which of the following assesses the research quality of university departments on the scale of 1 to 5 A: RAE B: The group C: Funding councils D: University teachers.

​预测性能的优劣需要一定的度量来衡量，常用的度量是（ ）。​ A: MAE（平均绝对误差） B: MSE（均方误差） C: RSE（相对平方误差） D: RAE（相对绝对误差）

下面对FA/D独立电调天线的远端电调功能描述不正确的是？ A: RCU内置 B: 通过校准通道传输 C: 可通过RAE更新对应角度的权值 D: 需要连接AISG线才能完成

The quiet heroism of mail delivery A) On Wednesday, a polar wind brought bitter cold to the Midwest. Overnight, Chicago reached a low of 21 degrees Fahrenheit below zero, making it slightly colder than Antarctica, Alaska, and the North Pole. Wind chills were 64 degrees below zero in Park Rapids, Minnesota, and 45 degrees below zero in Buffalo, North Dakota, according to the National Weather Service. Schools, restaurants, and businesses closed, and more than 1,000 flights were canceled. B) Even the United States Postal Service（USPS） suspended mail delivery. “Due to this arctic outbreak and concerns for the safety of USPS employees,”USPS announced Wednesday morning,“the Postal Service is suspending delivery Jan. 30 in some 3-digit ZIP Code locations.” Twelve regions were listed as unsafe on Wednesday; on Thursday, eight remained. C) As global surface temperatures increase, so does the likelihood of extreme weather. In 2018 alone, wildfires, volcanic eruptions, hurricanes, mudslides, and other natural disasters cost at least $49 billion in the United States. As my colleague Vann Newkirk reported, Puerto Rico is still confronting economic and structural devastation and resource scarcity from 2017’s Hurricane Maria. Natural disasters can wreck a community’s infrastructure, disrupting systems for months or years. Some services, however, remind us that life will eventually return, in some form, to normal. D) Days after the deadly 2017 wildfires in Santa Rosa, California, a drone（无人机） caught footage（连续镜头）of a USPS worker, Trevor Smith, driving through burned homes in that familiar white van, collecting mail in an affected area. The video is striking: The operation is familiar, but the scene looks like the end of the world. According to Rae Ann Haight, the program manager for the national-preparedness office at USPS, Smith was fulfilling a request made by some of the home owners to pick up any mail that was left untouched. For Smith, this was just another day on the job. “I followed my route like I normally do,” Smith told a reporter. “As I came across a box that was up but with no house, I checked, and there was mail—outgoing mail—in it. And so we picked those up and carried on.” E) USPS has sophisticated emergency plans for natural disasters. Across the country, 285 emergency-management teams are devoted to crisis control. These teams are trained annually using a framework known as the three Ps: people, property, product. After mail service stops due to weather, the agency’s top priority is ensuring that employees are safe. Then it evaluates the health of infrastructure, such as the roads that mail carriers drive on. Finally, it decides when and how to re-open operations. If the destruction is extreme, mail addressed to the area will get sent elsewhere. In response to Hurricane Katrina in 2005, USPS redirected incoming New Orleans mail to existing mail facilities in Houston. Mail that was already processed in New Orleans facilities was moved to an upper floor so it would be protected from water damage. F) As soon as it’s safe enough to be outside, couriers（邮递员）start distributing accumulated mail on the still-accessible routes. USPS urges those without standing addresses to file change-of-address forms with their new location. After Hurricane Katrina hit in 2005, mail facilities were set up in dozens of locations across the country in the two weeks that USPS was unable to provide street delivery. G) Every day, USPS processes, on average, 493.4 million pieces of mail—anything from postcards to Social Security checks to medicine. Spokespeople from both USPS and UPS told me all mail is important. But some mail can be extremely sensitive and timely. According to data released in January 2017, 56 percent of bills are paid online, which means that just under half of payments still rely on delivery services to be completed. H) It can be hard to identify which parcels are carrying crucial items such as Social Security checks, but USPS and UPS try their best to prioritize sensitive material. They will coordinate with the Social Security Administration to make sure that Social Security checks reach the right people in a timely fashion. After Hurricane Florence and Hurricane Michael last fall, USPS worked with state and local election boards to make sure that absentee ballots were available and received on time. I) Mail companies are logistics（物流）companies, which puts them in a special position to help when disaster strikes. In a 2011 USPS case study, the agency emphasized its massive infrastructure as a “unique federal asset” to be called upon in a disaster or terrorist attack. “I think we’re unique as a federal agency,” USPS official Mike Swigart told me, “because we’re in literally every community in this country … We’re obligated to deliver to that point on a daily basis.” J）Private courier companies, which have more dollars to spend, use their expertise in logistics to help revitalize damaged areas after a disaster. For more than a decade, FedEx has supported the American Red Cross in its effort to get emergency supplies to areas affected by disasters, both domestically and internationally. In 2012, the company distributed more than 1,200 MedPacks to Medical Reserve Corps groups in California. They also donated space for 3.1 million pounds of charitable shipping globally. Last October, the company pledged $1 million in cash and transportation support for Hurricanes Florence and Michael. UPS’s charitable arm, the UPS Foundation, uses the company’s logistics to help disaster-struck areas rebuild. “We realize that as a company with people, trucks, warehouses, we needed to play a larger role,” said Eduardo Martinez, the president of the UPS Foundation. The company employs its trucks and planes to deliver food, medicine, and water. The day before I spoke to Martinez in November, he had been touring the damage from Hurricane Michael in Florida with the American Red Cross. “We have an obligation to make sure our communities are thriving,” he said. K）Rebuilding can take a long time, and even then, impressions of the disaster may still remain. Returning to a normal life can be difficult, but some small routines—mail delivery being one of them—may help residents remember that their communities are still their communities. “When they see that carrier back out on the street,” Swigart said, “that’s the first sign to them that life is starting to return to normal.”