The Risk-Averse Static Stochastic Knapsack Problem

Author(s):  
Yasemin Merzifonluoglu ◽  
Joseph Geunes

This research proposes and analyzes new models for a stochastic resource allocation problem that arises in a variety of operations contexts. One of the primary contributions of the paper lies in providing a succinct, robust, and general model that can address a range of different risk-based objectives and cost assumptions under uncertainty. Although the model expression is relatively simple, it embeds a reasonably high degree of underlying complexity, as the analysis shows. In addition, in-depth analysis of the model, both in its general form and under various specific risk measures, uncovers some interesting and powerful insights regarding the problem trade-offs. Furthermore, this analysis leads to a highly efficient class of heuristic algorithms for solving the problem, which we demonstrate via numerical experimentation to provide close-to-optimal solutions. This computational benefit is a critical element for solving a class of broadly applicable larger problems for which our problem arises as a subproblem that requires repeated solution.

2021 ◽  
Vol 54 (3) ◽  
pp. 1-36
Author(s):  
Syed Wasif Abbas Hamdani ◽  
Haider Abbas ◽  
Abdul Rehman Janjua ◽  
Waleed Bin Shahid ◽  
Muhammad Faisal Amjad ◽  
...  

Cyber threats have been growing tremendously in recent years. There are significant advancements in the threat space that have led towards an essential need for the strengthening of digital infrastructure security. Better security can be achieved by fine-tuning system parameters to the best and optimized security levels. For the protection of infrastructure and information systems, several guidelines have been provided by well-known organizations in the form of cybersecurity standards. Since security vulnerabilities incur a very high degree of financial, reputational, informational, and organizational security compromise, it is imperative that a baseline for standard compliance be established. The selection of security standards and extracting requirements from those standards in an organizational context is a tedious task. This article presents a detailed literature review, a comprehensive analysis of various cybersecurity standards, and statistics of cyber-attacks related to operating systems (OS). In addition to that, an explicit comparison between the frameworks, tools, and software available for OS compliance testing is provided. An in-depth analysis of the most common software solutions ensuring compliance with certain cybersecurity standards is also presented. Finally, based on the cybersecurity standards under consideration, a comprehensive set of minimum requirements is proposed for OS hardening and a few open research challenges are discussed.


2021 ◽  
Vol 13 (1) ◽  
pp. 124-132
Author(s):  
Volodymyr Rudzinskyi ◽  
◽  
Bohdan Yemets ◽  
Serhii Melnychuk ◽  
Oleksandr Ryabchuk ◽  
...  

The article deals with some criteria that substantiate the design and operational performance of automobiles running on alternative fuels; economic efficiency of operation of such vehicles, their ecological conformity; the level of complexity of the design of converted automobiles; labor intensity of their maintenance, repair, etc. ; traction-speed and other different, in comparison with the basic, properties of automobiles while working on alternative fuel (AF); energy consumption and (or) cost price of AF; efficiency of power plant and (or) car on AF; the degree of commissioning (mass production) and further prospects for the development of the design of such automobiles; state of support developed structures at the national (local) level. An expert assessment of the adopted criteria in the order of their importance is made. Along with the analysis of scores, which are presented in points, it is used the ranking method to study the results of the survey of experts. This allows applying the values of the established optimal criteria to justify the operation of vehicles during their work on the AF. The analysis of the matrix correlation shows that the numerical estimates set by the accepted criteria are characterized by a high degree of correlation, and experts are generally unanimous in assessing their importance. The most important criteria for the operation of automobiles on the AF are economic efficiency, traction and speed and other, different compared to the basic, the properties of automobiles while working on the AF. Other criteria are also quite important, the weights for them are much higher than 7%, and they also should be taken into account while conducting an in-depth analysis and synthesis of indicators of optimal operation of automobiles on the AF. In addition, it is important that the group of criteria that characterize only one type of automobile when working on the AF (for example, the degree of commissioning) experts gave only about 17% of the importance.


2021 ◽  
Vol 14 (5) ◽  
pp. 785-798
Author(s):  
Daokun Hu ◽  
Zhiwen Chen ◽  
Jianbing Wu ◽  
Jianhua Sun ◽  
Hao Chen

Persistent memory (PM) is increasingly being leveraged to build hash-based indexing structures featuring cheap persistence, high performance, and instant recovery, especially with the recent release of Intel Optane DC Persistent Memory Modules. However, most of them are evaluated on DRAM-based emulators with unreal assumptions, or focus on the evaluation of specific metrics with important properties sidestepped. Thus, it is essential to understand how well the proposed hash indexes perform on real PM and how they differentiate from each other if a wider range of performance metrics are considered. To this end, this paper provides a comprehensive evaluation of persistent hash tables. In particular, we focus on the evaluation of six state-of-the-art hash tables including Level hashing, CCEH, Dash, PCLHT, Clevel, and SOFT, with real PM hardware. Our evaluation was conducted using a unified benchmarking framework and representative workloads. Besides characterizing common performance properties, we also explore how hardware configurations (such as PM bandwidth, CPU instructions, and NUMA) affect the performance of PM-based hash tables. With our in-depth analysis, we identify design trade-offs and good paradigms in prior arts, and suggest desirable optimizations and directions for the future development of PM-based hash tables.


Author(s):  
G. T. Alckmin ◽  
L. Kooistra ◽  
A. Lucieer ◽  
R. Rawnsley

<p><strong>Abstract.</strong> Vegetation indices (VIs) have been extensively employed as a feature for dry matter (DM) estimation. During the past five decades more than a hundred vegetation indices have been proposed. Inevitably, the selection of the optimal index or subset of indices is not trivial nor obvious. This study, performed on a year-round observation of perennial ryegrass (n&amp;thinsp;=&amp;thinsp;900), indicates that for this response variable (i.e. kg.DM.ha<sup>&amp;minus;1</sup>), more than 80% of indices present a high degree of collinearity (correlation&amp;thinsp;&amp;gt;&amp;thinsp;|0.8|.) Additionally, the absence of an established workflow for feature selection and modelling is a handicap when trying to establish meaningful relations between spectral data and biophysical/biochemical features. Within this case study, an unsupervised and supervised filtering process is proposed to an initial dataset of 97 VIs. This research analyses the effects of the proposed filtering and feature selection process to the overall stability of final models. Consequently, this analysis provides a straightforward framework to filter and select VIs. This approach was able to provide a reduced feature set for a robust model and to quantify trade-offs between optimal models (i.e. lowest root mean square error &amp;ndash; RMSE&amp;thinsp;=&amp;thinsp;412.27&amp;thinsp;kg.DM.ha<sup>&amp;minus;1</sup>) and tolerable models (with a smaller number of features &amp;ndash; 4 VIs and within 10% of the lowest RMSE.)</p>


2017 ◽  
Vol 43 (4) ◽  
pp. 765-787 ◽  
Author(s):  
Randall Germain ◽  
Herman Mark Schwartz

AbstractThe rise of China has sparked a debate about the economic and political consequences for the global economy of the internationalisation of the renminbi. We argue that the dominant focus of this literature – primarily the external conditions and requirements for a national currency to become an international currency – misspecifies the connections between the international and domestic requirements for currency internationalisation, as well as the potential to become the dominant international reserve currency. We correct this oversight by developing an integrated theoretical framework that highlights the domestic adjustment costs which a state must accommodate before its currency can carry the weight of internationalisation. These costs constitute a critical element of an international currency’s ‘political economy’, and they force states to negotiate contentious social trade-offs among competing domestic claims on finite public resources in a sustainable manner. Our analysis suggests that the likelihood of China being able to successfully negotiate the social costs associated with running a fully internationalised currency is currently very low, precisely because this will place unacceptable pressure on groups benefiting from the economic and political status quo. This further suggests that the American dollar will remain unchallenged as the global economy’s pre-eminent international currency for the foreseeable future.


1997 ◽  
Vol 20 (2) ◽  
pp. 279-303 ◽  
Author(s):  
Réjean Plamondon ◽  
Adel M. Alimi

This target article presents a critical survey of the scientific literature dealing with the speed/accuracy trade-offs in rapid-aimed movements. It highlights the numerous mathematical and theoretical interpretations that have been proposed in recent decades. Although the variety of points of view reflects the richness of the field and the high degree of interest that such basic phenomena attract in the understanding of human movements, it calls into question the ability of many models to explain the basic observations consistently reported in the field. This target article summarizes the kinematic theory of rapid human movements, proposed recently by R. Plamondon (1993b; 1993c; 1995a; 1995b), and analyzes its predictions in the context of speed/accuracy trade-offs. Data from human movement literature are reanalyzed and reinterpreted in the context of the new theory. It is shown that the various aspects of speed/ accuracy trade-offs can be taken into account by considering the asymptotic behavior of a large number of coupled linear systems, from which a delta-lognormal law can be derived to describe the velocity profile of an end-effector driven by a neuromuscular synergy. This law not only describes velocity profiles almost perfectly, it also predicts the kinematic properties of simple rapid movements and provides a consistent framework for the analysis of different types of speed/accuracy trade-offs using a quadratic (or power) law that emerges from the model.


Management ◽  
2021 ◽  
Author(s):  
Simone Carmine ◽  
Wendy K. Smith

Organizational paradox offers a theory of the nature and management of competing demands. Historically, the dominant paradigm in organizational theory depicted competing demands as trade-offs or dilemmas that could be resolved by choosing one option. In the late 1960s, scholars such as Joan Woodward, Paul Lawrence, and Jay Lorsch introduced contingency theory, suggesting that individuals resolve these tensions by taking the context and environment into account. Paradox theory offers an alternative approach, suggesting that these tensions cannot be resolved. By depicting competing demands as tensions that are not only contradictory, but also interdependent and persistent, paradox theory argues that actors need to accept, engage, and navigate tensions rather than resolve them. Foundational work on paradox in organizations emerged starting in the late 1970s and 1980s. This work drew from rich insights across a variety of disciplines, including Eastern philosophy (Taoism, Confucianism), Western philosophies (Hegel, Heraclitus), psychodynamics (Jung, Adler, Frankel), psychology (Schneider, Watzlawick), political science (Marx, Engel), communications and sociology (Taylor, Bateson), and negotiations and conflict resolution (Follett). More recent work has advanced foundational building blocks toward a theory of paradox. Underlying the theory of paradox is ontologies of dualism—two opposing elements that together form an integrated unity—and dynamism— ongoing change. Scholars have defined paradox as tensions that are contradictory, interdependent, and persistent, noting their dynamic, everchanging, cyclical nature. Some scholars describe the origins of paradox as inherent within systems, while others highlight their social construction through cognition, dialogue, and rationality. Still others explore the relationship between the inherent and socially constructed nature of tensions, depicting tensions as latent within a system, becoming salient through social construction and external conditions. Moreover, some scholars focus more on understanding the poles of paradox, while others depict the ongoing dynamic interaction and evolution. As paradox theory continues to grow and expand, scholars have also added complexity to our understanding, emphasizing paradoxes as nested across levels and as knotted and interwoven across various tensions, while also taking into account the power dynamics, uncertainty, plurality, and scarcity of systems within which paradoxes emerge. This article identifies scholarship that depicts these varied approaches and ideas, providing the foundations of paradox theory for scholars new to this field and in-depth analysis for those seeking to expand their understanding. Section 1 offers foundational work. Section 2 introduces early scholarship that launched the field. Section 3 includes work describing foundational building blocks toward a theory of paradox. Section 4 highlights research that recognizes the nested nature of paradox and describes how this theory has been applied across different levels. Section 5 includes papers that address the meta-theoretical and multi-paradigmatic aspect of paradox theory, noting how these ideas have been applied across phenomena and across theoretical lenses. Section 6 describes papers that draw on the varied methodological traditions associated with paradox. Finally, section 7 identifies several handbooks and special issues that offer an introduction to or integration of paradox theory.


Author(s):  
Іван Михайлович Грищенко ◽  
Олена Павлівна Кизимчук ◽  
Олег Олександрович Шевченко

The article seeks to discuss the issues of internationalization for higher education institutions that arose with the COVID-19 coronavirus pandemic, in particular, the suspension of both student and staff academic mobility. However, academic mobility is the fundamental premise for the internationalization of higher education where students who cross borders with the desire to change their lives and the strive for better prospects are the most critical element of this mobility. The mobility of all the education process participants has become an important driver in ensuring and promoting education transparency and the access to quality education for everyone. In fact, within the past six months, prospective students are increasingly changing their intentions to study abroad, or defer their enrolment plans for subsequent years. The aim of this paper is to explore possible solutions for further implementation of internationalization principles into all university's activities framework under the quarantine and post-quarantine period. The research findings from the in-depth analysis of a range of higher education institution performances have revealed that one of the most promising areas to enhance university internationalization is a shift from actual to virtual mobility which is based on communication within the information and educational environment. In particular, the design of new competitive online courses in English and their large-scale promotion on the international market is another priority objective for internationalization during the quarantine. Apparently, University positioning in a virtual environment is a crucial factor to build attractiveness and competitiveness of higher education institutions in the global settings.


2019 ◽  
Vol 16 (4) ◽  
pp. 251 ◽  
Author(s):  
Sarah M. Hayes ◽  
Nicole A. Ramos

Environmental contextTellurium can be more toxic than arsenic, but its fate in the surficial environment is poorly understood. We studied tellurium behaviour in semiarid mine tailings and found that most tellurium is associated with iron (oxy)hydroxides as tellurate (TeVI), the less toxic oxidation state. Iron (oxy)hydroxides are likely to control the fate of Te in the surficial environment and may effectively sequester Te oxyanions released by oxidative weathering. AbstractTellurium (Te) is a critical element owing to its use in solar technology. However, some forms are highly toxic. Few studies have examined Te behaviour in the surficial environment, thus little is known about its potential human and environmental health impacts. This study characterises two physicochemically distinct Te-enriched mine tailings piles (big and flat tailings) deposited by historic gold (Au) mining in the semiarid Delamar mining district, Nevada, USA. The big tailings are characterised by smaller particle size and higher concentrations of potentially toxic elements (up to 290mgTekg−1), which are enriched at the tailings surface. In contrast, the flat tailings have larger particle size and properties that are relatively invariant with depth. Based on the sulfate to sulfide ratio, the tailings were determined to be sulfate dominated, which suggested a high degree of weathering, although the flat tailings did contain significant amounts of sulfides (~40%). Tellurium X-ray absorption spectroscopy of the big tailings indicates that tellurate, the less toxic Te species, is the principal form of Te. Electron microscopy indicates that most of the Te present at the site is associated with iron (oxy)hydroxides, and sometimes with other potentially toxic elements, especially lead and antimony. Physiologically-based extraction tests indicate that substantially more Te is solubilised in synthetic stomach fluids than in lung fluids, with gastric bioaccessibility ranging from 13 to 31% of total Te. This points to low to medium bioaccessibility, which is common for iron (oxy)hydroxide-associated elements. Together, these results represent a preliminary assessment of Te surficial behaviour in a semiarid environment and indicate that Te in these tailings represent a moderate health concern.


2003 ◽  
Vol 35 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Cesar L. Escalante ◽  
Peter J. Barry

This study employs correlation relationships to measure the strength of trade-offs between business and financial risks as a representation of the strategic capital adjustment process. Under different business risk measures based on varying lengths of historical farm income data, results suggest that farmers tend to adopt a myopic perspective when contemplating risk-balancing plans. Cross-sectional regression results for two-time period models covering the decade of the 1980s and 1990s yielded important implications. The liquidity-constrained environment of the 1980s emphasizes the combination of risk-balancing plans, specialization, and market revenue-enhancing strategies. In the 1990s, risk balancing becomes compatible with risk-reducing crop diversification and insurance protection plans.


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