A combination of differential equations and convolution in understanding the spread of an epidemic

Nonlinear dynamical method of projecting the transmission of an epidemic is accurate if the input parameters and initial value variables are reliable. Here, such a model is proposed for predicting an epidemic. A method to supplement two variables and two parameters for this proposed model is demonstrated through a robust statistical approach. The method described here worked well in case of three continuous distributions. Model predictions could be lower estimates due to under-reporting of disease cases. Anad hoc procedure with a technical note is provided in the appendix An earlier version of this paper was presented at the annual conference of the Indian Society for Mathematical Modelling & Computer Simulation, Bangalore, November 14–15, 2002     

Survey of switching techniques in high-speed networks and their performance

One of the most promising approaches for high speed networks for integrated service applications is fast packet switching, or ATM (asynchronous transfer mode). ATM can be characterized by very high speed transmission links and simple, hard-wired protocols within a network. To match the transmission speed of the network links, and to minimize the overhead due to the processing of network protocols, the switching of cells is done in hardware switching fabrics in ATM networks. A number of designs have been proposed for implementing ATM switches. Although many differences exist among the proposals, the vast majority of them are based on self-routeing multistage interconnection networks. This is because of the desirable features of multi-stage interconnection networks such as self-routeing capability and suitability for VLSI implementation. Existing ATM switch architectures can be classified into two major classes: blocking switches, where blockings of cells may occur within a switch when more than one cell contends for the same internal link, and non-blocking switches, where no internal blocking occurs. A large number of techniques have also been proposed to improve the performance of blocking and non-blocking switches. In this paper, we present an extensive survey of the existing proposals for ATM switch architectures, focusing on their performance issues.     

A case of macrocystic cervical neurinoma diagnosed by MRI with Gd-DTPA

The authors report a rare case of a large cystic cervical neurinoma. A 45-year-old female was admitted to our clinic because of motor weakness of the right upper extremity, numbness of the right fingers and right posterior cervical pain. Metrizamide CT myelography demonstrated the outline of a low density mass. MRI showed a mass revealing low signal intensity on T1-weighted image, high signal intensity on T2-weighted image and marginal enhancement on contrast image with Gd-DTPA. The mass which was diagnosed as cystic tumor, was located in the intradural extramedullary space between C4 to C5 segments. After C4 through C5 laminectomy, the tumor was found to originate from the C5 anterior motor root. The tumor consisted mostly of a cystic part with a very thin solid compartment beneath the capsule. Postoperative course of the patient was uneventful. Although spinal neurinoma is one of the most common spinal tumors, an almost completely degenerated large cystic spinal neurinoma is extremely rare. MRI with Gd-DTPA was useful for the diagnosis of the cystic neurinoma by clearly enhancing the margin of the tumor.     

Effects of macrophage colony-stimulating factor (M-CSF) on lipopolysaccharide (LPS)-induced mediator production from monocytes in vitro

M-CSF is a macrophage-lineage-specific growth factor that causes proliferation and differentiation of progenitor cells in the bone marrow. To investigate the effects of M-CSF on more matured cells, human monocytes were cultured in the presence or absence of M-CSF for 6 days. Addition of M-CSF at more than 10(2) U/ml resulted in higher viability and caused morphological differentiation to large macrophage-like cells. LPS-induced mediator production was also compared between M-CSF-treated and control cell. Monocytes were incubated with or without M-CSF for 3 days, and were stimulated with 1 microgram/ml of LPS for 2 days. IL-1 beta was not detected in the both culture supernatants, and PGE2 production was not influenced by M-CSF. However, amounts of G-CSF, GM-CSF, IL-6, and TNF-alpha produced in response to 1 microgram/ml of LPS were 1.5 to 2 times greater from monocytes treated with 10(4) U/ml of M-CSF than from control cells. The priming effect of M-CSF on LPS-induced cytokine production was found to require 3-day preincubation, and reached a maximum at the concentration of 10(4) U/ml. M-CSF-treated cells responded to a 10 times lower concentration of LPS than control cells in terms of cytokine production. M-CSF was also shown by flowcytometric analysis to influence the expression of CD14, a receptor for LPS, which might render monocytes more sensitive to LPS.     

An ESR study of the film formation steps of vapor deposition polymerization of polyamic acid

A film of polyamic acid is formed by vapor deposition polymerization of pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA). We have taken ESR spectrum during the polymerization process and compared it with the ESR spectrum of films obtained from solution polymerization. In the intermediate polymers during vapor deposition polymerization, the amide bond (? CONH? ) is coplanar with the benzene ring and two protons in the PMDA molecule. This intermediate polymer has one unpaired electron that interacts with the two nitrogen nuclei equally. On the other hand, in the polymer obtained by solution polymerization, the amide bond and the benzene ring of PMDA are not coplanar. In this polymer, too, some of the molecules have an unpaired electron that seems to have almost no coupling with NH groups. These results imply that the polymer formation via vapor deposition proceeds through different intermediates and different molecular configurations from that via the solution process.     

Operation of HTS Toggle-Flip-Flop Circuit With Improved Layout Design

Toggle-flip-flop (T-FF) is one of the most important high-T_c superconducting single-flux quantum (HTS SFQ) circuit components and has been designed and fabricated by using YBa₂Cu₃ O_7-delta ramp-edge junction technology. The circuit layout of the T-FF was improved to suppress the junction critical current (I_c) spread in the circuit. Test circuits, which include a T-FF with a single output for evaluating the logic operation and measuring the operating frequency, were fabricated and their operation characteristics were investigated. The T-FF circuit with a single output was successfully operated and finite direct current (dc) supply current margins were obtained at temperatures from 27 to 34 K. Moreover, the maximum operating frequency of the T-FF was estimated to be 360 GHz at 4.2 K and 114 GHz at 41 K. In addition, reduction of dc supply current margins due to thermal noise was also investigated. According to the numerical simulation in which parasitic inductances were taken into account, the narrowest margin in the T-FF circuit wider than plusmn10% was maintained with a bit-error rate (BER) of 10^-6 up to 40 K     

TRVs and fault clearing stresses in extra-high-voltage radial networks

To cope with the high rate of increase of power demand in the main industrialized districts in Japan, 550-kV transmission systems covering the districts have been reinforced, with most of the main power plants connected directly to these systems. Through 550-/300-kV substations, the majority of power to the districts is supplied by 300-kV systems. To limit the excess short-circuit capacity in the 300-kV systems, they tend to be reconstructed as so-called radial networks. In radial networks with high short-circuit capacity and relatively small number of transmission lines connected to the substation busbars, the rate of rise of TRV can be far higher than standard value. This paper analyzes the transient recovery voltages (TRV) in such extra-high-voltage radial networks in Japan, together with the relevant stresses to circuit-breakers during fault clearings. Future system conditions have also been introduced. As the typical rate of rise of the TRV values, more than twice that of today's standard ones are probable.     

Robust stabilization of a magnetic suspension system using H∞ Control Theory

This paper presents the robust control design of a magnetic suspension system for a flexible beam which is a simplified model of an elastic rotor in a magnetic bearing system. To stabilize this magnetic suspension system which is unstable in nature, the H^infin; control theory is applied for a design of the control system. To apply the H^infin; control theory, a statespace model of an augmented plant with frequency-weighting functions is constructed. This augmented plant has two inputs which are the exogenous inputs and the control inputs, and two outputs which are the sensor outputs and the regulated outputs. Here we consider the mixed sensitivity problem. The H^infin; controller is implemented by a digital controller which is able to execute the computations very quickly. For the evaluation of the control performance, several experiments are made. The robustness of the closed-loop system is confirmed by the experimental results. The result of this study is useful for the control design of a magnetic bearing system.     

Stress intensity factors of microstructurally small crack

The stress intensity factor (SIF) is widely used for evaluating integrity of cracked components. Averaging the anisotropy of each crystal, the macroscopic behavior of polycrystalline materials is isotropic and homogenous in terms of elastic deformation. However, the anisotropic and/or inhomogeneous property influences on the stress field around a crack if the crack size is small in comparison with the grain. Thus, the SIF of the microstructurally small crack may differ from that in the isotropic body. In present study, the effect of anisotropic/inhomogeneous elasticity on the SIF is investigated by using the finite element analysis (FEA). At first, the SIFs of semi-circular crack in a single crystal and a polycrystalline material are calculated. These reveal that the magnitude of SIF is dependent not only on the crystal orientation but also on the deformation constraint by the neighboring crystals. Then, the statistical scatter of SIF due to the random orientation of crystal orientation in a polycrystal is examined by a Monte Carlo simulation.