目的探讨磁共振动态对比增强(dynamic contrast enhanced magnetic resonance imaging,DCE-MRI)的不同后处理模型[Tissue-4D和Omni-Kinetics(OK)软件]在鉴别脑胶质瘤不同级别中的价值。方法收集本院2013年1月至2019年7月共89例经术后病...目的探讨磁共振动态对比增强(dynamic contrast enhanced magnetic resonance imaging,DCE-MRI)的不同后处理模型[Tissue-4D和Omni-Kinetics(OK)软件]在鉴别脑胶质瘤不同级别中的价值。方法收集本院2013年1月至2019年7月共89例经术后病理证实的胶质瘤患者,其中Ⅱ级29例、Ⅲ级24例、Ⅳ级36例。患者均于术前行DCE-MRI检查,分别用Tissue-4D及OK后处理软件获得相应参数值。运用单因素方差分析比较不同级别胶质瘤参数差异,Spearman等级相关分析不同参数与胶质瘤分级的相关性,受试者工作特征(receiver operating characteristic,ROC)曲线分析各参数的曲线下面积(area under the curve,AUC)。结果两种后处理模型热点分析的Ktrans值、Tissue-4D的iAUC值和OK的Vp值在不同级别胶质瘤间差异均有统计学意义(P<0.05),Ⅳ级胶质瘤的Kep值低于Ⅱ级(P<0.05),Ⅳ级和Ⅲ级胶质瘤的Ve值高于Ⅱ级(P<0.05)。Ktrans参数AUC值为0.949(Ⅱ级vsⅣ级,P<0.01),诊断效能最高。Ktrans(OK)与胶质瘤级别之间相关性最强(r=0.775,P<0.01)。OK软件直方图参数,Ktrans值的第50百分位数(50th),Ve值的平均值、第75百分位数(75th)、第90百分位数(90th),Kep值的平均值、熵、50th及Vp值的平均值在鉴别Ⅱ级与Ⅲ级、Ⅱ级与Ⅳ级间差异均具有统计学意义(P<0.05),Vp值的能量、熵、50th、75th、90th及Kep值的能量,在鉴别Ⅱ级与Ⅳ级、Ⅲ级与Ⅳ级间的差异均具有统计学意义(P<0.05)。结论两种模型热点分析的Ktrans值及Ve值对胶质瘤分级均有较高的诊断效能,OK软件中直方图分析较热点分析参数更丰富、更全面。展开更多
Diesel engines meeting the latest emission regulations must be equipped with exhaust gas aftertreatment system,including diesel oxidation catalysts(DOC),diesel particulate filters(DPF),and selective catalytic reductio...Diesel engines meeting the latest emission regulations must be equipped with exhaust gas aftertreatment system,including diesel oxidation catalysts(DOC),diesel particulate filters(DPF),and selective catalytic reduction(SCR).However,before the final integration of the aftertreatment system(DOC+DPF+SCR)and the diesel engine,a reasonable structural optimization of the catalytic converters and a large number of bench calibration tests must be completed,involving large costs and long development cycles.The design and optimization of the exhaust gas aftertreatment system for a heavy-duty diesel engine was proposed in this paper.Firstly,one-dimensional(1D)and threedimensional(3D)computational models of the exhaust gas aftertreatment system accounting for the structural parameters of the catalytic converters were established.Then based on the calibrated models,the effects of the converter’s structural parameters on their main performance indicators,including the conversion of various exhaust pollutants and the temperatures and pressure drops of the converters,were studied.Finally,the optimal design scheme was obtained.The temperature distribution of the solid substrates and pressure distributions of the catalytic converters were studied based on the 3D model.The method proposed in this paper has guiding significance for the optimization of diesel engine aftertreatment systems.展开更多
This paper proposed improvements to the low bit rate parametric audio coder with sinusoid model as its kernel. Firstly, we propose a new method to effectively order and select the perceptually most important sinusoids...This paper proposed improvements to the low bit rate parametric audio coder with sinusoid model as its kernel. Firstly, we propose a new method to effectively order and select the perceptually most important sinusoids. The sinusoid which contributes most to the reduction of overall NMR is chosen. Combined with our improved parametric psychoacoustic model and advanced peak riddling techniques, the number of sinusoids required can be greatly reduced and the coding efficiency can be greatly enhanced. A lightweight version is also given to reduce the amount of computation with only little sacrifice of performance. Secondly, we propose two enhancement techniques for sinusoid synthesis: bandwidth enhancement and line enhancement. With little overhead, the effective bandwidth can be extended one more octave; the timbre tends to sound much brighter, thicker and more beautiful.展开更多
文摘目的探讨磁共振动态对比增强(dynamic contrast enhanced magnetic resonance imaging,DCE-MRI)的不同后处理模型[Tissue-4D和Omni-Kinetics(OK)软件]在鉴别脑胶质瘤不同级别中的价值。方法收集本院2013年1月至2019年7月共89例经术后病理证实的胶质瘤患者,其中Ⅱ级29例、Ⅲ级24例、Ⅳ级36例。患者均于术前行DCE-MRI检查,分别用Tissue-4D及OK后处理软件获得相应参数值。运用单因素方差分析比较不同级别胶质瘤参数差异,Spearman等级相关分析不同参数与胶质瘤分级的相关性,受试者工作特征(receiver operating characteristic,ROC)曲线分析各参数的曲线下面积(area under the curve,AUC)。结果两种后处理模型热点分析的Ktrans值、Tissue-4D的iAUC值和OK的Vp值在不同级别胶质瘤间差异均有统计学意义(P<0.05),Ⅳ级胶质瘤的Kep值低于Ⅱ级(P<0.05),Ⅳ级和Ⅲ级胶质瘤的Ve值高于Ⅱ级(P<0.05)。Ktrans参数AUC值为0.949(Ⅱ级vsⅣ级,P<0.01),诊断效能最高。Ktrans(OK)与胶质瘤级别之间相关性最强(r=0.775,P<0.01)。OK软件直方图参数,Ktrans值的第50百分位数(50th),Ve值的平均值、第75百分位数(75th)、第90百分位数(90th),Kep值的平均值、熵、50th及Vp值的平均值在鉴别Ⅱ级与Ⅲ级、Ⅱ级与Ⅳ级间差异均具有统计学意义(P<0.05),Vp值的能量、熵、50th、75th、90th及Kep值的能量,在鉴别Ⅱ级与Ⅳ级、Ⅲ级与Ⅳ级间的差异均具有统计学意义(P<0.05)。结论两种模型热点分析的Ktrans值及Ve值对胶质瘤分级均有较高的诊断效能,OK软件中直方图分析较热点分析参数更丰富、更全面。
基金Projects(2017YFC0211202,2017YFC0211301)supported by the National Key R&D Program of China。
文摘Diesel engines meeting the latest emission regulations must be equipped with exhaust gas aftertreatment system,including diesel oxidation catalysts(DOC),diesel particulate filters(DPF),and selective catalytic reduction(SCR).However,before the final integration of the aftertreatment system(DOC+DPF+SCR)and the diesel engine,a reasonable structural optimization of the catalytic converters and a large number of bench calibration tests must be completed,involving large costs and long development cycles.The design and optimization of the exhaust gas aftertreatment system for a heavy-duty diesel engine was proposed in this paper.Firstly,one-dimensional(1D)and threedimensional(3D)computational models of the exhaust gas aftertreatment system accounting for the structural parameters of the catalytic converters were established.Then based on the calibrated models,the effects of the converter’s structural parameters on their main performance indicators,including the conversion of various exhaust pollutants and the temperatures and pressure drops of the converters,were studied.Finally,the optimal design scheme was obtained.The temperature distribution of the solid substrates and pressure distributions of the catalytic converters were studied based on the 3D model.The method proposed in this paper has guiding significance for the optimization of diesel engine aftertreatment systems.
文摘This paper proposed improvements to the low bit rate parametric audio coder with sinusoid model as its kernel. Firstly, we propose a new method to effectively order and select the perceptually most important sinusoids. The sinusoid which contributes most to the reduction of overall NMR is chosen. Combined with our improved parametric psychoacoustic model and advanced peak riddling techniques, the number of sinusoids required can be greatly reduced and the coding efficiency can be greatly enhanced. A lightweight version is also given to reduce the amount of computation with only little sacrifice of performance. Secondly, we propose two enhancement techniques for sinusoid synthesis: bandwidth enhancement and line enhancement. With little overhead, the effective bandwidth can be extended one more octave; the timbre tends to sound much brighter, thicker and more beautiful.
