A numerical research on magnetohydrodynamic mixed convection flow in a lid-driven trapezoidal enclosure at non-uniform heating of bottom wall has been studied numerically. The enclosure consists of insulated top wall ...A numerical research on magnetohydrodynamic mixed convection flow in a lid-driven trapezoidal enclosure at non-uniform heating of bottom wall has been studied numerically. The enclosure consists of insulated top wall and cold side walls, too. It also contains a heated triangular block (<em>Rot</em> = 0<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span> - 90<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span>) located somewhere inside the enclosure. The boundary top wall of the enclosure is moving through uniform speed <em>U</em><sub>0</sub>. The geometry of the model has been represented mathematically by coupled governing equations in accordance with proper boundary conditions and then a two-dimensional Galerkin finite element based numerical approach has been adopted to solve this paper. The numerical computations have been carried out for the wide range of parameters Prandtl number (0.5 ≤ <em>Pr</em> ≤ 2), Reynolds number (60 ≤ <em>Re</em> ≤ 120), Rayleigh number (<em>Ra</em> = 10<sup>3</sup>) and Hartmann number (<em>Ha</em> = 20) taking with different rotations of heated triangular block. The results have been shown in the form of streamlines, temperature patterns or isotherms, average Nusselt number and average bulk temperature of the fluid in the enclosure at non-uniform heating of bottom wall. It is also indicated that both the streamlines, isotherm patterns strongly depend on the aforesaid governing parameters and location of the triangular block but the thermal conductivity of the triangular block has a noteworthy role on the isotherm pattern lines. Moreover, the variation of <em>Nu</em><sub>av</sub> of hot bottom wall and <em>θ</em><sub>av</sub> in the enclosure is demonstrated here to show the characteristics of heat transfer in the enclosure.展开更多
This paper proposes anoptimal fuzzy-based model for obtaining crisp priorities for Fuzzy-AHP comparison matrices.Crisp judgments cannot be given for real-life situations,as most of these include some level of fuzzines...This paper proposes anoptimal fuzzy-based model for obtaining crisp priorities for Fuzzy-AHP comparison matrices.Crisp judgments cannot be given for real-life situations,as most of these include some level of fuzziness and com-plexity.In these situations,judgments are represented by the set of fuzzy numbers.Most of the fuzzy optimization models derive crisp priorities for judgments repre-sented with Triangular Fuzzy Numbers(TFNs)only.They do not work for other types of Triangular Shaped Fuzzy Numbers(TSFNs)and Trapezoidal Fuzzy Numbers(TrFNs).To overcome this problem,a sum of squared error(SSE)based optimization model is proposed.Unlike some other methods,the proposed model derives crisp weights from all of the above-mentioned fuzzy judgments.A fuzzy number is simulated using the Monte Carlo method.A threshold-based constraint is also applied to minimize the deviation from the initial judgments.Genetic Algorithm(GA)is used to solve the optimization model.We have also conducted casestudiesto show the proposed approach’s advantages over the existingmethods.Results show that the proposed model outperforms other models to minimize SSE and deviation from initial judgments.Thus,the proposed model can be applied in various real time scenarios as it can reduce the SSE value upto 29%compared to the existing studies.展开更多
1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are cha...1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are changing,a non-uniform load that varies with time and lateral location is applied to the underlying ground.The consolidation phenomenon under two-dimensional(2D)conditions will keep pace with the construction of the embankment.In addition,because of evaporation and rainfall,the soils are mostly unsaturated.Therefore,it is meaningful to research the consolidation properties of unsaturated ground under non-uniform loading.展开更多
Intuitionistic trapezoidal fuzzy numbers and their operational laws are defined. Based on these operational laws, some aggregation operators, including intuitionistic trapezoidal fuzzy weighted arithmetic averaging op...Intuitionistic trapezoidal fuzzy numbers and their operational laws are defined. Based on these operational laws, some aggregation operators, including intuitionistic trapezoidal fuzzy weighted arithmetic averaging operator and weighted geometric averaging operator are proposed. Expected values, score function, and accuracy function of intuitionitsic trapezoidal fuzzy numbers are defined. Based on these, a kind of intuitionistic trapezoidal fuzzy multi-criteria decision making method is proposed. By using these aggregation operators, criteria values are aggregated and integrated intuitionistic trapezoidal fuzzy numbers of alternatives are attained. By comparing score function and accuracy function values of integrated fuzzy numbers, a ranking of the whole alternative set can be attained. An example is given to show the feasibility and availability of the method.展开更多
A comprehensive experimental study was carried out on the regular wave attenuation with a trapezoidal pontoontype floating breakwater(FB) in deep water. The functionalities of two simple FB geometries consist of a rec...A comprehensive experimental study was carried out on the regular wave attenuation with a trapezoidal pontoontype floating breakwater(FB) in deep water. The functionalities of two simple FB geometries consist of a rectangle and a trapezoid with the slope of 60° were investigated under the wave attack. A two-dimensional wave flume was used in the experiment; the incident, transmitted waves, mooring line forces and motion responses of the floating breakwaters were measured. Also the influence of the sea state conditions(incident wave height and wave period)and structural parameters(draught of the structure) were investigated using the trapezoidal FB. Our experimental results indicated that the trapezoidal FB significantly reduced the wave transmission and mooring line force when compared with rectangular FBs. A new formula was developed in order to predict the value of the transmission coefficient in trapezoidal FBs with the slope of 60°. Experimental data showed to be consistent with the results of the formula.展开更多
Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3 Ma 0.7. The formulation herein proposed extends wellknown aerodynamic theories, which are...Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3 Ma 0.7. The formulation herein proposed extends wellknown aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to generic trapezoidal wing planforms. Firstly, a thorough study is executed to assess the accuracy and limitation of analytical predictions, using unsteady results from two state-of-the-art computational fluid dynamics solvers as cross-validated benchmarks. Indicial functions are calculated for a step change in the angle of attack and for a sharp-edge gust, each for four wing configurations and three Mach numbers. Then, analytical and computational indicial responses are used to predict dynamic derivatives and the maximum lift coefficient following an encounter with a one-minus-cosine gust. It is found that the analytical results are in excellent agreement with the computational results for all test cases. In particular, the deviation of the analytical results from the computational results is within the scatter or uncertainty in the data arising from using two computational fluid dynamics solvers. This indicates the usefulness of the developed analytical theories.展开更多
In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at whic...In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at which the instability of the NAPL dissolution front can be initiated. This will require a huge number of finite elements if a whole NAPL dissolution system is simulated in the computational model. Even though modern supercomputers might be used to tackle this kind of NAPL dissolution problem, it can become prohibitive for commonly-used personal computers to do so. The main purpose of this work is to investigate whether or not the whole NAPL dissolution system of an annular domain can be replaced by a trapezoidal domain, so as to greatly reduce the requirements for computer efforts. The related simulation results have demonstrated that when the NAPL dissolution system under consideration is in a subcritical state, if the dissolution pattern around the entrance of an annulus domain is of interest, then a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.However, if the dissolution pattern away from the vicinity of the entrance of an annulus domain is of interest, then a trapezoidal domain can be used to replace an annular domain in the computational simulation of the NAPL dissolution system. When the NAPL dissolution system under consideration is in a supercritical state, a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.展开更多
Local scour around bridge abutments is a widespread problem that can result in structural failure. Collars can be used as a countermeasure to reduce the scour depth. In this study, the temporal scour development aroun...Local scour around bridge abutments is a widespread problem that can result in structural failure. Collars can be used as a countermeasure to reduce the scour depth. In this study, the temporal scour development around a wing-wall abutment was investigated with and without collars. The tests were carried out under clear-water conditions for different abutment lengths, with collars of different sizes placed at the bed level. When no collar was used in the experiments, 70% of the maximum scour depth occurred in less than 2 h. However, when a collar with a width greater than the length of the abutment was used, no scour was observed for up to 200 min from the beginning of the experiments. The results show that an increase in the collar width not only led to a lag time for the onset of scouring but also reduced the maximum scour depth. Moreover, an increased collar width led to a better performance in mitigating scouring around smaller abutments. Generally, the scour depth decreased by 9%-37% with different collar widths.展开更多
Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwellin...Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices;and forces for the reef model were measured by load cell.The results of flume experiments agree well with the numerical data.In addition,the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes,showing a more complicated flow structure than that of a stand-alone reef.Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef.The role of the reef in water flow is to reduce flow velocity and generate turbulence.展开更多
Bypass Dual Throat Nozzle(BDTN)is a novel type of fluidic thrust vectoring nozzle.To improve the infrared stealth performance of BDTN,a nozzle based on BDTN is proposed and numerically simulated.Each cross-section alo...Bypass Dual Throat Nozzle(BDTN)is a novel type of fluidic thrust vectoring nozzle.To improve the infrared stealth performance of BDTN,a nozzle based on BDTN is proposed and numerically simulated.Each cross-section along the x-axis of the novel nozzle becomes a trapezoid,which is named“BDTN-TRA.”The main numerical simulation results show that BDTN-TRA can produce a thrust vectoring angle when the upper or lower bypass valve is open.The angle difference between the two conditions mentioned above is usually approximately 1°-2°.Even if the two bypasses are closed,BDTN-TRA can produce a small thrust vectoring angle at around 3°-5°.When the sidewall angle increases from 60°to 90°,the thrust coefficient and thrust vectoring angle under each work condition usually decrease.A larger aspect ratio indicates better performance.As the aspect ratio increases over 7.2,the performance of BDTN-TRA is quite close to that of BDTN with rectangular cross-sections at the same aspect ratio.These features will benefit the control and trimming for future aircraft design,especially for the flying wing layout aircraft.Last but not least,BDTN-TRA has a more extraordinary mixing performance compared with BDTN.The distributions of static temperature and axial velocity along the x-axis of BDTN-TRA with sidewall angle of 60°decrease faster than those of BDTN.When the total temperature of the inlet equals 1600 K,the static temperature difference between BDTN-TRA with sidewall angles of 60°and 90°is over 360 K at twice the length of the nozzle downstream of the nozzle exit,which is the reflection for excellent infrared stealth for the fighter.展开更多
The fuzzy theory is invited in this paper to calculate weights of evaluation items, which is a very important stage in highway network evaluation. Highway network evaluation is a composite of various attributes that l...The fuzzy theory is invited in this paper to calculate weights of evaluation items, which is a very important stage in highway network evaluation. Highway network evaluation is a composite of various attributes that lack of pertinency and comparability, and their commonality is that they are more or less tainted with uncertainty, with different daily decision making problems of diverse intensity, the results can be misleading if the fuzziness of human decision-making is not taken into account. So we introduce fuzzy theory into the measurement of evaluating weights to overcome the issue and Analytic Hierarchy Process in scheme ranking. It is testified to be a more reliable way through the case study of Yangtze River Delta highway network evaluation.展开更多
Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied ...Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied based on the Taguchi analogy.The variation in the process parameters alters the kinetic energy dissipation and the deformation work performed at the interface,and dictates the interfacial wave amplitude and the mechanical strength of the dissimilar explosive clad.The optimum level of process parameters for attaining higher tensile and shear strength is computed by signal-to-noise ratio.Further,a mathematical model is developed for calculating tensile and shear strength of the clad,based on the regression analysis using statistical software Minitab-16,and the level of fit is determined by analysis of variance.展开更多
In Gengcun Colliery, Yima Coal Group Co. Ltd.the characteristics of the gateways of thick coal seam and the coal seam is with fully mechanized sublevel caving mining are that the thickness of roof coal seam of gateway...In Gengcun Colliery, Yima Coal Group Co. Ltd.the characteristics of the gateways of thick coal seam and the coal seam is with fully mechanized sublevel caving mining are that the thickness of roof coal seam of gateways is larger, their surrounding rocks are the whole-coal mass and the coal seam is prone to Spontaneous Combustion. With the natural equilibrium arch theory, the reasonable adjacent distance of No.11 mine-type metal supports was calculated in trapezoidal gateways based on these characteristics. Then, in-situ supporting experiments were carried out. The results indicate that under the action of virgin rock stress, the width of broken rocks zone of surrounding rocks is 1.7–2.0 m in return heading and 1.1–1.3 m in going headway. And their surrounding rocks belong to the Ⅳ-type soften rock and the Ⅲ-type common surrounding rock respectively. Therefore, under the movable abutment pressure, the gateways deformation is serious. It is suggested that the designed gateways have to use pre-broadened cross section to suit their deformation. At the same time, the accumulated water on gateway floor must be drained in time. These measures were taken in the 1302 and 1304 coal faces in Gengcun Colliery, and the satisfactory results have been obtained.展开更多
The former studies indicate that loading rates significantly affect dynamic behavior of brittle materials,for instance,the dynamic compressive and tensile strength increase with loading rates.However,there still are m...The former studies indicate that loading rates significantly affect dynamic behavior of brittle materials,for instance,the dynamic compressive and tensile strength increase with loading rates.However,there still are many unknown or partially unknown aspects.For example,whether loading rates have effect on crack dynamic propagating behavior(propagation toughness,velocity and arrest,etc).To further explore the effect of loading rates on crack dynamic responses,a large-size single-cleavage trapezoidal open(SCTO)specimen was proposed,and impacting tests using the SCTO specimen under drop plate impact were conducted.Crack propagation gauges(CPGs)were employed in measuring impact loads,crack propagation time and velocities.In order to verify the testing result,the corresponding numerical model was established using explicit dynamic software AUTODYN,and the simulation result is basically consistent with the experimental results.The ABAQUS software was used to calculate the dynamic SIFs.The universal function was calculated by fractal method.The experimental-numerical method was employed in determining initiation toughness and propagation toughness.The results indicate that crack propagating velocities,dynamic fracture toughness and energy release rates increase with loading rates;crack delayed initiation time decreases with loading rates.展开更多
Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matl...Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matlab/Simulink indicates that there is much more overshoot and fluctuating during the valve-positioning process. In order to improve the valve-positioning precision, the control method of trapezoidal velocity curve was studied. The simulation result showed that the positioning steady-state error was less than 0.0056%, whereas the peak error was less than 0.016% by using trapezoidal velocity curve at 10 positioning steps. A valve-positioning precision experimental device for the stepper motor of basis weight control valve was developed. The experiment results showed that the error ratio of 1/10000 positioning steps was 4% by using trapezoidal velocity curve. Furthermore, the error ratio of 10/10000 positioning steps was 0.5%. It proved that the valve-positioning precision of trapezoidal velocity curve was much higher than that of the constant frequency pulse signal control strategy. The new control method of trapezoidal velocity curve can satisfy the precision requirement of 10000 steps.展开更多
This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of G...This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of Goda's two points is used to separate the heights of incident,reflected and transmitted waves based on the experimental data.The possible factors affecting the wave attenuation properties of the double trapezoidal submerged breakwaters(i.e.,the relative submerged water depth,relative breakwater spacing,wave steepness and relative wave height) are investigated with respect to the reflection and transmission coefficients.The results show that there is a range,within which the breakwater spacing has little impact on the reflection coefficient,and the transmission coefficient tends to be a constant.The influence of the wave steepness is reduced while the breakwater spacing is too large or too small.Within the range of the relative wave height tested in this study,the reflection and transmission coefficients increase and decrease with the relative wave height,respectively.The double trapezoidal submerged breakwaters model indicates a good attenuation effect for larger wave steepness,big relative wave height and within the range of the relative breakwater spacing between 12.5 and 14 according to linear and cnoidal waves.The changes of wave energy spectra between the double submerged breakwaters on the flat-bed are investigated by the fast Fourier transform(FFT) method,showing that wave energy dissipation can be reached more effectively when the relative breakwater spacing is 12.5.展开更多
We investigate the spectral redshift of high-order harmonics of the H_2~＋（D_2~＋） molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation（TDSE）. The results show that ...We investigate the spectral redshift of high-order harmonics of the H_2~＋（D_2~＋） molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation（TDSE）. The results show that the spectral redshift of highorder harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses. Comparing with the H_2~＋ molecule, the shift of high-order harmonic generation（HHG） spectrum for the D_2~＋ molecule is more obvious.We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics.展开更多
Sentiment analysis,commonly called opinion mining or emotion artificial intelligence(AI),employs biometrics,computational linguistics,nat-ural language processing,and text analysis to systematically identify,extract,m...Sentiment analysis,commonly called opinion mining or emotion artificial intelligence(AI),employs biometrics,computational linguistics,nat-ural language processing,and text analysis to systematically identify,extract,measure,and investigate affective states and subjective data.Sentiment analy-sis algorithms include emotion lexicon,traditional machine learning,and deep learning.In the text sentiment analysis algorithm based on a neural network,multi-layer Bi-directional long short-term memory(LSTM)is widely used,but the parameter amount of this model is too huge.Hence,this paper proposes a Bi-directional LSTM with a trapezoidal structure model.The design of the trapezoidal structure is derived from classic neural networks,such as LeNet-5 and AlexNet.These classic models have trapezoidal-like structures,and these structures have achieved success in the field of deep learning.There are two benefits to using the Bi-directional LSTM with a trapezoidal structure.One is that compared with the single-layer configuration,using the of the multi-layer structure can better extract the high-dimensional features of the text.Another is that using the trapezoidal structure can reduce the model’s parameters.This paper introduces the Bi-directional LSTM with a trapezoidal structure model in detail and uses Stanford sentiment treebank 2(STS-2)for experiments.It can be seen from the experimental results that the trapezoidal structure model and the normal structure model have similar performances.However,the trapezoidal structure model parameters are 35.75%less than the normal structure model.展开更多
To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is ...To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is successfully equivalent to the rectangular one with both restricting the same optical field energy by adopting the perturbation method,Then,the equivalent rectangular core waveguide is decomposed into two slab waveguides by employing the modified effective-index method,The trapezoidal core waveguide scattering theory model is established based on the slab waveguide scattering theory.With the sidewalls surface roughness in the range from 0 to 100 nm in the single model trapezodial core waveguide,optical simulation shows excellent agreement with the results from the scattering loss model presented.The relationship between the dimension and side-wall roughness with the scattering loss can be determined in the trapezoidal core waveguide by the scattering loss model.展开更多
Trapezoidal pulse shaping algorithm is widely applied to improve signal-to-noise ratio(SNR), throughput and energy resolution with the properties of noise suppression, pile-up pulse separation and ballistic deficit co...Trapezoidal pulse shaping algorithm is widely applied to improve signal-to-noise ratio(SNR), throughput and energy resolution with the properties of noise suppression, pile-up pulse separation and ballistic deficit correction. The algorithm can be acquired by z transform method which is easier for derivation. However, the baseline drift of trapezoidal pulse appears because the noise superimposes on the input signal. In this paper,two new methods based on convergence analysis and noise suppression are proposed to remove the baseline drift resulting from trapezoidal pulse shaping. Simulations and experimental tests are carried out to verify the methods. The results demonstrate that the proposed methods can remove baseline drift in trapezoidal pulse shaping.展开更多
文摘A numerical research on magnetohydrodynamic mixed convection flow in a lid-driven trapezoidal enclosure at non-uniform heating of bottom wall has been studied numerically. The enclosure consists of insulated top wall and cold side walls, too. It also contains a heated triangular block (<em>Rot</em> = 0<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span> - 90<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span>) located somewhere inside the enclosure. The boundary top wall of the enclosure is moving through uniform speed <em>U</em><sub>0</sub>. The geometry of the model has been represented mathematically by coupled governing equations in accordance with proper boundary conditions and then a two-dimensional Galerkin finite element based numerical approach has been adopted to solve this paper. The numerical computations have been carried out for the wide range of parameters Prandtl number (0.5 ≤ <em>Pr</em> ≤ 2), Reynolds number (60 ≤ <em>Re</em> ≤ 120), Rayleigh number (<em>Ra</em> = 10<sup>3</sup>) and Hartmann number (<em>Ha</em> = 20) taking with different rotations of heated triangular block. The results have been shown in the form of streamlines, temperature patterns or isotherms, average Nusselt number and average bulk temperature of the fluid in the enclosure at non-uniform heating of bottom wall. It is also indicated that both the streamlines, isotherm patterns strongly depend on the aforesaid governing parameters and location of the triangular block but the thermal conductivity of the triangular block has a noteworthy role on the isotherm pattern lines. Moreover, the variation of <em>Nu</em><sub>av</sub> of hot bottom wall and <em>θ</em><sub>av</sub> in the enclosure is demonstrated here to show the characteristics of heat transfer in the enclosure.
文摘This paper proposes anoptimal fuzzy-based model for obtaining crisp priorities for Fuzzy-AHP comparison matrices.Crisp judgments cannot be given for real-life situations,as most of these include some level of fuzziness and com-plexity.In these situations,judgments are represented by the set of fuzzy numbers.Most of the fuzzy optimization models derive crisp priorities for judgments repre-sented with Triangular Fuzzy Numbers(TFNs)only.They do not work for other types of Triangular Shaped Fuzzy Numbers(TSFNs)and Trapezoidal Fuzzy Numbers(TrFNs).To overcome this problem,a sum of squared error(SSE)based optimization model is proposed.Unlike some other methods,the proposed model derives crisp weights from all of the above-mentioned fuzzy judgments.A fuzzy number is simulated using the Monte Carlo method.A threshold-based constraint is also applied to minimize the deviation from the initial judgments.Genetic Algorithm(GA)is used to solve the optimization model.We have also conducted casestudiesto show the proposed approach’s advantages over the existingmethods.Results show that the proposed model outperforms other models to minimize SSE and deviation from initial judgments.Thus,the proposed model can be applied in various real time scenarios as it can reduce the SSE value upto 29%compared to the existing studies.
基金supported by the National Nature Science Foundation of China(No.12172211)the National Key Research and Development Program of China(No.2019YFC1509800)。
文摘1 Introduction In highway construction,flled embankments are trapezoidal,and the ground is always improved by sand wells or columns.During embankment construction,because the width and height of the embankment are changing,a non-uniform load that varies with time and lateral location is applied to the underlying ground.The consolidation phenomenon under two-dimensional(2D)conditions will keep pace with the construction of the embankment.In addition,because of evaporation and rainfall,the soils are mostly unsaturated.Therefore,it is meaningful to research the consolidation properties of unsaturated ground under non-uniform loading.
基金supported by the National Natural Science Foundation of China (70771115).
文摘Intuitionistic trapezoidal fuzzy numbers and their operational laws are defined. Based on these operational laws, some aggregation operators, including intuitionistic trapezoidal fuzzy weighted arithmetic averaging operator and weighted geometric averaging operator are proposed. Expected values, score function, and accuracy function of intuitionitsic trapezoidal fuzzy numbers are defined. Based on these, a kind of intuitionistic trapezoidal fuzzy multi-criteria decision making method is proposed. By using these aggregation operators, criteria values are aggregated and integrated intuitionistic trapezoidal fuzzy numbers of alternatives are attained. By comparing score function and accuracy function values of integrated fuzzy numbers, a ranking of the whole alternative set can be attained. An example is given to show the feasibility and availability of the method.
文摘A comprehensive experimental study was carried out on the regular wave attenuation with a trapezoidal pontoontype floating breakwater(FB) in deep water. The functionalities of two simple FB geometries consist of a rectangle and a trapezoid with the slope of 60° were investigated under the wave attack. A two-dimensional wave flume was used in the experiment; the incident, transmitted waves, mooring line forces and motion responses of the floating breakwaters were measured. Also the influence of the sea state conditions(incident wave height and wave period)and structural parameters(draught of the structure) were investigated using the trapezoidal FB. Our experimental results indicated that the trapezoidal FB significantly reduced the wave transmission and mooring line force when compared with rectangular FBs. A new formula was developed in order to predict the value of the transmission coefficient in trapezoidal FBs with the slope of 60°. Experimental data showed to be consistent with the results of the formula.
基金the Royal Academy of Engineering for funding this researchthe use of the IRIDIS High Performance Computing Facility, and associated support services at the University of Southampton, in the completion of this work
文摘Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3 Ma 0.7. The formulation herein proposed extends wellknown aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to generic trapezoidal wing planforms. Firstly, a thorough study is executed to assess the accuracy and limitation of analytical predictions, using unsteady results from two state-of-the-art computational fluid dynamics solvers as cross-validated benchmarks. Indicial functions are calculated for a step change in the angle of attack and for a sharp-edge gust, each for four wing configurations and three Mach numbers. Then, analytical and computational indicial responses are used to predict dynamic derivatives and the maximum lift coefficient following an encounter with a one-minus-cosine gust. It is found that the analytical results are in excellent agreement with the computational results for all test cases. In particular, the deviation of the analytical results from the computational results is within the scatter or uncertainty in the data arising from using two computational fluid dynamics solvers. This indicates the usefulness of the developed analytical theories.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at which the instability of the NAPL dissolution front can be initiated. This will require a huge number of finite elements if a whole NAPL dissolution system is simulated in the computational model. Even though modern supercomputers might be used to tackle this kind of NAPL dissolution problem, it can become prohibitive for commonly-used personal computers to do so. The main purpose of this work is to investigate whether or not the whole NAPL dissolution system of an annular domain can be replaced by a trapezoidal domain, so as to greatly reduce the requirements for computer efforts. The related simulation results have demonstrated that when the NAPL dissolution system under consideration is in a subcritical state, if the dissolution pattern around the entrance of an annulus domain is of interest, then a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.However, if the dissolution pattern away from the vicinity of the entrance of an annulus domain is of interest, then a trapezoidal domain can be used to replace an annular domain in the computational simulation of the NAPL dissolution system. When the NAPL dissolution system under consideration is in a supercritical state, a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.
文摘Local scour around bridge abutments is a widespread problem that can result in structural failure. Collars can be used as a countermeasure to reduce the scour depth. In this study, the temporal scour development around a wing-wall abutment was investigated with and without collars. The tests were carried out under clear-water conditions for different abutment lengths, with collars of different sizes placed at the bed level. When no collar was used in the experiments, 70% of the maximum scour depth occurred in less than 2 h. However, when a collar with a width greater than the length of the abutment was used, no scour was observed for up to 200 min from the beginning of the experiments. The results show that an increase in the collar width not only led to a lag time for the onset of scouring but also reduced the maximum scour depth. Moreover, an increased collar width led to a better performance in mitigating scouring around smaller abutments. Generally, the scour depth decreased by 9%-37% with different collar widths.
基金Supported by the National Natural Science Foundation of China(Nos.31072246,31272703)
文摘Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices;and forces for the reef model were measured by load cell.The results of flume experiments agree well with the numerical data.In addition,the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes,showing a more complicated flow structure than that of a stand-alone reef.Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef.The role of the reef in water flow is to reduce flow velocity and generate turbulence.
基金support of the National Science and Technology Major Project,China(No.2019-II-0007-0027)the Defense Industrial Technology Development Program,China(No.JCKY2019605D001)+3 种基金the Advanced Jet Propulsion Creativity Center,Aero Engine Academy of China(No.HKCX2020-02-011)the Aeronautics Power Foundation,China(No.6141B09050383)the Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory of China,the Jiangsu Funding Program for Excellent Postdoctoral Talent,China(No.2022ZB214)the China Postdoctoral Science Foundation。
文摘Bypass Dual Throat Nozzle(BDTN)is a novel type of fluidic thrust vectoring nozzle.To improve the infrared stealth performance of BDTN,a nozzle based on BDTN is proposed and numerically simulated.Each cross-section along the x-axis of the novel nozzle becomes a trapezoid,which is named“BDTN-TRA.”The main numerical simulation results show that BDTN-TRA can produce a thrust vectoring angle when the upper or lower bypass valve is open.The angle difference between the two conditions mentioned above is usually approximately 1°-2°.Even if the two bypasses are closed,BDTN-TRA can produce a small thrust vectoring angle at around 3°-5°.When the sidewall angle increases from 60°to 90°,the thrust coefficient and thrust vectoring angle under each work condition usually decrease.A larger aspect ratio indicates better performance.As the aspect ratio increases over 7.2,the performance of BDTN-TRA is quite close to that of BDTN with rectangular cross-sections at the same aspect ratio.These features will benefit the control and trimming for future aircraft design,especially for the flying wing layout aircraft.Last but not least,BDTN-TRA has a more extraordinary mixing performance compared with BDTN.The distributions of static temperature and axial velocity along the x-axis of BDTN-TRA with sidewall angle of 60°decrease faster than those of BDTN.When the total temperature of the inlet equals 1600 K,the static temperature difference between BDTN-TRA with sidewall angles of 60°and 90°is over 360 K at twice the length of the nozzle downstream of the nozzle exit,which is the reflection for excellent infrared stealth for the fighter.
基金This paper is sponsored by Shanghai Municipal Commiottee and the Sate Development and Planning Committee.
文摘The fuzzy theory is invited in this paper to calculate weights of evaluation items, which is a very important stage in highway network evaluation. Highway network evaluation is a composite of various attributes that lack of pertinency and comparability, and their commonality is that they are more or less tainted with uncertainty, with different daily decision making problems of diverse intensity, the results can be misleading if the fuzziness of human decision-making is not taken into account. So we introduce fuzzy theory into the measurement of evaluating weights to overcome the issue and Analytic Hierarchy Process in scheme ranking. It is testified to be a more reliable way through the case study of Yangtze River Delta highway network evaluation.
文摘Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied based on the Taguchi analogy.The variation in the process parameters alters the kinetic energy dissipation and the deformation work performed at the interface,and dictates the interfacial wave amplitude and the mechanical strength of the dissimilar explosive clad.The optimum level of process parameters for attaining higher tensile and shear strength is computed by signal-to-noise ratio.Further,a mathematical model is developed for calculating tensile and shear strength of the clad,based on the regression analysis using statistical software Minitab-16,and the level of fit is determined by analysis of variance.
基金Project 0511051900 supported by Natural Science Foundation of Henan Province
文摘In Gengcun Colliery, Yima Coal Group Co. Ltd.the characteristics of the gateways of thick coal seam and the coal seam is with fully mechanized sublevel caving mining are that the thickness of roof coal seam of gateways is larger, their surrounding rocks are the whole-coal mass and the coal seam is prone to Spontaneous Combustion. With the natural equilibrium arch theory, the reasonable adjacent distance of No.11 mine-type metal supports was calculated in trapezoidal gateways based on these characteristics. Then, in-situ supporting experiments were carried out. The results indicate that under the action of virgin rock stress, the width of broken rocks zone of surrounding rocks is 1.7–2.0 m in return heading and 1.1–1.3 m in going headway. And their surrounding rocks belong to the Ⅳ-type soften rock and the Ⅲ-type common surrounding rock respectively. Therefore, under the movable abutment pressure, the gateways deformation is serious. It is suggested that the designed gateways have to use pre-broadened cross section to suit their deformation. At the same time, the accumulated water on gateway floor must be drained in time. These measures were taken in the 1302 and 1304 coal faces in Gengcun Colliery, and the satisfactory results have been obtained.
基金Projects(11672194,U19A2098)supported by the National Natural Science Foundation of ChinaProject(2018SCU12047)supported by Fundamental Research Funds for the Central Universities,ChinaProject(2018JZ0036)supported by the Project of Science and Technology of Sichuan Province,China。
文摘The former studies indicate that loading rates significantly affect dynamic behavior of brittle materials,for instance,the dynamic compressive and tensile strength increase with loading rates.However,there still are many unknown or partially unknown aspects.For example,whether loading rates have effect on crack dynamic propagating behavior(propagation toughness,velocity and arrest,etc).To further explore the effect of loading rates on crack dynamic responses,a large-size single-cleavage trapezoidal open(SCTO)specimen was proposed,and impacting tests using the SCTO specimen under drop plate impact were conducted.Crack propagation gauges(CPGs)were employed in measuring impact loads,crack propagation time and velocities.In order to verify the testing result,the corresponding numerical model was established using explicit dynamic software AUTODYN,and the simulation result is basically consistent with the experimental results.The ABAQUS software was used to calculate the dynamic SIFs.The universal function was calculated by fractal method.The experimental-numerical method was employed in determining initiation toughness and propagation toughness.The results indicate that crack propagating velocities,dynamic fracture toughness and energy release rates increase with loading rates;crack delayed initiation time decreases with loading rates.
基金supported by the International S&T Cooperation Program of China(GrantNo.2010DFB43660)National Natural Science Foundation of China(Grant No.51375286)Scientific Research Program Funded by Shaanxi Provincial Education Department(Program No.16JF005)
文摘Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matlab/Simulink indicates that there is much more overshoot and fluctuating during the valve-positioning process. In order to improve the valve-positioning precision, the control method of trapezoidal velocity curve was studied. The simulation result showed that the positioning steady-state error was less than 0.0056%, whereas the peak error was less than 0.016% by using trapezoidal velocity curve at 10 positioning steps. A valve-positioning precision experimental device for the stepper motor of basis weight control valve was developed. The experiment results showed that the error ratio of 1/10000 positioning steps was 4% by using trapezoidal velocity curve. Furthermore, the error ratio of 10/10000 positioning steps was 0.5%. It proved that the valve-positioning precision of trapezoidal velocity curve was much higher than that of the constant frequency pulse signal control strategy. The new control method of trapezoidal velocity curve can satisfy the precision requirement of 10000 steps.
基金Supported by the General Program of National Natural Science Foundation of China(No.50979066 and No.50979008)Ph.D.Programs Foundation of Ministry of Education of China(No.20094316110002)Scientific Research Fund of Department of Education, Hunan Province(No.10A006)
文摘This paper investigates the wave attenuation properties of the double trapezoidal submerged breakwaters on the flat-bed by conducting physical experiments subjected to linear and cnoidal incident waves.The method of Goda's two points is used to separate the heights of incident,reflected and transmitted waves based on the experimental data.The possible factors affecting the wave attenuation properties of the double trapezoidal submerged breakwaters(i.e.,the relative submerged water depth,relative breakwater spacing,wave steepness and relative wave height) are investigated with respect to the reflection and transmission coefficients.The results show that there is a range,within which the breakwater spacing has little impact on the reflection coefficient,and the transmission coefficient tends to be a constant.The influence of the wave steepness is reduced while the breakwater spacing is too large or too small.Within the range of the relative wave height tested in this study,the reflection and transmission coefficients increase and decrease with the relative wave height,respectively.The double trapezoidal submerged breakwaters model indicates a good attenuation effect for larger wave steepness,big relative wave height and within the range of the relative breakwater spacing between 12.5 and 14 according to linear and cnoidal waves.The changes of wave energy spectra between the double submerged breakwaters on the flat-bed are investigated by the fast Fourier transform(FFT) method,showing that wave energy dissipation can be reached more effectively when the relative breakwater spacing is 12.5.
基金Project supported by the National Natural Science Foundation of China(Grant No.61575077)the Graduate Innovation Fund of Jilin University(Grant No.2017107)
文摘We investigate the spectral redshift of high-order harmonics of the H_2~＋（D_2~＋） molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation（TDSE）. The results show that the spectral redshift of highorder harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses. Comparing with the H_2~＋ molecule, the shift of high-order harmonic generation（HHG） spectrum for the D_2~＋ molecule is more obvious.We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics.
基金supported by Yunnan Provincial Education Department Science Foundation of China under Grant construction of the seventh batch of key engineering research centers in colleges and universities(Grant Project:Yunnan College and University Edge Computing Network Engineering Research Center).
文摘Sentiment analysis,commonly called opinion mining or emotion artificial intelligence(AI),employs biometrics,computational linguistics,nat-ural language processing,and text analysis to systematically identify,extract,measure,and investigate affective states and subjective data.Sentiment analy-sis algorithms include emotion lexicon,traditional machine learning,and deep learning.In the text sentiment analysis algorithm based on a neural network,multi-layer Bi-directional long short-term memory(LSTM)is widely used,but the parameter amount of this model is too huge.Hence,this paper proposes a Bi-directional LSTM with a trapezoidal structure model.The design of the trapezoidal structure is derived from classic neural networks,such as LeNet-5 and AlexNet.These classic models have trapezoidal-like structures,and these structures have achieved success in the field of deep learning.There are two benefits to using the Bi-directional LSTM with a trapezoidal structure.One is that compared with the single-layer configuration,using the of the multi-layer structure can better extract the high-dimensional features of the text.Another is that using the trapezoidal structure can reduce the model’s parameters.This paper introduces the Bi-directional LSTM with a trapezoidal structure model in detail and uses Stanford sentiment treebank 2(STS-2)for experiments.It can be seen from the experimental results that the trapezoidal structure model and the normal structure model have similar performances.However,the trapezoidal structure model parameters are 35.75%less than the normal structure model.
基金Project(50735007) supported by the National Natural Science Foundation of ChinaProject(2010ZX04001-151) supported by Important National Science & Technology Specific Program of China
文摘To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is successfully equivalent to the rectangular one with both restricting the same optical field energy by adopting the perturbation method,Then,the equivalent rectangular core waveguide is decomposed into two slab waveguides by employing the modified effective-index method,The trapezoidal core waveguide scattering theory model is established based on the slab waveguide scattering theory.With the sidewalls surface roughness in the range from 0 to 100 nm in the single model trapezodial core waveguide,optical simulation shows excellent agreement with the results from the scattering loss model presented.The relationship between the dimension and side-wall roughness with the scattering loss can be determined in the trapezoidal core waveguide by the scattering loss model.
基金Supported by National High Technology Research and Development Program of China(863 Program)(No.2012AA061804-03)
文摘Trapezoidal pulse shaping algorithm is widely applied to improve signal-to-noise ratio(SNR), throughput and energy resolution with the properties of noise suppression, pile-up pulse separation and ballistic deficit correction. The algorithm can be acquired by z transform method which is easier for derivation. However, the baseline drift of trapezoidal pulse appears because the noise superimposes on the input signal. In this paper,two new methods based on convergence analysis and noise suppression are proposed to remove the baseline drift resulting from trapezoidal pulse shaping. Simulations and experimental tests are carried out to verify the methods. The results demonstrate that the proposed methods can remove baseline drift in trapezoidal pulse shaping.
