With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecolo...With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecological environment day by day,portland cement porous concrete(PCPC),as a novel building material,has attracted more and more attention from scientific researchers and engineers.PCPC possesses the peculiar pore structure,which owns numerous functions like river embankment protection,vegetation greening as well as air-cleaning,and has been of wide application in different engineering fields.This paper reviews the salient properties of PCPC,detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years(2010–2020),conducts the statistical analysis of the distribution rule of its major properties around the world,combines with the engineering application to summarize the excellent properties of PCPC,and makes a forecast of future research direction.展开更多
Letτbe a generalized Thue-Morse substitution on a two-letter alphabet{a,b}:τ(a)=ambm,τ(b)=bmam for the integer m≥2.Letξbe a sequence in{a,b}Z that is generated byτ.We study the one-dimensional Schr?dinger operat...Letτbe a generalized Thue-Morse substitution on a two-letter alphabet{a,b}:τ(a)=ambm,τ(b)=bmam for the integer m≥2.Letξbe a sequence in{a,b}Z that is generated byτ.We study the one-dimensional Schr?dinger operator Hm,λon l2(Z)with a potential given by v(n)=λVξ(n),whereλ>0 is the coupling and Vξ(n)=1(Vξ(n)=-1)ifξ(n)=a(ξ(n)=b).LetΛ2=2,and for m>2,letΛm=m if m≡0 mod 4;letΛm=m-3 if m≡1 mod 4;letΛm=m-2if m≡2 mod 4;letΛm=m-1 if m≡3 mod 4.We show that the Hausdorff dimension of the spectrumσ(Hm,λ)satisfies that dimHσ(Hm,λ)>logΛm/(log 64m+4).It is interesting to see that dimHσσ(Hm,λ)tends to 1 as m tends to infinity.展开更多
We study embeddings of the n-dimensional hypercube into the circuit with 2nvertices.We prove that the circular wirelength attains a minimum by gray coding;that was called the CT conjecture by Chavez and Trapp(Discrete...We study embeddings of the n-dimensional hypercube into the circuit with 2nvertices.We prove that the circular wirelength attains a minimum by gray coding;that was called the CT conjecture by Chavez and Trapp(Discrete Applied Mathematics,1998).This problem had claimed to be settled by Ching-Jung Guu in her doctoral dissertation“The circular wirelength problem for hypercubes”(University of California,Riverside,1997).Many argue there are gaps in her proof.We eliminate the gaps in her dissertation.展开更多
The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change ...The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films.展开更多
Chang’E-3 landed on the east of Sinus Iridum area on December 14,2013,performing China’s first successful soft landing on the lunar surface.We present the results on precision orbit determination and positioning of ...Chang’E-3 landed on the east of Sinus Iridum area on December 14,2013,performing China’s first successful soft landing on the lunar surface.We present the results on precision orbit determination and positioning of the lander and the rover.We describe the data,modeling,and methods used to achieve position knowledge over the period December 2–21,2014.In addition to the radiometric X-band range and Doppler tracking data,delta differential one-way ranging data are also used in the calculation,which show that they strongly improve the accuracy of the orbit reconstruction.Total position overlap differences are about 20 and 30 m for the 100 km 9 100 km and100 km9 15 km lunar orbit,respectively,increased by*50%with respect to CE-2 and at the same level as other lunar spacecrafts of recent era such as SELENE and lunar reconnaissance orbiter(LRO).The position error of the soft landing trajectory is less than 100 m.A kinematic statistical method is applied to determine the position of the lander and relative position of the rover with respect to the lander.The position difference of the lander is better than50 m compared to LRO photograph result.Compared with the delta very long baseline interferometry(VLBI)group delay between the lander and the rover,the delta VLBI phase delay can improve the relative position of the rover from*1,000 to*1 m.展开更多
基金supported by the Jiangsu Water Conservancy Science and Technology Project of China(2016036).
文摘With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecological environment day by day,portland cement porous concrete(PCPC),as a novel building material,has attracted more and more attention from scientific researchers and engineers.PCPC possesses the peculiar pore structure,which owns numerous functions like river embankment protection,vegetation greening as well as air-cleaning,and has been of wide application in different engineering fields.This paper reviews the salient properties of PCPC,detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years(2010–2020),conducts the statistical analysis of the distribution rule of its major properties around the world,combines with the engineering application to summarize the excellent properties of PCPC,and makes a forecast of future research direction.
基金supported by the National Natural ScienceFoundation of China(11871098)。
文摘Letτbe a generalized Thue-Morse substitution on a two-letter alphabet{a,b}:τ(a)=ambm,τ(b)=bmam for the integer m≥2.Letξbe a sequence in{a,b}Z that is generated byτ.We study the one-dimensional Schr?dinger operator Hm,λon l2(Z)with a potential given by v(n)=λVξ(n),whereλ>0 is the coupling and Vξ(n)=1(Vξ(n)=-1)ifξ(n)=a(ξ(n)=b).LetΛ2=2,and for m>2,letΛm=m if m≡0 mod 4;letΛm=m-3 if m≡1 mod 4;letΛm=m-2if m≡2 mod 4;letΛm=m-1 if m≡3 mod 4.We show that the Hausdorff dimension of the spectrumσ(Hm,λ)satisfies that dimHσ(Hm,λ)>logΛm/(log 64m+4).It is interesting to see that dimHσσ(Hm,λ)tends to 1 as m tends to infinity.
文摘We study embeddings of the n-dimensional hypercube into the circuit with 2nvertices.We prove that the circular wirelength attains a minimum by gray coding;that was called the CT conjecture by Chavez and Trapp(Discrete Applied Mathematics,1998).This problem had claimed to be settled by Ching-Jung Guu in her doctoral dissertation“The circular wirelength problem for hypercubes”(University of California,Riverside,1997).Many argue there are gaps in her proof.We eliminate the gaps in her dissertation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21573094,51502109,11774122,11574112,and 11474131)the National Found for Fostering Talents of Basic Science,China(Grant No.J1103202)the China Scholarship Council(CSC)obtained during the visit of Ning Sui to MPIA(Grant No.201706175038)
文摘The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films.
基金supported by the National Natural Science Foundation of China (11073047,11173052)the Science and Technology Commission of Shanghai (12DZ2273300)+2 种基金the National High Technology Research and Development Program of China (2012AA121603)the Planetary Sciences Laboratory of Chinese Academy of Sciencesthe Lunar Exploration Project of China
文摘Chang’E-3 landed on the east of Sinus Iridum area on December 14,2013,performing China’s first successful soft landing on the lunar surface.We present the results on precision orbit determination and positioning of the lander and the rover.We describe the data,modeling,and methods used to achieve position knowledge over the period December 2–21,2014.In addition to the radiometric X-band range and Doppler tracking data,delta differential one-way ranging data are also used in the calculation,which show that they strongly improve the accuracy of the orbit reconstruction.Total position overlap differences are about 20 and 30 m for the 100 km 9 100 km and100 km9 15 km lunar orbit,respectively,increased by*50%with respect to CE-2 and at the same level as other lunar spacecrafts of recent era such as SELENE and lunar reconnaissance orbiter(LRO).The position error of the soft landing trajectory is less than 100 m.A kinematic statistical method is applied to determine the position of the lander and relative position of the rover with respect to the lander.The position difference of the lander is better than50 m compared to LRO photograph result.Compared with the delta very long baseline interferometry(VLBI)group delay between the lander and the rover,the delta VLBI phase delay can improve the relative position of the rover from*1,000 to*1 m.
