Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated frame structures

A new rocking constraint device(RCD)is developed for three-dimensional(3D)base-isolated frame structures by connecting a custom-designed cylinder pair to provide vertical damping with replaceable damping components installed outside the cylinders when the superstructure undergoes translational motion,and rocking constraint capacity when the superstructure is susceptible to rocking.Theoretical formulas for calculating the damping and rocking constraint stiffness of the RCD are proposed.Two series of sinusoidal loading tests are conducted at different loading frequencies and amplitudes to verify the damping and rocking constraint performance of the RCD.The test results show that the cylinder without orifices on its piston can provide the desired damping with a replaceable damping component,and that the RCD can effectively suppress rocking.Although the vertical stiffness of an individual cylinder is affected by the location of the replaceable damping component and loading frequency,the average vertical stiffness of the two cylinders,which determines the rocking constraint stiffness of the RCD,is independent of the two factors.Comparisons of the test and theoretical results indicate that the errors of the proposed formulas for calculating the damping and rocking constraint stiffness of the RCD do not exceed 12.9%and 11.0%,respectively.

Gastric residual volume,safety,and effectiveness of drinking 250 mL of glucose solution 2-3 hours before surgery in gastric cancer patients:a multicenter,single-blind,randomized-controlled trial

Background:Carbohydrate drinking 2-3 hours before surgery has been widely adopted in colorectal operations.However,there is lit-tle direct evidence regarding its application in gastric cancer surgery.We aimed to evaluate the gastric residual volume,safety,and effectiveness of drinking 250 mL of 5%glucose solution 2-3 hours before elective gastric cancer surgery.Methods:We conducted an investigator-initiated,multicenter,randomized-controlled,parallel group,and equivalence trial.Eighty-eight patients with gastric adenocarcinoma were randomized into study or control group.Patients in the control group followed the traditional routine of 6-8 hours preoperative fasting,while those in the study group drank 250 mL of 5%glucose solution 2-3 hours be-fore surgery.Immediately following tracheal intubation,gastric contents were aspirated through gastroscopy.The primary outcome was preoperative gastric residual volume.Results:Eighty-three patients were eventually analysed in the study(42 in the study group and 41 in the control group).Two groups were comparable at baseline characteristics.There were no statistical differences in residual gastric fluid volumes(35.86±27.13 vs 27.70±20.37 mL,P=0.135)and pH values(2.81±1.99 vs 2.66±1.68,P=0.708)between the two groups.Preoperative discomfort was significantly more decreased in the study group than in the control group(thirst score:1.49±1.23 vs 4.14±2.07,P<0.001;hunger score:1.66±1.18 vs 3.00±2.32,P=0.007).There was no statistical difference in the incidence of postoperative complications(19.05%vs 17.07%,P=0.815).Conclusions:Drinking 250 mL of 5%glucose solution 2-3 hours before surgery in elective gastric cancer patients shows benefits in lowering thirst and hunger scores without increasing gastric residual volume and perioperative complications.