Can you imagine your doctor warning that taking a bath could be unhealthy? In the early 1800s , many doctors thought that tubs (浴缸) could carry diseases, so they advised against their use.【小题1】The White House did not even have a bathtub until 1851.

In the 19th century ,only one home out of six had a bathroom,【小题2】 On Saturday nights children all lined up for their turns to wash in a wooden tub in the kitchen. Mothers had to boil the water on the fire and carry it over to fill the tub.【小题3】

When the first bathtubs were introduced ,even their makers weren't sure whether the new fashion would last. They advertised their products as water containers that “could be used as bathing tubs”.

【小题4】By then most middle-class families had indoor taps (龙头). At first most tubs were made of wood, but as the popularity of the product increased, so did the creativity of tub makers. Before porcelain tubs there were rubber ones like the plastic swimming pools kids use today.

【小题5】Instead they tell their patients about the advantages of frequent bathing. Maybe one of the best reasons why doctors encourage frequent trips to the tub is that bathed patients smell better!

Most cars have seat belts as part of their equipment. Seat belts protect drivers and passengers in case of accidents. They also reduce the effect of a crash on the body.

【小题1】Worldwide, the devices have protected up to a million people. America first recognized the invention of an automobile seat belt in 1849. The government gave a patent to an engineer named Edward Claghorn of New York City so that others would not copy his invention of a safety device. 【小题2】This early version of safety belt was said to include hooks and other attachments for securing the person to a fixed object.

Other inventors followed with different versions of the seat belt. 【小题3】 It resulted from the work of a Swedish engineer, Nils Bohlin. His three-point, lap and shoulder seat belt first appeared on cars in Europe 50 years ago.

Nils Bohlin recognized that both the upper and lower body needed to be held securely in place. His invention contained a cloth strap(带子) that was placed across the chest and another strap across his hips(臀部).【小题4】

Volvo was the first company to offer the modern seat belt to its cars. This company also provided use of Nils Bohlin's design to other car-makers.

【小题5】He received a gold medal from the Royal Swedish Academy of Engineering Sciences in 1995. He died in Sweden in 2002.

CERTAIN CREATURES-namely, bees-have evolved to be skillful flying builders. To assemble (组装) a nest, worker insects team up to do various work to the specification of a complex design that ends up being many times their size. This process takes months, many times longer than the average lifespan of all but the queen. Meanwhile the insects must adjust as they go.

It is these insect building teams that inspired Mirko Kovac, a roboticist at Imperial College London, to develop a way to improve the flexibility of 3D printing. A typical 3D printer is limited by the range of its nozzle (喷嘴), and can only make objects smaller than itself. Dr Kovac’s team has removed these limitation by using flying robots.

Dr Kovac describes a system of flying robots that is composed of two types of multi-rotor drones: builders and scanners. The builders carry the 3D-printing nozzle. The scanners are robots equipped with cameras that are responsible for monitoring the progress of the builders.

The building process alternates between builders and scanners, layer by layer, printing and adjusting, until a structure is complete. First, a builder remains suspended over its area of operation and begins to release a jet or rush of the building material along its flight path. The choice of material is important——it must be lightweight enough for the drones to carry but strong enough to hold the subsequent layers that will be built on top. Once the builder robot has sprayed a layer of material, the scanner robot flies over, inspects the progress. The system then computes the next layer that the builder should make, while also correcting for any errors that might have been discovered in what has already been built.

Because the flying robots can, in theory, operate anywhere, they could fix things in dangerous or otherwise inaccessible places. Dr Kovac says that his robots could be used to spot and seal leaks in oil or gas pipelines, repair leaky insulation or fix cracks on tall buildings. Thinking more long term, Dr Kovac even sees a potential future for his construction robots, building on the surfaces of the Moon or Mars.