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Automation of fault-tolerant graceful degradation

DISTRIBUTED COMPUTING 2019年第1期32卷 1-25页

作者： Lin, Yiyan Kulkarni, Sandeep Jhumka, Arshad Michigan State Univ Dept Comp Sci & Engn E Lansing MI 48824 USA Univ Warwick Dept Comp Sci Coventry W Midlands England

Traditionally, (nonmasking and masking) fault-tolerance has focused on ensuring that after the occurrence of faults, the program recovers to states from where it continues to satisfy its original specification. However, a problem with this limited notion is that, in some cases, it may be impossible to recover to states from where the entire original specification is satisfied. For this reason, one can consider a fault-tolerant graceful-degradation program that ensures that upon the occurrence of faults, the program recovers to states from where a (given) subset of its specification is satisfied. Typically, the subset of specification satisfied thus would be the critical/important requirements. In this paper, we initially focus on automatically revising a given fault-intolerant program into a fault-tolerant gracefully degrading program. Specifically, we propose a two-step approach: In the first step, we transform the fault-intolerant program into a graceful program. This program is guaranteed to satisfy only the given subset of specification (e.g., critical requirements). In particular, this step involves adding new behaviors that will satisfy the given subset of the specification. The second step involves utilizing the original program and the graceful program to obtain a fault-tolerant gracefully degrading program. We also develop an algorithm to transform the gracefully degrading program into a distributed gracefully degrading program. Afterwards, the second phase of our transformation can be applied to generate a distributed fault-tolerant gracefully degrading program. We showcase the algorithm with three different non-trivial case studies. Finally, we formalize the problem of multi-graceful degradation and propose an algorithm that solves it and we use a complex case study to showcase the viability of the approach. All the algorithms have polynomial time complexity in the size of the state space of the original program.

关键词： AUTOMATION FAULT tolerance (Engineering) SPECIFICATIONS SET theory computer algorithms

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Exploring the immediate and short-term effects of peer advice and cognitive authority on Web search behavior

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INFORMATION PROCESSING & MANAGEMENT 2019年第3期56卷 1010-1025页

作者： Liu, Jiqun Wang, Yiwei Mandal, Soumik Shah, Chirag Rutgers State Univ 4 Huntington St New Brunswick NJ 08901 USA

An individual's Web search behavior can be influenced by a number of factors, including features and functions of a search engine as well as search education. In contrast to the long-lasting attention to the algorithm and interface dimensions of search, there is a lack of research concerned with the potential effects of user education on search behavior. To address this gap, we ran a three-session field-lab-combined study to examine the effects of user education from two distinct sources - peer advice and cognitive authority (operationalized as video-based student's advice and expert's advice respectively) - on Web search behavior in two different search task scenarios (i.e., factual specific and factual amorphous tasks). We also tested if these behavioral effects persist for a short period of time when the explicit search tips are removed. Using 185 task session data generated by 31 participants in two field and one lab sessions, this study demonstrates that: (1) both peer advice and cognitive authority are effective in stimulating immediate behavioral changes in Web search;(2) the immediate behavioral impact of search advice is broader in factual amorphous task than in factual specific task;(3) framing search tips as the advice from cognitive authority is more likely to generate continuing, short-term effects on Web search behaviors. This research has implications for the design of task-aware user education as well as the study of users' interactions with IR systems in general.

关键词： Web search engines computer algorithms Feature extraction computer users Information services user education

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A Simple Method for Peak Alignment Using Relative Retention Time Related to an Inherent Peak in Liquid Chromatography-Mass Spectrometry-Based Metabolomics

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JOURNAL OF CHROMATOGRAPHIC SCIENCE 2019年第1期57卷 9-16页

作者： Wang, Yang Ma, Li Zhang, Mengliu Chen, Meiwan Li, Peng He, Chengwei Yan, Chunyan Wan, Jian-Bo Univ Macau Inst Chinese Med Sci State Key Lab Qual Res Chinese Med Macau Peoples R China Jinan Univ Atmospher Environm Inst Safety & Pollut Control Guangzhou Guangdong Peoples R China Guangdong Pharmaceut Univ Coll Pharm Guangzhou 510006 Guangdong Peoples R China

Retention time (RT) shifts are inevitable in liquid chromatography-mass spectrometry (LC-MS)-based metabolomics studies. RT alignment, aligning peaks originating from the same feature to an identical RT, is a necessary step prior to multivariate data analysis. Many RT alignment software packages and various algorithms have been developed. In the present study, a simple method for peak alignment was proposed using relative RT related to an inherent peak in the chromatogram, and its performance on RT alignment in untargeted metabolomics was evaluated using an LC-MS dataset acquired from plasma samples from osteoporotic rats, and compared with the common MarkerLynx XS method using different RT window. RT alignment accuracy and relative standard deviation (RSD) value of the intensity of 79 selected ions in a chromatogram were employed to assess the alignment effectiveness of Method I (0.2 RT window), Method II (0.5 RT window) and Method III (relative RT). The overall RT alignment accuracy of these three methods was 67.7%, 77.2% and 90.9%, and 44.3%, 72.2% and 82.3% of the ions had intensity RSD values <30%, respectively. The results demonstrated that Method III using relative RT significantly reduced the influence caused by RT shifts in LC-MS-based metabolomics. Furthermore, Method I and Method III were applied to discover plasma biomarkers for osteoporosis in rats. Thirteen and nineteen ions were selected as potential biomarkers, respectively. Among them, only eight common ions were found, which demonstrated that different sets of biomarkers were obtained using those two RT alignment methods. The relative RT method exhibited fewer missing values, a lower RSD of peak intensity and better performance in pattern recognition, thereby showing the great potential in future metabolomics studies.

关键词： LIQUID chromatography-mass spectrometry OSTEOPOROSIS diagnosis METABOLOMICS computer algorithms ACCURACY

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Simple digital algorithm for improved performance in a boost PFC converter operating in CCM

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IET POWER ELECTRONICS 2019年第5期12卷 1102-1113页

作者： Nair, Harish Sudhakaran Narasamma, Lakshmi Indian Inst Technol Madras Dept Elect Engn Chennai Tamil Nadu India

In power factor correction (PFC) converters, achieving both good steady-state input current waveform and fast output dynamic response is a challenge. This is due to the effect of the double-line frequency ripple present in the sensed output voltage signal which tends to distort the reference current applied to the current controller, thus leading to a distorted input current waveform. Low bandwidth (BW) voltage loop designs to reduce this input current distortion make the output dynamic response very sluggish. A digital control algorithm for the estimation of the average value of the sensed output voltage is proposed in this study to achieve low total harmonic distortion input current and fast dynamic response with a higher BW voltage loop. The proposed algorithm is computationally less intensive and requires no additional sensors or circuitry. The effectiveness of the proposed control algorithm is validated through simulation and experimental tests on a 300 W boost PFC converter prototype operating in continuous conduction mode.

关键词： reference current line frequency Fasting Power factor correction Converters computer algorithms mean value current controller continuous conduction mode Dynamic response input current voltage loop output voltage

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Enhancing the stability of AHF

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IET POWER ELECTRONICS 2019年第5期12卷 1121-1130页

作者： Vaidya, Tushar Chatterjee, Kishore Indian Inst Technol Dept Elect Engn Mumbai Maharashtra India

Active harmonic filters (AHFs) have a problem of losing their stability when they are installed in a distribution network having power factor correction (PFC) capacitors. This study has made an effort to assess the stability margin of an AHF installed in a distribution network along with PFC capacitors. After establishing the underlying cause of instability, an attempt has been made in this study to propose a control algorithm, so that the problem of instability is overcome when these AHFs are made to operate in tandem with PFC capacitors. The effectiveness of the proposed control algorithm is established by carrying out detailed simulation studies of the system. A 30 kVA laboratory prototype of the AHF has been fabricated. Detailed experimental validations have been carried out utilising the aforesaid prototype to confirm the viability of the proposed scheme.

关键词： Blood Coagulation Factor VIII Tandem Power grids Power factor correction stability margin computer algorithms

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Control of airflow in ventilation systems using embedded systems on microcontrollers

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MICROSYSTEM TECHNOLOGIES-MICRO-AND NANOSYSTEMS-INFORMATION STORAGE AND PROCESSING SYSTEMS 2019年第11期25卷 4067-4076页

作者： Gama, Felipe O. S. Martins, Jose K. E. da C. de Miranda, Tiago F. Tome, Willy M. de F. Silva, Sergio N. Fernandes, Marcelo A. C. Fed Univ Rio Grande Norte UFRN Dept Comp Engn & Automat BR-59078970 Natal RN Brazil

This paper describes the development of a proportional-integral-derivative (PID) controller for regulation of the airflow in a ventilation system. The flow was adjusted by controlling the speed of the fan installed in the system. The PID control algorithm was developed for an embedded system in an Atmega 2560 microcontroller contained in an Arduino Mega development kit, where the airflow rate was detected by a Hall-effect sensor that generated a pulsed signal at a frequency proportional to the speed of the fan. Simulation results were used to parameterize the control algorithm, minimizing the benchtop development time. Full details of the procedure are presented in order to assist future PID proposals involving embedded systems in microcontrollers.

关键词： Ventilation Systems fan-in Embedded systems Proportional derivative control Microcontrollers computer algorithms

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Power quality improvement of single phase weak grid interfaced hybrid solar PV and wind system using double fundamental signal extracter-based control

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IET GENERATION TRANSMISSION & DISTRIBUTION 2019年第17期13卷 3988-3998页

作者： Gupta, Tripurari Nath Murshid, Shadab Singh, Bhim Indian Inst Technol Delhi Dept Elect Engn New Delhi 110016 India

In this study, a double fundamental signal extracter using third-order signal integrator-based control technique is used for the improvement of power quality of single phase grid interfaced with hybrid wind energy generation system (WEGS) and solar photovoltaic (PV) array under weak grid conditions. The control algorithm is proposed for the extraction of dual fundamental components of load current and to extract fundamental grid voltage for synchronisation to the grid. The main objective of the system is to establish secure, reliable and safe integration while mitigating several power quality issues such as total harmonic distortion (THD) of the grid current, DC current injection. The system operates in distribution static compensator mode in the absence of renewable energy sources and also, maintains the grid current THD as per the limit of the IEEE-519 standard. For optimal power extraction from WEGS as well as the solar PV array, perturb and observe algorithm is used. The prototype developed in the laboratory is tested under different operating conditions such as variable wind speed, grid voltage sag/swell, variable solar insolation, and varying load conditions.

关键词： Power quality load current gate voltage Total harmonic distortion single phase power extraction Solar PV Renewable energy computer algorithms Grid computing photovoltaic array Quality Improvement Control technology variable amplitude loading doffing system

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Fast distributed algorithms for testing graph properties

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DISTRIBUTED COMPUTING 2019年第1期32卷 41-57页

作者： Censor-Hillel, Keren Fischer, Eldar Schwartzman, Gregory Vasudev, Yadu Technion Israel Inst Technol Dept Comp Sci Haifa Israel

We initiate a thorough study of distributed property testingproducing algorithms for the approximation problems of property testing in the CONGEST model. In particular, for the so-called dense graph testing model we emulate sequential tests for nearly all graph properties having 1-sided tests, while in the general model we obtain faster tests for triangle-freeness and cycle-freeness, and in the sparse model we obtain a faster test for bipartiteness. In addition, we show a logarithmic lower bound for testing bipartiteness and cycle-freeness, which holds even in the stronger LOCAL model. In most cases, aided by parallelism, the distributed algorithms have a much shorter running time than their counterparts from the sequential querying model of traditional property testing. More importantly, the distributed algorithms we develop for testing graph properties are in many cases much faster than what is known for exactly deciding whether the property holds. The simplest property testing algorithms allow a relatively smooth transition to the distributed model. For the more complex tasks we develop new machinery that may be of independent interest.

关键词： DISTRIBUTED computing computer algorithms APPROXIMATION theory BIPARTITE graphs PARALLEL algorithms

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Design of adaptive threshold control algorithm based on real-time CPU operation patterns for mobile devices

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ELECTRONICS LETTERS 2019年第12期55卷 688-689页

作者： Cho, H. H. Eun, C. M. Jeong, O. H. Sogang Univ Dept Elect Engn Seoul South Korea

Thermal problems in conventional mobile devices are primarily managed by using software-based techniques due to compact sizes and limited power budgets. Since these software-based techniques incur inevitable performance degradation to reduce temperature, efficient thermal management techniques are essential for modern mobile devices. In this letter, the authors propose a novel control algorithm, which adaptively controls the threshold based on the power efficiency of mobile CPUs in real-time. The authors validate the thermal mitigation capability and system performance of their proposed scheme using a commercial smartphone. The evaluation results indicate that the proposed scheme reduces the CPU and PCB temperature by 1.20 and 1.38%, respectively, and simultaneously improves overall system performance by 5.44%.

关键词： System performance adaptive thresholding dynamic efficiency degradation of performance Mobile devices power budget central processing units computer algorithms

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Preface to the Special Issue on Algorithmic Game Theory

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THEORY OF COMPUTING SYSTEMS 2019年第1期63卷 2-3页

作者： Gairing, Martin Savani, Rahul Univ Liverpool Dept Comp Sci Liverpool L69 3BX Merseyside England

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