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Dali hit Key Bridge with the force of 66 heavy trucks at highway speed

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theconversation.com – Amanda Bao, Associate Professor of Civil Engineering Technology, Environmental Management and Safety, Rochester Institute of Technology – 2024-04-08 07:23:15

The Baltimore bridge didn't stand a .

AP Photo/Julia Nikhinson

Amanda Bao, Rochester Institute of Technology

A tile reading '26 milllion, pounds of force exerted by the Dali during its collision with the Francis Scott Key Bridge'

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The cargo ship Dali knocked down three main truss spans, constructed with connected steel elements forming triangles, on the Francis Scott Key Bridge just seconds after crashing into one of the bridge piers early on Tuesday morning, March 26, 2024.

The bridge collapse happened so fast that it left little time for the work crews on the bridge to escape. Civil engineers like me have been paying attention to this disaster, because we want to find ways to make like these large bridges more resilient. For a bridge this large to collapse would require a catastrophic collision force. But using some basic physics principles, we can actually estimate approximately what that force was.

Dali the Francis Scott Key Bridge.

The impulse momentum theorem

You can calculate the magnitude of the Dali's collision force using a fundamental physics principle called the impulse momentum theorem.

The theorem is derived directly from Newton's second law, which states that force equals mass times acceleration. The impulse momentum theorem adds time to both sides of this equation, to tell you force multiplied by time equals mass multiplied by the change of velocity when the force is applied.

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F*∆t = m*∆v.

To calculate the impulse momentum theory for Dali's collision, multiply its collision force with how long the collision lasted, and equate that with Dali's mass multiplied by its change in velocity before and after the crash. So, Dali's collision force has to do with its mass, how long the collision lasted, and how much it slowed down after the crash.

The numbers for Dali's crash

Dali weighs 257,612,358 pounds or 116,851 metric tonnes when it is fully loaded. It traveled at a speed of 10 miles per hour, or 16.1 kilometers per hour, before the collision; after crashing into the bridge pier, Dali slowed down to 7.8 miles per hour, or 12.6 kilometers per hour.

Another important parameter is the collision time, which refers to the period of time when the ship contacted the bridge during the crash, which caused Dali to suddenly slow.

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Nobody knows the exact collision time yet, but based on Dali's voyage data recorder and the Maryland Transportation Authority Police log, the total collision time was less than four seconds.

For cars crashing on a highway, the collision time is usually only half a second to one second. Dali's crash looks similar to how a vehicle might crash on a bridge pier, so it makes sense to use the similar collision time duration to estimate the collision force.

Dali's collision force

With those estimates and the impulse momentum theory, you can get a pretty good idea of what Dali's collision force probably was.

Dali's collision force is calculated by taking Dali's mass and multiplying it by Dali's velocity change before and after the crash, then dividing all that by the collision time duration. If you assume the collision time is only one second, that gives a collision force of 26,422,562 pounds.

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257,612,358 pounds/(32.2 ft/sec²) * (14.7 feet/sec – 11.4 feet/sec⁡) / 1 sec = 26,422,562 pounds.

For reference, the American Association of State Highway and Transportation Officials specifies that the collision force on a highway bridge pier from a truck crash is about 400,000 pounds.

With that said, the cargo ship Dali's collision force on the Baltimore Key Bridge pier is equivalent to the scenario of 66 heavy trucks driving with a speed of 60 miles per hour (97 km per hour) and hitting the bridge pier simultaneously. This magnitude is far beyond the force that the pier can withstand.

While designing a super robust bridge that can handle this level of collision force would be technically achievable, doing so would dramatically increase the cost of the bridge. Civil engineers are investigating different approaches that would reduce the force put directly on the piers, such as using energy absorbent protection barriers around the piers that dissipate the shock. These sorts of could prevent disasters like this in the future.The Conversation

Amanda Bao, Associate Professor of Civil Engineering Technology, Environmental Management and Safety, Rochester Institute of Technology

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Conversation

TikTok law threatening a ban if the app isn’t sold raises First Amendment concerns

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theconversation.com – Anupam Chander, Professor of and Technology, Georgetown – 2024-05-21 07:25:32

TikTok users worry about losing their social platform, but First Amendment rights are on the line, too.

AP Photo/Ted Shaffrey

Anupam Chander, Georgetown University and Gautam Hans, Cornell University

TikTok, the short- company with Chinese roots, did the most American thing possible on May 7, 2024: It sued the U.S. government, in the person of Merrick Garland, in federal court. The suit claims the federal law that took effect on April 24, 2024, banning TikTok unless it sells itself violates the U.S. Constitution.

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The law names TikTok and its parent company, ByteDance Ltd., specifically. It also applies to other applications and websites reaching more than a million monthly users that allow people to share information and that have ownership of 20% or more from China, Russia, Iran or North Korea. If the president determines that such applications or websites “present a significant threat to the national security,” then those apps and websites, too, must either be sold or banned from the U.S.

TikTok's suit says that the law violates the First Amendment by failing to evidence of the national security threat posed by the app and for failing to seek a less restrictive remedy. Despite legislators' claims to the contrary, the law forcing the divestiture of TikTok – the Protecting Americans from Foreign Adversary Controlled Applications Act – implicates First Amendment interests. In our view, it does so in ways that ripple beyond this specific case.

As a company incorporated in the United States that provides an online publishing platform, TikTok has a right protected by the First Amendment to select what messages – in this case, user – it chooses to publish.

A ban appears to us, scholars who study law and technology, to be a massive prior restraint, which is generally barred by U.S. courts. Prior restraint is action by the government to prevent speech, typically some form of publication, before it occurs.

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The First Amendment limits what the government can do to censor speech.

Speech in the crosshairs

The law's backers say that it is not a ban – all TikTok has to do is sell itself. These supporters describe the bill as a divestiture, a purely economic regulation that they say should insulate it from First Amendment . After the sale, users could happily keep on using TikTok, not caring who owns the company. But the law seems to us an attempt to control speech by mandating a change in ownership.

Changing the speech content on the app is the express goal of some of the law's backers. The principal author of the bill, former U.S. Rep. Mike Gallagher, who stepped down from office in April to join a venture capital firm partly backed by Microsoft, explained to The New York Times that he was principally concerned about the potential for the Chinese Communist Party to spread propaganda on the app. The Times and The Wall Street Journal have reported that passed this bill in part because of unsubstantiated accusations that TikTok was unfairly promoting one side in the Israel-Hamas war.

Imagine if the government told Jeff Bezos that he had to sell The Washington Post because it was worried that he might push a particular agenda using his control of the newspaper. Or to use a digital analogy, what if the government told Elon Musk that he had to sell X, formerly Twitter, because it didn't like his content moderation of legal speech? Those scenarios clearly have a connection to First Amendment protections.

Ownership matters

Transferring TikTok's ownership from one company to another matters greatly for the purposes of First Amendment analysis.

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Supreme Court Justice Elena Kagan observed during oral arguments in a case unrelated to TikTok's ownership that ownership can make a difference in an app. She noted that the sale of Twitter to Elon Musk changed the character of the app. Kagan said, “Twitter users one day woke up and found themselves to be X users and the content rules had changed and their feeds changed, and all of a sudden they were getting a different online newspaper, so to speak, in a metaphorical sense every morning.”

Indeed, The Washington Post found a rightward tilt after Twitter changed hands.

By forcing the sale of TikTok to an entity without ties to the Chinese Communist Party, Congress' intent with the law is to change the nature of the platform. That kind of government action implicates the core concerns that the First Amendment was designed to protect against: government interference in the speech of private parties.

U.S. Rep. Raja Krishnamoorthi, co-sponsor of the House bill on TikTok, pointed to another instance where the U.S. government ordered a Chinese company to sell a U.S. app. In 2019, the Committee on Foreign Investment in the United States ordered the new Chinese owners of Grindr to sell the dating app, which the Chinese owners did the following year. In that case, the foreign owners could not assert First Amendment rights in the United States, given that they were outside the U.S., and thus no court considered this issue.

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TikTok is First Amendment protection against the law forcing its sale or ban.

National security claims

The government hasn't disclosed to the public the national security concerns cited in the TikTok law. While such concerns, if accurate, might warrant some kind of intervention, some Americans are likely to decline to take claims of national security urgency on good faith. To address skepticism of secret government power, particularly when it involves speech rights, the government arguably needs to present its claims.

U.S. Sens. Richard Blumenthal and Marsha Blackburn, both of whom supported the TikTok law and have seen the government's secret evidence, called for the declassification of that information. We believe that's a vital step for the public to properly consider the government's claim that a ban is warranted in this instance. In any case, the courts will ultimately weigh the secret evidence in determining whether the government's national security concerns justified this intrusion upon speech.

What seems likely to happen, absent judicial invalidation or legislative repeal of the law, is a world in which TikTok cannot effectively operate in the United States in a year's time, with mobile app stores unable to push out updates to the software and Oracle Corp. unable to continue hosting the app and its U.S. user data on its servers. TikTok could go dark on Jan. 19, 2025, in the United States.The Conversation

Anupam Chander, Professor of Law and Technology, Georgetown University and Gautam Hans, Associate Clinical Professor of Law, Cornell University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The Conversation

AI chatbots are intruding into online communities where people are trying to connect with other humans

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theconversation.com – Casey Fiesler, Associate Professor of Information Science, of Colorado Boulder – 2024-05-20 07:27:05
AI chatbots are butting into human spaces.
gmast3r/iStock via Getty Images

Casey Fiesler, University of Colorado Boulder

A parent asked a question in a private Facebook group in April 2024: Does anyone with a child who is both gifted and disabled have any experience with New York public schools? The parent received a seemingly helpful answer that laid out some characteristics of a specific school, beginning with the context that “I have a child who is also 2e,” meaning twice exceptional.

On a Facebook group for swapping unwanted items near Boston, a user looking for specific items received an offer of a “gently used” Canon camera and an “almost-new portable air conditioning unit that I never ended up using.”

Both of these responses were lies. That child does not exist and neither do the camera or air conditioner. The answers came from an artificial intelligence chatbot.

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According to a Meta help page, Meta AI will respond to a post in a group if someone explicitly tags it or if someone “asks a question in a post and no one responds within an hour.” The feature is not yet available in all regions or for all groups, according to the page. For groups where it is available, “admins can turn it off and back on at any time.”

Meta AI has also been integrated into search features on Facebook and Instagram, and users cannot turn it off.

As a researcher who studies both online communities and AI ethics, I find the idea of uninvited chatbots answering questions in Facebook groups to be dystopian for a number of reasons, starting with the fact that online communities are for people.

Human connections

In 1993, Howard Rheingold published the book “The Virtual Community: Homesteading on the Electronic Frontier” about the WELL, an early and culturally significant online community. The first chapter with a parenting question: What to do about a “blood-bloated thing sucking on our baby's scalp.”

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Rheingold received an answer from someone with firsthand knowledge of dealing with ticks and had resolved the problem before receiving a callback from the pediatrician's office. Of this experience, he wrote, “What amazed me wasn't just the speed with which we obtained precisely the information we needed to know, right when we needed to know it. It was also the immense inner sense of security that comes with discovering that real people – most of them parents, some of them nurses, doctors, and midwives – are available, around the clock, if you need them.”

This “real people” aspect of online communities continues to be critical . Imagine why you might pose a question to a Facebook group rather than a search engine: because you want an answer from someone with real, lived experience or you want the human response that your question might elicit – sympathy, outrage, commiseration – or both.

Decades of research suggests that the human component of online communities is what makes them so valuable for both information-seeking and social support. For example, fathers who might otherwise feel uncomfortable asking for parenting advice have found a haven in private online spaces just for dads. LGBTQ+ youth often join online communities to safely find critical resources while reducing feelings of isolation. Mental health support forums provide young people with belonging and validation in addition to advice and social support.

Online communities are well-documented places of support for LGBTQ+ people.

In addition to similar findings in my own lab related to LGBTQ+ participants in online communities, as well as Black Twitter, two more recent studies, not yet peer-reviewed, have emphasized the importance of the human aspects of information-seeking in online communities.

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One, led by PhD student Blakeley Payne, focuses on fat people's experiences online. Many of our participants found a lifeline in access to an audience and community with similar experiences as they sought and shared information about topics such as navigating hostile systems, finding clothing and dealing with cultural biases and stereotypes.

Another, led by Ph.D student Faye Kollig, found that people who share content online about their chronic illnesses are motivated by the sense of community that comes with shared experiences, as well as the humanizing aspects of connecting with others to both seek and provide support and information.

Faux people

The most important of these online spaces as described by our participants could be drastically undermined by responses coming from chatbots instead of people.

As a type 1 diabetic, I follow a number of related Facebook groups that are frequented by many parents newly navigating the challenges of caring for a young child with diabetes. Questions are frequent: “What does this mean?” “How should I handle this?” “What are your experiences with this?” Answers from firsthand experience, but they also typically come with compassion: “This is hard.” “You're doing your best.” And of course: “We've all been there.”

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A response from a chatbot to speak from the lived experience of caring for a diabetic child, offering empathy, would not only be inappropriate, but it would be borderline cruel.

However, it makes complete sense that these are the types of responses that a chatbot would offer. Large language models, simplistically, function more similarly to autocomplete than they do to search engines. For a model trained on the millions and millions of posts and comments in Facebook groups, the “autocomplete” answer to a question in a support community is definitely one that invokes personal experience and offers empathy – just as the “autocomplete” answer in a Buy Nothing Facebook group might be to offer someone a gently used camera.

Meta has rolled out an AI assistant across its social and messaging apps.

Keeping chatbots in their lanes

This isn't to suggest that chatbots aren't useful for anything – they may even be quite useful in some online communities, in some contexts. The problem is that in the midst of the current generative AI rush, there is a tendency to think that chatbots can and should do everything.

There are plenty of downsides to using large language models as information retrieval systems, and these downsides point to inappropriate contexts for their use. One downside is when incorrect information could be dangerous: an eating disorder helpline or legal advice for small businesses, for example.

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Research is pointing to important considerations in how and when to design and deploy chatbots. For example, one recently published paper at a large human-computer interaction conference found that though LGBTQ+ individuals lacking social support were sometimes turning to chatbots for with mental health needs, those chatbots frequently fell short in grasping the nuance of LGBTQ+-specific challenges.

Another found that though a group of autistic participants found value in interacting with a chatbot for social communication advice, that chatbot was also dispensing questionable advice. And yet another found that though a chatbot was helpful as a preconsultation tool in a health context, patients sometimes found expressions of empathy to be insincere or offensive.

Responsible AI development and deployment means not only auditing for issues such as bias and misinformation, but also taking the time to understand in which contexts AI is appropriate and desirable for the humans who will be interacting with them. Right now, many companies are wielding generative AI as a hammer, and as a result, everything looks like a nail.

Many contexts, such as online support communities, are best left to humans.The Conversation

Casey Fiesler, Associate Professor of Information Science, University of Colorado Boulder

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Is hard water bad for you? 2 water quality engineers explain the potential benefits and pitfalls that come with having hard water

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theconversation.com – Sarah Blank, Master's Student in Civil Engineering, Iowa State – 2024-05-20 07:26:46
Do you know how hard your is?
Tatiana Maksimova/Moment via Getty Images

Sarah Blank, Iowa State University and Timothy Ellis, Iowa State University

When you turn on your faucet to get a glass of water or wash your face, you're probably not thinking about what's in your water – besides water. Depending on where you live and whether you have a water-softening system, your water might contain dissolved minerals such as calcium and magnesium. And these minerals can play a role in whether certain pollutants such as lead stay out of your water.

The more dissolved minerals, the “harder” your water. But is hard water actually good or bad for you?

As engineering researchers who study water quality, we have seen the effects – both good and bad – that soft and hard water can have on everything from plumbing to the human body.

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What is hard water?

Hard water is water that contains dissolved minerals such as calcium, magnesium, iron and manganese. Soft water contains lower concentrations of these minerals.

Hardness is measured in terms of calcium carbonate, CaCO₃, which is used as a reference point for comparing different minerals.

The amount of these minerals in a 's water supply varies by region. It depends on both where the water is coming from and how the water is treated.

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Communities that source their water from wells rather than surface water such as lakes, streams, rivers and reservoirs often start with hard water pretreatment. As groundwater moves through the soil to a well, it picks up minerals. At the same time, areas where the types of rock and sediment are more prone to dissolving in water may have harder water.

A map showing water hardness across the U.S., with the hardest water in the Midwest, West and Southwest.
Streamflow water hardness across the U.S., where purple and blue indicate softer water and white and red indicate harder water. This map was updated in 2005 by the U.S. EPA.
U.S. Geological Survey

Effects on water lines and distribution

Water that's too hard or too soft could damage pipes and lead to health and aesthetic concerns.

Since hard water has a higher mineral concentration, minerals can build up in pipes, which to clogged pipes in homes and public water systems. Hardness also creates more deposits at higher temperatures, so hot water heaters are prone to mineral buildup. In areas with hard water, water heaters have a shorter span.

A pipe with gray material around the inside.
A pipe that has a thick layer of mineral deposits inside of it.
Mevedech/Wikimedia Commons

But hard water can , too. While minerals from hard water can clog pipes, a thin layer of mineral deposition in water lines can protect you from ingesting toxins that could seep in from the pipe itself. Water without any minerals can play a role in pipe corrosion, because without a thin, protective layer of minerals, the water may start to eat away at the pipes, releasing metals from the pipes into the water. Drinking this water might mean ingesting metals such as lead, copper and iron.

While water that is too soft or too hard can have different effects on water lines, there is more chemistry than just hardness that plays a role in pipe corrosion and clogging. So, there's no specific hardness level that is a cause for concern. Water treatment plants take the appropriate measures to adjust for different hardness levels.

A large tank of water, with fences around the top.
Drinking water normally undergoes treatment at a plant before it makes its way to your home.
Florida Water Daily, CC BY

Effects on skin and hair

Whether you use hard or soft water to wash up can also have noticeable effects on your skin and hair.

Hard water is more likely to leave your skin dry. The minerals in hard water strip moisture from skin and create deposits that clog pores.

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Hard water can also strip the hair of moisture, leaving it dry and coarse. Dry hair is more prone to frizz, tangles and breakage. Mineral deposits can also build up on the hair and scalp, clogging your hair follicles and leading to dandruff and slowed hair growth.

Many households have their own water-softening systems. A water-softening system may help hair and skin dryness and buildup. But many of these systems trap and replace calcium and magnesium with sodium, a mineral that does not contribute to water hardness, to lower overall hardness. Increasing the water's sodium content may be a concern for anyone on a low-sodium diet.

Overall health benefits

Other than aesthetic and water heater concerns, drinking hard water is actually good for you and doesn't come with any serious adverse side effects.

For example, the extra magnesium and calcium you consume in hard water may a gentle solution to digestive issues and constipation.

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Also, researchers have found positive correlations between the hardness of drinking water and bone health. Since calcium is an essential mineral in bones, individuals in areas with drinking water that has more calcium may have higher bone mineral density and may be less prone to osteoporosis.

Researchers have also found that drinking hard water has been associated with a decrease in cardiovascular disease-related mortality. Magnesium helps regulate your cardiac muscles, while calcium keeps the sodium-potassium balance in your cardiac muscles in check, which they need to function.

Whether you have hard or soft water, don't worry too much. Water treatment plants take appropriate measures to ensure safe water for the communities they support.

To learn more about the water hardness in your area, you can contact your local water treatment plant about its specific water treatment . Private well owners can contact their state to find out the testing recommendations for their area.The Conversation

Sarah Blank, Master's Student in Civil Engineering, Iowa State University and Timothy Ellis, Associate Professor of Civil, Construction and Environmental Engineering, Iowa State University

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