The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction ...The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse actuator.The impact point easily deviates from the target,and thus the correction result cannot be readily evaluated.However,the cost of shooting tests is considerably high to conduct many tests for data collection.To address this issue,this study proposes an aiming method for shooting tests based on small sample size.The proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion center.The experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.展开更多
The latent heat storage(LHS)technique is of crucial importance in chemical energy engineering.Inspired by multi-bifurcated fern leaves,a mimic fern-fractal fin is designed to improve the thermal energy charging effici...The latent heat storage(LHS)technique is of crucial importance in chemical energy engineering.Inspired by multi-bifurcated fern leaves,a mimic fern-fractal fin is designed to improve the thermal energy charging efficiency.This paper develops a transient melting model of a rectangular LHS unit using fern-fractal fins,and their melting behaviors are compared with the conventional fins.Besides,a parametric optimization of fernfractal fins is conducted for maximizing the thermal efficiency based on the response surface method(RSM).The results indicate that the temperature uniformity is more superior and the melting duration is shorter for the fern-fractal LHS unit when compared with the conventional one.Interestingly,the fern-fractal LHS device presents a slower heat storage rate during the initial conduction-dominated and early convection-dominated melting stages,while a prominent melting enhancement is achieved during the later melting stage.The shortest melting time is obtained based on the RSM technique when a fern-fractal fin with length ratio α=0.94 and branch angle θ=54.7°is utilized.Compared with a conventional fin,the averaged heat storage rate increases by 88.3%,and the total melting time is declined by 40.3%for an optimized fern-fractal fin.展开更多
To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy...To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy grooves)were applied to the rake surface of PCBN tools by an optical fber laser marking machine.Through a combination of three dimensional cutting simulations and experiments,the influences of micro-texture on chip-tool contact area,cutting force,chip morphology,shear angle,and surface roughness during the cuting process were analyzed.The results indicated that the chip--tool contact area and cutting force of both non-textured and micro textured tools increased with increasing cutting speed,while the shear angle decreased with increasing cutting speed.The chip-tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non textured tool The chip-tool contact area and cutting force obtained by the wavy-groove micro textured tool were the smallest.The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool,and the chip morphology was more stable.The transverse-groove micro-textured tool had a better chip breaking efect.The chip rnadius generated by the lliptical groove micro textured tool was 0.96 cm,while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm.The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%-56.7%.Under the same cutting conditions,the five types of micro-textured tools gave a smaller chip--tool contact area,cutting force,chip radius,and surface roughness and a larger shear angle than the non-textured tool.In addition,the elliptical groove and wavy-groove micro-textured tools had better cuting performance.展开更多
The output displacement of the traditional symmetrical microgripper is large,but its micro-components or parts are easily damaged due to the uneven force exerted on the left and right jaws of the gripper.The output fo...The output displacement of the traditional symmetrical microgripper is large,but its micro-components or parts are easily damaged due to the uneven force exerted on the left and right jaws of the gripper.The output force of the traditional asymmetric microgripper is stable.However,its output displacement is small,typically half the output displacement of the symmetric microgripper.To solve these problems,in this study,we designed a large-displacement asymmetric microgripper.First,we calculated the relationship between the theoretical input and output variables based on their geometric relationship.Then,we analyzed the performance of the microgripper using finite element software.Lastly,we used a piezoelectric actuator as the input driver of the microgripper.The errors associated with the theoretical and simulated output displacements were 7.05%and 9.24%,respectively.At 150 V of driving voltage,the maximum output displacement was 224μm,and the actual magnificationwas 11.2 times.Microparts can be gripped in parallel and stably,which confirms the validity of the design.展开更多
Aiming to address the problem of the low amplification ratio of traditional microgrippers,a two-stage microgripper based on the principle of combined amplification was designed with a high amplification ratio and larg...Aiming to address the problem of the low amplification ratio of traditional microgrippers,a two-stage microgripper based on the principle of combined amplification was designed with a high amplification ratio and large displacement,using a simple and compact structure.The relationship between theoretical input variables and output variables were first calculated by a projection theorem.Secondly,the performance of the microgripper was analyzed by finite element analysis(FEA).Finally,the accuracy of the theoretical calculation and FEA was verified experimentally.The results show that the microgripper has high magnification and can be gripped in parallel,with self-adaptability for many irregular shaped micro objects.The actual magnification was 23.2×,which is greater than similar products.展开更多
我们进行计算液体动力学模拟用 volume-of-fluid 方法在 microfluidic T 连接调查水泡决裂的行为代表接口。水泡形态学的进化和流动地里的速度和压力的分布被分析，并且在水泡形态学上的主要隧道和分支之间的宽度比率的效果被评估。结...我们进行计算液体动力学模拟用 volume-of-fluid 方法在 microfluidic T 连接调查水泡决裂的行为代表接口。水泡形态学的进化和流动地里的速度和压力的分布被分析，并且在水泡形态学上的主要隧道和分支之间的宽度比率的效果被评估。结果显示那，隧道决裂，妨碍的决裂，联合决裂和非决裂在不同状况下面通过 T 连接在水泡流动期间被观察。整个水泡决裂进程经历扩展，压榨并且拧离开阶段，当非决裂进程经历扩展，推上演时。当在水泡内的速度具有为妨碍的决裂的寓言的分布时，我们发现在 squeeze 阶段，本地旋涡流动为隧道决裂在水泡的前面边形成。不管非决裂政体，有突然的压力落下，在 squeeze 发生在水泡的煤气液体的接口舞台，和在前面接口的压力落下在消沉区域比那远大。通过 T 连接的水泡决裂政体的转变随主要隧道的宽度比率的增加发生到分支，它顺序经历非决裂政体，隧道决裂政体和妨碍的决裂政体。流动政体图与幂定律关联被阴谋区分水泡 / 微滴决裂和非决裂政体，它也通过 T 连接描绘水泡和微滴决裂之间的差别。展开更多
基金the National Natural Science Foundation of China(Grant No.61973033)Preliminary Research of Equipment(Grant No.9090102010305)for funding the experiments。
文摘The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse actuator.The impact point easily deviates from the target,and thus the correction result cannot be readily evaluated.However,the cost of shooting tests is considerably high to conduct many tests for data collection.To address this issue,this study proposes an aiming method for shooting tests based on small sample size.The proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion center.The experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.
基金supported by the National Key R&D Program of China(2019YFB1504301)National Natural Science Foundation of China(51725602,51906039)Natural Science Foundation of Jiangsu Province(BK20180405)。
文摘The latent heat storage(LHS)technique is of crucial importance in chemical energy engineering.Inspired by multi-bifurcated fern leaves,a mimic fern-fractal fin is designed to improve the thermal energy charging efficiency.This paper develops a transient melting model of a rectangular LHS unit using fern-fractal fins,and their melting behaviors are compared with the conventional fins.Besides,a parametric optimization of fernfractal fins is conducted for maximizing the thermal efficiency based on the response surface method(RSM).The results indicate that the temperature uniformity is more superior and the melting duration is shorter for the fern-fractal LHS unit when compared with the conventional one.Interestingly,the fern-fractal LHS device presents a slower heat storage rate during the initial conduction-dominated and early convection-dominated melting stages,while a prominent melting enhancement is achieved during the later melting stage.The shortest melting time is obtained based on the RSM technique when a fern-fractal fin with length ratio α=0.94 and branch angle θ=54.7°is utilized.Compared with a conventional fin,the averaged heat storage rate increases by 88.3%,and the total melting time is declined by 40.3%for an optimized fern-fractal fin.
基金the Basic Scientific Research Program of the Educational Commission of Liaoning Province,China(Grant No.L2017LQN024).
文摘To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy grooves)were applied to the rake surface of PCBN tools by an optical fber laser marking machine.Through a combination of three dimensional cutting simulations and experiments,the influences of micro-texture on chip-tool contact area,cutting force,chip morphology,shear angle,and surface roughness during the cuting process were analyzed.The results indicated that the chip--tool contact area and cutting force of both non-textured and micro textured tools increased with increasing cutting speed,while the shear angle decreased with increasing cutting speed.The chip-tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non textured tool The chip-tool contact area and cutting force obtained by the wavy-groove micro textured tool were the smallest.The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool,and the chip morphology was more stable.The transverse-groove micro-textured tool had a better chip breaking efect.The chip rnadius generated by the lliptical groove micro textured tool was 0.96 cm,while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm.The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%-56.7%.Under the same cutting conditions,the five types of micro-textured tools gave a smaller chip--tool contact area,cutting force,chip radius,and surface roughness and a larger shear angle than the non-textured tool.In addition,the elliptical groove and wavy-groove micro-textured tools had better cuting performance.
基金Liaoning Provincial Education Department (L2017LQN024)
文摘The output displacement of the traditional symmetrical microgripper is large,but its micro-components or parts are easily damaged due to the uneven force exerted on the left and right jaws of the gripper.The output force of the traditional asymmetric microgripper is stable.However,its output displacement is small,typically half the output displacement of the symmetric microgripper.To solve these problems,in this study,we designed a large-displacement asymmetric microgripper.First,we calculated the relationship between the theoretical input and output variables based on their geometric relationship.Then,we analyzed the performance of the microgripper using finite element software.Lastly,we used a piezoelectric actuator as the input driver of the microgripper.The errors associated with the theoretical and simulated output displacements were 7.05%and 9.24%,respectively.At 150 V of driving voltage,the maximum output displacement was 224μm,and the actual magnificationwas 11.2 times.Microparts can be gripped in parallel and stably,which confirms the validity of the design.
基金supported by Department of Education of Liaoning Province Project(L2017LQN024)
文摘Aiming to address the problem of the low amplification ratio of traditional microgrippers,a two-stage microgripper based on the principle of combined amplification was designed with a high amplification ratio and large displacement,using a simple and compact structure.The relationship between theoretical input variables and output variables were first calculated by a projection theorem.Secondly,the performance of the microgripper was analyzed by finite element analysis(FEA).Finally,the accuracy of the theoretical calculation and FEA was verified experimentally.The results show that the microgripper has high magnification and can be gripped in parallel,with self-adaptability for many irregular shaped micro objects.The actual magnification was 23.2×,which is greater than similar products.
文摘我们进行计算液体动力学模拟用 volume-of-fluid 方法在 microfluidic T 连接调查水泡决裂的行为代表接口。水泡形态学的进化和流动地里的速度和压力的分布被分析，并且在水泡形态学上的主要隧道和分支之间的宽度比率的效果被评估。结果显示那，隧道决裂，妨碍的决裂，联合决裂和非决裂在不同状况下面通过 T 连接在水泡流动期间被观察。整个水泡决裂进程经历扩展，压榨并且拧离开阶段，当非决裂进程经历扩展，推上演时。当在水泡内的速度具有为妨碍的决裂的寓言的分布时，我们发现在 squeeze 阶段，本地旋涡流动为隧道决裂在水泡的前面边形成。不管非决裂政体，有突然的压力落下，在 squeeze 发生在水泡的煤气液体的接口舞台，和在前面接口的压力落下在消沉区域比那远大。通过 T 连接的水泡决裂政体的转变随主要隧道的宽度比率的增加发生到分支，它顺序经历非决裂政体，隧道决裂政体和妨碍的决裂政体。流动政体图与幂定律关联被阴谋区分水泡 / 微滴决裂和非决裂政体，它也通过 T 连接描绘水泡和微滴决裂之间的差别。
