Search

A novel two-step controlled basic water phase method has been developed for synthesizing size-tunable and water-soluble CdTe/Cd(OH) 2 core/shell quantum dots with high quantum yield and good stability. The size of the prepared CdTe/Cd(OH) 2 core/shell quantum dots can be easily manipulated by varying the concentrations of NaOH solution step by step. The maximal emission wavelengths of the series CdTe/Cd(OH) 2 core/shell QDs were from 513 nm to 610 nm (emission colors tuned from green to red). The CdTe/Cd(OH) 2 core/shell quantum dots not only possess high quantum yield (up to 83%) but also exhibit excellent photostability (being stable after being stored for more than 2 months). The CdTe/Cd(OH) 2 core/shell quantum dots were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction spectrometry, ultraviolet–visible spectrometry and fluorescence spectrometry. The water-soluble nature of the CdTe/Cd(OH) 2 core/shell quantum dots offers great potentiality for their chemical and biological applications. This method is easily controlled, low-cost and reproducible. So it is possible to extend this approach to the preparation of other size-tunable inorganic metal hydroxide capped core/shell quantum dots.

Our purpose in this paper is to show the integration properties of the intuitionistic fuzzy-valued Choquet integrals, by which improper applications of this type of Choquet integral in the multicriteria decision making can be avoided. We first propose some important operational properties of intuitionistic fuzzy values (IFVs) and give a short review of the methods of comparing IFVs in the framework of the multicriteria decision making. Then we give a detailed discussion on the aggregation properties of the intuitionistic fuzzy-valued Choquet integral (IFCI) and the intuitionistic fuzzy-valued conjugate Choquet integral (IFCCI). The difference in aggregation characteristics between the IFCI and the IFCCI in multicriteria decision making are also be investigated. Finally, we present an application of the IFCI and IFCCI-based multicriteria decision making method to assess the software development risks.

Abstract A down-hole pulsed pressure device to improve the quality of cement bonds during primary cementing has been developed. The prime purpose was to control gas and water channeling and enhance the cement slurry displacement efficiency, especially in holes with a small annular space, and in holes with large washed out spaces occupied by mud-cake and in gas wells that are susceptible to gas channeling. These problems are difficult to treat with chemical cement agents. It is shown that pulsing the curing cement can improve the cement slurry hydration, shortening the time between the initial and final cement gelation and abating the slurry weight loss effect. Our experiments show the pulsing frequency is best between 10–30 Hz and the pressure amplitude should be less than 5 MPa. The device is highly innovative, is easy to engage to the casing string (under the float collar) and has no effect on the casing design. It does not cause failure during cementing, and does not alter the traditional cementing technology. It has been applied to gas wells in several fields in Sichuan province in China. The pilot well had 11 gas layers and is 4180m (13,714 ft) in depth, and the hole was prone to lost circulation (1.09g/ cm3 mud) and cave in. The cemented well interval was drilled with a 152.4mm (6") bit and cased with a 127mm (5") liner. There are troublesome formations in the interval that caused difficulties in logging and while running the liner. The down-hole pulsing generator worked well with the 1.50g/cm3 cement slurry, but due to the complicated hole conditions the displacement was not finished when the liner became plugged with cement. But after drilling out the cement plug, the CBL and other logs showed the cement quality had been enhanced 50% compared to the offset wells. Then in application to another three wells we also achieved significantly improved cement bonds. So it has been verified that this device can significantly improve cementing, and is easy to apply in the field. We intend to continue to apply it to wells with troublesome formations and to all gas and oil wells with cementing problems.

In this paper, we study the sparsest solutions of linear complementarity problems (LCPs), which study has many applications, such as bimatrix games and portfolio selections. Mathematically, the underlying model is NP-hard in general. By transforming the complementarity constraints into a fixed point equation with projection type, we propose an regularization projection minimization model for relaxation. Through developing a thresholding representation of solutions for a key subproblem of this regularization model, we design a shrinkage-thresholding projection (STP) algorithm to solve this model and also analyze convergence of STP algorithm. Numerical results demonstrate that the STP method can efficiently solve this regularized model and get a sparsest solution of LCP with high quality. MSC:90C33, 90C26, 90C90.