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Demetrovic, J., L. O. Libkin i I. B. Muchnik. "Database models and closure operators". Cybernetics and Systems Analysis 27, nr 1 (styczeń 1991): 53–67. http://dx.doi.org/10.1007/bf01068647.
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Bandle, Maximilian, i Jana Giceva. "Database technology for the masses". Proceedings of the VLDB Endowment 14, nr 11 (lipiec 2021): 2483–90. http://dx.doi.org/10.14778/3476249.3476296.
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A wealth of technology has evolved around relational databases over decades that has been successfully tried and tested in many settings and use cases. Yet, the majority of it remains overlooked in the pursuit of performance (e.g., NoSQL) or new functionality (e.g., graph data or machine learning). In this paper, we argue that a wide range of techniques readily available in databases are crucial to tackling the challenges the IT industry faces in terms of hardware trends management, growing workloads, and the overall complexity of a rapidly changing application and platform landscape. However, to be truly useful, these techniques must be freed from the legacy component of database engines: relational operators. Therefore, we argue that to make databases more flexible as platforms and to extend their functionality to new data types and operations requires exposing a lower level of abstraction: instead of working with SQL it would be desirable for database engines to compile, optimize, and run a collection of sub-operators for manipulating and managing data, offering them as an external interface. In this paper, we discuss the advantages of this, provide an initial list of such sub-operators, and show how they can be used in practice.
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Sichert, Moritz, i Thomas Neumann. "User-defined operators". Proceedings of the VLDB Endowment 15, nr 5 (styczeń 2022): 1119–31. http://dx.doi.org/10.14778/3510397.3510408.
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In recent years, complex data mining and machine learning algorithms have become more common in data analytics. Several specialized systems exist to evaluate these algorithms on ever-growing data sets, which are built to efficiently execute different types of complex analytics queries. However, using these various systems comes at a price. Moving data out of traditional database systems is often slow as it requires exporting and importing data, which is typically performed using the relatively inefficient CSV format. Additionally, database systems usually offer strong ACID guarantees, which are lost when adding new, external systems. This disadvantage can be detrimental to the consistency of the results. Most data scientists still prefer not to use classical database systems for data analytics. The main reason why RDBMS are not used is that SQL is difficult to work with due to its declarative and set-oriented nature, and is not easily extensible. We present User-Defined Operators (UDOs) as a concept to include custom algorithms into modern query engines. Users can write idiomatic code in the programming language of their choice, which is then directly integrated into existing database systems. We show that our implementation can compete with specialized tools and existing query engines while retaining all beneficial properties of the database system.
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Al Marri, Wadha J., Qutaibah Malluhi, Mourad Ouzzani, Mingjie Tang i Walid G. Aref. "The similarity-aware relational database set operators". Information Systems 59 (lipiec 2016): 79–93. http://dx.doi.org/10.1016/j.is.2015.10.008.
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Jacyna-Gołda, Ilona, Mariusz Izdebski, Piotr Klimek i Rostislav Vašek. "Constructing a database structure in the problem of the assignment of air transport operators to commissioned tasks". MATEC Web of Conferences 294 (2019): 04004. http://dx.doi.org/10.1051/matecconf/201929404004.
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The article defines the database structure used in the issue of the assignment of air transport operators to commissioned transport tasks. The purpose of the work is to develop a database structure that fulfills the function of recording information, presenting results and processing calculated data. Presenting the database in a modular manner is a new concept of data flow management in the problem of the assignment of air transport operators to tasks. The issue of the assignment of air service operators to tasks is a complex optimization problem. The complexity of the database architecture used in the assignment of operators to tasks depends on the number of modules responsible for individual functions implemented in the process of determining the assignment of operators to tasks. In addition, the paper presents a mathematical model of the assignment of operators to tasks, includes basic data entered into the model and collected in the database, describes the assignment restrictions and the criterion function. In order to solve the problem, an optimization algorithm concept has been proposed to solve the analyzed problem. The problem of the assignment has been presented in the multi-criteria aspect.
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Petrosyan, Arthur S., i Gurgen S. Petrosyan. "Development of Management System for eduroam Database Updated Specification". Mathematical Problems of Computer Science 53 (10.07.2020): 57–62. http://dx.doi.org/10.51408/1963-0081.
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This paper presents a system developed to simplify the eduroam database management. The goal of the eduroam database is to provide the necessary information needed for the operation of the eduroam service and related supporting services like eduroam monitoring, service location maps and usage statistics, as well as the eduroam CAT tool. eduroam database specifications have been updated to the second version and the update has recently become mandatory, requiring many changes for databases of all National Roaming Operators (NRO). The solution presented here can be useful for NRO administrators to simplify the eduroam database management.
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Petrosyan, Arthur, i Gurgen Petrosyan. "Development of Management System for eduroam Database Updated Specification". Mathematical Problems of Computer Science 53 (10.07.2020): 57–62. http://dx.doi.org/10.51408/1963-0075.
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This paper presents a system developed to simplify the eduroam database management. The goal of the eduroam database is to provide the necessary information needed for the operation of the eduroam service and related supporting services like eduroam monitoring, service location maps and usage statistics, as well as the eduroam CAT tool. eduroam database specifications have been updated to the second version and the update has recently become mandatory, requiring many changes for databases of all National Roaming Operators (NRO). The solution presented here can be useful for NRO administrators to simplify the eduroam database management.
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Frieder, O. "Multiprocessor algorithms for relational-database operators on hypercube systems". Computer 23, nr 11 (listopad 1990): 13–28. http://dx.doi.org/10.1109/2.60877.
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Jaziri, Wassim, Najla Sassi i Dhouha Damak. "Using Temporal Versioning and Integrity Constraints for Updating Geographic Databases and Maintaining Their Consistency". Journal of Database Management 26, nr 1 (styczeń 2015): 30–59. http://dx.doi.org/10.4018/jdm.2015010102.
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The use of geographic data has become a widespread concern, mainly within applications related to spatial planning and spatial decision-making. Therefore, changing environments require databases adaptable to changes that occur over time. Thus, supporting geographic information evolution is essential and extremely important within changing environments. The evolution is expressed in the geographic database by series of update operations that should maintain its consistency. This paper proposes an approach for updating geographic databases, based on update operators and algorithms of constraints integrity checking. Temporal versioning is used to keep the track of changes. Every version presents the state of the geographic database at a given time. Algorithms of constraints integrity checking allow maintaining the database consistency upon its update. To implement our approach and assist users in the evolution process, the GeoVersioning tool is developed and tested on a sample geographic database.
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Maquen Nino, Gisella Luisa, Franklin Edinson Teran Santa Cruz, Consuelo Ivonne Del Castillo Castro i Rafael Damian Villon Prieto. "Best Practices for Relational Database Optimization using Microsoft SQL". Universidad Ciencia y Tecnología 26, nr 114 (28.06.2022): 29–38. http://dx.doi.org/10.47460/uct.v26i114.588.
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The main problem when querying a database is the response time. The research was of an applied type, using two databases: control and experimental. Three computers have been used to execute ten queries to the two databases, running 4 consecutive times and obtaining an average. The results found were that, of the ten consultations carried out, seven consultations obtained better results in the experimental DB and three in the control DB. It is concluded that the best practices to optimize a database are: to create clustered indexes on columns frequently used in searches or to perform sorts, create non-clustered indexes on primary or foreign keys that do not have clustered indexes, use calculated columns, operators, and listing of proper columns in queries, however, the use of indexes should be restricted because they affect insert, update, and delete operations.
Keywords: relational database, database optimization, SQL, indexing.
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Silva, Yasin N., Spencer S. Pearson, Jaime Chon i Ryan Roberts. "Similarity Joins: Their implementation and interactions with other database operators". Information Systems 52 (sierpień 2015): 149–62. http://dx.doi.org/10.1016/j.is.2015.01.008.
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Maslov, D. Y., M. S. Melnik i I. M. Serov. "The study of audiovisual information loads to assess their impact on the health of operators". Russian Journal of Occupational Health and Industrial Ecology, nr 9 (19.03.2020): 691. http://dx.doi.org/10.31089/1026-9428-2019-59-9-691-692.
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In the article is discussed the developed methods for determining the auditory and visual information load on vehicle operators, computer operators and programmers in order to identify harmful and dangerous factors of work activity. The scheme of a relational database for storage of biophysical parameters of operators operating under conditions of information loads for their further research has been developed.
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Zheng, Shuai, Fusheng Wang i James Lu. "Enabling Ontology Based Semantic Queries in Biomedical Database Systems". International Journal of Semantic Computing 08, nr 01 (marzec 2014): 67–83. http://dx.doi.org/10.1142/s1793351x14500032.
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There is a lack of tools to ease the integration and ontology based semantic queries in biomedical databases, which are often annotated with ontology concepts. We aim to provide a middle layer between ontology repositories and semantically annotated databases to support semantic queries directly in the databases with expressive standard database query languages. We have developed a semantic query engine that provides semantic reasoning and query processing, and translates the queries into ontology repository operations on NCBO BioPortal. Semantic operators are implemented in the database as user defined functions extended to the database engine, thus semantic queries can be directly specified in standard database query languages such as SQL and XQuery. The system provides caching management to boosts query performance. The system is highly adaptable to support different ontologies through easy customizations. We have implemented the system DBOntoLink as an open source software, which supports major ontologies hosted at BioPortal. DBOntoLink supports a set of common ontology based semantic operations and have them fully integrated with a database management system IBM DB2. The system has been deployed and evaluated with an existing biomedical database for managing and querying image annotations and markups (AIM). Our performance study demonstrates the high expressiveness of semantic queries and the high efficiency of the queries.
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Liu, Yulin, Zengwen Yu, Xiaoguang Yuan, Wenjun Ke, Zhi Fang, Tianfeng Du i Cuihong Han. "Assessing Database Contribution via Distributed Tracing for Microservice Systems". Applied Sciences 12, nr 22 (12.11.2022): 11488. http://dx.doi.org/10.3390/app122211488.
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Microservice architecture is the latest trend in software systems development and transformation. In microservice systems, databases are deployed in corresponding services. To better optimize runtime deployment and improve system stability, system administrators need to know the contributions of databases in the system. For the high dynamism and complexity of microservice systems, distributed tracing can be introduced to observe the behavior of business scenarios on databases. However, it is challenging to evaluate the database contribution by combining the importance weight of business scenarios with their behaviors on databases. To solve this problem, we propose a business-scenario-oriented database contribution assessment approach (DBCAMS) via distributed tracing, which consists of three steps: (1) determining the importance weight of business scenarios in microservice system by analytic hierarchy process (AHP); (2) reproducing business scenarios and aggregating the same operations on the same database via distributed tracing; (3) calculating database contribution by formalizing the task as a nonlinear programming problem based on the defined operators and solving it. To the best of our knowledge, our work is the first research to study this issue. The results of a series of experiments on two open-source benchmark microservice systems show the effectiveness and rationality of our proposed method.
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Liu, Guoxiu, Geng Yang, Huaqun Wang, Yang Xiang i Hua Dai. "A Novel Secure Scheme for Supporting Complex SQL Queries over Encrypted Databases in Cloud Computing". Security and Communication Networks 2018 (3.07.2018): 1–15. http://dx.doi.org/10.1155/2018/7383514.
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With the advance of database-as-a-service (DaaS) and cloud computing, increasingly more data owners are motivated to outsource their data to cloud database for great convenience and economic savings. Many encryption schemes have been proposed to process SQL queries over encrypted data in the database. In order to obtain the desired data, the SQL queries contain some statements to describe the requirement, e.g., arithmetic and comparison operators (+, -, ×, <, >, and =). However, to support different operators (+, -, ×, <, >, and =) in SQL queries over encrypted data, multiple encryption schemes need to be combined and adjusted to work together. Moreover, repeated encryptions will reduce the efficiency of execution. This paper presents a practical and secure homomorphic order-preserving encryption (FHOPE) scheme, which allows cloud server to perform complex SQL queries that contain different operators (such as addition, multiplication, order comparison, and equality checks) over encrypted data without repeated encryption. These operators are data interoperable, so they can be combined to formulate complex SQL queries. We conduct security analysis and efficiency evaluation of the proposed scheme FHOPE. The experiment results show that, compared with the existing approaches, the FHOPE scheme incurs less overhead on computation and communication. It is suitable for large batch complex SQL queries over encrypted data in cloud environment.
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Zarrillo, Marguerite L. "Using Decision Support System and Graphical User Interface to Choose Appropriate Lane Configurations at Toll Facilities". Transportation Research Record: Journal of the Transportation Research Board 1935, nr 1 (styczeń 2005): 8–16. http://dx.doi.org/10.1177/0361198105193500102.
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This study shows that tools can be devised to assist engineers and operators make decisions concerning a network of toll roads. A decision support system (DSS) was connected to a database containing highway network hourly geometric and traffic information for one typical day. The DSS provided operators with online tools that could assist with their hour-to-hour decisions concerning toll plaza lane configurations. This pilot study could be extended, and the DSS could be connected to a realtime database to assist operators with their day-to-day decisions. Operators could plan for special scheduled events in which traffic volumes are known to surge. Engineers could design lane configurations at toll facilities that could meet traffic requirements. Engineers could also design new interchange locations and predict the effect on toll plaza segments. They could also predict the effect of adding additional lanes to busy highway segments. Highway operators could determine the effects of an incident or other unscheduled lane closing at any particular hour of the day. Furthermore, they could schedule maintenance and lane closings for construction at hours of the day in which bottlenecks are at a minimum.
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Herskovits, E. H. "An Architecture for a Brain-Image Database". Methods of Information in Medicine 39, nr 04/05 (2000): 291–97. http://dx.doi.org/10.1055/s-0038-1634397.
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Abstract:The widespread availability of methods for noninvasive assessment of brain structure has enabled researchers to investigate neuroimaging correlates of normal aging, cerebrovascular disease, and other processes; we designate such studies as image-based clinical trials (IBCTs). We propose an architecture for a brain-image database, which integrates image processing and statistical operators, and thus supports the implementation and analysis of IBCTs. The implementation of this architecture is described and results from the analysis of image and clinical data from two IBCTs are presented. We expect that systems such as this will play a central role in the management and analysis of complex research data sets.
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Borisov, Alexey, i Sayaana Danilova. "Protection of personal data in databases and computer programs". E3S Web of Conferences 284 (2021): 04001. http://dx.doi.org/10.1051/e3sconf/202128404001.
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At the beginning of the article describes what restrictions caused the pandemic in 2020 caused by a new coronovirus infection the COVID-19. The article discusses the legitimacy of the processing of personal data using databases and programs, in particular, the problems of building, using and transmitting a database containing PD; storing PD in «cloud bases»; PD protection after database destruction. Comparative legal analysis of this institution in European and American legislation is carried out. In conclusion, it should be noted that the legislator understands the need to protect PD and is therefore taking appropriate measures to ensure the proper technical level of operators. At the end conclusions were drawn on this topic of the study.
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Qin, Lianke, Rajesh Jayaram, Elaine Shi, Zhao Song, Danyang Zhuo i Shumo Chu. "Adore". Proceedings of the VLDB Endowment 16, nr 4 (grudzień 2022): 842–55. http://dx.doi.org/10.14778/3574245.3574267.
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There has been a recent effort in applying differential privacy on memory access patterns to enhance data privacy. This is called differential obliviousness. Differential obliviousness is a promising direction because it provides a principled trade-off between performance and desired level of privacy. To date, it is still an open question whether differential obliviousness can speed up database processing with respect to full obliviousness. In this paper, we present the design and implementation of Adore: A set of D ifferentially O blivious RE lational database operators. Adore includes selection with projection, grouping with aggregation, and foreign key join. We prove that they satisfy the notion of differential obliviousness. Our differentially oblivious operators have reduced cache complexity, runtime complexity, and output size compared to their state-of-the-art fully oblivious counterparts. We also demonstrate that our implementation of these differentially oblivious operators can outperform their state-of-the-art fully oblivious counterparts by up to 7.4X.
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Kumar, Dr Vinod, Gagandeep Raheja i Sukhpreet Singh. "CRITICAL STUDY ON DATABASE AND PROMINENT PROGRAMMES". INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 4, nr 1 (1.02.2013): 44–47. http://dx.doi.org/10.24297/ijct.v4i1a.3034.
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The people who work with computers, the programmers, analysts, and operators who seem to live by rules of their own and seldom leave their own environment, tend to be very cynical towards the stories of electronic brains. This attitude will appear hardly surprising when one eventually learns that the computer is a very simple device and is as far removed from an electronic brain as a bicycle from a spaceship. Programmers in particular are the people most aware that computers are no substitute for the human brain; in fact, the preparation of work to be run on a computer can be one of the most mind-bending exercises encountered in everyday life. Databases and database systems have become an essential component of everyday life in modern society. In the course of a day, most of us encounter several activities that involve some interaction with a database. So in this paper we will talk about how to manage the different type of data involved in any form in the database.
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Marek, W., i C. Rauszer. "Query Optimization in the Databases Distributed by Means of Product Equivalence Relations". Fundamenta Informaticae 11, nr 3 (1.07.1988): 241–65. http://dx.doi.org/10.3233/fi-1988-11303.
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In this paper, we address the problem of query optimization in distributed databases. We show that horizontal partitions of databases, generated by products of equivalence relations, induce optimization techniques for the basic database operations (i.e., the selection, projection, and join operators). In the case of selection, our method allows for restriction of the number of blocks to be searched in the selection process and subsequent simplification of the selection formula at each block. For the natural join operation, we propose an algorithm that reduces the computation of fragments. Proofs of the correctness of our algorithms are also included.
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Sanghi, Anupam, Shadab Ahmed i Jayant R. Haritsa. "Projection-compliant database generation". Proceedings of the VLDB Endowment 15, nr 5 (styczeń 2022): 998–1010. http://dx.doi.org/10.14778/3510397.3510398.
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Synthesizing data using declarative formalisms has been persuasively advocated in contemporary data generation frameworks. In particular, they specify operator output volumes through row-cardinality constraints. However, thus far, adherence to these volumetric constraints has been limited to the Filter and Join operators. A critical deficiency is the lack of support for the Projection operator, which is at the core of basic SQL constructs such as Distinct, Union and Group By. The technical challenge here is that cardinality unions in multi-dimensional space, and not mere summations, need to be captured in the generation process. Further, dependencies across different data subspaces need to be taken into account. We address the above lacuna by presenting PiGen , a dynamic data generator that incorporates Projection cardinality constraints in its ambit. The design is based on a projection subspace division strategy that supports the expression of constraints using optimized linear programming formulations. Further, techniques of symmetric refinement and workload decomposition are introduced to handle constraints across different projection subspaces. Finally, PiGen supports dynamic generation, where data is generated on-demand during query processing, making it amenable to Big Data environments. A detailed evaluation on workloads derived from real-world and synthetic benchmarks demonstrates that PiGen can accurately and efficiently model Projection outcomes, representing an essential step forward in customized database generation.
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Essens, Peter J. M. D., Carol A. McCann i Mark A. Hartevelt. "An experimental study of the interpretation of logical operators in database querying". Acta Psychologica 78, nr 1-3 (grudzień 1991): 201–25. http://dx.doi.org/10.1016/0001-6918(91)90011-n.
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Dudakov, Sergey. "On Safety of Unary and Non-unary IFP-operators". Modeling and Analysis of Information Systems 25, nr 5 (28.10.2018): 525–33. http://dx.doi.org/10.18255/1818-1015-2018-5-525-533.
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In this paper, we investigate the safety of unary inflationary fixed point operators (IFPoperators). The safety is a computability in finitely many steps. IFP-operators exactly correspond to recursive SQL-queries hence this problem has a value for database theory. The problem appears from the fact that if recursive queries contain universe functions and relations, then its execution can fall into an infinite loop. Moreover, universal computational devices (Turing machines et al.) can be modelled by such queries. Hence the problem of the finite computability for such queries is undecidable. In our previous works we established some properties of a universe which imply the finite computability of all IFP-operators in the universe. Here, we investigate a connection between an arity of IFP-operators and their safety. We prove that some results for general IFP-operators don’t hold for unary ones. We construct a universe where all unary unnesed IFP-operators are safe. But in this universe there exist unsafe nested unary IFP-operators and unsafe unnested binary IFP-operators. This differs from general IFP-operators because in general case the safety of all unnesed IFP-operators implies the safety of all IFP-operators. Also there exist elementary equivalent universes where some unary unnesed IFPoperators become unsafe. For general IFP-operators it is also impossible.
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Burmistrov, V. I., I. V. Ivanov, E. I. Matkevich i E. A. Praskurnichiy. "ANALYSIS OF THE SIGNIFICANCE OF FACTORS CONTRIBUTING TO THE PILOTLESS VEHICLE ACCIDENT RATE". Aerospace and Environmental Medicine 56, nr 2 (2022): 73–84. http://dx.doi.org/10.21687/0233-528x-2022-56-2-73-84.
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Analysis of the air accident rates of MQ-1 Predators and MQ-9 Reapers from the Drone Crash Database in the period from 2001 till 2021 (12 countries, 174 accidents total) disclosed major factors, including human, for accidents. The main reason was structural faults and manufacturing defects due to, probably, long time in service. Frequency of accidents due to errors of experienced pilot-operator's varied between 19.4% and 22.9 % and due to errors in the course of skill training, 60–64.7 %. To reduce the accident rate, pilot-operators need to be trained on cutting-edge VR simulators and challenged by atypical stress situations such as multiple causation.
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DEZFULI, MOHAMMAD G., i MOSTAFA S. HAGHJOO. "WD-PWS: THE FIRST SEMANTICS FOR QUERYING OVER PROBABILISTIC DATA STREAMS WITH CONTINUOUS DISTRIBUTIONS". International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 21, nr 05 (październik 2013): 695–722. http://dx.doi.org/10.1142/s0218488513500335.
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Many emerging applications need continuous querying over uncertain event streams, mostly for online monitoring. These streaming uncertain events may come from radars, sensors, or even software hooks. The uncertainty is usually due to measurement errors, inherent ambiguities and privacy preserving reasons. To cover new requirements, we have designed and implemented a new system called Probabilistic Data Stream Management System (PDSMS) in Ref. 1. PDSMS is a data processing engine which runs continuous queries over probabilistic streams. However, lack of a semantics for probabilistic databases which supports continuous distributions prevented us from having a strong foundation for our query operators. It also precludes us from proving consistency and correctness of query operations especially after optimization and adaption. In fact, in the probabilistic database literature, there is no semantics available which covers continuous distributions. This limitation is very restrictive as in real-world, uncertainty is usually modeled by continuous distributions. In this paper, after presenting a basic probabilistic data model for PDSMS, we focus on querying and formally present the first semantics for probabilistic query operations which supports continuous distributions as well as discrete ones. Using this new semantics, we define our query operators (e.g. select, project, and join) formally without ambiguity and compatible with operators in relational algebra. Thus, we can leverage many transformation rules in relational algebra as well. This new semantics allows us to have different strictness levels and consistency between operators. We also proved many strictness theorems about different alternatives for query operators.
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Castelltort, Arnaud, i Anne Laurent. "Exploiting NoSQL Graph Databases and in Memory Architectures for Extracting Graph Structural Data Summaries". International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 25, nr 01 (luty 2017): 81–109. http://dx.doi.org/10.1142/s0218488517500040.
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NoSQL graph databases have been introduced in recent years for dealing with large collections of graph-based data. Scientific data and social networks are among the best examples of the dramatic increase of the use of such structures. NoSQL repositories allow the management of large amounts of data in order to store and query them. Such data are not structured with a predefined schema as relational databases could be. They are rather composed by nodes and relationships of a certain type. For instance, a node can represent a Person and a relationship Friendship. Retrieving the structure of the graph database is thus of great help to users, for example when they must know how to query the data or to identify relevant data sources for recommender systems. For this reason, this paper introduces methods to retrieve structural summaries. Such structural summaries are extracted at different levels of information from the NoSQL graph database. The expression of the mining queries is facilitated by the use of two frame-works: Fuzzy4S allowing to define fuzzy operators and operations with Scala; Cypherf allowing the use of fuzzy operators and operations in the declarative queries over NoSQL graph databases. We show that extracting such summaries can be impossible with the NoSQL query engines because of the data volume and the complexity of the task of automatic knowledge extraction. A novel method based on in memory architectures is thus introduced. This paper provides the definitions of the summaries with the methods to automatically extract them from NoSQL graph databases only and with the help of in-memory architectures. The benefit of our proposition is demonstrated by experimental results.
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AbdAllah, Nisreen, i Serestina Viriri. "Off-Line Arabic Handwritten Words Segmentation using Morphological Operators". Signal & Image Processing : An International Journal 11, nr 6 (30.12.2020): 21–36. http://dx.doi.org/10.5121/sipij.2020.11602.
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The main aim of this study is the assessment and discussion of a model for hand-written Arabic through segmentation. The framework is proposed based on three steps: pre-processing, segmentation, and evaluation. In the pre-processing step, morphological operators are applied for Connecting Gaps (CGs) in written words. Gaps happen when pen lifting-off during writing, scanning documents, or while converting images to binary type. In the segmentation step, first removed the small diacritics then bounded a connected component to segment offline words. Huge data was utilized in the proposed model for applying a variety of handwriting styles so that to be more compatible with real-life applications. Consequently, on the automatic evaluation stage, selected randomly 1,131 images from the IESK-ArDB database, and then segmented into sub-words. After small gaps been connected, the model performance evaluation had been reached 88% against the standard ground truth of the database. The proposed model achieved the highest accuracy when compared with the related works.
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Qiu, Jianrong, David B. Logan, Jennifer Oxley i Christopher Lowe. "Application of a Hurdle Model with Random Effects to Explore the Relationship between Operational Characteristics and Safety Performance". Transportation Research Record: Journal of the Transportation Research Board 2674, nr 8 (29.06.2020): 327–37. http://dx.doi.org/10.1177/0361198120928074.
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This study used the bus incident data in Victoria, Australia to establish the relationship between operational characteristics and the safety performance of bus operators. A series of count models were investigated to account for methodological challenges, including excess zeros and panel data structure. The empirical results highlighted the different effects operational characteristics had on the risk and prevalence of bus incidents. Operators of smaller size, providing non-route services and operating in regional areas had a lower risk of having any reported incidents compared with larger route operators and operators in areas of higher accessibility. In cases where at least one incident had been reported, incident frequency was higher for operators with higher fleet total travel distance, older fleets and better roadworthy performance (this factor being counterintuitive). Findings from this study provide safety regulators with evidence-driven opportunities to enhance bus safety, including improving incident reporting practices, the establishment of a comprehensive database for heavy vehicle operators, and specific efforts targeted at older fleets.
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BAGAI, RAJIV, i RAJSHEKHAR SUNDERRAMAN. "COMPUTING THE WELL-FOUNDED MODEL OF DEDUCTIVE DATABASES". International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 04, nr 02 (kwiecień 1996): 157–75. http://dx.doi.org/10.1142/s021848859600010x.
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The well-founded model is one of the most popular models of general logic programs, i.e. logic programs with negation in the bodies of clauses. We present a method for constructing this model for general deductive databases, which are logic programs without any function symbols. The method adopts paraconsistent relations as the semantic objects associated with the predicate symbols of the database. Paraconsistent relations are a generalization of ordinary relations in that they allow manipulation of incomplete as well as inconsistent information. The first step in the model construction method is to transform the database clauses into paraconsistent relation definitions involving these operators. The second step is to build the well-founded model iteratively. Algorithms for both steps are presented and their termination and correctness is also established.
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Lu, Yinghui, Zhiyuan Jiang, Kultegin Aydin, Johannes Verlinde, Eugene E. Clothiaux i Giovanni Botta. "A polarimetric scattering database for non-spherical ice particles at microwave wavelengths". Atmospheric Measurement Techniques 9, nr 10 (19.10.2016): 5119–34. http://dx.doi.org/10.5194/amt-9-5119-2016.
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Abstract. The atmospheric science community has entered a period in which electromagnetic scattering properties at microwave frequencies of realistically constructed ice particles are necessary for making progress on a number of fronts. One front includes retrieval of ice-particle properties and signatures from ground-based, airborne, and satellite-based radar and radiometer observations. Another front is evaluation of model microphysics by application of forward operators to their outputs and comparison to observations during case study periods. Yet a third front is data assimilation, where again forward operators are applied to databases of ice-particle scattering properties and the results compared to observations, with their differences leading to corrections of the model state. Over the past decade investigators have developed databases of ice-particle scattering properties at microwave frequencies and made them openly available. Motivated by and complementing these earlier efforts, a database containing polarimetric single-scattering properties of various types of ice particles at millimeter to centimeter wavelengths is presented. While the database presented here contains only single-scattering properties of ice particles in a fixed orientation, ice-particle scattering properties are computed for many different directions of the radiation incident on them. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident radiation. For ice particles that are small compared to the wavelength, the number of incident directions of the radiation is sufficient to compute reasonable estimates of their (randomly) orientation-averaged scattering properties. This database is complementary to earlier ones in that it contains complete (polarimetric) scattering property information for each ice particle – 44 plates, 30 columns, 405 branched planar crystals, 660 aggregates, and 640 conical graupel – and direction of incident radiation but is limited to four frequencies (X-, Ku-, Ka-, and W-bands), does not include temperature dependencies of the single-scattering properties, and does not include scattering properties averaged over randomly oriented ice particles. Rules for constructing the morphologies of ice particles from one database to the next often differ; consequently, analyses that incorporate all of the different databases will contain the most variability, while illuminating important differences between them. Publication of this database is in support of future analyses of this nature and comes with the hope that doing so helps contribute to the development of a database standard for ice-particle scattering properties, like the NetCDF (Network Common Data Form) CF (Climate and Forecast) or NetCDF CF/Radial metadata conventions.
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Van Houtte, Chris, Stephen Bannister, Caroline Holden, Sandra Bourguignon i Graeme McVerry. "The New Zealand Strong Motion Database". Bulletin of the New Zealand Society for Earthquake Engineering 50, nr 1 (31.03.2017): 1–20. http://dx.doi.org/10.5459/bnzsee.50.1.1-20.
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This article summarises work that has been undertaken to compile the New Zealand Strong Motion Database, which is intended to be a significant resource for both researchers and practitioners. The database contains 276 New Zealand earthquakes that were recorded by strong motion instruments from GeoNet and earlier network operators. The events have moment magnitudes ranging from 3.5 to 7.8. A total of 134 of these events (49%) have been classified as occurring in the overlying crust, with 33 events (12%) located on the Fiordland subduction interface and 7 on the Hikurangi subduction interface (3%). 8 events (3%) are deemed to have occurred within the subducting Australian Plate at the Fiordland subduction zone, and 94 events (34%) within the subducting Pacific Plate on the Hikurangi subduction zone. There are a total of 4,148 uniformly-processed recordings associated with these earthquakes, from which acceleration, velocity and displacement time-series, Fourier amplitude spectra of acceleration, and acceleration response spectra have been computed. 598 recordings from the New Zealand database are identified as being suitable for future use in time-domain analyses of structural response. All data are publicly available at http://info.geonet.org.nz/x/TQAdAQ.
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Koutsoukos, Dimitrios, Ingo Müller, Renato Marroquín, Ana Klimovic i Gustavo Alonso. "Modularis". Proceedings of the VLDB Endowment 14, nr 13 (wrzesień 2021): 3308–21. http://dx.doi.org/10.14778/3484224.3484229.
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The enormous quantity of data produced every day together with advances in data analytics has led to a proliferation of data management and analysis systems. Typically, these systems are built around highly specialized monolithic operators optimized for the underlying hardware. While effective in the short term, such an approach makes the operators cumbersome to port and adapt, which is increasingly required due to the speed at which algorithms and hardware evolve. To address this limitation, we present Modularis , an execution layer for data analytics based on sub-operators , i.e., composable building blocks resembling traditional database operators but at a finer granularity. To demonstrate the feasibility and advantages of our approach, we use Modularis to build a distributed query processing system supporting relational queries running on an RDMA cluster, a serverless cloud platform, and a smart storage engine. Modularis requires minimal code changes to execute queries across these three diverse hardware platforms, showing that the sub-operator approach reduces the amount and complexity of the code to maintain. In fact, changes in the platform affect only those sub-operators that depend on the underlying hardware (in our use cases, mainly the sub-operators related to network communication). We show the end-to-end performance of Modularis by comparing it with a framework for SQL processing (Presto), a commercial cluster database (SingleStore), as well as Query-as-a-Service systems (Athena, BigQuery). Modularis outperforms all these systems, proving that the design and architectural advantages of a modular design can be achieved without degrading performance. We also compare Modularis with a hand-optimized implementation of a join for RDMA clusters. We show that Modularis has the advantage of being easily extensible to a wider range of join variants and group by queries, all of which are not supported in the hand-tuned join.
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Mariani, J. A. "Realizing relational style operators and views in the Oggetto object-oriented database system". Information and Software Technology 35, nr 4 (kwiecień 1993): 207–16. http://dx.doi.org/10.1016/0950-5849(93)90068-e.
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Khanizadeh, Shahrokh, i Jamshid Ghavami. "UniBase: A Universal Database to View Images and Trace Pedigrees and Characteristics of Progenies". HortScience 39, nr 3 (czerwiec 2004): 473–74. http://dx.doi.org/10.21273/hortsci.39.3.473.
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UniBase is a Windows-based (95, 98, NT, 2000, or XP) user-friendly software package that was developed for those who are interested in creating their own instant databases, add information to an existing databases or import data and images from Excel in a choice of languages. The software is very useful for germplasm inventory (fruit crops, vegetables, ornamentals, agronomic crops, weeds, chemicals, insects, pests, animals, etc.) and can be used in any breeding program (animal, horticulture, agronomy, etc.) to trace pedigrees and view images and characteristics of progenies. The database can be searched using various criteria and the use of several operators. An unlimited number of images can be stored for each entry and several graphic formats including BMP, JPEG, GIF, TIFF, etc., can be used. Additional information on UniBase and available data and images can be obtained from the authors.
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GARRIDO, CARMEN, NICOLÁS MARÍN i OLGA PONS. "FUZZY INTERVALS TO REPRESENT FUZZY VALID TIME IN A TEMPORAL RELATIONAL DATABASE". International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 17, supp01 (sierpień 2009): 173–92. http://dx.doi.org/10.1142/s021848850900608x.
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Temporal databases offer a common framework to those database applications that need to store or handle different types of temporal data from a variety of sources. They allow the concept of time to be handled from the point of view of meaning, representation, and manipulation. Although at first sight the incorporation of time into a database might appear to be a direct and simple task, it is, however, quite complex: not only must new structures and specific operators be included, but the semantics of conventional DML sentences (insert, update, or delete) and queries must be appropriately changed. In addition, temporal information is not always as precise as desired since it might be affected by imprecision due to the use of natural language or to the nature of the information source. In this paper, we deal with the problem of the update (and, implicitly, insert and delete) and query operations when time is expressed by means of a fuzzy interval of dates.
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Liu, Zhipeng. "Research on Hot Operation of a Petrochemical Plant Based on Compound Edge Operator". Journal of Cases on Information Technology 25, nr 1 (29.08.2023): 1–23. http://dx.doi.org/10.4018/jcit.328768.
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In the operation of petrochemical plants, safety operation is the top priority, especially for the control of fire operation. In this paper, based on the real hot work in petrochemical plants, based on the extraction methods of different edge operators, the compound analysis of different edge operators can be carried out to visually detect the hot work of petrochemical workers in petrochemical plants, and based on the neural network algorithm, the convolution operation of edge data is carried out, and the data is input into the hot work database to build the hot work database and identify the flame. Remind the hot operation, according to the size of the flame to make a preliminary judgment on whether the danger, combined with the characteristics of the petrochemical device itself to add smoke identification. This method is of great significance to improve the thermal safety monitoring level of petrochemical plant.
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Kohnen, William. "2007 MTS Overview of Manned Underwater Vehicle Activity". Marine Technology Society Journal 42, nr 1 (1.03.2008): 26–37. http://dx.doi.org/10.4031/002533208786861236.
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There are approximately 100 active manned submersibles in operation around the world; in this overview we refer to all non-military manned underwater vehicles that are used for scientific, research, tourism, and commercial diving applications, as well as personal leisure craft. The Marine Technology Society committee on Manned Underwater Vehicles (MUV) maintains the only comprehensive database of active submersibles operating around the world and endeavors to continually bring together the international community of manned submersible operators, manufacturers and industry professionals. The database is maintained through contact with manufacturers, operators and owners through the Manned Submersible program held yearly at the Underwater Intervention conference.The most comprehensive and detailed overview of this industry is given during the UI conference, and this article cannot cover all developments within the allocated space; therefore our focus is on a compendium of activity provided from the most dynamic submersible builders, operators and research organizations that contribute to the industry and who share their latest information through the MTS committee. This article presents a short overview of submersible activity in 2007, including new submersible construction, operation and regulatory activity of research, tourism, commercial diving and recreational applications. The scope of this article is limited to active atmospheric submersibles, and does not include historical, ambient pressure, or laid-up submersibles, which would be an entire article on its own. For a complete overview that includes submersibles not covered in this article, readers are invited to peruse the MTS Manned Underwater Vehicle online database at the committee's website (www.mtsmuv.org).
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Chan, Mei Leng, Yoko Wong, Karen Tan, Joon Cheng Seng, Stephanie Jia Xian Ho, Claire Jing Wen Wong i Gerald Choon-Huat Koh. "Relicensing Practices of Taxi Drivers and Crane Operators Aged 70 Years and above in Singapore". Social Sciences 11, nr 2 (25.01.2022): 41. http://dx.doi.org/10.3390/socsci11020041.
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Singapore is a rapidly ageing society, underpinned by national policies to promote successful and active ageing. Whilst older worker participation in the workforce is encouraged, policymakers are challenged to ensure that work competency is not compromised with any normal age- and/or health-related changes. This paper will briefly outline how policymakers responded to the needs of two subgroups of older workers aged 70 years and above (taxi drivers; crane operators) who desire to continue working in the last two decades. Whilst a mandatory retirement age policy exists for older taxi drivers in Singapore, there is none for older crane operators. Despite this, stricter relicensing protocols were introduced for both types of workers, with active collaboration involving additional occupational therapy services for functional work competency assessments to complement the routine medical fitness screening. Comparisons will be made of these two relicensing frameworks, including the mention of any relevant studies to align with the call of evidence-based practices. In mid-2020, the relicensing policy for older taxi drivers was revised based on findings of a retrospective national database study. Currently, a 4-year national database study on older crane operators aged 70 years and above is being undertaken with preliminary findings to be reported.
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Arora, Sunaina, i Neeraj Kumari. "Recruitment Search Engines for Screening Resumes through AI by Using Boolean Search Functions". Journal of Asian Development 7, nr 2 (29.10.2021): 16–26. http://dx.doi.org/10.52941/jad.v7i2.23.
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The days are gone when hard copies of resumes were sent to recruiters and they used to screen and set aside non relevant resumes. Artificial Intelligence has taken up mundane tasks of recruiters by simplifying search algorithms and human computer interaction. Job Boards provide recruiters with a database of candidates powered by a search tool with lot of filters. The demonstration paper actually carries out searches on recruitment database access tools to filter the relevant applicants from a wide pool of data with the help of search engine tools in resume databases of various jobboards. It shows how Boolean operators get through better search results in few minutes. Recruiter job to get to the right candidate is sorted out with Artificial Intelligence so that they can focus more on strategic tasks. Future of AI in recruitment is immense. Already companies are empowering recruiters with 360 degree tools which help with all Human Resource Aspects.
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Ragland, David R., Niklas Krause, Birgit A. Greiner i June M. Fisher. "Studies of health outcomes in transit operators: Policy implications of the current scientific database." Journal of Occupational Health Psychology 3, nr 2 (1998): 172–87. http://dx.doi.org/10.1037/1076-8998.3.2.172.
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Chiwuike, Ukaoha Kingsley, i Igodan Charles Efosa. "Framework for client-server distributed database system for video rental operators association of Nigeria". International Journal of Academic Research 4, nr 6 (4.11.2012): 267–73. http://dx.doi.org/10.7813/2075-4124.2012/4-6/a.37.
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Boodala, Jagadish, Onkar Dikshit i Nagarajan Balasubramanian. "Deriving Multiple Representation Database: A Model Generalisation Approach". Proceedings of the ICA 2 (10.07.2019): 1–8. http://dx.doi.org/10.5194/ica-proc-2-10-2019.
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<p><strong>Abstract.</strong> The main aim of the research being conducted is to automatically derive multiple representation database through model generalisation. In this regard, this paper presents a detailed methodology of the derivation process of multiple representation database. The topographic information of three different levels of detail (LoDs) viz., LoD1 (1&thinsp;:&thinsp;10,000), LoD2 (1&thinsp;:&thinsp;25,000) and LoD3 (1&thinsp;:&thinsp;250,000) are considered for this research. The abstract LoDs, i.e., LoD2 and LoD3 are derived automatically by model generalisation. The method for linking corresponding features in all these LoDs is shown and thus deriving multiple representation database. The major component of the proposed methodology is the model generalisation process. The design of the model generalisation process which includes generalisation operators, classification hierarchies, geometric constraints, functional hierarchies and topological constraints are discussed in this article. The proposed methodology is currently in the implementation stage.</p>
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Vidulich, Michael A. "The Relationship between Mental Workload and Situation Awareness". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 44, nr 21 (lipiec 2000): 3–460. http://dx.doi.org/10.1177/154193120004402122.
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Mental workload and situation awareness are both outgrowths of the practical need to assess operators' performing and managing dynamic complex tasks. Mental workload refers to the cost placed on the human operator's cognitive processing abilities by performing the required task-related mental processing. Situation awareness is the operator's apprehension of the current situation. Common goals of designing a new system or modifying an existing one are often to reduce the operator's mental workload while increasing the operator's situation awareness. However, the empirical database obtained from concurrent evaluation of mental workload and situation awareness demonstrates that the two measures generally do not co-vary in such a simple fashion. The lack of a single straightforward correlation could be interpreted as an indication that mental workload and situation awareness must be considered independent of each other. However, parsing the available studies into sub-categories based on the type of manipulation that was investigated allows some possible relationships between mental workload and situation awareness to emerge. This suggests that researchers should continue to examine the relationship between these concepts and system evaluators should not consider mental workload or situation awareness in isolation from the other.
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Jiang, Tian, Zhongyi Wu, Yu Song, Xianglong Liu, Haode Liu i Haozhi Zhang. "Sustainable Transport Data Collection and Application: China Urban Transport Database". Mathematical Problems in Engineering 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/879752.
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Transport policy making process of national and local governments should be supported by a comprehensive database to ensure a sustainable and healthy development of urban transport. China Urban Transport Database (CUTD) has been built to play such a role. This paper is to make an introduction of CUTD framework including user management, data warehouse, and application modules. Considering the urban transport development features of Chinese cities, sustainable urban transport development indicators are proposed to evaluate the public transport service level in Chinese cities. International urban transport knowledge base is developed as well. CUTD has been applied in urban transport data processing, urban transport management, and urban transport performance evaluation in national and local transport research agencies, operators, and governments in China, and it will be applied to a broader range of fields.
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Liu, Bangchao, Youping Chen, Jingming Xie i Bing Chen. "Industrial Printing Image Defect Detection Using Multi-Edge Feature Fusion Algorithm". Complexity 2021 (4.10.2021): 1–10. http://dx.doi.org/10.1155/2021/2036466.
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Online defect detection system is a necessary technical measure and important means for large-scale industrial printing production. It is effective to reduce artificial detection fatigue and improve the accuracy and stability of industry printing line. However, the existing defect detection algorithms are mainly developed based on high-quality database and it is difficult to detect the defects on low-quality printing images. In this paper, we propose a new multi-edge feature fusion algorithm which is effective in solving this problem. Firstly, according to the characteristics of sheet-fed printing system, a new printing image database is established; compared with the existing databases, it has larger translation, deformation, and uneven illumination variation. These interferences make defect detection become more challenging. Then, SIFT feature is employed to register the database. In order to reduce the number of false detections which are caused by the position, deformation, and brightness deviation between the detected image and reference image, multi-edge feature fusion algorithm is proposed to overcome the effects of these disturbances. Lastly, the experimental results of mAP (92.65%) and recall (96.29%) verify the effectiveness of the proposed method which can effectively detect defects in low-quality printing database. The proposed research results can improve the adaptability of visual inspection system on a variety of different printing platforms. It is better to control the printing process and further reduce the number of operators.
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Tong, Shi Meng, Yong Zhi Wang, Feng Sun, Cheng Long Hao i Shou Ze Ren. "Design and Implementation of Mobile Meter Reading System Based on SOA". Applied Mechanics and Materials 687-691 (listopad 2014): 2112–15. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.2112.
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This paper mainly studies the design and implement of mobile meter reading system based on SOA. The mobile terminal can save offline power reading data in its local database and communicate online recorded data with the server through Web service interface based on the internet. The Web service components perform interaction with the database server. This system is developed by using programming language Java and embedded database SQLite on Android platform. This mobile application can be available to download customers' data from the server or update new meter reading data to the server and then the operators can accomplish their works conveniently during the interviewing with the customers without going back to the office.
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VERSTRAETE, JÖRG, GUY DE TRÉ, AXEL HALLEZ i RITA DE CALUWE. "USING TIN-BASED STRUCTURES FOR THE MODELLING OF FUZZY GIS OBJECTS IN A DATABASE". International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 15, supp01 (luty 2007): 1–20. http://dx.doi.org/10.1142/s0218488507004431.
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Traditional databases can manage only crisp information, a limitation that also holds for geographic information systems and spatial databases. In this paper, we present a technique based on triangulated irregular networks (or TINs for short) and fuzzy set theory to model imprecise or uncertain regions. A fuzzy region is represented by a Extended TIN, which allows for an associated value for each point of the region in the presented approach to be considered; this associated value will be a membership grade. As is common in fuzzy set theory, membership grades can indicate a degree of "belonging to the set"; in our approach these are the degree to which every crisp location belongs to the fuzzy region (membership grades in fuzzy set theory can have other interpretations7 as well, but these are not needed for the modelling of fuzzy regions). While modelling a fuzzy region as described provides a more accurate model of a real world situation, it does require many operators from the geographic realm to be extended and also new operators (mainly from the fuzzy realm) to be added at the object level. In this paper, from the GIS realm, the calculation of the surface area and the minimum bounding rectangle for fuzzy regions are considered; from the fuzzy realm the calculation of the α-cut is considered. Other operations (i.e. convex hull of a fuzzy region, distance between two fuzzy regions, …) are still under development.
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Aita, M., L. Zanier, E. Rijavec, V. Merlo, J. Menis, V. Della Mea, L. Deroma, R. Donato, F. Puglisi i G. Fasola. "Toward incident reporting (IR) systems: A safety culture survey within the oncology network of a northern Italian region". Journal of Clinical Oncology 27, nr 15_suppl (20.05.2009): e17527-e17527. http://dx.doi.org/10.1200/jco.2009.27.15_suppl.e17527.
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e17527 Background: Physicians are reluctant partners in error reporting. Insufficient evidence exists on what may affect IR in a specific cultural and organizational context. The primary endpoint of our study was to offer a critical perspective on the dominant attitudes toward IR systems among health operators of Friuli-Venezia Giulia cancer network. The survey was part of a Health Department patient safety project. Methods: A preliminary PubMed and ASCO database search was performed (keywords: incident/error reporting, attitudes, barriers, blame/safety culture, cancer, oncology, chemotherapy). Two web-based questionnaires were administered to health personnel of Oncology Units (OU) with developing and existing IR systems, respectively. Data were collected in a MySQL database and managed by PhpMyAdmin. SAS 9.1 was used for the analysis of frequency distributions. Results: Target population: 14 OU; 2 University Hospitals, 1 Scientific Institute for Research, Hospitalization, and Health Care (SIRHHC) (2 OU), 10 Hospital Centers; 262 operators (83 physicians, 172 nurses, 2 pharmacists, 5 technicians). Overall response rate: 44.6%; physician/nurse 59/36%; University Hospital (n = 99)/SIRHHC (n = 55)/Hospital Center (n = 101) 73%/9%/38%. Knowledge of risk management issues: 86% (90% of untrained operators from IR-free centers). Eighty-six percent of all operators showed a favourable attitude toward voluntary IR systems. Main reasons: patient safety improvement (65%); organizational growth (38%); professional duty (20.5%). A 78.5% preference for computerized forms was recorded. On a five-point scale, IR features rating 5 in >50% of the answers were: simplicity (85%); getting a feed-back (76%); exhaustivity (66%); adoption of organization more than individual recommendations (59%). Specific training, feedback guarantee and plainness of reporting forms were suggested by 90, 64, and 51% of all operators as essential measures for system acceptance and user satisfaction. Conclusions: Logistic and organizational factors (i.e., time constraints, work overload, resource allocation to incident reporting more than investigation and learning back) should be taken in account by county health directors aiming for successful reporting systems. No significant financial relationships to disclose.
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Hong, Zicong, Song Guo, Enyuan Zhou, Wuhui Chen, Huawei Huang i Albert Zomaya. "GriDB: Scaling Blockchain Database via Sharding and Off-Chain Cross-Shard Mechanism". Proceedings of the VLDB Endowment 16, nr 7 (marzec 2023): 1685–98. http://dx.doi.org/10.14778/3587136.3587143.
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Blockchain databases have attracted widespread attention but suffer from poor scalability due to underlying non-scalable blockchains. While blockchain sharding is necessary for a scalable blockchain database, it poses a new challenge named on-chain cross-shard database services. Each cross-shard database service (e.g., cross-shard queries or inter-shard load balancing) involves massive cross-shard data exchanges, while the existing cross-shard mechanisms need to process each cross-shard data exchange via the consensus of all nodes in the related shards (i.e., on-chain) to resist a Byzantine environment of blockchain, which eliminates sharding benefits. To tackle the challenge, this paper presents GriDB, the first scalable blockchain database, by designing a novel off-chain cross-shard mechanism for efficient cross-shard database services. Borrowing the idea of off-chain payments, GriDB delegates massive cross-shard data exchange to a few nodes, each of which is randomly picked from a different shard. Considering the Byzantine environment, the untrusted delegates cooperate to generate succinct proof for cross-shard data exchanges, while the consensus is only responsible for the low-cost proof verification. However, different from payments, the database services' verification has more requirements (e.g., completeness, correctness, freshness, and availability); thus, we introduce several new authenticated data structures (ADS). Particularly, we utilize consensus to extend the threat model and reduce the complexity of traditional accumulator-based ADS for verifiable cross-shard queries with a rich set of relational operators. Moreover, we study the necessity of inter-shard load balancing for a scalable blockchain database and design an off-chain and live approach for both efficiency and availability during balancing. An evaluation of our prototype shows the performance of GriDB in terms of scalability in workloads with queries and updates.