智能反射面辅助的无线网络加权和速率优化设计

针对智能反射面(intelligent reflecting surface, IRS)辅助的无线网络传输设计的目标是通过联合设计基站处的发送波束形成向量和IRS的反射系数,在满足基站发射功率和IRS单位模约束的条件下,使多个地面用户的加权和速率最大化。为了求解非凸的目标函数,提出一种交替优化方法,其中采用黎曼流形梯度(Riemannian manifold gradient, RMG)方法来优化反射系数,使用二分搜索法优化发送波束形成向量。此外,为了降低RMG方法的复杂度,设计了一种智能元素块坐标下降方法。仿真结果验证了所提算法的有效性,并且表明通过优化设计反射系数,IRS可显著提高无线网络的频谱效率。     

带内双频电磁辐射对频率步进连续波雷达的虚警干扰规律

为掌握带内双频电磁辐射对雷达的虚警干扰规律,以频率步进连续波雷达为研究对象,基于理论分析与效应试验,研究了虚警目标的电平变化规律、波形特征以及出现位置规律。结果表明:受试雷达在带内双频电磁辐射作用下,不考虑互调干扰时,至多产生两个位置随机的“山丘型”虚警目标,两者距离差与双频干扰频差有关。双频干扰中两分量互相压制,即当任一干扰分量强度恒定时,随着另一个分量的增强,前者形成的虚警目标电平缓慢下降,最终降速基本恒定,而后者形成虚警目标电平逐渐升高,直至电平恒定;若双频干扰信号两分量同比例增强,则两个虚警目标电平均在初期近似线性上升,而后增速逐渐降低至零。     

新型冠状病毒肺炎疫情全球爆发期间民众群体心理研究【专题】

本文从认知过程、情绪过程和意志过程这三种心理过程的角度对2020年初席卷全球的新冠肺炎疫情期间的民众群体心理进行数据收集与初步分析,并在此基础上提出疫情期间民众群体心理的管理建议与对策,具体包括：引导对于新冠肺炎疫情的正确群体认知、调节新冠肺炎疫情引起的消极群体情绪和控制可能引发次生危机的社会意志与行为倾向三个方面。     

Experimental study on the detonation process of a pulse detonation engine with ionized seeds

An experimental platform of a pulse detonation engine (PDE) was established to study the effect of different K₂CO₃ ionized seed mass contents on the detonation process. The pressure and ion concentration were detected in the detonation process of the PDE with different contents of ionized seeds. The initiation process of the PDE at different ignition frequencies was studied. The results show that the gas conductivity in the detonation process increased by adding ionized seeds to the PDE tube, and the conductivity increased with the increase in ionized seed mass content. With the increase in ionized seed mass content, the range of the conductivity decreased. The PDE was successfully ignited and formed a stable detonation wave at ignition frequencies of 5 Hz and 10 Hz, and the peak pressure of the stable detonation with the ignition frequency of 5 Hz was 17% higher than that with an ignition frequency of 10 Hz. The detonation wave intensity was weakened and degenerated to a shock wave that propagated in the tube without the fuel filled at the ignition frequency of 20 Hz.     

Military Off the Shelf Procurements: A Norwegian Case Study

Buying off the shelf procurements (OTS) has become an important part of the national acquisition strategy in several countries, and this paper seeks to bring empirical evidence on OTS as the preferred acquisition strategy by use of data from 2015 to 2022 investment portfolio of the Norwegian Armed Forces. We develop definitions for three categories of procurement – OTS, modified OTS and development projects – as well as a method to classify projects into these categories. Our first finding is that the characteristics of OTS projects correspond to modified OTS and development projects. Our second finding indicates that OTS projects perform better when it comes to the completion of projects according to the initial schedule, compared to development projects.     

Energy‐efficient scheduling for sustainable manufacturing systems with renewable energy resources

Environmentally friendly energy resources open a new opportunity to tackle the problem of energy security and climate change arising from wide use of fossil fuels. This paper focuses on optimizing the allocation of the energy generated by the renewable energy system to minimize the total electricity cost for sustainable manufacturing systems under time‐of‐use tariff by clipping the peak demand. A rolling horizon approach is adopted to handle the uncertainty caused by the weather change. A nonlinear mathematical programming model is established for each decision epoch based on the predicted energy generation and the probability distribution of power demand in the manufacturing plant. The objective function of the model is shown to be convex, Lipchitz‐continuous, and subdifferentiable. A generalized benders decomposition method based on the primal‐dual subgradient descent algorithm is proposed to solve the model. A series of numerical experiments is conducted to show the effectiveness of the solution approach and the significant benefits of using the renewable energy resources.     

Optimal allocation of minimal repairs in parallel and series systems

In reliability engineering, the concept of minimal repair describes that the repair brings the failed unit (eg, system or component) to the situation which is same as it was just before the failure. With the help of the well‐known Gamma‐Poisson relationship, this paper investigates optimal allocation strategies of minimal repairs for parallel and series systems through implementing stochastic comparisons of various allocation policies in terms of the hazard rate, the reversed hazard rate, and the likelihood ratio orderings. Numerical examples are presented to illustrate these findings as well. These results not only strengthen and generalize some known ones in the seminal work of Shaked and Shanthikumar, but also solve the open problems proposed by Chahkandi et al.'s study and Arriaza et al.'s study.     

基于层次分析法的军校学员体能训练评估

针对目前军校学员军事体育训练评估难以量化考核的问题,提出了基于层次分析法的军校学员体能训练评估方法。首先,通过建立评估指标体系,构建评估指标判断矩阵;其次,进行归一化并计算指标组合权重,构建评估基本模型;最后,利用评估模型对学员体能训练进行综合评估。结果表明本文提出的方法能够对军校学员体能训练进行有效评估,相比于传统考核评估方法更能反映出学员体能的真实状况,突出学员体能特征,开展针对性训练。      

Single‐machine scheduling with deadlines to minimize the total weighted late work

We consider scheduling a set of jobs with deadlines to minimize the total weighted late work on a single machine, where the late work of a job is the amount of processing of the job that is scheduled after its due date and before its deadline. This is the first study on scheduling with the late work criterion under the deadline restriction. In this paper, we show that (i) the problem is unary NP‐hard even if all the jobs have a unit weight, (ii) the problem is binary NP‐hard and admits a pseudo‐polynomial‐time algorithm and a fully polynomial‐time approximation scheme if all the jobs have a common due date, and (iii) some special cases of the problem are polynomially solvable.     

Oligopolistic contracting: Channel coordination under competition

We study contracts between a single retailer and multiple suppliers of two substitutable products, where suppliers have fixed capacities and present the retailer cost contracts for their supplies. After observing the contracts, the retailer decides how much capacity to purchase from each supplier, to maximize profits from the purchased capacity from the suppliers plus his possessed inventory (endowment). This is modeled as a noncooperative, nonzero‐sum game, where suppliers, or principals, move simultaneously as leaders and the retailer, the common agent, is the sole follower. We are interested in the form of the contracts in equilibrium, their effect on the total supply chain profit, and how the profit is split between the suppliers and the retailer. Under mild assumptions, we characterize the set of all equilibrium contracts and discuss all‐unit and marginal‐unit quantity discounts as special cases. We also show that the supply chain is coordinated in equilibrium with a unique profit split between the retailer and the suppliers. Each supplier's profit is equal to the marginal contribution of her capacity to supply chain profits in equilibrium. The retailer's profit is equal to the total revenue collected from the market minus the payments to the suppliers and the associated sales costs.