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druS last won the day on November 27 2021

druS had the most liked content!

About druS

  • Birthday 05/19/1962

Profile Information

  • Location
    Brisbane Australia
  • Interests
    Science - Inspired by Sean Carrol to attempt to learn the math behind Quantum, and picking up a life long love of biology at the same time.

    Rugby (Union), 4WD
  • College Major/Degree
    Bachelor Building
  • Favorite Area of Science
  • Occupation
    Technical Services (Construction and Engineering)

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Baryon (4/13)



  1. Yes - relates to how "efficiency" is measured on a scientific basis which does provide useful comparators and necessary for engineering. It's also what I was referring to when data is quoted for sales purposes. It's bit like COP (coefficient of performance) figures quoted for equipment. It's not the specific equipment data that determines efficiency but the entire system/plantroom along with the way the equipment is harnessed in installation, commissioning and operation. So my use of the word "efficiency" there would be technically incorrect. But those efficiency figures are not, I think, the full story when you are considering things. I would use efficiency figures comparing two heat pumps, or two burners. But I would add other measures when comparing across different systems. As I said, I think your measurement of energy usage in operation is a very good indicator for this. It works just as well in commercial as residential or any other environment. Amazed that the Aga is outlawed - there will be plenty of people unhappy about that.
  2. Hey studiot. Not managing both hot water and heating suggests a capacity issue. Or it could be overcome (or at least ameliorated) with the additional of thermal storage. Yes it's rare to need cooling in residential in the UK. It's why I never installed a condensing boiler at home when I lived there. Gas fired boilers have been declared a risk, wow. Does that extend to other firing systems and other fuels? Geez there would be a lot of country houses regretting loosing the Aga. Commercial is a different matter and I was comfortably able to apply my trade in England for 10 years before returning home to Aus. To be honest, in the hospital Environment I was talking about earlier, I'm surprised at the campus use of steam. Seems excessive. They do need it for sterilisation but that is nominal load at best. I wouldn't have expected potable hot water to justify the installation and steam to the air handlers 24/7/365 suggests other problems in the plant operation. Buildings in Brisbane do not usually require that much heat. Possibly for dehumidification which is required to operating theatres - again nominal load. Back to the thread - I would always question heat pumps unless there was a requirement for both heat and cooling. Gas burners are wonderfully efficient, even if they are demonised on the basis of carbon these days.
  3. studiot, Before I approach your thoughts I should state that I am currently installing major heat pump installations in a large Hospital in Brisbane as part of a project that is removing an old coal burning system. As I have said here on other occasions I am not a scientist (though I have returned to study science at Uni) but do deal with engineering, installation and commissioning loosely in air-conditioning and building services - the technology side of construction, if you will. I would agree that an air-cooled heat pump may not match a gas boiler in the residential environment. Also that the tech data published regarding "efficiencies" of heat pumps is used to suggest otherwise. Even engineers get confused on that. But it's like using a truck as a taxi, it's just not where the device is strong. Any refrigerant cycle will produce heat on one side and cold on the other. If you only harness one side you've missed half the benefit. Quite literally. Worse - in most air-conditioning systems that unused heat needs an additional heat rejection system which costs additional energy. If you have a need for cooling and heating, at the same time, NOTHING will match the efficiency of a heat pump. If you don't, then more investigation is required before you commit if you want the optimum solution. We've had to be creative in the hospital with dispersed plant rooms, having to tap in to the existing systems that are available as we spread from one end of the campus to the other. And we are competing with a very efficient centralised coal burning steam system. Tough gig to match that let alone beat it. In part it works like this: The huge coal burning boiler (which run a large steam system) are to be decommissioned. The coal burner, which all things being equal will not be beaten on efficiency by anything, will be replaced by smaller dispersed gas or electric fired steam generators. Coal is better than, gas, which is better than electric. <Don't trust those words, do the engineering, but mostly it is adequate as a generalisation>But all things are not equal. Overall capacity is reduced by a combination of thermal heat pumps (driving air-conditioning) and potable hot water heat pumps. And where we had to, we use residential style electric Hot Water Units just to get load down to make the rest of the system work. It's a negative on efficiency but against the full system one we could cope with. There is the obligatory and pointless but visible PV system thrown in - a green sticker slapped on the building as these days to be virtuous must be signalled to the world. They have their place (I have them at home) but this is not really it. The thermal heat pumps, on the hot side, feed thermal or potable hot water. On the cold side they feed whatever we could find - chilled water (on the return leg hence "pre-conditioning" the return water before it gets to the chillers); - condensate water (on the flow side giving additional cooling to equipment that needs it). It would have been pointless to install heat pumps that simply wasted the cold generated. On a personal basis I am now investigating heat pumps at home for pool heating combined with air-conditioning. It's problematic as we don't necessarily need to heat the pool in summer, when the air-conditioning is running. But I'm working on it. The trick on this one will be performance on "the shoulders", ie not either peak summer or winter but the messy bits between where the engineering is more tricky and much more experience is required. Your experience with efficiency measured as operational cost (and that is actually a very good indicator) comparing a heat pump (where half of the benefit simply goes to waste) compared with a gas boiler does not surprise me in the slightest. Your maintenance cost will increase as well, by the way. But it is wrong to call these systems twaddle. PS At home my hot water is an instantaneous gas system. I'd consider solar but there is not enough roof real estate once the extensive PV system was installed, it's a three phase system to cope with air-conditioning and pool pumping. It's working fabulously well. And I like my gas hot water.
  4. Proportionally, archaea to bacteria doesn't seem right.
  5. There has been a lot made of trisomy (and monosomy) here but I wonder if it is a particular issue for binary gender sports? In each case they are considered genetic disorder (according to my 1st year Biology text anyway). I would think that XO (Turners syndrome) would be considered female. Other monosomies in humans don't survive (as I understand it). Klinefelter's syndrome (XXY) would normally be considered male, but if a female gender designation was chosen I'm not sure this would have any major impact on elite sports. Paternal non-disjunction (XXX and XYY) would surely be easily enough designated male or female, both may give a form a physical advantage (height anyway) but I wouldn't think a male or female designation challenge would apply. Happy to be corrected on the above. Allele cross over on the X and Y chromosomes would probably be a different matter, is this common?
  6. I could use recommendations for self study intended to revise a maths unit where I did poorly. General topic is Introductory Calculus and Linear Algebra. The rest of this post is simply detail as to where I am and where I hope to go - so skip if bored. I completed precalculus with flying colours but fell apart in MTHS120 Calculus and Linear Algebra 1. I think I am actually fine (with a little revision) on the basics of integration, differentiation and matrix algebra. Worryingly my issue seems to have been at a deeper conceptual level. I am not permitted to repeat a unit that I actually passed but I have pretty much a whole trimester with no formal study later this year that I can use for self study revision. Maybe 4 months. For the educators here the unit text is CALCULUS Early Transcendentals - Anton et al And clearly I have my detailed study notes which replicate the lectures. The same text is used for the unit I am preparing for along with addition text in linear algebra. If that is the answer, fabulous. The unit learning outcomes are: 1. apply the concept of limit to a range of infinite sequences, relate this to the concept of continuity in the context of specific functions; 2. [abridged] derivatives applied to variable rates of change, maxima and minima, apply to one variable problems. 3. [abridged] definite integral, volume, accumulation, elementary anti-differentiation and changes in variable 4. solve systems of linear equations, and classify the solution sets as being either uniquely determined, underdetermined or overdetermined. So an example of where I am at - outcomes 2 and 3 I'm confident I can revise on my own. On continuity I am shaky. Classifying solution sets in linear equations I can possibly manage but I have no innate understanding as the what it means, why or why it is important. Anyway, hoping there are is some solid advice here on re-engaging with my maths pathway. Dru
  7. Surely, when a cell replaces itself and the cell dies, the chromosomes within that cell have been “replaced”. At exactly the same rate that cells are replaced, so are chromosomes. Surely.
  8. You are conflating issues. Electric vehicles, on the whole, are not currently self driving. Fossil fuelled vehicles can generally be made self driving as easily as electric vehicles. In the mean time hydrogen engines promise reciprocating engines and driving experience without emission. Like fossil fuelled vehicles, hydrogen vehicles could be made self driving. Electric and hydrogen vehicles only equate to nil emissions based on the original power source or method of production. In the mean time there is huge development in fossil fuelled engine efficiency. There may well be a cross over, likely even, but mandating the prohibition of well proven transport on this basis is spurious at best. You argue then that people should be forced to choose public transport - which depending on usage rates may or may not be more efficient than, I presume, current fossil fuelled vehicles. Which ignores the pre-existing skew to public transport in populated areas, irrespective of vehicle ownership. FWIW, in residential development there is a keen move toward “self drive, electric, on order” vehicles. It creates a lot of freedom in developments which are traditionally hemmed in by vehicle storage constraints. In short electric does not equate to self driving nor nil emission. And does not preclude driving pleasure. And has not necessarily won the low-emission battle. FWIW personally my main hobby/sport is 4wd. My idea of a perfect day is switching my 4wd into auto pilot early in the morning as I sleep in, or drink coffee, taking me to the trailhead. When I take over in a vehicle with true 4wd - motor to each wheel. True independent individual wheel control in the absence of differentials and axles. Those things get hung up on rocks. And the engineering for articulation can be so much superior without them. On the trail we want “off-idle torque” and diesel chews petrol, but electric where max torque is a a theoretical zero revs, well just wow. I’m getting worked up thinking about it. Knock myself out on the trail, then back on the bitumen I crack open a beer as I press the “take me home button” and turn on a video replaying the day’s antics. The vehicle is put into pool mode at home with a priority of picking me up and dropping me off during the work week. I’ve got no intention of losing things I love, like driving. And no intention of missing the advantages of new technology as it happens. But let’s take just a modicum of intelligence to suggestions that a love of driving should be banned in order to save the planet.
  9. Defining "life" gets interesting and does not have much consensus. Ability to reproduce/heritable information Metabolism/Homeostasis (organisms can maintain themselves) It is generally considered that cells are the fundamental building block of life. While "life" is not well defined you will find that there is pretty strong agreement on the items you mention: virus are not life forms "seeds" are gametes - a step in the reproduction of certain life forms. Prions are proteins, not life (though proteins are a good example of emergence in the world if life forms) On the whole biology (life) emerges from chemistry but chemicals are not life. Molecules are not really "destroyed" but the can be transformed into other molecules. Atoms are not life and on-the-whole are not destroyed (physicists will provide plenty of corrections to that statement). Interestingly the atoms in your body largely have been around for billions of years and started as star dust. The origin of matter and atoms themselves, is another fascinating topic. You might enjoy this - a podcast by a well known Physicist interviewing a biologist and talking about "what is life?" https://www.preposterousuniverse.com/podcast/2020/01/13/79-sara-imari-walker-on-information-and-the-origin-of-life/ In an attempt to not break rules, the podcast takes a broader view on the definition of life, considers software/IT and looks to how life might appear beyond earth.
  10. How does one large fan compare to many smaller? Other things being equal the single larger fan will be more energy efficient. But other things are never equal and the centralisation of the duct sytsem will come with more resistant. One thing being missed is static v volume (in the fan selection). So those :"smaller" fans will still have the same static and aren't really smaller at all in the one metric that dictates sizze of motor/power etc. Another thing - ducts can't really be pushed at more than 10m/s, for many reasons. Most designers will work to around 6m/s if they can get away with it. A lot of what is proposed here is impracticable.
  11. Thanks Swansont, it was what i thought I was looking for but turns out you knew better than me. Appreciated. Dru
  12. No doubt at all. Two different things though. The medical advice should be the medical advice. Period. Policy setting should hefor ed that advice but dictate a response that balances things with general matters. In this case those include: 1. the country can't allow students to miss a year of schooling 2. closing schools would have a dramatic impact on health workers who rely on support from the schooling system in order to do their job. 3. drastic measures on the economy have their own impact which will also ultimately impact health of the public as poverty increases. So I can understand a desire by those responsible for the policy settings to keep schools open if it can be justified. But none of that should allow medical advice to be anything other than medical advice. And before we get too down the track of a presumption of political meddling in medical advice, Australia is doing relatively well on a global scale. Our current growth rate is 0.83 and has been below 1 for about two weeks. Our hospitals are about to be permitted to return to elective surgery (important to me as my wife treatment for a brain tumour has been halted) - this because, at this stage, our health system is not a risk of being overwhelmed.
  13. Hopefully during this period of isolation for many of us, someone can find time to check this. Some introductory remarks, this is a maths subject not physics and they really don't care about units but they do care that you simplify the answer as an accurate expression before approximating with the calculator. I have struggled with the differentiation so would appreciate thoughts there. This is just the first part at this stage. QUESTION: The ideal gas law relates the temperature, pressure and volume of an ideal gas. For n moles of gas the pressure P, volume V, and temperature T are related by the equation: PV = nRT Where n is the ideal gas constant. If pressure is measured in kilopascals (kPa), volume in litres (L) and temperature in degrees kelvin (K) then R = 8.3145 kPaL/Kmol. a) Suppose that one mole of ideal gas is held in a closed container with a volume of 25 litres. If the temperature of the gas is increased at a rate of 3.5 kelvin/min, how quickly will the pressure increase? b) Suppose that the temperature of one mole of gas is held fixed at 300K, while the volume decreases at a rate of 2.0 litres/min. How quickly is the pressure of the gas increassing at the instant that the volume is 20 litres? Thanks in advance. Edit: updated with proposed answers to both parts of the Q.
  14. This seems inconsistent with the advice from the Chief Medical Officer in Australia. The view is that the risk of transmission in schools is low and that teachers greatest risk is from other teachers, that parents greatest risk is exposure to other parents during drop off. I understand that schools are a something of a petri dish for many virus, but the view here seems to be that this virus is different.
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