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Tsinghua Science and Technology

Issue 5 • Date Oct. 2005

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Displaying Results 1 - 22 of 22
  • [Front cover]

    Publication Year: 2005 , Page(s): c1
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    Freely Available from IEEE
  • Contents

    Publication Year: 2005 , Page(s): 1
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  • Ternary diffusion coefficients of 1-hexanol-hexane-toluene and 1-propanol-water-ethylene glycol by Taylor dispersion method

    Publication Year: 2005 , Page(s): 523 - 528
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1173 KB)  

    The Taylor dispersion method was used to measure diffusion coefficients of three-component liquid systems. An improved constrained nonlinear least-square method was used to evaluate the ternary diffusion coefficients directly by fitting the mathematical solutions of the dispersion equation to eluted solute peaks detected using a differential refractometer. Diffusion coefficients of the three-component system of acetone-benzene-CCl4, determined at 25°C, were used to test the procedure. The measured diffusion coefficients were compared with values obtained by optical interferometry and the diaphragm cell method. Ternary diffusion coefficients are also determinated for solutions of 1-hexanol-hexane-toluene and 1-propanolwater-ethylene glycol at 25°C, with an accuracy of approximately 0.05 m 2·s-1. View full abstract»

    Open Access
  • Rapid cloning and expression of glutaryl-7-aminocephalosporanic acid acylase genes from soil samples

    Publication Year: 2005 , Page(s): 529 - 534
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1862 KB)  

    A polymerase chain reaction (PCR)-based strategy was developed to rapidly obtain the gene encoding for an industrially important enzyme, glutaryl-7-aminocephalosporanic acid (GL-7-ACA) acylase. Different soil samples were cultured with a Pseudomonas selective medium to enrich specific microorganisms, and then the genomic DNA was extracted to serve as PCR templates. PCR primers for GL-7-ACA acylase gene amplification were designed on the basis of bioinformatics searches and analyses. The method was used to successfully amplify three GL-7-ACA acylase genes from different soil samples. The GL-7-ACA acylase genes were then cloned and overexpressed in Escherichia coli with a relatively high level of 266 unit • L −1. View full abstract»

    Open Access
  • Preparation and adsorption ability of polysulfone microcapsules containing modified chitosan gel

    Publication Year: 2005 , Page(s): 535 - 541
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    Chemically modified chitosan beads containing polyethyleneimine (PEl) were prepared to improve the metal ion adsorption capacity of the chitosan beads and their mechanical stability and to limit their biodegradability. The modified beads were encapsulated with the polymer material polysulfone by a novel surface coating method named the emulsion phase inversion method. The adsorption properties of the modified beads and the microstructures of the polysulfone coating layer were then analyzed. The experimental results showed that the PEl was successfully linked onto the chitosan beads. The density of the 2 /span>groups in the modified beads was significantly increased, while the water content was reduced. The coating layer thickness was about 200μm. The modified chitosan gel beads hed excellent Cu(ll)adsorption capcity, with a maximum Cu(ll) adsorption capacity 1.34 times higher than that of the unmodified beads. The result show that even with the polysulfone coating the adsorption kinetics of the modified beads is still better than those of the unmodified beads. The modification improve the mass transfer performance of the chitosan beads as well as the stability. View full abstract»

    Open Access
  • Transdermal delivery of piroxicam by surfactant mediated electroporation

    Publication Year: 2005 , Page(s): 542 - 547
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    A lipophilic, nonsteroidal antiinflammation drug, piroxicam, was administered by skin electroporation using short, high-voltage pulses. The transdermal delivery of piroxicam during the electroporation was buffered due to the higher partition in skin lipids than in aqueous environments, which is called entrapment. Entrapment is the main resistance to transdermal delivery of lipophilic drugs. Two types of surfactants were used to enhance the skin electroporation. Tween 80 (0.2 gIL) and sodium dodecyl sulphate (SOS, 3 mg/mL) improve the solubility and diffusion rate of the drug in the hydrophobic local transport regions and reduce the entrapment of piroxicam in the skin. The transdermal delivery rate of piroxicam is increased 30- to 50-fold. However, the entrapment of piroxicam in the skin still occurred when Tween 80 was added. The SOS provides higher and more stable transdermal delivery rates of piroxicam than Tween 80, and also reduces the entrapment of piroxicam in the skin. View full abstract»

    Open Access
  • Prediction of solid-liquid equilibrium for KCI in mixed water-ethanol solutions using the liquac model

    Publication Year: 2005 , Page(s): 548 - 553
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    The LIQUAC model is often used to predict vapor-liquid equilibria, osmotic coefficients, and mean ion activity coefficients for electrolyte systems. This paper describes a thermodynamic method to analyze solid-liquid equilibrium for electrolytes in mixed solvents solutions using the LIQUAC model. The KCI solubilities in mixed water-ethanol solutions are predicted with the LIQUAC model and its original interaction parameters. This method is also used to obtain new K+-ethanol interaction parameters in the LIQUAC model from the solubility data. The new interaction parameters accurately predict the vapor-liquid equilibrium data of K+ salts (including KCI, KBr, and KCOOCH3) in mixed water-ethanol solutions. The results illustrate the flexibility of the LIQUAC model which can predict not only vapor-liquid equilibrium but also solid-liquid equilibrium in mixed solvent systems. View full abstract»

    Open Access
  • Tin oxide and carbon composite (Sn6O4(OH)4/AG) as the anode in a lithium ion battery

    Publication Year: 2005 , Page(s): 554 - 560
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1664 KB)  

    A tin oxide and carbon composite (Sn6O4(OH)4/AG) with a Sn content of 0.15–0.30 was prepared by chemical deposition at normal pressures and temperatures. The structures of the artificial graphite (AG), the Sn6O4(OH)4, and the Sn6O4(OH)4/AG were analyzed using X-ray diffraction. The electrochemical lithiation was investigated by measuring the galvanostatic charge and discharge ratio. The electrochemical capacities of the three materials during the first discharge were 310 mAh/g (AG), 616 mAh/g (Sn6O4(OH)4/AG), and 1090 mAh/g (Sn6O4(OH)4). The discharge capacity of the Sn6O4(OH)4/AG was larger than the simple sum of the capacities provided by AG and Sn6O4(OH)4 with the same content. The cyclic performance of Sn6O4(OH)4/AG was also better than that of Sn6O4(OH)4 for voltages of 0 to 3 V. The results imply that the interaction between Sn and C in Sn6O4(OH)4/AG is very strong and effectively inhibits the volume expansion of the Sn. View full abstract»

    Open Access
  • Prediction of liquid-liquid equilibrium using the group solubility parameter model

    Publication Year: 2005 , Page(s): 561 - 566
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    The group solubility parameter (GSP) model was used to analyze the liquid-liquid equilibrium (LLE) of ternary and quaternary systems. The GSP parameters are divided into four dimensions representing the four major intermolecular forces. The values of the parameters were determined by regression using the nonlinear SIMPLEX optimization method to fit the LLE data of 548 ternary and 26 quaternary systems selected from the literature. LLE predictions of 8 ternary systems were then made using the fit parameters. Comparison of the results with predictions using the modified UNIFAC model shows that the GSP model has less adjustable parameters to achieve a similar accuracy and that the parameter values are easily acquired by analysis of available data. View full abstract»

    Open Access
  • Crocin synthesis mechanism in Crocus sativus

    Publication Year: 2005 , Page(s): 567 - 572
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    Saffron (Crocus sativus) cells can synthesize crocin, crocetin digentiobiosyl ester, in suspension cultures. The crocin family biosynthesis mechanism was studied using high pressure liquid chromatography (H PLC) to determinate the glucosyltransferase activity and to develop a method for synthesizing medicine from saffron cells. Previous studies indicated that two glucosyltransferases might be involved in the formation of crocetin glucosyl- and gentiobiosyl-esters. GTase 1 formed an ester bond between crocetin carboxyl groups and glucose moieties while GTase 2 catalyzed the formation of glucosidic bonds with glucosyl ester groups at both ends of the molecule. These enzymes can catalyze the formation of crocetin glucosides in vitro. GTase 1 activity is higher during the first four days of crocin glucosides biosynthesis, but decreases after four days. The formation and accumulation of crocin increase during the first six days and stabilized on the eighth day. View full abstract»

    Open Access
  • Morphological transformation of plant cells in vitro and its effect on plant growth

    Publication Year: 2005 , Page(s): 573 - 578
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2068 KB)  

    Enhancement of cell growth in suspension cultures is urgently needed in plant cell culture engineering. This study investigates the relationship between morphological transformation and cell growth in callus and suspension cultures of saffron cells belonging to the cell line C96 induced from Crocus sativus L. In the suspension culture, an unbalanced osmotic pressure between the intracell and extracell regions induced a large morphological transformation which affected normal division of the saffron cells. An increase in osmotic pressure caused by the addition of sucrose inhibits the vacuolation and shrinkage of cytoplasm in the cells. As the sucrose concentration increases, the total amount of accumulated biomass also increases. Besides the sucrose concentration, increased ionic strength and inoculation ratio also help restrain to a large extent the vacuolation and shrinkage of the cytoplasm in the suspended cells, which results in increased biomass. The conditions for optimal biomass are: Murashige and Skoog's (MS) medium with 40 g/Lsucrose and 60% (v/v) inoculation ratio. View full abstract»

    Open Access
  • Weak-keys in public key cryptosystems based on discrete logarithms

    Publication Year: 2005 , Page(s): 579 - 581
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    The discrete logarithm method is the foundation of many public key algorithms. However, one type of key, defined as a weak-key, reduces the security of public key cryptosystems based on the discrete logarithm method. The weak-key occurs if the public key is a factor or multiple of the primitive element, in which case the user's private key is not needed but can be obtained based on the character of the public key. An algorithm is presented that can easily test whether there is a weak-key in the cryptosystem. An example is given to show that an attack can be completed for the Elgamal digital signature if a weak-key exists, therefore validating the danger of weak-keys. Methods are given to prevent the generation of these weak-keys. View full abstract»

    Open Access
  • Multivariate statistical process monitoring using robust nonlinear principal component analysis

    Publication Year: 2005 , Page(s): 582 - 586
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (922 KB)  

    The principal component analysis (PCA) algorithm is widely applied in a diverse range of fields for performance assessment, fault detection, and diagnosis. However, in the presence of noise and gross errors, the nonlinear PCA (NLPCA) using autoassociative bottle-neck neural networks is so sensitive that the obtained model differs significantly from the underlying system. In this paper, a robust version of NLPCA is introduced by replacing the generally used error criterion mean squared error with a mean log squared error. This is followed by a concise analysis of the corresponding training method. A novel multivariate statistical process monitoring (MSPM) scheme incorporating the proposed robust NLPCA technique is then investigated and its efficiency is assessed through application to an industrial fluidized catalytic cracking plant. The results demonstrate that, compared with NLPCA, the proposed approach can effectively reduce the number of false alarms and is, hence, expected to better monitor real-world processes. View full abstract»

    Open Access
  • Image reconstruction using a genetic algorithm for electrical capacitance tomography

    Publication Year: 2005 , Page(s): 587 - 592
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1424 KB)  

    Electrical capacitance tomography (ECT) has been used for more than a decade for imaging dielectric processes. However, because of its ill-posed ness and non-linearity, ECT image reconstruction has always been a challenge. A new genetic algorithm (GA) developed for ECT image reconstruction uses initial results from a linear back-projection, which is widely used for ECT image reconstruction to optimize the threshold and the maximum and minimum gray values for the image. The procedure avoids optimizing the gray values pixel by pixel and significantly reduces the search space dimension. Both simulations and static experimental results show that the method is efficient and capable of reconstructing high quality images. Evaluation criteria show that the GA-based method has smaller image error and greater correlation coefficients. In addition, the GA-based method converges quickly with a small number of iterations. View full abstract»

    Open Access
  • Implementation of direct torque control scheme for induction machines with variable structure controllers

    Publication Year: 2005 , Page(s): 593 - 597
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (969 KB)  

    A torque control scheme for high-performance induction machine drives was developed to overcome some disadvantages of direct torque control (DTC). In the improved DTC method, the stator flux and the torque controllers use variable-structure control theory which does not require information about the rotor speed. Space vector modulation is applied to the voltage source inverter to reduce the torque, stator flux, and current ripples. The digital signal processor-based implementation is described in detail. The experimental results show that the system has good torque and stator flux response with small ripples. View full abstract»

    Open Access
  • On-line partial discharge monitoring and diagnostic system for power transformer

    Publication Year: 2005 , Page(s): 598 - 604
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1358 KB)  

    This paper introduces a computerized on-line partial discharge (PD) monitoring and diagnostic system for transformers. The system, which is already in use in a power station, uses wide-band active transducers and a data acquisition unit with modularized and exchangeable components. The system software is a power equipment monitoring and diagnostic system, which is based on the component object model, and was developed for monitoring multiple parameters in multiple power supply systems. The statistical characteristics of PDs in power transformers were studied using 7 experimental models for simulating PDs in transformers and 3 models for simulating interfering discharges in air. The discharge features were analyzed using a 3-D pattern chart with a three-layer back-propagation artificial neural network used to recognize the patterns. The results show that PDs in air and oil can be distinguished. The model can be used for interference rejection on-line monitoring of partial discharge in transformers. View full abstract»

    Open Access
  • Iterative method for constructing complete complementary sequences with lengths of 2mN

    Publication Year: 2005 , Page(s): 605 - 609
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (685 KB)  

    Complete complementary sequences are widely used in spectrum spread communications because of their ideal correlation functions. A previous method generates complete complementary sequences with lengths of Nn N (n, N ∊ Z+). This paper presents a new iterative method to construct complete complementary sequences with lengths of 2m N (m, N ∊ Z+). The analysis proves that this method can produce many sequence sets that do not appear in sequence sets generated by the former method, especially shorter sequence sets. The result will certainly increase the application of complete complementary sequences in communication engineering and related fields. View full abstract»

    Open Access
  • Advanced ECU software development method for fuel cell systems

    Publication Year: 2005 , Page(s): 610 - 617
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1457 KB)  

    The electronic control unit (ECU) in electrical powered hybrid and fuel cell vehicles is exceedingly complex. Rapid prototyping control is used to reduce development time and eliminate errors during software development. This paper describes a high-efficiency development method and a flexible tool chain suitable for various applications in automotive engineering. The control algorithm can be deployed directly from a Matlab/Simulink/Stateflow environment into the ECU hardware together with an OSEK real-time operating system (RTOS). The system has been successfully used to develop a 20-kW fuel cell system ECU based on a Motorola PowerPC 555 (MPC555) microcontroller. The total software development time is greatly reduced and the code quality and reliability are greatly enhanced. View full abstract»

    Open Access
  • Numerical investigation of fire smoke transport in the Tsinghua University Sports Center

    Publication Year: 2005 , Page(s): 618 - 622
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2250 KB)  

    Fire Dynamics Simulator v3.0 was used to investigate and assess fire smoke transport and management in a realistic indoor sports center. An atrium fire test case illustrated the code's superiority over code-type empirical models for both accuracy and capability. Four fire scenarios in the Tsinghua University Sports Center were then simulated. The smoke layer's descent speed was predicted for each case. The importance of the door effect was revealed and an additional mechanical ventilation system for the building was proved to be of no help. The door effect must be carefully considered in future fire safety designs. View full abstract»

    Open Access
  • Analysis of alignment influence on 3-D anthropometric statistics

    Publication Year: 2005 , Page(s): 623 - 626
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (779 KB)  

    Three-dimensional (3-D) surface anthropometry can provide much more useful information for many applications such as ergonomic product design than traditional individual body dimension measurements. However, the traditional definition of the percentile calculation is designed only for 1-D anthropometric data estimates. The same approach cannot be applied directly to 3-D anthropometric statistics otherwise it could lead to misinterpretations. In this paper, the influence of alignment references on 3-D anthropometric statistics is analyzed mathematically, which shows that different alignment reference points (for example, landmarks) for translation alignment could result in different object shapes if 3-D anthropometric data are processed for percentile values based on coordinates and that dimension percentile calculations based on coordinate statistics are incompatible with those traditionally based on individual dimensions. View full abstract»

    Open Access
  • Fuzzy multiple attribute decision making for evaluating aggregate risk in green manufacturing

    Publication Year: 2005 , Page(s): 627 - 632
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    Industrial risk and the diversification of risk types both increase with industrial development. Many uncertain factors and high risk are inherent in the implementation of new green manufacturing methods. Because of the shortage of successful examples and complete and certain knowledge, decision-making methods using probabilities to represent risk, which need many examples, cannot be used to evaluate risk in the implementation of green manufacturing projects. Therefore, a fuzzy multiple attribute decision-making (FMADM) method was developed with a three-level hierarchical decision-making model to evaluate the aggregate risk for green manufacturing projects. A case study shows that the hierarchical decision-making model of the aggregate risk and the FMADM method effectively reflect the characteristics of the risk in green manufacturing projects. View full abstract»

    Open Access
  • Economics and performance forecast of gas turbine combined cycle

    Publication Year: 2005 , Page(s): 633 - 636
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    Forecasts of the economics and performance of gas turbine combined cycle (GTCC) with various types of gas turbines will help power plant designers to select the best type of gas turbine for future Chinese powerplants. The cost and performance of various designs were estimated using the commercial software GT PRO. Improved GTCC output will increase the system efficiency which may induce total investment and will certainly increase the cumulative cash which then will induce the cost and the payback period. The relative annual fuel output increases almost in proportion to the relative GTCC output. China should select the gas turbine that provides the most economical output according to its specific conditions. The analysis shows that a GTCC power plant with a medium-sized 100 to 200MW output gas turbine is the most suitable for Chinese investors. View full abstract»

    Open Access

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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