The researchers analysed the sizes and structures of ash particles using a variety of techniques, such as atomic force microscopy, scanning electron microscopy and X-ray diffraction.

研究人员使用不同的技术研究了火山灰颗粒的尺寸和结构，例如原子力显微镜、电子扫描显微镜和X射线衍射。

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TV has even created sports categories. ESPN was the moving force behind the X Games, a showcase for competitions like street skating and snowmobile jumping.

电视创造了不同的电视节目，ESPN推出了表演如街上旱冰和雪上摩托车等运动的节目《X游戏》。

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The X-45N, however, emerged in response to a U.S. Air Force requirement, which dissolved last summer.

而X-45N，主要是根据美国空军要求设计制造，美国空军已于去年夏天终止了这一设计需求。

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But the U.S.Preventive Services Task Force advised women in their 40s to delay their first mammogram until age 50,and after 50, schedule the x-ray every other year.

VOA: standard.2009.12.25

Therefore, it'll compress by an unknown x, which is equal to mg divided by the force constant of the spring.

因此它的压缩量为 x,也就等于 mg 除以弹簧的弹性系数

耶鲁公开课 - 基础物理课程节选

It says, if you pull it to the right, so that x is positive, the spring will exert a force which is in the negative direction; that's why you have a minus sign.

就是说,如果你向右拉,x 取正值,弹簧产生的力方向为负,这就是这里用负号的原因

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Lieutenant Colonel Tom McIntyre, X-37B program manager for the Air Force Rapid Capabilities Office, explained the third X-37 flight will not only help the Air Force better evaluate and understand the vehicle's performance characteristics, but this first re-flight is an important step in the program.

ENGADGET: USAF relaunches its first X-37B on a slightly less mysterious spaceflight

This appears to be the mindset of the Air Force regarding its experimental X-37B space plane, the billion-dollar robotic vehicle's orbital flight being extended beyond the 270 days it was initially designed for.

ENGADGET: Air Force X-37B space plane books additional time on orbital cruise, orders another margarita

Public affairs officials at Wright-Patterson Air Force Base in Ohio, which is in charge of the X-51 development project, provided no updates.

MSN: Hypersonic aircraft taken out for a trial run on B-52 bomber