String model description of polarisation and angular distributions in pbar p -> Lambdabar Lambda at low energies

The observed polarisation of Lambda hyperons from the inclusive pA -> Lambda X reaction at high energies has previously been well described within the Lund string model through polarised ss quark pair production in the string breaking hadronisation process. This model is here applied to the exclusive pbar p -> Lambdabar Lambda reaction at low energies and compared to available data sets down to an incident beam momentum of 1.835 GeV/c. This required an extension of the diquark scattering model to involve three components: an isotropic part relevant close to threshold, a spectator part and a forward scattering part as in pA -> Lambda X at high energies. The observed angular distributions are then reproduced and, for momentum transfers above |t'| = 0.2 GeV^2, agreement with the measured polarisation is also obtained.Comment: 12 pages, 4 figures, submitted to Eur. Phys. J.

A Novel Approach to Reduction of Frictional Losses in a Heavy-Duty Diesel Engine by Reducing the Hydrodynamic Frictional Losses

An important parameter in the reduction of fuel consumption of heavy-duty diesel engines is the Power Cylinder Unit (PCU); the PCU is the single largest contributor to engine frictional losses. Much attention, from both academia and industry, has been paid to reducing the frictional losses of the PCU in the boundary and mixed lubrication regime. However, previous studies have shown that a large portion of frictional losses in the PCU occur in the hydrodynamic lubrication regime. A novel texturing design with large types of surface features was experimentally analyzed using a tribometer setup. The experimental result shows a significant reduction of friction loss for the textured surfaces. Additionally, the textured surface did not exhibit wear. On the contrary, it was shown that the textured surfaces exhibited a smaller amount of abrasive scratches on the plateaus (compared to the reference plateau honed surface) due to entrapment of wear particles within the textures. The decrease in hydrodynamic friction for the textured surfaces relates to the relative increase of oil film thickness within the textures. A tentative example is given which describes a method of decreasing hydrodynamic frictional losses in the full-scale application

Modelling and control of wooden chips to a sulphate digester

At the Skoghall pappermill, sulphatepaper pulp is produced in a continuous digester originally from 1969. To be able to maintain a high level of production there is a need for a process with few disturbances. Variations in how well the wooden chips are packed in the digester is one form of disturbance. Today there are no available measurements on how well the chips are packed. Instead this is regarded as being constant. The variation in the so called bulk density of the chips is mainly due to variations in the percentage with small dimensions. Chips are classified in relation to their size and one of the smallest classes is referred to as pin chips. These are believed to have a big impact on the bulk density. The amount of pin chips fluctuate more then the other classes, there by causing disturbances. The Skoghall pappermill has invested in a ScanChip. This is an instrument that measures the dimensions of the chips optically. ScanChip presents figures on chip quality, including a measurement of the bulk density. However, it has been shown that this measurement is not valid for the Skoghall pappermill. By using data from ScanChip a model that predicts how well the chips are packed has been devised. This value is the bulk density divided by the basic density. The model has proved to yield good results, despite a relatively small amount of data. A theoretical value of the amount of produced pulp has been computed based on the revolutions of the production screw that feeds chips into the digester. This value takes in consideration how well the chips are packed. The value has shown great similarities with the empirical measurements that are used today. A simulation during one month has shown that differences in the mixture of chips have effected the measurement of produced pulp with up to 7 ton/h. Chips are stored in open pile storages before they are being used in the process of transforming them into pulp. Four screws are used to move chips from the piles to conveyer belts. It has been shown in work done previously, that the movement of the screws contributes to variations in the amount of pin chips measured by ScanChip. During the work with this master’s thesis I have found that there are variations in the piles that make it difficult to predict the amount of pin chips accordingly. However by filtering the measurements of pin chips to remove these variations, the results are improved. A new way of controlling the movements of the screws was operational on the 10 of March and this improved the results. The direction in which the screws are moving influence the speed of the screws, mainly in the pile with the so called sawmill chips. By changing the amount of chips that each screw puts out, the differences in speed have been reduced. The mixtures found in the two piles are not completely homogenous. There are a greater amount of pin chips in the northern parts compared with the southern parts. This could be an effect of the wind direction, and will still cause variations

N\ue5gra reflektioner om tv\ue4r- respektive m\ue5ngvetenskap”. Arbete m\ue4nniska milj\uf6

This publication summarises some important aspects of science that still are valid. Especially so for broad or rather broad applied science disciplines. The content discussed are based on all of the different the authors’ experiences of the cross and multi-disciplinary research approaches. To some extent will it explain Engstr\uf6m’s standpoints with regard to explain which and how his publications are registered in Chalmers Public Library (CPL). This very publication was actually written during a period of time when we were engaged in an extensive research programme financed by the National Institute for Working Life in Solna (Cooperative for Optimisation of industrial production systems regarding Productivity and Ergonomics COPE). The advancements, as well as the organisational strains and scientific clashes, more or less forced us to clear out some particular aspects. This publication relay ought to be translated into English since it gives food for thoughts for both practitioners and scientists (see some of the other publications registered in CPL)

Precision of measurements of physical workload during standardised manual handling. Part II: Inclinometry of head, upper back, neck and upper arms.

For measuring the physical exposure/workload in studies of work-related musculoskeletal disorders, direct measurements are valuable. However, the between-days and between-subjects variability, as well as the precision of the method per se, are not well known. In a laboratory, six women performed three standardised assembly tasks, all of them repeated on three different days. Triaxial inclinometers were applied to the head, upper back and upper arms. Between-days (within subjects) and between-subjects (within tasks) variance components were derived for the 10th, 50th and 90th percentiles of the angular and the angular velocity distributions, and for the proportion of time spent in predefined angular sectors. For percentiles of the angular distributions, the average between-days variability was 3.4 degrees. and the between-subjects variability 4.0 degrees. For proportion of time spent in angular sectors, the variability depended on the percentage of time spent in the sector; the relative variability was scattered and large.. on average 103% between days and 56% between subjects. For the angular velocity percentiles. the average between-days variability was 7.9%. and the average between-subjects variability was 22%. The contribution of the measurement procedure per se to the between-days variability, i.e.. the imprecision of the method, was small: less than 2 degrees for angles and 3% for angular velocity. (C) 2005 Published by Elsevier Ltd