Reflection noise

PCA components with small variances may only reflect noise in the data. Such a plot looks like the profile of a mountain after a steep slope a more flat region appears that is built by fallen, deposited stones (called scree). Therefore, this plot is often named scree plot so to say, it is investigated from the top until the debris is reached. However, the decrease of the variances has not always a clear cutoff, and selection of the optimum number of components may be somewhat subjective. Instead of variances, some authors plot the eigenvalues this comes from PCA calculations by computing the eigenvectors of the covariance matrix of X note, these eigenvalues are identical with the score variances. 

If a model is stable in a split-half sense it is a clear indication that the model is real that it captures variation that not only pertains to the specific samples. If, on the other hand, some components are not stable in a split-half sense, it indicates that they reflect noise or that too few components are extracted. Hence, the model is not valid. It may also happen, though, that the phenomenon reflected in the nonstable component is simply only present in specific subsets. By including in the split-half analysis a model of the whole data set, this can be investigated by verifying if all components in the total model have significant scores in all subsets. 

Acoustic absorption in open-cell foams is very useful in quieting reflected noise. High thermal and high electrical insulation are due to the very low conductivity of the ubiquitous gas phase, and are definitely best at lowest density even choice of the... 

Simovich, S., Mehrotra, S., Franzon, P, and Steer, M. 1994. Delay and reflection noise macromodeling for signal integrity management of PCBs and MCMs. IEEE Trans. Comp. Pac., Man. Tech. Pt. B Adv. Pac. 17(l) 15-20. 

In the office situation, if it is open plan, use may be made of barriers of composite material, porous ceiling tiles and porous flooring to reduce noise transmission and reflection. Noise can come from conversation, older style printers, telephones and so on. Well designed partitioning in closed plan offices is also effective. Serious interference by ontside noise may be coming via windows. Double glazing can reduce this. 

Reflection noise degrades the transmitted signal through laser intensity fluctuations due to optical feedback from some interfaces such as the fiber end faces and the photodiode (PD) [41 -43]. This can be eliminated by using optical isolators and optical fibers with obliquely polished end faces. However, they cannot be applied to in-home and in-building networks because of their high installation cost. 

Here we demonstrate that the reflection noise can be significantly reduced in RoF systems by using GI POFs with a microscopic heterogeneous core. 

Inoue, A., Furukawa, R., Matsuura, M., and Koike, Y. (2014) Reflection noise reduction effect of graded-index plastic... 

Reflection noise in vertical cavity surface emitting lasers. A/ / . Phys. Lett., 63 (11), 1480-1482,... 

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