Longitudinal elastic waves in columns due to earthquake motion

An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake.     

Dislocation structures in deformed Cu-Ni-Zn alloy single crystals

It is known that Cu-Ni-Zn alloy has an ordered structure Cu₂NiZn (Ll₂) by annealing between 573 and 623 K. In the present experiments, the effects of annealing on the dislocation structure were studied on Cu-Ni-Zn single crystals with several compositions. Thin foils cut parallel to the {111} planes were observed in a transmission electron microscope. The results obtained are as follows. (i) In Cu-5Ni-5Zn, Cu-10Ni-10Zn and Cu-15Ni-15Zn (at%), the stress-strain behaviour, slip mode and dislocation structure did not change by annealing at 573 K. However, the slip mode became more concentrated and localized, and dislocations emitted from a source tended to stay on the same slip plane, as the nickel and zinc concentrations increased. (ii) However, those properties in Cu-20Ni-20Zn and Cu-25Ni-25Zn changed drastically by annealing. As the ordering proceeded, uniform distributions of superlattice dislocations were observed. A typical dislocation configuration, with long screw and wavy-edged superlattice dislocations, took the place of piled-up unit dislocations. (iii) The facts that edge-type superlattice dislocations formed dipoles and their clusters, and that the secondary dislocation density was much lower than the primary one, implied that the elastic interaction of the primary edge-type superlattice dislocations on the nearby parallel slip planes would control the work-hardening of ordered Cu₂NiZn alloy single crystals.     

Concentric X-braced frames with HSS bracing

Concentrically braced frames are stiff, strong systems frequently used to resist wind and seismic loading; in regions of high seismicity in the US special concentrically braced frames (SCBFs) are used. CBF configurations vary, but in low rise or other structures with modest levels of demands single-story, X-configured braced frames (X-braced) are commonly used. The brace sections used also vary but hollow structural sections (HSS) are the most common in the U.S. Although important, in part because low-rise structures sustain large demands, few research programs have focused on the single-story X-brace configuration. A large research program was undertaken to understand and improve the response of SCBFs with selected testing on single-story X braced SCBFs. The test matrix consisted of two, full-scale planar X-braced frame experiments and one nearly-full-scale three-dimensional X-braced frame. The tests were designed using a new design and detailing philosophy, called the Balanced Design Method. In this paper, application of this design method to the frame is investigated, with a focus on the center-splice connection. The results show that the ultimate inelastic deformation capacity of the system is less dependent on the specific design detail at this splice. Additionally, the bi-directional load testing indicated that the out-of-plane demands did not impact the system performance.     

Resistances to UV-C irradiation of Salmonella Typhimurium and Staphylococcus aureus in wet and dried suspensions on surface with egg residues

To clarify the effects of food sediments on ultraviolet-C (254 nm) sanitation in food-related environments, we examined the resistance of pathogenic bacteria (Salmonella Typhimurium and Staphylococcus aureus) cells, in wet and dried suspensions adhered with 1.5-15% w/v egg albumen, 1.5-15% yolk or 3.0-30% whole egg solutions, against UV-C irradiation. Bacterial suspensions (0.1 ml of 8 log CFU/ml) were put on 47 mmφ glass dishes and dried at room temperature (20-24 °C) for 180 min in a bio safety cabinet with ventilation. Viable S. Typhimurium and S. aureus cells in distilled water decreased during the drying period from 7.2 to 3.2 and from 8.0 to 6.5 log CFU/dish, respectively,. On the other hand, the bacteria cells were protected from drying by egg compounds, even by the lowest concentration. The UV-C treatment (0.16 mW/cm² for 10 min) showed a clear bactericidal effect in the absence of egg compounds. However, the bactericidal effect was inhibited by 15% yolk and 30% whole egg. Results in this study suggested that the small food sediment protect bacteria on the surfaces from dryness and UV-C irradiation and it might introduce cross contamination.     

Fabrication and characteristics of polyfluorene based organic photodetectors using fullerene derivatives

The characteristics of organic photodetectors (OPDs) by solution process using one of the polyfluorene derivatives poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) and two fullerene derivatives [6-6]phenyl-C61-butyric acid methyl ester (PCBM) or N-Ts aziridinofullerene (TsAF) are investigated. F8T2:PCBM devices showed good rectifying characteristics in a dark state and photosensitive characteristics, and fast frequency responses. Weight ratio of 1:1 device showed larger photocurrent than 1:4 device and obtained over 50 MHz of cutoff frequency under reverse bias voltage of 10 V. This result suggests that F8T2:PCBM device can be applied to a photodetector for detecting several tens of megahertz optical signals under blue light irradiation. The polarity of J–V characteristics of F8T2:fullerene derivative device is strongly affected by charge injection and extraction between fullerene derivative and electrodes.     

Cyclic loading behavior of EBF links constructed of ASTM A992 steel

Cyclic loading tests were conducted to study the behavior of link beams in steel eccentrically braced frames. A total of thirty-seven link specimens were constructed from five different wide-flange sections, all of ASTM A992 steel, with link length varying from short shear yielding links to long flexure yielding links. The occurrence of web fracture in shear yielding link specimens led to further study on the cause of these fractures. Since the link web fracture appeared to be a phenomenon unique to modern rolled shapes, the potential role of material properties on these fractures is discussed. Based on the test data, a change in the flange slenderness limit is proposed. The link overstrength factor of 1.5, as assumed in the current U.S. code provisions, appears to be reasonable. The cyclic loading history used for testing was found to significantly affect link performance. Test observations also suggest new techniques for link stiffener design and detailing for link-to-column connections.     

Microstructure and Dielectric Properties of YMnO3 Thin Films Prepared by Dip-Coating

YMnO₃ thin films with Y/Mn ratios from 1.00/1.05 to 1.00/0.90 were prepared by dip-coating from solution, in which starting materials were refluxed, and the effects of the Y/Mn ratio on the structure and dielectric properties of YMnO₃ thin films were investigated. XRD measurements indicated that the films with the Y/Mn ratios in this study were a single phase of polycrystalline YMnO₃. The lattice constants along the a -axis and c -axis lengthened with an increase in the Y/Mn ratio. FE-SEM micrographs of the films showed that the surface of the films became smoother and denser with an increase in the Y/Mn ratio. YMnO₃ thin films with good dielectric properties were obtained with an Y/Mn ratio of 1.00/0.90, which gave the smoothest and densest microstructure and the smallest leakage current.     

A new regenerative snubber circuit for large-capacity three-level GTO inverter systems

Increase in the capacity of GTOs has made remarkable progress in recent years. At present, 4.5-kV, 4.0-kA GTOs are commercially available, and 6.0-kV, 6.0-kA GTOs made from 6-inch silicon wafers are appearing. The 6-inch GTOs will be applied to our three-level GTO inverter system. In order to apply GTOs to voltage-source inverters, snubber circuits are necessary for limiting on the turn-on di/dt and turn-off dv/dt. To realize high efficiency of the system, regenerative snubber circuits are often applied. A conventional circuit applied to three-level GTO inverters had the problem of long paths created for snubber circuits of the inner GTOs. Another circuit using a current transformer for recovering the energy trapped in the snubber circuits of the inner GTOs has been presented. In this paper, a new regenerative snubber circuit is proposed, which is more suitable for three-level GTO inverter systems with many phase-legs. By applying the snubber circuit, all snubber energy generated by each GTO switching can be regenerated to the dc link. In addition, high current turn-off performance of both the inner and the outer GTOs is verified by several successful experimental results using 6-inch 6.0-kV, 6.0-kA GTOs. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 41–48, 1997     

Automated flow quantification for spin labeling MR imaging

Objective

The Time-Spatial Labeling Inversion Pulse (Time-SLIP) technique enables tracing of regional fluid flows without the use of contrast medium. The objective of this study is to quantify automatically slow and complex fluid flows using the Time-SLIP technique.

Materials and methods

Series images were acquired with a 1.5-T MRI scanner using the Time-SLIP technique with half-Fourier fast spin-echo (FSE) and balanced steady-state free precession (bSSFP) sequences. In this method, labeled fluid regions in images were automatically detected based on image processing techniques for a given point. The flow velocity of the labeled fluid region was calculated using regression fitting for the region’s position. To evaluate our method, constant and non-constant laminar flows in a water phantom were studied. In addition, volunteer experiments were conducted to quantify the flow of cerebrospinal fluid.

Results

In the constant flow experiments the correlation factor r ² between the flow velocity calculated from our method and the laminar peak velocity calculated from the volumetric flow rate was 0.9992 for the FSE sequence and 0.9982 for the bSSFP sequence. In the non-constant flow study, the flow velocity was calculated accurately for any period inversion time even when the flow velocity was changed, and the quantification error was negligible. In the volunteer experiments, r ² between the flow velocity calculated by the proposed method and that obtained by manual annotation was 0.9383.

Conclusion

The experimental results showed that our proposed method can quickly and accurately provide information on flow velocities especially for slower and complex flows. Our method is, therefore, expected to be useful in diagnostic support systems.