In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measuremen...In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were performed.Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g.The onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and analysed.Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process.During the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant grain.The calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were observed.The dynamic mechanical response process of the dummy propellant grain was analysed in detail.The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.展开更多
The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combinat...The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.展开更多
Background: Intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) can not only observe the diffusion of tissue water molecules but also reflect the blood perfusion information of tissue microcirculation. ...Background: Intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) can not only observe the diffusion of tissue water molecules but also reflect the blood perfusion information of tissue microcirculation. IVIM-DWI has been applied in many clinical areas. However, few studies have addressed the use of IVIM-DWI for the evaluation of transarterial chemoembolization (TACE) response in hepatocellular carcinoma (HCC) patients. Objectives: The purpose of the present study was to explore the role of IVIM-DWI for the therapeutic response of TACE for HCC. Materials and Methods: Twenty patients underwent IVIM-DWI scan on a 3.0T magnetic resonance imaging instrument 1 - 3 days before and 30 to 40 days after TACE. The values of IVIM-DWI parameters, including standard apparent diffusion coefficient (ADC), pure diffusion coefficient (Dslow), pseudo-diffusion coefficient (Dfast) and perfusion fraction (f) were measured. The values of IVIM-DWI parameters before and after TACE were compared using paired t tests. The values between responsive and non-responsive groups were compared using independent-samples t test. P 0.05 indicated statistical significance. Results: After TACE, the ADC and Dslow values in the tumors increased significantly, and the values of Dfast decreased significantly, while the values of f value did not change obviously. The ADC values in responsive group were remarkably higher than those in non-responsive group, the Dfast values in responsive group were significantly lower than those in non-responsive group, but the values of Dslow and f between the two groups were not different significantly. Conclusions: IVIM-DWI parameters can be used as potential markers for the therapeutic response of TACE for HCC.展开更多
1.Objective The study area is located at the southern Zhangguangcai range,which is thought to be the eastern part of the Central Asian Orogenic Belt(CAOB).The study area is closed to the eastern margin of the Songliao...1.Objective The study area is located at the southern Zhangguangcai range,which is thought to be the eastern part of the Central Asian Orogenic Belt(CAOB).The study area is closed to the eastern margin of the Songliao basin(Fig.1a).No petroleum exploration or related research work have been conducted in this area by far.Based on our most recent geological mapping,numerous hydrocarbon source rocks were firstly discovered within the Xinxing Formation,which is widely exposed from the central Jilin Province to the southeastern Heilongjiang province.The Xinxing Formation covers an area of nearly 1000 km2 with a total thickness of more than 1481 m(Regional Geology of Heilongjiang Province,1993).Therefore,the Xinxing Formation has huge potential to form oil and gas resources.This new discovery of hydrocarbon source rocks within the Xinxing Formation could provide critical clues for oil and gas resources’investigation in Northeast China,also may has important economic significance.展开更多
Nanostructured zeolitic imidazolate frameworks(ZIF-8) was incorporated into the mixture of poly(ethylene glycol) methyl ether acrylate(PEGMEA) and pentaerythritol triacrylate(PETA) to synthesize mixed matrix membranes...Nanostructured zeolitic imidazolate frameworks(ZIF-8) was incorporated into the mixture of poly(ethylene glycol) methyl ether acrylate(PEGMEA) and pentaerythritol triacrylate(PETA) to synthesize mixed matrix membranes(MMMs) by in situ polymerization for CO_2/CH_4 separation. The solvent-free polymerization between PEGMEA and PETA was induced by UV light with 1-hydroxylcyclohexyl phenyl ketone as initiator. The chemical structural characterization was performed by Fourier transform infrared spectroscopy. The morphology was characterized by scanning electron microscope. The average chain-to-chain distance of the polymer chains in MMMs was investigated by X-ray diffraction. The thermal property was evaluated by differential scanning calorimetry. The CH_4 and CO_2 gas transport properties of MMMs are reported. The relationship between gas permeation–separation performances or physical properties and ZIF-8 loading is also discussed. However, the permeation–separation performance was not improved in Robeson upper bound plot compared with original polymer membrane as predicted. The significant partial pore blockage and polymer rigidification effect around the ZIFs confirmed by the increase in glass temperature and the decrease in the d-spacing, were mainly responsible for the failure in performance improvement, which offset the high diffusion induced by porous ZIF-8.展开更多
In this paper,a nonlinear wave equation with variable coefficients is studied,interestingly,this equation can be used to describe the travelling waves propagating along the circular rod composed of a general compressi...In this paper,a nonlinear wave equation with variable coefficients is studied,interestingly,this equation can be used to describe the travelling waves propagating along the circular rod composed of a general compressible hyperelastic material with variable cross-sections and variable material densities.With the aid of Lou’s direct method1,the nonlinear wave equation with variable coefficients is reduced and two sets of symmetry transformations and exact solutions of the nonlinear wave equation are obtained.The corresponding numerical examples of exact solutions are presented by using different coefficients.Particularly,while the variable coefficients are taken as some special constants,the nonlinear wave equation with variable coefficients reduces to the one with constant coefficients,which can be used to describe the propagation of the travelling waves in general cylindrical rods composed of generally hyperelastic materials.Using the same method to solve the nonlinear wave equation,the validity and rationality of this method are verified.展开更多
Well-ordered hierarchically mesoporous/microporous carbon materials have been successfully fabricated by using dual soft-templating approach through compressed CO_(2).Pluronic F127 and different type of surfactants,in...Well-ordered hierarchically mesoporous/microporous carbon materials have been successfully fabricated by using dual soft-templating approach through compressed CO_(2).Pluronic F127 and different type of surfactants,including nonionic,cationic,and anionic surfactants,were used as dual templates to investigate the influence on the morphology and nanostructure of the as-prepared carbon samples.TEM,SEM,N2 sorption,wide-angle and small-angle XRD analysis were employed to reveal the well-ordered hierarchically micro-mesoporous structure with2 D hexagonal symmetry by using compressed CO_(2).The prepared HPC samples with different pressures as the catalyst carriers have been functioned by chlorosulfonic acid for the fructose conversion into HMF.Chlorosulfonic acid concentration,catalyst dosage and reaction temperature have been optimized for fructose-to-HMF transformation with the obtained catalyst.The performances of as-made HPC-SO_(3) H samples in HMF yield and reaction rate of fructose-to-HMF transformation have been investigated.The stability of the samples was also conducted in the dehydration of fructose to HMF for five cycles.The possible catalytic mechanism by using hierarchically porous carbon materials as catalyst support for fructose-to-HMF transformation was proposed.展开更多
Objective:To study the transmembrane transport of chemical components of Chinese herbs and to explore the function of platycodin D (PD) on biomembranes.Methods:Interaction between PD and the dipalmitoylphosphatidylcho...Objective:To study the transmembrane transport of chemical components of Chinese herbs and to explore the function of platycodin D (PD) on biomembranes.Methods:Interaction between PD and the dipalmitoylphosphatidylcholine (DPPC) bilayer was reproduced by molecular dynamics simulation with the Martini force field.A model validation and methodological study were first performed,and were based on simulation investigations of transmembrane transport for three herbal compounds with distinct hydrophilic properties.Results:PD increased the mobility of the DPPC bilayer since its aglycone strongly interacted with the hydrophobic layer,which broke the structure of the gate layer,and weakened the ordered performance of hydrophobic tails.Conclusion:The Martini force field was successfully applied to the study of the interaction between herbal compounds and a biological membrane.By combining the dynamics equilibrium morphology,the distribution of drugs inside and outside the biomembrane,and the interaction sites of drugs on the DPPC bilayer,factors influencing transmembrane transport of drugs were elucidated and the function of platycodin D in a biological membrane was reproduced.展开更多
Aging is linked to the deterioration of many physical and cognitive abilities and is the leading risk factor for Alzheimer’s disease. The growing aging population is a significant healthcare problem globally that res...Aging is linked to the deterioration of many physical and cognitive abilities and is the leading risk factor for Alzheimer’s disease. The growing aging population is a significant healthcare problem globally that researchers must investigate to better understand the underlying aging processes. Advances in microarrays and sequencing techniques have resulted in deeper analyses of diverse essential genomes(e.g., mouse, human, and rat) and their corresponding cell types, their organ-specific transcriptomes, and the tissue involved in aging. Traditional gene controllers such as DNA-and RNA-binding proteins significantly influence such programs, causing the need to sort out long non-coding RNAs, a new class of powerful gene regulatory elements. However, their functional significance in the aging process and senescence has yet to be investigated and identified. Several recent researchers have associated the initiation and development of senescence and aging in mammals with several well-reported and novel long non-coding RNAs. In this review article, we identified and analyzed the evolving functions of long non-coding RNAs in cellular processes, including cellular senescence, aging, and age-related pathogenesis, which are the major hallmarks of long non-coding RNAs in aging.展开更多
BACKGROUND Gastric cancer(GC)is a common malignant tumor of the digestive system with a high degree of malignancy.It usually develops insidiously without any specific symptoms in the early stages.As one of the disease...BACKGROUND Gastric cancer(GC)is a common malignant tumor of the digestive system with a high degree of malignancy.It usually develops insidiously without any specific symptoms in the early stages.As one of the diseases caused by abnormal gene changes,GC has abnormal expression of various oncogenes and products during its development.Tumor markers such as carcinoembryonic antigen(CEA),carbohydrate antigen 199(CA199)and carbohydrate antigen 724(CA724)are not expressed or lowly expressed in normal people,but significantly increased after carcinogenesis.Monitoring the changes in the levels of tumor markers such as CEA,CA199 and CA724 is conducive to early diagnosis and evaluation of the occurrence of some solid tumors.AIM To investigate the expression of CEA,CA199 and CA724 in GC and their correlation with clinical features,hoping to provide more effective markers for the early preventive diagnosis of GC.METHODS Of 87 patients with GC admitted to our hospital from September 2020 to December 2021 were included in the GC group,and another 80 healthy people who came to our hospital for physical examination with normal results during the same period were selected as the control group.The serum CEA,CA199,and CA724 levels were compared between the two groups,and the serum CEA,CA199,and CA724 levels were compared in patients with GC at different TNM stages,and the differences in the positive rates of CEA,CA199,and CA724 alone and in combination in detecting TNM stages of GC and GC were compared.In addition,the relationship between the levels of tumor markers CEA,CA199 and CA724 and the clinicopathological characteristics of GC patients was also analyzed.The relationship between the serum levels of CEA,CA199 and CA724 and the survival period of GC patients was analyzed by Pearson.RESULTS The serum levels of CEA,CA199 and CA724 in GC group were significantly higher than those in control group(P<0.05).With the increase of TNM stage,the serum CEA,CA199 and CA724 expression levels in GC patients increased significantly,and the differences between groups were statistically significant(P<0.05).The positive rate of the CA724 single test was higher than that of CEA and CA199 single test(P<0.05).The positive rate of the three combined tests was 95.40%(83/87),which was higher than that of CEA,CA199 and CA724 single tests.The difference was statistically significant(P<0.05).The combined detection positive rates of CEA,CA199,and CA724 in stages I,II,III,and IV of GC were 89.66%,93.10%,98.85%,and 100.00%respectively,all of which were higher than the individual detection rates of CEA,CA199,and CA724.The differences were statistically significant(P<0.05).There was no significant difference in serum CEA,CA199 and CA724 levels between GC patients with different genders,smoking history and alcohol history(P>0.05).However,the serum CEA,CA199 and CA724 levels were significantly higher in GC patients aged≥45 years,TNM stage III-IV,with lymph node metastasis and tumor diameter≥5 cm than in GC patients aged<45 years,TNM stage I-II,without lymph node metastasis and tumor diameter<5 cm(P<0.05).CONCLUSION The expression levels of serum tumor markers CEA,CA199 and CA724 in patients with GC are high and rise with the increase of TNM stage.The levels of CEA,CA199 and CA724 are related to age,TNM stage,lymph node metastasis and tumor diameter.The combined detection of CEA,CA199 and CA724 is helpful to improve the diagnostic accuracy of GC with high clinical guidance value.展开更多
如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站...如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站直流出口电压,达到限制短路电流的目的。首先,介绍MMC的拓扑结构及基于MMC的高压直流输电(MMC based high voltage direct current,MMC-HVDC)系统控制策略;其次,分析两段式限流保护策略的原理与直流故障电流特性,介绍MMC-HVDC系统的直流故障保护策略;最后,通过双端MMC-HVDC系统仿真实验,对所提限流保护策略的有效性进行验证。仿真结果表明,两段式限流保护策略可以有效降低断路器开断电流和吸收能量,节约成本。展开更多
Two-step conversion of methanol to aromatics via light hydrocarbons can significantly improve the conversion stability compared with direct aromatization of methanol,but it remains a challenge to achieve a high p-xyle...Two-step conversion of methanol to aromatics via light hydrocarbons can significantly improve the conversion stability compared with direct aromatization of methanol,but it remains a challenge to achieve a high p-xylene(PX)selectivity.Herein,silica coating was firstly used to passivate external acid sites of ZSM-5 catalyst for the aromatization of light hydrocarbons by the chemical liquid deposition method.With the increase of SiO_(2) deposition,the density of the external acid sites of the catalyst was decreased from 0.1 to 0.03 mmol·g^(-1),which inhibited the surface secondary reactions and increased the PX/X from 34.6% to 60.0%.In view of the fact that the aromatization process in the second step was partly inhibited as methanol was consumed in advance in the upper methanol-to-light hydrocarbons catalyst layer,part of methanol was directly introduced into the lower aromatization catalyst layer to promote the alkylation process during the aromatization,which decreased the toluene selectivity from 34.5% to 14.3% but increased the xylene selectivity from 40.0%to 55.3%.It was also found that an appropriate external acid density was needed for aromatization catalyst to strengthen the alkylation process and improve the selectivity of xylene under the conditions of methanol introduction.展开更多
Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) throu...Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) through a mild sulfuration and/or selenylation process of Ni(OH)_(2) supported on carbon cloth(CC).Through careful in-situ Raman spectroscopy and ex-situ X-ray photoelectron spectroscopy,surface reconstruction of NiS_(2),NiSe_(2),and Se-NiS_(2) during the OER process has been revealed.A potentialdependent study shows that Se-NiS_(2) undergoes surface evolution at lower potentials and requires the lowest potential for conversion to NiOOH as a highly OER-active species,accompanied by the leaching of SO_(4)^(2-) and SeO_(4)^(2-) that can again be adsorbed on the catalyst surface to enhance the catalytic activity.Density functional theory(DFT) calculations confirm that Se-NiS_(2) is more susceptible to surface oxidation through the OER process.Therefore,Se-NiS_(2) exhibits outstanding OER activity and stability in alkaline conditions,requiring an overpotential of 343 mV at a current density of 50 mA cm^(-2).A novel insight is provided by our work in understanding the surface reconstruction and electrocatalytic mechanism of Ni-based chalcogenides.展开更多
The safety problems encountered with lithium–sulfur batteries(LSBs)hinder their development for practical applications.Herein,a highly thermally conductive separator was constructed by cross‐weaving super‐aligned c...The safety problems encountered with lithium–sulfur batteries(LSBs)hinder their development for practical applications.Herein,a highly thermally conductive separator was constructed by cross‐weaving super‐aligned carbon nanotubes(SA‐C)on super‐aligned boron nitride@carbon nanotubes(SA‐BC)to create a composite film(SA‐BC/SA‐C).This separator was used to fabricate safe LSBs with improved electrochemical performance.The highly aligned separator structure created a uniform thermal field that could rapidly dissipate heat accumulated during continuous operation due to internal resistance,which prevented the development of extremely high temperatures.The array of boron nitride nanosheets endowed the composite separator with a large number of adsorption sites,while the highly graphitized carbon nanotube skeleton accelerated the catalytic conversion of high‐valence polysulfides into low‐valence polysulfides.The arrayed molecular brush design enabled the regulation of local current density and ion flux,and considerably alleviated the growth of lithium dendrites,thus promoting the smooth deposition of Li metal.Consequently,a battery constructed with the SA‐BC/SA‐C separator showed a good discharge capacity of 685.2 mAh g−1 over 300 cycles(a capacity decay of 0.026%per cycle)at 2 C and 60°C.This“three‐in‐one”multifunctional separator design strategy constitutes a new path forward for overcoming the safety problems of LSBs.展开更多
In this paper,we establish a large deviation principle for the stochastic generalized Ginzburg-Landau equation driven by jump noise.The main difficulties come from the highly non-linear coefficient and the jump noise....In this paper,we establish a large deviation principle for the stochastic generalized Ginzburg-Landau equation driven by jump noise.The main difficulties come from the highly non-linear coefficient and the jump noise.Here,we adopt a new sufficient condition for the weak convergence criterion of the large deviation principle,which was initially proposed by Matoussi,Sabbagh and Zhang(2021).展开更多
The role of α precipitates formed during aging in the fracture toughness and fracture behavior of β-type bio-titanium alloy Ti–29Nb–13Ta–4.6Zr(TNTZ) was studied. Results showed that the fracture toughness of the ...The role of α precipitates formed during aging in the fracture toughness and fracture behavior of β-type bio-titanium alloy Ti–29Nb–13Ta–4.6Zr(TNTZ) was studied. Results showed that the fracture toughness of the TNTZ alloy aged at 723 K decreases to the minimum of 72.07–73.19 kJ·m^(-2)when the aging time is extended to 4–8 h and then gradually increases and reaches 144.89 kJ·m^(-2)after 72 h. The decrease in fracture toughness within the aging time of 4–8 h is caused by the large stress concentration at the tip of acicular α precipitates with a high aspect ratio and the preferential crack propagation along the inhomogeneous acicular α precipitates distributed in “V-shape” and “nearly perpendicular shape”. When the aging time is extended to 8–72 h, the precrack tip is uniformly blunted, and the crack is effectively deflected by α precipitates with multi long axis directions, more high homogeneity, low aspect ratio, and large number density. Analysis of the effect of αprecipitates on the fracture behavior suggested that the number of long axis directions of α precipitates is the key controlling factor for the fracture behavior and fracture toughness of the TNTZ alloy aged for different times.展开更多
With the increasing proportion of renewable energy in the power market,the demands on government financial subsidies are gradually increasing.Thus,a joint green certificate-carbon emission right-electricity multi-mark...With the increasing proportion of renewable energy in the power market,the demands on government financial subsidies are gradually increasing.Thus,a joint green certificate-carbon emission right-electricity multi-market trading process is proposed to study the market-based strategy for renewable energy.Considering the commodity characteristics of green certificates and carbon emission rights,the dynamic cost models of green certificates and carbon rights are constructed based on the Rubinstein game and ladder pricing models.Furthermore,considering the irrational bidding behavior of energy suppliers in the actual electricity market,an evolutionary game based multi-market bidding optimization model is presented.Subsequently,it is solved using a composite differential evolutionary algorithm.Finally,the case study results reveal that the proposed model can increase profits and the consumption rate of renewable energy and reduce carbon emission.展开更多
Fungal infection is a major cause of crop and fruit losses.Recognition of chitin,a component of fungal cell walls,endows plants with enhanced fungal resistance.Here,we found that mutation of tomato LysM receptor kinas...Fungal infection is a major cause of crop and fruit losses.Recognition of chitin,a component of fungal cell walls,endows plants with enhanced fungal resistance.Here,we found that mutation of tomato LysM receptor kinase 4(SlLYK4)and chitin elicitor receptor kinase 1(SlCERK1)impaired chitin-induced immune responses in tomato leaves.Compared with the wild type,sllyk4 and slcerk1 mutant leaves were more susceptible to Botrytis cinerea(gray mold).SlLYK4 extracellular domain showed strong binding affinity to chitin,and the binding of SlLYK4 induced SlLYK4-SlCERK1 association.Remarkably,qRT–PCR analysis indicated that SlLYK4 was highly expressed in tomato fruit,andβ-GLUCURONIDASE(GUS)expression driven by the SlLYK4 promoter was observed in tomato fruit.Furthermore,SlLYK4 overexpression enhanced disease resistance not only in leaves but also in fruit.Our study suggests that chitin-mediated immunity plays a role in fruit,providing a possible way to reduce fungal infection-related fruit losses by enhancing the chitin-induced immune responses.展开更多
文摘In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were performed.Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g.The onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and analysed.Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process.During the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant grain.The calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were observed.The dynamic mechanical response process of the dummy propellant grain was analysed in detail.The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.
基金supported by the Scientific Research Fund of Yunnan Provincial Department of Education(2022Y286)15th Student Science and Technology Innovation and Entrepreneurship Action Fund Project of Yunnan Agricultural University(2022ZKX098)+1 种基金the Yunnan University Professional Degree Graduate Student Practical Innovation Fund Project(Grant Number ZC-22222374)the Scientific Research Fund Project of Yunnan Education Department(Grant Numbers 2023J1974 and 2023J1976).
文摘The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.
文摘Background: Intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) can not only observe the diffusion of tissue water molecules but also reflect the blood perfusion information of tissue microcirculation. IVIM-DWI has been applied in many clinical areas. However, few studies have addressed the use of IVIM-DWI for the evaluation of transarterial chemoembolization (TACE) response in hepatocellular carcinoma (HCC) patients. Objectives: The purpose of the present study was to explore the role of IVIM-DWI for the therapeutic response of TACE for HCC. Materials and Methods: Twenty patients underwent IVIM-DWI scan on a 3.0T magnetic resonance imaging instrument 1 - 3 days before and 30 to 40 days after TACE. The values of IVIM-DWI parameters, including standard apparent diffusion coefficient (ADC), pure diffusion coefficient (Dslow), pseudo-diffusion coefficient (Dfast) and perfusion fraction (f) were measured. The values of IVIM-DWI parameters before and after TACE were compared using paired t tests. The values between responsive and non-responsive groups were compared using independent-samples t test. P 0.05 indicated statistical significance. Results: After TACE, the ADC and Dslow values in the tumors increased significantly, and the values of Dfast decreased significantly, while the values of f value did not change obviously. The ADC values in responsive group were remarkably higher than those in non-responsive group, the Dfast values in responsive group were significantly lower than those in non-responsive group, but the values of Dslow and f between the two groups were not different significantly. Conclusions: IVIM-DWI parameters can be used as potential markers for the therapeutic response of TACE for HCC.
基金This research was financially supported by the China Geological Survey(DD20160049).
文摘1.Objective The study area is located at the southern Zhangguangcai range,which is thought to be the eastern part of the Central Asian Orogenic Belt(CAOB).The study area is closed to the eastern margin of the Songliao basin(Fig.1a).No petroleum exploration or related research work have been conducted in this area by far.Based on our most recent geological mapping,numerous hydrocarbon source rocks were firstly discovered within the Xinxing Formation,which is widely exposed from the central Jilin Province to the southeastern Heilongjiang province.The Xinxing Formation covers an area of nearly 1000 km2 with a total thickness of more than 1481 m(Regional Geology of Heilongjiang Province,1993).Therefore,the Xinxing Formation has huge potential to form oil and gas resources.This new discovery of hydrocarbon source rocks within the Xinxing Formation could provide critical clues for oil and gas resources’investigation in Northeast China,also may has important economic significance.
基金Supported by the National Natural Science Foundation of China(21776217,21506160)Tianjin Research Program of Application Foundation and Advanced Technology(14JCQNJC06400)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars(48)the Science and Technology Plans of Tianjin(16PTSYJC00110)
文摘Nanostructured zeolitic imidazolate frameworks(ZIF-8) was incorporated into the mixture of poly(ethylene glycol) methyl ether acrylate(PEGMEA) and pentaerythritol triacrylate(PETA) to synthesize mixed matrix membranes(MMMs) by in situ polymerization for CO_2/CH_4 separation. The solvent-free polymerization between PEGMEA and PETA was induced by UV light with 1-hydroxylcyclohexyl phenyl ketone as initiator. The chemical structural characterization was performed by Fourier transform infrared spectroscopy. The morphology was characterized by scanning electron microscope. The average chain-to-chain distance of the polymer chains in MMMs was investigated by X-ray diffraction. The thermal property was evaluated by differential scanning calorimetry. The CH_4 and CO_2 gas transport properties of MMMs are reported. The relationship between gas permeation–separation performances or physical properties and ZIF-8 loading is also discussed. However, the permeation–separation performance was not improved in Robeson upper bound plot compared with original polymer membrane as predicted. The significant partial pore blockage and polymer rigidification effect around the ZIFs confirmed by the increase in glass temperature and the decrease in the d-spacing, were mainly responsible for the failure in performance improvement, which offset the high diffusion induced by porous ZIF-8.
基金This work is supported by the National Natural Science Foundation of China(Nos.11672069,11702059,11232003,11672062)The Ph.D.Programs Foundation of Ministry of Education of China(No.20130041110050)+3 种基金the Research Startup Project Plan for Liaoning Doctors(No.20141119)the Fundamental Research Funds for the Central Universities(20000101)the Natural Science Foundation of Liaoning Province(No.20170540199)111 Project(B08014).
文摘In this paper,a nonlinear wave equation with variable coefficients is studied,interestingly,this equation can be used to describe the travelling waves propagating along the circular rod composed of a general compressible hyperelastic material with variable cross-sections and variable material densities.With the aid of Lou’s direct method1,the nonlinear wave equation with variable coefficients is reduced and two sets of symmetry transformations and exact solutions of the nonlinear wave equation are obtained.The corresponding numerical examples of exact solutions are presented by using different coefficients.Particularly,while the variable coefficients are taken as some special constants,the nonlinear wave equation with variable coefficients reduces to the one with constant coefficients,which can be used to describe the propagation of the travelling waves in general cylindrical rods composed of generally hyperelastic materials.Using the same method to solve the nonlinear wave equation,the validity and rationality of this method are verified.
基金supported by Beijing Natural Science Foundation (KZ201810028044)。
文摘Well-ordered hierarchically mesoporous/microporous carbon materials have been successfully fabricated by using dual soft-templating approach through compressed CO_(2).Pluronic F127 and different type of surfactants,including nonionic,cationic,and anionic surfactants,were used as dual templates to investigate the influence on the morphology and nanostructure of the as-prepared carbon samples.TEM,SEM,N2 sorption,wide-angle and small-angle XRD analysis were employed to reveal the well-ordered hierarchically micro-mesoporous structure with2 D hexagonal symmetry by using compressed CO_(2).The prepared HPC samples with different pressures as the catalyst carriers have been functioned by chlorosulfonic acid for the fructose conversion into HMF.Chlorosulfonic acid concentration,catalyst dosage and reaction temperature have been optimized for fructose-to-HMF transformation with the obtained catalyst.The performances of as-made HPC-SO_(3) H samples in HMF yield and reaction rate of fructose-to-HMF transformation have been investigated.The stability of the samples was also conducted in the dehydration of fructose to HMF for five cycles.The possible catalytic mechanism by using hierarchically porous carbon materials as catalyst support for fructose-to-HMF transformation was proposed.
基金The experiment was financially supported by the National Natural Science Foundation of China(81473364)Beijing Natural Science Foundation(7162122)Excellent Talents Training Subsidy Scheme of Beijing(2013D009999000003).
文摘Objective:To study the transmembrane transport of chemical components of Chinese herbs and to explore the function of platycodin D (PD) on biomembranes.Methods:Interaction between PD and the dipalmitoylphosphatidylcholine (DPPC) bilayer was reproduced by molecular dynamics simulation with the Martini force field.A model validation and methodological study were first performed,and were based on simulation investigations of transmembrane transport for three herbal compounds with distinct hydrophilic properties.Results:PD increased the mobility of the DPPC bilayer since its aglycone strongly interacted with the hydrophobic layer,which broke the structure of the gate layer,and weakened the ordered performance of hydrophobic tails.Conclusion:The Martini force field was successfully applied to the study of the interaction between herbal compounds and a biological membrane.By combining the dynamics equilibrium morphology,the distribution of drugs inside and outside the biomembrane,and the interaction sites of drugs on the DPPC bilayer,factors influencing transmembrane transport of drugs were elucidated and the function of platycodin D in a biological membrane was reproduced.
文摘Aging is linked to the deterioration of many physical and cognitive abilities and is the leading risk factor for Alzheimer’s disease. The growing aging population is a significant healthcare problem globally that researchers must investigate to better understand the underlying aging processes. Advances in microarrays and sequencing techniques have resulted in deeper analyses of diverse essential genomes(e.g., mouse, human, and rat) and their corresponding cell types, their organ-specific transcriptomes, and the tissue involved in aging. Traditional gene controllers such as DNA-and RNA-binding proteins significantly influence such programs, causing the need to sort out long non-coding RNAs, a new class of powerful gene regulatory elements. However, their functional significance in the aging process and senescence has yet to be investigated and identified. Several recent researchers have associated the initiation and development of senescence and aging in mammals with several well-reported and novel long non-coding RNAs. In this review article, we identified and analyzed the evolving functions of long non-coding RNAs in cellular processes, including cellular senescence, aging, and age-related pathogenesis, which are the major hallmarks of long non-coding RNAs in aging.
文摘BACKGROUND Gastric cancer(GC)is a common malignant tumor of the digestive system with a high degree of malignancy.It usually develops insidiously without any specific symptoms in the early stages.As one of the diseases caused by abnormal gene changes,GC has abnormal expression of various oncogenes and products during its development.Tumor markers such as carcinoembryonic antigen(CEA),carbohydrate antigen 199(CA199)and carbohydrate antigen 724(CA724)are not expressed or lowly expressed in normal people,but significantly increased after carcinogenesis.Monitoring the changes in the levels of tumor markers such as CEA,CA199 and CA724 is conducive to early diagnosis and evaluation of the occurrence of some solid tumors.AIM To investigate the expression of CEA,CA199 and CA724 in GC and their correlation with clinical features,hoping to provide more effective markers for the early preventive diagnosis of GC.METHODS Of 87 patients with GC admitted to our hospital from September 2020 to December 2021 were included in the GC group,and another 80 healthy people who came to our hospital for physical examination with normal results during the same period were selected as the control group.The serum CEA,CA199,and CA724 levels were compared between the two groups,and the serum CEA,CA199,and CA724 levels were compared in patients with GC at different TNM stages,and the differences in the positive rates of CEA,CA199,and CA724 alone and in combination in detecting TNM stages of GC and GC were compared.In addition,the relationship between the levels of tumor markers CEA,CA199 and CA724 and the clinicopathological characteristics of GC patients was also analyzed.The relationship between the serum levels of CEA,CA199 and CA724 and the survival period of GC patients was analyzed by Pearson.RESULTS The serum levels of CEA,CA199 and CA724 in GC group were significantly higher than those in control group(P<0.05).With the increase of TNM stage,the serum CEA,CA199 and CA724 expression levels in GC patients increased significantly,and the differences between groups were statistically significant(P<0.05).The positive rate of the CA724 single test was higher than that of CEA and CA199 single test(P<0.05).The positive rate of the three combined tests was 95.40%(83/87),which was higher than that of CEA,CA199 and CA724 single tests.The difference was statistically significant(P<0.05).The combined detection positive rates of CEA,CA199,and CA724 in stages I,II,III,and IV of GC were 89.66%,93.10%,98.85%,and 100.00%respectively,all of which were higher than the individual detection rates of CEA,CA199,and CA724.The differences were statistically significant(P<0.05).There was no significant difference in serum CEA,CA199 and CA724 levels between GC patients with different genders,smoking history and alcohol history(P>0.05).However,the serum CEA,CA199 and CA724 levels were significantly higher in GC patients aged≥45 years,TNM stage III-IV,with lymph node metastasis and tumor diameter≥5 cm than in GC patients aged<45 years,TNM stage I-II,without lymph node metastasis and tumor diameter<5 cm(P<0.05).CONCLUSION The expression levels of serum tumor markers CEA,CA199 and CA724 in patients with GC are high and rise with the increase of TNM stage.The levels of CEA,CA199 and CA724 are related to age,TNM stage,lymph node metastasis and tumor diameter.The combined detection of CEA,CA199 and CA724 is helpful to improve the diagnostic accuracy of GC with high clinical guidance value.
文摘如何对直流故障电流进行有效抑制是实现柔性直流电网大规模发展的关键。为此,研究模块化多电平变换器(modular multilevel converter,MMC)的控制方法,提出一种针对半桥型MMC的两段式限流保护策略,通过减少子模块的投入数目来降低换流站直流出口电压,达到限制短路电流的目的。首先,介绍MMC的拓扑结构及基于MMC的高压直流输电(MMC based high voltage direct current,MMC-HVDC)系统控制策略;其次,分析两段式限流保护策略的原理与直流故障电流特性,介绍MMC-HVDC系统的直流故障保护策略;最后,通过双端MMC-HVDC系统仿真实验,对所提限流保护策略的有效性进行验证。仿真结果表明,两段式限流保护策略可以有效降低断路器开断电流和吸收能量,节约成本。
基金financial support from the National Natural Science Foundation of China(21978191 and 22278292)Key Research and Development Project of Shanxi Province(International Science and Technology Cooperation Program)(201803D421011)。
文摘Two-step conversion of methanol to aromatics via light hydrocarbons can significantly improve the conversion stability compared with direct aromatization of methanol,but it remains a challenge to achieve a high p-xylene(PX)selectivity.Herein,silica coating was firstly used to passivate external acid sites of ZSM-5 catalyst for the aromatization of light hydrocarbons by the chemical liquid deposition method.With the increase of SiO_(2) deposition,the density of the external acid sites of the catalyst was decreased from 0.1 to 0.03 mmol·g^(-1),which inhibited the surface secondary reactions and increased the PX/X from 34.6% to 60.0%.In view of the fact that the aromatization process in the second step was partly inhibited as methanol was consumed in advance in the upper methanol-to-light hydrocarbons catalyst layer,part of methanol was directly introduced into the lower aromatization catalyst layer to promote the alkylation process during the aromatization,which decreased the toluene selectivity from 34.5% to 14.3% but increased the xylene selectivity from 40.0%to 55.3%.It was also found that an appropriate external acid density was needed for aromatization catalyst to strengthen the alkylation process and improve the selectivity of xylene under the conditions of methanol introduction.
基金supported by the financial support from the National Natural Science Foundation of China (21871065, 22071038, 22209129)the Heilongjiang Touyan Team (HITTY20190033)the Interdisciplinary Research Foundation of HIT (IR2021205)。
文摘Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) through a mild sulfuration and/or selenylation process of Ni(OH)_(2) supported on carbon cloth(CC).Through careful in-situ Raman spectroscopy and ex-situ X-ray photoelectron spectroscopy,surface reconstruction of NiS_(2),NiSe_(2),and Se-NiS_(2) during the OER process has been revealed.A potentialdependent study shows that Se-NiS_(2) undergoes surface evolution at lower potentials and requires the lowest potential for conversion to NiOOH as a highly OER-active species,accompanied by the leaching of SO_(4)^(2-) and SeO_(4)^(2-) that can again be adsorbed on the catalyst surface to enhance the catalytic activity.Density functional theory(DFT) calculations confirm that Se-NiS_(2) is more susceptible to surface oxidation through the OER process.Therefore,Se-NiS_(2) exhibits outstanding OER activity and stability in alkaline conditions,requiring an overpotential of 343 mV at a current density of 50 mA cm^(-2).A novel insight is provided by our work in understanding the surface reconstruction and electrocatalytic mechanism of Ni-based chalcogenides.
基金National Key R&D Program of China,Grant/Award Number:2022YFE0206500。
文摘The safety problems encountered with lithium–sulfur batteries(LSBs)hinder their development for practical applications.Herein,a highly thermally conductive separator was constructed by cross‐weaving super‐aligned carbon nanotubes(SA‐C)on super‐aligned boron nitride@carbon nanotubes(SA‐BC)to create a composite film(SA‐BC/SA‐C).This separator was used to fabricate safe LSBs with improved electrochemical performance.The highly aligned separator structure created a uniform thermal field that could rapidly dissipate heat accumulated during continuous operation due to internal resistance,which prevented the development of extremely high temperatures.The array of boron nitride nanosheets endowed the composite separator with a large number of adsorption sites,while the highly graphitized carbon nanotube skeleton accelerated the catalytic conversion of high‐valence polysulfides into low‐valence polysulfides.The arrayed molecular brush design enabled the regulation of local current density and ion flux,and considerably alleviated the growth of lithium dendrites,thus promoting the smooth deposition of Li metal.Consequently,a battery constructed with the SA‐BC/SA‐C separator showed a good discharge capacity of 685.2 mAh g−1 over 300 cycles(a capacity decay of 0.026%per cycle)at 2 C and 60°C.This“three‐in‐one”multifunctional separator design strategy constitutes a new path forward for overcoming the safety problems of LSBs.
基金partially supported by the National Natural Science Foundation of China(11871382,12071361)partially supported by the National Natural Science Foundation of China(11971361,11731012)。
文摘In this paper,we establish a large deviation principle for the stochastic generalized Ginzburg-Landau equation driven by jump noise.The main difficulties come from the highly non-linear coefficient and the jump noise.Here,we adopt a new sufficient condition for the weak convergence criterion of the large deviation principle,which was initially proposed by Matoussi,Sabbagh and Zhang(2021).
基金financially supported by the Natural Science Foundation of Liaoning Province,China (No.2022-MS-113)the Major technology projects of Liaoning Province,China (No.2019JH1/10100004)+1 种基金the National Natural Science Foundation of China (No.52271249)the Key Research and Development Program of Shaanxi,China(No.2023-YBGY-488)。
文摘The role of α precipitates formed during aging in the fracture toughness and fracture behavior of β-type bio-titanium alloy Ti–29Nb–13Ta–4.6Zr(TNTZ) was studied. Results showed that the fracture toughness of the TNTZ alloy aged at 723 K decreases to the minimum of 72.07–73.19 kJ·m^(-2)when the aging time is extended to 4–8 h and then gradually increases and reaches 144.89 kJ·m^(-2)after 72 h. The decrease in fracture toughness within the aging time of 4–8 h is caused by the large stress concentration at the tip of acicular α precipitates with a high aspect ratio and the preferential crack propagation along the inhomogeneous acicular α precipitates distributed in “V-shape” and “nearly perpendicular shape”. When the aging time is extended to 8–72 h, the precrack tip is uniformly blunted, and the crack is effectively deflected by α precipitates with multi long axis directions, more high homogeneity, low aspect ratio, and large number density. Analysis of the effect of αprecipitates on the fracture behavior suggested that the number of long axis directions of α precipitates is the key controlling factor for the fracture behavior and fracture toughness of the TNTZ alloy aged for different times.
基金supported by the National Key R&D Program of China(2017YFB0902200).
文摘With the increasing proportion of renewable energy in the power market,the demands on government financial subsidies are gradually increasing.Thus,a joint green certificate-carbon emission right-electricity multi-market trading process is proposed to study the market-based strategy for renewable energy.Considering the commodity characteristics of green certificates and carbon emission rights,the dynamic cost models of green certificates and carbon rights are constructed based on the Rubinstein game and ladder pricing models.Furthermore,considering the irrational bidding behavior of energy suppliers in the actual electricity market,an evolutionary game based multi-market bidding optimization model is presented.Subsequently,it is solved using a composite differential evolutionary algorithm.Finally,the case study results reveal that the proposed model can increase profits and the consumption rate of renewable energy and reduce carbon emission.
基金This work was supported by the Key Research and Development Program of Zhejiang Province(2021C02009,2021C02064-7,and 2022C02016)the National Natural Science Foundation of China(31770263 and 31970279)the National Key Research and Development Program of China(2018YFD1000800).
文摘Fungal infection is a major cause of crop and fruit losses.Recognition of chitin,a component of fungal cell walls,endows plants with enhanced fungal resistance.Here,we found that mutation of tomato LysM receptor kinase 4(SlLYK4)and chitin elicitor receptor kinase 1(SlCERK1)impaired chitin-induced immune responses in tomato leaves.Compared with the wild type,sllyk4 and slcerk1 mutant leaves were more susceptible to Botrytis cinerea(gray mold).SlLYK4 extracellular domain showed strong binding affinity to chitin,and the binding of SlLYK4 induced SlLYK4-SlCERK1 association.Remarkably,qRT–PCR analysis indicated that SlLYK4 was highly expressed in tomato fruit,andβ-GLUCURONIDASE(GUS)expression driven by the SlLYK4 promoter was observed in tomato fruit.Furthermore,SlLYK4 overexpression enhanced disease resistance not only in leaves but also in fruit.Our study suggests that chitin-mediated immunity plays a role in fruit,providing a possible way to reduce fungal infection-related fruit losses by enhancing the chitin-induced immune responses.
