Disqus - Latest Comments for jallen

Re: Insect-scale robots powered by combustion | Physics Today | AIP Publishing

jallen — Mon, 18 Sep 2023 17:19:03 -0000

Quite clever---essentially a new application of the Otto cycle engine but with linear rather than rotary motion. My question is whether the alcohol fuel is carried onboard the robot or supplied through thin tubes from an external source?

Re: Clean hydrogen edges toward competitiveness: Physics Today: Vol 75, No 8

jallen — Mon, 29 Aug 2022 14:29:15 -0000

Hydrogen may make sense where we need a compact or portable energy storage medium. Examples include aircraft and perhaps some other transportation. Be aware, however, that electrolysis is generally less than 70% efficient, and a binary, or combined cycle (Brayton + Rankine) generating plant might achieve about 55% efficiency. Figure 10% loss in compression, etc. and you are lucky if the the "round trip" storage efficiency is 35%. Thus when considering stationary installations, we must compare this with pumped water or batteries which can do better than 85%.

As far as flammability is concerned, hydrogen is not that bad, especially since most escaping H2 in the open will rise up and out of the way of ignition sources. People are too obsessed by the isolated incident of the Hindenburg fire.

Re: A First Step for Humans on Mars: NASA's Rover Makes Oxygen

jallen — Tue, 27 Apr 2021 11:44:51 -0000

Around 1970 whjile working at the Hamilton Standard Space Life Support Lab, we electrolyzed CO2 into oxygen and graphitic carbon. The process took place in a molten salt electrolyte of lithium chloride and lithium carbonate. The oxygen would bubble off a gold anode while the carbon deposited on a nickel cathode. The reduction was complete--no CO. The goal was to investigate the process for regenerating the atmosphere aboard long space flights.

Re: Soft Robots Deliver Medical Treatments

jallen — Fri, 02 Oct 2020 11:24:58 -0000

How big are these robots to allow them to circulate in blood vessels?

Re: Storing energy in red bricks

jallen — Wed, 09 Sep 2020 17:13:42 -0000

Do you have any quantitative information on how much energy we can store in each brick?

Re: Renewables not cheap

jallen — Sat, 18 Jan 2020 13:42:21 -0000

I agree that nuclear can be part of the mix, perhaps providing baseline power. In recent years, however, the cost of solar and wind per unit energy has fallen below that of combustion with either the Rankine or even binary Brayton-Rankine cycles. Consider that Texas, a state hardly biased towards "green" energy, is a leader in both solar and wind installations. I suggest you update your calculations.

Re: Renewables not cheap

jallen — Sat, 18 Jan 2020 10:29:01 -0000

Excellent point. A carbon tax, perhaps with rebates, would level the playing field.

Re: Renewables not cheap

jallen — Sat, 18 Jan 2020 10:28:11 -0000

This argument ignores what economists call "externalities." Who pays for the injury to the planet from coal combustion? Is ti wrong for the public to alleviate the higher price of clean energy?

Re: Renewables not cheap

jallen — Sat, 18 Jan 2020 10:25:52 -0000

No power source is totally free of impact. A more defensible argument would compare the problems of wind with those of fossil fuel combustion on a per kWh basis. The combustion evaluation would include damage from emissions, climate change, and catastrophic weather events caused by increased CO2. So I would urge Penny to do those quantitative evaluations. Otherwise the argument is like saying, "The drug will cure cancer but we must avoid it because the injection is painful.".

Re: Outrage machine strips gears over Peloton ad

jallen — Mon, 09 Dec 2019 12:00:11 -0000

Once again, let's not take the actions of an extreme minority within a movement it to judge the millions of more reasonable members. That's the logical fallacy behind prejudice: Find a few examples of obnoxious, especially stereotypical, behavior and use it to discredit a whole race, tribe, religion, or nationality. If I were prone to such fallacious thinking I might characterize conservatives as irrational based on the statements of Justin and Garry, but I realize their comments are those of isolated individuals, not conservatism generally. Most intelligent conservatives can debate within the laws of logic.

Also let's not rule out the possibility that some of the most preposterous statements might be uttered by agents provocateurs to embarrass the other side.

Re: Outrage machine strips gears over Peloton ad

jallen — Sun, 08 Dec 2019 16:26:13 -0000

I am a liberal (actually progressive) and I have no gripe with the commercial. I see the gift as a benefit to the woman's general health and fitness, not a husband's attempt to make her prettier. Let's not characterize a whole movement by the outrage of a few jerks.

Re: Startup Resonado Reinvents The Speaker With Its Flat Core Technology - IEEE Spectrum

jallen — Tue, 22 Oct 2019 11:30:27 -0000

This may not be the first flat speaker. I recall some years ago a speaker which, instead of the conventional cone, used a thin (2-3mm) sheet of wood as the vibrating element. There were also electrostatic speakers in which a charged diaphragm was alternately attracted and repelled by a driven back plate electrode. I don't know whether either of these designs became a commercial success. Remember that audiophiles are not always rational in their preferences.

Re: The Christian Worldview and Global Climate Change

jallen — Mon, 23 Apr 2018 09:08:00 -0000

The article appears to dodge the physics behind increased CO2 enhancing greenhouse effect, and the resulting warming driving the thermodynamic "engine" of atmosphere to become more powerful, e.g. stronger hurricanes and storms.

One serious distortion is about population control. No serious advocate of reducing population growth rates advocates mass abortion or euthanasia. The methods proposed center on access to birth control and women's rights. The latter means that women have the knowledge and independence to decide whether they want to bear large numbers of children, and in general they choose to have fewer.

Re: Sociologist Rodney Stark gets cranky about religion

jallen — Mon, 23 Apr 2018 08:55:50 -0000

Prof. Stark asserts that religious people have a significantly lower crime rate than the non-religious. What is the source of that conclusion? Most of my reading states that there is no significant difference in either distinctly moral or immoral behavior between the two groups.

Re: Pakistani physicist sees his country becoming a “fascist religious state”

jallen — Mon, 14 Aug 2017 12:04:51 -0000

DeTocqueville discussed the same problem in his 19th Century classic "Democracy in America. He warns against "the tyranny of the majority."

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Mon, 01 May 2017 08:51:22 -0000

This time it appears we (if you include the quoted author) agree on most points. As I have said several times, scientists should not claim total certainty. And treating opponents with disrespect is not only rude, but counterproductive. That Is why I have pressed for good manners.

On the matter of policy, the changes suggested by the climate movement are not necessarily destructive to the economy. There are already as many jobs in renewable energy as in fossil fuels, and as the cost of wind and solar decline even Texas is installing them. Having worked for 30 years in the solar industry, it has been a most rewarding and enjoyable experience, probably more fun than working in a coal mine. As for ideology, that argument might apply if the issue were limited to the US. In fact, as demonstrated by the Paris Agreement, nearly 200 countries with almost as many ideological leanings seem to share the conclusion that the world should migrate away from fossil fuels.

Finally, as I pointed out earlier, denying climate change and then sticking with fossil fuels is just as much a decision as what the climate movement advocates. Thus the deniers have a comparable intellectual obligation to defend their position. That is, they have to show by solid defensible science that continuing to add CO2 to the atmosphere will not enhance the greenhouse effect to the extent of causing serious global damage. Simply attacking the opponents position is not sufficient. For example do you refute the Stefan-Boltzmann equation, or the Planck Theory of thermal radiation, or the collisional broadening of CO2 absorption lines in the 10-micron band?

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Sun, 30 Apr 2017 15:10:37 -0000

So this cowardly conspiracy spans tens of thousands of scientists working for universities, and scientific societies in over a hundred countries and none has dared to challenge the official line?

Have you considered that if a scientist came up with a rigorous defensible rebuttal to climate change he would need to widen his lab door to accommodate the wheelbarrows of grant money from the Koch brothers and the fossil fuel industries?

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Sun, 30 Apr 2017 12:32:59 -0000

Could you have misread my earlier statements? I never claimed that current science was ultimate truth. In fact I asserted quite the opposite. I have have written papers that have made at least small changes. What I am arguing is that we have to act even on knowledge which is still imperfect in the philosophical sense. The example of aerodynamics (an inexact science) makes that point. In spite of the uncertainties, we still build airplanes that fly pretty much as designed. In this imperfect world with our admittedly imperfect science we still have to make decisions and create policies based on strong confidence. If we insist on perfect certainty we will accomplish nothing.

As for climate change, the science and evidence are well enough supported that we can make informed decisions based on them.

Conversely, the claim that we can continue adding CO2 to the atmosphere without serious adverse consequences to the planet is far less defensible. Of course if you can present a convincing physical model or theory to support that position, please do so. I invite you to send it to me and if it is convincing I will admit my error. I will even help you get it into proper form for a journal. You will the principal author. You can become a hero!

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Sat, 29 Apr 2017 08:35:40 -0000

The marchers whom I have heard vary in their positions on nuclear power While they recognize the risks, some believe it is the best short term option to minimize CO2 emissions. Perhaps you should attend the march and do so some reading.

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Sat, 29 Apr 2017 08:23:40 -0000

Glad you studied science in HS. Did you also learn that science, unlike religion and political ideology. does not claim absolute immutable truth? It is a constantly evolving discipline in which some principles are more confident than others. Still we rely on science for our very lives. For example, riding in an airplane, we rely on the somewhat inexact theories of turbulent flow aerodynamics. yet we are confident that the airplane will fly as deigned.

Once again, if you believe that the geological methods of estimating ancient climate, or our methods of evaluating the modern effects of added CO2 are incorrect, then publish your theories in the professional journals.

Since we are invoking our educational backgrounds, I have a Ph.D. in physics with my dissertation on atmospheric optics.

In school, did you also learn any manners?

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Fri, 28 Apr 2017 21:44:32 -0000

Actually, even Exxon has finally accepted climate change and is moving into green energy.

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Fri, 28 Apr 2017 21:42:11 -0000

The violence is indeed a problem and I urge you to organize a movement against it. I may join you. This march, however, is about Climate.

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Fri, 28 Apr 2017 21:39:20 -0000

Perhaps you should stop by the parking areas near the rally and count the gas guzzlers versus the efficient cars. and count those who use SEPTA (as I will).

Even if some marchers were hypocrites that would not negate the science behind climate change. But if you can refute it, then publish a scientific paper with your contrary theory.

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Fri, 28 Apr 2017 20:44:06 -0000

Once again you have not done your homework. We determine ancient climate and atmospheric chemistry from ice core analysis and geological records. If you believe these methods (or climate science generally) are incorrect, then I invite you to write a scientific paper and submit it to a professional journal or conference. That is how we improve science, not by sarcastic (and erroneous) remarks.

Re: Thousands to march Saturday in Philadelphia against climate change

jallen — Fri, 28 Apr 2017 20:36:53 -0000

Those who believe that climate change is wrong are invited to write scientific papers showing the errors in the theory, along with supporting science, math, and evidence. Then submit them to a professional journal or conference. That is how science gets corrected, not by sarcastic personal attacks.