Performance Comparison of Scramjet‐Driven Experimental DCW‐MHD Generators with Different Cross‐Sections

The purpose of this study is to examine the influence of the shape of the cross‐section of a scramjet engine‐driven experimental diagonal conducting wall (DCW)‐MHD generator on generator performance by three‐dimensional numerical analyses. We have designed MHD generators with symmetric square and circular cross‐sections, based on an experimental MHD generator with an asymmetric square cross‐section. Under the optimum load conditions, the electric power output reaches 26.6 kW for the asymmetric square cross‐section, 24.6 kW for the symmetric square cross‐section, and 22.4 kW for the circular cross‐section. The highest output is obtained for the experimental generator with the asymmetric square cross‐section. The difference in the electric power output is induced by the difference of flow velocity and boundary layer thickness. For the generator with the asymmetric square cross‐section, the average flow velocity is highest and the boundary layer is thinnest. The compression wave is generated with dependence on the channel shape. The difference in the flow velocity and boundary layer thickness is induced by the superposition of the compression wave. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(2): 9–16, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22403     

High-performance silicon photonics technology for telecommunications applications

By way of a brief review of Si photonics technology, we show that significant improvements in device performance are necessary for practical telecommunications applications. In order to improve device performance in Si photonics, we have developed a Si-Ge-silica monolithic integration platform, on which compact Si-Ge–based modulators/detectors and silica-based high-performance wavelength filters are monolithically integrated. The platform features low-temperature silica film deposition, which cannot damage Si-Ge–based active devices. Using this platform, we have developed various integrated photonic devices for broadband telecommunications applications.     

Experimental and semi-analytical studies on the aerodynamic forces acting on a vehicle passing through the wake of a bridge tower in cross wind

In a strong cross wind, sudden change of wind velocity in the wake of a bridge tower causes rapid change of the aerodynamic forces acting on a passing vehicle, which may result in an accident due to driver’s miss-steering. This paper discusses and clarifies the transient characteristics of the aerodynamic forces acting on a ground vehicle in high cross winds when the vehicle is passing through the wake of a bridge tower using a scale model in a wind tunnel experiment. Various parameters, such as wind speed and direction, type of vehicle and tower, were considered in the study.The side force and yawing moment acting on the vehicle model were measured using strain gauges on the model-supporting system that was designed as two cantilever beams with high stiffness. Characteristics of the aerodynamic forces acting on the vehicle model were described and the prediction methods that considered the wind non-uniformity acting on the vehicle were proposed and their applicability was studied.For the side force, the quasi-steady forces based on the relative wind velocity acting at the c.g. of the vehicle model generally agreed with the measured results. Changes in side force were found to be more or less proportional to the wind speed distribution. For the yawing moment, however, the quasi-steady prediction did not agree well with the measured results due to the wind non-uniformity. Therefore, a modified prediction method was proposed that included the effects of wind non-uniformity in a simple manner. Depending on the case, the agreement of prediction and measured results was still not good quantitatively, but from the qualitative point of view, the proposed prediction method could reproduce the yawing moment peak that was similar to the experimental results.     

Sphingolipids in immature and mature soybeans

Ceramides and cerebrosides were isolated from immature and mature soybeans, and structures of the constituents were investigated. As component fatty acids, normal, 2-hydroxy and 2,3-dihydroxy acids were found in ceramides, whereas only normal and 2-hydroxy acids were identified in cerebrosides. The principal fatty acid component was 2-hydroxylignoceric acid in ceramides, and 2-hydroxypalmitic acid in cerebrosides. Sphingoids in ceramides consisted mainly of trihydroxy bases, with 4-hydroxy-trans-8-sphingenine being predominant. In contrast, cerebrosides contained mainly dihydroxy bases, the principal constituent beingtrans-4,trans-8-sphingadienine. The only sugar in cerebrosides was glucose. The constituents of the two sphingolipids were similar to each other in immature and mature seeds. Possible metabolic relations of plant sphingolipids, based on composition, are discussed.     

Control of Traffic-Induced Vibrations of Elevated Urban Highways

Abstract: This paper studies the active control of traffic-induced vibrations of elevated highway bridges. In order to suppress the vibration, an active control device (AMD or ATMD) is installed beneath the bridge girder at the center. Three different feedback control algorithms are studied, depending on different levels of vehicle information used in control design, namely, (1) full-state feedback, (2) output feedback, and (3) constant-gain output feedback. The gains of the algorithms 1 and 2 are time-varying, while the gain of algorithm 3 is time-invariant. The numerical examples of bridge-control system responses, subjected to the moving vehicle, are computed. The results demonstrate the effectiveness of the active control in reducing the bridge responses. However, for the control design, the information of passing vehicles is found to be almost unnecessary for inclusion in the feedback, although for the response analysis, it is known that the vehicles form an essential part that should be incorporated in the system dynamic model. It is also found that the control performance of ATMD is higher than that of AMD. Finally, based on the understanding of the control characteristic, a new control concept is proposed. It is shown that the ATMD's performance can be further improved by the proposed control.     

Model-based design and experimental validation of active vibration control for a stress ribbon bridge using pneumatic muscle actuators

This paper describes the development of an active vibration control system for a light and flexible stress ribbon footbridge. The 13 m span carbon fiber reinforced plastic (CFRP) stress ribbon bridge was built in the laboratory of the Department of Civil and Structural Engineering, Berlin Institute of Technology. Its lightness and flexibility result in high vibration sensitivity. To reduce pedestrian-induced vibrations, very light pneumatic muscle actuators are placed at handrail level, introducing control forces. First, a reduced discretized analytical model is derived for the stress ribbon bridge. To verify the analytical prediction, experiments without feedback control are conducted. Based on this model, a delayed velocity feedback control strategy is designed. To handle the nonlinearities of the muscle actuator, a subsidiary force control is implemented. Then the control performance from numerical simulation is verified by experiments under free vibration. As a result, analytical analyses agree well with experimental results. It is demonstrated that handrail-introduced forces can efficiently control the first mode response.     

Concrete Crack Detection by Multiple Sequential Image Filtering

Abstract: This article presents a new robust automated image processing method for detecting cracks in surface images of concrete structures. This method involves two steps: (1) development of an image filter for detecting major cracks using genetic programming (GP), and (2) elimination of residual noise after filtering and detection of indistinct cracks by iterative applications of the image filter to the local regions surrounding the cracks. The proposed method can be used for the accurate detection of cracks in surface images recorded under various conditions. Moreover, the widths of the detected cracks can be quantified on the basis of the spatial derivatives of the brightness patterns. The estimated crack widths are in good agreement with those measured manually.     

环境振动响应下悬索桥的系统识别

对环境振动响应下悬索桥系统识别的应用进行研究和评估。为获得桥的动力特征,采用只有两个输出时间域的系统识别方法,即与Ibrahim时域方法相结合的随机衰减法,与特征系统实现算法相结合的自然励磁技术。研究两种方法的精度和效果并与有限元方法结果进行了比较。两种方法论证的系统识别的结果表明,环境振动测量可以提供桥动态特征的可靠信息。