Chitosan-Tripoly Phosphate (CS-TPP) Synthesis Through Cross-linking Process: the Effect of Concentration Towards Membrane Mechanical Characteristic and Urea Permeation
Crosslinking reactions are required to modify the functional groups on chitosan and to increase the number of active groups of chitosan. In this study crosslinking reaction of tripolyphospate (TPP) groups on chitosan was conducted in order to produce membrane which functions as candidate of hemodialysis membrane. The mole ratio between chitosan and NaTPP was varied to obtain the best composition of modified materials. Study of TPP concentration effect towards membrane characteristics was conducte durea permeation ability. The resulting membrane was then characterized including tests of thickness, water uptake, tensile strength and membrane hydrophilicity. The results showed that the best composition of membrane occurred in the addition of 0.691 g of NaTPP proved byin creasing water uptake (150%), its highest mechanical strength and releasing the percentage of urea permeation by 44%.
Distribution and Assessment of Fe and Mn in the Coastal Sediments of Sendang Biru, East Java, Indonesia
The high presence of heavy metals in sediment can affect the ecological and biological systems in East Java Indonesia. To monitor the environmental status of Fe and Mn, we investigated geochemical fraction and distribution of these metals at 8 sites in the sediment of Sendang Biru. BCR and Tessier sequential leaching methods were applied to leach Fe and Mn, respectively, due to high precision and accuracy of these methods. The pattern of geochemical fractions in sediment samples showed the maximum leached levels of Fe and Mn (>50%) in residual fractions in Sendang Biru Beach, indicating the natural effects surrounding sites. The portions of Fe and Mn in non-residual fractions located at Sendang Biru Port were higher compared with the site in the adjacent sea, indicating these metals were derived possibly from anthropogenic effects. The assessment from CF and Igeo calculations of Fe and Mn in sediment samples showed that the sediment near the Sendang Biru Port was moderately contaminated by Fe and Mn.
Surface roughness monitoring by singular spectrum analysis of vibration signals
Abstract This study assessed two methods for enhanced surface roughness (Ra) monitoring based on the application of singular spectrum analysis (SSA) to vibrations signals generated in workpiece-cutting tool interaction in CNC finish turning operations i.e., the individual analysis of principal components (I-SSA), and the grouping analysis of correlated principal components (G-SSA). Singular spectrum analysis is a non-parametric technique of time series analysis that decomposes a signal into a set of independent additive time series referred to as principal components. A number of experiments with different cutting conditions were performed to assess surface roughness monitoring using both of these methods. The results show that singular spectrum analysis of vibration signal processing discriminated the frequency ranges effective for predicting surface roughness. Grouping analysis of correlated principal components (G-SSA) proved to be the most efficient method for monitoring surface roughness, with optimum prediction and reliability results at a lower analytical-computational cost. Finally, the results show that singular spectrum analysis is an ideal method for analyzing vibration signals applied to the on-line monitoring of surface roughness.