The nonlinear effects of flexible pins on wind turbine gearboxes

Xiangyang Xu,Shaojiang Dong,Jiayuan Luo,Tianhong Luo 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8

The structure of flexible pin-type planetary gear systems used in wind turbine gearboxes can improve the load sharing ability of planetswhile saving space unlike straddle-type carriers. However, the nonlinear dynamic characteristic of this type of system is not fully developed. This work presents a coupled lumped-parameter dynamic model to demonstrate nonlinear effects. Gear contact loss nonlinearityand bearing clearance nonlinearity are integrated into this dynamical model, and the effects of flexible pins on the nonlinear dynamicresponses are discussed. The conclusions made are as follows: lower flexible pin stiffness can significantly reduce nonlinear effects;when pin stiffness is increased, contact loss still occurs in positions of strong vibration even if the planet gear bearings have higher ordersof magnitude of tangential load in the wind turbine gearbox; dynamic response peaks are asymmetric with a frequency sweep; only leftoblique "Soft" jumps occur, and the right oblique “Hard” jump phenomena rarely occur; planet gear supporting the bearing clearanceexists; and vibration chaos occurs in positions of strong vibration.

Recognizing F5-like stego images from multi-class JPEG stego images

( Jicang Lu ),( Fenlin Liu ),( Xiangyang Luo ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.11

To recognize F5-like (such as F5 and nsF5) steganographic algorithm from multi-class stego images, a recognition algorithm based on the identifiable statistical feature (IDSF) of F5-like steganography is proposed in this paper. First, this paper analyzes the special modification ways of F5-like steganography to image data, as well as the special changes of statistical properties of image data caused by the modifications. And then, by constructing appropriate feature extraction sources, the IDSF of F5-like steganography distinguished from others is extracted. Lastly, based on the extracted IDSFs and combined with the training of SVM (Support Vector Machine) classifier, a recognition algorithm is presented to recognize F5-like stego images from images set consisting of a large number of multi-class stego images. A series of experimental results based on the detection of five types of typical JPEG steganography (namely F5, nsF5, JSteg, Steghide and Outguess) indicate that, the proposed algorithm can distinguish F5-like stego images reliably from multi-class stego images generated by the steganography mentioned above. Furthermore, even if the types of some detected stego images are unknown, the proposed algorithm can still recognize F5-like stego images correctly with high accuracy.

Microblog User Geolocation by Extracting Local Words Based on Word Clustering and Wrapper Feature Selection

( Hechan Tian ),( Fenlin Liu ),( Xiangyang Luo ),( Fan Zhang ),( Yaqiong Qiao ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.10

Existing methods always rely on statistical features to extract local words for microblog user geolocation. There are many non-local words in extracted words, which makes geolocation accuracy lower. Considering the statistical and semantic features of local words, this paper proposes a microblog user geolocation method by extracting local words based on word clustering and wrapper feature selection. First, ordinary words without positional indications are initially filtered based on statistical features. Second, a word clustering algorithm based on word vectors is proposed. The remaining semantically similar words are clustered together based on the distance of word vectors with semantic meanings. Next, a wrapper feature selection algorithm based on sequential backward subset search is proposed. The cluster subset with the best geolocation effect is selected. Words in selected cluster subset are extracted as local words. Finally, the Naive Bayes classifier is trained based on local words to geolocate the microblog user. The proposed method is validated based on two different types of microblog data - Twitter and Weibo. The results show that the proposed method outperforms existing two typical methods based on statistical features in terms of accuracy, precision, recall, and F1-score.

Verification Algorithm for the Duplicate Verification Data with Multiple Verifiers and Multiple Verification Challenges

( Guangwei Xu ),( Miaolin Lai ),( Xiangyang Feng ),( Qiubo Huang ),( Xin Luo ),( Li Li ),( Shan Li ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.2

The cloud storage provides flexible data storage services for data owners to remotely outsource their data, and reduces data storage operations and management costs for data owners. These outsourced data bring data security concerns to the data owner due to malicious deletion or corruption by the cloud service provider. Data integrity verification is an important way to check outsourced data integrity. However, the existing data verification schemes only consider the case that a verifier launches multiple data verification challenges, and neglect the verification overhead of multiple data verification challenges launched by multiple verifiers at a similar time. In this case, the duplicate data in multiple challenges are verified repeatedly so that verification resources are consumed in vain. We propose a duplicate data verification algorithm based on multiple verifiers and multiple challenges to reduce the verification overhead. The algorithm dynamically schedules the multiple verifiers’ challenges based on verification time and the frequent itemsets of duplicate verification data in challenge sets by applying FP-Growth algorithm, and computes the batch proofs of frequent itemsets. Then the challenges are split into two parts, i.e., duplicate data and unique data according to the results of data extraction. Finally, the proofs of duplicate data and unique data are computed and combined to generate a complete proof of every original challenge. Theoretical analysis and experiment evaluation show that the algorithm reduces the verification cost and ensures the correctness of the data integrity verification by flexible batch data verification.

A City-Level Boundary Nodes Identification Algorithm Based on Bidirectional Approaching

( Zhiyuan Tao ),( Fenlin Liu ),( Yan Liu ),( Xiangyang Luo ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.8

Existing city-level boundary nodes identification methods need to locate all IP addresses on the path to differentiate which IP is the boundary node. However, these methods are susceptible to time-delay, the accuracy of location information and other factors, and the resource consumption of locating all IPes is tremendous. To improve the recognition rate and reduce the locating cost, this paper proposes an algorithm for city-level boundary node identification based on bidirectional approaching. Different from the existing methods based on time-delay information and location results, the proposed algorithm uses topological analysis to construct a set of candidate boundary nodes and then identifies the boundary nodes. The proposed algorithm can identify the boundary of the target city network without high-precision location information and dramatically reduces resource consumption compared with the traditional algorithm. Meanwhile, it can label some errors in the existing IP address database. Based on 45,182,326 measurement results from Zhengzhou, Chengdu and Hangzhou in China and New York, Los Angeles and Dallas in the United States, the experimental results show that: The algorithm can accurately identify the city boundary nodes using only 20.33% location resources, and more than 80.29% of the boundary nodes can be mined with a precision of more than 70.73%.

Steganalysis of adaptive JPEG steganography by selecting DCT coefficients according to embedding distortion

( Xiaofeng Song ),( Fenlin Liu ),( Chunfang Yang ),( Xiangyang Luo ),( Zhenyu Li ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.12

According to the characteristics of adaptive JPEG steganography which determines the changed DCT coefficients based on embedding distortion, a new steganalysis method by selecting the DCT coefficients with small distortion values is proposed. Firstly, the principle of adaptive JPEG steganography through minimizing distortion is introduced. Secondly, the practicability of selecting the changed DCT coefficients according to distortion values is studied. Thirdly, the proposed steganalysis method is given and the embedding sensitivity of the steganalysis feature extracted from the selected DCT coefficients is analyzed. Lastly, the implement processes of the proposed method are presented and analyzed in details. In the experiments, PQt, PQe and J-UNIWARD steganography are used as examples to verify the effect of the proposed steganalysis method for adaptive JPEG steganography. A serial experimental results show the detection accuracy can be improved obviously, especially when the payload is relatively low.

Optimal Gabor Filters for Steganalysis of Content-Adaptive JPEG Steganography

( Xiaofeng Song ),( Fenlin Liu ),( Liju Chen ),( Chunfang Yang ),( Xiangyang Luo ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

The existing steganalysis method based on 2D Gabor filters can achieve a competitive detection performance for content-adaptive JPEG steganography. However, the feature dimensionality is still high and the time-consuming of feature extraction is relatively large because the optimal selection is not performed for 2D Gabor filters. To solve this problem, a new steganalysis method is proposed for content-adaptive JPEG steganography by selecting the optimal 2D Gabor filters. For the proposed method, the 2D Gabor filters with different parameter settings are generated first. Then, the feature is extracted by each 2D Gabor filter and the corresponding detection accuracy is used as the measure for filter selection. Next, some 2D Gabor filters are selected by a greedy strategy and the steganalysis feature is extracted by the selected filters. Last, the ensemble classifier is used to assemble the proposed steganalysis feature as well as the final steganalyzer. The experimental results show that the steganalysis feature extracted by the selected optimal 2D Gabor filters also can achieve a competitive detection performance while the feature dimensionality is reduced greatly.

The Impact of Prolonged Duration of Untreated Illness on Clinical Correlates in Chronic Schizophrenia: Exploring the Relationship With Suicide Risk

Ke Zhang,Chenxi Wang,Lei Gou,Yaxi Li,Cui Li,Guoshuai Luo,Xiangyang Zhang 대한신경정신의학회 2024 PSYCHIATRY INVESTIGATION Vol.21 No.4

Objective Studies on duration of untreated psychosis are common in patients with schizophrenia, but few studies have investigated the relationship between duration of untreated illness (DUI) and suicide, especially in patients with chronic schizophrenia. Therefore, we intended to investigate the relationship between DUI and suicide and clinical correlates in patients with chronic schizophrenia.Methods A total of 1,555 Chinese patients with chronic schizophrenia were enrolled in this study. DUI was measured in years, reflecting the prolonged untreated periods observed in this population. Clinical correlates were assessed, including symptoms, cognitive functioning, and body mass index. Suicidal ideation and attempts were also examined. Statistical analyses, including multivariate models, were employed to investigate the associations between DUI and clinical correlates while controlling for potential confounders.Results The study revealed a significant proportion (23.3%) of patients with chronic schizophrenia in China received their first treatment after a 4-year delay, with the longest untreated duration reaching 39 years. Patients with longer DUI exhibited more severe negative symptoms, lower immediate memory scores, a higher likelihood of being overweight, and surprisingly, a reduced likelihood of suicidal ideation and attempts. Each additional year of untreated illness was associated with a 3% decrease in the risk of suicidal ideation and attempts.Conclusion The findings underscore the prevalence of extended untreated periods in Chinese patients with chronic schizophrenia and highlight the impact of DUI on negative symptoms, cognitive function, and body weight. Intriguingly, a longer DUI was associated with a lower risk of suicidal ideation and attempts.