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Objective To study if using autologous lung as a substitute of oxygenator in cardiopulmonary bypass is better than the conventional cardiopulmonary bypass with artificial oxygenator in pulmonary preservation.Methods Twelve piglets were randomly divided into two groups ( n = 6). The isolated lung perfusion model was established. The experimental animals underwent continuous lung perfusion for about 120 min. While the control animals underwent 90 min lung ischemia followed by 30 min reperfusion. Another 12 piglets were randomly divided into two groups ( n =6). The experimental animals underwent bi-ventricular bypass with autologous lung perfusion.While control animals underwent conventional cardiopulmonary bypass with artificial oxygenator. The bypass time and aortic cross clamping time were 135 min and 60 min respectively for each animal. The lung static compliance ( Cstat), alveolus-artery oxygen difference ( PA-aO2 ), TNF-α, IL-6 and wet to dry lung weight ratio (W/D) were measured. Histological and ultra-structural changes of the lung were also observed after bypass. Results After either isolated lung perfusion or cardiopulmonary bypass, the Cstat decreased, the PA-aO2 increased and the content of TNF-α increased for both groups, but the changes of experimental group were much less than those of control group. The lower W/D ratio and mild pathological changes in experimental group than those in control group were also demonstrated. Conclusion Autologous lung is able to tolerate the nonpalsatile perfusion. It can be used as a substitute to artificial ogygenator in cardiopulmonary bypass to minimize the inflammatory pulmonary injury caused mainly by ischemic reperfusion and interaction of the blood to the non-physiological surface of artificial oxygenator. 相似文献
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公路项目在建设过程中,必然会对周边的资源造成一定的负面影响,包括改变地形地貌以及对原有自然环境的破坏等,本文通过对公路在施工及运营过程中的环境保护措施和方法,以及对环境影响的评价制度与防范进行了综述,并且与国外的环境保护作对比,指出了我国未来的发展趋势。沥青路面是目前道路面层结构的主体,其材料再生利用的工程规模及其技术进步应与我国国民经济的发展,特别是道路交通事业的快速发展相适应,这是建设环境友好现代社会的基本条件之一。在实际工程中必须不断优化再生工艺并注重专用设备选择的合理性,才能实现这些目的。 相似文献
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Introduction Exposureofsecretkeysthreatensthesecurity ofadigitalsignaturegreatly.Totacklethisprob-lem,severaldifferentmethodshavebeenpro-posed,includingsecretsharing[1],thresholdsigna-ture[2],andproactivesignature[3].Thesemethods,however,needcooperativeandinteractivecompu-tationsinmultiplesevers,whicharequitecostly.Forwardsecuresignatureschemecanreducethe damageofkeyexposurewithoutcooperativeand interactivecomputations.Intheparadigmoffor-wardsecuresignature,thewholelifetimeofsigna-tureisdivid… 相似文献
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Introduction Ina(t,n)secretsharingscheme[1,2],asecret issharedamongnshareholders.Anytsharehold-erscancooperatetoreconstructthesecret,while fewerthantcan't.Theverifiablesecretsharing(VSS)[3,4]canverifythecorrectnessofthesecret sharesdistributedbyadealer.Animportantex-tensionofsecretsharingsystemsisthresholdcryp-tosystemschemes[5,6].Inproactiveschemes[7-11],thewholelifetimeofthesecretisdividedinto manytimeperiods,andsharesarerenewedineach period.PSSschemescanrenewthesharesofthe secret,butcan'… 相似文献
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以贵阳市地铁2号线阳明祠车站为背景,采用室内模型试验模拟大断面地铁车站施工过程中隧道塌方破坏过程,明确施工期间大断面隧道塌方破坏过程机制,对比分析围岩和路面的变形。结果表明:通过围岩重力作用模拟隧道施工过程中塌方过程,与实际塌方过程基本吻合,弥补了常规加载破坏的不足;围岩渐进破坏过程表现为裂隙出现-裂隙发展-裂隙贯通-围岩塌方,支护渐进破坏过程表现为变形缓慢增加-变形快速增加-裂缝快速发展-支护破坏;围岩渐进破坏与支护渐进破坏相互作用,共同发展;在实际施工过程中,当支护变形大幅增加时,应增加支护强度,同时还应及时注浆、打设长锚杆,以减缓围岩裂隙发展,阻断围岩渐进破坏过程。 相似文献
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ABSTRACTIn this article, we propose a new model called subjective-utility travel time budget (SU-TTB) model to capture travelers' risk-averse route choices. In the travel time budget (TTB) and mean-excess travel time (METT) model, a predefined confidence level is needed to capture the risk-aversion in route choice. Due to the day-to-day route travel time variations, the exact confidence level is hard to be predicted. With the SU-TTB model, we assume travelers' confidence level belongs to an interval that they may comply with in the route choice. The two main components of SU-TTB are the utility function and the TTB model. We can show that the SU-TTB can be reduced to the TTB and METT model with proper utility function for the confidence levels. We can also prove its equivalence with our recently proposed nonlinear-expectation route travel time (NERTT) model in some cases and give some new interpretation on the NERTT with this equivalence. Finally, we formulate the SU-TTB model as a variational inequality (VI) problem to model the risk-averse user equilibrium (RAUE), termed as generalized RAUE (GRAUE). The GRAUE is solved via a heuristic gradient projection algorithm, and the model and solution algorithm are demonstrated with the Braess's traffic network and the Nguyen and Dupuis's traffic network. 相似文献
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KONG Qiao-ling MA Jie State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai China 《船舶与海洋工程学报》2007,6(4)
The phase change characteristic of the power source of an underwater glider propelled by the ocean's thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process,but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees,the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change,and the slope of the temperature time history curve remains the same. However,the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size,boundary conditions,and the power source's cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38mm needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems. 相似文献