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The rapid development of the high frequency power conversion techniques makes great demands on the methods that can reduce the execution time of the program effectively. This paper is aiming at reducing the execution time of the program in several aspects such as sampling, complex expressions, and so on. As one of the most widely applied methods, reducing the execution time of the program at the cost of the memory space is adopted in this paper. Furthermore, in order to confirm the feasibility and superiority of programs that are proposed in this paper, they are compared with other programs that can realize the same function in terms of the execution time.

We propose a model for three-terminal thermionic heat engines based on semiconductor heterostructures. According to electron transport theory, we drive the formulas for the charge current and energy current flowing from the electron reservoir and we then obtain the power output and efficiency in the linear and nonlinear regimes. Furthermore, we analyze the performance characteristic of the thermionic heat engine and get the maximum power output by optimizing the performance parameters. Finally, we optimize the thermodynamic performance of the thermionic heat engine by maximizing the product of the power output and efficiency.

By linear perturbation theory, a sensitivity study is presented to calculate the contribution of the Mars gravity field to the orbital perturbations in velocity for spacecrafts in both low eccentricity Mars orbits and high eccentricity orbits (HEOs). In order to improve the solution of some low degree/order gravity coefficients, a method of choosing an appropriate semimajor axis is often used to calculate an expected orbital resonance, which will significantly amplify the magnitude of the position and velocity perturbations produced by certain gravity coefficients. We can then assess to what degree/order gravity coefficients can be recovered from the tracking data of the spacecraft. However, this existing method can only be applied to a low eccentricity orbit, and is not valid for an HEO. A new approach to choosing an appropriate semimajor axis is proposed here to analyze an orbital resonance. This approach can be applied to both low eccentricity orbits and HEOs. This small adjustment in the semimajor axis can improve the precision of gravity field coefficients and does not affect other scientific objectives.

We propose a model for a three-terminal quantum well heat engine with heat leakage. According to the Landauer formula, the expressions for the charge current, the heat current, the power output and the efficiency are derived in the linear-response regime. The curves of the power output and the efficiency versus the positions of energy levels and the bias voltage are plotted by numerical calculation. Moreover, we obtain the maximum power output and the corresponding efficiency, and analyze the influence of the heat leakage factor, the positions of energy levels and the bias voltage on these performance parameters.

Li1.0Nb0.6Ti0.5O3:3 wt% Eu3+ red phosphor was synthesized by sol-gel method. The influences of the pH value and the citric acid(CA)/metal cations(M) ratio on the luminescent properties of the samples were discussed. The properties of the samples were characterized by x-ray diffraction (XRD) and photoluminescence spectroscopy, respectively. The results showed that the samples were consist of 'M- phase'. Under the 466 nm excitation, the orange emission at 592 nm and the red emission at 612 nm could be observed. The emission intensity increased with the increasing of pH value firstly and then decreased. The optimum pH value was 5.5. Moreover, the emission intensity decreased with the increasing of CA/M ratio. The relatively high emission intensity of the sample could be obtained when the CA/M was 3:1. Emission spectra and CIE coordinate of Li1.0Nb0.6Ti0.5O3:3 wt% Eu3+ were superior to commercial red phosphor Y2O3:Eu3+, which showed the red phosphor could have potential application in the White-LED field.

In this study, we proposed and validated a novel and non-destructive experimental technology for measuring the permeation of binary gas mixture in nanoporous membranes. The traditional time lag rig was modified to examine the permeation characteristics of each gas component as well as that of the binary gas mixtures. The difference in boiling points of each species were explored. Binary gas mixtures of CO2/He were permeated through the nanoporous carbon molecular sieve membrane (CMSM). The results showed that, due to the strong interaction among different molecules and with the porous network of the membrane, the measured perm-selectivity or 'true selectivity' of a binary mixture can significantly deviate from the 'ideal selectivity' calculated form the permeation flux of each pure species, and this deviation is a complicated function of the molecular properties and operation conditions.

From the volume-limited main galaxy sample of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we construct three galaxy samples with different g-r colors and perform comparative studies of clustering properties among them. It is found that the redder galaxies preferentially inhabit the dense groups and clusters.

Using the three-dimensional galaxy local density in a comoving sphere with a radius of the distance to the fifth nearest galaxy for each galaxy, we construct two samples at both extremes of density from the volume-limited Main galaxy sample of the Sixth Data Release of the Sloan Digital Sky Survey (SDSS DR6). It is found that the sample at low density has a higher proportion of faint, blue, and late-type galaxies and a lower proportion of luminous, red, and early-type galaxies than the sample at high density. We also measure the projected local density , which is computed from the distance to the fifth nearest neighbor within a redshift slice ± 1000 km s-1 of each galaxy, and come to the same conclusions. In addition, we note that there is no significant difference between the mean luminosity and the mean colors of two samples (< 1 σ), which is consistent with the conclusion obtained by Deng and colleagues in 2007.

Using a volume-limited sample of Main Galaxies from the SDSS Data Release 5, we investigate the dependence of galaxy properties on local environment. For each galaxy, the local three-dimensional density is calculated. We find that galaxy morphologies strongly depend on local environment: galaxies in dense environments have predominantly early type morphologies, but other galaxy properties do not present significant dependence on local environment. Clearly, this puts a important constraint on proposed physical mechanisms.

From the Main galaxy data of the SDSS Data Release 4 (SDSS4), we have iden- tified close galaxy pairs at neighbourhood radius R = 100kpc by three-dimensional cluster analysis. Using the criterion that an "isolated galaxy pair" must be separated from its "nearest neighbor"by more than 500kpc, we constructed an isolated galaxy pair sample of 1158 pairs. We also constructed a random pair sample by randomly selecting 1158 galaxy pairs from the Main galaxy sample, which has the same redshift distribution as the isolated galaxy pair sample, and in which the two components of any pair have the same redshifts. Comparative studies of luminosity and size between the members of the galaxy pairs are performed. We find and further confirm there is no tendency for paired galaxies to have similar luminosities or sizes. From the isolated pair sample we also selected a subsample with the magnitude limit of the primary raised by 2 magnitudes,so as to include pairs in which the secondary is 2 mag- nitudes fainter than the primary. This subsample contains 82 pairs. A random pair sample is similarly constructed.

We study the super-large-scale structures in the Sloan Digital Sky Survey by cluster analysis, and examine the geometry and the properties of the member galaxies. Two subsamples are selected from the SDSS, Subsample 1 at the celestial equator and Subsample 2 further north. In Subsample 1 we discover two compact super-large-scale structures: the Sloan Great Wall and the CfA Great Wall. The Sloan Great Wall, located at a median redshift of z = 0.07804, has a total length of about 433 Mpc and a mean galaxy density of about six times that of the whole sample. Most of its member galaxies are of medium size and brightness. The CfA Great Wall, located at a median redshift of z = 0.03058, has a total length of about 251 Mpc and includes large percentages of faint and small galaxies and relatively fewer early-type galaxies.

We propose four different models of three-terminal quantum dot thermoelectric devices. From general thermodynamic laws, we examine the reversible efficiencies of the four different models. Based on the master equation, the expressions for the efficiency and power output are derived and the corresponding working regions are determined. Moreover, we particularly analyze the performance of a three-terminal hybrid quantum dot refrigerator. The performance characteristic curves and the optimal performance parameters are obtained. Finally, we discuss the influence of the nonradiative effects on the optimal performance parameters in detail.

For spin reorientation (SRT), the applications of sintering NdFeB permanent magnets are limited at low temperature. The sintering PrFeB permanent magnet (PM) presents no SRT and shows excellent magnetic properties at low temperature. The magnetic properties of bulk polycrystalline sintering Pr1-xNdxFeB (x - 0 and 0.8 correspond to P42II and N50M respectively) are studied in this paper. The results show that magnetic properties and stability of N50M are better than those of 42H at room temperature. With the decrease of temperature, the parameters of B-r, H-cb, and H-ci of P42H present a nearly linear increasing trend; Br and Hcb of N50M first increase and then decline, Hci presents an increasing trend. At 77 K, Br, H-ci, and J(r) of P42H are increased by 18.7%, 308%, and 17.1% respectively over than those at 300 K; at 120 K, Br, Hci, and Jr of N50M are increased by about 16.19%, 245%, and 12.6% respectively over than those at 300 K. The magnetic properties of P42H are better than those of N50M at low temperature. The sintering PrFeB is the preferred PM in various low temperature devices.

We investigate the efficiency at maximum power of a nanothermoelectric heat engine consisting of one spin-degenerate quantum dot embedded between two reservoirs at different temperatures and chemical potentials in an external magnetic field. Based on the stochastic master equation the maximum power and the corresponding efficiency at maximum power are calculated in different external magnetic fields. The result shows that both the maximum power and the corresponding efficiency at maximum power decrease with an increase of the external magnetic field. In the weak magnetic field the corresponding efficiency at maximum power is slightly larger than the Curzon—Ahlborn (CA) efficiency, while in the large magnetic field it is obviously lower than CA efficiency.

A Brownian microscopic heat engine, driven by temperature difference and consisting of a Brownian particle moving in a sawtooth potential with an external load, is investigated. The heat flows, driven by both potential and kinetic energies, are taken into account. Based on the master equation, the expressions for efficiency and power output are derived analytically, and performance characteristic curves are plotted. It is shown that the heat flow via the kinetic energy of the particle decreases. The efficiency of the engine is enhanced, but the power output reduces as the α shape parameter of the sawtooth potential increases. The influence of the α shape parameter on efficiency and power output is then analyzed in detail.

This paper investigates the peak-to-average power ratio (PAPR) theory in all-optical orthogonal frequency division multiplexing (OFDM) optical fibre communication systems. We find out that phase pre-emphasis could effectively reduce PAPR in all-optical OFDM communication systems which employ intensity modulation-direct detection (IM-DD) method. An equation is developed and proposed to calculate suitable phasing values for pre-emphasis. Furthermore, we find out that phase pre-emphasis cannot reduce PAPR effectively in all-optical OFDM systems that employ Phase Shift Keying (PSK) or Quadracture Amplitude Modulation (QAM) method.