APPLICATION OF MODERN ROBUST OPTIMAL DESIGN METHOD TO THE SHOCK ABSORBER IN A CAR*

To reduce the variation of velocity characteristic of the shock absorber in a car, a modern robust optimal design method is applied to its structural parameters design. Firstly, the method is used to obtain the robust values which have low sensitivity to velocity characteristic and analyze the influences of the parameters on velocity characteristic. Secondly, the method is used to obtain their maximum tolerances under the condition of ensuring product quality. The results obviously improve the velocity characteristic.     

HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AND GAS CHROMATOGRAPHY — MASS SPECTROMETRY METHODS FOR THE DETERMINATION OF IMIDACLOPRID,CHLORPYRIFOS, AND BIFENTHRIN RESIDUES IN TEA LEAVES

□ A sensitive, rapid, and reproducible high-performance liquid chromatography–diode array method and a gas chromatography/mass spectrometry method were developed to determine imidacloprid, chlorpyrifos, and bifenthrin in tea leaves. Solid-phase extraction (SPE) was employed for sample preparation. The extraction solvent used was acetonitrile:toluene (3:1, v/v). Linearity was observed in tea spiked with 0.4–6.0 µ g mL^?1 (n = 6) of imidacloprid, 0.8–15.0 µ g mL^?1 (n = 6) of chlorpyrifos, and 0.3–6.6 µ g mL^?1 (n = 6) for bifenthrin. The correlation coefficients obtained were higher than 0.99 for all pesticides. The limits of detection for imidacloprid, chlorpyrifos, and bifenthrin were 0.06, 0.12, and 0.05 mg kg^?1, respectively. The limits of quantification for imidacloprid, chlorpyrifos, and bifenthrin were 0.20, 0.40, and 0.17 mg kg^?1, respectively. Recoveries of the analytes were between 80% and 96% with RSDs <10% (intra-day and inter-day). The methods were applied to monitor pesticide residues in tea. The results obtained by both techniques indicated that their feasibility for practical applications.