As one kind of key components with enormous quantities and diversities, the bent tube parts satisfy the increasing needs for lightweight and high-strength product from both materials and structure aspects. The bent tu...As one kind of key components with enormous quantities and diversities, the bent tube parts satisfy the increasing needs for lightweight and high-strength product from both materials and structure aspects. The bent tubes have been widely used in many high-end industries such as aviation, aerospace, shipbuilding, automobile, energy and health care. The tube bending has become one of the key manufacturing technologies for lightweight product forming. Via the analysis of bending characteristics and multiple defects, advances on exploring the common issues in tube bending are summarized regarding wrinkling instability at the intrados, wall thinning （cracking） at the extrados, springback phenomenon, cross-section deformation, forming limit and process/ tooling design/optimization. Some currently developed bending techniques are reviewed in terms of their advantages and limitations. Finally, in view of the urgent requirements of high-performance complex bent tube components with difficult-todeform and lightweight materials in aviation and aerospace fields, the development trends and corresponding challenges are presented for realizing the precise and high-efficiency tube bending deformation.展开更多
AIM To investigate the expression of multiplegenes and the behavior of cellular biology ingastric cancer（GC）and other gastric mucosallesions and their relations to Helicobacter pylori（H.pylori）infection,tumor stag...AIM To investigate the expression of multiplegenes and the behavior of cellular biology ingastric cancer（GC）and other gastric mucosallesions and their relations to Helicobacter pylori（H.pylori）infection,tumor staging andhistological subtypes.METHODS Three hundred and twenty-sevenspecimens of gastric mucosa obtained viaendoscopy or surgical resection,and ABCimmunohistochemical staining were used todetect the expression of p53,p16,Bcl-2 andCOX-2 proteins.H.pylori was determined byrapid urea test combined with pathologicalstaining or<sup>14</sup>C urea breath test.Cellular image analysis was performed in 66 patients withintestinal metaplasia（IM）and/or dysplasia（Dys）.In 30 of them,both cancer and theparacancerous tissues were obtained at the timeof surgery.Histological pattern,tumor staging,lymph node metastasis,grading ofdifferentiation and other clinical data werestudied in the medical records.RESULTS p16 expression of IM or Dys wassignificantly lower in positive H.pylori chronicatrophic gastritis（CAG）than those withnegative H.pylori（CAG:54.8% vs 88.0%,IM:34.4% vs 69.6%,Dys:23.8% vs 53.6%,allP【0.05）,Bcl-2 or COX-2 expression of IM orDys in positive H.pylori cases was significantlyhigher than that without H.pylori（Bcl-2:68.8%vs23.9%,90.5% vs 60.7%;COX-2:50.0% vs10.8%,61.8% vs 17.8%;all P【0.05）.Themean number of most parameters of cellularimage analysis in positive H.pylori group wassignificantly higher than that in negative H.pylori group（Ellipser:53±14,40±12μm,Area<sub>1</sub>:748±572,302±202 μm<sup>2</sup>,Area<sub>2</sub>:3050±1661,1681±1990 μm<sup>2</sup>,all P【0.05;Ellipseb:79±23,58±15 μm,Ratio<sub>1</sub>:22%±5%,13%±4%,Ratio<sub>2</sub>:79%±17%,53%±20%,all P【0.01）.There was significant correlation between Bcl-2and histologic pattern of gastric carcinoma,andbetween COX-2 and tumor staging or lymph nodemetastasis（Bcl-2:75.0% vs 16.7%;COX-2:76.0% vs 20.0%,79.2% vs 16.7%;allP【0.05）.CONCLUSION p1l6, Bcl-2, and COX-2 but not p53 gene may play a role 展开更多
Zircon U-Pb age and Hf isotope, and major and trace element compositions were reported for granite at Quanyishang, which intruded into the Kongling complex in Yichang, Hubei Province. The results show that the Quanyis...Zircon U-Pb age and Hf isotope, and major and trace element compositions were reported for granite at Quanyishang, which intruded into the Kongling complex in Yichang, Hubei Province. The results show that the Quanyishang granite is rich in silicon and alkalis but poor in calcium and magnesium, and displays enrichment in Ga, Y, Zr, Nb but depletion in Sr and Ba, exhibiting the post-orogenic A-type affinity. 90% zircons from the granite are concordant, and give a middle Paleoproterozoic magmatic crystallization age (mean 1854 Ma). Initial Hf isotope ratios (176Hf/177Hf)i of the middle Paleoproterozoic zircons range from 0.280863 to 0.281134 and they have negative εHf(t) values with a minimum of -26.3. These zircons give the depleted mantle model ages (TDM) of 2.9―3.3 Ga (mean 3.0 Ga), and the average crustal model ages (Tcrust) of 3.6―4.2 Ga (mean 3.8 Ga). A Mesoarchean grain with 207Pb/206Pb age of 2859 Ma has a slightly high TDM (3.4 Ga) but similar Tcrust (3.8 Ga) to the Paleoproterozoic zircons. All these data suggest that the source materials of the Quanyishang A-type granite are unusually old, at least ≥2.9 Ga (even Eoarchean). The event of crustal remelting, which resulted in the formation of the Quanyishang granite in the middle Paleoproterozoic, recorded the cratonization of the Yangtze conti- nent. The process may have relation to the extension and collapse of the deep crust with Archean ages, in response to the transition stage of the assembly and breakup of the Columbia supercontinent.展开更多
Ulcerative colitis(UC)manifests as an etiologically complicated and relapsing gastrointestinal disease.The enteric nervous system(ENS)plays a pivotal role in rectifying and orchestrating the inflammatory responses in ...Ulcerative colitis(UC)manifests as an etiologically complicated and relapsing gastrointestinal disease.The enteric nervous system(ENS)plays a pivotal role in rectifying and orchestrating the inflammatory responses in gut tract.Berberine,an isoquinoline alkaloid,is known as its antiinflammatory and therapeutic effects in experimental colitis.However,little research focused on its regulatory function on ENS.Therefore,we set out to explore the pathological role of neurogenic inflammation in UC and the modulating effects of berberine on neuro-immune interactions.Functional defects of enteric glial cells(EGCs),with decreased glial fibrillary acidic protein(GFAP)and increased substance P expression,were observed in DSS-induced murine UC.Administration of berberine can obviously ameliorate the disease severity and restore the mucosal barrier homeostasis of UC,closely accompanying by maintaining the residence of EGCs and attenuating inflammatory infiltrations and immune cells overactivation.In vitro,berberine showed direct protective effects on monoculture of EGCs,bone marrowderived dendritic cells(BMDCs),T cells,and intestinal epithelial cells(IECs)in the simulated inflammatory conditions.Furthermore,berberine could modulate gut EGCs-IECs-immune cell interactions in the co-culture systems.In summary,our study indicated the EGCs-IECs-immune cell interactions might function as a crucial paradigm in mucosal inflammation and provided an infusive mechanism of berberine in regulating enteric neurogenic inflammation.展开更多
Soil salinity is a major environmental stress that restricts the growth and yield of crops.Understanding the physiological,metabolic,and biochemical responses of plants to salt stress and mining the salt tolerance-ass...Soil salinity is a major environmental stress that restricts the growth and yield of crops.Understanding the physiological,metabolic,and biochemical responses of plants to salt stress and mining the salt tolerance-associated genetic resource in nature will be extremely important for us to cultivate salt-tolerant crops.In this review,we provide a comprehensive summary of the mechanisms of salt stress responses in plants,including salt stress-triggered physiological responses,oxidative stress,salt stress sensing and signaling pathways,organellar stress,ion homeostasis,hormonal and gene expression regulation,metabolic changes,as well as salt tolerance mechanisms in halophytes.Important questions regarding salt tolerance that need to be addressed in the future are discussed.展开更多
Objective To investigate the prevalence of peripheral arterial disease (PAD) in China type 2 diabetic patients and to demonstrate the relationships between putative risk factors and PAD. Methods In total 1 397 type 2 ...Objective To investigate the prevalence of peripheral arterial disease (PAD) in China type 2 diabetic patients and to demonstrate the relationships between putative risk factors and PAD. Methods In total 1 397 type 2 diabetic patients aged 50 years and older were enrolled and determined ankle-brachial index (ABI) and brachial-ankle pulse wave velocity (baPWV) in 15 Class III Grade A hospitals in 7 major cities of China. Results Mean patient age was 63.7±8.2 years and mean duration of diabetes mellitus was 9.39±7.4 years. Two hundreds and seventy-two (19.47%) patients were diagnosed as PAD by ABI <0.9, 122 (18.37%) in male and 150 (20.46%) in female. PAD patients had a significantly longer duration of diabetes mellitus, higher hemoglobin Alc, and a significantly lower mean body mass index than non-PAD ones. Aging, smoking, and systolic blood pressure were found to be positively related with the prevalence of PAD. In terms of lipid profiles, no variable was found to relate with PAD. Notably, baPWV showed as the same significant guiding index for PAD, almost matched with ABI. Conclusions PAD is a common complication in China type 2 diabetic patients. Therefore, PAD screening and treatment should be emphasized for diabetic patients with high risk factors.展开更多
Dissipative Kerr solitons in resonant frequency combs offer a promising route for ultrafast mode-locking,precision spectroscopy and time-frequency standards.The dynamics for the dissipative soliton generation,however,...Dissipative Kerr solitons in resonant frequency combs offer a promising route for ultrafast mode-locking,precision spectroscopy and time-frequency standards.The dynamics for the dissipative soliton generation,however,are intrinsically intertwined with thermal nonlinearities,limiting the soliton generation parameter map and statistical success probabilities of the solitary state.Here,via use of an auxiliary laser heating approach to suppress thermal dragging dynamics in dissipative soliton comb formation,we demonstrate stable Kerr soliton singlet formation and soliton bursts.First,we access a new soliton existence range with an inverse-sloped Kerr soliton evolution—diminishing soliton energy with increasing pump detuning.Second,we achieve deterministic transitions from Turinglike comb patterns directly into the dissipative Kerr soliton singlet pulse bypassing the chaotic states.This is achieved by avoiding subcomb overlaps at lower pump power,with near-identical singlet soliton comb generation over twenty instances.Third,with the red-detuned pump entrance route enabled,we uncover unique spontaneous soliton bursts in the direct formation of low-noise optical frequency combs from continuum background noise.The burst dynamics are due to the rapid entry and mutual attraction of the pump laser into the cavity mode,aided by the auxiliary laser and matching well with our numerical simulations.Enabled by the auxiliary-assisted frequency comb dynamics,we demonstrate an application of automatic soliton comb recovery and long-term stabilization against strong external perturbations.Our findings hold potential to expand the parameter space for ultrafast nonlinear dynamics and precision optical frequency comb stabilization.展开更多
Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivi...Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivity and better thermal stability than yttria-stabilized zirconia(YSZ).However,the low Vickers hardness and toughness are the main shortcomings of RE;TaO-and REjNbOr that limit their applications as TBC materials.To increase the hardness,high entropy(Yu3Ybu3Er/3)sTaOr,(Y13YbnErns)NbO,and(Sm1/6Eu1/6Y 1/6Yb1/6Lu1/6Er1/6)3(Nb1/2Ta1/2)O7 are designed and synthesized in this study.These high entropy ceramics exhibit high Vickers hardness(10.912.0 GPa),close thermal expansion coefficients to that of single-principal-component RE3TaO,and RE;NbO,(7.9×10^-6-10.8×10-6 C-1 at room temperature),good phase stability,and good chemical compatibility with thermally grown Al2O3,which make them promising for applications as candidate TBC materials.展开更多
OBJECTIVE: To assess the effectiveness and safety of Kuntai capsule and hormone replacement therapy in treatment of perimenopausal syndrome.METHODS: Articles were retrieved from the databases Cochrane Database of Syst...OBJECTIVE: To assess the effectiveness and safety of Kuntai capsule and hormone replacement therapy in treatment of perimenopausal syndrome.METHODS: Articles were retrieved from the databases Cochrane Database of Systematic Reviews,Pub Med, Chinese National Knowledge Infrastructure, China Science and Technology Journal Database, and Wanfang Database. Only randomized controlled trials were included; 15 trials involving1243 patients were identified from January 2005 to April 2015. A systemic review and Meta-analysis of publications was performed. The review was limit-ed to randomized controlled trials that compared Kuntai capsule and hormone replacement therapy to treat perimenopausal syndrome for at least 3months. The primary outcome assessed was the treatment efficacy at 3 months, including effective rate of Kupperman menopausal scores, Kupperman menopausal scores, and blood estradiol(E2) or blood follicle stimulating hormone(FSH) levels.Other outcomes assessed were safety or adverse events, such as gastrointestinal complaints, breast distending pain, or vaginal bleeding.RESULTS: Kupperman menopausal scores showed no significant difference in effective rate [odds ratio(OR): 1.05, 95% confidence intervals(CI): 0.71 to1.55] and changes in FSH level [mean difference(MD): 2.14, 95% CI:-2.36 to 6.65]. There was a significant statistical difference in Kupperman menopausal scores(MD:-1.14, 95% CI:-2.03 to-0.25)and changes in E2level(MD:-16.41, 95% CI:-18.83to-13.69). There were fewer adverse events in the Kuntai capsule group than in the hormone replacement therapy group(OR: = 0.35, 95% CI: 0.25 to0.48, P < 0.01).CONCLUSION: Compared with hormone replacement therapy, Kuntai capsule can improve perimenopausal symptoms and blood E2 levels, and reduce the incidence of adverse events.展开更多
Patients with an influenza virus infection can be complicated by acute encephalopathy and encephalitis. To investigate the immune reactions involved in the neurocomplication, mouse microglia and astrocytes were isolat...Patients with an influenza virus infection can be complicated by acute encephalopathy and encephalitis. To investigate the immune reactions involved in the neurocomplication, mouse microglia and astrocytes were isolated, infected with human H1N1 and avian H5N1 influenza viruses, and examined for their immune responses. We observed homogeneously distributed viral receptors, sialic acid （SA）-a2,3-Galactose （Gal） and SA-a2,6-Gal, on microglia and astrocytes. Both viruses were replicative and productive in microglia and astrocytes. Virus-induced apoptosis and cytopathy in infected cells were observed at 24 h post-infection （p.i.）. Expression of IL-1β, IL-6 and TNF-a mRNA examined at 6 h and 24 h p.i. was up-regulated, and their expression levels were considerably higher in H5N1 infection. The amounts of secreted proinflammatory IL-1β, IL-6 and TNF-a at 6 h and 24 h p.i. were also induced, with greater induction by H5N1 infection. This study is the first demonstration that both human H1N1 and avian H5N1 influenza viruses can infect mouse microglia and astrocytes and induce apoptosis, cytopathy, and proinflammatory cytokine production in them in vitro. Our results suggest that the direct cellular damage and the consequences of immunopathological injury in the CNS contribute to the influenza viral pathogenesis. Cellular ＆ Molecular Immunology.展开更多
AIM： To assess the therapeutic effect of Caspase-1 inhibitors （ICE-I） on acute lung injury （ALI） in experimental severe acute pancreatitis （SAP）. METHODS： Forty-two SD rats were randomly divided into 3 groups...AIM： To assess the therapeutic effect of Caspase-1 inhibitors （ICE-I） on acute lung injury （ALI） in experimental severe acute pancreatitis （SAP）. METHODS： Forty-two SD rats were randomly divided into 3 groups： healthy controls （HC, n = 6）; SAP-S group （n = 18）; SAP-ICE-i group （n = 18）. SAP was induced by retrograde infusion of 5% sodium taurocholate into the bile-pancreatic duct. HC rats underwent the same surgical procedures and duct cannulation without sodium taurocholate infusion, in SAP-S group, rats received the first intraperitoneal injection of isotonic saline 2 h after induction of acute pancreatitis and a repeated injection after 12 h. In SAP-ICE-I group, the rats were firstly given ICE inhibitors intraperitoneally 2 h after induction of pancreatitis. As in SAP-S group, the injection was repeated at 12 h. Serum 1L-1β was measured by EUSA. Intrapulmonary expression of Caspase-1, IL-1β and IL-18 mRNA were detected by semi-quantitative RT-PCR. The wet/dry weight ratios and histopathological changes of the lungs were also evaluated. RESULTS： Serum IL-1β levels in SAP-S group were 276.77 ± 44.92 pg/mL at 6 h, 308.99 ± 34.95 pg/mL at 12 h, and 311.60 ± 46.51 pg/mL at 18 h, which were increased significantly （P 〈 0.01, vs HC）. in SAP- ICE-I group, those values were decreased significantly （P 〈 0.01, vs SAP-S）. intrapulmonary expression of Caspase-1, IL-1β and IL-18 mRNA were observed in the HC group, while they were increased significantly in the SAP-S group （P 〈 0.01, vs HC）. The expression of IL-lβ and IL-18 mRNA were decreased significantly in the SAP- ICE-I group （P 〈 0.01, vs SAP-S）, whereas Caspase-1 mRNA expression had no significant difference （P 〉 0.05）. The wet/dry weight ratios of the lungs in the SAP-S group were increased significantly （P 〈 0.05 at 6 h, P 〈 0.01 at 12 h and 18 h, vs HC） and they were decreased significantly in the SAP-ICE-I group （P 〈 0.05, vs SAP-S）.Caspase-1 inhibitors ameliorated the severity of展开更多
AIM：To evaluate the diagnostic role of serum RASSF1A promoter hypermethylation in gastric and colorectal adenocarcinoma. METHODS：Methylation-specific polymerase chain reaction （MSPCR） was used to examine the promo...AIM：To evaluate the diagnostic role of serum RASSF1A promoter hypermethylation in gastric and colorectal adenocarcinoma. METHODS：Methylation-specific polymerase chain reaction （MSPCR） was used to examine the promoter methylation status of the serum RASSF1A gene in 47 gastric adenocarcinoma patients, 45 colorectal adenocarcinoma patients, 60 patients with benign gastrointestinal disease （30 with benign gastric disease and 30 with benign colorectal disease）, and 30 healthy donor controls. Apaired study of RASSF1A promoter methylation status in primary tumor, adjacent normal tissue, and postopertive serum were conducted in 25 gastric and colorectal adenocarcinoma patients who later were underwent surgical therapy. RESULTS：The frequencies of detection of serum RASSF1A promoter hypermethylation in gastric （34.0%） and colorectal （28.9%） adenocarcinoma patients were significantly higher than those in patients with benign gastric （3.3%） or colorectal （6.7%） disease or in healthy donors （0%） （P 〈 0.01）. The methylation status of RASSF1A promoter in serum samples was consistent with that in paired primary tumors, and the MSPCR results for RASSF1A promoter methylation status in paired preoperative samples were consistent with those in postoperative serum samples. The serum RASSF1A promoter hypermethylation did not correlate with patient sex, age, tumor differentiation grade, surgical therapy, or serum carcinoembryonic antigen level. Although the serum RASSF1A promoter hypermethylation frequency tended to be higher in patients with distant metastases, there was no correlation between methylation status and metastasis. CONCLUSION：Aberrant CpG island methylation within the promoter region of RASSF1A is a promising biomarker for gastric and colorectal cancer.展开更多
The effects of tanshinone IIA on the proliferation of the human non-small cell lung cancer cell line A549 and its possible mechanism on the VEGFNEGFR signal pathway were investigated. The exploration of the interactio...The effects of tanshinone IIA on the proliferation of the human non-small cell lung cancer cell line A549 and its possible mechanism on the VEGFNEGFR signal pathway were investigated. The exploration of the interaction between tanshinone IIA and its target proteins provides a feasible platform for studying the anticancer mechanism of active components of herbs. The CCK-8 assay was used to evaluate the proliferative activity of A549 cells treated with tanshinone IIA (2.5-80 mu mol/E) for 24, 48 and 72 h, respectively. Flow cytometry was used for the detection of cell apoptosis and cell cycle perturbation. VEGF and VEGFR2 expression were studied by Western blotting. The binding mode of tanshinone IIA within the crystal stmcture of the VEGFR2 protein was evaluated with molecular docking analysis by use of the CDOCKER algorithm in Discovery Studio 2.1. The CCK-8 results showed that tanshinone IIA can significantly inhibit A549 cell proliferation in a dose- and time-dependent manner. Flow cytometry results showed that the apoptosis rate of tested group was higher than the vehicle control, and tanshinone IIA-treated cells accumulated at the S phase, which was higher than the vehicle control. Furthermore, the expression of VEGF and VEGFR2 was decreased in Western blot Finally, molecular docking analysis revealed that tanshinone IIA could be stably docked into the kinase domain of VEGFR2 protein with its unique modes to form H-bonds with Cys917 and pi-pi stacking interactions with Va1848. In conclusion, tanshinone IIA may suppress A549 proliferation, induce apoptosis and cell cycle arrest at the S phase. This drug may suppress angiogenesis by targeting the protein kinase domains of VEGF/VEGFR2. (C) 2015 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.展开更多
A field experiment with four treatments and four replicates in a randomized complete block design was conducted at the Changwu Experimental Station in Changwu County, Shaanxi Province, of Northwest China from 1998 to ...A field experiment with four treatments and four replicates in a randomized complete block design was conducted at the Changwu Experimental Station in Changwu County, Shaanxi Province, of Northwest China from 1998 to 2002. The local cropping sequence of wheat, wheat-beans, maize, and wheat over the 4-year period was adopted. A micro-plot study using ^15N-lahelled fertilizer was carried out to determine the fate of applied N fertilizer in the first year. When N fertilizer was applied wheat （years 1, 2 and 4） and maize （year 3） grain yield increased significantly （P 〈 0.05） （〉 30%）, with no significant yield differences in normal rainfall years （Years 1, 2 and 3） for N application at the commonly application rate and at 2/3 of this rate. Grain yield of wheat varied greatly between years, mainly due to variation in annual rainfall. Results of ^15N studies on wheat showed that plants recovered 36.6%-38.4% of the N applied, the N remained in soll （0-40 cm） ranged from 29.2% to 33.6%, and unaccounted-for N was 29.5%-34.2%. The following crop （wheat） recovered 2.1%- 2.8% of the residual N from N applied to the previous wheat crop with recovery generally decreasing in the subsequent three crops （beans, maize and wheat）.展开更多
The extraction of pavement cracks is always a hard task in image processing.In airport and road construction,cracking is the main factor for pavement damage,which can decrease the quality of pavement and affect transp...The extraction of pavement cracks is always a hard task in image processing.In airport and road construction,cracking is the main factor for pavement damage,which can decrease the quality of pavement and affect transportation seriously.Cracks also exist in other artificial or natural objects,such as buildings,bridges,tunnels,etc.Among all the object images,pavement crack images are the most complex,so the image processing and analysis for them is harder than other crack images.From the early image acquisition based on photography technology to the current 3 D laser scanning technology,the pavement crack image acquisition technology is becoming more convenient and efficient,but there are still challenges in the automatic processing and recognition of cracks in images.From the early global thresholding to deep learning algorithms,the research for crack extraction has been developed for about 40 years.There are many methods and algorithms that are satisfactory in pavement crack applications,but there is no standard until today.Therefore,in order to know the developing history and the advanced research,we have collected a number of literature in this research topic for summarizing the research artwork status,and giving a review of the pavement crack image acquisition methods and2 D crack extraction algorithms.Also,for image acquisition methods and pavement crack image segmentation,more detailed comparison and discussions are made.展开更多
Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in lam...Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in laminar-turbulent transition, the mechanism causing the mean flow profile to evolve swiftly from laminar to turbulent was that the modification of mean flow profile by the disturbances,when they became larger,led to a remarkable change of its stability characteristics. Though the most unstable T-S wave was of second mode for laminar flow, the first mode waves played the key role in the breakdown process in laminar-turbulent transition.展开更多
Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact co...Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element （3D-FE） model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that （1）with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. （2）Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel’s freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. （3）A modified Yoshida buckling test （YBT） is used to address the wrinkling mechanisms under normal constraints in tube bending： the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm×1 mm×57 mm （tube outer diameter×wall thickness×centerline bending radius） equals about 20% of initial wall thickness.展开更多
Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densificat...Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures.In order to overcome these obstacles,herein,porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C was prepared by a simple method combing in-situ reaction and partial sintering.Porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm^2·s^-1and good high temperature stability.The combination of these properties renders porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))Cpromising as light-weight ultrahigh temperature thermal insulation materials.展开更多
基金Foundation items： National Natural Science Foundation of China （50905144） State Key Laboratory of Materials Processing and Die ＆ Mould Technology, Huazhong University of Science and Technology （09-10）+2 种基金 NPU Foundation for Fundamental Research （JC201028） Fund of the State Key Laboratory of Solidification Processing in NWPU, Natural Science Basic Research Plan in Shaanxi Province （2011JQ6004） ＂111＂ Project （B08040）
文摘As one kind of key components with enormous quantities and diversities, the bent tube parts satisfy the increasing needs for lightweight and high-strength product from both materials and structure aspects. The bent tubes have been widely used in many high-end industries such as aviation, aerospace, shipbuilding, automobile, energy and health care. The tube bending has become one of the key manufacturing technologies for lightweight product forming. Via the analysis of bending characteristics and multiple defects, advances on exploring the common issues in tube bending are summarized regarding wrinkling instability at the intrados, wall thinning （cracking） at the extrados, springback phenomenon, cross-section deformation, forming limit and process/ tooling design/optimization. Some currently developed bending techniques are reviewed in terms of their advantages and limitations. Finally, in view of the urgent requirements of high-performance complex bent tube components with difficult-todeform and lightweight materials in aviation and aerospace fields, the development trends and corresponding challenges are presented for realizing the precise and high-efficiency tube bending deformation.
基金the Natural Science Foundation of the Educational Committee of Jiangsu Province,No.125FA9608.
文摘AIM To investigate the expression of multiplegenes and the behavior of cellular biology ingastric cancer（GC）and other gastric mucosallesions and their relations to Helicobacter pylori（H.pylori）infection,tumor staging andhistological subtypes.METHODS Three hundred and twenty-sevenspecimens of gastric mucosa obtained viaendoscopy or surgical resection,and ABCimmunohistochemical staining were used todetect the expression of p53,p16,Bcl-2 andCOX-2 proteins.H.pylori was determined byrapid urea test combined with pathologicalstaining or<sup>14</sup>C urea breath test.Cellular image analysis was performed in 66 patients withintestinal metaplasia（IM）and/or dysplasia（Dys）.In 30 of them,both cancer and theparacancerous tissues were obtained at the timeof surgery.Histological pattern,tumor staging,lymph node metastasis,grading ofdifferentiation and other clinical data werestudied in the medical records.RESULTS p16 expression of IM or Dys wassignificantly lower in positive H.pylori chronicatrophic gastritis（CAG）than those withnegative H.pylori（CAG:54.8% vs 88.0%,IM:34.4% vs 69.6%,Dys:23.8% vs 53.6%,allP【0.05）,Bcl-2 or COX-2 expression of IM orDys in positive H.pylori cases was significantlyhigher than that without H.pylori（Bcl-2:68.8%vs23.9%,90.5% vs 60.7%;COX-2:50.0% vs10.8%,61.8% vs 17.8%;all P【0.05）.Themean number of most parameters of cellularimage analysis in positive H.pylori group wassignificantly higher than that in negative H.pylori group（Ellipser:53±14,40±12μm,Area<sub>1</sub>:748±572,302±202 μm<sup>2</sup>,Area<sub>2</sub>:3050±1661,1681±1990 μm<sup>2</sup>,all P【0.05;Ellipseb:79±23,58±15 μm,Ratio<sub>1</sub>:22%±5%,13%±4%,Ratio<sub>2</sub>:79%±17%,53%±20%,all P【0.01）.There was significant correlation between Bcl-2and histologic pattern of gastric carcinoma,andbetween COX-2 and tumor staging or lymph nodemetastasis（Bcl-2:75.0% vs 16.7%;COX-2:76.0% vs 20.0%,79.2% vs 16.7%;allP【0.05）.CONCLUSION p1l6, Bcl-2, and COX-2 but not p53 gene may play a role
基金Supported by National Natural Science Foundation of China (Grant Nos. 90714002 and 40772042) National Basic Research Program of China (Grant No. 2006CB403502)
文摘Zircon U-Pb age and Hf isotope, and major and trace element compositions were reported for granite at Quanyishang, which intruded into the Kongling complex in Yichang, Hubei Province. The results show that the Quanyishang granite is rich in silicon and alkalis but poor in calcium and magnesium, and displays enrichment in Ga, Y, Zr, Nb but depletion in Sr and Ba, exhibiting the post-orogenic A-type affinity. 90% zircons from the granite are concordant, and give a middle Paleoproterozoic magmatic crystallization age (mean 1854 Ma). Initial Hf isotope ratios (176Hf/177Hf)i of the middle Paleoproterozoic zircons range from 0.280863 to 0.281134 and they have negative εHf(t) values with a minimum of -26.3. These zircons give the depleted mantle model ages (TDM) of 2.9―3.3 Ga (mean 3.0 Ga), and the average crustal model ages (Tcrust) of 3.6―4.2 Ga (mean 3.8 Ga). A Mesoarchean grain with 207Pb/206Pb age of 2859 Ma has a slightly high TDM (3.4 Ga) but similar Tcrust (3.8 Ga) to the Paleoproterozoic zircons. All these data suggest that the source materials of the Quanyishang A-type granite are unusually old, at least ≥2.9 Ga (even Eoarchean). The event of crustal remelting, which resulted in the formation of the Quanyishang granite in the middle Paleoproterozoic, recorded the cratonization of the Yangtze conti- nent. The process may have relation to the extension and collapse of the deep crust with Archean ages, in response to the transition stage of the assembly and breakup of the Columbia supercontinent.
基金supported by Science and Technology Commission of Shanghai Municipality,China(No.18431907100)technical assistance from the Platform of Molecular Imaging and Research,SIMM,CAS,Beijing,China.
文摘Ulcerative colitis(UC)manifests as an etiologically complicated and relapsing gastrointestinal disease.The enteric nervous system(ENS)plays a pivotal role in rectifying and orchestrating the inflammatory responses in gut tract.Berberine,an isoquinoline alkaloid,is known as its antiinflammatory and therapeutic effects in experimental colitis.However,little research focused on its regulatory function on ENS.Therefore,we set out to explore the pathological role of neurogenic inflammation in UC and the modulating effects of berberine on neuro-immune interactions.Functional defects of enteric glial cells(EGCs),with decreased glial fibrillary acidic protein(GFAP)and increased substance P expression,were observed in DSS-induced murine UC.Administration of berberine can obviously ameliorate the disease severity and restore the mucosal barrier homeostasis of UC,closely accompanying by maintaining the residence of EGCs and attenuating inflammatory infiltrations and immune cells overactivation.In vitro,berberine showed direct protective effects on monoculture of EGCs,bone marrowderived dendritic cells(BMDCs),T cells,and intestinal epithelial cells(IECs)in the simulated inflammatory conditions.Furthermore,berberine could modulate gut EGCs-IECs-immune cell interactions in the co-culture systems.In summary,our study indicated the EGCs-IECs-immune cell interactions might function as a crucial paradigm in mucosal inflammation and provided an infusive mechanism of berberine in regulating enteric neurogenic inflammation.
基金We are grateful to Zichen Xu for assistance in the preparation of the figures.This work was supported by the Strategic Priority Research Program(grant no.XDB27040101)of the Chinese Academy of Sciences.
文摘Soil salinity is a major environmental stress that restricts the growth and yield of crops.Understanding the physiological,metabolic,and biochemical responses of plants to salt stress and mining the salt tolerance-associated genetic resource in nature will be extremely important for us to cultivate salt-tolerant crops.In this review,we provide a comprehensive summary of the mechanisms of salt stress responses in plants,including salt stress-triggered physiological responses,oxidative stress,salt stress sensing and signaling pathways,organellar stress,ion homeostasis,hormonal and gene expression regulation,metabolic changes,as well as salt tolerance mechanisms in halophytes.Important questions regarding salt tolerance that need to be addressed in the future are discussed.
文摘Objective To investigate the prevalence of peripheral arterial disease (PAD) in China type 2 diabetic patients and to demonstrate the relationships between putative risk factors and PAD. Methods In total 1 397 type 2 diabetic patients aged 50 years and older were enrolled and determined ankle-brachial index (ABI) and brachial-ankle pulse wave velocity (baPWV) in 15 Class III Grade A hospitals in 7 major cities of China. Results Mean patient age was 63.7±8.2 years and mean duration of diabetes mellitus was 9.39±7.4 years. Two hundreds and seventy-two (19.47%) patients were diagnosed as PAD by ABI <0.9, 122 (18.37%) in male and 150 (20.46%) in female. PAD patients had a significantly longer duration of diabetes mellitus, higher hemoglobin Alc, and a significantly lower mean body mass index than non-PAD ones. Aging, smoking, and systolic blood pressure were found to be positively related with the prevalence of PAD. In terms of lipid profiles, no variable was found to relate with PAD. Notably, baPWV showed as the same significant guiding index for PAD, almost matched with ABI. Conclusions PAD is a common complication in China type 2 diabetic patients. Therefore, PAD screening and treatment should be emphasized for diabetic patients with high risk factors.
基金supported by the National Key R&D Program of China(2018YFA0307400)NFSC grant 61705033+3 种基金the 111 project(B14039)Lawrence Livermore National Laboratory contract B622827the Office of Naval Research award N00014-16-1-2094the National Science Foundation awards 1741707,1810506 and 1824568.
文摘Dissipative Kerr solitons in resonant frequency combs offer a promising route for ultrafast mode-locking,precision spectroscopy and time-frequency standards.The dynamics for the dissipative soliton generation,however,are intrinsically intertwined with thermal nonlinearities,limiting the soliton generation parameter map and statistical success probabilities of the solitary state.Here,via use of an auxiliary laser heating approach to suppress thermal dragging dynamics in dissipative soliton comb formation,we demonstrate stable Kerr soliton singlet formation and soliton bursts.First,we access a new soliton existence range with an inverse-sloped Kerr soliton evolution—diminishing soliton energy with increasing pump detuning.Second,we achieve deterministic transitions from Turinglike comb patterns directly into the dissipative Kerr soliton singlet pulse bypassing the chaotic states.This is achieved by avoiding subcomb overlaps at lower pump power,with near-identical singlet soliton comb generation over twenty instances.Third,with the red-detuned pump entrance route enabled,we uncover unique spontaneous soliton bursts in the direct formation of low-noise optical frequency combs from continuum background noise.The burst dynamics are due to the rapid entry and mutual attraction of the pump laser into the cavity mode,aided by the auxiliary laser and matching well with our numerical simulations.Enabled by the auxiliary-assisted frequency comb dynamics,we demonstrate an application of automatic soliton comb recovery and long-term stabilization against strong external perturbations.Our findings hold potential to expand the parameter space for ultrafast nonlinear dynamics and precision optical frequency comb stabilization.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.51672064 and 51972089).
文摘Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivity and better thermal stability than yttria-stabilized zirconia(YSZ).However,the low Vickers hardness and toughness are the main shortcomings of RE;TaO-and REjNbOr that limit their applications as TBC materials.To increase the hardness,high entropy(Yu3Ybu3Er/3)sTaOr,(Y13YbnErns)NbO,and(Sm1/6Eu1/6Y 1/6Yb1/6Lu1/6Er1/6)3(Nb1/2Ta1/2)O7 are designed and synthesized in this study.These high entropy ceramics exhibit high Vickers hardness(10.912.0 GPa),close thermal expansion coefficients to that of single-principal-component RE3TaO,and RE;NbO,(7.9×10^-6-10.8×10-6 C-1 at room temperature),good phase stability,and good chemical compatibility with thermally grown Al2O3,which make them promising for applications as candidate TBC materials.
文摘OBJECTIVE: To assess the effectiveness and safety of Kuntai capsule and hormone replacement therapy in treatment of perimenopausal syndrome.METHODS: Articles were retrieved from the databases Cochrane Database of Systematic Reviews,Pub Med, Chinese National Knowledge Infrastructure, China Science and Technology Journal Database, and Wanfang Database. Only randomized controlled trials were included; 15 trials involving1243 patients were identified from January 2005 to April 2015. A systemic review and Meta-analysis of publications was performed. The review was limit-ed to randomized controlled trials that compared Kuntai capsule and hormone replacement therapy to treat perimenopausal syndrome for at least 3months. The primary outcome assessed was the treatment efficacy at 3 months, including effective rate of Kupperman menopausal scores, Kupperman menopausal scores, and blood estradiol(E2) or blood follicle stimulating hormone(FSH) levels.Other outcomes assessed were safety or adverse events, such as gastrointestinal complaints, breast distending pain, or vaginal bleeding.RESULTS: Kupperman menopausal scores showed no significant difference in effective rate [odds ratio(OR): 1.05, 95% confidence intervals(CI): 0.71 to1.55] and changes in FSH level [mean difference(MD): 2.14, 95% CI:-2.36 to 6.65]. There was a significant statistical difference in Kupperman menopausal scores(MD:-1.14, 95% CI:-2.03 to-0.25)and changes in E2level(MD:-16.41, 95% CI:-18.83to-13.69). There were fewer adverse events in the Kuntai capsule group than in the hormone replacement therapy group(OR: = 0.35, 95% CI: 0.25 to0.48, P < 0.01).CONCLUSION: Compared with hormone replacement therapy, Kuntai capsule can improve perimenopausal symptoms and blood E2 levels, and reduce the incidence of adverse events.
基金supported by grants from National Natural Science Foundation of China(No.30571674 and No.30771988)Guangdong Natural Science Foundation(No.05008347 and No.04020239).
文摘Patients with an influenza virus infection can be complicated by acute encephalopathy and encephalitis. To investigate the immune reactions involved in the neurocomplication, mouse microglia and astrocytes were isolated, infected with human H1N1 and avian H5N1 influenza viruses, and examined for their immune responses. We observed homogeneously distributed viral receptors, sialic acid （SA）-a2,3-Galactose （Gal） and SA-a2,6-Gal, on microglia and astrocytes. Both viruses were replicative and productive in microglia and astrocytes. Virus-induced apoptosis and cytopathy in infected cells were observed at 24 h post-infection （p.i.）. Expression of IL-1β, IL-6 and TNF-a mRNA examined at 6 h and 24 h p.i. was up-regulated, and their expression levels were considerably higher in H5N1 infection. The amounts of secreted proinflammatory IL-1β, IL-6 and TNF-a at 6 h and 24 h p.i. were also induced, with greater induction by H5N1 infection. This study is the first demonstration that both human H1N1 and avian H5N1 influenza viruses can infect mouse microglia and astrocytes and induce apoptosis, cytopathy, and proinflammatory cytokine production in them in vitro. Our results suggest that the direct cellular damage and the consequences of immunopathological injury in the CNS contribute to the influenza viral pathogenesis. Cellular ＆ Molecular Immunology.
文摘AIM： To assess the therapeutic effect of Caspase-1 inhibitors （ICE-I） on acute lung injury （ALI） in experimental severe acute pancreatitis （SAP）. METHODS： Forty-two SD rats were randomly divided into 3 groups： healthy controls （HC, n = 6）; SAP-S group （n = 18）; SAP-ICE-i group （n = 18）. SAP was induced by retrograde infusion of 5% sodium taurocholate into the bile-pancreatic duct. HC rats underwent the same surgical procedures and duct cannulation without sodium taurocholate infusion, in SAP-S group, rats received the first intraperitoneal injection of isotonic saline 2 h after induction of acute pancreatitis and a repeated injection after 12 h. In SAP-ICE-I group, the rats were firstly given ICE inhibitors intraperitoneally 2 h after induction of pancreatitis. As in SAP-S group, the injection was repeated at 12 h. Serum 1L-1β was measured by EUSA. Intrapulmonary expression of Caspase-1, IL-1β and IL-18 mRNA were detected by semi-quantitative RT-PCR. The wet/dry weight ratios and histopathological changes of the lungs were also evaluated. RESULTS： Serum IL-1β levels in SAP-S group were 276.77 ± 44.92 pg/mL at 6 h, 308.99 ± 34.95 pg/mL at 12 h, and 311.60 ± 46.51 pg/mL at 18 h, which were increased significantly （P 〈 0.01, vs HC）. in SAP- ICE-I group, those values were decreased significantly （P 〈 0.01, vs SAP-S）. intrapulmonary expression of Caspase-1, IL-1β and IL-18 mRNA were observed in the HC group, while they were increased significantly in the SAP-S group （P 〈 0.01, vs HC）. The expression of IL-lβ and IL-18 mRNA were decreased significantly in the SAP- ICE-I group （P 〈 0.01, vs SAP-S）, whereas Caspase-1 mRNA expression had no significant difference （P 〉 0.05）. The wet/dry weight ratios of the lungs in the SAP-S group were increased significantly （P 〈 0.05 at 6 h, P 〈 0.01 at 12 h and 18 h, vs HC） and they were decreased significantly in the SAP-ICE-I group （P 〈 0.05, vs SAP-S）.Caspase-1 inhibitors ameliorated the severity of
文摘AIM：To evaluate the diagnostic role of serum RASSF1A promoter hypermethylation in gastric and colorectal adenocarcinoma. METHODS：Methylation-specific polymerase chain reaction （MSPCR） was used to examine the promoter methylation status of the serum RASSF1A gene in 47 gastric adenocarcinoma patients, 45 colorectal adenocarcinoma patients, 60 patients with benign gastrointestinal disease （30 with benign gastric disease and 30 with benign colorectal disease）, and 30 healthy donor controls. Apaired study of RASSF1A promoter methylation status in primary tumor, adjacent normal tissue, and postopertive serum were conducted in 25 gastric and colorectal adenocarcinoma patients who later were underwent surgical therapy. RESULTS：The frequencies of detection of serum RASSF1A promoter hypermethylation in gastric （34.0%） and colorectal （28.9%） adenocarcinoma patients were significantly higher than those in patients with benign gastric （3.3%） or colorectal （6.7%） disease or in healthy donors （0%） （P 〈 0.01）. The methylation status of RASSF1A promoter in serum samples was consistent with that in paired primary tumors, and the MSPCR results for RASSF1A promoter methylation status in paired preoperative samples were consistent with those in postoperative serum samples. The serum RASSF1A promoter hypermethylation did not correlate with patient sex, age, tumor differentiation grade, surgical therapy, or serum carcinoembryonic antigen level. Although the serum RASSF1A promoter hypermethylation frequency tended to be higher in patients with distant metastases, there was no correlation between methylation status and metastasis. CONCLUSION：Aberrant CpG island methylation within the promoter region of RASSF1A is a promising biomarker for gastric and colorectal cancer.
基金supported by the National Natural Science Foundation of China(No.81274135)
文摘The effects of tanshinone IIA on the proliferation of the human non-small cell lung cancer cell line A549 and its possible mechanism on the VEGFNEGFR signal pathway were investigated. The exploration of the interaction between tanshinone IIA and its target proteins provides a feasible platform for studying the anticancer mechanism of active components of herbs. The CCK-8 assay was used to evaluate the proliferative activity of A549 cells treated with tanshinone IIA (2.5-80 mu mol/E) for 24, 48 and 72 h, respectively. Flow cytometry was used for the detection of cell apoptosis and cell cycle perturbation. VEGF and VEGFR2 expression were studied by Western blotting. The binding mode of tanshinone IIA within the crystal stmcture of the VEGFR2 protein was evaluated with molecular docking analysis by use of the CDOCKER algorithm in Discovery Studio 2.1. The CCK-8 results showed that tanshinone IIA can significantly inhibit A549 cell proliferation in a dose- and time-dependent manner. Flow cytometry results showed that the apoptosis rate of tested group was higher than the vehicle control, and tanshinone IIA-treated cells accumulated at the S phase, which was higher than the vehicle control. Furthermore, the expression of VEGF and VEGFR2 was decreased in Western blot Finally, molecular docking analysis revealed that tanshinone IIA could be stably docked into the kinase domain of VEGFR2 protein with its unique modes to form H-bonds with Cys917 and pi-pi stacking interactions with Va1848. In conclusion, tanshinone IIA may suppress A549 proliferation, induce apoptosis and cell cycle arrest at the S phase. This drug may suppress angiogenesis by targeting the protein kinase domains of VEGF/VEGFR2. (C) 2015 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.
基金Project supported by the International Atom Energy Agency (IAEA) (NO. 302-D1-CRP-9986) and the National Basic Research Program of China (NO. 2005CB121102).
文摘A field experiment with four treatments and four replicates in a randomized complete block design was conducted at the Changwu Experimental Station in Changwu County, Shaanxi Province, of Northwest China from 1998 to 2002. The local cropping sequence of wheat, wheat-beans, maize, and wheat over the 4-year period was adopted. A micro-plot study using ^15N-lahelled fertilizer was carried out to determine the fate of applied N fertilizer in the first year. When N fertilizer was applied wheat （years 1, 2 and 4） and maize （year 3） grain yield increased significantly （P 〈 0.05） （〉 30%）, with no significant yield differences in normal rainfall years （Years 1, 2 and 3） for N application at the commonly application rate and at 2/3 of this rate. Grain yield of wheat varied greatly between years, mainly due to variation in annual rainfall. Results of ^15N studies on wheat showed that plants recovered 36.6%-38.4% of the N applied, the N remained in soll （0-40 cm） ranged from 29.2% to 33.6%, and unaccounted-for N was 29.5%-34.2%. The following crop （wheat） recovered 2.1%- 2.8% of the residual N from N applied to the previous wheat crop with recovery generally decreasing in the subsequent three crops （beans, maize and wheat）.
基金financially supported by the National Natural Science Fund in China(grant No.61170147)the National Natural Science Key Fund in China(grant No.U1401252).
文摘The extraction of pavement cracks is always a hard task in image processing.In airport and road construction,cracking is the main factor for pavement damage,which can decrease the quality of pavement and affect transportation seriously.Cracks also exist in other artificial or natural objects,such as buildings,bridges,tunnels,etc.Among all the object images,pavement crack images are the most complex,so the image processing and analysis for them is harder than other crack images.From the early image acquisition based on photography technology to the current 3 D laser scanning technology,the pavement crack image acquisition technology is becoming more convenient and efficient,but there are still challenges in the automatic processing and recognition of cracks in images.From the early global thresholding to deep learning algorithms,the research for crack extraction has been developed for about 40 years.There are many methods and algorithms that are satisfactory in pavement crack applications,but there is no standard until today.Therefore,in order to know the developing history and the advanced research,we have collected a number of literature in this research topic for summarizing the research artwork status,and giving a review of the pavement crack image acquisition methods and2 D crack extraction algorithms.Also,for image acquisition methods and pavement crack image segmentation,more detailed comparison and discussions are made.
基金supported by the National Natural Science Foundation of China(Grant No.90205021)the Foundation for the Author of National Excellent Doctoral Dissertation(FANEDD)of China(Grant No.200328)partially supported by Liu-Hui Center of Applied Mathematics,Nankai University and Tianjin University.
文摘Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in laminar-turbulent transition, the mechanism causing the mean flow profile to evolve swiftly from laminar to turbulent was that the modification of mean flow profile by the disturbances,when they became larger,led to a remarkable change of its stability characteristics. Though the most unstable T-S wave was of second mode for laminar flow, the first mode waves played the key role in the breakdown process in laminar-turbulent transition.
基金National Natural Science Foundation of China (59975076, 50905144)State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (09-10)+1 种基金NPU Foundation for Fundamental Research (JC201028)Fund of the State Key Laboratory of Solidification Process-ing in NWPU
文摘Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element （3D-FE） model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that （1）with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. （2）Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel’s freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. （3）A modified Yoshida buckling test （YBT） is used to address the wrinkling mechanisms under normal constraints in tube bending： the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm×1 mm×57 mm （tube outer diameter×wall thickness×centerline bending radius） equals about 20% of initial wall thickness.
基金supported by the National Natural Science Foundation of China under Grant Nos. U1435206 and 51672064Beijing Municipal Science & Technology Commission under Grant No. D161100002416001
文摘Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures.In order to overcome these obstacles,herein,porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C was prepared by a simple method combing in-situ reaction and partial sintering.Porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm^2·s^-1and good high temperature stability.The combination of these properties renders porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))Cpromising as light-weight ultrahigh temperature thermal insulation materials.
