Improved upper bound for the degenerate and star chromatic numbers of graphs

Let \(G=G(V,E)\) be a graph. A proper coloring of G is a function \(f:V\rightarrow N\) such that \(f(x)\ne f(y)\) for every edge \(xy\in E\). A proper coloring of a graph G such that for every \(k\ge 1\), the union of any k color classes induces a \((k-1)\)-degenerate subgraph is called a degenerate coloring; a proper coloring of a graph with no two-colored \(P_{4}\) is called a star coloring. If a coloring is both degenerate and star, then we call it a degenerate star coloring of graph. The corresponding chromatic number is denoted as \(\chi _{sd}(G)\). In this paper, we employ entropy compression method to obtain a new upper bound \(\chi _{sd}(G)\le \lceil \frac{19}{6}\Delta ^{\frac{3}{2}}+5\Delta \rceil \) for general graph G.     

基于次梯度投影的泛投资组合选择策略

在线投资组合选择(online portfolio selection)问题是当前量化投资领域一个重要的研究问题.近些年来,可投资标的的爆炸式增长急需能够有效计算的投资组合选择策略,而现有高绩效算法大多具有指数级或多项式级的时间复杂度,不利于在实际中应用.由此,本文提出了一种基于次梯度投影的泛投资组合选择策略SGP.将次梯度投影的思想应用到资产组合构建的过程中,得到策略的再平衡规则.理论上,本文分析了次梯度投影算法的竞争性能,证明了该策略是一个泛投资组合选择策略;并发现该算法具有线性时间复杂度.实证上,验证了SGP策略在美国与中国市场的表现.结果表明,SGP策略能够实现和最新的泛投资组合选择策略相当的收益率,而算法运行时间短于现有策略.参数敏感性分析表明SGP策略对参数选择不敏感;交易成本敏感性分析表明SGP策略能够承受合理的交易成本.     

线上线下融合模式下考虑战略顾客行为的供应链协调研究

在移动电商高速发展和移动支付日益便捷的时代，线上线下融合商务模式正日益成为传统零售、电子商务甚至快递物流企业转型升级的重要方向，影响着供应链运营管理及其优化决策。线上线下融合模式下的战略顾客行为不同于传统模式，其对于供应链运营管理及其优化决策的影响也不同于传统模式。基于O2O运作模式特征，运用战略顾客行为理论、供应链优化与协调理论，本文分别构建了"线上下单+线下体验+线下支付+自行提货"O2O模式1、"线上浏览+线下体验+线上购买+线下配送"O2O模式2、纯线下模式和纯线上模式下考虑战略顾客行为的供应链集中决策模型和契约协调模型，并进行了相应的数值分析，在此基础上，提出了相应的管理启示。研究结果表明：（1）无论是"线上下单+线下体验+线下支付+自行提货"O2O模式1还是"线上浏览+线下体验+线上购买+线下配送"O2O模式2，收益分享契约机制可以有效地实现战略顾客行为下的供应链协调。（2）对比两种O2O模式和两种非O2O模式，O2O模式1和O2O模式2能给供应链及其成员带来更多的利润，而纯线上模式和纯线下模式能给战略顾客带来更高的效用。（3）O2O模式下，制定较高的自提补贴和较低的折扣价格，有利于提高供应链及其成员的运营绩效。（4）O2O模式下，增强产品及其相关服务的实际体验效用，有利于提高供应链整体及其成员的运营绩效，有利于提高战略顾客的净效用。     

带工期指派的产品服务系统订单随机调度问题研究

针对由一个制造工厂和多个区域服务中心组成的服务型制造企业，研究了考虑生产时间和服务时间均具有随机性且工期可指派的产品服务系统（PSS）订单调度问题。首先以最小化订单提前、误工和工期指派费用的期望总额为目标构建问题的优化模型，然后分析目标函数近似值的最优性条件，据此提出加权最短平均生产时间排序规则，并结合该规则与插入邻域局部搜索设计了启发式算法对问题进行求解，最后通过数值仿真验证算法的可行性和有效性。研究表明，提前费用偏差对PSS订单调度与工期指派决策的影响很小，因此企业管理者无需准确估计库存费用也能制定出比较有效的PSS订单调度策略；而工期指派费用偏差对决策结果的影响非常大，因此企业管理者在决策时必须谨慎估计该项费用。     

Modeling the Adenoma and Serrated Pathway to Colorectal CAncer (ASCCA)

Several colorectal cancer (CRC) screening models have been developed describing the progression of adenomas to CRC. Currently, there is increasing evidence that serrated lesions can also develop into CRC. It is not clear whether screening tests have the same test characteristics for serrated lesions as for adenomas, but lower sensitivities have been suggested. Models that ignore this type of colorectal lesions may provide overly optimistic predictions of the screen‐induced reduction in CRC incidence. To address this issue, we have developed the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model that includes the adenoma‐carcinoma pathway and the serrated pathway to CRC as well as characteristics of colorectal lesions. The model structure and the calibration procedure are described in detail. Calibration resulted in 19 parameter sets for the adenoma‐carcinoma pathway and 13 for the serrated pathway that match the age‐ and sex‐specific adenoma and serrated lesion prevalence in the COlonoscopy versus COlonography Screening (COCOS) trial, Dutch CRC incidence and mortality rates, and a number of other intermediate outcomes concerning characteristics of colorectal lesions. As an example, we simulated outcomes for a biennial fecal immunochemical test screening program and a hypothetical one‐time colonoscopy screening program. Inclusion of the serrated pathway influenced the predicted effectiveness of screening when serrated lesions are associated with lower screening test sensitivity or when they are not removed. To our knowledge, this is the first model that explicitly includes the serrated pathway and characteristics of colorectal lesions. It is suitable for the evaluation of the (cost)effectiveness of potential screening strategies for CRC.     

汇率变动对中国物价的传递效应——从成本角度分析

本文利用反映加工贸易的非竞争型投入产出模型和计量经济模型相结合的方法,综合考虑进口品对国内品的替代作用和部门间的价格传导效应,从生产成本角度分情景测算了人民币升值对中国CPI和PPI的影响。测算结果表明,人民币升值可以有效缓解国内的通胀水平,但其传导效应并非是完全的,对CPI和PPI的传递率分别约为13.64%和17.80%。     

A dynamic product quality evaluation based pricing model for perishable food supply chains

Waste stemmed from inappropriate quality control and excessive inventories is a major challenge for perishable food management in grocery retail chains. Improvement of visibility and traceability in food supply chains facilitated by tracking and tracing technologies has great potential to improve operations efficiency. This research aims to reduce food spoilage waste and maximise food retailer's profit through a pricing approach based on dynamically identified food shelf life. The proposed model is evaluated through different pricing policies to exploit the benefits from utilising accurate product shelf life information captured through innovated tracking and monitoring technologies. Numerical analysis is conducted in an illustrative case study.     

Agent‐Based Recovery Model for Seismic Resilience Evaluation of Electrified Communities

In this article, an agent‐based framework to quantify the seismic resilience of an electric power supply system (EPSS) and the community it serves is presented. Within the framework, the loss and restoration of the EPSS power generation and delivery capacity and of the power demand from the served community are used to assess the electric power deficit during the damage absorption and recovery processes. Damage to the components of the EPSS and of the community‐built environment is evaluated using the seismic fragility functions. The restoration of the community electric power demand is evaluated using the seismic recovery functions. However, the postearthquake EPSS recovery process is modeled using an agent‐based model with two agents, the EPSS Operator and the Community Administrator. The resilience of the EPSS–community system is quantified using direct, EPSS‐related, societal, and community‐related indicators. Parametric studies are carried out to quantify the influence of different seismic hazard scenarios, agent characteristics, and power dispatch strategies on the EPSS–community seismic resilience. The use of the agent‐based modeling framework enabled a rational formulation of the postearthquake recovery phase and highlighted the interaction between the EPSS and the community in the recovery process not quantified in resilience models developed to date. Furthermore, it shows that the resilience of different community sectors can be enhanced by different power dispatch strategies. The proposed agent‐based EPSS–community system resilience quantification framework can be used to develop better community and infrastructure system risk governance policies.     

考虑异质性行为的灾后应急物资动态调度优化

在以人道主义为本的应急救援活动中，不可忽视被救灾民和施救决策者们异质性行为的影响。一方面，将各灾民因救援物资需求未被及时满足而呈现的差异化心理痛苦度量成经济损失，并纳入应急救援调度的社会成本这一决策目标中；另一方面，在灾后物资调度决策中，关注具有异质性偏好的各应急决策者所展现出的不同救援态度。结合面向联合机会约束规划的动态供需平衡限制，最终构建一个考虑灾民和决策者们异质性行为的多阶段灾后救援物资分配和应急路径优化模型。采用2008年汶川地震为案例背景，应用遗传算法对模型求解和参数分析，将仿真结果与不考虑异质性行为的传统救援调度方案进行比较，得出一些结论为构建高效的应急救援体系提供有益参考。