Effect of rigid inclusions on the sintering of mullite synthesized by sol-gel processing

The effect of crystalline particulate inclusions of mullite or zirconia on the sintering and crystallization of a mullite powder matrix was investigated as a function of the inclusion volume fraction and size. The mullite powder was synthesized by sol-gel processing and, within the limits of X-ray diffraction, was amorphous. Composites containing up to 22.5 vol % zirconia reached almost full density after sintering at 1500 °C for 1 h. Under identical conditions, the sintered density of the composites containing crystalline mullite inclusions was considerably lower. The zirconia inclusions were inert but the mullite inclusions enhanced the independent nucleation and growth rate of the mullite crystals in the matrix. The lower sintering rate of the matrix reinforced with crystalline mullite is attributed to the enhanced matrix crystallization.     

Hepatocellular carcinoma presenting as pyogenic liver abscess: characteristics, diagnosis, and management

We performed a 17-year retrospective analysis of 10 cases of hepatocellular carcinoma presenting as pyogenic liver abscess. Spontaneous tumor necrosis and biliary obstruction caused by tumor thrombi, superimposed with bacterial infection, were the two major pathogeneses. Exact diagnosis of the underlying hepatocellular carcinoma was made for five of the 10 patients before management was attempted. Main clinical manifestations included fever, chills, right-upper-quadrant pain, malaise, anorexia, jaundice, and hepatomegaly. Characteristics such as middle age and male sex, seropositivity for hepatitis B and/or hepatitis C, chronic liver disease, unexplained anemia, marked weight loss, and a severely inversed albumin/globulin ratio raise suspicions about the underlying hepatocellular carcinoma. Management strategies included percutaneous drainage (n = 3), surgical drainage (n = 4), and hepatectomy (n = 3) in addition to administration of parenteral antibiotics in all cases. The prognosis was dismal, with a mean survival of 3.5 months (range, 8 days to 6 months).     

A Molecular Dynamics Study of Lubrication Rheology of Polymer Fluids

This study investigated the characteristics of lubrication rheology for polymer fluids using the molecular dynamics method. The confining potential and FENE potential were used to describe the bonding force in a polymer chain. Both Poiseuille and Couette flows were simulated and the results are presented for the density distribution, velocity profiles, slip ratio, viscosity, and relation between shear stress and shear rate. The effects of the number of molecular layers and film thickness on the rheology characteristics were also investigated.     

A physical and scalable I-V model in BSIM3v3 for analog/digitalcircuit simulation

A new physical and continuous BSIM (Berkeley Short-Channel IGFET Model) I-V model in BSIM3v3 is presented for circuit simulation. Including the major physical effects in state-of-the art MOS devices, the model describes current characteristics from subthreshold to strong inversion as well as from the linear to the saturation operating regions with a single I-V expression, and guarantees the continuities of I_ds, conductances and their derivatives throughout all V_gs, V_ds, and T_bs, bias conditions. Compared with the previous BSIM models, the improved model continuity enhances the convergence property of the circuit simulators. Furthermore, the model accuracy has also been enhanced by including the dependencies of geometry and bias of parasitic series resistances, narrow width, bulk charge, and DIBL effects. The new model has the extensive built-in dependencies of important dimensional and processing parameters (e.g., channel length, width, gate oxide thickness, junction depth, substrate doping concentration, etc.). It allows users to accurately describe the MOSFET characteristics over a wide range of channel lengths and widths for various technologies, and is attractive for statistical modeling. The model has been implemented in the circuit simulators such as Spectre, Hspice, SmartSpice, Spice3e2, and so on     

Dual-band step-impedance bandpass filter for multimode wireless LANs

A step-impedance bandpass filter is presented for multimode wireless LANs. The filter has a new dual-band feature of two tunable passbands at desired frequencies and high out-of-band suppression, generated by incorporating step-impedance resonators in a comb-filter topology. It saves more than half the circuit size compared with the switch-type dual-band topology. The simulation and measurement results show the dual-band feature of two passbands at 2.45 and 5.75 GHz with 85 dB suppression at 3.5 GHz.     

A novel propagation modeling for microcellular communications inurban environments

A novel method for microcellular communications to predict propagation characteristics is presented in this paper. It takes into account multiple reflections among walls, ground, vehicles, as well as the transmission/reflection due to groups of trees. Although these are three-dimensional (3-D) problems, we can combine two-dimensional (2-D) ray tracing and simple 3-D geometric considerations to solve them in a very efficient way. We have investigated the propagation loss versus size, number, and locations of vehicles and groups of trees on a safe island. Our results show that the radio wave propagation exhibits severe fast fading, attenuation, and blockage due to reflection, transmission, and shadowing, respectively     

Technical refinement in the management of circumferentially avulsed skin of the leg

Between 1989 and 1994, 42 patients with circumferential skin avulsion of lower extremities were treated with full-thickness skin graft from defatted avulsed flap. Among them, 39 patients were run over by rubber tires during car accidents; the remaining 3 patients were victims of industrial accidents by roller machines. The full-thickness skin grafts were prepared from the avulsed skin flap in attachment to avoid junctional hypertrophic scarring. They were then secured with multiple skin staples to their anatomical position to improve skin graft take. Initial take of graft averaged 91 percent (ranged from 75 percent to 100 percent). Twelve patients underwent secondary overgrafting after tangential excision of non-viable skin graft. Follow-up averaging 2.6 years revealed stable wounds in most of the patients. Ten patients experienced occasional breakdown of skin graft in the patella and popliteal fossa, which was treated conservatively. Except for five who had deformed contours of the leg due to muscle transfers, the patients were satisfied with the cosmetic appearance of their legs. Compared with conventional methods, this approach provided better appearance and less contracture.     

Least squares subspace projection approach to mixed pixelclassification for hyperspectral images

An orthogonal subspace projection (OSP) method using linear mixture modeling was recently explored in hyperspectral image classification and has shown promise in signature detection, discrimination, and classification. In this paper, the OSP is revisited and extended by three unconstrained least squares subspace projection approaches, called signature space OSP, target signature space OSP, and oblique subspace projection, where the abundances of spectral signatures are not known a priori but need to be estimated, a situation to which the OSP cannot be directly applied. The proposed three subspace projection methods can be used not only to estimate signature abundance, but also to classify a target signature at subpixel scale so as to achieve subpixel detection. As a result, they can be viewed as a posteriori OSP as opposed to OSP, which can be thought of as a priori OSP. In order to evaluate these three approaches, their associated least squares estimation errors are cast as a signal detection problem ill the framework of the Neyman-Pearson detection theory so that the effectiveness of their generated classifiers can be measured by receiver operating characteristics (ROC) analysis. All results are demonstrated by computer simulations and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data     

Determination of the solidification curves of commercial aluminum alloys

The understanding of solidification curves is crucial for the control of many solidification processes. The solidification curves of seven commercial aluminum alloys (1050, 1070, 1100, 3003, 3004, 5052, and 7075) were determined by using a differential thermal analysis (DTA) coupled with a mathe-matical modeling method, which has advantages over the conventional quenching method or the solidification modeling method. With the proposed technique in this study, the whole spectrum of the solidification curve can be determined with high reliability, without requiring the knowledge of a number of thermophysical parameters, which are usually difficult to obtain.     

Effect of cationic surfactant on homogenization and polymerization of methyl methacrylate miniemulsion modified by chitosan

Homogenization of monomer droplets and polymerization of methyl methacrylate (MMA) miniemulsion, stabilized by a combination of cationic surfactants including different amounts of n‐hexadecyltrimethylammonium chloride (HTMA) and chitosan 100, were investigated. With increasing HTMA concentration or decreasing concentration of chitosan 100, the required ultrasonication time for the miniemulsion to reach a critically stabilized state is reduced. After polymerization, for higher HTMA concentrations, droplet nucleation dominates because of higher surface coverage of HTMA on the droplets. However, for lower HTMA concentrations, the size distributions (SDs) of final latex particles are different from those of the droplets. Because surface coverage of HTMA on the droplets is lower in this condition, both droplet nucleation and homogeneous and/or micellar nucleation occur simultaneously in the miniemulsion polymerization. On increasing the concentration of chitosan 100 in the system, the SD of the final latex particles is far different from that of the droplets. This is due to a decrease of the effective surface coverage of chitosan 100 and HTMA on the droplets. Consequently, the opportunity of collision coalescence of the droplets increases, and MMA molecules can diffuse out more easily into the aqueous phase. Droplet nucleation is, therefore, no longer the major source for the latex particles. Copyright © 2006 Society of Chemical Industry