Nonlinear vibration of an initially stressed laminated plate according to a higher-order theory

The nonlinear behavior of laminated plates in a general state of non-uniform initial stress was studied at large vibration amplitudes. The nonlinear governing equations of this study were derived using a higher-order theory approach. The results were compared with the Mindlin plate theory’s results. The results showed that the higher-order shear deformation terms had a significant influence on the plate in a large amplitude vibration when the thickness ratio decreases and the plate was stacked with less layers. In addition, the effect of Young’s modulus in the thickness direction on the frequency ratio was significant for the two-layered plate. However, the results of the four-layered plates were not affected too much.     

A Real-Time Visual Inspection System for Railway Maintenance: Automatic Hexagonal-Headed Bolts Detection

Rail inspection is a very important task in railway maintenance, and it is periodically needed for preventing dangerous situations. Inspection is operated manually by trained human operator walking along the track searching for visual anomalies. This monitoring is unacceptable for slowness and lack of objectivity, as the results are related to the ability of the observer to recognize critical situations. The correspondence presents a patent-pending real-time Visual Inspection System for Railway (VISyR) maintenance, and describes how presence/absence of the fastening bolts that fix the rails to the sleepers is automatically detected. VISyR acquires images from a digital line-scan camera. Data are simultaneously preprocessed according to two discrete wavelet transforms, and then provided to two multilayer perceptron neural classifiers (MLPNCs). The "cross validation" of these MLPNCs avoids (practically-at-all) false positives, and reveals the presence/absence of the fastening bolts with an accuracy of 99.6% in detecting visible bolts and of 95% in detecting missing bolts. A field-programmable gate array-based architecture performs these tasks in 8.09 mus, allowing an on-the-fly analysis of a video sequence acquired at 200 km/h     

Influences of Connecting Unit Architecture on the Performance of Tandem Organic Light‐Emitting Devices

The present work investigates the influence of the n‐type layer in the connecting unit on the performance of tandem organic light‐emitting devices (OLEDs). The n‐type layer is typically an organic electron‐transporting layer doped with reactive metals. By systematically varying the metal dopants and the electron‐transporting hosts, we have identified the important factors affecting the performance of the tandem OLEDs. Contrary to common belief, device characteristics were found to be insensitive to metal work functions, as supported by the ultraviolet photoemission spectroscopy results that the lowest unoccupied molecular orbitals of all metal‐doped n‐type layers studied here have similar energy levels. It suggests that the electron injection barriers from the connecting units are not sensitive to the metal dopant used. On the other hand, it was found that performance of the n‐type layers depends on their electrical conductivities which can be improved by using an electron‐transporting host with higher electron mobility. This effect is further modulated by the optical transparency of constituent organic layers. The efficiency of tandem OLEDs would decrease as the optical transmittance decreases.     

Model-based interpretation of ERS-1 SAR images of Arctic sea ice

Interpretation of Synthetic Aperture Radar (SAR) images of sea ice is complex because of the natural variability of sea ice and sensor-induced effects, such as speckle. Most of the research on SAR image interpretation has focused on the winter months and algorithms were developed to classify sea ice successfully under cold conditions. However, interpretation of SAR images during the seasonal transitions has proved difficult due to rapidly changing weather conditions. In this paper we address the application of SAR during the transition from summer to the fall freeze-up. This period is important because it signals the start of significant new ice growth, which affects the air-ocean heat exchange and injects brine into the upper layers of the ocean. We have interpreted SAR images of the sea ice in terms of the basic ice characteristics by using shipborne radar measurements of sea ice during the freeze-up and models derived from these measurements. We have shown that the model-based approach is effective in interpreting SAR images during this seasonal transition. This work also provides the physical mechanisms responsible for the large increase in backscatter observed at the end of the summer melt season.     

Environmental quality and its changes,an analysis using NDVI

Normalized difference vegetation index (NDVI) derived from SPOT HRV multispectral data was used to study the changing environmental quality of Hong Kong from 1987, 1991 and 1993 to 1995. Conventional change detection techniques such as image differencing or principal components analysis helped to highlight salient changes. These techniques, however, were less effective in identifying subtle changes, in particular the amount and quality of green space. Integrating the mean NDVI values at the Tertiary Planning Unit (TPU) level with census and land-cover data showed that the NDVI values were related to woodland, tall scrubland and high-density urban areas. It was also related to the level of crowding as depicted from a factor analysis of census data. Tracing the changing pattern of mean NDVI values revealed that areas with continuous increases in NDVI values are scattered around old urban districts experiencing improved landscaping. Areas of continuous decrease in NDVI values covered a large part of rural New Territories and western Hong Kong Island revealing the urban expansion process. This provided valuable information for the assessment of environmental quality for planning and management of the environment.     

Particulate Carbon Speciation by MnO2 Oxidation

A selective thermal oxidation method was developed for the speciation of carbonaceous aerosols collected on filters into organic carbon (OC) and elemental carbon (EC). The technique is based on studying the thermal oxidation of microcrystalline graphite by MnO₂as well as various organic compounds. The procedure uses a modified Dohrmann DC-52 carbon analyzer with a flame ionization detector to detect the CO₂resulting from the oxidation as methane after catalytic conversion. The results led to the selection of 525 °C as the optimal temperature for the oxidation of OC while leaving EC intact. After the organic oxidation, the sample is heated at 850° C, at which EC is oxidized rapidly and completely by MnO₂. Carbonates that may be present in either the particles or the filter medium are removed by acidification and heating to ～ 120°C prior to performing the organic and EC measurements. Analysis of split ambient particulate samples in which the OC levels had been reduced by solvent extraction produced EC results statistically the same as the original untreated samples. These results suggest that the speciation is not sensitive to the level of organics in the sample. During the Carbonaceous Species Methods Comparison Study (CSMCS) in which the participants analyzed 20 blind samples, with four being triplicates, this technique yielded results in good agreement with the average results of the participants, with coefficients of variation (CV) derived from the triplicate analysis being 2.1%, 2.6%, and 8.1%, respectively, for total, organic, and elemental carbon.     

Experiments on paper insulation in a corona environment

Insertion of an insulating paper between point-plane electrodes normally increases the total breakdown potential threshold, except when its position is next to the plane. A series of DC [both (+) and (-)] experiments was designed and conducted to examine this latter distinction. It was found that visual ionic spots on the paper surface are a dominant prebreakdown phenomenon. Local failure at one of such discrete spots ultimately brings about a streamer sparkover in air at a sufficiently high potential. This paper describes the variability and other characteristics of the pattern in a two-dimensional spot distribution. Related experiments reveal that, with double paper layers already in the barrier, the pattern of spots becomes less dense visually but the breakdown potential would increase for the case of (+) point but would decrease further for the case of (-) point if a third sheet is introduced. A sharply defined “dark” band on the double-layer side in which glow spots are absent was always observed to clearly bridge the separate domains of, respectively, single-layer and double-layer spot distributions. Also related were the mechanical agitations of the paper accompanying all phases of the different discharge activities     

EC-EGI: enriched complex EGI for 3D shape registration

Extended Gaussian image (EGI) and complex EGI (CEGI) have been widely used as the representation of 3D shapes for shape recognition and pose estimation. In this work, we extend the representations and present a new representation named enriched complex extended Gaussian image (EC-EGI). The representation follows the same framework of EGI and CEGI, which is to represent each surface patch of the target 3D shape as a weight at the associated spot on the surface of the Gaussian sphere. However, while the original CEGI uses a single complex number as the weight, the new representation uses three complex numbers, which are related to the centroid position of the surface patch in 3D. With the inclusion of more information in the new representation, not only could object pose be determined more accurately, but also some key ambiguities of shape representation that CEGI and EGI have also removed. The translation parameters in the pose estimation application could also be determined in a simpler and more accurate way. In addition, the Gaussian sphere partition problem of CEGI is no longer present. Experimental results on synthetic and real image data are shown to illustrate the performance of the proposed representation in pose estimation.     

Two-phase heuristic algorithms for full truckloads multi-depot capacitated vehicle routing problem in carrier collaboration

Collaborative transportation, as an emerging new mode, represents one of the major developing trends of transportation systems. Focusing on the full truckloads multi-depot capacitated vehicle routing problem in carrier collaboration, this paper proposes a mathematical programming model and its corresponding graph theory model, with the objective of minimizing empty vehicle movements. A two-phase greedy algorithm is given to solve practical large-scale problems. In the first phase, a set of directed cycles is created to fulfil the transportation orders. In the second phase, chains that are composed of cycles are generated. Furthermore, a set of local search strategies is put forward to improve the initial results. To evaluate the performance of the proposed algorithms, two lower bounds are developed. Finally, computational experiments on various randomly generated problems are conducted. The results show that the proposed methods are effective and the algorithms can provide reasonable solutions within an acceptable computational time.