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Traffic flow becomes unstable as the number of vehicles increases. At 15 vehicles per mile per lane, a single driver tapping the brakes can cause a lasting wave of traffic jams that spreads backward for miles. "This is a phase transition," explains Katsuhiro Nishinari, a traffic researcher — similar to water freezing into ice, where a small change (like a temperature drop) causes a dramatic shift in state (from liquid to solid).

Nishinari's earlier research revealed that ants searching for food keep smooth flow even when there are very large numbers of them. Their secret? Recent studies tracking desert ants show they travel in well-organized groups of 3 — 20 individuals, moving at nearly constant speeds with consistent spacing between one another — about three body lengths apart. Crucially, they never speed up to overtake slower-moving peers, which prevents the "sudden slowdowns" that jam human traffic.

Human drivers, by contrast, prioritize personal speed over collective efficiency, which is why jams occur. "We maximize individual interests, leading to bad jams," notes Nicola Pugno, an engineer studying the behavior of groups. Self-driving cars, however, could be programmed to cooperate: sharing real-time data with nearby vehicles to maintain steady speeds and distances, or avoiding overtaking altogether. This vehicle network would be analogous to ants on a trail, which use chemical smells to organize their movements to coordinate behavior while interacting with one another.

However, ants have advantages cars can't match. They can widen their trails when needed, while drivers are confined to fixed highway lanes. Moreover, ants never crash; they simply crawl over one another when paths cross.

Still, today's drivers can learn from ants: Nishinari advises avoiding following too closely. Leaving extra space between cars allows drivers to absorb sudden braking in heavy traffic, preventing the spread of traffic jams. "Just maintaining a safe distance," he says, "can keep traffic flowing smoothly even when there are large numbers of cars."

Then, something changed. Last year, my youngest child began piano lessons. I helped him recognize notes and celebrated his simple songs. Watching him reminded me how much I loved piano. Sitting at his first recital (演奏会), I knew it was time to try again — seriously this time. Before I lost courage, I emailed his teacher, Faria.

Faria welcomed adult learners, and I walked to her house in the snow for my first lesson. We started with basic scales and a simple Tchaikovsky piece. To my surprise, my fingers still remembered some of the movements. I practiced every night and slowly made progress. After more than two decades, I was playing again. But as pieces grew harder, I struggled. One day, I couldn't even play a basic scale. I felt embarrassed and thought about quitting once more.

That weekend, I watched my son learn to dive. He failed again and again until he did it. I realized learning anything new is mostly about failing. It's not talent; it's practice.

As adults, we often avoid what we're not good at. But returning to piano taught me something different. Now, I give myself a sticker each time I practice — not for perfection, but for showing up. My kids see me fail, try again, and slowly improve. There's no exam ahead, no performance, but just practice — and that's enough.

1.写信目的；

2.活动安排；

3.邀请理由。

注意：词数80词左右；可以适当增加细节，以使行文连贯。

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During the October holiday, my parents and I made a trip to Mount Wuyi, is lying at the junction (交叉点) of Fujian and Jiangxi provinces. It is a popular tourist attraction. In December 1999, Mount Wuyi was listed as the World's (culture) and natural heritage by the UNESCO.

With rich tourism resources, Mount Wuyi is a good place (relax) ourselves. As early as the Western Zhou Dynasty (1100-771 BCE), it was well-known as a place of interest. It is (amaze) that there are 2,527 kinds of plant species and about 5,000 species of wild animals. Some of them (face) great survival challenges in the past but now measures are being taken to protect them by the local people.

Mount Wuyi Scenic Area is (extreme) large. The distance between attractions is so long we were not able to visit all the sites in the mountain. We only reached some main attractions such Heavenly Tour Peak, Wuyi Palace, Dahongpao Tea Trees, Water Curtain Cave. These famous sights left us a deep (impress). Though tired, we enjoyed ourselves. We're looking forward to (explore) other attractions in Mount Wuyi next time.

Over the years, there have been a number of different techniques to help designers approach this important point. , they can get a little complex. But good news is that there're really only three kinds of decisions you need to make about color in your home: the small ones, the medium ones, and the large ones.

. They're the little spots of color like throw pillows, mirrors and baskets that most of us use to add visual interest to our rooms. Less tiring than painting your walls and less expensive than buying a colorful sofa, small color choices bring with them the significant benefit of being easily changeable.

Medium color choices are generally furniture pieces such as sofas, dinner tables or bookshelves. . They require a bigger commitment than smaller ones, and they have a more powerful effect on the feeling of a space.

The large color decisions in your rooms concern the walls, ceilings, and floors. Whether you're looking at wallpaper or paint, the time, effort and relative expense put into it are significant. .

A. While all of them are useful

B. Whatever you're looking for

C. If you're experimenting with a color

D. Small color choices are the ones we're most familiar with

E. It's not really a good idea to use too many small color pieces

F. So it pays to be sure, because you want to get it right the first time

G. Color choices in this range are a step up from the small ones in two major ways