浅谈移动Ad Hoc网络按需路由协议中的篡改攻击问题

由于移动Ad Hoc网络具有动态变化的特性以及自组织和多跳性的特点,更容易遭受多种恶意攻击。其中篡改攻击就是最严重的一种攻击。本文详细剖析了篡改攻击问题,针对此问题提出了一种简洁的解决方案。此方案利用路由发现过程中中间结点计算的MAC值以及邻居维护机制提供的认证信息一起能够很好的抵抗篡改攻击,提高了路由协议的安全性。     

基于复杂自适应供应网络脆弱性的突发风险研究

本文将全球化背景下的供应链系统视为复杂自适应供应网络,以复杂自适应供应网络脆弱性分析为视角,对当前供应链突发风险管理这个热点问题展开了研究,采用微观与宏观相结合、定性分析与定量分析相结合的方法对突发风险进行了分析,建立了突发事件条件下复杂自适应供应网络的脆弱性评价模型,并结合具体实例进行了验证。结果表明,供应链突发风险管理策略应该尽可能使得供应链各子系统脆弱性以及子系统各脆弱性因素之间的相互影响保持均衡,不存在相对脆弱的短板。这为企业从全局考虑改善供应链系统性能提供了的最佳途径。     

Security in the cyber supply chain: Is it achievable in a complex,interconnected world?

The Cold War, with its symmetry and certainties that shaped the way we make sense of the world, is over. We now live in a time when the unimaginably complex and inextricably interconnected systems of the cyber domain make nations, societies, and institutions highly vulnerable to disruption. A deep-rooted sense of denial prevents many of us from acknowledging just how vulnerable the cyber supply chain really is. We must act, or risk catastrophe—but any actions we might take must be rooted in the reality of the world as it is, rather than in the world we once knew.     

Agility,adaptability, and alignment: new capabilities for PSM in a post-pandemic world

Purchasing and Supply Management (PSM) was overwhelmed by a perfect storm during the Covid-19 emergency, in both the public and private sectors. Many organizations were caught unprepared, and it became evident that they did not have the capabilities needed to quickly react and respond to changes caused by the pandemic. This poses the questions of where and how PSM systems should evolve to better contribute to organizational responsiveness to crisis events in the future. In this Editorial, which introduces the “PSM learning from the pandemic: transforming for better crisis management” Notes and Debates special issue, the six contributions included in this issue are discussed. We relate the evidence included in the contribution to three critical capabilities of supply chains in the post-Covid-19 business environment – agility, adaptability, and alignment – and, in this editorial, we discuss how they can be conceptualized from a PSM perspective. From a theoretical perspective, we provide a starting point for future studies that want to focus on how these capabilities can be deployed in PSM, and how they impact the supply network design. From a managerial perspective, these definitions provide preliminary points of discussion on what organizations can do to enhance these capabilities in the future.     

Multilevel IRT models for the analysis of satisfaction for distance learning during the Covid-19 pandemic

The Covid-19 pandemic played a relevant role in the diffusion of distance learning alternatives to “traditional” learning based on classroom activities, to allow university students to continue attending lessons during the most severe phases of the pandemic. In such a context, investigating the students' perspective on distance learning provides useful information to stakeholders to improve effective educational strategies, which could be useful also after the end of the emergency to favor the digital transformation in the higher educational setting.Here we focus on the satisfaction in distance learning for Italian university students. We rely on data comprising students enrolled in various Italian universities, which were inquired about several aspects related to learning distance.We explicitly take into account the hierarchical nature of data (i.e., students nested in universities) and the latent nature of the variable of interest (i.e., students' learning satisfaction) through a multilevel Item Response Theory model with students' and universities' covariates.As the main results of our study, we find out that distance learning satisfaction of students: (i) depends on the University where they study; (ii) is affected by some students' socio-demographic characteristics, among which psychological factors related to Covid-19; (iii) is affected by some observable university characteristics.     

A Summary of Attack Methods and Confidentiality Protection Measures for Fully Automated Remote Analysis Systems

This paper presents a summary of the current state of research on reducing the risk of disclosure related to what may be called “non‐traditional” outputs for statistical agencies. Whereas traditional outputs include frequency tables, magnitude tables and public use microdata files, non‐traditional outputs include outputs associated with user‐defined exploratory data analysis and statistical modelling offered through a remote analysis system. In remote analysis, a system accepts a query from an analyst, runs it on data held in a secure environment, and then returns the results to the analyst. There is a considerable current interest in fully automated remote analysis systems, because these have the potential to enable agencies to respond to growing researcher demand for more and more detailed data. In practice, a range of protective measures is most effective in remote analysis, and the choice of this range depends heavily on the context including the regulatory environment, the dataset itself, and the purpose of the access. This paper provides a summary of known attack methods on remote analysis system outputs, focussing on exploratory data analysis and linear regression. The paper also summarizes the associated suggested protective measures designed to prevent disclosures and thwart attacks in fully automated remote analysis systems. Some commentary on the attacks and measures is provided.     

Deriving equity risk premium using dividend futures

In this paper I present a simple stock price decomposition model using the dividend discount model and dividend futures. The main contribution of this paper is the use of dividend futures which represent the risk-adjusted expectations of future dividends. This allows for the calculation of the implied equity risk premium and the decomposition of stock price movements into individual components. Due to the use of daily market data, this method can take into account the structural changes associated with falling interest rates and the Covid-19 pandemic. I empirically show the risk premium development of the S&P 500 Index and Euro Stoxx 50 Index in the last decade.     

直面网络经济--试论网络经济的内涵、形成及影响

当前网络经济以及企业如何在网络环境中生存和发展,已经成为管理学界和公司管理者最为热衷的话题之一。文章首先回答了什么是网络经济,肯定了网络经济是一种新型的经济形态,并简要说明了网络经济兴起的原因。最后重点论述了网络经济所产生的作用和影响,笔者认为对于这个问题可以从经济发展、产业结构和企业管理三个层面来分析。     

疫情防控常态化下的世界经济战略走向

新冠疫情的出现冲击了世界经济,从经济全球化和全球经济治理体系两个维度分析疫情对世界经济的影响以及世界经济未来走向,研究发现:(1)新冠疫情通过影响全球价值链、贸易投资和就业环境阻碍经济全球化进程,中美矛盾升级、原有治理体系规则未与时俱进和激进政策的不确定性对全球经济治理体系提出新的挑战;(2)新冠疫情强化了世界各国对人类命运共同体的认识,将人类命运共同体融入全球治理体系将是未来治理的重要趋势;(3)新冠疫情可能会使世界经济格局出现新的变化,而中国在此次疫情中高效率的抗疫举措将进一步提升自身在世界经济格局中的地位和参与度。     

Big data for cyber physical systems in industry 4.0: a survey

ABSTRACT

With the technology development in cyber physical systems and big data, there are huge potential to apply them to achieve personalization and improve resource efficiency in Industry 4.0. As Industry 4.0 is the relatively new concept originated from an advanced manufacturing vision supported by the German government in 2011, there are only several existing surveys on either cyber physical systems or big data in Industry 4.0. In addition, there are much less surveys related to the intersection between cyber physical systems and big data in Industry 4.0. However, cyber physical systems are closely related to big data in nature. For example, cyber physical systems will continuously generate a large amount of data which requires the big data techniques to process and help to improve system scalability, security, and efficiency. Therefore, we conduct this survey to bring more attention to this critical intersection and highlight the future research direction to achieve the fully autonomy in Industry 4.0.     

Nexus between drivers of COVID-19 and country risks

COVID-19 has disrupted all spheres of life, including country risk regarding the exposure of economies to multi-dimensional risk drivers. However, it remains unexplored how COVID-19 has impacted different drivers of country risk in a probabilistic network setting. This paper uses two datasets on country-level COVID-19 and country risks to explore dependencies among associated drivers using a Bayesian Belief Network model. The drivers of COVID-19 risk, considered in this paper, are hazard and exposure, vulnerability and lack of coping capacity, whereas country risk drivers are economic, financing, political, business environment and commercial risks. The results show that business environment risk is significantly influenced by COVID-19 risk, whereas commercial risk (demand disruptions) is the least important factor driving COVID-19 and country risks. Further, country risk is mainly influenced by financing, political and economic risks. The contribution of this study is to explore the impact of various drivers associated with the country-level COVID-19 and country risks in a unified probabilistic network setting, which can help policy-makers prioritize drivers for managing the two risks.     

Herding in the bad times: The 2008 and COVID-19 crises

The objective of this paper is to analyze the imitation behavior of investors in especially convulsed periods, such as the 2008 financial crisis and the recent global pandemic, both of which could affect investors' emotions and behavior, although both have different characteristics and might have different implications. The cross-sectional dispersion of returns is used to measure the level of herding in the markets of Spain and Portugal, using a survivorship-bias-free dataset of daily stock returns during the period January 2000–May 2021, in turn divided into several sub-periods classified as pre-2008 crisis, 2008 crisis, post-2008 crisis, Covid-19 and post Covid-19. Additionally, the existence is studied of differences between days of positive and negative returns, or between days of high volatility compared to the rest, and whether the cross-sectional dispersion of returns in one market is affected by the cross-sectional dispersion of returns in the other market. The results indicate that herding appears with greater intensity in periods prior to the crisis, disappearing during the financial crisis and reappearing, although with less intensity, after it, while it is not generally detected in Covid-19 times. However, herding behavior can be observed in the market during the pandemic on high volatility days.     

Mitigating shortage and distribution costs in damaged water networks

Recent events have sparked renewed interest in disaster mitigation for public infrastructures. Presidential Decision Directive 63 identifies water distribution as being among the most vital and vulnerable of our large-scale infrastructures. Water distribution networks are vulnerable to threats such as chemical and biological contamination, cyber attacks on computer-based management systems, and physical destruction from acts of nature and intentional attack. This research develops methods for configuring the undamaged portion of the water network to mitigate the consequences of physical destruction. The approach is to find a hydraulically feasible residual network that can be pressurized to meet the demand of a subset of demand sectors. Demand sectors not pressurized then receive water through truck distribution from pressurized sectors. The objective is to minimize weighted water shortage and water truck distribution costs by identifying sectors to pressurize along with an assignment of unpressurized sectors to pressurized sectors for water delivery by truck. The paper develops an optimization model, describes a solution method, and presents computational results for three example networks.     

Economic uncertainty and national bitcoin trading activity

This study analyzes the dynamics between bitcoin trading, price activities, and economic surprise shocks from a broad and novel perspective on a national level. We start by estimating the response of bitcoin trading in terms of volume and volatility to economic surprises. Following this, we extend our framework by applying a Generalized AutoRegressive Conditional Heteroskedasticity model to get an indication of the volatility reaction of national bitcoin activities to economic surprise shocks. Our results show that local and global shocks affect local bitcoin activities and trading volatilities, confirming that economic events affect bitcoin markets. We argue that increased trading activity, coupled with a price reaction, indicates that bitcoin might be considered a hedge or safe haven asset against economic uncertainty. We find evidence that bitcoin is treated as a speculative asset against negative economic policy uncertainty shocks in Canada pre-Covid-19. These results change during the Covid-19 pandemic, leading to a significant structural break. Here, we find indications that bitcoin might be treated as a safe-haven asset in New Zealand and Australia. This shows that bitcoin behaves differently depending on the studied country, underlining the importance of country-level studies. It also shows that bitcoin is a new asset that is evolving rapidly and that the period in which it is studied is important.     

一位痊愈返岗医生的7天

"很多人问我怎么不休息一下?医护力量这么紧张,我到一线,医治一个是一个,得对得起自己的良心。"赵智刚医生说接通电话时,赵智刚医生刚下夜班。那是2月8日早上,从7日下午5:30到8日早上8点,他工作了整整14.5个小时。这对一个刚刚痊愈3天的新冠肺炎患者来说,无疑是体力和精力上的巨大考验。     

基于Apriori算法的一种改进异常入侵检测模型的研究

近年来网络入侵检测系统成为计算机系统安全架构的关键性问题。异常攻击检测效果差是现有系统目前遇到的首要问题。因此,基于数据挖掘技术提出一种模型来预测新颖的攻击并实时生成防火墙规则。运用了Apriori算法来创建一个自动防火墙规则发生器用以监测新的异常攻击。结果表明改进后的算法高效的提高异常入侵检测系统的性能。     

Short-term Covid-19 forecast for latecomers

The number of new Covid-19 cases is still high in several countries, despite vaccination efforts. A number of countries are experiencing new and severe waves of infection. Therefore, the availability of reliable forecasts for the number of cases and deaths in the coming days is of fundamental importance. We propose a simple statistical method for short-term real-time forecasting of the number of Covid-19 cases and fatalities in countries that are latecomers—i.e., countries where cases of the disease started to appear some time after others. In particular, we propose a penalized LASSO regression model with an error correction mechanism to construct a model of a latecomer country in terms of other countries that were at a similar stage of the pandemic some days before. By tracking the number of cases in those countries, we use an adaptive rolling-window scheme to forecast the number of cases and deaths in the latecomer. We apply this methodology to 45 countries and we provide detailed results for four of them: Brazil, Chile, Mexico, and Portugal. We show that the methodology performs very well when compared to alternative methods. These forecasts aim to foster better short-run management of the healthcare system and can be applied not only to countries but also to different regions within a country. Finally, the modeling framework derived in the paper can be applied to other infectious diseases.     

Inclusive purchasing and supply chain resilience capabilities: Lessons for social sustainability

In the face of unexpected changes in their dynamic business environment, purchasing and supply chain (SC) managers have been challenged to boost SC resilience while maintaining their sustainability concerns. In this changing environment, this paper aims to explore: (1) how (social) sustainability affects SC resilience and (2) what the role of purchasing is for SC resilience. Through a dynamic capability view as the theoretical lens, we investigate whether and how an inclusive purchasing programme could enhance SC resilience capabilities to cope with the Covid-19 outbreak. We developed a Case study with various SC members of a multinational cosmetics company that, despite suffering from a sudden demand disruption during the outbreak, maintained its sustainability actions. The results show that four operational SC resilience capabilities were amplified: ‘visibility’, ‘adaptability’, ‘collaboration’ and ‘financial strength’. In addition, a new capability entitled ‘empowerment’ was mobilised during this period. These factors helped the inclusive purchasing maintenance and were essential to supporting social sustainability. In addition, our results show that sustainable PSM, which is overlooked in the literature, is key for SC resilience. This article contributes to theory and practice because it demonstrates the role and relevance of (inclusive) purchasing in a company's ability to cope with SC disruptions, such as those resulting from the outbreak.     

Factor market rivalry and interindustry competitive dynamics

We study competitive dynamics by using 10 years of data from the biotech industry on patent infringement lawsuits because they capture offensive actions and defensive responses. Results suggest that larger patent portfolios, long‐term partnerships, and short‐term agreements lead to factor market rivalry. Specifically, long‐term research partnerships are associated with lower proclivity and vulnerability to attack, while short‐term licensing and marketing agreements with increased proclivity and vulnerability to attack. Lastly, although nonbiotech companies attack biotech firms, the proclivity of the latter to launch cross‐industry attacks is not significant. We discuss how the results contribute to competitive dynamics research and theory.     

Covid-19 attacks the body of purchasing and supply management: A medical check of the immune system

Much like the immune system of the body, the ‘immune system’ of purchasing and supply management (PSM) is also affected by the Covid-19 virus. Medicine must hinder the spread of the virus and outbreak of disease, just as PSM must prevent risk events and handle supply disruptions. The existing debate on supply resilience and robustness can be demonstrated using this medical analogy. The purpose of this article was to perform a medical check of the ‘PSM immune system’ to identify lessons and research gaps when confronted with a low-frequency-high-impact event such as the pandemic. As a provocative note, this article identifies research gaps in elements of the immune system of PSM (e.g., helper cells – consultancy support or memory cells – feedback loops). The results call for a more holistic debate on the immune system of PSM. Two approaches for research on ‘conventional’ or ‘alternative’ risk management schools of thought are presented as a basis for future discourse on how to improve the PSM immune system.