静水压对立方钙钛矿CsSnX3(X=I, Br, Cl)光电性质的第一性原理探究

全无机无铅卤化物钙钛矿已经成为重要的新一代太阳能电池材料.采用密度泛函理论的第一性原理研究了不同静水压下CsSnX₃(X=I, Br, Cl)材料的晶体结构,电子结构和光学性能,并分析了其内在联系.结果表明施加静水压可使材料中Sn-X键长减小,使原子之间的耦合增强,带隙值减小,且随着卤族元素半径的增大,压力效应越明显;随着压力的增加,材料的吸收系数和复折射率增大,吸收光谱出现红移现象,在可见光区和近红外光区吸收增强.相比CsSnBr₃和CsSnCl₃,CsSnI₃在可见光区吸收最佳且受压力作用影响最小,更适用于钙钛矿太阳能电池材料.     

Density versions of Schur's theorem for ideals generated by submeasures

We characterize ideals of subsets of natural numbers for which some versions of Schur's theorem hold. These are similar to generalizations shown by Bergelson (1986) in [1] and Frankl, Graham and Rödl (1990) in [7]. Additionally, we prove a generalization of an iterated version of Ramsey's theorem.     

Er_xY_(1-x)Al_3(BO_3)_4晶体的生长和光谱性质

采用助熔剂法生长出了掺杂均匀的Er_xY_(1-X)Al_3(BO_3)_4厘米级优质单晶.测定了晶体的吸收、激发光谱.用Judd_Ofelt理论计算了晶体中Er~(3+)的十一条谱带的振子强度(ρ_(ad)和ρ_(md)以及Er~(3+)的强度参数Q_λ(λ-2、4、6).并由此计算了Er~(3+)不同能级之间跃迁的爱因斯坦自发辐射系数A_r、辐射寿命r、荧光分支比β_3以及积分发射截面Σ.根据这些参数讨论了在EYAB晶体中可能实现激光输出的通道.     

非晶态Fe40Ni38Mo4B18（2826MB）合金粉末的高压压结与磁性研究

 本文研究了非晶态软磁材料Fe₄₀Ni₃₈Mo₄B₁₈（2826MB）合金粉末在高压下加温压结成三维大尺寸产品的可行性，并通过压结样品的复数导磁率在弱交变磁场中的行为，探讨了压结条件对压结样品的软磁性能的影响。结果表明，在本实验所采用的压力范围内，压结温度对压结样品的性能的影响大于压结压力的影响。     

Quantaloids Describing Causation and Propagation of Physical Properties

A general principle of causal duality for physical systems, lying at the base of representation theorems for both compound and evolving systems, is proved; formally it is encoded in a quantaloidal setting. Other particular examples of quantaloids and quantaloidal morphisms appear naturally within this setting; as in the case of causal duality, they originate from primitive physical reasonings on the lattices of properties of physical systems. Furthermore, an essentially dynamical operational foundation for studying physical systems is outlined; complementary as it is to the existing static operational foundation, it leads to the natural axiomatization of causal duality in operational quantum logic.     

Stability Concepts in Topological Dynamics by Nonstandard Methods

It is known that it is not possible to introduce C⁰ -structural stability for whole systems in topological dynamics. Using the methods of Nonstandard Analysis, we suggest four different purely topological stability concepts for dynamical systems on compact subsets of Rⁿ. Classically these amount to considering the space of all systems on a given subset of Rⁿ as the fundamental entity when deforming a continuous system (instead of the space of all continuous systems as is normally done in topological dynamics). For two of the introduced stability concepts, we will show that all minimal flows are stable in this sense. Besides this, we will show that one of our stability concepts is related to what is called the pseudo orbit tracing property in a recently published book by Aoki and Hiraide and compare some of our results to the theory of dynamical systems as presented there.     

偶奇q相干态的振幅k次方(k>3)压缩性质

研究结果表明,只有当以k>3)为奇数时,偶q相干态呈现振幅k次方压缩性质;无论k为偶数还是奇数,奇q相干态均不呈现压缩性质。     

Gyrotropic and piezoelectric coefficients and attenuation of elastic waves in BaTiO3

Using Landau theory of phase transition, expressions for gyrotropic coefficients and piezoelectric coefficients are obtained for barium titanate in the tetragonal phase. Both coefficients vanish at the ferroelectric phase transition temperature. The piezoelectric coefficients tallied with the literature values. The attenuation coefficients for elastic waves propagating along the principal directions in tetragonal, orthorhombic and rhombohedral phases are derived based on Landau theory. It is predicted that there will be slight amplification for both longitudinal and transverse modes in the rhombohedral phase at a temperature close to the rhombohedral phase transition temperature.     

Commensurate and incommensurate spin fluctuations in YBa2Cu3O6+y

We present an interpretation of the recent neutron data on the commensurate and incommensurate spin fluctuations found in YBa₂Cu₃O_6+y based on a special configuration of the electronic dispersion and intervention from the d_x²−y²-wave superconducting phase. The observed switch-over between the commensurate and incommensurate fluctuation spectra at the change of frequency or temperature is naturally accounted within this scenario.     

The transient suppression for piezoelectric ceramic emission transducer

A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.