702 research outputs found
An Architecture for Distributed Energies Trading in Byzantine-Based Blockchain
With the development of smart cities, not only are all corners of the city
connected to each other, but also connected from city to city. They form a
large distributed network together, which can facilitate the integration of
distributed energy station (DES) and corresponding smart aggregators.
Nevertheless, because of potential security and privacy protection arisen from
trustless energies trading, how to make such energies trading goes smoothly is
a tricky challenge. In this paper, we propose a blockchain-based multiple
energies trading (B-MET) system for secure and efficient energies trading by
executing a smart contract we design. Because energies trading requires the
blockchain in B-MET system to have high throughput and low latency, we design a
new byzantine-based consensus mechanism (BCM) based on node's credit to improve
efficiency for the consortium blockchain under the B-MET system. Then, we take
combined heat and power (CHP) system as a typical example that provides
distributed energies. We quantify their utilities, and model the interactions
between aggregators and DESs in a smart city by a novel multi-leader
multi-follower Stackelberg game. It is analyzed and solved by reaching Nash
equilibrium between aggregators, which reflects the competition between
aggregators to purchase energies from DESs. In the end, we conduct plenty of
numerical simulations to evaluate and verify our proposed model and algorithms,
which demonstrate their correctness and efficiency completely
Differential Privacy-Based Online Allocations towards Integrating Blockchain and Edge Computing
In recent years, the blockchain-based Internet of Things (IoT) has been
researched and applied widely, where each IoT device can act as a node in the
blockchain. However, these lightweight nodes usually do not have enough
computing power to complete the consensus or other computing-required tasks.
Edge computing network gives a platform to provide computing power to IoT
devices. A fundamental problem is how to allocate limited edge servers to IoT
devices in a highly untrustworthy environment. In a fair competition
environment, the allocation mechanism should be online, truthful, and privacy
safe. To address these three challenges, we propose an online multi-item double
auction (MIDA) mechanism, where IoT devices are buyers and edge servers are
sellers. In order to achieve the truthfulness, the participants' private
information is at risk of being exposed by inference attack, which may lead to
malicious manipulation of the market by adversaries. Then, we improve our MIDA
mechanism based on differential privacy to protect sensitive information from
being leaked. It interferes with the auction results slightly but guarantees
privacy protection with high confidence. Besides, we upgrade our
privacy-preserving MIDA mechanism such that adapting to more complex and
realistic scenarios. In the end, the effectiveness and correctness of
algorithms are evaluated and verified by theoretical analysis and numerical
simulations
A k-hop Collaborate Game Model: Extended to Community Budgets and Adaptive Non-Submodularity
Revenue maximization (RM) is one of the most important problems on online
social networks (OSNs), which attempts to find a small subset of users in OSNs
that makes the expected revenue maximized. It has been researched intensively
before. However, most of exsiting literatures were based on non-adaptive
seeding strategy and on simple information diffusion model, such as
IC/LT-model. It considered the single influenced user as a measurement unit to
quantify the revenue. Until Collaborate Game model appeared, it considered
activity as a basic object to compute the revenue. An activity initiated by a
user can only influence those users whose distance are within k-hop from the
initiator. Based on that, we adopt adaptive seed strategy and formulate the
Revenue Maximization under the Size Budget (RMSB) problem. If taking into
account the product's promotion, we extend RMSB to the Revenue Maximization
under the Community Budget (RMCB) problem, where the influence can be
distributed over the whole network. The objective function of RMSB and RMCB is
adatpive monotone and not adaptive submodular, but in some special cases, it is
adaptive submodular. We study the RMSB and RMCB problem under both the speical
submodular cases and general non-submodular cases, and propose RMSBSolver and
RMCBSolver to solve them with strong theoretical guarantees, respectively.
Especially, we give a data-dependent approximation ratio for RMSB problem under
the general non-submodular cases. Finally, we evaluate our proposed algorithms
by conducting experiments on real datasets, and show the effectiveness and
accuracy of our solutions
Impact of Bt Cotton on the Farmer's Livelihood System in China
In order to analyze the impacts of Bt cotton on the farmers' livelihood system, we interviewed 169 farmers and extension personnel in the main cotton production areas in Hebei province in the year 2002 and 2003. An integrative method was used in which a multidisciplinary approach was employed including agronomy, economics and sociology. The results showed that the application of Bt cotton increased the cotton growing area as well as farmers' income. For 67% of the farmers interviewed, cotton area has been continuously increasing since 1997. The cotton net margin in one cropping cycle came out to be higher than the combined net margins of wheat and corn in two cropping cycles. The income from cotton played a significant role in the investment to education, leisure and health care. The socio-economic impacts of cotton production are nevertheless not yet optimal because there were still many factors limiting them. Lack of labor and land were the main limiting factors. Productivity is restrained by the high price of Bt cotton seeds which pushed farmers to keep seeds from their own cotton production (42% of the farmers in 2002 and 2003). Farmers are still lacking technical command in using Bt-cotton: 78% of the farmers admitted that while more than 94% of the farmers complained not getting information from local extension and technical services. More success in using Bt-cotton calls upon going beyond providing seeds and asks for continuous assistance from research and extension department, notably to achieve a full knowledge of the Bt-cotton characteristic so as to optimally integrate it into the farmers' system.China; Bt Cotton; biotechnologies; impact evaluation; Livelihood
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