On Generating Expected Kinetostatic Nonlinear Stiffness Characteristics by the Kinematic Limb-Singularity of a Crank-Slider Linkage with Springs

Being different from avoidance of singularity of closed-loop linkages, this paper employs the kinematic singularity to construct compliant mechanisms with expected nonlinear stiffness characteristics to enrich the methods of compliant mechanisms synthesis. The theory for generating kinetostatic nonlinear stiffness characteristic by the kinematic limb-singularity of a crank-slider linkage is developed. Based on the principle of virtual work, the kinetostatic model of the crank-linkage with springs is established. The influences of spring stiffness on the toque-position angle relation are analyzed. It indicates that corresponding spring stiffness may generate one of four types of nonlinear stiffness characteristics including the bi-stable, local negative-stiffness, zero-stiffness or positive-stiffness when the mechanism works around the kinematic limb-singularity position. Thus the compliant mechanism with an expected stiffness characteristic can be constructed by employing the pseudo rigid-body model of the mechanism whose joints or links are replaced by corresponding flexures. Finally, a tri-symmetrical constant-torque compliant mechanism is fabricated, where the curve of torque-position angle is obtained by an experimental testing. The measurement indicates that the compliant mechanism can generate a nearly constant-torque zone.

Effect of intra-operative chemotherapy with 5-fluorouracil and leucovorin on the survival of patients with colorectal cancer after radical surgery: a retrospective cohort study

Background:The effect of intra-operative chemotherapy(IOC)on the long-term survival of patients with colorectal cancer(CRC)remains unclear.In this study,we evaluated the independent effect of intra-operative infusion of 5-fluorouracil in combination with calcium folinate on the survival of CRC patients following radical resection.Methods:1820 patients were recruited,and 1263 received IOC and 557 did not.Clinical and demographic data were collected,including overall survival(OS),clinicopathological features,and treatment strategies.Risk factors for IOC-related deaths were identified using multivariate Cox proportional hazards models.A regression model was developed to analyze the independent effects of IOC.Results:Proportional hazard regression analysis showed that IOC(hazard ratio[HR]=0.53,95%confidence intervals[CI][0.43,0.65],P<0.001)was a protective factor for the survival of patients.The mean overall survival time in IOC group was 82.50(95%CI[80.52,84.49])months,and 71.21(95%CI[67.92,74.50])months in non-IOC group.The OS in IOC-treated patients were significantly higher than non-IOC-treated patients(P<0.001,log-rank test).Further analysis revealed that IOC decreased the risk of death in patients with CRC in a non-adjusted model(HR=0.53,95%CI[0.43,0.65],P<0.001),model 2(adjusted for age and gender,HR=0.52,95%CI[0.43,0.64],P<0.001),and model 3(adjusted for all factors,95%CI 0.71[0.55,0.90],P=0.006).The subgroup analysis showed that the HR for the effect of IOC on survival was lower in patients with stage II(HR=0.46,95%CI[0.31,0.67])or III disease(HR=0.59,95%CI[0.45,0.76]),regardless of pre-operative radiotherapy(HR=0.55,95%CI[0.45,0.68])or pre-operative chemotherapy(HR=0.54,95%CI[0.44,0.66]).Conclusions:IOC is an independent factor that influences the survival of CRC patients.It improved the OS of patients with stages II and III CRC after radical surgery.Trial registration:chictr.org.cn,ChiCTR 2100043775.