Boundary integral equation method for linear porous-elasticity with applications to soil consolidation

For physical phenomena governed by the Biot model of porous-elasticity, a reciprocal relation, similar to the Betti's recoprocal theorem in elasticity, is constructed in Laplace transformed space. Integrating the reciprocal relation enables one to formulate boundary integral equations. The fundamental kernels for the integral equations are solved in closed forms for the case of isotropic material. Numerical implementation of two-dimensional problems includes finite element ideas of discretization and polynomial interpolation, and numerical inversion of a Laplace transform. Practical applications of the method are found in consolidation problems in soils which contain compressible as well as incompressible pore fluids. Also, as a numerical experiment, consolidation of partially saturated soil is simulated and interesting phenomena are observed. The currently developed boundary integral equation method (BIEM) for porous-elasticity may be viewed as an efficient and accurate alternative of existing finite element and finite difference methods. For linear consolidation problems, application of BIEM is always preferred to the other numerical methods whenever possible.     

Preventive measures to reduce bioaerosol exposure during refuse collection: results of field studies in the real-life situation

The aim of the present research project was to investigate and evaluate technical and organisational measures targeted at bioaerosol reduction during the refuse collection and to determine the exposure of refuse collectors to dust, fungi and endotoxins in an on-the-job situation with different vehicle technologies and states of hygiene. The following technical factors were found to influence the bioaerosol concentration at the refuse collector's workplace: compaction method, lifting device control, rave rail height, hopper depth, design of intake area and dust interception. For instance, notably higher total fungal counts were recorded with rotating drum compaction than with packer plate compaction. A hinged lid closure at the lifting device in conjunction with a suction unit induced a positive effect. In addition, the automatic lifting system had a positive influence on rear-end loaders, as did loading operation control from the closed driver's cab on side loaders. Regular internal and external high-pressure cleaning of the lifting device at intervals of not more than 14 days is recommended as a basic rule for vehicle hygiene.     

Effect of kimchi powder level and drying methods on quality characteristics of breakfast sausage

This study was conducted to determine the effect of the addition of kimchi powder on the quality characteristics of meat batter and breakfast sausage. Breakfast sausages were supplemented with freeze dried kimchi powder (FKP) or hot air dried kimchi powder (HKP) at levels of 1% (FKP-1 and HKP-1) or 2% (FKP-2 and HKP-2). The emulsion stability, cooking yield, and apparent viscosity in meat batters improved with increments of kimchi powder (p < 0.05). Increased levels of kimchi powder in breakfast sausage decreased the L^∗ value, pH, and springiness, and increased the a^∗ value, b^∗ value, hardness, chewiness, and gumminess (p < 0.05). Sensory evaluations indicated that a higher overall acceptability was attained when the kimchi powder was added to breakfast sausage at a level of 2%.     

Investigation of nanoparticles by atomic and lateral force microscopy

Metallic nanoparticles have been produced on vitreous carbon substrates by means of thermal evaporation. From pictures of the particles, made by a high-resolution scanning electron microscope (HRSEM), a semispherical shape is suggested due to the total mass of deposited material. Atomic force microscopy (AFM) has been applied to this sample in order to get direct topographic information. The AFM has been operated with normal and super tips, the latter having a smaller cone angle and radius, thus following more precisely the contours of an object. Simultaneously lateral-force microscopic (LFM) images have been recorded. Major differences between the contents of HRSEM- and AFM-images are considered, emphasizing the important influence of the tips' geometry. Both the AFM and LFM line scans have been compared with and have qualitatively agreed with those calculated under simplifying assumptions.     

Residue analysis of pyrethroid insecticides in cereal grains, milled fractions and bread

A procedure is described for the residual analysis of eight pyrethroid insecticides at levels of 2-5 micrograms/kg. Residues are extracted from cereal grains, flour or bread with a mixture of acetonitrile/water (2 + 1) and are partitioned into petroleum ether. Clean-up is performed by gel permeation chromatography on Bio-Beads S-X3 and an additional Florisil column. Electron capture gas liquid chromatography on a non-polar SE-30 capillary column separates the isomers of the compounds. Under the conditions used in the experiments with cyfluthrin, cypermethrin, deltamethrin, fenvalerate, and permethrin, the compound levels in rye and wheat did not decrease significantly. Losses during milling and baking were small. Consequently, pyrethroid insecticides remain effective in grain stored over a long period of time. However, considerable residues result in the milled fractions as well as in different types of bread.     

Localization of wind turbine noise using a microphone array in wind tunnel measurements

An experimental investigation on scaled wind turbine models in a wind tunnel with a microphone array is presented. Our study focuses on the localization and quantification of aerodynamic noise sources on rotating wind turbine blades with the aim of identifying the contributing factors that have an impact on the source spectra. Therefore, wind tunnel measurements were conducted for three different blade geometries (NACA 4412 shape, Clark-Y shape, and sickle shape), five pitch angles between ?2° and +8° and five wind velocities between 5 and 13 ms^??1. For the localization of rotating sound sources with a microphone array, a rotating beamforming method based on the acoustic ray method is used. The Clean-SC deconvolution method was used to improve the resolution of the acoustic sources, and integrated spectra were calculated for the individual blades. The sound sources were localized at the wind turbine blades and assigned to the leading edge and trailing edge subregions. The results show a high dependency on the sound source distribution and the source strength with regard to the observed one-third octave bands, wind velocity, and blade geometry. Hence, the localization of rotating sound sources with a microphone array is a suitable method for the development of wind turbine blades that emit less noise.