3,576 research outputs found
Input and system identification of the Hualien soil-structure interaction system using earthquake response data
No full textThis paper presents an input and system identification technique for a soil-structure interaction system using earthquake response data. Identification is carried out on the Hualien large-scale seismic test structure, which was built in Taiwan for international joint research. The identified quantities are the input ground acceleration as well as the shear wave velocities of the near-field soil regions and Young's moduli of the shell sections of the structure. The earthquake response analysis on the soil-structure interaction system is carried out using the finite element method incorporating the infinite element formulation for the unbounded layered soil medium and the substructured wave input technique. The criterion function for the parameter estimation is constructed using the frequency response amplitude ratios of the earthquake responses measured at several points of the structure, so that the information on the input motion may be excluded. The constrained steepest descent method is employed to obtain the revised parameters. The simulated earthquake responses using the identified parameters and input ground motion show excellent agreement with the measured responses. Copyright 0 2003 John Wiley Sons, Ltd
Dynamic analysis of flexible rotors subjected to torque and force
No full textThe effect of the direction of application and magnitude of loads on the stability and natural frequency of flexible rotors is analyzed, when the rotors are subject to non-conservative torque and force. The stability criterion derived from the energy and variational principle is discussed and a general Galerkin method in which admissible functions are used is employed for numerical analysis. Illustrative examples are treated to demonstrate the analytical developments and the practical relevance of the work is discussed. (C) 1996 Academic Press Limite
Improved selectivity of oxide semiconductor type gas sensor using compensating element
No full textThe selectivity of SnO2 gas sensor for a hydrocarbon gas like i-C4H10 has been improved through the serial connection of a compensating element which is sensitive to the interfering gas. The devices were fabricated in 2 mm x 2 mm through the screen-printing technique. The sensing material, made of SnO2, was doped with Sb2O5 and treated with Pt catalyst to detect a hydrocarbon gas. The compensating material was composed of Sb2O5-doped SnO2 with Pd catalyst to detect interfering gas such as ethanol. The amount of resistance change in each material upon exposure to gas is differed depending on the kind of gas to be exposed, giving rise to an improvement in the selectivity of the device. (C) 2001 Elsevier Science B.V. All rights reserved.The authors wish to acknowledge the financial support of the Korean Research Foundation offered in the 1998 program year
SPECTRUM-SLICED FIBER AMPLIFIER LIGHT-SOURCE FOR MULTICHANNEL WDM APPLICATIONS
No full textWe propose a potentially inexpensive light source for multichannel WDM applications. The high-power amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), which is already in the single-mode fiber, can be efficiently divided into many channels by using an integrated optic WDM demultiplexer. This ''spectrum-sliced'' ASE can be used as light sources for WDM systems rather than several wavelength-selected DFB lasers. To demonstrate the principle, we sliced a 40-nm wide ASE spectrum of an EDFA with a narrow optical filter (3 dB bandwidth: 1.3 nm) and used the resulting source for the transmission of up to 1.7 Gb/s of data. These incoherent light sources suffer from the spontaneous-spontaneous beat noise. Thus, it is necessary to increase the optical bandwidth and/or decrease the electrical bandwidth (bit rate) to improve the signal-to-noise ratio, which, in turn, determines the transmission capacity of a WDM system using the proposed light source. We estimate that the total capacity would be about 40 Gb/s, realistically, since the channel spacing should be at least three times the optical bandwidth of each channel to avoid crosstalk
STUDY OF IRON MORDENITE CATALYSTS BY MOSSBAUER AND FERROMAGNETIC-RESONANCE SPECTROSCOPY FOR CARBON-MONOXIDE HYDROGENATION
No full textIron was loaded on mordenites with varying cation type and degree of dealumination, and their catalytic properties were characterized by means of Mossbauer and ferromagnetic resonance spectroscopy and carbon monoxide hydrogenation as a probe reaction. When iron was impregnated on mordenites, it was found that about 1.2 wt.-% of iron existed as ion-exchanged cationic iron in the oxide or hydroxide form. Iron oxide particles formed after calcination at 450-degrees-C showed a wide distribution in their size, ranging from cluster-sized superparamagnetic oxide to large particles of alpha-Fe2O3. After reduction at 450-degrees-C, iron oxide particles were sintered to be reduced to bimodally distributed metallic iron particles. Small iron particles generated on hydrogen-form mordenites are believed to be stabilized by some defect sites generated by dealumination of mordenite. On sodium-mordenite, extremely small and uniform iron clusters were generated because free sodium ions, which had been detached from the framework by previous ion exchange with impregnated iron ions, promoted reduction of ion-exchanged cationic irons. The result was applied to reduce ion-exchanged iron (FeNaM10) by injecting a high concentration of sodium ions into the pores of mordenite and about 27% of the iron was able to be reduced upon treatment in hydrogen gas at 450-degrees-C. These iron clusters showed lower activity but higher selectivity toward alkenes in the carbon monoxide hydrogenation reaction than conventional impregnated catalysts
Unique Ultrasonographic Findings of Isolated IgG4-Related Lymphadenopathy
Get PDFIgG4-related disease is a rare immune-mediated disease that can involve many organs in the body. The lymph node is also where IgG4-related diseases occur, but its histological structure is different from that of other organs. For this reason, pathologists have difficulty diagnosing IgG4-related lymphadenopathy. If there were specific imaging findings of IgG4-related lymphadenopathy, it would be of great help to pathologists. A 64-year-old male visited our hospital with right ankle pain. On physical examination, the right lower extremity showed severe swelling with wound dehiscence, and infection was suspected. On CT (128-MDCT, Somatom Definition Flash, Siemens Healthcare) taken at the lower extremity, multiple enlarged lymph nodes were incidentally noted in the right inguinal area. On ultrasonography, a “starry night sign” resembling hyperechoic follicles was observed in the enlarged lymph node. A core needle biopsy was performed, and IgG4-related lymphadenopathy was diagnosed. Laboratory examination showed hypergammaglobulinemia with marked elevated serum IgG4, corresponding to IgG4-related disease. Chest and abdominal imaging were evaluated, but there was no extranodal IgG4-related disease. IgG4-related lymphadenopathy showed a very unique ultrasonography imaging finding. The cortex was filled with diffusely scattered hyperechoic foci and some bright foci gathered to form a follicle. This imaging finding may help diagnose IgG4-related lymphadenopathy
Peripheral nerve sheath tumor: differentiation of malignant from benign tumors with conventional and diffusion-weighted MRI
No full textOBJECTIVES: To evaluate potential of conventional MRI and diffusion-weighted imaging (DWI) for differentiating malignant from benign peripheral nerve sheath tumors (PNSTs).
METHODS: Eighty-seven cases of malignant or benign PNSTs in the trunk or extremities that underwent conventional MRI with contrast enhancement, DWI, and pathologic confirmation between Sep. 2014 and Dec. 2017 were identified. Of these, 55 tumors of uncertain nature on MRI were included. Tumor size, signal, and morphology were reviewed on conventional MRI, and apparent diffusion coefficient (ADC) values of solid enhancing portions were measured from DWI. Patient demographics, MRI features, and ADC values were compared between benign and malignant tumors, and robust imaging findings for malignant peripheral nerve sheath tumors (MPNSTs) were identified using multivariable models.
RESULTS: A total of 55 uncertain tumors consisted of 18 malignant and 37 benign PNSTs. On MRI, tumor size, margin, perilesional edema, and presence of split fat, fascicular, and target signs were significantly different between groups (p < 0.05), as were mean and minimum ADC values (p = 0.002, p < 0.0001). Most inter-reader agreement was moderate to excellent (κ value, 0.45-1.0). The mean ADC value and absence of a split fat sign were identified as being associated with MPNSTs (odds ratios = 13.19 and 25.67 for reader 1; 49.05 and 117.91 for reader 2, respectively). The C-indices obtained by combining these two findings were 0.90 and 0.95, respectively.
CONCLUSIONS: Benign and malignant PNSTs showed different features on MRI and DWI. A combination of mean ADC value and absence of split fat was excellent for discriminating malignant from benign PNSTs.
KEY POINTS: • It is important to distinguish between malignant peripheral nerve sheath tumors (MPNSTs) and benign peripheral nerve sheath tumors (BPNSTs) to ensure an appropriate treatment plan. • On conventional MRI and diffusion-weighted imaging (DWI), MPNSTs and BPNSTs showed significant differences in tumor size, margin, presence of perilesional edema, and absence of split fat, fascicular, and target signs. • Absence of a split fat sign and mean apparent diffusion coefficient (ADC) values were robust imaging findings distinguishing MPNSTs from BPNSTs, with a C-index of > 0.9
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