Benzene emitted from glowing charcoal

Benzene was assessed as the predominant aromatic compound emitted from glowing charcoal and firewood embers. Concentrations measured above charcoal used for grilling exceeded 10 mg m(-3) at a 5% carbon dioxide level. Charcoal with a high carbon content released less benzene. Glowing wood pellets emitted less benzene than glowing firewood remainders. The emissions of ethene and propene relative to benzene were low for commercial charcoal and wood-pellet embers, but high for firewood ember. The proportions of methylbenzene and naphthalene from charcoal were typically only 10% relative to benzene, and those of benzofuran, dibenzofuran and benzonitrile were typically below 5%. The polycyclic aromatic hydrocarbon (PAH) indicator phenanthrene was below the 1% level. Adsorbent sampling and GC-MS were used for assessing all the aromatic compounds. Earlier studies of charcoal emissions have focused on carbon monoxide, PAH and dioxins. It is concluded that the carcinogenic benzene may be an even more severe health hazard to be addressed by exposure-decreasing measures.     

Saturation capacitance of thin oxide MOS structures and the effective surface density of states of silicon

The capacitance vs voltage curve of thin oxide (30–40 Å) MOS structures in strong accumulation was studied. The results were interpreted in terms of equivalent surface density of state masses, which was found to be 0·2 m₀ for the silicon valence band and 0·06 m₀ for the conduction band, for both 111 and 100 surfaces. The experimental density of state masses were shown to be much lower than the bulk values. Equivalent density of states masses were calculated from a surface quantization model and in this case agreement with the experiments was obtained for the valence band only.     

Statistical Threat Assessment for General Road Scenes Using Monte Carlo Sampling

This paper presents a threat-assessment algorithm for general road scenes. A road scene consists of a number of objects that are known, and the threat level of the scene is based on their current positions and velocities. The future driver inputs of the surrounding objects are unknown and are modeled as random variables. In order to capture realistic driver behavior, a dynamic driver model is implemented as a probabilistic prior, which computes the likelihood of a potential maneuver. A distribution of possible future scenarios can then be approximated using a Monte Carlo sampling. Based on this distribution, different threat measures can be computed, e.g., probability of collision or time to collision. Since the algorithm is based on the Monte Carlo sampling, it is computationally demanding, and several techniques are presented to increase performance without increasing computational load. The algorithm is intended both for online safety applications in a vehicle and for offline data analysis.     

Elements in rice from the Swedish market: 1. Cadmium, lead and arsenic (total and inorganic)

A survey of the levels of cadmium, lead and arsenic in different types of rice available on the Swedish retail market was carried out in 2001-03. The types of rice included long and short grain, brown, white, and parboiled white rice. The mean levels found were as follows: total As: 0.20 mg kg^-1, inorganic As: 0.11 mg kg^-1; Cd: 0.024 mg kg^-1; and Pb: 0.004 mg kg^-1. ICP-MS was used for the determination of As (total and inorganic) after acid digestion. Lead and cadmium were determined using graphite furnace atomic absorption spectrometry (GFAAS) after dry ashing. In countries where rice is a staple food, it may represent a significant contribution in relation to the provisional tolerable weekly intake for Cd and inorganic As.     

Large eddy simulations and rotational CARS/PIV/PLIF measurements of a lean premixed low swirl stabilized flame

This paper reports on numerical and experimental studies of a lean premixed low swirl stabilized methane/air flame. The burner is made up of a central perforated plate and an annular swirler. A premixed methane/air mixture at an equivalence ratio of 0.62 is injected to an ambient co-flow of air through the burner under atmospheric pressure and room temperature condition with a Reynolds number of 30,000. Stereoscopic Particle Image Velocimetry (PIV) and simultaneous OH/acetone Planar Laser Induced Fluorescence (PLIF) are used to characterize the flame front and the turbulence field downstream of the burner. The flame is stabilized in the low speed central region and in the inner shear-layer vortices, where ambient air dilution to the flame is found to eventually quench the reactions downstream. Rotational Coherent Anti-Stokes Raman Spectroscopy (RCARS) measurements are carried out to characterize the temperature field and the relative oxygen mole fraction field, which enables quantification of the air dilution to the flame. The experimental data provides a challenging test case for numerical simulation models owing to the stratification of the mixture and quenching of the flame. Large eddy simulations are carried out using a three-scalar level-set G-equation flamelet model, which is shown to capture the basic flame characteristics and quenching at the trailing edge of the flame.     

Topology optimization of frame structures with flexible joints

A method for structural topology optimization of frame structures with flexible joints is presented. A typical frame structure is a set of beams and joints assembled to carry an applied load. The problem considered in this paper is to find the stiffest frame for a given mass. By introducing design variables for beams and joints, a mass distribution for optimal structural stiffness can be found. Each beam can have several design variables connected to its cross section. One of these is an area-type design variable which is used to represent the global size of the beam. The other design variables are of length ratio type, controlling the cross section of the beam. Joints are flexible elements connecting the beams in the structure. Each joint has stiffness properties and a mass. A framework for modelling these stiffnesses is presented and design variables for joints are introduced. We prove a theorem which can be interpreted as the fact that the removal of structural elements, e.g. joints or beams, can be modelled by a small strictly positive material amount assigned to the element. This is needed for the computations of sensitivities used in the applied gradient based iterative method. Both two and three dimensional problems, as well as multiple load cases and multiple mass constraints, are treated.