The first hyperpolarizability and molecular frontier orbit properties of barbituric acid derivatives are studied at HF/6-31G level by coupled perturbed Hartree-Fock(CPHF) method.
采用耦合微扰（CPHF）方法在HF/6-31G水平上对巴比妥酸衍生物的第一超极化率和分子前线轨道性质进行了计算。
Constancy of chemical etch rate method was modified so as to reduce the influencing factors such as temperature and concentration of HF acid. The efficiency and accuracy are improved.
基于差动原理对HF酸恒定化学蚀刻速率法进行改进，以降低环境(温度、HF酸浓度等)变化对测量结果的影响，从而提高测量效率和测量准确性。
This article introduces the purpose, method and procedure of HF acid chemical clean for once through boiler, and comparison between chemical clean of different mediums is presented as well.
重点介绍直流锅炉氢氟酸酸洗的目的，方法及过程，还对不同介质的化学清洗进行了比较。
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