This work describes the separation and purification of lactic acid from diluted solution by HSPE （hybrid short path evaporation） and RD （reactive distillation） as coupled process. The results showed that it is pos...This work describes the separation and purification of lactic acid from diluted solution by HSPE （hybrid short path evaporation） and RD （reactive distillation） as coupled process. The results showed that it is possible to increase lactic acid concentration up to 4.7 times higher than the raw material concentration.展开更多
Fractionation of palm kernel oil （PKO） by short path distillation （SPD） at two feed flow rates （135 g/h and 195 g/h） and six distillation temperatures, TD,s （200, 210, 220, 230, 240 and 250 ℃） was investigate...Fractionation of palm kernel oil （PKO） by short path distillation （SPD） at two feed flow rates （135 g/h and 195 g/h） and six distillation temperatures, TD,s （200, 210, 220, 230, 240 and 250 ℃） was investigated. Other distillation parameters, such as vacuum pressure （0.001 mbar）, blade rotation speed （400 rpm） and temperature of the feed material （60 ℃） were kept constant. The fractionated products, known as residue and distillate, were analysed for physico-chemical properties including fatty acid composition （FAC）, triacylglycerol （TAG） composition, slip melting point （SMP）, thermal analysis by differential scanning calorimetry （DSC） and solid fat content （SFC）. Product yield was measured as well. Crystallisation behaviour of PKO and the fractionated products were studied by measurement of isothermal crystallisation, Tc,. at 0, 5, 10, 15, 20 and 25 ℃. The distillates, collected at all fractionation temperatures, were enriched with caprylic, capric and lauric acids. These fractions were also concentrated with low molecular weight and C36 TAGs. Distillates obtained at higher TDis （230-250 ℃） exhibited higher in SMP and SFC. On the other hand, the residual oils collected at all fractionation temperatures contained higher amount of long-chain fatty acid and palmitic acid. These fractions were enriched with high molecular weight TAGs. Residues obtained at lower Tois （200-220 ℃） were low in SMP and comparable SFC with PKO. Changes in fatty acid and TAG composition resulted in different crystallisation behaviour of the fractions. Distillates collected at all fractionation temperatures crystallised in a sharper peak while residues obtained at higher T Dis （230-250 ℃） showed broader crystallisation peaks, as shown by the DSC thermograms.展开更多
为解决复杂动态环境下全自主移动机器人路径规划存在的效率低、适应性差及多目标权衡难题,提出全自主移动机器人全局最优路径智能规划方法。利用图注意力网络与空间重构单元提取环境的全局最优路径特征,采用改进基于密度的带噪声应用空...为解决复杂动态环境下全自主移动机器人路径规划存在的效率低、适应性差及多目标权衡难题,提出全自主移动机器人全局最优路径智能规划方法。利用图注意力网络与空间重构单元提取环境的全局最优路径特征,采用改进基于密度的带噪声应用空间聚类(Density-Based Spatial Clustering of Applications with Noise,DBSCAN)算法实现静态/动态障碍物与通行区的精准划分,构建长短期记忆(Long Short-Term Memory,LSTM)运动预测模型与多传感器融合的障碍物轨迹预测模型。在改进蚁群算法框架下进行全局路径搜索,引入路径长度、时间、安全及能耗的复合权重。采用3次B样条曲线平滑优化路径,引入曲率约束以抑制龙格现象。实验显示,该方法在低负载时段平均路径偏差降低约33%,重规划次数减少约66%,动态避障成功率提高至98%;高负载时段平均路径偏差降低40%,重规划次数减少约52%,成功率达95%。展开更多
A numerical control (NC) tool path of digital CAD model is widely generated as a set of short line segments in machining. However, there are three shortcomings in the linear tool path, such as discontinuities of tange...A numerical control (NC) tool path of digital CAD model is widely generated as a set of short line segments in machining. However, there are three shortcomings in the linear tool path, such as discontinuities of tangency and curvature, huge number of line segments, and short lengths of line segments. These disadvantages hinder the development of high speed machining. To smooth the linear tool path and improve machining efficiency of short line segments, this paper presents an optimal feed interpolator based on G^2 continuous Bézier curves for the linear tool path. First, the areas suitable for fitting are screened out based on the geometric characteristics of continuous short segments (CSSs). CSSs in every area are compressed and fitted into a G^2 Continuous Bézier curve by using the least square method. Then a series of cubic Bézier curves are generated. However, the junction between adjacent Bézier curves is only G^0 continuous. By adjusting the control points and inserting Bézier transition curves between adjacent Bézier curves, the G^2 continuous tool path is constructed. The fitting error is estimated by the second-order Taylor formula. Without iteration, the fitting algorithm can be implemented in real-time environment. Second, the optimal feed interpolator considering the comprehensive constraints (such as the chord error constraint, the maximum normal acceleration, servo capacity of each axis, etc.) is proposed. Simulation and experiment are conducted. The results shows that the proposed method can generate smooth path, decrease the amount of segments and reduce machining time for machining of linear tool path. The proposed research provides an effective method for high-speed machining of complex 2-D/3-D profiles described by short line segments.展开更多
文摘This work describes the separation and purification of lactic acid from diluted solution by HSPE （hybrid short path evaporation） and RD （reactive distillation） as coupled process. The results showed that it is possible to increase lactic acid concentration up to 4.7 times higher than the raw material concentration.
文摘Fractionation of palm kernel oil （PKO） by short path distillation （SPD） at two feed flow rates （135 g/h and 195 g/h） and six distillation temperatures, TD,s （200, 210, 220, 230, 240 and 250 ℃） was investigated. Other distillation parameters, such as vacuum pressure （0.001 mbar）, blade rotation speed （400 rpm） and temperature of the feed material （60 ℃） were kept constant. The fractionated products, known as residue and distillate, were analysed for physico-chemical properties including fatty acid composition （FAC）, triacylglycerol （TAG） composition, slip melting point （SMP）, thermal analysis by differential scanning calorimetry （DSC） and solid fat content （SFC）. Product yield was measured as well. Crystallisation behaviour of PKO and the fractionated products were studied by measurement of isothermal crystallisation, Tc,. at 0, 5, 10, 15, 20 and 25 ℃. The distillates, collected at all fractionation temperatures, were enriched with caprylic, capric and lauric acids. These fractions were also concentrated with low molecular weight and C36 TAGs. Distillates obtained at higher TDis （230-250 ℃） exhibited higher in SMP and SFC. On the other hand, the residual oils collected at all fractionation temperatures contained higher amount of long-chain fatty acid and palmitic acid. These fractions were enriched with high molecular weight TAGs. Residues obtained at lower Tois （200-220 ℃） were low in SMP and comparable SFC with PKO. Changes in fatty acid and TAG composition resulted in different crystallisation behaviour of the fractions. Distillates collected at all fractionation temperatures crystallised in a sharper peak while residues obtained at higher T Dis （230-250 ℃） showed broader crystallisation peaks, as shown by the DSC thermograms.
文摘为解决复杂动态环境下全自主移动机器人路径规划存在的效率低、适应性差及多目标权衡难题,提出全自主移动机器人全局最优路径智能规划方法。利用图注意力网络与空间重构单元提取环境的全局最优路径特征,采用改进基于密度的带噪声应用空间聚类(Density-Based Spatial Clustering of Applications with Noise,DBSCAN)算法实现静态/动态障碍物与通行区的精准划分,构建长短期记忆(Long Short-Term Memory,LSTM)运动预测模型与多传感器融合的障碍物轨迹预测模型。在改进蚁群算法框架下进行全局路径搜索,引入路径长度、时间、安全及能耗的复合权重。采用3次B样条曲线平滑优化路径,引入曲率约束以抑制龙格现象。实验显示,该方法在低负载时段平均路径偏差降低约33%,重规划次数减少约66%,动态避障成功率提高至98%;高负载时段平均路径偏差降低40%,重规划次数减少约52%,成功率达95%。
基金Supported by National Natural Science Foundation of China(Grant No.50875171)National Hi-tech Research and Development Program of China(863 Program,Grant No.2009AA04Z150)
文摘A numerical control (NC) tool path of digital CAD model is widely generated as a set of short line segments in machining. However, there are three shortcomings in the linear tool path, such as discontinuities of tangency and curvature, huge number of line segments, and short lengths of line segments. These disadvantages hinder the development of high speed machining. To smooth the linear tool path and improve machining efficiency of short line segments, this paper presents an optimal feed interpolator based on G^2 continuous Bézier curves for the linear tool path. First, the areas suitable for fitting are screened out based on the geometric characteristics of continuous short segments (CSSs). CSSs in every area are compressed and fitted into a G^2 Continuous Bézier curve by using the least square method. Then a series of cubic Bézier curves are generated. However, the junction between adjacent Bézier curves is only G^0 continuous. By adjusting the control points and inserting Bézier transition curves between adjacent Bézier curves, the G^2 continuous tool path is constructed. The fitting error is estimated by the second-order Taylor formula. Without iteration, the fitting algorithm can be implemented in real-time environment. Second, the optimal feed interpolator considering the comprehensive constraints (such as the chord error constraint, the maximum normal acceleration, servo capacity of each axis, etc.) is proposed. Simulation and experiment are conducted. The results shows that the proposed method can generate smooth path, decrease the amount of segments and reduce machining time for machining of linear tool path. The proposed research provides an effective method for high-speed machining of complex 2-D/3-D profiles described by short line segments.
