Agglomeration process of dry ice particles produced by expanding liquid carbon dioxide

Formation of dry ice particles and their agglomeration process have been studied experimentally. The dry ice particles were produced by expanding liquid carbon dioxide at room temperature and pressure, and then introduced into an additional tube acting as an agglomeration chamber. In the experiments, the temperatures of the jet flow and the tube wall were measured by thermocouples, and dry ice particles in the jet flow were observed by a high speed camera with a zoom lens. It was found that two stages of temperature reduction occurred in the jet flow, corresponding to the agglomeration process. It was also found that the particle size of the agglomerates increased and the particle velocity decreased with increasing tube diameter. The agglomeration process of dry ice particles can be explained by the particle deposition and reentrainment, i.e. dry ice particles of several micrometers are deposited on the tube wall and form a deposition layer; then, agglomerates are reentrained from the layer into the jet flow.     

Structural evolution during mechanical alloying and annealing of a Nb-25at%Al alloy

Mixtures of pure elemental Al and Nb powders of Nb-25at%Al composition was mechanically alloyed, and structural evolution during high energy ball milling has been examined. Al dissolved in Nb from the early stage of the ball milling, and amorphization became noticeable after longer than five hours of milling. However the dissolution of Al in Nb was not completed before the amorphization. No intermetallic phase formed during the mechanical alloying. Before complete amorphization, metastable nitride of Nb_4.62N_2.14 (i.e., -NbN) with hexagonal structure has formed in nanocrystalline size through nitrogen incorporation from ambient environment. The lattice parameter of Nb increased significantly (up to 3.3433 Å after 5 hours of milling) during the milling. Upon annealing above 950 °C, Nb₂Al became the dominant feature with the -NbN, and Nb₃Al did not form from the samples milled at ambient environment. Nb₃Al appeared only from a sample milled at Ar environment. Structural evolution during mechanical alloying of the Nb-Al system is critically dependent the upon milling environment.     

Mechanical and thermal properties of silicon-carbide composites fabricated with short Tyranno® Si-Zr-C-O fibre

Silicon carbide (SiC) composites reinforced with 10–50 mass% (10.5–51.2 vol%) of short Tyranno® Si-Zr-C-O fibre (average length 0.5 mm) and 0–10 mol% of Al₄C₃as a sintering aid were fabricated using the hot-pressing technique. Firstly, the effect of Si-Zr-C-O fibre addition on the relative density (bulk density/true density) of the SiC composite hot-pressed at 1800 °C for 30 min was examined by fixing the amount of Al₄C₃to be 5 mol%. Although the relative density was reduced to 87.4% for 10 mass% of Si-Zr-C-O addition, further increases in the amount of Si-Zr-C-O fibre increased density to a maximum of 92.8% at 40 mass% of fibre addition. Secondly, the effect of varying the amount of Al₄C₃addition on the relative density was examined by fixing the amount of Si-Zr-C-O fibre to be 40 mass%. The optimum amount of Al₄C₃addition for the fabrication of dense SiC composite was found to be 5 mol%. The fracture toughness of the hot-pressed SiC composites with 20–40 mass% of Si-Zr-C-O fibre addition (amount of Al₄C₃: 5 mol%) was 3.2–3.4 MPa · m^1/2and approximately 1.5 times higher than that (2.39 MPa · m^1/2) of the hot-pressed SiC composite with no Si-Zr-C-O fibre addition. SEM observation showed evidence of Si-Zr-C-O fibre debonding and pull-out at the fracture surfaces. The hot-pressed SiC composite with 5 mol% of Al₄C₃and 40 mass% of Si-Zr-C-O fibre additions showed excellent heat-resistance at 1300 °C in air due to the formation of a SiO₂layer at and near exposed surfaces.     

Fiber designs with significantly reduced nonlinearity for very long distance transmission

A class of low-nonlinearity dispersion-shifted fibers based on depressed-core multistep index profiles is investigated. A systematic approach for designing these fibers in which a reference W-index profile is used to initiate the design ispresented. Transmission properties, including effective area, mode-field diameter, dispersion, dispersion slope, and cutoff wavelength, are evaluated for several design examples. The effects of varying fiber dimensions and indices on effective area and mode-field diameter are assessed. It is shown that there is a trade-off between these two properties and, generally, larger effective areas are associated with larger mode-field diameters. Dispersion-shifted single-mode fiber designs with effective areas of from 78 to 210 mum(2) and the corresponding mode-field diameter of from 8.94 to 14.94 mum, dispersion less than 0.07 ps/nm km, and dispersion slope of approximately 0.05 ps/nm(2) km are presented.     

多虚拟电厂接入的主动配电系统优化经济调度

在市场环境下,为促进含随机性可再生能源的消纳同时协调各经济主体矛盾并挖掘各主体价值和经济效益,本文提出一种基于分析目标级联理论的主动配网调度优化模型,以配网与虚拟电厂存在电能交互为建模背景。考虑虚拟电厂组成的多样性,设置风储型虚拟电厂以及含冷热电系统型虚拟电厂,各虚拟电厂可以分别与配网进行电能交互,各经济主体根据自身组成优化内部变量以及交互功率,通过分析目标级联法与其他主体协调交互功率实现分布式求解。最后通过IEEE33节点配电系统的算例仿真表明,调度结果能较好的反应主体经济性,得出风储型虚拟电厂有利于提高风电的消纳量,冷热电联供型虚拟电厂可以实现综合能源经济管理,分析目标级联法用于本文所提的模型背景是有效的。     

Fast crack detection method for large-size concrete surface images using percolation-based image processing

The detection of cracks on concrete surfaces is the most important step during the inspection of concrete structures. Conventional crack detection methods are performed by experienced human inspectors who sketch crack patterns manually; however, such detection methods are expensive and subjective. Therefore, automated crack detection techniques that utilize image processing have been proposed. Although most the image-based approaches focus on the accuracy of crack detection, the computation time is also important for practical applications because the size of digital images has increased up to 10 megapixels. We introduce an efficient and high-speed crack detection method that employs percolation-based image processing. We propose termination- and skip-added procedures to reduce the computation time. The percolation process is terminated by calculating the circularity during the processing. Moreover, percolation processing can be skipped in subsequent pixels according to the circularity of neighboring pixels. The experimental result shows that the proposed approach efficiently reduces the computation cost.     

电子鼻

描述了电子鼻的定义及产生的背景，讨论了开发电子鼻过程中所涉及的相关技术，并列举了目前的应用以及将来可能的应用。     

The road to surgical simulation and surgical navigation

The recent advantage of the power of graphic workstations has made it possible to handle 3D human structures in an interactive way. Real-time imaging of medical 3D or 4D images can be used not only for diagnosis, but also for various novel medical treatments. By elaborating on the history of the establishment of our laboratory, which focuses on medical virtual reality, we describe our experience of developing surgery simulation and surgery navigation systems according to our research results. In the case of surgical simulation, we mention two kinds of virtual surgery simulators that produce the haptic sensation of surgical maneuvers in the user’s fingers. Regarding surgical navigation systems, we explain the necessity of the augmented reality function for the encouragement of the ability of robotic surgery and its trial for clinical case.     

Cooperative problem solving by tufted capuchin monkeys (Cebus apella): Spontaneous division of labor, communication, and reciprocal altruism.

Using an experimentally induced cooperation task, the authors investigated whether tufted capuchin monkeys (Cebus apella) share the following 3 characteristics of cooperation with humans: division of labor, communication, and reciprocal altruism. In Experiment 1, the authors trained individual monkeys to perform the necessary sequence of actions for rewards and tested them in pairs to assess whether they could solve the task by spontaneously dividing the sequence of actions. All pairs solved this task. In Experiment 2, monkeys worked in the cooperation task and a task requiring no partner help. They looked at the partner significantly longer in the former task than in the latter, but communicative intent could not be determined. In Experiment 3, only 1 of 2 participants obtained a reward on each trial. Monkeys maintained cooperation when their roles were reversed on alternate trials. Their cooperative performances demonstrated division of labor; results suggest task-related communication and reciprocal altruism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatio-Temporal Tube data representation and Kernel design for SVM-based video object retrieval system

In this article, we propose a new video object retrieval system. Our approach is based on a Spatio-Temporal data representation, a dedicated kernel design and a statistical learning toolbox for video object recognition and retrieval. Using state-of-the-art video object detection algorithms (for faces or cars, for example) we segment video object tracks from real movies video shots. We then extract, from these tracks, sets of spatio-temporally coherent features that we call Spatio-Temporal Tubes. To compare these complex tube objects, we design a Spatio-Temporal Tube Kernel (STTK) function. Based on this kernel similarity we present both supervised and active learning strategies embedded in Support Vector Machine framework. Additionally, we propose a multi-class classification framework dealing with unbalanced data. Our approach is successfully evaluated on two real movies databases, the french movie “L’esquive” and episodes from “Buffy, the Vampire Slayer” TV series. Our method is also tested on a car database (from real movies) and shows promising results for car identification task.