Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conv...Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conventional rocks both in terms of rock structure and mechanical properties. In this study, mesoscale uniaxial compression experiments with five different loading directions were conducted on two kinds of reef limestones from the Maldives Islands and the South China Sea, respectively. The real-time high-resolution videos and images of failure processes were recorded simultaneously to investigate the fracture evolution and fracture surface roughness of reef limestones. It demonstrated that the reef limestones belonged to extremely soft to soft rocks, and their uniaxial compressive strength (UCS) values fluctuated with high discreteness. The mesoscale mechanical properties of reef limestones were highly anisotropic and mainly controlled by pore structure. The occurrence of dissolution pores in reef limestone tended to intensify mechanical anisotropy. With the integration of the fracture initiation and propagation features of reef limestones, it is supposed that the intrinsic mechanism of anisotropy was probably attributed to the differences in coral growth direction and dissolution. Furthermore, the quantified fracture surface roughness was revealed to have a good consistency with density and UCS for the reef limestones from the South China Sea. The findings are helpful for providing theoretical and experimental references for engineering construction in coral reef areas.展开更多
A male-specific SCAR DNA marker was developed using a RAPD DNA marker specific for male plants of Salacca zalacca var. zalacca （salak palm）. The marker is 1579 bp long and has a GC content of 38.5 %. Its sequence co...A male-specific SCAR DNA marker was developed using a RAPD DNA marker specific for male plants of Salacca zalacca var. zalacca （salak palm）. The marker is 1579 bp long and has a GC content of 38.5 %. Its sequence contains 1 or 2 open reading frames, indicating the marker is probably a coding region. No highly similar sequences were found in a search of the GenBank database. Sexes were identified using the SCAR DNA marker for three kinds of seedlings grouped by the number of seeds per fruit （1, 2 or 3）. The sex ratio of female to male did not differ significantly from 1：1 for the three kinds of seedlings, implying that the number of seeds per fruit is not a reliable index to identify the sex of a seedling.展开更多
To improve the precisions of pose error analysis for 6-dof parallel kinematic mechanism( PKM)during assembly quality control,a Sobol sequence based on Quasi Monte Carlo( QMC) method is introduced and implemented in po...To improve the precisions of pose error analysis for 6-dof parallel kinematic mechanism( PKM)during assembly quality control,a Sobol sequence based on Quasi Monte Carlo( QMC) method is introduced and implemented in pose accuracy analysis for the PKM in this paper. The Sobol sequence based on Quasi Monte Carlo with the regularity and uniformity of samples in high dimensions,can prevail traditional Monte Carlo method with up to 98. 59% and 98. 25% enhancement for computational precision of pose error statistics.Then a PKM tolerance design system integrating this method is developed and with it pose error distributions of the PKM within a prescribed workspace are finally obtained and analyzed.展开更多
In this paper, we designed a thermo-optic variable optical attenuator (VOA) based on quartz substrate, which consists of a Mach-Zehnder interferometer (MZI) and a thin film heater above the phase-modulation arm. The t...In this paper, we designed a thermo-optic variable optical attenuator (VOA) based on quartz substrate, which consists of a Mach-Zehnder interferometer (MZI) and a thin film heater above the phase-modulation arm. The transmission properties of the waveguide and attenuation characteristics of the device have been simulated by beam propagation method (BPM), and the simulated results illustrated that the designed VOA had good performance.展开更多
To promote the pose accuracy performance of a spatial parallel kinematic Mechanism( PKM) in service,a workshop oriented tolerance synthesis method based on design of experiment( DOE) is proposed,which involves two con...To promote the pose accuracy performance of a spatial parallel kinematic Mechanism( PKM) in service,a workshop oriented tolerance synthesis method based on design of experiment( DOE) is proposed,which involves two consecutive stages. In the first stage of DOE,the tolerance factor sensitivities are obtained according to initial tolerance settings with the consideration of the current manufacturing capacity,and the second stage of DOE makes use of them to produce multiple tolerance allocations which can adapt to current manufacturing capacity. A tolerance synthesis procedure is developed and integrated in tolerance design system for PKM. Comparing the results with peer method,the validity and practicability of this method is verified.展开更多
Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed wave...Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating（AWG） with 2% refractive index difference and a four-channel top-illuminated positive-intrinsicnegative photodetector（PD） array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 Gb E data center interconnections.展开更多
A high-performance monolithic integrated wavelength division multiplexing silicon(Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed wa...A high-performance monolithic integrated wavelength division multiplexing silicon(Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed waveguide grating, and each channel is integrated with a high-speed waveguide Ge-on-Si photodetector. The central wavelength, optical insertion loss, and cross talk of the array waveguide grating are 1550.6 nm, 5–8 dB, and-12 –-15 dB, respectively. The photodetectors show low dark current density of 16.9 mA∕cm^2 at-1 V and a high responsivity of 0.82 A/W at 1550 nm. High bandwidths of 23 and 29 GHz are achieved at 0 and-1 V, respectively. Each channel can operate at 50 Gbps with low input optical power even under zero bias,which realizes an aggregate data rate of 1.25 Tbps.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41977248 and 42207219)the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(CAS)(Grant No.IGGCAS-201903).
文摘Reef limestone is a biogenic sedimentary rock widely distributed in coral reef areas, acting as an important foundation for coast construction. Due to its special biogenic origin, reef limestone is different from conventional rocks both in terms of rock structure and mechanical properties. In this study, mesoscale uniaxial compression experiments with five different loading directions were conducted on two kinds of reef limestones from the Maldives Islands and the South China Sea, respectively. The real-time high-resolution videos and images of failure processes were recorded simultaneously to investigate the fracture evolution and fracture surface roughness of reef limestones. It demonstrated that the reef limestones belonged to extremely soft to soft rocks, and their uniaxial compressive strength (UCS) values fluctuated with high discreteness. The mesoscale mechanical properties of reef limestones were highly anisotropic and mainly controlled by pore structure. The occurrence of dissolution pores in reef limestone tended to intensify mechanical anisotropy. With the integration of the fracture initiation and propagation features of reef limestones, it is supposed that the intrinsic mechanism of anisotropy was probably attributed to the differences in coral growth direction and dissolution. Furthermore, the quantified fracture surface roughness was revealed to have a good consistency with density and UCS for the reef limestones from the South China Sea. The findings are helpful for providing theoretical and experimental references for engineering construction in coral reef areas.
基金supported by the State Administration of Forestry of China(Grant Numbers 201204307-03,2007-4-11,and 2012-LY-052)the Research Institute of Tropical Forestry,Chinese Academy of Forestry(Grant Number RITFKYYW2010-02)
文摘A male-specific SCAR DNA marker was developed using a RAPD DNA marker specific for male plants of Salacca zalacca var. zalacca （salak palm）. The marker is 1579 bp long and has a GC content of 38.5 %. Its sequence contains 1 or 2 open reading frames, indicating the marker is probably a coding region. No highly similar sequences were found in a search of the GenBank database. Sexes were identified using the SCAR DNA marker for three kinds of seedlings grouped by the number of seeds per fruit （1, 2 or 3）. The sex ratio of female to male did not differ significantly from 1：1 for the three kinds of seedlings, implying that the number of seeds per fruit is not a reliable index to identify the sex of a seedling.
基金Sponsored by the National Defense Basic Scientific Research Program(Grant No.A0320110019)the Shanghai Science and Technology Innovation Action Plan(Grant No.11DZ1120800)
文摘To improve the precisions of pose error analysis for 6-dof parallel kinematic mechanism( PKM)during assembly quality control,a Sobol sequence based on Quasi Monte Carlo( QMC) method is introduced and implemented in pose accuracy analysis for the PKM in this paper. The Sobol sequence based on Quasi Monte Carlo with the regularity and uniformity of samples in high dimensions,can prevail traditional Monte Carlo method with up to 98. 59% and 98. 25% enhancement for computational precision of pose error statistics.Then a PKM tolerance design system integrating this method is developed and with it pose error distributions of the PKM within a prescribed workspace are finally obtained and analyzed.
文摘In this paper, we designed a thermo-optic variable optical attenuator (VOA) based on quartz substrate, which consists of a Mach-Zehnder interferometer (MZI) and a thin film heater above the phase-modulation arm. The transmission properties of the waveguide and attenuation characteristics of the device have been simulated by beam propagation method (BPM), and the simulated results illustrated that the designed VOA had good performance.
基金Sponsored by the National Defense Basic Scientific Research Program(Grant No.A0320110019)the Shanghai Science and Technology Innovation Action Plan(Grant No.11DZ1120800)
文摘To promote the pose accuracy performance of a spatial parallel kinematic Mechanism( PKM) in service,a workshop oriented tolerance synthesis method based on design of experiment( DOE) is proposed,which involves two consecutive stages. In the first stage of DOE,the tolerance factor sensitivities are obtained according to initial tolerance settings with the consideration of the current manufacturing capacity,and the second stage of DOE makes use of them to produce multiple tolerance allocations which can adapt to current manufacturing capacity. A tolerance synthesis procedure is developed and integrated in tolerance design system for PKM. Comparing the results with peer method,the validity and practicability of this method is verified.
基金supported by the National High Technology Research and Development Program of China(No.2015AA016902)the National Natural Science Foundation of China(Nos.61435013 and 61405188)K.C.Wong Education Foundation
文摘Both the 4 × 20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies（ROSAs） were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating（AWG） with 2% refractive index difference and a four-channel top-illuminated positive-intrinsicnegative photodetector（PD） array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 Gb E data center interconnections.
基金National Key Research and Development Program of China(2017YFA0206404)National Natural Science Foundation of China(NSFC)(61435013,61534005,61604146)
文摘A high-performance monolithic integrated wavelength division multiplexing silicon(Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed waveguide grating, and each channel is integrated with a high-speed waveguide Ge-on-Si photodetector. The central wavelength, optical insertion loss, and cross talk of the array waveguide grating are 1550.6 nm, 5–8 dB, and-12 –-15 dB, respectively. The photodetectors show low dark current density of 16.9 mA∕cm^2 at-1 V and a high responsivity of 0.82 A/W at 1550 nm. High bandwidths of 23 and 29 GHz are achieved at 0 and-1 V, respectively. Each channel can operate at 50 Gbps with low input optical power even under zero bias,which realizes an aggregate data rate of 1.25 Tbps.
