A note on stability analysis of 2-D linear discrete systems based on the Fornasini–Marchesini second model: Stability with asymmetric Lyapunov matrix

A recently reported Lyapunov based criterion (Singh (2014) [7]) for the asymptotic stability of two-dimensional (2-D) linear discrete systems described by the Fornasini–Marchesini second local state-space (FMSLSS) model is reviewed. It is established in this paper that, despite utilizing a more general Lyapunov matrix, Singh's criterion will never lead to an enhanced stability region in the parameter-space as compared to that obtainable via Hinamoto–Lu's criterion.     

Optimal scheduling of single stage batch plants with direct heat integration

This paper addresses the multi-objective optimization problem arising in the operation of heat integrated batch plants, where makespan and utility consumption are the two conflicting objectives. A new continuous-time MILP formulation with general precedence variables is proposed to simultaneously handle decisions related to timing, product sequencing, heat exchanger matches (selected from a two-stage superstructure) and their heat loads. It features a complex set of timing constraints to synchronize heating and cooling tasks, derived from Generalized Disjunctive Programming. Through the solution of an industrial case study from a vegetable oil refinery, we show that major savings in utilities can be achieved while generating the set of Pareto optimal solutions through the ɛ-constraint method.     

Asymptotic stability of general linear methods for systems of linear neutral delay differential-algebraic equations

This paper is concerned with numerical stability of general linear methods (GLMs) for a system of linear neutral delay differential-algebraic equations. A sufficient and necessary condition for asymptotic stability of GLMs solving such system is derived. Based on this main result, we further investigate the asymptotic stability of linear multistep methods, Runge–Kutta methods, and block θ-methods, respectively. Numerical experiments confirm our theoretical result.     

Exploring the relationship between the physical properties of activated carbon catalysts and their efficiency in catalyzing hydrogen iodide decomposition to produce hydrogen

Using simple and efficient methods to synthesize biological activated carbon catalysts (ACCs) with the decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle as a typical reaction is urgently needed for the commercialization of hydrogen energy production and development. In this study, a series of ACCs with different specific surface areas (SSAs) and pore structures are prepared by comparing and controlling the changes in carbonization and activation methods of activated carbon (AC) preparation process. Hierarchical porous AC with larger SSA has higher HI decomposition efficiency. The representative samples H240H1h and H240C4h are hierarchical porous ACCs with 48.96% and 46.88% micropores, respectively, and have the highest catalytic activity in the entire series. The nitrogen adsorption and desorption curve is combined with pore size distribution data and analyzed using the capillary aggregation (Kelvin) and monolayer adsorption (Langmuir) theories. And ACC pore grading coefficient—which can improve data visualization—is introduced.     

热烧结矿竖式冷却过程传热特性

 与传统环冷相比，烧结竖冷拥有漏风率低、换热效率高的优势。为此利用竖冷试验装置，在某烧结厂取热风与热烧结矿研究了竖式冷却过程气固对流换热特性。研究表明，烧结矿竖式冷却过程中影响传热特性的主要因素为冷却风的流量及温度。烧结矿和冷却风对流换热系数随着烧结矿温度的升高而增大，且随着冷却风流量的增大以及冷却风温度的降低，对流换热系数也随之增大。基于白金汉定理，结合试验数据拟合得出了描述烧结矿与冷却风传热特性的准数关联式，其模拟性较好且平均相对误差为7.25%。     

水文序列相依变异识别的RIC定阶准则——以自回归模型为例

水文过程相依性是水文变异的主要表现形式之一,应用自回归模型对其进行拟合时合理确定模型阶数是一个难点问题。本文在分析AIC和BIC准则的基础上,提出了一种以原序列与其相依成分的相关系数作为拟合度指标,同时借用信息熵形式的函数式,作为模型不确定性度量指标的自回归模型定阶准则(简称RIC准则)。以AR(1)、AR(2)、AR(3)和AR(4)模型为例进行统计试验,将不同序列长度下该准则的定阶准确率与其他定阶准则进行比较,试验结果表明,RIC准则对于上述模型均具有较好的适应性,且定阶准确率远高于AIC准则,其中对于前三阶模型RIC准则优于BIC准则,但四阶模型略低于BIC准则。RIC准则的优势是可以同时满足模型定阶、相依程度分级与模型检验的需求,将其应用于实测水文序列分析,结果显示,该准则能较准确地识别自回归模型的阶数,且符合提出的"相依有变异而残差无变异的最小阶数"的检验标准。     

吸收烟气中低浓度CO2的操作条件分析

Mg(OH)2浆液是一种具备低再生能耗潜力的CO2吸收剂，为了推进其在CO2捕集领域的应用而展开研究。在填料塔中，使用真实烟气研究了各种操作条件下Mg(OH)2浆液对CO2的捕集效率。研究发现,填料种类、气体名义停留时间、液气比均对CO2捕集效率有影响。结果表明，增加气体名义停留时间无法有效改善液相传质，而提高液气比能够有效改善液相传质；在试验条件下，拉西环、鲍尔环和IMTP的总体积传质系数分别为8.5×10-7～5.0×10-6、1.8×10-6～4.0×10-6和1.9×10-7～2.9×10-6 mol/(m3·s·Pa)。     

煤矿下山巷道水与空气不耦合装药爆破技术对比研究

为了提高三级煤矿许用炸药能量利用率,改善爆破破岩效果，保证开采区的工作效率，对不耦合装药结构进行优化，以理论推导的方式分别得出空气不耦合与水不耦合装药系数对爆生气体准静压力的影响，并进行了对比分析；通过实验室爆破模型试验研究水和空气径向不耦合分别作用下爆炸应力波的传播分布特性，分析峰值应力与测点到炮孔比例距离、不耦合系数之间的关系，并与理论分析对比验证。结果表明：当不耦合系数相同时，炮孔处水不耦合装药爆炸应力波峰值高于空气不耦合装药，随着不耦合系数的增加，炮孔处爆炸应力波的峰值应力减小；模型试验测得同一测点的水不耦合装药峰值应力是空气不耦合装药峰值应力的1.15~1.52倍，峰值应力作用时间长于空气不耦合装药，同一测点水和空气不耦合装药结构测得的应力波及其峰值应力均随不耦合系数的增加呈负幂函数衰减，且空气不耦合装药时衰减得更快，与理论分析一致；贵州某煤矿下山巷道，于梯形掘进断面实施传统空气不耦合装药结构掏槽爆破，效果不甚理想，运用水不耦合装药爆破技术，提高了炮孔利用率，减小了岩石破碎块度，使爆堆集中，显著提高了岩石破碎效果与出渣效率。     

海水淡化用空心锥喷嘴喷淋性能理论及实验研究

设计开发一种具有高通量、低流阻特征的空心锥喷嘴,并通过理论与实验方法研究空心锥喷嘴的喷淋性能,基于准自由涡理论建立空心锥喷嘴内部流体流动的数学模型,阐明流量系数、喷淋锥角、喷嘴流量与喷嘴结构参数之间的定量关系,并利用多效蒸馏海水淡化喷淋实验台对理论计算结果进行实验测试和验证。研究结果表明:正常工作状态下喷嘴流量系数、喷淋锥角、喷淋流量等参数理论值与测量值之间的误差小于5%,验证了设计模型的准确性。同时根据实验测试数据,拟合得到该类型空心锥喷嘴喷淋锥角与雷诺数之间的经验公式,可为蒸馏海水淡化用大流量空心锥喷嘴的结构设计、工艺选型提供理论指导和数据支持。     

改进Elman神经网络在短期热负荷预测中的应用

热电厂的短期热负荷预测在城市集中供暖中起着至关重要的作用,直接影响热电厂的经济效益和热能利用率。电厂的短期热负荷一般采用神经网络预测模型进行预测,而BP神经网络应用最为广泛。Elman神经网络算法在BP神经网络基础上加入了承接层,作为一步延时算子,实现记忆能力,使系统具备适应时变能力,增强系统全局稳定性。但Elman神经网络算法模型的构造依然需要大量样本的支撑,而且输入层的变量多,导致预测时间依然很长,收敛速度慢。该文在Elman神经网络预测前,进行了相关系数预处理和对样本中异常值的平均化预处理,通过数据归一化运算,使Elman神经网络输入层变量大幅减少。仿真实验表明,改进的Elman神经网络算法使预测模型快速寻优,减少预测时间的同时明显提高预测精度。