Electronic properties of Fibonacci quasi-periodic heterostructures

We study the electronic states of different GaAs-AlAs Fibonacci quasi-perodic heterostructures grown along the (001) direction. We employ an empirical tight-binding Hamiltonian including spin-orbit coupling together with the surface Green function matching method. We present results for the eighth Fibonacci generation formed from different building blocks. We compare these results with those of the constituent quantum wells and with those of heterostructures containing the same number of GaAs and AlAs slabs after periodic repetition of the building blocks. No Fibonacci spectrum is found in the energy regions near the conduction and valence band edges of GaAs. A selective localization of the local density of states in the GaAs layers is found for many electronic states.     

Extending the color gamut and dynamic range of an sRGB image using a residual image

Image sources, such as digital camera captures and photographic negatives, typically have more information than can be reproduced on a photographic print or a video display. The information that is lost during the tone/color rendering process relates to both the extended dynamic range and color gamut of the original scene. In conventional photographic systems, most of this additional information is archived on the photographic negative and can be accessed by adjusting the way the negative is printed. However, most digital imaging systems have traditionally archived only a rendered video RGB image. As a result, it is not possible to make the same sorts of image manipulations that historically have been possible with conventional photographic systems. This suggests that there would be an advantage to storing images using an extended dynamic range/color gamut color encoding. However, because of file compatibility issues, digital imaging systems that store images using color encoding other than a standard video RGB representation (e.g., sRGB) would be significantly disadvantaged in the marketplace. In this article, we describe a solution that has been developed to maintain compatibility with existing file formats and software applications, while simultaneously retaining the extended dynamic range and color gamut information associated with the original scenes. With this approach, the input raw digital camera image or film scan is first transformed to the scene‐referred ERIMM RGB color encoding. Next, a rendered sRGB image is formed in the usual way and stored in a conventional image file (e.g., a standard JPEG file). A residual image representing the difference between the original extended dynamic range image and the final rendered image is formed and stored in the image file using proprietary metadata tags. This provides a mechanism for archiving the extended dynamic range/color gamut information, which is normally discarded during the rendering process, without sacrificing interoperability. Appropriately enabled applications can decode the residual image metadata and use it to reconstruct the ERIMM RGB image, whereas applications that are not aware of the metadata will ignore it and only have access to the sRGB image. The residual image is formed such that it will have negligible pixel values for those portions of the image that lie within the sRGB gamut, and will therefore be highly compressible. Tests on a population of 950 real customer images have demonstrated that the extended dynamic range scene information can be stored with an average file size overhead of about 8% compared to the sRGB images alone. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 251–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10160     

Surface electronic states in metal-porous silicon-silicon structures

The character of electronic states in porous silicon (PS)-Si, Pd-PS interfaces, and/or PS bulk at the formation of the metal-PS-silicon heterostructure was studied. The energy parameters were estimated using the deep-level transient spectroscopy and capacitance-voltage characteristics at the accounting of the voltage drop distribution along the structure. The analytical expression for voltage drop distribution along dielectric layer, porous layer and space charge region in silicon was obtained by solving the equation for continuity of the electrostatic induction vector. The electronic states studied were shown to manifest the quasi-continuous sub-band in the energy gap if the porous layer was 30-nm thick. Their density increased, as the energy position was being transformed to a deeper energy level of E_v+0.81 eV at the PS layer growing to 90 nm wide.     

Obtaining shorter regular expressions from finite-state automata

We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping.     

Influence and adjustment goals: Sources of cultural differences in ideal affect.

Previous studies have found that in American culture high-arousal positive states (HAP) such as excitement are valued more and low-arousal positive states (LAP) such as calm are valued less than they are in Chinese culture. What specific factors account for these differences? The authors predicted that when people and cultures aimed to influence others (i.e., assert personal needs and change others' behaviors to meet those needs), they would value HAP more and LAP less than when they aimed to adjust to others (i.e., suppress personal needs and change their own behaviors to meet others' needs). They test these predictions in 1 survey and 3 experimental studies. The findings suggest that within and across American and Chinese contexts, differences in ideal affect are due to specific interpersonal goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design optimization of 3D steel structures: Genetic algorithms vs. classical techniques

In this paper an elitist genetic algorithm (GA) developed by the authors is compared with common commercial solutions for complex structural optimization. After its prior validation on two-dimensional (2D) structures, the GA was tuned and improved in order to obtain structural elements with minimum weights that satisfy the ultimate limit states of the applicable building code. Subsequently, the same spatial structures were optimized using a commercial structural analysis program. Finally, the cost and weight improvements obtained using the GA, although at a higher computational cost, are discussed.     

压缩奇偶相干态的熵压缩特性

用数值方法讨论了相干态强度、相位角和压缩参数对压缩奇偶相干态位置熵和动量熵压缩特性的影响。结果表明，压缩奇偶相干态的位置熵和动量熵均可呈现压缩性，压缩偶相干态的最大熵压缩度比压缩奇相干态的要大。熵压缩度与相干态强度、相位角和压缩参数均有关系，但压缩因子对场熵压缩的影响最大。当其它条件一定时，压缩偶相干态在压缩参数|β|=O．95时，位置熵(或动量熵)的压缩度最大，但压缩奇相干态无此特点。     

Reversible changes of the fill factor in the ZnO/CdS/Cu(In,Ga)Se2 solar cells

The reversible persistent changes of the fill factor (FF) induced by the illumination and voltage bias along with changes in the electronic properties of the ZnO/CdS/Cu(In,Ga)Se₂ photovoltaic devices have been studied. Admittance spectroscopy and capacitance–voltage characterization reveal a correlation between the FF and the space charge distribution within the absorber. Our experiments provide evidence that a major source of FF loss in efficient devices is caused by excess negative charge close to the interface. We explain the persistent changes in the net acceptor concentration in the interface region by the relaxation effects due to compensating donors—the same mechanism, which leads to metastable changes of the doping level in the bulk of the absorber.     

Space-charge-limited currents for organic solar cells optimisation

Basic suppositions and microphysical origin of the occurrence of the space-charge-limited currents (SCLC) are presented in general and for the temperature-modulated space-charge-limited currents (TM-SCLC) in particular. The criteria are given for the spectroscopical method TM-SCLC to be used for localized electron states elucidation in organic semiconducting materials for organic solar cells optimization and modelling. The “visibility “of the localized states by SCLC method, i.e. the power of the SCLC method to distinguish the localized states, is tested by the modelling, varying the temperature, energy position of localized states and their concentration. Generally, it was determined that the SCLC measurements results are more reliable with the increased energy of the states, with their increased concentration and with decreased temperature. The correlation (or its absence) between the measured current and activation energy on applied voltage, expressed by the dependence of preexponential factor of conductivity on activation energy (Meyer–Neldel rule), gives the possibility to determine the energy range where the reconstruction of density of localized states function is reliable.