Impact of corrosion on fretting damage of electrical contacts

Electrical contacts are used in a large number of industrial applications, this includes all sorts of modern transportation: airplanes, trains and automobiles. Mechanical assemblies are subjected to vibrations and micro-displacements between mating surfaces are observed leading to fretting wear. Mechanical degradation can additionally be accelerated by a corrosive factor caused by variable humidity, temperature and corrosive gas attack. Fretting-corrosion leads to an increase of contact resistance or intermittent contact resistance faults as corrosion products change the nature of the interface primary through a range of film formation processes. In this work the impact of a corrosion product film formed on copper and gold surfaces on the electrical contact fretting behavior is shown. It has been observed that modification of the interface by the formation of the surface layer can surprisingly lead to increase of the electrical contact durability

Matrix Design for Optimal Sensing

We design optimal $2 \times N$ ($2 <N$) matrices, with unit columns, so that the maximum condition number of all the submatrices comprising 3 columns is minimized. The problem has two applications. When estimating a 2-dimensional signal by using only three of $N$ observations at a given time, this minimizes the worst-case achievable estimation error. It also captures the problem of optimum sensor placement for monitoring a source located in a plane, when only a minimum number of required sensors are active at any given time. For arbitrary $N\geq3$, we derive the optimal matrices which minimize the maximum condition number of all the submatrices of three columns. Surprisingly, a uniform distribution of the columns is \emph{not} the optimal design for odd $N\geq 7$.Comment: conferenc

Characteristics of reduced fat milks as influenced by the incorporation of folic acid

Folic acid plays an important role in the prevention of neural tube defects such as spina bifida and anencephaly, heart defects, facial clefts, urinary abnormalities and limb deficiencies. Milk and milk products serve as a potential source for folic acid fortification due to the presence of folate binding proteins which seem to be involved in the folate bioavailability. Though milk is a not a good source of folic acid, fortification could help in the prevention of the above mentioned defects. The objective of this study was to examine the physico-chemical characteristics of reduced fat milks fortified with folic acid. Reduced fat milks were prepared using 25, 50, 75 and 100% of the recommended dietary allowance of 400 micrograms of folic acid. Treatments included addition of folic acid at these levels before and after pasteurization. Color, pH, fat, protein, viscosity, folic acid concentration, folate binding protein concentration, folate binding protein profile, standard plate count and coliform counts were determined on days 1, 7, 14 and 21. A consumer acceptance test was conducted on day 7. Data from the consumer panel was analyzed using analysis of variance (PROC GLM) with means separation to determine the differences among treatments. Data obtained from the color, pH, fat, protein, viscosity, folic acid concentration, folate binding protein concentration, standard plate count and coliform counts were analyzed using the General Linear Model with a repeated measure in time by the Statistical Analysis System. Significant differences were determined at P\u3c0.05 using Tukey’s Studentized Range Test. There were no differences in the electrophoretic mobility of folate binding protein in the samples. The concentration of folic acid was significantly higher in reduced fat milks fortified with folic acid after pasteurization compared to the treatments to which folic acid was added before pasteurization. The consumer panelists did not find any significant differences in flavor, appearance and texture of folic acid fortified reduced fat milks compared to that of the control. Fortification of reduced fat milks with folic acid can be accomplished with out adversely affecting the product characteristics