A.G. Nikolaev

A.G. Nikolaev
University at Buffalo, The State University of New York | SUNY Buffalo · Department of Industrial and Systems Engineering

Ph.D. in Industrial Engineering (University of Illinois at Urbana-Champaign)

About

61
Publications
18,310
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1,014
Citations
Citations since 2016
30 Research Items
852 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150

Publications

Publications (61)
Article
Supersonic plasma flows with densities of 10¹³–10¹⁶ cm⁻³ find application in various fields of physics and technology such as surface modification, simulation of plasma impact in fusion facilities, and laboratory studies of space phenomena. The work outlined here describes a pulsed vacuum arc source of supersonic dense metal plasma flow. The design...
Article
Plasma containing deuterium ions is used, for example, to generate neutron flows. Neutrons are generated in nuclear reactions of interaction of accelerated ion beams extracted from deuterium plasma with a solid-state target containing heavy hydrogen isotopes – deuterium or tritium. Deuterium plasma was produced in two types of arc discharge with co...
Article
The urgency of the study of generation of beams and plasmas containing boron ions is caused by their application in ion-beam and plasma technologies of modification of the surface properties of not only semiconductors, but also structural materials. This is due to the fact that boron compounds are hard and chemically resistant materials that can be...
Chapter
We formulate and solve the problem of optimizing the structure of an information propagation network between multiple agents. In a given space of interests (e.g., information on certain targets), each agent is defined by a vector of their desirable information, called filter, and a vector of available information, called source. The agents seek to...
Article
Full-text available
The formation of deuterium ion beams in a vacuum arc with a deuterium-saturated zirconium cathode was studied using a MevvaV.Ru vacuum arc ion source. The multi-aperture ion-optical system of the source was replaced by a string ion-optical system to measure and compare the current–voltage characteristics and current density distributions over the b...
Article
Full-text available
We have investigated an atmospheric pressure discharge, similar to a plasma jet, in the N 2 and CO 2 gas flows. We have also carried out an experimental modeling with the argon Ar flow. It has been shown that the use of a tantalum cathode and a copper anode provides a stable discharge in the nitrogen and carbon dioxide flows. We have studied the de...
Article
The “post-Soviet space” consists of countries with a substantial fraction of the world’s population; however, unlike many other regions, its social media network landscape is still somewhat underexplored. This study aims to fill this gap. To this purpose, we use anonymised data on user friendships at VK.com (also known as VKontakte and, informally,...
Article
Results of investigation of the angular distribution and mass-to-charge fractions of the ion flow generated in a pulsed vacuum arc with lanthanum hexaboride and boron carbide cathodes are presented. It is shown that the discharge with such cathodes provides efficient generation of the plasma with a high fraction of boron ions with charge states fro...
Article
The general structure and the characteristics of the modernized experimental diagnostic stand developed at the Institute of High Current Electronics SB RAS, Tomsk, are presented. The stand is equipped with a vacuum-arc source of metal ions, and a diagnostic system that includes a time-of-flight spectrometer of the mass-charge composition of the ion...
Article
Generation of high charge state metal ions in arc plasma is investigated and methods of elevation of the average ion charge state are analyzed. To realize multiple ionization of the arc plasma, a strong magnetic field in the arc cathode area, an ark current spike, an injection of a high-current electron beam or a high-power microwave radiation flow...
Article
We show that vacuum arc plasma discharges with a current of several kiloamperes and duration of a few microseconds can generate multiply charged metal ions with charge states greater than 10+. The physical mechanism behind this is discussed, suggesting an optimum arc current for higher charge states depending on the pulse duration and cathode mater...
Article
This paper demonstrates the potential benefits of crowdsourcing last mile delivery by exploiting a social network of the customers. The presented models and analysis are informed by the results of a survey to gauge people’s attitudes toward engaging in social network-reliant package delivery to and by friends or acquaintances. It is found that usin...
Article
Background The emerging research on nurturing the growth of online communities posits that it is in part attributed to network effects, wherein every increase in the volume of user-generated content increases the value of the community in the eyes of its potential new members. The recently introduced metric engagement capacity offers a means of qua...
Article
Workforce management has long been an integral part of operational efforts aimed at maximizing revenues. The recent literature in this area has recognized the positive impact of social ties on workforce productivity, motivating new re-formulations of conventional operations research problems to more explicitly consider team building. This paper ins...
Article
Full-text available
This paper addresses the challenge of strategically maximizing the influence spread in a social network, by exploiting cascade propagators termed “seeds”. It introduces the Seed Activation Scheduling Problem (SASP) that chooses the timing of seed activation under a given budget, over a given time horizon, in the presence/absence of competition. The...
Conference Paper
Full-text available
This paper presents a new pedagogical paradigm ``Crowdlearning'', where students experience deeper learning through collaboratively creating learning materials for each other. Crowdlearning practice is envisioned to produce large ``banks'' of subject matter problems generated by students themselves, in a crowdsourced way, as the students learn new...
Article
Aims: To examine the nature and characteristics of both received and provided mutual support in a social network within an acute care hospital unit. Background: Current evidence regarding the social network in the health care workforce reveals the nature of social ties. Most studies of social network-related support that measured the characteris...
Article
Full-text available
An aging and more sedentary population requires interventions aimed at monitoring physical activity, particularly within the home. This research uses simulation, optimization, and regression analyses to assess the feasibility of using a small number of sensors to track movement and infer physical activity levels of older adults. Based on activity d...
Article
Product reviews and ratings are major quality indicators in online shopping systems. In making the decision about carrying a product as part of their inventory, an online seller often pays attention to the product's rating. However, when the observed average is based on a small number of individual user-submitted ratings, the decision-maker may not...
Article
Full-text available
This paper reports on the utility of social network analysis methods in the data fusion domain. Given fused data that combine multiple intelligence reports from the same environment, social network extraction and high value individual (HVI) identification are of interest. The research on the feasibility of such activities may help not only in metho...
Article
Full-text available
This paper presents a methodological framework to identify population-wide traveler type distribution and simultaneously infer individual travelers’ Origin-Destination (OD) pairs, based on the individual records of a shared mobility (bike) system use in a multimodal travel environment. Given the information about the travelers’ outbound and inbound...
Article
The influence maximization problem selects a set of seeds to initiate an optimal cascade of decisions. This paper uses parallel cascade evidence-based diffusion modelling, which views influence as a consequence of the evidence exchange between the connected actors, to investigate the temporal aspects of the social cascade propagation and effective...
Conference Paper
More and more businesses use social media to advertise their services. Such businesses typically maintain online social network accounts and regularly update their pages with advertisement messages describing new products and promotions. One recent trend in such businesses’ activity is to offer incentives to individual users for re-posting the adve...
Article
Full-text available
This paper develops a mathematical framework that relies on modern social network analysis theories for treating the nurse team formation and nurse scheduling (shift assignment) problems, accounting for signed social connections. These problems lie in assigning nurses to teams/shifts such that the constraints regarding both the working regulations...
Article
Full-text available
This paper presents a mathematical framework for treating the Team Formation Problem explicitly incorporating Social Structure (TFP-SS), the formulation of which relies on modern social network analysis theories and metrics. While recent research qualitatively establishes the dependence of team performance on team social structure, the presented fr...
Article
This paper presents an information theory-driven matching methodology for making causal inference from observational data. The paper adopts a "potential outcomes framework" view on evaluating the strength of cause-effect relationships: The population-wide average effects of binary treatments are estimated by comparing two groups of units-the treate...
Article
Full-text available
The advent and availability of technology has brought us closer than ever through social networks. Consequently, there is a growing emphasis on mining social networks to extract information for knowledge and discovery. However, methods for social network analysis (SNA) have not kept pace with the data explosion. In this review, we describe directed...
Article
Does the intensity of a social conflict affect political division? Traditionally, social cleavages are seen as the underlying cause of political conflicts. It is clear, however, that a violent conflict itself can shape partisan, social, and national identities. In this paper, we ask whether social conflicts unite or divide the society by studying t...
Article
The ability to design and employ groundwater distribution models plays an important role in the development and application of regional water management policies and resource exploration. This paper presents a probabilistic reasoning approach for estimating groundwater levels over a geological map based on a limited number of available observations...
Article
Full-text available
This paper introduces the notion of subjective evidence, which fuels a new parallel cascade influence propagation model. The model sheds light on the phenomena of belief reinforcement and viral spread of innovations, rumors, opinions, etc., in social networks. Network actors are assumed to be testing a Bayesian hypothesis, e.g., for making judgment...
Article
Although considerable progress has been made in understanding networks, their structure, and their development, little has been known about their effectiveness in the health care setting and their contributions to quality of care and patient safety.The purpose of this study was to examine studies using social network analysis (SNA) in the health ca...
Conference Paper
Full-text available
This paper reports on the utility of social network analysis methods in the data fusion domain. Given fused data that combines multiple intelligence reports from the same environment, social network extraction and High Value Individual (HVI) identification are of interest. The research on the feasibility of such activities may help not only in meth...
Article
This paper motivates and interprets entropy centrality, the measure understood as the entropy of flow destination in a network. The paper defines a variation of this measure based on a discrete, random Markovian transfer process and showcases its increased utility over the originally introduced path-based network entropy centrality. The re-defined...
Article
Full-text available
One of the biggest challenges in today’s social network analysis (SNA) is handling dynamic data. Real-world social networks evolve with time, forcing their corresponding graph representations to dynamically update by addition or deletion of edges/nodes. Consequently, a researcher is often interested in fast recomputation of important SNA metrics pe...
Article
Full-text available
Online pro-health social networks facilitating smoking cessation through web-assisted interventions have flourished in the past decade. In order to properly evaluate and increase the impact of this form of treatment on society, one needs to understand and be able to quantify its reach, as defined within the widely-adopted RE-AIM framework. In the o...
Article
New electronic forms of political communication have become increasingly popular in countries with weak democratic institutions. The effectiveness of these new forms of association in altering political behavior, however, remains uncertain even in developed democratic regimes. This paper investigates connections between regional variation in electo...
Conference Paper
This paper outlines an idea of creatively incentivizing home-owners to conserve electricity through a socially competitive lottery-based rewards system. The core idea of this work is in leveraging the power of social network influence to make consumers participate and compete in a lottery so that the resulting engagement consistently enhances the p...
Conference Paper
Online pro-health social networks have grown in the past decade. This position paper argues for the need of prescriptive research that would enable models of online interventions capable of assessing the effects imposed on social networks from the outside, e.g., by a strategic decision-maker (supervisor) possessing the full knowledge of the network...
Article
This paper describes traces of user activity around a alleged online social network profile of a Boston Marathon bombing suspect, after the tragedy occurred. The analyzed data, collected with the help of an automatic social media monitoring software, includes the perpetrator's page saved at the time the bombing suspects' names were made public, and...
Article
To make causal inferences from observational data, researchers have often turned to matching methods. These methods are variably successful. We address issues with matching methods by redefining the matching problem as a subset selection problem. Given a set of covariates, we seek to find two subsets, a control group and a treatment group, so that...
Article
Full-text available
Scientists in all disciplines attempt to identify and document causal relationships. Those not fortunate enough to be able to design and implement randomized control trials must resort to observational studies. To make causal inferences outside the experimental realm, researchers attempt to control for bias sources by postprocessing observational d...
Article
Conflicting and incomplete information of uncertain reliability is endemic to analytic communities supporting military, national, and homeland security operations. The prevalence of human-source information necessitates approaches for integrating diverse and sometimes inconsistent second hand observations. Given a set of attributed graphs represent...
Conference Paper
Full-text available
Today's social networks are getting larger, and the need to analyze datasets with millions of nodes and billions of edges is not uncommon any more. As a network of social relationships evolves by the addition of new nodes and edges, fast algorithms are desirable for the recomputation of key network measures such as actor centrality. The distributed...
Article
Full-text available
Passenger screening is a critical component of aviation security systems. This paper introduces the multistage sequential passenger screening problem (MSPSP), which models passenger and carry-on baggage screening operations in an aviation security system with the capability of dynamically updating the perceived risk of passengers. The passenger scr...
Article
Full-text available
This paper presents a framework for analyzing and comparing sub-optimal performance of local search algorithms for hard discrete optimization problems. The β-acceptable solution probability is introduced that captures how effectively an algorithm has performed to date and how effectively an algorithm can be expected to perform in the future. Using...
Article
This paper analyzes the performance of local search algorithms (guided by the best-to-date solution at each iteration) in visiting suboptimal solutions for hard discrete optimization problems. The β-acceptable solution concept is used to capture how effectively an algorithm has performed to date and how effectively an algorithm can be expected to p...
Chapter
Full-text available
Simulated annealing is a well-studied local search metaheuristic used to address discrete and, to a lesser extent, continuous optimization problems. The key feature of simulated annealing is that it provides a mechanism to escape local optima by allowing hill-climbing moves (i.e., moves which worsen the objective function value) in hopes of finding...
Article
Full-text available
This paper addresses a class of problems in which available resources need to be optimally allocated to a random number of jobs with stochastic parameters. Optimal policies are presented for variations of the sequential stochastic assignment problem and the dynamic stochastic knapsack problem, in which the number of arriving jobs is unknown until a...
Article
Full-text available
As of November 2008, the number of cell phone subscribers in the US exceeded 267 million, nearly three times more than the 97 million subscribers in June 2000. This rapid growth in cell phone use has led to concerns regarding their impact on driver performance and road safety. Numerous legislative efforts are under way to restrict hand-held cell ph...
Article
Full-text available
The events of September 11th, 2001 launched the world into a new era of aviation security policy, operations, and procedures. The very nature of aviation security makes such operations ill-equipped to rapidly respond to highly agile groups of people intent on inflicting harm to the air transportation system. This article provides an overview of avi...
Article
Full-text available
Designing effective aviation security systems has become a problem of national concern. Since September 11th, 2001 passenger screening systems have become an important component in the design and operation of aviation security systems. This paper introduces the Sequential Stochastic Passenger Screening Problem (SSPSP), which allows passengers to be...
Article
Full-text available
Catastrophic events often illustrate a nation’s preparedness in anticipating and preventing the extreme consequences of an intentional malicious attack. When terrorists hijacked four commercial aircraft for use as guided missiles against the World Trade Center and the Pentagon on September 11, 2001, the world’s population became aware of the human...
Article
Full-text available
Passenger screening is a critical component of aviation security systems. This paper introduces the sequential stochastic security design problem (SSSDP), which models passenger and carry-on baggage-screening operations in an aviation security system. SSSDP is formulated as a two-stage model, where in the first stage security devices are purchased...
Chapter
The present paper deals with peculiarities of vacuum arc ion sources employed to generate beams of gas and metal ions with the controllable ratio of ions of each type in a beam. The design and parameters of the sources are presented. The mass- charge state of ion beams is studied, and the dependence of the gas ion fraction in a beam on the length o...

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