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问题 单项选择题 A3/A4型题

随着DSA技术的发展，对于运动部位的DSA成像以及DSA成像过程中X线管与检测器同步运动而得到系列减影像，已成了事实。所以，将DSA成像过程中，X线管、人体和检测器规律运动的情况下，而获得DSA图像的方式，称之为动态DSA。按照C形臂的运动方式分为：旋转运动、岁差运动、钟摆运动和步进。这些检查技术，可实时动态三维显示。主要用于腹部、盆腔血管重叠的器官，以观察血管立体解剖关系的是（）

A.旋转运动

B.连续运动

C.岁差运动

D.步进

E.钟摆运动

答案

参考答案：C

实验题

测定一定质量的铝锌合金与强酸溶液反应产生的氢气的体积，可以求得合金中铝和锌的质量分数。现有下列实验用品：800 mL烧杯、100 mL量筒、短颈玻璃漏斗、铜网、铝锌合金样品、浓盐酸（密度1.19 g·mol-1）、水。按如图所示装置进行实验，完成下列问题（设合金样品完全反应，产生的气体体积不超过100 mL）。

（1）补充下列实验步骤，直到反应开始进行（铁架台和铁夹的安装可省略）：

①将称最后的合金样品用铜网小心包裹好，放在100 mL烧杯底部，把短颈漏斗倒扣在样品上面。

（2）合金样品用铜网包裹的目的是：_____________。
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单项选择题

The Turing machine is an abstract (71) of computer execution and storage introduced in 1936 by Alan Turing to give a mathematically precise definition of (72) . or ’mechanical procedure’. As such it is still widely used in theoretical computer science, especially in (73) theory and the theory of computation. The thesis that states that Turing machines indeed capture the informal notion of effective or mechanical method in logic and mathematics is known as Turing’s thesis.

Every Turing machine computes a certain (74) partial function over the strings over its alphabet. In that sense it behaves like a computer with a fixed program. However, as Alan luring already described, we can encode the action table of every Turing machine in a string. Thus we might try to construct a Turing machine that expects on its tape a string describing an action table followed by a string describing the input tape, and then computes the tape that the encoded Turing machine would have computed. As Turing showed, such a luring machine is indeed possible and since it is able to simulate any other Turing machine it is called a (75) Turing machine.

A universal Turing machine is Turing complete. It can calculate any recursive function, decide any recursive language, and accept any recursively enumerable language. According to the Church-Turing thesis, the problems solvable by a universal Turing machine are exactly those problems solvable by an algorithm or an effective method of computation, for any reasonable definition of those terms.

（72）处填（）。

A．operation

B．calculating

C．algorithm

D．mechanics
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