74 research outputs found
Correction to:Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy (Surgical Endoscopy, (2019), 33, 1, (110-121), 10.1007/s00464-018-6281-2)
No full textThe list of the CholeS management group, Collaborators and Data Validators were omitted from the Acknowledgments.</p
Correction to:Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy (Surgical Endoscopy, (2019), 33, 1, (110-121), 10.1007/s00464-018-6281-2)
No full textThe list of the CholeS management group, Collaborators and Data Validators were omitted from the Acknowledgments.</p
Correction to:Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy (Surgical Endoscopy, (2019), 33, 1, (110-121), 10.1007/s00464-018-6281-2)
No full textThe list of the CholeS management group, Collaborators and Data Validators were omitted from the Acknowledgments.</p
Gromit: Benchmarking the Performance and Scalability of Blockchain Systems
No full textThe growing number of implementations of blockchain systems stands in stark contrast with still limited research on a systematic comparison of performance characteristics of these solutions. Such research is crucial for evaluating fundamental trade-offs introduced by novel consensus protocols and their implementations. These performance limitations are commonly analyzed with ad-hoc benchmarking frameworks focused on the consensus algorithm of blockchain systems. However, comparative evaluations of design choices require macro-benchmarks for uniform and comprehensive performance evaluations of blockchains at the system level rather than performance metrics of isolated components. To address this research gap, we implement Gromit, a generic framework for analyzing blockchain systems. Gromit treats each system under test as a transaction fabric where clients issue transactions to validators. We use Gromit to conduct the largest blockchain study to date, involving seven representative systems with varying consensus models. We determine the peak performance of these systems with a synthetic workload in terms of transaction throughput and scalability and show that transaction throughput does not scale with the number of validators. We explore how robust the subjected systems are against network delays and reveal that the performance of permissoned blockchain is highly sensitive to network conditions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Data-Intensive System
Independent verification of validator performance in the XRP ledger
No full textThe XRP network (Ripple network) is a global transaction network that settles trans- actions in seconds. It is a technology that provides new opportunities for traditional fi- nancial institutions and startups. In the XRP network, participants depend on each other’s functioning. However, at present Ripple Labs, Inc. is the only actor monitor- ing some form of performance. This paper presents a way for independent individuals to verify the score of validators. Further- more, to improve the insight into the per- formance of validators, a new metric is in- troduced. Together these improvements con- tribute towards a healthy decentralised XRP network.CSE3000 Research ProjectComputer Science and Engineerin
Monitoring the Performance of the Pedestrian Transfer Function of Train Stations Using Automatic Fare Collection Data
No full textOver the last years all train stations in The Netherlands have been equipped with automatic fare collection gates and/or validators. All public transport passengers use a smart card to pay their fare. In this paper we present a monitor for the performance of the pedestrian function of train stations which is based on data from the automatic fare collection system. To our knowledge this is the first study that uses smart card data in the context of pedestrian behaviour at train stations. To illustrate the added value of the monitor, various applications for a number of train stations are presented.Transport & PlanningCivil Engineering and Geoscience
A TURING Test Approach to Intelligent System Validation
No full textThe authors present some ideas on developing a validity statement based on a Turing test -- like methodology with a set of test cases. The (anonymous) solutions of these test cases will be rated by a panel of expert validators. The methodology is called the Turing test, because a random process of distributing the test case with solutions to the different validators ensures that no validator knows who the author of a test case solution is. Their ratings are used for both the assessement of the experts' competence and the assessment of the system's validity. The objective of this is, of course, to make the result of the validation process (a validity statement) as objective as possible. Furthermore, in an effort to maximize objectivity, the approach includes a competence scale for each validator. The degree of competence is estimated by considering the experts' behavior while solving the test cases and rating the test case solutions
Consensus-less Security: A truly scalable distributed ledger
No full textDistributed ledger technology was expected to spark a technical revolution similar to the internet revolution. After the release of Bitcoin in 2008, many developments have significantly increased the performance of distributed ledger technology. Nevertheless, the first truly scalable ledger has yet to be deployed. All of them have issues with scaling in either the throughput, the number of nodes which can validate transaction or both. The concept behind a distributed ledger is that the integrity of the ledger is a shared responsibility. However, as soon as new technology emerges, also misuse surfaces, especially if there are financial gains involved. The general solution, to prevent such abuse, in distributed ledger technology is through the use of global consensus. If the majority of a network is honest, and we require a majority vote on the validity of a transaction, no malicious transactions will succeed. A downside of requiring a majority vote is that every node eligible to vote must contain full knowledge on all previous transactions. This work argues that the requirement of global consensus is a major limiting factor when it comes to the scalability of current ledgers. The goal of this work is to design a scalable distributed ledger whose security does not rely on global consensus. It proposes a novel algorithm that guarantees security, even under adversarial attack, by up to a third of the network exhibiting byzantine behavior. It does so using Trustchain, a pair-wise ledger designed by the Delft University of Technology, and `Fair Witness Selection Protocol', a newly designed publicly verifiable witness selection algorithm with an indicated message and communication complexity of . A mathematical lower-bound is given on the security level of the algorithm, and the security is reduced to the security of the underlying hash function. Several experiments were executed on the DAS-5 supercomputer to confirm the scalability of this work. These experiments show that the throughput of the network scales linearly, and has been tested up to 2500 nodes (simultaneously acting as validators and clients). To the best of the author's knowledge, it is the only ledger that has no theoretical limits on the number of clients, number of validators, or throughput. A peak-throughput of 7025 tx/s has been observed at a network size of 280 nodes. Furthermore, the total transaction time remained roughly constant at about 15 milliseconds regardless of the network size
Development of animated video media to improve adaptive behavior of MTsN 1 Tuban
No full textThe problem of this research is that the learning media used in the teaching and learning process have not been able to increase students' adaptive abilities significantly, so innovation in learning media is needed that can improve students' adaptive abilities. By using animated video media, it is hoped that it can improve students' adaptive abilities. This research is development research aimed at producing animated video learning media that is valid, practical and effective. The type of research that the author uses is research and development using the 4-D development model. From research conducted by the author at MTsN 1 Tuban (1), the assessment results obtained from each validator were 98% media expert validators, and 92.3% material expert validators. (2) the practicality test of the teacher response questionnaire assessment obtained a percentage of 94.2%, and the student response questionnaire obtained a percentage of 85.5%. (3) effectiveness test based on the results of the pretest post-test, it was obtained that students' adaptive abilities scored 100% complete. This proves that students experienced improvement after the Gain Normality Test was carried out
Invariant-Based Automatic Testing of Modern Web Applications
No full textAJAX-based Web 2.0 applications rely on stateful asynchronous client/server communication, and client-side run-time manipulation of the DOM tree. This not only makes them fundamentally different from traditional web applications, but also more error-prone and harder to test. We propose a method for testing AJAX applications automatically, based on a crawler to infer a state-flow graph for all (client-side) user interface states. We identify AJAX-specific faults that can occur in such states (related to e.g., DOM validity, error messages, discoverability, back-button compatibility) as well as DOM-tree invariants that can serve as oracles to detect such faults. Our approach, called ATUSA, is implemented in a tool offering generic invariant checking components, a plugin-mechanism to add application-specific state validators, and generation of a test suite covering the paths obtained during crawling. We describe three case studies, consisting of six subjects, evaluating the type of invariants that can be obtained for AJAX applications as well as the fault revealing capabilities, scalability, required manual effort, and level of automation of our testing approach. This paper is a pre-print of: Ali Mesbah, Arie van Deursen and Danny Roest. Invariant-Based Automatic Testing of Modern Web Applictions. IEEE Transactions on Software Engineering, 2011.Software TechnologyElectrical Engineering, Mathematics and Computer Scienc
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