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To explore the diagnostic value of MRI-DWI signal intensity value combined with serum PGI. PGII and CA199 in early gastric cancer. Sixty cases of gastric cancer patients admitted to our hospital from December 2019 to December 2020 were selected as the gastric cancer group and 80 cases of healthy volunteers who underwent physical examination in our hospital during the same period were selected as the healthy group. All the 60 patients underwent MRI-DWI examination, and the pathological diagnosis results were regarded as the gold standard. MRI-DWI images, MRI-DWI signal intensity values of patients with different degrees of gastric cancer differentiation. Serum PGI, PGII and CA199 levels of subjects in the two groups were compared. AUC was used to evaluate the diagnostic value of MRI-DWI signal intensity value combined with serum PGI, PG II and CA199 for early gastric cancer. In the healthy group, T1W1 showed relatively uniform low signal intensity. While T2WI showed no significant increase in signal intensity. In the gastric cancer group. There was diffuse gastric wall thickening, local thickening or mass formation; T1WI and WATS showed slightly lower signal intensity in the lesion area. T2WI, FLAIR and B-TFE showed slightly uneven or moderately increased signal intensity. DWI showed limited diffusion, and the signal intensity increased uniformly or more uniformly, and the range of increase was clear. The signal intensity of MRI-DWI was 89.12 ± 8.14 in patients with low differentiation, 82.17 ± 6.35 in patients with moderate differentiation, and 74.52 ± 4.53 in patients with high differentiation. There were significant differences in the signal intensity of MRI-DWI among the three groups, and the difference was statistically significant (F=12.214, P

The formation of ternary composite oxides in a high-temperature environment has laid the foundation for the design of high-temperature wear-resistant self-lubricating film. A series of Pb-Cr-O films with different Cr contents were prepared by incorporating different ratios of Pb-Cr into a target in the reactive magnetron sputtering system. The results showed that the hardness of the Pb-Cr-O films is greatly improved compared to the pure Pb-O film. In addition, the Pb29Cr4O67 film with the highest Cr content forms an amorphous structure due to the accumulation of Cr6+ at the grain boundary, which improves the H/E and H3/E2 of the film. At 600 °C, in contrast with the single PbO lubricating phase formed by pure Pb33O67 film, the Pb29Cr4O67 film forms a composite lubricating phase of Pb5CrO8 and PbO. This leads to a decreased wear rate as low as 7.2 × 10−6 mm3N−1m−1 while maintaining low coefficient of friction comparable to pure Pb33O67 film. At higher temperature of 700 °C, Cr element in Inconel 718 matrix diffuses into the Pb-based oxide film and forms Pb5CrO8 phase similar to Pb29Cr4O67 film, which improves the wear resistance of the Pb33O67 film while maintaining low friction coefficient of 0.15.

The reaction pathway of the isomerization in the process of butyl rubber bromination was proposed based on density functional theory (DFT) and MP2 calculations with the 6-31+G(d) basis set. The microstructural composition of the brominated butyl rubber was determined via proton nuclear magnetic resonance spectroscopy (1H-NMR).The transition state of isomerization reaction was identified. The geometries of the reactant, transition state, and product structures were optimized. The effect of solvation on model compounds was simulated using the polarizable continuum model (PCM). The energy barriers for isomerization reactions were calculated with different solvents (vacuum, n-hexane, and 245/105 mL n-hexane/dichloromethane (DCM) mixture). The increase in solvent polarity decreased the activation energy and facilitated the isomerization reaction. This finding was consistent with the experimental result.

The channel catfish virus (CCV, Ictalurid herpesvirus 1) has caused sustained economic losses in the fish industry because of its strong infectivity and pathogenicity. Thus, it is necessary to determine the function of viral proteins in the CCV infection process. The present study aimed to characterize CCV glycoprotein ORF59 and explore its impact on virus infection in host cells. Firstly, its exclusive presence in the membrane fraction of the cell lysate and subcellular localization verified that CCV ORF59 is a viral membrane protein expressed at late-stage infection. A protein blocking assay using purified His6 tagged ORF59, expressed in sf9 insect cells using a baculovirus expression system, indicated a dose-dependent inhibitory effect of recombinant ORF59 protein on virus invasion. Knockdown of the ORF59 using a short hairpin (shRNA) showed that ORF59 silencing decreased the production of infectious virus particles in channel catfish ovary cells. The results of this study suggest that recombinant ORF59 protein might inhibit CCV entry into the host cells. These findings will promote future studies of the key functions of glycoprotein ORF59 during CCV infection.

The channel catfish virus (CCV, Ictalurid herpesvirus 1) has caused sustained economic losses in the fish industry because of its strong infectivity and pathogenicity. Thus, it is necessary to determine the function of viral proteins in the CCV infection process. The present study aimed to characterize CCV glycoprotein ORF59 and explore its impact on virus infection in host cells. Firstly, its exclusive presence in the membrane fraction of the cell lysate and subcellular localization verified that CCV ORF59 is a viral membrane protein expressed at late-stage infection. A protein blocking assay using purified His6 tagged ORF59, expressed in sf9 insect cells using a baculovirus expression system, indicated a dose-dependent inhibitory effect of recombinant ORF59 protein on virus invasion. Knockdown of the ORF59 using a short hairpin (shRNA) showed that ORF59 silencing decreased the production of infectious virus particles in channel catfish ovary cells. The results of this study suggest that recombinant ORF59 protein might inhibit CCV entry into the host cells. These findings will promote future studies of the key functions of glycoprotein ORF59 during CCV infection.

The expression of herpesvirus genes during infection of tissue culture cells can be classified into three main classes: immediate-early (IE), early and late. The transcriptional regulation of herpesvirus IE genes is a critical regulatory step in the initiation of viral infection, with their regulation differing from that of early and late genes. Herein, we report that an IE gene (ORF3) promoter in channel catfish virus (CCV, Ictalurid herpesvirus 1) can be activated regardless of the presence or absence of CCV infection, indicating that the ORF3 promoter is efficiently driven by host-cell transcription factors in a viral infection-independent manner. The analysis of truncated promoter activity suggested that several transcription elements play a role in activating the ORF3 promoter, with the key cis-elements seemingly located in the flanking sequence of the start codon ATG. We further found that this flanking sequence contained multiple AT-rich sequences, and systematic mutational analyses showed that these AT-rich sequences affected normal transcription levels of the ORF3 promoter. To summarize, multiple AT-rich domains, representing the novel architecture of IE gene promoters in Ictalurid herpesvirus 1, serve as a cis-element for ORF3 transcription.

The VN-based coatings doped with different elements (carbon, aluminum and silver) were comprehensively investigated in terms of their chemical composition, structure, mechanical properties as well as tribological performance. Results revealed that introduction of aluminum into the coatings can enhance the hardness and modulus of coatings resulting from solution strengthening of Al and the formation of hard AlN phase. The sp2-hybrized carbon and VC phases were found in C-doped coatings, playing decisive roles in reducing the friction at room temperature and raising hardness of coatings, respectively. The addition of silver significantly changed the mechanical and high temperature tribological behavior of the coatings owing to their easy-shearing structure. All coatings had the lower friction coefficients at 550 °C than those at room temperature. Among them, the friction coefficient of VAlCN–Ag coating is as low as about 0.25 at 550 °C, which is closely related to the synergistic lubrication dominated by V2O5 and silver vanadate phases formed by tribochemical reaction on the worn surface, indicating a design of promising self-lubricating VN-based coatings working at high temperature.

The molybdenum nitride (MoN) film with multiphase structure (Mo 2 N, MoN and Mo) was successfully prepared using magnetron sputtering. The mechanical and tribological performances of the MoN film were both further improved by C-doping and heat treatment. The results show that compared to the MoN film, the MoCN film has smoother and denser microstructure, lower friction coefficient and wear rate, and an increased hardness of 28 GPa. The improved performance exhibited by the MoCN film is mainly attributed to the lubricating effect of forming amorphous carbon after doping with C element and high hardness of the sp 3 C C hybrid bond. However, different results exhibited on the MoN and MoCN films after heat treatment at 400 °C. Both the mechanical and tribological properties were improved in the MoN film but reduced in the MoCN film. This may be related to different crystallization of Mo and the change of amorphous carbon in the different film. This suggests that heat treatment is of great importance to the properties of MoN and MoCN films.

The aim of this paper is to gain insight for the transition of fracture initiation sites in notched tensile specimens. For this purpose, a stress triaxiality-dependent viscoplastic damage model was proposed for various types of notched tensile specimens, where the influence of stress triaxiality on damage, damage-free stress-strain curve and viscoplasticity was considered. Also, in this constitutive model, the consistency viscoplastic regularization method was used to solve the pathological mesh-dependent problem due to strain softening. A hybrid experimental-numerical approach was used to calibrate model parameters by using smooth and one type of round-notched tensile specimens. The same set of model parameters was then applied to predict ductile fracture for three other types of round-notched tensile specimens. Good agreement between experimental data and simulation results confirmed the transferability of model parameters to all types of tensile specimens considered and the ability of the proposed constitutive model to predict ductile fracture over a large range of positive stress triaxialities. This study found that at the onset of fracture critical damage parameters for all five types of tensile specimens were relatively constant, and fracture initiation sites in these specimens were associated with critical damage parameters, shifting from the center to the notch root. Therefore, the critical damage parameter was defined as a ductile fracture criterion and the fracture strain for all the five types of tensile specimens was successfully predicted.

The CrN-Ag composite coatings with various silver contents were prepared on 316L stainless steel by magnetron sputtering. The corrosion performance and antifouling properties (including anti-algae and antibacterial behaviors) of coatings in the artificial seawater were evaluated to give insight to potential marine applications. Results revealed that Ag-doped coatings exhibited worse corrosion resistance with increased silver, which indicated silver accelerated the reaction of the primary battery and promoted the occurrence of corrosion. However, opposite tendency was presented on anti-algae behavior. The coatings containing silver content of 13.18 at.% showed excellent anti-algae properties, and better antibacterial properties against Bacillus subtilis than Escherichia coli. The attachment of Chlorella, N. closterium and P. tricornutum on the surface of coating reduces by about 45%, 72% and 64%, respectively. The agglomerate of silver in the coatings with 18.37 at.% constrains its release and diffuse, which slowed down the corrosion reaction, embodying positive influence on corrosion resistance and negative effect on anti-algae behavior.

As a commonly used engineering material, the mechanical properties of titanium alloy under dynamic loads are closely related to their microstructure. In this work, the effects of solution treatment (ST) and solution and aging treatment (SAT) on the microstructure and dynamic compressive properties of Ti–6Al–4V alloy manufactured by selective laser melting were studied. The results showed that the microstructure of selective laser melted Ti–6Al–4V consisted of nearly full acicular α′ martensite, then the acicular α′ martensite was decomposed into α+β phase with basket-weave morphology with solution treatment. Clusters of α2 particles with size of several hundred nanometers were precipitated in the α plates further with solution and aging treatment. The ultimate compressive strength (UCS) of selective laser melted TC4 alloy was increased with the increasing strain rate, showing strong strain rate hardening effect. Stress collapse happened once the strain exceeded 1500/s, which is the dominant failure model of selective laser melted TC4 under impacting load. As expected, the UCS of the ST sample decreased, but the ductility increased compared with the as-built sample; however, both the UCS and ductility of the SAT samples were enhanced synergistically due to the widely distributed α2 precipitates. Besides, the SAT samples had the highest energy absorption compared with the as-built and ST counterparts under the same conditions, indicating that the SAT samples had better load-bearing capacities.

A new perspective of localized shear strain accumulation was proposed to elucidate the formation mechanism of fine granular area (FGA) generated in a high strength steel under very-high-cycle fatigue (VHCF). On the one hand, experiments of VHCF under the negative stress ratio of -1 was carried out, and the microstructure of FGA was found and characterized by using Scanning Electron Microscope, Transmission Electron Microscopy, and Transmission Kikuchi Diffraction. The results show that the FGA consists of high-density dislocations, sub-grains, and fine grains with high angle grain boundaries. On the other hand, the evolution of shear strain and fatigue damage at the vicinity of an inclusion was modelled by using crystal plasticity finite element method at both positive and negative stress ratios. The results show that although the overall strain in VHCF is negligible, significant shear strain is accumulated at the vicinity of the inclusion. Such a large local strain is the driving force for the formation of FGA. The results also suggest that with the accumulation of shear strain and damage, the positive stress ratio is gradually evolved into negative. This may explain why FGA has also been reported at positive stress ratios in some literatures.

Though modeling material cyclic plasticity in a probabilistic way can yield a more accurate result than deterministic modelling method, it is quite hard to perform uncertainty quantification for all the material parameters. In this paper, Sobol’s global sensitivity analysis is applied to cyclic plasticity model to investigate how the variation of these parameters affect fatigue reliability evaluation. A machine learning algorithm is proposed to improve the computational efficiency for failure probability assessment. The results of global sensitivity analysis show that fatigue damage parameters, elastic modulus and initial yield stress are very influential to fatigue reliability analysis while others are not.

Arbuscular mycorrhizal fungi (AMF) are ancient and ubiquitous soil microorganisms, which can form mutually beneficial association with most terrestrial plants. Within the symbiotic relationship, AMF helps their host plants to absorb nutrients such as nitrogen and phosphorus while obtains carbon from the hosts. AMF plays an important role in agricultural ecosystem, including promoting plant growth, improving crop quality, increasing plant stress resistance, stabilizing soil structure, keeping ecological balance, and maintaining a sustainable agricultural development. We summarized the research advances of AMF in terrestrial agro-ecosystem in recent years, by focusing on AMF species diversity, spatial and temporal distribution, and influence factors of AMF biodiversity in terrestrial agro-ecosystem of China. Further research works were also prospected.丛枝菌根真菌(AMF)是一种古老的、在自然界中普遍存在的土壤微生物,能与大部分陆生植物形成互惠互利的菌根共生体.在这种共生关系中,AMF从植物获取自身生长所需碳源的同时,帮助宿主吸收氮、磷等营养物质.AMF在农业生态系统中具有重要作用,能够促进植物生长、改善作物品质、提高植物抗逆性、稳定土壤结构、维护生态平衡和维持农业可持续发展.本文总结了近几年来陆地农业生态系统AMF的研究进展,着重从我国陆地农业生态系统AMF物种多样性、AMF生物多样性时空分布特征及影响AMF多样性的因素等几个方面,综述了陆地农业生态系统AMF的物种多样性,并对以后的研究进行了展望.

The aim of this investigation was to study the formation of white etching layer (WEL) induced by rolling contact fatigue (RCF) in a bearing steel. Through sectioning a failed bearing, the microstructure of the WEL was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and micro indentation test. The result showed that the WEL is harder than the matrix. It consists of refined grains of martensite, austenite and carbides. In contrast to the thermally-induced WELs, where the austenite is the result of phase transformation due to austenitization, the austenite in the WELs of the current study comes from the original retained austenite. No phase transformation occurred, indicating that the WEL was formed under deformation induced the mechanism. WELs and white etching areas (WEAs) were compared in detail. The result suggested that WELs and WEAs are actually the similar responses to large shear deformation in RCF of martensitic bearing steels.

Wind turbine gearbox bearings fail with the service life is much shorter than the designed life. Gearbox bearings are subjected to rolling contact fatigue (RCF) and they are observed to fail due to axial cracking, surface flaking, and the formation of white etching areas (WEAs). The current study reviewed these three typical failure modes. The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs. Although numerous studies have been carried out, the formation of WEAs remains unclear. The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors. WEAs were compared with adiabatic shear bands (ASBs) generated in the high strain rate deformation in terms of microstructural compositions, grain refinement, and formation mechanism. Results indicate that a number of similarities exist between them. However, substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.

In this paper, a systematic framework has been proposed to simulate the structure’s fatigue life scatter. At first, cyclic plastic model coupled with fatigue damage is employed for fatigue life prediction. To consider variability in material, a parameters’ sampling strategy has been proposed by modeling Coffin-Manson parameter’s uncertainty. Then support vector machine combined with Monte Carlo simulation is used to assess structure’s failure probability. The method is modified by subset simulation when facing small failure probability problems. In the end, a numerical example of three-layer extrusion container is given for demonstrating the sampling procedure of material variability when experimental data of material is limit.

Rotary-bending fatigue tests of Ti-6Al-4V alloy at very high-cycle regime were performed in air and 3.5% NaCl solution, respectively. The S-N curves exhibited the characteristic of horizontal asymptote (traditional fatigue limit) in laboratory air, while a lower fatigue limit was shown in 3.5% NaCl solution after around 3 × 108 cycles. The decrease of fatigue life was due to the generation of small surface defects in comparison with that in air. These defects were ascribed to the hydrogen-induced cracking and fatigue loading. The number of fatigue crack initiation sites decreases with increasing cycles. Only one crack origin site, dominated by slip mechanism, exists in each specimen at very high-cycle regime. The existing experimental S-N data of Ti-6Al-4V alloy from very high-cycle fatigue tests were also reviewed. It was shown that the fatigue life (R = −1) of Ti-6Al-4V alloy was predominantly influenced by the microstructure and not strongly sensitive to the loading mode and frequency (in the range from 52.5 Hz to 20 kHz) under air condition at room temperature.

Objective To investigate the effect of recipient's pre-transplant triglyceride (TG) abnormalities on early graft function (EGF) after kidney transplantation. Methods According to the inclusion and exclusion criteria, 154 identified living-kidney transplant recipients in the 309 Hospital of Chinese PLA from Jan. 2011 to Dec. 2014 were enrolled in present study, including 124 males and 30 females, and aged of 31.9±8.4 years. The cohort was divided into two groups: TG normal group (0.401.70mmol/L or require lipid lowering therapy, n=47). The incidences of poor early graft renal function (PEGF), slow graft function (SGF) and delayed graft function (DGF) were compared between the two groups, and then the serum creatinine (Scr) levels were compared among the patients showing immediate graft function (IGF) at 3rd, 7th and 30th day after transplantation. The ROC curve was drawn up taking TG as diagnosis index to explore the optimal cut-off value for predicting PEGF, SGF and DGF after transplantation. Results Compared with the TG normal group, the TG abnormalities group showed significantly higher incidence of PEGF and DGF (P

The purpose of this investigation was to study microstructural evolution leading to the formation of wear debris and white etching areas (WEA) in the subsurface of AISI 52100 steel during rolling contact fatigue (RCF). The specimens were tested using a roller-on-roller geometry testing machine. Surface damage was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Lamellar structures generated during the rubbing of crack faces give a clear picture of how wear debris is formed. In contrast to the previously reported WEA, which is composed of nano-ferrites generated under the mechanism of recrystallization, the WEA produced in the current RCF condition consists of an amorphous phase with nanocrystallites dispersed. Based on this, it is proposed that WEA can be classified into deformed WEA and transformed WEA depending on whether phase transformation occurs. In addition, the relationship between white etching crack (WEC) and WEA was discussed in detail. The result suggests that WEC does not initiate WEAs as it has been accepted. Instead, they form under different mechanisms.

Dynamic compressive mechanical responses of selective laser-melted Ti-6Al-4V alloy were studied in terms of the influences of scanning speed, building angle as well as impacting strain rate. It was found that the ultimate flow stress and energy absorption increased first and then dropped sharply as the scanning speed increased from 1.0 to 1.6 m/s, showing that the sample built at scanning speed of 1.2 m/s possessed the best dynamic mechanical properties. They increased straightly up as the building angle increased from 0° to 90°, but only the sample built at 45° ruptured with shearing fracture pattern. Moreover, the samples exhibited distinct strain rate hardening effect, as the applied strain rate increased from 900 to 2100/s, and the sample ruptured ultimately with mixed ductility/brittle fracture pattern. Volume fraction of LAGBs in samples increased from 9.1 to 18.9% and 21.4% after impacting at strain rates of 900/s and 2100/s, indicating that intenser dislocation was activated at a higher strain rate impacting, this is the main cause of enhancement in strength. This study provided an insight into the influence of high strain rate impact loading on the dynamic mechanical responses of SLMed TC4 alloy, which is conducive to further exploiting the performance potential of the SLMed materials.

White etching area (WEA) has become a big challenge for bearing failure under rolling contact fatigue. Despite of the extensive investigations, the origin of the WEA has not yet been well understood. This work attempts to elucidate the origin based on a new perspective that both the WEA and the shear band (SB) can be the common responses under shear plastic deformation in bearing steel, rather than the unique phenomenon in rolling contact fatigue. First, the SB is generated under quasi-static compression loading, indicating that the SB does not necessarily have to be adiabatic and is not limited to high strain rate loading. Second, the WEA is produced under rolling contact fatigue. The SB is compared with the WEA in terms of shear localization, microstructures, formation mechanism and crack development. The results suggest that both the SB and the WEA can be regarded as the shear localization under large plastic deformation. The SB consists of either nanocrystallines or well-developed equiaxed grains with transformed austenite. The WEA consists of either nanocrystallines or a mixed structure of amorphous phase and nanocrystallines with transformed austenite. Connecting the WEA with the SB provides a new insight into interpreting the origin and formation mechanism of the WEA, and help the further understanding of bearing failure under rolling contact fatigue.

In this work, the essential mechanism of “loss of passivation” (LOP) effect for a 13 wt. % Cr-type martensitic stainless steel (MSS) is studied via electrochemical and microstructure approaches. The MSSs were quenched at 1030 °C and then tempered at 440−600 °C. Electrochemical results show that the tempering range for “LOP” is 460−540 °C. Severe corrosion occurred on 520 °C-tempered MSS after being immersed in Cl− containing solution for 35 min. Transmission electron microscopy (TEM) observation towards the corroded area of 1030-520 sample reveals the massive precipitation of nano-sized Cr-rich carbides, which is the essential cause for the “LOP” of MSSs.

The sliding wear-induced grain coarsening of nano laminated structure in a martensite steel was investigated by using Transmission Electron Microscopy (TEM) and transmission Kikuchi diffraction (TKD). Microstructure was initially refined into nano laminated structure by dry sliding. In the subsequent lubricated sliding, the nano laminated structure became coarsened instead of being continuously refined. Equiaxed grains and subgrains were observed in the laminated structure under 60 min dry + 60 min lubricated sliding, as compared to the coarsened but still remained lamellar structure under 120 min dry + 60 min lubricated sliding. In contrast to the grain refinement, which was mechanically driven but thermally assisted, the grain coarsening was mechanically dominated without involving the thermal effect. The nano laminated structure did not show strong texture before and after coarsening. The continuous grain growth occurred even if the stress was reduced in the lubricated sliding. The high density of triple junctions in the nano laminated structure promotes grain boundary motion, facilitating the grain coarsening.

The microstructure evolution of adiabatic shear bands (ASBs) in AISI 52100 produced under high strain rate impact loading was investigated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A full view of the shear band formation and development was presented. The results reveal that no strain hardening effect occurred in the AISI 52100 under the dynamic loading. Two distinct regions of the ASBs and the transition region were observed. Driven by the high shear deformation and assisted by a thermal softening effect, the formation of ASBs started in the core region under the dominant mechanism of dynamic recrystallization. It is followed by the formation of neighbouring region under the co-action of both dynamic recovery and dynamic recrystallization. Then the transition region formed which was controlled by dynamic recovery. The core region of ASBs was consisted of subgrains and fine equiaxed grains. The grains were refined either through partitioning and breaking down the elongated subgrains by entangled dislocations clusters or through splitting and rotating the elongated subgrains into small grains under a synergistic effect of shearing and twisting. The amount and size of cementites were greatly reduced in ASBs due to cementite dissolution induced by large plastic deformation and dynamic recrystallization.

Surface wear and corrosion affect the service performance of steel wire rope. They usually appear alternately and interact. In this paper, the friction and wear properties of wire ropes with different corrosion types were investigated. Then, the interactions of the corrosion and wear on the residual strength of the rope samples were analysed. The results show that the corrosion had a strong influence on the coefficient of friction (COF) and temperature rise of the wire rope. Additionally, surface corrosion reduced the anti-wear properties and fatigue resistance of the rope. The effect of sulfuric acid corrosion was the most obvious, followed by that of sea-water and fresh water. The maximum breaking force of the wire rope with sulfuric acid corrosion decreased rapidly with the wear time, from approximately 49.9 kN–41.5 kN. Furthermore, under tensile load, the plastic deformation of the rope wires was closely related to the surface wear and corrosion condition. This study can provide basic data for the safe use and maintenance of steel wire rope.

In this paper, a continuum damage enhanced formulation of effective (undamaged) material properties is proposed to predict fracture behaviour of various notched tensile specimens and a compact tension (CT) specimen for a high-strength rail steel that is commonly known to be insensitive to change in hydrostatic stress. The presented constitutive model considers a thermodynamically nonlinear, isotropic continuum damage, and stress-triaxiality-dependent effective stress using a viscoplastic regularization method to reduce strain and damage localization at the sharp notch tip. Conventional loading-unloading tensile test for damage measurement and monotonic tensile test on a notched specimen are used to calibrate the constitutive equation which consists of a set of eight model parameters. Further validation is performed on the geometry transferability of the model parameters to three different notched tensile specimens in the high stress triaxiality regime. The calibrated constitutive model is then applied to simulate crack initiation and propagation in the mode I plane-strain condition, where the computed result of load versus crack mouth opening displacement shows good agreement with those determined from CT specimens. The study concludes that the critical damage parameters for fracture are relatively constant among different notched specimens of high-strength rail steel, and thus as a proper fracture criterion for crack initiation at and crack propagation from the sharp notch tip. The study also found that the complementing mechanisms for the stress-triaxiality-dependent damage evolution and strain-hardening-induced enhancement of effective matrix material properties, respectively, result in the overall hydrostatic-stress insensitivity, and thus is often regarded as a material that belongs to the classical J2 plasticity.

It is a big challenge to identify whether or not a high temperature rise at high strain rate is a prerequisite for shear instability in crystalline materials. In contrast to the prevailing report of shear instability at high strain rate loading, the shear band (SB) was generated at quasi-static loading in a martensite steel. This gives strong evidence that the high temperature rise is not essential as the quasi-static loading is not able to generate enough heat to initiate the shear instability. Different from the conventional narrow SB at high strain rate loading, a large patch of SB was firstly observed. Considerably localized melting occurred due to the abrupt fracture of SB. SB displays different TEM microstructures at melting and no-melting places. This indicates the significance of distinguishing the microstructure formed during shear instability from the one affected by the fracture of SB. The result suggests that the strain localization mechanism in this material is attributed to the microstructural change instead of the thermal softening. The findings provide a new insight into understanding the formation mechanism of SB from the perspective of microstructural evolution in crystalline materials.

This paper mainly studies the berthing ship target detection method of overhead-view image under the condition of a few training samples. Because of the limited training samples, we use the complete data set unrelated to the target detection task for pre-training to obtain a classification model, then expand the data according to a certain percentage and finally complete the training of the target detection model. This paper uses the idea of segmentation to solve the target detection problem. We adjusted the configuration of the region proposal network including the size of anchor frame and the threshold of non-maximum suppression according to the target morphology, so that the network generates a more accurate region of interest. Finally, the confidence levels, bounding-boxes and image masks of multi-objective generated concurrently. We performed experiments on self-made data sets which labeled from NWPU VHR-10 and produced good results, which proved the feasibility of this method in target detection of berthing ship target.

The evolution of nano-laminated structure generated in dry sliding wear of a high strength martensite steel was investigated by using Scanning Electronic Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gradient microstructure along the depth was observed with the top layer consisting of nano-laminated structure. During the sliding wear-induced plastic deformation, grains were refined and lamellar structures were formed as a result of generation of dislocation cell blocks bounded by geometrically necessary boundaries (GNBs) and incidental dislocation boundaries (IDBs). With increasing plastic shear strain and strain gradient, there is a continuous reduction in the spacing and length in dislocation cell blocks, leading to nano-laminated structures. The ultrafine nano-laminated structure with laminate spacing of 20 nm was observed at the sliding time of 120 min. However, the grain refinement is not a merely mechanical deformation process. The formation of Fe3O4 and FeO gave direct evidence that the highest temperature due to frictional heat could reach up to 600 °C. The result suggested that the formation of nano-laminated structure was governed by thermally-assisted plastic deformation.

The aim of the present study was to investigate magnetic resonance (MR) features of meningeal solitary fibrous tumors (SFTs) in order to improve their recognition. The study retrospectively analyzed MR manifestations in 12 cases of meningeal SFTs confirmed by surgery. The lesions were analyzed in terms of the site of their growth, growth mode, morphology, size, changes in the MR signal and the edge of the focus. The tumors were malignant in 3 cases, benign in 7 cases and borderline in 2 cases. A total of 3 cases spanned the tentorium cerebelli, 3 spanned the falx and another case was close to the falx. Overall, 4 superficial tumors were accompanied by adjacent bony destruction. One case was located at the triangular area created by the right lateral ventricles. The tumors were all lobular, with a large diameter and more cystic areas in the center of the focus. The signals were often heterogeneous. The parenchyma in the tumors was significantly enhanced. For certain tumors, the signal was usually inhomogeneous and not uniform. The MR features of a SFT were often similar to other intracranial tumors and easily misdiagnosed. There were certain innate characteristics, for example, the tumor was often a solitary large soft-tissue mass with an irregular edge and a clear boundary, with a lobulated contour, and was widely involved with other tissues. The tumors often grew across either the falx or tentorium cerebelli. A significantly inhomogeneous signal was found and either a low or low-high mixed signal on T2-weighted images in particular. These features are useful for the differential diagnosis of SFTs and other tumors.

Rolling contact fatigue (RCF) involves microstructural change in the subsurface of contact. The changed microstructure is generally termed as white etching area (WEA) as it appears white under optical microscope when etching in nital solution. WEA has been acknowledged as one of the primary failure modes in RCF since it causes severe local inhomogeneity of microstructure. It was reported that WEA consists of nano ferrites as martensite grains and carbides are significantly refined in the WEA. Some carbides are dissolved. In some cases, an amorphous-like structure was occasionally observed in the WEA, indicating that phase transformation may possibly occur. The WEAs were studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Electron back scattered diffraction (EBSD). The result showed that WEA is dominated with an amorphous phase with martensite, austenite and carbides embedded interior. A distinct interface between the matrix and the WEA was present. In addition to grain refinement down to nanometers, phase transformation including amorphization and austenitization happened in WEAs. The content of austenite was increased from 2% in the matrix to 20% in the WEA. The analysis showed that phase transformation is controlled by plastic deformation mechanism.

The high cycle fatigue of super duplex stainless steel of SAF 2507 was investigated by rotating bending fatigue test in both air and 3.5% NaCl environment. The results showed that there is no much reduction of the fatigue life in corrosive environment, which is 90% of the air fatigue strength. In air fatigue, failure happens in ductile mode with austenite grains having finer and straighter fatigue striations than ferrite grains. Width and spacing of striations vary with the orientation and locations when the second cracking occurs. It is not reliable to identify the phase by morphology of striations. In 3.5% NaCl environment, the fracture exhibits a mixed mode of cleavage and quasi-cleavage in ferrites and ductile in austenite grains.

In this paper, a series of scientifically rational index system is set up to evaluate the effect of energy saving and loss decreasing in power distribution networks. The establishment of the index system is based on a variety of new technical measures. According to the feature of wide range and weak consistency, an evaluation in power distribution networks based on rank correlation analysis is proposed. In such a way, the procedure is clear, simple and highly exercisable. With the application of evaluation process described in this paper, present situation in power distribution networks in a region is evaluated, which justifies the validity of the method.

Nowadays the main electrical wiring in medium-size and large-size thermal power units is mostly unit wiring. In the quarter of small reactive power load, some generators need to work in phase-lag operation during the daytime and in phase-advancement operation at night to meet the demand of voltage quality of their plant’s high-voltage side. This operation, however, will lower the voltage of auxiliary power and do harm to system’s stability. This paper proposes a kind of coordinated control strategy for generator-transformer’s voltage regulation. In this strategy, the main transformer should be on-load tap charger and the controller regulate the generator voltage and transformation ratio simultaneously when needed, thus the voltage quality of both high-voltage side and auxiliary power side can be insured and the generator no longer work in phase-advancement operation. This control strategy can be a meaningful proposal for AVC in smart grid in the future. Simulation result shows the stability and reliability of the proposed control strategy.