期刊文献+
共找到4篇文章
< 1 >
每页显示 20 50 100
CT辐射剂量所面临的挑战 被引量:17
1
作者 王骏 周桔 朱寿彭 《国外医学(放射医学核医学分册)》 2003年第4期187-189,共3页
尽管CT检查仅占所有检查的2%,而对于公众诊断性成像的接收剂量,CT却占20%左右。具有10mSv有效剂量的成人腹部检查会增加致癌风险1/2000。儿童对于放射线影响的灵敏度是中年人的10倍多,女孩比男孩更敏感。剂量增加的原因有:CT应用的偏差... 尽管CT检查仅占所有检查的2%,而对于公众诊断性成像的接收剂量,CT却占20%左右。具有10mSv有效剂量的成人腹部检查会增加致癌风险1/2000。儿童对于放射线影响的灵敏度是中年人的10倍多,女孩比男孩更敏感。剂量增加的原因有:CT应用的偏差、使用方便的结果、多层CT的危机、未意识到“非耦合效应”。医护人员要进行很好的培训,要意识到不断涌现的资料及实践中潜在的变化,根据进展修正方案。像进行传统X射线摄影一样,“合理使用低剂量(aslowasreasonablyachievable,ALARA)”原则也很适合于CT的应用。 展开更多
关键词 CT 辐射剂量 临床价值 “非耦合效应” 质量标准
下载PDF
Research on nonlinear characteristics of strata collapse because of the multi-frequency mining 被引量:2
2
作者 杨帆 胡振琪 +1 位作者 杨伦 麻凤海 《Journal of Coal Science & Engineering(China)》 2008年第2期308-310,共3页
Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum,using the method of on-site inspection and mathematical statistics,the regulation and nonlinear characteristic... Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum,using the method of on-site inspection and mathematical statistics,the regulation and nonlinear characteristics of strata collapse in mine stratum's multi-frequency mining were put forward and systemically studied.Study result shows that the influence of multi-frequency mining in mine stratum has the feature of multi-frequency incontinuity,multi-characteristic and multi-type nonlinear collapse,strata collapse activa- tion turned worse,presenting an accumulation effect of multi-frequency mining for the strata damage.With the example of multi-frequency mining in the mine,the real characte- ristics of strata collapse by multi-frequency mining and nonlinear characteristics of accu- mulative response damage were analyzed.Research achievements about the surface re- cover and controlling of strata collapse by the multi-frequency mining have instruction meaning. 展开更多
关键词 multi-frequency mining stratum collapse nonlinear coupling accumulative response
下载PDF
Dynamic Characteristics of the Crankshaft System with Coupling Effect 被引量:1
3
作者 S.H. Zhang K. Jia 《Journal of Energy and Power Engineering》 2010年第5期18-26,共9页
The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional... The nonlinear dynamic model of the marine diesel crankshaft system with a propeller and 6 cranks is established, in which the variable moment of inertia of the linkage and the piston, coupling effect between torsional and axial vibration, the actuating force applied on the piston, the actuating torque and force applied on the propeller is included. The governing equations of the model denote a strong nonlinear and non autonomous system. By numeric simulation, the dynamic response of the system to initial displacement and initial speed, variable moment of inertia, the pressure applied on the piston by combustion gas, the torque and the axial force applied on the propeller by fluid is researched respectively. According to the research results, the variable moment of inertia and coupling effect between torsional and axial vibration are the fundamental reason for nonlinear vibration. Different actuating factors can not only result in different frequency components of the response, but make the same frequency component have different vibration amplitude. The dynamic behavior of the system is not influenced obviously by the actuating torque and force applied on the propeller. There is obvious difference in sensitivity of the dynamic response in the different direction to the same actuating factor. 展开更多
关键词 Coupling effect between torsional and axial vibration nonlinear dynamic model crankshaft system dynamic response.
下载PDF
Asymmetric Coupling in Two-Lane Asymmetric Simple Exclusion Processes with Unequal Injection Rates: Effect of Different Hoping Rates
4
作者 肖松 陈晓瑜 刘艳娜 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第5期581-587,共7页
This paper investigates the effect of both unequal injection rates and different hopping rates on two-lane asymmetric simple exclusion processes(ASEPs) with asymmetric coupling. When the hopping rates of both lanes ar... This paper investigates the effect of both unequal injection rates and different hopping rates on two-lane asymmetric simple exclusion processes(ASEPs) with asymmetric coupling. When the hopping rates of both lanes are different, the system includes six steady phases, however, when the hopping rates of both lanes are same, the seventh phase(MC, MC) will exist in the system. Interestingly, with different hopping rates of both lanes, the densities of the system cannot be influenced by the non-zero vertical transition rate. Our theoretical arguments are in well agreement with extensively performed Monte Carlo simulations. 展开更多
关键词 asymmetric simple exclusion processes unequal injection rates different hoping rates mean fieldapproximation Monte Carlo simulations
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部