5,314 research outputs found
Construction of exact D-optimal designs by tabu search
No full textTabu search (TS) has recently emerged as a promising heuristic method for solving complex combinatorial optimization problems. By guiding the search using the so-called tabu list and accepting disimproved solutions at some iterations, TS helps alleviate the risk of being trapped at a local optimum. In this article, we introduce the essential features of TS, apply TS to the problem of constructing an exact D-optimal design for a main-effect or a quadratic model with a finite design space, and compare performances of TS and the Fedorov exchange algorithm (FEA) as modified by Nguyen and Miller (1992). Computational results indicate that although TS requires more computing time per try than FEA, its overall performance is generally better except for the case of quadratic models with a small number of factors. For some test problems, TS also identifies designs with larger determinants than the corresponding designs obtained by FEA
Preparation of oligonucleotide arrays with high-density DNA deposition and high hybridization efficiency
No full textIn DNA microarray produced by DNA-deposition technology, DNA-immobilization and -hybridization yields on a solid support are most important factors for its accuracy and sensitivity. We have developed a dendrimeric support using silylated aldehyde slides and polyamidoamine (PAMAM) dendrimers. An oligonucleotide array was prepared through a crosslinking between the dendrimeric support and an oligonucleotide. Both DNA-immobilization and -hybridization yields on the solid support increased by the modification with the dendrimers. The increase of the immobilization and hybridization efficiency seems to result from a three-dimensional arrangement of the attached oligonucleotide. Therefore, our dendrimeric support may provide a simple and efficient solution to the preparation of DNA microarrays with high-density DNA-deposition and high hybridization efficiency
Modification of aliphatic polyesters and their reactive blends with starch
No full textModified polycaprolactone was synthesized by melt reaction of PCL and reactive monomers such as glycidyl methacrylate (GMA) and maleic anhydride (MAH) in the presence of benzoyl peroxide in Brabender mixer. MAH showed a different grafting phenomenon compared to GMA. The reaction mechanism was discussed with different reactive monomers. Reactive blends of the PCL-g-GMA and the gelatinized starch with glycerin were prepared and their mechanical properties and biodegradabilities were investigated. Reactive blends of PCL-g-GMA and starch showed well-dispersed starch domain in the matrix and better mechanical strength than the unmodified PCL/starch blend. However, the reaction between PCL-g-GMA and starch induced a crosslinking during the reactive blending and this crosslinking in the blend lowered the biodegradation of the blend during the composting test. The biodegradability was investigated by the weight loss and surface morphology change of the blend in the composting medium
A study on the double insulating layer for HgCdTe MIS structure
No full textThe double insulating layer consisting of anodic oxide grown in H2O2 electrolyte and thermally evaporated ZnS fiIm was formed for HgCdTe metal-insulator-semiconductor (MIS) structure in connection with the improvement of HgCdTe surface passivation. It was found for the first time through transmission electron microscopy (TEM) observation that an interface layer of 15 nm in thickness was formed between ZnS and anodic oxide layer. The chemical compositions investigated by energy dispersive: spectroscopy (EDS) using TEM and XPS measurements of depth composition profile and Zn chemical state indicated that the interface layer is composed of ZnO. It can be deduced that ZnO interface layer was caused by the chemical reactions between Zn atoms adsorbed on the surface of anodic oxide and the oxygen atoms diffusing out to the oxide surface in the initial stage of ZnS evaporation. Also TEM high resolution image showed that the structure of anodic oxide layer was changed from the amorphous state to the nanocrystalline structure of 10 nm in diameter after the evaporation of ZnS. The resistivity of double insulating layer was measured to be about 10(10) Omega cm which was proper as an insulating layer for HgCdTe MIS device. The small optical reflectance of about 75 in the region of 5 mu m showed an anti-reflection effect of the double insulating layer. The measured high frequency C-V curve showed a large shift of Rat band voltage due to the high density of fixed oxide charges, about 1.2 x 10(12) cm(-2). The oxygen vacancies and possible cationic state of Zn in the anodic oxide layer were estimated to cause this high density of fixed oxide charges
MRAC load torque observer for position control of a brushless DC motor
No full textA new control method for the robust position control of a brushless DC (BLDC) motor using the adaptive load torque observer is presented. For a BLDC motor system, approximately linearized using the held-orientation method, it is shown that the augmented state variable feedback can be applicable to this system. To overcome the problem of the unknown parameter, or of parameter variation such as a flux linkage, a model following adaptive control mechanism is employed for the load torque observer. Stability analysis is carried out using the Lyapunov stability theorem. As a result, the robustness can be obtained without affecting the overall system response. The load disturbance detected by the adaptive O-observer is compensated for by feedforwarding the equivalent current having the fast response
Efficient transmit power allocation with partial feedback for closed-loop SQRD based V-BLAST systems
No full textThis letter proposes an efficient transmit power allocation using partial channel information feedback for the closed-loop sorted QR decomposition (SQRD) based V-BLAST systems. For the feedback information, the positive real-valued diagonal elements of R are forwarded to the transmitter. With the proposed transmit power allocation that is numerically derived by the Lagrange optimization method, the bit error rate performance of the system can be remarkably improved compare to the conventional open-loop SQRD based V-BLAST systems without increasing the receiver complexity
Application of MEUF on removal heavy metal in the wastewater containing chelating agent by using a cationic surfactant
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