359 research outputs found
A Ring Signature Trust Model for Project Review Based on Blockchain Smart Contract
The traditional offline review model of grid projects has the problems of high cost, high risk and low efficiency, making the project review insecure and inefficient. What is worse, the review data of a grid project are generally stored in a central database, which is vulnerable to attacks and not highly trustable. To solve the problems, this paper proposes a ring signature trust model based on smart contract, an important blockchain technology, for project review. The blockchain technology was introduced to build an online review platform for grid projects, greatly saving human and financial resources. Then, the consensus efficiency was improved with a trust-based node consensus mechanism. Besides, the ring signature was integrated with smart contract to allow review experts to submit their results anonymously, ensuring the fairness and impartiality of grid project review. On this basis, an efficient review system was established for grid projects, and a secure review environment was created, so that the review results will not be tampered with. The case analysis proves that the proposed method can effectively solve the problems of traditional grid project review, making the review system more secure and efficient. The research findings provide decision and theoretical supports for grid project review
Diffraction from deformed volume holograms: perturbation theory approach
We derive the response of a volume grating to arbitrary small deformations, using a perturbative approach. This result is of interest for two applications: (a) when a deformation is undesirable and one seeks to minimize the diffracted field's sensitivity to it and (b) when the deformation itself is the quantity of interest and the diffracted field is used as a probe into the deformed volume where the hologram was originally recorded. We show that our result is consistent with previous derivations motivated by the phenomenon of shrinkage in photopolymer holographic materials. We also present the analysis of the grating's response to deformation due to a point indenter and present experimental results consistent with theory
Fine-grained Poisoning Attack to Local Differential Privacy Protocols for Mean and Variance Estimation
Although local differential privacy (LDP) protects individual users' data
from inference by an untrusted data curator, recent studies show that an
attacker can launch a data poisoning attack from the user side to inject
carefully-crafted bogus data into the LDP protocols in order to maximally skew
the final estimate by the data curator.
In this work, we further advance this knowledge by proposing a new
fine-grained attack, which allows the attacker to fine-tune and simultaneously
manipulate mean and variance estimations that are popular analytical tasks for
many real-world applications. To accomplish this goal, the attack leverages the
characteristics of LDP to inject fake data into the output domain of the local
LDP instance. We call our attack the output poisoning attack (OPA). We observe
a security-privacy consistency where a small privacy loss enhances the security
of LDP, which contradicts the known security-privacy trade-off from prior work.
We further study the consistency and reveal a more holistic view of the threat
landscape of data poisoning attacks on LDP. We comprehensively evaluate our
attack against a baseline attack that intuitively provides false input to LDP.
The experimental results show that OPA outperforms the baseline on three
real-world datasets. We also propose a novel defense method that can recover
the result accuracy from polluted data collection and offer insight into the
secure LDP design
Removal of 17α-ethynylestradiol from aqueous solutions by a hybrid PAC/UF process
This study investigated the removal of 17α-ethynylestradiol (EE2) from water using activated carbon adsorption and powdered activated carbon/ultrafiltration (PAC/UF). EE2 was easily adsorbed by PAC. The adsorption of EE2 fitted the Freundlich model well. The influences of initial EE2 concentration, filtration rate, PAC dose, natural organic matter (NOM), and sodium dodecyl benzene sulfonate (SDBS) were investigated. The EE2 concentration and filtration rate had no significant effect on EE2 removal, whereas the addition of PAC had a significant effect on EE2 removal. The removal rate of EE2 increased dramatically from 7.01% to 80.03% as the PAC dose was increased from 0 to 10 mg/L. Both SDBS and NOM decreased the EE2 removal efficiency. The removal efficiency of EE2 in the PAC/UF process decreased from 86.77% to 42.64% as the SDBS concentration was increased from 0 to 50 mg/L. It was concluded that activated carbon adsorption and PAC/UF can be used for the effective removal of EE2 from water.Keywords: 17-α-ethynylestradiol, adsorption, ultrafiltration, PAC/UF process, removal efficienc
Resource recovery from digested manure centrate:Comparison between conventional and aquaporin thin-film composite forward osmosis membranes
We compared the performance of conventional and aquaporin thin-film composite forward osmosis (FO) membranes (denoted as HTI and AQP membrane, respectively) for concentration of digested manure centrate. Results show that the two FO membranes were capable to concentrate digested centrate for resource recovery. During concentration of digested manure centrate, a cohesive fouling layer formed on the HTI membrane surface, resulting in more dramatic flux decline and less fouling reversibility in comparison to the AQP membrane. The two FO membranes exhibited effective and comparable rejection of bulk organic matter, total phosphorus, and heavy metals, leading to their notable enrichment in digested manure centrate. By contrast, ammonium nitrogen (NH4 +-N) was only retained by approximately 40% using the two FO membranes with a slightly higher retention by the HTI membrane, since it was less negatively charged. As a result, total nitrogen was ineffectively rejected by the two FO membranes. It is noteworthy that the HTI membrane also contributed to higher rejection of most antibiotics than the AQP membrane, possibly due to enhanced retention by the fouling layer and retarded forward diffusion. Results from this study evidence the outperformance of the AQP membrane as a new generation FO membrane over its conventional counterpart with respect to antifouling property, while further improvement in membrane selectivity, particularly of monovalent cations (e.g. NH4 +-N), is needed to advance FO applications in resource recovery from challenging waste streams.</p
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