Thermoelectric properties of the n-type 85% Bi2 Te3-15% Bi2 Se3 alloys doped with Sbl3 and CuBr

The temperature dependence of the Hall mobility, Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit of the SbI3 and CuBr-doped 85% Bi2Te3-15% Bi2Se3 single crystals have been characterized at temperatures ranging from 77 K to 600 K. The scattering parameter in 85% Bi2Te3-15% Bi2Se3 single crystal was determined as 0.1 from the temperature dependence of the carrier mobility. With increasing the amount of Sbl3 or CuBr doping, the Seebeck coefficient of 85% Bi2Te3-15% Bi2Se3 decreased and the temperature at which the Seebeck coefficient shows a maximum shifted to higher temperature. Compared to the Sbl3-doped specimens, the CuBr-doped single crystals exhibited higher (m* / m0)3/2 c, implying that CuBr is a more effective dopant to improve the material factor and thus the figure-of-merit of 85% Bi2Te3-15% Bi2Se3. The maximum figure-of-merit of 2.0 × 10–3/K and 2.2 × 10–3/K was obtained for 0.1 wt % Sbl3-doped specimen and 0.03 wt % CuBr-doped specimen, respectively.     

On Stability of Constrained Receding Horizon Control with Finite Terminal Weighting Matrix

In this paper, a new stabilizing receding horizon control, based on a finite input and state horizon cost with a finite terminal weighting matrix, is proposed for time-varying discrete linear systems with constraints. We propose matrix inequality conditions on the terminal weighting matrix under which closed-loop stability is guaranteed for both cases of unconstrained and constrained systems with input and state constraints. We show that such a terminal weighting matrix can be obtained by solving a linear matrix inequality (LMI). In the case of constrained time-invariant systems, an artificial invariant ellipsoid constraint is introduced in order to relax the conventional terminal equality constraint and to handle constraints. Using the invariant ellipsoid constraints, a feasibility condition of the optimization problem is presented and a region of attraction is characterized for constrained systems with the proposed receding horizon control.     

Genetic-based fuzzy control for half-car active suspension systems

In this paper, a fuzzy controller is designed for automotive active suspension systems. A half-car model is used in order to consider the pitch angle of the body and the coupling dynamics of front and rear wheels. It is assumed that the three measurements of body acceleration, front suspension deflection and rear suspension deflection are available. The fuzzy control rules are separately designed for each measurement. After the fuzzy control rules are determined, a genetic algorithm is applied to tune the membership functions of these control rules. To measure the performance of the designed genetic-based fuzzy active suspension system, three road disturbance models are designed to simulate actual road conditions. The performance of the designed system is evaluated with respect to these disturbance models, and it is shown that the designed active suspension system provides good performance in improving ride quality and maintaining vehicle maneuvrability. It is also shown that the designed active suspension system shows robust performance with system model uncertainties.     

Signal processing for real-time identification of similar metals by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy(LIBS) is regarded as a promising technique for realtime sorting of scrap metals due to its capability of fast multi-elemental and in-air analysis. This work reports a method for signal processing which ensures high accuracy and high speed during similar metal sorting by LIBS. Similar metals such as aluminum alloys or stainless steel are characterized by nearly the same constituent elements with slight variations in elemental concentration depending on metal type. In the proposed method, the original data matrix is substantially reduced for fast processing by selecting new input variables(spectral lines) using the information for the constituent elements of similar metals. Specifically, principal component analysis(PCA) of full-spectra LIBS data was performed and then, based on the loading plots, the input variables of greater significance were selected in the order of higher weights for each constituent element. The results for the classification test with aluminum alloy, copper alloy,stainless steel and cast steel showed that the classification accuracy of the proposed method was nearly the same as that of full-spectra PCA, but the computation time was reduced by a factor of 20 or more. The results demonstrated that incorporating the information for constituent elements can significantly accelerate classification speed without loss of accuracy.     

Preparation of Al2TiO5 from alkoxides and the effects of additives on its properties

Al2TiO5 was prepared by the sol-gel method from alkoxides and its mechanical and thermal properties measured. The prepared Al2TiO5 powder was very fine and had a narrow particle-size distribution. The addition of mullite and Al2O3 to the prepared Al2TiO5 inhibited the grain growth during sintering, resulting in a decrease of microcracking and an increase of fracture strength. Al2TiO5/mullite composite exhibited a higher fracture strength than Al2TiO5/alumina composite. The thermal expansion coefficient of Al2TiO5 increased with the addition of mullite and alumina, and also increased with temperature up to 1000°C; however, it decreased in the temperature range between 1000 and 1200°C during heating, due to decomposition of Al2TiO5. The addition of mullite inhibited the decomposition of Al2TiO5, but the addition of Al2O3 accelerated it. Al2TiO5 prepared from metal alkoxides was also more stable than that prepared from the commercial alumina and titania powders. This revised version was published online in November 2006 with corrections to the Cover Date.     

Dielectrophoretic assembly of semiconducting single-walled carbon nanotube transistor

A novel burning technique for making a semiconducting single-walled carbon nanotubes (SWNTs) transistor assembled by the dielectrophoretic force was suggested. The fabrication process consisted of two steps. First, to align and attach a bundle of SWNTs between the source and drain, the alternating (AC) voltage was applied to the electrodes. When a bundle of SWNTs was connected between two electrodes, some of metallic nanotubes and semi-conducing nanotubes existed together. The second step is to burn the metallic SWNTS by applying the voltage between two electrodes. With increasing the voltage, more current flowed through the metallic SWNTs, thus, the metallic SWNTs burnt earlier than the semiconducting one. This technique enables to obtain only semi-conducting SWNTs connection in the transistor. Through the I-V characteristic graph, the moment of metallic SWNTs burning and the characteristic of semi-conducing nanotubes were verified.     

亚甲基兰在AC和TiO2/AC上的吸附及催化臭氧氧化

研究了活性炭(AC)和负载二氧化钛的活性炭(TiO2/AC)对亚甲基兰的吸附特性及单独臭氧氧化,AC催化臭氧氧化和TiO2/AC催化臭氧氧化处理水中亚甲基兰的效果.结果表明:AC、TiO2/AC吸附亚甲基兰均较好地符合一级动力学模型及Langmuir方程,AC对亚甲基兰的吸附性能优于TiO2/AC;催化臭氧氧化的脱色速率比单独臭氧氧化略高,且对亚甲基兰吸附性能好的AC作催化剂时脱色效率更高.催化臭氧氧化比单独臭氧氧化对亚甲基兰的矿化率有明显的提高,TiO2/AC的催化活性优于AC.在催化臭氧氧化过程中,伴随着亚甲基兰的分解生成一系列中间产物并逐渐完全氧化.