【Debunking rumors】
◎ Chen Xi, reporter of this newspaper
In the past few days, there has been a cold wave on the mainland, and the temperature in most areas has plummeted. This cold wave not only affected a wide area, but also accompanied by rain and snow.
Some rumors related to winter also took advantage of this cold wave to brush a wave of "presence": "triple" La Niña brings three times the cold, Dejung is currently the warmest clothing material, the longer the hot car in winter, the better, the white frost on persimmon cakes is a preservative... These rumors misled the masses and had a negative social impact.
Today, the reporter of Science and Technology Daily will take stock of the rumors in November one by one and use the power of science to smash them.
"Triplet" La Niña brings triple cold?
Truth: La Niña is just one of the factors that affect winter temperatures
According to the latest data released by the World Meteorological Organization, La Niña events that have been going on for a long time (hereinafter referred to as La Niña) are likely to continue until the end of this year or longer, which will be the first "triple" La Niña in the 21st century, that is, three consecutive La Niña winters in the northern hemisphere.
As soon as the news came out, it immediately attracted widespread attention, and some netizens gave their own "interpretation": "triple" La Nina will definitely bring three times the cold.
In this regard, Zhou Bing, chief expert of climate services at the National Climate Center, said that the "triple" La Niña is not a triple La Nina. The "triple" La Niña refers to the impact of La Niña for three consecutive winters starting in 2020, and the impact is not cumulative year after year, nor does it mean that the climate impact will double year by year.
La Niña refers to the persistent unusually cold sea surface temperature in the eastern and central equatorial Pacific, also known as anti-El Niño. When La Niñas appear, they are usually accompanied by global climate chaos. At this time, the mainland is prone to cold winters and hot summers, and the number of tropical cyclones making landfall on the mainland will be more than usual, and the phenomenon of "drought in the south and flooding in the north" will occur. In Indonesia, eastern Australia, northeastern Brazil and other places, there will be more rainfall; The equatorial region of Africa and the southeastern United States are prone to drought.
During most La Niña winters, cold air affecting the continent occurs more frequently. According to statistics, from the 90s of the 20th century to February 2022, in the autumn and winter when La Niña appeared, cold air affected the mainland a total of 141 times, of which 27 reached the level of cold wave.
"However, there are many factors that determine the temperature in winter, and La Niña is just one of many." Zhou Bing stressed that the winter temperature of the mainland is not only closely related to the strength of winter wind in East Asia, but also related to factors such as Arctic sea ice, Eurasian snow cover and atmospheric circulation system. Therefore, although La Niña winters have a greater probability of cold temperatures, it does not mean that there will be a cold winter.
After 1986, the frequency of La Niña's "encounters" with warm winters increased, with 1998 and 2020 being strong warm winters. The National Climate Center also pointed out in the "2022/2023 Winter and 2023 Spring Climate Trend Forecast" released on November 3, 2022 that it is expected that this winter (December 2022 to February 2023), the cold air intensity affecting the mainland is generally weak, and the temperature in most parts of the country is close to the same period of the year or high.
Relevant experts from the National Climate Center said that climate prediction is a highly professional scientific research business, which needs to be based on a large number of climate observation data and supported by high-resolution numerical prediction products in order to carry out comprehensive research and analysis, and finally carefully draw scientific conclusions.
Dejung is currently the warmest clothing material?
Truth: There are many materials similar to their warmth effect
As soon as the weather turns cold, many people start to prepare to buy thermal underwear. Go to the e-commerce platform to search for "thermal underwear", many goods packaging with the word "De Rong", De Rong has almost become the most frequent thermal clothing material this year. Many related businesses claim that Dejung can self-heat and is currently the warmest clothing material.
So, what are the facts?
"Dejung, a transliteration of the English word Dralon, is an acrylic fiber developed by an international life science group in Germany, and the main component is polyacrylonitrile fiber." Xu Lei, associate professor of the School of Textile Science and Engineering of Tianjin Polytechnic University, said in an interview with Science and Technology Daily that Derong is not a new thing, as early as 2011 it entered the mainland market.
"The warmth principle of Dejung has nothing to do with self-heating, but mainly related to the thermal conductivity of air." Xu Lei introduced that the thermal conductivity of an object represents its ability to transfer heat, and the thermal conductivity of air is low, which means that its ability to transfer heat is low, that is, heat is not easy to lose, so the more air the fabric can store, the better its warmth effect. The cross-section of De Rong is double T-shaped, not only is the fabric fluffy and thick, but the cross-section of this shape allows it to "lock" more static air, thus forming an insulation layer that reduces the heat dissipation of the human body.
"However, the statement that Dejung is currently the warmest material for clothing is incorrect." Xu Lei introduced that although the thermal conductivity of Dejung is only 0.05 watts / m Kelvin, which is relatively low in thermal insulation materials, there are many materials with similar warming effects in fiber materials.
In addition, the moisture absorption performance of De Rong is also relatively general. In contrast, cashmere materials are also warm, soft and comfortable, hygroscopic and elastic. Another example is the down jacket, whose high fluffiness can also retain a large amount of static air, thereby keeping warm and not easy to generate static electricity.
White cream on persimmon cake is a preservative?
Truth: White frost is a naturally occurring persimmon cream
Persimmon cake is a cake-like food made from persimmons and is one of the most anticipated dishes in winter. People who have eaten persimmon cakes know that there is a more or less white powder on persimmon cakes, but most people do not know what this layer of white frost is, so the Internet began to circulate that this is an artificially added preservative.
In this regard, Tian Shufen, a professor at Tianjin Agricultural College, said in an interview with a reporter from Science and Technology Daily that the white frost on persimmon cakes is called persimmon cream, which is a sugar frosting naturally formed in the production process of persimmon cakes, not a preservative, harmless to the human body, and consumers can eat it with confidence.
When making persimmon cakes, you first need to peel the persimmons, and then dry the peeled persimmons. During the drying process, persimmons will precipitate nutrients such as fructose and glucose, and after the water evaporates, these nutrients will slowly accumulate and crystallize, and finally form persimmon cream.
"Persimmon cream has the effects of moisturizing the lungs and relieving cough, stopping bleeding, giving birth to jin and throat, and has a certain effect on symptoms such as sore throat and cough." Tian Shufen introduced that at the same time, persimmon cream is rich in vitamin B_2, which also has a certain therapeutic effect on aphthous sores.
Generally speaking, the amount of persimmon cream on the outer layer of persimmon cake is determined by the temperature and drying time. The colder the weather and the longer the drying time, the sweeter the persimmon cake will be, and the persimmon cream will be relatively more. In the process of storage and transportation, if the ambient temperature rises, persimmon cream may melt and become less, which is what we often call "frost return".
However, consumers do not need to overly pursue the amount of persimmon cream, and need to be wary of unscrupulous merchants artificially sprinkling flour, starch and other substances on persimmon cakes in order to improve the "appearance" of persimmon cakes. The artificial "whitening" persimmon cake looks relatively white evenly, but as long as it is shaken lightly, the white powder on it will fall, and its taste is not the sweet feeling of persimmon cream.
The longer the hot car in winter, the better?
Truth: Overheating a car can damage the engine
Before exercising, people generally warm up in advance in order to reduce the injuries caused by exercise. Before the car is moving, it also needs to be "hot". Experienced drivers know that in winter, after the car starts in an outdoor low temperature environment, it needs to idle (so that the car engine runs in neutral) for a period of time and then drive normally.
However, many people have recently said that because it is too cold outdoors in winter, the longer the hot car time, the better, so that the engine can heat up more fully.
Is there any truth to this statement?
In this regard, Liu Jun, a teacher at the School of Automotive Engineering of Tianjin Vocational University, said in an interview with a reporter from Science and Technology Daily that due to the low outdoor temperature and poor fuel atomization in winter, it is best to make it gradually heat up when starting the engine outdoors, and it is not suitable to accelerate and use the engine to reduce engine wear and improve fuel economy.
In addition, under low temperature conditions, the fluidity of the oil in the engine will be reduced and the viscosity will be increased, which is difficult to quickly lubricate the engine. Therefore, it is necessary to warm up the car before driving in winter, but the damage to the car caused by excessive heating is not small.
"There are two main aspects to the damage to the car caused by too long a hot car. One is that it will cause carbon deposits (a scorched substance produced by unsaturated olefins and gums in the fuel at high temperatures during the operation of the engine), which will affect its performance, especially shorten the service life of the engine spark plug. Second, during idle operation, the fuel concentration is high, and long-term idle operation will waste fuel, increase pollutant emissions, and increase the work burden of three-way catalytic converters and particle traps (OPFs). Liu Jun explained.
For pure electric vehicles, Liu Jun reminded that the electric vehicle drive device is mainly composed of a motor, power battery and control system, and the energy that drives a pure electric vehicle comes from the battery, so there is no hot car problem. However, it should be noted that hybrid vehicles need to be hot, and when their driving range exceeds the cruising range in pure electric mode, they need to switch from pure electric mode to fuel mode, and if they are not hot, the engine will also be damaged. Therefore, in this case, it is better for the driver to warm up the car in fuel mode first, and then drive normally.
Source: Science and Technology Daily