在精密测量领域,He-Ne激光器是制造激光干涉仪的首选光源,因波长作为测量的"尺子",激光器的频率稳定性至关重要。介绍了双频激光器的稳频技术原理,利用调谐腔中平行光和垂直光的等光强点作为稳频点,以光强平衡为依据设计热伺...在精密测量领域,He-Ne激光器是制造激光干涉仪的首选光源,因波长作为测量的"尺子",激光器的频率稳定性至关重要。介绍了双频激光器的稳频技术原理,利用调谐腔中平行光和垂直光的等光强点作为稳频点,以光强平衡为依据设计热伺服控制电路,采用数字和模拟电路共同控制,实现了He-Ne双折射塞曼双频激光器的频率稳定。对大频差(7.95 MHz)的双频激光器进行拍频测试,单次频率稳定度达10-9量级,重复多次多日测量,频率不确定度达1.074×10-8(k=2)。同时对频差稳定度进行测试,频差波动范围在8 k Hz以内,相对偏差度为0.001,完全达到商用双频干涉仪的标准。展开更多
To understand better the impact on mist net capture rates of the activity height of birds, light intensity, bird richness and abundance, we compared data from mist nets and point counts at the Jianfengling Forest Area...To understand better the impact on mist net capture rates of the activity height of birds, light intensity, bird richness and abundance, we compared data from mist nets and point counts at the Jianfengling Forest Area, Hainan Island. Mist-nets were operated for a total of 7135 net-hours. A total of 587 individuals of 45 bird species were captured. The total mean capture rate was 8.6 ± 10.4 per 100 net-hours. A total of 4932 individuals of 107 bird species were recorded by visual observation alone and 7616 individuals of 120 species were recorded in a visual and aural combination. The Grey-cheeked Fulvetta (Alcippe morrisonia) was the most abundant species, accounting for 38.7% of total captures, 27.9% of visual observations and 22.2% of visual + aural observations. The capture number was correlated with the number observed. Thirty-one species were more likely to be captured than observed. Canopy species, such as members of the Corvidae and Dicruridae, were seldom captured. For all ground feeding species, the capture number was greater than that of observation. Some cryptic species, such as the Lesser Wren Babbler (Napothera epilepidota), Spotnecked Babbler (Stachyris striolata) and Cuckoo Owl (Glaucidium cuculoides) also had a higher relative capture rate than that of observations. There was a significant relationship between light intensity and the number of birds captured.展开更多
The Ho3＋/yb3＋ co-doped a-NaYF4 single crystal was grown successfully for the first time by a modified Bridgman method in which KF was used as assisting flux and a large temperature gradient （70-90℃ /cm） of solid-...The Ho3＋/yb3＋ co-doped a-NaYF4 single crystal was grown successfully for the first time by a modified Bridgman method in which KF was used as assisting flux and a large temperature gradient （70-90℃ /cm） of solid-liquid interface was adopted. Upconversion emissions at green -544 nm, red -657 and -751 nm were obtained under 980 nm laser diode excitation. The intensity at -544 nm was much stronger than those of -657 and -751 nm. The mechanisms of the upconversion emissions were investigated by studying the relationship between the upconversion intensity and pump power. The optimized Yb3＋ concentration was about 8.08moi% when Ho3＋ concentration was hold at about 1.0mol%. The results showed that Ho3＋/yb3＋ doped α-NaYF4 single crystal was a possible candidate upconversion material for the green solid-state laser.展开更多
Surface of Ultra-high molecular weight polyethylene （UHMWPE） fiber were treated by chromic acid chemical etching, pyrrole chemical vapour phase deposition and the complex of these two methods, respectively. The chan...Surface of Ultra-high molecular weight polyethylene （UHMWPE） fiber were treated by chromic acid chemical etching, pyrrole chemical vapour phase deposition and the complex of these two methods, respectively. The change of surface properties and structure of fibers were discussed by Fiour Transform Infrared Spectroscope （FTIR）, Dynamic Mechanical Analysis （DMA） and Scanning Electron Microscope （SEM）. The results show that some new oxygenous groups could be found on surface of UHMWPE fiber after chromic acid chemical etching, which enhanced intemolecular interaction with polypyrrcle. The adhesion of the fiber and resin natrix increased after pyrrole chemical vapour deposition. When chromic acid etching combined with pyrrole chemical vapor deposition, the treated fiber not only has the same properties as original fiber bat also outstanding adhesion to epoxy resin matrix, and its composites have better mechanic properties shear strength）, resulting from intemolecular interaction treated fiber and polypyrrole.展开更多
Aming at the problem of the low accuracy of low dynamic vehicle velocity under the environment of uneven distribution of light intensity,an improved adaptive Kalman filter method for the velocity error estimate by the...Aming at the problem of the low accuracy of low dynamic vehicle velocity under the environment of uneven distribution of light intensity,an improved adaptive Kalman filter method for the velocity error estimate by the fusion of optical flow tracking and scale mvaiant feature transform(SIFT)is proposed.The algorithm introduces anonlinear fuzzy membership function and the filter residual for the noise covariance matrix in the adaptive adjustment process.In the process of calculating the velocity of the vehicle,the tracking and matching of the inter-frame displacement a d the vehicle velocity calculation a e carried out by using the optical fow tracing and the SIF'T methods,respectively.Meanwhile,the velocity difference between theoutputs of thesetwo methods is used as the observation of the improved adaptive Kalman filter.Finally,the velocity calculated by the optical fow method is corrected by using the velocity error estimate of the output of the modified adaptive Kalman filter.The results of semi-physical experiments show that the maximum velocityeror of the fusion algorithm is decreased by29%than that of the optical fow method,and the computation time is reduced by80%compared with the SIFT method.展开更多
As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive,...As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of -10^7. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.展开更多
Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight. In order to enhance its absorption of sunlight,dark color zinc oxides have been...Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight. In order to enhance its absorption of sunlight,dark color zinc oxides have been prepared by traditional hydrothermal method directly using a zinc foil as both source and substrate. We found that we could tune the optical properties of ZnO samples by changing the temperature. In particular, increasing temperature could significantly reduce the reflectivity of solar energy in the visible range. We speculate that the phenomenon is relevant to the sharp cone morphology of the ZnO nanorods grown on the surface of Zn foils, which furthermore enhance refraction and reflection of light in the nanorods. The capacity to improve the light absorption of ZnO may have a bright application in raising the efficiency of solar cells.展开更多
In the simulation of Intensity Modulation-Direct Detection WDM Systems,when the dispersion and nonlinear effects play equally important roles,the intensity fluctuation caused by cross-phase modulation may be overestim...In the simulation of Intensity Modulation-Direct Detection WDM Systems,when the dispersion and nonlinear effects play equally important roles,the intensity fluctuation caused by cross-phase modulation may be overestimated as a result of the improper step size.Therefore,the step size in numerical simulation should be selected to suppress false XPM intensity modulation (keep it much less than signal power).According to this criterion,the step size is variable along the fiber.For a WDM system,the step size depends on the channel separation.Different type of transmission fiber has different step size.In the split-step Fourier method,this criterion can reduce simulation time,and when the step size is bigger than 100 meters,the simulation accuracy can also be improved.展开更多
Gravitational field produced by high-power laser is calculated according to the linearized Einstein field equation in weak field approximation. Gravitational Faraday effect of electromagnetic wave propagating in the a...Gravitational field produced by high-power laser is calculated according to the linearized Einstein field equation in weak field approximation. Gravitational Faraday effect of electromagnetic wave propagating in the above gravitational field is studied and the rotation angle of polarization plane of electromagnetic wave is derived. The result is discussed and estimated under the condition of present experiment facility.展开更多
文摘在精密测量领域,He-Ne激光器是制造激光干涉仪的首选光源,因波长作为测量的"尺子",激光器的频率稳定性至关重要。介绍了双频激光器的稳频技术原理,利用调谐腔中平行光和垂直光的等光强点作为稳频点,以光强平衡为依据设计热伺服控制电路,采用数字和模拟电路共同控制,实现了He-Ne双折射塞曼双频激光器的频率稳定。对大频差(7.95 MHz)的双频激光器进行拍频测试,单次频率稳定度达10-9量级,重复多次多日测量,频率不确定度达1.074×10-8(k=2)。同时对频差稳定度进行测试,频差波动范围在8 k Hz以内,相对偏差度为0.001,完全达到商用双频干涉仪的标准。
基金funded by the Kadoorie Farm and Botanical Garden and the Hong Kong Special Administrative Region,China
文摘To understand better the impact on mist net capture rates of the activity height of birds, light intensity, bird richness and abundance, we compared data from mist nets and point counts at the Jianfengling Forest Area, Hainan Island. Mist-nets were operated for a total of 7135 net-hours. A total of 587 individuals of 45 bird species were captured. The total mean capture rate was 8.6 ± 10.4 per 100 net-hours. A total of 4932 individuals of 107 bird species were recorded by visual observation alone and 7616 individuals of 120 species were recorded in a visual and aural combination. The Grey-cheeked Fulvetta (Alcippe morrisonia) was the most abundant species, accounting for 38.7% of total captures, 27.9% of visual observations and 22.2% of visual + aural observations. The capture number was correlated with the number observed. Thirty-one species were more likely to be captured than observed. Canopy species, such as members of the Corvidae and Dicruridae, were seldom captured. For all ground feeding species, the capture number was greater than that of observation. Some cryptic species, such as the Lesser Wren Babbler (Napothera epilepidota), Spotnecked Babbler (Stachyris striolata) and Cuckoo Owl (Glaucidium cuculoides) also had a higher relative capture rate than that of observations. There was a significant relationship between light intensity and the number of birds captured.
基金This work was supported by the National Natural Science Foundation of China （No.51472125, No.51272109） and K. C. Wong Magna Fund in Ningbo University.
文摘The Ho3＋/yb3＋ co-doped a-NaYF4 single crystal was grown successfully for the first time by a modified Bridgman method in which KF was used as assisting flux and a large temperature gradient （70-90℃ /cm） of solid-liquid interface was adopted. Upconversion emissions at green -544 nm, red -657 and -751 nm were obtained under 980 nm laser diode excitation. The intensity at -544 nm was much stronger than those of -657 and -751 nm. The mechanisms of the upconversion emissions were investigated by studying the relationship between the upconversion intensity and pump power. The optimized Yb3＋ concentration was about 8.08moi% when Ho3＋ concentration was hold at about 1.0mol%. The results showed that Ho3＋/yb3＋ doped α-NaYF4 single crystal was a possible candidate upconversion material for the green solid-state laser.
文摘Surface of Ultra-high molecular weight polyethylene （UHMWPE） fiber were treated by chromic acid chemical etching, pyrrole chemical vapour phase deposition and the complex of these two methods, respectively. The change of surface properties and structure of fibers were discussed by Fiour Transform Infrared Spectroscope （FTIR）, Dynamic Mechanical Analysis （DMA） and Scanning Electron Microscope （SEM）. The results show that some new oxygenous groups could be found on surface of UHMWPE fiber after chromic acid chemical etching, which enhanced intemolecular interaction with polypyrrcle. The adhesion of the fiber and resin natrix increased after pyrrole chemical vapour deposition. When chromic acid etching combined with pyrrole chemical vapor deposition, the treated fiber not only has the same properties as original fiber bat also outstanding adhesion to epoxy resin matrix, and its composites have better mechanic properties shear strength）, resulting from intemolecular interaction treated fiber and polypyrrole.
基金The National Natural Science Foundation of China(No.51375087,51405203)the Transformation Program of Science and Technology Achievements of Jiangsu Province(No.BA2016139)
文摘Aming at the problem of the low accuracy of low dynamic vehicle velocity under the environment of uneven distribution of light intensity,an improved adaptive Kalman filter method for the velocity error estimate by the fusion of optical flow tracking and scale mvaiant feature transform(SIFT)is proposed.The algorithm introduces anonlinear fuzzy membership function and the filter residual for the noise covariance matrix in the adaptive adjustment process.In the process of calculating the velocity of the vehicle,the tracking and matching of the inter-frame displacement a d the vehicle velocity calculation a e carried out by using the optical fow tracing and the SIF'T methods,respectively.Meanwhile,the velocity difference between theoutputs of thesetwo methods is used as the observation of the improved adaptive Kalman filter.Finally,the velocity calculated by the optical fow method is corrected by using the velocity error estimate of the output of the modified adaptive Kalman filter.The results of semi-physical experiments show that the maximum velocityeror of the fusion algorithm is decreased by29%than that of the optical fow method,and the computation time is reduced by80%compared with the SIFT method.
基金supported by the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province (No.16KJB510009 and No.17KJB510017)Jiangsu Province Natural Science Foundation of China (BK20150228)
文摘As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of -10^7. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.
基金supported by the National Natural Science Foundation of China(No.11575187)the National Key Research and Development Program(No.2016YFB0700205)
文摘Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight. In order to enhance its absorption of sunlight,dark color zinc oxides have been prepared by traditional hydrothermal method directly using a zinc foil as both source and substrate. We found that we could tune the optical properties of ZnO samples by changing the temperature. In particular, increasing temperature could significantly reduce the reflectivity of solar energy in the visible range. We speculate that the phenomenon is relevant to the sharp cone morphology of the ZnO nanorods grown on the surface of Zn foils, which furthermore enhance refraction and reflection of light in the nanorods. The capacity to improve the light absorption of ZnO may have a bright application in raising the efficiency of solar cells.
文摘In the simulation of Intensity Modulation-Direct Detection WDM Systems,when the dispersion and nonlinear effects play equally important roles,the intensity fluctuation caused by cross-phase modulation may be overestimated as a result of the improper step size.Therefore,the step size in numerical simulation should be selected to suppress false XPM intensity modulation (keep it much less than signal power).According to this criterion,the step size is variable along the fiber.For a WDM system,the step size depends on the channel separation.Different type of transmission fiber has different step size.In the split-step Fourier method,this criterion can reduce simulation time,and when the step size is bigger than 100 meters,the simulation accuracy can also be improved.
文摘Gravitational field produced by high-power laser is calculated according to the linearized Einstein field equation in weak field approximation. Gravitational Faraday effect of electromagnetic wave propagating in the above gravitational field is studied and the rotation angle of polarization plane of electromagnetic wave is derived. The result is discussed and estimated under the condition of present experiment facility.
