Effects of initial albumen quality and mineral oil–chitosan emulsion coating on internal quality and shelf‐life of eggs during room temperature storage

Effects of mineral oil (MO) and mineral oil–chitosan emulsion (MO:CH = 25:75) as coatings on internal quality and shelf‐life of eggs were evaluated during 5‐week storage at 25 °C. Eggs with three different initial albumen qualities [Haugh unit (HU): H = 87.8, M = 75.6 and L = 70.9] were evaluated. As storage time increased, HU and yolk index values decreased whereas weight loss increased. Coating with MO and/or 25:75 MO:CH emulsion could preserve the internal quality for at least 4 more weeks for H‐eggs and at least 3 more weeks for M and/or L‐eggs, all with weight losses <0.92%. All coated eggs had >70% positive purchase intent, and their colour differences at week 0 could not be detected by naked human eye (ΔE^* < 3.0, noncoated eggs as reference). Consumers significantly differentiated freshly MO‐coated from noncoated eggs on overall surface appearance. This study demonstrated that MO and 25:75 MO:CH emulsion coatings could preserve internal quality and prolong shelf‐life of eggs.     

焙烧多功能机组电缆拖链装置结构改进

分析焙烧多功能机组电缆拖链损坏原因,对比新、旧拖链装置结构,介绍改进后电缆拖链装置的优点。     

莱钢1 500 mm热轧带钢生产线工艺技术升级与改造

针对莱钢宽带线产能释放能力不足以及品种钢比例低等问题,对其进行了工艺技术升级与改造。主要介绍了热卷箱区域、精轧区域、层冷区域、卷取区域工艺设备的改造情况及全线自动控制系统的升级。改造后,2018、 2019年莱钢宽带线年产能分别达到204.33、211.71万t,较2017年产能增加41.31、48.69万t,品种钢比例分别提升7.92%、27.41%,取得了良好效果。该改造项目在在无预留精轧机基础的前提下新增末机架轧机,为落后产线实现改造升级提供了参考。     

腐蚀监控技术在炼油装置中的应用

随着原油品质的下降,在炼油过程中造成的腐蚀问题,受到广泛重视,腐蚀监控技术得到快速发展。炼油装置中的均匀腐蚀情况可以通过电阻探针监控法和电感探针监控法来进行监控,点腐蚀情况可以通过线性极化探针监测法和电化学噪声监控技术来进行监控,应力腐蚀情况可以通过氢通量测量技术和线性极化探针监控法来进行监控。基于这些腐蚀监控技术,建立腐蚀监控系统,用于全面监控炼油装置的腐蚀情况,基本实现了对炼油装置腐蚀情况的连续监测,以便及时给出应对措施,可有效预防腐蚀的发生,减少安全事故。     

特高压交流输电模型的建立与经济性优选分析

交流1 000 k V和500 k V具有不同的适用输电容量与距离范围。针对电源点送出的不同情况,应合理选择电压等级,并匹配相应的线路回数、串补度、开关站等。以往多采用BPA仿真软件通过连续潮流算法得到,但该方法计算调整复杂且费时,需对多种送电需求情况进行分析时计算量尤为庞大。提出一种基于交流线路输电能力的算法,采用Matlab软件编程实现交流输电模型建模及经济性优选方法。该方法可以在考虑电网强度等因素情况下,采用热限制、电压降落限制、稳定限制等约束条件,得到交流线路输电能力曲线。在此基础上,建立超、特高压交流输电模型,结合单位容量年费用比较法进行经济性优选,最终得到满足电源点送电任意输电容量和输电距离需求下的经济性最优交流输电电压等级及其输电模型配置,对于我国输电线路的规划建设具有重要的参考意义和实用价值。     

带遗传算子模拟植物生长算法在AGC机组调配经济性中的应用

建立AGC机组调配调节费用的数学模型,采用一种带遗传算子模拟植物生长算法(Plant Growth Simulation Algorithm,PGSA),应用于机组调配经济性研究。为解决完整模拟植物生长过程全局搜索可能速度过慢的问题,采用最优保留和最差杂交后保留的策略,可在加速计算速度的同时抑制早熟,防止陷入局部最优。此外,为防止新生长点过于聚集,采用K-means聚类算法对机组进行分类,并在长出新生长点时,同类机组选择差异性较大的变异方式。对于存在多个最优解,采用多解平均法,确保机组调配的公平性。通过计算结果对比验证了该算法的合理性及有效性。     

Optimal Placement of Phasor Measurement Units with Linear and Non-linear Models

Abstract—This article presents a non-linear programming-based model for the optimal placement of phasor measurement units. The optimal phasor measurement units placement is formulated to minimize the number of phasor measurement units required for full system observability and to maximize the measurement redundancy at all buses in a power system. A sequential quadratic programming algorithm is used for the solution of the proposed model. The existence of power flow and injection measurements, the limited phasor measurement units channel capacity, the lack of communication facilities in substations, and the single phasor measurement units loss are also incorporated into the initial proposed formulation. The non-linear programming model is applied to IEEE 14- and 118-bus test systems in MATLAB. The accuracy and the effectiveness of the proposed method is verified by comparing the simulation results to those obtained by a binary integer programming model also implemented in MATLAB. The comparative study shows that the proposed non-linear programming model yields the same number of phasor measurement units as the binary integer programming model. A remarkable advantage of the non-linear programming against binary integer linear programming is its capability to give more than one optimal solution, each one having the same minimum number of phasor measurement units (same minimum objective value), but at different locations.     

Multi-objective Phasor Measurement Unit Placement in Electric Power Networks: Integer Linear Programming Formulation

A multi-objective optimal phasor measurement unit placement model using integer linear programming is presented in this article. The proposed model simultaneously optimizes two objectives, i.e., minimization of phasor measurement unit numbers and maximization of measurement redundancy. To calculate the redundancy criteria, the single-line outage and the phasor measurement unit loss are considered simultaneously. A linear formulation is presented for both objective functions. Also herein, to address conflicting attributes and identify Pareto optimal solutions of the multi-objective optimal phasor measurement unit placement problem, a new multi-objective mathematical programming method is proposed. Finally, a new index, i.e., minimum distance to utopia point, is implemented to select the most preferred solution among the available Pareto front based options on the goal to achieve judicious decision makers. Two test systems, i.e., a modified 9-bus and an IEEE 118-bus test systems, are used to illustrate the effectiveness of the proposed framework.     

智能变电站过程层设备及二次回路优化研究

本文分析了合并单元智能终端集成装置实现的可行性和方法,研究了智能终端整合状态监测参量的可行性和方案,对智能终端和断路器二次回路进行了优化整合;本文对有载调压二次控制回路进行了整合和智能化方案研究,通过可编程逻辑控制器(Programmable Logic Controller,PLC)和变频控制,对变压器冷却系统实现了智能化。     

考虑风电场灵活性及出力不确定性的机组组合

大规模并网风电的出力不确定性及反调峰特性给电力系统运行,尤其是机组组合的安全可靠性、经济性带来了严峻的挑战。合理构建风电出力不确定性模型,并将新的优化方法,如随机优化、鲁棒优化等应用到机组组合中已成为当前的研究热点。首先对风电场潜在调节能力进行了探讨,提出了一种新的风电调度模式及相应的机组组合模型。风电场在新的调度模式下将转变为一个"灵活"的参与者,而机组组合模型同时计及了风电场出力的不确定性。然后,以修订后的IEEE 39节点系统为基本算例对所提方法进行了仿真分析,结果表明所提出的方法可有效地提高电力系统运行的整体性能。此外,所提方法还可用于评估系统对风电的接纳能力。