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The microstructure of particle-reinforced metal matrix composites (PMMCs) and its parameters (such as particle size distribution, particle volume fraction, particle shape, etc.) have a great influence on the elastic modulus of PMMC. In this paper, the intermingled fractal units (IFU) model was used to describe the microstructure of PMMCs. Based on the spring series-parallel connection model, an analytical method of predicting the elastic modulus was proposed, and the area fraction, size distribution, and interface of the reinforced particles were taken into consideration. The tensile experiments performed on three groups of the SiC/Al composite specimens with different microstructure (namely, of different particle shape, size, and volume fraction of reinforcing particles) were conducted to evaluate the elastic modulus and strength properties. The comparison between the predicted and experimental results has proved the applicability and effectiveness of the method proposed in this paper.

We propose an improved adaptive Type-II progressive censoring scheme, which can effectively guarantee that the test time will not exceed a certain threshold time. And the adaptive Type-II progressive censoring scheme is its special case. Based on this censoring scheme, the parameters, reliability and hazard functions of Burr-XII distribution were estimated. Firstly, we obtain the estimators of parameters, reliability and hazard functions by using the maximum likelihood estimation method. Subsequently, the approximate confidence intervals of the above statistics are obtained by using the asymptotic normality properties of maximum likelihood estimation and the Bootstrap method. Furthermore, based on the square loss function and the LINEX loss function, the point estimators and approximate confidence intervals of parameters are derived by using Bayesian method. A real data is used to illustrate and validate the advantages of the proposed improved adaptive Type-II progressive censoring scheme. Finally, the Monte Carlo simulations are performed to compare the behavior of improved adaptive Type-II progressive censoring scheme with adaptive Type-II progressive censoring scheme for different evaluation methods.

In order to reduce the vibration fatigue test time of aeronautical engineering components made of aluminum-alloy, a random vibration fatigue acceleration model under narrow-band excitation is proposed in this paper. A three-parameter S- N curve is adopted to consider the effect of small stress response, while a scale factor α is introduced to consider the effect of stress distribution. The random vibration fatigue tests of 2024-T3 and 7075-T6 aluminum-alloy specimens with elliptical holes are performed, where the vibration fatigue lives of load spectra with the same bandwidth and different excitation acceleration levels are obtained. The test results show that the proposed model is in sound agreement with the test results.

The hygroscopic behavior of vinylester resin and high strength glass fiber reinforced vinylester resin composites were examined here, including weight change and the resulting degradation of mechanical properties. The prepared resin and composites specimens were immersed in deionized water and artificial seawater with an applied temperature of 70 °C, and then the specimens were weighed at specified time intervals in combination with the observation of surface morphologies using a scanning electron microscope. Identification of variations of functional groups was also carried out using Fourier-transform infrared spectroscopy. Meanwhile, the mechanical properties for resin and the composite specimens were tested periodically. The observations on surficial morphologies and the test on weight change display that the vinylester resin hydrolyzes seriously after immersion in deionized water, and that the embedment of glass fiber effectively inhibits the moisture absorption and hydrolysis for resin matrix in composites. The results from the mechanical properties test reveal that the tensile strength of pure resin decreases by 35.3% after 7 days’ immersion and keeps small fluctuation in the sequent immersion duration. However, the compressive strength of pure resin consistently dwells at 100 ± 2 MPa during immersion. After immersion for 90 days, the tensile strength decreases by 28.5% and 38.4%, the compressive strength reduces by 7.2% and 16.6%, and the in-plane shear strength reduces by 16.6% and 15.2% for the composites immersed into deionized water and artificial seawater, respectively. The main highlights of this paper are that it provides a more comprehensive mechanical properties test in combination with the microscopic characterization on a matrix and its composites to reveal the aging behavior of composites under a hygroscopic environment.

Background Cancer patients are at a high risk of being infected with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), and are more likely to develop severe illness and have higher mortality once infected. In the COVID‐19 pandemic, it is urgent to understand the effects of antitumor therapy on the prognosis of patients with COVID‐19. Methods A systematic literature search was conducted in PubMed, Cochrane Library, Embase, MedRxiv, and Chinese National Knowledge Infrastructure (CNKI) until 21 June 2020. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were evaluated using a random effects model to analyze the effects of antitumor therapies on COVID‐19 patients. Results For cancer patients with COVID‐19, the death events related to antitumor treatment were higher than those with no antitumor treatment (OR = 1.55; 95% CI 1.07–2.25; p = 0.021). Compared with patients in the survival group, the non‐survival group showed no significant differences in patients who received antitumor therapy. Compared with patients in the non‐severe group, the severe group was more likely to receive antitumor therapy (OR = 1.50; 95% CI 1.02–2.19; p = 0.037) and there was a significant difference. The incidence of severe events was higher in the subgroup of chemotherapy (OR = 1.73; 95% CI 1.09–2.73). Conclusion The synthesized evidence suggests that cancer patients with COVID‐19 who received antitumor treatment shortly before symptom onset are more likely to experience severe symptoms and have high mortality. Receiving chemotherapy is an unfavorable factor for the prognosis of cancer patients with COVID‐19., Patients with cancer and COVID‐19 who received anti‐tumor treatment shortly before symptom onset are more likely to develop severe illness and have high a mortality. Receiving chemotherapy is an unfavorable factor for the prognosis of patients with COVID‐19.

Lanthanum can reduce absorption of phosphate by forming lanthanum phosphate complexes after oral administration of lanthanum carbonate tablets (FOSRENOL®) in patients. Based on the pH-responsive interaction of phosphate and lanthanum ions, the chitosan coated siRNA-loaded lanthanum phosphate nanoparticles (CS/LaP/siRNA NPs) were prepared for improving cancer treatment, in which polysaccharide chitosan was used as the outer shell to control the excessive growth of lanthanum phosphate complexes, and enable intestinal mucoadhesion. The CS/LaP/siEGFR NPs exhibited significant biological activities in human colorectal cancer HT-29 cells by the synergistic effects of siEGFRs and lanthanum ions, such as downregulation of EGFR and upregulation of miR-34a. Furthermore, significant tumor growth inhibition was observed in both transgenic C57BL/6-ApcMinC/Nju cancer mouse model and AOM/DSS chemically induced orthotopic colorectal cancer mouse model after intestinal instillation administration of CS/LaP/siEGFR NPs. Therefore, the lanthanum-based siRNA delivery system would provide a potential and efficient strategy for the treatment of colorectal cancers.

Radiation-induced intestinal injury is a common and critical complication of radiotherapy for pelvic or abdominal tumors, with limited therapeutic strategies and effectiveness. Sitagliptin, a dipeptidyl peptidase IV (DPP4) inhibitor, has previously been reported to alleviate total body irradiation- (TBI-) induced damage of hematopoietic system in mice, but its effect on radiation-induced intestinal injury remains unclear. In this study, we confirmed that Sitagliptin could not only protect mice from death and weight loss caused by whole abdominal irradiation (WAI) but also improve the morphological structure of intestine and the regeneration ability of enterocytes. In addition, Sitagliptin significantly inhibited the production of radiation-induced proinflammatory cytokines and reduced the number of apoptotic intestinal epithelial cells and γ-H2AX expression. In vitro, we demonstrated that Sitagliptin protected HIEC-6 cells from ionizing radiation, resulting in increased cell viability and reduced DNA damage. Mechanistically, the radiation protection of Sitagliptin might be related to the upregulation of NRF2 level and the decrease of NLRP3 inflammasome activity. Importantly, Sitagliptin significantly restored radiation-induced changes in bacterial composition. In conclusion, our results suggested that Sitagliptin could reduce WAI-induced intestinal injury in mice, which may provide novel therapeutic strategy for radiation-induced intestinal injury.

Background Bladder cancer (BLCA) is one of the most common malignancies worldwide. One of the main reasons for the unsatisfactory management of BLCA is the complex molecular biological mechanism. Annexin A1 (ANXA1), a Ca2+-regulated phospholipid-binding protein, has been demonstrated to be implicated in the progression and prognosis of many cancers. However, the expression pattern, biological function and mechanism of ANXA1 in BLCA remain unclear. Methods The clinical relevance of ANXA1 in BLCA was investigated by bioinformatics analysis based on TCGA and GEO datasets. Immunohistochemical (IHC) analysis was performed to detect the expression of ANXA1 in BLCA tissues, and the relationships between ANXA1 and clinical parameters were analyzed. In vitro and in vivo experiments were conducted to study the biological functions of ANXA1 in BLCA. Finally, the potential mechanism of ANXA1 in BLCA was explored by bioinformatics analysis and verified by in vitro and in vivo experiments. Results Bioinformatics and IHC analyses indicated that a high expression level of ANXA1 was strongly associated with the progression and poor prognosis of patients with BLCA. Functional studies demonstrated that ANXA1 silencing inhibited the proliferation, migration, invasion and epithelial–mesenchymal transition (EMT) of BLCA cells in vitro, and suppressed the growth of xenografted bladder tumors in vivo. Mechanistically, loss of ANXA1 decreased the expression and phosphorylation level of EGFR and the activation of downstream signaling pathways. In addition, knockdown of ANXA1 accelerated ubiquitination and degradation of P-EGFR to downregulate the activation of EGFR signaling. Conclusions These findings indicate that ANXA1 is a reliable clinical predictor for the prognosis of BLCA and promotes proliferation and migration by activating EGFR signaling in BLCA. Therefore, ANXA1 may be a promising biomarker for the prognosis of patients with BLCA, thus shedding light on precise and personalized therapy for BLCA in the future.

Two methods based on local stress responses are proposed to locate fatigue critical point of metallic notched components under non-proportional loading. The points on the notch edge maintain a state of uniaxial stress even when the far-field fatigue loading is multi-axial. The point bearing the maximum stress amplitude is recognized as fatigue critical point under the\ud condition of non-mean stress, otherwise the Goodman’s empirical formula is adopted to amend mean stress effect prior to the determination of fatigue critical point. Furthermore, the uniaxial stress state can be treated as a special multi-axial stress state. The Susmel’s fatigue damage parameter is employed to evaluate the fatigue damage of these points on the notch edge.\ud Multi-axial fatigue tests on thin-walled round tube notched specimens made of GH4169 nickel-base alloy and 2297 aluminum-lithium alloy are carried out to verify the two methods. The prediction results show that both the stress amplitude method and the Susmel’s parameter method can accurately locate the fatigue critical point of metallic notched components under multi-axial fatigue loading.

The fiber reinforced polymer/plastic (FRP) laminates are often subjected to random block spectrum loading in engineering. The simplified regular load in the laboratory fatigue tests is not sufficient to describe the actual fatigue damage history of FRP laminates. In order to explore the fatigue damage evolution of FRP laminates characterized by the residual stiffness degradation under complex random loads, some random block spectra are compiled based on the real engineering fatigue loads, and the fatigue tests of two FRP laminates, the E-glass/YPX-3300 glass fiber laminate and T700/YPX-3001 carbon fiber laminate, were conducted under the random block spectra. Four kinds of differently stacked laminates were prepared for each material. The residual stiffness degradation curves are obtained from the experiments. A stiffness degradation model proposed by the authors are used to correlate the residual stiffness evolution data. The results show that the residual stiffness degradation curves of different specimens can reach satisfactory consistency after correlation, though the original experiment data show a large dispersion. The residual stiffness degradation law of FRP laminates under random block spectrum is the same as that under constant amplitude spectrum. The proposed model can well characterize the residual stiffness degradation law of RRP laminates under random block spectrum.

The design and development of civil aircraft is a systematic engineering project with high precision and high complexity. Traditional aircraft requirements are based on document transmission, which is not intuitive and logical, and are easy to miss requirements in different scenarios The Model-based function analysis is a method that can identify and define all elements of a certain function. In the process of function analysis, the relation between the function interfaces can be determined and the relative requirements can be obtained, which can consequently ensure the validity and integrity of aircraft functional requirements. The functional modeling analysis is carried out based on a SysML model in this paper, and the function is described from the perspective of structural level, behavioral level and activity level by using graphical and hierarchical expression. The internal logic of the function is analyzed in depth to obtain the functional requirements of the aircraft.

In order to study the nonlinear dynamic behaviors of Thermal Protection System (TPS) and the nonlinear dynamic strength of the strain-isolation-pad (SIP), a two degree-of-freedom nonlinear dynamic theoretical model was presented under the acoustic excitation and base excitation. The tile is simplified as a mass point, a linear spring and a damping element, and the SIP is simplified as a mass point, a nonlinear spring and a damping element. On this basis, the solving process of the nonlinear theoretical model and the iterative process of the equivalent linear stiffness coefficient of SIP were derived by the statistical linearization method. The dynamic responses analyzed by the nonlinear theoretical model and linear theoretical model are compared. The nonlinear stiffness of SIP shows obvious influence on behaviors of TPS and dynamic stress of SIP, and the equivalent linear stiffness of SIP is related to the types of excitations. Finally, the influences on above dynamic responses by the nonlinear stiffness level of SIP were studied. The equivalent linear stiffness coefficient of SIP, acceleration of TPS and dynamic stress of SIP decrease with the increase of the nonlinear level for the stiffness of SIP.

A two degree-of-freedom uncertainty dynamic theoretical model under the acoustic and base excitations was presented to analyze the uncertainty dynamic behaviors of thermal protection system (TPS) and the uncertainty dynamic strength of strain-isolation-pad (SIP). The tile and SIP are both simplified as the combination of a mass point, a linear spring and a damping element, and all the dynamic parameters obey the normal distribution. The probability distributions of responses were derived from adopting the perturbation method. The difference method is used to analyze the sensitivity of the mean responses to random parameters, and the reasonable sensitivity values are obtained under a difference step which is equal to the standard deviation of the random parameter. The probability distributions calculated by the uncertainty theoretical model match well with the Monte Carlo numerical results, so the accuracy of the uncertainty dynamic theoretical model is verified. The researches in this paper provide a theoretical foundation for studying the uncertainty dynamic behaviors of TPS, analyzing uncertainty dynamic strength of SIP and intensifying the integrity and security of TPS.

A loosely coupled fluid-structural thermal numerical method is introduced for the thermal protection system (TPS) gap thermal control analysis in this paper. The aerodynamic heating and structural thermal are analyzed by computational fluid dynamics (CFD) and numerical heat transfer (NHT) methods respectively. An interpolation algorithm based on the control surface is adopted for the data exchanges on the coupled surface. In order to verify the analysis precision of the loosely coupled method, a circular tube example was analyzed, and the wall temperature agrees well with the test result. TPS gap thermal control performance was studied by the loosely coupled method successfully. The gap heat flux is mainly distributed in the small region at the top of the gap which is the high temperature region. Besides, TPS gap temperature and the power of the active cooling system (CCS) calculated by the traditional uncoupled method are higher than that calculated by the coupled method obviously. The reason is that the uncoupled method doesn't consider the coupled effect between the aerodynamic heating and structural thermal, however the coupled method considers it, so TPS gap thermal control performance can be analyzed more accurately by the coupled method.

The misorientation of nickel-base single crystal (NBSX) superalloy is always ignored in the current research, which in fact has a certain influence on the fatigue life of NBSXs. To investigate this influence, the fatigue tests of NBSX superalloy DD5 with different misorientation angles have been carried out at 980 °C, and the failure mechanism has been investigated based on the fractographic observation and crystal plastic finite element (CPFE) analysis. The effect of real misorientation on the fatigue life of NBSX has been quantified, which is also reported for the first time.