Influence of tunnel length on the pressure wave generated by high-speed trains passing each other

The prediction of the pressure wave amplitude produced when two trains pass each other in the tunnel is important to the train design for airtightness and tunnel conditions in China.In this paper,the key factors of this problem were firstly stud-ied based on theoretical analysis.The equation of the worst tunnel length for the global maximum and minimum pressure values was derived.Then,the influence of tunnel length on global minimum pressure and the critical region in which the global minimum pressure varies rapidly were investigated.Finally,a numerical method based on two-dimensional Na-vier-Stokes equations was established.Typical conditions of two trains passing-by in tunnels of different lengths were simulated.The theoretical and computational results agree with each other closely.

Effectiveness of six-step complex decongestive therapy for treating upper limb lymphedema after breast cancer surgery

BACKGROUND Complex decongestive therapy(CDT)is currently recommended as the standard treatment for lymphedema.CDT is a four-step detumescence therapy that can effectively treat upper limb lymphedema after breast cancer surgery,and is considered non-invasive,painless and without side effects.AIM To determine the effectiveness of a six-step CDT involving a foam granule bandage for the treatment of upper extremity lymphedema pressure after breast cancer surgical intervention.METHODS The study included 100 patients with upper extremity lymphedema after breast cancer surgery.The surgical methods were mastectomy plus axillary lymph node dissection and breast preservation plus sentinel lymph node biopsy.The study population was further divided into the experimental group and control group with 50 cases in each group.The control group was given conventional CDT(four-step method),which included skin care,freehand lymphatic drainage,foam granule pressurized bandage,and functional exercise.In the experimental group,a six-step CDT method was applied that involved a foam particle bandage combined with air wave pressure therapy in addition to the four steps of conventional CDT.Patients in both groups were given one course of treatment daily(20 times),and the changes in body moisture and subjective symptoms were measured before and after treatment,preoperatively and 20 times after treatment.RESULTS No statistically significant differences in 50-Hz bioelectrical impedance and extracellular moisture ratio were observed between the two groups before treatment,suggesting comparability of the baseline data.After treatment,the 50-Hz bioelectrical impedance of the experimental group was significantly higher than that in the control group,and the extracellular moisture ratio was significantly lower than that in the control group.A comparison of the differences between the two groups before and after treatment indicated that the treatment effect in the experimental group was better than that in the control group.After 20 treatments,according to subjective evaluations,the tightness and swelling of the limbs in the experimental group were significantly reduced as compared with those in the control group.CONCLUSION The six-step CDT method can effectively reduce lymphedema,promote lymphatic circulation,and alleviate the subjective symptoms of patients,and thereby improve the quality of life and treatment compliance among patients.