The effect of test methods and stress paths on the experimental value of the coefficient of earth pressure at rest, K0, was investigated under high pressures. The results indicate that the rigid pressure chamber and f...The effect of test methods and stress paths on the experimental value of the coefficient of earth pressure at rest, K0, was investigated under high pressures. The results indicate that the rigid pressure chamber and flexible lateral confining pressure medium method gives a stress ratio at the initial stage that is not the real K0. Moreover, K0 increases during the loading process becoming greater at high pressures. In the unloading process, however, K0 increases only at the initial stage but decreases thereafter. In addition, the incremental magnitude definition, K0=dσ3/dσ1, gives higher values than the total magnitude definition, K0=σ3/σ1, under loading. This is also true during initial stages of unloading. The experiment results also indicate that earth pressure at rest in deep and thick soils can be estimated by a power function of axial and confining pressures. It is necessary to choose the appropriate Kn to avoid some accidents.展开更多
Most power transfer studies involve contingencies and multi pattern scenarios that often can only be performed in reasonable time with the use of linear methods. In these works, the effect of reactive power flows in l...Most power transfer studies involve contingencies and multi pattern scenarios that often can only be performed in reasonable time with the use of linear methods. In these works, the effect of reactive power flows in line loading is neglected while formulating the problem for ATC （available transfer capability） calculations. This paper presents the determination of shunt reactive power compensation in the presence of FACTS （flexible AC transmission system） devices like： SSSC （static synchronous series compensator） and UPFC （unified power flow controller） for enhancement of power transfer capability of a power system incorporating the reactive power flows in ATC calculations. In doing so, redistribution of power flow takes place and therefore improves ATC of the system. Studies on a sample 5-bus power system model are carried out to illustrate the effect of shunt compensation along with line flow control.展开更多
Objective： Massive hemorrhage is lifethreatening during armed conflicts. Tourniquets are important medical devices used to reduce severe bleeding in trauma. The aim of this study was to empirically evaluate the curre...Objective： Massive hemorrhage is lifethreatening during armed conflicts. Tourniquets are important medical devices used to reduce severe bleeding in trauma. The aim of this study was to empirically evaluate the current tourniquets used in China and provide information to emergency nurses in selecting the appropriate tourniquet. Methods： Five tourniquets were self-applied by 20 healthy participants. The blood flow distal to the tourniquet site was assessed using vascular Doppler ultrasound. Application time, pain, numbness, and other parameters were evaluated. Results： The bladder tourniquet and windlass tourniquet effectively occluded arterial blood flow with success rates higher than 75% in both the upper and lower extremities. The Cargo-strap was the fastest to apply, taking（7.22=k2.30） s for the upper extremity and （6.48：k2.40） s for the lower extremity. The rubber tube was the most painful, and the improvised tourniquet was the least efficient. The success rates were higher in the lower extremity than in the upper extremity （P〈0.05, X^2=5.714）, Conclusions： The bladder tourniquet and the windlass tourniquet are efficient tourniquets, although the windlass is superior with respect to portability and pain. The Cargo-strap and rubber tourniquets have several disadvantages that reduce their suitability for field use. The improvised tourniquet is not recommended because of low efficiency and severe pain during implementation.展开更多
基金Projects 50534040 supported by the National Natural Science Foundation of ChinaBK2007040 by the Natural Science Foundation of Jiangsu ProvinceCX08B_103Z by the Post Graduate Research Projects of Jiangsu Province
文摘The effect of test methods and stress paths on the experimental value of the coefficient of earth pressure at rest, K0, was investigated under high pressures. The results indicate that the rigid pressure chamber and flexible lateral confining pressure medium method gives a stress ratio at the initial stage that is not the real K0. Moreover, K0 increases during the loading process becoming greater at high pressures. In the unloading process, however, K0 increases only at the initial stage but decreases thereafter. In addition, the incremental magnitude definition, K0=dσ3/dσ1, gives higher values than the total magnitude definition, K0=σ3/σ1, under loading. This is also true during initial stages of unloading. The experiment results also indicate that earth pressure at rest in deep and thick soils can be estimated by a power function of axial and confining pressures. It is necessary to choose the appropriate Kn to avoid some accidents.
文摘Most power transfer studies involve contingencies and multi pattern scenarios that often can only be performed in reasonable time with the use of linear methods. In these works, the effect of reactive power flows in line loading is neglected while formulating the problem for ATC （available transfer capability） calculations. This paper presents the determination of shunt reactive power compensation in the presence of FACTS （flexible AC transmission system） devices like： SSSC （static synchronous series compensator） and UPFC （unified power flow controller） for enhancement of power transfer capability of a power system incorporating the reactive power flows in ATC calculations. In doing so, redistribution of power flow takes place and therefore improves ATC of the system. Studies on a sample 5-bus power system model are carried out to illustrate the effect of shunt compensation along with line flow control.
文摘Objective： Massive hemorrhage is lifethreatening during armed conflicts. Tourniquets are important medical devices used to reduce severe bleeding in trauma. The aim of this study was to empirically evaluate the current tourniquets used in China and provide information to emergency nurses in selecting the appropriate tourniquet. Methods： Five tourniquets were self-applied by 20 healthy participants. The blood flow distal to the tourniquet site was assessed using vascular Doppler ultrasound. Application time, pain, numbness, and other parameters were evaluated. Results： The bladder tourniquet and windlass tourniquet effectively occluded arterial blood flow with success rates higher than 75% in both the upper and lower extremities. The Cargo-strap was the fastest to apply, taking（7.22=k2.30） s for the upper extremity and （6.48：k2.40） s for the lower extremity. The rubber tube was the most painful, and the improvised tourniquet was the least efficient. The success rates were higher in the lower extremity than in the upper extremity （P〈0.05, X^2=5.714）, Conclusions： The bladder tourniquet and the windlass tourniquet are efficient tourniquets, although the windlass is superior with respect to portability and pain. The Cargo-strap and rubber tourniquets have several disadvantages that reduce their suitability for field use. The improvised tourniquet is not recommended because of low efficiency and severe pain during implementation.
