Structured Raney Nickel Catalysts for Liquid‐Phase Hydrogenation

Structured catalysts consisting of metal sheets on which Raney nickel was deposited by the thermal spraying method were tested for the liquid‐phase hydrogenation of glucose to sorbitol and 2‐nitrotoluene to 2‐methylaniline, used as model reactions. Catalytic tests performed in a bench‐scale (1 L) reactor showed that the catalytic activity of Raney Ni sheets is significantly higher than the one of the pellets used for fixed‐bed applications, but lower than the activity of the powder catalyst used in slurry mode. The activity could be significantly improved when applying a two‐phase co‐current flow through a monolith. In this case, the activity was superior to the one obtained with the slurry catalyst. These results confirm the potential of Raney Ni monoliths as structured catalysts.     

Modeling video sources for real-time scheduling

What is the impact of the autocorrelation of variable-bit-rate (VBR) sources on real-time scheduling algorithms? Our results show that the impact of long term, or interframe, autocorrelation is negligible, while the impact of short term, or intraframe, autocorrelation can be significant. Such results are essentially independent of the video coding scheme employed. To derive these results, video sequences are modeled as a collection of stationary subsequences called scenes. Within a scene, a statistical model is derived for both the sequence of frames and of slices. The model captures the distribution and the autocorrelation function of real-time video data. In previous work, the pseudoperiodicity of the slice level auto-correlation function made it difficult to develop a simple yet accurate model. We present a generalization of previous methods that can easily capture this pseudoperiodicity and is suited for modeling a greater variety of autocorrelation functions. By simply tuning a few parameters, the model reproduces the statistic behavior of sources with different types and levels of correlation on both the frame and the slice level.     

An architecture for managing virtual circuit and virtual path services in ATM networks

ATM networks rely on the Virtual Circuit (VC) and Virtual Path (VP) concepts to provide unicast connection-oriented services with Quality of Service (QoS) guarantees. This paper presents a model for managing the configuration and performance of the VC and VP services in these networks. The model consists of a connection management architecture that provides the services and is instrumented for network management purposes, and a network management architecture that uses the OSI management model to provide access to the appropriate service monitoring and control functions. The network management architecture proposes complete managed object definitions that achieve a variety of monitoring and control objectives: service configuration, service performance at the call and cell level, and service control. The latter includes the capability to establish VPs and control their allocated networking capacity and also control parameters of the signaling system that affect the performance of the VC service. The architecture was implemented in its entirety on the Xunet ATM testbed, and several experiments were conducted to illustrate the trade-off between the throughput of the VC service and the allocation of capacity to VPs. The experiments further demonstrated that the signaling system can create throughput bottlenecks in the absence of VPs in the network, and therefore, the network operator can increase performance by controlling the VP distribution.     

The fate of organic pollutants in frozen waters: sunlight photodecomposition of uracil herbicides in frozen aqueous solutions

A study of the sunlight irradiation effects, during the winter, on two herbicides present in sensitized, frozen, aqueous solutions is reported. These solutions of bromacil (3-sec-butyl-5-bromo-6-methyluracil) and of terbacil (3-t-butyl-5-chloro-6-methyluracil) were exposed directly to sunlight or covered by different layers of ice. Both herbicides were rapidly decomposed by sunlight in the presence of sensitizers like methylene blue (1.0 ppm), rose bengal (2.0 ppm), and riboflavin (4.0 ppm), at different pH (6.8, 8.2 and 9.1) of the solutions.The best results were obtained in the alkaline range of pH. At least 70 or 75% (at pH 9.1) and 25 or 60% (at pH 8.2) of the initial amounts of bromacil or terbacil, respectively, were decomposed in the first 2 h of irradiation, using the above sensitizers. At pH 6.8, a practical rate of photodecomposition reaction was observed only in the terbacil experiments.When the frozen samples were covered by ice blocks, up to 11 cm thick, the amount of incident light reaching them was usually attenuated, but the photodecomposition reaction rates remained high enough to be of practical value.The extract residues of the irradiated solutions (6 h, pH 8.2) of bromacil (1.0 ppm MB) and terbacil (2.0 ppm RF), analyzed by TLC and by GC-MS, were found herbicide free. Only minute amounts of one and four decomposition products were present in the concentrated solutions of these residues of bromacil and terbacil, respectively.     

Drift correction in a multichannel integrated optical young interferometer

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift is such that the drift present in one of the channels can be determined by interpolation of the drift measured in the two adjacent channels. It is shown that a drift reduction of 10 times can be achieved as compared with the situation in which no correction is applied. We anticipate that these findings will permit the exploitation of the extreme sensitivity of interference-based sensors to a much greater extent.     

BIM时代的建筑教育

随着技术和文化的不断进步,建筑信息模型(BIM)促使建筑教育朝着新颖的方向发展。在建筑工作坊中BIM的学习氛围改变了师生之间以及设计沟通上的交流方式。因此BIM代表着思维方式的转变,对当代建筑的大量片段式教育提出了质疑。数字化进程的结果和在建筑教育中引发的思考是深刻的,并促进全新交互模式的产生。以社会网络为基础的社会智力和社会参与,与学习和知识的建构无缝对接,这近似于BIM的工作模式。     

Fast, ultrasensitive virus detection using a Young interferometer sensor

We report the application of an integrated optical Young interferometer sensor for ultrasensitive, real-time, direct detection of viruses. We have validated the sensor by detecting herpes simplex virus type 1 (HSV-1), but the principle is generally applicable. Detection of HSV-1 virus particles was performed by applying the virus sample onto a sensor surface coated with a specific antibody against HSV-1. The performance of the sensor was tested by monitoring virus samples at clinically relevant concentrations. We show that the Young interferometer sensor can specifically and sensitively detect HSV-1 at very low concentrations (850 particles/mL). We have further demonstrated that the sensor can specifically detect HSV-1 suspended in serum. Extrapolation of the results indicates that the sensitivity of the sensor approaches the detection of a single virus particle binding, yielding a sensor of unprecedented sensitivity with wide applications for viral diagnostics.