Hyperpolarized^(3)He nuclei have emerged as a significantly important approach in quantum precision measurement techniques,with extensive applications in fundamental physics,magnetometry,metrology,and beyond.In this s...Hyperpolarized^(3)He nuclei have emerged as a significantly important approach in quantum precision measurement techniques,with extensive applications in fundamental physics,magnetometry,metrology,and beyond.In this study,we report on the design and implementation of a^(3)He polarization system at the China Mianyang Research Reactor(CMRR),utilizing the metastabilityexchange optical pumping(MEOP)method.We employed a Merritt coil system consisting of four square coils to furnish a uniform holding field.We deployed a 2 W fiber laser to pump the metastable^(3)He atoms and conducted free induction decay(FID)detection of the polarized^(3)He nuclei using both pickup coil and optical methods.For the optical method,we used a50 m W linearly polarized distributed Bragg reflector(DBR)laser as the probe.We applied transverse light absorption polarimetry to measure the absolute nuclear polarization of the ground-state^(3)He.We have developed cell fabrication capabilities at the CMRR,and cells at various pressures ranging from 100 to 1000 Pa have been fabricated and evaluated.For a typical borosilicate cell with 100 Pa pressure,the absolute polarization is measured as Pn≈70%,and the transverse relaxation time is estimated as T2≈0.5 s.Moreover,we constructed a few aluminosilicate cells,each carefully filled with pure^(3)He at a pressure of 100 Pa.Subsequently,we conducted a comprehensive evaluation of their performance in the context of MEOP.展开更多
As urbanization is an evolutionary process of the open giant system of complex spaces,solutions should be sought based on the scientifi c method of "limited solutions to complex problems." Firstly,as people ...As urbanization is an evolutionary process of the open giant system of complex spaces,solutions should be sought based on the scientifi c method of "limited solutions to complex problems." Firstly,as people are the core of human settlements,urbanization should show its care for humans and thus for human settlements; secondly,a human settlement civilization should be cultivated on the basis of ecological civilization; thirdly,rural development should be promoted in units of county,in order to coordinate the urban-rural development; fourthly,it should encourage the decision-makers and think tanks to improve the management mechanism. As transformation becomes the general trend of this era,we need also to understand the Sciences of Human Settlements from the perspective of scientifi c transformation,which is expected to break new grounds in the Sciences of Human Settlements.展开更多
The primary theoretical framework of the Sciences of Human Settlements was established based on the researches and practices for decades. Nowadays, it is facing a new start in order to face the challenges of "tra...The primary theoretical framework of the Sciences of Human Settlements was established based on the researches and practices for decades. Nowadays, it is facing a new start in order to face the challenges of "transformation" and "restructuring" amid the process of urbanization. It means that, in both the theoretical and practical fields of the Sciences of Human Settlements, due attention should be paid to the discussions on urbanization strategies, the rethinking on balanced urban-rural development, the extension and integration of various disciplines, and the realization of experimental projects in various localities. The Sciences of Human Settlements should be more closely connected with related sciences and technologies and learn more from the traditional "Chinese wisdom," so as to establish the system of "Grand Science, Grand Humanism and Grand Arts." The practice of the Sciences of Human Settlements should highlight the integration of both strategies and methodologies, the completion of institutions, and the monitoring at the macro-level. Both the top-down strategic planning and design and the bottom-up comprehensive community construction are necessary. Now that the times of great transition brings us an opportunity to solve problems creatively, the Sciences of Human Settlements should be further researched and explored.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.U2230207,U2030209,12305114,and 12305125)Sichuan Science and Technology Program(Grant No.2024NSFSC1356)the National Key Research and Development Program of China(Grant Nos.2020YFA0406001,and 2020YFA0406002)。
文摘Hyperpolarized^(3)He nuclei have emerged as a significantly important approach in quantum precision measurement techniques,with extensive applications in fundamental physics,magnetometry,metrology,and beyond.In this study,we report on the design and implementation of a^(3)He polarization system at the China Mianyang Research Reactor(CMRR),utilizing the metastabilityexchange optical pumping(MEOP)method.We employed a Merritt coil system consisting of four square coils to furnish a uniform holding field.We deployed a 2 W fiber laser to pump the metastable^(3)He atoms and conducted free induction decay(FID)detection of the polarized^(3)He nuclei using both pickup coil and optical methods.For the optical method,we used a50 m W linearly polarized distributed Bragg reflector(DBR)laser as the probe.We applied transverse light absorption polarimetry to measure the absolute nuclear polarization of the ground-state^(3)He.We have developed cell fabrication capabilities at the CMRR,and cells at various pressures ranging from 100 to 1000 Pa have been fabricated and evaluated.For a typical borosilicate cell with 100 Pa pressure,the absolute polarization is measured as Pn≈70%,and the transverse relaxation time is estimated as T2≈0.5 s.Moreover,we constructed a few aluminosilicate cells,each carefully filled with pure^(3)He at a pressure of 100 Pa.Subsequently,we conducted a comprehensive evaluation of their performance in the context of MEOP.
文摘As urbanization is an evolutionary process of the open giant system of complex spaces,solutions should be sought based on the scientifi c method of "limited solutions to complex problems." Firstly,as people are the core of human settlements,urbanization should show its care for humans and thus for human settlements; secondly,a human settlement civilization should be cultivated on the basis of ecological civilization; thirdly,rural development should be promoted in units of county,in order to coordinate the urban-rural development; fourthly,it should encourage the decision-makers and think tanks to improve the management mechanism. As transformation becomes the general trend of this era,we need also to understand the Sciences of Human Settlements from the perspective of scientifi c transformation,which is expected to break new grounds in the Sciences of Human Settlements.
文摘The primary theoretical framework of the Sciences of Human Settlements was established based on the researches and practices for decades. Nowadays, it is facing a new start in order to face the challenges of "transformation" and "restructuring" amid the process of urbanization. It means that, in both the theoretical and practical fields of the Sciences of Human Settlements, due attention should be paid to the discussions on urbanization strategies, the rethinking on balanced urban-rural development, the extension and integration of various disciplines, and the realization of experimental projects in various localities. The Sciences of Human Settlements should be more closely connected with related sciences and technologies and learn more from the traditional "Chinese wisdom," so as to establish the system of "Grand Science, Grand Humanism and Grand Arts." The practice of the Sciences of Human Settlements should highlight the integration of both strategies and methodologies, the completion of institutions, and the monitoring at the macro-level. Both the top-down strategic planning and design and the bottom-up comprehensive community construction are necessary. Now that the times of great transition brings us an opportunity to solve problems creatively, the Sciences of Human Settlements should be further researched and explored.
