A Nonstationary Halley’s Iteration Method by Using Divided Differences Formula

This paper presents a new nonstationary iterative method for solving non linear algebraic equations that does not require the use of any derivative. The study uses only the Newton’s divided differences of first and second orders instead of the derivatives of (1).

Numerical optimisation and experimental validation of divided rail freight brake disc crown

In this study, numerical optimisation and experimental validation of a divided rail freight brake disc crown made of grey cast iron EN-GJL-250 is presented.The analysed brake disc is used in rail freight wagons and possesses a load capacity of 22.5 tons per axle. Two of the divided rail freight brake discs are mounted on each axle.With the aid of numerical analysis, the thermal dissipation properties of the brake disc were optimised and ventilation losses were reduced, and the numerical results were compared with experimental results. A one-way fluid–structure interaction analysis was performed. A computational fluid dynamic model of a divided rail freight brake disc, used to predict air flow properties and heat convection, was incorporated into a finite element model of the disc and used to evaluate the temperature of the disc. A numerical parametrical optimisation of cooling ribs of the brake disc was also performed, and novel optimised cooling ribs were developed. A transient thermal numerical analysis of the brake disc was validated using temperature measurements obtained during a braking test on a test bench. The ventilation losses of the brake disc were measured on a test bench specifically designed for the task, and the losses were compared to the simulation results. The experimentally obtained ventilation losses and temperature measurements compared favourably with the simulation results, confirming that this type of simulation process may be confidently applied in the future. Through systematic optimisation of the divided rail freight brake disc, ventilation losses were reduced by 37% and the mass was reduced by 21%, resulting in better thermal performance that will bring with it substantial energy savings.

Infinitesimal dividing modeling method for dual suppliers inventory model with random lead times

As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time demand＂, which may lead to an imprecise inventory cost. Through the real-time statistic of the inventory quantities, this paper considers the precise （Q, τ） inventory cost model of dual supplier procurement by using an infinitesimal dividing method. The traditional modeling method of the inventory cost for dual supplier procurement includes complex procedures. To reduce the complexity effectively, the presented method investigates the statistics properties in real-time of the inventory quantities with the application of the infinitesimal dividing method. It is proved that the optimal holding and shortage costs of dual supplier procurement are less than those of single supplier procurement respectively. With the assumption that both suppliers have the same distribution of lead times, the convexity of the cost function per unit time is proved. So the optimal solution can be easily obtained by applying the classical convex optimization methods. The numerical examples are given to verify the main conclusions.

Stability of the Dividing Distribution Function Method for ParticleSize Distribution Analysis in Small Angle X－Ray Scattering

The Dividing Distribution Function (DDF) method is one of the methods by which the particle size distribution of ultrafine powder can be evaluated from its small angle X-ray scattering data. In this paper, the stability of the solution obtained from DDF method has been investigated through optimizing the coefficient matrix, introducing a damping factor and a least square treatment. All calculations were accomplished with a microcomputer. It was shown that the average deviations of the size distribution obtained are not larger than the assigned random errors to the scattering intensities as long as the corresponding requirements are satisfied.

Shortcut Method of Design and Energy-Saving Analysis of Sargent Dividing Wall Column

The Sargent dividing wall column can implement four products separation sequences in one column based on Fully Thermally Coupled Distillation Column. The initial design parameters are required for the design optimization or dynamic control of the Sargent dividing wall column, and in order to make the rigorous simulation of the Sargent dividing wall column more conducive to convergence, a ten column model for complex Sargent column is established in this paper,and the shortcut design method of this model is proposed. The internal minimum vapor and liquid flow are obtained by the Underwood equations and the mass balance method and the V-min method. The separation for a 4-component shortcut mixture of pentane, hexane, heptane and octane was considered, while the initial values of design parameters and the ratio of vapor-liquid distribution of each column were calculated by using the shortcut design method of a ten column model. And by comparing the shortcut calculations with rigorous simulation results, the practicality and reliability of shortcut calculations were verified. The reason for energy saving was analyzed based on back-mixing. A virtual heat exchanger is proposed to make the Sargent dividing wall column more energy efficient.

Experimental and simulation of the reactive dividing wall column based on ethyl acetate synthesis

Reactive dividing wall column(RDWC) is a highly integrated unit which combines reaction distillation(RD) with dividing wall column separation technology into one shell, and it realized the chemical reaction and the separation of multiple product fractions simultaneously. In this paper, the reaction of esterification with acetic acid and ethanol to produce ethyl acetate was used as the research system, experiments and simulations of the RDWC were carried out. This system in the traditional process mostly used the homogeneous catalyst(e.g. sulfuric acid). However, in view of the corrosion of the equipment caused by the acidity of the catalyst, we used the heterogeneous catalysts – iron exchange resins – Amberlyst15 and proposed a novel catalyst loading method. Firstly,the reliability of the model of the simulation was verified by the experimental study on the change of liquid split ratio and reflux ratio. After that, the four-column model was established in Aspen Plus to analyze the effects of the amount of azeotropic agent, reflux ratio and acetic acid concentration. Finally, for a fair comparison, the economic analysis was conducted between traditional RD column and RDWC. The results showed that RDWC can save34.7% of total operating costs and 18.5% of TAC.

Convergence analysis for the Secant method based on new recurrence relations

A new convergence theorem for the Secant method in Banach spaces based on new recurrence relations is established for approximating a solution of a nonlinear operator equation. It is assumed that the divided difference of order one of the nonlinear operator is Lipschitz continuous. The convergence conditions differ from some existing ones and are easily satisfied. The results of the paper are justified by numerical examples that cannot be handled by earlier works.

一种基于Divide-and-Merge聚类算法的改进算法

BNAK-Divide-and-Merge聚类算法是基于David等人提出的Divide-and-Merge算法的一种改进算法。Divide-and-Merge算法是一种将自顶向下的分裂方法和自底向上的聚合方法相结合的聚类算法。虽然这个聚类算法已经通过众多实验表明其聚类的效率和质量,但是它在数据集很大的情况下分裂会很耗时间和空间资源,并且它需要阈值来确定聚类个数的方法也不是很理想。针对以上两个主要不足,对原算法进行改进。

中国数字鸿沟评价指标体系的构建及其测度

数字经济高速发展的同时,数字鸿沟渗透在产业发展、群众生活、金融服务、基础设施建设等方面,造成了一定程度的产业发展不平衡、贫富差距、信息不对称等问题。从区域、城乡、产业、企业方面提出了数字鸿沟分析基本框架,构建中国数字鸿沟评价的指标体系,采用熵值法为二级指标赋权,计算中国2017—2022年期间数字鸿沟指数。研究发现,近5年来数字鸿沟呈现扩张趋势,其中2017—2020年中国数字鸿沟的增长速度上升,2021年增速下滑,2022年则再次上升;分维度看,中国区域、产业数字鸿沟呈现扩大趋势,城乡数字鸿沟则逐渐弥合,企业维度的数字鸿沟呈现波动的趋势。研究表明,进行数字鸿沟治理,需要加强数字经济相关基础设施建设,深入实施“东数西算”工程;建立数字技术创新平台,发展电子商务与电子政务服务进行信息技术的推广;统筹各区域数字经济的协调发展、因地制宜,加强区域合作,畅通人才在区域间的就业渠道;建立数字化创新技术的政策激励制度,鼓励合适的产业与企业进行数字化转型;建立健全的政府、企业与社会合作机制,促进数字红利的均匀分配;建立数字技术使用的反馈机制,加强数字信息技术的普及工作,采取更加多元有效的措施缩小数字鸿沟。

基于空间投影和聚类划分的SVR加速算法

数据不仅能产生价值,还对统计学的科学发展提供了动力。随着科技的飞速发展,海量数据得以涌现,但大规模的数据会导致很多传统处理方法很难满足各领域对数据分析的需求。面对海量数据时代学习算法的低效性,分治法通常被认为是解决这一问题最直接、最广泛使用的策略。SVR是一种强大的回归算法,在模式识别和数据挖掘等领域有广泛应用。然而在处理大规模数据时,SVR训练效率低。为此,该文利用分治思想提出一种基于空间投影和聚类划分的SVR加速算法(PKM-SVR)。利用投影向量将数据投影到二维空间;利用聚类方法将数据空间划分为k个互不相交的区域;在每个区域上训练SVR模型;利用每个区域的SVR模型预测落入同一区域的待识别样本。在标准数据集上与传统的数据划分方法进行对比实验,实验结果表明该算法训练速度较快,并表现出更好的预测性能。

城乡数字鸿沟、生产经营方式与农业绿色发展

弥合城乡数字鸿沟可以有效提高农民数字素养,优化农业生产经营中要素配置,促进农业绿色发展。利用2010—2020年中国省级面板数据,以农业生产经营方式为切入点,对城乡数字鸿沟影响农业绿色发展的机理与路径进行实证检验。结果表明,城乡数字鸿沟对农业绿色发展存在显著的抑制作用,且城乡数字鸿沟能够显著降低农业生产经营的规模化和专业化水平,进而抑制农业绿色发展。进一步分析发现,城乡数字鸿沟主要从接入鸿沟和意识鸿沟两个方面,通过降低农业资源利用、农业绿色产出和绿色经济效益三个层面制约农业绿色发展,这种抑制作用在信息化发展高水平地区尤为显著,而二者之间的影响机制则主要体现在非粮食产区。最后,针对性提出了政策建议。

基于分频器理论的新能源电网暂态频率稳定分析方法

在分析输配电线路频率相关参数时,将频率固定为额定值的时域仿真法是电力系统暂态频率稳定分析的常用方法。然而,随着新能源比例不断提升,电网各节点频率时空分布差异更为显著,已有传统数值微分频率分析方法难以保证分析精度。因此,文中提出一种基于分频器理论的新型电力系统暂态频率分析方法。与传统频率分析方法相比,该方法所得节点频率可随节点间电气距离变化而改变,在暂态过程中可更准确地刻画瞬态条件,实现各节点实时频率准确获取。通过建立简单含风电的三端系统,分析了基于分频器理论的实现方式,通过仿真验证了所提方法的正确性和优越性,可为新型电力系统频率稳定分析和控制设计提供新的思路和参考方案。

基于量子电压的模数转换器性能评估

相比于用传统半导体器件研制的信号源,约瑟夫森任意波形发生器合成信号的幅值可溯源至自然常数,其输出波形具有超低噪声、超低失真的优点。使用约瑟夫森任意波形发生器评估了National Instruments公司24位数字采集卡PXI 5922的性能。其中,采用零补偿波形合成方法简化系统硬件结构,并且使用高精度、多比例的感应分压器提升评估效率。首先,在10 kHz的带宽内标定了PXI 5922单通道的增益及其稳定性、信噪比、无杂散动态范围、总谐波失真、信纳比和有效位数;其次,标定了PXI 5922两通道不同相位下的相位差;最后,结合电网的谐波情况,以60 Hz的基波频率为例,标定了PXI 5922在12阶谐波以内各谐波的幅度与相位响应。约瑟夫森任意波形发生器的超高精度和宽带输出能力在评估高精度模数转换器的性能方面具有广阔的应用前景。

基于优先级辅助分治策略的多星多站测控资源分配方法

随着商业测控的不断发展和在轨运行的商业卫星数量增多,针对商业地面测控资源有限,以及各种临时的任务需求导致的中低轨卫星测控资源紧张的问题,文章提出了一种基于优先级辅助分治策略的多星多站测控资源分配方法。经仿真分析,结果表明:该方法能够简单灵活的以较少的计算量和内存开销实现分配方案求解,该求解方案能够保证在优先级较高的卫星和任务优先获得调度资源的前提下,最大限度的为卫星和任务提供测控资源,可为测控资源调度系统建设提供参考。

基于参考电流增量法的感应分流器校验方法

感应分流器具有高准确度和高稳定性的电流比例,在电流互感器检定领域有着广泛的应用。文中提出了一种基于参考电流增量法原理的感应式分流器校验方法,文中介绍了参考电流增量法的基本原理;分析了参考电流互感器和差值电流测量线路的设计原理;搭建了感应分流器自校验的实验线路;对研制的双级感应分流器在50 Hz~1 kHz频率范围进行了校验,并对校验结果进行了不确定度分析。实验结果表明,在50 Hz~1 kHz频率范围内,双级感应分流器比值差测量合成标准不确定度优于5×10^(-8) A/A,相位差测量合成标准不确定度优于1×10^(-7) rad。

基于分消走泄法调节湿热体质治疗儿童变态反应性疾病

王有鹏教授通过多年临床经验,分析变态反应性疾病儿童的体质,发现此类儿童多为湿热体质,在治疗上多应用分消走泄法进行治疗。此外,阐述分消走泄法治疗湿热性变态反应性疾病的机理,列举出了分消走泄法代表方剂温胆汤系列合方在临床上的具体应用,如泻白散合温胆汤治疗咳嗽变异性哮喘、从龙汤合温胆汤治疗支气管哮喘、苍耳子散合温胆汤治疗过敏性鼻炎等,进一步印证了分消走泄法通过调节体质治疗儿童变态反应性疾病的有效性与新颖性。

我国居民数字素养鸿沟研究

弥合数字素养鸿沟是推进“数字中国”建设的必由之路。从数字化通用素养、生活应用素养和职业知识素养三个维度构建数字素养测度指标体系,基于2020年中国家庭追踪调查(CFPS)的数据,使用熵权-Topsis法测度我国居民数字素养,并从性别、年龄、学历、城乡和地区五个方面分析数字素养鸿沟。结果表明,我国居民数字素养存在个体和区域数字鸿沟;低学历居民、女性居民、老年人、农村居民存在显著的数字素养鸿沟;西部和东北地区居民相对于东部和中部地区居民数字素养鸿沟更为突出。应从加强数字素养教育、完善数字资源建设和提升区域协调性三个方面提升居民数字素养水平,弥合数字素养鸿沟。

四针汉诺塔问题的算法设计

对传统三针汉诺塔问题的递归求解算法进行简要分析和研究,在此基础上对四针汉诺塔问题进行深入研究,给出四针汉诺塔最优移动次数的算法,并通过穷举法分析提炼出最优参数的取值。

数据挖掘技术及应用课程的项目式教学实践

阐述在数据挖掘技术及应用课程中采用项目式对分课堂教学模式,通过课前任务驱动案例,利用“超星学习通”平台上传相关的网络资源,促使学生更有针对性地听讲,提高该课程的教学质量和教学效率。

复杂河网非恒定流计算模型──单元划分法

本文根据平原河网的水力特性，采用文献［１］的单元划分法，研究了复杂河网非恒定流计算问题，给出了数学模型，并用于镇江河网计算，效果令人满意．将计算结果与河网三级联解法计算结果比较，计算精度相当，并具有节省机时和内存的优点，实用性较强．