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 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
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
In a D-shaped twin-core fiber(DTCF),the central core is insensitive to the variation of the external environment,while the other core is highly sensitive.As an electro-optic polymer coated on a DTCF,the coupling betwe...In a D-shaped twin-core fiber(DTCF),the central core is insensitive to the variation of the external environment,while the other core is highly sensitive.As an electro-optic polymer coated on a DTCF,the coupling between the two cores varies with voltages applied to the polymer.Based on this,a superior all-fiber modulator is proposed that bears little coupling loss,prohibits mode mismatch,and provides a more stable working circumstance.A half-wave driving voltage(V_π)of 1.26 V is achieved.Moreover,a high modulation depth of 40 dB can be realized for a voltage of 2.7 V at a 1550 nm wavelength.展开更多
Design of new metamaterial (MTM) traveling-wave antenna with “d-formed” left-handed structure is proposed. The proposed MTM structure is designed at a height of 0.8 mm from the ground plane with almost 2 GHz bandwid...Design of new metamaterial (MTM) traveling-wave antenna with “d-formed” left-handed structure is proposed. The proposed MTM structure is designed at a height of 0.8 mm from the ground plane with almost 2 GHz bandwidth. The most interesting feature of the design is the ability of enhancing the gain and total efficiency of the antenna without negative effects of the other important parameters like bandwidth. By using the “d-shaped” MTM structure and printed planar technique, the bandwidth of the MTM traveling-wave antenna is significantly increased at a resonant frequency of 6 GHz and also a foot print area reduction of the antenna structure is provided. Antenna size is 7.2 × 5 × 0.8 mm3. The proposed antenna is suitable for RF portable devices operating at 6 GHz.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°.
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financially supported by the National Natural Science Foundation of China under Grant No.61525501
文摘In a D-shaped twin-core fiber(DTCF),the central core is insensitive to the variation of the external environment,while the other core is highly sensitive.As an electro-optic polymer coated on a DTCF,the coupling between the two cores varies with voltages applied to the polymer.Based on this,a superior all-fiber modulator is proposed that bears little coupling loss,prohibits mode mismatch,and provides a more stable working circumstance.A half-wave driving voltage(V_π)of 1.26 V is achieved.Moreover,a high modulation depth of 40 dB can be realized for a voltage of 2.7 V at a 1550 nm wavelength.
文摘Design of new metamaterial (MTM) traveling-wave antenna with “d-formed” left-handed structure is proposed. The proposed MTM structure is designed at a height of 0.8 mm from the ground plane with almost 2 GHz bandwidth. The most interesting feature of the design is the ability of enhancing the gain and total efficiency of the antenna without negative effects of the other important parameters like bandwidth. By using the “d-shaped” MTM structure and printed planar technique, the bandwidth of the MTM traveling-wave antenna is significantly increased at a resonant frequency of 6 GHz and also a foot print area reduction of the antenna structure is provided. Antenna size is 7.2 × 5 × 0.8 mm3. The proposed antenna is suitable for RF portable devices operating at 6 GHz.
