To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-s...To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.展开更多
Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coord...Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coordinate formulation(ANCF)method is established and the dynamic characteristics of a planar L-shaped pipe are analyzed.Firstly,the dynamic equations of the pipe element are derived,and then the overall equations of the pipe model are composed by matrix assembly.By solving equations,it is found that static deformation caused by fluid velocity occurs in the plane,with larger deformations at higher fluid velocities.Additionally,the study observes coupling between different modes and variations in modal shapes.Variations in arc segment structural parameters result in non-uniform changes in natural frequencies,with out-of-plane vibration presenting even more complexity,and the results are verified by ANSYS simulation.Subsequently,a comparison between experimental and theoretical results is conducted across three sets of structural parameters,the consistency between these results validates the engineering significance of the theoretical model.展开更多
In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power ...In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.展开更多
This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates ...This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.展开更多
A joint two-dimensional(2D)direction-of-arrival(DOA)and radial Doppler frequency estimation method for the L-shaped array is proposed in this paper based on the compressive sensing(CS)framework.Revised from the conven...A joint two-dimensional(2D)direction-of-arrival(DOA)and radial Doppler frequency estimation method for the L-shaped array is proposed in this paper based on the compressive sensing(CS)framework.Revised from the conventional CS-based methods where the joint spatial-temporal parameters are characterized in one large scale matrix,three smaller scale matrices with independent azimuth,elevation and Doppler frequency are introduced adopting a separable observation model.Afterwards,the estimation is achieved by L1-norm minimization and the Bayesian CS algorithm.In addition,under the L-shaped array topology,the azimuth and elevation are separated yet coupled to the same radial Doppler frequency.Hence,the pair matching problem is solved with the aid of the radial Doppler frequency.Finally,numerical simulations corroborate the feasibility and validity of the proposed algorithm.展开更多
In this paper,the disturbance propagation and active vibration control of a finite L-shaped beam axe studied.The dynamic response of the structure is obtained by the travelling wave approach.The active vibration suppr...In this paper,the disturbance propagation and active vibration control of a finite L-shaped beam axe studied.The dynamic response of the structure is obtained by the travelling wave approach.The active vibration suppression of the finite L-shaped beam is performed based on the structural vibration power flow.In the numerical calculation,the influences of the near field effect of the error sensor and the small error of the control forces on the control results are all considered.The simulation results indicate that the structural vibration response in the medium and high frequency regions can be effectively computed by the travelling wave method.The effect of the active control by controlling the power flow is much better than that by controlling the acceleration in some cases.And the control results by the power flow method are slightly affected by the locations of the error sensor and the small error of the control forces.展开更多
Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical proper...Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.展开更多
With the completion of the Qinghai-Tibetan Railway,economic development of related areas has been greatly accelerated.This,in return,calls for building or upgrading more roadways,especially high-grade roadways.In cold...With the completion of the Qinghai-Tibetan Railway,economic development of related areas has been greatly accelerated.This,in return,calls for building or upgrading more roadways,especially high-grade roadways.In cold regions,the thawing of permafrost can induce settlement damage of and even failure to railway(or roadway)embankments.Thermosyphons(self-powered refrigera-tion devices that are used to help keep the permafrost cool)have proved effective in mitigating thaw settlement by maintaining the thermal stability of the embankments.However,for high-grade roadway embankments of great width,stabilizing or cooling ef-fects of traditional geotechnological measures may be limited.To enhance the cooling effect of thermosyphons,an L-shaped thermosyphon was designed.A laboratory test was carried out to study the combined cooling effect of the L-shaped thermosyphon and thermal insulation applying to roadbed construction.The angle between the evaporator and condenser sections of the L-shaped thermosyphon is 134 degrees,and the L-shaped thermosyphon was inserted into the soil at an angle of 5 degrees with the road surface.The tested results show that the L-shaped thermosyphon is effective in removing heat from a roadway in winter.When the ambient air temperature is lower than the soil temperature,the thermosyphon is active and extracts the heat in the soil around it.When the ambient air temperature is higher than the soil temperature,the thermosyphon is inactive,and no heat is in-jected into the soil through the L-shaped thermosyphon.Compared to embankments with straight thermosyphons,the inner parts of the embankments with L-shaped thermosyphons were significantly cooled.It is hoped that the present study would be useful to the application of L-shaped thermosyphons in the construction of high-grade roadways in cold regions.展开更多
L-shaped plates have become an important focuses in structural vibration research. To determine their vibration characteristics, this paper applied a mobility power flow method. Firstly, the L-shaped plate was divided...L-shaped plates have become an important focuses in structural vibration research. To determine their vibration characteristics, this paper applied a mobility power flow method. Firstly, the L-shaped plate was divided into two substructures to simplify analysis. The coupled bending moment was then deduced by applying a continuous vibration property on the common edge. Next, the response on any point of the plate and the input and transmitted power flow formulas were calculated. Numerical simulations showed the distribution of the coupled bending moment and the response of the whole structure. The validity of this method was verified by the SEA approach.展开更多
Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,...Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,i.e.,the moment ratio of torsion to bending(γ)and the aspect ratio(column length-to-depth ratio,φ),were prepared for the experiment.In this study,the failure process,torsion-displacement hysteresis curves,and flexure-displacement hysteresis curves were obtained.The failure characteristics,mechanical behavior of specimens such as the failure patterns,hysteresis curves,rigidity degradation,ductility and energy dissipation,are analyzed.The experimental research indicated that the major failures of the specimens were bending failure,bending-shear failure and bending-torsion failure as the moment ratio of torsion to bending(γ)increased.The torsion-displacement hysteresis curves were pinched in the middle,formed a slip platform,and the phenomenon of“load drop”occurred after the peak load.The bending-displacement hysteresis curves were plump,which showed that bending capacity of the specimen was better than its torsion capacity.Additionally,the energy dissipation of the specimen was dominated by torsion in the early stage and ultimately governed by the bending moment in the later phase.Test results also indicated that the displacement ductility coefficient and interstory rotation angle of the failure point were less than 3.0 and 1/50,respectively,which means the test specimen performance does not meet the requirement of the Chinese Code for Seismic Design of Buildings(GB 50011-2014)in this respect.展开更多
Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed b...Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed by image analysis of cut surfaces and thickness measurements.Results show that air in OOA prepregs is evacuated in two ways.Most of the air is forced out of layers directly by vacuum before air accesses in prepregs closed.Very little entrapped air moves perpendicularly to outer layers under hydrostatic resin pressure.When a laminate contains less than 16 layers,voids can hardly be found in layers.When a laminate contains more than 16 layers,voids cannot be expelled completely during the window of vertical movement.As for stacking sequences,the synergetic effect of slip function and nest function determines the thickness and voids content of laminates.Results show that the average of single layer thickness of unidirectional layers is the lowest,and the average of single layer thickness of quasi-isotropic layers is the highest.The voids content of quasi isotropic is the highest,which is consistent with the theoretical analysis.展开更多
The basic scheme of the orientation detection system using L-shape reticle is introduced. The dimension of the patterns on the reticle of the system in practical applications is designed and an analysis of the princip...The basic scheme of the orientation detection system using L-shape reticle is introduced. The dimension of the patterns on the reticle of the system in practical applications is designed and an analysis of the principle of abstracting the orientation information of the target and the effects and formation method of self-adapting tracking gate is presented. The research result shows that the orientation detection system using L-shape reticle has a good effect on space-filtering, the signals that the orientation detection system sends out are easy to be processed by computer, its self-adapting tracking gate has a strong anti-interference ability, and the whole system＇s searching and tracking performances are quite high.展开更多
A single layer triangular patch antenna fed by an L-shaped probe was investigated numerically by using FDTD (Finite Difference Time Domain) method. It achieves >40% impedance bandwidth (VSWR<2) and stable radiat...A single layer triangular patch antenna fed by an L-shaped probe was investigated numerically by using FDTD (Finite Difference Time Domain) method. It achieves >40% impedance bandwidth (VSWR<2) and stable radiation pattern across the passband. The triangular patch antenna with two orientations of L-shaped probe has almost the same characteristics, such as impedance bandwidth and radiation pattern. The bandwidth vs feeding position was also investigated, the broadband characteristic can be observed when the feeding position is only in a small segment along the centerline.展开更多
In order to explore the cell composition and its metabolism,it is important to let computer recognize the cells and get the counts of different cells for a sample.This paper proposes an L-shaped envelop function and t...In order to explore the cell composition and its metabolism,it is important to let computer recognize the cells and get the counts of different cells for a sample.This paper proposes an L-shaped envelop function and the related fuzzy clustering method as a way to identify the megakaryocyte and the red cell from the sliced marrow image.This method is useful when the staining is insufficient and the color cannot be used as the identifying factor.This method uses the experimental histogram data to fit the L-shaped function and then use it as the envelop for the match test.The fuzzy c-means(FCM) performance index is used to test the adjacent area and get the minimum and finally secure the identification.The new method is not limited to megakaryocyte or red cell and can be used for general purposes of cell recognition.Tests show that this envelop function can ensure the recognition rate with different staining batches and can reach satisfied counting under similar illumination condition.展开更多
The behavior of L-Shaped RC （reinforced concrete） shear walls was investigated in the Erciyes University Earthquake Investigation Laboratory under the influence of constant axial load together with reversed cyclic l...The behavior of L-Shaped RC （reinforced concrete） shear walls was investigated in the Erciyes University Earthquake Investigation Laboratory under the influence of constant axial load together with reversed cyclic lateral load. The objective of this study was to evaluate the effects of cross sectional dimensions on the behavior of L-shaped structural members and to assess their earthquake performance. In order to investigate L-shaped RC structural members, the special experiment setup and four type of 1/2 scaled specimens which have different aspect ratio were constructed. The specimens were loaded in line with the major principal axes direction laterally. Axial load ratio was 0.1 and cross section height to thickness ratios were＇ 3：1, 5：1, 8：1, 10：1. Cross section thickness was 120 mm which corresponds to （360：120）, （600：120）, （960：120）, （1,200：120） wall legs cross sectional dimensions in mm. The specimens height was 1,500 mm, together with upper and lower slabs overall height was 2,000 mm. Concrete compression strength was 30 N/mm2, steel yield stress 420 N/mm2 and vertical reinforcement ratio was 1% for all specimens. According to the test results, the specimen of which the aspect ratio is 3 （360：120） has shown column behavior, the specimen of which the aspect ratio is 5 （600：120） has shown slender wall behavior and last two specimens of which the aspect ratios are 8 （960：120） and 10 （1,200：120） have shown squat wall behavior. When considering the cracking patterns and hysteretic behavior, since the aspect ratio 8, the specimens show flexure-shear interaction behavior and prone to brittle failure.展开更多
Two-stage problem of stochastic convex programming with fuzzy probability distribution is studied in this paper. Multicut L-shaped algorithm is proposed to solve the problem based on the fuzzy cutting and the minimax ...Two-stage problem of stochastic convex programming with fuzzy probability distribution is studied in this paper. Multicut L-shaped algorithm is proposed to solve the problem based on the fuzzy cutting and the minimax rule. Theorem of the convergence for the algorithm is proved. Finally, a numerical example about two-stage convex recourse problem shows the essential character and the efficiency.展开更多
In this paper, a simplified model of the bistable piezoelectric cantilever beam with magnets is established, and the potential energy of the bistable system is analyzed. We have proposed the bistable L-shaped beam str...In this paper, a simplified model of the bistable piezoelectric cantilever beam with magnets is established, and the potential energy of the bistable system is analyzed. We have proposed the bistable L-shaped beam structure, which has the same geometry dimensions of the bistable straight beam in the first time. The comparative study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam plays an important role in exploring excellent piezoelectric generator.The experiment structure includes the base layer and the piezoelectric layer. The harmonic excitation is given to the system.Theoretical analysis results show that the potential energy function of the system has two obvious steady potential wells. In addition, the depth of the upper potential well is different from that of the lower potential well when the gravity potential energy is considered. Experimental results demonstrate that the power generation for the straight beam is better than that of the horizontally placed L-shaped beam when the excitation amplitude is 450 m V. There is the existence that the energy harvesting capacity of the bistable L-shaped beam is better than that of the bistable straight beam when the excitation amplitude is 400 m V.Furthermore, the power generation of the bistable L-shaped beam with the upper potential well is obviously better than that of the bistable L-shaped beam with the lower potential well. In addition, comparing with the straight beam, the dynamic response of the bistable L-shaped beam is more complex when the external excitation frequency is changed. It is also observed that the distance between the magnets has the obvious influence on the dynamic response of the bistable system. It is very effective to select the appropriate distance between the magnets to improve the power generation of the bistable energy harvester under the fixed excitation conditions.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52176045)the National Science and Technology Major Project of China(No.J2019-I-0011-0011)。
文摘To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.
基金supported by the China National Funds for Distinguished Young Scholars(Grant No.12025204)the project of the National Natural Science Foundation of China(Grant No.12072181)the YEQISUN Joint Funds of the National Science Foundation of China(Grant No.U2341231).
文摘Research on pipe dynamics primarily focuses on in-plane vibration.However,pipes simultaneously experience in-plane and out-of-plane vibrations.Therefore,a three-dimensional dynamic model using the absolute nodal coordinate formulation(ANCF)method is established and the dynamic characteristics of a planar L-shaped pipe are analyzed.Firstly,the dynamic equations of the pipe element are derived,and then the overall equations of the pipe model are composed by matrix assembly.By solving equations,it is found that static deformation caused by fluid velocity occurs in the plane,with larger deformations at higher fluid velocities.Additionally,the study observes coupling between different modes and variations in modal shapes.Variations in arc segment structural parameters result in non-uniform changes in natural frequencies,with out-of-plane vibration presenting even more complexity,and the results are verified by ANSYS simulation.Subsequently,a comparison between experimental and theoretical results is conducted across three sets of structural parameters,the consistency between these results validates the engineering significance of the theoretical model.
基金supported by the National Basic Research Programof China (2011CB711102)the National Natural Science Foundation of China (10672017,11002045)
文摘In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.
基金supported by the National Natural Science Foundation of China(Grants 11772008,11172009,11372015,11232009,10872010,11290152,10732020)the Tianjin Natural Science Foundation(Grant 19JCZDJC32300).
文摘This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.
文摘A joint two-dimensional(2D)direction-of-arrival(DOA)and radial Doppler frequency estimation method for the L-shaped array is proposed in this paper based on the compressive sensing(CS)framework.Revised from the conventional CS-based methods where the joint spatial-temporal parameters are characterized in one large scale matrix,three smaller scale matrices with independent azimuth,elevation and Doppler frequency are introduced adopting a separable observation model.Afterwards,the estimation is achieved by L1-norm minimization and the Bayesian CS algorithm.In addition,under the L-shaped array topology,the azimuth and elevation are separated yet coupled to the same radial Doppler frequency.Hence,the pair matching problem is solved with the aid of the radial Doppler frequency.Finally,numerical simulations corroborate the feasibility and validity of the proposed algorithm.
基金Project supported by the National Natural Science Foundation of China(Nos.10672017 and 10632020)
文摘In this paper,the disturbance propagation and active vibration control of a finite L-shaped beam axe studied.The dynamic response of the structure is obtained by the travelling wave approach.The active vibration suppression of the finite L-shaped beam is performed based on the structural vibration power flow.In the numerical calculation,the influences of the near field effect of the error sensor and the small error of the control forces on the control results are all considered.The simulation results indicate that the structural vibration response in the medium and high frequency regions can be effectively computed by the travelling wave method.The effect of the active control by controlling the power flow is much better than that by controlling the acceleration in some cases.And the control results by the power flow method are slightly affected by the locations of the error sensor and the small error of the control forces.
基金Foundation of Key Laboratory of Coast Civil Structure Safety (Tianjin University),Ministry of EducationChinese Program for New Century Excellent Talents in University+1 种基金Seed Foundation of Tianjin UniversitySeed Foundation of Xinjiang University
文摘Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.
基金supported by National Natural Science Foundation of China(Grant No.40730736 and No.40601023)the National Hi-Tech Research and Development Plan(2008AA11Z103)the Western Project Program of the Chinese Academy of Sciences(No.KZCX2-XB2-10)
文摘With the completion of the Qinghai-Tibetan Railway,economic development of related areas has been greatly accelerated.This,in return,calls for building or upgrading more roadways,especially high-grade roadways.In cold regions,the thawing of permafrost can induce settlement damage of and even failure to railway(or roadway)embankments.Thermosyphons(self-powered refrigera-tion devices that are used to help keep the permafrost cool)have proved effective in mitigating thaw settlement by maintaining the thermal stability of the embankments.However,for high-grade roadway embankments of great width,stabilizing or cooling ef-fects of traditional geotechnological measures may be limited.To enhance the cooling effect of thermosyphons,an L-shaped thermosyphon was designed.A laboratory test was carried out to study the combined cooling effect of the L-shaped thermosyphon and thermal insulation applying to roadbed construction.The angle between the evaporator and condenser sections of the L-shaped thermosyphon is 134 degrees,and the L-shaped thermosyphon was inserted into the soil at an angle of 5 degrees with the road surface.The tested results show that the L-shaped thermosyphon is effective in removing heat from a roadway in winter.When the ambient air temperature is lower than the soil temperature,the thermosyphon is active and extracts the heat in the soil around it.When the ambient air temperature is higher than the soil temperature,the thermosyphon is inactive,and no heat is in-jected into the soil through the L-shaped thermosyphon.Compared to embankments with straight thermosyphons,the inner parts of the embankments with L-shaped thermosyphons were significantly cooled.It is hoped that the present study would be useful to the application of L-shaped thermosyphons in the construction of high-grade roadways in cold regions.
基金Supported by the National Natural Science Foundation under Grant No. 50675177.
文摘L-shaped plates have become an important focuses in structural vibration research. To determine their vibration characteristics, this paper applied a mobility power flow method. Firstly, the L-shaped plate was divided into two substructures to simplify analysis. The coupled bending moment was then deduced by applying a continuous vibration property on the common edge. Next, the response on any point of the plate and the input and transmitted power flow formulas were calculated. Numerical simulations showed the distribution of the coupled bending moment and the response of the whole structure. The validity of this method was verified by the SEA approach.
基金National Natural Science Foundation of China under Grant Nos.51268004 and 51578163Natural Science Foundation of Guangxi under Grant No 2016GXNSFDA380032Bagui Scholar Program of Guangxi under Grant No:[2019]79。
文摘Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,i.e.,the moment ratio of torsion to bending(γ)and the aspect ratio(column length-to-depth ratio,φ),were prepared for the experiment.In this study,the failure process,torsion-displacement hysteresis curves,and flexure-displacement hysteresis curves were obtained.The failure characteristics,mechanical behavior of specimens such as the failure patterns,hysteresis curves,rigidity degradation,ductility and energy dissipation,are analyzed.The experimental research indicated that the major failures of the specimens were bending failure,bending-shear failure and bending-torsion failure as the moment ratio of torsion to bending(γ)increased.The torsion-displacement hysteresis curves were pinched in the middle,formed a slip platform,and the phenomenon of“load drop”occurred after the peak load.The bending-displacement hysteresis curves were plump,which showed that bending capacity of the specimen was better than its torsion capacity.Additionally,the energy dissipation of the specimen was dominated by torsion in the early stage and ultimately governed by the bending moment in the later phase.Test results also indicated that the displacement ductility coefficient and interstory rotation angle of the failure point were less than 3.0 and 1/50,respectively,which means the test specimen performance does not meet the requirement of the Chinese Code for Seismic Design of Buildings(GB 50011-2014)in this respect.
文摘Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed by image analysis of cut surfaces and thickness measurements.Results show that air in OOA prepregs is evacuated in two ways.Most of the air is forced out of layers directly by vacuum before air accesses in prepregs closed.Very little entrapped air moves perpendicularly to outer layers under hydrostatic resin pressure.When a laminate contains less than 16 layers,voids can hardly be found in layers.When a laminate contains more than 16 layers,voids cannot be expelled completely during the window of vertical movement.As for stacking sequences,the synergetic effect of slip function and nest function determines the thickness and voids content of laminates.Results show that the average of single layer thickness of unidirectional layers is the lowest,and the average of single layer thickness of quasi-isotropic layers is the highest.The voids content of quasi isotropic is the highest,which is consistent with the theoretical analysis.
文摘The basic scheme of the orientation detection system using L-shape reticle is introduced. The dimension of the patterns on the reticle of the system in practical applications is designed and an analysis of the principle of abstracting the orientation information of the target and the effects and formation method of self-adapting tracking gate is presented. The research result shows that the orientation detection system using L-shape reticle has a good effect on space-filtering, the signals that the orientation detection system sends out are easy to be processed by computer, its self-adapting tracking gate has a strong anti-interference ability, and the whole system＇s searching and tracking performances are quite high.
文摘A single layer triangular patch antenna fed by an L-shaped probe was investigated numerically by using FDTD (Finite Difference Time Domain) method. It achieves >40% impedance bandwidth (VSWR<2) and stable radiation pattern across the passband. The triangular patch antenna with two orientations of L-shaped probe has almost the same characteristics, such as impedance bandwidth and radiation pattern. The bandwidth vs feeding position was also investigated, the broadband characteristic can be observed when the feeding position is only in a small segment along the centerline.
基金the National Nature Science Foundation of China(No.81170507)the Shanghai International Science and Technology Cooperation Foundation Project(No.11140903700)
文摘In order to explore the cell composition and its metabolism,it is important to let computer recognize the cells and get the counts of different cells for a sample.This paper proposes an L-shaped envelop function and the related fuzzy clustering method as a way to identify the megakaryocyte and the red cell from the sliced marrow image.This method is useful when the staining is insufficient and the color cannot be used as the identifying factor.This method uses the experimental histogram data to fit the L-shaped function and then use it as the envelop for the match test.The fuzzy c-means(FCM) performance index is used to test the adjacent area and get the minimum and finally secure the identification.The new method is not limited to megakaryocyte or red cell and can be used for general purposes of cell recognition.Tests show that this envelop function can ensure the recognition rate with different staining batches and can reach satisfied counting under similar illumination condition.
文摘The behavior of L-Shaped RC （reinforced concrete） shear walls was investigated in the Erciyes University Earthquake Investigation Laboratory under the influence of constant axial load together with reversed cyclic lateral load. The objective of this study was to evaluate the effects of cross sectional dimensions on the behavior of L-shaped structural members and to assess their earthquake performance. In order to investigate L-shaped RC structural members, the special experiment setup and four type of 1/2 scaled specimens which have different aspect ratio were constructed. The specimens were loaded in line with the major principal axes direction laterally. Axial load ratio was 0.1 and cross section height to thickness ratios were＇ 3：1, 5：1, 8：1, 10：1. Cross section thickness was 120 mm which corresponds to （360：120）, （600：120）, （960：120）, （1,200：120） wall legs cross sectional dimensions in mm. The specimens height was 1,500 mm, together with upper and lower slabs overall height was 2,000 mm. Concrete compression strength was 30 N/mm2, steel yield stress 420 N/mm2 and vertical reinforcement ratio was 1% for all specimens. According to the test results, the specimen of which the aspect ratio is 3 （360：120） has shown column behavior, the specimen of which the aspect ratio is 5 （600：120） has shown slender wall behavior and last two specimens of which the aspect ratios are 8 （960：120） and 10 （1,200：120） have shown squat wall behavior. When considering the cracking patterns and hysteretic behavior, since the aspect ratio 8, the specimens show flexure-shear interaction behavior and prone to brittle failure.
文摘Two-stage problem of stochastic convex programming with fuzzy probability distribution is studied in this paper. Multicut L-shaped algorithm is proposed to solve the problem based on the fuzzy cutting and the minimax rule. Theorem of the convergence for the algorithm is proved. Finally, a numerical example about two-stage convex recourse problem shows the essential character and the efficiency.
基金supported by the National Natural Science Foundation of China(Grant Nos.11772008,11172009,11372015,11232009,10872010,11290152&10732020)
文摘In this paper, a simplified model of the bistable piezoelectric cantilever beam with magnets is established, and the potential energy of the bistable system is analyzed. We have proposed the bistable L-shaped beam structure, which has the same geometry dimensions of the bistable straight beam in the first time. The comparative study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam plays an important role in exploring excellent piezoelectric generator.The experiment structure includes the base layer and the piezoelectric layer. The harmonic excitation is given to the system.Theoretical analysis results show that the potential energy function of the system has two obvious steady potential wells. In addition, the depth of the upper potential well is different from that of the lower potential well when the gravity potential energy is considered. Experimental results demonstrate that the power generation for the straight beam is better than that of the horizontally placed L-shaped beam when the excitation amplitude is 450 m V. There is the existence that the energy harvesting capacity of the bistable L-shaped beam is better than that of the bistable straight beam when the excitation amplitude is 400 m V.Furthermore, the power generation of the bistable L-shaped beam with the upper potential well is obviously better than that of the bistable L-shaped beam with the lower potential well. In addition, comparing with the straight beam, the dynamic response of the bistable L-shaped beam is more complex when the external excitation frequency is changed. It is also observed that the distance between the magnets has the obvious influence on the dynamic response of the bistable system. It is very effective to select the appropriate distance between the magnets to improve the power generation of the bistable energy harvester under the fixed excitation conditions.
