题目内容
Carpenters have known (51) centuries that some woods are tougher than others. Hickory(山核桃木), for example, was turned into axe handles and cartwheel spokes (车轮辐条) because it can absorb shocks without breaking. White oak (橡木), for example, is much more easily damaged, (52) it is almost as dense. Julian Vincent at Bathe University and his team were convinced the wood's internal structure could explain the differences.
Many trees have tubular(管状的) vessels that run (53) the trunk and carry water to the leaves. In oak they are large, and arranged in narrow bands, but in hickory they are smaller, and more evenly distributed. The researchers (54) this layout might distribute a blow's energy throughout the wood, soaking up a bigger hit. To test the idea, they drilled holes 0.65 millimeters across into a block of spruce(云杉), a wood with (55) vessels, and found that (56) withstood a harder knock. (57) when there were more than about 30 holes per square centimeter did the wood's performance drop off.
A uniform. substance doesn't cope well with knocks because only a small proportion of the material is actually (58) . All the energy from the blow goes towards breaking the material in one or two places, but often the pieces left (59) are pristine(未经破坏的).
"But instead of the energy being concentrated in one place, the holes provide many weak spots that all absorb energy as they break", says Vincent, "You are controlling the places (60) the wood breaks, and it can then absorb more (61) , more safely".
The researchers believe the principle could be applied to any material- (62) example, to manufacture lighter and more protective packaging. That could (63) be used in car bumpers (保险杠), crash barriers and armor for military vehicles, says Ulrike Wegst, (64) the Max Plank Institute for Mental Research in Stuttgart. But she emphasizes that you'd (65) to design the substance with the direction of force in mind. "The direction of loading is crucial", she says.
(51)
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Forecasting Methods
There are several different methods that can be used to create a forecast. The method a forecaster chooses depends upon the experience of the forecaster, the amount of information available to the forecaster, the level of difficulty that the forecast situation presents and the degree of accuracy or confidence needed in the forecast.
The first of these methods is the persistence method : the simplest of producing a forecast. The persistence method assumes that the conditions at the time of the forecast will not change. For example, if it is sunny and 37 degrees today, the persistence method predicts that it will be sunny and 37 degrees tomorrow. If two inches of rainfall today, the persistence method would predict two inches of rain for tomorrow. However, if weather conditions change significantly from day to day, the persistence method usually breaks down and is not the best forecasting method to use.
The trends method involves determining the speed and direction of movement for fronts, high and low pressure centers, and areas of clouds and precipitation (降雨量). Using this information, the forecaster can predict where he or she expects those features to be at some future time. For example, if a storm system is 1000 miles west of your location and moving to the east at 250 miles per day, using the trends method you would predict it will arrive in your area in 4 days. The trends method works well when systems continue to move at the same speed in the same direction for a long period of time. If they slow down, speed up, change , intensity or change direction, the trends forecast will probably not work well.
The climatology(气候学)method is another simple way of producing a forecast. This method involves averaging weather statistics accumulated over many years to make the forecast. For example, if you were using the climatology method to predict the weather for New York City on July 4th, you would go through all the weather data that has been recorded for every July 4th and take an average. The climatology method only works well when the weather pattern is similar to that expected for the chosen one of year. If the pattern is quite unusual for the given time of year, the climatology method will often fail.
The analog method(类推法) is a slightly more complicated method of producing a forecast. It involves examining today's forecast scenario and remembering a day in the past when the weather scenario(天气状况) looked very similar (an analog). The forecaster would predict that the weather in this forecast will behave the same as it did in the past. The analogy method is difficult to use because it is virtually impossible to find a predict analog. Various weather features rarely align themselves in the same locations they were in the previous time. Even small differences between the current time and the analog can lead to very different results.
What factor is NOT mentioned in choosing a forecasting method？
According to the writer, current technique has no room for improvement.
Accurate Timer
These days time is everything. Between meetings and appointments, deadlines and conference calls, my schedule requires that I know the time down to the minute. Even on weekends, I have a football team to coach, shows to tape and planes to catch. If I'm late, I'm sunk. The problem is that it's hard if my clocks aren't correct. Even the digital clocks can display time inaccurately. Dead batteries, time changes, any of these can cause a clock to be inaccurate. Now there is no need to worry, because advanced radio technology has produced a clock which gets the time directly from the U.S. Atomic Clock in Fort Collins, Colorado, the standard for time-keeping all over the world. The Atomic Clock by Acorn is the most accurate, reliable and convenient timepiece you can have.
Every morning at 1:00 a. m, this "smart" clock in Colorado automatically resets itself to the exact hour, minute and second. The U. S. Atomic Clock is accurate to ten billionths of a second per day. This means that the clock deviates less than one second over a one million-year period. The Atomic Clock even adjusts automatically for daylight saving time, so you don't have to remember to "spring forward" or "fall back". The desktop clock model is the only atomic Clock that will not lose time with low power or when you change its batteries.
The most accurate clock in the world is of no use if it is difficult to operate. The Acorn Atomic Clock is engineered in Germany using the latest scientific technology. It comes in two styles, the wall clock and the desktop model. Both are designed to be functional and easy to use. The desk clock's display features the exact time (in hours, minutes and seconds), month and date, or you can choose to display any two U. S. or world time zones. It weighs only eight ounces, and is the perfect travel clock It also has dual alarms, perfect for couples. Both the desktop and the wall models have an internal antenna for good reception without unattractive wires.
What is the passage mainly about？
Computers can understand clear and carefully dictated speech more accurately than spontaneous speech.
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