In traditional Chinese medicine(TCM),based on various pathogenic symptoms and the‘golden chamber’medical text,Huangdi Neijing,diabetes mellitus falls under the category‘collateral disease’.TCM,with its wealth of e...In traditional Chinese medicine(TCM),based on various pathogenic symptoms and the‘golden chamber’medical text,Huangdi Neijing,diabetes mellitus falls under the category‘collateral disease’.TCM,with its wealth of experience,has been treating diabetes for over two millennia.Different antidiabetic Chinese herbal medicines re-duce blood sugar,with their effective ingredients exerting unique advantages.As well as a glucose lowering effect,TCM also regulates bodily functions to prevent diabetes associated complications,with reduced side effects compared to western synthetic drugs.Chinese herbal medicine is usually composed of polysaccharides,saponins,al-kaloids,flavonoids,and terpenoids.These active ingredients reduce blood sugar via various mechanism of actions that include boosting endogenous insulin secretion,enhancing insulin sensitivity and adjusting key enzyme activity and scavenging free radicals.These actions regulate glycolipid metabolism in the body,eventually achiev-ing the goal of normalizing blood glucose.Using different animal models,a number of molecular markers are available for the detection of diabetes induction and the molecular pathology of the disease is becoming clearer.Nonetheless,there is a dearth of scientific data about the pharmacology,dose-effect relationship,and structure-activity relationship of TCM and its constituents.Further research into the efficacy,toxicity and mode of action of TCM,using different metabolic and molecular markers,is key to developing novel TCM antidiabetic formulations.展开更多
The development of aqueous battery with dual mechanisms is now arousing more and more interest.The dual mechanisms of Zn^(2+)(de)intercalation and I^(-)/I_(2)redox bring unexpected effects.Herein,differing from previo...The development of aqueous battery with dual mechanisms is now arousing more and more interest.The dual mechanisms of Zn^(2+)(de)intercalation and I^(-)/I_(2)redox bring unexpected effects.Herein,differing from previous studies using Zn I_(2)additive,this work designs an aqueous Bi I_(3)-Zn battery with selfsupplied I^(-).Ex situ tests reveal the conversion of Bi I_(3)into Bi(discharge)and Bi OI(charge)at the 1st cycle and the dissolved I^(-)in electrolyte.The active I^(-)species enhances the specific capacity and discharge medium voltage of electrode as well as improves the generation of Zn dendrite and by-product.Furthermore,the porous hard carbon is introduced to enhance the electronic/ionic conductivity and adsorb iodine species,proven by experimental and theoretical studies.Accordingly,the well-designed Bi I_(3)-Zn battery delivers a high reversible capacity of 182 m A h g^(-1)at 0.2 A g^(-1),an excellent rate capability with 88 m A h g^(-1)at 10 A g^(-1),and an impressive cyclability with 63%capacity retention over 20 K cycles at 10 A g^(-1).An excellent electrochemical performance is obtained even at a high mass loading of 6 mg cm^(-2).Moreover,a flexible quasi-solid-state Bi I_(3)-Zn battery exhibits satisfactory battery performances.This work provides a new idea for designing high-performance aqueous battery with dual mechanisms.展开更多
[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavo...[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavonoid glycosides were isolated and purified from the ethanol alcoholic extract of the roots of Liliaceae plant Chlorophytum comosum by silica gel column chromatography,macroporous resin column chromatography,Sephadex LH-20,and reverse column chromatography(ODS).The inhibitory activity of flavonoid glycosides on human nasopharyngeal carcinoma cells was analyzed by CCK-8 method,and the potential mechanism was preliminarily analyzed by molecular docking.[Results]Two flavonoid glycosides were identified as isovitexin 2″-0-rhamnoside and 7-2″-di-O-β-glucopyranosylisovitexin.Two flavonoid glycosides showed promising inhibitory effect on human nasopharyngeal carcinoma cell line 5-8F,with IC_(50) values of 24.8 and 27.5μmol/L,respectively.Molecular docking results showed that the potential targets of two flavonoid glycosides include CyclinD1,Bcl-2β-Catenin,ILK,TGF-β,in addition,two glycosides showed higher predicted binding affinity towards CyclinD1,which verifies the cytotoxicity of the two compounds on human nasopharyngeal carcinoma cell line 5-8F in vitro.[Conclusions]Two flavonoid glycosides are the active molecules in Chlorophytum comosum that can inhibit the proliferation of human nasopharyngeal carcinoma cells,and have the potential to be used in the research and development of anti nasopharyngeal carcinoma drugs.展开更多
This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism, which is a novel type of indexing mechanism that employs internal planetary transmissio...This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism, which is a novel type of indexing mechanism that employs internal planetary transmission structure. Firstly, the geometry and structure of the mechanism are discussed and the kinematic practicability is simulated with virtual prototype design. Then a 3D finite element model of the ring-plate planetary indexing cam mechanism is developed with the commercial software of MATLAB and ANSYS. Through the finite element analysis, the natural frequencies and the corresponding mode shapes are predicted in one motion cycle. On the basis of the virtual prototype design and finite element analysis, an experimental prototype is made and tested to validate the prediction of the dynamic characteristics. The agreement between experimental results and the finite element analysis testifies that the finite element model developed is applicable to the prediction of the dynamic characteristics of this type of mechanism.展开更多
One kind of movable-pair analysis method is adopted to analyze the configuration of a 3-7R (revolute-pair) parallel decoupling mechanism, and the mechanism's characteristics are summarized. The mechanism has three ...One kind of movable-pair analysis method is adopted to analyze the configuration of a 3-7R (revolute-pair) parallel decoupling mechanism, and the mechanism's characteristics are summarized. The mechanism has three orthogonal distributional branch-chains, and all movable pairs are rotational joints. The movable platform of the mechanism has x, y, z translational decoupling directions. Furthermore, in order to verify the mechanism's decoupling characteristics, the mechanism's kinematics analysis is solved, and the mechanism's direct/inverse kinematics model, input/output velocities and accelerations are deduced, which confirm its decoupling movement characteristics. Finally, one kind of mechanism link decomposed-integrated approach is adopted, and the mechanism's dynamics model is completed with the Lagrange method, which also proves its decoupling force characteristics. All of these works provide significant theory for the further study of the mechanism's control strategy, design, path planning etc.展开更多
The present research on moulded case circuit breaker(MCCB) focuses on the enhancement of current-limiting interrupting performance during short circuit, overload, under voltage and phase failure, involving electrics...The present research on moulded case circuit breaker(MCCB) focuses on the enhancement of current-limiting interrupting performance during short circuit, overload, under voltage and phase failure, involving electrics, magnetic, mechanics, thermal, material, friction, arc extinguishing, impact vibration, skin effect, etc. The rigid-flexible coupling of the parts and components of the metamorphic manipulating mechanism in multi-fields leads to the non-rigid, high frequency, high damping, singularity of the Euler-Lagrange equations which represents the multi-body dynamics. The small step iteration which is used for obtaining the instantaneous and short time critical interrupting performance of metamorphic mechanism appears inaccuracy. It is difficult to realize top-down design by existing CAD systems. Therefore, a metamorphic manipulating mechanism design method for MCCB using index reduced iteration(IRI) is put forward. The metamorphic manipulating mechanism of MCCB is decomposed into three mechanisms: main switch connector mechanism, electromagnet-drawbar-jump buckle mechanism, and bimetallic strip-drawbar mechanism, which is respectively described by electro-dynamic force, electromagnet force, and bimetallic strip force. The dummy part(virtual rigid) without moment of inertia and mass is employed as intermediate to join the flexible body and rigid body. The model of rigid-flexible coupling metamorphic mechanism multi-body dynamics is built. The differential algebraic equations(DAEs) of the multibody dynamics model are converted to pure ordinary differential equations(ODEs) by coordinate partition. Order reduced integration with multi-step and variable step-size is preceded based on IRI. The non-linear algebraic equations are solved in each integration step by Newton-Rapson iteration. There is no ill-condition and singularity of Jacobian matrix when step size reduces to zero. The independent prototype design system using ACIS R13, HOOPS V11.0 and Visual C++.NET 2003 has been developed, which verifies the effectiveness of the proposed method. The proposed method enhances the current-limiting interrupting performance of MCCB, and has reference significance for multi-body dynamics design for similar flexible metamorphic mechanisms in multi-fields.展开更多
We first design and analyze the contour surface of the globoidal indexing cam with the aid of computer, and then do optimum design according to the requirements of dynamics. Finally, we discuss the problem of the pres...We first design and analyze the contour surface of the globoidal indexing cam with the aid of computer, and then do optimum design according to the requirements of dynamics. Finally, we discuss the problem of the pressure angle of the globoidal indexing cam mechanism in detail and put forward a new concept of equivalent pressure angle.展开更多
Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above b...Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.展开更多
A new type of parallel indexing cam mechanism is discovered.The composition of the cam profile is proposed and the formulas of the mechanism parameters are established by synthesis of its configuration and size.The eq...A new type of parallel indexing cam mechanism is discovered.The composition of the cam profile is proposed and the formulas of the mechanism parameters are established by synthesis of its configuration and size.The equations for working pro- file and pressure angle of the cam are derived based on the inverse model and the derivative of pitch curve of cams.An example is given and demonstrates that it is available to design the new mechanism using the derived expressions.展开更多
Accurate and seamless auxiliary services in the power market can guarantee smooth and continuous power system operation. China’s new round of power system reform has entered a critical period, and reform implementati...Accurate and seamless auxiliary services in the power market can guarantee smooth and continuous power system operation. China’s new round of power system reform has entered a critical period, and reform implementation requires comprehensive improvements in the maturity of the supporting auxiliary service market. This study reviews the development status and evolution path of the European unified power market and the US regional power market, provides experience for the development of China’s regional power market, then identifies the key influencing factors of auxiliary service trading mechanism design in regional power markets. To analyze the rationality of the auxiliary service trading evaluation index, this paper established an evaluation model for assessing regional power markets. Using combined weight optimization, the gray correlation TOPSIS method was applied to comprehensively evaluate auxiliary service trading in the regional power market. Finally, the application of the proposed evaluation method was briefly analyzed to examine four regional power markets in China and evaluate the effectiveness of current market construction in different regions and provide suggestions for future market construction.展开更多
Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and str...Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and strain rate range of 0.011.00 s1. The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJmo11 in (a+β) region. Dynamic recrystallization is the major deformation mecha nism. Flow softening is dominated by dynamic recrystallization at 850950 ℃. TiB particles promote the recrystallization of laths. Globularization processes consist of four steps: for mation of subgrain after dynamic recovery in a plates; subgrain boundary migration caused by interracial instability; interfacial migration promoting phase wedge into a phase; disintegrating of a laths by diffusion processes; and grain boundary sliding. Globularization mechanisms during hot deformation processes of the Ti6A14V0.1B alloy with lamellar structure are continuous dynamic recrystallization.展开更多
The adsorption mechanism of O-isopropyl-S-[2-(hydroxyimino) propyl] dithiocarbonate ester(IPXPO) to chalcopyrite was investigated by using contact angle, in-situ atomic force microscopy(in-situ AFM), cyclic voltammetr...The adsorption mechanism of O-isopropyl-S-[2-(hydroxyimino) propyl] dithiocarbonate ester(IPXPO) to chalcopyrite was investigated by using contact angle, in-situ atomic force microscopy(in-situ AFM), cyclic voltammetry(CV) and X-ray photoelectron spectroscopy(XPS). The results of contact angle and in-situ AFM demonstrated that IPXPO adsorbed on chalcopyrite increases surface hydrophobicity and roughness. It was found by CV experiments that a layer passive film was formed. The results of XPS spectra further revealed that the thiol S atom, oxime N atom, and O atom in the IPXPO molecule might react with copper atoms to form Cu-S, Cu-N, and Cu-O bonds, respectively. An artificial mixed minerals flotation test indicated that under the condition of pH=6.79 and IPXPO initial concentration 5×10^(-5)mol/L, the flotation recovery of chalcopyrite reached about 90%, while for pyrite only 25%, suggesting that IPXPO is an excellent collector for flotation separation and enrichment of chalcopyrite.展开更多
In a simple semi-geostropic model on the equatorial β-plane, the theoretical analysis on the 30-60 day oscillation in the tropical atmosphere is further discussed based on the wave-CISK mechanism. The convection heat...In a simple semi-geostropic model on the equatorial β-plane, the theoretical analysis on the 30-60 day oscillation in the tropical atmosphere is further discussed based on the wave-CISK mechanism. The convection heating can excite the CISK-Kelvm wave and CISK-Rossby wave in the tropical atmosphere and they are all the low-frequency modes which drive the activities of 30-60 day oscillation in the tropics. The most favorable conditions to excite the CISK-Kelvin wave and CISK-Rossby wave are indicated: There is convection heating but not very strong in the atmosphere and there is weaker disturbance in the lower troposphere.The influences of vertical shearing of basic flow in the troposphere on the 30-60 day oscillation in the tropics are also discussed.展开更多
The solution for the forward displacement analysis(FDA) of the general 6-6 Stewart mechanism(i.e., the connection points of the moving and fixed platforms are not restricted to lying in a plane) has been extensive...The solution for the forward displacement analysis(FDA) of the general 6-6 Stewart mechanism(i.e., the connection points of the moving and fixed platforms are not restricted to lying in a plane) has been extensively studied, but the efficiency of the solution remains to be effectively addressed. To this end, an algebraic elimination method is proposed for the FDA of the general 6-6 Stewart mechanism. The kinematic constraint equations are built using conformal geometric algebra(CGA). The kinematic constraint equations are transformed by a substitution of variables into seven equations with seven unknown variables. According to the characteristic of anti-symmetric matrices, the aforementioned seven equations can be further transformed into seven equations with four unknown variables by a substitution of variables using the Grobner basis. Its elimination weight is increased through changing the degree of one variable, and sixteen equations with four unknown variables can be obtained using the Grobner basis. A 40th-degree univariate polynomial equation is derived by constructing a relatively small-sized 9 × 9 Sylvester resultant matrix. Finally, two numerical examples are employed to verify the proposed method. The results indicate that the proposed method can effectively improve the efficiency of solution and reduce the computational burden because of the small-sized resultant matrix.展开更多
Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huangg...Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.展开更多
Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbon...Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.展开更多
F_(10.7)指数是太阳活动的重要指标,准确预测F_(10.7)指数有助于预防和缓解太阳活动对无线电通信、导航和卫星通信等领域的影响.基于F_(10.7)射电流量的特性,在双向长短时记忆网络(Bidirectional Long Short-Term Memory Network,BiLSTM...F_(10.7)指数是太阳活动的重要指标,准确预测F_(10.7)指数有助于预防和缓解太阳活动对无线电通信、导航和卫星通信等领域的影响.基于F_(10.7)射电流量的特性,在双向长短时记忆网络(Bidirectional Long Short-Term Memory Network,BiLSTM)基础上融入注意力机制(Attention),提出了一种基于BiLSTM-Attention的F_(10.7)预报模型.在加拿大DRAO数据集上其平均绝对误差(MAE)为5.38,平均绝对百分比误差(MAPE)控制在5%以内,相关系数(R)高达0.987,与其他RNN模型相比拥有优越的预测性能.针对中国廊坊L&S望远镜观测的F_(10.7)数据集,提出了一种转换平均校准(Conversion Average Calibration,CAC)方法进行数据预处理,处理后的数据与DRAO数据集具有较高的相关性.基于该数据集对比分析了RNN系列模型的预报效果,实验结果表明,BiLSTM-Attention和BiLSTM两种模型在预测F_(10.7)指数方面具有较好的优势,表现出较好的预测性能和稳定性.展开更多
In order to investigate the influence on shale gas well productivity caused by gas transport in nanometer- size pores, a mathematical model of multi-stage fractured horizontal wells in shale gas reservoirs is built, w...In order to investigate the influence on shale gas well productivity caused by gas transport in nanometer- size pores, a mathematical model of multi-stage fractured horizontal wells in shale gas reservoirs is built, which considers the influence of viscous flow, Knudsen diffusion, surface diffusion, and adsorption layer thickness. A dis- crete-fracture model is used to simplify the fracture mod- cling, and a finite element method is applied to solve the model. The numerical simulation results indicate that with a decrease in the intrinsic matrix permeability, Knudsen diffusion and surface diffusion contributions to production become large and cannot be ignored. The existence of an adsorption layer on the nanopore surfaces reduces the effective pore radius and the effective porosity, resulting in low production from fractured horizontal wells. With a decrease in the pore radius, considering the adsorption layer, the production reduction rate increases. When the pore radius is less than 10 nm, because of the combined impacts of Knudsen diffusion, surface diffusion, and adsorption layers, the production of multi-stage fractured horizontal wells increases with a decrease in the pore pressure. When the pore pressure is lower than 30 MPa, the rate of production increase becomes larger with a decrease in pore pressure.展开更多
基金the National Key Research and Development Program of China,Grant/Award Number:2021YFD1600100 and 2022YFD1600303。
文摘In traditional Chinese medicine(TCM),based on various pathogenic symptoms and the‘golden chamber’medical text,Huangdi Neijing,diabetes mellitus falls under the category‘collateral disease’.TCM,with its wealth of experience,has been treating diabetes for over two millennia.Different antidiabetic Chinese herbal medicines re-duce blood sugar,with their effective ingredients exerting unique advantages.As well as a glucose lowering effect,TCM also regulates bodily functions to prevent diabetes associated complications,with reduced side effects compared to western synthetic drugs.Chinese herbal medicine is usually composed of polysaccharides,saponins,al-kaloids,flavonoids,and terpenoids.These active ingredients reduce blood sugar via various mechanism of actions that include boosting endogenous insulin secretion,enhancing insulin sensitivity and adjusting key enzyme activity and scavenging free radicals.These actions regulate glycolipid metabolism in the body,eventually achiev-ing the goal of normalizing blood glucose.Using different animal models,a number of molecular markers are available for the detection of diabetes induction and the molecular pathology of the disease is becoming clearer.Nonetheless,there is a dearth of scientific data about the pharmacology,dose-effect relationship,and structure-activity relationship of TCM and its constituents.Further research into the efficacy,toxicity and mode of action of TCM,using different metabolic and molecular markers,is key to developing novel TCM antidiabetic formulations.
基金funding from National Natural Science Foundation of China(52103053,52102312)Huxiang Young Talents of Hunan Province(2022RC1004)+1 种基金Macao Young Scholars Program(AM2021011)Foundation of State Key Laboratory of Utilization of Woody Oil Resource(GZKF202126)。
文摘The development of aqueous battery with dual mechanisms is now arousing more and more interest.The dual mechanisms of Zn^(2+)(de)intercalation and I^(-)/I_(2)redox bring unexpected effects.Herein,differing from previous studies using Zn I_(2)additive,this work designs an aqueous Bi I_(3)-Zn battery with selfsupplied I^(-).Ex situ tests reveal the conversion of Bi I_(3)into Bi(discharge)and Bi OI(charge)at the 1st cycle and the dissolved I^(-)in electrolyte.The active I^(-)species enhances the specific capacity and discharge medium voltage of electrode as well as improves the generation of Zn dendrite and by-product.Furthermore,the porous hard carbon is introduced to enhance the electronic/ionic conductivity and adsorb iodine species,proven by experimental and theoretical studies.Accordingly,the well-designed Bi I_(3)-Zn battery delivers a high reversible capacity of 182 m A h g^(-1)at 0.2 A g^(-1),an excellent rate capability with 88 m A h g^(-1)at 10 A g^(-1),and an impressive cyclability with 63%capacity retention over 20 K cycles at 10 A g^(-1).An excellent electrochemical performance is obtained even at a high mass loading of 6 mg cm^(-2).Moreover,a flexible quasi-solid-state Bi I_(3)-Zn battery exhibits satisfactory battery performances.This work provides a new idea for designing high-performance aqueous battery with dual mechanisms.
基金Supported by Youth Fund Project of Zhaoqing University(QZ202235)Zhaoqing Science and Technology Plan Project(2022040311011).
文摘[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavonoid glycosides were isolated and purified from the ethanol alcoholic extract of the roots of Liliaceae plant Chlorophytum comosum by silica gel column chromatography,macroporous resin column chromatography,Sephadex LH-20,and reverse column chromatography(ODS).The inhibitory activity of flavonoid glycosides on human nasopharyngeal carcinoma cells was analyzed by CCK-8 method,and the potential mechanism was preliminarily analyzed by molecular docking.[Results]Two flavonoid glycosides were identified as isovitexin 2″-0-rhamnoside and 7-2″-di-O-β-glucopyranosylisovitexin.Two flavonoid glycosides showed promising inhibitory effect on human nasopharyngeal carcinoma cell line 5-8F,with IC_(50) values of 24.8 and 27.5μmol/L,respectively.Molecular docking results showed that the potential targets of two flavonoid glycosides include CyclinD1,Bcl-2β-Catenin,ILK,TGF-β,in addition,two glycosides showed higher predicted binding affinity towards CyclinD1,which verifies the cytotoxicity of the two compounds on human nasopharyngeal carcinoma cell line 5-8F in vitro.[Conclusions]Two flavonoid glycosides are the active molecules in Chlorophytum comosum that can inhibit the proliferation of human nasopharyngeal carcinoma cells,and have the potential to be used in the research and development of anti nasopharyngeal carcinoma drugs.
基金Supported by the Key Project of Ministry of Education of China
文摘This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism, which is a novel type of indexing mechanism that employs internal planetary transmission structure. Firstly, the geometry and structure of the mechanism are discussed and the kinematic practicability is simulated with virtual prototype design. Then a 3D finite element model of the ring-plate planetary indexing cam mechanism is developed with the commercial software of MATLAB and ANSYS. Through the finite element analysis, the natural frequencies and the corresponding mode shapes are predicted in one motion cycle. On the basis of the virtual prototype design and finite element analysis, an experimental prototype is made and tested to validate the prediction of the dynamic characteristics. The agreement between experimental results and the finite element analysis testifies that the finite element model developed is applicable to the prediction of the dynamic characteristics of this type of mechanism.
基金The National High Technology Research and Development Program of China(863Program)(No.2006AA040202)
文摘One kind of movable-pair analysis method is adopted to analyze the configuration of a 3-7R (revolute-pair) parallel decoupling mechanism, and the mechanism's characteristics are summarized. The mechanism has three orthogonal distributional branch-chains, and all movable pairs are rotational joints. The movable platform of the mechanism has x, y, z translational decoupling directions. Furthermore, in order to verify the mechanism's decoupling characteristics, the mechanism's kinematics analysis is solved, and the mechanism's direct/inverse kinematics model, input/output velocities and accelerations are deduced, which confirm its decoupling movement characteristics. Finally, one kind of mechanism link decomposed-integrated approach is adopted, and the mechanism's dynamics model is completed with the Lagrange method, which also proves its decoupling force characteristics. All of these works provide significant theory for the further study of the mechanism's control strategy, design, path planning etc.
基金supported by National Basic Research Program of China(973 Program, Grant No. 2011CB706506)National S&T Great Special of China(Grant Nos. 2012ZX04010011, 2011ZX04014-131)+1 种基金National Science Foundation for Young Scholars of China(Grant No. 51005204)Postdoctoral Fund of China(Grant No. 20100471000)
文摘The present research on moulded case circuit breaker(MCCB) focuses on the enhancement of current-limiting interrupting performance during short circuit, overload, under voltage and phase failure, involving electrics, magnetic, mechanics, thermal, material, friction, arc extinguishing, impact vibration, skin effect, etc. The rigid-flexible coupling of the parts and components of the metamorphic manipulating mechanism in multi-fields leads to the non-rigid, high frequency, high damping, singularity of the Euler-Lagrange equations which represents the multi-body dynamics. The small step iteration which is used for obtaining the instantaneous and short time critical interrupting performance of metamorphic mechanism appears inaccuracy. It is difficult to realize top-down design by existing CAD systems. Therefore, a metamorphic manipulating mechanism design method for MCCB using index reduced iteration(IRI) is put forward. The metamorphic manipulating mechanism of MCCB is decomposed into three mechanisms: main switch connector mechanism, electromagnet-drawbar-jump buckle mechanism, and bimetallic strip-drawbar mechanism, which is respectively described by electro-dynamic force, electromagnet force, and bimetallic strip force. The dummy part(virtual rigid) without moment of inertia and mass is employed as intermediate to join the flexible body and rigid body. The model of rigid-flexible coupling metamorphic mechanism multi-body dynamics is built. The differential algebraic equations(DAEs) of the multibody dynamics model are converted to pure ordinary differential equations(ODEs) by coordinate partition. Order reduced integration with multi-step and variable step-size is preceded based on IRI. The non-linear algebraic equations are solved in each integration step by Newton-Rapson iteration. There is no ill-condition and singularity of Jacobian matrix when step size reduces to zero. The independent prototype design system using ACIS R13, HOOPS V11.0 and Visual C++.NET 2003 has been developed, which verifies the effectiveness of the proposed method. The proposed method enhances the current-limiting interrupting performance of MCCB, and has reference significance for multi-body dynamics design for similar flexible metamorphic mechanisms in multi-fields.
文摘We first design and analyze the contour surface of the globoidal indexing cam with the aid of computer, and then do optimum design according to the requirements of dynamics. Finally, we discuss the problem of the pressure angle of the globoidal indexing cam mechanism in detail and put forward a new concept of equivalent pressure angle.
文摘Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.
文摘A new type of parallel indexing cam mechanism is discovered.The composition of the cam profile is proposed and the formulas of the mechanism parameters are established by synthesis of its configuration and size.The equations for working pro- file and pressure angle of the cam are derived based on the inverse model and the derivative of pitch curve of cams.An example is given and demonstrates that it is available to design the new mechanism using the derived expressions.
基金supported by the Beijing Power Exchange Center (Study on the Medium and Long Term Time Division Transaction Mode and Balance Mechanism of Electric Power)supported by the National Natural Science Foundation of China(No. 72171082)。
文摘Accurate and seamless auxiliary services in the power market can guarantee smooth and continuous power system operation. China’s new round of power system reform has entered a critical period, and reform implementation requires comprehensive improvements in the maturity of the supporting auxiliary service market. This study reviews the development status and evolution path of the European unified power market and the US regional power market, provides experience for the development of China’s regional power market, then identifies the key influencing factors of auxiliary service trading mechanism design in regional power markets. To analyze the rationality of the auxiliary service trading evaluation index, this paper established an evaluation model for assessing regional power markets. Using combined weight optimization, the gray correlation TOPSIS method was applied to comprehensively evaluate auxiliary service trading in the regional power market. Finally, the application of the proposed evaluation method was briefly analyzed to examine four regional power markets in China and evaluate the effectiveness of current market construction in different regions and provide suggestions for future market construction.
基金supported by the International Science and Technology Corporation Foundation of China(No.2012DFG51540)
文摘Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and strain rate range of 0.011.00 s1. The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJmo11 in (a+β) region. Dynamic recrystallization is the major deformation mecha nism. Flow softening is dominated by dynamic recrystallization at 850950 ℃. TiB particles promote the recrystallization of laths. Globularization processes consist of four steps: for mation of subgrain after dynamic recovery in a plates; subgrain boundary migration caused by interracial instability; interfacial migration promoting phase wedge into a phase; disintegrating of a laths by diffusion processes; and grain boundary sliding. Globularization mechanisms during hot deformation processes of the Ti6A14V0.1B alloy with lamellar structure are continuous dynamic recrystallization.
基金Projects(22108114, 5180031184) supported by the National Natural Science Foundation of China。
文摘The adsorption mechanism of O-isopropyl-S-[2-(hydroxyimino) propyl] dithiocarbonate ester(IPXPO) to chalcopyrite was investigated by using contact angle, in-situ atomic force microscopy(in-situ AFM), cyclic voltammetry(CV) and X-ray photoelectron spectroscopy(XPS). The results of contact angle and in-situ AFM demonstrated that IPXPO adsorbed on chalcopyrite increases surface hydrophobicity and roughness. It was found by CV experiments that a layer passive film was formed. The results of XPS spectra further revealed that the thiol S atom, oxime N atom, and O atom in the IPXPO molecule might react with copper atoms to form Cu-S, Cu-N, and Cu-O bonds, respectively. An artificial mixed minerals flotation test indicated that under the condition of pH=6.79 and IPXPO initial concentration 5×10^(-5)mol/L, the flotation recovery of chalcopyrite reached about 90%, while for pyrite only 25%, suggesting that IPXPO is an excellent collector for flotation separation and enrichment of chalcopyrite.
文摘In a simple semi-geostropic model on the equatorial β-plane, the theoretical analysis on the 30-60 day oscillation in the tropical atmosphere is further discussed based on the wave-CISK mechanism. The convection heating can excite the CISK-Kelvm wave and CISK-Rossby wave in the tropical atmosphere and they are all the low-frequency modes which drive the activities of 30-60 day oscillation in the tropics. The most favorable conditions to excite the CISK-Kelvin wave and CISK-Rossby wave are indicated: There is convection heating but not very strong in the atmosphere and there is weaker disturbance in the lower troposphere.The influences of vertical shearing of basic flow in the troposphere on the 30-60 day oscillation in the tropics are also discussed.
基金Supported by National Natural Science Foundation of China(Grant No.51375059)National Hi-tech Research and Development Program of China(863 Program,Grant No.2011AA040203)+1 种基金Special Fund for Agro-scientific Research in the Public Interest of China(Grant No.201313009-06)National Key Technology R&D Program of the Ministry of Science and Technology of China(Grant No.2013BAD17B06)
文摘The solution for the forward displacement analysis(FDA) of the general 6-6 Stewart mechanism(i.e., the connection points of the moving and fixed platforms are not restricted to lying in a plane) has been extensively studied, but the efficiency of the solution remains to be effectively addressed. To this end, an algebraic elimination method is proposed for the FDA of the general 6-6 Stewart mechanism. The kinematic constraint equations are built using conformal geometric algebra(CGA). The kinematic constraint equations are transformed by a substitution of variables into seven equations with seven unknown variables. According to the characteristic of anti-symmetric matrices, the aforementioned seven equations can be further transformed into seven equations with four unknown variables by a substitution of variables using the Grobner basis. Its elimination weight is increased through changing the degree of one variable, and sixteen equations with four unknown variables can be obtained using the Grobner basis. A 40th-degree univariate polynomial equation is derived by constructing a relatively small-sized 9 × 9 Sylvester resultant matrix. Finally, two numerical examples are employed to verify the proposed method. The results indicate that the proposed method can effectively improve the efficiency of solution and reduce the computational burden because of the small-sized resultant matrix.
基金supported by the NSFC HSR Fundamental Research Joint Fund (Grant No.U1934213)。
文摘Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.
基金Funded by Joint Funds of the National Natural Science Foundation of China(No.U1904188)Jiangxi Provincial Department of Education Science and Technology Project(Nos.GJJ171079,GJJ181023 and GJJ181022)。
文摘Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.
文摘F_(10.7)指数是太阳活动的重要指标,准确预测F_(10.7)指数有助于预防和缓解太阳活动对无线电通信、导航和卫星通信等领域的影响.基于F_(10.7)射电流量的特性,在双向长短时记忆网络(Bidirectional Long Short-Term Memory Network,BiLSTM)基础上融入注意力机制(Attention),提出了一种基于BiLSTM-Attention的F_(10.7)预报模型.在加拿大DRAO数据集上其平均绝对误差(MAE)为5.38,平均绝对百分比误差(MAPE)控制在5%以内,相关系数(R)高达0.987,与其他RNN模型相比拥有优越的预测性能.针对中国廊坊L&S望远镜观测的F_(10.7)数据集,提出了一种转换平均校准(Conversion Average Calibration,CAC)方法进行数据预处理,处理后的数据与DRAO数据集具有较高的相关性.基于该数据集对比分析了RNN系列模型的预报效果,实验结果表明,BiLSTM-Attention和BiLSTM两种模型在预测F_(10.7)指数方面具有较好的优势,表现出较好的预测性能和稳定性.
基金supported by the National Natural Science Foundation of China (No. 51234007, No. 51490654, No. 51504276, and No. 51504277)Program for Changjiang Scholars and Innovative Research Team in University (IRT1294)+3 种基金the Natural Science Foundation of Shandong Province (ZR2014EL016, ZR2014EEP018)China Postdoctoral Science Foundation (No. 2014M551989 and No. 2015T80762)the Major Programs of Ministry of Education of China (No. 311009)Introducing Talents of Discipline to Universities (B08028)
文摘In order to investigate the influence on shale gas well productivity caused by gas transport in nanometer- size pores, a mathematical model of multi-stage fractured horizontal wells in shale gas reservoirs is built, which considers the influence of viscous flow, Knudsen diffusion, surface diffusion, and adsorption layer thickness. A dis- crete-fracture model is used to simplify the fracture mod- cling, and a finite element method is applied to solve the model. The numerical simulation results indicate that with a decrease in the intrinsic matrix permeability, Knudsen diffusion and surface diffusion contributions to production become large and cannot be ignored. The existence of an adsorption layer on the nanopore surfaces reduces the effective pore radius and the effective porosity, resulting in low production from fractured horizontal wells. With a decrease in the pore radius, considering the adsorption layer, the production reduction rate increases. When the pore radius is less than 10 nm, because of the combined impacts of Knudsen diffusion, surface diffusion, and adsorption layers, the production of multi-stage fractured horizontal wells increases with a decrease in the pore pressure. When the pore pressure is lower than 30 MPa, the rate of production increase becomes larger with a decrease in pore pressure.