The paper introduces some of the recent developments in beam diagnostics,which include the beam position measurement techniques with sub-micrometer resolution,the beam size measurement techniques with sub-micrometer r...The paper introduces some of the recent developments in beam diagnostics,which include the beam position measurement techniques with sub-micrometer resolution,the beam size measurement techniques with sub-micrometer resolution,and the bunch length measurement techniques with sub-picosecond resolution.The cavity beam position monitor and the digital BPM signal processing technique are introduced for the beam position measurement techniques. The laser wire beam profile monitor,and the optical transition radiation/optical diffraction radiation beam size monitor are introduced for the beam size measurement techniques.The spectral techniques of coherent radiation,the transverse deflecting cavity,the rf zero-phasing technique,and the electro-optic techniques are introduced for the bunch length measurement techniques.展开更多
The fabrication technique of micro/nano-scale speckle patterns with focused ion beam (FIB) system is studied for digital image correlation (DIC) measurement under a scanning electron microscope (SEM).The speckle patte...The fabrication technique of micro/nano-scale speckle patterns with focused ion beam (FIB) system is studied for digital image correlation (DIC) measurement under a scanning electron microscope (SEM).The speckle patterns are fabricated by directly etching the counterpart of the specimen to the black part of a template.Mean intensity gradient is used to evaluate the quality of these SEM images of speckle patterns fabricated based on different templates to select an optimum template.The pattern size depending on the displacement measurement sensitivity is adjusted by altering the magnification of FIB according to the relation curve of the etching size versus magnification.The influencing factors including etching time and ion beam current are discussed.Rigid body translation tests and rotation tests are carried out under SEM to verify the reliability of the fabricated speckle patterns.The calculated values are in good agreement with the imposed ones.展开更多
High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion(ICF) and optical communication. However, traditional optical vorti...High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion(ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam(PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm(GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation,which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.展开更多
Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and p...Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.展开更多
BACKGROUND Digital intraoral scanning,although developing rapidly,is rarely used in occlusal reconstruction.To compensate for the technical drawbacks of current occlusal reconstruction techniques,such as time consumpt...BACKGROUND Digital intraoral scanning,although developing rapidly,is rarely used in occlusal reconstruction.To compensate for the technical drawbacks of current occlusal reconstruction techniques,such as time consumption and high technical requirements,digital intraoral scanning can be used in clinics.This report aims to provide a way of selecting the most suitable maxillo-mandibular relationship(MMR)during recovery.CASE SUMMARY A 68-year-old man with severely worn posterior teeth underwent occlusal reconstruction with fixed prosthesis using digital intraoral scanning.A series of digital models in different stages of treatment were obtained,subsequently compared,and selected using digital intraoral scanning together with traditional measurements,such as cone beam computed tomography,joint imaging,and clinical examination.Using digital intraoral scanning,the MMR in different stages of treatment was accurately recorded,which provided feasibility for deciding the best occlusal reconstruction treatment,made the treatment process easier,and improved patient satisfaction.CONCLUSION This case report highlights the clarity,recordability,repeatability,and selectivity of digital intraoral scanning to replicate and transfer the MMR during occlusal reconstruction,expanding new perspectives for its design,fabrication,and postoperative evaluation.展开更多
Residual stress plays a vital role in the structural strength and stability. The determination of residual stress at single-point has become mature at present. However, the method to determine residual stress distribu...Residual stress plays a vital role in the structural strength and stability. The determination of residual stress at single-point has become mature at present. However, the method to determine residual stress distribution is still in shortage. For this problem, a finite element approach combined with slot milling method was developed in this study. In the method, firstly a slot is milled on the specimen surface to release the residual stress and then the released displacement field is measured by optical method, such as digital image correlation （DIC）, finally the finite element approach is used to determine the residual stress distribution along the slot. In order to verify the feasibility of the method, it was applied to study the residual stress introduced by shot peening, mainly about the stress distribution along the direction vertical to the shot peened surface. Since the influence depth of shot peening was too small, we utilized focused ion beam （FIB） to determine the microscale residual stress distribution. The result measured by X-ray diffraction （XRD） demonstrated that the method was feasible to determine the residual stress distribution.展开更多
Purpose Hundreds of digital beam position monitor processors(DBPM)are required to be produced during the construction of projects such as High Energy Photon Source(HEPS)and the upgrade project of the Beijing Electron ...Purpose Hundreds of digital beam position monitor processors(DBPM)are required to be produced during the construction of projects such as High Energy Photon Source(HEPS)and the upgrade project of the Beijing Electron Positron Collider(BEPCII),which brings great challenges to the test work.In order to achieve accurate,fast,and complete mass production tests of DBPMs,an automatic test system(ATS)has been developed in this article.Methods According to the test items of DBPM,the standardized testing softwareflow is designed based on virtual instru-ment program control technology and experimental physics and industrial control system(EPICS),which realize automatic adjustment of test parameters and automatic acquisition of test result data.Results and conclusions The ATS can realize one-button testing of channel coefficients,channel linearity,attenuator linearity,beam current dependence(BCD)and sampling signal-to-noise ratio(SNR),and generate test reports.The total test time is less than 3 minutes,which is significantly more efficient compared to manual testing.More than 90 BEPCII DBPMs has been tested by this ATS in the lab.The test results proved that such a system could automatically recognize defective products and satisfy the requirements of mass testing.展开更多
文摘The paper introduces some of the recent developments in beam diagnostics,which include the beam position measurement techniques with sub-micrometer resolution,the beam size measurement techniques with sub-micrometer resolution,and the bunch length measurement techniques with sub-picosecond resolution.The cavity beam position monitor and the digital BPM signal processing technique are introduced for the beam position measurement techniques. The laser wire beam profile monitor,and the optical transition radiation/optical diffraction radiation beam size monitor are introduced for the beam size measurement techniques.The spectral techniques of coherent radiation,the transverse deflecting cavity,the rf zero-phasing technique,and the electro-optic techniques are introduced for the bunch length measurement techniques.
基金supported by the National Basic Research Program of China (Grant Nos.2010CB631005 and 2011CB606105)the National Natural Science Foundation of China (Grant Nos.90916010 and 11172151)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20090002110048)
文摘The fabrication technique of micro/nano-scale speckle patterns with focused ion beam (FIB) system is studied for digital image correlation (DIC) measurement under a scanning electron microscope (SEM).The speckle patterns are fabricated by directly etching the counterpart of the specimen to the black part of a template.Mean intensity gradient is used to evaluate the quality of these SEM images of speckle patterns fabricated based on different templates to select an optimum template.The pattern size depending on the displacement measurement sensitivity is adjusted by altering the magnification of FIB according to the relation curve of the etching size versus magnification.The influencing factors including etching time and ion beam current are discussed.Rigid body translation tests and rotation tests are carried out under SEM to verify the reliability of the fabricated speckle patterns.The calculated values are in good agreement with the imposed ones.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2020A1515111143)the Natural Science Foundation of Guangdong Province(Grant Nos.2021A1515011532 and 2023ZDZX3022)Shenzhen Government’s Plan of Science and Technology(Grant Nos.JCYJ20220818100019040,RCYX20210609103157071,and JCYJ20230808105713028)。
文摘High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion(ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam(PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm(GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation,which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.
基金supported by the National Natural Science Foundation of China(Grant Nos.62101258,62071235 and 62271260)the Jiangsu Province Science&Technology Department(Grant No.BE2021017).
文摘Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.
文摘BACKGROUND Digital intraoral scanning,although developing rapidly,is rarely used in occlusal reconstruction.To compensate for the technical drawbacks of current occlusal reconstruction techniques,such as time consumption and high technical requirements,digital intraoral scanning can be used in clinics.This report aims to provide a way of selecting the most suitable maxillo-mandibular relationship(MMR)during recovery.CASE SUMMARY A 68-year-old man with severely worn posterior teeth underwent occlusal reconstruction with fixed prosthesis using digital intraoral scanning.A series of digital models in different stages of treatment were obtained,subsequently compared,and selected using digital intraoral scanning together with traditional measurements,such as cone beam computed tomography,joint imaging,and clinical examination.Using digital intraoral scanning,the MMR in different stages of treatment was accurately recorded,which provided feasibility for deciding the best occlusal reconstruction treatment,made the treatment process easier,and improved patient satisfaction.CONCLUSION This case report highlights the clarity,recordability,repeatability,and selectivity of digital intraoral scanning to replicate and transfer the MMR during occlusal reconstruction,expanding new perspectives for its design,fabrication,and postoperative evaluation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11672153,11232008 & 11227801)
文摘Residual stress plays a vital role in the structural strength and stability. The determination of residual stress at single-point has become mature at present. However, the method to determine residual stress distribution is still in shortage. For this problem, a finite element approach combined with slot milling method was developed in this study. In the method, firstly a slot is milled on the specimen surface to release the residual stress and then the released displacement field is measured by optical method, such as digital image correlation （DIC）, finally the finite element approach is used to determine the residual stress distribution along the slot. In order to verify the feasibility of the method, it was applied to study the residual stress introduced by shot peening, mainly about the stress distribution along the direction vertical to the shot peened surface. Since the influence depth of shot peening was too small, we utilized focused ion beam （FIB） to determine the microscale residual stress distribution. The result measured by X-ray diffraction （XRD） demonstrated that the method was feasible to determine the residual stress distribution.
基金funded by the Foundation ofYouth Innovation Promotion Association,CAS(No.Y202005)the Major achievements cultivation project of major scientific and technological infrastructure,CAS(No.NE01G74Y2)the National Natural Science Foundation of China(No.11805221).
文摘Purpose Hundreds of digital beam position monitor processors(DBPM)are required to be produced during the construction of projects such as High Energy Photon Source(HEPS)and the upgrade project of the Beijing Electron Positron Collider(BEPCII),which brings great challenges to the test work.In order to achieve accurate,fast,and complete mass production tests of DBPMs,an automatic test system(ATS)has been developed in this article.Methods According to the test items of DBPM,the standardized testing softwareflow is designed based on virtual instru-ment program control technology and experimental physics and industrial control system(EPICS),which realize automatic adjustment of test parameters and automatic acquisition of test result data.Results and conclusions The ATS can realize one-button testing of channel coefficients,channel linearity,attenuator linearity,beam current dependence(BCD)and sampling signal-to-noise ratio(SNR),and generate test reports.The total test time is less than 3 minutes,which is significantly more efficient compared to manual testing.More than 90 BEPCII DBPMs has been tested by this ATS in the lab.The test results proved that such a system could automatically recognize defective products and satisfy the requirements of mass testing.
