An Ordering Policy for Deteriorating Items with Time-Dependent Quadratic Demand and Salvage Value under Permissible Delay in Payment

The article deals with an economic order quantity (EOQ) inventory model for deteriorating items in which the supplier provides the purchaser a permissible delay in payment. This is so when deterioration of units in the inventory is subject to constant deterioration rate, demand rate is quadratic function of time and salvage value is associated with the deteriorated units. Shortages in the system are not allowed to occur. A mathematical formulation is developed when the supplier offers a permissible delay period to the customers under two circumstances: 1) when delay period is less than the cycle of time;and 2) when delay period is greater than the cycle of time. The method is suitable for the items like state-of-the-art aircrafts, super computers, laptops, android mobiles, seasonal items and machines and their spare parts. A solution procedure algorithm is given for finding the optimal order quantity which minimizes the total cost of an inventory system. The article includes numerical examples to support the effectiveness of the developed model. Finally, sensitivity analysis on some parameters on optimal solution is provided.

Time Evolution Caused by Hamiltonian Composed of Quadratic Combination of Canonical Operators and Time-Dependent Two-Mode Fresnel Operator

We show that the time-dependent two-mode Fresnel operator is just the time-evolutional unitary operator governed by the Hamiltonian composed of quadratic combination of canonical operators in the way of exhibiting SU（1,1） algebra. This is an approach for obtaining the time-dependent Hamiltonian from the preassigned time evolution in classical phase space, an approach which is in contrast to Lewis-Riesenfeld＇s invariant operator theory of treating timedependent harmonic oscillators.

Propagator for a Time-Dependent Damped Harmonic Oscillator with a Force Quadratic in Velocity

The propagator for a time-dependent damped harmonic oscillator with a force quadratic in velocity is obtained by making a specific coordinate transformation and by using the method of time-dependent invariant.

Inverse problem of quadratic time-dependent Hamiltonians

Using an algebraic approach, it is possible to obtain the temporal evolution wave function for a Gaussian wavepacket obeying the quadratic time-dependent Hamiltonian(QTDH). However, in general, most of the practical cases are not exactly solvable, for we need general solutions of the Riccatti equations which are not generally known. We therefore bypass directly solving for the temporal evolution wave function, and study its inverse problem. We start with a particular evolution of the wave-packet, and get the required Hamiltonian by using the inverse method. The inverse approach opens up a new way to find new exact solutions to the QTDH. Some typical examples are studied in detail. For a specific timedependent periodic harmonic oscillator, the Berry phase is obtained exactly.

An Optimal Policy with Quadratic Demand, Three-Parameter Weibull Distribution Deterioration Rate, Shortages and Salvage Value

The present paper focuses an optimal policy of an inventory model for deteriorating items with generalized demand rate and deterioration rate. Shortages are allowed and partially backlogged. The salvage value is included into deteriorated units. The main objective of the model is to minimize the total cost by optimizing the value of the shortage point, cycle length and order quantity. A numerical example is carried out to illustrate the model and sensitivity analyses of major parameters are discussed.

A Note on a One-Parameter Weibull Distributed Deteriorating Item EOQ Inventory Model with Varying Quadratic Demand and Delay in Payments

In this paper, an EOQ inventory model is developed for deteriorating items with variable rates of deterioration and conditions of grace periods when demand is a quadratic function of time. The deterioration rate considered here is a special type of Weibull distribution deterioration rate, i.e., a one-parameter Weibull distribution deterioration rate and it increases with respect to time. The quadratic demand precisely depicts of the demand of seasonal items, fashion apparels, cosmetics, and newly launched essential commodities like android mobiles, laptops, automobiles etc., coming to the market. The model is divided into three policies according to the occurrence of the grace periods. Shortages, backlogging and complete backlogging cases are not allowed to occur in the model. The proposed model is well-explained with the help of a simple solution procedure. The three numerical examples are taken to illustrate the effectiveness of the EOQ inventory model along with sensitivity analysis.

山东省2023-2032年物流需求预测分析——基于山东省2002-2022年经验数据

物流业已成为我国第三产业的重要组成部分,高质量的物流业发展对促进经济高效循环、扩大内需等具有重大意义。为了提高物流需求预测的精确度,提出一种基于组合模型预测物流需求的方法:以山东省为例,将灰色预测、二次指数平滑预测及线性回归组合模型应用于物流需求的预测,选取山东省国民经济指标和货运量作为主要影响因素构建指标体系,基于山东省2002—2022年实际历史数据建立模型,将三种模型的优势进行创新性组合,构建科学的组合预测模型以预测山东省未来十年的物流需求量。物流需求的准确预测对山东省的宏观经济有着重要指导作用,可以使山东省物流产业规划与发展及制造业的经验决策更加切实有效,为山东省物流发展提供科学依据。

基于预测需求量的物流仓储中心选址研究

为了解决目前物流仓储中心选址模型存在的脱离实际、需求不合理、成本模型不完备等问题。以长三角地区为例,采用二次指数平滑法预测出该地区27个中心城市未来3年的货物需求量,构建长三角地区物流仓储中心选址模型,利用K-means聚类算法和遗传算法进行仿真实验,并与多种算法进行对比分析。仿真实验表明,K-means聚类算法在求解备选仓储中心问题上有很好的效果,可以使仓储中心到需求点的总距离和最小,遗传算法相比于其他算法在求解仓储中心选址问题上求解速度更快、迭代次数更少、最终结果更精确。结果证明,使用K-means聚类算法和遗传算法求解长三角地区物流仓储中心可以大大提高该地区物流效率并降低物流成本。

Long-Term Electrical Load Forecasting in Rwanda Based on Support Vector Machine Enhanced with Q-SVM Optimization Kernel Function

In recent years, Rwanda’s rapid economic development has created the “Rwanda Africa Wonder”, but it has also led to a substantial increase in energy consumption with the ambitious goal of reaching universal access by 2024. Meanwhile, on the basis of the rapid and dynamic connection of new households, there is uncertainty about generating, importing, and exporting energy whichever imposes a significant barrier. Long-Term Load Forecasting (LTLF) will be a key to the country’s utility plan to examine the dynamic electrical load demand growth patterns and facilitate long-term planning for better and more accurate power system master plan expansion. However, a Support Vector Machine (SVM) for long-term electric load forecasting is presented in this paper for accurate load mix planning. Considering that an individual forecasting model usually cannot work properly for LTLF, a hybrid Q-SVM will be introduced to improve forecasting accuracy. Finally, effectively assess model performance and efficiency, error metrics, and model benchmark parameters there assessed. The case study demonstrates that the new strategy is quite useful to improve LTLF accuracy. The historical electric load data of Rwanda Energy Group (REG), a national utility company from 1998 to 2020 was used to test the forecast model. The simulation results demonstrate the proposed algorithm enhanced better forecasting accuracy.

SIMULATION OF INVENTORY POLICY FOR PRODUCT WITH PRICE AND TIME-DEPENDENT DEMAND FOR DETERIORATING ITEM

In a declining market for goods,we optimize the net profit in business when inventory management allows change in the selling prices n times over time horizon.We are computing optimal number of changes in prices,respective optimal prices,and optimal profit in each of the cycle for a deteriorating product.This paper theoretically proves that for any business setup there exists an optimal number of price settings for obtaining maximum profit.Theoretical results are supported by numerical examples for different setups(data set)and it is found that for every setup the dynamic pricing policy out-performs the static pricing policy.In our model,the deterioration factor has been taken into consideration.The deteriorated units are determined by the recurrence method.Also we studied the effect of different parameters on optimal policy with simulation.For managerial purposes,we have provided some“suggested intervals”for choosing parameters depending upon initial demand,which help to predict the best prices and arrival of customers(demand).

工业用地用水量指标的调研分析

对北方某城市部分企业 1998～ 2 0 0 1年用水量及用地进行了实地调查 ,采用“二次平均法”计算各类工业用地用水量水平。调研统计结果表明各类工业单位用地用水量已呈较稳定的态势。

基于二次插值法的交通需求组合模型算法

交通需求组合模型(CTDM)基于随机效用理论组合了出行—分布—方式—路径选择,突破了传统四步骤模型的局限,并可以描述为一个非线性规划问题.对求解CTDM的部分线性化算法进行分析,提出了在进行步长优化时使用二次插值法得到模拟最优步长的方法.使用经典路网Sioux Falls,将所提出的算法与连续平均法和精确线性搜索算法比较,验证了二次插值法的计算精度高,收敛速度快.

基于客流需求的城际列车时刻表模型改进研究

列车时刻表的编制是铁路旅客运输组织的关键问题,如何优化时刻表,最大限度缩短旅客的旅行时间,具有重要的理论和现实意义.然而,既有基于客流需求的时刻表优化模型大多数假设列车顺序固定或不允许列车间任意越行,离实际尚有一定差距.针对这一问题,本文以最小化旅客在站等待时间和在车旅行时间的线性加权为优化目标,综合考虑列车停站、区间运行、安全间隔、列车容纳能力等约束,在定序无越行和定序有限越行模型的基础上,构建了更一般的非定序任意越行混合整数二次规划模型,并利用ILOG CPLEX分别进行求解.最后,以某城际高铁为例进行案例研究.结果表明,本文所提的非定序任意越行模型求解质量最好,且能有效减少旅客全程旅行时间,具有可行性.

中国农村居民食物消费需求弹性研究

利用1985—2009年的省级面板数据,运用二次型几乎理想需求系统QUAIDS方法模拟中国农村居民食物消费需求系统,估算和比较了东中西三地区在各个时期的粮食、食用油、肉类、蛋类、水产品和蔬菜6种食物的消费支出弹性和需求价格弹性。研究结果表明,粮食、食用油和蛋类的消费支出弹性和需求自价格弹性都为缺乏弹性,消费需求受收入和价格的影响很小;肉类、水产品和蔬菜的消费支出弹性为富有弹性,即农村居民对肉类、水产品和蔬菜的消费需求受到收入的制约。另外,价格也是影响这些食物的消费的重要因素,尤其是水产品和蔬菜的消费需求对价格变化较为敏感。从区域来看,西部地区的粮食和水产品消费支出弹性均明显高于东部地区和中部地区,而其它食物消费支出弹性的地区差异较小。促进农民增收和稳定食物价格,特别是稳定粮食价格,仍然是保障居民食物消费和营养摄入的最重要措施。

考虑产能约束的模糊供应链网络均衡研究

在考虑制造商存在产能约束情形下,研究由多个相互竞争的制造商与零售商组成且零售商处面临着模糊需求的供应链网络均衡问题。利用模糊事件的可信性理论,推导零售商的模糊期望利润。通过变分不等式,构建具有模糊需求的单商品供应链网络均衡状态。最后,利用对数二次近似预测校正算法,讨论分析制造商产能约束对供应链均衡解的影响。

经济全球化对发达国家居民消费结构变化影响研究

通过建立二次几乎完美的需求系统(QUAIDS)模型,本文研究了经济全球化对22个OCED国家居民消费结构变化的影响。主要结论:第一,居民消费结构的升级方向是从对食品、衣着和家庭耐用品等可贸易商品的需求转移为对医疗保健、交通通讯和娱乐文化教育等不可贸易商品的需求;第二,经济全球化与居民消费结构演化方向一致,其中,对外贸易起主导作用,其影响作用远大于FDI;第三,相对于不可贸易商品,居民的可贸易商品消费受经济全球化影响的程度更大,其中,食品消费影响最大,医疗保健消费最小;第四,经济全球化对不同OECD国家居民消费结构变化的影响存在差异性,其中,对经济规模较大国家的作用效果更加明显。

燃料电池分散发电系统阳极部分的建模和控制

燃料电池分散发电系统要求安全性、可靠性和持久性,系统控制十分重要,而用户的实时功率需求以及多设备多仪表多性能参数的特点使整个系统的实时控制变得复杂。该文主要介绍发电系统阳极部分的结构设计和控制实现方法。系统参数关系的强非线性要求控制必须以动态仿真模型为基础。在实时数据的基础上进行物质量上的反馈计算,能够使进入电堆阳极的氢气在系统运行过程中始终维持在理想的湿度水平。将二次型性能指标引入单神经元自适应PID控制,通过调节二级减压阀的气体流量,可以很好地维持电堆膜阳极侧压力始终与阴极侧压力保持理想的压力差水平。经仿真验证系统运行性能良好。

基于二次卡尔曼滤波修正的尾气排放分布

监测机动车尾气排放并制定科学减排措施迫在眉睫,而如何反映由交通需求变化引起排放分布变化是建立尾气排放分布模型的核心问题.按照"交通需求推演-机动车比功率参数确定-交通排放"的思路,利用机动车比功率参数标定交通需求与尾气排放之间的量化关系.以交通需求数据为基础,通过二次卡尔曼滤波修正交通流状态数据和交通分布数据,并通过动态交通分配获取实时车辆工况参数,与典型车型工况曲线匹配,确定车辆比功率在不同速度区间分布,而后,将机动车行驶特征工况参数代入国际车辆排放(international vehicle emission,IVE)模型中确定排放因子,计算得到区域内机动车尾气排放强度.研究表明,以15 min为预测周期,利用二次卡尔曼滤波估计交通需求的平均相对误差为8.89%,且利用IVE尾气模型模拟具有较好的可靠性.预测结果显示,实现基于动态交通需求的行驶工况所构建的交通污染分布模型具有可行性,且二次卡尔曼滤波修正提供了精度的保证,该推演数据可用于分析尾气分布,评价交通改善措施对尾气排放影响,为制定减排策略提供依据.

基于综合需求响应的工业园区联络线功率控制

为平抑可再生能源系统所引起的联络线功率波动,工业园区通常采取整合园区内部所有源荷设备进行统一集中管理或基于电力需求响应的简单源荷互动运行模式,未能充分挖掘园区多能负荷综合需求响应的潜力。在分析工业园区用能特点的基础上,文中提出了一种基于综合需求响应的联络线功率控制方法,建立了园区与生产任务相关的储能、空调负荷以及电动汽车的综合需求响应特性模型,并通过激励多元用户进行需求响应以平抑功率的波动,有效实现了兼顾综合运行成本及跟踪控制误差的联络线功率控制。结合南方某蓄电池生产工业园区进行算例分析,结果表明该方法能降低园区经济损失,使内部负荷用户受益,并确保对联络线功率计划的有效跟踪。

基于组合预测模型的低值医用耗材库存需求预测

目的探讨组合预测模型在低值医用耗材管理中的应用,预测未来一段时间内低值医用耗材的库存需求。方法以杭州某三甲医院低值医用耗材2017年1月至2018年12月的历史领用数据为初始建模数据,采用基于二次指数平滑模型和灰色马尔科夫模型,分别利用变异系数法、简单加权法和方差倒数法来确定组合权重的组合预测模型,对低值医用耗材2019年1—4月的库存需求建立预测模型。结果利用三种组合预测模型分别计算得到的预测值的相对误差均值都远小于5%。其中使用方差倒数法确定权重的组合预测的预测准确度最高,其预测值的相对误差均值为1.39%,接近实际值。结论由方差倒数法确定权重的基于二次指数平滑模型和灰色马尔科夫模型的组合模型能够准确地对低值医用耗材进行短期预测,根据组合模型的预测值,可以为低值医用耗材的库存准备提供可靠依据。