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2022 ◽  
Vol 40 (2) ◽  
pp. 1-31
Author(s):  
Masoud Mansoury ◽  
Himan Abdollahpouri ◽  
Mykola Pechenizkiy ◽  
Bamshad Mobasher ◽  
Robin Burke

Fairness is a critical system-level objective in recommender systems that has been the subject of extensive recent research. A specific form of fairness is supplier exposure fairness, where the objective is to ensure equitable coverage of items across all suppliers in recommendations provided to users. This is especially important in multistakeholder recommendation scenarios where it may be important to optimize utilities not just for the end user but also for other stakeholders such as item sellers or producers who desire a fair representation of their items. This type of supplier fairness is sometimes accomplished by attempting to increase aggregate diversity to mitigate popularity bias and to improve the coverage of long-tail items in recommendations. In this article, we introduce FairMatch, a general graph-based algorithm that works as a post-processing approach after recommendation generation to improve exposure fairness for items and suppliers. The algorithm iteratively adds high-quality items that have low visibility or items from suppliers with low exposure to the users’ final recommendation lists. A comprehensive set of experiments on two datasets and comparison with state-of-the-art baselines show that FairMatch, although it significantly improves exposure fairness and aggregate diversity, maintains an acceptable level of relevance of the recommendations.


2022 ◽  
Vol 18 (1) ◽  
pp. 1-31
Author(s):  
Chaojie Gu ◽  
Linshan Jiang ◽  
Rui Tan ◽  
Mo Li ◽  
Jun Huang

Low-power wide-area network technologies such as long-range wide-area network (LoRaWAN) are promising for collecting low-rate monitoring data from geographically distributed sensors, in which timestamping the sensor data is a critical system function. This article considers a synchronization-free approach to timestamping LoRaWAN uplink data based on signal arrival time at the gateway, which well matches LoRaWAN’s one-hop star topology and releases bandwidth from transmitting timestamps and synchronizing end devices’ clocks at all times. However, we show that this approach is susceptible to a frame delay attack consisting of malicious frame collision and delayed replay. Real experiments show that the attack can affect the end devices in large areas up to about 50,000, m 2 . In a broader sense, the attack threatens any system functions requiring timely deliveries of LoRaWAN frames. To address this threat, we propose a LoRaTS gateway design that integrates a commodity LoRaWAN gateway and a low-power software-defined radio receiver to track the inherent frequency biases of the end devices. Based on an analytic model of LoRa’s chirp spread spectrum modulation, we develop signal processing algorithms to estimate the frequency biases with high accuracy beyond that achieved by LoRa’s default demodulation. The accurate frequency bias tracking capability enables the detection of the attack that introduces additional frequency biases. We also investigate and implement a more crafty attack that uses advanced radio apparatuses to eliminate the frequency biases. To address this crafty attack, we propose a pseudorandom interval hopping scheme to enhance our frequency bias tracking approach. Extensive experiments show the effectiveness of our approach in deployments with real affecting factors such as temperature variations.


Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 320
Author(s):  
Muttahid Ull Hoque ◽  
Deepak Kumar ◽  
Yves Audet ◽  
Yvon Savaria

In this article, the concept of a 22-kW microwave-powered unmanned aerial vehicle is presented, where the critical system architecture is analyzed and modeled for wirelessly transferring microwave power to the flying UAVs. The microwave system transmitting power at a 35 GHz frequency was found to be suitable for low-cost and compact architectures. The size of the transmitting and receiving systems are optimized to 108 m2 and 90 m2, respectively. A linearly polarized 4 × 2 rectangular microstrip patch antenna array has been designed and simulated to obtain a high gain, high directivity, and high efficiency in order to satisfy the power transfer requirement. The numerically simulated gain, directivity, and efficiency of the proposed patch antenna array are 13.4 dBi, 14 dBi, and 85%, respectively. Finally, a rectifying system (rectenna) is optimized using the Agilent advanced design system (ADS) software as a microwave power receiving system. The proposed rectenna has an efficiency profile of more than 80% for an RF input power range of 9 to 18 dBm. Moreover, the RF-to-DC conversion efficiency and DC output voltage of the proposed rectenna is 80% and 3.5 V, respectively, for a 10 dBm input power at 35 GHz with a load of 1500 Ω.


2022 ◽  
Vol 386 ◽  
pp. 111567
Author(s):  
Bin Liu ◽  
Xinying Zhang ◽  
Fang Liu ◽  
Wenqiang Dou ◽  
Jibing Wang

ijd-demos ◽  
2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Deliya Gustiani

Abstract This study describes the conflict management carried out by the Bogor City Government over the conflicts that occurred between the Forum Muslim Bogor and the Chinese Community. In this conflict, it was found that there was intolerance that occurred in the people of Bogor City ahead of the Cap Go Meh celebration in 2019. Where the case of intolerance was carried out by issuing a circular issued by the Forum Muslim Bogor through social media. The letter was circulated very widely which contained an appeal to the Bogor City Government not to facilitate the Cap Go Meh/Bogor Street Festival celebration and called for the Muslim community not to participate in the event because it was considered to damage the faith. In this study, the focus will be on conflict resolution efforts carried out by the Bogor City Government using the theory of Conflict Management and Critical System Heuristics. The research method used is descriptive qualitative research method. Therefore, this study will look at how the conflict resolution carried out by the Bogor City Government towards the conflict. Keywords: conflict resolution, bogor city government, cap go meh.     Abstrak Penelitian ini menjelaskan mengenai manajemen konflik yang dilakukan oleh Pemerintah Kota Bogor atas konflik yang terjadi antara Forum Muslim Bogor dengan Masyarakat Tionghoa. Dalam konflik ini ditemukan adanya intoleransi yang terjadi dimasyarakat Kota Bogor menjelang perayaan Cap Go Meh tahun 2019. Dimana kasus intoleransi tersebut dilakukan dengan cara mengeluarkan surat edaran yang dilakukan oleh Forum Muslim Bogor melalui media sosial. Surat tersebut beredar sangat luas yang mana berisikan mengenai seruan kepada Pemerintah Kota Bogor agar tidak memfasilitasi Perayaan Cap Go Meh/Bogor Street Festival dan menyerukan agar masyarakat muslim tidak berpartisipasi dalam acara tersebut karena dinilai dapat merusak akidah. Dalam penelitian ini akan lebih fokus terhadap upaya resolusi konflik yang dilakukan  oleh Pemeritah Kota Bogor dengan menggunakan teori Manajemen Konflik dan Critical System Heuristic. Adapun metode penelitian yang digunakan adalah metode penelitian deskriptif kualitatif. Penelitian ini akan melihat bagaimana resolusi konflik yang dilakukan Pemerintah Kota Bogor terhadap konflik tersebut. Kata Kunci: resolusi konflik, pemerintah kota bogor, cap go meh. 


Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2453
Author(s):  
Dmitry Zegzhda ◽  
Evgeny Pavlenko ◽  
Elena Aleksandrova

This paper looks at the problem of cybersecurity in modern cyber-physical and information systems and proposes an immune-like approach to the information security of modern complex systems. This approach is based on the mathematical modeling in information security—in particular, the use of immune methods to protect several critical system nodes from a predetermined range of attacks, and to minimize the success of an attack on the system. The methodological approach is to systematize the tasks, means and modes of immunization to describe how modern systems can counter the spread of computer attacks. The main conclusions and recommendations are that using an immunization approach will not only improve the security of systems, but also define principles for building systems that are resistant to cyber attacks. The immunization approach enables a symmetrical response to an intruder in a protected system to be produced rapidly. This symmetry provides a step-by-step neutralization of all stages of a cyber attack, which, combined with the accumulation of knowledge of the attacker’s actions, allows a base of defensive responses to be generated for various cyber attack scenarios. The theoretical conclusions are supported by practical experiments describing real-world scenarios for the use of immunization tools to protect against cyber threats.


2021 ◽  
Vol 156 (A2) ◽  
Author(s):  
V Rumawas ◽  
B E Asbjørnslett

Most serious accidents at sea are caused by minor incidents that escalated into an uncontrolled situation. This study is aiming to develop a model to investigate the likelihood of fatal accidents, given that a critical incident has already occurred. The focus of the study is on human behaviour, adopting a hardware reliability perspective. The vessel is considered as a safety-critical system to be protected by several barriers. The crew role is modelled as active barriers and distinguishing between different functions: perception, decision and action. A Markov approach is proposed to model different situations on the vessel. A mathematical model to estimate the probability of failure in an emergency situation is formulated. A new parameter is defined for the survivability of a vessel, given that a critical incident has taken place. The methods were applied to examine ship-platform collisions cases and the results show strong benefits for diagnosing and evaluating accidents from a human factors perspective as well as for training purposes.


2021 ◽  
Author(s):  
Yahya Hamood Al Naumani ◽  
Abdul Aziz Ahmed Al Abri ◽  
Mahmood Ahmed Al Ruqaishi

Abstract Emergency Shutdown (ESD) and Blowdown (BDV) valves are the final elements part of the Safety Instrumented Functions (SIF) in which are deployed in oil and gas assets. They are classified as safety critical equipment to prevent major accident hazards. The conventional method of proof testing these valves is to close/open them fully, and thus require a process shutdown. In general, planned process shutdown is only viable every two to four years. Such infrequent and limited tests lead to imperfect testing and degrade the reliability of safety instrumented functions. Accordingly, this paper presents the work done to develop a comprehensive maintenance strategy that addresses lifecycle management of safety instrumented function in operate phase which help reduce the potential of process safety incidents. In summary, the innovative approach presented by this paper offers best practice of safety critical system integrity management implementation to achieve the highest standards of operational excellence.


2021 ◽  
Author(s):  
◽  
Leo Browning

<p>Networks of nanomaterials sit at a confluence of desirable features for the fabrication of advanced electronic devices, including facile fabrication, high conducting element density, and novel electrical characteristics. The spatial conduction through carbon nanotube (CNT) and Ag-Ag₂S-Ag atomic switch networks was investigated to determine how better to implement them in novel sensing and computation device platforms.  Selective gating of localized regions of CNT networks with varying densities was investigated. To achieve this, lithographically defined FET structures were developed that allowed gating of localised regions of the CNT FET network area. The CNT FET device sensitivity to gating of different regions of the CNT network was measured for devices with network densities close to the percolation threshold. A 10² increase in sensitivity to local gating for CNT FET devices with low network densities was observed compared with high-density CNT networks. Networks densities were all well below a density where metallic shorts could be present, so the trends observed were attributed to m-s junction dominated gating of the network. A better understanding of the dominant conduction in CNT network FETs at low network densities is important for tuning their properties for use as novel biosensing platforms or a tunable connectivity conducting film.  A CNT network simulation was developed to test the effects of local gating on networks of bundled CNTs with varying densities. Up to 70,000 bundles on a 60 µm x 60 µm simulated network area were used to generate an electrical network of field sensitive elements where the gate field could be spatially modified to investigate the effect of local gating. Monte Carlo methods were used to simulate large numbers of random networks with m-s junctions as the dominant gate-dependent element. Networks with 13.5% metallic bundles were shown to exhibit trends in local gating similar to the experimental systems. Current density maps showed key conduction paths in low-density devices, which supports a model of m-s junction dominance to explain the local and global gate responses measured in experimental CNT FET systems.  Prototype Ag-Ag₂S-Ag atomic switch networks (ASN) device were fabricated using spray-coated silver nanowires which were sulfurised using gas-phase sulfur after deposition. Electrical formation of memristive junctions and hysteretic switching curves were shown under swept voltage bias demonstrating memristive behaviour. ASN devices have been demonstrated to show critical dynamics and memristive characteristics due to the complex connection of atomic switches formed at Ag-Ag₂S-Ag junctions between wires.  A fabrication and measurement protocol for ASN based neuromorphic devices on multi-electrode array (MEA) platforms was developed. The electrical measurement system was designed and deployed to facilitate time-resolved measurement across multiple channels simultaneously on those MEA platforms. Under DC bias, MEA-based ASN devices showed switching events with a power-law distribution over two orders of magnitude of conductance changes and time intervals consistent with self-organized criticality within the network. The dynamic response of the critical system was measured across the network area. Changes in the relative voltage across the ASN network area were observed using 16 channel MEA platforms, showing spatiotemporal variation in voltage across the network. Novel application of principal component analysis to ASNswas used to demonstrate reduction of dimension while preserving relative voltage changes. This paves the way for scalable analysis of the complex dynamic signals from critical ASN systems.</p>


2021 ◽  
Author(s):  
◽  
Leo Browning

<p>Networks of nanomaterials sit at a confluence of desirable features for the fabrication of advanced electronic devices, including facile fabrication, high conducting element density, and novel electrical characteristics. The spatial conduction through carbon nanotube (CNT) and Ag-Ag₂S-Ag atomic switch networks was investigated to determine how better to implement them in novel sensing and computation device platforms.  Selective gating of localized regions of CNT networks with varying densities was investigated. To achieve this, lithographically defined FET structures were developed that allowed gating of localised regions of the CNT FET network area. The CNT FET device sensitivity to gating of different regions of the CNT network was measured for devices with network densities close to the percolation threshold. A 10² increase in sensitivity to local gating for CNT FET devices with low network densities was observed compared with high-density CNT networks. Networks densities were all well below a density where metallic shorts could be present, so the trends observed were attributed to m-s junction dominated gating of the network. A better understanding of the dominant conduction in CNT network FETs at low network densities is important for tuning their properties for use as novel biosensing platforms or a tunable connectivity conducting film.  A CNT network simulation was developed to test the effects of local gating on networks of bundled CNTs with varying densities. Up to 70,000 bundles on a 60 µm x 60 µm simulated network area were used to generate an electrical network of field sensitive elements where the gate field could be spatially modified to investigate the effect of local gating. Monte Carlo methods were used to simulate large numbers of random networks with m-s junctions as the dominant gate-dependent element. Networks with 13.5% metallic bundles were shown to exhibit trends in local gating similar to the experimental systems. Current density maps showed key conduction paths in low-density devices, which supports a model of m-s junction dominance to explain the local and global gate responses measured in experimental CNT FET systems.  Prototype Ag-Ag₂S-Ag atomic switch networks (ASN) device were fabricated using spray-coated silver nanowires which were sulfurised using gas-phase sulfur after deposition. Electrical formation of memristive junctions and hysteretic switching curves were shown under swept voltage bias demonstrating memristive behaviour. ASN devices have been demonstrated to show critical dynamics and memristive characteristics due to the complex connection of atomic switches formed at Ag-Ag₂S-Ag junctions between wires.  A fabrication and measurement protocol for ASN based neuromorphic devices on multi-electrode array (MEA) platforms was developed. The electrical measurement system was designed and deployed to facilitate time-resolved measurement across multiple channels simultaneously on those MEA platforms. Under DC bias, MEA-based ASN devices showed switching events with a power-law distribution over two orders of magnitude of conductance changes and time intervals consistent with self-organized criticality within the network. The dynamic response of the critical system was measured across the network area. Changes in the relative voltage across the ASN network area were observed using 16 channel MEA platforms, showing spatiotemporal variation in voltage across the network. Novel application of principal component analysis to ASNswas used to demonstrate reduction of dimension while preserving relative voltage changes. This paves the way for scalable analysis of the complex dynamic signals from critical ASN systems.</p>


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