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As an increasingly recognized optical interferometric technique for nondestructive testing and evaluation, shearography has attracted extensive interest in various industrial applications. However, it suffers from the ignorance of the whole process of dynamic surface deformation and the difficulty in determining the depth-resolved information of inhomogeneities. In this regard, a novel speckle pattern interferometric modality named photothermal radar shearography is proposed. Unlike the differential mode of conventional shearography, the present work focuses on the dynamic surface displacement field channel technique with more comprehensive understanding of the subsurface structural information. With the utilization of frequency modulated photothermal excitation, the depth-distributed information of subsurface structures and inhomogeneities is encoded into the induced dynamic surface deformation. Using Hilbert transform and least-square method solved by discrete cosine transform, the time-domain interference signal of each pixel from the recorded speckle patterns sequence is demodulated and unwrapped to obtain the transient full-field shearographic phase distribution which indicates the dynamic surface deformation. In the meanwhile, incrementally delayed cross-correlation matched filtering allows for the localization of axial energy distribution to generate depth-selective structural display for tomography. This proposed transient-based interferometric methodology thus enables depth-tomographic profiles and three-dimensional visualization of subsurface anomalies for the first time, which significantly improves the superiority and attractiveness of shearography in providing insight into the status, performance and reliability of industry.

Defect classification task is of great benefit to evaluating the safety performance of equipment and providing useful feedback information for discovering production process problems. This paper presents a semisupervised learning (SSL) framework for transient thermography detection to employ the temporal and spatial information encoded into the 3D transient thermal tensor data and provide pixel-level classification results for defect types. The time and frequency domain physical models for transient thermal evolution of different kinds of defects are established to illustrate the theoretical foundation of defects classification based on transient thermography. The semisupervised multiclass Laplacian SVM (MCLSVM) is proposed to enable involving the abundant unlabeled data for enhancing learning performance in practical industrial applications where labeled samples are insufficient and labeling work is costly and laborious. A case study on silicone insulating materials with various types of artificial simulated internal defects validates the stronger generalized ability of the proposed method. This work for the first time proposes a SSL framework in transient thermography-based defect detection studies. It is believed that our proposed method is quite inspired for introducing SSL techniques to transient thermography for preferable performance in practical industrial applications.

Background Esophageal squamous cell carcinoma (ESCC) remains a challenging malignancy with poor prognosis and limited therapeutic methods. However, recent clinical trials of immune checkpoint inhibitors (ICIs) have shown promising results in the treatment of lethal malignancies. The second-line treatment of late-stage ESCC was approved based on the results of KEYNOTE-180, KEYNOTE-181 and ATTRACTION-1, ATTRACTION-3. Combining ICIs with chemotherapy in neoadjuvant therapy may benefit patients with locally advanced, resectable ESCC. Methods A two-arm phase II trial was launched in July 2019 in Henan Cancer Hospital. The primary outcome measure will be completed within 21 months. The pathological complete response (pCR) rate is the primary endpoint, and the secondary endpoints include overall survival (OS), disease-free survival (DFS), the toxicities of the neoadjuvant toripalimab plus chemotherapy, the relationship between combined positivity score (CPS) of specimen and the treatment response, the relationship between lymphocyte infiltration and the treatment response, the progression-free survival (PFS) rate, and adverse events (AEs). It was assumed that the pCR rate of this trial might be 25%. Therefore, the 30 enrolled patients could reject the hypothesis at 75% (α=0.1). Discussion The study will determine the safety and efficacy of neoadjuvant immunochemotherapy for ESCC and provide enough evidence for phase III clinical trials. Trial registration Clinical Trials.gov, NCT03985670, Registered: October 24, 2019, https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0008Z9D&selectaction=Edit&uid=U0002MIY&ts=2&cx=-i71o4q. Registry name: "Teripalimab Plus Chemotherapy in Local Advanced Esophageal Cancer".

Background The accuracy of clinical N staging of esophageal squamous cell carcinoma is suboptimal. As an important station of lymph node metastasis, station C201 (right recurrent laryngeal nerve nodes) has rarely been evaluated alone. We aimed to explore an effective way to evaluate the right recurrent laryngeal nerve nodes in thoracic esophageal squamous cell carcinoma. Methods We retrospectively analyzed 628 thoracic esophageal squamous cell carcinoma patients who underwent radical resection without neoadjuvant therapy from two Chinese cancer centers. The diameter of the short axis of the largest right recurrent laryngeal nerve node (DC201) was measured on contrast-enhanced multi-slice computed tomography (MSCT). Right recurrent laryngeal nerve nodes were examined by postoperative pathologic results. The receiver operating characteristic (ROC) curve was generated to assess the diagnostic capabilities of DC201 to determine the right recurrent laryngeal nerve nodes status. Results ROC curve analysis revealed that the optimal cut-off point of DC201 was 6 mm, with an area under curve (AUC), sensitivity, specificity, and Youden index of 0.896, 71.9%, 88.8%, and 0.607 respectively. When the cut-off point of DC201 was set to 10 mm, sensitivity, specificity and the Youden index were 14.1%, 99.6% and 0.137 respectively. Among 128 patients with right recurrent laryngeal nerve node metastasis, 71 and 108 patients had the largest right recurrent laryngeal nerve node located above the suprasternal notch level and in the tracheoesophageal groove respectively. Conclusions When DC201 ≥6.0 mm instead of DC201 ≥10 mm was used to dictate the right recurrent laryngeal nerve nodes metastasis, contrast-enhanced MSCT could evaluate the status of right recurrent laryngeal nerve nodes with high sensitivity and specificity. The largest right recurrent laryngeal nerve nodes were mainly located in the tracheoesophageal groove and/or above the suprasternal notch.

Background Understanding the genetic basis of cancer risk is a major international endeavor. The emergence of next-generation sequencing (NGS) in late 2000’s has further accelerated the discovery of many cancer susceptibility genes. The use of targeted NGS-based multigene testing panels to provide comprehensive analysis of cancer susceptible genes has proven to be a viable option, with the accurate and robust detection of a wide range of clinically relevant variants in the targeted genes being crucial. Methods We have developed and validated a targeted NGS-based test for hereditary cancer risk assessment using Illumina’s NGS platform by analyzing the protein-coding regions of 35 hereditary cancer genes with a bioinformatics pipeline that utilizes standard practices in the field. This 35-gene hereditary cancer panel is designed to identify germline cancer-causing mutations for 8 different cancers: breast, ovarian, prostate, uterine, colorectal, pancreatic, stomach cancers and melanoma. The panel was validated using well-characterized DNA specimens [NIGMS Human Genetic Cell Repository], where DNA had been extracted using blood of individuals whose genetic variants had been previously characterized by the 1000 Genome Project and the Coriell Catalog. Results The 35-gene hereditary cancer panel shows high sensitivity (99.9%) and specificity (100%) across 4820 variants including single nucleotide variants (SNVs) and small insertions and deletions (indel; up to 25 bp). The reproducibility and repeatability are 99.8 and 100%, respectively. Conclusions The use of targeted NGS-based multigene testing panels to provide comprehensive analysis of cancer susceptible genes has been considered a viable option. In the present study, we developed and validated a 35-gene panel for testing 8 common cancers using next-generation sequencing (NGS). The performance of our hereditary cancer panel is assessed across a board range of variants in the 35 genes to support clinical use.

Human actions are often captured by multiple cameras (or sensors) to overcome the significant variations in viewpoints, background clutter, object speed, and motion patterns in video surveillance, and action recognition systems often benefit from fusing multiple types of cameras (sensors). Therefore, adaptive fusion of the information from multiple domains is mandatory for multiview human action recognition. Two widely applied fusion schemes are feature-level fusion and score-level fusion. We point out that limitations still exist and there is tremendous room for improvement, including the separate computation of feature fusion and action recognition, or the fixed weights for each action and each camera. However, previous fusion methods cannot accomplish them. In this paper, inspired by nature, the above limitations are addressed for multiview action recognition by developing a novel adaptive fusion and category-level dictionary learning model (abbreviated to AFCDL). It can jointly learn the adaptive weight for each camera and optimize the reconstruction of samples toward the action recognition task. To induce the dictionary learning and the reconstruction of query set (or test samples), the induced set for each category is built, and the corresponding induced regularization term is designed for the objective function. Extensive experiments on four public multiview action benchmarks show that AFCDL can significantly outperforms the state-of-the-art methods with 3% to 10% improvement in recognition accuracy.

Bolted flange joints are indispensable components in process industries due to the good sealing, assemble and disassemble capacities. Generally, the flange rigidity characterized by the rotation angle is a key index to evaluate the sealing tightness of flange joints. However, the rotation angle of flange is usually too small (less than 1°) to monitor during the assemble and operation stages. Accordingly, a novel flexure magnifying mechanism is designed to measure the small rotation angle of flange joints under internal pressure and external bending moment. The magnification factor and calculation approach of the flexure amplification mechanism are deduced and verified by experimental data and finite element simulation. Results indicate that the proposed measuring apparatus has good performance to monitor the maximum rotation angle. It is of great interest that the measured location of the maximum rotation angle is in good agreement with that in the experiment, and the average error is 7.3%, which is acceptable for practical application. Additionally, the leakage rate at the top of flange joints slowly and almost linearly increases with the increment of external bending moment ascribing to the decrease the gasket stress near the top of flange joints.

Air-coupled ultrasonic testing (ACUT) has many advantages over other non-destructive testing (NDT) methods, among which the most outstanding one is completely no contamination of the sample. Therefore, it can be applied in various conditions where liquid coupling media is not suitable. With the development of ACUT, it is found that mismatch between air and solid is one of the biggest difficulties confronting researchers, and electromechanical film (EMFi) with low acoustic impedance can be a promising solution when used as vibration element in air-coupled ultrasonic transducers. In this contribution, one planar and two spherically focused EMFi-based transducers were designed, fabricated, and their properties were characterized through frequency response test as well as focal length test. Then imaging experiments of PMMA samples were performed to demonstrate the possibility and feasibility of EMFi transducers in non-contact testing.

This paper presents the study of creep-fatigue interaction damage and creep rupture limit for 9–12% Cr steam turbine rotor under coupled cyclic thermal-mechanical loadings that alter in phase and out of phase. The investigation is implemented using the Linear Matching Method (LMM) and based on the newly developed creep-fatigue and creep rupture evaluation procedures. Latest experimental creep data of FB2 which belongs to 9–12% Cr heat-resistant steel family is employed to calculate creep-related damage and creep rupture bearing capacity of steam turbine rotor. Various factors that affect creep and fatigue damage of steam turbine rotor are analyzed and discussed, including dwell period and rotating speed of rotor. From the parametric studies, the damage locations and cycles to failure induced by creep and fatigue mechanism are presented respectively. Moreover, through creep rupture analyses for varying desired fracture time, the novel creep rupture curves under multi-type double-cyclic-loading conditions are given and further compared with cyclic plasticity failure curve. These surrogate-model analyses offer a deep understanding of structural responses of steam turbine rotor under long-term high temperature operation and provide critical loading conditions to be referenced for smooth running.

In the quest to realize a scalable quantum network, semiconductor quantum dots (QDs) offer distinct advantages including high single-photon efficiency and indistinguishability, high repetition rate (tens of GHz with Purcell enhancement), interconnectivity with spin qubits, and a scalable on-chip platform. However, in the past two decades, the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50$\%$ and the distances were limited from a few meters to kilometers. Here, we report quantum interference between two single photons from independent QDs separated by 302 km optical fiber. The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band. The observed interference visibility is 0.67$\pm$0.02 (0.93$\pm$0.04) without (with) temporal filtering. Feasible improvements can further extend the distance to 600 km. Our work represents a key step to long-distance solid-state quantum networks., 14 pages, 5 figures

In this paper, the distinction between material ratchetting and structural ratchetting is clarified, and the concept of constant life diagram is extended to depict low cycle fatigue life boundary in structural design. To provide a novel one-stop solution for structural fatigue and ratchetting problems, a Unified Procedure for Fatigue and Ratchet Analysis (UPFRA) has been proposed. The UPFRA has been successfully applied to two different engineering structures considering complex geometry and temperature-dependent material properties. By comparing the results with ABAQUS step-by-step inelastic analysis, the UPFRA has been verified to be a robust engineering tool with great accuracy, usability, and efficiency.

Multifunctional sensing devices with high flexibility, high sensitivity, and scalable fabrication are inevitable components of Internet of Things (IoT) for human-machine interfaces, structural health monitoring, and soft robots. Herein, high-performance flexible sensor arrays using carboxymethylcellulose (CMC) and its composite were developed for mechanical and thermal stimuli detection by laser direct writing. CMC contains abundant carbon precursors for strain-sensitive laser-carbonized CMC (LC-CMC), while the incorporation of graphene oxide (GO) into CMC leads to the formation of thermal-sensitive laser-carbonized GO/CMC (LC-GO/CMC). The LC-CMC-based strain sensor delivers gauge factors of 487.7 (strain8.5%) and 8557 (8.5%strain14%), with long-term stability over 10 000 cycles. With 0.2 wt % GO, the LC-GO/CMC-based device provides a temperature coefficient of resistance of -0.289% °C

Notched structures widely exist in steam turbine components in fossil power plant, e.g., the groove of the rotor, etc. Previous studies indicate that creep failures occur at the groove of the rotor or the adjacent regions. Thus, it is essential to study the creep failure behavior of the notched structures for the safe operation of the system. In this work, creep tests of the simulated steam turbine component have been conducted at the temperature of 605 °C, and the creep-damage constitutive equation is used to track the evolution behavior of creep strain and damage of this component. The influence of structural and loading configurations on creep failure behavior of the component is discussed. Results demonstrate that the shearing failure at the contact area between the blade root and the rotor is observed for the tested component, while the cracking at the groove of the rotor is not found. Creep-damage constitutive equation employed in this work could provide an adequate solution of the simulated component. Parametric studies indicate that creep crack initiation and creep failure of the simulated components may occur at the contact region (i.e., between the blade root and the rotor) and the groove of the rotor, which is closely related to structural and loading configurations of the components.

In the present paper, a modified fatigue life model is proposed based on stress field intensity (SFI) approach, where the average weight function is introduced as the denominator of the traditional model and a modified definition of the fatigue zone is given using the concept of characteristic stress. Combined with finite element analysis, the fatigue life predictions of a central hole specimen from the literature and the notched plate specimens/a simulated engineering component conducted by the authors are carried out by the new model. Results indicate that the predicted lives are in good agreement with the experimental results and the modified stress field intensity approach is convenient for practical use. Keywords: Fatigue, Life prediction, Stress field intensity, Multi-axial stress state

Background Neoadjuvant therapy plus oesophagectomy has been accepted as the standard treatment for patients with potentially curable locally advanced oesophageal cancer. No completed randomized controlled trial (RCT) has directly compared neoadjuvant chemotherapy and neoadjuvant chemoradiation in patients with oesophageal squamous cell carcinoma (ESCC). The aim of the current RCT is to investigate the impact of neoadjuvant chemotherapy plus surgery and neoadjuvant chemoradiotherapy plus surgery on overall survival for patients with resectable locally advanced ESCC. Methods This open label, single-centre, phase III RCT randomized patients (cT2-T4aN + M0 and cT3-4aN0M0) in a 1:1 fashion to receive either the CROSS regimen (paclitaxel 50 mg/m2; carboplatin (area under the curve = 2), q1w, 5 cycles; and concurrent radiotherapy, 41.4 Gy/23 F, over 5 weeks) or neoadjuvant chemotherapy (paclitaxel 175 mg/m2; and cisplatin 75 mg/m2, q21d, 2 cycles). Assuming a 12% 5-year overall survival difference in favour of the CROSS regimen, 80% power with a two-sided alpha level of 0.05 and a 5% dropout each year for an estimated 3 years enrolment, the power calculation requires 456 patients to be recruited (228 in each group). The primary endpoint is 5-year overall survival, with a minimum 5-year follow-up. The secondary endpoints include 5-year disease-free survival, toxicity, pathological complete response rate, postoperative complications, postoperative mortality and quality of life. A biobank of pre-treatment and resected tumour tissue will be built for translational research in the future. Discussion This RCT directly compares a neoadjuvant chemotherapy regimen with a standard CROSS regimen in terms of overall survival for patients with locally advanced ESCC. The results of this RCT will provide an answer for the controversy regarding the survival benefits between the two treatment strategies. Trial registration NCT04138212, date of registration: October 24, 2019.

High-performance flexible pressure sensors are highly demanded in wearable electronics for various applications. Herein, a flexible pressure sensor was designed using carbon nanotube (CNT)-wrapped polydimethylsiloxane (PDMS) microspheres (MSs). Compared to the device with flat configuration, the sensor with CNT-wrapped PDMS MSs has an enhanced sensitivity of −0.111 kPa−1, with a lowest detectable pressure of 0.02 kPa, response time approximately 0.1 s, as well as a long-term dynamic stability more than 10,000 cycles. The sensors with CNT-wrapped PDMS MSs show the potential to be integrated into wearable electronics for real-timely monitoring the physiological signals.

In this study, a laser-microengineered wearable pressure sensor was developed. The sensor offers a sensing range from 0.005 to 50.0 kPa, a sensitivity approximately -0.107 kPa−1, and high durability (>10,000 cycles). The finite element simulation shows that the external forces are amplified and transmitted by the laser-engineered microstructures, contributing to the enhanced sensitivity of the device. The laser-microengineered sensors are promising to be applied in the electronic skin for detecting various external stimuli.

High performance antireflection (AR) coating is essential to the conversion efficiency ( η ) enhancement of PV devices. In this work, an AR structure based on syringe-shaped ZnO nanorod arrays was obtained by two-step aqueous solution method. The morphology of the syringe-shaped nanorods can be easily regulated by changing experiment parameters of each growth step. With this structure, the surface reflection of multi-crystalline silicon solar cell was effectively suppressed below 5% over a wide range of wavelengths. Meanwhile, the short-circuit current density and η of the solar cell were increased up to 34.98 mA/cm 2 and 17.16%, enhancements of ~37% and ~41% from those on bare surface. These results are attributed to the ultrasharp tips on the tops of nanorods can make the effective refractive index gradual increasing from air to the bottom of ZnO nanorods, which leads to enhanced light trapping on the solar surface.

The combination of air-coupled ultrasonic testing (ACUT) and ultrasonic Lamb wave is featured with long-distance propagation and high sensitivity to discontinuities, which is a promising method for rapid and accurate inspection of plate-like materials and lightweighted structures. However, dispersive nature of Lamb wave, signal attenuation plus inevitable noises would lead to low signal-to-noise ratio (SNR). To address this problem, phase coded excitation and pulse compression technique are proposed in this paper to achieve higher SNR by over 10 dB in received signals. 13-bit and 1-carrier-period Barker code is employed as both main lobe peak and Peak Side-lobe Level (PSL) are relatively high. It is demonstrated that A0 mode Lamb wave has good localization ability for defects based on these SNR-enhanced signals. Furthermore, Damage Index (DI) and modified Reconstruction Algorithm for the Probabilistic Inspection of Damage (RAPID) are applied to realize ultrasonic imaging based defect evaluation. Results show that the imaging results agree well with the actual artificial defects in terms of size and shape. Lamb-wave-based air-coupled ultrasonic testing, combined with DI and ultrasonic imaging algorithm, could be a potential way in the NDT of lightweighted structures.

Non-collinear wave mixing recently has been proposed to detect and localize micro-damage in materials. It is proved sensitive to the interaction angle α of the incident waves. In this work, the relationship between the acoustic nonlinearity parameter χ and the α is studied by numerical simulations and experimental measurements based on the nonlinear interaction of two shear waves. A single-peak change in the normalized acoustic nonlinearity parameter χ ′ of the mixing wave versus the incident angle is observed from numerical simulations and then is verified by experiments. The results show a -6 dB decrease of χ ′ corresponds to a deviation of about 4° in the incident angle. Meanwhile, the detection and localization of plastic deformation is also conducted on an aluminum alloy based on the scanning of non-collinear wave mixing, in which the distribution of the acoustic nonlinearity is similar to that of the plastic strain.

There are many power plant components operating at elevated temperatures, subjected to the combined mechanical and thermal loading conditions. The shakedown problem is an important topic for the safe operation of these high temperature components. This work mainly addresses the shakedown analysis of the pressure pipeline with an oblique nozzle at elevated temperatures using the Linear Matching Method (LMM). Parametric studies on main factors affecting the shakedown boundary are conducted. The results indicate that the LMM analysis tool is adequate to identify the shakedown boundary of the component, verified by the ABAQUS step-by-step analysis. Regarding to the angle of the oblique nozzle, the ratchet limit is enhanced with the increasing angle, while the reverse plasticity limit increases until a maximum value is reached, and then presents a certain decrease. This implies that designers should make some compromises on the limit load and reverse plasticity limit when determining an economic angel of the oblique nozzle. In addition, parametric studies demonstrate that the diameter-to-thickness ratios of the oblique nozzle and the main pipe have a remarkable effect on the reverse plasticity and ratchet limit of the component.

This paper presents physical and experimental studies of the static component of Lamb waves (SCLWs) induced by partially closed cracks. The generation mechanism of SCLWs was investigated according to the nonlinear interaction between Lamb waves and partially closed cracks with various lengths, widths and orientation angles in finite element simulations. It was found that the SCLWs are more sensitive to the crack length, width and orientation angle as compared with the second harmonic Lamb waves. Fatigue crack evolution was further experimentally detected in aluminum alloy plates using SCLWs. Consistent with the simulation results, the acoustic nonlinearity parameter increases monotonically with increasing fatigue crack length. We show that the SCLWs are sensitive to partially closed cracks and can serve as a potential method to quantitatively evaluate the evolution of partially closed crack in metal plates. The findings of this study pave the way for the detection of partially closed crack using SCLWs in the field of nondestructive evaluation and structural health monitoring.

Limit load is an important parameter in structural integrity assessment of cracked components. In this work, the limit loads of an actual dissimilar metal welded joint (DMWJ) for joining safe end to pipe-nozzle of a reactor pressure vessel have been investigated based on extensive three-dimensional finite element analyses. The effects of a wide range of crack sizes and locations on limit loads have been analyzed. The results show that for shorter and shallower cracks, the limit loads are mainly determined by global plastic yielding of safe end material with the lowest yield strength, and the crack sizes have nearly no effect on them. For longer and deeper cracks, the limit loads are mainly determined by general yielding of the ligament area ahead of a crack. With increasing crack length or depth, the limit load decreases. With moving crack locations from the pipe-nozzle through buttering and weld metal to safe end, the limit load decreases. The normalized limit load solutions for the DMWJ are given.

Physics-informed neural network has strong generalization ability for small dataset, due to the inclusion of underlying physical knowledge. Two strategies are enforced to incorporate physics constraints to a deep neural network in this work. One is to obtain extended features through physics-informed feature engineering, and the other is to incorporate physics-informed loss function into deep neural network as constraints. Conventional machine learning models, deep neural network and physics-informed neural network are applied to predict creep-fatigue life of 316 stainless steel. Results show that physics-informed neural network presents better prediction accuracy than deep neural network and conventional machine learning models.

In this work, the fracture prediction method based on two-parameter J-Ad* (J-integral and a new load-independent unified constraint parameter Ad*) with considering both in-plane and out-of-plane constraints has been investigated for semi-elliptical surface cracks in plates under bending. The crack initiation locations and fracture initiation loads for different crack sizes have been comparatively predicted and analyzed by using the two-parameter J-Ad* and the conventional single-parameter J-integral. The predicted results based on the two-parameter J-Ad* approach have been verified by finite element simulation based on the GTN (Gurson–Tvergaard–Needleman) micromechanics model. The results indicate that the two-parameter approach can provide more accurate predictions. The conventional single parameter approach can produce conservative (for shorter and shallower cracks) or non-conservative (for longer and deeper cracks) results. It is recommended that in the application of the two-parameter approach, for obtaining the best prediction accuracy, the two parameters should be calculated at the crack initiation location.

To improve the shortcomings of peak over threshold (POT) extrapolation method and reflect the diversity and dynamics of road conditions, an improved POT extrapolation method to reconstruct the load sequence in the middle of threshold is proposed. Based on the improved extrapolated load, the distribution characteristics of mean and amplitude are analyzed and the two-dimensional joint probability distribution is established. To discuss the influence of low load strengthening characteristics on fatigue life under random load, based on the two-dimensional joint probability distribution, the theory of low load strengthening is introduced in compiling load spectrum. The fatigue life predicted by 8-level load spectrum and 10-level strengthened load spectrum are compared with the test results, respectively. Which verifies the effectiveness and accuracy of life prediction based on improved POT extrapolation and low load strengthening under random load.

Fatigue life prediction of engineering components is essential for safe operation of mechanical systems. Energy based models have attracted much attention due to the combined considerations of stress and strain behavior, especially in low cycle fatigue regime. In this work, a new plastic strain energy density (PSED) based life prediction model for notched components subjected to cyclic loading is proposed, in which cyclic stress-strain responses under stress- and strain-controlled modes are both introduced. Experimental tests on 304 stainless steel smooth and notched plate/bar components are conducted for calibrations and verifications. The prediction capability of the proposed model is verified by experimental results.

In practical engineering, the measured differential settlement can be gained by monitoring the points beneath the tank wall and it can induce the buckling of the tank even with a small amplitude. In general, Fourier series is adopted to decompose the measured differential settlement into harmonic components with various wave numbers. However, the question that which harmonic components should be considered is a main challenge for buckling investigations of the tank under measured differential settlement. In this work, a recommendation for harmonic components needed for consideration was proposed when decomposing measured differential settlement into harmonic components in terms of Fourier series. Moreover, the effects of the harmonic components considered on buckling behavior of floating roof tanks and conical roof tanks were discussed. The results presented that three monitoring points can make a first estimate of ovalling and the harmonic components considered should be smaller than and equal to [ N ]/3 ([] is the rounding function and N is the number of the monitoring points). The introduction of the harmonic component with a high wave number can cause the change of the buckling modes of the tanks under differential settlement, including floating roof tanks and conical roof tanks. Meanwhile, it can decrease the buckling strength of the floating roof tank more significantly than that of the conical roof tank.

Axially push-pull cyclic tests of a low strength rotor steel were performed up to the very high cycle fatigue regime at ambient environment under ultrasonic frequency. Fatigue tests were interrupted at selected number of cycles for surface morphology observation and roughness measurement with the help of a 3D surface measurement system (Alicona InfiniteFocusSL). The fatigue extrusions and slip band developed on the specimen surface were recorded. The influence of stress level on the number and morphology of slip band was discussed. The surface roughness of fatigue specimens was found to be increased with the increasing of fatigue cycles. The fatigued specimens were finally cracked from surface or interior micro-defects after observation of fracture surface by scanning electron microscopy. The internal damage behavior consists of crack initiation and early propagation from micro-defect, crack growth within the fish eye, and fast crack growth. It is observed that there exists a competition between surface and internal fatigue damage in the very high cycle fatigue regime, i.e., surface damage is gradually developed with the increasing of fatigue cycles, while the critical interior micro-defect can be dominant for fatigue cracking.

Dielectric elastomers (DEs) are the polymers capable of inducing deformation under electrical stimulation. When subject to a voltage across its thickness, the material reduces in thickness and expands in area. This paper presents a new method to analyze deformation and stress distribution response of the dielectric elastomer actuator (DEA) model under different applied voltage. An equal-biaxial pre-strained circular actuator model was built. The Yeoh strain energy potential and the collocation method are used for describing the large strain actuation response and stress distribution. The study in this paper has shown that: the stress and the stretch distributions in the passive region of the DE actuator depend on the radial distance from the center at the calculation point of the passive region and the magnitude of the applied voltage; with the same excitation applied voltage, we can get a larger deformation actuation by choosing an appropriate pre-stretch ratio; the influence of the non-ideal material has seriously affected the actual deformation of the DE actuators. This analytical model has a reference potential for the design optimization of high performance DEA systems and the model-based control of the DEA robot.

Raising the operating temperature to increase electricity production in the nuclear power industry is a practical solution in the aspect of efficiency and emissions reduction. However, regarding structural integrity, such high temperature has a significant impact on the life of nuclear power plant components. The superheater tube plate is one of the most critical parts under exposures of very high temperature in the boiler system of the power plant. This study investigates creep-cyclic plasticity behaviour of a superheater outlet tube plate under extremely sophisticated thermo-mechanical loading and evaluates creep-fatigue damage endurance, using the modified LMM eDSCA. Temperature-dependent material properties are employed to calculate more practicable structural behaviour and lifetime prediction. The results clearly present the criticality of the effects of non-isothermal loading and multiple dwells on the structural integrity of the tube plate. Also, this study clarifies critical factors that cause dominant damage to the tube plate by providing total damages using various damage assessment models, of which results show the trend of the conservativeness of each damage assessment model, compared to experiment result.

Micro-structured pressure sensors with broad pressure sensing range, high sensitivity and rapid response speeds are highly desired for epidermal electronic skin. The widely used methods to fabricate micro-structured pressure sensors are lithography and biomaterial-replicating, which are either complex in preparation procedure or uncontrollable in micro-structure morphology. In this work, laser micro-structured wearable pressure sensors with high-performance are developed for epidermal electronic skin. Laser micro-engineering, with scalability, high-efficiency, and controllability, is employed to prepare a series of micro-structures on elastomers for modulating and enhancing the sensitivity of the sensors. The device with micro-domes owns a sensitivity of -1.82 kPa-1, which is approximately 17 times better than the one based on long micro-ridges. Due to the reduced viscous properties of the elastomers by laser micro-engineering, the sensor based on micro-domes demonstrates rapid response/relaxation speeds of 0.036 and 0.052 s, respectively, and a detection limit of 0.001 kPa. Additionally, the device has a good durability (6,000 cycles) with a repeatability deviation of 1.44%, confirming its stability. Combined with near field communication technology, the sensor has been investigated as epidermal electronic skin for health monitoring.

Deep learning is a particular kind of machine learning, which achieves great power and flexibility by a nested hierarchy of concepts. A general life prediction method for components under creep, fatigue and creep-fatigue conditions is proposed. Fatigue, creep and creep-fatigue data of a typical austenitic stainless steel (i.e., 316) are integrated. Conventional machine learning models (e.g., support vector machine, random forest, Gaussian process regression, shallow neural network) and deep learning model (e.g., deep neural network) are applied for life predictions. Results show that deep learning model exhibits better prediction accuracy and generalization ability than conventional machine learning model.

In this paper, the Bree diagram is extended to consider the progressive buckling failure and a direct approach for structural progressive buckling design considering ratcheting deformation is developed. Firstly, the progressive buckling mechanism of structures subjected to the combination of constant and cyclic loadings is sufficiently discussed. Then, a two-stage direct approach is developed based on the Linear Matching Method and nonlinear buckling analysis, which can generate progressive buckling design curves in the extended Bree diagram. To illustrate the application of the direct approach to progressive buckling design, a cylindrical shell model with an opening is provided as a numerical example. Furthermore, geometrical effects, e.g. the opening size and the shell thickness, on the progressive buckling limit are investigated. Formulas for progressive buckling design of cylindrical shells with various geometrical parameters are derived by fitting curves. Compared with other methods, the direct approach could predict accurate progressive buckling load.

Axially loaded push-pull tests of a low strength Cr−Ni−Mo−V steel welds using cross-weld specimens with different sizes were conducted up to the very high cycle fatigue regime under ultrasonic frequency. Results showed that smaller samples had higher fatigue strength with interior cracking predominant at the weld metal. Fine granular area characteristic of polycrystalline features close to micro-defects was indicative of higher fatigue strength with implications of cyclic hardening, and was related to localization of plastic deformation. A physical criterion for formation of fine granular area was proposed as the ratio of accumulation to release rates of cyclic plastic energy was higher than one. It was found that the size effect on fatigue strength of the low strength welds was coupled with frequency effect, an issue that both current deterministic and probabilistic approaches were unable to rationalize, was actually dependent on tensile strength as well as extrinsic factors such as cyclic hardening and micro-defect distribution.

Flexible sensor matrix with functionalities for multiple stimuli detection has prospect applications in structural health monitoring, internet of things, soft robotics, etc. However, fabrication of the sensor matrix in a simple, highly efficient, and scalable manner is still a challenge. To address this, a femtosecond (fs) laser micro-fabrication method is developed to fabricate a sensor matrix integrated with temperature and pressure sensor arrays. Through the programmable control of laser irradiation manner including scanning velocity, laser power, and laser irradiation intervals, the temperature and pressure sensor arrays were fabricated by the fs laser. The temperature sensors have a temperature coefficient of resistance of −0.52%/°C, higher than commercial temperature sensor based on platinum. The pressure sensors deliver a sensitivity of −2.01 kPa−1, a response speed of 0.030 s, a detection window from 0.001 to 80 kPa, and high mechanical stability. When the fs laser micro-fabricated pressure and temperature sensor arrays are integrated together, the sensor matrix could simultaneously detect external mechanical and thermal stimuli.

To address accurately creep responses of notched components under displacement-controlled condition, a time-dependent stress and strain estimation method (i.e. modified Neuber’s method) for notched components under displacement-controlled condition has been proposed, with the deformation characteristics at the far field (i.e. the uniform part) of the component considered. The applicability of the proposed method to notched plates with different geometrical configurations is verified, providing more accurate stress and strain predictions of the notched component than the general Neuber’s rule.

Background Neoadjuvant chemotherapy (NAC) and neoadjuvant chemoradiotherapy (NACR) are the standard treatments for esophageal squamous cell carcinoma (ESCC). However, the 5-year overall survival (OS) rate is still far from satisfactory. In recent years, immune checkpoint inhibitors (ICIs) have shown promising results in the treatment of ESCC. More than 20 phase II clinical trials have been launched to explore combinations of ICIs in the neoadjuvant setting for ESCC. Based on our phase II clinical trial, a two-arm phase III trial was launched in Henan Cancer Hospital. ICIs combined with NAC may usher in a new era and may benefit locally advanced, resectable ESCC patients. Methods A two-arm phase III trial was launched in April 2020 in Henan Cancer Hospital. Patient recruitment will be completed within 18 months. The primary endpoint is event-free survival (EFS). The secondary endpoints include pathologic complete response (pCR), disease-free survival (DFS) rate, overall response rate (ORR), R0 resection rate, major pathologic response (MPR), adverse events (AEs), complication rate and quality of life (QOL). A biobank of pretreatment, resected tumor tissue and paired blood samples will be built for translational research in the future. Discussion This RCT directly compares NAC with neoadjuvant toripalimab plus chemotherapy in terms of EFS for locally advanced ESCC. The results may usher in a new era of resectable ESCC treatment. Trial registration NCT04280822 (https://www.clinicaltrials.gov/ct2/show/NCT04280822). Registered title: "A Phase III, Randomized Controlled Study of Neo-adjuvant Toripalimab (JS001) in Combination with Chemotherapy versus Neo-adjuvant Chemotherapy for Resectable Esophageal Squamous Cell Carcinoma". Version 1.0/Nov. 21, 2019.

The buckling design criteria of elliptical heads in ASME VIII-1, ASME NH, and RCC-MRx are reviewed and compared. Accordingly, an external pressure chart (EPC) based buckling design approach is developed for elliptical heads in the creep range. Results indicate that for instantaneous buckling design, RCC-MRx predicts higher allowable pressure compared with ASME NH, which is ascribed to the smaller design factor. The proposed method produces a similar result with that given by ASME VIII-1. By contrast, the proposed method leads to a reasonably conservative result with the factor n of 0.03 for the creep buckling design. While the simplified method in RCC-MRx provides an over-conservative solution.

A Direct Steady Cycle Analysis (DSCA) method within the Linear Matching Method (LMM) framework is proposed to assess the fatigue life accurately and efficiently for components with arbitrary geometries and cyclic loads. Temperature-dependent stress-strain relationships considering the strain hardening described by the Ramberg-Osgood (RO) formula are discussed and compared with those results obtained by the Elastic-Perfectly Plastic (EPP) model. Additionally, a Reversed Plasticity Domain Method (RPDM) based on the shakedown and ratchet limit analysis method and the DSCA approach within the LMM framework (LMM DSCA) is recommended to design cyclic load levels of Low Cycle Fatigue (LCF) experiments with predefined fatigue life ranges. Based on the ASME code, the material properties at the mean temperature through the wall thickness are used to assess the fatigue life. However, the proposed method can estimate the fatigue life considering the temperature-dependent material properties with strain hardening effect according to the temperature distribution, which is closer to the true operating condition.

The impact of notch is one of the major problems that remain to be solved when predicting fatigue life. The zone of notch root has serious stress concentration condition. Stress field intensity (SFI) approach is an advanced volumetric method for fatigue life prediction. This paper makes further research and puts forward a modified approach based on it. A numerical example and an engineering notched specimen are analyzed by finite element approach to prove the validity of new approach. The modified SFI approach shows good fatigue life prediction and is convenient for practical use.

Mask-free formation of patterned active materials on elastomers without involving complicate processes is a grand challenge in developing E-skins. Here, a laser direct writing technique is developed to fabricate SiC-based strain sensor arrays for E-skins.

Stretchable strain sensors with high sensitivity or gauge factor (GF), large stretchability, and long-term durability are highly demanded in human motion detection, artificial intelligence, and electronic skins. Nevertheless, to develop high-sensitive sensors without sacrificing the stretchability cannot be realized using simple device configurations. In this work, an acid-interface engineering (AIE) method was proposed to develop a stretchable strain sensor with high GF and large stretchability. The AIE generates a layer of SiO x at the interface between the carbon nanotube (CNT) film and Ecoflex, playing a key role in enhancing the sensor's GF. Compared to devices without AIE (GF = 2.4), the ones with AIE are significantly improved. At an AIE time of 10 min, the GF up to 1665.9 is achieved without sacrificing the stretchability (>100%). The AIE-generated cracks are found to modulate the electrical behaviors and enhance the GFs of sensors with AIE through the crack-induced rapid reduction in the electrical conduction pathway, which is manipulated by the CNTs bridging over the cracks. The device with AIE proves its high mechanical durability through a cycling test (>10 000 cycles) at a high strain up to ∼80%, further paving its practical applications in various human motion detections.

Nonlinear guided waves mixing technology gains an ascending attention in nondestructive testing field as its capability to resist measuring device nonlinearity. However, recent studies in this topic mainly focus on theoretical analysis. In this article, Lamb waves counter-propagating mixing is explored using a numerical simulation method. Two fundamental Lamb modes(S0 at 1.13 and S0 at 1.82MHz) are selected based on the internal resonance criteria. The mixing wave mode is S1 at 2.95 MHz. A local microdefect is simulated by employing hyperelastic material properties in some regions. Results show that there is a positive correlation of nonlinear acoustic parameter and material degradation level in mixing zone and there is no correlation between nonlinear acoustic parameter and material degradation in fundamental waves propagating routine, which indicate that mixing signal is sensitive to local material defects.

A plate under cyclic loading, containing two coplanar surface flaws with both identical and dissimilar sizes, is considered in the present study. By conducting detailed step-by-step finite element analyses, the conservatism contained in different combination rules for multiple coplanar flaws provided by fitness-for-service codes (ASME, BS7910, API579 and GB/T19624) have been quantitatively assessed for the fatigue failure mode. The findings show that the re-characterization guideline provided by ASME and BS7910 may cause non-conservative estimations when two crack sizes are similar, whereas API579 and GB/T19624 lead to excessively pessimistic predictions for almost all the cases. Based on the fatigue crack growth life, we suggest a new combination rule and conclude that it always yields a reasonable estimation with necessary conservatism, for various initial crack depths, material constants and relative sizes of two cracks.

We report a MAPbI3-based self-powered photodetector (SPPD). It has a dual sensing mechanism that relies on the joint properties of a photoelectric effect and a triboelectric effect of the perovskite material. Both the photoconductivity and the surface triboelectric density of the MAPbI3-based composite thin film are significantly altered upon solar illumination, which results in considerable reduction of the output voltage. The SPPD exhibits excellent responsivity (7.5 V W(-1)), rapid response time (80 ms), great repeatability, and broad detection range that extends from UV to visible regions. This work presents a route to designing high-performance self-powered photodetectors from the aspect of materials.

An idealized tri-material assumption is established to describe the constitutive relationship of mismatched welded joints by considering the influence of heat affected zone (HAZ). The fracture parameters and C * are estimated for mismatched welded joints with HAZ cracks by finite element analysis with ABAQUS. A middle crack tension (M(T)) specimen is utilized in the analysis for different material properties and geometries of the weldment. The influence of mechanical property and geometry on the fracture parameters J and C * of the specimen is discussed for the welded joints with HAZ crack. The results suggest that the HAZ property is a significant factor in the estimation of J and C * for the mismatched welded joint with HAZ crack.