Tired of standing in line? Wait a bit longer, and you may never have to again. Everyone from Amazon to Silicon Valley start­ups is trying to eliminate lines in retail (零售) stores.

Amazon has opened 24 of its Amazon Go stores, which use cameras and artificial intelligence to see what you’ve taken off shelves and charge you as you walk out. Some start­ups are closely copying Amazon’s approach to using AI­powered cameras fixed in ceilings.But others are trying an entirely different way to skip the checkout: smart shopping carts. These companies have added cameras and sensors (传感器) to the carts, and are using AI to tell what you’ve placed in them. A built­in scale weighs items, in case you have to pay by the pound for an item. Customers pay by using a credit card, or through an online payment system. When customers exit the store, a green light on the shopping cart indicates that their orders are complete, and they’re charged.

The start­ups behind the smart shopping carts, including Caper and Veeve, say it’s much easier to add technology to the shopping cart than to an entire store. Amazon Go stores rely on hundreds of cameras in the ceiling. The shelves also include sensors to tell when an item is removed. Ahmed Beshry, co­founder of Caper, believes the technology to run Amazon Go is too expensive to use in a large grocery store. Neither Caper nor Veeve has said how much their smart shopping carts will cost, making it difficult to compare the different formats. Shariq Siddiqui, CEO of Veeve, said he’s finding increased interest from retailers given Amazon’s steady expansion of Amazon Go since the first Amazon Go store opened in Seattle in 2018. “We’re always happy when Amazon is doing something,” Siddiqui said. “They force retailers to get out of their old school thinking.”

Each time a business uses artificial intelligence and cameras, it raises questions about customer privacy and the impact on jobs.Beshry notes that the cameras in his smart shopping cart point down into the cart, so only customers’ hands and part of their arms will be captured (拍摄) by cameras.

Until now ,scientists have been unable to make use of water droplets (水滴) to produce a significant amount of power. 【小题1】 While we can't consider umbrellas as generators (发电机) , the latest approach shows there might be a way to get power from rain showers at a level of efficiency that makes these systems practical.

New research has found a method that could produce enough power from a single droplet of rain to light up 100 LED lights. 【小题2】 It is several thousand times than before.

" 【小题3】   It shows that a drop of 100 microlitres water released from a height of 5.9 inches can generate the power that can light up 100 small LED lights,"said biomedical engineer WangZuankai from the City University of Hong Kong.

That sounds like a surprising amount of power ,but the engineers used some wonderful tricks to make it happen. 【小题4】   They have been looking into this type of power production for years , but the physics of converting the energy of raindrops into electricity are much harder to do than getting the energy from a rising tide or a flowing stream.

Although scientists have made great progress , they have to do a lot more experiments. 【小题5】 However , the researchers hope to have a model ready in the next five years.

For astronomers who are sighted, the Universe is full of visual wonders. From shimmering planets to shinning galaxies(星系), the universe is impressively beautiful. But those who are visually impaired cannot share that experience. So astronomers have been developing alternative ways to convey(传递)scientific information.

Recently, the journal Nature Astronomy published the latest in a series of articles on the use of sonification in astronomy. Sonification describes the change of data into digital audio(声音)files, which allows them to be heard, as well as read and seen.

In August, Kimberly Arcand, a data-visualization expert and science communicator at the Center for Astrophysics and others transformed some of the first images of the black hole at the centre of the Perseus cluster from the James Webb Space Telescope into sound. They worked under the guidance of people who are blind to map the intensity and colours of light in the headline-grabbing pictures into audio. The sonification of an image of gas and dust in a distant nebula(星云), for instance, uses loud high-frequency sounds to represent bright light near the top of the image, but lower-frequency loud sounds to represent bright light near the image’s centre. The black hole sonification translates data on sound waves travelling through space-created by the black hole’s impact on the hot gas that surrounds it-into the range of human hearing.

Scientists in other fields have also experimented with data sonification. Some have explored whether it can help with discovering Alzheimer’s disease from brain scans. Sound has even been used to describe ecological shifts caused by climate change in an Alaskan forest, with researchers assigning various musical instruments to different tree species.

In the long run, such approaches need to be strictly evaluated to determine what they can offer that other techniques cannot. For all the technical accuracy displayed in individual projects, the Nature Astronomy series points out that there are no universally accepted standards for sonifying scientific data, and little published work that evaluates its effectiveness.