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| regent1 = [[Lohara dynasty#Second Lohara dynasty|Udayānadeva]]<ref name=”govinda”>{{Cite book |last=Pillai |first=P. Govinda |url=https://books.google.com/books?id=sep5EAAAQBAJ&pg=PT150 |title=The Bhakti Movement: Renaissance or Revivalism? |date=2022-10-04 |publisher=Taylor & Francis |isbn=978-1-000-78039-0 |quote=Muslim rule was finally and firmly established in Kashmir by Shah Mir by deposing the last Hindu ruler, Kota Rani (1338-9). She was the widow of the last Hindu King of Kashmir, Udayana Deva (1323-38).|language=en}}</ref>

| regent1 = [[Lohara dynasty#Second Lohara dynasty|Udayānadeva]]<ref name=”govinda”>{{Cite book |last=Pillai |first=P. Govinda |url=https://books.google.com/books?id=sep5EAAAQBAJ&pg=PT150 |title=The Bhakti Movement: Renaissance or Revivalism? |date=2022-10-04 |publisher=Taylor & Francis |isbn=978-1-000-78039-0 |quote=Muslim rule was finally and firmly established in Kashmir by Shah Mir by deposing the last Hindu ruler, Kota Rani (1338-9). She was the widow of the last Hindu King of Kashmir, Udayana Deva (1323-38).|language=en}}</ref>

| reg-type1 = Monarch

| reg-type1 = Monarch

| succession = [[Maharaja|Maharani]] of [[Kashmir Valley|Kashmir]]

| succession = [[ of |Kashmir]]

| reign = 1338 − 1339<ref name=”govinda”/><ref name=”koul”>{{cite book|url=https://books.google.com/books?id=CW78DwAAQBAJ&pg=PA207|page=207|title=The Exiled Pandits of Kashmir: Will They Ever Return Home?|isbn=978-9811565373|year=2020|last1=Koul |first1=Bill K. }}</ref>

| reign = 1338 − 1339<ref name=”govinda”/><ref name=”koul”>{{cite book|url=https://books.google.com/books?id=CW78DwAAQBAJ&pg=PA207|page=207|title=The Exiled Pandits of Kashmir: Will They Ever Return Home?|isbn=978-9811565373|year=2020|last1=Koul |first1=Bill K. }}</ref>

| predecessor = [[Lohara dynasty#Second Lohara dynasty|Udayānadeva]]

| predecessor = [[Lohara dynasty#Second Lohara dynasty|Udayānadeva]]

| successor = Position abolished<br>[[Shah Mir]] (as [[List of monarchs of Kashmir|Sultan of Kashmir]])

| successor = Position abolished<br>[[Shah Mir]] (as [[List of monarchs of Kashmir|Sultan of Kashmir]])

| house = [[Lohara dynasty]]

| house = [[Lohara dynasty]]

| father = Rāmachandra

| father = Rāmachandra


Latest revision as of 13:32, 17 October 2024

Last Queen of Kashmir

Kota Rani (died 1344) was the last ruler of the Hindu Lohara dynasty in Kashmir. She was also the last female ruler of Kashmir. She was regent for her new husband because of the minority of her son in 1323−1338, and ruled as monarch in 1338−1339. She was deposed by Shah Mir, who became the second Muslim ruler of Kashmir after Rinchan who converted to Islam and ruled as Sultan Sadr-ud-din.

Kota Rani was the daughter of Ramachandra, the commander-in-chief of Suhadeva, the king of Lohara dynasty in Kashmir. Ramachandra had appointed an administrator, Rinchan, a Ladakhi. Rinchan became ambitious. He sent a force in the fort, in the guise of merchants, who took Ramachandra’s men by surprise. Ramachandra was killed and his family was taken prisoner.

To earn local support, Rinchan appointed Rawanchandra, the son of Ramachandra, as administrator of Lar and Ladakh, and married his sister Kota Rani.[5] He employed Shah Mir as a trusted courtier, who had entered Kashmir earlier and had been given an appointment in the government.[citation needed]
Rinchan converted to Islam and adopted the name of Sultan Sadruddin. He died as a result of an assassination after ruling for three years.[citation needed]

Kota Rani was first appointed as a regent for Rinchan’s young son. Later she was persuaded to marry Udayanadeva by the elders. [citation needed]

Udayanadeva became the ruler of Kashmir, but Kota Rani practically ruled the kingdom. After Udayanadeva died in 1338, Kota Rani became the ruler of Kashmir in her own right.[2]

Kota Rani had two sons. Rinchan’s son was under the charge of Shah Mir and Udayanadeva’s son was taught by Bhatta Bhikshana. Kota Rani appointed Bhatta Bhikshana as her prime minister.[citation needed]

Shah Mir pretended to be sick, and when Bhatta Bhikshana visited him, Shah Mir jumped out of his bed and killed him.[6] According to the historian Jonaraja, she committed suicide and offered her intestines to him as a wedding gift.[citation needed] According to the Kashmiri historian Jonaraja, Shah Mir killed both of her sons.

She was very intelligent and a great thinker. She saved the city of Srinagar from frequent floods by getting a canal constructed, named after her and called “Kute Kol”.[7] This canal gets water from Jhelum River at the entry point of city and again merges with Jhelum river beyond the city limits.[citation needed]

  • Rakesh Kaul’s historical novel The Last Queen of Kashmir is based on Kota Rani’s life and legend.[8]
  • In August 2019, Reliance Entertainment and Phantom Films announced that they would be making a movie on Kota Rani.[9][10]
  1. ^ a b Pillai, P. Govinda (4 October 2022). The Bhakti Movement: Renaissance or Revivalism?. Taylor & Francis. ISBN 978-1-000-78039-0. Muslim rule was finally and firmly established in Kashmir by Shah Mir by deposing the last Hindu ruler, Kota Rani (1338-9). She was the widow of the last Hindu King of Kashmir, Udayana Deva (1323-38).
  2. ^ a b Koul, Bill K. (2020). The Exiled Pandits of Kashmir: Will They Ever Return Home?. p. 207. ISBN 978-9811565373.
  3. ^ “PSA dossier calls Mehbooba Mufti Kota Rani, Kashmir’s Hindu queen who ‘poisoned’ rivals”.
  4. ^ Culture and political history of Kashmir, Prithivi Nath Kaul Bamzai, M.D. Publications Pvt. Ltd., 1994.
  5. ^ “Queens, poets, academics, mystics: A calendar celebrates 12 inspirational women of Kashmir”.
  6. ^ Mihir Balantrapu, Kota, the fortress (Book review of The Last Queen of Kashmir), The Hindu, 5 August 2016.
  7. ^ “Kota Rani: Phantom Films to produce film on last Hindu queen of Kashmir. Details inside”. 27 August 2019.
  8. ^ “Madhu Mantena To Make Biopic On Kota Rani, Last Hindu Queen Of Kashmir”.

Kota Rani: Difference between revisions

Use our infographic to predict this year’s Nobel prize winners – Physics World

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Use our infographic to predict this year’s Nobel prize winners – Physics World






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What Is An IP67 Rating?

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What Is An IP67 Rating?

IP Ratings (Ingress Protection) is a standard that defines how good the batteries are against solid objects and liquids. Understanding IP Ratings is crucial when choosing batteries for different applications, as it indicates the level of protection the batteries offer against environmental factors.

What Is An IP67 Rating?

An IP67 rating is a standard used to define the level of protection provided by a product against the ingress of solid particles and liquids. In simple terms, it indicates the product’s ability to withstand dust, dirt, and water. The IP67 rating is commonly associated with products that are considered “waterproof” rather than just “water-resistant.”

what is an ip67 rating

Definition of IP67

The IP in IP67 stands for Ingress Protection, and the 67 represents the level of protection the product offers. The first digit (6) indicates the level of protection against solid particles, while the second digit (7) denotes the protection against liquids. In the case of IP67, the product is completely protected against dust and can withstand immersion in water up to 1 meter for 30 minutes.

Explanation of the IP Code System

The IP code system is an internationally recognized standard (IEC 60529) that classifies and rates the degree of protection provided by a product against the intrusion of solid objects, dust, accidental contact, and water. The code consists of the letter “IP” followed by two digits and, in some cases, additional letters.

Importance of IP Ratings

IP ratings are crucial as they provide consumers and businesses with a clear understanding of the environmental protection a product offers. This information helps in making informed decisions when selecting products for specific applications, ensuring that they are suitable for use in various conditions.

IP67 vs. IP65 and IP66 Ratings

Key Differences

The key differences between IP67, IP65, and IP66 ratings lie in the level of protection they offer. While all three ratings provide some degree of protection against dust and water, the IP67 rating offers a higher level of protection compared to IP65 and IP66.

Comparing Levels of Protection

IP65-rated products offer protection against low-pressure water jets and limited dust ingress, making them “water-resistant.” IP66-rated products protect powerful water jets and limit dust ingress. On the other hand, IP67-rated products offer complete protection against dust and can withstand immersion in water, making them “waterproof.”

Common Misconceptions

One common misconception is that all “water-resistant” products are capable of withstanding complete submersion in water, which is not the case. It’s important to understand the specific IP rating of a product to determine its level of protection accurately.

Understanding the Ingress Protection (IP) Code System

Breaking Down the IP Code

The IP code is broken down into two digits, each with a specific meaning. The first digit represents the protection against solid objects, while the second digit represents the protection against liquids. Additional letters may be included to indicate other forms of protection, such as protection against mechanical impacts or hazardous parts.

Interpretation of the Numbers

The numbers range from 0 to 6, with 0 indicating no protection and 6 indicating complete protection. For example, a product with a rating of IP6X would be completely protected against dust, while a product with a rating of IPX6 would be protected against powerful water jets.

Understanding the Letters

In some cases, additional letters may be included in the IP code to indicate specific protection. For example, the letter “K” is used to denote protection against the ingress of dust and water during high-pressure and high-temperature washdowns.

Benefits of IP67-Rated Products

Superior Protection Against Dust

IP67-rated products offer complete protection against dust, ensuring that no solid particles can penetrate the product and cause damage to its internal components.

Immersion in Water

These products can withstand immersion in water up to 1 meter for 30 minutes, making them suitable for use in wet environments without the risk of water damage.

Durability in Harsh Environments

IP67-rated products are designed to withstand harsh environmental conditions, making them ideal for outdoor use, industrial settings, and other demanding applications.

Applications of IP67-Rated Products

Consumer Electronics

Smartphones, smartwatches, and Bluetooth speakers are often designed with IP67 ratings to ensure protection against dust and water, providing peace of mind to users.

Industrial Equipment

Industrial machinery, control panels, and electrical enclosures often require IP67-rated components to ensure reliable operation in dusty and wet conditions.

Outdoor Lighting

Outdoor LED lights, garden lights, and floodlights are commonly equipped with IP67 ratings to withstand exposure to the elements and ensure long-term durability.

How to Identify IP67-Rated Products

Reading Product Specifications

When shopping for products, carefully read the product specifications to identify the IP rating. Look for clear indications of the level of protection against dust and water.

Recognizing IP67 Certification

Look for official IP67 certification labels or markings on the product packaging or documentation, indicating that the product has been tested and certified to meet the IP67 standard.

Tips for Purchasing IP67-Rated Items

When purchasing IP67-rated items, consider the specific environmental conditions in which the product will be used. Ensure that the IP67 rating aligns with the level of protection required for the intended application.

Conclusion

In conclusion, the IP67 rating provides a high level of protection against dust and water, making it suitable for a wide range of applications, from consumer electronics to industrial equipment. Understanding the IP code system and the benefits of IP67-rated products is essential for making informed purchasing decisions and ensuring the reliability and durability of products in various environments. By being aware of the specific IP rating of a product, consumers and businesses can confidently select products that meet their environmental protection requirements.

Getting a good fingerprint via Raman Spectra

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Getting a good fingerprint via Raman Spectra

Getting a good fingerprint via Raman SpectraWe are delighted to share that the January 2023 issue of Laser Focus World magazine will feature an article written by our own Cicely Rathmell, VP of Marketing, and Senior Staff Scientist, Dr. Dieter Bingemann. Getting a good fingerprint via Raman spectra details how variability in Raman spectra can be significantly reduced through good optical design and a few simple calibration measurements and corrections.

Modern Raman applications require a high degree of unit-to-unit agreement between individual spectrometers to deliver consistent, dependable answers in the field. Learn how carefully applied adjustments to wavelength, wavenumber, and intensity can correct variations both between spectrometers and because of daily environmental changes.

Read the full article, as published in Laser Focus World: Getting a good fingerprint via Raman Spectra


Curious to learn more?

We used our tech note, Reproducible Raman Measurements, as the basis for the Laser Focus World article, which provides additional details and background for those in the field. In this tech note, we demonstrate our recommendations for achieving reproducible Raman spectra through calibration measurement and corrections on a set of seven different, but identically designed and configured, 830 nm WP Raman systems with integrated laser and probe optics (WP 830-L) using a sample solution of glucose in water inside a polystyrene cuvette, inserted into a sample holder, which in turn is directly attached to the front lens of the spectrometer.

Read the full tech note, Reproducible Raman Measurements, or learn more about the WP 830 Raman Spectrometer used in this demonstration. Have other questions about the correction process, or OEM Raman system development in general? Contact us

 


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fluid dynamics – How to determine the alpha value of artificial viscosity in smoothed particle hydrodynamics?

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fluid dynamics – How to determine the alpha value of artificial viscosity in smoothed particle hydrodynamics?

I am confused about how to choose an appropriate value of $\alpha$ in the artificial viscosity. The value that I deduced is far from the recommended value and led to great numerical instability.

Artificial viscosity is introduced into the momentum equation of smoothed particle hydrodynamics:
$$
\Pi_{ij}=-\alpha h\frac{c_i+c_j}{\rho_i+\rho_j}\frac{\boldsymbol{v}_{ij}\cdot\boldsymbol{r}_{ij}}{{r_{ij}}^2+\epsilon h^2},
$$

where $\alpha$ is a dimensionless factor, $h$ is SPH kernel radius and $c$ is the speed of sound. The artificial viscosity is related to the physical dynamic viscosity (Pa*s) by
$$
\mu=\frac{\rho\alpha hc}{8}
$$

for two-dimensional cases (1). Hence, if the values of $h$, $c$ and $\mu$ are given, we can estimate the value of $\alpha$ as
$$
\alpha=\frac{8\mu}{\rho hc}.
$$

When it comes to the sound of speed, in order to both limit the density variation within 1% ($\delta\rho/\rho\sim v^2/c^2$) and allow an acceptable timestep (by the CFL condition), $c$ is also artificial, and customary to be $10v_\mathrm{max}$, where $v_\mathrm{max}$ is the maximal fluid velocity (2,3). As to the case of dam break with the initial water column height of $H_0$, the estimate of $v_\mathrm{max}$ is
$$
v_\mathrm{max}=\sqrt{2gH_0}.
$$

So Monaghan set $c$ as $\sqrt{200gH_0}$ in (2).

Assume the initial spacing between fluid particles is $H_0/N$, and the SPH kernel radius is triple the spacing,
$$
h=3\frac{H_0}{N}.
$$

Now we may obtain a proper value of $\alpha$:
$$
\alpha=\frac{8\mu}{\rho\cdot(3H_0/N)\cdot 10\sqrt{2gH_0}}=\frac{2\sqrt{2}}{15}\frac{\mu N}{\rho\sqrt{gH_0^3}}
$$

In the case of dam break, one can assume that $\mu=1\times 10^{-3}~\mathrm{Pa\cdot s}$ (water), $\rho=1000~\mathrm{kg/m^3}$, $100\leq N\leq 1000$, $0.1~\mathrm{m}\leq H_0 \leq 1~\mathrm{m}$, $g=9.81~\mathrm{m/s^2}$, and we may estimate that
$$
6\times10^{-6}\leq\alpha\leq2\times10^{-3}.
$$

This is way too far from the recommended range of $\alpha$ which is 0.01-1.
And when I used the estimated alpha value to simulate the dam break, it could not converge as expected. So, I wonder whether there is any mistake in my estimation, or any misunderstanding of the SPH theory. Any comments or advice will be appreciated!

=========================

Happy to know that the question is reopened. These days I tested different speeds of sound ($c_0$) with Morris’s laminar viscosity model (4), and was surprised to observe that $c_0$ lower than $10v_\mathrm{max}$ can lead to a more stable pressure field!

N.B. To ensure the laminar flow, $H_0$ was set as 0.002 m such that Reynolds number=396. Other parameters are:
$\Delta L=3\times10^{-5}~\mathrm{m}, ~h=1.5\Delta L,~\Delta t=0.2h/c_0$.

$c_0$ is set to be 10, 5, 2.5 and 1.5 times of $v_\mathrm{max}$.

I compared the SPH results with those obtained by COMSOL two-phase laminar flow:

fluid dynamics – How to determine the alpha value of artificial viscosity in smoothed particle hydrodynamics?

COMSOL showed that the velocity is between 0-0.18 m/s and the pressure difference is about 9 Pa. Lowering the speed of sound did not alter the velocity field significantly, but did stabilize the pressure field. This is really astonishing. It seems that $\delta\rho/\rho$ did not decrease as quickly as $v^2/c_0^2$. For example, when $c_0=1.5v_\mathrm{max}$, it showed that $\delta\rho/\rho=0.133$ while $v^2/c_0^2=0.36$.

References

  1. Monaghan, J. J. Smoothed particle hydrodynamics. Rep. Prog. Phys. 68, 1703–1759 (2005).

  2. Monaghan, J. J. Simulating Free Surface Flows with SPH. Journal of Computational Physics 110, 399–406 (1994).

  3. Monaghan, J. J. Smoothed Particle Hydrodynamics and Its Diverse Applications. Annual Review of Fluid Mechanics 44, 323–346 (2012).

  4. Morris, J. P., Fox, P. J. & Zhu, Y. Modeling low Reynolds number incompressible flows using SPH. Journal of Computational Physics 136, 214–226 (1997).

User:Joseralopez – Wikipedia

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Kota Rani: Difference between revisions

From Wikipedia, the free encyclopedia

Kota Rani: Difference between revisions

Dark Matter Black Holes Could Fly through the Solar System Once a Decade

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Dark Matter Black Holes Could Fly through the Solar System Once a Decade

Dark Matter Could Be Hiding Out as Atom-Sized Black Holes

The universe’s hidden mass may be made of black holes, which could wobble the planets of the solar system when they pass by

Dark Matter Black Holes Could Fly through the Solar System Once a Decade

This story sounds wild—even incredible. Black holes! Dark matter! Jostling planets! Yet the scenario is plausible—and testable soon.

Black holes the size of an atom that contain the mass of an asteroid may fly through the inner solar system about once a decade, scientists say. Theoretically created just after the big bang, these examples of so-called primordial black holes could explain the missing dark matter thought to dominate our universe. And if they sneak by the moon or Mars, scientists should be able to detect them, a new study shows.

Such black holes could have easily arisen right after the universe was born, when space is thought to have expanded hugely in a fraction of a second. During this expansion, tiny quantum fluctuations in the density of space would have grown larger, and some spots may have become so dense that they collapsed into black holes scattered throughout the cosmos. If dark matter is fully explained by such black holes, their most likely mass, according to some theories, would range from 1017 to 1023 grams—or about that of a large asteroid.

If primordial black holes are responsible for dark matter, they probably zip through the solar system about every 10 years, a new study found. If one of these black holes comes near a planet or large moon, it should push the body off course enough to be measurable by current instruments. “As it passes by, the planet starts to wobble,” says Sarah R. Geller, a theoretical physicist now at the University of California, Santa Cruz, and co-author of the study, which was published on September 17 in Physical Review D.* “The wobble will grow over a few years but eventually it will damp out and go back to zero.”


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Study team member Tung X. Tran, then an undergraduate student at the Massachusetts Institute of Technology, built a computer model of the solar system to see how the distance between Earth and nearby solar system objects would change after a black hole flyby. He found that such an effect would be most noticeable for Mars, whose distance scientists know within about 10 centimeters. For a black hole in the middle of the mass range, “we found that after three years the signal would grow to between one to three meters,” Tran says. “That’s way above the threshold of precision that we can measure.” The Earth-Mars distance is particularly well tracked because scientists have been sending generations of probes and landers to the Red Planet.

If scientists detect a disturbance, they must determine whether the planet was pushed by a black hole or just a plain old asteroid. By tracking the wobble pattern over time, they can trace the trajectory of the object and predict where it will head in the future. “We actually get really rich information from the pattern of perturbations,” says study co-author Benjamin V. Lehmann of M.I.T. “We’d need to convince ourselves that it’s really a black hole by telling observers where to look.” If the object is an asteroid, telescopes should be able to see it. Plus, most asteroids come from within the solar system and therefore orbit on the same plane as the planets. A primordial black hole, on the other hand, would be coming from far away and would likely have a different trajectory than that of an asteroid.

Another potential way to look for primordial black holes in the solar system would be to analyze data from asteroids, particularly the asteroid Bennu, which has been tracked very precisely by the ongoing space mission OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer). “After reading [the team’s] paper, I think we can try to dig into OSIRIS-REx data to see if we can see this effect,” says Yu-Dai Tsai, an astrophysicist at Los Alamos National Laboratory. “I think it’s a promising direction to look at.” Tsai and his colleagues studied how the probe’s Bennu measurements could be used to look for other forms of dark matter in a paper published September 20 in the journal Communications Physics.

Primordial black holes are an increasingly appealing solution to the puzzle of dark matter, an invisible form of mass that physicists think makes up most of the matter in our universe. Because they can only “see” this matter through its gravitational effects on regular matter, its identity has remained elusive. Many favored theories of its makeup have failed to pan out. For decades physicists thought dark matter was likely to take the form of so-called weakly interacting massive particles (WIMPs). Yet generations of ever more sensitive experiments meant to find these particles have come up empty, and particle accelerators have also seen no sign of them. “Everything is on the table because WIMPs have been put in such a corner, and they were the dominant paradigm for decades,” says astrophysicist Kevork Abazajian of the University of California, Irvine, who wasn’t involved in the Physical Review D study. “Primordial black holes are really gaining popularity.”

Physicists are also recognizing that dark matter may not interact with regular matter through any force other than gravity. Unlike WIMPs, which could also touch regular matter through the weak force, black holes would be detectable only through their gravitational pull. “Given that we are still searching for the correct way to detect dark matter interacting with ordinary matter, it is particularly important to explore probes based on the gravitational force it produces, which is the only interaction of dark matter whose strength is already known and the only interaction we are sure exists,” says theoretical physicist Tim M. P. Tait of U.C. Irvine, who was also not involved in the M.I.T. team’s new research. “This is a really interesting idea and one that is timely.”

In a coincidence, an independent team published a paper about its search for signs of primordial black holes flying near Earth in the same issue of Physical Review D. The researchers’ simulations found that such signals could be detectable in orbital data from Global Navigation Satellite Systems, as well as gravimeters that measure variations in Earth’s gravitational field. The two papers are complementary, says David I. Kaiser of M.I.T., a co-author of the study on Earth-Mars distance measurements.

Although these black holes could be passing relatively nearby, the chances that one could move through a human body are incredibly low. If that were to happen to you, though, it wouldn’t be fun: as the tiny black hole moved through you, it would tug everything toward it, causing cells to crush together in deadly fashion. Its minuscule volume, however, would at least prevent you from getting sucked in.

*Editor’s Note (9/24/24): This sentence was edited after posting to correct Sarah Geller’s current affiliation.

Joy Dunn ’08: Bridging careers in aerospace manufacturing and fusion energy with a focus on intentional inclusion

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Joy Dunn ’08: Bridging careers in aerospace manufacturing and fusion energy with a focus on intentional inclusion

“A big theme of my life has been focusing on intentional inclusion and how I can create environments where people can really bring their whole authentic selves to work,” says Joy Dunn ’08. As the head of operations at Commonwealth Fusion Systems, an MIT spinout working to achieve commercial fusion energy, Dunn looks for solutions to the world’s greatest climate challenges—while creating an open and equitable work environment where everyone can succeed.

This theme has been cultivated throughout her professional and personal life, including as a Young Global Leader at the World Economic Forum and as a board member at Out for Undergrad, an organization that works with LGBTQ+ college students to help them achieve their personal and professional goals. Through her careers both in aerospace and energy, Dunn has strived to instill a sense of equity and inclusion from the inside out.

Developing a love for space

As Dunn was growing up, her parents supported her interest in space and space exploration. Here she is at space camp, where she learned what it takes to be an astronaut and had fun building and launching model rockets. Courtesy of Joy Dunn.

Dunn’s childhood was shaped by space. “I was really inspired as a kid to be an astronaut,” she says, “and for me that never stopped.” Dunn’s parents—both of whom had careers in the aerospace industry—encouraged her from an early age to pursue her interests, from building model rockets to visiting the National Air and Space Museum to attending space camp. A large inspiration for this passion arose when she received a signed photo from Sally Ride—the first American woman in space—that read, “To Joy, reach for the stars.”

As her interests continued to grow in middle school, she and her mom looked to see what it would take to become an astronaut, asking questions such as “what are the common career paths?” and “what schools did astronauts typically go to?” They quickly found that MIT was at the top of that list, and by seventh grade, Dunn had set her sights on the Institute.

After years of hard work, Dunn entered MIT in the fall of 2004 with a major in aerospace, aeronautical, and astronautical engineering (AeroAstro). At MIT, she remained fully committed to her passion while also expanding into other activities such as varsity softball, the MIT Undergraduate Association, and the Alpha Chi Omega sorority.

One of the highlights of Dunn’s college career was Unified Engineering (Course 16), a year-long course required for all AeroAstro majors that provides a foundational knowledge of aerospace engineering—culminating in a team competition where students design and build remote-controlled planes to be pitted against each other. “My team actually got first place, which was very exciting. And I honestly give a lot of that credit to our pilot. He did a very good job of not crashing!” In fact, that pilot was Warren Hoburg ’08, a former assistant professor in AeroAstro and current NASA astronaut training for a mission on the International Space Station.

Pursuing her passion at SpaceX 

An MIT internship at SpaceX led to Dunn’s being hired as a propulsion development engineer at the company, where she helped build the thrusters for the Dragon spacecraft. After several promotions, she became the senior manager responsible for building the whole vehicle. Courtesy of Joy Dunn.

Dunn’s undergraduate experience culminated with an internship at the aerospace manufacturing company SpaceX in the summer of 2008. “It was by far my favorite internship of the ones that I had in college. I got to work on really hands-on projects and had the same amount of responsibility as a full-time employee.”

By the end of the internship, she was hired as a propulsion development engineer for the Dragon spacecraft where she helped to build the thrusters for the first Dragon mission. Eventually, she transferred to the role of manufacturing engineer. “A lot of what I’ve done in my life is building things and looking for process improvements,” so it was a natural fit. From there, she rose through the ranks, eventually becoming the senior manager of spacecraft manufacturing engineering where she oversaw all the manufacturing, test, and integration engineers working on Dragon. “It was pretty incredible to go from building thrusters to building the whole vehicle,” she says.

During her tenure, Dunn also co-founded SpaceX’s Women’s Network and its LGBT affinity group, Out and Allied. “It was about providing spaces for employees to get together and provide a sense of community,” she says. Through these groups, she helped start mentorship and community outreach programs, as well as helped grow the pipeline of women in leadership roles for the company.

In spite of all her successes at SpaceX, she couldn’t help but think about what came next. “I had been at SpaceX for almost a decade and had these thoughts of, ‘do I want to do another tour of duty or look at doing something else?’ The main criteria I set for myself was to do something that is equally or more world-changing than SpaceX.”

A pivot to fusion

It was at this time in 2018 that Dunn received an email from a former mentor asking if she had heard about a fusion energy startup called Commonwealth Fusion Systems (CFS) that worked with the MIT Plasma Science and Fusion Center. “I didn’t know much about fusion at all. I had heard about it as a science project that was still many, many years away as a viable energy source.”

After learning more about the technology and company, “I was just like ‘holy cow, this has the potential to be even more world-changing than what SpaceX is doing.’” She adds, “I decided that I wanted to spend my time and brainpower focusing on cleaning up the planet instead of getting off it.”

After connecting with CFS CEO Bob Mumgaard SM ’15, PhD ’15, Dunn joined the company and returned to Cambridge as the head of manufacturing. While moving from the aerospace industry to fusion energy was a large shift, she said her first project—building a fusion-relevant, high-temperature superconducting magnet capable of achieving 20 tesla—tied back into her life of being a builder who likes to get her hands on things.

Over the course of two years, she oversaw the production and scaling of the magnet manufacturing process. When she first came in, the magnets were being constructed in a time-consuming and manual way. “One of the things I’m most proud of from this project is teaching MIT research scientists how to think like manufacturing engineers,” she says. “It was a great symbiotic relationship. The MIT folks taught us the physics and science behind the magnets, and we came in to figure out how to make them into a more manufacturable product.”

Dunn inspects progress on the construction of the new CFS campus in Devens, Massachusetts, where facilities will house the company’s manufacturing operations and its SPARC fusion device. Dunn is now head of operations, responsible for manufacturing, facilities and construction, safety, and quality. Courtesy of Commonwealth Fusion Systems.

In September 2021, CFS tested this high-temperature superconducting magnet and achieved its goal of 20 tesla. This was a pivotal moment for the company that brought it one step closer to achieving its goal of producing net-positive fusion power. Now, CFS has begun work on a new campus in Devens, Massachusetts, to house their manufacturing operations and SPARC fusion device. Dunn plays a pivotal role in this expansion as well. In March 2021, she was promoted to the head of operations, which expanded her responsibilities beyond managing manufacturing to include facilities, construction, safety, and quality. “It’s been incredible to watch the campus grow from a pile of dirt…into full buildings.”

In addition to the groundbreaking work, Dunn highlights the culture of inclusiveness as something that makes CFS stand apart to her. “One of the main reasons that drew me to CFS was hearing from the company founders about their thoughts on diversity, equity, and inclusion, and how they wanted to make that a key focus for their company. That’s been so important in my career, and I’m really excited to see how much that’s valued at CFS.” The company has carried this out through programs such as Fusion Inclusion, an initiative that aims to build a strong and inclusive community from the inside out.

Dunn stresses “the impact that fusion can have on our world and for addressing issues of environmental injustice through an equitable distribution of power and electricity.” Adding, “That’s a huge lever that we have. I’m excited to watch CFS grow and for us to make a really positive impact on the world in that way.”


This article appears in the Spring 2022 issue of Energy Futures.

European Space Agency launches Hera mission to investigate asteroid ‘crash-scene’ – Physics World

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NIO China: Avoiding Thermal Distortions after E-Coating & Baking with BiW Assembly Simulation

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NIO China: Avoiding Thermal Distortions after E-Coating & Baking with BiW Assembly Simulation

Introduction

During the heating and cooling treatments involved in coating electrophoresis or post-painting baking, the body side outer panel of a Body in White (BiW) may suffer permanent plastic deformations such as buckles or waves. These defects significantly impact the quality of the vehicle. Typically, these deformations arise due to:

  1. Local temperature differences between the side outer panel and the inner panels during the heating-cooling cycle, which can cause uneven deformations and leave defects on the surface of the outer skin panel after cooling.
  2. The differing thermal expansion coefficient of steel and aluminum in hybrid BiW structures, which can cause localized plastic strain on the surface of the steel side outer panel during the heating-cooling cycle.

In a steel-aluminum hybrid BiW, both issues may exist simultaneously, and compared to structures made entirely of steel or aluminum, these problems are more frequent. Addressing these issues in tryout or production involves extensive validation countermeasures across departments and is highly inefficient.

However, these issues can be effectively avoided if identified and verified at the initial product development stage using CAE simulation tools. This proactive approach significantly reduces the likelihood and severity of such problems during manufacturing.

This article introduces the application of AutoForm-Assembly Thermal-Curing module in analyzing and preventing these issues.

Analyzing Baking Distortion with AutoForm-Assembly Thermal-Curing Module

In the simulation, several key physical parameters critically influence the results and must be accurately set and defined in the material card:

  • Thermal expansion coefficient is the most influential parameter in the electrophoretic baking simulation with AutoForm-Assembly.
  • Thermal conductivity indicates the material’s heat conduction difficulty.
  • Convective heat transfer coefficient reflects the heat transfer capacity between the fluid and the solid surface. It must be defined for the simulated object and the environment during the electrophoretic baking simulation stage.

Pre-Processing Steps

Several steps are required during pre-processing.

First, parameters such as material thickness direction, material thickness, material physical model, and thermodynamic parameters are set. The imported subassembly in this scenario is shown in Figure 1.

In the process planning stage, the number of operations is established, along with which part/subassembly is assembled in each operation, resulting in an assembly sequence tree shown in Figure 2.

NIO China: Avoiding Thermal Distortions after E-Coating & Baking with BiW Assembly Simulation

Figure 1: Subassembly imported to AutoForm-Assembly

Figure 2: Assembly sequence tree

During loading and fixation, for each operation, it’s necessary to establish the loading sequence (Figure 3), loading direction, positioning, and clamping strategy to ensure the stability of each part/subassembly during joining.

Next is joining and gluing; spot welding, bonding (Figure 4), and Flow Drilling Screw (FDS) are used in our case. Since FDS is not yet integrated into the software, rivets are used as a substitute model.

Figure 3: Loading sequence

Figure 4: Glues used in simulation

Finally, in the simulation, the thermodynamic parameters (thermal expansion coefficient, thermal conductivity coefficient and convective heat transfer coefficient) are defined for each part and material. The heat transfer coefficients are set at 45mW/mmk for steel, 220mW/mmk for cast aluminum, and 23.3mW/mmk for hot-formed steel. The convective heat transfer coefficient between the body and the environment is set at 0.02 mW/(mm^2·K). Additionally, the heating and temperature holding times during baking are configured to align with real process condition.

Interpretation of the Simulation Results

The quality of the simulation results for side panel deformation is primarily determined by the extent of deformation and the virtual oil stone performance, as illustrated in Figure 5.

Figure 5: Deformation of side outer panel

The significant bulging of 1.9mm in the lower area of the side outer panel is due to the aluminum extrusion beam’s higher thermal expansion coefficient compared to the other steel panels (see Figure 6). This deformation is generated during the heating-cooling cycle. If the value of this plastic deformation shows a gradient change, with no abrupt variations in the local area, then the surface defect can hardly be detected in the actual vehicle. Consequently, this variable serves as an indicator of structural stiffness, which can be used to optimize stiffness during preliminary structural design.

Figure 6: Aluminum extrusion beam of body side assembly

Figure 7 shows the virtual oil stone results. An abrupt value of max. 0.17mm was observed on both sides of the lower end of B-pillar area. Combining these results, we can conclude that waves are generated in this area.

Figure 7: Virtual stoning results along X direction

The results shown in Figure 7 typically indicate potential surface defects such as pits or waves under physical conditions. Thus, this output is used to evaluate the final indicator of surface quality affected by baking deformation.

Validation of the Simulation Results

Figures 8 and 9 compare the actual outer panel before and after electrophoresis, highlighting the deformation trends and their correlation with the simulated results.

Figure 8: BiW before electrophoresis & baking

Figure 9: State after electrophoresis & baking

The bulging deformation is easily detectable at the lower end of the B-pillar area, matching the trends shown in Figure 5.

Figure 10: Scanned result of B-pillar area after electrophoresis

Figure 10 shows the scanned results of the B-pillar area’s deviation from the nominal design after electrophoresis. Compared with Figure 5, the bulging deformation shows a high correlation with the simulation results both in trend and distribution, indicating considerable accuracy in the assembly simulation of baking deformation.

Conclusion

The issue of side panel baking deformation has long been a challenge within the automotive industry. Due to limitations in analysis tools, it has been difficult to effectively evaluate the influence of structural stiffness design on mitigating this issue. Traditionally, the solution has involved adding extra reinforcing patches, which not only decrease efficiency, but also increase costs. However, the adoption of Thermal-Curing technology now allows for a precise evaluation of baking deformation of the side panel, enabling the effective improvement of structural design. This approach significantly reduces the risks associated with this problem during vehicle manufacturing and reduces the cost of using extra patches.

Additionally, this type of analysis can also be applied to other sub-assemblies, such as doors with different material types, further extending the potential benefits.

Testimonial from NIO

Mr. Tu, Head of the Digital Simulation Team, emphasizes the broader relevance of these issues: “Many other companies face similar baking deformation issues in hybrid BiW; it is highly recommended to use AutoForm Assembly to do early analysis and to reduce potential losses in the tryout and production stages!”

About the authors:

Xiaowen Tu heads the Digital Simulation Technology Team and is an expert in the stamping process at NIO’s Foresight Manufacturing Engineering Department, bringing 22 years of experience in the automotive industry with proficiency in numerical simulation technology.

Pengpeng Liu Xiaoqian Pan is an integral member of the NIO-Foresight Manufacturing Process Innovation Center Team.

JuLei Wu Lei Liu is a key representative of the NIO-Manufacturing Engineering (BiW System) Department. On behalf of our fans at FormingWorld.com, thank you for this excellent case study.

Thanks also to Xu Jian & Shadow Lu from AutoForm for organizing this post.