Showing papers by "Shanghai Jiao Tong University published in 1998"

An EBIT-Based Model of Dynamic Capital Structure

Abstract: Much of the literature on optimal capital structure has taken the unlevered firm value to be the underlying state variable, even though the unlevered firm ceases to exist after a capital structure change occurs. This approach has been a source of confusion, leading to conflicting views on the relationship between the levered and unlevered firm value at the moment of a capital structure change. Moreover, these frameworks imply that the role of government is to create a 'tax benefit' cash-flow into a firm, when in practice much of the cash that flows out of a firm is typically paid to government via taxes. To circumvent these difficulties, we take the claim to future EBIT as the underlying state variable, and assume that it is invariant to changes in capital structure. In such a framework, all claims to EBIT (equity, debt, government) are treated in a consistent fashion. In particular, the government claim is correctly modeled as an outflow of EBIT via taxes, rather than as an inflow of 'tax benefits'. This distinction dramatically affects the payout ratio, which in turn affects both the probability of bankruptcy and predicted yield spreads. In addition, the invariance feature of the state variable makes this framework ideal for investigating optimal dynamic capital structure strategy. When firms are permitted to increase their level of outstanding debt in the future, predicted leverage ratios are consistent with those observed.

ASCA Measurements of Silicon and Iron Abundances in the Intracluster Medium

Abstract: We analyzed the ASCA X-ray data of 40 nearby Clusters of galaxies, whose intracluster-medium temperature distributes in the range of 0.9-10 keV. We measured the Si and Fe abundances of the intracluster medium, spatially averaging over each Cluster, but excluding the central ~ 0.15/I^Q1 Mpc region in order to avoid any possible abundance gradients and complex temperature structures. The Fe abundances of these Clusters are 0.2-0.3 solar, with only weak dependence on the temperature of the intracluster medium, hence on the Cluster richness. In contrast, the Si abundance is observed to increase from 0.3 to 0.6-0.7 solar from the poorer to richer Clusters. These results suggest that the Supernovae of both type-Ia and type-II significantly contribute to the metal enrichment of the intracluster medium, with the relative contribution of type-II Supernovae increasing towards richer Clusters. We suggest a possibility that a considerable fraction of type-II Supernova products escaped from poorer Systems.

Multicasting optical cross connects employing splitter-and-delivery switch

Abstract: A new splitter-and-delivery (SAD) switch having multicasting capability is proposed. It is best implemented in a single silicon board using planar silica waveguide technology. Less than -40-dB crosstalk is achievable by an auxiliary action of the optical gate. Three optical cross-connect architectures employing the SAD switch are proposed. They are strictly nonblocking and have multicasting capability. Furthermore, they have wavelength or fiber modular structures and are expandable when the number of the fibers and the wavelengths increase a few or by a few times. The expanding method and other important issues are discussed in detail.

Homotopy analysis method: a new analytic method for nonlinear problems

Abstract: In this paper, the basic ideas of a new analytic technique, namely the Homotopy Analysis Method (HAM), are described. Different from perturbation methods, the validity of the HAM is independent on whether or not there exist small parameters in considered nonlinear equations. Therefore, it provides us with a powerful analytic tool for strongly nonlinear problems. A typical nonlinear problem is used as an example to verify the validity and the great potential of the HAM.

Robust right coprime factorization and robust stabilization of nonlinear feedback control systems

Abstract: Robust right coprime factorization and robust stabilization of nonlinear feedback control systems are studied. The concept of robust right coprime factorization of nonlinear operators for feedback control systems is introduced. Some conditions for the robustness of a right coprime factorization of a nonlinear plant under unknown but bounded perturbations are derived. An example with a closed-form solution is included to illustrate the general theory and a step-by-step construction of the robust factorization and the robust stabilization.

Method for detecting all-zero DCT coefficients ahead of discrete cosine transformation and quantisation

Abstract: The authors present a new algorithm for detecting all-zero DCT coefficient blocks before discrete cosine transformation and quantisation in very low bit rate video coding. The proposed algorithm uses the sum of absolute difference (SAD) of each motion compensation block as the criteria. Because the SAD can be obtained after motion estimation, no additional computation is required. Results show that the proposed algorithm can be used to reduce the amount of computation significantly without sacrificing video coding quality.

Nondegradative melt functionalization of polypropylene with glycidyl methacrylate

Abstract: The melt grafting of glycidyl methacrylate (GMA) onto powdered isotactic polypropylene (PP) in a Haake Rheocord RC90 mixer was studied. Grafting degrees were determined by nonaqueous back titration of trichloroacetic acid with sodium hydroxide. The extent of degradation and crosslinking of PP during grafting was indicated by the melt-flow rates (MFR) of the grafted samples. The influences of GMA concentration, initiator type and concentration on grafting degree, reaction efficiency, and degradation were evaluated. A novel method was developed to obtain a high grafting degree with little degradation of PP using acrylamide (AM) as the initiating agent. The grafting process occurred before or during the melting of PP (i.e., solid-state grafting), at which temperature crosslinking is preferred over chain scission. Primary free radicals generated from the rapid decomposition of AM have a higher tendency to attack GMA molecules than PP chains. At the same estimated amount of primary radicals, both grafting degree and grafting efficiency increase with decreasing decomposition temperature of the initiator (for the same decomposition half-life) in the order of AM > benzoyl peroxide (BPO) > 2,5-di(t-butylperoxy)-2,5-dimethyl-3-hexyne (LPO). FunctionalizedPP with the desired grafting degree and little degradation of PP could be obtained by the use of mixed initiators. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1957–1963, 1998

Reliability analysis of circulant graphs

Abstract: The circulant graphs are of particular interest as models of communication networks. In this work, we present new reliability analysis results for circulants based on the concept of restricted edge connectivity, which generalizes the super-λ property of a graph. We evaluate the restricted edge connectivity λ′ and the number of i-cutsets Ni(G), λ ≤ i < λ′, for any circulant graph explicitly. This improves the previous results on the subject. © 1998 John Wiley & Sons, Inc. Networks 31:61–65, 1998

A new Razumikhin theorem for delay difference equations

Abstract: In this paper, we established a new Razumikhin-type theorem on stability for delay difference equations.

Discovery of the Central Excess Brightness in Hard X-Rays in the Cluster of Galaxies Abell 1795

Abstract: Using the X-ray data from ASCA, spectral and spatial properties of the intracluster medium (ICM) of the cD cluster Abell 1795 are studied up to a radial distance of ~12' (~1.3 h50−1 kpc). The ICM temperature and abundance are spatially rather constant, although the cool emission component is reconfirmed in the central region. The azimuthally averaged radial X-ray surface brightness profiles are very similar between soft (0.7-3 keV) and hard (3-10 keV) energy bands, and neither can be fitted with a single-β model due to a strong data excess within ~5' of the cluster center. In contrast, double-β models can successfully reproduce the overall brightness profiles both in the soft and hard energy bands, as well as that derived with the ROSAT PSPC. Properties of the central excess brightness are very similar over the 0.2-10 keV energy range spanned by ROSAT and ASCA. Thus, the excess X-ray emission from the core region of this cluster is confirmed for the first time in hard X-rays above 3 keV. This indicates that the shape of the gravitational potential becomes deeper than the King-type one toward the cluster center. Radial profiles of the total gravitating matter, calculated using the double-β model, reveal an excess mass of ~3 × 1013 M☉ within ~150 h50−1 kpc of the cluster center. This suggests a hierarchy in the gravitational potential corresponding to the cD galaxy and the entire cluster.

A PDES/STEP-based information model for computer-aided process planning

Abstract: Computer Aided Process Planning (CAPP) constitutes one of the most essential elements in Computer Integrated Manufacturing (CIM). Although many CAPP systems have been reported in literature during the last two decades, few of them are compatible enough to integrate easily with other systems in the CIM environment. One major reason is the lack of an effective method to represent the information required by CAPP, and to unify such information with the information of other systems in the CIM environment. Indeed, this problem has received relatively inadequate attention in the recent research of CAPP systems. In this paper, an information model for CAPP is developed by using the object-oriented modeling and the Product Data Exchange Step / STandard of Exchange Product data (PDES/STEP) techniques. The model consists of the part information model, the process plan information model, and the production resource information model. The EXPRESS language or the EXPRESS-G diagram is used to represent these models. Indeed, the proposed information model will greatly improve the CAPP system’s capability of effective integration with other systems in the CIM environment, and, ultimately, to facilitate the implementation of the whole CIM strategy in manufacturing enterprises.

The interfacial reaction characteristics in SiC/Al composite above liquidus during remelting

Abstract: The development of interfacial reaction between matrix and reinforcement during the remelt recycling is critical to the commercialization and sustainable-development of metal matrix composite, but it is very difficult to characterize the interfacial reaction between the reinforcement and matrix melt above the liquids using a conventional experimental method. In this paper, the interfacial reaction characteristics in SiCp/Al composite above liquids were investigated using liquid metal X-ray diffraction and differential scanning calorimeter (DSC). A solute-rich region with much more Si content above liquids was observed in the composite melt, and the experimental results also showed that the interfacial reaction feature is associated with the solute-rich region with much more Si content. Mechanism for the observed phenomena was discussed in detail.

Structure and spectroscopic characterization of polycrystalline vanadyl phthalocyanine (VOPc) films fabricated by vacuum deposition

Abstract: The polycrystalline VOPc films in phases I, II, and a less-crystallized α-form have been fabricated on an indium-tin-oxide-glass substrate. Room-temperature and low-temperature visible absorption spectroscopy. Fourier-transform infrared spectra, and X-ray diffraction patterns have been used to characterize and analyze the packing structures and interactions of VOPc molecules. Bethe splitting. broadening, and redshift of the Q absorption band have been observed in the three packing structures. Thermochromism was found in phase II and the less-crystallized α-form, but not in phase I, from the temperature dependence of the absorption spectra. The liquid nitrogen was found to be effective in the crystallization of VOPc molecules.

Pitting behavior of SiCp 2024 Al metal matrix composites

Abstract: The effects of the volume fraction of SiC particulate reinforcements and the concentration of chloride ions in solution on the localized corrosion characteristics of SiCp/2024 Al metal matrix composites (MMC) were investigated. A scanning micro reference electrode (SMRE) technique was employed to study the dynamic process of pitting initiation and development on the surface of the composites at open-circuit potential. Potentiodynamic polarizations were performed to characterize the electrochemical behavior of the MMCs. The morphology of the localized attack on the MMC sample after corrosion tests were examined by scanning electron microscopy (SEM). The results of electrochemical measurement showed that the composites were less resistant to pit initiation than the corresponding unreinforced metrix alloy. Increase in the volume fraction of SiCp reinforcement in the SiCp/2024 Al composites resulted in a significant decrease of pitting potential. In situ potential mapping of active centers on the surfaces of the composites revealed that local breakdown of passivity and initiation of micro pitting corrosion could take place even at an open-circuit potential which was more negative than the pitting potential, and the number of active centers on the surfaces of the composites increased as the volume fraction of SiC particulates in MMCs increased. Micro-structural analysis indicated that pitting attack on the composites mainly occurred at SiCp-Al interfaces or inclusions-Al interfaces.

Nonlinear system modeling by competitive learning and adaptive fuzzy inference system

Abstract: Modeling nonlinear systems by neural networks and fuzzy systems encounters problems such as the conflict between overfitting and good generalization and low reliability, which requires a great number of fuzzy rules or neural nodes and uses very complicated learning algorithms. A new adaptive fuzzy inference system, combined with a learning algorithm, is proposed to cope with these problems. First, the algorithm partitions the input space into some local regions by competitive learning, then it determines the decision boundaries for local input regions, and finally, based on the decision boundaries, it learns the fuzzy rule for each local region by recursive least squares (RLS). In the learning algorithm, the key role of the decision boundaries is highly emphasized. To demonstrate the validity of the proposed learning approach and the new adaptive fuzzy inference system, four examples are studied by the proposed method and compared with the previous results.

Effects of reinforcement oxidation on the mechanical properties of SiC particulate reinforced aluminum composites

Abstract: The microstructures and mechanical properties of artificially oxidized and as-received silicon carbide particle (SiCp) reinforced pure aluminum and 2024Al composites were investigated. It was shown that surface oxidation of SiCp increased the tensile strength and fracture strain of the pure Al based composite. Diffusion of aluminum into SiO 2 during fabrication of the composite, which increased the diffusion bonding between the SiC particle and the aluminum matrix, is thought to be responsible for the increases in strength and ductility. However, the strength and ductility of the oxidized SiCp reinforced 2024Al composite were much lower than those of the as-received SiCp reinforced 2024Al composite. Based on the experimental results from DSC, TEM, EDX and SEM fractography analyses, it is suggested that the interfacial reactions related to SiO 2 depleted the magnesium in the matrix and subsequently decreased the amount of the age strengthening phase containing magnesium. The lower level of strengthening in the matrix and the formation of a thick interfacial reaction layer, which was continuous and brittle, finally led to the lower strength and ductility of the artificially oxidized SiCp reinforced composite.

Monopoly Pricing When Customers Queue

Abstract: It takes time to process purchases and as a result a queue of customers may form. The pricing and service rate decisions of a monopolist who must take this into account are characterized. We find that an increase in the average number of customers arriving in the market either has no effect on the monopoly price, or else causes the monopolist to reduce the price in the short run. In the long run the monopolist will increase the service rate and raise the price. When customer preferences are linear the equilibrium is socially efficient. When preferences are not linear equilibrium will not normally be socially efficient.

Reverse atom transfer radical polymerization of methyl acrylate using AIBN as the initiator under heterogeneous conditions

Abstract: Reverse atom transfer radical polymerization of methyl acrylate in the presence of a conventional radical initiator (2,2′-azoisobutyronitrile, AIBN) in bulk was successfully implemented via a new polymerization procedure. The system first reacts at 65–70°C for ten hours, then polymerizes at 100°C. Various mole ratios of AIBN to CuIICl2 were used in this work, all of which result in a well-controlled radical polymerization with high initiation efficiency and narrow molecular weight distribution, i.e., the polydispersity is as low as Mw/Mn = 1.36.

New Structural Dynamic Condensation Method for Finite Element Models

Abstract: A new iterative method is proposed for the reduction of finite element models arising in test-analysis correlation, model updating, finite element modeling, vibration control, structural dynamic optimization, and so on. Based on the modified eigenvalue equation and the eigenvalue shifting technique, two constraint equations for the dynamic condensation matrix, which relates the deformations associated with the master and slave degrees of freedom, are derived. Two iterative schemes are presented for solving the constraint equations. In the second constraint equation, because the dynamic condensation matrix has nothing to do with the eigenpairs of the reduced model, it is unnecessary to calculate them in every iteration. This makes the iterative scheme more computationally efficient than the usual scheme, especially when the number of the master degrees of freedom is large. The accuracy of eigenvalues and eigenvectors of the reduced model is examined in every iterative step. The comparison of the present method with some typical iterative schemes proposed in the past shows that the new one has the highest accuracy. Numerical examples are also presented to show the efficiency of the proposed method.