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This paper describes the merits and demerits of different sensors for measuring propellant gas pressure, the applicable range of the frequently used dynamic pressure calibration methods, and the working principle of absolute quasi-static pressure calibration based on the drop-weight device. The main factors affecting the accuracy of pressure calibration are analyzed from two aspects of the force sensor and the piston area. To calculate the effective area of the piston rod and evaluate the uncertainty between the force sensor and the corresponding peak pressure in the absolute quasi-static pressure calibration process, a method for solving these problems based on the least squares principle is proposed. According to the relevant quasi-static pressure calibration experimental data, the least squares fitting model between the peak force and the peak pressure, and the effective area of the piston rod and its measurement uncertainty, are obtained. The fitting model is tested by an additional group of experiments, and the peak pressure obtained by the existing high-precision comparison calibration method is taken as the reference value. The test results show that the peak pressure obtained by the least squares fitting model is closer to the reference value than the one directly calculated by the cross-sectional area of the piston rod. When the peak pressure is higher than 150 MPa, the percentage difference is less than 0.71%, which can meet the requirements of practical application.

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An efficient pseudo four‐component procedure for the construction of chromeno[4,3‐d]pyrimidin‐5‐ones, a type of coumarin‐fused pyrimidines, from 4‐aminocoumarins, two molecules of aromatic aldehydes and ammonium iodide under metal‐free conditions is developed. The coumarin‐pyrimidine hybrids readily undergo sequential hydrolysis and alkylation to give all‐carbon substituted pyrimidines in excellent yields. One‐pot synthesis of pyrimidines from readily available 4‐aminocoumarins and other commodity chemicals is exemplified.

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