A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floa...A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floating turbines exhibit six degrees of freedom motion,potentially intensifying the cavitation on the blade surfaces.This study selects three types of oscillatory motions from the six degrees of freedom:roll,yaw,and pitch.Computational fluid dynamics(CFD)methods are used for numerical calculations,and transient simulations of multiphase flow are conducted on the basis of the Reynolds-Averaged Navier-Stokes(RANS)model.Research has revealed strong correlations between flow velocity,the blade tip speed ratio,and cavitation.During oscillatory motion,the motion period and amplitude also significantly impact cavitation.In roll motion,the cavitation rate can increase by up to 59%with decreasing period,whereas in pitch and yaw motions,the increases are 7.57 times and 36%larger,respectively.With an increase in amplitude during roll motion,the cavitation rate can increase by up to 1.08 times,whereas in pitch and yaw motions,the increases are 3.49 times and 45%,respectively.The cavitation rate on the blade surfaces is the highest in pitch motion,followed by roll and yaw motions.展开更多
The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the s...The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the seawall(constrained to pitch mode)are considered to examine the influence of the DOF of the WEC on the wave energy extraction performance.Results show that the piston-mode water resonance in the gap and the coupled WEC and water column resonant motion significantly influence the wave energy extraction efficiency.At low frequency,the case with a 3-DOF WEC has a broader high-efficiency bandwidth than that with a heaving WEC.However,3-DOF WEC exhibits worse performance at high frequencies.The frequency response of the wave energy capture width ratio(CWR)for the pitching WEC case shows a trimodal trend under the specified conditions.It showcases the best overall wave energy extraction performance in terms of the high-efficiency bandwidth.Furthermore,a parametric study indicates that the gap distance between the WEC and the seawall has tremendous effects on the CWR of both cases.As the position of the hinge point of the pitching WEC changes,the CWR at the low and high frequencies shows opposite trends.展开更多
BACKGROUND The degree of obstruction plays an important role in decision-making for obstructive colorectal cancer(OCRC).The existing assessment still relies on the colorectal obstruction scoring system(CROSS)which is ...BACKGROUND The degree of obstruction plays an important role in decision-making for obstructive colorectal cancer(OCRC).The existing assessment still relies on the colorectal obstruction scoring system(CROSS)which is based on a comprehensive analysis of patients’complaints and eating conditions.The data collection relies on subjective descriptions and lacks objective parameters.Therefore,a scoring system for the evaluation of computed tomography-based obstructive degree(CTOD)is urgently required for OCRC.AIM To explore the relationship between CTOD and CROSS and to determine whether CTOD could affect the short-term and long-term prognosis.METHODS Of 173 patients were enrolled.CTOD was obtained using k-means,the ratio of proximal to distal obstruction,and the proportion of nonparenchymal areas at the site of obstruction.CTOD was integrated with the CROSS to analyze the effect of emergency intervention on complications.Short-term and long-term outcomes were compared between the groups.RESULTS CTOD severe obstruction(CTOD grade 3)was an independent risk factor[odds ratio(OR)=3.390,95%confidence interval(CI):1.340-8.570,P=0.010]via multivariate analysis of short-term outcomes,while CROSS grade was not.In the CTOD-CROSS grade system,for the non-severe obstructive(CTOD 1-2 to CROSS 1-4)group,the complication rate of emergency interventions was significantly higher than that of non-emergency interventions(71.4%vs 41.8%,P=0.040).The postoperative pneumonia rate was higher in the emergency intervention group than in the non-severe obstructive group(35.7%vs 8.9%,P=0.020).However,CTOD grade was not an independent risk factor of overall survival and progression-free survival.CONCLUSION CTOD was useful in preoperative decision-making to avoid unnecessary emergency interventions and complications.展开更多
2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures...2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.展开更多
[Objective] In order to study the relations among different positions, degrees of substitution and antioxidant ability. [Method] N, O-carboxymethyl chitosan （NOA, NOB and NOC）with various degrees of substitution （D...[Objective] In order to study the relations among different positions, degrees of substitution and antioxidant ability. [Method] N, O-carboxymethyl chitosan （NOA, NOB and NOC）with various degrees of substitution （DS）were obtained by etherizing chito-oligosacchaside. Their structure and substituted degree were characterized and their antioxldant activity to·OH was evaluated. [ Result] The IC50 s of NOA ,NOB and NOC were 0.15 ,0. 29 ,0. 23 mg/ml while their DSs of -NH2 position（DSN） were 0.51,0.29 and 0.38 and DSo were 0. 74 ,0. 84 ,0. 97respectively.[ Conclusion] With the increase of DSN ,antioxidant activity of N,O-carboxymethyl chitosan oligosaccharide to·OH was up.展开更多
Freezing of gait is a significant and debilitating motor symptom often observed in individuals with Parkinson's disease.Resting-state functional magnetic resonance imaging,along with its multi-level feature indice...Freezing of gait is a significant and debilitating motor symptom often observed in individuals with Parkinson's disease.Resting-state functional magnetic resonance imaging,along with its multi-level feature indices,has provided a fresh perspective and valuable insight into the study of freezing of gait in Parkinson's disease.It has been revealed that Parkinson's disease is accompanied by widespread irregularities in inherent brain network activity.However,the effective integration of the multi-level indices of resting-state functional magnetic resonance imaging into clinical settings for the diagnosis of freezing of gait in Parkinson's disease remains a challenge.Although previous studies have demonstrated that radiomics can extract optimal features as biomarkers to identify or predict diseases,a knowledge gap still exists in the field of freezing of gait in Parkinson's disease.This cross-sectional study aimed to evaluate the ability of radiomics features based on multi-level indices of resting-state functional magnetic resonance imaging,along with clinical features,to distinguish between Parkinson's disease patients with and without freezing of gait.We recruited 28 patients with Parkinson's disease who had freezing of gait(15 men and 13 women,average age 63 years)and 30 patients with Parkinson's disease who had no freezing of gait(16 men and 14 women,average age 64 years).Magnetic resonance imaging scans were obtained using a 3.0T scanner to extract the mean amplitude of low-frequency fluctuations,mean regional homogeneity,and degree centrality.Neurological and clinical characteristics were also evaluated.We used the least absolute shrinkage and selection operator algorithm to extract features and established feedforward neural network models based solely on resting-state functional magnetic resonance imaging indicators.We then performed predictive analysis of three distinct groups based on resting-state functional magnetic resonance imaging indicators indicators combined with clinical features.Subsequently,we conducted 100 additional five-fold cross-validations to determine the most effective model for each classification task and evaluated the performance of the model using the area under the receiver operating characteristic curve.The results showed that when differentiating patients with Parkinson's disease who had freezing of gait from those who did not have freezing of gait,or from healthy controls,the models using only the mean regional homogeneity values achieved the highest area under the receiver operating characteristic curve values of 0.750(with an accuracy of 70.9%)and 0.759(with an accuracy of 65.3%),respectively.When classifying patients with Parkinson's disease who had freezing of gait from those who had no freezing of gait,the model using the mean amplitude of low-frequency fluctuation values combined with two clinical features achieved the highest area under the receiver operating characteristic curve of 0.847(with an accuracy of 74.3%).The most significant features for patients with Parkinson's disease who had freezing of gait were amplitude of low-frequency fluctuation alterations in the left parahippocampal gyrus and two clinical characteristics:Montreal Cognitive Assessment and Hamilton Depression Scale scores.Our findings suggest that radiomics features derived from resting-state functional magnetic resonance imaging indices and clinical information can serve as valuable indices for the identification of freezing of gait in Parkinson's disease.展开更多
The evaluation of sustainable land use is the key issue in the field of studying the sustainable land utilization. In general analysis, the sustainable land use is evaluated respectively from its ecological sustainabi...The evaluation of sustainable land use is the key issue in the field of studying the sustainable land utilization. In general analysis, the sustainable land use is evaluated respectively from its ecological sustainability, economic sustainability and social sustainability in China and other countries in recent years. Although this evaluation is an important work, it seems insufficient and hard to comprehensively reflect the whole degree of land use sustainability. Thus, to make up this deficiency, this paper brings forward the evaluation indexes, which make it possible to quantitatively reflect the whole degree of land use sustainability, namely, the concept of ＂degrees of overall land use sustainability＂ （Dos）, and research and measurement development of the method of and calculation in Dos. Taking the evaluation of the degree of land use sustainability in county regions of Yunnan Province as the actual example for analysis, results are basically as follows： 1） The degree of land use sustainability （Dos） is the ration index to organically and systematically integrate the degree of ecological friendliness （DeF）, the degree of economic viability （Dev） and the degree of social acceptability （Dsa）, able to comprehensively reflect the whole sustainability degree of regional land use 2） Based on the value of Dos, the grading system and standard for the sustainability of land use may be established and totally divided into five grades, namely, the high-degree sustainability, middle-degree sustainability, low-degree sustainability, conditional sustainability and non-sustainability. Meanwhile, the standard for distinguishing sustainability grades has also been confirmed so as to determine the nature of sustainability degrees in different grades. This makes the possibility for the combination of nature determination with ration in research result and provides with the scientific guideline and decision-making gist for better implementation of sustainable land use strategy. 3） The practice in evaluation of sustainability degree in county regional land use in Yunnan shows that the value of the degree of land use sustainability （Dos） of whole Yunnan Province is only 58.39, belonging to the grade of low-degree sustainability. Two thirds of counties in the whole province represent the grade of ＂conditional sustainability＂ and ＂non-sustainability＂ in the sustainability of land use. Among these counties, 11.11 % shows ＂non- sustainability＇. The lowest degree of land use sustainability appears especially in the middle plateau mountain region of Northeast Yunnan, where the value of Dos in most counties （districts） is below 40 %, belonging to the grade of ＂non-sustainability＂. The sustainability degree in the karst mountainous region in lower-middle plateau mountain region in Southeast Yunnan is generally low and the value of sustainability degree （Dos） in most of the counties （cities and districts） is below 55. The value of sustainability degree （Dos） in most of the counties （cities and districts） in the north, west, northwest and southwest parts of Yunnan is below 55. This article also analyzes the reasons of low degree of sustainability in land use in Yunnan and puts forward the countermeasures to increase the degree of sustainability in land use in the whole province.展开更多
Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrod...Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrodynamic performance and power capture efficiency of the buoy is physically modeled.Amplitudes of unidirectional and coupled motions are compared to analyze the interaction effect between freedoms under conditions with and without power take-off damping.The capture width ratio and corresponding growth rates are also calculated.Results show that the buoy makes a periodic sinusoidal(or approximate)movement in every DOF.Coupling effect can cause an increase in the amplitude in one DOF and a decrease in the amplitudes of the others.This phenomenon shows that the kinematic energy of the buoy redistributes to all DOFs compared with the unidirectional conditions.Adding DOFs can improve the power absorption of the buoy in most cases,but the number of DOFs is not the more the better.展开更多
A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced...A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.展开更多
Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studi...Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studies examining soil particle volume fractal dimension in alpine grasslands.To study the volume fractal dimension of soil particles （D） and its relationships with soil salt,soil nutrient and plant species diversity,we conducted an experiment on an alpine grassland under different disturbance degrees：non-disturbance （N0）,light disturbance （L）,moderate disturbance （M） and heavy disturbance （H）.The results showed that （1） Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance.（2） Shannon-Wiener diversity index,Pielou＇s evenness index and Margalef richness index reached their highest values at the M degree,indicating that moderate disturbance is beneficial to the increase of plant species diversity.（3） In the L and M degrees,there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter （SOM）.In the H degree,D was significantly and positively correlated with total salt （TS）.The results suggested that to a certain extent,D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics.（4） For the L degree,there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree,there was a significant negative correlation between D and Pielou＇s evenness index.展开更多
Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mat...Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20°/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.展开更多
Aging in oak barrels is widely used in enology which could bring flavor changes and aromatic complexity to wines.In the present study,the aroma compounds were analyzed from the‘Merlot’dry red wines,which were fermen...Aging in oak barrels is widely used in enology which could bring flavor changes and aromatic complexity to wines.In the present study,the aroma compounds were analyzed from the‘Merlot’dry red wines,which were fermented in two types of fermenters(stainless steel tank and rotated oak barrel)and aged in six types of oak barrels(three geographic origins×two toasting degrees)for different time(0,3,6 and 9 months,respectively).Results showed that 30 volatiles were associated with barrels and increased during oak aging.The fermenters could influence the intensities of the toast,leathery,smoky,fruity,floral and caramel aromas.The concentration of whisky lactone,eugenol,cis-isoeugenol,and the intensities of the toast and spicy aromas were highest in the wines aged in American oak and were lowest in the wines aged in French oak barrels.The concentrations of guaiacol,syringol,trans-isoeugenol,furfural alcohol,vanilla,cis-whisky lactone enabled the medium toasting barrels to be distinguished from the light toasting ones.The compounds originating from the barrels could be used to distinguish the types of different barrels,but the other general grape-derived and fermentation-derived volatiles could not.The fermenters,oak species and toasting degrees of the barrels all had significant effects on the aroma profiles of the aged‘Merlot’dry red wines,but the influence of the geographic origin was not obvious.展开更多
High degrees of freedom(DOF)for K^(+)movement in the electrolytes is desirable,because the resulting high ionic conductivity helps improve potassium-ion batteries,yet requiring support from highly free and flammable o...High degrees of freedom(DOF)for K^(+)movement in the electrolytes is desirable,because the resulting high ionic conductivity helps improve potassium-ion batteries,yet requiring support from highly free and flammable organic solvent molecules,seriously affecting battery safety.Here,we develop a K^(+)flux rectifier to trim K ion’s DOF to 1 and improve electrochemical properties.Although the ionic conductivity is compromised in the K^(+)flux rectifier,the overall electrochemical performance of PIBs was improved.An oxidation stability improvement from 4.0 to 5.9 V was realized,and the formation of dendrites and the dissolution of organic cathodes were inhibited.Consequently,the K||K cells continuously cycled over 3,700 h;K||Cu cells operated stably over 800 cycles with the Coulombic efficiency exceeding 99%;and K||graphite cells exhibited high-capacity retention over 74.7%after 1,500 cycles.Moreover,the 3,4,9,10-perylenetetracarboxylic diimide organic cathodes operated for more than 2,100 cycles and reached year-scale-cycling time.We fabricated a 2.18 Ah pouch cell with no significant capacity fading observed after 100 cycles.展开更多
The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized wi...The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic matter.The medium-metamorphized coal,capable of turning into a plastic state and cake in the range of investigated temperatures(350～450 ℃),is desulphurized with the greatest difficulty.The chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.展开更多
The two-rotational-degrees-of-freedom（2R） parallel mechanism（PM） with two continuous rotational axes（CRAs） has a simple kinematic model.It is therefore easy to implement trajectory planning,parameter calibration...The two-rotational-degrees-of-freedom（2R） parallel mechanism（PM） with two continuous rotational axes（CRAs） has a simple kinematic model.It is therefore easy to implement trajectory planning,parameter calibration,and motion control,which allows for a variety of application prospects.However,no systematic analysis on structural constraints of the 2R-PM with two CRAs has been performed,and there are only a few types of 2R-PM with two CRAs.Thus,a theory regarding the type synthesis of the 2R-PM with two CRAs is systematically established.First,combining the theories of reciprocal screw and space geometry,the spatial arrangement relationships of the constraint forces applied to the moving platform by the branches are explored,which give the 2R-PM two CRAs.The different distributions of the constraint forces in each branch are also studied.On the basis of the obtained structural constraints of branches,and considering the geometric relationships of constraint forces in each branch,the appropriate kinematic chains are constructed.Through the reasonable configuration of branch kinematic chains corresponding to every structural constraint,a series of new 2R-PMs with two CRAs are finally obtained.展开更多
The degree of spatial similarity plays an important role in map generalization, yet there has been no quantitative research into it. To fill this gap, this study first defines map scale change and spatial similarity d...The degree of spatial similarity plays an important role in map generalization, yet there has been no quantitative research into it. To fill this gap, this study first defines map scale change and spatial similarity degree/relation in multi-scale map spaces and then proposes a model for calculating the degree of spatial similarity between a point cloud at one scale and its gener- alized counterpart at another scale. After validation, the new model features 16 points with map scale change as the x coordinate and the degree of spatial similarity as the y coordinate. Finally, using an application for curve fitting, the model achieves an empirical formula that can calculate the degree of spatial similarity using map scale change as the sole independent variable, and vice versa. This formula can be used to automate algorithms for point feature generalization and to determine when to terminate them during the generalization.展开更多
Quadruped robot dynamic gaits have much more advantages than static gaits on speed and efficiency, however high speed and efficiency calls for more complex mechanical structure and complicated control algorithm. It be...Quadruped robot dynamic gaits have much more advantages than static gaits on speed and efficiency, however high speed and efficiency calls for more complex mechanical structure and complicated control algorithm. It becomes even more challenging when the robot has more degrees of freedom.As a result, most of the present researches focused on simple robot, while the researches on dynamic gaits for complex robot with more degrees of freedom are relatively limited. The paper is focusing on the dynamic gaits control for complex robot with twenty degrees of freedom for the first time. Firstly, we build a relatively complete 3 D model for quadruped robot based on spring loaded inverted pendulum(SLIP) model, analyze the inverse kinematics of the model, plan the trajectory of the swing foot and analyze the hydraulic drive. Secondly, we promote the control algorithm of one-legged to the quadruped robot based on the virtual leg and plan the state variables of pace gait and bound gait. Lastly, we realize the above two kinds of dynamic gaits in ADAMS-MATLAB joint simulation platform which testify the validity of above method.展开更多
A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-R...A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-RPU-UPR rigid parallel mechanism with the method of optimization of motion/force transfer characteristic.R,P and U represent rotation,translation and universal pairs,respectively.Firstly,inverse kinematics and Jacobian matrix are analyzed for the dimensional synthesis.Then,output transmission indexes of branches in the parallel mechanism are given.Dimensional synthesis is completed based on the normalized design parameter.And optimization of flexure joints based on constrained energy is carried out.Afterwards,the novel compliant mechanism is obtained by direct replacing method.Mechanical model of the compliant mechanism including static stiffness and input stiffness is built based on the pseudo-rigid body modeling method and virtual work principle.Finally,FEA simulation by Ansys Workbench is carried out to verify DOF,effectiveness of the dimension synthesis,and compliant model.Optimization of motion/force transfer characteristic is first applied for the design of compliant mechanisms to suppress drift of rotation axis in the paper.展开更多
With respect to the decision making problems where a lot of fuzzy and grey information always exists in the real-life decision making information system methods as fuzzy mathematics, it is difficult for such uncertain...With respect to the decision making problems where a lot of fuzzy and grey information always exists in the real-life decision making information system methods as fuzzy mathematics, it is difficult for such uncertainty probability, and interval numbers to deal with. To this end, based on the thought and method of grey numbers, grey degrees and interval numbers, the concept of dominance grey degree is defined. And then a method of ranking interval grey numbers based on the dominance grey degree is proposed. After discussing the relevant properties, the paper finally uses an example to demonstrate the effectiveness and applicability of the model. The result shows that the proposed model can more accurately describe uncertainty decision making problems, and realize the total ordering process for multiple-attribute decision-making problems.展开更多
A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is est...A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is established by expanding the essential terms of the assumed stress field as polynomials in the natural coordinates of the element. The homogeneous equilibrium equations are imposed in a variational sense through the internal displacements which are also expanded in the natural coordinates, while the tractionfree conditions along the inclined side are satisfied exactly. The use of such special element in the finite element solution is shown to be highly accurate when only a very coarse element mesh is used for plates with V-shaped rounded notches or inclined sides.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52171261).
文摘A floating horizontal-axis tidal current turbine(HATT)is an underwater power generation device where cavitation inevitably occurs on blade surfaces,severely affecting a turbine’s lifespan.Under wave action,these floating turbines exhibit six degrees of freedom motion,potentially intensifying the cavitation on the blade surfaces.This study selects three types of oscillatory motions from the six degrees of freedom:roll,yaw,and pitch.Computational fluid dynamics(CFD)methods are used for numerical calculations,and transient simulations of multiphase flow are conducted on the basis of the Reynolds-Averaged Navier-Stokes(RANS)model.Research has revealed strong correlations between flow velocity,the blade tip speed ratio,and cavitation.During oscillatory motion,the motion period and amplitude also significantly impact cavitation.In roll motion,the cavitation rate can increase by up to 59%with decreasing period,whereas in pitch and yaw motions,the increases are 7.57 times and 36%larger,respectively.With an increase in amplitude during roll motion,the cavitation rate can increase by up to 1.08 times,whereas in pitch and yaw motions,the increases are 3.49 times and 45%,respectively.The cavitation rate on the blade surfaces is the highest in pitch motion,followed by roll and yaw motions.
基金supported by the Key R&D Program of Shandong Province,China(No.2021ZLGX04)the National Natural Science Foundation of China(No.52171284)。
文摘The interaction between regular waves and an oscillating wave energy converter(WEC)in front of a vertical seawall is investigated using a 2D analytical model.A three-degree of freedom(DOF)WEC and a WEC hinged to the seawall(constrained to pitch mode)are considered to examine the influence of the DOF of the WEC on the wave energy extraction performance.Results show that the piston-mode water resonance in the gap and the coupled WEC and water column resonant motion significantly influence the wave energy extraction efficiency.At low frequency,the case with a 3-DOF WEC has a broader high-efficiency bandwidth than that with a heaving WEC.However,3-DOF WEC exhibits worse performance at high frequencies.The frequency response of the wave energy capture width ratio(CWR)for the pitching WEC case shows a trimodal trend under the specified conditions.It showcases the best overall wave energy extraction performance in terms of the high-efficiency bandwidth.Furthermore,a parametric study indicates that the gap distance between the WEC and the seawall has tremendous effects on the CWR of both cases.As the position of the hinge point of the pitching WEC changes,the CWR at the low and high frequencies shows opposite trends.
基金the Youth Foundation of Fujian Provincial Health Commission,No.2021QNA014the Construction Project of Fujian Province Minimally Invasive Medical Center,No.[2021]76.
文摘BACKGROUND The degree of obstruction plays an important role in decision-making for obstructive colorectal cancer(OCRC).The existing assessment still relies on the colorectal obstruction scoring system(CROSS)which is based on a comprehensive analysis of patients’complaints and eating conditions.The data collection relies on subjective descriptions and lacks objective parameters.Therefore,a scoring system for the evaluation of computed tomography-based obstructive degree(CTOD)is urgently required for OCRC.AIM To explore the relationship between CTOD and CROSS and to determine whether CTOD could affect the short-term and long-term prognosis.METHODS Of 173 patients were enrolled.CTOD was obtained using k-means,the ratio of proximal to distal obstruction,and the proportion of nonparenchymal areas at the site of obstruction.CTOD was integrated with the CROSS to analyze the effect of emergency intervention on complications.Short-term and long-term outcomes were compared between the groups.RESULTS CTOD severe obstruction(CTOD grade 3)was an independent risk factor[odds ratio(OR)=3.390,95%confidence interval(CI):1.340-8.570,P=0.010]via multivariate analysis of short-term outcomes,while CROSS grade was not.In the CTOD-CROSS grade system,for the non-severe obstructive(CTOD 1-2 to CROSS 1-4)group,the complication rate of emergency interventions was significantly higher than that of non-emergency interventions(71.4%vs 41.8%,P=0.040).The postoperative pneumonia rate was higher in the emergency intervention group than in the non-severe obstructive group(35.7%vs 8.9%,P=0.020).However,CTOD grade was not an independent risk factor of overall survival and progression-free survival.CONCLUSION CTOD was useful in preoperative decision-making to avoid unnecessary emergency interventions and complications.
基金the National Natural Science Foundation of China(No.52378411)for the support in this research.
文摘2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.
基金Supported by Shanghai Leading Academic Discipline(Project No.T1102)Shanghai Commission of Education Scientific Research Project(07zz134)~~
文摘[Objective] In order to study the relations among different positions, degrees of substitution and antioxidant ability. [Method] N, O-carboxymethyl chitosan （NOA, NOB and NOC）with various degrees of substitution （DS）were obtained by etherizing chito-oligosacchaside. Their structure and substituted degree were characterized and their antioxldant activity to·OH was evaluated. [ Result] The IC50 s of NOA ,NOB and NOC were 0.15 ,0. 29 ,0. 23 mg/ml while their DSs of -NH2 position（DSN） were 0.51,0.29 and 0.38 and DSo were 0. 74 ,0. 84 ,0. 97respectively.[ Conclusion] With the increase of DSN ,antioxidant activity of N,O-carboxymethyl chitosan oligosaccharide to·OH was up.
基金supported by the National Natural Science Foundation of China,No.82071909(to GF)the Natural Science Foundation of Liaoning Province,No.2023-MS-07(to HL)。
文摘Freezing of gait is a significant and debilitating motor symptom often observed in individuals with Parkinson's disease.Resting-state functional magnetic resonance imaging,along with its multi-level feature indices,has provided a fresh perspective and valuable insight into the study of freezing of gait in Parkinson's disease.It has been revealed that Parkinson's disease is accompanied by widespread irregularities in inherent brain network activity.However,the effective integration of the multi-level indices of resting-state functional magnetic resonance imaging into clinical settings for the diagnosis of freezing of gait in Parkinson's disease remains a challenge.Although previous studies have demonstrated that radiomics can extract optimal features as biomarkers to identify or predict diseases,a knowledge gap still exists in the field of freezing of gait in Parkinson's disease.This cross-sectional study aimed to evaluate the ability of radiomics features based on multi-level indices of resting-state functional magnetic resonance imaging,along with clinical features,to distinguish between Parkinson's disease patients with and without freezing of gait.We recruited 28 patients with Parkinson's disease who had freezing of gait(15 men and 13 women,average age 63 years)and 30 patients with Parkinson's disease who had no freezing of gait(16 men and 14 women,average age 64 years).Magnetic resonance imaging scans were obtained using a 3.0T scanner to extract the mean amplitude of low-frequency fluctuations,mean regional homogeneity,and degree centrality.Neurological and clinical characteristics were also evaluated.We used the least absolute shrinkage and selection operator algorithm to extract features and established feedforward neural network models based solely on resting-state functional magnetic resonance imaging indicators.We then performed predictive analysis of three distinct groups based on resting-state functional magnetic resonance imaging indicators indicators combined with clinical features.Subsequently,we conducted 100 additional five-fold cross-validations to determine the most effective model for each classification task and evaluated the performance of the model using the area under the receiver operating characteristic curve.The results showed that when differentiating patients with Parkinson's disease who had freezing of gait from those who did not have freezing of gait,or from healthy controls,the models using only the mean regional homogeneity values achieved the highest area under the receiver operating characteristic curve values of 0.750(with an accuracy of 70.9%)and 0.759(with an accuracy of 65.3%),respectively.When classifying patients with Parkinson's disease who had freezing of gait from those who had no freezing of gait,the model using the mean amplitude of low-frequency fluctuation values combined with two clinical features achieved the highest area under the receiver operating characteristic curve of 0.847(with an accuracy of 74.3%).The most significant features for patients with Parkinson's disease who had freezing of gait were amplitude of low-frequency fluctuation alterations in the left parahippocampal gyrus and two clinical characteristics:Montreal Cognitive Assessment and Hamilton Depression Scale scores.Our findings suggest that radiomics features derived from resting-state functional magnetic resonance imaging indices and clinical information can serve as valuable indices for the identification of freezing of gait in Parkinson's disease.
文摘The evaluation of sustainable land use is the key issue in the field of studying the sustainable land utilization. In general analysis, the sustainable land use is evaluated respectively from its ecological sustainability, economic sustainability and social sustainability in China and other countries in recent years. Although this evaluation is an important work, it seems insufficient and hard to comprehensively reflect the whole degree of land use sustainability. Thus, to make up this deficiency, this paper brings forward the evaluation indexes, which make it possible to quantitatively reflect the whole degree of land use sustainability, namely, the concept of ＂degrees of overall land use sustainability＂ （Dos）, and research and measurement development of the method of and calculation in Dos. Taking the evaluation of the degree of land use sustainability in county regions of Yunnan Province as the actual example for analysis, results are basically as follows： 1） The degree of land use sustainability （Dos） is the ration index to organically and systematically integrate the degree of ecological friendliness （DeF）, the degree of economic viability （Dev） and the degree of social acceptability （Dsa）, able to comprehensively reflect the whole sustainability degree of regional land use 2） Based on the value of Dos, the grading system and standard for the sustainability of land use may be established and totally divided into five grades, namely, the high-degree sustainability, middle-degree sustainability, low-degree sustainability, conditional sustainability and non-sustainability. Meanwhile, the standard for distinguishing sustainability grades has also been confirmed so as to determine the nature of sustainability degrees in different grades. This makes the possibility for the combination of nature determination with ration in research result and provides with the scientific guideline and decision-making gist for better implementation of sustainable land use strategy. 3） The practice in evaluation of sustainability degree in county regional land use in Yunnan shows that the value of the degree of land use sustainability （Dos） of whole Yunnan Province is only 58.39, belonging to the grade of low-degree sustainability. Two thirds of counties in the whole province represent the grade of ＂conditional sustainability＂ and ＂non-sustainability＂ in the sustainability of land use. Among these counties, 11.11 % shows ＂non- sustainability＇. The lowest degree of land use sustainability appears especially in the middle plateau mountain region of Northeast Yunnan, where the value of Dos in most counties （districts） is below 40 %, belonging to the grade of ＂non-sustainability＂. The sustainability degree in the karst mountainous region in lower-middle plateau mountain region in Southeast Yunnan is generally low and the value of sustainability degree （Dos） in most of the counties （cities and districts） is below 55. The value of sustainability degree （Dos） in most of the counties （cities and districts） in the north, west, northwest and southwest parts of Yunnan is below 55. This article also analyzes the reasons of low degree of sustainability in land use in Yunnan and puts forward the countermeasures to increase the degree of sustainability in land use in the whole province.
基金the support of the National Key R&D Program of China (No. 2018YFB1501900)the National Natural Science Fund of China (No. 41706100)+3 种基金the Shandong Provincial Natural Science Key Basic Program (No. ZR2017ZA 0202)the Special Projects for Marine Renewable Energy (No. GHME2016YY02)the Shandong Provincial Key Laboratory of Ocean Engineeringthe Qingdao Municipal Key Laboratory of Ocean Renewable Energy
文摘Increasing degrees of freedom(DOFs)is a useful way to raise the power capture efficiency of oscillating wave energy converters.Thus,this study proposes a buoy with three DOFs,which are surge,heave,and pitch.The hydrodynamic performance and power capture efficiency of the buoy is physically modeled.Amplitudes of unidirectional and coupled motions are compared to analyze the interaction effect between freedoms under conditions with and without power take-off damping.The capture width ratio and corresponding growth rates are also calculated.Results show that the buoy makes a periodic sinusoidal(or approximate)movement in every DOF.Coupling effect can cause an increase in the amplitude in one DOF and a decrease in the amplitudes of the others.This phenomenon shows that the kinematic energy of the buoy redistributes to all DOFs compared with the unidirectional conditions.Adding DOFs can improve the power absorption of the buoy in most cases,but the number of DOFs is not the more the better.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No.N110304008)the National Natural Science Foundation of China(Grant No.61374137)
文摘A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.
基金financially supported by the National Basic Research Program of China(2009CB825103)
文摘Fractal geometry is an important method in soil science,and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors.However,there have been few studies examining soil particle volume fractal dimension in alpine grasslands.To study the volume fractal dimension of soil particles （D） and its relationships with soil salt,soil nutrient and plant species diversity,we conducted an experiment on an alpine grassland under different disturbance degrees：non-disturbance （N0）,light disturbance （L）,moderate disturbance （M） and heavy disturbance （H）.The results showed that （1） Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance.（2） Shannon-Wiener diversity index,Pielou＇s evenness index and Margalef richness index reached their highest values at the M degree,indicating that moderate disturbance is beneficial to the increase of plant species diversity.（3） In the L and M degrees,there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter （SOM）.In the H degree,D was significantly and positively correlated with total salt （TS）.The results suggested that to a certain extent,D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics.（4） For the L degree,there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree,there was a significant negative correlation between D and Pielou＇s evenness index.
基金financially supported by the National Natural Science Foundation of China(Grant No.51279106)the Special Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110073110009)
文摘Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20°/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.
基金the financial support received from The Key Project of R&D Program of Ningxia Hui Autonomous Region,China(2022BBF01003)China Agriculture Research System of MOF and MARA(CARS-29).
文摘Aging in oak barrels is widely used in enology which could bring flavor changes and aromatic complexity to wines.In the present study,the aroma compounds were analyzed from the‘Merlot’dry red wines,which were fermented in two types of fermenters(stainless steel tank and rotated oak barrel)and aged in six types of oak barrels(three geographic origins×two toasting degrees)for different time(0,3,6 and 9 months,respectively).Results showed that 30 volatiles were associated with barrels and increased during oak aging.The fermenters could influence the intensities of the toast,leathery,smoky,fruity,floral and caramel aromas.The concentration of whisky lactone,eugenol,cis-isoeugenol,and the intensities of the toast and spicy aromas were highest in the wines aged in American oak and were lowest in the wines aged in French oak barrels.The concentrations of guaiacol,syringol,trans-isoeugenol,furfural alcohol,vanilla,cis-whisky lactone enabled the medium toasting barrels to be distinguished from the light toasting ones.The compounds originating from the barrels could be used to distinguish the types of different barrels,but the other general grape-derived and fermentation-derived volatiles could not.The fermenters,oak species and toasting degrees of the barrels all had significant effects on the aroma profiles of the aged‘Merlot’dry red wines,but the influence of the geographic origin was not obvious.
基金supported by the National Natural Science Foundation of China(Nos.U20A20247 and 51922038).A.M.R.acknowledges the seed funding provided by the R.A.Bowen Endowed Professorship funds at Clemson University.
文摘High degrees of freedom(DOF)for K^(+)movement in the electrolytes is desirable,because the resulting high ionic conductivity helps improve potassium-ion batteries,yet requiring support from highly free and flammable organic solvent molecules,seriously affecting battery safety.Here,we develop a K^(+)flux rectifier to trim K ion’s DOF to 1 and improve electrochemical properties.Although the ionic conductivity is compromised in the K^(+)flux rectifier,the overall electrochemical performance of PIBs was improved.An oxidation stability improvement from 4.0 to 5.9 V was realized,and the formation of dendrites and the dissolution of organic cathodes were inhibited.Consequently,the K||K cells continuously cycled over 3,700 h;K||Cu cells operated stably over 800 cycles with the Coulombic efficiency exceeding 99%;and K||graphite cells exhibited high-capacity retention over 74.7%after 1,500 cycles.Moreover,the 3,4,9,10-perylenetetracarboxylic diimide organic cathodes operated for more than 2,100 cycles and reached year-scale-cycling time.We fabricated a 2.18 Ah pouch cell with no significant capacity fading observed after 100 cycles.
文摘The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic matter.The medium-metamorphized coal,capable of turning into a plastic state and cake in the range of investigated temperatures(350～450 ℃),is desulphurized with the greatest difficulty.The chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.
基金Supported by National Natural Science Foundation of China(Grant No.51405425)Hebei Provincial Natural Science Foundation of China(Grant No.E2014203255)Independent Research Program Topics of Young Teachers in Yanshan University,China(Grant No.13LGA001)
文摘The two-rotational-degrees-of-freedom（2R） parallel mechanism（PM） with two continuous rotational axes（CRAs） has a simple kinematic model.It is therefore easy to implement trajectory planning,parameter calibration,and motion control,which allows for a variety of application prospects.However,no systematic analysis on structural constraints of the 2R-PM with two CRAs has been performed,and there are only a few types of 2R-PM with two CRAs.Thus,a theory regarding the type synthesis of the 2R-PM with two CRAs is systematically established.First,combining the theories of reciprocal screw and space geometry,the spatial arrangement relationships of the constraint forces applied to the moving platform by the branches are explored,which give the 2R-PM two CRAs.The different distributions of the constraint forces in each branch are also studied.On the basis of the obtained structural constraints of branches,and considering the geometric relationships of constraint forces in each branch,the appropriate kinematic chains are constructed.Through the reasonable configuration of branch kinematic chains corresponding to every structural constraint,a series of new 2R-PMs with two CRAs are finally obtained.
基金funded by the Natural Science Foundation Committee,China(41364001,41371435)
文摘The degree of spatial similarity plays an important role in map generalization, yet there has been no quantitative research into it. To fill this gap, this study first defines map scale change and spatial similarity degree/relation in multi-scale map spaces and then proposes a model for calculating the degree of spatial similarity between a point cloud at one scale and its gener- alized counterpart at another scale. After validation, the new model features 16 points with map scale change as the x coordinate and the degree of spatial similarity as the y coordinate. Finally, using an application for curve fitting, the model achieves an empirical formula that can calculate the degree of spatial similarity using map scale change as the sole independent variable, and vice versa. This formula can be used to automate algorithms for point feature generalization and to determine when to terminate them during the generalization.
基金supported by the National Science Fund for Distinguished Young Scholars of China(51225503)the National Natural Science Foundation of China(61603076)the Fundamental Research Funds for the Central Universities(ZYGX2016J116)
文摘Quadruped robot dynamic gaits have much more advantages than static gaits on speed and efficiency, however high speed and efficiency calls for more complex mechanical structure and complicated control algorithm. It becomes even more challenging when the robot has more degrees of freedom.As a result, most of the present researches focused on simple robot, while the researches on dynamic gaits for complex robot with more degrees of freedom are relatively limited. The paper is focusing on the dynamic gaits control for complex robot with twenty degrees of freedom for the first time. Firstly, we build a relatively complete 3 D model for quadruped robot based on spring loaded inverted pendulum(SLIP) model, analyze the inverse kinematics of the model, plan the trajectory of the swing foot and analyze the hydraulic drive. Secondly, we promote the control algorithm of one-legged to the quadruped robot based on the virtual leg and plan the state variables of pace gait and bound gait. Lastly, we realize the above two kinds of dynamic gaits in ADAMS-MATLAB joint simulation platform which testify the validity of above method.
基金National Natural Science Foundation of China(Grant No.51975007).
文摘A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-RPU-UPR rigid parallel mechanism with the method of optimization of motion/force transfer characteristic.R,P and U represent rotation,translation and universal pairs,respectively.Firstly,inverse kinematics and Jacobian matrix are analyzed for the dimensional synthesis.Then,output transmission indexes of branches in the parallel mechanism are given.Dimensional synthesis is completed based on the normalized design parameter.And optimization of flexure joints based on constrained energy is carried out.Afterwards,the novel compliant mechanism is obtained by direct replacing method.Mechanical model of the compliant mechanism including static stiffness and input stiffness is built based on the pseudo-rigid body modeling method and virtual work principle.Finally,FEA simulation by Ansys Workbench is carried out to verify DOF,effectiveness of the dimension synthesis,and compliant model.Optimization of motion/force transfer characteristic is first applied for the design of compliant mechanisms to suppress drift of rotation axis in the paper.
基金supported by the National Natural Science Foundation of China(7117310471171113+8 种基金70901041712712267130107571301064)the Humanities and Social Sciences of Education Ministry(12YJC630262)the Jiangsu Province University Philosophy and Social Sciences for Key Research Program(2012ZDIXM030)the Jiangsu Innovation Program for Graduate Education and the Fundamental Research Funds for the Central Universities(CXLX12 0175)the Nanjing University of Aeronautics and Astronautics(NUAA)Innovation and Excellence Program for PHD Dissertation(BCXJ12-12)NUAA Program for I-U-R(NC2012006)
文摘With respect to the decision making problems where a lot of fuzzy and grey information always exists in the real-life decision making information system methods as fuzzy mathematics, it is difficult for such uncertainty probability, and interval numbers to deal with. To this end, based on the thought and method of grey numbers, grey degrees and interval numbers, the concept of dominance grey degree is defined. And then a method of ranking interval grey numbers based on the dominance grey degree is proposed. After discussing the relevant properties, the paper finally uses an example to demonstrate the effectiveness and applicability of the model. The result shows that the proposed model can more accurately describe uncertainty decision making problems, and realize the total ordering process for multiple-attribute decision-making problems.
文摘A new kind of quadrilateral assumed stress hy- brid membrane element with drilling degrees of freedom and a traction-free inclined side has been developed based on an extended Hellinger-Reissner principle which is established by expanding the essential terms of the assumed stress field as polynomials in the natural coordinates of the element. The homogeneous equilibrium equations are imposed in a variational sense through the internal displacements which are also expanded in the natural coordinates, while the tractionfree conditions along the inclined side are satisfied exactly. The use of such special element in the finite element solution is shown to be highly accurate when only a very coarse element mesh is used for plates with V-shaped rounded notches or inclined sides.
