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1.
目的 从包装功能实现的角度分析研究时间–温度指示器和食品新鲜度指示器的原理、类型与发展趋势,指出开发设计时间–温度指示器和食品新鲜度指示器应完成的包装功能,为有效实现包装交流功能提供研究思路和技术支持。方法 列出现有食品包装功能在物理环境、周围环境和人类环境下的实现矩阵,通过研究时间–温度指示器和食品新鲜度指示器的实现原理和所满足的包装交流功能,探讨这2种技术提高矩阵中分值较低元素的可行性。结果 时间–温度指示器监测食品所经历的时间、温度的完整历程,有助于提高实现矩阵中ComA元素的分值;食品新鲜度指示器提供生理变化或微生物生长引起的食品质量变化的定性或半定量信息,有助于提高实现矩阵中ComH元素的分值。结论 时间–温度指示器和食品新鲜度指示器能够有效提升食品包装的交流功能,保证消费者安全,减少资源浪费,具有广阔的发展前景。 相似文献
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《Calphad》2021
Sodium hexatitanate (Na2Ti6O13) was reported as an anode side material for Sodium ion batteries owing to low material cost, high energy efficiency, good thermal stability and long cycle life. Therefore, studies pertaining to the thermodynamic properties of Na2Ti6O13 are indispensable for improving its service performance. However, a significant number of literature reviews concerning thermodynamic properties indicated that heat capacity of Na2Ti6O13 at high temperatures should be confirmed. In this study, the 99.5% purity of Na2Ti6O13 sample was successfully prepared via solid-state reaction using TiO2 and Na2CO3 as initial materials. Heat capacity of the as-synthesized samples in the temperature range of 573–1523 K was measured using a multi-high temperature calorimeter 96 line. Heat capacity, Cp, from 298.15 to 1573 K was modeled as a polynomial formula with a prediction error of 3%: Cp = 474.08143 + 0.06286T-8.04068 × 106 T−2 (J⋅mol−1⋅K−1). In combination with the low-temperature data, heat capacity of Na2Ti6O13 from 0 to 1573 K was given in present study. Values of changes in enthalpy, Gibbs free energy and entropy in the temperature range of 298.15–1573 K were calculated based on the temperature dependence of heat capacity. 相似文献
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现有文献针对计及转子变流器(RSC)控制的双馈感应风电机组(DFIG)定子短路电流解析表达,将定子磁链当作一阶直流衰减分量或忽略功率外环控制。基于DFIG电压、磁链和RSC控制方程,得到定子电流关于定子电压和定子功率的传递函数,提出定子电流的精确解析表达式。基于RSC内、外环PI参数关系,推导直流分量衰减时间常数和角频率关于PI参数的表达式。分析了RSC内外环PI参数对定子电流直流衰减分量的影响。仿真结果验证了解析表达式的准确性,为PI参数选取和保护装置测量、整定提供依据。 相似文献
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酸枣仁油取自药食同源的酸枣仁,是一种安全的保健食用油,综述近年来有关酸枣仁油的提取工艺、组成成分分析及其生物活性研究,为酸枣仁油的进一步开发与应用提供参考。现有研究表明,酸枣仁油生产工艺简单,成品油中含有大量不饱和脂肪酸,其中油酸和亚油酸含量最高,同时还含有多种脂溶性成分。酸枣仁油具有多种生物活性,如镇静催眠、改善记忆力、抗抑郁、抗氧化、血脂调节及抗肿瘤等,但其发挥生物活性的物质基础及作用机理尚未完全明确,有待进一步研究。酸枣仁油的安全及多活性特点赋予其巨大的开发与应用潜力,相关产品具有广阔的市场前景。 相似文献
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The object of study is nonlinear stationary controlled system of ordinary differential equations with constant disturbance in the right part. The problem of constructing the synthesising control function providing the transfer of this system from the initial state to the origin is considered. The sufficiently simple for numerical implementation algorithm of solution of the above-mentioned problem is obtained. It is shown that for local null controllability of the considered system, it is sufficient that the conditions of the Kalman's type were satisfied. In addition, the estimates restricting the choice of initial conditions and external disturbances under which the transfer is guaranteed are obtained. The main idea of the method of construction of the desired control function consists in reducing the original problem to stabilisation of a special kind linear non-stationary system and solving the Cauchy problem for an auxiliary system of ordinary differential equations closed by stabilising control. The simplicity of the realisation of this algorithm is determined by the construction of the auxiliary system and its stabilisation that could be obtained by analytical methods. The effectiveness of the method is illustrated by solving the problem of crane control and its numerical simulation. 相似文献
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Matthew E. Wilhelm Anne V. Le Matthew D. Stuber 《American Institute of Chemical Engineers》2019,65(12):e16836
We present a deterministic global optimization method for nonlinear programming formulations constrained by stiff systems of ordinary differential equation (ODE) initial value problems (IVPs). The examples arise from dynamic optimization problems exhibiting both fast and slow transient phenomena commonly encountered in model-based systems engineering applications. The proposed approach utilizes unconditionally stable implicit integration methods to reformulate the ODE-constrained problem into a nonconvex nonlinear program (NLP) with implicit functions embedded. This problem is then solved to global optimality in finite time using a spatial branch-and-bound framework utilizing convex/concave relaxations of implicit functions constructed by a method which fully exploits problem sparsity. The algorithms were implemented in the Julia programming language within the EAGO.jl package and demonstrated on five illustrative examples with varying complexity relevant in process systems engineering. The developed methods enable the guaranteed global solution of dynamic optimization problems with stiff ODE–IVPs embedded. 相似文献
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Kshitij Mall Ehsan Taheri Prathamesh Prabhu 《American Institute of Chemical Engineers》2021,67(6):e17209
This study investigates the application of a recently developed construct, the uniform trigonometrization method (UTM), to the singular control problems in chemical engineering. The UTM involves minimal modifications to the original problem, thereby generating near-singular control solutions that can be used for conceptual design and serve as an alternate to direct techniques like nested and simultaneous approaches. Eight classical singular control problems with known analytical solutions and three complex singular control problems from chemical engineering domain are solved in this study. The results obtained using the UTM for these problems are found to match well with the literature and are of higher resolution as compared to the results obtained using a direct pseudospectral-based solver. The ability of the UTM to handle complex chemical engineering problems with both singular controls and state path constraints has also been demonstrated in this study. 相似文献