更多"Nowadays, no document is safe any m"的相关试题:
[单项选择]Nowadays, no document is safe any more. Counterfeiting. once the domain of skilled deceivers that used expensive engraving and printing equipment, has gone mainstream since the price of desktop publishing systems has dropped. In ancient times, counterfeiting was a hanging offence. Today, desktop counterfeiters have little reason to worry about prison, because the systems they use are ubiquitous (普遍存在的) and there is no means of tracing forged documents to the machine that produced them. This, however, may soon change thanks to technology development by George Chiu, an anti-counterfeiting engineer.
His approach is based on detecting imperfections in the print quality of documents. Old-school scientists were able to trace documents to particular typewriters based on quirks (构槽) of the individual keys. He employs a similar approach, exploiting the fact that the rotating (转动) drums and mirrors inside a printer are imperfect pieces of engineering which leave unique patterns of banding
A. the quirks of the keys of the typewriters
B. the drums and mirrors of the printers
C. the subtle flaws of printing devices
D. the special skills of the experts
[单项选择]No document is safe any more. Faking once the domain of skilled deceivers that used expensive engraving (雕刻) and printing equipment, has gone mainstream since the price of desktop-publishing systems has dropped. In ancient times, faking was a hanging offence. Today, desktop counterfeiters have little reason to worry about prison, because the systems they use are universal and there is no means of tracing forged documents to the machine that produced them. This, however, may soon change thanks to technology development by George Chiu, an anti-faking engineer.
His approach is based on detecting imperfections in the print quality of documents. Old-school court scientists were able to trace documents to particular typewriters based on quirks (沟槽) of the individual keys. He employs a similar approach, exploiting the fact that the rotating drums and mirrors inside a printer are imperfect pieces of engineering which leave unique patterns of banding in their products.
Although th
A. affordable printers make it possible for anyone to forge documents
B. the American Secret Service will be able to trace any document
C. every printed document will be secretly marked out through high-tech
D. counterfeiters have more advanced technology to use
[单项选择]
Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射), or carbon-14, dating. One key to understanding how and why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons (质子) and six neutrons (中子) in its nucleus(原子核). Carbon-14,or C-14,is a radioactive,unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay(衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby’s radiocarbon dating technique, the weak radioactive emissions (放射)from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C-14 atoms in the ’sam
A. Right
B. Wrong
C. Not mentioned
