Synthesis of clay–carbon nanotube hybrids: Growth of carbon nanotubes in different types of iron modified montmorillonite

In the present study, montmorillonite–carbon nanotube hybrids were synthesized by catalytic decomposition of ethylene over iron montmorillonite surfaces modified by different experimental procedures. SEM and STEM analyses reveal the presence of carbon nanotubes attached to the clay layers and X-ray diffraction results indicate that sodium montmorillonite layers were intercalated with iron species during the ion-exchange processes and further delaminated due to the growth of carbon nanotubes. It is expected that montmorillonite–carbon nanotube hybrids will be beneficiary for improvement of mechanical properties in polymer nanocomposites due to their pre-exfoliated internal structure and the presence of surface carbon nanotubes which may significantly enhance reinforcing effect.     

Aerosol lidar intercomparison in the framework of the EARLINET project. 2. Aerosol backscatter algorithms

An intercomparison of aerosol backscatter lidar algorithms was performed in 2001 within the framework of the European Aerosol Research Lidar Network to Establish an Aerosol Climatology (EARLINET). The objective of this research was to test the correctness of the algorithms and the influence of the lidar ratio used by the various lidar teams involved in the EARLINET for calculation of backscatter-coefficient profiles from the lidar signals. The exercise consisted of processing synthetic lidar signals of various degrees of difficulty. One of these profiles contained height-dependent lidar ratios to test the vertical influence of those profiles on the various retrieval algorithms. Furthermore, a realistic incomplete overlap of laser beam and receiver field of view was introduced to remind the teams to take great care in the nearest range to the lidar. The intercomparison was performed in three stages with increasing knowledge on the input parameters. First, only the lidar signals were distributed; this is the most realistic stage. Afterward the lidar ratio profiles and the reference values at calibration height were provided. The unknown height-dependent lidar ratio had the largest influence on the retrieval, whereas the unknown reference value was of minor importance. These results show the necessity of making additional independent measurements, which can provide us with a suitable approximation of the lidar ratio. The final stage proves in general, that the data evaluation schemes of the different groups of lidar systems work well.     

CIB working commission W87

Jens Knocke of the National Swedish Institute of Building Research and coordinator of the commission of 75 experts from 25 countries demonstrates how 'builders' all over the world are open to legal action if their product, the building, with its installations and landscaping fails to satisfy any of a long range of 'user' requirements.     

Tracking Multiple Moving Objects for Real-Time Robot Navigation

This paper proposes a method for detecting and tracking the motion of a large number of dynamic objects in crowded environments, such as concourses in railway stations or airports, shopping malls, or convention centers. With this motion information, a mobile vehicle is able to navigate autonomously among moving obstacles, operating at higher speeds and using more informed locomotion strategies that perform better than simple reactive manoeuvering strategies. Unlike many of the methods for motion detection and tracking discussed in the literature, our approach is not based on visual imagery but uses 2D range data obtained using a laser rangefinder. The direct availability of range information contributes to the real-time performance of our approach, which is a primary goal of the project, since the purpose of the vehicle is the transport of humans in crowded areas. Motion detection and tracking of dynamic objects is done by constructing a sequence of temporal lattice maps. These capture the time-varying nature of the environment, and are denoted as time-stamp maps. A time-stamp map is a projection of range information obtained over a short interval of time (a scan) onto a two-dimensional grid, where each cell which coincides with a specific range value is assigned a time stamp. Based on this representation, we devised two algorithms for motion detection and motion tracking. The approach is very efficient, with a complete cycle involving both motion detection and tracking taking 6 ms on a Pentium 166 MHz. The system has been demonstrated on an intelligent wheelchair operating in railway stations and convention centers during rush hour.     

Characterization of Cement-Based Materials Using Diffuse Ultrasound

The objective of this research is to develop a quantitative understanding of the propagation of ultrasonic waves in cement-based materials by examining specimens made of a portland cement-paste matrix and glass bead “aggregate.” The incident ultrasonic waves are broadband and contain wavelengths on the order of the glass bead scatterers. Experimentally measured ultrasonic waves are interpreted using diffusion theory to quantitatively measure dissipation and diffusion coefficients as functions of frequency and microstructure. These results provide a basic understanding of the effect of some features of the microstructure on the propagation of ultrasonic waves, as well as supplying a first step in the characterization of distributed damage using ultrasonic methodologies.     

Safety of food contact silicone rubber: Liberation of volatile compounds from soothers and teats

The release of volatile compounds from soothers and teats made from silicone rubber has been investigated. Firstly, measurements of the total release of volatiles were performed according to the method in the draft European standard (CEN). Weight losses of 0.17-0.80% after four hours at 200 °C were observed using gravimetric measurements. One product had a weight loss above the proposed CEN limit of 0.5%. Secondly, the volatile compounds were identified using a thermal desorption/cold trap injector on a gas chromatograph equipped with infrared spectroscopic (IR) and mass spectrometric (MS) detectors. The main compounds were siloxane oligomers and aliphatic hydrocarbons. One teat released about 0.1 mg diethyl phthalate (DEP), which is considered to be quite a high quantity. Limited amounts of the antioxidant 3,5-di-t-butyl-4-hydroxytoluene (BHT) were found in most samples.     

The oxidative dehydrogenation of ethane by perovskite type catalysts containing oxides of strontium, cerium and ytterbium

Compounds with the general formula SrCe_1−xYb_xO_3-0.5x have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), temperature programmed reduction (TPR) and BET, and tested for catalytic activity with respect to dehydrogenation of ethane to ethene. XRD indicates that the solubility limit of Yb₂O₃ in SrCeO₃ is about 10 %, above which a second phase is formed. Furthermore, Yb:SrCeO₃ is unstable in the presence of CO₂ as it reacts to SrCO₃ and Yb:CeO₂. TPR measurements indicate that Ce may be reduced from tetra- to the trivalent state. BET measurements yielded specific surface areas of approximately 1m²/g. The different catalyst compositions were tested in a continuous flow tubular reactor with two different partial pressures of oxygen at 500, 600 and 700 °C. A maximum yield of 49 % was obtained at 700 °C. Possible reaction mechanisms are discussed.     

A Comparative Study Of Discomfort Caused By Indoor Air Pollution,Thermal Load And Noisec

The relative importance of sensory air pollution, thermal load and noise was studied under controlled conditions in two identical environmental chambers. In one chamber subjects were exposed to various levels of either thermal load or poor indoor air quality. For each condition tested in this chamber, the subjects were exposed to a number of noise levels in an adjacent chamber with neutral thermal conditions and good indoor air quality in order to determine a noise level causing the same degree of discomfort. A total of 68 comparisons of the conditions in the two chambers were made by the same group of 16 subjects after one-minute exposure in each chamber. In the operative temperature range of 23–29°C, a 1°C change in operative temperature was found to have the same effect on human comfort as a change in perceived air quality of 2.4 decipol or a change in noise level of 3.9 dB. For levels of perceived air quality up to 10 decipol, a 1 -decipol change in perceived air quality had the same effect on human comfort as a change in noise level of 1.2 dB. A relationship between traffic noise level and percentage dissatisfied was established