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[IEEE 2018 Prognostics and System Health Management Conference (PHM-Chongqing) - Chongqing, China (2018.10.26-2018.10.28)] 2018 Prognostics and System Health Management Conference (PHM-Chongqing) - A Remaining Useful Life Prediction Method for T/R Module Based on Index Similarity
摘要： T/R module is an important part of large phased array radar antenna array, the remaining useful life (RUL) prediction is of great significance for equipment support personnel to master current health status and improve maintenance support ability. At first, the key indexes of multi-state degradation are extracted by association rule, by calculating the similarity of the key indexes and combining the RUL of similar samples, the RUL information corresponding to the key indexes is obtained. The RUL prediction results of T/R module are obtained according to the weight of different indexes. The practicability and effectiveness of the proposed method are verified by example analysis and comparison, which provide theoretical guidance for the RUL prediction of electronic equipment. The proposed method is of great significance for maintenance support personnel of the military equipment to plan the maintenance resources reasonably and improve the combat effectiveness of the equipment.
关键词： index,T/R module,association rule,multi-state degradation,remaining useful life prediction,entropy weight method
更新于2025-09-23 15:22:29
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In situ TiN-reinforced CoCr2FeNiTi0.5 high-entropy alloy composite coating fabricated by laser cladding
摘要： The fcc structural CoCr2FeNiTi0.5 high-entropy alloy (HEA) composite coating with TiN particles reinforced was acquired by laser cladding on the commercial 904L stainless steels. The results show that phase structure is mainly composed of fcc solid solution and TiN phases. The coating exhibits excellent structural stability below 850 °C. The microstructure consists of irregular dendrite and TiN particles. Transmission electron microscopy (TEM) results reveal that the close-packed plane of fcc phase is (111) with interplanar spacing of * 0.208 nm. The interface between TiN and fcc matrix is semi-coherent. And the angle of boundary between dendrite and matrix is * 65°. The hardness and corrosion resistance of coating have much improvement compared with those of substrate.
关键词： Semi-coherent interface,High-entropy alloy,Laser cladding,TiN particle reinforced
更新于2025-09-23 15:22:29
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Thermodynamics and structural stability of tissues for bio-imaging analysis – The case of intracranial aneurysm rupture risk assessment
摘要： Based on thermodynamic principles, structure stability analysis like stress response and fracture formation is well established for inorganic but not for organic bio-materials. In this study, three equations were established to assess intracranial aneurysm (IA) rupture risk based on patient's IA and internal carotid artery (ICA) angiography images, by incorporating tissue thermodynamics. Our objectives are: (1) establish foundations to help understand the physics behind the observed morphological changes prior to IA rupture, and (2) provide first-principles equations to aide in rupture risk assessment. Subsequently, we validated the new equations using available experimental and numerical simulation results, and revealed new IA rupture physics. In particular, our models correlated well with most of the available experiment and computer fluid dynamics simulation data. Among the three common structure failure modes, the axial stress and the bending moment loading are the control mechanism. The rupture risk reaches its peak when (1) the aneurysm inclination angle (ω) is close to 63.4°, (2) IA diameter / ICA diameter ?1, and (3) IA length / IA diameter ≈1.6. This study provides strong physical foundations and sound understanding to aid in rupture risk assessment. It presents insights on detailed thermodynamics that govern the previously observed IA rupture behaviors, reported from both experiments and numerical simulations. By integrating angiography images with first-principles tissue thermodynamics, we (1) advance the IA research, which is currently dominated by experimental and imaging-data-statistic approaches, and (2) introduce Calphad research into a new exciting research field - bio-imaging analysis.
关键词： Young's Modulus,Entropy,Thin-walled cylinders,Bio-imaging,Intracranial aneurysm
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Analysis of NsRCM in BiForSAR Imagery
摘要： As for the bistatic forward-looking synthetic aperture radar (BiForSAR) imaging, frequency-domain imaging algorithms integrated with autofocus is advisable to get a well focused BiForSAR image in the presence of uncompensated motion errors. Nevertheless, a severe drawback of the autofocus algorithms is that they are only capable of removing one-dimensional azimuth phase errors. In range direction, there exists nonsystematic range cell migration (NsRCM) originated from motion errors and RCM correction procedure in frequency domain imaging algorithms as well. In this paper, the causes of different NsRCM in BiForSAR imaging are analyzed, and the corresponding relationship between different NsRCM is deduced. Based on the analyses, we propose an autofocus NsRCM correction scheme for BiForSAR imagery using frequency domain imaging algorithms, being capable of eliminating the range-dependent NsRCM.
关键词： Bistatic Forward-looking Synthetic Aperture Radar (BiForSAR),autofocus,nonsystematic range cell migration (NsRCM),minimum-entropy,spatially-variant
更新于2025-09-23 15:22:29
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Noise Estimation for Image Sensor Based on Local Entropy and Median Absolute Deviation
摘要： Noise estimation for image sensor is a key technique in many image pre-processing applications such as blind de-noising. The existing noise estimation methods for additive white Gaussian noise (AWGN) and Poisson-Gaussian noise (PGN) may underestimate or overestimate the noise level in the situation of a heavy textured scene image. To cope with this problem, a novel homogenous block-based noise estimation method is proposed to calculate these noises in this paper. Initially, the noisy image is transformed into the map of local gray statistic entropy (LGSE), and the weakly textured image blocks can be selected with several biggest LGSE values in a descending order. Then, the Haar wavelet-based local median absolute deviation (HLMAD) is presented to compute the local variance of these selected homogenous blocks. After that, the noise parameters can be estimated accurately by applying the maximum likelihood estimation (MLE) to analyze the local mean and variance of selected blocks. Extensive experiments on synthesized noised images are induced and the experimental results show that the proposed method could not only more accurately estimate the noise of various scene images with different noise levels than the compared state-of-the-art methods, but also promote the performance of the blind de-noising algorithm.
关键词： additive white Gaussian noise,local gray statistic entropy,image sensor,Poisson-Gaussian noise,noise estimation,local median absolute deviation
更新于2025-09-23 15:22:29
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Submodularity issues in value-of-information-based sensor placement
摘要： The value of information represents a rational metric for guiding the optimization of sensing efforts to support infrastructure system management under uncertainty. Unfortunately, this metric lacks the property of submodularity. Submodularity can be intuitively understood as a diminishing returns property, whereby the incremental benefit of a specific measurement is higher when the set of other available measures is smaller. Metrics which exhibit this property can be optimized using efficient greedy approaches, with certain guarantees on the near-optimality of the results. In this paper, we examine the issue of submodularity related to the optimization of sensor monitoring schemes using the value of information metric. We illustrate how greedy optimization approaches using value of information can lead to sub-optimal solutions for sensing in certain situations. We also examine how one potential heuristic approach involving a submodular surrogate metric (e.g. the conditional entropy) might be used to avoid some of these shortcomings.
关键词： Entropy,Value of Information,Optimization,Submodularity
更新于2025-09-23 15:21:21
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The Generated Entropy Monitored by Pyroelectric Sensors
摘要： Entropy generation in irreversible processes is a critical issue that affects the failure and aging of electrical, chemical or mechanical systems. The promotion of energy conversion ef?ciency needs to reduce energy losses, namely to decrease entropy generation. A pyroelectric type of entropy detector is proposed to monitor energy conversion processes in real time. The entropy generation rate can be derived from the induced pyroelectric current, temperature, thermal capacity, pyroelectric coef?cient and electrode area. It is pro?table to design entropy detectors to maintain a small thermal capacity while pyroelectric sensors minimize geometrical dimensions. Moreover, decreasing the electrode area of the PZT cells could avoid affecting the entropy variation of the measured objects, but the thickness of the cells has to be greatly reduced to promote the temperature variation rate and strengthen the electrical signals. A commercial capacitor with a capacitance of 47 μF and a maximum endured voltage of 4 V were used to estimate the entropy to act as an indicator of the capacitors’ time-to-failure. The threshold time was evaluated by using the entropy generation rates at about 7.5 s, 11.25 s, 20 s and 30 s for the applied voltages of 40 V, 35 V, 30 V and 25 V respectively, while using a PZT cell with dimensions of 3 mm square and a thickness of 200 μm.
关键词： sensor,entropy,energy conversion,pyroelectric effect,failure
更新于2025-09-23 15:21:21
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A Silicon PUF based Entropy Pump
摘要： The security level of many cryptographic protocols and secure systems is determined by the strength of the cryptographic keys, which can be measured by entropy. Finding an entropy source that can generate secure keys with high entropy is a very challenging problem and it is normally associated with high cost. Instead of looking for a low-cost entropy source, we study in this article how to improve the entropy generated by a low-entropy source. Unlike the existing approaches based on hash function or cryptographic protocols, our solution leverages the intrinsic randomness in physical properties such as silicon physical unclonable functions (PUFs). Silicon PUF is a piece of circuitry that can capture certain intrinsic on-chip variations that were introduced during the chip fabrication process. It is generally believed that such variations are random and unpredictable. In this article, we demonstrate that the silicon PUF can be used as an effective entropy pump to boost low-entropy keys. Our approach is based on a recently developed highly ?exible ring oscillator (RO) PUF. When we use the low-entropy key to con?gure the RO PUF, we ?nd that the corresponding PUF response exhibits higher entropy, which means that the key’s entropy has been improved. We implement our design on Nexys 4 Artix-7 FPGA board and demonstrate that the con?gurable PUF structure can successfully enhance the entropy of input keys. Compared to the other entropy enhancement methods, our PUF based entropy pump has the lowest hardware cost. Moreover, we apply this in a password enhancement application to provide robust high entropy passwords that can resist attacks such as the pre-compute attack.
关键词： Cryptographic keys,Silicon PUF,Entropy,Password enhancement
更新于2025-09-23 15:21:21
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Gradation of diabetic retinopathy on reconstructed image using compressed sensing
摘要： This study explores neovascularisation and lesion detection in an integrated framework for gradation in diabetic retinopathy (DR). Imaging is assumed to be done from sub-sample measurements following compressed sensing. Blind estimation of the scale of the matched filter (MF) followed by fuzzy entropy maximisation is done for extraction and classification of the thick and the thin vessels. Mutual information (MI) between vessel density and tortuosity of the thin vessel class is maximised in two dimensions (2D) for neovascularisation detection. For lesion detection, MI between the maximum MF response and the maximum Laplacian of Gaussian filter response is jointly maximised in 2D. The outcomes are then combined in a common platform for gradation in DR. Simulation results demonstrate that 95% images of each of DRIVE, STARE and DIARETDB1 databases and 94% images of MESSIDOR database are correctly graded by the proposed method when 80% measurement space is considered.
关键词： compressed sensing,lesion detection,diabetic retinopathy,fuzzy entropy,mutual information,neovascularisation
更新于2025-09-23 15:21:21
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Microstructure and properties of CeO2-doped CoCrFeMnNi high entropy alloy fabricated by laser metal deposition
摘要： Rare earth elements are usually regarded as e?cient additives for property enhancement of many types of alloys. In the present study, the CoCrFeMnNi high entropy alloy (HEA) was doped with CeO2, and such composites were for the ?rst time obtained by the laser metal deposition (LMD) process. The microstructure, phase compositions, microhardness and crystallographic texture of the HEA/CeO2 composites were investigated. It was demonstrated that CoCrFeMnNi HEA/CeO2 samples were successfully obtained by the LMD process. Meanwhile, small irregular shape oxides rich in Mn and Cr were observed in the HEA/ CeO2 composite. Rare earth element Ce was found to be evenly distributed throughout the sample. Heterogeneous dendritic microstructure with a long columnar grains oriented along the build direction was observed. The measured average microhardness is 181.72 ± 9.72 HV0.1.
关键词： Composite,CeO2,High entropy alloy,Laser metal deposition,Additive manufacturing,CoCrFeMnNi
更新于2025-09-23 15:21:01