The object matter of the foreword part is to describe the aim of this article, its research area and expectation, and its value both in practice and theory.
引言部分主要说明本文写作的目的、涉及范围、相关领域的前人研究成果，研究设想、理论意义和实际价值、创新性。
Experimental Verification: Theory formula is the average value of the random variable mathematical expectation (estimated) formula.
实验验证：理论平均值公式就是随机变量取值的数学期望(估计)计算公式。
This is reflected in the fact that the vacuum expectation value of the field squared is nonzero in quantum field theory. Therefore there exist the so called vacuum fluctuations.
这反映在量子场论中场量平方的真空平均值不为零，这就是所谓的真空涨落。
In the quantum statistical theory, the density operator is introduced in the statistical system. The expectation value of an obeservable can be obtained by the use of the density operator.
在量子统计中，对统计系综引入了密度算符，力学量的平均值可以利用密度算符求出。
In the quantum statistical theory, the density operator is introduced in the statistical system. The expectation value of an obeservable can be obtained by the use of the density operator.
在量子统计中，对统计系综引入了密度算符，力学量的平均值可以利用密度算符求出。
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