A Deep Spatio-Temporal Fuzzy Neural Network for Passenger Demand Prediction

In spite of its importance, passenger demand prediction is a highly challenging problem, because the demand is simultaneously influenced by the complex interactions among many spatial and temporal factors and other external factors such as weather. To address this problem, we propose a Spatio-TEmporal Fuzzy neural Network (STEF-Net) to accurately predict passenger demands incorporating the complex interactions of all known important factors. We design an end-to-end learning framework with different neural networks modeling different factors. Specifically, we propose to capture spatio-temporal feature interactions via a convolutional long short-term memory network and model external factors via a fuzzy neural network that handles data uncertainty significantly better than deterministic methods. To keep the temporal relations when fusing two networks and emphasize discriminative spatio-temporal feature interactions, we employ a novel feature fusion method with a convolution operation and an attention layer. As far as we know, our work is the first to fuse a deep recurrent neural network and a fuzzy neural network to model complex spatial-temporal feature interactions with additional uncertain input features for predictive learning. Experiments on a large-scale real-world dataset show that our model achieves more than 10% improvement over the state-of-the-art approaches.Comment: https://epubs.siam.org/doi/abs/10.1137/1.9781611975673.1

Dragoon: Private Decentralized HITs Made Practical

With the rapid popularity of blockchain, decentralized human intelligence tasks (HITs) are proposed to crowdsource human knowledge without relying on vulnerable third-party platforms. However, the inherent limits of blockchain cause decentralized HITs to face a few "new" challenges. For example, the confidentiality of solicited data turns out to be the sine qua non, though it was an arguably dispensable property in the centralized setting. To ensure the "new" requirement of data privacy, existing decentralized HITs use generic zero-knowledge proof frameworks (e.g. SNARK), but scarcely perform well in practice, due to the inherently expensive cost of generality. We present a practical decentralized protocol for HITs, which also achieves the fairness between requesters and workers. At the core of our contributions, we avoid the powerful yet highly-costly generic zk-proof tools and propose a special-purpose scheme to prove the quality of encrypted data. By various non-trivial statement reformations, proving the quality of encrypted data is reduced to efficient verifiable decryption, thus making decentralized HITs practical. Along the way, we rigorously define the ideal functionality of decentralized HITs and then prove the security due to the ideal-real paradigm. We further instantiate our protocol to implement a system called Dragoon, an instance of which is deployed atop Ethereum to facilitate an image annotation task used by ImageNet. Our evaluations demonstrate its practicality: the on-chain handling cost of Dragoon is even less than the handling fee of Amazon's Mechanical Turk for the same ImageNet HIT.Comment: small differences from a version accepted to appear in ICDCS 2020 (to fix a minor bug

Vegetation dynamics in the climate of West Africa

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (p. 211-224).The climate of West Africa exhibits significant variability at the time scale of decades. The persistent drought of the past three decades is an example of such variability. This study investigates the role of vegetation dynamics in shaping the low-frequency variability of the climate over West Africa. A zonally symmetric, synchronously coupled biosphere-atmosphere model (ZonalBAM) which includes explicit representation of vegetation dynamics has been developed, and has been validated using observations on both the atmospheric and biospheric climate. The model is then used to study the dynamics of the coupled biosphere-atmosphere system over West Africa. Based on the model sensitivity to initial conditions and the resilience of the coupled system with respect to perturbations, we demonstrate that the coupled biosphere-atmosphere system over West Africa has multiple equilibrium states, with reversible transitions between different equilibria. The two-way biosphere-atmosphere feedback is a significant process in both climate persistence and climate transition. Based on long-term climate simulations using ZonalBAM driven with the observed sea surface temperature (SST) variations, our study shows that vegetation dynamics is a significant process in shaping the climate variability of West Africa. The response of the regional climate system to large-scale forcings is significantly regulated by vegetation dynamics. The relatively slow response of vegetation to changes in the atmosphere is a significant mechanism that acts to enhance the low-frequency rainfall variability. Climate transitions between different equilibria act as another mechanism contributing to the low-frequency rainfall variability - multi-decadal fluctuations can take place as a collective reflection of climate persistence at one equilibrium and climate transition towards another. Vegetation dynamics seems to play an important role in the development and persistence of the current Sahel drought. The most likely scenario for the triggering mechanism of the Sahel drought would involve a combination of several processes including regional changes in land cover as well as changes in the patterns of global and regional SST distributions. However, regardless of the nature of the triggering mechanism, the response of the natural vegetation to the atmospheric changes is the critical process in the development and persistence of the observed drought.by Guiling Wang.Ph.D

A Survey on Consortium Blockchain Consensus Mechanisms

Blockchain is a distributed ledger that is decentralized, immutable, and transparent, which maintains a continuously growing list of transaction records ordered into blocks. As the core of blockchain, the consensus algorithm is an agreement to validate the correctness of blockchain transactions. For example, Bitcoin is a public blockchain where each node in Bitcoin uses the Proof of Work (PoW) algorithm to reach a consensus by competing to solve a puzzle. Unlike a public blockchain, a consortium blockchain is an enterprise-level blockchain that does not contend with the issues of creating a resource-saving global consensus protocol. This paper highilights several state-of-the art solutions in consensus algorithms for enterprise blockchain. For example, the HyperLedger by Linux Foundation includes implementing Practical Byzantine Fault Tolerance (PBFT) as the consensus algorithm. PBFT can tolerate a range of malicious nodes and reach consensus with quadratic complexity. Another consensus algorithm, HotStuff, implemented by Facebook Libra project, has achieved linear complexity of the authenticator. This paper presents the operational mechanisms of these and other consensus protocols, and analyzes and compares their advantages and drawbacks.Comment: under submissio

FRP structure design method based on equality of stiffness: case study and practice

Nowadays, Fiber reinforced polymer materials are getting widely used in civil engineering. They have some advanced engineering characters like high stiffness-to-weight ratio, high strength-to-weight ratio, anti-electromagnetic interference, electrical isolation and its long time durability. Metal and concrete, those main kinds of construction material, are prone to be failed before the structure service life because of the environmental attacks. Those harsh attacks are oxidization, acidification, high temperature and alkali corrosion. After the maintenance methods like isolating the attacks or protecting plastic skins, the interfaces between the protections are easily to be cracked and it caused the same worry on durability problems. Fiber reinforced polymer stands for a new era of civil engineering and surely the traditional material can be substituted by fiber reinforced polymer. This paper wants to unfold a case study on how fiber reinforced polymer worked in civil structures