Photoconductive and Photovoltaic Properties in Cadmium Bismuth Aluminate Glasses

Photo-induced phenomena such as photoconductive and photovoltaic effects were investigated for the glasses in CdO-Bi(2)O(3)-Al(2)O(3) system. Photoconductive effect was characterized by a slow decay of photocurrent (persitent photoconductivity). The decay rate decreased with increasing CdO content and decreasing Bi(2)O(3) content. Photovoltage was very small at room temperature but increased to an obvious value on heating. The photoconductivity and photovoltage were increased with CdO content and enhanced by heat treatment in air. The valence band spectra of X-ray photoelectron spectroscopy showed that the hybridization of Cd 4d and O 2p orbitals increases with decreasing Bi(2)O(3) content and increasing CdO content in the glasses. As the results maximum tends to flat. This type of band structure inhibits the rapid recombination of electrons and holes. The persistent photoconductivity of the glasses may be attributed to deep energy level of DX centers. Deep energy levels of the glasses are able to prevent the recombination because they have a repulsive barrier for both electron emission and capture

Multispecies Coevolution Particle Swarm Optimization Based on Previous Search History

A hybrid coevolution particle swarm optimization algorithm with dynamic multispecies strategy based on K-means clustering and nonrevisit strategy based on Binary Space Partitioning fitness tree (called MCPSO-PSH) is proposed. Previous search history memorized into the Binary Space Partitioning fitness tree can effectively restrain the individuals’ revisit phenomenon. The whole population is partitioned into several subspecies and cooperative coevolution is realized by an information communication mechanism between subspecies, which can enhance the global search ability of particles and avoid premature convergence to local optimum. To demonstrate the power of the method, comparisons between the proposed algorithm and state-of-the-art algorithms are grouped into two categories: 10 basic benchmark functions (10-dimensional and 30-dimensional), 10 CEC2005 benchmark functions (30-dimensional), and a real-world problem (multilevel image segmentation problems). Experimental results show that MCPSO-PSH displays a competitive performance compared to the other swarm-based or evolutionary algorithms in terms of solution accuracy and statistical tests

Ambiguity aversion and optimal derivative-based pension investment with stochastic income and volatility

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jedc.2018.01.023 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/This paper provides a derivative-based optimal investment strategy for an ambiguity-adverse pension investor who faces not only risks from time-varying income and market return volatility but also uncertain economic conditions over a long time horizon. We derive a robust dynamic derivative strategy and show that the optimal strategy under ambiguity aversion reduces the exposures to market return risk and volatility risk and that the investor holds opposite positions for the two risk exposures. In the presence of a derivative, ambiguity has distinct effects on the optimal investment strategy. More important, we demonstrate the utility improvement when considering ambiguity and exploiting derivatives and show that ambiguity aversion and derivative trading significantly improve utility when return volatility increases. This improvement becomes more significant under ambiguity aversion over a long investment horizon.National Natural Science Foundation of China under Grant [71771220, 71721001, 71571195, 11371155, 11326199, 11771158]Major Program of the National Social Science Foundation of China [No. 17ZDA073]Fok Ying Tung Education Foundation for Young Teachers in the Higher Education Institutions of China [No. 151081]Guangdong Natural Science Foundation for Research Team [No. 2014A030312003]Guangdong Natural Science Funds for Distinguished Young Scholars [No. 2015A030306040]Natural Science Foundation of Guangdong Province of China [No. 2014A030310195]Insurance Society of China [No. ISCKT2016-N-l-07

Femtosecond laser nanostructuring in glass with sub-50nm feature sizes

We report on controllable production of nanostructures embedded in a porous glass substrate by femtosecond laser direct writing. We show that a hollow nano-void with a lateral size of ~40 nm and an axial size of ~1500 nm can be achieved by manipulating the peak intensity and polarization of the writing laser beam. Our finding enables direct construction of 3D nanofluidics inside glass.Comment: 15 pages, 4 figure

Diving Deep into the Preimage Security of AES-like Hashing

Since the seminal works by Sasaki and Aoki, Meet-in-the-Middle (MITM) attacks are recognized as an effective technique for preimage and collision attacks on hash functions. At Eurocrypt 2021, Bao et al. automated MITM attacks on AES-like hashing and improved upon the best manual result. The attack framework has been furnished by subsequent works, yet far from complete. This paper elucidates three key contributions dedicated in further generalizing the idea of MITM and refining the automatic model on AES-like hashing. (1) We introduce S-box linearization to MITM pseudo-preimage attacks on AES-like hashing. The technique suits perfectly with superposition states to preserve information after S-box with an affordable cost. (2) We propose distributed initial structures, an extension on the original concept of initial states, that selects initial degrees of freedom in a more versatile manner to enlarge the search space. (3) We exploit the structural similarities between encryption and key schedule in constructions (e.g. Whirlpool and Streebog) to model propagations more accurately and avoid repeated costs. Weaponed with these innovative techniques, we further empower the MITM framework and improve the attack results on AES-like designs for preimage and collision. We obtain the first preimage attacks on 10-round AES-192, 10-round Rijndael-192/256, and 7.75-round Whirlpool, reduced time and/or memory complexities for preimage attacks on 5-, 6-round Whirlpool and 7.5-, 8.5-round Streebog, as well as improved collision attacks on 6- and 6.5-round Whirlpool

Bismuth-doped zinc aluminosilicate glasses and glass-ceramics with ultra-broadband infrared luminescence

Abstract Broadband infrared luminescence covering the optical telecommunication wavelength region of O, E and S bands was observed from bismuth-doped zinc aluminosilicate glasses and glass-ceramics. The spectroscopic properties of the glasses and glass-ceramics depend on the thermal-treatment history. With the appearance of gahnite (ZnAl 2 O 4 ) crystalline phase, the fluorescent peak moves to longer wavelength, but the fluorescent intensity decreases. The $1300 nm fluorescence with a FWHM larger than 250 nm and a lifetime longer than 600 ls possesses these optical materials with potential applications in laser devices and broadband amplifiers. The broad infrared luminescence from the bismuth-doped zinc aluminosilicate glasses and glass-ceramics might be from BiO or bismuth clusters rather than from Bi 5+ and Bi 3+