Volume 13,Issue 4,2017 Table of Contents
LI Kai-li
,
ZHANG Jia-shun
,
AN Jun-ming
,
LI Jian-guang
,
WANG Liang-liang
,
WANG Yue
,
WU Yuan-da
,
YIN Xiao-jie
,
HU Xiong-wei
2017, 13(4):241-244.
DOI: 10.1007/s11801-017-7076-8
Abstract:
A 25-channel 200 GHz arrayed waveguide grating (AWG) based on Si nanowire waveguides is designed, simulated and fabricated. Transfer function method is used in the simulation and error analysis of AWG with width fluctuations. The 25-channel 200 GHz AWG exhibits central channel insertion loss of 6.7 dB, crosstalk of −13 dB, and central wavelength of 1 560.55 nm. The error analysis can explain the experimental results of 25-channel 200 GHz AWG well. By using deep ultraviolet lithography (DUV) and inductively coupled plasma etching (ICP) technologies, the devices are fabricated on silicon-on-insulator (SOI) substrate. This work has been supported by the National Key Research and Development Program of China (No.2016YFB0402504), and the National Natural Science Foundation of China (Nos.61435013 and 61405188). E-mail:zhangjiashun@semi.ac.cn
A 25-channel 200 GHz arrayed waveguide grating (AWG) based on Si nanowire waveguides is designed, simulated and fabricated. Transfer function method is used in the simulation and error analysis of AWG with width fluctuations. The 25-channel 200 GHz AWG exhibits central channel insertion loss of 6.7 dB, crosstalk of −13 dB, and central wavelength of 1 560.55 nm. The error analysis can explain the experimental results of 25-channel 200 GHz AWG well. By using deep ultraviolet lithography (DUV) and inductively coupled plasma etching (ICP) technologies, the devices are fabricated on silicon-on-insulator (SOI) substrate.
2017, 13(4):245-249.
DOI: 10.1007/s11801-017-7070-1
Abstract:
In order to satisfy the demands for diffractive telescopes in space exploration, a new deployable space diffractive telescope is designed. The structure and geometrical sizes of the spontaneously deployable telescope are preliminarily designated through the Serrurier truss principle and the optimized design theory. The finite element model of the deployable structure is established, and its deployed characteristics are analyzed. The prototype of the spontaneously deployable structure is constructed and some experiments are carried out to study its characteristics. Experimental results indicate that the deployable structure is 2.95 m in length, its repetitive deployed precision can reach less than 2 mm, the off-center error is less than 0.3 mm, and its deployed precision can be adjusted to micrometer level by actuators when it has deployed. It has simple structure, low mass, steady and reliable deployment, as well as higher precision for space diffractive telescopes.
In order to satisfy the demands for diffractive telescopes in space exploration, a new deployable space diffractive telescope is designed. The structure and geometrical sizes of the spontaneously deployable telescope are preliminarily designated through the Serrurier truss principle and the optimized design theory. The finite element model of the deployable structure is established, and its deployed characteristics are analyzed. The prototype of the spontaneously deployable structure is constructed and some experiments are carried out to study its characteristics. Experimental results indicate that the deployable structure is 2.95 m in length, its repetitive deployed precision can reach less than 2 mm, the off-center error is less than 0.3 mm, and its deployed precision can be adjusted to micrometer level by actuators when it has deployed. It has simple structure, low mass, steady and reliable deployment, as well as higher precision for space diffractive telescopes.
2017, 13(4):250-253.
DOI: 10.1007/s11801-017-7072-z
Abstract:
An optical transceiver with a novel optical subassembly structure is proposed in this paper, which achieves high coupling efficiency and low assembly difficulty. The proposed optical transceiver consumes 0.9 W power and retains a small size of 28 mm×16 mm×3 mm. The fabrication process of the silicon substrate and the assembly process of the optical transceiver are demonstrated in details. Moreover, the optical transceiver is measured in order to verify its transmission performance. The clear eye diagrams and the low bit error rate (BER) less than 10-13 at 10 Gbit/s per channel show good transmission characteristics of the designed optical transceiver.
An optical transceiver with a novel optical subassembly structure is proposed in this paper, which achieves high coupling efficiency and low assembly difficulty. The proposed optical transceiver consumes 0.9 W power and retains a small size of 28 mm×16 mm×3 mm. The fabrication process of the silicon substrate and the assembly process of the optical transceiver are demonstrated in details. Moreover, the optical transceiver is measured in order to verify its transmission performance. The clear eye diagrams and the low bit error rate (BER) less than 10-13 at 10 Gbit/s per channel show good transmission characteristics of the designed optical transceiver.
2017, 13(4):254-258.
DOI: 10.1007/s11801-017-7038-1
Abstract:
When a structure material is damaged by impact events, the reliability and lifetime of the material will be severely affected. So impact location is considered as the prime approach for structural health and damage monitoring. In this study, a novel fiber Bragg grating (FBG) impact location system based on broadband light source is designed, aiming at the shortcoming of existing location systems based on FBG. An improved localization algorithm based on the time difference of arrival (TDoA) is proposed for impact location. According to this algorithm, the impact position can be accurately predicted without wave velocity. Impact planar location experiments are carried out for verification of the FBG impact location system and algorithm on a400 mm×400 mm×3 mm aluminum alloy plate. The resulted locating error shows high precision and good stability of the proposed system. This work has been supported by the National Natural Science Foundation of China (Nos.61503218, 61403233, 61573226 and 61473176), the Excellent Young and Middle-Aged Scientist Award Grant of Shandong Province of China (No.BS2013DX018), and the Natural Science Foundation of Shandong Province for Outstanding Young Talents (No.ZR2015JL021). E-mail:pangdan@163.com
When a structure material is damaged by impact events, the reliability and lifetime of the material will be severely affected. So impact location is considered as the prime approach for structural health and damage monitoring. In this study, a novel fiber Bragg grating (FBG) impact location system based on broadband light source is designed, aiming at the shortcoming of existing location systems based on FBG. An improved localization algorithm based on the time difference of arrival (TDoA) is proposed for impact location. According to this algorithm, the impact position can be accurately predicted without wave velocity. Impact planar location experiments are carried out for verification of the FBG impact location system and algorithm on a400 mm×400 mm×3 mm aluminum alloy plate. The resulted locating error shows high precision and good stability of the proposed system.
2017, 13(4):259-262.
DOI: 10.1007/s11801-017-7071-0
Abstract:
A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated. The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter (MPF). In order to obtain notch frequency response, a Fourier-domain optical processor (FD-OP) is introduced to control the amplitude and phase of the optical carrier and phase modulation sidebands. By adjusting the polarization controller (PC), different numbers of taps are got, such as 6, 8, 10 and 12. And the wavelength spacing of the multi-wavelength laser is 0.4 nm. The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz, 3.30 GHz, 2.64 GHz and 2.19 GHz, respectively. With the additional phase shift introduced by FD-OP, the notch position is continuously tuned in the whole free spectral range (FSR) of 27.94 GHz. The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz. This work has been supported by the National Natural Science Foundation of China (No.11444001), and the Municipal Natural Science Foundation of Tianjin in China (No.14JCYBJC16500). E-mail:cynever@163.com
A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated. The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter (MPF). In order to obtain notch frequency response, a Fourier-domain optical processor (FD-OP) is introduced to control the amplitude and phase of the optical carrier and phase modulation sidebands. By adjusting the polarization controller (PC), different numbers of taps are got, such as 6, 8, 10 and 12. And the wavelength spacing of the multi-wavelength laser is 0.4 nm. The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz, 3.30 GHz, 2.64 GHz and 2.19 GHz, respectively. With the additional phase shift introduced by FD-OP, the notch position is continuously tuned in the whole free spectral range (FSR) of 27.94 GHz. The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz.
MO Ao-qiang
,
CAO Da-peng
,
WANG Wu-yang
,
LI Xue-yan
,
MI Bao-xiu
,
GAO Zhi-qiang
,
LIANG Zhong-cheng
2017, 13(4):263-267.
DOI: 10.1007/s11801-017-7088-4
Abstract:
The photovoltaic performance of dye-sensitized solar cells (DSSCs) is enhanced by modifying the binary room temperature ionic liquid (RTIL) electrolyte with additives and iodine. The average photoelectric conversion efficiency (PCE) of 6.39% is achieved. Through electrochemical impedance spectroscopy (EIS), cyclic voltammetry scans and incident photon-to-current conversion efficiency (IPCE) data, the working principles are analyzed. The enhancement is mainly attributed to the improvement of short circuit current which is caused by the reduction of overall internal resistance of the devices. Durability tests are measured at room temperature, and the long-term stability performance can be maintained. This work has been supported by the National Natural Science Foundation of China (No.61474064). E-mail:zcliang@njupt.edu.cn
The photovoltaic performance of dye-sensitized solar cells (DSSCs) is enhanced by modifying the binary room temperature ionic liquid (RTIL) electrolyte with additives and iodine. The average photoelectric conversion efficiency (PCE) of 6.39% is achieved. Through electrochemical impedance spectroscopy (EIS), cyclic voltammetry scans and incident photon-to-current conversion efficiency (IPCE) data, the working principles are analyzed. The enhancement is mainly attributed to the improvement of short circuit current which is caused by the reduction of overall internal resistance of the devices. Durability tests are measured at room temperature, and the long-term stability performance can be maintained.
2017, 13(4):268-270.
DOI: 10.1007/s11801-017-7036-3
Abstract:
The rectangular optical filter is one of the most important optical switching components in the dense wavelength division multiplexing (DWDM) fiber-optic communication system and the intelligent optical network. The integrated high-order silicon microring resonator (MRR) is one of the best candidates to achieve rectangular filtering spectrum response. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high-order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 μm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully. This work has been supported by the National Natural Science Foundation of China (No.61205062), the Scientific Research Project of Hubei Education Department (No.B2015191), and the Project of Hubei Province Universities Outstanding Youth Scientific Innovation Team (Nos.T201431 and T201633). E-mail:onlyfish@126.com
The rectangular optical filter is one of the most important optical switching components in the dense wavelength division multiplexing (DWDM) fiber-optic communication system and the intelligent optical network. The integrated high-order silicon microring resonator (MRR) is one of the best candidates to achieve rectangular filtering spectrum response. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on high-order MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 μm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.
2017, 13(4):271-274.
DOI: 10.1007/s11801-017-7055-0
Abstract:
We fabricated organic light-emitting diodes (OLEDs) with the thermally activated delayed fluorescence (TADF) material of 4CzIPN, which show better stability compared with the 4,4’-Bis(carbazol-9-yl)biphenyl (CBP) based devices. The half lifetime of the device using 4CzIPN as host material has doubled, and a slower voltage rise compared with that of CBP-based devices has been achieved, which indicates the improvement of stability. We attribute the better stability to the good film morphology and difficult crystallization property of 4CzIPN. Our results suggest that employing the 4CzIPN as host material can be a promising way of fabricating OLEDs with longer operation lifetime.
We fabricated organic light-emitting diodes (OLEDs) with the thermally activated delayed fluorescence (TADF) material of 4CzIPN, which show better stability compared with the 4,4’-Bis(carbazol-9-yl)biphenyl (CBP) based devices. The half lifetime of the device using 4CzIPN as host material has doubled, and a slower voltage rise compared with that of CBP-based devices has been achieved, which indicates the improvement of stability. We attribute the better stability to the good film morphology and difficult crystallization property of 4CzIPN. Our results suggest that employing the 4CzIPN as host material can be a promising way of fabricating OLEDs with longer operation lifetime.
2017, 13(4):275-278.
DOI: 10.1007/s11801-017-7059-9
Abstract:
To address the challenges of non-cooperative and remote acoustic detection, an all-fiber laser Doppler vibrometer (LDV) is established. The all-fiber LDV system can offer the advantages of smaller size, lightweight design and robust structure, hence it is a better fit for remote speech detection. In order to improve the performance and the efficiency of LDV for long-range hearing, the speech enhancement technology based on optimally modified log-spectral amplitude (OM-LSA) algorithm is used. The experimental results show that the comprehensible speech signals within the range of 150 m can be obtained by the proposed LDV. The signal-to-noise ratio (SNR) and mean opinion score (MOS) of the LDV speech signal can be increased by 100% and 27%, respectively, by using the speech enhancement technology. This all-fiber LDV, which combines the speech enhancement technology, can meet the practical demand in engineering.
To address the challenges of non-cooperative and remote acoustic detection, an all-fiber laser Doppler vibrometer (LDV) is established. The all-fiber LDV system can offer the advantages of smaller size, lightweight design and robust structure, hence it is a better fit for remote speech detection. In order to improve the performance and the efficiency of LDV for long-range hearing, the speech enhancement technology based on optimally modified log-spectral amplitude (OM-LSA) algorithm is used. The experimental results show that the comprehensible speech signals within the range of 150 m can be obtained by the proposed LDV. The signal-to-noise ratio (SNR) and mean opinion score (MOS) of the LDV speech signal can be increased by 100% and 27%, respectively, by using the speech enhancement technology. This all-fiber LDV, which combines the speech enhancement technology, can meet the practical demand in engineering.
2017, 13(4):279-281.
DOI: 10.1007/s11801-017-7037-2
Abstract:
An integral imaging display system based on negative lens array in real mode is proposed in this letter. Compared with the conventional integral imaging system with positive lens array, the negative one has a huge advantage on viewing angle. The minimum viewing angle of the imaging display system based on negative lens array is the maximum viewing angle of the positive one with the same parameters. And the imaging display system based on negative lens array can enhance the viewing angle to 180° with special parameters. Other parameters, such as resolution and depth-of-field, are the same in both systems. Another advantage is that the proposed imaging display system based on negative lens array can fill the image area gap between 0 and 2f. The feasibility of our proposed method is experimentally proved. This work has been supported by the National Natural Science Foundation of China (No.11474169) and the Hebei Provincial Science Foundation for Youths (No.F2016402115). E-mail:XXJiao@hebeu.edu.cn
An integral imaging display system based on negative lens array in real mode is proposed in this letter. Compared with the conventional integral imaging system with positive lens array, the negative one has a huge advantage on viewing angle. The minimum viewing angle of the imaging display system based on negative lens array is the maximum viewing angle of the positive one with the same parameters. And the imaging display system based on negative lens array can enhance the viewing angle to 180° with special parameters. Other parameters, such as resolution and depth-of-field, are the same in both systems. Another advantage is that the proposed imaging display system based on negative lens array can fill the image area gap between 0 and 2f. The feasibility of our proposed method is experimentally proved.
2017, 13(4):282-286.
DOI: 10.1007/s11801-017-7048-z
Abstract:
This paper describes a novel finite element thermal analysis model for an AlGaInP-LED micro-array device. We also conduct a transient analysis for the internal temperature field distribution of a 5×5 array device when a 3×3 unit is driven by pulse current. In addition, for broader applications, a simplified thermal analysis model is introduced and its accuracy is verified. The internal temperature field distribution of 100×100 units is calculated using the simplified model. The temperature at the device center reaches 360.6 °C after 1.5 s. In order to solve the heat dissipation problem of the device, an optimized heat dissipation structure is designed, and the effects of the number and size of the heat dissipation fins on the thermal characteristics of the device are analyzed. This work has been supported by the Young Scientists Fund of the National Natural Science Foundation of China (No.61204055). E-mail:gaofl@jlu.edu.cn
This paper describes a novel finite element thermal analysis model for an AlGaInP-LED micro-array device. We also conduct a transient analysis for the internal temperature field distribution of a 5×5 array device when a 3×3 unit is driven by pulse current. In addition, for broader applications, a simplified thermal analysis model is introduced and its accuracy is verified. The internal temperature field distribution of 100×100 units is calculated using the simplified model. The temperature at the device center reaches 360.6 °C after 1.5 s. In order to solve the heat dissipation problem of the device, an optimized heat dissipation structure is designed, and the effects of the number and size of the heat dissipation fins on the thermal characteristics of the device are analyzed.
2017, 13(4):287-290.
DOI: 10.1007/s11801-017-7053-2
Abstract:
In order to meet the application requirement of a certain long wavelength infrared (LWIR) seeker, a small volume, light weight and passively athermalized infrared (IR) objective is designed in this paper. The two-lens telephoto structure is adopted by merely using aluminum alloy as the housing material. By balancing the thermo-optical coefficient and thermal expansion coefficient of materials, an athermalized IR seeker with effective focal length of 90 mm and F number of 1.2 is achieved. The whole optical length is 75 mm, and the weight is only 234 g. The objective can remain fine imaging quality under temperature range from −40°C to 60 °C, which is beneficial to the lightweight design of IR seekers. This work has been supported by the National Natural Science Foundation of China (Nos.11372309 and 61304017), and the Knowledge Innova- tion Program of the Chinese Academy of Sciences (No.YYYJ-1122). E-mail:wangj@ciomp.ac.cn
In order to meet the application requirement of a certain long wavelength infrared (LWIR) seeker, a small volume, light weight and passively athermalized infrared (IR) objective is designed in this paper. The two-lens telephoto structure is adopted by merely using aluminum alloy as the housing material. By balancing the thermo-optical coefficient and thermal expansion coefficient of materials, an athermalized IR seeker with effective focal length of 90 mm and F number of 1.2 is achieved. The whole optical length is 75 mm, and the weight is only 234 g. The objective can remain fine imaging quality under temperature range from −40°C to 60 °C, which is beneficial to the lightweight design of IR seekers.
2017, 13(4):291-294.
DOI: 10.1007/s11801-017-7108-4
Abstract:
Quaternary chalcogenide Cu2FeSnS4 (CFTS) nanoparticles, as a kind of potential absorber layer material in thin film solar cells (TFSCs), were successfully synthesized by using a convenient solvothermal method. Alkali element K is incorporated into CFTS thin films in order to further improve the surface morphology and the optical properties of related films. X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) were used to characterize the phase purity, morphology and composition of CFTS particles and thin films. The results show that the particle elemental ratios of Cu/(Fe+Sn) and Fe/Sn are 1.2 and 0.9, respectively, which are close to the characteristics of stoichiometric CFTS. The band gaps of CFTS films before and after doping K ions are estimated to be 1.44 eV and 1.4 eV with an error of ±0.02 eV. This work has been supported by National Natural Science Foundation of China (No. 51674026), and the Fundamental Research Funds for the Central Universities in 2015 (No.FRF-BD-15-004A). E-mail:chywang@yeah.net
Quaternary chalcogenide Cu2FeSnS4 (CFTS) nanoparticles, as a kind of potential absorber layer material in thin film solar cells (TFSCs), were successfully synthesized by using a convenient solvothermal method. Alkali element K is incorporated into CFTS thin films in order to further improve the surface morphology and the optical properties of related films. X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) were used to characterize the phase purity, morphology and composition of CFTS particles and thin films. The results show that the particle elemental ratios of Cu/(Fe+Sn) and Fe/Sn are 1.2 and 0.9, respectively, which are close to the characteristics of stoichiometric CFTS. The band gaps of CFTS films before and after doping K ions are estimated to be 1.44 eV and 1.4 eV with an error of ±0.02 eV.
14 Synthesis of monoclinic structure gallium oxide film on sapphire substrate by magnetron sputtering
SUN Jian-xu
,
MI Wei
,
ZHANG De-shuang
,
YANG Zheng-chun
,
ZHANG Kai-liang
,
HAN Ye-mei
,
YUAN Yu-jie
,
ZHAO Jin-shi
,
LI Bo
2017, 13(4):295-298.
DOI: 10.1007/s11801-017-7065-y
Abstract:
Gallium oxide (Ga2O3) films were deposited on singlecrystalline sapphire (0001) substrate by radio frequency (RF) magnetron sputtering technique in the temperature range of 300—500 °C. The microstructure of the β-Ga2O3 films were investigated in detail using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results show that the film prepared at 500 °C exhibits the best crystallinity with a monoclinic structure (β-Ga2O3). Structure analysis reveals a clear out-of-plane orientation of β-Ga2O3 || Al2O3 (0001). The average transmittance of these films in the visible wavelength range exceeds 90%, and the optical band gap of the films varies from 4.68 eV to 4.94 eV which were measured by an ultraviolet-visible-near infrared (UV-vis-NIR) spectrophotometer. Therefore, it is hopeful that the β-Ga2O3 film can be used in the UV optoelectronic devices. #$TABThis work has been supported by the National Natural Science Foundation of China (Nos.61274113, 61404091, 61505144, 51502203 and 51502204), the Opening Fund of Key Laboratory of Silicon Device Technology in Chinese Academy of Sciences, and the Tianjin Natural Science Foundation (Nos.14JCZDJC31500 and 14JCQNJC00800).#$TABE-mail:miwei1986@yeah.net
Gallium oxide (Ga2O3) films were deposited on singlecrystalline sapphire (0001) substrate by radio frequency (RF) magnetron sputtering technique in the temperature range of 300—500 °C. The microstructure of the β-Ga2O3 films were investigated in detail using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results show that the film prepared at 500 °C exhibits the best crystallinity with a monoclinic structure (β-Ga2O3). Structure analysis reveals a clear out-of-plane orientation of β-Ga2O3 || Al2O3 (0001). The average transmittance of these films in the visible wavelength range exceeds 90%, and the optical band gap of the films varies from 4.68 eV to 4.94 eV which were measured by an ultraviolet-visible-near infrared (UV-vis-NIR) spectrophotometer. Therefore, it is hopeful that the β-Ga2O3 film can be used in the UV optoelectronic devices.
2017, 13(4):299-303.
DOI: 10.1007/s11801-017-7062-1
Abstract:
The interaction of continuous wave (CW) fiber laser with Ti-6Al-4V alloy is investigated numerically and experimentally at different laser fluence values and ambient pressures of N2 atmosphere to determine the melting time threshold of Ti-6Al-4V alloy. A 2D-axisymmetric numerical model considering heat transfer and laminar flow is established to describe the melting process. The simulation results indicate that material melts earlier at lower pressure (8.0 Pa) than at higher pressure (8.8×104 Pa) in several milliseconds with the same laser fluence. The experimental results demonstrate that the melting time threshold at high laser fluence (above 1.89×108 W/m2) is shorter for lower pressure (vacuum), which is consistent with the simulation. While the melting time threshold at low laser fluence (below 1.89×108 W/m2) is shorter for higher pressure. The possible aspects which can affect the melting process include the increased heat loss induced by the heat conduction between the metal surface and the ambient gas with the increased pressure, and the absorption variation of the coarse surface resulted from the chemical reaction. This work has been supported by the National Natural Science Foundation of China for Young Scholars (No.11402120), the Jiangsu Provincial Natural Science Foundation for Young Scholars (No.BK20140796), and the Fundamental Research Funds for the Central Universities (No.30915015104). E-mail:hanbing@njust.edu.cn
The interaction of continuous wave (CW) fiber laser with Ti-6Al-4V alloy is investigated numerically and experimentally at different laser fluence values and ambient pressures of N2 atmosphere to determine the melting time threshold of Ti-6Al-4V alloy. A 2D-axisymmetric numerical model considering heat transfer and laminar flow is established to describe the melting process. The simulation results indicate that material melts earlier at lower pressure (8.0 Pa) than at higher pressure (8.8×104 Pa) in several milliseconds with the same laser fluence. The experimental results demonstrate that the melting time threshold at high laser fluence (above 1.89×108 W/m2) is shorter for lower pressure (vacuum), which is consistent with the simulation. While the melting time threshold at low laser fluence (below 1.89×108 W/m2) is shorter for higher pressure. The possible aspects which can affect the melting process include the increased heat loss induced by the heat conduction between the metal surface and the ambient gas with the increased pressure, and the absorption variation of the coarse surface resulted from the chemical reaction.
2017, 13(4):304-308.
DOI: 10.1007/s11801-017-7077-7
Abstract:
Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind equalization algorithm is used to preprocess M-ary phase shift keying (MPSK) subcarrier modulation signal in receiver. Mountain clustering is adopted to get the clustering centers of MPSK modulation constellation diagram, and the modulation order is automatically identified through the k-nearest neighbor (KNN) classifier. The experiment has been done under four different weather conditions. Experimental results show that the convergent of constellation diagram is improved effectively after using the subspace blind equalization algorithm, which means that the accuracy of modulation recognition is increased. The correct recognition rate of 16PSK can be up to 85% in any kind of weather condition which is mentioned in paper. Meanwhile, the correct recognition rate is the highest in cloudy and the lowest in heavy rain condition. This work has been supported by the National Natural Science Foundation of China (No.61671375), and the Industrial Research of Science and Technology Plan of Shaanxi Province (No.2016GY-082). E-mail:chdh@xaut.edu.cn
Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind equalization algorithm is used to preprocess M-ary phase shift keying (MPSK) subcarrier modulation signal in receiver. Mountain clustering is adopted to get the clustering centers of MPSK modulation constellation diagram, and the modulation order is automatically identified through the k-nearest neighbor (KNN) classifier. The experiment has been done under four different weather conditions. Experimental results show that the convergent of constellation diagram is improved effectively after using the subspace blind equalization algorithm, which means that the accuracy of modulation recognition is increased. The correct recognition rate of 16PSK can be up to 85% in any kind of weather condition which is mentioned in paper. Meanwhile, the correct recognition rate is the highest in cloudy and the lowest in heavy rain condition.
2017, 13(4):309-313.
DOI: 10.1007/s11801-017-7052-3
Abstract:
This paper proposes a robust auto-focus (AF) measure based on inner energy. In general, the inner energy of noise pixels is close to zero because the magnitude of gradient and the direction of the noise pixels are random. Therefore, the inner energy can effectively eliminate the influence of noise on image quality assessment. But the gradients of near edge points are consistent with those of edge points, so the inner energy of edge pixels is relatively large, and the detail information of the image can be highlighted. Experimental results indicate that compared with traditional methods, the proposed method has higher accuracy, fewer local peaks, stronger robustness and better practicability. In particular, the evaluation results are close to the subjective evaluation of the human eyes. These results illustrate that the proposed method can be applied in automatic focusing. This work has been supported by the National Natural Science Foundation of China (Nos.U1509207 and 61325019). E-mail:weihuang@tjut.edu.cn
This paper proposes a robust auto-focus (AF) measure based on inner energy. In general, the inner energy of noise pixels is close to zero because the magnitude of gradient and the direction of the noise pixels are random. Therefore, the inner energy can effectively eliminate the influence of noise on image quality assessment. But the gradients of near edge points are consistent with those of edge points, so the inner energy of edge pixels is relatively large, and the detail information of the image can be highlighted. Experimental results indicate that compared with traditional methods, the proposed method has higher accuracy, fewer local peaks, stronger robustness and better practicability. In particular, the evaluation results are close to the subjective evaluation of the human eyes. These results illustrate that the proposed method can be applied in automatic focusing.
2017, 13(4):314-317.
DOI: 10.1007/s11801-017-7061-2
Abstract:
To solve the problem that the accurate information of hand cannot be obtained by particle filter, a hand tracking algorithm based on particle filter combined with skin-color adaptive gradient vector flow (GVF) snake model is proposed. Adaptive GVF and skin color adaptive external guidance force are introduced to the traditional GVF snake model, guiding the curve to quickly converge to the deep concave region of hand contour and obtaining the complex hand contour accurately. This algorithm realizes a real-time correction of the particle filter parameters, avoiding the particle drift phenomenon. Experimental results show that the proposed algorithm can reduce the root mean square error of the hand tracking by 53%, and improve the accuracy of hand tracking in the case of complex and moving background, even with a large range of occlusion. This work has been supported by the National Natural Sciencal Foundation of China (No.61403274), and the Tianjin Technology Project of Intelligent Manufacturing (No.15ZXZNGX00160). E-mail:agwu@tju.edu.cn
To solve the problem that the accurate information of hand cannot be obtained by particle filter, a hand tracking algorithm based on particle filter combined with skin-color adaptive gradient vector flow (GVF) snake model is proposed. Adaptive GVF and skin color adaptive external guidance force are introduced to the traditional GVF snake model, guiding the curve to quickly converge to the deep concave region of hand contour and obtaining the complex hand contour accurately. This algorithm realizes a real-time correction of the particle filter parameters, avoiding the particle drift phenomenon. Experimental results show that the proposed algorithm can reduce the root mean square error of the hand tracking by 53%, and improve the accuracy of hand tracking in the case of complex and moving background, even with a large range of occlusion.
2017, 13(4):318-320.
DOI: 10.1007/s11801-017-7041-6
Abstract:
Shimony-Holt (CHSH) inequality and investigate the robustness of the CHSH-class inequality in the bit-flip noisy environment. We obtain the experimental results of CHSH inequalityand analog CHSH inequalityas SCHSH=2.64±0.02 and SanalogCHSH=2.76±0.02, respectively, and prove that the analog CHSH inequality is more robust against bit-flip noise than the CHSH inequality. It provides better advantages for the experimental study and application. This work has been supported by the National Natural Science Foundation of China (Nos.11174224, 11404246 and 11447225), and the Natural Science Foundation of Shandong Province (Nos.ZR2013FM001, BS2015DX015 and ZR2014JL029). E-mail:zhaojiaqiang@wfu.edu.cn
Shimony-Holt (CHSH) inequality and investigate the robustness of the CHSH-class inequality in the bit-flip noisy environment. We obtain the experimental results of CHSH inequalityand analog CHSH inequalityas SCHSH=2.64±0.02 and SanalogCHSH=2.76±0.02, respectively, and prove that the analog CHSH inequality is more robust against bit-flip noise than the CHSH inequality. It provides better advantages for the experimental study and application.
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