5,130 results on '"Unavailability"'
Search Results
2. Thors Hammer und das Unverfügbare: Eine Replik auf Kurt Greiners Versuch über ein allgemeines Funktionsparadigma in der Psychotherapie(-wissenschaft).
- Author
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Burda, Gerhard
- Abstract
Kurt Greiner has invited responses to his article «Psychotherapie als Textmedizin» published in the last issue of Psychotherapie-Wissenschaft. In it, he endeavors to distinguish psychotherapy science from the scientific paradigm on a hermeneutic basis and to identify psychotherapy as a text-scientific process across modalities. My reply notes, firstly, that terms such as training of suffering text competence, text medicine or functionality can be understood as signals in the wrong direction. Secondly, it is noted that the reference to the hermeneutic tradition lacks important further developments. This is about alterity, difference or the unavailable, i. e. a dimension of psychotherapy and consequently of psychotherapy science that should not be neglected. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Condiţia prezentării certificatului de atestare fiscală la înstrăinare ca limită a dreptului de proprietate.
- Author
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BOTU, Cristian-Codrin
- Subjects
LEGAL documents ,JUSTICE administration ,JURISPRUDENCE ,LEGISLATORS - Abstract
Copyright of Romanian Case Law Review / Revista Română de Jurisprudenţă is the property of Universul Juridic Publishing House and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2024
4. Analysis of the Operational Reliability of Different Types of Switching Substations Using the Monte Carlo Method
- Author
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Franjo Pranjić and Peter Virtič
- Subjects
switchgear ,switching devices ,high voltage ,operating reliability ,unavailability ,failure interval ,Technology - Abstract
This study investigates the operational reliability of different types of switching substations within the context of power systems, employing the Monte Carlo method for analysis. The research focuses on evaluating the reliability of high-voltage substations, including single-busbar systems, double-busbar systems, and switchgears with a ring-type power supply. By conducting simulations and analyzing statistical data on device reliability, the study aims to identify the most reliable implementation of switching substations. The results are presented through graphical representations and comparative tables, highlighting the impact of factors such as the number of switching elements and their connection on operational reliability. The findings indicate that configurations with a greater number of busbars and a parallel connection of switching elements exhibit higher operational reliability. The study provides insights to inform decision-making in the construction of new switching substations, emphasizing the importance of stable operation within power systems.
- Published
- 2024
- Full Text
- View/download PDF
5. Experimental Survey of Algorithms for the Calculation of Node Traversal Probabilities in Multi-valued Decision Diagrams
- Author
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Mrena, Michal, Kvassay, Miroslav, Kacprzyk, Janusz, Series Editor, van Gulijk, Coen, editor, Zaitseva, Elena, editor, and Kvassay, Miroslav, editor
- Published
- 2023
- Full Text
- View/download PDF
6. Availability of Medicines
- Author
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Jenzer, Helena, Groesser, Stefan, Miljković, Nenad, Le Brun, Paul, editor, Crauste-Manciet, Sylvie, editor, Krämer, Irene, editor, Smith, Julian, editor, and Woerdenbag, Herman, editor
- Published
- 2023
- Full Text
- View/download PDF
7. Study of Testing Strategy for Performance Analysis of Actuator Layer in Safety Instrumented System
- Author
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Mechri, Walid, Simon, Christophe, Kacprzyk, Janusz, Series Editor, Theilliol, Didier, editor, and Korbicz, Józef, editor
- Published
- 2023
- Full Text
- View/download PDF
8. Hybrid Berth Allocation for Bulk Ports with Unavailability and Stock Level Constraints
- Author
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Lyu, Xiaohuan, Schulte, Frederik, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, de Armas, Jesica, editor, Ramalhinho, Helena, editor, and Voß, Stefan, editor
- Published
- 2022
- Full Text
- View/download PDF
9. A renewal process model with failure based PM and imperfect CM for unavailability exploration
- Author
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Jahoda, Pavel and Bris, Radim
- Published
- 2022
- Full Text
- View/download PDF
10. Discrete Model for a Multi-Objective Maintenance Optimization Problem of Safety Systems.
- Author
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Briš, Radim and Tran, Nuong Thi Thuy
- Subjects
- *
SYSTEM safety , *DIRECTED acyclic graphs , *FLUID injection , *VARIABLE costs , *MAINTENANCE , *CONDITION-based maintenance - Abstract
The aim of this article was to solve a multi-objective maintenance optimization problem by minimizing both unavailability and cost through the use of an optimal maintenance strategy. The problem took into account three different system designs upon which the objective functions are dependent, and the time to start preventive maintenance (PM) was used as a decision variable. This variable was optimized for all system components using a discrete maintenance model that allows for the specification of several discrete values of the decision variable in advance to find the optimal one. The optimization problem was solved using innovative computing methodology and newly updated software in MATLAB, which was used to quantify the unavailability of a complex system represented through a directed acyclic graph. A cost model was also developed to compute the cost of different maintenance configurations, and the optimal configuration was found. The results for a selected real system (a real fluid injection system adopted from references) showed that unavailability was less sensitive to variations in maintenance configurations, while cost variations were more noticeable in relation to different maintenance configurations. Applying PM, the increasing value of the decision variable increased cost because it led to more frequent corrective maintenance (CM) actions, and recovery times due to CM were more expensive than recovery times due to PM. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
11. NEGOCIAÇÃO COLETIVA E LEGISLAÇÃO TRABALHISTA: ANÁLISE CRÍTICA DA DECISÃO NO TEMA 1046 DA REPERCUSSÃO GERAL DO SUPREMO TRIBUNAL FEDERAL.
- Author
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DE BRITTO PEREIRA, RICARDO JOSÉ MACEDO and DA SILVEIRA BORGES DE FREITAS, FLAVIO
- Subjects
- *
COLLECTIVE labor agreements , *LABOR laws - Published
- 2023
12. PFD analysis of LNG fuel gas supply system for improving combined-cycle power plant safety
- Author
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Teerawat Thepmanee, Amphawan Julsereewong, and Sawai Pongswatd
- Subjects
Combined-cycle power plant ,Fuel gas supply ,Probability failure on demand ,Reliability block diagram ,Fault tree ,Unavailability ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
In order to determine an unavailability of each safety function subsystem that influences on an overall unavailability of entire protection system for safety analysis and enhancement, a modeling is required. This article presents a safety system modeling to evaluate the detected–undetected failures and repairable behaviors of each safety function subsystem in the studied fuel gas supply system (FGSS), which is utilized in a combined-cycle power plant. The proposed modeling deals with probability of failure on demand (PFD) analysis for calculation of the unavailability of three safety function subsystems, which are gas analytical subsystem (GAS), fuel gas controller subsystem (FGC), and shutdown valve subsystem (SDV). The interested GAS includes two different groups of gas analyzers in 2-out-of-2 (2oo2) voting scheme, when using three gas analyzers in each group in 2-out-of-3 and diagnosis (2oo3D) voting scheme. The interested FGC consists of two controllers in 2oo2 voting scheme, when the structure of each controller is in 1-out-of-1 and diagnosis (1oo1D) voting scheme. The interested SDV consists of two shutdown valves, which are installed in 1-out-of-2 (1oo2) voting scheme. The reliability block diagram is utilized for representative of combination of all three safety function subsystems, and the fault tree is utilized for calculation of PFD unavailability of each safety function subsystem. As the results obtained from the proposed safety function modeling, the influence of three safety function subsystems on the total unavailability of the FGSS is described. In addition, an example of the proposed modeling application to provide two guidelines for effective engineering design and operation is also presented. The first is a guideline to implement an effective human machine interface (HMI) at an operator workstation for real-time monitoring of the studied FGSS in the presence of failures that can be automatically detected by device diagnosis. The latter is a guideline to maintain and troubleshoot the failures that can be revealed by proof test. Based on diagnostic information and proof test results, operation and maintenance savings can be achieved.
- Published
- 2022
- Full Text
- View/download PDF
13. The Fixed Wireless Path
- Author
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Morais, Douglas H and Morais, Douglas H
- Published
- 2021
- Full Text
- View/download PDF
14. Forbidden fruit or soured grapes? Long-term effects of the temporary unavailability and rationing of US news websites on their consumption from the European Union.
- Author
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Thurman, Neil, Sly, James, Wilczek, Bartosz, and Fletcher, Richard
- Subjects
- *
DATA protection , *NEWS websites , *NEWS consumption , *RATIONING , *GRAPES , *PRODUCT elimination - Abstract
In May 2018, hundreds of websites located outside the European Union (EU), including USAToday.com, became completely or partially unavailable to EU citizens as a number of publishers decided to comply with an EU data protection regulation (GDPR) by blocking access. Several of the sites that started to exclude EU users continued to do so for months or years, even though some of their competitors, like the New York Times, never adopted a policy of exclusion. These differing strategies allowed us to conduct a quasi-experimental study on the effects of temporary product unavailability and temporary rationing. We find that both temporary product withdrawal and temporary rationing can have long-term effects. In our case, monthly unique visitors in the months and even years after full access was restored were between 44% and 61% lower than they had been before the restrictions were imposed, with a wider market contraction explaining only part of these falls. We also find distinct differences between the effects of temporarily rationing and temporarily withdrawing websites. Although both strategies lead to a long-term loss in visitors, rationing appears to increase a website's desirability for some consumers. After rationing was lifted, USAToday.com's reduced audience consumed the title more deeply and frequently than had been the case before rationing was imposed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
15. Resonanzraum Hotel
- Author
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Reichel, Katrin and Reichel, Katrin
- Abstract
Das Leben beschert uns viele Möglichkeiten, Resonanz mit der Welt um uns herum zu finden. Indem wir uns auf unsere Umgebung einlassen und uns von ihr beeinflussen lassen, können wir eine tiefere Verbindung zu uns selbst und anderen aufbauen. Das in Resonanz treten mit dem Raum ist der Grundmodus jedes lebendigen menschlichen Daseins. Jeden Tag treten wir in Beziehung zu unserer Umwelt, egal ob mit anderen Menschen, Tieren, der Natur, Maschinen, Dingen oder Materialien... Doch unsere Welt ist geprägt durch die Beschleunigung und das ständige in Reichweite bringen. Alles muss immer optimiert und schneller gemacht werden. Dieser „Zwang“ zur Steigerung und Neuerfindung führt zu einer psychischen Überforderung, die unsere Beziehungen zu uns selbst und anderen stört. Sind wir also noch in der Lage uns erreichen und berühren zu lassen? Wollen wir die Welt um uns herum noch hören? Das Ziel der vorliegenden Arbeit ist diesem Phänomen entgegenzuwirken und eine neue Art Raum zu schaffen, in der wir Resonanzerfahrung sammeln. Einen Ort, der uns erreicht und uns etwas bedeutet. Das Hotel nimmt in dieser Arbeit eine besondere Rolle ein. Es dient als Aufenthaltsort, bei dem die Menschen ihrem stressigen Alltag für eine kurze Zeit „entkommen“ können und bietet eine andere Art und Weise mit den Menschen, dem Ort und der Kultur in Beziehung zu treten. Eine Architektur als Zeichen der Entschleunigung - im Leben einen Gang runter schalten, eine Pause gönnen, entspannen und berühren lassen., Masterarbeit Universität Innsbruck 2024
- Published
- 2024
16. Really Ageing Systems Undergoing a Discrete Maintenance Optimization.
- Author
-
Briš, Radim and Jahoda, Pavel
- Subjects
- *
DISCRETE systems , *DISTRIBUTION (Probability theory) , *SPARE parts , *ON-demand computing , *SYSTEM failures , *MATHEMATICAL optimization , *WEIBULL distribution , *MAINTENANCE - Abstract
In general, a complex system is composed of different components that are usually subject to a maintenance policy. We take into account systems containing components that are under both preventive and corrective maintenance. Preventive maintenance is considered as a failure-based preventive maintenance model, where full renewal is realized after the occurrence of every nth failure. It offers an imperfect corrective maintenance model, where each repair deteriorates the component or system lifetime, the probability distribution of which gradually changes via increasing failure rates. The reliability mathematics for unavailability quantification is demonstrated in the paper. The renewal process model, involving failure-based preventive maintenance, arises from the new corresponding renewal cycle, which is designated a real ageing process. Imperfect corrective maintenance results in an unwanted rise in the unavailability function, which can be rectified by a properly selected failure-based preventive maintenance policy; i.e., replacement of a properly selected component respecting both cost and unavailability after the occurrence of the nth failure. The number n is considered a decision variable, whereas cost is an objective function in the optimization process. The paper describes a new method for finding an optimal failure-based preventive maintenance policy for a system respecting a given reliability constraint. The decision variable n is optimally selected for each component from a set of possible realistic maintenance modes. We focus on the discrete maintenance model, where each component is realized in one or several maintenance mode(s). The fixed value of the decision variable determines a single maintenance mode, as well as the cost of the mode. The optimization process for a system is demanding in terms of computing time because, if the system contains k components, all having three maintenance modes, we need to evaluate 3k maintenance configurations. The discrete maintenance optimization is shown with two systems adopted from the literature. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
17. Critical Elements Analysis of Water Supply Systems to Improve Energy Efficiency in Failure Scenarios.
- Author
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Perelman, Gal and Fishbain, Barak
- Subjects
WATER supply ,WATER analysis ,CRITICAL analysis ,LINEAR programming ,CONDITIONED response ,PRODUCTION planning - Abstract
Water supply systems (WSS) are significant energy consumers, which makes it crucial to find methods to increase energy efficiency. A novel approach is presented here to locate and quantify the most vulnerable elements in terms of energetic efficiency. The method is based on a linear programming (LP) optimization model and the elimination of different components in the system to analyze their impact on energy costs. Pump reallocation is then suggested as a novel dynamic design paradigm for temporary changes in the system to cope with extreme scenarios. Exposing the critical components of WSS improves maintenance prioritization and inventory and contributes to the planning of future investments in the system. Pump reallocation provides an innovative approach for response to critical conditions, it is suggesting rethinking the design concepts to incorporate not just long-term solutions but also rapid, temporary steps in response to failures. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
18. The Burden of Unavailable Drugs Cost to Patients Admitted to Internal Medicine Ward of Tikur Anbessa Specialized Hospital
- Author
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Hussien MA, Haile EB, and Demisse BN
- Subjects
burden ,unavailability ,hospital pharmacy ,Medicine (General) ,R5-920 - Abstract
Misgana Ayele Hussien, Eyerusalem Berhanemeskel Haile, Bezawit Negash Demisse Department of Pharmaceutics and Social Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, EthiopiaCorrespondence: Bezawit Negash Demisse Email bezawit.negash@aau.edu.etPurpose: To assess the burden of unavailable drugs cost to patients admitted to TikurAnbessa Specialized Hospital’s internal medicine ward. Costs of medications obtained inside and outside the pharmacy and other burdens associated with drugs’ unavailability are also estimated and explored.Patient and Methods: A facility-based cross-sectional study design was conducted from November 9 to November 23, 2020. Quantitative data on medication costs were collected from patients admitted to TikurAnbessa Specialized Hospital internal medicine ward B8. Qualitative information was collected from patients, caregivers, and health care professionals through interviews to assess the burdens of unavailability of pharmaceuticals on patients and the health care system.Results: A total of 32 patients were enrolled in the study. Participants’ age ranged from 14 to 92. Eighteen (56.25%) paid in cash for medications bought within the hospital pharmacy, while the remaining 14 (43.75%) were treated for free. A total of 68 medicines were prescribed during the study period. Of this, 33 (48.53%) medicines were not available in the hospital pharmacy. The total costs of patients were 78.07$ and 1530.84$ when purchased from inside and outside the hospital pharmacy, respectively. The average price of medications per patient ranged from 0.025 to 8.41$ inside the hospital pharmacy, where the average cost per patient outside the hospital pharmacy ran from 0.128 to 54.67$. For the qualitative part, four patients and/or caregivers and five health care professionals were interviewed, and three key themes emerged from the thematic analysis: (i) awareness of the availability of medication, (ii) management of the burden of stock out, and (iii) impact of the stock out.Conclusion: The study came up with a result that the hospital pharmacy has high unavailability of medication. Patients complain about unwanted and unreasonably expenditure to purchase pharmaceuticals from outside pharmacies and associated delayed treatment.Keywords: burden, unavailability, hospital pharmacy
- Published
- 2021
19. Inspection–Maintenance-Based Availability Optimization of Feeder Section Using Particle Swarm Optimization
- Author
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Tiwary, Aditya, Kacprzyk, Janusz, Series Editor, Pal, Nikhil R., Advisory Editor, Bello Perez, Rafael, Advisory Editor, Corchado, Emilio S., Advisory Editor, Hagras, Hani, Advisory Editor, Kóczy, László T., Advisory Editor, Kreinovich, Vladik, Advisory Editor, Lin, Chin-Teng, Advisory Editor, Lu, Jie, Advisory Editor, Melin, Patricia, Advisory Editor, Nedjah, Nadia, Advisory Editor, Nguyen, Ngoc Thanh, Advisory Editor, Wang, Jun, Advisory Editor, Bansal, Jagdish Chand, editor, Das, Kedar Nath, editor, Nagar, Atulya, editor, Deep, Kusum, editor, and Ojha, Akshay Kumar, editor
- Published
- 2019
- Full Text
- View/download PDF
20. Elaboration of a theory of resistance
- Author
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Wiegerling Klaus
- Subjects
reflexive term ,support ,unavailability ,constructivism ,reality ,actuality ,facticity ,Philosophy (General) ,B1-5802 - Abstract
The theory of resistance here elaborated is based on considerations current since the 18th century and concern the proof of reality of the external world. However, what is ignored in the course of these proofs are the social, psychological, and in particular the logical aspects of resistance. The idea of a theory of resistance is inspired by tendencies in the philosophy of technology, as well as other current philosophical and scientific lines of thought that obscure their metaphysical underpinnings, advocating a position of complete achievability of human and natural relations. The theory of resistance seeks to show that resistance is a reflexive term that concerns relations, not objects or those relations that can be expressed in qualities and quantities. Furthermore, this concept has a positioning role, important in epistemological, as well as ethical and anthropological sense. Resistance is a central, although not the sole characteristic of reality. As an ethical category, it is articulated, for example, in the idea of dignity if understood as hostility to mere typologization and subjection to calculation. The theory of resistance does not advocate some existing reality, but limits the domain of validity of constructivist and narrativist theories.
- Published
- 2021
- Full Text
- View/download PDF
21. VERIFICAREA MĂSURILOR ASIGURĂTORII PE PARCURSUL PROCESULUI PENAL.
- Author
-
GHERGHE, VICENȚIU-RĂZVAN
- Abstract
Copyright of Dreptul is the property of Union of Jurists of Romania and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2022
22. Discrete Model for a Multi-Objective Maintenance Optimization Problem of Safety Systems
- Author
-
Radim Briš and Nuong Thi Thuy Tran
- Subjects
multi-objective optimization ,unavailability ,cost ,maintenance ,acyclic graph ,alternating renewal process ,Mathematics ,QA1-939 - Abstract
The aim of this article was to solve a multi-objective maintenance optimization problem by minimizing both unavailability and cost through the use of an optimal maintenance strategy. The problem took into account three different system designs upon which the objective functions are dependent, and the time to start preventive maintenance (PM) was used as a decision variable. This variable was optimized for all system components using a discrete maintenance model that allows for the specification of several discrete values of the decision variable in advance to find the optimal one. The optimization problem was solved using innovative computing methodology and newly updated software in MATLAB, which was used to quantify the unavailability of a complex system represented through a directed acyclic graph. A cost model was also developed to compute the cost of different maintenance configurations, and the optimal configuration was found. The results for a selected real system (a real fluid injection system adopted from references) showed that unavailability was less sensitive to variations in maintenance configurations, while cost variations were more noticeable in relation to different maintenance configurations. Applying PM, the increasing value of the decision variable increased cost because it led to more frequent corrective maintenance (CM) actions, and recovery times due to CM were more expensive than recovery times due to PM.
- Published
- 2023
- Full Text
- View/download PDF
23. EXPOSITION EINER THEORIE DER WIDERSTÄNDIGKEIT.
- Author
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Wiegerling, Klaus
- Subjects
INTERPERSONAL relations ,IDEA (Philosophy) ,EIGHTEENTH century ,HOSTILITY ,DIGNITY - Abstract
Copyright of Filozofija i Drustvo is the property of University of Belgrade, Institute for Philosophy & Social Theory and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
- Full Text
- View/download PDF
24. Kittsteiner's History Out of Joint.
- Author
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Wimmer, Mario
- Subjects
- OUT of Control (Book), KITTSTEINER, Heinz Dieter, 1942-2008, KANT, Immanuel, 1724-1804
- Abstract
In this article, I portray both the "thinking historian" Heinz-Dieter Kittsteiner and his philosophical analysis of the unavailability of the historical process. In his book Out of Control (2004), Kittsteiner builds on Immanuel Kant's concept of the historical sign to demonstrate how history is out of joint due to the contingent character of the historical process. This understanding demands a new theory of historical time and of historiographical practice, which I reconstruct through a close reading of a chapter of Kittsteiner's book. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
25. Context-based Automated Responses of Unavailability in Mobile Messaging.
- Author
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Jain, Pranut, Farzan, Rosta, and Lee, Adam J.
- Subjects
- *
TEXT messages , *SENSORY perception , *INFORMATION sharing , *COMMUNICATION , *CLUSTER analysis (Statistics) - Abstract
People are not always able to respond immediately to incoming messages on their mobile devices, either due to engagement in another task or simply because the moment is inconvenient for them. This delay in responding could affect social relationships, as there are often expectations associated with mobile messaging and people may experience a lingering pressure to attend to their messages. In this work, we investigate an approach for generating automated contextual responses on behalf of message recipients when they are not available to respond. We first identify several types of contextual information that can be obtained from a user's smartphone and explore whether those can be used to explain unavailability. We then assess users' perception of the usefulness of these sensor-based categories and their level of comfort with sharing such information through a Mechanical Turk survey study. Our results show emergent groups with varying preferences with regards to the usefulness and comfort in sharing two types of contextual information: user state and device state. Further, we also observed a strong influence of message context (i.e., message urgency and social tie strength) in users' perceptions of these auto-generated messages. Our research provides understanding of users' perceptions of sharing context through an autonomous agent that can help design and create effective approaches towards enabling communication awareness. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
26. Reconfiguration of the real distribution network and providing a new resilience index, considering the uncertainty of renewable energy sources and digital protection devices in order to improve the resilience.
- Author
-
Rezaei, Maryam Faghihi and Ghobadpour, Saman
- Subjects
- *
RENEWABLE energy sources , *DIGITAL technology , *POWER distribution networks , *RESTRAINING orders , *NATURAL disasters , *INFRASTRUCTURE (Economics) - Abstract
• The new resilience index, which includes the resilience indices of RESs and the unavailability index of DOCR and DS-DOCR digital relays, is presented independently. • The parameters of DOCR and DS-DOCR digital relays are optimized to reduce the total operating time of the relays and achieve protection coordination, taking into account the unavailability constraint of one of the digital relays due to their failure. • The unavailability constraint of DOCR and DS-DOCR digital relays is taken into account, it creates a better response and eventually improves the resilience in distribution networks. Electric energy, as the most widely used form of energy, has always captured human attention to itself; however, with the climate change and the increase of natural phenomena, it is now necessary to provide solutions to improve the resilience of the network. Resilience is defined as the capability of the system to maintain an acceptable level of performance against a severe disturbance and return to its original condition in an appropriate period of time, which demonstrates the degree of endurance, vulnerability, and reversibility of an infrastructure system. The occurrence of adverse weather conditions and natural disasters causes extensive losses and power outages in distribution networks; and the number and severity of such incidents have seen an increase in recent years. Therefore, it is of great significance to evaluate the resilience of the network and its reversibility capability in dealing with adverse weather conditions. In this paper, after defining the concept of resilience in distribution networks, its characteristics are determined; and then, modeling common natural events such as floods and storms, and introducing a new index to evaluate resilience in distribution networks with digital directional overcurrent relays (DOCR) and Digital dual-setting directional overcurrent relays (DS-DOCR) in the presence of renewable energy sources (RES), the proposed scheme is presented. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
27. Really Ageing Systems Undergoing a Discrete Maintenance Optimization
- Author
-
Radim Briš and Pavel Jahoda
- Subjects
unavailability ,imperfect repair ,failure-based replacement ,renewal theory ,optimization ,Mathematics ,QA1-939 - Abstract
In general, a complex system is composed of different components that are usually subject to a maintenance policy. We take into account systems containing components that are under both preventive and corrective maintenance. Preventive maintenance is considered as a failure-based preventive maintenance model, where full renewal is realized after the occurrence of every nth failure. It offers an imperfect corrective maintenance model, where each repair deteriorates the component or system lifetime, the probability distribution of which gradually changes via increasing failure rates. The reliability mathematics for unavailability quantification is demonstrated in the paper. The renewal process model, involving failure-based preventive maintenance, arises from the new corresponding renewal cycle, which is designated a real ageing process. Imperfect corrective maintenance results in an unwanted rise in the unavailability function, which can be rectified by a properly selected failure-based preventive maintenance policy; i.e., replacement of a properly selected component respecting both cost and unavailability after the occurrence of the nth failure. The number n is considered a decision variable, whereas cost is an objective function in the optimization process. The paper describes a new method for finding an optimal failure-based preventive maintenance policy for a system respecting a given reliability constraint. The decision variable n is optimally selected for each component from a set of possible realistic maintenance modes. We focus on the discrete maintenance model, where each component is realized in one or several maintenance mode(s). The fixed value of the decision variable determines a single maintenance mode, as well as the cost of the mode. The optimization process for a system is demanding in terms of computing time because, if the system contains k components, all having three maintenance modes, we need to evaluate 3k maintenance configurations. The discrete maintenance optimization is shown with two systems adopted from the literature.
- Published
- 2022
- Full Text
- View/download PDF
28. Synchronization of Complex Dynamical Networks Subject to DoS Attacks: An Improved Coding–Decoding Protocol
- Author
-
Hao Shen, Jianlong Qiu, Mengping Xing, and Jianquan Lu
- Subjects
Lyapunov stability ,Computer science ,String (computer science) ,Denial-of-service attack ,Computer Science Applications ,Human-Computer Interaction ,Control and Systems Engineering ,Synchronization (computer science) ,Electrical and Electronic Engineering ,Unavailability ,Communications protocol ,Algorithm ,Software ,Information Systems ,Data transmission ,Coding (social sciences) - Abstract
This article investigates the synchronization of communication-constrained complex dynamic networks subject to malicious attacks. An observer-based controller is designed by virtue of the bounded encode sequence derived from an improved coding-decoding communication protocol. Moreover, taking the security of data transmission into consideration, the denial-of-service attacks with the frequency and duration characterized by the average dwell-time constraint are introduced into data communication, and their influence on the coder string is analyzed explicitly. Thereafter, by imposing reasonable restrictions on the transmission protocol and the occurrence of attacks, the boundedness of coding intervals can be obtained. Since the precision of data is generally limited, it may lead to the situation that the signal to be encoded overflows the coding interval such that it results in the unavailability of the developed coding scheme. To cope with this problem, a dynamic variable is introduced to the design of the protocol. Subsequently, based on the Lyapunov stability theory, sufficient conditions for ensuring the input-to-state stability of the synchronization error systems under the communication-constrained condition and malicious attacks are presented. The validity of the developed method is finally verified by a simulation example of chaotic networks.\enlargethispage-8pt.
- Published
- 2023
29. Data center selection through service broker policy in cloud computing environment
- Author
-
Bhubaneswari Bisoyi, Biswajit Nayak, and Prasant Kumar Pattnaik
- Subjects
business.industry ,End user ,Computer science ,Cloud computing ,General Medicine ,Service provider ,computer.software_genre ,Virtual machine ,Server ,Overhead (computing) ,Data center ,Unavailability ,business ,computer ,Computer network - Abstract
The concept of cloud computing is well known for the sharing of resources, data and information for which it deals with several services like servers, storage, applications. Service broker based on service broker policies handles the routing between data center and user base. The cloud service providers are responsible for providing different application ad infrastructure services to the end user through data centers. Due to the distribution of data centers in several geographical locations, there may be the possibility of overload and in result in unavailability to end users. The study aims to increase the efficiency of the system by choosing proper selection of policy. Service broker policy not only reduces overloading of data center but also enables to choose proper data center. The study discusses the different parameters like response time, processing time and cost that helps to reduce associated overhead and increase performance by selecting proper data center based on service broker policies. This paper also presents the simulation of service broker policy algorithms for the different parameter’s like response time, processing time, cost of assigned virtual machine and data transfer cost.
- Published
- 2023
30. Der lange Weg in die Anerkenntnis des Unverfügbaren: Zum Erleben von Trennung und Abschied in zwei analytisch fundierten Alterspsychotherapien (Teil II).
- Author
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Alegiani, Regine
- Abstract
The long way towards acknowledgement of the unavailable. On separation and farewell in two analytical psychotherapies at old age In this second part of the entire report, the first part of which appeared in an earlier issue (4/2019: 381–394), the author once again focusses on conflicts connected with fear of annihilation when facing separation, thereby concentrating on repeated approaches to calm and to overcome the respective inner turmoil. She tries to release herself from her inclination to focus on the analyst's person and the therapeutical relationship. Instead she attempts to decisively bundle her attention on the contents of the joint work. By doing so she becomes aware of a strong striving for autonomy which thus far had been obscured by early traumatic experiences of separation and an exuberant need for love and closeness. By her own effort she is now able to release the analyst from a longing commitment which, if it were to remain, would set the spiral of repetition in motion again and again. The therapeutically effective support consists in helping her to direct the desire for love – in the sense of a reversal – to where it can be lived meaningfully. For instance, by actively turning it to the community and its social needs, thus filling it with contents aligned with reality. The author finally is able to accept the unavailability of a significant other and the insight that we will not be relieved of the work on the impositions of life. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
31. A HOLISTIC APPROACH TO ENTROPY IN SCIENCE EDUCATION.
- Author
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Akbulut, Faruk and Altun, Yuksel
- Subjects
SCIENCE education ,MEDICAL misconceptions ,ENTROPY ,RESEMBLANCE (Philosophy) ,ALTERNATIVE fuels ,HIGH school students - Abstract
Entropy is a concept with an extreme controversy which many scientists have been trying to explain. Some of the approaches employed in its definition contradict each other, which made it extremely difficult for high school and college students to understand. Boltzmann was the first person who brought a statistical explanation to entropy and linking it with the disorder concept (S = klnw). The point which received the highest amount of criticism is the similarity between the visual regulation in everyday life and regulation of particles, which is the metaphor that causes the highest number of misconceptions. The primary goal of this study is to go down the roots of the controversy surrounding the entropy concept and propose solutions. In the framework of all these difficulties, the concept was investigated with an integrated and simple approach. In this pretext, the macroscopic and microscopic features of entropy, the difficulties and misconceptions encountered, and the methods used in its education have been thoroughly examined. The final step was developing a "Tripod Approach" to facilitate the explanation of this complicated concept and fill the gaps in this area. In addition to it, alternative energy and probability-based and integrated entropy description, which reflects the essence of both macroscopic and microscopic approaches, was presented, and this description is expected to be a solution for the controversy resulting from the disorder concept. [ABSTRACT FROM AUTHOR]
- Published
- 2020
32. A Fast Adequacy Analysis for Radial Distribution Networks Considering Reconfiguration and DGs.
- Author
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Arefi, Ali, Ledwich, Gerard, Nourbakhsh, Ghavameddin, and Behi, Behnaz
- Abstract
The current searching schemes in reliability evaluation of radial distribution systems require complicated and extensive codes, that contribute to the majority of the CPU times. This paper proposes a new one-step method operating with a set of binary descriptor matrices, replacing the searching, to calculate load and system reliability indices. In this technique, ‘fuse to branch’ and ‘switch to branch’ are introduced and employed to facilitate the solutions along with the use of bus-injection to branch-current matrices. In this approach, the cross-connects operation, islanding mode of small-scale DGs, and network constraints are also considered as part of the adequacy evaluation. The proposed technique is highly efficient for long-term distribution network planning and optimization where many cross-connects are involved. The proposed technique is applied to RBTS Bus 2 and 4, as well as a realistic 747-node distribution network. Results for the large distribution planning of the 747-node network demonstrate the computational time is reduced from 61 days using the traditional method to 4.6 hours based on the proposed technique. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
33. An FTA Method for the Unavailability of Supply in Gas Networks Supported by Physical Models.
- Author
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Gjorgiev, Blaze, Antenucci, Andrea, Volkanovski, Andrija, and Sansavini, Giovanni
- Subjects
- *
FAULT trees (Reliability engineering) , *SOCIAL networks , *MAINTENANCE , *GAS analysis , *GASES , *SCHEDULING - Abstract
This paper presents a fault tree analysis (FTA) method for the unavailability of supply of gas networks. The method is based on the automatic generation of fault trees, which estimate the probability of disruption of the gas delivery from terminals/storages to the demand nodes. Moreover, it allows probabilistic analyses of the availability of gas supply to individual demand nodes and to the overall gas network. To assess the importance of each network component, the risk achievement worth and the risk reduction worth importance measures are utilized. The developed method can identify weakness in the gas network and can guide expansion planning and maintenance scheduling activities. Furthermore, the developed framework is enriched by steady-state analysis of the gas network operations performed using a physical flow/pressure model. The impact of a component failure on the gas supply interruption at different demand nodes is assessed by the physical model in retrospective to the FTA results. The framework is exemplified with reference to the reduced gas network of Great Britain. The results provide insights to support a robust reliability assessment of the gas network. Moreover, the probability mapping of the most important components in the gas network informs optimal strategies for maintenance scheduling as well for prioritizing improvements of the gas network aimed at significant risk reduction. Remarkably, the failure of components identified as most important according to the FTA importance measures may not have significant effects on the gas supply. A discussion on the range of applicability and limitations of the two methodologies is provided. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
34. A bi‐objective optimization approach for the maintenance planning of networked systems.
- Author
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Li, Wanshan and Zhang, Chi
- Subjects
- *
MAINTENANCE , *MAINTENANCE costs , *RELIABILITY in engineering , *ECONOMIC development - Abstract
Networked systems, such as telecommunications, transportation, and power transmission, are critical for the economic development and social well‐being of a society and are required to keep the prescribed demand continuously satisfied. Therefore, when planning maintenance actions for such a system, the adverse influence on its reliability caused by the unavailability of the components in the process of being maintained needs to be taken into account. To deal with this problem, we propose a new bi‐objective optimization approach to determine the Pareto optimal maintenance plans for a networked system, simultaneously maximizing its reliability within the concerned planning horizon and minimizing the total maintenance cost. Both perfect and imperfect maintenance actions are considered. The proposed approach can well balance the influence of maintenance actions on a networked system's reliability during their implementation and after being completed and, thus, can help ensure its reliability of continuously satisfying the prescribed demand. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
35. Procedimiento técnico para la reparación de componentes del motor Waukesha L7044
- Author
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Márquez Girón, Raúl Gustavo, León Gutiérrez, Jamilton Humberto, Márquez Girón, Raúl Gustavo, and León Gutiérrez, Jamilton Humberto
- Published
- 2023
36. Load balancing between fog and cloud in fog of things based platforms through software-defined networking
- Author
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Gustavo B. Figueiredo, Ernando Batista, and Cassio Prazeres
- Subjects
General Computer Science ,Edge device ,Computer science ,business.industry ,Local area network ,The Internet ,Cloud computing ,Orchestration (computing) ,Load balancing (computing) ,Unavailability ,business ,Software-defined networking ,Computer network - Abstract
The Internet of Things (IoT) allows for the coordination and orchestration of a large number of physical and virtual objects connected to the Internet. Sensors used in IoT applications may be in remote locations with an unstable network infrastructure or with limited management of their functions due to processing overload on devices responsible for performing their management (i.e. IoT Gateways) through IoT services. A failure or overload on a network link associated with an IoT Gateway, or failure on the IoT Gateway itself due to processing overload, may result in temporary or even permanent unavailability in IoT applications (Web, Mobile, and Desktop). To address these problems, this paper presents a solution for the need to execute load balancing for the Fog of Things Platforms (in the Fog, and between Fog and Cloud) via the programmability through the use of Software-Defined Networks (SDN). The IoT environment proposed in this work is based on the Fog of Things (FoT) paradigm, which proposes the provision of processing, storage and IoT services at edge devices (local network), optimizing , when possible, the use of IoT services in the Cloud.
- Published
- 2022
37. Optimized Task Allocation for IoT Application in Mobile-Edge Computing
- Author
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Jialei Liu, Chunhong Liu, Gao Guowei, Shangguang Wang, and Bo Wang
- Subjects
Scheme (programming language) ,Mobile edge computing ,Computer Networks and Communications ,Computer science ,business.industry ,Distributed computing ,Computer Science Applications ,Task (computing) ,Resource (project management) ,Hardware and Architecture ,Server ,Signal Processing ,Enhanced Data Rates for GSM Evolution ,Unavailability ,Internet of Things ,business ,computer ,Information Systems ,computer.programming_language - Abstract
With the rapid upgrading and explosive growth of Internet of Things (IoT) devices in mobile edge computing, more and more IoT applications with high resource requirements are developed and utilized. Meanwhile, there are large quantities of edge nodes (e.g., switches and edge servers) with limited resources, higher operating costs, and certain failure probabilities in mobile edge computing environment. Therefore, when an IoT application is split into multiple collaborative tasks and offloaded into multiple edge clouds, there is an urgent need to increase the availability level of the task allocation scheme and the resource utilization of edge servers under the condition of certain communication delay. In this paper, we first present a joint optimization objective to evaluate the unavailability level, communication delay, and resource wastage while allocating the same batch of IoT applications to multiple edge clouds. We then propose an approach to minimize the joint optimization objective under the condition of certain communication delay. Finally, we performed a comprehensive simulation experiment analysis to demonstrate that our proposed approach is superior to other related approaches.
- Published
- 2022
38. A novel mixed integer programming model for freight train travel time estimation
- Author
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Bijan Taslimi, Panos M. Pardalos, Farnaz Babaie Sarijaloo, and Hongcheng Liu
- Subjects
Schedule ,Information Systems and Management ,General Computer Science ,Operations research ,business.industry ,Computer science ,Rail freight transport ,Management Science and Operations Research ,Solver ,Complex network ,Industrial and Manufacturing Engineering ,Resource (project management) ,Modeling and Simulation ,Train ,Unavailability ,business ,Integer programming - Abstract
Travel time estimation is a crucial problem in the field of transportation. While this problem has been extensively studied for over-the-road and air travel modes of transportation and researchers have accomplished substantial advancements in improving the accuracy of the related models, we still observe a significant lack of accurate methods for estimating the travel time of freight trains. The planned train schedule is often dramatically affected by the delays that occur in complex networks due to various reasons such as train movement conflicts, resource unavailability, and unforeseen conditions. We develop a novel mixed integer programming model to address this problem. Considering the current train schedule, characteristics of the railroads, availability of resources, operational restrictions, different types of delay, and congestion-related factors, the proposed model obtains the estimated travel time of trains by minimizing the total amount of deviation from the planned timetable. This optimization scheme enables us to impose all business constraints and network restrictions on the model. Our proposed formulation is generic and can be utilized for other railway networks with minor modifications. To evaluate our model, we use the network characteristics and planned trains movement data of Prorail in Netherlands. The model is implemented in Julia and solved with Gurobi solver efficiently which demonstrates the superiority of our approach.
- Published
- 2022
39. On Designing Strategy-Proof Budget Feasible Online Mechanisms for Mobile Crowdsensing With Time-Discounting Values
- Author
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Shuo Yang, Guihai Chen, Jiapeng Xie, Xiaofeng Gao, Zhenzhe Zheng, and Fan Wu
- Subjects
Consumption (economics) ,Mechanism design ,Incentive ,Competitive analysis ,Risk analysis (engineering) ,Computer Networks and Communications ,Computer science ,Property (programming) ,Electrical and Electronic Engineering ,Unavailability ,Time preference ,Private information retrieval ,Software - Abstract
Mobile crowdsensing has become increasingly popular due to its ability to collect a massive amount of data with the help ofmany individual smartphone users. Due to the rationality of smartphone users, designing an incentive mechanism to compensate the participants for their resources consumption is critical in attracting more participation. Offline incentive mechanism design has been widely studied in various crowdsensing applications, whereas the online scenario, is much more challenging due to the unavailability of future information when the platform makes user selection decisions. In this paper, we investigate the problem of online crowdsensing by considering a critical property that the values of users contributions decrease as time goes by. The time-discounting property is common in inter-temporal choice scenarios but has not been carefully addressed in mechanism design perspective. To handle this problem, we propose a new method to select users based on a time-related threshold, and present a strategyproof framework where participants prefer to submit their true types, instead of manipulating the market by misreporting their private information. We prove that our mechanisms can achieve computational efficiency, budget feasibility, strategy-proofness, and a constant competitive ratio.
- Published
- 2022
40. Medicine shortages: there are solutions! Actions to take to reduce medicine shortages.
- Author
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Ryan, Michael J.
- Subjects
- *
INVENTORY shortages , *STAKEHOLDER analysis , *INFORMATION resources management , *MOTIVATION (Psychology) , *UNCERTAINTY , *DRUGS , *COMMUNICATION , *INTERPROFESSIONAL relations , *PHARMACEUTICAL industry - Abstract
The aim of this paper is to propose solutions to reduce the number and frequency of medicine shortages in Australia. Some of the many factors that contribute to medicine shortages, such as manufacturers' production processes and business decisions, are outside the control of Australian stakeholders. But there are many factors that are within the control of stakeholders, including poor communication between stakeholders, incomplete and inaccurate information, unhelpful practices and attitudes of hospital tender authorities, and lack of certainty and incentives for manufacturers in relation to pharmaceutical tenders. The following strategies are designed to address these issues and achieve a significant reduction in the number and frequency of medicine shortages in Australian hospitals. They include improving communication and understanding between stakeholders, providing higher quality information on likely usage, changing practices of hospital tender authorities to better meet stakeholder requirements, and increasing incentives for manufacturers to participate in hospital tenders. The six key actions to implement the medicine shortage-reducing strategies are: (1) initiate a biannual forum for hospitals and industry; (2) establish a medicines substitutes information service operating nationally; (3) share information on likely changes to hospital usage; (4) reform stock allocation strategies; (5) introduce incentives for manufacturers; and (6) change hospital tender authority practices and policies. The first step to reduce medicine shortages is for stakeholders to think differently about the problem, and to act more collaboratively using the proposed strategies and actions, as a framework for change. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
41. State-of-Charge Estimation of Lithium-Ion Batteries Subject to Random Sensor Data Unavailability: A Recursive Filtering Approach
- Author
-
Hui Chen, Licheng Wang, and Engang Tian
- Subjects
Nonlinear system ,State of charge ,Optimization problem ,Control and Systems Engineering ,Bernoulli distribution ,Computer science ,Electrical and Electronic Engineering ,Covariance ,Unavailability ,Upper and lower bounds ,Algorithm ,Random variable - Abstract
In this paper, the estimation problem of the state of charge (SOC) of Lithium-ion batteries is investigated. In order to truly reflect the unreliability of the sensor measured data, the data missing phenomenon with respect to the sensor measurement (e.g.~the terminal voltage) is taken into account for the addressed estimation issue. By introducing a stochastic variable obeying the Bernoulli distribution with a known probability, the random occurrence of the sensor measurement unavailability is well characterized. The second-order resistor-capacitor equivalent circuit model, where the model parameters are identified by the recursive least square method, is developed to govern the dynamical behaviors of an Lithium-ion battery. A data-unavailability-resistant nonlinear recursive filtering algorithm is proposed to estimate the real SOC in an unreliable industrial environment. An upper bound of the filtering error covariance is obtained, which is further minimized at each sampling instant. In addition, the filter gain is recursively parameterized by solving an optimization problem with respect to two coupled recursive Riccati-like equations, thereby being suitable for the online implementation. Finally, extensive experiments are conducted to demonstrate the validity of the proposed filtering approach.
- Published
- 2022
42. Predicting LncRNA-Disease Association Based on Generative Adversarial Network
- Author
-
Lin Tang, Wei Zhou, Biao Du, and Lin Liu
- Subjects
Discriminator ,business.industry ,Computer science ,Process (engineering) ,media_common.quotation_subject ,Association (object-oriented programming) ,Stability (learning theory) ,Machine learning ,computer.software_genre ,Drug Discovery ,Genetics ,Humans ,Molecular Medicine ,Genetic Predisposition to Disease ,RNA, Long Noncoding ,Pairwise comparison ,Artificial intelligence ,Unavailability ,business ,Function (engineering) ,Molecular Biology ,computer ,Genetics (clinical) ,media_common ,Generator (mathematics) - Abstract
Background: Increasing research reveals that long non-coding RNAs (lncRNAs) play an important role in various biological processes of human diseases. Nonetheless, only a handful of lncRNA-disease associations have been experimentally verified. The study of lncRNA-disease association prediction based on the computational model has provided a preliminary basis for biological experiments to a great degree so as to cut down the huge cost of wet lab experiments. Objective: This study aims to learn the real distribution of lncRNA-disease association from a limited number of known lncRNA-disease association data. This paper proposes a new lncRNA-disease association prediction model called LDA-GAN based on a Generative Adversarial Network (GAN). Method: Aiming at the problems of slow convergence rate, training instabilities, and unavailability of discrete data in traditional GAN, LDA-GAN utilizes the Gumbel-softmax technology to construct a differentiable process for simulating discrete sampling. Meanwhile, the generator and the discriminator of LDA-GAN are integrated to establish the overall optimization goal based on the pairwise loss function. Results: Experiments on standard datasets demonstrate that LDA-GAN achieves not only high stability and high efficiency in the process of confrontation learning but also gives full play to the semisupervised learning advantage of generative adversarial learning framework for unlabeled data, which further improves the prediction accuracy of lncRNA-disease association. Besides, case studies show that LDA-GAN can accurately generate potential diseases for several lncRNAs. Conclusion:: We introduce a generative adversarial model to identify lncRNA-disease associations.
- Published
- 2022
43. Adaptive Fuzzy Control for Uncertain Mechatronic Systems With State Estimation and Input Nonlinearities
- Author
-
Tong Yang, Yongchun Fang, and Ning Sun
- Subjects
Lyapunov function ,Equilibrium point ,Computer science ,Fuzzy control system ,Computer Science Applications ,symbols.namesake ,Nonlinear system ,Exponential stability ,Control and Systems Engineering ,Control theory ,symbols ,Electrical and Electronic Engineering ,Unavailability ,Actuator ,Information Systems - Abstract
In the field of practical engineering, the performance of mechatronic systems is influenced by model uncertainties, velocity unavailability, input nonlinearities (e.g., actuator deadzones/ faults), etc. Moreover, some complex nonlinear dynamics do not satisfy the linear parameterization condition. Hence, due to intractable approximation errors, some existing controllers may obtain only uniformly ultimately bounded results and require velocity feedback to accomplish online estimation. To overcome the above obstacles, this paper designs a new output feedback controller to fulfill accurate trajectory tracking and obtain state estimates for a class of Euler-Lagrange mechatronic systems. Specifically, we first construct a group of auxiliary variables to accurately recover velocities without numerical differential operations. Then, by employing only the available output information, unknown model knowledge and actuator deadzones/faults are simultaneously approximated online; more importantly, the asymptotic stability of the system equilibrium point is guaranteed by strict theoretical analysis. Another merit of the proposed controller is that the approximation errors are addressed in a new way, where no discontinuous robust terms are required; hence, the chattering problem is effectively alleviated. To the best of our knowledge, for uncertain Euler-Lagrange mechatronic systems with actuator deadzones/faults, this paper proposes the first solution to eliminate tracking errors and accurately recover unmeasurable states by continuous control signals. The asymptotic convergence of closed-loop signals is proven based on Lyapunov methods, and the performance of the proposed controller is validated by hardware experiments.
- Published
- 2022
44. Quorums over codes
- Author
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Anwitaman Datta, Frederique Oggier, School of Computer Science and Engineering, and School of Physical and Mathematical Sciences
- Subjects
Computer Networks and Communications ,Sequential consistency ,Computer science ,Distributed computing ,Node (networking) ,Locality ,Quorums ,Theoretical Computer Science ,Consistency (database systems) ,Artificial Intelligence ,Hardware and Architecture ,Erasure Codes ,Code (cryptography) ,Computer science and engineering [Engineering] ,Read-Modify-Write ,Unavailability ,Software ,Sequential Consistency ,Complement (set theory) ,Coding (social sciences) - Abstract
We consider the design and analysis of quorum systems over erasure coded warm data (with low frequency of writes and accesses in general) to guarantee sequential consistency under a fail-stop model while supporting atomic read-modify-write operations by multiple clients. We propose a definition of asymmetric quorum systems that suit the framework of coded data by explicitly exploiting the structural properties of code and instantiate it over distinct families of coding strategies: maximum distance separable (MDS) codes and codes with locality, and we indicate a mechanism for synchronizing stale nodes using differential updates, which again exploits the code structures. The proposed quorum system’s behavior is analyzed theoretically, exploring several aspects: viability of quorums under node unavailability; contention of resources between read and write operations; and quorum load. We complement these theoretical exploration with simulation based experiments to quantify the behavior of the proposed mechanism. The overall study demonstrates the feasibility and practicality of quorums over codes under practicable assumptions for achieving a stringent form of consistency, specifically, sequential consistency, while the stored data is being mutated by potentially multiple processes that might read and then modify the existing data. We achieve this in-place, without having to resort to store multiple versions of the data. Ministry of Education (MOE) Accepted version Anwitaman Datta’s research is supported by the Ministry of Education (MoE), Singapore, under its Academic Research Fund Tier 1 (Project ID: 2018- T1-002-076) for the project titled ‘StorEdge: Data store along a cloud-to-thing continuum with integrity and availability’.
- Published
- 2022
45. Iterative Learning Control: Practical Implementation and Automation
- Author
-
Samer S. Saab, David Kors, Rayana H. Jaafar, Mohamad Orabi, and Dong Shen
- Subjects
Adaptive control ,business.industry ,Computer science ,Iterative learning control ,Control engineering ,Automation ,law.invention ,Industrial robot ,Control and Systems Engineering ,law ,Control theory ,Robot ,Process control ,Electrical and Electronic Engineering ,Unavailability ,business - Abstract
Iterative learning control (ILC) has been well recognized for its output tracking ability in systems that perform repetitive tasks, such as robot manipulators. In practice, however, the application of ILC remains challenging as it generally requires the repetition of the initial settings and such industrial manipulators do not provide measurements of actual joint positions. This article presents a practical and fully automated implementation of ILC for industrial robot manipulators while assuming complete model uncertainty and the unavailability of joint velocity measurements. We propose the employment of a dedicated controller tasked only with bringing the arm back to its initial position while reducing the joint position reinitialization error after every iteration. We show that the convergence of the position tracking error is bounded by the initial mismatch. Finally, we provide experimental justification of the proposed approach on a 4-DOF commercial robot manipulator while only using the measurements of relative joint positions and show that our fully automated process outperforms two ILC algorithms with thorough manual homing.
- Published
- 2022
46. Dynamic Task Placement for Deadline-Aware IoT Applications in Federated Fog Networks
- Author
-
Sanjay Kumar, Indranil Sarkar, Neeraj Kumar, and Mainak Adhikari
- Subjects
Computer Networks and Communications ,Computer science ,business.industry ,Node (networking) ,Distributed computing ,Controller (computing) ,Context (computing) ,Cloud computing ,Computer Science Applications ,Task (project management) ,Resource (project management) ,Hardware and Architecture ,Signal Processing ,Minification ,Unavailability ,business ,Information Systems - Abstract
In the era of the Internet of Things (IoT), fog computing has become an enticing concept for supporting delay-sensitive tasks by offering versatile and convenient computing and communication services to the end-users, in conjunction with cloud services. Most of the existing researches mainly draws attention to the communication delay minimization and completion time reduction in the hierarchical fog networks without giving the priority to select the suitable computing device during failure or resource unavailability of the current computing devices. By motivating the above-mentioned challenges, in this paper, we propose a deadline-aware dynamic task placement (DDTP) strategy to offload and place the tasks to a suitable computing device in fog networks. In this context, we design a new federated fog framework consisting of several fog clusters in which the cluster head, termed as master fog node, acts as a fog controller that controls and manages the data distribution among the other fog nodes, termed as slave fog nodes. The proposed DDTP strategy selects the suitable computing device for each incoming task as per the deadline and ensures to meet the deadline constraints of the tasks using a dynamic task allocation policy. Finally, a dispatch-constrained offloading policy is developed to reassign the failed tasks to the available fog nodes in the network. Comprehensive simulation results depict the efficiency of the proposed strategy over the existing baseline algorithms in terms of various performance matrices.
- Published
- 2022
47. Resilience of hydropower plants to flow variation through the concept of flow elasticity of power: Theoretical development
- Author
-
Dibesh Shrestha, Suresh Marahatta, Laxmi Prasad Devkota, Pawan Khatri, and Utsav Bhattarai
- Subjects
Elasticity (cloud computing) ,Electricity generation ,Renewable Energy, Sustainability and the Environment ,business.industry ,Streamflow ,Flow (psychology) ,Environmental science ,Production (economics) ,Unavailability ,Environmental economics ,business ,Resilience (network) ,Hydropower - Abstract
Fluctuation in hydro-electricity production is primarily attributed to natural and human-induced flow variations. Reduced electricity generation because of unavailability of flow inflicts significant upward pressure on the sources and prices. Despite studies on the impact of externalities on river flow variation, there is a distinct research gap on the responsiveness of hydropower plants to change in flow. This study has introduced a novel concept of flow elasticity of power ( e ) to assess the resilience of hydropower projects to flow variation. The theoretical aspect has been established for run-of-river (ROR) and storage-type (ST) cases separately and validated at two projects, one of each type, located in the Budhigandaki Basin in central Nepal. Responsiveness of hydro-projects to the topographical parameters are also dealt with here. For ROR systems, wide-ranging values of e indicate varying levels of resilience to power generation and loss of resources. For ST projects, the response differs according to emptying, filling and ROR-equivalent phases. Furthermore, strong topographical implications on power production and its elasticity are evident. This concept of e sets out a significant research contribution in the hydropower sector and demonstrates its possibility of direct application in projects in ‘priori’ as well as ‘posteriori’ while planning/designing and updating stages, respectively. The e coefficient scientifically informs the planners and developers on the sensitivity of the powerplants to hydrological variations and topography ultimately benefitting the existing global challenge to minimize the loss of precious resources for sustainable hydropower development.
- Published
- 2022
48. Single-machine scheduling with machine unavailability periods and resource dependent processing times
- Author
-
Dvir Shabtay
- Subjects
050210 logistics & transportation ,Mathematical optimization ,021103 operations research ,Information Systems and Management ,Single-machine scheduling ,General Computer Science ,Job shop scheduling ,Computer science ,05 social sciences ,0211 other engineering and technologies ,Approximation algorithm ,02 engineering and technology ,Interval (mathematics) ,Function (mathematics) ,Management Science and Operations Research ,Industrial and Manufacturing Engineering ,Resource (project management) ,Modeling and Simulation ,Bounded function ,0502 economics and business ,Unavailability - Abstract
We study a single-machine scheduling problem, where each of the job processing times is a bounded linear decreasing function of the amount of resource allocated to its processing operation, and there is a single and fixed machine-unavailability interval that begins at time T . A solution is given by (i) partitioning the jobs into two sets, corresponding to the set of jobs to be processed before and after the unavailability period; and (ii) defining the amount of resource allocated to the processing operation of each of the jobs. A solution is feasible if the total processing time of all jobs assigned to be processed before the unavailability period does not exceed T . Our aim is to find a feasible solution that minimizes the makespan plus the total resource consumption cost. As the problem is known to be NP-hard even for constant processing times, we focus on the design of pseudo-polynomial time and approximation algorithms. Extension to the case of a fixed number of unavailability intervals is also provided.
- Published
- 2022
49. Perceived stress factors and coping strategies of COVID ward nurses:Psychological impact of COVID 19
- Author
-
Bharathy R, Sophia Vijayananthan, Mary Jancy Joy, and Ilavarasi Jesudoss
- Subjects
Coronavirus disease 2019 (COVID-19) ,Stress (linguistics) ,Unavailability ,Psychology ,Clinical psychology - Abstract
The Corona Virus Disease 2019 (COVID-19) outbreak, which began in Wuhan, China in 2019, has now spread to every corner of the globe. Nurses dealing with COVID patients, in particular, are overburdened around the world. Nurses have been forced to make unavoidable lifestyle adjustments due to disruptions in their everyday work routines and active changes in procedures and policies. This study aimed at determining psychological impact of COVID 19 pandemic (perceived stressors, stress reducing factors, coping strategies) among nursing personnel involved in caring patients with COVID 19. Nursing staff who had taken care of patients with COVID 19 for minimum period of two weeks completed the self-administered instrument. The data was analyzed using descriptive and inferential statistics. Inconvenience due to constant use of Personnel Protective Equipment (PPE) (94 %) and lock down restrictions (93 %), vaccine unavailability (90%), and uncertainty of treatment steps were the main sources of stress for the nurses (89 %). The majority of the nursing staff (72%) was stressed about the risk of developing an infection and 75 % of the staff was concerned about the risk of transmitting COVID to their family members and friends. Trusting GOD for protection, adhering to strict infection control measures and lockdown restrictions were all coping strategies that helped them deal with the pandemic. More than 90% of nurses accepted that their coping mechanisms included engaging in relaxation/diversional activities, maintaining a well-balanced diet and getting adequate rest.
- Published
- 2021
50. Nested Bilevel Optimization for DERA Operation Strategy: A Stochastic Multiobjective IGDT Model With Hybrid Endogenous/Exogenous Scenarios
- Author
-
Nima Amjady, Mohsen Yazdaninejad, and Nikos Hatziargyriou
- Subjects
Mathematical optimization ,Wind power ,Computer Networks and Communications ,Computer science ,business.industry ,Decision theory ,computer.software_genre ,Bilevel optimization ,Stochastic programming ,Computer Science Applications ,News aggregator ,Operator (computer programming) ,Control and Systems Engineering ,Distributed generation ,Electrical and Electronic Engineering ,Unavailability ,business ,computer ,Information Systems - Abstract
An aggregation of distributed energy resources (DERs) can bring economic and technical benefits for the DER owners and system operator. However, the operation of DERs encounters various uncertainties, which can seriously impact the benefits of DER aggregation. This article presents a new operation optimization approach for an aggregator of DERs considering the unavailability of DERs (as discrete uncertainty sources) as well as forecast uncertainties of electricity prices, solar powers, and wind powers (as continuous uncertainty sources). The proposed approach for DER aggregator (DERA) operation optimization comprises stochastic multiobjective information-gap decision theory (IGDT) to model these discrete and continuous uncertain variables. Moreover, a hybrid endogenous/exogenous scenario generation method is incorporated into the proposed approach to enhance the efficiency of the stochastic programming part by producing decision-dependent scenario trees. The proposed approach is formulated as a nested bilevel optimization model. The proposed approach is compared with other DERA operation optimization models using an out-of-sample analysis method. The comparative results illustrate the superiority of the proposed stochastic multiobjective IGDT approach over various deterministic, stochastic, and IGDT methods. In addition, the high tractability of the proposed solution method is illustrated, while its linearization error for the stochastic multiobjective IGDT problem is well below 1%.
- Published
- 2021
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