I see a contradiction between statements in the two linked articles, so I'm confused.
BBC: Gill Fine, FSA director of consumer choice and dietary health, said:..."What it shows is that there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food."
postpeakpublishing: According to the study's Executive Summary: "This review does not address contaminant content (such as herbicide, pesticide and fungicide residues) of organically and conventionally produced foodstuffs or the environmental impacts of organic and conventional agricultural practices."
I can see how the study would fail to show evidence of additional benefits, if it didn't address contaminant content. But that same omission makes it impossible for this study to show that there is no evidence of such benefits.
I resolve my confusion by concluding that Gill Fine (ironically, an executive of the agency that commissioned the study) either didn't read the Executive Summary, or has poor reading comprehension.
If you use energy that decelerates the object, the force of gravity will de-orbit it
Changing the object's energy is what changes the orbit. Gravity does not. There are two ways (that I know of) to change the object's energy. One way is dissipation as heat (braking through the atmosphere). The other is to transfer the energy to or from something else. I can suggest three means of accomplishing the second: propulsion, collision, and tethering.
Gravity does not *change* the orbit. Gravity is the curvature of spacetime that *defines* the orbit (and all possible orbits). Which is not the same as "saying that there is no real effect of gravity".
I'm working in the ISS's inertial frame of reference. Here gravity is a fictitious force, no more a force than centrifugal force is.
I'm well aware of that you could model it as a real force and work in a non-inertial frame of reference. But whether you choose to do so or not is completely beside the point. An object in orbit, not being acted on by (real) forces, will have a constant total energy. The change in energy required to deorbit an object doesn't come from gravity, even if you are working in the Earth's non-inertial frame. You seem to disagree but I'm not sure why.
I wasn't being pedantic but now I will be: "Work" is force integrated over distance. Gravity is not a force so does no work. Actual work will change the geodesic path followed by an object (the ground hitting the object will do this in a big way, for example).
Actually gravity curves spacetime. The ISS will follow a geodesic path (a straight line is a special case: a geodesic in flat space), to the extent it isn't acted on by external forces. There is always going to be some decay of an orbit because of external forces, but Earth's gravity will never change the object's orbit. Without the external forces it would stay up forever. (To be pedantic, since gravity according to general relativity isn't a force, you could have perturbations of the orbit that aren't caused by "external forces" that would result in the object crashing to Earth, but that's not how we'd want to de-orbit the ISS.)
It has to do with glycemic index. GP is not saying you can take in more calories than you expend without gaining weight. If the calories are in the form of a high-GI food then they will be converted to fat fairly quickly, and will be harder to burn off. If they are in the form of a low-GI food then they will be absorbed slowly and the body will be able to expend more of those calories through normal metabolic processes. If identical twins try two diets with the same caloric intake, one with high GI and one with low GI, then this theory says the twin with the high GI diet will end up fatter than the other twin.
"Gravity" is not what you use to achieve the change in kinetic energy required to de-orbit an object. You need to fire rockets to slow the thing down. Once the speed is reduced enough so that perigee is within Earth's atmosphere, then atmospheric braking does the rest.
Series hybrid advocates always make that first claim. The theory is, when used to make electricity, the engine can be run more efficiently. There are a couple of possibilities. One is simply that the engine is small enough to provide a maximum battery charge, but not a peak motor draw... so you're using the battery to level performance peaks and valleys, rather than needed an engine that can respond this way. That's fine, but it also implies that, worst-case, you wind up in some kind of "Turtle" mode... which the Prius can, too, when it needs both battery and ICE buy only ICE is available (very rare in the 2001+ models, fairly common in the 1998-2000 model from what I hear). This obviously has to overcome something the loss of efficiency in generator (5%), motor (5%) and battery (10-15%), depending on just how you do it. I remain skeptical.
I understand the theory. "Series is more efficient than parallel" is likely true in very particular conditions. I see HSD as optimized for two circumstances: In start-stop driving, regenerative braking recovers some of the loss that would otherwise be burned as heat in the brakes; and in long-distance cruising, because the hybrid system allows use of a smaller engine (having more power is useful for acceleration but at constant reasonable highway speeds is just going to burn more fuel, so cover the acceleration needs with a supplemental motor that isn't always driving the wheels). Some Prius drivers like to use pulse driving which I described in another post, to avoid any mechanicalelectrical conversions when cruising, thereby getting some of the very high MPGs that have been reported. One could joke that you could get the benefits of pulse driving all the time in a Prius by taking out the electrical drive components, but then you wouldn't have regenerative braking so it would be less efficient for driving in urban or suburban situations with lots of stop signs or traffic lights (not to mention that acceleration would be painfully slow).
In the first circumstance, both series and parallel hybrids can take advantage of regenerative braking; I'm not sure if either is inherently more efficient in such conditions. In the second circumstance, I think the series drive is at a disadvantage since it will always have the dual conversion loss, and the parallel drive won't. And at least in HSD systems, the power-split device allows the engine to turn at a near-optimum RPM over a range of conditions, so that advantage isn't reserved for series hybrids (HSD is actually described, at least by wikipedia, as a series-parallel hybrid, due to the mode where one MG powers the other -- giving it the best of both worlds, I suppose).
I wasn't aware that the 2010 Prius already came in a plug-in version (even if only in fleet cars); I thought it was still a year or two away.
I wonder at what cruising speeds the electric path would transport no power in a Prius.
Prius enthusiasts refer to this a "dead-band driving". There are two possible cases. The first is that you are accelerating at a rate that requires exactly the amount of power that the ICE is producing, so there is no excess going to the battery and no power being drawn from the battery. Thus the tank-to-wheel efficiency is at its maximum (I don't recall for certain, but I think the Atkinson cycle engine is somewhere around 37% efficiency compared to low 30s for Otto cycle). The second possibility is during coasting; normally this will result in power transfer from the wheels to the battery, but if you depress the accelerator just slightly then the wheels are essentially spinning freely and you maximize coasting distance. The ICE shuts off during coasting (not under all circumstances, but this is often the case), which means you only burn gasoline during acceleration. Alternating between these two modes, say over a 10 MPH difference between minimum and maximum speeds, results in "pulse driving" which is how some drivers get 60 MPG or higher from their Priuses; they avoid the mechanical/electrical/mechanical conversion loss.
Huh? You can't get a single joule to the wheels without first converting it to electrical and then back to mechanical energy. That's two conversions. You lose energy with each conversion. How is that more efficient?
2: Easier to swap out the fuel source (just bolt-in a new generator)
Huh? A generator is not a fuel source. I'm not sure what you mean. Perhaps you should clarify this statement.
3: You can run the darn things on pure-grid if your trips are short enough
I don't think parallel hybrids have an inherent limitation there. Plug-in Priuses are in development (and some people have spent big bucks to have their Priuses converted to plug-in already).
I'm trying to figure out where in your description of parallel hybrids you state something contrary to what he said, but I couldn't (although your example of an electric motor driving front wheels and gasoline engine driving rear wheels doesn't correspond to any vehicle I've ever heard about). I think he does understand the difference (unlike the poster he was responding to). It's true that "A series car typically has the electric motor inline with the engine to provide boost" isn't a good description of series, but I take "inline" to mean that the motor is directly in the power path from engine to wheel, which is correct. Remove the motor and there is no way to get power from the engine to the wheels. His description fails in that the phrase "to provide boost" is wrong (unless he means that the electric motor does have torque at 0 RPM which the ICE doesn't), but otherwise I think he was pretty accurate.
So what? Do you have the same indignation at speed bumps and stop signs?
First, the purpose of my post was to correct the poster above me; that's not an expression of indignation. If I get irritated at cyclists, it's more often for their disregard of both the law and common-sense safety, but then that applies to many motorists as well.
I don't feel indignation about stop signs, which are there to promote safety. From what I see in my area, though, most cyclists hold stop signs in utter contempt.
Speed bumps strike me as a "feel-good" safety measure; I'm not aware of any proof that they actually make things safer. Do they cause greater energy consumption like stop signs? Not really, since drivers tend to choose a speed that can be maintained fairly constantly in the presence of speed bumps; there are always multiple speed bumps and they are usually either in parking lots, or in residential areas where there are already stop signs, so the tendency of speed bumps is to reduce the peak speed between stop signs, which reduces energy consumption. That is, accelerating from a stop sign to 40 MPH and stopping again will consume more energy than accelerating to 20 MPH (due to speed bumps) and stopping again, over the same distance.
Nevertheless, for you comparison to be even remotely fair, you'd have to compare the total amount of energy wasted to get a person from point A to point B utilizing both methods of transportation. I'm no physicist, but I'm willing to bet the biker is going to come out on top in most circumstances.
Again you miss the point: that I was correcting the previous poster. I'm all for more people cycling to reduce energy consumption. But you can't cite fairness, because cycling is not a practical choice for most people, and for some it is not an available choice at all. The argument is not against cycling; it's about the effect some cyclists' habits have on others.
Where I live, I'd estimate that between 25% and 50% of the drivers regularly run stop signs -- and in many of those cases I don't just mean the typical California roll, I mean blatant cruising through the intersection. But it seems like close to 100% of the cyclists run them, and in their case most often it's without the slightest squeeze on the brake levers.
I suspect it's because they just don't want to work too hard. Slowing down costs energy for both car and cyclist, but the driver of a car doesn't get very tired from stepping on the pedal.
Slashdot Mirror
I see a contradiction between statements in the two linked articles, so I'm confused.
BBC: Gill Fine, FSA director of consumer choice and dietary health, said: ..."What it shows is that there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food."
postpeakpublishing: According to the study's Executive Summary: "This review does not address contaminant content (such as herbicide, pesticide and fungicide residues) of organically and conventionally produced foodstuffs or the environmental impacts of organic and conventional agricultural practices."
I can see how the study would fail to show evidence of additional benefits, if it didn't address contaminant content. But that same omission makes it impossible for this study to show that there is no evidence of such benefits.
I resolve my confusion by concluding that Gill Fine (ironically, an executive of the agency that commissioned the study) either didn't read the Executive Summary, or has poor reading comprehension.
and therefore aren't actually present in sufficient quantities to present much of a threat
Combining non sequitur and straw man in one, nice!
At the risk of sounding off-topic, that "Operational Transform (OT)" in the protocol is too close to "Operating Thetan (OT)" for my comfort.
If you use energy that decelerates the object, the force of gravity will de-orbit it
Changing the object's energy is what changes the orbit. Gravity does not. There are two ways (that I know of) to change the object's energy. One way is dissipation as heat (braking through the atmosphere). The other is to transfer the energy to or from something else. I can suggest three means of accomplishing the second: propulsion, collision, and tethering.
Gravity does not *change* the orbit. Gravity is the curvature of spacetime that *defines* the orbit (and all possible orbits). Which is not the same as "saying that there is no real effect of gravity".
I'm working in the ISS's inertial frame of reference. Here gravity is a fictitious force, no more a force than centrifugal force is.
I'm well aware of that you could model it as a real force and work in a non-inertial frame of reference. But whether you choose to do so or not is completely beside the point. An object in orbit, not being acted on by (real) forces, will have a constant total energy. The change in energy required to deorbit an object doesn't come from gravity, even if you are working in the Earth's non-inertial frame. You seem to disagree but I'm not sure why.
It *is* being done here on Earth -- see photosynthesis. You just need a broader definition of "we".
Ah well, there's bound to be a car analogy in every /. story these days.
I wasn't being pedantic but now I will be: "Work" is force integrated over distance. Gravity is not a force so does no work. Actual work will change the geodesic path followed by an object (the ground hitting the object will do this in a big way, for example).
Actually gravity curves spacetime. The ISS will follow a geodesic path (a straight line is a special case: a geodesic in flat space), to the extent it isn't acted on by external forces. There is always going to be some decay of an orbit because of external forces, but Earth's gravity will never change the object's orbit. Without the external forces it would stay up forever. (To be pedantic, since gravity according to general relativity isn't a force, you could have perturbations of the orbit that aren't caused by "external forces" that would result in the object crashing to Earth, but that's not how we'd want to de-orbit the ISS.)
Except most soft drinks don't use sugar in the US, they use high-fructose corn syrup
Er...fructose is a sugar.
I was going to write a long critique of your apathy but decided it was too much trouble.
Is that apathy or laziness?
It has to do with glycemic index. GP is not saying you can take in more calories than you expend without gaining weight. If the calories are in the form of a high-GI food then they will be converted to fat fairly quickly, and will be harder to burn off. If they are in the form of a low-GI food then they will be absorbed slowly and the body will be able to expend more of those calories through normal metabolic processes. If identical twins try two diets with the same caloric intake, one with high GI and one with low GI, then this theory says the twin with the high GI diet will end up fatter than the other twin.
"Gravity" is not what you use to achieve the change in kinetic energy required to de-orbit an object. You need to fire rockets to slow the thing down. Once the speed is reduced enough so that perigee is within Earth's atmosphere, then atmospheric braking does the rest.
Escape velocity is approximately twice orbital velocity...Extremely rough terms
I'll say. The actual factor is the square root of 2 (assuming by "orbital velocity" we are referring to a circular orbit).
TFA repeatedly misuses apostrophes to form plurals ("userID's").
You should see the mobile devices of the day -- they had 3-foot displays.
I want to see this 13-foot monitor!
Series hybrid advocates always make that first claim. The theory is, when used to make electricity, the engine can be run more efficiently. There are a couple of possibilities. One is simply that the engine is small enough to provide a maximum battery charge, but not a peak motor draw... so you're using the battery to level performance peaks and valleys, rather than needed an engine that can respond this way. That's fine, but it also implies that, worst-case, you wind up in some kind of "Turtle" mode... which the Prius can, too, when it needs both battery and ICE buy only ICE is available (very rare in the 2001+ models, fairly common in the 1998-2000 model from what I hear). This obviously has to overcome something the loss of efficiency in generator (5%), motor (5%) and battery (10-15%), depending on just how you do it. I remain skeptical.
I understand the theory. "Series is more efficient than parallel" is likely true in very particular conditions. I see HSD as optimized for two circumstances: In start-stop driving, regenerative braking recovers some of the loss that would otherwise be burned as heat in the brakes; and in long-distance cruising, because the hybrid system allows use of a smaller engine (having more power is useful for acceleration but at constant reasonable highway speeds is just going to burn more fuel, so cover the acceleration needs with a supplemental motor that isn't always driving the wheels). Some Prius drivers like to use pulse driving which I described in another post, to avoid any mechanicalelectrical conversions when cruising, thereby getting some of the very high MPGs that have been reported. One could joke that you could get the benefits of pulse driving all the time in a Prius by taking out the electrical drive components, but then you wouldn't have regenerative braking so it would be less efficient for driving in urban or suburban situations with lots of stop signs or traffic lights (not to mention that acceleration would be painfully slow).
In the first circumstance, both series and parallel hybrids can take advantage of regenerative braking; I'm not sure if either is inherently more efficient in such conditions. In the second circumstance, I think the series drive is at a disadvantage since it will always have the dual conversion loss, and the parallel drive won't. And at least in HSD systems, the power-split device allows the engine to turn at a near-optimum RPM over a range of conditions, so that advantage isn't reserved for series hybrids (HSD is actually described, at least by wikipedia, as a series-parallel hybrid, due to the mode where one MG powers the other -- giving it the best of both worlds, I suppose).
I wasn't aware that the 2010 Prius already came in a plug-in version (even if only in fleet cars); I thought it was still a year or two away.
I wonder at what cruising speeds the electric path would transport no power in a Prius.
Prius enthusiasts refer to this a "dead-band driving". There are two possible cases. The first is that you are accelerating at a rate that requires exactly the amount of power that the ICE is producing, so there is no excess going to the battery and no power being drawn from the battery. Thus the tank-to-wheel efficiency is at its maximum (I don't recall for certain, but I think the Atkinson cycle engine is somewhere around 37% efficiency compared to low 30s for Otto cycle). The second possibility is during coasting; normally this will result in power transfer from the wheels to the battery, but if you depress the accelerator just slightly then the wheels are essentially spinning freely and you maximize coasting distance. The ICE shuts off during coasting (not under all circumstances, but this is often the case), which means you only burn gasoline during acceleration. Alternating between these two modes, say over a 10 MPH difference between minimum and maximum speeds, results in "pulse driving" which is how some drivers get 60 MPG or higher from their Priuses; they avoid the mechanical/electrical/mechanical conversion loss.
In random order:
1: More efficient.
Huh? You can't get a single joule to the wheels without first converting it to electrical and then back to mechanical energy. That's two conversions. You lose energy with each conversion. How is that more efficient?
2: Easier to swap out the fuel source (just bolt-in a new generator)
Huh? A generator is not a fuel source. I'm not sure what you mean. Perhaps you should clarify this statement.
3: You can run the darn things on pure-grid if your trips are short enough
I don't think parallel hybrids have an inherent limitation there. Plug-in Priuses are in development (and some people have spent big bucks to have their Priuses converted to plug-in already).
I'm trying to figure out where in your description of parallel hybrids you state something contrary to what he said, but I couldn't (although your example of an electric motor driving front wheels and gasoline engine driving rear wheels doesn't correspond to any vehicle I've ever heard about). I think he does understand the difference (unlike the poster he was responding to). It's true that "A series car typically has the electric motor inline with the engine to provide boost" isn't a good description of series, but I take "inline" to mean that the motor is directly in the power path from engine to wheel, which is correct. Remove the motor and there is no way to get power from the engine to the wheels. His description fails in that the phrase "to provide boost" is wrong (unless he means that the electric motor does have torque at 0 RPM which the ICE doesn't), but otherwise I think he was pretty accurate.
Citation here.
So what? Do you have the same indignation at speed bumps and stop signs?
First, the purpose of my post was to correct the poster above me; that's not an expression of indignation. If I get irritated at cyclists, it's more often for their disregard of both the law and common-sense safety, but then that applies to many motorists as well.
I don't feel indignation about stop signs, which are there to promote safety. From what I see in my area, though, most cyclists hold stop signs in utter contempt.
Speed bumps strike me as a "feel-good" safety measure; I'm not aware of any proof that they actually make things safer. Do they cause greater energy consumption like stop signs? Not really, since drivers tend to choose a speed that can be maintained fairly constantly in the presence of speed bumps; there are always multiple speed bumps and they are usually either in parking lots, or in residential areas where there are already stop signs, so the tendency of speed bumps is to reduce the peak speed between stop signs, which reduces energy consumption. That is, accelerating from a stop sign to 40 MPH and stopping again will consume more energy than accelerating to 20 MPH (due to speed bumps) and stopping again, over the same distance.
Nevertheless, for you comparison to be even remotely fair, you'd have to compare the total amount of energy wasted to get a person from point A to point B utilizing both methods of transportation. I'm no physicist, but I'm willing to bet the biker is going to come out on top in most circumstances.
Again you miss the point: that I was correcting the previous poster. I'm all for more people cycling to reduce energy consumption. But you can't cite fairness, because cycling is not a practical choice for most people, and for some it is not an available choice at all. The argument is not against cycling; it's about the effect some cyclists' habits have on others.
You left out Section 14-286b, which supports his position.
Where I live, I'd estimate that between 25% and 50% of the drivers regularly run stop signs -- and in many of those cases I don't just mean the typical California roll, I mean blatant cruising through the intersection. But it seems like close to 100% of the cyclists run them, and in their case most often it's without the slightest squeeze on the brake levers.
I suspect it's because they just don't want to work too hard. Slowing down costs energy for both car and cyclist, but the driver of a car doesn't get very tired from stepping on the pedal.