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Motivation In most tissue-based biomedical research, the lack of sufficient pathology training images with well-annotated ground truth inevitably limits the performance of deep learning systems. In this study, we propose a convolutional neural network with foveal blur enriching datasets with multiple local nuclei regions of interest derived from original pathology images. We further propose a human-knowledge boosted deep learning system by inclusion to the convolutional neural network new loss function terms capturing shape prior knowledge and imposing smoothness constraints on the predicted probability maps. Results Our proposed system outperforms all state-of-the-art deep learning and non-deep learning methods by Jaccard coefficient, Dice coefficient, Accuracy and Panoptic Quality in three independent datasets. The high segmentation accuracy and execution speed suggest its promising potential for automating histopathology nuclei segmentation in biomedical research and clinical settings. Availability and implementation The codes, the documentation and example data are available on an open source at: https://github.com/HongyiDuanmu26/FovealBoosted. Supplementary information Supplementary data are available at Bioinformatics online.

The output power of each photovoltaic (PV) module is different in the single-phase cascaded H-bridge (CHB) PV grid-connected inverter due to irradiance intensity, ambient temperature, and aging degree of PV modules. When the PV modules are operating at their respective maximum power points, the corresponding dc-side voltages of the H-bridge units drift due to uneven power distribution, which will cause the maximum power point tracking failure. As a result, the grid current will deteriorate and even the system will become unstable. The power routing control methods based on fundamental voltage reconstruction, third harmonic injection and hybrid pulse width modulation can realize unequal power distribution between H-bridges to ensure the system stable operation. This article summarizes the abovementioned typical power routing control methods, derives the expressions of power routing ranges of different methods, then comprehensively and deeply compares the power routing capabilities of various methods qualitatively and quantitatively. The simulation results of a single-phase seven-level CHB PV grid-connected inverter demonstrate the validity of the theoretical analyses.

The aim of this study is to characterize and assess failure modes and the effect of structural parameters of honeycomb sandwich structure. The semi-finite element model of honeycomb sandwich structure under four-point bending load is established by a parametric method. Laminate delamination is exhibited by a contact algorithm with the mixed-mode damage model. Experiments are conducted to obtain load-displacement curves of honeycomb sandwich structure and thereby verify the applicability of finite element model. The failure modes of honeycomb sandwich structure have also been identified by comparing the experimental results with the numerical results. The effects of structural parameters on the mechanical properties of honeycomb sandwich structure are discussed. Results demonstrate that the overall stiffness of honeycomb structure is closely related to the honeycomb cell size such as length, height and foil thickness. In addition, the strength of honeycomb sandwich structure is sensitive to stacking sequence of composite laminate with different fiber orientation. The main failure modes of honeycomb sandwich structure are laminate fracture, delamination, core buckling and wrinkling. The achievements in this study have guiding significance to design high-performance sandwich structure.

Three-phase photovoltaic (PV) solid-state transformer based on cascaded H-bridge topology has a considerable prospect in high-voltage and high-power applications. Normally, each phase of the three-phase converter is designed to have the same number of modules, each of which is composed of an isolated dc–dc converter in cascade with an HB, and all the modules are able to transmit the same active power. However, if partial modules fail, the number of actual operation modules in three phases may be different, resulting in the active powers of the modules in the fault phase higher than those in the normal phase. The unbalanced active powers cause different heat dissipation requirements, violating the principle of modular design. For this issue, this article proposes a power balance control method which calculates a zero-sequence voltage to be injected into the system based on the number of modules in three phases and is able to ensure that all modules will have almost the same active powers under fault conditions. In addition, combined with redundancy design, it is also analyzed that all modules do not suffer from overmodulation even if the amplitudes of modulation voltages increase after being compensated by the proposed zero-sequence voltage. The validity of the proposed method is verified by simulation and experimental results.

Due to the nonuniform solar irradiance, unequal ambient temperatures, or inconsistent degradation of photovoltaic (PV) modules in three-phase cascaded H-bridge (CHB) PV inverter, the unbalanced output power among PV modules will lead to the imbalanced power between phases and bridges, resulting in unbalanced or even distorted grid current between three phases, which cannot meet the requirements of grid codes. Concerning this issue, this article proposes a novel power equalization method based on the combination of hybrid modulation strategy and zero-sequence injection methods, which deals with interbridge power imbalance by hybrid modulation and interphase power imbalance by zero-sequence injection methods. By utilizing the proposed method, three-phase-balanced grid currents with low total harmonic distortion are able to be achieved even when the interbridge and the interphase power are seriously unbalanced. In addition, each H-bridge cell in three-phase CHB inverter uses square-wave modulation, which maximizes the dc-side voltage utilization of each H-bridge cell, thus extending its power balance region. Experimental results achieved by a laboratory prototype of a three-phase seven-level CHB inverter demonstrate both feasibility and validity of the proposed method.

The effect of salt spray and salt solution on the fatigue properties of 2024-T3 aluminum alloy plate used for aircraft fuselage structure have been investigated by combining Digital Image Correlation (DIC) technology with in-situ corrosion fatigue test. For this purpose, an in-situ corrosion fatigue platform was designed for gas and liquid phases. Fatigue experimental investigation was carried out in salt spray and salt solution environments respectively, the crack propagation process was monitored by the DIC technology and the influences of NaCl concentration on fatigue life and crack growth rate were analyzed under the two kinds of corrosive environments. Moreover, the failure mechanism is discussed based on the micro-morphology of fracture and the composition of corrosion products. Experimental results demonstrated that for the corrosion fatigue in salt spray environment, there is a competition between the hydrogen embrittlement and the crack tip closure effect caused by corrosion products, which results in fatigue life decreasing with the increase of NaCl concentration first and then increasing. The fatigue life (with 3.50 wt.% NaCl salt spray) is the lowest, which is 82.9% of that in air, while the fatigue life (with 5.00 wt.% NaCl salt spray) is 112.6% of that in air. But for the corrosion fatigue in the NaCl salt solution environment, there is no obvious crack tip closure effect. In the 5.00 wt.% NaCl salt solution environment, fatigue life is 74.2% of that in air. The microfractures and strain nephogram of specimens revealed the stress concentration caused by corrosion pits, which might be the main factor for the decrease of fatigue life.

Particle swarm optimization (PSO) is a widely used method that can provide good parameters for the motion controller of mobile robots. In this paper, an improved PSO algorithm that optimize the control PID parameters of a specific robot have been proposed. This paper first presents a brief review of recently proposed PSO methods, and then presents a detailed analysis of the PID optimization algorithm, which uses H∞ theory to reduce the search space and fuses the information entropy to ensure the diversity of particles. Simulations in Matlab show that the algorithm can improve the convergence speed and get a better global optimization ability than the standard PSO algorithm. Experimental results present a sound effects for the control of the negative pressure adsorption motor in the power grid pipeline robot during its adsorption along the circular movements, which verifies the effectiveness of the proposed method.

For single-phase cascaded H-bridge (CHB) photovoltaic (PV) inverters, all the PV modules are able to operate at the maximum power point, which is beneficial to energy harvesting. However, due to the stochastically variable irradiance level and ambient temperature, the unbalanced output powers among PV modules may cause the overmodulation of the H-bridges with higher power, ultimately resulting in a distorted grid current. In this paper, a novel harmonic compensation strategy is proposed. Compared to the existing methods, it can not only ensure that CHB inverter operates at unity power factor with small dc-bus voltage ripple but also keep the total harmonic distortion of grid current in acceptable range under some heavy power unbalance conditions, so it has a good overall performance. Simulation and experimental results validate the effectiveness and feasibility of the proposed method.

Lightning strike is a complicated process involving multi-field coupling. In order to investigate the thermal damage mechanism of carbon fiber reinforced composites subject to lightning swept stroke, a complete numerical method is presented. Numerical model of lightning discharge is established based on Magneto Hydro Dynamics (MHD) and calculated by FLUENT secondary development technology. Considering aerodynamic flow effect, channel formation and evolution process during lightning discharge is analyzed for lightning current waveform A. Thermal-electric Coupling model is presented according to Radial Basis Function (RBF) interpolation theory, which is implemented by compiling program to make lightning current and heat energy inject into composite laminate. Consequently, damage mechanism of composite laminate under lightning swept stroke is studied based on the coupled numerical model and element deletion method. Ablation damage morphology of composite laminate is analyzed to understand plasma expansion and reattachment in arc root. The results show that aerodynamic flow makes the lightning channel move fast and composite laminate is deteriorated due to thermal damage.

This article combines experimental tests and theoretical studies to study the deformation behavior of SMA materials under uniaxial tension cycles considering residual strain and damage. In the laboratory test of SMA material, the critical phase transformation temperatures are firstly measured by DSC curve, and then do the uniaxial tensile test to measure the young's modulus of the martensite and austenite, finally the stress-strain relationship curve under uniaxial tension cycle is approximated, and the relationship between residual strain and cycle number is approximated, then the relationship between damage factor and cycle number is derived by the relationship between the attenuation of the Young's modulus and the cycle number. In the theoretical research, fully consider the influence of damage on the material's permanent maturity in a single cycle and consider the change of residual strain during the cycle, a thermodynamic constitutive model that can simulate the cyclic deformation behavior of SMA materials considering damage and residual strain is established and the numerical results were compared with the experimental results to verify the correctness of the model.

Coal spontaneous combustion is a great threat to mine safety, and gas is the key index to describe coal spontaneous combustion. Taking the coal samples of different kinds of coal as research object, the temperature programmed oxidation experiment was carried out, and the gases produced by coal samples at different temperatures were collected and analyzed by gas chromatography. This research studied the variation characteristics of gas species and gas concentrations in different coal samples during heating oxidation. The experimental results show that different coal samples produce different kinds of gases in the process of heating and oxidation. The order of gas production is CO, C2H6, C2H4, C3H8, and the relationship between gas production and temperature is approximately exponential. With the increase of coal metamorphic degree, the turning point temperature of sharp rise in coal sample gas production rate become higher, the oxidation ability of coal sample decreases, and the quantity of gas production decreases during the same time period. Keywords: Heating and oxidation, Metamorphic degree of coal, Oxidizing ability, Gas chromatography

In order to investigate the effect of low velocity impact damage on fatigue performance of aluminum alloy 2024-T3 thin sheets used in the airframe, the digital image correlation (DIC) analysis was conducted to evaluate fatigue failure of specimens containing various impact damages induced by hemispherical and U-shaped inserts. 2D and 3D strain fields calculated from digital speckle images were applied to analyze the fatigue crack nucleation and propagation. The effects of impact energy, dent dimension and insert shape on the fatigue life are discussed according to the experimental data which could be fitted to a 2-order empirical equation. Fatigue crack nucleation is intensively dominated by the dent geometry resulting from the impact process, the crack initiated around the dent propagates by a combined failure mode of I and III under dynamic loading. The dent could redistribute the strain field on the surface of dented specimens through DIC nephogram analysis. In addition, the simulation based on ABAQUS/Explicit could provide a reliable strain field distributed on the concave surface of dented specimens, while the fatigue life prediction acquired from Fe-safe shows close agreement with experimental data, which could be further used in fatigue life evaluation of impacted components.

Due to the seawater splash, rain water scouring and prolonged exposure, the aircrafts serviced in sea-coast or marine environment always suffered liquid corrosion effects under certain temperature. 2024-T4 aluminum alloy had been widely used in aircrafts fuselage. During service, the actual process was close to the alternate mode of “Ground Corrosion + Air Fatigue”, in which alternate corrosion factors had greatly effects on multiaxial fatigue life of 2024-T4 aluminum alloy. For the purpose of evaluating the influence of alternate corrosion time, corrosion temperature, corrosion solution flow rate and pH value on the fatigue performance, a multi-parameter regulated liquid corrosion device was designed. Multiaxial fatigue tests were performed under constant amplitude sinusoidal wave loading with constant tension-torsion ratio 3 in air. The fracture was observed by scanning electron microscope. The results indicated a reduction tendency of multiaxial fatigue life with the increase of alternate corrosion time, corrosion temperature and corrosion solution flow rate as well as the decrease of pH value. The influence order of relevant factors was: alternate corrosion time > corrosion temperature > corrosion solution flow rate > solution pH value. The effects of alternate time and temperature immersed in solution on corrosion resistance of 2024-T4 aluminum alloy are investigated by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS) tests. The observed mechanical behavior and associated phenomena were directly linked to microstructure characteristics such as corrosion pits and micro-cracks. The cyclic hardening appeared in both axial and tangential direction at the beginning stage. With the consideration of corrosion effect on the fatigue property, the equivalent corrosion life was proposed to characterize the influence of corrosion and to predict the alternate corrosion - fatigue life. Fine results were obtained with all data in 2× scatter band.

Liver cancer is one of the leading causes of cancer deaths in Asia and Africa. It is caused by the Hepatocellular carcinoma (HCC) in almost 90% of all cases. HCC is a malignant tumor and the most common histological type of the primary liver cancers. The detection and evaluation of viable tumor regions in HCC present an important clinical significance since it is a key step to assess response of chemoradiotherapy and tumor cell proportion in genetic tests. Recent advances in computer vision, digital pathology and microscopy imaging enable automatic histopathology image analysis for cancer diagnosis. In this paper, we present a multi-resolution deep learning model HistoCAE for viable tumor segmentation in whole-slide liver histopathology images. We propose convolutional autoencoder (CAE) based framework with a customized reconstruction loss function for image reconstruction, followed by a classification module to classify each image patch as tumor versus non-tumor. The resulting patch-based prediction results are spatially combined to generate the final segmentation result for each WSI. Additionally, the spatially organized encoded feature map derived from small image patches is used to compress the gigapixel whole-slide images. Our proposed model presents superior performance to other benchmark models with extensive experiments, suggesting its efficacy for viable tumor area segmentation with liver whole-slide images.

Cascaded H-bridge multilevel inverter is the best choice in large-scale photovoltaic power generation system and has a good application prospect.With the increase of the number of modules in cascade, the probability of open-circuit fault of switch tube will also increase. This paper proposes a open-circuit fault diagnosis method for cascaded H-bridge photovoltaic inverter. The output voltage of each H-bridge module is collected at the top or bottom of the carrier and used as the criterion for determining open-circuit faults. After the diagnosis is completed, measures are adopted to reduce the degree of fault. Accurate positioning of the fault switch tube is accomplished in one carrier cycle. Simulation results have verified the effectiveness of the proposed method.

Digital imaging plays a critical role for image guided diagnosis and clinical trials, and the amount of image data is fast growing. There are two major requirements for image data management: scalability for massive scales and support of comprehensive queries. Traditional Picture Archiving and Communication Systems (PACS for short) are based on relational data management systems and suffer from limited scalability and query support. Therefore, new systems that support fast, scalable and comprehensive queries on image data are highly demanded. In this paper, we introduce two alternative approaches: DCMRL/XMLStore (RL/XML for short)-a parallel, hybrid relational and XML data management approach, and DCMDocStore (DOC for short)-a NoSQL document store approach. DCMRL/XMLStore manages DICOM images as binary large objects and metadata as relational tables and XML documents based on IBM DB2, which is parallelized through data partitioning. DCMDocStore manages DICOM metadata as JSON objects, and DICOM images as encoded attachments in MongoDB running on multiple nodes. We have delivered two open source systems DCMRL/XMLStore and DCMDocStore. Both systems support scalable data management and comprehensive queries. We also evaluated them with nearly one million DICOM images from National Biomedical Imaging Archive. The results show that, DCMDocStore demonstrates high data loading speed, high scalability and fault tolerance. DCMRL/XMLStore provides efficient queries, but comes with slower data loading. Traditional PACS systems have inherent limitations on flexible queries and scalability for massive amount of images.

Generative adversarial networks (GANs) have been highly successful for generating realistic synthetic data. In healthcare, synthetic data generation can be helpful for producing annotated data and improving data-driven research without worries on data privacy. However, electronic health records (EHRs) are noisy, incomplete and complex, and existing work on EHR data is mainly devoted to generating discrete elements such as diagnosis codes and medications or frequent laboratory values. In this work, we propose SMOOTH-GAN, a novel approach for generating reliable EHR data such as laboratory values and medications given diagnosis codes. SMOOTH-GAN takes advantage of a conditional GAN architecture with WGAN-GP loss, and is able to learn transitions between disease stages with high flexibility over data customization. Our experiments demonstrate the model’s effectiveness in terms of both statistical similarity and accuracy on machine learning based prediction. To further demonstrate the usage of our model, we apply counterfactual reasoning and generate data with occurrence of multiple diseases, which can provide unique datasets for artificial intelligence driven healthcare research.

The influence of soil heterogeneity is studied on the bending of circular thin plates using two modified Vlasov foundation models. The model parameters are determined reasonably using an iterative technique. According to the principle of minimum potential energy and considering transversely isotropic soils and Gibson soils, the governing differential equations and boundary conditions for circular thin plates on two modified Vlasov foundations are derived using a variational approach, respectively. The determination of attenuation parameters is a difficult problem, which has hindered the further application of the Vlasov foundation model. The equation that must be satisfied by the attenuation parameter is determined, and an iterative method is used to solve the problem. A comparative analysis is conducted between two modified Vlasov models and the traditional Vlasov model. The results show that the governing equations and boundary conditions for circular thin plates resting on two modified foundations are consistent with those for a circular thin plate on traditional two-parameter foundation after degradation. The accuracy and reliability of the proposed solutions are demonstrated by comparing the obtained results with those reported in the literature. The heterogeneity of soils, including the transversely isotropic soils and Gibson soils, has a certain effect on characteristic parameters of the foundation models as well as the deformations and internal forces of circular thin plates. The present study could be employed as a reference for future engineering designs.

Pressure pipes have broad applications in aviation, space flight, mechanical engineering, industrial and civil architecture etc. Instability destruction is their main failure mode. Firstly, in this paper, a complex fluid-solid coupling problem was simplified as a buckling problem of a pipe under two stresses which were along the pipe wall. The two stresses consisted of a compressive stress which was perpendicular to the pipe wall and a tangential stress which was parallel to the pipe wall. Secondly, the buckling performs of the pressured pipe were discussed by finite element analysis method under a working state and an off-working state, respectively. Some obtained conclusions were drawn as follows by the analysis in this paper.1). Provided the tangential stress is unchanged, by increasing compressive stress eigenvalue buckling critical load increases and nonlinear buckling critical load decreases.2). Provided the compressive stress is unchanged, when the direction of the tangential stress is same as that of the axial pressure, by increasing the absolute value of tangential stress the buckling critical load decreases; provided the compressive stress is unchanged, when the direction of the tangential stress is in the opposite direction of the axial pressure, by increasing the absolute value of tangential stress the buckling critical load increases.

Due to the unequal solar radiations or dust accumulation of photovoltaic modules in a single-phase cascaded H-bridge photovoltaic inverter, the unbalanced output power among photovoltaic modules will make the H-bridges with higher power overmodulation, resulting in deteriorated grid current. Concerning this issue, this paper proposes an optimized third harmonic compensation strategy that injects moderate amount of third harmonic into the overmodulation H-bridges to keep the amplitudes of their modulation waveforms just being unity, then compensates the same amount of opposite harmonic sequence and properly distributes it to rest of the H-bridges. The proposed method can ensure that all the power units will be free from overmodulation under some heavy power imbalance conditions and will not increase the third harmonic component of the grid current. The validity and effectiveness of the proposed method is verified by simulation and experimental results.

Mechanical properties of aircraft composite laminate after lightning strike are predicted and verified based on the combination of experiment and numerical simulation. Axial compression experiment of composite laminate containing lightning strike damage is carried out and failure modes of experimental samples under three kinds of electrical current waveforms are evaluated. The main failure modes include fiber fracture, matrix cracking and delamination. The final failure load decreases with the increase of actual integral action of lightning strike. Compression failure process of composite laminate is simulated using progressive damage analysis methods such as Hashin criterion, Maximum stress criterion and TSERPES criterion, respectively. Numerical simulation and experiment results are compared and coincided well. Percentage error of Hashin criterion is the minimum compared with those of TSERPES criterion and Maximum stress criterion. Stress concentration mainly appears in both angle sides on the fixed end and lightning damage regions of composite laminate.

Intelligent photovoltaic (PV) module monitoring can automatically locate the position of panels and monitor the status of PV modules, which is of great significance for PV plants operation and maintenance. As a new communication method in the field of PV monitoring, the monitoring of PV modules based on power line communication is the future trend of PV power plants monitoring due to its low maintenance cost and strong anti-interference ability. This paper presents an intelligent PV module monitoring scheme based on the parallel resonant coupling unit, which uses the dc bus as the communication channel and modula-tes the monitoring data into a high-frequency form to carry out the carrier communication. By using the parallel resonant coupling, the high-frequency carrier wave is injected into the dc bus, which improves the system efficiency and anti-interference ability. In addition, an adaptive level decision circuit is proposed to improve the flexibility and scalability of the communication system by adaptively changing the reference level of the decision circuit. Experimental results achieved by a developed power line transceiver demonstrate both feasibility and validity of the proposed scheme.

Pre-damages which contain pre-deformation and pre-corrosion have influences on multiaxial fatigue properties. In this paper, the effect of pre-tension of 1%, 2%, 3% and 4% as well as pre-torsion of 10°, 20°, 30° and 40° on fatigue life of 2024-T4 aluminum alloy under corrosion conditions is evaluated. Multiaxial fatigue tests are performed under constant amplitude sinusoidal wave loading with tension-torsion ratio of 3 in air at room temperature. The results indicate a reduction tendency of pre-corrosion multiaxial fatigue life with the pre-deformation level in the same pre-corrosion time. With the same pre-deformation level, the pre-corrosion multiaxial fatigue life decreases as pre-corrosion time increases. Pitting caused by corrosion is observed on the surface of specimens. The observed mechanical behavior and associated phenomena are directly linked to microstructure characteristics such as surface defects, corrosion pits and micro-cracks. The analysis of mechanism reveals that the synergistic combination of pre-deformation and pre-corrosion is more detrimental than that of either one acting separately. The alternate cyclic hardening and softening appear in the axial direction. The cyclic softening in the tangential direction becomes more serious with the increase of pre-deformation. The typical morphology of corrosion fatigue can be observed on the fracture. Involving the damage factors of single pre-damage conditions, which include pre-deformation and pre-corrosion effects, the damage factor for pre-corroded multiaxial fatigue after pre-deformation is deduced. Fine results are achieved according to the above methods with most predicted life in 2× scatter band.

In the complex environments, sampling control has been extensively applied in continue-time systems by means of digital sensors with high reliability and stability. In this paper, swarming movement (or containment consensus) of fractional-order multi-agent systems (FOMAS) with sampling control are studied. Firstly, the collaborative control of fractional-order multi-agent systems with multiple leaders and sapling data is analyzed in an undirected network without delays. A necessary and sufficient condition is presented for the bounded value of sampling period to ensure the containment consensus of FOMAS. Then, by applying Laplace transformation and stability theorem, containment consensus of distributed FOMAS with time delays is investigated in an undirected network. A necessary and sufficient condition is obtained for the bounded value of sampling period and a critical value of delays. Finally, numerical simulations are shown to verify the results.

Transformerless cascaded H-bridge inverters have the advantages of low cost and high efficiency in low-power applications. However, the leakage currents resulting from the parasitic capacitors may increase system losses, electromagnetic interference, and safety concerns. To reduce the leakage current, this paper first establishes the equivalent common-mode circuit of the inverter with the parasitic capacitance and analyzes the characteristics of leakage current in the symmetrical and asymmetrical filter inductance circuit, respectively. The analysis shows that the traditional phase disposition pulse width modulation or phase-shift pulse width modulation cannot solve the leakage current issues, but modifying the modulation methods can eliminate the system leakage current in the symmetrical circuit, and it has a little effect in the asymmetrical circuit. For this reason, a modified phase disposition pulse width modulation for the symmetrical circuit, which can eliminate the leakage current effectively with simple implementation, is proposed. Simulation and experimental results are reported, along with evaluation and comparison results, against a conventional carrier-based pulse width modulation method.

This study aims to evaluate the applicability of the degraded stiffness matrix and the redefined characteristic length models in the finite element analysis of composite laminates under low-velocity impact. Implemented by the user-defined VUMAT subroutine in ABAQUS, various damage models are used to predict the damage behavior in the composite laminates, meanwhile, the user-defined VUCHARLENGTH subroutine is applied to define the characteristic length to match the damage mode. Cohesive elements are inserted between the adjacent piles to model the delamination. The applicability of different damage models is investigated by comparing the global mechanical response and local damage behavior. A new characteristic length calculation method is proposed to apply in the low-velocity impact simulation for laminates. The numerical results show that the degraded stiffness matrix proposed by both Maimi and Matzenmiller can accurately predict the global mechanical responses in the complicated damage accumulation case, while the model of PEE (the principle of energy equivalence) and Linde aren’t suitable for the low-velocity impact simulation. As for the characteristic length model, the redefined characteristic length model can obtain more accurate global mechanical responses with the impact energy increasing compared with the predictions of default characteristic length model.

The modulation strategy LMZVM (large, middle, and zero vector modulation) can be widely adopted in the three-level 7 photovoltaic (PV) inverter, because it reduces the ground current and produces little neutral-point (NP) voltage in normal operation. However, in low-voltage ride-through (LVRT) operation, the NP voltage fluctuation becomes large and has not been researched nowadays. In this paper, according to this problem, four critical weighing factors about the NP voltage based on symmetrical component method are proposed. We can see that the maximum peak-to-peak value among all dip types happens when the single-phase grid voltage dips to 0. Then, an original balancing strategy, which replaces the zero vector with two opposite P-type or N-type small vectors of equal duty cycle, is put forward. Experimental results are provided to validate that the proposed strategy can reduce the NP voltage fluctuation in LVRT operation.

In aircraft engineering, an increase of internal pressure in a hydraulic pipe increases the probability of pipe damage, leading to crack propagation becoming a serious issue. In this study, the extended finite element method (XFEM) is applied to simulate initial crack propagation in hydraulic pipes and to investigate the influence factors. Stress intensity factors are extracted to verify the mesh independence of XFEM, which is based on the level set method and unit decomposition method. A total of 30 finite element models of hydraulic pipes with cracks are established. The distribution of von Mises stress under different initial crack lengths and internal pressures is obtained to analyze the change of load-carrying capacity in different conditions. Then, a total of 300 finite element models of hydraulic pipes with different initial crack sizes and locations are simulated under different working conditions. The relationship between the maximum opening displacement and crack length is analyzed by extracting the opening displacement under different initial crack lengths. The length and depth of the initial crack are changed to analyze the factors affecting crack propagation. The opening size and crack propagation length are obtained in different directions. The results show that radial propagation is more destructive than longitudinal propagation for hydraulic pipes in the initial stage of crack propagation.

The recent technological advancement in digital pathology has enabled 3D tissue-based investigation of human diseases at extremely high resolutions. Discovering and verifying spatial patterns among massive 3D micro-anatomic biological objects such as blood vessels and cells derived from 3D pathology image volumes plays a pivotal role in understanding diseases. However, the exponential increase of available 3D data and the complex structures of biological objects make it extremely difficult to support spatial queries due to high I/O, communication and computational cost for 3D spatial queries. In this demonstration, we present our scalable in-memory based spatial query system iSPEED for large-scale 3D data with complex structures. Low latency is managed by storing in memory with progressive compression including successive levels of detail on object level. On the other hand, low computational cost is achieved by pre-generation of global spatial indexes in memory and additional on-demand generation of indexing at run-time. Furthermore, iSPEED applies structural indexing on complex structured objects in multiple query types to gain performance advantage. During query processing, the memory footprint of iSPEED is minimal due to its indexing structure and progressive decompression on-demand. We demonstrate iSPEED query capability with three representative queries: 3D spatial joins, nearest neighbor and spatial proximity estimation on multiple datasets using a web based RESTful interface. Users can furthermore explore the input data structure, manage and adjust query pipeline parameters on the interface. PVLDB Reference Format: Hoang Vo, Yanhui Liang, Jun Kong, and Fusheng Wang. iSPEED: a Scalable and Distributed In-Memory Based Spatial Query System for Large and Structurally Complex 3D Data.

The uneven irradiation and temperature in photovoltaic (PV) modules of three-phase cascaded B-bridge (CHB) inverters will cause the unbalanced output power between solar panels, resulting in unbalanced grid current between three phases. In addition, since each phase can be regarded as a single-phase inverter, the second harmonic voltage pulsation of dc-side capacitors is a problem to be solved. To solve these two problems, a third harmonic injection optimization method on the basis of fundamental frequency zero sequence is proposed in this paper. The third harmonic with the same amplitude of fundamental modulated wave signal is injected into the modulated wave signal when the amplitude of synthesized wave signal is no greater than unity. Otherwise, the amplitude of third harmonic is decreased correspondingly to ensure the amplitude of synthesized wave signal being unity. With this method, the dc-side voltage pulsation is effectively restrained and the power balancing limit of CHB inverter is expanded. The feasibility and effectiveness of this method are verified by an experimental prototype of a three-phase seven-level CHB inverter.

Health care is undergoing a big data revolution, with vast amounts of information supplied from numerous sources, leading to major paradigm shifts including precision medicine and AI-driven health care among others. Yet, there still exist significant barriers before such approaches could be adopted in practice, including data integration and interoperability, data sharing, security and privacy protection, scalability, and policy and regulatory issues. Blockchain provides a unique opportunity to tackle major challenges in health care and biomedical research, such as enabling data sharing and integration for patient-centered care, data provenance allowing verification authenticity of the data, and optimization of some of the health care processes among others. Nevertheless, technological constraints of current blockchain technologies necessitate further research before mass adoption of blockchain-based health care data management is possible. We analyze context-based requirements and capabilities of the available technology and propose a research agenda and new approaches towards achieving intelligent health care data management using blockchain.

Cardiac MRI left ventricular (LV) detection is frequently employed to assist cardiac registration or segmentation in computer-aided diagnosis of heart diseases. Focusing on the challenging problems in LV detection, such as the large span and varying size of LV areas in MRI, as well as the heterogeneous myocardial and blood pool parts in LV areas, a convolutional neural network (CNN) detection method combining discriminative dictionary learning and sequence tracking is proposed in this paper. To efficiently represent the different sub-objects in LV area, the method deploys discriminant dictionary to classify the superpixel oversegmented regions, then the target LV region is constructed by label merging and multi-scale adaptive anchors are generated in the target region for handling the varying sizes. Combining with non-differential anchors in regional proposal network, the left ventricle object is localized by the CNN based regression and classification strategy. In order to solve the problem of slow classification speed of discriminative dictionary, a fast generation module of left ventricular scale adaptive anchors based on sequence tracking is also proposed on the same individual. The method and its variants were tested on the heart atlas data set. Experimental results verified the effectiveness of the proposed method and according to some evaluation indicators, it obtained 92.95% in AP50 metric and it was the most competitive result compared to typical related methods. The combination of discriminative dictionary learning and scale adaptive anchor improves adaptability of the proposed algorithm to the varying left ventricular areas. This study would be beneficial in some cardiac image processing such as region-of-interest cropping and left ventricle volume measurement.

SHPB system was widely used to investigate the dynamical mechanical performances of materials. In this study, the mechanical performances of T700/BA9916 composite material were investigated through experiment and numerical simulation. The true stress-strain curves of composite samples were obtained, and the influences of temperatures and strain-rates on the mechanical performances of composite samples were discussed. The finite element model of SHPB setup was established, and the compression mechanical performances of composite samples were simulated. T700/BA9916 composite material exhibited significant temperature softening and strain-rate enhancement effect during experimental. The compression failure strength and elastic modulus increased with the increase in strain-rates while the failure strain decreased. The compression failure strength and elastic modulus decreased with the rise in temperatures while the failure strain increased. The composite samples didn’t exhibit typical brittle failure at high temperature but significant temperature softening effect. A plateau phase existed between incident wave and reflection wave, and the slope of plateau phase was small when temperatures were low while that was large when temperatures were high. The numerical results were compared with experimental results to validate the proposed numerical method can be used to simulate the mechanical performances of composite materials.

Lightning strikes generate large amounts of energy. Thus, composite structures subjected to lightning strikes undergo significant physicochemical changes. In this study, the thermal shock damage and three-phase transition of a composite reinforced panel were investigated through a numerical simulation, an experiment, and ultrasonic C-scanning. An anisotropic constitutive model and PUFF equation of state (EOS) were proposed to study the damage behaviors of composite materials. The dynamical damage behaviors and three-phase transition of the composite reinforced panel were simulated using the proposed constitutive model and PUFF EOS. Finally, a lightning experiment and ultrasonic C-scanning were conducted to validate the numerical results. Obvious fiber upwarping and swelling were observed in the numerical simulation. The melted and vaporized materials caused a reverse thermal shock effect, which led to concave pits, buckling and internal damages in the composite reinforced panel. The numerical results were compared with experimental results and scanning results to validate that the proposed constitutive model and modified PUFF EOS can be well used to simulate the dynamical damage behaviors of composite materials. The simulated damage behaviors of the composite reinforced panel agreed well with the behaviors observed in the experiment.

In this paper, in order to select a better material between aluminum alloy and composite for the connective parts which is on a folded omega stringers stiffened composite panel under an axial compression, numerical investigation is conducted. The axial compression is divided into two stages which are buckling and post-buckling. By using software ABAQUS, 9 models were analyzed respectively. By comparing among the 9 models, firstly, composite joints have the highest collapse load with the same T stringer or without T stringer and next are aluminum alloy joints. Secondly, aluminum alloy T stringer has the highest buckling load and collapse load than composite one with the same joints or without joints and the composite T stringer the second. Thirdly, the joints and the T stringer are compulsory, because either the joints or the T stringer or both of them can enhance buckling load and collapse load remarkably. An important question for future studies is that the failure mechanisms occurring at the connective parts including their surrounding areas and choosing reasonable failure criterion for the material of these sections have to be researched by numerical methods and experimental tests.

In order to assess various design concepts and choose a kind of covering cap design scheme which can meet the requirements of airworthiness standard and ensure the safety of fuel tank. Using finite element software ANSYS/LS- DYNA, the impact process of covering cap of aircraft fuel tank by projectile were simulated, in which dynamical characteristics of simple single covering cap and gland double-layer covering cap impacted by titanium alloy projectile and rubber projectile were studied, as well as factor effects on simple single covering cap and gland double-layer covering cap under impact region, impact angle and impact energy were also studied. Though the comparison of critical damage velocity and element deleted number of the covering caps, it shows that the external covering cap has a good protection effect on internal covering cap. The regions close to boundary are vulnerable to appear impact damage with titanium alloy projectile while the regions close to center is vulnerable to occur damage with rubber projectile. Equivalent strain in covering cap is very little when impact angle is less than 15°. Element deleted number in covering cap reaches the maximum when impact angle is between 60°and 65°by titanium alloy projectile. While the bigger the impact angle and the more serious damage of the covering cap will be when rubber projectile impact composite covering cap. The energy needed for occurring damage on external covering cap and internal covering cap is less than and higher than that when single covering cap occur damage, respectively. The energy needed for complete breakdown of double-layer covering cap is much higher than that of single covering cap.

Biochars are carbon-rich products derived from biomass through pyrolysis, and are useful for soil fertility enhancement and carbon sequestration. Most agricultural and forestry residues could be used for biochars production. In this study, biochars were produced from rice straw, bamboo culm, and reed straw under different pyrolysis temperatures. The physiochemical and morphological properties, and PAHs content of biochars were investigated for determining the effect of protective gas and pyrolysis temperatures on biochars under different pyrolysis processes. Rice straw, bamboo culm (8 years old), and giant reed straw were used in this study. These three organic materials were converted into biochars by slow pyrolysis using a lab-scale fixed bed pyrolysis reactor. Treatment temperatures of slow pyrolysis were 400, 500, 600 and 700 °C with or without the application of high purity nitrogen (>99.999 %) as the protective gas. We found that the high-temperature pyrolysis produced lower biochar yield (25.84–28.84 %) than the low-temperature pyrolysis (29.44–34.4 %). However, the BET and C content of biochar under the high-temperature pyrolysis process was higher. The low H/C and O/C ratios of the biochars produced at higher temperature pyrolysis, was 0.08–0.10, 0.01–0.22, respectively, which showed that the carbon in these biochars was unsaturated. The PAHs content decreased with increasing pyrolysis temperature. Bamboo culms pyrolysed at 700 °C had the lowest concentration of ∑16PAH (10.06 μg kg−1). The pyrolysis temperature significantly affected the properties of the resultant biochars (P 0.05).

Public transport, especially the bus transport, can reduce the private car usage and fuel consumption, and alleviate traffic congestion. However, when traveling in buses, the travelers not only care about the waiting time, but also care about the crowdedness in the bus itself. Excessively overcrowded bus may drive away the anxious travelers and make them reluctant to take buses. So accurate, real-time and reliable passenger demand prediction becomes necessary, which can help determine the bus headway and help reduce the waiting time of passengers. Based on a large database from a real bus system, this paper aims to present a passenger demand prediction system for mobile users. The system includes a server-side bus information data stream processing and mining program and a client-side mobile application for Android smartphones. The server program continuously monitors for each bus stop the number of passengers waiting at the bus stop, the number of passengers that will pass the bus stop, as well as the traffic conditions in the area around the stop. It delivers real time bus and traffic information to mobile users via restful web services. The client-side location-based mobile application consumes these services to help mobile users make informed transportation choices. For example the availability of buses might be a deterrent when they are too crowded. However, there are three major challenges for predicting the passenger demands on bus services: inhomogeneous, seasonal bursty periods and periodicities. To overcome the challenges, we propose three predictive models and further take a data stream ensemble framework to predict the number of passengers. We develop a prototype system with different types of Android based mobile phones and comprehensively experiment over a 22-week period. The evaluation results suggest that the proposed system achieves outstanding prediction accuracy among 86,411 passenger demands on bus services, more than 78% of them are accurately forecasted. Build a passenger demand prediction system for mobile users.Propose a method for detecting parking places.Present the design of knowledge base.Build a location-based mobile application for mobile users.

The effects of hole reaming (HR) after pre-fatigue damage on fatigue performance of AA2198-T8 were studied by using the digital image correlation (DIC) technique. The influences of stress distribution of the rivet hole on fatigue life were studied. When maximum axial strain is equal to 0.0005, the number of fatigue cycles is suggested as the fatigue crack initiation life. The prediction of fatigue lives by the calculation method combining Paris law and ABAQUS, and the experimental results are within a factor of 1.2-scatter band. This work provides a reference for the maintenance of fatigue damaged rivet holes in aircraft structure.

Background With increased specialization of health care services and high levels of patient mobility, accessing health care services across multiple hospitals or clinics has become very common for diagnosis and treatment, particularly for patients with chronic diseases such as cancer. With informed knowledge of a patient’s history, physicians can make prompt clinical decisions for smarter, safer, and more efficient care. However, due to the privacy and high sensitivity of electronic health records (EHR), most EHR data sharing still happens through fax or mail due to the lack of systematic infrastructure support for secure, trustable health data sharing, which can also cause major delays in patient care. Objective Our goal was to develop a system that will facilitate secure, trustable management, sharing, and aggregation of EHR data. Our patient-centric system allows patients to manage their own health records across multiple hospitals. The system will ensure patient privacy protection and guarantee security with respect to the requirements for health care data management, including the access control policy specified by the patient. Methods We propose a permissioned blockchain-based system for EHR data sharing and integration. Each hospital will provide a blockchain node integrated with its own EHR system to form the blockchain network. A web-based interface will be used for patients and doctors to initiate EHR sharing transactions. We take a hybrid data management approach, where only management metadata will be stored on the chain. Actual EHR data, on the other hand, will be encrypted and stored off-chain in Health Insurance Portability and Accountability Act–compliant cloud-based storage. The system uses public key infrastructure–based asymmetric encryption and digital signatures to secure shared EHR data. Results In collaboration with Stony Brook University Hospital, we developed ACTION-EHR, a system for patient-centric, blockchain-based EHR data sharing and management for patient care, in particular radiation treatment for cancer. The prototype was built on Hyperledger Fabric, an open-source, permissioned blockchain framework. Data sharing transactions were implemented using chaincode and exposed as representational state transfer application programming interfaces used for the web portal for patients and users. The HL7 Fast Healthcare Interoperability Resources standard was adopted to represent shared EHR data, making it easy to interface with hospital EHR systems and integrate a patient’s EHR data. We tested the system in a distributed environment at Stony Brook University using deidentified patient data. Conclusions We studied and developed the critical technology components to enable patient-centric, blockchain-based EHR sharing to support cancer care. The prototype demonstrated the feasibility of our approach as well as some of the major challenges. The next step will be a pilot study with health care providers in both the United States and Switzerland. Our work provides an exemplar testbed to build next-generation EHR sharing infrastructures.

Heart failure (HF) is among the most costly diseases to our society, and the prevalence keeps on increasing these days. Early detection of HF plays a vital role in saving lives through adjusting lifestyles and drug interventions that can slow down disease progression or prevent HF. There are many cardiovascular risk factors associated with HF, and they often coexist. In this paper, we assess the predictive value of pathological factors for early HF detection through a social network based approach. We use electronic health records (collected from the project HeartCarer) and compute the similarity of risk factors. The similarity values are used to construct an unweighted and a weighted medical social network. The constructed medical social network is further divided into a HF high-risk group and HF low-risk group using a group division algorithm. Patients in the high-risk group will be suggested for early screening. To evaluate the prediction value of our method, we perform four experiments based on real world data. The results demonstrate the high effectiveness of our method on heart failure risk assessment, with the best accuracy close to 90%.

Focusing on the loading sequential effects on the multiaxial fatigue damage accumulation, tests including two series of constant amplitude loadings and 12 groups of two-step loading spectra were conducted on 7075-T651 aluminum alloy. Under the same equivalent stress amplitude, the multiaxial fatigue life raises with the increase of stress amplitude ratio. Fatigue damage accumulation rate is decreased by the two-step loading interaction. Cyclic loading curves and fracture morphology analysis reveal that the loading step corresponding to lower fatigue life is dominant. Considering the stress amplitude ratio effects and loading interaction, a non-linear accumulative damage model is proposed based on the modified Basquin’s criterion. The proposed model provides a more accurate calculation of accumulative fatigue damage compared with the other four commonly used models. Fine life prediction results are obtained by the proposed model with all predicted data within a factor of three.

In this paper, based on the metamaterial principle of phase compensation, the broadband and high integration filter is designed. And by using the varactor diode loading technology to change the electromagnetic parameters (relative permittivity and relative permeability), the filter can be tunable in frequency. A dumbbell shaped slot metamaterial filter is designed in this paper. The measured results show that: the filter can be continuously tunable in the X band by loading varactor diode on the unit structure. when the varactor diode increases from 0.1pF to 0.7pF, the center frequency of the filter is decreased from 11.0GHz to 9.1GHz, the bandwidth is 25% (8.7GHz-11.2GHz), and the return loss minimum is 17dB, the insertion loss maximum is 1.2dB.

Spatial cross-matching operation over geospatial polygonal datasets is important to a variety of GIS applications. However, it involves extensive computation cost associated with intersection and union of a geospatial polygon pair from large scale datasets. This mandates for exploration of parallel computing capabilities such as GPU to increase the efficiency of such operations. In this paper, we present a CPU-GPU hybrid platform to accelerate the cross-matching operation of geospatial datasets. The computing tasks are dynamically scheduled to be executed either on CPU or GPU. To accommodate geospatial datasets processing on GPU using pixelization approach, we convert the floating point-valued vertices into integer-valued vertices with an adaptive scaling factor as a function of area of minimum bounding box. We test our framework over Natural Earth Dataset and achieve 10x speedup on NVIDIA GeForce GTX750 GPU and 14x speedup on Tesla K80 GPU over 280,000 polygon pairs in one tile and 400 tiles in total. We also investigate the effects of input data size to the IO / computation ratio and note that the sufficiently large input data size is required to better utilize the computing power of GPU. Finally, with comparison between two GPUs, our results demonstrate that the efficient cross-matching comparison can be achieved with a cost-effective GPU.

Increased availability of large amounts of address data provides opportunities for data driven studies to improve decision making in business applications and support precision public health with high resolution geolocations. Geocoding large number of addresses is challenging due to high cost and often disclosure of sensitive data to vendors over the Web. Most geocoders take advantage of Web APIs which require sending private addresses over the Internet, which may not be an option for many applications with sensitive data including public health and geo-medicine. Meanwhile, the cost for geocoding massive number of addresses could be high and becomes a major hurdle for many users. To overcome these challenges, we developed an open source on-premise geocoding software EaserGeocoder, which uses a novel integrative geocoding model to achieve high accuracy through integrating multiple open data sources. EaserGeocoder takes advantage of machine learning based approaches to determine best answers from multiple data sources. EaserGeocoder can also be easily parallelized to achieve high scalability through parallelized search and distributed computing. EaserGeocoder is on a par with commercial geocoding systems, outperforms open source systems, and is available for free.

Recent advancements in systematic analysis of high resolution whole slide images have increase efficiency of diagnosis, prognosis and prediction of cancer and important diseases. Due to the enormous sizes and dimensions of whole slide images, the analysis requires extensive computing resources which are not commonly available. Images have to be tiled for processing due to computer memory limitations, which lead to inaccurate results due to the ignorance of boundary crossing objects. Thus, we propose a generic and highly scalable cloud-based image analysis framework for whole slide images. The framework enables parallelized integration of image analysis steps, such as segmentation and aggregation of micro-structures in a single pipeline, and generation of final objects manageable by databases. The core concept relies on the abstraction of objects in whole slide images as different classes of spatial geometries, which in turn can be handled as text based records in MapReduce. The framework applies an overlapping partitioning scheme on images, and provides parallelization of tiling and image segmentation based on MapReduce architecture. It further provides robust object normalization, graceful handling of boundary objects with an efficient spatial indexing based matching method to generate accurate results. Our experiments on Amazon EMR show that MaReIA is highly scalable, generic and extremely cost effective by benchmark tests.

Cellular phenotypic features derived from histopathology images are the basis of pathologic diagnosis and are thought to be related to underlying molecular profiles. Due to overwhelming cell numbers and population heterogeneity, it remains challenging to quantitatively compute and compare features of cells with distinct molecular signatures. In this study, we propose a self-reliant and efficient analysis framework that supports quantitative analysis of cellular phenotypic difference across distinct molecular groups. To demonstrate efficacy, we quantitatively analyze astrocytomas that are molecularly characterized as either Isocitrate Dehydrogenase (IDH) mutant (MUT) or wildtype (WT) using imaging data from The Cancer Genome Atlas database. Representative cell instances that are phenotypically different between these two groups are retrieved after segmentation, feature computation, data pruning, dimensionality reduction, and unsupervised clustering. Our analysis is generic and can be applied to a wide set of cell-based biomedical research.

A new damage feature index is presented for the structural health monitoring based on Hilbert-Huang transform (HHT). The energy marginal spectrum of the dynamic signal is used to construct damage characteristic parameter, which can reflect the signal energy variation and benefit the structural damage detection. A sinusoidal wave with frequency change and a composite plate vibration experiment with pre-defined damage are designed to verify the effectiveness of characteristic parameter in damage detection. Results obtained from simulation and test show that the extracted non-model-based damage feature index is available and sensitive in damage detection of time-varying system.