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Posts posted by Externet

  1. Thanks. 

    Yes, I need a part made and wanted to have a sense of which material would be convenient.  I do not know if hardness is what I have to look for. 

    'Deformability' plus 'resiliency' to act as a seal/gasket between surfaces would make more sense 🤔   Gathering several different materials to evaluate how they perform under 5000 psi after CNC machined.

  2. Was trying to find hardness figures for nylon, delrin, ABS, teflon,  poliethylenes ...  and got lost in too many scales Shore, Brinnell flavors, Vickers, Rockwell, and metric and not metric,  

    Is so much variety needed ?  No consensus ?  Very nasty to see so many and looking for the proper conversion.  😱

  3. Good day.  Let me know if I learned it right :


    The color of the lens is the color of a laser the goggle does NOT protect.

    The color of the lens is the one the laser beam color can pass trough.

    The protection from a laser is by reflecting, absorbing or blocking the beam and which of the three cannot be told by the color of the lens.

    Goggles can protect against several laser wavelengths except the one of the lenses.




  4. Hello.

    Blue plus red emitters are used as grow light.  The resulting hue is the sum of red+blue.  Or is it the difference ?  If the sum; what color is the difference of their wavelengths ? 

    LED Grow Light Lamp 81/169LEDs Growth Lights Hydroponic Full Spectrum ...


    And what is the intended meaning for 'full spectrum' ?   (Image borrowed from the web)

  5. Hi.

    Similar situation yesterday...  One judge decided to eliminate face masks against covid19.   If hundreds of other judges do not coincide with that ruling against CDC; is it just ?  In the event of future deaths due to the no-mask ruling, will the judge be guilty ?  

  6. The definition of justice I prefer says that   - justice is to constantly and permanently impart to each one what is deserved -

    Is it just when only one judge of thousands decides to free/reverse/pardon someone accused of a crime ?   Implies that justice is subject to personal opinions, not a set rule that fits consensus.


    On 3/11/2022 at 6:28 PM, ScienceNostalgia101 said:

    How do the initial costs and maintenance costs of each compare, and how does that depend on the scale on which the photovoltaics and/or thermal solar are being used?

    Hi.  If the equipment installed cost is minimal, everything tends to work well for the pocket.  The marketing of solar water heaters are made for the pockets of vendor and installers to be happier than the customer.   Heating water from photovoltaics does not offer a good efficiency as the photovoltaic panels are only ~18% efficient; and heating panels at least triple that.

    Heating water differs a great amount on your location climate.  You may need to shield the elements from wind and cold losses... or not, with a great repercussion in costs.

    Last year I made a heater for a friend in Florida and he cannot be happier.   Installed in series before his electric water heater turned very lazy now.

    well/municipal water source ------->solar heater------->electric water heater------->house distribution

    The method I used very similar to 30+ metres thin wall black 2 inch cheap irrigation polyethylene pipe as :

    outdoor shower hot water Archives - Outdoor Shower Company

  8. Hello all.

    Never had it fully clear, voids in knowledge...    If a solution has -say all- the elements dissolved in water, and a direct electric current is passed in it;  what elements will deposit on the electrodes if the voltage is 0.1V ; if it is 0.2V; if it is 0.5V; ... ... ... if it is 1.0V ?

    Can you cite examples for each voltage please, and which table tells it ?  Electronegativity ?  Electrochemical series ?  Standard electrode potentials ?

  9. Good day.

    Somewhere read that elements can be extracted from seawater by

    - Adsorption by amidoxime-based polymers -- what is that and where to source such ?

    - Electro chemical cells ---  What determines ignoring/rejecting sodium and chlorine ions from the process and collect only other than those ?  Any 'special' voltage to ignore Cl and Na ions ?

  10. The companies that build the plexiglas separators for bank cashiers can surely do it. Probably cheap using leftovers that otherwise go to the dumpster.

    Total Security Solutions Process - Custom Bulletproof Barriers

    Edited - added.  Just make sure anchoring properly the whole or the theft will include the clear safe box...

  11. Good day.   Perhaps will be better in other subforum, please move as deserved.

    Food can be analyzed telling its amount of protein, carbohydrates, fats, minerals and all the components ingested and their weights.

    If the body is not using/storing something by digestive, genetic or absortion defect, how is that to be determined ?  Can a blood/tissue test tell if a person has deficiency of -say potassium- or -say carbohydrates- , even with abundant enough consumption of those in food ?  And the reverse, can some analysis tell there is too much -say protein intake- ?

    Is there a recommended percentage of the human body composition ?   When I used to work in aquaculture, the determining growth element was phosphorus.  If there was not enough of it in the food, growth was proportionally delayed/impaired no matter how much food was ingested.  That was determined by comparing the elements constituting the body of a shrimp and the elements found in their food 🤨

    If there was enough phosphorus in food, the other elements absortion increased to reach the balance proportions.

  12. Good day all.

    A male and female pair of nearby trees that need each other to produce fruit by pollination have both two main branches.  If one branch is removed on each tree and swap-grafted with the other sex branch; will it work as if there were two self-serving separate trees ?

    Seen 'salad' trees multi-grafted to produce varieties of -say peaches- but never read anything like what am asking...🤨

  13. Hi all.  

    Photovoltaic solar panels are around 18% efficient.  That means a 1m panel should yield about 180 Watts to heat something electrically at full sun.

    What is the typical efficiency extracting heat directly from sun radiation, assuming also 1KW/m2  irradiance as in a 1m uncovered coil like :


    Would it be around 60% ?  Wind and thermal losses should be taking a good chunk, right ?

  14. Hello all.

    Many years ago, saw painters (overseas) using milk to prepare their something, did not pay enough attention; unsure if was for a sub-base to walls or the finish paint itself.   Remember seeing a never-sanded glass-like smooth surface on walls before applying paint.  Perhaps that was the intention ?  How does it work, how come there is no bacterial degradation with something prepared with milk ?  

    I do have search engines but not interested in proportions and preparation, but more on your chemical explanation part of it.

  15. Hi.

    Hens do lay eggs without intervention of males of the species.  That has to be a considerable expense and waste of resources. What is going on ?

    Why do eagles, ducks, pelicans... do not ?  Or do they ?

  16. When in need to feed a starving -say dog- to keep alive;  is a less valuable and proper choice to feed such dog with a mole or with a chicken ?   We humans can prefer to 'discard' the life of a mole to feed the dog instead of a more 'appreciated' chicken.  If that dog did bite your child, is the value the same ?

    Or, why humans prefer to not fish whales that consume millions of lives daily instead of maintaining alive millions of shrimp ?   What can induce thinking the life of a giraffe is better to keep than the life of a beetle ?  Is size a factor ?    Is useability a factor ?  Is sentiment a factor ?  Your cat is more valuable to you than a feral cat in Namibia is to that native human there.  Humans can give a value of preference that am trying to take out of consideration.  Do all lives have the same rights to survive ?

    Am not good enough about expressing myself.  Hope there is a recognizable idea above.

  17. Greetings.

    Is there intrinsic value (not given by humans) to different species ?   Which is more valuable ?  

    A mouse or a rabbit ?

    A sardine or a shrimp ?

    A camel or a donkey ?

    A watermelon plant or a maize plant ?

    A bee or a wasp ? 

    A vulture or a seagull ?

    Or are all lives the same value,  be it a hummingbird or a crab ?  


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