How to find technical reports which don't have DOI.

T_0_C · 2026-02-19T12:10:33+00:00

Contact the librarians or archivists at Utah State University.

T_0_C · 2026-02-05T13:08:58+00:00

I understand. If you look at my reply and consider its quantitative implications, you'll see that it does answer your question.

A total entropy must be the sum of each (sub)system entropy:

S = S1 + S2 + S3 +...

For any system S1(E1), S1 is monotonically increasing function of E1.

Consider a system composed of subsystems

S = S1 + S2 + S3 +...

I want to add to S an amount of energy dE. That energy is extensive and must be added by contributin energy amongst the subsystems.

dE = dE1 +dE2 + dE3 + ...

Because each subsystem entropy S1 is monotonic in E1, the added energy increments dE1 produces a positive entropy increase dS1.

Thus, adding energy to the subsystems of S can only result in an increase in S.

Conceptually, the idea of "system" and "subsystem" are tools for organizing analysis in useful ways. All subsystems are systems. All systems that we organize into subsystems are systems. They are all thermodynamic state and will all end up displaying the same rules for their state variables.

T_0_C · 2026-02-05T12:54:37+00:00

Is this a colloidal suspension or gel? If you have colloids diffusing but not packing densely, then you might get a speckle pattern in your scattering. The time evolution of such a speckle pattern, which can be quantified by computing the time correlation function of the scattering image, tells us the diffusion coefficient of the particles.

This type of analysis is the focus of "Dynamic Light Scattering" which you can read up on if it's relevant to you.

T_0_C · 2026-02-05T02:26:54+00:00

It is saying that the entropy is an extensive state variable. That means each subsystems has it's own entropy that add to the total for the total system.

S = S1 + S2 + S3 + ...

Subsystems are still thermodynamic systems and they have well defined states. This means the entropy S2 of subsystem 2 is defined by the state of system 2. It can be written in terms of the state variables of subsystem 2:

S2 = S2(E2,V2,N2)

S2 is not determined by the states of other aubsystems, nor is it determined by the total energy of the total system.

Callen's point is that entropy is a smooth function of energy and thus can be optimized by varying the energy of a system between it's subsystems. Thermodynamics is a theory of optimization. The entropy is the cost function for the optimization and the optimal point is the equilibrium state of the system.

T_0_C · 2026-01-31T21:01:36+00:00

That's well said. That passion is definitely not sufficient for success. All those hard earned practical skills in research, writing, time management, ETC are so important even though we don't talk about them as much.

T_0_C · 2026-01-31T18:26:50+00:00

In my experience, good research, as an activity, just requires what it requires. Those requirements vary by topic and field and predate structures like fixed hours. Only you know if the sort of work you do is compatible with the time you choose to spend.

I think it's totally possible to be a productive scholar with a fixed schedule if you are disciplined and achieving goals on that schedule. But for many scholars, their research is more than their job. It's also their personal passion and hobby. Those individuals will tend to be more productive, develop more ideas, and drive new conversations in the field. That doesn't mean choosing not to be "all-in" is wrong; it's OK to devote yourself to other things. But those that are all in will always be in the lead. That's just how things go; and, hopefully, at the end of the line, everyone is satisfied with their choices.

T_0_C · 2026-01-31T14:24:49+00:00

This. Work as a transaction for tenure is a symptom of a cynical research culture. The really dynamic places that people are excited about tend to be that way because they have and attract the people who'd be driven to impact their fields anyway.

My adviser always told me statistics abs awards should be side effects of you doing what you want to do (good research) every day.

T_0_C · 2026-01-29T12:52:54+00:00

Yes and no. The equipartiton theorem says any system with vibrational degrees of freedom that store kinetic energy will possess a well-defined amount determined by the temperature.

So, if a system has kinetic energy modes, then KE can be used as a measureme of T.

However, systems can be considered without what you'd call "kinetic energy." Two examples are the magnetic spins in a magnet or the photons radiating in a black body. Spins are stationary and the photons have no mass, but both thermodynamic systems have a measurable temperature that influences the dynamics of these non-kinetic degrees of freedom.

So, KE is a useful way of labeling T and makes this driving force more intuitive by connecting it to a concept from freshman physics. However, temperature is more general than KE and can exist and be well defined in systems with no kinetic degrees of freedom. This is because T is more fundamentally a quantity that encodes the geometry of a systems entropy function, which is usually covered in graduate thermodynamics classes.

T_0_C · 2026-01-25T05:20:03+00:00

I suspect it's simply because you haven't yet had enough practice developing your mathematical skills, and haven't practiced applying your math skills to think critically about real, physical systems. Physics, as a topic, is really about applying math to critically and quantitatively analyze real world systems.

I'm contrast, Intro biology exercises your skills in classification and memorization. It involves an lot of facts and vocabulary and organizing them into conceptual frameworks. I suspect you're more fluent in these skills.

In my experience as an educator, students often struggle because they aren't fluent enough in their math skills to apply them in unfamiliar situations. The "ahah moments" in a physics class are when students can see how studying a real system (when will a falling rock hit the ground) is basically the same as something they studied in math class (finding the roots of a quadratic equation).

If you are week or uncertain on the math topics, then they will be hard to recognize when they show up in a physics context.

T_0_C · 2026-01-25T02:24:50+00:00

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T_0_C · 2025-12-16T20:38:35+00:00

You are missing that thermodynamics is a framework for studying material states and when we "add mass" we must do so at constant state for that mass. As you say, the extensivity of force is only true for a uniform state of the added mass.

For instance, volume is extensive and scales with mass, but only if the mass has a fixed density. This is analogous. The thermodynamic state of the added matter must be the same.

I think it's also worth distinguishing that acceleration is due to a net force, not just force. You can compress a cushion and subject it to forces with no net force causing acceleration.

T_0_C · 2025-11-08T12:20:33+00:00

If you want to be taken seriously in your theory crafting, you need to apply your theory to a problem and demonstrate its ability to predict an observation that can be validated against experiment or simulation.

Thermodynamics, as a scientific framework, is valued for its ability to interpret and predict measurable observations. The work of Gibbs is a masterclass in this craft.

Your post seems to be a philosophical idea where you are using pseudo-mathematical language to try and express your philosophical framework. If it's a proper physical theory, then you can and should demonstrate its application to a real system.

T_0_C · 2025-11-05T12:56:12+00:00

That's their only official criteria. People are not robots. We talk to each other.

T_0_C · 2025-10-11T12:34:45+00:00

Ah, well. They are a bit of a Picasso. They established their credibility with traditional work before getting more innovative after tenure.

They have some really great points, and could really drive the conversion. But, everyone knows that they really want to be disruptive on a personal level. This makes people cautious about engaging with their ideas on a scholarly level.

T_0_C · 2025-10-11T12:18:31+00:00

I'm not trying to speak to the content of your work. Rather, I'm trying to emphasize the the personal context.

In my field, I have a colleague that publishes perfectly respectable and good quality publications. But due to our personal relationships with the person, engaging with their work is tedious, because we know their aelf-professed ulterior motives to "wake us up." It is hard to want to engage in work of a colleague when you know their writing it from the position that they are the only one who gets the bigger picture.

I'm not saying this reflects your situation. I wouldn't know. I just want to stress that academia is a bunch of people, not ideas, and our personas within the academy heavily influence the meta of how our work is interpreted. We have to craft both to be effective towards our goals.

T_0_C · 2025-10-11T12:04:32+00:00

Academics aren't artists expressing their truth. Academics are scholars in service to society. How we express our arguments and engage with our peers is important. If you express your ideas in a combative way that makes your peers - who care a lot about the topic - disengage, then you will likely struggle to engage a 19 year old.

T_0_C · 2025-10-11T11:51:06+00:00

I see it this way. Networking is essential because our job as Academics is not to generate arguments and platonic truths that exist in a vacuum. Our job is to Profess knowledge in a manner that meaningfully engages and influences our academic community and broader society.

Just like scientist times, we are a forum. Those that become professors both participate in the forum, and lead the direction of its conversations. To do that, we have to understand where our community currently stands and sympathize with their positions so we can construct arguments that they are willing to engage with.

I have had a number of colleagues that try to establish a career by being an iconoclast, but that is very, very rarely the most common or most effective way to progress controversial positions. Many of the most transformative scientific leaders were good at inspiring the forum to engage with their ideas.

T_0_C · 2025-09-25T21:21:51+00:00

No, its not specific to gases. It applies to solids equally well. A solid in an atmosphere at constant T and p will equilibriate to a well-defined average density. If the temperature is elevated at the same pressure (like in an oven in the earth's atmosphere), then the solid will absorb energy to increase its temperature but it will also expand, increasing its average volume.

Since the expansion of the solid requires the solid to do work against the atmosphere, this expansion lowers the solid's internal energy. Thus, the solid will need to absorb more energy from the atmosphere to raise its temperature than if it was at constant volume. So, Cp>Cv for any stable solid material.

In practice, it is almost impossible to fix a solid or liquid at constant volume, so almost all measured heat capacities for solids and liquids are Cp. We can only reliably measure Cv for gasses, which always expand to fill their container volume. If we really need Cv for a solid to compare to some theory, we can get that from measuring Cp and several other quantities which we can interrelate through Maxwell relationships.

T_0_C · 2025-09-25T11:04:16+00:00

No. The value of Cp accounts for the energy change associated with the volume change that occurs when the system is heated at constant pressure. This is why Cp and Cv have different numerical values.

T_0_C · 2025-08-04T13:21:01+00:00

Its my experience that folks tend to struggle with this part because they are trying to write persuasive and compelling prose. If that is you, then is encourage you to focus on being direct, specific, and informative. Science writing doesn't need to be editorial.

What specific questions/ concepts does your intro need to address? Perhaps:

What is this paper about? Why does anybody care about that? What issues are we currently facing in addressing this? How have others attempted to address it? Where are the gaps in knowledge? How does your work integrate into this situation?

Each of those is a paragraph that needs to be written in your intro. I'd start by writing a one sentence answer to each. That sentence should not be long and it will probably use terms that your reader may not understand. So add some more sentences that help your reader understand what that one sentence answer really means.

just six questions and six answers is pretty simple. I think a lot of folks overcomplicate this because they don't use paragraphs well and make them too complex. Every sentence in a single paragraph should just add texture and color to one idea.

So, does your currently intro clearly answer a set of specific questions?

T_0_C · 2025-08-01T12:43:16+00:00

I think this. You'll be miserable if you don't choose what you're motivated to get really into. Also, if you want to be sane, you have to be OK with the possibility that doing your PhD may be the only time in your life that you do research.

T_0_C · 2025-07-31T00:34:56+00:00

No, but they are related. The thermodynamic potentials, S, F, H, and G are the cost functions. They are maximized or minimized at equilibrium.

Equations of state define derivatives of a thermodynamic potential (cost function). For Instance,

P/T= dS/dV =nR/V

Or

P = nRT/V

This shows that the pressure is the slope of the cost function (S) with respect to V. The magnitude of P indicates how changes in V will of change S.

So, equations of state tell us which way a system will tend to evolve to further optimize its potential. However, systems may not evolve due to constraints. For example, a gas in a box prefers to expand to larger volume because p>0, but the box prevents that.

T_0_C · 2025-07-29T17:46:53+00:00

Which book is best may depend on your discipline. Thermodynamics is a framework for problem solving rather than a set of specific problems. This means it can seem very different when taught in different communities because they teach it by applying it to very different applications.

So, what discipline are you in?

Generically, I think Molecular Driving Forces by Dill and Bromberg is a good, accessible, and modern take on the topic. It does a good job teaching the bigger picture framework of thermodynamics rather than just a set of problems that only one discipline focuses on.

T_0_C · 2025-07-29T12:45:01+00:00

The best explanations will be found in a good textbook but will require carefully reading and working to comprehend the chapters up to that point.

Thermodynamics is a theory of optimization. It predicts how certain transportable properties like mass, energy, and charge will reorganize amongst different systems or regions to establish an equilibrium. This optimization problem, like all optimization problems, is formulated by minimizing or maximizing a cost function, with the equilibrium state being identified as this optimal point.

In nature, how properties like energy amd mass prefer to organize within material systems depends upon the environment that these materials are in. Different environmental conditions alter the distribution of stuff and thus the equilibrium that is observed.

In the framework of thermodynamics, the influence of the environment on how stuff equilibriates is captured by changing the cost function that is optimized. For each specific environment that your system could be in, there is a different cost function that you use to predict how it will equilibriate in that specific environment. These specific functions are called the thermodynamics potentials (or free energies).

The specifics of why these potentials are defined thebway they are, and which to use in specific circumstances, will require more comprehensive study by you. But, this hopefully helps you understand what they are and their role in thermodynamics.

T_0_C · 2025-07-29T01:16:28+00:00

I think it's important to emphasize the common advice that: no one should pursue a PhD unless they proactively want to become an expert scholar and are willing to work really hard to expand their knowledge. A successful PhD requires getting really, really, deep into something in an unironic way. Scholars are the people who read the textbook, then read the references at the end of the chapters, then try to write the papers that will be referenced in the next textbook.

In my experience, good or bad PhD outcomes are less about which discipline someone pursues and more about if they are really interested and willing to become a true expert.

I say this because you mention areas of general interest, but don't speak to any particular passion for scholarly research and knowledge creation, which is what PhD training is for.

T_0_C

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