【推荐1】We usually think of archaeology as lots of painstaking work by brave explorers. But today, long-hidden cities are being revealed (显露) from the air, where modern archaeologists use laser pulses (激光脉冲) to discover the sign of ancient life buried below thick surface.   

Lidar, short for “light detection and ranging”, needs directing rapid laser pulses at the ground from an airplane. Software catches the time and wavelength of the pulses reflected from the surface and connects it with GPS and other data to produce a precise 3D map of the landscape below.

In recent years, lidar exposed an ancient city in western Mexico called Angamuco. The discovery of this long-lost Mexican metropolis (大都) is especially meaningful.

“To think that this large city existed in the heartland of Mexico for all this time and nobody knew it was there is kind of amazing,” says Chris Fisher, an archaeologist at Colorado State University who led the expedition.

The city extended over ten square miles. “That is a huge area with a lot of people,” says Fisher. “You are talking about 40. 000 building foundations, which is about the same number of building foundations that are on the island of Manhattan.” Archaeologists were surprised when they saw Angamuco’s city plan. The monuments (纪念碑) were largely concentrated in eight zones around the edges rather than being located in one large center.

Archacologists discovered signs of the buried city in 2007 and attempted to explore it using a traditional way. But the team soon realized that it would take at least ten years to outline the whole metropolis. In 2011, they began using lidar to map nearly 14 square miles. Researchers now believe that more than 100. 000 people lived in Angamuco from about AD 1000 to AD 1350. That makes it the biggest city in western Mexico at the time or at least the biggest city we know about so far.

“Everywhere you point the lidar instrument, you find something new.” says Fisher. “Right now. every textbook has to be rewritten. and two years from now. they’re going to have to be rewritten again.”

【推荐2】Zero-emission large passenger aircraft powered by hydrogen will be technically possible in five years, according to Airbus, but they will not enter service for at least a decade as the price of the fuel needs to come down.

The prediction comes from Glenn Llewellyn, vice-president of zero-emissions technology at the pan-European plane-maker. He said that while Airbus planned to demonstrate hydrogen-powered aircraft in 2025, over the next 10 years, hydrogen won’t be more economical than the fossil fuel.

For passengers to be flying genuinely emissions free aboard hydrogen-powered planes—which emit only water and heat — their fuel needs to come from hydrogen produced via renewable sources such as wind and solar, he added.

In an interview ahead of the Bloomberg NEF London Summit, Mr. Llewellyn said, “We already see massive increases in the amount of renewable energy being produced across the world. Wind energy production has multiplied by two over the last five years and solar energy production has multiplied by four.”

A further challenge is building up the ecosystem that hydrogen aircraft, along with other forms of transport, will need. This ranges from creating the fuel from electrolysis to split water into hydrogen and oxygen powered by renewable energy, to the actual transport of the gas and fueling systems for it at airports.

However, Mr. Llewellyn predicted that there was enough interest in the sector to make this happen. He added, “There are a number of independent institutes that have mapped out how hydrogen costs can come down over the next decades. We see a 30pc reduction in renewable hydrogen costs in 2030 compared to where it is today, and a 50pc reduction in renewable hydrogen costs by 2050.”

【推荐3】Range anxiety(里程焦虑), the fear of running out of power before being able to recharge an electric vehicle, may be a thing of the past, according to a team of Penn State engineers who are looking at lithium iron phosphate batteries(磷酸铁锂电池) that have a range of 250 miles with the ability to charge in 10 minutes.

“We developed a pretty clever battery for mass-market electric vehicles,” said Chao-Yang Wang, a professor and director of the Electrochemical Engine Center at Penn State. “There is no more range anxiety and this battery is affordable”. The researchers also say that the battery should be good for 2 million miles in its lifetime.

They report today in Nature Energy that the key to long-life and rapid recharging is the battery’s ability to quickly heat up to 140 degrees Fahrenheit, for charge and discharge, and then cool down when the battery is not working.

The battery uses a self-heating approach previously developed in Wang’s center. The self-heating battery uses a thin nickel foil(镍箔) with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. Once electrons flow it rapidly heats up the nickel foil through resistance heating and warm the inside of the battery. Once the battery’s internal temperature is 140 degrees F, the switch opens and the battery is ready for rapid charge or discharge.

“This battery has slenderized weight, volume and cost,” said Wang. “I am very happy that we finally found a battery that will benefit the mainstream consumer mass market.” According to Wang, these smaller batteries can produce a large amount of power upon heating—40 kilowatt hours and 300 kilowatts of power. An electric vehicle with this battery could go from zero to 60 miles per hour in 3 seconds and would drive like a Porsche, he said. “This is how we are going to change the environment and not contribute to just the luxury cars,” said Wang. “Let everyone afford electric vehicles.”

【推荐1】English is a very interesting language. It has borrowed words from many other languages. Immigrants (移民) coming into the United States have contributed many words to the language, which have kept their original pronunciation. “Coolie” and “kowtow” were taken from the Chinese language, “kamikaze” from Japanese, “shampoo” from Indian, “blitz” from German, “amigo” and “Los Angeles” from Spanish and so on.

Many students have studied English for years, some as many as eight. However, some students still have difficulty in speaking fluent English. Some know many words, but are unable to discern them when native speakers use them. In our oral English classes we will focus on speaking and listening to native English speakers. Because we are trying to train your ears to hear English and your mouths to speak intelligible (易理解的) English, we will have a rule that ONLY ENGLISH will be spoken in our English classes. Anyone speaking Chinese in class will be required to pay a fine (罚款) in order to encourage the speaking and understanding of English. If teachers enter a classroom and discover that anyone is speaking Chinese, they will require everyone in the room to pay the fine. It is everyone’s job to enforce the English-Only rule. It is for your benefit. It is because we want to accustom (使习惯于) your ears to hearing English.

Other subjects may be learned only from books but the only way to learn a foreign language is to SPEAK IT! Students are often nervous about speaking in class at first but we hope to make the classes fun, so you will forget your nervousness and learn to speak out. Enjoy your classes.