Full-Scale Test of Continuity Diaphragms in Skewed Concrete Bridge Girders

Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48° was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab. Thus, the bridge deck would provide the continuity over the support, improve the riding quality, enhance the structural redundancy, and reduce the expansion joint installation and maintenance costs.     

Prevalence and survival of Campylobacter in Egyptian dairy products

Campylobacter is a leading foodborne pathogen that poses an interesting paradox of being frequently transmitted by foodstuffs, yet showing sensitivity to food preservation procedures. In the present study, 227 samples of milk and dairy products were randomly collected and examined for the presence of Campylobacter spp. Samples were collected from the Egyptian area Abou-Homos, where the pathogen had been previously shown to be a major causative agent of intestinal disease. Potential Campylobacter isolates were speciated using a multiplex PCR assay targeting the housekeeping gene lpxA. Only raw milk and fresh Domiati cheese samples were found to contain Campylobacter jejuni at low incidence rates. Using a selected C. jejuni isolate recovered in this study, it was shown that the pathogen maintained its viability in Domiati cheese more than in yoghurt, yet it survived in both products more than expected. This suggests that this foodborne strain of C. jejuni may develop adaptive strategies that aid survival under food preservation conditions, which contradicts with what is known about this pathogen as a stress-sensitive organism.     

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Carbon nanotube/silver (CNT/Ag) nanocomposites include CNT volume fraction up to 10?vol.% were prepared by chemical reduction in solution followed by spark plasma sintering. Multiwalled CNTs underwent surface modifications by acid treatments, the Fourier transform infrared spectroscopy data indicated several functional groups loaded on the CNT surface by acid functionalisation. The acid-treated CNTs were sensitised and activated. Silver was deposited on the surface of the activated CNTs by chemical reduction of alkaline silver nitrate solution at room temperature. The microstructures of the prepared CNT/Ag nanocomposite powders were investigated by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy and X-ray powder diffraction analysis. The results indicated that the produced CNT/Ag nanocomposite powders have coated type morphology. The produced CNT/Ag nanocomposite powders were sintered by spark plasma sintering. It was observed from the microstructure investigations of the sintered materials by HRSEM that the CNTs were distributed in the silver matrix with good homogeneity. The hardness and the tensile properties of the produced CNT/Ag nanocomposites were measured. By increasing the volume fraction of CNTs in the silver matrix, the hardness values increased but the elongation values of the prepared CNT/Ag nanocomposites decreased. In addition, the tensile strength was increased by increasing the CNTs volume fraction up to 7.5?vol.%, but the sample composed of 10?vol.% CNT/Ag was fractured before yielding.     

Constellation constrained multiuser multiple‐input multiple‐output for high capacity and error performance over correlated fading channels

Channels' correlation has direct impact to degrade the capacity and reliability of multiple‐input multiple‐output (MIMO) systems considerably. In this paper, new signal constellation designs are investigated to mitigate fading correlation and maximize the capacity and error performance of multiuser MIMO (MU‐MIMO) over correlated channels, which is a major research challenge. Two methods are studied in a novel constellation constrained MU‐MIMO approach, namely, unequal power allocation and rotated constellation. Based on principles of maximizing the minimum Euclidean distance (d_min) of composite received signals, users' data can be recovered using maximum likelihood joint detection irrespective of correlation values. Compared with the identical constellation scenario in conventional MU‐MIMO, it is shown that constellation rearrangement of transmitted signals has direct impact to resolve the detection ambiguity when the channel difference is not sufficient, particularly in moderate to high correlations. Extensive analysis and simulation results demonstrate the superiority of proposed technique to capture most of the promised gains of multiantenna systems and application for future wireless communications. Copyright © 2014 John Wiley & Sons, Ltd.     

An Algorithm for Perspective Viewing of Objects Represented by Octrees

A new algorithm is presented for viewing three-dimensional objects, represented by an octree, from an arbitrary location. The algorithm generates aperspective view of the objects while eliminating hidden surfaces. The viewer can be located anywhere inside or outside the objects. The algorithm presented in this short notefixes an artifact that is generated by a previously published algorithm due to Meagher when the viewer is located in certain regions in space. The new algorithm traverses the octree in a back-to-front order and recursively chooses correct orders for visiting the sons of non-leaf nodes.     

Reconstruction d’obstacles métalliques de forme simple

In this paper, the author presents a method that allows partial or complete reconstruction of the shape of perfectly conducting body from a multifrequency analysis of its back-scattered far-field. The method is based on the physical optics approximation. The fundamental equations are first recalled, then through the example of the sphere, the parameters of practical interest (bandwidth, number of frequencies, noisy data can be assessed). The effect of a variation of these parameters on the reconstruction process are then investigated.     

Diffraction par des ouvertures dans la paroi d’un obstacle conducteur. Les différentes approches usuelles du problème

The problem of electromagnetic wave interaction with conducting bodies having apertures in their surfaces is of a great practical interest and is now the purpose of great attention. The various methods described here do not present the same advantages. Thus it is interesting to review them in order to define their range of applications. The author presents rigorous and approximate methods and he illustrates them by different examples.     

双音和WCDMA调制阻塞的有效IM2分量评估

引言近年来随着第3代(3G)无线网络在日本(IMT-2000)、欧洲(UMIST)和美国(CDMA2000)的推广,3G移动手机所需的低成本、低功耗和小形状系数的用户设备(UE)变得重要起来。采用硅工艺、电路设计技术实现的直接下变频接收结构是3G手机高集成平台的一种有前途的系统方案。本文给出3G无线电的商业用全集成零中频接收机方案(图1)。广泛讨论接收机输入2阶截点(IIP2),因为它是直接变频接收机的关键性能指标。在此给出测量、仿真和计算结果。直接变频接收机结构如图1所示,直接变频或零中频接收机结构是实现接收机完全片上集成的途经,直接解调信…     

Liver microcirculation analysis by red blood cell motion modeling in intravital microscopy images

Intravital microscopy has been used to visualize the microcirculation by imaging fluorescent labeled red blood cells (RBCs). Traditionally, microcirculation has been modeled by computing the mean velocity of a few, randomly selected, manually tracked RBCs. However, this protocol is tedious, time consuming, and subjective with technician related bias. We present a new method for analyzing the microcirculation by modeling the RBC motion through automatic tracking. The tracking of RBCs is challenging as in each image, as many as 200 cells move through a complex network of vessels at a wide range of speeds while deforming in shape. To reliably detect RBCs traveling at a wide range of speeds, a window of temporal template matching is applied. Then, cells appearing in successive frames are corresponded based on the motion behavior constraints in terms of the direction, magnitude, and path. The performance evaluation against a ground truth indicates the detection accuracy up to 84% TP at 6% FP and a correspondence accuracy of 89%. We include an in-depth discussion on comparison of the microcirculation based on motion modeling from the proposed automated method against a mean velocity from manual analysis protocol in terms of precision, objectivity, and sensitivity.     

Bias voltage effect on the dielectric properties of organic–inorganic blend SiNWs elaborated via metal assisted chemical etching

The electrical proprieties of poly (3-hexylthiophene): Silicon nanowires (P3HT: SiNWs) nanocomposite was investigated by impedance spectroscopy technique. The effect of bias voltage under and without illumination was discussed. Indeed, the imaginary part of the impedance shows a high relaxation frequency related to Maxwell–Wagner–Sillars (MWS) polarization. The relaxation time was found in the range of ms and it was shifted towards high frequency with increasing the bias voltage especially at 0.6 V At bias voltage equal to V_th and under illumination, the conductivity increases because the trapped charges acquire the necessary energy to escape from the interface and the hopping time found was reduced. This indicates a change of the conduction mechanism. The Cole–Cole diagram was excellently fitted through an equivalent circuit including a chemical capacitance Cµ, a contact electrical resistance Rs and recombination resistance Rp.