| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Rydefalk, Staffan
(författare)
-
Fluctuations in the regular transmittance of dispersions of straight circular cylinders with a diameter much larger than the wavelength of the radiation
- 1998
-
Ingår i: Journal of the Optical Society of America A. - 0740-3232. ; 15:6, s. 1689-1697
-
Tidskriftsartikel (refereegranskat)abstract
- The expected value and the variance of the regular transmittance of a dilute dispersion of slender straight circular cylinders with a diameter much larger than the wavelength of the radiation are studied theoretically in relation to the dimensions of the cylinders and the diameter of the radiation beam used. Both monodisperse and heterodisperse dispersions are considered. The study is Limited to two particle categories: (i) particles that are short and (ii) particles that are long but thin compared with the diameter of the radiation beam. The expected value is a function of concentration and particle diameter. The variance is proportional to the concentration. The variance is also proportional to particle length in the case of short particles but not in the case of long particles. The results explain interesting possibilities for the characterization of dispersions of large cylindrical particles shown earlier in industrial on-line applications.
|
|
| 7. |
- Rydefalk, Staffan
(författare)
-
Theory of fluctuations in the regular transmittance through a dispersion of large cylindrical particles : extension to higher concentrations
- 1999
-
Ingår i: Journal of the Optical Society of America A. - 0740-3232. ; 16:11, s. 2737-2745
-
Tidskriftsartikel (refereegranskat)abstract
- It has been shown in a previous paper [J. Opt. Sec. Am. A 15, 1689 (1998)] that the expected value and the Variance of the fluctuating regular transmittance through a dispersion of slender cylinders can be used to measure properties such as the size and concentration of the dispersed particles. The theory is valid, however, only for very low concentrations or very short path lengths. In practical applications, such as on-line applications, it is often desirable to work at higher concentration X path-length products p to avoid complicated sensor constructions. An extension of the previous theory toward higher values of p is presented. It is based on the assumption of the independence of the regular transmittance of parallel layers of the dispersion. The extended theory shows that information about the dispersion found in the expected Value and variance at very low values of p can also be obtained for higher values of p with a few simple expressions. Therefore applications possible in the case of low p values are also possible for higher p values. Two experimental examples have been included to facilitate the discussion of the theory presented.
|
|
| 8. |
|
|
| 9. |
- Bäckström, Mikael, 1963-
(författare)
-
On Monitoring and Control of Machining Processes
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis presents several aspects related to the industrial and academic activities associated with monitoring and control of the machining process and machine tools A survey of the industrial situation identified some key factors for a successful implementation of monitoring and control techniques. Applicable, relatively simple, systems for cutting-process monitoring and adaptive control are available on the commercial market today but the degree of industrial utilisation of the technique is low because the systems are experienced as hard to operate and use, and are at the same time considered unreliable. In order to promote a higher degree of industrial utilisation more work has to be devoted raising the performance of the system solutions. An Integrated Supervisory Process Control (ISPC) concept is presented as an approach dealing with multi-purpose control requirements utilising the individual advantages of several sensors and modelling techniques. The ISPC system is supposed to operate as a conceptual integration of sensors, process models and different control modules. Two prototype systems, based on five-axis machining centres, for real-time control of the machining process are outlined. Different strategies for monitoring and control are developed, implemented and experimentally tried out, and the studies conducted demonstrate results that encourage further research work devoted to verification of the proposed control concept. The results obtained in the initial experiments utilising methods for process control and monitoring, such as double exponential smoothing technique (DES), multivariate monitoring applied to signal tracking and artificial neural networks applied to cutting torque control, reveal that the different techniques have potential to improve the performance of monitoring and control tasks, thus contributing to the creation of more sophisticated and reliable solutions in the ISPC concept.
|
|
| 10. |
- Kadefors, Roland, et al.
(författare)
-
Recruitment of low threshold motor-units in the trapezius muscle in different static arm positions
- 1999
-
Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 42:2, s. 359-375
-
Tidskriftsartikel (refereegranskat)abstract
- A prevailing hypothesis for development of myalgia symptoms in the trapezius muscle is based on observations that in stereotypic activation of muscle the same low-threshold motor-units are the first ones to be recruited, and that these units are active throughout the contraction, until total relaxation. The theory suggests that these units are the first ones in monotonous repetitive work to be subject to degenerative processes, causing pain. The present project was undertaken to evaluate to what extent recruitment of motor-units in the trapezius muscle is position-specific, i.e. if there are motor-units that are recruited over a wide range of arm postures. Fine wire electrode pairs, inserted 2 cm lateral to the midpoint between the acromion and the C7 spinous processus, were used for signal acquisition. Methods for decomposition of the interference patterns were developed, allowing identification of single motor-units in signals registered in different arm positions. Voluntary recruitment of motor-units in the descending portion of the trapezius muscle was studied in 24 different arm positions (0–90 shoulder flexion, 0–45 humeral abduction, and 45–135 elbow flexion) in three subjects. The results showed that the wire electrode technique and the signal processing algorithm employed allowed motor-unit identification in nonisometric conditions. It was found that low threshold motor-units in the trapezius muscle, active over a wide range of arm positions, could be identified in all three subjects. We refer to those as Cinderella, or C, units. These results support the research hypothesis addressed.
|
|
