通过动三轴试验对冻融循环后的石灰改良土的动力特性进行了研究,分析了动应力幅值、冻融循环次数、冷却温度、围压对土体累计塑性变形的影响,并建立了动应力和冻融循环作用共同影响下的累计塑性变形的预测模型;基于此进一步分析了掺灰...通过动三轴试验对冻融循环后的石灰改良土的动力特性进行了研究,分析了动应力幅值、冻融循环次数、冷却温度、围压对土体累计塑性变形的影响,并建立了动应力和冻融循环作用共同影响下的累计塑性变形的预测模型;基于此进一步分析了掺灰比、冻融循环次数对临界动应力的影响,确定了素土的临界动应力小于80 k Pa、石灰改良土的临界动应力为150~250 k Pa;在标准状态下的路基动回弹模量标准值MR的基础上引入冻融循环条件下路基土模量折减系数Kη和路基回弹模量湿度调整系数Ks,得到了在冻融循环作用及路基土体湿度共同影响下的路基回弹模量,其石灰改良土在路基工作区顶面和底面的回弹模量分别为70.18、58.48 MPa,能够满足路基回弹模量的要求。展开更多
为研究乳清多肽(whey protein hydrolysates,WPH)对反复冻融猪肉糜氧化和品质的影响规律及机理,本实验将不同质量分数(5%、10%、15%)WPH添加到生猪肉糜中,进行不同冻融循环(0~9)处理,检测冻融后肉糜解冻损失、硫代巴比妥酸(thiobarbitur...为研究乳清多肽(whey protein hydrolysates,WPH)对反复冻融猪肉糜氧化和品质的影响规律及机理,本实验将不同质量分数(5%、10%、15%)WPH添加到生猪肉糜中,进行不同冻融循环(0~9)处理,检测冻融后肉糜解冻损失、硫代巴比妥酸(thiobarbituricacid reactive substances,TBARS)值、挥发性盐基氮(total volatile base nitrogen,TVB-N)值、质构特性、流变学模量损耗、蛋白羰基含量以及拉曼光谱的变化情况。结果表明,未经冻融时,样品组与空白组各指标之间都无明显差异(P>0.05)。冻融处理后,猪肉糜的解冻损失率由2.67%~2.93%升高至7.00%~12.4%,其中15%WPH明显抑制了解冻损失的增加(P<0.05),提高了肉糜保水性。当冻融循环达到7~9次后,添加15%WPH组抑制肉糜TVB-N值、TBARS值以及羰基含量升高均比空白组和未水解乳清多肽组效果好(P<0.05)。在质构方面,随着冻融次数的增加,猪肉糜硬度、弹性、内聚性和咀嚼性均呈现明显的下降趋势。冻融9次时,15%WPH可使猪肉糜咀嚼性从9.63 g升高到17 g;冻融5次时,15%WPH组的弹性高达到0.69,超过丁基羟基茴香醚(butylatedhydroxyanisole,BHA)阳性空白组;WPH组和BHA组的硬度和内聚性均显著高于空白组;不同添加量WPH对猪肉糜质构都有改善作用,其中高剂量组效果最好。流变学结果显示,WPH组猪肉糜损耗模量G’’降低比较明显。拉曼光谱表明,添加15%WPH有效抑制了冻融循环过程中肉蛋白α-螺旋含量下降、β-折叠含量上升的现象,保护了蛋白质二级结构。实验表明,在冻融循环过程中,WPH起到抑制猪肉糜氧化和改善产品品质的作用。展开更多
In seasonally frozen soil regions,freezing-thawing action and hydrothermal effect have strong influence on physical and mechanical behavior of shallow soil.A field experiment on the Loess Plateau in Northwest China wa...In seasonally frozen soil regions,freezing-thawing action and hydrothermal effect have strong influence on physical and mechanical behavior of shallow soil.A field experiment on the Loess Plateau in Northwest China was carried out to analyze the freezing-thawing process and hydrothermal characteristics of shallow soil considering the climate influence.The results show that the maximum seasonal freezing depth under bare ground surface in this area is from 20 cm to 50 cm.The ground temperature shows a similar changing trend with air temperature,but it has lagged behind the air temperature,and the ground temperature amplitude exponentially decreases with the increase of soil depth.The seasonally frozen soil has experienced four typical stages:unfrozen period,alternate freezing period,freezing period and alternate thawing period.The freezing-thawing process is characterized by unidirectional freezing and bidirectional thawing.The water content of shallow soil is significantly affected by air temperature,evaporation and precipitation,and the soil water content shows a"low-high-low"changing trend with the increase of depth.The soil temperature and water content interact with each other,and are often coupled.The variation trend of soil moisture with time is consistent with the change trend of the ground temperature with time in each soil layer,andthe degree of consistency is higher in the near surface soil than that in the lower layer.Also,the spatial-temporal characteristics of soil moisture and temperature is that the volumetric water content and ground temperatureof near surface soil have strong variability,and the range valueKa and coefficient of variation Cvof soil water content and ground temperaturein different seasons show a decreasing trend with the increase of depth.展开更多
文摘通过动三轴试验对冻融循环后的石灰改良土的动力特性进行了研究,分析了动应力幅值、冻融循环次数、冷却温度、围压对土体累计塑性变形的影响,并建立了动应力和冻融循环作用共同影响下的累计塑性变形的预测模型;基于此进一步分析了掺灰比、冻融循环次数对临界动应力的影响,确定了素土的临界动应力小于80 k Pa、石灰改良土的临界动应力为150~250 k Pa;在标准状态下的路基动回弹模量标准值MR的基础上引入冻融循环条件下路基土模量折减系数Kη和路基回弹模量湿度调整系数Ks,得到了在冻融循环作用及路基土体湿度共同影响下的路基回弹模量,其石灰改良土在路基工作区顶面和底面的回弹模量分别为70.18、58.48 MPa,能够满足路基回弹模量的要求。
文摘为研究乳清多肽(whey protein hydrolysates,WPH)对反复冻融猪肉糜氧化和品质的影响规律及机理,本实验将不同质量分数(5%、10%、15%)WPH添加到生猪肉糜中,进行不同冻融循环(0~9)处理,检测冻融后肉糜解冻损失、硫代巴比妥酸(thiobarbituricacid reactive substances,TBARS)值、挥发性盐基氮(total volatile base nitrogen,TVB-N)值、质构特性、流变学模量损耗、蛋白羰基含量以及拉曼光谱的变化情况。结果表明,未经冻融时,样品组与空白组各指标之间都无明显差异(P>0.05)。冻融处理后,猪肉糜的解冻损失率由2.67%~2.93%升高至7.00%~12.4%,其中15%WPH明显抑制了解冻损失的增加(P<0.05),提高了肉糜保水性。当冻融循环达到7~9次后,添加15%WPH组抑制肉糜TVB-N值、TBARS值以及羰基含量升高均比空白组和未水解乳清多肽组效果好(P<0.05)。在质构方面,随着冻融次数的增加,猪肉糜硬度、弹性、内聚性和咀嚼性均呈现明显的下降趋势。冻融9次时,15%WPH可使猪肉糜咀嚼性从9.63 g升高到17 g;冻融5次时,15%WPH组的弹性高达到0.69,超过丁基羟基茴香醚(butylatedhydroxyanisole,BHA)阳性空白组;WPH组和BHA组的硬度和内聚性均显著高于空白组;不同添加量WPH对猪肉糜质构都有改善作用,其中高剂量组效果最好。流变学结果显示,WPH组猪肉糜损耗模量G’’降低比较明显。拉曼光谱表明,添加15%WPH有效抑制了冻融循环过程中肉蛋白α-螺旋含量下降、β-折叠含量上升的现象,保护了蛋白质二级结构。实验表明,在冻融循环过程中,WPH起到抑制猪肉糜氧化和改善产品品质的作用。
基金This study was funded by the National Natural Science Foundation of China(grant number 51769013)the Basic Research Innovation Group of Gansu Province(20JR5RA478).
文摘In seasonally frozen soil regions,freezing-thawing action and hydrothermal effect have strong influence on physical and mechanical behavior of shallow soil.A field experiment on the Loess Plateau in Northwest China was carried out to analyze the freezing-thawing process and hydrothermal characteristics of shallow soil considering the climate influence.The results show that the maximum seasonal freezing depth under bare ground surface in this area is from 20 cm to 50 cm.The ground temperature shows a similar changing trend with air temperature,but it has lagged behind the air temperature,and the ground temperature amplitude exponentially decreases with the increase of soil depth.The seasonally frozen soil has experienced four typical stages:unfrozen period,alternate freezing period,freezing period and alternate thawing period.The freezing-thawing process is characterized by unidirectional freezing and bidirectional thawing.The water content of shallow soil is significantly affected by air temperature,evaporation and precipitation,and the soil water content shows a"low-high-low"changing trend with the increase of depth.The soil temperature and water content interact with each other,and are often coupled.The variation trend of soil moisture with time is consistent with the change trend of the ground temperature with time in each soil layer,andthe degree of consistency is higher in the near surface soil than that in the lower layer.Also,the spatial-temporal characteristics of soil moisture and temperature is that the volumetric water content and ground temperatureof near surface soil have strong variability,and the range valueKa and coefficient of variation Cvof soil water content and ground temperaturein different seasons show a decreasing trend with the increase of depth.
