Broad-band MMICs based on modified loss-compensation method using 0.35-/spl mu/m SiGe BiCMOS technology

Using the concept of loss compensation, novel broad-band monolithic microwave integrated circuits (MMICs), including an amplifier and an analog multiplier/mixer, with LC ladder matching networks in a commercial 0.35-mum SiGe BiCMOS technology are demonstrated for the first time. An HBT two-stage cascade single-stage distributed amplifier (2-CSSDA) using the modified loss-compensation technique is presented. It demonstrates a small-signal gain of better than 15 dB from dc to 28 GHz (gain-bandwidth product=157 GHz) with a low power consumption of 48 mW and a miniature chip size of 0.63 mm² including testing pads. The gain-bandwidth product of the modified loss-compensated CSSDA is improved approximately 68% compared with the conventional attenuation-compensation technique. The wide-band amplifier achieves a high gain-bandwidth product with the lowest power consumption and smallest chip size. The broad-band mixer designed using a Gilbert cell with the modified loss-compensation technique achieves a measured power conversion gain of 19 dB with a 3-dB bandwidth from 0.1 to 23 GHz, which is the highest gain-bandwidth product of operation among previously reported MMIC mixers. As an analog multiplier, the measured sensitivity is better than 3000 V/W from 0.1 to 25 GHz, and the measured low-frequency noise floor and corner frequency can be estimated to be 20 nV/sqrt(Hz) and 1.2 kHz, respectively. The mixer performance represents state-of-the-art result of the MMIC broad-band mixers using commercial silicon-based technologies     

Effects of free convection and mass transfer on the flow past an impulsively moving infinite vertical circular cylinder

The effects of free convection and mass transfer are taken into account for the Stokes' problem of the flow near an impulsively moving infinite vertical circular cylinder. Expressions of the velocity, temperature, concentration and skin friction of the fluid in closed form are obtained by the Laplace transform technique. The results based on various values of the parameters Gr (Grashof number), Gm (modified Grashof number), Sc (Schmidt number) and Pr (Prandtl number) are given in graphical form. It will be seen that there is a rise in the velocity due to the presence of a foreign mass. But higher Sc yields the lower velocity and skin friction. As the radius of the circular cylinder approaches to infinite, the results presented in this paper agree with those of V.M. Soundalgekar's and C.K. Chen's etc. for the flow past an impulsively moving infinite vertical plate.     

Densitometry determination of dioxins using gold nanoparticlemodified dioxin response element probes

This study aims to develop a rapid and sensitive densitometry bioassay of dioxins. It is known that dioxin ligand can bind heterodimeric aryl hydrocarbon receptor (AhR) and trigger the formation of the complex of dioxin-AhR, AhR nuclear translocator (Arnt), and dioxin-responsive element (DRE). We have established a rapid and sensitive method using nanoparticle-modified DRE probes based on dioxin-dependent binding of DRE to AhR complex. Dioxins can trigger the binding of nanoparticle-modified DRE probe to AhR complex. The nanoparticle-modified DRE probes in the dioxin-AhR-Arnt-DRE complexes immobilized on the microplates were detected by measuring optical density after silver enhancement. Results showed that as little as 0.01 pM of TCDD could be detected. Dioxins could be quantified accurately with the linear range from 1 nM to 0.01 pM. The coefficient of variation was 5≈8% in this bioassay. The optical density of nanoparticle-based silver enhancement was produced in a dose- and time- dependent manner. The dioxin concentrations in fly ash samples determined by this bioassay were comparable with that by the standard HRGC/HRMS. Thus this bioassay is a sensitive and convenient cell-free bioassay of dioxin that is suitable for screening of dioxins in environmental or food matrices.     

Isothermal crystallization kinetics and melting behavior of nylon/saponite and nylon/montmorillonite nanocomposites

DSC thermal analysis and X‐ray diffraction have been used to investigate the isothermal crystallization behavior and crystalline structure of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliating the layered silicates by subsequent polymerization. The DSC isothermal results reveal that introducing saponite into the nylon structure causes strongly heterogeneous nucleation induced change of the crystal growth process from a two‐dimensional crystal growth to a three dimensional spherulitic growth. But the crystal growth mechanism of nylon/montmorillonite nanocomposites is a mixed two‐dimensional and three‐dimensional spherulitic growth. The activation energy drastically decreases with the presence of 2.5 wt % clay in nylon/clay nanocomposites and then slightly increases with increasing clay content. The result indicates that the addition of clay into nylon induces the heterogeneous nucleation (a lower ΔE) at lower clay content and then reduces the transportation ability of polymer chains during crystallization processes at higher clay content (a higher ΔE). The correlation among crystallization kinetics, melting behavior, and crystalline structure of nylon/clay nanocomposites is also discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2196–2204, 2004     

Synthesis and characterization of a positive‐working,aqueous‐base‐developable photosensitive polyimide precursor

A positive‐working, aqueous‐base‐developable photosensitive polyimide precursor based on poly(amic ester)‐bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2′‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and bis(n‐butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300°C produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass‐transition temperature at 356°C and a 5% weight loss at 474°C in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and ¹H‐NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoquinone photoactive compound showed a sensitivity of 150 mJ/cm² and a contrast of 1.65 in a 3 μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 μm was obtained from this composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 352–358, 2002     

基于Generative Component的中国古建筑参数化设计

为有效分析古建筑,利用参数化建模软件Generative Component（GC）,结合编程设计对中国古建筑主要结构和构件进行参数化分析,找出其内在结构的规律性及各构件之间的参数关系,实现古建筑的数字化、参数化描述,生成参数可修改的结构化三维模型.     

Extraction of genomic DNA and detection of single nucleotide polymorphism genotyping utilizing an integrated magnetic bead-based microfluidic platform

This study presents a new magnetic bead-based microfluidic platform, which integrates three major modules for rapid leukocytes purification, genomic DNA (gDNA) extraction and fast analysis of genetic gene. By utilizing microfluidic technologies and magnetic beads conjugated with CD_15/45 antibodies, leukocytes in a human whole blood sample can be first purified and concentrated, followed by extraction of gDNA utilizing surface-charge switchable, DNA-specific, magnetic beads in the lysis solution. Then, specific genes associated with genetic diseases can be amplified by an on-chip polymerase chain reaction (PCR) process automatically. The whole pretreatment process including the leukocytes purification and gDNA extraction can be performed in an automatic fashion with the incorporation of the built bio-separators consisting of microcoils array within less than 20 min. The detection of single nucleotide polymorphism (SNP) genotyping of methylenetetra-hydrofolate reductase (MTHFR) C677T region associated with an increased risk of genetic diseases was further performed to demonstrate the capability of the proposed system. The extracted gDNA can be transported into a micro PCR chamber for on-chip fast nucleic acid amplification of detection genes with minimum human intervention. Hence, the developed system may provide a powerful automated platform for pretreatment of human leukocytes, gDNA extraction and fast analysis of genetic gene.     

High-capacity reversible data hiding by maximum-span pairing

In this paper, we propose a reversible data hiding method for ordered dithered halftone images. To achieve reversibility and high capacity, the proposed method decomposes an ordered dithered halftone into a maximal number of subimage pairs with the same characteristic, and then hides data with a subimage-swapping operation, which converts a subimage pair into a subimage pair with opposite characteristic. Besides, this method maintains good visual quality by exchanging neighboring pixels instead of flipping individual pixels. Experimental results show that this method has the highest capacity among the existing reversible data hiding methods. A reversible authentication watermarking system is also proposed using this reversible watermarking method and it shows better visual quality compared to an existing method.     

Numerical simulation of detonation using an adaptive Cartesian cut-cell method combined with a cell-merging technique

A second-order accurate scheme for the Cartesian cut-cell method developed previously by the authors [Ji H, Lien F-S, Yee E. Comput. Methods Appl. Mech. Eng. 198 (2008), 432] is generalized for application to both two- and three-dimensional inviscid compressible flow problems. A cell-merging approach is used to address the so-called “small cell” problem that has plagued Cartesian cut-cell methods. In the present cell-merging approach, the conservative variables are stored at the cut-cell centroid (including the non-merged and merged cut-cells) rather than at the Cartesian cell center. Although this approach results in a more complicated search algorithm for the determination of the neighbor cells (required for the computation of the spatial gradients of the conservative variables), this approach enables the straightforward formulation of a higher than first-order accurate discretization scheme in the vicinity of the (complex and irregular) internal boundaries of the flow domain. Six test cases (including detonation problems) are used to demonstrate the accuracy and capability of the adaptive cut-cell method, for which both mesh refinement and derefinement techniques are employed in the case of an unsteady shock diffraction problem.     

Building strength models for high-performance concrete at different ages using genetic operation trees, nonlinear regression, and neural networks

Because the behavior of HPC at early age may be rather different at late age, this study proposed to establish the strength models of HPC at different ages, and to explore the difference between these models. A large number of experimental data were used to compare accuracy of the three model building techniques, nonlinear regression analysis (NLRA), back-propagation networks (BPN), and genetic operation trees (GOT). The results showed: (1) when NLRA was employed to establish the prediction model, the approach to establish HPC strength models based on the three separate data sets was more accurate than that used to establish HPC strength models for the total data set. (2) If an explicit formula is necessary, GOT is the best choice to build concrete strength models at medium and late ages (i.e., more than 14 days), while NLRA provides greater accuracy at early ages (i.e., less than 14 days); otherwise, BPN is the best choice.