Use of nonlinear mathematical models has been majorly based on in vitro gas production(GP) data generated when substrates are incubated with rumen liquor from fistulated steers. However,existing evidence suggests that...Use of nonlinear mathematical models has been majorly based on in vitro gas production(GP) data generated when substrates are incubated with rumen liquor from fistulated steers. However,existing evidence suggests that rumen liquor from slaughtered cattle of unknown dietary history also generates quantifiable in vitro GP data. Fitting and description of GP data obtained from 4 diets incubated with rumen liquor from slaughtered cattle was evaluated using single-pool exponential model with discrete lag time(EXPL), logistic(LOG), Groot's(GRTS) and Gompertz(GOMP) models. Diets were formulated by varying proportions of Rhodes grass(Chloris gayana) hay and a concentrate mixed on dry matter basis to be: 1,000 g/kg Rhodes grass hay(RGH) and 0 of the concentrate(D1), 900 g/kg RGH and 100 g/kg concentrate(D2), 800 g/kg RGH and 200 g/kg concentrate(D3), 700 g/kg RGH and 300 g/kg concentrate(D4). Dietary kinetics for the models were determined by measuring GP at 2,4.8,10.18,24.36,48.72,96 and 120 h. Model comparison was based on derived GP kinetics, graphical analysis of observed versus predicted GP profiles plus residual distribution and goodness-of-fit from analysis of root mean square error(RMSE), adjusted coefficient of determination(Adj-R^2) and Akaike's information criterion(AIC). Asymptotic GP, half-life and fractional rate of GP differed(P < 0.001) among the 4 models. The RMSE, Adj-R^2 and AIC ranged from 1.555 to 4.429,0.906 to0.984 and 2.452 to 15.874, respectively, forall diets compared across the 4 models. Based on the goodness-of-fit statistical criterion, GP profiles of D1 were more appropriately fitted and described by GRTS and GOMP than the EXPLand LOG models. The GRTS model had the lowest AIC value for D2(2.452). Although GRTS model had the most homogenous residual dispersion for the 4 diets, all the 4 models exhibited a sigmoidal behavior.Therefore, rumen liquor from slaughtered cattle of unknown dietary history can be used to derive nutritionally important feed parameters, but choice of the most appropriate展开更多
A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systemat...A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron micro- scope with the aim of investigating the effect of the steel＇s microstructure on its performance. All examined performance parameters exhib- ited a substantial decrease in the cases of samples heat-treated at temperatures near 700℃. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700℃, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical perform- ances were established to facilitate processing adjustments.展开更多
提出并设计出一种旋转直接驱动电液压力伺服阀(Rotary direct drive electro-hydraulic pressure control servo valve,RDDPV),该阀通过偏心驱动机构将力矩电机旋转运动转化为功率阀芯的直线运动,进而改变进回油窗口节流面积比,输出相...提出并设计出一种旋转直接驱动电液压力伺服阀(Rotary direct drive electro-hydraulic pressure control servo valve,RDDPV),该阀通过偏心驱动机构将力矩电机旋转运动转化为功率阀芯的直线运动,进而改变进回油窗口节流面积比,输出相应负载压力;通过电机位置和输出压力的电反馈闭环实现伺服控制。建立RDDPV非线性数学模型,研究了偏心驱动机构参数对伺服阀动静态特性的影响,确定了阀的主要结构参数。根据理论分析结果制作RDDPV样机,并在试验台上测试了基本特性,试验结果与理论结果一致,表明该阀具有较高的动静态性能,可应用于飞机防滑刹车等稳准快性能要求较高的压力伺服控制系统。展开更多
Based on the nonlinear geometric theory of extensible rods, an exact mathematical model of thermal post_buckling behavior of uniformly heated elastic rods with axially immovable ends is developed, in which the arc len...Based on the nonlinear geometric theory of extensible rods, an exact mathematical model of thermal post_buckling behavior of uniformly heated elastic rods with axially immovable ends is developed, in which the arc length s(x) of axial line and the longitudinal displacement u(x) are taken as the basic unknown functions. This is a two point boundary value problem of first order ordinary differential equations with strong non_linearity. By using shooting method and analytical continuation, the nonlinear boundary value problems are numerically solved. The thermal post_buckled states of the rods with transversely simply supported and clamped ends are obtained respectively and the corresponding numerical data tables and characteristic curves are also given.展开更多
基金the Livestock and Fisheries Programme(LFP 04) of the Association for Strengthening Agricultural Research in Eastern and Central Africa(ASARECA-RC12_LFP-04 under the auspices of the World Bank for providing financial support to undertake this research
文摘Use of nonlinear mathematical models has been majorly based on in vitro gas production(GP) data generated when substrates are incubated with rumen liquor from fistulated steers. However,existing evidence suggests that rumen liquor from slaughtered cattle of unknown dietary history also generates quantifiable in vitro GP data. Fitting and description of GP data obtained from 4 diets incubated with rumen liquor from slaughtered cattle was evaluated using single-pool exponential model with discrete lag time(EXPL), logistic(LOG), Groot's(GRTS) and Gompertz(GOMP) models. Diets were formulated by varying proportions of Rhodes grass(Chloris gayana) hay and a concentrate mixed on dry matter basis to be: 1,000 g/kg Rhodes grass hay(RGH) and 0 of the concentrate(D1), 900 g/kg RGH and 100 g/kg concentrate(D2), 800 g/kg RGH and 200 g/kg concentrate(D3), 700 g/kg RGH and 300 g/kg concentrate(D4). Dietary kinetics for the models were determined by measuring GP at 2,4.8,10.18,24.36,48.72,96 and 120 h. Model comparison was based on derived GP kinetics, graphical analysis of observed versus predicted GP profiles plus residual distribution and goodness-of-fit from analysis of root mean square error(RMSE), adjusted coefficient of determination(Adj-R^2) and Akaike's information criterion(AIC). Asymptotic GP, half-life and fractional rate of GP differed(P < 0.001) among the 4 models. The RMSE, Adj-R^2 and AIC ranged from 1.555 to 4.429,0.906 to0.984 and 2.452 to 15.874, respectively, forall diets compared across the 4 models. Based on the goodness-of-fit statistical criterion, GP profiles of D1 were more appropriately fitted and described by GRTS and GOMP than the EXPLand LOG models. The GRTS model had the lowest AIC value for D2(2.452). Although GRTS model had the most homogenous residual dispersion for the 4 diets, all the 4 models exhibited a sigmoidal behavior.Therefore, rumen liquor from slaughtered cattle of unknown dietary history can be used to derive nutritionally important feed parameters, but choice of the most appropriate
基金the China Special Equipment Inspection and Research Institutethe State Key Laboratory for Advanced Metals and Materials, respectively
文摘A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron micro- scope with the aim of investigating the effect of the steel＇s microstructure on its performance. All examined performance parameters exhib- ited a substantial decrease in the cases of samples heat-treated at temperatures near 700℃. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700℃, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical perform- ances were established to facilitate processing adjustments.
文摘提出并设计出一种旋转直接驱动电液压力伺服阀(Rotary direct drive electro-hydraulic pressure control servo valve,RDDPV),该阀通过偏心驱动机构将力矩电机旋转运动转化为功率阀芯的直线运动,进而改变进回油窗口节流面积比,输出相应负载压力;通过电机位置和输出压力的电反馈闭环实现伺服控制。建立RDDPV非线性数学模型,研究了偏心驱动机构参数对伺服阀动静态特性的影响,确定了阀的主要结构参数。根据理论分析结果制作RDDPV样机,并在试验台上测试了基本特性,试验结果与理论结果一致,表明该阀具有较高的动静态性能,可应用于飞机防滑刹车等稳准快性能要求较高的压力伺服控制系统。
文摘Based on the nonlinear geometric theory of extensible rods, an exact mathematical model of thermal post_buckling behavior of uniformly heated elastic rods with axially immovable ends is developed, in which the arc length s(x) of axial line and the longitudinal displacement u(x) are taken as the basic unknown functions. This is a two point boundary value problem of first order ordinary differential equations with strong non_linearity. By using shooting method and analytical continuation, the nonlinear boundary value problems are numerically solved. The thermal post_buckled states of the rods with transversely simply supported and clamped ends are obtained respectively and the corresponding numerical data tables and characteristic curves are also given.
