With the technical development of new warhead designs and improvised explosive device protection,irregular casing filled with explosive has been paid more attention recently. In this paper, we studied the fragmentatio...With the technical development of new warhead designs and improvised explosive device protection,irregular casing filled with explosive has been paid more attention recently. In this paper, we studied the fragmentation of a type of D-shaped casing, which is a common asymmetric casing in the field of warhead design. Based on the radiograph technique, static explosive experiments were conducted with D-shaped casings under four different eccentric initiation ratios to explore their fragmentation. A numerical model was then established to simulate the dynamic response of D-shaped casing filled with explosive. The results of numerical simulation were found to agree well with the experimental data.According to the results of numerical simulation and experimental data, the dynamic responses of Dshaped casing were analyzed. The results of the current work pave way for the innovative design of new warhead and for further studying the dynamic response of asymmetric casing.展开更多
To investigate the failure process and characteristics of D-shaped tunnels under different maximum principal stress directions θ, true-triaxial tests were conducted on cubic sandstone samples with a through D-shaped ...To investigate the failure process and characteristics of D-shaped tunnels under different maximum principal stress directions θ, true-triaxial tests were conducted on cubic sandstone samples with a through D-shaped hole. The test results show that the failure process can be divided into 4 periods:calm, buckling deformation, gradual buckling and exfoliation of rock fragment, and formation of a Vshaped notch. With an increase in θ from 0° to 90°, the size of the rock fragments first decreases and then increases, whereas the fractal dimension of the rock fragments first increases and then decreases. Meanwhile, the failure position at the left side shifts from the sidewall to the corner and finally to the floor, whereas the failure position at the right side moves from the sidewall to the spandrel and finally to the roof, which is consistent with the failure position in underground engineering. In addition, the initial vertical failure stress first decreases and then increases. By comparing the results,the failure severities at different maximum principal stress directions can be ranked from high to low in the following order: 90°>60°>30°>45°>0°.展开更多
A stable Q-switched erbium doped fiber laser emitting at 1558 nm is demonstrated using a cadmium selenide（CdSe） material coated onto a side-polished D-shape fiber as the saturable absorber（SA）. By elevating the in...A stable Q-switched erbium doped fiber laser emitting at 1558 nm is demonstrated using a cadmium selenide（CdSe） material coated onto a side-polished D-shape fiber as the saturable absorber（SA）. By elevating the input pump power from the threshold of 91 mW to the maximum available power of 136 mW, a pulse train with a maximum repetition rate of 57.44 kHz, minimum pulse width of 3.76 us, maximum average output power of7.99 mW, maximum pulse energy of 0.1391 uJ, and maximum peak power of 36.99 mW are obtained. The signalto-noise ratio of the spectrum is measured to be around 75 dB. This CdSe based SA is simple, robust, and reliable,and thus suitable for making a portable pulse laser source.展开更多
Open-loop flow control method was used to affect the development of a turbulent wake behind a D-shaped bluff body. Loud speakers were embedded inside the bluff body to produce two zero-net-mass- flux jets through 2 mm...Open-loop flow control method was used to affect the development of a turbulent wake behind a D-shaped bluff body. Loud speakers were embedded inside the bluff body to produce two zero-net-mass- flux jets through 2 mm-wide span-wise slots located along the upper and lower edges on the rear wall. The drag forces for different actuation amplitudes （Cμ, the ratio between the momentum of the actuating jets and the moment deficit caused by the bluff body） and frequencies （StA） were examined. The effects of the phase difference in the two jets （0 and π） were also studied. It was found that when Cμ was 0.1%, a drag reduction up to 5% was achieved when the velocities of the two jets varied in phase at a frequency of 5tA = 0.16. When the velocities of the two jets varied π out of phase, significant drag increase was observed.展开更多
Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock bla...Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics disturbances.The biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape hole.High-speed camera and digital image correlation(DIC)were used to capture the failure process and strain field of specimen.The test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact load.Under this circumstance,the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load,indicating dynamic tensile failure.The high static prestress provides the initial stress field,while the impact load disrupts the stress equilibrium,result in the stress or strain concentration in the sidewall of the D-shape hole,inducing rockburst.Moreover,the rockburst process can be divided into(1)calm stage,(2)crack initiation,propagation,and coalesce stage,(3)spalling stage and(4)rock fragments ejection stage.Impact load triggers rockburst occurrence,while vertical stress further determines the rockburst characteristics.The influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress,thus inducing more severe rockburst.展开更多
A high sensitivity D-shaped hole double-cladding fiber temperature sensor based on surface plasmon resonance(SPR)is designed and investigated by a full-vector finite element method.Within the D-shaped hole doublecladd...A high sensitivity D-shaped hole double-cladding fiber temperature sensor based on surface plasmon resonance(SPR)is designed and investigated by a full-vector finite element method.Within the D-shaped hole doublecladding fiber,the hollow D-section is coated with gold film and then injected in a high thermo-optic coefficient liquid to realize the high temperature sensitivity for the fiber SPR temperature sensor.The numerical simulation results show that the peaking loss of the D-shaped hole double-cladding fiber SPR is hugely influenced by the distance between the D-shaped hole and fiber core and by the thickness of the gold film,but the temperature sensitivity is almost insensitive to the above parameters.When the thermo-optic coefficient is -2.8×10^(-4)∕℃,the thickness of the gold film is 47 nm,and the distance between the D-shaped hole and fiber core is 5μm,the temperature sensitivity of the D-shaped hole fiber SPR sensor can reach to -3.635 nm∕℃.展开更多
A new D-shaped tellurite photonic crystal fiber sensor based on the four-wave mixing(FWM)effect with the surface plasmon resonance(SPR)effect is designed and optimized.The substrate of the D-shaped photonic crystal fi...A new D-shaped tellurite photonic crystal fiber sensor based on the four-wave mixing(FWM)effect with the surface plasmon resonance(SPR)effect is designed and optimized.The substrate of the D-shaped photonic crystal fiber(D-PCF)is tellurite glass,and the polished surface is plated with the gold film and hydrogen gas-sensitive film.An air hole of the inner cladding,which is plated with the gold film and methane gas-sensitive film,is selected as the second sensing channel to simultaneously measure the concentration of hydrogen and methane.Based on the four-wave mixing,the wavelength shifts of the Stokes and anti-Stokes spectra resulting from the variation of the gas concentration can be used to accurately detect the concentrations of methane and hydrogen.Meanwhile,it is found that the SPR effect can increase the wavelength shifts,which means the sensitivity of methane and hydrogen augment.After parameter optimization,the maximum sensitivities of methane and hydrogen are 4.03 nm/%and-14.19 nm/%,respectively.Both the linearities are up to 99.9%.The resolution of methane is 1.25×10^(-2)%and hydrogen is 7.14×10^(-3)%.Moreover,the fiber length of this sensor is only 20mm,which is conducive to the construction of a compact or ultra-compact embedded FWM fiber sensor.展开更多
Iris recognition technology recognizes a human based on his/her iris pattern. However, the accuracy of the iris recognition technology depends on accurate iris localization. Localizing a pupil region in the presence o...Iris recognition technology recognizes a human based on his/her iris pattern. However, the accuracy of the iris recognition technology depends on accurate iris localization. Localizing a pupil region in the presence of other low-intensity regions, such as hairs, eyebrows, and eyelashes, is a challenging task. This study proposes an iris localization technique that includes a localizing pupillary boundary in a sub-image by using an integral projection function and two-dimensional shape properties （e.g., area, geometry, and circularity）. The limbic boundary is localized using gradients and an error distance transform, and the boundary is regularized with active contours. Experimental results obtained from public databases show the superiority of the Drooosed techniaue over contemporary methods.展开更多
基金supported by the National Natural Science Foundation of China [grant number 11772059]the National KeyResearch and Development Program of China [grant number 2017yfc0822300]+1 种基金the 111 Project[grant number G20012017001]the Foundation of State Key Laboratory of Explosion Science and Technology of China[grant number KFJJ13-1Z]
文摘With the technical development of new warhead designs and improvised explosive device protection,irregular casing filled with explosive has been paid more attention recently. In this paper, we studied the fragmentation of a type of D-shaped casing, which is a common asymmetric casing in the field of warhead design. Based on the radiograph technique, static explosive experiments were conducted with D-shaped casings under four different eccentric initiation ratios to explore their fragmentation. A numerical model was then established to simulate the dynamic response of D-shaped casing filled with explosive. The results of numerical simulation were found to agree well with the experimental data.According to the results of numerical simulation and experimental data, the dynamic responses of Dshaped casing were analyzed. The results of the current work pave way for the innovative design of new warhead and for further studying the dynamic response of asymmetric casing.
基金This work was supported by the National Natural Science Foun-dation of China(Nos.52174098,41630642,and 51904335).
文摘To investigate the failure process and characteristics of D-shaped tunnels under different maximum principal stress directions θ, true-triaxial tests were conducted on cubic sandstone samples with a through D-shaped hole. The test results show that the failure process can be divided into 4 periods:calm, buckling deformation, gradual buckling and exfoliation of rock fragment, and formation of a Vshaped notch. With an increase in θ from 0° to 90°, the size of the rock fragments first decreases and then increases, whereas the fractal dimension of the rock fragments first increases and then decreases. Meanwhile, the failure position at the left side shifts from the sidewall to the corner and finally to the floor, whereas the failure position at the right side moves from the sidewall to the spandrel and finally to the roof, which is consistent with the failure position in underground engineering. In addition, the initial vertical failure stress first decreases and then increases. By comparing the results,the failure severities at different maximum principal stress directions can be ranked from high to low in the following order: 90°>60°>30°>45°>0°.
文摘A stable Q-switched erbium doped fiber laser emitting at 1558 nm is demonstrated using a cadmium selenide（CdSe） material coated onto a side-polished D-shape fiber as the saturable absorber（SA）. By elevating the input pump power from the threshold of 91 mW to the maximum available power of 136 mW, a pulse train with a maximum repetition rate of 57.44 kHz, minimum pulse width of 3.76 us, maximum average output power of7.99 mW, maximum pulse energy of 0.1391 uJ, and maximum peak power of 36.99 mW are obtained. The signalto-noise ratio of the spectrum is measured to be around 75 dB. This CdSe based SA is simple, robust, and reliable,and thus suitable for making a portable pulse laser source.
基金supported by the National Basic Research Program(2014CB744100)State Key Laboratory of Aerodynamics(SKLA20130102)Dalian University of Technology(DUT14LK07)
文摘Open-loop flow control method was used to affect the development of a turbulent wake behind a D-shaped bluff body. Loud speakers were embedded inside the bluff body to produce two zero-net-mass- flux jets through 2 mm-wide span-wise slots located along the upper and lower edges on the rear wall. The drag forces for different actuation amplitudes （Cμ, the ratio between the momentum of the actuating jets and the moment deficit caused by the bluff body） and frequencies （StA） were examined. The effects of the phase difference in the two jets （0 and π） were also studied. It was found that when Cμ was 0.1%, a drag reduction up to 5% was achieved when the velocities of the two jets varied in phase at a frequency of 5tA = 0.16. When the velocities of the two jets varied π out of phase, significant drag increase was observed.
基金supported by the National Natural Science Foundation of China(Grant No.42077244)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020005)。
文摘Rockburst has always been a challenge for the safe construction of deep underground engineering.This study investigated the rockburst characteristics in highly-stressed D-shape tunnels under impact loads from rock blasting and other mining-related dynamics disturbances.The biaxial Hopkinson pressure bar was utilized to apply varying biaxial prestress and the same impact loads to cube specimens with D-shape hole.High-speed camera and digital image correlation(DIC)were used to capture the failure process and strain field of specimen.The test results demonstrate that the D-shape hole specimen experience rockburst under coupled static stress and impact load.Under this circumstance,the rockburst mechanism of the D-shaped hole specimens involves spalling in sidewall induced by impact load,indicating dynamic tensile failure.The high static prestress provides the initial stress field,while the impact load disrupts the stress equilibrium,result in the stress or strain concentration in the sidewall of the D-shape hole,inducing rockburst.Moreover,the rockburst process can be divided into(1)calm stage,(2)crack initiation,propagation,and coalesce stage,(3)spalling stage and(4)rock fragments ejection stage.Impact load triggers rockburst occurrence,while vertical stress further determines the rockburst characteristics.The influence range and magnitude of strain concentration zone and displacement deformation of the tunnel surrounding rock increases with increasing vertical stress,thus inducing more severe rockburst.
基金National Natural Science Foundation of China(NSFC)(61525501)
文摘A high sensitivity D-shaped hole double-cladding fiber temperature sensor based on surface plasmon resonance(SPR)is designed and investigated by a full-vector finite element method.Within the D-shaped hole doublecladding fiber,the hollow D-section is coated with gold film and then injected in a high thermo-optic coefficient liquid to realize the high temperature sensitivity for the fiber SPR temperature sensor.The numerical simulation results show that the peaking loss of the D-shaped hole double-cladding fiber SPR is hugely influenced by the distance between the D-shaped hole and fiber core and by the thickness of the gold film,but the temperature sensitivity is almost insensitive to the above parameters.When the thermo-optic coefficient is -2.8×10^(-4)∕℃,the thickness of the gold film is 47 nm,and the distance between the D-shaped hole and fiber core is 5μm,the temperature sensitivity of the D-shaped hole fiber SPR sensor can reach to -3.635 nm∕℃.
基金funded by the National Natural Science Foundation of China(Grant No.51874301)Primary Research&Development Plan of Xuzhou City(Grant No.KC20162).
文摘A new D-shaped tellurite photonic crystal fiber sensor based on the four-wave mixing(FWM)effect with the surface plasmon resonance(SPR)effect is designed and optimized.The substrate of the D-shaped photonic crystal fiber(D-PCF)is tellurite glass,and the polished surface is plated with the gold film and hydrogen gas-sensitive film.An air hole of the inner cladding,which is plated with the gold film and methane gas-sensitive film,is selected as the second sensing channel to simultaneously measure the concentration of hydrogen and methane.Based on the four-wave mixing,the wavelength shifts of the Stokes and anti-Stokes spectra resulting from the variation of the gas concentration can be used to accurately detect the concentrations of methane and hydrogen.Meanwhile,it is found that the SPR effect can increase the wavelength shifts,which means the sensitivity of methane and hydrogen augment.After parameter optimization,the maximum sensitivities of methane and hydrogen are 4.03 nm/%and-14.19 nm/%,respectively.Both the linearities are up to 99.9%.The resolution of methane is 1.25×10^(-2)%and hydrogen is 7.14×10^(-3)%.Moreover,the fiber length of this sensor is only 20mm,which is conducive to the construction of a compact or ultra-compact embedded FWM fiber sensor.
基金supported by in-house PhD Program of COMSATS Institute of Information Technology,Islamabad Campus Pakistan
文摘Iris recognition technology recognizes a human based on his/her iris pattern. However, the accuracy of the iris recognition technology depends on accurate iris localization. Localizing a pupil region in the presence of other low-intensity regions, such as hairs, eyebrows, and eyelashes, is a challenging task. This study proposes an iris localization technique that includes a localizing pupillary boundary in a sub-image by using an integral projection function and two-dimensional shape properties （e.g., area, geometry, and circularity）. The limbic boundary is localized using gradients and an error distance transform, and the boundary is regularized with active contours. Experimental results obtained from public databases show the superiority of the Drooosed techniaue over contemporary methods.
基金partial financial support from the National Natural Science Foundation of China (No. 52101231)the Science Fund of Shandong Laboratory of Yantai Advanced Materials and Green Manufacturing,China (No. AMGM2021F09)the Natural Science Foundation of Shandong Province,China (No. ZR2021QE044)。
