Browsing by Author "Zhang, G."

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    Analyzing Transient Phenomena in the Time Domain Using the Feature Selective Validation (FSV) Method
    (IEEE, 2013-05-24) Jauregui, R.; Zhang, G.; Rojas-Mora, J.; Ventosa, O.; Silva, F.; Duffy, A. P.; Sasse, Hugh G.
    The increasing application of simulation tools to increasingly complex problems makes the use of validation tools essential to improve confidence in the veracity of those simulation results. IEEE Standard 1597.1 is the first true standard for the validation of computational electromagnetics method. This standard uses the feature selective validation (FSV) method as the key quantification tool. However, despite its many advantages, there have been some interesting issues surrounding the validation of transients. This paper presents a new approach to the validation of a set of generally representative transient types using the FSV method and shows how the previously experienced limitations can be overcome. In order to analyze the main parameters associated with transient comparison, a survey which included 20 experts was conducted. This information was used to identify the significant regions that need to be taken into account in the transient comparison. Finally, using the statistics obtained by the experts, a new solution was defined and its
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    Cloud-Assisted Secure eHealth Systems for Tamper-Proofing EHR via Blockchain
    (Elsevier, 2019-02-14) Cao, S.; Zhang, G.; Liu, P.; Zhang, X.; Neri, Ferrante
    The wide deployment of cloud-assisted electronic health (eHealth) systems has already shown great benefits in managing electronic health records (EHRs) for both medical institutions and patients. However, it also causes critical security concerns. Since once a medical institution generates and outsources the patients' EHRs to cloud servers, patients would not physically own their EHRs but the medical institution can access the EHRs as needed for diagnosing, it makes the EHRs integrity protection a formidable task, especially in the case that a medical malpractice occurs, where the medical institution may collude with the cloud server to tamper with the outsourced EHRs to hide the medical malpractice. Traditional cryptographic primitives for the purpose of data integrity protection cannot be directly adopted because they cannot ensure the security in the case of collusion between the cloud server and medical institution. In this paper, a secure cloud-assisted eHealth system is proposed to protect outsourced EHRs from illegal modification by using the blockchain technology (blockchain-based currencies, e.g., Ethereum). The key idea is that the EHRs only can be outsourced by authenticated participants and each operation on outsourcing EHRs is integrated into the public blockchain as a transaction. Since the blockchain-based currencies provide a tamper-proofing way to conduct transactions without a central authority, the EHRs cannot be modified after the corresponding transaction is recorded into the blockchain. Therefore, given outsourced EHRs, any participant can check their integrity by checking the corresponding transaction. Security analysis and performance evaluation demonstrate that the proposed system can provide a strong security guarantee with a high efficiency.
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    Design and implementation of membrane controllers for trajectory tracking of nonholonomic wheeled mobile robots
    (IOS Press, 2016) Wang, X.; Zhang, G.; Neri, Ferrante; Jiang, T.; Zhao, J.; Gheorghe, M.; Ipate, F.; Lefticaru, R.
    This paper proposes a novel trajectory tracking control approach for nonholonomic wheeled mobile robots. In this approach, the integration of feed-forward and feedback controls is presented to design the kinematic controller of wheeled mobile robots, where the control law is constructed on the basis of Lyapunov stability theory, for generating the precisely desired velocity as the input of the dynamic model of wheeled mobile robots; a proportional-integral-derivative based membrane controller is introduced to design the dynamic controller of wheeled mobile robots to make the actual velocity follow the desired velocity command. The proposed approach is defined by using an enzymatic numerical membrane system to integrate two proportional-integral-derivative controllers, where neural networks and experts' knowledge are applied to tune parameters. Extensive experiments conducted on the simulated wheeled mobile robots show the effectiveness of this approach.
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    General overview of areas for enhancements in the FSV method
    (2013) Jauregui, R.; Ventosa, O.; Silva, F.; Azpurua, M.; Zhang, G.; Duffy, A. P.
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    Geometry based Three-Dimensional Image Processing Method for Electronic Cluster Eye
    (IOS Press, 2018-01-22) Wu, S.; Zhang, G.; Zhu, M.; Jian, T.; Neri, Ferrante
    In recent years, much attention has been paid to the electronic cluster eye (eCley), a new type of artificial compound eyes, because of its small size, wide field of view (FOV) and sensitivity to motion objects. An eCley is composed of a certain number of optical channels organized as an array. Each optical channel spans a small and fixed field of view (FOV). To obtain a complete image with a full FOV, the images from all the optical channels are required to be fused together. The parallax from unparallel neighboring optical channels in eCley may lead to reconstructed image blurring and incorrectly estimated depth. To solve this problem, this paper proposes a geometry based three-dimensional image processing method (G3D) for eCley to obtain a complete focused image and dense depth map. In G3D, we derive the geometry relationship of optical channels in eCley to obtain the mathematical relation between the parallax and depth among unparallel neighboring optical channels. Based on the geometry relationship, all of the optical channels are used to estimate the depth map and reconstruct a focused image. Subsequently, by using an edge-aware interpolation method, we can further gain a sharply focused image and a depth map. The effectiveness of the proposed method is verified by the experimental results.
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    Improvement in the Definition of ODM for FSV
    (IEEE, 2012-12-25) Zhang, G.; Duffy, A. P.; Sasse, Hugh G.; Wang, L.; Jauregui, R.
    It has been found that the feature-selective validation (FSV) method may demonstrate inconsistencies in the results when applied to the comparison of zero-crossing datasets. This type of data is typical of time-domain-based electromagnetic compatibility validation. This paper investigates the source of this inconsistency and proposes a solution. The reason was investigated using a set of typical transient data, which was related to the derivation of the formulas of FSV. It is demonstrated that the problem can be alleviated by enhancing the definition of the offset difference measure. The resulting enhanced performance of FSV is assessed by comparing the results with visual assessment. It is demonstrated that the improvement increases the agreement between FSV prediction and visual assessment. Meanwhile, this modification has a very limited effect on the comparison of other data structures which do not cross the axis.
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    Investigating Confidence Histograms and Classification in FSV: Part I. Fuzzy FSV
    (IEEE, 2013) Di Febo, D.; de Paulis, F.; Orlandi, A.; Zhang, G.; Sasse, Hugh G.; Duffy, A. P.; Wang, L.; Archambeault, B.
    One important aspect of the feature selective validation (FSV) method is that it classifies comparison data into a number of natural-language categories. This allows comparison data generated by FSV to be compared with equivalent “visual” comparisons obtained using the visual rating scale. Previous research has shown a close relationship between visual assessment and FSV generated data using the resulting confidence histograms. In all cases, the category membership functions are “crisp”: that is data on the FSV value axis fall distinctly into one category. An important open question in FSV-based research, and for validation techniques generally, is whether allowed variability in these crisp category membership functions could further improve agreement with the visual assessment. A similar and related question is how robust is FSV to variation in the categorization algorithm. This paper and its associated “part II” present research aimed at developing a better understanding of the categorization of both visual and FSV data using nonsquare or variable boundary category membership functions. This first paper investigates the level of improvement to be expected by applying fuzzy logic to location of the category boundaries. The result is limited improvement to FSV, showing that FSV categorization is actually robust to variations in category boundaries.
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    Investigating Confidence Histograms and Classification in FSV: Part II-Float FSV
    (IEEE, 2013) Di Febo, D.; Archambeault, B.; Zhang, G.; Sasse, Hugh G.; Duffy, A. P.; Wang, L.; de Paulis, F.; Orlandi, A.
    One important aspect of the feature selective validation (FSV) method is that it classifies comparison data into a number of natural-language categories. This allows comparison data generated by FSV to be compared with equivalent “visual” comparisons obtained using the visual rating scale. Previous research has shown a close relationship between visual assessment and FSV generated data using the resulting confidence histograms. In all cases, the category membership functions are “crisp”: that is data on the FSV-value axis falls distinctly into one category. The companion paper to this Investigating Confidence histograms and Classification in FSV: Part I. Fuzzy FSV investigated whether allowing probabilistic membership of categories could improve the comparison between FSV and visual assessment. That paper showed that such an approach produced limited improvement and, as a consequence, showed that FSV confidence histograms are robust to flexibility in category boundaries. This paper investigates the effect of redefining some, but not all, category boundaries based around the mode category. This “float” approach does show some improvement in the comparison between FSV and visual assessment.
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    Performance Improvement of FSV in a Special Situation
    (2011) Zhang, G.; Wang, L.; Duffy, A. P.
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    Role of apoptosis and Bcl-2/Bax in the development of tubulointerstitial fibrosis during experimental obstructive nephropathy.
    (Karger, 2001-03-01) Oldroyd, S. D.; Huang, L. H.; Yang, B.; Zhang, G.; Li, Y.; Ye, R.; El Nahas, Abdel Meguid