In order to achieve high-precision, controllable rotation of uniaxial birefringent crystal particles, we study the principle of optical rotation due to the transfer of spin angular momentum from light to birefringent crystal particles. The interaction process between the beam and particles is affected by various factors existed actually, for instance: the reflection of beam on the crystal surface, laser power, the set of angle between the crystal optical axis and surface, radius, phase difference between the ordinary ray and extraordinary ray. According to the analysis of these factors, the theoretical model of optical rotation is reconstructed. The theoretical curves of calcium carbonate and silicon particles chosen as experimental material between the rotational frequency and the radius are simulated and calculated. The result shows that the rotation frequency is inversely proportional to the cube of radius, and compared the performance of modified model with traditional model. The birefringent particles are rotated by optical tweezers in the experiment, and rotation frequency is measured with the same laser power. According to the experimental results of optical rotation, the modified Friese theoretical model is proved to be the reasonably and excellence, in addition, the result shows the maximum frequency of calcium carbonate is 19.1Hz, and the maximum frequency of silicon particles is 11.5Hz. The rationality of our experiment is testified by compared with theoretical analysis. Our study has great directive significance to the design of optical driven micro-mechanical motor and the material selection of rotor.
{"title":"Rotational analysis of birefringent crystal particles based on modified theory in optical tweezers","authors":"Yong Wei, Yan-ying Zhu, Wenzhe Yao, H. Pei","doi":"10.1117/12.2179434","DOIUrl":"https://doi.org/10.1117/12.2179434","url":null,"abstract":"In order to achieve high-precision, controllable rotation of uniaxial birefringent crystal particles, we study the principle of optical rotation due to the transfer of spin angular momentum from light to birefringent crystal particles. The interaction process between the beam and particles is affected by various factors existed actually, for instance: the reflection of beam on the crystal surface, laser power, the set of angle between the crystal optical axis and surface, radius, phase difference between the ordinary ray and extraordinary ray. According to the analysis of these factors, the theoretical model of optical rotation is reconstructed. The theoretical curves of calcium carbonate and silicon particles chosen as experimental material between the rotational frequency and the radius are simulated and calculated. The result shows that the rotation frequency is inversely proportional to the cube of radius, and compared the performance of modified model with traditional model. The birefringent particles are rotated by optical tweezers in the experiment, and rotation frequency is measured with the same laser power. According to the experimental results of optical rotation, the modified Friese theoretical model is proved to be the reasonably and excellence, in addition, the result shows the maximum frequency of calcium carbonate is 19.1Hz, and the maximum frequency of silicon particles is 11.5Hz. The rationality of our experiment is testified by compared with theoretical analysis. Our study has great directive significance to the design of optical driven micro-mechanical motor and the material selection of rotor.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115894546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fabry–Pérot interferometer is a multi-beam interferometer, with the advantage of high spectral resolution, and can be used to research the fine structure of the matter. The application of Fabry–Pérot interferometer in spectral imaging instrument will improve the spectral resolution. And it can also enhance the structural efficiency and promote the miniaturization of the spectral imaging instrument, which makes it convenient to be used in aviation and space applications. Here, we propose a method of hyperspectral Imaging based on Tunable Fabry–Pérot interferometer. At first, the time-domain interferogram is obtained by adjusting the cavity length during shooting, then, the corresponding relationship between the interferogram and the spectral curve can be described by the theoretical model of multi-beam interference, and linear equations can be obtained by discretizing the theoretical model. Finally, the spectral curve can be obtained by solving the equations. Good results come out of the simulation of this method. It has high precision and spectral resolution.
{"title":"Simulation of hyperspectral imaging based on tunable Fabry-Pérot interferometer","authors":"Chengmiao Liu, Jianxin Li, Yusheng Sun, R. Zhu","doi":"10.1117/12.2180220","DOIUrl":"https://doi.org/10.1117/12.2180220","url":null,"abstract":"Fabry–Pérot interferometer is a multi-beam interferometer, with the advantage of high spectral resolution, and can be used to research the fine structure of the matter. The application of Fabry–Pérot interferometer in spectral imaging instrument will improve the spectral resolution. And it can also enhance the structural efficiency and promote the miniaturization of the spectral imaging instrument, which makes it convenient to be used in aviation and space applications. Here, we propose a method of hyperspectral Imaging based on Tunable Fabry–Pérot interferometer. At first, the time-domain interferogram is obtained by adjusting the cavity length during shooting, then, the corresponding relationship between the interferogram and the spectral curve can be described by the theoretical model of multi-beam interference, and linear equations can be obtained by discretizing the theoretical model. Finally, the spectral curve can be obtained by solving the equations. Good results come out of the simulation of this method. It has high precision and spectral resolution.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116510705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Local memory architecture plays an important role in high performance massively parallel vision chip. In this paper, we propose an enhanced memory architecture with compact circuit area designed in a full-custom flow. The memory consists of separate master-stage static latches and shared slave-stage dynamic latches. We use split transmission transistors on the input data path to enhance tolerance for charge sharing and to achieve random read/write capabilities. The memory is designed in a 0.18 μm CMOS process. The area overhead of the memory achieves 16.6 μm2/bit. Simulation results show that the maximum operating frequency reaches 410 MHz and the corresponding peak dynamic power consumption for a 64-bit memory unit is 190 μW under 1.8 V supply voltage.
{"title":"Enhanced memory architecture for massively parallel vision chip","authors":"Zhe Chen, Jie Yang, Liyuan Liu, N. Wu","doi":"10.1117/12.2179447","DOIUrl":"https://doi.org/10.1117/12.2179447","url":null,"abstract":"Local memory architecture plays an important role in high performance massively parallel vision chip. In this paper, we propose an enhanced memory architecture with compact circuit area designed in a full-custom flow. The memory consists of separate master-stage static latches and shared slave-stage dynamic latches. We use split transmission transistors on the input data path to enhance tolerance for charge sharing and to achieve random read/write capabilities. The memory is designed in a 0.18 μm CMOS process. The area overhead of the memory achieves 16.6 μm2/bit. Simulation results show that the maximum operating frequency reaches 410 MHz and the corresponding peak dynamic power consumption for a 64-bit memory unit is 190 μW under 1.8 V supply voltage.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124990495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yucui Dong, Fansheng Chen, Yun Wang, Xiaofeng Su, Wei Wang
It is always affected by the influence of limb atmosphere when the space-based remote sensing systems detect spatial targets using limb observation mode. In this paper, the characteristics of the limb atmosphere and the impact of limb atmosphere to target observation are theoretical modeled. Based on the model, we propose an algorithm to compute the vertical structure of atmosphere radiance through the image of limb atmosphere as well as the star image. Realization of atmosphere radiance under similar situation can then be computed based on inversion algorithm proposed in the paper. The stellar images of different areas including areas over Antarctic and Equator are captured by in-orbit space borne camera. The method of how to inverse from the gray image to atmosphere limb radiance in engineering applications is described in detail and statistical analysis of the result of inversion to limb atmosphere radiance is conducted whose trend is consistent with simulation result of MODTRAN which increases at lower altitude to a peak value then drop to zero slowly while there are two peaks in the statistical radiance distribution curves illustrating the polar light over Antarctic.
{"title":"A limb atmospheric radiance inversion method based on a sun-synchronous orbit satellite","authors":"Yucui Dong, Fansheng Chen, Yun Wang, Xiaofeng Su, Wei Wang","doi":"10.1117/12.2180861","DOIUrl":"https://doi.org/10.1117/12.2180861","url":null,"abstract":"It is always affected by the influence of limb atmosphere when the space-based remote sensing systems detect spatial targets using limb observation mode. In this paper, the characteristics of the limb atmosphere and the impact of limb atmosphere to target observation are theoretical modeled. Based on the model, we propose an algorithm to compute the vertical structure of atmosphere radiance through the image of limb atmosphere as well as the star image. Realization of atmosphere radiance under similar situation can then be computed based on inversion algorithm proposed in the paper. The stellar images of different areas including areas over Antarctic and Equator are captured by in-orbit space borne camera. The method of how to inverse from the gray image to atmosphere limb radiance in engineering applications is described in detail and statistical analysis of the result of inversion to limb atmosphere radiance is conducted whose trend is consistent with simulation result of MODTRAN which increases at lower altitude to a peak value then drop to zero slowly while there are two peaks in the statistical radiance distribution curves illustrating the polar light over Antarctic.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127144375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiping Xu, Zizhao Zhao, Wei‐Wen Lan, Lei Sha, Cheng Qian
This paper discusses the adaptive fuzzy control and neural network BP algorithm in large flat automatic leveling control system application. The purpose is to develop a measurement system with a flat quick leveling, Make the installation on the leveling system of measurement with tablet, to be able to achieve a level in precision measurement work quickly, improve the efficiency of the precision measurement. This paper focuses on the automatic leveling system analysis based on fuzzy controller, Use of the method of combining fuzzy controller and BP neural network, using BP algorithm improve the experience rules .Construct an adaptive fuzzy control system. Meanwhile the learning rate of the BP algorithm has also been run-rate adjusted to accelerate convergence. The simulation results show that the proposed control method can effectively improve the leveling precision of automatic leveling system and shorten the time of leveling.
{"title":"Study on application of adaptive fuzzy control and neural network in the automatic leveling system","authors":"Xiping Xu, Zizhao Zhao, Wei‐Wen Lan, Lei Sha, Cheng Qian","doi":"10.1117/12.2179681","DOIUrl":"https://doi.org/10.1117/12.2179681","url":null,"abstract":"This paper discusses the adaptive fuzzy control and neural network BP algorithm in large flat automatic leveling control system application. The purpose is to develop a measurement system with a flat quick leveling, Make the installation on the leveling system of measurement with tablet, to be able to achieve a level in precision measurement work quickly, improve the efficiency of the precision measurement. This paper focuses on the automatic leveling system analysis based on fuzzy controller, Use of the method of combining fuzzy controller and BP neural network, using BP algorithm improve the experience rules .Construct an adaptive fuzzy control system. Meanwhile the learning rate of the BP algorithm has also been run-rate adjusted to accelerate convergence. The simulation results show that the proposed control method can effectively improve the leveling precision of automatic leveling system and shorten the time of leveling.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114527298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An ultrasonic hydrophone based on a dual polarization distributed Bragg reflector (DBR) fiber laser is described, and its application to detecting the vector medical ultrasound is demonstrated. The principle of the hydrophone is based on the detection of output beat frequency signal modulated by ultrasound. The amplitude, frequency and orientation of the ultrasound can be determined by the using the upper and lower sideband frequency. It has been found that the hydrophone has an orientation recognizable ability which the piezoelectric ultrasonic immersion transducer doesn’t have. It suggests that the type of hydrophone can provide an alternative to piezoelectric hydrophone technology.
{"title":"A fiber DBR laser based vector hydrophone for ultrasonic medical applications","authors":"Han Wang, Xi Guo, Jingyi Gao, Chengang Lyu","doi":"10.1117/12.2178433","DOIUrl":"https://doi.org/10.1117/12.2178433","url":null,"abstract":"An ultrasonic hydrophone based on a dual polarization distributed Bragg reflector (DBR) fiber laser is described, and its application to detecting the vector medical ultrasound is demonstrated. The principle of the hydrophone is based on the detection of output beat frequency signal modulated by ultrasound. The amplitude, frequency and orientation of the ultrasound can be determined by the using the upper and lower sideband frequency. It has been found that the hydrophone has an orientation recognizable ability which the piezoelectric ultrasonic immersion transducer doesn’t have. It suggests that the type of hydrophone can provide an alternative to piezoelectric hydrophone technology.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133461010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surface deformation is the crucial factor for the imaging performance of the lithographic object lens in the manufacturing process. Simulation of surface deformation can predict the degradation of the wavefront error caused by surface deformation, find the lens which is most sensitive to the surface deformation even in the design phase. We develop a method to simulate the surface deformation by Zernike polynomials in this paper. In fact, the surface deformation generated in the manufacturing process is random. However, it does not mean that they have no rules at all. We analysize the Zernike coefficients distribution of the interferential data, and build a model to simulate the surface deformation. The model can generate random-surface-deformation according to the input RMS/PV bound in the form of INT file type, which can be added to the lens surface directly in the optical design program CODEV. The results show that the surface deformation generated by our model can simulate the interferential data very well.
{"title":"Simulation of surface deformation for the lithographic object lens by Zernike polynomials","authors":"Bin Cong, Tongxun Yi","doi":"10.1117/12.2175664","DOIUrl":"https://doi.org/10.1117/12.2175664","url":null,"abstract":"Surface deformation is the crucial factor for the imaging performance of the lithographic object lens in the manufacturing process. Simulation of surface deformation can predict the degradation of the wavefront error caused by surface deformation, find the lens which is most sensitive to the surface deformation even in the design phase. We develop a method to simulate the surface deformation by Zernike polynomials in this paper. In fact, the surface deformation generated in the manufacturing process is random. However, it does not mean that they have no rules at all. We analysize the Zernike coefficients distribution of the interferential data, and build a model to simulate the surface deformation. The model can generate random-surface-deformation according to the input RMS/PV bound in the form of INT file type, which can be added to the lens surface directly in the optical design program CODEV. The results show that the surface deformation generated by our model can simulate the interferential data very well.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130453678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Fourier transform spectrometer without slit has the advantages of high radiation throughput and high spatial resolution. It can be used for detecting more details of the spectral and spatial information. We present the initial structure of the collimator and objective based on the analysis of the principle of the Fourier transform spectrometer. Then the collimator and objective are optimized by Zemax. The MTF of the cut-off frequency is great than 0.7. The tunable lateral shearing splitter is used as the interferometer, which makes the system more compact compared with the system using Sagnac lateral shearing splitter. The method to calculate the geometric dimension of the splitter is presented. Then the complete Fourier transform spectrometer is designed. The MTF of the cut-off frequency is great than 0.6. And the largest RMS of the spot is less than 6μm.
{"title":"System design of Fourier transform imaging spectrometer using tunable lateral shearing splitter","authors":"Xin Meng, Jianxin Li, Caixun Bai, R. Zhu","doi":"10.1117/12.2179843","DOIUrl":"https://doi.org/10.1117/12.2179843","url":null,"abstract":"The Fourier transform spectrometer without slit has the advantages of high radiation throughput and high spatial resolution. It can be used for detecting more details of the spectral and spatial information. We present the initial structure of the collimator and objective based on the analysis of the principle of the Fourier transform spectrometer. Then the collimator and objective are optimized by Zemax. The MTF of the cut-off frequency is great than 0.7. The tunable lateral shearing splitter is used as the interferometer, which makes the system more compact compared with the system using Sagnac lateral shearing splitter. The method to calculate the geometric dimension of the splitter is presented. Then the complete Fourier transform spectrometer is designed. The MTF of the cut-off frequency is great than 0.6. And the largest RMS of the spot is less than 6μm.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134131127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nan Chen, Zhengfen Li, Shengyou Zhong, Mei Zou, L. Yao
An incremental sigma-delta ADC is designed for column-parallel ADC array in CMOS image sensor. Sigma-delta modulator with single-loop single-bit structure is chosen for power consumption and performance reasons. Second-order modulator is used to reduce conversion time, without stability problem and large area accompanied by higher order sigma-delta modulator. The asymmetric current mirror amplifier used in integrator reduces more than 30% power dissipation. The digital filter and decimator are implemented by counters and adders with significantly reduced chip area and power consumption. A Clock generator is shared by 8 ADCs for trade-off among power, area and clock loading. The ADC array is implemented in a 0.18-μm CMOS technology and clocked at 10 MHz, and the simulated resolution achieves 15-bit with 255 clock cycles. The average power consumption per ADC is 118 μW including clock generator, and the area is only 0.0053 μm2.
{"title":"A 15-bit incremental sigma-delta ADC for CMOS image sensor","authors":"Nan Chen, Zhengfen Li, Shengyou Zhong, Mei Zou, L. Yao","doi":"10.1117/12.2180830","DOIUrl":"https://doi.org/10.1117/12.2180830","url":null,"abstract":"An incremental sigma-delta ADC is designed for column-parallel ADC array in CMOS image sensor. Sigma-delta modulator with single-loop single-bit structure is chosen for power consumption and performance reasons. Second-order modulator is used to reduce conversion time, without stability problem and large area accompanied by higher order sigma-delta modulator. The asymmetric current mirror amplifier used in integrator reduces more than 30% power dissipation. The digital filter and decimator are implemented by counters and adders with significantly reduced chip area and power consumption. A Clock generator is shared by 8 ADCs for trade-off among power, area and clock loading. The ADC array is implemented in a 0.18-μm CMOS technology and clocked at 10 MHz, and the simulated resolution achieves 15-bit with 255 clock cycles. The average power consumption per ADC is 118 μW including clock generator, and the area is only 0.0053 μm2.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"9522 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129491389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The revolution in dual-band infrared focal plane arrays over the past ten years has induced a significant impact on dual-band imaging system design. There are numerous challenges facing dual-band imaging system design using traditional methods. In this paper, Wavefront Coding technique is used to offer the potential implementation of infrared dual-band achromatic and diffraction-limited imaging by using simple optics. An example in terms of a one-element dual-band infrared imager is given.
{"title":"Dual-band infrared optical imaging system design by wavefront coding","authors":"Q. Fu","doi":"10.1117/12.2179330","DOIUrl":"https://doi.org/10.1117/12.2179330","url":null,"abstract":"The revolution in dual-band infrared focal plane arrays over the past ten years has induced a significant impact on dual-band imaging system design. There are numerous challenges facing dual-band imaging system design using traditional methods. In this paper, Wavefront Coding technique is used to offer the potential implementation of infrared dual-band achromatic and diffraction-limited imaging by using simple optics. An example in terms of a one-element dual-band infrared imager is given.","PeriodicalId":225534,"journal":{"name":"Photoelectronic Technology Committee Conferences","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124907951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}