The deployable mechanisms consisting of square units are widely applied in aeronautics and astronautics,biomedicine, architecture and other fields, and joint clearance in such a mechanism is unavoidable. This study is...The deployable mechanisms consisting of square units are widely applied in aeronautics and astronautics,biomedicine, architecture and other fields, and joint clearance in such a mechanism is unavoidable. This study is carried out to accurately investigate the dynamic property of the mechanism.Firstly,a dynamics model was built by considering the motion characteristics between elements of joint with clearances. Secondly,based on Floures contact force model and LuGre friction force model,the tangential and normal contact force of revolute pair element with clearance were calculated respectively. Finally,square combined mechanisms' dynamic analytical method considering joint clearance was investigated, and constraint renege problem was resolved by adopting Baumgarte stable constraint method in integration process.Analytical result indicates that the impact of joint clearance on dynamic property of square combined mechanism should not be neglected.展开更多
The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important on...The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important one.The aim of this study is to improve the selective properties of codends for banded scad.Size selectivity of 2 traditional diamond mesh codends,with mesh size 25 and 30 mm(defined as D25 and D30,respectively),and 4 new combined square and diamond mesh codends,with25 mm square-mesh and 25 mm diamond-mesh(S25+D25),30 mm square-mesh and 25 mm diamondmesh(S30+D25),35 mm square-mesh and 25 mm diamond-mesh(S35+D25),and 35 mm square-mesh and18 mm diamond-mesh(S35+D18),were tested for banded scad in shrimp beam trawl fishery of the South China Sea.A total of 54 valid hauls were finished using the covered codend method,and 5750 banded scad were caught.Selective parameters were obtained using the logistic equation with the maximum likelihood method,by incorporating the between-haul variation.The results show that the present minimum mesh size for shrimp beam trawl in the South China Sea,25-mm diamond mesh size,is insufficient to release immature banded scad.The S35+D25 codend is proved to be the most eff ective codend to release immature banded scad,and its 50%retention length(L _(50))is larger than the minimum landing size(MLS=63.5 mm)of banded scad.However,the 95%confidence intervals of L _(50) overlap among the three combined mesh codends,the S25+D25,S30+D25 and S35+D25 codend.For a sustainable exploitation of banded scad,larger mesh sizes are suggested to be investigated for the combined mesh codends.展开更多
The article studies the oscillation features of the water in the square moon pool under the circumstances of wave-flow combined conditions. Comparing with the results of experiments of the square moon pool, a series o...The article studies the oscillation features of the water in the square moon pool under the circumstances of wave-flow combined conditions. Comparing with the results of experiments of the square moon pool, a series of studies reveal that the water piston oscillation phenomenon is quite similar to that of the circular one. Two types of oscillation are exhibited under different incoming wave periods, i.e. self-excited oscillation and forced oscillation. The difference between the circular and square moon pool is that the attack angle makes greater influences on the square one. "Beating phenomenon" is also found in the square moon pool which is not mentioned of the circular one.展开更多
AIM: To assess the outcomes of combined 23-gauge sutureless vitrectomy and clear corneal phacoemulsification with intraocular lens implantation for rhegmatogenous retinal detachment(RRD) repair.METHODS: This was a ret...AIM: To assess the outcomes of combined 23-gauge sutureless vitrectomy and clear corneal phacoemulsification with intraocular lens implantation for rhegmatogenous retinal detachment(RRD) repair.METHODS: This was a retrospective, consecutive,noncomparative, interventional case series of 30 eyes of30 patients who underwent combined sutureless vitrectomy and clear corneal cataract surgery for the repair of RRD. The principal outcome measures were primary anatomical success rate, reasons for redetachment, final visual acuity, and surgical complications.RESULTS: Primary reattachment was achieved in 27eyes(90.0%). The reasons for redetachment(3 eyes, 10%)were incomplete laser retinopexy, persistent chronic subretinal fluid, and proliferative vitreoretinopathy,respectively. The logarithm of the minimum angle of resolution visual acuity(mean±SD) improved from 0.76±0.74 preoperatively to 0. 21 ± 0. 37 6 months’ postoperatively(P 【0.0001). Postoperative hypotony was not detected,but 1 eye( 3. 3 %) had increased intraocular pressure(30 mm Hg) with spontaneous resolution. No endophthalmitis developed during follow-up. Macular pucker was detected in 3 eyes(10.0%).· CONCLUSION: Combined 23-gauge sutureless vitrectomy and clear corneal phacoemulsification with intraocular lens implantation for RRD repair was proven safe and effective. It may provide not only the known advantages of conventional combined surgery, but also additional advantages such as less conjunctival fibrosis and the maintenance of stable intraocular pressure with low risks of postoperative hypotony and intraocular pressure elevation.展开更多
Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of...Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of power system. To cope with the problems existing in the ESDD predicting by multivariate linear regression (MLR), back propagation (BP) neural network and least squares support vector machines (LSSVM), a nonlinear combination forecasting model based on wavelet neural network (WNN) for ESDD is proposed. The model is a WNN with three layers, whose input layer has three neurons and output layer has one neuron, namely, regarding the ESDD forecasting results of MLR, BP and LSSVM as the inputs of the model and the observed value as the output. In the interest of better reflection of the influence of each single forecasting model on ESDD and increase of the accuracy of ESDD prediction, Morlet wavelet is used to con-struct WNN, error backpropagation algorithm is adopted to train the network and genetic algorithm is used to determine the initials of the parameters. Simulation results show that the accuracy of the proposed combina-tion ESDD forecasting model is higher than that of any single model and that of traditional linear combina-tion forecasting (LCF) model. The model provides a new feasible way to increase the accuracy of pollution distribution map of power network.展开更多
A fast edge detection method basing on the combination of fuzzy subsets is developed, in which the detection of an edge as a classification problem will be considered, partitioning the image into two portions: the edg...A fast edge detection method basing on the combination of fuzzy subsets is developed, in which the detection of an edge as a classification problem will be considered, partitioning the image into two portions: the edge portion and the non-edge portion. The latter one, as the main constituent of an image, consists of the object and its background. Removing the non-edge portion from an image, the remainder is nothing but the edge of this image. As far as the fuzziness of the edge of an image is concerned, some fuzzy operations can be made. In this paper, the gray level histogram is partitioned into several sub-regions, and some operations are performed with the associated fuzzy subsets corresponding to those sub-edges in the sub-regions on the gray-level-square-difference histogram, and the edge of this image is finally obtained. Practical examples in this paper illustrate that, the described method is simple and effective to achieve an ideal edge image.展开更多
The influences of various kinds of UV-absorbers, antioxidants and their mixtures on UV-aging resis- tance of transparent unsaturated polyester FRP are studied by artificial aocelerating aging test.The results show tha...The influences of various kinds of UV-absorbers, antioxidants and their mixtures on UV-aging resis- tance of transparent unsaturated polyester FRP are studied by artificial aocelerating aging test.The results show that the UV-aging resistance of com- bined stabilizers is better than single stabilizer. It is concluded that the cooperative effect of UV -absorbers is caused bg the increase of wave leng- th and intensity of the absorption light the coopora- tive effect of UV-absorbers and antioxidants is caused by Dreventing the photo-oxidantion.展开更多
The calibration model for simultaneous deter-mination of chlorogenic acid and baicalin in heat-clearing and detoxicating oral liquid was built by partial least squares and near infrared spectroscopy, and the method of...The calibration model for simultaneous deter-mination of chlorogenic acid and baicalin in heat-clearing and detoxicating oral liquid was built by partial least squares and near infrared spectroscopy, and the method of spectral pre-treatment was discussed. Building model from calibration set obtained good results, and vali-dated by prediction. According to heat-clearing and detoxicating oral liquid from 30 batches of 6 factories, the correlation coefficient of chloro-genic acid and baicalin model are 0.9993 and 0.9923, The root mean square error of cross validation (RMSECV) are 0.467 and 0.480, and the standard Error of prediction (SEP) of chloro- genic acid and baicalin are 0.356 and 0.370 re-spectively. The correlation coefficients in pre-diction set are 0.9997 and 0.9969, prediction results are accurate and reliable. This method can be applied in rapid analysis of heat- clearing and detoxicating oral liquid, and it is fit for on-line detection and has a wide application prospect.展开更多
We propose a cavity length demodulation method that combines virtual reference interferometry（VRI） and minimum mean square error（MMSE） algorithm for fiber-optic Fabry–Perot（F-P） sensors. In contrast to the conv...We propose a cavity length demodulation method that combines virtual reference interferometry（VRI） and minimum mean square error（MMSE） algorithm for fiber-optic Fabry–Perot（F-P） sensors. In contrast to the conventional demodulating method that uses fast Fourier transform（FFT） for cavity length estimation,our method employs the VRI technique to obtain a raw cavity length, which is further refined by the MMSE algorithm. As an experimental demonstration, a fiber-optic F-P sensor based on a sapphire wafer is fabricated for temperature sensing. The VRI-MMSE method is employed to interrogate cavity lengths of the sensor under different temperatures ranging from 28°C to 1000°C. It eliminates the ＂mode jumping＂ problem in the FFT-MMSE method and obtains a precision of 4.8 nm, corresponding to a temperature resolution of 2.0°C over a range of 1000°C. The experimental results reveal that the proposed method provides a promising, high precision alternative for demodulating fiber-optic F-P sensors.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.51175422)
文摘The deployable mechanisms consisting of square units are widely applied in aeronautics and astronautics,biomedicine, architecture and other fields, and joint clearance in such a mechanism is unavoidable. This study is carried out to accurately investigate the dynamic property of the mechanism.Firstly,a dynamics model was built by considering the motion characteristics between elements of joint with clearances. Secondly,based on Floures contact force model and LuGre friction force model,the tangential and normal contact force of revolute pair element with clearance were calculated respectively. Finally,square combined mechanisms' dynamic analytical method considering joint clearance was investigated, and constraint renege problem was resolved by adopting Baumgarte stable constraint method in integration process.Analytical result indicates that the impact of joint clearance on dynamic property of square combined mechanism should not be neglected.
基金Supported by the Special Fund for Agro-scientific Research in the Public Interest(No.201203018)
文摘The shrimp beam trawl fishery in the northern South China Sea is characterized by high by-catch and poor selectivity problems.Among by-catch species,banded scad(Caranx(Atule)kalla)is economically the most important one.The aim of this study is to improve the selective properties of codends for banded scad.Size selectivity of 2 traditional diamond mesh codends,with mesh size 25 and 30 mm(defined as D25 and D30,respectively),and 4 new combined square and diamond mesh codends,with25 mm square-mesh and 25 mm diamond-mesh(S25+D25),30 mm square-mesh and 25 mm diamondmesh(S30+D25),35 mm square-mesh and 25 mm diamond-mesh(S35+D25),and 35 mm square-mesh and18 mm diamond-mesh(S35+D18),were tested for banded scad in shrimp beam trawl fishery of the South China Sea.A total of 54 valid hauls were finished using the covered codend method,and 5750 banded scad were caught.Selective parameters were obtained using the logistic equation with the maximum likelihood method,by incorporating the between-haul variation.The results show that the present minimum mesh size for shrimp beam trawl in the South China Sea,25-mm diamond mesh size,is insufficient to release immature banded scad.The S35+D25 codend is proved to be the most eff ective codend to release immature banded scad,and its 50%retention length(L _(50))is larger than the minimum landing size(MLS=63.5 mm)of banded scad.However,the 95%confidence intervals of L _(50) overlap among the three combined mesh codends,the S25+D25,S30+D25 and S35+D25 codend.For a sustainable exploitation of banded scad,larger mesh sizes are suggested to be investigated for the combined mesh codends.
基金support of "111" project which was from China Education Department( No. B07019)
文摘The article studies the oscillation features of the water in the square moon pool under the circumstances of wave-flow combined conditions. Comparing with the results of experiments of the square moon pool, a series of studies reveal that the water piston oscillation phenomenon is quite similar to that of the circular one. Two types of oscillation are exhibited under different incoming wave periods, i.e. self-excited oscillation and forced oscillation. The difference between the circular and square moon pool is that the attack angle makes greater influences on the square one. "Beating phenomenon" is also found in the square moon pool which is not mentioned of the circular one.
文摘AIM: To assess the outcomes of combined 23-gauge sutureless vitrectomy and clear corneal phacoemulsification with intraocular lens implantation for rhegmatogenous retinal detachment(RRD) repair.METHODS: This was a retrospective, consecutive,noncomparative, interventional case series of 30 eyes of30 patients who underwent combined sutureless vitrectomy and clear corneal cataract surgery for the repair of RRD. The principal outcome measures were primary anatomical success rate, reasons for redetachment, final visual acuity, and surgical complications.RESULTS: Primary reattachment was achieved in 27eyes(90.0%). The reasons for redetachment(3 eyes, 10%)were incomplete laser retinopexy, persistent chronic subretinal fluid, and proliferative vitreoretinopathy,respectively. The logarithm of the minimum angle of resolution visual acuity(mean±SD) improved from 0.76±0.74 preoperatively to 0. 21 ± 0. 37 6 months’ postoperatively(P 【0.0001). Postoperative hypotony was not detected,but 1 eye( 3. 3 %) had increased intraocular pressure(30 mm Hg) with spontaneous resolution. No endophthalmitis developed during follow-up. Macular pucker was detected in 3 eyes(10.0%).· CONCLUSION: Combined 23-gauge sutureless vitrectomy and clear corneal phacoemulsification with intraocular lens implantation for RRD repair was proven safe and effective. It may provide not only the known advantages of conventional combined surgery, but also additional advantages such as less conjunctival fibrosis and the maintenance of stable intraocular pressure with low risks of postoperative hypotony and intraocular pressure elevation.
文摘Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of power system. To cope with the problems existing in the ESDD predicting by multivariate linear regression (MLR), back propagation (BP) neural network and least squares support vector machines (LSSVM), a nonlinear combination forecasting model based on wavelet neural network (WNN) for ESDD is proposed. The model is a WNN with three layers, whose input layer has three neurons and output layer has one neuron, namely, regarding the ESDD forecasting results of MLR, BP and LSSVM as the inputs of the model and the observed value as the output. In the interest of better reflection of the influence of each single forecasting model on ESDD and increase of the accuracy of ESDD prediction, Morlet wavelet is used to con-struct WNN, error backpropagation algorithm is adopted to train the network and genetic algorithm is used to determine the initials of the parameters. Simulation results show that the accuracy of the proposed combina-tion ESDD forecasting model is higher than that of any single model and that of traditional linear combina-tion forecasting (LCF) model. The model provides a new feasible way to increase the accuracy of pollution distribution map of power network.
文摘A fast edge detection method basing on the combination of fuzzy subsets is developed, in which the detection of an edge as a classification problem will be considered, partitioning the image into two portions: the edge portion and the non-edge portion. The latter one, as the main constituent of an image, consists of the object and its background. Removing the non-edge portion from an image, the remainder is nothing but the edge of this image. As far as the fuzziness of the edge of an image is concerned, some fuzzy operations can be made. In this paper, the gray level histogram is partitioned into several sub-regions, and some operations are performed with the associated fuzzy subsets corresponding to those sub-edges in the sub-regions on the gray-level-square-difference histogram, and the edge of this image is finally obtained. Practical examples in this paper illustrate that, the described method is simple and effective to achieve an ideal edge image.
文摘The influences of various kinds of UV-absorbers, antioxidants and their mixtures on UV-aging resis- tance of transparent unsaturated polyester FRP are studied by artificial aocelerating aging test.The results show that the UV-aging resistance of com- bined stabilizers is better than single stabilizer. It is concluded that the cooperative effect of UV -absorbers is caused bg the increase of wave leng- th and intensity of the absorption light the coopora- tive effect of UV-absorbers and antioxidants is caused by Dreventing the photo-oxidantion.
文摘The calibration model for simultaneous deter-mination of chlorogenic acid and baicalin in heat-clearing and detoxicating oral liquid was built by partial least squares and near infrared spectroscopy, and the method of spectral pre-treatment was discussed. Building model from calibration set obtained good results, and vali-dated by prediction. According to heat-clearing and detoxicating oral liquid from 30 batches of 6 factories, the correlation coefficient of chloro-genic acid and baicalin model are 0.9993 and 0.9923, The root mean square error of cross validation (RMSECV) are 0.467 and 0.480, and the standard Error of prediction (SEP) of chloro- genic acid and baicalin are 0.356 and 0.370 re-spectively. The correlation coefficients in pre-diction set are 0.9997 and 0.9969, prediction results are accurate and reliable. This method can be applied in rapid analysis of heat- clearing and detoxicating oral liquid, and it is fit for on-line detection and has a wide application prospect.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61377091 and61505152)the Pre-research Field Foundation of China(No.6140243010116QT69001)the Applied Basic Research Program of Wuhan,China(No.2017010201010102)
文摘We propose a cavity length demodulation method that combines virtual reference interferometry（VRI） and minimum mean square error（MMSE） algorithm for fiber-optic Fabry–Perot（F-P） sensors. In contrast to the conventional demodulating method that uses fast Fourier transform（FFT） for cavity length estimation,our method employs the VRI technique to obtain a raw cavity length, which is further refined by the MMSE algorithm. As an experimental demonstration, a fiber-optic F-P sensor based on a sapphire wafer is fabricated for temperature sensing. The VRI-MMSE method is employed to interrogate cavity lengths of the sensor under different temperatures ranging from 28°C to 1000°C. It eliminates the ＂mode jumping＂ problem in the FFT-MMSE method and obtains a precision of 4.8 nm, corresponding to a temperature resolution of 2.0°C over a range of 1000°C. The experimental results reveal that the proposed method provides a promising, high precision alternative for demodulating fiber-optic F-P sensors.
