Collisional quantum interference （CQI） on the intramolecular rotational energy transfer is observed in an experiment with a static cell, and the integral interference angles are measured. To obtain more accurate inf...Collisional quantum interference （CQI） on the intramolecular rotational energy transfer is observed in an experiment with a static cell, and the integral interference angles are measured. To obtain more accurate information, an experiment with a molecular beam is carried out, and thereby the relationship between the differential interference angle and the scattering angle is obtained. Based on the first-Born approximation of time-dependent perturbation theory, the theoretical model of CQI is developed in an atom-diatom system in the condition of the molecular beam, with the long-range interaction potential taken into account. The method of measuring correctly the differential interference angle is presented. The tendencies of the differential interference angle changing with the impact parameter and rel- ative velocity are discussed. The theoretical model presented here is important for understanding or performing the experiment in the molecular beam.展开更多
To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the...To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the atom-diatomic [case（a）] molecule system in detail. For the 2∏ electronic state in Hund＇s case （a）, the degree of the differential interference is also discussed. The differential interference angles of NO（X^2∏） are calculated quantitatively for the rotational energy transfer in Hund＇s case （a） induced by collision with He, Ne and Ar atoms. The method to calculate the differential interference angle is presented. Several factors that affect the differential interference angle are investigated. Finally the variation of the differential interference angle with the impact parameter and relative velocity is discussed.展开更多
High volume aerosol samplers at Great Wall Station in Antarctica were used to collect 73 aerosol samples between January 2012 and November 2013. The main ions in these aerosol samples, Cl^-, NO3-, SO4^2-, Na＋, K＋, ...High volume aerosol samplers at Great Wall Station in Antarctica were used to collect 73 aerosol samples between January 2012 and November 2013. The main ions in these aerosol samples, Cl^-, NO3-, SO4^2-, Na＋, K＋, Ca2＋, Mg2＋, NH4＋, as well as methane sulfonic acid, were analyzed using ion chromatography. Trace metals in these samples, including Pb, Cu, Cd, V, Zn, Fe, and Al, were determined by inductively-coupled plasma mass spectrometry. Results showed that sea salt was the main component in aerosols at Great Wall Station. Most ions exhibited significant seasonal variations, with higher concentrations in summer and autumn than in winter and spring. Variations in ions and trace metals were related to several processes（or sources）, including sea salt emission, secondary aerosol formation, and anthropogenic pollution from both local and distant sources. The sources of ions and trace metals were identified using enrichment factor, correlation, and factor analyses. Clearly, Na＋, K＋, Ca2＋, and Mg2＋were from marine sources, while Cu, Pb, Zn, and Cd were from anthropogenic pollution, and Al and V were mainly from crustal sources.展开更多
Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of sc...Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of scalability,state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of longrange LiDAR,including the number of pixels(resolvable points)and beam quality.Here,we experimentally demonstrate the pixelated DOPA concept,which overcomes the scaling challenges of classical(continuous)DOPAs by introducing a new design degree of freedom:the discretization of the optical delay lines distribution network into blocks.We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network,incorporated in both the continuous DOPA and the pixelated DOPA variations.The small-scale demonstration circuits can scan over a field of view of 15°×7.2°,where the continuous DOPA provides 16×25 pixels,while the pixelated DOPA provides 4×25 pixels,for a 1500 to 1600 nm wavelength sweep.The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB,which is higher than that of the continuous version,with a median of 3.6 dB.In addition,the ratio of the main beam to the background radiation pattern is 11 dB(median value)for the pixelated DOPA,while for the continuous DOPA,it is 9.5 dB.This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA.The degree of discretization,combined with other design parameters,will potentially enable better control over the beam quality,while setting practical values for the number of pixels for large-scale DOPAs.展开更多
Room-temperature ferromagnetism with a Curie temperature higher than 380 K was studied in GaN: Mn thin films grown by metal-organic chemical vapor deposition. By etching artificial microstructures on the GaN: Mn layer...Room-temperature ferromagnetism with a Curie temperature higher than 380 K was studied in GaN: Mn thin films grown by metal-organic chemical vapor deposition. By etching artificial microstructures on the GaN: Mn layer,strong magnetic responses were observed in the magnetic force microscopy (MFM) measurement,which revealed that the films were independent of dopant particles and clusters. Numerical simulation on the data of atomic force microscope (AFM) and MFM measurements covering the whole microstructure validated the formation of long range magnetic order. This result excluded a variety of controversial origins of room-temperature ferromagnetism in the GaN: Mn and gave a strong evidence of our GaN: Mn as the intrinsic diluted magnetic semiconductor (DMS). The forwarded method for accurate characterization of long range magnetic order could be applied to a wide range of DMS and diluted magnetic oxide (DMO) systems.展开更多
Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation （4G） mobile communications is being paid more attention. ...Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation （4G） mobile communications is being paid more attention. Wireless cognitive location （WCL） techniques for next generation wireless networks have been proposed in recent years. This article investigates the changes of the positioning accuracy of WCL algorithm when different methods are adopted to measure the short-range （SR） information. By fJrst completing Cramer-Rao lower bound （CRLB） analysis of the WCL algorithm with SR measurements based on time of arrival （TOA） and received signal strength （RSS）, it is discovered that TOA-based or time difference of arrival （TDOA） -based SR measurement can make WCL algorithms achieve higher accuracy than RSS mode, which is also verified by numerical simulation in the article. The conclusions can instruct the design of novel WCL-based location algorithms.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10374040）,
文摘Collisional quantum interference （CQI） on the intramolecular rotational energy transfer is observed in an experiment with a static cell, and the integral interference angles are measured. To obtain more accurate information, an experiment with a molecular beam is carried out, and thereby the relationship between the differential interference angle and the scattering angle is obtained. Based on the first-Born approximation of time-dependent perturbation theory, the theoretical model of CQI is developed in an atom-diatom system in the condition of the molecular beam, with the long-range interaction potential taken into account. The method of measuring correctly the differential interference angle is presented. The tendencies of the differential interference angle changing with the impact parameter and rel- ative velocity are discussed. The theoretical model presented here is important for understanding or performing the experiment in the molecular beam.
基金Project supported by the National Natural Science Foundation of China (Grant No 10374040)the Fund of the Educational Department of Liaoning Province, China (Grant No 20060347)
文摘To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the atom-diatomic [case（a）] molecule system in detail. For the 2∏ electronic state in Hund＇s case （a）, the degree of the differential interference is also discussed. The differential interference angles of NO（X^2∏） are calculated quantitatively for the rotational energy transfer in Hund＇s case （a） induced by collision with He, Ne and Ar atoms. The method to calculate the differential interference angle is presented. Several factors that affect the differential interference angle are investigated. Finally the variation of the differential interference angle with the impact parameter and relative velocity is discussed.
基金supported by the National Natural Science Foundation of China (Grant nos. 41230529 and 41476172)the Chinese Polar Environment Comprehensive Investigation & Assessment Programs (Grant no. CHINARE2012-15 for 01-04-02, 02-01, and 03-0402)Chinese International Cooperation Projects, Chinese Arctic and Antarctic Adminstration (Grant nos. 2015DFG22010, IC201201, IC201308 and IC201513)
文摘High volume aerosol samplers at Great Wall Station in Antarctica were used to collect 73 aerosol samples between January 2012 and November 2013. The main ions in these aerosol samples, Cl^-, NO3-, SO4^2-, Na＋, K＋, Ca2＋, Mg2＋, NH4＋, as well as methane sulfonic acid, were analyzed using ion chromatography. Trace metals in these samples, including Pb, Cu, Cd, V, Zn, Fe, and Al, were determined by inductively-coupled plasma mass spectrometry. Results showed that sea salt was the main component in aerosols at Great Wall Station. Most ions exhibited significant seasonal variations, with higher concentrations in summer and autumn than in winter and spring. Variations in ions and trace metals were related to several processes（or sources）, including sea salt emission, secondary aerosol formation, and anthropogenic pollution from both local and distant sources. The sources of ions and trace metals were identified using enrichment factor, correlation, and factor analyses. Clearly, Na＋, K＋, Ca2＋, and Mg2＋were from marine sources, while Cu, Pb, Zn, and Cd were from anthropogenic pollution, and Al and V were mainly from crustal sources.
文摘Dispersive optical phased arrays(DOPAs)offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation,and therefore low control complexity and low power consumption.However,in terms of scalability,state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of longrange LiDAR,including the number of pixels(resolvable points)and beam quality.Here,we experimentally demonstrate the pixelated DOPA concept,which overcomes the scaling challenges of classical(continuous)DOPAs by introducing a new design degree of freedom:the discretization of the optical delay lines distribution network into blocks.We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network,incorporated in both the continuous DOPA and the pixelated DOPA variations.The small-scale demonstration circuits can scan over a field of view of 15°×7.2°,where the continuous DOPA provides 16×25 pixels,while the pixelated DOPA provides 4×25 pixels,for a 1500 to 1600 nm wavelength sweep.The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB,which is higher than that of the continuous version,with a median of 3.6 dB.In addition,the ratio of the main beam to the background radiation pattern is 11 dB(median value)for the pixelated DOPA,while for the continuous DOPA,it is 9.5 dB.This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA.The degree of discretization,combined with other design parameters,will potentially enable better control over the beam quality,while setting practical values for the number of pixels for large-scale DOPAs.
基金supported by the National Natural Science Foundation of China (Grant Nos.60577030,60776041,60876035)the National Key Basic Research Special Foundation of China (Grant Nos.TG2007CB307004,2006CB921607)
文摘Room-temperature ferromagnetism with a Curie temperature higher than 380 K was studied in GaN: Mn thin films grown by metal-organic chemical vapor deposition. By etching artificial microstructures on the GaN: Mn layer,strong magnetic responses were observed in the magnetic force microscopy (MFM) measurement,which revealed that the films were independent of dopant particles and clusters. Numerical simulation on the data of atomic force microscope (AFM) and MFM measurements covering the whole microstructure validated the formation of long range magnetic order. This result excluded a variety of controversial origins of room-temperature ferromagnetism in the GaN: Mn and gave a strong evidence of our GaN: Mn as the intrinsic diluted magnetic semiconductor (DMS). The forwarded method for accurate characterization of long range magnetic order could be applied to a wide range of DMS and diluted magnetic oxide (DMO) systems.
基金the National Natural Science Foundation of China (60496312)The Hi-Tech Research and Development Program of China (2006AA01Z260 and 2006AA01Z283)+1 种基金NCET project (05-01160)111 Project (B07005)
文摘Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation （4G） mobile communications is being paid more attention. Wireless cognitive location （WCL） techniques for next generation wireless networks have been proposed in recent years. This article investigates the changes of the positioning accuracy of WCL algorithm when different methods are adopted to measure the short-range （SR） information. By fJrst completing Cramer-Rao lower bound （CRLB） analysis of the WCL algorithm with SR measurements based on time of arrival （TOA） and received signal strength （RSS）, it is discovered that TOA-based or time difference of arrival （TDOA） -based SR measurement can make WCL algorithms achieve higher accuracy than RSS mode, which is also verified by numerical simulation in the article. The conclusions can instruct the design of novel WCL-based location algorithms.
