This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be ...This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.展开更多
This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF ...This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF controller consists of a nominal characteristic trajectory (NCT) and a PI compensator. A notch filter is added as a part of the compensator to eliminate the vibration due to the mechanical resonance of the plant. The objective of the NCTF controller is to make the object motion follow the NCT and end at its origin. The NCTF controller is designed based on a simple open-loop experiment of the object. The parameters identification and an exact model of the plant are not necessary for controller design. The performance response of improved NCTF controller is evaluated and discussed based on results of simulation. The effect of the design parameters on the robustness of the NCTF controller to inertia and friction variations is evaluated and compared with conventional PID controller. The results show that the improved NCTF controller has a better positioning performance and is much more robust than the PID controller.展开更多
为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂...为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂对荔枝汁风味及营养品质的影响。结果显示抗坏血酸和没食子酸抑制剂处理的样品与新鲜汁相比的色差值最小;整体香气轮廓显示葡萄糖氧化酶抑制蒸煮异味效果最佳,其次为迷迭香酸;电子鼻结果显示葡萄糖氧化酶处理的荔枝汁与新鲜汁最为接近,其次是儿茶素和邻苯三酚。挥发性成分的主成分分析结果显示抗坏血酸抑制剂处理的样品与新鲜汁最接近,其次为没食子酸、儿茶素、迷迭香酸。降硫率结果显示葡萄糖氧化酶的降硫效果最为显著,对二甲基硫醚、二甲基三硫醚、甲硫基丙醛的抑制率均达到100%,对二甲基二硫醚的抑制率为61.11%。营养品质方面,多酚类抑制剂与抗坏血酸处理的总酚、总黄酮含量和抗氧化性较新鲜汁均显著上升(P<0.05),而葡萄糖氧化酶处理的总酚、总黄酮含量较新鲜汁上升但抗氧化活性与新鲜汁无显著差异。综合色泽、pH、香气轮廓、营养品质以及降硫效果等因素进行偏最小二乘判别分析(partial least squares discriminant analysis,PLS-DA),发现葡萄糖氧化酶对荔枝汁整体品质影响最好。本研究可为荔枝以及其他热敏性水果加工过程中品质提升提供参考依据。展开更多
为了探究不同稳定化处理对米糠风味成分的影响,该研究采用电子鼻与全二维气相色谱-质谱联用技术(Comprehensive Two-dimensional Gas Chromatography-time-of-flight Mass Spectrometry,GC×GC-TOFMS),结合偏最小二乘判别分析(Parti...为了探究不同稳定化处理对米糠风味成分的影响,该研究采用电子鼻与全二维气相色谱-质谱联用技术(Comprehensive Two-dimensional Gas Chromatography-time-of-flight Mass Spectrometry,GC×GC-TOFMS),结合偏最小二乘判别分析(Partial Least Squares Discriminant Analysis,PLS-DA)和相对气味活度值(Relative Odor Activity Value,ROAV)对米糠挥发性风味物质的变化进行了系统分析。结果表明:不同稳定化处理方法对米糠风味的影响存在显著差异,共检测到99种挥发性香气化合物,包括6种醛类、10种酮类、22种烷烃类、12种醇类、28种萜烯类、8种酯类及13种其他化合物。其中,红外处理对米糠风味影响不大,而高压蒸汽处理有效降低了米糠的异味(吲哚)。变量重要性投影(Variable Importance in Projection,VIP)共筛选出23种潜在差异性物质,4种不同稳定化处理后米糠中的香叶基丙酮和(-)-柠檬烯等潜在差异性物质相对含量显著减少。ROAV值表明,烘烤、微波和高压蒸汽稳定化处理后米糠关键风味物质(ROAV>1)均减少,2-正戊基呋喃、甲庚基烯酮和香茅烯等8种物质为不同稳定化米糠风味差异的关键风味物质。该研究对不同稳定化处理的米糠挥发性风物质进行差异分析,为提升米糠产品附加值及品质提供理论依据。展开更多
以炭焙奇丹种岩茶为研究对象,采用电子鼻、全二维气相色谱-嗅闻-质谱(comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry,GC×GC-O-MS)联用技术研究挥发性风味化合物、脂肪酸、氨基酸和小分子糖在...以炭焙奇丹种岩茶为研究对象,采用电子鼻、全二维气相色谱-嗅闻-质谱(comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry,GC×GC-O-MS)联用技术研究挥发性风味化合物、脂肪酸、氨基酸和小分子糖在焙火过程中的变化。采用正交偏最小二乘判别分析确定了9种关键差异化合物:(E,E)-2,4-庚二烯醛、3,5-辛二烯-2-酮、α-紫罗酮、(E,E)-2,4-己二烯醛、芳樟醇、苯乙醛、天冬氨酸、丝氨酸和D-阿拉伯糖。本研究结果为标准化武夷岩茶焙火工艺、建立客观的品质评价体系及定向产品开发提供了数据支撑和理论依据。展开更多
文摘This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.
文摘This paper describes an improvement of the existing nominal characteristic trajectory following (NCTF) as a practical control method for a two-mass rotary point-to-point (PTP) positioning systems. Generally, the NCTF controller consists of a nominal characteristic trajectory (NCT) and a PI compensator. A notch filter is added as a part of the compensator to eliminate the vibration due to the mechanical resonance of the plant. The objective of the NCTF controller is to make the object motion follow the NCT and end at its origin. The NCTF controller is designed based on a simple open-loop experiment of the object. The parameters identification and an exact model of the plant are not necessary for controller design. The performance response of improved NCTF controller is evaluated and discussed based on results of simulation. The effect of the design parameters on the robustness of the NCTF controller to inertia and friction variations is evaluated and compared with conventional PID controller. The results show that the improved NCTF controller has a better positioning performance and is much more robust than the PID controller.
文摘为了减少荔枝汁在加热后产生的“蒸煮”异味,筛选了邻苯三酚、没食子酸、迷迭香酸、儿茶素、抗坏血酸及葡萄糖氧化酶六种抑制剂,从色泽、pH、香气轮廓、电子鼻、挥发性成分、降硫率以及总酚、总黄酮、抗氧化特性等角度去评价六种抑制剂对荔枝汁风味及营养品质的影响。结果显示抗坏血酸和没食子酸抑制剂处理的样品与新鲜汁相比的色差值最小;整体香气轮廓显示葡萄糖氧化酶抑制蒸煮异味效果最佳,其次为迷迭香酸;电子鼻结果显示葡萄糖氧化酶处理的荔枝汁与新鲜汁最为接近,其次是儿茶素和邻苯三酚。挥发性成分的主成分分析结果显示抗坏血酸抑制剂处理的样品与新鲜汁最接近,其次为没食子酸、儿茶素、迷迭香酸。降硫率结果显示葡萄糖氧化酶的降硫效果最为显著,对二甲基硫醚、二甲基三硫醚、甲硫基丙醛的抑制率均达到100%,对二甲基二硫醚的抑制率为61.11%。营养品质方面,多酚类抑制剂与抗坏血酸处理的总酚、总黄酮含量和抗氧化性较新鲜汁均显著上升(P<0.05),而葡萄糖氧化酶处理的总酚、总黄酮含量较新鲜汁上升但抗氧化活性与新鲜汁无显著差异。综合色泽、pH、香气轮廓、营养品质以及降硫效果等因素进行偏最小二乘判别分析(partial least squares discriminant analysis,PLS-DA),发现葡萄糖氧化酶对荔枝汁整体品质影响最好。本研究可为荔枝以及其他热敏性水果加工过程中品质提升提供参考依据。
文摘为了探究不同稳定化处理对米糠风味成分的影响,该研究采用电子鼻与全二维气相色谱-质谱联用技术(Comprehensive Two-dimensional Gas Chromatography-time-of-flight Mass Spectrometry,GC×GC-TOFMS),结合偏最小二乘判别分析(Partial Least Squares Discriminant Analysis,PLS-DA)和相对气味活度值(Relative Odor Activity Value,ROAV)对米糠挥发性风味物质的变化进行了系统分析。结果表明:不同稳定化处理方法对米糠风味的影响存在显著差异,共检测到99种挥发性香气化合物,包括6种醛类、10种酮类、22种烷烃类、12种醇类、28种萜烯类、8种酯类及13种其他化合物。其中,红外处理对米糠风味影响不大,而高压蒸汽处理有效降低了米糠的异味(吲哚)。变量重要性投影(Variable Importance in Projection,VIP)共筛选出23种潜在差异性物质,4种不同稳定化处理后米糠中的香叶基丙酮和(-)-柠檬烯等潜在差异性物质相对含量显著减少。ROAV值表明,烘烤、微波和高压蒸汽稳定化处理后米糠关键风味物质(ROAV>1)均减少,2-正戊基呋喃、甲庚基烯酮和香茅烯等8种物质为不同稳定化米糠风味差异的关键风味物质。该研究对不同稳定化处理的米糠挥发性风物质进行差异分析,为提升米糠产品附加值及品质提供理论依据。
文摘以炭焙奇丹种岩茶为研究对象,采用电子鼻、全二维气相色谱-嗅闻-质谱(comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry,GC×GC-O-MS)联用技术研究挥发性风味化合物、脂肪酸、氨基酸和小分子糖在焙火过程中的变化。采用正交偏最小二乘判别分析确定了9种关键差异化合物:(E,E)-2,4-庚二烯醛、3,5-辛二烯-2-酮、α-紫罗酮、(E,E)-2,4-己二烯醛、芳樟醇、苯乙醛、天冬氨酸、丝氨酸和D-阿拉伯糖。本研究结果为标准化武夷岩茶焙火工艺、建立客观的品质评价体系及定向产品开发提供了数据支撑和理论依据。
