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Rain streaks showing in images or videos would severely degrade the performance of computer vision applications. Thus, it is of vital importance to remove rain streaks and facilitate our vision systems. While recent convolutinal neural network based methods have shown promising results in single image rain removal (SIRR), they fail to effectively capture long-range location dependencies or aggregate convolutional channel information simultaneously. However, as SIRR is a highly illposed problem, these spatial and channel information are very important clues to solve SIRR. First, spatial information could help our model to understand the image context by gathering long-range dependency location information hidden in the image. Second, aggregating channels could help our model to concentrate on channels more related to image background instead of rain streaks. In this paper, we propose a non-local channel aggregation network (NCANet) to address the SIRR problem. NCANet models 2D rainy images as sequences of vectors in three directions, namely vertical direction, transverse direction and channel direction. Recurrently aggregating information from all three directions enables our model to capture the long-range dependencies in both channels and spaitials locations. Extensive experiments on both heavy and light rain image data sets demonstrate the effectiveness of the proposed NCANet model.

In the study, we retrospectively reviewed cases of patients with acute mushroom poisoning admitted to seven hospitals from May 2016 to May 2021. In total, we analyzed 153 acute mushroom poisoning cases. Of these patients, 135 survived and 18 died; no correlation of Ganoderma lucidum treatment with in-hospital mortality was observed (odds ratio = 1.598, P = 0.589). We further analyzed 61 patients who survived with liver injury according to whether they were treated with G. lucidum. Both length of hospital stay and hospitalization expenses in the G. lucidum treatment group were significantly lower than the control, with values of 6.69 ± 3.98 days vs. 9.27 ± 5.30 days (t = 2.174, P = 0.034) and 16,336.49 ± 12,615.76 CNY vs. 27,540.08 ± 23,709.57 CNY (t = 2.382, P = 0.020), respectively. Moreover, cases with a blood purification treatment time48 h of the G. lucidum group were significantly less than that of the control (30% vs. 69.23%; χ2 = 4.891, P = 0.027). As a result, G. lucidum seems to be a beneficial treatment in acute mushroom poisoning with liver injury.

This paper studies the influence of hybrid disorders on acoustic transmission characteristic in pipeline with periodic elastic HRs. Band gap structures (BGs) for infinite period are investigated by transfer matrix method and finite element method respectively, and fit well with the corresponding transmission loss (TL) for finite regular periods. By introducing a certain degree of uncertainty level, Interval analysis method is used to convert uncertain parameter problems into two deterministic models. Frequency response function (FRF) for near-periodic structure with single disorder and BGs for quasi-periodic structure with multiple disorders considering cavity radius and periodic length are investigated. The existence of disorders in periodic structure would always reduce attenuation interval and intensity, some disturbance would even change the original acoustic transmission characteristic and excite completely new attenuation zones. The sensitivity of pipeline acoustic vibration transfer characteristic to disorder parameter depends on attenuation mechanism, as for periodic elastic HRs pipeline, acoustic propagation stability is more sensitive to characteristic of locally resonant unit. The work in this paper enriches the stability analysis of pipeline with elastic HRs, which would provide theoretical reference for noise and vibration reduction design in practical engineering applications.

In this paper, the transformed strain rate of environmental fatigue correction factor (Fen), which is used to consider the influence of PWR primary coolant environment on material fatigue, is studied. EPRI’s guideline and the AFCEN’s probationary phase rule (RPP) No.3 of Volume VI in RCC-M 2017 edition provide two different calculation methods of transformed strain rate separately. NUREG CR-6909 gives two versions of prediction models of Fen for Low alloy steel, nickel base alloy and austenitic stainless steel which are the three main materials of the primary circuit system. In this paper, the model and transients of Sample 2 in EPRI’s guideline are selected for calculation and comparison, so as to verify whether the analysis method is reasonable. Firstly, the fatigue analysis in air is carried out, and then based on the combination, the detailed calculation of strain rate is carried out to calculate environmental fatigue results. The analysis results are compared with the results of guideline, and the valuesare close. Then, the main pipeline safety injection nozzle components with small fatigue margin in PWR are selected to carry out environmental fatigue analysis. In the analysis, different methods of calculating modified strain rates are used, and different prediction models in CR-6909 are used. The coefficient of Fen integrated in RPP3 isconsidered, and the effects of various calculation methods on the results are compared. The results show that for austenitic stainless steel, the results of RCC-M RPP3 method are mostly less than those of EPRI guidelines. Compared with the prediction model of NUREG CR-6909 version 0, the prediction model version 1 greatly decreases the Fen results.

This paper proposes an improved transfer matrix method (TMM) algorithm to calculate frequency response function (FRF) for finite periods of periodic composite pipelines structures. Traditional TMM usually generate instable matrix and inaccurate calculation results for Phononic crystals (PCs) pipeline. Under the assumption that periodic distribution of pipeline structure with no intermediate excitation, the main idea of the improved algorithm is to reasonably divide finite periodic pipeline into several effective segments, then the transfer relationship of state vector for each connected pipe part could be expressed individually, thereby realizing the calculation order reduction by expanding the dimension of overall stiffness matrix. This improved algorithm could effectively avoid cumulative error caused by diagonal sparse matrix operations, thus getting true dynamic response to calculate exact FRF curves. Moreover, this algorithm could fundamentally improve the accuracy and stability of traditional TMM calculations. The transverse FRF for finite periods calculated by improved TMM shows excellent consistency with corresponding band gap structures (BGs), validate the correctness of derived theory and algorithm. This improved TMM algorithm supplies an effective method for FRF calculation of finite pipeline periods, and also provide effective verification of BGs for infinite structures, which could guide the vibration and noise reduction design of pipeline system.

This paper studies the influence of disordered parameters on vibration transmission characteristic of pipeline structure with periodic support. Transverse Band Gap structures (BGs) for perfect period and frequency response function (FRF) for finite periods are investigated and fit well with each other. By introducing a certain degree of uncertainty level, interval method is used to convert uncertain parameter problem into two deterministic models. FRF for near-periodic structure with single disorder and BGs for quasi-periodic structure with multiple disorders are investigated concerning support stiffness and periodic length. The existence of disorders in periodic structure would always reduce the attenuation intensity and interval, and some disturbance would even generate new intermediate attenuation zones. Elastic wave propagation with periodic support is much more sensitive to periodic length rather than support stiffness, as the sensitivity is closely related with attenuation mechanism. Therefore, such defects should be carefully avoided in design and manufacturing this kind of periodic pipeline structures. The work in this paper enriches the stability analysis of the pipeline structure with periodic support, and provides reference for the research of noise and vibration reduction of pipeline system in practical engineering.

In practical hardware platforms such as FPGA or DSP, the FFT operation is based on a length of 2^L. However, due to the system limitation, the length of sampled signal would be not equal to 2^L. Thus, zero-padding is performed on the signal before FFT operation. Most traditional sinusoidal frequency estimation methods are for signals without zero-padding. When applying these methods to the zero-padded signal, the performances would degrade. To solve this problem, a novel frequency estimation method for zero-padded signal is proposed in this paper. In the proposed method, the analytical expression of the DFT signal after zero-padding is derived. Then an amplitude ratio function is defined between the two DFT samples nearest to the true frequency. Based on the monotonic property of the ratio function, Newton-Raphson method or bisection search is used to estimate the residual frequency. Two implementation flows are proposed, with similar performance and computational complexity. Experimental results show that the proposed method achieves better RMSE performance than the traditional methods. More importantly, the proposed estimation method can be applied to both the zero-padded signal and the non-padding signal.

Linear frequency modulated (LFM) signal is widely used in wideband radars, where stretch processing is commonly adopted to reduce the processing bandwidth. In this paper, we propose a fast acceleration and velocity estimation method for wideband stretching LFM radars based on mutual bias correction. In this method, cross-correlation is carried out on adjacent stretched echoes to integrate scattering energy. By deriving the relationship between the two-dimensional (2D) spectrum of the cross-correlation result and the motion parameters, it is found that the frequency of the 2D spectrum peak is determined by the acceleration and the velocity. We first estimate a coarse acceleration using the frequency of the 2D spectrum peak on the slow time, and then construct a compensation function to estimate the coarse velocity. To obtain high precision estimation, we develop a mutual bias correction (MBC) process to reduce the bias of the coarse estimates. Experimental results show that the proposed method achieves much smaller root mean square error (RMSE) with comparable computational cost, compared to existing state-of-the-art methods.

This review reports the most current evidence on the effects of exercise interventions on improving physical function, daily living activities and quality of life in community-dwelling frail older adults. CBMdisc, CNKI, Wanfang, VIP, MEDLINE, Cochrane Central Register of Controlled Trials (Central), Pubmed, Embase, Web of Science and EBSCO were searched from inception to July 2019. Exercise interventions were found to improve knee extension strength and normal speed and were beneficial in lower Time up and go test (TUG) and improving semi-tandem, Berg balance scale (BBS), Short Physical Performance Battery (SPPB), Physical Performance Test (PPT) and Activities of daily living (ADL). Further well-designed studies are needed to explore the most effective intervention type and dose.

In this study, by employing the intra-pulse cross-correlation (IPCC) operation, an unambiguous velocity estimation method is proposed for narrow-band long-range radars with high carrier frequency and low pulse repetition frequency. This estimation algorithm is simple and could be easily implemented in existing radar systems without changing the radar hardware or the pulse transmitting scheme. Comparing with the slow time dimension correlation algorithm, the accuracy of the proposed intra-pulse frequency domain method is greatly improved, and the brute-force search for the unknown motion parameters is also unnecessary. By first setting a small frequency offset of the IPCC operation, the unambiguous velocity region could be significantly enlarged. Using the relatively coarse but unambiguous estimates and increasing the frequency offset step by step, the IPCC is repeatedly applied to obtain more accurate estimates. Note that the estimation results of the IPCC algorithm could be used in the maximum-likelihood estimator for ambiguity resolution. The Cramer-Rao bound for the proposed algorithm is derived, and the optimal frequency offset in the sense of estimation accuracy is also analysed. Through numerical simulations for both synthetic and real radar data, the effectiveness of the proposed estimation algorithm is verified.

For maneuvering targets, their motion during long observing time will deteriorate the integration results and degrade the performance of range and motion parameters estimation. To solve this problem, a computationally efficient method based on the time-reversal (TR) process and maximum likelihood (ML) principle, i.e., TR-MLE is proposed. The proposed method decouples the joint parameter estimation problem into two simpler problems, which not only increases the efficiency but also improves the estimation performance in low signal-noise-ratio. Furthermore, a fast method using Chirp-Z transform and Newton's method is developed for a more efficient implementation. The theoretical analysis of the noise properties after the TR process is carried out. Then, the corresponding Cramer–Rao lower bound that can evaluate the performance loss introduced by the TR process is discussed in detail. Simulated data and real data are used to assess the performance of the proposed method.

Ginsenoside-Rg1 (G-Rg1), a saponin that is a primary component of ginseng, is effective against inflammatory diseases. The P2X purinoceptor 7 (P2X7) receptor is an ATP-gated ion channel that is predominantly expressed in immune cells and plays a key role in inflammatory processes. We investigated the role of G-Rg1 in sepsis-related cardiac dysfunction and the underlying mechanism involving the regulation of the P2X7 receptor. We detected cell viability, cytotoxicity, cellular reactive oxygen species (ROS) levels, and mitochondrial membrane potential (MMP) with or without G-Rg1 in lipopolysaccharide (LPS)- or hypoxia/reoxygenation (H/R)-induced H9c2 cell models of ischemia/reperfusion injury. We applied cecal ligation and puncture (CLP) to induce a mouse model of sepsis and measured the survival duration and cardiac function of CLP mice. Next, we quantified the ROS level, MMP, respiratory chain complex I-IV enzymatic activity, and mitochondrial fusion in CLP mouse heart tissues. We then investigated the role of G-Rg1 in repairing LPS-induced cell mitochondrial damage, including mitochondrial superoxidation products. The results showed that G-Rg1 inhibited LPS- or H/R-induced cardiomyocyte apoptosis, cytotoxicity, ROS levels, and mitochondrial damage. In addition, G-Rg1 prolonged the survival time of CLP mice. G-Rg1 attenuated LPS-induced superoxide production in the mitochondria of cardiomyocytes and the excessive release of cytochrome c from mitochondria into the cytoplasm. Most importantly, G-Rg1 suppressed LPS-mediated induction of proapoptotic Bax, activated Akt, induced GSK-3β phosphorylation, and balanced mitochondrial calcium levels. Overall, G-Rg1 activates the Akt/GSK-3β pathway through P2X7 receptors to inhibit sepsis-induced cardiac dysfunction and mitochondrial dysfunction.

Magnetorheological elastomer (MRE) is a kind of smart material, whose mechanical property can be controlled by the external magnetic field quickly and reversibly. The damping property of MRE is one of the most concerned properties when designing MRE based devices. In this work, the influence of gamma radiation on the damping property of MRE was investigated. Six different exposures of gamma radiation were applied to the MRE samples. The highest gamma radiation dose was up to 1 × 105 Gy(Si), which can cover most of the engineering application scenarios. The influence of gamma radiation on the damping-strain relation and the damping-magnetic-field relation were studied. The probable mechanisms were discussed in detail. It is found that the gamma radiation does not affect the variation trend of loss factor of MRE with increasing strain amplitude or magnetic flux density. But it affects the variation trend of the maximum change of strain-induced or magnetic-field-induced loss factor of MRE. Besides, with constant strain and constant magnetic flux density, the loss factor of MRE shows w-shape variation trend with increasing gamma radiation dose. It is considered to be resulted from the combined action of the intrinsic damping and the interfacial friction damping of MRE.

Fuel assembly is located in the reactor core, which is the key component of nuclear power plant reactor. Its structural integrity will directly affect the safety and reliability of nuclear reactor operation. Fretting wear between fuel rod and grid supports caused by flow induced vibration is currently one of the main causes of fuel rod failure, which is also the most concerned phenomenon in fuel assembly design. Based on the random vibration theory and considering the interaction between fuel rod and support grid, a theoretical model and evaluation criteria for response prediction are proposed for the three possible flow induced vibration mechanisms in Pressurized Water Reactor (PWR) fuel assemblies, namely, turbulent excitation, fluidelastic instability and vortex shedding. At the same time, based on the Archard’s equation, the fretting wear analysis model of fuel rods is established, which is suitable for industrial application. The effects of transverse velocity, axial velocity and fluid density on the response of flow induced vibration and fretting wear of fuel rods are studied. The results show that the amplitude/wear depth varies with the transverse velocity in a quadratic way, exponentially with the axial velocity, and linearly with the fluid density. The established analysis process and evaluation method can provide technical support for the design and optimization of fuel assembly.

In the stress and fatigue evaluation of primary nuclear equipment, thermal stress calculation and fatigue curve have a great impact on the calculation results. There is a problem of stability in the step integral when calculating the thermal stress. The transient heat conduction changes rapidly near the initial temperature time point. It is critical to choose the right sub steps. In the nuclear code, the design fatigue curve in the air environment is given by applying a factor of 2 on stress or a factor of 20 on cycles. The factors are used to consider various influences such as data scatter, structure size, surface roughness and load. The factors of fatigue curves in ASME BPVC 2007 edition + 2009 addendum and French AFCEN’s RCC-M 2017 edition RPP 2 have changed. Due to the changes of the original test data and modificative factors, the new fatigue curve and the original fatigue curve are crossed. In code case N-761 of ASME, fatigue curves considering the influence of primary coolant environment are given under different strain rates. In the calculation of thermal transient using commercial ANSYS software, the setting of time step has a great influence on the thermal stress. This paper compares and analyzes the influence of different calculation methods on the thermal stress at different positions of the model. The effect of different fatigue curves on fatigue life is also discussed considering different air design curve and different strain rate fatigue curve in water. The results show that the fatigue results obtained by using the modified ASME or RCC-M air fatigue curve are smaller than those before the change when the usage factor is large to a certain extent. After considering the environmental fatigue curve, the fatigue results increase significantly. The accuracy of thermal stress calculation can be significantly improved by adding time points and refining time steps near the time points after the transient sharply changes, otherwise the influence of thermal stress on stress and fatigue results will be underestimated obviously.

In this paper, the vibration propagation characteristic is investigated for periodic composite pipeline with crack damage. A novel modified transfer matrix method (TMM) is developed to investigate transverse Band Gap structures (BGs) considering fluid structure interaction, and validated by frequency response function (FRF) for finite period. Field transfer matrix is developed for straight pipeline conveying fluid, and point transfer matrix is derived for circumferential cracks damage based on spring hinge model, which could estimate the equivalent rotational stiffness by local flexibility coefficient method. It’s demonstrated that the existence of small crack damage has negligible effect on BGs, while severe crack damage has significant influence on vibration propagation even it only exists in a single cell. Meanwhile, the difference of FRF between cracked and perfect pipeline provides new idea in diagnosing the crack status. The influence of crack damage on BGs is mainly attributed to the equivalent rotational stiffness. Location of crack damage could affect the stiffness ratio of composite pipeline, and result in the change of original BGs. This study enriches the theoretical TMM for pipeline systems vibration with crack damage, and provides some reference for the stability design of periodic pipeline structures.

In this paper, vibration attenuation characteristic of periodic composite pipeline is studied, focusing on the fluid structure interaction (FSI). Besides fluid velocity and pressure, Poisson coupling and friction coupling are also taken into consideration. A novel modified transfer matrix method (TMM) is proposed to investigate the distribution of band gap structures (BGs), and attenuation intensity within stop band frequency is also accurately predicted. BGs and Frequency response function for axial, transverse, torsional and their coupled modes are calculated and validated with each condition, and display excellent consistency with Shen’s results. In order to explore FSI effect of different models, pipe without fluid loading, with inner fluid taken as additional mass and pipe considering FSI effect are all presented. It is found that BGs with Bragg scattering mechanism are generated in all three models, but the distribution differs greatly, thus the FSI effect could not be ignored in practical engineering applications. The work in this paper provides novel method and useful reference for noise and vibration reduction of pipeline system conveying fluid.

In this paper, transmission characteristic of periodic composite pipeline is investigated for axial vibration, focusing on friction coupling effect. A novel transfer matrix method is developed to calculate band gap structures (BGs) with the consideration of different forms of viscous friction. Frequency response function for finite periods is obtained and shows good consistency with BGs for infinite periods. The energy dissipation caused by viscous friction exists in the entire frequency range, as friction coupling is always distributed along the pipe element. Meanwhile, the attenuation intensity is relatively small compared with that induced by Bragg scattering mechanism. Therefore, viscous friction is not affecting the overall trend of BGs, only exhibiting certain attenuation in pass band frequency range. The effect of kinematic viscous coefficients on axial BGs are systematically examined in different friction models. Attenuation intensity goes up with increasing kinematic viscous coefficients, in addition, energy dissipation caused by frequency dependent friction model is generally higher than that of steady state friction condition. Moreover, frictional dissipation shows more sensitivity to high frequency. The research in this paper enriches fluid structure interaction theory of pipe element, which is also expected to be helpful in controlling the dynamical behaviors of pipeline system conveying fluid.

A coupling extended multiscale finite element and peridynamic method is developed for the quasi-static mechanical analysis of large-scale structures with crack propagation. Firstly, a novel incremental peridynamic (PD) formulation based on the ordinary state-based PD model is derived utilizing the Taylor expansion technique. To combine the high computational efficiency of the EMsFEM and advantages of dealing with discontinuous problems of the PD, a coupling strategy based on the numerical base function is proposed, in which the displacement constraint relationships between the coarse element nodes of the EMsFEM and the material points of the PD among the coupling domain are constructed by the numerical base functions and are represented by a coupling strain energy function using the Lagrange multiplier method. Then, a bilinear softening material model is adopted to describe the damage and failure of the bond, and the incremental-iterative algorithms are applied to obtain the steady-state solutions. Finally, several representative numerical examples are presented, and the results demonstrate the accuracy and efficiency of the proposed coupling method for the quasi-static mechanical analysis of large-scale structures with crack propagation. Comparing with the single EMsFEM and PD method, the present coupling method can reduce much computational cost and well deal with crack problems, simultaneously.

To elucidate the evolution of structural topology with the medium-range order of growing silicon films fabricated by plasma enhanced chemical vapor deposition with highly diluted hydrogen, we established a the model for a realistic network of growth films based on continuous random networks. We combined the kinetic Monte Carlo method with the interactions of various atomic-scale mechanisms from first-principles density-functional-theory computations and molecular-dynamics computations. To quantitatively characterize the short- and medium-range order, in addition to the higher order of the structural network, we applied a fluctuation transmission electron microscopy simulation and the pair correlation function to measure information about local order regions in film network. Interestingly, we found that the inflexion temperature of surface SiH3 coverage directly affected the silicon hydride crystallization process by forming much chemisorption from physisorption of surface hydride species. More interestingly, based on the atomic-scale chemical mechanism of the growth process of film, our results first realistically rendered the continuous disorder-order phase transition from structural topology, which is differed from previous knowledge that the amorphous to polycrystalline transition is a discontinuous short-range-order to long-range-order phase transition. Especially, we predicted the temperature dependence of evolution of structural network of the film and elucidated that the growing silicon film formed a nanocrystalline structural network at very low temperatures, relative to those of thermal annealing. This result was ascribed to interactions and competitions between various mechanisms and critically due to the dissociation mechanism and H-induced crystalline mechanism of silicon hydride, which isn’t depend on only one of the model mechanisms of surface diffusion model, etching model and annealing model. These results provide significant new physical insight into an experimentally relevant process for optimizing a strategy of deposition condition.

The prediction of deep horizontal displacement of slope soil is an important part of slope deformation monitoring, which has important guiding significance for the prevention of slope safety accidents. Holt-Winters model is suitable to predict the data series of deep horizontal displacement of slope soil, which show both trend growth and seasonal fluctuation. Firstly, this paper selected the data set as the original data for empirical analysis which is deep horizontal displacement of soil after pretreatment from the specific slope monitoring project, then used the Holt-winters’ damped model to perform data mining, finally, compared with the traditional prediction methods including the neural-network model and the k-nearest neighbor classification. The results show that the damped Holt-winters model has the highest prediction accuracy.

This review paper provides insights the into current developments in additive manufacturing (AM) techniques. The comprehensive presentations about AM methods, material properties (i.e., irradiation damage, as-built defects, residual stresses and fatigue fracture), experiments, numerical simulations and standards are discussed as well as their advantages and shortages for the application in the field of nuclear reactor. Meanwhile, some recommendations that need to be focused on are presented to advance the development and application of AM techniques in nuclear reactors. The knowledge included in this paper can serve as a baseline to tailor the limitations, utilize the superiorities and promote the wide feasibilities of the AM techniques for wide application in the field of nuclear reactors.

The progress brought by the deep learning technology over the last decade has inspired many research domains, such as radar signal processing, speech and audio recognition, etc., to apply it to their respective problems. Most of the prominent deep learning models exploit data representations acquired with either Lidar or camera sensors, leaving automotive radars rarely used. This is despite the vital potential of radars in adverse weather conditions, as well as their ability to simultaneously measure an object’s range and radial velocity seamlessly. As radar signals have not been exploited very much so far, there is a lack of available benchmark data. However, recently, there has been a lot of interest in applying radar data as input to various deep learning algorithms, as more datasets are being provided. To this end, this paper presents a survey of various deep learning approaches processing radar signals to accomplish some significant tasks in an autonomous driving application, such as detection and classification. We have itemized the review based on different radar signal representations, as it is one of the critical aspects while using radar data with deep learning models. Furthermore, we give an extensive review of the recent deep learning-based multi-sensor fusion models exploiting radar signals and camera images for object detection tasks. We then provide a summary of the available datasets containing radar data. Finally, we discuss the gaps and important innovations in the reviewed papers and highlight some possible future research prospects.

The environmental fatigue correction factor (Fen) is mainly used to analyze the influence of the coolant environment on the fatigue life of primary metal materials. Because the calculation of the transformed strain rate is related to the stress history of the component structure, how to determine the strain rate is the most critical step in calculating the Fen. The approaches of the detailed method were given by the Electric Power Research Institute (EPRI) guidelines and RCC-M-2017 Edition Section VI- RPP No. 3 separately, so a gap analysis was performed between the two methods. Furthermore, another average method was also proposed to determine the average strain rate and strain range. Based on the analysis benchmark provided in the EPRI guideline, a simple case study was performed to account for the effect on the fatigue life in applications with different strain rate approaches and different Fen expressions. Finally, two industry case studies were also completed, including on materials of low alloy steel, austenitic stainless steel, and nickel-base alloy. We suggest adopting a more accurate detailed method, and its methodology is recommended to provide more reasonable solutions.

A new numerical simulation method is developed for the evaluation of thermal and mechanical analyses of manufactured structures with Metal Inert Gas (MIG) welding on the basis of the peridynamics. The peridynamic formulations of the weak coupled thermo-mechanical problems are derived based on a heat transfer model and a microplastic model. To simulate the MIG welding process, a birth–death material point method in the peridynamic framework is proposed to model the addition of weld metal to the workpiece. To simplify the calculation process and improve the computational efficiency due to no need of updating the neighbourhoods of material points, an additional scalar field is introduced in the equations to describe the birth and death states of the material points. In addition, the present method is applied to simulate a classical model of two plates being joined together by the MIG welding. The results indicate that the residual tensile deformations are formed in the welded area while the residual compressive deformations are formed far from the wild line after the release of the clamps on account of the plastic deformation. These results also demonstrate the validity of the present method for the simulation of the MIG welding by comparing with the reference solution.

The Fracture evaluation is important in the structural integrity analysis of nuclear equipment which is subjected to the effects of neutron irradiation. The increment of ductile and brittle transition temperature is mainly due to the neutron irradiation, thermal ageing and strain ageing. In addition to above these factors, the high carbon macro-segregation of low-alloy steels also increases the risk of fast fracture failure as the carbon positive macro-segregation will lead to the increasing transition temperature of low-alloy steels. In this work, a relationship between the carbon content and the increment of transition temperature is developed and is used to the fast fracture failure analysis of the highest carbon content region in steam generator channel head. Results show that ratio between the calculated stress intensity factor considering safety coefficient suggested by ASME design code and the critical stress intensity factor is less than one, which indicates a safe design for the highest carbon content region in steam generator channel head.

In this paper, a class of bandpass frequency selective structures (FSSs) with improved out-of-band rejection is proposed by using stacked slotlines. The proposed FSS consists of a periodic array of slotlines etched in pieces of single-layer printed circuit boards, which are vertically placed along the periodic plane and then stacked together with a certain distance. Due to this special arrangement, slotline resonators are constructed based on the desired propagation modes, thus leading to a stable bandpass filtering response in a wide frequency range. To better understand the operating principle, design procedure of this class of FSSs with uniform slotline unit cells, inductor-loaded uniform slotline unit cells, and stepped-impedance slotline unit cells is presented step by step. In particular, the equivalent transmission line models are established and the even–odd mode analysis method is introduced to intensively analyze the resonant and filtering mechanisms. As two examples, a single-polarized FSS and a dual-polarized one, both based on stepped-impedance slotline unit cells, are designed, fabricated, and measured. Measured results indicate that the proposed FSSs feature miniaturized unit-cell size, wide upper rejection band, and stable frequency filtering response under a large variation of incident angles.

Millimeter-wave radar has proven to have a good range estimation accuracy and is less influenced by weather conditions. However, it is difficult for radar to recognize objects, and it is prone to cause a false alarm. In this paper, we present an object detection and classification by jointly using a radar and camera sensors for traffic surveillance applications. The proposed method fuses the Regions of Interest (ROIs) generated on each of the detection results obtained independently from radar and camera sensors. Reducing the high false alarm of a radar sensor is the main aim of the fusion method. Then, a Convolutional Neural Network (CNN) is used to classify the final fused detected objects into one of the six-vehicle categories; Sedan, Truck, Minivan, Bus, Microbus, and SUV. The proposed method was verified using real data. Results obtained demonstrate the good performance of the proposed fusion approach in traffic surveillance context.

Synthetic Aperture Radar (SAR) Imaging and Time of Flight (ToF) Imaging are two popular approaches for terahertz (THz) 3D imaging nowadays. Both systems above require broadband operations and coherent detection, which requires complicated and costly hardware. Generally, 3D imaging is difficult for those objects with large-curvature features in the case of both optical and THz systems. In this paper, we propose a simple but effective 3D imaging approach, which works in the point-cloud imaging mode. Our in-house THz lenses can focus the THz wave very well and it can gather reflected power within a large angle, thus making the decent 3D imaging feasible. By introducing the entropy concept for threshold optimization, decent figures can be obtained in case of poor raw data with a low signal-to-noise (SNR) ratio. In experiments, our system outperforms the commercial Terahertz Time-Domain Spectroscopy (THz-TDS) system. The proposed method could benefit industrial production, heritage studies, etc.

The irradiation induced variations in microstructure and mechanical properties of the Cu64Zr36 metallic glasses (MGs) are investigated via large-scale molecular dynamics simulations. The irradiation condition is modeled by sequential and prolonged collision cascades. The simulation results show a simultaneous decrease of the density and the fraction of Cu-centered full icosahedron (CCFI) clusters in the irradiated samples. This microstructural evolution induced by the prolonged irradiation is proposed to be responsible for the change of deformation mode of tested samples under uniaxial tensile loading. When increasing the irradiation dose, the ultimate tensile strength of MG samples decreases gradually, while their deformation mechanism switches from localized shear banding to ductile necking and finally to ideally plastic flow, enhancing the MG ductility. Careful atomic-scale examinations on the initiation and development of shear transformation zones (STZs) are carried out for a better understanding of the irradiation-induced ductility enhancement in MGs. Two related effects of the irradiation are unveiled. On the one hand, the irradiation releases the stored strain energy by promoting the STZ activation within the MG matrix. On the other hand, the irradiation damages restrain the propagation of shear band through the innovatively proposed two-unit “STZ-vortex” mechanism. Under the combined effect of these two mechanisms, the low-temperature ductility of irradiated MGs is improved and the brittle-like failure driven by single shear banding is prevented.

Fatigue is a significant degradation mode that affects nuclear power plants around the world.A fewself-designed computer codes have been developed forfatigue analysis. The Nuclear Power Institute of China has finalized an in-house computer code called FAC_NPIC for evaluating fatigue according to international standards. FAC_NPIC extracts stress data from finite element analysis results or manual input and is independent of specific finite element software. The “rubberband” peak-and-valley detection algorithm searches for extreme stress values automatically, and the modified rainflow-3D algorithm captures the features of secondary fluctuations. This paper presents transient combination schemes and how seismic loading effects are handled, as well asexamples of input and output files. A simple benchmark calculationwasconducted and compared with the literature. The results showed that all key features of FAC_NPIC work well.Despite differences in fatigue algorithms, good agreement with thestandards was achieved.

The sea clutter modeling is critical to the radar design and assessment of relevant detection algorithms. In this paper, we investigate a family of generalized autoregressive conditional heteroscedastic (GARCH) processes to model the sea clutter as a time series, in which the current variance is dependent on historical information. The most general model (so-called the ALLGARCH model) provides more flexible variance structures to model non-Gaussian, asymmetry, and nonlinear properties of the clutter. However, after going through the usage of the ALLGARCH model, we find that it is not very suitable because the coefficients of the model, which are numerous, would be difficult to estimate in a real-time operating environment. Meanwhile, we find that some of the coefficients are negligible under almost all kinds of sea environments and weather conditions. Motivated by these observations, we propose a novel GARCH model for sea clutter modeling, which is a generalization of the nonlinear-asymmetric GARCH (NAGARCH) model. Considering the correlation between adjacent clutter returns, autoregressive terms are also introduced. By systematically analyzing practical sea clutter data under different sea environments, we demonstrate that the proposed model achieves comparable fitting effect to some commonly used statistical models. Also, we develop the corresponding generalized likelihood ratio test (GLRT) algorithm for the new model. Numerical simulations exhibit that the proposed detector achieves higher probability of detection, comparing with the AR-GARCH detector.

High linearity and low noise are important conditions for high-resolution imaging in wideband linear frequency modulation (LFM) radar systems, where stretch processing is commonly adopted. However, in practice, hardware may introduce amplitude and phase distortions to radar signals. The distortions will increase the range sidelobes (RSLs) of the dechirped returns and cause the decline of imaging quality. Traditional time-domain RSL correction methods are greatly influenced by time delay and can only be used in a small range window. To solve the problem, we propose a novel frequency-domain RSL correction (FDRC) method in this paper. For FDRC, we first multiply the extracted distortion and the stretched return by a baseband LFM signal and then perform the correction in the frequency domain. Both theoretical and simulation results show that the proposed method provides equivalent performances in RSLs compared to other existing distortion correction methods in a large range window. Besides, the proposed method can be much easily implemented in practical radar systems.

Linearly frequency modulation (LFM) pulse train and linearly stepped frequency (LSF) pulse train are mostly used in radar systems. However, the estimation performance of target motion parameters may be affected by the high recurrent lobe levels and the rangeDoppler coupling phenomenon appearing in ambiguity function (AF). In multi-target scenarios, the estimation performance becomes even worse. The Costas frequency-modulation coded (CFMC) LFM pulse train has an ideal thumbtack-shaped AF, thus it can provide motion parameter estimation with high precision. However, the estimation of target motion parameter for the coherent CFMC LFM pulse train has not been investigated in depth. In this paper, we first analyze the properties of the AF of the CFMC LFM pulse train. Based on its convexity and narrow mainlobe width, a fast method to implement the maximum likelihood estimator (MLE) is proposed to estimate the motion parameters. To reduce the computation complexity, the Chirp-Z Transform (CZT) is introduced. Then, the CramerRao lower bounds (CRLBs) on range, velocity and acceleration for frequency-modulation coded (FMC) pulse train are derived. It is shown that the CRLBs are relevant to the frequency coding patterns. Finally, Monte Carlo simulations are performed to verify the performance of the MLE. The results show that the performance of our proposed method can achieve the CRLBs when the signal-noise ratio (SNR) is higher than the threshold SNR.

In steam generators and other heat exchangers, there are a lot of tube bundles subjected to two-phase cross-flow. The fluctuating pressure on tube bundle structure caused by turbulence can induce structural vibration. The power spectral density (PSD) of buffeting force is usually required as the input of random vibration analysis. Since there is no generally accepted method to compute the normalized buffeting forces, the acknowledged upper bound of buffeting forces due to two-phase flow is absent. This paper presents a new set of upper bound of buffeting forces in two-phase flow by modifying the mixture velocity proposed by de Langre. The new upper bound is compared with the one based on single-phase flow, and de Langre’s upper bound when two-phase flow is considered. Through a sample of steam generator tube subjected to non-uniform two-phase cross-flow, the random vibration responses based upon three types of upper bounds are computed. The proposed upper bound lies between the one derived from single-phase flow modeling and the one proposed by de Langre. It turns out that the newly proposed upper bound could cover sufficient experimental data sets of the buffeting force and is below the de Langre’s bound over a wide frequency range.

Fe-Ni-Co-based shape memory alloys (SMAs) enjoy a wide application prospect in seismic protection structures or components owing to their advantages of high strength, excellent cold workability and low material cost. In this study, the effects of microstructure and grain orientation on the shape memory effect (superelasticity) were investigated, which could offer theoretical guidance for microstructure and texture control during the fabrication process of high-performance Fe-Ni-Co-based SMAs. The results showed that, the recoverable strain values by theoretical calculation of the alloy on , and orientations were 9.1%, 7.4% and 1.2%, respectively, and the recoverable strain became maximum near the grain orientation of . For improving the shape memory performance, both the directional solidification technology and rolling + recrystallization technology could be adopted to effectively control the formation of the microstructure with strong grain orientation. Based on this, an equiaxed-grained Fe-Ni-Co based SMAs with strong {hk0} texture was prepared by 98.5% rolling deformation, recrystallization at 1220℃ for 1h and aging treatment at 600℃ for 96h. It exhibited superelastic strain of 3.2%, residual strain of 0.7%, and tensile strength of approximately 960MPa. Compared with the conventional forging Fe-Ni-Co-based SMAs (without superelasticity), the superelasticity of the alloy fabricated by microstructure and texture control was enhanced significantly.

In this paper, theoretical solutions of free transverse vibration for tapering pipe considering variable cross section have been investigated using Bessel function in low frequency domain. Natural frequency was calculated by transfer matrix method (TMM) based on an accurate theoretical model. The effectiveness and validity of TMM with Bessel function was confirmed in comparison with TMM of discrete uniform pipe and Finite Element Method. Furthermore, dimensionless model was proposed to avoid the singularity, instability and overflow in calculation. The geometry effect, such as tapering ratio, thickness-radius and length-radius ratio influence on the nature frequency was explored. The present study was envisaged to provide useful insights for dynamic analysis of pipeline systems.

This paper is dedicated to designing the overall structural topology for the lightweight design of an automobile wheel. A simplified two-dimensional finite element analysis (FEA) model for the wheel is established, in which the whole wheel structure is first defined as design domain during topology optimization. A rotationally periodic constraint is introduced to design the wheel into structural topology consisting of rotationally repetitive modules. Further, compliance-based topological design under multiple load cases within single module is carried out. In order to achieve a uniform deflection and stiffness distribution around the circumference of wheel, a weighted compliance under multiple load cases is taken as the objective function. In addition, some factors significantly affecting the structural topology are discussed.

Parameter estimation of polynomial-phase signals (PPSs) observed in additive white Gaussian noise (AWGN) is addressed. Most of the existing estimators cannot work on a fully identifiable region. Using the algebraic number theory, McKilliam et al. proposed a least squares unwrapping (LSU) estimator, which can operate on the entire identifiable region. However, its computational load may be large, especially when the number of samples is large. In this study, the authors first extend the amplitude-weighted phase-based estimator (AWPE) for sinusoidal and chirp signals to PPSs and derive a time domain maximum likelihood estimator. The performance is analysed and compared with the Cramer–Rao lower bound (CRLB). Then, the authors propose an iterative compound time-frequency domain parameter estimation method, which includes a coarse estimation step and a fine estimation step conducted by the discrete polynomial phase transform and AWPE estimator, respectively. Monte–Carlo simulations show that the proposed method can work on the entire identifiable region and that it outperforms the existing state-of-the-art estimators. Its computational complexity is considerably lower than that of the LSU estimator, while its threshold signal-to-noise ratio is a few decibels higher than that of the LSU estimator.

Vortex-induced vibration of a three-dimensional flexible tube is one of the key problems to be considered in many engineering situations. This paper aims to investigate the nonlinear dynamic behaviors and response characteristics of a three-dimensional tube under turbulent flow. The three-dimensional unsteady, viscous, incompressible Navier–Stokes equation and LES turbulence model are solved with the finite volume approach, and the dynamic equilibrium equations are discretized by the finite element theory. A three-dimensional fully coupled numerical model for vortex-induced vibration of flexible tube is proposed. The model realized the fluid–structure interaction with solving the fluid flow and the structure vibration simultaneously. Based on this model, Response regimes, trajectory, phase difference, fluid force coefficient and vortex shedding frequency are obtained. The nonlinear phenomena of lock-in, phase-switch are captured successfully. Meanwhile, the limit cycle, bifurcation of lift coefficient and displacement are analyzed using phase portrait and Poincare section. The results reveal that, a quasi-upper branch occurs in the present fluid-flexible tube coupling system with high mass-damping and low mass ratio. There is no bifurcation of lift coefficient and lateral displacement occurred in the three-dimensional flexible tube submitted to uniform turbulent flow.

Objective To evaluate the beneficial effects of hydroxysafflor yellow A (HSYA) on monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) in rats, and to investigate the main pathophysiological mechanism of HSYA in preventing development of MCT-induced PAH. Methods Four groups (control, control with HSYA treatment, MCT-exposed, and MCT-exposed with HSYA treatment) were evaluated at day 28 following MCT exposure. Haemodynamic measurements, right ventricular hypertrophy, morphometry, inflammatory cytokines and oxidant expression were assessed. Results HSYA significantly reduced haemodynamic changes, right ventricular hypertrophy and morphometric changes induced by exposure to MCT. HYSA also suppressed MCT-induced inflammation and oxidative stress in rat pulmonary tissue. Conclusions Experimental MCT-induced PAH may be reduced by HSYA treatment, and the mechanism may involve suppression of inflammation and oxidative stress.