29 research outputs found
Measuring message gossiping in P2P networks and providing incentives in cryptocurrencies
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 47-48).In this thesis, we present Plutus, an efficient and game-theoretically proven incentive mechanism for Algorand, a proof-of-stake cryptocurrency. In order to operate, Algorand requires users to constantly propagate messages but has no mechanism to incentivize users to do so. Plutus solves this problem by keeping track of each message propagation path and rewarding the users who propagated messages using a lottery. We implemented a prototype of Plutus on top of Algorand to measure the performance and overhead of Plutus. Experimental results show that with Plutus, Algorand's block confirmation time increases by only 7% and that there is no penalty on Algorand's scalability.by Rotem Hemo.M. Eng
Hemo-dynamics
No full textPraise for Hemo-Dynamics: “This book provides an elegant and intuitive derivation of the fundamental mathematics underlying fluid flow, and then applies these in a straightforward way to pulsatile blood flow in all its complexity. One of the triumphs of the book is that Zamir succeeds in making essential concepts such as the Navier-Stokes equations completely accessible to any reader with a knowledge of basic calculus. The author succeeds in conveying both the beauty of his subject matter, and his passion for the elegance and intricacies of fluid flow more generally.” Lindi Wahl, PhD, Professor of Applied Mathematics, The University of Western Ontario “Incredible, the figures alone are to die for… At first glance “Hemo-Dynamics” seems like a deep engineering and modeling dive into the mechanical properties of the cardiovascular system, blood, and how they interact to generate flow and pressure. However, the text is laid out in a stepwise manner and I was especially impressed in the way that the key conceptual figures illustrate the essential concepts. In keeping with the philosophical underpinnings of engineering, Professor Zamir has also constructed his book so that the format, text, equations and the figures are self-reinforcing. This is a book that will be of great use to those who seek to understand the cardiovascular system from a mechanical and modeling perspective.” Michael J. Joyner, MD, Professor of Anesthesiology, Mayo Clinic, Rochester, MN
Scaling Byzantine Agreements for Cryptocurrencies
No full text© 2017 Copyright is held by the owner/author(s). Algorand is a new cryptocurrency that confirms transactions with latency on the order of a minute while scaling to many users. Algorand ensures that users never have divergent views of confirmed transactions, even if some of the users are malicious and the network is temporarily partitioned. In contrast, existing cryptocurrencies allow for temporary forks and therefore require a long time, on the order of an hour, to confirm transactions with high confidence. Algorand uses a new Byzantine Agreement (BA) protocol to reach consensus among users on the next set of transactions. To scale the consensus to many users, Algorand uses a novel mechanism based on Verifiable Random Functions that allows users to privately check whether they are selected to participate in the BA to agree on the next set of transactions, and to include a proof of their selection in their network messages. In Algorand’s BA protocol, users do not keep any private state except for their private keys, which allows Algorand to replace participants immediately after they send a message. This mitigates targeted attacks on chosen participants after their identity is revealed. We implement Algorand and evaluate its performance on 1,000 EC2 virtual machines, simulating up to 500,000 users. Experimental results show that Algorand confirms transactions in under a minute, achieves 125× Bitcoin’s throughput, and incurs almost no penalty for scaling to more users
Whāriki : beyond simple : an exhibition report presented as partial fulfilment of the requirements for the degree of Masters of Māori Visual Arts, Massey University, Palmerston North, New Zealand
No full textThis thesis/exhibition report is an explication of the significance and relationship of Kai rāranga, rāranga whāriki and their relationship with whānau, hapū and iwi. It explores the impetus behind and relationships important in, and to the production of whāriki.
Through the exploration of these relationships the necessity for whāriki wānanga throughout Aotearoa and having wānanga as the preferred medium of imparting knowledge pertaining to rāranga whāriki and for continuity in the production of whāriki is emphasised.
It touches on the Māori convention of tono that facilitates interaction between the Kai rārangaresearcher and the Kai tono-researched negating the sometimes invasive convention of ethics approval and formalised contractual obligations.
It follows the pathway of author and Kai rāranga, Te Hemo Ata Henare’s, coming to be of her mahi whāriki practice. It is an intimate account that extends from function and technique to foundational connectivity to the wider roopu whāriki and those who have preceded us with templates of excellence that recognise the importance of the whakapapa of Māori whakaaro, our epochs and eons of transcendent time and the interconnectedness of all things in and through these patterned processes (Jackson, 2013; Marsden, 2003; Tamanui, 2013). As Karani Sonny Pāpuni said;
“…you take this whāriki home with you and then a piece of us will always be with your whānau” (Mate ki Tātahi [Sonny] Pāpuni, personal communication, May 17 1991).
A clear objective emerging out of this research exercise was to produce a body of work in the form of an exhibition of whāriki and to produce a pictorial and written explication of the process and praxis of whāriki wānanga. However, through the research process, I was returned; i hoki atu ki te timatatanga ō oku mahi, so I could come to know and be.
The theme that emerges through rāranga whāriki is the inseparability and the multiplicity of whakapapa and/or whanaungatanga that the Kai rāranga embodies essential for the continuation of the praxis of rāranga whāriki that can only be described as extraordinarily ‘Beyond Simple’
Studies on Donaggio Reaction and Micro-determination of urinary protein Part Ⅲ Devised simple Donaggio-Sato Reaction using a hemo aglutination board instead of the test-tube
No full textAuthor devised a simple Donaggio-Sato Reaction using a hemo aglutination board instead of the test-tube, and obtained the following results. 1) Value obtained from Donaggio Reaction and that from this devised method had a good relation each other. 2) This Reaction method was confirmed to be utilized enough well to all members of a mass examination. 3) Statistically significant increase in. both Donaggio Reaction value and α1-acid glycoprotein in the urine of students just after their routine exercise of running suggested that Donaggio Reaction positive substance and α1-glycoprotein have an intimate relationship between them
Algorand: Scaling Byzantine Agreements for Cryptocurrencies
No full textAlgorand is a new cryptocurrency system that can confirm transactions
with latency on the order of a minute while scaling to many users.
Algorand ensures that users never have divergent views of confirmed
transactions, even if some of the users are malicious and the network is
partitioned. In contrast, existing cryptocurrencies allow for temporary
forks and therefore require a long time, on the order of an hour, to confirm transactions with
high confidence.
Algorand uses a new Byzantine Agreement (BA) protocol to reach consensus
among users on the next set of transactions. To scale the consensus to
many users, Algorand uses a novel mechanism based on Verifiable Random
Functions that allows users to privately check whether they are selected
to participate in the BA to agree on the next set of transactions,
and to include a proof of their selection in their network messages.
In Algorand\u27s BA protocol, users do not keep any private state except
for their private keys, which allows Algorand to replace participants
immediately after they send a message. This mitigates targeted attacks
on chosen participants after their identity is revealed.
We implement Algorand and evaluate its performance on 1,000 EC2 virtual
machines, simulating up to 500,000 users. Experimental results show that
Algorand confirms transactions in under a minute, achieves 30
Bitcoin\u27s throughput, and incurs almost no penalty for scaling to
more users
Donaggio反応及び尿微量蛋白定量法に関する研究 第3報 血球凝集板によるDonaggio・佐藤法の簡便測定法について
No full textAuthor devised a simple Donaggio-Sato Reaction using a hemo aglutination board instead of the test-tube, and obtained the following results. 1) Value obtained from Donaggio Reaction and that from this devised method had a good relation each other. 2) This Reaction method was confirmed to be utilized enough well to all members of a mass examination. 3) Statistically significant increase in. both Donaggio Reaction value and α1-acid glycoprotein in the urine of students just after their routine exercise of running suggested that Donaggio Reaction positive substance and α1-glycoprotein have an intimate relationship between them
Post-Processing of Data Gathered Using Tomographic Particle Image Velocimetry on a Phantom of an Intracranial Aneurysm: Hemo-dynamic Quantaties: Wall Shear Stress, Time Averaged WSS, Oscillating shear index and the Transverse WSS
No full textThe third biggest cause of death in the western world is the stroke which is often caused by an aneurysm. Recent literature proposes the Wall Shear Stress (WSS), the Time-Averaged Wall Shear Stress (TAWSS), the Oscillatory Shear Index (OSI) and the Transverse WSS (Trans-WSS) as possible factors influencing the initiation, growth and rupture of intracranial aneurysms (IA). Currently, scientist and doctors are still in disagree on the biggest factors of rupture of an IA. In this research project, Tomographic Particle Image Velocimetry (TPIV) is used to acquire data to calculate these before mentioned hemodynamic quantities. The experiment captured 2040 images during one simulated cardiac cycle in a phantom reflecting an IA. To obtain the WSS, TAWSS, OSI and Trans-WSS on the wall of the phantom these images were post-processed using Davis, Tecplot and Python. The hemodynamic quantities are successfully calculated and visualized on 3D models of the aneurysm. An accurate result for these hemodynamic quantities was achieved when using a minimum of 51 images evenly spread out during a cardiac cycle. In cases without time constraints, it is still recommended to use as many images as possible to account for local WSS fluctuations. In further research the data structure in DaVis should be altered to a constant Cartesian coordinate structure for every dataset of the phantom. This will remove the biggest error and will greatly increase the value of this thesis and the analysis of these quantities.Applied Physic
Flow behaviour of labeled red blood cells in microchannels : a confocal micro-PTV assessment
No full textThe development of optical experimental techniques
has contributed to obtain explanations on the blood flow
behaviour through microvessels. Although the past results have
been valuable, detailed studies on the flow properties of blood in
the microcirculation have been limited by several technical factors
such as poor spatial resolution and difficulty to obtain quantitative
detailed measurements at such small scales. In recent years, due to
advances in computers, optics, and digital image processing techniques,
it has become possible to combine particle tracking methods
with confocal microscopes. As a result, this combination has
greatly increased the resolution of the conventional PIV systems
and consequently provided additional detailed description on the
blood cells motion not obtainable by traditional methods. In this
work, we will show an overview of the most recent results on the
blood flow behaviour in microchannels obtained by state-of-the-art
confocal micro-PIV/PTV system.Program in Engineering, from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), 2007 Global COE Program “Global Nano-Biomedical Engineering Education and Research Network”, Japan. Grant-in-Aid for Science and Technology (PTDC/SAU-BEB/108728/2008, PTDC/SAU-
BEB/105650/2008 and PTDC/EME-MFE/099109/2008) from the Science and Technology Foundation (FCT) and COMPETE, Portugal. The author would like to thank Professor Takami Yamaguchi, Professor Shigeo Wada and Dr. Takuji Ishikawa for their valuable suggestions and discussion during this research work
