In this paper, we present non-full-active Super-Sbox analysis which can detect non-ideal properties of a class of AES-based permutations with a low complexity. We apply this framework to SHA-3 round-2 candidates ECHO and Grøstl. The first application is for the full-round (8-round) ECHO permutation, which is a building block for 256-bit and 224-bit output sizes. By combining several observations specific to ECHO, our attack detects a non-ideal property with a time complexity of 2 182 and 2 37 amount of memory. The complexity, especially in terms of the product of time and memory, is drastically reduced from the previous best attack which required 2 512 × 2 512. Note that this result does not impact the security of the ECHO compression function nor the overall hash function. We also show that our method can detect nonideal properties of the 8-round Grøstl-256 permutation with a practical complexity, and finally show that our approach improves a semi-freestart collision attack on the 7-round Grøstl-512 compression function. Our approach is based on a series of attacks on AES-based hash functions such as rebound attack and Super-Sbox analysis. The core idea is using a new differential path consisting of only non-full-active states.
Nowadays, the localization and identification of acoustic emission (AE) source is widely utilized to structural health monitoring (SHM) of complex metallic structures. However, traditional AE source localization methods are generally difficult to localize and characterize AE sources in plate-like structure that has complex geometric features. To alleviate the problem, a novel AE source localization method based on all-phase fast Fourier transform and multiple cross-correlation analysis is proposed in this article. Moreover, least squares and Geiger iteration algorithm are applied to determine the coordinates of AE sources. In addition, an improved Bayesian information criterion (BIC) version named autoregressive BIC (i.e., AR-BIC) is presented to increase the accuracy of source localization. To validate the performance of the proposed approach, the classical pencil lead break tests are carried out on a 316 L stainless steel with 10 laser cladding layers. Experimental waveforms are generated from AE sources near laser cladding layers, the surface of the structure, and on its edges. Additionally, to evaluate the performance of the proposed approach in three-dimensional AE source localization, an industrial storage tank is used to acquire three-dimensional AE sources through manually striking. Finally, to further verify the effectiveness of the proposed approach, comparisons with conventional AE source location methods (i.e., PAC or SAMOS AE acquisition system, Newton’s method, and multiple cross-correlation based on Geiger algorithm) and two representative approaches (i.e., deep learning and Bayesian methodology) for localizing AE sources generated by complex metallic structures are conducted. The comparative results demonstrate the effectiveness and superiority of the proposed method in AE-based SHM of complex metallic structures.
The high-speed data acquisition equipment which is based on NI and LabVIEW software was used to establish the acoustic emission (AE) signal collection platform, and adopted wavelet analysis method to extract the weak of AE signal waveform from noise, aiming at the localization of AE source on plywood surface. The signal cross-correlation analysis method is used to determine the time difference between the AE signals and the different sensors,so that further calculates the average propagation speed of AE signal on the plywood surface. A kind of AE signal source localization method which is based on the cross-correlation method was proposed according to the principle of geometric positioning, and verified by means of the testing experiment which selected the lead break to simulate AE source. This paper has shown that wavelet analysis can effectively extract AE signal waveform, and the localization method based on cross-correlation principle can precisely calibrate the position of AE signal source.
Based on the real-time environmental constraints in urban regional construction, this paper constructed a bi-level decentralized low-carbon optimal dispatching model of the urban regional integrated energy system (RIES), including the park integrated energy systems (IESs). In this model, a bi-level optimal allocation model of carbon emission constraints between the urban and the park is proposed for the first time. The upper urban will formulate the real-time carbon emission constraints based on real-time environmental monitoring, decomposing the historical carbon emissions to the lower park IESs; the lower park will meet the real-time carbon emission constraints during optimization. We through the upper urban with the lower park between the bi-level decentralized optimization to ensure that the objective function's upper urban power, natural gas, and heat distribution network system is minimum total network loss. In addition, it is necessary to ensure the minimum operating cost of each park IESs and focus on how to meet the requirements of the overall environment of urban RIES. Furthermore, we study the influence of optimal allocation strategy of carbon emission constraints on network loss, and operating cost of urban RIES under different scenarios. Then, an improved analytical target cascading (ATC) method is applied to solve the bilevel decentralized optimal dispatching model of urban RIES. Finally, an example under three different scenarios is given to verify the superiority and effectiveness of the proposed model and the improved method.
In 2015, the number of complaints against airlines in Macau increased considerably. In today's keen competitive business environment, maintaining a good reputation and positive word-of-mouth within the industry is essential to increase competitiveness. Hence, Macau low-cost carriers should gather more customer feedback to improve their product and service quality. Macau passengers would speak to the management, their friends and family, and media and even choose boycott the companies when they feel dissatisfied with their travel experiences. The present study aimed to investigate the behavior of passengers in Macau toward low-cost carriers. A qualitative approach was adopted using a sample of 20 respondents who had previously submitted complaints to low-cost carriers. Semi-structured questions were asked in the in-depth interview. The results demonstrated the rationale behind the complaints. Perception of complaint behavior of Macau low-cost carriers' passengers was discovered. Recommendations were proposed to provide insights for industrial practitioners.
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