Guozhen Su

Hot-Carrier Solar Cells With Quantum Well and Dot Energy Selective Contacts

In this paper, we simulate hot-carrier solar cells (HCSCs) with quantum well and dot energy selective contacts (ESCs) and derive the power outputs and efficiencies of HCSCs, including three energy loss mechanisms. The effects of the shape of the electron energy spectrum on the electric current densities and heat flux densities of HCSCs are discussed based on the ballistic transport theory. Performance characteristics pertaining to the extraction energy level and the transmission energy width are revealed. The key parameters of HCSCs are optimally designed. The results obtained show that thermalization losses due to non-ideal ESCs are one of the main energy dissipation mechanisms decreasing the efficiency of HCSCs and the performance of an HCSC can be more significantly improved by using quantum dot ESCs than quantum well ESCs.

Conditional statistical properties of the complex systems having long-duration memory

A new concept of the available force is proposed to investigate the performance of the complex systems having long-duration memory. Since the covariance of average velocity in double time interval and available force equals zero, it is possible to calculate the conditional probability distribution function (CPDF) within the systems. It is found that the asymmetric CPDF of the velocity between two adjacent time intervals can be derived from the symmetrical CPDF between the available force and the double time interval velocity. Two typical currency exchange databases, i.e., EUR/USD and GBP/USD, which collect the minutely opening exchange prices from 1 January 1999 to 31 December 2011, are adopted as examples. It is found that the analytical CPDF needs only six parameters for an arbitrary system. By calculating the CPDF in the currency exchange databases, it is shown that the results are well fitted by our analytical expression. The analytical CPDF can also be used to calculate the conditional expectation and the conditional variance of velocity. Interestingly, the two databases show that the conditional expectation of the velocity between two adjacent time intervals is not monotonic, while the conditional variance tends to monotonic. All of these results are well described by our theory. It is worthwhile to note that the analytical CPDF is a general expression. It is valid not only for current exchange systems but also for any complex systems having long-duration memory.

STATISTIC CHARACTERISTICS OF QUANTUM GASES IN A CONFINED SPACE

With the help of the Euler–MacLaurin formula, the statistic characteristics of quantum gases confined in a rectangular box are investigated by using a unified way. Three components of the pressure tensor and the internal energy of the system are analytically derived. The important relation between the pressure tensor and the internal energy is strictly proved. It is pointed out that these results are different from those obtained in literature and textbooks under the thermodynamic limit condition. Moreover, the pressure of the system is rationally introduced with the help of the property of the diagonal tensor, so that some thermodynamic functions of the system may be conveniently obtained. The statistic characteristics of quantum and classical gases confined in some different containers are discussed, the influence of the size effect of the containers on the properties of gases is analyzed and some new significant results are obtained.

Probability distribution function of complex systems

Based on the probability distribution observed in some complex systems and an assumption that the entropies of complex systems satisfy a pseudo additivity, it is expounded that a new probability distribution function is suitable for not only a single complex system but also a coupling complex system, and consequently, a statistical theory of complex systems can be established in the extensive-like framework.

THE EFFECTS OF A FINITE NUMBER OF PARTICLES ON TWO TRAPPED QUANTUM GASES

The effects of a finite number of particles on the thermodynamic properties of ideal Bose and Fermi gases trapped in any-dimensional harmonic potential are investigated. The orders of relative corrections to the thermodynamic quantities due to the finite number of particles are estimated in different situations. The results obtained for the two trapped quantum gases are compared, and consequently, it is shown that the finite-particle-number effects for the condensed Bose gas (a Bose gas with Bose–Einstein Condensation (BEC) occurring in the system) are much more significant than those for the Fermi gas and normal Bose gas (a Bose gas without BEC).