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Evaluation of Influence of Multiple Scattering Effect in Light-Scattering-Based Applications

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Chinese Physics Letters 2007年第6期24卷 1763-1766页

作者：徐升华孙祉伟 nml Institute of Mechanics Chinese Academy of Sciences Beijing 100080

The extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the ＇blind zone＇ in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles.

关键词： T-MATRIX METHOD COLLOIDAL STABILITY TURBIDITY MEASUREMENT MICROSCOPICAPPROACH RATE CONSTANTS COAGULATION INDEX

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

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Chinese Physics Letters 2005年第12期22卷 3199-3202页

作者：刘捷孙祉伟阿燕 nml Institute of Mechanics Chinese Academy of Sciences Beijing 100080

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.

关键词： PERIKINETIC COAGULATION RAPID COAGULATION SHEAR-FLOW GRAVITY AGGREGATION DISPERSION STABILITY

Laser Interferometer Used for Satellite-Satellite Tracking: an On-Ground Methodological Demonstration

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Chinese Physics Letters 2012年第7期29卷 295-297页

作者： LI Yu-Qiong LUO Zi-Ren LIU He-Shan DONG Yu-Hui JIN Gang National Microgravity Laboratory(nml) Institute of MechanicsChinese Academy of SciencesBeijing 100190

A Chinese satellite gravity mission called SAGM (Space Advanced Gravity Measurements) is now taken into *** meet its designed requirement,the measurement precision of the laser ranging system used to measure the inter-satellite distance change has to be better than l00nm/Hz1/2 within a broad bandwidth from 0.1mHz to *** equal arm heterodyne Mach-Zehnder interferometer has been built on ground to demonstrate the measurement principle of a laser ranging system,which potentially can be used for both SAGM and future GW (gravitational wave) space *** of the equal arm length,the laser frequency noise has been significantly suppressed in the ***,the sensitivity better than 1nm/Hz1/2 in a frequency range of 0.15 mHz-0.375 Hz has been *** result shows that the proposed methodology has very promising feasibility to meet the requirements of SAGM and of GW space antennas as well.

关键词： interferometer antennas heterodyne

Principle demonstration of fine pointing control system for inter-satellite laser communication

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Science China(Technological Sciences) 2015年第3期58卷 449-453页

作者： DONG YuHui LIU HeShan LUO ZiRen LI YuQiong JIN Gang National Microgravity Laboratory (nml) Institute of Mechanics Chinese Academy of Sciences University of Chinese Academy of Sciences

Due to high data rates and reliability,inter-satellite laser communication has developed rapidly in these ***,the stability of the laser beam pointing is still a key technique which needs to be solved;otherwise,the beam pointing jitter noise would reduce the communication quality or,even worse,would make the inter-satellite laser communication *** this purpose,a bench-top of the fine beam pointing control system has been built and tested for inter-satellite laser *** pointing offset of more than 100rad is produced by the steering *** beam pointing control system turned on,the offset could be rapidly suppressed to lower than 100 nrad in less than 0.5 ***,the pointing stability can be kept at 40 nrad for yaw motion and 62 nrad for pitch motion,when the received beam jitter is set at 20rad.

关键词： laser beam pointing control inter-satellite laser communication heterodyne laser interferometer differential wave-front sensing(DWS) technique

Multi-channel phasemeter and its application in the heterodyne laser interferometry

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Science China(Technological Sciences) 2015年第4期58卷 746-749页

作者： LIU He Shan DONG Yu Hui LUO Zi Ren LI Yu Qiong JIN Gang National Microgravity Laboratory (nml) Institute of Mechanics Chinese Academy of Sciences School of Physics Chinese Academy of Sciences

The mission to detect gravitational wave in space requires a not only sophisticated but also ultra-precise laser interferometric measurement system. Within a single spacecraft, tens of interferometric beat signals are generated at the same time and they also need to be processed simultaneously. In this paper, a multi-channel phasemeter which can parallelly process the signals is constructed. The test shows that a sensitivity of 2n grad/√Hz could be achieved in the frequency range of 0.1 to 10 Hz. We also utilize the phasemeter to evaluate the performance of a heterodyne laser interferometer.

关键词： phasemeter laser interferometer gravitational waves detection

Protein microarray biosensors based on imaging ellipsometry techniques and their applications

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Protein & Cell 2011年第6期2卷 445-455页

作者： Yu Niu Gang Jin nml Institute of MechanicsChinese Academy of SciencesBeijing 100190China Graduate School of the Chinese Academy of Sciences Beijing 100049China

After years of development,biosensors based on imaging ellipsometry and biosensors based on total internal reflection imaging ellipsometry have been successfully implemented in various engineering *** experimental set... 详细信息

关键词： biosensor protein microarray imaging ellipsometry total internal reflection imaging ellipsometry applications

Effect of ion-beam assisted deposition on the film stresses of TiO_2 and SiO_2 and stress control

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Acta Mechanica Sinica 2012年第5期28卷 1382-1388页

作者： Yu-Qiong Li Hua-Qing Wang Wu-Yu Wang Zhi-Nong Yu He-Shan Liu Gang Jin National Microgravity Laboratory(nml) Institute of MechanicsChinese Academy of Sciences School of Optoelectronics Beijing Institute of Technology Optical Thin Film Center Daheng New Epoch Technology Inc. Beijing General Research Institute for Nonferrous Metals Division of Mineral Research and Material Energy

Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO2 and SiO2, and comparison was made between the film stresses prepared respectively by the conventional process and the ion-beam assisted deposition. The effect of ion-beam assisted deposition on the film stresses of TiO2 and SiO2 was investigated in details, and the stress control methodologies using on-line adjustment and film doping were put forward. The results show that the film stress value of TiO2 prepared by ion-beam assisted deposition is 40 MPa lower than that prepared by conventional process, and the stress of TiO2 film changes gradually from tensile stress into compressive stress with increasing ion energy; while the film stress of SiO2 is a tensile stress under ion-beam assisted deposition because of the ion-beam sputtering effect, and the film refractive index decreases with increasing ion energy. A dynamic film stress control can be achieved through in-situ adjustment of the processing parameters based on the online film stress measuring technique, and the intrinsic stress of film can be effectively changed through film doping.

关键词： Film stress Stress controlling Ion-beam as-sisted deposition Hartmann-Shack sensor

A comprehensive simulation of weak-light phase-locking for space-borne gravitational wave antenna

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Science China(Technological Sciences) 2016年第5期59卷 730-737页

作者： DONG YuHui LIU HeShan LUO ZiRen LI YuQiong JIN Gang National Microgravity Laboratory (nml) Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100190 China QUEST Centre of Quantum Engineering and Space-Time Research Leibniz Universitat Hannover Hannover 30167 Germany Max-Planck-Institude for Gravitational Physics (Albert Einstein Institute) Hannover 30167 Germany

A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracked well with the received transmitting light under different noise level, and the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed. This result was then confirmed by a benchtop experimental test. The required LISA noise floor was recovered from the simulation which proved the validity of the simulation program. In order to convert the noise function into real time data with random characteristics, an algorism based on Fourier transform was also invented.

关键词： weak-light phase-locking gravitational wave detection heterodyne laser interferometer

Compressive elastic behavior of single-crystalline 4H-silicon carbide(SiC) nanopillars

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Science China(Technological Sciences) 2021年第1期64卷 37-43页

作者： FAN SuFeng LI XiaoCui FAN Rong LU Yang Department of Mechanical Engineering City University of Hong KongHong Kong 999077China Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China Nanomanufacturing Laboratory(nml) Center for Advanced Structural Materials(CASM)City University of Hong Kong Shenzhen Research InstituteShenzhen 518057China

As a wide-bandgap semiconductor, 4H-SiC is an ideal material for high-power and high-frequency devices, and plays an increasingly important role in developing our country’s future electric vehicles and 5G techniques. Practical applications of SiCbased devices largely depend on their mechanical performance and reliability at the micro-and nanoscales. In this paper, singlecrystal [0001]-oriented 4H-SiC nanopillars with the diameter ranging from ~200 to 700 nm were microfabricated and then characterized by in situ nanomechanical testing under SEM/TEM at room temperature. Loading-unloading compression tests were performed, and large, fully reversible elastic strain up to ~6.2% was found in nanosized pillars. Brittle fracture still occurred when the max strain reached ~7%, with corresponding compressive strength above 30 GPa, while in situ TEM observation showed few dislocations activated during compression along the [0001] direction. Besides robust microelectromechanical system(MEMS), flexible device and nanocomposite applications, the obtained large elasticity in [0001]-oriented 4H-SiC nanopillars can offer a fertile opportunity to modulate their electron mobility and bandgap structure by nanomechanical straining,the so called "elastic strain engineering", for novel electronic and optoelectronic applications.

关键词： silicon carbide elastic deformation compressive behavior in situ SEM/TEM elastic strain engineering