In astronomy,the brightness of a source is typically expressed in terms of magnitude.Conventionally,the magnitude is defined by the logarithm of received flux.This relationship is known as the Pogson formula.For recei...In astronomy,the brightness of a source is typically expressed in terms of magnitude.Conventionally,the magnitude is defined by the logarithm of received flux.This relationship is known as the Pogson formula.For received flux with a small signal to noise ratio（S/N）,however,the formula gives a large magnitude error.We investigate whether the use of Inverse Hyperbolic Sine function（hereafter referred to as the Asinh magnitude）in the modified formulae could allow for an alternative calculation of magnitudes for small S/N flux,and whether the new approach is better for representing the brightness of that region.We study the possibility of increasing the detection level of gravitational microlensing using 40 selected microlensing light curves from the 2013 and 2014 seasons and by using the Asinh magnitude.Photometric data of the selected events are obtained from the Optical Gravitational Lensing Experiment（OGLE）.We found that utilization of the Asinh magnitude makes the events brighter compared to using the logarithmic magnitude,with an average of about 3.42×10^（-2）magnitude and an average in the difference of error between the logarithmic and the Asinh magnitude of about 2.21×10（-2）magnitude.The microlensing events OB140847 and OB140885 are found to have the largest difference values among the selected events.Using a Gaussian fit to find the peak for OB140847 and OB140885,we conclude statistically that the Asinh magnitude gives better mean squared values of the regression and narrower residual histograms than the Pogson magnitude.Based on these results,we also attempt to propose a limit in magnitude value for which use of the Asinh magnitude is optimal with small S/N data.展开更多
Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version...Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version of a previously developed spectroscopic lensing search method to the SDSS-Ⅲ BOSS and proposed a list of highly possible candidates.Follow-up CFHT Megacam imaging observations were performed for five systems,and two out of five are probably strong lensing systems with at least one image close to the central galaxy,although no counter images are detected.展开更多
During the design process of Blu-ray disc optical pick-up （BD OPU）, the optical system and the collimator lens design is especially important. This paper designs an optical system and some lenses for＇the BD OPU, in...During the design process of Blu-ray disc optical pick-up （BD OPU）, the optical system and the collimator lens design is especially important. This paper designs an optical system and some lenses for＇the BD OPU, including collimator lens, beam shaping lens for laser beam shaping, and cylinder lens for signal detecting. In this OPU, we use a triplet lens to collimate the laser beam. At the same time, we build a series of assembly jigs to make sure that each lens can be put into the OPU basement properly. At last, we get the reading spot image and S-curve photo of OPU, which can be used to read Blu-ray disc （BD）.展开更多
基金DIKTI Kementerian Riset Teknologi dan Pendidikan Tinggi for the 2014 research grant with contract number: 1062d/I1.C0I/PL/2014
文摘In astronomy,the brightness of a source is typically expressed in terms of magnitude.Conventionally,the magnitude is defined by the logarithm of received flux.This relationship is known as the Pogson formula.For received flux with a small signal to noise ratio（S/N）,however,the formula gives a large magnitude error.We investigate whether the use of Inverse Hyperbolic Sine function（hereafter referred to as the Asinh magnitude）in the modified formulae could allow for an alternative calculation of magnitudes for small S/N flux,and whether the new approach is better for representing the brightness of that region.We study the possibility of increasing the detection level of gravitational microlensing using 40 selected microlensing light curves from the 2013 and 2014 seasons and by using the Asinh magnitude.Photometric data of the selected events are obtained from the Optical Gravitational Lensing Experiment（OGLE）.We found that utilization of the Asinh magnitude makes the events brighter compared to using the logarithmic magnitude,with an average of about 3.42×10^（-2）magnitude and an average in the difference of error between the logarithmic and the Asinh magnitude of about 2.21×10（-2）magnitude.The microlensing events OB140847 and OB140885 are found to have the largest difference values among the selected events.Using a Gaussian fit to find the peak for OB140847 and OB140885,we conclude statistically that the Asinh magnitude gives better mean squared values of the regression and narrower residual histograms than the Pogson magnitude.Based on these results,we also attempt to propose a limit in magnitude value for which use of the Asinh magnitude is optimal with small S/N data.
基金partly supported by the National Key Basic Research and Development Program of China(No.2018YFA0404501 to SM)the National Natural Science Foundation of China(Grant Nos.11821303 and 11761131004 to SM)
文摘Strong lensing is one of the most spectacular views in the universe.Many cosmological applications have been proposed,but the number of such lensing systems is still limited.In this work,we applied an improved version of a previously developed spectroscopic lensing search method to the SDSS-Ⅲ BOSS and proposed a list of highly possible candidates.Follow-up CFHT Megacam imaging observations were performed for five systems,and two out of five are probably strong lensing systems with at least one image close to the central galaxy,although no counter images are detected.
基金the project cooperated by Optical Memory National Engineering Research Center,Tsinghua University and Philips Investment Co.,Ltd.
文摘During the design process of Blu-ray disc optical pick-up （BD OPU）, the optical system and the collimator lens design is especially important. This paper designs an optical system and some lenses for＇the BD OPU, including collimator lens, beam shaping lens for laser beam shaping, and cylinder lens for signal detecting. In this OPU, we use a triplet lens to collimate the laser beam. At the same time, we build a series of assembly jigs to make sure that each lens can be put into the OPU basement properly. At last, we get the reading spot image and S-curve photo of OPU, which can be used to read Blu-ray disc （BD）.
