Volume 11 (2011): Issue 5 (January 2011)

Recently there has been a growing interest in the selection of product colors for design engineering purposes and for quality control. The selection is generally based on color samples and the quality control is carried out with specific measurement instruments. In low quantity production it is common to avoid instrumental color measurement using human control personnel instead. For such subjective color judgment it is necessary to have standardized illumination that is usually produced by high cost daylight simulator lamps. Our aim was to build a cost effective daylight simulator with halogen incandescent light sources that can match the parameters (CCT, CRI, MI_vis and Illumination) of the similar but more expensive products.

If magnetorheological (MR) fluids are stored in porous materials, when excited by the external magnetic field, MR fluid will be drawn out and produce MR effect, which could be used to solve the following problems of the MR damper, such as the seal, volume and the cost of MR fluid damper. In this paper, the effect of structure of metal foams on the performance of MR fluid is investigated; the relationship between the penetrability and the porosity of the metal foams is measured, the change of MR fluid performance flowing though the metal foams is obtained. It shows that, after flowing through metal foams, the change of performance of MR fluid is about 2.5%. Compared to the sponge, the porous metal foams have the obvious advantages in high porosity and rigidity, which provide a convenient and low-cost way to design the MR damper.

The effects of dimensional resonance of magnetoplasmic waves in semiconductors were investigated. It was demonstrated that these effects could be used to measure the strong magnetic fields. Possible ways to design contactless magnetic field sensors operating at room or at cryogenic temperature, such as that of liquid nitrogen are discussed. It has been shown that for strong field sensor a semiconductor material of high carrier mobility μ, density N and compact RF system for registration of dimensional resonance of magnetoplasmic waves in helicon resonator is needed.

Low frequency vibrations occurring in ground transportation are of interest in research of the driver's and the passenger's comfort and in seating dynamics research. Piezoelectric accelerometers commonly used for vibration measurement are not well suited for the analysed frequency range. Hence, other sensors capable of measuring accelerations down to the sub-Hertz region have to be used. MEMS acceleration sensors are particularly suitable for such purposes. A compact measuring system employing two three-axial MEMS accelerometers interfaced via a USB data acquisition unit to a laptop was designed and constructed. The digitised data were then processed by scripts in Matlab® with the aim of analysing both the effect of vibration on a seated person and the dynamic properties of the seat. Preliminary results of a test run with a passenger automobile are presented.

Oil palm trunks infected by Ganoderma boninense disease have been studied using density and ultrasonic characterizations. The ultrasonic characterizations have been performed using a commercial ultrasonic instrument at the frequency of 54 kHz. The measurements have been done in 3 zones: inner zone, central zone and peripheral zone. It was found that the stem density of the oil palm infected by Ganoderma boninense disease was reduced by 50% in comparison to the original healthy trunk. From this effect the velocity of the ultrasonic wave propagated through the Longitudinal, Radial, and Tangential directions is lower for the trunk infected by Ganoderma boninense disease compared to a healthy trunk. For the 10 cm thickness of samples, the ultrasonic velocity for all transit directions was in range of 260 - 750 ms^-1 for the infected sample, whereas for healthy samples was in the range of 460 - 900 ms^-1. These results are very useful for the detection of the area which has been affected by the disease.

The aim of this research was to establish the reliability and factorial validity of different isometric basic characteristics of F-t curve related to leg extensors in well trained and healthy Serbian males and females. Sample consisted of 159 examinees. In order to assess characteristics of the F-t isometric leg extensor force, tensiometric probe and standardized "seating leg extension" test were used. The measurement range was defined by 4 variables regarding the contractile characteristics of the leg extensor isometric muscle force - 1) the level of the achieved maximal force - F_maxLegExtISO, 2) the indicator of basic (general) level of rate of force development - RFD_{BASICLegExtISO}, 3) the time necessary to reach maximal force - tF_maxLegExtISO, 4) basic synergy index. The results showed a high statistical significance of p<0.001 in representability, generalizability and reliability for all the characteristics observed in both genders (Spearman-Brown r - 0.715 to 0.967 for males and 0.713 to 0.941 for females). As for the methodology aspect of testing, the factor analysis demonstrated the necessity of conducting at least three trials, choosing the best result from the two last trials.