, that puts her age around ±58 years. Is that a common age for a Chinese professor to retire? no idea, tbh...
The only certitude on her retirement we'll have is when the university updates their page...
She was not graduated in 1982. She was a freshwoman (likely with age 18 +- 1) in 1982. So she is around 51. Professors do not retire at 51. I highly doubt oyzw's statement about her retirement. His English is not good, obviously. He might mean that she is retired from the EmDrive work.
posts follow each other at such a pace that we cant see/read each others posts anymore..
I did suggest the same thing (a linguistic problem), a few posts earlier...
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1467826#msg1467826 -
#1026 by OnlyMe on 31 Dec, 2015 14:46
-
....
Great post, yet I disagree with the portion highlighted in blue. I honestly feel like I'm flying blind without some sort of acceptable theory of operation in mind (at least acceptable to me). The current theories on the table make no sense. It is no wonder why EmDrive is not progressing. The experimental results are sitting in the noise floor. Sure, trial and error may get better results, better RF engineering may get better results. Actually understanding how it works and exactly why it does what it supposedly does, is what gets results.
An analogy. Can you imagine what kind of boon doggle it would be to try and improve the operation of a transistor without knowledge of Quantum Mechanics? Making a semiconductor work well requires in depth understanding of such things.
There is no requirement for EmDrive to require "obviously New Physics."
The intent was that until there is a credible working theory, engineering a working system should be the goal.
There are many suggestions for what should be tested that obviously depart from what we know of the designs that past claims are based on. Unless you have unlimited funding and other resources, trying to find out how variations might affect the results before you have repeatable results, seems premature.
So I said, "catch the rabbit before cooking it"..., meaning first confirm what has been claimed.., prove those claims repeatable, before spending too much time and money chasing the what if we changed this or that, to see what might happen. -
#1027 by TheTraveller on 31 Dec, 2015 15:02
-
Yes ！ D - big: D - 290 mm small: 170 mm L - center: 240 mm TE013（pure copper sheet （ thickness 1.25 mm ））. If you need TE012, I can modify the mould.I'm worried that this entire argument (from the first Rodal post) is going to insult / drive off Chinese contributors. Might I suggest that we assume the information given is likely correct.
Have learned he/she has a TE013 molded frustum for sale.
Asking for more detailed engineering data.
Thanks for the data.
Can you send VNA scan to verify the resonance freq and bandwidth?
Are the end plates flat, spherical at vertex radius, stepped back or something else. How are they attached to the frustum?
Phil -
#1028 by Tellmeagain on 31 Dec, 2015 15:18
-
Someone with the same username oyzw has been active in Chinese forums and previously posted having knowledge of Shawyer's SPR rotary test rig, for example:
http://bit.ly/1R0zbbaQuoteoyzw published in 2015-9-19 10:54
Also
...You downloaded complete experimental video SPR business? On the air suspension platform EMdrive microwave signal has been swept from the low frequency to high frequencyQuoteoyzw published in 2015-9-18 23:19
[SNIPPED]
Oh, I have the support of entrepreneurs and postdoctoral experiment
Need TellMeAgain or someone else fluent in Chinese to provide better translation from the Chinese forums to interpret this information
The first quote (In answering a previous post from user "寒江毒钓" that "I personally support oyzw. How is your experiment going? Wish you do well! If you can get (positive) experiment result, theory is not important" ): Have you downloaded the complete experiment video of the SPR company? On the air suspension platform EMdrive's microwave signal has been swept from the low frequency to high frequency (Your google translation is amazing... But I do not know whether he referred to SPR video, Yang's experiment, or His own.)
The second quote: (When asked how his own experiments went) Oh, I have support from entrepreneurs and post docs (on my own experiment) . -
#1029 by Tellmeagain on 31 Dec, 2015 15:27
-
Quote
Wrought iron Posted at 2014-2-20 08:42
This is a good thing, ah, there is no experimental video ah, Yang did you move in?
No boat experiment can not be convincing.
Need TellMeAgain or someone else fluent in Chinese to provide better translation from the Chinese forums to interpret this information
Wrought iron's post:QuoteQuotepershine (another user) posted in 2014-2-19 23:35
You could not convince us if you do not do a boat experiment.
This is a good thing. Do you have a video of the experiment? Did yang recruit you?
-
#1030 by Rodal on 31 Dec, 2015 15:35
-
Quote
Wrought iron Posted at 2014-2-20 08:42
This is a good thing, ah, there is no experimental video ah, Yang did you move in?
No boat experiment can not be convincing.
Need TellMeAgain or someone else fluent in Chinese to provide better translation from the Chinese forums to interpret this information
Wrought iron's post:QuoteQuotepershine (another user) posted in 2014-2-19 23:35
You could not convince us if you do not do a boat experiment.
This is a good thing. Do you have a video of the experiment? Did yang recruit you?
And if you are curious, I am the Wrought iron who have debated with him for years.
Thank you. What does "boat experiment" mean specifically? Does it refer to:
1) an EM Drive on a rotary platform suspended on an air bearing as in SPR Shawyer experiment video of the EM Drive Demonstrator
2) An EM Drive on a "boat" floating in a liquid fluid
3) something else -
#1031 by Tellmeagain on 31 Dec, 2015 15:37
-
Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
-
#1032 by Rodal on 31 Dec, 2015 15:40
-
Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
Excellent point. This point was actually discussed in EM Drive threads 1 and 2 (the need for rectilinear motion rather than rotary motion for a number of reasons including the Lorentz force).
Great discussions we had
A number of people perhaps could come back to the forum ?
-
#1033 by rfmwguy on 31 Dec, 2015 16:24
-
Monomorphic on another forum has a horizontal air slide which I think is safer and just as effective as a boat on WATER...did I say WATER and 4kV?Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
Excellent point. This point was actually discussed in EM Drive threads 1 and 2 (the need for rectilinear motion rather than rotary motion for a number of reasons including the Lorentz force).
Great discussions we had
A number of people perhaps could come back to the forum ? -
#1034 by Rodal on 31 Dec, 2015 16:28
-
Nobody mentioned water. Also, Shell early on proposed these concepts and how to address isolation. There are a number of non-conductive liquids (certainly less conductive than the very polar water molecule) that also have greater viscosity and hence damping value to dampen oscillations. For example, here is a DoItYourself using vegetable oil with a computer:
Monomorphic on another forum has a horizontal air slide which I think is safer and just as effective as a boat on WATER...did I say WATER and 4kV?Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
Excellent point. This point was actually discussed in EM Drive threads 1 and 2 (the need for rectilinear motion rather than rotary motion for a number of reasons including the Lorentz force).
Great discussions we had
A number of people perhaps could come back to the forum ?
http://www.tomshardware.com/reviews/strip-fans,1203.html -
#1035 by VAXHeadroom on 31 Dec, 2015 16:28
-
The geometrical axisymmetry of the frustum of the cone is presently not being exploited. However, assuming full axisymmetry would only produce fully axisymmetric electromagnetic modes. One would not be able to get the TM212 mode that NASA obtains in their experimental measurements for example.
A number of modes are not fully axisymmetric but display m-fold symmetry (where "m" is the first quantum number in TEmnp or TMmnp modes). The following images shows the lowest TEmn and TMmn modes, for arbitrary "p":
Only modes with m=0 are fully axisymmetric (for example TE012) . For m=1 one has to model half of the circular cross-section (and one can impose symmetry on the boundaries). For higher m>1 one has to model "smaller pie slices". So, it looks like one could at least save 50% of the mesh by exploiting axisymmetry
More problematic, it would preclude non-fully axisymmetric modes. To exploit axisymmetry one would have to determine what is the maximum number of poles around the circumference one wants to model: it would effectively set a pre-defined limit on the "m" and "n" quantum numbers that the model could model for TEmnp and TMmnp modes.
This is further complicated by the fact that Meep has revealed asymmetric modes not present in cylindrical cavities. Imposing axysymmetry would get rid of such asymmetric modes. For example, an asymmetric placement of an antenna, or an asymmetric placement of a waveguide can excite asymmetric modes in a real cavity, and it is useful for the designer to know this.
Actually, one of the greatest contributions of Meep analysis has been to make this asymmetric modes evident, and show how difficult it is to achieve axisymmetric resonant modes with antennas.
Well...here's my first shot at computing an endplate 'energy' picture from the meep data.
I hesitate to call this the thermal signature because I'm guessing at the equation.
This picture was generated with the following algorithm:
(where each frame element is the <x,y,z> H field 3 vector)
for each frame 1..112
for each row
for each col
sum[row][col] += abs( VCos_Angle(data[frame][row][col] , z) ) * vlength(data[frame][row][col]);
This sum is then output as the height of a cylinder and colored as in the picture. Elements whose resulting value < 1e-6 are ignored. The "MAX" shown is automatically computed as the highest value of the sum array. The MIN is 0 to 3 decimal points as shown. Values are in 'meep units'.
This was my best guess at a reasonable way to compute this. If a different algorithm is desired, let me know.
This meep model file is from aero modeling SeeShells' device. It is the same data as used to generate the H field animations I've been posting.
It looks pretty darn close to both TM12 and TE12!
Doing this for the small end is pretty trivial. Doing it for the conical section is a son-of-a-gun, but I'm working on it
-
#1036 by Rodal on 31 Dec, 2015 16:32
-
Good effort, as it uncovers some problems:
The geometrical axisymmetry of the frustum of the cone is presently not being exploited. However, assuming full axisymmetry would only produce fully axisymmetric electromagnetic modes. One would not be able to get the TM212 mode that NASA obtains in their experimental measurements for example.
A number of modes are not fully axisymmetric but display m-fold symmetry (where "m" is the first quantum number in TEmnp or TMmnp modes). The following images shows the lowest TEmn and TMmn modes, for arbitrary "p":
Only modes with m=0 are fully axisymmetric (for example TE012) . For m=1 one has to model half of the circular cross-section (and one can impose symmetry on the boundaries). For higher m>1 one has to model "smaller pie slices". So, it looks like one could at least save 50% of the mesh by exploiting axisymmetry
More problematic, it would preclude non-fully axisymmetric modes. To exploit axisymmetry one would have to determine what is the maximum number of poles around the circumference one wants to model: it would effectively set a pre-defined limit on the "m" and "n" quantum numbers that the model could model for TEmnp and TMmnp modes.
This is further complicated by the fact that Meep has revealed asymmetric modes not present in cylindrical cavities. Imposing axysymmetry would get rid of such asymmetric modes. For example, an asymmetric placement of an antenna, or an asymmetric placement of a waveguide can excite asymmetric modes in a real cavity, and it is useful for the designer to know this.
Actually, one of the greatest contributions of Meep analysis has been to make this asymmetric modes evident, and show how difficult it is to achieve axisymmetric resonant modes with antennas.
Well...here's my first shot at computing an endplate 'energy' picture from the meep data.
I hesitate to call this the thermal signature because I'm guessing at the equation.
This picture was generated with the following algorithm:
(where each frame element is the <x,y,z> H field 3 vector)
for each frame 1..112
for each row
for each col
sum[row][col] += abs( VCos_Angle(data[frame][row][col] , z) ) * vlength(data[frame][row][col]);
This sum is then output as the height of a cylinder and colored as in the picture. Elements whose resulting value < 1e-6 are ignored. The "MAX" shown is automatically computed as the highest value of the sum array. The MIN is 0 to 3 decimal points as shown. Values are in 'meep units'.
This was my best guess at a reasonable way to compute this. If a different algorithm is desired, let me know.
This meep model file is from aero modeling SeeShells' device. It is the same data as used to generate the H field animations I've been posting.
It looks pretty darn close to both TM12 and TE12!
Doing this for the small end is pretty trivial. Doing it for the conical section is a son-of-a-gun, but I'm working on itQuoteThis meep model file is from aero modeling SeeShells' device. It is the same data as used to generate the H field animations I've been posting.
(I thought that Shell and aero were expecting TE01 instead of TE12)(completely different mode !!! )
Actually the mode shown by the Meep model does not look like any of these modes, really...
That's the reason why I had suggested making this verification comparison
All Meep runs need verification to compare with reality The problem is not with Meep, the issue is with the particular models, including pre-processing and post-processing
pardon the word "garbage" in this slide from the Internet, showing the basic issue, the word "garbabe" is not meant to be offensive, it is enshrined in computer science:
https://en.wikipedia.org/wiki/Garbage_in,_garbage_out
-
#1037 by rfmwguy on 31 Dec, 2015 16:35
-
Should be non-conductive AND non-flammable.
Nobody mentioned water. Also, Shell early on proposed these concepts and address isolation. There are a number of non-conductive liquids (certainly less conductive than the very polar water molecule) that also have greater viscosity and hence damping value to dampen oscillations. For example, here is a DoItYourself using vegetable oil with a computer:
Monomorphic on another forum has a horizontal air slide which I think is safer and just as effective as a boat on WATER...did I say WATER and 4kV?Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
Excellent point. This point was actually discussed in EM Drive threads 1 and 2 (the need for rectilinear motion rather than rotary motion for a number of reasons including the Lorentz force).
Great discussions we had
A number of people perhaps could come back to the forum ?
http://www.tomshardware.com/reviews/strip-fans,1203.html
I must have missed Shell's boat comments...otherwise my Spidey-sense would have compelled me to post a snarky comment about water. -
#1038 by SeeShells on 31 Dec, 2015 16:38
-
I was helping Monomorphic out on his air slide with some thoughts and I liked the idea.
Monomorphic on another forum has a horizontal air slide which I think is safer and just as effective as a boat on WATER...did I say WATER and 4kV?Second. Because a rotary platform that can move half a circle can be caused by Lorentz force. Only a straight movement is convincing.
Excellent point. This point was actually discussed in EM Drive threads 1 and 2 (the need for rectilinear motion rather than rotary motion for a number of reasons including the Lorentz force).
Great discussions we had
A number of people perhaps could come back to the forum ? -
#1039 by VAXHeadroom on 31 Dec, 2015 17:01
-
Well...here's my first shot at computing an endplate 'energy' picture from the meep data.
What model are you running?
I hesitate to call this the thermal signature because I'm guessing at the equation.
This picture was generated with the following algorithm:
(where each frame element is the <x,y,z> H field 3 vector)
for each frame 1..112
for each row
for each col
sum[row][col] += abs( VCos_Angle(data[frame][row][col] , z) ) * vlength(data[frame][row][col]);
This sum is then output as the height of a cylinder and colored as in the picture. Elements whose resulting value < 1e-6 are ignored. The "MAX" shown is automatically computed as the highest value of the sum array. The MIN is 0 to 3 decimal points as shown. Values are in 'meep units'.
This was my best guess at a reasonable way to compute this. If a different algorithm is desired, let me know.
This meep model file is from aero modeling SeeShells' device. It is the same data as used to generate the H field animations I've been posting.
It looks pretty darn close to both TM12 and TE12!
Doing this for the small end is pretty trivial. Doing it for the conical section is a son-of-a-gun, but I'm working on itQuoteThis meep model file is from aero modeling SeeShells' device. It is the same data as used to generate the H field animations I've been posting.
(I thought that Shell and aero were expecting TE01 instead of TE12)(completely different mode !!! )
Actually the mode shown by the Meep model does not look like any of these modes, really...
That's the reason why I had suggested making this verification comparison
All Meep runs need verification to compare with reality The problem is not with Meep, the issue is with the particular models
pardon the word "garbage" which is not meant to be offensive, it is enshrined in computer science:
https://en.wikipedia.org/wiki/Garbage_in,_garbage_out
I'm a programmer, I totally understand GIGO
There are a LOT of steps in this chain, and some guesswork on my part, so each of those requires scrutiny.
FIRST and foremost in my mind: is the algorithm (posted above) correct?
Following right behind that is: did I implement it correctly? i.e. does this output accurately reflect what the meep model generates? If I have that right then we work back up the chain to the meep model itself.
One note: This looks to me to match the data I see in the animations. Of course part of the same tool chain is used (conversion of the CSV files output from the h5totxt to the POV-Ray include files using C++ code I wrote), so the errors could be common to that. I have manually spot-checked data values and found them to have been copied correctly from input to output, but peer review is a 'very good thing'.
