Cities are difficult to navigate (导航) at the best of times, but for people with disabilities they can be like courses with hurdles and bring inconvenience to disabled people.

A UK national travel survey found that adults with mobility difficulties took 39% fewer trips than those with no disability in 2017. Yet that could change as devices and cities grow smarter. Assistive tech is playing a big role in the transformation. The global value of the industry is expected to increase from $14 billion in 2015 to $30.8 billion in 2024, according to Zion Market Research.

One of the things that could transform lives is a smart walking stick designed by engineers from Young Guru Academy (YGA) in Turkey. The WeWalk stick has a sensor that detects hurdles above chest level and uses vibrations (振动) to warn the user. It can be paired with a smartphone to help navigation, and is connected with a voice assistant and Google Maps.

Ceylan, who has been blind since birth, says that connecting the stick to the Internet of Things and smart city solutions makes it user-friendly. “As a blind person, when I am at the Metro station I don’t know which is my exit ... I don’t know which bus is approaching ... which stores are around me. That kind of information can be provided with the WeWalk,” he says.

“The smart walking stick is really an exciting initiative that will make a huge difference to some people,” says Anna Lawson, the director of the Center for Disability Studies at Leeds University in the United Kingdom. “But they are very expensive ... they’re not going to be available to the vast majority of disabled people,” she added.

Bryan Matthews, a lecturer at the Institute for Transport Studies at the University of Leeds, shares the concerns about cost. He says there should also be a focus on inclusive design, and anything that helps people navigate their environment is positive.

Every machine and power station, even renewable energy like wind and solar, creates waste heat that is simply lost in the atmosphere. Thankfully, scientists and engineers are devoted to collecting heat and transforming it into useful electricity. Now researchers at Penn State University have created a flexible thermoelectrie (热电的)generator that wraps around hot water or exhaust(排气)pipes, turning heat into electricity.

Flexible devices are more efficient because they attach to pipes in factories or on vehicles without having to be glued on like rigid devices.Then the thermoelectric materials turn temperature differences between the surface fixed to the pipe and the cooler outer surface into electric current -called the Seebeck effect

Thermophotovoltaic(热光伏的)devices are another promising way to use this waste heat. University of Michigan engineers have created a precisely machined thermophotovoltaic cell that could be used to generate electricity from extra renewable power. The cells would use heat and turn it into electricity on demand, in a form that is much cheaper than batteries, say its creators.

One of the factors crucial to any device’s thermoelectric efficiency is its material. If higher electrical energy can be created with smaller temperature differences, then the materials are said to have a high ZT value. Using a special material scientists have doubled the previous best. The random distribution of atoms in their material slows down the way heat passes through it, making the thermoelectric effect last longer, able to power sensors and small computer processors. Low temperature generation includes computers and cars, making pyroelectrics(热电体)particularly useful for squeezing more energy out of electronic systems.

Another relative advantage is inexpensive materials. More abundant elements like tin is cheap and abundant, with high ZTvalues when combined in the right way. Their use could lead to greener car engines.

And when it comes to personal electronics, thermoelectries could eventually beat traditional charging hardware. Chinese researchers have built a wristband that gathers body heat to power a LED and may be able to power smartwatches or other mobile devices in the future.

Radar is an electronic device that detects planes, ships, coastlines, landmarks, and even storm clouds. The name radar comes from the first letters of the words “radio direction and ranging”. As the human eye uses light waves to see, radar “sees” with radio waves. Without radar, planes could not land safely in bad weather and ships could not move safely in thick fog. 【小题1】

In the 1800s it was discovered that radio waves could be reflected from objects. But scientists did not make great advances in radar research until the 1930s, when the world was threatened by war. 【小题2】 It has been used widely in almost every conflict(冲突) since then.

Echoes make it possible for radar to work. When a beam of radio waves is sent out, it strikes an object and returns an echo. This echo is picked up by radar and recorded on a screen similar to television screens. On the screen an observer sees a flash and that can show the direction and distance of the object. 【小题3】

Airport control towers use radar to guide planes in for safe landings. Almost all large ships depend on radar to prevent collisions with icebergs or other ships. 【小题4】 Weather forecasters “see” the size, direction, and speed of storms on radar screens. Astronomers can even use radar to measure accurately the distance from the earth to the moon. Thus, the device has helped achieve major advancements.

【小题5】It guards us against possible enemy attacks. We have ballistic missile(弹道导弹) warning systems that can warn us against attacks when missiles are more than 1,000 miles away. Other radar systems can also warn us against enemy aircraft and even spying space satellites.